IC261 is a potent and selective inhibitor of the kinase enzyme CK1δ (casein kinase 1 delta). It is widely used in biochemical and pharmacological research to study the role of CK1δ in cellular processes such as circadian rhythm regulation, DNA damage response, and Wnt signaling pathway modulation. Due to its ability to cross the blood-brain barrier, IC261 is also employed in neuroscience research to investigate the impact of CK1δ inhibition on neuronal function and neurodegenerative conditions. Additionally, it has been explored in cancer research for its potential to disrupt cell cycle progression and induce apoptosis in tumor cells, particularly in models of acute myeloid leukemia and other malignancies where CK1δ is overactive. Its selectivity makes it a valuable tool compound for target validation and mechanistic studies in drug discovery.