We read with great interest the article by Tew et al1 on the association between increased gene expression of integrin αE and granzyme A (GZMA) and clinical remission to etrolizumab treatment in patients with ulcerative colitis (UC). This report follows the recent publication of the phase II trial on etrolizumab, describing its moderate potential as induction therapy for UC.2 Etrolizumab is a humanized monoclonal immunoglobulin (Ig)G1 antibody that targets integrin subunit β7 and, therefore, both αEβ7 and α4β7.