A novel immunosuppressive agent, more specifically an immunosuppressive agent comprising, as an active ingredient, a heterocyclic compound represented by the general formula (I) (wherein X or other variables are as defined in the specification) or a pharmaceutically acceptable salt thereof； a novel heterocyclic compound represented by the general formula (II) (wherein X or other variables are as defined in the specification) or a pharmaceutically acceptable salt thereof； and use of the compound or salt as an antitumor agent.本發明係有關新穎的免疫抑制劑，更詳細為關於以一般式(I)[X等如專利說明書中定義]所示之雜環式化合物，或以其藥學上可容許的鹽為有效成份之免疫抑制劑。又本發明係有關以一般式(II)[X等如專利說明書中定義]所示之新穎的雜環式化合物，或其藥學上可容許的鹽，進而亦與其新穎化合物，或其藥學上可容許的鹽之抗腫瘤劑的用途相關。
