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T A Grese

Publications and source records attributed to T A Grese.

7 recordsLinked to original sources
PubMed2001

Photochemical synthesis of N-arylbenzophenanthridine selective estrogen receptor modulators (serms).

Selective estrogen receptor modulators are an emerging class of pharmaceutically important molecules. Many compounds in this class contain an aminoethoxyaryl moiety attached to a polycyclic framework at an asymmetric carbon atom. To assess whether this carbon atom can be replaced by nitrogen, we have employed a Ninomiya enamide photocyclization for the rapid synthesis of a novel N-arylbenzophenanthridine framework, 4. Further elaboration of 4 into a new structural class of achiral, nonsteroidal estrogen receptor modulators is described.

Animals↗
PubMed2001

Bexarotene metabolism in rat, dog, and human, synthesis of oxidative metabolites, and in vitro activity at retinoid receptors.

The metabolism of bexarotene, a rexinoid recently approved in the United States for treatment of cutaneous T-cell lymphoma, was studied using liver slices from untreated rats and dogs, liver microsomes from untreated and pretreated rats, and pooled human liver microsomes. Metabolite profiles were examined in bile and plasma from rats and dogs, and plasma from humans treated with bexarotene. Four metabolites, racemic 6-hydroxy-bexarotene, racemic 7-hydroxy-bexarotene, 6-oxo-bexarotene, and 7-oxo-bexarotene, were synthesized and their binding to, and transactivation of retinoid receptors were examined. Qualitatively similar metabolite profiles were observed in the microsomal and liver slice extracts; the predominant metabolites were 6-hydroxy-bexarotene and glucuronides of parent or hydroxylated metabolites. Pretreatment of rats with bexarotene induced hepatic microsomal bexarotene metabolism. The hydroxy and oxo metabolites were observed in plasma of rats, dogs, and humans treated with bexarotene and 6-hydroxy-bexarotene was a major circulating metabolite. The oxidative metabolites were more abundant relative to parent in plasma from humans than from rat or dog. The predominant biliary metabolites in rat and dog were bexarotene acyl glucuronide and a glucuronide of oxidized bexarotene, respectively. Since bexarotene elimination is primarily biliary in these species, these metabolites represent the main bexarotene metabolites in rats and dogs. The binding of synthetic metabolites to retinoid receptors was much reduced relative to parent compound. The metabolites exhibited minimal activity in transactivating retinoic acid receptors and had reduced activity at retinoid X receptors relative to bexarotene. Thus, while there is substantial systemic exposure to the oxidative metabolites of bexarotene, they are unlikely to elicit significant retinoid receptor activation following bexarotene administration.

Animals↗
PubMed1998

Synthesis and pharmacology of conformationally restricted raloxifene analogues: highly potent selective estrogen receptor modulators.

The 2-arylbenzothiophene raloxifene, 1, is a selective estrogen receptor modulator (SERM) which is currently under clinical evaluation for the prevention and treatment of postmenopausal osteoporosis. In vivo structure-activity relationships and molecular modeling studies have indicated that the orientation of the basic amine-containing side chain of 1, relative to the stilbene plane, is an important discriminating factor for the maintenance of tissue selectivity. We have constructed a series of analogues of 1 in which this side chain is held in an orientation which is orthogonal to the stilbene plane, similar to the low-energy conformation predicted for raloxifene. Herein, we report on the synthesis of these compounds and on their activity in a series of in vitro and in vivo biological assays reflective of the SERM profile. In particular, we describe their ability to (1) bind the estrogen receptor, (2) antagonize estrogen-stimulated proliferation of MCF-7 cells in vitro, (3) stimulate TGF-beta3 gene expression in cell culture, (4) inhibit the uterine effects of ethynyl estradiol in immature rats, and (5) potently reduce serum cholesterol and protect against osteopenia in ovariectomized (OVX) rats without estrogen-like stimulation of uterine tissue. These data demonstrate that one of these compounds, LY357489,4, is among the most potent SERMs described to date with in vivo efficacy on bone and cholesterol metabolism in OVX rats at doses as low as 0.01 mg/kg/d.

Animals↗
PubMed1998

Selective estrogen receptor modulators (SERMs).

Naturally occurring estrogens, such as 17 beta-estradiol and estrone, have traditionally been thought to play a central role in the development and maintenance of the female reproductive system and secondary sexual characteristics. In recent years, their beneficial effects on the skeleton, the cardiovascular system, and the central nervous system, as well as the cancer risks associated with long term exposure have also been recognized. The widespread use of "antiestrogens" such as tamoxifen for the prevention and treatment of breast cancer has revealed that such compounds, while functioning as estrogen antagonists in mammary tissue, actually mimic the effects of estrogen in other tissues. The search for more selective agents has led to the development of raloxifene, a Selective Estrogen Receptor Modulator, which functions as an estrogen antagonist in the breast and uterus and as an estrogen agonist in the skeleton and cardiovascular system. Recent progress in the development of SERMs is the subject of this review, with an emphasis on structure activity relationships and on their effects in non-traditional target tissues.

Animals↗
PubMed1997

Molecular determinants of tissue selectivity in estrogen receptor modulators.

Interaction of the estrogen receptor/ligand complex with a DNA estrogen response element is known to regulate gene transcription. In turn, specific conformations of the receptor-ligand complex have been postulated to influence unique subsets of estrogen-responsive genes resulting in differential modulation and, ultimately, tissue-selective outcomes. The estrogen receptor ligands raloxifene and tamoxifen have demonstrated such tissue-specific estrogen agonist/antagonist effects. Both agents antagonize the effects of estrogen on mammary tissue while mimicking the actions of estrogen on bone. However, tamoxifen induces significant stimulation of uterine tissue whereas raloxifene does not. We postulate that structural differences between raloxifene and tamoxifen may influence the conformations of their respective receptor/ligand complexes, thereby affecting which estrogen-responsive genes are modulated in various tissues. These structural differences are 4-fold: (A) the presence of phenolic hydroxyls, (B) different substituents on the basic amine, (C) incorporation of the stilbene moiety into a cyclic benzothiophene framework, and (D) the imposition of a carbonyl "hinge" between the basic amine-containing side chain and the olefin. A series of raloxifene analogs that separately exemplify each of these differences have been prepared and evaluated in a series of in vitro and in vivo assays. This strategy has resulted in the development of a pharmacophore model that attributes the differences in effects on the uterus between raloxifene and tamoxifen to a low-energy conformational preference imparting an orthogonal orientation of the basic side chain with respect to the stilbene plane. This three-dimensional array is dictated by a single carbon atom in the hinge region of raloxifene. These data indicate that differences in tissue selective actions among benzothiophene and triarylethylene estrogen receptor modulators can be ascribed to discrete ligand conformations.

Animals↗
PubMed1997

Structure-activity relationships of selective estrogen receptor modulators: modifications to the 2-arylbenzothiophene core of raloxifene.

The 2-arylbenzothiophene raloxifene, 1, is a selective estrogen receptor modulator which is currently under clinical evaluation for the prevention and treatment of postmenopausal osteoporosis. A series of raloxifene analogs which contain modifications to the 2-arylbenzothiophene core have been prepared and evaluated for the ability to bind to the estrogen receptor and inhibit MCF-7 breast cancer cell proliferation in vitro. Their ability to function as tissue-selective estrogen agonists in vivo has been assayed in a short-term, ovariectomized (OVX) rat model with end points of serum cholesterol lowering, uterine weight gain, and uterine eosinophil peroxidase activity. These studies have demonstrated that (1) the 6-hydroxy and, to a lesser extent, the 4'-hydroxy substituents of raloxifene are important for receptor binding and in vitro activity, (2) small, highly electronegative 4'-substituents such as hydroxy, fluoro, and chloro are preferred both in vitro and in vivo, (3) increased steric bulk at the 4'-position leads to increased uterine stimulation in vivo, and (4) additional substitution of the 2-aryl moiety is tolerated while additional substitution at the 4-, 5-, or 7-position of the benzothiophene results in reduced biological activity. In addition, compounds in which the 2-aryl group is replaced by alkyl, cycloalkyl, and naphthyl substituents maintain a profile of in vitro and in vivo biological activity qualitatively similar to that of raloxifene. Several novel structural variants including 2-cyclohexyl, 2-naphthyl, and 6-carbomethoxy analogs also demonstrated efficacy in preventing bone loss in a chronic OVX rat model of postmenopausal osteopenia, at doses of 0.1-10 mg/kg.

Adenocarcinoma↗