Relugolix is a gonadotropin-releasing hormone (GnRH) receptor antagonist being developed and tested by Myovant Sciences. An oral once-daily drug, it is intended to treat endometriosis, as well as for uterine fibroids and hormone-sensitive prostate cancer (HSPC).

By inhibiting GnRH receptors in the anterior pituitary gland, the major organ of the hormonal system in the brain, relugolix rapidly reduces circulating gonadotropins (so-called because they stimulate the gonads, or testes and ovaries) — with the two main gonadotropins being luteinizing hormone (LH), and follicle-stimulating hormone (FSH). Such inhibition leads to the suppression of estrogen in women and testosterone in men. The drug has been seen to improve the symptoms of uterine fibroids and endometriosis in women, and decreases prostate-specific antigen (PSA) levels in men with advanced prostate cancer.

According to Myovant, clinical testing, supported by a preclinical development program, indicates that Relugolix could be an important advancement in treatment options for women with endometriosis and uterine fibroids and an alternative to injectable therapies for men with HSPC.

Relugolix research

In a research article published in the European Journal of Pharmacology in 2014, researchers reported that Relugolix may prove to be a useful therapy for hormone-dependent diseases like endometriosis, uterine fibroids, and prostate cancer.

In a double-blind, placebo-controlled Phase 2 clinical trial in 487 patients with endometriosis (NCT01458301), women who received Relugolix experienced statistically significant reductions in non-menstrual and menstrual pelvic pain. The multicenter study evaluated the safety of Relugolix at three doses (10 mg, 20 mg, and 40 mg) administered orally once daily for 12 weeks. Efficacy was exploratory and was assessed using leuprorelin as a drug comparator. The primary endpoint was the reduction of pelvic pain as measured by the Visual Analogue Scale.

An extension study (NCT01452685) looked at the long-term safety and efficacy of Relugolix, again at three doses (10 mg, 20 mg, and 40 mg) administered orally each day for 24 weeks in 397 women with endometriosis-associated pain who had participated in the preceding 12-week study. Its primary endpoint was safety, including assessment of change in bone mineral density using dual energy X-ray absorptiometry. Results showed that treatment with Relugolix for 24 weeks was generally well tolerated and demonstrated pelvic pain reduction similar to leuprorelin. Relugolix also demonstrated similar benefits to injectable leuprorelin in this Phase 2 study.

The 12-week findings from the Phase 2 trial were presented at the 13th World Congress on Endometriosis (WCE), in Vancouver, Canada, while the 24-week data from the extension study were presented at the 19th European Congress of Endocrinology (ECE), in Lisbon, Portugal.

The drug was also evaluated in a double-blind, placebo-controlled Phase 2 clinical trial in 216 women with uterine fibroids (NCT01452659), with results showing that the treatment led to a reduction in menorrhagia, or heavy menstrual bleeding.

In two randomized Phase 2 studies in men with advanced prostate cancer (NCT02135445 and NCT02083185), Relugolix suppressed serum testosterone to castrate levels and decreased PSA.

Across all Phase 2 studies, the company reported that Relugolix was generally well-tolerated and its safety profile was consistent with its mechanism of action.

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