An orally bioavailable tricyclic coumarin-based sulfamate with potential antineoplastic activity. Steroid sulfatase inhibitor BN 83495 selectively binds to and inhibits steroid sulfatase (STS), which may inhibit the production of locally active estrogens and so inhibit estrogen-dependent cell growth in tumor cells, such as those of the breast, ovary, and endometrium. STS is a cytoplasmic enzyme responsible for the conversion of circulating inactive estrone sulfate and estradiol sulfate to biologically active unconjugated estrone and estradiol, respectively.