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): (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； and m and n are integers each independently selected from 1 and 2, or a pharmaceutically acceptable salt thereof.
