The introduction of biologic therapies, including anti-tumor necrosis factor (anti-TNF) inhibitors, has dramatically altered our approach to treating IBD in recent decades; however, up to 30% of patients do not respond to initial anti-TNF treatment (primary non-responder) and an additional 50% of responders will lose their response during treatment (secondary non-responders) (109–112). Here, TNF is linked to inflammatory bowel disease.