In recent years, more and more evidence has emerged confirming the involvement of CDK5 in the formation and spread of cancers and neurodegenerative diseases, such as Alzheimer’s disease (AD), amyotrophic lateral sclerosis (ALS), frontotemporal dementia (FTD), Huntington’s disease (HD), and Parkinson’s disease (PD), as well as in stroke and diabetes [218,219,220]. Here, CDK5 is linked to Alzheimer disease.