A Multicenter Phase 2, Randomized, Double-Blind, Efficacy and Safety Study of Enzalutamide Versus Bicalutamide in Men With Prostate Cancer Who Have Failed Primary Androgen Deprivation Therapy

Inclusion Criteria:

- Males age 18 or older;

- Histologically or cytologically confirmed adenocarcinoma of the prostate;

- Ongoing androgen deprivation therapy

- Serum testosterone level ≤ 50 ng/dL (1.73 nmol/L) at the Screening visit;

- Progressive disease at study entry defined by PSA progression and/or radiographic
progression that occurred while the patient was on primary androgen deprivation
therapy

- Asymptomatic or mildly symptomatic from prostate cancer;

- Eastern Cooperative Oncology Group (ECOG) performance status of 0-1;

- Estimated life expectancy of ≥ 12 months;

- Able to swallow the study drug and comply with study requirements.

Exclusion Criteria:

- Severe concurrent disease, infection, or co-morbidity;

- Known or suspected brain metastasis or active leptomeningeal disease;

- History of another invasive malignancy within the previous 5 years other than
curatively treated non-melanomatous skin cancer and American Joint Committee on
Cancer (AJCC) Stage 0 or Stage 1 cancers that have a remote probability of
recurrence;

- Absolute neutrophil count < 1,500/µL, or platelet count < 100,000/µL, or hemoglobin <
9 g/dL at the Screening visit;

- Total bilirubin, alanine aminotransferase (ALT) or aspartate aminotransferase (AST) >
2.5 times the upper limit of normal (ULN) at the Screening visit;

- Creatinine > 2 mg/dL at the Screening visit;

- Albumin < 3.0 g/dL at the Screening visit;

- History of seizure or any condition that may predispose to seizure;

- Clinically significant cardiovascular disease;

- Gastrointestinal disorder affecting absorption (e.g., gastrectomy, active peptic
ulcer disease within last 3 months);

- Major surgery within 4 weeks of enrollment;

- Use of opiate analgesics for pain from prostate cancer within 4 weeks of enrollment;

- Radiation therapy for treatment of the primary tumor within 3 weeks of enrollment;

- Prior ketoconazole, abiraterone, or cytotoxic chemotherapy for prostate cancer;

- Use of antiandrogens within 4 weeks prior to enrollment;

- Prior disease progression, as assessed by the Investigator, while receiving
bicalutamide;

- Participation in a previous clinical trial of enzalutamide or an investigational
agent that inhibits the androgen receptor or androgen synthesis (patients who
received placebo are acceptable);

- Use of an investigational agent within 4 weeks of enrollment;

- Use of herbal products that may have hormonal anti-prostate cancer activity and/or
are known to decrease PSA levels (e.g., saw palmetto) or systemic corticosteroids for
prostate cancer within 4 weeks of enrollment;

- Any condition or reason that, in the opinion of the Investigator, interferes with the
ability of the patient to participate in the trial, which places the patient at undue
risk, or complicates the interpretation of safety data.