Strategies for targeting cytokines in inflammatory bowel disease

Cytokines produced by immune cells contribute to the development and perpetuation of inflammatory bowel disease (IBD), namely Crohn's disease and ulcerative colitis, by regulating various aspects of the inflammatory response. Pro-inflammatory cytokines trigger chronic intestinal inflammation, tissue damage, carcinogenesis and perpetuation of disease and suppress the resolution of inflammation in IBD. The clinical success of antibodies that neutralize tumour necrosis factor (TNF) and the cytokine IL-12p40 in individuals with IBD has underscored this concept. Moreover, genetic and preclinical studies have emphasized the crucial role of IL-23 in IBD, leading to clinical approval of antibodies targeting this cytokine. Multiple studies have also investigated the administration of cytokines with assumed anti-inflammatory effects, but this approach has yet to show any real clinical benefit in individuals with IBD. Recent studies have targeted the cytokine network through the use of multi-cytokine blockers (for example, Janus kinase (JAK) inhibitors), IL-2-induced regulatory T cells or advanced combination therapies that use multiple cytokine blockers simultaneously (for example, anti-TNF along with anti-IL-23 antibodies). This Review will focus on our current understanding of how cytokines produced by innate and adaptive immune cells contribute to IBD pathogenesis and discuss how their modulation may inform future treatments for IBD.