A multicenter phase I study of inebilizumab, a humanized anti-CD19 monoclonal antibody, in Japanese patients with relapsed or refractory B-cell lymphoma and multiple myeloma

This multicenter, phase I, open-label dose escalation study evaluated safety, tolerability, pharmacokinetics, and preliminary anti-tumor activity of inebilizumab in Japanese patients with relapsed/refractory diffuse large B-cell lymphoma (DLBCL), chronic lymphocytic leukemia (CLL), follicular lymphoma (FL), or multiple myeloma (MM) who were ineligible for hematopoietic stem cell transplantation. Patients received inebilizumab 2, 4, or 8 mg/kg intravenously on days 1 and 8 of the first 28-day cycle, and once every 28 days thereafter, with a 12 mg/kg cohort added. Twenty patients (11 FL, six DLBCL, two CLL, and one MM) received inebilizumab at four dose levels (2 mg/kg cohort, n = 3; 4 mg/kg cohort, n = 7; 8 mg/kg cohort, n = 4; 12 mg/kg cohort, n = 6). Three patients experienced dose-limiting toxicities: grade 4 neutropenia/grade 3 leukopenia (n = 1, 12 mg/kg) and grade 3 infusion reaction (n = 1 each, 4 mg/kg and 12 mg/kg); the maximum tolerated dose was 8 mg/kg. Four (three FL and one DLBCL) patients achieved complete response; eight (six FL and two DLBCL) achieved partial response. Overall response rate was 60%. Over the dose ranges evaluated, the pharmacokinetic profile of inebilizumab in Japanese patients was generally dose proportional. This phase I study showed acceptable toxicity and preliminary and promising efficacy of inebilizumab in patients with relapsed/refractory FL and DLBCL.