A Study to Evaluate Enzalutamide After Abiraterone in Metastatic Castration-Resistant Prostate Cancer

Inclusion Criteria

• Subject has histologically confirmed adenocarcinoma of the prostate without neuro-endocrine differentiation or small cell features.
• Subject has metastatic disease documented by bone scan or by soft tissue disease observed by Computed Tomography/Magnetic Resonance Imaging (CT/MRI) at screening, or within ≤30 days prior to Day 1.
• In the setting of castrate levels of testosterone ≤1.7 nmol/L (or ≤50 ng/dL), subject has progressive disease at study entry defined as PSA rise determined by a minimum of 2 rising PSA levels with an interval of ≥ 1 week between each assessment. The PSA value at the screening visit should be ≥ 2 ng/mL WITH or WITHOUT:
• Soft tissue disease progression defined by Response Evaluation Criteria In Solid Tumors (RECIST 1.1) at screening, or within ≤30 days prior to Day 1. Measurable disease is not required for entry. Lymph nodes ≥ 2 cm are considered measurable disease (Prostate Cancer Clinical Trials Working Group (PCWG2)).
• Bone disease progression defined by at least 2 new lesions on bone scan at screening, or within ≤30 days prior to Day 1.
• Subject must have received a minimum of 24 weeks of treatment with abiraterone acetate within its approved label indication and has discontinued use at least 4 weeks prior to start of study drug at Day 1.
• If the subject has received previous treatment with chemotherapy for prostate cancer, this must be limited to no more than one prior line of docetaxel, and must have been used prior to abiraterone acetate therapy.
• Subject receives and will continue to receive ongoing androgen deprivation with Luteinizing-hormone-releasing hormone (LHRH) analogue therapy throughout the course of the study or has had a bilateral orchiectomy.
• Subject is asymptomatic or mildly symptomatic from prostate cancer:
• The score on Brief Pain Inventory - Short Form (BPI-SF) Question #3 must be < 4.
• No use of opiate analgesics for prostate cancer-related pain currently or anytime within 4 weeks prior to screening.

Exclusion Criteria

• Subject has prior use of ketoconazole for the treatment of prostate cancer.
• Subject has prior use of cabazitaxel.
• Subject has prior use of enzalutamide.
• Subject has received ANY anti-neoplastic therapy (including antiandrogens and chemotherapy) following abiraterone acetate discontinuation and prior to start of study drug at Day 1.
• Subject has a known or suspected hypersensitivity to enzalutamide, or any components of the formulation used.
• Subject has known or suspected brain metastases or active leptomeningeal disease.
• Subject has history of seizure or any condition that may predispose to seizure (e.g., prior stroke or significant brain trauma).