Combination of teriflunomide and interferon as follow-up therapy after fingolimod-associated PML.

Progressive multifocal leukoencephalopathy (PML) is one of the most important adverse events in relapsing-remitting MS (RRMS) patients treated with disease-modifying therapies (DMTs). Especially natalizumab is known to increase the risk for PML, depending on the John Cunningham virus (JCV) index in serum and the number of years on therapy with natalizumab.1 Fingolimod and dimethyl fumarate are associated with a considerably lower risk of PML.2