Small molecule ago-allosteric modulators of the human glucagon-like peptide-1 (hGLP-1) receptor.

Following our previous publication describing the biological profiles, we herein describe the structure-activity relationships of a core set of quinoxalines as the hGLP-1 receptor agonists. The most potent and efficacious compounds are 6,7-dichloroquinoxalines bearing an alkyl sulfonyl group at the C-2 position and a secondary alkyl amino group at the C-3 position. These findings serve as a valuable starting point for the discovery of more drug-like small molecule agonists for the hGLP-1 receptor.

New beta-alanine derivatives are orally available glucagon receptor antagonists.

A weak human glucagon receptor antagonist with an IC50 of 7 microM was initially found by screening of libraries originally targeted to mimic the binding of the glucagon-like peptide (GLP-1) hormone to its receptor. Optimization of this hit for binding affinity for the glucagon receptor led to ligands with affinity in the nanomolar range. In addition to receptor binding, optimization efforts were made to stabilize the molecules against fast metabolic turnover. A potent antagonist of the human human glucagon receptor was obtained that had 17% oral availability in rats with a plasma half-life of 90 min. The major metabolites of this lead were identified and used to further optimize this series with respect to pharmacokinetic properties. This final optimization led to a potent glucagon antagonist that was orally available in rats and dogs and was efficacious in lowering blood glucose levels in a diabetic animal model.

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.

Optimization of alkylidene hydrazide based human glucagon receptor antagonists. Discovery of the highly potent and orally available 3-cyano-4-hydroxybenzoic acid [1-(2,3,5,6-tetramethylbenzyl)-1H-indol-4-ylmethylene]hydrazide.

Highly potent human glucagon receptor (hGluR) antagonists have been prepared employing both medicinal chemistry and targeted libraries based on modification of the core (proximal) dimethoxyphenyl group, the benzyl ether linkage, as well as the (distal) benzylic aryl group of the lead 2, 3-cyano-4-hydroxybenzoic acid (3,5-dimethoxy-4-isopropylbenzyloxybenzylidene)hydrazide. Electron-rich proximal aryl moieties such as mono- and dimethoxy benzenes, naphthalenes, and indoles were found to be active. The SAR was found to be quite insensitive regarding the linkage to the distal aryl group, since long and short as well as polar and apolar linkers gave highly potent compounds. The presence of a distal aryl group was not crucial for obtaining high binding affinity to the hGluR. In many cases, however, the affinity could be further optimized with substituted distal aryl groups. Representative compounds have been tested for in vitro metabolism, and structure-metabolism relationships are described. These efforts lead to the discovery of 74, NNC 25-2504, 3-cyano-4-hydroxybenzoic acid [1-(2,3,5,6-tetramethylbenzyl)-1H-indol-4-ylmethylene]hydrazide, with low in vitro metabolic turnover. 74 was a highly potent noncompetitive antagonist of the human glucagon receptor (IC(50) = 2.3 nM, K(B) = 760 pM) and of the isolated rat receptor (IC(50) = 430 pM, K(B) = 380 pM). Glucagon-stimulated glucose production from isolated primary rat hepatocytes was inhibited competitively by 74 (K(i) = 14 nM). This compound was orally available in dogs (F(po) = 15%) and was active in a glucagon-challenged rat model of hyperglucagonemia and hyperglycemia.

Human glucagon receptor antagonists based on alkylidene hydrazides.

A series of alkylidene hydrazide derivatives containing an alkoxyaryl moiety was optimized. The resulting hydrazide-ethers were competitive antagonists at the human glucagon receptor. Pharmacokinetic experiments showed fast clearance of most of the compounds tested. A representative compound [4-hydroxy-3-cyanobenzoic acid (4-isopropylbenzyloxy-3,5-dimethoxymethylene)hydrazide] with an IC50 value of 20 nM was shown to reduce blood glucose levels in fasted rats.