MS Drug Tysabri Reactivates Brain Disease Virus, Study Finds

The multiple sclerosis and Crohn’s disease drug Tysabri puts patients at greater risk of developing a potentially deadly brain disease by awakening the virus that causes the disease and making the virus even stronger, according to a new study.

At least 13 Tysabri patients have contracted the disease, called progressive multifocal leukoencephalopathy (PML), since the drug debuted in 2004. PML is caused by the JC virus and occurs when the virus sneaks past the body’s immune defenses and penetrates the brain.

In MS patients, Tysabri, known generically as natalizumab, is used to suppress the immune system to prevent the system from wrongly attacking nerve cells. Tysabri is designed to keep T cells from reaching the brain, where they mistakenly destroy nerve tissue, causing the symptoms of multiple sclerosis. The drug also is approved for treating the gastrointestinal disorder, Crohn’s disease.

Problems with Tysabri prompted the Food and Drug Administration to remove the drug from the market in 2005, just months after it had been approved. The drug was allowed back on the market a year later after stronger warning labels about the risks of liver damage and PML were added to the packaging.

Researchers from Harvard Medical School and Beth Israel Deaconess Medical Center studied 19 MS patients who had just started taking Tysabri. The patients were examined after taking Tysabri for three, six, 12, and 18 months.

They found that patients on the drug had more of the virus in their urine and blood. After one year of Tysabri treatments, the patients had detectable levels of JC virus in their urine.

Tysabri is a joint venture between drug makers Biogen and Elan Corp. Officials say the odds of contracting PML from Tysabri is about 1 in 1,000.

Biogen officials said the study was small and lacked a control group, which calls into question the findings.

No related posts.