PROBLEM TO BE SOLVED : To provide a method for assessing an appropriate therapeutic dose of S1P modulator BAF312 (1-{4-[1-(4-cyclohexyl-3-trifluoromethyl-benzyloxyimino)-ethyl]-2-ethyl-benzyl}-azetidine-3-carboxylic acid) to administer it to a patient in need thereof. SOLUTION : The method comprises the steps of : (i) examining whether the patient has a poor metabolizer genotype or not; and (ii) when the patient does not have the poor metabolizer genotype, administering a standard therapeutic dose of BAF312 or pharmaceutically acceptable salt thereof to the patient; or (iii) when the patient has the poor metabolizer genotype, either (a) administering the S1P modulator BAF312 or pharmaceutically acceptable salt thereof at a dose less than the standard therapeutic dose to the patient or (b) not administering the S1P modulator BAF312 or pharmaceutically acceptable salt thereof to the patient. SELECTED DRAWING : None COPYRIGHT : (C)2019, JPO&INPIT