TYSABRI increases the risk of progressive multifocal leukoencephalopathy (PML)
PML is an opportunistic viral infection of the brain caused by the John Cunningham virus (JCV) that usually leads to death or severe disability. There is no known treatment, prevention, or cure for PML. Infection by the JC virus is required for the development of PML.
PML risk associated with TYSABRI may vary in each patient, and the decision to start or continue TYSABRI requires individualized assessment, based on a combination of 3 known risk factors:
Balancing benefits and risks―based on postmarketing data out to 6 years from ~69,000 US TYSABRI patients―can inform decisions about treatment over time
Estimated US Incidence of PML Stratified by Risk Factora,b
aThe risk estimates are based on postmarketing data in the United States from approximately 69,000 TYSABRI-exposed patients. The anti-JCV antibody status was determined using an anti-JCV antibody test (ELISA) that has been analytically and clinically validated and is configured with detection and inhibition steps to confirm the presence of JCV-specific antibodies with an analytical false negative rate of 3%.
bData beyond 6 years of treatment are limited.