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

• Published in: Blood 2020-11, Vol.136 (Supplement 1), p.1-2
• Main Authors: Nadeem, Omar, Mo, Clifton C, Laubach, Jacob P., Bianchi, Giada, Redd, Robert, Barth, Peter, Bayliss, Trevor J., Sanchorawala, Vaishali, Shune, Leyla, Distaso, Alexandra, Dalton, Virginia, Sperling, Adam S, Amweg, Laura, McKenney, Mary, Colson, Kathleen, Millard, Ella L, Hou, Isabella, Savell, Alexandra, Masone, Kelly, Munshi, Nikhil C., Ghobrial, Irene M., Anderson, Kenneth, Richardson, Paul G.
• Format: Article
• Language: English
• ISSN: 0006-4971; 1528-0020
• DOI: 10.1182/blood-2020-141549

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. Methods: This is a phase I/II multicenter, single-arm, open label study evaluating the combination of twice weekly ixazomib with pomalidomide and dexamethasone in RRMM. Primary objective for phase I portion is to determine safety and the maximum tolerated dose (MTD) of this combination using a standard 3+3 dose escalation design. Ixazomib is studied at doses of 3mg or 4mg on days 1, 4, 8, 11, pomalidomide at a dose of 2mg, 3mg and 4mg on days 1-14 and dexamethasone is administered at a dose of 12mg on days 1, 2, 4, 5, 8, 9, 11, 12 (8mg for patients > 75 years old) on a 21 day cycle (Table 1). Patients were included if they received 2 prior lines of therapy, but 1 prior line was allowed if first line treatment included a PI and an immunomodulatory agent and disease relapse occurred within 60 days of last therapy. Patients who received prior ixazomib were excluded. Results: At the time of data cutoff, 12 patients have been enrolled across cohorts 0, 1 and 2 and enrollment in the final cohort 3 is ongoing. Median age at the time of enrollment was 70 years old with slight male predominance (58%). ISS stage at diagnosis was II or greater in 75% of patients and 9 out of 12 (75%) patients had high-risk FISH as follows: del 17p (17%