Histrelin acetate, sold under many brand name like Vantas, Supprelin LA and others, is a nonapeptide analog of gonadotropin-releasing hormone (GnRH) with more potency than other available GnRH agonist analogues such as leuprolide acetate and goserelin acetate for the treatment of prostate cancer. Histrelin acetate only has small differences in two-dimensional structures when compared with leuprolide acetate and goserelin acetate. However, the three-dimensional structures are markedly different due to sequence alterations, which affect the binding of these agents to the GnRH receptor and hence results in different potency.
It is well recognized that testosterone, which is produced by the hypothalamic-pituitary-gonadal axis, plays an essential role in the growth and perpetuation of prostate tumor cells. Therefore the treatment goal of prostate cancer is often to reduce testosterone to the level of castration. The pharmacologic action of histrelin acetate is to bring about the suppression of testosterone. In the initial treatment, histrelin acetate induces a transient rise of follicle-stimulating hormone (FSH) and luteinizing hormone (LH) in serum by stimulating pituitary GnRH receptors and then LH causes an unabiding surge of testosterone in turn, which occurs within 2-3 days and lasts for about 7 days in general. However, chronic treatment leads to desensitization and down-regulation of GnRH receptors and a suppression of LH, FSH, and testosterone later.
Histrelin acetate, one of the most popular GnRH agonist analogues owing to its more potency than others, has been developed as an effective drug for the treatment of prostate cancer. Meanwhile histrelin acetate is available in treating hormone-sensitive cancer of uterine fibroids in women. In addition, histrelin acetate is also proved to be very effective in the treatment of central precocious puberty in children. The basic mechanism of action is that histrelin acetate suppresses the secretion of gonadotrope.
Pharmacokinetics and metabolism
Different from other available GnRH agonist analogues which are injected into the body, histrelin acetate is inserted subcutaneously in the inner aspect of the upper arm under local anesthesia using the custom-built hydrogel delivery system, which provides a more constant rate about 50 μg/day of histrelin acetate release over 1 year. A single metabolite of histrelin acetate, which roots in C-terminal dealkylation of histrelin acetate, has been confirmed in human hepatocytes.
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