Analysts: Tysabri scrips will suffer

When Biogen Idec announced last week that a potentially fatal brain infection had cropped up again in Tysabri patients, markets reacted swiftly--and negatively. But investors were only guessing at how that new information might affect new scrips for the drug, which has been hailed as a miracle treatment by many multiple sclerosis patients. Now, financial analysts have done some number-crunching to quantify those long-term effects. And the news isn't good.

Deutsche Bank analyst Mark Schoenbaum told investors that his best-case scenario pegged Tysabri at 75,000 users by 2013--not nearly the 100,000 patients Biogen had been shooting for by 2010. Under more conservative estimates, Schoenbaum predicted 56,000 Tysabri patients, again by 2013. And worst case? If more safety problems emerge, the drug could get pulled from the market--again. (For what it's worth, though, other analysts have said they don't expect Tysabri to be withdrawn.)

Meanwhile, a JP Morgan analyst estimated that the number of Tysabri patients by 2010 would be only 50,000--even before the two cases of progressive multifocal leukoencephalopathy (PML) were reported. The analyst said he doesn't expect that estimate to drop much further.

- read the story in the Boston Globe