Shares in Elan ended trading in the US yesterday virtually flat, down 3 cent to $27.27, following final approval from the US Federal Drugs Administration to sell its Antegren drug, a treatment for multiple sclerosis. In Dublin the shares were also flat, ending the day down 3 cent at €20.87.

However, analysts were extremely upbeat yesterday about the FDA approval which had been expected. Some analysts forecast that the treatment could reap sales of more than €3 billion a year.

The treatment will be rebranded as Tysabri when it is launched by Elan and Biogen Idec of the US who also developed it.

The two companies held a joint conference call yesterday, but did not disclose the price it will sell the product at, which analyst Mr Ian Hunter of Goodbody Stockbrokers said was a bit disappointing.

However, this information is expected within days.

He said Tysabri was expected to be on the market within a few weeks and this was very positive for a new drug to be coming to market so quickly.

Mr Robert Brisbourne of Merrion Stockbrokers said the news was welcome, if expected, and would be a relief for Elan.

He also expects it to become the leading treatment in relapse remitting multiple sclerosis.

The US approval, announced after the markets closed on Tuesday, marks the final step in a turnround for Elan. The company was forced to sell most of its products to avoid collapse, following an accounting scandal two years ago that sent its shares plummeting 98 per cent.

But the company is now Europe's second-largest biotechnology company, largely as a result of the anticipated success of Antegren.

Antegren is a synthetic human antibody that prevents nerve cell damage by stopping immune cells moving from the bloodstream into the brain, where they cause damage to nerve fibres.