AstraZeneca has bought many drugs firms during the past year

CAT was responding to media reports saying AstraZeneca was close to buying it in a deal valuing the antibody firm at about £600m ($1.13bn).

The company confirmed "it is currently in discussions with AstraZeneca Plc which may or may not lead to an offer".

AstraZeneca is Europe's third-biggest drug maker.

In March, it said profits during the first three months of the year had risen 38% to $2.04bn (£1.2bn).

Back in November 2004, AstraZeneca invested £75m in CAT, as the pair said they would work together on developing the next generation of anti-inflammatory drugs

Cancer therapy

If a deal goes through it will be the latest in a buying spree for AstraZeneca over the past year.

It paid £121m buying Cambridge-based biotech firm Kudos Pharmaceuticals, and also agreed a deal worth up to £173m with US firm Targacept to develop a treatment for Alzheimer's disease and schizophrenia.

Back in November it signed an agreement worth £195m to licence septic shock treatment CytoFab from UK rival Protherics.

In March it agreed to pay $200m to American group Abraxis BioScience to get the right to jointly promote its Abraxane cancer therapy.