New cases of progressive multifocal leukoencephalopathy (PML) in patients taking monoclonal antibody drugs raise concerns about the risk of this rare and deadly neurodegenerative disease associated with use of such drugs.
In late October, the US Food and Drug Administration (FDA) and Genentech warned physicians that a third patient being treated with rituximab for rheumatoid arthritis had developed PML, the first such patient to have no previous history of treatment with a tumor necrosis factor antagonist (http://www.fda.gov/downloads/Safety/MedWatch/SafetyInformation/SafetyAlertsforHumanMedicalProducts/UCM187792.pdf). About 100 000 patients with rheumatoid arthritis have taken the drug to date, according to the FDA.
Kuehn BM. Monoclonal Antibody Concerns. JAMA. 2009;302(20):2194. doi:10.1001/jama.2009.1704