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)
Last updated:
Last updated
The date of the most recent update for each trial record in the Canadian Clinical Trial Search Portal.
2026-07-11
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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)
Intervention/treatment:
Intervention/treatment
Name given to the drug used in the clinical trial. This may be a code name, a chemical name of the active ingredient, a non-proprietary name or brand name.
KEYTRUDA (PEMBROLIZUMAB) / XTANDI (ENZALUTAMIDE)
Medical condition:
Medical condition
The disease or condition that's being studied in the clinical trial.
PROSTATE CANCER
Protocol code:
Protocol Code
An alpha-numeric sequence generated by the sponsor that can vary in length. Used as a reference to help identify a specific clinical trial protocol. Formerly referred to as 'protocol number'.
991-00 / MK-3475-991
Control number:
Control number
A unique 6-digit identification number Health Canada assigns to each clinical trial application.
235209
Status:
Trial Status
The status for the clinical trial as a whole. Note that the status for each site may be different and should always be confirmed with the clinical trial sponsor. Health Canada uses information provided by the sponsor to an international clinical trial registry to determine status values for each clinical trial. Status values on the portal can include:
• Not yet recruiting - Participants are not yet being recruited or enrolled at any site. • Recruiting - Participants are currently being recruited. • Active, not recruiting - The clinical trial is ongoing but new participants are not currently being recruited or enrolled. • On hold - The clinical trial has been temporarily stopped, but it may start again. • Closed - The clinical trial has either ended normally and participants are no longer being examined or treated, or it has stopped early and will not start again. • Unknown - The status of the clinical trial has not been verified in the registry in the last 2 years. Please contact the sponsor. • No match, ongoing - Please contact sponsor for status information. • Other - Please contact sponsor for status information.
Closed
Approved:
Approved
The date that the clinical trial has been determined to meet Health Canada’s regulatory requirements. For drug clinical trials, this means that a no objection letter or an authorization was issued.
February 20, 2020
Date Completed:
Date completed
The date of the last participant’s last visit in the global study. The completion date may be actual or estimated, depending what was provided to the registry. Estimated completion dates may be in the past or future.
Trial phase:
Trial phase
The stage of a clinical trial, based on factors such as the objectives of the trial and number of participants. Phase data displayed in the portal is taken from international registry data.
For more information see "Phases of drug trials" on the Definitions webpage
This is an external link. The information is not authorized by the Government of Canada.
Eligibility
Eligibility
The characteristics people must have or the requirements they must meet to participate in the clinical trial. Eligibility criteria include both inclusion criteria (must have for a person to participate) and exclusion criteria (prevent a person from participating).
Review the exact criteria from the registry or the sponsor before making a decision to participate. The following values may be available on the portal:
Sex: an eligibility criteria based on biological characteristics. Information in the portal is based on available data and will default to 'all' when no other data is available.
Age: The age a person must be to participate in the clinical trial.
Accepts Healthy Volunteers: People who do not have the disease or condition can participate in the clinical trial.
Sex:
MALE
Age
18 Years and older
Accepts healthy volunteers:
No
Contacts and locations
Contact
Contact
Information for an individual or organisation that can respond to questions about this clinical trial. This information comes from the international registry.
Name
Senior Vice President, Global Clinical Development
The sponsor conducts the clinical trial and is responsible for every aspect. For example this could be a company, a university or an individual researcher.
MERCK CANADA INC
Locations
Ontario
Niagara Health System - St. Catharines ( Site 0107)
St. Catharines, Ontario, L2S 0A9
The Ottawa Hospital ( Site 0100)
Ottawa, Ontario, K1H 8L6
Quebec
Centre Hospitalier de l Universite de Montreal - CHUM ( Site 0109)
Montreal, Quebec, H2X 3E4
Centre intégré de cancérologie du CHU de Québec Université Laval, Hôpital de l'Enfant-Jésus ( Site 0101)
Québec, Quebec, G1J 1Z4
CISSS de la Monteregie-Centre ( Site 0105)
Greenfield Park, Quebec, J4V 2H1
CIUSSS Ouest de l Ile - St-Mary s Hospital ( Site 0106)
