Relugolix

Relugolix, also known as TAK-385, is a luteinizing hormone-releasing hormone (LH-RH) receptor antagonist administered orally. By preventing LH-RH from binding with the LH-RH receptor in the anterior pituitary gland and suppressing the secretion of luteinizing hormone (LH) and follicle stimulation hormone (FSH) from the anterior pituitary gland, TAK-385 controls the effect of LH and FSH on the ovary, reduces the level of estrogen in blood, which is known to be associated with the development of endometriosis and uterine fibroids, and is expected to improve the symptoms of these disorders. (In Vitro) :Relugolix exhibits strong binding affinity (IC50=0.32 nM) for the monkey receptor comparable to that for the human receptor (IC50=0.33 nM) while displaying a 30000-fold decrease for the rat receptor (IC50=9800 nM) . The antagonistic in vitro activity of TAK-385 with respect to the human receptor (IC90=18 nM) exceeded that for the monkey receptor (IC90=1700 nM) by 95-fold in the presence of 40% serum. (In Vivo) :Relugolix (oral administration; 1-3 mg/kg; single dose for pharmacokinetic study) exhibits a good pharmacokinetic profile and obvious suppressive effects of circulating LH levels in monkeys at a dose of 1 mg/kg. The pharmacokinetic profile exhibits with 16.0 ng/mL, 2.7 h, and 90.1 ng for Cmax, Tmax, and AUCo, respectively in male cynomolgus monkeys.Relugolix (oral administration; 3, 10 or 30 mg/kg; twice daily; 4 weeks) significantly decreases the testis weight, and reduces the ventral prostate weight at 3 mg/kg and decreases it to castrate levels at 10 mg/kg in male hGNRHR-knock-in mice.Relugolix (oral administration; 30, 100 or 200 mg/kg; twice daily; 4 weeks) induces constant diestrous phases in all mice within the first week at 100 mg/kg, and significantly decreases the weights of ovaries and uteri at this dose after 4 weeks in female hGNRHR-knock-in mice.