A Phase 1 interventional study of Mervometostat (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 84 sites in 8 countries. Open to participants aged 18 Years and older. Per ClinicalTrials.gov, last updated 2026-08-24.
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.
Part 1 and Part 2 (Closed for enrollment).
Part 3 Key Inclusion Criteria:
Part 3 Key Exclusion Criteria:
Participants with SCLC, CRPC and FL will receive mevrometostat at escalating dose levels
Drug: Mervometostat (PF-06821497)
Participants with FL will receive mevrometostat at escalating dose levels
Drug: Mervometostat (PF-06821497)
Participants with mCRPC will receive mevrometostat at escalating dose levels.
Drug: Mervometostat (PF-06821497)
Participants with mCRPC and SCLC will receive mevrometostat at escalating dose levels in combination with SOC.
Drug: Mervometostat (PF-06821497) · Drug: Enzalutamide
Participants with CRPC will receive mevrometostat in combination with SOC or SOC alone.
Drug: Mervometostat (PF-06821497) · Drug: Enzalutamide
Participants with CRPC will receive mevrometostat at one or two doses
Drug: Mervometostat (PF-06821497)
Participants will receive mevrometostat at one or two doses
Drug: Mervometostat (PF-06821497)
Participants with mCRPC will receive mevrometostat at a different dose/dosing regimen than that of Part 2B in combination with SOC
Drug: Mervometostat (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: Mervometostat (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: Mervometostat (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
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.
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