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Study on Talazoparib 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 testosterone in the body is reduced to very low levels. The study is testing a combination of two medications: talazoparib and enzalutamide. Talazoparib is a medication that may help stop cancer cells from repairing themselves, while enzalutamide is used to block the effects of testosterone, which can fuel the growth of prostate cancer cells.

The purpose of the study is to determine if the combination of talazoparib and enzalutamide is more effective than enzalutamide alone in treating mCRPC. Participants in the study will be randomly assigned to receive either the combination of talazoparib and enzalutamide or a placebo with enzalutamide. The study will be conducted over a period of up to 24 months, during which participants will take the medications orally in the form of capsules. The study aims to see if this combination can help prolong the time before the cancer progresses, as assessed by medical imaging techniques.

Throughout the study, participants will have regular check-ups and tests to monitor their health and the effects of the treatment. The study will also look at the safety of the medication combination and how it is processed in the body. This research is important for understanding new ways to treat mCRPC and potentially improve outcomes for patients with this challenging form of cancer.

The research process

The trial runs in 6 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, participants will be required to provide a signed and dated informed consent document. This document confirms that all relevant aspects of the study have been explained and understood.

    Participants must meet specific criteria, such as being at least 18 years old, having a life expectancy of at least 12 months, and being able to swallow the study treatment.

  2. Step 2

    Initial assessments

    Participants will undergo initial assessments to confirm eligibility. This includes confirming a diagnosis of metastatic castration-resistant prostate cancer and ensuring ongoing androgen deprivation therapy.

    Additional tests may include blood tests, imaging scans, and assessments of disease progression.

  3. Step 3

    Treatment phase part 1

    In Part 1 of the treatment phase, the starting dose of talazoparib in combination with enzalutamide will be determined. Both medications are taken orally.

    Participants will be monitored for safety events and the effects of the medication.

  4. Step 4

    Treatment phase part 2

    In Part 2, participants will receive either talazoparib with enzalutamide or a placebo with enzalutamide. This phase is double-blind, meaning neither participants nor researchers know who receives the active medication.

    The goal is to assess the effectiveness of the medication in prolonging the time without disease progression.

  5. Step 5

    Ongoing monitoring

    Throughout the study, participants will have regular visits for monitoring. This includes laboratory tests, imaging scans, and assessments of health status.

    Participants must comply with scheduled visits and study procedures.

  6. Step 6

    End of study

    The study is estimated to end by December 31, 2025. Participants will have a final assessment to evaluate the overall impact of the treatment.

    Participants will be informed about the results and any further steps if necessary.

Who can join the trial?

16 criteria

  • Must be at least 18 years old. In Japan, must be at least 20 years old.
  • Must have a performance status of 0 or 1 on the Eastern Cooperative Oncology Group (ECOG) scale, which measures how well you can perform daily activities.
  • Must have a life expectancy of at least 12 months, as determined by the study doctor.
  • Must be able to swallow the study medication and have no known allergies to the study drugs or their ingredients.
  • If sexually active and capable of ejaculating, must agree to use a condom during sex from the first dose of study treatment until 4 months after the last dose. If the partner is a woman who can become pregnant, she must also use an additional highly effective form of birth control during this time.
  • Must agree not to donate sperm from the first dose of study treatment until 4 months after the last dose.
  • Must provide a signed and dated informed consent form, indicating that you understand the important details of the study.
  • Must be willing and able to attend scheduled visits, follow the treatment plan, and undergo laboratory tests and other study procedures.
  • Must have a confirmed diagnosis of prostate cancer that is not of the small cell or signet cell type. If there is no previous diagnosis, a new biopsy must confirm the diagnosis and support biomarker analysis.
  • Must have metastatic castration-resistant prostate cancer (mCRPC) that is either asymptomatic or causes only mild symptoms, with a pain score of less than 4 on a specific questionnaire.
  • For Part 2 of the study (optional for Part 1): Must have an assessment of DDR mutation status through blood, tissue, or historical analysis, with sponsor approval. Biopsies of certain organs are not allowed solely for study eligibility.
  • For Part 2 of the study (optional for Part 1): Must consent to provide a saliva sample for genetic testing, unless prohibited by local regulations.
  • Must be surgically or medically castrated, with a serum testosterone level of 50 ng/dL or lower at screening. If not surgically castrated, ongoing hormone therapy must have started at least 4 weeks before the study and continue throughout.
  • Must have metastatic disease in the bone or soft tissue, as shown by scans done within 6 weeks before the study. Measurable soft tissue disease is not required.
  • Must have progressive disease at study entry, shown by one or more of the following: rising prostate-specific antigen (PSA) levels, soft tissue disease progression, or bone disease progression.
  • Use of bone-strengthening medications like bisphosphonates or denosumab before the study is allowed but not required.

Who cannot join the trial?

3 criteria

  • Patients who have a different type of cancer other than Metastatic Castration-resistant Prostate Cancer.
  • Patients who are not male, as the study is only for male participants.
  • Patients who are considered part of a vulnerable population, which means they might need special protection or care.
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Investigated drugs

  • Talazoparib

    is a medication used in this clinical trial to treat prostate cancer that has spread to other parts of the body and is resistant to standard hormone therapy. It works by blocking a specific protein in cancer cells, which helps to stop the cancer from growing and spreading. In this study, talazoparib is being tested to see if it can improve the outcomes for patients when used together with another medication.

  • Enzalutamide

    is another medication used in this trial. It is a type of hormone therapy that helps to slow down the growth of prostate cancer by blocking the effects of male hormones that can promote cancer growth. Enzalutamide is already used to treat prostate cancer, and in this study, it is being combined with talazoparib to see if the combination is more effective than enzalutamide alone.

What is already known about the treatment

Talazoparib – Talazoparib is administered orally in the form of capsules and is currently being studied in clinical trials for its effectiveness in treating metastatic castration-resistant prostate cancer. It is being evaluated in combination with another medication, enzalutamide, to see if it can help prolong the time patients live without their cancer worsening. Talazoparib works by blocking a protein that helps repair damaged DNA in cancer cells, which can lead to the death of these cells. It belongs to a class of drugs known as PARP inhibitors, which are used to treat certain types of cancer by preventing cancer cells from repairing themselves.

Investigated diseases

Metastatic Castration-resistant Prostate Cancer – This is a type of prostate cancer that continues to grow and spread to other parts of the body despite low levels of testosterone. It typically progresses by spreading to bones and lymph nodes, causing pain and other symptoms. The cancer cells in this condition are resistant to treatments that lower testosterone, a hormone that usually fuels prostate cancer growth. Over time, the disease can lead to complications such as bone fractures and spinal cord compression. The progression of the disease is often monitored through imaging tests and blood markers. As the cancer advances, it may cause more severe symptoms and impact daily activities.
Trial detailsLast updated 7 Oct 2026
Age18+ yearsPhasePhase IIITrial ID2023-509087-20-00Protocol codeC3441021Estimated enrolment1 127 patientsSponsorPfizer Inc.

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