A single dose of posttransplant cyclophosphamide (PTCy) provided effective prophylaxis against acute graft-versus-host disease (GVHD) in patients who underwent hematopoietic stem cell transplantation (HSCT) using human leukocyte antigen (HLA) matched-unrelated donors. These study findings were reported in the American Journal of Hematology.

For patients undergoing allogeneic HSCT with haploidentical donors, PTCy as a component of GVHD prophylaxis has shown efficacy, and PTCy has also been effective in patients undergoing HLA matched-related and matched-unrelated bone marrow transplantation. However, outcomes with the use of PTCy have been mixed in different settings, and its use may raise the risk of infectious complications.

In this single-arm trial (ClinicalTrials.gov Identifier: NCT02065154), patients who had HLA matched-unrelated donors underwent myeloablative peripheral blood stem cell allogeneic HSCT. Following HSCT, they received a single dose of PTCy with tacrolimus and mycophenolate mofetil as GVHD prophylaxis. The primary study endpoint was determination of the cumulative incidence of grade 2-4 acute GVHD at day 100 after allogeneic HSCT. Cumulative incidence of chronic GVHD and multiple survival outcomes were among the secondary endpoints.

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The study enrolled 39 patients, among whom 36 had 8/8 HLA matched-unrelated donors, and 3 had 7/8 HLA matched-unrelated donors. One fatality occurred before engraftment within the first 30 days following HSCT, but the other 38 patients (97%) achieved engraftment.

The day-100 cumulative incidence of grade 2-4 acute GVHD was 30% (95% CI, 15.2%-40.1%), and grade 3-4 acute GVHD was 5% (95% CI, 2.1%-8.2%). The cumulative incidence of mild chronic GVHD at 2 years was 15% (95% CI, 7.1%-23.3%), moderate chronic GVHD was 15% (95% CI, 8.4%-23.3%), and severe chronic GVHD was 18% (95% CI, 12.6%-27.4%).

Nonrelapse mortality occurred with a 2-year cumulative incidence of 34% (95% CI, 18.6%-49.6%), and the 2-year cumulative incidence of relapse was 21% (95% CI, 7.6%-33.4%). At 2 years, progression-free survival was an estimated 45% (95% CI, 29.5%-61.3%) and overall survival an estimated 51% (95% CI, 34.7%-66.5%).

The researchers determined that the protocol using a single dose of PTCy was associated with a low incidence of severe acute GVHD, without raising relapse risk. However, they also determined there was no evidence of a mitigation of chronic GVHD risk compared with a regimen using 2 doses of PTCy.


Jamy O, Innis-Shelton R, Bal S, et al. Phase II clinical trial of one dose of post-transplant cyclophosphamide for graft versus host disease prevention following myeloablative, peripheral blood stem cell, matched-unrelated donor transplantation. Am J Hematol. Published online July 20, 2021. doi:10.1002/ajh.26296