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Background Janus Kinases (JAK), including JAK1, JAK2, JAK3 and TYK2, have garnered increasing interest as therapeutic targets for several chronic inflammatory diseases such as inflammatory bowel disease (IBD). Although oral small molecule JAK inhibitors are being used in the clinics as an effective treatment for moderate-to-severe ulcerative colitis, nonethelessthey can lead to severe systemic immunosuppression, which is associated with an increased risk of infections. Our project aimed to develop a nanomedicine that induced JAK1 mRNA degradation within the intestinal mucosa with little systemic distribution. Methods The NEWDEAL project (H2020) developed both potent small interfering RNAs (siRNA) specific for JAK1 (siJAK1) or TNF (siTNF), and lipid nanoparticles (CL40) as nano-vectors. Their biodistribution in a mice colitis model was analyzed using labeled AF488-siJAK1 complexed to CL40 and given intrarectally (IR) for 3 consecutive days. In vivo cellular uptake was determined by FACS analysis. To induce colitis, C57/Bl6 mice received 2.5% dextrate sulfate sodium (DSS) in drinking water for 5 days. To determine efficacy of siRNAs, mice started DSS on day 0 and received IR administrations of siRNAs alone or complexed with CL40 nanoparticles on days -3, -2, -1, 1, 3, 5 and 7. On day 9, mice were sacrificed and disease activity index (DAI), histological score, fecal inflammatory markers and qPCR of targeted genes were analyzed. Results Colonic phagocytic cells - such as macrophages, neutrophils and monocytes - are the main targets cells of the siRNA-CL40 nanocomplexes following IR administration. A small percentage of cells in the draining lymph nodes captured siRNA CL40 nanocomplexes, remaining almost undetectable in spleen. This suggests a localized effect of the siRNA nanocomplexes after IR administration. While siJAK1-alone effectively reduced JAK1 mRNA expression in the distal colon, it did not improve intestinal inflammation induced by administering DSS. siTNF-CL40 treatment, though not siTNF-alone, significantly decreased intestinal inflammation in the DSS colitis model of treated mice, revealing significant protection from weight loss, lower histological scores, and reduced production of fecal lipocalin. Conclusion In summary, these results show that despite effectively reducing JAK1 mRNA expression, siJAK1 administration does not ameliorate colitis in a DSS mice model. However, we showed that a locally delivered siTNF-nanocomplex has the capacity to improve clinical, macroscopic and histological symptoms as well as fecal biomarkers in DSS colitic mice. We conclude not only that siRNA-CL40 target delivery is a good therapeutic strategy, but also that siTNF-CL40 is effective in locally treating intestinal inflammation.

P056 Local nanocarrier delivery of JAK1 siRNA for IBD treatment: an in vivo mouse model