Cholesteryl ester transfer protein (CETP) inhibitors based on cyclic urea, bicyclic urea and bicyclic sulfamide cores.

Cholesteryl ester transfer protein (CETP) inhibitors reduce the transfer of cholesteryl esters from the high-density lipoprotein (HDL-C) to apolipoprotein such as VLDL/LDL, with exchange of triglycerides. Thus, this inhibition increases the HDL-C levels, which is believed to lower the risk for heart disease and stroke. We report here a series of CETP inhibitors based on the cyclic, bicyclic urea and sulfamide cores. These CETP inhibitors exemplified by 15, 31, and 45 demonstrated in vitro potency in inhibiting the CETP transfer activity, and 15, 31 showing in vivo efficacy to increase HDL-C levels in cynomolgus-CETP transgenic mice. The synthesis and biological evaluations of these CETP inhibitors are described.

Accelerating the discovery of DGAT1 inhibitors through the application of parallel medicinal chemistry (PMC).

The parallel medicinal chemistry (PMC) was effectively applied to accelerate the optimization of diacylglycerol O-acyltransferase I (DGAT-1) inhibitors. Through a highly collaborative and iterative library design, synthesis and testing, a benzimidazole lead was rapidly and systematically advanced to a highly potent, selective and bioavailable DGAT1 inhibitor with the potential for further development.

Benzimidazole-based DGAT1 inhibitors with a [3.1.0] bicyclohexane carboxylic acid moiety.

Previously disclosed benzimidazole-based DGAT1 inhibitors containing a cyclohexane carboxylic acid moiety suffer from isomerization at the alpha position of the carboxylic acid group, generating active metabolites which exhibit DGAT1 inhibition comparable to the corresponding parent compounds. In this report, we describe the design, synthesis and profiling of benzimidazole-based DGAT1 inhibitors with a [3.1.0] bicyclohexane carboxylic acid moiety. Our results show that single isomer 3A maintains in vitro and in vivo inhibition against DGAT1. In contrast to previous lead compounds, 3A does not undergo isomerization during in vitro hepatocyte incubation study or in vivo mouse study.

Effects of small interfering RNA-mediated hepatic glucagon receptor inhibition on lipid metabolism in db/db mice.

Hepatic glucose overproduction is a major characteristic of type 2 diabetes. Because glucagon is a key regulator for glucose homeostasis, antagonizing the glucagon receptor (GCGR) is a possible therapeutic strategy for the treatment of diabetes mellitus. To study the effect of hepatic GCGR inhibition on the regulation of lipid metabolism, we generated siRNA-mediated GCGR knockdown (si-GCGR) in the db/db mouse. The hepatic knockdown of GCGR markedly reduced plasma glucose levels; however, total plasma cholesterol was increased. The detailed lipid analysis showed an increase in the LDL fraction, and no change in VLDL HDL fractions. Further studies showed that the increase in LDL was the result of over-expression of hepatic lipogenic genes and elevated de novo lipid synthesis. Inhibition of hepatic glucagon signaling via siRNA-mediated GCGR knockdown had an effect on both glucose and lipid metabolism in db/db mice.

Use of [13C18] oleic acid and mass isotopomer distribution analysis to study synthesis of plasma triglycerides in vivo: analytical and experimental considerations.

We have previously reported on a liquid chromatography-mass spectrometry method to determine the disposition of [(13)C18]-oleic acid following intravenous and oral administration in vivo. This approach has enabled us to study a variety of aspects of lipid metabolism including a quantitative assessment of triglyceride synthesis. Here we present a more rigorous evaluation of the constraints imposed upon the analytical method in order to generate accurate data using this stable-isotope tracer approach along with more detail on relevant analytical figures of merit including limits of quantitation, precision, and accuracy. The use of mass isotopomer distribution analysis (MIDA) to quantify plasma triglyceride synthesis is specifically highlighted, and a re-evaluation of the underlying mathematics has enabled us to present a simplified series of equations. The derivation of this MIDA model and the significance of all underlying assumptions are explored in detail, and examples are given of how it can successfully be applied to detect differences in plasma triglyceride synthesis in lean and high-fat diet fed mouse models. More work is necessary to evaluate the applicability of this approach to triglyceride stores with slower rates of turnover such as in adipose or muscle tissue; however, the present report provides investigators with the tools necessary to conduct such studies.

Structure-activity relationship of linear tetrapeptides Tic-DPhe-Arg-Trp-NH2 at the human melanocortin-4 receptor and effects on feeding behaviors in rat.

The melanocortin subtype-4 receptor (MC4R) has been implicated in the control of feeding behavior and body weight regulation. A series of tetrapeptides, based on Tic-DPhe-Arg-Trp-NH2-a mimic of the putative message sequence "His-Phe-Arg-Trp" and modified at the DPhe position, were prepared and pharmacologically characterized for potency and selectivity. Substitution of His with Tic gave peptides with significant increases in selectivity. The effects of the substitution pattern of DPhe were investigated and it has significant influences on potency and the level of the maximum cAMP accumulation. Intracerebroventricular administration of peptide 10 induced significant inhibition of cumulative overnight food intake and feeding duration in rats.

Potent DGAT1 Inhibitors in the Benzimidazole Class with a Pyridyl-oxy-cyclohexanecarboxylic Acid Moiety.

We report the design and synthesis of a series of novel DGAT1 inhibitors in the benzimidazole class with a pyridyl-oxy-cyclohexanecarboxylic acid moiety. In particular, compound 11A is a potent DGAT1 inhibitor with excellent selectivity against ACAT1. Compound 11A significantly reduces triglyceride excursion in lipid tolerance tests (LTT) in both mice and dogs at low plasma exposure. An in vivo study in mice with des-fluoro analogue 10A indicates that this series of compounds appears to distribute in intestine preferentially over plasma. The propensity to target intestine over plasma could be advantageous in reducing potential side effects since lower circulating levels of drug are required for efficacy. However, in the preclinical species, compound 11A undergoes cis/trans epimerization in vivo, which could complicate further development due to the presence of an active metabolite.

Contribution of the tetrodotoxin-resistant voltage-gated sodium channel NaV1.9 to sensory transmission and nociceptive behavior.

The transmission of pain signals after injury or inflammation depends in part on increased excitability of primary sensory neurons. Nociceptive neurons express multiple subtypes of voltage-gated sodium channels (NaV1s), each of which possesses unique features that may influence primary afferent excitability. Here, we examined the contribution of NaV1.9 to nociceptive signaling by studying the electrophysiological and behavioral phenotypes of mice with a disruption of the SCN11A gene, which encodes NaV1.9. Our results confirm that NaV1.9 underlies the persistent tetrodotoxin-resistant current in small-diameter dorsal root ganglion neurons but suggest that this current contributes little to mechanical thermal responsiveness in the absence of injury or to mechanical hypersensitivity after nerve injury or inflammation. However, the expression of NaV1.9 contributes to the persistent thermal hypersensitivity and spontaneous pain behavior after peripheral inflammation. These results suggest that inflammatory mediators modify the function of NaV1.9 to maintain inflammation-induced hyperalgesia.