Charlotte Admyre [1], Heike Schmitt [2], Ulrike Billmeier [2], Julia Ulmschneider [2], Thomas Knittel [1], Arezou Zargari [1], Markus F Neurath [2], Raja Atreya [2]

Affiliates

InDex Pharmaceuticals, Tomtebodavägen 23a, SE-171 77 Stockholm, Sweden [1], Medical Clinic 1, Friedrich-Alexander-University Erlangen-Nürnberg, Erlangen, Germany [2]

Abstract

BACKGROUND
Cobitolimod is a Toll-like receptor 9 (TLR9) agonist which has demonstrated clinical efficacy and a favourable safety profile in patients with active ulcerative colitis (UC). To gain a deeper understanding of its mechanism of action, we analyzed the efficacy of cobitolimod in an experimental colitis model and in peripheral blood or mucosal immune cells of UC patients.

METHODS
The immunomodulatory effects of rectally applied cobitolimod were evaluated in the dextran sulfate sodium (DSS)-induced colitis model. Peripheral blood or mucosal immune cells from UC patients were incubated with cobitolimod in vitro and IL-10 and IL-17 expression was determined by PCR, ELISA and flow cytometry. Furthermore, colon biopsies from UC patients that participated in two clinical trials with local application of cobitolimod (EudraCT number: 2006-001846-15 and ClinicalTrials.gov identifier: NCT01493960), were analyzed by immunohistochemistry for IL-10, FoxP3 and IL-17 expressing cells.

RESULTS
Cobitolimod ameliorated DSS-induced colitis, as it significantly reduced the disease activity index and endoscopic colitis grade of the mice. Th17 cells and proinflammatory IL-17 and IL-6 cytokines in intestinal specimen as well as IL-17 in the serum were significantly decreased after cobitolimod treatment.
Peripheral blood or mucosal immune cells from UC patients incubated with cobitolimod, demonstrated significantly decreased IL-17 and increased IL-10 expression compared to controls. Immunohistochemical analysis of colon biopsies from UC patients taken before and four weeks after local cobitolimod treatment, clearly indicated a significant induction of IL-10+ and a pronounced reduction of IL-17+ mucosal immune cells, which were not observed in the placebo group. In addition, FOXP3+ T-cells (T-reg cells) were significantly increased in the colon of UC patients upon cobitolimod treatment.

CONCLUSIONS
Local administration of cobitolimod modulates the immune response in experimental colitis as well as in UC patients. Our studies demonstrate that cobitolimod decreases IL-17 and the number of Th17 cells, while it increases mucosal IL-10 and T-reg cells, thus modulating the Th17/T-reg imbalance in intestinal inflammation. In conclusion, cobitolimod addresses new therapeutic targets in the immunopathogenesis of UC, leading to anti-inflammatory effects.