Ixazomib maintenance therapy in newly diagnosed multiple myeloma: An integrated analysis of four phase I/II studies.

OBJECTIVES: To evaluate the safety and efficacy of maintenance therapy with the oral proteasome inhibitor ixazomib in patients with newly diagnosed multiple myeloma (NDMM) not undergoing transplantation. METHODS: Data were pooled from four NDMM phase I/II studies; patients received induction therapy with once- or twice-weekly ixazomib plus lenalidomide-dexamethasone (IRd), melphalan-prednisone (IMP), or cyclophosphamide-dexamethasone (ICd), followed by single-agent ixazomib maintenance, given at the last tolerated dose during induction, until disease progression, death, or unacceptable toxicity. RESULTS: A total of 121 patients achieved stable disease or better after induction (weekly IRd, n = 25; twice-weekly IRd, n = 18; weekly or twice-weekly IMP, n = 35; weekly ICd, n = 43) and received ≥ 1 dose of ixazomib maintenance. Grade ≥ 3 drug-related adverse events occurred in 24% of patients during maintenance; each event was reported in ≤2% of patients. Rates of complete response were 22% after induction and 35% after maintenance. A total of 28 patients (23%) improved their response during maintenance. CONCLUSIONS: Ixazomib maintenance following ixazomib-based induction is associated with deepening of responses and a positive safety profile with no cumulative toxicity in patients with NDMM not undergoing transplantation, suggesting that ixazomib is feasible for long-term administration. Phase III investigation of ixazomib maintenance is ongoing.

A phase I/II dose-escalation study investigating all-oral ixazomib-melphalan-prednisone induction followed by single-agent ixazomib maintenance in transplant-ineligible newly diagnosed multiple myeloma.

This phase I/II dose-escalation study investigated the all-oral ixazomib-melphalan-prednisone regimen, followed by single-agent ixazomib maintenance, in elderly, transplant-ineligible patients with newly diagnosed multiple myeloma. Primary phase I objectives were to determine the safety and recommended phase II dose of ixazomib-melphalan-prednisone. The primary phase II objective was to determine the complete plus very good partial response rate. In phase I, patients were enrolled to 4 arms investigating weekly or twice-weekly ixazomib (13 28-day cycles or nine 42-day cycles) plus melphalan-prednisone. In phase II, an expansion cohort was enrolled at the recommended phase II ixazomib dose. Of the 61 patients enrolled, 26 received the recommended phase II dose (ixazomib 4.0 mg [days 1, 8, 15] plus melphalan-prednisone 60 mg/m2 [days 1-4], 28-day cycles). Of the 61 enrolled patients, 36 (13 of 26 in the recommended phase II dose cohort) received single-agent ixazomib maintenance (days 1, 8, 15; 28-day cycles). In phase I, 10/38 patients reported dose-limiting toxicities in cycle 1, including grade 3 and/or 4 neutropenia (n=6) and thrombocytopenia (n=4). Complete plus very good partial response rate was 48% (48% at recommended phase II dose), including 28% (22%) complete response or better; responses deepened during maintenance in 34% (33%) of evaluable patients. After median follow up of 43.6 months, median progression-free survival was 22.1 months. Adverse events were mainly hematologic events, gastrointestinal events, and peripheral neuropathy. This study demonstrates the feasibility, tolerability, and activity of ixazomib-melphalan-prednisone induction and single-agent ixazomib maintenance in transplant-ineligible newly diagnosed multiple myeloma patients. clinicaltrials.gov identifier 01335685.