Dose‐escalation study of tabalumab with bortezomib and dexamethasone in Japanese patients with multiple myeloma

B-cell activating factor (BAFF) promotes the survival and adhesion of multiple myeloma (MM) cells. Tabalumab (LY2127399) is an anti-BAFF monoclonal antibody. This phase 1, multicenter, open-label, nonrandomized, dose-escalation study evaluated the safety, tolerability, pharmacokinetics, pharmacodynamics and efficacy of tabalumab in combination with bortezomib and dexamethasone in Japanese patients with relapsed or refractory MM (RRMM). Sixteen patients received intravenous i.v. tabalumab 100 mg (Cohort 1, n = 4) or i.v. tabalumab 300 mg (Cohort 2, n = 12) in combination with oral dexamethasone 20 mg/day and i.v. or s.c. bortezomib 1.3 mg/m(2) . All patients had treatment-emergent adverse events (TEAE) possibly related to study treatment; the most common TEAE were thrombocytopenia (81.3%), lymphopenia (43.8%) and increased alanine aminotransferase (43.8%). Two (20.0%) dose-limiting toxicities were observed, both in Cohort 2 (tabalumab 300 mg), which was below the predefined cutoff for tolerability (