A study testing tulmimetostat with darolutamide or abiraterone in patients with metastatic hormone-sensitive prostate cancer

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What is this study about?

This study is for men with metastatic hormone-sensitive prostate cancer, which is a type of prostate cancer that has spread to other parts of the body but still responds to treatments that lower hormone levels. The study will test several medications in different combinations. The main medication being studied is tulmimetostat, also known by its code name DZR123 or CPI-0209. This medication will be tested in combination with darolutamide and also in combination with abiraterone. All participants will continue to receive treatment that lowers testosterone levels, called androgen deprivation therapy, along with medications from the group called gonadotropin releasing hormone analogues. Some participants may also receive medications from the glucocorticoids group as part of their treatment.

The study has two parts with different purposes. The first part will determine the appropriate doses of tulmimetostat when given together with darolutamide and when given together with abiraterone. This part will also look at how safe these combinations are and how well people tolerate them. The second part will compare how well tulmimetostat combined with darolutamide works compared to darolutamide given alone. The main goal is to see how many men achieve very low levels of a substance in the blood called PSA, which is a marker used to monitor prostate cancer. This will be measured at six months and confirmed by a second measurement at least three weeks later.

During the study, participants will take the study medications as tablets by mouth. The study will monitor various aspects of how the treatment affects the cancer and the participant’s health. This includes measuring changes in PSA levels, checking how long it takes for the cancer to grow or spread using imaging scans, measuring overall survival, and evaluating tumor size changes. The study will also carefully track any side effects and how well participants tolerate the medications by looking at things like dose changes, treatment interruptions, and any problems with blood tests, vital signs, or heart function tests. Blood samples will be collected to measure the levels of the study medications in the body.

1 Starting treatment and initial assessment

The study consists of two main parts: Phase I and Phase II. Your participation will depend on which phase you enter.

Before beginning the study treatment, you must already be receiving androgen deprivation therapy (a treatment that lowers male hormones) for at least 1 month but not more than 24 months. You will continue this therapy throughout the study.

Your testosterone level must be at or below 50 ng/dL, which is considered a low level.

2 Phase I treatment options

If you are enrolled in Phase I, you will receive one of two treatment combinations to determine the appropriate dose:

Option 1: You will take tulmimetostat (also called DZR123) by mouth in combination with darolutamide tablets by mouth.

Option 2: You will take tulmimetostat by mouth in combination with abiraterone tablets by mouth.

During the first 28 days of treatment, you will be closely monitored for any side effects to help determine the recommended dose for future participants.

3 Phase II treatment assignment

If you are enrolled in Phase II, you will be randomly assigned to one of two treatment groups:

Group 1: You will receive tulmimetostat by mouth in combination with darolutamide tablets by mouth.

Group 2: You will receive darolutamide tablets by mouth alone, without tulmimetostat.

The assignment to either group will be done randomly, similar to flipping a coin, and neither you nor your doctor can choose which group you will be in.

4 Ongoing treatment period

You will continue taking your assigned medication(s) by mouth as directed.

You must continue your androgen deprivation therapy throughout the entire treatment period.

The specific dosage, frequency, and duration of each medication will be determined based on the phase of the study and the findings from earlier participants.

5 Regular monitoring and assessments

Throughout the study, you will undergo regular monitoring, which includes:

Blood tests to measure your PSA levels (prostate-specific antigen, a protein produced by the prostate that can indicate disease activity). The goal is to see if your PSA level drops to less than 0.2 ng/mL at 6 months, confirmed by a second measurement at least 3 weeks later.

Blood tests to check your bone marrow and organ function.

Monitoring of vital signs such as blood pressure and heart rate.

ECG (electrocardiogram) tests to check your heart’s electrical activity.

Imaging scans to assess any changes in the cancer and to monitor for disease progression.

Assessment of any side effects you may experience, which will be classified according to a standard scale.

6 Blood sample collection for medication levels

Blood samples will be collected at specific times to measure the levels of the study medications in your bloodstream.

In Phase I, this includes measuring levels of tulmimetostat, darolutamide, and abiraterone (depending on which combination you receive).

In Phase II, this includes measuring levels of tulmimetostat and darolutamide.

These measurements help determine how your body processes the medications.

7 Assessment of treatment response

Your response to treatment will be evaluated through several measures:

Changes in your PSA levels, including whether they decrease to less than 0.2 ng/mL or less than 0.1 ng/mL, and whether they drop by at least 50% from the starting level.

Imaging scans to determine if the cancer has remained stable, decreased in size, or progressed.

The length of time before the disease progresses or before it becomes resistant to hormone therapy.

Monitoring for any bone-related complications such as fractures, spinal cord compression, need for bone surgery, or need for radiation therapy to relieve bone pain.

8 Management of side effects

If you experience side effects, your treatment may be adjusted. This could include:

Temporarily stopping the medication (dose interruption).

Reducing the amount of medication you take (dose reduction).

In some cases, discontinuing the study medication if necessary.

All side effects will be recorded and evaluated for their type, frequency, and severity.

9 Continuation of treatment

You will continue treatment as long as you are benefiting from it and not experiencing unacceptable side effects.

The total duration of your participation in the study will be determined by your individual response to treatment and the overall study timeline.

The study is expected to continue until May 2032, though your individual participation may be shorter or longer depending on your specific circumstances.

10 End of treatment follow-up

After you stop taking the study medication, you will continue to be monitored for:

Overall survival (how long you live after starting the study).

Time until the disease progresses or becomes resistant to treatment.

Any long-term side effects from the treatment.

The development of any serious complications related to the cancer.

Who Can Join the Study?

You must be an adult man who is 18 years old or older
You must have metastatic hormone-sensitive prostate cancer, which means prostate cancer that has spread to other parts of the body and still responds to hormone treatment, with at least one confirmed area where the cancer has spread, either in the bone, soft tissue, internal organs, or both
Your cancer must not have neuroendocrine or small cell features, which are specific types of cancer cells
Your testosterone level must be at or below 50 ng/dL (or 1.7 nM), which is considered a low level achieved through treatment
Your ECOG performance status must be 0 to 2, which is a measure of how well you can perform daily activities, ranging from fully active to capable of self-care but unable to work
Your bone marrow and organs must be functioning adequately, as shown by blood tests and other examinations
You must have started androgen deprivation therapy (ADT), which is a hormone treatment that lowers male hormones, at least 1 month but no more than 24 months before joining the study, and be willing to continue this treatment during the study
You may have received one previous taxane-based therapy, which is a type of chemotherapy, but you must not have experienced disease progression while on it. In Phase II of the study, no more than 25% of participants can have had prior taxane treatment
You may have previously used certain hormone treatments called ARPI (abiraterone, enzalutamide, darolutamide, or apalutamide) under specific conditions: if used during biochemical recurrence or curative treatment for any length of time as long as it was stopped before the cancer spread to other parts of the body, or if used after the cancer spread, for any duration in Phase I or for 6 months or less in Phase II. You cannot be currently taking darolutamide
You may have had previous radiation therapy directed at the prostate or surgery on the prostate. Radiation must be completed before joining the study, and surgery must have been done at least 2 weeks before

Who Cannot Join the Study?

The study is only for male patients, so female patients cannot participate
Patients who are not adults cannot participate in this study
Patients with metastatic hormone-sensitive prostate cancer who do not meet the specific requirements for this condition cannot participate. This means the cancer has spread to other parts of the body and still responds to hormone treatment
Patients who are taking medications that may interact with tulmimetostat, which is an experimental drug being tested in this study, may not be able to participate
Patients who are taking medications that may interact with darolutamide, which is a hormone therapy drug used to treat prostate cancer, may not be able to participate
Patients who are taking medications that may interact with abiraterone, which is another hormone therapy drug that blocks the production of certain hormones, may not be able to participate
Patients with other serious medical conditions that could affect their safety during the study may not be able to participate
Patients who have participated in other clinical trials recently may not be eligible
Patients with abnormal laboratory test results that indicate problems with their liver, kidneys, or blood cells may not be able to participate
Patients who are unable to follow the study requirements or attend all scheduled visits may not be able to participate

Where you can join this trial?

Verified and Recommended Sites

No sites found in this category

Verified Sites

Site Name	City	Country
Bellvitge University Hospital	L'hospitalet De Llobregat	Spain
University Hospital Jena KöR	Jena	Germany
Hospital Clinico San Carlos	Madrid	Spain
IRCCS Humanitas Research Hospital	Rozzano	Italy

Other Sites

Site Name	City	Country
Hopitaux Universitaires Pitie Salpetriere	Paris	France
Orszagos Onkologiai Intezet	Budapest	Hungary
Azienda Socio Sanitaria Territoriale Di Cremona	Cremona	Italy
Hospital Universitario Puerta De Hierro De Majadahonda	Majadahonda	Spain
Institut Godinot	Reims	France
Universita’ Degli Studi Di Verona	Verona	Italy
Semmelweis University	Budapest	Hungary
Centre Hospitalier Universitaire De Nantes	Nantes	France
Centre Hospitalier Universitaire De Rennes	Rennes	France
Hopital Beaujon	Clichy	France
University Of Szeged	Szeged	Hungary
Uuktrentqwonghojsfkpo Eyaiq Acb	Essen	Germany
Hwdgrbni Vydz dndmhrly	Barcelona	Spain
Czrzzm Odlmx Lwnzyel	Lille	France

Trial status

Country	Status	Recruitment Start
France	Recruiting	26.02.2026
Germany	Recruiting	26.02.2026
Hungary	Recruiting	26.02.2026
Italy	Recruiting	26.02.2026
Spain	Recruiting	26.02.2026

Trial locations

Investigated drugs:

Tulmimetostat (also known as DZR123) is an investigational medication being studied for the treatment of prostate cancer. It works by targeting specific proteins in cancer cells that help control how genes are turned on or off, which may help slow or stop cancer growth.

Darolutamide is a medication used to treat prostate cancer. It works by blocking the effects of male hormones like testosterone that can help prostate cancer cells grow and spread throughout the body.

Abiraterone is a medication used to treat prostate cancer. It works by reducing the amount of male hormones, particularly testosterone, that the body produces. These hormones can fuel the growth of prostate cancer cells.

Metastatic Hormone-Sensitive Prostate Cancer – This is a type of prostate cancer that has spread beyond the prostate gland to other parts of the body, such as bones or lymph nodes. The cancer cells still respond to hormones, particularly testosterone, which means that lowering hormone levels can slow down the growth of the cancer. In this stage, the disease has already moved from its original location but can still be controlled by treatments that reduce male hormones in the body. Patients may experience symptoms such as bone pain, difficulty urinating, or fatigue as the cancer spreads. The hormone-sensitive nature means the cancer cells require testosterone to grow and multiply. Over time, some cancer cells may become resistant to hormone-based approaches and the disease may progress to a more advanced form.

Trial ID:

2025-521873-15-00

Protocol code:

CDZR123C12101

Trial Phase:

Human Pharmacology (Phase I) – Other

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A study testing tulmimetostat with darolutamide or abiraterone in patients with metastatic hormone-sensitive prostate cancer

What is this study about?

Who Can Join the Study?

Who Cannot Join the Study?