A Phase I/Ii Study Of Twice Weekly Ixazomib Plus Pomalidomide And Dexamethasone In Relapsed And Refractory Multiple Myeloma: Results From Phase I Dose Escalation Cohorts

Introduction: Treatment of relapsed and refractory multiple myeloma (RRMM) continues to evolve as most patients are lenalidomide (LEN) refractory at the time of first relapse with its widespread use in both induction and maintenance therapy. Pomalidomide, bortezomib and dexamethasone in RRMM has demonstrated significant activity and improvement in progression-free survival in LEN-refractory patients (Richardson et al Lancet Oncol 2019 Jun;20(6):781-794). Ixazomib is a novel oral proteasome inhibitor (PI) that is currently approved in combination with LEN and dexamethasone in RRMM. Ixazomib is administered on a once weekly schedule and its oral route of administration is particularly attractive, not least in the context of the current COVID-19 pandemic. Twice weekly dosing of ixazomib has been studied in combination with LEN demonstrating promising activity in NDMM (Richardson et al, Br J Haematol. 2018 Jul;182(2):231-244). Moreover, safety and efficacy has been shown in RRMM as twice weekly monotherapy on this schedule (Richardson et al, Blood 2014 Aug 14;124(7):1038-46). We hypothesized that a twice weekly ixazomib schedule in combination with pomalidomide and dexamethasone will lead to enhanced efficacy and comparable safety in RRMM.