Compounds of formula (I), in which R.sub.1 and R.sub.2 are independently a substituted phenyl group, where the substituents are as defined in the claims and with the proviso that at least one of the substituents is a cyano, carboxy or (C.sub.1-4)alkoxycarbonyl group, are inhibitors of CCR9 activity useful for therapeutic treatment, particularly of irritable bowel disease.