As far as the UC pathology is concerned, the effects of ST 261, given orally or intrarectally, were investigated at different dosages, in preclinical experimentation, either after a single trinitrobenzene sulphonic acid (TNBS) administration (acute colitis) or after repeated TNBS administrations (reactivated colitis). The results showed a reduction in the damaged colon area both in acute model and reactivated colitis, even if the beneficial effect of restoration of TNBS-induced alterations of tissue morphology is more evident in the reactivated colitis model, particularly after oral administration.