Inclusion Criteria:

          -  Age ≥ 18 years

          -  Patients with a diagnosis of adenocarcinoma of the prostate

          -  Patients with BCR (PSA becomes detectable, with absolute value ≥1) following
             prostatectomy who have no evidence of metastatic disease based on radiographic
             assessment.

          -  Patients with BCR following radiation therapy who have no radiographic involvement per
             mpMRI and CT (RTOG-ASTRO Phoenix criteria), size of pelvic nodes ≤1 cm, and whose
             MRI-directed prostate biopsies are negative.

          -  Patients must be free of serious comorbidity as determined by investigator.

          -  Clinical laboratory values at screening:

          -  Serum testosterone level ≥150 ng/dL

          -  Hemoglobin ≥9.0 g/dL, independent of transfusion and/or growth factors within 3 months
             prior to randomization

          -  Platelet count ≥100,000 /µL independent of transfusion and/or growth factors within 3
             months prior to randomization

          -  Serum albumin ≥3.0 g/dL

          -  GFR >45 mL/min

          -  Serum potassium ≥3.5 mmol/L

          -  Serum total bilirubin ≤1.5 × ULN (Note: In subjects with Gilbert's syndrome, if total
             bilirubin is >1.5 × ULN, measure direct and indirect bilirubin and if direct bilirubin
             is ≤1.5 × ULN, subject may be eligible)

          -  Aspartate aminotransferase (AST) or alanine aminotransferase (ALT) <2.5 × ULN

          -  Medications known to lower the seizure threshold (see list under prohibited meds,
             Appendix 3) must be discontinued or substituted at least 4 weeks prior to study entry.

          -  Agrees to use a condom (even men with vasectomies) and another effective method of
             birth control if he is having sex with a woman of childbearing potential or agrees to
             use a condom if he is having sex with a woman who is pregnant while on study drug and
             for 3 months following the last dose of study drug. Must also agree not to donate
             sperm during the study and for 3 months after receiving the last dose of study drug.

          -  Written, informed consent to participate in this study.

        Exclusion Criteria:

          -  PSA doubling time >12 months

          -  Positive for HIV or chronic hepatitis B or hepatitis C infection

          -  Another primary malignancy that has not been in remission for at least 2 years.
             Non-melanoma skin cancer allowed.

          -  Use of herbal products that may decrease PSA levels (e.g., saw palmetto) or systemic
             corticosteroids greater than the equivalent of 10 mg of prednisone per day within 4
             weeks of screening laboratory studies.

          -  Any other condition, including concurrent medical condition, social circumstance or
             drug dependency, which in the opinion of the investigator could compromise patient
             safety and/or compliance with study requirements

          -  History of any of the following:

               -  Seizure or known condition that may pre-dispose to seizure (e.g. prior stroke
                  within 1year to randomization, brain arteriovenous malformation, Schwannoma,
                  meningioma, or other benign CNS or meningeal disease which may require treatment
                  with surgery or radiation therapy)

               -  Severe or unstable angina, myocardial infarction, symptomatic congestive heart
                  failure, arterial or venous thromboembolic events (eg, pulmonary embolism,
                  cerebrovascular accident including transient ischemic attacks), or clinically
                  significant ventricular arrhythmias within 6 months prior to randomization Any
                  condition that in the opinion of the investigator, would preclude participation
                  in this study

          -  Current evidence of any of the following:

               -  Uncontrolled hypertension

               -  Gastrointestinal disorder affecting absorption

               -  Active infection (eg, human immunodeficiency virus [HIV] or viral hepatitis) Any
                  condition that in the opinion of the investigator, would preclude participation
                  in this study