Non-steroidal and steroidal sulfamates: new drugs for cancer therapy

The development of inhibitors to block the formation of estrone and 5-androstenediol from sulfated precursors is an important new strategy for the treatment of breast cancer. In this study a series of tricyclic coumarin sulfamates (665-668 COUMATE) and a tricyclic oxepin sulfamate have been synthesised and tested for their ability to inhibit estrone sulfatase activity (E1-STS). In addition the effect of the steroid-based E1-STS inhibitor, 2-methoxyestrone-3-O-sulfamate (2-MeOEMATE) on the morphology of MDA-MB-231 cells and breast tumour-derived fibroblasts was also examined. The tricyclic coumarin sulfamates and oxepin sulfamate were potent inhibitors of E1-STS activity with IC(50)s ranging from 8 to 250 nM. Of this series 667 COUMATE was the most potent inhibitor (IC(50)=8 nM) and was three-times more potent than estrone-3-O-sulfamate (EMATE, IC(50)=25 nM). 667 COUMATE did not stimulate the growth of MCF-7 breast cancer cells and is therefore devoid of estrogenicity. In vivo, 667 COUMATE inhibited E1-STS activity in rat liver tissue to a similar extent to that of EMATE. 2-MeOEMATE had a marked effect on the morphology of MDA-MB-231 cells and breast tumour-derived fibroblasts causing a significant increase in the number of rounded cells. 667 COUMATE and 2-MeOEMATE therefore offer considerable potential for development for cancer therapy.