The present invention provides 2-[(3,5-difluoro-3-methoxy-1,1-biphenyl-4-yl)amino]nicotinic acid, or a pharmaceutically acceptable salt or N-oxide or solvate or deuterated derivative thereof, for use in the treatment of psoriasis.本發明提供用於牛皮癬治療之2-[(3,5-二氟-3-甲氧基-1,1-聯苯-4-基)氨基]菸鹼酸(2-[(3,5-difluoro-3-methoxy-1,1-biphenyl-4-yl)amino]nicotinic acid)、或其醫藥上可接受之鹽類或氮氧化物(N-oxide)或溶劑合物(solvate)或氘化衍生物(deuterated derivative)。