Risk of Natalizumab-Associated Progressive Multifocal Leukoencephalopathy

Progressive multifocal leukoencephalopathy (PML) is associated with natalizumab treatment. We quantified the risk of PML in patients with multiple sclerosis, according to the presence or absence of three risk factors: positive status with respect to anti–JC virus antibodies, prior use of immunosuppressants, and increasing duration of natalizumab...