A Safety and Efficacy Study of Oral MDV3100 in Chemotherapy-Naive Patients With Progressive Metastatic Prostate Cancer

Randomized, Double Blind Treatment Period:

Inclusion Criteria:

- Histologically confirmed adenocarcinoma of the prostate without neuroendocrine
differentiation or small cell features

- Ongoing androgen deprivation therapy with a GnRH analogue or bilateral orchiectomy

- Progressive disease despite androgen deprivation therapy as defined by rising PSA
levels or progressive soft tissue or bony disease

- No prior treatment with cytotoxic chemotherapy

- Asymptomatic or mildly symptomatic from prostate cancer

Exclusion Criteria:

- Severe concurrent disease, infection, or co-morbidity that, in the judgment of the
Investigator, would make the patient inappropriate for enrollment

- Known or suspected brain metastasis or active leptomeningeal disease

- History of another malignancy within the previous 5 years other than curatively
treated non-melanomatous skin cancer

Open-Label Treatment Period:

The following inclusion criteria apply to patients receiving enzalutamide or placebo during
double-blind treatment.

Eligible patients must meet all inclusion criteria.

- Received randomized double-blind treatment in PREVAIL;

- Open-label day 1 visit is within 6 months after this amendment is approved and becomes
effective at the study site;

- Is willing to maintain androgen deprivation therapy with a gonadotropin-releasing
hormone (GnRH) agonist/antagonist or has had a bilateral orchiectomy;

The exclusion criteria apply only to patients starting new treatment with enzalutamide
after receiving placebo as randomized treatment. Each patient must not meet any of the
following criteria:

- Has taken commercially available enzalutamide (Xtandi);

- Severe concurrent disease, infection, or co-morbidity that, in the judgment of the
Investigator, would make the patient inappropriate for enrollment

- Known or suspected brain metastasis or active leptomeningeal disease