A Phase 3 International, Multicenter, Double-blind, Placebo-controlled Study of the Safety, Efficacy, and Tolerability of Intravenous Antegren (Natalizumab) in Subjects With Moderate to Severely Active Crohn's Disease

The purpose of this study is to determine the safety and efficacy of natalizumab in individuals diagnosed with moderately to severely active Crohn's disease. It is thought that natalizumab may stop the movement of certain cells, known as white blood cells, into bowel tissue. These cells are thought to cause damage in the bowel leading to the symptoms of Crohn's disease.