A Phase 1/2 study of teclistamab, a humanized BCMA × CD3 bispecific Ab in Japanese patients with relapsed/refractory MM.

We characterized the safety and efficacy of the bispecific antibody teclistamab in Japanese patients with relapsed/refractory multiple myeloma (RRMM). Patients were pretreated with a proteasome inhibitor (PI), immunomodulatory drug (IMiD), and anti-CD38 monoclonal antibody (mAb). The primary endpoint was frequency and type of treatment-emergent adverse events (TEAEs) in phase 1, and overall response rate (ORR; ≥ partial response [PR]) in phase 2. In phase 1, 14 patients received once-weekly (QW) subcutaneous teclistamab (0.72 mg/kg [n = 5]; 1.5 mg/kg [n = 5]; 3 mg/kg [n = 4]). No dose-limiting toxicities were observed. As of April 2024, 26 phase-2 patients received the recommended phase-2 dose (QW) (RP2D: 1.5 mg/kg) of teclistamab. Biweekly (Q2W) dosing was allowed after maintaining response for ≥ 6 months. At a median follow-up of 14.32 months, ORR was 76.9% (≥ very good PR: 76.9%; ≥ complete response: 65.4%). Median duration of response, progression-free survival, and overall survival were not reached. Common TEAEs included CRS (grade ≤ 2), neutropenia, and infections. No patient had immune effector cell-associated neurotoxicity syndrome (ICANS) and dose reductions. Teclistamab demonstrated deep and durable responses in Japanese patients with RRMM, consistent with the global pivotal MajesTEC-1 study, supporting the potential for a new standard of care for Japanese RRMM patients.