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4-{[(4-Cyanophenyl)(4H-1,2,4-triazol-4-yl)amino]methyl}phenyl sulfamate and its ortho-halogenated (F, Cl, Br) derivatives are first-generation dual aromatase and sulfatase inhibitors (DASIs). Structure-activity relationship studies were performed on these compounds, and various modifications were made to their structures involving relocation of the halogen atom, introduction of more halogen atoms, replacement of the halogen with another group, replacement of the methylene linker with a difluoromethylene linker, replacement of the para-cyanophenyl ring with other ring structures, and replacement of the triazolyl group with an imidazolyl group. The most potent in vitro DASI discovered is an imidazole derivative with IC50 values against aromatase and steroid sulfatase in a JEG-3 cell preparation of 0.2 and 2.5 nM, respectively. The parent phenol of this compound inhibits aromatase with an IC50 value of 0.028 nM in the same assay., (Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

4-(((4-Cyanophenyl)(4H-1,2,4-triazol-4-yl)amino)methyl)phenyl sulfamate (6 a) was the first dual aromatase-sulfatase inhibitor (DASI) reported. Several series of its derivatives with various linker systems between the steroid sulfatase (STS) and the aromatase inhibitory pharmacophores were synthesised and evaluated in JEG-3 cells. The X-ray crystal structures of the aromatase inhibitors, DASI precursors 42 d and 60, and DASI 43 h were determined. Nearly all derivatives show improved in vitro aromatase inhibition over 6 a but decreased STS inhibition. The best aromatase inhibitor is 42 e (IC(50)=0.26 nM) and the best DASI is 43 e (IC(50 aromatase)=0.45 nM, IC(50 STS)=1200 nM). SAR for aromatase inhibition shows that compounds containing an alkylene- and thioether-based linker system are more potent than those that are ether-, sulfone-, or sulfonamide-based, and that the length of the linker has a limited effect on aromatase inhibition beyond two methylene units. Compounds 43 d-f were studied in vivo (10 mg kg(-1), single, p.o.). The most potent DASI is 43 e, which inhibited PMSG-induced plasma estradiol levels by 92 % and liver STS activity by 98 % 3 h after dosing. These results further strengthen the concept of designing and developing DASIs for potential treatment of hormone-related cancers.

By introducting the steroid sulfatase inhibitory pharmacophore into aromatase inhibitor 1 (YM511), two series of single agent dual aromatase-sulfatase inhibitors (DASIs) were generated. The best DASIs in vitro (JEG-3 cells) are 5, (IC50(aromatase) = 0.82 nM; IC50(sulfatase) = 39 nM), and 14, (IC50(aromatase) = 0.77 nM; IC50(sulfatase) = 590 nM). X-ray crystallography of 5, and docking studies of selected compounds into an aromatase homology model and the steroid sulfatase crystal structure are presented. Both 5 and 14 inhibit aromatase and sulfatase in PMSG pretreated adult female Wistar rats potently 3 h after a single oral 10 mg/kg dose. Almost complete dual inhibition is observed for 5 but the levels were reduced to 85% (aromatase) and 72% (sulfatase) after 24 h. DASI 5 did not inhibit aldosterone synthesis. The development of a potent and selective DASI should allow the therapeutic potential of dual aromatase-sulfatase inhibition in hormone-dependent breast cancer to be assessed.