PROBLEM TO BE SOLVED: To provide a novel agent for treating or preventing graft-versus-host disease that can be used for treating or preventing a patient of graft-versus-host disease.SOLUTION: An agent for treating or preventing graft-versus-host disease contains a senescent cell removing agent as an active ingredient. The senescent cell removing agent is preferably ABT-263 represented by the formula (I).SELECTED DRAWING: NoneCOPYRIGHT: (C)2020,JPO&INPIT【課題】移植片対宿主病の患者の治療又は予防に用いることができる新規な移植片対宿主病の治療剤又は予防剤を提供する。【解決手段】移植片対宿主病の治療剤又は予防剤は、老化細胞除去剤を有効成分として含有する。前記老化細胞除去剤は、下記式（Ｉ）で表されるＡＢＴ－２６３が好ましい。［化１］【選択図】なし
