Thiazole derivative and applications thereof

A compound represented by formula (I), or an isomer or a pharmaceutically acceptable salt thereof,

• wherein,
• R1 is selected from H, C1-4 alkyl or C3-6 cycloalkyl;
• R2 and R3 are independently selected from H, or are independently selected from C1-3 alkyl optionally substituted by 1, 2 or 3 R;
• R4, R5, and R6 are independently selected from H, F, Cl, Br or I, or are independently selected from the group consisting of phenyl, 5- to 6-membered heteroaryl, and 5- to 6-membered heteroaryl-O—, each of which is optionally substituted by 1, 2 or 3 R;
• ring A is selected from C5-7 cycloalkyl or 5- to 8-membered heterocycloalkyl;
• R is selected from F, Cl, OH, NH2, —COOH, C1-3 alkyl, C1-3 alkoxy, —N,N-di(C1-3 alkyl)amino, or C1-3 alkyl-C(═O)O—;
• the heteroatom or heteroatom group in the 5- to 6-membered heteroaryl and the 5- to 8-membered heterocycloalkyl is independently selected from —S—, —O—, —NH—, or N;
• and
• in any of the above cases, the number of the heteroatom or heteroatom group is independently selected from 1, 2 or 3.