Pomalidomide (POM) with Low-Dose Dexamethasone (LoDEX) in Patients with Relapsed and Refractory Multiple Myeloma (RRMM): Outcomes Based on Prior Treatment Exposure

There are currently limited effective treatment options for patients (pts) with RRMM with prior exposure to lenalidomide (LEN), bortezomib (BORT) and chemotherapy. In a multicenter, randomized phase 2 study, POM with or without LoDEX (n=221) was active in RRMM pts who had received ≥2 prior therapies, including LEN and BORT (Richardson PG, et al. Blood 2011;118:abs 634); activity was also observed in those with disease refractory to LEN, BORT, or both (Vij R, et al. J Clin Oncol 2012;30:abs 8016). Here we characterize outcomes in the POM+LoDEX group (n=113) according to the prior treatment exposure.

Pts with RRMM who had received ≥2 prior therapies, including LEN and BORT, and had progressive disease (PD) within 60 days of their last treatment were randomized (1:1 ratio) to POM+LoDEX (POM, 4 mg/day for days 1–21 of a 28-day cycle; LoDex, 40 mg/week) or POM alone. At randomization, pts were stratified by age, prior number of treatments, and prior thalidomide exposure. At progression, pts receiving POM alone could receive POM+LoDEX at investigator's discretion. All pts received thromboprophylaxis (daily low-dose aspirin). The endpoints in this study were progression-free survival (PFS), response rates (using European Bone Marrow Transplantation [EBMT] criteria), duration of response, time to response, overall survival (OS), and safety. Response data according to prior therapy were assessed by investigator assessment.

All 113 pts assigned to POM+LoDEX had prior exposure to LEN (100%), BORT (100%), and steroids (100%). Most pts had also received prior alkylator therapy (93%), stem cell transplant (SCT) (73%), and thalidomide (THAL) (68%); 49% had received prior anthracyclines. Regimens immediately prior to study entry included BORT (50%), LEN (39%), cyclophosphamide (13%), THAL (8%), vorinostat (8%), carfilzomib (5%), and melphalan (5%). The median number of exposures to LEN and BORT in prior lines was once (range 1–4) and twice (range 1–6), respectively.

The majority of pts (80%) had received >3 prior therapies. The overall response rate (ORR) was 48% and 30% in pts who had received ≤3 and >3 prior therapies, respectively. Of the pts who had ≤3 vs > 3 prior therapies, 9% vs 1% pts achieved complete response (CR), 39% vs 29% pts achieved partial response (PR), 9% vs 12% pts achieved minimal response (MR) and 44% vs 36 % pts achieved stable disease (SD), respectively.

ORR was 34% and appeared similar regardless of prior exposure to alkylators (33%), anthracyclines (35%), SCT (35%), or THAL (35%). Median duration of response was also similar in pts who had received prior alkylators (8.4 mos), anthracyclines (10.1 mos), SCT (7.7 mos), and THAL (7.7 mos). Of the 69 pts who had a best response of SD or PD to their last prior antimyeloma therapy, 21 pts (12 SD and 9 PD) achieved a PR and 3 pts (1 SD and 2 PD) achieved a CR with POM+LoDEX treatment. Responding pts had longer time to progression (TTP; 11.1 mos) with POM+LoDex compared with the TTP (4.4 mos) observed with their last antimyeloma regimen prior to study.

The most common grade 3–4 adverse events in the POM+LoDEX group were neutropenia (41%), anemia (22%), pneumonia (22%), thrombocytopenia (19%), and fatigue (14%). The incidence of at least 1 grade 3–4 adverse event was 100% in pts with ≤ 3 prior therapies, and 88% in pts with >3 therapies.

The combination of POM+LoDEX has demonstrated an ORR of 34% in heavily pretreated pts with RRMM who have been previously exposed to LEN, BORT, steroids, and other treatments. Early treatment of POM+LoDEX (≤3 prior therapies) achieved better ORR (48%) compared with pts who received POM+LoDex later (>3 prior therapies; ORR, 30%).

Vij:Onyx: Consultancy, Research Funding; Millennium Pharma: Speakers Bureau; Celgene: Consultancy, Research Funding, Speakers Bureau. Off Label Use: Pomalidomide is an investigational drug and is not approved for the treatment of patients with any condition. Hofmeister:Celgene: Advisory Board Other, Honoraria. Richardson:Celgene, Millennium, Johnson & Johnson: Advisory Board Other. Jagannath:Onyx Pharma: Honoraria, Membership on an entity's Board of Directors or advisory committees; Merck Sharp & Dohme: Honoraria, Membership on an entity's Board of Directors or advisory committees; Millennium Pharma: Honoraria, Membership on an entity's Board of Directors or advisory committees; Celgene: Honoraria, Membership on an entity's Board of Directors or advisory committees. Siegel:Onyx: Advisory Board, Advisory Board Other, Honoraria, Speakers Bureau; Millennium Pharma: Advisory Board, Advisory Board Other, Honoraria, Speakers Bureau; Celgene: Advisory Board Other, Honoraria, Speakers Bureau; Merck: Advisory Board, Advisory Board Other, Honoraria, Speakers Bureau. Baz:Celgene, Millennium, Bristol Myers Squibb, Novartis: Research Funding. Chen:Celgene: Employment, Equity Ownership. Zaki:Celgene: Employment, Equity Ownership. Larkins:Celgene: Employment, Equity Ownership. Anderson:Acetylon, Oncopep: Scientific Founder, Scientific Founder Other; Celgene, Millennium, BMS, Onyx: Membership on an entity's Board of Directors or advisory committees.