Structure-activity relationships of bisphenol A analogs at estrogen receptors (ERs): Discovery of an ERα-selective antagonist

Our multi-template approach for drug discovery, focusing on protein targets with similar fold structures, has yielded lead compounds for various targets. We have also shown that a diphenylmethane skeleton can serve as a surrogate for a steroid skeleton. Here, on the basis of those ideas, we hypothesized that the diphenylmethane derivative bisphenol A (BPA) would bind to the ligand-binding domain of estrogen receptors (ERs) in a similar manner to estradiol and act as a steroid surrogate. To test this idea, we synthesized a series of BPA analogs and evaluated their structure-activity relationships, focusing on agonistic/antagonistic activities at ERs and ER alpha/ER beta subtype selectivity. Among the compounds examined, 18 was found to be a potent ER alpha-antagonist with high selectivity over ER beta and androgen receptor under our assay conditions. A computational docking study suggested that 18 would bind to the antagonistic conformation of ER alpha. ER alpha-selective antagonists, such as 18, are candidate agents for treatment of breast cancer. (C) 2013 Elsevier Ltd. All rights reserved.