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A Study of Tulmimetostat and Luxdegalutamide Compared to Standard Treatment in Men with Advanced Prostate Cancer That No Longer Responds to Hormone Therapy

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What is this trial about?

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

This study involves people with metastatic castrate resistant prostate cancer, which is a type of advanced prostate cancer that has spread to other parts of the body and no longer responds to treatments that lower testosterone levels. The study will test two investigational medicines called tulmimetostat (also known as DZR123) and JSB462 (also known as luxdegalutamide) given together. These medicines will be compared to standard treatments, which may include abiraterone, enzalutamide, docetaxel, or cabazitaxel, along with medicines from groups called glucocorticoids and gonadotropin releasing hormone analogues. The purpose of this study is to find out if the combination of tulmimetostat and luxdegalutamide is safe and effective in treating this type of prostate cancer.

The study has two main parts. The first part will determine the appropriate doses of the two investigational medicines when given together and will assess their safety and how well the body tolerates them. This part will also measure how well the treatment works by checking levels of a substance in the blood called PSA, which is a marker for prostate cancer. The second part of the study will compare the combination of tulmimetostat and luxdegalutamide with standard treatments to see which works better at reducing PSA levels after six months of treatment. Throughout the study, doctors will monitor for any side effects and measure how the cancer responds to treatment using blood tests and imaging scans such as CT scans, MRI scans, or bone scans.

Participants will receive their assigned treatment and will be followed to see how long it takes before the cancer gets worse, how long they live, and whether tumors shrink or disappear. The study will also track any bone-related problems such as fractures or the need for radiation therapy to relieve bone pain. All medicines in this study are taken by mouth as tablets or capsules, except for docetaxel and cabazitaxel which are given through a vein. People joining this study must have prostate cancer that has spread and has continued to grow despite previous treatments that lower testosterone, and they must have received at least one prior treatment with medicines such as abiraterone, enzalutamide, darolutamide, or apalutamide.

The research process

The trial runs in 12 steps – from screening to follow-up. Each step says what happens and what the team monitors.

  1. Step 1

    Treatment assignment

    The study consists of different parts. Depending on the part of the study, treatment may be assigned in different ways.

    In Part 1a (dose escalation), the treatment combination of tulmimetostat and JSB462 (luxdegalutamide) will be given at doses determined by the study protocol to find the appropriate dose.

    In Part 1b (dose expansion), the treatment combination will be given at the doses identified in Part 1a to further evaluate safety and response.

    In Part 2, assignment to treatment will be randomized. This means that either the combination of tulmimetostat and JSB462 or a standard of care treatment will be assigned. The standard of care treatment may include abiraterone, docetaxel, cabazitaxel, or enzalutamide, depending on prior treatments received.

  2. Step 2

    Baseline imaging and assessments

    Before starting treatment, imaging scans will be performed. These may include CT scans, MRI scans, or bone scans to document the extent of disease.

    Blood tests will be performed to measure PSA (prostate-specific antigen) levels and testosterone levels.

    Additional safety assessments will include laboratory tests, vital signs (blood pressure, heart rate, temperature), and electrocardiograms (ECGs, which measure heart activity).

  3. Step 3

    Start of study treatment

    Treatment will begin according to the assigned group.

    If assigned to the combination treatment, tulmimetostat and JSB462 (luxdegalutamide) will be taken by mouth as tablets or film-coated tablets.

    If assigned to standard of care treatment, the specific medication will depend on prior treatments. Abiraterone and enzalutamide are taken by mouth as tablets. Docetaxel and cabazitaxel are given through a vein (intravenously).

    The exact dosage and frequency of administration will be determined by the study protocol and communicated by the study team.

    Continuation of androgen deprivation therapy (treatment to keep testosterone levels low) is required throughout the study.

  4. Step 4

    Regular monitoring visits

    Regular visits will be scheduled to monitor health and response to treatment.

    At these visits, blood samples will be collected to measure PSA levels and to assess safety through laboratory tests.

    For participants receiving the combination treatment, blood samples will also be collected to measure the levels of tulmimetostat and JSB462 in the bloodstream.

    Physical examinations, vital signs measurements, and electrocardiograms may be performed at specified visits.

    Any side effects or symptoms experienced will be recorded and assessed according to standard medical criteria.

  5. Step 5

    PSA response assessment at 3 months

    At approximately 3 months after starting treatment, PSA levels will be assessed to determine if there has been a reduction.

    A PSA50 response is defined as a reduction of at least 50% from the baseline PSA level, confirmed by a second measurement at least 3 weeks later.

  6. Step 6

    PSA response assessment at 6 months

    At approximately 6 months after starting treatment, PSA levels will be assessed again.

    This is a key time point for evaluating the biochemical response to treatment.

    A PSA50 response at 6 months is one of the main outcomes being measured in this study.

  7. Step 7

    Imaging assessments

    Imaging scans (CT, MRI, or bone scans) will be performed at scheduled intervals to assess whether the disease has progressed, remained stable, or responded to treatment.

    The timing of these scans will be determined by the study protocol.

    Disease progression is evaluated using standardized criteria that assess changes in tumor size, new lesions, or changes in bone disease.

  8. Step 8

    PSA response assessment at 9 and 12 months

    PSA levels will continue to be monitored at 9 months and 12 months after starting treatment.

    These assessments help to track the ongoing response to treatment over time.

  9. Step 9

    Management of side effects

    Throughout the study, any side effects will be monitored and managed as needed.

    Depending on the type and severity of side effects, the study treatment may be temporarily stopped (dose interruption), the dose may be reduced (dose reduction), or treatment may be discontinued.

    All side effects will be evaluated and graded according to standard medical criteria.

  10. Step 10

    Long-term follow-up

    Treatment will continue as long as there is benefit and side effects are manageable.

    If the disease progresses or side effects become unacceptable, treatment may be stopped.

    After stopping treatment, follow-up visits will continue to monitor overall health and survival.

    The study will track radiographic progression-free survival (time until disease progression or death), overall survival (time until death from any cause), and other long-term outcomes.

  11. Step 11

    Assessment of skeletal events

    Throughout the study, any bone-related complications will be monitored.

    These may include new bone fractures, spinal cord compression, need for bone surgery, or need for radiation therapy to relieve bone pain.

    The time to the first such event will be recorded as part of the study outcomes.

  12. Step 12

    End of study participation

    Participation in the study will end when treatment is discontinued and follow-up assessments are completed.

    The total duration of participation will vary depending on how long treatment continues and how long follow-up is required.

    The study is estimated to continue until December 2030.

Who can join the trial?

7 criteria

  • You must be a man who is 18 years of age or older.
  • You must have a confirmed diagnosis of adenocarcinoma of the prostate, which is a type of cancer that starts in the prostate gland. This diagnosis must be confirmed by examining tissue samples under a microscope. Your cancer must not have features of neuroendocrine or small cell types, which are different forms of cancer cells.
  • You must have at least one metastatic lesion, which means the cancer has spread from the prostate to other parts of your body. This must be visible on imaging scans such as a CT scan, MRI, or bone scan performed within 28 days before starting treatment.
  • You must have progressive metastatic castrate resistant prostate cancer, which means your cancer continues to grow despite having very low levels of male hormones. The progression must be shown by at least one of the following: your PSA level (a protein in the blood that can indicate prostate cancer activity) has increased at least twice with measurements taken at least one week apart, or your cancer has grown in soft tissues based on imaging scans, or new areas of cancer have appeared in your bones on a bone scan.
  • Your blood level of testosterone, which is a male hormone, must be very low (below 50 nanograms per deciliter or below 1.7 nanomoles per liter). This low level is called castrate level.
  • You must have previously received treatment with at least one second generation ARPI, which is a type of hormone therapy medication. These medications include abiraterone, enzalutamide, darolutamide, or apalutamide. Your cancer must have continued to grow despite this treatment.
  • Depending on which part of the study you join, there are different requirements for prior chemotherapy, which is a type of cancer treatment using strong medications. For some parts of the study, you may have received chemotherapy before, while for other parts you must not have received certain types of chemotherapy for your current stage of cancer.

Who cannot join the trial?

5 criteria

  • The study information provided does not contain specific exclusion criteria, which are reasons why someone cannot participate in the study
  • This study is only for male patients, so female patients cannot participate
  • This study is designed for adults and older adults, so younger age groups cannot participate
  • Only patients with metastatic castrate resistant prostate cancer, which is an advanced form of prostate cancer that no longer responds to treatments that lower testosterone levels and has spread to other parts of the body, can participate in this study
  • Patients who do not meet the specific medical condition requirements for this type of prostate cancer cannot participate
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Investigated drugs

Tulmimetostat (also known as DZR123) is an investigational medication being studied in this trial. It works by targeting certain proteins in cancer cells that help control how genes are turned on or off. By blocking these proteins, the medication may help slow down or stop the growth of prostate cancer cells.

JSB462 (also known as luxdegalutamide) is an investigational medication that blocks the action of male hormones called androgens. These hormones can fuel the growth of prostate cancer. By blocking these hormones, this medication may help control the cancer's growth in patients whose cancer has stopped responding to other hormone treatments.

Standard of care treatment refers to the currently accepted and widely used treatments for metastatic castrate resistant prostate cancer. These are established therapies that doctors regularly prescribe based on current medical guidelines. In this trial, the combination of the two investigational medications will be compared to these standard treatments to see which approach works better.

What is already known about the treatment

  • Tulmimetostat

    Tulmimetostat is an investigational medication currently being studied in clinical trials for the treatment of advanced prostate cancer that has spread to other parts of the body and no longer responds to hormone therapy. This drug works at the cellular level by blocking certain proteins that help cancer cells grow and survive, specifically targeting enzymes that control how genes are turned on and off in cancer cells. It is being tested in combination with another experimental drug called luxdegalutamide to see if this combination can slow down cancer growth better than current standard treatments. Tulmimetostat belongs to a class of medications known as epigenetic inhibitors, which means it affects how cancer cells read their genetic instructions without changing the actual DNA sequence.

  • Luxdegalutamide

    Luxdegalutamide, also known as JSB462, is an experimental medication being evaluated in clinical trials for treating prostate cancer that has spread throughout the body and continues to grow despite treatments that lower male hormones. This drug works by blocking the effects of male hormones on cancer cells in a more complete way than older medications, preventing these hormones from helping the cancer grow and survive. It is being tested in combination with tulmimetostat to determine if using both drugs together can provide better results than existing treatment options for patients whose cancer has stopped responding to standard hormone-blocking therapies. Luxdegalutamide belongs to a class of drugs called androgen receptor inhibitors, which block the signals that male hormones send to prostate cancer cells.

Investigated diseases

Metastatic Castrate Resistant Prostate Cancer – This is an advanced form of prostate cancer that has spread beyond the prostate gland to other parts of the body. The disease continues to grow and progress even when the levels of male hormones, particularly testosterone, have been reduced to very low levels through medical treatment or surgical removal of the testicles. In this condition, cancer cells have developed the ability to survive and multiply without needing normal amounts of testosterone. The cancer may spread to bones, lymph nodes, or other organs in the body. Patients with this condition have typically already received hormone therapy that initially worked but eventually stopped being effective. As the disease progresses, it becomes increasingly resistant to standard hormone-based treatments.
Trial detailsLast updated 7 Oct 2026
Age18+ yearsPhasePhase ITrial ID2025-521880-10-00Protocol codeCDZR123A12107Estimated enrolment188 patientsSponsorNovartis Pharma AG

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