Biogen Idec, Elan Report Two New Cases of Rare Brain Infection in Tysabri Patients

Cambridge, MA-based Biogen Idec (NASDAQ: BIIB) and Ireland’s Elan reported some serious bad news this afternoon on their multiple sclerosis drug Tysabri. Two new patients taking the drug in Europe have developed the rare and often fatal brain infection progressive multifocal leukoencephalopathy, or PML, according to a regulatory filing with the Securities and Exchange Commission.

The filing says that one patient, in Europe, developed PML after taking Tysabri by itself for about 17 months. The patient has remained stable at home and able to walk, according to the statement. The second patient, who took Tysabri for 14 months after having taken other medicines for multiple sclerosis, is currently hospitalized, according to the company.

Tysabri has a painful history with PML. The drug was pulled from the market in February 2005 after doctors discovered two cases of the rare infection, which can be deadly. The FDA allowed Tysabri back to the market in July 2006 after deciding that the benefit of the drug—the most effective yet against MS—was worth the risk. As recently as last week, Biogen and Elan reported there were no new cases of PML since Tysabri was reintroduced with a strict monitoring program, and that 31,800 patients were taking it worldwide. The drug, Biogen’s fastest-growing product, is vital to the company’s financial future, and has been estimated to generate $2.8 billion in annual sales at current prices in 2010.

Biogen’s stock dropped 19 percent on the news at 5:58 p.m. Eastern time in after-hours trading to $56.56. The company is planning to have a conference call with investors at 8:30 a.m. Eastern time tomorrow morning.

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