Discovery and optimization of novel pyridines as highly potent and selective glycogen synthase kinase 3 inhibitors.

Glycogen synthase kinase-3 plays an essential role in multiple biochemical pathways in the cell, particularly in regards to energy regulation. As such, Glycogen synthase kinase-3 is an attractive target for pharmacological intervention in a variety of disease states, particularly non-insulin dependent diabetes mellitus. However, due to homology with other crucial kinases, such as the cyclin-dependent protein kinase CDC2, developing compounds that are both potent and selective is challenging. A novel series of derivatives of 5-nitro-N2-(2-(pyridine-2ylamino)ethyl)pyridine-2,6-diamine were synthesized and have been shown to potently inhibit glycogen synthase kinase-3 (GSK3). Potency in the low nanomolar range was obtained along with remarkable selectivity. The compounds activate glycogen synthase in insulin receptor-expressing CHO-IR cells and in primary rat hepatocytes, and have acceptable pharmacokinetics and pharmacodynamics to allow for oral dosing. The X-ray co-crystal structure of human GSK3-ß in complex with compound 2 is reported and provides insights into the structural determinants of the series responsible for its potency and selectivity.

Synthesis, Binding Mode, and Antihyperglycemic Activity of Potent and Selective (5-Imidazol-2-yl-4-phenylpyrimidin-2-yl)[2-(2-pyridylamino)ethyl]amine Inhibitors of Glycogen Synthase Kinase 3.

In an effort to identify new antidiabetic agents, we have discovered a novel family of (5-imidazol-2-yl-4-phenylpyrimidin-2-yl)[2-(2-pyridylamino)ethyl]amine analogues which are inhibitors of human glycogen synthase kinase 3 (GSK3). We developed efficient synthetic routes to explore a wide variety of substitution patterns and convergently access a diverse array of analogues. Compound 1 (CHIR-911, CT-99021, or CHIR-73911) emerged from an exploration of heterocycles at the C-5 position, phenyl groups at C-4, and a variety of differently substituted linker and aminopyridine moieties attached at the C-2 position. These compounds exhibited GSK3 IC50s in the low nanomolar range and excellent selectivity. They activate glycogen synthase in insulin receptor-expressing CHO-IR cells and primary rat hepatocytes. Evaluation of lead compounds 1 and 2 (CHIR-611 or CT-98014) in rodent models of type 2 diabetes revealed that single oral doses lowered hyperglycemia within 60 min, enhanced insulin-stimulated glucose transport, and improved glucose disposal without increasing insulin levels.

Selective glycogen synthase kinase 3 inhibitors potentiate insulin activation of glucose transport and utilization in vitro and in vivo.

Insulin resistance plays a central role in the development of type 2 diabetes, but the precise defects in insulin action remain to be elucidated. Glycogen synthase kinase 3 (GSK-3) can negatively regulate several aspects of insulin signaling, and elevated levels of GSK-3 have been reported in skeletal muscle from diabetic rodents and humans. A limited amount of information is available regarding the utility of highly selective inhibitors of GSK-3 for the modification of insulin action under conditions of insulin resistance. In the present investigation, we describe novel substituted aminopyrimidine derivatives that inhibit human GSK-3 potently (K(i) < 10 nmol/l) with at least 500-fold selectivity against 20 other protein kinases. These low molecular weight compounds activated glycogen synthase at approximately 100 nmol/l in cultured CHO cells transfected with the insulin receptor and in primary hepatocytes isolated from Sprague-Dawley rats, and at 500 nmol/l in isolated type 1 skeletal muscle of both lean Zucker and ZDF rats. It is interesting that these GSK-3 inhibitors enhanced insulin-stimulated glucose transport in type 1 skeletal muscle from the insulin-resistant ZDF rats but not from insulin-sensitive lean Zucker rats. Single oral or subcutaneous doses of the inhibitors (30-48 mg/kg) rapidly lowered blood glucose levels and improved glucose disposal after oral or intravenous glucose challenges in ZDF rats and db/db mice, without causing hypoglycemia or markedly elevating insulin. Collectively, our results suggest that these selective GSK-3 inhibitors may be useful as acute-acting therapeutics for the treatment of the insulin resistance of type 2 diabetes.