The European Medicines Agency (EMA) has started a review of the multiple sclerosis medicine Tysabri (natalizumab). The aim of the review is to assess whether the advice given to healthcare professionals and patients on how to manage the known risk of progressive multifocal leukoencephalopathy (PML) with this medicine should be revised in the light of new scientific evidence.
PML is a rare brain infection caused by John Cunningham virus (JCV), which has symptoms that may be similar to those of a multiple sclerosis attack, and may result in severe disability or death. It is already known that the risk of PML increases the longer a patient has been receiving Tysabri, especially in patients treated for more than two years. The risk of PML is also higher if the patient used immunosuppressant medicines (medicines that reduce the activity of the immune system) before starting Tysabri, or if the patient has tested positive for antibodies against the virus that causes PML (a sign that the virus may be present in the body).
Scientific evidence on PML is rapidly growing. New data seem to indicate that the methods used to calculate the risk of PML may need to be revised and that testing for PML in patients with no symptoms may need to be performed more frequently than currently recommended. New diagnostic tests have recently been developed and there is a need to assess whether this has an impact on the current prescribing advice.
EMA will now evaluate the available data on the risk of PML with Tysabri with the aim of better defining the risk of PML and identifying further measures to minimise it, and will issue an opinion on whether changes to the marketing authorisation are needed.
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