TNF and inflammatory bowel disease: Initial importance was placed on decreased drug trough levels and the development of anti-drug antibodies leading to increased clearance of the drug, however, there have also been reports of higher levels of certain MMPs in non-responders, leading to drug cleavage and inactivation, and finally the suggestion of non-TNF-α mediated inflammation in certain IBD sub-groups, or the inability of anti-TNF-α agents to reach the level of intestinal inflammation [91,92,93].