Search

Recent literature has suggested the benefit of selective PPARdelta agonists for the treatment of atherosclerosis and other disease states associated with the metabolic syndrome. Herein we report the synthesis and structure-activity relationships of a series of novel and selective PPARdelta agonists. Our search began with identification of a novel benzothiophene template which was modified by the addition of various thiazolyl, isoxazolyl, and benzyloxy-benzyl moieties. Further elucidation of the SAR led to the identification of benzofuran and indole based templates. During the course of our research, we discovered three new chemical templates with varying degrees of affinity and potency for PPARdelta versus the PPARalpha and PPARgamma subtypes.

We have previously described the design and development of CI-988, a peptoid analogue of CCK-4 with excellent binding affinity and selectivity for the CCK-B receptor. Due to its anxiolytic profile in animal models of anxiety, this compound was developed as a clinical candidate. However, during its development, it was determined that CI-988 had low bioavailability in both rodent and nonrodent species. In the clinic, it was further established that CI-988 had poor bioavailability. Thus, there was a need to identify an analogue with an improved pharmacokinetic (PK) profile. The poor bioavailability was attributed to poor absorption and efficient hepatic extraction. We envisaged that reducing the molecular weight of the parent compound (5, MW = 614) would lead to better absorption. Thus, we synthesized a series of analogues in which the key alpha-methyltryptophan and adamantyloxycarbonyl moieties, required for receptor binding, were kept intact and the C-terminus was extensively modified. This SAR study led to the identification of tricyclo[3.3.1.1(3,7)]dec-2-yl [1S-[1 alpha(S*)2 beta]-[2-[(2-hydroxycyclohexyl)amino]-1-(1H-indol-3- ylmethyl)-1-methyl-2-oxoethyl]carbamate (CI-1015, 31) with binding affinities of 3.0 and 2900 nM for the CCK-B and CCK-A receptors, respectively. The compound showed CCK-B antagonist profile in the rat ventromedial hypothalamus assay with a Ke of 34 nM. It also showed an anxiolytic like profile orally in a standard anxiety paradigm (X-maze) with a minimum effective dose (MED) of 0.1 microgram/kg. Although the compound is less water soluble than CI-988, oral bioavailability in rat was improved nearly 10 times relative to CI-988 when dosed in HP beta CD. The blood-brain permeability of CI-1015 (31) was also enhanced relative to CI-988 (5). On the basis of the overall improved pharmacokinetic profile as well as enhanced brain penetration, CI-1015 (31) was chosen as a development candidate.

1. 15-Lipoxygenase (15-LO) has been implicated in the pathogenesis of atherosclerosis because of its localization in lesions and the many biological activities exhibited by its products. To provide further evidence for a role of 15-LO, the effects of PD 146176 on the development of atherosclerosis in cholesterol-fed rabbits were assessed. This novel drug is a specific inhibitor of the enzyme in vitro and lacks significant non specific antioxidant properties. 2. PD 146176 inhibited rabbit reticulocyte 15-LO through a mixed noncompetitive mode with a Ki of 197 nM. The drug had minimal effects on either copper or 2,2'-azobis(2-amidinopropane)hydrochloride (ABAP) induced oxidation of LDL except at concentrations 2 orders higher than the Ki. 3. Control New Zealand rabbits were fed a high-fat diet containing 0.25% wt./wt. cholesterol; treated animals received inhibitor in this diet (175 mg kg-1, b.i.d.). Plasma concentrations of inhibitor were similar to the estimated Ki (197 nM). During the 12 week study, there were no significant differences in weight gain haematocrit, plasma total cholesterol concentrations, or distribution of lipoprotein cholesterol. 4. The drug plasma concentrations achieved in vivo did not inhibit low-density lipoprotein (LDL) oxidation in vitro. Furthermore, LDL isolated from PD 146176-treated animals was as susceptible as that from controls to oxidation ex vivo by either copper or ABAP. 5. PD 146176 was very effective in suppressing atherogenesis, especially in the aortic arch where lesion coverage diminished from 15 +/- 4 to 0% (P < 0.02); esterified cholesterol content was reduced from 2.1 +/- 0.7 to 0 micrograms mg-1 (P < 0.02) in this region. Immunostainable lipid-laden macrophages present in aortic intima of control animals were totally absent in the drug-treated group. 6. Results of these studies are consistent with a role for 15-LO in atherogenesis.

The metabolism of CI-976, a potent inhibitor of liver and intestinal acyl coenzyme A:cholesterol acyltransferase, was investigated in isolated rat hepatocytes and Wistar rats after oral administration. The major metabolite observed both in vitro and in vivo was identified as the 6-carbon, chain-shortened 5,5-dimethyl-6-oxo-[(2,4,6-trimethoxyphenyl)amino]hexanoic acid (M-4). M-4 was determined to be formed from the omega-carboxylic acid 11,11-dimethyl-12-oxo-12-[(2,4,6-trimethoxyphenyl)amino]dodecanoic acid (M-1) via the 2- and 4-carbon, chain-shortened intermediate metabolites [9,9-dimethyl-10-oxo-10-[(2,4,6-trimethoxyphenyl)amino]decanoic acid (M-2) and 7,7-dimethyl-8-oxo-8-[(2,4,6-trimethoxyphenyl)amino]octanoic acid (M-3)], respectively. M-1 was, in turn, determined to be derived from omega-hydroxy CI-976. A minor metabolite, identified in vitro and in vivo, was a novel 5-carbon, chain-shortened derivative, 6,6-dimethyl-7-oxo-7-[(2,4,6-trimethoxyphenyl)amino]heptanoic acid (M-5). M-5 was shown not to be formed from either M-1 or the omega-hydroxy derivative. Separate incubation of CI-976 (omega-oxidation and beta-oxidation pathways) and M-1 (beta-oxidation only) indicated a potential gender difference in the omega-oxidation of CI-976. Both the omega-oxidation and beta-oxidation pathways were enhanced by clofibrate and phenobarbital induction, and CI-976 metabolism was completely inhibited when coincubated with SKF525A pointing to cytochrome P450-mediated metabolism, presumably CYP4A. Etomoxir and L-carnitine had minor effects on the beta-oxidation of M-1, indicating beta-oxidation occurs predominately within peroxisomes.

Nephrolithiasis is caused by several biochemical mechanisms, identification of which allows specific therapy that may prevent recurrences. In patients with their first kidney stone, careful evaluation is needed to identify those at highest risk for recurrence. Extensive evaluation of this subgroup should lead to proper diagnosis and management of nephrolithiasis, resulting in lower morbidity for these patients.

In the present studies, we examined the effect of flavonoids on the endothelial cell expression of adhesion molecules, an early step in inflammation and atherogenesis. Addition of tumor necrosis factor-alpha (TNF) to human aortic endothelial cells (HAECs) led to the induction of vascular cell adhesion molecule-1 (VCAM-1) expression and enhancement in expression of intercellular adhesion molecule-1 (ICAM-1). A flavonoid, 2-(3-amino-phenyl)-8-methoxy-chromene-4-one (PD 098063), markedly inhibited TNF-induced VCAM-1 cell-surface expression in a concentration-dependent fashion with half-maximal inhibition at 19 mumol/L but had no effect on ICAM-1 expression. Another structurally distinct flavonoid, 2-phenyl-chromene-4-one, similarly selectively decreased VCAM-1 expression. The inhibition in cell-surface expression of VCAM-1 by PD 098063 correlated with decreases in steady-state mRNA levels, but there was no effect on ICAM-1 mRNA levels. The decrease in VCAM-1 mRNA levels was not due to changes in mRNA stability but rather resulted from a reduction in the rate of transcription of the gene. However, electrophoretic mobility shift assays using nuclear extracts from TNF-induced HAECs treated with PD 098063 failed to show a decrease in the activation of NF-kappa B, indicating that inhibition of activation of this transcription factor may not be its mode of action. Similarly, PD 098063 did not affect chloramphenicol acetyltransferase reporter gene activity in TNF-inducible minimal VCAM-1 promoter constructs containing two NF-kappa B sites, suggesting that the compound does not affect the transactivation driven by these sites. We conclude that this compound selectively blocks agonist-induced VCAM-1 protein and gene expression in HAECs by NF-kappa B-independent mechanism(s).

We recently described our initial structure-activity relationship (SAR) studies on a series of N-phenyl-N'-aralkyl- and N-phenyl-N'-(1-phenylcycloalkyl)ureas as inhibitors of acyl-CoA: cholesterol acyltransferase (ACAT). From this series of analogs, compound 1 (PD 129337) was identified as a potent inhibitor of ACAT with an IC50 value of 17 nM. It was also shown to dose-dependently lower plasma cholesterol in cholesterol-fed rats. However, further investigation led to the suggestion that this compound was poorly absorbed, due to a lack of efficacy when administered by gavage in an aqueous vehicle. To overcome this deficiency, we continued our SAR study on this novel series of ACAT inhibitors using an acute in vivo screen in which the compounds are administered to rats in an aqueous, CMC/Tween suspension vehicle. Modification of the N'-phenyl moiety by incorporating functional groups which were amenable to forming salts and/or polar groups to reduce lipophilicity led to the identification of several inhibitors which displayed excellent efficacy employing this protocol. Overall, substitution on the phenyl ring in the ortho, meta, or para positions led to inhibitors with only a slight decrease in potency in vitro compared to the parent unsubstituted compound. Bulkier groups in the para position tended to lower the ACAT inhibitory activity in vitro. Polar groups, such as carboxyl (33,34), lowered in vitro activity significantly, suggesting that polar-ionic interactions are disfavored for the enzyme activity. From this series, compound 28 was evaluated further in secondary in vivo screens. In a chronic cholesterol-fed rat model of hypercholesterolemia, compound 28 dose-dependently reduced nonHDL cholesterol and significantly elevated HDL cholesterol. It showed significantly greater aqueous solubility than the parent compound 1. However, it was shown to cause adrenal toxicity in guinea pigs. This led us to design a series of homologs (44-51) with increased basicity and lower lipophilicity. Some of these compounds were more potent ACAT inhibitors in vitro and demonstrated excellent hypocholesterolemic activity in vivo. Interestingly, compound 45, unlike 28, did not produce adrenal toxicity in guinea pigs and demonstrated excellent lipid-modulating activity in the chronic model of preestablished dyslipidemia in rats.

We have synthesized a series of N-phenyl-N'-aralkyl and N-phenyl-N'-(1-phenylcycloalkyl)ureas as inhibitors of acyl-CoA:cholesterol acyltransferase (ACAT). This intracellular enzyme is thought to be responsible for the esterification of dietary cholesterol; hence inhibition of this enzyme could reduce diet-induced hypercholesterolemia. For this series of compounds, the in vitro ACAT inhibitory activity was improved by increasing the bulk of the 2,6-substituents on the phenyl ring. Additionally, we found that spacing of the aromatic rings was critical for ACAT inhibitory activity. A phenyl ring five atoms away from the requisite 2,6-diisopropylphenyl moiety was optimal for in vitro activity. Substitution alpha to the N'-phenyl moiety enhanced in vitro potency. In the case of phenylcycloalkyl ureas, ACAT inhibitory activity was independent of the size of the cycloalkyl ring. From this series of analogs, compound 25, which had excellent in vitro potency for inhibiting ACAT, was found to lower plasma cholesterol by 73% in vivo when administered in the diet at 50 mg/kg in an animal model of hypercholesterolemia. In this model, compound 25 lowered plasma cholesterol dose dependently and was as efficacious as the Lederle ACAT inhibitor CL 277082.

A study of structure-activity relationships of substituted beta-ketoamide ACAT inhibitors I and II was performed. The results of this study suggest that whereas the beta-keto group was tolerated with no loss in activity, beta-hydroxy and oxime moieties led to significantly reduced activity in vitro and in vivo. The most potent inhibitor from the acyclic series (I) (11, IC50 = 0.006 microM) contained a C-13 alkyl chain. This compound reduced plasma total cholesterol by 38% and 66% at 3 and 30 mg/kg, respectively, in cholesterol-fed rats. Dimethylation alpha to the anilide core (5) and subsequent N-methylation of the amide NH (6) decreased in vitro potency significantly. It was also found that high potency was retained with inhibitors which incorporated the carbonyl into a lactam ring (II).

In order to further define the structural features necessary for potent inhibition of acyl-coenzyme A:cholesterol acyltransferase (ACAT) in vitro and cholesterol lowering in vivo, systematic study of bioisosteric replacements for the amide bond in our previously identified series of fatty acid anilide ACAT inhibitors was undertaken. Only replacement of amide bonds with isosterases having both hydrogen bond donor and acceptor functionalities yielded compounds retaining ACAT inhibitory activity. Replacement of the amide bond with the urea bioisostere yielded compounds that were potent ACAT inhibitors in vitro and efficacious hypocholesterolemic agents in vivo. Examination of the structure activity relationships in the phenyl ring and alkyl portion of the N-phenyl-N'-alkylureas revealed that 2,6-diisopropyl substitution was optimal in the phenyl ring. When the 2,6-diisopropyl moiety was kept constant, potency in vitro and in vivo was maintained with straight and branched alkyl groups from 6 to 18 carbons in length.

A series of fatty acid anilides was prepared, and compounds were tested for their ability to inhibit the enzyme acyl-CoA:cholesterol acyltransferase (ACAT) in vitro and to lower plasma total cholesterol and elevate high-density lipoprotein cholesterol in cholesterol-fed rats in vivo. The compounds reported were found to fall into two subclasses with different anilide SAR. For nonbranched acyl analogues, inhibitory potency was found to be optimal with bulky 2,6-dialkyl substitution. For alpha-substituted acyl analogues, there was little dependence of in vitro potency on anilide substitution and 2,4,6-trimethoxy was uniquely preferred. Most of the potent inhibitors (IC50 less than 50 nM) were found to produce significant reductions in plasma total cholesterol in cholesterol-fed rats. Additionally, in vivo activity could be improved significantly by the introduction of alpha,alpha-disubstitution into the fatty acid portion of the molecule. A narrow group of alpha,alpha-disubstituted trimethoxyanilides, exemplified by 2,2-dimethyl-N-(2,4,6-trimethoxyphenyl)dodecanamide (39), was found to not only lower plasma total cholesterol (-60%) in cholesterol-fed rats but also elevate levels of high-density lipoprotein cholesterol (+94%) in this model at the screening dose of 0.05% in the diet (ca. 50 mg/kg).

Studies were performed to develop techniques to assess renin mRNA in a single microdissected juxtaglomerular apparatus (JGA) of rabbit using the polymerase chain reaction (PCR) method of amplification of cDNA sequences. In preliminary studies synthetic oligonucleotide primers corresponding to regions in the rat renin cDNA sequence, which are highly conserved between mouse, rat, and man, were found to yield good amplification efficiency with a rat renin cDNA template, but little product was observed with rabbit cDNA template. We therefore employed a nested primer PCR cloning technique to clone an 839 base pair portion of the rabbit renin cDNA to obtain species-specific sequence information for primer design. Here we report the nucleotide sequence of a partial rabbit renin cDNA clone and the use of species-specific primers that permit semiquantitative assessment of rabbit mRNA levels in the single JGA.

The synthesis for trans and cis tricyclic bis(dioxopiperazine)s 5 and 6 from pyrazine-2,3-dicarboxamide (7) is described. Stereoselective antimetastatic activity differences for these analogues were observed following pretreatment of B16-F10 melanoma cells in vitro. Activities for these isomers were compared with selected intermediates, and the data are discussed in relation to previous results obtained with cis- and trans-cyclopropane analogues.

Several [1,2,4]triazolo[4,3-a]quinoxalines that were reported as antidepressants in the patent literature were found to possess moderate affinity for the adenosine A1 and A2 receptors. On the basis of structural parallels with adenine and adenosine, the N-cyclopentyl derivative was synthesized and found to have improved affinity and selectivity for the A1 receptor. In the N-cyclopentyl series, affinity was optimal with trifluoromethyl substitution at the 1-position, resulting in a compound (9) with 7.3 nM A1 affinity and 138-fold selectivity for the A1 receptor.

Extracellular adenosine receptors have been divided into two major subtypes, called A1 and A2. Substitution of the adenosine molecule with appropriate groups at C2 or N6 is known to impart selectivity for the A2 receptor over the A1 receptor. In the present study, we investigated whether substitution at both C2 and N6 would have additive effects on the A2/A1 affinity ratio, thereby providing compounds with greater A2 selectivity than presently available agents. Disappointingly, additivity appeared to hold only when an A1-selective group was present at N6. For instance, 2-(phenylamino) substitution of the A1-selective agonist N6-cyclopentyladenosine resulted in a 70-fold shift in selectivity in favor of the A2 receptor, but the same substitution applied to the A2-selective agonist N6-[2-(3,5-dimethoxyphenyl)-2-(2-methylphenyl)ethyl]adenosine resulted in a 100-fold loss of affinity with no change in A2 selectivity.

Geometric isomers of 2,11-bis(morpholinomethyl)tetrahydrodipyrazino[1,2-a:2',1'-c]pyraz ine-1, 3,10,12-(2H,4H,9H,11H)-tetrone (3 and 4) and the parent bisimides (1 and 2) were studied for their stereoselective antimetastatic activity in the Lewis Lung carcinoma model. The morpholinomethyl cis-syn-trans isomer 4 was more effective as an inhibitor of metastasis than the other three analogues. Using a postamputation protocol, the order of decreasing activity was cis morpholinomethyl analogue 4 greater than trans morpholinomethyl analogue 3 greater than parent cis imide 2 greater than parent trans imide 1. Increased activity observed for the morpholinomethyl derivatives may reflect differences in solubility and delivery (prodrug) or an intrinsic antitumor activity of the morpholinomethyl-N functionality.