CDK5 and Parkinson disease: Previous studies have shown that TFP5, which was a 24-aa peptide (Lys254-Ala277) derived from truncated p35, competed with p25 for binding to CDK5, inhibited CDK5/p25 hyperactivity, and improved Alzheimer’s disease (AD) and Parkinson’s disease (PD) outcomes in vivo14, 15.