Fusion Pharmaceuticals Inc. announced that the first patient has been dosed in the Phase 2 portion of the AlphaBreak trial evaluating FPI-2265 (225Ac-PSMA I&T) in patients with metastatic castration-resistant prostate cancer (mCRPC). The AlphaBreak trial is a Phase 2/3, randomized, open-label, multicenter study to evaluate the safety and efficacy of FPI-2265 in patients with mCRPC previously treated with 177Lu-PSMA radiotherapy. The Phase 2 dose optimization portion is designed to evaluate whether there are added safety and/or efficacy benefits of two alternative dosing regimens in comparison to the previously studied regimen of 100 kBq/kg every eight weeks.

The Phase 2 portion of the AlphaBreak trial is expected to complete enrollment of approximately 60 patients by the end of 2024. Following analysis of the Phase 2 data and an end of Phase 2 meeting to determine the recommended Phase 3 dosing regimen with the U.S. Food and Drug Administration (FDA), the Phase 3 global registration portion of the AlphaBreak trial will enroll approximately 550 patients and is expected to begin in 2025. FPI-2265 is an actinium-225 based PSMA targeting RC, for mCRPC, currently in a Phase 2 trial.

Actinium-225 emits alpha particles and holds the promise of being a next-generation radioisotope in cancer treatment. By delivering a greater radiation dose over a shorter distance, alpha particles such as actinium-225 have the potential for more potent cancer cell killing, and targeted delivery, thereby minimizing damage to surrounding healthy tissue.