Combination of post-transplant cyclophosphamide and anti-thymocyte globulin for haploidentical stem cell transplantation in pediatric patients with acute leukemia

The increasing number of patients undergoing haploidentical hematopoietic stem cell transplantation (HSCT) for the treatment of acute leukemia has raised concerns about determining the optimal conditioning regimen and graft source in this context. This study evaluated outcomes of dual in vivo T-cell depleted HSCT in 70 pediatric patients with acute leukemia. The transplantation protocol included a radiation-free myeloablative conditioning (MAC) regimen comprising busulfan, cyclophosphamide, and rabbit anti-thymocyte globulin (ATG), followed by post-transplant cyclophosphamide (Pt-Cy). Results indicated successful engraftment in nearly 95% of patients within 30 days. Acute graft-versus-host disease (aGvHD) occurred in 42.65% within 100 days, and chronic GvHD (cGvHD) in 9.57% over four years. The 2-year overall survival (OS) was 69.86%, and the GvHD-free, relapse-free survival (GRFS) was 35.76%. The 2-year cumulative incidence of relapse was 35.7%, and non-relapse mortality (NRM) was 11.66%. Notably, patients with T-cell acute lymphoblastic leukemia (T-ALL) exhibited significantly higher mortality and relapse rates than those with B-cell lineage. Overall, these findings support the feasibility of this dual in vivo T-cell depletion platform in pediatric haploidentical HSCT, with sustained engraftment, a low incidence of cGvHD, and clinically acceptable survival outcomes.