Post transplantation cyclophosphamide (PTCy) combination with low-dose anti-thymocyte globulin (ATG) for gvhd prophylaxis in unmanipulated haploidentical peripheral blood stem cell transplantation without ATG in conditioning regimen

Abstract In haploidentical peripheral blood stem cell transplantation (haplo-PBSCT), the combination of anti-thymocyte globulin and post-transplant cyclophosphamide (ATG/PTCy) has a synergistic impact in preventing graft-versus-host disease (GVHD), and almost all published protocol added different dose ATG to conditioning regimen. However, we explore the efficacy and safety of post transplantation cyclophosphamide (PTCy) combination with low-dose of antithymocycle globulin (ATG) for the prevention of graft versus host disease (GVHD) in haploidentical peripheral blood stem cell transplantation. We retrospectively included 35 adult patients with acute leukemia who underwent haplo-PBSCT at our hospital, following the same myeloablative conditioning regimen and using standard-dose PTCy (50 mg/kg on days +3, +4) combined with low-dose ATG (1.25 mg/kg，on days +8) for the prophylaxis of GVHD from July 2021 february 2024. 32 patients had successful hematopoietic reconstruction. The median follow-up time for all patients was 18.2 months, respectively. The cumulative incidence rate of aGVHD was 34.29%, of which the cumulative incidence rate of grade Ⅱ-Ⅳ and grade Ⅲ-Ⅳ was 11.43%, 8.57%. The incidence of extensive cGVHD was 11.42%, of which localized cGVHD was 5.71% and generalized cGVHD was 5.71%. Additionally, The probability of 1-year and 2-year overall survival, disease-free survival, 85.71%, 82.76%, 85.71% and 78.82%, respectively. The recurrence rate was only 8.57%. Our findings suggest that combining PTCy with low-dose ATG for preventing graft-versus-host disease (GVHD) in haploidentical peripheral blood stem cell transplantation results in a lower risk of acute and chronic GVHD, as well as a lower risk of relapse. This approach also improves disease-free survival (DFS) and overall survival (OS), offering a promising new method for enhancing transplant outcomes.