The present invention relates to a therapeutic agent represented by the General formula (I), or a pharmacologically acceptable salt thereof, or a solvate of the compound or the salt thereof:The therapeutic agent comprises a substance having the activity of inhibiting kinase activity of fibroblast growth factor receptor 2 (“FGFR2”). The therapeutic agent can be used for treating undifferentiated gastric cancer, and can also be used to treat organisms comprising a cell overexpressing FGFR2 or a cell expressing mutant FGFR2, or both. The present invention further relates to a pharmaceutical composition comprising an FGFR2 inhibitory and methods of treatment therewith. The present invention also relates to a method for predicting the effect of an FGFR2 inhibitory substance on a patient.
