Leuprolide acetate 22.5 mg 12-week depot formulation in the treatment of patients with advanced prostate cancer

Two open-label, multicenter studies were conducted to evaluate the efficacy and safety of a long-acting depot formulation of leuprolide acetate (22.5 mg) administered intramuscularly every 12 weeks to patients with stage D2 prostate cancer. Clinical evaluations were performed every 12 weeks, and serum testosterone levels were monitored biweekly or weekly for 24 weeks. Onset of castrate levels (less than or equal to 50 ng/dL) of testosterone was achieved within 30 days of the initial depot injection in 87 (95%) of the 92 assessable patients enrolled in the two studies. Mean testosterone levels remained well within the castrate range throughout each dosing interval. Two patients experienced a transient escape (testosterone levels >50 ng/dL on two consecutive determinations). Delay of an injection of up to 2 weeks did not have an effect on testosterone suppression: in 16 patients in whom the depot injection was delayed by 3 to 14 days, testosterone values remained within the castrate range. A favorable objective tumor response (no progression) to treatment occurred in 85% of the patients. Prostate-specific antigen and prostatic acid phosphatase decreased by 50% or more in 96% and 84% of patients, respectively, with elevated pretreatment values and at least one treatment value. Assessment of local disease status and overall performance status showed improvement or stability in most patients. The most common adverse events were hot flashes (59%), pain (27%), and testicular atrophy (21%). The 22.5-mg depot formulation of leuprolide, which acts in a manner similar to the monthly 7.5-mg depot formulation, was shown to be effective and safe in treating patients with advanced prostate cancer.