The invention provides, inter alia, methods of reducing gastrointestinal immune-related adverse events, such as
colitis and
diarrhea, in subjects undergoing an immune treatment, such as an immune
oncology treatment, such as anti-CTLA4
antibody and anti-PD-1
antibody combination treatment for
melanoma. In certain aspects, the methods encompass administering a therapeutically effective amount of a polypeptide that inhibits MAdCAM-
integrin binding, such as an anti-α4β7
integrin antibody, such vedolizumab or a related antibody.