ZEN003694 and Enzalutamide Versus Enzalutamide Monotherapy in Metastatic Castration-Resistant Prostate Cancer

A Randomized Phase 2b Study of ZEN003694 in Combination With Enzalutamide Versus Enzalutamide Monotherapy in Patients With Metastatic Castration-Resistant Prostate Cancer

This is an open-label, randomized, Phase 2b study of ZEN003694 in combination with enzalutamide vs. enzalutamide monotherapy in patients with mCRPC who have progressed on prior abiraterone by PCWG3 criteria. Disease must have progressed on only abiraterone by PCWG3 criteria prior to study entry.

The patient population will be separated into two cohorts:

Cohort A: Patients with poor response to prior abiraterone defined as:

• Abiraterone started in hormone-sensitive prostate cancer (HSPC) disease setting: < 12 months duration on abiraterone or failure to achieve PSA nadir of 0.2 ng/mL while taking abiraterone, or;
• Abiraterone started in castrate-resistant prostate cancer (CRPC) disease setting: < 6 months duration on abiraterone or failure to achieve PSA50 response while on abiraterone

Cohort B: Patients with response to prior abiraterone, defined as:

• Abiraterone started in hormone-sensitive prostate cancer (HSPC) disease setting: ≥ 12 months duration on abiraterone and nadir PSA < 0.2 ng/mL, or;
• Abiraterone started in castrate-resistant prostate cancer (CRPC) disease setting: ≥ 6 months duration on abiraterone and confirmed PSA50 response

Study Overview

• Status: Recruiting
• Conditions: Metastatic Castration-Resistant Prostate Cancer
• Intervention / Treatment: Drug: ZEN003694; Drug: Enzalutamide

• Study Type: Interventional
• Enrollment (Estimated): 200
• Phase: Phase 2

Contacts and Locations

• Study Contact: Name: Zenith Study Team; Phone Number: 587-390-7865; Email: ZEN003694-201@zenithepigenetics.com

Study Locations

• China
  • Anhui
    • Hefei, Anhui, China, 230002
      • Recruiting
      • Anhui Provincial Hospital
  • Chongqing Municipality
    • Chongqing, Chongqing Municipality, China, 400030
      • Recruiting
      • Chongqing Cancer Hospital
  • Fujian
    • Xiamen, Fujian, China, 361003
      • Recruiting
      • The first affiliated hospital of xiamen university
  • Henan
    • Zhengzhou, Henan, China, 450000
      • Recruiting
      • Henan Cancer Hospital
  • Hubei
    • Wuhan, Hubei, China, 430079
      • Recruiting
      • Hubei Cancer Hospital
    • Wuhan, Hubei, China, 430030
      • Recruiting
      • Tongji Hospital of Tongji Medical College, Huazhong University of Science & Technology
  • Hunan
    • Changsha, Hunan, China, 410006
      • Recruiting
      • Hunan Cancer Hospital
  • Jiangsu
    • Nanjing, Jiangsu, China, 210008
      • Recruiting
      • Nanjing Drum Tower Hospital
  • Liaoning
    • Shenyang, Liaoning, China, 110042
      • Withdrawn
      • Liaoning Cancer Hospital
  • Shaanxi
    • Xi'an, Shaanxi, China, 71000
      • Recruiting
      • The First Affiliated Hospital of Xi'an Jiaotang University
  • Shanghai Municipality
    • Shanghai, Shanghai Municipality, China, 200032
      • Recruiting
      • Fudan University Shanghai Cancer Center
    • Shanghai, Shanghai Municipality, China, 200072
      • Recruiting
      • Shanghai Tenth People's Hospital
  • Shanxi
    • Taiyuan, Shanxi, China, 030001
      • Recruiting
      • First Hospital of Shanxi Medical University
  • Sichuan
    • Chengdu, Sichuan, China, 610072
      • Recruiting
      • Sichuan Provincial People's Hospital
  • Zhejiang
    • Hangzhou, Zhejiang, China, 310014
      • Recruiting
      • Zhejiang Provincial People's Hospital
• United States
  • California
    • Los Angeles, California, United States, 90027
      • Recruiting
      • California Research Institute
    • San Francisco, California, United States, 94158
      • Recruiting
      • University of California, San Francisco
    • Whittier, California, United States, 90603
      • Recruiting
      • Innovative Clinical Research Institute
  • Colorado
    • Lakewood, Colorado, United States, 80228
      • Recruiting
      • Colorado Urology
  • Florida
    • Margate, Florida, United States, 33063
      • Recruiting
      • D&H Cancer Research Center, LLC
    • Plantation, Florida, United States, 33322
      • Recruiting
      • BRCR Global
  • Louisiana
    • Baton Rouge, Louisiana, United States, 70809
      • Withdrawn
      • Hematology Oncology Clinic
  • Maryland
    • Columbia, Maryland, United States, 21044
      • Recruiting
      • Maryland Oncology Hematology, P.A.
  • Michigan
    • Ann Arbor, Michigan, United States, 48109
      • Recruiting
      • University of Michigan Rogel Cancer Center
  • New York
    • New York, New York, United States, 10065
      • Completed
      • Weill Cornell Medical College - New York Presbyterian Hospital
  • North Carolina
    • Asheville, North Carolina, United States, 28806
      • Recruiting
      • Messino Cancer Center
  • Oregon
    • Portland, Oregon, United States, 97223
      • Recruiting
      • Northwest Cancer Specialists, P.C.
  • Tennessee
    • Nashville, Tennessee, United States, 37209
      • Recruiting
      • Urology Associates, P.C.
  • Texas
    • Austin, Texas, United States, 78731
      • Recruiting
      • Texas Oncology - Central South
  • Virginia
    • Fairfax, Virginia, United States, 22031
      • Recruiting
      • Virginia Cancer Specialists
  • Washington
    • Seattle, Washington, United States, 98109
      • Recruiting
      • Seattle Cancer Care Alliance

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: 18 years and older (Adult, Older Adult)
• Accepts Healthy Volunteers: No

Description

Inclusion Criteria:

1. Males age ≥ 18 years
2. Metastatic, castration-resistant, histologically confirmed prostate cancer
3. Surgical castration or continuous medical castration for ≥ 8 weeks prior to screening; serum testosterone < 50 ng/dL confirmed within 4 weeks of first administration of study drug
4. Have progressed on prior abiraterone treatment by PCWG3 criteria
5. Patients who are not candidates for chemotherapy in the opinion of the investigator or patients who decline chemotherapy

6. Cohort A only - Patient must meet definition of poor responder to abiraterone by one of the following:

   1. Abiraterone started in hormone-sensitive prostate cancer (HSPC) disease setting: < 12 months duration on abiraterone or failure to achieve PSA nadir of 0.2 ng/mL while taking abiraterone
   2. Abiraterone started in castrate-resistant prostate cancer (CRPC) disease setting: < 6 months duration on abiraterone or failure to achieve a PSA50 response

7. Cohort B only - Patient must meet definition of responder to abiraterone by one of the following:

   1. Abiraterone started in hormone-sensitive prostate cancer (HSPC) disease setting: ≥ 12 months duration on abiraterone and nadir PSA < 0.2 ng/mL
   2. Abiraterone started in castrate-resistant prostate cancer (CRPC) disease setting: ≥ 6 months duration on abiraterone and PSA50 response
8. Eastern Cooperative Oncology Group (ECOG) performance status of 0 or 1

Exclusion Criteria:

1. Any history of brain metastases, prior seizure, conditions predisposing to seizure activity
2. Have previously received an investigational BET inhibitor (including previous participation in this study or a study of ZEN003694)
3. Receipt of prior second-generation androgen receptor inhibitors (e.g. enzalutamide, apalutamide, darolutamide, proxalutamide). Receipt of first-generation AR antagonists (e.g. bicalutamide, nilutamide, flutamide) does not count towards this limit.
4. Have received prior chemotherapy in the metastatic castration-resistant setting (prior chemotherapy in the hormone-sensitive setting is allowed provided last dose was at least 6 months prior to first dose of study drug)
5. Have received prior systemic anti-cancer therapy within 2 weeks or five half-lives, whichever is shorter, prior to the first administration of study drug
6. Have received exogenous administration of testosterone therapy since discontinuation of abiraterone.
7. Failure to recover to Grade 1 or lower toxicity related to prior systemic therapy (excluding alopecia and neuropathy) prior to study entry
8. Radiation therapy within 2 weeks of the first administration of study drug

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Treatment
• Allocation: Randomized
• Interventional Model: Parallel Assignment
• Masking: None (Open Label)

Number of Arms

4

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Experimental: Cohort A - ZEN003694 + Enzalutamide; Patients will be administered enzalutamide (160 mg) orally once daily for 21 days prior to the initiation of the combination therapy (Lead-in) to reach steady state concentration (Css) prior to Cycle 1. After the Lead-in, ZEN003694 (72 mg) will be administered orally one daily in combination with daily enzalutamide for 28-day cycles.	Drug: ZEN003694; 72 mg PO QD; Other Names: ZEN-3694; Drug: Enzalutamide; 160 mg PO QD; Other Names: MDV3100; Xtandi®
Active Comparator: Cohort A - Enzalutamide; Patients will be administered enzalutamide (160 mg) orally once daily for 21 days prior to Cycle 1 Day 1 (Lead-in). After the Lead-in, patients will be administered enzalutamide 160 mg orally once daily for 28-day cycles. Active control patients will have the option to cross-over to treatment with ZEN003694 in combination with enzalutamide upon confirmed radiographic progression by PCWG3 criteria by independent central review.	Drug: Enzalutamide; 160 mg PO QD; Other Names: MDV3100; Xtandi®
Experimental: Cohort B - ZEN003694 + Enzalutamide; Patients will be administered enzalutamide (160 mg) orally once daily for 21 days prior to the initiation of the combination therapy (Lead-in) to reach steady state concentration (Css) prior to Cycle 1. After the Lead-in, ZEN003694 (72 mg) will be administered orally one daily in combination with daily enzalutamide for 28-day cycles.	Drug: ZEN003694; 72 mg PO QD; Other Names: ZEN-3694; Drug: Enzalutamide; 160 mg PO QD; Other Names: MDV3100; Xtandi®
Active Comparator: Cohort B - Enzalutamide; Patients will be administered enzalutamide (160 mg) orally once daily for 21 days prior to Cycle 1 Day 1 (Lead-in). After the Lead-in, patients will be administered enzalutamide 160 mg orally once daily for 28-day cycles. Active control patients will have the option to cross-over to treatment with ZEN003694 in combination with enzalutamide upon confirmed radiographic progression by PCWG3 criteria by independent central review.	Drug: Enzalutamide; 160 mg PO QD; Other Names: MDV3100; Xtandi®

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Cohort A: Radiographic progression-free survival (rPFS) by BICR	Time from date of randomization to the date of first disease radiographic progression or death for any reason. Radiographic progression disease will be evaluated by RECIST 1.1 and PCWG3.	Randomization up to 30 months

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Cohorts A + B: Radiographic progression-free survival (rPFS) by BICR	Time from date of randomization to the date of first disease radiographic progression or death for any reason. Radiographic progression disease will be evaluated by RECIST 1.1 and PCWG3	Randomization up to 30 months
Cohort A: Radiographic progression-free survival (rPFS) by investigator assessment	Time from date of randomization to the date of first disease radiographic progression or death for any reason. Radiographic progression disease will be evaluated by RECIST 1.1 and PCWG3.	Randomization up to 30 months
Cohort A + B: Radiographic progression-free survival (rPFS) by investigator assessment	Time from date of randomization to the date of first disease radiographic progression or death for any reason. Radiographic progression disease will be evaluated by RECIST 1.1 and PCWG3.	Randomization up to 30 months
Cohort A: Progression-free survival (PFS) by investigator assessment	Time from date of randomization to the date of first disease radiographic progression, clinical progression, or death for any reason. Radiographic progression of disease will be evaluated by RECIST 1.1 and PCWG3 by investigator assessment. Clinical progression is significant pain increase or clinical deterioration that requires initiating another line of treatment.	Randomization up to 30 months
Cohort A + B: Progression-free survival (PFS) by investigator assessment	Time from date of randomization to the date of first disease radiographic progression, clinical progression, or death for any reason. Radiographic progression of disease will be evaluated by RECIST 1.1 and PCWG3 by investigator assessment. Clinical progression is significant pain increase or clinical deterioration that requires initiating another line of treatment.	Randomization up to 30 months
Cohort A: Overall survival (OS)	Time from date of randomization to the date of death from any cause	Randomization up to 30 months
Cohort A + B: Overall survival (OS)	Time from date of randomization to the date of death from any cause	Randomization up to 30 months
Cohort A: PSA50 response rate	PSA response is a reduction in serum PSA concentration of ≥50% from baseline.	Randomization up to 30 months
Cohort A + B: PSA50 response rate	PSA response is a reduction in serum PSA concentration of ≥50% from baseline.	Randomization up to 30 months
Objective response rate (ORR)	Proportion of the patients who have either a complete response (CR) or partial response (PR) by RECIST 1.1 criteria who have measurable disease at baseline.	Randomization up to 30 months
Patient-reported health status and quality of life (QoL) measured by European Organization for Research and Treatment of Cancer Quality of Life Questionnaire Core 30 (EORTC QLQ-C30)	EORTC QLQ-C30: cancer-specific instrument with 30 questions to assess the participant QoL. First 28 questions used to evaluate 5 functional scales (physical, role, cognitive, emotional, social), 3 symptom scales (fatigue, nausea and vomiting, pain) and other single items (dyspnea, appetite loss, insomnia, constipation, diarrhea, financial difficulties). Each question assessed on a 4-point scale (1= not at all, 2= a little, 3= quite a bit, 4= very much); functional scales: higher score = better level of functioning; symptom scale: higher score = more severe symptoms; for single items: higher score= more severe problem. Last 2 questions used to evaluate global health status (GHS)/QoL. Each question was assessed on 7-point scale (1= very poor to 7= excellent). Scores averaged, transformed to 0-100 scale; higher score=better quality of life/better level of functioning.	Screening and Day 1 of every 28-day Cycle up to 30 months
Patient-reported health status and quality of life (QoL) measured by European Organization for Research and Treatment of Cancer Quality of Life Questionnaire Prostate Module (EORTC QLQ-PR25).	EORTC QLQ-PR25: prostate cancer specific instrument with 25 questions used in conjunction with EORTC QLQ-C30 to assess the participant QoL. Used to evaluate 5 multi-item scales (urinary, bowel, and hormonal treatment-related symptoms, sexual activity, and sexual functioning) and one single item (problems due to incontinence aid use). Each question assessed on a 4-point scale (1= not at all, 2= a little, 3= quite a bit, 4= very much). Scores averaged, transformed to 0-100 scale; higher score=better quality of life/better level of functioning.	Screening and Day 1 of every 28-day Cycle up to 30 months
Time to initiation of chemotherapy	Time from date of randomization to the first dose of chemotherapy.	Randomization up to 30 months
Time to first skeletal related event (SRE)	Time from date of randomization to the first SRE such as pathological fracture, surgery/radiotherapy for pain/prevention of fracture, hypercalcemia, and spinal cord compression.	Randomization up to 30 months
Measure plasma concentrations of ZEN003694 and the active metabolite ZEN003791	Plasma concentrations of ZEN003694 and the active metabolite ZEN003791 will be measured.	Cycle 1 Day 1: Pre-dose, 1 hour, 2 hours, and 4 hours post-dose; Cycle 2 Day1: Pre-dose, 1 hour, 2 hours, and 4 hours post-dose
Cohort A: Assess efficacy endpoints for patients enrolled in the USA		Randomization up to 30 months
Cohort A + B: Assess efficacy endpoints for patients enrolled in the USA		Randomization up to 30 months

Collaborators and Investigators

• Sponsor: Zenith Epigenetics
• Collaborators: Astellas Pharma Inc; Newsoara Biopharma Co., Ltd.

Study record dates

Study Major Dates

• Study Start (Actual): September 8, 2021
• Primary Completion (Estimated): December 1, 2026
• Study Completion (Estimated): June 1, 2027

Study Registration Dates

• First Submitted: July 14, 2021
• First Submitted That Met QC Criteria: July 22, 2021
• First Posted (Actual): August 2, 2021

Study Record Updates

• Last Update Posted (Actual): May 8, 2026
• Last Update Submitted That Met QC Criteria: May 6, 2026
• Last Verified: May 1, 2026

More Information

Terms related to this study

• Keywords: mCRPC; Enzalutamide; ZEN003694; ZEN-3694; BETi; Bromodomain; Xtandi®
• Additional Relevant MeSH Terms: Urogenital Diseases; Genital Diseases; Genital Neoplasms, Male; Urogenital Neoplasms; Neoplasms by Site; Neoplasms; Genital Diseases, Male; Prostatic Diseases; Male Urogenital Diseases; Prostatic Neoplasms; enzalutamide
• Other Study ID Numbers: ZEN003694-201

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: NO

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: Yes
• Studies a U.S. FDA-regulated device product: No