New Test Could Identify Brain Infection Risk Among Tysabri Users

Federal drug regulators have approved a new test that could help identify those at risk of developing a rare, but often fatal, brain infection from the multiple sclerosis drug Tysabri and other immunosuppressants.

On January 20, the FDA announced in a Tysabri drug safety communication that people at high risk of developing progressive multifocal Leukoencephalopathy (PML) could be identified through a test for JC virus antibodies.

PML is a rare and deadly brain infection that is believed to be caused when some immunosuppressant drugs, like Tysabri, disable the immune system enough for the JC virus to take hold. The January 20 announcement only mentions use of the test for multiple sclerosis patients taking Tysabri, however.

Tysabri (natalizumab) is an intravenous injection given every 28 days to treat multiple sclerosis (MS) and Crohn’s disease. Manufactured by Biogen Idec Inc. and marketed with Elan Corp PLC, Tysabri has been shown to prevent relapse, cognitive decline and vision loss associated with MS.

A temporary Tysabri recall was issued in 2005, after three users developed PML, which attacks the central nervous system, damaging and inflaming the white matter areas of the brain. The drug was reintroduced in July 2006 with stronger warnings about the potential risk of a PML brain infection from Tysabri and the drug was only made available under strict usage guidelines. More than 100 Tysabri patients have been diagnosed with PML since the drug was reintroduced.

The FDA has identified three risk factors that increase the odds of a Tysabri patient developing PML:

• The presence of anti-JCV antibodies, which indicate that the JC virus is present in the body
• Treatment with Tysabri for longer than two years
• Treatment with other immunosuppressants before being placed on Tysabri

Patients with all three risk factors appear to have the highest chances of being diagnosed with PML.

There is currently no cure or treatment for PML, but the FDA hopes that the Stratify JCV Antibody ELISA test can help determine patient risk, which could play a role in deciding whether Tysabri is the right drug for them.

The FDA will update the label of Tysabri to indicate that testing positive for the JCV antibodies indicates an increased risk of the rare brain infection.

The announcement comes days after the FDA issued a warning about reported cases of PML brain infections with Adcetris, a lymphoma drug. It is unclear whether the test could be used on Adcetris users as well.

In 2009, reports of PML brain infections from Raptiva, a psoriasis drug marketed by Genentech, Inc., led to that drug being removed from the market. Unlike Tysabri, which has remained available with strong warnings for consumers, it was determined that the risk of Raptiva brain infection side effects outweighed the benefits provided in treating psoriasis.