Everybody wants to get rid of EBV and there are a number of trials testing tenofovir alafenamide fumarate (TAF). This current study however reported that Tenofovir targets JC virus and so inhibits the development of PML. So this is good news. NDG treated PML in a different way but having an active antiviral iss great news. Obviously this is an n=1 and so needs repeating in a bigger study.. However there are loads of people getting the Tenofovir, surely they could look to find JC virus DNA which would be at a lower level than during PML.
Torkildsen Ø, Bru ANS, Behzadi GIN, Myhr KM. Successful Treatment of Progressive Multifocal Leukoencephalopathy With Tenofovir Alafenamide Fumarate. Neurol Neuroimmunol Neuroinflamm. 2026 ;13(1):e200522. doi: 10.1212/NXI.0000000000200522. Epub 2025 Nov 25. PMID: 41289545; PMCID: PMC12646825.
Objectives: Progressive multifocal leukoencephalopathy (PML) is a rare, often fatal CNS infection caused by reactivation of JC virus, typically in immunocompromised patients. No effective antiviral therapy has been established. We report a case of PML in a patient with multiple sclerosis (MS) treated with fingolimod, who received oral tenofovir alafenamide fumarate (TAF).
Methods. This is a single-patient case report from Stavanger University Hospital, Norway. A 67-year-old woman with secondary progressive MS developed progressive neurologic symptoms during fingolimod treatment. MRI and CSF analyses confirmed PML with detectable JCV DNA. Fingolimod was discontinued, and oral TAF 50 mg/d was initiated. Clinical course, MRI changes, and CSF biomarkers were monitored over 6 months.
Results:At baseline, JCV DNA was 4,940 international units [IU]/mL in CSF and the Expanded Disability Status Scale (EDSS) score was 8.5. Four days after TAF initiation, partial radiologic improvement was observed. After 3 and 6 months, JCV DNA was undetectable (<1,000 IU/mL). The patient remained clinically stable with unchanged EDSS score and tolerated TAF without adverse effects. MRI showed regression of PML lesions but development of new MS activity after fingolimod withdrawal.
Discussion: This case demonstrates temporal association between TAF initiation and virologic clearance of JCV, suggesting potential antiviral activity.
Source: multiple-sclerosis-research.org