Minor histocompatibility antigen (mHAg)-specific alloreactive donor T cells cause graft vs. host disease (GVHD) in matched related donor allogeneic hematopoietic cell transplantation (HCT). In a phase I trial, we expanded and infused (on day -2) mHAg-specific donor regulatory T cells (Treg) together with sirolimus-based pharmacologic prophylaxis to examine safety and preliminary efficacy of this GVHD prevention approach. We employed a 3+3 phase I design escalating Treg dose in 4 levels: 0.5 x 105/kg, 1 x 105/kg, 2 x 105/kg, and 4 x 105/kg. Dose-limiting toxicity (DLT) included grade 4-5 related infusion reaction, grade 4-5 unexpected organ toxicity, grade III-IV acute GVHD, or treatment-related death. Secondary and exploratory measures examined acute and chronic GVHD, survival outcomes, and Treg clone (TCR-Seq) expansion in culture, and in-vivo longevity and expansion post-HCT. 15 subjects were included (N=3 each per dose levels 1-3, and N=6 in dose level 4). No DLT were observed, and 4 x 105/kg Treg was identified as MTD. Median follow up for survivors was 41.7 months (range 14.5-72.8). The day 100 cumulative incidence of grade II-IV acute GVHD was 13% (95% CI 2-35%). NIH moderate/severe chronic GVHD by 1 year was 6.7% (95% CI 0.36-27%) and by 3 years was 20% (95%CI 4.4-44%). Overall survival was 73% (95% CI 54-100%). Treg clones expanded in culture, and demonstrated post-HCT lineage fidelity, persistence, and in-vivo expansion. This translational trial supports mHAg-specific expanded donor Treg as a novel GVHD prevention strategy, and demonstrates expanded donor Treg clones can persist and expand through one-year post-HCT. NCT01795573.

Chronic GVHD is less frequent after post-transplant cyclophosphamide (PTCy)–based prophylaxis, but its clinical characteristics and outcomes compared with chronic GVHD following non-PTCy approaches remain understudied. We addressed this through a single-center retrospective study of 1,534 consecutive adult transplants (PTCy: n = 477; non-PTCy: n = 1,057) using matched related or matched/mismatched unrelated donors. The cumulative incidence of NIH moderate/severe chronic GVHD was significantly lower after PTCy (17% v 46%; P < .001). Among chronic GVHD-affected patients (PTCy: n = 163; non-PTCy: n = 656), chronic GVHD after PTCy involved fewer organ sites, had lower severity scores, and less NIH moderate/severe disease overall. However, this profile did not translate into improved survival. Univariate analysis demonstrated higher non-relapse mortality (24-month NRM: 22% v 13%; P = .014) for the PTCy group, while on multivariate analysis NRM was associated with increased age, NIH overall moderate/severe chronic GVHD severity, prior grade III/IV acute GVHD, reduced platelet count and increased bilirubin. Chronic GVHD after PTCy was associated with increased infectious complications despite reduced immunosuppressive (IS) therapy and higher rates of complete IS discontinuation. Overall, PTCy-based prophylaxis was associated with a lower incidence and severity of chronic GVHD, and after adjustment for established prognostic factors, mortality following chronic GVHD diagnosis was comparable to that observed after non-PTCy prophylaxis approaches. Multicenter validation of these findings and novel strategies to mitigate non-relapse mortality in chronic GVHD are warranted.

Patients tapering and discontinuing immune suppression (IS) often develop graft vs. host disease (GVHD) after allogeneic hematopoietic cell transplantation (HCT). We prospectively enrolled HCT patients at relevant time points of initiation of taper of last systemic IS agent (cohort 1) or at time of complete IS stop (cohort 2) to identify rates and determinants of failure. Actual IS taper practice was recorded, and patients were followed for scheduled and event-driven clinical data and research blood samples. Success was defined as complete discontinuation of IS and durable freedom from GVHD; failure as GVHD during/after taper (cohort 1), or after IS stop (cohort 2). Median follow-up post-HCT was 53 months (range 10–141). Cohort 1 enrolled at median 15.6 months post-HCT. Failure during IS taper occurred in 43% (60% total considering failure during IS taper and after IS stop). Median time to failure was 8.3 months (range 1.1–39.5), manifesting as acute (26%) or chronic (74%) GVHD. Cohort 2 enrolled at median of 25 months post-HCT. Subsequent failure occurred in 44% at median of 4.5 months (range 0.1-27.1) manifesting as acute GVHD (20%) or chronic GVHD (80%). This prospective cohort study provides new insight into GVHD risk during IS taper/discontinuation and establishes a biologic sample repository for investigation into immune tolerance.

BACKGROUND:Data on transplant outcomes of obese patients undergoing allogeneic hematopoietic cell transplant (alloHCT) have demonstrated conflicting results both in regard to the prognostic significance of obesity and appropriate dosing of chemotherapy to balance toxicity and efficacy. OBJECTIVES:We retrospectively evaluated 751 acute myeloid leukemia (AML) patients who underwent alloHCT at the Moffitt Cancer Center from 2010-2021 to compare transplant outcomes of obese (BMI ≥30 kg/m2) and non-obese patients (BMI <30 kg/m2). Transplant related outcomes included time to engraftment, acute graft-versus-host disease (aGVHD), moderate-severe chronic graft-versus-host disease (cGVHD), relapse, non-relapse mortality (NRM), relapse free survival (RFS), and overall survival (OS). STUDY DESIGN:Data was collected via internal database supplemented by direct records review. Univariate Cox regression models were developed using baseline variables, and multivariate Cox regression models were built using significant variables from univariate analysis and backwards selection. Similarly, Fine & Gray subdistribution hazard models were built when competing risks were present. Kaplan Meier curves were utilized to show RFS and OS. The time-to-event outcomes with competing risks were summarized by cumulative incidence curves. In the subgroup of patients with BMI ≥30 kg/m2 receiving melphalan based conditioning (n = 78), we compared outcomes in patients who received melphalan dosed on total body weight versus adjusted body weight. RESULTS:The cohort of 751 patients included 246 (32.8%) with BMI ≥30 kg/m2, and 505 (67.2%) with BMI <30 kg/m2. Median follow up time was 50 months. Engraftment did not differ between groups. The cumulative incidence of grade 2-4 aGVHD was 49% for patients with BMI ≥30 kg/m2 and 44% for patients with BMI <30 kg/m2, (P = .28), while the cumulative incidence of moderate to severe cGVHD was 24% versus 25% (P = .56). The cumulative incidence of relapse at 2 years was 23% versus 27% for patients with BMI ≥30 kg/m2 and BMI <30 kg/m2 respectively (P = .41), and cumulative incidence of NRM at 1 year was 14% versus 15% (P = .94). OS at 2 years was 64% versus 59% for patients with BMI ≥30 kg/m2 and BMI <30 kg/m2, respectively (P = .35). In multivariable analysis, BMI was not shown to affect aGVHD, moderate to severe cGVHD, NRM, RFS, relapse, or OS. In the analysis of obese patients who received melphalan, no significant differences in outcomes were found between those receiving melphalan dosed by total body weight versus adjusted body weight. CONCLUSIONS:In this study of North American AML patients receiving alloHCT with varying conditioning and GVHD prophylaxis, including post-transplant cyclophosphamide, there were no significant differences in clinical outcomes between patients with BMI ≥30 kg/m2 compared to patients with BMI <30 kg/m2.

PURPOSE This phase I-Ib trial evaluated a novel CD40L blocking antibody, BMS-986004, for the prevention of graft-versus-host disease (GVHD) after unrelated donor allogeneic hematopoietic cell transplantation (HCT). PATIENTS AND METHODS A total of 34 patients were treated at three centers. The safety and biologic activity of single-dose BMS-986004 (675 mg [n = 6] and 1,500 mg [n = 6]; one-time dose) were evaluated. Safety of prolonged dosing was then examined in separate cohorts (drug administration every 2 weeks × 3 [n = 3], 5 [n = 3] or 7 doses [n = 16]). Included patients received 8/8 HLA-matched unrelated donor peripheral blood stem-cell HCT and sirolimus/tacrolimus GVHD prophylaxis. Comprehensive HCT outcome data were collected through 2 years, inclusive of GVHD outcomes, immune reconstitution and infections, and biologic correlative studies. RESULTS BMS-986004, a single, one-time dose of 1,500 mg was identified as the safe and biologically active single-dose regimen, and prolonged dosing cohorts demonstrated safety through the seven-dose duration regimen. In phase Ib (n = 16), grade II-IV acute GVHD was 25% with no grade III or IV acute GVHD. Moderate-severe chronic GVHD at 2 years was 18.4%. Considering all patients (n = 34), a total of five deep venous thrombosis (DVT) events occurred and no significant association was detected between DVT and serial D-dimer and TAT levels. There was no evidence for excess infectious complications or cytomegalovirus reactivation. Two-year estimates were the following: Non-relapse mortality 15.3% (95% CI, 5.4% to 29.8%), relapse 22% (95% CI, 9.5% to 37.8%), and overall survival 77.8% (95% CI, 58.7% to 88.8%). CONCLUSION This trial demonstrates that next-generation CD40L blocking antibodies can be used safely in HCT recipients and supports initial clinical efficacy in the prevention of GVHD. Further study is needed in larger populations to verify these outcomes.

Background: Previous studies have shown that allogeneic peripheral blood stem cell transplantation (PBSCT) from an HLA haploidentical (haplo) donor followed by graft-versus-host disease (GVHD) prophylaxis with post-transplant cyclophosphamide (PTCy) results in lower relapse rates and improved DFS when compared to haplo bone marrow transplant (BMT) with PTCy. However, PBSCT leads to higher rates of GVHD. It is unknown whether the benefits of haplo PBSCT may be nullified in older patients (>60 years) by a higher susceptibility to GVHD and transplant related toxicity. Thus, we sought to determine if older patients receiving haplo PBSCT with PTCy experience significantly worse outcomes than younger patients. Methods: We evaluated 121 adult patients with hematologic malignancies treated at the Moffitt Cancer Center with allogeneic haplo PBSCT followed by PTCy and compared outcomes of patients ≥60 years (n = 55) versus patients <60 years (n = 66). Results: The cumulative incidence of non-relapse mortality (NRM) from the competing risk regression analysis was worse for the older patient group (SHR = 4.05, 95% CI: 1.43–11.47, p = 0.008). However, there was no significant difference between groups in graft-versus-host disease (GVHD), relapse, disease-free survival (DFS), or overall survival (OS). Instead, hematopoietic comorbidity index (HCT-CI) ≥ 3 was associated with worse DFS (HR = 1.87, 95% CI: 1.04–3.34, p = 0.035) and OS (HR = 1.98, 95% CI: 1.03–3.84, p-value = 0.042). Subgroup analysis of patients ≥60 years showed a trend toward improved 2-year OS with fludarabine/cyclophosphamide/total body irradiation (Flu/Cy/TBI) versus fludarabine/busulfan: 71% versus 53% (HR = 0.47, p = 0.121). In patients over 70 years (n = 14), NRM was 8% and OS was 76% at 1 year. Conclusion: Given similar OS and DFS between patients aged >60 years and those <60, haplo PBSCT with PTCy appears to be an appropriate transplant platform for older patients.

BackgroundRelated human leukocyte antigen (HLA)-haploidentical bone marrow transplantation (BMT) with posttransplant cyclophosphamide may be curative for sickle cell disease. However, graft failure, severe graft-versus-host disease (GVHD), infections, and mortality remain a concern. We evaluated a novel conditioning regimen followed by related HLA-haploidentical BMT in adults with sickle cell disease.MethodsIn a phase 2, open-label, single-arm, multicenter study, 54 eligible participants from 19 U.S. centers were enrolled. Of these, 42 (78%) received transplantation with conditioning including antithymocyte globulin, fludarabine, cyclophosphamide, thiotepa, and total body irradiation. GVHD prophylaxis included posttransplant cyclophosphamide, mycophenolate mofetil, and sirolimus. The primary outcome was event-free survival at 2 years, while secondary outcomes included overall survival and other transplant-related end points.ResultsThe median age at enrollment was 22.8 years (range, 15.5 to 43.2), and the median follow-up period was 37.2 months (range, 20.4 to 56.4). The 2-year event-free and overall survival rates were 88.0% (95% confidence interval [CI], 73.5 to 94.8%) and 95.0% (95% CI, 81.5 to 98.7%), respectively. Two participants experienced primary and another secondary graft failure. The incidence of grade-3-to-4 acute GVHD at day 100 was 4.8% (95% CI, 0.9 to 14.4%), while the 2-year chronic GVHD rate was 22.4% (95% CI, 10.9 to 36.4%). Two of the four reported deaths were due to early infectious complications.ConclusionsHLA-haploidentical BMT is an accessible and potentially curative therapy for adults with sickle cell disease. Adverse events were those anticipated from this procedure, including GVHD. (Funded by the National Heart, Lung, and Blood Institute and the National Cancer Institute; BMT CTN 1507; ClinicalTrials.gov number, NCT03263559) In this phase 2, open-label, single-arm study, adults with sickle cell disease were treated with a modified conditioning regimen involving thymoglobulin, thiotepa, cyclophosphamide, and fludarabine followed by haploidentical bone marrow transplantation and graft-versus-host disease prophylaxis. The primary outcome was 2-year posttransplant event-free survival. After a median follow-up period of 37.2 months, the 2-year event-free and overall survival rates were 88.0% (95% CI, 73.5 to 94.8%) and 95.0% (95% CI, 81.5 to 98.7%), respectively.

Background While potentially curative for myeloproliferative neoplasms (MPNs), the effectiveness of allogeneic hematopoietic cell transplant (HCT) is limited by post-transplant relapse. Given its efficacy in myelofibrosis (MF), favorable safety profile, and oral route of administration, the JAK2 inhibitor fedratinib may prove effective as a maintenance therapy for MPNs in the post-transplant setting. Additionally, models of JAK2 inhibition argue for potential utility in preventing graft-versus-host disease (GVHD) while preserving the graft-versus-tumor (GVT) effect (Betts. PNAS. 2018). As a JAK2-specific inhibitor, fedratinib may prevent GVHD while still preserving the GVT effect. Thus, maintenance fedratinib is a rational strategy to decrease both relapse and, possibly, GVHD in patients with MPNs following HCT. Methods In this single center phase I trial, patients who underwent allogeneic HCT for a MPN or myelodysplastic syndrome (MDS)/MPN overlap syndrome were treated with fedratinib starting between days +60 to +100 and then continued until 1-year post-transplant. Eligibility required adequate organ function, as well as neutrophil and platelet engraftment. JAK2 mutation was not required for eligibility as fedratinib has shown efficacy in JAK2 negative patients with myelofibrosis. Patients with a history of blast phase/acute myeloid leukemia, or those on glucocorticoids for GVHD were excluded. The trial followed a 3+3 design to determine the maximum tolerated dose (MTD) of fedratinib where dose level (DL) 1 was 200 mg daily, DL2 was 300 mg daily, and DL3 was 400 mg daily. An additional 25 patients will be enrolled in a phase II expansion cohort at the MTD. The dose limiting toxicity (DLT) window was 30 days from initiation of fedratinib where DLTs were defined as Wernicke's encephalopathy, grade 4 cytopenias, or any other grade 3 adverse event attributable to the study drug by CTCAE version 5.0. Secondary endpoints included progression free survival (PFS), overall survival (OS), and chronic GVHD at 1-year post-transplant. Results Eleven subjects are evaluable beyond the DLT monitoring window: 5 with MF, 5 with chronic myelomonocytic leukemia (CMML), and 1 with MDS/MPN overlap-unclassified. JAK2 mutation was detected in 3 subjects prior to transplant. The median age of subjects was 66 (range 40-75) years. Transplant regimens included reduced intensity conditioning for 9 (82%) subjects, matched unrelated donor for 10 (91%) subjects, and post-transplant cyclophosphamide based GVHD prophylaxis for 11 (100%) subjects. The median follow-up is 10.7 (range 3.9-26.2) months. The median time to initiate fedratinib was day +77 (range 62-100) and continued for a median of 151 days (range 31-304). Three subjects were treated at DL1, 3 at DL2, and 5 at DL3. DL3 was identified as the MTD with no DLTs observed at any DL during the 30-day observation window. One subject on DL3 experienced grade 4 cytopenias beyond the DLT window, requiring interruption in therapy but, per protocol, resumed fedratinib at a reduced dose of 300mg daily after resolution of the DLT. Four subjects withdrew from the trial (1 at DL1, 1 at DL2, and 2 at DL3) at a median of 46 days (range: 31-142) due to adverse events that did not meet DLT criteria (hyperkalemia, nausea, and anemia). No therapy related deaths occurred. One subject on DL1 developed severe chronic GVHD, but there were no other cases of moderate or severe chronic GVHD at any dose level. For all treated subjects, the median OS was not reached and median PFS was 12.4 months, with 2 subjects in DL1 and 1 subject in DL2 experiencing relapse in the first year. OS at 1 year was 100%. CONCLUSION In this phase I trial of fedratinib maintenance after allogeneic HCT, fedratinib 400mg daily was safe and identified as the MTD. However, 4 subjects withdrew from the trial prior to completing a full year of maintenance. The phase II expansion cohort is currently enrolling patients at the MTD to confirm safety and evaluate long term efficacy of this maintenance strategy.

INTRODUCTION Pre-transplant detectable measurable residual disease (MRD) is associated with increased risk of relapse and mortality after allogeneic hematopoietic cell transplantation (alloHCT) in patients with acute myeloid leukemia (AML) in morphological complete remission (CR). In post hoc analysis of randomized phase 3 trial, myeloablative (MAC) but not the reduced-intensity conditioning (RIC) is shown to mitigate the negative impact of MRD positivity (MRDpos) on alloHCT outcomes of AML (Hourigan, JCO 2019). However, only minority of patients in the RIC cohort of that study received fludarabine and melphalan (FluMel), which in several registry and single institutional reports showed outcomes comparable to MAC. We studied the effect of FluMel RIC in comparison to fludarabine and busulfan (FluBu) MAC on alloHCT outcomes of MRDpos AML in CR. METHODS We retrospectively studied patients with pre-HCT MRDpos AML in CR who received their first alloHCT at our institution from 2015-2022. FluMel consisted of Mel total dose of 100-140 mg/m2 and FluBu with PK-targeted IV daily average Bu AUC of 5300, both in combination with Flu total dose of 150-160 mg/m2. MRD status prior to alloHCT was assessed by either multiparametric flow cytometry, molecular testing (next generation sequencing or polymerase chain reaction) or by cytogenetics. Primary objective was to compare the overall survival (OS) between FluMel and FluBu. Secondary objectives included leukemia-free survival (LFS), relapse and non-relapsed mortality (NRM). RESULTS A total of 191 eligible patients were identified: FluMel was used in 120 (63%) patients while 71 (37%) patients received FluBu. Median age was 61 years (range, 21-77) at HCT and 43.5% of patients had HCT comorbidity index (CI) of 3+. At diagnosis, 63.9% of patients had adverse risk AML by 2022 European LeukemiaNet stratification and 28.7% of all patients had secondary AML. Graft versus host disease (GVHD) prophylaxis consisted of posttransplant cyclophosphamide (PTCy)-based regimen in 44.5% of patients, tacrolimus/sirolimus in 38.2% and tacrolimus/methotrexate in 16.8% of patients. Peripheral blood was the stem cell source in 98% of patients, while most used donor type was matched unrelated (MUD, 59.7%), followed by matched sibling (17.3%), haploidentical (15.7%) and mismatched unrelated (7.3%) donor. FluMel and FluBu groups were comparable in baseline characteristics, except for FluMel group having higher proportion of patients with age ³60 years (76.7% vs 5.6%, p<0.001), Karnofsky score <90 (28.3% vs 12.7%, p=0.02), ELN adverse risk AML (71.1% vs 50.7%, p=0.01) and MUD (66.7% vs 47.9%, p<0.001). Comparing FluMel vs FluBu groups, the 2-year probability of OS was 64% vs 68% (p=0.20), LFS was 58% vs 70% (p=0.09), relapse was 20% vs 22% (p=0.77) and NRM was 22.0% vs 8.7% (p=0.01). In multivariable analysis after adjusting for patient age, HCT-CI and ELN risk, there were no statistically significant differences between the FluMel and FluBu groups in OS (HR=0.7, p=0.41), LFS (HR=0.9, p=0.75), relapse (HR=0.7, p=0.31) or NRM (HR=1.5, p=0.68) CONCLUSIONS RIC FluMel provides clinical outcomes similar to MAC FluBU in patients receiving alloHCT for AML in MRDpos CR. These data suggest that low risk of relapse and favorable survival can be extended to older and less fit patients if FluMel RIC is used for alloHCT in high-risk MRDpos AML.

Mycophenolate mofetil (MMF) is commonly included in post-transplant cyclophosphamide (PTCy) based graft-versus-host disease (GVHD) prophylaxis after haploidentical (haplo) hematopoietic cell transplant (HCT). In the non-PTCy setting, higher MMF dose/kg has been shown to reduce rates of acute graft-versus-host disease (GVHD). When used in conjunction with PTCy, MMF is dosed at 15 mg/kg three times daily up to a maximum dose of 3 g/day. Thus, patients who weigh ≥67 kg receive 3 g/day and a variable dose/kg of MMF. We investigated the impact of MMF dose/kg on clinical outcomes following haploidentical PBSCT with PTCy-based GVHD prophylaxis. All consecutive adult patients with hematologic malignancies receiving haploidentical T cell replete peripheral blood stem cell transplant (PBSCT) with PTCy/MMF and either tacrolimus or sirolimus at the Moffitt Cancer Center or City of Hope between April 2014-August 2020 were included. For analyses, MMF dose relative to patient actual body weight (mg/kg/day), was stratified into categories of low (<29 mg/kg/day), low intermediate (29-34 mg/kg/day), high intermediate (35-41 mg/kg/day), and high (>41 mg/kg/day). Three hundred eighty-six patients were included. Of these, 54 patients received low dose, 73 low intermediate, 137 high intermediate and 122 high dose MMF by relative weight exposure. In multivariate analysis, low MMF dose exposure was associated with reduced rates of relapse in comparison to the high dose group (HR = 0.45, 95% CI: 0.21 to 0.94, P = .03). This led to superior PFS among patients with low compared to high MMF dose exposure (HR = 0.58, 95% CI: 0.34 to 0.99, P = .045). MMF relative dose exposure was not associated with engraftment, GVHD, nonrelapse mortality, or OS. In this study of patients receiving haploidentical PBSCT with PTCy based GVHD prophylaxis, low MMF dose/kg was associated with improved rates of relapse and PFS. Future prospective studies should investigate optimal dosing strategies of MMF when given with the PTCy regimen.

Background. Human herpesvirus 6B (HHV-6B) frequently reactivates following allogeneic stem cell transplant (alloHCT). Consensus guidelines note that haploidentical alloHCT may represent a high-risk population for which there is little evidence; this warrants further investigation. Methods. In this single-center retrospective study, we evaluated 188 consecutive adult patients receiving haploidentical alloHCT between 11/2014 and 11/2020 and compared outcomes between patients with HHV-6B reactivation receiving targeted antiviral therapy and those who were clinically observed. Results. Of the 58 included patients, 21 (36.2%) received antiviral therapy for HHV-6B reactivation with foscarnet (n = 19) or ganciclovir (n = 2). There were no differences in patient or disease characteristics between treated and observed patients. Treated patients were more likely to have high-level DNAemia (85.7% vs 40.5%; P < .001) and had higher peak viral quantitative measurements (median log10, 4.65 vs 3.84; P < .001). The median time to clearance from plasma (interquartile range) was 13 (7.25-20.00) days for all patients and was not significantly different between groups. There were no differences in episodes of encephalitis, grade III/IV acute graft-vs-host disease (GVHD), or time to neutrophil or platelet engraftment among treated vs observed patients. Day 100 nonrelapse mortality was not significantly different in the multivariate analysis; however, the presence of central nervous system symptoms was strongly associated with worse survival (hazard ratio, 4.11; 95% CI, 1.27-13.34; P = .018). Conclusions. We did not observe a difference in clinical outcomes between the treated and observed groups of patients with HHV-6B reactivation following haploidentical alloHCT. With the rising use of haploidentical transplant and post-transplant cyclophosphamide GVHD prevention platforms, prospective studies are needed to further characterize the risk and outcomes associated with HHV-6B reactivation and therapy.

Allogeneic hematopoietic stem cell transplant (HCT) remains the only cure for many hematologic malignancies, but this costly and highly specialized elective procedure is prone to health disparities. Historically, underrepresented minorities (African/non-Hispanic Black, Hispanic/Latinx, Asian, Native American, Pacific Islander) have lower utilization rates of HCT.1 Among many barriers to transplant, the requirement to identify an 8/8 human leukocyte antigen (HLA) matched donor, including a matched sibling donor (MSD) or matched unrelated donor (MUD), precluded many racial and ethnic minority (REM) patients from reaching HCT as the likelihood of identifying such a donor for REM patients ranges from 16% to 52% compared to over 75% for white non-Hispanic (WNH) patients.2 For patients without an HLA-matched donor, incorporating HLA haploidentical (haplo) or HLA mismatched unrelated donors (MMUD) into donor search algorithms significantly increases the feasibility of HCT. The development of post-transplant cyclophosphamide (PTCy) as graft-versus-host disease (GVHD) prophylaxis has allowed for HLA haplo and MMUD HCT with comparable outcomes to HLA-matched HCT.3, 4 By broadening the donor pool to include HLA mismatched donors, PTCy allows for almost every transplant-eligible patient, including REM patients, to have a suitable donor.3 While more REM patients can now receive an HCT, there remains a paucity of data addressing whether REM patients who receive a mismatched donor HCT with PTCy experience similar outcomes as WNH patients. The aim of this study was to address this gap in literature and compare outcomes between REM and WNH patients who received an HLA mismatched transplant with PTCy. This retrospective study included all consecutive adult patients who underwent an HLA mismatched HCT with PTCy for a hematologic malignancy at the Moffitt Cancer Center between January 2014 and June 2022. Relevant demographic and clinical information were obtained from the Moffitt Blood and Marrow Transplant Research and Analysis Information Network (BRAIN) database and additional data collection was extracted via manual chart review. All endpoints were calculated from the time of HCT and compared between four groups: WNH, white-Hispanic, Black, and Other. The patients comprised in the "Other" category included those who identified as Asian, biracial, and multiracial. Patients were categorized based on self-reported race and ethnicity. Two-sided p-values ≤ .05 were considered statistically significant. The backward elimination method with a p-stay value of .05 was applied for building multivariable models. This study was approved by the Institutional Review Board. A total of 302 patients were included of which 59% (n = 179) of patients identified as WNH, 14% (n = 41) as white-Hispanic, 16% (n = 48) as Black, 7% (n = 21) as biracial or multiracial, and 4% (n = 11) identified as Asian (Table 1). The median follow-up for survivors was 27 months (range 1.84–82.82). At 100 days post-transplant, the cumulative incidence of grade II-IV acute GVHD (aGVHD) was 37% [95% CI, 30%–44%] for WNH patients, 32% [95% CI, 18%–46%] for white-Hispanic patients, 29% [95% CI, 17%–42%] for Black patients, and 24% [95% CI, 11%–39%] for patients of Other races (p = .31; Figure 1A). In multivariate analyses (MVA, Table S1), after adjusting for patient age, conditioning intensity, and donor relation, race/ethnicity was not a risk factor for grade II-IV aGVHD (p = .30). The cumulative incidence of moderate/severe chronic GVHD (cGHVD) at 24 months was (Figure 1B): 20% [95% CI, 14%–26%] for the WNH patients, 23% [95% CI, 11%–37%] for white-Hispanic patients, 16% [95% CI, 7.1%–29%] for Black patients, and 26% [95% CI, 13%–42%] for patients of Other races. After adjusting for patient age, conditioning intensity, and donor relation, race/ethnicity was not associated with the risk of moderate/severe cGVHD (p = .87). At 24 months, the incidence of relapse was 26% [95% CI 19%–33%] for WNH patients, 26% [95% CI, 13%–42%] for white-Hispanic patients, 30% [95% CI, 17%–46%] for Black patients, and 19% [95% CI, 7.3%–34%] for patients of Other races (p = .98; Figure 1C). In MVA, after adjusting for disease risk index (DRI) and conditioning intensity, race/ethnicity was not associated with the risk of relapse (p = .85). High DRI (HR 2.32; 95% CI, 1.47–3.65; p ≤ .001) was associated with higher risks of relapse compared to low/intermediate DRI. Additionally, myeloablative conditioning (MAC, HR 0.65; 95% CI, 0.40–1.06) and reduced intensity conditioning (RIC, HR 0.41; 95% CI, 0.22–0.78) were associated with lower risk of relapse than non-myeloablative (NMA, p = .02). At 100 days post-transplant, the incidence of NRM was 8.9% [95% CI, 5.3%–14%] for WNH patients, 9.8% [95% CI, 3.1–21%] for white-Hispanic patients, 4.2% [95% CI, 0.75%–13%] for Black patients, and 15% [95% CI, 5.3%–29%] for patients of Other races (p = .77; Figure 1D). Adjusting for Karnofsky performance scale (KPS), and donor age, race/ethnicity was not associated with NRM (p = .84). Notably, donor age ≥40 years (HR 1.92; 95% CI, 1.16–3.18; p = .01) [reference group donor age <40] and KPS <90 (HR 2.03; 95% CI, 1.20–3.43) [reference group KPS ≥90] were associated with a higher risk of NRM. A total of 57 patients had NRM events. The most common cause of NRM death was infection (n = 24), followed by organ failure (n = 22), and GVHD (n = 11). Cause of death was similarly distributed across race (p = .46) and ethnicity (p = .61). The RFS probability at 24 months was 54% [95% CI 47%–63%] for WNH patients, 59% [95% CI, 44%–78%] for white-Hispanic patients, 49% [95% CI, 36%–68%] for Black patients, and 57% [95% CI, 42%–77%] for patients of Other races (p = .87, Figure 1E). In MVA, after adjusting for Karnofsky performance scale (KPS), DRI, type of insurance, and donor age, race/ethnicity was not associated with RFS (p = .65). KPS <90 (HR 1.54; 95% CI, 1.05–2.24; p = .03) [reference group KPS ≥90], High DRI (HR 2.15; 95% CI, 1.50–3.09; p ≤ .001) [reference group: low/intermediate DRI], Tricare insurance (HR 2.14; 95% CI, 1.10–4.19; p = .01) [reference group: commercial/employer based], and a donor age ≥40 (HR 1.53; 95% CI, 1.07–2.17; p = .02) [reference group donor age <40] were associated with worse RFS outcomes. OS at 24 months was 63% [95% CI, 55%–71%] for WNH patients, 71% [95% CI, 58%–87%] for white-Hispanic patients, 51% [95% CI, 37%–71%] for Black patients, and 62% [95% CI, 47%–82%] for patients of Other races (p = .89, Figure 1F). After adjusting for DRI and donor age, MVA again showed that race/ethnicity was not a prognostic factor for OS (p = .55). High DRI (HR 2.46; 95% CI, 1.69–3.59; p ≤ .001) [reference group: low/intermediate DRI] and a donor age ≥40 (HR 1.63; 95% CI, 1.13–2.35; p = .01) [reference group donor age <40] were associated with significantly worse OS outcomes. PTCy was developed as GVHD prophylaxis to safely transplant patients with HLA haploidentical donors, thus addressing the lack of donor availability that has been one of the main causes of disparities for racial and ethnic minorities requiring HCT.1-4 Despite its utility as a solution to HCT disparities related to donor availability, there is limited data evaluating outcomes of allogeneic HCT specifically in REM patients who have received PTCy. This study shows that REM patients who receive an HLA mismatched HCT with PTCy have similar outcomes to WNH patients. Previous studies with traditional calcineurin inhibitor (CNI)-based GVHD prophylaxis have shown that even the subset of REM patients who reached transplant still experienced inferior transplant-related outcomes compared to WNH patients.1 In contrast to CNI-based GVHD prophylaxis, our results suggest that PTCy may be a critical factor in balancing disparities in outcomes across racial and ethnic groups receiving allogeneic HCT. Beyond expanding the pool of donors available for HCT, other factors inherent to the PTCy platform may be contributors to the favorable outcomes in REM patients. Previous studies have shown that racial and ethnic minorities, especially Black patients, are more genetically diverse, resulting in a greater degree of donor/recipient genetic disparity such as minor antigen mismatches, even in the setting of an HLA-matched donor.2 As PTCy is known to successfully mitigate the risks of alloreactivity related to genetic disparity, it is likely that PTCy decreases the significance of such untested mismatches that are more prevalent in genetically heterogeneous populations.5 Rather than race/ethnicity, other known risk factors such as high DRI and older donor age are better predictors of poor prognosis. However, in contrast to prior literature showing inferior HCT outcomes in beneficiaries of government-sponsored insurance, our data showed patients with Medicaid had an improved probability of RFS in comparison to patients with commercial insurance.6 This may reflect the effects of PTCy to lower the risks of GVHD and decrease the need for prolonged, expensive treatments that would be burdensome for most Medicaid patients. Conversely, our data showed patients with military Tricare insurance had worse RFS, which may reflect the anecdotal experience that these patients continue to experience delays in insurance authorization related to transplant consultation and treatment. However, due to small sample sizes of these groups, additional investigation would be necessary to confirm the significance of these findings. Based on our results, PTCy mitigates the effect of HCT health disparities by equalizing outcomes between WNH and REM patients in the setting of HLA mismatched allogeneic HCT. Our data provides further evidence to support the increased use of HLA mismatched donor or haploidentical donors HCT with PTCy to expand utilization and access to curative therapy for REM patients. Rawan Faramand receives research funding from Gilead. Aleksandr Lazaryan provides consultancy, receives Honoria, and is a member of the scientific advisory board for Sanofi. Hien Liu has a membership on the board of directors of the advisory committee at BioLineRx. Michael Jain receives research funding from Incyte; provides consultancy and receives honoraria from Myeloid Therapeutics; receives research funding from Loxo@Lilly; provides consultancy and receives honoraria and research funding from Gilead. Taiga Nishihori is on the Speakers Bureau at Medexus Pharmaceuticals and receives personal fees from Karyopharm and Novartis outside the submitted work. Nelli Bejanyan provides consultancy and receives research funding from Orca Bio, CareDx Pharma, CRISPR, Sanofi, CTI BioPharma, Medexus Pharmaceuticals, and Magenta. Hany Elmariah receives research funding from Bristol Myers Squibb and serves on the advisory board for Shoreline Biosciences. The remainder of the authors have no conflicts of interest to disclose. Informed patient consent was not necessary for this work. Table S1. Multivariate analysis of transplant outcomes. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.

Fludarabine (Flu) and melphalan (Mel) reduced-intensity conditioning is frequently used for allogenic hematopoietic cell transplant (allo-HCT) in patients with acute myeloid leukemia (AML) and myelodysplastic syndromes (MDS). However, there is limited evidence on the impact of Mel dosing on toxicities and clinical outcomes of allo-HCT. We retrospectively compared 8/8 HLA-matched donor allo-HCT outcomes of 345 patients with AML or MDS receiving total Mel dose of 100 mg/m(2) (Mel-100, n = 62) versus 140 mg/m(2) (Mel-140, n = 283) in combination with Flu. Median age at allo-HCT was 66 years and median follow-up was 36.5 months. For Mel-100 versus Mel-140 groups, any grade gastrointestinal (GI) toxicity rates were 40.3% versus 67.8% (P < .001), day 100 grade II to IV acute graft-versus-host disease (GVHD) rates were 21.0% versus 43.1% (P = .001) and 2-year chronic GVHD rates were 17.4% versus 27.1% (P = .033). In multivariable analysis, Mel-140 resulted in higher risks of GI toxicity (HR = 1.83, P = .013), grade II to IV acute GVHD (HR=2.35, P = .003), and moderate/severe chronic GVHD (HR = 3.13, P = .007). Total Mel dose had no independent impact on oral mucositis, nonrelapse mortality, relapse, relapse-free survival, and overall survival. While independent validation of our observation is warranted, our findings support using Mel-100 in combination with Flu to minimize allo-HCT toxicities and morbidities related to GVHD.

Fludarabine (Flu) and melphalan (Mel) reduced-intensity conditioning is frequently used for allogenic hematopoietic cell transplant (allo-HCT) in patients with acute myeloid leukemia (AML) and myelodysplastic syndromes (MDS). However, there is limited evidence on the impact of Mel dosing on toxicities and clinical outcomes of allo-HCT. We retrospectively compared 8/8 HLA-matched donor allo-HCT outcomes of 345 patients with AML or MDS receiving total Mel dose of 100 mg/m

Introduction Post-transplant cyclophosphamide (PTCy) is a widely adopted graft-versus-host disease (GVHD) prophylactic strategy for HLA-haploidentical donor hematopoietic cell transplant (HCT) and has recently been proven superior to calcineurin inhibitor-based GVHD prophylaxis in matched donor transplants (Bolaños-Meade. NEJM. 2023). Nonetheless, both HLA mismatched donor and PTCy are independent risk factors for cytomegalovirus (CMV) infections, which may result in morbidity and mortality (Goldsmith. Blood. 2021). Letermovir is effective in reducing the risk of clinically significant CMV infection (csCMVi) and improving survival, though data supporting its use in patients receiving PTCy is limited (Marty, NEJM. 2017). This study aims to assess the real-world effectiveness of letermovir in preventing csCMVi in this high-risk population. Methods This retrospective study included 331 adult patients who underwent allogeneic HCT with PTCy at the Moffitt Cancer Center between 2014 and 2022. The primary endpoint was the incidence of csCMVi, defined as CMV viremia with CMV PCR >650 international units (IU) or evidence of CMV organ disease. Secondary endpoints included adverse effects attributed to letermovir, time to neutrophil engraftment, incidence of chronic GVHD, non-relapse mortality (NRM), relapse free survival (RFS), relapse, and overall survival (OS). Endpoints were compared across three groups by recipient serostatus: 1) CMV negative (CMV-), CMV positive and did not receive letermovir (CMV+/No LET), and 3) CMV positive and received letermovir (CMV+/LET). Results Of 331 included patients, 61 (18%) were CMV+ and received letermovir due to high-risk categorization after adoption of letermovir as standard of practice. Of 270 patients who did not receive letermovir, 148 (45%) were CMV+ and either underwent HCT before letemovir was adopted or could not obtain due to cost/insurance issues, and 122 (37%) were CMV-. The median age was 61 and 78% of patients identified as Caucasian. Donors included haploidentical (40%), matched unrelated (38%), mismatched unrelated (12%), and matched sibling (11%), with 96% receiving peripheral blood stem cells. Median follow-up time was 24 months. The cumulative incidence of csCMVi at day+100 was 11% (95% CI: 5-21%) in CMV+/LET, 45% (95% CI: 37-53%) in CMV+/No LET and 7% (95% CI: 4-13%) in CMV- patients (p<0.01). In multivariate analysis (MVA), CMV+/No LET had a higher risk of csCMVi compared to CMV+/LET (HR=2.96, 95% CI: 1.66-5.27, p<0.01). CMV- had a lower risk of csCMVi (HR=0.41, 95% CI: 0.18-0.92, p=0.03) compared to CMV+/LET. CMV disease was reported in 18 patients across the entire cohort. No grade 4 CMV disease was identified in CMV+/LET patients compared to 3 patients in CMV+/No LET. At day+100, the cumulative incidence of CMV disease was 2% (95% CI: 0.1-8%) in CMV+/LET, 10% (95% CI: 6-16%) in CMV+/No LET and 1% (95% CI: 0.1-4%) in CMV- patients (p<0.01). For patients with csCMVi, the median duration of antiviral treatment was 22 days for CMV+/LET, 33 days for CMV+/No LET, and 30 days for CMV- patients (p=0.14). The median time from date of transplant to antiviral treatment was 97 days for CMV+/LET, 42 days for CMV+/No LET, and 54 days for CMV- patients (p=0.01). Of 61 patients receiving letermovir, 8 (13%) discontinued letermovir early due to treatment related adverse events (gastrointestinal toxicity, cytopenias) at a median of 82 days (range: 37-90) with no reported occurrences of csCMVi afterwards. Incidence of csCMVi at 1 year increased in CMV+/LET from 11% at day+100 to 21% at 1 year. There were no associations between letermovir and recipient CMV serostatus on time to neutrophil engraftment, chronic GVHD, 1-year NRM, relapse, RFS, or OS. Conclusion Our findings support the use of letermovir prophylaxis during the first 100 days post-allogeneic HCT with PTCy in both HLA matched and mismatched donors to reduce the incidence of csCMVi. For patients receiving letermovir who developed csCMVi, time to csCMVi was delayed and the duration of therapy was reduced, thus decreasing exposure to antiviral therapy and minimizing associated adverse effects. Future studies should evaluate strategies to address late onset csCMVi beyond day+100, such as continued PCR monitoring or extended duration of prophylaxis. As PTCy is increasingly utilized, letermovir prophylaxis may address a major limitation of this transplant platform and improve patient outcomes.

Background: Post-transplant cyclophosphamide (PTCy) was developed as a graft-versus-host disease (GVHD) prophylactic regimen that allows for the use of haploidentical related donors and has more recently been adopted as a standard regimen for matched donor and mismatched unrelated donor (MMUD) transplant. Though effective in preventing GVHD, cyclophosphamide can be associated with an increased risk of cardiac toxicity. We evaluated cardiac toxicity in alloHCT with PTCy versus calcineurin inhibitor (CNI) based GVHD prophylactic regimens. Methods: We retrospectively compared cardiac toxicity between PTCy and CNI in all consecutive patients who received an alloHCT for hematologic malignancy at the Moffitt Cancer Center from 2018-2021. The primary outcome was incidence of cardiac toxicity within 3 months of transplant, where cardiac toxicity was defined as decrease in left ventricular ejection fraction (LVEF) >10% from baseline, cardiogenic pulmonary edema requiring treatment, pericarditis, arrhythmia, or acute coronary syndrome/elevated troponin. Secondary outcomes included overall survival (OS), progression-free survival (PFS), and non-relapse mortality (NRM). Outcomes were also studied in the subgroup of patients with baseline cardiac comorbidities and in the subgroup of patients receiving PTCy. Cardiac comorbidities were defined as a history of coronary artery disease (CAD), myocardial infarction (MI), arrhythmias, LVEF <50%, valve disease, or pericardial effusion. Results: A total of 653 patients were included: 48% (n=314) received a PTCy regimen and 51% (n=339) received a CNI regimen. At the time of alloHCT, 69 (10.5%) patients had baseline cardiac comorbidities: 27 (9.0%) in the PTCy group and 44 (13%) in the CNI group (p<0.01). In the PTCy group, cardiac comorbidities included 15 CAD/MI, 8 arrhythmias, 1 LVEF < 50%, 1 valve disease, and 2 pericardial effusions. In the CNI group, cardiac comorbidities included 20 CAD/MI, 15 arrhythmia, 5 LVEF <50%, 2 valvular disease, and 2 pericardial effusions. The incidence of cardiac toxicity at 3 months was 28% for the PTCy group and 23% for the CNI group (p=0.15). In multivariate analysis for the entire cohort, there was no difference in cardiac toxicity between the two groups (p=0.10). Acute lymphocytic leukemia (ALL) was associated with a higher risk of cardiac toxicity than acute myeloid leukemia (AML; HR=2.21; CI: 1.25-3.90; p< 0.01), while lymphoma was associated with lower risk of cardiac toxicity compared to AML (HR=0.19; CI: 0.04-0.87; p=0.03). Myeloablative fludarabine/busulfan was associated with a lower incidence of cardiac toxicity compared to fludarabine/melphalan (HR=0.38; CI: 0.24-0.60; p<0.01). There was no significant difference in OS or NRM at day 100 in patients who received PTCY versus CNI. In subgroup analysis of patients with baseline cardiac comorbidities, the cumulative incidence of cardiac toxicity at 3 months was 23% in the PTCy group and 23% in the CNI group (p=0.95). OS and NRM in this subgroup were also similar between the PTCy and CNI groups. In the PTCy subgroup, multivariable analysis showed a higher incidence of cardiac toxicity within 3 months of HCT in patients with ALL compared to AML (HR=2.65; CI 1.38-5.10; p< 0.01). Additionally, the risk of cardiac toxicity was lower with myeloablative fludarabine/busulfan compared to fludarabine/melphalan (HR=0.37; 0.19-0.71; p<0.01). Conclusion: Our study suggests that PTCy does not significantly increase the risk of cardiac toxicity compared to CNI. Among patients with baseline cardiac comorbidities, cardiac toxicity was also similar between the groups. For patients receiving PTCy, cardiac toxicity was instead associated with ALL and the use of melphalan-based conditioning regimens. These results suggest that PTCy remains a suitable option for GVHD prophylaxis even in patients with underlying cardiac disease.

Impact of JAK2/mTOR blockade on human T cell responses toward CMV, EBV, Influenza, and tetanus stimulation. A, B) Graphs show the recall proliferation of CD4+ and CD8+ T cell proliferation in response to CEFT peptides. C, D) Graph shows the frequency of IFNy+, CD107a+ CD4+ or cos+ T cells after stimulation with CEFT peptides.

The table shows adverse events per CTCAE version 5 encountered during the PAC/SIR/TAC phase I trial.