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

About This Trial

This study is testing whether adding a new experimental drug to a standard prostate cancer medicine, enzalutamide, works better than taking enzalutamide alone.
It is designed for men with advanced prostate cancer that has spread and continued to grow after treatment with another medicine called abiraterone.
The trial is meant for patients who either cannot receive chemotherapy or choose not to have it.
Before considering this study, you should know that you may be randomly assigned to receive only the standard medicine, and men who have a history of seizures or have previously taken enzalutamide are not eligible to join.

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

Age Range: 18 years and older
Gender: Male
Who This Trial is For: This study is testing whether adding a new experimental drug to a standard prostate cancer medicine, enzalutamide, works better than taking enzalutamide alone.

Full Eligibility Criteria

Inclusion Criteria

Males age ≥ 18 years
Metastatic, castration-resistant, histologically confirmed prostate cancer
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
Have progressed on prior abiraterone treatment by PCWG3 criteria
Patients who are not candidates for chemotherapy in the opinion of the investigator or patients who decline chemotherapy
Cohort A only - Patient must meet definition of poor responder to abiraterone by one of the following:
- 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
- Abiraterone started in castrate-resistant prostate cancer (CRPC) disease setting: < 6 months duration on abiraterone or failure to achieve a PSA50 response
Cohort B only - Patient must meet definition of responder to abiraterone by one of the following:
- Abiraterone started in hormone-sensitive prostate cancer (HSPC) disease setting: ≥ 12 months duration on abiraterone and nadir PSA < 0.2 ng/mL
- Abiraterone started in castrate-resistant prostate cancer (CRPC) disease setting: ≥ 6 months duration on abiraterone and PSA50 response
Eastern Cooperative Oncology Group (ECOG) performance status of 0 or 1

Exclusion Criteria

Any history of brain metastases, prior seizure, conditions predisposing to seizure activity
Have previously received an investigational BET inhibitor (including previous participation in this study or a study of ZEN003694)
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.
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)
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
Have received exogenous administration of testosterone therapy since discontinuation of abiraterone.
Failure to recover to Grade 1 or lower toxicity related to prior systemic therapy (excluding alopecia and neuropathy) prior to study entry
Radiation therapy within 2 weeks of the first administration of study drug