Evaluation of 5-aminosalicyltaurine as a colon-specific prodrug of 5-aminosalicylic acid for treatment of experimental colitis

We previously reported that 5-aminosalicyltaurine (taurine-conjugated 5-ASA, 5-ASA-Tau) showed a potential as a colon-specific prodrug of 5-aminosalicylic acid (5-ASA) by in vitro evaluation. In this report, we in vivo-evaluated 5-ASA-Tau as a colon-specific prodrug for treatment of experimental colitis. Taurine conjugation of 5-ASA greatly reduced absorption of 5-ASA from the intestine. Oral administration of taurine-conjugated 5-ASA not only increased the colonic delivery efficiency of 5-ASA but also decreased the systemic absorption of free 5-ASA as compared with that of 5-ASA and, moreover, taurine is similarly effective to known colon-specific carriers for 5-ASA, glycine and aspartic acid, suggesting that taurine conjugation is an efficient way to increase the therapeutic effect and to reduce the adverse effects of 5-ASA. Intracolonic treatment with combined 5-ASA/taurine additively ameliorated TNBS-induced colitis rats indicating that taurine acted as not only a promoiety but also a therapeutically active agent. Furthermore, 5-ASA-Tau is slightly more effective than sulfasalazine in alleviating the colonic inflammation induced by TNBS. Taken together, our data suggest that 5-ASA-Tau is a potential colon-specific prodrug of 5-aminosalicylic acid with improved therapeutic activity against inflammatory bowel disease.