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New advice may help early detection of PML and improve patients’ outcomes
EMA’s Pharmacovigilance Risk Assessment Committee (PRAC) has completed its review of the risk of progressive multifocal leukoencephalopathy (PML) with the multiple sclerosis medicine Tysabri (natalizumab) and has recommended new measures to minimise this risk. PML is a rare and very serious brain infection caused by John Cunningham (JC) virus.
Recent studies suggest that early detection and treatment of PML when the disease is asymptomatic (is still in the initial stages and shows no symptoms) are critically important in limiting the degree of brain damage and resulting disability caused by the disease. Asymptomatic cases of PML can be detected on an MRI scan. On the basis of this data, the PRAC concluded that for patients at higher risk of PML more frequent MRI scans (e.g. every 3 to 6 months) should be considered.
Known risk factors for the development of PML in patients treated with Tysabri are the presence of antibodies against JC virus (a sign that a person has been exposed to the virus), treatment with Tysabri for more than two years, and use of immunosuppressant medicines (medicines that reduce the activity of the immune system) before starting Tysabri. Patients who have all three risk factors are considered at higher risk of PML.
New data from clinical studies suggest that, in patients who have not been treated with immunosuppressants before starting Tysabri, the level of antibodies (index) relates to the level of risk for PML. More specifically, current evidence suggests that the risk of PML is small, and lower than previously estimated, at antibody index values of 0.9 or less, and increases substantially in patients with index values above 1.5 who have been treated with Tysabri for longer than 2 years. Therefore, the PRAC concluded that patients with a high antibody index who have not used immunosuppressants before Tysabri and have been treated with Tysabri for more than 2 years are also considered at higher risk of PML.
In patients at higher risk of developing PML, treatment with Tysabri should only be continued if benefits outweigh the risks.
For patients who have a low antibody index and have not used immunosuppressant medicines before starting Tysabri, the PRAC recommends repeating the antibody test every 6 months once they have taken Tysabri for longer than 2 years.
In patients who tested negative for JC virus antibodies, the antibody test should be repeated every 6 months.
If PML is suspected at any time, treatment with Tysabri must be stopped until PML has been excluded.
The PRAC recommendation will now be forwarded to the Committee for Medicinal Products for Human Use (CHMP) for the adoption of EMA final opinion. Further details including advice for patients and healthcare professionals will be published at the time of the CHMP opinion.