VX-984 (M9831) is a selective inhibitor of ATR (Ataxia Telangiectasia and Rad3-related) kinase, a key component of the DNA damage response pathway. It is primarily investigated for its potential in cancer therapy, enhancing the efficacy of DNA-damaging agents such as chemotherapy and radiation by inhibiting DNA repair mechanisms in cancer cells. This selectively increases cancer cell sensitivity to treatment while sparing healthy cells. Research focuses on its use in combination therapies for solid tumors and hematologic malignancies, with ongoing clinical trials evaluating safety and efficacy in various cancers including breast, ovarian, and prostate cancers.