The agency made the recommendation last week based on new data indicating that early detection of John Cunningham (JC) virus – which causes progressive multifocal leukoencephalopathy (PML) – improves patient outcomes.
“Recent studies suggest that early detection and treatment of PML when the disease is asymptomatic 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 - every 3 to 6 months - should be considered.”
Tysabri is a monoclonal antibody that targets a protein called ‘α4β1 integrin’ that is found on the surface of leucocytes, which are the cells involved in the inflammatory process that damages the nerve cells in patients with MS.
The drug reduces the inflammation and lessens nerve damage. However, shortly after it was approved in the US 2004 co-developers Biogen Idec (now called Biogen) and Elan (now part of Perrigo) withdrew it from the market because of a suspected link to three cases of PML.
The drug was relaunched in the US in March 2006 after a safety review found no new cases of PML among more than 2,000 patients treated for MS in clinical trials and in commercial use. It was also approved in Europe in 2006.
MS patients treated with Tysabri are regularly tested for JC virus antibodies, which is an indication they have been infected by the virus and a risk factor for PML development.
Sufferers who have been treated with immunosuppressant drugs prior to the mAb are deemed to be at high risk of PML
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.