Irosustat

Irosustat, also known as STX64, BN83495 and 667 coumate, is a potent, irreversible inhibitor of steroid sulfatase. Inhibition of steroid sulfatase (STS), the enzyme responsible for the hydrolysis of steroid sulfates, represents a potential novel treatment for postmenopausal women with hormone-dependent breast cancer. Estrone and DHEA are formed by this sulfatase pathway and can be converted to steroids (estradiol and androstenediol, respectively), which have potent estrogenic properties. STX64 (667 coumate) is a potent tricylic coumarin-based sulfamate that irreversibly inhibits STS activity (IC50 = 8 nM in a placental microsomal assay system) . Estrone sulfamate (EMATE) is also a potent STS inhibitor, but has estrogenic activity. (In Vitro) :Irosustat (667 COUMATE) is a potent steroid sulfatase inhibitor, with an IC50 of 8 nM. Irosustat (667 COUMATE) inhibits steroid sulphatase (STS) activity in MCF-7 cells with an IC50 of 0.2 nM, but has no effect on the morphology or proliferation of MCF-7 cells at 10 μM. (In Vivo) :Irosustat potently inhibits rat liver, with inhibition of >90% when at a 1 mg/kg concentration. Irosustat (2 mg/kg, p.o. for 5 d) blocks the uterine growth stimulated by oestrone sulfate (E1S) in ovariectomized rats. In addition, Irosustat (2, 10 mg/kg, p.o.) plus E1S dose-dependently decreases the growth of NMU-induced mammary tumors in ovariectomized rats. Irosustat (667 COUMATE; 10 mg/kg, p.o.) shows 97.9 ± 0.06% inhibition on steroid sulphatase (STS) activity in rat liver.