Bortezomib, tacrolimus, and methotrexate for prophylaxis of graft-versus-host disease after reduced-intensity conditioning allogeneic stem cell transplantation from HLA-mismatched unrelated donors.

Graft-versus-host disease (GVHD) is a significant complication of allogeneic stem cell transplantation (alloSCT). The proteasome inhibitor bortezomib has immunomodulatory properties of potential benefit for GVHD control. We undertook a phase 1 trial of bortezomib, tacrolimus, and methotrexate for GVHD prophylaxis after reduced-intensity conditioning alloSCT using human leukocyte antigen-mismatched unrelated donors. Twenty-three patients were enrolled. Bortezomib dose levels of 1, 1.3, and 1.5 mg/m2 were evaluated with 5, 3, and 5 patients, respectively. Ten additional patients were accrued at the 1.3 mg/m2 bortezomib dose level. Bortezomib-related toxicity was minimal. With a 12-month median follow-up, grade II-IV acute GVHD occurred in 3 patients, a 180-day cumulative incidence of 13%. Chronic GVHD occurred in 9 patients, a 1-year cumulative incidence of 41%. At 1-year, the nonrelapse mortality was zero, cumulative incidence of relapse/progression was 29%, and overall, progression-free, and event-free survival were 75%, 64%, and 59%, respectively. Bortezomib is a promising novel immunomodulatory agent in allogeneic transplantation. This study was registered at http://www.clinicaltrials.gov as #NCT00369226.