The 48^th Annual Meeting of the European Society for Blood and Marrow Transplantation: Physicians – Poster Session (P001 – P578)

19 – 23 March, 2022 ● Virtual Meeting

Copyright: Modified and published with permission from https://www.ebmt.org/annual-meeting

Sponsorship Statement: Publication of this supplement is sponsored by the European Society for Blood and Marrow Transplantation. All content was reviewed and approved by the EBMT Committee, which held full responsibility for the abstract selections.

Acute Leukaemia

P001 Post-transplant cyclophosphamide based anti-GVHD prophylaxis in patients with all treated in cr with ALLO-HCT from haploidentical vs HLA-mismatched unrelated donors: An ALWP EBMT analysis

A. Nagler ¹, M. Labopin², M. Arat³, P. Reményi⁴, Y. Koc⁵, D. Blaise⁶, E. Angelucci⁷, J. Vydra⁸, A. Kulagin⁹, G. Socié¹⁰, M. Rovira¹¹, S. Sica¹², M. Aljurf¹³, Z. Gülbas¹⁴, N. Kröger¹⁵, E. Brissot¹⁶, Z. Peric¹⁷, S. Giebel¹⁸, M. Mohty¹⁶

¹Chaim Sheba Medical Center, Ramat Gan, Israel, ²Saint-Antoine Hospital, AP-HP, Paris, France, ³Demiroglu Bilim University, Istanbul, Turkey, ⁴Dél-pesti Centrumkórház – Országos Hematológiai és Infektológiai Intézet, Budapest, Hungary, ⁵Medicana International Hospital Istanbul, Istanbul, Turkey, ⁶Institut Paoli-Calmettes, Marseille, France, ⁷Ospedale San Martino, Genova, Italy, ⁸Institute of Hematology and Blood Transfusion, Prague, Czech Republic, ⁹Raisa Gorbacheva Memorial Research Institute for Paediatric Oncology, St Petersburg, Russian Federation, ¹⁰AP-HP Hospital Saint Louis, Paris, France, ¹¹Institute of Hematology & Oncology, Barcelona, Spain, ¹²Universita Cattolica S. Cuore, Istituto di Ematologia, Rome, Italy, ¹³King Faisal Specialist Hospital & Research Centre, Riyadh, Saudi Arabia, ¹⁴Anadolu Medical Center Hospital, Kocaeli, Turkey, ¹⁵University Hospital Eppendorf, Hamburg, Germany, ¹⁶Hôpital Saint-Antoine, AP-HP, Paris, France, ¹⁷University Hospital Center Zagreb, Zagreb, Croatia, ¹⁸Maria Sklodowska-Curie National Research Institute of Oncology, Gliwice, Poland

Background: Post-transplant cyclophosphamide (PTCy)-based anti-GVHD prophylaxis pioneered in haploidentical (Haplo) transplantation is being increasingly used in other transplantation settings. Both Haplo and mismatched unrelated donor (MMUD) transplantation are valid options in patients with ALL in the absence of a MRD.

Methods: The study aim was to compare the outcomes of adult patients with ALL in CR who underwent Haplo versus 9/10 MMUD transplantation with PTCy in 2010-2020. Multivariate analysis adjusting for potential confounding factors was performed using a Cox’s proportional-hazards regression model for main outcomes.

Results: This study included 781 pts: Haplo-678, MMUD-103. Median follow-up was 24 (range, 11.3-45.6) and 19 (5.3-39.0) months, respectively (p = 0.61). Median age was 38 (18-75) and 40 (19-73) years (p = 0.51) and 65% and 66% were male, respectively (p = 0.76). Year of transplant was 2018 vs 2017 (p = 0.68). 39% and 43% were Ph-, 35% and 38% were Ph + , and 26% and 19% had T ALL, respectively (p = 0.3). Disease status at transplant was CR1 in 67% and 64%, and CR2 in 33% and 36% of the patients, respectively (p = 0.54). Conditioning was myeloablative in 70% and 69%, (p = 0.19) in Haplo and MMUD, respectively. Fewer Haplo than MMUD patients received TBI (48% vs 59%, respectively, p = 0.038) while more Haplo compared with MMUD were performed with a BM graft (37% vs 16%, p < 0.0001), respectively. The most frequent immunosuppression agents added to PTCy were MMF/cyclosporine A, and MMF/tacrolimus. ATG was administered in 8% and 21% of the transplants, respectively (p < 0.0001). Engraftment (day 60) was 96.5% vs 97.1% (p = 0.77) in Haplo vs MMUD, respectively. Incidence of day 180 aGVHD grade II-IV and III-IV was 31.6% vs 21.4% (p = 0.034), and 11.1% vs 8.2% (p = 0. 34), respectively. 2-y cGVHD and extensive cGVHD were 33% vs 36% (p = 0.69), and 12% vs 10% (p = 0.55) in Haplo vs MMUD, respectively. Main causes of death were leukemia (42% vs 57%), infection (30% vs 13%), and GVHD (14% vs 7.7%). 2y relapse incidence (RI), NRM, LFS, OS and GRFS were 26% vs 31% (p = 0.18), 22% vs 13% (p = 0.1), 52% vs 55% (p = 0.45), 61% vs 70% (p = 0.45), and 42% vs 45% (p = 0.60), for Haplo and MMUD, respectively. On multivariate analysis, NRM and RI were similar between Haplo and MMUD, HR = 1.45 (95% CI 0.8-2.6, p = 0.21) and HR = 0.8 (95% CI 0.5-1.3, p = 0.38), respectively. LFS, OS and GRFS were comparable, HR = 1.0 (95% CI 0.7-1.5, p = 0.8), HR = 1.2 (95% CI 0.8-1.8, p = 0.46) and HR = 1.0 (95% CI 0.8-1.5, p = 0.7), respectively. aGVHD was significantly higher with Haplo, HR = 1.7 (95% CI 1-2.8, p = 0.023), while aGVHD grade III-IV and cGVHD did not differ significantly between the 2 transplant groups. Additional prognostic factors for HSCT outcomes were disease status for all parameters excluding GVHD; age for NRM, LFS and OS. Ph⁺ was a favorable predictive factor for RI and OS. RI was higher with reduced intensity conditioning while OS was lower with PB grafts. A female to male donor/recipient combination was associated with a higher incidence of cGVHD.

Conclusions: Outcomes of Haplo and MMUD transplants for pts with ALL in CR are similar, apart from a higher incidence of aGVHD with Haplo transplants.

Disclosure: Nothing to declare

P004 Sequential conditioning with high dose melphalan followed by busulfan and fludarabine in eldery patients with relapsed or refractory (r/r) acute myeloid leukemia (AML)

M.-A. Urbahn¹, C. Reicherts¹, A. Pohlmann¹, S. Call¹, E. Eßeling¹, M. Floeth¹, J. Marx¹, J. Albring¹, J.-H. Mikesch¹, C. Schliemann¹, G. Lenz¹, M. Stelljes ¹

¹University Hospital Münster, Münster, Germany

Background: During the last decades, outcomes of patients with AML, receiving an alloSCT in complete remission (CR) have improved significantly, whereas the prognosis of patients transplanted with r/r AML remained dismal. Sequential conditioning regimens (e.g. FLAMSA-based or high-dose melphalan based) might improve outcomes of patients with r/r AML, particular in younger patients. A recent retrospective analysis showed promising survival data in younger patients conditioned with high dose melphalan, followed by 8 Gy TBI and fludarabine, while for elderly patients this intense therapy was associated with significant toxicities.

Methods: In our retrospective study 99 patients, aged > 55 years, with r/r AML transplanted at the BMT-center of University Hospital of Muenster between 2014 and 2021, were included. Median age was 67 years (range 55-76), the median HCT-CI-score was 2 (range 0-10). Thirteen patients were initially diagnosed with favorable risk, 37 patients with intermediate risk, and 49 patients with adverse risk AML (ELN 2017). At transplant, 65 patients had primary refractory AML, 15 patients had AML refractory to salvage treatment and 19 patients had untreated relapsed AML. Median bone marrow (BM) blast count prior to start of conditioning was 30% (range 5-90%). 75 patients received melphalan on day -11 at a dose of 100 mg/m² and 24 patients at a dose of 140 mg/m² followed by fludarabine (4 x 30 mg/m²) and busulfan (cumulative dose on 2 days of 6,4 mg/kg body weight) on days -5 to -1 prior to transplant. One patient received a BM graft, all other patients received peripheral stem cell grafts from matched-related donors (MRD, 16 patients), from matched-unrelated donors (MUD, 10/10 HLA-matched, 62 patients) or from mismatched-unrelated donors (MMUD, 9/10 matched, 21 patients). Median follow-up of surviving patients was 749 days after transplant.

Results: Overall survival (OS) rates at 1 and 2 years were 51% (95% CI, 41-61%) and 42% (95% CI, 32-53%), respectively. Cumulative incidences (C.I.) of relapse and non-relapse mortality (NRM) at 1 and 2 years were 14% (95% CI, 8-23%), 19% (95% CI, 12-30%) and 35% (95% CI, 26-46%), and 37% (95% CI, 29-49%), respectively. The 2-year-OS of patients with primary refractory AML, secondary refractory AML or untreated relapse showed no significant difference, with 46% (95% CI, 33-59%), 37% (95% CI, 9-65%) and 28% (95% CI, 7-50%), respectively. Patients with low disease burden (<20% BM blasts prior start of conditioning) had a C.I. of relapse of 6% (95% CI, 2-23%), compared to 28% (95% CI, 16-50%) and 32% (95% CI, 17-59%) for patients with 20-50% or >50% BM blasts (p .04). Furthermore, patients transplanted from a MMUD donor had a significantly higher risk of NRM of 70% (95% CI, 53-95%), as compared to patients transplanted from a MUD (30%, 95% CI, 21-45%) or MRD (24%, 95% CI, 9-63%) (p .001).

Conclusions: Our data suggest that high dose melphalan-based sequential conditioning combined with busulfan and fludarabine followed by alloSCT is a feasible treatment option in elderly patients with r/r AML, which allows long term survival of >40% in this high-risk patient group.

Disclosure: Nothing to declare.

P005 HLA-haploidentical transplantation with PTCY in AML patients with active disease at transplantation: Better survival with bm than with PBSC in patients >55 years

F. Baron ¹, M. Labopin^2,3,4, J. Tischer⁵, F. Ciceri⁶, A.M. Raiola⁷, D. Blaise⁸, S. Sica⁹, J. Vydra¹⁰, R. Fanin¹¹, F. Stölzel¹², A. Busca¹³, J.L. Diez-Martin¹⁴, Y. Koc¹⁵, A. Nagler¹⁶, M. Mohty^2,4,3

¹Laboratory of Hematology, GIGA-I3, University of Liege and CHU of Liege, Liege, Belgium, ²EBMT Paris Study Office/CEREST-TC, Paris, France, ³Saint Antoine Hospital, Paris, France, ⁴INSERM UMR 938, Paris, France, ⁵Klinikum Grosshadern, Med. Klinik III, Munich, Germany, ⁶Ospedale San Raffaele s.r.l., Haematology and BMT, Milano, Italy, ⁷IRCCS Ospedale Policlinico San Martino, Genova, Italy, ⁸Programme de Transplantation & Therapie Cellulaire, Centre de Recherche en Cancérologie de Marseille, Institut Paoli Calmettes, Marseille, France, ⁹Fondazione Policlinico Universitario A. Gemelli IRCCS, Dipartimento di Diagnostica per Immagini, Radioterapia Oncologica ed Ematologia, Roma, Italy, ¹⁰Institute of Hematology and Blood Transfusion, Prague, Czech Republic, ¹¹Azienda Ospedaliero Universitaria di Udine, Division of Hematology, Udine, Italy, ¹²University Hospital Dresden, Medical Clinic I, TU Dresden, Dresden, Germany, ¹³S.S.C.V.D Trapianto di Cellule Staminali, A.O.U Citta della Salute e della Scienza di Torino, Torino, Italy, ¹⁴Hospital Gregorio Marañón, Sección de Trasplante de Medula Osea, Madrid, Spain, ¹⁵Medicana International Hospital, Bone Marrow Transplant Unit, Istanbul, Turkey, ¹⁶Division of Hematology and Bone Marrow Transplantation, The Chaim Sheba Medical Center Tel Hashomer, Ramat Gan, Israel

Background: The best stem cell source for T-cell replete HLA-haploidentical transplantation with post-transplant cyclophosphamide (PTCy) remains to be determined. In patients with active acute myeloid leukemia (AML) at transplantation, one could speculate that the use of peripheral blood stem cells (PBSC) versus bone marrow (BM) could be associated with higher graft-versus-leukemia effects. These considerations prompted us to perform a retrospective study within the EBMT registry to assess this question.

Methods: Inclusion criteria included adult AML patients with primary refractory or relapsed AML, first allogeneic transplantation with an HLA-haploidentical donor with PTCy as graft-versus-host disease (GVHD) prophylaxis, transplantation between 2010 and 2020, and no in vivo T-cell depleted grafts. Primary endpoint was leukemia-free survival (LFS).

Results: A total of 668 patients (249 BM and 419 PBSC recipients) met the inclusion criteria. This include 380 patients with primary refractory AML, 229 in first relapse and 59 in second relapse at transplantation. Median follow-up was 36 months. Median age was 57 years (IQR, 45-64 years). There was a statistical interaction between patient age and stem cell source on LFS (P < 0.01 for age < or > 55 years). The analyses were thus performed separately for patients < or > 55 years of age. In multivariate Cox models, among patients < 55 years (n = 301, 114 BM and 187 PBSC), the use of PBSC versus BM resulted in comparable relapse incidence (HR = 0.85, P = 0.34), nonrelapse mortality (HR = 0.91, P = 0.8), LFS (HR = 0.82, P = 0.2; Figure 1) and overall survival (OS; HR = 0.81, P = 0.2) in multivariate Cox models.

The use of PBSC was associated with higher incidence of grade II-IV acute GVHD (HR = 2.02, P = 0.01) and no significant difference in incidence of chronic GVHD (HR = 1.42, P = 0.3). In contrast, in patients > 55 years of age (n = 367, 135 BM and 232 PBSC), the use of PBSC versus BM was associated with higher nonrelapse mortality (HR = 1.64, P = 0.015), comparable relapse incidence (HR = 1.17, P = 0.43), lower LFS (HR = 1.39, P = 0.02, Figure 1) and lower OS (HR = 1.35, P = 0.03). Incidences of grade II-IV acute (HR = 1.55, P = 0.13) and chronic (HR = 1.2, P = 0.55) GVHD were comparable in the 2 groups of patients.

Conclusions: Our data suggest that in patients > 55 years of age with active AML at HLA-haploidentical transplantation, the use of BM instead of PBSC as stem cell source results in lower nonrelapse mortality and better LFS and OS. In contrast among younger patients, the use of PBSC results in at least comparable LFS and OS.

Disclosure: The authors have no COI to disclose

P006 Molecular genetic changes and mrd after first induction chemotherapy were related with prognosis in acute lymphoblastic lkukemia

X. Sun ¹, X. Liu², Y. Li³, Y. Jiang^1,3, X. Sui^1,3, X. Wang^1,3,4,5, X. Fang^1,3

¹Shandong Provincial Hospital, Cheeloo College of Medicine, Shandong University, Jinan, China, ²The Affiliated Yantai Yuhuangding Hospital of Qingdao University, Yantai, China, ³Shandong Provincial Hospital Affiliated to Shandong First Medical University, Jinan, China, ⁴School of Medicine, Shandong University, Jinan, China, ⁵Shandong Provincial Engineering Research Center of Lymphoma, Jinan, China

Background: The changes of genetic information play an important role in the pathogenesis and recurrence of acute lymphoblastic leukemia (ALL), but there is no consistent conclusion about the impact of molecular genetic changes on the diagnosis and prognosis of the disease. The purpose of our study was to investigate the frequency spectrum of gene mutation and its prognostic significance in combination with minimal residual disease (MRD) and hematopoietic stem cell transplantation (HSCT) in adolescents and adults ALL patients aged ≥15 years old.

Methods: The basic characteristics, cytogenetics, molecular genetics, MRD, treatment regimen and survival outcome of ALL patients who were first diagnosed in Shandong Provincial Hospital and Yantai Yuhuangding Hospital from January 1, 2014 to May 1, 2021 were collected. Correlation analysis and survival analysis were performed by R and SPSS25 software, respectively.

Results: A total of 353 patients were included in this study, of which 90.6% of the 128 patients with next-generation sequencing (NGS) results had at least one mutation, and 66.41% of the patients had polygenic (≥ 2) mutations. NOTCH1, PHF6, RUNX1, JAK3 and PTEN were the most common mutations in T-ALL, while FAT1, TET2, NARS, KMT2D, FLT3 and RELN were the most common in B-ALL. The incidence of NOTCH1, JAK3, PTEN, PHF6 and JAK1 in T-ALL is higher than that in B-ALL. Correlation analysis revealed common mutation patterns, which were significantly different between T-ALL and B-ALL. Then the prognostic factors of 92 patients with B-ALL were analyzed, including sex, age, white blood cell count, Ph chromosome status, HSCT, hepatitis B virus infection status, MRD level and bone marrow remission status after induction chemotherapy, and genes with mutation frequency ≥ 6. Univariate analysis showed that FLT3 mutation (P = 0.048), TP53 mutation (P = 0.088) and RELN mutation (P = 0.037) were adverse factors affecting the overall survival (OS) of B-ALL patients. Patients with negative MRD after induction therapy (P = 0.007) and receive HSCT (P = 0.003) had better OS. Multivariate analysis revealed that MRD ≥ 1% after induction chemotherapy (P = 0.007), RELN mutation (P = 0.022) and TP53 mutation (P = 0.012) were independent risk factors for OS. Patients who undergo HSCT tended to have better OS, but there was no statistical significance in multivariate analysis (P = 0.079). NOTCH1 mutation (P = 0.018) and recurrence (P = 0.000) were independent adverse prognostic factors of event-free survival. In addition, our study also found that among the 52 patients who achieved negative MRD (MRD < 0.01%) after the first induction chemotherapy, there was no significant difference in OS between the transplantation group (n = 26) and the non-transplantation group (n = 26), and the average age of the non-transplantation group was significantly higher than that of the transplantation group (41.16 vs 32.58 years old, P = 0.049).

Conclusions: The distribution of gene mutations and the co-occurrence and repulsion of mutant genes in patients with ALL are closely related to the immunophenotype of patients. RELN and TP53 mutations are significantly associated with poor prognosis in patients with ALL. Patients with high sensitivity to chemotherapy do not seem to benefit from HSCT, which may be associated with high transplant-related complications and mortality and need to be confirmed in large prospective studies.

Disclosure: The authors declare that they have no competing interests.

Funding: This study was funded by the National Natural Science Foundation (grant nos. 82070203, 81770210, 81473486 and 81270598), the Key Research and Development Program of Shandong Province (grant no. 2018CXGC1213), the Technology Development Projects of Shandong Province (grant no. 2017GSF18189), the Translational Research Grant of NCRCH (grant nos. 2021WWB02 and 2020ZKMB01), the Technology Projects of Jinan (grant nos. 201704092 and 202019044), the Taishan Scholars Program of Shandong Province, Shandong Provincial Engineering Research Center of Lymphoma, and Academic Promotion Programme of Shandong First Medical University (grant no. 2019QL018).

P007 Autologous versus haploidentical stem cell transplantation in adult patients with acute myelogenous leukemia in first complete remission with undetectable minimal residual disease: Chinese data

J. Chen^1,2,3, Y. Ding ^1,2,3, X. Zhang⁴, E. Jiang⁵, L. Liu⁶, H. Huang⁷, J. Hu⁸, J. Wang⁹, Y. Zhang¹⁰, M. Labopin¹¹, I. Khevelidze¹¹, E. Polge¹¹, A. Nagler^11,12, M. Mohty¹¹, D. Wu^1,2,3, N.-C. Gorin¹¹

¹National Clinical Research Center for Hematologic Diseases, Jiangsu Institute of Hematology, The First Affiliated Hospital of Soochow University, Suzhou City, Jiangsu Province, China, ²Institute of Blood and Marrow Transplantation, Collaborative Innovation Center of Hematology, Soochow University, Suzhou City, Jiangsu Province, China, ³Key Laboratory of Stem Cells and Biomedical Materials of Jiangsu Province and Chinese Ministry of Science and Technology, Suzhou City, Jiangsu Province, China, ⁴Medical Center of Hematology, Xinqiao Hospital, Chongqing, China, Institute of Hematology and Blood Diseases Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, Tianjin, China, ⁶The First Affiliated Hospital of Chongqing Medical University, Chongqing, China, ⁷The First Affiliated Hospital of Zhejiang University, Hangzhou, China, ⁸Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China, ⁹The Affiliated Hospital of Guizhou Medical University, Guiyang, China, ¹⁰The Second People’s Hospital of Huai’an, Huaian, China, ¹¹EBMT Global Committee and Acute Leukemia Working Party, Hopital Saint-Antoine APHP and Sorbonne University, Paris, France, ¹²Division of Hematology and Bone Marrow Transplantation, The Chaim Sheba Medical Center, Tel-HashomerIsr, Israel

Background: Stem cell transplantation (SCT) is a potentially curative post-remission therapy for intermediate-risk acute myeloid leukemia (AML) patients. For patients in first remission (CR1) with negative measurable residual disease (MRD) and without a HLA-matched donor, both autologous SCT (ASCT) and haploidentical donor SCT (haplo-SCT) were acceptable options, but it is controversial that which one is preferred.

Methods: A retrospective study was conducted in 8 Chinese centers. The inclusion criteria were: 1) adult patients >18 years old; 2) diagnosis as AML with intermediate-risk according to ELN 2017; 3) ASCT or haplo-SCT underwent between 2010-2019; 4) in CR1 and MRD negative before transplant. The Primary endpoint was overall survival (OS). Secondary endpoints were progression-free survival (PFS), cumulative incidence of relapse (CIR), treatment-related mortality (TRM), and graft-versus-host disease-free and relapse-free survival (GRFS).

Results:

Totally 299 patients were enrolled in this study, including 97 recepients after ASCT and 202 recipients after haplo-SCT (Table 1). The median follow-up was 28 months in ASCT group versus 35 months in haplo-SCT group. Compared to haplo-SCT, patients after ASCT had increased 3-year CIR (27.0% ± 0.2% versus 13.5% ± 0.1%, p = 0.004) but reduced 3-year TRM (3.5% ± 0.0% versus 12.0% ± 0.0%, p = 0.013), which led to similar 3-year OS (80.8% ± 4.3% versus 79.2% ± 3.1%, p = 0.796) and PFS (69.5% ± 5.0% versus 73.7% ± 3.3%, p = 0.504). Moreover, the 3-year GRFS was remarkable better in ASCT group (69.5% ± 5.0% versus 55.9% ± 3.6%, p = 0.009) (Figure 1), which implied a survival with superior quality of life (QoL). In multivariate analysis, haplo-SCT independently related to an improved CIR, while increased TRM and reduced GRFS. Additionally, age more than 50 was associated with the worse OS, CIR and GRFS.

Table 1 Characteristics of patients.

		Auto (n = 97)	Haplo (n = 202)
Age (median, range)		36 (18-64)	36 (18-62)
Sex (cases)	Male/Female	57/40	121/81
Karyotype abnormalities at diagnosis (cases)		21	70
Molecular Abnormalities at diagnosis (cases)	FLT3-ITD	3	21
	NPM1	8	17
	WT1	22	27
Median interval from diagnosis to transplant (Months)		6	5
Single courses of induction before transplant (cases)		59	141
Courses of Consolidation before transplant ≤2 (cases)		33	151

Conclusions: We concluded that both ASCT and haplo-SCT were applicable for patients with intermediate-risk AML in MRD-negative CR1, but the absence of GVHD might potentially favor the QoL for patients receiving ASCT. Randomized trials are needed to confirm our conclusion.

Disclosure: Nothing to disclose

P008 Impact of donor and patient TGFB1 − 1347C > T variant in acute myeloid leukemia after hematopoietic stem cell transplantation

I. Martin ¹, A. Perez¹, M. Tormo¹, E. Villamon¹, J.C. Hernandez-Boluda¹, J.L. Piñana¹, C. Solano¹

¹Hospital Clínico Universitario de Valencia. INCLIVA Research Institute. University of Valencia., Valencia, Spain

Background: Transforming growth factor β1 (TGFβ1) is a pleiotropic regulatory cytokine secreted after hematopoietic stem cell transplantation (HSCT) by both donor T-cells and platelets and by recipient endothelial, connective and epithelial cells. TGFB1 − 1347C > T variant affects TGFB1 transcription and plasma levels and has been associated after HSCT with worse overall survival (OS) or graft versus host disease (GvHD).^1,2

References:

1.-Arrieta-Bolaños E, et al. Polymorphism in TGFB1 is associated with worse non-relapse mortality and overall survival after stem cell transplantation with unrelated donors. Haematologica. 2016;101:382-90.

2.- Kövy P, et al. Investigation of TGFB1 -1347C > T variant as a biomarker after allogeneic hematopoietic stem cell transplantation. Bone Marrow Transplant. 2020;55:215-223.

Methods: The study included 65 patients who underwent HSCT for acute myeloid leukemia (AML) disease. HSCT were performed between April 2013 and January 2021 at our single centre. OS was calculated from the day of HSCT until death for any cause or last follow up. Genomic DNA from donor and patient pairs was extracted from pre-transplant peripheral blood. TGFB1 − 1347C > T variant was determined by high resolution melting analysis on a LightCycler® 480 instrument (Roche Diagnostics) using an original primer design (Forward: 5′-CATGGGAGGTGCTCAGTAAA-3′; Reverse: 5′-AGGCTGGGAAACAAGGTAGG-3′). The effect of TGFB1 − 1347C > T variant was assessed in all three models: genotypic (CC vs. CT vs. TT), recessive (CC&CT vs. TT) and dominant (CC vs. CT&TT). The association of the clinical characteristics with the genetic findings was analyzed with the SPSS statistical program (v.20.0) and P values <0.05 were considered as statistically significant.

Results: The median OS for patients after HSCT was 13 months (range, 0 – 78 months). Patient −1347C > T frequencies were CC: 24 (39%), CT: 27 (43%), TT: 11 (18%) [patient DNA was not available in 3 cases] and donor −1347C > T frequencies were CC: 31 (49%), CT: 25 (40%), TT: 7 (11%) [donor DNA was not available in 2 cases]. In the overall series, patients with TT donor showed compared to CT&CC genotypes a trend towards a higher incidence of acute GvHD grade III-IV (29% vs. 4%, P = 0.084). In addition, patients with TT genotype and TT donor had a significantly higher frequency of acute GvHD grade III-IV than the remaining patients (40% vs. 4%, P = 0.013). Interestingly, in the non-myeloablative subgroup (n = 47), patients with TT genotype had a lower OS compared to CC and CT genotypes (median, 20 vs. 30 vs. 55 months, P = 0.026; Fig. 1). On the other hand, in myeloablative subgroup (n = 18), patients with CC donor had a lower relapse-free survival compared to CT&TT genotypes (median, 25 vs. 50 months, P = 0.046).

Conclusions: In our series of AML with HSCT analyzed, TGFB1 − 1347C > T variant was screened using a rapid and novel procedure and was associated with patients′ clinical outcome, especially in non-myeloablative conditioning. If these results were confirmed in a larger series, the analysis of that polymorphism could be useful in HSCT.

Disclosure: Nothing to declare

P009 Post-transplant cyclophosphamide separates graft-versus host disease (GVHD) and graft versus leukemia (gvl) effects after HLA- matched stem-cell transplantation (sct) for AML

A. Shimoni ¹, C. Peczynski², M. Labopin², A. Kulagin³, E. Meijer⁴, J. Cornelissen⁵, F. Ciceri⁶, G. Choi⁷, J. Sanz⁸, M. Rovira⁹, G. Van Gorkom¹⁰, N. Kröger¹¹, Y. Koc¹², J. Vydra¹³, J. Diez-Martin¹⁴, C. Solano¹⁵, P. Chiusolo¹⁶, A. Nagler¹, M. Mohty¹⁷

¹Chaim Sheba Medical Center, Tel-Hashomer, Israel, ²ALWP EBMT, Paris, France, ³First State Pavlov Medical University, St Petersburg, Russian Federation, ⁴VU University Medical Center, Amsterdam, Netherlands, ⁵Erasmus MC Cancer Institute, Rotterdam, Netherlands, ⁶Ospedale San Raffaele, Milano, Italy, ⁷University Medical Center Groningen, Groningen, Netherlands, ⁸University Hospital La Fe, Valencia, Spain, ⁹Hospital Clinic Barcelona, Barcelona, Spain, ¹⁰University Hospital Maastricht, Maastricht, Netherlands, ¹¹University Hospital Eppendorf, Hamburg, Germany, ¹²Medicana International Hospital, Istanbul, Turkey, ¹³Institute of Hematology and Blood Transfusion, Prague, Czech Republic, ¹⁴Hospital Gregorio Marañón, Madrid, Spain, ¹⁵Hospital Clínico de Valencia, Valencia, Spain, ¹⁶Universita Cattolica S. Cuore, Rome, Italy, ¹⁷Saint-Antoine Hospital, Paris, France

Background: The association of GVHD and GvL after allogeneic SCT is well-established but has not been confirmed in recent years with the introduction of new transplantation techniques. Post-transplant cyclophosphamide (PTCy) has been used for GVHD prevention in haplo-identical transplantation and more recently also in HLA- matched SCT. We have shown that there was no association between GVHD and GVL in the haplo-identical setting with PTCy but it was not determined if this is related to the PTCy effect or to the haplo-identical setting itself.

Methods: We assessed the impact of acute and chronic GVHD on SCT outcomes in patients with AML following SCT with conventional GVHD prophylaxis or PTCy by using Cox proportional-hazard analysis with acute and chronic GVHD as time- dependent variables.

Results: 12,653 patients received a first allogeneic SCT between the years 2010-2019, from HLA- matched siblings (n = 6726, 53%) or 10/10 matched- unrelated donors (n = 5927, 47%), using standard GVHD prevention regimens. The median age was 52 years (range, 18-80). Status at SCT was CR1 (n = 10478, 83%) or CR2 (n = 2175, 17%). The conditioning regimen was RIC (n = 5711, 45%) or MAC (n = 6942, 55%). The incidence of acute GVHD grade II-IV and III-IV at 180 days was 23.8% and 7.5%, respectively. The incidence of chronic GVHD and extensive chronic GVHD at 2 years was 37% and 16.3%, respectively. Acute GVHD grade II was associated with lower relapse risk (HR 0.85, P = 0.002), higher risk of non-relapse mortality (NRM) (HR 1.5, P < 0.0001) and lower overall-survival (OS) (HR 1.49, P < 0.0001) in comparison with no or grade I GVHD. Similarly, acute GVHD grade III-IV was associated with lower relapse (HR 0.76, P = 0.003), higher NRM (HR 6.21, P < 0.0001) and lower OS (HR 6.1, P < 0.0001). Extensive chronic GVHD was associated with lower relapse (HR 0.69, P < 0.0001), higher NRM (HR 2.83, p < 0.0001) and lower OS (HR 2.74, P < 0.0001). Limited chronic GVHD was not associated with any of these outcomes.PTCy was given to 508 patients after SCT from HLA- matched siblings (n = 234, 46%) or 10/10 matched- unrelated donors (n = 274, 54%). The median age was 48.5 years (range, 18-72). Status at SCT was CR1 (n = 437, 86%) or CR2 (n = 71, 14%). The conditioning regimen was RIC (n = 215, 42%) or MAC (n = 293, 58%). The incidence of acute GVHD grade II-IV and III-IV at 180 days was 22.8% and 6.2%, respectively. The incidences of chronic GVHD and extensive chronic GVHD at 2 years was 35.5% and 17.7%, respectively.Acute GVHD II-IV was associated with a non-statistically different risk of relapse (HR 1.37, P = 0.15), higher risk of NRM (HR 3.34, P = 0.0005) and lower OS (HR 1.92, P = 0.001). Chronic GVHD was not associated with risks of relapse (HR 0.99, P = 0.98), NRM (HR 1.11, P = 0.83) or OS (HR 0.73, P = 0.19). The relatively low number of GVHD events in the PTCy setting did not allow differentiation between acute and chronic GVHD grading.

Conclusions: GVHD and GVL are strongly associated in contemporary allogeneic SCT. However, in the PTCy setting these two effects can be separated and GVHD is not associated with reduced risk of post-transplant relapse.

Disclosure: Nothing to declare

P010 Comparison of haploidentical and matched unrelated donor HSCT with uniform posttransplantation cyclophosphamide GVHD prophylaxis in de novo AML

D. Zhogolev ¹, N. Volkov¹, A. Beynarovich¹, A. Smirnova¹, Y. Vlasova¹, E. Babenko¹, T. Gindina¹, I. Barkhatov¹, A. Alyanskiy¹, E. Morozova¹, I. Moiseev¹, S. Bondarenko¹, A. Kulagin¹

¹RM Gorbacheva Research Institute, Pavlov University, St. Petersburg, Russian Federation

Background: Allogeneic hematopoietic stem cell transplantation (alloHSCT) from a haploidentical related donor (haploHSCT) is an important alternative for patients with acute myeloid leukemia (AML) in the absence of an HLA-matched donor. A substantial number of studies were published comparing matched unrelated donor (MUD) HSCT with conventional GVHD prophylaxis to haploHSCT with posttransplantation cyclophosphamide (PTCY). Several recent studies comparing both haplo and MUD HSCT with PTCY identified better outcomes after MUD HSCT. Our study aimed to compare the results of MUD and haploidentical alloHSCT both performed with PTCY prophylaxis.

Methods: A total of 182 adult patients with de novo AML in CR1/CR2, who underwent alloHSCT at RM Gorbacheva Research Institute (CIC 725) between 2013-2021, were included. HaploHSCT was performed in 47 patients (haplo group), MUD alloHSCT was performed in 135 patients (MUD group). Median age was 31 (range 18-68) and 33 (range 18-59) years, 22 (46%) and 60 (44.4%) patients were male respectively. Most patients in both groups had intermediate ELN risk: 36 (76.6%) and 101 (74.8%) respectively. The ratio of patients in CR1 and CR2 prior to HSCT was comparable: 27 (57.4%) and 20 (42.6%) in haplo group, 94 (69,6%) and 41 (30.4%) in MUD group. Most patients received conditioning regimens with reduced intensity: 41 (87.2%) and 112 (83%) respectively. All patients received PTCY-based GVHD prophylaxis. Groups were statistically different only by graft source due to much more frequent use of bone marrow in haplo group: 23 (48.9%) vs 8 (5.93%) in MUD group (p < 0.001).

Results: Median follow-up after alloHSCT in survivors was 26.6 months. Engraftment was achieved by 74,5% of patients in haplo group and 97% in MUD group (p < 0.001). Two-year OS was 55% and 82% (p < 0.001), EFS was 54% and 80% (p < 0.0001), GRFS was 38% and 53% (p = 0.021) in haplo and MUD groups respectively. The cumulative incidence of NRM at 2 years was 37% and 14% (p = 0.0014), RI was 19% and 7% (p = 0.014). Day-100 cumulative incidence of grade II-IV aGVHD was 27.7% and 11.1% (p = 0.013), with no significant difference for grade III-IV aGVHD (p = 0.427). In a more detailed study of the haplo group, it was found that the use of bone marrow as a graft source reduced EFS by 22% (p = 0.036) and increased RI by 27% (p = 0.049). In the multivariate analysis haploidentical donors had significantly reduced EFS (p = 0.026), status of CR2 significantly reduced GRFS (p = 0.029), bone marrow as a graft source did not significantly impact OS, EFS, GRFS.

Conclusions: In this study we demonstrated the significant superiority of MUD HSCT over haploHSCT for de novo AML in adult patients when both are performed with PTCY prophylaxis. At the same time, haploHSCT remains an important and often the only option for patients without an available HLA-matched donor. Due to the revealed possible difference in EFS and RI between graft sources in the haplo group, further research is needed to identify the best graft source for replete haploHSCT. A significant advantage in GRFS has been demonstrated in patients in CR1, which allows for early consideration of the HSCT in patients with primary AML.

Disclosure: Nothing to declare.

P011 Allogeneic transplantation for adults with acute megakaryoblastic leukemia, a study from acute leukemia working party of the european society for blood and marrow transplantation (ebmt)

E. Maffini ¹, M. Labopin², A. Huynh³, G. Choi⁴, I.W. Blau⁵, P. Lewalle⁶, W. Bethge⁷, M. Schaap⁸, P. Chevallier⁹, T. Schroeder¹⁰, U. Platzbecker¹¹, E. Verburgh¹², G. Bug¹³, J. Esteve¹⁴, A. Bazarbachi¹⁵, F. Lanza¹, A. Nagler¹⁶, M. Mohty¹⁷

¹Hematology and Stem Cell Transplant Unit, Ravenna Public Hospital and Romagna Transplant Network, Ravenna, Italy, ²EBMT ALWP Office, Paris, France, ³CHU - Institut Universitaire du Cancer Toulouse, Oncopole, I.U.C.T-O, Toulouse, France, ⁴University Medical Centre Groningen, University of Groningen, Groningen, Netherlands, ⁵Medizinische Klinik m. S. Hämatologie, Onkologie und Tumorimmunologie, Charité Universitätsmedizin, Berlin, Germany, ⁶Jules Bordet Institute, Université Libre de Bruxelles, Bruxelles, Belgium, ⁷University of Tuebingen, Medizinische Klinik, Tuebingen, Germany, ⁸University Medical Center, Nijmegen, Netherlands, ⁹CHU Nantes, Dept. d’Hematologie, Nantes, France, ¹⁰University Hospital Dept. of Bone Marrow Transplantation, Essen, Germany, ¹¹Medical Clinic and Policlinic 1, Hematology and Cellular Therapy, University Hospital Leipzig, Leipzig, Germany, ¹²University of Cape Town, Clinical Haematology, Cape Town, Cape Town, South Africa, ¹³Medizinische Klinik II, Hamatologie/onkologie, Universitätsklinikum Frankfurt Main, Frankfurt am Main, Germany, ¹⁴Hospital Clínic of Barcelona, IDIBAPS, University of Barcelona, Barcelona, Spain, ¹⁵American University of Beirut Medical Center, Beirut, Lebanon, ¹⁶Sheba Medical Center, Tel-Hashomer, Tel-Aviv university, Tel Aviv, Israel, ¹⁷Saint Antoine Hospital, Paris, France

Background: Acute megakaryoblastic leukemia (AMKL) is a rare subtype of acute myeloid leukemia, arising from megakaryocytes. As survival rates are extremely poor due to higher rates of disease relapse (RI), consolidation treatment with an allogeneic hematopoietic cell transplantation (HCT) might offer the best chance of cure for patients in remission.

Methods: We report on a retrospective analysis on adults affected by AMKL in first complete remission (CR1) that received a first allogeneic HCT, both from unrelated donors (UD) or HLA-matched sibling donors (MSD). Graft source was mainly peripheral blood (87%), or bone marrow (13%). All patients underwent transplantation between January 2000 and December 2020 and their data were reported to the ALWP of the EBMT.

Results: A total of 201 patients (median age 48 years, 117 male and 84 female) were included in the analysis. Median follow-up for the entire population was 5.2 years. Donors were HLA-matched siblings (n = 98), 10/10 UD (n = 48), 9/10 UD (n = 17) and 38 were missing data on UD HLA-compatibility. Patients transplanted from UD were older (p < 0.01), more often presented the combination female donor to male recipient (p < 0.01) and more frequently received a reduced-intensity-conditioning (p < 0.01). Cytogenetic risk was intermediate in 54 patients, poor in 54 and not available in 93. Ninety-eight % of patients engrafted. The estimated 5-year rates of overall survival (OS) were 41.4% (95% CI 33.6 - 48.9), leukemia-free survival (LFS) 35.6% (95% CI 28.3-43), RI 40.5% (95% CI 33.2-47.7) and non-relapse mortality (NRM) 23.9% (95% CI 17.7-30.6) (Fig.1). Five-year GVHD-free, relapse-free survival (GRFS) was 26.8% (95% CI 20.3 - 33.7) overall. Global incidence of grade III-IV acute graft-versus host-disease (GVHD) at day-180 was 8.8% (95% CI 5.3-13.3), while 2-year extensive chronic GVHD incidence was 17.5% (95% CI 12.1-23.7). In multivariate model, patients transplanted from UD tended to have a trend towards higher rates of NRM (hazard ratio [HR] 1.90, 95% CI 0.99-3.63, p = .0053). Patient age (as incremental value, per 10 years), was associated with higher rates of NRM (HR 1.30, 95% CI 1.03-1.66, p = .03) and worse OS (HR 1.21, 95% CI 1.05-1.40, p = .01), as well as adverse cytogenetics with RI (HR 2.17, 95% CI 1.30-3.61, p = .003) and LFS (HR 1.58, 95% CI 1.04-2.40, p = .03), in multivariate analysis.

Figure 1. Relapse incidence (RI), non-relapse mortality (NRM), leukemia-free survival (LFS) and overall survival (OS) for patients transplanted from HLA-matched siblings (blue line) and from UD (red line).

Conclusions: Allogeneic HCT could be curative in a proportion of adult AMKL patients in CR after induction treatment. Patients transplanted from UD had increased rates of NRM.

Disclosure: Nothing to declare

P012 Autologous versus haploidentical stem cell transplantation in adult patients with acute myelogenous leukemia in first remission with undetectable minimal residual disease: A European preliminary analysis

N.C. Gorin ¹, J. Chen², M. Labopin³, E. Nur⁴, E. Borlenghi⁵, J. Cornelissen⁶, F. Ciceri⁷, T. Zuckerman⁸, G. Van Gorkom⁹, D. Caballero¹⁰, S. Sica¹¹, I. Khevelidze³, E. Polge³, A. Nagler¹², D. Wu², M. Mohty¹

¹Paris Sorbonne University, Paris, France, ²National Clinical Research Center for Hematologic Diseases, Jiangsu Institute of Hematology, Suzhou, China, ³Hopital Saint-Antoine APHP, EBMT Paris Office, Paris, France, ⁴Amsterdam University Medical Centers, Amsterdam, Netherlands, ⁵Spedali Civili, Hematology Division, Brescia, Italy, ⁶Erasmus MC Cancer Institute, Rotterdam, Netherlands, ⁷Ospedale San Raffaele s.r.l., Milano, Italy, ⁸Rambam Medical Center, Haifa, Israel, ⁹University Hospital, Maastricht, Netherlands, ¹⁰Hospital Clínico, Salamanca, Spain, ¹¹Universita Cattolica S. Cuore, Roma, Italy, ¹²The Chaim Sheba Medical Center, Tel-Hashomer, Ramat-Gan, Israel

Background: For adult patients with acute myelogenous leukemia (AML), numerous patient and disease prognostic factors have been shown to impact the outcome following stem cell transplantation.

In the past decade, several studies have shown the importance of the evaluation of minimal residual disease (MRD); undetectable MRD (uMRD) in particular at transplant, has been recognized as the most important predictor of favorable outcome, possibly erasing previously recognized poor prognostic factors.

At the present time, there is no consensus on the consolidation therapy to offer to intermediate-risk patients in CR. The recent GIMEMA AML 1310 trial of risk adapted MRD directed therapy has shown equivalent outcome for AML patients autografted (ASCT) in uMRD-CR1 or allografted in the case of persisting MRD positivity.

Methods: Using the EBMT registry, we collected data from 344 autografted patients and 200 patients who received a T-cell replete haploidentical (Haplo) transplant from January 2010 to December 2019.

Results: The distribution of molecular markers was not even: for autografted patients, a NPM1 mutation was present in 63% and FLT3-ITD in 24% while it was 46% and 50% for Haplo (p < 0.0002 for each). The stem cell source was peripheral blood in 97% for ASCT and 64% for Haplo (p < 0.0001). In the autografted population the myeloablative conditioning (MAC) consisted essentially (69%) of the combination of busulfan + cyclophosphamide or busulfan + high-dose melphalan. For Haplo the conditioning regimen was MAC in 48% and reduced intensity in 52%. All Haplo recipients received posttransplant cyclophosphamide (PTCY) for GVHD prophylaxis.

The outcome at 3 years posttransplant is indicated below (univariate p):

Relapse NRM LFS OS

Auto 50.5%[44.6-56.1] 7.1%[4.5-10.4] 50.3%[44.6-55.7] 67%[61.4-71.9]

Haplo 14.5%[9.3-20.7] 23.6%[17.5-30.2] 65.2%[57.6-71.8] 72.6%[65.3-78.6]

P value 0.001 0.001 0.005 0.5

Post Haplo, the rates of acute GVHD grades III-IV, chronic GVHD, and severe chronic GVHD at 3 years were 7%, 42%, and 17% respectively. The GVHD/relapse-free survival (GRFS) was 54%.

31% of autografted patients and 6% of Haplo received a second transplant.

On multivariate analysis, Haplo was significantly associated with a higher NRM, a lower RI, and a higher LFS. Overall survival was not significantly different from ASCT. Other prognostic factors were patient age, and the presence of NPM1 and FLT3ITD mutations. No center effect was observed.

Table 2

Conclusions: For adult patients with AML with uMRD-CR1, Haplo with PTCY resulted in a superior LFS of 65% versus 50% at 3 years and a GRFS of 54%. By intention to treat there was no difference for OS.

Disclosure: No conflict of interest

P013 Influence of the expression of genes characteristic of leukemic stem cells on the results of allogeneic HSCT in children with acute myeloid leukemia

Z. Rakhmanova¹, O. Paina¹, I. Barkhatov¹, I. Kazantsev¹, A. Sadykov¹, P. Kozhokar¹, A. Frolova¹, L. Tsvetkova¹, E. Babenko¹, T. Gindina¹, A. Alyanskiy¹, A. Kulagin¹, I. Moiseev¹, E. Semenova¹, L. Zubarovskaya ¹

¹RM Gorbacheva Research Institute, Pavlov University, Saint Petersburg, Russian Federation

Background: Leukemic stem cells (LSCs), which play a crucial role in pediatric AML, are distinguished by a specific mRNA-expression signature. Recently, a six-gene leukemic stem cell score (pLCS6) value have been shown to be an effective prognostic marker independent of minimal residual disease (MRD) (Abdelrahman H. Elsayed et al., 2020). However, although initial high-pLCS6 status is associated with worse prognosis even in subsequent alloHSCT recipients, there is yet no data on pre-transplant pLCS6 measurement prognostic value.

Methods: Gene expression profiling by RT-PCR was performed in 50 AML patients receiving alloHSCT in different disease status. Complete remission 1 (CR1) or CR2 was documented in 74% (n = 37) of children, 26% (n = 13) of patients had active disease before alloHSCT. The retrospective study cohort included 37 children with AML at CR1 or CR2 receiving alloHSCT from matched related (n = 3, 8%), matched unrelated (n = 15, 41%) or haploidentical donor (n = 19, 51%) in RM Gorbacheva Research Institute during 2014-2021 period. The median age was 6(1-18) years. In 28 (76%) cases myeloablative and in 9 (24%) non-myeloablative conditioning regimen was used. In 78% (n = 29) of cases the GVHD prophylaxis regimen included post-transplant cyclophosphamide. The gene expression profiling was performed via RT-PCR for DNMT3B, GPR56, CD34, SOCS2, SPINK2, IL2RA, FAM30A and ABL genes with subsequent pediatric six-gene leukemic stem cell score (pLSC6) calculation by previously described equation: (DNMT3b x 0.189) + (GPR56 х 0.054) + (СD34 х 0.0171) + (SOCS2 x 0.141) + (SPINK2 x 0.109) + (FAM30A x 0.0516).1 If an appropriate sample was available, the post-transplant pLSC6 value was also evaluated. After the median pLSC6 was determined all patients were divided into low-pLSC6 and high-pLSC6 groups.

Results: A total of 18/37 (49%) patients had high-pLSC6 pre-transplant score value. Only 6/18 of high-pLSC6 patients with CR1-2 were MRD-positive. The post-transplant pLSC6 value was measured in 14 patients, in 85% cases the pre-transplant high-pLSC6 values converted to low-pLSC6. The linear regression analysis including patients with pre-transplant response as well as patients with active disease showed no association between blast count/MRD and pLSC6 values (OR 1.002; 95% CI: 0.979, 1.025). The 1-year RFS in CR patients was not significantly different between low-pLSC6 (78.9%) and high-pLSC6 (66.7%) patients (p = 0.62). However, while none of the clinical factors were significant in the multifactor analysis, the early relapse rate in CR patients was significantly higher in high-pLSC6 subgroup compared to low-pLSC6 (22% and 0%, accordingly; p = 0.03).

Conclusions: Although current results do not support pLSC6 assay value as an indication for alloHSCT, there is still a tendency to worse prognosis in children with pre-transplant high-pLSC6 score in spite of the evidence of graft-versus-leukemia effect on LSCs. The pre-transplant high-pLSC6 status may, therefore, be a factor for pre-emptive post-transplant intervention in the future independent of blast count and MRD. As the effectiveness of this study is limited by its retrospective design, it warrants further research in a larger prospective cohort.

Disclosure: The study was supported by Fund for promoting innovation «Fund-M», grant № 0059546.

P014 The clinical characteristics and prognosis of aya and older adult early t-cell precursor leukemia/lymphoma: A real-world multicenter study in China

J. Xiao ¹, Z. Cai², H. Wang³, X. Li¹, B. Zhou¹, Y. Liu¹, Y. Wang¹, P. Xu⁴, L. Wang⁵, D. Wu¹, L. Dou³, H. Zhou², Y. Xu¹

¹The First Affiliated Hospital of Soochow University, Suzhou, China, ²Nanfang Hospital, Southern Medical University, Guangzhou, China, ³Chinese PLA General Hospital, Beijing, China, ⁴Nanjing Drum Tower Hospital, Nanjing, China, ⁵Ruijin Hospital Affiliated to Shanghai Jiao Tong University School of Medicine, Shanghai, China

Background: Early T-cell precursor lymphoblastic leukemia/lymphoma (ETP-ALL/LBL) is a hematological malignancy originating from immature T lymphoblastic cells with high rate of treatment resistance and poor long outcome. Hitherto, studies of survival outcomes in ETP-ALL/LBL were still controversial. Data of large cohort in ETP-ALL/LBL are still lacking.

Methods: In this retrospective analysis, we performed a real-world multicenter study to explore the clinical characteristics and prognosis of adolescent and young adults (AYA) and older adult ETP leukemia/lymphoma. A total of 103 patients with ETP-ALL/LBL in five centers in China between January 2016 and February 2021 were included in this study. Outcomes were assessed in terms of overall survival (OS) and relapse-free survival (RFS).

Results: The median age was 29 years (range, 15–70 years). Next-generation sequencing was performed in 94 patients and revealed that NOTCH1 (35.1%, 33 cases) was the most frequently mutated gene, followed by JAK3 (16.0%, 15 cases), PHF6 (13.80%, 13 cases) and EZH2 (11.70%, 11 cases). Complete remission (CR) was obtained in 74.2% (72/97) of patients, and 6 relapsed/refractory patients received a decitabine combined with AAG priming regimen as reinduction therapy with a CR rate of 50%. With a median follow-up of 18 months (0.5–60 months), the 2-year overall survival (OS) and relapse-free survival (RFS) rates for the entire cohort were 54% and 57.7%, respectively. Allogeneic stem cell transplantation (allo-SCT) was performed in 59.8% (58/97) of patients. Patients who experienced transplantation in CR had better OS than transplantation in NR (P = 0.029, HR: 0.3625, 95%CI 0.1005 to 1.308), while the RFS was no statistical significance. (P = 0.078, HR:0.4431, 95% CI 0.1340 to 1.465). Patients who were MRD negative at transplantation had better OS and RFS than those who were MRD positive (OS: P = 0.032, HR: 0.3306, 95%CI 0.09829 to 1.112; RFS: P = 0.0035, HR: 0.2492, 95%CI 0.07993 to 0.7770). Additionally, there was no statistical significance in the OS and RFS of HLA-matched and HLA-mismatched patients (OS: P = 0.63, HR: 0.7996, 95% CI 0.3144 to 2.034, RFS: P = 0.97, HR: 0.9844, 95% CI 0.3982 to 2.433). The 2-year OS of patients was 68% in the allo-SCT group and 26% in the chemotherapy group (p < 0.001, HR: 0,2567, 95% CI 0.1336 to 0.4932). A multivariate analysis suggested that allo-SCT and CR after the first course induction were independent prognostic factors for OS.

Conclusions: Collectively, we reported the largest cohort study with AYA and older adult ETP-ALL/LBL, and we found that ETP-ALL/LBL was highly invasive and had a poor long-term prognosis. Allo-SCT could significantly improve ETP-ALL/LBL patient survival.

Disclosure: Nothing to declare.

P015 Outcome prediction by the knowledge bank approach in AML patients undergoing allogeneic stem cell transplantation

L. Herrmann¹, L. Bischof ¹, D. Backhaus¹, D. Brauer¹, G.-N. Franke¹, V. Vucinic¹, U. Platzbecker¹, M. Jentzsch¹, S. Schwind¹

¹University of Leipzig Medical Center, Leipzig, Germany

Background: In acute myeloid leukemia (AML) current risk stratification (e.g. by the European LeukemiaNet (ELN) 2017) relies on diagnostic genetic aberrations and help to inform treatment decisions, including those for an allogeneic stem cell transplantation (HSCT) in first remission. Recently Gerstung et al. (Nature Genetics, 2017) developed a knowledge bank (KB)-based algorithm based on demographic, clinical, and genetic data to predict individual outcomes. Two studies validated the feasibility of KB prediction in AML patients consolidated with chemotherapy. However, a validation in a HSCT-treated cohort, crucial with respect to informed decisions towards HSCT, is missing.

Methods: We analyzed 545 AML patients (median age at diagnosis 62, range 21-77 years) receiving a non-myeloablative (77%) or reduced-intensity (23%) HSCT (60% were in first remission). Clinical variables included in the KB were available for our cohort, while our gene mutation panel did not include 17/58 of genes included in the KB. KB predictions 3 years after diagnosis were calculated by using the adapted transplant strategy and compared to the observed outcomes using receiver operating characteristics (ROC) curves. In addition, the measurable residual disease (MRD) status at HSCT was evaluated in patients with material available and based on NPM1 mutation and BAALC, MN1, and WT1expression.

Results: The KB approach had an area under the curve (AUC) to predict 3-year OS of 0.69 (95% CI 0.62-0.72) which was not significantly different compared to the AUC of the ELN2017 risk stratification (0.66 [95% CI 0.57-0.71], P = 0.23), and worse compared to the published results in patients receiving chemotherapy (AUC_KB = 0.80, Bill et al. 2021). However, in a multivariate analysis the KB prediction for 3-year OS significantly impacted OS (OR 6.25, CI 2.9-13.2) after adjustment for the MRD-corrected remission status at HSCT and Aikaike Information criterion (AIC) comparison with a model including the ELN2017 classification demonstrated the model containing the KB prediction as preferable. When introducing arbitrary cut-offs according to the KB prediction for OS at 3 years, we observed a clear separation of OS curves according to a KB value of <20, 20-39, and ≥ 40 (with higher values indicating a higher likelihood for OS, P < 0.001). Regarding other endpoints for which the KB algorithm provides outcome prediction, we observed the highest probability to correctly predict non-remission death (AUC_KB = 0.75), restricted prediction for death in first remission (AUC_KB = 0.61) or after relapse (AUC_KB = 0.63), but good outcome prediction for being alive after relapse (AUC_KB = 0.77) or being alive in first remission (AUC_KB = 0.69).

Conclusions: For HSCT treated AML patients the KB-based outcome prediction for HSCT treated patients was inferior compared to previous studies of patients receiving chemotherapy. The likely reason for the inferiority is the introduction of confounders (e.g. donor selection, graft-versus-host-disease), especially for treatment-related mortality, not integrated in and not predictable by the current KB algorithm. Inclusion of these additional factors might allow for a more precise outcome prediction for AML patients receiving HSCT.

Disclosure: Nothing to disclose

P016 Midostaurin maintenance vs ALLO SCT vs W&W in flt3 mutated AML. A “real life” multicenter study

A. de la Fuente ¹, M. Diaz Beya², P. Beneit³, A. Fernandez⁴, M. Arnan⁵, A. Garrido⁶, S. Vives-Polo⁷, M. Garcia Fortes⁸, A. Sampol⁹, J. Labrador¹⁰, A. Garcia Guinon¹¹, C. Gil¹², J. Bergua Burgues¹³, M.t. Olave Rubio¹⁴, M.L. Amigo¹⁵, X. Ortin¹⁶, M. Cervera¹⁷, M. Estevez¹, A. Diaz Lopez¹⁸, J. Serrano¹⁹, M. Tormo²⁰

¹MD Anderson CC Madrid, Madrid, Spain, ²H. U. Clinic IDIBAPS, Barcelona, Spain, ³H. U. San Juan de Alicante, Alicante, Spain, ⁴H. Central de Asturias, Oviedo, Spain, ⁵ICO Hospitalet L’Hospitalet de LLobregat, Barcelona, Spain, ⁶H. de la Santa Creu i Sant Pau, Barcelona, Spain, ⁷ICO H. Germans Trias i Pujol, Barcelona, Spain, ⁸H. Virgen de la Victoria, Malaga, Spain, ⁹H. U. Son Espases, Palma de Mallorca, Spain, ¹⁰H. U. de Burgos, Burgos, Spain, ¹¹H. U. Arnau de Vilanova, Lleida, Spain, ¹²H. U. General de Alicante, Alicante, Spain, ¹³H. U. San Pedro de Alcantara, Caceres, Spain, ¹⁴H. U. Lozano Blesa, Zaragoza, Spain, ¹⁵H. U. Morales Meseguer, Murcia, Spain, ¹⁶H. U. Verge de la Cinta Instituto Perz Virgili, Tortosa, Spain, ¹⁷ICO H. U. Joan XXIII, Tarragona, Spain, ¹⁸Fundacion MD Anderson, Madrid, Spain, ¹⁹H. U. Reina Sofia, Cordoba, Spain, ²⁰Clinico Universitario Instituto de Investigación Sanitaria INCLIVA, Valencia, Spain

Background: Introduction: FLT3-ITD mutation is associated with adverse prognosis (ELN2017, Dohner et al, Blood 2017) and SCT has been the standard of treatment for FLT3 mutated AML for decades. Midostaurin (Midos) has been approved in combination with intensive chemotherapy (IC) for FLT3-mutated AML, midostaurin maintenance was part of the treatment schedule in the RATIFY trial but not randomly explored (Stone et al, N Engl J Med 2017).

Methods: Aims: The aims of this study are to analyze safety and effectiveness of midostaurin maintenance in FLT3 AML in a “real-world” setting and to evaluate maintenance versus alloSC versus W&W and the impact of risk factors.

Methods: We carried out a retrospective multicenter study (MDA-AML-2018-06) in 27 Spanish centers. Inclusion criteria: age >18 years, FLT3-mutated AML diagnosis according to WHO criteria and start of treatment with midostaurin in combination with IC between June 2016 and December 2020. We evaluated the response according to 2017 ELN criteria, toxicity according to CTCAE v4.0 and overall survival (OS) by Kaplan-Meier. Statistical analysis was performed using SPSS program version 20.0.

Results: Results: A total of 175 (93 female) patients were included, median age 53 (18-76) median OS for the whole population not reached, 24months OS 68%. Of those who achieved CR after Induction1or2 144 (81.4%) patients, 24p received maintenance, 76p were consolidated with alloSCT and 41p proceed to W&W (table 1).

Safety: AE during maintenance were one case of QT prolongation which required Midos discontinuation. No cases of febrile neutropenia and no cases of deaths related to Midos.

Regarding OS the ELN2017 classification resulted in a trend of differences in all groups maintenance, alloSCT and W&W. We observed significant differences for maintenance versus W&W (p0.001) in low and intermediate risk patients. Comparing maintenance vs alloSCT we observe no differences in the Int ELN2017 group.

Table 1

Patients who achieved CR after Induction1 and/or Induction2 Total n 144
	Maintenance	alloSCT	W&W
Total	24	76	41
Madian Age	61 (31-73)	51 (18-69)	56 (23-76)
ELN2017 Low	16	11	21
ELN2017 Int	7	45	16
ELN2017 High	0	16	3
Lost	1	4	1

Conclusions: Conclusions: Our experience confirms safety of maintenance therapy in AML FLT3 patients after intensive chemotherapy. We also observed a benefit for maintenance versus W&W in low and intermediate risk population.

Clinical Trial Registry: Not registered at Clinical Trials

Approved by National Ethics Comitie

Disclosure: Study founded by Novartis

P017 The ebmt disease risk stratification system (drss) allows prediction of relapse after allogeneic hematopoietic cell transplantation for acute myeloid leukemia

Y. Kadri ¹, M. Phan¹, J. Bergeron¹, N. Bambace¹, L. Bernard¹, S. Cohen¹, J.-S. Delisle¹, T. Kiss¹, S. Lachance¹, D.-C. Roy¹, J. Roy¹, G. Sauvageau¹, O. Veilleux¹, I. Ahmad¹

¹Institut universitaire d’Hémato-Oncologie et de Thérapie cellulaire - Hôpital Maisonneuve-Rosemont - Université de Montréal, Montreal, Canada

Background: Using EBMT registry data, the DRSS has been proposed to predict relapse risk after allogeneic hematopoietic cell transplantation (HCT) across disease subtypes and remission states ordered in 55 categories and 5 risk levels (Shouval R et al. Lancet Haematol. 2021). For acute myeloid leukemia (AML) the DRSS combines ELN risk group, remission rank, and de novo vs. secondary AML in 19 categories. We sought to determine its reproducibility in a cohort of subjects transplanted for AML.

Methods: Data from a single-centre cohort of adult AML patients transplanted between 01/07/2015 and 30/06/2020 was analysed retrospectively. Baseline characteristics and outcomes were extracted, and Fine-Gray regression was used to determine the association between cumulative incidence of relapse (CIR) and patient, disease, and transplant characteristics, as well as the influence of graft-versus-host disease (GVHD) as a time-dependent covariate. Model selection techniques were used to select the least number of significant predictors of CIR.

Results: In this cohort of 89 patients, median follow-up was 2.7 years (interquartile range: 0.9-3.2) and CIR was 29% at 5 years (95% confidence interval: 19-40). The study of the association between CIR and patient age >60 years, donor type (related matched, haploidentical, matched unrelated, cord blood), DRSS category, chronic (c) GVHD yielded a model using two covariates: DRSS and cGVHD, to predict CIR (hazard ratio (HR) 0.38, p = 0.03 and HR 0.43, p = 0.12, respectively). Univariate graphic representation of CIR according to DRSS is shown in Figure 1.

Conclusions: In adults with AML, cumulative incidence of relapse after allogeneic HCT can be predicted by DRSS across all donor types and age groups.

Disclosure: Nothing to declare.

P018 Structural analysis of leukemia-associated protein tyrosine phosphatase ptpn21 and protein interaction network analysis of its wild type and mutants

Z. Qian ^1,2, L. Chen², J. Zhang³, Y. Zheng², C. Zhou(corresponding auther)^3,2, H. Xiao(corresponding auther)^1,2

¹Sir Run Run Shaw Hospital, Hang Zhou, China, ²Zhejiang University School of Medicine, Hang Zhou, China, ³Sir Run Run Shaw Hospital, Hang Zhou, China

Background: Protein tyrosine phosphatase non-receptor type 21 (PTPN21) gene mutations and its elevated expression level have been reported in different type of tumors. We have also found that PTPN21 gene mutations are associated with disease relapse in B-cell acute lymphoblastic leukemia (B-ALL) patients. However, the structure and molecular mechanism of PTPN21 wild type and mutations remain to be determined.

Methods: We use protein crystallization and X-ray diffraction to determine the structure of protein PTPN21. We further used miniTurbo-mass spectrometry analysis to study the difference of protein interaction networks between PTPN21 wild-type protein and PTPN21 mutant proteins in living cells.

Results: We have determined the structure of FERM domain and PTP domain of PTPN21. We also found that compared with PTPN21 wild-type protein, three PTPN21 mutant proteins, which were involved in the pathogenetic process of relapse of B–ALL, significantly reduce the binding affinity to 202 proteins and increase the interaction with 119 proteins in cells. The KEGG pathway analysis showed involvement in the vesicle docking, extra-cellular matrix(ECM) receptor interaction, MAPK pathway and so on. Notably, the most remarkably decreased interacting proteins of all three PTPN21 mutations are centrosome associated protein HP5, the Hippo pathway component WWC2, the trafficking protein TMED10, actin binding protein FSCN1 and a newly emerged cell fate regulators as well as the Hippo pathway kinase LATS1.

Conclusions: ALL-associated PTPN21 mutant proteins may promote cell-matrix interaction, MAPK signaling, the Hippo pathway and the expansion of centrosomal amplification to assist B-ALL cells to survive chemotherapy and disease relapse.

Disclosure: Nothing to declare

P019 Thiotepa, busulfan and fludarabine: A conditioning-regimen for adult patients with acute lymphoblastic leukemia

A. Banet ^1,2, A. Bazarbachi³, M. Labopin^1,2, R. Duléry^1,2, F. Malard^1,2, Z. Van de Wyngaert^1,2, A. Bonnin¹, V. Radici¹, R. Belhocine¹, S. Sestili¹, J. El-Cheikh³, M. Mohty^1,2, E. Brissot^1,2

¹APHP, Hôpital Saint-Antoine, Service d’Hématologie Clinique et de Thérapie Cellulaire, Paris, France, ²Sorbonne Université, INSERM UMR 938, Centre de Recherche Saint-Antoine (CRSA), Paris, France, ³Bone Marrow Transplantation Program, American University of Beirut Medical Center, Beirut, Lebanon

Background: For acute lymphoblastic leukemia (ALL) patients, total body irradiation (TBI) based conditioning regimens are often the first choice, considering their positive impact on relapse incidence. However, TBI is associated with toxicity and long-term morbidity, and its accessibility can be a major issue for many hematological centers. Several studies have shown an equivalence in clinical outcomes with chemotherapy-based conditioning, notably with the use of thiotepa. We performed a retrospective bicenter study to evaluate the outcome of adult ALL patients who had received, before allogeneic hematopoietic stem cell transplantation (allo-HCT), a thiotepa-busulfan-fludarabine (TBF) myeloablative conditioning regimen with reduced toxicity.

Methods: Fifty-five patients (not eligible to high dose TBI) from Saint-Antoine Hospital (Paris, France) or the American University of Beirut Medical center (Beirut, Lebanon), received a TBF regimen consisting of 1-2 days of thiotepa (5mg/kg/day), 2-3 days of busulfan (130 mg/m2), and 5 days of fludarabine (30 mg/m2). The repartition of conditioning-regimen was 34.5% of T2B3F, 32.7% of T1B3F, 30.9% of T1B2F, and 1.8% of T2B2F. The median age of the patients was 51 years (range 17 to 72.4). Twenty-eight (50.9%) were male. Most patients had a diagnosis of B-ALL (93%) and 7% of T-ALL. Forty-two (76.4%) patients had a high-risk cytogenetic ALL. At the time of transplant 52 (94.5%) patients were in complete remission, 2 patients had a positive minimal residual disease (MRD) and 1 patient was refractory. For assessment of minimal residual disease (MRD): 27 (50%) patients had a Philadelphia chromosome, 8 (14.8%) had an immunoglobulin (Ig) and/or T-cell receptor (TCR) rearrangement, and 4 (7.4%) had an MLL rearrangement. The remaining MRD assessments were carried out using multiparameter flow cytometry. Peripheral blood stem cells were the main stem cell source (90.9%). Twenty-seven (49.1%) patients were transplanted from a matched sibling donor, 12 (21.8%) from a matched unrelated donor, and 16 (29.1%) from a haploidentical donor. The graft-versus-host disease (GVHD) prophylaxis was cyclosporine A (CsA) alone (32.7%), or CsA with mycophenolate mofetil. In addition, antithymocyte globulin (ATG) was used for a median of 2 days, and patients with a haploidentical donor received low-dose ATG and post-transplant cyclophosphamide (PT-Cy). All patients engrafted at a median time of 15 days (range, 5-27).

Results: With a median follow-up of 43 months, 2- and 5-year overall survival (OS) was 73.2 % (95% CI: 58.9 - 83.2) and 64% (95% CI: 48.8 - 75.7), respectively. At 2 years, leukemia-free survival (LFS) and GVHD-free, relapse-free survival (GRFS) were 59.5% and 57.6%, and at 5 years, 53.4% and 51.8%, respectively. The 5-year non-relapse mortality (NRM) was 15%. The day 180 cumulative incidence (CI) of grade II-IV acute GVHD and grade III-IV acute GVHD were 44.7% and 6.4%, respectively. At 2 years, the CI of chronic GVHD and extensive chronic GVHD was 16.9% and only 1.9%, respectively.

Conclusions: Our retrospective study does suggest that using TBF as the conditioning regimen in adult ALL patients is a promising option with acceptable toxicity.

Disclosure: Nothing to declare

P020 Patterns of relapse and outcomes in patients with acute leukemia post allogenic transplantation

M. Saroha ¹, N. Jindal¹, D.S. Philip², A. Chichra¹, S.P. Mirgh¹, A. Gokarn¹, S. Punatar¹, L. Nayak¹, A. Bonda¹, L.J Mathew¹, S. Kannan¹, N. Khattry¹

¹Advanced Centre for Treatment, Research and Education in Cancer (ACTREC), Tata Memorial Centre, Mumbai, India, ²Regional Cancer Centre, Trivandrum, India

Background: With improvement in transplant related mortality (TRM), relapse is the major factor affecting survival post HSCT. Prognosis of patients with acute leukemia (AL) relapsing after HSCT is dismal. We analysed incidence and patterns of relapse, factors predicting relapse and determinants of post relapse OS (PROS).

Methods: This is a single centre retrospective analysis of AL patients who underwent 10/10 or 9/10 matched related or unrelated ASCT from January 2008 to December 2019. AL included lymphoid (ALL), myeloid (AML) and mixed phenotypic (MPAL) leukemias. Nineteen patients with AML had active disease; rest were in complete remission at ASCT. Conditioning included either full intensity regimens [TBI-cyclophosphamide (Cy), busulfan (Bu) - Cy or Fludarabine (Flu) – Bu] or reduced intensity regimens (Flu based). GVHD prophylaxis consisted of calcineurin inhibitor (CNI) with either methotrexate or MMF or PTCY with CNI and MMF. Factors studied as predictors of relapse were DRI, EBMT risk score, HCT-CI, transplant conditioning intensity (TCI), mixed chimerism (MC) at day 30, 90, 180 and 360, grade II-IV aGVHD and cGVHD. Treatment after diagnosis of relapse was at the discretion of treating physician. Ongoing immunosuppresion (if any) was stopped. In general, patients received 1 or more DLI and/or immunomodulatory or targeted agents (lenalidomide, dasatinib or imatinib, nivolumab, palbociclib, etc). Patients with morphological relapse were treated with chemotherapy with or without DLI. Some patients with extramedullary relapse (EMR) received radiotherapy. Factors analysed for effect on PROS were time to relapse (TTR), TCI, DRI and prior aGVHD or cGVHD. Cumulative incidence of relapse (CIR) was calculated using competing risk regression with TRM being the competing event.

Results: Total of 162 AL patients underwent HSCT. Sixty four (39%) relapsed. Of these, 52 (81%) had medullary relapse (MR), 8 had EMR and 4 had combined relapse. Among isolated MR, 41 (78.8%) were morphological, 3 were cytogenetic, 3 were flowcytometric, and 5 were molecular relapse. CIR at 1 yr and 2 yr was 24% (95%CI; 18%-31%) and 33% respectively (95% CI; 26%-40%).Significant factors associated with relapse were MC at day 90 (p = 0.004) and day 180 (p = 0.001) and absence of aGVHD (p = 0.01) and cGVHD (p = 0.00). However, cGVHD was present in 5/8 with EMR as compared to 12/56 with MR or combined relapse (p = 0.026). Similarly, more patients with MR and combined relapse had MC at relapse (28/51, 54.9%) compared to none with EMR (p = 0.005). Median PROS was 4.2 months while 1 yr PROS was 31.1%. Factors associated with better PROS included low - intermediate DRI (5.3 vs 1.1 months with high DRI, p = 0.004) and receipt of targeted therapy (median PROS 16.5 vs 6.4 months with conventional chemotherapy alone, p = 0.016).

Conclusions: About 40% of AL patients experienced relapse post ASCT. Patients with MC (at any time through day +180) and those without acute or chronic GVHD were more likely to have MR or combined relapse. Presence of aGVHD or cGVHD and full donor chimerism did not protect against EMR. Survival after relapse was poor, however those with low and intermediate DRI, and those who received targeted therapies post relapse fared better.

Disclosure: Nothing to declare

P022 Similar OS and DFS after atg or post-transplant cyclophosphamide (PT-CY) as GVHD prophylaxis in patients with all in cr 1 after allogeneic stem cell transplantation

C. Niederwieser ¹, R. Massoud¹, C. Langebrake¹, R. Adjalle¹, D. Janson¹, F. Ayuk¹, W. Christine¹, N.-M. Kröger¹

¹UKE Hamburg Eppendorf, Hamburg, Germany

Background: Anti-thymocyte globulin(ATG) is widely used to prevent graft-versus-host disease(GVHD) after allogeneic peripheral blood stem cell transplantation(HSCT). High dose cyclophosphamide post-transplant is used as a potent agent for GVHD prophylaxis in matched related(MRD), matched unrelated (MUD), mismatched unrelated(MMUD) and haploidentical HSCT. In this retrospective analysis, we compared the use of ATG to post-transplant cyclophosphamide(PT-CY) on leucocyte engraftment, acute and chronic GVHD, overall survival(OS), disease free survival(DFS), non-relapse mortality(NRM) relapse incidence(RI).

Methods: A total of 57 patients with ALL in CR1 were treated with a preparative regimen of TBI 12Gy in combination with cyclophosphamide or fludarabine between 2002 and 2021. Of the 57, 38.6% patients received ATG and 61.4% PT-CY with calcineurin inhibitors±mycophenolate mofetil. Median age was 37(11-56) years and the majority were male(52.6%). ALL patients(35.1% bcr/abl⁺) were treated according to GMALL protocols including prophylactic cerebral irradiation in 49.1%. MRD positivity was observed in 45.6% and negative in 43.9% of patients. Patients were positive for CMV in 57.9%. Karnofsky score was median 80(60-100)%. Donors were median 32(5-57) years old. More male(66.7%) than female donors and more unrelated(71.9%) than related(28.1%) were used. Included in this analyses were, for the PT-CY group MRD(n = 9), MUD(n = 17), MMUD(n = 4) and haploidentical(n = 5) and for the ATG group MRD(n = 2), MUD(n = 14), MMUD(n = 5). Most of the donors were CMV positive(59.6%) and more PBSC 89.5% than bone marrow were given. Of the six patients receiving bone marrow four received PT-CY and two received ATG, two were related and four were unrelated.

Results: Patients characteristics were equally distributed in both treatment groups regarding patient age, gender and bcr/abl⁺(Table 1), but statistically significant differences were noted in pre-transplant radiation therapy(p = 0.02) and related/unrelated donors (p = 0.01). MRD status was not different between the groups. Engraftment was observed in all patients except two in the ATG group. Recovery of WBC was faster in PT-CY as in ATG group. No difference in acute and chronic GVHD was observed between the two groups. After a median follow-up of 2.77 (range 0.05-13.14) years, OS of all patients was 76.7% at 3 years, 72.0 ± 9% in the PT-CY group and 81.8%±8 in the ATG group. DFS of all patients resulted in 72.8% at 3 years, 66.7 ± 8.7% in PT-CY and 81.0 ± 8.6% in ATG treated patients. Only bone marrow source (p = 0.03) remained an independent factor for OS after accounting for type of SCT, ATG and prophylactic cerebral irradiation. For DFS type of SCT remained as a trend (p = 0.07). RI for PT-CY was 9.1 ± 5.1% and for ATG 4.5 ± 4.6%, while NRM was 21.2 ± 7.3 und für 13.6 ± 7.5% for PT-CY and ATG treated patients, respectively. When analysing only patients receiving peripheral blood, there only was a difference between the related and unrelated(p = 0.03) and no difference in outcome and GVHD.

Conclusions: The use of PT-CY for GVHD-prophylaxis resulted in faster leucocyte engraftment, but similar acute and chronic GVHD incidence, OS and DFS. Bone marrow source was the only independent risk factor for OS. This finding needs to be confirmed in a larger more homogenous cohort.

Disclosure: Nothing to disclose

P023 Integrated genomic and single-cell molecular analyses of donor cell leukemia after haploidentical allogeneic hematopoietic stem cell transplantation

H. Chen ¹, W. Pan¹, X. Zhao¹, H. Xiao (Corresponding auther)¹

¹Sir Run Run Shaw Hospital, Zhejiang University School of Medicine, Hangzhou, China

Background: Allogeneic hematopoietic stem cell transplantation (allo-HSCT) remains an efficient therapy for hematologic malignancies. Relapse of acute leukemia following allo-HSCT usually represents return of an original disease clone. The development of de novo hematological malignancies in cells of donor origin is a rare but severe complication, known as donor cell leukemia (DCL). To date, the reported patients with DCL are mainly following HLA-matched sibling or unrelated donor HSCT. We present here a rare case of late-onset DCL that developed in HSCT recipient and not in his HLA haploidentical father donor. To reveal the precise etiologic mechanisms of such DCL, we integrated genomic and single-cell molecular analyses.

Methods: We performed short tandem repeat (STR) analysis on bone marrow (BM) samples obtained from patient pre-HSCT and relapse post-HSCT, and donor PBSC sample. Genomic DNA was isolated and subjected to whole-exome sequencing (WES) from specimens of BM sample at relapse post-HSCT, and buccal mucosal specimen from the patient, as well as BM cells and the buccal mucosal specimen from the donor. 10x Genomics single-cell RNA sequencing was performed on patient’s BM sample at relapse post-HSCT and donor’s BM sample.

Results: STR analysis confirmed that leukemia cells originated from the donor. We compared data sets from donor and DCL samples in order to detect variants that expandedå 3-fold or de novo in DCL with WES. The mutation affected C17orf97 (chr17: p.Asp220_Pro229del) has been present in donor BM cells, while at a 7-fold higher frequency in the DCL sample, with variant allele frequency (VAF) from 3.85% to 30%. The evolution of DCL was further associated with the acquisition of mutations in IDH1 (chr2: p.Arg119Trp; VAF = 6.98%) and NSD1 (chr5: p.His2205Asp; VAF = 10%). In addition, we also found ATF7IP (chr12: p.Gly1122AspfsTer53) mutation with VAF = 5.41% and ZNF33A (chr10: p.Cys607Tyr) mutation with 9.64%, which have not been reported in leukemia.

To better reveal the hematopoietic hierarchy and leukemic transformation involved in DCL progression, 10X Genomics single-cell RNA sequencing was performed. We deciphered an atlas covering 22399 cells and 12 major cell types (20 clusters) according to the established markers of hematopoietic populations. We observed an increase in the fraction of granulocyte-monocyte progenitors, while decreased proportions of mature monocytes and neutrophils within DCL cells. We next performed differential gene expression analyses between healthy donor and DCL hematopoietic stem and progenitor cells (CD34⁺ckit⁺ cells), 245 differentially expressed genes (p <0.05, log2FC > 2) was found. KEGG analysis revealed the top2 enrichment of pathways related to metabolic pathways and pathways in cancer. To understand the specific HSPC subpopulations involved in DCL, 4 transcriptionally distinct clusters were identified. HSPCs from donor and DCL harbour distinct transcriptional programs, and GO analysis in cluster2 (from DCL) showed enrichment of the pathway related to myeloid cell differentiation. CRIP1 and LGALS1, recently reported associated with AML, are the top2 significantly differentially expressed genes in cluster2.

Conclusions: Our study distinguishes HSPCs from healthy haploidentical donor and DCL at a single-cell resolution. With the help of integrated genomic and single-cell molecular analyses, we provide more comprehensive mechanisms of DCL after allo-HSCT.

Disclosure: Nothing to declare

P024 Can allogeneic stem cell hematopoietic transplant with any type of donor be the standard post-remission treatment in intermediate-risk acute myeloid leukemia in first complete remission?

J.M. Cerezo Martín ¹, A. Bermúdez-Rodriguez¹, M.d.l.M. Colorado¹, P. Munoz², S. Fernandez-Luis¹, L. Yañez¹, G. Martin¹, N. Fernandez¹, J.A. Calvo¹, A. Insunza Gaminde¹, C. Montes¹, S. González¹, A. Batlle¹, M. Briz¹, I. Romon¹, M. Sanchez-Escamilla¹, J.L. Arroyo³, E. Ocio¹

¹Hospital Universitario Marqués de Valdecilla, Santander, Spain, ²Instituto de investigación sanitaria Valdecilla (IDIVAL), Santander, Spain, ³Banco de Sangre y Tejidos de Cantabria (BSTC), Santader, Spain

Background: Allogeneic hematopoietic stem cell transplantation (Allo-HSCT) as post-remission treatment in cytogenetically defined intermediate-risk Acute Myeloid Leukemia (AML) in first complete remision (CR1) is effective, but has been associated with high transplant-related mortality (TRM). The aim of this study is to analyze the outcome of this procedure using HLA-identical sibling, unrelated or alternative donors.

Methods: We conducted an observational retrospective study in all patients with intermediate-risk cytogenetically defined (Upon The European LeukemiaNet 2017 criteria) AML in CR1 who underwent an allo-HSCT in our center between 2010 and 2020. The primary endpoint was OS, secondary outcomes were relapse-free survival (RFS), cumulative incidence of relapse and TRM. Minimal residual disease (MRD) was measured by flow cytometry (using a cut off of 0,01%) and/or RT-PCR (NPM1). A multivariate Cox regression model was performed.

Results: We analyzed 58 patients with a median age of 58 (R 19-82) years. Ten (17,2%) patients had negative MRD and 29 (50%) had an unrelated donor (5 had a 9/10 HLA allelic match) at the moment of transplant. Forthy three (74,1%) patients received myeloablative conditioning regimens (Table 1). The median time from diagnosis to transplant was 5 (IR 4-7) months.

With a median follow up of 40 months, the OS at 1, 2 and 3 years was 88% (95% CI 77-98%), 84% (95% CI 72-96%) and 78% (95% CI 64-92%) respectively (Figure 1). The RFS at 1 and 3 years was 88% (95% CI 77-99%) and 73% (95% CI 58-88%), the cumulative incidence of relapse at 1 and 3 years was 7% (95% CI 2-15%) and 14% (95% CI 7-25%) and the TRM at 1, 2 and 3 years was 7% (95% CI 2-15%), 11% (95% CI 4-20%) and 15% (95% CI 7-26%) respectively.

Among all the clinical features which could be related to OS: group of age, gender, conditioning, MRD and type of donor were included in the multivariate analysis. A non-myeloablative conditioning (HR 15 p = 0,01) an haplo-identical donor (HR 6 p = 0,03) and an unknown/undefine MRD (HR 13 p = 0,03) were associated with a significant higher risk of death. Age and gender showed no differences.

Group of age		Type of Donor
<50	20 (34,5%)	HLA-identical sibling	15 (25,9%)
50-65	23 (39,7%)	Unreleated	29 (50%)
>65	15 (25,9%)	Haplo-identical	14 (24,1%)
Gender		Minimal residual disease
Men	32 (55%)	Negative	10 (17,2%)
Conditioning		Positive	31 (53,4%)
Myeloablative	43 (74,1%)	Undefined/Unknown	17 (29,3%)
Non myeloabaltive	15 (25,8%)

Conclusions: Allo-HSCT in patients with an intermediate-risk LMA in CR1 is the standard consolidation therapy at our institution mainly when a HLA identical sibling or unrelated donor is available, and especially when using a myeloablative conditioning, as it is associated with low TRM and a high RFS.

Disclosure: Nothing to declare

P025 Risk factors for central nervous system relapse after allogeneic H-SCT in flt3-mutated AML

K. Kouidri ¹, R. Toenges¹, S. Pfaff¹, S. Lindner^2,1, J. Riemann¹, F. Lang¹, H. Serve¹, A. Cremer¹, G. Bug¹

¹Goethe University Hospital Frankfurt am Main, Frankfurt, Germany, ²Memorial Sloan Kettering Institute, New York, United States

Background: Nearly 30% of AML patients harbour a FMS-like tyrosin-kinase 3-gene alteration (FLT3) driver mutation. The increased relapse risk associated with internal tandem duplications (ITD) may be counteracted by allogeneic hematopoietic stem cell transplantation (allogeneic HSCT) followed by FLT3 inhibitor (FLT3i) maintenance.

We here describe risk factors for post-HSCT central nervous system (CNS) relapse, an uncommon but prognostically extremely unfavourable event in adult FLT3-mutated AML.

Methods: We retrospectively analysed data of 39 patients with FLT3-ITD (n = 34) and/or TKD-mutated AML (n = 5) who were transplanted 2017-2020 at our institution. Minimal residual disease (MRD) was determined prior to and 60-100 days after allogeneic HSCT by qRT-PCR (NPM1mut, n = 26; KMT2A-PTD, n = 2; JAK2mut, RUNX1/RUNX1T1, NUP98-NSD1, n = 1 each) or multicolour flow cytometry, (n = 8). Cumulative incidence of relapse (CIR) was calculated with non-relapse mortality as competing risk and survival probabilities were compared by log-rank test.

Results: At the time of allogeneic HSCT, 6 patients (15%) were in MRD-negative CR (molCR), 24(61%) in MRD-positive CR and 9(23%) had active disease. All patients achieved CR with 30(77%) molCR and FLT3i was started prophylactically (n = 11) or pre-emptively (n = 11) at a median of 54(range, 41-713) days post-HSCT for a median of 12.6 months. Reasons for no FLT3i were allogeneic HSCT before 2019 (n = 12), renal insufficiency (n = 1), FLT3-TKD only (n = 3) and early relapse (n = 1).

With a median follow-up of 27 months in surviving patients, probability of OS was 67.9% at 3 years. Ten patients relapsed at a median of 9.3(range, 3.3-33.6) months post-HSCT, the CIR was 32%. Survival was significantly longer in patients with molCR vs no molCR post-HSCT (OS: not reached vs. 30.4 months, p = 0.004; relapse-free survival: not reached vs. 9.1 months, p < 0.001), while other factors, such as cytogenetic risk, total body irradiation-based conditioning, RIC vs MAC, use of FLT3i pre-HSCT or post-HSCT had no significant impact on survival.

Meningeal leukemia (n = 5) or CNS chloroma (n = 1) were observed as late events at a median of 16.3 months post-HSCT and occurred on Sorafenib (n = 2), Gilteritinib (n = 1) or decitabine-based salvage therapy after failure of FLT3i (n = 3). All patients with CNS relapse had active disease at allogeneic HSCT (median: 14% bone marrow blasts) and no molCR post-HSCT. CNS relapse was preceded by hematologic relapse in 5/6 patients by a median of 2.7 months.

Table 5

Conclusions: Patients with FLT3-mutated AML and active disease at the time of allogeneic HSCT, combined with failure to achieve MRD-negativity after allogeneic HSCT have a high risk of CNS-relapse and leukemic death. This was not abrogated by pre-emptive or salvage-therapy with FLT3i or HMA and prophylactic intrathecal therapy may be considered to avoid CNS relapse.

Disclosure: Gesine Bug, Honoraria: Jazz, Celgene, Gilead, Novartis, Hexal, Pfizer, Eurocept

P026 Allogeneic hematopoietic stem cell transplantation for adult acute lymphoblastic leukemia: A multicenter retrospective study

D. Alzetta ¹, C. Borghero², I.M. Cavattoni³, F. Benedetti⁴, M. Krampera⁴, A. Billio³, M. Ruggeri², C. Tecchio⁴

¹IRCSS Centro di Riferimento Oncologico (CRO) di Aviano, Aviano, Italy, ²Ospedale San Bortolo di Vicenza, Vicenza, Italy, ³Ospedale centrale di Bolzano, Bolzano, Italy, ⁴Azienda Ospedaliera Universitaria Integrata di Verona, Verona, Italy

Background: Despite progress in therapies, allogeneic hematopoietic stem cell transplantation (alloHCT) still plays a pivotal role in the treatment of adult Acute Lymphoblastic Leukemia (ALL). Nevertheless, relapse and non-relapse mortality remain a significant concern. The aim of this retrospective real-life study was to evaluate overall survival (OS), disease-free survival (DFS) and non-relapse mortality in a multicenter series of adult ALL patients undergoing alloHSCT.

Methods: The study included adult patients, affected by either B-ALL (Ph negative or positive) or T-ALL, who underwent alloHSCT in three Italian Bone Marrow Transplant Centers between July 2003 and July 2020. Patient outcomes were evaluated by univariate analysis based on variables defined as pre-alloHSCT [i.e., ALL phenotype, white blood cell count (WBC) at diagnosis, number of complete remissions (CR)], alloHSCT-related [i.e., EBMT risk score, donor type], and post-alloHSCT [Graft versus Host Disease (GvHD) and minimal residual disease (MRD)]. The observation period ended on October 2020.

Results: 133 subjects with a median age of 40 (range: 18-70) years were enrolled. Patients were affected by Ph- (66) or Ph + (33) B-ALL (33), and T-ALL (34). With a median follow-up of 18.5 (range: 0.9-187.5) months, OS was 47.4% (median survival: 37.4 (range: 0.9-187.5) months) and DFS 67.7% (median survival not reached). Relapse mortality accounted for 24% and non- relapse mortality for 28.6% of deaths.

According to univariate analysis, DFS had a better trend in patients with T as compared to B phenotype (p = 0.09) (A) and in those with negative MRD (immunophenotypic detection) before alloHSCT (p = 0.08). The number of pre-alloHSCT complete remissions (CR1 vs CR > 1) did not affect DFS (p = 0.08). Patients with matched unrelated donors had a better DFS as compared to those with matched related (p = 0.07) (B). DFS was significantly higher in patients with GVHD (p = 0.002). Among B-ALL patients, a WBC count at diagnosis > 30.000/mmc had a negative impact (p = 0.09). Ph- B-ALL and T-ALL patients with a negative immunophenotypic MRD at day +90 after alloHSCT showed a better DFS (p = 0.005) (C), Ph+ B-ALL patients with a major molecoular response at day +21 had better DFS (p = 0.003) (D). OS and non-relapse mortality were lower in patients with EBMT score ≥ 4 (p = 0.01)

Conclusions: This real-life study confirms that in adult ALL patients alloHSCT is effective, though associated to a significant transplant-related mortality that can be predicted by the EBMT score. A negative post-alloHSCT immunophenotypic MRD (day + 90) and a major molecular response (day + 21) are predictive for a favorable outcome in Ph- B- and T-ALL, and Ph+ B-ALL, respectively.

Disclosure: Nothing to declare

P027 The outcome of AML and mds patients relapsed after allogeneic transplantation, single centre experience

M. Šťastná Marková ¹, A. Vítek¹, V. Válková¹, M. Kouba¹, L. Nováková¹, P. Cetkovský¹, J. Vydra¹

¹Institute of Haematology and Blood Transfusion, Praha 2, Czech Republic

Background: Although allogeneic transplantation in high risk myeloid malignancies is the best way of consolidation, relapse of the original disease remains the major cause of transplant failure, the treatment is difficult and until now there is no definite way how to deal with it.

Methods: We retrospectively evaluated 186 AML and 51 MDS patients transplanted between years 2001 and 2021 who relapsed after transplantation. The therapeutic approach was individual considering the status of the patient, risk of the disease assessment and the patient’s will. For the evaluation the patients were divided into three groups. 1) no chemotherapy approach (including immunosuppression tapering and DLI only), 2) low dose chemotherapy considering of either low dose ARA-C or 5-azacytidine or both, including five patients treated with addition of gilteritinib, 3) high dose chemotherapy considering of antracyclin and ARA-C base regimens, or/and second transplant. The majority of the patients were in parallel additionally treated with DLI.

Results: In AML: the survival in 1, 2 and 5 years was 7%, 3% and 0% in no chemotherapy gr., 38%, 31% and 19% in low dose gr.,and 42%, 32%, and 20% in high dose gr. In MDS 7% in no chemotherapy gr., 15%, 13% and 12% in low dose gr., 51% 36% and 32% in high dose group. No statistical difference in OS was found between treated groups. Time of relapse from transplant significantly influenced the overall survival in all tested time points (3, 6 and 12 months) OS in 2 years 25%, 22% and 32%. Not surprisingly the patients who achieved remission with any type of chemotherapy had OS better in 2 years comparing to those, who did not (60% vs 5%). Anyway 43% of patients suffered from subsequent relapse. 21% of patients who achieved remission died from treatment related complications (toxicity or GVHD). There was no substantial difference in the outcome between AML and MDS patients.

Conclusions: Although the outcome of the AML/MDS patients relapsed after transplantation is very poor, many of them can profit from additional treatment and some of them achieve further remission. Immunomodulation with DLI is considered to play substantial role and its prophylactic and preemptive use is promising. New drugs such as venetoclax or gilteritinib need to be introduced and evaluated.

Disclosure: I have no conflict of interest.

P028 Control leukemia by inducing anti-cancer immune reactivity in vivo? potential of a dc-triggered mechanism

H. Schmetzer ¹, D. Amberger¹, L. Klauer¹, E. Rackl¹, M. Atzler¹, S. Ugur¹, A. Rank², M. Inngjerdingen³, T. Baudrexler¹, B. Eiz-Vesper⁴, C. Schmid²

¹University Hospital Großhadern, Ludwig-Maximilians-University Munich, Munich, Germany, ²University Hospital Augsburg, Ludwig-Maximilians-University, Augsburg, Germany, ³Oslo University Rikshospitalet, Oslo, Norway, ⁴Institute for Transfusion Medicine, Hannover Medical School, Hannover, Germany

Background: There are virtually no treatment options for therapy-refractory or relapsed AML/MDS and high rates of relapse in successfully treated patients.

Methods: The combination of the (clinically approved) immune-modulatory compounds GM-CSF + Prostaglandine 1 (PGE1; the combination referred to as KIT M) converts myeloid blasts into dendritic cells of leukemic origin (DC_leu). After stimulation with DC_leu, antileukemic (T) cells are activated. Kit M treatment may be an attractive tool for immunotherapy in myeloid leukemia.

Results: 1. ex vivo: Treatment of 65 leukemic WB samples with KIT M does not induce blast proliferation, but triggers generation of mature DC/DC_leu and reduces tolerogenic DC. Kit treated WB activates the adaptive and innate immune system after MLC (T cell proliferation, antitumor-supportive T cells (TCRgd,Tb7), memory cells (Tcm,Tb7cm) and downregulates immune suppressive T cells (Treg4 and 8). Moreover leukemia specific (interferon g (_g) and/or degranulating (_deg)) adaptive (_g-degT4,T8,TCRgd,Tb7,Tcm) and innate cells (_g-degNK,NKb7,CIKb7) are increased and regulatory cells (_g-degTreg4) downregulated. In addition, blast lysis is increased vs control. Ex vivo achieved blast lysis correlates positively with frequences of mature DC/DC_leu, leukemia specific T3,T4,T8,TCRgd,Tb7 and NK cells and negatively with Treg4 and 8. Blast lysis does not correlate with age, sex, ELN risktype, blast counts, or response to chemotherapy.

2. In vivo - rats: Kit M treatment of 3 leukemically diseased (vs 3 control) rats (followed by sacrification after treatment) leads to reduced blasts and Tregs in blood and spleen and increased DC_leu and memory-like T cells.

3. In vivo - human: Kit M therapy was offered to a 72 year old pancytopenic male as an individual salvage attempt (applied as continuous infusion), after discussion with the ethical commitee, the patient’s information about the experimental nature of the treatment and his written consent. The treatment was well tolerated and the patient improved clinically. Neutrophils in WBC increased from 10% to 50%, thrombocytes reached 100 G/l after 24 days. Immune monitoring showed a continuous increase of proliferating and non-naïve Tcells, NK, CIK- and NKT-, TH17 cells, B_mem-cells and DC in PB. The production of IFNg producing T-, CIK and NKT-cells was demonstrated, suggesting an in vivo production/activation of (potentially leukemia-specific) cells. Immune stimulatory effects decreased after discontinuation of therapy. After 4 weeks of treatment, the patient was discharged in good clinical condition. Unfortunately, at two weeks from discharge, AML progressed and the patient died few days later.

Conclusions: Treatment of WB ex vivo with Kit M leads to activation of adaptive and innate (leukemia specific) immune reactive cells (and downregulated suppressive mechanisms) via a DC/DC_leu triggered mechanism – resulting in significantly improved blast lysis compared to controls (independent of patients‘ risk classification, MHC, age or sex). In vivo treatment of leukemically diseased rats or humans was well tolerated, led to an increase of platelets and granulocytes and stable (low) blast counts in PB – probably mediated by a (leukemia specifically) DC/DC_leu activated immune system. A dose defining clinical trial in carefully selected patients to confirm clinical safety and underscore clinical efficacy is being prepared.

Disclosure: Helga Schmetzer is associated with Modiblast Pharma GmbH

P029 Second allogeneic hematopoietic cell transplantation in relapsed acute myeloid leukemia – retrospective analysis of the outcome

A. Lojko-Dankowska ¹, M. Matuszak¹, E. Bembnista¹, D. Dytfeld¹, A. Nowicki¹, A. Wache¹, L. Gil¹

¹Poznan University of Medical Sciences, Poznań, Poland

Background: The second allogeneic hematopoietic stem cell transplantation (alloHSCT) is the most effective treatment option for patients (pts) with acute myeloid leukemia (AML) who relapsed after the first alloHSCT. The strategy of this procedure, especially optimal reinduction, choice of donor and type of conditioning remain unknown.

Methods: We retrospectively analyzed the outcome of the second alloHSCT in 40 pts (21 women, 19 men) with AML, transplanted in one center between 2005 and 2020. At the first alloHSCT most pts (36) were transplanted in complete remission (CR) – 26 pts in CR1, 8 pts in >CR1, 4 pts were transplanted with active disease (nonCR). Most pts (32) received myeloablative first conditioning. Donor at first alloHSCT was sibling (16), unrelated (23) or haploidentical (1). The median time between first alloHSCT and relapse of disease was 10 (3-120) months; 13 pts relapsed within 6 months, 6 pts later than 2 years, one after 10 years. Only seven pts presented graft versus host disease (GvHD) symptoms after first alloHSCT. At the time of the second transplant median age was 41 (20-69) years. All but two pts received reinduction chemotherapy (based on Flag or Clag – 28 pts, HDAraC- 9 pts) before the second alloHSCT. At the time of the second transplant 28 pts were in CR, 12 were transplanted in nonCR. Before the second alloHSCT pts received myeloablative (n = 14) or reduced-intensity (n = 26) conditioning regimen and peripheral blood stem cells (PBSC) (n = 39) or bone marrow cells (n = 1) from matched sibling donors (n = 11), matched/mismatch unrelated donors (n = 13) or haploidentical donors (n = 16). 22 pts received second alloHSCT from the same donor as for the first transplant, 18 from different ones.

Results: Neutrophil engraftment was achieved in 35 patient, with median time 22 days, range 10-47. Eight pts (20%) died up to 100 days due to transplant related reason (infection, MOF). GVHD was seen in 7 pts only – acute in 5 pts, chronic in 3. Relapse occurred in 17 (42%) pts and was the cause of death in 15 of them. The median time between the second alloHSCT and relapse was 7 (2-30) months. After the median follow-up of 40 months, 15 (37%) pts remained alive with 14 in remission of disease. Median overall survival (OS) was 16 months. The one-year and five-year OS was 63% and 35%, respectively. In Cox-model-based tests only disease status at time of second alloHSCT (CR vs nonCR) significantly improve OS – one-year and five-year OS was 76% and 48% vs 49% and 15% respectively (HR 95% CI 0.39 (0.17-0.89); p = 0,02), with no influence of time to relapse, conditioning, donor type and GvHD status. Of the patients who have been transplanted in CR 14 (50%) remain alive, while of those who were not in CR only one is alive.

Conclusions: The second alloHSCT remains a curative option for patients with AML relapsing after first alloHSCT, however achievement of complete remission before transplantation is required for successful treatment. The rate of transplant related mortality is high. Most patients died due to relapse of disease.

Disclosure: Nothing to declare

P030 Pre-conditioning endothelial activation and stress index (easix) predicts allogeneic hematopoietic stem cell transplantation outcomes

K.Y. Kim ^1,2, D. Kwag^1,2, J.Y. Lee^1,2, J.H. Lee^1,2, T.Y. Kim^1,2, G.-J. Min^1,2, S.-S. Park^1,2, S. Park^1,2, J.-H. Yoon^1,2, S.-E. Lee^1,2, K.-S. Eom^1,2, Y.-J. Kim^1,2, S. Lee^1,2, C.-K. Min^1,2, S.-G. Cho¹, J.W. Lee¹, B.-S. Cho^1,2, H.J. Kim^1,2

¹Catholic Hematology Hospital, Seoul St. Mary’s Hospital, Seoul, Korea, Republic of, ²Leukemia Research Institute, College of Medicine, The Catholic University of Korea, Seoul, Korea, Republic of

Background: Endothelial Activation and Stress Index (EASIX)—lactate dehydrogenase (U/L)×creatinine (mg/dL)/thrombocytes (10⁹/L)—was reported to be useful in predicting outcomes after allogeneic hematopoietic stem cell transplantation (allo-HSCT). However, due to controversies regarding the validity and usefulness of this simple predictive marker, EASIX needs to be verified in various cohorts. Thus, we investigated whether the EASIX measured before allo-HSCT conditioning (EASIX-pre) correlates with transplant-related outcomes in acute myeloid leukemia (AML) patients who underwent allo-HSCT at a single center in Korea, and compared its predictive ability with the established prognostic indices.

Methods: We conducted a pilot study with AML patients who received allo-HSCT in 2017 among a prospective observation cohort for acute leukemia, in the Catholic Hematology Hospital, Korea (CRIS# KCT0002261). Each patient’s EASIX-pre was calculated one day before allo-HSCT conditioning. We evaluated the association between EASIX-pre and overall survival (OS) or failure (relapse or non-relapse mortality)-free survival (FFS) after allo-HSCT using the Kaplan-Meier estimates and the Cox model. We inspected whether EASIX-pre correlates to cumulative incidences of non-relapse mortality (NRM), relapse, acute graft versus host disease (aGVHD), transplant-associated thrombotic microangiopathy (TA-TMA) and sinusoidal obstruction syndrome (SOS), using cumulative incidence estimates and the Fine-Gray model. The usefulness of EASIX-pre in predicting death in 2 years after allo-HSCT was compared with other known predictive indices—The European Group for Blood and Marrow Transplantation (EBMT) risk score, Hematopoietic Cell Transplantation-specific Comorbidity Index (HCT-CI), Pretransplant Assessment of Mortality Score (PAM score)—using receiver operating characteristic (ROC) curves and their area under curve (AUC).

Results: A total of 117 patients were included in this study. In our analyses, EASIX-pre showed strong association with OS and FFS. The hazard ratios for OS and FFS per 1 increment in EASIX (log 2 scale) were 1.37 (95% confidence interval (CI): 1.20–1.55, p < 0.001) and 1.36 (95% CI: 1.19–1.54, p < 0.001), respectively. EASIX-pre correlated with OS and FFS in each subgroup stratified according to their pre-HSCT disease status, cytogenetic risk, HSCT donor, and conditioning intensity. Also, EASIX-pre showed significant relationship with the cumulative incidence of NRM (coefficient of Fine-Gray subdistribution hazard model: 1.38, 95% CI: 1.14–1.66, p < 0.001), rather than those of relapse (coefficient: 1.17, 95% CI: 0.97–1.37, p = 0.055). There were no significant associations of EASIX-pre with the cumulative incidence of aGVHD (p = 0.756), TA-TMA (p = 0.893), and SOS (p = 0.923) after allo-HSCT. In predicting death in 2 years after allo-HSCT, EASIX-pre showed high predictability, of which AUC of ROC curve was 0.7534, which was comparable to other established prognostic indices (Figure 1). EASIX-pre cut-off of highest accuracy was 2.1 (log 2 scale).

Conclusions: This study is the first to show the validity of EASIX-pre as a prognostic index in a cohort of Asian patients with AML. EASIX-pre significantly associated with the patient’s OS, FFS, and NRM. EASIX-pre had comparable predictive capacity with established prognostic scores. Although EASIX is known to be a marker that reflects endothelial stress, we did not find a significant association with vascular stress-related complications, such as GVHD, TA-TMA, and SOS. This pilot analysis warrants further validation with larger prospective cohorts.

Clinical Trial Registry: CRIS# KCT0002261

https://cris.nih.go.kr/cris/search/detailSearch.do?seq=8588&search_page=L&search_lang=E&lang=E

Disclosure: Nothing to declare

P031 Allogenic stem cell transplantation and peri transplant strategies in patients with relapsed/refractory or intermediate/high risk npm1 mutated acute myeloid leukemia – a single center experience

P. Jäger ¹, C. Rautenberg², J. Kaivers¹, S. Geyh¹, U. Germing¹, K. Nachtkamp¹, T. Schroeder², G. Kobbe¹

¹University Hospital Düsseldorf, Düsseldorf, Germany, ²Hospital Essen, Essen, Germany, Essen, Germany

Background: The prognosis of patients with nucleophosmin 1 gene mutated (NPM1^mut) acute myeloid leukemia (AML) depends on the presence of concomitant chromosomal aberrations and mutations. Although, patients with isolated NPM1 mutation are considered to convey a favorable prognosis, relapse still remains the most common cause of treatment failure and allogeneic hematopoietic blood stem cell transplantation (alloHSCT) as second line therapy is required to achieve durable molecular remissions. Patients who relapse molecularly or morphologically after or during conservative chemotherapy require immediate therapy to achieve a molecular or at least hematological remission again prior transplant. Patients with ratio > 0.5 of FMS-like tyrosine kinase 3 internal tandem duplication (FLT3-ITD^high) or adverse chromosomal aberrations have a poorer outcome and are therefore considered as candidates for first line alloHSCT in first remission.

Methods: Here we demonstrate our single center experience concerning alloHSCT and peri-transplant strategies in 73 patients with relapsed/refractory good or intermediate/high risk NPM1^mut AML out of whom 55 patients received an alloHSCT at our center since 2008.

Results: After a median follow-up of 2.7 years from alloHSCT, patients with hematologic complete remission (CR) compared to patients with morphological active disease (HR + ) had an estimated 2-y-OS of 73% vs. 62% (ns) and an estimated 2-y-RFS of 63% vs. 20% (P = 0.0070). Focusing on patients with CR before alloSCT, those with no detection of minimal residual disease (MRD-) showed a trend towards higher RFS compared to MRD + patients with a 2-y-RFS of 79% versus 47% (ns). This was not reflected in a different 2-y-OS (78% vs 75%, ns). Patients with FLT3-ITD^high and MRD + CR before alloHSCT showed a trend towards a lower 2-y-RFS compared to patients without FLT3-ITD^high (29% vs 62%, ns). Focusing on patients with second line indication for alloHSCT because of inadequate response or relapse post or during therapy we analyzed status of high dose cytarabine based salvage chemotherapy (S-CT). Thirteen patients got s-CT with 8 patients achieving CR (MRD- n = 6, MRD + n = 2). Sequential conditioning with FLAMSA without previously performed S-CT showed similarly good OS but a high risk of relapse. Patients with HR + showed a 2-y-OS of 52% and a 2-y-RFS of 24%, whereas patients with MRD + CR and MRD- CR showed quite similar 2-y-OS of 80% and 83% but a different 2-y-RFS of 62% and 83%, suggesting effective relapse strategies like hypomethylating agents (HMA) and donor lymphocyte infusion (DLI), especially in case of late and molecular relapse, detected by intensive MRD monitoring.

Conclusions: Patients with second line indication for alloHSCT have an excellent chance of long-term remission if they are MRD- before alloHSCT. Patients with MRD + CR also have a good chance of long-term remission if no FLT3-ITD^high mutation is present. To achieve a second remission S-CT is effective. Only the group of patients with HR + during therapy present a clinical challenge. For all groups, sufficient relapse strategies after alloHSCT such as HMA and DLI exist, especially if the relapse occurs late and was diagnosed early by intensive MRD monitoring.

Disclosure:

Thomas Schroeder

JAZZ, Pfizer, BMS advisory boards, lecture fees

JAZZ, BMS research funding

P032 Viale-t: A randomized, open-label, phase 3 study of venetoclax in combination with azacitidine after allogeneic stem cell transplantation in patients with acute myeloid leukemia

C. Craddock ¹, U. Platzbecker², M. Heuser³, V. Pullarkat⁴, S. Chaudhury⁵, D. Wu⁶, S. Addo⁷, B. Chyla⁷, Q. Jiang⁷, P. Lee⁷, J.E. Wolff⁷

¹University of Birmingham, Birmingham, United Kingdom, ²University Hospital in Leipzig, Leipzig, Germany, ³Hannover Medical School, Hannover, Germany, ⁴City of Hope, Duarte, United States, ⁵Ann & Robert H. Lurie Children’s Hospital of Chicago, Northwestern Feinberg School of Medicine, Chicago, United States, ⁶The First Affiliated Hospital of Soochow University, Soochow, China, ⁷AbbVie Inc, North Chicago, United States

Background: Acute myeloid leukemia (AML) is an aggressive malignancy and is the most common and second most common form of acute leukemia in adults and children, respectively. The combination of the highly selective BCL-2 inhibitor venetoclax and the hypomethylating agent azacitidine was shown to be safe and effective in clinical trials (DiNardo et al. Blood. 2019;133:7-17; DiNardo et al. N Engl J Med. 2020;383:617-629) and is approved by the United States Food and Drug Administration and European Medicines Agency for the treatment of patients with AML who are not eligible to receive intensive chemotherapy. Following allogeneic stem cell transplantation (alloSCT), most patients do not receive antileukemic therapy; however, an unmet need remains as disease relapse and graft-versus-host disease (GvHD) commonly occur posttransplant. In addition to the antileukemic effect of venetoclax shown in clinical studies, preclinical studies suggest venetoclax may mitigate the risk of GvHD. VIALE-T is a Phase 3, randomized, open-label trial in progress (NCT04161885) evaluating the safety and efficacy of venetoclax in combination with azacitidine versus best supportive care (BSC) as maintenance therapy following alloSCT in patients with AML.

Methods: This Phase 3 study consists of 2 parts (Figure). Key inclusion criteria include diagnosis of AML; plans to receive alloSCT or have received alloSCT within the past 30 days; bone marrow blasts <10% before pretransplant conditioning and <5% posttransplant; have received myeloablative, or reduced intensity, or nonmyeloablative pretransplant conditioning protocols. Grafts are allowed from various sources (bone marrow, peripheral blood stem cells, cord blood cells). Patients must be ≥18 years old for Part 1 and ≥12 years old for Part 2. Additionally, patients must meet key laboratory values for absolute neutrophil count (Part 1, ≥1500/µL; Part 2, ≥1000/µL), platelet count (Part 1, ≥80,000/µL; Part 2, ≥50,000/µL), bilirubin ≤3 times the upper limit of normal, and creatinine clearance >30 mL/min. Patients who have received venetoclax and had no history of disease progression while receiving venetoclax are eligible.

Part 1 evaluates dose levels of venetoclax combined with azacitidine to determine the recommended Phase 3 dose (RP3D), which will be confirmed in approximately 12 additional patients enrolled in the Safety Expansion Cohort. Part 2 will be a randomized, open-label evaluation of the RP3D of venetoclax combined with azacitidine and BSC versus BSC only in adults and children aged 12 years or older. All venetoclax-treated patients will receive antibiotic prophylaxis during Cycle 1.

The primary endpoint for Part 1 is the frequency of dose-limiting toxicities. The primary endpoint for Part 2 is relapse-free survival as assessed by an independent review committee. Key secondary endpoints for Part 2 include overall survival, GvHD-free relapse-free survival, and the rate of patients without higher grade GvHD at 90 days after randomization. Enrollment into the Safety Expansion Cohort will be completed in 2021. Part 2 will enroll approximately 400 patients across approximately 175 participating study sites in 17 countries, with recruitment beginning in 2022.

Results: N/A

Conclusions: N/A

Clinical Trial Registry: NCT04161885 https://clinicaltrials.gov/

Disclosure: CC has served as a consultant for AbbVie and Bristol Myers Squibb; has participated in speakers’ bureaus for AbbVie and Bristol Myers Squibb; and has received research support from Bristol Myers Squibb. UP has received honoraria from AbbVie and Bristol Myers Squibb. MH has served as a consultant for AbbVie, Agios, Bristol Myers Squibb, Daiichi Sankyo, Jazz Pharmaceuticals, Kura Oncology, Novartis, Pfizer, PinotBio, Roche, and TOLREMO; has received honoraria from AbbVie, Eurocept Pharmaceuticals, Jazz Pharmaceuticals, Janssen, Novartis, and Takeda; and has received research support from Astellas, Bayer AG, BerGenBio, Daiichi Sankyo, Jazz Pharmaceuticals, Karyopharm, Novartis, Pfizer, and Roche. VP has served as a consultant and an advisory board member for AbbVie, has participated in speakers’ bureaus for AbbVie, and has received honoraria from AbbVie. SC has participated in advisory boards for bluebird bio, Viacord, and AbbVie; and has received research support from Bristol Myers Squibb and Karius. DW reports no conflict of interest. SA, BC, QJ, PL, and JW are employees of AbbVie and may hold stock or stock options in AbbVie.

Venetoclax is being developed in collaboration between AbbVie and Genentech. AbbVie funded this study and participated in the study design, research, analysis, data collection, interpretation of data, reviewing, and approval of the publication. All authors had access to relevant data and participated in the drafting, review, and approval of this publication. No honoraria or payments were made for authorship. Medical writing support was provided by Laura Ruhge, PhD of Bio Connections, LLC, funded by AbbVie.

P033 Optimization of fludarabine-pharmacokincetics to reduce the ri in AML patients after allogeneic stem cell transplantation

T. Thavayogarajah ¹, D. Müller², G. Nair¹, S. Balabanov¹, M.G. Manz¹, U. Schanz¹

¹University Hospital Zurich, Zürich, Switzerland, ²University Hospital Zürich, Institute of Clinical Chemistry, Zürich, Switzerland

Background: Acute myeloid leukemia (AML) is a hematological, clonal malignancy of the myeloid stem cell precursors, which is proliferative and is characterized by clonal evolution and genetic heterogeneity. For adverse risk acute myeloid leukemias, allogeneic stem cell transplantation (allo HCT) is one of the most potent curative options. Unfortunately, disease relapse is still around 40% in the first year after HSCT.

In allo HCT, fludarabine is a frequently used agent, mainly in reduced intensity conditioning regimes. It is often combined with busulfan for which dose individualization based on pharmacokinetics with area under the curve (AUC) determination is used successfully for many years.

It was already shown that fludarabine exposure might be predictive for the survival in allo HCT and it is suggested that individualized dosing can improve the survival after transplantation within the first year. Actually for the fludarabine dose calculation in adults, only the body surface area is used, which might either result in too high exposition causing increased toxicity or with too low exposure and increased relapse incidence (RI).

With the aim to reduce RI we established pharmacokinetic measurements for fludarabine in addition to the established ones for busulfan.

Methods: Fludarabine was measured with a validated LC-MS/MS method. The exposure as AUC was calculated for each patient using a three-compartmental model (adapted from Langenhorst et al.) in n = 13 consecutive patients receiving a conditioning regime with fludarabine being diagnosed with the acute myeloid leukemia.

Fludarabine was given on days -7 to -2 with a dose calculation based on 30mg/m² with an infusion rate of 30 minutes. The time points of analysis were 30 minutes, 4h, 6h, and 7h after the end of infusion. In addition patients received peroral busulfan 4mg/kg bw on days -3 and -2 and ATG 10mg/kg bw (Grafalon®) on days -4 to -1.

Results: So far, there is no dose individualization based on pharmacokinetic parameters for fludarabine specifically suggested in AML patients. The general study published by Langenhorst et al. that mixed up benign and malignant hematological malignancies, suggests lower fludarabine AUC than we observed in our patients.

We have seen that the fludarabine AUC were higher within our patients. In the analysis of Langenhorst et al. the optimal AUC was postulated to be 20 mg*h/l. In our (n = 19) AML patients the median of the AUC was 42.97 (+/− 11.5) mg*h/l, twice as high than the suggested level for an optimal toxicity profile. However, none of our patients experienced any acute toxicity (within 30 days after transplant).

Moreover, there was also no major toxicity seen at day 100. So far, we did not see a reduced RI, despite the AUC was much higher than the suggested optimal levels.

Conclusions: In a regimen with more (6 vs 4), but lower single fludarabine dosage (30mg/m2 vs 40mg/m2) and a shorter infusion duration (30min vs 60min) resulting in higher AUC (40mg*h/l vs 20 mg*h/l) than previously published, we did not observe an increase in transplant-related toxicity or a lower RI in AML patients.

Disclosure: Tharshika Thavayogarajah - Research grant from the Kurt-and Senta Herrmann Foundation

Nothing further to declare.

P034 Relevance of vitamin d in patients undergoing HLA matched allogenic stem cell transplant for acute leukaemia

N. Jindal ¹, M. Saroha¹, S.P. Mirgh¹, A. Chichra¹, A. Gokarn¹, S. Punatar¹, P. Chavan¹, L. Nayak¹, A. Bonda¹, L.J Mathew¹, S. Kannan¹, N. Khattry¹

¹Advanced Centre for Treatment, Research and Education in Cancer (ACTREC), Tata Memorial Centre, Navi Mumbai, India

Background: In HSCT, vitamin D deficiency has been associated with increased complications, primarily chronic GvHD, with a potential impact on survival. Results from various studies however, have not been consistent. At our center, vitamin D levels are done in all patients as part of pre-transplant assessment. This analysis was conducted to study the incidence of vitamin D deficiency, its correctability following oral replacement and the impact of vitamin D levels on transplant outcomes.

Methods: This was a single center retrospective study. Patients of Acute leukaemia (AL) who underwent fully matched or 9/10 transplants (related/unrelated) between 2008 and 2019 were included. In all patients, vitamin D levels were measured at the time of referral to the transplant unit for HSCT counselling (baseline vitamin D). Vitamin D deficiency was defined as 25-hydroxy vitamin D3 level less than 20 ng/mL. Prior to January 2012, patients with vitamin D deficiency did not receive correction. From January 2012 onwards, those with deficiency received replacement with oral vitamin D (60,000 IU weekly for 8 weeks followed by maintenance with 800 IU/day). For patients who received correction, vitamin D level was repeated after 4 months. Based on vitamin D level within 120 days of transplant (peri transplant vitamin D), patients were categorised as either vitamin D replete (>20 ng/ml) or deplete (≤20 ng/ml). Transplant outcomes were compared between these two groups.

Results: One hundred and sixty two patients of AL underwent HLA matched transplants during the study period. Baseline vitamin D levels were available for 145 patients. Of these, 126 (86.9%) were deficient at baseline. One hundred and six out of these 126 patients with vitamin D deficiency (84.1%) received correction. Eighty three patients (78.3%) achieved levels above 20 ng/ml and 11 remained deplete. For 12 patients, repeat levels were not available and these were excluded from subsequent analysis. In all, 31 patients were deplete and 102 were replete in the peri-transplant period.

The median peri-transplant serum vitamin D level was 34 ng/ml (range 20.4-102.4 ng/ml) in the replete group and 15.0 ng/ml (7.7-19.8 ng/ml) in the deplete group. Both groups were matched for age, diagnosis, EBMT score and disease risk index (DRI). Between the deplete and replete groups, there were no significant differences in time to neutrophil or platelet engraftment, CMV reactivation, day 100 absolute lymphocyte count, aGVHD, cGVHD and TRM. PFS and OS (figure 1) were also comparable between the two groups.

Figure 1: Overall survival in vitamin D replete and deplete groups

Conclusions: The incidence of vitamin D deficiency was high in our patients. In a majority of patients, the levels normalized following adequate oral supplementation. Patients who were vitamin D deficient in the peri-transplant period did not have inferior outcomes, suggesting a limited role of vitamin D in influencing transplant outcomes in our patient cohort.

Clinical Trial Registry: Not applicable.

Disclosure: Nothing to declare.

P035 Evaluation of different maintenance treatment strategies after allogeneic hematopoietic stem cell transplantation in flt3 positive AML patients

E. Stauffer ¹, A. Fraccaroli¹, H. Drolle¹, M. von Bergwelt¹, J. Tischer¹

¹University Hospital Munich, Munich, Germany

Background: Relapse remains the most frequent type of treatment failure after allogeneic hematopoietic stem cell transplantation (allo-HSCT). Particularly patients with FLT3 mutations have an increased risk of relapse and thus a lower chance of cure. Hence, there is further medical need to evaluate different maintenance therapies strategies after allo-HSCT regarding their impact on outcome including the classic one with application of prophylactic donor lymphocyte infusion (pDLI) only.

Methods: We performed a retrospective study of 132 FLT3-positive patients who underwent allo-HSCT at our center from 2005-2021. Patients in complete remission (CR) were put under maintenance therapy if lacking any signs of higher grade GvHD, severe infection or organ toxicity. Since 2005 pDLIs were used applied in up to three escalating doses with respect to the donor type. Sorafenib was regularly administered from 2018 onwards, starting with 200mg up to 800mg daily for an expected duration of 24 months. Overall survival (OS), progression-free survival (PFS), non-relapse mortality (NRM) as well as adverse events (AEs) were evaluated, retrospectively.

Results: We identified 19 patients (15%) from our underlying cohort who were considered for maintenance therapy and of whom eleven were treated with Sorafenib and eight underwent pDLI only. Of the entire cohort, 21 died from early death, 35 suffered from GvHD requiring steroid treatment and 14 were lost to follow up while the rest of the patients was not eligible for other reasons including corresponding comorbidities.

Independent of the chosen post transplantation treatment strategy the estimated one- and two-year OS for the entire cohort was 78/70% with a median follow up of 2.1 years (range 7 months-6.3 years). One- and two-year PFS was 72/64%, respectively. Our preliminary analysis points towards an increased therapy efficacy in the Sorafenib group compared to the DLI group. 2 out of 8 patients in the DLI group died, one due to relapse. Up to now, no relapse or death was recorded in the sorafenib group. Further, we did not observe major differences in both groups when regarding AEs leading to similarly therapy interruption in both groups (Sorafenib n = 3, DLI n = 3).

Conclusions: Maintenance therapy after allo-HSCT has gained increasing importance in recent years. Our data indicate that Sorafenib and pDLI only are both well tolerated after transplantation. However, patients treated with Sorafenib might have a more prominent survival benefit. In our cohort only a minority of patients was eligible for a maintenance therapy while median follow up differed significantly among the groups. Further studies might elucidate whether more patients are applicable when inclusion criteria were extended.

Disclosure: Nothing to declare

P036 Outcome of acute leukemia in infants: A report from a single third level center in madrid, spain

B. Ochoa Fernández ¹, V. Galán-Gómez¹, P. Guerra-García¹, S. Sanromán¹, I. Martínez Romera¹, I. Losantos Garcia¹, B. González¹, A. Pérez-Martínez¹

¹La Paz University Hospital, Madrid, Spain

Background: Leukemia in infants is rare, and one of the most challenging diseases in pediatric hematology/oncology. Survival rates are poor compared with leukemia in older children despite the use of maximally intensified standard therapies, and the indication for hematopoietic stem cell transplantation (HSCT) is restricted to specific subgroups with poor-risk factors.

Methods: We reported a retrospective analysis of a cohort of 39 patients diagnosed with infant leukemia during the period 1990-2020 who received treatment at the Pediatric Hemato-Oncology Service of a tertiary hospital in Madrid, Spain.

Results: Within our study period, we diagnosed 39 cases with infant leukemia out of 588 cases of childhood leukemia (incidence of 6.6%). 61.5% were females and 38.5% were males. The median age at diagnosis was 5.8 months (IQR 5.4) and 20 (51.2%) patients were under 6 months of age. A total of 27 (69%) patients were affected by acute lymphoblastic leukemia (ALL), 11 (28%) patients by acute myeloblastic leukemia (AML), and 1 (3%) patient by mixed phenotype acute leukemia. At diagnosis, 12 (30.8%) had leukocytosis >300.000/mm3, 22 (59.5%) presented MLL gene rearrangements and 2 (5.1%) suffered from CNS involvement. Induction failure and relapse occur in 8 (20.5%) and 14 patients (35.9%) respectively. The median duration of first remission before relapse was 4 months (IQR: 6.7). A total of 26 patients (66.6%) received HSCT, 24 (92.3%) in first complete remission. With a median follow-up period of 15 months, the 5-year event-free survival and 5-year overall survival at 5 years was 56.7% (SD 4.6) and 44.9% (SD 4.2) respectively. In a multivariate analysis, younger age at diagnosis was associated with poor outcome (p = 0.027). HSCT reduced the risk of mortality by 81.8% (p = 0.001), with transplant patients in first complete remission having a longer survival compared to the rest (p = 0.002). Transplanted related mortality was 31.6% and relapse after HSCT occurs in 7 patients (17.9%).

Conclusions: Most of the infant leukemias diagnosed in our center were ALL. The main risk factors (hyperleukocytosis, MLL) and relapse were found more frequently in the group of patients with ALL, although this difference was not statistically significant. Most of the patients received HSCT, with a favorable impact on overall survival, especially when it was performed in first complete remission. Our results suggest that HSCT seems to be a good and efficient choice of treatment for selected patients. However, there is still a big issue to decide which patient should undergo transplantation and more studies are needed to reevaluate the eligibility criteria for HSCT in this group of patients.

Disclosure: nothing to declare

P037 Post-transplant treatment in high-risk acute myeloid leukaemia: A single center real-life experience

G. Cavallaro ¹, A. Grassi¹, C. Pavoni¹, M.C. Micò¹, A. Algarotti¹, D. Taurino¹, G. Rizzuto¹, F. Lussana¹, A. Rambaldi¹

¹ASST Papa Giovanni XXIII, Bergamo, Italy

Background: Disease relapse is still the major cause of transplant failure and it is associated with a dismal outcome. In the last years, a better characterization of genomic profile of acute myeloid leukemia made post-transplant target therapies available in cases deemed at high risk of relapse, or frankly relapsed. We report our experience in the use of innovative target therapies (FLT3 inhibitors, venetoclax with or without hypomethylating agents or low dose cytarabine) as pre-emptive therapy in high-risk disease or in cases of molecular or hematological relapse.

Methods: We analyzed 24 patients transplanted in our Centre from 2015 to 2021, with a median follow-up of 10 months (range 2.5-70.5). Our study population comprises acute myeloid leukemia cases, the majority of which (18/24) is considered at high risk, either according to ELN 2017 classification (6/24) or due to high-risk clinical features (12/24, hyperleukocytosis, s-AML, advanced disease). Donor was matched unrelated in 79% of patients and peripheral blood stem cells was the graft source in 91.7% of cases. Conditioning regimen was myeloablative in 54.2% of cases. Only 12.5% of patients achieved a complete remission disease status at transplant; the rest of the study group had pre-transplant active disease (41.7%) or minimal residual disease (MRD) positivity (45.8%).

Results: Our study population started a post-transplant therapy either for hematological (12/24) or molecular relapse/persistent disease (12/24) and median time to treatment start was 2.4 months. 54.2% of patients was started on FLT3-inhibitors (gilteritinib 3/24, sorafenib 10/24) and 45.8% was started on venetoclax with or without a second drug (venetoclax and hypomethylating agents in 5/24, venetoclax and cytarabine in 3/24, venetoclax single agent in 3/24). We performed a univariate analysis on overall survival (OS) and leukemia free survival (LFS). OS for our study population was 39%, as shown in Figure 1. We observed no significant difference regarding the type of conditioning regimen, the donor type and the graft source. Similarly no differences were seen if, at conditioning before transplant, patients had an active hematological disease or an MRD positivity. On the contrary, a timely beginning of the post-transplant therapy to treat minimal residual disease rather than an overt hematological relapse was significantly associated to a better LFS (P 0.0274). Finally, patients with FLT3 mutated patients are those benefit the most of post-transplant treatment.

Figure 1

Conclusions: Post-transplant therapy is feasible and induces a significant improvement in LFS in a very high-risk AML patient population. The clinical benefit seems more pronounced for patients treated with FLT3 inhibitors, especially when therapy is promptly started before an overt relapse.

Disclosure: Nothing to declare

P038 Off-label venetoclax in combination with hympomethylating agents for post-allogeneic HSCT AML relapse

F. Serpenti ¹, S. Mariarita¹, G. Galassi¹, G. Saporiti¹, F. Grifoni¹, N. Rampi¹, F. Cavallaro¹, K. Barbullushi¹, E. Tagliaferri¹, M. Goldaniga¹, L. Baldini¹, N.S. Fracchiolla¹, F. Onida¹

¹Fondazione IRCCS Ca’ Granda Ospedale Maggiore Policlinico, Milan, Italy

Background: Recently, Venetoclax-hypomethylating agents (HMA) combination improved outcomes of untreated and relapsed/refractory acute myeloid leukemia (AML). We hereby report our experience of venetoclax + HMA +/− DLI for post-transplant AML at our center.

Methods: We conducted an observational retrospective study to report response rate and safety of venetoclax + HMA in a cohort of AML patients relapsed after HSCT. Venetoclax was administered off-label in association with or added to ongoing HMA therapy. Venetoclax was given after a short ramp-up continuously until response and then in 21 out of 28 days cycles. Dosage was reduced in case of concomitant CYP3A4 inhibitors. Venetoclax was temporarily discontinued in case of grade 4 cytopenia or infection. In case of multiple neutropenic febrile episodes, grade >3 infection or worsening of ECOG > 2, venetoclax was permanently discontinued.

Results: From September 2016 to March 2021, 11 patients were treated with venetoclax + HMA for post HSCT AML relapse. Their characteristic are summarized in Table 1. One patient was treated for molecular relapse, all others for hematological relapse. Venetoclax was added to HMA after a median of 2 cycles of HMA (0-10); three patients started directly with the combination therapy; all had active disease at start of venetoclax. Five (45%) patients received DLI, with one infusion per cycle at incremental doses. Reasons for not giving DLI were active GvHD, no availability and previous use.

Nine (82%) patients experienced grade ≥3 toxicity (8 hematological, 3 infectious, 1 gastroenteric). Five (45%) patients had to stop venetoclax prematurely after a median time of 35 days (25-46); two of them still proved to have benefited from therapy (1 CRi and 1 MRD negativity after molecular relapse). Both had received DLI, with a median response duration of 1,5 month.

Six patients did not permanently discontinue venetoclax, but at least one temporary suspension was required in four of them. Median duration of therapy was 90 days (37-341). Among these six patients, four had NR (3 DLI), one had PR and one achieved CR with MRD negativity, lasting 12 months.

Median OS was 122 days from venetoclax start.

		Range
Median age	65 y	31-72
ELN risk: favorable (3), intermediate (5), adverse (3)
Disease status at transplant: CR1 (4), CR2 (4), PR2 (1), active (2)
Median time from transplant to relapse	196 d	27-1443
Median number of previous lines	3	1-4
DLI: yes (5), no (6)
HMA: Azacitidine (10), Decitabine (1)
Venetoclax dose (mg): 400 (no interaction, 4), 200 (concomitant isavuconazole, 2), 50 (concomitant posaconazole, 5)

Conclusions: Venetoclax-HMA combination induced CR in 27% of these heavily pre-treated patients. The major challange lies in optimizing venetoclax therapy due to higher toxicity rates compared to historical pre-transplant cohorts. At end of study, all patients eventually relapsed, suggesting long-term control is difficult without a second HSCT. Further studies focusing on appropriate patient selection and treatment schedule are warranted in this setting.

Disclosure: No disclosure

P039 Allogeneic bone marrow transplant in infant with acute leukemia

M. Ben Khaled ¹, A. Nasri², S. Rekaya³, I. Ben Fraj⁴, M. Fathi⁵, O. Monia⁵

¹immune hematology pediatrix departement, Tunis, Tunisia, ²immune-hematology pediatric departement, Tunis, Tunisia, ³immune hematology pediatric departement, Tunis, Tunisia, ⁴immune hematology pediatric deparetment, Tunis, Tunisia, ⁵immune hematology departement, Tunis, Tunisia

Background: Despite significant therapeutic progress in recent years, acute leukemia that appears early in the first two years of life still have a poor prognosis with high mortality rate as well as a considerable risk of relapse. The bone marrow transplant improved the prognosis especially by integrating Haplo-identical hematopoietic stem cell transplantation (haplo-HSCT). This study, aimed to describe the outcome of a single center experience with HSCT in early childhood acute leukemia in Tunisia.

Methods: This was a retrospective study carried out in immune-hematology pediatric department of Tunisia between 2010 and 2020 and including children aged under 2 years old who underwent HSCT for acute leukemia.

Results: Among 21 patients included, 11 had acute myeloid leukemia, 9 had acute lymphoid leukemia and one patient had an ambiguous Lineage leukemia. Most patients (n = 20) were in their first complete remission (CR1), only one was in his second remission (n = 1) (CR2). Ten patients (48%) underwent geno-identical HSCT, and 11 (52%) underwent an haplo- HSCT. The median age of the patients was 14 months old with a sex ratio= 0.3. Ten of these patients had a positive MRD before HSCT. Most patients had Thiotepa-busulfan-fludarabine as a conditioning regimen. The graft-versus-host disease prophylaxis was based ciclosporin (n = 10) and post transplant cyclophosphamide + MMF + ciclosporin (n = 11). Four patients presented CMV reactivation. Three patients had a grade III/IV acute graft-versus-host disease (GVHD). Four patients died after relapse following HSCT. One patient died of transplant-related causes. The 2-years overall survival and disease-free survival (DFS) are 79% and 73%, respectively. The haplo-HSCT and geno-identical HSCT offered similar outcome.

Conclusions: These results support the fact that HSCT is a great option in the treatment of the early childhood acute leukemias, especially when used in CR1. Further studies should be performed to determine the long-term effects of the HSCT.

Disclosure: we confirm that there are no competing interests to declare and no relevant financial or non financial interests to report.

P040 Philadelphia chromosome-like acute lymphoblastic leukemia: First experience of diagnostics and description of clinical cases

K. Afanaseva ¹, O. Pirogova¹, A. Evdokimov¹, A. Smirnova¹, I. Barkhatov¹, E. Babenko¹, T. Gindina¹, I. Moiseev¹, S. Bondarenko¹, A. Kulagin¹

¹RM Gorbacheva Research Institute, Pavlov University, St. Petersburg, Russian Federation

Background: Ph-like ALL is a subtype of ALL with poor prognosis and undefined prevalence in Russian population of adult patients mainly due to diagnostic challenges. Simultaneously, there is no standard approach to the diagnosis and most of the methods used are not financially and technically available in clinical laboratories. Here we present the screening diagnostic algorithm and description of several clinical cases.

Methods: The study included 26 patients with B-ALL, median age 31 (19-78) years, who were diagnostically screened for Ph-like ALL from 2020 to 2021. It is cost and time consuming to screen for Ph-like ALL by searching directly for specific translocations with the particular gene-partners and mutations. Due to this reason the screening algorithm used in our laboratory is based on the determination of the signaling pathways involved in a particular case in order to choose targeted therapy (TKI/JAK-inhibitor). Algorithm is based on measurement of B-lymphoblasts’ cell-surface TSLP levels with further screening for rearrangements in genes by DNA-specific FISH probes (ABL1, ABL2, CSF1R, PDGFRB, JAK2, CRLF2) or qPCR (CRLF2) (Figure 1).

Results: According to the diagnostic algorithm the Ph-like incidence was 8 of 26 cases (30,7%). The most frequent finding was CRLF2 gene rearrangement (n = 4, 15,4%) (Table 1). Two patients were diagnosed with Ph-like during primary diagnosis of ALL, while others in 1st or subsequent relapses. Five patients proceed to alloHSCT, 4 of them are still in CR at the moment of last follow-up. Two patients received dasatinib after alloHSCT: patient #1 with the prophylactic aim, patient #2 in combination with chemotherapy in 3^rdrelapse. Despite early dasatinib administration, patient #2 demonstrated r/r course of the disease after alloHSCT. Patient #3 with both EPOR and CRLF2 rearrangements died in the progression without response to the combination therapy with Inotuzamab ozogamicin and ruxolitinib. At the same time, patients #5 and #8 with CRLF2 rearrangement and extramedullary disease did not receive JAK2-inhibitors and still in CR after alloHSCT for 12 and 45 months, respectively.

Table 7 Table 1. Ph-like ALL patients’ characteristics

Conclusions: Diagnosis of Ph-like ALL may not rely on the definite gene expression phenotype, but rather on the identification of a genetic aberration in the signaling related genes. A panel of FISH probes covering the most common translocations can be employed as a screening tool. Our limited clinical experience demonstrated potential resistance even to combination therapies with TKI and JAK inhibitors. Apparently, these patients are likely to benefit from alloHSCT as soon as possible in CR, but optimal strategies are yet to be determined.

Disclosure: Nothing to declare

P041 Real-life validation of prognostic risk stratification according to eln 2017 in patients with AML and allogeneic hematopoietic stem cell transplantation

C. Aparicio Pérez ¹, F. Salas Hernández¹, A.C. González Teomiro¹, E. Paumard Rodríguez¹, E. García Torres¹, R. Rojas Contreras¹, J. Sánchez García^1,2, J. Serrano López^1,2, C. Martín Calvo¹

¹Reina Sofia University Hospital, Cordoba, Spain, ²IMIBIC, Cordoba, Spain

Background: The impact of genetic risk profiles on the outcomes of patients with acute myeloid leukemia (AML) following allogeneic hematopoietic stem cell transplantation (HCT) has not yet been fully established. The objective of this work is to study whether the application of European LeukemiaNet (ELN) 2017 scale improves prognostic risk stratification with respect to ELN2010 and Medical Research Council (MRC).

Methods: We included 37 adult AML patients treated with PETHEMA AML chemotherapy protocols and who underwent allogeneic HCT at our institution between June 2017 and November 2021 and were studied at diagnostic using the Spanish PLATAFOLMA PETHEMA. NPM1 and FLT3-ITD were determined by melting curve analysis and standard PCR-EC technique according to Thiede et al (Blood 2002) in ABI 3130 Analyzer (Thermofisher). For NGS, the commercial panel Myeloid SolutionTM (Sophia Genetics) KAPA Kit amplification libraries and sequencing on ILUMINA Myseq platform were used. Variant analysis was performed using DDM software (Sophia Genetics).

Baseline demographic, disease characteristics, transplant procedures and mutations by functional groupsare summarized in Table 1. The prognostic risk was established according to MRC, ELN2010 and ELN2017 classification.

Variable	Total cohort (n = 37)
Age (years)
• Median (range)	56 (30-59)
Sex (%)
• Female	14 (40.5)
• Male	22 (59.5)
Diagnostic (%)
• De novo	31 (83.8)
• s-AML	6 (16.2)
MRC cytogenetic (%)
• Favorable	2 (5.4)
• Intermediate	25 (67.6)
• Unfavorable	10 (27)
ELN 2010 (%)
• Favorable	2(5.4)
• Intermediate	24 (64.9)
• Unfavorable	11(29.7)
ELN 2017 (%)
• Favorable	4 (10.8)
• Intermediate	16 (43.2)
• Unfavorable	17 (46)
Status preHCT (%)
• CR1	25 (67.6)
• CR2 or more	4 (10.8)
• Refractory	10 (21.3)
Donor type (%)
• Related matched	10 (27)
• Unrelated matched	4 (18.8)
• Haploidentical related	21 (56.8)
Functional mutations group (%)
• Signaling pathways/kinases	19 (51.4)
• Epigenetic modification	20 (54.1)
0. DNA methylation	4 (10.8)
1. Chromatin Modifiers	7 (18.9)
• Nucleophosmin	2 (5.4)
• Tumor suppressors	8 (21.6)
• Transcription factors	5 (13.5)
• Spliceosome complex	2(5.4)
• Fusion transcription factors

Results: The majority of the patients (91.6%) had at least one mutation at diagnosis. The median number of mutations was 3 (0-6). Grouped by functional groups, the most frequent were those related to DNA methylation (54.1%) and signaling/kinase pathways (51.4%). The most prevalent were FLT3 (45.9%), IDH1/IDH2 (24.3%), TET2 and NPM1 (18.9%) followed by N-RAS and DMT3A (16.2%).

The overall survival (OS) analysis according to ELN17, although not showing statistically significant differences between the 3 groups (LongRank p = 0.219) with a 2-year OS estimate of 100%, 65.8% and 50.2% in the favorable, intermediate and unfavorable group; respectively, establishes greater differences between intermediate and unfavorable group than the risk stratification according to ELN 2010 and MRC (p = 0.702 and p = 0.614, respectively).

Progression-free survival (PFS) according to ELN2017 did not reach statistical significance, possibly due to the small number of patients included (p = 0.465) with an estimated 2-year PFS of 50%, 30.8% and 45.8% in the favorable, intermediate and unfavorable group, respectively.

Our data show a higher OS in patients with mutations in genes involved in signaling pathways (including FLT3) compared to non-mutated patients with a 2-year OS estimate 71.8 % vs 47.8 %; reaching statistical significance (p = 0.037). In addition, FLT3 mutated patients showed a lower risk of relapse compared to non-mutated patients with a cumulative incidence of relapseat two years of 32.6% vs. 65.1% (p = 0.034). No other individual mutations showed differences in survival or cumulative incidence of relapse.

Conclusions: In our series, ELN 2017 shows better prognostic stratification between intermediate and unfavorable groups, although without statistically significant differences with respect to ELN 2010 and MRC. FLT3 mutated patients showed a strikingly lowrisk of relapse, related in part to treatment with FLT3 inhibitors prior and/or after transplant. New studies including a larger number of patients are needed to corroborate our results.

Disclosure: Nothing to declare

P042 Treatment of children with acute lymphoblastic leukemia and history of high-risk relapse with bone marrow transplantation at the national institute of pediatrics, Mexico

A. Olaya-Vargas ¹, C. Galvan-Diaz¹, H.d.P. Salazar-Rosales¹, G. Lopez- Hernandez¹, A. Del Campo-Martinez¹, N. Ramirez-Uribe¹, Y. Melchor-Vidal², R. Rivera-Luna², A. Olaya-Nieto³

¹Instituto Nacional de Pediatria, Mexico City, Mexico, ²Centro Medico ABC, Mexico City, Mexico, ³Saint Luke Escuela de Medicina, Mexico City, Mexico

Background: Acute lymphoblastic leukemia (ALL) is a malignant disease that arises from several cooperative genetic mutations in a single B or T lymphoid progenitor. The collaborative work of the last 60 years has led ALL to be a fatal disease in all of the cases, to a curable disease in more than 90% of cases in developed countries, however in Mexico a high percentage of children with ALL have high-risk relapses and the prognosis is less than 16% with conventional treatments only with chemotherapy, the objective of the present study was to determine the survival of patients treated with bone marrow transplant patients with high-risk relapsed ALL

Methods: An observational, analytical and retrospective study was carried out INP patients of either sex from 0 to 18 years old who had received hematopoietic progenitor cell transplantation with a diagnosis of "ALL" and high-risk relapse were included. The patients received an allogeneic transplant with conditioning based on TBI/CFM/VP16: With the statistical program SPSS version 25, descriptive statistics were obtained according to the type of variable. A Kolmogórov-Smirnov test will be performed to fit a normal distribution. Of the qualitative variables, absolute frequencies and percentages were obtained. Survival curves for global and disease-free survival were performed using the Kaplan Meier method and the influence of risk factors will be evaluated using the log-Rank method.

Results: A total of 47 patients undergoing stem cell transplantation with a diagnosis of high-risk relapsed ALL were included, with a predominance of males with a male: female ratio of 3: 1, the minimum age of the patients was 3 years and a maximum of 19 years, in 47% of the cases the transplant was performed after the first relapse, in 89% of the cases the leukemias were precursors B. The overall survival was 79 and the event-free survival was 71 with a 5-year follow-up, among the variables that were analyzed as: Initial risk assigned (0.112),Hypodiploidy (0.133), Development of EICHa (0.242), ALL Ph + (0.312), Year in which the TCPH was carried out (0.348), source cell (0.570), Remission number (0.598), CNS + (0.694), 100% compatibility (0.738), Immunophenotype of ALL at Dx (0.825), Relapse rate (0.911). No statistical significance was found.

Figure 1. Among the 47 patients, a follow-up of between 1 and 114 months was achieved. For the purposes of the survival study, the Kaplan-Meier method established a maximum limit to the follow-up time of 60 months (5 years), obtaining a probability of that patients survive 5 years after HSCT of 0.71.

Conclusions: The survival of children with high-risk relapse ALL in the study was 71% at 5 years compared with the survival of less than 16% of children who received 2nd-line chemotherapy treatment reported by other groups in Mexico.

Disclosure: All authors declare that they have no conflict of interest with the publication of this study.

Cesar Galván-Diaz, Haydee Salazar-Rosales Gerardo Lopez-Hernandez, Nideshda Ramírez-Uribe, Ángeles Del Campo-Martínez, Yadira Melchor-Vidal, Roberto Rivera-Luna, Alberto Olaya-Nieto, Alberto Olaya-Vargas.

P043 Feasibility of myeloablative ALLO-SCT from haploidentical donor in AML patients older than 70 years: A single-centre experience

K. Barbullushi ¹, F. Cavallaro¹, F. Serpenti¹, A. Bosi¹, C. De Magistris¹, N.S. Fracchiolla¹, G. Galassi¹, F. Grifoni¹, M.C. Goldaniga¹, M.C. Mocellin¹, G.N. Saporiti¹, M. Sciumè¹, N. Rampi¹, L. Baldini¹, F. Onida¹

¹Fondazione IRCCS Ca’ Granda Ospedale Maggiore Policlinico, Milano, Italy

Background: Median age of acute myeloid leukemia (AML) onset is around 68 years old. Allogeneic hematopoietic stem cell transplantation (allo-SCT), the curative landmark for high-risk AML, is generally not recommended to patients older than 70 years due to higher transplant-related morbidity and mortality. However, with recent improvements in transplant procedures, allo-SCT could be offered to thoroughly selected older patients. Here we report favorable outcome in a series of patients aged ≥70 transplanted from HLA-haploidentical donors following treosulfan-based myeloablative conditioning (MAC).

Methods: We retrospectively collected data of 4 patients older than 70 consecutively transplanted from 11/2019 to 10/2021 at our Centre. The conditioning regimen (TTF) included treosulfan 10 or 12 g/mq from day -6 to day -4, fludarabine 30 mg/mq from day -6 to day -2 and a single dose of thiotepa 5 mg/kg on day -3. Patients underwent allo-SCT from haploidentical donor with peripheral blood as a stem cell source; graft versus host disease (GvHD) prophylaxis included ATG 1.25 mg/kg on days -3 and -2, post-transplant cyclophosphamide (PTCy) 50 mg/mq on days +3 and +4, mycophenolate mofetil (MMF) and cyclosporine (CsA) from day +5. CMV-positive patients underwent prophylaxis with letermovir until day +100.

Results: Patient and transplant characteristics are shown in Table 1. Median time from diagnosis to allo-SCT was 219 days (175-640). Treosulfan dose was 10 g/mq in the 3 patients aged 74-yo and 12 g/mq in the patient aged 71-yo. Median number of days to neutrophil and platelet engraftment was 18.5 (16-22) and 13 (11-23), respectively. Early complications included neutropenic fever (highest grade III), atrial fibrillation (highest grade III) and mucositis (grade II). Two patients developed grade I acute GvHD involving only the skin, fully recovered with low-dose prednisone. One patient developed mild chronic cutaneous GvHD with no indication to treatment. Worsening of cardiac ejection fraction from 52% at baseline to 45% was documented in one patient 400 days post allo-SCT. After a median follow-up of 361 days (51-539), all patients were alive in complete remission, with full donor chimerism.

Table 9 Table 1 Patients characteristics at transplant

Conclusions: Positive outcome of this case series confirms the feasibility of haploidentical myeloablative allo-SCT for AML patients older than 70 years, with no major complications. The TTF conditioning regimen with single administration of thiotepa was very well tolerated. Low dose ATG associated to the classic PTCy/CsA/MMF platform seems to be very effective in preventing both acute and chronic GvHD. Altogether, our experience support the inclusion of fit patients older than 70 years in MAC allo-SCT programs.

Disclosure: Nothing to declare

P044 Allogeneic hematopoietic stem cell transplantation in elderly patients with acute myeloid leukemia: A single center experience

O. Ilhan ¹, G. Yavuz¹, G. Cengiz Seval¹, S. Civriz Bozdag¹, M. Kurt Yuksel^1,1, P. Topcuoglu¹, O. Arslan¹, M. Ozcan¹, T. Demirer¹, G. Gurman¹, M. Beksac¹

¹Ankara University, Ankara, Turkey

Background: The incidence of most hematologic malignancies increases with age. Aging is related with a greater prevalence of impaired functional status and comorbidities. Although cure of malignant and non-malignant hematological diseases is potentially possible with alloHSCT, it could lead to significant transplant-related mortality. Decision making about referral to allo-HSCT in older adults is a challenging task. In this study we aim to present our geriatric allo-HSCTs.

Methods: From 2004 to 2021, 31 patients (age ≥ 60) underwent allo-HSCT in our center included to this retrospective study. Pre-transplant status as well as posttransplant toxicities, complications and outcomes were determined.

Results: Patient characteristics and transplant results are summarized in Table-1. Twenty-three patients were between the ages of 60-65, and 8 patients were over 65 years of age. Neutrophil engraftment (>0.5x109 /L) occurred in a median of 19 days (range: 11-38) and platelet engraftment (20x109 /L) in 24 days (range: 15-36). Post-transplant complications are detailed in the table. Acute graft versus host disease (aGvHd) was occured in 9 patients (29%) and chronic graft versus host disease (cGvHD) seven patients (22%) were diagnosed with a relapse and 1 year relapse-free survival was 45%. The 1-year and 2-year OS were detected as 45% and 19%. At the end of the long-term follow-up of the patients, 20 patients died, the most common cause ofdeath was relapse of the primary disease.

Conclusions: Since increasing number of older patients being diagnosed with hematologic malignancies, this trend of increasing number of allo-HSCT will continue. Tolerability and effectiveness are lesser, toxicity is higher in older adults. Although study population is relatively small, reduced-intensity conditioning and pre-transplant remission status may be related to beter survival. Comprehensive geriatric assessment may be considered prior to alloHSCT for global evaluation.

Disclosure: Nothing to declare.

P045 Long term follow-up after allogeneic stem cell transplantation in pediatric acute myeloid leukemia patients

H. Bouarab¹, M. Benakli ¹, F. Mehdid¹, N. Rahmoune¹, M. Baazizi¹, D. Ait Ouali¹, S. Zerkout¹, F. Louar¹, F. Harieche¹, R.-M. Hamladji¹, R. Ahmed Nacer¹

¹Pierre and Marie Curie Center, Algiers, Algeria

Background: Allogeneic hematopoietic stem cell transplantation (allo-HSCT) in pediatric acute myeloid leukemia (AML) patients (pts) is widely recommended with an HLA identical donor. This retrospective study describes the long-term results of this procedure in a single-center series, among pts whose age is less than 18 years.

Methods: Between September 1998 and December 2020, 161 pts younger than 18 years with AML underwent allo-HSCT. Median age was 11 years (4-17) and sex-ratio (M/F):1. The average time from diagnosis to transplant was 9 months (3-73). At the time of the transplant, 132 pts were in first complete remission (CR1), 21 pts in second CR and 8 pts in active disease. Myeloablative conditioning regimens based on Busulfan were used in 155 pts with Cyclosporine-Methotrexate as prophylaxis of GVHD. Six pts were transplanted from a haploidentical donor with addition of mycophelonate as prophylaxis of GVHD. The grafts used are peripheral blood stem cells in 147 pts with an average rate of CD34 cells:8,07.10⁷/kg (1,5-23,9), bone marrow in 13 pts with an average rate of nucleated cells: 3,33.10⁸/kg, and cord blood in 2 pts with a rate of NC: 4,4.10⁸/kg. At September 2021, the minimal follow-up (FU) was 11 months and maximal FU was 276 months.

Results: Aplasia was observed in all pts with median day of neutrophils engraftment was 15 days (13-29). Eighty thirteen pts (60%) required RBC transfusions (1,4 unit/pt) and 150 pts (97%) needed platelet transfusions (1,7 units/pt). Three pts presented a moderate veino-occlusive disease. Acute GVHD occurred in 44 pts (28%) including 34 (22%) grade II-IV. Chronic GVHD was seen in 53 pts (38%) with extensive form in 39 pts. Twenty-one pts (13%) showed CMV reactivation on average at day 72 (19-237). Forty pts (26%) relapsed (26 pts in CR1, 8 pts in CR2 and 6 pts with blast crisis at the time of the transplant). Disease status before transplant (CR1 vs CR2) affect the incidence of relapse (p:0,05). After follow-up of 103 months (11-276), 91 pts (56,5%) are alive in CR and 70 pts (43,5%) died within 30 pts (18,6%) from TRM (acute GVHD:16, severe infection:9, early rejection :2, capillary leak syndrome:1, kidney failure:2) and 40 from relapse (24,8%). The overall survival (OS) and disease free survival (DFS) are 54% and 53% respectively. CR1 is associated with better EFS in univariate analysis (60% vs 29%, p:0,05).

Conclusions: In our practice, on the absence of cytogenetics and molecular genotyping analysis, allo-HSCT from an HLA matched family donor became the standard of care for treatment of childhood AML. This retrospective study with long-term follow-up shows interesting results; however, monitoring for long-term complications after HSCT needs special consideration.

Disclosure: Nothing to declare

Aplastic Anaemia

P046 Correlation of donor chimerism and outcomes in children with severe aplastic anemia after hematopoietic stem cell transplantation

S. Crowell¹, R. Abu-Arja¹, H. Rangarajan¹, V. Pai¹, J. Stanek¹, R. Bajwa ¹

¹Nationwide Childrens Hospital, Columbus, United States

Background: Routine blood counts and donor chimerism studies are monitored regularly after engraftment in patients with severe aplastic anemia (SAA) following HSCT. Mixed chimerism (MC) may be associated with cytopenia, graft rejection/failure or poor graft function

Methods: This is a retrospective chart review of patients with SAA who underwent allogeneic HSCT at Nationwide Children’s hospital between 2007-2021. Whole blood and sorted chimerism (CD3 and CD33) were performed using PCR-based testing. Mixed chimerism was defined as donor chimerism of 5-95%. Data on patient demographics, transplant details and outcomes were collected in a secure database and results were analyzed using descriptive statistics.

Results: Eighteen patients (10 males) with SAA underwent HSCT, with 14 patients having sufficient chimerism and outcome data to be included in this study. Median age at HSCT was 9 years (range: 4-17); 7 received HSCT from MSD, 5 from MUD and 2 from haploidentical donors. Cyclophosphamide with or without fludarabine, and alemtuzumab or rabbit ATG (n = 10) were the common conditioning regimens with low dose TBI used in 4 patients. At day +30, mean whole blood (WB), CD3 and CD33 donor chimerism were 97%, 90%, and 98%, respectively. While the mean CD33 donor chimerism, stayed >95% at all time points studied, the mean CD3 donor rapidly fell and reached a nadir of 46% (range:11-99%) by day +100 (Fig 1). With continued immunosuppression, the CD3 chimerism gradually increased to 74% (range:48-100%) by day +180 and then stabilized around a mean of 85% (range:62-100%) on follow-up. A similar pattern was observed for patients given either Alemtuzumab or rATG. Overall, mixed chimerism were seen in 7/14 patients (50%) in whole blood, 11/14 (79%) in the CD3 fraction and 2/14 (14%) in CD33 fraction on at least one timepoint post-HSCT. One patient with Down syndrome, died from pneumococcal septicemia but had WB, CD3, and CD33 chimerism of 98, 98 and 99% respectively at 4 years after HSCT. Two patients developed recurrence of SAA at 45 and 21 months after MSD HSCT, had donor chimerism of 79 and 91%, 74 and 90%, and 89% and 100% in WB, CD3 and CD33 fractions respectively at the time of recurrence of SAA. One underwent a successful second HSCT while the other is in planning stages for a second HSCT. Cytopenia was noted in 3/14 (21.4%) patients (excluding the 2 with recurrence of SAA) at a mean of 107 days (range 89-130) after HSCT but fully recovered subsequently. Thirteen patients are alive at the time of this report with a mean follow up of 4 years (range 0.5 to 10).

Conclusions: After HSCT, patients with SAA showed sustained and stable mean CD33 donor chimerism of ≥95% at all time points while the CD3 chimerism reached a nadir of 46% around day +100, before slowly recovering in all patients. More importantly, there was no correlation between CD3 chimerism at any time point after HSCT with conditioning regimen, serotherapy, development of cytopenia, overall survival, graft failure or recurrence of SAA.

Disclosure: All authors have nothing to declare

P049 Long-term outcome in fanconi anemia patients from the italian national database

E. Ricci¹, F. Bagnasco¹, M. Faraci ¹, G. Dell’Orso¹, A. Risitano², P. Farruggia³, A. Zatterale⁴, E. Cappelli¹, A. Todiere⁵, C. Dufour¹, F. Pierri¹

¹Istituto G. Gaslini, Genova, Italy, ²AORN San Giuseppe Moscati Avellino, Avellino, Italy, ³A.R.N.A.S. Ospedali Civico, Di Cristina e Benfratelli, Palermo, Italy, ⁴Formerly ASL Napoli 1, Napoli, Italy, ⁵IRCCS Ospedale San Martino, Genova, Italy

Background: Bone marrow failure (BMF) is the main cause of morbidity and mortality in Fanconi Anemia (FA) patients. Hematopoietic Stem Cell Transplantation (HSCT) is the only therapeutic option capable to durably correct hematopoiesis. However, HSCT also negatively affect development of post-transplant solid tumors namely especially head and neck or lower gynecological squamous-cell carcinoma (SCC). A previous analysis of 97 FA patients from the Italian national database (Svahn J et al Am J Hematol 2016), demonstrated that the majority of patients developed cytopenia during the follow-up but 32 subjects maintained a mild/moderate cytopenia without need for HSCT. Overall survival (OS) of the whole original cohort was 74.2%.

Methods: This is an extension study in which we evaluate, over a longer follow-up (ended on 31/05/2021), the cohort of 32 FA patients who had a marginally compromised hematopoiesis in the original study. Demographic data, presence, grade and trend of cytopenia, defined according to international guidelines, HSCT characteristics and the development of secondary cancer were recorded.

Results: Of the 32 patients evaluated cytopenia was present in 90.6% at diagnosis. At the time of the first pathological blood count, 53.1% had mild cytopenia, 40.6% moderate and 6.3% severe; at the end of the follow up of the original study 9.4% had no cytopenia, 43.8% mild, 31.2% moderate and 15.6% severe. Among 32 patients only 26 were evaluable with a median follow-up of 9.5 years (IQR 6.25-12.75, range 0-27.0). 38.5% (10/26) maintained stable cytopenia (1 have no cytopenia, 6 mild, 2 moderate, 1 severe), in 11.5% (3/26) cytopenia worsened, while 50% (13/26) underwent HSCT.

Indications for HSCT were: progression of BMF (10/26, 76.9%) clonal evolution (2/26), unknown (1/26). Donor type was: matched-sibling (MSD) (46.2%), alternative (AD) (23.1%) or haplo (15.4%). The source of cells was bone marrow (38.5%), peripheral blood (30.8%) and bone marrow + cord blood from the same donor (15.4%).

One patient developed a uterine cervix SCC and two women a precancerous lesion (in both cases HPV-related low-grade squamous intraepithelial lesions of uterine cervix). They were all FANCA mutated and none underwent HSCT. The 5.8 years OS of this cohort was 92.3% (2/26 died for transplant-related mortality).

Conclusions: This extension study confirms that in FA cytopenia tends to progress overtime but that a proportion of patients maintain a stable level of hematopoiesis. These data outline the need for a close and prolonged follow-up to identify the more suitable moment to transplant FA patients, considering the different variables, like the available donor, the HLA matching and the patient’s comorbidities.

Disclosure: Nothing to declare

P050 Haploidentical stem cell transplantation with post-transplant cyclophosphamide in patients with aplastic anemia: A gatmo-tc experience

A.L. Basquiera ¹, P.G. Longo², G.A. Ferini³, A. Cia⁴, S. Cruset⁵, M.L. Rizzi⁶, M.V. Suen¹, P. Duarte⁷, M. Cattaneo⁸, G. Kusminsky², J. Bordone⁵, G. Jaimovich⁴

¹Hospital Privado Universitario de Córdoba, Córdoba, Argentina, ²Hospital Universitario Austral, Pilar, Argentina, ³Hospital Italiano de Buenos Aires, Buenos Aires, Argentina, ⁴Fundación Favaloro, Buenos Aires, Argentina, ⁵Hospital de Alta Complejidad El Cruce, Florencio Varela, Argentina, ⁶Sanatorio Allende, Córdoba, Argentina, ⁷CEMIC, Buenos Aires, Argentina, ⁸CETRAMOR, Rosario, Argentina

Background: Aplastic Anemia is a benign disease associated with significant morbidity and mortality in severe forms. For those patients without an HLA-identical donor or not responding to immunosuppression treatment, a related HLA-haploidentical donor is an immediately available donor source.

Methods: Retrospective study of patients with a diagnosis of severe or very severe aplastic anemia who underwent haploidentical stem cell transplantation (Haplo-SCT) using post-transplant cyclophosphamide (PT-Cy) between 2016 and 2021 from Argentine centers affiliated to GATMO-TC. We analyzed overall survival, the cumulative incidence of acute and chronic graft versus host disease (aGVHD and cGVHD), and graft failure.

Results: A total of 20 patients were reported (median age 19; IQR 12-27; 65% below 21 years), without response to immunosuppression treatment (n = 18).

The median interval from diagnosis to transplant was 9.72 months (IQR 5.5 – 14.9) and the median pre-transplant serum ferritin level was 2956 ng/ml (IQR 1532 - 3355).

Donors (median age 32.8 years) were: parents (n = 12; 60%), siblings (n = 7; 35%) and children (n = 1; 5%). Stem cell source was peripheral blood (n = 11; 55%) and bone marrow (n = 9; 45%). The conditioning regimen was predominantly a combination of fludarabine, Cy, and low dose total body irradiation (TBI) (n = 15; 75%). All patients received PT-Cy, antithymocyte globulin was used in 11 patients (55%), and all patients received either tacrolimus (n = 12; 60%) or cyclosporine (n = 8; 40%).

The cumulative incidence at day 28 of neutrophil recovery was 95% (median 16 days), and day-28 platelet recovery of more than 20,000/microliters and 50,000/microliters was 80% (median 18.5 days) and 65% (median 24.5 days), respectively. Two patients developed primary graft failure and secondary graft failure, respectively; both received bone marrow as a stem cell source. The cumulative incidence of aGVHD at day 100 was 42.3% (Grade I: 12.5%; Grade II: 75%; y Grade III: 12.5%); with a trend to a higher rate with peripheral blood (54.5% vs 27.5%; p = 0.074). One-year cumulative incidence of cGVHD was 26.1% (Mild: 57.6%; Moderate: 11.1%; and Severe: 33.3%). Two-year overall survival was 84.4% (CI95% 59-95). Variables associated with better survival were: age below 21 years (100% vs 57%; p = 0.020), tacrolimus-based prophylaxis (100% vs 62%; p = 0.041) and conditioning regimen Baltimore-type vs others (93% vs 60%; p = 0.079). Death causes were: refractory GVHD (n = 1), primary graft failure and sepsis (n = 1).

Conclusions: Haplo-SCT with PT-Cy is an option for patients without response to immunosuppression treatment and without an HLA-identical donor. Advantages such as the widespread availability and a lower cost of graft acquisition compared with other alternatives sources make Haplo-SCT the best choice. Some key factors such as conditioning regimen and GVHD prophylaxis might have an impact on the results of the procedure.

Disclosure: Nothing to declare.

P051 Hematopoietic stem cell transplantation (HSCT) to treat pure red cell aplasia (PRCA)

S. Zhou ¹, M. Xiong², J. Zhu², W. Ling², H. Wang², G. Wang²

¹Bone Marrow Transplantation Beijing Ludaopei Hospital, Beijing, China, ²Bone Marrow Transplantation, Hebei Yanda Ludaopei Hospital, Langfang, China

Background: Pure red cell aplastic anemia (PRCA) is a heterogeneous syndrome characterized by a simple erythroid hematopoietic disorder. The main clinical symptom is anemia. Most patients become transfusion dependent, and are at considerable risk for infection and of the syndrome to evolve into leukemia. At present, about 50% of patients can achieve remission,mainly through immunosuppressive therapy. Hematopoietic stem cell transplantation (HSCT) has also been used in patients who are unresponsive to glucocorticoids, but data on outcomes on these patients are scarce in China.

Methods: We retrospectively analyzed the clinical characteristics of 6 patients with PRCA who underwent HSCT in our hospital from May 2019 to November 2021. Two patients had a congenital form of PRCA and 4 patients had acquired PRCA. All patients were unresponsive to glucocorticoids prior to HSCT. The male to female ratio was 2:4. The median age was 30.5 months (range: 17-42 months). The median disease course from diagnosis to transplant was 29 months (range: 13-42). Four patients received umbilical cord blood-HSCT. The conditioning regimen was fludarabine (40mg/m²/d×5days IV) + Ara-C (2g/m²/d×5days IV) + Bu(0.8mg-1.2mg/Kg Q6h×4days) + cyclophosphamide (1.8g/m²/d×2days) +ATG (thymoglobuline, Sanofi, 1.25mg/Kg/d×2days). One patientunderwent a matched unrelated donor (MUD) HSCT. Another patientunderwent a haplo-HSCT with the following conditioning regimen: fludarabine (40mg/m²/d×3days IV) + Ara-C (2g/m²/d × 3days IV) + Bu(0.8mg-1.2mg/Kg Q6h×4days) + cyclophosphamide (1.5g/m²/d×2days) +ATG (thymoglobuline, Sanofi, 1.25mg/Kg/d ×4days). For GVHD prophylaxis, we used CsA/tacrolimus plus sMTX for all of the patient.

Results: All 6 patients tolerated the pre-treatment well. The total implantation rate was 100%. The median time of neutrophil engraftment was 12.5 days (range: 11-21 days). The median time to platelet engraftment was 18.5 days (range: 11-75 days). During the median follow-up period of 25.5months (range: 6-30 months), all patients had complete donor chimerism and became transfusion-independent by subsequent normalization of hemoglobin levels. The incidence of CMV was 50% (3 of 6 patients). Following transplantation, EBV DNA load was undetectable among all of patients who were infected with EBV. Grade II aGVHD occurred in 1 patients (16.7% incidence) . One patients had cGVHD. All patients survived, with an overall survival rate of 100%.

Conclusions: In our small cohort of 6 PRCA patients, we demonstrate that HSCT has a high implantation rate and overall survival rate, and may become a viable therapeutic option for these patients. Nevertheless, because of the risk of transplant-related death, careful selection of HSCT candidates and the optimal timing of HSCT is necessary. Future studies need to examine the PRCA patient characteristics that are likely to result in a successful HSCT as well as the optimal time for a patient to undergo transplantation.

Disclosure: Nothing to declare

Autoimmune Diseases

P052 NT-proBNP measurements during cyclophosphamide conditioning in patients undergoing autologous haemopoietic stem cell transplantation for systemic sclerosis suggest increased cardiac strain

R. Penglase ¹, E. Brenu², H. Englert¹, S. Milliken¹, B. Withers¹, N. Karki¹, J. Perram¹, H. Tao¹, L. Girgis¹, A. Jabbour¹, E. Kotlyar¹, D. Ma¹, J. Moore¹

¹St Vincent’s Hospital, Sydney, Australia, ²University of Notre Dame, Sydney, Australia

Background: Autologous haematopoietic stem cell transplantation (AHSCT) is a well-established therapeutic option for severe systemic sclerosis (SSc), however application is limited by treatment-induced cardiotoxicity apparent during conditioning, particularly in the setting of established cardiac disease. In this study we examined the impact of cyclophosphamide conditioning therapy on cardiac enzymes over the transplantation period.

Methods: The records of all patients from 2017 who underwent AHSCT for SSc at our hospital were retrospectively reviewed to identify those with cardiac enzyme measurement pre- and during conditioning therapy. All patients who received treatment were enrolled in AHSCT clinic trials approved by the St Vincent’s Hospital ethics committee. Statistical analysis was performed by one way analysis of variance (ANOVA) or Mann-Whitney U test.

Results: Chart review identified 22 patients with measurement of proBNP and/or troponin I during conditioning. Four patients underwent a repeat AHSCT procedure, giving a total of 26 conditioning episodes. All patients received cyclophosphamide (Cy) conditioning at doses between 50-200mg/kg divided over 4 days (D-5 to D-2); patients who received <200mg/kg had either pre-existing cardiac disease or other significant risk factors. Patients who received lower doses of Cy conditioning had significantly higher NTproBNP at baseline compared to the standard dose group (265 vs 67.5 ng/L, p < 0.01). In all patients, NTproBNP was significantly increased from D-5 to D-1 compared to baseline (p < 0.01) with a peak at D-1. Peak NTproBNP was higher in the lower dose group compared to the standard dose group, however this was not statistically significant. The relative increase of NTproBNP was higher in the standard dose group (1329% vs 271%), however this did not reach statistical significance (p = 0.09). Following transplantation, the median NTproBNP returned to baseline. There was no significant changes in troponin I during Cy conditioning.

Conclusions: In summary, these data suggests that Cy conditioning induces markers of cardiac stress in an already high-risk population. Further data are needed to explore the relationship between relative NTproBNP increase during conditioning and Cy dose. Measures to reduce cardiovascular risk during the conditioning period are warranted.

Clinical Trial Registry: ACTRN12617000216314 https://www.anzctr.org.au/Trial/Registration/TrialReview.aspx?id=371990.

Disclosure: Nothing to declare

P053 Residual recipient t-cells are responsible for severe lupus nephritis in rals-associated lupus nephritis persistence after allogeneic, matched sibling donor transplant

S. Senthil ¹, R. Hanasoge-nataraj¹, D. Bonney¹, H. Campbell¹, P. Riley¹, M. Shenoy¹, S. Hughes¹, R. Wynn¹

¹Royal Manchester Children’s Hospital, Manchester, United Kingdom

Background: RAS-associated lymphoproliferative syndrome (RALS) is a relatively new entity causing defects in intrinsic pathways of apoptosis. Although management has been mainly with immunosuppression, we report haematopoietic stem cell transplant for refractory autoimmunity and for lupus-associated nephritis. We report persistent lupus nephritis despite achievement of fully donor myeloid and B-lymphoid engraftment and speculate that residual recipient T-cells are responsible for persistent disease manifestations.

Methods: Retrospective review of the patient’s case records and laboratory investigations was undertaken.

Results: An 18 months old boy presented with autoimmune haemolytic anaemia and immune thrombocytopenia with leucocytosis and monocytosis. He had a gross splenomegaly, a leucoerythroblastic blood picture and raised fetal haemoglobin raising concerns of underlying Juvenile myelomonocytic leukemia (JMML). Further investigations revealed a high titre of anti-double stranded DNA antibodies and antinuclear antibodies. Investigations for Autoimmune lymphoproliferative syndrome (ALPS) were negative. Bone marrow assessment revealed hypercellular marrow with no increase in blast population with normal cytogenetic studies. Next generation sequencing from peripheral blood revealed a somatic gain of function mutation of NRAS leading to a diagnosis of RALS. The immune cytopenias were refractory to treatment with steroids and multiple immunosuppressants. In view of refractory autoimmunity, he was treated with a matched sibling donor(MSD) bone marrow transplant with Fludarabine, treosulfan and thiotepa conditioning at 30 months of age. He engrafted at 22 days after transplant with a donor chimerism of 90%. However, there was a rapid loss of donor chimerism with concurrent autologous haematopoietic reconstitution. Consequently, he had recurrence of primary disease manifesting as monocytosis with splenomegaly alongside lupus nephritis.On account of refractory and severe, biopsy-proven lupus nephritis induced by the underlying RALD, he had a second MSD bone marrow transplant from a different sibling at 38 months of age with Fludarabine, busulfan and alemtuzumab conditioning. He remains engrafted with 100% donor myeloid and B-lymphoid chimerism, but with persistent rising mixed T cell chimerism. He has relapsed, persistent lupus nephritis and a recurrently raised titre of anti-DS-DNA antibodies, despite treatment with steroids, immunosuppresants, Rituximab, Bortezomib. After a diligent multidisciplinary input, it is decided to use Daratumomab, a CD38 directed monoclonal antibody in an attempt to eradicate the recipient T cells, which is inferred to be the principal cause of the underlying lupus nephritis.

Conclusions: HCT for treatment of autoimmunity in RALS has not been documented in literature to the best of our knowledge. Further data is needed to ascertain the unique complications associated with HSCT in RALS.While mixed T cell chimerism does not affect outcome in non malignant transplants in general, it is proposed that residual inflammatory activated autologous cells here drive persistent disease manifestations, and that full donor T cell chimersim is required to fully control disease.

Disclosure: Nothing to declare.

P054 Encephalitis and thrombotic microangiopathy after mrna sars-cov2 vaccine in a patient with chronic GVHD: A case report

C. Mayor Bastida ¹, A. Puchol Crespo¹, S. Diaz Lopez¹, A. Figuera Alvarez¹, A. Alegre Amor¹, B. Aguado Bueno¹

¹Hospital La Princesa, Madrid, Spain

Background: Hematopoietic stem cell transplantation (HCT) recipients have a high risk of mortality with COVID-19 because of severe immune dysregulation¹. Several vaccines have been developed whose safety has been proven, however, infrequent complications include neurological complications² or autoimmune phenomena³. Moreover, there are still scarce data on its safety and tolerability in recipients of allogenic hematopoietic stem cell transplant⁴.

Methods: We report a case of acute encephalopathy and subsequent thrombotic microangiopathy within two weeks of receiving the first dose of mRNa SARS-COV2 vaccine (Moderna).

Results: 68-year-old male recipient of allogenic matched unrelated donor transplantation in 2009 because of AML. Since then in complete remission.

As postransplant complications he presented extensive severe chronic sclerotic cutaneous, ocular and pulmonary chronic graft-versus-host disease (cGVHD) that required immunosuppressive treatment with systemic steroids and photopheresis for several years. In addition to chronic kidney disease and adrenal insufficiency for which he was under treatment with steroids until now.

He presented to the emergency department with motor aphasia, generalized tremor and fever. The patient had received the first dose of mRNa SARS-COV2 vaccine (Moderna) 20 days earlier. In laboratory tests, hemoglobin 15 g/dL, platelets 212,000/mm³ and leukocytosis of 19,920/mm³ with neutrophilia and lymphocytosis. CT brain scan and lumbar puncture were performed whitout significant alterations. We started antibiotic therapy with Ceftazdime, Ampicillin, Vancomycin and Acyclovir. The study was extended with brain MRI and electroencephalogram, which ruled out ischemic phenomena. Negative onconeurolane and PF4–heparin antibodies. Everything suggested that the most likely cause was acute post-vaccinal encephalitis. We started treatment with high dose steroids and plasma replacements with symptom improvement 48 hours later. All microbiological cultures were negative.

One week after admission, anemia and thrombopenia were observed, reaching a platelets 40,000/mm³ with worsening renal function, increase LDH up to 415U/L, uncontrolled hypertension, 4% of schistocytes in blood smears and ADAMTS13 within normal range. Bone marrow study was performed and was in complete remission. Steroids 1 mg/kg/12h and immunoglobulins were administrated with initial response the first week with subsequent worsening after 10 days. Plasma exchange was restarted with clinical and analytical response after two weeks: recovery of thrombopenia, optimal blood presure control and disappearance of schistocytes.

All this established a possible diagnosis of thrombotic microangiopathy secondary to post-vaccinal autoimmune phenomena.

Conclusions: Hematopoietic transplant recipients who developed COVID-19 have worse prognosis. Vaccination of these patients is one of the best preventive strategies. However, the efficacy and safety of these vaccines in transplant recipients is currently lacking^4,5 The most frequently hematological adverse effects are cytopenias and worsening or establishment of GVHD⁶.

This is a patient with severe cGVHD who, after first dose of vaccine, presented with encephalopathy without infectious or ischemic cause, with favourable outcome after immunosuppressive treatment and plasma exchanges. One week later, he presented thrombopenia, anemia, impaired renal function and schistocytosis; test to rule out vaccine induced immune thrombotic thrombocytopenia (VITT) was negative.

So we conclude that it was an autoimmune thrombotic microangiopathy, reflecting a complex inumnologic process in patient with cGVHD with the vaccine as the only identified trigger factor.

Disclosure: Nothing to declare

CAR-based Cellular Therapy – Clinical

P055 3rd-generation CD19-directed chimeric antigen receptor t-cells (carts) for relapsed/refractory chronic lymphocytic leukemia (cll) – results from an academic phase 1/2 trial (hd-car-1)

P. Derigs ¹, A. Kunz¹, P. Dreger¹, A. Schmitt¹, M.-L. Schubert¹, M. Brüggemann², H. Bernhard³, G. Kobbe⁴, A. Lindemann⁵, M. Rummel⁶, L. Wang¹, B. Michels¹, P. Waldhoff¹, F. Korell¹, P. Pavel⁷, A.D Ho¹, C. Müller-Tidow¹, M. Schmitt¹

¹University Hospital Heidelberg, Heidelberg, Germany, ²University Hospital Kiel, Kiel, Germany, ³Klinikum Darmstadt, Darmstadt, Germany, ⁴University Hospital Düsseldorf, Düsseldorf, Germany, ⁵Onkologie in Ettlingen, Ettlingen, Germany, ⁶University Hospital Giessen, Giessen, Germany, ⁷Institute for Clinical Transfusion Medicine and Cell Therapy (IKTZ), Heidelberg, Germany

Background: CD19-directed CART therapy has become a standard of care in various B-cell malignancies. However, application of CD19 CARTs in CLL has been hampered by the disease-inherent T-cell dysfunction. Here, we show preliminary results obtained with HD-CAR-1, a 3^rd generation CD19-directed CART, in patients with high-risk r/r CLL.

Methods: HD-CAR-1 is an investigator-initiated trial evaluating efficacy and safety of escalating doses of CD19-directed CARTs comprising CD28 and 4-1BB as costimulatory molecules in patients with advanced B-cell malignancies after fludarabine/cyclophosphamide lymphodepletion. Leukapheresis, manufacturing, administration, patient monitoring and follow-up were all conducted in-house at the Heidelberg University Hospital. Patients with CLL were eligible if they had failed chemoimmunotherapy and at least one pathway inhibitor and/or alloHCT.

Results: Between Oct 2018 and Nov 2021, 32 patients were enrolled of whom seven had CLL. Patients with CLL had a median age of 62 years and had received two to ten prior treatment lines. All patients were r/r to therapy with at least one pathway inhibitor, and three patients were in addition r/r to alloHCT. TP53 abnormalities were present in six of seven patients. Disease status at lymphodepletion was CR in three patients, PR in two patients, SD in one patient and PD in one patient. Despite heavy pretreatment, leukapheresis yielded sufficient T-cell numbers for production in all instances. CART manufacturing was successful for all seven patients. Dose levels administered were I ( = 0.1x10⁷ CARTs/m²) in one patient, II ( = 0.5x10⁷ CARTs/m²) in one patient, and V ( = 10x10⁷ CARTs/m²) in five patients. Rapid CART expansion was observed in four of five patients evaluable so far. Peak levels ranged between 37,792 and 369,756 copy numbers/µg PBMC DNA and correlated with administered CART dose level. Toxicity was moderate with a single case of CRS > G2 and no severe neurotoxicity. However, prolonged G4 neutropenia occurred in one of five patients with ANC recovery on day +32. Responses were observed in all five patients evaluable for response with CRs in three patients treated at dose level V.

Conclusions: Homebrewed 3^rd generation HD-CAR-1 CART could be successfully generated for heavily pretreated patients with high-risk CLL and exerted a promising safety and efficacy profile.

Clinical Trial Registry: ClinicalTrials.gov Identifier: NCT03676504

Disclosure: P.De.: received an honorarium for a scientific presentation by MSD. M.S.: funding for collaborative research from Apogenix, Hexal and Novartis, travel grants from Hexal and Kite, financial support for educational activities and conferences from bluebird bio, Kite and Novartis, board member for MSD and (co-)PI of clinical trials of MSD, GSK, Kite and BMS, as well as co-Founder and shareholder of TolerogenixX Ltd. P.Dr.: consultancy for AbbVie, AstraZeneca, Gilead, Janssen, Novartis, Riemser, Roche; speakers bureau for AbbVie, Gilead, Novartis, Riemser, Roche; research support from Neovii and Riemser. C.M.-T.: consultancy Advisory Board for Pfizer and Janssen, and has received grants and research support from Pfizer, Daiichi Sankyo, BiolineRx and Bayer AG. A.S.: travel grants from Hexal and Jazz Pharmaceuticals, research grant from Therakos/Mallinckrodt and co-founder of TolerogenixX LtD. M.-L.S.: consultancy for Gilead. All other authors report no potential conflicts of interest.

P056 Cost-effectiveness of axicabtagene ciloleucel as second-line therapy for patients large b-cell lymphoma (lbcl) in the united states

M.-A. Perales¹, J. Kuruvilla², J. Thornton Snider³, S. Vadgama³, R. Blissett⁴, F. El-Moustaid⁴, N. Smith⁴, A. Patel³, P. Johnston ⁵

¹Memorial Sloan Kettering Cancer Center, New York, United States, ²University of Toronto, Toronto, Canada, ³Kite Pharmaceuticals, Santa Monica, United States, ⁴Maple Health Group, LLC, New York, United States, ⁵Mayo Clinic, Rochester, United States

Background: ZUMA-7 (NCT03391466) is a global, randomized, Phase 3 trial of axicabtagene ciloleucel (axi-cel), an autologous anti-CD19 chimeric antigen receptor T-cell (CAR T) therapy, vs. standard of care (SoC: salvage chemoimmunotherapy followed by high-dose therapy with autologous stem cell rescue [auto-SCT] for responders) in second-line large B-cell lymphoma (2L LBCL). Axi-cel demonstrated a statistically significant and clinically meaningful improvement in event-free survival, and despite 56% of the SoC arm receiving third-line (3L) CAR T therapy, a trend toward improved OS was observed. This study estimated the cost-effectiveness of axi-cel versus SoC from a third-party US payer perspective in the 2L setting.

Methods: We developed a three-state partitioned-survival model to estimate lifetime cost and benefits. Health care resource use, adverse event (AE) rates, and survival data were taken from the ZUMA-7 trial where possible, costs (including acquisition, administration, monitoring, auto-SCT, 3L treatment [including 3L CAR T after SoC treatment], and AEs) from published sources (in 2021 USD), and utilities from the literature. Long-term EFS and OS were estimated using mixture cure modelling methods. A 3% discount rate was applied to costs and health effects. The model estimated expected life years (LYs), quality-adjusted life years (QALYs), total costs, and the incremental cost-effectiveness ratio (ICER). Additional model outputs included health state occupancy, spending on 2L/3L treatments and granular costs. One-way and probabilistic sensitivity analyses were performed to test model robustness.

Results: The model projected median OS was 59 months for the axi-cel arm and 25 months for the SoC arm (Figure 1). Incremental LY and QALY gains for axi-cel versus SoC were 1.34 and 1.37, respectively. The discounted incremental cost for axi-cel versus SoC was $119,055. Despite the higher upfront treatment costs with axi-cel, the high cost of 3L treatment in the SoC arm due to CAR T use was one key cost category that reduced the difference in cost between the two arms (axi-cel: $144,281; SoC: $373,162; difference: -$228,341). Incremental costs and QALY differences resulted in an ICER of $87,026/QALY versus SoC. At a willingness-to-pay threshold of $150,000/QALY, probabilistic sensitivity analysis demonstrated that axi-cel has a 72% probability of being cost-effective versus SoC.

Figure 1. Projected 5-Year Survival Outcomes for Axi-Cel and SoC

 

Table 1. Discounted Cost-Effectiveness Results

	LYs	Costs	QALYs
Axi-cel	9.14	$683,698	7.08
SoC	7.80	$564,642	5.71
Incremental	1.34	$119,055	1.37
Incremental cost effectiveness ratio, axi-cel vs. SoC			$87,026

Abbreviations: Axi-cel: axicabtagene ciloleucel; SoC, standard of care; LYs, life-years; QALYs, quality-adjusted life-years

Conclusions: Findings from this study suggest a sizable improvement in quality and length of life after axi-cel compared to SoC. While incremental costs are higher with 2L CAR T use, the offsets in 3L CAR T use lead to a limited incremental cost difference resulting in a highly cost-effective ICER by US standards. In addition to meaningfully improving key clinical endpoints, axi-cel is a cost-effective treatment option that can address an important unmet need.

Clinical Trial Registry: Not applicable

Disclosure: JTS, SV, and AP are employees and shareholders of Kite Pharmaceuticals.

FE, RB, and NS received consulting fees from Kite Pharmaceuticals.

MP: employment with Memorial Sloan Kettering Cancer Center; honoraria from AbbVie, Astellas, Bellicum, Celgene, Bristol Myers Squibb, Incyte, Karyopharm, Kite, a Gilead Company, Miltenyi Biotech, MorphoSys, Nektar Therapeutics, Novartis, Takeda, VectivBio AG and Vor Biopharma; consultancy or advisory role for Merck, Omeros, OrcaBio; research funding from Incyte, Kite, a Gilead Company, and Miltenyi; and other relationships with DSMB, Cidara Therapeutics, Medigene, Sellas Life Sciences and Servier.

JK: honoraria from Amgen, AstraZeneca, Bristol Myers Squibb, Celgene, Gilead, Janssen, Karyopharm, Merck, Novartis, Roche, and Seattle Genetics; consultancy or advisory role for AbbVie, Bristol Myers Squibb, Gilead, Karyopharm, Merck, Roche, and Seattle Genetics; and research funding from Roche and Janssen.

PJ: nothing to disclose.

P057 Predicting grade 2-4 crs with the modified easix (measix) score in patients with nhl treated with anti cd19 car-t cells

E. Galli ^1,2, A. Di Rocco³, F. Sorà^1,2, F. Autore¹, M.A. Limongiello¹, I. Innocenti¹, S. Giammarco¹, E. Metafuni¹, U. La Rocca³, W. Barberi³, S. Pepe³, M. Ansuinelli³, L. Laurenti^1,2, A. Bacigalupo^1,2, P. Chiusolo^1,2, A.P. Iori³, M. Martelli³, S. Hohaus^1,2, S. Sica^1,2

¹Dipartimento di Diagnostica per Immagini, Radioterapia Oncologica ed Ematologia, Fondazione Policlinico Universitario A. Gemelli IRCCS, Roma, Italy, ²Sezione di Ematologia, Dipartimento di Scienze Radiologiche ed Ematologiche, Università Cattolica del Sacro Cuore, Rome, Italy, ³Dipartimento di Medicina Traslazionale e di Precisione, Università di Roma Sapienza, Rome, Italy

Background: Prediction and management of CAR-T cells specific toxicities, mainly cytokine release syndrome (CRS) and immune effector cell–associated neurotoxicity syndrome (ICANS), represent a challenge for physicians. An emerging role is being assigned to the interaction between inflammation and endothelium. In the setting of allogeneic stem cells transplantation, Endothelial Activation and Stress Index (EASIX) can predict endothelial impairment and patients outcomes. We aimed to assess the predictive value of a modified EASIX (mEASIX) towards occurrence of CRS.

Methods: m-EASIX was calculated as described by Pennisi et al (BloodAdv 2021) as [CRP (mg/dL) x LDH (mg/dL)/ platelets count (109 cells/L)]; we applied log transformation using base 2 (log2) in order to reduce skewness. We retrospectively analyzed 33 patients with DLBCL/PMBL treated in the two adults CAR-T centers in Rome from 2019 to 2021 both with tisa-cel and axi-cel. mEASIX was assessed at baseline, and 2 and 4 days after CAR-T cells infusion. We then explored the role of procalcitonin and the ability of mEASIX to predict outcomes.

Results: Seven patients had no CRS, seven had a grade 1 CRS, while 19/33 (56%) patients had grade 2-3 CRS. Patients with grade 2-4 CRS had higher mEASIX at baseline (median -0.9 vs 4.5, p > 0.001) and at day 0, 2 and 4. In order to assess if mEASIX calculated on day 2 or 4 after CAR-T cells infusion could predict the development of a grade 2-4 CRS on the same day, we performed a ROC analysis and identified that mEASIX of 6.4 had 100% sensitivity and 71% specificity in predicting grade 2-4 CRS. An mEASIX of 6.4 or more at day 2 or 4 had associated with grade 2-4 CRS in 27% of cases during the same day (vs 2% among patients with mEASIX lower than 6.4, p = 0.002). Moreover, higher mEASIX during day 2 and 4 also predicted CRS 2-4 anytime during hospitalization. Procalcitonin (PCT) was not different in patients with CRS graded 0-1 vs 2-4 (0.16 vs 0.21 ng/ml, p = 0.11). However, patients with PCT > 0.5 ng/ml had higher mEASIX (median, 4,6 vs 7,8, p = 0,001).Patients with higher mEASIX (>6.4) were more likely to develop grade 3-4 cytopenia between day 30 and 90. Progression free survival was similar both for patients who experienced grade 0-1 vs 2-4 CRS (p = 0.58) and for patients with mEASIX higher or lower than 6.4 at any timepoint.

Conclusions: In this analysis, anyway, we confirmed that baseline mEASIX correlated with higher risk for developing grade 2-4 CRS. Nevertheless, patients with higher mEASIX had also higher procalcitonin, thus infectious etiology of hyperpyrexia still needs to be carefully investigated when CRS is suspected. With the limitations of our study, we were not able to confirm the correlation between mEASIX and ICANS and PFS as reported elsewhere. We identified a daily cut-off of mEASIX as able in forecasting the development of a CRS of grade 2-4; this information could alarm the physician and lead to intensified patients monitoring before severe CRS occurrence, possibly facilitating an immediate intervention.

Disclosure: Nothing to declare.

P058 Long-term (5 year) overall survival in zuma-1, the pivotal study of axicabtagene ciloleucel (axi-cel) in patients with refractory large b-cell lymphoma (LBCL)

C.A. Jacobson ¹, F.L. Locke², A. Ghobadi³, D.B. Miklos⁴, L.J. Lekakis⁵, O.O. Oluwole⁶, Y. Lin⁷, B.T. Hill⁸, J.M. Timmerman⁹, A. Deol¹⁰, P.M. Reagan¹¹, P. Stiff¹², I.W. Flinn¹³, U. Farooq¹⁴, A.H. Goy¹⁵, J. Muñoz¹⁶, T. Siddiqi¹⁷, R.R. Shen¹⁸, A.A. Bot¹⁸, J. Dong¹⁸, K. Singh¹⁸, C. Spooner¹⁸, R. Karalliyadda¹⁸, J.J. Kim¹⁸, Y. Zheng¹⁸, S.S. Neelapu¹⁹

¹Dana-Farber Cancer Institute, Boston, United States, ²Moffitt Cancer Center, Tampa, United States, ³Washington University School of Medicine, St. Louis, United States, ⁴Stanford University School of Medicine, Stanford, United States, ⁵Sylvester Comprehensive Cancer Center, University of Miami Health System, Miami, United States, ⁶Vanderbilt-Ingram Cancer Center, Nashville, United States, ⁷Mayo Clinic, Rochester, United States, ⁸Cleveland Clinic Foundation, Cleveland, United States, ⁹UCLA David Geffen School of Medicine, Los Angeles, United States, ¹⁰Karmanos Cancer Center, Wayne State University, Detroit, United States, ¹¹University of Rochester School of Medicine, Rochester, United States, ¹²Loyola University Chicago Stritch School of Medicine, Maywood, United States, ¹³Sarah Cannon Research Institute and Tennessee Oncology, Nashville, United States, ¹⁴University of Iowa, Iowa City, United States, ¹⁵John Theurer Cancer Center, Hackensack University Medical Center, Hackensack, United States, ¹⁶Banner MD Anderson Cancer Center, Gilbert, United States, ¹⁷City of Hope National Medical Center, Duarte, United States, ¹⁸Kite, a Gilead Company, Santa Monica, United States, ¹⁹The University of Texas MD Anderson Cancer Center, Houston, United States

Background: Axi-Axi-cel, an autologous anti-CD19 chimeric antigen receptor (CAR) T-cell therapy, is approved for treatment of patients with relapsed/refractory LBCL with ≥2 prior therapies. In the 2-year analysis of ZUMA-1 (NCT02348216), the objective response rate (ORR) was 83%, with a 58% complete response (CR) rate (Locke et al. Lancet Oncol. 2019). After ≥4 years of follow-up, median OS was 25.8 months with a 4-year OS rate of 44% (Jacobson C, et al. ASH 2020. #1187). Event-free survival (EFS) has emerged as a robust surrogate of OS in hematologic cancers. Here we report updated survival results from phase 2 of ZUMA-1 after ≥5 years of follow-up, including an exploratory evaluation of the association of 5-year OS and EFS at 12 and 24 months.cel, an autologous anti-CD19 chimeric antigen receptor (CAR) T-cell therapy, is approved for treatment of patients with relapsed/refractory LBCL with ≥2 prior therapies. In the 2-year analysis of ZUMA-1 (NCT02348216), the objective response rate (ORR) was 83%, with a 58% complete response (CR) rate (Locke et al. Lancet Oncol. 2019). After ≥4 years of follow-up, median OS was 25.8 months with a 4-year OS rate of 44% (Jacobson C, et al. ASH 2020. #1187). Event-free survival (EFS) has emerged as a robust surrogate of OS in hematologic cancers. Here we report updated survival results from phase 2 of ZUMA-1 after ≥5 years of follow-up, including an exploratory evaluation of the association of 5-year OS and EFS at 12 and 24 months.

Methods: After leukapheresis, eligible patients received conditioning chemotherapy followed by a target dose of 2×106 anti-CD19 CAR T cells/kg. The primary endpoint was ORR. Comparisons of OS by EFS, defined as the time from axi-cel infusion until progressive disease (PD), initiation of new lymphoma therapy (excluding stem cell transplant [SCT]), or death by any cause, were analyzed via Kaplan-Meier estimates.

Results: As of August 11, 2021, 101 patients received axi-cel with a median follow-up of 63.1 months. With ≥5 years of follow-up, median OS was 25.8 months with a 5-year OS rate of 42.6% (95% CI, 32.8-51.9). The median OS among complete responders was not reached (5-year OS rate, 64.4% [95% CI, 50.8-75.1]). Since the 4-year analysis, 1 death and 1 PD were observed. Median EFS was 5.7 months, with a 12-mo EFS rate of 42.8% (95% CI, 33.0-52.3) and a 24-mo EFS rate of 37.7% (95% CI, 28.3-47.2), respectively. In patients with an EFS event by Month 12 (EFS12; n = 57) versus without EFS12 (n = 44), 5-year OS rates were 5.3% (95% CI, 1.4-13.2) versus 90.9% (95% CI, 77.6-96.5), respectively. In patients with an EFS event by Month 24 (EFS24; n = 62) versus without EFS24 (n = 39), 5-year OS rates were 11.3% (95% CI, 5.0-20.5) versus 92.3% (95% CI, 78.0-97.5), respectively.

Since the 4-year analysis, there have been no new safety signals. Overall, 34 patients (34%) were still alive and received no subsequent therapy (excluding SCT) or axi-cel retreatment; median time to next therapy was 8.7 months, as previously reported. Of treated patients, 59 (58%) have died, primarily due to PD (45%; n = 45), followed by other reasons (9%; n = 9), adverse events (4%; n = 4), and secondary malignancy unrelated to axi-cel (1%; n = 1).

Median peak CAR T-cell levels were numerically higher in patients with ongoing response at Month 60 and were considerably lower in patients who relapsed and nonresponders. A similar trend was observed with CAR T-cell expansion by area under the curve from Day 0 to 28.

Conclusions: In this long-term survival analysis of ZUMA-1 with ≥5 years of follow-up, axi-cel induced long-term OS with no new safety signals. Axi-cel demonstrated longer OS in patients without EFS12 and EFS24 versus patients with events at these timepoints. These data potentially support EFS as a surrogate endpoint for long-term OS in refractory LBCL.

Clinical Trial Registry: Clinical Trial Registry: NCT02348216

https://clinicaltrials.gov/ct2/show/NCT02348216

Disclosure: Caron A. Jacobson: honoraria from Kite, a Gilead Company, Celgene, Novartis, Bluebird bio, Epizyme, Humanigen, Pfizer, Precision BioSciences, Nkarta, Lonza, and AbbVie; consultancy or advisory role for Kite, a Gilead Company, Celgene, Novartis, Pfizer, Humanigen, Precision BioSciences, Nkarta, Bluebird bio, Lonza, Pfizer, Ispen and AbbVie; speakers’ bureau participation for Axis and Clinical Care Options; research funding from Pfizer; and travel support from Kite, a Gilead Company, Celgene, Novartis, Precision Biosciences, Lonza, Pfizer, and Humanigen.

P059 Outcome after relapse post cd19 car t-cells in children and young adults with relapsed/refractory b-cell precursor acute lymphoblastic leukemia (R/R B-ALL)

A. Alonso-Saladrigues ¹, A. Faura Morros¹, A. Català Temprano^1,2,3, S. Pont Martí^1,4,3, E. García Rey¹, M. Camós Guijosa^1,2,3, J.L. Dapena Diaz¹, N. Conde Cuevas¹, I.M. Isola¹, N. Vega-García^3,4, E. Esperanza-Cebollada^4,3, I. Jordan García¹, S. Bobillo Perez¹, L. Alsina-Manrique¹, A. Deyá¹, C. Rivera-Pérez¹, J. Marsal¹, J. Vinent-Genestar¹, C. Llanos Principe⁵, G. Pedrals Portabella¹, G. Morón-Cazalilla¹, M. Juan^6,7, M. Torrebadell^4,3,2, S. Rives^1,3,2

¹Hospital Sant Joan de Déu, Esplugues de Llobregat, Spain, ²Centro de Investigación Biomédica en Red de Enfermedades Raras (CIBERER). Instituto de Salud Carlos III, Madrid, Spain, ³Leukemia and other Pediatric Hemopathies, Developmental Tumors Biology Group. Institut de Recerca Hospital Sant Joan de Déu, Esplugues de Llobregat, Spain, ⁴Hematology Laboratory. Hospital Sant Joan de Déu, Esplugues de Llobregat, Spain, ⁵Fundació Sant Joan de Déu, Esplugues de Llobregat, Spain, ⁶Hospital Clínic, Barcelona, Spain, ⁷Plataforma Inmunoteràpia SJD-Clínic, Esplugues de Llobregat, Spain

Background: CAR-T therapy has improved the outcome of pediatric patients with R/R B-ALL. However, about half of them (41-51%) relapse. There is scarce information about treatment and prognosis in patients relapsing after CAR-T.

The aim of the study is to describe the type of relapse, management and outcome in pediatric and young adults patients with R/R B-ALL relapsing CD19 CAR T-cells.

Methods: We analyzed a cohort of consecutive patients under 25 years relapsing after CAR19 T-cells in a single center from Jan-2016 to Nov-2021.

Results: Fifty-six patients were infused (Tisagenlecleucel: n = 39, ARI_0001-cells: n = 17) and 51 (91%) achieved complete remission (CR) with negative measurable residual disease. Twenty-one (42%) relapsed at a median of 8.9mo (range:2.2-28.4), 5 beyond 1 year. Thirteen patients (62%) had CD19- relapses, all in bone marrow (BM); median 4.9mo (range:2.2-18.6). Eight patients had CD19 + relapses, median 15.1mo (range:3.0-28.4); 3/8 in BM, 2 combined (BM and CNS) and 3 isolated extramedullary disease (EMD) (testes, breast, subcutaneous). All patients with CD19- relapses had persistent B-cell aplasia (BCA) whereas among CD19 + relapses all except two with isolated EMD had lost BCA before relapse. With a median follow-up of 28.6mo, the cumulative incidence of relapse at 24mo was 30.7%(19.5-46.4)

Regarding treatment and outcome of patients relapsing after CAR T-cells (Table1), 3 patients relapsing <1mo from data cut-off were excluded. Among 18 relapsed patients, 8 died from progressive disease (PD). Ten patients achieved a subsequent CR (5 with inotuzumab, 3 with chemotherapy and 2 with blinatumomab). Two died from PD; 7/10 were bridged to HSCT. Three died from transplant-related mortality (TRM). Only 5 patients remained in CR at the data cut-off, 4/5 bridged to transplant. Of these, 2 are in remission >1 year after HSCT and 2 patients are <3 months since HSCT.

Reinfusion with CAR19 T-cells was performed in 3 patients (CD19 + relapses) and was unsuccessful. Two achieved CR with blinatumomab after reinfusion failure.

Five patients are alive with disease: 2 patients with CD19- relapse with a follow-up since relapse <1 month and 3 CD19 + with 1, 2, and 11mo of follow-up, respectively.

Relapsed patients (n = 21)	CD19- relapse (n = 13)	CD19 + relapse (n = 8)
Female	7	2
Age at infusion (years)	7 (1-24)	9 (5-18)
Prior EMD	5	5
Prior HSCT/Inotuzumab/Blinatumomab	8/1/1	6/0/0
TREATMENT AND OUTCOME AFTER RELAPSE
Inotuzumab/Blinatumomab/Reinfusion	6ª/0/0	0/2b/3c
Chemotherapy/Palliative	3d/1	2e/1
HSCT after CR	4 (3 alive in CR)	3 (alive in CR)

ª1 patient discontinued inotuzumab and died from PD, 5 achieved CR, 4 were bridged to HSCT, one died from TRM and 3 are alive in CR (28, 3 and 0.5 months after HSCT). ^bBoth achieved CR, one was bridged to 2nd HSCT and died from TRM, in the other a 2nd HSCT is planned. ^cReinfusion was unsuccessful in the 3 patients.^dOne achieved CR and was bridged to HSCT (<1 mo after SCT at data cut-off). ^eBoth achieved CR, 1 died from TRM, 1 is alive in CR 27months after HSCT.

Conclusions: The outcome of patients who relapse after CART19 therapy is very poor and therapeutic options are scarce. Although CR can be achieved in some patients with inotuzumab or blinatumomab (CD22 + and CD19 + disease, respectively) consolidation with HSCT treatment is needed and long-term remission is very rare.

Clinical Trial Registry: CTL019: EudraCT 2013-003205-25/EudraCT 2016-001991-31 and approved tisagenlecleucel; ARI-0001 cells EudraCT 2016-002972-29

Disclosure: A.A.S: consultant or advisory role (Novartis), travel grants (Novartis),

S.R.: consultant or advisory role (Novartis, Jazz-Pharma, Shire/Servier, Amgen, Cellectis, Celgene/Bristol Myers Squibb), travel grants (Novartis, Jazz-Pharma, Shire/Servier, Amgen, Celge), honoraria (Novartis, Jazz-Pharma, Celgene, Shire/Servier, Amgen),

A.C.: consultant or advisory role (Novartis, Celgene), travel grants (Novartis, Celgene), honoraria (Novartis,Celgene).

M-T: consultant or advisory role (Novartis), travel grants (Novartis), honoraria (Shire/Servier),

M.J.: Consultant role at Grifols in 2018.

P060 A glimpse of clinical & laboratory features of carhlh syndrome in patients receiving bcma car-t cells

C. Zu ¹, K. Wang¹, Q. Zhang¹, F. Ni¹, L. Zhou¹, M. Zhang¹, A.H. Chang², Y. Zhang², J. Cui¹, Y. Hu¹, H. Huang¹

¹the First Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, China, ²Shanghai Yake Biotechnology, Ltd., Shanghai, China

Background: CAR-T cell therapy has been one of the most arresting immunotherapies in the treatment of cancers. With its widening application, a number of characteristic toxicities have also been identified, and amongst them is an increasingly recognized severe toxicity resembling hemophagocytic lymphohistiocytosis (carHLH).

Methods: We retrospectively identified and profiled patients who developed carHLH following BCMA CAR-T therapy in our center. For this work, the diagnostic criteria of carHLH proposed by Neelapu et al were adopted. Patients received CAR-T therapy were then divided into 3 groups: patients developed CRS and carHLH (carHLH group), patients developed grade ≥ 3 CRS alone (severe CRS group), and patients developed grade ≤ 2 CRS or no CRS (mild/no CRS group). And factors associated with or predictive of carHLH were explored.

Results: Amongst 99 patients treated with BCMA CAR-T cells, a considerable portion (20.2%) have developed carHLH. In the context of CRS (96 patients), we report a carHLH rate of 20.8% (21 patients). Preliminary cytokine profiling revealed a cytokine storm partially resembles that of severe CRS (e.g., elevated levels of IL-4 and IL-6), but significant elevation in the peak levels of IFN-γ and IL-10 were found in carHLH group in comparison to severe CRS group, indicating a different cytokine network lying under the development of carHLH. Thus, further investigation using a broadened panel is being conducted, and the results are still incomplete. Coagulopathy has been proposed to be one of the manifestations of carHLH, but our analysis of related biomarkers showed only a decrease in fibrinogen with a potential risk to bleed, which might alternatively relate to liver injury.Regarding baseline characteristics, disease burden is a prominent factor associated with the development of carHLH (median: 11.04% in carHLH group vs. 1.495% in severe CRS and mild/no CRS groups together). In addition, we found that baseline T:NK ratio in peripheral blood was negatively related to the development of carHLH, the patients who experienced carHLH had a lower T:NK ratio at the baseline (median: 2.8422 in carHLH group vs. 5.894 in severe CRS and mild/no CRS groups together), which is the opposite of one of the previous carHLH study in the context of anti-CD22 CAR-T. Whether this was a coincidence or this represented different features of carHLH following CAR-T therapies of different targets need more investigations to elucidate.

Conclusions: Although for now, we generally believe that carHLH develops on the basis of CRS, but additional pathophysiological mechanisms, apart from the shared ones, definitely play a role in the evolution between these inflammatory syndromes. And in view of the life-threatening complications which CarHLH can be associated with, it’s imperative to establish precise recognition and proper management of carHLH. Both require more detailed description of carHLH in different contexts.

Clinical Trial Registry: NCT03716856

Disclosure: The research was funded by the National Natural Science Foundation of China (grant No. 81730008, 81770201, He Huang), Key Project of Science and Technology Department of Zhejiang Province (grant No. 2019C03016, 2018C03016-2, He Huang), and Key R&D Project of Zhejiang Science and Technology Department (grant No. 2020C03G201358, He Huang). The authors declare no other potential conflict of interest.

P061 Cytokine scoring system can effectively evaluate the severity of crs after cart

H. Wang ¹, D. Wang¹, M. Chen¹, L. Qiu¹, X. Li¹, S. Fu¹

¹Hebei Yanda Lu Daopei Hospital, Langfang, China

Background: Cytokine detection is an important basis for evaluating Cytokine Release Syndrome (CRS). To study the role of cytokines in CRS evaluation and to make a rapid and simple quantitative scoring system, we conducted this study.

Methods: From March 2020 to February 2021, 111 patients with refractory relapsed B-ALL were treated with CD19-CAR T at Hebei Yanda Lu Daopei Hospital. Blood samples were collected after CART treatment D0, D4, D7, D14, D21 and D28.the concentrations of 24 serum cytokines were detected by flow cytometry: IFNγ, IL-1β, IL-2, IL-6, IL-10, IL-12p70, TNFα, TNFβ, IL-4, IL-5, IL-8, IL-17A, IL-17F, IL-22, IL-2RA, MCP-1, MIP-1α, GM-CSF, IL-15, GranzymeB, REG3a, ST-2, TNFRI, and Elafin. The integral formula was made according to the test values of 34 cases, and the test values of the other 77 cases were calculated by the formula.

Results: The changes of IL-1β, IL-2, IL-6, IL-10, IL-17F, GM-CSF, ST-2, TNFRI, REG3a and IFN-γ were statistically different at different time points (all P < 0.05). D7-d10 was the peak, and D28 basically returned to normal, which was consistent with the clinical manifestations of the patients, the proportion and cell number of CAR T cells, CD3 + T cells and CD8 + T cells in peripheral blood. It can also distinguish different levels of CRS. The scoring formula = ∑βi*Si, where βi refers to the weight of the ith cytokine; Si refers to the score of the ith cytokine. The score of the ith cytokine is determined according to whether the peak level of the ith cytokine exceeds 3 times of the base value. The 34 patients with different CRS grades were randomly selected, and the weight of each cytokine was found to be: IFN-γ, IL-2, IL-6, IL-10, ST-2, IL-8, and GM-CSF was 2 points. The weight of IL-2RA, IL-17F, REG3a, IL-1β, McP-1 and TNFRI was 1 point. The weight of IL-4, IL-5, IL-22, IL-15 and IL-12P70 was 0.5 points; The weight of Elafin, TNFα and Granzyme B was -1 point. If the score is ≤8, belongs to CRS 0-1; if > 8, < 18, CRS 2; if ≥18, CRS 3-4. Tested in the other 77 patients, the sensitivity was 89.61%, the specificity was 96%, the positive predictive value was 95.83%, and the negative predictive value was 90%. In particular, the sensitivity was 91.55%, the specificity was 99%, the positive predictive value was 98.48%, and the negative predictive value was 92% in the identification of patients with grade 0-1.

Conclusions: The evaluation method of immune status after treatment of CART obtained in this study provides an effective tool for simple, scientific and rapid evaluation of high information data, especially for objective judgment and early detection of CRS.

Disclosure: Nothing to declare

P062 Cytomegalovirus impact in b-cell lymphoma patients treated with chimeric antigen receptor t-cell therapy

E. Marquez-Algaba¹, B. Pernas², J. Esperalba¹, I. Los-Arcos¹, C. Carpio¹, G. Iacoboni¹, P. Barba ¹, I. Ruiz-Camps¹

¹Vall d’Hebron University Hospital, Barcelona, Spain, ²University Hospital of A Coruña, A Coruña, Spain

Background: CD19-directed chimeric antigen receptor (CAR) T-cell has revolutionized the treatment paradigm of relapsed/refractory B-cell Non-Hokdgkin’s lymphoma (B-NHL). Bacterial and fungal infections have been well described, but many questions remain unanswered regarding the role of cytomegalovirus (CMV) in this setting. We studied the incidence and risk factors associated to CMV reactivation and CMV disease.

Methods: We retrospectively reviewed the consecutive CMV viral load determinations of B-NHL treated with CAR T-cells from July 2018 to September 2021. CMV-seronegative patients, and previous allogeneic stem cell transplant recipients were excluded. Significant CMV viral load was defined as higher than 1000 IU/mL.

Results: Overall, 98 patients met the inclusion criteria. Median age was 61 years (IQR 53-68), and 63 were men (64.3%). Median number of previous therapeutic lines was 2 (IQR 2-3). All patients had a clinical follow-up of 2 months, and 83 patients had at least 3 CMV viral load determinations during the first 2 months after CAR-T treatment.

Among patients who fulfilled the inclusion criteria, 44 (44.9%) had at least one positive CMV determination in peripheral blood. Of them, 24 patients (24.5%) had a significant CMV viral load (CMV > 1000), and in 7 patients it was greater than 10000 UI/mL (Log > 4). Six patients were excluded from the analysis for presenting CMV reactivation before receiving CAR-T therapy. Median time from treatment to reactivation was 18 days (IQR 7-15.5), and the median duration of viremia was 8 days (IQR 5-24).

Baseline variables as age, median number of previous lines, median number of CD3 cell count, ferritin levels, or D-dimer levels before lymphodepleting chemotherapy were not related with CMV > 1000.

The only independent risk factor associated with a higher risk of CMV > 1000 was having received dexamethasone and/or tocilizumab within the first month (72.2% vs. 27.8%; adjusted OR 3.07 [IC 95% (1.2-8.0) p = 0.021]. No relationship was observed with hypogammaglobulinemia, or the product administered. The median lymphocyte count in the moment of reactivation was 0.5 x 10⁹/L (IQR 0.2-0.6 x 10⁹/L).

No patient had evidence of CMV disease, and only the patients with viral load superior to 10000 UI/mL received treatment with ganciclovir or valganciclovir. Of these, one presented valganciclovir-induced neutropenia.

Conclusions: CMV monitoring can be useful during the first 2 months after CAR T-cell therapy, especially in those receiving dexamethasone and/or tocilizumab. CMV replication has doubtful clinical significance in this setting, so treatment should be carefully individualized assessing risk-benefit in terms of toxicity.

Disclosure: We declare no conflict of interest. This study was not funded.

P063 Autologous stem cell transplantation induces an higher percentage of exhausted t-cells in dlbcl patients before leukapheresis for car-t cells. Do we need timely leukapheresis strategies?

M. Farina ¹, M. Chiarini², A. Beghin³, A. Leoni¹, E. Accorsi Buttini¹, K. Bosio^1,4, F. Colnaghi¹, I. Volonghi⁵, L. Poli⁵, C. Almici⁶, E. Ferrari⁶, M.L. Sala⁶, A. Bianchetti⁶, D. Moratto², S. Bernardi^1,4, N. Polverelli¹, A. Turra¹, E. Morello¹, D. Brugnoni², F. Porta⁷, A. Lanfranchi³, A. Re⁸, M. Malagola¹, D. Russo¹

¹Unit of Blood Diseases and Bone Marrow Transplantation, Cell Therapies and Hematology Research Program, University of Brescia, ASST Spedali Civili di Brescia, Brescia, Italy, ²Flow Cytometry Unit, Section of Hematology and Blood Coagulation, Clinical Chemistry Laboratory, ASST Spedali Civili di Brescia, Brescia, Italy, ³Stem Cell Laboratory, Section of Hematology and Blood Coagulation, Clinical Chemistry Laboratory, ASST Spedali Civili di Brescia, Brescia, Italy, ⁴Research Center Ail (CREA) - ASST Spedali Civili di Brescia, Brescia, Italy, ⁵U.O.C. Neurology, Center for Neuromuscular Diseases, University of Brescia, ASST Spedali Civili di Brescia, Brescia, Italy, ⁶Laboratory for Stem Cells Manipulation and Cryopreservation, ASST Spedali Civili di Brescia, Brescia, Italy, ⁷UO Pediatric OncoHematology, ASST Spedali Civili di Brescia, Brescia, Italy, ⁸UOC Hematology, ASST Spedali Civili di Brescia, Brescia, Italy

Background: CAR-T cells therapy is an highly effective third line salvage treatment in relapsed/refractory diffuse large B-cell lymphomas (DLBCL), primary mediastinal B-cell lymphomas (PMBCL) and Acute Lymphoblastic Leukemia (ALL), but up to 60% of patients still relapse. CAR-T cells generated from “exhausted” T-lymphocyte (Ly) have been correlate with a worse response. In this prospective study, we assessed the fitness of pre-apheresis Ly for evaluating the impact of previous treatments on the T-cells repertoire.

Methods: From January 2021, Ly-subsets were evaluated at the time of leukapheresis in 13 patients: 11 DLBCL, 1 PMBCL and 1 ALL. Since cryopreservation of the apheresed Ly is allowed for Kymriah, 8 DLBCL patients were enrolled in a “pre-emptive” Ly-apheresis program, scheduling leukapheresis as soon as possible in patients selected for the following poor prognostic risk factors: refractory to first line of treatment; PET positivity before ASCT; first complete response less than 12 months.

Combinations of monoclonal antibodies directed against CD45RA, CCR7, CD3, CD4, and CD8 were used by Flow Cytometry to evaluate the following CD4 + /CD8 + T-ly subsets: T-naïve (CD45RA + CCR7 + ); T-central memory (CD45RA-CCR7 + ); T-effector memory (CD45RA-CCR7-); T-terminally differentiated (CD45RA + CCR7-). All stained samples were acquired on a Canto II (BD Bioscience) flow cytometer and analyzed using DIVA software version 8.0.2. Continuous variables were compared using Mann-Whitney test.

Results: Table1 shows the main patients’ clinical characteristics. Mainly, 8/11 High-Risk DLCBL patients received one line treatment (R-DAEPOCH or R-CHOP), including ASCT according to the Centre policy. Only ASCT had a significative impact on Ly-subsets distribution. In particular, in patients who had not previously received ASCT, CD4/CD8 ratio, percentage of CD4-naïve and CD8-naïve were significantly higher (p = 0,04; p = 0.006 and p = 0.012, respectively). The effects of ASCT on Ly-subsets distribution were detected even after one year from ASCT. No other significant differences were found between patients who received previously ASCT or not, except for age (66 [57-70] vs. 49 [29-59], p = 0.01). Patients with ALL or PMBCL had few circulating naïve T-cells, similarly to the patients who underwent ASCT before leukapheresis.

Table1

	Results (range)
Patients	13
Median age (ys)	61 (29-70)
Male/Female	3/8
Disease
• DLBCL	11
• PMBCL	1
• ALL	1
High/Inter-High IPI score DLBCL	6
Status disease at leukapheresis:
• Refractory/relapse	7
• Complete/partial response	6
ASCT before leukapheresis	7
CAR-T cells infused	7

Conclusions: Previous ASCT in DLBCL patients can result in a significant more percentage of “exhausted” T-Ly at the time of leukapheresis. This may lead to an higher percentage of “exhausted” CAR-T cells and, potentially, to their reduced efficacy. In patients at higher risk of relapse after ASCT a “pre-emptive” leukapheresis should be considered a timely clinical option to cryopreserve more “fit” T-Ly to be sent for manufacturing in case of relapse.

Disclosure: Nothing to declare

P064 Characterization of cd19car-t cells produced with the clinimacs prodigy® platform: Effects of production cycle length and clinical history of the donor with regard to HSCT

E. Malakhova ¹, D. Pershin¹, E. Kulakovskaya¹, V. Vedmedskaya¹, M. Fadeeva¹, T. Sozonova¹, S. Glushkova¹, A. Kazachenok¹, Y. Muzalevskii¹, G. Novichkova¹, M. Maschan¹

¹Dmitry Rogachev National Medical Research Center of Pediatric Hematology, Oncology and Immunology, Moscow, Russian Federation

Background: Chimeric antigen receptor (CAR) T cells targeting CD19 antigen provide a highly effective immunotherapy for B cell malignancies. The anti-tumor effect depends on high proliferative and cytotoxic activity of CAR T cells, hence the importance of proper in vitro assessment of the CAR T cell functionalities. This study compares functional properties of CD19 CAR T cells obtained from patients without a history of HSCT vs. HSCT recipients vs. healthy donors, and CAR-T manufactured with either a short (7 day) or long (11 day) protocol.

Methods: The study enrolled patients with relapsed/refractory B cell acute lymphoblastic leukemia who met inclusion criteria for the clinical protocol at the Dmitry Rogachev National Medical Research Center of pediatric hematology, oncology and immunology. A total of 78 cell products were derived from patients who never received HSCT (‘auto’, n = 50), patients who received HSCT within 4 to 24 months before (‘pseudo-auto’, n = 19), or haploidentical healthy donors (‘haplo’, n = 9). The production was performed based on the automated CliniMACS Prodigy® system with the full cycle lasting 11 days (n = 50) or 7 days (n = 28). The lentiviral vector transduction efficiency was determined for all CAR T cell products by direct staining. Functional testing of the final CAR T cell products included degranulation assay (measuring CD107a externalization by CD4 + and CD8 + lymphocytes, n = 33) and TNFα and IFNγ secretion assay upon incubation with the target cell line JeKo-1 (n = 41). The flow cytometry measurements were based on the customary surface and intracellular staining protocols with commercially available antibodies. Cytotoxicity of CAR T cells towards the target cell line JeKo-1 was assessed using the Incucyte® Live-Cell Analysis system.

Results: T lymphocytes from pseudo-autologous donors were transduced with lentiviral vectors more efficiently than the cells from autologous donors. Besides, the longer 11-day manufacturing afforded significantly higher transduction efficiency than the shorter 7-day cycles. On the other hand, CAR T cells manufactured over 7-day process showed higher rates of degranulation than the 11-day cycle products. CD 4+ CAR T cells from haploidentical donors showed a higher level of degranulation compared to autologous donors. The rates of cytokine production and cytotoxic activity of CAR T cells were similar in all groups (p > 0.05).

Conclusions: The established protocol affords a stable cell product with high anti-tumor activity and functional properties largely independent of clinical history of the donor. Moreover, CAR T cells produced in an expedite time-frame of 7 days exhibit the same (and in certain aspects even higher) anti-tumor activity as the cells obtained in 11-day production cycles. For patients with rapid progression, reduction of the waiting time between apheresis and CAR T cell infusion to 7 days may be vital.

Disclosure: Nothing to declare

P065 Dynamics of car-t cells therapy associated cytopenias: A single-center experience

R.M. Martin-Rojas ¹, R. Bailén^1,2, G. Oarbeascoa^1,2, M. Bastos-Oreiro^1,2, I. Gómez-Centurión^1,2, P. Fernández-Caldas^1,2, D. Conde-Royo^1,2, C. Muñoz^1,2, S. Sabell^1,2, J. Anguita^1,2,3, J.L. Díez-Martín^1,2,3, M. Kwon^1,2

¹Hospital General Universitario Gregorio Marañon, Madrid, Spain, ²Gregorio Marañon Health Research Institute, Madrid, Spain, ³Universidad Complutense de Madrid, Madrid, Spain

Background: CAR-T cell therapy is approved for adult patients with relapsed/refractory diffuse large B-cell lymphoma (DLBCL) or primary mediastinal lymphoma (PML) after two or more lines of therapy. Prolonged cytopenias have been reported in 30-60% of patients undergoing CAR-T cell therapy, but information about its dynamics and etiology is scarce.

Methods: We conducted a retrospective study of consecutive patients with a DLBCL or PML undergoing commercial CAR-T cell therapy in our center between June 2019 and September 2021. We analyzed blood cell counts pre-lymphodepletion and during hospitalization. This information was correlated with clinical and analytical parameters.

Results: 54 patients were included. Median age was 58 years (range 22-79). 34 patients (63%) were treated with Axicabtagene ciloleucel (Axi-cel).Patients had received a median of 2 prior lines of therapy (range 2-6) and 35.2% had undergone a previous HSCT. 47 patients (87%) received bridging therapy (Table 1).

TABLE 1. PATIENTS GENERAL CHARACTERISTICS

	Axi-cel (n = 34)	Tisa-cel (n = 20)	p
Age, median (range)	57.5 (22-79)	62.5 (35-75)	0.154
Sex, female (%)	19 (55.8%)	7 (35%)	0.138
DLBCL, n (%)	27 (79.41%)	16 (80%)	0.505
Bone marrow infiltration at diagnosis, n (%)	5 (14.7%)	3 (15%)	0.977
Previous transplantation, n (%)	10 (29.4%)	9 (45%)	0.247
Prior lines, median (range)	2 (2-5)	2 (2-6)	0.692
Bridging Therapy, n (%)	31 (91.2%)	16 (80%)	0.238
CRS, n (%)	31 (91.2%)	16 (80%)	0.238
ICANS, n (%)	15 (44.1%)	3 (15%)	0.055

Median hospitalization was 23 days (range 11-87) and 47 patients (87%) showed profound neutropenia (ANC ≤ 500/μL), lasting >7 days in 42 patients (77.8%). 28 patients (51.9%) showed profound thrombocytopenia (≤50000/ μL) and 31 (57.4%) anemia (≤8g/dL). Cytopenias during hospitalization were more frequent with Axi-cel, with higher rates of neutropenia (97% vs 70%; p = 0.004), thrombocytopenia (61.7% vs 35%; p = 0.05) and prolonged cytopenias (90.9% vs 60%; p = 0.007, Figure 1).

FIGURE 1. CYTOPENIAS DURING HOSPITALIZATION

 

On day +28 post CAR-T, 28 patients (56%) showed persistent cytopenias: 3 (6%) neutropenia, 9 (18%) thrombocytopenia and 16 (32%) both, with higher rates of cytopenias at day +28 with Axi-cel (36.8% vs 67.7%; p = 0.03).

Cytopenias during hospitalization were related to treatment with Axi-cel (p = 0.004) and bridging therapy (p < 0.001), while its prolonged duration was associated with Axi-cel (p = 0.007), bridging therapy (p = 0.011) and progressive disease (p = 0.05). Cytopenias on day +28 were related to Axi-cel (p = 0.03), bridging therapy (p = 0.03), higher ferritin levels (p = 0.01), CRS (p = 0.003) and ICANS (p = 0.05).

A multivariate analysis using logistic regression showed that bridging therapy (OR 25.4; 95% CI 2.2-29.1; p = 0.009) and treatment with Axi-cel (OR 17.9; 95% CI 1.3-24.7; p = 0.03) were independent predictors for profound cytopenias during hospitalization, while no independent predictor was found for its duration nor for day +28 cytopenias.

Conclusions: Profound cytopenias were frequent in our cohort, with up to 87% of cases during hospitalization and 56% on day +28, being bridging therapy and use of Axi-cel independent predictors for its development. Improving the knowledge on these cytopenias can contribute to a better outpatient management.

Disclosure: Nothing to declare

P066 CD19-specific car-t cells for the treatment of cns chloromas in children with relapsed/refractory b-cell acute lymphoblastic leukemia

S. Shahid ¹, M. Cancio¹, S.S. Haque¹, Y. Khakoo¹, E. McWilliams¹, B.D. Santomasso¹, A. Scaradavou¹, B. Spitzer¹, S.L. Wolden¹, J.J. Boelens¹, K.J. Curran¹

¹Memorial Sloan Kettering Cancer Center, New York, United States

Background: Chimeric antigen receptor (CAR)-T cell therapy has revolutionized the treatment paradigm for children with relapsed/refractory (R/R) B-cell acute lymphoblastic leukemia (B-ALL). Effective treatment of extramedullary central nervous system (CNS) B-ALL with CAR-T cells has been reported, however little is known about the effectiveness of CAR-T cells for bulky CNS disease. While CNS chloromas are an extremely rare presentation of R/R B-ALL, they have been reported, are difficult to treat in heavily pre-treated patients, and are associated with poor outcomes. Herein, we report the effectiveness and safety of CD19-directed CAR-T cell consolidation with tisagenlecleucel in two pediatric patients with B-ALL CNS chloromas.

Methods: Medical records of 2 pediatric patients with R/R pre-B-ALL treated with tisagenlecleucel for CNS chloromas at MSKCC were reviewed. Clinical course, treatment, and outcomes are discussed here. Additionally, all pediatric patients who received tisagenlecleucel from 2018-2021 at MSKCC were evaluated based on CNS disease (spinal fluid flow cytometry/cytology and/or presence of chloroma) at time of treatment to evaluate toxicities and clinical outcomes.

Results: Patient 1 was diagnosed with standard-risk pre-B-ALL (CNS1) at age 5. She had 2 isolated CNS relapses followed by a concurrent medullary and CNS relapse, which was treated with allogeneic hematopoietic stem cell transplantation (allo-HSCT) and post-transplant intrathecal chemotherapy for CNS prophylaxis. Sixteen months after allo-HSCT, she was found to have a CNS chloroma with a concurrent medullary relapse. She underwent subtotal surgical resection of the chloroma, focal proton radiation (2400cGy), and bridging chemotherapy (vincristine/mercaptopurine) followed by tisagenlecleucel. She experienced minimal toxicities: grade I cytokine release syndrome (CRS) and grade II immune effector cell-associated neurotoxicity syndrome (ICANS) requiring 2 doses of dexamethasone. She achieved a complete response (CR) at 1-month after tisagenlecleucel with a negative brain MRI, and she maintained disease control for 6 months. She developed an isolated CNS2 relapse 6 months post-treatment, responded to a second infusion of tisagenlecleucel with no toxicities, and is now undergoing a second allo-HSCT.

Patient 2 was diagnosed with standard-risk pre-B-ALL (CNS1) at age 3. Fourteen years after initial diagnosis, he had a late isolated CNS relapse. He subsequently had a second isolated CNS relapse 3.5 years later followed 2 years later by a third isolated CNS relapse. Fourteen months after his third relapse, brain MRI revealed a CNS chloroma, which was treated with surgical resection, focal proton radiation (2400cGy), and then tisagenlecleucel. He experienced minimal toxicities: grade I CRS and no ICANS. He achieved a CR at 1-month after CAR-T cell treatment. Thirteen months later, he has maintained no evidence of disease.

Upon further review of all pediatric patients treated with tisagenlecleucel at MSKCC (n = 20), 30% (n = 6) had CNS disease at time of tisagenlecleucel treatment, of which 33% (n = 2) developed ICANS (both grade II), 33% (n = 2) relapsed after treatment, and 83% (n = 5) remain alive to date.

Conclusions: Two pediatric patients with R/R B-ALL with CNS chloromas were successfully treated with tisagenlecleucel, both achieving a CR at 1-month post-treatment. Both patients had minimal treatment-associated CNS toxicities. Our experience highlights consideration of CD19-directed CAR-T cell therapy in pediatric patients with CNS chloromas.

Disclosure:

Boelens, Jaap J. discloses consulting or advisory roles (Avrobio; Advanced Clinical; Bluerock; Omeros; Race Oncology; Sanofi; Equillium; Medexus; Sobi). Curran, Kevin J. discloses consulting or advisory role (Novartis; Mesoblast) and research funding (Juno Therapeutics; Novartis; Celegene; Cellectis). The remaining authors have no conflicts of interest to declare relevant to this abstract.

P067 Early lymphocyte collection for cart production in patients with relapsed/refractory diffuse large b cell lymphoma improves t cell parameters

S. Grisariu ^1,2, T. Sharon¹, B. Avni^1,2, M. Assayag¹, A. Bitansky Kremer¹, N. Goldschmidt^1,2, N. Asherie¹, S. Kfir-Erenfeld¹, M. E.Gatt^1,2, P. Stepensky^1,2

¹Hadassah University Hospital, Jerusalem, Israel, ²The Hebrew University of Jerusalem, Jerusalem, Israel

Background: The majority of patients with diffuse large B cell lymphoma (DLBCL) undergoing adoptive transfer of CD19-directed CAR T cells have been exposed to multiple rounds of cytotoxic therapies. It has been noted that the quality of the collected T cells is a significant factor determining their toxicity and efficacy. In order to explore the influence of early T cell collection, we have conducted a study comparing T cells parameters of patients who underwent lymphocyte collection after failure of first line therapy for DLBCL (early apheresis) with patients who underwent lymphocyte collection after second line therapy or later (late apheresis).

Methods: Patients were assigned to groups according to referral time: early versus late. Blood samples were collected at the day of apheresis, representing the starting material for manufacturing. Immune phenotyping (FACS) was performed for T cell subpopulations, differentiation and exhaustion markers (CD3, CD4, CD8, CD45RA, CCR7, CD27, CD28, TIM-3, LAG-3). T cell activation and proliferation were analyzed using PBMCs labelled with carboxyfluorescein succinimidyl ester (CFSE) and anti-CD3/ CD28 or (phytohemagglutinin) PHA.

Results: Thirty-six patients were enrolled: 15 to the early group and 21 to the late group. The mean percentage of circulating CD3 + lymphocytes was 48.9 ± 3.5 and 58.5 ± 1 in the late and early group, respectively (p < 0.05) (Fig.). The early group had a significantly higher proportion of CD8 + lymphocytes (p < 0.05) and a lower proportion of CD4 + lymphocytes (p < 0.01) compared to the late group (Fig.). Among CD4 + and CD8 + T cells, the early samples showed increase of both naïve (p = 0.07, p < 0.005) and central memory T cells (T_CM) (p < 0.0005, p < 0.05), and a reduction of effector memory (T_EM) (p < 0.05, p < 0.005) and effector T cells (T_EF) (p < 0.05, ns), respectively. (Fig.) Both CD4 + and CD8 + T lymphocytes showed higher expression of the exhaustion markers, TIM-3 and LAG-3 in the late apheresis group (p < 0.0001). CD8 + cells analysis revealed a significant increase of senescent CD27⁻/CD28⁻ T-cells, in the late group compared to the early group (p < 0.05). In the early samples there was a significant increase in T-cell proliferation, in response to either stimulus: anti CD3/CD28 or PHA in both CD4 (p < 0.001) and CD8 (p < 0.05) subsets.

Conclusions: Early apheresis, after first line of chemotherapy, shows abundance of T lymphocytes, mainly CD8 + cells, with an improved quality of the starting material, represented by a higher percentage of naïve, less exhausted and senescent cells. Furthermore, early apheresis shows a higher T cell proliferation potential. These improved parameters in the initial collected product may have an influence on the manufacturing process and eventually on the efficacy of the infused CAR T cells.

Disclosure: "Nothing to declare"

P068 Chimeric antigen receptor t-cell therapy in the czech republic

F. Folber ¹, R. Pytlík², K. Polgárová³, L. Sramkova⁴, J. Šrámek⁵

¹Masaryk University Hospital Brno, Brno, Czech Republic, ²Institute of Haematology and Blood Transfusion, Praha, Czech Republic, ³General University Hospital, Praha, Czech Republic, ⁴Charles University and University Hospital Motol, Praha, Czech Republic, ⁵University Hospital Pilsen, Plzeň, Czech Republic

Background: The program of cellular therapy with chimeric antigen receptor T-cells (CAR-T) has been established in the Czech Republic in 2019. Since then, five centers have been certified for tisagenlecleucel (tisa-cel), axicabtagene ciloleucel (axi-cel), or both. This report summarizes all the treatment that has been administered so far.

Methods: All patients treated with commercial tisa-cel or axi-cel in the Czech Republic until August 2021 were included into this retrospective analysis. The data were analysed for overall response rate (ORR) and complete remission (CR) rate, incidence and severity of cytokine release syndrome (CRS) and immune effector cell-associated neurotoxicity syndrome (ICANS), and progression-free (PFS) and overall survival (OS). CRS and ICANS were graded according to ASTCT consensus criteria.

Results: A total number of 66 patients were included into this analysis, 51 treated with tisa-cel and 15 with axi-cel.

Tisa-cel was infused in 43 patients with B-cell non-Hodgkin lymphomas (B-NHL). ORR was observed in 47% patients, while CR was reached in 35%. CRS occurred in 74% of cases (grade 3 or higher in 16%), and ICANS in 23% (grade 3 or higher in 2%). Six-month PFS and OS estimates were 37% and 52%, respectively. Better PFS was observed in patients with pre-treatment CRP below median (p = 0.02), and in patients who developed CRS (p = 0.03).

Tisa-cel was infused in 8 patients with B-cell precursor acute lymphoblastic leukemia (B-ALL), of whom 5 were children and young adults under the age of 18. All patients but one (88%) achieved a CR. CRS occurred in 63% of cases (none grade 3 or higher), and ICANS in 25% (one grade 4). Six-month EFS and OS estimates were 50% and 88%, respectively.

Axi-cel was infused in 15 B-NHL patients (including primary mediastinal B-cell lymphoma, PMBCL). ORR was observed in 69% of cases, CR in 46%. CRS occurred in 80% of cases (none of them grade 3 or higher), and ICANS in 33% (grade 3 or higher in 3 patients). Six-month PFS and OS estimates were 69% and 74%, respectively. Better survival was observed in patients with PMBCL but the difference was not statistically significant.

Conclusions: Cellular therapy with commercial CAR-T products is a well-established treatment modality for patients with relapsed/refractory B-NHL and B-ALL. Real world data observed in our nation-wide cohort are comparable to already published results of larger patient populations.

Disclosure: Nothing to declare

P069 CD34 selected stem cell boost can safely improve cytopaenias following car-t therapy

K. Mullanfiroze ¹, A. Lazareva¹, J. Chu¹, L. Williams¹, S. Burridge¹, J. Silva¹, R. Chiesa¹, K. Rao¹, G. Lucchini¹, S. Ghorashian¹, R. Hough², C. Roddie², P. Amrolia¹

¹Great Ormond Street Hospital, London, United Kingdom, ²University College London Hospitals, London, United Kingdom

Background: Prolonged cytopaenias are an under-recognised toxicity of Chimeric Antigen Receptor-T cell(CART) therapy for B-cell malignancies(53% of B-ALL patients in the ELIANA study had grade 3-4 neutropenia persisting beyond day 28). Persistent cytopaenias post-CART have been associated with baseline cytopaenias and pro-inflammatory milieu(Rejeski et al, Blood, 2021). Cytopaenias generally resolve spontaneously over 2-3 months post-CART therapy but some patients develop prolonged cytopaenias associated with susceptibility to infection(s) and/or transfusion dependence and a hypoplastic bone marrow(BM). Cytopaenias can be treated with an unconditioned CD34 stem-cell boost in those who have undergone prior stem cell transplant(SCT).

We reviewed our institutional data on outcomes with this approach.

Methods: Data was retrospectively analysed from paediatric and young adults with relapsed/refractory(r/r) B-ALL treated with CART therapy and who received CD34 stem-cell boost from their SCT donor between May 2016 and December 2021 at 2 centres in the UK. Demographic details, disease status and cytopaenias pre-CD34 stem-cell boost, toxicity and outcomes were collated.

Results: Over 5 years, 103 patients received CART therapy for r/r B-ALL. Seven (6.7%) of these patients received an unconditioned CD34 stem-cell boost from their SCT donor due to severe grade 3-4 cytopaenia (pancytopenia in 6/7, bicytopenia in 1/7) beyond 1 month after CART. CD34 stem-cell boost was infused at median of 2.6 months (range 2-16.5m) after CART therapy. All 7 demonstrated BM hypoplasia for age without a clear drug or viral etiology and were MRD negative. Three(43%) had ongoing invasive fungal infections at CD34 stem-cell infusion. Median age at CD34 stem-cell boost was 16 years(range 11-27y). All patients were heavily pre-treated and had undergone previous SCT and 6/7 received CART in > 2 relapse. Four(3 CD19, 1 CD19/CD22 directed) received CAR as per CARPALL study(NCT02443831), 1 received CD19/CD22 directed CAR as per AMELIA study(NCT03289455), 1 received licensed product Tisagenlecleucel and 1 received allogenic CD19 directed CAR as per CARD study(NCT02893189). Median CD34 and CD3 doses in the infused product were 6.75 x10⁶/kg(range 2.5-11.2x10⁶/kg) and 0.19x10⁴/kg(range 0.07-1.22x10⁴/kg) respectively. CD34 boost was well tolerated:1 patient developed grade 2 cytokine release syndrome(CRS) at day 10 but no acute or chronic GVHD was observed. Two patients were not evaluable for response to CD34 stem-cell boost:1 died due to gastro-intestinal haemorrhage caused by disseminated Mucormycosis on day 24 and 1 relapsed at day 38. Of the 5 evaluable patients one had transient recovery of the bicytopenia followed by ongoing cytopenias until demise while 4 patients recovered neutrophils >1x10⁹/L without GCSF, were blood and platelet transfusion independent by a median of day 42 (range 11-192 days), day 33 (range 4-106 days) and day 33 (range 7-73 days) respectively. At a median follow-up of 9 months(range 24 days-2.5 years) from CD34 stem-cell boost, 5 died (2:relapse, 2:infections, 1: further therapy related complications) and 2 were alive, in CR with normal blood counts at last follow up.

Conclusions: Unconditioned CD34 stem-cell boost is well tolerated and can ameliorate prolonged cytopaenias post-CART therapy. However, CRS is a potential complication after the infusion due to the presence of CD19⁺ progenitors within the CD34 selected product.

Disclosure: None

P070 Bridging chemotherapy strategies in children undergoing cart-cells for all

M. Oporto Espuelas ¹, S. Burridge¹, K. Watt², D. Bonney², A. Vora¹, V. Pavasovic¹, S. Samarasinghe¹, J. Bartram¹, A. Rao¹, P. Ancliff¹, S. Farish¹, R. Chiesa¹, K. Rao¹, G. Lucchini¹, J. Montibeller Furtado-Silva¹, A. Lazareva¹, K. Mullanfiroze¹, M. Ballasch¹, P. Amrolia¹, S. Ghorashian¹

¹Great Ormond Street Hospital, London, United Kingdom, ²Royal Manchester Childrens Hospital, Manchester, United Kingdom

Background: Low tumour burden prior to CART-cell infusion for B-ALL is associated with less CRS toxicity and improved survival^1,2. The choice of bridging chemotherapy (BCT) is crucial to achieve adequate disease control and avoid toxicity-related infusion delays; however, there is no consensus as to which is the optimal strategy.

We have analysed the use of BCT in two of the UK’s largest CART-cell centres in terms of both feasibility to deliver CART-infusion on time and efficacy in reducing large/bulky tumour burden.

Methods: We performed a descriptive analysis on restrospectively collected data. BCT was defined as systemic anti-leukaemic treatment given between leukapheresis and lymphodepletion. A BCT course was defined as a particular chemotherapy schedule given with the intent to control disease. Disease burden was measured by flow cytometry or molecular MRD for patients with <5% disease and confirmed by a local consultant in each case.

Results: Data was collected from 49 paediatric patients who underwent 70 BCT courses (median number of courses per patient was 1, range 0-3). Patient characteristics are shown in Table 1. Thirty-two patients (65.3%) received their CART-cell infusion on the expected date, whereas 15 patients (30.6%) suffered a delay, 1 patient (2%) died prior to infusion. A total of 20 patients (40.6%) experienced some kind of toxicity, leading to an infusion delay in 15 (75%) of them. The majority (n = 11) of these suffered from an infection or likely infection. Other non-infectious reasons for delay included leukoencephalopathy, small bowel obstruction and difficulties in disease control (n = 3, 20%). BCT regimens were heterogeneous; we have grouped them in 5 categories in decreasing order of popularity: Capizzi-like (n = 28; MTX + VCR as per UKALL-2011 - up to 9 variations were recorded in this cohort), Maintenance (n = 12; oral 6MP + MTX), Inotuzumab (n = 11; single 0.5-0.8 mg/m2 doses to avoid toxicity), HiDAC (n = 7; AraC in doses 9-12 g/m2), and Other (n = 12; including exclusive intrathecal therapy, TKI and other miscellaneous schedules). Maintenance was usually given to hold/maintain low-level disease. Inotuzumab was not given as upfront BCT. Both Inotuzumab and Capizzi regimens seemed effective in debulking disease.

Table 1. Patient characteristics.

Median age	7.9 y (0.9-15.7)
Female/male	22 (44.9%)/27 (55.1%)
CART (Tisagenlecleucel/CARPALL)	48 (98%)/1 (2%)
Infant/Ph+ ALL	11 (22.4%)/3 (6.1%)
Prior SCT	24 (49%)
Isolated CNS disease	7 (14.3%)
BM + Extramedullary disease - CNS/Other	12 (24.5%) - 5/7
Refractory	29 (59.2%)
Median number of relapses	1 (0-4)
Previous CART-cell therapy	2 (4.1%)

Conclusions: The ideal BCT schedule should achieve adequate disease control with minimal toxicity facilitating timely CART-cell infusion. Capizzi-like and Inotuzumab regimens may be suitable agents to debulk disease. Infection is the most common reason for delays in infusion.

Disclosure: No conflict of interest of any of the authors.

P071 Humoral and t cell immune responses to anti-sars-cov-2 vaccines in pediatric & patients with anti-cd19 car-t-induced b-cell aplasia

A. Jarisch ¹, E. Wiercinska², S. Huenecke², M. Bremm¹, C. Cappel¹, J. Hauler¹, E. Rettinger¹, J. Soerensen¹, H. Hellstern², H. Boenig², P. Bader¹

¹Division of Pediatric Stem Cell Transplantation and Immunology, University Hospital Frankfurt, Frankfurt, Germany, ²German Red Cross Blood Service BaWüHe, Institute Frankfurt, Frankfurt, Germany

Background: COVID-19 disease is caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2); its course can be severe, the overall mortality approaching 1.5%. Patients with malignant diseases and an impaired immune system, especially patients after hematopoietic stem cell transplantation (HSCT) and immune cell therapy, have an increased risk of an aggravated course of the disease or death and despite the expectation of less than optimal vaccine responsiveness were granted prioritized access. Inherently, patients with anti-CD19 CAR-T-mediated B-cell aplasia would be incapable of generating humoral responses, so that assessment of the vaccine-induced cellular immunity was all the more important to gauge whether the vaccine can induce meaningful protection.

Methods: The prospective study included 8 patients aged >12 years (and hence, eligible for SARS-CoV-2 vaccination) diagnosed with multiply relapsed B-cell precursor acute lymphoblastic leukaemia (ALL) and treated with anti-CD19 chimeric antigen receptor T-cell (CAR-T19) therapy between 2016 and 2021.

The primary endpoint was the detection of humoral and cell-mediated response to vaccine. Secondary endpoints included the incidence of grade 3 or 4 adverse events and GVHD exacerbation and the influence of the vaccine to CAR T cells and lymphocyte subset.

Results: Even though half the patients exhibited sub-normal lymphocyte counts and marginal CD4/CD8 ratios, after two vaccinations all showed brisk T-cell responsiveness to spike protein, predominantly in the CD4 compartment which was qualitatively well within the range of healthy controls.

In none of the patients severe vaccine-associated (grade 3 or 4) adverse events were observed. None of the eight patients developed a cytopenia post vaccination.

When looking at the differentiation of the CD4 + and CD8 + T cells into naïve, central-, effector memory and EMRA T cells, also no significant changes in composition could be observed. The slight changes which could be seen in an increase of the naïve T4 and T8 cell subpopulation is probably related to the restoration of the naïve T-cell pool in the course of immune regeneration after stem cell transplantation. The effectory compartment (TEM and TEMRA) showed no significant changes with respect to expansion of these cells.

Conclusions: We posit that SARS-CoV-2 mRNA vaccines induce meaningful cellular immunity in patients with isolated B-cell deficiency due to anti-CD19 CAR-T therapy.

Clinical Trial Registry: The study was approved by Goethe University Medical Center’s ethics committee (case number 2021-180).

Disclosure: "Nothing to declare"

P072 Validation of collection and cryopreservation of autologous mononuclear cells intended for car-t cells production

I. Bojanic ¹, S. Mazić¹, V. Rimac¹, I.L. Burnać¹, K. Gojčeta¹, B. Golubić Ćepulić¹, I. Aurer¹

¹University Hospital Centre Zagreb, Zagreb, Croatia

Background: Apheresis and cell processing facilities, although experienced in HPC collection, could face challenges when introducing the collection and storage of cells intended for manufacturing of cellular therapy products, because the validation of collection and cryopreservation of other cell types is needed. The aim is to present results of validation of collection and cryopreservation of autologous mononuclear cells (MNC) and lymphocytes subpopulation intended for CAR-T cells production.

Methods: Collection and cryopreservation of lymphocytes for production of autologous T cell immunotherapy tisagenlekleucel (Kymriah, Novartis) in University Hospital Centre Zagreb started at the end of 2019. Leukapheresis were performed on Spectra Optia system (Terumo BCT) using CMNC procedure and acid citrate dextrose A (ACD-A) anticoagulant. All patients received prophylactic continuous intravenous calcium gluconate. Leukapheresis product was considered eligible for CAR-T product manufacturing if specification requirements were met: total nucleated cells (TNC) ≥ 2x10⁹, CD3 + lymphocytes ≥1x10⁹, and ≥3% CD3 + lymphocytes. Collection efficiency (CE1) for MNC and CD3 + cells was calculated based on pre- and postapheresis MNC and CD3 + cells peripheral blood counts. Cells were cryopreserved with DMSO cryoprotectant and controlled-rate freezing. The effect of cryopreservation on the recovery of lymphocyte subpopulations was evaluated in cryovials representative of cryopreserved products using flow cytometer BD FACSCanto II.

Results: From December 2019 to November 2021, two children and two young adult patients with ALL, and 23 adults with DLBCL underwent leukapheresis. The median age was 57 years (range 5-71), and median body weight was 75 kg (range 21-109). 15 patients required central venous catheter, while in 12 patients peripheral veins were used. In all patients, except in one child, the target number of cells was obtained with one leukapheresis. The median of total blood volume (TBV) processed was 2,1 (range 1,4-2,8) during 240 min (range 160-300). In two procedures heparin was added to resolve clotting. In only one patient mild symptoms of hypocalcaemia were observed. Median of collected TNC was 8,9x10E9 (range 0,7-27,7), and CD3 + cells 4,1x10E9 (range 0,7-11,1). Median of CE1 for MNC was 24% (range 2,4-32), and for CD3 + cells 43,4% (range 18,9-56,8). The number of CD3 + cells in peripheral blood significantly correlated with CD3 + cell yields (correlation coefficient r = 0.680, p < 0,0001). All leukapheresis products were cryopreserved on the day of apheresis. The median recovery of CD3 + cells after cryopreservation was 79% (range 34,8-106,4), CD4 + cells 83,5% (range 15,1-136,9), CD8 + cells 84,8% (range 34,1-145,7), CD19 + cells 96,3% (range 41,8-107,7) and CD56 + cells 74,7% (range 8,3-121,1).

Conclusions: Leukapheresis is an efficient and safe procedure for the collection of cells for cellular therapy production. CE1 calculated for CD3 + lymphocytes exhibited a relatively wide range, therefore further evaluation of factors affecting apheresis performance is necessary. Results of CE1 validation for CD3 + cells allow calculation of required TBV processing based on patient’s pre CD3 + count and optimization of the apheresis procedure. The recovery of different lymphocyte populations after thawing was lower compared to the results of our previous validation of CD34 + cell recovery, and further clarification of the different tolerance to cryopreservation of cell subpopulations in apheresis products is needed.

Disclosure: Nothing to declare.

P073 Study of specific lineage chimerism as an early biomarker of risk of relapse after anti-cd19 cart therapy in patients previously treated with an allogeneic HSCT

I. Martínez-Romera¹, V. Galán Gómez¹, B. González Martínez¹, P. Guerra García¹, S. San Román Pacheco¹, D. Corral Sánchez¹, Y. Mozo del Castillo¹, D. Bueno Sánchez¹, L. Sisinni¹, A. González Guerrero¹, S. Castellano Dámaso¹, A. Balas Pérez², A. Pérez-Martínez ¹

¹University Hospital La Paz, Madrid, Spain, ²Centro de Transfusión, Madrid, Spain

Background: Treatment based on target CD19 protein by a chimeric antigenic receptor expressed on T lymphocytes (antiCD19 CAR-T) is a novel immunotherapy that has led to a revolution in the management and treatment of relapse and refractory (r/r) B cell acute lymphoblastic leukemia (B-ALL) even after an allogenic hematopoietic stem cell transplant (HSCT) relapse. After antiCD19 CART therapy, the successful functionally effective of the CAR-T is monitored by bone marrow negative minimal residual disease but also by the absence of peripheral CD19⁺ B lymphocytes (B cell aplasia). In addition, continuous chimerism monitoring after HSCT is a routinely well-established method which is critical for early therapeutic interventions. So, in patients who have received an allogenic-HSCT prior to treatment with antiCD19 CAR-T, monitoring of chimerism and lineage-specific chimerism on CD19⁺ and CD3⁺ cells could be a helpful complementary tool to early evaluate the risk of relapse and it could also help to propose early treatment.

Methods: We describe four B-ALL pediatric patients who received anti-CD19 CART therapy in the setting of a relapse after an allogeneic HSCT. They all received fludarabine and cyclophosphamide (FluCy) lymphodepleting regimen. Lineage chimerism in peripheral blood (PB) and bone marrow (BM) was done in all of them periodically after the CART infusion.

Results: In patient 1, mixed chimerism was observed specifically in the CD3⁺ lineage, and it reverted with the administration of serial donor lymphocyte infusion (DLI). In the case of patients 2 and 4, a loss of chimerism was observed in the CD19⁺ lymphocytes subset without being accompanied by a loss of B cell aplasia. In these patients, treatment with DLI, although it could turn back to complete chimerism in patient 2, did not prevent the later progression to relapse in both. In patient 3, mixed chimerism in CD19⁺ subset was associated with very early loss of B cell aplasia. Given that after these findings an allogenic HSCT was indicated, he did not receive DLI.

Conclusions: The CD19⁺ lineage mixed chimerism but not CD3⁺ lineage mixed chimerism monitored by single tandem repeat (STR) techniques could anticipate earlier than B cell aplasia determined by flow cytometry, the antiCD19 CAR-T lack of persisting functionally effective and leukemia relapse. Treatment with DLI would not avoid relapse but could recover CD3⁺ full donor chimerism. We suggest that continuous lineage chimerism analysis should be a routinely tool for monitoring in patients who received anti-CD19 CART after an allogeneic HSCT and achieved complete remission, because it could help to propose early treatment. However, the role of DLI in this setting looks useless, although prospective studies should be proposed.

Disclosure: Nothing to declare.

P074 Autologous stem cell boost for prolonged severe cytopenia after treatment with cd19-car-t-cells for refractory diffuse large b-cell lymphoma –two case reports

L. Gaksch ¹, B. Huber-Krassnitzer¹, B. Uhl¹, A. Bainschab¹, I.A. Sifferlinger¹, H. Sill¹, P. Schlenke², K. Rosskopf², C. Beham-Schmid³, P. Neumeister¹, H.T. Greinix¹

¹Division of Hematology, Medical University of Graz, Graz, Austria, ²Medical University of Graz, Graz, Austria, ³Diagnostic and Research Institute of Pathology, Medical University of Graz, Graz, Austria

Background: CD19-targeted chimeric antigen receptor modified T-cell (CAR-T) infusion is an established treatment in relapsed or refractory diffuse large B-cell lymphomas (DLBCL). While early adverse events like cytokine release syndrome (CRS) and neurotoxicity are well investigated, in late occurring complications like prolonged cytopenias the underlying mechanisms are still unclear. Grade 3-4 neutropenia, anemia and thrombocytopenia at day 30 have been reported in 48% of patients given axicabtagene-ciloleucel (axi-cel) infusion in the ZUMA-1 and ZUMA-9 trials. We present two patients who received an autologous peripheral blood stem cell (PBSC) boost for prolonged severe cytopenias.

Methods: Patient A, a 65 year old man, received an autologous PBSC transplantation for DLBCL in partial remission, but relapsed 106 days later. Patient B, a 69 year old woman had an early relapse of a DLBCL and was not eligible for autologous PBSC transplantation due to progression under salvage treatment. Both patients fulfilled the criteria of the Austrian CAR-T-cell platform and thus, were eligible for anti-CD19 CAR-T-cell infusion with axi-cel (Yescarta ®) after lympho-depleting chemotherapy with 3 doses of cyclophosphamide 500mg/m² and fludarabine 30mg/m² body surface area. While patient A did not reveal any acute adverse events after CAR-T-cell infusion, patient B developed CRS grade I and obtained consecutively tocilizumab on days +9 and +10. Both individuals suffered from prolonged WHO grade 4 neutropenia, anemia and thrombocytopenia beyond day 30 including G-CSF refractory neutropenia. Therefore, bone marrow examination was performed at days 40 and 33 after CAR-T-cell infusion revealing no signs of DLBCL or myelodysplastic syndrome (MDS) but severely hypoplastic marrow involving all three cell lines. Therefore, we administered stored autologous PBSCs of 2.99 and 2.86 x10⁶ CD34⁺/kg body weight 48 and 33 days after CAR-T-cell infusion.

Results: Leukocyte engraftment (ANC > 500/μL) supported by G-CSF stimulation occurred 3 and 11 days after autologous PBSC boost. Platelet engraftment with platelets over 20.000/μL was observed in patient A 40 days after autologous PBSC boost. In patient B no platelet engraftment could be achieved within an observation period of 52 days after autologous PBSC boost. No signs of clinical infection or bleeding were observed both patients showed persistent complete metabolic remission of their malignancies at days +158 and +63 after CAR-T-cell infusion.

Conclusions: Autologous PBSC boost seems to be a rescue therapy for prolonged severe cytopenia after CAR-T-cell therapy. Reducing the duration of late cytopenia could lower risk of infectious complications and improve outcome of patients given CAR-T-cell therapy.

Disclosure: Nothing to declare

P075 CD72 is a promising substitute for cd19 as a malignant b cell target in immunotherapy and a rough b gating marker for flow cytometry detection

H. Wang ¹, A. Wang¹, M. Gong¹, M. Chen¹, X. Wu¹, J. Zhen¹

¹Hebei Yanda Lu Daopei Hospital, Langfang, China

Background: CD19-Chimeric Antigen Receptors T cell(CAR-T) has made a very big progress in treatment of B acute lymphoblastic leukemia(B-ALL) and lymphoma. CD19 is a very good target for CAR-T treatment and pan- B marker for Flow Cytometry(FCM) detection for it’s high coverage on B malignancies. However, 13%-60% cases were CD19 dim or negative when relapsed after CD19-CAR-T, so it’s urgent to find a substitute for CD19 not only as a new target of CAR-T but pan-B marker for FCM detection.

Methods: From October 2020 to August 2021, 315 newly diagnosed patients with hematological tumor in Hebei Yanda Lu Daopei Hospital were investigated for immunophenotyping. 350 bone marrow minimal residual diseases(MRD) tests were performed in 200 B-ALL patients. 3 Laser 10-color FACS Canto Plus was used for FCM detection, and Diva and kaluza softwares were used to analyze data. Combining rough B gates were set as CD24 or CD19 positive and CD72, cCD79a or CD19 positive, and MRD were detected by multi dimensional radar photos for quick and intuitive observation.

Results: 1. In 315 patients with hematological tumors, the positive rate of CD72 was 97.73%(129/132) in ALL-B, and 100%(32/32) in lymphoma, which includes 3 Burkitt lymphoma, 5 chronic lymphocytic leukemia (CLL), 8 diffuse large B-cell lymphoma (DLBCL), 2 follicular lymphoma (FL), 1 hair cell leukemia (HCL), 1 lymphoplasmacytic lymphoma (LPL), 4 mantle cell lymphoma (MCL), 7 marginal zone lymphoma (MZL), and 1 small cell lymphoma (SLL). CD72 positive rate was 10.27%(17/151) in non-B-cell tumors, including 10.85%(14/129) in AML, 40%(2/5) in mixed phenotype acute leukemia(MPAL), 14.29%(1/7) in T-ALL/LBL, and 0%(0/10) in multiple myeloma(MM). These results suggest that CD72 is a marker comparable to CD19 for its coverage, specificity and expression intensity are comparable to that of CD19, it can be used as a rough B gating marker for FCM MRD of post-targeted therapy and a highly effective target for further CAR-T therapy of CD19-negative relapsed cases. 2. In MRD detection, CD72 combined with CD19 and cCD79a can cover all B cells, with sensitivity and specificity as high as 100%. 3. different from old analysis methods in which many gate strategies and dot plots were used to analyze data, a multi-parameter and multi-dimention radar photo could offer a quick and high efficient method.

Conclusions: CD72 is highly expressed in B-cell tumors and may be an effective B cell marker after CD19. It can be used not only as a gating marker of B-ALL MRD, but also as a highly promising biomarker for further targeted therapy of CD19 negative relapsed cases.

Disclosure: Nothing to declare

P076 Developing a dietetic service for patients undergoing car-based cellular therapy; evaluated with patient reported experience and outcome measures

J. Morgan ¹, H. Long¹

¹Cardiff & Vale UHB, Cardiff, United Kingdom

Background: There is limited evidence regarding the role of nutrition during a CAR-based cellular therapy transplant. However, patients experience similar nutritional challenges to a HSCT. Patients will have increased nutritional requirements and experience side effects of their underlying condition including side effects of the transplant, which affects nutritional intake. Malnourished patients have poorer outcomes than well-nourished patients with 10% weight loss being regarded as a clinical prognostic factor. Nutrition & Dietetics at the University Hospital Wales has set up a service for CAR-T patients.

Methods: The dietitian benchmarked the service, developed the Dietetic nutrition pathway, worked as part of the CART MDT, developed patient nutritional resources and developed nutritional guidelines. Patients had a consultation with the dietitian during or just after apheresis for nutritional assessment and information sharing. The patients were supported with nutritional pre-habilitation until admission, for those who required it. Nutrition support and advice was provided by the dietitian during their inpatient stay for their CART cell therapy which continued until 30 days post- CART. Following this, patients who had ongoing nutritional challenges continued to have dietetic support regularly. All patients continued to have nutritional assessment, advice and support at 3 month and 6 month clinic appointments. Data collected for outcome measures included weight and patients reported experience measures (PREMs) using a questionnaire.

Results: 14 patients received their CART and experienced the dietetic service. All patient’s received nutritional support dietary advice in the pre-hab phase. 21% (n = 14) of patients required more aggressive nutritional pre-hab including nutritional supplementation. 100% (n = 14) of patients received nutrition support dietary advice and nutritional supplements during their inpatient stay with 14.3% (n = 14) of patients requiring nasogastric feeding during their CART. Mean weight loss in the pre-hab phase was 3.4% (range 0-12.5% median 2.3%) and mean weight loss from pre-hab to discharge at 30 days post-transplant was 6.6%.(range 0-23.2%, median 6.78%). Regarding PREMs, 100% (=14) of patients reported they strongly agreed that the dietetic input was clear, concise, easy to understand and empowered them to make dietary changes. 100% (n = 14) also reported they strongly agreed that they benefited from the dietetic service and patient information.

Conclusions: 21% (n = 14) of patients experienced weight loss above the 10% clinical prognostic factor. Patients experience of the dietetics service was very positive. The dietetic service to the CART patients will continue. Future development of this service will also include outcomes including bioelectrical impedance analysis (BIA) and hand grip strength.

Disclosure: Nothing to declare

P077 CAR-T as a bridge therapy in a case of all late resistant relapse

M. Comini¹, A. Beghin¹, V.M. Folsi², M. Chiarini³, E. Soncini², F. Bolda¹, D. Russo⁴, A. Lanfranchi¹, F. Porta ²

¹Stem Cell Laboratory, Section of Hematology and Blood Coagulation, Clinical Chemistry Laboratory, ASST Spedali Civili, Brescia, Italy, ²Pediatric Onco-Hematology and BMT Unit, Children’s Hospital, ASST Spedali Civili, Brescia, Italy, ³Flow Cytometry Unit, Section of Hematology and Blood Coagulation, Clinical Chemistry Laboratory, ASST Spedali Civili, Brescia, Italy, ⁴Dipartimento di Scienze Cliniche e Sperimentali, University of Brescia, Brescia, Italy

Background: CAR-T is an innovative anti-cancer therapy, treating B-cell ALL in children and young adults up to age 25. Despite a significantly increased survival in patients with ALL in the last decades, 2-3% of patients show a disease refractory to chemotherapy treatments and about 10-15% eventually relapse.

Methods: The first pediatric patient candidate to CAR-T therapy at the Children’s Hospital of Brescia was a 12-years-old girl diagnosed in 2015 with Non-Hodgkin B Lymphoma, stage III involving bone, CNS with BOM negative. She underwent therapy according to the LNH-97 protocol and achieved stop therapy in July 2017.

In January 2021, relapse occurred with a common B-ALL phenotype, CNS negative, AIEOP LLA REC 2003 protocol was started. Over the end of the therapy, persistence of blasts was present with strongly positive MRD. Therefore InterALL-HR-2010 R3 + Bortezomib protocol was given with, nevertheless, persistence of disease at the end of the treatment, with a marrow infiltrate of 12%.

In March 2021, she was enrolled in CAR-T program and autologous T lymphocytes were collected.

Results: In May 2021, after lymphodepleting therapy, 1.6 x 10⁸ CD3 + CAR-T cells were infused (Kymriah).

On post infusion day+4, patient presented fever, hypotension, hypoxemia attributable to CRS grade II associated with an increase of IL-6 (peak at day+7, 266 ng/L, range<7 ng/L). She was treated with a single dose of Tocilizumab with benefit and resolution of symptoms.

On day+17,+ 30,+ 60 MRD was negative.

At days+1,+3,+7,+10,+14,+16,+30,+86,+115,+120,+146 the presence of CAR-T was analyzed by flow cytometry and by a highly sensitive technique: digital droplet PCR(ddPCR), CAR-T were detected already on day+1 in ddPCR with a peak at day+10.

Five months after CAR-T infusion, patient lost B cell aplasia and MRD resulted positive with a rapid loss of CAR T cells.

Soon after she received HSCT from MUD after conditioning therapy with total body irradiation, Fludarabine and Thymoglobulin. HSCT was performed with a positive selection of CD34 + (10x10⁶ CD34 + /Kg infused) cells and T controlled addback (30x10⁶ CD3 + /Kg infused) from PBSC.

After HSCT, patient was monitored and MRD became negative in presence of cutaneous GvHD stage II. Donor chimerism performed on CD34 + cells from BM was 97.3%. Analysis of BM, moreover, showed persistence of CAR-T cells. The surprisingly persistence of CAR-T after HSCT can be explained by the results of the study of donor chimerism performed with ddPCR, that show 12% of autologous cells.

Conclusions: Monitoring of CAR-T cells with a very highly sensitive techniques, such as ddPCR, is of critical importance because it has been demonstrated that even low concentrations of CAR-T could have a therapeutic function.

However, in this case, the sudden decrease of CAR-T circulating cells and the appearance even of a very low number of B cells, suggested to immediately proceed to HSCT. In fact, MRD short after became slightly positive. CAR-T is an innovative therapy, several studies nevertheless, are ongoing to understand if it is a definitive therapy or a bridge to transplant. In our case it was the latter. It’s no clear if persistence of CAR-T after allogeneic HSCT could have a role of relapse prevention.

Disclosure: Nothing to declare

P078 Feasibility of autologous stem cell transplantation as bridging therapy prior to cd19 car-t in r/r large b cell lymphoma

E. Galli ^1,2, F. Sorà^1,2, S. Hohaus^1,2, S. Bellesi¹, F. Autore¹, M.A. Limongiello¹, I. Innocenti¹, E. Metafuni¹, S. Giammarco¹, L. Laurenti^1,2, P. Chiusolo^1,2, A. Bacigalupo^1,2, S. Sica^1,2

¹Dipartimento di Diagnostica per Immagini, Radioterapia Oncologica ed Ematologia, Fondazione Policlinico Universitario A. Gemelli IRCCS, Roma, Italy, ²Sezione di Ematologia, Dipartimento di Scienze Radiologiche ed Ematologiche, Università Cattolica del Sacro Cuore, Rome, Italy

Background: Peripheral blood autologous stem cells transplantation (PBSCT) has played pivotal role as consolidation for relapsed or high risk lymphomas, while its role is discussed in CAR-T cells era. Lower disease burden has been associated with better outcome after treatment with CAR-T cells; the intensity and role of bridging therapy has not been clearly stated. In this study, we aimed to assess the feasibility of PBSCT as bridging therapy before treatment with CAR-T cells in the setting of relapsed/ refractory B cell lymphomas.

Methods: We retrospectively analyzed six patients who had received FEAM-conditioned PBSCT as a bridging to CAR-T: we focused on cytopenias, specific CAR-T toxicities and outcomes.

Results: At the time of eligibility for CAR-T, all patients had ECOG 0-1, three had elevated LDH and five out of six had an IPI score of 3 or more. All patients had either refractory or early relapsed NHL. After lymphocyte collection was completed, patients were hospitalized for receiving PBSCT. Median time from lymphocyte collection to the beginning of bridging with PBSCT therapy was 6 days (range 1-44 days). Main toxicities related to PBSCT were grade 3 infections and grade 4 cytopenias. No unexpected toxicities were observed. Patients were discharged at a median of 12 days (range 11-15) after PBSCT. CAR-T manufacturing process took a median of 31 days. At the time of arrival of the product in our center, five of the six patients had been already discharged from the hospital after PBSCT. Prior to CAR-T cell conditioning, disease response to bridging with PBSCT was evaluated using PET-CT. Three patients obtained complete (CR) or partial (PR) response, two were in stable disease (SD) and one in progressive disease (PD) (Figure 1A).

Before the start of lymphodepletion, complete blood counts (CBC) had recovered from PBSCT with no grade 4 cytopenia. Median time from arrival of frozen CAR-T cells at our center and start of lymphodepletion was 22 days (12-46). Median time from PBSCT to CAR-T cells infusion was 50 days (48-74).

All patients experienced CRS, with only one grade 3 CRS, and no ICANS was documented. In terms of anti-lymphoma efficacy of PBSCT bridging, overall response at one month from CAR-T cell infusion was obtained in five out of six patients (83%), with three (50%) CR and two PR; responses were stable with those five patients still being alive without disease progression at median follow-up of 6 months after CAR-T.

Conclusions: We conclude that PBSCT is a feasible option as bridging therapy prior to CAR-T, with reasonable toxicities and efficient action on disease bulk. We than provide a review of literature on this topic.

Disclosure: Nothing to declare.

P079 Commercial manufacturing experience of tisagenlecleucel in europe: >3 years journey

M. Rodrigues¹, D. Kuzan², A. Yallouridis³, J.-M. Saffar², B. Eschgfaeller ¹

¹Novartis Pharma AG, Basel, Switzerland, ²Novartis Pharmaceutical Corporation, East Hanover, United States, ³Novartis (Hellas) S.A.C.I, Athens, Greece

Background: Tisagenlecleucel (Kymriah), an autologous CD19-directed CAR-T-cell therapy, has been approved by the European Medicines Agency in Aug 2018 for the treatment of children and young adults (aged up to and including 25 years) with relapsed/refractory (r/r) B-cell acute lymphoblastic leukemia and adults with r/r diffuse large B-cell lymphoma. Here, we discuss >3-year commercial tisagenlecleucel manufacturing experience across the four manufacturing sites in Europe and US (Les Ulis, France; Stein, Switzerland; Fraunhofer, Germany; and Morris Plains, US), for patients in Europe.

Methods: Tisagenlecleucel manufacturing process involves leukapheresis to collect patients’ peripheral blood mononuclear cells, which are cryopreserved and shipped to the manufacturing site. This is followed by enrichment and activation of T cells, transduction of the lentiviral vector containing the anti-CD19 CAR transgene, activation with anti-CD3/CD28 antibody-coated beads, expansion in cell culture, washing, and formulation of the viable cells into a cryopreservation medium, and shipping back for infusion (Tyagarajan, 2020).

Manufacturing success rate (MSR) was defined as the proportion of patients for whom the manufactured product met the commercial release criteria of the total number of patients leukapheresed. Shipment success rate (SSR) was defined as the proportion of patients for whom the manufactured product was shipped for infusion.

Results: Novartis has a significant global commercial manufacturing footprint with six sites located across the globe (US, France, Switzerland, Germany, Japan, and Australia) and a treatment network of >340 certified centers worldwide, including 164 centers in Europe. This allows for immediate manufacturing availability, thereby meeting the needs of patients. As of Aug-2021, tisagenlecleucel has been manufactured for more than 5300 patients worldwide.

For patients in Europe, the SSR was consistently high at 96%, and the MSR increased progressively from 84% in 2018 to 93% in 2021 (Figure). The corresponding out-of-specification (OOS) rates decreased considerably between 2018 and 2021 from 13% to 5%, with the viability OOS rates decreasing from 9% to 0%. The median turnaround time (apheresis pickup to delivery back to center) has improved from 33 days at launch in 2018 to 26 days currently.

Since the approval of tisagenlecleucel in 2018, a key goal has been to upscale and continuously improve manufacturing success, decrease OOS rate, and minimize the turnaround time in the commercial settings to meet the needs of a global patient population. In July 2021, two key process and analytical improvements have been introduced. Firstly, an alternate serum source (5% plasma-derived human AB serum) which further improves process robustness with a trend towards improved growth and higher peak cell counts. Secondly, a simplified sample preparation procedure for final product cell count and viability measurement, which is more reflective of final product at infusion.

Conclusions: Tisagenlecleucel’s current global commercial manufacturing footprint and treatment network are well-positioned to meet the anticipated increase in demand for CAR-T therapies. Over the last 3 years, SSR remained high at 96% and MSR improved to 93%. Continuous investment in process improvements has helped improve manufacturing capacity, robustness of manufacturing and testing processes, as well as speed and reliability to deliver tisagenlecleucel to patients in need of treatment.

Disclosure: All authors are employees of Novartis.

P080 Universal anti-cd123 car-γδt cells combined with donor lymphocytes infusion for relapsed acute myeloid leukemia after allogeneic hematopoietic stem cell transplantation

R. Zhang¹, R. Jiang ¹, X. Chen¹, J. Yao¹, Q. Liu¹, Y. Shi¹, Y. Cao¹, M. Gong¹

¹Chinese Academy of Medical Sciences & Peking Union Medical College,Institute of Hematology & Blood Diseases Hospital, Tianjin, China

Background: Patients with acute myeloid leukemia (AML) relapsed after allogenic hematopoietic stem cell transplantation (allo-HSCT) have poor prognosis although some therapeutic options including hypomethylating agents, chemotherapy, donor lymphocyte infusion (DLI), or a second allo-SCT could be adopted. The anti-CD123 chimeric antigen receptor-γδT (CAR-γδT), which is a promising therapeutic target for AML, might be a new way for relapsed AML after allo-HSCT.

Methods: A 43-year-old male patient with AML transformed from myelodysplastic syndrome underwent haploidentical-SCT in June 2019. Before transplantation, the percentage of primordial monocytes in bone marrow was 22%. Flow cytometry showed: primordial monocytes expressed CD34, CD123, HLA-DR. He received a myeloablative conditioning regimen and a successful hematopoietic reconstitution. Bone marrow examination showed complete remission with minimal residual disease (MRD) negative. Segment tandem repeat (STR) showed complete donor chimerism. To prevent relapse, the patient received 6 cycles of Azacytidine (50mg/m²/d*5d, once a month) since 4 months after haplo-SCT.

He suffered MRD positive (1.47%) relapse in July 2020. One cycle of Azacytidine combined with low-dose Cytarabine (20mg/m²/d*7) and 2 courses of Venetoclax (400mg/d*28) were administered successively. After above treatment, he experienced extensive chronic graft versus host disease (cGVHD) involving skin, eyes and mouth. Unfortunately, in December 2020, 1.5 years after haplo-SCT, he suffered hematological relapse. The percentage of primordial monocytes was 9.5% and STR dropped to 78.83%.

Universal anti-CD123 CAR-γδT cells were prepared from a third party umbilical cord blood. In brief, the γδT cells were selected using TCRg/d + T Cell Isolation Kit (Miltenyi) and stimulated with an anti-gd TCR antibody. Activated gd T cells were transduced with an anti-CD123 CAR-carrying lentivirus. Cell product were manufactured by Senlangbio company.

Pre-treatment was Fludarabine 50mg/d*5 and Melphalan 50mg/d *2. The patient received universal anti-CD123 CAR-γδT (2.5 × 10⁶/kg) and 7-days later, G-CSF mobilized and cryopreserved donor mononuclear cells (1.98 × 10⁸/kg) were infused including 0.693 × 10⁸/kg CD34 + stem cell and 1.67 × 10⁷/kg CD3 + T cell. Sirolimus(0.5mg/d) was started after donor cells infusion for GVHD-prophylaxis.

Results: After pre-treatment, MRD was 3.69% and STR was dropped to 61.12%. The universal anti-CD123 CAR-γδT proliferated rapidly from day+3 to day+7 and then decreased. The patient experienced grade 1 cytokines release syndrome including fatigure, nausia, headache and without neurotoxic syndrome. Seven days after CAR-γδT infusion, the bone marrow test showed: AML-MRD was negative and STR was increased to 90.24% and then donor mononuclear cells were infused. On day17 after CAR-γδT infusion, he was in agranulocytosis stage and suffered bacteremia and received antibiotic treatment. The patient achieved MRD negative remission and complete donor chimerism 21-days after CAR-γδT infusion. He did not develop acute GVHD or new onset cGVHD and sirolimus was stopped 1 month after donor lymphocyte infusion. There was an interesting finding that the number of universal anti-CD123 CAR-γδT increased again after donor cells infusion which might be due to the CD123 antigen expressed on donor cells (Figure-A,B). Six months later, the patient suffered hematological relapse again and received supportive treatment.

Conclusions: Universal anti-CD123 CAR-γδT combined with donor lymphocytes infusion seems to be an effective and safe treatment for AML relapsed after allo-HSCT.

Disclosure: no conflict of interest statement

P081 Successfull management of post- car-t cell cold aglutinin mediated refractory autoimmune hemolytic anemia with daratumumab

E. Erdoğan¹, M. Uluköylü Mengüç¹, K. Yalçın², C. Hemşinlioğlu³, E. Ovalı³, S. Ratip ¹

¹Acıbadem Altunizade Hospital, Istanbul, Turkey, ²Medical Park Hospital, Istanbul, Turkey, ³Acıbadem Labcell Cellular Therapy Center, Istanbul, Turkey

Background: CAR-T cell is an effective treatment in B cell malignancies. Cytokine Release Syndrome and CNS toxicity are the most frequent adverse reactions following CAR-T cell infusion. Although hemolytic anemia has been reported following hematopoietic stem cell translantation, cold aglutinin mediated hemolytic anemia after CAR-T cell infusion has not been reported. Anti CD20 therapies are the preferred first line therapy in cold agglutinin-mediated hemolytic anemia but response is usually not sustainable. Daratumumab, a novel anti CD38 monoconal antibody which has been approved for treatment of plasma cell dyscrasias is a logical option in refractory immune hemolytic anemia when conventional therapies fail as it targets autoantibody-producing plasma cells.

Methods: A 22 years old male patient received anti CD-19 directed academic CAR-T cell (ISIKOK-19) infusion due to relapsed acute lymphoblastic leukemia following haploidentical stem cell transplantation from his mother. He presented with post CAR-T cell refractory autoimmune hemolytic anemia. The case report presents treatment approach with Daratumumab for this patient.

Results: Patient with relapsed acute lymphoblastic leukemia following haploidentical stem cell transplantation was discharged on day +43 of CAR-T cell infusion but had to be re-admitted with acute Coombs positive hemolytic anemia on day +87. Bone marrow analysis was consistent with morphological and flow cytometric remission with full donor chimerism. Peripheral blood CAR-T cell level was adequate. Initial work-up excluded infectious and post-transplant lymphoproliferative etiologies. Low dose methylprednisolone of 20mg was chosen as first line treatment in order to avoid CAR-T cell apoptosis by steroid treatment. When there was no response IVIG was administered. Again no response was obtained. Autoantibodies were determined to be cold agglutinin in nature and weekly rituximab was commenced on day +92 . Anemia requiring massive transfusion persisted with severe hyperbilirubinemia reaching 30 mg/dL. Patient was administered a total of 97 units of RBC transfusion from beginning of hemolytic anemia and considering patient’s severe condition and lack of rituximab response, Daratumumab 16 mg/kg per week was commenced on day + 137. Following the first dose patient’s hemoglobin level continued to fall and blood transfusion and pulse steroid treatment at 250mg of prednisolone for 3 days had to be performed. Second, third and fourth doses of Daratumumab were administered weekly as scheduled. Transfusion requirement decreased from the second dose of Daratumumab, but patient received a total of 18 units of RBC transfusion whilst on 2 weeks of Daratumumab therapy. Steroid treatment was weaned down and stopped while consecutive weekly doses of Daratumumab continued. Patient reached a stable hemoglobin level following the third dose of daratumumab and remains steroid and transfusion free following the 4th and final dose of Daratumumab.

Conclusions: Cold agglutinin mediated hemolytic anemia post CAR-T cell treatment is a complex entity with lack of evidence based treatment . Anti CD38 monoclonal antibody daratumumab induces rapidly depletion of antibody producing plasma cells and can be an option in steroid, IVIG and Rituximab refractory cold agglutinin mediated autoimmune hemolytic anemia in CAR-T cell patients.

Disclosure: No conflict of interest

CAR-based Cellular Therapy – Preclinical

P082 Enhancement of long-term functionality of cd19 car-t cells by overexpression of tcf-1

H. Yao ¹, L. Wang¹, T. Sauer¹, S. Wang², M. Lin¹, Q. Chen¹, H. Han¹, Y. Ding¹, G. Jiang¹, B. Neuber¹, M.-L. Schubert¹, C. Kleist¹, V. Eckstein¹, C. Müller-Tidow¹, A. Schmitt¹, M. Schmitt¹

¹Heidelberg University, Heidelberg, Germany, ²Jiangsu Province People’s Hospital, Nanjing, China

Background: Chimeric antigen receptor T (CAR-T) cells mediate impressive anti-tumor effects in B cell malignancies, but fewer than 50% of patients experienced long-term disease control due to T cell exhaustion, which is a state of antigen-specific T cell dysfunction and subsequent physical deletion. During exhaustion, T cells can upregulate various inhibitory receptors, including PD-1, Lag-3, Tim-3, and progressively loss their effector function and proliferative capacity. The transcription factor T cell factor 1 (TCF-1) plays an important role in T cell development and maturation. T cells expressing a high level of TCF-1 exhibit a stem-cell-like phenotype and maintain a better proliferative capacity. To investigate the role of TCF-1 in CD19 CAR-T cells, we performed this study.

Methods: CD19 CAR-T cells were manufactured using the third-generation retroviral CAR vector (SFG.CD19.CD28/4-1BB/ζ). Double transduced T (DT-T) cells were generated using the same CD19 CAR vector with an extra TCF-1 vector (SFG.CD70_1F6.CH3-IgG4h-CH2-IgG4h.Tcf7.NGFR). The expansion of CAR-T cells during the manufacturing was determined by cell counting. The apoptotic state of CAR-T cells at the end of generation was evaluated by western blot using anti-PARP, anti-caspase-3, and anti-cleaved caspase-3 antibodies. The cytokine release capacity of CAR-T cells was analyzed by an intracellular cytokine staining. Moreover, a co-culture system was applied to determine the long-term function of CAR-T cells, where effector cells and target cells were plated at a 1:1 or 1:2 ratio, followed by a repetitive tumor challenge. The proliferative capacity of CAR-T cells, the number of challenging procedures, the number of residual tumor cells, and the exhaustion status of CAR-T cells were investigated in a co-culture assay using flow cytometry.

Results: Both CD19 CAR-T cells and DT-T cells were successfully generated with a stable transduction efficiency (CD19 CAR-T cells: 80.2%±5.21, DT-T cells: 55.1% ± 5.91) as well as a potent and specific killing capacity. Of note, DT-T cells at the end of generation showed downregulated expression of PARP and cleaved caspase 3, suggesting a lower tendency to apoptosis than CD19 CAR-T cells. The array resulted in a greater cell number of DT-T cells than CD19 CAR-T cells. Although DT-T cells showed a lower killing efficiency in a 4-hour killing assay due to the reduction of cytokines (CD19 CART group: TNF-α 67.68% ± 4.57, IFN-γ 42.6% ± 10.1, CD107a 82.4% ± 4.2, DT group: TNF-α 52.3 ± 3.9, IFN-γ 29.6%±8.1, CD107a 61.8%±8.1), they exhibited a superior functionality than CD19 CAR-T cells in the long-term killing assay. An improved proliferative capability was observed in DT-T cells throughout the co-culture, showing a great expansion(Day11, NT 41.97E7 ± 15.37E6, CD19 CART 28.53E6 ± 9.6E6, DT46.61E6 ± 10.69E6). The inhibitory receptors (PD-1, Tim-3, and Lag3) were reduced on DT-T cells when compared with CD19 CAR-T cells. The long-term killing ability of DT-T cells was dramatically improved, which was evidenced by an increased number of challenging procedures and a powerful reduction of residual tumor cell number.

Conclusions: Overexpression of TCF-1 might constitute a novel way to improve the functionality of CAR-T cells through the reduction of apoptosis, the improvement of proliferation, and the enhancement of the resistance to exhaustion.

Disclosure: Nothing to declare

P083 Disruption of cin85 enhances proliferation and cytotoxicity of cd19-specific car-t cells

M. Lin ¹, Q. Chen¹, L. Wang¹, D. Sedloev¹, B. He^1,2, X. Yu¹, H. Han¹, G. Jiang¹, H. Yao¹, A. Schmitt¹, M. Schmitt¹, C. Müller-Tidow¹, T. Sauer¹

¹University Clinic Heidelberg, Heidelberg, Germany, ²Nanfang Hospital, Guangzhou, China

Background: CD19-specific chimeric antigen receptor (CAR) T-cells (CD19CARTs) have significantly improved the outcome of patients with relapsed B-cell malignancies such as acute lymphoblastic leukemia (ALL) and certain type of non-Hodgkin’s lymphoma (NHL). However, despite treatment with CD19CARTs, a significant proportion of patients eventually relapse, highlighting the need to further improve the functionality of CD19-CAR T-cell products. CIN85 protein, also known as SH3 domain-containing kinase-binding protein1 (SH3KBP1), has been shown to inhibit T-cell activation through its interaction with phosphatase suppressor of TCR signaling-2 (Sts-2) within the T-cell receptor (TCR) complex. As the CAR-mediated activation of T-cells depends on pivotal components of the TCR, we hypothesized that the disruption of CIN85 may lead to the enhancement of CAR-mediated T cell activation, hereby improving the proliferation and anti-tumor efficacy of CD19 CAR T-cells.

Methods: Two days after activation using CD3 and CD28-specific antibodies, T-cells from healthy donors were retrovirally transduced with a third generation CD19 CAR construct containing the CD28 and 4-1BB co-stimulatory domain followed by a CRISPR/Cas9-mediated disruption of the CIN85 gene using ribonucleoprotein (RNP) complexes on day 6 (CIN85KO-CD19CARTs). Successful CAR transduction and CIN85 gene disruption were confirmed by flow cytometry (FACS) and western blot (WB) respectively. Subsequently, we performed in vitro studies to evaluate proliferation capacity, viability/apoptosis, and potential changes in the T-cell phenotype of CIN85KO-CD19CARTs. In addition, cytokine production upon antigen stimulation was determined by intracellular cytokine staining (ICS) and cytotoxicity was tested using a standard chromium (Cr51) release assay.

Results: During ex-vivo expansion, CIN85KO promoted enhanced proliferation of CD19CARTs compared to non-modified CD19CARTs leading to a higher expression of the proliferation marker Ki67 as detected by flow cytometry. In addition, we noticed a higher percentage of CAR expressing T cells in the CIN85-KO-CD19CART product compared to the control CAR T-cells. CIN85KO-CD19CARTs showed a higher surface expression of markers associated with T-cell activation such as CD69, CD25, HLA-DR, Tim-3, PD-1 and LAG-3 than CD19CARTs whereas CIN85 disruption did not affect the CD4/CD8 composition of the CAR T-cell product. Importantly, higher activation status did not lead to a higher rate of apoptosis and cell death on CIN85KO CD19 CAR T-cells. In both, the CD4 positive and CD8 positive subpopulations, a higher percentage of CIN85-CD19CARTs expressed surface markers associated with a central memory and effector memory phenotype whereas a lower percentage of CIN85-CD19CARTs exhibited a terminally differentiated T cell phenotype compared to non-modified CD19-CARTs. Functionally, CIN85-CD19CARTs secreted a significantly higher amount of activating cytokines such as IFN-γ, TNF-α and IL-2 and exhibited a stronger cytotoxic activity in the 51Cr release assay upon stimulation with CD19-positive tumor cells than CD19CARTs.

Conclusions: Disruption of CIN85 enhances proliferation, activation, and cytotoxic activity of CD19CARTs, while at the same time skewing the cells to a more favorable T-cell phenotype. Our results warrant further in-vitro and in-vivo studies to determine the potential of this approach to improve the functionality of CAR T-cells products .

Disclosure: Nothing to declare

P084 Impact of serum-free media on the expansion and functionality of cd19.car t cells

F. Eberhardt ¹, A. Keib¹, A. Hückelhoven-Krauss¹, G. Jiang¹, A. Reichman¹, A. Schmitt¹, C. Müller-Tidow¹, M. Schmitt¹

¹University Hospital Heidelberg, Heidelberg, Germany

Background: Fetal bovine serum (FBS) or human serum (HS) is widely used in the production of chimeric antigen receptor T cells (CARTs). To overcome a lot-to-lot inconsistency and a risk of contamination the use of chemically-defined, animal-component free medium would be desirable. In this study, we compared three serum-free media to CART medium containing FBS.

Methods: After 12 days of CD19.CART culture, we assessed expansion, viability, transduction efficiency and phenotype by flow cytometry. Functionality of CARTs was tested by intracellular staining, chromium release assay and long-term co-culture assay: CARTs co-cultured with tumor cells for the period of 30 day were subjected to multiparametric flow cytometry.

Results: CARTs were cultured in different media such as Fujifilm™ Prime-XV™ T Cell CDM (FF), Takara Bio™ LymphoONE™ T-Cell Expansion Xeno-Free Medium (TB) or CellGenix™ TCM GMP-Prototype (CG). These CART cultures did not vary in terms of expansion and viability when compared to FBS-containing medium. Transduction efficiency and CD4 + /CD8 + ratio of CARTs were significantly lower for CARTs cultured in TB (64.5% vs. 86.5%, P = 0.0167; 1.4 vs. 2.8, P = 0.0319) and CG (65.8% vs. 86.5%, P = 0.0358; 1.5 vs. 2.8, P = 0.0232) compared to CARTs of serum-containing medium. The functionality of CARTs was tested by intracellular staining and chromium release assay. CARTs of CG had the highest frequency of IFNγ + and IFNγ + TNF-α + CARTs compared to CARTs cultured with serum (22.5% vs. 7.6%, P = 0.0194; 15.3% vs. 6.2%, P = 0.0399). IFNγ-expression of CARTs cultured in TB was also significantly higher (16.9% vs. 7.6%, P = 0.0336). These findings corresponded to the results of chromium release assay. On average of four effector-to-target cell ratios CARTs of CG showed the highest cytotoxicity (P = 0.0182), CARTs of FF showed a similar high effectiveness (P = 0.0482) and CARTs of TB had also a higher rate of killed tumor cells (P = 0.0428) than CARTs cultured with FBS. Phenotyping on day 12 of CART production did not show a significant difference in expression of exhaustion markers PD-1, LAG-3 and TIM-3. CARTs cultured in FF had a higher percentage of central memory CARTs (40.0% vs. 14.3%, P = 0.0470) than CARTs cultured with FBS, whereas CARTs of CG (9.8% vs. 14.3%, P = 0.0092) and TB (6.1% vs. 14.3%, P = 0.0210) had a significantly lower frequency. In contrast, CARTs of FF (6.2% vs. 24.2%, P = 0.0029) and CG (11.0% vs. 24.2%, P = 0.0468) had a lower frequency of naïve CARTs. Long-term cytotoxicity was tested by co-culture assay. Cells cultured with FBS showed the highest CART expansion and lowest expansion of target cells indicating the best long-term cytotoxicity of CARTs. On day 30 of co-culture CARTs cultured in FF, TB and CG had a higher expression of LAG-3 (non-significant; 91.7% vs. 41.1%, P = 0.0306; 86.8% vs. 41.1%, P = 0.0205) and TIM-3 (77.3% vs. 32.5%, P = 0.0159; 90.8% vs. 32.5%, P = 0.0034; 68.1% vs. 32.5%, P = 0.0294) compared to CARTs cultured with FBS.

Conclusions: We could demonstrate that functionality and expansion of CARTs are maintained in serum-free media. Given the advantages of freedom from bovine material and consistent quality, serum-free media keep promise for the future development of the field of GMP manufacturing of CARTs.

Disclosure: A.S.: Hexal and Jazz Pharmaceuticals (travel grants), Therakos/Mallinckrodt (research grant), TolerogenixX Ltd. (co-founder and part-time employee). C.M.-T.: Bayer AG (research support), Pfizer and Janssen-Cilag GmbH (advisory board member), Pfizer, Daiichi Sankyo, BiolineRx (grants and/or provision of investigational medical products), Pfizer (clinical trial financial support). M.S.: Apogenix, Hexal and Novartis (research support), Hexal and Kite (travel grants), bluebird bio, Kite and Novartis (financial support for educational activities and conferences), MSD (advisory board member), MSD, GSK, Kite and BMS ((co-)PI of clinical trials), TolerogenixX Ltd. (co-founder and shareholder). The other authors have no COI.

P085 Thomsen-friedenreich antigen cd176 as a new target of car-t cells to control multiple carcinomas

L.M. Beermann¹, M. Umland¹, A. Bonifacius ¹, A.C. Dragon¹, L. Ruhl¹, P. Kehler², J. Gellert², T. Lischke², K. Zimmermann¹, S. Riese¹, F. Thol¹, B. Maecker-Kolhoff¹, A. Schambach¹, R. Blasczyk¹, M. Hudecek³, B. Eiz-Vesper¹

¹Hannover Medical School, Hannover, Germany, ²Glycotope, Berlin, Germany, ³University Hospital Würzburg, Würzburg, Germany

Background: The generation and administration of Chimeric Antigen Receptor (CAR)-T cells represents a therapeutic approach that is approved for the treatment of distinct hematological malignancies and evaluated intensively for the extension to other tumor entities including solid tumors. CAR-T cell therapy relies on autologous lymphocytes, which are transduced to express a tumor antigen-specific CAR and transferred back into the patient, where they exhibit potent anti-tumor activity. However, CAR-T cells also cause adverse side effects such as the potentially life-threatening cytokine release syndrome. Moreover, CD19 CAR-T cell therapy does not distinguish between healthy and malignant B cells, indicating the necessity to develop CAR-T cells against more suitable target molecules. Nearly 80% of carcinomas and leukemia are positive for glycan structures from the Thomsen-Friedenreich (TF) antigen family, one of whose members is CD176 (Galβ1-3GalNAcα1-R). Due to different modifications (e.g. sialylation or fucosylation), CD176 is not accessible for ligand binding on healthy cells, but exposed on several carcinomas including hepatocellular, breast, colorectal and lung carcinomas as well as various leukemic cells. Thus, CD176 is a potential target for immunotherapy of multiple carcinomas.

Methods: We designed a 2^nd generation CAR to direct T cells against the carbohydrate epitope CD176. The ability of this CD176 CAR to initiate T cell signaling upon distinct target recognition of different carcinomas was tested in a reporter assay using a variety of tumor cell lines with different levels of CD176 expression as target cells. These included healthy CD176-negative cells, CD176-positive lung, breast and pancreatic cancer, as well as acute myeloid leukemia cell lines. Furthermore, primary CD176 CAR-T cells were generated and their functionality assessed in co-cultures with the same target cells evaluating the potential treatment of different tumor entities.

Results: A reporter assay revealed that T cell activation initiated by the CD176 CAR constructs upon recognition of cell lines derived from different carcinomas was specific to the presence of CD176. Upon co-cultivation of primary CD176 CAR-T cells with the same CD176-positive cells, the expression of activation markers (e.g. CD69) and the release of pro-inflammatory cytokines (e.g. IFN-γ, TNF-α) was equally upregulated in a target-specific manner. Moreover, the engineered T cells released cytotoxic mediators (e.g. granzyme B, granulysin) and exhibited cytotoxicity towards different cancer cell lines determined by 7-AAD staining in flow cytometry and confirmed by real-time impedance measurements (xCELLigence). Taken together, CD176-specific CAR-T cells were generated and showed a CD176-specific cytotoxicity towards a variety of different cancer cell lines.

Conclusions: Due to its differential modification – being accessible for ligand or antibody binding on malignant cells, but not accessible on healthy tissue – the carbohydrate antigen CD176 is a promising target for cancer immunotherapy. Our results demonstrate that CD176-specific CAR-T cells specifically recognize and react towards target cells from different tumor entities. Generating CAR-T cells targeting a structure present on a variety of tumor entities might allow for the simultaneous targeting of multiple carcinomas in the future.

Disclosure: Nothing to declare.

P086 Cell therapy based on nkg2d-car transduced cytotoxic cells against acute myeloid leukemia

L. Córdoba ^1,2, E. Castellano^1,2, A. Valeri^1,2, P. Rio³, A. García-Ortiz^1,2, J. Encinas¹, E. Maroto^1,2, D. Lee⁴, D.J Powell Jr⁵, J. Martínez López^1,2, A. Leivas^1,2

¹Hospital Universitario 12 de Octubre, Madrid, Spain, ²Centro Nacional de Investigaciones Oncológicas, Madrid, Spain, ³Centro de Investigaciones Energéticas, Medioambientales y Tecnológicas, Madrid, Spain, ⁴The Research Institute at Nationwide Children’s Hospital, Ohio, United States, ⁵University of Pennsylvania, Philadelphia, United States

Background: Acute Myeloid Leukemia (AML) is a hematological malignancy still incurable for almost all patients. Chimeric Antigen Receptor (CAR) therapy is showing astonishing results in other hematological disorders but remains challenging in AML since no specific antigens have been described yet. Using NKG2D as a CAR, a natural NK receptor with 8 ligands (NKG2DLs) overexpressed in several tumors, could surmount AML targeting limitations. T cells are considered the gold standard immune effector cells for CAR therapy, but they show some toxicities that could be overcome using other cells such as activated and expanded natural killer cells (NKAE), that can be used in an allogeneic context with no GvHD, have natural anti-tumor properties and have demonstrated to be clinically safe. In this project we analyze the anti-leukemia activity and safety of peripheral blood NKAE cells lentivirally transduced with an NKG2D-41BB-CD3z CAR.

Methods: Peripheral blood mononuclear cells (PBMCs) from healthy donors (HD) and/or AML patients were cocultured during 7 days with the irradiated cell line k562-mb21-41BBL, when NKAEs were isolated by magnetic immunodepletion and lentivirally transduced with an NKG2D-41BB-CD3z CAR. CAR expression was measured up to 13 days post-transduction by flow cytometry. Cytotoxic activity against AML cell lines was performed by Propidium Iodide and Annexin V staining. Toxicity was evaluated by Europium-TDA assays. Effector cells were characterized by flow cytometry and Cytometric Bead Arrays were done to study cytokine release profile.

Results: AML can be targeted with an NKG2D CAR since all patients studied express at least one NKG2DL. Primary NK cells can be lentivirally transduced with an NKG2D CAR, showing a modest but stable CAR expression up to 13 days after transduction (23% ±4,7% NKG2D + , 33,35% ±4,25% GFP + ). CAR-NKAE cells perform robust cytotoxicity towards MOLM-13 AML cell line after 24h of coculture at an effector:target ratio of 1:1, exerting a quasi-total lysis of AML cells. This represents a significant increase in anti-leukemia effect compared to untransduced NKAE (92,6% ±0,3% vs 72,2% ±10%, p = 0,0138). Surface expression of relevant molecules for NK activity showed that NKp30, NKp44 (natural cytotoxicity receptors), CD69 (early activation marker), CD25 (IL2R alpha chain), FasL (mediates FasL-mediated cytotoxicity), NKp80 (C-type lectin-like surface-activating receptor) and TRAIL (TNF-Related Apoptosis Inducing Ligand) were more expressed by transduced NKAE. Cytokine release profile revealed a higher production of IL-6, IL-17A, sFasL and IFNg by CAR-NKAE. These results suggest that the studied mechanisms could be underlying the increased anti-tumor activity shown by CAR-NKAE. We did not observe relevant toxic effect of none of the cells against PBMCs from HD. Low toxicity was found against NL-20 lung cell line, but there were no differences between NKAE and CAR-NKAE.

Conclusions: Our preliminary results show that primary NK cells from HD and/or AML patients can be lentivirally transduced with a second generation NKG2D CAR, exerting a robust anti-leukemia activity towards AML cell lines and a safe profile over healthy tissues. Therefore, NKG2D CAR NKAE could be considered a promising approach to treat AML.

Disclosure: DJPJ holds patents in CAR-T-cell therapy field. DAL declares an equity interest, advisory role, and intellectual property licensing to CytoSen Therapeutics and Kiadis Pharma, and advisory role with Caribou BioSciences and Courier Biosciences. PR has licensed medicinal products and receives research funding and equity from Rocket Pharmaceuticals, Inc., Patents & Royalties, Research Funding. The remaining authors declare no competing interests.

P087 Comparison of second and third generation car33-t cells in terms of proliferation and cytotoxicity in acute myeloid leukemia

A. Lauk ¹, Y. Liu^1,2,3, H. Yao¹, M.-L. Schubert¹, S. Wang^1,4,5, M.F. Blank¹, C. Cui^1,6, M. Janssen¹, C. Schmidt¹, S. Göllner¹, C. Kleist¹, F. Zhou¹, J.-U. Rahfeld⁷, T. Sauer¹, M. Schmitt¹, C. Müller-Tidow^1,2,3

¹University hospital Heidelberg, Heidelberg, Germany, ²Molecular Medicine Partnership Unit (MMPU), Heidelberg, Germany, ³European Molecular Biology Laboratory (EMBL), Heidelberg, Germany, ⁴First Affiliated Hospital of Nanjing Medical University, Nanjing, China, ⁵Collaborative Innovation Center for Cancer Personalized Medicine, Nanjing, China, ⁶Shanghai University of Medicine and Health Sciences, Shanghai, China, ⁷Fraunhofer Institute for Cell Therapy and Immunology IZI, Halle (Saale), Germany

Background: Since CD33 is expressed on over 90% of acute myeloid leukemia (AML) blasts and leukemic stem cells and is indispensable for cell survival, it is a promising target for immunotherapy in AML, such as CAR-T cells or antibody drug conjugates.

Methods: To compare the functionalities of second generation CARs and third generation CARs we generated two second generation anti-CD33 CAR (CAR33) with either 4-1BB or CD28 as costimulatory domains and a third generation CAR33. We evaluated the proliferation and cell viability of second and third generation CAR33-T cells. The cytolytic capacity of the CAR33-T cells against AML cell lines, primary AML blasts and human stem and progenitor cells (HSPCs), was determined by Chromium51 release assay and the antigen-specific response by cytokine secretion assay. The long-term killing capacity was assessed by coculturing CAR-T cells with target cells for 10 days with rechallenging of the CAR-T cells on every second day. To prove the antigen specificity of CAR33-T cells, functional assays were performed against CD33 positive and negative target cells.

Results: First, the cytotoxicities of CAR33-T cells are antigen-specific and antigen-dependent. Only CD33-positive, but not CD33-negative cells were killed by CAR33-T cells and could stimulate CAR33-T cells to secrete cytokines. Second, we found that the second generation CAR33-T cells with CD28 as costimulatory domain (2G.CD28.CAR33-T) had comparable viability but reduced proliferation capacity compared to the third generation CAR33-T cells (3G.CAR33-T), whereas the second generation CAR33-T cells with costimulatory domain 4-1BB (2G.4-1BB.CAR33-T) expanded less with lower viability. In terms of short- and long-term killing capacity and levels of cytokine release 2G.CD28.CAR33-T cells and 3G.CAR33-T cells showed similar abilities, while 2G.4-1BB.CAR33-T cells exhibited the lowest potential.

Conclusions: In summary, third generation CAR33-T cells exhibited improved properties in terms of viability and proliferation as well as short- and long-term anti-tumor activity when compared to second generation CAR33-T cells.

Disclosure: Maximilian Felix, Blank: Molecular Health GmbH (consultant)

Maria-Luisa, Schubert: Kite/Gilead, Takeda (consultant).

Michael, Schmitt: Apogenix, Hexal and Novartis (research support). Hexal, Kite/Gilead (travel grants). Bluebird bio, Kite, Novartis (financial support for educational activities and conferences). MSD (advisory board member). MSD, GSK, Kite, BMS ((co-)PI of clinical trials). TolerogenixX Ltd. (co-founder and shareholder).

Carsten, Müller-Tidow: Bayer AG (research support). Pfizer, Janssen-Cilag GmbH (advisory board member). Pfizer, Daiichi Sankyo, BiolineRx (grants and/or provision of investigational medicinal products).

Christian, Kleist: TolerogenixX Ltd. (co-founder and shareholder).

Tim, Sauer: Pfizer, Gilead, Amgen, Takeda, Astellas, BMS (advisory board member), AbbVie, Pfizer (financial support for educational activities and conferences), Matterhorn Biosciences, Ridgelien Discovery (consultant).

P089 Cd19-car-inkt cell activity is enhanced by pd-1 checkpoint inhibition while preventing alloreactivity

E. Moraes Ribeiro¹, A.-M. Nitulesco¹, R. Schairer¹, H. Keppeler¹, F. Korkmaz¹, B. Neuber², C. Schneidawind¹, M. Schmitt², D. Schneidawind ¹

¹University Hospital Tuebingen, Tuebingen, Germany, ²University Hospital Heidelberg, Heidelberg, Germany

Background: Relapse and graft-versus-host disease (GvHD) are the main causes of morbidity and mortality after allogeneic hematopoietic cell transplantation (HCT). We recently showed that human iNKT cells inhibit alloreactive donor T cells and promote graft-versus-leukemia (GvL) effects. Now, we aim to further enhance the antileukemic potential of iNKT cells by introducing a chimeric antigen receptor (CAR) while maintaining their tolerogenic properties making them an ideal cytotherapeutic candidate to treat relapse after allogeneic HCT.

Methods: CD19-CAR-iNKT cells were co-cultured with acute lymphoblastic leukemia (ALL) and Burkitt lymphoma (BL) cells. Cytotoxicity was analyzed by subsequent multiparametric flow cytometry and multiplex analysis. To assess the immunomodulatory properties of CD19-CAR-iNKT cells, T-cell activation (flow cytometry) and proliferation (CFSE dilution) of conventional T cells were analyzed after co-culture with allogeneic mo-DCs in presence or absence of CD19-CAR-iNKT cells.

Results: CD19-CAR-iNKT cells showed robust cytotoxic activity against ALL and BL cell lines and primary patient cells. Multiplex analysis revealed the release of inflammatory cytokines such as IFN-γ and TNF as well as cytotoxic effector molecules like granzyme A, granzyme B and perforin. Interestingly, PD-1 expression was increased on CD19-CAR-iNKT cells after being challenged with lymphoma cells. Consequently, adding the checkpoint inhibitor nivolumab further increased the activity of CD19-CAR-iNKT cells. Regarding their tolerogenic properties, CD19-CAR-iNKT cells retained their ability to induce apoptosis of mo-DCs through CD1d signaling independent of the CAR resulting in reduced activation and proliferation of alloreactive T cells.

Conclusions: We demonstrate that CD19-CAR-iNKT cells efficiently lyse CD19 + leukemia and lymphoma cells through their CAR while preventing alloreactive T cell responses interacting with dendritic cells. Checkpoint inhibition may further increase their cytotoxic activity without exacerbating the risk of GVHD after allogeneic HCT making them an ideal cytotherapeutic to treat relapse in this challenging clinical setting.

Disclosure: Nothing to declare

P090 Functionality and endurance of gmp-standard bcma-car-t cells at different timepoints

G. Jiang ¹, A. Keib¹, U. Höpken², B. Neuber¹, J. Joedicke², D. Sedloev¹, L. Wang¹, A. Reichman¹, A. Hückelhoven-Krauss¹, B. He¹, F. Eberhardt¹, C. Müller-Tidow¹, M. Wermke³, A. Rehm², A. Schmitt¹, M. Schmitt¹

¹University Clinic Heidelberg, Heidelberg, Germany, ²Max-Delbrück Center for Molecular Medicine (MDC), Berlin, Germany, ³University Hospital Carl Gustav Carus Dresden, Dresden, Germany

Background: Multiple myeloma is a hematological disease characterized by an uncontrolled proliferation of plasma cells. New therapeutical agents developed survival rates but the outcome of the disease remains to be improved. The search for target antigens for CAR-T cell therapy against multiple myeloma yielded with the B-cell maturation antigen (BCMA) a possible candidate. Several studies of BCMA-directed CAR-T-cell therapy showed promising results.

Methods: Second generation BCMA-CAR-T cells were manufactured at GMP standard by using the CliniMACS Prodigy^® device. Cytokine-release in BCMA-CAR-T cells after stimulation with BCMA positive versus negative myeloma cell lines, U266/HL60, was determined by intracellular staining and flow cytometry. The short-term cytotoxic potency of CAR-T cells was evaluated by chromium-51 release, while the long-term potency used co-culture (3 days/round) at the effector:target cell ratio of 1:1 and 1:4. To evaluate the activation and exhaustion of CAR-T cells, exhaustion markers were assessed by flow cytometry. Stability was tested by comparison of these evaluation on different timepoints: d0 as well as d + 14 and d + 90 of cryopreservation.

Results: BCMA-CAR-T cells can release much more cytokines upon stimulation with U266 cells in all donors (20.29 ± 4.868 and 1.193 ± 0.560, P = 0.0199; 20.16 ± 5.122 and 0.764 ± 0.597, P = 0.0194; 62.21 ± 2.029 and 1.348 ± 0.134, P = 0.0004) but not HL60 cells (1.820 ± 0.866 and 1,193 ± 0.560, P = 0.3102; 1.533 ± 0.627 and 0.764 ± 0.597, P = 0.0921; 2.922 ± 0.667 and 1.348 ± 0.134, P = 0.0602). Interestingly TNFa release was higher than IFNg on every timepoint (58.80 ± 8.890 and 18.92 ± 4.604, P = 0.0188; 59.35 ± 4.000 and 20.68 ± 5.198, P = 0.0179; 72.19 ± 2.379 and 63.32 ± 0.723, P = 0.0266). For CD8 + BCMA-CAR-T cells, TNFa and IFNg had the same level of cytokine-release (47.61 ± 10.07 and 30.00 ± 1.143, P = 0.076; 40.99 ± 10.42 and 33.88 ± 8.733, P = 0.1922; 72.85 ± 4.142 and 68.48 ± 4.195, P = 0.4590). However, CD4 + BCMA-CAR-T cells had lower level of IFNg than TNFa (10.40 ± 3.332 and 61.86 ± 10.57, P = 0.0065; 63.99 ± 6.929 and 13.50 ± 5.956, P = 0.0134; 49.82 ± 4.682 and 76.72 ± 4.737, P = 0.0345). There was no significant difference in cytokine-release after cryopreservation: neither double positive CAR-T cells (P = 0.9350) nor single positive (TNFa/IFNg) CAR-T Cells (P = 0.2786, P = 0.2489). Killing efficiency of U266 cells correlated with the dose of CAR-T cells in a classical 4-hour chromium-release assay. There was no significant difference after cryopreservation on timepoints d + 14 or d + 90 (P = 0.1300, P = 0.9602). As for long-term potency, after 3-rounds co-culture, BCMA-CAR-T cells reached to dominant position while U266 cells nearly disappeared at both ratios. As for endurance of BCMA CAR-T cells function, BCMA CAR-T cells kept their ability to kill all U266 cells over six rounds. Exhaustion markers were detected to evaluate CAR-T cells: LAG3 declined when CAR-T cells were activated and proliferated but decreased when they failed to kill; PD1 showed a similar trend as LAG3 but TIM3 had a curve trend.

Conclusions: BCMA-CAR-T cells manufatured under GMP conditions possessed the ability for robust and specific killing of target tumor cells with a higher release of cytokines. Even after 14 or 90 days of cryopreservation, their cytotoxic functions were maintained at the same level. This give clinicians enough time to schedule the timepoint of BCMA CAR-T cell application to the patient.

Disclosure: Nothing to declare

Cellular Therapies other than CARs

P091 Unmanipulated donor lymphocyte infusion (dli) after ab-t and b-cell depleted haploidentical stem cell transplantation

C. Rosignoli¹, F. Galaverna ¹, D. Pagliara¹, M. Algeri¹, R. Carta¹, M. Becilli¹, E. Girolami¹, S. Biagini¹, G. Li Pira¹, G. Leone¹, A. Meschini¹, S. Lazzaro¹, G. Del Principe¹, E. Boccieri¹, F. Quagliarella¹, M.L. Catanoso¹, C. Canino¹, F. Del Bufalo¹, P. Merli¹, F. Locatelli^1,2

¹Istituto di Ricovero e Cura a Carattere Scientifico Ospedale Pediatrico Bambino Gesù, Rome, Italy, ²Sapienza University, Rome, Italy

Background: Allogeneic hematopoietic stem cell transplant (allo-HSCT) represents an effective curative option for several malignant diseases; relapse remains the main cause of treatment failure. ab-T and B-cell depleted haploidentical HSCT offers a unique platform to evaluate the effect of post-HSCT Donor Lymphocyte Infusion (Haplo-DLI) in high-risk patients.

Methods: Between August 2016 and July 2021, 32 high-risk patients received unmanipulated haplo-DLI after an ab-T and B-cell depleted haploidentical-HSCT (tab.1). Haplo-DLI were prophylactic in 19 cases due to high-risk disease [very high risk at diagnosis, previous allo-HSCT and positive minimal residual disease (MRD) at HSCT] and pre-emptive in 13 cases due to early post-transplant positive MRD.

Results: Haplo-DLI were infused at median time of 4,2 months after transplant (range 1-43). Median CD3 + , CD4 + and CD8 + infused cells were 0,473x10^6/kg (range 0,059-3,044), 0,289x10^6/kg (range 0,022-2,140) and 0,160x10^6/kg (range 0,012-0,069), respectively. Fifteen patients received more than one infusion (table 1). Six patients developed grade III-IV acute GvHD at a median of 43 days after Haplo-DLI (range 34-76), the cumulative incidence of this complication being 19% (95% CI 9-38%). Seven out of 13 patients (54%) who received pre-emptive Haplo-DLI remained disease-free over time, while response rate for prophylactic haplo-DLI was 74% (14/19). With a median follow-up of 24 months, global progression free survival (PFS) and overall survival (OS) were 64% (95% CI 45-78%) and 71% (95% CI 50-84%), respectively; non relapse mortality (NRM) was 13% (95% CI 5-13%).

Table 1. Patients characteristics.

Median age at transplant, ys (range)	7 (0-24)
Sex, M/F	16/16
Disease, n (%)
ALL	21 (66)
AML	7 (22)
MDS	2 (6)
CML	1 (3)
HL	1 (3)
Disease status at HSCT, n (%)
MRD-	13 (41)
MRD +	14 (44)
active disease	5 (16)
Previous allo-HSCT, n (%)	7 (22%)
Conditioning, n (%)
MAC	28 (87)
RIC	4 (12)
DLI indication, n (%)
prophylaxis	19 (57)
pre-emptive	13 (43)
Time interval between HSCT- 1^ DLI
median days (range)	120 (24-1238)
Number of DLI, n (%)
2	17 (53)
3	8 (25)
4	7 (22)
CD3x10^6/kg (median) (range)	0,473[MP1] (0,059-3,044)
CD4 × 10^6/kg (median) (range)	0,289 [MP2] (0,022-2,140)
CD8 × 10^6/kg (median) (range)	0,130[MP3] (0,012-0,069)

ALL, acute lymphoblastic leukemia; AML, acute myeloid leukemia; CML, chronic myeloid leukemia; DLI, donor lymphocyte infusion; GvHD, graft versus hosti disease; HL, Hodgkin lymphoma, HSCT, hematopoietic stem cell transplant; MAC, myeloablative conditioning; MDS, myelodysplastic syndrome; MRD, minimal residual disease; RIC, reduced intensity conditioning.

Conclusions: Unmanipulated haplo-DLI after ab-T and B-cell depleted haploidentical-HSCT were feasible and safe, with encouraging result in terms of PFS and clearance of MRD.

Disclosure: Nothing to declare

P092 Use of mesenchymal stromal cells under special situations for complications of allogeneic HSCT. A single center experience

R. Alonso Trillo ¹, M. Vicente², M.E. Martínez-Muñoz³, C. Fernández-Maqueda³, C. De Miguel³, G. Bautista³, R. Sánchez¹, T. Martín¹, R. Zafra¹, N. Panadero³, I. Salcedo^3,2, F.R. Duarte^1,3,2

¹Fundación para la Investigación Biomédica Hospital Universitario Puerta de Hierro, Majadahonda, Spain, ²Universidad Autónoma de Madrid, Madrid, Spain, ³Hospital Puerta de Hierro, Majadahonda, Spain

Background: Mesenchymal Stromal Cells (MSC) are multipotent non-hematopoietic cells with immunomodulatory and regenerative properties that are being used as a treatment for allogeneic HSCT complications. Access to advanced-therapy medicinal products on a named-patient compassionate-use basis is available in special situations and requires pharmacovigilance and subsequent audit and investigation of their safety and efficacy.

Methods: Retrospective analysis of the use of MSC in our center in a compassionate-use basis for complications of allogeneic HSCT (2006 to 2021). Use of MSC in clinical trials are excluded. We use an AEMPS approved investigational MSC product derived from bone marrow of healthy donors and expanded under GMP conditions (PEI 10-146).

Results: Sixty-two allogeneic HSCT recipients (37 male, 60%; median age 48 years, range 17-73; 29 AML/MDS, 10 ALL, 8 NHL/CLL, 4 MM, 4 SAA, 7 other indications; 27 matched related, 15 matched unrelated, 14 cords and 6 haploidentical donors) received a total of 248 infusions (median 4, range 1-16) of approximately 1x10⁶ MSC cells/kg for the following transplant complications: 50 GVHD (81%), 8 hemorrhagic cystitis (HC; 13%), 3 cytopenia (5%) and 1 transplant-associated thrombotic microangiopathy (2%). GVHD target organ involvement included 39 gastrointestinal (78%), 34 cutaneous (68%) and 18 hepatic (36%), with severity score 2, 3 and 4 in 20 (40%), 17 (34%) and 13 (26%), respectively. One GVHD case with concomitant CMV infection received MSC as first-line to spare further immunosuppression with corticosteroids, but all others had MSC as second-line after failure of corticosteroids, alone in 14 cases (29%) and in association with other drugs (etanercept, ruxolitinib, alemtuzumab, basiliximab and vedolizumab) in the rest. Thirty-seven patients (74%) achieved an overall response at day +28 from MSC treatment, including 17 (34%) with complete response and 20 with partial response (40%). All-cause mortality was 26% (13/50) at 90 days from treatment. Clinical response to MSC was associated with survival at day 90 (p = 0.003). Eight cases with grade 3 (3, 37%) or 4 (5, 63%) HC refractory to first-line therapy (most commonly continuous saline irrigation and hyaluronic acid) received MSC as a named-patient compassionate-use basis, achieving 3 complete responses, 2 partial responses and 3 refractory cases by day +28 from treatment. By day +90, four patients died and the other four were in complete response from their HC. Overall, in our named-patient compassionate-use series in the various indications, overall response rate at day +28 was 69%, complete response rate 32%, and 44 patients (71%) were alive 90 days after the first MSC infusion.

Conclusions: In the absence of formal regulatory approval, access to MSC in special situations including named-patient compassionate-use is available for life-threatening transplant complications which cannot be treated satisfactorily with authorized alternatives. This study audits our practice with MSC in transplant complications and suggests that their use is safe and effective in this setting.

Disclosure: Nothing to declare

P094 The role of donor gamma delta t cells in acute myeloid leukemia control after allogeneic hematopoietic cell transplantation

N. Bejanyan ¹, M. Davila¹, C. Cubitt¹, X. Yu¹, J. Kim¹, J. Kroeger¹, B. Bhatnagar², J. Conejo-Garcia¹, C. Anasetti¹

¹Moffitt Cancer Center, Tampa, United States, ²Wheeling Hospital, Wheeling, United States

Background: Relapse after allogeneic hematopoietic cell transplantation (HCT) is the leading cause of mortality in patients with acute myeloid leukemia (AML). Increased recovery of γδ T lymphocytes after HCT is associated with better disease-free survival. The γδ T cells have MHC-independent, potent cytotoxic activity against AML and other neoplastic cells. Thus, donor γδ T cells can play an important role in regulating AML relapse after HCT. We assessed if γδ T cell clonality, distinct clones or specific receptor expression can predict AML relapse prevention after HCT.

Methods: We used previously frozen banked bone marrow biopsy samples containing viable mononuclear cells, obtained at AML diagnosis, at 3 months and at relapse after HCT. We performed flow cytometry sorting of γδ T cells, extraction of genomic DNA and γδ T cell clonality assessment by T cell receptor γ locus (TRG) sequencing (ImmunoSEQ platform). Multiparametric flow cytometry was used to assess the expression of γδ T cell receptors and AML blast ligands.

Results: We identified 24 adult (18 years and older) patients with available bone marrow samples who received their first HCT for AML in complete remission: 12 patients did not relapse, and 12 patients relapsed after HCT. Non-relapsed patients had higher TRG clonotype diversity at 3 months post-HCT as compared to the relapsed patients. Non-relapsed vs. relapsed patients had higher expression of TIGIT (46.5% vs. 34.2%, p = 0.03) and CTLA4 (72.8% vs. 34.6%, p = 0.05) receptors on γδ T cells (CD3 + /γδ TCR + ) but similar expression of NKG2D/CD314 (60.2% vs. 79.2%, p = 0.15). The expression of corresponding ligands on AML blasts at diagnosis for CD155 (TIGIT ligand) was 11.4% vs. 17.9% (p = 0.85), for CD86 (CTLA-4 ligand) was 69.3% vs. 64.7% (p = 0.88) and for MICA/B (NKG2D ligand) was 3.2% vs. 0.26% (p = 0.1) in non-relapsed vs. relapsed patients, respectively.

Comparing 3-month and relapsed samples in patients relapsing after HCT, there was decreased TRGV9-1, TRGV7-1 and TRGJP-1 repertoires from 3 months to relapse. Conversely, the usage of TRGV5-1 gene was increased at the time of relapse.

Conclusions: We found that higher diversity of donor TRG clonotypes are associated with AML relapse prevention after HCT. In addition, decreased usage of TRGV9-1 and TRGV7-1 genes influences higher relapse risk after HCT. This study findings can help to implement γδ T cell immunotherapy strategies against AML.

Disclosure: Funding Source: ORIEN NOVA Award M2Gen

COI: Nelli Bejanyan serves on advisory board for Medexus pharma, Magenta therapeutics and CTI Biopharma.

Marco Davila has equity in Adaptive Biotechnologies and Precision Biosciences, and has received licensing fees and research support from Atara Biotherapeutics and CRISPR.

P095 Sequential conditioning with flamsa-fludarabine-busulfan does not improve outcomes after allogeneic-stem cell transplantation when compared with treosulfan-fludarabine conditioning in higher risk mds patients

R. Massoud ¹, E. Klyuchnikov¹, H. Naim¹, N. Gagelmann¹, A. Kunte¹, C. Langebrake¹, R. Adjalle¹, D. Janson¹, F. Ayuk¹, C. Wolschke¹, N. Kröger¹

¹University Medical Center Hamburg-Eppendorf, Hamburg, Germany

Background: Sequential therapy as conditioning in allogeneic stem cell transplantation (SCT) is frequently used in higher risk MDS, but comparisons with another regimen are rare.

Methods: In this retrospective study conducted at the University Medical Center Hamburg/Germany we compared the impact of FLAMSA-Busulfan-Fludarabine (n = 81) with Treosulfan-Fludarabine (n = 95) conditioning on post-transplant outcomes in MDS. FLAMSA-FB regimen consists of fludarabine (30 mg/m²; total dose 120 mg/m²), amsacrine (100 mg/m²; total dose 400 mg/m²), and cytarabine (1 g/m²; total dose 4 g/m²) therapy from days -11 to -8, followed by a three-day interval without therapy and busulfan from day -4 to -3 with a total dose of 6.4mg/Kg and fludarabine on day -4 and -3 (30 mg/m², total dose 60mg/m²). Treo-Flu regimen consisted of Treosulfan (12 g/m², total dose 36 mg/m²) on days -6 to -4 and fludarabine (30 mg/m²; total dose 150 mg/m²) on days -6 to -2.

Results: In the FLAMSA-FB group 11 patients (13%) had related donor (MRD 11% MMRD 2%) and 70 patients (86%) had unrelated donors (MUD 54% MMUD 32%), compared to 17 patients from MRD (18%) and 78 patients from unrelated donor (MUD 61% MMUD 21%) in the Treo-Flu group (p = 0.1). ATG was the major GvHD prophylaxis in both arms. Second allograft was seen only in the Treo-Flu group (n = 9) and the median number of blasts in bone marrow at transplantation were higher in the FLAMSA-FB than in the Treo-Flu group (9vs 2%, p < 0001) IPSS- low, intermediate 1 and 2 and high risk was 3%,15%,57% and 26% in the FLAMSA-FB arm and 13%, 53%, 25% and 9% in the Treo-Flu arm, respectively.

Median platelet and neutrophil engraftment were significantly delayed in the Treo-Flu group when compared to the FLAMSA-FB group: 15 vs 12 days(p = 0.02) and 13 vs 12 days (p = 0.009).

The cumulative incidences of aGVHD grade II-IV, III-IV and cGvHD were similar between the two groups: 37%, 9% and 49% in the FLAMSA-FB group and 37%, 16% and 47% in the Treo-Flu group (p = 0.2; p = 0.7 and p = 0.9, respectively).

The cumulative incidence of non-relapse mortality at 5 years and relapse was 23% and 35% in the FLAMSA-FB and 14% and 23% in the Treo-Flu group (p = 0.07 and p = 0.06, respectively). After a median follow-up of 30 months (range, 1-218), the 3-year overall Survival (OS) and progression free survival (PFS) were in a univariate analysis higher in the Treo-Flu group: 72 vs 51% (p = 0.001) and 58 vs 45% (p = 0.04), respectively.

In a multivariable analysis for OS only low IPSS (low-intermediate I vs Intermediate II-high risk) (HR = 0.2, 95%CI 0.2-0.95, p = 0.037) was associated with improved OS. Conditioning regimen, patient age (≤61 vs >61) donor age ((≤34 vs >34), type of Donor (MRD vs MUD vs MMRD vs MMUD), status at transplant (progressive/refractory disease vs others) and blasts in bone marrow (≤3.5 vs >3.5) had no significant impact on OS.

Conclusions: Acknowledging the retrospective nature of our study, our results suggest that sequential conditioning with FLAMSA-FB does not improve survival in MDS-patients undergoing allo-SCT.

Disclosure: nothing to decalre

P096 Gene editing of the immune checkpoint nkg2a enhances allogenic nk cell mediated cytotoxicity against patient-derived primary multiple myeloma cells

T. Bexte ^1,2,3, J. Alzubi^4,5, L.M. Reindl^1,2, P. Wendel^1,2,3, R. Schubert⁶, E. Salzmann-Manrique⁷, I. von Metzler⁸, T. Cathomen^4,5, E. Ullrich^1,2,3

¹Experimental Immunology, Hospital of the Goethe University Frankfurt, Frankfurt, Germany, ²Frankfurt Cancer Institute, Goethe-University, Frankfurt am Main, Germany, ³German Cancer Consortium (DKTK) partner site Frankfurt/Mainz, Frankfurt am Main, Germany, ⁴Institute for Transfusion Medicine and Gene Therapy, Medical Center – University of Freiburg, Freiburg, Germany, ⁵Center for Chronic Immunodeficiency, University of Freiburg, Freiburg, Germany, ⁶Hospital of the Goethe University Frankfurt, Frankfurt, Germany, ⁷Hospital of the Goethe University Frankfurt, Frankfurt am Main, Germany, ⁸Hospital of the Goethe University Frankfurt, Frankfurt am Main, Germany

Background: Natural Killer (NK) cells are known for their high intrinsic cytotoxic capacity and the possibility to be applied as ‘off-the-shelf’ third party donor cell therapy. In cancer patients suffering from multiple myeloma (MM), an elevated number of NK cells has been correlated with a higher overall-survival rate. However, NK cell function can be impaired by upregulation of inhibitory receptors, such as immune checkpoint NKG2A (natural killer group 2A).

With the aim to overcome suppression of anti-tumor NK cell function, we used the CRISPR-Cas9 nuclease to knockout (KO) the killer cell lectin like receptor C1 (KLRC1) locus encoding NKG2A in primary NK cells, which led to significant increase in NK-cell mediated cytotoxicity against both MM cell lines and patient-derived MM cells.

Methods: Primary NK cells were isolated from PBMCs from healthy donors. Upon transfer of KLRC1-targeting CRISPR-Cas9 nuclease, KLRC1 KO-NK cells were expanded using IL-15 cytokine under feeder-cell free conditions. KLRC1 KO was analyzed using Tracking of Indels by Decomposition (TIDE), T7 endonuclease I (T7E1) assay and next-generation sequen cing (NGS). NKG2A expression of KO-NK cells was compared to non-edited NK cells (NT-NK cells) by flow cytometry. Cytotoxicity of NK cells was analyzed against MM-tumor cell lines and allogenic MM patient-derived tumor cells.

Results: The chosen CRISPR-Cas9 nuclease disrupted 70-86% of KLRC1 alleles, as evaluated by T7E1 (70%), TIDE (75%), or NGS (86%). KLRC1 KO significantly reduced NKG2A expression on gene-edited NK cells analyzed after three weeks of cultivation compared to NT-NK cell population (KO-NK cells 43.5% vs NT-NK cells 90%; n = 10, p < 0.05).

Inhibition of NKG2A-expressing NK cells is mainly related to HLA-E ligand expression, which is often over expressed in anti-tumor response and can be particularly upregulated by IFN-γ. After 24h co-culture of IFN-γ pre-stimulated U266 tumor cells, they showed increased lyses induced by NKG2A KO-NK cells compared to NT-NK cells at different effector:target (E:T) ratio (E:T 2.5:1, 40% vs 15.5%, 1:1, 42.2% vs 13.4%, 0.5:1, 12.3% vs 5.6%; n = 4, p < 0.05). Additionally, after co-culture of NK cells with non-stimulated MM1.S, significantly higher lyses for NKG2A KO-NK cells compared to NT-NK killing capacity could be shown (E:T 2.5:1, 82% vs 70%; 1:1, 82.2% vs 61%; 0.5:1, 72.3% vs 38.9%; n = 5, p < 0.5).

To address the increased killing capacity in a preclinical setting, we isolated primary tumor cells from bone marrow aspirates of differently treated MM patients. Allogenic NKG2A KO-NK cells showed significantly higher primary MM tumor cells lyses as compared to allogenic NT-NK cells (E:T 2.5:1, 40.7% vs 35.5%, 1:1, 36.7% vs 30.8%, 0.5:1, 29.7% vs 25.6%; n = 10 p < 0.05).

Conclusions: Taken together, the deletion of inhibitory KLRC1-NK cell receptor resulted in a significantly increased NK cell-mediated cytotoxicity against allogenic patient-derived MM cells.

Our protocol for gene editing of NK cells provides a robust platform to perform variety of further modulations to design NK cell-based therapeutic approaches to overcome immune checkpoint inhibition against different tumor entities.

Disclosure: E.U. has a sponsored research project with Gilead and BMS. T.C. has a sponsored research collaboration with Cellectis and is a scientific advisor to Excision BioTherapeutics. The other authors declare no competing financial interest.

P098 Cerebrospinal fluid parameters in patients with progressive multifocal leukoencephalopathy receiving allogeneic t cell therapy

N. Möhn ¹, L. Grote-Levi¹, S. Nay¹, P. Schwenkenbecher¹, F. Hopfner¹, K.-W. Sühs¹, A. Bonifacius¹, S. Tischer-Zimmermann¹, B. Maecker-Kolhoff¹, B. Eiz-Vesper¹, G. Höglinger¹, T. Skripuletz¹

¹Hannover Medical School, Hannover, Germany

Background: Progressive multifocal leukoencephalopathy (PML) is a serious opportunistic viral disease of the brain caused by the human polyomavirus 2 (HPyV-2) (previously known as: JC polyomavirus). It usually affects patients with significantly impaired cellular immune defenses. The majority of patients suffer from an underlying malignant hematological disease. The natural course of PML is usually fatal, especially in this group of patients; about 90% die within a few months. To date, there is no approved therapy for PML and all antiviral strategies have failed in trials. Since 2018 several case reports and case series reporting successful treatment with allogeneic virus-specific T cells have been published.

Methods: Sixteen PML patients have received at least one infusion of virus-specific T cells at the Department of Neurology at Hannover Medical School on a compassionate use basis. T cells were manufactured from HLA-partially matched healthy donors using cytokine capture system and immunomagnetic selection. According to current publications, this is the largest cohort worldwide as far as we know. Enriched human polyomavirus 1 (HPyV-1) specific T cells, a close relative of HPyV-2, were used in all of the cases. All patients were closely monitored by clinical examination, MRI imaging and laboratory analysis. CSF analysis included cell count, albumin quotient, detection of oligoclonal bands, determination of HPyV-2 viral load, analysis of HPyV-2 antibody specificity index, and measurement of neurofilaments (phosphorylated heavy chain, pNfH).

Results: Therapy has been completed in 16 patients, who received between one and five T-cell infusions with an interval of usually two or four weeks between doses. As underlying diseases they suffered from lymphoproliferative disorders (n = 9), autoimmune diseases (n = 3), lymphopenia (n = 2), acquired immune deficiency syndrome (n = 1), and breast cancer (n = 1). Median observation time between first T-cell administration and last follow-up was 3 months (1-12 months). Improvement in neurological symptoms occurred in 10 cases (62.5%), and symptoms remained stable in two cases (12.5%). A total of four patients (25%) experienced worsening of symptoms during therapy, of which three patients (19%) died of PML. The median cell count at baseline lumbar puncture prior to the first infusion was 1/µl (1-16/µl), the median albumin quotient was 7.4 (3.3-11.6), and the proportion of patients with positive oligoclonal bands as evidence of intrathecal immunoglobulin G synthesis was 71% at the first CSF analysis and as high as 80% at the second. Comparison of first and last CSF analysis showed a decrease in CSF pNfH in patients with improvement or stabilization of symptoms, while the values increased in patients with poor outcome (p = 0.0040). Furthermore, a decrease in HPyV-2 viral load between first and last CSF analysis correlated with a positive outcome (p = 0.0013).

Conclusions: Therapy with allogeneic virus-specific T cells leads to an improvement or stabilization of neurological symptoms in the majority of patients. Close monitoring of patients is crucial, and a reduction in viral load as well as a decrease in pNfH in the CSF indicate to be positive prognostic markers. However, controlled clinical trials are needed to better assess the efficacy of the therapy and to identify further prognostic factors.

Disclosure: Nothing to declare.

P099 Patient-tailored adoptive immunotherapy with ebv-specific t cells from related and unrelated donors

A. Bonifacius¹, S. Tischer-Zimmermann¹, B. Lamottke¹, R. Schultze-Florey¹, L. Goudeva¹, H.-G. Heuft¹, L. Arseniev¹, R. Beier¹, G. Beutel¹, G. Cario², B. Fröhlich³, J. Greil⁴, L. Hansmann⁵, J. Hasenkamp⁶, M. Höfs⁷, P. Hundsdörfer⁵, E. Jost⁸, K. Kafa⁹, N. Kröger¹⁰, S. Mathas^5,11, R. Meisel¹², M. Nathrath¹³, M. Putkonen¹⁴, S. Ravens¹, E. Sala¹⁵, M. Sauer¹, R. Schroers¹⁶, N.-K. Steckel⁷, R.U. Trappe¹⁷, M. Verbeek¹⁸, E.-M. Wagner-Drouet¹⁹, D. Wolff²⁰, R. Blasczyk¹, B. Eiz-Vesper¹, B. Maecker-Kolhoff ¹

¹Hannover Medical School, Hannover, Germany, ²University Hospital Schleswig-Holstein, Kiel, Germany, ³University Children’s Hospital Muenster, Muenster, Germany, ⁴University Children’s Hospital Heidelberg, Heidelberg, Germany, ⁵Charité - Universitätsmedizin Berlin, Berlin, Germany, ⁶University Medicine Göttingen, Göttingen, Germany, ⁷University Hospital of Essen, Essen, Germany, ⁸Rheinisch-Westfälische Technische Hochschule Aachen University, Aachen, Germany, ⁹Martin Luther University Halle-Wittenberg, Halle, Germany, ¹⁰University Hospital Eppendorf, Hamburg, Germany, ¹¹Max-Delbrück-Center (MDC) for Molecular Medicine, Berlin, Germany, ¹²Heinrich Heine University Düsseldorf, Düsseldorf, Germany, ¹³Klinikum Kassel, Kassel, Germany, ¹⁴Turku University Hospital, Turku, Finland, ¹⁵University Hospital of Ulm, Ulm, Germany, ¹⁶Knappschaftskrankenhaus University Hospital, Bochum, Germany, ¹⁷Ev. Diakonie-Krankenhaus, Bremen, Germany, ¹⁸Technical University of Munich, Munich, Germany, ¹⁹Johannes Gutenberg-University Medical Centre, Mainz, Germany, ²⁰University of Regensburg, Regensberg, Germany

Background: Epstein-Barr virus (EBV) causes significant morbidity and mortality in immunocompromised patients. Functional EBV-specific cellular immunity can be restored by adoptive T-cell transfer in patients with EBV-associated complications following transplantation or immunosuppression. The current study explores results of a personalized T-cell manufacturing program evaluating donor, patient, T-cell product and outcome data.

Methods: Patient-tailored clinical-grade EBV-specific T cells from stem cell, haplo-identical family or third-party donors were manufactured by stimulation and immunomagnetic selection using the CliniMACS Plus or Prodigy device and PepTivator EBV EBNA-1 and Select. T-cell donors were selected by best HLA-matching (minimum 3/6 matches in HLA-A, -B, -DR) and EBV-specific T-cell precursor frequency in peripheral blood. Consecutive manufacturing processes were evaluated and patient outcome and side effects were retrieved by retrospective chart analysis. In a subset of 18 patients, EBV-specific T cell frequencies were monitored in peripheral blood by interferon-γ ELISpot assay following stimulation with peptide pools.

Results: Forty clinical-grade EBV-specific T-cell products from stem cell (n = 13), family (n = 9) or unrelated third-party donors (n = 18) were generated between 2015 and 2019 for n = 37 patients with hematopoietic stem cell (HSCT, n = 27), solid organ (SOT, n = 5) or no (n = 5) transplantation history. Median time from initiation of third party donor search to CTL manufacturing start was 10.1 days. There was no significant difference in terms of cell yield and purity in the final T-cell products from stem cell, family or third party registry donors. Three products have not been infused due to prior death or cure. Thirty-four patients received 1-12 (median 2.0) EBV-CTL products (fresh and cryopreserved); the median number of transferred cells for the first transfer was 2.7x10⁴ CD3⁺ cells/kg body weight (bw) in stem cell donor products and 1.4x10⁴ CD3⁺ cells/kg bw when derived from third party donors. EBV-CTL led to complete clinical response in 19 of 31 patients, who survived at least three weeks after transfer. Complete viral clearance was documented in 13 of 20 HSCT patients, for whom data were available. Responses did not correlate with transferred CTL numbers. While no infusion-related toxicities were reported, two HSCT patients developed de novo GvHD (skin °I, n = 1; liver °IV, n = 1) after T-cell transfer, both had received EBV-CTL from the stem cell donor. These two patients had received CTL numbers above median (3.04x10⁴ and 5.0x10⁴ CD3⁺ cells/kg bw, respectively). EBV-specific T cells could be detected in 15 of 18 monitored patients (83.3 %) after transfer and detection of antiviral T-cell responses correlated with a favorable clinical response in these patients.

Conclusions: Personalized clinical-grade manufacturing of EBV-CTL from stem cell, family or third-party donors is fast and feasible. Adoptive transfer of manufactured EBV-CTL is effective and safe regardless of EBV-CTL donor origin. Timely production of EBV-CTL from pre-characterized registry donors is a valuable alternative to cryopreserved CTL lines for patients lacking an EBV-positive stem cell donor. Transfer of EBV-CTL to patients being immunocompromised for other reasons than in a transplantation context provides an attractive new option, which should be further explored in clinical trials.

Disclosure: Nothing to declare.

P100 Spectral flow cytometry of t-cell subsets in donor lymphocyte infusions reveals phenotypical differences associated with therapeutic outcome in patients with myeloid malignancies

R. Sikora ¹, I. Odak¹, L.M. Bayir¹, M. Beck^2,1, M. Drenker², Y. Xiao¹, J. Schneider^2,1, E. Dammann², M. Stadler², M. Eder², A. Ganser², R. Förster¹, C. Könecke^2,1, C.R. Schultze-Florey^2,1

¹Institute of Immunology, Hannover Medical School, Hannover, Germany, ²Hannover Medical School, Hannover, Germany

Background: Donor lymphocyte infusions (DLI) hold the potential to re-induce remission in patients suffering from relapsed myeloid malignancies after allogeneic hematopoietic stem cell transplantation (HSCT). Analysis of the cell product with regard to prediction of response to DLI is largely missing. Here, we perform in-depth investigation of surface molecules present on donor T-cells in respect of clinical outcome.

Methods: In this prospective clinical study, we enrolled 14 patients with relapsed myeloid malignancies (Table1) after HSCT, who were treated with unmodified DLI. The median follow-up was 22 months post first DLI. An aliquot of the infused DLI product was collected and 30 color-spectral flow cytometry for extensive immunophenotyping of T-cells was performed. Functional markers, such as 4-1BB, LAG3, NRP1, PD1, TIGIT, TIM3, VISTA were included in the staining panel. Results were evaluated both, via conventional 2D-gating and complementary unsupervised cluster analysis by Uniform Manifold Approximation and Projection (UMAP). Statistical analyses were performed with unpaired t-test or Mann-Whitney-Wilcoxon test.

	No relapse after DLI (n = 5)	Relapse after DLI (n = 9)
Age at DLI, median (range)	67 (22-75)	51 (24-61)
Disease
AML	4	7
sAML	1	1
MDS	-	1
No. of DLI, median (range)	2 (2)	2 (1-3)
Time point 1st DLI, mo post-HSCT, median (range)	24 (6-28)	11 (2-47)
Dose 1st DLI, median CD3+/kg BW, median (range)	0.7 × 107 (0.5-1.1 × 107)	1 × 107 (0.5-1.8 × 107)
GvHD post DLI, median	4	6
Patients alive at 24 months post DLI, n (%)	3 (60)	2 (22)

Results: After DLI treatment, 5 patients had a durable remission, whereas 9 patients developed a subsequent relapse (Table1).

Patients without relapse after DLI had received significantly lower numbers of CD4⁺conventional (Tconv) effector-memory (CD45RA^-CCR7^+/−, EM) cells compared to relapsing patients (1.4 × 10⁶/kg BW (range 4.6 × 10⁵-1.4 × 10⁶) vs. 3.6 × 10⁶/kg BW (1.4-6.3 × 10⁶), P = .03). Also, the absolute numbers of EM-like regulatory T-cells was lower in patients without relapse (0.6 × 10⁵/kg BW (4.5-8.9 × 10⁴) vs. 1.6 × 10⁵/kg BW (3.7 × 10⁴-2.3×10⁶), P = .02). Additionally, frequencies of CD4⁺ naïve (CD45RA⁺CCR7⁺) Tconv were higher in patients without relapse (53.75% (31.34-84.77%) vs. 32.65% (14.96-53.59%), P = .01).

UMAP analysis of DLI cell products revealed a subpopulation of CD4⁺EM-like cells, which had lower frequencies in patients without relapse. Moreover, lower frequencies of CD8⁺EM-like cells were seen in this group. Of note, CCR5⁺ expression within this CD8⁺EM-like population was significantly lower in patients without relapse (1.34% (0.23-2.98%) vs. 5.04% (1.74-13.33%), P = .002).

Next, functional markers were analysed based on their mean fluorescence intensity (MFI). Patients without relapse showed lower MFI values of VISTA on CD4⁺naïve and EM-like cells. Along the same lines, we observed lower PD1 expression on CD8⁺naïve-like and CD4⁺EM-like cells in the same group .

With regard to GVHD post DLI, UMAP analysis of functional markers revealed lower PD1 expression on CD8⁺effector-like cells in patients developing GVHD when compared to patients without GVHD.

Conclusions: In conclusion, we identified phenotypical differences of T-cells within the DLI cell product comparing patients with and without relapse after DLI. Therefore, deep phenotyping of the DLI product might be useful for prediction of response to therapy, including GVHD. However, this dataset is limited by the small cohort size. Further validation in a larger cohort is underway.

Disclosure: Nothing to declare.

P102 Relapse prophylaxis post-haploidentical bone marrow transplantation and cyclophosphamide (haplo/cy) by infusion of donor-derived expanded/activated γδ t cells: A phase i trial

L. Lamb ¹, S. Abhyankar², R. Soder², M. ter Haak¹, T. Bruns², S. Youngblood¹, J. McGuirk²

¹IN8Bio, Inc., Birmingham, United States, ²The University of Kansas Cancer Center, Westwood, United States

Background: Effector γδ T cells immediately recognize and kill malignant cells in a broad-based non-MHC restricted manner. Increases in circulating donor-derived γδ T cells during post-bone marrow transplant (BMT) recovery have been significantly associated with improved disease-free survival (DFS). Relapse post-Haplo/Cy BMT occurs in approximately 45% of patients. We sought to mitigate relapse in this context by expanding, activating, and infusing donor-derived haploidentical γδ T cells. We now report preliminary clinical and biologic correlative findings from the first cohort of patients who have been treated with ex vivo expanded and activated donor γδ T cells (EAGD). This single-center Phase I clinical trial represents the first systemic infusion of allogeneic EAGD cells in the post-BMT setting

Methods: Standard of care reduced-intensity flu/cy/TBI conditioning was followed by an unmanipulated bone marrow graft and 50mg/m² Cy on days +3 and +4 post-transplant. EAGD were manufactured using the Miltenyi Prodigy^® bioreactor and cryopreserved. The product was infused intravenously within 5 days of neutrophil engraftment (ANC > 500/µL X 3d). Peripheral blood was collected at EAGD infusion and monthly thereafter through day +90, with additional collections every 6 months through 1 year. Biologic parameters included multiparameter flow cytometric immunophenotyping and single cell cytokine analysis of the EAGD graft. Peripheral blood analysis includes leukocyte count and differential, immunophenotyping, and serum Th1/Th2/Th17 cytokine analysis. Primary endpoints include dose-limiting toxicities (DLT) and grade 3-4 adverse events while secondary endpoints include incidence of acute and chronic GvHD, relapse, and overall survival.

Results: Three patients have received the first dose level of 1 x 10⁶ EAGD/kg. All three patients remain in morphologic complete remission at 20.1, 17.8, and 6.1 months post-BMT. One patient is receiving ongoing hypomethylating therapy for the occurrence of recipient chimerism. Grade 1-2 toxicities include constipation, CMV reactivation, emesis, fatigue, and hypomagnesaemia. Steroid-responsive cutaneous acute Grade I-II GVHD has been observed in all patients with one patient experiencing Grade II intestinal GvHD. No chronic GVHD, DLTs, treatment-related ≥ grade 3 adverse events, or cytokine release syndrome has occurred. EAGD grafts contained 88.7%-99.2% Vγ9Vδ2 + γδ T cells with small populations of NK cells and <1.0 x 10⁵ αβ T cells/kg. EAGD principally expressed Granzyme B, MIP1α, MIP1β, and IL-2. Significant peripheral lymphodepletion persisted through the first 100 days post-BMT followed by slow recovery of CD4 + , CD8 + , γδ T and B cells. NK cells remained within the low normal range throughout. T cells transitioned from a CD45 + CD27- effector phenotype to CD45RA^-CD27^+/− central to effector memory phenotype as recovery progressed. CD3⁺CD4⁺CD25^hiFoxP3⁺ Treg cells remained <3% of circulating T cells. Preliminary serum cytokine analysis revealed an initial inflammatory environment with predominant expression of IFNγ, and TNFα and T cell expression of Granzyme B, MIP1α, IFNα, and TNFα that gradually decreased as recovery progressed.

Conclusions: Early indications suggest that EAGD transfusion with the initial dose level of 1 x 10⁶ EAGD/kg has manageable toxicity and an appropriate immune recovery profile with 3 of 3 patients alive and progression-free.

Clinical Trial Registry: https://clinicaltrials.gov/ct2/show/NCT03533816

Disclosure: The clinical trial is conducted as an Investigator-Initiated Trial with the Kansas University Cancer Center as the sponsor and Dr. Joseph P. McGuirk as the Principal Investigator. The trial is funded by IN8Bio, a US public biopharmaceutical company. Dr. McGuirk also received funding through the Kansas University Cancer Center from Kite, Novartis, Bristol Myers Squibb, and Allovir as a site investigator for ongoing clinical trials. Dr. Lawrence Lamb, Mariska ter Haak, and Samantha Youngblood are employees of IN8Bio.

P103 Influence of t-memory cell doses on post-transplant infections and GVHD rates

P.L. Tan ^1,2,3,4, C. Vyas⁵, F. Yeap^1,2,3,4, L.P. Koh^1,2,3,4

¹National University Hospital, Singapore, Singapore, ²National University Cancer Institute, Singapore, Singapore, ³National University Health System, Singapore, Singapore, ⁴National University of Singapore, Singapore, Singapore, ⁵Jaslok Hospital and Research Centre, Mumbai, India

Background: Allogeneic T-memory cells (Tm) co-infused with T-cell depleted (TCD) peripheral blood stem cells (PBSC) is known to protect against post-transplant infections. However, the effective Tm dose for infections protection relative to engraftment/ cytokine release syndrome (ES/ CRS) and graft-versus-host disease (GVHD) risks is unknown. Many programs, including ours, set Tm doses arbitrarily because data guiding Tm dosing is lacking. Between 2014 and 2019, we systematically reduced Tm doses in 54 paediatric patients transplanted consecutively using published experiences and our patients’ outcomes as guidance.

Methods: We retrospectively reviewed transplant outcomes, including infections, graft failure (GF), ES/ CRS and GVHD rates in patients given Tm (denoted by CD45RO + ) doses categorised in 3 strata (S): S1: > 3 to 11 x 10⁶/kg (N = 17); S2: > 11 to 31 x 10⁶/kg (N = 20), and S3: > 31 to 330 x 10⁶/kg (N = 17). Transplant indications included cancers (N = 42) and non-cancers (N = 12) diseases. PBSC were T-cell depleted as the main form of GVHD prophylaxis with: CD34 + selection (N = 4), CD3 + depletion (N = 48) or alpha-beta T-cells depletion (N = 2). The majority of patients (N = 34) received non-radiation based preparative regimens. Anti-microbial prophylaxis included echinocandins and ganciclovir. ES/CRS and GVHD were pre-emptively treated.

Results: The median age of patients in the 3 strata were: 94 (range, 9 to 231); 84 (range, 10 to 192); 48 (range, 6 to 183) months; and their donors: 38 (range, 14 to 56); 37 (range, 21 to 52); 38 (range, 31 to 52) years, respectively. The CD34 + cell doses co-infused with Tm in the 3 strata were: 18 (range, 14 to 32); 18 (range, 7 to 45); and 20 (range, 13 to 57) x 10⁶/kg, respectively. The CD3 + cell doses in the stem cell products averaged 1.72 (range, 0.0 to 4.97) x 10⁴/kg. Transplant outcomes including cytomegalovirus (CMV), adenovirus (ADV), BK virus (BKV), and fungal infections, GF, ES/ CRS, acute and chronic GVHD rates in the 3 strata are summarised in Table 1. Infections, GF and chronic GVHD rates were not statistically different among patients in the 3 strata. However, ES/CRS and acute GVHD rates were statistically different in patients receiving different Tm doses. At a median follow-up of 452.5 (range, 18 – 1965) days, the 3-year overall survival was not statistically different among patients in the 3 strata (Figure 1): (S1) 69.6% vs. (S2) 69.2% vs. (S3) 80.2% (p = 0.692).

Table 17 Table 1: Tm Dose Strata and Transplant Outcomes

Figure 1: Overall Survival of 54 patients Given Different Tm Doses

Conclusions: There appears to be no infection protective advantage with higher Tm doses. However, ES/CRS and acute GVHD rates were significantly different with different Tm doses. This preliminary data supported the Tm dosing strategy used in our program.

Disclosure: Nothing to declare.

P104 Processing of one total blood volume is sufficient to perform extracorporeal photopheresis with spectra optia cmnc protocol. A study with focus on a patient safety

R. Małachowski ¹, A. Borowik¹, M. Mordak¹, I. Dereń-Wagemann¹, J. Lange¹, K. Suchnicki¹, M. Sędzimirska¹, D. Sosnowska¹, J. Dybko¹

¹The Lower Silesian Oncology Center in Wrocław, Wrocław, Poland

Background: The total blood volume (TBV) to process during extracorporeal photopheresis (ECP) and sufficient number of collected mononuclear cells (MNCs) is not clearly defined. Cell yields vary between apheresis devices. The duration of ECP may affect the clinical benefit but also pose a threat to a patient’s safety. In this study we have made an attempt to determine if the blood volume processed can be minimized to increase the patient’s safety, concurrently preserving the ECP therapeutic effect.

Methods: 23 patients (F/M – 12/11, median age 52 (17-66)) who have underwent allogeneic hematopoietic cells transplantation complicated by steroid resistant chronic graft-versus-host disease were enrolled in the study. A median number of 10 (3-30) procedures was performed between January 2019 and October 2021 with 1 or 2 TBV being processed.

ECP was achieved in an offline manner. MNCs were collected with the Spectra Optia device (Terumo BCT) continuous mononuclear cell collection (cMNC) protocol. The final product was irradiated with UVA-PIT (PIT Medical Systems GmbH).

Results: 100 ECP procedures with 1TBV processed and 79ECP procedures with 2TVB processed procedures were performed. No statistical difference in patient age, body weight and TBV was observed between the compared sets of data. The procedures where 1TBV was processed resulted in shorter duration than 2TVB procedure: 114 min (88-189) vs 224 min (158-253), p < 0,001; lower product volume 104 mL (65-200) vs 210 mL (139-237), p < 0,001, lower MNC content 4,42 × 10¹² (0,08-20,84) vs 11,3 (2,4-30,1), p < 0,001 and lower MNC content per kg body weight 159,8 ×10⁶/kg body weight (24,4-373,1) vs 75,7 (2,1-235,4), p < 0,001. The MNC CE1 collection efficiency was 37,3% (4,1-99,9) for 1TBV and 44,9% (14,3-81,6) for 2TBV, p = 0,004. Parameters characterizing the patient safety i. e. platelet drop and ACD(A) infused per patient were lower for the procedures with 1TBV processed: 18,1% (-71,2-63,4) vs 34,2% (-15,0-48,1), p < 0,001 and 449 mL (161-694) vs 752 mL (439-1101), p = 0,004 respectively.

The clinical response rate was 77,3% for the skin (n = 22), 100,0% for the liver (n = 5), 0,0% for the gastrointestinal (GI) tract (n = 5), 42,9% for ocular GVHD (n = 7), 55,6 for oral GVHD (n = 9), 50,0% for the musculoskeletal system (n = 2), and 100,0% for bronchiolitis obliterans (n = 2).

Conclusions: Although there is no consensus on the MNC cell dose to be irradiated in ECP, Worel et al. has indicated a cut-off MNC level 13,9×10⁶ /kg body weight which predicts 75% overall response. Except for one patient who was leukopenic, all of our patients have reached (and often significantly exceeded) the cut-off MNC /kg body weight level. The MNC count collected during 1TVB cycle was comparable or higher to those reported by other authors who have also concluded an efficacious ECP therapeutic effect. This preliminary analysis shows that it is possible to collect sufficient number of MNC through processing of one total blood volume. Moreover, this approach increases patient’s safety by lowering the ACD(A) volume infused, lowering platelet loss and improving patient comfort by lowering the time of the procedure. The presented data and response ratio support processing 1TBV with Spectra Optia cMNC protocol for UV irradiation.

Disclosure: Nothing to declare.

P105 Clinical experience of using multivirus-specific t cells produced by ifnγ-directed immunomagnetic separation in patients with post-HSCT severe viral infections

V. Vedmedskia ¹, D. Pershin¹, M. Fadeeva¹, A. Kazachenok¹, R. Nikolaev¹, E. Malakhova¹, E. Kulakovskaya¹, S. Glushkova¹, T. Sozonova¹, E. Osipova¹, L. Shelikhova¹, M. Maschan¹, G. Novichkova¹

¹Dmitry Rogachev National Medical Research Center of Pediatric Hematology, Oncology and Immunology, Moscow, Russian Federation

Background: Viral infections is a major cause of post-HSCT complications and transplant-related mortality. Delayed post-HSCT immune reconstitution fails to support the resistance to common infections with CMV, AdV, EBV and other opportunistic agents. In the context of other post-HSCT complications such as graft-vs-host disease and graft hypofunction, this failure may lead to longer-term immune deficiency with severe consequences. The CliniMACS Prodigy® platform (Miltenyi Biotec) allows obtaining IFNγ-secreting virus-specific lymphocyte-enriched cell products by immunomagnetic separation (IMS). Here we present clinical experience of using such products in patients with post-HSCT viral infections.

Methods: The study enrolled 5 patients with post-HSCT viral complications, receiving infusions of virus-specific cell products. Magnetic separation of IFNγ + lymphocytes obtained from a haploidentical donor by leukapheresis was performed using the CliniMACS Prodigy platform in accordance with the recommended protocol. In vitro stimulation was performed with PepTivator® peptide pools (Miltenyi Biotec) in combinations corresponding to the current condition of the patient and possibly preventing related complications (see the Table). Subpopulation composition of cell product was assessed by flow cytometry using routine surface staining for CD3, CD4, CD8 and IFNγ. The median content of viable T lymphocytes in the cell product was 35%. The median content of virus-specific interferon-expressing T cells in the graft was 90%.

The median infusion dose was 39.27 ∙ 10³ of viable CD3 + cells per kg weight (min 11 ∙ 10³/kg, max 432 ∙ 10³/kg). The median time after HSCT at the moment of infusion was 125 days (min 30 days, max 1.5 years). Viremia was monitored by PCR. Detection and monitoring of virus-specific donor T cells was performed by IFNγ ELISpot assay.

Results: Robust response to the treatment correlating with the ELISpot data was observed in 4 of 5 patients. Clinical and laboratory indicators for the patients are given in the Table:

Table 18

Conclusions: Infusions of multivirus-specific lymphocytes obtained by IFNγ-directed IMS provide effective treatment of viral complications that arise during post-HSCT immune reconstitution. Polyspecific antigenic stimulation performed in advance may facilitate prevention of viral complications during post-HSCT immune reconstitution.

Disclosure: Nothing to declare

P106 Stem cell therapy in children with neurological disease: Association between adverse effects and total nucleated cells parameters

H. Ramírez Durán ¹, J.C. López Quezada¹, S.A. Sánchez García¹, C.A. de la Cruz de la Cruz¹, I.Y. Velasco Ruiz¹, O. González Llano¹, C. Mancías Guerra¹

¹Hospital Universitario "Dr. José Eleuterio González", Monterrey, Mexico

Background: Subarachnoid placement of bone marrow (BM)-derived total nucleated cells (TNCs) has been reported to be safe and relatively easy to perform in children with cerebral palsy (CP) and autism spectrum disorder (ASD).

Methods: This was a retrospective, open-label trial to assess the side effects, safety, and tolerability of a single subarachnoid BM-derived TNC injection in patients with CP and ASD. Patients aged between 1 and 18 years were included in this study. The outpatient-based autologous BM stimulation consisted of 10 mg/kg/day G-CSF subcutaneously for 3 days. The procedure was performed under sedation and local anesthesia. We harvested 8 mL/kg of body weight of BM, filtered on a laminar flow cabiet, centrifuged, and enumerated using CD34 + and CD45 + flow cytometry.

Caretakers were instructed to contact the research team if they developed symptoms.

Results: Between May 2009 and December 2021, 640 patients were treated with BM-derived TNCs, 303 patients with ASD (47.3%) and 337 patients with CP (52.7%). The median age was 6 years (range,1 month to 18 years). Males comprised 71.6% of the study population, and 28.4% were women. Almost half of the patients (n = 309,48.3%) presented with any symptoms after the procedure. The characteristics of the study population are summarized in Table 1.

Among the patients with ASD, the most common symptom was vomit/nausea in 63 patients (20.5%). Headache/irritability affected children over 60 months of age (p = 0.038). There was an association in patients reporting vomiting and nausea with a larger TNC volume infused (median 6.2 ml) (p = 0.003) and with fewer absolute neutrophil count (ANC) infused (p = 0.026).

In children diagnosed with CP, symptoms were present in 160 patients (51.8%). We found an association between age >60 months and headache/irritability (p = 0.004).

Conclusions: There was no association between symptomatic patients and leukocyte count or CD34 + x106/kg infused. The study reported an incidence of up to 309 (48.3%) symptoms after subarachnoid TNC administration. These secondary effects were not related to the laboratory parameters of the cells (leukocyte count or CD34 + x106/kg infused), but only the volume infused was associated with nausea and vomiting in children with autism older than five years of age. In most cases, these symptoms can be satisfactorily controlled without hospital admission, so we can consider it a safe procedure and possibly improve the quality of life of patients.

Disclosure: Nothing to declare

P107 Adoptive transfer of allogenic hpyv-1-virus specific t cells improves clinical outcome of patients suffering from progressive multifocal leukoencephalopathy

L. Grote-Levi ¹, N. Möhn¹, S. Nay¹, P. Schwenkenbecher¹, F. Hopfner¹, W. Sühs¹, A. Bonifacius¹, S. Tischer-Zimmermann¹, B. Maecker-Kolhoff¹, B. Eiz-Vesper¹, G. Höglinger¹, T. Skripuletz¹

¹Hannover Medical School, Hannover, Germany

Background: Progressive multifocal leukoencephalopathy represents an opportunistic viral infection of the brain with potential fatal outcome. Triggered by an immunosuppressive constitution, e.g. oncological diseases, chronic viral infections or immunosuppressive therapy in autoimmune disease/transplantation, affected individuals suffer reactivation of latently existing infection by human polyomavirus 2 (HPyV-2, former: JCV), which leads to lytic destruction of the brain parenchyma. The diagnosis is based on a triade of suitable clinical symptoms, typical MR-imaging findings and detection of HPyV-2 in cerebrospinal fluid (CSF)/brain biopsy. No approved effective therapy exists to date, but adoptive transfer of allogenic human polyomavirus 1 (HPyV-1) specific T cell proves to be a promising approach - basing on induction of immune reaction by cross-reaction due to partial equal epitopes of HPyV-1 and HPyV-2.

Methods: Since March 2020, patients referred to our clinic suffering from defined, progressive PML were analyzed regarding endogenous amount of HPyV-1/ HPyV-2-virus specific T cells. If examination presented insufficient amount, adoptive HPyV-1-specific T cell transfer, extracted from partially human leukocyte antigen compatible donors, was initiated. Dosage varied between 2.0 × 10e4 and 1.0 × 10e4 CD3 + T cells per kg body weight. Targeted therapy regime included at least two doses of allogenic T cells. Follow up investigations included routine neurological examination which partially included examination of 55 m walking distance and Montreal cognitive assessment scale, CSF analysis to investigate HPyV-2 level, virus specific T cells within blood and magnetic resonance imaging.

Results: Sixteen PML-patients received at least one dose of allogenic T cells and were followed up > six weeks after therapy initiation, fifteen patients completed aimed application of two doses. Follow up examination time varied between 42 and 379 days. The majority, eleven patients, suffered from oncological disease, two patients had a history of immunosuppressive disease, two patients suffered from idiopathic lymphopenia and one patient had acquired immune deficiency syndrome but developed PML despite sufficient antiretroviral therapy. In total, ten of sixteen patients showed improvement of symptoms, two patients presented with clinical stabilization and four patients suffered from progression of disease. Of ten patients course-controlled by walking distance/Montreal cognitive assessment scale, two patients showed objective improvement within walking distance and cognition with one further patient exhibiting improvement within cognition alone. Other investigated patients suffered from severe paresis or aphasia, so that examination tools did not fit to exhibit improvement demonstrated by elsewhere diagnostic.

Conclusions: Allogenic HPyV-1-virus specific T cell therapy shows promising therapeutic approach in patients suffering from PML leading to an improvement or stabilization within the majority of treated patients, but examination of walking distance and cognition by Montreal cognitive assessment scale alone appears to be inadequate to show full therapy response. Despite the need of large controlled clinical trials to better assess the efficacy of therapy, further investigations regarding specific clinical scores are needed.

Disclosure: Nothing to declare.

P109 Invariant natural killer t cells protect from cytomegalovirus reactivation after allogeneic hematopoietic cell transplantation

D. Schneidawind ¹, S. Duerr-Stoerzer¹, H. Keppeler¹, R. Beck², K. Hamprecht², L. Kanz¹, C. Schneidawind¹

¹University Hospital Tuebingen, Tuebingen, Germany, ²Institute of Medical Virology and Epidemiology of Viral Diseases, Tuebingen, Germany

Background: Cytomegalovirus (CMV) reactivation is common after allogeneic hematopoietic cell transplantation (HCT) and may result in fatal CMV disease. Invariant natural killer T (iNKT) cells are potent modulators of the immune system preventing graft-versus-host disease (GVHD) while promoting graft-versus-leukemia (GVL) effects. It is thought that iNKT cells selectively influence mediators of both innate and adaptive immunity. Here, we investigated the impact of iNKT cells on virus control after allogeneic HCT.

Methods: We report a single-center prospective observational study designed to investigate the impact of graft iNKT cells on early CMV reactivation in peripheral blood measured by weekly PCR from patient plasma. The primary endpoint was defined as detection of CMV DNA within 100 days following allogeneic HCT. Secondary endpoints were incidence of GVHD, non-relapse mortality (NRM), event-free survival (EFS) and overall survival (OS). The graft composition was studied by flow cytometry.

Results: Median age of patients (n = 50) was 57 years (range 25-76). Two thirds of patients were CMV IgG seropositive and about half of donors were latently infected with CMV. Reactivation of CMV was noted in 23 (46%) patients after a median of 39 days (range 11-59). iNKT-cell numbers were significantly decreased (0.1% vs. 0.3%, p = 0.0001) in patients with early cytomegaloviremia. We also found a significantly reduced cumulative incidence of CMV reactivation after 100 days in patients with higher numbers of iNKT cells in their allograft (24% vs. 68%; p = 0.002). Acute GVHD °II-IV was observed in 5 (10%) patients. Also, extensive chronic GVHD occurred in 5 (10%) patients. Cumulative incidence of relapse or progression and NRM as competing risks at 2 years were 26% and 28%, respectively. 38% of all patients died during a median follow-up of 27 months resulting in a 2-year EFS of 47% and a 2-year OS of 61%.

Conclusions: This study provides evidence that graft iNKT cells improve post-transplant immunity towards reactivation of latent virus infections. Therefore, iNKT-cell enriched grafts or adoptive transfer of iNKT cells are compelling cytotherapeutic strategies to improve outcomes after allogeneic HCT.

Disclosure: Nothing to declare.

P110 Allogeneic stem cell transplantation with 3-days busulfan plus fludarabine as conditioning regimen for patients with relapsed or refractory t- and nk/t-cell lymphomas

J.H. Lee ¹, D.-H. Yang², J.-C. Jo³, Y.J. Lee³, W.-S. Lee⁴, Y.S. Choi⁵, J.H. Moon⁶, Y.R. Do⁷

¹Dong-A University College of Medicine, Seogu, Korea, Republic of, ²Chonnam National University Hwasun Hospital, Hwasun, Korea, Republic of, ³Ulsan University Hospital, University of Ulsan College of Medicine, Ulsan, Korea, Republic of, ⁴Busan Paik Hospital, Inje University College of Medicine, Busan, Korea, Republic of, ⁵Ajou University School of Medicine, Suwon, Korea, Republic of, ⁶Kyungpook National University Hospital, School of Medicine, Kyungpook National University, Daegu, Korea, Republic of, ⁷Keimyung University School of Medicine, Dongsan Medical Center, Daegu, Korea, Republic of

Background: Peripheral T-cell lymphomas (PTCL) and NK/T-cell lymphoma (NKTCL) share common characteristics of high chemotherapy resistance with frequent relapses and rapid disease progression. Efforts to improve outcome have incorporated autologous (auto-SCT) and allogeneic stem-cell transplantation (Allo-SCT). Allo-SCT has been to show a plateau of survival in responding patients, and even complete responses in patients who relapsed after various chemotherapy regimens. Although attempts to apply Allo-SCT in adult PTCL and NKTCL are steadily increasing, cases are still scarce so that there are very few prospective trials. Even though Allo-SCT could improve survival in relapsed and refractory patients who would otherwise have grave prognosis, there are several unsolved problems: suitable patient populations, HSCT timing (first relapse versus beyond first-relapse) and proper conditioning intensity and regimens (myeloablative conditioning vs. reduced-intensity conditioning).

Methods: Peripheral T-cell lymphomas (PTCL) and NK/T-cell lymphoma (NKTCL) share common characteristics of high chemotherapy resistance with frequent relapses and rapid disease progression. Efforts to improve outcome have incorporated autologous (auto-SCT) and allogeneic stem-cell transplantation (Allo-SCT). Allo-SCT has been to show a plateau of survival in responding patients, and even complete responses in patients who relapsed after various chemotherapy regimens. Although attempts to apply Allo-SCT in adult PTCL and NKTCL are steadily increasing, cases are still scarce so that there are very few prospective trials. Even though Allo-SCT could improve survival in relapsed and refractory patients who would otherwise have grave prognosis, there are several unsolved problems: suitable patient populations, HSCT timing (first relapse versus beyond first-relapse) and proper conditioning intensity and regimens (myeloablative conditioning vs. reduced-intensity conditioning).

Results: Fifteen patients received Allo-SCT with Bu3Flu6 conditioning regimen for relapsed and refractory T- and NK/T-cell lymphomas. Median age was 54 years (range, 33-65 years) and median previous lines of therapies was 2 (range, 1-3). 53.3% of the patients had received auto-SCT. Stem cell source were PB and CB in 14 patients and 1 patient, respectively; stem cell donor type were full-matched sibling and unrelated donor in 46.7% and 40% of the patients, respectively. After a median 3 cycles of salvage chemotherapies, 66.7 % and 33.3% of the patients were in CR and PR, respectively, before enrollment to the study, and for 5 patients who were in PR before Allo-SCT, 3 patients further achieved CR after Allo-SCT with Bu3Flu6. After a median follow-up duration of 17.7 months (range, 2.13-51.47 months), 2-year PFS and OS were 77.8% (95% CI, 45.5-92.3%), and 68.4% (95% CI, 35.9-86.8%), respectively. All patients engrafted neutrophils and platelets rapidly with a median of 12 and 12 days, respectively. There were no unexpected regimen-related toxicities including sinusoidal obstruction syndrome, hemorrhagic cystitis, and sepsis. Grade 3-4 acute graft-versus-host disease (GVHD) and moderate-to-severe chronic GVHD occurred in 40% and 60% patients, of which chronic GVHD combined with infection lead to death in 2 patients.

Conclusions: 3-days Bu and 6-days Flu combination as a conditioning regimen is effective with tolerable safety profile for relapsed or refractory T- and NK/T-cell lymphoma patients who are undergoing Allo-SCT.

Clinical Trial Registry: NCT02859402

Disclosure: This work was supported by Korea Otsuka Pharmaceutical Co., LTd. This study would not have been possible without the cooperation of the Korean lymphoma transplantation group (KLTG) and the Consortium for Improving Survival of Lymphoma (CISL). The authors have no conflicts of interest to declare.

P111 Fibroblast-like cells present in an apheresis collected haematopoietic progenitor cell fraction

R. Cockeran ¹, T.N. Glatt¹

¹South African National Blood Service, Johannesburg, South Africa

Background: The collection of haematopoietic progenitor stem cells (HPSC) using an apheresis method for the treatment of various haematological malignancies is a standard procedure performed by the South African National Blood Service. Mesenchymal stromal cells (MSC) are CD45 negative fibroblast-like cells that have the potential to regulate immune and inflammatory responses, including possibly preventing and treating engraftment failure and graft-versus-host disease. This study investigated the possibility of the presence of MSCs in the HPSCs collection fraction. This would allow for using the same collection to obtain both HPSC and MSCs, thereby not only treating the malignancy, but also the potential side effects of the treatment.

Methods: The HPSC collections were performed in mobilized donors as per standard apheresis protocols. Signed consent was obtained to use excess HPSC that were not required for the patients for research purposes. The HPSC collections were de-identified prior to being sent to the research laboratory. The mononuclear cells were isolated using a density gradient, followed by a CD45 bead isolation. The CD45 negative mononuclear cells were incubated in Dulbecco’s Modified Eagle Medium (DMEM) in the presence of 10% foetal bovine serum (FBS), or 5% human platelet lysate (HPL - produced by SANBS) and 2% penicillin-streptomycin, in a humidified 37°C CO₂ incubator. Cell culture media was changed every 2-3 days, with trypsonising and splitting of cell numbers when 80% confluence was reached. The presence of fibroblast-like cells was visually evaluated using a phase-contrast microscope.

Results: A total of three donations were obtained and the cells processed. The cells for each donation were grown in both FBS and HPL. The presence of fibroblast-like cells was seen in both culture conditions; Figure 1 shows the unstained fibroblast-like cells grown in the presence of HPL.

Figure 1: Fibroblast-like cells grown in HPL (unstained) from HPSC apheresis collection

Conclusions: The presence of fibroblast-like cells in three HPSC apheresis donations shows promise for the use of this fraction as a potential source of MSCs that can regulate immune and inflammatory responses. Future research will include the culturing of the fibroblast-like cells to larger numbers to facilitate the identification of these cells and confirm if they are indeed MSCs.

Clinical Trial Registry: N/A

Disclosure: Nothing to declare

P112 Granulocyte transfusion in patients with mucositis after allogeneic hematopoietic stem cell transplantation

E. Yildizhan¹, F. Varol², S. Ciftci², E. Tubay², A. Unal ²

¹Kayseri City Hospital, Kayseri, Turkey, ²Erciyes University, Kayseri, Turkey

Background: Allogeneic hematopoietic stem cell transplantation (HSCT), provides curative treatment chance for many patients with hematologic malignancy. But the complications such as infections, mucositis, and graft versus host disease are the main obstacles to be overcome in the post-transplantation period. Moreover, each of these complications can provoke the others. Granulocyte transfusion can be a reasonable option to support this critical neutropenic period, however, there are not enough randomized controlled trials, and the utility of this approach is controversial. This study aimed to evaluate the efficacy of granulocyte transfusion in allogeneic HSC recipients.

Methods: We retrospectively examined the data of patients who underwent allogeneic HSCT because of acute leukemia, in Erciyes University Hospital, Bone Marrow Transplantation Center, between 2019 and2020. Thirty-one patients who have severe neutropenia lasting more than 15 days (absolute neutrophil count ≤0.5x 10⁹/L) or severe infection or mucositis (grade 2-4) were considered eligible for granulocyte transfusion. Eleven patients who have an appropriate donor received granulocyte transfusion. The remaining 20 patients were considered as a control group and received conventional treatment for mucositis and infection. The clinical course was considered as ‘favorable’ if neutrophile recovery was achieved or the clinical symptoms and signs improved proceeding one week of treatment.

Granulocyte concentrates were collected using apheresis from donors stimulated with corticosteroid and GCSF.

Results: The number of patients suffering from mucositis was 6 (54.5%) in the granulocyte receiving group and only two of them responded to granulocyte transfusion favorably. Fourteen (70.0%) patients had mucositis in the control group and 5 of them were responsive to conventional treatment. Engraftment failure was seen in 3 patients in the granulocyte receiving group and there was no engraftment failure in the control group. Engraftment times for neutrophil and platelet were not significantly different between the two groups. The duration of hospitalization after transplantation was significantly longer in the granulocyte receiving group (p < 0.05). There was no adverse event related to granulocyte transfusion.

Conclusions: In the present study, granulocyte transfusion did not provide any clinical benefit in the treatment of mucositis and in neutrophile recovery. Given the small size of the population, more comprehensive studies are needed.

Disclosure: Nothing to declare

Chronic Leukaemia and Other Myeloproliferative Disorders

P113 The outcome of allogeneic hematopoietic stem cell transplantation for patients with primary myelofibrosis

K. Sun ¹, X.C.-H. Tsai¹, J.-H. Liu², S.-C. Hsu¹, W.-C. Chou¹, X.-W. Liao², H.-A. Hou¹, B.-S. Ko², H.-F. Tien¹, J.-L. Tang², M. Yao¹

¹National Taiwan University Hospital, Taipei, Taiwan, Province of China, ²National Taiwan University Cancer Center, Taipei, Taiwan, Province of China

Background: Primary myelofibrosis (PMF) is a clonal myeloproliferative neoplasm and is associated with marrow fibrosis, extramedullary hematopoiesis, and the propensity of leukemia transformation. Allogeneic hematopoietic stem cell transplantation (allo-HSCT) is the only curative option, but the reports regarding outcomes of patients with PMF receiving allo-HSCT the literature were heterogeneous. In this study, we aimed to evaluate the efficacy and safety of allo-HSCT in patients with PMF.

Methods: From 1996 to 2020, we consecutively enrolled 35 PMF patients who received allo-HSCT at our institute. Next-generation sequencing focusing on 54 myeloid disease-related gene mutations was performed in 29 patients who had enough specimens. The survival was calculated from the date of allo-HSCT.

Results:

The median age at allo-HSCT was 57.6 years. According to the Dynamic International Prognostic Scoring System plus (DIPSS-plus) risk stratification right before the HSCTs, 8.6% of patients were categorized in the intermediate-1; 40%, intermediate-2; and 51.4%, high-risk group. Nineteen (54.3%) patients had JAK2 V617F mutation, 2 (5.7%) MPL mutation, 5 (14.3%) CALR mutation, 1 triple-negative, and 6 (17%) unknown because there was no specimen for retrospective analysis (mostly diagnosed before 2006). Eleven (31%) patients had high molecular risk mutations (HMR), defined as ASXL1, EZH2, SRSF2, and IDH1/2 mutations. Twenty-five (71.4%) patients received reduced-intensity conditioning, which is associated with better NRM compared to myeloablative conditioning (MAC) (not reached vs. 7.9 months, P = 0.05), and earlier leukocyte engraftment (12 days vs. 15 days, P = 0.02).

The median duration from diagnosis to allo-HSCT was 13.5 months (range 1.2-279.9 months). Eighteen (51.4%) patients received spleen management before allo-HSCT, including 5 with splenectomy and 13 with splenic irradiation. With the median follow-up of 54.9 months, the median overall survival (OS) was 20.0 months and the 5-year survival rate was 35.5% (Figure 1). The 1-year cumulative incidence of relapse (CIR) was 26.6% and 1-year non-relapse mortality (NRM) was 25.2%. Of the 18 mortality cases, 9 patients died of infection (including 1 graft failure), 4 died of the disease, and 4 died of graft-versus-host disease (GvHD). The 100-day cumulative incidence of grade 2-4 acute GvHD was 47%. Intriguingly, age or donor source has no prognostic impact on OS, NRM, or CIR. Similarly, there was no difference in terms of CIR, NRM, and OS among patients with various DIPSS-plus risks. Intriguingly, patients with spleen management had a trend of lower NRM but similar CIR and OS compared with those without. Furthermore, the patients with HMR share similar outcomes with those without HMRs, suggesting that HSCT may alleviate the negative prognostic impact of HMR mutations.

Conclusions: Allo-HSCT has the potential to cure some PMF patients. However, it remains to be a challenging task. Finding strategies to reduce CIR and NRM and improve the outcome is warranted. The role of spleen management before allo-HSCT needs to be further clarified in larger cohorts.

Disclosure: Nothing to declare

P114 Results of therapy for patients with advanced phases of chronic myeloid leukemia

E. Morozova ¹, M. Barabanshchikova¹, Y. Vlasova¹, K. Yurovskaya¹, T. Gindina¹, I. Barkhatov¹, I. Moiseev¹, A. Kulagin¹

¹RM Gorbacheva Research Institute, Pavlov University, St. Petersburg, Russian Federation

Background: Despite the widespread use of 2nd and 3rd generation tyrosine kinase inhibitors (TKIs), patients with advanced phase CML, blast crisis (BC) or accelerated phase (AP), still have poor prognosis. This study compares the results of conservative therapy and allo-HSCT in patients with advanced CML

Methods: This retrospective study includes 162 patients with CML BC/AP. All patients received TKIs, in some cases (n = 62/20) followed by allo-HSCT. All patients received allo-HSCT with a reduced dose intensity conditioning regimen (fludarabine 180 mg/m2, busulfan 8-14 mg/kg or melphalan 140 mg/m2). In post-transplant period TKIs, mostly dasatinib (n = 36), were reinitiated in 42 cases. Non-transplant group consisted of patients with disease progression, late transplant center referral, or patients refusing the procedure. In these cases TKIs (2^nd or 3^rd generation in most cases) were continued as monotherapy (n = 60) or in combination with chemotherapy (n = 20). Allo-HSCT and TKI groups did not differ in age, sex, comorbidity, disease phase or presence of additional chromosomal aberrations (ACAs) (Tab.1). OS and EFS were defined as the time from treatment initiation (allo-HSCT/TKI) to death and/or loss of response/post-transplant relapse. The response was assessed in accordance with the recommendations of the European Leukemia Net.

Results: A total of 71 (86%) patients engrafted. Gr2-4 aGVHD developed in 21(29%), Gr3-4 aGVHD in 14(20%), and cGVHD in 18(27%) of cases (severe cGVHD in 4 cases). Within 100 days past allo-HSCT the cumulative risk of relapse and NRM were 10% and 18%, accordingly. With a median follow-up of 44(1–344) months the cumulative relapse rate was 39% with 26 patients receiving subsequent DLIs and TKIs achieving complete molecular response (CMR) in 9, and progressing in 19 cases, accordingly. In TKIs group 71 patients were available for follow-up with 36(59%) progressing on therapy, and 25 achieving complete hematologic (CHR, n = 22), cytogenetic (CHR, n = 1) or molecular (CMR, n = 2) response, accordingly. Among 10 patients without history of BC one did not respond to therapy, while 9 achieved CHR (т=5), CCR (n = 2) or CMR (n = 2). Sixty-nine patients died due to disease progression.

The allo-HSCT effect on OS of patients with AP or BC was also assessed by landmark analysis for 2 and 3 years with maximal phase onset chosen as a starting point. In 2 years the allo-HSCT significantly improved OS in patients with history of BC (71%) compared to TKI recipients (28%; p < 0.0001). In Cox’s regression model allo-HSCT was also associated with higher OS compared to TKIs (HR 0.37; 95%CI 0.15-0.89; p = 0.026). Three-year landmark analysis have also demonstrated allo-HSCT advantage with 82% OS compared with 32% in TKIs recipients (p < 0.0001; Fig 1) with this advantage retained in Cox regression model with allo-HSCT being a positive (RR 0.22; 95% CI 0.07-0.74; p = 0.014) and history of BC a negative (RR 20.5; 95% CI 2.77-151.45; p = 0.003) influence on 5-year OS.

Conclusions: Despite of TKIs being the mainstay of therapy in CP CML, allo-HSCT still remains the only curative option for poor-prognosis patients. A timely referral to transplant center may salvage a patient in AP or BC.

Disclosure: Nothing to declare

P115 What can we do to improve the management of HSCT eligible patients with cmml in latin america?

F. Duarte ¹, F. Onida², T.E.J.S. Sousa³, V. Funke⁴, V.A. Colturato⁵, N. Hamerschlak⁶, N. Vilela⁷, M.C. Macedo⁸, A. Vigorito⁹, R.D.A. Soares¹⁰, A. Paz¹¹, M. Stevenazzi¹², A.E. Hallack Neto¹³, G. Bettarello¹⁴, B. Gusmão¹⁵, M.A. Salvino¹⁶, R.F. Calixto¹⁷, M.C.R. Moreira¹⁸, G.M. Teixeira¹⁹, C.C. Silva⁶, R.P.G. Lemes³, Y.O. Garcia³, E.J.d.A. Paton²⁰, V. Rocha²¹, A. Enrico²², C. Bonfim²³, R. Chiattone²⁴, A.J. Simioni⁵, C. Arrais²⁵, É.O.M. Coelho²⁶, L. Diaz¹²

¹University Hospital Walter Cantídio, Hematology, Fortaleza, Brazil, ²Universidade de Milão, Milão, Italy, ³Hematology Research Laboratory - Federal Universityof Ceara, Fortaleza, Brazil, ⁴Federal University of Paraná, Bone Marrow Transplantation, Curitiba, Brazil, ⁵Hospital do Câncer Amaral Carvalho - Fundação Amaral Carvalho, Bone Marrow Transplant, Jaú, Brazil, ⁶Hospital Israelita Albert Einstein, Bone Marrow Transplant, São Paulo, Brazil, ⁷Hospital de Câncer Infantojuvenil de Barretos, Bone Marrow Transplant, Barretos, Brazil, ⁸Instituto Brasileiro de Controle do Cancer, Bone Marrow Transplant, São Paulo, Brazil, ⁹Universidade Estadual de Campinas - UNICAMP/Hemocentro, Bone Marrow Transplant, Campinas, Brazil, ¹⁰Natal Hospital Center, Bone Marrow Transplant, Natal, Brazil, ¹¹Hospital das clínicas de Porto Alegre, Bone Marrow Transplant, Porto Alegre, Brazil, ¹²Centro TPH-SMI Serviço Médico Integral, Bone Marrow Transplant, Montevideo, Uruguay, ¹³Hospital Universitário Universidade Federal de Juiz de Fora, Bone Marrow Transplantation, Juiz de Fora, Brazil, ¹⁴Unidade de Transplante de Medula Óssea Pietro Albuquerque - ICDF, Bone Marrow Transplantation, Brasilia, Brazil, ¹⁵Hospital São José, Bone Marrow Transplantation, São Paulo, Brazil, ¹⁶Hospital Universitário Prof. Edgard Santos, Bone Marrow Transplantation, Salvador, Brazil, ¹⁷Real Hospital Português de Beneficência em Pernambuco, Bone Marrow Transplantation, Recife, Brazil, ¹⁸CEMO-INCA, Bone Marrow Transplantation, Rio de Janeiro, Brazil, ¹⁹Hospital das Clínicas -Universidade Federal de Minas Gerais- Transplante de Medula Óssea, Belo Horizonte, Brazil, ²⁰ONCOBIO Serviço de Saúde S.A., Bone Marrow Transplantation, Nova Lima, Brazil, ²¹Hospital das Clínicas da Faculdade de Medicina da Universidade de São Paulo, Bone Marrow Transplantation, São Paulo, Brazil, ²²Hospital Italiano La Plata, Bone Marrow Transplantation, La Plata, Argentina, ²³Hospital Pequeno Principe, Bone Marrow Transplantation, Curitiba, Brazil, ²⁴Hospital Samaritano de São Paulo, Bone Marrow Transplantation, São Paulo, Brazil, ²⁵Hospital Sírio Libanês, Bone Marrow Transplantation, São Paulo, Brazil, ²⁶Hospital Santa Joana, Bone Marrow Transplantation, Recife, Brazil

Background: Hematopoietic Stem Cell Transplantation (HSCT) in Chronic Myelomonocytic Leukemia (CMML) has a very important role, for being the only curative procedure in high-risk patients. Despite this statement, there is a small number of transplants in this pathology in Latin America. OBJECTIVE to evaluate the HSCT scenario in Latin America.

Methods: Data from 29 patients with LMMC from 32 centers of the Latin American Registry of Transplantation in MDS, from April/1988 to December/2020, were analyzed. Statistical analysis was performed using the R program. Survival was analyzed using the Kaplan Meier curve and the prognostic factors, by Cox proportional risk.

Results: The mean age was 56, 52 years, with a predominance of males (79,31%, n = 23) and Caucasian (89,66%, n = 26). According to R-IPSS stratification patients were Very Low risk (3,45%,n = 1), Low risk (10,34%, n = 3), Intermediate (17,24%, n-5), High Risk/ Very High Risk (13,80%, n = 4). About 55,17% had not stratification. A total of 24,14% of patients received more than 20 unities of red blood cells and 27,59% received more than 15 unities of platelets. A total of 23 (79,31%) of patients underwent treatment before BMT, in which 47,82% took Hypomethylating. The Myeloablative regimen was the most frequent (62,07%, n = 18), followed by the Reduced Intensity (20,69%, n = 6) and Non-myeloablative (17,24%, n = 5). In 72,41% of cases, the donors were related, and of these, 10.34% were haploidentical; 17.24% not related. The main sources of cells used were peripheral blood (62,07%, n = 18) and bone marrow (37,93%, n = 11). Post-transplant complications were observed in 72.41% (n = 21. The most frequent was infection (57.14%), mainly by CMV (45.45%); acute GVHD (42.86%), chronic GVHD (33.33%) and veno-occlusive disease (9.52%). Recurrence occurred in 30% of cases. The frequency of deaths was 37.93% (n = 11). The survival probability of transplanted patients was 47.40% in 5 years. In the Cox regression model, the risk of death was 6.72 times greater in ≥ 65 years patients (p = 0.015) (CI95%: 1,44 - 31,40). Cox’s model was evaluated using the proportional hazards hypothesis. The Global and individual Schoenfeld test was performed and the adequacy of the model was demonstrated. Patients were also stratified according to Bournemouth scores: 55,1% (n = 16) were high risk and 44,9%, (n = 13)were low risk. For MDAPS score patients were classified as: Low (13,7%, n = 4); Intermediate 1 (3,44%, n = 1), Intermediate 2 (20,6%, n = 6) and high (58,6%, n = 18). Regarding Mayo score, patients were stratified as: low (17,24%, n = 5); intermediate (17,24%, n = 5); high (65,51, n = 19%).

Conclusions: This is the first study of HSCT in CMML performed in Latin American. It presents the difficulties of correct diagnosis and possibilities of HSCT and reflects the efforts of different centers for conducting patients to the correct diagnosis therapeutic strategies, including the management of pre and post HSCT. Age at HSCT was the only factor that influenced in OS. The advances in technology around molecular features of this disease are gradually being incorporated into clinical protocols and has been show a powerful tool for better predicting outcomes. However, in some centers the molecular approach is still a challenge.

Disclosure: Nothing to declare

Conditioning Regimens

P118 Thiotepa-based reduced-intensity conditioning are a valid alternative to total-body irradiation-based regimens in patients with acute lymphoblastic leukemia: A study of the alwp of the ebmt

G. Battipaglia¹, M. Labopin², S. Mielke³, A. Ruggeri ⁴, Z. Nur Ozkurt⁵, J.H. Bourhis⁶, W. Rabitsch⁷, I. Yakoub-Agha⁸, G. Grillo⁹, J. Sanz¹⁰, W. Arcese¹¹, Y. Novis¹², N. Fegueux¹³, S. Giebel¹⁴, A. Nagler¹⁵, M. Mohty¹⁶

¹Federico II University of Naples, Naples, Italy, ²EBMT Statistical Unit, Paris, France, ³Karolinska University Hospital, Dept. of Hematology, Stockholm, Sweden, ⁴Ospedale San Raffaele s.r.l., Haematology and BMT, Milano, Italy, ⁵Gazi University Faculty of Medicine, Hematology, Besevler, Ankara, Turkey, ⁶Gustave Roussy Cancer Campus, BMT Service, Villejuif, France, ⁷Internal Medicine I, BMT-Unit, Vienna General Hospital-Medical University of Vienna, Vienna, Austria, ⁸CHU de Lille LIRIC, INSERM U995, Université de Lille, Lille, France, ⁹ASST Grande Ospedale Metropolitano Niguarda, Milano, Italy, ¹⁰Hematology University Hospital La Fe, Valencia, Spain, ¹¹Tor Vergata¨ University of Rome, Stem Cell Transplant Unit, Policlinico Universitario Tor Vergata, Rome, Italy, ¹²Hospital Sirio-Libanes, Hematology Bone Marrow Transplant Unit, Sao Paulo, Brazil, ¹³CHU Lapeyronie, Département d`Hématologie Clinique, Montpellier, France, ¹⁴Maria Sklodowska-Curie Cancer Center and Institute of Oncology, Gliwice Branch, Gliwice, Poland, ¹⁵Chaim Sheba Medical Center, Tel-Hashomer, Israel, ¹⁶Sorbonne Universités, UPMC Univ Paris 06, INSERM, Centre de Recherche Saint-Antoine (CRSA), Paris, France

Background: Total body irradiation (TBI) at myeloablative doses is superior to chemotherapy-based regimens in young patients with acute lymphoblastic leukemia (ALL) undergoing allogeneic hematopoietic stem cell transplantation (allo-HSCT). However, in elderly and unfit patients, where reduced-intensity conditioning (RIC) regimens are preferred, whether a TBI- or chemotherapy-based approach is better is an unexplored issue. Thiotepa is an alkylating agent with radiomimetic activity and capability to cross the blood-brain barrier, that is used as part of ALL conditioning regimens. The aim of the current study is to compare transplant outcomes after RIC with TBI- or thiotepa-based regimens in ALL.

Methods: Included were patients aged ≥40 years undergoing allo-HSCT for ALL in first complete remission between 2000-2020, receiving a RIC regimen containing either TBI- (4-6 Grays, Gy) or thiotepa-based regimen.

Results: We identified a total of 265 patients, including 117 receiving TBI- (4 Gy, n = 65; 6 Gy, n = 52) and 148 receiving a thiotepa-based RIC regimen. Median age was 56 (range 40-72) versus 59 (range 40-75) years for TBI and thiotepa, respectively (p = 0.32). Thiotepa was more frequently associated to busulfan and fludarabine (n = 88) while TBI was more frequently associated to cyclophosphamide and fludarabine (n = 52), fludarabine alone (n = 27) or cyclophosphamide alone (n = 17). Most patients were diagnosed with Philadelphia positive ALL in both groups (59% for TBI and 55.4% for thiotepa, p = 0.14); T-ALL was diagnosed in 26 and 24 patients receiving TBI or thiotepa, respectively. HLA-identical and mismatched sibling donors were more frequent with thiotepa (35% versus 31% for matched and 21% versus 11% for mismatched siblings) while unrelated donors were more frequent in the TBI group (58% versus 44%) (p = 0.03). A longer interval from diagnosis to transplant was observed with thiotepa (6.7 versus 5.5 months, p < 0.01). Stem cell source was predominantly peripheral blood (94% for TBI and 81% for thiotepa, p < 0.01). The mainly used graft-versus-host disease (GVHD) prophylaxis was cyclosporine with either methotrexate or mycophenolate mofetil in both groups. In vivo T-cell depletion was more frequently used in the TBI group (54% versus 40%, p = 0.02). No imbalances for Karnofsky score (<90 in in 22% and 23% for TBI and thiotepa, p = 0.81) were observed. A Sorror score of 1-2 or ≥3 was observed in 19% and 20% of patients receiving TBI and 26% and 27% of those receiving thiotepa, respectively (p = 0.19). In univariate analysis, no differences were observed in transplant outcomes (for TBI vs thiotepa: relapse 23% versus 28%, p = 0.24; non-relapse mortality, 20% versus 26%, p = 0.61; leukemia-free survival, 57% versus 46%, p = 0.12; overall survival, 67% versus 56%, p = 0.18; GVHD/relapse-free survival, 45% versus 38%, p = 0.21; grade II-IV acute GVHD, 30% in both groups, p = 0.84; grade III-IV acute GVHD, 9% versus 10%, p = 0.89) except for chronic GVHD that was higher for TBI-based regimens (43% versus 29%, p = 0.03). However, in multivariate analysis we observed no differences in transplant outcomes according to the conditioning regimen used.

Conclusions: In patients aged more than 40 years receiving a RIC regimen, use of thiotepa-based regimen may represent a valid alternative to TBI-based regimens due to no differences in the main transplant outcomes.

Clinical Trial Registry: In patients aged more than 40 years receiving a RIC regimen, use of thiotepa-based regimen may represent a valid alternative to TBI-based regimens due to no differences in the main transplant outcomes.

Disclosure: No COI to disclose

P119 Excellent outcome with fb4 regimen in patients with myeloid malignancies older than 55 and with hct-ci score

D. Avenoso ¹, M. de Farias¹, H. Alshehri¹, P. Krishnamurthy¹, V. Mehra¹, A. Kulasekararaj¹, S. Gandhi¹, A. Pagliuca¹, F. Dazzi¹, H. Wood¹, M. Kenyon¹, Y.T. Leung¹, A. Eaton¹, M. Cuadrado¹, P. Hardefeldt¹, V. Potter¹

¹King’s College Hospital NHS Foundation Trust, London, United Kingdom

Background: Allogeneic haematopoietic stem cell transplant (HSCT) is considered a curative strategy for acute myeloid leukaemia (AML) and myelodysplastic syndrome (MDS) with excess of blasts or complex/adverse cytogenetic.

The evaluation of comorbidities with HCT-CI score and the upper limit of 55 years for administering myeloablative conditioning (MAC) are common strategies to minimise HSCT non-relapse mortality (NRM). Despite multiple studies performed previously, this remains an area of uncertainty and precise data guiding MAC selection are still needed.

Herein we report the outcome of patients affected with AML and MDS conditioned with MAC.

Methods: HSCT was performed with GCSF mobilised peripheral blood stem cells. Conditioning protocol was with fludarabine 30 mg/m² days -7, -6, -5, -4, -3 busulfan 3.2 mg/Kg days -6, -5, -4, -3 (FB4); graft versus host disease (GVHD) prophylaxis consisted of thymoglobulin (ATG 5 mg/Kg) or Campath 60 mg (27 and 94 patients, respectively) and single-agent ciclosporin 3 mg/Kg (therapeutic level of 150-200) until d + 56 and then tapered in absence of GVHD.

Results: Between January 2016 and November 2020, 121 patients (77 AML, 44 MDS) with a median age of 56 (19-73) had FB4 conditioning. A median of 5.5x10⁶ CD34 + /Kg was infused (3.1 – 8). Donors were: 21 full matched siblings, 76 full matched unrelated donors, 24 mismatched unrelated donors.

Patients aged > 55 were 64 (53%). HCT-CI score <2 and ≥2 was present in 48 and 73 patients, respectively.

Two years overall survival (OS) was 55% with a median OS of 42 months. No septic death before engraftment or primary graft failure were noted. Median time to neutrophils ≥1000/mL was 12 days (10-18), and 10 days (8-48) to platelets ≥ 20.000/mL. Median CD3 and CD15 chimerism at day 365 were 98% and 100%. Incidence of acute GVHD was 60% (grade III-IV 9%); overall chronic GVHD rate was 33% (moderate 14%, severe 7%). Incidence of venous occlusive disease (VOD) was 7%, no VOD-deaths were recorded. Cumulative incidence of relapse was 19%. Flow cytometry minimal residual disease (MRD) was positive in 28 patients at the time of HSCT and didn’t affect the OS. There was no significant difference in OS when patients were stratified according to age even if there is a non-significant trend for patients younger than 55.

Age at HSCT did not influence NRM but was higher in patients with higher HCT-CI: 10% versus 43% if HCT-CI was <2 and ≥2, respectively (P 0.04). Two years OS for patients aged ≥ 55 and with HCTI-CI < 2 and for those with HCTI-CI ≥ 2 were 63% (median OS not reached in this group) and 45%, respectively. Three years OS was 57% and 42%, respectively.

Conclusions: This analysis supports the feasibility of FB4 conditioning in patients affected with AML and MDS regardless of age. The decision for myeloablation should rely on comorbidities and disease characteristics rather than chronological age, especially for those with positive MRD at the time of HSCT.

Disclosure: Nothing to declare

P121 Comparison of fludarabine/melphalan(flumel) with fludarabine/melphalan/bcnu or thiotepa(fbm/ftm) in patients with AML undergoing allogeneic hematopoietic cell transplantation – a registry study on behalf of the ebmt alwp

J. Duque-Afonso ¹, J. Finke¹, M. Ngoya², M. Labopin², E. Nicholson³, P. Kottaridis⁴, C. Craddock⁵, E. Tholouli⁶, R. Protheroe⁷, E.M. Wagner-Drouet⁸, A. Bloor⁹, T. Valerius¹⁰, K.M.O. Wilson¹¹, B.N. Savani¹², A. Spyridonidis¹³, A. Nagler¹⁴, M. Mohty¹⁵

¹University of Freiburg/Klinik für Innere Medizin I, Freiburg, Germany, ²EBMT Paris Study Office/Hopital Saint Antoine, Paris, France, ³Royal Marsden Hospital, London, United Kingdom, ⁴University College London Hospital, London, United Kingdom, ⁵Birmingham Centre for Cellular Therapy and Transplantation/Queen Elizabeth Hospital Birmingham, Birmingham, United Kingdom, ⁶Manchester Royal Infirmary, Manchester, United Kingdom, ⁷University Hospitals Bristol and Weston NHS Foundation Trust, Bristol, United Kingdom, ⁸University Medical Center Mainz, Oncology and Pneumology, Mainz, Germany, ⁹The Christie NHS Foundation Trust, Stem Cell Transplantation Unit/Manchester University, Manchester, United Kingdom, ¹⁰University Medical Center Schleswig-Holstein, Kiel, Germany, ¹¹University Hospital of Wales, Cardiff, United Kingdom, ¹²Division of Hematology and Oncology, Vanderbilt University Medical Center, Nashville, TN, United States, ¹³University Hospital of Patras, Patras, Greece, ¹⁴Hematology Division, Chaim Sheba Medical Center, Tel Hashomer, Israel, ¹⁵Sorbonne Université/Hopital Saint-Antoine, Paris, France

Background: Conditioning protocols for patients undergoing allogeneic hematopoietic cell transplantation (allo-HCT) are developing continuously to improve their anti-leukemic efficacy and to reduce their toxicity. A recent developed score (transplantation conditioning intensity or TCI) considers the intensity of conditioning as a continuum and not as “classical” defined myeloablative or reduced intensity conditioning. In previous studies, we compared two of the most used conditioning protocols from the intermediate TCI score based on one alkylating agent as fludarabine/melphalan (FluMel) vs. fludarabine/treosulfan (FluTreo) using the EBMT ALWP registry, which serve as basis for the comparison of the present study.

Methods: In the present study, we compared the conditioning protocol FluMel with conditioning protocols based on FluMel (fludarabine 150 mg/m2, melphalan 140mg/m2) or with the addition of a second alkylating agent as FBM (fludarabine, mean 150mg/m2, carmustine 300-400mg/m2 and melphalan, mean 110 mg/m2) or FTM (fludarabine, mean 150mg/m2, thiotepa 5-10mg/kg and melphalan, mean 110 mg/m2). FBM and FTM have been shown to be equivalent at the dosages used in this study. We used following inclusion criteria: first allo-HCT from a matched sibling donor (MSD) or unrelated donor (UD) for patients with AML in complete remission (CR), (3) transplantation date between January 1st, 2009 and December 31st, 2020, (4) with an unmanipulated peripheral blood graft.

Results: We included 3417 adult patients with acute myeloid leukemia (AML) in complete remission (CR) from the registry of the EBMT Acute Leukemia Working Party, 2567 patients were conditioned with FluMel and 850 patients in FBM/FTM. The median follow-up was 4.0 years in FluMel and 3.0 years in FBM/FTM cohorts.

Patients in the FBM/FTM group were older (59.9 years vs. 59.0 years, p < 0.001) and had a worse Karnofsky performance score (KPS < 90, 27.1% vs. 20.1%, p < 0.001). Additional transplant characteristics as female donor (FBM/FTM: 28.2% vs. 32.4%, p = 0.02), CR1 status at allo-HCT (FBM/FTM: 82% vs 78.1%, p = 0.02), matched sibling donor (FBM/FTM: 21.1 vs. 31.7%, p < 0.0001) and in vivo T-cell depletion (anti-thymocyte-globuline in 75.8% of FBM/FTM patients, alemtuzumab more used in 66% of FluMel patients) were different among cohorts.

In univariate analysis, patients in FBM/FTM group showed a better overall survival at 2 years (65.9% vs. 58.7%, p = 0.03) but a higher incidence of aGvHD II-IV at day 100 (25.8% vs. 16.8%, p < 0.0001) compared to patients treated with FluMel. In multivariate analysis, patients treated with FBM/FTM showed a trend for improved overall survival (FluMel with HR 1.17, 95%CI 1-1.38, p = 0.057) and leukemia-free survival (HR 1.14, 95%CI 1-1.3, p = 0.059) compared to FluMel treated patients. No significant differences were observed in relapse incidence (HR 1.12, 95%CI 0.94-1.33, p-value 0.21) and non-relapse mortality (HR 1.14, 95% CI 0.88-1.49, p-value 0.32).

Conclusions: In conclusion, the addition of a second alkylating agent (BCNU/carmustine or thiotepa) to FluMel as FBM/FTM conditioning seems to improve overall survival while maintaining similar toxicity in AML patients in CR undergoing allo-HCT. Due to several limitations of the study including the retrospective nature of the study and unbalanced patient characteristics, these data should be interpreted with caution.

Disclosure: Nothing to declare

P122 Fludarabine and melphalan conditioning with thiotepa versus total body irradiation for haploidentical hematopoietic stem cell transplantation (haplo-sct)

S. Saengboon ¹, U.R. Popat¹, K. Alzahrani¹, R. Mehta¹, A. Olson¹, J. Chen¹, P. Kebriaei¹, E. Shpall¹, R.E. Champlin¹, S.A. Srour¹

¹The University of Texas MD Anderson Cancer Center, Texas, United States

Background: Remarkable improvements in haplo-SCT outcomes are made since the introduction of posttransplant cyclophosphamide (PTCy)-based GVHD prophylaxis. There remains, however, no consensus regarding best conditioning platform; choice of regimen is mostly dependent on center experience. Fludarabine (total 160 mg/m²)/Melphalan (100-140 mg/m²) combined with thiotepa (5 mg/kg) (FMT) vs 2 Gy total body irradiation (TBI) are two reduced-intensity regimens commonly used at our center. We present here the largest single center study to compare the transplant outcomes in patients with acute leukemia and MDS who underwent haplo-SCT using FMT vs FM/TBI.

Methods: We included all consecutive AML/MDS and ALL patients who underwent haplo-SCT between 01/2012 and 12/2019 and received FMT or FM/TBI with PTCy/Tacrolimus/MMF GVHD prophylaxis. Primary objectives were to compare PFS and OS by conditioning regimen. Secondary objectives included cumulative incidence (CI) of NRM, CIR, and GVHD.

Results: 134 patients with a median age of 52 (IQR 35-60) years were identified, 64 (48%) received FMT and 70 (52%) received FM/TBI. Table 1 summarizes baseline characteristics. At a median follow up of 3 years, the 3-year PFS/OS rates were 33%/47% and 37%/53% in the FMT and FM/TBI, respectively (p = 0.127 for PFS; p = 0.107 for OS). One-year NRM rates for FMT and FM/TBI were 37% and 23% (HR 0.585, 95% 0.325-1.050; p = 0.072). The CIR at 1/3 years were 19%/ 25% for FMT and 23%/27% for FM/TBI (p = 0.690). In UVA, age ≥ 55, high/very-high DRI, HCT-CI > 3, and reduced-dose melphalan 100 mg/m² were significantly associated with inferior PFS and OS. In MVA, high/very high DRI (HR 1.950, 95%CI 1.248-3.046; p = 0.003) and HCT-CI > 3 (HR 1.586, 95%CI 1.009-2.493; p = 0.046) were associated with worse PFS. In MVA for OS, age≥ 55 (HR 1.997, 95%CI 1.093-3.650; p = 0.024), high/very-high DRI (HR 2.020, 95%CI 1.263-3.231; p = 0.003) and HCT-CI > 3 (HR 1.747, 95%CI 1.090-2.798; p = 0.020) were associated with inferior survival. In MVA for NRM, age≥ 55 (HR 2.646, 95%CI 1.453-4.816; p = 0.001) was associated increased NRM, with a trend for lower NRM with FM/TBI (HR 0.617, 95%CI 0.341-1.115; p = 0.110). Grades 3-4 acute GvHD at day 100 were 5% and 6% for FMT and FM/TBI, respectively (p = 0.8). The CI rates of chronic GvHD at 3 years for FMT and FM/TBI were 19% and 12%, respectively (p = 0.2)

Variable	All Patients	Flu/Mel/Thio	Flu/Mel/TBI	P-Value
	(N = 134)	(N = 64)	(N = 70)
Age at transplant
<55 years	71 (52.99%)	33 (51.56%)	38 (54.29%)	0.863
≥55 years	63 (47.01%)	31 (48.44%)	32 (45.71%)
Gender
Male	82 (61.19%)	40 (62.50%)	42 (60.00%)	0.86
Female	52 (38.81%)	24 (37.50%)	28 (40.00%)
Disease Subtype
AML/MDS	103 (76.87%)	48 (75.00%)	55 (78.57%)	0.684
ALL	31 (23.13%)	16 (25.00%)	15 (21.43%)
KPS at transplant
KPS 90 - 100	65 (57.52%)	38 (71.70%)	27 (45.00%)	0.005
KPS < 90	48 (42.48%)	15 (28.30%)	33 (55.00%)
DRI
Low/Intermediate DRI	76 (57.14%)	32 (50.00%)	44 (63.77%)	0.118
High/Very High DRI	57 (42.86%)	32 (50.00%)	25 (36.23%)
HCT-CI
HCT-CI ≤ 3	83 (61.94%)	39 (60.94%)	44 (62.86%)	0.86
HCT-CI > 3	51 (38.06%)	25 (39.06%)	26 (37.14%)
Melphalan dose
100 mg/m2	68 (50.75%)	25 (39.06%)	43 (61.43%)	0.015
140 mg/m2	66 (49.25%)	39 (60.94%)	27 (38.57%)
Patient CMV status
Seropositive	122 (91.04%)	59 (92.19%)	63 (90.00%)	0.767
Seronegative	12 (8.96%)	5 (7.81%)	7 (10.00)
Stem cell source
Bone marrow	117 (87.31%)	60 (93.75%)	57 (81.43%)	0.039
Peripheral blood	17 (12.69%)	4 (6.25%)	13 (18.57%)

Conclusions: FMT and FM/TBI conditioning with PTCy/Tacrolimus/MMF GVHD prophylaxis showed comparable survival outcomes in haplo-SCT. There was a trend for better outcomes with FM/TBI related to decreased NRM. Prospective controlled studies to optimize conditioning regimen for haplo-SCT are needed.

Disclosure: Nothing to declare

P123 Efficacy of treosulfan in combination with fludarabine as conditioning regimen in allogeneic transplantation as compared with a myeloablative conditioning using busulfan and fludarabine

J.Á. Calvo Sánchez ¹, S. Fernández García¹, L. Aranguren del Castillo², S. Fernández-Luis¹, L. Yáñez San Segundo¹, A. Insunza Gaminde¹, N. Fernández Escalada¹, G. Martín Sánchez¹, M.M. Colorado Araújo¹, M. López Duarte¹, M. Sánchez Escamilla¹, C. Montes Gaisán¹, J.I. Romon Alonso¹, J.L. Arroyo Rodríguez¹, E.M. Ocio San Miguel¹, M.A. Bermúdez Rodríguez¹

¹Marqués de Valdecilla University Hospital, Santander, Spain, ²Cruces University Hospital, Barakaldo, Spain

Background: Myeloablative conditioning schemes are the gold standard conditioning therapy in patients with acute myeloid leukemia (AML) or myelodysplastic syndrome (MDS) that underwent allogeneic haemopoietic stem cell transplantation.

Reduced toxicity conditioning regimens, such as treosulfan-fludarabine (Treo-flu), have been increasingly used for treating comorbid and elderly patients, and they could be as effective as standard myeloablative, with fewer toxicity and mortality rates in relation with the procedure.

Our primary objective was to compare overall survival (OS) and relapse free survival (RFS) in patients as contrast with standard myeloablative regimens. Our secondary objectives were evaluating toxicity and GVHD incidence.

Methods: We retrospectively studied 97 patients, diagnosed with AML (n = 71) and MDS (n = 26), that underwent allogeneic stem cell transplantation at our institution between the years 2012-2020. Control myeloablative conditioning regimen was Bu-Flu (n = 67)[Busulfan total dose: 9,6-12,8mgr/Kg, fludarabine 160mg/m2]. Treo-Flu was used in 30 patients [Treosulfan total dose: 30-42 g/m2 (in 5 and 25 patients), fludarabine 150mg/m2]. Busulfan levels were not extracted as a rule.

Results: Patient’s characteristics of both conditioning regimens were similar, excluding age (62 vs 54 p = 0,003) and HCT-CI score >3 (66,7% vs 44,8% p = 0,037) that were higher in Treo-Flu patients, as shown in table 1. Treosulfan group had more patients with uncontrolled disease (33% vs 16% p = 0,057).

With a median follow up of 50,5 months (11,7-109,4 months), there weren’t significant differences between treosulfan and busulfan in 3-year overall survival (64% vs 73% p = 0,101), relapse free survival (64% vs 65% p = 0,385) and relapse-free mortality (21% vs 14%; p = 0,164) .

The presence of grade >2 toxicity with treosulfan (40%) was lower than with busulfan (59,7%; p = 0,057). These results rely mostly on the presence of mucositis, which was significantly lower in treosulfan group (13,3% vs 49,3%; p = 0,001). There weren’t significant differences on GI, hepatic, pulmonary, renal or cardiac toxicity between both groups. There were no differences between CMV or fungal infections.

There weren’t significant differences between both conditioning regimens neither in 100-days cumulative incidence of severe aGVHD (7% vs 9%; p = 0,766) nor 3-year cumulative incidence of moderate-severe cGVHD (32% vs 34%; p = 0,591).

	All patients	BuFlu	TreoFlu	p value
	n = 97	n = 67	n = 30
Age, median (min-max)	57 (19-73)	54 (19-70)	62 (26-73)	0,003
Sex, n (%)				0,107
Male	54 (55,7)	34 (50,7)	20 (66,7)
Female	43 (44,3)	33 (49,3)	10 (33,3)
Diagnoses, n (%)				0,595
AML	71 (73,2)	49 (73,1)	22 (73,3)
MDS	26 (26,8)	18 (26,9)	8 (26,7)
Disease status, n (%)				0,260
Complete remission	76 (78,4)	56 (83,6)	20 (66,7)
Partial remission	5 (5,2)	3 (4,5)	2 (6,7)
Progression/refractory	11 (11,3)	5 (7,5)	6 (20)
Never treated	5 (5,2)	3 (4,5)	2 (6,7)
Prior treatment lines, median (min-max)	1 (0-4)	1 (0-4)	1 (0-3)	0,102
HCT-CI score, n (%)				0,037
<3	47 (48,5)	37 (55,2)	10 (33,3)
≥3	50 (51,5)	30 (44,8)	20 (66,7)
Donor, n (%)				0,566
HLA-matched sibling	29 (29,9)	22 (32,8)	7 (23,3)
HLA-haploidentical sibling	19 (19,6)	11 (16,4)	8 (26,7)
HLA-matched unrelated	44 (45,4)	30 (44,8)	14 (46,7)
HLA-mismatched unrelated	5 (5,2)	4 (6)	1 (3,3)
Stem cell source, n (%)				0,064
Bone marrow	64 (66)	48 (71,6)	16 (53,3)
Peripheral blood	33 (34)	19 (28,4)	14 (46,7)
GvHD prophilaxis, n (%)				0,243
Calcineurin inhibitor + MMF/MTX	67 (69,1)	46 (68,7)	21 (70)
Cy post + FK + MMF	20 (20,6)	12 (17,9)	8 (26,7)
Cy post	10 (10,3)	9 (13,4)	1 (3,3)
ATG	28 (28,9)	18 (26,9)	10 (33,3)	0,338

Conclusions: Considering patient selection and retrospective study limitations, in our experience treosulfan-fludarabine as allogeneic transplant conditioning regimen, regarding OS and RFS, offers similar results as myeloablative busulfan-based, despite patients were older with more comorbidity and poor disease status at transplantation.

Disclosure: Nothing to declare

P124 High dose intravenous busulfan increases risk for hemorrhagic cystitis in allogenic hematopoietic stem cell transplant patients

A. Santos Carreira ¹, M.Q. Salas², M. Remberger³, A. Datt Law⁴, W. Lam⁴, I. Pasic⁴, D.(.H. Kim⁴, F.V. Michelis⁴, A. Viswabandya⁴, A. Gerbitz⁴, J.H. Lipton⁴, R. Kumar⁴, C. Cserti⁵, T. Mazzulli⁶, M. Hassan⁷, J. Mattsson¹

¹University of Toronto/ Princess Margaret Cancer Centre, Toronto, Canada, ²Hospital Clinic de Barcelona, Barcelona, Spain, ³Uppsala University Hospital, Uppsala, Sweden, ⁴University of Toronto/Princess Margaret Cancer Centre, Toronto, Canada, ⁵University of Toronto/ University Health Network, Toronto, Canada, ⁶University of Toronto/Mount Sinai Hospital, Toronto, Canada, ⁷Karolinska Institutet/ Karolinska University Hospital, Stockholm, Sweden

Background: This study investigates the incidence and risk factors for hemorrhagic cystitis (HC) in a large cohort of adults undergoing allogeneic hematopoietic stem cell transplantation (alloHSCT) from a single Institution.

Methods: Between January 2015 and June 2021, 960 adults underwent first alloHSCT at our Institution and included in the study. Data was collected retrospectively and updated in October 2021.

Results: Overall, the median age was 58 years, 45.7% of patients underwent MUD alloHSCT, and 252 received MAC regimens. Of the 252 patients transplanted using MAC regimens, 81.4% received high doses of intravenous busulfan (HD BU). PTCY was given to 72.4% patients, and among them, 91.4% received dual T-cell depletion with ATG.

Overall, the cumulative incidences of grade 2-4 and grade 3-4 HC at day +180 were 13.2% and 5.8%, respectively, and the median of days to grade 2-4 and 3-4 HC were 39 and 44 days. BK virus was analyzed on 95% of cases and only 60% with HC grade 2-4 were positive. Additionally, the level of BK did not correlate with severity. Those patients receiving HD BU (Day + 180 23.1% vs 10.5%) had higher incidences of grade 2-4 HC than those that did not. Patients receiving PTCY (the majority of them in combination with ATG-CsA) had comparable incidences of grade 2-4 HC (Day + 180 14.6% vs 10.5%, P = 0.12). Additionally, patients with blood group O had higher incidence of grade 3-4 HC than patients with other blood groups (7.7% vs 3.9%, P = 0.002).

A multivariate analysis exploring risk factors for grade 2-4 and 3-4 HC was calculated including conditioning regimen, HCT-CI, donor type, blood group, and GVHD prophylaxis. The administration of HD BU (HR 3.06, P < 0.001) and the use of PTCY (HR 1.69, P < 0.001) were found to be risk factors for being diagnosed with grade 2-4 HC.

Secondary to the results obtained in the cumulative incidence and MVA analyses, the effect of HD BU and PTCY was explored in detail. The 545 patients receiving HD BU without PTCY were 1.9 times more likely to have grade 2-4 HC compared with patients that did not received any of these drugs (P = 0.038). The 90 patients that received HD BU with PTCY-based GVHD prophylaxis were 4.6 times more likely to present grade 2-4 HC compared with patients that did not received any of these drugs (P < 0.001). The use of PTCY, without HD BU did not increase the probability of grade 2-4 HC in our analysis (HR 1.4, P = 0.20).

Conclusions: The incidence of grade 2-4 HC at our Institution was 13.2%. HD intravenous BU was found to be an independent predictor for grade 2-4 HC; and when combined with PTCY the risk increased x2.38 times. PTCY-based GVHD prophylaxis, alone, did not increase the probability of HC in our study.

Patients receiving MAC alloHSCT with HD intravenous BU combined with PTCY-based GVHD prophylaxis may need change in supportive care with forced diuresis and increased dose of MESNA.

Disclosure: Nothing to declare

P125 AUC targeted busulfan administration can overcome the negative impact of pre-transplant mrd positivity in intermediate risk AML patients

E. Klyuchnikov¹, A. Badbaran¹, C. Langebrake¹, R. Massoud¹, P. Freiberger¹, F. Ayuk¹, C. Wolschke¹, U. Bacher², N. Kröger ¹

¹University Cancer Center Hamburg-Eppendorf, Hamburg, Germany, ²University of Bern, Bern, Switzerland

Background: The pre-transplant minimal residual disease (MRD) has a negative impact on post-transplant survival in AML patients due to increased relapse risk. An increased busulfan dosage may lead to lower relapses, however it may be also associated with increased NRM. Due to its narrow therapeutic index, the therapeutic drug monitoring approach based on the calculation of area under the curve (AUC) was developed to optimize the busulfan exposition. In this study, we compared post-transplant outcomes after the administration of personalized or fixed busulfan dosage in patients with intermediate risk AML focusing on pre-transplant MRD status.

Methods: 86 patients (male = 48; median age 56 years, 21-73) with intermediate risk AML and available pre-transplant MRD data (multicolored flow cytometry, “different from normal” approach, according to ELN guidelines), who received allografts (matched, n = 61; mismatched, n = 25) during 2015-2020 years at the University Cancer Centre Hamburg-Eppendorf were included. 33 patients received personalized busulfan dosage (AUC) after model-based AUC-calculation and 53 fixed busulfan dosage (12.8 mg/kg bw iv, n = 30; 9.6 mg/kg bw iv, n = 15, 6.4 mg/kg bw iv, n = 8). There were more females in the AUC group (67% vs 30%, p = 0.01). The myeloablative busulfan/fludarabine regimen was the most used in the both groups (82% and 58%, respectively). Patients from non-AUC group received more post-transplant cyclophosphamide than ATG as GvHD prophylaxis (25% vs 6%, p = 0.022).

Results: The median follow up was 27 months (1-61). The relapses were lower in pre-transplant MRD^neg patients (11%, 5-25% vs 35%, 22-51%, p = 0.008) and in those who received MAC (19%, 11-31%) vs RIC (65%, 20-93%, p = 0.04). The non-AUC led to higher relapses at 3 years (35%, 23-49% vs 6%, 2-19%, p = 0.02) resulting in lower 3-year LFS (55%, 40-70% vs 78%, 54-91%, p = 0.009) and OS (69%, 54-81% vs 82%, 60-93%, p = 0.05) comparing to AUC. The NRM at 3 years was not different (AUC: 7%, 2-19% vs non-AUC: 10%, 5-21%, p = 0.48). The aGvHD at 1 year (AUC: 21%, 11-37% vs non-AUC: 14%, 7-27%, p = 0.41) and cGvHD at 3 years (AUC: 57%, 40-73% vs non-AUC: 45%, 31-60%, p = 0.30) were not significantly different.

Of the pre-transplant MRD^pos patients, those from AUC group (n = 13) showed lower relapses at 3 years (8%, 1-36% vs 49%, 31-67%, p = 0.07) resulting in higher 3-year LFS (92%, 69-98% vs 41% 24-61%, p = 0.023) and OS (100% vs 58%, 39-75%, p = 0.032) compared with non-AUC group (n = 31). The NRM at 3 years was not significantly different (AUC: 0%, non-AUC: 10%, 3-28%, p = 0.24).

Of the pre-transplant MRD^neg patients, there were no significant differences concerning relapses at 3 years (5%, 1-24% vs 17%, 6-40%, p = 0.32), NRM at 3 years (6%, 1-28% vs 9%, 3-27%, p = 0.56), 3-year LFS (84%, 61-95% vs 74%, 52-88%, p = 0.43) and OS (84%, 61-95% vs 84%, 61-95%, p = 0.92) between AUC (n = 19) and non-AUC (n = 23) groups, respectively.

Conclusions: The personalized, AUC-based, busulfan administration as part of conditioning seems to overcome the negative impact of pre-transplant MRD positivity with acceptable NRM in patients with intermediate risk AML undergoing allo-HSCT.

Disclosure: Nothing to declare

P126 Optimising in vivo alemtuzumab levels in matched unrelated haematopoietic stem cell transplantation

M. Madkhali ^1,2, C. Wright^1,3, K. Pearce¹, S. Pagan¹, P. Singh¹, L. Duncan³, J. Lam¹, G. Erskine¹, J. Macdonald¹, A. Resteu¹, P. Milne¹, A. Publicover^1,3, E. Hurst³, V. Bigley^1,3, G. Hale⁴, M. Collin^1,3

¹Newcastle University/Translational and Clinical Research Institute, Newcastle, United Kingdom, ²Ministry of Health/Jazan Health/Samtah General Hospital, Samtah, Saudi Arabia, ³Northern Centre for Bone Marrow Transplantation, Newcastle, United Kingdom, ⁴Geoff Hale Developments, Oxford, United Kingdom

Background: Alemtuzumab is a humanised monoclonal antibody specific for CD52 that depletes T cells in vivo and reduces acute and chronic graft versus host disease (GVHD). Alemtuzumab is highly efficient at preventing acute and chronic GVHD in Fludarabine and Melphalan (FM) conditioning but at the cost of prolonged immunosuppression, increased infections, and relapse. The optimal dose and scheduling of Alemtuzumab is not defined, particularly in the matched unrelated donor (MUD) setting where empiric flat-dosing, unsupported by pharmacokinetics, is the rule.

Methods: In this retrospective single centre study we compared two empiric dose reductions from the original 100mg dose regimen (Kottaridis et al., 2000). These were introduced as policy changes in an attempt to minimise excessive T cell depletion. From 2015-2018, 48 patients received 60mg (30mg on days -4 and -2) (FMA60) and from 2019-2021,40 patients received 30mg delivered on day -1 (FMA30). Transplant serum samples were available from 21 FMA60 and 16 from FMA30 at days 0, +7 and +14. Alemtuzumab levels were measured by ELISA assay. All Patients were transplanted with fludarabine 150mg/m2 and melphalan 140mg/m2 conditioning chemotherapy at the Northern Centre for Bone Marrow Transplantation (Newcastle upon Tyne Hospitals UK). We compared the overall incidence and severity of acute GVHD in the two cohorts. Overall survival (OS) and relapse free survival (RFS) were analysed by Kaplan Meier compared with log-rank tests.

Results: On all days, the mean (SD) of Alemtuzumab concentration were significantly different between FMA60 and FMA30 cohorts. Respectively, Alemtuzumab on day 0 was 6.22 (2.09) ug/ml and 3.33 (0.97) ug/ml (p < 0.0002); on day+7: 2.385 (1.456) ug/ml and 0.8423 (0.4431) ug/ml (p = 0.0003), on day +14: 1.124 (0.8435) ug/ml and 0.4768 (0.4907) ug/ml (p = 0.0410). No differences were observed in the incidence and severity of acute GVHD between the two cohorts (Chi-square test p = 0.6801). In FMA60, GVHD was 43.75%, 8.33% and 2.08% compared with 50%, 2.5% and 2.5% in FMA30 for grades I, II and III, respectively. Comparable OS and RFS were observed; OS (log-rank test p = 0.742), the OS at 2 years were 66% and 68% in the FMA 60 and FMA 30, respectively. The hazard ratio for death in FMA 60 versus FMA 30 was 1.121 (95% CI 0.518-2.426) p = 0.772. RFS (log-rank test p = 0.698), the hazard ratio for death in FMA 60 against FMA 30 was 1.208 (95% CI 0.465-3.140) p = 0.698.

Conclusions: This retrospective analysis reports the in vivo level of Alemtuzumab on day 0, +7 and +14 in recipients of 60mg (delivered on days -4 and -2) and 30mg (day -1) in MUD transplant. The results confirm that 30mg of Alemtuzumab on day -1 is effective in preventing GVHD in MUD transplant.

Disclosure: No conflicts of interest to declare.

P127 Total body irradiation-based conditioning versus chemotherapy before allogeneic stem cell transplantation for adults with acute lymphoblastic leukemia

N. Ben Abdeljelil ¹, R. Ouerghi¹, S. Ladeb¹, D. Belloumi¹, L. Torjemane¹, S. Mekni¹, T. Ben othman¹

¹Centre National de Greffe de Moelle Osseuse, Tunis, Tunisia

Background: Total body irradiation (TBI) is a part of the standard myeloablative conditioning regimen before allogeneic stem cell transplantation (allo-HSCT) for patients with acute lymphoblastic leukemia (ALL) but not available in all center. This study aimed to compare TBI-based conditioning to chemotherapy in term of graft-versus host disease (GVHD), overall survival (OS), event-free survival (EFS), non-relapse mortality (NRM) and cumulative incidence (CI) of relapse.

Methods: Retrospective study was conducted in adult patients who underwent allo-HSCT from HLA-identical sibling donors between January 2012 and July 2021. Conditioning regimen consisted TBI plus etoposide or cyclophosphamide (Cy). Non TBI-regimen consisted of busulfan (iv) plus Cy (Bu-Cy) or fludarabine plus busulfan plus Cy (FBC) or thiotepa plus busulfan plus fludarabine (TBF). GVHD prophylaxis consisted of cyclosporine and short course of methotrexate +/− antithymocyte globulin (ATG).

Results: Sixty patients were included. Patient characteristics were similar between the two groups (table1). Patients conditioned with TBI were more likely to have delayed platelet engraftment and mucositis grade II-IV (p = 0.03, p < 10^-3, respectively). Cumulative incidences of acute GVHD grade II-IV and chronic GVHD were not significantly different between TBI and non-TBI groups (53.6% vs 34.4 %, p = 0.11 and 49.7% vs 33.1%, p = 0.42, respectively). CMV infection(s) were not significantly different between TBI and non-TBI groups (35.7% vs 31.3 %, respectively, p = 0.11). The median follow-up was 36 months (range, 2 - 116 months).There were no statistically significant differences between groups in terms of OS and EFS (65.7% for TBI group vs 50.6% for non-TBI group, p = 0.22 and 58.2% vs 49%, p = 0.27, respectively). Patients from both groups had a comparable CI of NRM (25.5% vs 19.1%, p = 0.73, respectively). TBI group had lower CI of relapse compared to non-TBI group with no significant difference (13.3% vs 29.3%, p = 0.79, respectively).

Table1. Patient characteristics.

Patient characteristics	TBI-based regimen (n = 28)	Non-TBI based regimen n = 32	p
Median age (range), years	28 (17-49)	32 (17-48)	0.31
Sex-ratio	1.33	3.6	0.08
Diagnosis			0.4
B-ALL, n (%)	14 (50%)	20 (62.5%)
T-ALL, n (%)	12 (43%)	10 (31.3%)
Mixed lineage leukemia, n (%)	2 (7%)	2 (6.2%)
Median time diagnosis-allo-HSCT (range), months	6 (2-137)	7 (3-41)	0.05
Disease status before transplant, n (%)			0.55
CR1	21 (75%)	26 (81%)
>CR1	7 (25%)	6 (19%)
HCT-CI score ≥ 2, n (%)	8 (28.6%)	3 (9.4%)	0.05
ABO mismatch, n (%)			0.55
Matched	18 (64.3%)	17 (53.2%)
Major or bidirectional or minor	10 (35.7%)	15 (46.8%)
Stem cell source, n (%)			0.35
Bone marrow	12(43%)	10(31%)
Peripheral blood stem cell	26(57%)	22(69%)
GVHD prophylaxis			0.92
Cyclosporine and methotrexate +/−ATG	27(96.4%)	31(96.9%)
Cyclosporine	1 (3.6%)	1 (3.1%)

Conclusions: Chemotherapy-based conditioning seems to be an alternative to TBI-based conditioning. Prospective studies in adults ALL comparing TBI-based regimen to homogeneous group of chemotherapy-based regimen are warranted to validate this finding.

Disclosure: Nothing to declare

P129 Low dose anti t-lymphocyte globulin in high t-cell content PBSC graft: Improving transplant outcomes in post-transplant cyclophosphamide platform

E. Xue¹, F. Lorentino¹, M.T. Lupo Stanghellini¹, F. Giglio¹, S. Piemontese¹, D.T. Clerici¹, F. Farina¹, S. Mastaglio¹, A. Bruno², E. Campodonico³, R. Nitti³, M. Marcatti¹, A.A. Assanelli¹, C. Corti¹, F. Ciceri^1,3, J. Peccatori¹, R. Greco ¹

¹IRCCS San Raffaele Scientific Institute, Milan, Italy, ²Vita-Salute San Raffaele, Milan, Italy, ³VIta-Salute San Raffaele, Milan, Italy

Background: For decades, anti-T lymphocyte globulin (ATLG) has been adopted as part of conditioning before hematopoietic stem cell transplants (HSCT). In recent years, the use of post-transplant cyclophosphamide (PT-Cy), initially introduced for haploidentical HSCT, has spread consistently throughout several HSCT settings, showing comparable results. We recently reported increased risk of both acute and chronic graft versus host disease (GvHD) in patients receiving a high CD3⁺ cell counts within the graft. In this setting, we aimed to investigate the potential benefit of the co-administration with PT-Cy and a low, post-transplant ATLG dose.

Methods: Starting from 2019, 21 patients were transplanted using peripheral blood grafts containing more than 300*10⁶/kg and were administered PT-Cy 50 mg/kg on day+3 and day+4 with the addition of ATLG 5 mg/kg on day+5 (Grafalon, Neovii) (study group). Using a 1:2 matched-pair analysis, we compared the outcomes with 42 patients transplanted prior to 2019 with a PBSC graft containing a CD3⁺ counts above 300*10⁶/kg, who received PT-Cy without additional ATLG (control group). In both groups, GvHD prophylaxis included sirolimus (with mycophenolic acid in HLA-mismatched and unrelated transplants).

Results: Patient and transplant characteristics are shown in Table 1. Median follow up was 538 days in the study group and 1450 days in the control group. 30-day cumulative incidence of platelet engraftment was lower in the study group (29% versus 45%, p = 0.03). There was a non-significant trend of higher rate of poor graft function in the study group (29% versus 19%, p = 0.52). In terms of immune-reconstitution, the long-term negative impact of ATLG was evident on the CD4⁺ subsets. However, we documented no differences in term of CMV, HHV6, EBV, adenovirus and BK virus reactivation incidence, and there was a non-significantly higher incidence of invasive fungal infection (7/21 cases versus 9/42 cases p = 0.36). We observed a non-significant trend toward a lower day-100 CI of grade 3-4 aGvHD in the study group 10% versus 19% (p = 0.48), whereas 1-year CI of cGvHD was significantly lower (15% versus 41%, p = 0.04). Survival outcomes were comparable between the groups: 1-year TRM 19% versus 19% (p = 0.9); 1-year relapse rate 25% versus 24% (p = 0.9); 1-year PFS 56% versus 57% (p = 0.9), 1-year OS was 75% versus 69% (p = 0.49).

Table 1 - Patient and transplant characteristics.

	Study Group	Control Group	P value
	PT-Cy + ATLG	PT-Cy
	N = 21	N = 42
Median patient age at HSCT (range)	60 (24-71)	56 (22-77)	0.691
Median donor age at HSCT (range)	41 (18-68)	34 (18-70)	0.41
Gender
Female	N = 9	N = 16	0.71
Male	N = 12	N = 26
Disease type
ALL	N = 2	N = 6	0.974
AML	N = 13	N = 23
MPN/MDS	N = 4	N = 8
MM/Lymphoma	N = 2	N = 5
Disease status
CR1	N = 7	N = 13	1
CR > 1	N = 7	N = 13
Not in CR	N = 7	N = 16
Type of HSCT
MRD	N = 4	N = 7	0.881
MUD	N = 4	N = 12
MMUD	N = 4	N = 7
MMRD	N = 9	N = 16
Conditioning regimen$
MAC	N = 13	N = 30	0.567
RTC	N = 8	N = 12
Median CD3+ infused (106/kg)	464 (409-496)	399 (347-511)	0.197

^$ Myeloablative regimen include: Treosulfan-Fludarabine +/−Melphalan/Thiotepa/Total body Irradiation, Reduced toxicity regimen include Treosulfan-Fludarabine

Conclusions: Combining PT-Cy with low ATLG dose in high T-cell content PBSC graft translated into a low rate of chronic GvHD incidence, without impacting relapse incidence and survival outcomes.

Disclosure: The authors declare no conflict of inter

P130 Full donor chimerism in patients undergoing HSCT with a reduced conditioning regimen after one or two alkylating agents: A single center experience

C. Arevalo ¹, A. Paviglianiti^1,2, A. Mussetti^1,2, M. Peña^1,2, L. Hurtado¹, S. Gonzalez¹, K. Meriem¹, R. Parody³, A. Sureda^1,2,4

¹Institut Catala d’Oncologia-Hospitalet, Barcelona, Spain, ²Institut d’Investigacio Biomèdica de Bellvitge, Barcelona, Spain, ³University Hospital of Virgen del Rocio, Sevilla, Spain, ⁴University of Barcelona, Barcelona, Spain

Background: Allogeneic hematopoietic stem cell transplantation (HSCT) is a potentially curative therapy for several hematological disorders, therefore improving conditioning regimens can have an important impact on outcomes. Hereby, we report a single center experience of HSCT with one or two alkylating agents as conditioning regimen with special focus on chimerism

Methods: We collected data from 2010 to 2020, identifying 75 adult patients, diagnosed with either lymphoid or myeloid disease undergoing HSCT from HLA identical siblings or matched unrelated donor (MUD), with reduced-intensity thiotepa-busulfan-fludarabine (TBF) in a dose of 10mg/kg (two days), 3.2mg/kg (two days) and 30mg/kg (3 days) respectively or busulfan-fludarabine (BF) (same doses, but busulfan for 3 days) as conditioning regimen and with available chimerism data. Full donor chimerism was defined as having >95% donor alleles. Graft source was peripheral blood stem cell in all patients. The study aimed to assess the rate of full donor (FD) chimerism at day 30 and 100, in patients receiving TBF or BF as conditioning regimen.

Results: Baseline characteristics of the population are described in figure 1. Summarizing, the median age was 58 years, 64% had an intermediate disease risk index and 88% of were in complete remission. Donor type was HLA identical sibling in 65%. Conditioning regimen was BF in 67% patients (n = 50). The median time of neutrophil and platelet engraftment were 16 (range 10–28) and 13 (range 5–45) days, respectively. Thirty-three patients experienced acute GvHD, 12 of them grade 4. The cumulative incidence (CI) of chronic GvHD was 16% (95% CI 9-28) at 1 year, there were no significant differences between BF and TBF conditioning (18% vs 11%, p = 0.90). The CI of non-relapse mortality (NRM) at 100 day and 1 year was 8% (95% CI 4-17) and 21% (95% CI 13-33), respectively. NRM was not significantly different between patients receiving BF vs TBF at 100 day (4% vs 16%) and at 1 year (20% vs 21%) (p = 0.17). The CI of relapse at 100 days and 1 year was 18% (95%CI 11-29) and 35% (95%CI 25-48), respectively. Relapse was not statistically different between the two groups (p = 0.45) at 100 day nor at 1 year. Overall survival and disease free survival were 57% (95% CI 39-72%) and 44% (95% CI 33-56%) at 1 year, respectively. Overall survival was not statistically different for patients receiving BF vs TBF (56% vs 58%; p = 0,61) nor was disease free survival (BF 40% vs TBF 56%; p = 0,51). A FD chimerism at 30 day was achieved for 62% (n = 21) of the patients receiving TBF while 96% of the patients in the BF group had less than FD chimerism (p < 0.001). At 100 days, almost all patients (95%) in the TBF group achieved a FD chimera comparing to BF group (42%) (p < 0.001). Nine patients received donor lymphocyte infusion, 8 of them in the BF group (6 = disease relapse; 1= mixed chimerism; 1= graft failure).

Conclusions: The combination of two alkylating agents is associated with a higher chance of achieving a FD chimerism at 30 days and 100 days without significant survival advantages.

Disclosure: No discloures

P131 Overall survival in advanced stage mantle cell lymphoma after early autologous stem cell transplantation with cisplatin, etoposide, cytarabine and melphalan (peam) as a conditioning regimen

D. Franco-Saenz ¹, B.L. Acosta-Maldonado¹, J.F. Téllez-Manríquez¹, L.M. Valero-Saldaña¹, B. Gutiérrez-Gutiérrez¹

¹Instituto Nacional de Cancerologia, Ciudad de Mexico, Mexico

Background: Chemoimmunotherapy in advance stage mantle cell lymphoma is not curative. Autologous hematopoietic stem cell transplantation (ASCT) currently is the standard of treatment for patients in first remission diagnosed with Mantle cell Lymphoma (MCL) OS has been improved by using induction chemoimmunotherapy conventional and higher intensity, and maintenance therapy as by GELA study reports 75%. LyMa Trial has proven improvement in the global survival and progression-free survival. In this study we aimed to describe overall survival (OS) diagnosed Mantle cell lymphoma (MCL) with PEAM as a conditioning regimen.

Methods: A retrospective study was conducted on patients diagnosed with MCL and ASCT as consolidation therapy at the Instituto Nacional de Cancerología in Mexico City between 2011 and 2020. PEAM condition regimen: Cisplatin 100mg/m² (-4), etoposide 750 mg/m² (-4,-3), cytarabine 800mg/m² (-4,-3,-2) and melphalan 140mg/m² (-4). OS results were obtained using the Kaplan-Meier method.

Results: We analyzed 15 patients with MCL after ASCT as consolidation therapy, a median follow-up of 4.58 years, the median age at transplantation was 54-years (range 39-68y), with male predominance (86.7%). Nine patients with at least one comorbidity, the most predominant being diabetes mellitus type II (66.6%). All patients with clinical stage III-IV, 20% of them with bone marrow infiltration.

All patients received one line of chemoimmunotherapy, most were treated with R-CHOP plus /or R-DHAP(86%). Eleven patients (73.3%) with complete response, three (20%) with partial response before ASCT. Fourteen patients (93.3%) received PEAM plus rituximab as myeloablative conditioning regimen. Neutrophil recovery median was 10 days, nine patients (66.6%) developed febrile neutropenia. Twelve patients (80%) received maintenance with rituximab. Eleven (73.3%) had complete response at last follow up after ASCT, three (20%) with relapsed disease, one stable disease. Three patients relapsed, two (66.6%) died. The OS at 5-years was 84.8%.

Graph 1. Overall Survival

Conclusions: Conventional chemoimmunotherapy is effective followed by ASCT as consolidation therapy in mantle cell lymphoma with advanced stage disease. We describe higher OS 5-years (84.8%) as compared with other series (57% and 75%) with similar chemoimmunotherapy and conventional conditioning regimen.

Disclosure: Nothing to declare

P132 High-intensity treosulfan-etoposide-fludarabine conditioning can be safely used in combination with major GVHD prevention platforms in children with leukemia

E. Zhuravel ¹, M. Perminova², G. Seregin¹, M. Ilushina², M. Zhuravel¹, R. Khismatullina², B. Kurmanov¹, M. Klimentova², E. Burtsev¹, L.S. Shelikhova², G. Bronin¹, M.M. Maschan²

¹Morozov Children’s Hospital, Moscow, Russian Federation, ²Dmitry Rogachev National Medical Research Center of Pediatric Hematology, Oncology and Immunology, Moscow, Russian Federation

Background: Treosulfan-based conditioning regimens are widely used among children with leukemia. Treosulfan is usually combined with fludarabine and either melphalan or thiotepa. Due to frequent interruptions of market availability of melphalan and thiotepa, there is an unmet need for alternative safe and effective combinations. There are reports of the use of treosulfan/fludarabine/etoposide regimens among adult patients, but this approach is not well-studied in pediatric HSCT. We performed a retrospective analysis of the clinical use of treosulfan/fludarabine/etoposide regimen in a cohort of children with leukemia, treated at two sites in Moscow: Dmitriy Rogachev National Medical Researh Center of Pediatric Hematology, Oncology and Immunology and Morozov Children’s Hospital, Moscow.

Methods: Sixty-five pediatric patients (41-male, 24-female) received conditioning with treosulfan (42g/m²), fludarabine (150 mg/m²) and etoposide (60mg/kg) before allogeneic HSCT between 2018 to 2021. HSCT indications included acute lymphoblastic leukemia (ALL), n = 43 (66%) (B-ALL n-31, T-ALL n-12), acute myeloid leukemia, n = 18 (27.7%), bi-lineage leukemia, n = 3 (4.6%) and JMML n = 1 (1.5%). In 8 patients, it was the 2nd HSCT. The source of HSC was PBSC in 60 cases (92%), and BM in 5 cases (8%). Haploidentical family donors were used in 52 cases (80%), matched related and unrelated donors in 10 and 3 cases, respectively. Three GVHD prevention approaches were used: 35 patients received posttransplant cyclophosphamide (PtCy) on days+3, +4 at 50 mg/m²/day, tacrolimus and MMF with unmanipulated HSCs. In 26 cases ex-vivo αβ T cell depletion combined with abatacept and bortezomib was used. In 4 patients with a matched BM transplant calcineurin inhibitor-based regimen was used. Median follow-up was 12.5 months.

Results: Neutrophil and platelet engraftment was recorded in 61 of 65 cases. All cases of primary graft failure were seen among ex-vivo depletion cohort, of them 3 were successfully re-transplanted. The median time to neutrophil engraftment was 16 days (8-47), 12 days in ex-vivo depletion and 18 days in PtCy cohorts, respectively. The median time to platelet engraftment was 16 days (11 - 55), 13 in ex-vivo depletion and 25 in PtCy cohorts, respectively. Most common toxicities affected skin, liver and GI. Cutaneous toxicity grade I-IV was seen in 32 patients (49%), of them 5 cases with grade III-IV (15.6%). Hepatic toxicity grade I-II was observed in 19 patients (29.2%), no cases of grade III-IV liver toxicity were recorded. The most frequent type of toxicity was gastrointestinal toxicity, seen in 58 cases (89.2%). GI toxicity was graded as grade I-II in 46 patients (80%), grade III-IV in 12 patients (20%). Renal toxicity grade I-II was observed in 4 cases (6.5%). Acute GVHD II-IV was observed in 30 patients (36.1%), severe forms of acute GVHD, grade III-IV, were recorded in 10 patients (15.4%). Early (day + 100) non-relapse mortality was not recorded.

Conclusions: The conditioning regimen based on Treo42/Flu150/VP60 was safe, ensuring engraftment and tolerable short-term toxicity among children with acute leukemia. This regimen can be combined with two key GVHD prevention platforms, ex-vivo αβT cell depletion and PtCy, with minimal non-relapse mortality. Long-term outcomes should be evaluated prospectively.

Disclosure: Nothing to declare

P133 Chemokine receptor 4 directed endoradiotherapy with [¹⁷⁷lu]-pentixather in addition to total body irradiation as conditioning regimen for relapsed/refractory acute myeloid leukemia - a retrospective analysis

K. Braitsch ¹, M. Hefter¹, K. Koch¹, K. Nickel¹, K.S Goetze¹, W. Weber¹, F. Bassermann¹, M. Eiber¹, M. Verbeek¹, P. Herhaus¹

¹Technical University of Munich, Munich, Germany

Background: Patients with relapsed or refractory (r/r) acute myeloid leukemia (AML) have poor prognosis but cure is possible with allogeneic hematopoietic stem cell transplantation (allo-HSCT). Myeloablative total body irradiation (TBI) based conditioning is often used in AML patients refractory to standard chemotherapy. Feasibility of chemokine receptor 4 (CXCR4) directed endoradiotherapy (ERT) has previously been shown in patients with CXCR4 expression on leukemic blasts. Here, we retrospectively report on six chemo-refractory, relapsed AML patients that received ERT with CXCR4-targeting [¹⁷⁷Lu]-Pentixather combined with TBI and chemotherapy prior to allo-HSCT.

Methods: In this retrospective, single center analysis data from six consecutive patients with r/r AML treated between February 2019 and September 2021 were included. All patients had active AML and were either refractory to induction and salvage chemotherapy or had refractory relapse. In-vivo CXCR4 expression on leukemic blasts was confirmed in all patients by [⁶⁸Ga]-Pentixafor PET-imaging. Conditioning consisted of [¹⁷⁷Lu]-Pentixather ERT as compassionate use on day (d) -15, TBI (8-10 Gy) on d-9 to d-7 and chemotherapy, based on donor type. Chemotherapy regimens were fludarabine 30mg/m² d-5 to d-2 or 60mg/m²cyclophosphamide on d-5 and d-4 for matched donors and fludarabine 30mg/m² d-6 to d-2 plus cyclophosphamide 14,5mg/m² d-6 to d-5 for haploidentical or mismatch donors. Immunosuppression for matched donors consisted of antithymocyte globulin (5-10mg/kg d-3 to d-1), mycophenolatmotefil and a calcineurin inhibitor. For haploidentical donors post-transplant cyclophosphamide was used according to standard of care. In this retrospective analysis, we assessed response, toxicity, overall survival, engraftment rates and adverse events.

Results: Median patient age was 47 (42-57). 5 patients had de novo AML and one secondary (s)AML. In median, patients had previously received 4 (3-7) lines of intensive therapy, including allo-HSCT in n = 3 patients. Median injected activity of [¹⁷⁷Lu]-Pentixather was 12.6 GBq (11.5-16.1). All patients received a peripheral blood stem cell graft with a median of 5.9 (4.9-10.3) x 10⁶ CD34 + cells/kg. During hospital stay, n = 4 patients required intensive care treatment and n = 2 mechanical ventilation. Response evaluation by bone marrow biopsy was available for n = 5 patients, n = 4 achieved complete remission with incomplete count recovery (CRi) and n = 1 morphologic leukemia-free state (MLFS). One patient was refractory and regenerated with 11% blasts in the peripheral blood at day 11. Time to leukocyte recovery in the n = 4 responding patients was 25 (16-28) days, one patient had received a stem cell boost after initial graft failure. Two patients are still alive at month 21 and 20 after allo-HSCT, n = 3 died during hospital stay and n = 1 after a relapse. Causes of death were respiratory failure (n = 1), sepsis (n = 1), refractory disease (n = 1) and relapse (n = 1). In the two surviving patients, kidney function remained normal with creatinine levels of 0.8 and 0.9 mg/dl, respectively.

Conclusions: Conditioning with CXCR4-directed ERT plus TBI is feasible and response rates in this heavily pre-treated patient cohort were promising. No acute kidney toxicity related to radiation dosage was observed and engraftment was not impaired in this small cohort. The results warrant prospective studies.

Disclosure: Nothing to declare

P134 Potential pharmacokinetics interactions between busulfan and iron chelation in children given HSCT for non-malignant diseases

F. Compagno ¹, A. Bartoli², S. De Gregori², S.I. Tripodi¹, A. Agostini¹, A. Panigari¹, S. Boghen¹, M. Siciliano³, M. De Cicco³, P. Comoli³, G. Giorgiani¹, R. Albertini⁴, M. Zecca¹

¹Pediatric Hematology/Oncology, Fondazione IRCCS Policlinico San Matteo, Pavia, Italy, ²Clinical Biochemistry - Clinical and Experimental Pharmacokinetics Unit, Fondazione IRCCS Policlinico San Matteo, Pavia, Italy, ³Cell Factory, Fondazione IRCCS Policlinico San Matteo, Pavia, Italy, ⁴Clinical Biochemistry, Fondazione IRCCS Policlinico San Matteo, Pavia, Italy

Background: Busulfan (BU) therapeutic drug monitoring (TDM) is performed in order to avoid over exposure and toxicity and/or under exposure and reduce efficacy. In our Center, BU TDM is performed for every patient receiving BU, and the dose is adjusted in order to achieve a target area under the curve (AUC) within the range 3696-5538 ng x h/m. We observed an unexpected increase in BU AUC in children who were treated before HSCT with deferasirox or deferoxamine for iron overload. BU undergoes glutathione conjugation and subsequent oxidative metabolism. Deferasirox inhibits multiple oxidative enzymes of the cytochrome P450 family, and this could explain the decreased clearance of BU.

Methods: We retrospectively analyzed 28 pediatric patients (age range, 1-16 years; median 6.7 years) affected by a non-malignant disease (10 thalassemia major, 17 sickle cell disease, 1 thalasso-drepanocitosis), who underwent allogeneic HSCT between 2018 and 2020. They received a Bu-based conditioning regimen (initial BU dose 1 mg/kg every 6 hours), in association with Thiotepa and Fludarabine. 25% of the patients had received pre-transplant iron chelation to treat/prevent iron overload, with deferasirox or deferoxamine, until the beginning of the conditioning regimen. Blood samples were collected at fixed time points after the first dose of BU, in order to calculate the median concentration at steady state (Css) and derivate the value of AUC.

Results: In all tested patients, BU exposure after the first dose, based on body weight, had a median level of 6422 ng x h/mL (range, 3604-10758). In the patient who received iron chelation, BU exposure was higher than expected (median 8459; range, 6872-10758), as compared to that of children who did not receive iron chelation (median 6017; range, 3604 - 8250) (Fig.1). A total of 8 patients required a Bu adjustment, 5 of them (62.5%) had received iron chelation before HSCT, whereas the other 3 (37.5%) had not, with a statistically significant difference (Chi-square P = 0.009). After BU dose reduction, AUC was measured again after the fifth/ninth dose and it decreased to 4484-7789 ng x h/mL. Unfortunately, for 2 patients the dose reduction was not sufficient to ensure an adequate BU exposure: in one of the patient BU dose was reduced by 18%, whereas in the other, even with a 40% dose reduction, an adequate plasma level could not be achieved. In the four patients with adequate exposure after dose reduction, Bu dose was reduced by 21% to 50%.

Conclusions: Pharmacokinetic studies dealing with drug-drug interactions between BU and iron chelation therapy are extremely limited. The administration of iron chelation immediately before the conditioning regimen may result in a systemic BU over-exposure. An earlier discontinuation of iron chelation treatment may be necessary in these patients, and TDM remains mandatory in order to optimize the dose for each patient.

Disclosure: Nothing to declare

P135 GVHD prophylaxis with post transplant cyclophosphamide after allo-HSCT with mismatched unrelated and haploidentical donors: Risk of CMV reactivation at letermovir discontinuation

M.C. Mico’¹, A. Algarotti¹, C. Pavoni¹, D. Taurino¹, G. Borleri¹, G. Cavallaro¹, A. Grassi¹, A. Rambaldi^1,2

¹Division of Hematology, ASST Papa Giovanni XXIII, Bergamo, Italy, ²University of Milan, Milan, Italy

Background: The use of post-transplant cyclophosphamide (PTCy) has significantly changed the approach to the graft versus host disease (GvHD) prophylaxis in patients undergoing allogenic stem cell transplantation (allo-HSCT). However, PTCy can increase the rate of infections, in particular of cytomegalovirus (CMV).

Methods: We retrospectively analyzed the clinical outcomes of 68 adult patients (AML = 38, MDS = 7, ALL = 9, NHL/CLL = 8, CML = 3, MF = 2, HD = 1) who underwent allo-HSCT (between December 2011 and September 2021) from mismatch unrelated (MMUD, 9/10) (n = 21), and haploidentical (Haplo) (n = 47) donors. All patients received PTCy as GvHD prophylaxis. Seventeen patients with a positive CMV serology, had a CMV prophylaxis with letermovir.

Results: With a median follow-up of 1.9 (range. 0.05-9.7) years, the Overall Survival (OS) of MMUD and Haplo was 73% vs 71% . The non-relapse mortality (NRM) was 16% vs. 11% for MMUD and Haplo, respectively. The incidence of relapse was 34% for Haplo and 17% for MMUD. The intensity of the conditioning regimen, reduced (n = 24) or myeloablative (n = 44) had no effect on these outcomes.By uni and multivariate analysis, more aGvHD (grade II-IV) was associated to MMUD than haplo donors (HR 4.77, CI 1.62-14. in univariate analysis; HR 5 .12, CI 1.57-16.7 in multivariate) with no difference in term of cGvHD. The use of PBSC was significantly associated to a better overall survival, better neutrophil engraftment and reduced risk of poor marrow function/ rejection with no impact on GvHD. None of the patients treated with letermovir had CMV reactivation during CMV prophylaxis (Fig. 1). However, those who had less than 50 CD4 + cells at discontinuation (day 100) invariably showed CMV reactivation, subsequently. By multivariate analysis, CMV reactivation was associated with a better DFS (HR 0.34, CI 0.14-0.83) and OS (HR 0.3; CI 0.12-0.96).

Conclusions: The main outcomes of allo-HSCT after MMUD and Haplo transplant with PTCy as GvHD prophylaxis, were similarly favorable although transplants with MMUD showed an increased risk of aGvHD. When letermovir was discontinued, patients with less than 50 CD4 + T cells in the peripheral blood were at high risk of CMV reactivation.

Disclosure: Nothing to declare

P136 Decreased glomerular filtration rate is related to increased mucositis in autologous stem cell transplantation conditioned with high dose melphalan

A. Lobo-Olmedo¹, J. Arzuaga-Méndez ^1,2, A. Balerdi^1,2, E. Amutio^1,2, J.C. García-Ruiz^1,2

¹Cruces University Hospital, Barakaldo, Spain, ²Biocruces Bizkaia Health Research Institute, Barakaldo, Spain

Background: Melphalan toxicity, in particular oral and intestinal mucositis, is increased in patients with low glomerular filtration rate (GFR). Thus, melphalan dose in autologous stem cell transplantation (ASCT) is adjusted from 200 mg/m² to 140 mg/m² in patients with adjusted GFR < 30 mL/min/1.73m². Our aim is to study the incidence of grade 4 mucositis in patients with mild reduction in GFR (GFR < 90 and >30 ml/min/1.73m²) that underwent ASCT conditioned with melphalan 200 mg/m².

Methods: We retrospectively analysed the incidence of oral or intestinal mucositis that required parenteral nutrition (oral mucositis WHO grade 4 or intestinal mucositis CTCAE grade >3) in consecutive patients that underwent ASCT between January 2016 and June 2020, according to the patient GFR on the day of melphalan administration. Secondary variables were time from infusion to discharge, need of intensive care and transplant-related mortality on day +100 (TRM D100).

Results: Of the 129 patients included, 90 had a GFR ≥ 90 and 39 had a GFR between 30 and 90 ml/min/1.73m². 24 (26%) patients with GFR ≥ 90 and 22 (56%) with GFR < 90 presented mucositis that required parenteral nutrition (relative risk 2.11, p = 0.0011). Time from infusion to discharge was also higher in patients with GFR < 90 (median of 21 vs. 18 days, p = 0.035). There was no significant difference in the need of intensive care and there was no TRM D100 in any of the groups.

Conclusions: Patients undergoing ASCT conditioned with high dose melphalan are at increased risk of needing parenteral nutrition due to oral or intestinal mucositis if they have reduced GFR (90 to 30 ml/min/1.73m²). This fact, however, does not translate into increased risk of intensive care need or transplant related mortality.

Disclosure: Nothing to declare

P137 Autologous stem cell transplantation using cyclophosphamide and total body irradiation for t- cell lymphomas

U. Şahin ¹, A. Gokmen¹, S.M. Urlu¹, E. Soydan¹, M. Kurdal Okcu¹, Ö. Arslan², M. Özcan²

¹Medicana International Ankara Hospital, Hematology and Bone Marrow Transplantation Unit, Ankara, Turkey, ²Ankara University Faculty of Medicine, Ankara, Turkey

Background: T-cell lymphomas (PTCLs) constitute a rare and clinically aggressive group of lymphomas, which has more than 20 histologic subtypes according to WHO 2008 classification. PTCL not otherwise specified (NOS), angioimmunoblastic T-cell lymphoma (AITL) and anaplastic large cell lymphoma (ALCL) are called nodal PTCL and account for approximately 60% of cases. The reported median survival ranges from 22 to 49 months and 5-year survival is less than 30%. High-dose chemotherapy followed by autologous stem cell transplantation (ASCT), has been proven to be beneficial both as a consolidation and in the relapse setting. However, the optimal conditioning regimen for ASCT in patients with T-cell lymphoma is not specified.

Methods: All adult T-cell lymphoma patients who underwent consolidative or salvage ASCT in our center between 2012 and 2021 have been identified and medical records were retrospectively reviewed. Standard CY (cyclophosphamide) - TBI (total body irradiation) regimen, which consisted of CY 120 mg/kg total dose and 12 Gy TBI in fractionated doses, was utilized for conditioning.

Results: A total of 36 patients, of whom 22 were male (61.1%), was identified. The median age at diagnosis was 51 (23-67). The histologic subtypes included: ALCL, ALK(-), n = 9 (25.0%); ALCL, ALK( + ), n = 3 (8.3%); AITCL, n = 9 (25.0%), PTCL, NOS, n = 10 (27.8%), hepatosplenic T-cell lymphoma, n = 2 (5.5%); NK/T cell lymphoma, n = 2 (5.5%), enteropathy-associated T-cell lymphoma, n = 1 (2.8%). All patients with ALCL, ALK( + ) were transplanted at either CR2 or for salvage of refractory disease. Most of the patients had advanced and high risk disease at diagnosis [Ann/Arbor stage 3-4 disease was present in 85.7% and international prognostic index (IPI) was intermediate or high in 80.0%]. Most of the patients underwent consolidative ASCT in CR1 (n = 4, 66.7%). The median follow-up was 10 months (0-106). The median time from diagnosis to ASCT was 7 months (4-45)Overall survival (OS) and progression-free survival (PFS) at 12 months after ASCT were 86.0% [95% confidence interval (CI): 74.2-97.8] and 45.0% (95% CI: 27.4-62.6), respectively. Non-relapse mortality (NRM) at 3, 6, 9 and 12 months after ASCT were 6.0% (95% CI: 0-13.8), 10.0% (95% CI: 0-39.4), 14.0% (95% CI: 2.2-15.8) and 14.0% (95% CI: 2.2-15.8), respectively. OS was better among patients transplanted at CR1, when compared to CR2 and primary refractory patients (p < 0.05). Four patients with aggressive and high risk disease could proceed to allogeneic transplantation, three of whom are still alive with a median follow-up of 14.5 months (7-77). Grade 3-4 adverse events were rare and neutrophil engraftment was achieved in all patients, except one with refractory disease after ASCT.

Kaplan-Meier plot comparing the OS for patients at CR1 versus CR2 and refractory disease (p < 0.05, log-rank test).

Conclusions: This study cohort included mainly nodal PTCLS (86%) with high risk and advanced disease profile. ASCT utilizing CY-TBI may provide an important benefit when used in consolidation and as a salvage without increasing toxicity and NRM. It may serve as a bridge for allogeneic transplantation in patients with aggressive and high risk disease. Consolidation at CR1 may provide a greater benefit.

Clinical Trial Registry: N/A

Disclosure: The authors have no conflict of interest to disclose.

P138 Comparison of git toxicity of the beam vs team conditioning before autologous transplantation in patients with lymphomas

B. Břízová ¹, A. Jungová¹, D. Lysák¹, Š. Jiří¹, V. Bergerová¹, P. Jindra¹

¹Faculty hospital Pilsen, Pilsen, Czech Republic

Background: High-dose chemotherapy followed by autologous transplantation (ASCT) is currently the standard of treatment for relapsed or refractory non-Hodgkin’s lymphomas (NHL) and Hodgkin’s lymphoma (HL). Despite the absence of direct data from prospective studies, BEAM, consist of carmustine (BCNU) in combination with etoposide, cytarabine and melphalan, is considered the common conditioning. The recent lack of BCNU has led to the search for alternative regimens. One of the most promising seems to be TEAM, in which BCNU is replaced by thiotepa. Thiotepa penetrates the CNS better, but there are concerns about increased, especially gastrointestinal, toxicity. At the same time, there is a lack of strong data demonstrating the comparable effectiveness of the two conditionings. Therefore, we decided to retrospectively compare the GIT toxicity of the TEAM regimen, which we started using in July 2018, with the previously used BEAM regimen.

Methods: Retrospective analysis of 142 consecutive patients with lymphomas autologous transplanted after the administration of the BEAM (2014-2018) or TEAM (2018-2021) conditioning at the Department of Hematology and Oncology.

Results: In the group of 142 patients with the age median of 58 years (21-74) there were 85 men (60 %). The BEAM regimen was administered to 82 patients (58 %) with the age median of 59 years (22-74), and TEAM to 60 patients (42 %) with the age median of 58 years (21-73) (p = 0.83). Of the diagnoses, the most common was DLBCL - 12 vs 27, HL - 21 vs 8, MCL - 16 vs 4, T-NHL - 12 vs 8, other lymphomas were represented sporadically, in total 16 vs 13 patients. There was no significant difference between the representation of diagnosis. In the first remission of the disease, we transplanted 43 vs 22 patients (p = 0.29), in the second and next remission 26 vs 22 patients (p = 0.74). 13 vs 16 patients (p = 0.22) were transplanted in the primary induction failure, it means progressive and chemorefractory disease. None or only very mild GIT toxicity (grade 0-I) was present in 53 resp. 28 patients (p = 0.32). Grade II GIT toxicity occurred in 11 resp. 12 patients (p = 0.49), grade III in 12 resp. 16 patients (p = 0.21) and finally the most severe grade IV with the need to move to the ICU in 1 resp. 3 patients (p = 0.32). In 5 resp. 1 patient it was not possible to determine GIT toxicity. Parenteral nutrition was used in 13 (16%) resp. 22 patients (37%) (p = 0.04). TRM during hospitalization was 0%, in 3 months 2% for both conditionings (p = 1.0).

Conclusions: Our data demonstrate that despite comparable objective GIT toxicity, the TEAM regimen has a significantly higher need for total parenteral nutrition. However, the overall TRM is comparatively low for both regimens.

Disclosure: Nothing to declare

P139 Clinical outcomes of reduced intensity tbf conditioning regimen in adult patients undergoing allogeneic stem cell transplantation for lymphoid malignancies

M. Peña Domingo ^1,2, A. Paviglianiti^1,2, L. Hurtado Ortega¹, S. Gonzalez Rodriguez¹, M. Kara², E. Domingo-Domenech^1,2, E. Gonzalez-Barca^1,2,3, A. Mussetti^1,2, A. Sureda Balari^1,2,3

¹Institut Català d’Oncologia-Hospitalet, Barcelona, Spain, ²Institut d’Investigacio Biomèdica de Bellvitge (IDIBELL), Barcelona, Spain, ³Bellvitge Health Sciences Campus, University of Barcelona, Barcelona, Spain

Background: Reduced intensity conditioning (RIC) is associated with lower non-relapse mortality (NRM) and significant disease control in alloHCT recipients. The optimal conditioning regimen in alloHCT for lymphoid malignancies remains unclear. To date, no data are available regarding the use of thiotepa, busulfan and fludarabine (TBF) in adult patients allografted for lymphoma.

Methods: Between February 2019 and August 2021, 30 patients diagnosed with lymphoid malignancies received a first alloHCT conditioned with a TBF-based RIC regimen at our institution. All consecutive patients were included in the study and data were collected retrospectively. Low-dose TBF RIC was defined as the use of 5 mg/kg of thiotepa (2.5 mg/Kg/day from days -6 and -5) while a high-dose TBF-RIC was considered as the administration of 10 mg/Kg of thiotepa (5 mg/Kg/day from days -6 and -5). Low-dose thiotepa was generally administered to patients with an HCT-specific Comorbidity Index >3 or considered frail. Two doses of 3.2 mg/Kg/day of busulfan and 150 mg/m² (50 mg/m² from days -4 to-2) of fludarabine were administered in all patients. Post-transplant cyclophosphamide-based graft-versus-host disease (GVHD) prophylaxis was used for both haploidentical and matched unrelated donors (>9/10 HLA compatibility).

Main outcome variables were overall survival (OS), progression-free survival (PFS), NRM, relapse incidence/progression of disease (RI/POD), cumulative incidence of acute (aGVHD) and chronic GVHD (cGVHD), and hematological recovery. Probabilities of OS and PFS were calculated using the Kaplan-Meier estimator method, and NRM, RI/POD, GVHD and hematological recovery as cumulative incidences.

Results: Baseline characteristics are summarized in Figure 1. Overall, the median age was 55 (range 33-70) years, and 15 patients (50%) received haploidentical donor grafts. Nineteen (63.3%) patients were in complete remission prior to alloHCT. Median follow-up among survivors was 517 (range 96-993) days. At 18-months, OS, PFS, NRM and RI/POD were 53% (95% confidence interval [CI], 33-70%), 40% (95% CI, 21-58%), 38% (95% CI, 19-57%) and 22% (95% CI, 4-40%), respectively. Of the 13 patients who died during follow up, causes of death were: 2 relapses and 11 transplant toxicities (9 = infections, 1=aGVHD, 1= endothelial complications). Eighty-two % of toxicity-related deaths were observed during the first 3 months from transplant. The cumulative incidence of neutrophil engraftment at day +30 was 87% (95% CI, 75-99%). The cumulative incidence of grade II-IV and grade III-IV aGVHD at day +100 was 20% (95% IC, 6-34%) and 7% (95% CI, 0-16%), respectively. The cumulative incidence of all grade cGVHD at +18 months was 16% (95% CI, 1-31%), with only 3 patients presenting with moderate-severe cGVHD. On univariate analysis, no prognostic factors were observed in terms of OS, PFS and NRM. However, having an interval between diagnosis and alloHCT >2 years was associated to decreased relapse risk (18 months NRM: 7% vs 52%, p = 0.01). Thiotepa dose was not significantly associated to clinical outcomes.

Conclusions: In our series, RIC TBF allows efficient disease control at the expense of increased incidence of severe early toxicities. Despite a higher NRM, OS was similar to other RIC regimens used for lymphoid malignancies. This regimen could be considered for fit patients with high-risk lymphoid diseases.

Disclosure: The authors declare no conflicts of interest

P140 Update on a pilot study: Flumeltbi peripheral blood HLA-haploidentical stem cell transplantation with post-transplant cyclophosphamide and bortezomib (Cy2Bor3)

S. Vuyyala ¹, E. Peres¹, K. Neme¹, N. Mikulandric¹, S. Wautelet¹, D. Pelland¹, N. Zagar¹, M.A. Trapp¹, S. Rohrer¹, E. Henne¹, S. Szymanski¹, J. Emole¹, M.H Abidi¹, S. Farhan¹

¹Henry Ford Health System, Detroit, United States

Background: Bortezomib (Bor) can inhibit the proliferation of dendritic cells (DCs) and block the expression of co-receptors CD80, CD86 and secretion of cytokines IL-12 and TNF-α and hence the ability of DCs to activate T cells. We started a pilot study incorporating the addition of bortezomib to post-transplant cyclophosphamide (PTCY) in the setting of peripheral blood (PB) HLA-haploidentical stem cell transplantation (Haplo-SCT).

Methods: This is a single center open label pilot study. Eligible patients received Fludarabine Melphalan TBI 200 cGy as conditioning followed by haplo-SCT and PTCY. Bor was administered at 1.3mg/m2 on day+1, 4 and 7. Tacrolimus and MMF were started at day+5

Results: Seven patients were enrolled so far, five males and 2 females. Median age was 58 years (26-60). Donors were 3 brothers, 3 sons and 1 mother. Disease risk index was high in 3, intermediate in 3 and low in 1. Three patients had AML, two had ALL and MM, one had ALL and one had CML. CMV recipient status was negative in one and positive in 6. Median HCT-CI was 3(1-4). Median CD34 and CD3 infused were 4.13 x10^6 and 1.7x10^8/ kg recipient respectively, all were cryopreserved except 2. Four patients had CRS before Cy infusion with ASTCT grade of 1. Six patients had grade 3 hypokalemia around day+ 4-5. Five patients had grade 3 mucositis and 2 had grade 1. Four patients had neutropenic fever and one patient had engraftment fever. Median neutrophils and platelets engraftment were 16 and 26 days respectively. Chimerism post SCT was > =99% donor at day 30 for all patients. Six patients are off tacrolimus with median time to be off it was 187.5 days. Five pts had aGVHD with maximum grade of I in 3 patients, II in one patient and III in one patient at a median 50days post SCT. None developed early hematuria, four had late hematuria with highest grade of 4. Two patients were positive for BK virus. One patient had reactivation of CMV, 2 had EBV and one had adenovirus, all resolved. Three pts had HHV6 that resolved. Of the 5 patients who were evaluable, one developed moderate chronic GVHD. So far the median time to follow up is 455 days (70-1239) with relapse and subsequently death in one patient who had high risk AML with 3 different inductions prior to SCT. . At 1 year for 4 evaluable patients IgG were >400 mg/dl and CD4 > 350 cells/ul.

Survival Probability

Conclusions: Cy2Bor3 post PB Haplo-SCT was well tolerated. Although small number of patients and limited but encouraging results so far. The trial is ongoing.

Clinical Trial Registry: ClinicalTrials.gov ID: NCT03850366.

Disclosure: Nothing to declare

P141 Allogeneic hematopoietic cell transplantation for hodgkin lymphoma post anti-pd1 inhibitors: Incorporation of post-transplant cyclophosphamide in the conditioning regimen

E. Gavriilaki ¹, Z. Bousiou¹, P. Dolgyras¹, I. Batsis¹, D. Mallouri¹, M. Iskas¹, C. Damplia¹, S. Papaemmanouil¹, A. Syrigou¹, T. Asteri¹, T. Geroukis¹, G. Arsos², N. Stavroyianni¹, A. Anagnostopoulos¹, I. Sakellari¹

¹G Papanicolaou Hospital, Thessaloniki, Greece, ²Aristotle University of Thessaloniki, Thessaloniki, Greece

Background: Although allogeneic hematopoietic cell transplantation (alloHCT) remains the only curative option for Hodgkin lymphoma (HL), efficacy and safety of anti-PD1 (Programmed cell death protein 1) inhibitors have revolutionized HL treatment. Importantly, complications of alloHCT post anti-PD1 inhibitors have raised questions regarding its feasibility. Therefore, we investigated efficacy and safety of alloHCT post anti-PD1 inhibitors compared to a historical group of alloHCT before the introduction of anti-PD1.

Methods: We retrospectively studied patients that underwent alloHCT for HL at our JACIE-accredited center over the last decade (2010-2020). We divided them into two groups according to the treatment period: anti-PD1 and historical control group. We analyzed pre-transplant (age, disease status, previous lines), transplant (donor, graft, conditioning), and post-transplant (graft-versus-host-disease/GVHD, treatment-related mortality/TRM, relapse, and overall survival/OS) characteristics.

Results: In total, 21 patients received alloHCT for HL. Among them, 3 patients from the historical control group received anti-PD1 due to relapse post alloHCT and were excluded from further analysis. We studied 18 patients (7 in the anti-PD1 period and 11 controls), with median age 32.5 years, suffering from classical HL (12:nodular sclerosis, 3:mixed cellularity, 1:lymphopenic). All patients had undergone autologous HCT at a median of 4 years earlier, 14 with primary refractory chemo-sensitive disease and 4 with chemo-resistant disease. Among them, 8 presented with a positive PET/CT scan after autologous and 10 with relapse at a median of 13.4 (range 8-19) months.

Brentuximab vedotin (BV) had been administered post autologous HCT only in patients of the anti-PD1 group; with 2 achieving partial remission, 1 complete metabolic remission (CMR) and 1 progressive disease. Upon progression, patients of the anti-PD1 group received nivolumab for 18 (5-32) cycles. The patient that had achieved CMR with BV, received a combination of nivolumab-BV. Historical controls proceeded to alloHCT following chemotherapy upon progression.

Both groups received alloHCT at a similar disease, 11 patients had active disease at alloHCT, while 7 CR (p = 0.205). Donors were mainly unrelated (12/18, p = 0.421). Reduced toxicity conditioning regimen was administered in both groups (Thiotepa-Fludarabine-Cyclophosphamide with Antithymocyte Globulin 5mg/kg in unrelated donors). Post-transplant cyclophosphamide (Baltimore’s protocol) was also given in the 4 more recent patients (p = 0.011). All grafts were PBSC with a median of 5.45x10⁶ cells/kg (p = 0.263).

With a median follow-up of 16.3 (1.1-94.7) months, cumulative incidence (CI) of acute and chronic GVHD were similar between groups. Furthermore, 2-year TRM CI did not differ (28.6% in anti-PD1 versus 27.3% in historical controls, p = 0.951). Interestingly, the 4 patients that received post-transplant cyclophosphamide presented no TRM. Only one patient relapsed post alloHCT in the historical control group, while no patient from the anti-PD1. Therefore, 2-year OS was similar between groups (66.7% in the anti-PD1 versus 60.0% in controls, p = 0.982). OS was associated only with type of donor, significantly higher in unrelated donors (p = 0.044).

Conclusions: Our single-center experience suggests comparable outcomes of alloHCT post anti-PD1 to historical controls. Adoption of novel modalities, such as post-transplant cyclophosphamide, have led to encouraging results. Further studies are needed to determine the optimal tailored approach for chemo-refractory HL.

Clinical Trial Registry: ΝΑ

Disclosure: Nothing to declare

P143 Clofarabine followed by reduced intensity conditioning as a sequential concept prior to allogeneic HSCT in three patients with advanced staged cutaneous t cell lymphoma

E. Stauffer ¹, A. Fraccaroli¹, H. Drolle¹, M. Flaig¹, L. Heinzerling¹, M. von Bergwelt¹, S. Theurich¹, J. Tischer¹

¹University Hospital Munich, Munich, Germany

Background: The prognosis of patients with refractory, advanced stage primary cutaneous T cell lymphoma remains poor particularly in patients with transformed mycosis fungoides (MF). In these cases, conventional cytotoxic regimens induce only short-lived responses and lymphoma relapses occur even more aggressively thereafter. Allogeneic hematopoietic stem cell transplantation (allo-HSCT) provides a potentially curative treatment option for clinically suitable patients. However, the optimal approach to these patients including bridging treatment to conditioning and transplant remains undefined. Here, we report on three consecutive patients with high-risk MF that received tumor reduction and reduced intensity condition (RIC) in a sequential concept prior to allo-HSCT.

Methods: Three patients with advanced stage MF including one large-cell transformation were consecutively treated at our transplant center. All patients received multiple skin directed and systemic treatments including PUVA (n = 2), retinoids (n = 3), IFN-alpha (n = 3) and chemotherapy (n = 2) and brentuximab (n = 3) prior to allo-HSCT. All three patients were in PR prior to transplantation.

To reduce tumor burden, all patients received clofarabine shortly before RIC in terms of a sequential therapy concept. Conditioning consisted of fludarabine, cyclophosphamide and melphalan. Bone marrow (n = 2) and peripheral blood stem cells (n = 1) were used as graft source. Donor type was HLA-haploidentical in two and HLA-matched unrelated in one patient. In all cases, cyclosporine or tacrolimus and mycophenolate mofetil as well as post-transplantation cyclophosphamide (PTCY) were used for graft versus-host disease (GVHD) prophylaxis.

Results: Clofarabine induced rapid treatment responses in all patients and subsequent RIC could be performed without significantly increased toxicities. At day +30, lymphoma staging demonstrated profound remissions (PR in 2 cases) while complete donor chimerism was detectably in the peripheral blood and bone marrow in all patients. All patients engrafted, no primary graft rejection was seen. Acute GvHD > = Grade 2 was observed in 2 patients responding to the application of steroids in both. However, all three patients relapsed after a median time of 2.6 months but responded to subsequent treatments.

Conclusions: Using clofarabine as a salvage treatment prior to RIC in a sequential allo-HSCT concept may be a considerable strategy for patients with advanced cutaneous T cell lymphoma. However, as all patients relapsed within the first year after transplantation, further investigation is needed to determine the optimal post-transplant approach including early immunomodulatory maintenance treatments.

Disclosure: Nothing to declare

P144 Team versus beam conditioning regimen for autologous stem cell transplantation in malignant lymphomas. Retrospective comparison of toxicity

J. Stevkova ¹, D. Belada¹, M. Lanska¹, B. Visek¹, A. Zavrelova¹, P. Zak¹, J. Radocha¹

¹University Hospital Hradec Kralove, Czech Republic and Charles University, Faculty of Medicine in Hradec Kralove, Hradec Kralove, Czech Republic

Background: Autologous stem cell transplantation (auto-SCT) is an important therapeutic approach for malignant lymphoma. Conditioning chemotherapy with alkylating agents such as BEAM and TEAM is the most commonly used in this indication. Our study compares the toxicity profiles of the BEAM and TEAM conditioning.

Methods: 48 patients (20 women, 28 men), mean age 53.5 years, who underwent auto-SCT for malignant lymphoma were retrospectively analyzed. BEAM (carmustine, etoposide, cytarabine, melphalan) was used in 24 patients between November 2015 and April 2019, TEAM (thiotepa, etoposide, cytarabine, melphalan) was used in 24 patients between June 2018 and September 2021.

Results: The indications for auto-SCT included: 16 patients with diffuse large B-cell lymphomas, 9 with mantle cell lymphomas, 10 with T-cell lymphomas, 4 with follicular lymphomas, and 9 with Hodgkin lymphoma. Grade 4 neutropenia was present in all patients in both groups. The median time to neutrophil engraftment for the TEAM and BEAM arm was 10.5 (9-15) days and 10 (5-15) days, respectively (p = 0.322). Grade 4 thrombocytopenia was present in all patients in both groups. The median time to platelet engraftment for TEAM and BEAM was 13 days (9-22) and 11 days (9-16), respectively (p = 0.341). Mucositis grade 4 was observed in 22/24 (91.7%) of patients receiving TEAM compared to 20/24 (83.3%) of patients receiving BEAM (p = 0.383). Mucositis grade 2-3 was observed in the 2/24 (8.3%) in TEAM cohort compared to 4/24 (12.5%) of patients in the BEAM cohort (p = 0.383). Febrile neutropenia developed in 15/24 (62.5%) of patients receiving TEAM compared to 12/24 (50%) of patients receiving BEAM (p = 0.383). Sepsis developed in 7/24 (29.1%) of patients after TEAM compared to 5/24 (20.8%) of patients after BEAM (p = 0.505). The infectious complications were as follows: 1/24 (4.2%) patient had colitis and 1/24 (4.2%) had pneumonia after TEAM ; 1/24 (4.2%) patient had urinary tract infection and 1/24 (4.2%) had soft tissue infection after BEAM. Transplant-related mortality on day 100 was 2/24 (8.3%) of patients receiving TEAM compared to 3/24 (12.5%) of patients receiving BEAM (p = 0.637). The reason for death was sepsis in all cases.

Conclusions: Our retrospective analysis documents a similar result regarding engraftment, toxicity profile, and transplant-related mortality between BEAM and TEAM conditioning prior to auto-SCT.

Disclosure: Nothing to declare.

P145 Haplo-identical hematopoietic stem cell transplantation using a combination of g-csf mobilized bone marrow and peripheral blood cells in high-risk hematological malignancies

D. Ait Ouali¹, M. Benakli ¹, F. Mehdid¹, M. Baazizi¹, N. Rahmoune¹, S. Akhrouf¹, H. Bouarab¹, S. Zerkout¹, F. Louar¹, R. Benouattas¹, F. Harieche¹, R.-M. Hamladji¹, R. Ahmed Nacer¹

¹Pierre and Marie Curie Center, Algiers, Algeria

Background: Hematopoietic stem cell transplantation (HSCT) from an haplo-identical donor has been demonstrated to provide the best chances of a cure for many children in need of an allograft but who lack a sibling donor. We propose a retrospective study of 36 pts who benefited the “Beijing protocol” using myeloablative conditioning regimen with G-CSF mobilized/primed grafts

Methods: From May 2013 to January 2017, 36 haplo-identical HSCT were used in 36 pts with hematological malignancies (7 AML, 20 ALL, 5 CML, 2 AL biphenotypic, 2 MDS). Median age was 24 years (5-55) and sex-ratio (M/F):3. The diagnosis transplant delay was 29 months (6-138). At the time of the transplant, 7 pts were in first complete remission (CR), 20 pts in second CR and 4 pts in active disease. The donors used were parents (21), siblings (14) or offspring (1); with median age: 41 years (13-65). The degree of compatibility (HLA A, B and DR) was 3/6 (24 cases), 4/6 (10 cases) and 5/6 (2 cases). CMV status between donor/recipient was high risk in 36 cases. The ABO incompatibility is major in 8 cases, minor in 10 cases. The conditioning regimen used associated Busilvex 9.6 mg/kg, Aracytine 8 g/m², Cyclophosphamide 3.6 g/m² for 36 pts. The GVHD prophylaxis included the combination Ciclosporin Methotrexate, Mycophenolate mofetil and Thymoglobulin (10 mg/kg) and received an G-CSF mobilized/primed grafts: bone marrow and Peripheral blood stem cells. Median dose infused CD34 + cells: 4,42 10⁶/kg (1,35-19,9), nuclear cells: 6,45 x 10⁷/kg (0,59-21,53). At November 2021, the minimal follow-up delay was 58 months and maximal 102 months.

Results: Aplasia was observed in all pts with median duration of 15 days (13-34). The median day of neutrophils engraftment was 17 days (11-27). One pt presented transplant associated micro-angiopathy (MAT). Two pts presented an early rejection (5%). Acute GVHD grade II-IV occurred in 14 pts (43%) on average at day 42 (16-100). Chronic GVHD was seen in 9 pts (36%) with extensive form in 4 pts on average at day 210 (150-240). Sixteen pts (50%) showed CMV reactivation on average at day 45 (28-149). Seven cases of haemorrhagic cystitis (21%) (one grade 4) are observed . Ten pts (27%) relapsed, of which 4 pts were blast crisis at the time of the transplant. After follow-up of 42 months (58-102), 17 pts (47%) are alive and 19 pts (53%) died within 9 pts (25%) from TRM (acute GVHD:02, severe infection:4, haemorrhagic cystitis:1, TRALI syndrome:1, early rejection :1) And 10 from relapse (27%) and the overall survival (OS) and disease free survival (DFS) are 47% and 44% respectively.

Conclusions: Our study shows that haplo-identical HSCT using the Beijing is a well-validated approach and feasible in patients with advanced malignancies, associated with prompt engraftment, acceptable rates of GVHD, TRM and survivals.

Disclosure: Nothing to declare

P146 Single centre experience of efficacy and toxicity of reduced-dose melphalan conditioning (140 mg/m2 or 110 mg/m2) in autologous stem cell transplantation for multiple myeloma

E. Troy-Barnes¹, D. Melotti ¹, M. Camilleri¹, J. Horder¹, F. Newrick¹, J. Marfil¹, L. Lee², A.S. Mahmood³, B. Wisniowski³, X. Papanikolaou¹, A. Wechalekar³, J. Sive¹, R. Popat⁴, K. Yong², N. Rabin¹, C. Kyriakou¹

¹University College London Hospitals NHS Foundation Trust, London, United Kingdom, ²University College London Cancer Institute, London, United Kingdom, ³University College London Centre for Amyloidosis & Acute Phase Proteins, London, United Kingdom, ⁴National Institute for Health Research University College London Hospitals Clinical Research Facility, London, United Kingdom

Background: Autologous stem cell transplantation (ASCT) is a key component of treatment for multiple myeloma (MM) following induction therapy. The efficacy and safety of high-dose melphalan 200 mg/m2 conditioning is well-established in fit, non-elderly (<65-70 years) patients. Although historical data has demonstrated increased toxicity with melphalan 200 mg/m2 in patients with renal failure, there is limited up-to-date literature demonstrating the safety and efficacy of low dose conditioning (140 mg/m2 or 110 mg/m2) in renal failure and other subgroups with high transplant comorbidity index.

Methods: A retrospective analysis was performed on 81 MM patients who underwent first ASCT with low-dose conditioning following induction therapy at a single centre between 2006-2020. The primary outcome was ASCT-related toxicity, and secondary outcomes were overall survival (OS); progression free survival (PFS), depth of response and renal function. Univariate and multivariate analysis was performed for age, renal function, co-morbidities, performance status, ISS/R-ISS, high-risk cytogenetics and depth of response prior to ASCT.

Results: Of 81 patients, 31 (38%) were female, 34 (42%) were >65 years (mean age 61.5, IQR 56-68). 76 (94%) patients had MM (34 (45%) light chain and 42 (55%) had IgG or IgA MM); the remainder (6%) had other conditions (AL amyloidosis, monoclonal gammopathy of renal significance, multifocal plasmacytoma). ISS was ≥2 in 46 (57%) at diagnosis; 18 (22%) had high-risk cytogenetics.

Prior to ASCT, mean GFR was 45 mL/min, IQR 61-27; mean left ventricular ejection fraction was 61%, IQR 66-55; 5 (6%) had poor performance status (Karnofsky < 80). Induction therapy included a PI in 66 (82%) and IMID in 45 (56%).

Mean duration of admission was 24.7 days, IQR 18-25; mean time to neutrophil engraftment was 11.4 days, IQR 11-12. 4 (5%) patients had worsening of renal function during their ASCT admission meeting definition of acute kidney injury by RIFLE criteria; mean creatinine clearance at 100 days was 69 mL/min, IQR 89-57. Mortality at 100 days was 1/81 (1%). Disease status as per IMWG criteria prior to ASCT was Very Good Partial Response (VGPR) or better in 57 (70%), Partial Response (PR) in 20 (25%) patients. Staging data at 3 month post-ASCT was available for 71 patients, of which 52 (73%) were in VGPR or CR, and 15 (21%) were in PR.

Mean follow-up period was 30 months, IQR 12-42. Median OS was 6.2 years. Median PFS was 2.3 years, with a significantly better median PFS (2.8 years vs 1.6 years) for patients <70 years old vs patients aged >70 (p-value 0.045); at latest review mean GFR was 67, IQR 89-50.

Early relapse/progression within <18 months was observed in 17/81 (21%) patients.

Conclusions: Our data suggest that autograft with low-dose melphalan conditioning is a feasible, safe and effective therapeutic option in patients deemed unfit for high-dose melphalan. This analysis provides real world data to support clinical decision making in MM that will be benefited from high-dose alkylating agent. The renal status did not significantly impact on toxicity or efficacy outcomes. In this cohort older patients had significantly inferior PFS.

Disclosure: Nothing to declare.

P147 Long-term follow-up of auto-hct with tbi-based conditioning regimen in patients with peripheral t-cell lymphomas: A single-center analysis

T. Czerw ^1,2, A. Smagur^1,2, A. Chwieduk¹, M. Sadus-Wojciechowska¹, J. Najda¹, W. Mendrek¹, M. Sobczyk-Kruszelnicka¹, A. Frankiewicz¹, M. Ociepa-Wasilkowska¹, M. Dzierzak-Mietla¹, I. Mitrus¹, M. Krawczyk-Kulis¹, J. Holowiecki¹, S. Giebel¹

¹Maria Sklodowska-Curie National Research Institute of Oncology, Gliwice Branch, Gliwice, Poland, ²These authors contributed equally to this work, Gliwice, Poland

Background: Peripheral T-cell lymphomas (PTCLs) are relatively rare and heterogeneous group of lymphoproliferative disorders accounting for 10%–15% of all non-Hodgkin lymphomas. High-dose consolidation therapy with autologous stem cell support (auto-HCT) is considered beneficial for transplant-eligible patients with newly diagnosed and relapsed disease. The evidence is based on retrospective analyses which included heterogeneity of mainly chemotherapy-based conditioning regimens. Achieving complete remission (CR) before auto-HCT is one of the strongest predictors of the outcome. We report on a retrospective, single institution analysis of auto-HCT with total body irradiation (TBI)-based conditioning regimen in patients with PTCLs in CR1.

Methods: Patient selection included all 23 consecutive adult patients with PTCLs in CR1 undergoing auto-HCT between 2010-2019 in the Department of Bone Marrow Transplantation and Onco-Hematology, National Research Institute of Oncology, Gliwice Branch, Poland. Eighteen of them were conditioned with 12Gy TBI (given in 3 fractions of 4Gy on 3 consecutive days) combined with 120mg/kg cyclophosphamide. Five patients (aged above 60 y.o. at transplantation) were conditioned with 8Gy TBI given in 2 fractions of 4Gy combined with bendamustine 160-200mg/m² given on 2 consecutive days. The group characteristics were as follows: median age at transplantation 52 years (range, 22-68); PTCL subtype (PTCL-not otherwise specified-8; angioimmunoblastic T-cell lymphoma-4; anaplastic large cell lymphoma ALK(-)-4, ALK( + )-6, enteropathy associated T-cell lymphoma -1); Ann Arbor stage at diagnosis (II-5; III-12; IV-6); median number of pre-transplant chemotherapy lines: 1 (1-2).

Results: All transplants were performed with use of peripheral blood as a source of stem cells. The median number of transplanted CD34 + cells was 8.6 (2.0-24.8) x 10^6 /kg b.w. of the recipient. All patients engrafted and the median time to neutrophil recovery was 10 days (9-13). With the median follow-up of 92 months (26-134) only 1 patient experienced relapse. Six patients died of other causes: one patient died 5 months after transplantation whereas the remaining 5 patients died at a time longer than 1 year after auto-HCT (median 64 months (17-91). The probability of overall survival at 5 and 8 years after auto-HCT was 87% (+/− 7%) and 68% (+/− 11%), respectively. The probability of progression-free survival at 5 and 8 years after auto-HCT was 82% (+/− 8%) and 63% (+/− 12%), respectively.

Conclusions: Our long-term follow-up analysis shows that TBI seems to be an effective part of conditioning regimen before auto-HCT for PTCLs allowing potentially to achieve good disease control.

Disclosure: Nothing to declare

P148 Reduced intensity conditioning regimen with treosulfan for second allogeneic stem cell transplantation in patients with acute myeloid leukemia or myelodysplastic syndrome. A single-centre experience

J. Stevkova ¹, B. Visek¹, M. Lanska¹, A. Zavrelova¹, K. Doskocilova¹, J. Radocha¹, P. Zak¹

¹University Hospital Hradec Kralove, Czech Republic and Charles University, Faculty of Medicine in Hradec Kralove, Hradec Kralove, Czech Republic

Background: Second allogeneic stem cell transplantation (SCT2) is associated with a high risk of peri-transplant and post-transplant mortality. Reduced intensity conditioning regimens (RIC), usually based on busulfan and fludarabine (Bu-Flu), are usually chosen in these cases. The aim of our retrospective study was to evaluate the effect and toxicity of a conditioning regimen containing treosulfan (Treo) instead of busulfan.

Methods: In our retrospective analysis, 15 patients transplanted at our center between June 2012 and February 2019 were included (9 women, 6 men, mean age 50 years). There were 12 patients with acute myeloid leukemia (AML) (including 7 cases of secondary AML), 2 patients with myelodysplastic syndrome (MDS), and 1 patient with chronic myelomonocytic leukemia (CMML). Complete remission was achieved in 3/15 (20%) of the patients before aloSCT; In 9/15 (60%) of patients, sequential chemotherapy was used before SCT2 due to disease activity. All patients received peripheral stem cells from HLA-matched unrelated donors; RIC Thymoglobulin-Treo-Flu was used as a conditioning regimen. Graft versus host disease prophylaxis consisted of tacrolimus combined with mycophenolate mofetil. The HLA match was 10/10 in 13/15 (86%) of the patients and 9/10 in 2/15 (14%) of the patients. Fourteen patients had a comorbidity index (HCT-CI) 0; one patient had a HCT-CI 3.

Results: Neutrophil engraftment was achieved in 13/15 (86%) of patients, in platelets in all patients. The median time to neutrophil and platelet engraftment was 14 (11-21) days and 11 (10-20), respectively. Donor chimerism 99-100% on day +30 was achieved in all patients; on day +100 donor chimerism 100% was achieved in 13/15 (86%) of patients (2 patients had early relapse). Acute GvHD developed in 6/15 (40%) of patients (grade ≥ 3-4 in 13%) and extensive chronic GvHD (grade 4) in 1/15 (6%) of patients. At the median follow-up of 63 months, 10/15 (66,6%) of the patients have died: in 7 cases due to relapse, in 2 cases due to severe posttransplant lymphoproliferative disease, 1 patient died from acute GvHD. GRFS (GvHD-free, relapse-free survival) at 1 year was 33%. The median overall survival was 13.6 months.

Conclusions: Our data indicate a favorable safety profile and high efficacy of Treo-containing RIC in a selected group of patients undergoing SCT2. The advantages of this regimen are low peri-transplant and early post-transplant mortality and the ability to induce 100% chimerism early after transplantation.

Disclosure: Nothing to declare.

P149 Low dose anti-thymocyte globulin with posttransplant cyclophosphamide haploidentical stem cell transplantation for high risk hematologic malignancies – umc ljubljana, slovenia experience

P. Novak ¹, M. Sever¹, K. Šlajpah¹, N. Gredelj¹

¹UMC Ljubljana, Ljubljana, Slovenia

Background: Haploidentical stem cell transplantation (haploSCT) rate is increasing worldwide, mostly due to its clinical efficiency and accessibility. Bone marrow used to be the preferred stem cell source in the haploSCT because it is less immunogenic and causes less graft versus host disease (GvHD) than peripheral blood stem cells (PBSC). To prevent relapse in high risk hematologic malignancies, at UMC Ljubljana, Slovenia we decided to use PBSC with low dose anti-thymocyte globulin (ATG) in combination with posttransplant cyclophosphamide (PTCy).

Methods: We analyzed six high risk leukemia patients who underwent haploSCT with low dose ATG (Grafalon) 5 mg/kg on day -3, -2, -1 (15 mg/kg total dose) and thiotepa -6, -5 (total dose 10 mg/kg), busulfan -4, -3, -2 (total dose 9,6 mg/kg), fludarabine -4, -3, -2 (total dose 150 mg/m²), PTCy 50 mg/kg on day +3 and +5 conditioning regimen with cyclosporine and mycophenolate mofetil for GvHD prophylaxis since May 2020. At the time of haploSCT the median patient age was 64 years (26-67). 4/6 (67%) had secondary AML with MDS related changes, two of them resistant to primary induction but in CR after second induction, one (17%) had primary resistant AML, one (17%) patient had early T-ALL. 5/6 (83%) patients were in CR1 before the haploSCT.

Results: All patients received a myeloablative TBF protocol with ATG and PTCy and all received PBSC at median dose of 4 x10⁶/kg CD34 + cells. Median time to neutrophil engraftment was 15 days. One patient died due to intracranial bleeding before engraftment. We did not observe acute or chronic GvHD. Two patients had CMV reactivation after letermovir prophylaxis discontinuation. All patients remain in remission. The mean survival time is 15 months (95% CI 9,6-20,3) with OS 83%.

Conclusions: For patients with high risk leukemia and no matched sibling or unrelated donor haploSCT with peripheral blood stem cells and low dose ATG combined with PTCy is an encouraging treatment option resulting in low GvHD and disease relapse rate.

Disclosure: Nothing to declare

P150 Determination of transplant conditioning intensity: A real-life data

İ. Yavaşoğlu ¹, A.H. Eroğlu Küçükdiler¹, A.Z. Bolaman¹

¹Aydin Adnan Menderes University, Aydin, Turkey

Background: The pre-transplantation conditioning regimen in allogeneic hematopoietic stem cell transplantation (Allo-SCT) is important in early morbidity, non-relapse mortality, and long-term disease control. It is difficult to standardize the conditioning regimens in Allo-SCT. In this sense, the concept of ‘transplant conditioning intensity (TCI) score’, which has been developed recently, has become important [1].

Methods: Eighty-three patients with various diagnoses who underwent allo-SCT at the Hematology Department of Aydın Adnan Menderes University between the years of 2014-2020 were included in the study, which was designed to be single-center, retrospective. Regarding donor compatibility, we have included all allogeneic transplantation procedures, performed as related or unrelated 9-10/10, as well as haploidentical transplantations. Myeloablative, reduced intensity regimen (RIC), and non-myeloablative conditioning regimens were used in accordance with the diagnoses. Of the patients; the rates of myeloid malignancy, lymphoid malignancy, and aplastic anemia were 65%, 30%, and 5%, respectively.

Results: The distribution of conditioning regimens according to the TCI score group was as follows: 13 patients had a low, 44 patients an intermediate, and 30 patients a high TCI score. The mean age was 42 ± 3 in the low group, 48 ± 2 in the intermediate group, and 36 ± 2 in the high group, respectively. No statistical difference was found with Kaplan Meier between the three groups (Fig. 1). Low TCI had a mean survival of 42.1 ± 10.5 months, intermediate 61.3 ± 13.7, high 43.2 ± 8.9 months.

Conclusions: Although it is not statistically significant, the longer life expectancy may increase the interest in the RIC, although the mean age is higher in those with the intermediate TCI score. It is important to increase the use of TCI in practice.

Disclosure: Nothing to declare

Experimental Transplantation and Gene Therapy

P151 Wolman cd34+ cells transduced with cd11blipa lentivirus drives lysosomal acid lipase enzyme expression

A. Guha ¹, J. Potter¹, R. Wynn¹, B. Bigger²

¹Manchester Foundation Trust, Manchester, United Kingdom, ²University of Manchester, Manchester, United Kingdom

Background: Wolman disease (WD) is a lysosomal storage disorder (LSD) that is caused by complete deficiency of lysosomal acid lipase (LAL). There is a pathogenic variant in the LIPA gene which maps to chromosome 10q23. It is an infantile onset lethal disease characterised by lysosomal accumulation of cholesteryl esters (CE) and triglycerides (TG) predominantly in hepatocytes and macrophages.

Symptoms and signs develop due to large accumulation of CE and TG in the lysosomes of Kupffer cells and hepatocytes as well as in macrophages throughout the viscera. Untreated, infants do not survive beyond the first year of life.

Treatment includes enzyme replacement therapy (ERT) and haematopoietic stem cell transplant (HCT). The long-term use of ERT is limited by ongoing gastrointestinal symptoms, neutralising

anti-drug antibodies (ADA), the need for life long central venous access and the financial implications of treatment. HCT has a high transplant related morbidity and GvHD mortality. An engraftment defect has been reported with the majority of patients having a mixed chimerism.

Autologous ex vivo haematopoietic stem cell gene therapy (HSC-GT) is an emerging treatment in LSD. HSC-GT eliminates the risk of GvHD and reduces the need for immunosuppression. By delivering a transgene that includes a promotor, there is the capacity to drive overexpression and achieve supra-physiological levels of enzyme.

Methods: Wolman CD34 + cells were transduced with a CD11bLIPA lentivirus at a multiplicity of infection (MOI) of 25,50 and 100 with and without transduction enhancers (TE). Transduction efficiency, vector copy number and enzyme levels were evaluated. Additionally Wolman CD34 + and unaffected CD34 + were compared, investigating colony forming unit (CFU) total, distribution and LAL enzyme level activity.

Results: As expected Wolman CD34 + cells had minimal LAL enzyme activity. After transduction of Wolman CD34 + cells with CD11bLIPA LV, the deficient CD34 + cells were able to achieve significantly higher levels of enzyme activity to that of unaffected controls (Figure 1).

Transduction without TEs achieved a vector copy number (VCN) between 1.5 and 3. With higher VCN (achieved with TEs) the enzyme activity is significantly higher than unaffected CD34 + ; ‘supraphysiological’, however with MOI 100 there was reduction in overall colonies. There was no significant difference in the CFU distribution between Wolman and Unaffected. The transduction efficiency >90% in all CFU’s.

Figure 1:

Conclusions: We have demonstrated ex vivo transduction of human Wolman CD34 + stem cells drives LAL activity and that the optimal MOI was reduced by transduction enhancers without associated toxicity.

To further demonstrate efficacy and to assess toxicity and safety, we aim to show direct macrophage correction and reduction of oxysterols in normal and Wolman macrophages derived from peripheral blood and transduce normal or Wolman CD34 + cells into NSG mice for biodistribution and toxicology outcomes.

Disclosure: Nothing to declare

P152 Eltrombopag in fanconi anemia patients infused with very low numbers of gene corrected cells

J. Iriondo ¹, J. Zubicaray¹, P. Rio², L. Ugalde², E. Sebastian¹, S. Navarro², N. Garcia de Andoin³, A. Catalá⁴, M. Ivanova¹, J. Surralles⁵, M. Garcia-Abos³, J. Gonzalez de Pablo¹, J.J. Uriz³, J. Schwartz⁶, J. Soulier⁷, J. Bueren², J. Sevilla¹

¹Fundación Biomédica Hospital Niño Jesús, Madrid, Spain, ²CIEMAT/CIBERER/Fund. Jiménez Díaz, Madrid, Spain, ³Hospital Universitario Donostia, Donostia/San Sebastian, Spain, ⁴Hospital Sant Joan de Déu, Barcelona, Spain, ⁵IIB Sant Pau - Fundació Institut de Recerca Hospital de Sant Pau, Barcelona, Spain, ⁶Rocket Pharmaceuticals Inc., New York, United States, ⁷Université de Paris, Institut de Recherche Saint-Louis, Paris, France

Background: Allogeneic HSCT currently constitutes the only available therapy which can revert the bone marrow failure (BMF) characteristic of Fanconi Anemia (FA). In the absence of a compatible donor, androgens may be used in FA patients, although other agents are being tested in clinical trials. In this respect, there are two ongoing clinical studies evaluating the safety and efficacy of eltrombopag in FA patients. From preclinical models, it has been postulated that this drug promotes DNA repair in FA HSCs through the non-homologous end joining repair mechanism, improving genome integrity, cell survival, and HSC functionality. In addition to these approaches, gene therapy has conferred preliminary evidence of safety and efficacy in phase I and II studies, in patients receiving autologous gene corrected CD34 + cells exceeding threshold levels and during early stages of BMF.

The aim of this study is to analyze the safety and efficacy of eltrombopag in FA patients who had been infused in the phase I clinical trial with very low numbers of corrected CD34 + cells.

Methods: We report the hematologic and molecular course of four patients initially included in the gene therapy clinical trial FANCOLEN-1 (NCT03157804) who had an evolution of BMF. Two of them were treated with eltrombopag under a “compassionate use program” and the other two were included in the clinical trial FANCREV (EUDRACT 2020-002703-18). During follow-up, peripheral blood counts (PBC), BM studies including cytogenetics, and vector copy number (VCN) analyses were carried out to assess the efficacy and safety of eltrombopag in these patients.

Results: Patients received treatment with eltrombopag for a duration between 3 and 12 months. No medication-related adverse events, including clonal evolution, were observed during their follow-up. One patient showed a modest increase in PBC counts after 3 months of treatment and remained free of transfusion requirements. In the remaining cases no sustained hematologic response was observed. In BM aspirations performed during the course of therapy, a decreasing trend in CD34 + cell numbers was observed. Strikingly, the analysis of VCNs in BM showed more marked increases in the proportion of gene corrected cells as compared to analyses performed prior to eltrompopag treatment.

Conclusions:

• 1. No relevant adverse effects, including clonal events, were observed during eltrombopag treatment in FA patients previously infused with very low numbers of gene corrected CD34 + cells.

• 2. The evolution of PBC counts during the treatment period does not allow us to conclude that eltrombopag mediated clinically relevant hematologic responses.

• 3. The proportion of gene-corrected cells in BM increased in all patients.

Although current data does not enable detection of a sustained eltrombopag-mediated benefit in the hematopoiesis of FA patients previously infused with very low numbers of gene corrected CD34 + cells, this drug promoted a more marked proliferative advantage of gene corrected cells compared to analyses performed prior to eltrombopag treatment. In order to evaluate the potential impact of eltrompopag in FA gene therapy, studies with a longer follow-up will be conducted in patients infused with autologous gene corrected cells, potentially at earlier stages of BMF.

Clinical Trial Registry: EudraCT 2020-002703-18

Disclosure: Julián Sevilla: Consultant/Advisor/Honorarium (Amgen, Novartis, Miltenyi, Sobi, Rocket Pharmaceuticals) and has licensed medicinal products from Rocket Pharmaceuticals.

Juan Bueren: Consultant/Advisor/Honorarium and has licensed medicinal products from Rocket Pharmaceuticals.

Jonathan D. Schwartz: employee and equity shareholder for Rocket Pharmaceuticals.

P153 Haploidentical stem-cell transplantation for children with acute leukemia, using αβ + t cell /cd19 + b-cell depletion, a single center experience

G. Dadi ¹, E. Jacoby^1,2, B. Bielorai^1,2, A. Toren^1,2

¹Division of Pediatric Hematology and Oncology, The Edmond and Lily Safra Children’s Hospital, Sheba Medical Center, Ramat Gan, Israel, ²Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel

Background: HLA haploidentical stem cell transplantation using αβ + T Cell /CD19 + B-cell depletion (αβHaplo-SCT) has been utilized in the last decade as an alternative approach to matched donor allogeneic transplantation in children with hematological malignancies^1-4. We report a single center experience using αβHaplo-SCT in children with acute leukemias between 2013-2020.

Methods: Data regarding donor/recipient, conditioning regimen, and graft characteristics were noted. Study endpoints were overall survival (OS), event free survival (EFS, relapse, death, or rejection), leukemia-free survival (LFS), non-relapse mortality (NRM), acute graft-versus-host disease (aGVHD), chronic graft-versus-host disease (cGVHD) and graft-versus-host disease, relapse-free survival (GRFS)⁵.

Chi-square test or Fisher’s exact test were used to compare categorical variables, and continuous variables were analyzed using Mann-Whitney non-parametric testing.

Cox proportional hazards regression models were constructed and analyzed using SPSS 25.

Results: Thirty-eight children with acute leukemia underwent αβHaplo-SCT, Most for advanced disease (≥CR2, or refractory) and third had prior HSCT. Patient’s median age was 8.5 years. Conditioning regimen was total body irradiation (TBI) based in 55% of children and 45% were conditioned with combination of Fludarabine, Treosulfan or Melphalan and Thiotepa. Patients received serotherapy as part of the conditioning, using anti-thymocyte globulin. Eighteen patients had more than 3X10^4 /kg of αβ T cells in the graft and received GVHD prophylaxis with mycophenolate mofetil ². No patient had donor’s HLA antibodies.

Thirty-four patients had primary engraftment and four had primary rejection. Median time for neutrophils engraftment was ten days and for platelets thirteen. Six patients had secondary rejection (median time 27 days). Using TBI was associated with higher engraftment and less rejection compared to chemotherapy only but did not reach a statistical significance (94% vs 82% p = 0.3 and 9% vs 23% p = 0.37, respectively).

Thirteen patients developed grade 1-2 aGVHD, age was a significant risk factor (11 Vs 6.5 P = 0.023). No patient developed grade 3-4 aGVHD and one developed extensive cGVHD.

Twenty-two patients were alive at last follow up with 5 years OS of 51%, and EFS of 42%. EFS was longer for patients with higher graft composition of γ/δ T cells (54% Vs 26%, P = 0.04).

Nine patients had relapse, all were males (34% vs 0%, P = 0.026). LFS probability was 72%. GRFS probability was 47.5%.

Eleven patients had NRM, mostly due to sepsis. CMV reactivation was common (50%) at a median time of 27 days, treated preemptively according to established guidelines.⁶

An expansion of NK cells was noted at day 30 of transplantation than reconstituted at three months. CD4/8 T cells and B cells recovered at six months. Immunoglobulins were supplemented as part of infection prophylaxis during immune recovery.

Conclusions: αβHaplo-SCT offers a cure for children with multiple relapses, or those who failed prior SCT with OS of 51%. Higher composition of γ/δ T cells had less rejections. Older age was a significant risk factor for grade 1-2 aGVHD. Chronic GVHD was rare. The role of prophylactic immunosuppression needs to be validated through a prospective trial. Immune reconstitution is slow, necessitating close follow up for viral reactivation, and preemptive prophylaxis is crucial for survival.

Disclosure: No conflict of interest

P154 Venetoclax added to sequential flamsa + alkylator based conditioning for allogeneic hematopoietic stem cell transplantation, a retrospective single center case series of the flamsaclax approach

G. Kobbe ¹, E. Schuler¹, P. Jäger¹, B. Bärmann¹, R. Fenk¹, F. Schulz¹, S. Gehring¹, T. Ulrych¹, K. Nachtkamp¹, U. Germing¹

¹University Hospital Düsseldorf, Düsseldorf, Germany

Background: Relapse is the most common cause of treatment failure after allogeneic hematopoietic stem cell transplantation (aHSCT) in patients with high-risk myeloid malignancies. Increasing conditioning intensity before aHSCT has not been able to improve transplant results because of increased treatment related mortality (TRM) especially in elderly, comorbid patients. Venetoclax has been shown to greatly enhance efficacy of conventional chemotherapy as well as hypomethylating agents while increasing mainly hematologic toxicity. Experience in combining Venetoclax with intensive conditioning therapy, where hematotoxicity can be suspended by aHSCT so far is limited.

Methods: Starting in 2018, we added Venetoclax to Fludarabine/Amsacrine/Ara-C (FLAMSA) + alkylator based sequential conditioning regimen (FLAMSAClax) in individual patients with poor prognosis myeloid malignancies. All patients gave written informed consent for individualized treatment. We now retrospectively collected data on 11 patients (9 AML, 1 MDS, 1 CMML, 6 female, median age 57, range 20-66) who had a minimum follow up of 300 days after transplant. All patients had active disease at transplant (8 refractory, 3 untreated) and 10 had high-risk genetics. Various doses of Venetoclax (100-400mg/d) were given in addition to FLAMSA and stopped one day before alkylator treatment (8 Melphalan, 3 Treosulfan).

Results: No additional extrahematologic toxicity was observed. There was 1 laboratory TLS, but no TRM. WBC and PLT reconstitution occurred on day + 12 (median, range 8-19 for WBC > 1000/ul) and on day + 14 (median, range 10-31 for PLT > 20000/ul). aGvHD grade III/IV occurred in 2 and severe cGvHD in 1 patient. At day +30, ten patients were in CR or CRi, 1 with molecular disease persistence. One patient had blast persistence but achieved molecular CR after salvage with HMA + Venetoclax. After a median follow up of 600 days (range 304-1001) for surviving patients, 10 patients (91%) are alive, 8 in molecular CR and 2 currently receive salvage therapy for relapse. So far 3 patients relapsed (day + 175, +267 and +855) and 1 finally died after salvage and 2^nd transplant from disease progression.

Conclusions: Venetoclax added to sequential FLAMSA + alkylator based conditioning seems to be feasible and highly effective in patients with poor risk myeloid malignancies. The FLAMSAClax approach should therefore be studied in a controlled prospective trial.

Clinical Trial Registry: NA

Disclosure: GK has received honoraria for an advisory role from Abbvie and Eurocept as well as travel support from Medac. All other authors have nothing to declare.

P155 Allogeneic hematopoietic stem cell transplantation in patients with adult onset leukoencephalopathy with axonal spheroids

G.-N. Franke ¹, V. Vucinic¹, B. Schetschorke¹, J. Claßen², U. Platzbecker¹, W. Köhler²

¹University of Leipzig Medical Center, Leipzig, Germany, ²University of Leipzig Medical Center, Leukodystrophy Clinic, Leipzig, Germany

Background: Adult onset leukoencephalopathy with axonal spheroids (ALSP) is a very rare disease and belongs to the heterogenouos groups of leukodystrophies. ALSP is a hereditary disease caused by a mutation in the CSF1R gene, presenting with progressive neurological symptoms, usually in the 4^th or 5^th decade and death within 5-6 years after onset of symptoms. The CSF1R gene is associated with phosphatase and kinase proteins regulating the function of macrophages, microglia and neuronal pathways. Dysbalances and disturbances caused by the CSF1R mutation lead to progressive inflammation and white matter lesions. Patients (pts) with leukodystrophies might benefit from allogeneic hematopoietic stem cell transplantation (allo-HSCT) by exchanging part of the host’s microglia through donor cells.

Methods: Two male patients with ALSP and CSF1R gene mutations and white matter lesions in the MRI underwent allo-HSCT at our center. Pt 1, a 49 year old male, was diagnosed in 2017, when he developed gait disturbances and a speech disorder, mainly due to a severe dyspraxia. Pt 2, a 47 year old male, underwent extensive neurological assessment in 2016 for left-sided sensomotor dysfunstions, visual disturbances and progressive cognitive deficits. He also had a family history with his mother, maternal grandmother, two maternal aunts and one older brother dying from early onset dementia and one younger, still asymptomatic, brother. The CSF1R mutation was also found in his two brothers. Due to the lack of material, no analyses are available from his mother, grandmother and aunts.

Results: Pt 1 was transplanted in 2019 from an HLA-identical sibling not carrying the mutation, while Pt 2 received a transplant from an unrelated HLA-identical male donor in 2020. Both pts were conditioned with busulfan (9.6 mg/kg BW) and fludarabine (180 mg/m²). Immunosuppression (IS) consisted of anti-thymoglobulin, cyclosporine A (CsA) and short course methotrexate. Both pts promptly engrafted and IS could be tapered without signs of acute or chronic GvHD.

Transient deterioration of the neurological functions was seen in both pts in the first 6 months after HSCT, followed by improvement to pre-HSCT status. 2.5 years after allo-HSCT, the symptoms of dyspraxia and dysarthria of pt 1 have improved, he is walking without limitations and has stable cognition . Pt 2 presented with progressive MRI changes 6 months after transplantation and deterioration of gait and speech. In the last evaluation 1.25 years after allo-HSCT, he clearly improved in gait and speech, his MRI was stable.

Conclusions: ALSP is a usually fatal neurological disease caused by CSF1R gene mutations. Allo-HSCT has the potential to prevent further destruction of brain by replacing the recipient’s microglia through donor cells and thus stabilization of the neurological functions after 6-12 months.

Disclosure: Nothing to declare

P156 Haploidentical stem cell transplant for haematological malignancies: Real world experience from a developing country

P. Mehta ¹, N. Yadav¹, R. Halder¹, N. Agrawal², R. Ahmed¹, D. Bhurani¹

¹Rajiv Gandhi Cancer Institute & Research Centre, Delhi, India, ²Rajiv Gandhi Cancer Institute & research Centre, Delhi, India

Background: Haploidentical peripheral blood hematopoietic cell transplantation(HaploSCT) has become the preferred alternative donor transplant program, owing to its logistic and cost advantages. However, the data from developing countries is not sufficient enough to hold this statement true for them.

Methods: It is a retrospective observational study hospital record based study where the outcome of Haplo-SCT was analysed using standard statistics.

Results: Between March 2015 and April 2021, 74 patients underwent 75 haploidentical transplantations at our institution. Median age was 31(9-60) years and indications included malignant disorders in majority (96%). Conditioning regimens included myeloablative (38.7%), nonmyeloablative regimens (44%) and reduced intensity (17.3%). GVHD prophylaxis was post-transplant cyclophosphamide on day+3,4 with Mycophenolate and Cyclosporine from day+5 onwards. Peripheral blood stem cells were the predominant graft source. Majority (92%) had CMV reactive donor and recipient combination. Median cell dose (CD34) was 5.26 (1.8-8.09) x10⁶/kg. Median engraftment for neutrophils and platelets was 14 (11-32) and 15 (10-43) days respectively. Nine (12.1%) patients had rejection (primary = 8, secondary=1). CMV reactivation was observed in 52 (69.3%) patients. The cumulative incidence of acute GVHD was 37.3% with 32.1% incidence of grade III-IV acute GVHD and 14.2% patients were steroid refractory. Chronic GVHD was seen in 16% and one fourth patients had extensive chronic GVHD. Sixty-four(85.3%) culture positive bacterial infections (Gram positive= 14, Gram negative=50) were observed in 44 patients whereas 32.4% patients had fungal infection and 17.5% had viral infections. TRM within 30 days, 30-100days and >100days was 8(10.6%), 14(18.6%),16(21.3%) patients respectively. Common causes of death were sepsis and relapse.

Conclusions: We emphasize haploidentical SCT offers a reasonable hope of cure for patients with hematological malignancies, though infections, GVHD, relapse are still deal-breakers in our experience which we are striving to overcome in our prospective studies.

Clinical Trial Registry: Not Applicable

Disclosure: No conflict of interest.

Graft-versus-host Disease – Clinical

P157 Real-world data on ruxolitinib in steroid-refractory acute intestinal graft-versus-host-disease

F. Biavasco ¹, G. Ihorst², R. Wäsch¹, C. Wehr¹, H. Bertz¹, J. Finke¹, R. Zeiser¹

¹University Medical Center Freiburg, Freiburg, Germany, ²Clinical Trials Center Freiburg, Freiburg, Germany

Background: Acute graft-versus-host disease affecting the lower gastrointestinal tract (GI-GVHD) is a major life-threatening complication of allogeneic hematopoietic cell transplantation and is frequently resistant to glucocorticosteroid-therapy (SR). Higher overall response rates and failure-free survival of ruxolitinib compared to best available second-line therapy (SLT) was recently reported in a phase-III trial. However, real-world data and external validation of these promising results are lacking.

Methods: To determine the outcome of patients with GI-GVHD in the era of ruxolitinib, we retrospectively analyzed patients who developed GI-GVHD over a 6-year period to determine therapy-responsiveness and survival.

Results: A total of 144 patients developed GI-GVHD and 83 (58%) were SR. Ruxolitinib was most commonly used (74.3%) as SLT. Overall and complete response (CR) to ruxolitinib on day 28 were similar to what reported in REACH2 trial (60.0% and 27.3% respectively, Figure 1A). A durable CR was observed in ruxolitinib-treated patients at day 56 in 31.6% and in other single-agent SLT in 16.7% (Figure 1B). Around one fourth of patients could achieve a CR even after third-line (25.8%) and fourth-line therapy (25.0%). Moreover, SR-GVHD patients experienced a lower 5-year overall survival (OS) (34.8% vs 53.3%, p = 0.0014) and higher cumulative incidence of 12-months non-relapse-mortality (NRM) (39.2% vs 14.3%, p = 0.016) compared to glucocorticosteroid-sensitive patients. Interestingly, SR-GVHD patients who achieved CR on day 28 experienced higher 5-year OS (56.3% vs 14.9%, p < 0.0001) and lower 12-months NRM (13.8% vs 77.4%, p < 0.0001) compared to non-responders, having an outcome comparable to glucocorticoid-sensitive patients (Figure 1C).

Conclusions: These real-world unselected data confirm the response rate to ruxolitinib as SLT in SR-GI-GVHD obtained in REACH2 trial and the poor outcome of SR-GI-GVHD. Additionally they show improved OS of ruxolitinib-CR-responders and indicate that first-line therapy failure still allows for a considerable CR rate upon SLT.

Disclosure: Rober Zeiser received honoraria from Incyte, Novartis and Mallinckrodt, was supported by the Deutsche Forschungsgemeinschaft (DFG), Germany for the SFB 1479 OncoEscape P01, Project ID: 441891347 to RZ, SFB1160 to RZ, ZE 872/4-2, TRR167 to RZ, Deutsche Krebshilfe (grant number 70113473), the Jose-Carreras Leukemia foundation grant number DJCLS 01R/2019.

P158 Bortezomib maintenance after upfront allogeneic transplantation in myeloma patients: Less chronic GVHD and immunosuppression but still no impact on survival

J.-S. Claveau ^1,2, R. LeBlanc², I. Ahmad², J.-S. Delisle², J. Roy²

¹Mayo Clinic, Rochester, United States, ²Maisonneuve-Rosemont Hospital, Montreal, Canada

Background: Allogeneic (allo) hematopoietic stem cell transplant (HCT) has curative potential in multiple myeloma (MM) but remains hampered by high rates of relapse and chronic (c) GVHD. We recently completed a prospective phase II study (LeBlanc R, BMT 2021) in newly diagnosed MM using bortezomib (BTZ) maintenance after tandem autologous (auto) + alloHCT aimed at decreasing relapse. Based on previous clinical observations, we hypothesized that BTZ could also decrease incidence and severity of cGVHD.

Methods: Using the 2015 NIH criteria, we retrospectively reviewed the incidence and organ distribution of cGVHD, as well as duration of immunosuppression in 2 contemporaneous cohorts: patients receiving BTZ maintenance q2 weeks for 1 year after alloHCT, and tandem transplants without BTZ maintenance. After autologous HCT, patients from both cohorts received an outpatient nonmyeloablative conditioning followed by G-CSF mobilized donor stem cells. GVHD prophylaxis consisted of mycophenolate mofetil and tacrolimus tapered by D + 100 (sibling donors) or D + 180 (unrelated donors) in both groups. Cumulative incidences of cGVHD were estimated using competing-risk methods including relapse, second transplantation and death.

Results: Between 2014 and 2018, 41 patients received BTZ maintenance, whereas 57 patients did not. Myeloma subtypes were similar in both groups. Baseline characteristics showed no difference except that patients in the BTZ group had younger donors (40 years vs. 52 years) and more unrelated donors (59% vs. 12%). Incidences of grade II-IV acute GVHD at day+180 were similar in both cohorts (17.1% vs. 26.6%, p = 0.518). At 2 years, incidences of overall (61.0% vs. 84.2%, p = 0.001) and moderate/severe cGVHD (44.7% vs. 66.7%, p = 0.003, Fig. 1) were significantly lower in BTZ than in non-BTZ recipients. After univariate analysis, overall mouth (56% vs. 79%, p = 0.025), skin (34% vs. 56%, p = 0.041) and liver (32% vs. 54%, p = 0.039) involvement were less frequent in BTZ patients. We elected to choose donor age, sex, CD34 + cell dose, major ABO mismatch, recipients’ CMV status and grade II-IV acute GVHD as variables to perform multivariable analysis. Following multivariate Fine-Gray regression, not receiving BTZ was associated with higher overall incidence of cGVHD (HR 2.38, p = 0.002) and moderate/severe cGVHD (HR 2.39, p = 0.004). The cumulative incidence of prednisone initiation at 5 years was 42.2% in BTZ and 78.3% in non-BTZ recipients (p < 0.001). The cumulative incidence of tacrolimus resumption at 5 years was also lower in BTZ than in non-BTZ recipients (30.1% vs. 73.6%, p < 0.001). Probability of being alive and off immunosuppressants at 3 years were 86% for BTZ patients vs. 47% for non-BTZ patients (p < 0.001). NRM at 2 and 5 years were 4.9% and 8.8% in BTZ recipients vs. 1.8% and 5.4% in non-BTZ recipients (p = 0.575). We observed no impact of BTZ on 5-year OS (82.9% vs. 83.4%, p = 0.938) and PFS (49.5% vs. 58.5%, p = 0.277) respectively in patients receiving or not BTZ.

Conclusions: Although it had no impact on survival, BTZ maintenance led to a significant reduction in incidence and severity of cGVHD with shorter duration of immunosuppressants. BTZ maintenance should be considered as a valid option in MM receiving upfront auto-alloHCT.

Clinical Trial Registry: N/A

Disclosure: The authors declare no conflicts of interest.

P159 Belumosudil for chronic graft-versus-host disease after 2 or more prior lines of systemic therapy: Long-term safety follow-up of the pivotal phase 2 rockstar study (kd025-213)

C. Cutler ¹, S. Lee², S. Pavletic³, B. Blazar⁴, L. Green⁵, Z. Yang⁵, D. Eiznhamer⁵, J. Ieyoub⁵

¹Dana Farber Cancer Institute, Boston, United States, ²Fred Hutchinson Cancer Center, Seattle, United States, ³Center for Cancer Research, National Cancer Institute, Bethesda, United States, ⁴University of Minnesota, Minneapolis, United States, ⁵Kadmon Corporation, New York, United States

Background: Belumosudil is a novel oral selective rho-associated coiled-coil–containing protein kinase-2 inhibitor designed for the treatment of cGVHD following an allogeneic hematopoietic cell transplant. We report the 2-year, long-term, follow-up safety results from the ROCKstar study.

Methods: This open-label, randomized, multicenter study evaluated belumosudil 200 mg QD (n = 66) and BID (n = 66) in patients with cGVHD (aged 21-77 years) who received 2 to 5 prior LOTs; cutoff date for the long-term follow-up was August 19, 2021.

Results: Median age was 56 years, median time from diagnosis to enrollment was 28 months, median prednisone dose was 0.19 mg/kg/d, 67% of patients had severe cGVHD, 52% had ≥4 organs involved, 73% had received ≥3 prior LOTs (including ibrutinib [34%] or ruxolitinib [29%]) and 73% were refractory to their last LOT. Median treatment duration was 10 months, with 29% of patients receiving belumosudil for ≥24 months. The ORR (95% CI) with belumosudil 200 mg QD and BID was 74% (62%-84%) and 77% (65%-87%), respectively. Belumosudil continued to be well tolerated (Table). The primary reasons for drug discontinuation were adverse events [AEs] (n = 17 [13%]; 7 experienced AEs that were not drug related), progression of underlying malignancy (n = 5 [4%]) and progression of cGVHD (n = 16 [20%]). Twenty percent and 10% of patients experienced ≥1 drug-related AE that led to dose modification and interruption, respectively. Forty-eight percent and 32% of patients experienced ≥1 AE not drug related that led to dose modification and interruption, respectively.

AEs observed at all grades in ≥30% of patients included fatigue (39%), diarrhea (35%), nausea (31%) and cough (30%). Grade ≥3 AEs observed in ≥5% of patients included hypertension (8%), pneumonia (8%) and hyperglycemia (5%). Grade ≥3 cytopenias included anemia (4%), neutropenia (2%) and leukopenia (1%). At least 1 serious AE occurred in 44% of patients. There was 1 case of cytomegalovirus reactivation.

Of all patients, 5% had ≥1 grade ≥3 drug-related hepatic disorder, 14% had increased gamma-glutamyltransferase, 12% had increased aspartate aminotransferase, 10% had increased alanine aminotransferase and 1% had increased bilirubin.

The median corticosteroid dose reduction was 50%. Corticosteroid discontinuation was observed in 27% of patients. Calcineurin inhibitor dose reduction and discontinuation was observed in 54% and 27% of patients, respectively.

Table

Safety overview	Belumosudil 200 mg QD	Belumosudil 200 mg BID	Total
	(n = 66)	(n = 66)	(N = 132)
Median months of treatment	9	12	10
Any AE, n (%)	65 (99)	66 (100)	131 (99)
Grade ≥3 AEs, n (%)	41 (62)	38 (58)	79 (60)
Any serious AE, n (%)	30 (46)	28 (42)	58 (44)
Any drug-related AE, n (%)	50 (76)	42 (64)	92 (70)
Any drug-related grade ≥3 AE, n (%)	14 (21)	11 (17)	25 (19)
Any drug-related serious AE, n (%)	6 (9)	3 (5)	9 (7)
Any AE leading to death, n (%)	4 (6)	5 (8)	9 (7)

 

Conclusions: Belumosudil remained well tolerated, with low rates of cytopenias. AE and drug discontinuation rates were comparable to those reported in Cutler et al, 2021. Patients have continued to sustain belumosudil therapy and achieve clinically meaningful responses.

Clinical Trial Registry: NCT03640481

Disclosure: Corey Cutler is a consultant and advisor for Janssen, Mesoblast, Syndax Pharmaceuticals Inc, Omeros, Incyte Corporation, Jazz Pharmaceuticals, Mallinckrodt, CareDx and Pfizer; has been a pro bono consultant for Kadmon Corporation; and has not received any payment for consulting in the past year. Stephanie J. Lee is on a steering committee for Incyte Corporation and has received research funding from Amgen, AstraZeneca, Incyte Corporation, Kadmon Corporation, Novartis Pharmaceuticals Corporation, Pfizer, Syndax Pharmaceuticals Inc and Takeda. Steven Pavletic received research support from the Center for Cancer Research at the National Cancer Institute through the National Institutes of Health Intramural Research Program, which includes Clinical Research Development Agreements with Celgene, Actelion, Eli Lilly, Pharmacyclics and Kadmon Corporation. Bruce R. Blazar is a cofounder of Tmunity Therapeutics, is a consultant and advisor for Magenta Therapeutics and Blue Rock Therapeutics and has received research funding from Blue Rock Therapeutics, Children’s Cancer Research Fund and Kids First Fund. Laurie Green, Zhongming Yang, David Eiznhamer and Jonathan Ieyoub have stock options in and are employees of Kadmon Corporation.

P161 Fecal microbiota transplantation in the treatment of acute gastrointestinal graft-versus-host disease: A retrospective survey of the transplant complications working party of EBMT

J. Bilinski¹, G.W. Basak ¹, K. Halaburda², D. Wu³, O. Goloshchapov⁴, S. Maury⁵, A. Tanase⁶, G. Van Gorkom⁷, A. Delie⁸, T. Kerre⁸, O. Penack⁹, I. Moiseev⁴, H. Schoemans¹⁰, C. Koenecke¹¹, S. Corbacioglu¹², Z. Peric¹³

¹Medical University of Warsaw, Warsaw, Poland, ²Institute of Hematology and Transfusion Medicine, Warsaw, Poland, ³China Suzhou, First Affiliated Hospital of Soochow University, Suzhou, China, ⁴Pavlov University, St. Petersburg, Russian Federation, ⁵Hôpital Henri Mondor, Creteil, France, ⁶undeni Clinical Institute, Bucharest, Romania, ⁷University Hospital Maastricht, Maastricht, Netherlands, ⁸Ghent University Hospital, Ghent, Belgium, ⁹Charité Universitätsmedizin Berlin, Berlin, Germany, ¹⁰University Hospitals Leuven, Leuven, Belgium, ¹¹Hannover Medical School, Hannover, Germany, ¹²University Hospital Regensburg, Regensburg, Germany, ¹³University of Zagreb, Zagreb, Croatia

Background: Loss of intestinal bacterial diversity, a relative shift toward bacterial monocolonization (i.e. with Enterococci) and colonization with antibiotic-resistant bacteria (ARB) before allogeneic hematopoietic stem cell transplantation (alloHCT) are observed in gastrointestinal (GI) acute graft-versus-host disease (aGvHD) patients. Allogeneic gut microbiota may modulate systemic immune responses, which has been proven in many microbiota dependent diseases. Fecal microbiota transplantation (FMT) is able to restore gut microbiota diversity and has been successfully used for recurrent Clostridioides difficile infection as well as for the treatment of autoimmune diseases (i.e. ulcerative colitis). Recently, studies of the use of FMT to treat (steroid-refractory (SR) intestinal) aGvHD have shown promising results. Our aim was to identify EBMT centers who perform FMT in this indication and summarize procedure modalities, application regimens, indications and outcome.

Methods: The study was performed by Transplant Complications Working Party (TCWP) between May 2018 and May 2020 and used a 2-step approach. In the first step we conducted a survey among EBMT centers with >100 alloHCTs since 2010 to identify cases, while in second, we retrospectively collected details of performed FMTs.

Results: A total of 10 centers reported 32 patients. Among these, 27 patients (25 adults and 2 children) met inclusion criteria and had undergone 52 FMTs. Most of the reported patients were already published elsewhere separately. 24/2/1 patients had steroid refractory/dependent/de novo GI aGvHD, respectively and concomitant indications to perform FMT were C. difficile infection in 3 and ARB colonization in 14 of subjects. 22 patients (81%) had grade III-IV gut aGvHD and 24 (89%) overall III-IV aGvHD. Almost all patients (25, 93%) had an unrelated stool microbiota donor and obtained FMT as an infusion (25, 93%) or capsules (1, 4%). Most of the patients received FMT through gastrointestinal/duodenal tube (23, 85%) and the procedure was performed as multiple administration regimen (FMT sessions; in 20 patients, 74%). Overall aGvHD response rate (ORR) at day 28 post-FMT reached 63% (17/27); with 12 patients achieving complete response (CR; 44%) and additional 5 patients achieving partial response (PR; 19%). Additionally, successful ARB decolonization was achieved in 8 out of 14 previously colonized patients (57%). It is also important to highlight that 20 patients (74%) were treated with antibiotics during the first two weeks after FMT, which could have negatively impacted the ORR. In total, 2 cases of sepsis as severe adverse events were reported.

Conclusions: In this one of the largest cohort of patients published to date, undergoing FMT after alloHCT, we found high response rates of aGVHD as well as decolonization of ARB. To enable a broader clinical use of this promising approach, more evidence from prospective clinical trials as well as a standardization of FMT modalities is needed.

Disclosure: OP has no COIs directly related to this manuscript.

OP has received honoraria or travel support from Astellas, Gilead, Jazz, MSD, Neovii Biotech, Novartis, Pfizer and Therakos. He has received research support from Gilead, Incyte, Jazz, Neovii Biotech and Takeda. He is member of advisory boards to Jazz, Gilead, MSD, Omeros, Priothera, Shionogi and SOBI.

P162 Prospective multicenter non interventional observational study on the use of anti-human t-lymphocyte immunoglobulin (atlg) in unrelated donor transplantation in adults with haematological malignancies (atos study)

J. Finke ¹, C. Schmoor¹, F. Ayuk², J. Hasenkamp³, M. Verbeek⁴, E.-M. Wagner⁵, K. Schäfer-Eckart⁶, J. Tischer⁷, C. Schmid⁸, M. Kaufmann⁹, M. Eder¹⁰, H. Bertz¹, O. Grichina¹

¹University of Freiburg Medical Center, Freiburg, Germany, ²University Medical Center Hamburg-Eppendorf, Hamburg, Germany, ³University of Göttingen Medical Center, Göttingen, Germany, ⁴Medical Center TU Univerity München, München, Germany, ⁵Mainz University Medical Center, Mainz, Germany, ⁶Medical Center Nürnberg Nord, Nürnberg, Germany, ⁷Medical Center LMU University München, München, Germany, ⁸University Medical Center Augsburg, Augsburg, Germany, ⁹Robert Bosch Krankenhaus Stuttgart, Stuttgart, Germany, ¹⁰University Medical School Hannover, Hannover, Germany

Background: Long-term follow-up from the prospective randomized phase III multicenter[PDJF1] trial (RCT) comparing a standard GvHD prophylaxis with cyclosporine A and methotrexate with or without additional pretransplant anti-human T-lymphocyte immunoglobulin (ATLG, Grafalon) (20mg/kg/day, days -3 to -1) in unrelated donor hematopoietic cell transplantation after myeloablative conditioning resulted in a significant reduction of acute and chronic GvHD without compromising relapse and survival (Finke et al., Lancet Hematol 2017).

Methods: ATOS is a subsequent prospective non-interventional observational study evaluating the outcome of patients receiving ATLG in unrelated donor transplantation in routine clinical practice without the selective measures of a clinical trial. No control group was included. Patients’ characteristics and outcomes were compared to 103 patients in the ATLG treatment arm of our RCT. Primary endpoint was severe GvHD and relapse-free survival (SGRFS).

Results: Between May 2013 and March 2015, 13 transplant centers included 165 patients with haematological malignancies (age median 54, range 18-77 years) in early (45%), intermediate (18%) or advanced (37%) disease receiving marrow (N = 6) or PBSC (N = 159) from 10/10 matched (78%) or mismatched (22%) donors after myeloablative (51%) or reduced intensity conditioning (RIC) (49%).

GvHD prophylaxis consisted of calcineurin inhibitors, mainly CSA (93%) with MTX or MMF and ATLG. Different dosing regimens were allowed according to current center practice. Median total ATLG dose was 46 (IQR 32-60, range 15-91) mg/kg. Median follow-up was 70 months (range 11-91 months). ATLG dose differed strongly between centers, so dose effects cannot be separated from center effects.

As compared to our RCT, patients in ATOS were older, had a more advanced disease status, RIC, HLA 10/10 match and PBSC transplantation were more frequent, and given median ATLG dose was lower.

Incidences of aGvHD (0.56), aGvHD III-IV (0.13), relapse (0.33), relapse mortality (0.24), non-relapse mortality (0.24), and disease-free (0.43) and overall survival rates (0.52), (all 5-years), were similar to the results in the ATLG arm of our RCT. Five-year incidences of cGvHD (0.42), and severe cGvHD (0.27) were higher as compared to results in the ATLG arm of our RCT (any 0.31, severe 0.14), which may be due to different reporting procedures. As a result of these differences, also the 5-year rate of SGRFS was lower in ATOS (0.27) as compared to the ATLG arm in our RCT (0.34).

In general, the comparison of outcomes in ATOS and the RCT has to take into account the differences in patient characteristics and treatment procedures. In multiple regression models adjusting for these differences, the largest difference in outcome was seen with respect to severe cGvHD (ATOS vs ATLG arm RCT: hazard ratio 2.79, 95%-confidence interval [1.20,6.51], p = 0.017). All other adjusted comparisons resulted in 95%-confidence intervals of the hazard ratio overlapping the value of one.

Adverse drug reactions occurred at a rate and severity that are consistent with the known safety profile, and are clinically manageable.

Conclusions: The long-term experience in routine clinical practice confirms the results shown in our RCT, namely the GvHD protective effect of ATLG without compromising relapse and non-relapse mortality rates.

Clinical Trial Registry: German clinical trials register DRKS00004581

Disclosure: JF: Neovii, Medac Riemser

P163 Graft versus host disease related eosinophilic fasciitis

C. Hidalgo-Calleja¹, D. Martín-Hidalgo², C. Román Curto¹, L. Vázquez López¹, E. Pérez-López¹, M. Cabrero Calvo¹, A.Á. Martín-López¹, M.D. Caballero Barrigón¹, L. López-Corral ¹

¹University Hospital, Salamanca, Spain, ²Salamanca University, Salamanca, Spain

Background:

Chronic Graft Versus Host Disease (cGVHD) simulating eosinophilic fasciitis (EF) is a rare complication after allogeneic transplantation of hematopoietic progenitors (allo-TPH). EF related cGVHD is an underdiagnosed and challenging complication due to the lack of knowledge about its pathogenesis, refractoriness to traditional immunosuppressive agents and their negative impact on physical function and quality of life.

The aim of this study is to describe the clinical-biological characteristics and response to treatment of a case series of EF related cGVHD.

Methods: Prospective observational study to describe the clinical and diagnostic evaluation characteristics of patients with EF-like follow-up in our multidisciplinary cGVHD consultations since March 2014 to present. 118 patients were evaluated, 39 of whom (33%) developed fasciitis. Joint and fascial cGVHD was diagnosed if the patient had NIH joint and fascia score ≥1. Clinical variables analyzed in the entire cohort were the baseline and transplant-related characteristics and clinical assessment of cGVHD including time from all-HCT to enrollment, cGVHD type, organs affected and NIH global score. In addition, in the fasciitis group, complementary laboratory and imaging tests as well as the therapeutic approach and response were detailed. Diagnosis and classification were performed according to 2015 NIH and treatment response in EF-like according to the response criteria redefined by Inamoto 2020.

Regarding statistical analysis, a descriptive analysis of frequencies was performed and nonparametric tests were used for comparisons (X² or Fisher’s exact test for categorical variables or the Mann-Whitney test for continuous variables). The analyses were performed using the SPSS 25.0 statistical package (SPSS, Chicago, IL, USA).

Results: From March 2014 to present, 118 patients were evaluated in the multidisciplinary cGVHD consultation and 39 patients (33%) developed fasciitis. No differences regarding baseline and transplant-related characteristics neither clinical assessment of cGVHD was found between patients with or without fascial involvement. The clinical characteristic of EF related cGHVD are described in Table 1. After a 3 median lines of treatment, the vast majority of patients achieved some degree of response, with a complete response rate of 41%.

Table 1.- Clinical-biological characteristics and therapies administered in patients with fasciitis (n = 39).

Nonspecific prodromal symptoms
• Absent	8 (20.5%)
• Stiffness	33 (84.6%)
• Arthromyalgias	24 (61.3%)
• Edemas	11 (28.2%)
• Cramps	9 (23.0%)
• Skin tightness	29 (74.4%)
Joint contracture	14 (35.8%)
Affected range of motion (ROM):Mild/moderate / severe	23 (59.0%)/10 (25.6%)/1 (2.6%)
Limitation of upper limb mobility:
• P-ROM shoulders	23 (58.9%)
• P-ROM elbows	13 (33.4%)
• P-ROM wrists/fingers	19 (50.0%)
Limitation of mobility of lower limbs:
• P-ROM ankles	14 (35.9%)
Concomitant skin sclerosis	35 (89.7%)
Eosinophilia at diagnosis (>500/mm3)	21 (53.8%)
Positive autoantibodies	10 (25.7%)
Imaging tests performed: • Rx/MRI / Echo	2 (5.1%)/2 (5.1%)/3 (7.7%)
Median number of treatment lines (range)	3 (1-7)
First-line treatment
• Corticosteroids	37 (94.4%)
Rescue treatment
• Extracorporeal photopheresis	25 (64.1%)
• Ruxolitinib	8 (20.5%)
• Imatinib	10 (25.6%)
• Others	11 (28.2%)

Conclusions: Fascial/articular involvement needs to be recognized and evaluated early with validated scales. In our knowledge, our cohort is the second largest series reported. Literature addressing fascial/joints complications related to cGVHD are scarce. The search for new biomarkers, the use of advanced imaging techniques and multidisciplinary approach may help to improve the prognosis of patients with cGVHD.

Disclosure: This work was partially supported by the Education Council and Health Council of the Junta de Castilla y León (GRS 2183/A/20), Spain.

P164 Methotrexate or mycophenolate mofetil with cyclosporine and antithymocyte globulin in matched unrelated donor transplantation for acute myeloid leukemia with busulfan-fludarabine reduced-intensity conditioning: An alwp study

G. Battipaglia¹, J.-E. Galimard ², M. Labopin², G. Socié³, E. Forcade⁴, C.E. Bulabois⁵, U. Schanz⁶, N. Fegueux⁷, S. Mielke⁸, K. Carlson⁹, E. Deconinck¹⁰, J. Maertens¹¹, G. Guillerm¹², P. Turlure¹³, T. Gedde-Dahl¹⁴, A. Nagler¹⁵, M. Mohty¹⁶

¹Federico II University of Naples, Naples, Italy, ²EBMT Statistical Unit, Paris, France, ³Hopital St. Louis, Dept.of Hematology – BMT, Paris, France, ⁴Service d’Hématologie Clinique et Thérapie Cellulaire, CHU Bordeaux, Bordeaux, France, ⁵CHU Grenoble Alpes - Université Grenoble Alpes, Service d`Hématologie, Grenoble, France, <sup>6</sup>University Hospital, Clinic of Hematology, Zurich, Switzerland, <sup>7</sup>CHU Lapeyronie, Département d`Hématologie Clinique, Montpellier, France, ⁸Karolinska University Hospital, Dept. of Hematology, Stockholm, Sweden, ⁹Dept of Hematology, University Hospital, Uppsala, Sweden, ¹⁰Hopital Jean Minjoz, Service d`Hématologie, Besançon, France, <sup>11</sup>University Hospital Gasthuisberg, Dept. of Hematology, Leuven, Belgium, <sup>12</sup>C.H.R.U de Brest, Service Onco-Hematologie, Brest, France, <sup>13</sup>CHRU Limoges, Service d`Hématologie Clinique, Limoges, France, ¹⁴Institute of clinical medicine, University of Oslo, Oslo, Norway, ¹⁵Chaim Sheba Medical Center, Tel-Hashomer, Israel, ¹⁶Sorbonne Universités, UPMC Univ Paris 06, INSERM, Centre de Recherche Saint-Antoine (CRSA), Paris, France

Background: Graft-versus-host disease (GVHD) prophylaxis in matched unrelated donor (MUD) allogeneic hematopoietic stem cell transplantation (allo-HSCT) is mainly based on the use of a calcineurin inhibitor with either short course methotrexate (MTX) or mycophenolate mofetil (MMF). When using peripheral blood as stem cell source (PBSC), addition of antithymocyte globulin (ATG) significantly reduces the incidence of chronic GVHD (cGVHD). Reduced-intensity conditioning regimen (RIC) with fludarabine and busulfan (BuFlu) is largely used in this setting.

Methods: Included were adults ≥18 years undergoing first allo-HSCT for acute myeloid leukemia (AML) in complete remission (CR) from a MUD and receiving PBSC and a BuFlu-RIC with ATG, transplanted between 2010-2019. Patients receiving cyclosporine (CsA) with either MTX or MMF were included and transplant outcomes with these GVHD prophylaxis were compared.

Results: We identified a total of 1001 patients, including 517 receiving CsA+MMF (MMF group) and 484 receiving CsA+MTX (MTX group). Patients in the MMF group were younger (61 versus 63 years, p < 0.01) and less frequently seropositive for CMV (60% versus 72%). No imbalances were observed for other characteristics. Most patients were transplanted in first CR (85% versus 81% in MMF and MTX groups 1 and 2, respectively, p = 0.12). With a median follow-up of 3 years for both groups, 2-years (2y) relapse incidence (RI) was 26% versus 32% in MMF and MTX groups (p = 0.20) while non-relapse mortality (NRM) was lower in the MTX group (9% versus 15%, p = 0.02). No differences were observed in 2y-overall survival (OS, 64% versus 69% in MMF and MTX groups, respectively, p = 0.10) and 2y-leukemia-free survival (LFS, 59% in both groups, p = 0.70) while a higher 2y-GVHD/relapse-free survival (GRFS) was found in the MTX group (52% versus 46%, p < 0.01). Of note, both grade II-IV and III-IV acute GVHD (aGVHD) were lower in the MTX-group (18% and 4% compared to 37% and 11% in the MMF group, p < 0.01). Similarly, cGVHD of all grades and extensive cGVHD were lower in the MTX group (29% and 8% compared to 36% and 17% in the MMF group, p < 0.05 for all grades and p < 0.01 for extensive cGVHD). These results were confirmed in multivariate analysis with lower NRM (HR 0.63, 95% CI 0.44-0.92, p = 0.01) and higher GRFS (HR 0.80, 95% CI 0.65-0.99, p = 0.04) in the MTX group. Use of CsA+MTX was also associated to lower grade II-IV (HR 0.45, 95% CI 0.32-0.62, p < 0.01) and grade III-IV (HR 0.39, 95% CI 0.23-0.67, p < 0.01) aGVHD and lower cGVHD (HR 0.71, 95% CI 0.56-0.90, p < 0.01) and of extensive cGVHD (HR 0.39, 95% CI 0.22-0.68, p < 0.01). Neither RI (HR = 1.20, 95% CI 0.94-1.52), p = 0.14) or LFS (HR 0.99; 95% CI 0.81-1.21, p = 0.93) or OS (HR 0.85, 95% CI 0.69-1.05, p = 0.13) differed significantly between the two groups.

Conclusions: In MUD allo-HSCT GVHD prophylaxis containing CsA+MTX and CsA+MMF were not significantly different in term of LFS and OS. However, CsA+MTX better prevented both acute and chronic GVHD, subsequently reducing NRM and providing higher GRFS compared to CsA+MMF when a BuFlu RIC with ATG is used in MUD-PBSC allo-HSCT.

Disclosure: No COI to disclose

P165 Triple agents GVHD prophylaxis for HLA matched donor: Post-transplant cyclophosphamide versus thymoglobulines and methotrexate

E. Metafuni ¹, S. Giammarco¹, M.A. Limongiello¹, F. Sorà¹, E. Galli¹, N. Piccirillo¹, L. Teofili¹, A. Bacigalupo¹, S. Sica¹, P. Chiusolo¹

¹Fondazione Policlinico Universitario Agostino Gemelli, Roma, Italy

Background: HLA matched donor has represented the most used stem cell source in last decades. The main graft-verus-host disease (GvHD) prophylaxis platform includes calcineurin inhibitors with methotrexate (MTX) or mycophenolate mofetil (MFA), but recently cyclophosphamide post-transplant (CY) emerged as reliable alternative, not only for haploidentical donors.

Methods: We retrospectively analyzed post-transplant outcomes in HLA matched allogeneic stem cell transplantation (HSCT) between March 2015 and May 2021, comparing two GvHD prophylaxis platforms. The first included cyclosporine A 3 mg/Kg from day 0 (CSA), MFA 30 mg/Kg from day +1 to day +36 and CY 50 mg/kg on day +3 and +5 (n = 91). The second one included CSA 3 mg/kg from day 0 to day 60 and then tapering until day +180, MTX 15 mg/m2 on day +1, 10 mg/m2 on day +3, +6 and +11, and rabbit thymoglobulines 2.5 mg/kg on day -1 (ATG) (n = 111).

Results: One year (1-yr) cumulative incidence of moderate/severe chronic GvHD (cGvHD) was of 14.7% (95% CI 8.7-24.9) in the CSA/MFA/CY group and 26% (95% CI 18.5-36.5) in the CSA/MTX/ATG group (p = 0.04). In multivariate analysis, CY-based prophylaxis (HR 0.45, p = 0.02), complete remission status of the underlying disease at transplant (HR 0.40, p = 0.007) and a previous acute GvHD (aGvHD) (HR 2.14, p = 0.003) resulted as independent variables for moderate/severe cGvHD occurrence. Moreover, 1-yr graft-relapse free survival (GRFS) was of 58.2% (95% CI 47.4-67.6) in the CSA/MFA/CY group and 43.2% (95% CI 33.9-52.2) in the CSA/MTX/ATG group (p = 0.01). In multivariate analysis, CY-based prophylaxis (HR 0.59, p = 0.01) complete remission status of the underlying disease at transplant (HR 0.65, p = 0.03) and the use of a female donor (HR 1.51, p = 0.05) emerged as independent variables for GRFS. Considering the occurrence of viral infections after transplant, 1-yr EBV viremia occurred in 22.6% (95% CI 15.2-33.7) in the CSA/MFA/CY group and in 64.3% (95% CI 55.5-74.7) of the CSA/MTX/ATG group (p < 0.0001). Multivariate analysis identified CY-based prophylaxis (HR 0.30, p < 0.0001), a previous aGvHD (HR 1.74, p = 0.01) and a previous CMV infection (HR 2.88, p < 0.0001) as independent variables for EBV infection. Finally, 1-yr cumulative incidence of CMV viremia was of 23.6% (95% CI 14.3-39) in the CSA/MFA/CY group and 57% (95% CI 48.4-67.2) in the CSA/MTX/ATG group (p < 0.0001). Multivariate analysis revealed CY-based prophylaxis (HR 0.41, p = 0.007), a diagnosis of acute leukemia or myelodysplasia (HR 2.10, p = 0.02), a familial donor (HR 0.22, p = 0.0001) and CMV seropositive recipient (HR 5.73, p = 0.0008) as independent variables for CMV infection.No differences among the two groups were identified for aGvHD occurrence, disease free survival, transplant-related mortality or overall survival.

Conclusions: Patients receiving HLA matched transplant experienced a low incidence of moderate/severe cGvHD, EBV viremia and CMV viremia and a better GRFS when GvHD prophylaxis is realized using CY with CSA and MFA.

Disclosure: Nothing to declare

P166 Ten years of steroid refractory acute graft-versus-host disease in pediatric allogeneic hematopoietic stem cell transplantation: What have we learned?

A.B Verbeek ¹, S.A Jansen^2,3, E.GJ von Asmuth¹, A.C Lankester¹, C.A Lindemans^2,3, E.P Buddingh¹

¹Leiden University Medical Center, Leiden, Netherlands, ²Princess Máxima Center for Pediatric Oncology, Utrecht, Netherlands, ³University Medical Center, Utrecht, Netherlands

Background: Steroid refractory acute Graft-versus-Host Disease (SR-aGvHD) in children after allogeneic hematopoietic stem cell transplantation (alloHSCT) is associated with high morbidity and mortality. We aimed to assess clinical course and outcomes of pediatric SR-aGvHD.

Methods: We performed a retrospective nationwide multicenter cohort study in the Netherlands. All patients aged 0-18 transplanted between 2010 and 2020 with SR-aGvHD were included. For each patient, weekly clinical aGvHD grade and stage, immunosuppressive treatment and clinical outcomes were collected. The primary study endpoint was clinical course of SR-aGvHD over time, which was graphically analyzed. As a secondary outcome, factors influencing overall survival and remission were identified using a multistate Cox model.

Results: Between 2010 and 2020, 786 children received an alloHSCT. 158 patients (20%) suffered from grade II-IV aGvHD, which occurred after a median of 34.5 days. 81 patients (51%) required second line therapy after first line treatment with steroids (Table 1).

Second line therapy was started after a median of 8 days after aGvHD diagnosis. 42 patients (52%) required three or more lines of therapy. One year after start of second line therapy, 34 patients (42%) were alive and in remission of their SR-aGvHD and 33 patients (41%) had died. 14 patients (17%) had persistent GvHD. Figure 1 displays clinical course since start of second line therapy.

Cord blood (CB) grafts were associated with a significantly lower chance of achieving remission of SR-aGvHD than bone marrow (BM) or peripheral blood stem cell (PBSC) grafts (HR 0.51, 95% CI 0.28-0.94, p = 0.032). Older age was associated with higher mortality: children aged 13.9-17.9 (fourth quartile) had a significantly higher hazard of death compared to children aged 0.175-3.01 (first quartile) (HR 2.64, 95% CI 1.05-6.63, p = 0.04). When modelling the interaction between age and graft source, we found that in BM/PBSC grafts older age was also significantly associated with lower remission rates (HR 0.89, 95% IC 0.83-0.96, p = 0.003). Underlying diagnosis, donor matching or choice of second line therapy were not associated with outcome.

Pulmonary manifestation of GvHD leading to respiratory insufficiency was an important cause of death in our cohort, accounting for 10/38 deaths (26%).

Table 1. Highlight of patient and treatment characteristics.

		N = 81
Age	Median (range)	8.9 (0.2-17.9)
Diagnosis	Hematologic malignancy	40 (49%)
	Inborn errors of immunity	16 (20%)
	Bone marrow failure	10 (12%)
	Other	15 (19%)
Second line therapy	Mesenchymal stromal cells	39 (48%)
	Infliximab/Etanercept	27 (33%)
	Basiliximab	4 (4.9%)
	Combination therapy	11 (14%)

 

Figure 1. Clinical course after start of second line therapy

Conclusions: Our study demonstrates that SR-GvHD confers a high mortality risk in pediatric HSCT. Older age and use of CB grafts are associated with an unfavorable outcome. Novel treatment strategies to prevent SR-GvHD and timely initiation of second line interventions are pivotal to further reduce GvHD-related mortality.

Disclosure: Nothing to declare

P167 Ruxolitinib as an effective and steroid-sparing first-line treatment in newly-diagnosed bos patients after hematopoietic stem cell transplantation

X. Zhang ¹, X. Zhao¹, S. Zhang¹, C. Liang¹, L. Zhang¹, M. Hao¹, J. Wei¹, R. Zhang¹, S. Feng¹, Y. He¹, E. Jiang¹, M. Han¹

¹Institute of Hematology and Blood Diseases Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, Tianjin, China

Background: Bronchiolitis obliterans syndrome (BOS) is a life-threatening pulmonary complication of chronic graft versus host disease (cGVHD) after allogeneic hematopoietic stem cell transplantation (HSCT). The classic first-line therapy of BOS is systemic steroids to prevent progression. However, patients with steroid-refractory BOS did not get a significant improvement in pulmonary function. Furthermore, long-term systemic steroids usage may cause serious complications such as infection. In this study, we retrospectively investigated the outcome of ruxolitinib as first-line therapy in treating newly-diagnosed BOS patients.

Methods: All patients who underwent an allogeneic HSCT for a hematological malignancy between January 2019 and June 2021 at the Institute of Hematology and Blood Diseases Hospital, CAMS and PUMC were retrospectively screened. BOS diagnosis uses the criteria of the National Institute of Health (NIH) consensus. Ruxolitinib therapy was begun with an initial dosage of 5 mg twice daily (BID), then a maintenance dosage of 10 mg. The dose of ruxolitinib could be reduced if severe adverse events occurred. Steroids and other immune-suppression agents were added according to the clinical situation. All patients received anti-fungus prophylaxis and FAM therapy in addition to the ruxolitinib therapy. Treatment response included both symptoms response (SR) and disease responses (DR). Symptom response (SR), which was evaluated in the first two weeks after ruxolitinib administration, was defined as relieving respiratory symptoms, elevated peripheral blood oxygen saturation (SpO₂ ≥ 96%), and significant improvements in CT scans. We evaluated ruxolitinib disease response (DR) in the 3^rd month. The ruxolitinib administration to DR was defined as CR (Complete Response) when clinical symptoms significantly alleviated and FEV1% pred (FEV 1% prediction) increased by more than 75%; partial response (PR) was defined by FEV1% pred levels increased or symptoms improved with stabilization of FEV1% pred. Nonresponse (NR) was defined by worsened clinical status and PFTs, or FEV1% pred decreased to less than 5% with stable symptoms.

Results:

We identified seven BOS patients. A median time of 300 days (ranged from 103 to 489 days) elapsed between the time of HSCT and diagnosis of BOS. Five patients were treated with steroids at the same time. The average initial daily dose of methylprednisolone was 48.4 milligrams per day (ranged from 6–80 milligrams). It is inspiring that all patients achieved SR within only two weeks after ruxolitinib therapy. Concerning disease response, six patients (85.7%) achieved CR, and one (14.3%) achieved PR (Figure 1). The mean FEV1% pred at diagnosis of BOS was 58.05%, and increased to 79.47% three months after ruxolitinib therapy, suggesting the therapy was effective. At the same time, the steroid dose was reduced to 50% of the initial dose in about two weeks (ranged from 7 to 16 days) and ended within two months of ruxolitinib treatment (ranging from 23 to 58 days).

Conclusions: All patients taking ruxolitinib as first-line therapy achieved remarkable responses with a CR rate of 85.7%. It is also noteworthy that ruxolitinib as first-line therapy in BOS could significantly shorten steroid therapy duration and reduce total steroid dose. Additionally, ruxolitinib was well tolerated, no severe infection or relapse was reported.

Disclosure: The authors declare no conflicts of interest.

P168 Impact of timing of cyclosporine-a administration in graft-versus-host-disease and patient outcomes in haploidentical hematopoietic stem cell transplantation

A. Banet ^1,2, N. Stocker^1,2, F. Malard^1,2, M. Labopin^1,2, E. Brissot^1,2, Z. Van de Wyngaert^1,2, V. Radici¹, A. Bonnin¹, M. Memoli¹, A. Genthon^1,2, O. Legrand^1,2, T. Leedra¹, R. Belhocine¹, S. Sestili¹, M. Mohty^1,2, R. Duléry^1,2

¹APHP, Hôpital Saint-Antoine, Service d’Hématologie Clinique et de Thérapie Cellulaire, Paris, France, ²Sorbonne Université, INSERM UMR 938, Centre de Recherche Saint-Antoine (CRSA), Paris, France

Background: In a haploidentical setting, graft-versus-host disease (GVHD) prophylaxis is now widely based on the combination of post-transplantation cyclophosphamide (PTCY), cyclosporine-A (CsA), and mycophenolate mofetil (MMF). It has been shown that high concentration of CsA in the first week after haploidentical hematopoietic cell transplantation (HCT) is associated with a reduced incidence of acute GVHD. However, the optimal timing of CsA initiation remains controversial. We performed a single-center retrospective study comparing the incidence of GVHD and patient outcomes after haploidentical HCT according to the timing of CsA initiation.

Methods: All consecutive adult patients undergoing haploidentical HCT from November 2013 to December 2020 were included according to the following criteria: (1) peripheral blood stem cell graft, (2) hematological malignancy, and (3) thiotepa-based conditioning regimen with a total thiotepa dose of 5 mg/kg. GVHD prophylaxis consisted of a combination of CsA, MMF, anti-thymocyte globulin (ATG, 2.5 to 5 mg/kg) and PTCY in all patients. CsA was either initiated at day – 3 before HCT (group 1, from November 2013 until July 2017) or the day after last administration of PTCY (group 2, from August 2017 until December 2020).

Results: The study included 131 patients (57 in group 1, 74 in group 2). The median age was 58 years (range, 15-74) and 78 (60%) patients were male. Patients in group 1 were younger (median age 53 versus 60 years, p = 0.007) and received a graft with a lower number of CD34 + cells (5.5x10⁶/kg versus 7.2x10⁶/kg, p = 0.015). The sequential conditioning regimen was the most used in group 1 (52.6%), whereas a reduced intensity conditioning was the most used in group 2 (47.3%) (p = 0.042). One hundred and twenty-six patients (96%) engrafted, with a median time for neutrophil recovery of 18 days (range, 9-30) in group 1 versus 17 days (range, 13-55) in group 2 (p = 0.016). At day + 180 after HCT, there was no difference in terms of incidence of grade II-IV acute GVHD (21% in group 1, 22% in group 2, p = 0.83) or grade III-IV acute GVHD (11% in group 1, 7% in group 2, p = 0.29) between the two groups. At 2 years, the incidence of chronic GVHD was also similar in both groups (32% in group 1, 21% in group 2, p = 0.21). With a median follow-up of 49 months (95% CI 48-59) for group 1 and 19 months (95% CI 15-27) for group 2, non-relapse mortality was 23% and 17%, relapse incidence 23% and 15 %, disease-free survival 56 % and 68%, overall survival 67% and 76%, GVHD-free, relapse-free survival 32% and 47% at 2 years in group 1 and group 2, respectively (p values are non-significant). In multivariable analysis, the timing of CsA initiation had no significant impact on survival outcomes and on the risk of acute or chronic GVHD.

Conclusions: These results suggest that in haploidentical HCT with peripheral blood stem cells, and GVHD prophylaxis combining CsA, MMF, ATG and PTCY, CsA can be initiated either at day-3 before HCT or the day after the last administration of PTCY, without impacting the risk of GVHD or survival outcomes.

Disclosure: nothing to declare

P169 Early results of phase i study of shr0302, a selective jak1 inhibitor, combined with prednisone in first-line treatment of cgvhd after allo-hsct

H. Qiu¹, J. Niu¹, X. Sun¹, H. Li², J. Yang¹, C. Huang¹, Y. Cai¹, K. Zhou¹, Y. Tong¹, L. Wan¹, X. Song ¹

¹Shanghai General Hospital, Shanghai, China, ²Jiangsu Hengrui pharmaceuticals Co., Ltd., Shanghai, China

Background: Chronic graft-versus-host-disease (cGVHD) is one of the major complications after allogeneic hematopoietic stem cell transplantation (allo-HSCT) with an incidence of 40% to 70%. cGVHD is also the common cause of late non-relapse-related death in patients undergoing allo-HSCT, and seriously affects their quality of life. SHR0302 is a Janus kinase (JAK) 1 selective inhibitor that has demonstrated efficacy in preclinical models of GVHD. Herein, we reported the safety and efficacy of SHR0302 in combination with prednisone as first-line therapy for newly diagnosed cGVHD after allo-HSCT.

Methods: This was a single-center, open-label, and phase I study. The study enrolled patients who had a confirmed diagnosis of first-episode moderate/severe cGVHD requiring systemic immunosuppressive therapy after allo-HSCT with an age limitation of 18-70. cGVHD was defined according to national institutes of health (NIH) criteria. Patients were treated with SHR0302 plus prednisone daily. For every patient, prednisone was administered at an initial dose of 1 mg/kg/d, and was tapered according to patient’s response after two weeks of treatment. Dose-escalation of SHR0302 was performed in a 3 + 3 design at doses of 1 mg/d, 2 mg/d, 4 mg/d, 6 mg/d, and 8 mg/d. Primary endpoints are safety and tolerability of SHR0302 and prednisone. Secondary endpoints include the overall response rate (ORR) at week 4 of treatment and the recommended Phase II dose (RP2D). Dose-limiting toxicities (DLTs) were defined as grade 4 hematologic toxicity or grade 3 non-hematologic toxicity related to SHR0302 that occurred in the first 28 days of study treatment.

Results: As of December 1^st, 2021, 15 patients were enrolled in 5 dose levels with 3 patients in every dose level. The median age was 48 (31-64) years, and the median follow-up was 17 (4 -59) weeks. 5 patients (33%) had moderate cGVHD, 10 patients (67%) had severe cGVHD, and the median cGVHD NIH score was 4 (3-7). As of data cutoff, only 1 patient (7%) had discontinued therapy due to lack of efficacy.

Only one DLT, grade 4 hypercholesterolemia, was observed among 3 patients who received 8 mg/d of SHR0302. The patient who experienced DLT had preexisting hypercholesterolemia. 3 additional patients would be enrolled to receive 8 mg/d of SHR0302 plus prednisone to determine the maximum tolerated dose. 14 patients experienced adverse events (AEs) related to SHR0302 (93%), and 2 patients experienced grade ≥3 AEs related to SHR0302 (13%). The most common SHR0302-related AEs included hypercholesterolemia (67%), hypertriglyceridemia (33%) and platelet count decreased (27%). No SHR0302-related serious adverse event occurred.

At 4 weeks after being treated with SHR0302 and prednisone, 3 patients (20%) achieved complete response, and 11 patients (73%) achieved partial response among 15 evaluable patients. The ORR at week 4 was 93%, just 1 patient showed no response to treatment.

Conclusions: In summary, SHR0302 plus prednisone was well tolerated and demonstrated encouraging efficacy in patients with steroid-naive cGVHD, warranting continued clinical investigations.

Clinical Trial Registry: NCT04146207

Disclosure: Nothing to declare.

P171 Clinical and economic burden associated with graft-versus-host disease (GVHD) following allogeneic hematopoietic cell transplantation (allo-hsct) in france

D. Michonneau ¹, N. Quignot², H. Jiang², D. Reichenbach³, M. Kelly⁴, A. Burrell⁵, X. Zhang³, K. Thiruvillakkat³, M. Mohty⁶

¹Hospital Saint-Louis, Paris, France, ²Certara France, Paris, France, ³CSL Behring, King of Prussia, United States, ⁴CSL Behring, West Sussex, United Kingdom, ⁵Anita Burrell Consulting, Flemington, United States, ⁶Hospital Saint-Antoine, Paris, France

Background: There is a need for new therapies to prevent and treat GvHD following allo-HSCT; however, contemporary evidence on the burden of the disease in France is not available. This study aimed to investigate the clinical outcomes, healthcare resource utilization (HCRU), and costs associated with GvHD in France, by type – acute (aGvHD), chronic (cGvHD), or both (a + cGvHD).

Methods: A nationwide cohort study using administrative claims from the French Health Insurance database, SNDS, identified 6385 adult patients who received allo-HSCT for hematologic malignancies between January 2012 and December 2018. Relapse was explored using re-admission diagnoses and treatments. Propensity score matching was undertaken to compare patients who developed GvHD (by type) vs patients who did not develop GvHD (‘noGvHD’) for occurrence of severe infection during follow-up (defined using hospital discharge diagnosis codes), all-cause death, HCRU, and costs.

Results: The mean age of the cohort was 51.1 years; 58% were male; 2668 (42%) patients had no recorded diagnosis code for GvHD, 2002 (31%) experienced an aGvHD episode, 411 (7%) had cGvHD, and 1304 (20%) had a+cGvHD. Patients with GvHD had slightly lower rates of relapse, with 276 (14%), 61 (15%), and 220 (17%) patients with evidence of relapse in the aGvHD, cGvHD and a+cGvHD subgroups, respectively, vs 486 (18%) patients in the noGvHD subgroup. For comparisons, 1934, 408, and 1268 matched pairs were retained for the aGvHD, cGvHD and a+cGvHD subgroups, respectively. Patients with aGvHD and a+cGvHD had an increased rate of hospitalization for severe infection, with a rate ratio (RR) (95% CI) of 1.32 (1.23-1.41) and 1.14 (1.05-1.24), respectively vs noGvHD; rate of severe infection was similar for patients with cGvHD vs without GvHD. Patients with aGvHD had an increased mortality rate, (RR [95% CI], 1.55 [1.41-1.70] vs noGvHD); mortality rate was slightly higher (although not statistically significant) for a+cGvHD vs noGvHD and similar between patients with cGvHD and those without GvHD. Patients with aGvHD and a+cGvHD had significantly more overnight hospitalizations per patient-year (mean rates: 4.3 vs 3.3 and 4.2 vs 3.2 admissions, respectively; p < 0.001) than those without GvHD. Total direct costs (including hospitalizations, outpatient visits, drugs dispensed) were 1.18, 1.53, and 1.89 times higher (p < 0.001) for patients with aGvHD, cGvHD, and a+cGvHD, respectively, vs noGvHD. Inpatient care (including drugs dispensed during hospitalization) cost was the primary driver of increased HCRU and costs.

Conclusions: GvHD was associated with significant clinical and economic burden post-allo-HSCT. Patients with GvHD, and in particular, patients with aGvHD and a+cGvHD, had a higher rate of infection and higher mortality. This clinical burden translated into increased HCRU and costs, with patients with aGvHD, cGvHD, and a+cGvHD having a statistically significant higher total direct cost vs noGvHD patients. There is a continued need for effective prophylaxis and treatment options for GvHD, which could prevent clinical burden for patients, as well as the increased cost of allo-HSCT due to GvHD.

Disclosure: David Michonneau reports consultancy for Novartis and Incyte, and honoraria from Jazz Pharmaceuticals.

Nadia Quignot reports consulting fees paid to Certara contracted with CSL for implementing the analyses.

Heng Jiang reports consulting fees paid to Certara contracted with CSL for implementing the analyses, and stock ownership from Certara.

Dawn Reichenbach reports employment and stock options from CSL Behring.

Maebh Kelly reports employment from CSL Behring.

Anita Burrell reports consultancy for CSL Behring and Neumentum

Xiang Zhang reports employment from CSL Behring.

Kris Thiruvillakkat reports employment, stock options and salary from CSL Behring.

Mohamad Mohty reports honoraria from Adaptive Biotechnologies, Amgen, Astellas, BMS, Celgene, Gilead, GSK, Janssen, Novartis, Oncopeptides, Pfizer, Sanofi, and Takeda; and research funding from Celgene, Janssen, and Sanofi.

P173 Incidence and risk factors for hyponatremia induced by post-transplant cyclophosphamide in allogeneic hematopoietic cell transplantation

M. Gómez Hernando ¹, A. Pedraza¹, L. Quintana², E. Carcelero³, G. Riu³, I. Monge³, A. Domenech¹, M.T. Solano¹, M. Suárez-Lledo¹, N. Martinez-Cibrian¹, L. Rosiñol¹, G. Gutiérrez-Garcia¹, E. Carreras⁴, J. Esteve¹, A. Urbano-Ispizua¹, F. Fernández Avilés¹, C. Martínez¹, M. Rovira¹, M.Q. Salas¹

¹Institute of Hematology and Oncology, Hospital Clinic de Barcelona, IDIBAPS, Barcelona, Spain, ²Institute of Nephrology and Urology, Hospital Clinic de Barcelona, IDIBAPS, Barcelona, Spain, ³Pharmacology Unit, Hospital Clinic de Barcelona, IDIBAPS, Barcelona, Spain, ⁴Fundació Josep Carreras, Barcelona, Spain

Background: The use of post-transplant cyclophosphamide (PTCY) is becoming prevalent in alloHCT due to it efficacy for GVHD prevention. Intravenous cyclophosphamide-associated hyponatremia is an uncommon adverse effect attributed to an indirect inappropriate antidiuretic hormone release followed with a reduction in the ability of the kidney to excrete water. This study investigates the incidence and risk factors for hyponatremia in adults undergoing PTCY-based alloHCT.

Methods: Between January 2018 and December 2020, 90 adults with hematological disorders underwent first alloHCT combined with PTCY-based GVHD prophylaxis at our Institution. Intravenous PTCY was administered at a dose of 50 mg/kg/day IV on day +3 and +4 at 9 am and followed by tacrolimus from day +5, alone; for matched related and unrelated donor alloHCT (n = 79, 87.8%), and combined with tacrolimus and mycophenolate when haploidentical donors were selected (n = 11, 12.2%). Patients received intravenous fluid therapy with glucosaline 5% 1L/8h and bicarbonate 1/6M 500ml/12h from day +2 to +4. Following our standard Institutional protocols, sodium level was routinely monitored two hours before and 12 hours after every dose of cyclophosphamide.

Hyponatremia was defined as plasma sodium levels < 135 mEq/L), and severe hyponatremia was defined as plasma sodium levels < 125 mEq/L). Data was collected retrospectively and updated in November 2021. Risk factors for hyponatremia were explored using Regression Logistics Models.

Results: Overall, the median age was 51 years, 40 (44.4%) patients were females, and 49 (54.4%) underwent MAC alloHCT. Hyponatremia was diagnosed in 80% of patients, and in 5.6% of the cases was severe. The majority of episodes were diagnosed 12h after the first dose of cyclophosphamide (73.3%). Four patients (4.4%) had symptomatic hyponatremia, and in all these cases the sodium levels were inferior to 125 mEq/L.

Forty-one (45.6%) patients required specific treatment: all were started on oral sodium supplementation or fluid therapy with glucosaline 5% was replaced by normal saline. Hypertonic serum supplementation was given for symptomatic severe hyponatremia. The second dose of PTCY had to be reduced to 40 mg/kg in 1 patient and delayed in an additional one. Out of the overall 72 patients presenting with hyponatremia following PTCY, 57 (79.2%) successfully recovered in a median of 2 days from diagnosis. Hyponatremia did not result in non-reversible sequelae in any patient. Higher doses of cyclophosphamide (>5000mg and >7000 mg) were not associated with higher rates of hyponatremia (p = 0.32 and p = 0.346, respectively). Patient’s age (>60 years) (p = 0.205), sex (p = 0.0.601) and the conditioning regimen intensity (p = 0.249) were not found to be predictors for hyponatremia.

Conclusions: This study reports for the first time the incidence of hyponatremia after PTCY administered for GVHD prevention. Hyponatremia was found to be a prevalent adverse effect after PTCY infusion, although the incidence of symptomatic hyponatremia was low.

Based on these results, sodium levels after PTCY infusion should be carefully monitored, and hyperhydration using intravenous normal saline may be prioritized to decrease the rates of this complication.

Disclosure: No conflict of interest to disclose.

P174 Host versus graft HLA-dpb1 mismatches promote clinical graft versus host disease

C. Wright ¹, G. Reid¹, C. Lendrem¹, L. Duncan², R. Luke², E. Hurst², A. Publicover¹, V. Bigley¹, M. Collin¹

¹Newcastle University, Newcastle upon Tyne, United Kingdom, ²Northern Centre for Bone Marrow Transplantation, Newcastle upon Tyne, United Kingdom

Background: HLA matching is crucial to donor selection in allo-HSCT. HLA-DPB1 mismatches between donor and recipient are known to increase GVHD and can be unidirectional in the Graft-versus-Host or Host-versus-Graft direction. Recent data highlight the potential of host resident T-cells to cause cutaneous inflammation in xenograft models. In this study we sought to determine whether unidirectional HVG mismatches could cause clinical manifestations of GVHD.

Methods: 183 patients transplanted at a single UK centre between 2013 and 2018 with 10/10 matched unrelated donor (MUD) PBSC transplants for malignant and non-malignant conditions were retrospectively scored for DP mismatch permissivity and directionality using the T-cell epitope (TCE) algorithm (https://www.ebi.ac.uk/ipd/imgt/hla/dpb.html), and compared with 71 12/12 sibling donor transplants (Sib) for onset of any acute-type GVHD within 6 months of transplant including classic acute, late onset and acute/chronic overlap. Conditioning regimens included MAC (n = 4), RIC (n = 175), Kroger (n = 15), FLAMSA (n = 38) and Seattle (n = 22) protocols. T cell depletion strategies included alemtuzumab (n = 180), ATG (n = 48) and T-replete (n = 26). Cumulative incidence of GVHD by DP mismatch status was adjusted for death from any cause as a competing risk. A multivariate regression was performed controlling for age, diagnosis, T-cell depletion, conditioning protocol and CMV status.

Results: With death from any cause as a competing risk, there was a significant difference in GVHD incidence according to DP mismatch group (p < 0.001) (Figure). Multivariable hazard ratios were calculated demonstrating 12/12 MUD and 12/12 sibling transplants had the lowest GVHD incidence, then permissive DP mismatch, then non-permissive HVG with the highest incidence of GVHD in the non-permissive GVH group (Table). 12/12 MUD transplants demonstrated no significant increase in GVHD incidence compared to 12/12 sibling transplants. 6 month overall survival was adverse for HVG HLA-DPB1 mismatches compared to the other groups (p < 0.05). The only co-variate predicting GVHD by multivariate competing risks regression was the permissivity and directionality of DP mismatch (p = 3.2x10^-9), with age, diagnosis, T-cell depletion, conditioning protocol and CMV risk group failing to reach significance. The maximal grade of GVHD reached in the HVG group was grade I in 40% and grade II in 60%, with no grade III or above GVHD in the HVG group.

DP mismatch status	Multivariable Hazard Ratio GVHD (95%CI)	p
12/12 MUD (n = 41)	Reference	NA
12/12 Sib (n = 71)	1.53 (0.85-2.8)	0.16
Permissive (n = 76)	2.42 (1.36-4.3)	<0.01
Non-permissive HVG (n = 23)	3.88 (1.88-8.0)	<0.001
Non permissive GVH (n = 43)	6.41 (3.52-11.7)	<0.001

Conclusions: These data show that DP mismatching is the major cause of excess GVHD in patients receiving unrelated donor transplants in this cohort with mostly T-depleted transplant regimens. The surprising observation that HVG DPB1 mismatches are associated with a higher risk of GVHD supports recent findings that host resident T-cells may play a role in GVHD pathogenesis. The role of HVG reactions in the pathogenesis of GVHD or as a separate entity which is indistinguishable from clinical GVHD, requires further elucidation.

Disclosure: Nothing to declare

P176 The use of vedolizumab as second-line therapy for steroid-refractory gastrointestinal acute graft-versus host disease in children

G. Bronin ¹, M. Zhuravel¹, A. Lifshits¹, G. Seregin¹, E. Zhuravel¹, B. Kurmanov¹, I. Taishikhina¹, E. Burtsev¹, E. Kumirova¹, M. Maschan^1,2

¹Morozov Children’s Hospital, Moscow, Russian Federation, ²Dmitriy Rogachev National Medical Researh Center of Pediatric Hematology, Oncology and Immunology, Moscow, Russian Federation

Background: The gastrointestinal (GI) graft-versus host disease (GVHD) remains to be challenging and life-threatening complication of hematopoietic stem cell transplantation (HSCT) in children. Steroid based treatment of this condition remains a universal standard first-line therapy. Despite authorization of new agents for second-line therapy, steroid refractory GI GVHD awaits safer and more effective therapeutic approach.

Methods: Clinical and laboratory data from 9 children (5 boys and 4 girls) aged from 1 to 17 years treated with anti-α4β7 integrin monoclonal antibody (vedolizumab) for severe (grade 3-4) steroid-refractory GI GVHD were analyzed. The diagnosis of GVHD was proven by biopsy in all cases. The patients and their parents gave informed consent for the off-label use of the medication and publication of the results.

Results: The indications for HSCT were acute lymphoblastic leukemia (ALL) in 3 cases, acute myeloid leukemia in 4 cases, Diamond–Blackfan anemia (DBA) in 1 case and metachromatic leukodystrophy (MLD) in 1 case. HSCT from haploidentical family donors (haplo) were performed in all 7 cases of leukemia and HSCT from matched unrelated donor (MUD) were performed in DBA and MLD cases. Source of HSC were PBSC in cases of haplo and BM in cases of MUD. In all cases posttransplant cyclophosphamide (PtCy) on days+3, +4 at 50 mg/m²/day, CNI and MMF with unmanipulated HSCs was used as GVHD prevention approach. Grade III-IV GI GVHD occurred between day +25 to day +320 (median time day +100). In 5 cases we used vedolizumab as a third line therapy after unsuccessful treatment with methylprednisone and ruxolitinib, and in 4 cases we started vedolizumab as a fourth line therapy (after methylprednisone, ruxolitinib and tumor necrosis factor inhibitors). Median time of start of vedolizumab therapy was 14 days after manifestation of GI GVHD. In all cases we continued ruxolitinib course and performed withdrawal of steroids with slow gradual dose reduction during vedolizumab treatment. In 2 cases we combined the course of anti-α4β7 integrin antibodies and extracorporeal photopheresis. We use vedolizumab as intravenous infusion 6 mg/kg and repeated this dose weekly until resolution of GI GVHD symptoms. The number of injections varied from 1 to 4. Four patients received 2 injections, 3 patients -3, 1 patient – 1 and 1 – 4 injections. The median time of response was 33 days after start of vedolizumab treatment. Eight patients survived with complete resolution of GI GVHD symptoms. Six of them during vedolizumab treatment and two demanded additional lines of immunosuppressive drugs after discontinuation of vedolizumab. One patient died from GI GVHD associated complications. We did not see any significant side effects of vedolizumab in any case, but it was quite difficult to assess in this heavily pretreated group of patients.

Conclusions: Targeted approach to the treatment of steroid-refractory grade 3-4 GI GVHD with the use of anti-α4β7 integrin monoclonal antibody (vedolizumab) can be promising curative option in pediatric HSCT patients. Further prospective evaluation of this approach is clearly warranted.

Disclosure: Nothing to declare

P177 Predictive value of st2, reg3a and magic algorithm in survival and complications related to haploidentical transplantation with post-trasplant cyclophosphamide: Single center experience

M. Fonseca Santos ¹, M. Garcia Alvarez^1,2, L.A. Corchete Sanchez^1,2, M. Salinero¹, A. Rodriguez Rodriguez¹, D. Alonso Castronuño¹, E. Alejo Alonso¹, J.M. Navarro Garcia¹, A. Hernandez Sanchez¹, A.A. Martin¹, A. Avendaño Pita¹, M. Baile Gonzalez¹, A. Cabero Martinez¹, E. Perez Lopez¹, M. Cabrero Calvo¹, R. Garcia-Sanz¹, F. Sanchez-Guijo Martin^2,1, L. Vazquez Lopez¹, M.D. Caballero Barrigon^1,2, M. Alcoceba^2,1, L. Lopez Corral^2,1

¹Hospital Universitario de Salamanca, Salamanca, Spain, ²CIBERONC, Madrid, Spain

Background: Recent studies describe protein biomarkers in peripheral blood associated to allogeneic-stem-cell transplantation (allo-SCT) outcomes. To date, two studies have focused on haploidentical allo-SCT with post-transplant cyclophosphamide (haplo-SCT). These works evaluate two and seven biomarkers - including ST2 and REG3α- in limited time-points (days + 15 and +30) but do not include the analysis of the MAGIC algorithm, validated with the combination of these 2 biomarkers as a predictor of higher Non Relapse Mortality (NRM).

We are analysing ST2, REG3a and MAGIC algorithm early weekly after haplo-SCT and its association with Graft-versus-host disease (GVHD) and transplant outcomes.

Methods: Prospective study with 151 consecutive patients who underwent haplo-SCT at University Hospital of Salamanca (2012-2020). The panel was analysed in serial serum samples collected on days 0, +3, +7, +14 and +21 in 81 patients.

ST2 and REG3α serum concentration was established by Lumynex X-MAP, comparing the median luminescence levels between groups using Wilcoxon-Mann-Whitney test. Cut-off points for each cytokine were estimated using Cutoff-Finder application in R. MAGIC algorithm was determined from the ST2 and REG3α values considering a threshold of =0.16. Log-rank was used to compare survival curves. Multivariable analyses were carried out with Cox regression, including the most significant clinical variables.

Results: Patients’ and transplant characteristics are shown in table 1:

Characteristics	n (%)
Recipient/donor age; median (range)	50 (16-73)/39 (14-75)
Recipient/donor male sex	85 (56)/85 (56)
Male receptor/Female donor	37 (24)
Hematological disease
AML / MDS	63 (42)/19 (13)
HL / NHL	22 (15)/24 (16)
ALL	9 (6)
CMML	5 (3)
Others	4 (5)
Previous treatments ≥2	93 (61)
Previous autologous transplantation	35 (23)
Previous allogenic transplantation	13 (8)
Disease risk index ≥ high and very high	27 (18)
Sorror, n (%) >3	44 (29)
Conditioning
Myeloablative	35 (23)
Flu (150mg/m2) + Bu (9,6mg/Kg) + Thio (10mg/Kg)	29 (19)
Flu(150mg/m2)+Bu (9,6 mg/kg) + Cy(29mg/kg)	6 (4)
Reduced intensity	112 (73)
Flu (150 mg/m2) + Bu (3,2 ó 6,4mg/Kg) + Cy (29mg/Kg)	99 (65)
Flu (150 mg/m2) + TBI (2Gy) + Cy (29 mg/kg)	5 (3)
Flu(150mg/m2)+Bu(6,4mg/kg)+Thio(10mg/kg)	8 (5)
Sequential	5 (4)
GVHD prophylaxis
Tacro + MMF + Cy	148 (98)
CsA + MMF + Cy	3 (2)
CD34 + x108 infused dose, median (range)	6,26 (2.59-9,34)
Graft source: Peripheral blood	148 (98)
Median follow up months, n (range)	35 (9-87)
Overall Survival (OS) 2 years	66%
PFS 2 years	60%
NRM day 100 / 1 year	14% / 24%
Cumulative incidence of aGVHD II-IV day 180	57%
Cumulative incidence of aGVHD III-IV day 180	13%
GRFS (Graft versus host-free relapse-free survival) 2 years	49%

Table 1. Patients’ and transplant characteristics

Higher levels of ST2 were associated with aGVHD (II-IV day +21, III-IV day +14), higher NRM 1-year (+0, +7, +14), lower OS 2-years (+7, +14) and GRFS 2-years (+14, +21). Higher levels of REG3α were associated with aGVHD III-IV ( + 14), higher NRM 1-year (0, 7, 14, 21), lower OS 2-years (0, +7, +14, +21) and lower GRFS-2y (+14). Similarly, the inclusion of MAGIC algorithm in multivariate analysis, distinguished two statistically significant risk groups for GRFS ( + 14), OS (0, +14) and NRM 1-year (0, +14) (Image 1). OS was independently associated with HCT-CI ≥ 3, ST2 (0, +7, 14, +21) and REG3α (0, +14, +21) levels, NRM with ST2 (0, +14), REG3α (14) levels and HCT-CI ≥ 3. ST2 ( + 7, +14, +21) REG3α ( +14) levels and HCT-CI ≥ 3 were the only variables independently associated to GRFS.

Multivariate analysis with the MAGIC algorithm revealed and independent association to GRFS ( +14) and OS (0, +14) together with HCT-CI ≥ 3.

Conclusions: These results confirm the prognostic role of ST2, REG3α and MAGIC algorithm in haplo-SCT outcomes in the largest single-centre cohort to date of a homogeneous series of haplo-SCT. We also demonstrate, for the first time, the MAGIC algorithm prognostic impact in haplo-SCT on day +14.

Standarization in prospective and larger series is required before its incorporation into the clinical practice.

Disclosure: Nothing to declare

P178 Pancreatic atrophy and recovery after allogeneic hematopoietic cell transplantation: Predictive factors and prognosis

Y. Okada ¹, H. Nakasone¹, Y. Nakamura¹, M. Kawamura¹, S. Kawamura¹, J. Takeshita¹, N. Yoshino¹, Y. Misaki¹, K. Yoshimura¹, S. Matsumi¹, A. Gomyo¹, A. Tanihara¹, M. Tamaki¹, M. Kusuda¹, K. Kameda¹, S.-i. Kimura¹, S. Kako¹, Y. Kanda¹

¹Jichi Medical University Saitama Medical Center, Saitama, Japan

Background: Pancreatic atrophy after allogeneic hematopoietic cell transplantation (HCT) is one of symptoms associated with chronic graft-versus-host disease (GVHD). Although pancreatic atrophy has been considered to cause exocrine insufficiency and weight loss, it remains to be elucidated what kind of recipients could recover their body weight (BW) or pancreatic thickness. In addition, the prognostic effect of pancreatic atrophy has not been clarified.

Methods: We retrospectively analyzed 171 recipients who received allogeneic bone marrow transplantation or peripheral blood stem cell transplantation at Jichi Medical University Saitama Medical Center between January 2008 and December 2018. The measurement of pancreas was performed every year after their transplantation if the recipients received CT scan. Pancreatic thickness was defined as a sum of the widths which were perpendicular lines to the long axis of pancreas in the following three regions of pancreas: the head, body, and tail of pancreas. We evaluated them using the closest CT scan images to the time-points of 1, 2, 3, and 4 years after HCT. Pancreatic atrophy was defined as 20% or more loss of thickness.

Results: Fifty-five recipients demonstrated pancreatic atrophy after HCT. While the BW of the recipients without pancreatic atrophy recovered gradually (P < 0.001), those with atrophy did not show that trend (P = 0.12) by linear mixed models. The 3-year simple cumulative incidence of pancreatic atrophy was 31.3%, while the 3-year current cumulative incidence of pancreatic atrophy, treating pancreatic atrophy as a reversible event, was 15.9%. Moderate and severe chronic GVHD tended to be slightly higher in the atrophy group (47.3% vs 37.9%), whereas these recipients tended to show the recovery of pancreatic thickness (30.8% vs 10.3%). HCT from female donor to male recipient showed superior pancreatic recovery than other donor and recipient sex combination. Although their pancreatic thickness seemed comparable between the recipients who continued and stopped immunosuppressant (IST) at one year (P = 0.87) and 2 years (P = 0.11) after HCT, that tended to decrease at 3 years (P = 0.064), and finally, the difference became significant at 4 years (P = 0.027).Pancreatic atrophy treated as a time-dependent covariate was significantly associated with inferior overall survival (OS) (HR 4.85, P < 0.001) and an increased risk of non-relapse mortality (NRM) (HR 5.38, P < 0.001), while it was not associated with disease relapse (HR 1.45, P = 0.47).

Conclusions: The recipients with pancreatic atrophy did not tend to recover their BW after HCT, and those who could stop IST demonstrated the recovery of pancreatic thickness. Moderate and severe chronic GVHD was associated with both pancreatic atrophy and recovery, which indicated that pancreatic atrophy might be mainly developed as a manifestation of chronic GVHD and could be reversible if the allogeneic response was controlled. Moreover, pancreatic atrophy was significantly associated with an increased risk of NRM, leading to inferior OS. These results suggest the importance of monitoring pancreatic thickness after HCT. Further prospective investigations are warranted to clarify the significance of pancreatic atrophy on clinical outcomes.

Disclosure: Nothing to declare.

P179 Safety of home care in patients with previous autologous stem cell transplant pursuing allogeneic stem cell transplantation

M. Garcia-Recio ¹, A.C. Pedraza¹, C. Jimenez-Vicente¹, A. Martinez-Roca¹, C. Gallego¹, P. Ayora¹, T. Solano¹, M. Suárez-Lledó¹, L.G. Rodriguez-Lobato^1,2, C. Martínez¹, L. Rosiñol¹, M.Q. Salas¹, M. Rovira¹, G. Gutierrez-García¹, F. Fernandez-Avilés¹

¹Hospital Clinic of Barcelona, Barcelona, Spain, ²Institut d’Investigacions Biomèdiques August Pi I Sunyer (IDIBAPS), Barcelona, Spain

Background: Home care has been associated with fewer infections, decreased acute GVHD, TRM, and improved survival in patients receiving allogeneic SCT (allo-SCT) (Gutiérrez-García et al., 2020; Svahn et al., 2008). The effect of previous autologous SCT (ASCT) on those advantages is unknown. We analyzed outcomes of home-cared allo-SCT patients with prior ASCT.

Methods: Since 2015, consecutive adult patients with hematological malignancies undergoing at-home allo-SCT with prior ASCT were included and classified considering GVHD prophylaxis: post-transplant cyclophosphamide (PTCy) (group 1) or tacrolimus plus mofetil mycophenolate (TK/MMF) (group 2). Groups 3 and 4 included matched hospitalized patients to groups 1 and 2, respectively.

Results: Since 2015, 56 patients pursued home-cared allo-SCT in our center and, of those, 15 had previously received an ASCT. Baseline characteristics were comparable between home-cared and the respective matched hospitalized series (table 1). Median follow-up was 1.4 years (0.6-3.3). Similar mucositis, renal failure, and haemorrhagic cystitis incidence and grade distribution were observed across the 4 groups. Home care did not provide benefit in neutropenic fever, pathogen detection, multidrug-resistant microorganisms, aspergillosis, or viral reactivation. Similar time to engraftment and length of stay were observed between matched at-home and inpatient groups. Graft rejection was not observed. Acute and chronic GVHD incidence and grade distribution were homogeneous except for comparisons between groups 2 and 4 (grade 3-4 acute GVHD cumulative incidence of 0% vs 40%, q = 0.003) (figure 1). No differences in relapse, TRM, PFS, or OS were observed.

Table 1. Patient characteristics.

	At-home PTCy	At-home non-PTCy	In-patient PTCy	Inpatient non-PTCy	2-sided p value
Patients (n)	7	8	6	5
Age (years)	31 (25-60)	53 (29-64)	45 (23-59)	50 (42-57)	0.58
Median HCT-CI	2 (0-4)	3 (0-4)	3 (0-3)	2 (0-3)	0.19
Diagnosis					0.99
AML/MDS	0 (0%)	1 (12.5%)	0 (0%)	1 (20%)
Lymphoma	6 (85.7%)	5 (62.5%)	5 (83.3%)	2 (40%)
MM	1 (14.3%)	2 (25%)	1 (16.7%)	2 (40%)
Donor					0.414
*Related	4 (57.1%)	5 (62.5%)	4 (66.7%)	1 (20%)
*Unrelated	3 (42.9%)	3 (37.5%)	2 (33.3%)	4 (80%)
HLA compatibility
*Identical	3 (42.9%)	8 (100%)	2 (33.3%)	5 (100%)	0.011
*Mismatched 7/8	1 (14.3%)	0 (0%)	1 (16.7%)	0 (0%)
*Haploidentical	3 (42.9%)	0 (0%)	3 (50%)	0 (0%)
CMV risk					0.93
Low	2 (28.6%)	3 (37.5%)	2 (33.3%)	1 (20%)
Intermediate	4 (57.1%)	4 (50%)	3 (50%)	3 (60%)
High	1 (14.3%)	1 (12.5%)	1 (16.7%)	1 (20%)
Conditioning regimen intensity
*MAC	0 (0%)	3 (37.5%)	1 (16.7%)	1 (20%)	0.35

¹Differences only observed between unmatched groups.

^oConsidering sample size, medians are given with their respective minimum and maximum values.

Figure 1. Cumulative probability of grade 3-4 acute GVHD for home-cared patients vs. controls.

Conclusions: Patients with previous ASCT can safely receive an allo-SCT in home care units regardless GVHD prophylaxis and without negative effect on toxicity or survival. Benefit in grade 3-4 acute GVHD incidence was observed in home-cared patients receiving TK/MMF compared with matched hospitalized patients. Other characteristic benefits associated with home care were not detected.

Disclosure: M.G.R. received honoraria from Janssen and Takeda. L.G.R.L. received honoraria from Janssen and travel grants from Janssen and Amgen. A.C.P., C.J.V, A.M.R., C.G., P.A., T.S., M.S.L., C.M., L.R., M.Q.S., M. R., G.G.G. and F.F.A. have nothing to declare.

P180 The ATG dose and tlc don’t impact on the development of GVHD and viral reactivations in patients undergoing cd34+ selected allogeneic hematopoietic cell transplantation

Á. Sánchez Cayuela ¹, V. Navarro², E. Roldan Galvan¹, M.L. Fox¹, O. Salamero García¹, I. Ruiz Camps³, A. Pérez González¹, P. Barba Suñol¹, F. Bosch Albareda¹, D. Valcárcel Ferreiras¹, G. Ortí Pascual¹

¹Vall d’Hebron University Hospital, Barcelona, Spain, ²Oncology Data Science Group, Vall d’Hebron Institute of Oncology, Barcelona, Spain, ³Vall d’Hebron University Hospital, Barcelona, Spain

Background: A baseline total lymphocyte count (TLC) has been reported to correlate with the development of graft-versus-host disease (GvHD) in patients undergoing T-cell depleted (TCD) allogeneic hematopoietic cell transplant (allo-HCT) using antithymocyte globulin (ATG). We aimed to study the role of TLC and ATG on the development of GvHD and viral reactivations (VR) in patients undergoing ex vivo CD34 + selected allo-HCT.

Methods: We retrospectively analyzed data of patients undergoing a CD34 + selected allo-HCT between 2016 and 2021 at our institution. All patients signed a written inform consent. The CD34 + selection allo-HCT platform consisted on ex vivo CD34 + selection plus in vivo TCD with ATG 2.5 mg/Kg/day (2 days in HLA matched donors and 3 days in HLA mismatch donors). Primary endpoint was to study the association of the ATG dose and TLC with the development of acute GvHD (aGvHD) and VR. Secondary endpoints were NRM, RI, PFS and OS. Prognostic variables were: age, conditioning regimen, ATG, TLC, type of donor, disease diagnosis, disease status, HCT-CI, VR (CMV, Adenovirus and EBV), CD3 + , CD19 + and CD16 + CD56 + (NK) cells and CMV status. Associations between ATG, TLC with the number of VR and GvHD were calculated using the logistic model. Survival outcomes were calculated using Kaplan Meier method. The Proportional Hazards model was used to calculate HR and risk associations. We used R-software 4.1.1 for statistical analysis.

Results: A total of 51 patients were included, with complete data in 39 patients. The median follow up was 32.9 months (range, 20.2-42.3). The median dose of ATG per patient was 154.5 mg (range 121.5 – 189) and the mean of the TLC at allo-HCT was 161.5x10^6/L (SD ± 420.16).The cumulative incidence of aGvHD at 100 days was 15.8% (CI95%, 5.1%-25.2%).

We did not observe any associations between the ATG dose and the TLC with GvHD. Interestingly, we observed a trend towards an increased risk of adenoviremia in those patients with higher ATG exposure (p = 0.07). Nevertheless, we did not observe any further association between ATG, TLC with the number of viral reactivations.

The 2-year NRM was 26% (CI95%, 12%-37.7%), the 2-year RI was 22.5% (CI95%, 6.1%-36.1%), the 2-year PFS was 59.1% (CI95% 46.7%-74.8%) and the 2-year OS was 60.5% (CI95%, 48% -76.3%). RIC (p = 0.008) and older patient’s age (p = 0.031) were associated with higher NRM. In contrast, a lower NK cell count at 3 months was associated with lower NRM (p = 0.004). RIC allo-HCT was associated with lower OS (p = 0.005). In MVA, a lower NK cell count at 3 months was associated with lower NRM (HR = 0, CI95% 0-0,21, p = 0.030) and RIC was associated with lower OS (HR = 8.57, CI95% 1.6 - 45.78, p = 0.012). RI and PFS MVA did not identify any prognostic variables.

Conclusions: In this homogeneous cohort of CD34 + selected allo-HCT, ATG and TLC were not associated with GvHD or VR. However, the use of a RIC was associated with a lower OS. Further studies with a larger number of patients are warranted.

Disclosure: Guillermo Ortí Pascual: BMS, Incyte, Novartis, Pfizer.

P181 HLA molecular mismatch and its implication in the alloresponse and outcomes after hematopoietic stem cell transplantation

M. Gómez Hernando ¹, J. Torres Canizales², C. Arnaldos-Pérez², J.L. Caro², C. Serra², E. Palou², M.Q. Salas¹, A. Pedraza¹, M. Rovira¹, C. Martínez Muñoz¹

¹Hematopoietic Stem Cell Transplantation Unit, Hospital Clínic de Barcelona, IDIBAPS, Barcelona, Spain, ²Hospital Clínic de Barcelona, Barcelona, Spain

Background: Higher HLA mismatch has been associated with worse clinical outcomes in the context of allogeneic stem cell transplantation (alloSCT). Traditionally, HLA disparity has been evaluated at the allele level. Recent in silico tools (PIRCHE and HLA-EMMA) are capable of assessing molecular mismatch (MM) differences. PIRCHE can predict the number of peptides presented by HLA molecules. On the other hand, HLA-EMMA compares HLA polymorphic amino acids between mismatches exposed on the surface of an HLA molecule. However, in the alloSCT the association of MM according to these tools and clinical outcomes has not been extensively investigated so far. The aim of this study is to analyze the relation between MM graft-versus-host disease (GvHD), relapse and early immune reconstitution.

Methods: We conducted a retrospective analysis of patients who underwent alloSCT in our center between 2018 and 2020 comparing those who received HLA-identical with HLA mismatched transplants from both related and unrelated donors . High resolution HLA typing was used to analyzed HLA genes and MM was evaluated with both PIRCHE and HLA-EMMA softwares in GvH and host-versus-graft (HvG) directions. PIRCHE and HLA-EMMA scores were divided in low or high categories according to the analysis of receiver operating characteristic (ROC) curves. The data of early immune reconstitution included the levels of lymphocytes and monocytes on day 15, 30, 45, 60 and 90 after transplant.

Results: 103 patients (10/10 HLA identical=67, HLA non-identical=36) had undergone alloSCT with a median age of 51 years (20-71). Patient characteristics are detailed in table 1. Median follow-up was 1.6 years. There were no differences in Overall Survival (OS) and Relapse-free survival at 3 years. Patients who developed acute GvHD obtained a significantly lower score in PIRCHE in class I in the HvG direction (p = 0.033). Non-relapsed patients presented significantly higher PIRCHE score (>5 MM) in HLA class I in HvG direction (p = 0.047). However, no differences were found in HLA-EMMA nor in GvH direction. Early immune reconstitution in patients with greater PIRCHE score (>5 MM) displayed higher levels of lymphocytes on day 60 after transplant in HvG direction (p = 0.024). Cumulative incidence of relapse was higher in >5 MM PIRCHE in this direction (p = 0,0558).

Conclusions: HLA-MM in PIRCHE in the HvG direction is associated with a higher risk of acute GVHD and relapse and an improvement in early immune reconstitution. HLA molecular analysis could be useful for donor selection and management of patients post-transplant . The implications of HLA-MM according to these in silico tools in alloSCT outcomes deserve further investigation.

Disclosure: No conflicts of interest to disclose

P182 Post-transplant cyclophosphamide, abatacept, and short course of tacrolimus (cast) for graft-versus-host disease prevention following haploidentical hematopoietic stem cell transplantation

AS. Al-Homsi ¹, F. Cirrone¹, K. Cole¹, K. Stocker¹, B. Bruno¹, JA. Suarez-Londono¹, S. Gardner¹, J. Goldberg¹, M. Abdul Hay¹

¹New York University, New York, United States

Background: Haploidentical (HI) hematopoietic stem cell transplant (HSCT) substantially expands the pool of available donors. However, a recent large registry study showed inferior outcomes of HI HSCT compared to MUD HSCT when both groups received identical post-transplant cyclophosphamide-based graft-versus-host-disease (GvHD). This was mainly due to higher rates of GvHD, underscoring the need for improved GvHD prophylaxis following HI HSCT. Abatacept (A) prevents T-cell co-stimulation by blocking the CD80I86-CD26 axis via its extracellular CTLA4 domain. Shortening the duration of tacrolimus may alleviate the burden of its unwanted effects.

Methods: We therefore initiated a clinical trial for patients with hematological malignancies undergoing HI HSCT. Patients received mobilized peripheral blood grafts from first-degree HI related donors. GvHD prevention consisted of PTCy (50mg/kg IV on day +3 and +4), A (10mg/kg IV on day +5, +14 and +28) and tacrolimus (T) (starting on day +5 at 0.02mg/kg/day, by continuous IV). The dose of T was adjusted to maintain a trough level of 5-12 ng/mL. Tacrolimus taper was started on day +60 over a period of 4 weeks.

Results: Since September 2020, 28 patients have been enrolled. Median age was 60 (18-73) years. There was 17 males and 11 females. Treated conditions included: AML (9), MDS (5), ALL (9), T-cell NHL (3), others (2). Disease risk index was intermediate in 18 and high in 9 patients. Nine patients had active disease at enrollment. Seventeen patients received myeloablative conditioning. CMV serology for recipients and donors were −/− (9), +/+ (14), −/+ (1,) and +/− (4). For the 27 patients already evaluable for engraftment, median time to ANC and platelet engraftment are 18 (14-30) and 27 (16-67) days. All 27 patients achieved full whole blood donor chimerism by day +30. Median follow-up was 6.6 months. Five patients developed grade II-IV acute GVHD and 2 patient developed grade III acute GvHD. There was no case of grade IV acute GvHD. Two patients developed chronic, 1 mild (skin only) and 1 severe (skin, eyes and oral cavity). There was no case of steroid-refractory GvHD. Only 3 patients did not complete the planned T taper by day +90. Six patients required systemic steroids. CMV reactivation rate was 33%. One patient had EBV reactivation and required preemptive therapy with 2 weekly rituximab doses. Seven patients developed BK reactivation. There were no cases of adenovirus or HHV-6 virus reactivation. Five patients developed transient renal insufficiency (4 in the setting of acute sepsis and 1 with thrombotic microangiopathy that resolved after tapering off T). One patient developed sinusoidal occlusive disease that resolved with therapy. Other toxicities included self-limiting rise in bilirubin. One patient with adult T-cell leukemia/lymphoma and 1 patient with ALL relapsed. All other patients remain disease-free.

Conclusions: Our ongoing study suggests that CAST with abbreviated course of T is safe and yields low rates of acute GvHD. Based on a planned interim analysis, the study continues to enroll patients. The results of a larger cohort with longer follow-up will be presented at the meeting.

Clinical Trial Registry: NCT04503616

Disclosure: A S Al-Homsi

Advisory Board: BMS and Celyad

Consultancy: Daiichi Sankyo

P183 Post transplantation cyclophosphamide based GVHD prophylaxis across donor types – a single center experience

J. Vydra ¹, L. Nováková¹, M. Šťastná Marková¹, V. Válková¹, M. Koubová¹, B. Čemusová¹, R. Pytlík¹, A. Vítek¹, P. Cetkovský¹

¹Institute of Hematology and Blood Transfusion, Prague, Czech Republic

Background: Post transplant cyclophosphamide (ptCy) has been shown to improve outcomes of hematopoietic cell transplantation (HCT) from HLA mismatched related and unrelated donors. We analyzed retrospectively outomes of HCT from matched unrelated donors (MUD), mismached unrelated donors (MMUD) and haploidentical (HAPLO) donors using uniform GvHD prophylaxis with ptCy and compared these to a contemporary cohort of HCT from matched sibling donors (MSD) using standard prophylaxis.

Methods: Data on transplants performed at the Institute of Hematology and Blood Transfusion in Prague were retrieved from local transplant databases. All patients signed informed consent with data collection and anonymous analysis. Conditioning was either myeloablative (Bu/Flu or Bu/Cy) or reduced intensity (Flu/Mel). GvHD prophylaxis consisted of PtCy, cyclosporine and mycophenolate in MUD, MMUD and HAPLO groups. Standard prophylaxis in MSD group was tacrolimus and mycophenolate. Kaplan-Meier survival estimates, Cox proportional hazard models and competing risk cumulative incidence estimates were calculated.

Results: 218 patients were included in the analysis. Patient characteristics are summarised in Table.

OS at 2 years was 82% (95% CI 73-92%) in MSD group and 83% (95% CI 74-93%), 82% (95% CI 72-94%) and 73% (95% CI 62-86%) in HAPLO, MMUD and MUD groups (P = 0.4).

In multivariate analysis, only increasing age (HR 1.05, 95% CI 1.01-1.08 for each year) and commorbidities (HCT-CI > 1, HR 1.91 – 95% CI 1.09-3.33) were are associated with decreased overall survival (Figure). Non relapse mortality and incidence of relapse did not differ significantly between groups (P = 0.34) and were 10% and 27% for all patients, respectively. Acute GVHD grade III-IV was seen in 8% of patients in MSD group and 10%, 10% and 3.4% after HAPLO, MMUD and MUD HCT (P = 0.5). Chronic GVHD was seen in 69%, 62%, 64% and 31% of MSD, HAPLO, MMUD and MSD groups (P = 0.04).

Conclusions: GvHD prophylaxis with ptCy led to equivalent outcomes of HCT from MUD, MMUD and haploidentical donors when compared to a cohort of transplants from matched sibling donors without ptCy in a retrospective, single center analysis.

Table.

	MSD N = 62	HAPLO N = 55	MMUD N = 46	MUD N = 55	P
Age	49.0 [41.0;57.0]	53.0 [40.5;62.0]	45.0 [38.0;55.0]	54.0 [39.2;61.0]	0.073
HCT-CI > 1	12 (19.4%)	16 (29.1%)	7 (15.2%)	19 (34.5%)	0.086
MA-Bu	52 (83.9%)	36 (65.5%)	38 (82.6%)	39 (70.9%)
RIC-Flu/Mel	10 (16.1%)	19 (34.5%)	8 (17.4%)	16 (29.1%)
Bone marrow	2 (3.23%)	0 (0.00%)	5 (10.9%)	2 (3.64%)
Peripheral blood prog. cells	60 (96.8%)	55 (100%)	41 (89.1%)	53 (96.4%)	0.05
Acute leukemia	32 (51.6%)	30 (54.5%)	26 (56.5%)	32 (58.2%)	0.250
Myelodysplastic syndrome	9 (14.5%)	13 (23.6%)	11 (23.9%)	15 (27.3%)
Other	21 (33.9%)	12 (21.8%)	9 (19.6%)	8 (14.5%)

Figure

Disclosure: Nothing to declare

P184 High expression of cd62l as a signature of steroid-refractory/resistant GVHD revealed by immune profiling and machine learning

Y. Ding ¹, L. Wang¹, M. Ni^1,2, B. Neuber¹, M.-L. Schubert¹, T. Sauer¹, A. Krauss¹, T. Luft¹, U. Hegenbart¹, S. Schönland¹, V. Eckstein¹, W. Krueger³, R. Yerushalmi⁴, K. Beider⁴, A. Nagler⁴, C. Müller-Tidow¹, P. Dreger¹, M. Schmitt¹, A. Schmitt¹

¹University Clinic Heidelberg, Heidelberg, Germany, ²Guizhou Medical University, Guizhou, China, ³University Clinic Greifswald, Greifswald, Germany, ⁴Chaim Sheba Medical Center, Tel Hashomer, Israel

Background: Steroid-refractory graft versus host disease (SR-GvHD) remains a major complication leading to a high morbidity and mortality post allogeneic hematopoietic stem cell transplantation (allo-HSCT), despite significant advances in the last few years. Therefore, an effective way to identify SR-GvHD as early as possible could provide an opportunity to start second-line therapy at an early stage. In our study, a comprehensive immune profiling was performed to analyze the phenotype of cell subsets in different GvHD and healthy donor models. Machine learning was used to find critical factors from the huge multidimensional immune profiling dataset and to construct an accurate prediction model for SR-GvHD.

Methods: Samples of ten patients without GvHD post allo-HSCT, eleven patients with steroid-sensitive aGvHD, 19 patients with SR-aGvHD ≥ II° and twelve with moderate to severe SR-cGvHD were included in this study. Glucksberg and NIH criteria were used for clinical staging of aGvHD and cGvHD. A comprehensive phenotypical analysis of monocytes, T cells, B cells, and NK cells was evaluated by multicolor flow cytometry. Unsupervised dimensional reduction and clustering algorithms were used to unearth the immunological and clinical data. Several different machine learning algorithms were used for the construction of prediction models.

Results: A pipeline for the discovery of biomarkers using machine learning was established for the FACS data analysis. Several distinct disease-specific subsets of monocytes, T cells and NK cells were discovered by unsupervised analysis strategies, and were further validated by manual analysis strategy. Clinical parameters had no influence on these disease-specific subsets. Moreover, the SR-GvHD groups, showed significant higher expression of CD62L on T, NK cells compared to the other two groups, CD3⁺CD62L⁺ T cells (no aGvHD vs. SR-aGvHD: 14.75% vs. 54.78%, p < 0.001; steroid-sensitive aGvHD vs. SR-aGvHD: 18.03% vs. 54.78%, p < 0.001), CD56⁺CD62L⁺ NK cells (no aGvHD vs. SR-aGvHD: 15.96% vs. 60.46%, p < 0.001; steroid-sensitive aGvHD vs. SR-aGvHD: 18.52% vs. 60.46%, p < 0.001),suggesting its important role in SR-GvHD. The groups of no aGvHD post allo-HSCT and steroid-sensitive aGvHD were similar in their immune profiling. Furthermore, lasso regression and random forest algorithms were used to screen potential predictors for SR-aGvHD. A prediction model was constructed based on the CD62L expression of CD3 + T, CD4 + T, NK and B cells. The specificity and sensitivity of the model was examined by ROC analysis showing a good prediction with an AUC of 0.867.

Conclusions: An effective algorithm for the definition of biomarkers was established using machine learning in our current study. The upregulation of CD62L on T and NK cells was defined as a robust predictor for SR-GvHD.

Disclosure: The authors declare no competing financial interests, except the following: Funding was provided by Mallinckrodt to AS and MS for the documentation of the clinical course and for the analysis of patient immune cells; MS received funding for collaborative research from Apogenix, Hexal and Novartis and travel grants from Hexal and Kite; he received financial support for educational activities and conferences from bluebird bio, Kite and Novartis; he is a board member for MSD and (co-)PI of clinical trials of MSD, GSK, Kite and BMS. AS received travel grants from Hexal and Jazz Pharmaceuticals. MS and AS are co-founders and shareholders of TolerogenixX Ltd. AS and LW are part-time and full-time employees, respectively, of TolerogenixX Ltd.

P185 Cytokine trajectories and risk of acute graft-versus-host disease after allogeneic hematopoietic cell transplantation

L.K. Gjærde ^1,2, A.G. Zucco^3,2, J.H. von Stemann^1,2, L. Minculescu¹, J.A. Møller¹, P.T. Brooks^1,2, M.B. Hansen¹, J. Reekie³, S.R. Ostrowski^1,2, H. Sengeløv^1,2

¹Rigshospitalet, Copenhagen, Denmark, ²University of Copenhagen, Copenhagen, Denmark, ³PERSIMUNE Center of Excellence, Copenhagen, Denmark

Background: Acute graft-versus-host disease (GvHD) remains a major cause of morbidity and mortality after allogeneic hematopoietic cell transplantation (HCT). We aimed to investigate whether cytokine trajectories early post-HCT were associated with developing acute GvHD.

Methods: We measured 25 cytokines by ELISA or Luminex in 254 stored plasma samples obtained around day +7 (N = 92), +14 (N = 77) and +28 (N = 85) in 116 patients who underwent HCT with myeloablative conditioning between 2015 and 2018 (median age: 47 [min–max: 18–71] years, 52% transplanted for acute leukemia, 71% with a matched unrelated donor, 25% received anti-thymocyte globulin [ATG] and 41% received 12 Gy total-body irradiation [TBI]). All 254 plasma samples were obtained before an eventual diagnosis of grade II–IV acute GvHD. Longitudinal cytokine levels were smoothed using polynomial loess regression with 95% confidence interval (CI) bands. For each cytokine, a joint survival model was fitted, in which longitudinal mixed-effects model estimates of the cytokine level were used in a proportional hazards spline model to estimate hazard ratios (HR, all per log increase) of grade II–IV acute GvHD (adjusted for donor type, receipt of ATG and receipt of 12 Gy TBI).

Results: 35 (30%) patients developed grade II–IV acute GvHD at a median of 32 (Q1–Q3: 27–42) days after HCT. Stratified crude cytokine trajectories early post-HCT (Figure) revealed that patients who later developed acute GvHD had higher interferon-γ (IFNγ) levels from around day +20 to +35, higher interleukin-2-receptor-α (IL2Rα) levels from around day +10 to +35, a smaller decline in interleukin-6 (IL6) levels from around day +10 to +35, higher interleukin-17A (IL17) levels from around day +10 to +30, and more increasing tumor necrosis factor-α (TNFα) and suppression of tumorigenicity-2 (ST2) levels from around day +20 to +35. In the converging 22 joint survival models (the models for interleukin-1, interleukin-22, and E-selectin did not converge), we found that—after adjusting for donor type and receipt of ATG and TBI—higher levels of IL17 (HR: 1.22, CI: 1.00–1.49, p = 0.05) and lower levels of glycoprotein 130 (gp130, an interleukin-6 signal transducer, HR: 0.22, CI: 0.05–0.95, p = 0.04) and transforming growth factor-β1 (TGFβ1, HR: 0.37; CI: 0.15–0.94, p = 0.04) were associated with subsequent acute GvHD. Other cytokines associated with acute GvHD, albeit not with statistical significance at the 0.05 level, were TNFα (HR: 2.29, CI: 0.84–6.21, p = 0.11), IL2Rα (HR: 2.16, CI: 0.71–6.56, p = 0.17) and IL6 (HR: 1.40, CI: 0.95–2.07, p = 0.09).

Conclusions: Crude early post-HCT trajectories of IFNγ, IL2Rα, IL6, IL17, TNFα and ST2 differed according to later development of grade II–IV acute GvHD in adults undergoing myeloablative HCT. After adjustment for donor type and receipt of ATG and TBI, high levels of IL17 and low levels of gp130 and TGFβ1 were associated with increased risk of acute GvHD. Our findings warrant further prognostic and mechanistic research of the candidate cytokine trajectories to determine their role in predicting and causing or preventing acute GvHD.

Disclosure: Nothing to declare.

P186 Similar outcomes of ptcy and atg based GVHD prophylaxis in hematopoietic cell transplantation from matched unrelated donors

J. Vydra ¹, P. Jindra², V. Válková¹, M. Karas², M. Šťastná Marková¹, D. Lysák², L. Nováková¹, J. Šrámek², M. Hrabětová², P. Cetkovský¹

¹Institute of Hematology and Blood Transfusion, Prague, Czech Republic, ²University Hospital Pilsen, Pilsen, Czech Republic

Background: Post transplant cyclophosphamide (ptCy) has been shown to improve outcomes of HLA mismatched hematopoietic stem cell transplantation (HCT). Role of ptCy in HLA matched unrelated donor HCT is less well established. We analyzed retrospectively outomes of transplantation from matched unrelated donors using ptCy based GVHD prophylaxis and compared these outcomes to standard ATG based prophylaxis.

Methods: Data on transplants performed at the Institute of Hematology and Blood Transfusion in Prague and in Pilsen Teaching Hospital were retrieved from local transplant databases. All patients signed informed consent with data collection and anonymous analysis. Conditioning was either myeloablative (Bu/Flu or Bu/Cy) or reduced intensity (Flu/Mel). GvHD prophylaxis consisted of PtCy, cyclosporine and mycophenolate (ptCy group) or ATG, cyclosporine and either mycophenolate or methothrexate (ATG group). Kaplan-Meier survival estimates and competing event cumulative incidence curves were calculated and compared using log-rank and Gray’s tests.

Results: 383 patients were included, 315 in the standard ATG group and 68 in the ptCy group. Patient characteristics are summarized in Table 1. OS at 2 years was 75,6% (95% CI 63-90%) and 72,6% (95% CI 65,8-80%) after ptCy and ATG, respectively (Figure 1A). Cumulative incidence of NRM within 2 years was 9% after ptCy and 19% after ATG (P = 0,023); incidence of relapse was 28% after ptCy and 38% after ATG (P = 0,089). Incidence of acute GVHD grade 1-2 was 35% and 28% (P = 0,56); incidence of grade 3-4 aGVHD was 3,5% and 7,5% (P = 0,28) in ptCy and ATG groups, respectively. Incidence of moderate and severe chronic GvHD was 4,2% after ptCy and 18% after ATG (P = 0,03 for moderate and 0,3 for severe cGVHD); mild cGVHD was seen in 17% (ptCy) and 25% (ATG) of cases.

Table 1

	ATG (N = 315)	ptCy (N = 68)	P
Age	50.0 (13.1)	48.9 (11.6)	0.504
HCT-CI			0.547
0-1	174 (63.5%)	48 (70.6%)
2-3	74 (27.0%)	15 (22.1%)
>3	26 (9.49%)	5 (7.35%)
Conditioning			0.002
MA-Bu	155 (49.2%)	48 (70.6%)
RIC-FluMel	160 (50.8%)	20 (29.4%)
Graft	266 (84.7%)	67 (98.5%)	0.001
PBPC	47 (15.0%)	1 (1.47%)
Bone marrow
Donor age	31.4 (8.30)	32.8 (8.41)	0.235

 

Conclusions: GvHD prophylaxis with ptCy and ATG led to similar outcomes after allogeneic hematopoietic cell transplantation from matched unrelated donors in this retrospective analysis of data from two centers.

Disclosure: Nothing to declare

P187 Anti-thymocyte globulin (atg) equalize the incidence of graft-versus-host disease (GVHD) among unrelated and identical sibling donor transplantation

A. Cia ¹, N. Fernandez Escobar¹, A. Requejo¹, M. Castro², G. Bentolila³, G. Jaimovich¹

¹Favaloro Foundation University Hospital, Capital Federal, Argentina, ²Sanatorio Anchorena, Capital Federal, Argentina, ³FUNDALEU, Capital Federal, Argentina

Background: GVHD is the main cause of morbidity and mortality associated with allogeneic hematopoietic stem cell transplantation (HSCT) with an incidence rate of 40-60%. Addition of ATG has shown to reduce its incidence. We report the results of the prophylactic use of ATG in a group of patients (pts) undergoing HSCT.

Methods: From March 2018 to June 2021 we conducted a prospective multicenter study including 95 consecutive pts.: 33 transplanted with an identical sibling donor(ISD), 33 with an HLA-matched unrelated donor(MUD) and 18 with an HLA 1 miss-matched donor (MMUD). Conditioning regimen was according to institutional protocol. GVHD prophylaxis included tacrolimus and methotrexate plus ATG (Timoglobulina®Sanofi) 2.25 mg/kg days -3 and -2. GVHD incidence, relapse and death were recorded. Acute GVHD (aGvHD) and chronicGVHD (cGVHD) were defined using Glucksberg criteria and NIH clinical grading respectively. Median and interquartile range (IQR) were used to describe non-parametric data, group comparison with X2, Kaplan Meyer curve and multi-sample log Rank test for survival analysis, considering a statistically significant p value of less than 0.05.

Results: 42 pts were male and donors were female in 56% (n:54). Conditioning regimen was myeloablative in 81% (n:77). Median time to neutrophil and platelet engraftment were 17 days (range 15-21) and 17 days (range 12-20) respectively. 6/95 pts presented graft failure. aGVHD incidence was 36% (n:34), grades I-II 19% (n:19) and III-IV 16% (n:15). Incidence of grades III-IV did not varied according to donor: 15% (n:7) for ISD, 9% (n:3) for MUD and 27% (n:5) for MMUD (X2 3.06, p0.21). Overall incidence of cGVHD was 23% (n:21): Grades mild 6% (n:6), moderate 11% (n:11) and severe 4% (n:4). According to donor type, severe cGVHD was 2% (n:1), 3% (n:1) and 11% (n:2) using ISD, MUD and MMUD respectively (X2 2.65, p0.26). At one year, 15/79 pts (19%) were under immunosuppressive treatment. Transplant related mortality at day 100 was 9% (n:9). Most frequent cause was sepsis (n:4). In 31 pts CMV reactivation was detected (more than one reactivation in 6 pts of which 5 had GVHD) and 7 reactivated EBV infection. None evolved to PTLD.

Median follow-up time was 524 days (IQR 168-833). cGVHD–free and relapse-free survival (combined endpoint) at 1 year was 57% (n:54) of 79 evaluables patients. cGVHD and relapse free survival at 1 year was 48% for IDS (33-63%CI), 66% for MUD (47-81%CI) and 38% for MMUD (21-60%CI). No significant difference was found according to donor type (X2 4.98; p0.083) Fig1

Conclusions: No difference was observed in the incidence of aGVHD, cGvHD and combined endpoint at 12 months between the different types of donor. This could suggest that ATG could equalize transplants results using different types of donor. To confirm these findings, studies with a higher level of evidence are required.

Disclosure: Nothing to declare

P188 First-line steroid-free systemic treatment of acute and chronic graft-versus-host disease after novel prophylaxis regimens in adults

I. Moiseev ¹, M. Barabanshikova¹, A. Dotsenko¹, A. Smirnova¹, Y. Vlasova¹, E. Morozova¹, S. Bondarenko¹, A. Kulagin¹

¹RM Gorbacheva Research Institute, Pavlov University, Saint-Petersburg, Russian Federation

Background: Since early studies of graft-versus-host disease (GVHD) (Sullivan et al., 1981 and Kennedy MS et al., 1985) no agent was randomized against corticosteroids (CS), but rather additional immunosuppressive agents in combination with CS were tested against CS alone. Nonetheless these early studies identified comparable efficacy of calcineurin inhibitor (CNI) cyclosporine A (CsA) to CS, which was subsequently abrogated by introduction of CNIs in GVHD prophylaxis. Recently several CNI-free protocols were introduced based on posttransplantation cyclophosphamide (PTCY) (NCT02294552, NCT02806375) and alpha/beta ex vivo depletion (NCT02337595). Under these protocols steroid-sparing regimens were evaluated. Here we report the outcome of first line GVHD treatment without CS in patients from these protocols.

Methods: The study comprised 74 patients, 44% were allografted from matched related donor (MRD), 42% from matched unrelated donor (MUD) and 14% from haploidentical donor. Underlying disease was acute myeloid leukemia in 21%, acute lymphoblastic leukemia in 27%, primary myelofibrosis in 15%, chronic myeloid leukemia in 11% and other malignant diseases in 26%. Twenty patients were treated for acute GVHD (aGVHD) after single-agent PTCY, 23 were treated for chronic GVHD (cGVHD) after single-agent PTCY, 11 patients were treated for de novo cGVHD after PTCY, tacrolimus and MMF combination, 13 – after PTCY and ruxolitinib combination and 7 after ex vivo depletion. Overall 34 patients were treated for aGVHD (grade II – 44%, grade III- 47% and grade IV – 9%) and 40 for cGVHD (60% moderate and 40% severe by NIH criteria). CNIs were used as the first line treatment in 80% of patients, sirolimus in 10%, and TKIs, rituximab and ruxolitinib in another 10%.

Results: Overall response rate (ORR) was significantly higher in chronic GVHD than in acute (80% vs 47%, p = 0.031). However the incidence of complete response (CR) was not different (43% vs 35%, p = 0.53). Median time to partial response (PR) was 35 days in aGVHD and 6 months in cGVHD. Median time to CR was 67 days in aGVHD and 16 months in cGVHD. 2-year failure-free survival was 21% in aGVHD and 81% in cGVHD (p < 0.001, figure A), while overall survival was 76% and 95% in these groups, respectively (p = 0.017). In refractory aGVHD the response to CS administration was 39%, and ORR to all lines in aGVHD was 94% (figure B). In refractory cGVHD 71% achieved a response after CS administration and ORR to all lines was 98%. Among aGVHD and cGVHD patients 47% and 63% did not receive systemic antibiotics, 79% and 90% systemic antimycotics, 35% and 73% systemic antivirals, 62% and 85% did not require hospital re-admission for complications or progressive disease during the course of treatment. GVHD severity in acute (HR 4.69, 95%CI 2.08-10.13, p < 0.001), in chronic disease (HR 5.0, 95%CI 0.96-26.22, p = 0.057) was predictive for response.

Conclusions: An attempt to achieve a response without CS in the first line is justified for patients with cGVHD and grade II aGVHD in CNI-free patients after novel GVHD prophylaxis regimens. This approach does not compromise subsequent response to steroids or second-line agents and is associated with low incidence of complications and re-admissions.

Clinical Trial Registry: NCT02294552, NCT02806375, NCT02337595

Disclosure: Nothing to disclose

P189 Pembrolizumab and allotransplants for relapsed refractory classical hodgkin lymphoma

K. Halahleh ¹, I. Muradi², D. Al-Rimawi¹, M. Ma’koseh³

¹King Hussein Cancer Center and Foundation, Amman, Jordan, ²Al-Ahliyya Amman University, Amman, Jordan, ³King Hussein Cancer Center and foundation, Amman, Jordan

Background: Pembrolizumab is safe and effective in persons with rrHL and has been used as a bridge to allo-SCT. There is concern, prior to allo-SCT pembrolizumab use might increase the risk of graft-versus-host disease (GvHD) and other IRAE [2-3].

Methods: Retrospective comparative cohort study,22 subjects included(Jan,2017 to July, 2019). 2 cohorts(prior to SCT pembrolizumab use,n-9), and 13 with no prior pembrolizumab. All received RIC SCT and PBSC grafts. aGvHD, cGvHD, CRS, reported, compared, and survival outcomes calculated. All had similar baseline characteristics.

Subject-, disease- and transplant-related variables displayed in Table 1.

Table 31

Results: Median follow up was 9mo (range:7.7-44.5mo). The median time from the last dose of pembrolizumab to SCT 67 d (range, 42- 135d). All subjects (n-9) in pembrolizumab cohort achieved CR after SCT, compared to 84.6%(n-11) in the no pembrolizumab cohort;

100-day grade 2-4 aGvHD was 63.6% (n-14), more in pembrolizumab (89%,46%; P = 0.04); and 75%(9) vs 37.5%(3),P = 0.062) had grade 3-4.1-year cumulative incidence of moderate-severe cGvHD was 41%(n-9), more in pembrolizumab cohort (55.5% vs 30.7%; P = 0.378). GvHD was not influenced by any variable, but with a trend toward higher GvHD with prior pembrolizumab use (P = 0.074; P = 0.08). No VOD in either cohort, however, there was 1 subject with TAM, 2 CRS reported in pembrolizumab cohort, within 14 days post-SCT. All treated with steroids (1mg/kg) within 14 days with a quick benefit.

2- year OS, PFS for the entire cohort were 76.7%(95% CI:56.9-91.8) and 51.3%(95%CI: 29.8-72.6) respectively. No difference in survival outcomes in univariate analysis. However, when we analyzed subjects, who attained CR, or PR before SCT, 2-year OS 92.3 vs 33.3%; P = 0.05) and 2-year PFS 57.0% vs 33.3%; P = 0.03) respectively.

2-year CIR was 27.3%(n-6/22).When we analyzed subjects according to prior pembrolizumab use, no significant difference was evident between 2 cohorts (33.3%, 23.1%; P = 0.807). Taking into account subjects in CR at SCT, 2-year CIR was 14.9%, with no significant difference between 2 cohorts (46.15%, 36.51%; P = 0.93). 2-year NRM 18%(n-4/22) for the entire cohort; more in no pembrolizumab (11% vs 23%; P = 0.0093).In the pembrolizumab cohort, deaths were attributed to GvHD of the gut and lung(n-2), recurrent pneumonia(n-2), compared with lung cGvHD and DP (n-1), CMV colitis and DP (n-2) in the no pembrolizumab cohort.

Conclusions: Pembrolizumab PRIOR to all-SCT results in favorable outcomes, enhanced PFS, in subjects who received SCT in CR, and decrease the risk of relapse, but at the cost of increased grade 2-4 aGvHD without increased NRM.

Clinical Trial Registry: NA

Disclosure: All authors has nothing to disclose

P190 Clinical analysis of air-leak syndrome following allogeneic hematopoietic stem cell transplantation in pediatric patients

W. Zhao ¹, M. Chen¹, Y. Zhao², H. Wang², P. Lu², M. Xiong²

¹Beijing Lu Daopei Hospital, Beijing, China, ²Hebei Yanda Lu Daopei Hospital, Langfang, Sanhe, China

Background: Air-leak syndrome (ALS) occurs when there is leakage of gas from the alveoli resulting in clinical symptoms that include cough, dyspnea and hypoxemia. ALS is an independent poor prognosis factor among adult patients who have received hematopoietic stem cell transplantation (HSCT), which the 5-year overall survival (OS) is less than 30%. However, the clinical features of ALS among post-transplant pediatric patients have rarely been explored.

Methods: We retrospectively reviewed 2,206 pediatric patients who received an allo-HSCT between January 2013 and December 2019 at the Hebei Yanda Lu Daopei Hospital and analyzed the role of ALS in their prognosis following HSCT.

Results: Twenty-eight pediatric patients (16 male and 12 female) were diagnosed with ALS: 16 patients with acute myeloid leukemia, 9 patients with acute lymphoblastic leukemia, and 3 patients with aplastic anemia. Twenty-one of the patients received a complete remission status prior to HSCT and 7 patients were in non-remission. The median patient age was 12 years (1-16) and the follow-up time was 871 days (55-2,973). The median OS time was 429 days (55-1614). The most frequent adverse event accompanying the ALS was hypoxemia which occurred in 92.8% of the patients, followed by wheezing and coughing, which occurred in 67.9% and 53.5% of the patients, respectively. Chest pain related to breathing occurred in 21.4% of the patients. ALS types included mediastinal emphysema, subcutaneous emphysema, pneumothorax, scrotal emphysema, peritoneal meteorism, pneumopericardium, intestinal wall and intraspinal emphysema. Following treatment of the ALS, 18 patients survived (18/28, 64.3%) and 10 patients died of respiratory failure or infection (10/28, 35.7%). We divided ALS into two categories: 15 cases of bronchiolitis obliterans syndrome (BOS) and 13 cases of idiopathic pneumonia syndrome (IPS). Patients with BOS-related ALS had a better prognosis compared to those with IPS, who were more likely to die in the early stage of ALS (80% versus 46% in the IPS and BOS groups, respective; P = 0.037). Logical regression analysis showed that, greater than 7 years of age (P = 0.028), non-remission prior to HSCT (P = 0.022), use of tacrolimus (P = 0.005), pulmonary graft-versus-host disease (GVHD) before +163 days (P = 0.004), Grade III-IV acute GVHD (P = 0.001), extensive chronic GVHD (P <0.001), were independent risk factors for ALS. Primary GVHD before +23.5 days (P = 0.021) and IPS type (P = 0.037) were independent risk factors of poor prognosis following an ALS diagnosis. Disease state prior to HSCT, pulmonary infection, TBI pre-treatment, donor type did not have a statistically significant (P > 0.05) effect on patient survival. Additionally, we found that fluticasone, azithromycin, and montelukast (FAM) could significantly improve the prognosis following ALS in our patients (P = 0.005). Compared with IPS, patients with BOS appeared to benefit from imatinib (P = 0.055), ruxolitinib (P = 0.009), and pirfenidone (P = 0.044).

Conclusions: ALS is a rare and poor prognosis complication of HSCT, particularly IPS-related ALS. The OS of ALS in our hospital is significantly higher than that cited in previous reports which may be related to early diagnosis and timely FAM treatment.

Disclosure: Nothing to declare

P191 Comparison of regulatory t cell subpopulation between antithymocytic globulin and post-transplantcyclophosphamide for prevention of the GVHD in patients undergoing allogeneic hematopoietic stem cell transplantation

B.-Y. Heo¹, S. Choi¹, S.-H. Yeon¹, P.T.T. Doung¹, M.-W. Lee¹, D.-Y. Jo¹, J. Kwon¹, I.-C. Song ¹

¹Chungnam National University, Daejeon, Korea, Republic of

Background: Antithymocytic globulin (ATG) and post-transplant cyclophosphamide (PTCy) are frequently used regimens for graft-versus-host disease (GVHD) prophylaxis. However, there is lack of data about the difference of regulatory

T cell (Treg) subpopulation between these two regimens.

Methods: We collected peripheral blood sample at day+21 after allogeneic hematopoietic stem cell transplantation (Allo-HSCT). We analyzed Treg subpopulation by flow-cytometer and classified Treg into 3 subgroups: naïve, effector and non-suppressive Treg. And, we compared overall survival (OS), the cumulative incidence of acute and chronic GVHD, relapse rate between ATG and PTCy group.

Results: We enrolled 39 patients (25 in ATG, 14 in PTCy) in total. In ATG group, 9 and 16 patients underwent human leukocyte antigen (HLA) matched-sibling donor and unrelated donor HSCT, respectively. In PTCy group, 9 patients underwent haplo-identical HSCT and 5 patients underwent HLA-matched unrelated donor HSCT. The conventional CD25 + FOXP3 + Treg count of CD4 + T cell was 6.49% in ATG and 13.34% in PTCy (p = 0.0086). The naïve Treg count of CD4 + T cell was 4.87% in ATG and 5.95% in PTCy (p = 0.32). The effector Treg count of CD4 + T cell was 3.89% in ATG and 6.31% in PTCy (p = 0.16). The non-suppressive Treg count of

CD4 + T cell was 23.67% in ATG and 19.00% in PTCy (p = 0.25). The cumulative incidence of Grade 2 to 4 acute GVHD was 16.2% in ATG and 36.5% in PTCy (p = 0.15) and extensive chronic GVHD was 19.1% in ATG and 16.7% in PTCy (p = 0.955) And, OS and relapse rate were not statistically different between two group.

Conclusions: There were more conventional CD25 + FOXP3 + Tregs in PTCy group than in ATG group, which was a result of the fact that there were more naïve and effector Treg in PTCy group. PTCy showed similar clinical outcomes with ATG group, although there were more haplo-identical HSCT in PTCy group. This may be because there were more Tregs in the PTCy group, which effectively prevents GVHD.

Disclosure: Nothing to declare

P192 Treatment pattern characterization and outcomes in chronic graft versus host disease patients treated with extracorporeal photopheresis in clinical practise in Sweden

F. Schain¹, C. Boissin², T. Laczik³, S. Fedeli³, M. Remberger⁴, O. Blennow⁵, J. Dykes⁶, T. Eich⁷, C. Jones¹, J. Mattsson⁸, G. Berlin ⁹

¹Schain Research, Bromma, Sweden, ²Karolinska Institutet, Stockholm, Sweden, ³KTH Royal Institute of Technology, Stockholm, Sweden, ⁴Uppsala University and Uppsala University Hospital, Uppsala, Sweden, ⁵Karolinska University Hospital, Stockholm, Sweden, ⁶Clinical Immunology and Transfusion Medicine, Lund, Sweden, ⁷Uppsala University, Uppsala, Sweden, ⁸Princess Margaret Cancer Centre and University of Toronto, Toronto, Canada, ⁹Linköping University, Linköping, Sweden

Background: Extracorporeal photopheresis (ECP) is frequently used in clinical practise to treat moderate to severe chronic Graft versus Host Disease (cGVHD), however there is limited data available to describe treatment patterns and outcomes associated with this treatment outside clinical trials.

Methods: Patients ³18 years with a record of an allogeneic hematopoietic stem cell transplantation (HSCT) in the Swedish Patient Register between January 2006 and July 2020 were identified (n = 2708). Among these, patients with ECP treatment from 3 months post HSCT (index) and onwards were included (n = 183). The data was linked to other nationwide longitudinal and population-based registers; the Prescribed Drug Register, the Cause of Death Register, the Cancer Register and the Longitudinal Integrated Database for Health Insurance and Labor Market Studies (LISA) for follow-up until December 2020. The median follow-up time was 2.7 years.

Results: The median age at index was 58 years (interquartile range [iqr] 1-3; 38-61), and 65.6% (n = 120) were male. The median time from index date to the first ECP exposure was 7.8 months (iqr 1-3; 3.0-19.0) and the median number of ECP treatments given was 18 (iqr 1-3; 4-39). The average time spent in healthcare decreased over follow-up time; 68.9%, and 22.1% the first and fifth follow-up year, respectively. During the 3-month period before the first ECP treatment, 90.0% (n = 165) received cyclosporine, 9.8% (n = 18) received tacrolimus and 3.8% (n = 7) received ruxolitinib, respectively. During the same period 52.5% (n = 96) received prednisolone and/or prednisone. When comparing the 3-month period prior to the first ECP treatment [reference] with 3-month periods during the first year after ECP initiation, there was a decrease in the cumulative dose dispensed by pharmacies per patient-time for prednisone/prednisolone (1,381 mg [reference] versus 658 mg [9-12 months post ECP initiation], p = <0.001) and cyclosporin (12,242 mg [reference] versus 3,501 mg ([9-12 months post ECP initiation] p < 0.001). The incidence rate of infections during the 3-month period prior to ECP initiation was 79.2% and decreased over time to 59.1% ([9-12 months post ECP initiation] p < 0.001). The median overall survival time from index was 6.0 years. The direct medical cost per patient-year decreased from 27,719 euro to 1,981 euro when comparing the first versus fifth follow-up year from index. Similarly, among patients < 66 years at index (n = 130), illness-related time absent from work decreased from 73.2% to 31.9%, with a corresponding decrease in productivity loss from 20,358 euro to 7,211 euro per patient-year.

Conclusions: ECP treatment was associated with reduced use of corticosteroids, immunosuppressive agents, and fewer infections. Furthermore, cost and healthcare utilization decreased over time.

Disclosure: Frida Schain is an employee and own stocks in Schain Research AB. Christina Jones in an employee of Schain Research AB. Constance Boissin, Tamas Laczik and Stefano Fedeli were interns at Schain Research AB and have received payments for analytical work. Mallinckrodt has been the sponsor of the study and Schain Research AB has received payments from Mallinckrodt.

P193 Long-term follow-up of ruxolitinib for therapy in corticosteroid refractory chronic graft-versus-host disease: A single center-experience

N. Mandaci Şanli¹, E. Karakuş¹, M. Keklik¹, A. Unal ¹

¹Erciyes University, Kayseri, Turkey

Background: Steroid–resistant graft-versus-host disease (GvHD) is a major challenge after allogeneic stem cell transplantation and associated with significant morbidity and mortality There is no therapeutic standard defined beyond calcineurin inhibitors (CNI) and steroids. Pre-clinical evidence indicates the potent anti-inflammatory properties of the ruxolitinib and efficacy of ruxolitinib against GVHD have been described recently.

Methods: In this retrospective study, 16 patients had received ruxolitinib as salvage therapy for corticosteroid–refractory chronic GVHD. All patients had moderate (9/16, 56.2%) to severe (7/16, 43.8%) cGVHD. The most frequent underlying diseases were: acute myeloid leukemia (8, 50%), acute lymphoblastic leukemia (5, 31.3%), Hodgkin’s disease (1, 6.3%), myelodysplastic syndrome (1, 6.3%), or T-cell lymphoma (1, 6.3%). All of the patients received myeloablative conditioning regimens. Grading of cGVHD and response (complete and partial organ based on clinician assessments) was performed

Results: The median age was 48 years (range, 30-67). Median cGVHD time was 12 months (range: 2-44). Types of GVHD involvements: liver 7/16 (43.8%), lung 2/16 (12.5%), oral mucosa 1/11 (6.3%), oral mucosa and liver 1/11 (6.3%), skin 2/16 (12.5%), oral mucosa and skin 2/11 (12.6%), skin and gastrointestinal system 1/11 (6.3%). The median number of previous GVHD-therapies was 2.5 (range 1-5). The median dose administered was 20 mg (7 patients) and 10mg (9 patients) daily divided in two doses. Overall response rate was 75.1% (12/16) which was obtained after a median of 40 days of treatment, 43.8% (7/16) reached complete response, and 31.3% (5/16) partial response. cGVHD exacerbation developed in 4 patients during ruxolitinib therapy. Median follow-up and ruxolitinib-treatment was 15 months (range: 2-54). While 68.8% (11/16) of patients were alive, 30.2% (5/16) of patients died (2 of the 5 patients developed disease recurrence). Cytopenia, CMV-reactivation and infections were observed during ruxolitinib-treatment for cGVHD (respectively, 7/16, 43.9%; 6/16, 68.9%; and 11/16, 37.6%)

Conclusions: Ruxolitinib in the real-life setting is an effective and safe treatment option for cGVHD, with an overall response rate of 75.1% for chronic graft-versus-host disease, in heavily pretreated patients.

Disclosure: Nothing to declare

P194 Pharmacokinetics of different tacrolimus formulations for GVHD prevention after allogeneic hematopoietic stem cell transplantation

D.N. Marco¹, G. Gutiérrez-García^1,2, I. Monge³, G. Riu³, E. Carcelero³, J.R. Roma³, M. Suárez-Lledó^1,2, M.Q. Salas^1,2, N. Martínez-Cibrian^1,2, A. Pedraza¹, A. Doménech¹, L. Rosiñol^1,2, F. Fernández-Avilés^1,2, M. Rovira^1,2, C. Martínez ^1,2

¹Institute of Hematology and Oncology, Hospital Clinic of Barcelona, Barcelona, Spain, ²Institut d’Investigacions Biomèdiques August Pi i Sunyer (IDIBAPS), Barcelona, Spain, ³Hospital Clinic of Barcelona, Barcelona, Spain

Background: Tacrolimus (TK) is a pivotal immunosuppressant agent used for GVHD prevention after allogeneic hematopoietic stem cell transplantation (allo-HSCT). TK is usually given intravenously (IV) in the early phase after allo-HSCT and then switched to twice-daily (BID: bis in die) oral administration. In addition to IV and BID TK formulations, once-daily modified-release (QD: quaque die) formulation is available. In solid organ transplantation, BID and QD formulations have been shown to have the same efficacy and safety profile. However, in alloHSCT there is little experience with the use of QD. We analyzed pharmacokinetics of the classic IV TK vs. the oral (BID and QD) formulations used from the beginning of transplantation.

Methods: Two-hundred and thirty-eight patients were enrolled: 74 started immunosuppression with IV TK (Prograf®, 0.03mg/kg by continuous perfusion), 73 with BID (Tacni®, 0.6mg/kg/12h), and 91 with QD (Advagraf®, 0.12-0.18mg/kg/24h). The dose was subsequently modified in order to maintain a TK through level (C₀) of 5-15ng/mL. Those patients receiving IV formulation were switched to either of the two oral formulations as soon as they could tolerate oral administration. For the purpose of this analysis, C₀ at 48 hours, 7, 14, 21, and 28 days after d0 were recorded as well as acute GVHD and adverse effects of TK (acute kidney injury [AKI], thrombotic microangiopathy [TMA], and neurotoxicity within the first 3 months).

Results: With the exception of the first 48h, only a small percentage of patients had sub-therapeutic TK levels (23% at 48h, 3% at 7d, 6% at 14d, 3% at 21d, and 3% at 28d). Additionally, despite close C₀ monitoring and dose adjustments, a higher proportion of patients presented TK overdosing (>15ng/mL) at different timepoints after alloHCT (23% at 48h, 28% at 7d, 22% at 14d, 20% at 21d, and 26% at 28d) (Figure 1).At 48 hours, C₀ levels were significantly higher with IV TK than with oral formulations, resulting in lower proportion of patients with C₀ < 5ng/mL (IV TK 14% vs. BID 27%, p = 0.037; and vs. QD 28%, p = 0.027) and higher proportion with C₀ > 15ng/mL (IV TK 23% vs. BID 11%, p = 0.027; and QD 11%, p = 0.042). Sub-therapeutic TK levels at 48 hours and at 7d were associated to a higher incidence of grade II-IV GVHD (31% vs. 21% at 48h, p = 0.088; and 8% vs. 0.6% at 7d, p = 0.001). AKI was observed in 180 (76%) patients (grade 1 n = 77, grade 2 n = 79, and grade 3 n = 24) with no significant differences between IV TK, BID, and QD. Ten (4%) and 14 (6%) patients developed TMA and neurotoxicity, respectively, with no differences between groups.

Figure 1. TK C₀ levels according to different TK formulations (IV TK, intravenous; BID, twice-daily oral; QD, once-daily modified-release).

Conclusions: IV TK allows reaching therapeutic levels more quickly than oral formulations. Our results show that a quarter of the patients have supra-therapeutic TK levels regardless of the formulation used, and despite close monitoring. Considering that sub-therapeutic levels are associated with increased risk of GVHD, the use of TK IK subsequently switching to VO appears to be the best option.

Disclosure: All authors declare no conflicts of interest.

P195 Prophylactic defibrotide is effective for acute graft versus host disease as well as sinusoidal obstructive syndrome

E. Kircali¹, G. Cengiz Seval¹, S. Civriz Bozdag¹, M. Kurt Yuksel¹, P. Topcuoglu¹, O. Arslan¹, M. Ozcan¹, T. Demirer¹, G. Gurman¹, M. Beksac¹, O. Ilhan¹, S.K. Toprak ¹

¹Ankara University, Ankara, Turkey

Background: Defibrotide is an antithrombotic, anti-inflammatory, profibrinolytic and antiischemic drug composed predominantly of single-stranded polydeoxy ribonucleotides. It is mainly used to prevent and treat sinusoidal endothelial cell damage in sinusoidal obstruction syndrome (SOS) after allogeneic stem cell transplantation (Allo-SCT), with acceptable toxicity. As the data showing that defibrotide may have a protective effect on activated endothelial cells become widespread, and it has been shown in preclinical studies that defibrotide suppresses heparanase gene expression, which is thought to have a great effect on acute graft versus host disease (aGvHD) the role of this drug in aGvHD has also become evident, the hypothesis that defibrotide may have a role in aGVHD has been developed. In this study, we investigated the relationship between defibrotid and aGvHD based on this hypothesis.

Methods: Between January 2014 and May 2021, 345 patients who underwent allogeneic stem cell transplantation (Allo-SCT) were included for this analysis in our center. In 116 (33.6%) of these patients, the risk of SOS was found to be high (busulfan will be used in the preparation regimen, gemtuzumab ozogamicin was used in the 3 months before the transplant, the abdominal region will be irradiated, in these patients with active hepatitis B or C infection, the preparation regimen will be started. Similarly, 25 mg/kg/dose prophylactic defibrotide was used in 4 equal doses for 21 days. Patients who used defibrotide for therapeutic purposes were not included in the study. The patients who underwent ASCT from a fully matched sibling donor, fully matched unrelated, or a 9/10 HLA-matched unrelated donor were included whereas cord blood transplants were not.

Results: The female to male ratio was 143/202 and the median age was 43 (18-72). The distribution of ASCT indications according to defibrotide absent and present groups were as follows: acute myeloid leukemia(AML,n = 142) 88(62%)/54(38%), acute lymphoblastic leukemia(ALL,n = 64) 46(71,9 %)/18(28.1 %), myelodysplastic syndrome(MDS,n = 26) 17(65.4%)/9(34.6%), aplastic anemia(AA, n =18) 12(66.7%)/6(33.3%), mycosis fungoides(MF,n = 13) 9(69.2%)/4(30.8 %), chronic myeloid leukemia(CML,n = 13) 10(76.9%)/ 3(23.1%), primary myelofibrosis(PMF,n = 11) 6(54.5%)/5(45.5%), Hodgkin’s lymphoma(HL,n = 7) 6(85.7 %)/1(14.3), peripheral T cell lymphoma(PTCL,n = 7) 7(100%)/0 and other(n = 44) 28(63.6%)/16(36.4 %), respectively. The distribution did not differ statistically between the groups (p = 0,537). We performed a multivariate analysis to examine the effect of defibrotide on the risk of developing aGvHD and the degree of aGvHD, and observed that prophylactic defibrotide significantly reduced the risk of developing aGvHD (p = 0.001). Similarly, in patients who have developed aGvHD, total Glucksberg degree of aGvHD is attenuated with prophylactic defibrotide, too (p = 0,049).

Conclusions: aGvHD is one of the life-threatening early complications of AKHN and is still the most important cause of non-recurrent mortality. Therefore, any approach that can reduce the risk and degree of aGvHH may be clinically important.To our knowledge, this is the largest study that evaluate the effectiveness of defirotide on GvHH, but prospective randomized controlled studies are warranted to verify our data.

Disclosure: Nothing to declare

P196 Prospective analysis of the incidence and outcome of late acute and chronic graft-versus-host disease from multiple transplant centers

R. Langer ¹, A. Lelas², L. Desnica², M. Rittenschober³, A. Piekarska⁴, A. Sadowska-Klasa⁴, I. Sabol⁵, H. Greinix⁶, A. Dickinson⁷, M. Inngjerdingen⁸, A. Lawitschka³, R. Vrhovac², D. Pulanic², S. Klein⁹, J.M. Middeke¹⁰, M. Grube¹, E. Holler¹, M. Edinger¹, W. Herr¹, D. Wolff¹

¹University Hospital Regensburg, Regensburg, Germany, ²University Hospital Centre Zagreb, Zagreb, Croatia, ³St. Anna Children`s Hospital, Medical University of Vienna, Vienna, Austria, ⁴Medical University of Gdansk, Gdansk, Poland, ⁵Rudjer Boskovic Institute, Zagreb, Croatia, ⁶Medical University of Graz, Graz, Austria, ⁷Newcastle University Faculty of Medical Sciences, Newcastle upon Tyne, United Kingdom, ⁸Institute of Clinical Medicine, University of Oslo, Oslo, Norway, ⁹University Medical Center Mannheim, Mannheim, Germany, ¹⁰University Hospital Dresden, Dresden, Germany

Background: Chronic Graft-versus-Host Disease (cGvHD) is the most serious late complication of allogeneic hematopoietic stem cell transplantation (allo-HSCT). Our aim was to capture the current incidence of cGvHD and late acute GvHD (laGvHD) based on the 2014 NIH consensus criteria and its impact on transplant related mortality (TRM), relapse (R), and overall survival (OS) within a multi-center analysis including transplant centers from Regensburg, Mannheim, Dresden, Vienna, Zagreb and Gdańsk.

Methods: The analysis was performed on 317 consecutively transplanted patients, 296 adults and 21 pediatrics, who underwent first allo-HSCT in 2017. Endpoints were OS, TRM and R at last follow-up and second transplantation with the latter being censored. Patients with TRM or R before day 100 after allo-HSCT were excluded from cumulative incidence (CI) analysis of cGvHD.

Results: CI of laGvHD were 9.5% (adults) and 4.8% (pediatric) (median d onset 137, range 100-415), while CI of cGvHD of the patient cohort at risk was 43.6% (adults) (median d onset 198, range 68-1051) in a median observation time of 397 days. The type of onset of cGvHD was de novo in 45 (41.3%), quiescent in 54 (49.5%) and progressive in 10 (9.2%) patients, respectively. In adults, the use of ATG (n = 137) or post-transplant cyclophosphamide (n = 62) as prophylactic agents led to a significantly (p < 0.01) lower incidence of cGvHD compared to standard prophylaxis (n = 116) (33.3% and 31.9% vs. 61.5%).

	Adults with allo-HSCT (n = 296)	Pediatrics with allo-HSCT (n = 21)	Adults at risk (n = 250)	Pediatrics at risk (n = 19)
no GvHD	107 (36.1%)	15 (71.4%)	70 (28.0%)	13 (68.4%)
aGvHD	127 (42.9%)	6 (28.6%)	118 (47.2%)	6 (31.6%)
laGvHD	28 (9.5%)	1 (4.8%)	28 (11.2%)	1 (5.3%)
cGvHD	109 (37.2%)	2 (9.5%)	109 (43.6%)	2 (10.5%)
mild	56 (51.4%)	0 (0.0%)	56 (51.4%)	0 (0.0%)
moderate	43 (38.5%)	1 (50.0%)	43 (38.5%)	1 (50.0%)
severe	10 (8.3%)	1 (50.0%)	10 (8.3%)	1 (50.0%)

By exclusion of the early mortality (d 100: TRM 7.6%, R 6.3%, OS 91.2%) and start of CI on day 100 of the remaining 269 patients at risk for cGvHD or laGvHD TRM was significantly higher in patients with aGvHD and cGvHD compared to no cGvHD (19.3% and 9.0% vs. 5.4%; p = 0.0036). OS was significantly higher in patients with cGvHD compared to patients without cGvHD (77.7% vs. 61.1%; logrank test p = 0.0006; HR 0.3396, 95%CI 0.1939-0.5945) since diagnosis of cGvHD resulted in a significant lower relapse rate compared to patients without cGvHD (17.9% vs. 32.6%; logrank test p < 0.0001, HR 0.216, 95%CI 0.115-0.405). We didn’t find a significant influence of onset type or maximum severity grade of cGvHD on TRM and R. We also found a significant better OS in patients with mild and moderate cGvHD compared to patients without cGvHD, but not for severe cGvHD forms (mild: 94.3%; moderate: 70.7%; severe: 55.6% vs. no cGvHD: 61.1%; p = 0.001; p = 0.0426 and p = 0.9645).

OS for adults after diagnosis of cGvHD

 

Conclusions: The analysis revealed an improved survival with mild and moderate GvHD compared to patients without cGvHD due to a reduced relapse rate. In contrast, severe cGvHD negatively affected OS and future aims should focus on prevention of severe forms to improve OS and quality of life. Interestingly, the prognosis of patients with cGvHD appeared to be better compared to past cohorts.

Disclosure:

Prof. Dr. med. Daniel Wolff received research funds from Novartis and honoraria from Amgen, Neovii, Novartis, Mallinckrodt, Incyte and Takeda.

Radovan Vrhovac received honoraria from Novartis, Pfizer, Abbvie and MSD.

Dr. Anita Lawitschka, MD received honoraria from Novartis.

Dr. med. Jan Moritz Middeke received honoraria from advisory board Novartis.

Univ.-Prof. Dr. med. univ. Greinix, Hildegard received honoraria for participation in advisory boards and speakers bureau from gilead, BMS/celgene, sanofi, takeda, Therakos.

Prof. Dr. med. Ernst Holler received honoraria from Advisory board MEDAC, Maatpharma, pharmabiome and Novartis, speakers bureau Neovii.

P197 Myeloid-derived suppressor cells predict response to ruxolitinib-corticosteroids therapy for acute graft versus host disease

B. Peng ^1,2, L. Dou^3,2,4, J. Yang², D. Liu^3,2

¹The Fifth Medical Center of Chinese PLA General Hospital, Beijing, China, ²Medical School of Chinese PLA, Beijing, China, ³the Fifth Medical Center of Chinese PLA General Hospital, Beijing, China, ⁴The second School of Clinical Medicin, Southern Medical University, Guangzhou, China

Background: Acute graft versus host disease (aGVHD) remains one of the principal causes of nonrelapse mortality (NRM) following hematopoietic stem cell transplantation (HSCT). Systemic corticosteroids are often used as first-line therapy for aGVHD, but nearly 50% of the aGVHD patients are resistant to steroids. It has been reported that ruxolitinib combined with steroids was tolerable in patients with newly diagnosed aGVHD with improved overall response rate (ORR). However, the optimal predictor for predicting response to this novel first-line treatment has not been established clearly. Myeloid-derived suppressor cells (MDSC) are a group of myeloid cells with immunosuppressive activity, including granulocytic MDSCs (G-MDSC), monocytic MDSC (M-MDSC) and early-stage MDSC (e-MDSC). This study focused on the kinetics of MDSC during the treatment of ruxolitinib combined with steroids for aGVHD, and explored the relationship between MDSC and response to treatment.

Methods: Peripheral blood (PB) samples from patients who underwent HSCT were prospectively obtained for regular evaluation of MDSC reconstitution after transplantation. Flow cytometry was utilized to monitor MDSC recovery at different time points. And in cases with aGVHD, MDSC frequency before and after aGVHD treatment (+3 days, +7 days, +14 days and +28 days) were also monitored. MDSC suppression assay was performed to verify the inhibition of MDSC on T cell proliferation through the co-culture of purified CD8 + T cell and MDSC isolated from the PB of patients.

Results: Changes of G-MDSC kinetics observed during ruxolitinib-corticosteroids treatment are significant and showed an upward trend after initiation of therapy (P = 0.012). The ratio of G-MDSC to PB CD45 + cells on day 3 after aGVHD therapy was significantly higher than that of day 3 prior to aGVHD. In contrast to G-MDSC, M-MDSC showed a decreasing trend after aGVHD treatment (P = 0.004). Ratios of E-MDSC at different time points were also obviously different during aGVHD treatment (P = 0.010). The G-MDSC of the ruxolitinib-corticosteroids sensitive group increased significantly from baseline after treatment, while the G-MDSC of the combined treatment resistant group showed no noticeable change (Figure 1) . In the MDSC suppression assay, MDSC markedly inhibited T cell proliferation (proliferation index: no MDSC, 9.24 ± 8.10 vs. with MDSC, 5.45 ± 4.05; P = 0.037).

Conclusions: MDSC recovery is closely related to the response to ruxolitinib-corticosteroids as first-Line therapy for newly diagnosed aGVHD. Patients with lower G-MDSC levels at baseline and 7-21 days after HSCT were more likely to develop aGVHD resistance to ruxolitinib combined with corticosteroids than controls. The kinetics of MDSC subpopulations may be used to predict the duration of response to this novel first-line treatment.

Clinical Trial Registry: None

Disclosure: Nothing to declare

P198 Relationship within anaerobicidal antibiotics, clostridium difficile infection and the development and degree of digestive graft versus host disease

A. Borrero Borrego ¹, L. González Pinedo¹, M.K. Torres Ochando¹, M.T. Borrero Borrego², G. Strigkos², M.D.M. Perera Álvarez¹

¹Hospital Universitario de Gran Canaria Doctor Negrin, Las Palmas de Gran Canaria, Spain, ²University of Utrecht, Utrecht, Netherlands

Background: Severe digestive graft versus host disease (GVHD) is a topic of great importance after allogeneic Hematopoietic Stem Cell tTransplantation (allo-HSCT), since it is difficult to treat and the involvement of the digestive system is described in almost all cases of fatal acute GVHD. It is also known that the recruitment of inflammatory cells is dependent on bacterial translocations in the intestinal wall, leading to an increasing interest in factors that could take part in this process.

Methods: We performed an observational and retrospective analysis in a single-center study, of all patients that underwent to allo-HSCT from January/2019 to March/2021 (N = 71) and analyzed all the possible pre-transplant conditions and during it, which could determine the development of digestive GVHD, such as, antibiotics guided by multi-resistant bacteria isolated in rectal exudates, clostridium difficile infection and mucositis. The primary outcome was the risk of developing upper and lower acute GVHD. We adjusted logistic regression model included transplantation characteristics, GVHD risk factors and adjunctive antibiotic exposures as covariates.

Results: A total of 71 patients were included in the full cohort. There were no differences regarding the distribution by sex. The average age was 47. The main transplanted pathology was acute leukemia. The types of HSCT were: 56.3% (40/71) haploidentical, 24% (17/71) non related, 17% (12/71) HLA identical and 2 mismatch.

The standard prophylaxis of GVHD was High Dose Cyclophosphamide on days + 3/+ 4 followed by anticalcineurinic and Mycophenolate mofetil from day +5.

We used standard antibiotic prophylaxis with quinolones. Multi-resistant (MR) bacterias were discovered in 20% (13/64) of patients at admission date, and from the rest, 15% acquired resistance during hospital stay; no relationship was observed between colonization with MR bacteria and the development of digestive GVHD.

Empirical antibiotic therapy in our center is with third generation cephalosporins (cefepime). 93% (66/71) suffered from febrile neutropenia and of these, 82% (54/66), were treated with cefepime combined or in monotherapy. 33% (21/66) used combined therapy, being the main group of antibiotics: glucopeptides (28), piperacilina tazobactam (15), carbapenems (20) and Ceftazidime-avibactam (4). None of them was associated, in adjusted models, with an increased risk of GVHD.

Mucositis grades II-IV was present in 41% (29/71) of patients, having received 76% (22/29) of those, a myeloablative conditioning regimen. Clostridium difficile infection was discovered in 18% (13/71) of patients.

20 patients developed digestive GVHD: 30% (6/20) grades III-IV and 75% (15/20) grades II-IV, and we observed an association between the infection with clostridium difficile and an increased risk of GVHD (adjusted odds ratio (aOR) 6.33; 95% confidence interval (CI) 1.7 – 23.5), as well as with an increased risk of grade II-IV GVHD (not statistically significant).

Conclusions: Clostridium difficile must be carefully studied in allo-HSCT patients and prevention strategies should be made, in order to control this entity; as it has been related to digestive GVHD according to the bibliography and as it has been shown in our study. No recommendations could be made about the antibiotic strategy and more studies should be performed in this way.

Disclosure: Nothing to declare.

P199 Low-dose antithymocyte globulin plus low-dose posttransplant cyclophosphamide could mitigate the risk of graft versus host disease after haploidentical transplantation from maternal/collateral donors

X. Song¹

¹Shanghai General Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China

Background: Maternal and collateral donors were associated with higher incidence of acute graft-versus-host disease (aGvHD) after haploidentical hematopoietic stem cell transplantation (haplo-HSCT).

Methods: To improve the efficiency of GvHD prophylaxis in haplo-HSCT with maternal and collateral donors, a novel regimen which was composed of low-dose ATG and low-dose PTCy combined with CsA and MMF had been developed in our center. We performed a retrospective study on 50 patients diagnosed with hematological malignancies after maternal/collateral haplo-HSCT (20 with ATG-based regimen for GvHD prophylaxis and 30 with the low-dose ATG/PTCy-based regimen).

Results: The 180-day cumulative incidences (CIs) of grades II-IV and III-IV acute GvHD were 24.1% and 7.6% in the low-dose ATG/PTCy-based group, which were significantly lower than that in the ATG-based group (51.6% and 27.7%). In low-dose ATG/PTCy-based group, the 2-year probability of overall survival (OS) and relapse-free survival (RFS) were 70.9% and 71.1%, which were higher than that in ATG-based group with OS of 43.2% and RFS of 44.1%. Furthermore, according to multivariate analysis, the low-dose ATG/PTCy-based regimen significantly reduced the risk of grade II-IV (HR = 0.237, 95% CI 0.067-0.829; P = 0.024) and grade III-IV aGvHD (HR = 0.015, 95% CI 0.000-0.899; P = 0.044) as a positive risk factor.

Conclusions: The results suggested that low-dose ATG with low-dose PTCy could be a novel regimen to effectively prevent acute GvHD after maternal/collateral donor transplantation.

Disclosure: Nothing to declare.

P201 Exocrine pancreatic insufficiency as an atypical manifestation of chronic graft versus host disease following allogeneic hematopoietic stem cell transplantation

A. Puchol Crespo ¹, I. Iturrate Basarán¹, C. Mayor Bastida¹, S. Díaz López¹, A. Alegre Amor¹, Á. Figuera Álvarez¹, B. Aguado Bueno¹

¹Hospital La Princesa, Madrid, Spain

Background: Graft-versus-host disease (GVHD) remains a major complication after allogeneic hematopoietic stem cell transplantation (HSCT). The diagnosis of chronic GVHD is complex, as it can potentially affect almost any organ/tissue¹. Rare forms of GVHD have been described in the literature including neurological, myofascial and cardiac involvement among others^2,3; to date, few reports have evaluated pancreas involvement in cGVHD. The major difficulty is to be suspicious in the face of the huge number of different clinical presentations of this postHSCT complication, as the one we show in our case report.

Methods: We report a case of pancreatic atrophy as a manifestation of cGVHD.

Results: A 42-year-old woman was diagnosed with AML in 2018 with NPM1 and FLT3/ITD + . Abnormal karyotype 47XX + mar, MLL negative. The patient had a morphologic complete remission after induction chemotherapy cytarabine and anthracycline, with positive minimal residual disease (MRD). It was followed by early consolidation with 2 cycles with high dose cytarabine and Midostaurin, achieving MRD negative before transplantation. She received and allogeneic peripheral blood HSCT from a matched unrelated female donor, with Cyclophosphamide and Busulfan (CyBu) conditioning regimen. Prophylaxis for GVHD with standard course of methotrexate and cyclosporine. She experienced acute grade II skin GVHD and diarrhoea that cleared after 2 weeks of prednisolone therapy.

Six months after transplantation cyclosporine was discontinued. For the next three months she gradually presented with weight loss (4 kg), steatorrhea and abnormal liver function tests. Due to GVHD suspicion 0.5 mg/kg/day course of Prednisone was started. The stool examination was negative for infectious causes of diarrhoea. Faecal elastase level was 5 mcg/g (normal > 200mcg/g). Breath test with ¹³C-mixed triglycerides was 20.75% (normal > 29% exhaled). Magnetic resonance imaging (MRI) showed remarkable diffuse pancreatic atrophy.

The clinical diagnosis was exocrine pancreatic insufficiency due to pancreatic atrophy, most likely as a form of cGVHD after allogenic stem cell transplantation. The patient received pancreatic enzyme supplement (Kreon 10.000 U, containing lipase 10.000U, protease 600U and amylase 8.000U) as required, starting on day +258, and nutritional support. After three months, steatorrhea was fully resolved, being able to taper prednisone without worsening, with progressive weight gain, stabilizing at her initial weight 6 months later.

Despite the clinical improvement, the pancreas atrophy persisted in the following MRIs. She didn’t suffer GVHD relapse nor needed to restart immunosuppressive treatment at any point of the follow-up.

Conclusions: There are few cases of pancreatic insufficiency after HSCT reported in the literature, being the most common form of presentation weight loss and steatorrhea. The etiology of pancreatic atrophy after HSCT is not fully known, although it shows a significant association with cGVHD, with greater loss of pancreatic glandular tissue than patients without cGVHD. In this population, the presence of gastrointestinal (GI) cGVHD is significant, suggesting that pancreatic atrophy might be a part of GI cGVHD. HSCT receptors that develop persistent fat malabsorption symptoms should be tested for exocrine pancreatic insufficiency, liable to be treated with oral enzyme supplements. All cases should be reported in order to better define and diagnose this rare entity.

Disclosure: Nothing to declare.

P202 Assessment of efficacy and toxicity of methotrexate in the treatment of chronic graft-versus-host disease

I. Gonçalves Ramos ¹, G. Fatobene¹, A. Costa Cordeiro¹, A. Ferreira Meneses¹, M. Fonseca¹, J. Manuel Carranza Jara¹, L. Netto Chaer¹, L. Carolina Barbosa Mariano¹, V. Rocha¹

¹University of São Paulo, São Paulo, Brazil

Background: Allogeneic hematopoietic stem cell transplantation (HSCT) is associated with several complications, including chronic graft-versus-host disease (cGVHD) in 30-70% of HSCTs. Chronic GVHD has impact on quality of life and mortality, often requiring multiple therapeutic lines. Among available therapeutic options, methotrexate is an attractive one as it is a potentially low-cost, effective alternative associated with reduced toxicity. However, previous studies were relatively small or included heterogeneous groups of patients. The aim of this analysis was to assess the impact of methotrexate on the treatment of cGVHD in adult patients.

Methods: Retrospective evaluation of electronic medical charts of patients. Eligible patients were those with diagnosis of cGVHD according to the 2014 NIH consensus criteria treated with methotrexate in second line or beyond between January 2014 and November 2020. Additionally, patients were required to have received at least 4 doses of methotrexate and have a minimum follow-up time of 3 months after starting this therapy. Best overall response (BOR) at 6 months was the primary endpoint, whereas secondary endpoints included failure-free survival, cumulative incidence of steroid withdrawal, overall survival, and toxicity.

Results: Twenty-one patients receiving methotrexate for treatment of cGVHD were identified; two of whom were excluded for having less than 3 months of follow-up period. The analysis included 19 patients with a median follow-up of 18 months (range, 3 to71). The cumulative incidence of BOR at 6 months was 63% (11/19 patients), 16% of which (3/19 patients) corresponding to complete response, and 43% (8/19 patients) to partial response. Among patients with severe and moderate cGVHD, BOR were 37% (3/8 patients) and 45% (5/11 patients), respectively. The cumulative incidence of steroid discontinuation at 6 months was 60% (95% confidence interval [CI] 29-81%). Skin, mouth and liver were the most affected organs in evaluable patients; only two patients presented fascia/joint involvement. Failure-free survival at 6 months was 90% (95% CI 64-97%), and the overall survival at 1 year was 88% (95% CI 59-97%). Little methotrexate-attributable toxicity was observed, with only one case of renal toxicity and one case of liver toxicity, both at grade. One patient had disseminated adenoviral infection on methotrexate and other concomitant immunosuppressive drugs, which was not fatal. The median time between the start of methotrexate and BOR was 92 days (17-180, n = 11), and the maximum dose was 7.3 mg/m² (min-max3.2-13.4).

Conclusions: Patients receiving methotrexate for the treatment of cGVHD had an overall response rate comparable to previous studies in the literature and showed favorable toxicity and tolerance profiles. These advantages combined with its low cost make this medication an interesting option in resource-constrained countries. Apart from its retrospective nature, this analysis has relevant limitations: lack of a comparative group, organ-specific responses, and a formal evaluation of cost-effectiveness. Studies defining the ideal dose of methotrexate in cGVHD and encompassing a larger number of participants are necessary for a more accurate assessment of the role of this medication in the treatment of cGVHD.

Disclosure: Nothing to declare.

P203 Treatment of graft-versus-host disease with extracorporeal photopheresis. Experience in a center

P. López de Ugarriza ¹, P.C. Tamayo Arroyo¹, E. Martínez Revuelta¹, J.M. García Gala¹, M.Á. Fernández Rodríguez¹

¹Hospital Universitario Central de Asturias, Oviedo, Spain

Background: Extracorporeal photopheresis (ECP) is an immunomodulatory therapy mainly indicated in cutaneous T lymphoma treatment, acute graft-versus-host disease (aGVHD) and chronic graft-versus-host disease (cGVHD) after allogeneic hematopoietic stem cell transplant (AHSCT), solid organ transplant rejection and conventional treatment resistant autoimmune disorders. Among its advantages, it stands out that it does not produce immunosuppression or drug interactions with complementary immunosuppressive treatment. Although it has been shown to be effective, safe and well tolerated, reported responses are highly variable. The objective of this study is to describe the experience in our center in the treatment of graft-versus-host disease (GVHD) with ECP.

Methods: Medical histories of those patients who received treatment with ECP for both aGVHD and cGVHD in our center were retrospectively reviewed. The analysis period was from 2014 to 2021.

Results: 28 patients were included in the study. The average age was 41,21 years (5-68). For all of them, 20/28 (71,42%) were men. Related to type of AHSCT, patients who received an unrelated donor transplant, HLA-matched sibling donor transplant and haploidentical donor transplant were 17/28 (60,71%), 8/28 (28,57%) and 3/28 (10,71%) respectively. The diagnosis that motivated the transplant was Acute Lymphoblastic Leukemias in 8/28 (28,57%), Acute Myeloblastic Leukemias in 8/28 (28,57%), Chronic Myeloproliferative Neoplasms in 4/28 (14,28%), Non-Hodgkin Lymphomas in 4/28 (14,28%), and other diagnoses in 4/28 (14,28%). All patients (28/28; 100%) received at least one adjuvant immunosuppressant treatment and 17/28 (60,71%) received three. Many patients (24/28; 85,71%) had cGVHD. Clinical involvement related to GVHD that patients presented most frequently was cutaneous (25/28; 89,28%) followed by digestive (12/28; 42,85%), joint (5/28; 17,85%), hepatic (4/28; 14,28%) and respiratory (2/28; 7,14%). Most patients (25/28, 89,28%) required the placement of a central venous catheter. Mean number of procedures performed was 26,53 (2-51). 3/28 (10,71%) patients performed more than one cycle of procedures. The response to ECP was complete, partial and non-response in 8/28 (28,57%), 12/28 (42,85%) and 8/28 (28,57%) respectively. Of the 5/28 (17,85%) patients who died, the cause was aGVHD in 2/5 (40%) and intercurrent infection was the cause in 3/5 (60%). No complications were detected with ECP except catheter-related infection. It was detected in 8 episodes (28,57%) that involve 7/28 (25%) patients. A patient died because of catheter-related infection.

Conclusions: ECP is an immunomodulatory procedure, safe and excellently tolerated in patients with GVHD that offers the advantage of being able to be administered together with other immunosuppressive treatments without interactions. Two thirds of patients with GVHD experience a total or partial response so the treatment is effective and should be considered associated with immunosuppression.

Disclosure: Nothing to declare

P204 Apoptosis and cytokine secretion of t cells during ecp treatment for cgvhd using the amicus™ blue™ online ecp system

Y. Ventura-Carmenate ¹, Y.M. Castillo-Aleman¹, C.A. Villegas-Valverde¹, A.A. Bencomo-Hernandez¹, M. Al Amin¹, M.A. Martinez¹, F.M. Al Kaabi¹

¹Abu Dhabi Stem Cells Center, Abu Dhabi, United Arab Emirates

Background: ECP is an immunomodulatory therapy for T-cell mediated diseases. Although the immunological mechanisms are not fully understood, it is known that the induction of apoptosis is a central mechanism of ECP. Following ECP, the cytokine profile is modified toward upregulation of immunosuppressive factors and downregulation of co-stimulatory molecules. These immune responses can help attenuate inflammatory conditions such as GvHD. We performed a prospective analysis of apoptosis and cytokine secretion by flow cytometry in ECP treated cells of steroid refractory cGvHD patients. ECP was performed with the Amicus Blue™ online system (Fresenius Kabi, Germany).

Methods: Seventy-five ECP procedures (n = 75) were performed in 3 female patients from May 2021 to December 2021. Samples (2mL) of the collected cells were taken before the addition of 8-methoxypsoralen (8-MOP) and after UVA photoactivation. The samples were re-suspended in 3mL of RPMI 1640 culture medium with 10% AB serum and incubated at 37°C in 5% CO2 for 24, 48, and 72 hours. Apoptosis measurement was performed by flow cytometry using the DxFlex flow cytometer (Beckman Coulter, USA) and the Beckman Coulter Annexin A5 FITC/7AAD kit (IM3614) according to the instructions, and with the additional use of reagents Beckman Coulter CD45-APC AF 750 (A79392) and CD3-APC (IM2467). The expression of two cytokines, TNFα and IFNy, was assessed by flow cytometry using the DxFlex flow cytometer on CD4 + T and CD8 + T cells before and after 24hr in the culture at 37°C in 5% CO2. The samples were either stimulated with CytoStim™ (Miltenyi Biotec), or with PBS (negative control), and incubated at 37°C and 5% CO₂ for 2hr. Brefeldin A was added and incubated for 6hr, and fixation and permeabilization were performed. Staining was performed with monoclonal antibodies (Miltenyi Biotec): CD3-APC, CD4-Vio® Bright B515, CD8-VioGreen™, IFNγ-PE, TNFα-PE-Vio® 770 Fixed Dye and Viobility 405/452. Data were processed using Kaluza C Software v1.1 with a minimum of 150,000 acquired events. The one-way ANOVA test for paired samples was performed with GraphPad Prism v.8 (La Jolla, USA) and considered statistically significant for p < 0.05.

Results: We used simultaneous staining with annexin V-FITC and 7ADD to measure apoptosis. After in vitro culture of ECP treated cells, 13% (5-20%) of CD3 + T cells were apoptotic at 48hr compared to 31.3% (23-46%) at 72hr, with only 30.3% (24-40.1%) viable cells (p = 0.03). Untreated cells maintained up to 80% viability after 72hr. The number of TNFα-secreting TCD8 cells was significantly higher in pre-ECP stimulated samples (p = 0.001). A decrease in T cells secreting IFNy was also observed in the post-ECP stimulated samples without statistical significance.

TCD3 apoptosis induced by ECP and (B) Intracellular flow cytometric enumeration of IFNу/TNFα secreting CD4, CD8-T cells

Conclusions: Our results for ECP-induced apoptosis at 72hr with the Amicus Blue ECP system were comparable to published literature. Reduction of TNFα after ECP treatment may have a direct role in reducing the progress of cGvHD. ECP performed with the Amicus Blue system resulted in a reduction of TNFα and IFNу levels in the treated cells, as expected.

Disclosure: Nothing to declare

P205 Routine use of anti-thymocyte globulin (atg) results in low incidence of severe graft-versus-host disease: A single center experience

F. Kovácsová ¹, M. Krejčí¹, B. Weinbergerová¹, M. Tomíška¹, T. Kabut¹, F. Folber¹, J. Mayer¹

¹Masaryk University Hospital Brno, Brno, Czech Republic

Background: Anti-thymocyte globulin (ATG, Grafalon) is a mix of polyclonal rabbit anti T-cell antibodies used to reduce the risk of graft rejection and acute and chronic graft-versus-host disease (GVHD) in the setting of an allogeneic hematopoietic stem cell transplantation (alloHSCT). The aim of this study was to find out the cumulative incidence (CI) of GVHD while using ATG at our institution, and to compare this incidence among various patient subgroups.

Methods: From all the patients who underwent their first alloHSCT at our department between 2006 and 2020 we excluded those who did not receive ATG. We studied the cumulative incidence and severity of acute (100-day CI) and chronic GVHD (24-month CI), and differences depending on HLA matching, conditioning regimen intensity, and the underlying disease.

Results: We identified 481 patients in the defined time period. Eighty-three of them were excluded for not having received ATG due to heterogeneous reasons (e.g. obsolete conditioning regimens, non-malignant diseases, bone marrow stem cell source, high risk of relapse), making this subgroup unevaluable. A total number of 398 patients were included into this analysis, 203 with acute myeloid leukemia (AML) or myelodysplastic syndrome (MDS), 69 with acute lymphoblastic leukemia (ALL), 44 with lymphoma, 40 with myeloproliferative neoplasms, 30 with chronic lymphocytic leukemia (CLL), and 12 others. Acute GVHD was observed in 44.7% patients (grade III and IV in 11.6%), chronic GVHD in 37.6% (extensive in 7.1%). Incidence of GVHD using an unrelated donor was higher than in related donor HSCT (acute GVHD 49.0% vs. 34.8%, respectively, p = 0.01; chronic GVHD 40.5% vs. 30.6%, respectively, p = 0.02). Higher incidence of both acute and chronic GVHD was observed in the case of HLA mismatch (53.0%, 44.6%, respectively) compared with the group of fully matched (10 out of 10) unrelated donor HSCT (45.1%, 34.9%, respectively). Myeloablative conditioning was administered in 27.6%, and reduced intensity in 72.4% patients. Incidence of acute GVHD was higher among the patients who received reduced intensity conditioning than in the subgroup with myeloablative conditioning regimen (48.9% vs. 34.0%; p = 0.02). The same was observed for chronic GVHD (42.0% vs. 26.0%; p˂0.01). Incidence of GVHD was also higher in myeloid malignancies (statistically insignificant), but this can be explained by more frequent use of reduced intensity conditioning in this subgroup.

Conclusions: With the routine use of ATG the incidence of severe grades (III to IV) acute and chronic GVHD was as low as 11.6% and 7.1%, respectively. There were significant differences in the incidence according to conditioning regimen intensity and HLA matching.

Disclosure: Nothing to declare.

P206 JAK 1/2 inhibitor (ruxolitinib) might have a positive effect on MDSCS

J. Yang ¹, B. Peng¹, S. Fang¹, K. Qian¹, H. Wang¹, Y. Wen¹, Y. Jiao¹, D. Liu¹, L. Dou¹

¹the Fifth Medical Center of Chinese PLA General Hospital, Beijing, China

Background: Graft-versus-host disease (GVHD) is the major cause of non-relapse mortality (NRM) after allogeneic hematopoietic stem-cell transplantation (HCT). The response rate to first-line corticosteroid therapy for aGVHD patients is approximately 50%. The overall survival of steroid-refractory aGVHD patients is only approximately 30%. A new first-line therapy to improve the efficacy of treatment for aGVHD is of great significance.

Methods: We performed a prospective, open-label trail (NCT04061876) in my transplantation center and prospectively observed the kinetic characteristics of lymphocyte subsets and MDSC were monitored, and then we compared them in steroids-ruxolitinib group (n = 23), free-aGVHD group (n = 20) and steroids group (n = 23). Healthy human PBMC was treated with different concentrations of JAK 1/2 inhibitor (Ruxolitinib) to detect the effects on differentiation and function of MDSC.

Results: In all aGVHD patients treated with Steroids-Ruxolitinib therapy, the Day 28 CR rate was 78.26% (18/23). On day 28 after treatment, patients had lower level of CD4⁺CD29⁺ T cells (P = 0.08) than that of pre-treatment, whereas levels of other lymphocyte subsets in this study were higher than that of pre-treatment; CD8⁺CD28^- T cells (P = 0.03) significantly increased in patients with aGVHD than that in patients without aGVHD, so did CD8⁺CD28^- T/CD8⁺CD28⁺ T cell ratio (P = 0.03). Compared with patients without aGVHD, patients with aGVHD had lower level of G-MDSC, especially on day 14 after allo-HSCT (P = 0.04). Compared with pre-treatment, M-MDSC was higher in CR patients on day 3 and 7 post-treatment(P₃ = 0.01, P₇ = 0.03), e-MDSC was higher on day 28 post treatment (P = 0.01). Moreover, compared with CR patients, M-MDSC was lower in refractory aGVHD patients on day 3 post-treatment (P = 0.01) and e-MDSC was lower on day 28 post-treatment (P = 0.01). Compared with steroids group, MDSC in steroids-ruxolitinib group was higher, with the most significant difference in M-MDSC (P₃ = 0.03; P₇ = 0.01; P₁₄ = 0.04). In the vitro differentiation model of peripheral blood mononuclear cell (PBMC), JAK 1/ 2 inhibitors can promote MDSC and Treg most (P_e-MDSC = 0.01; P_G-MDSC = 0.05; P_M-MDSC = 0.02; P_Treg = 0.04), at 1.0 μM JAK 1/2 inhibitor (Ruxolitinib) treated for 72 h; We also found JAK 1/ 2 inhibitor can increase the expression of S100A8(P = 0.004), S100A9 (P = 0.04) and NO(P = 0.03), at a concentration of 1.0 μM.

Conclusions: The response rate of the novel first-line therapy, Steroids-Ruxolitinib, for aGVHD was promising in patients with moderate and high "Minnesota and MAGIC" risk. Moreover, the novel first-line therapy has a small impact on the immune reconstitution of patients after allo-HSCT. Patients with a better response with novel aGVHD first line therapy have higher level of MDSCs, compared to refractory ones. JAK 1/2 inhibitor can promote the differentiation and function of MDSCs.

Disclosure: This work was partially supported by grants from the National Natural Science Foundation of China (Nos. 82070178, 81770203,81700122, 81270610), Military Translational Medicine Fund of Chinese PLA General Hospital (ZH19003). Medical big data and artificial intelligence development fund of Chinese PLA General Hospital (2019MBD-016, 2019MBD-008). Military medical support innovation and generate special program(21WQ034). Special Research Found for health protection(21BJZ30).

P207 Long-term outcome in patients receiving imatinib for steroid-refractory chronic GVHD/ for refractory chronic graft-versus-host disease with fibrotic features: A single-center experience

N. Mandaci Şanli¹, E. Karakuş¹, A. Unal ¹, M. Keklik¹

¹Erciyes University, Kayseri, Turkey

Background: Pathogenesis of chronic graft-versus-host disease (cGVHD) is incompletely defined. Standard treatment is lacking for steroid-dependent/refractory cases; Recent insights suggest that several players and different pathways are involved, including imbalance of T and B cells and exaggerated collagen production. therefore, the potential usefulness of tyrosine kinase inhibitors (TKIs) has been suggested, based on their potent antifibrotic effect.

Methods: We performed in our clinic including 11 patients with refractory cGVHD, given imatinib at a starting dose of 100 mg per day. All patients had active cGVHD with measurable involvement of skin or other districts and had previously failed at least 2 treatment lines. The most frequent underlying diseases were: acute myeloid leukemia (7/11, 63.6%), acute lymphoblastic leukemia (3/11, 27.3%), and chronic myeloid leukemia (1/11, 9.1%). All of the patients received myeloablative conditioning regimens. Grading of cGVHD and response (complete and partial organ based on clinician assessments) was performed

Results: Patient median age was 42 years (range, 30-57 years), and median duration of cGVHD was 24 months (range, 2-300 months). All patients had moderate (37/11, (63.6%) to severe (4/11, 36.4%) cGVHD. Patients developed sclerotic skin lesions (8/11, 72.1%), lichen planus-like lesions (1/11, 9.1%), gastrointestinal and sclerotic skin lesions (1/11, 9.1%), liver and skin lesions (1/11, 9.1%). The median number of previous GVHD-therapies was 2 (range 2-5). Median imatinib treatment was 54 months (range: 3-108). Median follow-up was 77 months (range: 3-107). Overall 10 patients achieved a partial response and 1 patient complete response (CR) at 6 months of treatment. 3 of the patients responding as a partial response in the first year turned into a complete response during their follow-up. 2 patients discontinued imatinib therapy at year 4 of CR. They have been followed for a year without cGVHD treatment. While 1 patient responding as a partial response discontinued imatinib treatment after two years, another 1 patient discontinued imatinib treatment after three years. However, these two patients stopped treatment by themselves and one has been followed for 2 years and the other for 6 years in partial remission. 1 patient responding as a partial response in the first year turned into a flare after two years of imatinib treatment. All of the patients included in the study are still alive and 6 of the patients are still in a partial response. Of those patients responding to imatinib, the rate of GVHD-relapse was 9% (1/11) for fibrotic cGVHD. Imatinib-related, grade 3 to 4 toxicity included fluid retention, infections, and anemia were observed during the cGVHD treatment (respectively 2/11, 18.2%; 1/11, 9.1%; and 1/11, 9.1%).

Conclusions: Our findings suggest that imatinib is a promising treatment for patients with refractory fibrotic cGVHD

Disclosure: Nothing to declare

P208 Escalating combinatory first-line treatment for severe acute GVHD after hematopoietic stem cell transplant

F. Saraceni ¹, I. Scortechini¹, G. Mancini¹, A. Fiorentini¹, F.R. Colaneri¹, A.F. Lotito¹, S. Guerzoni¹, B. Puglisi¹, I. Federici¹, R. Bencivenga¹, B. Costantini¹, V. Bisraoui Huaman¹, S. Angeletti¹, M. Montanari¹, A. Olivieri¹

¹Ancona University Hospital, Ancona, Italy

Background: Acute graft-versus-host disease (aGVHD) is a major cause of morbidity and mortality after hematopoietic stem cell transplant (HSCT). High dose steroids remain the standard of care as first-line treatment for severe aGVHD, however less than 40% of patients show a long durable remission following such approach.

Methods: We retrospectively analyzed the outcome of 23 consecutive patients who developed grade 3-4 aGVHD and received an escalating combinatory first-line treatment at our institution.

Results: Donor was matched sibling (n = 1), matched unrelated (n = 12) or haploidentical (n = 10). Stem cell source was PBSC in 90% of the patients. Conditioning was myeloablative (MAC) or reduced-intensity (RIC) in 35% and 65% of the patients, respectively. aGVHD involved skin, GI, and liver in 87%, 83% and 17% of the patients, respectively. All patients received prednisone or methylprednisolone at a dose > = 1 mg/kg as first treatment. Response was evaluated at day 3 and 5 since start of steroids. In patients with symptoms progression at day 3 or stable disease at day 5 extracorporeal photopheresis (ECP) was added (n = 12 patients). In all patients with stage > =2 lower GI involvement, Ruxolitinib 10 mg twice daily was added within 5 days since start of steroids (n = 7 patients). ECP schedule included two treatments per week for 8 weeks with a subsequent individual reduction of treatment frequency. Response to first line treatment was evaluated at day 28 and day 56. In patients treated with steroids + ECP the overall response rate (ORR) at day 28 was 75% (n = 9), with 58% (n = 7) achieving CR. In patients treated with steroids + ECP + Ruxolitinib the ORR was 86% (n = 6), with 67% (n = 4) achieving CR (Figure 1). The durable ORR at day 56 was 58% (n = 7/12) in patients treated with steroids + ECP and 71% (n = 5/7) in patients treated with steroids + ECP + ruxolitinib. Median time on steroids was 12 days. ECP was well tolerated; the only adverse event recorded was mild thrombocitopenia in 4 patients. 5 patients receiving ruxolitinib experienced grade 2 anemia or thrombocytopenia, the latter leading to drug discontinuation in 2 patients. 13 patients received ECP and 3 patients received Ruxolitinib as second line treatment for steroid refractory or steroid dependent GVHD. 2 patients with lower GI involvement received vedolizumab as second line therapy. Median time to second line treatment was 24 days. 5 patients died; 4 due to infectious complications secondary to refractory GVHD, 1 of pulmonary embolism with GVHD in complete response. Median overall survival of the global population was 20 months.

Conclusions: In conclusion, an escalating combinatory first-line treatment with a backbone of steroids and ECP, and the addition of Ruxolitinb in patients with lower GI involvement seems feasible and associated with a promising response rate, allowing a rapid steroid taper.

Disclosure: Nothing to declare

P209 Retrospective single center analysis of alpha 1 antitrypsin for steroid-refractory acute graft-versus-host-disease of the gut after multiple lines of pretreatment

K. Nickel ¹, K. Braitsch¹, R. Eichner¹, K. Koch¹, I. Miller¹, L. Oßwald¹, F. Bassermann¹, P. Herhaus¹, M. Verbeek¹

¹Klinikum rechts der Isar der TU München, München, Germany

Background: Steroid-refractory acute Graft-versus-Host-Disease (SR-aGvHD) after allogenic hematopoietic stem cell transplantation (allo-HSCT) is challenging and associated with high morbidity and mortality. So far, no standard second-line therapy for SR-aGvHD has been established. Response rates of second-line immunosuppressive drugs are often disappointing. Also toxicity and especially infective complications are common issues. Alpha 1 antitrypsin (AAT1) is a serine protease inhibitor with antiapoptotic, anti-inflammatory and immunomodulatory effects, which showed efficacy in animal models on inflammatory disorders and autoimmune diseases, as well as promising results in a prospective clinical trial as second-line therapy for SR-GvHD. Safety of long-term AAT1 substitution in patients with inherited AAT deficiency without increased rates of infection was previously shown.

Methods: In a single center retrospective analysis we investigated the use of AAT1 in patients with grade III-IV SR-aGvHD of the gut. Steroid-refractory was defined by missing clinical benefit after the administration of 2 mg /kg prednisolone over at least 5 days. All patients had previously received at least one off-label second-line treatment for SR-aGvHD. AAT1 was administered intravenously twice a week for 4 weeks with 60 mg/kg. We analysed overall response rate (ORR), drug related toxicity and overall survival (OS). The response was assessed clinically using MAGIC criteria for aGvHD.

Results: We retrospectively analysed 14 patients with a median age of 53 (36-69) years treated for SR-aGvHD after allo-HSCT at our center. 4 patients had grade III aGvHD and 10 patients had grade IV GvHD with at least grade III gut involvement in all 14 patients. Biopsies were performed to confirm a histological GvHD. One patient received a bone marrow graft while the other 13 patients received peripheral blood stem cell grafts. 12 patients had matched unrelated donors (MUD) and 2 patients had haploidentical sibling donors. GvHD prophylaxis after allo-HSCT consisted of anti-thymocyte globulin (ATG), ciclosporin A and mycophenolatmofetil (MMF) for MUD and post-transplant cyclophosphamide, tacrolimus and MMF for haploidentical donors. In median, patients previously received 3 (1-6) lines of GvHD treatment before AAT1 administration, including ruxolitinib, methotrexate, calcineurininhibitors, etanercept, extracorporal photopheresis and mesenchymal stromal cells. 12 patients received all 8 doses of AAT1. One patient died before treatment completion due to infective complications. One other patient even received 2 cycles of AAT1 (16 doses) after responding to the first cycle and relapsing 5 weeks after administering the 8th dose. GvHD manifestations improved in 8 of 14 (57%) patients by day 28 after first dose of AAT1. 3 patients achieved complete remission (CR) and 5 achieved partial remission (PR). AAT1 was well-tolerated and no toxicities attributable to AAT1 were observed. At the last follow-up 5 of the 14 patients were alive with a follow-up of up to 77 weeks after allo-HSCT. Causes of death were infections in 5 patients and progression of GvHD in 4 patients.

Conclusions: In this retrospective analysis, AAT1 showed good efficacy in heavily pre-treated patients with SR-GvHD and gut involvement with an ORR of 57% and a CR rate of 21% while having a well-tolerable safety profile.

Clinical Trial Registry:

Disclosure: Nothing to declare

P210 Mesenchymal stromal cells in patients with iii-iv grade steroid-refractory acute graft versus host disease: 8 years of experience

A. Bukauskas ¹, A. Slobinas^1,2, R. Jucaitienė¹, I. Šlepikienė¹, A. Žučenka^1,2, V. Pečeliūnas^1,2, I. Trociukas¹, L. Griškevičius^1,2

¹Vilnus University Hospital Santaros Klinikos, Vilnius, Lithuania, ²Faculty of Medicine, Institute of Clinical Medicine, Vilnius University, Vilnius, Lithuania

Background: Bone marrow-derived mesenchymal stromal cells (MSCs) are one of the salvage therapy options for steroid-refractory acute graft versus host disease (SR-aGVHD). Herein we present 8 years of experience in Vilnius University Hospital Santaros Klinikos.

Methods: All patients developed biopsy-proven grade III-IV SR-aGVHD after allogeneic hematopoietic stem cell transplantation (HSCT) or donor lymphocyte infusion (DLI). SR-aGVHD was managed with bone marrow-derived MSCs manufactured in a hospital setting. MSCs target dose was 1x10e6 cells/kg body weight administered intravenously once weekly. Treatment response was evaluated on day 7, day 14, and day 28. The patients were evaluated for overall survival. The data were collected prospectively.

Results: 45 adult SR-aGVHD (Grade III-41 and Grade IV-4) patients, with a median of 54 (19-66) years, received MSCs as salvage treatment. 34 patients (76%) were transplanted due to acute leukemia. Involvement of the gastrointestinal tract, skin, and liver were 93%, 44%, and 29 %, respectively. One organ was affected in 18 (40%) (gastrointestinal involvement in 94 % of the cases), two organs in 24 (53%), and three organs in 3 (7%) patients. The median time from HSCT/DLI to MSCs treatment was 11 (2-217) days and the median dose was 1x10e6/kg (0,68-1,33). 19 patients received ≤ 3 MSC doses and 26 patients > 3 doses. The median observation time was 2 months (range – 0-97) and the median observation time of surviving patients was 57 months (range – 7-97). Response rates and overall survival are represented in Table 1 and Figure 1.

Table 1. Response rate and overall survival.

<

Characteristics	SR-aGVHD patients (N = 45)
Day 7 response rate	CR-0 (0%)
	PR-7 (15,5%)
	SD-36 (80%)