FIELD: chemistry.SUBSTANCE: invention relates to organic chemistry and specifically to a heterocyclic compound of formula (1) or a pharmaceutically acceptable salt thereof, where R1: (1–1) hydrogen, (1–2) pyrazolyl, (1–3) pyrimidinyl, (1–4) pyridyl, having 1–2 substitutes selected from halogen, cyano, C1-C6 alkyl, C1-C6 alkylsulphonyl and halogen-substituted methyl, (1–5) oxazolyl, having one C1-C6 alkyl group, (1–6) pyrazinyl, optionally substituted with 1 group selected from halogen and C1-C6 alkyl, (1–7) phenyl, having 1–2 substitutes selected from halogen and halogen-substituted methyl, (1–8) (pyridine 1-oxide)yl, having 1–2 substitutes selected from halogen and halogen-substituted methyl, (1–9) halogen-substituted thiazolyl, (1–10) C1-C6 alkyl-substituted isoxazolyl, (1–11) cyclopropyl-substituted 1,2,4-oxadiazolyl, or (1–12) phenyl； R2: hydrogen or C1-C6 alkoxy； R3: (3–1) hydrogen, (3–2) C1-C6 alkoxy, (3–3) C1-C6 alkoxy C1-C6 alkoxy, (3–4) C1-C6 alkyl, (3–5) halogen, (3–6) benzyloxy, or (3–7) hydroxy； R4: (4–1) pyridyl, optionally having a substitute selected from halogen, cyano, hydroxy, pyrrolidinyl, C1-C6 alkyl, C1-C6 alkylthio, C1-C6 alkylsulphonyl, C1-C6 alkoxy and halogen-substituted C1-C6 alkyl, R5: (5–1) hydrogen, (5–2) C1-C6 alkyl, or (5–3) C1-C6 alkoxy； R6: (6–1) hydrogen, (6–2) C1-C6 alkoxy C1-C6 alkyl, or (6–3) C1-C6 alkyl optionally substituted with one cyclopropyl group, wherein R6 is attached to only one of N in 1-position and N in 3-position of imidazole skeleton, R6 is attached to N in 1-position when the bond between N in 3-position and C in 2-position of the imidazole backbone is a double bond, and R6 is attached to N in 3-position, when the bond between N in 3-position and C in 2-position of the imidazole backbone is a single bond； R7: (7–1) hydrogen, (7–2) halogen, (7–3) C1-C6 alkyl, (7–4) hydroxymethyl, (7–5) halogen-substituted C1-C6 alkyl, or (7–6) cyano； A is a single bond when R1 is hydrogen, and A is C1-C2 alkylene, when R1 represent
