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Multiple Sclerosis Health Center

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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


"With the publication of our case, we wish to create awareness that treatment with any form of fumaric acid may bear the risk of developing PML," Schulz said.

In their response, Biogen countered that while patients had been only tracked for an average of two years at the time Tecfidera received FDA approval for MS, many of the patients in these trials have now been on the drug for five years with no reports of PML. The company added that over the 20 years that German patients have used Fumaderm, only three case reports of PML have arisen, and those cases involved additional risk factors for the illness.

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.

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