The RESTORE trial: What did we learn about multiple sclerosis?

In their article MS disease activity in RESTORE: A randomized 24-week natalizumab treatment interruption study,(1) Fox and colleagues carefully evaluated a very specific question: what happens if a specific treatment for multiple sclerosis (MS) is temporarily stopped? To many people, this would seem an unusual question. It does not seem logical. Why would a treatment, if it were working, be stopped? The answer is that some treatments can have long-term side effects. In others, like natalizumab, it has been observed that long-term treatment, which is aimed at the immune system, can cause problems with the way that our bodies respond to certain viruses.