Efficacy of triptorelin pamoate 11.25 mg administered subcutaneously for achieving medical castration levels of testosterone in patients with locally advanced or metastatic prostate cancer

Objectives: Gonadotropin-releasing hormone agonists are widely used as androgen deprivation therapy in many men with locally advanced or metastatic prostate cancer. Gonadotropin-releasing hormone agonists are delivered by intramuscular injection every 1, 3 or 6 months, but in some patients subcutaneous injection may be more appropriate. This study assessed the efficacy and safety profile of the gonadotropin-releasing hormone agonist, triptorelin pamoate, when administered by the subcutaneous route. Methods: In this multicentre, open-label, single-arm study, androgen deprivation therapy-naïve men with locally advanced or metastatic prostate cancer received the gonadotropin-releasing hormone agonist triptorelin pamoate 11.25 mg (3-month formulation) by the subcutaneous route twice (at baseline and 13 weeks later). The co-primary efficacy endpoints were the proportion of patients with a castration level of serum testosterone (<50 ng/dl) after 4 weeks, and of these, those still castrated after 26 weeks. Results: Of the 126 treated patients, 123 [97.6%; 95% confidence interval (CI): 93.2–99.5)] were castrated 4 weeks after the first subcutaneous injection, and 115/119 patients (96.6%; 95% CI: 91.6–99.1) castrated at 4 weeks maintained castration at 26 weeks. Median prostate-specific antigen levels were reduced by 64.2 and 96.0% at 4 and 26 weeks, respectively. The probability of maintaining a testosterone level <20 ng/dl up to 26 weeks was 90.0% (95% CI: 85.0–95.0). The most frequently occurring treatment-related adverse events were typical of gonadotropin-releasing hormone agonist treatment (hot flushes, increased weight, erectile dysfunction and hyperhidrosis). Conclusions: This study demonstrates that triptorelin pamoate 11.25 mg administered by the subcutaneous route every 3 months is as efficacious and well tolerated as administration via the intramuscular route in men with locally advanced or metastatic prostate cancer