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Study of Pembrolizumab and Enzalutamide for Patients with Metastatic Castration-Resistant Prostate Cancer

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What is this trial about?

A plain-language summary of the goals, design and what participants do

This clinical trial is focused on studying a type of prostate cancer known as Metastatic Castration-Resistant Prostate Cancer (mCRPC). This is a form of prostate cancer that continues to grow and spread even when the amount of male hormones in the body is reduced to very low levels. The study is testing a combination of two treatments: Pembrolizumab, also known by its code name MK-3475, and Enzalutamide. Pembrolizumab is a medication that helps the immune system fight cancer, while Enzalutamide is used to block the effects of male hormones that can promote cancer growth. The trial will compare the effects of these two drugs together against a combination of a placebo and Enzalutamide.

The purpose of the study is to see if the combination of Pembrolizumab and Enzalutamide can help patients live longer and slow down the progression of the cancer compared to the placebo and Enzalutamide. Participants in the study will receive either the combination of Pembrolizumab and Enzalutamide or the placebo and Enzalutamide. The study will monitor the participants over a period to assess their overall survival and the time it takes for the cancer to progress as seen on medical imaging tests.

Throughout the study, participants will receive regular check-ups and assessments to monitor their health and the effects of the treatment. The study aims to provide valuable information on the effectiveness of combining Pembrolizumab with Enzalutamide in treating this challenging form of prostate cancer. The trial is expected to continue until 2025, providing insights that could lead to improved treatment options for patients with mCRPC.

The research process

The trial runs in 4 steps – from screening to follow-up. Each step says what happens and what the team monitors.

  1. Step 1

    Joining the study

    Upon joining the study, you will be randomly assigned to one of two groups. One group will receive a combination of pembrolizumab and enzalutamide, while the other group will receive a placebo with enzalutamide. A placebo is a substance with no active medication, used to compare the effects of the actual drug.

  2. Step 2

    Medication administration

    If you are in the group receiving pembrolizumab, it will be administered as an intravenous infusion. This means the medication will be given through a vein in your arm. The dosage is 25 mg/mL, and the frequency and duration will be determined by the study team.

    You will also take enzalutamide orally, which means you will swallow the medication in pill form. The dosage and frequency will be provided by the study team.

  3. Step 3

    Monitoring and assessments

    Throughout the study, you will undergo regular monitoring and assessments to evaluate your health and the effects of the treatment. This may include blood tests, imaging scans like CT or MRI, and other evaluations as needed.

    The study aims to compare overall survival and progression-free survival between the two groups. Progression-free survival refers to the length of time during and after treatment that the cancer does not get worse.

  4. Step 4

    Completion of the study

    The study is expected to continue until February 28, 2025. Your participation may last until the study ends or until you and the study team decide it is best for you to stop.

    After completing the study, you may have follow-up visits to monitor your health and gather additional information about the long-term effects of the treatment.

Who can join the trial?

5 criteria

  • Must have a confirmed diagnosis of adenocarcinoma of the prostate, which is a type of prostate cancer, without any small cell cancer features.
  • Prostate cancer must have progressed while on androgen deprivation therapy (a treatment to lower male hormones) or after surgical removal of the testicles, within 6 months before joining the study.
  • Must have current evidence of metastatic disease, meaning the cancer has spread to other parts of the body, shown by bone lesions on a bone scan or soft tissue disease on a CT or MRI scan.
  • Must be undergoing ongoing androgen deprivation therapy with serum testosterone levels less than 50 ng/dL (a measure of male hormone levels).
  • Only male participants are eligible for this study.

Who cannot join the trial?

3 criteria

  • Patients who do not have Metastatic Castration-Resistant Prostate Cancer cannot participate. This is a type of prostate cancer that has spread to other parts of the body and does not respond to treatments that lower testosterone.
  • Only male patients can participate in this study.
  • Patients who are part of a vulnerable population cannot participate. This means groups of people who might be at a higher risk of harm or exploitation.
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Investigated drugs

  • Pembrolizumab

    is a type of medication known as an immunotherapy. It works by helping your immune system fight cancer cells. In this trial, pembrolizumab is being tested to see if it can help improve survival in patients with a specific type of prostate cancer that has spread to other parts of the body and is resistant to standard hormone therapy.

  • Enzalutamide

    is a medication used to treat prostate cancer. It works by blocking the effects of male hormones that can promote the growth of cancer cells. In this trial, enzalutamide is used in combination with pembrolizumab to see if the two medications together can be more effective in treating prostate cancer than enzalutamide alone.

What is already known about the treatment

  • Pembrolizumab

    Pembrolizumab is administered as an intravenous infusion, meaning it is given directly into the bloodstream through a vein. It is currently being studied in clinical trials for its effectiveness in treating metastatic castration-resistant prostate cancer, a type of advanced prostate cancer. The main therapeutic indication for pembrolizumab in this trial is to improve overall survival and delay disease progression. At the molecular level, pembrolizumab works by blocking a protein called PD-1 on immune cells, which helps the immune system recognize and attack cancer cells. It is classified as an immune checkpoint inhibitor, a type of drug that helps the body's immune system fight cancer.

  • Enzalutamide

    Enzalutamide is taken orally in the form of a capsule or tablet. It is an established medication used in the treatment of metastatic castration-resistant prostate cancer, and it is being evaluated in combination with pembrolizumab in clinical trials. The main therapeutic indication for enzalutamide is to slow the growth and spread of prostate cancer. Enzalutamide works by blocking the action of male hormones, such as testosterone, which can promote the growth of prostate cancer cells. It is classified as an androgen receptor inhibitor, a type of drug that interferes with the signals that tell cancer cells to grow.

Investigated diseases

Metastatic Castration-Resistant Prostate Cancer – This is a type of prostate cancer that continues to grow and spread despite low levels of testosterone, which is typically achieved through medical or surgical castration. The disease is characterized by the cancer cells' ability to thrive even when androgen levels are reduced to very low levels. It often spreads to bones, lymph nodes, and other parts of the body. As the cancer progresses, patients may experience symptoms such as bone pain, urinary issues, and fatigue. The progression of the disease is monitored through imaging studies and prostate-specific antigen (PSA) levels. Over time, the cancer may become more aggressive and resistant to standard therapies.
Trial detailsLast updated 2 Oct 2026
Age18+ yearsPhasePhase IIITrial ID2022-500785-10-00Protocol codeMK-3475-641Estimated enrolment1 164 patientsSponsorMerck Sharp & Dohme LLC

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