FIELD: chemistry.SUBSTANCE: invention relates to the field of organic chemistry, specifically to a heterocyclic compound of formula (I) or a pharmaceutically acceptable salt thereof, where R1 is C1-6 alkyl, C3-6 cycloalkyl, substituted C3-6 cycloalkyl, C1-4 alkoxy, C1-4 alkoxy-C1-6 alkyl, C1-4-alkoxy-C1-4 alkoxy, C1-6-alkoxycarbonyl-C1-6-alkyl, carboxy-C1-4alkyl, C1-4-haloalkyl, C1-4-haloalkoxy, substituted phenyl, 5-6 membered heterocycloalkyl containing 1 heteroatom, selected from N and O, substituted 4-6 membered heterocycloalkyl, containing 1 heteroatom selected from N and O, tetrahydrofuran-C1-4-alkoxy, tetrahydrofuranyloxy, tetrahydropyranyloxy, furan, a substituted 5-6 membered heteroaryl containing 1 to 2 heteroatoms, selected from N, amino, substituted amino, wherein the substituted cycloalkyl, substituted phenyl, substituted heterocycloalkyl and substituted heteroaryl are substituted by one to two substituents, independently selected from halogen, C1-6-alkyl, C1-4-haloalkyl, C1-4-hydroxyalkyl, C1-4-alkylsulfonyl-C1-4 alkyl, C1-4 alkoxycarbonyl, C1-4 alkoxy and C1-4 alkoxy C1-4 alkyl, and wherein the substituted amino is substituted on the nitrogen atom by one to two substituents, independently selected from C1-4 alkyl； R2 is -COOH, tetrazol-5-yl, [1,3,4] oxadiazol-2-thion-5-yl； R3 is phenyl, substituted phenyl, substituted dihydropyridinyl, 5-9 membered mono or bicyclic heteroaryl, containing 1 to 3 heteroatoms selected from N, S and O, or substituted 5 to 6 membered heteroaryl, containing 1-2 heteroatoms selected from N, S and O, wherein the substituted phenyl, substituted dihydropyridinyl and substituted heteroaryl are substituted with one to two substituents, independently selected from hydroxy, oxo, halogen, C1-6-alkyl, C3-6-cycloalkyl, C1-4-haloalkyl, C1-4-haloalkoxy, hydroxy-C1-4-alkoxy, C1-4-alkoxy, C1-4-alkylsulfonyl, amino substituted with the nitrogen atom by C1-4-alkyl； A1 is a link； A2 represents -CR14R15-, -NR16-, -O-, -S-； A3 represents -CR17
