More specifically, the present invention provides a cinnoline derivative of the formula (I): ##STR4## wherein X is --O-- or a group of the formula: ##STR5## (wherein R4 is a hydrogen atom or C1 -C5 alkyl group such as methyl group, propyl group, pentyl group or the like); A is a group of the formula: ##STR6## (wherein n is an integer selected from 1 to 5, R5 is a hydrogen atom, C1 -C5 alkyl group