Introduction: Vedolizumab is a monoclonal antibody that selectively blocks α4β7 integrin and has already been approved for use in patients with moderate-to-severe ulcerative colitis both as first and second line. Etrolizumab is a monoclonal antibody still being tested, which acts with a dual mechanism by selectively inhibiting both α4β7 and αEβ7 integrins.Areas covered: This review provides an overview of the literature data of vedolizumab and etrolizumab, in order to define their role in the treatment of patients with moderate-to-severe ulcerative colitis.Expert opinion: Etrolizumab and vedolizumab block the α4β7 integrin with a similar action mechanism. However, the inhibition of αEβ7 integrin by etrolizumab distinguishes the two anti-integrins making them 'cousin' drugs. Phase 3 clinical trials are needed to confirm the promising etrolizumab's efficacy data and to resolve any doubts about its safety, allowing a clearer comparison with vedolizumab.
Keywords: Vedolizumab; etrolizumab; selectivity; ulcerative colitis.