VE-821 is primarily utilized in research settings as a potent and selective inhibitor of ATR kinase, a key enzyme involved in the DNA damage response pathway. Its application is significant in studying the mechanisms of DNA repair and cellular responses to genotoxic stress. Researchers use VE-821 to investigate the role of ATR in cancer biology, as inhibiting ATR can sensitize cancer cells to DNA-damaging therapies like chemotherapy and radiation. This makes it a valuable tool for exploring potential combination therapies to enhance the efficacy of existing cancer treatments. Additionally, VE-821 aids in understanding the broader implications of ATR inhibition in normal cells, helping to assess the therapeutic window and potential side effects of targeting this pathway.