A Drug-Drug Interaction Study of Abiraterone Acetate Plus Prednisone With Dextromethorphan and Theophylline in Patients With Metastatic Castration-Resistant Prostate Cancer

Inclusion Criteria: * Histologically or cytologically confirmed adenocarcinoma of the prostate without neuroendocrine differentiation or small cell histology * Documented metastatic disease * Documented prostate specific antigen (PSA) progression according to Prostate Cancer Working Group 2 criteria, with PSA value \>=2 ng/mL despite medical or surgical castration, or prostate cancer progression documented by radiographic progression according to Response Evaluation Criteria In Solid Tumors criteria * Surgically or medically castrated with testosterone levels of \<50 ng/dL * Eastern Cooperative Oncology Group (ECOG) Performance Status of \<=2 * Group A only: genomic testing at screening indicating CYP2D6 extensive metabolizer status * Protocol-defined laboratory values Exclusion Criteria: * Serious or uncontrolled co-existent non-malignant disease, including active and uncontrolled infection * Group A only: genomic testing at screening indicating CYP2D6 non-extensive metabolizer status, or prior treatment with dextromethorphan-containing medication or any medication that is a strong inhibitor or inducer of CYP2D6 within 5 half-lives of that drug or 7 days, whichever is longer, prior to Cycle 1 Day -8 * Group B only: prior treatment with theophylline or any medication that is a strong inhibitor or inducer of CYP1A2 within 5 half-lives of that drug or 7 days, whichever is longer, prior to Cycle 1 Day -8 * Abnormal liver function * Uncontrolled hypertension (repeated systolic blood pressure \>=160 mmHg, or diastolic blood pressure \>=95 mmHg) * Active or symptomatic viral hepatitis or chronic liver disease * Known brain metastasis * History of pituitary or adrenal dysfunction * Clinically significant heart disease as evidenced by myocardial infarction, or arterial thrombotic events in the past 6 months, severe or unstable angina, or New York Heart Association Class III or IV heart disease or cardiac ejection fraction measurement of \<50% at baseline * History of gastrointestinal disorders (medical disorders or extensive surgery) which may interfere with the absorption of the study drug * Surgery or local prostatic intervention within 28 days of the first dose, and any clinically relevant sequelae from the surgery must have resolved prior to Cycle 1 Day 1 * Radiotherapy or immunotherapy within 28 days, or single fraction of palliative radiotherapy within 14 days of administration of Cycle 1 Day 1 * Any acute toxicities due to prior therapy that have not resolved * Current enrollment in an investigational drug or device study or participation in such a study within 28 days of Cycle 1 Day 1 * Previous abiraterone acetate or other investigational CYP17 inhibitor (eg, TAK-700)