Leukoencephalopathy risk factors ID'd for MS drug

Leukoencephalopathy risk factors ID'd for MS drug

(HealthDay) -- Drug company researchers say they've determined which multiple sclerosis patients are most vulnerable to developing a rare brain infection while taking a powerful drug called Tysabri (natalizumab).

Even the multiple sclerosis patients at highest risk of developing the brain infection face low odds of getting it while on Tysabri, but the infection can be deadly.

"Now we can identify which risk group each patient is in. This will help doctors and patients make better decisions," said Dr. Gary Bloomgren, lead author of a study released Wednesday and vice president of drug safety at Biogen Idec, which makes the drug.

About 100,000 patients have taken Tysabri at least once. The drug, which is used mainly to delay the progression of multiple sclerosis, has been on the market since 2006. It originally went on the market in 2005 but was removed due to medical problems that some patients encountered, Bloomgren said.

Tysabri is expensive, costing about $40,000 a year. It dampens the immune system, potentially reducing the inflammation that is a major part of multiple sclerosis. Dampening the immune system, however, can allow an infection known as the JC virus to wreak havoc on the brain and cause a condition called progressive multifocal leukoencephalopathy.

The JC virus is extremely common, affecting about half of adults by middle age, but the immune system normally keeps it under control so it causes no symptoms. If unleashed, however, progressive multifocal leukoencephalopathy can cause cognitive problems, such as unusual behavior, paralysis and problems with vision, speech and balance, said study co-author Dr. Sandra Richman, senior medical director at Biogen Idec.

Once the symptoms appear, doctors usually advise patients to stop the treatment, she said. Progressive multifocal leukoencephalopathy often causes permanent disability, and can be deadly.

In 2010, the U.S Food and Drug Administration added a new warning about the rare brain infection to Tysabri's label. The drug also is used to treat Crohn's disease.

In January, the FDA approved a test to determine the risk of brain infection in Tysabri users.

In the new study, the researchers examined various statistics to figure out which multiple sclerosis patients were at highest risk of progressive multifocal leukoencephalopathy if they take Tysabri. Blood samples of nearly 5,900 patients with multiple sclerosis were analyzed.

Just more than 1 percent of patients showed signs of exposure to the JC virus, had taken immune-suppressing drugs before Tysabri and had been on Tysabri for 25 to 48 months.

The risk for those who hadn't been exposed to the JC virus was 120 times smaller at 0.009 percent.

Patients who worry about progressive multifocal leukoencephalopathy "may think about it differently because of the low risk in that subgroup of patients," Bloomgren said.

Multiple sclerosis patients who have been exposed to the JC virus but haven't taken immune-suppressing drugs while on Tysabri may choose to continue taking the drug, said Dr. Scott Zamvil, a professor of neurology at the University of California-San Francisco.

"Patients who are on the drug don't want to come off because it's that potent of a drug," he said. "It is the most potent of the currently approved drugs."

Patients need to talk to their physicians and weigh the benefit of the medication versus the potential risk, Zamvil said.

The study appears in the May 17 issue of the New England Journal of Medicine.

More information: Full Text (subscription or payment may be required)
Editorial (subscription or payment may be required)

add to favorites email to friend print save as pdf

Related Stories

FDA clears safety test to screen Tysabri patients

Jan 20, 2012

(AP) -- The Food and Drug Administration on Friday approved a new diagnostic test to help identify patients who have an increased risk of developing a rare brain infection while taking Biogen Idec's multiple sclerosis drug ...

Withdrawn MS drug returns to market

May 24, 2007

Just months after receiving FDA approval, natalizumab, a medication for the treatment of multiple sclerosis (MS) and other inflammatory disorders, was voluntarily withdrawn by its manufacturers after three patients developed ...

Recommended for you

Obama addresses West Africans on facts about Ebola

2 hours ago

President Barack Obama urged West Africans on Tuesday to wear gloves and masks when caring for Ebola patients or burying anyone who died of the disease. He also discouraged the traditional burial practice ...

Gluten-free diet benefits asymptomatic EmA+ adults

2 hours ago

(HealthDay)—Asymptomatic individuals with endomysial antibodies (EmA) benefit from a gluten-free diet (GFD), according to a study published in the September issue of Gastroenterology.

Another US health worker infected with Ebola

2 hours ago

A third American health worker has tested positive for the Ebola virus while working with patients in West Africa, the Christian missionary group SIM said Tuesday.

UN implores all countries to help on Ebola

4 hours ago

The international group Doctor Without Borders warned Tuesday that the world is 'losing the battle' against Ebola, while U.N. officials implored all countries to quickly step up their response by contributing health experts ...

Travel restrictions could worsen Ebola crisis: experts

9 hours ago

Travel restrictions could worsen West Africa's Ebola epidemic, limiting medical and food supplies and keeping out much-needed doctors, virologists said Tuesday as the disease continued its deadly spread.

User comments