Biogen Idec Inc. is developing a drug that may repair the damage to the nervous system done by multiple sclerosis (MS). Biogen found the reason why cells in MS lesions weren"t generating new myelin and discovered an antibody, which may block that function and could allow myelin to regenerate. The antibody has been shown to be effective in animal tests and helped the mice grow new myelin, while reducing the effects of disease progression, compared with untreated mice.