Multiple sclerosis patients treated with Tysabri (natalizumab) have a 10 times greater risk of developing a deadly brain virus, according to new findings. The virus – John Cunningham virus (JCV) – is a pathogen that causes a rare and deadly condition known as progressive multifocal leukoencephalopathy (PML).
The link between Tysabri and PML is not new. In fact, there have been numerous previous studies that have shown an increased risk of PML due to Tysabri use.
Experts still believe that even though Tysabri may increase the risk of PML, it is still a beneficial medication for multiple sclerosis patients, and doctors should weigh the pros and cons when prescribing it.
The researchers explained that the virus is typically well managed by the body’s own immune system, but in those patients with a weakened immune system, that’s when the virus can become serious.
The study involved 525 German and 711 French multiple sclerosis patients who were all on Tysabri. Both groups of patients had their blood levels monitored for JCV antibodies over the course of 15 months and two years respectively.
Antibodies for JCV were higher in patients taking Tysabri, which reveals exposure of the virus, thus increasing the risk of developing PML, the doctors suggested.
Research lead Dr. Heinz Wiendl said, “An increase in the levels of anti-JCV antibodies could signify an increased risk of PML.” He added, Tysabri “did appear to increase the levels of anti-JCV antibodies, and this higher level may be associated with a higher risk of PML. The results of this study underscore the need for frequent monitoring of anti-JCV antibodies in people who are being treated with [Tysabri] for multiple sclerosis.”
Researchers recommend patients speak with their doctors in regard to concerns about Tysabri.