Feasibility of Long-Term Proteasome Inhibition in Multiple Myeloma by In-Class Transition from Bortezomib to Ixazomib

Abstract Background The ongoing US MM-6 study is investigating in-class transition (iCT) from parenteral bortezomib-based induction to all-oral ixazomib-lenalidomide-dexamethasone (ixazomib-Rd) with the aim of increasing proteasome inhibitor (PI)-based treatment adherence/duration while maintaining quality of life (QoL) and improving outcomes. Patients and Methods US community sites are enrolling non-transplant-eligible newly diagnosed multiple myeloma (MM) patients with no evidence of progressive disease after 3 cycles of bortezomib-based therapy to receive ixazomib-Rd (up to 39 cycles or until progression/toxicity). Patients use mobile/wearable digital devices to collect actigraphy (activity/sleep) data and electronically complete QoL/treatment satisfaction/medication adherence questionnaires. Primary endpoint: progression-free survival (PFS); key secondary endpoints include response rates and therapy duration. Results At data cutoff, 84 patients had been treated (median age 73 years; 44% ≥ 75 years; 49% male; 15% black/African American; 10% Hispanic/Latino); 62% of patients remain on therapy. Mean duration of total PI therapy was 10.1 months and of ixazomib-Rd was 7.3 months. With 8 months median follow-up, 12-month PFS rate was 86% (95% confidence interval, 73–93) from both the start of bortezomib-based treatment and the start of ixazomib-Rd. Overall response rate was 62% (complete response [CR], 4%; very good partial response [VGPR], 25%; partial response [PR], 33%) after bortezomib-based induction and 70% (CR, 26%; VGPR, 29%; PR, 15%) after iCT. The ixazomib-Rd safety profile was consistent with previous clinical trial data. QoL/treatment satisfaction were maintained. Conclusion US MM-6 patients are representative of the real-world US MM population; iCT may permit prolonged PI-based therapy with promising efficacy, without impacting patients’ QoL/treatment satisfaction.