Protherics, the international biopharmaceutical company based in Cheshire, has seen its share price rise by up to 40% after receiving a number of informal takeover approaches.

A statement issued by Protherics, which has a research facility in Runcorn, Cheshire, says the board is considering various offers.

"There can be no certainty that any formal offer will be made," said a spokeswoman, who went on to say that terms could not yet be confirmed.

This morning, shares in Protherics - which specialises in critical care and cancer products - jumped 25 per cent to 48 pence.

Finncap analyst Keith Redpath told Reuters that another pharmaceutical with a major presence in Cheshire may be interested.

"I would suggest that AstraZeneca could be one of these parties," he said.

Protherics is currently focused on building a specialist sales and marketing capability to distribute cancer therapy Voraxaze when it is approved in the US in 2010.