A pharmaceutical composition is provided that has a low toxicity, demonstrates superior physicochemical properties and pharmacokinetics, and has superior peripheral blood lymphocyte count lowering activity. The pharmaceutical composition contains a compound having general formula (I): [Chemical Formula 1] (wherein R1 represents a methyl group or an ethyl group, R2 represents a methyl group or an ethyl group, and R3 represents a phenyl group substituted with 1 to 3 substituents selected from the group consisting of a halogen atom, a lower alkyl group, a cycloalkyl group, a lower alkoxy group, a halogeno lower alkyl group, a lower aliphatic acyl group and a cyano group), a pharmacologically acceptable salt thereof or a pharmacologically acceptable ester thereof.
