Another UK biotechnology firm has lost its independence – Acambis is to be taken over by Sanofi-Aventis.

The French drugmaker’s vaccines arm Sanofi Pasteur is to pay around £276 million in cash for Acambis, or £1.90 per share. This equates to a premium of 65.2% to the latter’s stock price of £1.15 at the close of business on July 24. Importantly, Sanofi said it has received “irrevocable undertakings to vote in favour of the scheme” from Invesco Asset Management and Goldman Sachs which together hold a stake of just over 42% of the Cambridge-based firm.

The Sanofi bid comes as no great surprise especially as the firm has already got collaborations in place with Acambis. These include the latter’s most advanced programme, ChimeriVax-JE for Japanese encephalitis, which is in Phase III, as well as vaccines against West Nile virus and dengue, both of which are in Phase II.

Wayne Pisano, chief executive of Sanofi Pasteur, said that “this mutually beneficial acquisition is a logical step”, building upon the firms’ “decade-long partnership". On a conference call announcing the deal, his counterpart at Acambis, Ian Garland, said the transaction is "fair and reasonable," given the firm's pipeline, plus the risks associated with early-stage development projects and "also taking into account the current financial market conditions”.

The UK firm’s chairman, Peter Fellner, said that since a new management team had been appointed in 2007, the company had made important advances progressing its pipeline “and securing its mid-term financial position”. Sanofi recognises those advances and has made an offer “at a substantial premium”.

He added that “Sanofi will benefit strategically not only from Acambis's pipeline and technologies but also from its significant US-based R&D and manufacturing infrastructure". The biggest benefit, in the short-term at least, is that the UK company was recently awarded a $425 million, ten-year contract by the Centers for Disease Control and Prevention to provide it with a warm-base manufacturing capability for the ACAM2000 smallpox vaccine which has been stockpiled by the US Government.

The deal was announced late on Friday but investors have responded positively this morning. At 10.30 UK time, Acambis shares had shot up 60.3% to £1.86, and Shawn Manning, an analyst at Landsbanki, said that the tie-up with Sanofi “validates our thesis that Acambis is a high value stock that is trading well below fair value".

In a research note, he added that "the acquisition of Acambis underlines Landsbanki's view that there still remains significant upside opportunity for the selective investor".