János Tibor Kodra

Small-molecule agonists for the glucagon-like peptide 1 receptor.

The peptide hormone glucagon-like peptide (GLP)-1 has important actions resulting in glucose lowering along with weight loss in patients with type 2 diabetes. As a peptide hormone, GLP-1 has to be administered by injection. Only a few small-molecule agonists to peptide hormone receptors have been described and none in the B family of the G protein coupled receptors to which the GLP-1 receptor belongs. We have discovered a series of small molecules known as ago-allosteric modulators selective for the human GLP-1 receptor. These compounds act as both allosteric activators of the receptor and independent agonists. Potency of GLP-1 was not changed by the allosteric agonists, but affinity of GLP-1 for the receptor was increased. The most potent compound identified stimulates glucose-dependent insulin release from normal mouse islets but, importantly, not from GLP-1 receptor knockout mice. Also, the compound stimulates insulin release from perfused rat pancreas in a manner additive with GLP-1 itself. These compounds may lead to the identification or design of orally active GLP-1 agonists.

Novel glucagon receptor antagonists with improved selectivity over the glucose-dependent insulinotropic polypeptide receptor.

Optimization of a new series of small molecule human glucagon receptor (hGluR) antagonists is described. In the process of optimizing glucagon receptor antagonists, we counter-screened against the closely related human gastric inhibitory polypeptide receptor (hGIPR), and through structure activity analysis, we obtained compounds with low nanomolar affinities toward the hGluR, which were selective against the hGIPR and the human glucagon-like peptide-1 receptor (hGLP-1R). In the best cases, we obtained a >50 fold selectivity for the hGluR over the hGIPR and a >1000 fold selectivity over the hGLP-1R. A potent and selective glucagon receptor antagonist was demonstrated to inhibit glucagon-induced glycogenolysis in primary rat hepatocytes as well as to lower glucagon-induced hyperglycemia in Sprague-Dawley rats. Furthermore, the compound was shown to lower blood glucose in the ob/ob mouse after oral dosing.

Human glucagon receptor antagonists with thiazole cores. A novel series with superior pharmacokinetic properties.

The aim of the work presented here was to design and synthesize potent human glucagon receptor antagonists with improved pharmacokinetic (PK) properties for development of pharmaceuticals for the treatment of type 2 diabetes. We describe the preparation of compounds with cyclic cores (5-aminothiazoles), their binding affinities for the human glucagon and GIP receptors, as well as affinities for rat, mouse, pig, dog, and monkey glucagon receptors. Generally, the compounds had slightly less glucagon receptor affinity compared to compounds of the previous series, but this was compensated for by much improved PK profiles in both rats and dogs with high oral bioavailabilities and sustained high plasma exposures. The compounds generally showed species selectivity for glucagon receptor binding with poor affinities for the rat, mouse, rabbit, and pig receptors. However, dog and monkey glucagon receptor affinities seem to reflect the human situation. One compound of this series, 18, was tested intravenously in an anesthetized glucagon-challenged monkey model of hyperglucagonaemia and hyperglycaemia and was shown dose-dependently to decrease glycaemia. Further, high plasma exposures and a long plasma half-life (5.2 h) were obtained.

Long acting analogue of the calcitonin gene-related peptide induces positive metabolic effects and secretion of the glucagon-like peptide-1.

The pharmacological potential of Calcitonin gene-related peptide (CGRP) beyond vasodilation is not completely understood and studies are limited by the potent vasodilatory effect and the short half-life of CGRP. In particular, the effects of CGRP on metabolic diseases are not clarified. A peptide analogue of the α form of CGRP (αAnalogue) with prolonged half-life (10.2 ± 0.9h) in rodents was synthesised and used to determine specific metabolic effects in 3 rodent models; normal rats, diet-induced obese rats and the Leptin deficient mouse model (ob/ob mice). The αAnalogue (100 nmol/kg) induced elevated energy expenditure and reduced food intake after single dosing in normal rats. In addition, the αAnalogue increased levels of circulating Glucagon-Like Peptide-1 (GLP-1) by >60% and a specific concentration dependent CGRP-induced GLP-1 secretion was verified in a murine L-cell line. Two weeks treatment of the type 2 diabetic ob/ob mice with the αAnalogue caused reduction in fasting insulin levels (199 ± 36 pM vs 332 ± 68 pM) and a tendency to reduce fasting blood glucose (11.2 ± 1.1mM vs 9.5 ± 0.5mM) and % glycosylated haemoglobin (HbA1c) (5.88 ± 0.17 vs 5.12 ± 0.24), demonstrating a potential anti-diabetic effect. Furthermore, two weeks treatment of diet-induced obese rats with the αAnalogue caused reduction in food intake and a significant decline in body weight (3.6 ± 1.9 gvs. -36 ± 1.1g). We have demonstrated that long-acting CGRP analogues may have a therapeutic potential for the treatment of type 2 diabetes through positive metabolic effects and effect on GLP-1 secretion.

Structural insight into antibody-mediated antagonism of the Glucagon-like peptide-1 Receptor.

The Glucagon-like peptide-1 receptor (GLP-1R) is a member of the class B G protein-coupled receptor (GPCR) family and a well-established target for the treatment of type 2 diabetes. The N-terminal extracellular domain (ECD) of GLP-1R is important for GLP-1 binding and the crystal structure of the GLP-1/ECD complex was reported previously. The first structure of a class B GPCR transmembrane (TM) domain was solved recently, but the full length receptor structure is still not well understood. Here we describe the molecular details of antibody-mediated antagonism of the GLP-1R using both in vitro pharmacology and x-ray crystallography. We showed that the antibody Fab fragment (Fab 3F52) blocked the GLP-1 binding site of the ECD directly and thereby acts as a competitive antagonist of native GLP-1. Interestingly, Fab 3F52 also blocked a short peptide agonist believed to engage primarily the transmembrane and extracellular loop region of GLP-1R, whereas functionality of an allosteric small-molecule agonist was not inhibited. This study has implications for the structural understanding of the GLP-1R and related class B GPCRs, which is important for the development of new and improved therapeutics targeting these receptors.