Two patients involved in clinical trials of Tysabri, have contracted a rare and fatal disease, Elan’s multiple sclerosis (MS); one has already died. Withdrawal of the drug, eliminates all hope that it will be allowed back on the market this year, or ever.
Both patients were taking Tysabri with Avonex, an established MS drug developed by Biogen Idec. Confirming the second case, the companies said in a joint statement that, for now, there was no evidence that either drug taken on its own was linked to PML.
Walter Atwood, Brown University on Rhode Island specialises in progressive multifocal leukoencephalopathy (PML), the disease contracted by the two men, has said that even if it could be shown that Tysabri alone had not been responsible, it would take time to confirm this and it would make little difference for Tysabri. “Two cases out of 500 is pretty huge. Such a representative number in the order of 2-4% would be more typical in Aids patients,” he said. “The general incidence of the disease is between one in 100,000 and one in 500,000 and this is the first time PML has ever shown up in an MS patient to my knowledge.”
Even if shown to be effective on its own a long-term trial would be needed. Unfortunately there is no treatment for PML. Medical experts doubt the prospects of a quick return for the drug; it was expected to produce revenues of up to $4 billion (€3 billion) a year by 2008 and turn Elan profitable by the end of 2006.