Cyclin-dependent kinase 5 (CDK5) is a serine-threonine protein kinase that plays a significant role in neuronal development. In association with p25, CDK5 abnormally phosphorylates a number of cellular targets involved in neurodegenerative disorders. Using active site homology and previous structure-activity relationships, a new series of potent CDK5 inhibitors was designed. This report describes the optimization of 6-oxo-1,6-dihydropyridines as CDK5 inhibitors.