Onyx Pharmaceuticals has updated results from the phase IIb 003-A1 study of single-agent carfilzomib, a next generation proteasome inhibitor, in patients with relapsed and refractory multiple myeloma.

Carfilzomib achieved a clinical benefit rate (CBR) (minimal response or greater) in the study population of 37% with a duration of response (DOR) of 8.3 months.  The primary endpoint, overall response rate (ORR) (defined as partial response or greater) was 24% with a median duration of response (DOR) of 7.8 months.  Patients entered the study after receiving a median of five prior lines of therapy (corresponding to a median of 13 anti-myeloma agents). The median overall survival (OS) for all patients in the study, regardless of response to drug, was 15.6 months. Overall survival for the best responding patients (partial response or greater) is continuing to mature (subject to additional patient observations) and is currently 20.7 months.

The most common grade 3/4 adverse events were thrombocytopenia (29%), anemia (24%), lymphopenia (20%), and neutropenia (11%).

Two hundred and sixty-six patients with relapsed and refractory multiple myeloma were enrolled in the study, and 257 patients were evaluable for response. The primary endpoint was ORR. Secondary endpoints included CBR, DOR, OS, and safety.