Aguayo‐Hiraldo, Paibel

Introduction: Immune-mediated graft failure (also termed graft rejection) is a feared complication of hematopoietic stem cell transplant (HSCT) and there is no effective intervention. Multiple pre-transplant risk factors for graft failure are known and recent studies from our groups identified interferon gamma (IFNγ) as a mechanistically important and pharmacologically targetable cytokine involved in graft failure pathophysiology. CXCL9, a downstream marker of IFNγ production, was also identified as a biomarker. We describe an international multicenter retrospective pooled analysis of emapalumab (EMA), an IFNγ neutralizing agent, for the prevention/treatment of immune-mediated graft failure after HSCT. Methods: The safety and preliminary efficacy of EMA were studied in predominantly pediatric patients who received EMA using two different strategies: 1) graft failure treatment and 2) graft failure prophylaxis. Patients at US centers were treated with EMA if they developed clinical and laboratory signs of graft failure after HSCT. All treatment patients met 2 or more of the following criteria: 1) HLA mismatched donor and/or prior graft failure, 2) unexplained fever >39°C (or >38°C if prior history of graft failure) after HSCT, 3) absolute neutrophil count decline after initial engraftment, 4) delayed neutrophil engraftment after HSCT, 5) real-time CXCL9 > 2.5x upper limit of normal (ULN). Temperature and CXCL9 cutoffs were based on a prior graft failure biomarker publication (Sabulski et al, Blood Advances 2021). Patients treated at European centers received prophylactic EMA to prevent graft failure if they were deemed at high-risk prior to transplant. High-risk patients had a prior history of graft failure after HSCT or had two or more of the following established risk factors: a) affected by a disease with high risk of graft failure, including acquired severe aplastic anemia, thalassemia, primary HLH; b) ex-vivo T cell-depleted stem cell product; c) transplant from unrelated cord blood unit or mismatched related/unrelated donor. Results: Thirty-six HSCTs used EMA for graft failure treatment or prophylaxis and were included in this study.EMA was used for graft failure treatment in 25 HSCTs wherein patients developed clinical and laboratory signs of graft failure (Table 1). Most HSCTs in the treatment cohort were performed for bone marrow failure syndromes (n=16). All patients tolerated EMA without complications and no side effects or infections were attributed to EMA. Fifty six percent (14/25) of patients treated with EMA for impending graft failure engrafted and had resolution of graft failure concerns, while the remaining 44% suffered graft failure. Responders had a median ANC of 0.29 x10 3 cells/μL (range 0.05-0.79) prior to EMA, which increased to a median of 0.6 x10 3cells/μL (range, 0-5.1) and 2.97 x10 3 cells/μL (range, 0.85-8.7) on days 3 and 7 after EMA dosing. Eighty percent (20/25) of CXCL9 levels were elevated in the treatment cohort prior to EMA dosing. The median CXCL9 level prior to EMA dosing was elevated 2.4 x ULN (range, 0.3-157.8). The median pre-EMA CXCL9 level in patients who ultimately suffered graft failure in the treatment cohort was 3.3x ULN (range, 0.7-157.8) compared to a median of 2.2x ULN (range, 0.3-30.4) in subjects who had signs of graft failure but did not suffer graft failure (p=0.24). Eleven patients received prophylactic EMA based on a prior history of graft failure or other pre-transplant risk factors. EMA was well tolerated in these patients and 91% (10/11) of patients engrafted while one patient with prior history of graft failure suffered recurrent graft failure. The pre-HSCT (day -2) CXCL9 level in the lone prophylactic patient who suffered graft failure was 4x the ULN. Conclusions: This study reports the largest cohort of HSCTs that used EMA therapy for the novel purpose of treating or preventing graft failure. EMA was well tolerated in all patients. Efficacy conclusions are preliminary and limited by the study design, however our treatment study successfully identified a cohort of patients with a markedly high graft failure rate (44%) and we show preliminary evidence to suggest emaplaumab prevented graft failure in patients who had signs of impending graft failure at the time of treatment. The safety and preliminary efficacy observations in this study support a larger prospective study of IFNγ blockade for graft failure prevention after HSCT.

Abstract Late acute graft-versus-host disease (GVHD) is defined as de novo acute GVHD presenting beyond 100 days after allogeneic hematopoietic cell transplantation (HCT) without manifestations of chronic GVHD. Data are limited regarding its characteristics, clinical course, and risk factors because of underrecognition and changes in classification. We evaluated 3542 consecutive adult recipients of first HCTs at 24 Mount Sinai Acute GVHD International Consortium (MAGIC) centers between January 2014 and August 2021 to better describe the clinical evolution and outcomes of late acute GVHD. The cumulative incidence of classic acute GVHD that required systemic treatment was 35.2%, and an additional 5.7% of patients required treatment for late acute GVHD. At the onset of symptoms, late acute GVHD was more severe than classic acute GVHD based on both clinical and MAGIC algorithm probability biomarker parameters and showed a lower overall response rate on day 28. Both clinical and biomarker grading at the time of treatment stratified the risk of nonrelapse mortality (NRM) in patients with classic and late acute GVHD, respectively, but long-term NRM and overall survival did not differ between patients with classic and late acute GVHD. Advanced age, female-to-male sex mismatch, and the use of reduced intensity conditioning were associated with the development of late acute GVHD, whereas the use of posttransplant cyclophosphamide–based GVHD prevention was protective mainly because of shifts in GVHD timing. Because overall outcomes were comparable, our findings, although not definitive, suggest that similar treatment strategies, including eligibility for clinical trials, based solely on clinical presentation at onset are appropriate.

Abstract Background: A major cause of mortality in patients receiving hematopoietic stem cell transplantation (HCT) is acute graft-versus-host disease (GVHD), a multiorgan disorder that includes the skin, liver and gastrointestinal tract. We have previously identified elafin, a protease inhibitor overexpressed in inflamed epidermis, as a diagnostic biomarker of GVHD in the skin, the most commonly involved GVHD organ. However, our initial study was limited to a subset of patients with isolated skin GVHD. The main driver of nonrelapse mortality (NRM) in HCT patients is GI GVHD. Two biomarkers, Regenerating islet-derived 3a (REG3α) and Suppressor of tumorigenesis 2 (ST2), have since been validated as biomarkers of GI GVHD that predict long-term outcomes in patients treated for GVHD. We undertook this study to determine the utility of elafin as a prognostic biomarker of acute GVHD in the general population of previously unstudied acute GVHD patients, and to compare it to ST2 and REG3α. Study Design: 526 patients who received systemic corticosteroid treatment for skin GVHD were analyzed from the Mount Sinai Acute GVHD International Consortium (MAGIC), which includes patients from 25 HCT centers. We used ELISA to measure serum concentrations of elafin, ST2 and REG3α. Patients were divided randomly into equal training and validation sets; and we developed a competing risk regression model for 6-month NRM using elafin concentration in the training set. We developed additional models for 6-month NRM using concentrations of ST2 and REG3α, or the combination of all three biomarkers as predictors. We then constructed ROC curves to evaluate the predictive accuracy of each model and to analyze the ability of each model to stratify patients into high- and low-risk groups. We analyzed the cumulative incidence of 6-month NRM and overall survival in each model and compared the accuracy of each model in the validation set. Results: The area under the receiver operating curve (AUROC) for elafin alone was 0.55 whereas it was 0.75 and statistically superior (P = 0.02) for the combination of ST2 and REG3α. The combination of 3 biomarkers produced an AUROC of 0.76 that was not significantly better than the two biomarker model (P = 0.10). Elafin concentrations, either alone or in combination with ST2 and REG3α, did not produce higher hazard ratios of NRM (data not shown). Patients in the low-risk elafin group paradoxically demonstrated a higher incidence of 6-month NRM, although this difference was not statistically significant (17% vs. 11%, P=0.19), and both overall survival at 6 months (68% vs. 68%, P>0.99) and four-week response (78% vs. 78%, P=0.98) were similar in the low- and high-risk elafin groups (Figure 1). As demonstrated in previous data sets, the combination of ST2 and REG3α divided patients into two groups with a nearly five-fold difference in NRM (6.7% vs. 31%, P <0.001). Conclusion: We demonstrated that serum elafin concentrations measured at the initiation of systemic treatment for acute GVHD in a multicenter population of patients treated systemically for acute GVHD do not predict 6-month NRM, overall survival, or treatment response. As seen in previous studies, serum concentrations of the GI GVHD biomarkers ST2 and REG3α were significant predictors of NRM and the addition of elafin levels did not improve their accuracy. These results underscore the importance of GI disease in driving NRM in patients who develop acute GVHD. Figure 1. Cumulative incidence of nonrelapse mortality and overall survival in high and low risk groups Six-month cumulative incidences of nonrelapse mortality (NRM) in high (solid line) and low (dotted line) risk groups defined by optimized biomarker thresholds (upper panels) and six-month overall survival estimated using the Kaplan-Meier method (lower panels). (A) Cumulative incidence of NRM (14%) and overall survival (75%) in the total validation set (N=263). (B) Cumulative incidence of NRM in the low (N=150) and high (N=113) elafin group (17% vs. 11%, P=0.19). Overall survival in the low and high elafin group (68% vs. 68%, P > 0.99). (C) Cumulative incidence of NRM in the low (N=175) and high (N=88) ST2 + REG3a group (6.7 vs. 31%, P < 0.001). Overall survival in the low and high ST2 + REG3a group (77% vs. 51%, P < 0.001). (D) Cumulative incidence of NRM in the low (N=180) and high (N=83) elafin + ST2 + REG3a group (7.0 vs. 30%, P < 0.001). Overall survival in the low and high elafin + ST2 + REG3a group (79% vs. 64%, P < 0.001). Figure 1 Figure 1. Disclosures Ozbek: Viracor: Patents & Royalties: GVHD biomarker patent with royalties from Viracor. DeFilipp: Omeros, Corp.: Consultancy; Incyte Corp.: Research Funding; Regimmune Corp.: Research Funding; Syndax Pharmaceuticals, Inc: Consultancy. Grupp: Novartis, Kite, Vertex, and Servier: Research Funding; Jazz Pharmaceuticals: Consultancy, Other: Steering committee, Research Funding; Novartis, Roche, GSK, Humanigen, CBMG, Eureka, and Janssen/JnJ: Consultancy; Novartis, Adaptimmune, TCR2, Cellectis, Juno, Vertex, Allogene and Cabaletta: Other: Study steering committees or scientific advisory boards. Hexner: Blueprint medicines: Membership on an entity's Board of Directors or advisory committees, Research Funding; Tmunity Therapeutics: Research Funding; PharmaEssentia: Membership on an entity's Board of Directors or advisory committees. Kitko: Co-investigator on two NIH grants as part of the cGVHD consortium: Research Funding; Vanderbilt University Medical Center: Current Employment; PER: Other: PER - CME educational talks about GVHD; Horizon: Membership on an entity's Board of Directors or advisory committees. Qayed: Novartis: Honoraria; Mesoblast: Honoraria; Medexus: Honoraria. Reshef: ilead, BMS, Precision, Immatics, Atara, Takeda, Shire, Pharmacyclics, Incyte: Research Funding; Bayer: Consultancy; Gilead and Novartis: Honoraria; BMS, Regeneron, TScan, Synthekine, Atara, Jasper, Bayer: Consultancy. Levine: Incyte: Consultancy, Research Funding; Viracor: Patents & Royalties: GVHD biomarker patent with royalties from Viracor; Mesoblast: Consultancy, Research Funding; Equillium Bio: Membership on an entity's Board of Directors or advisory committees; X4 Pharmaceuticals: Membership on an entity's Board of Directors or advisory committees; Talaris Therapeutics: Membership on an entity's Board of Directors or advisory committees; Jazz Pharmaceuticals: Membership on an entity's Board of Directors or advisory committees; Omeros: Membership on an entity's Board of Directors or advisory committees; Symbio: Membership on an entity's Board of Directors or advisory committees; Biogen: Research Funding; Kamada: Research Funding. Ferrara: Eurofins Viracor: Consultancy, Other: Royalties. Chen: Incyte: Consultancy; Gamida: Consultancy.