A Phase 1 interventional study of Mevrometostat (PF-06821497) and Enzalutamide in Metastatic Castration Resistant Prostate Cancer (mCRPC), Small Cell Lung Cancer (SCLC) and Follicular Lymphoma (FL), sponsored by Pfizer. Recruiting at 85 sites in 8 countries. Open to participants aged 18 Years and older. Per ClinicalTrials.gov, last updated 2026-10-15.
Sponsored by Pfizer · Phase 1, Interventional, and Treatment
The purpose of this study is to learn about the safety and effects of the study medicine (called Mevrometostat) for the possible treatment of Relapsed/ Refractory Small Cell Lung Cancer (SCLC), Castration Resistant Prostate Cancer (CRPC) and Follicular Lymphoma (FL). The study consists of 3 parts; Part 1 and 2 enrolled participants with SCLC, metastatic CRPC, and FL are closed for enrollment.
Part 3, which is open for enrollment is seeking men who:
All participants in Part 3 of this study will receive mevrometostat and/ or enzalutamide. Part 3 consists of 2 sub studies each has an assessment phase and a maintenance phase. The Part 3 DDI substudy consist of 2 cohorts, Cohort 1 (monotherapy cohort) and Cohort 2 (Combination cohort).
In the assessment phase:
After completion of the assessment phase, participants will enter the maintenance phase where they will receive mevrometostat 2 times a day and enzalutamide 1 time a day by mouth until their cancer is no longer responding.
The study will look at the experiences of participanrs receiving the study medicine. This will help see if the study medicine is safe and effective.
This is an open label, multi center, Phase 1 dose escalation and dose expansion study of mevrometostat (PF-06821497) administered orally BID as a single agent or in combination with SOC to patients with CRPC, SCLC, and FL. The study consists of three parts (Part 1, Part 2, and Part 3) along with the Japan and China monotherapy cohorts. Part 1 and Part 2 are closed for enrollment. Part 1 tested monotherapy in 3 cohorts (Parts 1A, 1B, and 1C); Part 2 tested combination therapy in Parts 2A (dose escalation), 2B and 2C (does expansion).
Part 3 consists of the Bioequivalence (BE) and drug-drug interaction (DDI) substudies and are open for enrollment. The BE substudy will test between 2 mevrometostat formulation to confirm that they work in the body the same way. The DDI substudy will evaluate the effect of a strong CYP3A4 (an enzyme in your body that breaks down/ removes drugs) inhibitor on the PK of mevrometostat; a strong CYP3A4 inhibitor may slow down the breakdown/ removal of drugs in your body. The Sponsor may choose to delay or discontinue any cohorts or substudies.
1,301 studies on the registry are indexed under Small Cell Lung Carcinoma; 367 are open to participants now.
This study's planned enrollment of 453 is above the median of 56 across 1,077 interventional studies indexed under Small Cell Lung Carcinoma.
Browse Small Cell Lung Carcinoma 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.
Part 1 and Part 2 (Closed for enrollment).
Part 3 Key Inclusion Criteria:
Part 3 Key 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.
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.
The study doctor’s estimate of how long someone is likely to live. Criteria use it so that people can stay in the study long enough for it to answer its question.
On an ECG, the QT interval is the time the heart’s lower chambers take to activate electrically and recover in each beat. QTc is that time adjusted for heart rate (QTcF by Fridericia’s formula, QTcB by Bazett’s). Some medicines lengthen it, and a long QTc can raise the risk of a dangerous heart rhythm.
The study may name a correction formula and a limit in milliseconds, often around 450–480.
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.
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.
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.
Life expectancy
The study doctor’s estimate of how long someone is likely to live. Criteria use it so that people can stay in the study long enough for it to answer its question.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
QT and QTc
On an ECG, the QT interval is the time the heart’s lower chambers take to activate electrically and recover in each beat. QTc is that time adjusted for heart rate (QTcF by Fridericia’s formula, QTcB by Bazett’s). Some medicines lengthen it, and a long QTc can raise the risk of a dangerous heart rhythm.
The study may name a correction formula and a limit in milliseconds, often around 450–480.
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.
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.
Participants with SCLC, CRPC and FL will receive mevrometostat at escalating dose levels
Drug: Mevrometostat (PF-06821497)
Participants with FL will receive mevrometostat at escalating dose levels
Drug: Mevrometostat (PF-06821497)
Participants with mCRPC will receive mevrometostat at escalating dose levels.
Drug: Mevrometostat (PF-06821497)
Participants with mCRPC and SCLC will receive mevrometostat at escalating dose levels in combination with SOC.
Drug: Mevrometostat (PF-06821497) · Drug: Enzalutamide
Participants with CRPC will receive mevrometostat in combination with SOC or SOC alone.
Drug: Mevrometostat (PF-06821497) · Drug: Enzalutamide
Participants with CRPC will receive mevrometostat at one or two doses
Drug: Mevrometostat (PF-06821497)
Participants will receive mevrometostat at one or two doses
Drug: Mevrometostat (PF-06821497)
Participants with mCRPC will receive mevrometostat at a different dose/dosing regimen than that of Part 2B in combination with SOC
Drug: Mevrometostat (PF-06821497) · Drug: Enzalutamide
In the assessment phase, each enrolled participant will receive single doses of the 2 different mevrometostat formulations in 3 periods with alternating dosing and washout between each dose. In the maintenance phase, each participant will receive mevrometostat 2 times a day and enzalutamide 1 time a day.
Drug: Mevrometostat (PF-06821497) · Drug: Enzalutamide
The DDI substudy assessment phase will consist of 2 Cohorts, Cohort 1 (monotherapy cohort) and Cohort 2 (combination cohort). In the Cohort 1 assessment phase, each enrolled participant will receive a combination of mevrometostat and itraconazole based on preset schedule. In the Cohort 2 assessment phase, each enrolled participant will receive a combination of mevrometostat, enzalutamide, and itraconazole based on preset schedule. In the maintenance phase, each participant will receive mevrometostat 2 times a day and enzalutamide 1 time a day.
Drug: Mevrometostat (PF-06821497) · Drug: Enzalutamide · Drug: Itraconazole
Oral continuous
Also known as: EZH2i
Oral continuous
Also known as: Xtandi
Oral solution
Also known as: Sporanox, Tolsura, Onmel
Percentage of patients with dose limiting toxicities (DLTs) to determine the maximum tolerated dose (MTD)
First cycle DLTs will be utilized to determine the MTD
Time frame: Baseline up to 90 days
Overall safety profile including adverse events
Adverse Events will be graded by National Cancer Institute Common Terminology Criteria for Adverse Events (NCI CTCAE version \[4.03\])
Time frame: Baseline up to approximately 2 years
Preliminary efficacy determination as evaluated by disease specific response criteria
Objective response using Response Evaluation Criteria in Lymphoma (RECIL) for lymphoma, Response Evaluation Criteria in Solid Tumors (RECIST) 1.1 for solid tumors including Small Cell Lung Cancer (SCLC) and Prostate Cancer Working Group 3 (PCWG3) for Castration Resistant Prostate Cancer (CRPC). Progression-free survival in Part 2B in patients with CRPC.
Time frame: Through study completion, approximately 2 years past last patient first visit.
Overall safety profile including laboratory abnormalities
Laboratory abnormalities as characterized by type, frequency, severity (as graded by NCI CTCAE version \[4.03\]), and timing.
Time frame: Baseline up to approximately 2 years
Overall safety profile including vital signs
Vital sign changes from baseline including blood pressure, heart rate, ECG changes.
Time frame: Baseline up to approximately 2 years
Evaluate time to event mevrometostat and enzalutamide vs enzalutamide alone including radiographic prgression free survival
PCWG3
Time frame: Baseline until disease progression or death or through study completion (approx 2 years)
Evaluate time to event anti-tumor activity of mevrometostat including progression-free survival (PFS), PSA50, Duration of Response (DoR), Time to first skeletal related event and Time to symptomatic skeletal related event, depending on tumor type.
Time to event endpoints based on Response Evaluation Criteria in Lymphoma (RECIL) for lymphoma, Response Evaluation Criteria in Solid Tumors (RECIST) 1.1 for solid tumors including Small Cell Lung Cancer (SCLC) and Prostate Cancer Working Group 3 (PCWG3) for Castration Resistant Prostate Cancer (CRPC)
Time frame: Baseline and every 21 days through time of confirmed disease progression, unacceptable toxicity, or through study completion, approximately 2 years.
Evaluate overall survival
Median time to death proportion of patients alive at 6 months, 1 year, and 2 years.
Time frame: Baseline up to approximately 2 years
Pharmacokinetic Parameters: Maximum Observed Plasma Concentration (Cmax)
Single dose and multiple dose PK will be calculated as data permits
Time frame: At specific timepoints from Cycle 1 day 1 to End of Treatment visit
Pharmacokinetic Parameters: Time to Reach Maximum Observed Plasma Concentration (Tmax)
Single dose and multiple dose PK will be calculated as data permits
Time frame: At specific timepoints from Cycle 1 day 1 to End of Treatment visit
Pharmacokinetic Parameters: Area Under the Curve (AUC)
Single dose and multiple dose PK will be calculated as data permits
Time frame: At specific timepoints from Cycle 1 day 1 to End of Treatment visit
Pharmacokinetic Parameters: Apparent Oral Clearance (CL/F)
Single dose and multiple dose PK will be calculated as data permits
Time frame: At specific timepoints from Cycle 1 day 1 to End of Treatment visit
Pharmacokinetic Parameters: Apparent Volume of Distribution (Vz/F)
Single dose and multiple dose PK will be calculated as data permits
Time frame: At specific timepoints from Cycle 1 day 1 to End of Treatment visit
Pharmacokinetic Parameters: Plasma Decay Half-Life (t1/2)
Singe dose and multiple dose PK will be calculated as data permits
Time frame: At specific timepoints from Cycle 1 day 1 to End of Treatment visit
Evaluate the impact of mevrometostat on patient reported outcomes.
Quality of Life and Time to Functional Status Deterioration as assessed by FACT-P.
Time frame: At specific time-points from Cycle 1 Day 1 to End of Treatment visit.
Impact of mevrometostat in combination with enzalutamide, enzalutamide alone and mevrometostat alone on symptoms and symptomatic toxicity
Questionnaire customized from PRO-CTCAE.
Time frame: At specific time points from Cycle1 Day 1 to end of treatment
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Plan to share: No — 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.
Started Apr 2018 (actual). Primary completion is estimated for Apr 2028, 120 months after the start.
Of 111 industry-sponsored phase 1 interventional studies under Small Cell Lung Carcinoma, half reached primary completion within 44 months of starting (the median), counting those still running; a quarter within 29 and three quarters within 63. This study's planned 120 months is above that.
Counting every sponsor, half of 143 studies reached it within 46 months; a quarter within 29 and three quarters within 64.
How these figures are worked out, and which studies are left out of them.
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 ↗
Eligibility is decided by the study team. Share this record with your doctor or contact the team directly.
Contact study teamGet an email when the registry record changes — status, dates, results — or when someone posts here.
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Studies of the drug tested here: Mevrometostat