Efficacy and Safety of Pembrolizumab (MK-3475) Plus Enzalutamide Plus Androgen Deprivation Therapy (ADT) Versus Placebo Plus Enzalutamide Plus ADT in Participants With Metastatic Hormone-Sensitive Prostate Cancer (mHSPC) (MK-3475-991/KEYNOTE-991)
Public ClinicalTrials.gov record NCT04191096. Field values are reproduced from the official study page; the official ClinicalTrials.gov record remains the source of truth for eligibility, enrollment, and contact information.
Data is sourced from official ClinicalTrials.gov public API records. Always review the official ClinicalTrials.gov record for the latest information.
Official title
A Phase 3, Randomized, Double-blind Trial of Pembrolizumab (MK-3475) Plus Enzalutamide Plus ADT Versus Placebo Plus Enzalutamide Plus ADT in Participants With Metastatic Hormone-Sensitive Prostate Cancer (mHSPC) (KEYNOTE-991)
Brief summary
Reproduced verbatim from the official ClinicalTrials.gov record. Not medical advice.
This study will assess the efficacy and safety of pembrolizumab plus enzalutamide plus Androgen Deprivation Therapy (ADT) versus placebo plus enzalutamide plus ADT in participants with mHSPC. The primary hypothesis is that in participants with mHSPC, the combination of pembrolizumab plus enzalutamide plus ADT is superior to placebo plus enzalutamide plus ADT with respect to 1) radiographic progression-free survival (rPFS) per Prostate Cancer Working Group (PCWG)-modified Response Evaluation Criteria in Solid Tumors (RECIST) 1.1 as assessed by blinded independent central review (BICR) and 2) overall survival (OS). As of 19-JAN-2023, the study was unblinded and all study participants stopped ongoing treatment with pembrolizumab/placebo and will continue to receive Standard of Care treatment until meeting protocol-specified discontinuation criteria if deriving clinical benefit. Safety analysis will be performed at the end of the study; there will be no further analyses for efficacy and electronic patient-reported outcome (ePRO) endpoints collected from participants beyond the IA1 cutoff date. All study participants will stop ongoing treatment with pembrolizumab/placebo. Exceptions may be requested for study participants who, in the assessment of their study physician, are benefitting from the combination of enzalutamide and pembrolizumab, after consulting with the Sponsor. All other study participants should be discontinued from study and be offered standard of care (SOC) treatment as deemed necessary by the Investigator. If enzalutamide as SOC is not accessible off study to the participant, central sourcing may continue. As of Amendment 04, disease progression will no longer be centrally verified, participants will only be assessed locally. As of Amendment 4, Second Course treatment is not an option for participants. There are currently no participants in the Second Course Phase.
Study identification
- NCT ID
- NCT04191096
- Recruitment status
- Completed
- Study type
- Interventional
- Phase
- Phase 3
- Enrollment
- 1,251 participants
Conditions and interventions
Conditions
Interventions
- Pembrolizumab Biological
- Enzalutamide Drug
- Androgen Deprivation Therapy (ADT) Drug
- Placebo Other
Biological · Drug · Other
Eligibility (public fields only)
- Age range
- 18 Years and older
- Sex
- Male
- Healthy volunteers
- Healthy volunteers not accepted
This page does not interpret eligibility. Detailed inclusion and exclusion criteria are on the official ClinicalTrials.gov record.
Study timeline
- Start date
- Feb 11, 2020
- Primary completion
- Oct 30, 2022
- Completion
- Apr 7, 2026
- Last update posted
- Apr 28, 2026
2020 – 2026
United States locations
- U.S. sites
- 27
- U.S. states
- 19
- U.S. cities
- 25
| Facility | City | State | ZIP | Site status |
|---|---|---|---|---|
| Alaska Clinical Research Center ( Site 0274) | Anchorage | Alaska | 99503 | — |
| Providence Alaska Medical Center ( Site 0276) | Anchorage | Alaska | 99508 | — |
| City of Hope Medical Center ( Site 0217) | Duarte | California | 91010 | — |
| UCLA Hematology/Oncology - Santa Monica ( Site 0241) | Los Angeles | California | 90404 | — |
| University of Colorado, Anschutz Cancer Pavilion ( Site 0236) | Aurora | Colorado | 80045 | — |
| Hartford HealthCare Medical Group ( Site 0212) | Manchester | Connecticut | 06042 | — |
| Smilow Cancer Center at Yale-New Haven ( Site 0250) | New Haven | Connecticut | 06510 | — |
| Sibley Memorial Hospital ( Site 0275) | Washington D.C. | District of Columbia | 20016 | — |
| Winship Cancer Institute of Emory University ( Site 0209) | Atlanta | Georgia | 30322-1013 | — |
| The University of Chicago ( Site 0264) | Chicago | Illinois | 60637 | — |
| Springfield Clinic [Springfield, IL] ( Site 0240) | Springfield | Illinois | 62702 | — |
| Cotton-O'Neil Cancer Center ( Site 0228) | Topeka | Kansas | 66606 | — |
| The Sidney Kimmel Comprehensive Cancer Center ( Site 0204) | Baltimore | Maryland | 21287 | — |
| St. Vincent Frontier Cancer Center-Research ( Site 0213) | Billings | Montana | 59102 | — |
| Comprehensive Cancer Centers of Nevada ( Site 0269) | Las Vegas | Nevada | 89169 | — |
| Laura and Isaac Perlmutter Cancer Center at NYU Langone Health ( Site 0270) | New York | New York | 10016 | — |
| Weill Cornell Medical College ( Site 0263) | New York | New York | 10065 | — |
| Associated Medical Professionals of NY ( Site 0251) | Syracuse | New York | 13210 | — |
| Duke University ( Site 0206) | Durham | North Carolina | 27710 | — |
| TriState Urologic Services PSC Inc. dba The Urology Group ( Site 0253) | Cincinnati | Ohio | 45212 | — |
| MidLantic Urology ( Site 0273) | Bala-Cynwyd | Pennsylvania | 19004 | — |
| Ralph H. Johnson VA Center ( Site 0256) | Charleston | South Carolina | 29401 | — |
| Carolina Urologic Research Center ( Site 0259) | Myrtle Beach | South Carolina | 29572 | — |
| Urology Associates [Nashville, TN] ( Site 0233) | Nashville | Tennessee | 37209 | — |
| Inova Health System ( Site 0205) | Fairfax | Virginia | 22031 | — |
| Urology of Virginia ( Site 0224) | Virginia Beach | Virginia | 23462 | — |
| Fred Hutchinson Cancer Center ( Site 0258) | Seattle | Washington | 98109 | — |
Site contact phone numbers, emails, and investigator names are intentionally not displayed here. Open the official ClinicalTrials.gov record for site contact information.
Non-U.S. locations
This page focuses on the U.S. directory. The official record also lists 207 non-U.S. sites.
About this trial record page
- What this page shows
- Public field values for ClinicalTrials.gov record NCT04191096, including study identification, conditions, interventions, eligibility (age, sex, healthy volunteer), timeline, and U.S. site list.
- What this page does not do
- No medical advice, eligibility judgments, treatment recommendations, study quality scoring, or AI-generated medical summaries. No site contact phone numbers, emails, or investigator names.
- Where the data comes from
- Sourced from the official ClinicalTrials.gov public API. The official record is the source of truth.
- Last refresh
- Last update posted Apr 28, 2026 · Synced Sep 5, 2026
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Open the official record
The complete protocol, eligibility criteria, and contact information for NCT04191096 live on ClinicalTrials.gov.