CHIR-99021 (CT99021) HCl is widely used in research for its role as a potent and selective inhibitor of glycogen synthase kinase-3 (GSK-3). It is particularly valuable in stem cell studies, where it enhances the maintenance and expansion of pluripotent stem cells by promoting self-renewal. This compound is also utilized in regenerative medicine to improve the efficiency of reprogramming somatic cells into induced pluripotent stem cells (iPSCs). Additionally, it has shown potential in neurobiological research, where it aids in studying mechanisms related to neuronal differentiation and survival. Its application extends to cancer research, as it helps investigate pathways involved in tumor growth and metastasis.