This study will explore whether a combination of the investigational drug mevrometostat (PF-06821497) and enzalutamide will work better than taking enzalutamide alone in participants with mCSPC who are ARPI naïve and have not yet received chemotherapy in the mCSPC setting.
Male participants aged ≥18 years (or the minimum age of consent in accordance with local regulations) at screening.
Histologically or cytologically confirmed adenocarcinoma of the prostate without small cell features.
Metastatic prostate cancer documented by positive bone scan (for bone disease) or metastatic lesion(s) on CT or MRI (for soft tissue/visceral disease).
Resolution of acute effects of any prior therapy to either baseline severity or CTCAE Grade ≤1 (except for AEs which do not constitute a safety risk in the investigator's judgement).
Any medical or psychiatric condition including recent (within the past year) or active suicidal ideation/behavior or laboratory abnormality that may increase the risk of study participation or, in the investigator's judgment, make the participant inappropriate for the study.
Clinically significant cardiovascular disease.
Known or suspected brain metastasis or active leptomeningeal disease.
Participants must be treatment naïve at the mCSPC stage, eg, participants cannot have received any cytotoxic chemotherapy with the following exceptions: Treatment with first-generation antiandrogen (ADT) agents is allowed for mCSPC.
Parallel
Mevrometostat
DrugOral continuous
Placebo
DrugOral continuous
Enzalutamide
DrugOral continuous
Radiographic Progression Free Survival (rPFS)
rPFS is defined as the time from randomization until PD based on BICR assessment per RECIST v1.1 (soft tissue disease) and PCWG3 (bone disease), or death due to any cause, whichever occurs first.
Overall survival (OS)
OS defined as the time from the date of randomization until the date of death due to any cause.
Objective response in measurable soft tissue disease
The proportion of participants with measurable soft tissue disease at baseline who have a confirmed objective response of CR or PR per RECIST v1.1 will be summarized along with the 95% CI.
Duration of Response (DoR) in measurable soft tissue disease
The DoR is defined as the time from the first objective evidence of soft tissue response (CR or PR, whichever is earlier) to radiographic progression or death due to any cause whichever occurs first.
Prostate Specific Antigen Response
The proportion of participants with a 50% decline from baseline in PSA that is confirmed by a second consecutive value at least 21 days later in participants with detectable PSA values at baseline will be calculated for each treatment arm.
