Tysabri Brain Infection Reported in another Multiple-Sclerosis Patient

According to a report in the Wall Street Journal, another multiple sclerosis patient has developed a rare and often fatal brain infection, known as progressive multifocal leukoencephalopathy, or PML, as a possible side effect of Tysabri.

After it was first introduced in 2004, Tysabri was pulled from the market after three cases of PML were reported among users, two of which resulted in death.

Tysabri was reintroduced in 2006 with more stringent usage guidelines to limit the risk of users developing the brain infection. However, this latest report is at least the sixth new PML infection to occur since the drug’s return.

Progressive multifocal leukoencephalopathy (PML) is an extremely rare infection that affects the central nervous system, causing damage and inflammation of the brain’s white matter at multiple areas.

The brain infection is untreatable and usually results in death, with early symptoms such as loss of vision, weakness, paralysis, impaired speech and cognitive decline.

Tysabri (natalizumab), which is manufactured and distributed jointly by Elan Corporation and Biogen Idec, is an intravenous injection administered every 28 days for treatment of multiple sclerosis (MS) or Crohn’s Disease.

In August 2008, the FDA issued a MedWatch Alert about the additional reports of Tysabri PML brain infections that have surfaced since the drug was reintroduced. At that time, the FDA indicated that they were evaluating what, if any, additional regulatory actions may be necessary to protect users from the potential Tysabri side effects and doctors were urged to closely monitor patients taking the drug for symptoms of the rare brain infection.

Earlier this month, similar brain infection side effects led Genentech, Inc. to issue a Raptiva recall for their once-weekly psoriasis injection after one possible and three confirmed cases of progressive multifocal leukoencephalopathy (PML) were found among users of the drug.

While the manufacturers of Tysabri originally intended to obtain at least 100,000 users of the medication by 2010, there are currently only about 40,000 multiple sclerosis patients taking the drug. However, sales have been increasing, with the drug generating first quarter 2009 revenue of $165 million for Biogen Idec, a 44% increase from the same quarter last year.