Health officials in the US have cleared the way for the multiple sclerosis drug Tysabri to return to the market.
The drug, which is produced by the Irish pharmaceutical company Élan, had been withdrawn after it was linked to a rare brain disease.
When it was first approved in 2004, Tysabri was considered a ‘wonder drug’ in the treatment of MS. However, last year it was voluntarily removed by Élan and Biogen, when two patients taking the drug died of a brain infection.
The withdrawal caused shares in Élan to fall by 70% in just one day.
Since then many patients with MS have called for its re-introduction arguing that the drug's benefits outweigh its risks.
The US Food and Drug Administration has now cleared the way for Tysabri to be put back on the market.
However, restrictions have been imposed on the sale of the drug. It can only be given to patients who have not responded to other MS treatments and it cannot be prescribed in combination with other MS drugs.
Élan has welcomed the return of Tysabri as has MS Ireland which represents multiple sclerosis sufferers.
But the markets reacted less favourably. In trading on the New York Stock Exchange yesterday, shares in Élan and Biogen dropped on foot of the decision that the drug can only be used on a restricted basis.
