ZEN-3694, Enzalutamide, and Pembrolizumab for the Treatment of Metastatic Castration-Resistant Prostate Cancer
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ClinicalTrials.gov Identifier: NCT04471974 |
Recruitment Status :
Recruiting
First Posted : July 15, 2020
Last Update Posted : March 1, 2023
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Condition or disease | Intervention/treatment | Phase |
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Castration-Resistant Prostate Carcinoma Metastatic Prostate Adenocarcinoma Metastatic Prostate Small Cell Carcinoma Stage IV Prostate Cancer AJCC v8 Stage IVA Prostate Cancer AJCC v8 Stage IVB Prostate Cancer AJCC v8 | Drug: BET Bromodomain Inhibitor ZEN-3694 Drug: Enzalutamide Biological: Pembrolizumab | Phase 2 |

Study Type : | Interventional (Clinical Trial) |
Estimated Enrollment : | 54 participants |
Allocation: | Non-Randomized |
Intervention Model: | Parallel Assignment |
Masking: | None (Open Label) |
Primary Purpose: | Treatment |
Official Title: | A Phase 2 Study of BET Bromodomain Inhibitor ZEN-3694 in Combination With Enzalutamide Plus Pembrolizumab in Metastatic Castration Resistant Prostate Cancer |
Actual Study Start Date : | January 26, 2021 |
Estimated Primary Completion Date : | December 31, 2025 |
Estimated Study Completion Date : | December 31, 2025 |

Arm | Intervention/treatment |
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Experimental: Safety Cohort
Patients receive 96mg pembrolizumab IV over 30 minutes on day 1, BET bromodomain inhibitor ZEN-3694 PO QD and enzalutamide PO QD on days 1-21. Patients not on enzalutamide prior to study enrollment or have previously discontinued enzalutamide receive BET bromodomain inhibitor ZEN-3694 beginning on day 1 of cycle 2. Cycles repeat every 21 days in the absence of disease progression or unacceptable toxicity.
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Drug: BET Bromodomain Inhibitor ZEN-3694
Given PO
Other Names:
Drug: Enzalutamide Given PO
Other Names:
Biological: Pembrolizumab Given IV
Other Names:
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Experimental: Cohort A: Transdifferentiated mCRPC
Patients receive pembrolizumab IV over 30 minutes on day 1, BET bromodomain inhibitor ZEN-3694 PO QD and enzalutamide PO QD on days 1-21. Patients not on enzalutamide prior to study enrollment or have previously discontinued enzalutamide receive BET bromodomain inhibitor ZEN-3694 beginning on day 1 of cycle 2. Cycles repeat every 21 days in the absence of disease progression or unacceptable toxicity.
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Drug: BET Bromodomain Inhibitor ZEN-3694
Given PO
Other Names:
Drug: Enzalutamide Given PO
Other Names:
Biological: Pembrolizumab Given IV
Other Names:
|
Experimental: Cohort B: mCRPC without evidence of transdifferentiation
Patients receive pembrolizumab IV over 30 minutes on day 1, BET bromodomain inhibitor ZEN-3694 PO QD and enzalutamide PO QD on days 1-21. Patients not on enzalutamide prior to study enrollment or have previously discontinued enzalutamide receive BET bromodomain inhibitor ZEN-3694 beginning on day 1 of cycle 2. Cycles repeat every 21 days in the absence of disease progression or unacceptable toxicity.
|
Drug: BET Bromodomain Inhibitor ZEN-3694
Given PO
Other Names:
Drug: Enzalutamide Given PO
Other Names:
Biological: Pembrolizumab Given IV
Other Names:
|
- Composite Response Rate [ Time Frame: Up to 3 years ]Defined as either objective response per Response Evaluation Criteria in Solid Tumors (RECIST) 1.1 criteria (complete response (CR), partial response (PR)) or confirmed >= 50% decline from serum prostate-specific antigen (PSA) at baseline confirmed by repeat measurement performed ≥ 4 weeks later for each study cohort. To be considered evaluable for PSA50 response, patients must have a serum PSA >=2 ng/mL at baseline. To be considered evaluable for objective response, patients must have measurable soft tissue disease by RECIST 1.1 criteria on baseline scan assessment. The composite response rate along with 95% confidence interval will be reported for participants in each study cohort.
- Objective Response Rate (ORR) [ Time Frame: Up to 3 years ]Objective response is defined as a complete response (CR), partial response (PR)) for the subset of patients with measurable soft tissue disease by RECIST 1.1 criteria. ORR will be reported along with 95% confidence interval for each study cohort. To be considered evaluable for objective response, patients must have measurable soft tissue disease by RECIST 1.1 criteria on baseline scan assessment Only those participants who have measurable disease present at baseline, have received at least one cycle of therapy, and have had their disease re-evaluated will be considered evaluable for response.
- Median Duration of Response [ Time Frame: Up to 3 years ]The duration of overall response is measured from the time measurement criteria are met for CR, PR, or stable disease (SD) (whichever is first recorded) until the first date that recurrent or progressive disease is objectively documented (taking as reference for progressive disease the smallest measurements recorded since the treatment started). The duration of overall CR is measured from the time measurement criteria are first met for CR until the first date that recurrent disease is objectively documented. Stable disease is measured from the start of the treatment until the criteria for progression are met, taking as reference the smallest measurements recorded since the treatment started. The median duration of response will be reported along with 95% confidence interval for each study cohort, for the subset of patients with measurable soft tissue disease by RECIST 1.1 criteria.
- Progression-free survival (PFS) [ Time Frame: Up to 3 years ]PFS is defined as the duration of time from start of treatment to time of progression or death, whichever occurs first. Will be determined for each cohort using Kaplan-Meier product limit method.
- PSA50 response proportion [ Time Frame: Up to 3 years ]PSA50 response is a >= 50% decline from baseline in serum PSA, confirmed by repeat measurement >= 4 weeks later. The PSA50 response proportion will be reported along with 95% confidence interval for each study cohort, for the subset of PSA-evaluable patients (serum PSA >= 2 ng/mL at baseline).
- Overall survival (OS) [ Time Frame: Up to 3 years ]The median overall survival along with 95% confidence interval will be determined from the date of first dose of protocol-defined therapy until death from any cause, using the Kaplan-Meier product limit method. Patients who withdraw from study will be censored for analysis of overall survival using the date of study withdrawal.
- Incidence of treatment-related adverse events [ Time Frame: Up to 30 days post-last dose ]All participants will be evaluable for toxicity from the time of their first protocol-defined treatment on C1D1. Will be recorded and severity graded using Common Terminology Criteria for Adverse Events version 5.0.The frequency and severity of adverse events will be descriptively reported

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Ages Eligible for Study: | 18 Years and older (Adult, Older Adult) |
Sexes Eligible for Study: | Male |
Accepts Healthy Volunteers: | No |
Inclusion Criteria:
- Participants must have histologically confirmed prostate adenocarcinoma at the time of diagnosis, with subsequent development of metastatic castration-resistant prostate cancer. Patients with de novo small cell prostate cancer at the time of diagnosis are excluded from study participation
- Evidence of disease progression by PSA and/or radiographic progression by Prostate Cancer Working Group 3 (PCWG3) criteria at the time of study entry
- Patients must be evaluable for the primary endpoint of composite response, and must have either serum PSA > 2 ng/mL during Screening and/or measurable disease by Response Evaluation Criteria in Solid Tumors (RECIST) 1.1 criteria
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Safety lead-in only:
- Metastatic castration resistant prostate cancer with evidence of disease progression by PCWG3 criteria at study entry
- Progression on at least one prior androgen signaling inhibitor (e.g. abiraterone/prednisone, enzalutamide, apalutamide, darolutamide)
- No prior chemotherapy for the treatment of metastatic castration-resistant prostate cancer (mCRPC). Prior chemotherapy administered in the castration-sensitive setting is allowed provided last dose of chemotherapy is > 6 months prior to cycle 1 day 1 (C1D1)
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Phase 2 Cohort A (transdifferentiated mCRPC) only:
a. Participants must have clinicogenomic evidence of treatment emergent small cell neuroendocrine prostate cancer as defined by one or more of the following.
i. Histologic evidence of small cell neuroendocrine prostate cancer on metastatic tumor biopsy and/or
ii. Presence of loss-of-function mutation or deletion of RB1 on a Clinical Laboratory Improvement Act (CLIA)-approved genomic-sequencing platform and/or
iii. Low PSA secretors as defined by meeting all of the following criteria during screening period -
- Serum PSA >=2 ng/mL,
- Radiographic progression by PCWG3 criteria,
- Presence of > 5 metastases on conventional imaging and/or
iv. Presence of at least one soft tissue lesion measuring > 1 cm that is negative on PSMA PET. A negative lesion on PSMA PET is defined as uptake below the background uptake in the liver.
b. No more than two prior lines of chemotherapy administered in the mCRPC setting. Chemotherapy administered in the castration-sensitive setting does not count towards this limit.
c. Measurable disease by RECIST 1.1 criteria.
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Phase 2 Cohort B (mCRPC without transdifferentiation) only:
- Patients must not meet any criteria of transdifferentiation as outlined above
- Progression on at least one prior androgen signaling inhibitor (e.g. abiraterone/prednisone, enzalutamide, apalutamide, darolutamide)
- No prior chemotherapy for the treatment of mCRPC. Prior chemotherapy administered in the castration-sensitive setting is allowed provided last dose of chemotherapy is > 6 months prior to C1D1
- Castrate level of serum testosterone at study entry (< 50 ng/dL). Patients without prior bilateral orchiectomy are required to remain on luteinizing hormone-releasing hormone (LHRH) analogue treatment for duration of study
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No other systemic anti-cancer therapies administered other than LHRH analogue within 14 days or, 5 half-lives, whichever is shorter, prior to initiation of study treatment. Adverse events related to prior anti-cancer treatment must have recovered to grade =< 1 with the exception of any grade alopecia and grade =< 2 neuropathy
a. Patients receiving enzalutamide prior to study entry may continue treatment at their current enzalutamide dose level without requirement for wash-out period
- Age >= 18 years
- Eastern Cooperative Oncology Group (ECOG) performance status =< 1 (Karnofsky performance status >= 70%)
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Demonstrates adequate organ function as defined below:
- Absolute neutrophil count >= 1,500/ per microliter (mcL)
- Platelets >= 100,000/mcL
- Hemoglobin >= 9.0 g/dL
- Total bilirubin =< 1.5 x institutional upper limit of normal, unless elevated due to Gilbert's syndrome and direct bilirubin is within normal limits
- Aspartate aminotransferase (AST) (serum glutamic oxaloacetic transaminase (SGOT) =< 3 x institutional upper limit of normal (=< 5 x upper limit of normal (ULN) in presence of liver metastases)
- Alanine aminotransferase (ALT) (serum glutamate pyruvate transaminase (SGPT)) =< 3 x institutional upper limit of normal (=< 5 x ULN in presence of liver metastases)
- Serum creatinine =< 1.5 x institutional upper limit of normal OR calculated creatinine clearance glomerular filtration rate (GFR) >= 50 mL/min/1.73 m^2 , calculated using the Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equation
- Ability to understand a written informed consent document, and the willingness to sign it
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Patients must agree to use adequate contraception prior to the study, for the duration of study participation, and 60 days after last administration of study treatment. Adequate contraception includes:
- Patients who are sexually active should consider their female partner to be of childbearing potential if she has experienced menarche and is not postmenopausal (defined as amenorrhea > 24 consecutive months) or has not undergone successful surgical sterilization. Even women who use contraceptive hormones (oral, implanted, or injected), an intrauterine device, or barrier methods (diaphragms, condoms, spermicide) should be considered to be of childbearing potential
- Patients who have undergone vasectomy themselves should also be considered to be of childbearing potential
- Acceptable methods of contraception include continuous total abstinence, or double-barrier method of birth control (e.g. condoms used with spermicide, or condoms used with oral contraceptives). Periodic abstinence and withdrawal are not acceptable methods of contraception
- Patients must be willing to undergo metastatic tumor biopsy during screening. If no metastatic lesion is safely accessible to tumor biopsy, this requirement will be waived. Bone or soft tissue lesion is allowed, but soft tissue will be prioritized. If a patient has archival tissue obtained within 90 days of C1D1 the requirement for fresh tumor biopsy will be waived
Exclusion Criteria:
- Has participated in a study of an investigational product and received study treatment or used an investigational device other than those specified in the protocol within 2 weeks of C1D1
- Hypersensitivity to ZEN-3694, pembrolizumab, enzalutamide, or any of its excipients
- Has received prior radiotherapy within 2 weeks of C1D1. Participants must have recovered from all radiation-related toxicities, not require corticosteroids, and not have had radiation pneumonitis. A 1-week washout is permitted for palliative radiation (=< 2 weeks of radiotherapy) to non-central nervous system (CNS) disease
- Receipt of prior pembrolizumab or another immune checkpoint inhibitor (e.g. nivolumab, ipilimumab). Prior treatment with sipuleucel-T is allowed
- Receipt of a radiopharmaceutical (e.g. radium-223, 177Lu-prostate-specific membrane antigen (PSMA) within 6 weeks prior to C1D1
- Prior treatment with a bromodomain inhibitor (BETi)
- Individuals with concurrent second malignancy requiring active treatment at study entry. Non-melanoma skin cancer, non-muscle invasive bladder cancer, and other carcinomas-in-situ are allowable exceptions
- Has an active autoimmune disease that has required systemic treatment in the past 2 years (i.e., with use of disease modifying agents, corticosteroids or immunosuppressive drugs). Patients on low dose oral weekly methotrexate are allowed. Replacement therapy (e.g., thyroxine, insulin, or physiologic corticosteroid replacement therapy for adrenal or pituitary insufficiency) or treatment with drugs (e.g. methimazole, neomercazol, carbamazole, etc.) that function to decrease the generation of thyroid hormone by a hyper-functioning thyroid gland (e.g., in Graves' disease) is not considered a form of systemic treatment of an autoimmune disease
- Has received a live vaccine or live-attenuated vaccine within 30 days prior to the first dose of study drug. Administration of killed vaccines is allowed.
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Cardiac condition as defined as one or more of the following:
- QT interval by Fridericia (QTcF) > 480 ms (machine or manual read allowed)
- Uncontrolled supraventricular arrhythmia or ventricular arrhythmia requiring treatment
- New York Heart Association (NYHA) congestive heart failure class III or IV
- History of unstable angina, myocardial infarction, or cerebrovascular accident within 6 months prior to C1D1
- History of seizure or pre-disposing condition (e.g. brain metastases)
- Has a diagnosis of immunodeficiency or is receiving systemic steroid therapy at a prednisone equivalent dose of > 10 mg daily or other form of immunosuppressive therapy within 7 days prior to first dose of study drug
- Human immunodeficiency virus (HIV)-infected individuals on effective anti-retroviral therapy with undetectable viral load within 6 months are eligible for this trial (screening not required in the absence of risk factors)
- For participants with evidence of chronic hepatitis B virus (HBV) infection (positive hepatitis B surface antigen (HBsAg) and/or hepatitis B core antibody (HBcAb)), the HBV viral load must be undetectable at the time of study enrollment (screening not required in the absence of risk factors)
- Chronic active hepatitis C virus (HCV) infection defined as positive viral load (screening not required in the absence of risk factors)
- Has a history of (non-infectious) pneumonitis/interstitial lung disease that required steroids or has current pneumonitis/ interstitial lung disease
- Has an active infection requiring intravenous antibiotics within 7 days prior to C1D1
- Use of a prohibited concomitant medication within 7 days of C1D1
- Major surgery within 28 days prior to C1D1. Minor procedures including biopsies, dental surgery, cataract surgery, or outpatient procedure are allowed
- Has a history or current evidence of any condition, therapy, or laboratory abnormality that might confound the results of the study, interfere with the subject's participation for the full duration of the study, or is not in the best interest of the subject to participate, in the opinion of the treating investigator
- Has known psychiatric or substance abuse disorders that would interfere with cooperation with the requirements of the trial.

To learn more about this study, you or your doctor may contact the study research staff using the contact information provided by the sponsor.
Please refer to this study by its ClinicalTrials.gov identifier (NCT number): NCT04471974
Contact: UCSF Genitourinary Medical Oncology Recruitment | 877-827-3222 | GUTrials@ucsf.edu |
United States, California | |
University of California, San Francisco | Recruiting |
San Francisco, California, United States, 94143 | |
Contact: UCSF Genitourinary Medical Oncology Recruitment 877-827-3222 GUTrials@ucsf.edu | |
Contact cancertrials@ucsf.edu | |
Principal Investigator: Rahul Aggarwal, MD | |
United States, Michigan | |
University of Michigan | Recruiting |
Ann Arbor, Michigan, United States, 48109 | |
Principal Investigator: Joshi Alumkal, MD |
Principal Investigator: | Rahul R Aggarwal, MD | University of California, San Francisco |
Responsible Party: | Rahul Aggarwal, Principal Investigator, University of California, San Francisco |
ClinicalTrials.gov Identifier: | NCT04471974 |
Other Study ID Numbers: |
20551 NCI-2020-04495 ( Registry Identifier: CTRP (Clinical Trial Reporting Program) ) |
First Posted: | July 15, 2020 Key Record Dates |
Last Update Posted: | March 1, 2023 |
Last Verified: | February 2023 |
Individual Participant Data (IPD) Sharing Statement: | |
Plan to Share IPD: | No |
Studies a U.S. FDA-regulated Drug Product: | Yes |
Studies a U.S. FDA-regulated Device Product: | No |
Product Manufactured in and Exported from the U.S.: | No |
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