A Study to Learn About the Investigational Medicine Called PF-06821497 (Mevrometostat) in Men With mCRPC Who Were Previously Treated With Abiraterone Acetate for Prostate Cancer (MEVPRO-1).

Eligibility Criteria

Inclusion Criteria:

* Histologically or cytologically confirmed adenocarcinoma of the prostate without small cell features.
* Metastatic disease in bone documented on bone scan, or in soft tissue documented on CT/MRI scan.
* Progressive disease in the setting of surgical or medical castration.
* Eastern Cooperate Oncology Group (ECOG) performance status 0 - 2, with life expectancy of at least 6 months as assessed by the investigator.

Exclusion Criteria:

* Any medical or psychiatric condition including recent (within the past year) or active suicidal ideation/behavior or laboratory abnormality that may make the participant. inappropriate for the study.
* Clinically significant cardiovascular disease.
* Known or suspected brain metastasis or active leptomeningeal disease or clinically significant history of seizure.
* Prior treatment for prostate cancer at any stage with any cytotoxic chemotherapy, radioligand therapy, androgen receptor signaling inhibitors (ARSi) including enzalutamide, apalutamide, darolutamide, poly ADP-ribose polymerase (PARP) monotherapy or other systemic anti-cancer treatment. with the following exceptions:

1. Treatment with first-generation antiandrogen agents, if discontinued prior to randomization
2. Docetaxel treatment is allowed for mCSPC, as long as no signs of failure, or disease progression occurred during treatment or within 3 months of treatment completion.
* Previous administration with an investigational product within 30 days or 5 half-lives preceding the first dose of study intervention (whichever is shorter).
* Inadequate organ function.