The combined effect of inhibiting both ACAT and HMG-CoA reductase may directly induce atherosclerotic lesion regression.

We hypothesized that coadministration of avasimibe and simvastatin would limit size, composition and extent of atherosclerotic lesions and potentially promote lesion regression, since bioavailable ACAT inhibitors decrease monocyte-macrophage enrichment and HMG-CoA reductase inhibitors limit smooth muscle cell migration and proliferation. Male New Zealand white rabbits were sequentially fed a 0.5% cholesterol, 3% peanut oil, 3% coconut oil diet for 9 weeks and a chow-fat diet for 6 weeks prior to drug administration. A time zero control group was necropsied prior to drug administration and the progression control was fed various diets but untreated. Avasimibe (10 mg/kg), simvastatin (2.5 mg/kg) or combination of avasimibe (10 mg/kg) with simvastatin (2.5 mg/kg) were administered in the chow-fat diet for 8 weeks. Plasma total cholesterol exposure was unchanged by avasimibe but was reduced 21% by both simvastatin alone and in combination with avasimibe. Combination of avasimibe and simvastatin decreased VLDL-cholesterol exposure by 56%. VLDL+IDL lipid composition was similar in the progression control and simvastatin-treated animals. Administration of avasimibe alone or in combination with simvastatin reduced the cholesteryl ester fraction and increased the triglyceride fraction to comparable extents. Relative to the progression control, avasimibe plus simvastatin markedly decreased thoracic aortic cholesteryl ester content and lesion coverage by 50% and aortic arch lesion size and macrophage area by 75 and 73%, respectively. With respect to lesion regression, avasimibe+simvastatin decreased aortic arch lesion size by 64% and monocyte-macrophage area by 73% when compared to time zero. Based on these data, we conclude that despite changes in plasma total and lipoprotein cholesterol exposure and lipoprotein composition comparable to monotherapy, inhibition of both ACAT and HMG-CoA reductase may not only directly blunt lesion progression but also promote regression of pre-established atherosclerotic lesions.

Matrix metalloproteinase inhibition attenuates left ventricular remodeling and dysfunction in a rat model of progressive heart failure.

BACKGROUND: Matrix metalloproteinase (MMP) activation contributes to tissue remodeling in several disease states, and increased MMP activity has been observed in left ventricular (LV) failure. The present study tested the hypothesis that MMP inhibition would influence LV remodeling and function in developing LV failure. METHODS AND RESULTS: LV size and function were measured in 5 groups of rats: (1) obese male spontaneously hypertensive heart failure rats (SHHF) at 9 months (n=10), (2) SHHF at 13 months (n=12), (3) SHHF rats treated with an MMP inhibitor during months 9 to 13 (PD166793 5 mg. kg(-1). d(-1) PO; n=14), (4) normotensive Wistar-Furth rats (WF) at 9 months (n=12), and (5) WF at 13 months (n=12). Plasma concentrations of the MMP inhibitor (116+/-11 micromol/L) reduced in vitro LV myocardial MMP-2 activity by approximately 100%. LV function and geometry were similar in WF rats at 9 and 13 months. LV peak +dP/dt was unchanged at 9 months in SHHF but by 13 months was reduced in the SHHF group compared with WF (3578+/-477 versus 5983+/-109 mm Hg/s, P

Structure-activity relationships and pharmacokinetic analysis for a series of potent, systemically available biphenylsulfonamide matrix metalloproteinase inhibitors.

A series of biphenylsulfonamide derivatives of (S)-2-(biphenyl-4-sulfonylamino)-3-methylbutyric acid (5) were prepared and evaluated for their ability to inhibit matrix metalloproteinases (MMPs). For this series of compounds, our objective was to systematically replace substituents appended to the biphenyl and alpha-position of 5 with structurally diverse functionalities to assess the effects these changes have on biological and pharmacokinetic activity. The ensuing structure-activity relationship (SAR) studies showed that biphenylsulfonamides substituted with bromine in the 4'-position (11c) significantly improved in vitro activity and exhibited superior pharmacokinetics (C(max), t(1/2), AUCs), relative to compound 5. Varying the lipophilicity of the alpha-position by replacing the isopropyl group of 11c with a variety of substituents, in general, maintained potency versus MMP-2, -3, and -13 but decreased the oral systemic availability. Subsequent evaluation of its enantiomer, 11c', showed that both compounds were equally effective MMP inhibitors. In contrast, the corresponding hydroxamic acid enantiomeric pair, 16a (S-isomer) and 16a' (R-isomer), stereoselectivity inhibited MMPs. For the first time in this series, 16a' provided nanomolar potency against MMP-1, -7, and -9 (IC(50)'s = 110, 140, and 18 nM, respectively), whereas 16a was less potent against these MMPs (IC(50)'s = 24, 78, and 84 microM, respectively). However, unlike 11c, compound 16a' afforded very low plasma concentrations following a single 5 mg/kg oral dose in rat. Subsequent X-ray crystal structures of the catalytic domain of stromelysin (MMP-3CD) complexed with inhibitors from closely related series established the differences in the binding mode of carboxylic acid-based inhibitors (11c,c') relative to the corresponding hydroxamic acids (16a,a').

Lipid-lowering effects of WAY-121,898, an inhibitor of pancreatic cholesteryl ester hydrolase.

WAY-121,898 is an inhibitor of pancreatic cholesteryl ester hydrolase (pCEH). After confirming its in vitro potency and relative lack of a major effect on acyl-CoA:cholesterol acyltransferase (ACAT), it was found that this compound lowers plasma cholesterol in cholesterol-fed, but not chow-fed, rats. Measures of liver cholesteryl ester content and the direct determination of cholesterol absorption (lymph-fistula model) show that inhibition of cholesterol absorption is at least one mechanism for the observed cholesterol lowering. However, WAY-121,898 was also active when administered parenterally to cholesterol-fed rats, and in cholesterol-fed hamsters cholesterol-lowering occurred with oral dosing despite no change in cholesterol absorption, suggesting other modes of action possibly relating to inhibition of liver CEH. Combination treatment in cholesterol-fed rats with the ACAT inhibitor CI-976 resulted in a greater-than-additive reduction in plasma cholesterol, implying that both pCEH and ACAT may play a role in cholesterol absorption in this species. In rabbits, WAY-121,898 prevented the rise in plasma cholesterol due to the feeding of cholesteryl ester but not in rabbits fed (free) cholesterol. In guinea pigs, the compound induced an increase in adrenal cholesteryl ester mass. Taken together, the overall profile in these animal models suggests that WAY-121,898 inhibits more than just the intestinal (lumenal) pCEH, and that the role of this enzyme in cholesterol metabolism may be different within and across species, the former depending upon the dietary cholesterol load.

alpha-Substituted malonester amides: tools to define the relationship between ACAT inhibition and adrenal toxicity.

We prepared a series of alpha-substituted malonester amides that were evaluated for their ability to inhibit acyl-CoA:cholesterol O-acyl transferase activity in vitro and to lower plasma total cholesterol levels in a variety of cholesterol-fed animal models. Compounds of this series were also useful in examining the relationship between adrenal toxicity and ACAT inhibition. One compound from this series, 9f, was a potent inhibitor of ACAT in both the microsomal and cellular assays. It was also bioavailable as determined by both a bioassay and a HPLC-UV assay. This compound was evaluated in both guinea pig and dog models of adrenal toxicity and compared to tetrazole amide 15. In the most sensitive species, the dog, both of these compounds achieved good plasma levels; however, compound 9f caused adrenal necrosis, whereas compound 15 had no effect on the adrenal gland. This adds to the growing body of evidence that the adrenal toxicity observed with ACAT inhibitors may not be mechanism related.

Inhibitors of acyl-CoA:cholesterol O-acyltransferase (ACAT) as hypocholesterolemic agents: synthesis and structure-activity relationships of novel series of sulfonamides, acylphosphonamides and acylphosphoramidates.

Sulfoacetic acid, phosphoramidate, and phosphoramide analogs of the ACAT inhibitors, CI-999 and CI-1011 were synthesized. The structure-activity relationships of these compounds as ACAT inhibitors are described.

Inhibitors of acyl-CoA:cholesterol O-acyltransferase. synthesis and pharmacological activity of (+/-)-2-dodecyl-alpha-phenyl-N-(2,4,6-trimethoxyphenyl)-2H-tetrazole-5- acetamide and structurally related tetrazole amide derivatives.

A series of tetrazole amide derivatives of (+/-)-2-dodecyl-alpha-phenyl-N-(2,4,6-trimethoxyphenyl)-2H-tetrazole-5- acetamide (1) was prepared and evaluated for their ability to inhibit acyl-CoA: cholesterol O-acyltransferase (ACAT) in vitro and to lower plasma total cholesterol in vivo. For this series of compounds, our objective was to systematically replace substituents appended to the amide and tetrazole moieties of 1 with structurally diverse functionalities and assess the effect that these changes have on biological activity. The ensuing structure-activity relationship (SAR) studies identified aryl (7b) and heteroaryl (7f,g) replacements for 2,4,6-trimethoxyphenyl that potently inhibit liver microsomal and macrophage ACAT in vitro and exhibit good cholesterol lowering activity (56-66% decreases in plasma total cholesterol at 30 mg/kg), relative to 1, when compared in the acute rat model of hypercholesterolemia. Replacement of the alpha-phenyl moiety with electron-withdrawing substituents (13e-h), however, significantly reduced liver microsomal ACAT inhibitory activity (IC50 > 1 microM). This is in contrast to electron-donating substituents (13ij,m-q), which produce IC50 values ranging from 5 to 75 nM in the hepatic microsomal assay. For selected tetrazole amides (1, 7b, 13n,o), reversing the order of substituents appended to the 2- and 5-positions in the tetrazole ring (36a-d), in general, improved macrophage ACAT inhibitory activity and provided excellent cholesterol-lowering activity (ranging from 65% to 77% decreases in plasma total cholesterol at 30 mg/kg) in the acute rat screen. The most potent isomeric pair in this set of unsubstituted methylene derivatives (13n and 36a) caused adrenocortical cell degeneration in guinea pigs treated with these inhibitors. In contrast, adrenal glands taken from guinea pigs treated with the corresponding alpha-phenyl-substituted analogs (7b and 36c) were essentially unchanged compared to untreated controls. Subsequent evaluation of 7b and 36c in a rabbit bioassay showed that both compounds and/or their metabolities were present in plasma after oral dosing. Unlike 7b and 36c, compound 1 and related 2,4,6-trimethoxyanilides (13j, 30c,d) showed poor oral activity in the rabbit bioassay. Nevertheless, in cholesterol-fed rabbits, both systemically available (7b, 36c) and poorly absorbed inhibitors (1, 36d) were more effective in lowering plasma total cholesterol than the fatty acid amide CI-976.

Inhibitors of acyl-CoA:cholesterol O-acyltransferase. 17. Structure-activity relationships of several series of compounds derived from N-chlorosulfonyl isocyanate.

Several series of acyl-CoA:cholesterol O-acyltransferase inhibitors were prepared by the stepwise addition of nitrogen, oxygen, and sulfur nucleophiles to N-chlorosulfonyl isocyanate. The (aminosulfonyl)ureas 3-44 were the most potent inhibitors in vitro, with several compounds having IC50 values < 1 microM. Although the other series of compounds were not as potent in vitro, many compounds did display good in vivo activity in cholesterol-fed rats. Several of the oxysulfonyl carbamates (including CI-999, 115) showed excellent lipid-lowering activity in the chronic in vivo screen, demonstrating significant cholesterol lowering in a pre-established hypercholesterolemic state.

Antiatherosclerotic activity of inhibitors of 3-hydroxy-3-methylglutaryl coenzyme A reductase in cholesterol-fed rabbits: a biochemical and morphological evaluation.

Atherosclerotic lesion development was assessed in the thoracic aorta and chronically denuded iliac-femoral artery of hypercholesterolemic New Zealand White rabbits using inhibitors of 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase which have previously been shown to possess varying degrees of hepatoselectivity in rats. Atorvastatin, previously known as CI-981 (2.5 mg/kg), PD135022 (1.0 mg/kg), simvastatin (2.5 mg/kg), lovastatin (2.5 mg/kg), PD134965 (1.0 mg/kg), pravastatin (2.5 mg/kg) and BMY22089 (2.5 mg/kg) were added to a 0.5% cholesterol, 3% peanut, 3% coconut oil diet and fed for 8 weeks. Although reductions in plasma total cholesterol of 27% to 60%, VLDL-cholesterol of 31% to 71% and plasma total cholesterol exposure of 37% to 43% were obtained, no correlation between these parameters and vascular lipid content, lesion size or monocyte-macrophage content was noted. Iliac-femoral lipid content was unchanged; however, atorvastatin and simvastatin significantly reduced the cholesterol content of the thoracic aorta by 45%-62%. Atorvastatin and PD135022 reduced the size of the iliac-femoral lesion by 67% and monocyte-macrophage content by 72%. Simvastatin, lovastatin and PD134965 decreased the monocyte-macrophage content; however, lesion size was unchanged. Pravastatin and BMY22089 had no effect on lesion size or content. No compound significantly reduced the extent of thoracic aortic lesions. We concluded that changes in plasma lipids and lipoproteins noted with the various HMG-CoA reductase inhibitors did not account for the beneficial effect on atherosclerotic lesion development. The antiatherosclerotic potential of the HMG-CoA reductase inhibitors was compound-specific and clearly not a class effect.

Inhibitors of acyl-CoA:cholesterol O-acyltransferase. 11. Structure-activity relationships of several series of compounds derived from N-(chlorocarbonyl) isocyanate.

Five series of compounds (4-9) derived from N-(chlorocarbonyl) isocyanate have been synthesized and evaluated for their ability to inhibit the enzyme acyl-CoA:cholesterol O-acyltransferase and lower plasma cholesterol levels in cholesterol-fed rats. Structure-activity relationships indicate that the imino dicarboxylates (6 and 7) and the oxycarbonyl thiocarbamates (8) are the most potent and efficacious series. In these series, the combination of a 2,6-diisopropylphenyl group and an aliphatic alkyl group with a chain length between 6 and 14 carbon atoms gives good activity in vitro and in vivo. In addition, a hydrogen donor is required to maintain good in vitro activity, and the acidic proton on the central nitrogen in these series appears to be important for in vivo activity.

Inhibitors of acyl-CoA:cholesterol O-acyl transferase (ACAT) as hypocholesterolemic agents. 8. Incorporation of amide or amine functionalities into a series of disubstituted ureas and carbamates. Effects on ACAT inhibition in vitro and efficacy in vivo.

A series of disubstituted ureas containing amide or amine groups was prepared and evaluated for their ability to inhibit acyl-CoA:cholesterol O-acyl transferase in vitro and to lower plasma total cholesterol in a variety of cholesterol-fed rat models in vivo. The presence of polar or ionizable functionalities within this class of compounds may impart greater aqueous solubility to those compounds and thus allow improved transport to the enzyme location within the intestinal enterocyte. Compounds from this class exhibit good cholesterol lowering in a chronic cholesterol-fed rat model of hypercholesterolemia even when dosed in an aqueous vehicle. In general, the amine-containing compounds were more potent and efficacious than the amides in the acute rat model of hypercholesterolemia. Further structure-activity relationship studies showed that the preferred position of the amide/amine group was beta to the urea moiety and not alpha, and that in this series, the presence of a secondary amine (or amide) proton is required for good in vitro potency. One of these compounds, 9n(-), lowered plasma total cholesterol (-47%) and elevated high-density lipoprotein cholesterol (+256%) when dosed in an aqueous vehicle to rats with preestablished hypercholesterolemia.

Inhibitors of cholesterol biosynthesis. 6. trans-6-[2-(2-N-heteroaryl-3,5-disubstituted- pyrazol-4-yl)ethyl/ethenyl]tetrahydro-4-hydroxy-2H-pyran-2-ones.

A series of N-heteroaryl-substituted mevalonolactones were prepared and evaluated for their ability to inhibit the enzyme HMG-CoA reductase both in vitro and in vivo, and to lower plasma cholesterol in a hypercholesterolemic dog model. The goal of the strategy employed was to design an inhibitor which possessed the pharmacological properties of lovastatin (1), and the physicochemical properties (increased hydrophilicity) of pravastatin (2). Two compounds 20a and 20b, were more potent than lovastatin at inhibiting cholesterol biosynthesis both in vitro and in vivo. In terms of plasma cholesterol lowering, 20a was much more efficacious than lovastatin. In addition to possessing increased biological activity, these compounds are significantly less lipophilic than lovastatin, in fact, 20b has a CLOGP value comparable to pravastatin.

Hepatic and nonhepatic sterol synthesis and tissue distribution following administration of a liver selective HMG-CoA reductase inhibitor, CI-981: comparison with selected HMG-CoA reductase inhibitors.

Since cholesterol biosynthesis is an integral part of cellular metabolism, several HMG-CoA reductase inhibitors were systematically analyzed in in vitro, ex vivo and in vivo sterol synthesis assays using [14C]acetate incorporation into digitonin precipitable sterols as a marker of cholesterol synthesis. Tissue distribution of radiolabeled CI-981 and lovastatin was also performed. In vitro, CI-981 and PD134967-15 were equipotent in liver, spleen, testis and adrenal, lovastatin was more potent in extrahepatic tissues than liver and BMY21950, pravastatin and PD135023-15 were more potent in liver than peripheral tissues. In ex vivo assays, all inhibitors except lovastatin preferentially inhibited liver sterol synthesis; however, pravastatin and BMY22089 were strikingly less potent in the liver. CI-981 inhibited sterol synthesis in vivo in the liver, spleen and adrenal while not affecting the testis, kidney, muscle and brain. Lovastatin inhibited sterol synthesis to a greater extent than CI-981 in the spleen, adrenal and kidney while pravastatin and BMY22089 primarily affected liver and kidney. The tissue distribution of radiolabeled CI-981 and lovastatin support the changes observed in tissue sterol synthesis. Thus, we conclude that a spectrum of liver selective HMG-CoA reductase inhibitors exist and that categorizing agents as liver selective is highly dependent upon method of analysis.

Therapeutic potential of ACAT inhibitors as lipid lowering and anti-atherosclerotic agents.

Hypercholesterolemia is one of the few independent risk factors definitively linked to increased morbidity and mortality due to myocardial infarction. One possible therapy of current interest is the prevention of the absorption of dietary cholesterol by inhibiting the enzyme, acyl-CoA: cholesterol acyltransferase (ACAT), which catalyses the intracellular formation of cholesterol esters. Evidence is now accumulating that suggests that ACAT inhibition may not only lower plasma cholesterol levels, but may also have a direct effect at the artery wall, where ACAT has been shown to be responsible for the accumulation of cholesterol esters in arterial lesions. Drago Sliskovic and Andrew White discuss the importance of ACAT in the lipid transport system and the consequences of its inhibition in a variety of tissues, with emphasis on both lipid-lowering and anti-atherosclerotic effects.

Inhibitors of cholesterol biosynthesis. 3. Tetrahydro-4-hydroxy-6-[2-(1H-pyrrol-1-yl)ethyl]-2H-pyran-2-one inhibitors of HMG-CoA reductase. 2. Effects of introducing substituents at positions three and four of the pyrrole nucleus.

A series of trans-tetrahydro-4-hydroxy-6-[2-(2,3,4,5-substituted-1H-pyrrol-1-yl) ethyl]-2H-pyran-2-ones and their dihydroxy acids were prepared and tested for their ability to inhibit the enzyme HMG-CoA reductase in vitro. Inhibitory potency was found to increase substantially when substituents were introduced into positions three and four of the pyrrole ring. A systematic exploration of structure-activity relationships at these two positions led to the identification of a compound ((+)-33,(+)-(4R)-trans-2-(4-fluororphenyl)-5-(1-methylethyl)-N,3- diphenyl-1- [(tetrahydro-4-hydroxy-6-oxo-2H-pyran-2-yl)ethyl]-1H-pyrrole-4- carboxamide) with five times the inhibitory potency of the fungal metabolite compactin.

Inhibitors of cholesterol biosynthesis. 4. trans-6-[2-(substituted-quinolinyl)ethenyl/ethyl]tetrahydro-4-hydroxy-2 H-pyran-2-ones, a novel series of HMG-CoA reductase inhibitors.

A series of substituted quinoline mevalonolactones were prepared and evaluated for their ability to inhibit the enzyme HMG-CoA reductase both in vitro and (cholesterol biosynthesis) in vivo. Since previous studies suggested that the 4-(4-fluorophenyl) and 2-(1-methylethyl) substituents afforded optimum potency, attention was focused on variations at position 6 of the quinoline ring. Biological evaluation of a small number of analogues bearing a variety of 6-substituents showed that modification at this position had little effect on potency. Several compounds (8b, 8e, and 11) were identified that showed comparable potency to compactin and mevinolin in both the in vitro and in vivo assays.

Hep-G2 cells and primary rat hepatocytes differ in their response to inhibitors of HMG-CoA reductase.

CI-981, a novel synthetic inhibitor of HMG-CoA reductase, was previously reported to be highly liver-selective using an ex vivo approach. In order to determine liver-selectivity at the cellular level, CI-981 was evaluated in cell culture and compared to lovastatin, pravastatin, fluvastatin and BMY-21950. Using human cell lines, none of the compounds tested showed liver-selectivity, i.e. strong inhibition of cholesterol synthesis in Hep-G2 cells (liver model) but weak inhibition in human fibroblasts (peripheral cell model). In contrast, all drugs tested produced equal and potent inhibition of sterol synthesis in primary cultures of rat hepatocytes, and CI-981, pravastatin and BMY-21950 were more than 100-fold more potent in rat hepatocytes compared to human fibroblasts. Since all compounds were also equally potent at inhibiting sterol synthesis in a rat subcellular system and in vivo, the data suggest that the use of Hep-G2 cells may not be the cell system of choice in which to study inhibition of hepatic cholesterogenesis or to demonstrate liver selectivity of inhibitors of HMG-CoA reductase.

Inhibitors of cholesterol biosynthesis. 1. trans-6-(2-pyrrol-1-ylethyl)-4-hydroxypyran-2-ones, a novel series of HMG-CoA reductase inhibitors. 1. Effects of structural modifications at the 2- and 5-positions of the pyrrole nucleus.

A novel series of trans-6-(2-pyrrol-1-ylethyl)-4-hydroxypyran-2-ones and their dihydroxy acid derivatives were prepared and evaluated for their ability to inhibit the enzyme HMG-CoA reductase in vitro. A systematic study of substitution at the 2- and 5-positions of the pyrrole ring revealed that optimum potency was realized with the 2-(4-fluorophenyl)-5-isopropyl derivative 8x, which possessed 30% of the in vitro activity of the potent fungal metabolite compactin (I). A molecular modeling analysis led to the description of a pharmacophore model characterized by (A) length limits of 5.9 and 3.3 A for the 2- and 5-substituents, respectively, as well as an overall width limit of 10.6 A across the pyrrole ring from the 2- to the 5-substituent and (B) an orientation of the ethyl(ene) bridge to the 4-hydroxypyran-2-one ring nearly perpendicular to the planes of the parent pyrrole, hexahydronaphthalene, and phenyl rings of the structures examined (Figure 3, theta = 80-110 degrees). Attempts to more closely mimic compactin's polar isobutyric ester side chain with the synthesis of 2-phenylpyrroles containing polar phenyl substituents resulted in analogues with equal or slightly reduced potencies when compared to the 2-[(unsubstituted or 4-fluoro)phenyl]pyrroles, supporting the hypothesis that inhibitory potency is relatively insensitive to side-chain polarity or charge distribution in this area.