Lower sales of Tysabri predicted

Analysts alter targets after illnesses reported

Financial analysts are predicting the number of patients using Tysabri will fall far below Biogen Idec Inc.'s forecast, following the Cambridge biotech company's disclosure last week that two more patients using the multiple sclerosis drug contracted a potentially fatal brain disease.

In an investor note yesterday, Deutsche Bank analyst Mark Schoenebaum said even under his best scenario, Tysabri will only have about 75,000 users by 2013, far short of the company's goal of 100,000 by 2010. In a more conservative scenario, Schoenebaum predicts just 56,000 patients will use the drug by 2013. And in the worst case, he said, the drug could get pulled from the market if more safety problems emerge.

Close to 32,000 patients currently use the treatment, which has been approved by the Food and Drug Administration to treat multiple sclerosis and severe forms of Crohn's disease.

JPMorgan analyst Geoffrey Meacham wrote in a note last week that even before the news of two new cases of progressive multifocal leukoencephalopathy, called PML, Wall Street's forecasts for the number of Tysabri patients by 2010 had been half Biogen Idec's predictions. Based on that, Meacham wrote, analysts' estimates will probably not fall dramatically further.

Biogen Idec shares rights to Tysabri with its Irish partner, Elan Corp. Both companies' stocks were pounded last week after the disclosure of the new PML cases, even though Biogen Idec has long warned that PML is a possible side effect of Tysabri use. The US label for the drug estimates that one in 1,000 could contract the brain disease, but many doctors and patients argue the drug is worth the risk after other therapies have failed because it has proven remarkably effective in reducing flare-ups of multiple sclerosis symptoms.

Multiple sclerosis disrupts the flow of information from the brain, causing symptoms from numbness to paralysis. It affects more than 400,000 in the United States.

Todd Wallack can be reached at twallack@globe.com.