Shares in Elan surged by more than 20 per cent in Dublin yesterday after the release of scientific data on its multiple sclerosis (MS) treatment, Tysabri, underlined the efficacy of the drug.
However, the stock later gave up some of the gains as continued uncertainty over the safety of the drug overshadowed the data and analysts remained divided over Tysabri's prospects of returning to the market.
The drug has been suspended since the end of February when it was voluntarily withdrawn by Elan and Biogen Idec, its partner in the development of Tysabri, after two patients developed a rare brain disorder called progressive multifocal leukoencephalopathy (PML).
The detailed scientific data, released at the annual meeting of the American Academy of Neurology (AAN) on Tuesday, fleshed out headline data first released in February.
The data, derived from a two-year trial of 942 MS patients, showed that Tysabri was much more effective than existing therapies in reducing the number of flare-ups of MS.
In addition to cutting relapse rates by 67 per cent, it reduced by 42 per cent the risk of greater disability compared with a placebo.
However, Goodbody analyst Ian Hunter noted that there was nothing really new in the information issued.
"It's basically the scientists poring over the detail," he said.
Elan stock closed 10 per cent higher at €3.25 in Dublin but off its earlier highs as some of those who bought in at lower levels sought to take profits.
Investor attention also switched back to the long path Elan and Biogen must tread if they are to bring Tysabri back to the market.
In New York, the main market where Elan stock is traded, the shares finished 13.5 per cent higher at $4.28.
Meanwhile, doctors attending the AAN meeting in Florida remained sceptical about Tysabri's chances of a comeback.
"It won't come back," Dr Douglas R. Jeffery, associate professor of neurology at the Wake Forest University School of Medicine in Winston-Salem, North Carolina, told the Boston Globe.
"When you study a very small population and then you move a drug to a broad patient population, you see things you didn't see before."
