The present invention relates to the use of Volasertib or a pharmaceutically acceptable salt thereof or the hydrate thereof for treating myelodysplastic syndrome (MDS).本發明係關於沃拉賽蒂(Volasertib)或其醫藥上可接受之鹽或其水合物用以治療骨髓化生不良症候群(myelodysplastic syndrome;MDS)之用途。