Carfilzomib monotherapy in Japanese patients with relapsed or refractory multiple myeloma: A phase 1/2 study

This multicenter, open‐label phase 1/2 study evaluated single‐agent carfilzomib in 50 heavily pretreated Japanese patients with relapsed/refractory multiple myeloma (median of five prior treatments). In phase 1, patients were dosed at three levels: 15, 20, or 20/27 mg/m(2). Maximum tolerated dosage was not reached at the tolerability evaluation. Patients in phase 2 were treated with 20/27 mg/m(2) carfilzomib. Median duration of exposure to carfilzomib in the 20/27 mg/m(2) group at this final analysis was 4.7 months (range: 0.3‐39.4). Overall response rate in the 20/27 mg/m(2) group, primary endpoint of the study, was 22.5% (n = 9) (95% confidence interval, 12.3‐37.5) with 2.5% (n = 1) stringent complete response. Median progression‐free survival and overall survival in the 20/27 mg/m(2) group were 5.1 months (95% CI, 2.8‐13.6) and 22.9 months (95% CI, 14.1‐not estimable), respectively. Frequently occurring grade ≥3 adverse events in the 20/27 mg/m(2) group included lymphopenia (72.5%), neutropenia (40.0%), and leukopenia (32.5%). Giving long‐term carfilzomib monotherapy led to long‐term overall survival for heavily pretreated multiple myeloma patients with a favorable safety profile. Carfilzomib monotherapy can be a good option for heavily pretreated multiple myeloma patients.