Shares in pharmaceutical company Elan have fallen sharply in New York after reports that 'significant' liver injury occurred in some multiple sclerosis patients as early as six days after their first dose of Tysabri.
The US Food & Drug Administration (FDA) said Elan and its partner Biogen had notified doctors of the problems.
The FDA said Tysabri should be discontinued in patients with jaundice or other evidence of significant liver injury. The drug will remain on the market in the US and talks are continuing with EU regulators.
Elan shares were down 4% on the New York Stock Exchange, though the news came after the Dublin market had closed.
In January, the two companies said that more than 21,000 patients worldwide were using Tysabri on a commercial and clinical basis. It is understood the problem affects only one in 1,000 patients.
The drug returned to the market in July 2006. It had been withdrawn in February 2005 after the deaths of two patients involved in trials of the drug from a rare brain disease, PML.
'At Biogen and Elan, patient safety is our highest priority,' the companies said in the letter to doctors. 'We are committed to ensuring that healthcare professionals continue to receive the necessary information to prescribe Tysabri appropriately.'
The companies, which market the product together, issued the warning letter after patients developed unusually high levels of liver enzymes in the blood, a sign of liver injury, according to the letter. The injury recurred in some patients after they were given another dose of the drug, 'providing evidence that Tysabri caused the injury,'' according to the letter.
