ABSTRACT
New diphenolic azoles as highly selective estrogen receptor-beta agonists are reported. The more potent and selective analogues of these series have comparable binding affinities for ERbeta as the natural ligand 17beta-estradiol but are >100-fold selective over ERalpha. Our design strategy not only followed a traditional SAR approach but also was supported by X-ray structures of ERbeta cocrystallized with various ligands as well as molecular modeling studies. These strategies enabled us to take advantage of a single conservative residue substitution in the ligand-binding pocket, ERalpha Met(421) --> ERbeta Ile(373), to optimize ERbeta selectivity. The 7-position-substituted benzoxazoles (Table 5) were the most selective ligands of both azole series, with ERB-041 (117) being >200-fold selective for ERbeta. The majority of ERbeta selective agonists tested that were at least approximately 50-fold selective displayed a consistent in vivo profile: they were inactive in several models of classic estrogen action (uterotrophic, osteopenia, and vasomotor instability models) and yet were active in the HLA-B27 transgenic rat model of inflammatory bowel disease. These data suggest that ERbeta-selective agonists are devoid of classic estrogenic effects and may offer a novel therapy to treat certain inflammatory conditions.
Subject(s)
Isoxazoles/chemical synthesis , Phenols/chemical synthesis , Receptors, Estrogen/agonists , Androgen Antagonists/chemical synthesis , Androgen Antagonists/chemistry , Androgen Antagonists/pharmacology , Animals , Animals, Genetically Modified , Anti-Inflammatory Agents, Non-Steroidal/chemical synthesis , Anti-Inflammatory Agents, Non-Steroidal/chemistry , Anti-Inflammatory Agents, Non-Steroidal/pharmacology , Binding Sites , Body Temperature/drug effects , Bone Diseases, Metabolic/prevention & control , Cell Line, Tumor , Crystallography, X-Ray , Drug Design , Estrogen Receptor beta , Female , HLA-B27 Antigen/genetics , Humans , Isoxazoles/chemistry , Isoxazoles/pharmacology , Male , Mice , Models, Molecular , Organ Size/drug effects , Phenols/chemistry , Phenols/pharmacology , Prostate/anatomy & histology , Prostate/drug effects , Radioligand Assay , Rats , Rats, Sprague-Dawley , Receptors, Estrogen/chemistry , Structure-Activity Relationship , Transcription, Genetic/drug effects , Uterus/anatomy & histology , Uterus/drug effectsABSTRACT
A series of 2-(4-hydroxy-phenyl)-benzofuran-5-ols with relatively lipophilic groups in the 7-position of the benzofuran was prepared and the affinity and selectivity for ER beta was measured. Many of the analogues were found to be potent and selective ER beta ligands. Additional modifications at the benzofuran 4-position as well as at the 3'-position of the 2-phenyl group were found to further increase selectivity. Such modifications led to compounds with <10 nM potency and >100-fold selectivity for ER beta.
Subject(s)
Benzofurans/chemical synthesis , Estrogen Receptor beta/agonists , Benzofurans/metabolism , Cell Line, Tumor , Estrogen Receptor beta/chemistry , Estrogen Receptor beta/metabolism , Humans , Insulin-Like Growth Factor Binding Protein 4/genetics , Ligands , RNA, Messenger/analysis , Structure-Activity RelationshipABSTRACT
A new series of ERbeta (ERbeta) selective ligands has been prepared. One of the compounds 6, structurally related to the phytoestrogen apigenin 4, displays a binding preference for ERbeta over ERalpha of over 40-fold. In addition to its binding selectivity, 6 was able to potently induce metallothionein (an ERbeta specific response in human SAOS-2 cells) while demonstrating low potency in an ERalpha dependant ERE-tk luciferase assay in MCF-7 cells. Such receptor and cell selectivity could make 6 a useful molecular probe for better understanding the role of ERbeta in mammalian physiology.
