How it Works
Relugolix is an oral, once-daily, gonadotropin-releasing hormone (GnRH) receptor antagonist. By inhibiting GnRH receptors in the anterior pituitary gland, relugolix rapidly reduces the circulating gonadotropins luteinizing hormone (LH) and follicle-stimulating hormone (FSH), leading to the suppression of estrogen in women and testosterone in men. Suppression of these hormones improves the symptoms of uterine fibroids and endometriosis in women and decreases prostate-specific antigen (PSA) levels in men with advanced prostate cancer.
In a double-blind, placebo-controlled Phase 2 clinical trial in 216 patients with uterine fibroids, women who received relugolix experienced a statistically significant reduction in menorrhagia, or heavy menstrual bleeding. In a double-blind, placebo-controlled Phase 2 clinical trial in 487 patients with endometriosis, women who received relugolix experienced statistically significant reductions in non-menstrual and menstrual pelvic pain. In two randomized Phase 2 studies in approximately 228 men with advanced prostate cancer, oral once-daily relugolix suppressed serum testosterone to castrate levels and decreased PSA. Across all phase 2 studies, relugolix was generally well-tolerated and its safety profile was consistent with its mechanism of action. Takeda is currently conducting two Phase 3 studies in women with uterine fibroids in Japan.
Unlike GnRH agonists, relugolix does not cause transient increases in gonadotropin secretion (flare), which can result in an initial worsening of clinical symptoms. Moreover, upon treatment discontinuation, its effects diminish quickly and hormone levels rapidly return to baseline. We believe relugolix, when co-administered with low-dose estrogen and progesterone add-back therapy, will preserve bone mineral density in women and increase tolerability.