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Prashant Kapoor, MD, FACP


AACR 2023: First-in-Human Study Results on New Bispecific Antibody in Resistant Myeloma

By: Celeste L. Dixon
Posted: Monday, May 1, 2023

Patients with multiple myeloma may have another eventual treatment option, once others have failed: REGN5459, a B-cell maturation antigen (BCMA) × CD3 bispecific antibody. The results of the agent’s first-in-human study were presented at the American Association for Cancer Research (AACR) Annual Meeting 2023 (Abstract CT013) by Attaya Suvannasankha, MD, of Indiana University Simon Cancer Center, Indianapolis, and colleagues. The longest response was ongoing for more than 22 months.

Preclinical work demonstrated that REGN5459 binds to BCMA on multiple myeloma cells and with low affinity to CD3 on T cells, triggering T-cell activation and plasma cell depletion with low cytokine release. In this phase I/II study, the team assessed the safety, tolerability, and dose-limiting toxicities of REGN5459 monotherapy in 43 enrolled patients with relapsed or refractory multiple myeloma who had exhausted all available treatment options.

The recommended phase II dose of REGN5459 was determined to be 480 mg. In phase II, the researchers assessed REGN5459’s preliminary antitumor activity, per overall response rate, which was 100%. Overall, the median time to response was 0.8 months. Of the eight patients with a complete response or better with available measurable residual disease (MRD) results, four achieved MRD negativity at the 10-5 threshold.

All patients experienced at least one treatment-emergent adverse event, and 74% had treatment-emergent adverse events of grade 3 or higher. One patient developed immune effector cell–associated neurotoxicity syndrome (grade 2). Overall, 63% of patients experienced serious treatment-emergent adverse events, and 16% had treatment-emergent adverse events leading to treatment discontinuation. Of note, no cytokine-release syndrome of grade 3 or higher occurred in patients who received the recommended phase II dose.

Dr. Suvannasankha and co-investigators believe REGN5459 warrants further research.

Disclosure: The study authors’ disclosure information can be found at

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