The purpose of this study is to assess the safety and activity of ARN-509 in men with advanced castration resistant prostate cancer. Patients will first be enrolled into Phase 1 of the study to identify a tolerable dose for the Phase 2 portion of the study. In the Phase 2, 3 different cohorts of patients will be enrolled to evaluate the safety and activity of ARN-509.

NON-METASTATIC CRPC

Inclusion Criteria

1. Histologically or cytologically proven prostate cancer with high risk for development of metastases, defined as either a PSA value >=8 ng/mL within the last 3 months or PSA Doubling Time <=10 months
2. Ongoing androgen depletion therapy with a Gonadotropin Releasing Hormone (GnRH) analogue or inhibitor, or orchiectomy (i.e., surgical or medical castration)
3. Castrate levels of serum testosterone of less than or equal to 50 ng/dL
4. Eastern Cooperative Oncology Group (ECOG) performance status of 0-1
5. A life expectancy of at least 3 months

Exclusion Criteria

1. Distant metastases, including CNS and vertebral or meningeal involvement
2. Prior treatment with MDV3100
3. Prior treatment with abiraterone
4. Prior treatment with ketoconazole
5. Concurrent treatment with medications known to have seizure potential
6. Concurrent treatment with corticosteroids. If they are already on steroids, patients will be allowed to enroll on the study but will need to taper off as soon as possible.
7. QTc > 450 msec
8. History of seizure or condition that may predispose to seizure
9. Evidence of severe or uncontrolled systemic disease or HIV infection

METASTATIC CRPC, TREATMENT-NAIVE

Inclusion Criteria

1. Histologically or cytologically proven prostate cancer with progressive disease based on either PSA or radiographic progression
2. Ongoing androgen depletion therapy with a Gonadotropin Releasing Hormone (GnRH) analogue or inhibitor, or orchiectomy (i.e., surgical or medical castration)
3. Castrate levels of serum testosterone of less than or equal to 50 ng/dL
4. Eastern Cooperative Oncology Group (ECOG) performance status of 0-1
5. A life expectancy of at least 3 months

Exclusion Criteria

1. History of, or current metastases in the brain or untreated spinal cord compression
2. Prior treatment with MDV3100
3. Prior treatment with abiraterone
4. Prior treatment with ketoconazole
5. Concurrent treatment with medications known to have seizure potential
6. Concurrent treatment with corticosteroids. If they are already on steroids, patients will be allowed to enroll on the study but will need to taper off as soon as possible.
7. QTc > 450 msec
8. History of seizure or condition that may predispose to seizure
9. Evidence of severe or uncontrolled systemic disease or HIV infection

METASTATIC CRPC, CHEMOTHERAPY-NAIVE, POST-ABIRATERONE

Inclusion Criteria

1. Histologically or cytologically proven prostate cancer with progressive disease based on either PSA or radiographic progression
2. Ongoing androgen depletion therapy with a Gonadotropin Releasing Hormone (GnRH) analogue or inhibitor, or orchiectomy (i.e., surgical or medical castration)
3. Castrate levels of serum testosterone of less than or equal to 50 ng/dL
4. Eastern Cooperative Oncology Group (ECOG) performance status of 0-1
5. A life expectancy of at least 3 months
6. Patients must have received a minimum of 6 months of abiraterone treatment prior to disease progression

Exclusion Criteria

1. History of, or current metastases in the brain or untreated spinal cord compression
2. Prior treatment with MDV3100
3. Prior treatment with ketoconazole
4. Concurrent treatment with medications known to have seizure potential
5. Concurrent treatment with corticosteroids. If they are already on steroids, patients will be allowed to enroll on the study but will need to taper off as soon as possible.
6. QTc > 450 msec
7. History of seizure or condition that may predispose to seizure
8. Evidence of severe or uncontrolled systemic disease or HIV infection

A copy of the manuscript must be provided to the sponsor for review at least 60 days before submission for publication or presentation. If requested in writing, such publication will be withheld for up to an additional 60 days.