Identification and pharmacological characterization of multiple allosteric binding sites on the free fatty acid 1 receptor.

Activation of FFA1 (GPR40), a member of G protein-coupling receptor family A, is mediated by medium- and long-chain fatty acids and leads to amplification of glucose-stimulated insulin secretion, suggesting a potential role for free fatty acid 1 (FFA1) as a target for type 2 diabetes. It was assumed previously that there is a single binding site for fatty acids and synthetic FFA1 agonists. However, using members of two chemical series of partial and full agonists that have been identified, radioligand binding interaction studies revealed that the full agonists do not bind to the same site as the partial agonists but exhibit positive heterotropic cooperativity. Analysis of functional data reveals positive functional cooperativity between the full agonists and partial agonists in various functional assays (in vitro and ex vivo) and also in vivo. Furthermore, the endogenous fatty acid docosahexaenoic acid (DHA) shows negative or neutral cooperativity with members of both series of agonists in binding assays but displays positive cooperativity in functional assays. Another synthetic agonist is allosteric with members of both agonist series, but apparently competitive with DHA. Therefore, there appear to be three allosterically linked binding sites on FFA1 with agonists specific for each of these sites. Activation of free fatty acid 1 receptor (FFAR1) by each of these agonists is differentially affected by mutations of two arginine residues, previously found to be important for FFAR1 binding and activation. These ligands with their high potencies and strong positive functional cooperativity with endogenous fatty acids, demonstrated in vitro and in vivo, have the potential to deliver therapeutic benefits.

Novel Series of Potent Glucokinase Activators Leading to the Discovery of AM-2394.

Glucokinase (GK) catalyzes the phosphorylation of glucose to glucose-6-phosphate. We present the structure-activity relationships leading to the discovery of AM-2394, a structurally distinct GKA. AM-2394 activates GK with an EC50 of 60 nM, increases the affinity of GK for glucose by approximately 10-fold, exhibits moderate clearance and good oral bioavailability in multiple animal models, and lowers glucose excursion following an oral glucose tolerance test in an ob/ob mouse model of diabetes.

Highly regioselective Diels-Alder reactions toward oroidin alkaloids: use of a tosylvinyl moiety as a nitrogen masking group with adjustable electronics.

[reaction: see text] The use of the p-toluenesulfonyl (Ts) and tosylvinyl (Tsv) groups as nitrogen masking groups imparted high regioselectivity in Diels-Alder reactions directed toward members of the oroidin-derived marine alkaloid family. The electron-withdrawing Tsv group was utilized as an electronically adjustable nitrogen-protecting group as subsequent hydrogenation provided the more electron-rich tosylethyl (Tse) group. This electronic adjustment strategy avoided a protecting group exchange and provided the required electronics for the key chlorination/ring-contraction sequence.

Divergent approach to imino sugar C-glycosides using imino glycals: application to the stereocontrolled synthesis of (+)-deoxoprosophylline.

Tri-O-acetyl imino glucal 2 is readily made and shown to undergo a variety of Lewis acid mediated carbon-carbon bond forming reactions at C-1 of the piperidine nucleus. In all the reactions studied, the beta-anomer is predominant.

Improving the Pharmacokinetics of GPR40/FFA1 Full Agonists.

We recently reported the discovery of a potent GPR40 full agonist AM-1638 (1). Herein, we describe our efforts in improving the drug-like properties of the full agonists through the systematic introduction of polar groups in the C-, D-, and A-rings. This led to the discovery of new GPR40 full agonists with significantly improved pharmacokinetic propeties. Compound 8 and 20 also showed potent in vivo efficacy in oral glucose tolerance tests in mice in addition to the improvement in properties.

Optimization of GPR40 Agonists for Type 2 Diabetes.

GPR40 (FFA1 and FFAR1) has gained significant interest as a target for the treatment of type 2 diabetes. TAK-875 (1), a GPR40 agonist, lowered hemoglobin A1c (HbA1c) and lowered both postprandial and fasting blood glucose levels in type 2 diabetic patients in phase II clinical trials. We optimized phenylpropanoic acid derivatives as GPR40 agonists and identified AMG 837 (2) as a clinical candidate. Here we report our efforts in searching for structurally distinct back-ups for AMG 837. These efforts led to the identification of more polar GPR40 agonists, such as AM-4668 (10), that have improved potency, excellent pharmacokinetic properties across species, and minimum central nervous system (CNS) penetration.

Activation of FFA1 mediates GLP-1 secretion in mice. Evidence for allosterism at FFA1.

FFA1 (GPR40) and GPR120 are G-protein-coupled receptors activated by long-chain fatty acids. FFA1 is expressed in pancreatic ß-cells, where it regulates glucose-dependent insulin secretion, and GPR120 has been implicated in mediating GLP-1 secretion. We show here that FFA1 co-localizes with GLP-1 in enteroendocrine cells and plays a critical role in glucose management by mediating GLP-1 secretion in vivo. Corn oil induces GLP-1 secretion in wild type mice and in GPR120-/- mice, but not in FFA1-/- mice. α-Linolenic acid, an endogenous ligand of FFA1, induces GLP-1 secretion in GLUTag cells and in primary fetal mouse intestinal cells. Synthetic partial FFA1 agonists do not stimulate GLP-1 secretion in mice, but partial and full agonists combined function cooperatively to enhance receptor activation and GLP-1 secretion both in vitro and in vivo. We conclude that allosterism at FFA1 can contribute to postprandial glucose management by stimulating insulin secretion via an extrapancreatic mechanism of action, and that GPR120 in GLP-1 secretion requires further investigation.

Discovery and Optimization of Potent GPR40 Full Agonists Containing Tricyclic Spirocycles.

GPR40 (FFAR1 or FFA1) is a target of high interest being pursued to treat type II diabetes due to its unique mechanism leading to little risk of hypoglycemia. We recently reported the discovery of AM-1638 (2), a potent full agonist of GPR40. In this report, we present the discovery of GPR40 full agonists containing conformationally constrained tricyclic spirocycles and their structure-activity relationships leading to more potent agonists such as AM-5262 (26) with improved rat PK profile and general selectivity profile. AM-5262 enhanced glucose stimulated insulin secretion (mouse and human islets) and improved glucose homeostasis in vivo (OGTT in HF/STZ mice) when compared to AM-1638.

Discovery of AM-1638: A Potent and Orally Bioavailable GPR40/FFA1 Full Agonist.

GPR40 (FFA1) is a G-protein-coupled receptor, primarily expressed in pancreatic islets, the activation of which elicits increased insulin secretion only in the presence of elevated glucose levels. A potent, orally bioavailable small molecule GPR40 agonist is hypothesized to be an effective antidiabetic posing little or no risk of hypoglycemia. We recently reported the discovery of AMG 837 (1), a potent partial agonist of GPR40. Herein, we present the optimization from the GPR40 partial agonist 1 to the structurally and pharmacologically distinct GPR40 full agonist AM-1638 (21). Moreover, we demonstrate the improved in vivo efficacy that GPR40 full agonist 21 exhibits in BDF/DIO mice as compared to partial agonist 1.

A potent class of GPR40 full agonists engages the enteroinsular axis to promote glucose control in rodents.

Type 2 diabetes is characterized by impaired glucose homeostasis due to defects in insulin secretion, insulin resistance and the incretin response. GPR40 (FFAR1 or FFA1) is a G-protein-coupled receptor (GPCR), primarily expressed in insulin-producing pancreatic ß-cells and incretin-producing enteroendocrine cells of the small intestine. Several GPR40 agonists, including AMG 837 and TAK-875, have been disclosed, but no GPR40 synthetic agonists have been reported that engage both the insulinogenic and incretinogenic axes. In this report we provide a molecular explanation and describe the discovery of a unique and potent class of GPR40 full agonists that engages the enteroinsular axis to promote dramatic improvement in glucose control in rodents. GPR40 full agonists AM-1638 and AM-6226 stimulate GLP-1 and GIP secretion from intestinal enteroendocrine cells and increase GSIS from pancreatic islets, leading to enhanced glucose control in the high fat fed, streptozotocin treated and NONcNZO10/LtJ mouse models of type 2 diabetes. The improvement in hyperglycemia by AM-1638 was reduced in the presence of the GLP-1 receptor antagonist Ex(9-39)NH(2).

Preparation and reactivity of imino glycals: stereocontrolled, divergent approach to imino sugars.

The synthesis of 3,4,6-tri-O-acetyl imino D-glucal 2 from D-glucal is reported. This imino glycal participates in a variety of Lewis acid mediated carbon-carbon bond forming reactions by allylic displacement of the C-3 acetate group by added nucleophiles. Allyl silanes, trimethylsilyl enol ethers, alkenes and dialkyl zinc reagents serve as suitable reaction partners. In all the cases studied, the beta-anomer is predominant. Using imino glycal 8, epimeric at C-5, it is established that the configuration at C-5 of the piperidine ring plays a major role in controlling the stereochemical outcome. These results are rationalised by invoking the intermediacy of a conjugated N-acyliminium ion. A short stereocontrolled synthesis of (+)-deoxoprosophylline is achieved using this chemistry. Additionally, imino glucal 2 is transformed into bromo piperidine 16, whose X-ray crystal structure is determined. Bromide 16 participates in palladium catalysed Stille and Suzuki cross-couplings allowing access to C-2 substituted imino sugars 17 and 18. In other studies, imino sugar C-glycosides 21 and 22 are made by combining the Lewis acid mediated carbon-carbon bond forming reactions with stereospecific dihydroxylations.