Since then, one phase II and two phase III trials have shown that alemtuzumab reduces the relapse rate, compared with the active comparator interferon beta-1a (IFNβ-1a), in treatment-naïve and treatment-experienced MS up to 10 years from disease onset. Furthermore, in two of these trials, alemtuzumab reduced the risk of accumulating disability compared with IFNβ-1a; indeed alemtuzumab treatment led to an improvement in disability and reduction in cerebral atrophy.