Oxford BioMedica is up 3.75p, or 20%, at 22.5p on rumours drug giant Sanofi Aventis may be interested in buying it.
The biopharmaceutical firm, which specialises in the development and commercialisation of gene-based medicines, is already a partner of the French pharmaceutical group.
Oxford BioMedica has signed a global licensing agreement with Sanofi to develop and commercialise TroVax for the treatment of cancer - a deal worth up to €518m (£385m) if all development and registration targets are met for certain defined indications, in addition to royalties on future sales.
Sanofi will post its full-year results tomorrow and investors might find out more then. The group is known to be keen to get further into biologics. But neither company is commenting so far.