Tysabri Linked to Fourth Case of Brain Infection


Tysabri is known generically as natalizumab and made by Biogen Idec Inc (BIIB.O) and Elan Corp (ELN.I)(ELN.N) of Ireland. Earlier this week, Biogen reported the fourth case of progressive multifocal leukoencephalopathy (PML), a serious brain infection. This most recent case occurred in a European patient who had been taking the drug for 26 months.

Tysabri is used to treat multiple sclerosis (MS), an auto-immune disease in which the body mistakenly attacks the fatty myelin coating surrounding nerve cells. Tysabri had been pulled off the market in 2004 soon after it was introduced into the market. The drug was then placed back on the market in 2006 because there are so few good options for MS patients.

The company's website and the drug insert make it clear that PML is a risk of Tysabri.


"Tysabri increases you chance of getting a rare brain infection that usually causes death or severe disability. This infection is called progressive multifocal leukoencephalopathy (PML). PML usually happens in people with weakened immune systems. No one can predict who will get PML. Your chances may be higher if you are also being treated with medicines that weaken your immune system, including other MS treatments. If you use Tysabri alone to treat your MS, you can still get PML. It is not known if the length of time on treatment with Tysabri Increases your chance of getting PML. There is no known treatment, prevention, or cure for PML. If you take Tysabri, it is important to call your doctor right away if you have any new or worsening medical problems (such as a new or sudden change in your thinking, eyesight, balance, or strength or other problems) that have lasted over several days. Tell all your doctors that you are getting treatment with Tysabri."

Asked for comment on this latest development, Lily Jung, MD, a neurologist specializing in MS at the Swedish Neuroscience Institute, in Seattle, Washington, speaking on behalf of the American Academy of Neurology, pointed out that natalizumab is a very effective drug. "Risks are present with any medication, and for each patient we should think about the risks and indications for the drug," Dr. Jung told Medscape Neurology & Neurosurgery.

Dr. Olaf Stuve, a neurologist at the University of Texas Southwestern Medical School in Dallas, said in a statement "Natalizumab is very effective in keeping pro-inflammatory cells out of the brain to reduce damage from MS, but by doing so it may promote infection in some people."

Dr Stuve said about 43,000 people had taken natalizumab since 2006.

FDA Information on Tysabri