The withdrawal of Tysabri in mid-Feburary not only "gutted" both Elan and Biogen Idec, but also hit the share prices of other publicly traded biopharmaceutical firms, sending the Burrill Biotech Select Index tumbling to end February down 2 per cent.

The index is now down 7 per cent since the beginning of the year.

"The news about Tysabri couldn't have come at a worse time, following as it did in the footsteps of tremendous controversy surrounding the use of COX-2 inhibitors," said Steven Burrill, CEO of San Francisco based life sciences merchant bank, Burrill & Company.

Three biotech firms debuted on the public markets during the month, although all have ended the month trading below their issue prices.

Favrille, a biopharmaceutical company focused on cancer and diseases of the immune system, has a non-Hodgkin's lymphoma drug in Phase III clinical trials. Icagen began to enrol patients in a Phase II trial for sickle cell disease, but ended the month down 10 per cent. And Theshold Pharmaceuticals raised less than half of its planned US$86 million, and ended the month flat.

There were no FDA approvals in February, noted Burrill, but Gilead Sciences did receive approval from European Commission to market its HIV drug Truvade.