Conclusions
Positive status with respect to anti–JC virus antibodies, prior use of immunosuppressants, and increased duration of natalizumab treatment, alone or in combination, were associated with distinct levels of
PML risk in natalizumab-treated patients with multiple sclerosis. (Funded by Biogen Idec and
Elan Pharmaceuticals.)
http://www.nejm.org/doi/full/10.1056/NEJMoa1107829?