Trial Targeting Gut Bacterial Androgen Production to Reverse Therapeutic Resistance to Abiraterone in Patients With Metastatic Prostate Cancer

Eligibility Criteria

• * Males aged 18 years of age and above.
• * Prostate adenocarcinoma
• * Absolute PSA ≥ 2.0 ng/mL at screening.
• * PSA (+/- radiographic) progression after having been on abiraterone and prednisone for at least 12 weeks.
• * Must be maintained on a GnRH analogue or have undergone orchiectomy.
• * Participants must have a life expectancy ≥ 6 months
• * Ability to swallow study medication tablets
• * Willing to abstain from alcohol during and for 14 days after treatment with metronidazole
• * Willing and able to collect urine and stool samples per protocol
• * Active infection or other medical condition that would make dexamethasone use contraindicated
• * Any chronic medical condition requiring a higher systemic dose of corticosteroid
• * Pathological finding consistent with small cell carcinoma of the prostate
• * Has imminent or established spinal cord compression based on clinical findings and/or MRI.
• * Chronic liver disease with Child-Pugh class C cirrhosis (see calculator in protocol)
• * Bilirubin \>3x ULN or AST and ALT \>5x ULN
• * Congenital prolonged QTc syndrome or QTc \> 500 msec (non-paced rhythm)
• * History of pituitary or adrenal dysfunction
• * Uncontrolled diabetes (Hemoglobin A1c \> 10%) or increasing doses of insulin within the past 4 weeks due to poorly controlled glucoses.
• * Administration of an investigational therapeutic or invasive surgical procedure (not including surgical castration) within 30 days of Cycle 1 Day 1 or currently enrolled in an investigational drug study
• * Any other serious illness or medical condition that would, in the opinion of the investigator, make this protocol unreasonably hazardous, including, but not limited to:
• * Any uncontrolled major infection.
• * Crohn's disease or ulcerative colitis.
• * Known or suspected toxic megacolon and/or known small bowel ileus.
• * Known allergy to any of the compounds under investigation.
• * On antibacterial therapy within 30 days prior to administration of study treatment.
• * Any condition or situation which, in the opinion of the investigator, would put the subject at risk, or interfere with the subject's participation in this study.