Discovery of a potent and selective ROMK inhibitor with improved pharmacokinetic properties based on an octahydropyrazino[2,1-c][1,4]oxazine scaffold.

Following the discovery of small molecule acyl piperazine ROMK inhibitors, the acyl octahydropyrazino[2,1-c][1,4]oxazine series was identified. This series displays improved ROMK/hERG selectivity, and as a consequence, the resulting ROMK inhibitors do not evoke QTc prolongation in an in vivo cardiovascular dog model. Further efforts in this series led to the discovery of analogs with improved pharmacokinetic profiles. This new series also retained comparable ROMK potency compared to earlier leads.

Discovery of a novel sub-class of ROMK channel inhibitors typified by 5-(2-(4-(2-(4-(1H-Tetrazol-1-yl)phenyl)acetyl)piperazin-1-yl)ethyl)isobenzofuran-1(3H)-one.

A sub-class of distinct small molecule ROMK inhibitors were developed from the original lead 1. Medicinal chemistry endeavors led to novel ROMK inhibitors with good ROMK functional potency and improved hERG selectivity. Two of the described ROMK inhibitors were characterized for the first in vivo proof-of-concept biology studies, and results from an acute rat diuresis model confirmed the hypothesis that ROMK inhibitors represent new mechanism diuretic and natriuretic agents.

Estrogen receptor ligands. Part 16: 2-Aryl indoles as highly subtype selective ligands for ERalpha.

A novel class of indole ligands for estrogen receptor alpha have been discovered which exhibit potent affinity and high selectivity. Substitution of the bazedoxifene skeleton to the linker present in the HTS lead 1a provided 22b which was found to be 130-fold alpha-selective and acted as an antagonist of estradiol activity in uterine tissue and MCF-7 cancer cells.

Estrogen receptor ligands. Part 14: application of novel antagonist side chains to existing platforms.

Two novel side chains which had previously been found to enhance antagonist activity in the dihydrobenzoxathiin SERM series were applied to three existing platforms. The novel side chains did not improve the antagonist activity of the existing platforms.

Estrogen receptor ligands. Part 13: Dihydrobenzoxathiin SERAMs with an optimized antagonist side chain.

An optimized side chain for dihydrobenzoxathiin SERAMs was discovered and attached to four dihydrobenzoxathiin platforms. The novel SERAMs show exceptional estrogen antagonist activity in uterine tissue and an MCF-7 breast cancer cell assay.

Estrogen receptor-beta regulates tryptophan hydroxylase-1 expression in the murine midbrain raphe.

BACKGROUND: Distinct expression patterns of estrogen receptor (ER)-alpha and ER-beta are displayed in the murine central nervous system. ER-beta is the predominant form of the receptor expressed in the murine midbrain dorsal raphe nucleus (DRN). Tryptophan hydroxylase (TPH) is abundantly expressed in the serotonergic neurons of the DRN and is regulated by estrogen in both the monkey and the guinea pig. METHODS: In this study we used immunocytochemistry to show that ER-beta and TPH are colocalized in the serotonergic cells of the murine DRN. We utilized the ER-alpha and ER-beta gene deletion mouse models and in situ hybridization to demonstrate that ER-beta is responsible for regulating TPH1 mRNA expression. RESULTS: Estrogen increased TPH1 mRNA expression in the DRN of wild type and ER-alpha knockout mice (alpha-ERKO) but not ER-beta knockouts (beta-ERKO). CONCLUSIONS: These data indicate that ER-beta is responsible for mediating estrogen regulated TPH1 expression in the murine DRN.

Differential hormonal regulation of tryptophan hydroxylase-2 mRNA in the murine dorsal raphe nucleus.

BACKGROUND: Recently a novel tryptophan hydroxylase isoform (TPH2) was identified and shown to be highly expressed in the central nervous system (CNS). Hormonal effects on TPH2 mRNA expression in the rodent dorsal raphe nucleus (DRN) are unknown. METHODS: In situ hybridization histochemistry and real-time reverse transcriptase-polymerase chain reaction (RT-PCR) were used to assess the effects of dexamethasone or estradiol on TPH2 mRNA levels in the DRN of C57/Bl6 mice. RESULTS: Dexamethasone reduced TPH2 mRNA levels in the DRN of both ovx female and intact male mice. Reduction of TPH2 mRNA in the DRN was blocked by co-administration of mifepristone. Estradiol had no detectable effect on TPH2 mRNA levels in the DRN. CONCLUSIONS: TPH2 mRNA is regulated by glucocorticoids but not estradiol in the mouse DRN. Glucocorticoid-mediated reduction of TPH2 message may have relevance to the etiology of major depression, psychotic major depression in particular, where elevated glucocorticoids are one hallmark of the disease.

Estrogen receptor ligands. Part 10: Chromanes: old scaffolds for new SERAMs.

The discovery, synthesis, and SAR of chromanes as ER alpha subtype selective ligands are described. X-ray studies revealed that the origin of the ER alpha-selectivity resulted from a C-4 trans methyl substitution to the cis-2,3-diphenyl-chromane platform. Selected compounds from this class demonstrated very potent in vivo antagonism of estradiol in an immature rat uterine weight assay, effectively inhibited ovariectomy-induced bone resorption in a 42 days treatment paradigm, and lowered serum cholesterol levels in ovx'd adult rat models. The best antagonists 8F and 12F also exhibited potent inhibition of MCF-7 cell growth and were shown to be estrogen receptor down-regulators (SERDs).

Estrogen receptor ligands. Part 11: Synthesis and activity of isochromans and isothiochromans.

The ring oxygen and sulfur analogs of lasofoxifene, 1a and 1b, were synthesized in an attempt to impart ERalpha selectivity, as found in the closely related dihydrobenzoxathiin compound I, recently discovered in these laboratories. The resulting isochroman and isothiochroman compounds were found to exhibit equipotent binding affinities to the ER isoforms and were less active in the inhibition of estradiol-triggered uterine growth when compared to I and lasofoxifene.

Estrogen receptor ligands. Part 9: Dihydrobenzoxathiin SERAMs with alkyl substituted pyrrolidine side chains and linkers.

A series of dihydrobenzoxathiin SERAMs with alkylated pyrrolidine side chains or alkylated linkers was prepared. Minor modifications in the side chain or linker resulted in significant effects on biological activity, especially in uterine tissue.

Estrogen receptor ligands. Part 7: Dihydrobenzoxathiin SERAMs with bicyclic amine side chains.

A series of benzoxathiin SERAMs with bicyclic amine side chains was prepared. Minor modifications in the side chain resulted in significant effects on biological activity, especially in uterine tissue.

Estrogen receptor ligands. Part 8: Dihydrobenzoxathiin SERAMs with heteroatom-substituted side chains.

A series of benzoxathiin SERAMs with heteroatom-substituted amine side chains was prepared. Minor modifications in the side chain resulted in significant effects on biological activity, especially in uterine tissue.

Estrogen receptor ligands. Part 6: Synthesis and binding affinity of dihydrobenzodithiins.

Dihydrobenzodithiin compounds (1-6) were prepared to explore the expansion of the dihydrobenzoxathiin lead compounds I-III as SERAMs (Selective Estrogen Receptor Alpha Modulators). The dihydrobenzodithiin compounds generally maintained a high degree of selectivity for ERalpha over ERbeta, however, they lacked the in vivo antagonism/agonism activity exhibited by the lead class in an immature rat uterine growth model.

Estrogen receptor ligands. Part 5: The SAR of dihydrobenzoxathiins containing modified basic side chains.

Dihydrobenzoxathiin analogs (1-11) with modifications on the basic side chain region were prepared and evaluated for estrogen/anti-estrogen activity in both in vitro and in vivo models. The compounds generally maintained a high degree of selectivity for ERalpha over ERbeta, similar to the original lead compound I. Many of the compounds also maintained high potency in the inhibition of human carcinoma MCF-7 cell growth. However, all were less potent in the inhibition of estradiol-triggered uterine growth. This work demonstrates the sensitive nature of modification to the antagonist basic side chain region.

Estrogen receptor ligands. II. Discovery of benzoxathiins as potent, selective estrogen receptor alpha modulators.

The discovery and synthesis of dihydrobenzoxathiins as potent, ERalpha subtype selective ligands are described. The most active analogue, 4-D, was found to be 50-fold selective in a competitive binding assay and 100-fold selective in a transactivation assay in HEK-293 cells. The alpha selectivity was postulated to lie in the interaction of the sulfur atom of the benzoxathiin ring with the two discriminating residues in the binding pocket of the receptor isoforms.