PROBLEM TO BE SOLVED : To provide methods of treating a cancer characterized by the presence of a mutant allele of IDH1 (isocitrate dehydrogenase 1) or IDH2 (isocitrate dehydrogenase 2).SOLUTION : The present invention provides methods of treating a cancer characterized by the presence of a mutant allele of IDH1 (isocitrate dehydrogenase 1) or IDH2 (isocitrate dehydrogenase 2), comprising the step of administering to subject in need thereof a dipeptide derivative compound of Formula I, as an inhibitor of the enzyme, or a pharmaceutically acceptable salt, tautomer, isotopologue, or hydrate thereof.SELECTED DRAWING : NoneCOPYRIGHT : (C)2019, JPO&INPIT