Re Amgen Collaboration

Cambridge Antibody Tech Group PLC
24 December 2003

03/CAT/31

FOR IMMEDIATE RELEASE

07.00 GMT, 02.00 EST Wednesday 24 December 2003

For further information contact:

Cambridge Antibody Technology                               Weber Shandwick Square Mile (Europe)
Tel: [phone]                                   Tel: [phone]
Peter Chambre, Chief Executive Officer                      Kevin Smith
Rowena Gardner, Director of Corporate Communications        Rachel Lankester

                                                            BMC Communications/The Trout Group (USA)
                                                            Tel: [phone]
                                                            Brad Miles, ext 17 (media)
                                                            Brandon Lewis, ext 15 (investors)



CAMBRIDGE ANTIBODY TECHNOLOGY AND AMGEN RESTRUCTURE EXISTING AGREEMENT

Cambridge, UK... Cambridge Antibody Technology Group plc (LSE: CAT; NASDAQ:
CATG) today announces the restructuring of an existing antibody development and
marketing collaboration agreement between CAT and Immunex Corporation,
subsequently acquired by Amgen Inc., in which Amgen takes over responsibility
for the future development of the antibodies covered by the agreement.  CAT will
have the right to receive milestone and royalty payments upon the success of
these programmes.

Under the terms of the agreement, Amgen will take responsibility for the further
development and marketing of the therapeutic antibody candidates isolated by CAT
against two targets on which the parties agreed to collaborate and will bear all
the associated costs. In return, CAT will receive from Amgen an initial fee and
potential milestone payments and royalties on future sales.

One candidate has been delivered by CAT to Amgen.  A second candidate is the
subject of a continuing research programme funded by Amgen and conducted by CAT
and will be delivered to Amgen in due course.

Peter Chambre, CAT's Chief Executive Officer, commented, "We are delighted
to have signed this agreement with Amgen.  Over the last twelve months we have
reviewed our product portfolio with the intention of focusing our investment on
a number of core programmes. This agreement allows us to do this, whilst
retaining a significant interest in the success of the two antibody candidates
which CAT has helped to develop against Amgen targets."



                              ENDS



Notes to Editors



Cambridge Antibody Technology (CAT):

•         CAT is a UK-based biotechnology company using its proprietary
technologies and capabilities in human monoclonal antibodies for drug discovery
and drug development. Based near Cambridge, England, CAT currently employs
around 280 people.

•         CAT is a leader in the discovery and development of human therapeutic
antibodies and has an advanced proprietary platform technology for rapidly
isolating human monoclonal antibodies using phage display and ribosome display
systems. CAT has extensive phage antibody libraries, currently incorporating
more than 100 billion distinct antibodies. These libraries form the basis for
the Company's strategy to develop a portfolio of antibody-based drugs.

•         Three CAT human therapeutic antibody products are now in clinical
development, with two further product candidates in pre-clinical development.

•         HUMIRA(TM), the leading CAT-derived antibody, isolated and optimised
in collaboration with Abbott has been approved by the US Food and Drug
Administration for marketing in the US and by the European Commission for
marketing in the EU as a treatment for rheumatoid arthritis.

•         Five further licensed CAT-derived human therapeutic antibodies in
clinical development, with three further licensed product candidates in pre-
clinical development.

•         CAT has alliances with a number of pharmaceutical and biotechnology
companies to discover, develop and commercialise human monoclonal antibody-based
products. CAT has co-development programmes with Amrad, Elan and Genzyme.

•         CAT has also licensed its proprietary technologies to several
companies. CAT's licensees include: Abbott, Amgen, Chugai, Human Genome
Sciences, Merck & Co, Pfizer and Wyeth Research.

•         CAT is listed on the London Stock Exchange and on NASDAQ since June
2001. CAT raised £41m in its IPO in March 1997 and £93m in a secondary offering
in March 2000.


Application of the Safe Harbor of the Private Securities Litigation Reform Act
of 1995: This press release contains statements about Cambridge Antibody
Technology Group plc ("CAT") that are forward looking statements. All statements
other than statements of historical facts included in this press release may be
forward looking statements within the meaning of Section 21E of the Securities
Exchange Act of 1934. These forward looking statements are based on numerous
assumptions regarding the company's present and future business strategies and
the environment in which the company will operate in the future. Certain factors
that could cause the company's actual results, performance or achievements to
differ materially from those in the forward looking statements include: market
conditions, CAT's ability to enter into and maintain collaborative arrangements,
success of product candidates in clinical trials, regulatory developments and
competition. We caution investors not to place undue reliance on the forward
looking statements contained in this press release. These statements speak only
as of the date of this press release, and we undertake no obligation to update
or revise the statements.


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            The company news service from the London Stock Exchange