A Phase Ib/II Open-label Study of AMO959 With Lutetium (177Lu) Vipivotide Tetraxetan (AAA617) in Combination With ARPI in Adult Participants With PSMA-positive mCRPC

This study will consist of two phases: 1. The escalation phase (Ib) will consist of provisionally three dose level cohorts of 3-6 participants investigating the safety, tolerability, and to determine the recommended dose for expansion (RDE) of AMO959 with standard dose of AAA617 +/- ARPI (abiraterone or enzalutamide). Initially AMO959 monotherapy will be administered, and then AMO959 will be given along with AAA617 in the same participants. Dose escalation meetings (DEMs) will occur when all participants in a dose level cohort have completed the DLT evaluation period or have experienced a DLT prior to the end of the evaluation period. 2. The Phase II will follow with 25 participants per arm randomized in a 1:1:1 ratio treated at the RDE(s) of AMO959 along with AAA617 and ARPI (abiraterone or enzalutamide) and AAA617 and ARPI (abiraterone or enzalutamide).