Alarelin

Alarelin is a synthetic nine-amino-acid GnRH (gonadotropin-releasing hormone) agonist developed and approved in China for controlled ovarian hyperstimulation in assisted reproductive technology (ART). It is several times more potent than native GnRH and is used to trigger ovulation in IVF and other ART protocols. It is not approved in the US or EU but is widely used in Chinese reproductive medicine.

Alarelin binds with high affinity to GnRH receptors (GnRHR) in pituitary gonadotroph cells, initially stimulating a surge release of luteinizing hormone (LH) and follicle-stimulating hormone (FSH). In acute use, this LH surge triggers final oocyte maturation and ovulation, making it useful as a trigger shot in antagonist IVF cycles. Chronic administration, like other GnRH agonists, leads to GnRHR downregulation and pituitary desensitization, resulting in hypogonadal suppression. Alarelin's biological activity in gonadotropin secretion stimulation is described as many times greater than native GnRH in both in vivo and in vitro rat pituitary models. The D-amino acid substitution in its structure (similar to other GnRH agonists) confers resistance to enzymatic degradation and prolonged receptor binding.

Alarelin has been studied extensively in Chinese clinical trials for ART applications including IVF, controlled ovarian hyperstimulation (COH), and intrauterine insemination (IUI). Chinese studies demonstrate equivalent or superior oocyte retrieval rates versus hCG triggers, with potentially lower risk of ovarian hyperstimulation syndrome (OHSS) in certain protocols. Animal studies in sheep demonstrate enhanced follicular development and modulation of gonadotropin receptor expression. The research base is primarily Chinese-language publications; limited English peer-reviewed data is available. Active immunization studies with alarelin in sheep show durable suppression of reproductive function.

Peptides commonly paired with Alarelin for synergistic effects.