The purpose of this study is to evaluate the safety, tolerability, pharmacokinetics, and preliminary activity of RO7656594 in participants with advanced or metastatic prostate cancer. It will also identify recommended doses and regimens for RO7656594 for subsequent studies.

Key Inclusion Criteria:

1. Eastern Cooperative Oncology Group (ECOG) performance status ≤1.
2. Metastatic prostate adenocarcinoma without small-cell carcinoma or neuroendocrine features.
3. Prior therapy with a second-generation androgen receptor (AR)-targeted therapy (e.g., abiraterone, enzalutamide, apalutamide, darolutamide).
4. Prior therapy with a taxane regimen or are considered ineligible for treatment with a taxane regimen or have refused treatment with a taxane regimen, unless otherwise specified.
5. For participants with a known pathogenic breast cancer gene 1 (BRCA1) or BRCA2 mutation: prior therapy with a poly (adenosine diphosphate (ADP)-ribose) polymerase (PARP) inhibitor, or are considered ineligible for treatment with a PARP inhibitor, if such therapy is approved and available.

Key Exclusion Criteria:

1. Treatment with any approved systemic anti-cancer therapy within 14 days or 5 drug elimination half-lives (whichever is longer, not to exceed 28 days) prior to the first study treatment.
2. Treatment with any investigational agent within 28 days prior to the first study treatment.
3. Treatment with any previous AR protein degrader.
4. Untreated central nervous system (CNS) metastases or leptomeningeal disease.

Note: Other protocol specified inclusion/exclusion criteria may apply.

For eligible studies, qualified researchers may request access to individual patient level clinical data. See Roche's commitment to transparency of clinical study information here: https://go.roche.com/data\_sharing