(S)-Ceralasertib is primarily used in the field of oncology as a potent and selective inhibitor of the ataxia telangiectasia and Rad3-related (ATR) kinase. This kinase plays a critical role in the DNA damage response, particularly in the repair of DNA replication stress. By inhibiting ATR, (S)-Ceralasertib disrupts the ability of cancer cells to repair damaged DNA, leading to cell death. This makes it a promising therapeutic agent for treating various types of cancers, especially those with defects in DNA repair pathways or those that are resistant to conventional therapies. It is often studied in combination with other treatments, such as chemotherapy or radiation, to enhance their efficacy. Clinical trials are ongoing to evaluate its effectiveness and safety in patients with solid tumors and hematologic malignancies.