Abstract
Optimal therapy for the growing number of patients with lenalidomide (LEN)-refractory multiple myeloma in their first relapse remains poorly defined. We therefore undertook a randomized phase 2 study to evaluate the efficacy and safety of combining the oral proteasome inhibitor ixazomib (IXA) with pomalidomide (POM) and dexamethasone (DEX) in this patient population. The overall response rate (ORR) for POM-DEX was 43.6%, and for IXA-POM-DEX, it was 63.2%. The depth of response, measured by the attainment of at least a very good partial response, favored triplet therapy over doublet therapy (28.9% vs 5.1%; P = .0063). A preplanned interim analysis after 75% of the progression events had occurred demonstrated an improvement in progression-free survival (PFS) that favored IXA-POM-DEX and that crossed the predefined boundary of superiority, leading to release of the study results. With additional follow-up, the median PFS for POM-DEX was 7.5 months (95% confidence interval [CI], 4.8-13.6 months) vs 20.3 months for IXA-POM-DEX (95% CI, 7.7-26.0 months; hazard ratio, 0.437; upper 90% bound = 0.657). The ORR and median PFS for 26 of 30 eligible patients who crossed over from the doublet to the triplet therapy at disease progression was 23.1% and 5.6 months, respectively. Overall survival was similar between the 2 groups. More hematologic toxicities were seen with the triplet therapy, but nonhematologic adverse events were similar between the 2 arms. Our data support further testing of this all-oral triplet therapy in comparison with current standard triplet therapy in the context of phase 3 studies for patients with LEN-refractory disease at first relapse. This trial was registered at www.clinicaltrials.gov as #NCT02004275.