HLA-mismatched Transplantation Research Articles

Histocompatibility assessment in hematopoietic stem cell transplantation: recommendations from the Italian Society for Immunogenetics and Transplantation Biology (Associazione Italiana di Immunogenetica e Biologia dei Trapianti - AIBT).

The outcome of allogeneic hematopoietic stem cell transplantation (HSCT) is significantly influenced by the degree of HLA histocompatibility between donor and recipient. To provide shared indications for required histocompatibility testing and interpretation before HSCT, the Italian Society for Immunogenetics and Transplantation Biology (Associazione Italiana di Immunogenetica e Biologia dei Trapianti [AIBT]) gathered members and created a working group to discuss and develop recommendations for histocompatibility assessment in HSCT.After a review of the literature and multiple panel discussions, AIBT developed up-to-date recommendations for the resolution levels of HLA typing, histocompatibility definitions of patients and donors, importance of anti-HLA antibodies, and significance of NK alloreactivity, which are reported in this document. These recommendations have been shared with the Italian Group for Bone Marrow Transplantation (Gruppo Italiano per il Trapianto di Midollo Osseo, cellule staminali emopoietiche e terapia cellulare [GITMO]) and the Italian National Center for Transplantation (Centro Nazionale Trapianti [CNT]). Notably, the increased use of HLA-mismatched transplantation (i.e., mismatched unrelated, haploidentical) in recent years has made these indications even more relevant for the standardization and improvement of quality of care.This document represents a useful instrument for health care workers involved in the field of HSCT, enhancing synergy with transplant physicians and enabling greater optimization of the available resources.

Real-World Outcomes of Graft-versus-Host Disease after Allogeneic Hematopoietic Stem Cell Transplantation in Japan: Retrospective Analysis of the Transplant Registry Unified Management Program Registry

Allogeneic hematopoietic stem cell transplantation (allo-HSCT) is an important therapeutic option for patients with hematological malignancies. However, the development of graft-versus-host disease (GVHD) after allo-HSCT remains a challenge. Although systemic steroid therapy is the established first-line therapy for acute GVHD (aGVHD) and chronic GVHD (cGVHD), many patients are unresponsive or resistant to corticosteroid therapy, and the response is insufficient. To evaluate the clinical characteristics of patients who developed aGVHD and cGVHD after allo-HSCT. This noninterventional, retrospective study used large national registry data from the Transplant Registry Unified Management Program. The study included 29,690 patients with hematological diseases who underwent their first allo-HSCT between January 2010 and December 2019. The primary endpoints of this study were the cumulative incidence of aGVHD and cGVHD. The secondary endpoints were overall survival (OS) and non-relapse mortality (NRM) of patients with aGVHD and cGVHD and OS and NRM of patients who received second-line therapy for aGVHD. Of 29,690 patients who underwent allo-HSCT, 2,807, 6,167, 10,556, 774, and 9,339 patients received related bone marrow (RBM), related peripheral blood (RPB), unrelated bone marrow, unrelated peripheral blood (UPB), and unrelated cord blood, respectively. The cumulative incidence of aGVHD (grades II-IV) at 100 days was high after the related and unrelated mismatched transplantation. Furthermore, response rate for the first- and second-line therapy for aGVHD was low in the RBM/RPB-mismatched (59.6%/61.6%) and UPB-mismatched subgroup (45.5%), respectively. The 3-year NRM in patients with aGVHD was high in the RPB and UPB mismatched subgroups (37.9% and 31.2%, respectively). Developing a novel treatment for steroid-refractory aGVHD is necessary to improve transplant outcomes, particularly for patients undergoing HLA-mismatched transplantation.

Outcomes of HLA-mismatched HSCT with TCRαβ/CD19 depletion or post-HSCT cyclophosphamide for inborn errors of immunity

AbstractHLA-mismatched transplants with either in vitro depletion of CD3+ T-cell receptor (TCR)αβ/CD19 (TCRαβ) cells or in vivo T-cell depletion using posttransplant cyclophosphamide (PTCY) have been increasingly used for patients with inborn errors of immunity (IEIs). We performed a retrospective multicenter study via the EBMT registry on 306 children with IEIs undergoing their first transplant between 2010 and 2019 from an HLA-mismatched donor using TCRαβ (n = 167) or PTCY (n = 139). The median age for hematopoietic stem cell transplantation (HSCT) was 1.2 years (range, 0.03-19.6 years). The 3-year overall survival (OS) was 78% (95% confidence interval (CI), 71-84) after TCRαβ and 66% (57-74) after PTCY (P = .013). Pre-HSCT morbidity score (hazard ratio [HR], 2.27; 1.07-4.80, P = .032) and non-busulfan/treosulfan conditioning (HR, 3.12; 1.98-4.92, P < .001) were the only independent predictors of unfavorable OS. The 3-year event-free survival (EFS) was 58% (50%-66%) after TCRαβ and 57% (48%-66%) after PTCY (P = .804). The cumulative incidence of severe acute graft-versus-host disease (GvHD) was higher after PTCY (15%, 9%-21%) than TCRαβ (6%, 2%-9%, P = .007), with no difference in chronic GvHD (PTCY, 11%, 6%-17%; TCRαβ, 7%, 3%-11%, P = .173). The 3-year GvHD-free EFS was 53% (44%-61%) after TCRαβ and 41% (32%-50%) after PTCY (P = .080). PTCY had significantly higher rates of veno-occlusive disease (14.4% vs TCRαβ 4.9%, P = .009), acute kidney injury (12.7% vs 4.6%, P = .032), and pulmonary complications (38.2% vs 24.1%, P = .017). Adenoviremia (18.3% vs PTCY 8.0%, P = .015), primary graft failure (10% vs 5%, P = .048), and second HSCT (17.4% vs 7.9%, P = .023) were significantly higher in TCRαβ. In conclusion, this study demonstrates that both approaches are suitable options in patients with IEIs, although they are characterized by different advantages and outcomes.

Improving Unrelated Donor Equity: Assessing Mismatched Donor Opportunities with Real-World Data in a Minority-Predominant Cohort

Recent advances in graft-versus-host disease (GVHD) prophylaxis including post-transplant cyclophosphamide (PTCy) and abatacept have significantly improved outcomes following HLA-mismatched allogenic hematopoietic stem cell transplantation (allo-HSCT) and have tremendous potential for reducing racial disparities in donor availability. A recent small study employing bone marrow as the source of stem cells showed similar outcomes after 5/8 versus 7/8 matches and is currently being tested in a larger study using peripheral blood stem cells. In this study, we examine real-world alternative donor HSCT options for a minority-predominant cohort in the Bronx, NY, focusing on the availability of lesser-matched (5/8 to 7/8) donors. Records of patients who underwent HLA typing at Montefiore Medical Center (2019 to 2022) were reviewed. The National Marrow Donor Program registry was queried to evaluate the availability of donors with at least 99% likelihood of HLA match at various levels (5/8, 6/8, 7/8, 8/8). Two hundred forty-one patients were included, 70% were non-White. Although the availability of ≥7/8 donors was less common in non-White patients, 100% of patients from each group had at least one or more 5/8 and 6/8 HLA-matched donors and more than 80% of these patients had >100 potential 5/8 and 6/8 HLA-matched donors. There was no statistical difference by race or ethnicity in the mean number of donors at 5/8 and 6/8 HLA-match levels. We demonstrate through real-world data that patients from diverse ethnic and racial backgrounds have access to 5/8 and 6/8 HLA-matched donors for allo-HSCT, potentially eliminating disparities in donor availability and allowing prioritization of other donor selection characteristics such as donor age, sex, ABO, and B leader matching. Further work is needed to study whether the use of mismatched donors offers a more potent graft-versus malignancy effect and optimal GVHD prophylaxis.

Interim Results of a Phase I/II Trial of Intermediate-Dose Post-Transplantation Cyclophosphamide after Reduced Intensity Conditioned HLA-Mismatched Bone Marrow Transplantation for Older or Unfit Patients

Interim Results of a Phase I/II Trial of Intermediate-Dose Post-Transplantation Cyclophosphamide after Reduced Intensity Conditioned HLA-Mismatched Bone Marrow Transplantation for Older or Unfit Patients

Comparison of long-term outcomes after first HLA-mismatched unrelated donor transplantation with single unrelated cord blood transplantation using reduced-intensity or reduced-toxicity conditioning

BackgroundNo comparative data have shown significant survival differences between HLA-mismatched unrelated donor (MMUD) transplantation and cord blood (CB) transplantation, each with reduced-intensity/reduced-toxicity conditioning (RIC/RTC). However, advances in graft-versus-host disease (GVHD) prophylaxis might help update current strategies. MethodsWe retrospectively compared the outcomes of first allogeneic hematopoietic cell transplantation from MMUDs (n = 15) or single unrelated CB (n = 35) after RIC/RTC. ResultsThe median age was 60 years. The MMUD group had a numerically lower 100-day incidence of grade III–IV acute GVHD (7% vs. 29%, P = 0.079) and non-relapse mortality (0% vs. 40%, P = 0.12). Eight MMUD recipients received anti-thymocyte globulin, bortezomib, or posttransplant cyclophosphamide for GVHD prophylaxis. They did not develop grade III–IV acute GVHD. The MMUD group had significantly better 5-year overall survival than the CB group (62% vs. 31%, P = 0.021), although relapse rates were similar. A multivariable analysis and sensitivity analysis also showed trends toward higher overall survival in the MMUD group. ConclusionMMUD with better GVHD prophylaxis might be preferred over CB in patients with older age and comorbidities.

Selecting the Right Alternative Donor: Comparison of Outcomes of HLA-Mismatched Alternative Donor Hematopoietic Cell Transplantations in Adult Patients with Acute Lymphoblastic Leukemia Regarding KIR-Ligand Mismatch

Background: Allogeneic hematopoietic cell transplantation from cord blood (CBT) or haploidentical donor (HIDT) has proved to be a viable option for patients unable to find a human leukocyte antigen (HLA)-matched conventional donor. However, few single-centered studies have compared outcomes of the two alternative donor transplantations in adult acute lymphoblastic leukemia (ALL). Aim: Our aim is to compare outcomes of adult ALL patients treated with CBT with those treated with HIDT. Secondly, we tried to find out factor that could be considered in selecting donor for alternative donor transplantation to improve clinical outcomes. Methods: We compare outcomes of adult ALL patients treated with CBT (n=134) between 2008 and 2022 with those treated with HIDT (n=47) between 2018 and 2022.Conditioning regimen for CBT consisted of total body irradiation (12Gy) plus cytarabine (9g/m 2) plus fludarabine (150mg/m 2). Graft-versus-host disease (GVHD) prophylaxis was attempted using tacrolimus and mycophenolate mofetil. For HIDT, we used reduced toxicity conditioning (RTC) regimen including fludarabine (150mg/m 2) plus busulfan (6.4mg/kg). GVHD prophylaxis was done with ATG 1.5mg for 4 days plus short course methotrexate (MTX) (15mg/m 2) plus tacrolimus. Killer cell immunoglobulin-like receptor (KIR) ligand mismatch was calculated in both GVH and HVG direction using HLA-KIR ligand database, and its effect on clinical outcomes of alternative donor transplantation was investigated. Results: In HIDT, CD34+ cell count (´10 6/kg) was significantly higher (7.4 vs. 0.1, P&amp;lt;0.001), and the patients were older (49 vs. 33.5, P&amp;lt;0.001) compared to CBT. Other characteristics, such as cytogenetic risk and leukocyte count at diagnosis, did not show significant difference between the two groups. Incidence of acute GVHD II-IV (51.1% vs. 50.0%), III-IV (25.5% vs. 17.9%), and moderate to severe chronic GVHD (10.8% vs. 11.0%) between HIDT vs. CBT were similar. After median follow-up of 39.4 months (range: 5.5-167.4), HIDT showed higher cumulative incidence of relapse (CIR) compared to CBT (47.9% vs. 18.9%, P&amp;lt;0.001), which remained true even after stratifying by age subgroup (Age&amp;lt;40: P=0.033, Age≥40: P=0.002). Conversely, CBT showed higher non-relapse mortality (NRM) than HIDT (22.8% vs. 9.0%, P=0.038), but the same was true only in the older age subgroup (Age&amp;lt;40: P=0.484, Age≥40: P=0.002). These effects summed up to produce comparable results in estimated 3-year disease-free survival (DFS) of CBT and HIDT (58.4% vs. 43.5%, P=0.103), especially in the older subgroup (38.7% vs. 40.7%, P=0.897). Multivariate analysis also revealed that HIDT was related with higher relapse (HR 3.47; 95%CI 1.92-6.27, P&amp;lt;0.001), and CBT with higher NRM (HR 4.18; 95%CI 1.42-12.3, P=0.009). GVH direction KIR ligand mismatching worked for lower 3-year DFS in CBT (40.3% vs. 74.4%, P=0.007), although CIR and NRM did not show significant difference (27.8% vs. 15.6%, P=0.178; 35.0% vs 18.4%, P=0.057, respectively). On the other hand, the mismatch resulted in lower incidence of acute GVHD II-IV (32.0% vs. 54.2%, P=0.011). The trend remained when such effect was investigated separately in CBT and HIDT, but it was not statistically significant (33.3% vs. 53.1%, P=0.082; 28.6% vs. 57.6%, P=0.053, respectively). Conclusions: Our data shows higher NRM in CBT, and unexpected higher relapse rate in HIDT. Age of the patient should be considered when choosing CBT, because in older patients CBT showed notably worse NRM compared to HIDT. Higher incidence of relapse in HIDT may be attributable to ALL disease characteristics itself or insufficient elimination of leukemic cells by RTC regimen with stronger GVHD prophylaxis. Similar to what is known in acute myeloid leukemia, GVH direction KIR incompatibility showed protective effect against acute GVHD in ALL. However, the mismatch resulted in worse DFS in ALL patients treated with CBT, but not in those treated with HIDT. Possible explanation to this phenomenon is that the number of NK cells in cord blood was insufficient for mismatch-induced graft-versus-leukemia effect, while its immune response against infected cells was suppressed by the same mechanism that resulted in lower acute GVHD. Keywords: Acute lymphoblastic leukemia, Cord blood transplantation, Haploidentical donor transplantation, HLA-mismatched transplantation, Killer-cell immunoglobulin like receptor

Mismatched Unrelated Donor Transplantation with Ptcy-Based Gvhd Prophylaxis Is Associated with Better Survival Than Double Unit Umbilical Cord Blood Transplantation in Patients with AML in First CR: A Study from the ALWP of the EBMT

Background: The best donor option for acute myeloid leukemia (AML) patients lacking an HLA-matched donor has remained unknown. The recently reported BNT CTN 1101 trial observed higher non-relapse mortality (NRM) and lower overall survival (OS) in patients randomized to double-unit unrelated umbilical cord blood transplantation (dCBT) in comparison to those randomized to HLA-haploidentical bone marrow transplantation with post-transplant cyclophosphamide (PTCy)-based graft-versus-host disease (GVHD) prophylaxis 1. In addition, recent registry studies observed at least as good transplantation outcomes in AML patients given grafts from 9/10 HLA-matched unrelated donor (UD 9/10) with PTCy-based GVHD prophylaxis as those given grafts from HLA-haploidentical donors 2,3. These observations prompted us to perform a retrospective registry study comparing hematopoietic cell transplantation (HCT) outcomes between UD 9/10 and dCBT. Methods: Inclusion criteria consisted of adult patient, AML in CR1 at transplantation, either peripheral blood stem cells (PBSC) from UD 9/10 with PTCy as GVHD prophylaxis or dCBT, transplantation between 2013 and 2021, and no in vivo T-cell depletion. Results: A total of 208 dCBT patients and 270 UD 9/10 allo-HCT were included. The 180-day cumulative incidence of grade II-IV acute GVHD was 29% in UD 9/10 versus 44% in dCBT recipients (P=0.001). The 2-year cumulative incidences of relapse and of NRM were 23.5% and 12.5%, respectively, in UD 9/10 recipients versus 27% (P=0.39) and 18% (P=0.07), respectively in dCBT recipients. Two-year OS and LFS were 70% and 64%, respectively, in UD 9/10 recipients versus 60% (P=0.016) and 55% (P=0.028), respectively in dCBT recipients. In multivariate analyses, in comparison with UD 9/10 recipients, dCBT patients had a higher non-relapse mortality (HR=2.35, 95% CI: 1.23-4.48; P=0.01), comparable relapse incidence (HR=1.12, 95% CI: 0.67-1.86; P=0.66), lower leukemia-free survival (HR=1.5, 95% CI: 1.01-2.23; P=0.047), and lower overall survival (HR=1.66, 95% CI: 1.08-2.55; P=0.02). Conclusions: In summary, our results suggest that transplantation outcomes are better with UD 9/10 with PTCy-based GVHD prophylaxis than with dCBT for AML patients in CR1. These data might support the use of UD 9/10 with PTCy-based GVHD prophylaxis in AML patients lacking an HLA-matched donor. References Fuchs, E. J. et al. Double unrelated umbilical cord blood vs HLA-haploidentical bone marrow transplantation: the BMT CTN 1101 trial. Blood 137, 420-428 (2021).Baron, F. et al. Comparison of HLA-mismatched unrelated donor transplantation with post-transplant cyclophosphamide versus HLA-haploidentical transplantation in patients with active acute myeloid leukemia. Bone Marrow Transplant. 57, 1657-1663 (2022).Battipaglia, G. et al. Post-transplant cyclophosphamide in one-antigen mismatched unrelated donor transplantation versus haploidentical transplantation in acute myeloid leukemia: a study from the Acute Leukemia Working Party of the EBMT. Bone Marrow Transplant. 57, 562-571 (2022).

Comparison between Post-Transplant Cyclophosphamide Use and Conventional Prophylaxis of Graft-Versus-Host Disease: A Retrospective Study

Introduction: In order to modify the immune response balance between donor and recipient in the context of haploidentical transplantation, the use of post-transplant cyclophosphamide (PTCy), which reduces the population of recipient alloreactive T cells, has become the preferred strategy for graft-versus-host disease (GVHD) prophylaxis. Recently, this approach has also been tested and validated in HLA-matched related or unrelated transplants, as well as in unrelated transplants with HLA mismatch. However, high doses of PTCy can cause cardiac toxicity, hemorrhagic cystitis, and potentially increase the incidence of viral infections. Therefore, comparative studies are needed to evaluate the outcomes of PTCy use compared to other conventional GVHD prophylaxis strategies. Objective: To evaluate the outcomes of patients undergoing allogeneic peripheral blood stem cell transplantation (PBSCT) and to compare the use of post-transplant cyclophosphamide with other GVHD prophylaxis strategies. Patients and Methods: Retrospective analysis of consecutive patients transplanted between March 2014 and March 2023 at two transplant centers. The median follow-up was 24 months (range: 3-116 months). Results: A total of 118 adult patients undergoing PBSCT were included. There were 70 HLA-matched related donors, 28 HLA-matched unrelated donors, and 20 unrelated donors with one HLA mismatch. The median age was 52 years (range: 18 to 80), with a majority being male (51%). The most common diagnoses were acute myeloid leukemia (37%), acute lymphoblastic leukemia (18%), and myelodysplastic syndrome (18%). The disease risk index (DRI) was considered low or intermediate in 53% of cases, high in 31%, and very high in 16%. The majority of patients (76%) had a low risk of transplant-related complications (HCT-CI). Most patients received reduced-intensity conditioning regimens (78%), and the majority (72%) received some sort of T-cell depletion, with 36 (31%) patients receiving PTCy and 49 (41%) receiving ATG. No significant differences were found between the groups (PTCy vs. non-PTCy) in overall survival at 24 months (65% vs. 61%, p = 0.71, respectively), disease-free survival at 24 months (55% vs. 53%, p = 0.76), non-relapse mortality at 24 months (21% vs. 23%, p = 0.84), relapse rate at 24 months (24% vs. 24%, p = 0.61), neutrophil engraftment at 30 days (89% vs. 93%, p = 0.49), and incidence of grade II-IV acute GVHD at 100 days (31% vs. 29%, p = 0.99), grade III-IV acute GVHD at 100 days (6% vs. 12%, p = 0.22), chronic GVHD at 24 months (42% vs. 50%, p = 0.51), and moderate/severe chronic GVHD at 24 months (19% vs. 23%, p = 0.66). There was also no difference in the incidence of infections, including viral infections and cytomegalovirus reactivation. Conclusions: The use of PTCy demonstrated similar clinical outcomes to other GVHD prophylaxis strategies, without an increased risk of infections or mortality. Therefore, PTCy can be considered a viable, safe, and cost-effective option for GVHD prophylaxis in the context of HLA-matched and HLA-mismatched transplants.

Interindividual HLA Evolutionary Divergence in Single HLA-Mismatched Unrelated Donor Hematopoietic Cell Transplantation for Malignant Hematological Disorders: A Report on Behalf of the Cellular Therapy and Immunobiology Working Party of the EBMT

In allogeneic hematopoietic cell transplantation (allo-HCT), alloreactive T-cell responses (graft versus leukemia - GvL and graft versus host disease - GvHD) are mediated by the interaction between recipient antigens and donor lymphocytes via human leukocyte antigen (HLA) molecules. HLA evolutionary divergence (HED) is a metric recently implemented as a functional proxy for the structural variability between two homologous HLA alleles at their peptide binding sites, mirroring quantitative differences in pathogen and cancer-related immunopeptidomes ( A). 1 Here, we hypothesize that differences in and between donor and recipient HEDs at given loci may modulate the direction and the intensity of alloreactivity, informing on post-transplant outcomes. We tested this hypothesis in onco-hematologic patients undergoing allo-HCT from a single HLA-A, -B, -C, -DRB1, or -DQB1 (9/10) mismatched unrelated donor (MMUD) at EBMT centers. We included patients with selected hematological malignancies, receiving a thymoglobulin-based T cell depletion, for whom complete clinical and HLA information was available in the EBMT database. We deployed individual locus-specific recipient/donor HED (HED-R, HED-D) metrics as previously described 1, and conceptualized two novel interindividual HED scores accounting for functional differences at the mismatched HLA loci ( A). The latter were considered as: 1) DeltaHED, quantifying the relative directional difference between HED-D and HED-R and informing on differences in immunopeptidome sizes, potentially capturing the direction and the intensity of the alloreactive response (GvH or HvG); 2) HEDmismatch, describing the HED of the mismatched locus as a proxy for the qualitative differences in immunopeptidomes between donor and recipient ( B). Using multivariable Cox regression (cause-specific) models adjusted for relevant clinical variables, we investigated the associations of HED-R, DeltaHED and HEDmismatch, analyzed as continuous variables, with relapse free survival (RFS), overall survival (OS), non-relapse mortality (NRM), relapse and grade II-IV acute and chronic GvHD. For each outcome and in each mismatched subgroup, we built separate models for these immunogenetic parameters and checked for proportional hazards assumption (PHA). To account for multiple comparisons, only p-values &amp;lt;0.01 were considered significant. Overall, 4639 adult patients, with available HLA data, received a 9/10 MMUD allo-HCT between 2010 and 2019 for acute leukemia (N=3853, 83%), myelodysplastic syndromes or myeloproliferative neoplasms (N=786, 17%). Median recipient age was 53.5 (IQR 40.2-61.9) with a male/female ratio of 1.28, whilst median donor age was 33.1 (IQR 24.5-40). Majority of patients (90%) received peripheral blood stem cells and were mismatched with their donors for locus A (33%), followed by C (21%), B (15%), DQB1 (14%) and DRB1 (6%). When analyzing the impact of HED-related parameters in each model, we observed that most recurrent associations with outcomes occurred with DRB1-related metrics. In the DRB1-mismatched subgroup (N=276), a time-varying association was found for HEDmismatch of DRB1 locus with higher HEDmismatch leading to worse RFS [HR:1.25 at t=0, (95% CI 1.1-1.42), p&amp;lt;0.001] and lower OS [HR:1.23 at t=0, (95%CI 1.08-1.41), p=0.002]. The strength of this associations declined over time for both endpoints (respectively RFS: HR:0.91, 95% CI 0.86-0.97, p=0.005 and OS: HR:0.93, 95% CI 0.88-0.98, p=0.013). The (directional) DeltaHED DRB1 measure instead did not display any impact on outcomes. In the same subgroup, higher HED-R in the locus C showed also a time-varying association with NRM at transplant [HR:1.89, (95% CI 1.29-2.85), p=0.002], progressively declining over time (HR:0.77, 95% CI 0.65-0.92, p=0.003). Furthermore, DRB1 HED-R modulated the probability of survival in B-mismatched subgroup, being higher scores associated with reduced OS [HR:1.03, (95%CI 1.01-1.06), p=0.009]. Here, we provide an immunogenetic benchmark to explore donor-recipient interactions in MMUD allo-HCT, demonstrating how different HLA configurations within the mismatched loci, in particular for DRB1 genes, can influence post-transplant outcomes. Given the peculiar associations observed, HED may have a role in driving early GvL effects, informing on future donor selection strategies in high-risk patients.

Targeting TFH cells is a novel approach for donor-specific antibody desensitization of allograft candidates: an in vitro and in vivo study.

The presence of donor-specific antibodies (DSA) are associated with graft failure either following human leukocyte antigen (HLA)-mismatched allogeneic stem cell transplantation or after organ transplantation. Although targeting B cells and plasma cells have been used for desensitization, there have been reports of failure. T-follicular helper (Tfh) cells assist B cells in differentiating into antibody-secreting plasma cells. We used haploidentical allograft as a platform to investigate the possibility of targeting Tfh cells to desensitize DSA. The quantities of circulating Tfh (cTfh) cell subsets in allograft candidates were abnormal, and these cells, including the cTfh2 and cTfhem cell subsets, were positively related to the production of anti-HLA antibodies. Ex vivo experiments showed that the cTfh cells of anti-HLA antibody-positive allograft candidates could induce B cells to differentiate into DSA-producing plasmablasts. The immune synapse could be involved in the assistance of cTfh cells to B cells in antibody production. In vitro experiments and in vivo clinical pilot studies indicated that targeting cTfh cells with sirolimus can inhibit their auxiliary function in assisting B cells. Ex vivo and in vivo studies demonstrated the effect of sirolimus and rituximab on DSA desensitization compared with either sirolimus or rituximab alone (60%, 43.75%, and 30%, respectively). Our findings provide new insight into the role of Tfh cells in the pathogenesis of DSA production in HLA-mismatched transplant candidates. Our data also indicate that targeting Tfh cells is a novel strategy for DSA desensitization and combination of sirolimus and rituximab might be a potential therapy. The prospective cohort of this study is registered at http://www.chictr.org.cn as #ChiCTR-OPC-15006672.

Impact of HLA-mismatched unrelated transplantation in patients with adult T-cell leukemia/lymphoma.

This Japanese nationwide retrospective study investigated the impact of HLA-mismatched unrelated transplantation for adult T-cell leukemia-lymphoma (ATL) patients who received transplantation between 2000 and 2018. We compared 6/6 antigen-matched related donor (MRD), 8/8 allele-matched unrelated donor (8/8MUD), and 1 allele-mismatched unrelated donor (7/8MMUD) in the graft-versus-host direction. We included 1191 patients; 449 (37.7%) were in the MRD group, 466 (39.1%) in the 8/8MUD group, and 276 (23.7%) in the 7/8MMUD group. In the 7/8MMUD group, 97.5% of patients received bone marrow transplantation, and no patients received post-transplant cyclophosphamide. The cumulative incidences of non-relapse mortality (NRM) and relapse at 4 years, and the probabilities of overall survival at 4 years in the MRD group were 24.7%, 44.4%, 37.5%, in the 8/8MUD group were 27.2%, 38.2%, and 37.9%, and in the 7/8MMUD group were 34.0%, 34.4%, and 35.3%, respectively. The 7/8MMUD group had a higher risk of NRM (hazard ratio (HR) 1.50 [95% CI, 1.13-1.98; P = 0.005]) and a lower risk of relapse (HR 0.68 [95% CI, 0.53-0.87; P = 0.003]) than the MRD group. The donor type was not a significant risk factor for overall mortality. These data suggest that 7/8MMUD is an acceptable alternative donor when an HLA-matched donor is unavailable.

Gene therapy in sickle cell disease: Attitudes and informational needs of patients and caregivers.

Sickle cell disease (SCD) is an inherited blood disorder that results in serious morbidity and early mortality. Novel therapies for SCD, most notably genetic therapies (GTs) and HLA-mismatched donor hematopoietic cell transplantation, are in clinical trials. While potentially curative, these interventions are some of the most intensive treatments for SCD and are associated with serious and life-altering side effects, which may manifest several years after treatment. Little is known about knowledge, beliefs, and attitudes of individuals with SCD, or their caregivers, toward existing and these emerging therapies. Patients with SCD at least 13 years of age (n=66) and caregivers (n=38) were surveyed about knowledge, attitudes, and beliefs surrounding treatments for SCD. Only 4.8% felt "extremely knowledgeable" about GT for SCD while the majority (63.4%) reported little knowledge. Overall, health literacy was low among respondents. Most respondents had a neutral attitude regarding the safety of GT for SCD, and whether it was a good treatment for the disorder (56.7% and 58.6%, respectively). Only a few respondents endorsed the idea that GT was "unsafe" or "not a good treatment" (5.8% and 4.8%, respectively). There was an association between increasing knowledge about GT and agreement that it is safe (p=.012) and a good treatment for SCD (p=.031). Given that very few patients with SCD feel knowledgeable about GT and a majority have neutral feelings about the safety and utility of this new approach, culturally appropriate patient-centered education is urgently needed as these treatments get regulatory approval and proceed to the clinic.

Effect of Graft-versus-Host Disease on Post-Transplantation Outcomes following Single Cord Blood Transplantation Compared with Haploidentical Transplantation with Post-Transplantation Cyclophosphamide for Adult Acute Myeloid Leukemia

The possibility that HLA mismatches could reduce relapse after alternative HLA-mismatched allogeneic hematopoietic cell transplantation (HCT) is an attractive concept for treating acute myeloid leukemia (AML). However, it remains unclear whether the prognostic effect of graft-versus-host disease (GVHD) on survival differs between recipients of single-unit cord blood transplantation (CBT) and recipients of haploidentical HCT using post-transplantation cyclophosphamide (PTCy-haplo-HCT) for AML. The objective of this retrospective study was to compare the effect of acute GVHD and chronic GVHD on post-transplantation outcomes between recipients of CBT and recipients of PTCy-haplo-HCT. We retrospectively evaluated the effect of acute and chronic GVHD on post-transplantation outcomes following CBT and PTCy-haplo-HCT in adults with AML (n=1981) between 2014 and 2020 using a Japanese registry database. In univariate analysis, the probability of overall survival was significantly greater in patients who developed grade I-II acute GVHD (P < .001, log-rank test) and limited chronic GVHD (P < .001, log-rank test) among CBT recipients, but these effects were not significant among PTCy-haplo-HCT recipients. In multivariate analysis, in which the development of GVHD was treated as a time-dependent covariate, the effect of grade I-II acute GVHD on reducing overall mortality differed significantly between CBT and PTCy-haplo-HCT (adjusted hazard ratio [HR] for CBT, .73, 95% confidence interval [CI], .60 to .87; adjusted HR for PTCy-haplo-HCT, 1.07; 95% CI, .70 to 1.64; P for interaction=.038). Our data demonstrate that grade I-II acute GVHD was associated with a significant improvement in overall mortality in adults with AML receiving CBT but not in recipients of PTCy-haplo-HCT.

Different effects of thymoglobulin on acute leukemia with pre-transplant residual blasts in HLA mismatch transplantation.

Anti-thymocyte globulin (ATG) is widely used to reduce acute and chronic graft-versus-host disease (a/cGVHD), one of the leading causes of morbidity and mortality after allogeneic hematopoietic stem cell transplantation (HSCT). As the removal of alloreactive T cells by ATG may also reduce the graft-versus-leukemia effect, the question of whether ATG use affects relapse incidence and survival outcomes in acute leukemia patients with pre-transplant bone marrow residual blasts (PRB) remains controversial. Here, we evaluated the impact of ATG on transplant outcomes in acute leukemia patients with PRB (n = 994) who underwent HSCT from HLA 1-allele mismatched unrelated donors (MMUD) or HLA 1-antigen mismatched related donors (MMRD). In MMUD with PRB (n = 560), multivariate analysis demonstrated that ATG use significantly decreased grade II-IV aGVHD (hazard ratio [HR], 0.474; P = 0.007) and non-relapse mortality (HR, 0.414; P = 0.029) and marginally improved extensive cGVHD (HR, 0.321; P = 0.054) and GVHD-free/relapse-free survival (HR, 0.750; P = 0.069). We concluded that ATG had different effects on transplant outcomes using MMRD and MMUD, and its use would be beneficial to decrease a/cGVHD without increasing non-relapse mortality and relapse incidence in acute leukemia patients with PRB following HSCT from MMUD.

308 - Access: A Multi-Center, Phase II Trial of HLA-Mismatched Unrelated Donor Hematopoietic Cell Transplantation with Post-Transplantation Cyclophosphamide for Patients with Hematologic Malignancies

308 - Access: A Multi-Center, Phase II Trial of HLA-Mismatched Unrelated Donor Hematopoietic Cell Transplantation with Post-Transplantation Cyclophosphamide for Patients with Hematologic Malignancies

357 - Outcomes after HLA-Mismatched Unrelated Donor Hematopoietic Stem Cell Transplantation with Post-Transplant Cyclophosphamide for Graft-Vs-Host Disease Prophylaxis: A Systematic Review and Meta-Analysis

357 - Outcomes after HLA-Mismatched Unrelated Donor Hematopoietic Stem Cell Transplantation with Post-Transplant Cyclophosphamide for Graft-Vs-Host Disease Prophylaxis: A Systematic Review and Meta-Analysis

336 - Abatacept for the Prevention of Graft Versus Host Disease in Pediatric Patients Receiving 7/8 HLA-Mismatched Unrelated Transplant for Hematologic Malignancies: A Real-World Analysis

336 - Abatacept for the Prevention of Graft Versus Host Disease in Pediatric Patients Receiving 7/8 HLA-Mismatched Unrelated Transplant for Hematologic Malignancies: A Real-World Analysis

Abstract B121: HLA-mismatched unrelated donor hematopoietic cell transplantation with post-transplant cyclophosphamide improves clinical outcomes for racial and ethnic minority patients with hematologic malignancies

Abstract Introduction: Racial and ethnic disparities exist in three areas related to hematopoietic cell transplantation (HCT): donor availability, access, and post-HCT outcomes. A significant barrier to access to HCT for patients (pts) of racial or ethnic minorities (REM) is the limited availability of fully matched donors (i.e., grafts matched at HLA-A, -B, -C, and -DRB1 loci) in volunteer registries. While mismatched unrelated donor (MMUD) grafts (i.e., &amp;lt;7/8 match) can be offered to pts without matched donors, MMUD HCT results in poor survival when traditional graft-versus-host disease (GVHD) prophylaxis (PPx) is used. GVHD PPx with post-transplantation cyclophosphamide (PTCy) is associated with favorable survival after haploidentical HCT, and promising outcomes have been reported in a prospective multicenter study utilizing PTCy in MMUD HCT. Herein, we analyzed the outcomes of an ethnically diverse cohort of pts who underwent MMUD HCT with PTCy at two large urban transplant centers. Objectives and Methods: Subjects receiving HCT from an MMUD from 2010-to 2020 at the University of Miami and Memorial Sloan-KetteringCancer Center were included. Pts were stratified by age, HCT indication, race/ethnicity, graft type, conditioning intensity, disease status, and degree of HLA mismatch. The primary study endpoint was one-year overall survival (OS). Secondary endpoints were event-free survival (EFS), non-relapse mortality (NRM), and cumulative incidence of acute and chronic GVHD. Results: A total of 82 pts were evaluated. The median age at HCT was 60 years (21-75), the most common indication for HCT was acute leukemia (51%), 41% of pts received an ablative conditioning regimen, and 50% received peripheral blood (PB) grafts. Forty-four percent identified as non-Hispanic white (NHW), and 56% identified as REM (Non-Hispanic Black: 30%; Hispanic: 64%; Asian/Pacific: 4.3%). The two groups (NHW vs. REM) were well-matched for leading HCT indication, disease-risk index, degree of mismatch, and disease status at HCT. REM pts were younger (median age at HCT 65 vs 56 years for NHW, p=0.001) and more likely to receive a PB graft (63% vs 40%, P = 0.04). One-year OS was 75%, EFS was 69%, and NRM was 16% for the entire cohort. Grade 3-4 acute GVHD at day 180 post-HCT was 15%, and one-year severe chronic GVHD was 9%. OS was comparable between 7/8-matched and highly-mismatched (&amp;lt;6/8) HCT recipients (75% vs. 76%, respectively; P &amp;gt;0.9). There were no differences in one-year OS (77% vs 74%, p = 0.9) and EFS (63% vs 72%, p = &amp;gt;0.9) between NHW and REM pts. Similarly, rates of acute (17% vs 13%, p = 0.5) and chronic GVHD (5.7% vs 11%, p = 0.5) were comparable between NHW and REM pts. Conclusion: PTCy resulted in encouraging clinical outcomes following MMUD HCT. Post-HCT OS, RFS, and GVHD rates were comparable between NHW and REM pts and those receiving 7/8 or highly mismatched grafts. Favorable post-HCT outcomes following MMUD with PTCy may increase HCT utilization and access for REM pts. Citation Format: Antonio M. Jimenez Jimenez, Sunil Iyer, Krishna Komanduri, Samantha Brown, Trent Wang, Stephanie Chinapen, Denise Pereira, Sean Devlin, Mark Goodman, Amer Beitinjaneh, Craig Sauter, Lazaros Lekakis, Miguel Angel Perales, Doris Ponce, Brian Shaffer. HLA-mismatched unrelated donor hematopoietic cell transplantation with post-transplant cyclophosphamide improves clinical outcomes for racial and ethnic minority patients with hematologic malignancies [abstract]. In: Proceedings of the 15th AACR Conference on the Science of Cancer Health Disparities in Racial/Ethnic Minorities and the Medically Underserved; 2022 Sep 16-19; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2022;31(1 Suppl):Abstract nr B121.

HLA-haploidentical stem cell transplantation

HLA-haploidentical stem cell transplantations using posttransplant cyclophosphamide (PTCy-haplo) rapidly increased worldwide. In Japan, the number of HLA-haploidentical stem cell transplantation cases exceeded related HLA-matched transplants in 2020. Recent retrospective studies using Japanese registry data have reported comparable transplantation outcomes between PTCy-haplo and HLA-matched unrelated and cord blood transplantations. PTCy-haplo was initially developed in the bone marrow transplantation setting after non-myeloablative conditioning but has recently become widely used in peripheral blood stem cell transplantation and myeloablative conditioning. Peripheral blood stem cell transplantation increases the occurrence of graft-versus-host disease but may have more improved transplant outcomes compared with bone marrow transplantation. Other factors, such as the number of infused cluster of differentiation 34-positive cells, donor age, HLA class II mismatch, HLA-B leader, and reduced PTCy dosage, may also contribute to the outcome of PTCy-haplo transplantations. Furthermore, PTCy has been reportedly effective in related/unrelated HLA-matched transplantation and HLA-mismatched unrelated transplantations. A prospective phase II trial using PTCy in patients who underwent HLA-matched and 1-2 allele-mismatched transplantation is ongoing in Japan. Patient enrollment has already been completed, and the results will be revealed soon. Using PTCy to sufficiently reduce the occurrence of graft-versus-host disease will make performing allogeneic transplants with a higher safety level possible.