AZD-6738 is a potent and selective inhibitor of ataxia telangiectasia and Rad3-related (ATR) kinase, a key protein in the DNA damage response pathway. It is primarily used in cancer research and therapy development, especially in tumors with defects in DNA repair mechanisms. By inhibiting ATR, AZD-6738 prevents cancer cells from repairing DNA damage caused by chemotherapy or radiation, thereby enhancing the effectiveness of these treatments. It shows promise in combination therapies with agents like cisplatin or ionizing radiation, particularly in cancers such as ovarian, lung, and certain types of breast cancer. AZD-6738 is also being studied in tumors with ATM deficiency, where cancer cells rely heavily on ATR for survival, making them more vulnerable to ATR inhibition. This synthetic lethality approach allows targeted killing of cancer cells while sparing normal tissues. In preclinical and clinical trials, AZD-6738 has demonstrated the ability to overcome treatment resistance and improve outcomes in hard-to-treat cancers. Its role in sensitizing tumors to existing therapies makes it a valuable candidate in the development of more effective, personalized oncology treatments.