Steroid-refractory (SR) acute gastrointestinal (GI) graft-versus-host disease (GVHD) is associated with significant mortality in allogeneic hematopoietic cell transplantation recipients. We retrospectively evaluated the efficacy of tocilizumab for the treatment of SR biopsy-proven acute lower GI GVHD in 16 consecutive adult transplant recipients between October 2015 and July 2016. Tocilizumab 8 mg/kg was administered every 2 weeks until achievement of complete response, defined as resolution of all manifestations of GI GVHD, or until patients had progression or initiation of other therapy. Ten of 16 patients (62.5%; 95% CI, 0.39–82) achieved a complete response after a median time of 11 days (range, 2–28 days) from tocilizumab initiation. The median time to response onset (improvement in stage by at least 1) was 1 day (range, 1–4 days). Tocilizumab was administered at a median of 9 days (range, 3–75 days) from GVHD diagnosis and 10 days (range, 3–75 days) from initiation of high-dose steroids. At a median follow-up of 7.6 months (range, 0.8–27.7 months) from initiation of tocilizumab, 6/16 (37.5%) patients are alive and free of their underlying hematologic malignancy. Tocilizumab appears to be a highly active agent for the treatment of severe SR lower GI acute GVHD.
Acute graft-versus-host disease (GVHD) remains the leading cause of non-relapse mortality following allogeneic hematopoietic cell transplantation (HCT) . With standard prophylaxis, GVHD occurs in 30–50% of human leukocyte antigen-matched transplants from related donors and 50–70% from unrelated donors . The initial treatment of acute GVHD consists of high-dose corticosteroids, associated with overall response rates ranging from 40 to 60% . Patients who develop steroid-refractory (SR) GVHD have a dismal prognosis, with a median overall survival (OS) of 6 months . The outcomes in patients with SR GVHD involving the gastrointestinal (GI) tract, long considered the most difficult to treat organ in this disease, are even worse as nearly all cases of severe GI GVHD are fatal . Moreover, despite the overall decline of acute GVHD rates, the incidence of acute GI GVHD has actually been steadily rising . Therefore, there is an urgent need for more effective therapies for the treatment of SR GI GVHD.
Interleukin (IL)-6 is a pleiotropic cytokine that has been implicated in the physiology of numerous immune-mediated diseases. Biologic functions of IL-6 include critical roles in B- and T-cell differentiation as well as promoting recruitment and anti-apoptosis of T lymphocytes . IL-6 signaling also serves as an important mediator of immune cell trafficking to inflamed tissues and lymphoid organs . Importantly, levels of IL-6 and IL-6 receptor have been found to be increased in mice with GVHD, with the highest expression observed in the visceral organs . The critical role of IL-6 signaling in GI GVHD has evoked interest in utilizing tocilizumab, a humanized anti-IL-6 receptor monoclonal antibody, for the treatment of GI GVHD. Blockade of IL-6 receptor signaling resulted in a reduction in GVHD-related mortality in murine models . Furthermore, several early reports describe encouraging activity of tocilizumab for the treatment of GI GVHD after HCT [11, 12]. We report our experience and outcomes in a group of 16 consecutive patients who received tocilizumab for severe SR GI GVHD.
Subjects and methods
We retrospectively evaluated the efficacy of tocilizumab for the treatment of SR biopsy-proven GVHD isolated to the GI tract in 16 consecutive adult allogeneic HCT recipients treated at the University of Pennsylvania between October 2015 and July 2016. Patients with multi-organ GVHD involvement were not included in the analysis. SR GI GVHD was defined as progressive symptoms after 3 days or no improvement after 7 days of methylprednisolone 2 mg/kg/day. Tocilizumab was administered intravenously at a dose of 8 mg/kg every 2 weeks until achievement of complete response (CR) or progression or initiation of other therapy. A maximum of six doses were permitted. Upon achievement of response to tocilizumab, all other immunosuppressive therapies were tapered according to institutional guidelines. This retrospective analysis was approved by the Institutional Review Board of the University of Pennsylvania.
Response and outcomes
The primary variable of interest was CR which was defined as resolution of all manifestations of GI GVHD. Acute GVHD was graded according to the modified Glucksberg criteria . Secondary end-points included partial response (PR), OS, and toxicity. PR was defined as improvement in GVHD stage by at least 1. Progression or no response of GI GVHD was defined as worsening of GI symptoms or no reduction in GVHD stage after at least 7 days of tocilizumab initiation, respectively. OS was defined as the time interval between date of HCT and death from any cause or censored at last follow-up. Toxicity was assessed using the National Cancer Institute Common Terminology Criteria for Adverse Events version 4. With respect to infection monitoring, blood, urine and tissue-directed cultures were obtained for bacterial and fungal pathogens as clinically indicated. All patients had weekly quantitative cytomegalovirus (CMV) testing performed using real-time PCR. Serologic testing for other viral infections such as Epstein-Barr Virus (EBV), adenovirus, and Human Herpesvirus (HHV)-6 were obtained at the discretion of the treating physician. Serum levels of pro-inflammatory cytokines (IFN-γ, IL-2, IL-2R, IL-6, IL-7, IL-15, TNF-α) were measured prior to the start of tocilizumab using multiplex arrays.
Baseline and treatment characteristics were examined with descriptive statistics. Continuous variables are reported as their median. Kaplan–Meier analysis was used to estimate median OS. A log-rank test was used for comparison of OS curves.
Patient- and disease-related characteristics are described in Table 1. Patients were generally high risk by virtue of older age (median 58 years), disease risk index (high/very high 56%), and hematopoietic cell transplantation—specific comorbidity index (score ≥ 3 63%). The majority of patients (10/16; 63%) were transplanted for AML in first or greater remission (7/10; 70%). Conditioning regimen and GVHD prophylaxis was according to our institutional guidelines and dependent on the underlying disease and graft source. GI GVHD developed a median of 49 days (range, 15–211 days) after HCT and the diagnosis was confirmed by tissue biopsy in all cases. Of 16 patients, 15 (94%) had grade 3 SR lower tract GI GVHD. One patient had grade 2 SR GVHD with symptoms predominantly limited to the upper GI tract. At the time of tocilizumab initiation, no other organs were affected by GVHD. All patients failed at least one prior therapy and 12/16 (75%) progressed through multiple GVHD therapies before starting tocilizumab (Table 2).
Tocilizumab was administered at a median of 9 days (range, 3–75 days) from GVHD tissue diagnosis and 10 days (range, 3–75 days) from initiation of high-dose steroids. Ten of 16 patients (62.5%; 95% CI, 0.39–82) achieved a CR after a median time of 11 days (range, 2–28 days) from tocilizumab initiation. The median time to response onset (improvement in GVHD stage by at least 1) was 1 day (range, 1–4 days). The median number of tocilizumab doses administered was 2 (range, 1–4 doses). Four patients achieved a CR after a single dose and six patients required multiple doses of tocilizumab to achieve CR (two doses n = 4; 3 doses n = 1; 4 doses n = 1). One patient who had > 1500 mL/day of diarrhea prior to initiation of tocilizumab achieved a PR 4 days after the first dose of tocilizumab. This patient received three additional doses of tocilizumab but continued to have ongoing diarrhea, which was quantified as < 500 mL/day. This patient’s GVHD treatment was eventually switched to an alternative agent after four tocilizumab doses.
At the time of last follow-up, all 10 patients who achieved a CR to tocilizumab had their immunosuppressive medications tapered to varying degrees. The median corticosteroid dose among responders decreased from 2 mg/kg/day (range, 1.2–2 mg/kg/day) to 0.09 mg/kg/day (range, 0–1 mg/kg/day) within a median of 5.09 months. Three responders discontinued all systemic immunosuppression after completion of tocilizumab within a median of 12.4 months (range, 2.35–15.4 months).
Of the 11 patients who had a response (CR + PR), 3 (27%) did not have recurrence of GI GVHD after cessation of tocilizumab. Of the 10 patients who achieved a CR, 7 had recurrence of GI GVHD after a median of 3.69 months (range, 1.36–10.91 months) after the last dose of tocilizumab and were treated with a variety of other immunosuppressive agents. No patient received additional tocilizumab following recurrent symptoms.
At a median follow-up of 7.6 months (range, 0.8–27.7 months) from initiation of tocilizumab, 6/16 (37.5%) patients are alive and free of their underlying hematologic malignancy. This includes 6/11 (54.5%) responders (CR + PR) and 0/5 (0%) non-responders. The median OS was significantly longer in responders compared with non-responders (16.0 vs. 1.2 months; P < .0001), as demonstrated in Fig. 1. Of the five patients who did not respond, all died from complications related to GI GVHD. In the group of 11 patients who responded (CR or PR), 2 died from complications related to GI GVHD, 2 patients died from biopsy-proven liver GVHD that developed after tocilizumab initiation and 1 patient’s death was attributed to disease relapse that was diagnosed prior to the start of tocilizumab.
We also measured serum levels of pro-inflammatory cytokines (IFN-γ, IL-2, IL-2R, IL-6, IL-7, IL-15, TNF-α) prior to the start of tocilizumab using multiplex arrays. The median serum IL-6 level prior to the start of tocilizumab was 10 pg/mL, with a range from 0–146 pg/mL (normal 0–12). No associations between serum levels of pro-inflammatory cytokines, including IL-6, and tocilizumab response could be identified (data not shown).
No infusion reactions were observed. Four patients developed infections during tocilizumab treatment with a total of 12 infectious episodes, 8 of which were of bacterial origin. Two episodes of candidemia were observed. In addition, two patients developed CMV viremia within 1 month of starting tocilizumab. Both cases of CMV were successfully treated with ganciclovir. Although routine screening for viral infections was not done in asymptomatic patients, when evaluated for fevers, there was no evidence of EBV, HHV-6, or adenovirus reactivation. Infections occurred at a median of 20 days (range, 12–40 days) after the start of corticosteroids, and 15 days (range, 4–27 days) after the start of tocilizumab. Three patients developed transient neutropenia (grade 1 n = 2; grade 3 n = 1) after initiation of tocilizumab. All cases of neutropenia resolved within 1 week from occurrence. Six patients had evidence of liver dysfunction after starting tocilizumab. There were six cases of transient ≥ grade 2 hepatotoxicity, with five patients developing elevated liver transaminase levels and one patient developing hyperbilirubinemia. In one case, liver abnormalities were shown by biopsy to be related to liver GVHD. Abnormal liver function tests resolved in 3/6 cases within 1 week of stopping tocilizumab. No patient required dose reduction or discontinuation of tocilizumab due to toxicity.
SR GVHD remains a major cause of morbidity and mortality after allogeneic HCT. Despite application of a multitude of different immunosuppressive agents over many years, various approaches have had little impact on the poor prognosis and no standard of care has been identified . In this study, we demonstrated that tocilizumab is a highly active agent for the treatment of severe SR acute GVHD of the GI tract with a CR rate of 62.5% and median OS of 7.6 months in all patients, but a median OS of 16 months in patients who responded to tocilizumab. The onset of tocilizumab’s activity was quite rapid as the majority of patients required two or fewer doses to achieve a response. We typically discontinued tocilizumab after a CR and/or at the time of hospital discharge in responding patients. Only 3 of the 10 complete responders remained free of GI GVHD after discontinuation of tocilizumab. It is not known if a more extended course of tocilizumab would have resulted in a response in the non-responders, or if a more sustained response would have been observed in the patients who had GI GVHD recurrence. Interestingly, pre-treatment serum levels of pro-inflammatory cytokines, in particular IL-6, were not elevated in the majority of patients and were not associated with likelihood of response to tocilizumab. To the best of our knowledge, this is the largest retrospective series of patients who received tocilizumab for the treatment of biopsy-proven SR acute GVHD of the lower GI tract.
The results of our study provide additional support for the emerging role of IL-6 receptor signaling blockade with tocilizumab for attenuating GVHD, particularly GVHD involving the GI tract. This association is consistent with preclinical studies that have demonstrated a direct relationship between IL-6 signaling and T-lymphocyte alloreactivity in the visceral organs [8,9,10, 14]. Dampening IL-6 signaling has been shown to increase regulatory T-cell production while concurrently reducing the production of pro-inflammatory Th1 and Th17 cells. Furthermore, higher IL-6 and IL-6 receptor levels are found in the colon microenvironment than in other organs, highlighting the organ-specific nature of IL-6 in promoting GI GVHD biology . In addition, IL-6 has been shown to have direct toxic effects on intestinal epithelial tissues and blockade of endogenous IL-6 with an anti-IL-6 receptor monoclonal antibody reduced the amount of intestinal epithelial cell apoptosis, further extending the inverse association between IL-6 signaling and GI integrity . Notably in our patients, pre-treatment serum levels of pro-inflammatory cytokines, in particular IL-6, were not elevated in the majority of subjects and were not associated with likelihood of response to tocilizumab. IL-6 may be functioning locally and elevated levels may not necessarily be found in the circulation. Measurement of IL-6 is not likely to be a useful biomarker to either choose therapy for GI GVHD or to identify patients likely to respond to tocilizumab.
Tocilizumab for the treatment of GI GVHD in HCT recipients has been previously examined in several small studies with varying efficacy and impact on survival [11, 12, 15]. In a retrospective analysis of eight HCT recipients with refractory acute (n = 6) or chronic GVHD (n = 2) of any organ, tocilizumab administered at a dose of 8 mg/kg every 3–4 weeks resulted in a response rate of 62.5% with 25% (n = 2) achieving a CR . Interestingly, the two patients who achieved a CR had GI GVHD, with responses characterized by complete resolution of diarrhea. Another retrospective study consisting of nine HCT recipients with SR acute GVHD of any organ who were treated with tocilizumab 8 mg/kg every 3–4 weeks had a 44% response rate but a dismal median OS of only 26 days . In our study, the median OS was 7.6 months in all recipients but 16 months in responders whereas no non-responders were alive at last follow-up, confirming the very poor prognosis associated with SR GVHD in patients that do not respond to second line therapy. These varying results are likely due to a multitude of factors, including heterogeneity in studied populations with respect to GVHD organ involvement, previous lines of GVHD therapy and tocilizumab dosing interval. We attempted to overcome the aforementioned heterogeneity by analyzing 16 consecutive HCT recipients who had severe biopsy-proven SR acute GVHD limited to the lower GI tract. Given the aforesaid associations between IL-6 signaling and GI epithelium integrity, we only administered tocilizumab to patients who had GI GVHD without other organ involvement. Furthermore, the majority of patients in our analysis received tocilizumab as initial therapy following high-dose corticosteroid failure. Utilizing tocilizumab earlier in the SR GI GVHD treatment algorithm may be beneficial as likelihood of response to SR GVHD treatment generally decreases with increasing lines of therapy. In addition, we administered tocilizumab every 2 weeks as opposed to every 3–4 weeks based on prior reports of early GI symptom recurrence with the extended interval dosing approach, which may have resulted in improved results (William Drobyski, personal communication).
There are several limitations to this analysis. This was a retrospective study, though our clinical practice during this time period was to use tocilizumab for SR GVHD limited to the GI tract, and therefore we were able to analyze a consecutive group of patients treated with a relatively consistent approach. The duration of tocilizumab administration was not standardized and was dependent on response (or lack of response), and duration of hospitalization; outpatient use of tocilizumab was not feasible in many cases. It is not known if longer, more rigorous administration of tocilizumab would have resulted in different outcomes. Nevertheless, these encouraging results extend support for the emerging concept of tailoring GVHD therapeutics according to specific organ involvement. Cytokines are among the critical effector molecules involved in GVHD pathogenesis and cytokine expression is highly variable based on affected tissues . Numerous novel agents that target specific immune mechanisms associated with GI GVHD biology have demonstrated promising activity or are under active investigation, including natalizumab (NCT02176031), alpha-1-antitrypsin, and vedolizumab [17, 18]. It remains to be seen whether these or other strategies will have a significant benefit on the long-term outcomes of GI GVHD. Given the challenges of treating GVHD, substantial emphasis remains on preventing its occurrence. As such, encouraging results have been observed with tocilizumab for prevention of GVHD as several prospective trials have demonstrated that the addition of tocilizumab to standard immune suppression results in a low incidence of GVHD [19, 20]. Notably, the benefit of adding tocilizumab to standard GVHD prophylaxis is particularly apparent in reducing the risk of GI GVHD . Detailed evaluation of tocilizumab’s activity in treating GI GVHD through prospective clinical trials is warranted.
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Conflict of interest
The authors declare that they have no conflict of interest.
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Ganetsky, A., Frey, N.V., Hexner, E.O. et al. Tocilizumab for the treatment of severe steroid-refractory acute graft-versus-host disease of the lower gastrointestinal tract. Bone Marrow Transplant 54, 212–217 (2019). https://doi.org/10.1038/s41409-018-0236-z
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