Efficacy and safety of a 3-month dosing regimen of degarelix in Japanese patients with prostate cancer: a phase II maintenance-dose-finding study

Objective: To evaluate the efficacy and safety of degarelix 3-month depot in Japanese patients with prostate cancer. Methods: In this Phase II, open-label, parallel-group study, 155 Japanese prostate cancer patients were randomized to treatment with degarelix administered subcutaneously at a maintenance dose of 360 or 480 mg every 84 days for 12 months, after receiving an initial dose of 240 mg. The primary endpoint was the cumulative probability of serum testosterone ≤0.5 ng/ml (Days 28-364). Secondary endpoints included percent change in serum prostate-specific antigen level and proportion of patients with prostate-specific antigen failure at Day 364. For safety, adverse events were evaluated. Results: The cumulative probability of serum testosterone ≤0.5 ng/ml (Days 28-364) was 88.3% (95% confidence interval: 77.9-94.0%) and 97.2% (95% confidence interval: 89.4-99.3%) in the 360 and 480 mg groups, respectively. The median percent change in serum prostate-specific antigen level from baseline to Day 364 was -95.05% and -96.43% in the 360 and 480 mg groups, respectively; the proportion of patients with prostate-specific antigen failure was 2.7% and 1.3%. The most frequent adverse event was injection site reaction; however, this did not cause any patient to discontinue treatment. Conclusions: The 3-month dosing regimen of degarelix 360/480 mg was effective and well tolerated for treatment of Japanese prostate cancer patients. The 480 mg group showed a higher cumulative castration rate than the 360 mg group; thus, 480 mg was considered to be the optimal clinical dosage for future Phase III trials.