Researchers are looking for a better way to treat men at high-risk of biochemical recurrence (BCR) of prostate cancer.

BCR means that in men who had prostate cancer and were treated by either surgery and/ or radiation therapy, the blood level of a specific protein called PSA rises. PSA is a marker of prostate cancer cells activity. The PSA increase means that the cancer has come back even though conventional imaging such as computed tomography (CT) scans, magnetic resonance imaging (MRI) and bone scans does not show any lesion of prostate cancer. Recently a more sensitive imaging method called prostate-specific membrane antigen [PSMA] positron emission tomography [PET]) /computed tomography [CT]) scan may identify prostate cancer lesions not detectable by conventional imaging. Men with BCR have a higher risk of their cancer spreading to other parts of the body, particularly when PSA levels raised to a certain limit within a short period of time after local therapies. Once the cancer spreads to other parts of the body, it can become even harder to treat.

In men with prostate cancer, male sex hormones (also called androgens) like testosterone can help the cancer grow and spread. To reduce androgens levels in these patients, there are treatments that block androgens production in the body called androgen deprivation therapy (ADT). ADT is often used to stop prostate cancer. Another way to stop prostate cancer growth and spread is to block the action of androgen receptors on prostate cancer cells called androgen receptor inhibitors (ARIs). The new generation ARIs including darolutamide can block the action of androgens receptors and are available for the treatment of prostate cancer in addition to ADT. It is already known that men with prostate cancer benefit from these treatments.

The main objective of this study is to learn if the combination of darolutamide and ADT prolongs the time that the participants live without their cancer getting worse, or to death due to any cause, compared to placebo (which is a treatment that looks like a medicine but does not have any medicine in it) and ADT given for a pre-specified duration of 24 months.

To do this, the study team will measure the time from the date of treatment allocation to the finding of new cancer spread in the participants by using PSMA PET/CT, or death due to any cause. The PSMA PET/CT scans is performed using a radioactive substance called a "tracer" that specifically binds to the prostate-specific membrane antigen (PSMA) which is a protein often found in large amounts on prostate cancer cells.

To avoid bias in treatment, the study participants will be randomly (by chance) allocated to one of two treatment groups. Based on the allocated treatment group, the participants will either take darolutamide plus ADT or placebo plus ADT twice daily as tablets by mouth. The study will consist of a test (screening) phase, a treatment phase and a follow-up phase. The treatment duration is pre-specified to be 24 months unless the cancer gets worse, the participants have medical problems, or they leave the study for any reason. In addition, image guided radiotherapy (IGRT) or surgery is allowed and your doctor will explain the benefits and risks of this type of therapy.

During the study, the study team will:

• take blood and urine samples.
• measure PSA and testosterone levels in the blood samples
• do physical examinations
• check the participants' overall health
• examine heart health using electrocardiogram (ECG)
• check vital signs
• check cancer status using PSMA PET/CT scans, CT, MRI and bone scans
• take tumor samples (if required)
• ask the participants if they have medical problems

About 30 days after the participants have taken their last treatment, the study doctors and their team will check the participants' health and if their cancer worsened. The study team will continue to check this and regularly ask the participants questions about medical problems and subsequent therapies until they leave the study for any reason or until they leave the study for any reason or until the end of the study, whatever comes first.

Inclusion Criteria:

• Capable of giving signed informed consent as described which includes compliance with the requirements, restrictions listed in the informed consent form (ICF), and in this protocol.
• Male ≥18 years of age at the time of signing the informed consent.
• Histologically or cytologically confirmed adenocarcinoma of prostate.
• Prostate cancer initially treated by: radical prostatectomy (RP) followed by adjuvant radiotherapy (ART), or salvage radiotherapy (SRT), or RP in participants who are unfit for (or refused) ART or SRT, or primary radiotherapy (RT).
• High-risk biochemical recurrence (BCR), defined as Prostate-specific antigen doubling time (PSADT) <12 months calculated using the formula provided by the Sponsor, and PSA ≥0.2 ng/mL after ART or SRT post RP or after RP in participants who are unfit for ART or SRT (local or central values accepted), or PSA ≥2 ng/mL above the nadir after primary RT only (local or central values accepted).
• Participants must undergo prostate-specific membrane antigen positron emission tomography/computed tomography (PSMA PET/CT) within the 42-day Screening period using either 18F-DCFPyL (piflufolastat F 18) or 68Ga-PSMA-11 which will be assessed by blinded independent central review (BICR) to identify at least one PSMA PET/CT lesion of prostate cancer.
• Serum testosterone ≥150 ng/dL (5.2 nmol/L) (local assessment is allowed whenever central assessment cannot be done).
• Eastern Cooperative Oncology Group (ECOG) performance status of 0 or 1.
• Blood counts at screening: Hemoglobin ≥9.0 g/dL (participant must not have received blood transfusion within 7 days prior to sample being taken); Absolute neutrophil count (ANC) ≥1.5x10^9/L (participant must not have received any growth factor within 4 weeks prior to sample being taken); Platelet count ≥100x10^9/L.
• Screening values of: Alanine aminotransferase (ALT) ≤1.5 x upper limit of normal (ULN); Aspartate aminotransferase (AST) ≤1.5 x ULN; Total bilirubin (TBL) ≤1.5 ULN, (except participants with a diagnosis of Gilbert's disease); Estimated glomerular filtration rate (eGFR) >40 ml/min/1.73 m^2 calculated by the CKD-EPI formula.
• Sexually active male participants must agree to use contraception as detailed in the protocol during the Treatment period and for at least 1 week after the last dose of study treatment, and refrain from donating sperm during this period.

Exclusion Criteria:

• Pathological finding consistent with small cell, ductal or ≥50 % component of neuroendocrine carcinoma of the prostate.
• History of bilateral orchiectomy.
• Metastases or recurrent /new malignant lesions in prostate gland/bed seminal vesicles, lymph nodes below the CIA bifurcation on conventional imaging (CI) as assessed by BICR during screening.
• Brain metastasis on PSMA PET /CT by BICR at screening.
• High-risk BCR after primary radiotherapy with new loco-regional lesions on screening PSMA PET/CT who are eligible for curative salvage prostatectomy.

Note: Participants treated with curative salvage prostatectomy after primary RT who meet the PSA criteria (inclusion criteria 5) may be considered for the study.

• Prior treatment with second generation (e.g. enzalutamide, apalutamide) androgen receptor inhibitors (ARIs) and CYP 17 inhibitors (e.g., abiraterone) within 18 months prior to signing of the ICF.
• Prior treatments with PSMA-radiotherapeutics within 12 months prior to randomization.
• Prior radiotherapy (including image-guided radiotherapy) as primary, adjuvant or salvage treatment completed within 8 weeks prior to signing of the ICF.
• Any prior malignancy (other than adequately treated basal cell or squamous cell skin cancer, superficial bladder cancer, or any other cancer in situ currently in complete remission) within 5 years.
• History of pelvic radiotherapy for other malignancy.

Availability of this study's data will later be determined according to Bayer's commitment to the EFPIA/PhRMA "Principles for responsible clinical trial data sharing". This pertains to scope, timepoint and process of data access. As such, Bayer commits to sharing upon request from qualified researchers patient-level clinical trial data, study-level clinical trial data, and protocols from clinical trials in patients for medicines and indications approved in the US and EU as necessary for conducting legitimate research. This applies to data on new medicines and indications that have been approved by the EU and US regulatory agencies on or after January 01, 2014.

Interested researchers can use www.vivli.org to request access to anonymized patient-level data and supporting documents from clinical studies to conduct research. Information on the Bayer criteria for listing studies and other relevant information is provided in the member section of the portal.