ENTYVIO® (vedolizumab) is used to treat certain bowel disorders (ulcerative colitis, Crohn's disease). In these conditions, the body's defense system attacks healthy tissues in the gut, causing symptoms such as abdominal pain, blood in the stool, and diarrhea. Vedolizumab belongs to a class of drugs known as monoclonal antibodies. It works by blocking the actions of a certain natural substance (integrin) in the body. This helps to decrease swelling (inflammation) in the gut, which lessens symptoms and may slow or stop damage from these bowel disorders.