AZD1390 is a potent and selective inhibitor of ataxia telangiectasia mutated (ATM) kinase, a key protein involved in the DNA damage response pathway. It is primarily developed for use in cancer therapy, where it enhances the effectiveness of radiation and certain DNA-damaging chemotherapeutic agents. By inhibiting ATM, AZD1390 prevents cancer cells from efficiently repairing radiation-induced DNA double-strand breaks, leading to increased tumor cell death. This makes it a promising radiosensitizer, particularly in tumors that rely heavily on the ATM pathway for DNA repair. It is being investigated in clinical trials for its potential in treating solid tumors, including brain metastases and other localized cancers, especially when combined with radiotherapy. Its ability to cross the blood-brain barrier further supports its use in central nervous system tumors.