Nicotinic acid and DP1 blockade: studies in mouse models of atherosclerosis.

The use of nicotinic acid to treat dyslipidemia is limited by induction of a "flushing" response, mediated in part by the interaction of prostaglandin D(2) (PGD(2)) with its G-protein coupled receptor, DP1 (Ptgdr). The impact of DP1 blockade (genetic or pharmacologic) was assessed in experimental murine models of atherosclerosis. In Ptgdr(-/-)ApoE(-/-) mice versus ApoE(-/-) mice, both fed a high-fat diet, aortic cholesterol content was modestly higher (1.3- to 1.5-fold, P < 0.05) in Ptgdr(-/-)ApoE(-/-) mice at 16 and 24 weeks of age, but not at 32 weeks. In multiple ApoE(-/-) mouse studies, a DP1-specific antagonist, L-655, generally had a neutral to beneficial effect on aortic lipids in the presence or absence of nicotinic acid treatment. In a separate study, a modest increase in some atherosclerotic measures was observed with L-655 treatment in Ldlr(-/-) mice fed a high-fat diet for 8 weeks; however, this effect was not sustained for 16 or 24 weeks. In the same study, treatment with nicotinic acid alone generally decreased plasma and/or aortic lipids, and addition of L-655 did not negate those beneficial effects. These studies demonstrate that inhibition of DP1, with or without nicotinic acid treatment, does not lead to consistent or sustained effects on plaque burden in mouse atherosclerotic models.

Plasma lipid profiling across species for the identification of optimal animal models of human dyslipidemia.

In an attempt to understand the applicability of various animal models to dyslipidemia in humans and to identify improved preclinical models for target discovery and validation for dyslipidemia, we measured comprehensive plasma lipid profiles in 24 models. These included five mouse strains, six other nonprimate species, and four nonhuman primate (NHP) species, and both healthy animals and animals with metabolic disorders. Dyslipidemic humans were assessed by the same measures. Plasma lipoprotein profiles, eight major plasma lipid fractions, and FA compositions within these lipid fractions were compared both qualitatively and quantitatively across the species. Given the importance of statins in decreasing plasma low-density lipoprotein cholesterol for treatment of dyslipidemia in humans, the responses of these measures to simvastatin treatment were also assessed for each species and compared with dyslipidemic humans. NHPs, followed by dog, were the models that demonstrated closest overall match to dyslipidemic humans. For the subset of the dyslipidemic population with high plasma triglyceride levels, the data also pointed to hamster and db/db mouse as representative models for practical use in target validation. Most traditional models, including rabbit, Zucker diabetic fatty rat, and the majority of mouse models, did not demonstrate overall similarity to dyslipidemic humans in this study.

The design and synthesis of potent, selective benzodiazepine sulfonamide bombesin receptor subtype 3 (BRS-3) agonists with an increased barrier of atropisomerization.

Bombesin receptor subtype 3 (BRS-3) is an orphan G-protein coupled receptor expressed primarily in the hypothalamus which plays a role in the onset of both diabetes and obesity. We report herein our progress made towards identifying a potent, selective bombesin receptor subtype-3 (BRS-3) agonist related to the previously described MK-7725(1) Chobanian et al. (2012) that would prevent atropisomerization through the increase of steric bulk at the C-2 position. This would thereby make clinical development of this class of compounds more cost effective by inhibiting racemization which can occur over long periods of time at room/elevated temperature.

Improved efficacy for ezetimibe and rosuvastatin by attenuating the induction of PCSK9.

Reducing circulating LDL-cholesterol (LDL-c) reduces the risk of cardiovascular disease in people with hypercholesterolemia. Current approaches to reduce circulating LDL-c include statins, which inhibit cholesterol synthesis, and ezetimibe, which blocks cholesterol absorption. Both elevate serum PCSK9 protein levels in patients, which could attenuate their efficacy by reducing the amount of cholesterol cleared from circulation. To determine whether PCSK9 inhibition could enhance LDL-c lowering of both statins and ezetimibe, we utilized small interfering RNAs (siRNAs) to knock down Pcsk9, together with ezetimibe, rosuvastatin, and an ezetimibe/rosuvastatin combination in a mouse model with a human-like lipid profile. We found that ezetimibe, rosuvastatin, and ezetimibe/rosuvastatin combined lower serum cholesterol but induce the expression of Pcsk9 as well as the Srebp-2 hepatic cholesterol biosynthesis pathway. Pcsk9 knockdown in combination with either treatment led to greater reductions in serum non-HDL with a near-uniform reduction of all LDL-c subfractions. In addition to reducing serum cholesterol, the combined rosuvastatin/ezetimibe/Pcsk9 siRNA treatment exhibited a significant reduction in serum APOB protein and triglyceride levels. Taken together, these data provide evidence that PCSK9 inhibitors, in combination with current therapies, have the potential to achieve greater reductions in both serum cholesterol and triglycerides.

The use of stable-isotopically labeled oleic acid to interrogate lipid assembly in vivo: assessing pharmacological effects in preclinical species.

The use of stable isotopically labeled substrates and analysis by mass spectrometry have provided substantial insight into rates of synthesis, disposition, and utilization of lipids in vivo. The information to be gained from such studies is of particular benefit to therapeutic research where the underlying causes of disease may be related to the production and utilization of lipids. When studying biology through the use of isotope tracers, care must be exercised in interpreting the data to ensure that any response observed can truly be interpreted as biological and not as an artifact of the experimental design or a dilutional effect on the isotope. We studied the effects of dosing route and tracer concentration on the mass isotopomer distribution profile as well as the action of selective inhibitors of microsomal tri-glyceride transfer protein (MTP) in mice and diacylglycerol acyltransferase 1 (DGAT1) in nonhuman primates, using a stable-isotopically labeled approach. Subjects were treated with inhibitor and subsequently given a dose of uniformly ¹³C-labeled oleic acid. Samples were analyzed using a rapid LC-MS technique, allowing the effects of the intervention on the assembly and disposition of triglycerides, cholesteryl esters, and phospholipids to be determined in a single 3 min run from just 10 µl of plasma.

11beta-HSD1 inhibition ameliorates metabolic syndrome and prevents progression of atherosclerosis in mice.

The enzyme 11beta-hydroxysteroid dehydrogenase (HSD) type 1 converts inactive cortisone into active cortisol in cells, thereby raising the effective glucocorticoid (GC) tone above serum levels. We report that pharmacologic inhibition of 11beta-HSD1 has a therapeutic effect in mouse models of metabolic syndrome. Administration of a selective, potent 11beta-HSD1 inhibitor lowered body weight, insulin, fasting glucose, triglycerides, and cholesterol in diet-induced obese mice and lowered fasting glucose, insulin, glucagon, triglycerides, and free fatty acids, as well as improved glucose tolerance, in a mouse model of type 2 diabetes. Most importantly, inhibition of 11beta-HSD1 slowed plaque progression in a murine model of atherosclerosis, the key clinical sequela of metabolic syndrome. Mice with a targeted deletion of apolipoprotein E exhibited 84% less accumulation of aortic total cholesterol, as well as lower serum cholesterol and triglycerides, when treated with an 11beta-HSD1 inhibitor. These data provide the first evidence that pharmacologic inhibition of intracellular GC activation can effectively treat atherosclerosis, the key clinical consequence of metabolic syndrome, in addition to its salutary effect on multiple aspects of the metabolic syndrome itself.

Antiobesity effect of MK-5046, a novel bombesin receptor subtype-3 agonist.

Bombesin receptor subtype-3 (BRS-3) is an orphan G protein-coupled receptor implicated in the regulation of energy homeostasis. Here, we report the biologic effects of a highly optimized BRS-3 agonist, (2S)-1,1,1-trifluoro-2-[4-(1H-pyrazol-1-yl)phenyl]-3-(4-{[1-(trifluoromethyl)cyclopropyl]methyl}-1H-imidazol-2-yl)propan-2-ol (MK-5046). Single oral doses of MK-5046 inhibited 2-h and overnight food intake and increased fasting metabolic rate in wild-type but not Brs3 knockout mice. Upon dosing for 14 days, MK-5046 at 25 mg · kg(-1) · day(-1) reduced body weight of diet-induced obese mouse by 9% compared with vehicle-dosed controls. In mice, 50% brain receptor occupancy was achieved at a plasma concentration of 0.34 ± 0.23 µM. With chronic dosing, effects on metabolic rate, rather than food intake, seem to be the predominant mechanism for weight reduction by MK-5046. The compound also effectively reduced body weight in rats and caused modest increases in body temperature, heart rate, and blood pressure. These latter effects on temperature, heart rate, and blood pressure were transient in nature and desensitized with continued dosing. MK-5046 is the first BRS-3 agonist with properties suitable for use in larger mammals. In dogs, MK-5046 treatment produced statistically significant and persistent weight loss, which was initially accompanied by increases in body temperature and heart rate that abated with continued dosing. Our results demonstrate antiobesity efficacy for MK-5046 in rodents and dogs and further support BRS-3 agonism as a new approach to the treatment of obesity.

The effects of simvastatin treatment on plasma lipid-related biomarkers in men with dyslipidaemia.

BACKGROUND: Lipidomic biomarkers will facilitate the development of novel anti-atherosclerotic therapies. OBJECTIVE: To evaluate the responses of circulating biomarkers to simvastatin treatment. METHODS: A randomized, cross-over study in men with mixed dyslipidaemia was used to compare effects of simvastatin 40 mg/day with placebo. RESULTS: Plasma concentrations of nine fatty acids (FA; of 33 evaluated) were reduced significantly by simvastatin. No changes in the rates of FA synthesis or in hepatic lipase or lipoprotein lipase activities were apparent. Circulating proprotein convertase subtilisin/kexin type 9 (PCSK9) levels increased. CONCLUSION: We identified lipidomic biomarkers of simvastatin treatment effect that are consistent with statin inhibition of 3-hydroxy-3-methyl-glutaryl coenzyme A (HMG-CoA) reductase (ClinicalTrials.gov: NCT00935259).

Discovery of pyrimidine carboxamides as potent and selective CCK1 receptor agonists.

A series of six-membered heterocycle carboxamides were synthesized and evaluated as cholecystokinin 1 receptor (CCK1R) agonists. A pyrimidine core proved to be the best heterocycle, and SAR studies resulted in the discovery of analog 5, a potent and structurally diverse CCK1R agonist.

Discovery of a piperazine urea based compound as a potent, selective, orally bioavailable melanocortin subtype-4 receptor partial agonist.

We report the discovery of piperazine urea based compound 1, a potent, selective, orally bioavailable melanocortin subtype-4 receptor partial agonist. Compound 1 shows anti-obesity efficacy without potentiating erectile activity in the rodent models.

Body temperature as a mouse pharmacodynamic response to bombesin receptor subtype-3 agonists and other potential obesity treatments.

Treatment of rodents with a bombesin receptor subtype-3 (BRS-3) agonist reduces food intake and increases fasting metabolic rate, causing weight loss with continued treatment. In small mammals, core body temperature (T(b)) is regulated in part by nutritional status, with a reduced T(b) during fasting. We report that fed Brs3 knockout mice have a lower T(b), which is discordant with their nutritional status. Treatment of wild-type mice with a BRS-3 agonist increased T(b), more so when the baseline T(b) was reduced such as by fasting or during the inactive phase of the light cycle. With repeated BRS-3 agonist dosing, the T(b) increase attenuated despite continued weight loss efficacy. The increase in T(b) was not prevented by inhibitors of prostaglandin E (PGE) production but was partially reduced by a ß-adrenergic blocker. These results demonstrate that BRS-3 has a role in body temperature regulation, presumably secondary to its effect on energy metabolism, including effects on sympathetic tone. By making use of this phenomenon, the reversal of the fasting T(b) reduction was developed into a sensitive single-dose pharmacodynamic assay for BRS-3 agonism and other antiobesity compounds acting by various mechanisms, including sibutramine, cannabinoid-1, and melanin-concentrating hormone-1 receptor blockers, and melanocortin, ß3-adrenergic, and cholecystokinin-1 receptor agonists. These drugs increased both the fasted T(b) and the fasted, resting metabolic rates. The T(b) assay is a robust, information-rich assay that is simpler and has a greater throughput than measuring metabolic rate and is a practical, effective tool for drug discovery.

Dihydro-pyrano[2,3-b]pyridines and tetrahydro-1,8-naphthyridines as CB1 receptor inverse agonists: synthesis, SAR and biological evaluation.

Synthesis and structure-activity relationships of cannabinoid-1 receptor (CB1R) inverse agonists based on dihydro-pyrano[2,3-b] pyridine and tetrahydro-1,8-naphtyridine scaffolds are presented. Rat food intake and pharmacokinetic evaluation of 13g, 13i, 13k and 17a revealed these compounds to be highly efficacious orally active modulators of CB1R.

Furo[2,3-b]pyridine-based cannabinoid-1 receptor inverse agonists: synthesis and biological evaluation. Part 1.

The synthesis, SAR and binding affinities of cannabinoid-1 receptor (CB1R) inverse agonists based on furo[2,3-b]pyridine scaffolds are described. Food intake, mechanism specific efficacy, pharmacokinetic, and metabolic evaluation of several of these compounds indicate that they are effective orally active modulators of CB1R.

Discovery of potent, selective, and orally bioavailable 3H-spiro[isobenzofuran-1,4'-piperidine] based melanocortin subtype-4 receptor agonists.

Design, synthesis, and SAR of a series of 3H-spiro[isobenzofuran-1,4'-piperidine] based compounds as potent, selective and orally bioavailable melanocortin subtype-4 receptor (MC4R) agonists are disclosed.

Discovery of highly potent and efficacious MC4R agonists with spiroindane N-Me-1,2,4-triazole privileged structures for the treatment of obesity.

We report an SAR study of MC4R analogs containing spiroindane heterocyclic privileged structures. Compound 26 with N-Me-1,2,4-triazole moiety possesses exceptional potency at MC4R and potent anti-obesity efficacy in a mouse model. However, the efficacy is not completely mediated through MC4R. Additional SAR studies led to the discovery of compound 32, which is more potent at MC4R. Compound 32 demonstrates MC4R mediated anti-obesity efficacy in rodent models.

Discovery of substituted biphenyl imidazoles as potent, bioavailable bombesin receptor subtype-3 agonists.

We report SAR studies on a novel non-peptidic bombesin receptor subtype-3 (BRS-3) agonist lead series derived from high-throughput screening hit RY-337. This effort led to the discovery of compound 22e with significantly improved potency at both rodent and human BRS-3.

Discovery of a spiroindane based compound as a potent, selective, orally bioavailable melanocortin subtype-4 receptor agonist.

We report the design, synthesis and properties of spiroindane based compound 1, a potent, selective, orally bioavailable, non-peptide melanocortin subtype-4 receptor agonist. Compound 1 shows excellent erectogenic activity in the rodent models.

Spiroindane based amides as potent and selective MC4R agonists for the treatment of obesity.

We report a series of potent and selective MC4R agonists based on spiroindane amide privileged structures for potential treatments of obesity. Among the synthetic methods used, Method C allows rapid synthesis of the analogs. The series of compounds can afford high potency on MC4R as well as good rodent pharmacokinetic profiles. Compound 1r (MK-0489) demonstrates MC4R mediated reduction of food intake and body weight in mouse models. Compound 1r is efficacious in 14-day diet-induced obese (DIO) rat models.

ApoA-I mimetic peptides promote pre-ß HDL formation in vivo causing remodeling of HDL and triglyceride accumulation at higher dose.

Reverse cholesterol transport promoted by HDL-apoA-I is an important mechanism of protection against atherosclerosis. We have previously identified apoA-I mimetic peptides by synthesizing analogs of the 22 amino acid apoA-I consensus sequence (apoA-I(cons)) containing non-natural aliphatic amino acids. Here we examined the effect of different aliphatic non-natural amino acids on the structure-activity relationship (SAR) of apoA-I mimetic peptides. These novel apoA-I mimetics, with long hydrocarbon chain (C(5-8)) amino acids incorporated in the amphipathic α helix of the apoA-I(cons), have the following properties: (i) they stimulate in vitro cholesterol efflux from macrophages via ABCA1; (ii) they associate with HDL and cause formation of pre-ß HDL particles when incubated with human and mouse plasma; (iii) they associate with HDL and induce pre-ß HDL formation in vivo, with a corresponding increase in ABCA1-dependent cholesterol efflux capacity ex vivo; (iv) at high dose they associate with VLDL and induce hypertriglyceridemia in mice. These results suggest our peptide design confers activities that are potentially anti-atherogenic. However a dosing regimen which maximizes their therapeutic properties while minimizing adverse effects needs to be established.

From Screening to Targeted Degradation: Strategies for the Discovery and Optimization of Small Molecule Ligands for PCSK9.

Proprotein convertase substilisin-like/kexin type 9 (PCSK9) is a serine protease involved in a protein-protein interaction with the low-density lipoprotein (LDL) receptor that has both human genetic and clinical validation. Blocking this protein-protein interaction prevents LDL receptor degradation and thereby decreases LDL cholesterol levels. Our pursuit of small-molecule direct binders for this difficult to drug PPI target utilized affinity selection/mass spectrometry, which identified one confirmed hit compound. An X-ray crystal structure revealed that this compound was binding in an unprecedented allosteric pocket located between the catalytic and C-terminal domain. Optimization of this initial hit, using two distinct strategies, led to compounds with high binding affinity to PCSK9. Direct target engagement was demonstrated in the cell lysate with a cellular thermal shift assay. Finally, ligand-induced protein degradation was shown with a proteasome recruiting tag attached to the high-affinity allosteric ligand for PCSK9.