Good clinical activity and favorable toxicity profile of once weekly bortezomib, fotemustine, and dexamethasone (B-MuD) for the treatment of relapsed multiple myeloma

Since multiple myeloma (MM) is still not-curable, the management of relapse remains challenging. Given the known efficacy of alkylating agents in MM, we conducted a phase I/II study to test a new three drug combination in which Fotemustine (Muphoran), an alkylating agent of nitrosurea family, was added to bortezomib + dexamethasone backbone (B-MuD) for the treatment of MM relapsed patients. Fotemustine was administered at two dose levels (80-100 mg/m² i.v.) on day 1. The original 21-day schedule was early amended for extra-hematological toxicity and a 35-day schedule was adopted (Bortezomib 1.3 mg/m² i.v. on days 1, 8, 15, and 22, Dexamethasone 20 mg i.v. on days 1, 8, 15, and 22) for a total of six courses. Twenty-four patients were enrolled. The maximum tolerated dose of Fotemustine was 100 mg/m². The overall response rate was of 62% (CR 8%, VGPR 33%, and PR 21%). The median OS was 28.5 months, the median progression-free survival (PFS) was 19.1 months. B-MuD resulted effective in patients previous exposed to bortezomib without difference of response (P = 0.25) and PFS (P = 0.87) when compared to bortezomib-naive patients. Thrombocytopenia was the most common AE overall. In conclusion, B-MuD is an effective and well tolerated combination in relapsed MM patients even in advanced disease phase.