Abarelix Depot, a GnRH antagonist, v LHRH superagonists in prostate cancer: differential effects on follicle-stimulating hormone. Abarelix Depot study group.

Purpose: A Phase II clinical study contrasted the endocrinologic and biochemical efficacy of Abarelix Depot, a gonadotropin-releasing hormone (GnRH) antagonist, with luteinizing hormone releasing-hormone (LHRH) superagonists, with or without additional antiandrogens, in men with prostate cancer.

Methods: This study was open-label and treated 242 men. Abarelix Depot 100 mg was administered by intramuscular injection to 209 men, and LHRH, with or without an antiandrogen, was administered to 33 men according to the formulation used. Serum concentrations of follicle-stimulating hormone (FSH) and other hormones were measured at baseline and at specified time points for the first 85 days of the study. Median serum concentrations of FSH at baseline were similar for the two treatment groups.

Results: Men treated with LHRH superagonists, with or without an antiandrogen, had a surge in the serum concentration of FSH on day 2 before FSH concentrations started to decline. Men in the Abarelix Depot group had an immediate and sustained decrease in the serum concentration of FSH.

Conclusion: Recent data suggest that FSH may be an independent growth factor for prostate cancer. The Abarelix Depot-induced decreased in FSH may have a role in the treatment of men with endocrine- responsive disease or for those men whose disease has escaped from hormone sensitivity.