A compound of the formula (I): wherein Ring A and Ring B are (1) Ring A is anoptionally substituted unsaturated monocyclic heterocyclic ring, and Ring B isan optionally substituted unsaturated monocyclic heterocyclic ring, anoptionally substituted unsaturated fused heterobicyclic ring, or an optionallysubstituted benzene ring, (2) Ring A is an optionally substituted benzenering, and Ring B is an optionally substituted unsaturated monocyclicheterocyclic ring, an optionally substituted unsaturated fused heterobicyclicring, or an optionally substituted benzene ring, or (3) Ring A is anoptionally substituted unsaturated fused heterobicyclic ring, wherein -NR-group and -CH2- group are both on the same ring of the unsaturated fusedheterobicyclic ring, and Ring B is an optionally substituted monocyclicunsaturated heterocyclic ring, an optionally substituted unsaturated fusedheterobicyclic ring, or an optionally substituted benzene ring； and R is ahydrogen atom, a lower alkyl group, a lower alkanoyl group or a loweralkoxycarbonyl group, or a pharmaceutically acceptable salt thereof, or aprodrug thereof.
