Elan shares jumped nearly 19 per cent on the Dublin market this morning after the company published trial results showing that Tysabri slows disability in relapsed MS patients.
Elan and Biogen published the results from a pivotal-stage trial of the suspended Tysabri, showing that it slows disability in relapsed MS patients.
The two-year data from the AFFIRM Phase III monotherapy trial show that treatment with Tysabri led to a significant reduction in disability progression, the rate of clinical relapses and brain lesions in patients with relapsing forms of multiple sclerosis.
Tysabri was withdrawn from the market in February after a patient died from a rare brain infection. A second patient was later determined to have died from the same infection and a third was diagnosed with the condition, progressive multifocal leukoencephalopathy, but lived.
But industry analysts said the news did not address the safety problems that had led to its withdrawal and an early comeback looked unlikely. "This confirms Tysabri's significant benefit for patients," said Richard Parkes of ING Financial Markets.
"But it doesn't change the fact that we have now seen three cases of a potentially fatal side effect. The risk-benefit profile at the moment looks unattractive," added Mr Parkes, who rates the stock a "sell".
Elan shares, which slumped 90 per cent in the wake of the drug's withdrawal in February after a patient died, were up 19 per cent at €3.48 in Dublin this morning.
But analysts reiterated that Elan and Biogen still faced a tough uphill battle to persuade the US Food and Drug Administration that any risks associated with Tysabri could be outweighed by the benefits.
"Patients will only be willing to try it, and importantly doctors will only be willing to prescribe it, if this risk can be defined," Jack Gorman, analyst at Davy Stockbrokers in Dublin, wrote in a research note.
But even if Tysabri does make a comeback, the drug looks to have lost its blockbuster potential for good, analysts said.
"The best case is probably that this drug gets back to the market at some point and is restricted to those patients that aren't responding to other therapies," said ING's Parkes.
"In that case it could be a $500 million drug - but we would view that as quite unlikely," he said of a treatment once tipped as a product that could sell more than $2 billion a year.