Oral ixazomib-dexamethasone versus oral pomalidomide-dexamethasone for lenalidomide-refractory, proteasome inhibitor-exposed multiple myeloma (MM) patients: A global, multicenter, randomized, open-label, phase 2 trial.

Abstract

8020 Background: MM patients (pts) often receive several lines of therapy with multiple drug combinations and, as lenalidomide (R)-containing regimens are commonly used as first-line therapy, R-free options for subsequent lines are necessary. Additionally, as pts age and become less tolerant to treatment, more convenient regimens, such as all-oral options, with less toxicity are needed. Dexamethasone (dex)-based doublets are effective and tolerable in this setting. Methods: Proteasome inhibitor (PI)-exposed and/or intolerant and R-refractory pts who had ≥2 prior therapies (N = 122) were randomized 3:2 to receive: ixazomib (ixa) 4 mg (5.5 mg from cycle 2 if tolerated) on day (d) 1, 8, 15, and dex 20 mg (≥75 years [yrs], 10 mg) on d 1, 2, 8, 9, 15, 16, 22, 23; or pomalidomide (pom) 4 mg on d 1–21, and dex 40 mg (≥75 yrs, 20 mg) on d 1, 8, 15, 22, in 28-d cycles until progressive disease (PD) or unacceptable toxicity. Pts were stratified by age ( < 65 vs ≥65 yrs), International Staging System (ISS) disease stage at study entry (I/II vs III), and prior lines of therapy (2 vs ≥3). The study was powered to test the primary endpoint of progression-free survival (PFS). Results: In the ixa-dex (n = 73) vs pom-dex (n = 49) arms, median age was 72 vs 68 yrs (36% vs 18% ≥75 yrs), 25% vs 22% of pts had ISS stage III MM, and 52% vs 53% had received ≥3 prior therapies (per stratification). At data cutoff (5/31/2020), 19% vs 20% of pts were ongoing on treatment with ixa-dex vs pom-dex; primary reasons for discontinuation were PD (47% vs 57%) and adverse events (AEs; 23% vs 12%). With median follow-up of 15.3 vs 17.3 months (mos), median PFS (mPFS) was 7.1 vs 4.8 mos with ixa-dex vs pom-dex (hazard ratio [HR] 0.847; 95% confidence interval [CI] 0.535–1.341; p = 0.477); the Table shows mPFS by prior lines, and secondary endpoints. Pts received a median of 6 cycles with both ixa-dex (range 1–25) and pom-dex (range 1–27); 64% of ixa-dex pts were able to escalate to a 5.5 mg dose of ixa. 69% vs 81% of ixa-dex vs pom-dex pts had grade (G) ≥3 AEs, 51% vs 53% had serious AEs, 39% vs 36% had an AE leading to drug discontinuation, 44% vs 32% had an AE leading to dose reduction, and 13% vs 13% died on study. Health-related quality of life (HRQoL; EORTC QLQ-C30/MY20, and EQ-5D-5L) was maintained, and similar between arms. Conclusions: Ixa-dex prolonged PFS vs pom-dex in these heavily pretreated, PI-exposed and/or intolerant, R-refractory pts, but the difference was not statistically significant. Ixa-dex was well tolerated, with lower G≥3 AE rates vs pom-dex, and comparable HRQoL. Clinical trial information: NCT03170882.