https://orcid.org/0000-0003-1661-718X
Key Points
Ixazomib added to pomalidomide and dexamethasone improved progression-free survival for lenalidomide-refractory patients in first relapse.
The safety profile of the ixazomib-pomalidomide-dexamethasone triplet was favorable and support phase III study of this all-oral regimen.
Optimal therapy for the growing number of patients with lenalidomide (LEN)-refractory multiple myeloma (MM) in first relapse remains poorly defined. We therefore undertook a randomized phase II study evaluating the efficacy and safety of combining the oral proteasome inhibitor ixazomib (IXA) with pomalidomide (POM) and dexamethasone (DEX) for this patient population. The overall response rate (ORR) for POM-DEX was 43.6% and 63.2% for IXA-POM-DEX. Depth of response, as measured by attainment of a very good partial response or better favored the triplet over the doublet, 28.9% vs 5.1%, respectively (p = 0.0063). A pre-planned interim analysis after 75% of the progression events had occurred demonstrated a progression-free survival (PFS) advantage favoring IXA-POM-DEX 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]). ORR and median PFS for the 26 of 30 eligible patients who crossed over from the doublet to the triplet at progression was 23.1% and 5.6 months, respectively. Overall survival was similar between the two groups. More hematologic toxicities were seen with the triplet, but non-hematologic adverse events were similar between the two arms. Our data support further testing of this all-oral triplet vs current standard triplet therapy in the context of phase III studies for patients with LEN-refractory disease in first relapse. This trial is registered at www.clinicaltrials.gov as NCT02004275.
