A compound represented by formula (I):
(wherein Ar1 represents a phenyl group which may have 1 to 3 substituents, or a non-substituted 5- or 6-membered aromatic heterocyclic group; Ar2 represents (i) a non-substituted phenyl group, (ii) a phenyl group which has been substituted by a lower alkyl group having 1 to 3 groups or atoms selected from among a carbamoyl group, an amino group, a hydroxyl group, a lower alkoxy group, and a halogen atom, or (iii) a 5- or 6-membered nitrogen-containing aromatic heterocyclic group which has been substituted by 1 to 3 groups or atoms selected from among a lower alkyl group, a lower alkynyl group, a lower alkanoyl group, a carbamoyl group, a cyano group, an amino group, a hydroxyl group, a lower alkoxy group, and a halogen atom; and X represents a group represented by formula (II):
(wherein the ring structure represents a 4- to 7-membered heterocyclic group which may have, in addition to the nitrogen atom shown in formula (II), one heteroatom selected from among nitrogen, oxygen, a sulfur, and which may be substituted by 1 to 4 groups or atoms selected from among a lower alkyl group, a carbamoyl group, an amino group, a hydroxyl group, a lower alkoxy group, an oxo group a lower alkanoyl group, a lower alkylsulfonyl group, and a halogen atom)), a salt thereof, a solvate of the compound or the salt, and a drug.