Buserelin

Buserelin is a synthetic nonapeptide analog of gonadotropin-releasing hormone (GnRH), incorporating a D-serine(tBu) substitution at position 6 and an ethylamide modification at the C-terminus. These modifications increase its potency to approximately 20-50 times that of native GnRH and enhance its resistance to enzymatic degradation. Developed by Hoechst (now Sanofi), buserelin has been used clinically since the early 1980s and is one of the longest-established GnRH agonists in medical practice.

Buserelin is available in multiple formulations including subcutaneous injection, intranasal spray, and depot implant preparations. This versatility in administration routes has contributed to its widespread adoption in clinical practice, particularly in Europe, Canada, and the United Kingdom, where it is more commonly prescribed than in the United States (where leuprolide and goserelin dominate the market).

In oncology, buserelin is used for the treatment of hormone-sensitive advanced prostate cancer, achieving and maintaining castrate levels of testosterone. In gynecology, it is employed in the management of endometriosis, uterine fibroids, and as a key component of IVF protocols for pituitary downregulation. The drug is particularly popular in European IVF clinics, where both the intranasal and subcutaneous formulations are used in long and short stimulation protocols.

Buserelin's role in assisted reproduction extends to its use in triggering final oocyte maturation when used as a single dose in GnRH antagonist IVF protocols. This application, known as the "GnRH agonist trigger," reduces the risk of ovarian hyperstimulation syndrome (OHSS) compared to traditional hCG triggers, making it especially valuable in high-responder patients.