Comparison of the efficacy of pre-transplant and post-transplant antithymocyte globulin combined with post-transplant cyclophosphamide for graft-versus-host disease prophylaxis in myeloablative haploidentical peripheral blood stem cell transplantation.

Although post-transplant cyclophosphamide (PTCy) is widely used to prevent graft-versus-host disease (GVHD), its protective effect remains inadequate in patients undergoing myeloablative haploidentical peripheral blood stem cell transplantation (haplo-PBSCT). We retrospectively evaluated the efficacy of PTCy combined with either pre-transplant or post-transplant antithymocyte globulin (ATG) for GVHD prevention in 114 haplo-PBSCT recipients. The PTCy+FTATG group (n = 74) received ATG at a total dose of 5 mg/kg on days -3 to -1, together with PTCy at 25 mg/kg on days +3 and +4. The PTCy+PTATG group (n = 40) received PTCy at 50 mg/kg on days +3 and +4, followed by ATG at 2.5 mg/kg on day +8. Both univariate and multivariate analyses showed that PTCy+FTATG prophylaxis significantly lowered the risk of grade II-IV acute GVHD (9.5% vs 27.5% [HR 0.24; 95% CI: 0.10-0.59; P = 0.002]) and grade III-IV acute GVHD (5.4% vs 17.5% [HR 0.19; 95% CI: 0.07-0.54; P = 0.002]). The 2-year cumulative incidence of chronic GVHD was 16.7% in the PTCy+FTATG group and 27.5% in the PTCy+PTATG group (P = 0.15). At 2 years, overall survival (OS), progression-free survival (PFS), and graft-versus-host disease-free relapse-free survival (GRFS) were 87.8% vs 72.5% (P = 0.04), 82.2% vs 65.0% (P = 0.03), and 78.1% vs 55.0% (P = 0.005), respectively. These results suggest that half-dose PTCy combined with low-dose pre-transplant ATG may be a promising strategy for GVHD prophylaxis.