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# Regeneron Prostate Cancer Trial Stops Enrollment
- URL: https://www.fdaweb.com/regeneron-prostate-cancer-trial-stops-enrollment/
- Published: 2023-08-04T12:00:00.000Z
- Updated: 2026-09-14T18:48:27.000Z
- Author: David McFarland
- Tags: Drugs, #legacy-id-D5155030

After reporting two patient deaths, Regeneron says it has discontinued enrollment in a Phase 1 prostate cancer study of REGN5678, the company’s PSMAxCD38 costimulatory bispecific antibody, used in combination with a full-dose of its programmed death receptor-1 inhibitor Libtayo (cemiplimab-rwlc). The company says it plans to assess REGN5678 combinations with lower doses of Libtayo. It also plans to enroll patients in a REGN5678 monotherapy cohort, as well as in combination with other immunotherapy modalities. Recently released [preliminary data](https://ascopubs.org/doi/abs/10.1200/JCO.2023.41.6%5Fsuppl.154?ref=fdaweb.com) on REGN5678 plus cemiplimab in patients with prostate cancer showed the first evidence of clinical activity of a CD28 co-stimulatory bispecific antibody in solid tumors.