Weekly carfilzomib and dexamethasone in Japanese patients with relapsed or refractory multiple myeloma: A phase 1 and PK/PD trial

This open‐label multicenter phase 1 study evaluated the safety, tolerability, efficacy, pharmacokinetics and pharmacodynamics of weekly carfilzomib and dexamethasone (Cd) in Japanese patients with relapsed or refractory multiple myeloma (RRMM). Carfilzomib was administered by 30‐minute intravenous infusion on Days 1, 8 and 15 in a 28‐day cycle starting at 20 mg/m² on Day 1/Cycle 1 and 70 mg/m² thereafter until progressive disease or unacceptable toxicity. Dexamethasone 40 mg was administered on Days 1, 8, 15 and 22 in Cycles 1‐9 and on Days 1, 8 and 15 thereafter. Six patients were enrolled between March 2015 and June 2015. Patients had received a median of 4.5 (range, 4‐8) prior regimens; all patients had previous therapies with bortezomib and immunomodulatory drugs. Of the 6 patients, 1 had a dose‐limiting toxicity (DLT), and tolerability was confirmed. The DLT was grade 3 thrombotic microangiopathy, which was considered serious and occurred on Day 11/Cycle 1. All 6 patients (100%) experienced at least 1 grade ≥3 adverse event (AE). Two patients (33.3%) experienced AE (also considered adverse drug reactions) leading to study discontinuation: thrombotic microangiopathy (Day 11/Cycle 1) and thrombotic thrombocytopenic purpura (Day 6/Cycle 2). The overall response rate was 83.3% (95% confidence interval, 43.6‐97.0). The weekly Cd regimen at a carfilzomib dose of 20/70 mg/m² was well‐tolerated among Japanese patients with RRMM. Our results could be the basis for the further development of carfilzomib treatment considering safety profiles including microangiopathy‐related events and efficacy.