Biogen Idec (NASDAQ: BIIB) and Elan Corporation, plc (NYSE: ELN) announced results of a study demonstrating that TYSABRI® (natalizumab) promoted regeneration and stabilization of damage done to the myelin sheath, as measured by advanced MRI technology. Damage to the myelin sheath causes the symptoms of multiple sclerosis (MS). Additional posters will also be presented during the Congress highlighting the ability of TYSABRI, in some patients, to improve physical function and patient reported outcomes on cognition, quality of life, and fatigue. TYSABRI is the first approved MS therapy with reported data suggesting that some of the signs of disease progression can be stopped. The strong efficacy profile demonstrated in clinical trials is enhanced further from these data and may help redefine success in MS.