Discovery of Potent and Selective Quinoxaline-Based Protease-Activated Receptor 4 (PAR4) Antagonists for the Prevention of Arterial Thrombosis.

PAR4 is a promising antithrombotic target with potential for separation of efficacy from bleeding risk relative to current antiplatelet therapies. In an effort to discover a novel PAR4 antagonist chemotype, a quinoxaline-based HTS hit 3 with low µM potency was identified. Optimization of the HTS hit through the use of positional SAR scanning and the design of conformationally constrained cores led to the discovery of a quinoxaline-benzothiazole series as potent and selective PAR4 antagonists. The lead compound 48, possessing a 2 nM IC50 against PAR4 activation by γ-thrombin in platelet-rich plasma (PRP) and greater than 2500-fold selectivity versus PAR1, demonstrated robust antithrombotic efficacy and minimal bleeding in the cynomolgus monkey models.

Discovery of Potent Protease-Activated Receptor 4 Antagonists with in Vivo Antithrombotic Efficacy.

In an effort to identify novel antithrombotics, we have investigated protease-activated receptor 4 (PAR4) antagonism by developing and evaluating a tool compound, UDM-001651, in a monkey thrombosis model. Beginning with a high-throughput screening hit, we identified an imidazothiadiazole-based PAR4 antagonist chemotype. Detailed structure-activity relationship studies enabled optimization to a potent, selective, and orally bioavailable PAR4 antagonist, UDM-001651. UDM-001651 was evaluated in a monkey thrombosis model and shown to have robust antithrombotic efficacy and no prolongation of kidney bleeding time. This combination of excellent efficacy and safety margin strongly validates PAR4 antagonism as a promising antithrombotic mechanism.

Utilization of an Active Site Mutant Receptor for the Identification of Potent and Selective Atypical 5-HT2C Receptor Agonists.

Agonism of the 5-HT2C receptor represents one of the most well-studied and clinically proven mechanisms for pharmacological weight reduction. Selectivity over the closely related 5-HT2A and 5-HT2B receptors is critical as their activation has been shown to lead to undesirable side effects and major safety concerns. In this communication, we report the development of a new screening paradigm that utilizes an active site mutant D134A (D3.32) 5-HT2C receptor to identify atypical agonist structures. We additionally report the discovery and optimization of a novel class of nonbasic heterocyclic amide agonists of 5-HT2C. SAR investigations around the screening hits provided a diverse set of potent agonists at 5-HT2C with high selectivity over the related 5-HT2A and 5-HT2B receptor subtypes. Further optimization through replacement of the amide with a variety of five- and six-membered heterocycles led to the identification of 6-(1-ethyl-3-(quinolin-8-yl)-1H-pyrazol-5-yl)pyridazin-3-amine (69). Oral administration of 69 to rats reduced food intake in an ad libitum feeding model, which could be completely reversed by a selective 5-HT2C antagonist.

Discovery of 5-chloro-4-((1-(5-chloropyrimidin-2-yl)piperidin-4-yl)oxy)-1-(2-fluoro-4-(methylsulfonyl)phenyl)pyridin-2(1H)-one (BMS-903452), an antidiabetic clinical candidate targeting GPR119.

G-protein-coupled receptor 119 (GPR119) is expressed predominantly in pancreatic ß-cells and in enteroendocrine cells in the gastrointestinal tract. GPR119 agonists have been shown to stimulate glucose-dependent insulin release by direct action in the pancreas and to promote secretion of the incretin GLP-1 by action in the gastrointestinal tract. This dual mechanism of action has generated significant interest in the discovery of small molecule GPR119 agonists as a potential new treatment for type 2 diabetes. Herein, we describe the discovery and optimization of a new class of pyridone containing GPR119 agonists. The potent and selective BMS-903452 (42) was efficacious in both acute and chronic in vivo rodent models of diabetes. Dosing of 42 in a single ascending dose study in normal healthy humans showed a dose dependent increase in exposure and a trend toward increased total GLP-1 plasma levels.

Synthesis and structure-activity relationship of dihydrobenzofuran derivatives as novel human GPR119 agonists.

Through appropriate medicinal chemistry design tactics and computer-assisted conformational modeling, the initial lead A was evolved into a series of dihydrobenzofuran derivatives 3 as potent GPR119 agonists. This Letter describes the optimization of general structure 3, including the substituent(s) on dihydrobenzofuran, the R(1) attachment on right-hand piperidine nitrogen, and the left-hand piperidine/piperazine and its attachment R(2). The efforts led to the identification of compounds 13c and 24 as potent human GPR119 modulators with favorable metabolic stability, ion channel activity, and PXR profiles.

Synthesis and SAR of potent and selective tetrahydropyrazinoisoquinolinone 5-HT(2C) receptor agonists.

The 5-HT2C receptor has been implicated as a critical regulator of appetite. Small molecule activation of the 5-HT2C receptor has been shown to affect food intake and regulate body weight gain in rodent models and more recently in human clinical trials. Therefore, 5-HT2C is a well validated target for anti-obesity therapy. The synthesis and structure-activity relationships of a series of novel tetrahydropyrazinoisoquinolinone 5-HT2C receptor agonists are presented. Several members of this series were identified as potent 5-HT2C receptor agonists with high functional selectivity against the 5-HT2A and 5-HT2B receptors and reduced food intake in an acute rat feeding model upon oral dosing.

Synthesis and SAR of 2,3,3a,4-tetrahydro-1H-pyrrolo[3,4-c]isoquinolin-5(9bH)-ones as 5-HT2C receptor agonists.

A series of 2,3,3a,4-tetrahydro-1H-pyrrolo[3,4-c]isoquinolin-5(9bH)-ones is described, several examples of which exhibit potent 5-HT(2C) agonism with excellent selectivity over the closely related 5-HT(2A) and 5-HT(2B) receptors. Compounds such as 38 and 44 were shown to be effective in reducing food intake in an acute rat feeding model.

Identification of potent 11mer glucagon-like peptide-1 receptor agonist peptides with novel C-terminal amino acids: Homohomophenylalanine analogs.

We report the identification of potent agonists of the Glucagon-Like Peptide-1 Receptor (GLP-1R). These compounds are short, 11 amino acid peptides containing several unnatural amino acids, including (in particular) analogs of homohomophenylalanine (hhPhe) at the C-terminal position. Typically the functional activity of the more potent peptides in this class is in the low picomolar range in an in vitro cAMP assay, with one example demonstrating excellent in vivo activity in an ob/ob mouse model of diabetes.

Tricyclic dihydroquinazolinones as novel 5-HT2C selective and orally efficacious anti-obesity agents.

Agonists of the 5-HT(2C) receptor have been shown to suppress appetite and reduce body weight in animal models as well as in humans. However, agonism of the related 5-HT(2B) receptor has been associated with valvular heart disease. Synthesis and biological evaluation of a series of novel and highly selective dihydroquinazolinone-derived 5-HT(2C) agonists with no detectable agonism of the 5-HT(2B) receptor is described. Among these, compounds (+)-2a and (+)-3c were identified as potent and highly selective agonists which exhibited weight loss in a rat model upon oral dosing.

Discovery of (R)-9-ethyl-1,3,4,10b-tetrahydro-7-trifluoromethylpyrazino[2,1-a]isoindol- 6(2H)-one, a selective, orally active agonist of the 5-HT(2C) receptor.

Robust pharmaceutical treatment of obesity has been limited by the undesirable side-effect profile of currently marketed therapies. This paper describes the synthesis and optimization of a new class of pyrazinoisoindolone-containing, selective 5-HT2C agonists as antiobesity agents. Key to optimization of the pyrazinoisoindolone core was the identification of the appropriate substitution pattern and functional groups which led to the discovery of (R)-9-ethyl-1,3,4,10b-tetrahydro-7-trifluoromethylpyrazino[2,1-a]isoindol-6(2H)-one (58), a 5-HT2C agonist with >300-fold functional selectivity over 5-HT2B and >70-fold functional selectivity over 5-HT2A. Oral dosing of 58 reduced food intake in an acute rat feeding model, which could be completely reversed by a selective 5-HT2C antagonist and caused a reduction in body weight gain in a 4-day rat model.