The primary purpose of this study is to determine the pharmacokinetics (PK) and pharmacodynamics (PD) of Debio 4228.

Inclusion Criteria:

1. Participant with histologically confirmed diagnosis of prostate cancer, with one of the following:

   1. Newly diagnosed androgen-sensitive locally advanced or metastatic disease; or
   2. Localized disease not suitable for local primary intervention with curative intent.

2. Participant judged by the Study Investigator to be candidate for continuous androgen deprivation therapy (ADT).

3. Baseline morning serum testosterone levels >150 ng/dL at screening visit.

4. Eastern Cooperative Oncology Group (ECOG) performance status of 0-2.

5. Life expectancy of at least 6 months.

6. Adequate bone marrow, hepatic, and renal function at the screening visit.

[Note: Other protocol and subprotocol-defined criteria apply]

Exclusion Criteria:

1. Previous ADT (neoadjuvant or adjuvant hormonal therapy) for ≥6 months duration and <6 months treatment-free interval before start of screening.
2. Participant requires combination with androgen deprivation therapy with the exception of enzalutamide.
3. History of bilateral orchiectomy, adrenalectomy, or hypophysectomy.
4. Received chemotherapy or cryotherapy within 8 weeks prior to the start of screening for the treatment of prostate cancer.
5. Abnormal cardiovascular function or diabetes.
6. Use of exogenous testosterone within 6 months before the start of screening.
7. Major surgery within 4 weeks before the start of screening.
8. Cancer disease within the last two years except for prostate cancer and some skin cancers.

[Note: Other protocol and subprotocol-defined criteria apply]

Males with advanced prostate cancer.