Results of a phase I/II study (NCT01365559) of carfilzomib (CFZ) replacing bortezomib (BTZ) in BTZ-containing regimens for BTZ-treated patients (pts) with relapsed and refractory multiple myeloma (MM).

8599 Background: Recent data has shown that single-agent CFZ can produce responses among MM pts refractory to previous treatment regimens including those containing BTZ. We conducted an intrapatient phase I/II trial investigating the safety and efficacy of CFZ as a replacement for BTZ in BTZEcontaining regimens to which pts have progressed. Methods: Eligible pts progressed while receiving their most recent BTZEcontaining regimen after at least 4 doses of BTZ at ≥1.0 mg/m² in ≤4 weeks per cycle. CFZ replaced BTZ in each regimen via intravenous administration over 30 min on days 1, 2, 8, 9, 15, and 16 of each cycle. Treatment continued using the same dose(s) and schedule(s) of each drug administered in the BTZEcontaining regimen. CFZ doses were escalated on each of the first 4 cycles from 20 to 27, 36, and 45 mg/m² or until a maximum tolerated dose (MTD) was reached for that regimen. Results: Of 37 enrolled pts, 33 were evaluable for efficacy and 37 for safety. Pts received a median of 4 prior treatments (r...