PROBLEM TO BE SOLVED: To provide a novel inhibitor of histone deacetylase 8 (HDAC8).SOLUTION: The present invention relates to compounds of general formula V or their pharmacologically acceptable salts, N-oxides or prodrugs. The present invention also relates to a HDAC8 inhibitor therapeutic method by using the HDAC8 inhibitor alone or in combination with another compound.【課題】ヒストン脱アセチル化酵素８（ＨＤＡＣ８）の新規インヒビターの提供。【解決手段】下記一般式Ｖの化合物若しくはそれらの薬学的に許容可能な塩、Ｎ－オキシド又はプロドラッグ。又、該ＨＤＡＣ８インヒビターを、単独で及び他の化合物と組み合わせたＨＤＡＣ８インヒビターの治療方法。【選択図】図１
