Talazoparib Plus Enzalutamide After Progression to Abiraterone in Metastatic Prostate Cancer: (TEAM PC)

The purpose of this clinical trial is to determine the anti-tumor activity of talazoparib plus enzalutamide as first line treatment for metastatic castration resistant prostate cancer (mCRPC) in participants whose disease has progressed on abiraterone. The main questions it aims to answer are: * Does talazoparib plus enzalutamide improve efficacy in metastatic castration resistant prostate cancer (mCRPC) compared to enzalutamide alone? * What is the time to disease progression \[radiographic, Prostate Specific Antigen (PSA), clinical\] in participants treated with talazoparib plus enzalutamide after progression on abiraterone? * What medical problems do participants have when receiving talazoparib plus enzalutamide? Researchers will compare the combination of talazoparib and enzalutamide as a first-line treatment for mCRPC to see if the combination improves the PSA response rate and delays progression compared to enzalutamide alone. The safety and tolerability of the combination (talazoparib and enzalutamide) will also be studied

This is a multicenter, open-label, randomized, phase II trial to evaluate the efficacy of the combination of talazoparib plus enzalutamide versus enzalutamide as first line treatment for metastatic castration resistant prostate cancer (mCRPC) in participants whose disease has progressed to abiraterone based treatment for metastatic hormone sensitive prostate cancer (mHSPC). Participants who meet the eligibility criteria will be randomized 1:1 to the experimental arm (enzalutamide and talazoparib) or control arm (enzalutamide) and will receive treatment until disease progression, unacceptable toxicity, death or discontinuation from the study treatment for any other reason. Prostate cancer is the second most common malignancy in men worldwide with an estimated annual global incidence of 1.3 million and over 375,000 deaths. Aggressive variant prostate cancer is a clinically defined subset of metastatic castration resistant prostate cancers (mCRPC) characterized by the absence of response to androgen receptor (AR) targeted agents and neuroendocrine features. The treatments that are currently available are not effective, representing an unmet clinical need. The combination of talazoparib, a potent selective PARP inhibitor (PARPi) and enzalutamide (androgen receptor signaling inhibitor; ARSi) demonstrated in the TALAPRO-2 study improved efficacy in metastatic castration resistant prostate cancer (mCRPC) participants with and without DNA damage response (DDR) gene alterations as first line treatment (1L) compared to enzalutamide alone. Up to 78 participants will be enrolled and randomized 1:1 to the experimental and control arms.Up to 19 participants will be allocated into the experimental arm in Stage 1. An interim analysis will be triggered once each patient on the experimental arm has been followed up for at least 16 weeks (or earlier if response status can be ascertained definitively) to decide whether to proceed to Stage 2 or discontinue the study. If greater than or equal to 6 responses are observed, recruitment will continue to Stage 2, enrolling 20 more participants on each arm; otherwise, the trial will stop. Estimated duration of the study: 36 months. Accrual is expected to be completed in 18 months. Median treatment duration has been estimated in 10 months. After completion of (or discontinuation from) treatment, participants will be followed up for survival until end of study (EoS) that will occur at 18 months after the enrollment of the last patient included in the trial, unless premature termination of the study. It is hypothesized that after progression to abiraterone, the addition of talazoparib to enzalutamide as 1L for mCRPC will result in improved PSA response rate and delayed progression compared to enzalutamide alone.