The invention relates to the essentially pure Λ/-[({2-[4-(2-Ethyl-4,6-dimethyl-1H-imidazo[4,5-c]pyridin-1-yl)phenyl]ethyl}amino)carbonyl]-4-methylbenzenesulfonamide Polymorph Forms A and B and to processes for the preparation of, compositions containing and to the uses of, such crystal forms.