Histrelin

Histrelin is a synthetic nonapeptide analog of gonadotropin-releasing hormone (GnRH) that incorporates a D-histidine(benzyl) substitution at position 6, making it approximately 100-200 times more potent than native GnRH. What distinguishes histrelin from other GnRH agonists is its unique drug delivery system — a small subcutaneous implant that provides continuous, consistent drug release for a full 12 months, requiring only annual replacement.

The histrelin implant (approximately 3 cm long) is placed subcutaneously in the inner aspect of the upper arm during a minor outpatient procedure under local anesthesia. It contains 50 mg of histrelin acetate embedded in a hydrogel polymer matrix that controls the rate of drug release. This technology ensures stable plasma drug levels, eliminating the peaks and troughs associated with intermittent injection formulations and providing reliable hormone suppression throughout the year.

Histrelin is marketed as Vantas for the palliative treatment of advanced prostate cancer and as Supprelin LA for the treatment of central precocious puberty (CPP) in children. The 12-month implant offers significant advantages in terms of compliance, particularly valuable in the pediatric CPP population where consistent suppression is essential and in prostate cancer patients where any interruption in androgen suppression could be clinically detrimental.

Clinical studies have demonstrated that the histrelin implant achieves testosterone suppression to castrate levels within 4 weeks in prostate cancer patients and maintains this suppression for at least 12 months. In CPP, the implant provides effective suppression of pubertal progression with documented preservation of growth potential. Studies have shown the implant may remain effective beyond 12 months, with some evidence supporting up to 24 months of efficacy, though annual replacement remains the standard recommendation.