I did see the NEJM report today...however, even though the patient had stopped immunosuppressants 8 mos. previous, he had been on that therapy for 5 years, and there is no way to demonstrate that his immune system was functioning normally when he began Tysabri infusion. In fact, his immune system may well have been very abnormal after such protracted immunosuppressant therapy.

The best evidence I know of is that there have been no cases since, and while we must wait and see, every day which passes without incident makes everyone a little more confident in the safety of Tysabri in monotherapy. So, time wil tell; but I'm not holding my breath at this point.