A Phase 3 interventional study of Mevrometostat and Placebo in Metastatic Castration Sensitive Prostate Cancer (mCSPC), Hormone Sensitive Prostate Cancer and Prostate Cancer, sponsored by Pfizer. Recruiting at 319 sites in 26 countries. Open to male participants aged 18 Years and older. Per ClinicalTrials.gov, last updated 2026-10-14.
Sponsored by Pfizer · Phase 3, Interventional, and Treatment
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.
This is a global, multicenter, randomized, double-blind, placebo-controlled Phase 3 study evaluating mevrometostat in combination with enzalutamide versus placebo in combination with enzalutamide in participants with mCSPC who have not received systemic anticancer treatments with the exception of androgen-deprivation therapy (ADT) and first-generation antiandrogen agents. Prior therapy with up to 3 months of ADT (chemical or surgical) is allowed, with no radiographic evidence of disease progression or rising PSA levels prior to Day 1.
This study consists of a Screening Phase, Randomization, Treatment Phase, Safety Follow-up, and Long-Term Follow-up. Participants will be randomized on a 1:1 basis to receive (Arm A) mevrometostat (PF-06821497) in combination with enzalutamide, or (Arm B) placebo in combination with enzalutamide.
7,046 studies on the registry are indexed under Prostatic Neoplasms; 1,580 are open to participants now.
This study's planned enrollment of 1,000 is above the median of 60 across 5,348 interventional studies indexed under Prostatic Neoplasms.
Browse Prostatic Neoplasms studies →Pfizer is the lead sponsor of 3,334 studies on the registry; 149 are open to participants now.
Of its 601 completed or terminated interventional studies of FDA-regulated products, 391 (65%) have results posted.
Counted across the registry records on this site, refreshed daily.
Go through the criteria one by one — yes, no or not sure — and take the list to your doctor or the study team. Kept in this browser only.
Exclusion Criteria
Underlined terms in the criteria open these too. Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
The diagnosis was confirmed by looking at a sample under a microscope: tissue from a biopsy or surgery (histology), or cells from a fluid or needle sample (cytology).
Your pathology report is the document that shows this.
Cancer that has spread from where it began to other parts of the body. “Metastatic” cancer is cancer that has spread this way.
The US National Cancer Institute’s scale of how severe an adverse event is — any unwanted medical event during a study, such as a symptom, an illness or an abnormal test result, whether or not a treatment caused it. Whether it did is judged separately.
“Side effects of earlier treatment resolved to grade 1 or less” means they have settled to mild or gone.
A scale of how much an illness limits everyday activity. For people being assessed to join a study, scores run from 0 (fully active) to 4; lower is more active.
Studies most often ask for 0–1 or 0–2. Your doctor gives the score; the WHO scale uses the same steps. The full scale also has 5, which records death.
Judged by the study doctor to matter for your health or for the study. It is a doctor’s decision, so ask the study team if you are unsure whether something counts.
Cancer deposits in the brain from a cancer that started elsewhere in the body (CNS metastases include the spinal cord).
Studies differ: some leave out any brain metastases, some accept ones treated and stable for some weeks. Check what this study allows.
Cancer that has spread to the leptomeninges, the thin layers covering the brain and spinal cord, and the fluid between them. It is not the same as brain metastases.
Criteria often treat it separately, and many studies leave it out even where treated brain metastases are allowed.
A drug or device being studied in a clinical trial.
It may be new, or already approved and being studied for another use, dose or form. Criteria often leave out people who took part in another study of one within a recent period, commonly 30 days or five half-lives.
CYP3A is a group of enzymes, mainly CYP3A4, in the liver and gut that break down many medicines. Some medicines, supplements and foods (grapefruit, St John’s wort) slow them down or speed them up, which changes how much of a study drug stays in the body.
Studies list them so they can be avoided or switched; bring a list of everything you take, including supplements.
An allergy, or another reaction of the immune system, to a substance. “Hypersensitivity to the study drug” means a known allergic reaction to it — not every side effect a medicine can have.
The other ingredients in a medicine besides the active drug, such as fillers, colours or preservatives.
Histologically or cytologically confirmed
The diagnosis was confirmed by looking at a sample under a microscope: tissue from a biopsy or surgery (histology), or cells from a fluid or needle sample (cytology).
Your pathology report is the document that shows this.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Metastases
Cancer that has spread from where it began to other parts of the body. “Metastatic” cancer is cancer that has spread this way.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
CTCAE grade
The US National Cancer Institute’s scale of how severe an adverse event is — any unwanted medical event during a study, such as a symptom, an illness or an abnormal test result, whether or not a treatment caused it. Whether it did is judged separately.
“Side effects of earlier treatment resolved to grade 1 or less” means they have settled to mild or gone.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
ECOG performance status
A scale of how much an illness limits everyday activity. For people being assessed to join a study, scores run from 0 (fully active) to 4; lower is more active.
Studies most often ask for 0–1 or 0–2. Your doctor gives the score; the WHO scale uses the same steps. The full scale also has 5, which records death.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Clinically significant
Judged by the study doctor to matter for your health or for the study. It is a doctor’s decision, so ask the study team if you are unsure whether something counts.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Brain metastases
Cancer deposits in the brain from a cancer that started elsewhere in the body (CNS metastases include the spinal cord).
Studies differ: some leave out any brain metastases, some accept ones treated and stable for some weeks. Check what this study allows.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Leptomeningeal disease
Cancer that has spread to the leptomeninges, the thin layers covering the brain and spinal cord, and the fluid between them. It is not the same as brain metastases.
Criteria often treat it separately, and many studies leave it out even where treated brain metastases are allowed.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Investigational drug or device
A drug or device being studied in a clinical trial.
It may be new, or already approved and being studied for another use, dose or form. Criteria often leave out people who took part in another study of one within a recent period, commonly 30 days or five half-lives.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
CYP3A (CYP3A4) inhibitors and inducers
CYP3A is a group of enzymes, mainly CYP3A4, in the liver and gut that break down many medicines. Some medicines, supplements and foods (grapefruit, St John’s wort) slow them down or speed them up, which changes how much of a study drug stays in the body.
Studies list them so they can be avoided or switched; bring a list of everything you take, including supplements.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Hypersensitivity
An allergy, or another reaction of the immune system, to a substance. “Hypersensitivity to the study drug” means a known allergic reaction to it — not every side effect a medicine can have.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Excipients
The other ingredients in a medicine besides the active drug, such as fillers, colours or preservatives.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Participants will receive mevrometostat/PF-06821497 (875 mg) BID (twice daily) + enzalutamide 160 mg QD (once daily)
Drug: Mevrometostat · Drug: Enzalutamide
Participants will receive Placebo BID (twice daily) + enzalutamide 160 mg QD (once daily)
Drug: Placebo · Drug: Enzalutamide
Oral continuous
Also known as: PF-06821497
Oral continuous
Oral continuous
Also known as: Xtandi
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.
Time frame: Randomization up to approximately 4 years
Overall survival (OS)
OS defined as the time from the date of randomization until the date of death due to any cause.
Time frame: Randomization up to approximately 9 years
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.
Time frame: Randomization up to approximately 4 years
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.
Time frame: Randomization up to approximately 4 years
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.
Time frame: Randomization up to approximately 4 years
Time to prostate specific antigen (PSA) progression
Time from the date of randomization to the date of the first PSA progression.
Time frame: Randomization up to approximately 4 years
Time to initiation of antineoplastic therapy
Time from randomization to first use of new antineoplastic therapy for prostate cancer.
Time frame: Randomization up to approximately 4 years
Time to first symptomatic skeletal event
Time from randomization to first tumor-related symptomatic bone fracture, surgery or radiotherapy to the bone, and spinal cord compression, whichever occurs first.
Time frame: Randomization up to approximately 4 years
Time from randomization to CRPC
Time from randomization to the first date of CRPC event.
Time frame: Randomization up to approximately 4 years
Incidence of Adverse Events
Type, incidence, severity \[as graded by National Cancer Institute (NCI) common terminology criteria for adverse events (CTCAE) v5.0\], seriousness and relationship to study medications of AEs.
Time frame: Randomization up to approximately 5 years
To evaluate the PK of mevrometostat when dosed in combination with enzalutamide
PK characterized by pre-dose trough and post-dose plasma concentrations of PF-06821497 at selected visits.
Time frame: Cycle 3 Day 1 to last PK draw at Cycle 5 Day 1 (cycle length is 28 days)
Change from baseline in patient reported pain symptoms per Brief Pain Inventory-Short Form (BPI-SF)
Analysis of Brief Pain Inventory-Short Form (BPI-SF) will be based on the pain severity score (mean of individual BPI-SF items 3, 4, 5 and 6), the pain interference score (mean of items 9A-9G), and the single BPI-SF Item 3.
Time frame: Randomization up to approximately 5 years
Change from baseline in health-related quality of life (HRQoL) per Functional Assessment of Cancer Therapy - Prostate (FACT-P)
Change from baseline in HRQoL (FACT-P total score) will be presented. The FACT-P total score will be calculated based on the participant responses to the 39 items in the FACT-P questionnaire.
Time frame: Randomization up to approximately 5 years
Time to definitive deterioration in patient-reported health related quality of life (HRQoL) per FACT-P
Defined as the time from randomization to onset of definitive deterioration in FACT-P total score, which is defined as \>10 point decrease from baseline and no subsequent observations with a \<10 point decrease from baseline FACT-P total score
Time frame: Randomization up to approximately 5 years
Patient-reported outcomes in cancer specific symptoms - time to definitive deterioration
Change from baseline and time to definitive deterioration in participant-reported prostate cancer specific functioning, and symptoms per EORTC QLQ-PR25
Time frame: Randomization up to approximately 5 years
Change from baseline and time to confirmed deterioration in participant-reported fatigue symptoms per BFI
Change from baseline and time to confirmed deterioration in participant-reported fatigue symptoms (fatigue severity and fatigue interference) as per BFI.
Time frame: Randomization up to approximately 5 years
Change from baseline in participant-reported general health status per EQ-5D-5L
Participants will self-rate their current state of mobility, self-care, usual activities, pain/discomfort, and anxiety/depression by choosing 1 of 5 possible responses that record the level of severity (no problems, slight problems, moderate problems, severe problems, or extreme problems) within each dimension.
Time frame: Randomization up to approximately 5 years
To assess circulating tumor DNA (ctDNA) at baseline and on treatment to evaluate tumor burden
Evaluation of ctDNA burden at baseline and on study.
Time frame: Baseline up to approximately 4 years
Prostate Specific Antigen Response, Undetectable PSA after Randomization
The proportion of participants with undetectable PSA values after randomization, in participants with detectable PSA values at baseline, will be calculated for each treatment arm.
Time frame: Randomization up to approximately 4 years
Showing the first 100 of 319 sites across 26 countries. Choose a country and city above to see the rest.
Plan to share: Yes — Pfizer will provide access to individual de-identified participant data and related study documents (e.g. protocol, Statistical Analysis Plan (SAP), Clinical Study Report (CSR)) upon request from qualified researchers, and subject to certain criteria, conditions, and exceptions. Further details on Pfizer's data sharing criteria and process for requesting access can be found at: https://www.pfizer.com/science/clinical_trials/trial_data_and_results/data_requests.
Data sharing details ↗ · www.pfizer.com
From the registry record's own update history. This site started tracking changes on Sep 25, 2026; for anything earlier, see the record history on ClinicalTrials.gov ↗
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Studies of the drug tested here: Mevrometostat