115^ Background: This open phase I trial assessed the bioavailability, and the effect of food on the bioavailability of ODM-201 600mg tablets compared to a 600mg capsule formulation. Efficacy, safety, and tolerability of ODM-201 were studied in the extension period. Methods: The study had two parts: a pharmacokinetic (PK), and a safety and tolerability part. Dosing was 600mg bid with or without food. In the PK part, three single doses of ODM-201 were given over 3 weeks. In the extension part patients could continue treatment until disease progression or until an intolerable adverse event or condition that prevented further dosing of ODM-201. Results: Thirty men with metastatic chemotherapy-naive castration-resistant prostate cancer (CRPC) were enrolled, the median age was 68. The median prostate-specific antigen (PSA) was 18.2 ng/mL and testosterone 23.1 ng/dL at baseline. Food interaction was observed when ODM-201 formulations were administered after a high fat content breakfast compared to administratio...