Histrelin: in advanced prostate cancer.

Histrelin is a gonadotropin-releasing hormone agonist available in a diffusion-controlled reservoir drug delivery system for subcutaneous implantation. The subcutaneous histrelin implant provided sustained suppression of serum testosterone, luteinizing hormone (LH) and prostate-specific antigen levels for up to 1 year in patients with advanced prostate cancer in two phase II or III trials. In the noncomparative, multicentre, phase III study, serum testosterone was suppressed to castrate levels (i.e. < or =50 ng/dL) within 4 weeks in all patients who received a histrelin acetate 50 mg implant, with 99-100% of histrelin implant recipients maintaining castrate levels for the remainder of the 1-year treatment period. Such efficacy was provided irrespective of patient age or stage of disease. Although a transient surge in serum testosterone levels occurred after placement of the initial histrelin implant, no acute elevations in testosterone or LH levels were observed in patients whose implant was replaced after 1 year of therapy and suppression of these hormones continued to be maintained. The histrelin implant was generally well tolerated in patients with advanced prostate cancer in the phase III trial and in a pooled analysis. No patients prematurely discontinued treatment because of adverse events, most of which were the consequence of hormone suppression.