Novel therapeutic targets for inflammatory bowel disease.

Inflammatory bowel disease (IBD), including Crohn's disease (CD) and Ulcerative Colitis (UC), are immune mediated conditions associated with progressive damage of the inflamed gut tissue, and have a considerable impact on the patient's quality of life. The pathogenesis remains uncertain, but it is clear that complex mechanisms associated with host and luminal factors are involved, generating an unbalance between pro- and anti-inflammatory signaling. It is well established that the purpose of an adequate and complete control of the intestinal inflammation measured not only by clinical symptoms, but also with more objective data such as fecal biomarkers (calprotectin) and endoscopy. The treat to target approach possibly correlates with minor risk for complications associated with IBD, specially surgery and cancer. The most studied inflammatory pathway in IBD, is described to be dependent of the pro-inflammatory cytokine tumor necrosis factor-alfa (TNF-α), and compose the first line studies for development of biological drugs, in this case, targeting specifically the action of TNF-α. Even though, the use of anti-TNFs drugs are associated with improvement of the inflammation in some patients, a great portion do not respond at first or lose response over time. These findings made clear about the possibility of other mechanisms involved in perpetuating the chronic inflammatory state. Many years of intensive research have led to the identification of different inflammatory pathways that form the basis of the intensive drug development that we are experiencing today. These novel drugs include agents that target leukocyte trafficking, Interleukin (IL) 23, Janus kinases (JAK), Sphingosine 1 phosphate (S1P) and Smad7, an inhibitor of the immunosuppressive cytokine transforming growth factor β1 (TGF-β1). In this manuscript, we aim to review the most promising late-stage drug candidates for the treatment of IBD.