This invention relates to a novel crystalline form (Form A) of 1-(4-{1-[(E)-4-cyclohexyl-3-trifluoromethyl-benzyloxyimino]-ethyl}-2-ethyl-benzyl)-azetidine-3-carboxylic acid (Compound I), to pharmaceutical compositions comprising this crystalline form, to processes for forming it and to its use in medical treatment.