Results from a Phase II Study of Isatuximab As a Single Agent and in Combination with Dexamethasone in Patients with Relapsed/Refractory Multiple Myeloma

Background: Isatuximab (ISA) targets CD38-expressing tumor cells through a combination of activities, including antibody-dependent cellular cytotoxicity, direct pro-apoptotic activity, and complement-dependent cytotoxicity. A phase I study evaluating ISA monotherapy demonstrated promising clinical activity in 35 patients with relapsed/refractory multiple myeloma (RRMM) (Martin T et al, J Clin Oncol 2014; 32:8532). This is an ongoing phase II study (NCT01084252) with 2 stages: stage 1 to select the dose for stage 2 of the study, and stage 2 to assess efficacy and safety of ISA monotherapy or in combination with dexamethasone in RRMM. In stage 1, patients were randomized to 1 of 3 dose groups: ISA 3 mg/kg Q2W, 10 mg/kg Q2W × 2 cycles then Q4W, or 10 mg/kg Q2W. Based on pharmacokinetic data, a fourth dose of 20 mg/kg QW × 4 doses then Q2W was added. The overall response rates (ORRs) for the 4 dosing schemes were 4% (1/23), 20% (5/25), 29% (7/24), and 24% (6/25), respectively. Based on these results, a dose of 20 mg/kg QW for cycle 1 followed by 20 mg/kg Q2W in subsequent cycles was chosen for stage 2 of the study (Richter J et al, J Clin Oncol 2016;34:8005). Here, we report the baseline characteristics and demographic data from stage 2 at the selected dosing scheme from stage 1. Full safety and efficacy data will be presented at the meeting.Methods: This study enrolled patients with MM who had previously received an immunomodulatory drug and a proteasome inhibitor. Patients received ISA monotherapy (20 mg/kg on Day 1, 8, 15, and 22 [QW] of cycle 1 followed by 20 mg/kg on Day 1 and 15 [Q2W] of subsequent cycles) or ISA in combination with dexamethasone (40 mg/day [20 mg/day in patients ≥75 years old]). The primary objective was to evaluate the activity of ISA as monotherapy and in combination with dexamethasone in patients with RRMM in terms of ORR.Results: A total of 165 patients received at least 1 cycle of treatment. Median age was 67 (37-85) years. Median time from diagnosis to first dose was 5.35 (0.7-23.0) years. Median number of prior lines was 4 (2-11) and median number of prior regimens was 6 (2-17). Patients received a median of 5 (1-17) cycles of treatment, with a median duration of exposure of 22 (1-69) weeks. Discontinuation occurred in 106 (64.2%) patients due to adverse events (15 patients, 9.1%), disease progression (85 patients, 51.5%), or patient decision (6 patients, 3.6%).Conclusion: The full efficacy and safety data for this heavily pre-treated RRMM population will be available for presentation at the meeting.Funding: Sanofi

Duke Scholars

Author Cristina Gasparetto Medicine, Hematologic Malignancies and Cellular Therapy