[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(R 0 )C(O)-lower alkylene-CO 2 R 0 , lower alkylene-CO 2 R 0 , lower alkenylene-CO 2 R 0 , -O-lower alkylene-CO 2 R 0 ,-O-(lower alkylene which may be substituted with -CO 2 R 0 )-aryl or -O-lower alkenylene-CO 2 R 0 (wherein R 0 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.本發明提供一種具有優良血小板凝集阻礙作用之化合物。本發明為發現於1位上具有低級烷基、環烷基等；3位上具有－N(R0)C(O)－低級伸烷基－CO2R0、低級伸烷基－CO2R0、低級伸烯基－CO2R0、－O－低級伸烷基－CO2R0、－O－(可被－CO2R0取代之低級伸烷基)－芳基、－O－低級伸烯基－CO2R0(但，R0為H或低級烷基)；6位上具有鹵素；7位上具有環結構之取代基所取代之胺基為特徵之喹啉酮衍生物或其製藥學上可被容許之鹽，其具有優良的P2Y12阻礙作用。又，亦確認這些喹啉酮衍生物具有優良的血小板凝集阻礙作用。由以上得知這些喹啉酮衍生物或其製藥學上可被容許之鹽可作為血小板凝集阻礙劑使用。
