By Thomas Gryta Of DOW JONES NEWSWIRES NEW YORK -(Dow Jones)- Biogen Idec Inc. (BIIB) amended the U.S. label of multiple sclerosis treatment Tysabri, sold with Elan Corp. PLC (ELN), on Friday to reflect that the risk of a rare brain infection rises with longer usage. The changes, which were expected, note that the occurrence of progressive multifocal leukoencephalopathy, or PML, in patients treated for 24 to 36 months is "generally similar" to the 1-in-1,000 rate seen in clinical trials. The changes warn that there is limited experience with the drug beyond three years of treatment. Lazard Capital Markets' analyst Joel Sendek said the changes appeared to be benign. "We do not expect physicians to significantly change their Tysabri prescribing habits in the near-term," Sendek said in a research note. He continues to project 2010 Tysabri sales of $1.1 billion. Biogen had previous said it was discussing a label change with the Food and Drug Administration to include duration-related risk, but some on Wall Street had feared it would include suggestion for duration limits, or taking a "holiday" from treatment. Barclays Capital analyst Jim Birchenough wrote Friday that he believes the new label will ultimately slow sales growth of the drug. Biogen shares closed up 3.1% to $45.76 Friday, while Elan rose 6.2% to $6.58. Aside from duration information, the updated label includes details on using plasma-exchange therapy, which removes large molecules from the body's blood circulation, thereby accelerating removal of Tysabri and theoretically improving the immune response to PML infection. It also explains that inflammation of the rebuilding of the immune system can occur following discontinuation of Tysabri in patients with PML. The label update comes after 24 cases of PML, including four deaths, have been confirmed in Tysabri patients since it was removed from the market for 18 months beginning in 2005 because of a link to PML, including two other deaths. The drug, allowed back on the market after patients and physicians pushed for its return, is key to the growth of both Biogen and Elan. It produces nearly $1 billion in yearly revenue. The European agency's Committee for Medicinal Products for Human Use, known as CHMP, has started a review of Tysabri because of the PML cases. Despite the PML risk, Tysabri is widely seen as one of the most effective MS treatments on the market, especially for those with severe cases who have few other options, and it is consistently defended by the MS community. -By Thomas Gryta, Dow Jones Newswires; 212-416-2169; thomas.gryta@dowjones.com
