Active not recruitingPHASE3INTERVENTIONAL

Study of Pembrolizumab (MK-3475) Plus Enzalutamide Versus Placebo Plus Enzalutamide in Participants With Metastatic Castration-resistant Prostate Cancer (mCRPC) (MK-3475-641/KEYNOTE-641)

This research study, called KEYNOTE-641, is designed to find out if adding a drug called pembrolizumab to standard treatment (enzalutamide) is better for men with advanced prostate cancer. This is specifically for prostate cancer that has spread to other parts of the body (metastatic) and is no longer responding to hormone therapy (castration-resistant). The study aims to see if the combination of pembrolizumab and enzalutamide helps men live longer and stops the cancer from growing or spreading compared to taking enzalutamide alone. Participants would not have received chemotherapy for their advanced prostate cancer, or they may have previously taken another drug called abiraterone.

At a glance

Status

Active not recruiting

Phase

PHASE3

Sponsor

Merck Sharp & Dohme LLC

Enrolment target

1,244

Start

28 Jul 2019

Estimated completion

29 May 2026

Prostatic Neoplasms

What is this study about?

You might be looking at this information because you or someone you care about has prostate cancer that has spread and is no longer responding to standard hormone treatments. This type of cancer is called metastatic castration-resistant prostate cancer, or mCRPC for short. Doctors are always looking for better ways to treat this condition.

This study is testing a new approach by combining two medicines: pembrolizumab and enzalutamide. Enzalutamide is a standard treatment that works by blocking hormones that can fuel prostate cancer growth. Pembrolizumab is a type of immunotherapy, which means it helps your own immune system fight the cancer. The main goal of this research is to see if giving these two drugs together is more effective than giving enzalutamide alone. Researchers want to know if the combination helps men live longer and if it stops the cancer from growing or spreading for a longer time.

This is a Phase 3 study, which means it's a large, important trial where new treatments are compared with existing ones to find out if they should become standard care. The study is particularly for men who haven't had chemotherapy for their advanced prostate cancer, or who have previously used a drug called abiraterone (either successfully or if it stopped working for them).

Key takeaways

The study tests a new combination of drugs for advanced prostate cancer.
It aims to see if adding pembrolizumab to enzalutamide helps men live longer and slows cancer growth.
Participants will receive either pembrolizumab plus enzalutamide, or a placebo plus enzalutamide.
Regular check-ups, blood tests, and scans will be part of the study.
You can stop participating at any time.
This study is for men whose prostate cancer isn't responding to hormone therapy and has spread.

Who may be eligible?

To be part of this study, you would need to be a man with prostate cancer that has spread to other parts of your body (metastatic) and is no longer responding to hormone treatment. Your doctors would have confirmed this type of cancer with tests.

You would also need to have shown that your prostate cancer has continued to grow despite hormone blocking treatment within the last six months. Importantly, your cancer would need to show up on scans, like bone scans or CT/MRI scans. You might have already taken a drug called abiraterone, or not at all previously. Your general health would need to be considered good enough to take part in the study, and your testosterone levels would need to be low due to ongoing hormone therapy.

Could this study suit you?

Answer these quick questions to see if you may be eligible. This is a guide only — the research team makes the final call.

Are you a man with prostate cancer that has spread?
Has your prostate cancer continued to grow despite hormone therapy?
Do your scans show evidence of cancer spread (e.g., in bones or soft tissues)?
Have you not had chemotherapy for your advanced prostate cancer, or have you previously taken abiraterone?
Do you have a generally good health status (ECOG performance status 0 or 1)?
Are you able to provide a recent sample of your cancer tissue (biopsy)?

Answer every question to see your result.

What does participation involve?

If you join this study, you would be randomly assigned to one of two groups: one group would receive pembrolizumab plus enzalutamide, and the other would receive a placebo (dummy drug) plus enzalutamide. Neither you nor your doctor would know which group you are in. You would take the study medicines regularly.

Throughout the study, you would attend regular appointments for health checks, blood tests, and scans (like CT/MRI and bone scans) to monitor your health and how the treatment is working. Doctors would take tissue samples (biopsies) at certain times to learn more about your cancer. The total duration of your participation could vary, as you would continue treatment as long as it's helping and you're not experiencing severe side effects, followed by a period of regular follow-up to track your health.

Potential risks and benefits

Taking part in any clinical trial involves potential benefits and risks. The potential benefits of this study include receiving new, cutting-edge treatment that might be more effective than current approaches for your advanced prostate cancer. However, there's no guarantee the treatment will work for you. Potential risks include side effects from the medications, which your study team will explain in detail. You have the right to withdraw from the study at any time, for any reason, without it affecting your future medical care.

Locations (259)

Some site locations are approximate. We're improving this — please verify with the trial team before travelling.

University of South Alabama, Mitchell Cancer Institute ( Site 0065)
Verified postcode
Mobile, United States
Providence Medical Foundation-Oncology ( Site 0069)
Verified postcode
Fullerton, United States
UCLA Hematology/Oncology - Santa Monica ( Site 0081)
Verified postcode
Los Angeles, United States
University of Colorado Cancer Center ( Site 0022)
Verified postcode
Aurora, United States
Smilow Cancer Hospital at Yale New Haven ( Site 0038)
Verified postcode
New Haven, United States
Moffitt Cancer Center ( Site 0080)
Verified postcode
Tampa, United States
Georgia Cancer Center at Augusta University ( Site 0026)
Verified postcode
Augusta, United States
Mount Sinai Hospital ( Site 0042)
Verified postcode
Chicago, United States
Methodist Hospitals. ( Site 0008)
Verified postcode
Merrillville, United States
Tulane Cancer Center ( Site 0066)
Verified postcode
New Orleans, United States
University of Massachusetts Worcester ( Site 0053)
Verified postcode
Worcester, United States
Cancer & Hematology Centers of Western Michigan ( Site 0013)
Verified postcode
Grand Rapids, United States

Common questions

What is 'metastatic castration-resistant prostate cancer'?

This means prostate cancer that has spread to other parts of the body and is no longer being controlled by standard hormone treatments that lower testosterone.

What are pembrolizumab and enzalutamide?

Enzalutamide is a hormone-blocking drug. Pembrolizumab is an immunotherapy that helps your body’s immune system fight cancer.

Why is a 'placebo' used in the study?

A placebo is a dummy drug. It helps researchers fairly compare the new combination treatment with standard care to see if the new treatment is truly better.

Will I know which treatment I'm getting?

No, you would be 'blinded,' meaning you wouldn't know if you're getting pembrolizumab or the placebo, in addition to enzalutamide. This avoids bias in the results.

What does a 'Phase 3' study mean?

Phase 3 means this is a large study comparing the new treatment to standard care. If successful, it could lead to the new treatment becoming widely available.