A phase 1 multiple-dose study of orteronel in Japanese patients with castration-resistant prostate cancer

Orteronel (TAK-700) is a non-steroidal, selective, reversible inhibitor of 17,20-lyase. We evaluated the safety, tolerability, pharmacokinetics, pharmacodynamics, and antitumor effect of orteronel with or without prednisolone in Japanese patients with castration-resistant prostate cancer (CRPC).

We conducted a phase 1 study in men with progressive and chemotherapy-naïve CRPC. Patients received orteronel orally at doses of 200-400 mg twice daily (BID) with or without oral prednisolone (5 mg BID). Dose-limiting toxicity (DLT) was assessed during Cycle 1 (28 days). Patients could continue study treatment until any of criteria for treatment discontinuation were met. Gonadotropin-releasing hormone therapy was continued in patients without prior orchidectomy.

Fifteen patients were enrolled and administered at least one dose of orteronel. No DLTs were reported during Cycle 1 in this study. Adverse events (AEs) were reported in all 15 patients. Most common AEs (>30%) were hyperlipasemia (47%), hyperamylasemia (40%), and constipation (33%). Acute pancreatitis (Grades 2 and 3) and pancreatitis (Grade 1) were complicated in three patients during the study. Dose-dependent increase in plasma orteronel concentrations was indicated over the 200-400 mg BID dose range. Prednisolone coadministered did not alter PK of orteronel. Serum testosterone was rapidly suppressed below the lower limit of quantification across all doses. Of 15 subjects, 13 achieved at least a 50% reduction from baseline in prostate-specific antigen.

Orteronel at doses up to 400 mg BID was tolerable in Japanese CRPC patients. The present results support further evaluation of orteronel with or without prednisolone.