Multiple myeloma (MM) patients who have become refractory to bortezomib (BORT) and refractory or otherwise ineligible for thalidomide or lenalidomide (LEN) have a poor prognosis, with a median overall survival (OS) of 9 months (Kumar. Leukemia.
2012). There is no standard treatment available for these patients. Pomalidomide (POM) is a novel immunomodulatory drug that has shown activity in LEN- and BORT-refractory patients (Vij. ASCO 2012). MM-003 is an open-label, multicenter, phase 3 trial designed to compare the efficacy and safety of POM + low-dose dexamethasone (LoDEX) vs high-dose dexamethasone (HiDEX) in a population of patients who are refractory to both LEN and BORT. Here we present the final progression-free survival (PFS) and interim OS analysis of MM-003.
Methods: Eligible patients with primary refractory or relapsed and refractory disease were enrolled. All patients with documented disease progression during treatment or within 60 days of completing their last myeloma therapy (including ≥ 2 consecutive cycles of LEN and BORT either alone or in combination), were randomized 2:1 to receive either POM + LoDEX (arm A) or HiDEX alone (arm B). Patients progressing on HiDEX had the opportunity to receive POM in the companion trial, MM-003C. Patients in arm A received POM 4 mg on days 1-21 and DEX 40 mg (20 mg for patients > 75 years of age) on days 1, 8, 15, and 22 in a 28-day cycle. Patients in arm B received DEX 40 mg (20 mg for patients > 75 years of age) on days 1-4, 9-12, and 17-20 in a 28-day cycle. Treatment was continued until progressive disease or unacceptable toxicity. Patients were stratified by age (≤ 75 vs > 75 years), disease population (refractory vs refractory and relapsed vs refractory and intolerant [intolerant to BORT only]), and number of prior therapies (2 vs > 2). The primary endpoint was PFS; secondary endpoints included safety, OS, overall response rate (ORR; ≥ partial response) by IMWG and EBMT criteria, duration of response, time to progression, and quality of life. OS was to be tested only if PFS would be statistically significant; therefore, alpha was controlled at 0.05 2-sided for both PFS and OS.
Results: The Data and Safety Monitoring Board (DSMB) reviewed the protocol-specified final analysis results. 455 patients were randomized from March 2011 to Sept 2012. 302 patients received POM + LoDEX, and 153 patients received HiDEX. At the time of analysis, 45% of patients in arm A and 25% of patients in arm B remained on study. The median number of prior therapies was 5 (range, 1-17). 72% of patients were refractory to both LEN and BORT. At the PFS final analysis, with a median follow-up of 18 weeks, PFS was significantly longer with POM + LoDEX vs HiDEX alone (median 15.7 vs 8.0 weeks; 267 total events; hazard ratio [HR], 0.45; P < .001). OS interim analysis was performed as planned; OS also was significantly longer with POM + LoDEX vs HiDEX alone (median not reached vs 34 weeks; 134 events; HR, 0.53; P< .001), crossing the prespecified O'brien-Fleming superiority boundary. This includes 45 pts who received POM after progressing on HiDEX. Median duration of treatment was 12.4 weeks in arm A and 8 weeks in arm B. Following DSMB review of the data, immediate crossover of arm B patients to arm A was recommended. Overall, 25% of patients in arm A and 38% in arm B died, with progressive disease and infections as the primary reasons. Frequent grade 3/4 hematologic toxicities included neutropenia (42% in arm A vs 15% in arm B), thrombocytopenia (21% vs 24%), and febrile neutropenia (7% vs 0%). Other toxicities (grade 3/4) were predominantly infections (24% vs 23%), hemorrhage (3% vs 5%), glucose intolerance (3% vs 7%), neuropathy (1% vs 1%), and venous thromboembolism (1% vs 0%). The primary reason for discontinuation was progressive disease: 35% arm A and 49% arm B. Complete results will be presented at the meeting.
Conclusions: POM + LoDEX significantly increased PFS and OS compared with HiDEX in patients who are refractory to LEN and BORT, a population with limited treatment options. The OS superiority boundary was crossed. Based on these data, POM + LoDEX should become the new standard of care in patients who have exhausted the novel agents, LEN and BORT.