The present invention relates to a compound which is (+)-1,4-dihydro-7-[(3S,4S)-3-methoxy-4-(methylamino)-1-pyrrolidinyl]-4-oxo-1-(2-thiazolyl)-1,8-naphthyridine-3-carboxylic acid for use in treating a hematologic cancer, wherein the compound is prepared to be administered in a dose of 60 mg/m 2 - 110 mg/m 2 .