Biogen: Tysabri patients have PML

Biogen Idec CEO James Mullen predicted it, and now it's happened: Two Tysabri patients have come down with the potentially fatal brain infection, progressive multifocal leukoencephalopathy, or PML, that caused Biogen to withdraw the multiple-sclerosis treatment back in 2005. This time around, though, the company doesn't plan to pull the med or further restrict it.

As you know, Tysabri was allowed back onto the market [1] in July 2006 under a strict risk-management program. Since then, 31,600 patients have started on the drug, and Biogen (and its partner Elan) won an additional indication for Crohn's disease. Mullen had been predicting that 100,000 patients would be using Tysabri by 2010, with quarterly sales of $250 million or better by the end of this year.

It's unclear whether this news will decimate those sales. Investors seem to think so; both Biogen and Elan have seen their shares drop precipitously this morning. And the fact that the sickest PML patient--who's now hospitalized--was only taking Tysabri for 14 months, because the duration of treatment seems to be a factor in the disease. (Previous PML patients had used Tysabri for some two years before discovering they had it.) This patient had used other MS drugs before taking Tysabri, which also appears to be a risk factor. The other patient, who's at home and ambulatory, had been on Tysabri for 18 months, and hadn't used any other MS treatments before.

But patients know about the PML risks before they go on Tysabri; the risk-management program makes sure of that. And so far, the number of PML cases appears to be in line with the statistical risk listed on the drug's label. So we'll have to watch the scrip numbers to see whether verification of that risk deters patients.

- read the Wall Street Journal article [2]
- see the story [3] in the Boston Herald

Related Articles:
Biogen CEO: Tysabri to reach $1B in 2008 [4]
No new PML cases for Tysabri [5]
Watchdog endorses use of Tysabri for severe MS [6]
After reintroduction, Tysabri builds patient base [7]
FDA allows Tysabri back on market [1]