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Procedure may cut risk of Tysabri complication

Replacing plasma, the yellowish liquid component of blood, may help head off a rare brain infection that has been linked to Biogen Idec Inc.'s Tysabri drug for multiple sclerosis.

Three procedures to remove and replace 12 patients' plasma with an alternative fluid rapidly cleared Tysabri from their bloodstreams, according to research that will be presented tomorrow at a conference in Prague and was released yesterday in a statement.

Tysabri was temporarily withdrawn from the US market in 2005 after the infection, which causes a condition called progressive multifocal leukoencephalopathy or PML, struck three patients, killing two of them.

Regulators allowed Biogen and its partner Elan Corp. to resume selling the drug last year because of its patient benefits, and the company is seeking ways to make Tysabri safer.

The findings "are encouraging as they show the removal of Tysabri is faster following plasma exchange," said study leader Bhupendra Khatri, director of the Regional MS Center at Aurora St. Luke's Medical Center in Milwaukee, in the statement. "Time will tell whether plasma exchange develops as an effective treatment approach for PML."

Biogen shares fell 29 cents to $67.12 in Nasdaq trading. The stock has climbed 36 percent this year.

PML affects people with impaired immune systems, and has been linked to other drugs, such as the cancer medicine Rituxan, made by Biogen and Genentech Inc.

Biogen and Elan said yesterday that 17,000 patients had taken Tysabri as of Sept. 30, and no new cases of PML linked to the treatment have been reported.

Also yesterday, PDL BioPharma Inc. and Biogen Idec said their experimental multiple sclerosis drug, currently sold as a transplant medicine, helped reduce brain and spinal cord damage caused by the neurological disease, in a study.

Results showed that patients given the drug, called daclizumab, in combination with interferon-beta, a standard MS therapy, had 72 percent fewer lesions after six months, compared with patients given interferon-beta alone. Both studies will be presented at the Congress of the European Committee for Treatment and Research in Multiple Sclerosis.

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