The effect of carfilzomib (CFZ) in patients (Pts) with bortezomib (BTZ)-naive relapsed or refractory multiple myeloma (MM): Updated results from the PX-171-004 study.

8026 Background: CFZ, a selective epoxyketone proteasome inhibitor, has potent, sustained action and lacks many BTZ-associated off-target activities. Durable activity has been observed in pts with advanced relapsed/refractory (R/R) MM, including those whose disease progressed on a BTZ-containing regimen. PX-171-004 is an ongoing phase (ph) II study of single-agent CFZ in pts with relapsed MM following 1–3 prior regimens. Here we present updated response, toxicity, and duration of response (DOR) data on BTZ-naive pts treated on this study. Methods: Pts in 2 sequential cohorts (Cohort 1 and Cohort 2) received IV CFZ on Days 1, 2, 8, 9, 15, 16 of every 28-day cycle (C), for up to 12 C. Both cohorts received 20 mg/m2 in C1; Cohort 2 dose escalated to 27 mg/m2 for C2–12. Primary endpoint was overall response rate (ORR) per IMWG criteria. Secondary endpoints were clinical benefit response (CBR), progression-free survival (PFS), DOR, overall survival (OS), time to progression (TTP), and safety. Results: 123 BTZ-...