Discovery of benzothiazole-based adenosine A2B receptor antagonists with improved A2A selectivity.

The highly potent but modestly selective N-(2-amino-4-methoxy-benzothiazol-7-yl)-N-ethyl-acetamide derivative 2 was selected as the starting point for the design of novel selective A(2B) antagonists, due to its excellent potency, and good drug-like properties. A series of compounds containing nonaromatic amides or ureas of five- or six-membered rings, and also bearing an m-trifluoromethyl-phenyl group (shown to impart superior potency) was prepared and evaluated for their selectivity against the A(2A) and A(1) receptors. This work resulted in the identification of compound 30, with excellent potency and high selectivity against both A(2A) and A(1) receptors.

Discovery of orally active carboxylic acid derivatives of 2-phenyl-5-trifluoromethyloxazole-4-carboxamide as potent diacylglycerol acyltransferase-1 inhibitors for the potential treatment of obesity and diabetes.

Diacylglycerol acyltransferase-1 (DGAT-1) is the enzyme that catalyzes the final and committed step of triglyceride formation, namely, the acylation of diacylglycerol with acyl coenzyme A. DGAT-1 deficient mice demonstrate resistance to weight gain on high fat diet, improved insulin sensitivity, and reduced liver triglyceride content. Inhibition of DGAT-1 thus represents a potential novel approach for the treatment of obesity, dyslipidemia, and metabolic syndrome. In this communication, we report the identification of the lead structure 6 and our lead optimization efforts culminating in the discovery of potent, selective, and orally efficacious carboxylic acid derivatives of 2-phenyl-5-trifluoromethyloxazole-4-carboxamides. In particular, compound 29 (DGAT-1 enzyme assay, IC(50) = 57 nM; CHO-K1 cell triglyceride formation assay, EC(50) = 0.5 µM) demonstrated dose dependent inhibition of weight gain in diet induced obese (DIO) rats (0.3, 1, and 3 mg/kg, p.o., qd) during a 21-day efficacy study. Furthermore, compound 29 demonstrated improved glucose tolerance determined by an oral glucose tolerance test (OGTT).

4-Substituted-7-N-alkyl-N-acetyl 2-aminobenzothiazole amides: drug-like and non-xanthine based A2B adenosine receptor antagonists.

7-N-Acetamide-4-methoxy-2-aminobenzothiazole 4-fluorobenzamide (compound 1) was chosen as a drug-like and non-xanthine based starting point for the discovery of A(2B) receptor antagonists because of its slight selectivity against A(1) and A(2A) receptors and modest A(2B) potency. SAR exploration of compound 1 described herein included modifications to the 7-N-acetamide group, substitution of the 4-methoxy group by halogens as well as replacement of the p-flouro-benzamide side chain. This work culminated in the identification of compound 37 with excellent A(2B) potency, modest selectivity versus A(2A) and A(1) receptors, and good rodent PK properties.

C-8 Modifications of 3-alkyl-1,8-dibenzylxanthines as inhibitors of human cytosolic phosphoenolpyruvate carboxykinase.

New modifications on the C-8 4-aminobenzyl unit of the previously reported 3-alkyl-1,8-dibenzylxanthine inhibitors of cPEPCK are presented. The most active compound reported here is the 5-chloro-1,3-dimethyl-1H-pyrazole-4-sulfonic acid amide derivative 2 with an IC(50) of 0.29+/-0.08 microM. An X-ray analysis of a heteroaromatic sulfonamide is presented showing a new pi-pi interaction.

X-ray structures of two xanthine inhibitors bound to PEPCK and N-3 modifications of substituted 1,8-dibenzylxanthines.

The analysis of the X-ray structures of two xanthine inhibitors bound to PEPCK and a comparison to the X-ray structure of GTP bound to PEPCK are reported. The SAR at N-1, N-7 and developing SAR at C-8 are consistent with information gained from the X-ray structures of compounds 1 and 2 bound to PEPCK. Representative N-3 modifications of compound 2 that led to the discovery of 3-cyclopropylmethyl and its carboxy analogue as optimal N-3 groups are presented.

Modified 3-alkyl-1,8-dibenzylxanthines as GTP-competitive inhibitors of phosphoenolpyruvate carboxykinase.

The first non-substrate like inhibitors of human cytosolic phosphoenolpyruvate carboxykinase (PEPCK) competitive with GTP are reported. An effort to discover orally active compounds that improve glucose homeostasis in Type 2 diabetics by reversibly inhibiting PEPCK led to the discovery of 1-allyl-3-butyl-8-methylxanthine (5). We now report modifications at N-1 and C-8 that improved the in vitro activity of the initial xanthine HTS hit by 100-fold and a developing SAR for this class of inhibitor.

Crystal structure of human cytosolic phosphoenolpyruvate carboxykinase reveals a new GTP-binding site.

We report crystal structures of the human enzyme phosphoenolpyruvate carboxykinase (PEPCK) with and without bound substrates. These structures are the first to be determined for a GTP-dependent PEPCK, and provide the first view of a novel GTP-binding site unique to the GTP-dependent PEPCK family. Three phenylalanine residues form the walls of the guanine-binding pocket on the enzyme's surface and, most surprisingly, one of the phenylalanine side-chains contributes to the enzyme's specificity for GTP. PEPCK catalyzes the rate-limiting step in the metabolic pathway that produces glucose from lactate and other precursors derived from the citric acid cycle. Because the gluconeogenic pathway contributes to the fasting hyperglycemia of type II diabetes, inhibitors of PEPCK may be useful in the treatment of diabetes.