A Randomized, Double-Blind, Placebo-Controlled, Parallel-Group, Multicenter Study to Determine the Safety and Efficacy of Natalizumab in Subjects With Relapsing-Remitting Multiple Sclerosis

The purpose of this study is to determine the safety and efficacy of natalizumab in the treatment of individuals who have been diagnosed with relapsing remitting multiple sclerosis (MS). It is hoped that natalizumab will prevent certain types of white blood cells from moving out of the bloodstream into organs, including the brain, that are being damaged by autoimmune disease (a disease in which the body's own immune system attacks certain organs). These white blood cells are thought to cause inflammation that can result in lesions (small areas of damage) in the brain. These lesions are thought to be the cause of relapses and disability in MS.