Objectives: The investigational objectives of this open, noncomparative phase I study were to determine the pharmacokinetic profile of a single dose of 11.25 mg leuprorelin acetate, the effective duration of the chemical castration (serum testosterone < or = 1.73 nmol/l) and safety in patients with locally advanced and/or metastatic carcinoma of the prostate foreseen for chemical castration, in the hope that such a dose of leuprorelin acetate may be suitable as a depot formulation to be administered 3-monthly to these patients.
Methods: A total of 24 males up to 85 years old with histologically proven advanced carcinoma of the prostate were enrolled in the study to obtain 18 eligible patients. Each patient was given 11.25 mg of leuprorelin acetate in a depot formulation subcutaneously after reconstitution in 2 ml of a special suspension vehicle. The study period lasted 24 weeks. Patients whose serum testosterone levels reincreased prior to the end of the observation period of 24 weeks were withdrawn from the study and received the monthly depot formulation of 3.75 mg of leuprorelin acetate.
Results: The 3M-depot formulation of leuprorelin acetate ensured continuous and constant drug release and effective suppression of testosterone serum levels to castration range for at least 13 weeks. After an initial rise, 5 alpha-dihydrotestosterone as well as the gonadotropin serum levels of luteinizing hormone and follicular stimulating hormone reflected the testosterone serum pattern.
Conclusion: The results of this study show that the 3M-depot preparation of leuprorelin acetate is effective in suppressing the serum testosterone levels to the castration range for a targeted period of at least 13 weeks.