The present invention provides a compound represented by general formula (1) below or a pharmaceutically acceptable salt thereof: wherein: X is selected from heteroaryl etc., Y1 and Y2 are selected from —N═ etc., Y3 and Y4 are selected from —CH═ etc., A is selected from sulfamide etc., R1 is selected from hydrogen etc., and R2 is selected from C1-6 alkyl etc. The compound or salt has sufficiently high antitumor activity, and is useful in the treatment of cell proliferative disorders, particularly cancers. The present invention also provides a pharmaceutical composition containing the compound or salt as an active ingredient.