A clinical study of 22.5 mg. La-2550: A new subcutaneous depot delivery system for leuprolide acetate for the treatment of prostate cancer.

Purpose: The safety, efficacy and pharmacokinetics of a unique 3-month subcutaneous depot of leuprolide acetate were investigated in patients with prostate cancer.

Materials And Methods: This open label, noncomparative, 6-month multicenter study enrolled 117 patients diagnosed with adenocarcinoma of the prostate. LA-2550 (22.5 mg. depot) (Atrix Laboratories, Fort Collins, Colorado) was administered subcutaneously once every 3 months. The primary efficacy parameter was serum testosterone 50 ng./dl. or less. Pharmacokinetics were analyzed in a subset of 22 patients.

Results: Of the 117 enrolled patients 111 (98%) completed the 6-month study. Five patients withdrew for nontreatment related events and 1 was withdrawn because he received less than a full dose of the study drug. By day 28, 98% of patients had serum testosterone 50 ng./dl. or less and 84% had achieved 20 ng./dl. or less. By day 35 all patients had 50 ng./dl. or less testosterone. A patient with a breakthrough response after testosterone suppression on day 49 (112 ng./dl.) regained suppression (27 ng./dl.) 14 days after the second injection (day 98). At study completion all patients had 50 ng./dl. or less testosterone (mean plus or minus standard error of mean 10.1 +/- 0.07) and 104 of the 111 (94%) had 20 ng./dl. or less. From baseline to month 6 mean luteinizing hormone decreased from 9.2 +/- 1.1 to 0.08 +/- 0.01 mIU/ml. and mean prostate specific antigen decreased more than 98%. No flare reactions were observed and patient assessments of bone pain and urinary symptoms were unchanged. The most common treatment related adverse event was hot flashes, which were mild in 57% of cases, moderate in 12% and severe in 0%.

Conclusions: LA-2550 (22.5 mg. depot) produced and maintained safe and effective suppression of serum testosterone to well below the medical castrate level of 50 ng./dl. or less.