MLR-1023 Is a Potent and Selective Allosteric Activator of Lyn Kinase In Vitro That Improves Glucose Tolerance In Vivo

2(1H)-pyrimidinone, 5-(3-methylphenoxy) (MLR-1023) is a candidate for the treatment of type 2 diabetes. The current studies were aimed at determining the mechanism by which MLR-1023 mediates glycemic control. In these studies, we showed that MLR-1023 reduced blood glucose levels without increasing insulin secretion in vivo. We have further determined that MLR-1023 did not activate peroxisome proliferator-activated alpha, delta, and gamma receptors or glucagon-like peptide-1 receptors or inhibit dipeptidyl peptidase-4 or alpha-glucosidase enzyme activity. However, in an in vitro broad kinase screen MLR-1023 activated the nonreceptor-linked Src-related tyrosine kinase Lyn. MLR-1023 increased the V-max of Lyn with an EC50 of 63 nM. This Lyn kinase activation was ATP binding site independent, indicating that MLR-1023 regulated the kinase through an allosteric mechanism. We have established a link between Lyn activation and blood glucose lowering with studies showing that the glucose-lowering effects of MLR-1023 were abolished in Lyn knockout mice, consistent with existing literature linking Lyn kinase and the insulin-signaling pathway. In summary, these studies describe MLR-1023 as a unique blood glucose-lowering agent and show that MLR-1023-mediated blood glucose lowering depends on Lyn kinase activity. These results, coupled with other results (J Pharmacol Exp Ther 342:23-32, 2012), suggest that MLR-1023 and Lyn kinase activation may be a new treatment modality for type 2 diabetes.