Post-Amadori AGE inhibition as a therapeutic target for diabetic complications: a rational approach to second-generation Amadorin design

Aminoguanidine and pyridoxamine (Pyridorintrade mark), two major inhibitors of advanced glycation end product (AGE) formation, have entered clinical trials for diabetic nephropathy. They share no structural similarity and are believed to inhibit AGE formation by entirely different mechanisms. Pyridoxamine is a post-Amadori AGE inhibitor-that is, an "Amadorin"-whereas aminoguanidine primarily scavenges reactive dicarbonyl precursors to AGEs. However, pyridoxamine also has a limited potential to react with dicarbonyls. We thus embarked on an effort to develop second-generation Amadorins with low nucleophilicity. Our hypothesis was that we could improve specificity for inhibiting the post-Amadori pathway by minimizing the potential for scavenging small dicarbonyl intermediates. This mechanism-based strategy has led to a rational drug design program that has successfully produced candidate Amadorins, among them the novel compound BST-4997. This Amadorin has greater post-Amadori potency than pyridoxamine but possess no dicarbonyl scavenging activity. Prototypical inhibitors like BST-4997 provide a unique tool to help identify relevant AGE pathways that contribute to diabetic complications. Targeting AGE inhibition differs significantly from traditional approaches to drug discovery and thus represents a new paradigm for the drug industry that should be recognized.