PROBLEM TO BE SOLVED: To provide compounds useful as fibroblast growth factor receptor 4(FGFR4) inhibitors.SOLUTION: The invention provides compounds of formula I or pharmaceutically acceptable salts. Also provided are pharmaceutical compositions containing the compounds of formula I or salts and pharmaceutically acceptable carriers. Further provided is the use of the pharmaceutical compositions for treating hepatocellular carcinoma.SELECTED DRAWING: None【課題】線維芽細胞増殖因子受容体4(FGFR4)阻害剤として有用な化合物の提供。【解決手段】式Iの化合物又はその薬学的に許容可能な塩。式Iの化合物又は塩と、薬学的に許容可能なキャリアとを含む医薬組成物。肝細胞癌の治療のための前記医薬組成物。【選択図】なし