MS Drug Tysabri Tied to Brain Infection

Two multiple sclerosis patients in
Europe have come down with a rare, serious brain infection called PML (progressive
multifocal leukoencephalopathy ).

The patients, who are in stable condition, are the first confirmed cases of
PML in Tysabri users since the drug was reintroduced in the U.S. and approved
in Europe two years ago, according to Biogen Idec and Elan, the companies that
co-market Tysabri.

As of July 31, one of the patients is at home and walking; the other patient
is hospitalized, according to Biogen Idec's report to the U.S. Securities and
Exchange Commission (SEC).

Biogen Idec learned of the first case on July 30 and the second case a day
later, and filed the SEC report yesterday; Biogen Idec has also reported the
cases to the FDA and regulators in Europe. The FDA is reviewing the data and is
in discussions with Biogen Idec.

Tysabri already carries a "black box" warning -- the FDA's sternest
warning -- about PML risk. PML risk-management programs have been in place for
two years for U.S. and European Tysabri users. Education and awareness about
PML risk "was critical" in identifying and managing the two new PML
cases, says Naomi Aoki, Biogen Idec's director of public affairs.

Given the known risk of PML, new cases aren't unexpected, notes Aoki. But
she says Tysabri is "an important therapeutic option for patients,
especially for patients who have very aggressive MS or whose MS has continued
to progress despite treatment with other therapies -- and the risk-benefit
ratio of the drug remains favorable."

Tysabri and PML

Tysabri is a monoclonal antibody given by a health care professional. In the
U.S., it's approved to treat patients with relapsing forms of MS in order to
reduce the frequency of flare-ups, and to treat Crohn's disease.

The FDA first approved Tysabri in 2004. PML cases led Tysabri's makers to
voluntarily take the drug off the U.S. market in
February 2005 . The
FDA allowed Tysabri to return to the U.S. market in June 2006, after an
FDA advisory panel recommended doing so.

Biogen Idec and Elan reintroduced Tysabri in the U.S. in July 2006; at the
same time, the drug was approved in the European Union. The FDA approved
Tysabri for the treatment of Crohn's disease in
January 2008 .

By Miranda Hitti
Reviewed by Louise Chang
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