Shares in Irish pharmaceutical company Elan have fallen sharply today after another patient taking its multiple sclerosis drug Tysabri was diagnosed with a potentially life-threatening brain illness progressive multifocal leukoencephalopathy (PML).
Tysabri is jointly marketed by Irish pharmaceutical firm Elan and its partner Biogen. Elan shares were trading down 16.5 per cent at €4.88 on the Dublin market by 11.25am.
The diagnosis is the third Tysabri patient diagnosed with PML since the drug's reintroduction to the market in 2006.
The drug was withdrawn in early 2005 in the US when the first cases of (PML) in patients using Tysabri emerged.
Tysabri was subsequently withdrawn from the market after three patients, two of whom died, were found to have contracted the illness. It was reapproved for usage by the US Food and Drug Administration (FDA) in the middle of 2006.
The report from Biogen last night sent its shares down as much as $6.94, or 17 per cent, to $35 in extending trading on the Nasdaq Stock Market.
In this latest case the patient was diagnosed after 14 Tysabri infusions, Biogen said last night in a statement.
An Elan spokeswoman said this morning the "emphasis" in the prescribing information for Tysabri had been changed since October 3rd following a review carried out after the two PML cases in July.
This information shows the infection may occur in patients taking the drug as a sole treatment.
In a briefing note to investors this morning Davy analyst Jack Gorman said the case, the third since its re-launch should not come as a surprise.
"One new PML case, although bad for near-term sentiment in these markets, should not be a surprise and does not alter our view substantially".
"It is likely that regulators will seek to include this newly confirmed case on the EU and US labels. However, the PML occurrence rate remains well below what is contained on the label, and we would be surprised if any more stringent action will be considered at this time," he said.
Davy recently raised its Tysabri targets. It said the new PML diagnosis will "continue to make clinicians apprehensive about putting new patients on the drug".
Elan said 34,800 patients in the US and Europe were being treated with the drug.
Biogen chief executive officer James Mullen said Tysabri generated worldwide sales of $236 million in the third quarter.
"We got confirmation of PML in a Tysabri patient today," said Naomi Aoki, a Biogen spokeswoman, in a telephone interview. "She is currently under the care of her treating physician." Ms Aoki declined to comment on the patient's condition.