Ireland’s Elan Corporation and US partner, Biogen Idec, saw millions wiped off their share prices yesterday on the shock news that they were suspending sales of their highly touted multiple sclerosis offering, Tysabri (natalizumab), just three months after it won coveted US approval [[24/11/04a]], after one patient died from a rare central nervous system disease.

The two firms, which have also suspended dosing in all clinical trials, say they made their decision after the death of a patient receiving Tysabri in combination with another Biogen Idec MS drug, Avonex (interferon beta-1a), in a clinical trial. The patient was confirmed to have been suffering from the potentially fatal condition, known as progressive multifocal leukoencephalopathy. There was also another suspected, non-fatal, case. Both patients had received the combination therapy for more than two years, but the firms note that there have been no reports of PML in patients treated with Avonex – a product that has been on the market since 1996.

Elan’s shares tumbled by as much as 71% in New York yesterday, while Biogen Idec fell 47% on the Nasdaq. Tysabri – formerly known as Antegren – is seen as key to reviving Elan’s future. The Irish company had been expecting the product to ultimately become the market-leading treatment for all forms of relapsing remitting MS [[08/02/05a]]. Tysabri had been the jewel in Elan’s crown and was widely expected to be the catalyst behind the Irish company’s turnaround. The firm, which teetered on the brink of bankruptcy a couple of years ago [[08/02/02b]], had been optimistic of a return to profitability in 2006 at the hands of Tyasabri [[28/10/04c]], [[10/06/02a]], [[03/05/02c]]. Although Elan and Biogen Idec say that they will work to understand the possible risk of PML, which could lead to a possible re-initiation of dosing in clinical trials and future market re-introduction, the present situation remains bleak. Elan is expected to amend its full-year 2005 financial forecasts within the next few days.