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Ingredient in New MS Drug Linked to Serious Brain Disease

Reports found four psoriasis patients who took similar drug developed rare but sometimes deadly condition

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PML is caused by the JC virus, which normally lies dormant in the body and causes no harm. About half of multiple sclerosis patients have antibodies to the JC virus in their blood, suggesting a current or former infection. When the immune system is depleted by illnesses like cancer or AIDS or suppressed by certain medications, the virus can flare and destroy nerve cells in the brain.

Ironically, PML is a lot like multiple sclerosis, but it progresses more rapidly as it causes weakness, paralysis, confusion, memory loss and loss of vision or speech. Quick treatment can stop the damage, although patients may be permanently disabled.

PML is rare, but it is so serious that Genentech pulled its psoriasis treatment Raptiva off the market in 2009 after reports of four cases in patients who were taking the biologic medication. Biologic drugs are medications derived from living organisms that are used to prevent certain diseases, including ones where the immune system malfunctions.

Another biologic, Tysabri, a treatment for multiple sclerosis and Crohn's disease, was shelved in 2005 for about a year after three patients involved in clinical trials of the drug developed PML. Tysabri returned to the market in 2006 with strict new safeguards in place. Before starting the drug, for example, patients must get an MRI of their brains. They also may get blood tests to check for antibodies to the JC virus. They also are monitored by doctors every three to six months while taking the medication, which is also made by Biogen.

No such precautions are currently recommended for Tecfidera, which has been hailed as a less toxic alternative to other treatments. Other multiple sclerosis drugs are known to cause flu-like symptoms, chest pain, and heart, liver and eye problems.

In clinical trials, the main side effects reported with Tecfidera were comparatively mild, and included facial flushing, stomach upset and low white blood cell counts.

"The main reason why our [psoriasis] patient developed PML after three years of treatment with Fumaderm is prolonged lymphocytopenia [low white blood cell counts]," Schulz said. "In both BG-12 trials published in the New England Journal of Medicine in 2012, 4 percent to 5 percent of patients developed this kind of severe lymphocytopenia and are in my view at risk to also develop PML."

Dr. Robert Fox is a staff neurologist at the Mellen Center for Multiple Sclerosis at the Cleveland Clinic in Ohio, and he was also on the steering committee for one of the studies that tested the medication.

He called the new PML case reports, "very important additions to our understanding of this class of therapy." Fox, who has in the past also been a paid consultant for Biogen, added that, "although we haven't seen any PML cases in patients treated with Tecfidera, I think there's good reason to apply the lessons learned here to Tecfidera."

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