Haploidentical hematopoietic stem cell transplantation for hematologic malignancies: a novel conditioning regimen with anti-T lymphocyte immunoglobulin instead of anti-thymocyte globulin for in vivo T cell depletion

We evaluated the safety and efficacy of a novel protocol for haploidentical stem cell transplantation (haplo-SCT) in 312 patients with hematologic malignancies. The protocol evolved from the Beijing platform replacing ATG with ATLG; adding Fludarabine and removing cytarabine and Simustine. GVHD prophylaxis combined Basiliximab and low-dose cyclophosphamide post-transplant; overall, the conditioning duration was shortened. Median times to neutrophil and platelet recovery were both 11 days. Graft rejection occurred in 0.96% of patients. Cumulative incidences of grades II-IV and III-IV acute GVHD by day 200 were 35.3% and 8.9%, respectively. Probabilities of total and extensive chronic GVHD at 2 years were 40.7% and 14.7%. CMV viremia was observed in 35.6% of patients, with a 1.9% 100-day CMV pneumonia incidence and no CMV-related mortality. Cumulative incidences of non-relapse mortality at 100 days, 1 year, and 2 years were 2.9, 4.4, and 6.6%. The 4-year OS, RFS, and GRFS rates were 78.9, 70.7, and 47.3%. Older recipient age was associated with higher NRM, while positive pre-transplant MRD predicted worse OS, RFS, and higher relapse incidence. Our novel protocol for haplo-SCT is associated with low infection rates and acceptable risks of graft failure, severe GVHD, and mortality, representing a safe and effective haploidentical transplantation strategy.