Relugolix (INN) (developmental code name TAK-385) is a non-peptide, orally-active, selective antagonist of the gonadotropin-releasing hormone receptor (GnRHR) (IC50 = 0.12 nM) that is under development for clinical use by Takeda. It is currently in phase II clinical trials for the treatment of endometriosis, uterine leiomyoma, and prostate cancer.
A single oral administration of relugolix at a dose of 3 mg/kg has been found to suppress luteinizing hormone levels for more than 24 hours in castrated cynomolgus monkeys, indicating a long duration of action. The drug (80–160 mg/day) has been found to reduce testosterone levels to sustained castrate levels in men with once-daily chronic administration. Lower dosages (10–40 mg/day) are being studied in the treatment of endometriosis and uterine leiomyoma to achieve partial sex hormone suppression. The reasoning behind partial suppression for these conditions is to reduce the incidence and severity of menopausal symptoms such as hot flushes and to avoid bone mineral density changes caused by estrogen deficiency that can eventually lead to osteoporosis.