Weekly Carfilzomib, Cyclophosphamide and Dexamethasone (wCCd) in Newly Diagnosed Multiple Myeloma Patients: A Phase I- II Study

Background Carfilzomib is a novel second generation proteasome-inhibitor with significant anti MM activity and favorable toxicity profile, including very limited neurotoxicity and neutropenia. This Phase I/II study was designed to determine the maximum tolerated dose (MTD) of once weekly carfilzomib combined with cyclophosphamide-dexamethasone (wCCd) and to assess safety and efficacy of this combination in elderly patients with newly diagnosed MM. Here we report the first findings from the Phase I dose-escalation and expansion portions. Enrolment in the phase II portion is ongoing.

Methods In the Phase I, the standard 3+3 dose-escalation scheme was adopted, with Carfilzomib as the only escalating agent starting at 45 mg/m² (level 0), maximal planned dose 70 mg/m² (level 2), and 36 mg/m², if needed (level -1), given IV on days 1, 8, 15 in 28-day cycles. Oral cyclophosphamide was administered at 300 mg/m² on days 1, 8, 15 and oral dexamethasone at 40 mg on days 1, 8, 15, 22 for all dose levels. Dose escalation of Carfilzomib was based on dose-limiting toxicities (DLTs) occurring in cycle 1. After completion of 9 cycles, patients receive 28-day maintenance cycles with Carfilzomib (days 1, 8, 15) at the maximum tolerated dose (MTD) defined by the Phase I study until disease progression or intolerance. The objectives were to determine the MTD and assess activity and safety.

Results As of June 15, 2014, 28 newly diagnosed MM patients were enrolled. Median age was 74 years, 29% of patients were older than 75 years, 36% had ISS stage III, 24% had unfavorable FISH profile [t(4;14) or t (14;16) or del17p]. Twelve patients were enrolled in the Phase I portion of the study. At dose level 0 (Carfilzomib 45 mg/m²) no DLT was reported; at dose level 1 (Carfilzomib 56 mg/m²), 1 of 6 patients experienced DLT, consisting of grade 3 creatinine increase; at dose level 2 (Carfilzomib 70 mg/m²) no DLT occurred. The MTD of weekly Carfilzomib was thus established as 70 mg/m².

Toxicity and response data are available for 25 patients, who have completed at least the first cycle; 3 patients are currently receiving their first cycle of treatment. Grade 3-4 drug-related adverse events occurred in less than 15% of patients and included neutropenia (12%, 3 patients), anemia (12%, 3 patients), acute pulmonary edema (8%, 2 patients), pulmonary embolism (4%, 1 patient), creatinine increase (4%, 1 patient), nausea (4%, 1 patient), and fatigue (4%, 1 patient). No peripheral neuropathy was observed. Overall, the wCCd regimen was well tolerated, 3 patients (12%) required Carfilzomib dose reduction (grade 3 creatinine increase, grade 3 transaminase increase and grade 2 fever) and 3 patients (12%) required drug discontinuation due to adverse events (2 acute pulmonary edemas and 1 creatinine increase).

Patients received a median of 5 cycles (range 1-9). After 4 induction cycles, 83% of patients achieved at least partial response, 39% at least very good partial response, and 22% complete response. Responses improved over time, as shown in table 1. During the study, only 2 patients progressed and 1 patient died, due to acute pulmonary edema considered probably related to treatment.

Conclusions This is the first prospective study evaluating once weekly carfilzomib in treatment-naïve MM. wCCd therapy appears safe and effective in newly diagnosed MM patients. Responses became deeper with subsequent cycles and toxicities were manageable. The response rate observed with weekly carfilzomib compares favorably with similar studies with standard twice weekly carfilzomib infusion. Updated results will be presented at the meeting.