Patent ID: 8853242

Claim:
A compound of formula (I) or a pharmaceutically acceptable salt thereof: (wherein the symbols have the following meanings: : aryl, cycloalkyl, cycloalkenyl or monocyclic nitrogen-containing heterocyclic group, Z 1 , Z 2 , Z 3 , Z 4 and Z 5 : one of any of them is a nitrogen atom, and the others are carbon atoms, in which the nitrogen atom is optionally oxidized to form an N-oxide, R 1 , R 2 and R 3 : each independently represents H, lower alkyl, halogen, halogeno-lower alkyl, —CN, —NO 2 , —OR a , —S-lower alkyl, —O-halogeno-lower alkyl, —CO 2 R a , —C(O)NR b R c , —SO 2 -lower alkyl, or -lower alkylene-OR a , R 4 , R 5 and R 6 : each independently represents H, lower alkyl, cycloalkyl, halogen, halogeno-lower alkyl, —CN, —NO 2 , —OR a , —SO 2 -lower alkyl, —O-halogeno-lower alkyl, —CO 2 R a , —C(O)NR b R c , —SO 2 -lower alkyl, or lower alkylene-OR a , R a , R b and R c : each independently represents H or lower alkyl, and R 7 and R 8 : each independently represents H or lower alkyl).