Irish biotech group Elan and its US partner Biogen have agreed to pitch their stalled multiple sclerosis drug Tysabri as a treatment on its own rather than to use alongside other immunosuppressant drugs.

The decision increases the prospects of Tysabri winning approval from the US Food and Drugs Administration (FDA) next month to bring the drug back to market.

It marks a change of approach from US group Biogen, which had earlier hoped to continue to market the breakthrough drug for use alongside its older MS treatment Avonex.

Tysabri was pulled from the shelves 12 months ago after it was implicated in the diagnosis of a rare brain disease in two trial patients, one of whom died. In both instances, Tysabri had been given alongside Avonex.

While a third case, also fatal, that emerged later was not linked to Avonex, the patient had been treated extensively with other immunosuppressant drugs.

Elan and Biogen have conducted what they say is the largest safety evaluation of its kind ever undertaken and are confident that the outcome, along with updated clinical data and a new risk management programme and new labelling will secure Tysabri's re-entry to market.

An FDA advisory committee is holding a two-day public hearing on the drug, beginning on March 7th.

The US regulator, which last week sanctioned the restart of Tysabri infusions for people on the original clinical trials, is committed to announcing a decision on the drug's return by the end of March.