De novo design, synthesis, and evaluation of novel nonsteroidal phenanthrene ligands for the estrogen receptor.

Although there are many estrogen receptor antagonists with improved tissue selectivity profiles compared with tamoxifen, optimal tissue selectivity has not yet been demonstrated. As such there is still a need for additional diversity and new chemical scaffolds to allow for exploration of improved tissue selectivity. Here, we describe the discovery of a novel phenanthrene scaffold for estrogen receptor ligands utilizing a ligand based de novo design approach. The nanomolar binding of phenanthrenes, 12b,c, 14b,c, and 15 against human recombinant ER(alpha) indicates that our ligand based de novo design approach was successful. From a gene transfection assay, 12b,c, 14b,c, and 15 displayed only antagonistic activity with no observable agonistic activity. The alkyl 9,10-dihydrophenanthrene 16 (presumably a racemic mixture) was a substantially more potent ER binder than the phenanthrenes. It also displayed only antagonistic activity and was effective at inhibiting estradiol stimulated MCF-7 cell proliferation. These results demonstrate that this phenanthrene (and 9,10-dihydrophenanthrene) scaffold warrants further study as potential selective estrogen receptor modulators and/or pure antiestrogens.