I have to take issue with the notion that risk increases with time. IMO, there is no evidence of this. In fact, I think that there is evidence that it does not increase with time. 4 PML cases occurred in patients with 10-19 months of treatment, 4 in patients with 20-29 months of treatment, 4 in patients with 30-39 months of treatment. (there might be 3 and 5 instead of 4-4-4 in there somewhere...)
Anyway, almost all the cases have been among the 1st wave of patients in the EU that took the drug. These were the very sickest patients and were patients who did not go through US TOUCH program. There have been almost no PML cases in the growing population of patients who adopted more methodically later.
Note, too, that according to NEJM this week, one of the 2 US cases contracted PML after having been on 5 uninterrupted years of azathioprine therapy (in other words, he had no immune system early on.) Azathioprine is a causative factor for PML.
This article is further off base because it fails to consider alternative outcomes for the 45,000 patients with active disease that are currently being treated with Tysabri. Clinical trial statistics would seem to state that interferon (current standard of care) patients experience 0.75 relapses per year. Tysabri patients experience almost 0.5 fewer relapses per year. And 5% of relapses are said to result in death or serious disability (lameness, blindness, etc.)
On an annual basis, Tysabri prevents over 20,000 annual relapses that would have occurred in patients on what is standard-of-care treatment (INFb) and over 1,000 annually would have been equivalent in severity to PML. Annually.
So far, we have 12 PML cases balanced against probably 2,500 relapses of equivalent severity. IMO, Tysabri is still a no-brainer choice and, in my opinion, articles like the WSJ article amount to disinformation. |
