Synthesis and evaluation of 11?-(4-substituted phenyl) estradiol analogs: transition from estrogen receptor agonists to antagonists.

ABSTRACT: As part of our program to develop estrogen receptor (ER) targeted imaging and therapeutic agents we chose to evaluate 11?-substituted estradiol analogs as a representative scaffold. Previous synthetic studies provided an entry into this class of compounds and other work indicated that 11?-(substituted aryl) estradiol analogs were potent antagonists of the ER. Little information existed about the specific structural features involved in the transition from agonism to antagonism for the 11?-aryl estradiol analogs or their potential as scaffolds for drug conjugation.We prepared and characterized a series of 11?-(4-Substituted phenyl) estradiol analogs using modifications of existing synthetic methods. The new compounds, as well as standard steroidal agonists and antagonists, were evaluated as competitive ligands for the ER?-LBD. Functional assays used the induction of alkaline phosphatase in Ishikawa cells to determine potency of the compounds as ER agonists or antagonists.The synthetic strategy successfully generated a series of compounds in which the 4-substituent was sequentially modified from hydroxyl to methoxy to azidoethoxy/N,N-dimethylaminoethoxy and eventually to a prototypical 1,4-naphthoquinone-containing moiety. The new compounds all retained high relative binding affinity (RBA) for the ER?-LBD, ranging from 13-83% that of estradiol. No subtype selectivity was observed. More importantly, the transition from agonist to antagonist activity occurs at the 4-methoxy stage where the compound is a mixed antagonist. More notably, antagonism appeared to be more dependent upon the size of the 11?-substituent than upon the nature of the terminal groupWe have developed a synthetic strategy that provides facile access to potent 11?-(4-substituted phenyl) estradiol analogs. The resultant compounds retain high affinity for the ER?-LBD and, more importantly, demonstrate potent antagonist activity in cells. Large functionalities distal to the 11?-phenyl ring had little additional effect on either affinity or efficacy, suggesting the incorporation of diverse imaging or biologically active groups can be attached without significantly compromising the ER-binding capacity. Future studies are in progress to exploit the 11?-aryl estradiol analogs as potential drug delivery systems and imaging agents.

SUBMITTER: Hanson RN 

PROVIDER: S-EPMC3581310 | biostudies-literature | 2012 Jun

REPOSITORIES: biostudies-literature