Adrian Wai-Hing Cheung

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).

Structure–Activity relationship of linear peptide Bu-His-DPhe-Arg-Trp-Gly-NH2 at the human melanocortin-1 and -4 receptors: histidine substitution

Systematic substitution of His(6) residue using non-selective hMC4R pentapeptide agonist (Bu-His(6)-DPhe(7)-Arg(8)-Trp(9)-Gly(10)-NH(2)) as the template led to the identification of Bu-Atc(6)(2-aminotetraline-2-carboxylic acid)-DPhe(7)-Arg(8)-Trp(9)-Gly(10)-NH(2) which showed moderate selectivity towards hMC4R over hMC1R. Further SAR studies resulted in the discovery of Penta-5-BrAtc(6)-DPhe(7)-Arg(8)-Trp(9)-Gly(10)-NH(2) and Penta-5-Me(2)NAtc(6)-DPhe(7)-Arg(8)-Trp(9)-Gly(10)-NH(2) which are potent hMC4R agonists and are inactive in hMC1R, hMC3R and hMC5R agonist assays.

Structure-activity relationship of linear peptide Bu-His6-DPhe7-Arg8-Trp9-Gly10-NH2 at the human melanocortin-1 and -4 receptors: DPhe7 and Trp9 substitution.

A series of pentapeptides, based on hMC4R pentapeptide agonist (Bu-His(6)-DPhe(7)-Arg(8)-Trp(9)-Gly(10)-NH(2)), was prepared in which either DPhe(7) or Trp(9) residue was systematically substituted. A number of interesting DPhe surrogates (D-Thi, D-3-CF(3)Phe, D-2-Nal and D-3,4-diClPhe) as well as Trp surrogates (2-Nal and Bta) were identified in this study.

Structure–activity relationship of cyclic peptide penta-c[Asp-His6-DPhe7-Arg8-Trp9-Lys]-NH2 at the human melanocortin-1 and -4 receptors: His6 substitution

A series of MT-II related cyclic peptides, based on potent but non-selective hMC4R agonist (Penta-c[Asp-His(6)-DPhe(7)-Arg(8)-Trp(9)-Lys]-NH(2)) was prepared in which His(6) residue was systematically substituted. Two of the most interesting peptides identified in this study are Penta-c[Asp-5-ClAtc-DPhe-Arg-Trp-Lys]-NH(2) and Penta-c[Asp-5-ClAtc-DPhe-Cit-Trp-Lys]-NH(2) which are potent hMC4R agonists and are either inactive or weak partial agonists (not tested for their antagonist activities) in hMC1R, hMC3R and hMC5R agonist assays.

7-Phenyl-pyrido[2,3-d]pyrimidine-2,4-diamines: novel and highly selective protein tyrosine phosphatase 1B inhibitors.

High throughput screening of the Roche compound collection led to the identification of diaminopyrroloquinazoline series as a novel class of PTP1B inhibitors. Structural modification of diaminopyrroloquinazoline series resulted in pyrido[2,3-d]pyrimidine-2,4-diamine series which was further optimized to give compounds 5 and 24 as potent, selective (except T-cell phosphatase) PTP1B inhibitors with good mouse PK properties.

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.

Identification of an Adamantyl Azaquinolone JNK Selective Inhibitor.

3-[4-((1S,2S,3R,5S,7S)-5-Hydroxyadamantan-2-ylcarbamoyl)benzyl]-4-oxo-1-phenyl-1,4-dihydro-[1,8]naphthyridine-2-carboxylic acid methyl ester (4) was identified as a novel, druglike and selective quinolone pan JNK inhibitor. In this communication, some of the structure-activity relationship of the azaquinolone analogues leading to 4 is discussed. The focus is on how changes at the amide functionality affected the biochemical potency, cellular potency, metabolic properties, and solubility of this class of JNK inhibitors. Optimization of these properties led to the identification of the adamantyl analogue, 4. 4 achieved proof of mechanism in both rat and mouse TNF-α challenge models.

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.