Natalizumab-associated PML has improved survival compared with PML in other populations. Disability in survivors ranged from mild to severe. A shorter time from symptom onset to diagnosis and localized disease on MRI at diagnosis were associated with improved survival. These data suggest that earlier diagnosis through enhanced clinical vigilance and aggressive management may improve outcomes.

Objective To use the large dataset from the Tysabri Outreach: Unified Commitment to Health (TOUCH) program to compare progressive multifocal leukoencephalopathy (PML) risk with natalizumab extended interval dosing (EID) vs standard interval dosing (SID) in patients with multiple sclerosis (MS). Methods This retrospective cohort study included anti-JC virus antibody-positive patients (n = 35,521) in the TOUCH database as of June 1, 2017. The effect of EID on PML risk was evaluated with 3 planned analyses using Kaplan-Meier methods stratified by prior immunosuppressant use. Risk of PML was analyzed by Cox regression adjusted for age, sex, prior immunosuppressants, time since natalizumab initiation, and cumulative number of infusions.