A Study of Terbium 161 (161Tb)-RAD402 in Participants With CRPC

The purpose of this study is to establish the safety profile, biodistribution, pharmacokinetics (PK), and radiation dosimetry of 161Tb-RAD402, to determine the maximum tolerated dose (MTD) and/or recommended Phase 2 dose (RP2D), and to evaluate preliminary anti-tumor activity in participants with locally advanced or metastatic Castration-Resistant Prostate Cancer (CRPC). The study is divided into 2 phases. Phase 1 is the dose escalation phase to establish the safety profile of 161Tb-RAD402 and to determine the MTD and/or RP2D of 161Tb-RAD402 using a Bayesian Optimal Interval (BOIN) design. Phase 2a is the dose expansion phase at the RP2D to confirm the safety of the MTD and/or RP2D and to evaluate preliminary anti-tumor activity of 161Tb-RAD402 using a probability of success design for Prostate Specific Antigen (PSA)50 based on a Bayesian beta-binomial design. Participants ≥ 18 years of age with CRPC who have documented disease progression during or after their most recent line of anticancer therapy will be eligible to enroll. Each phase consists of a Screening Period, a Treatment and Imaging Period, and a Safety and Long-term Follow-up Period.