6-oxo-6,7,8,9,10,11-hexahydrocyclohepta[c][1]benzopyran-3-yl sulfaMate

Irosustat (667 COUMATE) is a potent steroid sulfatase inhibitor, with an IC ₅₀ of 8 nM. Irosustat (667 COUMATE) inhibits steroid sulphatase (STS) activity in MCF-7 cells with an IC ₅₀ of 0.2 nM, but has no effect on the morphology or proliferation of MCF-7 cells at 10 μM.

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.