A phase II study of post-transplant cyclophosphamide combined with tacrolimus for GVHD prophylaxis after HLA-matched related/unrelated allogeneic hematopoietic stem cell transplantation.

A combination of three post-transplant drugs, cyclophosphamide (PTCy), a calcineurin inhibitor, and mycophenolate mofetil, has long been used for prophylaxis of graft-versus-host-disease (GVHD) after HLA-haploidentical allogeneic hematopoietic cell transplantation (allo-HCT). Recently, this combination has been used following HLA-matched allo-HCT as well, but the optimal combination of drugs for GVHD prophylaxis in an HLA-matched setting remains unclear. This prospective phase II study evaluated the safety and efficacy of PTCy plus tacrolimus (TAC) for GVHD prophylaxis after allo-HCT from HLA-matched related donors (MRD) or HLA-matched unrelated donors (MUD). The cumulative incidences of grades II-IV and III-IV acute GVHD at 100 days post-transplantation were 18% and 5.9%, respectively, in the MRD group, and 18% and 9.1%, respectively, in the MUD group. The cumulative incidences of moderate to severe chronic GVHD at 1 year were 12% and 9.1% in the MRD and MUD groups, respectively. The 1-year overall survival rates in the MRD and MUD groups were 88% and 64%, respectively, and the 1-year GVHD-free, relapse free survival rates were 59% and 50%, respectively. These results suggest that GVHD prophylaxis with a less intensive double drug combination (PT/Cy and TAC) might be feasible after HLA-matched allo-HCT.Clinical Trial Notation This trial was a prospective single-center trial registered at the University Hospital Medical Information Network Clinical Trials Registry (UMIN-CTR; identification number: UMIN000023890) and the Japan Registry of Clinical Trials (jRCTs051180143).