The agent of the present invention is 2-amino-2- [4- (3-benzyloxyphenylthio) -2-chlorophenyl] ethyl-propane-1,3-diol or a pharmaceutically acceptable salt thereof It is an active ingredient, and inhibits the recurrence of hematological malignancies and / or improves the survival rate of patients undergoing hematopoietic stem cell transplantation for the treatment of hematological malignancies.本發明之藥劑以2-胺基-2-[4-(3-苄氧基苯硫基)-2-氯苯基]乙基-丙烷-1,3-二醇或其藥學上容許之鹽為有效成分，且對為了治療血液惡性腫瘤而接受造血幹細胞移植的患者抑制血液惡性腫瘤之復發，及/或提高存活率。
