Bortezomib-based immunosuppression after reduced-intensity conditioning hematopoietic stem cell transplantation: randomized phase II results.

Aprior phase I/II trial of bortezomib/tacrolimus/methotrexate prophylaxis after human leukocyte antigen (HLA)-mismatched reduced intensity conditioning allogeneic hematopoietic stem cell transplantation documented low acute graft--host disease incidence, with promising overall and progression-free survival. We performed an open-label three-arm 1:1:1 phase II randomized controlled trial comparing grade II-IV acute graft--host disease between conventional tacrolimus/methotrexate (A) bortezomib/tacrolimus/methotrexate (B), and bortezomib/sirolimus/tacrolimus (C), in reduced intensity conditioning allogeneic transplantation recipients lacking HLA-matched related donors. The primary endpoint was grade II-IV acute graft--host disease incidence rate by day +180. One hundred and thirty-eight patients (A 46, B 45, C 47) with a median age of 64 years (range: 24-75), varying malignant diagnoses and disease risk (low 14, intermediate 96, high/very high 28) received 7-8/8 HLA-mismatched (40) or matched unrelated donor (98) grafts. Median follow up in survivors was 30 months (range: 14-46). Despite early immune reconstitution differences, day +180 grade II-IV acute graft--host disease rates were similar (A 32.6%, B 31.1%, C 21%; =0.53 for A B, =0.16 for A C). The 2-year non-relapse mortality incidence was similar (A 14%, B 16%, C 6.4%; =0.62), as were relapse (A 32%, B 32%, C 38%; =0.74), chronic graft--host disease (A 59%, B 60% C 55%; =0.66), progression-free survival (A 54%, B 52%, C 55%; =0.95), and overall survival (A 61%, B 62%, C 62%; =0.98). Overall, the bortezomib-based regimens evaluated did not improve outcomes compared with tacrolimus/methotrexate therapy. .