A study to investigate which of two different tablet formulations of ODM-201 is best suited for use in the further development of the compound in the treatment of metastatic chemotherapy-naive castration-resistant prostate cancer. Patients successfully completing the bioavailability study will be able to receive further treatment with the current capsule formulation of ODM-201 until progression of their disease with the safety and tolerability of ODM-201 being assessed throughout.

Inclusion Criteria:

• Written informed consent (IC) obtained.
• Histologically confirmed adenocarcinoma of prostate
• Progressive metastatic disease
• Ongoing androgen deprivation therapy with a luteinising hormone-releasing hormone (LHRH) analogue or antagonist or bilateral orchiectomy
• Adequate bone marrow, hepatic and renal function
• Able to swallow the ODM-201 whole as a capsule or tablet.

Exclusion Criteria:

• Previous chemotherapy for prostate cancer.
• Known metastases in the brain.
• History of other malignancy within the previous 5 years, except a basal cell carcinoma of skin.
• Known gastrointestinal condition that can significantly affect the absorption of the study treatment.