The etiology of inflammatory bowel disease (IBD) is unknown. However, chronic inflammation from T cell activation and its subsequent tissue damage is implicated in the pathogenesis of IBD. Vedolizumab (VDZ), a monoclonal antibody against α4β7 integrin that prevents T cell homing to intestinal mucosae, has shown efficacy in treating both ulcerative colitis (UC) and Crohn’s disease (CD), with greater efficacy in UC. We aimed at identifying immunophenotypic and gene regulatory characteristics that could predict which IBD patients will benefit from VDZ therapy.