From the Merck Manual
In multiple sclerosis, the immune system attacks and damages the layer of tissue (myelin) that covers nerve cells in the brain, spinal cord, and optic nerves. If myelin is damaged or destroyed, the nerve cells involved do not work properly. A recent study describes the first drug that is designed to repair damaged myelin. This new drug was shown to repair myelin in tests done in animals, so this was a preliminary study to see whether the drug would also repair myelin in people.
Michael C. Levin, MD, Professor of Neurology, University of Tennessee Health CenterMore