The present invention provides a nitrogen-containing heterocyclic compound or a pharmaceutically acceptable salt thereof having an inhibitory effect on the production of kynurenine, represented by formula (I): (wherein R 6 and R 7 may be the same or different and each represent a hydrogen atom or the like, R 8 , R 9 , R 10 , and R 11 may be the same or different and each represent a hydrogen atom or the like, R 1 represents lower alkyl which may be substituted with cycloalkyl, or the like, and R 3 represents optionally substituted aryl or an optionally substituted heterocyclic group).
