Post-transplant cyclophosphamide versus antithymocyte globulin as GVHD prophylaxis for 10/10 HLA-matched unrelated allogeneic hematopoietic stem cell transplantation.

Abstract After T-cell replete haploidentical stem cell transplantation, GVHD prophylaxis with post-transplant cyclophosphamide (PT-Cy) is now evaluated in unrelated donor (UD) transplants, where antithymocyte globulin (ATG) remains standard. We report the outcome of patients transplanted from HLA-10/10 matched unrelated donor (MUD) treated with PT-Cy (n=30), in comparison with a historical cohort treated with ATG (n=64). In the PT-Cy group, we observed lower 2-4 acute GVHD (23% vs. 45%, p=0.014), lower chronic GVHD (all grades: 13% vs 33%, p=0.029; moderate to severe: 10% vs. 27%, p=0.039) but no difference in the relapse (20% vs. 11%, p=0.628), non-relapse mortality (3% vs 11%, p=0.169), progression free survival (77% vs 78%, p=0.638) and overall survival (87% vs 83%, p=0.602). Neutrophil (19 vs 17 days, p=0.049) and platelet (26 vs 10 days, p<0.001) recovery was significantly delayed in the PT-Cy group. Then, we followed the GVHD and the immunosuppressive treatments (IST) prevalence in disease free patients as marker of quality of life. At 6 months, 5% and 36% in the PT-Cy group were living with GVHD and IST, versus 26% (p=0.030) and 64% (p=0.049). We conclude that PT-Cy is an effective GVHD prophylaxis in 10/10-HLA MUD allo-SCT, representing a valuable alternative to ATG.