The objective of this study was to determine the efficacy and safety of low-dose recombinant interleukin-2(IL-2) administered to patients with acute lymphoblastic malignancy at high-risk of relapse after unmanipulated HLA-identical or HLA-haploidentical allogeneic hematopoietic stem cell transplantation (allo-HSCT). We studied 19 patients with acute lymphoblastic malignancy who underwent IL-2 treatment for a high probability of disease recurrence after allo-HSCT between July 2004 and June 2006 at Peking University Institute of Hematology. With a median follow-up of 6 months (range, 3–19 months) after the first IL-2 therapy, 14 of 15 evaluable patients in our cohort were disease-free (93.33%), whereas one patient in ‘high risk’ pretransplantation category relapsed. Toxicities from IL-2 were mainly fever, pain, redness and swelling at the injection site. Four patients left the study because of hyperpyrexia. Local and reversible chronic GVHD was observed in 6 of 15 patients (40%). Similar cGVHD occurrences were observed between the two groups of patients undergoing HLA-identical HSCT (three of seven patients) and HLA-haploidentical HSCT (two of six patients), respectively. In conclusion, low-dose IL-2 subcutaneous administration from 100 days for a prolonged period could be a safe and effective strategy to prevent relapse in acute lymphoblastic malignancy patients with high risk of recurrence after unmanipulated allo-HSCT.
Allogeneic hematopoietic stem cell transplantation (allo-HSCT) is the most effective therapeutic approach for many hematological malignancies. However, post-transplant relapse remains a major problem owing to the residual quiescent and drug-resistant malignant clones.1, 2 Dose escalation strategies in the conditioning regimens significantly reduced the probability of relapse, but failed to improve survival, because of the toxicity of the applied high-dose chemotherapy and TBI.3 Strategies to reduce the immunosuppressant resulted in greater morbidity and mortality from GVHD without an increase of long-term overall survival.
There is considerable evidence that a GVL effect mediated by donor cells contributes to the antineoplastic effect on the recipient's residual disease.4, 5 Although GVHD appears to be associated with GVL, new approaches for adoptive immune therapy have been pursued to separate GVHD and GVL reactions. Donor lymphocyte infusions (DLI) might induce or augment the GVL effect and thereby induce second remission in patients relapsed after allo-HSCT. However, it might also result in GVHD or bone marrow failure/aplasia.6 A different approach for dissecting GVHD and GVL is the administration of recombinant cytokines to modulate effector cell responses. Many groups focused on the use of IL-2 and it seems to have some GVL enhancing effect in murine models,5, 7 whereas blockade of IL-2 production by post transplant GVHD prophylaxis with CsA was associated with a higher risk of relapse.8 Extensive clinical trials have demonstrated that IL-2 may induce the regression of human cancers, improving disease-free survival in a proportion of patients who relapsed after HSCT and did not respond well to DLI alone, as well as with a low regimen-related toxicity.9, 10, 11, 12 However, IL-2 therapy might also increase the incidence or severity of GVHD as the mechanisms for GVL might be shared by GVHD. Consequently, there is limited experience for IL-2 therapy following non-T-cell-depleted allo-HSCT, particularly after unmanipulated HLA-haploidentical blood and marrow transplantation. In this study, we analyzed the efficacy and safety of low-dose recombinant interleukin-2 for patients after unmanipulated allogeneic transplantation without T-cell depletion in vitro.
Materials and methods
Patients with acute lymphoblastic malignancy (n=19) were considered candidates for recombined interleukin 2 (IL-2, provided by RuiDeHe Medicine industry limited company, China) therapy, if they were evaluated as having a high probability of disease recurrence post-HSCT. The pretransplantation risk category for acute lymphoblastic malignancies included ‘standard-risk’ or ‘high-risk’. Standard-risk ALL patients were those in first CR (CR1). High-risk ALL patients were those in other than CR1, or in CR1 with high-risk cytogenetics, such as t(9;22) or t(4;11). The criteria for high probability of disease relapse after HSCT included: (1) Standard-risk patients with evidence of minimal residual disease (MRD) after HSCT detected by flow cytometry; (2) High-risk patients. Pretreatment evaluation included a physical exam, Karnofsky performance scale evaluation, chest X-ray, electrocardiogram, complete blood count, liver and renal function tests. To fulfill eligibility criteria for study entry, patients were required to have a good performance status (ECOG 0–1) and normal or near normal laboratory parameters of hepatic and renal function. Patients were required to have an absolute neutrophil count above 1.0 × 109/l and a platelet count of 20 × 109/l independent of transfusion, to be free of active infection and GVHD at protocol entry. All patients and their donors gave written informed consent, and this study was approved by the Institutional Review Board and the Ethics Committee at Peking University People's Hospital.
Patients and donors had allele-level molecular typing performed at HLA-A, -B, -C and -DRB1. Allo-HSCT donors included six HLA-identical siblings, 11 HLA haploidentical relatives and in two cases of HLA-matched unrelated donors. A combination of granulocyte colony-stimulating factor (G-CSF)-primed bone marrow and PBSCs were used as a stem cell source in 17 patients, whereas PBSCs of the matched unrelated donors mobilized with G-CSF were transplanted in the other two cases. T-cell depletion in vitro was not employed in any case.
Conditioning, prophylaxis and treatment of GVHD
The recipients of HLA-identical sibling (n=6) allo-HSCT received myeloablative therapy that included a combination of cytosine arabinoside (Ara-C; 2 g/m2 × 1 day), busulfan (12 mg/kg), cyclophosphamide (1.8 g/m2 × 2 days) and Simustine (MeCCNU; 250 mg/m2). For haploidentical (n=11) or unrelated donor (n=2) allo-HSCT, the conditioning of the recipients included a combination of cytosine arabinoside (Ara-C 4 g/m2 × 2 days), busulfan (12 mg/kg), cyclophosphamide (1.8 g/m2 × 2 days), Simustine (250 mg/m2) and rabbit anti-human thymocyte immunoglobulin (ATG 10 mg/kg × 4 days). Prophylaxis of acute GVHD was the same for all patients and consisted of CsA and short-term methotrexate with mycophenolate mofetil. Haploidentical myeloablative regimens and GVHD treatment protocols have been previously described in detail.13, 14
Nineteen patients were scheduled to receive the first cycle of IL-2 at a dose of 1 million units per day subcutaneously for a period of 14 days. After a 14-day rest, another cycle started. Physical examination, Karnofsky performance scale evaluation, laboratory monitoring of hematologic, hepatic and renal function were done weekly during the first cycle, then before and after each cycle. The alternating protocol continued until the occurrence of one of the following conditions: (1) patients were unable to tolerate the treatment; (2) primary disease relapsed; (3) patients developed GVHD; (4) IL-2 had been administered for 12–18 months after transplantation; (5) subject decided to withdraw from the study.
Nineteen recipients of allo-HSCT were treated with IL-2 at Peking University Institute of Hematology between July 2004 and June 2006. Median age was 22 years (range, 5–46 years). Diseases for which HSCT was performed included ALL (n=18, B-ALL 13, T-ALL 4, unclassified 1), and non-Hodgkin's lymphoma (n=1). Pretransplantation risk categories included five patients in the high-risk group and 14 cases in the standard-risk group. At IL-2 protocol entry, two patients relapsed after HSCT and retained CR2 after DLI, one patient relapsed at lymph node and controlled after radiation therapy, nine patients were detected with minimal residual disease, two patients with meningeal leukemia (n=2) and the remaining five patients were categorized into the high-risk group before allo-HSCT. Characteristics of the 15 evaluable patients in the context were presented in Table 1.
IL-2 therapy was begun at a median of 174 days post allo-HSCT (range, 105–578 days). Four patients did not complete one cycle because of hyperpyrexia. Up to the final follow-up in June 2006, the remaining 15 patients had received a median of three cycles (range, 1–18 cycles) of IL-2 administration. Among them, one standard-risk patient was withdrawn from IL-2 administration because the MRD level returned to negative after one cycle, the first patient of this study received 18 cycles of IL-2 treatment and the remaining patients continued to receive IL-2 treatment until the occurrence of discontinuation signs.
Toxicities of IL-2
Before and after IL-2 therapy, the Karnofsky performance scale was 84.0±8.3 scores and 84.7±7.4 scores (P=0.67), respectively. As summarized in Table 2, fever was the major toxicity during the subcutaneous IL-2 therapy. Four patients left the study because of hyperpyrexia. Pain (n=2), redness (n=3) and swelling (n=3) at the injection site were tolerable and reversible toxicities. No hepatic or renal dysfunction was confirmed to be related to IL-2 therapy. There was no discontinuity of IL-2 therapy because of the hematological suppression.
None of the 19 patients had signs of GVHD before the onset of IL-2. Among 15 patients who survived over 100 days, six patients (40%) developed limited chronic GVHD, the presence of skin rashes, during IL-2 therapy. Of them, one patient recovered after short-term treatment with prednisone (0.5 mg/kg per day). The skin rashes on the remaining five patients disappeared after completing IL-2 treatment without administration of any immunosuppressive agents. Furthermore, similar cGVHD occurrences were observed in the patients undergoing HLA-haploidentical HSCT (two of six patients) and HLA-identical HSCT (three of seven patients) in this cohort. All of the six patients remained free of GVHD through the last follow-up.
With the median follow-up of 6 months (range, 3–19 months) after the first IL-2 therapy, 14 of 15 evaluable patients with acute lymphoblastic malignancies at ‘high-risk’ of disease recurrence were disease free (93.33%). Only one patient, who received allo-HSCT in third CR for B-ALL, relapsed at 3.5 months post IL-2 administration.
Although IL-2 was identified based on its potent T-cell growth-factor activity more than 20 years ago,15, 16 recent studies have demonstrated that IL-2 is also critical for the establishment and maintenance of immune tolerance in vivo.17, 18 Saturation of high-affinity IL-2 receptors by low-dose IL-2 to CML patients after allo-HSCT and patients with cancers resulted in the in vivo selective expansion of CD56brightCD3− NK cells10, 11, 12 as well as CD4+CD25+ regulatory T cells (Tregs) in peripheral blood,19 which results in dissecting GVL from GVHD effects. On the basis of extensive experimental data in animal models and results of treatment and prevention of relapse post allo-HSCT,7, 10, 11, 12 we investigated the safety and efficacy of low-dose IL-2 administration for prolonged periods as prophylactic immunotherapy in patients with acute lymphoblastic malignancies after unmanipulated allo-HSCT, particularly for patients undergoing non-T-cell-depleted HLA-haploidentical HSCT.
Fever, hypotension, jaundice and azotemia were common complications, when relatively high daily doses of IL-2 were used in most of the previous trials. By contrast, despite four patients leaving the study because of hyperpyrexia, no other serious infusion-related adverse events were observed in our cohort, which made outpatients more compliant for IL-2 therapy. In contrast to high-dose IL-2 therapy for relatively short intervals, the prolonged treatment period with low dose IL-2 may result in a progressive increase in NK cell number and activity, which may play a critical role in inducing or augmenting the GVL phenomenon as witnessed by the association between de novo chronic GVHD and freedom from post transplant disease relapse.20 Consistent with the above presumption, 14 of 15 patients with a high probability of disease recurrence in our cohort were disease free (93.33%) after a follow-up of 6 months (range, 3–19 months) after the first IL-2 therapy. Given the lack of a control group and short follow-up in our primary study, the conclusion that disease-free survival could be improved through prophylactic IL-2 treatment should be validated by more data.
Unmanipulated allo-HSCT is associated with a lower relapse than T-cell-depleted HSCT.21 IL-2 therapy after non-T-cell-depleted allo-HSCT could potentially induce a greater GVL effect by stimulating the proliferation of alloreactive T cells in the marrow and, thereby, further reduce the relapse rate. Nevertheless, fear of inducing severe GVHD has limited the application of IL-2 to patients undergoing allo-HSCT without TCD. In the present study, local and reversible chronic GVHD occurred in 6 of 15 patients (40%) after unmanipulated HLA-identical or mismatched allo-HSCT with prophylactic IL-2 administration, which was not higher than the rate reported in our previous study.13 However, a prospective control study is necessary to address whether the prophylactic IL-2 administration increases GVHD rate of the recipients after unmanipulated HLA-identical or mismatched allo-HSCT. Besides the low-dose IL-2 and alternate protocol we applied, the low toxicities might be attributed to better immune reconstitution in the recipients at a median of 174 days (range, 105–578 days) rather than early after HSCT when we started IL-2 treatment. Presumably, IL-2 is more effective for GVL effect because of low tumor burden at the MRD stage after HSCT. This finding is in accordance with previous publications on animal models and clinical studies in the allogeneic setting, which indicate that the longer the time interval between HSCT and the administration of donor T-lymphocytes, the stronger the patient's resistance to GVHD.22, 23
Prophylactic DLI has proven to be an effective means to prevent relapse of high-risk leukemia post-HSCT. However, DLI can be accompanied by undesirable side effects including GVHD and myelosuppression, which lead to a considerable amount of treatment-related morbidity and mortality.24, 25 Our preliminary data suggest that low-dose IL-2 subcutaneous administration for a prolonged period is relatively safe and potentially effective to improve the disease-free survival of ALL patients at a high risk of relapse following unmanipulated allo-HSCT. Notably, IL-2 treatment might be feasible for patients undergoing HLA-haploidentical HSCT without enhancing the occurrence of GVHD. Taken together, prophylactic administration of IL-2 may be a promising immunotherapeutic approach for ALL patients who are likely to relapse after allo-HSCT. Considering a limited number of patients were observed with relatively short follow-up in the present study, further prospective random control studies with larger cases are necessary to confirm our pilot observations.
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This work was supported by High Technology Research and Development Program of China (No. 2006AA02Z4A0), Key Project Foundation of the Ministry of Public Health and Program for Innovative Research Team in University (No.IRT0702).
About this article
- acute lymphoblastic malignancy
- hematopoietic stem cell transplantation
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