The present invention relates to pyrazine compounds useful as inhibitors of ATR protein kinase. The invention also relates to pharmaceutically acceptable compositions comprising the compounds of this invention； methods of treating of various diseases, disorders, and conditions using the compounds of this invention； processes for preparing the compounds of this invention； intermediates for the preparation of the compounds of this invention； and methods of using the compounds inin vitroapplications, such as the study of kinases in biological and pathological phenomena； the study of intracellular signal transduction pathways mediated by such kinases； and the comparative evaluation of new kinase inhibitors.The compounds of this invention have formulaI:wherein the variables are as defined herein.本發明係關於可作為ATR蛋白質激酶之抑制劑使用之吡化合物。本發明亦關於包含本發明化合物之藥學上可接受之組合物；使用本發明化合物治療各種疾病、病症及症狀之方法；製備本發明化合物之方法；用於製備本發明化合物之中間物；及在活體外應用上使用該化合物之方法，譬如激酶在生物學與病理學現象上之研究；藉由此種激酶所媒介之胞內訊息轉導途徑之研究；及新穎激酶抑制劑之比較評估。本發明化合物具有式I：其中變數均如本文中所定義。
