The efficacy and safety of degarelix, a GnRH antagonist: a 12-month, multicentre, randomized, maintenance dose-finding phase II study in Japanese patients with prostate cancer.

Objective: To assess the efficacy and safety of degarelix, a new gonadotropin-releasing hormone antagonist, for achieving and maintaining serum testosterone suppression (≤0.5 ng/ml) during the 12-month treatment of Japanese patients with prostate cancer.

Methods: This Phase II study was conducted as a multicentre, randomized, parallel-group, open-label study. A total of 273 patients with adenocarcinoma of the prostate (any stage) were treated. Degarelix was administered subcutaneously at an initial dose of 240 mg followed by monthly maintenance doses of either 80 or 160 mg for a total of 12 doses. The treatment continued for 12 months.

Results: Dose regimens of 240/80 and 240/160 mg maintained castrate levels of testosterone in 94.5 and 95.2% of the patients, respectively. After 3 days, 99.3 and 98.5% of the patients, respectively, reached these levels without a testosterone surge. Prostate-specific antigen levels decreased rapidly following degarelix administration and remained low throughout the study. Best overall response rates according to RECIST were 71.4 (20/28) and 72.7% (16/22), respectively. Eighteen patients (6.6%) withdrew from the study due to adverse events. The most common adverse events were injection site reactions; other adverse events included hot flush, nasopharyngitis, weight increase and pyrexia.

Conclusions: Both monthly degarelix dosing regimens were found to be effective in testosterone suppression without a testosterone surge, prostate-specific antigen reductions and anti-tumour effect in Japanese patients with prostate cancer, as was shown in the overseas Phase III study. Degarelix was also well tolerated.