Sales of multiple sclerosis drug Tysabri grew by 12 per cent in the fourth quarter of 2010, according to figures provided yesterday by US biotech group Biogen Idec.

The company produces and markets the drug in association with Irish pharma group Elan.

Sales of Tysabri rose a higher-than-expected 12 per cent to $333 million, Biogen said yesterday.

At the end of December, about 56,600 patients were taking Tysabri worldwide, an increase of 1,700 patients in the fourth quarter and 8,200 in 2010. Analysts at Deutsche Bank said the figures were “modestly ahead of consensus”.

Elan will not report its fourth-quarter figures until next week.