The Discovery of N-((2H-Tetrazol-5-yl)methyl)-4-((R)-1-((5r,8R)-8-(tert-butyl)-3-(3,5-dichlorophenyl)-2-oxo-1,4-diazaspiro[4.5]dec-3-en-1-yl)-4,4-dimethylpentyl)benzamide (SCH 900822): A Potent and Selective Glucagon Receptor Antagonist

Imidazolone as an Amide Bioisostere in the Development of β-1,3-N-Acetylglucosaminyltransferase 2 (B3GNT2) Inhibitors

B3GNT2 is responsible for elongation of cell surface long-chain polylactosamine, which influences the regulation of the immune response, making it an attractive target for immunomodulation. In the development of amide containing B3GNT2 inhibitors guided by structure-based drug design, imidazolones were found to successfully serve as amide bioisosteres. This novel imidazolone isosteric strategy alleviated torsional strain of the amide bond on binding to B3GNT2 and improved potency, isoform selectivity, as well as certain physicochemical and pharmacokinetic properties. Herein, we present the synthesis, SAR, X-ray cocrystal structures, and in vivo PK properties of imidazol-4-ones in the context of B3GNT2 inhibition.

Novel one-pot synthesis of imidazolinones from esters: a concise synthesis of GSK2137305

A new copper-catalyzed one-pot reaction resulted in the practical synthesis of imidazolinones in moderate yields from esters. The use of inexpensive copper iodide as the catalyst, (NH4)2CO3 as the nitrogen source and readily available starting materials makes this process economically viable. Applying this protocol to the synthesis of GSK2137305, a concise approach was developed to obtain GSK2137305 from the ester in only three steps with an overall yield of 26.9%.

Treatment of Obese Insulin-Resistant Mice With an Allosteric MAPKAPK2/3 Inhibitor Lowers Blood Glucose and Improves Insulin Sensitivity

The prevalence of obesity-induced type 2 diabetes (T2D) is increasing worldwide, and new treatment strategies are needed. We recently discovered that obesity activates a previously unknown pathway that promotes both excessive hepatic glucose production (HGP) and defective insulin signaling in hepatocytes, leading to exacerbation of hyperglycemia and insulin resistance in obesity. At the hub of this new pathway is a kinase cascade involving calcium/calmodulin-dependent protein kinase II (CaMKII), p38α mitogen-activated protein kinase (MAPK), and MAPKAPK2/3 (MK2/3). Genetic-based inhibition of these kinases improves metabolism in obese mice. Here, we report that treatment of obese insulin-resistant mice with an allosteric MK2/3 inhibitor, compound (cmpd) 28, ameliorates glucose homeostasis by suppressing excessive HGP and enhancing insulin signaling. The metabolic improvement seen with cmpd 28 is additive with the leading T2D drug, metformin, but it is not additive with dominant-negative MK2, suggesting an on-target mechanism of action. Allosteric MK2/3 inhibitors represent a potentially new approach to T2D that is highly mechanism based, has links to human T2D, and is predicted to avoid certain adverse effects seen with current T2D drugs.

Landmark studies on the glucagon subfamily of GPCRs: from small molecule modulators to a crystal structure

The glucagon subfamily of class B G protein-coupled receptors (GPCRs) has been proposed to be a crucial drug target for the tretmaent of type 2 diabetes. The challenges associated with determining the crystal structures of class B GPCRs relate to their large amino termini and the lack of available small molecule ligands to stabilize the receptor proteins. Following our discovery of non-peptidic agonists for glucagon-like peptide-1 receptor (GLP-1R) that have therapeutic effects, we initiated collaborative efforts in structural biology and recently solved the three-dimensional (3D) structure of the human glucagon receptor (GCGR) 7-transmembrane domain, providing in-depth information about the underlying signaling mechanisms. In this review, some key milestones in this endeavor are highlighted, including discoveries of small molecule ligands, their roles in receptor crystallization, conformational changes in transmembrane domains (TMDs) upon activation and structure-activity relationship analyses.

Recent progress in the development of small-molecule glucagon receptor antagonists

The endocrine hormone glucagon stimulates hepatic glucose output via its action at the glucagon receptor (GCGr) in the liver. In the diabetic state, dysregulation of glucagon secretion contributes to abnormally elevated hepatic glucose output. The inhibition of glucagon-induced hepatic glucose output via antagonism of the GCGr using small-molecule ligands is a promising mechanism for improving glycemic control in the diabetic state. Clinical data evaluating the therapeutic potential of small-molecule GCGr antagonists is currently emerging. Recently disclosed clinical data demonstrates the potential efficacy and possible therapeutic limitations of small-molecule GCGr antagonists. Recent pre-clinical work on the development of GCGr antagonists is also summarized.

Total synthesis of tricladins A and B and identification of their absolute configuration

A concise synthesis of both (S)- and (R)-enantiomers of tricladins A and B from l-Boc alanine was achieved. The diastereomeric intermediates were separated by chiral column chromatography, and the absolute configuration of the 2-position was assigned by observed NOE interactions with the known stereogenic center at the 5-position. By comparison of all synthesized final enantiomers with the corresponding natural products, we concluded that the natural tricladins A and B must have the (R)-configuration.

Ablation of glucagon receptor signaling by peptide-based glucagon antagonists improves glucose tolerance in high fat fed mice

Modification to the structure of glucagon has provided a number of glucagon receptor antagonists with possible therapeutic application for diabetes. These novel peptide analogs include desHis(1)Pro(4)Glu(9)-glucagon and desHis(1)Pro(4)Glu(9)(Lys(30)PAL)-glucagon. This study has evaluated the metabolic benefits of once daily administration of desHis(1)Pro(4)Glu(9)-glucagon and desHis(1)Pro(4)Glu(9)(Lys(30)PAL)-glucagon in high fat (45%) fed mice for 15 days. Administration of desHis(1)Pro(4)Glu(9)-glucagon and desHis(1)Pro(4)Glu(9)(Lys(30)PAL)-glucagon had no significant effect on body weight, food intake or circulating glucose concentrations during the treatment period. However, both peptides significantly (P<0.05 to P<0.01) reduced circulating plasma insulin concentrations from day 6 onwards. Oral glucose tolerance and insulin sensitivity, as assessed by exogenous insulin administration, were significantly (P<0.01 to P<0.001) improved by both desHis(1)Pro(4)Glu(9)-glucagon and desHis(1)Pro(4)Glu(9)(Lys(30)PAL)-glucagon. These metabolic benefits were accompanied by significantly (P<0.01) increased pancreatic insulin stores. No significant differences in blood triacylglycerol or cholesterol levels were noted with desHis(1)Pro(4)Glu(9)-glucagon, however desHis(1)Pro(4)Glu(9)(Lys(30)PAL)-glucagon treatment significantly (P<0.01) increased HDL-cholesterol levels. Glucagon-mediated elevations of glucose and insulin were effectively (P<0.01 to P<0.001) annulled in both treatment groups on day 15. Interestingly, glucose levels during an intraperitoneal glucose tolerance test were not altered by either desHis(1)Pro(4)Glu(9)-glucagon or desHis(1)Pro(4)Glu(9)(Lys(30)PAL)-glucagon treatment. These data provide further evidence that glucagon antagonism could provide an effective means of treating T2DM.