Adaptive Abiraterone Therapy for Metastatic Castration Resistant Prostate Cancer

Prior treatment

• Except GnRH analogue therapy, any other therapies for prostate cancer (excluding bisphosphonate and denosumab) must be discontinued 3 weeks before the first dose of study drugs.
• Prior treatments with Cyp 17 inhibitors like TAK-700/Orteronel, ketoconazole, radium 223 or docetaxel (up to 6 cycles of docetaxel given in the non CRPC setting is allowed). Prior treatment with Sipuleucel-T is allowed.
• Treatment with any investigational compound within 30 days prior to the first dose of study drugs
• Diagnosis or treatment for another systemic malignancy within 2 years before the first dose of study drugs, or previously diagnosed with another malignancy \& have any evidence of residual disease. Potential participants with non-melanoma skin cancer or carcinoma in situ of any type are not excluded if they have undergone complete resection.

Other illness

• Uncontrolled hypertension despite appropriate medical therapy (blood pressure of greater than 160 mmHg systolic and 90 mmHg diastolic at 2 separate measurements no more than 60 minutes apart during the Screening period). Note: May be rescreened after adjustments of antihypertensive medications
• Unstable symptomatic ischemic heart disease, ongoing arrhythmias of Grade \> 2 \[National Cancer Institute (NCI) Common Terminology Criteria for Adverse Events (CTCAE), version 4.03\], New York Heart Association (NYHA) Class III or IV heart failure
• Known human immunodeficiency virus (HIV) infection, active chronic hepatitis B or C not contained with anti-viral therapy, life threatening illness unrelated to cancer, or any serious medical or psychiatric illness that could, in investigator's opinion, potentially interfere with participation in this study.
• Known gastrointestinal (GI) disease or GI procedure that could interfere with the GI absorption or tolerance of study drugs, including difficulty swallowing tables

Other

• Documented central nervous system (CNS) metastases or liver metastasis
• Delayed healing of wounds, ulcers, and/or bone fractures
• Inability to comply with protocol requirements

• Histologically or cytologically confirmed adenocarcinoma of the prostate (the availability archival prostate tumor sample is preferred not required)
• Asymptomatic or minimally symptomatic (not requiring opioids for cancer related pain) metastatic castration resistant prostate cancer (CRPC) patients on abiraterone as standard of care and achieved at least 50% decline of their pre-treatment prostatic specific antigen (PSA)
• Performance status Eastern Cooperative Oncology Group (ECOG) 0-2
• Adequate organ function
• Stable medical condition, including the absence of acute exacerbations of chronic illnesses, serious infections or major surgery within 28 days prior to study enrollment
• Prior surgical castration or concurrent use of gonadotropin-releasing hormone (GnRH) analogue (i.e. medical castration) with testosterone at screening \<50 ng/dL.
• Ability to give written informed consent