After being withdrawn from the market, Tysabri was brought back under the
TOUCH program (which is strictly controlled by the FDA), and the thought was that if
Tysabri was used as a monotherapy, the risk for PML would not be as significant.
Unfortunately, this proved not to be the case. At the end of July 2008, it was revealed that there were 2 new cases of PML in Europe - in people who were on Tysabri as their only treatment.