Efficacy and safety of leuprolide acetate 6-month depot for suppression of testosterone in patients with prostate cancer.

Background: This open-label study evaluated the efficacy and safety of a new leuprolide acetate 45 mg 6-month depot formulation in 151 men with prostate cancer who received 2 intramuscular injections administered 24 weeks apart.

Methods: The primary efficacy measurement was the proportion of patients achieving suppression of serum testosterone to ≤ 50 ng dl(-1) from week 4 through week 48. Adverse events (AEs) and hormonal and safety laboratory values were monitored.

Results: The primary efficacy end point was achieved in 93.4% of subjects (95% confidence interval (89.2%, 97.6%)). There were nine escapes from testosterone suppression during the study, none of which were accompanied by a rise in PSA. By week 4, mean testosterone concentration was suppressed below castrate levels to 15.9 ng dl(-1); suppression was maintained for the entire 24-week duration of each depot injection. No mean increase in testosterone was observed after the second injection. Mean PSA levels were maintained below 3 ng ml(-1) from week 14 through the 48-week treatment period. The most frequent AE was flushing (58.3%). Injection site reactions were reported in 24.5% of patients.

Conclusions: Leuprolide acetate 45 mg 6-month depot demonstrated rapid and sustained testosterone suppression through 12 months and was well tolerated. This 6-month leuprolide acetate depot will decrease the number of annual injections in the treatment of prostate cancer.