Haploidentical Hematopoietic Cell Transplantation Research Articles

Haploidentical hematopoietic cell transplantation with or without an unrelated cord blood unit for adult acute myeloid leukemia: a multicenter, randomized, open-label, phase 3 trial

sCoinfusion of unrelated cord blood (UCB) units in haploidentical hematopoietic cell transplantation (haplo-HCT) (haplo-cord HCT) for hematopoietic malignancies showed promising results in previous reports, but the efficiency of haplo-cord HCT in acute myeloid leukemia (AML) still lacks sufficient evidence. This multicenter, randomized, phase 3 trial (ClinicalTrials.gov NCT03719534) aimed to assess the efficacy and safety of haplo-cord HCT in AML patients. A total of 268 eligible patients aged 18–60 years, diagnosed with measurable residual disease in AML (excluding acute promyelocytic leukemia), with available haploidentical donors and suitable for allotransplantation, were randomly allocated (1:1) to receive haplo-cord HCT (n = 134) or haplo-HCT (n = 134). The 3-year overall survival (OS) was the primary endpoint in this study. Overall median follow-up was 36.50 months (IQR 24.75–46.50). The 3-year OS of Haplo-cord HCT group was better than haplo-HCT group (80.5%, 95% confidence interval [CI]: 73.7–87.9 vs. 67.8% 95% CI 60.0–76.5, p = 0.013). Favorable progression-free survival (70.3%, 95% CI 62.6–78.8 vs. 57.6%, 95% CI 49.6–67.0, p = 0.012) and cumulative incidence of relapse (12.1%, 95% CI 12.0–12.2 vs. 30.3%, 95% CI 30.1–30.4, p = 0.024) were observed in haplo-cord HCT group. Grade 3–4 adverse events (AEs) within two years posttransplantation in the two groups were similar. Haplo-cord HCT patients exhibited a faster cumulative incidence of neutrophil recovery (p = 0.026) and increased T-cell reconstitution in the early period posttransplantation. Haplo-cord HCT can improve OS in AML patients without excessive AEs, which may exert additional benefits for recipients of haplo-HCT.

Postmortem pathologic findings in dogs that underwent total body irradiation and hematopoietic cell transplant: A case series of five dogs with B-cell multicentric lymphoma.

Alternative therapies that can help achieve complete remission in dogs with lymphoma include total body irradiation and hematopoietic cell transplant, though there are few reports describing successes and pathologic sequelae of these procedures. During a 10-year period, 94 dogs with multicentric lymphoma received a hematopoietic cell transplant following total body irradiation at North Carolina State University College of Veterinary Medicine. Seven of these 94 dogs (7%) died prior to discharge, five (5%) of which presented for postmortem examination. Of these dogs, four received an autologous hematopoietic cell transplant, while one received a haploidentical allogeneic hematopoietic cell transplant. All five dogs had bone marrow depletion with all hematopoietic lines affected. Three had systemic candidiasis, while two had bacterial infections. To the authors' knowledge, this is the first report to document pathologic findings and development of systemic mycoses in dogs post total-body irradiation therapy and hematopoietic cell transplant.

The state of the art in the treatment of severe aplastic anemia: immunotherapy and hematopoietic cell transplantation in children and adults.

Acquired aplastic anemia (AA) is an immune-mediated bone marrow (BM) failure where marrow disruption is driven by a cytotoxic T-cell-mediated autoimmune attack against hematopoietic stem cells. The key diagnostic challenge in children, but also in adults, is to exclude the possible underlying congenital condition and myelodysplasia. The choice of treatment options, either allogeneic hematopoietic cell transplantation (alloHCT) or immunosuppressive therapy (IST), depends on the patient's age, comorbidities, and access to a suitable donor and effective therapeutic agents. Since 2022, horse antithymocyte globulin (hATG) has been available again in Europe and is recommended for IST as a more effective option than rabbit ATG. Therefore, an update on immunosuppressive strategies is warranted. Despite an improved response to the new immunosuppression protocols with hATG and eltrombopag, some patients are not cured or remain at risk of aplasia relapse or clonal evolution and require postponed alloHCT. The transplantation field has evolved, becoming safer and more accessible. Upfront alloHCT from unrelated donors is becoming a tempting option. With the use of posttransplant cyclophosphamide, haploidentical HCT offers promising outcomes also in AA. In this paper, we present the state of the art in the management of severe AA for pediatric and adult patients based on the available guidelines and recently published studies.

Sigle Agent of Posttransplant Cyclophosphamide Without Calcineurin Inhibitor Controls Severity of Experimental Chronic GVHD.

Chronic graft-versus-host disease (GVHD) is a major cause of late death and morbidity following allogeneic hematopoietic cell transplantation (HCT), but its pathogenesis remains unclear. Recently, haplo-identical HCT with post-transplant cyclophosphamide (Haplo-HCT with PTCY) was found to achieve a low incidence rate of acute GVHD and chronic GVHD. However, while the pathogenesis of acute GVHD following Haplo-HCT with PTCY has been well investigated, that of chronic GVHD remains to be elucidated, especially in HLA-matched HCT with PTCY. Based on its safety profile, PTCY is currently applied for the human leucocyte antigen (HLA)-matched HCT setting. Here, we investigated the mechanisms of chronic GVHD following HLA-matched HCT with PTCY using a well-defined mouse chronic GVHD model. PTCY attenuated clinical and pathological chronic GVHD by suppressing effector T-cells and preserving regulatory T-cells compared with a control group. Additionally, we demonstrated that cyclosporine A (CsA) did not show any additional positive effects on attenuation of GVHD in PTCY-treated recipients. These results suggest that monotherapy with PTCY without CsA could be a promising strategy for the prevention of chronic GVHD following HLA-matched HCT.

Immunosuppression-Free Status at 1 Year after Haploidentical Hematopoietic Cell Transplantation with Post-Transplantation Cyclophosphamide

The development of chronic graft-versus-host disease (GVHD) in 1-year survivors after matched related or unrelated hematopoietic cell transplantation was shown to be associated with higher nonrelapse mortality (NRM) and worse overall survival (OS). The impact of chronic GVHD requiring immunosuppression (IS) for recipients of haploidentical transplantation (HIDT) with post-transplantation cyclophosphamide (PTCy) who have survived to 1 year post-transplantation has not been studied previously and was investigated for this analysis. A total of 322 adult patients who underwent HIDT at our center were included in this study. The effect of IS-free status on post-transplantation outcomes was assessed. The median follow-up for survivors was 63.9 months (range, 18.3 to 165 months). A total of 163 patients (65%) were IS-free at 1 year post-HIDT. Baseline characteristics of this group were similar to those of patients still requiring IS, except for higher percentages of female donor-male recipient pairs (28% versus 15%; P =.03) and female donors (48% versus 30%; P =.008). Logistic regression to identify patients more likely to be on IS at 1 year post-HIDT identified the use of a female donor as a significant risk factor (odds ratio, 2.11; P = .009). In a Cox regression analysis, patients requiring IS at 1 year post-transplantation had higher NRM (hazard ratio [HR], 4.18; 95% confidence interval [CI], 1.80 to 6.72; P < .001) and showed a trend toward worse disease-free survival (DFS) (HR, 1.59; 95% CI, .95 to 2.66; P =.08), with no impact on OS (HR, 1.44; 95% CI, .90 to 2.31; P = .13) or relapse (HR, .77; 95% CI, .37 to 1.61; P = .49). These results indicate that use of a female donor is a significant risk factor for requiring IS at 1 year post-HIDT. Additionally, chronic GVHD requiring IS at 1-year post-HIDT no significant effect on relapse but is associated with higher NRM and a trend toward worse DFS.

Pretransplantation predictors of survival in nonremission acute myeloid leukemia treated with haploidentical transplantation using steroid-based GVHD prophylaxis.

Haploidentical hematopoietic cell transplantation (HCT) using glucocorticoids for acute graft-versus-host disease prophylaxis (GC-haplo) may become a curative treatment option for nonremission acute myeloid leukemia (AML). This retrospective study aimed to identify pre-HCT predictors of survival in a cohort of 97 nonremission AML treated with GC-haplo in Hyogo Medical University Hospital between 2010 and 2020. Relapse and primary induction failure included in 70 (72%) and 27 (28%) patients, respectively. Sixty-one patients (63%) had undergone previous HCT. Multivariate analysis revealed that ≤ 6 months' duration between first complete remission (CR1) and first relapse (Rel1) (CR1-Rel1 interval) (hazard ratio 2.11, 95% confidence interval [CI] 1.15-3.89, P = 0.016) and serum albumin before starting the conditioning treatment of ≤ 3.5 g/dL (hazard ratio 1.80, 95%CI 1.09-2.96, P = 0.022) as risk factors for overall survival. Among three groups categorized according to serum albumin and CR1-Rel1 interval, the best 3-year overall survival was observed in patients with albumin > 3.5 g/dL and CR1-Rel1 interval > 6 months or primary induction failure (50.2%, 95%CI 28.9%-68.3%, P < 0.001), revealing that survival could be predicted using albumin and past CR duration in patients with very high-risk AML not in remission before GC-haplo.

Dual T cell depletion for graft versus host disease prevention in peripheral blood haploidentical hematopoietic cell transplantation for adults with hematological malignancies.

The ideal immunosuppressive agents to complement post-transplant cyclophosphamide (PTCy) in PBSC-based haploidentical hematopoietic cell transplantation (haplo-HCT) remain debated. This study looks at our experience with ATG-PTCy-Cyclosporine (CsA) prophylaxis in PB haplo-HCT since 2015. Between October 2015 and December 2021, 157 adults underwent haploidentical hematopoietic cell transplantation (haplo-HCT) using a GVHD prophylaxis regimen comprising rabbit-ATG, PTCy, and CsA. Among these patients, 76.4% received a total ATG dose of 4.5 mg/kg, and 23.5% received 2 mg/kg. T-cell replete peripheral blood stem cell (PBSC) grafts were infused on day 0. The study reported a median follow-up of 32 months (range 0.3-61.64) for survivors. The cumulative incidence of grade II-IV and grade III-IV acute GVHD at day +100 was 26.3% and 9.5%, respectively. Moderate/severe chronic GVHD at 1 year was 19.9%. The 2-year overall survival (OS) was 49.4%, with a relapse-free survival (RFS) of 44.6%. In multivariate analysis, older patients, and those with high/very-high disease risk indices (DRI) were at higher risk for worse OS and higher non-relapse mortality (NRM). The study confirms that using PTCy and ATG (4.5 mg/kg), alongside CsA is safe and effective in preventing GVHD when using peripheral blood as the stem cell source in haploidentical hematopoietic cell transplantation (haplo-HCT).

Human herpesvirus type 6 reactivation after haploidentical hematopoietic cell transplantation with post-transplant cyclophosphamide and antithymocyte globulin: risk factors and clinical impact

Human herpesvirus type 6 (HHV6) reactivation after haploidentical hematopoietic cell transplantation (HCT) with post-transplant cyclophosphamide (PT-Cy) has been scarcely studied, especially when antithymocyte globulin (ATG) is added to the graft-versus-host disease (GvHD) prophylaxis. We conducted a retrospective cohort study in 100 consecutive patients receiving haploidentical HCT with PT-Cy. We systematically monitored HHV6 DNA loads in blood samples on a weekly basis using quantitative PCR until day +100. The 100-day cumulative incidence of HHV6 reactivation was 54%. Clinically significant HHV6 infections were rare (7%), associated with higher HHV6 DNA loads, and had favorable outcomes after antiviral therapy. The main risk factor for HHV6 reactivation was a low absolute lymphocyte count (ALC) &lt; 290/µL on day +30 (68% versus 40%, p = 0.003). Adding ATG to PT-Cy did not increase the incidence of HHV6 reactivation (52% with ATG versus 79% without ATG, p = 0.12). Patients experiencing HHV6 reactivation demonstrated delayed platelet recovery (HR 1.81, 95% CI 1.07-3.05, p = 0.026), higher risk of acute grade II-IV GvHD (39% versus 9%, p &lt; 0.001) but similar overall survival and non-relapse mortality to the other patients. In conclusion, our findings endorse the safety of combining ATG and PT-Cy in terms of the risk of HHV6 reactivation and infection in patients undergoing haploidentical HCT. Patients with a low ALC on day +30 face a higher risk of HHV6 reactivation and may require careful monitoring.

Abatacept and Ptcy with Cyclosporine or Sirolimus As Gvhd Prophylaxis in Haploidentical HCT: Understanding the Immunobiology in Improving the Outcome.

Abatacept and Ptcy with Cyclosporine or Sirolimus As Gvhd Prophylaxis in Haploidentical HCT: Understanding the Immunobiology in Improving the Outcome.

Optimal Rabbit Antithymocyte Pharmacokinetics (PK) Is Associated with Improved Disease-Free Survival (DFS) in TCR-Αβ/CD19-Depleted Pediatric Haploidentical Hematopoietic Cell Transplantation for Hematologic Malignancies

Optimal Rabbit Antithymocyte Pharmacokinetics (PK) Is Associated with Improved Disease-Free Survival (DFS) in TCR-Αβ/CD19-Depleted Pediatric Haploidentical Hematopoietic Cell Transplantation for Hematologic Malignancies

Tcrαβ-Depleted Haploidentical Hematopoietic Cell Transplantation for Pediatric Patients with Severe Aplastic Anemia

Tcrαβ-Depleted Haploidentical Hematopoietic Cell Transplantation for Pediatric Patients with Severe Aplastic Anemia

Early Immune Reconstitution Is Similar in Patients with and without Acute GvHD Undergoing Haploidentical HCT with Post-Transplant Cyclophosphamide As Gvhd Prophylaxis.

Early Immune Reconstitution Is Similar in Patients with and without Acute GvHD Undergoing Haploidentical HCT with Post-Transplant Cyclophosphamide As Gvhd Prophylaxis.

Twenty years in the making: tolerance in a living-related kidney transplant recipient.

Kidney transplant recipients require lifelong immunosuppression to prevent graft rejection. However, immunosuppression is associated with adverse effects. A minority of kidney transplant recipients can be weaned off immunosuppression and maintain theirgraft function, a situationreferred to as "functional or operational tolerance". We describe a case of a 70-year-old man who received a haploidentical hematopoietic cell transplant for lymphoma 22years before receiving a kidney transplant from the same donor and was weaned off all immunosuppression by four months post-transplant. Tolerance was present, and there has been no graft rejection or graft vs. host disease. This case demonstrates successful long-term hematopoietic chimerism and functional tolerance after receiving a kidney transplant from the same donor.

Outcomes with HLA-matched unrelated donor versus haploidentical hematopoietic cell transplantation

We investigated the outcomes after adult haploidentical (haplo) and matched unrelated donor (MUD) hematopoietic cell transplantation (HCT) in a single-center study (n = 452) including 276 MUD and 176 haplo transplants. Myeloablative (37%) and reduced-intensity conditioning (63%) were performed. Graft sources included peripheral blood (50%) and bone marrow (50%). GVHD prophylaxis included tacrolimus/methotrexate (53%) and post-transplant cyclophosphamide-based (47%). In MUD versus haplo HCT recipients, a similar incidence of neutrophil engraftment (18 vs 17 days, p = 0.895), grade II-IV acute GVHD (51% vs 50%, p = 0.773), relapse (26% vs 23%, p = 0.578), non-relapse mortality (22% vs 23%, p = 0.817), 1-year disease-free survival (62% vs 63%. p = 0.921), and 1-year overall survival (73% vs 74%, p = 0.744) were observed. Earlier platelet engraftment (22 vs 27 days, p < 0.001) and higher chronic GVHD (45% vs 35%, p = 0.040) were noted in MUD as compared to haplo HCT. Allogeneic transplantation should be done promptly whenever indicated, utilizing either matched unrelated or haploidentical donors.

Genetically corrected RAG2-SCID human hematopoietic stem cells restore V(D)J-recombinase and rescue lymphoid deficiency

AbstractRecombination-activating genes (RAG1 and RAG2) are critical for lymphoid cell development and function by initiating the variable (V), diversity (D), and joining (J) (V(D)J)-recombination process to generate polyclonal lymphocytes with broad antigen specificity. The clinical manifestations of defective RAG1/2 genes range from immune dysregulation to severe combined immunodeficiencies (SCIDs), causing life-threatening infections and death early in life without hematopoietic cell transplantation (HCT). Despite improvements, haploidentical HCT without myeloablative conditioning carries a high risk of graft failure and incomplete immune reconstitution. The RAG complex is only expressed during the G0-G1 phase of the cell cycle in the early stages of T- and B-cell development, underscoring that a direct gene correction might capture the precise temporal expression of the endogenous gene. Here, we report a feasibility study using the CRISPR/Cas9-based “universal gene-correction” approach for the RAG2 locus in human hematopoietic stem/progenitor cells (HSPCs) from healthy donors and RAG2-SCID patient. V(D)J-recombinase activity was restored after gene correction of RAG2-SCID-derived HSPCs, resulting in the development of T-cell receptor (TCR) αβ and γδ CD3+ cells and single-positive CD4+ and CD8+ lymphocytes. TCR repertoire analysis indicated a normal distribution of CDR3 length and preserved usage of the distal TRAV genes. We confirmed the in vivo rescue of B-cell development with normal immunoglobulin M surface expression and a significant decrease in CD56bright natural killer cells. Together, we provide specificity, toxicity, and efficacy data supporting the development of a gene-correction therapy to benefit RAG2-deficient patients.

Low- versus standard-dose post-transplant cyclophosphamide as GVHD prophylaxis for haploidentical transplantation.

Haploidentical haematopoietic cell transplantation (haplo-HCT) using post-transplant cyclophosphamide (PTCY) as graft-versus-host disease (GVHD) prophylaxis is the standard of care for various haematological malignancies. The original PTCY dose after haplo-HCT was 100 mg/kg, but no dose-finding studies have been performed to identify the optimal dose. We performed a retrospective analysis to compare standard-dose PTCY (100 mg/kg) with reduced-dose PTCY (80 mg/kg): 969 in the standard-dose group and 538 in the reduced-dose group. As there was a significant difference between the two groups regarding patient and transplant characteristics, we performed propensity score (PS) matching. After PS matching, 425 patients in each group were included. The probabilities of 2-year OS were 55.9% in the standard-dose group and 47.0% in the reduced-dose group (p = 0.36). The cumulative incidences of 2-year non-relapse mortality were 21.3% in the standard-dose group and 20.5% in the reduced-dose group (p = 0.55). There was no significant difference in the incidence of acute (grade II-IV 29.2% [95% CI, 24.9-33.6] vs. 25.3% [95% CI, 21.3-29.6]; grade III-IV 7.3% [95% CI, 5.1-10.0] vs. 6.6% [95% CI, 4.5-9.3]) or chronic GVHD. In conclusion, reduced- and standard-dose PTCY were comparable in terms of major clinical outcomes.

High Exposure of Rabbit Anti-Thymocyte Globulin (ATG) Is Strongly Associated with Inferior DFS in Pediatric Patients with Malignancy Undergoing Alpha-Beta T-Cell Depleted Haploidentical HCT

The PTCTC ONC1401 trial reported a 75% 2-year disease-free survival (DFS) for pediatric patients with acute leukemia or MDS undergoing AB-TCR/CD19 depleted (AB-TCD) haploidentical HCT. Patients ≥10 years had significantly worse DFS. Conditioning for AB-TCD HCT typically includes rATG (Thymoglobulin®) 3 mg/kg/day on days -12 to -10. Models of rATG pharmacokinetics (PK) show slower clearance in older children. We hypothesized worse DFS seen in older patients may be due to excessive in vivo T-cell depletion by residual rATG post HCT. Patients undergoing first AB-TCD haploidentical HCT with rATG as the sole serotherapy agent for treatment of malignancy from Dec 2015 to Jan 2023 were included. Patients were treated on PTCTC ONC1401 or institutional prospective trials of AB-TCD. Minimal residual disease (MRD) was determined by the best-available method (multi-parameter flow or next-generation sequencing) for each patient. Predicted pre- and post-HCT AUC of rATG (in AU*day/mL) were retrospectively determined using the software platform InsightRx© (InsightRx, Inc., San Francisco, CA) and a validated PK model for rATG clearance. Quadratic regression was used to identify optimal target windows of rATG exposure for cumulative incidence and Kaplan-Meier estimations. Multivariate analysis (MVA) Cox regression models were built using all covariates with a univariate p-value &amp;lt;0.2. The dataset included 134 patients ( Table 1); median (range) follow-up of survivors was 3.4 years (0.5-7.6). The median age at HCT was 12.3 years (0.4-27.4), and median donor age was 32 years (5-61). The median infused cell doses for CD34 and AB-T-cells were 15.2 (2.5-45.8) x10^6/kg and 7.0 (0.1-27.6) x10^4/kg. The 100-day incidence of rejection was 11.3% (5.8-16.8) with a 3-year EFS of 59% (50.2-67.8). The 3-year incidence of non-relapse mortality (NRM) and relapse were 13.8% (6.9-20.7) and 21.4% (13.8-29). The 100-day incidence of grades 2-4 and 3-4 aGVHD were 24.4% (16.2-32.6) and 8.5% (3.4-13.6), while 3-year incidence of cGVHD was 16.7% (9.1-24.3). The 3-year DFS and OS were 67.6% (59.2-76) and 73.8% (64-83.6). Increased 3-year NRM was seen in patients ≥10 years: 19.9% (10.6-31.4) vs. 5.6% (0.1-13.4) ( p=0.03); in those with sibling vs. parent donors: 27.3% (12.4-42.2) vs. 8.5% (1.6-15.4) (p=0.008); and CMV mismatched donors: 25.5% (9.1-41.3) vs. 10.4% (3.3-17.5) ( p=0.03). There was no difference in relapse between MRD-techniques, so these were combined for subsequent analyses. Lower 3-year relapse was seen in patients who were MRD-negative: 12.6% (5.5-19.7) vs. 45.7% (26.7-64.7) ( p&amp;lt;0.001); and who received targeted small-molecule therapy post-HCT: 0% (0-19.8) vs. 24.1% (15.5-32.7) ( p=0.04). The median predicted pre-HCT AUC of rATG was 63.7 AU*day/mL (16.4-109). A pre-HCT exposure of ≥40 AU*day/mL was associated with decreased rejection: 8.1% (3-13.2) vs. 27.3% (8.8-45.9; p=0.008). A pre-HCT exposure of &amp;lt;80 AU*day/mL was associated with lower 3-year TRM: 8% (1.7-14.3) vs. 33.4% (14.8-52; p&amp;lt;0.001). The 3-year EFS for patients with a pre-HCT AUC of 40-79.9 AU*day/mL was 69.7% (58.7-80.7) vs. 45.4% (31.9-58.9) for those not in goal range ( p=0.004). The median post-HCT AUC of rATG was 9.5 AU*day/mL (1-42.5). There was no different in grade 2-4 (p=0.61) or grade 3-4 (p=0.25) aGVHD or cGVHD (p=0.9) between those with low (&amp;lt;13 AU*day/mL) vs. high (≥13 AU*day/mL) exposure. A low post-HCT AUC was associated with both lower 3-year NRM: 7.2% (0.9-13.5) vs. 28.1% (11.6-44.6) ( p=0.002), and lower 3-year relapse incidence: 15.5% (7-23.7) vs. 34.3% (18.6-50) ( p=0.01). In MRD-negative patients, low vs. high post-HCT rATG AUC was associated with a 3-year DFS of 81.2% (71-91.4) vs. 60.2% (42-78.4) ( p=0.03); in MRD-positive patients, low vs. high post-HCT rATG AUC was associated with a 3-year DFS of 69.3% (47.9-90.7) vs. 17.9% (0.1-39.5) ( p&amp;lt;0.001). MVA showed that high post-HCT rATG exposure, MRD-positivity, and CMV-mismatched donors were associated with worse 3-year DFS ( Table 2). We identified optimal windows for rATG exposure - pre-HCT of 40-79.9 AU*day/mL, post-HCT &amp;lt;13 AU*day/mL - associated with lower rates of rejection, NRM, relapse, and improved DFS. Validation with prospective drug levels and an independent cohort would strengthen these conclusions. Our data indicates that model-based dosing of rATG to target pre- and post-HCT exposure may be superior to weight-based dosing in patients undergoing AB-TCD HCT.

Haploidentical Hematopoietic Cell Transplant with Post-Transplant Cyclophosphamide Expedites Donor-Derived Immune Reconstitution in a Pediatric Severe Aplastic Anemia Cohort

Severe aplastic anemia (SAA) is a life-threatening, idiopathic process involving the immune-mediated destruction of hematopoietic stem cells. Treatment involves immunosuppressive therapy (IST) and/or allogeneic hematopoietic cell transplantation (HCT). The latter has recently been optimized with use of a post-transplant cyclophosphamide (PTCy) based graft-versus-host disease (GvHD) platform, permitting successful HCT with only half-HLA-matched haploidentical donors. In pediatrics, this platform results in &amp;gt;90% overall survival with low rates of GvHD and graft failure. However, reports on donor chimerism and immune reconstitution are limited. We hypothesized that a PTCy platform would expedite CD3 donor engraftment and CD4 T cell recovery. In a phase III clinical trial, we treated three cohorts of pediatric (age &amp;lt;/=25 years) patients with SAA requiring alloHCT: MUD, MSD, and HAPLO. The MUD cohort included n=15 recipients of 7-8/8 HLA-matched unrelated donor grafts (n=5 7/8, n=10 8/8) with median age 14 years (range 2-17 years), following cyclophosphamide (Cy) 50 mg/kg, fludarabine (Flu) 200 mg/m 2, rabbit anti-thymocyte globulin (rATG) 9 mg/kg total dose rabbit and low dose total body irradiation (TBI) at 200 cGy. The MSD cohort included n=9 recipients of 8/8 HLA-matched sibling donor grafts with median age 15 years (range 12-24 years), following Cy 200 mg/kg and 9 mg/kg rATG. The HAPLO cohort included n=4 recipients of 4/8 HLA-matched related donor grafts with median age 8.5 years (range 2-21 years) following Cy 29 mg/kg, Flu 150 mg/m 2, 9 mg/kg rATG, and low dose TBI at 200 cGy. GvHD prophylaxis consisted of 30 days of mycophenolate mofetil, and 100 days of a calcineurin inhibitor (followed by an 8-10 week taper), with the HAPLO cohort additionally receiving post-transplant Cy (PTCy) 50 mg/kg/day on days +3 and +4. Peripheral blood lymphocyte counts and peripheral blood and bone marrow donor chimerism were evaluated on days +100, +180 and +365. Recipient characteristics were largely equivalent between cohorts, with 43% receiving IST prior to HCT. Clonality was overrepresented in the HAPLO cohort (2 of 4, 1 with monosomy 7 myelodysplastic syndrome and 1 with a large PNH clone), with only 2 of 15 in the MUD and none in the MSD cohorts. Active controlled infections at the time of HCT were additionally overrepresented in the HAPLO cohort, with disseminated pseudomonas in 1. The MUD cohort had 1 with Rhizopus invasive sinusitis (none in the MSD cohort). Achievement of neutrophil engraftment was statistically significantly delayed in the HAPLO cohort at a median of 17 days compared to 12 for MSD and 14 for MUD, p=0.004), however there were no episodes of primary or secondary graft failure. With only a single late death from intracranial hemorrhage in the MUD cohort, OS was equivalent at 2 years (100% in MSD and HAPLO cohorts, 93.3% in MUD). GvHD rates were low with only 1 (MUD) experiencing grade II acute GvHD, and 1 (MUD) experiencing mild chronic GvHD. Immune reconstitution varied by cohort with statistically significantly greater CD3 peripheral blood donor chimerism (p&amp;lt;0.001) as well as CD4 (p=0.04) and CD8 (p=0.03) T cell counts over time for the HAPLO recipients (CD3 chimerism in Fig 1, CD4 count in Fig 2; 2-way ANOVA fixed effects model). Considering a CD4 &amp;gt;200 cell/uL as clinically meaningful, we assessed the proportion of each cohort achieving this milestone at each timepoint. While each cohort had an increase in proportion achieving CD4&amp;gt;200 over time, the HAPLO cohort reached 50% with CD4 &amp;gt;200 at day +100, compared to 11% MUD and 0% MSD (p=0.09). At day +180, the proportion with CD4 &amp;gt;200 were 36% MUD, 25% MSD and 75% HAPLO (1 yr: 90% MUD, 100% MSD and HAPLO). Donor availability remains a challenge to successful transplant for patients with SAA, and haploidentical matches overcome donor limited accessibility. PTCy as GvHD prophylaxis is associated with low incidences of graft failure and severe GvHD. While PTCy might be anticipated to inhibit donor T cells and immune reconstitution, our data, albeit limited by small cohorts, demonstrates superior and more efficient CD3 donor engraftment and CD4 T cell count recovery following HAPLO HCT with PTCy compared to non-PTCy based MUD and MSD cohorts.

Haploidentical Hematopoietic Cell Transplantation Combined with an Unrelated Cord Blood Unit for Adult Acute Myeloid Leukemia Results in Improved Survival Compared to Haploidentical Hematopoietic Cell Transplantation: Results of a Multicenter, Randomized, Phase III Trial

Introduction Haploidentical hematopoietic cell transplantation (haplo-HCT) is a potent treatment to improve the prognosis of acute myeloid leukemia (AML), but relapse and graft-versus-host disease (GVHD) related to dysregulation of alloreactivity are still the main causes of death posttransplantation. Cord blood graft usually has a promising graft-versus-leukemia effect with a lower cumulative incidence of GVHD. To improve the transplantation strategy, haplo-cord HCT combining haploidentical and unrelated cord blood (UCB) grafts (haplo-cord HCT) has been attempted. Previous studies showed significant improvement in prognosis in B-cell acute lymphoblastic leukemia or refractory acute leukemia patients with haplo-cord HCT compared to haplo-HCT. However, outcomes of haplo-cord HCT for AML patients are not yet clear. This is the first multicentric randomized trial designed specifically for the efficacy and safety of haplo-cord HCT for AML. Methods This is a multicenter, randomized, open-label, phase III study conducted in 5 centers in China (NCT03719534). Patients aged 18-60 years, diagnosed with AML (except for acute promyelocytic leukemia) with measurable residual disease, had an available haploidentical donor and were suitable for allotransplantation were enrolled. Patients were randomized 1:1 to receive UCB and haploidentical grafts infusion after Bu/Cy-based regimen or haploidentical graft infusion only after Bu/Cy-based regimen. The UCB unit, which had at least 3/6 matched HLA loci to the recipient and more than 1×10 4 CD34 + cells/kg of recipient weight, was infused immediately after resuscitation and eight hours before the haploidentical graft infusion. The primary endpoint was 3-year overall survival (OS) and secondary endpoints included progression-free survival (PFS), cumulative incidence of relapse (CIR), and non-relapse mortality (NRM). Results From June 1, 2017, to June 30, 2021, 268 patients were enrolled (Table 1). With a median follow-up of 36.00 months, the 3-year OS was 80.5% (95% CI 73.7-87.9) in the haplo-cord HCT group and 67.8% (95% CI 60.0-76.5) in the haplo-HCT group, respectively (p=0.013, figure 1A). Haplo-cord HCT group showed favorable 3-year PFS and CIR than haplo-HCT group (PFS: 70.3%, 95% CI 62.6-78.8 vs. 57.6%, 95% CI 49.6-67.0, p=0.012; CIR: 12.1%, 95% CI 12.0-12.2 vs. 30.3%, 95% CI 30.1-30.4, p=0.024, figure 1B,C). The 3-year NRM was similar in the two groups (figure 1D). Within two years posttransplantation, the most common grade 3-4 adverse events (AEs) in the haplo-cord HCT and haplo-HCT groups were infections (33.8% and 29.1%), acute GVHD (20.3% and 12.7%) and chronic GVHD (12.0% and 16.4%). AEs leading to death occurred in 8.3% of haplo-cord HCT and 14.9% haplo HCT patients. Post- hoc analysis showed similar median levels of haploidentical chimerism in bone marrow (BM) between the two groups. However, UCB microchimerism was detected in the haplo-cord HCT patients by SNP-NGS in +1m posttransplantation (BM: 0.3%, IQR 0.04-1.6; peripheral blood: 0.06%, IQR 0.03-0.4) and its chimerism percentage decreased with time (figure 1E). Compared to haplo-HCT group, haplo-cord HCT group showed a faster cumulative incidence of neutrophil recovery (p=0.026, figure 1F) and a similar cumulative incidence of platelet recovery. Monitor of immune reconstitution showed a more rapidly increasing rate of T cells in the early period after transplantation in the haplo-cord HCT group (figure 1G). Improved recovery of Th2 (p=0.042), Th17 (p=0.047), Treg (p=0.045), and Tc2 (p=0.045) cells was observed in haplo-HCT group. Conclusions Coinfusion of a UCB unit in haplo-HCT can improve OS in AML patients without excessive AEs, and affect T-cell reconstitution pattern posttransplantation. Haplo-cord HCT could serve as a suitable therapeutic option for this patient population.

Effectiveness of In Vivo T-Cell Depleted Regimen Containing Porcine Antilymphocyte Globulin and Rabbit Antithymocyte Globulin in Preventing Acute Gvhd after Haploid Hematopoietic Stem Cell Transplantation

Objective To compare the clinical efficacy of porcine antilymphocyte globulin (p-ALG) and rabbit antithymocyte globulin (r-ATG) in the treatment of hematologic malignancies using haploid hematopoietic stem cell transplantation (haplo- HSCT), this study was conducted. Methods This was a single center retrospective analysis of 178 subjects who received haplo-HSCT with p-ALG or r-ATG from January 2020 to December 2022. The patients were divided into three groups according to the doses of p-ALG or r-ATG used in the conditioning regimens. The study evaluated and compared the occurrence of early fever, graft versus host disease (GVHD), infection, and survival among the three groups of patients. Results A total of 178 patients were enrolled in the study with a median age of 30 (14-61) years, including 95 men and 83 women. The median follow-up time post-transplantation was 20.1 (1.7-36.9) months. The study included 57 patients in the p-ALG 75mg/kg group, 49 patients in the p-ALG 90mg/kg group, and 72 patients in the r-ATG 7.5mg/kg group, respectively. The incidences of neutrophil and platelet engraftment, respectively, were 100%,93.5%, and 91.3% (p=0.133); 100%, 93.6%, 90.3% (p=0.033) in P-ALG 75mg/kg, P-ALG 90mg/kg and r-ATG 7.5mg/kg. The median time to neutrophil engraftment was 11 days for the P-ALG 75mg/kg group, 12 days for the P-ALG 90mg/kg group, and 12 days for the r-ATG 7.5mg/kg group (p=0.133). The median time to platelet engraftment was 12 days for the P-ALG 75mg/kg group, 14 days for the P-ALG 90mg/kg group, and 13 days for the r-ATG 7.5mg/kg group (p=0.033). In the p-ALG 75mg/kg, p-ALG 90mg/kg, and r-ATG 7.5mg/kg groups, 16 patients (28.1%), 24 patients (49.0%) and 35 patients (48.6%) developed fever within 14 days after transplantation, respectively. Cytokine release syndrome was found to be the most common cause of fever. The incidence of grades Ⅱ-Ⅳ acute GVHD (aGVHD) and grades Ⅲ-Ⅳ aGVHD, respectively, were 15.8%, 12.2%, and 12.5% (p=0.853); 5.3%, 2.0%, and 5.6% (p=0.523) in P-ALG 75mg/kg, P-ALG 90mg/kg and r-ATG 7.5mg/kg. The cumulative incidence of chronic GVHD at 1 year was 14.0%, 10.2%, and 15.3% (p=0.731) in the three groups. 43.9%, 71.4%, and 61.1% of patients in the p-ALG 75mg/kg, p-ALG 90mg/kg and r-ATG 7.5mg/kg groups, respectively, experienced at least one infection within 1 year after haplo-HSCT (p=0.0.13). Notably, the CMV infection rate in the p-ALG 75mg/kg group was significantly lower than in the p-ALG 90mg/kg and r-ATG 7.5mg/kg groups. The 2-year overall survival (OS) rates of p-ALG 75mg/kg, p-ALG 90mg/kg and r-ATG 7.5mg/kg groups were 78.2%, 70.6%, and 72.3% (p=0.491). The cumulative incidence of 2-year relapse were 33.0%, 29.8%, and 30.0% (p=0.834). ConclusionsCompared with r-ATG group, the p-ALG 75mg/kg group showed a lower incidence of infection. However, there were no significant differences between the two groups in terms of the incidence of grades Ⅱ-Ⅳ aGVHD, 2-year overall survival (OS), and 2-year cumulative incidence of relapse. p-ALG (75mg/kg) has a comparable effect on the prevention of GVHD after haplo-HSCT with a lower incidence of infection. Keywords: Porcine antilymphocyte globulin; Rabbit antithymocyte Globulin; Haploidentical hematopoietic cell transplantation; Graft versus host disease; Infection