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OP004 The TLR9 agonist cobitolimod induces anti-inflammatory effects and balances the Th17/T-reg cell response in ulcerative colitis

H. Schmitt1*, U. Billmeier1, J. Ulmschneider1, C. Admyre2, T. Knittel2, A. Zargari2, M.F. Neurath1, R. Atreya1

1Friedrich-Alexander-University Erlangen-Nürnberg, First Department of Medicine, Erlangen, Germany, 2InDex Pharmaceuticals AB, Stockholm, Sweden

Background

The DNA-based oligonucleotide cobitolimod (DIMS0150) is a toll-like receptor 9 (TLR9) agonist and has demonstrated clinical efficacy and a favourable safety profile in inducing clinical remission in patients with active ulcerative colitis (UC). To gain a deeper understanding of its mechanism of action, we analysed 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 sulphate sodium (DSS)-induced colitis model. Isolated 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 quantitative PCR, ELISA, and flow cytometry. Furthermore, histological slides from colon biopsies of steroid refractory UC patients that participated in two randomised, double-blind, multicentre clinical trials with local application of cobitolimod (EudraCT number: 2006-001846-15 and ClinicalTrials.gov identifier: NCT01493960), were analysed by immunohistochemical staining for IL-10, FoxP3, and IL-17 expressing cells.

Results

Cobitolimod treatment ameliorated DSS-induced colitis, as it significantly reduced the disease activity index and endoscopic colitis grade and increased the body weight of the mice. Th17 cells and proinflammatory IL-17A, IL-17F, 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 with controls. Quantitative 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, regulatory FOXP3+ T cells (T-reg cells) were significantly increased in the colon of UC patients upon cobitolimod treatment.

Conclusion

Local administration of the TLR9 agonist cobitolimod modulates the immune response in a mouse model of colitis as well as in UC patients. Our studies demonstrate that cobitolimod treatment decreases IL-17 expression and the number of Th17 cells, while it increases mucosal IL-10 expression and the quantity of 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 pronounced anti-inflammatory effects.