A Study to Evaluate the Safety and Efficacy of Relugolix in Men With Advanced Prostate Cancer

Key Inclusion Criteria:

1. Has histologically or cytologically confirmed diagnosis of adenocarcinoma of the prostate.
2. Is a candidate for, in the opinion of the investigator, at least 1 year of continuous androgen deprivation therapy for the management of androgen-sensitive advanced prostate cancer with 1 of the following clinical disease state presentations:

   1. Evidence of biochemical (PSA) or clinical relapse following local primary intervention with curative intent, such as surgery, radiation therapy, cryotherapy, or high-frequency ultrasound and not a candidate for salvage treatment by surgery; or
   2. Newly diagnosed androgen-sensitive metastatic disease; or
   3. Advanced localized disease unlikely to be cured by local primary intervention with either surgery or radiation with curative intent.
3. Has a serum testosterone at the Screening visit of ≥ 150 ng/dL (5.2 nanomoles \[nmol\]/liter \[L\]).
4. Has a serum PSA concentration at the Screening visit of \> 2.0 ng/milliliter (mL) (2.0 microgram \[μg\]/L), or, when applicable, post radical prostatectomy of \> 0.2 ng/mL (0.2 μg/L) or post radiotherapy, cryotherapy, or high frequency ultrasound \> 2.0 ng/mL (2.0 μg/L) above the post interventional nadir.
5. Has an Eastern Cooperative Oncology Group performance status of 0 or 1 at initial screening and at baseline.

Key Exclusion Criteria:

1. In the investigator's opinion, is likely to require chemotherapy or surgical therapy for symptomatic disease management within 2 months of initiating androgen deprivation therapy.
2. Previously received gonadotropin-releasing hormone analog or other form of androgen deprivation therapy (estrogen or antiandrogen) for \> 18 months total duration. If androgen deprivation therapy was received for ≤ 18 months total duration, then that therapy must have been completed at least 3 months prior to baseline. If the dosing interval of the depot is longer than 3 months, then the prior androgen deprivation therapy must have been completed at least as long as the dosing interval of the depot.
3. Previous systemic cytotoxic treatment for prostate cancer (for example, taxane-based regimen).
4. Metastases to brain per prior clinical evaluation.
5. Participants with myocardial infarction, unstable symptomatic ischemic heart disease, cerebrovascular events, or any significant cardiac condition within the prior 6 months.
6. Active conduction system abnormalities.
7. Uncontrolled hypertension.