T-cell Replete Research Articles

Prognostic significance of early nk cell recovery in pediatric t-cell replete allogeneic hematopoietic stem cell transplantation.

Early immune reconstitution, particularly of natural killer (NK) cells with strong graft-versus-leukemia effects, is crucial for the prognosis of patients undergoing allogeneic hematopoietic stem cell transplantation (allo-HSCT). This retrospective study examined 122 pediatric patients with acute lymphoblastic leukemia (ALL) or acute myeloid leukemia (AML) who underwent T-cell replete allo-HSCT at the Children's Hospital of Soochow University from 2019 to 2021. Peripheral blood lymphocyte counts on days 30 and 60 post-transplant were analyzed, focusing on NK cell recovery and its impact on overall survival (OS), relapse-free survival (RFS), non-relapse mortality (NRM), relapse, graft-versus-host disease, and CMV reactivation. Patients were categorized into high and low NK cell groups by the median NK cell counts at day 30 (NK30) and day 60 (NK60) after HSCT. Patients with high NK30 and NK60 levels had significantly better 3-year OS rates compared to their respective low NK count groups (86.8% ± 4.7% versus 67.6% ± 7.0%, P = 0.046; 95.7% ± 3.0% versus 63.7% ± 8.7%, P < 0.001, respectively). NK60 was found to be an independent predictor for 3-year OS and RFS in multivariate analysis. Early NK reconstitution was also related to lower NRM rates. However, this correlation disappeared in patients with ALL and those undergoing haploidentical transplantation. In addition, A positive association between early T cell and NK cell reconstitution was found in our study. Higher NK cell counts on days 60 can predict superior OS, RFS and lower NRM in pediatric AML allo-HSCT patients.

Outpatient ATG-free hematopoietic transplantation for aplastic anemia in limited-resource environments offers excellent results: Data from a single LATAM center

ObjectiveTo document the results of outpatient hematopoietic stem cell transplantation (HSCT) from the peripheral blood (PB) of sibling donors without anti-thymocyte globulin (ATG) in the conditioning regimen. Material and methodsPatients from a low-income population with severe AA who received a PB, unmanipulated sibling HLA-identical HSCT between 2000 and 2020 at a single institution were studied. Survival was the primary outcome. ResultsForty-one transplants were performed. Time between diagnosis and transplant was five months (1–104). Median age was 37 (range, 4–61) years; 25 (61 %) recipients were males and 32 (78 %) had treatment failure, 9 (22 %) have not received treatment. ATG was administered in 5 (12.2 %) cases; the graft source was PB in 38 (92.7 %) transplants. Twenty-six (63.4 %) transplants were carried out in the outpatient setting. Infections developed in 14 (34.1 %) patients. Primary graft failure (GF) occurred in 3 (7.3 %) patients. The 15-year OS was 81 %, EFS was 77.4 %. Patients with high pre-HSCT transfusion burden had lower OS (p = 0.035) and EFS (p = 0.026). Previous treatment failure and age were not associated with lower OS (p = 0.115, p = 0.069) or EFS (p = 0.088, p = 0.5, respectively). ConclusionsHLA-identical T-cell replete outpatient HSCT from the PB of sibling donors for AA patients using ATG-free conditioning offers excellent long-term survival.

Haploidentical HSCT in the Treatment of Pediatric Hematological Disorders.

Allogeneic hematopoietic stem cell transplantation has become a treatment option for otherwise non-curative conditions, both malignant and benign, affecting children and adults. Nevertheless, the latest research has been focusing extensively on transplantation from related and unrelated haploidentical donors, suitable for patients requiring emergent hematopoietic stem cell transplantation (HSCT) in the absence of an HLA-matched donor. Haploidentical HSCT (haplo-HSCT) can be an effective treatment for non-malignant pediatric disorders, such as primary immunodeficiencies or hemoglobinopathies, by enabling a much quicker selection of the appropriate donor for virtually all patients, low incidence of graft-versus-host disease (GVHD), and transplant-related mortality (TRM). Moreover, the outcomes of haplo-HSCT among children with hematological malignancies have improved radically. The most demanding tasks for clinicians are minimizing T-cell-mediated alloreactivity as well as early GVHD prevention. As a result, several T-cell depletion approaches, such as ex vivo T-cell depletion (TCD), and T-cell replete approaches, such as a combination of anti-thymocyte globulin (ATG), post-transplantation cyclophosphamide (PTCy), cyclosporine/tacrolimus, mycophenolate mofetil, or methotrexate, have been taken up. As more research is needed to establish the most beneficial form of therapy, haplo-HSCT is currently considered an alternative donor strategy for pediatric and adult patients with complications like viral and bacterial infections, invasive fungal disease, and GVHD.

Peripheral blood stem cell versus bone marrow graft for patients ≥60 years undergoing reduced intensity conditioning haploidentical transplantation for acute myeloid leukemia in complete remission: An analysis of the Acute Leukemia Working Party of the European Society for Blood and Marrow Transplantation.

In the context of T-cell replete haploidentical stem cell transplantation (Haplo-SCT) using post-transplantation cyclophosphamide (PT-Cy), it is still unknown whether peripheral blood (PB) or bone marrow (BM) is the best graft source. While PB is associated with a higher incidence of graft-versus-host disease (GVHD), it may induce a stronger graft-versus-leukemia effect compared to BM, notably in acute myeloid leukemia (AML). From the EBMT registry database, we compared T-cell replete PB (n = 595) versus BM (n = 209) grafts in a large cohort of 804 patients over the age of 60 years who underwent Haplo-SCT with PT-Cy for an AML in first or second complete remission. The risk of acute GVHD was significantly higher in the PB group (Grade II-IV: HR = 1.67, 95% CI [1.10-2.54], p = 0.01; Grade III-IV: HR = 2.29, 95% CI [1.16-4.54], p = 0.02). No significant difference was observed in chronic GVHD or non-relapse mortality. In the PB group, the risk of relapse was significantly lower in the PB group (HR = 0.65, 95% CI [0.45-0.94], p = 0.02) and leukemia-free survival was significantly better (HR = 0.76, 95% CI [0.59-0.99], p = 0.04), with a trend toward better overall survival (HR = 0.78, 95% CI [0.60-1.01], p = 0.06). We conclude that in the specific context of Haplo-SCT with PT-Cy, PB grafts represent a valid option to decrease the risk of relapse and improve outcome of older AML patients who usually do not benefit from conditioning intensification.

Model-Based Antithymocyte Globulin in αβhaplo-Hematopoietic Stem Cell Transplantation Facilitates Engraftment, Expedites T Cell Recovery, and Mitigates the Risk of Acute Graft-versus-Host Disease

In αβ T-cell/CD19 B-cell depleted hematopoietic stem cell transplantation (αβhaplo-HSCT) recipients, antithymocyte globulin (ATG; Thymoglobulin) is used for preventing graft rejection and graft-versus-host disease (GVHD). The optimal dosing remains to be established, however. Here we present the first comparative analysis of 3 different ATG dosing strategies and their impact on immune reconstitution and GVHD. Our study aimed to evaluate the effects of 3 distinct dosing strategies of ATG on engraftment success, αβ+ and γδ+ T cell immune reconstitution, and the incidence and severity of acute GVHD in recipients of αβhaplo-HSCT. This comparative analysis included 3 cohorts of pediatric patients with malignant (n = 36) or nonmalignant (n = 8) disease. Cohorts 1 and 2 were given fixed ATG doses, whereas cohort 3 received doses via a new nomogram, based on absolute lymphocyte count (ALC) and body weight (BW). Cohort 3 showed a 0% incidence of day 100 grade II-IV acute GVHD, compared to 48% in cohort 1 and 27% in cohort 2. Furthermore, cohort 3 (the ALC/BW-based cohort) had a significant increase in CD4+ and CD8+ naïve T cells by day 90 (P = .04 and .03, respectively). Additionally, we found that the reconstitution and maturation of γδ+ T cells post-HSCT was not impacted across all 3 cohorts. Cumulative ATG exposure in all cohorts was lower than previously reported in T cell-replete settings, with a lower pre-HSCT exposure (<40 AU*day/mL) correlating with engraftment failure (P = .007). Conversely, a post-HSCT ATG exposure of 10 to 15 AU*day/mL was optimal for improving day 100 CD4+ (P = .058) and CD8+ (P = .03) immune reconstitution without increasing the risk of relapse or nonrelapse mortality. This study represents the first comparative analysis of ATG exposure in αβhaplo-HSCT recipients. Our findings indicate that (1) a 1- to 2-fold ATG to ATLG bioequivalence is more effective than previously established standards, and (2) ATG exposure post-HSCT does not adversely affect γδ+ T cell immune reconstitution. Furthermore, a model-based ATG dosing strategy effectively reduces graft rejection and day 100 acute GVHD while also promoting early CD4+/CD8+ immune reconstitution. These insights suggest that further optimization, including more distal administration of higher ATG doses within an ALC/BW-based strategy, will yield even greater improvements in outcomes.

The range of haploidentical transplant protocols in sickle cell disease: all haplos are not created equally.

The ideal curative therapy for sickle cell disease (SCD) must be applicable across all ages and include individuals with strokes and preexisting heart, lung, and kidney disease. Myeloablative, matched sibling donor hematopoietic stem cell transplant (HCT) for children with SCD has shown excellent outcomes over the past 3 decades but has been restricted due to the limited availability of a human leukocyte antigen-matched sibling donor (10%-15%) and increased treatment-related death in adults with myeloablative conditioning. To overcome these 2 significant barriers to curative therapy in SCD, related haploidentical HCT has become an active area of research. The use of related haploidentical donors (first- and second-degree relatives) increases the donor pool to at least 90% of those eligible across the life span. Importantly, most adults, even with strokes or significant comorbidities, can tolerate the nonmyeloablative conditioning regimen without treatment-related death. Since 2013, at least 3 related haploidentical HCT strategies have emerged as potential curative therapies for SCD: (1) a nonmyeloablative, T-cell replete, bone marrow transplant with thiotepa and posttransplant cyclophosphamide with a goal of complete donor chimerism; (2) a nonmyeloablative, in vivo T-cell depletion, using peripheral blood stem cells (PBSCs) with a goal of stable mixed donor-recipient chimerism; and (3) a myeloablative, ex vivo T-cell depletion using PBSCs and advanced-technology graft manipulation, with a goal of complete donor chimerism. We review the similarities, differences, outcomes, and gaps in knowledge with these 3 haploidentical HCT approaches for SCD.

Improved Gvhd-Relapse Free Survival of Ex Vivo αβtcr/CD19 Depleted Allo-Sct Combined with In Vivo T Cell Depletion with ATG When Compared to T Cell Replete Transplantations with or without the Addition of ATG

Introduction The aim of allogeneic stem cell transplantation (allo-SCT) is to reach graft-versus-host disease, relapse free survival (GRFS). To reduce the incidence of graft-versus-host disease (GVHD), we have developed an allo-SCT platform combining ex vivo αβTCR/CD19 depletion with in vivo T-cell depletion through administration of antithymoglobulin (ATG). Here we compare GRFS to historical cohorts of T-cell replete allo-SCT. Methods Adults with hematological malignancies and transplanted between 2011 and 2022 were included in this retrospective analysis. Written informed consent was obtained in accordance with the JACIE guidelines. Clinical data was extracted from the EBMT registry. 3 cohorts were identified. Cohort A: Allo-SCT of unmanipulated peripheral blood derived mononuclear cells (PBMCs) of matched related donors (MRD) after non-myeloablative (NMA) or myeloablative (MA) conditioning without ATG. Cohort B: Allo-SCT of unmanipulated PBMCs of 10/10 or 9/10 matched unrelated donors (MUD) after NMA or MA conditioning with ATG. Patients in cohorts A &amp; B received dual immunosuppression with cyclosporin (CsA) and mycophenolic acid (MMF). Cohort C: Allo-SCT of αβTCR/CD19 depleted PBMCs of MRD and MUD (10/10 and 9/10) after ATG and a myeloablative conditioning as previously described[1]. Patients in cohort C received 28 days of MMF. Cumulative incidence (CI) of GVHD was defined as time to onset of GVHD, with relapse and death as competing events. Overall survival (OS) was defined as time to death from any cause. CI of relapse was defined as time to relapse, with death as a competing event. Non-relapse mortality (NRM) was defined as time to death, without relapse or progression. Event free survival (EFS) was defined as the time to relapse, graft failure or death. GRFS was defined as the time to relapse, aGVHD 3-4 or extensive cGVHD, graft failure or death. CI of CMV and EBV reactivations were calculated with relapse and death as competing events. Results 341 patients were included (cohort A: N=63; cohort B: N=150; cohort C: N=128) (table 1). In T cell replete allo-SCT (A&amp;B) ATG was administered to recipients of MUD and MA conditioning was administered to patients &amp;lt; 40 years with acute leukemia. In cohort C, all patients received ATG and an MA conditioning, regardless of age or underlying malignancy. This explains differences donor types and intensity of conditioning between the cohorts (table 1). Other clinical characteristics were comparable. Two year OS (A=66.7%; B=58.7%; C=63.8%) and EFS (A=57.1%; B=52%; C=55.7%) was comparable between the cohorts. Two year CI of relapse was also comparable (A=30%; B=23%; C=28%). Two year NRM appeared higher in B, but this difference did not reach significance (A= 9.8%; B=24%; C=15%). The CI of aGVHD grade 2-4 and 3-4 at day 100 was significantly higher in T cell replete allo-SCT with MUD (2-4; A=23%; B=37%; C=20% (p=0.002); 3-4: A=5%; B=16%; C=4.7% (p=0.043)). The incidence of extensive cGVHD was significantly higher in T cell replete allo-SCT of MRD. (A= 25%; B=13%; C= 2.3% (p=&amp;lt; 0.001)). The low incidence of grade 3-4 aGVHD and extensive cGVHD without an increase in relapse or NRM, translated into a superior 2 year GRFS in patients receiving ATG combined with an αβTCR/CD19 allograft (C=55.6%) as compared to T cell replete allo-HSCT of MRD (A=38.1%) and MUD (B=40.8%) (Figure 1, p=0.04). This difference remained significant in a multivariate analysis. Conclusion We demonstrate that αβTCR/CD19 depletion combined with ATG, with a myeloablative conditioning and a very short course of immunosuppression results in very low incidences of life-threatening GVHD and an improved GRFS as compared to T cell replete allo-SCT for adult patients up to the age of 70. This is likely to positively impact the long term quality of life in survivors of allo-SCT[2]. In addition, this platform provides a window for additional early post allo-interventions to further improve the control of underlying hematological malignancies. 1. de Witte, M.A., et al., alphabeta T-cell graft depletion for allogeneic HSCT in adults with hematological malignancies. Blood Adv, 2021. 5(1): p. 240-249. 2. Oerlemans, S., et al. Relapse and severe Graft-versus-Host Disease have a negative impact on long-term symptoms and quality of life of patients three years after allogeneic haematopoietic stem cell transplantation. Annual meeting EBMT 2022.

Post-Transplant T Cell Clonotype Diversity Is Associated with Survival in Patients with TP53-Mutated Acute Myeloid Leukemia

Background TP53 mutations are associated with unfavorable outcomes in various cancer types and present an obstacle to achieving sustained remission in acute myeloid leukemia (AML). Even with allogeneic hematopoietic stem cell transplantation (HSCT), the risk of relapse approximates 80%, with dismal long-term survival. This could imply methods of immune escape in TP53 mutated leukemias that allow them to evade the graft-versus-leukemia (GVL) effect, which is a critical mechanism of disease control with HSCT. This study investigates the dynamics of immune reconstitution at single-cell resolution in TP53-mutated AML at pre- and multiple post-HSCT timepoints in patients who either remain in long-term remission or relapse following HSCT. Methods We collected 26 longitudinal bone marrow aspirates and 1 peripheral blood sample from 12 patients with TP53-mutated AML who underwent HSCT at the Dana-Farber Cancer Institute between 2015-21. All patients received HLA-matched T-cell replete HSCT in morphologic remission, with standard tacrolimus/methotrexate-based prophylaxis and peripheral blood stem cells. We categorized the patients into two cohorts based on their treatment response: long-term remission (&amp;gt;3.5 years, cohort 1, n=4) or relapse (cohort 2, n=8). We performed paired 5' single-cell RNA and T cell receptor (TCR) sequencing on sorted viable mononuclear from each sample and CD3+ T cells from selected samples using 10x Genomics procedures. In total, we analyzed 44 samples (27 mononuclear, 17 CD3+), resulting in 250,640 high-quality single-cell transcriptomes, including 137,649 T cells and NK cells. Data analysis was performed using Cell Ranger Multi (10x Genomics) and R 4.3 with the tidyverse 2.0, Seurat 5.1, and scRepertoire 1.1 packages. Results We focused our initial analysis on the 2-6-month post-HSCT period that is critical for immune reconstitution. This included eight samples from seven patients in the two cohorts (1: remission, 2: relapse, pink box in Figure 1). Of these 7 patients, 4 were in the relapse cohort, with these relapses occurring &amp;gt;4 months post-HSCT. No significant difference in T-cell chimerism was seen between these 7 patients in this 2-6 month period. Based on canonical gene expression signatures, we annotated cell types and selected T cells for further evaluation (Figure 2). First, we found that the CD4/CD8 ratio differed between the cohorts, indicating a relative CD8+ T cell expansion in the relapse cohort (cohort 1: 1.69, cohort 2: 0.55, P&amp;lt;0.0001). Second, we found lower TCR diversity in the relapse cohort (inverse Simpson index, cohort 1: 234.6, cohort 2: 83.0, P&amp;lt;0.0001). This difference remained significant when subsampling the same number of T cells per patient and when restricting all samples to the 3 to 4-month timepoint. Considering the disparity in CD8 T cell numbers between the cohorts, we also analyzed repertoire diversity, specifically in CD8+ T cells, and found that the observed significance persisted. To further investigate TCR diversity, we overlaid T cell clonotypes (cells that share the same TCR sequence) in a UMAP visualization, which highlighted increased hyperexpanded CD8+ T cells in the relapse cohort (Figure 2). Finally, we found that greater clonotype expansion was correlated with the expression of key T cell genes, including CD8A, CD8B, PRF1, NKG7, and GZMA. These results suggest that cytotoxic CD8+ T cells link lower TCR diversity to the likelihood of disease relapse. Conclusions By performing deep analysis of single-cell gene expression linked to TCR clonotypes, we discover new insights into the biology of hematopoietic reconstitution after HSCT of patients with TP53-mutated AML. Despite having analyzed a limited number of samples, we find that patients who remain in long-term remission have significantly higher CD8+ TCR diversity between 2-6 months post-HSCT, while those who relapsed between 5-18 months post-HSCT showed lower TCR diversity and hyperexpanded CD8+ clones at the same timepoints. This work suggests that early post-HSCT TCR diversity could be a biomarker associated with GVL and warrants further study. In ongoing and future analyses, we will mine the current dataset for further insights into the factors influencing survival in TP53-mutated AML patients. We also plan to extend the measurement of TCR diversity as a predictor of survival for validation in a larger cohort.

TBI-Containing with T-Cell Replete Full Haplotype Mismatched Hematopoietic Stem Cell Transplantation in Adult Patients with De Novo Acute Myeloid Leukemia

Acute myeloid leukemia (AML) is the 2nd most frequent developing hematologic malignancy with deep heterogeneity, but unfortunately the majority of patients relapse even after allogeneic hematopoietic stem cell transplantation (HSCT) in complete remission (CR). We have developed allogeneic HSCT from familial mismatched/haploidentical donors (FMT) in adult patients with a single disease entity of AML lacking of both HLA-identical siblings and well-matched unrelated donors (WMUD) from the mid 1990s. Previously, several pilot studies of FMT performed with various total body irradiation (TBI)-based conditioning regimens (2~12 gray) with or without post-transplant cyclophosphamide (PT-Cy) as a graft-versus-host disease (GvHD) prophylaxis were reported. Here, we demonstrate about the encouraging outcomes of FMT using unmanipulated peripheral blood donor stem cells (PBSCs) and de-escalated dose of TBI (4~8 gray) containing conditioning regimen without T-cell depletion manner. Although PT-Cy as a specific GvHD prophylaxis regimen is increasingly used for both adult and pediatric FMT, our group investigated the clinical outcomes in adult patients with de novo AML who received full haplotype mismatched HSCT after TBI containing preparation regimen consisted of fractionated TBI (total 4 gray for elderly and 8 gray for &amp;lt;60 years old), fludarabine (150 mg/m 2/day), busulfex (6.4mg/kg/day), and anti-thymocyte globulin (ATG). For GvHD prophylaxis, rabbit ATG (thymoglobulin, Genzyme, 1.25mg/kg/day for 4 days at D-4 to D-1) and a combination of tacrolimus and short-term methotrexate was used. G-CSF mobilized unmanipulated PBSCs were used with a median CD34+ dose of 6.5 x 10 6/kg (1~25.6). From 2008 to the end of 2022, total 429 adult patients were enrolled, and data demonstrated that our trial of intermediate-dose of ATG and reduced toxicity of TBI-containing conditioning regimen to reduce graft-failure even for high levels of donor-specific antibody titer, early transplant-related mortality, critical cytomegalovirus (CMV) disease, and emerging post-transplant lymphoproliferative disease with rapid immune recovery has shown very successful outcomes. Briefly, the median absolute neutrophil count recovery was 12 days (10~26) and the platelet of 14 days (5~38). There was no either primary or secondary graft-failures at all. With a median follow-up of 36.5 months (2~242) for survivors, overall survival rate (OS) and relapse-free survival (RFS) for patients in any CR (n=338) and relapse/refractory status (n=91) were 62.9% vs. 34.3% and 59.5% vs. 32.2%, respectively. Although there was no significant difference in the subgroup analysis, de novo and young aged patients in any CR showed the best OS 73% (Figure 1). Cumulative incidences of acute GvHD and chronic GvHD were 66% (59-73), 70% (63-76), respectively. The incidences of moderate to severe acute GvHD and chronic GvHD were 16.1%, 30.5%, respectively. By univariate and multivariate analyses, patient's age &amp;lt;54 (p=0.043), pre-HSCT CR1 (p &amp;lt;0.001), absence of mod to severe chronic GvHD (p &amp;lt;0.001), and use of post-transplant iron-chelating agent (p=0.001) were the statistically significant in the study. The GvHD-free and relapse-free survival rate in CR1 was 62.4% for younger patients (age &amp;lt;54) and 47.9% for older patients (p=ns). The non-relapse mortality rate was 27.2% for all enrolled patients and 16% for CR patients. The rapidity of immune recovery was also compared with our old control cohort when we performed T-cell depletion using the CliniMACS system, and it showed a significant reconstitution of CD4+ cells (&amp;gt;300/ul) at 3 months post-FMT compared to the much delayed T-cell depleted FMT. Of note, CMV DNAemia was relatively higher (76.9%) than reported in other studies, likely due to the use of ATG and the endemic region of our country. Therefore, we suggest that the strategic reduction of fractionated TBI 4~8 gray-based conditioning with unmanipulated PBSCs graft without PT-Cy seems feasible with favorable outcomes for adult patients with de novo AML undergoing FMT in CR, especially even in a certain subgroup of elderly patients with AML.

Treosulfan Compared to Busulfan in Allogeneic Haematopoietic Stem Cell Transplantation for Myelofibrosis: A Registry-Based Study from the Chronic Malignancies Working Party of the EBMT

Background The optimal conditioning prior to allogeneic stem cell transplantation (HSCT) for myelofibrosis (MF) remains an ongoing matter of debate. There is a paucity of randomized trials robustly showing superiority of one over another. Registry studies comparing reduced intensity conditioning (RIC) versus myeloablative conditioning (MAC) regimens did not show significant differences in overall survival (OS). Recently, a multi-center phase 3 trial in MDS-AML reported an advantage of fludarabine-treosulfan (TREO) over fludarabine-busuflan (BU) RIC (Lancet Haematol Beelen et al 2020). The role of this large EBMT registry study was to compare outcomes of MF HSCT following TREO and BU based MAC or RIC regimens. Methods Patients with MF transplanted from a T-cell replete graft between 2010-2018 following BUMAC, BURIC or TREO were identified in the EBMT registry. Patients who were transformed into AML were excluded. Centers were contacted to participate in additional data collection. 63 centers included a total of 536 patients of whom 6 patients were excluded due to missing data for major endpoints (relapse or regimen). The role of TREO was tested in multi-variable models adjusted on major prognostic factors especially those who were not well balanced between groups and using multiple imputation for missing values. Results Most TREO (n=73) patients received it in combination with FLUDARABINE (95%) and most BU (n=457) received FLUDARABINE +/- other (93%). Median total dose received of TREO was 42 g/m2 and median dose of BU was 8mg/kg. Main differences between the 3 groups were: 1) Recipient age; patients were the oldest in the RIC group (median age 61 years, (IQR: 55-65), the youngest in BUMAC (56 years, (IQR: 51-62)), and intermediate in the TREO group (59 years, (IQR: 54-64); 2) Performance status; Karnofsky score was &amp;lt; 80 in 20%, 30%, 42% in the TREO, BUMAC and BURIC groups, respectively; 3) Comorbidity score (HCT-CI) was lowest in the MAC group (HCT-CT ‘low’ in 56%, 45% and 37% of BUMAC, BURIC and TREO groups); 4) Disease status; patients in the TREO group were more often transplanted with progressive disease (58% vs 30% in BUMAC and 34% in BURIC); 5) JAK inhibitor prior to HSCT; a higher proportion of patients in the TREO group were treated with a JAK inhibitor before HSCT (61% vs 50% in BUMAC and 42% in BURIC); 6) Cytomegalovirus (CMV) donor/ recipient status; CMV combinations were more frequently donor recipient -/- in the TREO cohort (41% vs 28% in MAC and 36% in RIC); 7) an HLA matched sibling donor was less frequently used in TREO group (18% vs. 28% in BURIC and 36% in BUMAC). The 3 groups were well balanced regarding period of transplantation, MF classification (primary versus secondary), splenomegaly at time of transplantation, chromosome abnormalities, MF related symptoms, DIPSS score, GVHD prophylaxis and use of ATG. Median time to neutrophil recovery was 17 days (range: 6-54), with no differences between the 3 groups. Cumulative incidence of engraftment at day 30 was 91.5% (95%CI: 89.1-93.9), with no differences between the 3 groups. Cumulative incidence of grade 2-4 acute GVHD at 120 days for the entire cohort was 23% (95%CI: 19-26%); similar in the 3 groups. Three-year OS was 62% (95% CI 58 -66), 3-year PFS was 49% (45-53). At 3 years, cumulative incidence of relapse was 26% (22-29) and NRM was 25% (21-29). Figure 1 shows OS, PFS, NRM and cumulative incidence of relapse (CIR) according to regimen. Multiple variables Cox models after selection are shown in Table 1. TREO group had a significantly better OS than BUMAC (HR: 0.61, 95%CI: 0.39-0.93), BURIC had similar OS to BUMAC (HR: 0.92, 95%CI: 0.68-1.26) and there was a trend for a better OS with TREO over BURIC (HR: 0.66, 95%CI: 0.41-1.05). The same trend was also observed for PFS with a significant advantage of TREO over BUMAC (HR: 0.57, 95%CI: 0.38-0.84) and BURIC (HR: 0.60, 95%CI: 0.39-0.91) while BURIC had a similar risk to BUMAC (HR: 1.05, 95%CI: 0.80-1.39). The improvement of OS and PFS was related to a lower NRM (HR: 0.44, 95%CI: 0.24-0.80 TREO vs BUMAC; HR: 0.54, 95%CI: 0.28-1.04 TREO vs BURIC) and same relapse risk with TREO over BU (TREO vs BUMAC, HR: 0.71, 95%CI: 0.42-1.20; TREO vs BURIC, HR: 0.63, 95%CI: 0.36-1.11). Conclusion TREO based regimens compared to BU based shows better PFS in MF HSCT. This advantage was also confirmed for OS and NRM when compared to BUMAC. More specific prospective studies are needed to confirm findings from this registry based study.

A retrospective analysis to evaluate if KIR B haplotype donors associate with a reduced risk of relapse in patients with haematological malignancies following haploidentical transplantation at the Blood and Bone Marrow Transplant Unit at Hammersmith Hospital ICHNHST.

Relapse is a major cause of treatment failure in haploidentical haematopoietic progenitor cell transplant (HPCT) with PTCy. Natural killer cells suppress graft versus host disease and mediate the graft versus leukaemia effect, driven by killer cell immunoglobulin-like receptors (KIRs). Emerging research suggests that donor KIR genotype may influence graft outcome in haploidentical transplants with varying impacts between patient cohorts. This study investigates whether donors with greater KIR B motifs associate with outcomes such as greater relapse-free survival (RFS), overall survival (OS), nonrelapse mortality (NRM), acute graft versus host disease (GvHD) and infection. The study cohort included 98 haploidentical donor-recipient (D/R) pairs (myeloablative n = 37, RIC n = 61) with various haematological malignancies, receiving primary T-cell replete haploidentical HSCT with PTCγ. Following KIR SSO genotyping, donors are categorised into neutral (n = 63) or better and best (n = 35), based on KIR B motif content. Kaplan-Meier and Cox regression survival functions are performed to investigate associations with outcomes. Our results show that the better and best category has significantly poorer RFS (p = 0.013; hazard ratio [HR] 3.16, 95% CI 1.21-8.24: p = 0.018). The greater risk of relapse associated with poorer OS (p = 0.011; HR 2.24, 95% CI 1.18-4.24: p = 0.01) in the better and best category. The competing KIR receptor-ligand and missing licensing proof models failed to predict transplant outcomes. Here, we show neutral donors associate with favourable outcomes in T-cell replete haplo-HPCT with PTCγ after categorisation using the KIR B content model, due to the increased risk of relapse associated with the use of better and best donors.

T-cell replete cord transplants give superior outcomes in high-risk and relapsed/refractory pediatric myeloid malignancy.

Stem cell transplant (SCT) outcomes in high-risk and relapsed/refractory (R/R) pediatric acute myeloid leukemia (AML) and myelodysplastic syndrome (MDS) have been historically poor. Cord blood (CB) allows T-cell replete CB transplant (TRCB), enabling enhanced graft-versus-leukemia. We consecutively collected data from 367 patients undergoing TRCB (112patients) or other cell source (255 patients) SCT for pediatric AML/MDS in the United Kingdom and Ireland between January 2014 and December 2021. Data were collected about the patient's demographics, disease, and its treatment; including previous transplant, measurable residual disease (MRD) status at transplant, human leukocyte antigen-match, relapse, death, graft versus host disease (GvHD), and transplant-related mortality (TRM). Univariable and multivariable analyses were undertaken. There was a higher incidence of poor prognosis features in the TRCB cohort: 51.4% patients were MRD positive at transplant, 46.4% had refractory disease, and 21.4% had relapsed after a previous SCT, compared with 26.1%, 8.6%, and 5.1%, respectively, in the comparator group. Event free survival was 64.1% within the TRCB cohort, 50% in MRD-positive patients, and 79% in MRD-negative patients. To allow for the imbalance in baseline characteristics, a multivariable analysis was performed where the TRCB cohort had significantly improved event free survival, time to relapse, and reduced chronic GvHD, with some evidence of improved overall survival. The effect appeared similar regardless of the MRD status. CB transplant without serotherapy may be the optimal transplant option for children with myeloid malignancy.

Posttransplantation cyclophosphamide expands functional myeloid-derived suppressor cells and indirectly influences Tregs.

Posttransplantation cyclophosphamide (PTCy), given on days+3 and+4, reduces graft-versus-host disease (GVHD) after allogeneic hematopoietic cell transplantation (HCT), but its immunologic underpinnings are not fully understood. In a T-cell-replete, major histocompatibility complex-haploidentical murine HCT model (B6C3F1→B6D2F1), we previously showed that PTCy rapidly induces suppressive mechanisms sufficient to prevent GVHD induction by non-PTCy-exposed donor splenocytes infused on day+5. Here, in PTCy-treated mice, we found that depleting Foxp3+ regulatory T cells (Tregs) in the initial graft but not the day+5 splenocytes did not worsen GVHD, yet depleting Tregs in both cellular compartments led to fatal GVHD induced by the day+5 splenocytes. Hence, Tregs were necessary to control GVHD induced by new donor cells, but PTCy's impact on Tregs appeared to be indirect. Therefore, we hypothesized that myeloid-derived suppressor cells (MDSCs) play a complementary role. Functionally suppressive granulocytic and monocytic MDSCs were increased in percentages in PTCy-treated mice, and MDSC percentages were increased after administering PTCy to patients undergoing HLA-haploidentical HCT. PTCy increased colony-stimulating factors critical for MDSC development and rapidly promoted the generation of MDSCs from bone marrow precursors. MDSC reduction via anti-Gr1 treatment in murine HCT did not worsen histopathologic GVHD but resulted in decreased Tregs and inferior survival. The clinical implications of these findings, including the potential impact of expanded MDSCs after PTCy on engraftment and cytokine release syndrome, remain to be elucidated. Moreover, the indirect effect that PTCy has on Tregs, which in turn play a necessary role in GVHD prevention by initially transplanted or subsequently infused T cells, requires further investigation.

Allogeneic hematopoietic stem cell transplantation to cure sickle cell disease: A review.

Sickle cell disease (SCD) had first been mentioned in the literature a century ago. Advancement in the molecular basis of the pathophysiology of the disease opens the door for various therapeutic options. Though life-extending treatments are available for treating patients with SCD, allogeneic hematopoietic stem cell transplantation (HSCT) is the only option as of yet. A major obstacle before HSCT to cure patients with SCD is the availability of donors. Matched sibling donors are available only for a small percentage of patients. To expand the donor pool, different contrasting approaches of allogeneic HSCT like T-cell replete and deplete have been tested. None of those tested approaches have been without the risk of GvHD and graft rejection. Other limitations such as transplantation-related infections and organ dysfunction caused by the harsh conditioning regimen need to be addressed on a priority basis. In this review, we will discuss available allogeneic HSCT approaches to cure SCD, as well as recent advancements to make the approach safer. The center of interest is using megadose T-cell-depleted bone marrow in conjugation with donor-derived CD8 veto T cells to achieve engraftment and tolerance across MHC barriers, under reduced intensity conditioning (RIC). This approach is in phase I/II clinical trial at the MD Anderson Cancer Centre and is open to patients with hemoglobinopathies.

The Impact of Graft CD3+ T-Cell Dose on the Outcome of T-Cell Replete Human Leukocyte Antigen-Mismatched Allogeneic Hematopoietic Peripheral Blood Stem Cells Transplantation.

Data on whether the graft CD3-positive (CD3+) T-cell dose in T-cell-replete human leukocyte antigen (HLA)-mismatched allogeneic hematopoietic peripheral blood stem cells transplantation (PBSCT) influences post-transplant outcomes are controversial. Using King Hussein Cancer Center (KHCC) Blood and Marrow Transplantation (BMT) Registry database, 52 adult subjects, receiving the first T-cell-replete HLA-mismatched allogeneic hematopoietic PBSCT for acute leukemias or myelodysplastic syndrome, were identified, from January 2017 to December 2020. The cutoff value of graft CD3+ T-cell dose was identified using the receiver operating characteristic (ROC) formula and Youden's analysis. Subjects were divided into two cohorts: cohort 1 with low CD3+ T-cell dose (n = 34) and cohort 2 with high CD3+ T-cell dose (n = 18). Correlative analyses were performed between CD3+ T-cell dose and the risk of graft-versus-host disease (GvHD), relapse, relapse-free survival (RFS), and overall survival (OS). P-values were two-sided and considered significant when P < 0.05. Subject covariates were displayed. Subject's characteristics were comparable, except for higher nucleated cells and more female donors in the high CD3+ T-cell cohort. The 100-day cumulative incidence of acute GvHD (aGvHD) was 45±7% and 3-year cumulative incidence of chronic GvHD (cGvHD) was 28±6.7%. There was no statistically significant difference between the two cohorts in aGvHD (50% vs. 39%, P = 0.4) or cGvHD (29% vs. 22%, P = 0.7). The 2-year cumulative incidence of relapse (CIR) was 67.5±16.3% for low compared with 14.3±6.8% for high CD3+ T-cell cohort (P = 0.018). Fifteen subjects relapsed and 24 have died, 13 due to disease relapse. There was an improvement in 2-year RFS (94% vs. 83%; P = 0.0022) and 2-year OS (91% vs. 89%; P = 0.025) in low CD3+ T-cell cohort compared with high CD3+ T-cell cohort. Graft CD3+ T-cell dose is the only significant risk factor for relapse (P = 002), and OS (P = 0.030) in univariate analysis which was maintained in multivariate for relapse (P = 0.003), but not for OS (P = 0.050). Our data suggest that high graft CD3+ T-cell dose is associated with lower risk of relapse, and might improve long-term survival, but has no influence on the risk of developing aGvHD or cGvHD.

T-Cell Replete Unrelated Cord Blood Transplant Give Superior Outcomes to Other Donor Sources in High Risk and Relapsed/Refractory Paediatric Myeloid Malignancy

Introduction: Outcomes of alternate donor haematopoietic stem cell transplant (SCT) in high-risk (HR) and relapsed or refractory (R/R) paediatric acute myeloid leukaemia (AML) and myelodysplastic syndrome (MDS) have been poor historically. Cord blood (CB) allows T-cell replete transplant, potentially enabling enhanced graft-versus-leukaemia (GVL) in patients with myeloid malignancies. We report the utility of T-replete CB (TRCB) transplant in high-risk paediatric myeloid malignancies in a large multi-centre national analysis, compared with patients transplanted with similar disease and at the same time using other donor sources. Methods: Data was collected from consecutive patients undergoing TRCB transplant for paediatric AML or MDS in 10 UK and Republic of Ireland paediatric bone marrow transplant centres between January 2014 and December 2021. The comparator group consisted of consecutive paediatric patients undergoing either a T-cell depleted (i.e. plus serotherapy) CB SCT or a transplant using any other cell source (matched sibling, matched/mismatched unrelated donor, or haplo-identical donor) at the same centres over the same period for the same indication. Information was gathered directly from the centre using an agreed data proforma and cross-checked for accuracy and completeness against the BSBMT/EBMT data submissions of each centre. Results: Data for 367 patients was analysed in this retrospective analysis which included 112 TRCB recipients and 255 patients in the comparator group. Median follow up was 2 years in the TRCB cohort and 4.5 years in the comparator group. All rates are quoted at 2 years. The median ages were 6.5 years in the TRCB group and 8.9 in the comparator, 91% of each group were AML. The TRCB cohort appeared to be a worse prognosis group with 51.4% of patients flow MRD positive at transplant compared with 26.1% in the comparator group (p <0.001), 46.4% had physician-defined refractory disease at transplant and 21.4% had relapsed following a previous SCT, compared with 8.6% refractory and 5.1% previous SCT in the comparator group (p<0.001 and p<0.001). Within the TRCB cohort Overall survival (OS) and Event Free Survival (EFS) were 64.7% and 64.1%, with EFS of 50% in those that were flow MRD positive at SCT and 79% for flow MRD negative patients (p= 0.009). EFS stratified by clinical disease status was 60.9% for those with primary refractory disease (n=29), 46.5% in those with relapsed refractory disease (n=23), 67% for those in high risk CR1 (n=38) and 79.6% for those in CR2 (n=22). For the 24 patients who had received a previous BMT, EFS was 69%. 67% TRCB recipients developed acute GVHD, of which 30% was grade 3-4, but the rates of chronic GVHD were very low at 5%. To allow for the imbalance in baseline characteristics, a multivariate analysis (MVA) was performed: the TRCB cohort had significantly improved EFS (0.57(0.35-0.91), p=0.019) and time to relapse (0.46(0.26-0.81), p=0.008) with some evidence of improved OS (0.65(0.39-1.07), p = 0.088). The effect appeared similar for MRD positives and negatives (interaction p=0.29 EFS and 0.67 relapse). Figures 1 and 2 highlight the strikingly superior EFS and relapse risk in the TRCB cohort for MRD positive patients in univariate analysis. Transplant-related mortality (TRM) was higher in the TRCB setting, 12% vs 7% (2.05 (1.05, 4.01), p=0.036) but rates of chronic GVHD were significantly lower with TRCB compared to other SCT types, 4.9% vs 19.4% (0.25(0.10, 0.62), p=0.003). Conclusion: This is the largest reported analysis of TRCB outcomes in HR paediatric myeloid malignancy, and we demonstrate excellent results, even in refractory disease. Our data show significantly superior outcomes for patients receiving TRCB compared with other transplant cell sources, owing to a lower relapse risk in the CB setting. This is likely to reflect enhanced GVL effects with TRCB compared with alternate donor sources requiring T-cell depletion. Despite higher TRM in the TRCB setting, when adjusted for the confounding variable of more MRD positive patients in this group, EFS and relapse are highly significant with a strong trend for improved OS. Our data suggests that CB transplant without serotherapy may be the optimal transplant option for children with HR and R/R AML/MDS, particularly with strategies to mitigate the higher TRM. This potential practice change warrants exploration in a large prospective randomised controlled trial. Figure 1View largeDownload PPTFigure 1View largeDownload PPT Close modal

Rapid Immune Reconstitution and Elevated Regulatory T Cell Frequencies in Patients Treated with Orca-T

BACKGROUND Immune reconstitution following myeloablative allogeneic hematopoietic stem cell transplant (MA-alloHSCT) is significantly delayed for T cell depleted allografts when compared to T-cell replete allografts, a feature that has been implicated in higher rates and grades of infection, less GVT, and worse overall survival. Orca-T is a high precision cell therapy currently being investigated for the treatment of certain hematological malignancies otherwise treated with MA-alloHSCT. The cellular drug products of Orca-T (HSPCs, Tregs, and Tcons) are administered at high purity, in controlled doses, and on an established schedule with the intent to reconstitute the blood and immune system while controlling GVHD. Here, we present data on the immune reconstitution in 100 adult patients who received Orca-T. METHODS In the context of an ongoing multicenter Phase Ib clinical trial of Orca-T in recipients with hematologic malignancies (NCT04013685), we performed longitudinal measurements (days -28, 28, 56, 100, 180, and 365 post-transplant) of immune reconstitution in the first 100 consecutive patients. With fresh whole blood, clinical 5-part leukocyte differentials were performed at clinical sites, and lymphocyte subset frequencies were measured by flow cytometry in a central lab. Principal component analysis (PCA) was performed to investigate potential associations with recipient sex (male vs. female) and donor relation (related vs. unrelated). RESULTS Longitudinal peripheral blood counts of platelets, WBCs, neutrophils, lymphocytes, monocytes, T cells, B cells, and NK cells are presented in Table 1. T cell and B cell counts were readily observed at days 28 and 56 respectively, and increased with each subsequent time point. Median NK cell levels were observed to be in the normal range at all post-transplant time points. CD4+ T cell and Treg cell counts exhibited similar post-transplant patterns with both being appreciably present at d28 and increasing with each subsequent time point. Strikingly, relative to the level measured in 75 corresponding PBSC donors, the Treg frequency among CD4+ T cells was significantly elevated at all time points post-transplant (Figure 1). Median CD8+ T cell counts increased for the first 6 months post-transplant and then plateaued in the normal range. Upon PCA, very few significant differences were observed in 2-group comparisons of recipient sex and donor relation. CONCLUSIONS Orca-T patients exhibit early immune reconstitution of each of the major leukocyte and lymphocyte subsets hypothesized to control relapse and infection. Concomitantly, elevated Treg frequencies were also observed. This feature of immune reconstitution profiles of Orca-T recipients may be correlated to the reduced occurrence and severity of acute and chronic GVHD in these patients (Meyer et al., EHA 2022, #S237). Similar immune reconstitution profiles were observed in patients of disparate sex and regardless of donor relation. Prospective comparisons of immune reconstitution between Orca-T and standard-of-care patients will be performed in our ongoing phase 3 clinical trial (NCT05316701). Figure 1View largeDownload PPTFigure 1View largeDownload PPT Close modal

HLA B-Leader Mismatch Is Associated with Poor Outcomes in NIMA/NIPA Mismatched Haploidentical Sibling Donor HCT

Background: Sibling haplo donors can be broadly categorized as non-inherited maternal (NIMA) or paternal (NIPA) antigen mismatched based on the non-shared haplotype with the recipient. Older studies with non-PTCy prophylaxis suggested a benefit of NIMA-mismatched over NIPA-mismatched donors, but the same has not been studied with PTCy prophylaxis, especially in the context of increasing recognition of the impact of specific loci HLA-mismatches in haplo HCT, such as the B-leader, which is a leader peptide that is preferentially bound by HLA-E, the ligand for natural killer (NK) receptor NKG2. Objective: To compare the outcomes of NIMA-vs NIPA-mismatched haplo sibling donors and specific loci HLA-mismatches in the setting of T-cell replete HCT with PTCy prophylaxis. Results: We included 57 patients: 29 were NIMA-mismatched and 28 were NIPA-mismatched. Median age at HCT (31 yrs vs 37 yrs, p=0.1) and donor age (32 yrs vs 41 yrs, p=0.1) were similar in both groups. Most received RIC (72% vs 68%, p=0.5), BM graft (79% vs 82%, p=0.8), had HCT-CI >3 (55% vs 54%, p=0.9) and low/intermediate DRI (62% vs 54%, p=0.4) and were ABO matched (65% vs 71%, p=0.8) with the donor. There was a significantly higher proportion of female-donor to male-recipients in the NIMA- than NIPA-mismatched group (55% vs 21%, p=0.005). Specific HLA-mismatches were similar in both groups: B-leader (52% vs 32%, p=0.1), DRB1 (96% each), DQB1 (90% vs 86%, p=0.5), DPB1 (76% vs 79%, p=0.9). The median follow-up was 38 vs 13 months. There were no graft failures, and the median time to engraftment was similar (18 vs 19 days, p=0.3). The cumulative incidence of grade II-IV aGVHD was 31% vs 58%, p=0.04; with no differences in grade III-IV aGVHD (10% vs 11%, p=0.9), cGVHD (11% vs 13%, p=0.9); NRM (28% vs 33%, p=0.9), relapse (21% vs 11%, p=0.4), or OS (54% vs 55%, p=0.8) in NIMA-vs NIPA-mismatched, respectively. In multivariate analysis, NIMA-mismatch (HR 0.1, 95% CI 0.02-0.6, p=0.01 in females) and HLA-A mismatch (HR 0.2, 95% CI 0.1-0.6, p=0.005) were associated with significantly lower risk of grade II-IV aGVHD, while age at HCT >50 yr was high risk for grade II-IV aGVHD (HR 2.7, 95% CI 1.1-6.9, p=0.04). No factor predicted grade III-IV aGVHD, cGVHD or relapse, likely related to a small number of events. B-leader mismatch was associated with high NRM (HR 3.8, 95% CI 1.04-13, p=0.04), poor PFS (HR 2.7, 95% CI 1.1-6.7, p=0.03), and a trend for lower OS (HR 2.4, 95% CI 0.9-6.3, p=0.06). High/very-high DRI was associated with high NRM (HR 4.4, 95% CI 1.5-13, p=0.008) and poor OS (HR 2.6, 95% CI 1-6.6, p=0.05). HCT-CI >3 (HR 2.9, 95% CI 0.9-8.8, p=0.05) was associated with poor OS. Neither NIMA-mismatch nor any other independent HLA-locus mismatches (except B-leader) had an impact on NRM, relapse, PFS, or OS. Conclusion: Among sibling haplo donors, a B-leader matched donor should be prioritized whenever possible. When multiple B-leader matched donors are available, considering the sample size limitations, our data suggest that a donor mismatched at A-locus (lower aGVHD) and/or a NIMA-mismatched donor (lower aGVHD in females) could be selected. Figure 1View largeDownload PPTFigure 1View largeDownload PPT Close modal

Improved Grfs Observed in a Multicenter Prospective Study of Tcrαβ- and CD45RA-Depleted Haploidentical Transplant in Children with Acute Leukemia

Objective: To test the hypothesis that TCRαβ- and CD45RA-depleted haploidentical hematopoietic stem cell transplantation (HSCT) with a reduced-intensity conditioning regimen and short-course graft-versus-host disease (GVHD) prophylaxis in children with refractory/relapse/high-risk acute leukemia (AL) could reduce the incidence of acute/chronic GVHD without compromising the graft versus leukemia effect, resulting in improved GVHD-free/relapse-free survival (GRFS). METHODS: The outcome of TCRαβ- and CD45RA-depleted haploidentical HSCT (TCD group) was compared with that of concurrent traditional haploidentical HSCT (control group) during the same time period. The proportion of cases in TCD group and control group was 1:2. The incidence of grade II-IV aGVHD, cGVHD, transplant-related mortality (TRM), CMV and EBV reactivation rate, leukemia relapse, overall survival (OS), event-free survival (EFS) were analyzed. GRFS was defined as patients survived without relapse, grade II-IV aGVHD, or moderate to severe cGVHD. RESULTS: From November 2020 to May 2022, 28 patients were enrolled in the TCD group and 56 patients in the control group from three centers in China with median follow-up time of 8 months（range, 2.5-20）and 7.5 months（range, 0.5-20）, respectively. There were no statistically significant differences in age, gender, type of leukemia, pretransplant disease status, degree of HLA mismatch, and number of infused CD34+ cells between the two groups. The TCD group received a reduced-intensity conditioning with TBI 3Gy, -8D; cyclophosphamide 60mg/kg/D, -7D; fludarabine 40mg/m2/D, -7 to -4D; busulfan 3.2-4.8mg/kg/D, -5 to -4D; and melphalan 70mg/m2/D, -3 to -2D. GVHD prophylaxis lasted only 1 month with mycophenolate mofetil from -1D to +30D. The control group received a conventional T-cell replete haploidentical HSCT with myeloablative conditioning and GVHD prophylaxis. The median time of neutrophil and platelet engraftment was 10 days (range, 9-13) and 12 days (range, 9-56) respectively in the TCD group, which were both faster than the control group with 13 days (range, 8-20) and 18 days (range, 8-74) respectively (P < 0.05). The incidence of graft failure was higher in TCD group (5/28, 1 primary failure and 4 secondary failures) than in control group (2/56, all primary failures, P = 0.013). The incidence of grade II-IV aGVHD (22% vs 42.6%, P = 0.071) and cGVHD (10.0% vs 42.0%，P=0.010) were lower in the TCD group than the control group. None of the patients in the TCD group developed moderate or severe cGVHD or TRM. TCD group also have lower incidence of CMV or EBV reactivation and hemorrhagic cystitis compared to the control group (21.4% vs 49.1%, 18.5% vs 46.3%, and 10.7% vs 39.3%, all P<0.05). The relapse rates was comparable between the two groups (4/28 versus 6/56; P = 0.725). One patient died in the TCD group (who received a salvage haploidentical transplantation after graft failure, relapsed again half a year later, and then died of severe hemorrhagic cystitis after third HSCT). Seven (7/56) patients died of TRM in the control group. The 1-year OS (100% vs 85.8%±5.2%) and EFS (72.4%±9.0% vs 68.0%±8.3%) were similar between the two groups (P > 0.050), but the GRFS of TCD group was significantly better than the control group (63.3%±10.1% vs 35.3%±8.5%，P=0.036). CONCLUSIONS: TCRαβ- and CD45RA-depleted HSCT engrafted faster with very low incidences of a/cGVHD，virus reactivation , and TRM. There was no apparent increased risk of relapse, resulting in an improved GRFS. Graft failure remains a problem but all patients could be successfully regrafted without additional TRM, in part because their general status remained relatively well after their initial reduced-intensity conditioning. Figure 1View largeDownload PPTFigure 1View largeDownload PPT Close modal

Allogeneic Blood or Marrow Transplantation (alloBMT) Using Haploidentical Grandchildren Donors and Post-Transplant Cyclophosphamide (PTCy) -Based Gvhd Prophylaxis

Background: High dose PT-Cy allows the safe and effective use of haploidentical relatives as an allograft source. This platform increased the pool of related donors to include haploidentical siblings, parents, and children; more recently, second-and third-degree relatives have also been shown to be safe allograft donors. There is no consensus on the ideal donor; our standard practice is to prioritize young relatives such as siblings, children, or rarely parents- is safe and feasible. AlloBMT using nonmyeloablative (NMA) conditioning is safe and feasible in select patients aged 70 and above, a large group with hematologic malignancies. An increasing number of older patients have been treated with allogeneic blood or marrow transplantation (alloBMT) using related haploidentical donors. Older patients are more likely to have older siblings and children, and recent reports associated older donor age with worse outcomes. Therefore, we report the safety and utility of grandchildren (GC) as haploidentical donors and compare outcomes to patients with children donors. Methods: We reviewed records of patients at Johns Hopkins Hospital who received T-cell replete related allogeneic haploidentical donor blood or marrow grafts. We identified eight hundred and seven consecutive adults (≥18 years) between May 1, 2016, to October 1, 2021. Patients with aggressive myeloid and lymphoid malignancies were included. Only the first transplant was included for patients who received more than one transplant. All patients received NMA conditioning consisting of fludarabine, cyclophosphamide, and total body irradiation at 200 or 400 cGy. GVHD prophylaxis consisted of PT-Cy on days 3 and 4, followed by mycophenolate mofetil and either tacrolimus or sirolimus starting on day 5. Statistical analysis was performed using t-test, Wilcoxon rank sum test, or Chi-square test. Overall survival (OS), progression-free survival (PFS), relapse and non-relapse mortality (NRM) were estimated using Kaplan-Meier methods. Additionally, propensity score matching analysis (PSMA) for patient's age, BMT year, and graft source was performed. Results: Analysis was done on four hundred and sixty patients who received grafts from children donors and twenty-nine grandchildren donors. The median follow-up for patients was 28.8 (range 0.2 - 70.8) and 30 (range 0.8-50.4) months in children and GC, respectively. The most common diagnosis in both groups was acute leukemia compromising about a third of the patients, followed by myelodysplastic syndrome/ myeloproliferative disorders and Non-Hodgkin's (Table 1). Median age of patients in the GC group was 11 years older, 73 years (range 57-78) compared to 62 years (range 36 - 78) in the children group. The median age of children donors was 30 years (range 12-52), and 21 years (range 14-34) in the GC group. Patients in the GC group had higher comorbidities compared to patients in the children group, with a median hematopoietic cell transplantation comorbidity index (HCT-CI) of 2 (range 1-5) and 1 (range 0-7) respectively, (P=0.001). There was almost twice as many patients with HCT-CI of ≥3 in the GC compared to the children group, 38% and 21% respectively. The use of marrow vs PBSC as the graft source was not significantly different between the two groups (table 1). The two-year cumulative incidence of NRM was statistically significant higher for the GC group at 27% compared to 12% in the children group (P= 0.02). Since NRM is more likely in older patients, and older patients were more likely to be in GC group, we performed a PSMA. When matched for age, BMT-year and HCT-CI, PSMA did not show significant differences in NRM (HR 1.49, 95% 0.7-3.4, P=0.35). Similarly, OS, relapse and PFS did not show differences before or after PSMA. The two-year OS was 58% and 64% for children and GC, respectively (HR 0.82, 95% CI 0.36-1.88, P=0.63). Two-year relapse cumulative incidence was 24% and 7% for children and grandchildren, respectively (HR 0.45, 95% CI 0.15-1.34, P=0.15). Two-year PFS was comparable 52% and 56% for children and GC groups, respectively (HR 0.93, 95% CI 0.5-1.73, P=0.82) (fig. 1). Conclusions: Despite older age and comorbidities, the outcomes of alloBMT from grandchildren were at least as good as those from children, with 2-year OS of 64% and 58%, respectively. Choosing grandchildren as donors was associated with promising outcomes and should be examined further. Figure 1View largeDownload PPTFigure 1View largeDownload PPT Close modal