I've been following the reported incidence of cases of progressive multifocal leukoencephalopathy (PML) in patients who use Tysabri over the years. For many months, reports of new cases were found in news publications such as Bloomberg. However, public reports have been released less and less frequently.
Biogen Idec has released the latest figures for PML cases and deaths following Tysabri infusions for multiple sclerosis. The total number of cases have reached 212 PML cases and 46 deaths in Tysabri MS patients as of March 1, 2012.
I have updated the chart on the right to reflect this recent report. This chart is under copyright. Please do not reproduce without permission.
As of March 1, 2012, there have been 212 PML cases, of which 122 have been in the European Economic Area (EU), 80 in the United States and 10 in rest of world (other). 46 of the 212 patients with PML have died.
In 54 natalizumab-treated MS patients who developed PML and in whom serum samples were available 6-187 months prior to the onset of PML, all 54 patients had anti-JCV antibodies detected.
Samples were available from 86 patients at the time of PML diagnosis and all 86 tested positive for anti-JCV antibodies.
In addition, one sample, collected from a patient at the time of PML diagnosis following a cycle of plasma exchange (PLEX) tested negative for anti-JCV antibodies. Because this sample was collected immediately following PLEX, and PLEX removes antibodies from the circulation, the information obtained from this sample is unreliable.
One patient tested anti-JCV antibody positive two months before PML diagnosis. Previously, the patient had tested anti-JCV antibody negative 15 months prior to PML diagnosis, indicating that they had been exposed to the JC virus at some point between the two tests.
Source: Biogen Idec (16/03/12) as shared by Multiple Sclerosis Resource Centre.