Disclosed are 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. The quinolone derivatives have excellent platelet aggregation inhibitory activity. A method of using the compounds is also disclosed.
