Shares in Elan Corporation leapt over a quarter of their value this morning after the company revealed a safety review of its beleaguered multiple sclerosis drug, Tysabri (natalizumab), had uncovered no new cases of the central nervous system disorder that proved its downfall. Tysabri – originally touted as a blockbuster – was suspended from the market just three months following its approval after one death from a rare brain infection called PML [[24/11/04a]], [[01/03/05a]]. It has since been linked to three confirmed cases of PML, including two fatalities – not the five deaths speculated in June [[14/06/05c]].

In a statement this morning, Elan and partner Biogen Idec said they planned to pursue regulatory submissions for Tysabri in Crohn’s disease and rheumatoid arthritis in the third quarter and are “taking preliminary steps to restart clinical trials in MS.” The safety review evaluated more than 90% of the 2,000 eligible patients from clinical studies by conducting both a neurological exam and a magnetic resonance imaging scan to determine any adverse effects of Tysabri. No new confirmed cases of PML were identified.

The news has cheered investors, who suggest Tysabri could make a re-appearance on the US market as soon as next year.