Phase I trial of TAK-385 in hormone treatment-naïve Japanese patients with nonmetastatic prostate cancer.

This open-label, phase I dose-finding study evaluated the gonadotropin-releasing hormone antagonist, TAK-385, in Japanese patients with nonmetastatic prostate cancer. In a two-part design, patients received daily oral TAK-385 at doses of 320 (loading, day 1)/80 (maintenance, day 2 and thereafter), 320/120, 320/160, or 360/120 mg for 28 days in a dose-escalation phase (part A, n = 13), and at 320/80 or 320/120 mg for up to 96 weeks in a randomized expansion phase (part B, n = 30). Primary endpoint in both parts was safety, including dose-limiting toxicity in part A. Secondary endpoints included pharmacokinetics, pharmacodynamics, and prostate-specific antigen concentration. Ten (77%) patients in part A and all patients in part B experienced an adverse event; hot flush (part A, n = 4; part B, n = 15), viral upper respiratory tract infection (part A, n = 1; part B, n = 10), and diarrhea (part B, n = 8) were most frequent. No dose-limiting toxicities were observed (part A). In 12 evaluable patients (part A), TAK-385 was rapidly absorbed after a single loading dose; on day 28 (maintenance dose), median steady-state Tmax was ~1-2 hours and mean t1/2z was 67-79 hours. All doses rapidly reduced testosterone concentrations to castration levels within 1 week. Durable reductions in prostate-specific antigen of >90% from baseline were observed through 96 weeks. TAK-385 appeared tolerable and resulted in sustained reductions in testosterone to castration levels at all doses. The lowest loading/maintenance dose required for a clinical effect was 320/80 mg. ClinicalTrials.gov: NCT02141659.