Originally the FDA decision on whether to allow the companies to re-launch Tysabri was due in March 2006. This date has now been put back to June 28, 2006, allowing the regulatory agency additional time to review safety information.
The drug was voluntarily withdrawn from the market three months after its approval for sale following a link between its use and a rare and potentially fatal brain disease called progressive multifocal (PML). Three patients developed the disease while taking Tysabri in a clinical trial. No additional cases have been reported, however, and the companies were allowed to resume testing the safety of the treatment earlier this year.
Tysabri has proven to be much more effective than most existing multiple sclerosis (MS) drugs, making it likely to have a large impact on the MS market upon its anticipated return. Furthermore, an FDA advisory committee has already ruled unanimously in favor of the drug’s comeback, citing its ability to prevent symptoms reoccurring as a key reason for releasing it again, albeit on more restricted terms of sale.
News of the FDA’s decision to extend its review sent shares in Biogen falling by 21 cents to $48.10, while Elan was even more badly hit with a 55 cents decrease to $13.80.