PROBLEM TO BE SOLVED: To provide a Wip1 inhibitor targeted for cancer treatment.SOLUTION: A Wip1 protein phosphatase inhibitor includes a compound represented by the chemical formula, as an effective component. [In the formula, X is R or -SeR, and R and R each independently represents a hydrocarbon group, an aromatic hydrocarbon group or a heterocyclic group which may have a functional group.] A phenyl diselenide is exemplified as a specific compound.COPYRIGHT: (C)2014,JPO&INPIT【課題】がん治療等の標的となるWip1阻害剤の提供。【解決手段】以下の化学式で表される化合物を有効成分とする、Wip1プロテインホスファターゼ阻害剤。[式中のXはR’又は-SeR’であり、R及びR’は、それぞれ独立に、官能基を有してもよい炭化水素基、芳香族炭化水素基又は複素環基を示す。]フェニルジセレニドが具体的化合物として例示される。【選択図】なし