PML Risk Stratification and Monitoring in Natalizumab Treatment

Risk Factors and Stratification

The presence of anti-JCV antibodies, particularly with high index values, is a risk factor for PML development in patients treated with natalizumab, as noted by the Journal of Neurology, Neurosurgery and Psychiatry 1, 2
Risk stratification based on anti-JCV antibody index indicates that JCV antibody-negative patients have a PML risk of approximately 1 in 10,000, while JCV antibody-positive patients with an index ≤1.5 have a PML risk of approximately 1 in 5,882, and those with an index >1.5 have a PML risk of approximately 1 in 855 3

The Journal of Neurology, Neurosurgery and Psychiatry recommends brain MRI screening every 3-4 months for natalizumab-treated patients at high risk of PML (JCV seropositive, treatment duration ≥18 months) 3, 4, 5
For patients at lower risk (JCV seronegative), annual brain MRI assessment is recommended, according to Nature Reviews Neurology 4, 5
The MRI protocol should include FLAIR, T2-weighted, and diffusion-weighted imaging, as suggested by the Journal of Neurology, Neurosurgery and Psychiatry and Nature Reviews Neurology 3, 4, 5

Enhanced pharmacovigilance, including brain MRI every 3-4 months for up to 12 months, is required in patients who switch from natalizumab to other therapeutics, such as fingolimod, alemtuzumab, and dimethyl fumarate, as recommended by Nature Reviews Neurology 4, 5