Phase 1 study of isatuximab monotherapy in Chinese patients with relapsed/refractory multiple myeloma

In this multi-center, Phase-1 study (NCT03733717), we characterized the pharmacokinetics (PK) of the anti-CD38 antibody isatuximab (Isa) after IV administration (primary objective), and evaluated safety, immunogenicity, and preliminary anti-myeloma activity in Chinese patients with relapsed/refractory multiple myeloma (RRMM). Isa 20-mg/kg was administered weekly (QW) in cycle 1, then biweekly (Q2W). Twenty-one extensively pretreated RRMM patients (median 4 prior lines; 95.2% refractory to last regimen), received ≥ 1 dose of Isa. After first IV-infusion, mean maximum observed concentration was 402 μg/mL and mean area-under-the-concentration-versus-time curve (first 1-week dosing interval) 37,000 μg·h/mL. After repeated administration, exposure (C_trough) increased 3.11-folds (day 1/cycle 2) versus first administration (day 8/cycle 1). Safety findings were consistent with the known Isa safety profile, with no new safety signals. Any-causality, grade ≥ 3 treatment-emergent adverse events (TEAEs) were reported in 47.6% of patients. Serious, treatment-related AEs occurred in 2 patients. Isa treatment was generally well tolerated; only 1 patient discontinued due to TEAE. Preliminary efficacy results showed a 19.0% overall response rate (clinical benefit, 33.3%). Our results demonstrate a PK profile for Isa comparable to prior findings in Western and other East-Asian populations, as well as safety and tolerability of treatment with IV Isa 20-mg/kg QW-Q2W in Chinese RRMM patients.Trial registration: The trial was registered with ClinicalTrials.gov; NCT03733717. Date of first trial registration: 07/11/2018.