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Approach to JCV testing with natalizumab biosimilar: a UK consensus statement

Dobson, Ruth; Arun, Tarunya; Varley, James; Chataway, Jeremy; Brownlee, Wallace; Gallagher, Paul; Giovannoni, Gavin; ... Coles, Alasdair; + view all (2025) Approach to JCV testing with natalizumab biosimilar: a UK consensus statement. Multiple Sclerosis and Related Disorders , 100 , Article 106541. 10.1016/j.msard.2025.106541. (In press). Green open access

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Abstract

Biosimilars have an important role to play in healthcare, with the potential to reduce costs and widen access to treatment. We welcome the use of biosimilars in the treatment of multiple sclerosis. Serological testing for JC virus is mandated as part of safety monitoring in those treated with natalizumab. All PML risk stratification data to date has come from the use of the “Stratify” JC virus (JCV) serostatus test. The “Immunowell” test used to define JCV serostatus (used with Tyruko) does not always give equivalent results to the Stratify test (used with Tysabri), particularly around thresholds used to define risk of progressive multifocal leukoencephalopathy (PML). In comparison to the Stratify test, Immunowell appears more likely to report a positive JCV index. However, negative results using Immunowell show a high rate of agreement with Stratify, which allows for a rational safety strategy. There remains a real risk that a proportion of patients will be inappropriately classified as being at higher risk of PML, and therefore denied the option of natalizumab, a highly effective therapy, or undergo unnecessarily burdensome monitoring, with resultant cost to the NHS and anxiety. We provide guidance for patients with discordant results between assays, aiming to balance the need for rigorous safety monitoring with patient access to highly effective therapy and unnecessary monitoring burden on healthcare services.

Type: Article
Title: Approach to JCV testing with natalizumab biosimilar: a UK consensus statement
Location: Netherlands
Open access status: An open access version is available from UCL Discovery
DOI: 10.1016/j.msard.2025.106541
Publisher version: https://doi.org/10.1016/j.msard.2025.106541
Language: English
Additional information: © 2025 The Author(s). Published by Elsevier B.V. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).
Keywords: Science & Technology, Life Sciences & Biomedicine, Clinical Neurology, Neurosciences & Neurology, Multiple sclerosis, Natalizumab, JC virus, Biosimilar, Progressive multifocal leukoencephalopathy
UCL classification: UCL
UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences
UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences > Faculty of Brain Sciences
UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences > Faculty of Brain Sciences > UCL Queen Square Institute of Neurology
URI: https://discovery.ucl.ac.uk/id/eprint/10215703
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