CDK5 and Alzheimer disease: TFP5, an inhibitory peptide of Cdk5/p25, significantly reduced tau hyperphosphorylation, neurofilament accumulation and restored synaptic function and behavior abnormalities in transgenic AD model mice as well as the mice overexpressing p25 through attenuating Cdk5 hyperactivity (Shukla et al., 2013, 2017).