A Study of Opevesostat (MK-568)4 in Japanese Participants With Metastatic Castration-resistant Prostate Cancer (mCRPC) (MK-5684-005)

The main inclusion and exclusion criteria include but are not limited to the following:

Inclusion Criteria:

• Has histologically- or cytologically-confirmed adenocarcinoma of the prostatewithout small cell histology

• Has current evidence of metastatic disease documented by either bone lesions on bonescan and/or soft tissue disease by computed tomography/magnetic resonance imaging (CT/MRI)

• Has ongoing androgen deprivation with serum testosterone <50 ng/dL (<1.7 nmol/L)

• Participants receiving bone anti-resorptive therapy (including, but not limited tobisphosphonate or denosumab) must have been on stable doses for ≥4 weeks prior tothe start of study intervention.

• Has progressed on or after treatment with at least 1 line of NHAs in metastatichormone-sensitive prostate cancer (mHSPC) or in castration-resistant prostate cancer (CRPC) for a minimum of 12 weeks (e.g. abiraterone, enzalutamide, darolutamide,apalutamide), and with at least 1 line of taxane-based chemotherapy in mHSPC or inCRPC, or ineligibility for chemotherapy

• Has an Eastern Cooperative Oncology Group (ECOG) performance status of 0 or 1 within 10 days prior to allocation

• If capable of producing sperm, participant must agree to the following during thestudy treatment period and for at least 7 days after the last dose of opevesostat:Refrain from donating sperm, plus EITHER be abstinent OR must agree to use malecondom.

Exclusion Criteria:

• Has a history of pituitary dysfunction

• Has brain metastases

• History of a second malignancy, unless potentially curative treatment has beencompleted with no evidence of malignancy for 3 years

• Has an active or uncontrolled autoimmune disease that has required systemictreatment in past 2 years (ie, with use of disease modifying agents,corticosteroids, or immunosuppressive drugs)

• Has an active infection or other medical condition that would make corticosteroidcontraindicated

• Has serious persistent infection within 2 weeks prior to the start of the studyintervention

• Participants on an unstable dose of thyroid hormone therapy within 6 months prior tothe start of the study intervention

• Has poorly controlled diabetes mellitus

• Hypotension: systolic blood pressure (BP) < 110 mmHg, or uncontrolled hypertension:systolic BP ≥ 160 mmHg or diastolic BP ≥ 95 mmHg, in 2 out of 3 recordings withoptimized antihypertensive therapy

• Has active or unstable cardio/cerebro-vascular disease, including thromboembolicevent

• Is unable to swallow orally administered medication or known gastrointestinal (GI)disease or GI procedure that may interfere with absorption of study intervention

• Has undergone major surgery including local prostate intervention (excludingprostate biopsy) within 28 days prior to the start of the study intervention and notadequately recovered from the toxicities and/or complications

• Has received aldosterone antagonist (e.g. spironolactone, eplerenone) and phenytoinwithin 4 weeks prior to the start of the study intervention

• Has received radiotherapy within 4 weeks prior to the start of the studyintervention, or radiation related toxicities, requiring corticosteroids

• Has received chemotherapy within the last 4 weeks (2 weeks for oral or weeklychemotherapy; 6 weeks for nitrosoureas and mitomycin C) prior to the start of thestudy intervention

• Has received prior enzalutamide and apalutamide within 3 weeks, or abiraterone anddarolutamide within 2 weeks prior to the start of the study intervention

• Systemic use of the following medications within 2 weeks prior to the start of studyintervention: strong cytochrome P450 (CYP)3A4 inducers: e.g., carbamazepine,rifampicin, phenobarbital, phenytoin, St John's Wort) and strong CYP3A4 inhibitors:e.g., itraconazole, ketoconazole, posaconazole, voriconazole, clarithromycin,telithromycin, grapefruit juice

• Received a live or live-attenuated vaccine within 30 days before the first dose ofstudy intervention. Administration of killed vaccines are allowed.

• Has used herbal products that may have hormonal anti-prostate cancer activity and/orare known to decrease PSA levels (eg, saw palmetto) within 4 weeks prior to thestart of the study intervention

• Has received treatment with 5-α reductase inhibitors (eg, finasteride ordutasteride), estrogens, and/or cyproterone within 4 weeks prior to the start of thestudy intervention

• Has received an investigational agent or has used an investigational device within 4weeks prior to study intervention administration

• History of human immunodeficiency virus (HIV) infection

• Has a history of Hepatitis B or active Hepatitis C virus

• Has a "superscan" bone scan

• Has a diagnosis of immunodeficiency or is receiving chronic systemic steroid therapy (in dosing exceeding 10 mg daily of prednisone equivalent) or any other form ofimmunosuppressive therapy within 7 days prior to the start of the study intervention