Provided is a kynurenine production inhibitor comprising a nitrogen-containing heterocyclic compound represented by formula (I):(wherein R50 and R51 may be the same or different and each represent a hydrogen atom or the like, G1 and G2 may be the same or different and each represent a nitrogen atom or the like, X represents formula (III):(wherein m1 and m2 may be the same or different and each represent an integer of 0 or 1, Y represents an oxygen atom or the like, and R6 and R7 may be the same or different and each represent a hydrogen atom or the like),R1 represents optionally substituted lower alkyl or the like, R2 represents a hydrogen atom or the like, and R3 represents optionally substituted lower alkyl or the like), and the like.
