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.