Tysabri isn't back on the market yet, but the odds have dramatically increased that it soon will be. That has set in motion considerable calculations among investors in companies that make medications for the same disease. At stake is a market in which most MS drugs have annual sales of at least $1 billion, representing the largest source of revenue for their respective companies. A panel of medical experts on Wednesday said Tysabri, developed by Elan ( ELN) and Biogen Idec ( BIIB), should return to the market. Within minutes, stock watchers on both sides of the Atlantic were trying to assess how Tysabri would affect competitors' sales and stock prices. Other players in the MS market include Switzerland's Serono ( SRA), which makes Rebif and Novantrone, Israel's Teva Pharmaceutical Industries ( TEVA), the maker of Copaxone, and Germany's Schering AG ( SHR), the seller of a drug called Betaseron. Another MS drug is Avonex, from Biogen, and it accounted for $1.54 billion of corporate revenue, on nearly two-thirds of the total, last year. Novantrone is the only MS drug with annual sales below $1 billion. Assuming the Food and Drug Administration supports its panel's recommendation, Tysabri's ultimate impact will depend on how many restrictions are imposed on the drug and how often doctors prescribe it, given its dramatic history . The FDA is expected to act by the end of March. If it does, Biogen and Elan say they could move quickly to make the drug available. And don't forget the European Union. Kelly Martin, Elan's chief executive, told an S.G. Cowen conference in Boston that he expects EU regulators to rule on the drug by midyear, meaning Tysabri could be launched during the second half of 2006.
Shareholders of most competitors shrugged off Wednesday's unanimous vote by the advisory committee supporting Tysabri, partly because the panel suggested the FDA include labeling with the drug that contains a warning about a potentially lethal side effect, a brain disease called PML.