The topically applied Toll-like receptor 9 (TLR9) agonist cobitolimod is a first-in-class DNA-based oligonucleotide that demonstrated therapeutic efficacy in clinical trials with ulcerative colitis (UC) patients. We here characterized its anti-inflammatory mechanism in UC.
Luminal cobitolimod administration was evaluated in an experimental DSS-induced colitis model. Cultured blood and mucosal cells from UC patients were treated with cobitolimod and analyzed via microarray, qRT-PCR, ELISA and flow cytometry. Intestinal slides of cobitolimod treated UC patients were analyzed by immunohistochemistry.
Cobitolimod administration markedly suppressed experimental colitis activity and microarrays analyses demonstrated mucosal IL10 upregulation and suppression of IL17 signaling pathways. Cobitolimod treatment was associated with significant induction of mucosal IL10+ Tr1 and Treg cells and suppression of Th17 cells. TLR9 knockout mice indicated that cobitolimod requires TLR9 signaling for IL10 induction. In UC patients, mucosal TLR9 levels correlated with severity of inflammation. Cobitolimod inhibited IL17A and IL17F, but increased IL10 and FoxP3 expression in cultured intestinal UC T cells. Cobitolimod-mediated suppression of intestinal IL17+ T cells was abrogated by IL10 blockade. Furthermore, cobitolimod led to heightened IL10 production by wound healing macrophages. Immunohistochemistry in intestinal biopsies of cobitolimod treated UC patients indicated increased presence of IL10+ mononuclear and regulatory T cells, as well as reduction of IL17+ cells.
Our studies suggest that activation of TLR9 via cobitolimod might represent a novel therapeutic approach in UC, as it suppresses Th17 cells and induces anti-inflammatory IL10+ macrophages and regulatory T cells, thereby modifying the dysregulated intestinal cytokine balance.