Inflammatory bowel disease (IBD), including ulcerative colitis and Crohn's disease, is typified by a chronic gastrointestinal inflammatory microenvironment, driven in part by the excessive infiltration and retention of intestinal-homing lymphocytes. A recent class of drugs designed to impair lymphocyte homing, so-called "anti-trafficking agents" (ATAs), have shown some success and include approved drugs such as natalizumab and vedolizumab, which target integrins and impair their interaction with adhesion molecules on epithelial cells. In the case of natalizumab, which targets the α4 integrin subunit, this has also resulted in undesirable blockade of lymphocyte CNS trafficking and reported cases of progressive multifocal leukoencephalopathy (PML). Etrolizumab is a humanized IgG1κ monoclonal antibody directed against the β7 subunit of gastrointestinal α4β7 and αEβ7 integrins that, due to its target specificity, appears as or more efficacious than vedolizumab and without the CNS effects of natalizumab. Etrolizumab is currently under investigation for the treatment of ulcerative colitis and Crohn's disease.