The optimal dose of rabbit antithymocyte globulin (ATG, ImtixSangstat) minimizing infections without increasing graft-versus-host disease (GVHD) is unknown in T cell-replete, G-CSF-primed haploidentical hematopoietic stem cell transplantation (haplo-HSCT). Four hundred and eight patients were enrolled in this multicenter study to evaluate the effect of 7.5 mg/kg and 10.0 mg/kg rabbit ATG on viral infections and GVHD prophylaxis after haplo-HSCT. The primary endpoint was EBV DNAemia within 1 year posttransplantation. The 1-year incidence of EBV DNAemia was 20.7% (95% confidence interval, 15.4–26.5) and 40.0% (33.3–46.6) in the 7.5 mg/kg and 10.0 mg/kg groups, respectively (P < 0.001). The 100-day cumulative incidence of grade II to IV aGVHD was 27.1% (21.1–33.4) and 25.4% (19.6–31.5) in the 7.5 mg/kg and 10.0 mg/kg ATG groups, respectively (P = 0.548). The 2-year incidence of chronic GVHD was 34.6% (27.8–41.4) and 36.2% (29.1–43.2) in the 7.5 mg and 10.0 mg groups (P = 0.814). The 1-year incidence of CMV DNAemia was 73.4% (67.2–79.4) and 83.4% (77.5–87.9) in the 7.5 mg/kg and 10.0 mg/kg groups (P = 0.038). The 3-year overall survival posttransplantation was 69.5% (63.2–75.8) and 63.5% (56.2–70.8), and the disease-free survival was 62.2% (55.3–69.1) and 60.3% (53.0–67.6) in the 7.5 mg/kg and 10.0 mg/kg groups, respectively (OS: P = 0.308; DFS: P = 0.660). The counts of EBV- and CMV-specific cytotoxic T cells (CTLs) were higher in the 7.5 mg/kg group than in the 10.0 mg/kg group early posttransplantation. Compared with 10.0 mg/kg, 7.5 mg/kg ATG for GVHD prophylaxis was associated with reduced EBV and CMV infections without increased incidence of GVHD in haplo-HSCT, probably by affecting EBV- and CMV-specific CTLs. clinicaltrials.gov, NCT01883180 . Registered 14 June 2013.

PURPOSE: It remains controversial whether busulfan-based versus total body irradiation (TBI)–based regimens have comparable outcomes in patients with acute lymphoblastic leukemia (ALL) undergoing allogeneic hematopoietic stem-cell transplantation (allo-HSCT). We investigated the efficacy and toxicity of busulfan plus cyclophosphamide (BuCy) and TBI plus cyclophosphamide (TBI-Cy) conditioning in allo-HSCT for adult standard-risk B-cell-ALL in first complete remission (CR1).PATIENTS AND METHODS: We performed an open-label, randomized phase III trial at 13 hospitals in China. Eligible patients (age 14-65 years) had standard-risk ALL in CR1. Patients were randomly assigned (1:1) to BuCy (0.8 mg/kg four times per day on days –7 to –4 and cyclophosphamide 60 mg/kg once daily on days –3 to –2) or TBI-Cy (4.5 Gy TBI on days –5 to –4 and cyclophosphamide 60 mg/kg once daily on days –3 to –2). The primary end point was 2-year overall survival. Analysis was per protocol. This trial is registered with ClinicalTrials.gov (identifier: NCT02670252 ) and is complete.RESULTS: Between January 2016 and February 2020, 275 patients were assigned to receive BuCy (273 assessed) and 275 to TBI-Cy (272 assessed). The 2-year overall survival was 76.6% (95% CI, 71.7 to 81.8) and 79.4% (74.7 to 84.4; P = .457; difference 2.9%; 95% CI, –4.1 to 9.8; P = .022), indicating noninferiority of BuCy. The 2-year relapse was 20.2% (95% CI, 15.6 to 25.1) and 18.4% (14.0 to 23.2; P = .616), and the nonrelapse mortality was 11.0% (95% CI, 7.6 to 15.0) and 11.0% (7.7 to 15.1; P = .988) in the BuCy and TBI-Cy groups, respectively. There were no differences in regimen-related toxicity, graft-versus-host disease, or late effects between the two groups.CONCLUSION: The BuCy regimen has noninferior efficiency and safety as TBI-Cy (4.5 Gy × 2) for patients with adult standard-risk B cell-ALL in CR1 undergoing HLA-matched allo-HSCT.

Background: Compared with HLA-matched sibling donor (MSD) transplant, the outcomes of haploidentical donor (HID) transplant for refractory acute leukemia need to be further explored. In this study, we compared the outcomes of HID with MSD for refractory acute leukemia. Patients and methods: This study population came from two prospective multicenter trials (NCT01883180, NCT02673008). Two hundred and seventy-eight patients with refractory acute leukemia were enrolled in this study, including 119 in HID group and 132 in MSD group. Sequential intensified conditioning was employed in all patients, and donor lymphocyte infusion (DLI) was administered in patients in the absence of active GVHD and according to minimal residual disease (MRD) from day + 60 post-transplantation for preventing relapse. Results: The complete remission of leukemia by day + 30 post-transplant were 94% and 93%, respectively, in HID and MSD groups (p = .802). The 1-year incidence of grades II–IV acute GVHD was 62% and 54% (p = .025), and 3-year incidence of chronic GVHD was 55% and 55% (p = .789), respectively, in two groups. HID transplant had lower incidence of first episode of MRD positivity and relapse than MSD transplant (28% vs 45%, p = .006; 26% vs 38%, p = .034). There was higher infection-related mortality in HID than MSD (8% vs 2%, p = .049) within the first 100 days’ post-transplant. The 5-year overall survival was 46% and 42% (p = .832), respectively; the 5-year disease-free survival was 43% and 39% (p = .665), in HID and MSD groups, respectively. Conclusions: HID transplant has lower relapse, but higher infection-related mortality and similar survival rates in refractory acute leukemia by the strategy of sequential intensified conditioning followed by DLI compared with MSD transplant.

Granulocyte colony-stimulating factor (G-CSF)-mobilized peripheral blood stem cells (G-PBSC) has largely replaced unstimulated bone marrow (un-BM) for allografting because of accelerated engraftment, but with a higher morbidity and mortality of graft-versus-host-disease (GVHD). Recent studies suggested that G-CSF-primed BM (G-BM) had similar engraftment but lower morbidity and mortality of GVHD comparing to G-PBSC. A prospective, randomized, multicenter study was conducted to compare G-BM with G-PBSC as the grafts in allogeneic hematopoietic stem cell transplantation (allo-HSCT) for acute leukemia in first complete remission (CR1). Totally 101 adult leukemia in CR1 undergoing HLA-identical sibling transplants were randomized into G-BM or G-PBSC group. The primary study endpoint was GVHD-free/relapse-free survival (GRFS). Both the engraftment of neutrophil and platelet were 2 days later in G-BM than in G-PBSC group (P = 0.412, P = 0.39). G-BM group showed significantly lower II–IV acute GVHD (aGVHD) and similar III–IV aGVHD compared with G-PBSC group (12.2% vs 28.8% for II–IV, P = 0.048; 4.1% vs 9.6% for III–IV aGVHD, P = 0.267, respectively). The overall cumulative incidence of chronic GVHD (cGVHD) at 3 years were 22.3% ± 6.3% and 44.8% ± 7.6% (P = 0.026), respectively, and extensive cGHVD were 4.5% ± 3.1% and 15% ± 5.3% (P = 0.08), respectively, in G-BM and G-PBSC groups. Two groups had similar 3-year relapse, transplant-related mortality (TRM), overall survival (OS), and disease-free survival (DFS) (all P > 0.05). G-BM group showed significantly higher probability of GRFS than G-PBSC group (73.5% ± 6.3% vs 55.8% ± 6.9% at 1 year, P = 0.049; 69.0% ± 6.7% vs 49.7% ± 7.0% at 2 and 3 years, P = 0.03, respectively). Graft content analysis revealed statistically higher frequency of myeloid-derived suppressor cells (MDSCs) in the G-BM than in G-PBSC grafts (P < 0.01), and recipients received statistically higher numbers of MDSCs in G-BM than in G-PBSC group (P = 0.045). Numbers of MDSCs infused to patients were negatively correlated with the severity of aGVHD (P = 0.032, r = −0.214). Multivariate analysis showed that MDSC cell dose below the median (HR = 3.49, P < 0.001), recipient age (HR = 2.02, P = 0.039), and high risk of disease (HR = 2.14, P = 0.018) were independent risk factors for GRFS. G-BM grafts lead a better GRFS and less GVHD associated with a higher MDSCs content compared with G-PBSC grafts.

The immunomodulatory effects of granulocyte colony-stimulating factor (G-CSF) on T cells result in a low incidence of acute graft-versus-host disease (aGVHD) in G-CSF-mobilized allogeneic peripheral blood stem cell transplantation (G-PBSCT). However, the exact mechanism remains unclear. Regulatory γδ T cells (γδTregs), characterized by the presence of TCRγδ and Foxp3, have aroused great concern in the maintenance of immune tolerance. We hypothesized that γδTregs might involve in the immunomodulatory effects of G-CSF mobilization. The expression and immunomodulatory function of γδTreg subsets in peripheral blood of donors before and after G-CSF treatment in vivo and in vitro were evaluated by flow cytometry and CFSE assays. To investigate the effects of γδTregs on aGVHD, the association between γδTreg subsets in grafts and aGVHD in recipients was estimated. The proportions of Vδ1Tregs, CD27+Vδ1Tregs and CD25+Vδ1Tregs were significantly increased in peripheral blood after G-CSF treatment in vivo. γδTregs could be generated in vitro by stimulating with anti-TCRγδ in the presence of G-CSF. The immune phenotype, proliferation suppression function, and cytokine secretion of G-CSF-induced γδTregs were similar to that of transforming growth factor-β (TGF-β)-induced γδTregs. The clinical data demonstrated that the proportion of CD27+Vδ1Tregs in grafts was significantly lower in the patients who experienced aGVHD than in those who did not develop aGVHD (P = 0.028), and the proportions of other γδTreg subsets in grafts did not differ significantly between the two groups. The best cutoff value for CD27+Vδ1Treg proportion in grafts in prediction of aGVHD was 0.33%, with an area under the curve value of 0.725 (P = 0.043). Eight patients (26.7%) were classified as the low-CD27+Vδ1Treg group (< 0.33%), and 22 patients (73.3%) as the high-CD27+Vδ1Treg group (≥ 0.33%). The incidence of aGVHD was higher in the low-CD27+Vδ1Treg group than in the high-CD27+Vδ1Treg group (75.0% versus 22.7%, P = 0.028). G-CSF could induce the generation of γδTregs in vivo and in vitro, and γδTregs might participate in aGVHD regulation in G-PBSCT.