Provided is a kynurenine production inhibitor comprising a nitrogen-containing heterocyclic compound represented by formula (I): (wherein R 50 and R 51 may be the same or different and each represent a hydrogen atom or the like, G 1 and G 2 may be the same or different and each represent a nitrogen atom or the like, X represents formula (III): (wherein m 1 and m 2 may be the same or different and each represent an integer of 0 or 1, Y represents an oxygen atom or the like, and R 6 and R 7 may be the same or different and each represent a hydrogen atom or the like), R 1 represents optionally substituted lower alkyl or the like, R 2 represents a hydrogen atom or the like, and R 3 represents optionally substituted lower alkyl or the like), and the like.
