PX-171–004, a multicenter phase II study of carfilzomib (CFZ) in patients with relapsed myeloma: An efficacy update

8537 Background: Carfilzomib (CFZ) is a proteasome inhibitor, active against hematologic malignancies. Preclinically, CFZ overcomes bortezomib (BTZ) resistance in multiple tumors, including myeloma (MM). PX-171–004 is an ongoing Phase II study evaluating safety and efficacy of CFZ in MM patients with relapsed disease after 1–3 prior therapies. Overall Response Rate (ORR) of 35.5% for all subjects was previously reported (ASH 2008); updated data are now available. Methods: Patients were divided into two cohorts: BTZ-naive and BTZ-exposed. CFZ 20 mg/m2 was administered Days 1, 2, 8, 9, 15 and 16 in a 28-day cycle, for up to 12 cycles. Dexamethasone 4 mg po was administered prior to each dose in Cycle 1. The primary endpoint was ORR, defined as Partial Response (PR) or better. Secondary endpoints included Duration Of Response (DOR) and Time To Progression (TTP). Results: 31 patients were enrolled; 14 (45%) BTZ-naive and 17 (55%) BTZ-exposed. Of the BTZ-exposed cohort, 2 subjects received BTZ exclusively as a...