This report critically examines the therapeutic potential of inhibiting CDK5 in cancer and Alzheimer's disease. It explores the role of CDK5 in various biological processes, including cell cycle regulation, neuronal migration, and synaptic plasticity. The report discusses the advantages of CDK5 inhibition, such as its potential in targeting tumor-initiating cells (TICs) and its involvement in neurodegenerative disorders like Alzheimer's disease and ALS. It also addresses the disadvantages, including potential side effects and the complexity of CDK5's multifaceted roles. The report delves into the mechanisms of CDK5 inhibition, including the use of small molecule inhibitors like Roscovitine, and analyzes the impact of CDK5 on cell death, EMT, and neuronal function. The report reviews relevant literature, including books and journals, to support its arguments and conclusions, highlighting the need for further research to fully understand the therapeutic implications of CDK5 inhibition in these diseases.