A method of treating vitiligo, including prophylaxis, in a subject in need thereof, comprising administering to said subject a pharmaceutically effective amount of a compound of Formula (I):wherein:X is CR1 or N；Y is CH, C or N；R1 is hydrogen, C1-6alkoxy or C1-6alkyl；R2 is hydrogen, C1-6alkoxy, halo, —C(O)C1-6alkyl, CN, halo-C1-6alkyl or —C(O)NR4R5；R3 is hydrogen or C1-6alkoxy；R4 is hydrogen or C1-6alkyl:R5 is hydrogen or C1-6alkyl； andm and n are integers each independently selected from 1 and 2, or a pharmaceutically acceptable salt thereof.
