The present invention relates to the HDM2-p53 interaction inhibitors (S)-5-(5-Chloro-1-methyl-2-oxo-1,2-dihydro-pyridin-3-yl)-6-(4-chloro-phenyl)-2-(2,4-dimethoxy-pyrimidin-5-yl)-1-isopropyl-5,6-dihydro-1H-pyrrolo[3,4-d]imidazol-4-one (HDM201), or a pharmaceutically acceptable non-covalent derivative thereof, for use in the treatment of patients with hematological tumors, wherein the drug is administered by an extended low dose dosing regimen.
