[Problem] To provide a compound having excellent platelet aggregation inhibitory activity.[Means for Resolution] It was found that quinolone derivatives characterized in that these have lower alkyl, cycloalkyl or the like at the 1-position -N(R0)C(O)-lower alkylene-CO2R0, lower alkylene-CO2R0, lower alkenylene-CO2R0, -O-lower alkylene-CO2R0,-O-(lower alkylene which may be substituted with -CO2R0)-aryl or -O-lower alkenylene-CO2R0 (wherein R0 is H or lower alkyl) at the 3-position halogen at the 6-position and amino group substituted with a substituent group having a ring structure at the 7-position, respectively, or pharmaceutically acceptable salts thereof, has excellent P2Y12 inhibitory activity. In addition, it was confirmed that these quinolone derivatives also have excellent platelet aggregation inhibitory activity. Based on the above, these quinolone derivatives or pharmaceutically acceptable salts thereof are useful as platelet aggregation inhibitors.
