PowderJect could become the latest Oxfordshire biotech company to be taken over by a rival.

The company, based at Oxford Science Park, said negotiations over an offer were at an advanced stage.

The offer is believed to be for £500m from US rival Chiron.

Last month, Oxford GlycoSciences, at Milton Park, near Abingdon, was the victim of a hostile takeover bid by Celltech.

OGS staff have been told Celltech aims to keep as many of the firm's 300 employees as possible.

PowderJect was the first UK biotech company to pay a dividend to shareholders, following a sharp rise in pre-tax profits.

Chiron is thought to be offering about 550p a share for PowderJect, which is the world's largest independent vaccine maker.

The US group has been stalking PowderJect since talks collapsed in disagreement over the price in November, when the Oxford company also received a bid from pharmaceutical giant GlaxoSmithKline, which owns 5.4 per cent of Powderject's shares. The bids were made after PowderJect's share price plummeted, with £90m wiped off the value of the company following the withdrawal of a tuberculosis vaccine because of a potency problem.

But news of the takeover bids pushed the share price back up and since then the company has been boosted by record financial figures.

Chief executive Paul Drayson owns seven per cent of the company, which he founded using technology developed by his father-in-law, Oxford engineering don Brian Bellhouse.

The family holds 13 per cent of the company.

Prof Bellhouse's invention has given PowderJect the lead in needle-free injections.

The company is also developing and testing pioneering DNA vaccines, designed to fight HIV and Hepatitis C as well as influenza.

Record sales of its flu vaccine Fluvirin and a controversial contract to supply the British Government with smallpox jabs -- for use in case of bioterror attack -- boosted turnover to £158.5m in the year to March 31 -- up from £113m.

The company announced that it would pay a maiden dividend of 3p after pre-tax profits rose from £100,000 to £23.5m.

Fluvirin - now the world's second best-selling flu vaccine -- saw sales rise 40 per cent to £93.2m, driven by business in the US as well as growing interest in parts of the Far East and the southern hemisphere.