Enhanced therapeutic effect of LK-423 in treating experimentally induced colitis in rats when administered in colon delivery microcapsules.

LK-423 is a phthalimido-desmuramyl-dipeptide derivative with immunomodulating activity. In the present study the therapeutic efficacy of a colon-specific drug delivery system–LK-423 microcapsules–was examined in the 2,4,6-trinitrobenzene sulphonic acid (TNBS)-induced ulcerative colitis model in rats. The colon-specific delivery of the drug using microcapsules relies on the combination of pH (outer gastroresistant coating), time (inner retard coating of Eudragit® RS and RL) and enzyme (pectin core) controlled drug release mechanisms. The optimal in vitro dissolution profile for LK-423 delivery to the colon of rats was obtained after coating newly developed LK-423 loaded pectin cores with 20% w/w of retard coating with a Eudragit® RS/RL ratio of 8.5/1.5 and 30% w/w of enteric coating. Orally administered LK-423 microcapsules were therapeutically more beneficial in treating TNBS-induced ulcerative colitis in rats than orally or rectally administered LK-423 in the form of suspension. Clinical activity scores and colon weight to length ratio were insignificantly lower and the macroscopically estimated degree of healing was significantly greater. On the histological level, the administration of LK-423 microcapsules resulted in most physiological regeneration of intestinal mucosa, indicated by regular architecture of all mucosal tissue components, what is probably related to local drug delivery near the site of inflammation achieved using microcapsules. These results demonstrate that LK-23 colon delivery microcapsules enhance the therapeutic efficacy of the drug and therefore appear to be a useful approach for treating various inflammatory diseases in the large intestine.