YU238259 is primarily used in research settings as a potent and selective inhibitor of the enzyme cyclin-dependent kinase 5 (CDK5). It has shown promise in studies related to neurodegenerative diseases, where abnormal CDK5 activity is linked to neuronal damage and cell death. Due to its ability to cross the blood-brain barrier, YU238259 is valuable in preclinical models for evaluating therapeutic strategies in conditions such as Alzheimer's disease and other tauopathies. Additionally, it has been employed in cancer research to explore the role of CDK5 in tumor cell proliferation and survival, particularly in neuroblastoma and glioblastoma. Its high selectivity reduces off-target effects, making it a useful tool compound in mechanistic studies.