Posttransplant Cyclophosphamide for Prevention of Graft-versus-Host Disease: The Prospective Randomized HOVON-96 Trial

Intermediate-dose posttransplantation cyclophosphamide for myeloablative HLA-haploidentical bone marrow transplantation

ABSTRACT

High-dose posttransplantation cyclophosphamide (HD-PTCy), given at 50 mg/kg/day on days +3/+4, is a standard-of-care graft-versus-host disease (GVHD) prophylaxis for allogeneic hematopoietic cell transplantation (HCT). Our murine MHC-haploidentical HCT studies suggested intermediate-dose PTCy produces superior GVHD control compared with HD-PTCy and PTCy is maximally effective on day +4. We conducted a single-institutional prospective phase 1/2 trial to reduce PTCy dosing to 25 mg/kg/day on days +3/+4 or on day +4 only for myeloablative HLA-haploidentical bone marrow HCT using PTCy, sirolimus, and mycophenolate mofetil. Among 35 patients, 89% were ethnic/racial minorities, 46% had high/very-high-risk disease, and median comorbidity score was 3. The phase 1 dose-limiting-toxicity, grade III-IV acute GVHD, was not observed after either reduced-PTCy dose level. PTCy 25 mg/kg/day on days +3/+4 (intermediate-dose (ID)-PTCy; n = 23), the phase 2 dose, resulted in no grade II-IV acute GVHD; 2-year cumulative incidences of chronic GVHD requiring systemic immunosuppression, nonrelapse mortality, and relapse were 13%, 17%, and 22%, and 2-year overall survival, disease-free survival, and GVHD-free/relapse-free survival were 61%, 61%, and 52%. In exploratory analysis compared with HD-PTCy (n = 5), ID-PTCy resulted in significantly faster engraftment and T-cell reconstitution, fewer transfusions, less mucositis, and reduced severity of BK-virus-associated cystitis/urethritis; area-under-the-curve exposure of 4-hydroxycyclophosphamide (4HCY), a key cyclophosphamide metabolite, correlated with these outcomes but not with chronic GVHD occurrence. Ideal-body-weight-based PTCy dosing best approximated 4HCY exposure. ID-PTCy is effective and has apparent clinical benefits compared with HD-PTCy. Before broader implementation, further studies are needed to confirm these findings and define optimal PTCy dosing across various donor/graft types. This trial was registered at www.clinicaltrials.gov as #NCT03983850.

NIH Chronic Graft-versus-Host Disease Consensus Conference 2025 Update

In 2020, the third NIH Consensus Development Project on Criteria for Chronic Graft-versus-Host Disease (GVHD) Clinical Trials was held with the goals of identifying gaps in understanding, prevention and treatment of chronic graft-versus-host disease (GVHD) and making actionable recommendations that would advance the field. An interim meeting was held in October 2024 to review progress on the 2020 recommendations. Each group was charged with reviewing their previous recommendations, assessing whether the field is on track to eventually achieve the goals, and considering whether recommendations should be modified in light of new data or insufficient progress. This manuscript summarizes the Working Groups' reports and helps define the research agenda for future studies in chronic GVHD. Overall, modest progress has been made on most initiatives. Some studies in progress will address key recommendations and results are eagerly anticipated.

Low rates of chronic graft-versus-host disease with ruxolitinib maintenance following allogeneic HCT

ABSTRACT

Despite recent advances in graft-versus-host disease (GVHD) prophylaxis, novel approaches to effective prevention of chronic GVHD (cGVHD) remain of high importance. In this prospective, multicenter, phase 2 trial, ruxolitinib, an oral inhibitor of Janus kinase (JAK) 1 and 2, was administered as maintenance therapy after reduced-intensity allogeneic hematopoietic cell transplantation (HCT). GVHD prophylaxis consisted of tacrolimus and methotrexate. Ruxolitinib began between day +30 to 100 and was administered continuously in 28-day cycles for up to 24 cycles. Seventy-eight participants were enrolled before HCT; 63 participants received the intervention. The median start date of ruxolitinib after HCT was day +45. The most common grade ≥3 adverse events were neutropenia, thrombocytopenia, and anemia. Seven participants experienced grade ≥3 infectious events. GVHD-free, relapse-free survival at 1 year after HCT, the primary end point, was 70%. Grade 3 to 4 acute GVHD at 6 months was 4.8%, and moderate-severe cGVHD at 2 years was 16%. cGVHD requiring systemic therapy was 9.5% at 1 year and 13% at 2 years. Overall survival and progression-free survival at 2 years were 76% and 68%, respectively. Prolonged administration of ruxolitinib following HCT is associated with low rates of clinically significant cGVHD. The incorporation of JAK inhibition into GVHD prevention approaches warrants further investigation. This trial was registered at www.clinicaltrials.gov as #NCT03286530.

Improved GVHD-free and relapse-free survival after ex vivo αβTCR and CD19 depleted allogeneic HSCT compared to T cell replete HSCT

Allogeneic hematopoietic stem cell transplantation (allo-HSCT) aims to cure patients without inducing severe graft-versus-host disease (GVHD) or relapse. In prospective studies of mostly pediatric patients with haploidentical donors, ex vivo αβTCR/CD19 depletion has shown to have low incidences of GVHD, but data for adults with matched related (MRD) or unrelated donors (MUD) remain limited. We analyzed the outcomes of recipients who received a myeloablative regimen plus ATG, followed by an αβTCR/CD19-depleted allograft (cohort D+ATG (n = 122)), and compared outcomes to T cell-replete cohorts (cohort R (N = 60)); without ATG; R+ATG = with ATG (N = 129) in a single-center retrospective analysis. In D+ATG, the incidence of aGVHD grade III-IV was 7%, compared to 13% in R and 16% in R+ATG (p = 0.09). Extensive cGVHD was reduced from 23% in R and 10% in R+ATG to 2% in D+ATG (p < 0.001). The reduced incidence of cGVHD led to a superior GVHD-relapse-free survival (GRFS) of 56.7% in D+ATG versus 36.7% in R and 42.8% in R+ATG (p = 0.03) at 2 years. In conclusion, the combination of myeloablative conditioning, ATG, and ex vivo αβTCR/CD19 depletion appears to be a promising approach to enhance GRFS in adult patients up to 75 years of age undergoing allo-HSCT.

Update in GVHD Prophylaxis: Novel Pharmacologic and Graft Manipulation Strategies

Prevention of graft-versus-host disease (GVHD) is critical to successful allogeneic hematopoietic cell transplantation (HCT), but for many years was difficult to achieve. Advances in the understanding of allogeneic HCT biology and immunology have paved the way for novel clinical approaches to GVHD prophylaxis, highlighted by the broad adoption of posttransplant cyclophosphamide and the approval of abatacept by the US Food and Drug Administration to prevent acute GVHD. Patients undergoing allogeneic HCT are now experiencing severe acute GVHD at historically low rates, and significant improvements in preventing chronic GVHD are also being achieved. This review highlights key pharmacological approaches and graft manipulation strategies being used or investigated for GVHD prophylaxis. Furthermore, we discuss the ongoing unmet needs in GVHD prevention and the challenges in addressing these areas in future clinical trials.

GVHD prophylaxis in matched related stem cell transplantation: Why post-transplant cyclophosphamide can be recommended a study by the EBMT transplant complications working party

Rabbit anti-thymocyte globulin (rATG) reduced chronic GVHD after matched related donor (MRD) allogeneic stem cell transplantation (alloSCT) from 69% to 32% in a randomized trial and is the recommended standard in Europe. Post-transplantation Cyclophosphamide (PTCy) is an emerging alternative but lacks such solid data in MRD alloSCT. We therefore analyzed outcomes of rATG (n = 4140) vs. PTCy (n = 1069) in adult patients with hematologic malignancies undergoing MRD alloSCT between 2017 and 2021 in the EBMT database. The provided hazard ratios (HR) and P-values are adjusted for potential risk factors using multivariate analysis. Results are given at 2 years after alloSCT for all endpoints except for acute GVHD (100 days). The main difference was a lower relapse incidence after PTCy vs. rATG (26.2% vs. 32.8%; HR 0.78 [CI 95%: 0.66-0.92], p = 0.003). Interaction analyses confirmed the consistency of this result across different disease risk index and conditioning intensity subgroups. Other major transplant outcomes showed no significant differences: non-relapse mortality, overall survival, progression-free survival, GVHD-free relapse-free survival, incidence and severity of acute GVHD as well as chronic GVHD. In summary, PTCy results in comparable GVHD and survival outcomes but lower relapse rates compared to rATG. We conclude that PTCy can be recommended in MRD alloSCT.

Evolution of Allogeneic Stem Cell Transplantation: Main Focus on AML

In recent years, treatments in the field of hematologic malignancies have undergone significant evolution; allogeneic hematopoietic stem cell transplantation (allo-HSCT) has shifted from an "ultimate" therapy to becoming a component of a comprehensive therapeutic strategy for acute myeloid leukemia (AML). Advances in risk stratification (including molecular profiling and measurable residual disease assessment), conditioning regimens, and graft-versus-host disease (GVHD) prophylaxis-such as post-transplant cyclophosphamide-have improved outcomes and expanded donor selection and transplant eligibility. We should not only focus on the transplantation procedure but also consider various therapeutic components, including chemotherapy, targeted therapy (possibly including chimeric antigen receptor T-cell therapy), and post-transplant maintenance therapy, which need to be orchestrated within the broader context of leukemia treatment. In this review, we summarized key developments in allo-HSCT for AML and aim to "decipher" each component of transplantation.

GvHD prophylaxis with tacrolimus, sirolimus, and mycophenolate mofetil after reduced intensity conditioning hematopoietic stem cell allogeneic transplantation

We present the largest prospective real-world experience in 159 patients who received the triple combination of tacrolimus/sirolimus/mycophenolate mofetil after reduced intensity conditioning allogeneic hematopoietic stem cell transplantation (RIC-alloHSCT) from matched-related (MRD), matched-unrelated (MUD) or mismatched-unrelated donors (MMURD). Despite the high-risk and elderly population, non-relapse mortality (NRM) at day +100 and 1 year was 5.1% and 8.6%. Grades 2-4 and 3-4 acute Graft-versus-host disease (GvHD) at day +180 was 30.3% and 13%, respectively. Chronic GvHD at 1 and 3 years was 23.2% and 41% and for moderate/severe was 13.2% and 26.6%, respectively. With a median follow-up of 20 months, the 1- and 3-year progression-free survival was 60% and 49%, the GvHD-free relapse-free survival was 44% and 32%, and the overall survival was 70.3% and 61%, respectively, for the entire cohort. Patients receiving allo-HSCT from MMURD showed a higher incidence of aGvHD with impact on survival endpoints. GvHD prophylaxis with the triple-drug combination tacrolimus/sirolimus/mycophenolate mofetil showed excellent results in terms of NRM, GvHD and survival in a high-risk, frail and elderly population in the context of RIC-HSCT from MRD and MUD. The subgroup of patients receiving RIC-HSCT from MMURD might probably benefit from other prophylaxis strategies.

Post-transplant cyclophosphamide in matched donor transplantation: are we there yet?

Graft-versus-host disease (GvHD) is a frequent cause of morbidity and mortality after allogeneic hematopoietic stem cell transplantation (alloHCT) and optimal approaches for its prevention have been recently updated. Post-transplant cyclophosphamide (PTCy) has demonstrated impressive results in the setting of haploidentical donor transplantation, allowing for a more widespread application of alloHCT. For this reason, over the years, several groups have implemented the use of PTCy in the context of transplantation from HLA-matched related and unrelated donors, as a replacement for standard GvHD prophylaxis based on calcineurin inhibitors and methotrexate. With increasing results from retrospective studies and new insights from prospective clinical trials, this comprehensive reevaluation of the literature aims to clarify the precise role of PTCy in this context. This review will summarize and critically discuss the overall results of the use of PTCy in alloHCT from HLA-matched donors, unmet needs, and future perspectives.

[Ocular graft versus host disease]

Ocular graft versus host disease (GVHD) following allogeneic hematopoietic stem cell transplantation (HSCT) is predominantly an inflammatory and destructive ocular surface disease with increasing incidence. It not only leads to a reduced quality-of-life but can also impair vision and in severe cases lead to blindness. The occurrence of GVHD can lead to a severe, often refractory disorders of the ocular surface, which is associated with chronic inflammation. The occurrence of corneal involvement is a major problem. The establishment of comprehensive care structures and individually adapted stage-appropriate treatment in interdisciplinary collaboration with colleagues in hemato-oncology is therefore of particular importance.

Post-Transplant Cyclophosphamide-Based GVHD Prophylaxis After Peripheral Blood Stem Cell HLA Identical Transplantation in Patients with Lymphoma: A Prospective Observational Study

Allogeneic stem cell transplantation (allo-SCT) from HLA-identical donors (HLAid) could be an effective salvage treatment for relapsed/refractory lymphoma. In this setting, standard graft-versus-host disease (GVHD) prophylaxis is based on cyclosporine and methotrexate, with the addition of anti-thymocyte globulin, at least for matched, unrelated donors. Promising data using post-transplant cyclophosphamide (PT-Cy) have been reported from retrospective studies in patients receiving allo-SCT from HLAid donors. Here, we report the results of a single-center, prospective observational study exploring the main outcomes of GVHD prophylaxis based on PT-Cy in 27 patients receiving HLAid donor transplantation for relapsed/refractory lymphoma. With a median follow-up of 38 months, 3-year GVHD-relapse-free survival and PFS and OS were 70.4%, 81.5%, and 88.9%, respectively. The 1-year cumulative incidence (CI) of non-relapse mortality (NRM) was 7.4%. The 6-month CI of acute GVHD was 7.4%, and the 1-year CI of extensive chronic GVHD was 7.7%, with no grade IV GVHD events or deaths from GVHD. Relapse was reported in three patients (1-year relapse incidence: 11%), and two died of progressive disease. No graft failure was observed. This study shows that PT-Cy may be an effective strategy to prevent GVHD in patients with lymphoma receiving HLAid transplantation. It is associated with low NRM and reasonable disease control.

Impact of Underlying Disease and Total Body Irradiation on the Incidence of Graft-Versus-Host Disease After Allogeneic Hematopoietic Cell Transplantation

Multiple factors have been described to influence the risk of acute or chronic graft-versus-host disease (aGVHD or cGVHD) after allogeneic hematopoietic cell transplantation (HCT), including underlying chronic myeloid leukemia (CML) and high-dose total body irradiation (TBI). However, the impact of the underlying disease or low-dose TBI on the risk of GVHD in the modern era has not been determined. The objective of this study was to determine risk factors for GVHD in the modern era in the setting of antithymocyte globulin (ATG)-based GVHD prophylaxis. This retrospective study included 1219 patients with hematologic malignancy who underwent first peripheral blood allogeneic HCT using myeloablative fludarabine and busulfan conditioning ± low-dose total body irradiation, along with ATG, cyclosporine, and methotrexate as GVHD prophylaxis. The adjusted cumulative incidence of GVHD was compared between patient subgroups using multivariable competing risks regression. When disregarding the underlying disease, risk factors for grade 2-4 aGVHD were donor type other than matched sibling donor (non-MSD) and lack of low-dose TBI (non-TBI). Risk factors for grade 3-4 aGVHD were non-MSD, non-TBI, and CMV donor negative/recipient positive serostatus (D-R+). Risk factors for moderate-severe cGVHD were ≤9/10 HLA match, non-male/male donor/recipient sex, and non-TBI. In models including the underlying disease, additional significant risk factors were chronic lymphocytic leukemia (CLL) for grade 2 to 4 aGVHD (sub-hazard ratio over acute myeloid leukemia [SHR] 3.16, 95% CI 1.97-5.08, P < .001); CLL and acute lymphoblastic leukemia (ALL) for grade 3-4 aGVHD (SHR for CLL 3.54, 95% CI 1.54-8.17, P = .003 and SHR for ALL 2.26, 95% CI 1.26-4.04, P = .006); and myelofibrosis (MF) for moderate-severe cGVHD (SHR 2.14, 95 CI 1.34-3.41, P = .001). In the modern era when using ATG for GVHD prophylaxis, newly identified risk factors include CLL and non-TBI for grade 2-4 aGVHD; CLL, ALL, and non-TBI for grade 3-4 aGVHD; and MF and non-TBI for moderate-severe cGVHD. These findings, if confirmed in a separate cohort, should be taken into consideration when tailoring the prophylaxis and monitoring of GVHD.

Budesonide, Added to PTCy-Based Regimen, for Prevention of Acute GI GVHD After Allogeneic Stem Cell Transplantation

Oral budesonide exerts local effects with negligible systemic glucocorticoid activity, due to rapid first-pass metabolism, therefore, could potentially be efficacious in preventing gastrointestinal (GI) acute GVHD (aGVHD). We explored the use of budesonide, added to posttransplant cyclophosphamide (PTCy), tacrolimus, and mycophenolate mofetil, for prevention of GI aGVHD after allogeneic hematopoietic stem cell transplantation (AHSCT) in a prospective observational study and treated 80 patients with a median age of 53 years (range 19-74). Results were compared with a publicly available CIBMTR dataset of 646 patients who received PTCy-based GVHD prophylaxis (CIBMTR Study # GV17-02) (control). Cumulative incidence (CI) of 3-month grade 2-4 and grade 3-4 aGVHD in the budesonide and control groups were 3.8% vs. 34.4% (p < 0.001) and 1.3% vs. 9.8% (p = 0.029), respectively. One-year GRFS (70.5% vs. 31.5%, p < 0.001), PFS (73.4% vs. 52.8%, p = 0.003), and OS (80.1% vs. 64.2%, p = 0.038) were significantly higher in the budesonide group compared with control group. Propensity score-adjusted analyses showed that the addition of budesonide significantly decreased risk of aGVHD grade 2-4 (HR 0.29, p < 0.001), grade 3-4 (HR 0.12, p = 0.045), and cGVHD (HR 0.22, p < 0.001), which resulted in better GRFS (HR 0.38, p < 0.001), PFS (HR 0.58, p = 0.012), and OS (HR 0.72, p = 0.044). Similar results were found when using propensity score-matched analysis restricted to recipients of haploidentical transplantation. In conclusion, addition of budesonide to PTCy-based GVHD prophylaxis is safe and effective in preventing severe acute GI GVHD with significantly improved GRFS. These results could facilitate transition to peripheral blood grafts for all allogeneic transplant recipients.

FDA-approved therapies for chronic GVHD

ABSTACT

Despite novel prophylactic regimens, chronic graft-versus-host disease (cGVHD) remains a challenging complication after allogeneic hematopoietic cell transplantation. cGVHD can affect multiple organs and reduces quality of life, and treatment can cause serious adverse effects. In the past 10 years, the drugs ibrutinib, ruxolitinib, belumosudil, and axatilimab were approved by the US Food and Drug Administration (FDA) for cGVHD. Here, we discuss which signaling pathways and cell types are targeted, the clinical studies that were the basis for FDA approval, and future directions for clinical research.

Multicentre adaptive randomised trial of GvHD prophylaxis following unrelated donor stem cell transplantation comparing Thymoglobulin versus calcineurin inhibitor-based or sirolimus-based post-transplant cyclophosphamide (Methods of T cell Depletion, MoTD trial)

INTRODUCTION

Graft-versus-host disease (GvHD) remains a major complication of allogeneic stem cell transplantation (allo-SCT), affecting 30-70% of patients (representing 800 new patients per year in the UK). The risk is higher in patients undergoing unrelated allo-SCT. About 1 in 10 patients die as a result of GvHD or through complications of its treatment. In patients who survive GvHD and or the complications of treatment, about 1 in 3 patients develop chronic GvHD which has a negative impact on quality of life (QoL). Many transplant protocols use alemtuzumab or anti-thymocyte globulin (ATG) in combination with a calcineurin inhibitor (CNI) and mycophenolate mofetil as GvHD prophylaxis; however, the outcomes of these treatments are complicated by high rates of infection and therefore the development of improved GvHD prophylaxis strategies represents a major unmet need.

METHODS AND ANALYSIS

The Methods of T-Cell Depletion trial is a prospective, multicentre, adaptive randomised trial in patients undergoing reduced intensity-conditioned unrelated donor allo-SCT. The trial will compare the novel GvHD prophylaxis regimens post-transplant cyclophosphamide (PTCy) in combination with a CNI or sirolimus (PTCy-CNI or PTCy-sirolimus, respectively) to a current standard-of-care GvHD prophylaxis involving the use of Thymoglobulin (a specific brand of ATG containing rabbit polyclonal antibodies). The primary outcome measure is GvHD-free, relapse-free survival at 1 year. Secondary outcomes include cumulative incidence of acute grade II-IV GvHD at 1 year, cumulative incidence of moderate and severe chronic GvHD at 1 year, overall survival at 1 year and cumulative incidence of non-relapse mortality at 1 year.

ETHICS AND DISSEMINATION

The protocol was approved by the West Midlands, Edgbaston Research Ethics Committee (20/WM/0195); initial approval was received on 11 September 2020, current protocol version (V.4.0) approval on 25 July 2023. The Medicines and Healthcare products Regulatory Authority also approved all protocol versions. The results of this trial will be disseminated through national and international presentations and peer-reviewed publications.

TRIAL REGISTRATION NUMBER

EudraCT Number: 2019-002419-24.ISRCTN Number: 50290131.

Post-transplant cyclophosphamide with post-engraftment anti-thymocyte globulin reduce moderate to severe chronic graft-versus-host disease in peripheral stem cell transplantation from HLA-matched unrelated and haploidentical donors

Post-transplantation cyclophosphamide (PTCy) has unique advantages for graft-versus-host disease (GVHD) prophylaxis after allogeneic hematopoietic stem cell transplantation (allo-HSCT). In this single-center retrospective landmark analysis, we evaluated chronic GVHD (cGVHD) and clinical outcomes in patients receiving PTCy, tacrolimus, and post-engraftment low-dose anti-thymocyte globulin (PTCy-ATG) as GVHD prophylaxis after HLA-matched unrelated or haploidentical donor transplantation. Two historical patient groups receiving calcineurin inhibitor-based GVHD prophylaxis were used as control groups. A total of 71 patients with myeloid malignancies undergoing allo-HSCT with myeloablative conditioning regimens were included in the analysis. The 3-year cumulative incidences of cGVHD and moderate to severe cGVHD (M/S cGVHD) were 39.2% (95%CI 27.4%-51.0%) and 11.5% (95%CI 4.1%-18.9%), respectively, in the PTCy-ATG group, and only one instance of bronchiolitis obliterans (BO) was observed. The disease-free survival (DFS), overall survival (OS), and GVHD-free and relapse-free survival rates were 94.0% (95%CI 88.3%-99.7%), 93.0% (95%CI 87.1%-98.9%) and 83.8% (95%CI 75.0%-92.6%) respectively. Of note, the PTCy-ATG group presented with a significantly lower incidence of M/S cGVHD and BO, which translated into superior OS in multivariate analysis. In this retrospective analysis, we observed that PTCy-ATG-based GVHD prophylaxis was associated with a lower incidence of M/S cGVHD and better transplantation outcomes beyond day 100, which invites prospective evaluation.

Applicability and validation of different prognostic scores in allogeneic hematopoietic cell transplant (HCT) in the post-transplant cyclophosphamide era

We investigated the predictive capacity of six prognostic indices [Karnofsky Performance Status (KPS), Hematopoietic Cell Transplant-Specific Comorbidity Index (HCT-CI), Disease Risk Index (DRI), European Bone Marrow Transplantation (EBMT) and Revised Pre-Transplantation Assessment of Mortality (rPAM) Scores and Endothelial Activation and Stress Index (EASIX)] in 205 adults undergoing post-transplant cyclophosphamide (PTCy)-based allo-HCT. KPS, HCT-CI, DRI and EASIX grouped patients into higher and lower risk strata. KPS and EASIX maintained appropriate discrimination for OS prediction across the first 2 years after allo-HCT [receiver operating characteristic curve (area under the curve (AUC) > 55 %)]. The discriminative capacity of DRI and HCT-CI increased during the post-transplant period, with a peak of prediction at 2 years (AUC of 61.1 % and 61.8 %). The maximum rPAM discriminative capacity was at 1 year (1-year AUC of 58.2 %). The predictive capacity of the EBMT score was not demonstrated. This study validates the discrimination capacity for OS prediction of KPS, HCT-CI, DRI and EASIX in PTCy-based allo-HCT.

Time-restricted versus standard-duration immunosuppression after allogeneic hematopoietic stem cell transplantation: Results of the prospective randomized HOVON-96 trial

Cyclosporine A combined with mycophenolate mofetil (CsA/MMF) has become an established regimen for the prevention of graft-versus-host disease (GVHD) following non-myeloablative (NMA) allogeneic hematopoietic stem cell transplantation (alloHSCT). However, the optimal duration of immunosuppression (IS) has not yet been defined and overtreatment is of concern. We hypothesized that time-restricted IS with CsA/MMF would increase the proportion of patients with non-severe GVHD compared to standard-duration IS, thereby resulting in reduction of the relapse rate and improvement of progression-free survival (PFS) and overall survival (OS). In a prospective randomized, multicenter, phase III trial, patients were allocated (1:1) to standard or time-restricted IS. A total of 389 patients were randomized, of whom 369 were transplanted (184 vs. 185 patients). The primary endpoint, the proportion of patients with non-severe GVHD defined as acute GVHD grades I-II without gut involvement or chronic GVHD not requiring systemic treatment within 180 days posttransplant, was 23% after standard-duration IS versus 24% after time-restricted IS (odds ratio: 1.02; 95% confidence interval (CI) 0.63-1.66, p = 0.92). The cumulative incidence of grade III-IV acute GVHD at 6 months posttransplant was not significantly different (14% vs. 18%; p = 0.20). The two-year cumulative incidence of chronic extensive GVHD was 50% versus 46% (p = 0.62). There were no significant differences in the rates of relapse/progression, non-relapse mortality, PFS, OS, and GVHD-free, relapse-free survival. Time-restricted IS with CsA/MMF did not increase the proportion of patients with non-severe GVHD, and secondary outcomes were not different compared to standard-duration IS following NMA-matched alloHSCT.

Cardiac events occurring after allogeneic hematopoietic cell transplantation with post-transplant cyclophosphamide. Study conducted on behalf of the GETH-TC

This multicenter study investigates the incidence and predictors of cardiac events (CE) following allo-HCT with PTCY in 453 AML patients. CE occurred in 57 (12.3%) patients within a median of 52 days (IQR: 13-289), with day 100 and 5-year cumulative incidences of 7.7% and 13.5%. Early (first 100 days) and late CE occurred at rates of 7.7% and 4.8%. The most prevalent CE were heart failure (n = 18, 31.6%), pericardial complications (n = 16, 28.1%), and arrhythmia (n = 14, 24.6%). The proportions of patients older than 55 years (64.9% vs. 46.1%, P = 0.010), with hypertension (36.8% vs. 18.4%, P = 0.001) and dyslipidemia (28.1% vs. 11.1%, P = 0.001) were higher in patients with CE. Patients undergoing haplo-HCT trend to have more CE (68.4% vs. 56.8%, P = 0.083). The multivariate regression analysis revealed that only hypertension (HR 1.88, P = 0.036) and dyslipidemia (HR 2.20, P = 0.018) were predictors for CE, with no differences according to donor type (haplo-HCT vs. others: HR 1.33, P = 0.323). Among the 57 patients with CE, the mortality rate was 12.2%. Notably, the diagnosis of CE negatively impacted NRM (HR 2.57, P = 0.011) and OS (HR 1.80, P = 0.009), underscoring necessity of aggressively treating cardiovascular risk factors, and implementing post-transplant cardiac monitoring protocols to prevent these complications.

High activity of the new myeloablative regimen of gemcitabine/clofarabine/busulfan for allogeneic transplant for aggressive lymphomas

Refractory aggressive lymphomas can be treated with allo-SCT, pursuing a graft-vs-lymphoma effect. While reduced intensity conditioning is safe, tumors often progress rapidly, indicating the need for more active conditioning regimens. The preclinical synergy we saw between gemcitabine (Gem), clofarabine (Clo) and busulfan (Bu) against lymphoma cell lines led us to study Gem/Clo/Bu clinically. Eligibility: age 12-65, refractory aggressive B-NHL, T-NHL or Hodgkin, with a matched donor. Infusional Gem was dose-escalated on days (d) -6 and -4 (475-975 mg/m2/day), followed by Clo (40 mg/m2/day) and Bu (target AUC, 4000 μMol min/day) (d -6 to -3). CD20+ tumors received rituximab. GVHD prophylaxis included ATG (MUD), tacrolimus and MMF. We compared their outcomes to matched-pair concurrent controls receiving Flu/Mel + matched allo-SCT. We enrolled 64 patients, median age 46 (17-63), 31 B-NHL/22 T-NHL/11 Hodgkin, 36 MSD/28 MUD (all PBPC), median 4 (2-10) prior therapies; 18 prior auto-SCT, 42 active diseases at allo-SCT (12 PD). Toxicities (mucositis and transaminitis) were manageable. Gem/Clo/Bu was myeloablative yielding early full donor chimerism. Grades II-IV/III-IV acute GVHD rates of 37% and 18%; chronic GVHD of 33% (13% severe); NRM at D100/1 year was 7% and 18%. ORR/CR rates: 78%/71% (B-NHL), 93%/93% (T-NHL), 67%/67% (Hodgkin). At a median follow-up of 60 (12-110) months, EFS/OS rates: 36%/47%. Gem/Clo/Bu patients had better median EFS (12 vs. 3 months, P = 0.001) and OS (25 vs. 7 months, P = 0.003) than 113 Flu/Mel matched-pair controls. The new myeloablative regimen Gem/Clo/Bu has limited toxicity and high activity in allo-SCT for aggressive lymphomas, yielding better outcomes than concurrent matched-pair controls receiving Flu/Mel.

Cardiac events after allo-HCT in patients with acute myeloid leukemia

ABSTRACT

This multicenter study sponsored by the GETH-TC investigates the incidence and predictors of early (first 100 days) and late cardiac events (CEs; ECEs and LCEs, respectively) after allo-HCT in patients with acute myeloid leukemia (AML) treated with anthracyclines, focusing on exploring the impact of PTCY on cardiac complications and the impact of CEs on OS and NRM. A total of 1020 patients with AML were included. PTCY was given to 450 (44.1%) adults. Overall, 94 (9.2) patients experienced CEs, with arrythmias, pericardial complications, and heart failure the most prevalent. ECEs occurred in 49 (4.8%) patients within a median of 13 days after allo-HCT, whereas LCEs were diagnosed in 45 (4.4%) patients within a median of 3.6 years after transplant. Using PTCY increased the risk for ECEs in multivariate analysis (hazard ratio [HR], 2.86; P = .007) but did not significantly affect the risk for LCEs (HR, 1.06; P = .892). The impact of variables on outcomes revealed was investigated using multivariate regression analyses and revealed that the diagnosis of CEs decreased the likelihood of OS (HR, 1.66; P = .005) and increased the likelihood of NRM (HR, 2.88; P < .001). Furthermore, despite using PTCY increased ECEs risk, its administration was beneficial for OS (HR, 0.71; P = .026). In conclusion, although the incidence of CEs was relatively low, it significantly affected mortality. Standard doses of PTCY increased ECE risk but were associated with improved OS. Therefore, protocols for preventing cardiac complications among these patients are needed.

Post-transplant cyclophosphamide compared to sirolimus/tacrolimus in reduced intensity conditioning transplants for patients with lymphoid malignancies

Despite novel cellular and immunomodulatory therapies, allogeneic hematopoietic stem cell transplantation (HSCT) remains a treatment option for lymphoid malignancies. Post-transplant cyclophosphamide (PTCY) is increasingly employed for graft vs. host disease (GVHD) prophylaxis. This study aims to evaluate the safety and efficacy of PTCY in reduce intensity (RIC) HSCT for patients with lymphoid neoplasms compared to sirolimus with tacrolimus (SIR/TAC). The primary endpoint was to compare grade III-IV acute GVHD, severe chronic GVHD, and relapse-free survival (GRFS) between the two GVHD prophylaxis strategies. This study, conducted from January 2012 to December 2020, included 171 consecutive patients (82 in the PTCY and 89 in the SIR/TAC group). Results revealed a significantly decreased incidence of moderate and severe forms of chronic GVHD in PTCY cohort (5.8% [95% CI, 1.8 to 13.1]) versus the SIR/TAC cohort (39.6% [95% CI, 29.3 to 49.7] (p < 0.001)). Other outcomes, including GRFS (PTCY [45.9% (95% CI, 35.8-58.7)] and SIR/TAC groups [36.8% (95% CI, 28-48.4)], (p = 0.72)), non-relapse mortality (NRM), relapse and overall survival (OS) were similar in both groups. Interestingly, the failure to achieve GRFS was mainly attributed to GVHD in the SIR/TAC group, while disease relapse was the primary reason in the PTCY cohort.

Tacrolimus versus cyclosporine a combined with post-transplantation cyclophosphamide for AML In first complete remission: a study from the acute leukemia working party (EBMT)

Choice of calcineurin inhibitor may impact the outcome of patients undergoing T-cell replete hematopoietic cell transplantation (HCT) with post-transplant cyclophosphamide (PT-Cy) and mycophenolate mofetil (MMF) for prophylaxis of graft-versus-host disease (GVHD). We retrospectively analyzed 2427 patients with acute myeloid leukemia (AML) in first remission transplanted from a haploidentical (n = 1844) or unrelated donor (UD, n = 583) using cyclosporine A (CSA, 63%) or tacrolimus (TAC, 37%) and PT-Cy/MMF. In univariate analysis, CSA and TAC groups did not differ in 2-year leukemia-free or overall survival, cumulative incidence (CI) of relapse or non-relapse mortality. CI of severe grade III-IV acute GVHD was lower with TAC (6.6% vs. 9.1%, p = 0.02), without difference in grade II-IV acute GVHD or grade III-IV acute GVHD/severe chronic GVHD, relapse-free survival (GRFS). In multivariate analysis, TAC was associated with a lower risk of severe grade III-IV acute GVHD solely with haploidentical donors (HR 0.64 [95% CI, 0.42-0.98], p = 0.04), but not UD (HR 0.49 [95% CI, 0.2-1.21], p = 0.12). There was no significant difference for chronic GVHD. In conclusion, PT-Cy/MMF-based GVHD prophylaxis resulted in favorable OS and GRFS, irrespective of the CNI added. In haploidentical HCT, TAC seemed to prevent severe acute GVHD more effectively than CSA without impact on other outcome parameters.

Comparison of Three Graft-versus-Host Disease Prophylaxis Strategies after T Cell-Replete Haploidentical Hematopoietic Transplantation: Tacrolimus versus Calcineurin Inhibitors + Mycophenolate Mofetil versus Sirolimus + Mycophenolate Mofetil

Since the introduction of post-transplantation cyclophosphamide (PTCy), haploidentical hematopoietic stem cell transplantation (haploSCT) has become a real alternative for patients who lack other eligible donors. The standard graft-versus-host disease (GVHD) prophylaxis after PTCy has been a calcineurin inhibitor (CNI) plus mycophenolate mofetil (MMF) (up to day +35), but promising results with sirolimus (with or without MMF) and single-agent tacrolimus have been published recently. This multicenter retrospective study compared the outcomes of 372 adult haploSCT recipients who received conditioning with thiotepa, busulfan, and fludarabine (TBF), PTCy, and additional GVHD prophylaxis with 1 of 3 strategies: cohort A, single-agent tacrolimus (n = 222); cohort B, CNI + MMF (n = 49); or cohort C, sirolimus + MMF (n = 101). No differences among the 3 cohorts were found in terms of grade II-IV acute GVHD (20% in cohort A, 25% in cohort B, and 30% in cohort C) or grade III-IV acute GVHD (9%, 6%, and 15%, respectively) at 100 days; however, cohort A had the lowest incidence of overall chronic GVHD (24%, 47%, and 52%, respectively; P = .001) and moderate-severe chronic GVHD (13%, 35%, and 33%, respectively; P = .001). There were no differences in 3-year overall survival, progression-free survival, nonrelapse mortality, or relapse among the 3 cohorts. Overall, our study suggests that single-agent tacrolimus, CNI + MMF, and sirolimus + MMF GVHD prophylaxis lead to similar outcomes following haploSCT with TBF and PTCy, with a low incidence of grade III-IV acute GVHD, although possible differences in chronic GVHD require further investigation.

Unrelated donor transplantation with posttransplant cyclophosphamide vs ATG for myelodysplastic neoplasms

ABSTRACT

It has been reported in prospective randomized trials that antithymocyte globulin (ATG)-based graft-versus-host disease (GVHD) prophylaxis has benefits in the setting of allogeneic hematopoietic stem cell transplantation (allo-HSCT) with unrelated donors (UDs). However, the optimal GVHD prophylaxis strategy has been challenged recently by the increasing use of posttransplant cyclophosphamide (PTCY). We report from the European Society for Blood and Marrow Transplantation registry the outcomes of 960 patients with myelodysplastic neoplasms who underwent allo-HSCT from UD with PTCY or ATG as GVHD prophylaxis. The primary outcomes were overall survival (OS) and progression-free survival (PFS). The disease characteristics were similar in both groups. Day 28 neutrophil engraftment was significantly better with ATG (93% vs 85%). Over a median follow-up of 4.4 years, the 5-year OS was 58% with PTCY, and 49% in the ATG group. The 5-year PFS was higher for PTCY at 53% vs 44% for ATG. Grade 2 to 4 acute GVHD incidence was lower when PTCY was used (23%), whereas there was no difference in the incidence of chronic GVHD at 5 years. Multivariable analyses confirmed better OS and PFS with PTCY with a hazard ratio (HR) for ATG of 1.32 (1-1.74) and a better PFS for PTCY with a HR for ATG of 1.33. This study suggests that GVHD prophylaxis using PTCY instead of ATG in this setting remains a valid option. Further prospective randomized studies would be essential to confirm these results.

Graft Versus Host Disease Prophylaxis in Matched Donor Stem Cell Transplantation: Post-transplantation Cyclophosphamide Combinations Versus Methotrexate/Tacrolimus

BACKGROUND

The use of post-transplant cyclophosphamide (PTCy) is highly effective in preventing graft versus host disease (GVHD) for haploidentical allogeneic hematopoietic stem cell transplantation (allo-HSCT). There is limited data on the role of PTCy as GVHD prophylaxis in matched-sibling and fully matched-unrelated donor (MSD/MUD) allo-HSCT.

METHODS

Our single-center retrospective study aims to compare outcomes of PTCy alone or in combination with mycophenolate mofetil and tacrolimus (PTCy/MMF/TAC) relative to methotrexate and tacrolimus (MTX/TAC). The primary endpoint of our study was GVHD-free, relapse free survival (GRFS). Secondary endpoints were overall survival (OS), disease free survival (DFS), and incidence of severe acute and chronic GVHD. We identified 74 adult patients who underwent MSD/MUD allo-HSCT at our institution from 2015 to 2023.

RESULTS

Within our cohort, 33.8% (n = 25) received MTX/TAC, while 54.0% (n = 40) received PTCy/MMF/TAC, and 12.2% (n = 9) received PTCy alone. Patients receiving PTCY had the longest time to neutrophil engraftment relative to MTX/TAC (15 days vs. 12 days, P = .010). PTCy/MMF/TAC was associated with improved GRFS relative to MTX/TAC (hazard ratio [HR] = HR 0.42, 95% CI 0.19-0.93, P = .031), which persisted when controlling for age. Incidence of chronic GVHD was lower in the PTCy/MMF/TAC group compared to MTX/TAC (1-year 9.0% vs. 30.1%, HR 0.19, 95% CI 0.06-0.59, P = .005). However, OS and DFS were comparable across all groups.

CONCLUSIONS

Our results demonstrate decreased rates of severe chronic GVHD resulting in improved GRFS when using PTCy/TAC/MTX as GVHD prophylaxis compared to MTX/TAC in MSD/MUD.

Comparable relapse incidence after unrelated allogeneic stem cell transplantation with post-transplant cyclophosphamide versus conventional anti-graft versus host disease prophylaxis in patients with acute myeloid leukemia: A study on behalf of the Acute Leukemia Working Party of the European Society for Blood and Marrow Transplantation

We compared relapse incidence (RI) post-unrelated transplantation with post-transplant cyclophosphamide (PTCy) versus no PTCy graft-versus-host disease (GVHD) prophylaxis, in 7049 acute myeloid leukemia (AML) patients in remission, 707 with PTCy, and 6342 without (No PTCy). The patients in the PTCy group were younger, 52.7 versus 56.6 years (p < .001). There were more 9/10 donors in the PTCy group, 33.8% versus 16.4% (p < .001), and more received myeloablative conditioning, 61.7% versus 50.2% (p < .001). In the No PTCy group, 87.7% of patients received in vivo T-cell depletion. Neutrophil and platelet engraftment were lower in the PTCy versus No PTCy group, 93.8% and 80.9% versus 97.6% and 92.6% (p < .001). RI was not significantly different in the PTCy versus the No PTCy group, hazard ratio (HR) of 1.11 (95% confidence interval [CI] 0.9-1.37) (p = .31). Acute GVHD grades II-IV and III-IV, were significantly lower in the PTCy versus the No PTCy group, HR of 0.74 (95% CI 0.59-0.92, p = .007) and HR = 0.56 (95% CI 0.38-0.83, p = .004), as were total and extensive chronic GVHD, HRs of 0.5 (95% CI 0.41-0.62, p < .001) and HR = 0.31 (95% CI 0.22-0.42, p < .001). Non-relapse mortality (NRM) was significantly lower with PTCy versus the No PTCy group, HR of 0.67 (95% CI 0.5-0.91, p = .007). GVHD-free, relapse-free survival (GRFS) was higher in the PTCy versus the No PTCy group, HR of 0.69 (95% CI 0.59-0.81, p = .001). Leukemia-free survival (LFS) and overall survival (OS) did not differ between the groups. In summary, we observed comparable RI, OS, and LFS, significantly lower incidences of GVHD and NRM, and significantly higher GRFS in AML patients undergoing unrelated donor-hematopoietic stem cell transplantation with PTCy versus No PTCy GVHD prophylaxis.

A prospective study of posttransplant cyclophosphamide for unrelated donor peripheral blood stem cell transplant with special attention to graft content and the impact of a higher γδ T cell dose

Posttransplant cyclophosphamide (PtCy) has been shown to decrease post-hematopoietic stem cell transplant acute and chronic graft-versus-host disease (GVHD). In this study, PtCy was used in 44 patients along with mycophenolate and tacrolimus with HLA matched (29) and mismatched (15) unrelated donors to determine the impact of graft content on outcome; thus, all patients had flow cytometric analysis of their graft content including the number of B cells, NK cells, and various T cell subsets. Higher γδ T cell dose was associated with the development of acute GVHD (p = .0038). For PtCy, further studies of the cell product along with further graft manipulation, such as selective γδ T cell depletion, could potentially improve outcomes.

High-dose alemtuzumab and cyclosporine vs tacrolimus, methotrexate, and sirolimus for chronic graft-versus-host disease prevention

ABSTRACT

Chronic graft-versus-host disease (cGVHD) remains a significant problem for patients after allogeneic hematopoietic stem cell transplantation (allo-HSCT). Although in vivo lymphodepletion for cGVHD prophylaxis has been explored in the myeloablative setting, its effects after reduced-intensity conditioning (RIC) are not well described. Patients (N = 83) with hematologic malignancies underwent targeted lymphodepletion chemotherapy followed by a RIC allo-HSCT using peripheral blood stem cells from unrelated donors. Patients were randomized to 2 GVHD prophylaxis arms: alemtuzumab and cyclosporine (AC; n = 44) or tacrolimus, methotrexate, and sirolimus (TMS; n = 39), with the primary end point of cumulative incidence of severe cGVHD. The incidence of severe cGVHD was lower with AC vs TMS prophylaxis at 1- and 5-years (0% vs 10.3% and 4.5% vs 28.5%; overall, P = .0002), as well as any grade (P = .003) and moderate-severe (P < .0001) cGVHD. AC was associated with higher rates of grade 3 to 4 infections (P = .02) and relapse (52% vs 21%; P = .003) with no difference in 5-year GVHD-free-, relapse-free-, or overall survival. AC severely depleted naïve T-cell reconstitution, resulting in reduced T-cell receptor repertoire diversity, smaller populations of CD4Treg and CD8Tscm, but a higher ratio of Treg to naïve T-cells at 6 months. In summary, an alemtuzumab-based regimen successfully reduced the rate and severity of cGVHD after RIC allo-HSCT and resulted in a distinct immunomodulatory profile, which may have reduced cGVHD incidence and severity. However, increased infections and relapse resulted in a lack of survival benefit after long-term follow-up. This trial was registered at www.ClinicalTrials.gov as #NCT00520130.

[Chinese expert consensus on the diagnosis and treatment of chronic graft-versus-host disease (2024)]

Chronic graft-versus-host disease (cGVHD) is a common and severe complication following allogeneic hematopoietic stem cell transplantation, which significantly impacts patients' survival and quality of life. In recent years, notable progress has been made in the diagnosis, prevention, and treatment of cGVHD, driven by the emergence of novel therapies such as targeted drugs and the advancement of clinical research. This consensus, based on the latest developments in cGVHD research and growing data from evidence-based medicine, has been revised and updated from the "Chinese consensus on the diagnosis and management of chronic graft-versus-host disease (2021)" to better guide clinical practice.

PTCy vs CNI-based GVHD prophylaxis in HLA-matched transplants for Hodgkin lymphoma: a study of the LWP of the EBMT

ABSTRACT

Studies comparing the efficacy of posttransplant cyclophosphamide (PTCy) to conventional calcineurin inhibitor (CNI)-based graft-versus-host disease (GVHD) prophylaxis regimens in patients with Hodgkin lymphoma (HL) are scarce. This study aimed to compare the outcomes of patients with HL undergoing hematopoietic stem cell transplantation (HSCT) from HLA-matched donors who received GVHD prophylaxis with either PTCy- or conventional CNI-based regimens, using data reported in the European Society for Blood and Marrow Transplantation database between January 2015 and December 2022. Among the cohort, 270 recipients received conventional CNI-based prophylaxis and 176 received PTCy prophylaxis. Notably, PTCy prophylaxis was associated with delayed hematopoietic recovery but also with a lower risk of chronic (25% vs 43%; P < .001) and extensive chronic GVHD (13% vs 28%; P = .003) compared with the CNI-based cohort. The 2-year cumulative incidence of nonrelapse mortality and relapse was 11% vs 17% (P = .12) and 17% vs 30% (P = .007) for PTCy- and CNI-based, respectively. Moreover, the 2-year overall survival (OS), progression-free survival (PFS), and GVHD-free, relapse-free survival (GRFS) were all significantly better in the PTCy group compared with the CNI-based group: 85% vs 72% (P = .005), 72% vs 53% (P < .001), and 59% vs 31% (P < .001), respectively. In multivariable analysis, PTCy was associated with a lower risk of chronic and extensive chronic GVHD, reduced relapse, and better OS, PFS, and GRFS than the CNI-based platform. Our findings suggest that PTCy as GVHD prophylaxis offers more favorable outcomes than conventional CNI-based prophylaxis in adult patients with HL undergoing HSCT from HLA-matched donors.

Acute T-cell lymphoblastic leukemia: chimeric antigen receptor technology may offer a new hope

Acute lymphoblastic leukemia (ALL) is a prevalent malignancy affecting the hematopoietic system, encompassing both B-cell ALL (B-ALL) and T-cell ALL (T-ALL). T-ALL, characterized by the proliferation of T-cell progenitors in the bone marrow, presents significant treatment challenges, with patients often experiencing high relapse rates and poor long-term survival despite advances in chemotherapy and hematopoietic stem cell transplantation (HSCT). This review explores the pathogenesis and traditional treatment strategies of T-ALL, emphasizing the promising potential of chimeric antigen receptor (CAR) technology in overcoming current therapeutic limitations. CAR therapy, leveraging genetically modified immune cells to target leukemia-specific antigens, offers a novel and precise approach to T-ALL treatment. The review critically analyzes recent developments in CAR-T and CAR-NK cell therapies, their common targets, optimization strategies, clinical outcomes, and the associated challenges, providing a comprehensive overview of their clinical prospects in T-ALL treatment.

Post-transplant-cyclophosphamide and short-term Everolimus as graft-versus-host-prophylaxis in patients with relapsed/refractory lymphoma and myeloma-Final results of the phase II OCTET-EVER trial

BACKGROUND

Conditioning regimens and the choice of immunosuppression have substantial impact on immune reconstitution after allogeneic hematopoietic stem cell transplantation (aHSCT). The pivotal mechanism to maintain remission is the induction of the graft-versus-tumor effect. Relapse as well as graft versus host disease remain common. Classic immunosuppressive strategies implementing calcineurin inhibitors (CNI) have significant toxicities, hamper the immune recovery, and reduce the anti-cancer immune response.

METHODS

We designed a phase II clinical trial for patients with relapsed and refractory lymphoid malignancies undergoing aHSCT using a CNI-free approach consisting of post-transplant cyclophosphamide (PTCy) and short-term Everolimus after reduced-intensity conditioning and matched peripheral blood stem cell transplantation. The results of the 19 planned patients are presented. Primary endpoint is the cumulative incidence and severity of acute GvHD.

RESULTS

Overall incidence of acute GvHD was 53% with no grade III or IV. Cumulative incidence of NRM at 1, 2, and 4 years was 11%, 11%, and 16%, respectively, with a median follow-up of 43 months. Cumulative incidence of relapse was 32%, 32%, and 42% at 1, 2, and 4 years after transplant, respectively. Four out of six early relapses were multiple myeloma patients. Overall survival was 79%, 74%, and 62% at 1, 2, and 4 years. GvHD-relapse-free-survival was 47% after 3 years.

CONCLUSIONS

Using PTCy and short-term Everolimus is safe with low rates of aGvHD and no severe aGvHD or cGvHD translating into a low rate of non-relapse mortality. Our results in this difficult to treat patient population are encouraging and warrant further studies.

Allogeneic hematopoietic stem-cell transplantation for patients with Richter transformation: a retrospective study on behalf of the Chronic Malignancies Working Party of the EBMT

Management of Richter transformation (RT) is particularly challenging, with survival estimates <1 year. We report on outcomes of 66 RT patients undergoing allogeneic-HCT (allo-HCT) between 2008 and 2018 registered with the EBMT. Median age at allo-HCT was 56.2 years (interquartile range (IQR), 51.3-63.1). Median time from RT to allo-HCT was 6.9 months (IQR, 4.9-11) and 28 (42.4%) were in complete remission (CR). The majority underwent reduced intensity conditioning (66.2%) using peripheral blood derived stem cells. Eighteen (27.3%) patients had a matched sibling donor, 24 (36.4%) a matched unrelated donor and the remaining were mismatched. Median follow-up was 6.6 years; 1- and 3- year overall and progression free survival (PFS) (95% CI) was 65% (54-77) and 39% (27-51) and 53% (41-65) and 29% (18-40), respectively. Patients in CR at time of allo-HCT had significantly better 3-year PFS (39% vs. 21%, p = 0.032). Cumulative incidences of grade II-IV acute graft versus host disease (GVHD) at day +100 was 41% (95% CI 29-53) and chronic GVHD at 3 years was 53% (95% CI 41-65). High rates of non-relapse mortality (NRM) were observed; 38% (95% CI, 26-50) at 3 years. Although potentially curative, approaches to reduce considerable NRM and chronic GVHD rates are required.

Post-transplant cyclophosphamide, calcineurin inhibitor, and mycophenolate mofetil compared to anti-thymocyte globulin, calcineurin inhibitor, and methotrexate combinations as graft-versus-host disease prophylaxis post allogeneic stem cell transplantation from sibling and unrelated donors in patients with acute myeloid leukemia: a study on behalf of the Acute Leukemia Working Party of the European Society for Blood and Marrow Transplantation

Post-transplant cyclophosphamide plus calcineurin inhibitor (CNI)(tacrolimus or cyclosporine A) plus mycophenolate mofetil (PTCy/TAC or CSA/MMF) and anti-thymocyte globulin plus CNI (tacrolimus or cyclosporine A) plus methotrexate (ATG/TAC or CSA/MTX) are common graft-versus-host disease (GVHD) prophylaxis regimens. We compared the two regimens in patients with acute myeloid leukemia (AML) undergoing allogeneic transplantation from matched siblings or unrelated donors. 402 received PTCy/TAC or CSA/MMF and 5648 received ATG/TAC or CSA/MTX. Patients in the PTCy-based group were younger (48.7 vs. 51.5 years, p = 0.024) and there was a higher frequency of patient cytomegalovirus seropositivity and female donor to male patient combination in this group (77.8% vs. 71.8%, p = 0.009 and 18.4% vs. 14.4%, p = 0.029, respectively). More patients in the PTCy-based group received reduced-intensity conditioning (51.5% vs. 41%, p < 0.0001). No differences were observed in the incidence of acute GVHD grade II-IV and III-IV (21.2% vs. 20.4%, p = 0.92 and 8.1% vs. 6%, p = 0.1) or 2-year total and extensive chronic GVHD (33.7% vs. 30%, p = 0.09 and 10.7% vs. 11.2%, p = 0.81) between the groups. In the multivariate analysis, all transplant outcomes did not differ between the groups. PTCy/CNI/MMF and ATG/CNI/MTX are alternative regimens for GVHD prophylaxis in AML patients.

Graft-versus-tumor effect of post-transplant cyclophosphamide-based allogeneic hematopoietic cell transplantation

Post-transplant cyclophosphamide (PTCy) is becoming the standard prophylaxis for graft-versus-host disease (GVHD) in HLA-haploidentical allogeneic hematopoietic cell transplantation (allo-HCT) and in HLA-matched allo-HCT. Immune reconstitution in the post-transplant setting may influence the graft-versus-tumor (GVT) effect because PTCy has a profound effect on T cell and natural killer cell functions and their reconstitution after allo-HCT. However, many recent studies have shown that the incidence of relapse after allo-HCT with PTCy is comparable to that after conventional allo-HCT. To further improve the outcomes, it is critical to establish a strategy to maintain or effectively induce the GVT effect when using PTCy as a platform for GVHD prophylaxis. However, there is a paucity of studies focusing on the GVT effect in allo-HCT with PTCy. Therefore, focusing on this issue may lead to the establishment of more appropriate strategies to improve transplantation outcomes without exacerbating GVHD, including novel therapies involving cell modification.

Engineering the best transplant outcome for high-risk acute myeloid leukemia: the donor, the graft and beyond

Allogeneic hemopoietic cell transplantation remains the goal of therapy for high-risk acute myeloid leukemia (AML). However, treatment failure in the form of leukemia relapse or severe graft-versus-host disease remains a critical area of unmet need. Recently, significant progress has been made in the cell therapy-based interventions both before and after transplant. In this review, the Stem Cell Engineering Committee of the International Society for Cell and Gene Therapy summarizes the literature regarding the identification of high risk in AML, treatment approaches before transplant, optimal transplant platforms and measures that may be taken after transplant to ideally prevent, or, if need be, treat AML relapse. Although some strategies remain in the early phases of clinical investigation, they are built on progress in pre-clinical research and cellular engineering techniques that are already improving outcomes for children and adults with high-risk malignancies.

Outcomes of Antithymocyte Globulin-Post-Transplantation Cyclophosphamide-Cyclosporine-Based versus Antithymocyte Globulin-Based Prophylaxis for 10/10 HLA-Matched Unrelated Donor Allogeneic Hematopoietic Cell Transplantation

In 2015, dual T cell depletion with antithymocyte globulin (ATG) and post-transplantation cyclophosphamide (PTCy) combined with cyclosporine A (CsA) replaced our prior institutional graft-versus-host disease (GVHD) prophylaxis regimen of 4.5 mg/kg ATG, CsA, and mycophenolate mofetil (MMF) (ATG-based) in 10/10 HLA-matched unrelated donor (MUD) peripheral blood allogeneic hematopoietic stem cell transplantation (allo-HCT). The initial ATG dose of 4.5 mg/kg [ATG(4.5)/PTCy] was reduced to 2 mg/kg [ATG(2)/PTCy] in 2018. This study compares the results obtained from 444 adults undergoing MUD allo-HCT at our institution who received ATG(4.5)/PTCy (n = 127) or ATG(2)/PTCy (n = 223) with those who received ATG-based prophylaxis without PTCy (n = 84). The rates of grade II-IV and grade III-IV acute GVHD (aGVHD) at day +100 and moderate/severe chronic GVHD (cGVHD) at 1 year were 35.7%, 21.6%, and 14.7%, respectively, in patients receiving ATG-based prophylaxis without PTCy; 16.5%, 4.9%, and 4.3% in patients receiving ATG(4.5)/PTCy; and 23.3% (P = .004), 8.0% (P < .001), and 14.1% (P =.006) in patients receiving ATG(2)/PTCy. One-year overall survival (OS), nonrelapse mortality (NRM), and GVHD-free relapse-free survival (GRFS) were 69.8%, 25.3%, and 52.0%, respectively, for patients receiving ATG-based prophylaxis without PTCy; 82.7%, 17.3%, and 59.8% for patients receiving ATG(4.5)/PTCy; and 78.3% (P = .446), 14.7% (P = 101), and 56.2% (P = .448) for patients receiving ATG(2)/PTCy. On univariate analyses, the use of ATG(2)/PTCy was associated with a lower risk of NRM (hazard ratio, .54; P = .023) compared with the use of ATG-based prophylaxis without PTCy. ATG(2)/PTCy prophylaxis effectively prevents GVHD and is associated with comparable relapse risk, OS, and GRFS as seen with ATG(4.5)/PTCy and ATG-based prophylaxis without PTCy.

Posttransplant cyclophosphamide beyond haploidentical transplantation

Posttransplant cyclophosphamide (PTCy) has practically revolutionized haploidentical (Haplo) hematopoietic cell transplantation (HCT). Comparisons between Haplo with PTCy and unrelated donor (URD) with conventional graft-versus-host disease (GVHD) prophylaxis have shown comparable overall survival with lower incidences of GVHD with Haplo/PTCy and led to the following question: is it PTCy so good that can be successfully incorporated into matched related donor (MRD) and URD HCT? In this review, we discuss other ways of doing PTCy, PTCy in peripheral blood haploidentical transplants, PTCy in the context of matched related and matched unrelated donors, PTCy with mismatched unrelated donors, and PTCy following checkpoint inhibitor treatment. PTCy is emerging as a new standard GVHD prophylaxis in haploidentical, HLA-matched, and -mismatched HCT.

Graft-versus-host-disease prophylaxis with ATG or PTCY in patients with lymphoproliferative disorders undergoing reduced intensity conditioning regimen HCT from one antigen mismatched unrelated donor

Post-transplant cyclophosphamide (PTCY) has been introduced as graft-versus-host disease (GvHD) prophylaxis in mismatched and matched unrelated hematopoietic cell transplant (HCT). However, data comparing outcomes of PTCY or ATG in patients undergoing a 1 antigen mismatched HCT for lymphoproliferative disease are limited. We compared PTCY versus ATG in adult patients with lymphoproliferative disease undergoing a first 9/10 MMUD HCT with a reduced intensity conditioning regimen from 2010 to 2021. Patients receiving PTCY were matched to patients receiving ATG according to: age, disease status at transplant, female to male matching, stem cell source and CMV serology. Grade II-IV acute GvHD at 100 day was 26% and 41% for the ATG and PTCY group, respectively (p = 0.08). Grade III-IV acute GvHD was not significantly different between the two groups. No differences were observed in relapse incidence, non-relapse mortality, progression-free survival, overall survival and GvHD-relapse-free survival at 1 year. The cumulative incidence of 1-year extensive chronic GvHD was 18% in the ATG and 5% in the PTCY group, respectively (p = 0.06). In patients with lymphoproliferative diseases undergoing 9/10 MMUD HCT, PTCY might be a safe option providing similar results to ATG prophylaxis. Due to the limited number of patients, prospective randomized trials are needed.

Allogeneic Stem Cell Transplantation in Refractory Acute Myeloid Leukaemia

Refractory acute myeloid leukaemia is very difficult to treat and represents an unmet clinical need. In recent years, new drugs and combinations of drugs have been tested in this category, with encouraging results. However, all treated patients relapsed and died from the disease. The only curative option is allogeneic transplantation through a graft from a healthy donor immune system. Using myeloablative conditioning regimens, the median overall survival regimens is 19%. Several so-called sequential induction chemotherapies followed by allogeneic transplantation conditioned by reduced intensity regimens have been developed, improving the overall survival to 25-57%. In the allogeneic transplantation field, continuous improvements in practices, particularly regarding graft versus host disease prevention, infection prevention, and treatment, have allowed us to observe improvements in survival rates. This is true mainly for patients in complete remission before transplantation and less so for refractory patients. However, full myeloablative regimens are toxic and carry a high risk of treatment-related mortality. In this review, we describe the results obtained with the different modalities used in more recent retrospective and prospective studies. Based on these findings, we speculate how allogeneic stem cell transplantation could be modified to maximise its therapeutic effect on refractory acute myeloid leukaemia.

Posttransplant cyclophosphamide in unrelated and related peripheral blood stem cell transplantation from HLA-matched and 1 allele mismatched donor

Posttransplant cyclophosphamide (PTCy)-based graft-versus-host disease (GVHD) prophylaxis has been increasingly used in HLA-haploidentical transplantation and recent studies also demonstrated the efficacy of PTCy in HLA-matched transplantation. We conducted a prospective multicenter phase II study to evaluate the safety and efficacy of PTCy with tacrolimus and mycophenolate mofetil in 43 patients who underwent HLA-matched (n = 21), 1 allele mismatched (n = 20), or 2 allele mismatched (n = 2) peripheral blood stem cell transplantation (PBSCT) following myeloablative (n = 28) or reduced-intensity (n = 15) conditioning. The incidence of grade III-IV acute GVHD at 100 days was 2.3%. The incidences of grades II-IV acute GVHD, all grade chronic GVHD, and moderate to severe chronic GVHD at 2 years were 16.3%, 14.0%, and 4.7%, respectively. Overall survival, disease-free survival, and non-relapse mortality at 2 years were 75.3%, 74.0%, and 7.0%, respectively. GVHD-free, relapse-free survival at 2 years was 67.0%. The rate of off-immunosuppressants in patients who survived without relapse at 2 years was 85.4%. These results indicate that PTCy is a valid option for GVHD prophylaxis in both HLA-matched and HLA 1-2 allele mismatched PBSCT.

How adoptive transfer of components of the donor immune system boosts GvL and prevents GvHD in HLA-haploidentical hematopoietic transplantation for acute leukemia

Why a new Perspective in allogeneic hematopoietic transplantation? A summary. Nowadays, for high-risk acute leukemia patients without an HLA-matched donor (sibling or volunteer), hematopoietic transplants that use HLA-haploidentical grafts combined with enhanced post transplant immune suppression (i.e., high-dose cyclophosphamide) are widely used. They are associated with low TRM rates. However, they are also associated with significant chronic GvHD while they only partially abrogate leukemia relapse rates. One may speculate that post-transplant immune suppression, required for GvHD prophylaxis, weakens the anti-leukemic potential of the graft. Historically, haploidentical transplants became feasible for the first time through transplantation of T cell-depleted peripheral blood hematopoietic progenitor cells. Lack of post-transplant immune suppression allowed the emergence of donor-versus-recipient NK-cell alloreactions that eradicated AML. In an attempt to improve these results we recently combined an age-adapted, irradiation-based conditioning regimen with transplant of T-cell-depleted grafts and infusion of regulatory and conventional T cells, without any post transplant immune suppression. With the obvious limitations of a single center experience, this protocol resulted in extremely low relapse and chronic GvHD rates and, consequently, in a remarkable 75% chronic GvHD/relapse-free survival in over 50 AML patients up to the age of 65 many of whom at high risk of relapse.

Severity and organ distribution of chronic graft-versus-host disease with posttransplant cyclophosphamide-based versus methotrexate/calcineurin inhibitor-based allogeneic hematopoietic cell transplantation

The reduced risk of chronic graft-versus-host-disease (GVHD) with posttransplant cyclophosphamide (ptCy) in the setting of haploidentical related donor and more recently, with HLA-matched related and matched and mismatched unrelated donor allogeneic transplantation has been established. There is, however, paucity of data to show if ptCy impacts chronic GVHD pathogenesis, its phenotype and evolution after HCT regardless of the donor status. We examined the differences in chronic GVHD incidence and presentation in 314 consecutive patients after receiving their first allogeneic transplantation (HCT) using ptCy-based GVHD prophylaxis (ptCy-HCT; n = 120; including 95 with haploidentical related donor) versus conventional calcineurin inhibitor-based prophylaxis (CNI-MUD; n = 194) between 2012 and 2019. The 1-year cumulative incidence of all-grade chronic GVHD and moderate/severe chronic GVHD was 24% and 12%, respectively, after ptCy-HCT and 40% and 23% in the CNI-MUD recipients (p = 0.0003 and 0.007). Multivariable analysis confirmed that use of CNI-based GVHD prophylaxis and peripheral blood stem cell graft as the risk factors for chronic GVHD. The cumulative incidence of visceral (involving ≥1 of the following organs: liver, lungs, gastrointestinal tract, serous membranes) chronic GVHD was significantly higher with CNI-MUD vs. ptCy-HCT (27% vs. 15% at 1 year, p = 0.009). The incidence of moderate/severe visceral chronic GVHD was 20% in CNI-MUD group vs. 7.7% in the ptCy-HCT group at 1 year (p = 0.002). In addition, significantly fewer ptCy-HCT recipients developed severe chronic GVHD in ≥3 organs (0.8%) vs. 8.8% in the CNI-MUD group at 1-year posttransplant (p = 0.004). There was no significant different in relapse, non-relapse mortality, and relapse-free and overall survival between the two groups. Further investigation is needed to confirm that reduced risk and severity of chronic GVHD, less visceral organ distribution with ptCy-HCT leads to improved quality of life.

CRISPR/Cas9 deletion of MIR155HG in human T cells reduces incidence and severity of acute GVHD in a xenogeneic model

ABSTRACT

Acute graft-versus-host disease (GVHD) is a major complication of allogeneic hematopoietic cell transplantation (allo-HCT). Using preclinical mouse models of disease, previous work in our laboratory has linked microRNA-155 (miR-155) to the development of acute GVHD. Transplantation of donor T cells from miR-155 host gene (MIR155HG) knockout mice prevented acute GVHD in multiple murine models of disease while maintaining critical graft-versus-leukemia (GVL) response, necessary for relapse prevention. In this study, we used clustered, regularly interspaced, short palindromic repeats (CRISPR)/Cas9 genome editing to delete miR-155 in primary T cells (MIR155HGΔexon3) from human donors, resulting in stable and sustained reduction in expression of miR-155. Using the xenogeneic model of acute GVHD, we show that NOD/SCID/IL2rγnull (NSG) mice receiving MIR155HGΔexon3 human T cells provide protection from lethal acute GVHD compared with mice that received human T cells with intact miR-155. MIR155HGΔexon3 human T cells persist in the recipients displaying decreased proliferation potential, reduced pathogenic T helper-1 cell population, and infiltration into GVHD target organs, such as the liver and skin. Importantly, MIR155HGΔexon3 human T cells retain GVL response significantly improving survival in an in vivo model of xeno-GVL. Altogether, we show that CRISPR/Cas9-mediated deletion of MIR155HG in primary human donor T cells is an innovative approach to generate allogeneic donor T cells that provide protection from lethal GVHD while maintaining robust antileukemic response.

Post-transplant cyclophosphamide versus anti-thymocyte globulin after reduced intensity peripheral blood allogeneic cell transplantation in recipients of matched sibling or 10/10 HLA matched unrelated donors: final analysis of a randomized, open-label, multicenter, phase 2 trial

The use of post-transplantation cyclophosphamide (PTCy) for graft-versus-host disease (GVHD) prophylaxis is not established after reduced intensity conditioning (RIC) hematopoietic stem cell transplantation (HSCT) from fully matched donors. This was a randomized, open-label, multicenter, phase 2 trial. All patients received a RIC regimen with fludarabine, intravenous busulfan for 2 days (Flu-Bu2), and a peripheral blood stem cell (PBSC) graft from a matched related or 10/10 HLA-matched unrelated donor. Patients were randomly assigned to receive anti-thymocyte globulin (ATG) 5 mg/kg plus standard GVHD prophylaxis or PTCy 50 mg/kg/d at days +3 and +4 plus standard GVHD prophylaxis. The primary endpoint was the composite endpoint of GVHD- and relapse-free survival (GRFS) at 12 months after HSCT. Eighty-nine patients were randomly assigned to receive either PTCy or control prophylaxis with ATG. At 12 months, disease-free survival was 65.9% in the PTCy group and 67.6% in the ATG group (P = 0.99). Cumulative incidence of relapse, non-relapse mortality, and overall survival were also comparable in the two groups. GRFS at 12 months was 54.5% in the PTCy group versus 43.2% in the ATG group (P = 0.27). The median time to neutrophil and platelet count recovery was significantly longer in the PTCy group compared to the ATG group. Except for day +30, where EORTC QLQ-C30 scores were significantly lower in the PTCy compared to the ATG group, the evolution with time was not different between the two groups. Although the primary objective was not met, PTCy is effective for GVHD prophylaxis in patients receiving Flu-Bu2 conditioning with a PBSC graft from a fully matched donor and was well tolerated in term of adverse events and quality of life. This trial was registered at clinicaltrials.gov: NCT02876679.

Prophylaxis and management of graft-versus-host disease after stem-cell transplantation for haematological malignancies: updated consensus recommendations of the European Society for Blood and Marrow Transplantation

Graft-versus-host disease (GVHD) is a major factor contributing to mortality and morbidity after allogeneic haematopoietic stem-cell transplantation (HSCT). In the last 3 years, there has been regulatory approval of new drugs and considerable change in clinical approaches to prophylaxis and management of GVHD. To standardise treatment approaches, the European Society for Blood and Marrow Transplantation (EBMT) has updated its clinical practice recommendations. We formed a panel of one methodologist and 22 experts in the field of GVHD management. The selection was made on the basis of their role in GVHD management in Europe and their contributions to the field, such as publications, presentations at conferences, and other research. We applied the GRADE process to ten PICO (patient, intervention, comparator, and outcome) questions: evidence was searched for by the panel and graded for each crucial outcome. In two consensus meetings, we discussed the evidence and voted on the wording and strengths of recommendations. Key updates to the recommendations include: (1) primary use of ruxolitinib in steroid-refractory acute GVHD and steroid-refractory chronic GVHD as the new standard of care, (2) use of rabbit anti-T-cell (thymocyte) globulin or post-transplantation cyclophosphamide as standard GVHD prophylaxis in peripheral blood stem-cell transplantations from unrelated donors, and (3) the addition of belumosudil to the available treatment options for steroid-refractory chronic GVHD. The EBMT proposes to use these recommendations as the basis for routine management of GVHD during allogenic HSCT. The current recommendations favour European practice and do not necessarily represent global preferences.

Opportunistic Infections in Patients Receiving Post-Transplantation Cyclophosphamide: Impact of Haploidentical versus Unrelated Donor Allograft

Post-transplantation cyclophosphamide (PTCy) is an effective strategy for graft-versus-host disease (GVHD) prophylaxis and is the standard of care for haploidentical hematopoietic cell transplantation (HCT). It is increasingly used for matched and mismatched unrelated donor (MUD/MMUD) HCT, but infections remain a concern. The objective of this study was to evaluate the characteristics and risk factors for infections in haploidentical and unrelated donor HCT recipients treated with PTCy-based GVHD prophylaxis. This single-center retrospective study examined 354 consecutive adults undergoing HCT with PTCy-based GVHD prophylaxis (161 MUD/MMUD; 193 haploidentical) between 2015 and 2022. Opportunistic infections (OIs), including cytomegalovirus (CMV), adenovirus (AdV), Epstein-Barr virus (EBV), and invasive fungal disease (IFD), were assessed from day 0 through day +365. The 1-year cumulative incidence functions of OIs and nonrelapse mortality (NRM) were calculated using dates of relapse and repeat HCT as competing risks. Secondary analysis evaluated risk factors for OIs and NRM using univariate and multivariable Cox regression models. Haploidentical HCT recipients had an increased risk of OIs compared to unrelated donor allograft recipients (39% for haploidentical versus 25% for MUD/MMUD; hazard ratio [HR], 1.70; 95% confidence interval [CI], 1.16 to 2.49; P = .006). On multivariable analysis, haploidentical donor (HR, 1.50; 95% CI, 1.01 to 2.23; P = .046), prior HCT (HR, 1.99; 95% CI, 1.29 to 3.09; P = .002), and diagnosis of aGVHD (HR, 1.47; 95% CI, 1.02 to 2.14; P = .041) were associated with increased risk of OIs. NRM within the first year was not significantly different between the 2 cohorts (HR, 1.11; 95% CI, .64 to 1.93; P = .70). Overall, haploidentical donor was a significant risk factor for OIs in patients receiving PTCy, although 1-year NRM was not different between haploidentical HCT and MUD/MMUD HCT recipients. CMV and AdV infections were significantly increased among haploidentical HCT recipients, whereas the incidences of EBV infection and IFD were similar in the 2 cohorts. Our findings may have implications for infection monitoring and prophylaxis in the setting of PTCy, particularly in haploidentical HCT recipients.

Post-Transplantation Cyclophosphamide and Tacrolimus for Graft-versus-Host Disease Prevention after Allogeneic Hematopoietic Cell Transplantation from HLA-Matched Donors Has More Advantages Than Limitations

This study compared the efficacy of graft-versus-host disease (GVHD) prophylaxis with post-transplantation cyclophosphamide (PTCy) and tacrolimus (Tac) versus other regimens in 272 adults undergoing peripheral blood (PB) allogeneic hematopoietic cell transplantation (allo-HCT) from HLA-matched donors. Of these 272 patients, 95 (34.9%) received PTCy/Tac. The times to neutrophil and platelet engraftment were longer in the PTCy/Tac group (20 days versus 16 days for neutrophils and 19 days versus 12 days for platelets). The day +30 cumulative incidence (CuI) of bacterial bloodstream infection was higher in the PTCy/Tac group (43.2% versus 13.0%; P < .001). The CuIs of grade II-IV and grade III-IV acute GVHD (aGVHD) at day +180 were 14.7% and 4.2%, and the CuI of moderate/severe cGVHD at 2 years was 2.4% in the PTCy/Tac group and 41.8% (hazard ratio [HR], .29; P < .001), 15.8%, (HR, .24; P = .007), and 47.0% (HR, .05; P < .001), respectively, in the no-PTCy group. The duration of immunosuppression was shorter in patients receiving PTCy/Tac (6.2 months versus 9.0 months; P < .001). PTCy/Tac patients had higher OS (2 years: 74.3% versus 60.9%; HR, .54; P = .012), lower NRM (2 years: 8.6% versus 15.8%; HR, .54; P = .11), comparable CuI of relapse (2 years: 26.0% versus 24.4%; HR, 1.03; P = .89), and higher GRFS (2 years: 59.1% versus 16.7%; HR, .32; P < .001). Using PTCy/Tac in HLA-matched PB allo-HCT improved transplantation outcomes at out institution compared with previous prophylactic regimens, including a higher probability of survival despite more delayed engraftment and a higher rate of bacterial infection.