A comparative study of GVHD prophylaxis using low dose ATG versus PTCy for PBSCT based on two independent prospective cohorts.

Both anti-thymocyte globulin (ATG) and post-transplant cyclophosphamide (PTCy) have shown prophylactic effects on graft-versus-host disease (GVHD) in multiple phase III studies. We conducted a comparative study of for low dose ATG (thymoglobulin) versus PTCy for GVHD prophylaxis in peripheral blood stem cell transplantation (PBSCT). The ATG (n = 67) and PTCy (n = 40) groups included patients enrolled in multicenter phase II studies (JSCT-ATG15 and JSCT-PTCY19, respectively). The probability of GVHD-free and relapse-free survival at 2 years as the primary endpoint was not significantly different between these two groups (57.9% for ATG vs. 67.8% for PTCy, P = 0.49). Both neutrophil and platelet engraftments were both significantly shorter in the ATG group than in the PTCy group (neutrophils: median 13 days vs. 15 days, P = 0.007; platelets: median 20 days vs. 27 days, P = 0.007). The cumulative incidences of acute and chronic GVHD, relapse, non-relapse mortality, and off-immunosuppressant use were similar between these two groups. The probabilities of overall and progression-free survival were 83.4% and 70.0% in the ATG group and 76.5% and 75.2% in the PTCy group, respectively, with no significant differences. These data indicate that low dose ATG and PTCy are equivalent for GVHD prophylaxis for PBSCT.