This invention provides an
interleukin-31 (IL-31) production inhibitor and a pharmaceutical composition comprising the inhibitor. The invention also provides a novel compound useful as an
active ingredient for an IL-31 production inhibitor. These comprise a compound represented by the following formula (1) or a salt thereof as an
active ingredient: wherein A is a -NH-N=C(R1)- group, a
divalent N-containing 5-membered heterocyclic group, or a -NH-CO- group, wherein R1 is a
hydrogen atom or a C1-4
alkyl group, B is the same or different and is a C1-6
alkyl group optionally having one hydroxyl group, a mono or di(C1-6
alkyl)amino group optionally having one hydroxyl group, a
halogen atom, a halo C1-6 alkyl group, a C2-6 alkynylene group, or a carboxy group, wherein at least one C1-6 alkyl group in the mono or di (C1-6 alkyl) amino group is optionally attached to a
carbon atom adjacent to a
carbon atom in the
phenyl group to which it is attached, to form a 5- to 6-membered ring, and n is an integer of 1 to 5.