Anti-CD38 antibody isatuximab monotherapy for Japanese individuals with relapsed/refractory multiple myeloma: An update of the phase 1/2 ISLANDs study

The primary analysis of the phase 1/2 ISLANDs study in Japanese individuals with relapsed/refractory multiple myeloma (RRMM) showed that isatuximab monotherapy was well tolerated and effective, even in participants with high-risk cytogenetic abnormalities. Here, we report a prespecified second analysis conducted 20 months after the first dosing of the last participant ( identifier: NCT02812706). The primary objectives were to evaluate the safety and tolerability of isatuximab in phase 1 and to evaluate the efficacy of isatuximab, including assessment of overall response rate (ORR) at the recommended dose (RD), in phase 2. In phase 1, three participants received isatuximab 10 mg/kg every week (QW) for 4 weeks/cycle followed by every 2 weeks (Q2W) and five participants received 20 mg/kg QW/Q2W. Since no dose-limiting toxicities occurred in phase 1, 20 mg/kg QW/Q2W was identified as the RD for the phase 2 study (n = 28). At the time of data cut-off, three participants (one in phase 1 and two in phase 2) continued to receive isatuximab; disease progression and treatment-related adverse events were the most common reasons for treatment discontinuation. The overall safety profile was consistent with the primary analysis. One death, not related to isatuximab treatment, was reported since the first analysis. The ORR and clinical benefit rate remained unchanged from the primary analysis at 36.4% (95% confidence interval [CI]: 20.4%-54.9%) and 54.5% (95% CI: 36.4%-71.9%), respectively. The median progression-free survival (PFS) was 5.6 months, longer than the median PFS reported in the primary analysis (4.7 months), whereas median overall survival was not reached. Overall, isatuximab 20 mg/kg QW/Q2W had an acceptable safety and tolerability profile and showed promising antitumor activity in Japanese individuals with RRMM.