CAT Micromet Enzon Agreement

Cambridge Antibody Tech Group PLC
03 September 2003


03/CAT/21

FOR IMMEDIATE RELEASE

07.00 BST, 02.00 EST Wednesday 3 September 2003

For further information contact:           Weber Shandwick Square Mile (Europe)

Cambridge Antibody Technology              Tel: [phone]

Tel: [phone]                  Kevin Smith

Peter Chambre, Chief Executive Officer     Rachel Lankester

John Aston, Chief Financial Officer

Rowena Gardner,Director of Corporate
Communications

Micromet AG                                BMC Communications/The Trout Group (USA)

Jens Hennecke, Ph.D. Associate Director    Tel: [phone]
Businesss
                                           Brad Miles, ext 17 (media)
Development, Tel: [phone]
                                           Brandon Lewis, ext.15 (investors)
Evelyn Wolf, Manager Public Relations,
                                           Enzon:
Tel: [phone]
                                           Kenneth J. Zuerblis, Vice President,
Ines-Regina Buth, Manager Investor         Finance & CFO,
Relations,
                                           Tel: [phone]
Tel: [phone]
                                           Euro RSCG Life NRP, Mark R. Vincent,
                                           Media

                                           Relations, Tel : [phone]

Micromet, Enzon and Cambridge Antibody Technology sign Cross-Licence Agreement
in the Field of Single-Chain Antibodies and Phage Display

Expanded opportunities for the development of novel antibody therapeutic
products

Cambridge, UK, Munich, Germany and Bridgewater, NJ ... Cambridge Antibody
Technology (LSE:CAT; NASDAQ:CATG), Micromet AG (private), and Enzon
Pharmaceuticals, Inc. (NASDAQ:ENZN) today announce that they have signed a
non-exclusive cross-licence agreement, under which all three parties obtain
substantial freedom to conduct research under certain of each others'
intellectual property, as well as the right to develop a defined number of
therapeutic and diagnostic antibody-based products. CAT obtains expanded access
to Micromet's and Enzon's joint patent estate in the field of single-chain
antibody technology (SCA) and both Micromet and Enzon gain rights to
intellectual property in antibody phage display controlled by CAT.

This cross-licence agreement builds on existing alliances: that of Micromet and
Enzon, where both parties combined their significant patent estates and
complementary expertise in the field of SCAs; and the licence agreement first
entered into among CAT, Enzon and Creative BioMolecules in 1996. In addition to
the cross-licensing of intellectual property under this agreement, Enzon and CAT
have both agreed to withdraw their pending oppositions to each others' European
patents in the area of diabodies.

Under the terms of the agreement, Micromet and Enzon obtain the right within the
framework of their collaboration to use CAT's intellectual property in phage
display to create and

commercialise novel antibody products against a defined number of targets. In
addition, Enzon and Micromet each receive options to develop and commercialise
antibody products outside of their alliance. CAT receives options to develop and
commercialise diagnostic and therapeutic SCA products and broad rights to
SCA-based technologies for research, including the right to sublicense to
collaboration partners. In addition CAT receives a two-year option to licence
SCA technology for use in antibody microarrays. The cross-licence agreement is
structured to maximally incentivise all three parties to develop and
commercialise antibody-based products.

Christian Itin, PhD, Micromet's Chief Business Officer commented, "The SCA IP
estate consolidated between Enzon and Micromet in 2002 and the CAT-MRC IP estate
to antibody phage display are robust in their respective spaces. The present
transaction provides each of the companies access to relevant complementary IP,
supporting each company's business case on attractive commercial terms."

Peter Chambre, CAT's Chief Executive Officer, commented, "We view this
cross-license agreement with Micromet and Enzon as important to our commitment
to the development and commercialisation of therapeutic antibodies. Not only
does CAT obtain access to a broad commercial opportunity in SCA, but through
this agreement CAT enjoys greater flexibility in respect of its collaboration
partners. All three companies stand to benefit from this consolidation of
intellectual property which underpins the exploitation of antibody-based drugs."

Uli Grau, Enzon's Chief Scientific Officer, commented, "With this cross-licence
Enzon is able to strengthen our leading position in the growing field of
antibody therapies, which we intend to leverage to expand our product
portfolio."

-ENDS-



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 290
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.

HUMIRATM, 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 as a treatment for rheumatoid arthritis.
Approval in Europe is expected by Abbott in mid-2003.

Eight further CAT-derived human therapeutic antibodies are at various stages of
clinical trials. There are five candidate therapeutic antibodies 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 Amgen, 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.

CAT Phage Display Patents

CAT is the exclusive licensee of patents from the Medical Research Council whose
claims cover the discovery and development of human antibodies using phage
display.

CAT has successfully resolved all of its principal outstanding patent
litigation. In December 2002, CAT settled all patent disputes with MorphoSys and
Crucell. Those agreements demonstrated the strength of CAT's patent position and
provided evidence of CAT's commitment to licensing its patent portfolio. They
also gave CAT a stake in the future success of those companies and ended the
distraction of patent litigation. In addition, CAT has entered into a
cross-licensing arrangement with XOMA for antibody-related technologies.

CAT has also entered into an agreement with Dyax Corporation to expand access
and freedom to operate under each other's phage display patents, an agreement
which also included the removal of CAT's obligation to pay royalties to Dyax on
antibody products it develops, except in respect of HUMIRATM.


    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 CAT's present and future business
    strategies and the environment in which CAT will operate in the future.
    Certain factors that could cause CAT'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.

Micromet AG:

Micromet AG, a private Munich-based biotechnology company, puts novel concepts
in immunotherapy to work. Using proprietary technologies, the Company is
building a strong pipeline of innovative drug candidates for the treatment of
cancer, inflammation and autoimmune disease. Two candidates are currently in
clinical trials.

The Company has established a powerful drug development platform based on its
BiTETM technology ("Bispecific T cell engagers"), a unique drug format that
leverages the outstanding cytotoxic potential of T cells, the most powerful '
killer cells' of the human immune system. In addition Micromet is exploiting the
potential of SCAs (single-chain antibodies) for the development of novel drug
formats under a multiyear strategic collaboration with Enzon Inc.

Micromet has integrated infrastructure and expertise in all disciplines of drug
design and development. For further information, please visit the company's web
site at www.micromet.de.

Micromet AG, Staffelseestr. 2, 81477 Munich, Germany

Enzon Pharmaceuticals:

Enzon Pharmaceuticals is a biopharmaceutical company dedicated to the discovery,
development and commercialization of therapeutics to treat life-threatening
diseases.

The company has developed or acquired a number of marketed products, including
PEG-INTRON, marketed by Schering-Plough, and ABELCET, which is marketed in North
America by Enzon. Enzon's product-focused strategy includes an extensive drug
development program that leverages the Company's PEG modification and
single-chain antibody (SCA(R)) technologies. Internal research and development
efforts are complemented by strategic transactions that provide access to
additional products, projects, and technologies.

Enzon has several drug candidates in various stages of development,
independently and with partners.


    Except for the historical information herein, the matters discussed in this
    news release include forward-looking statements that may involve a number of
    risks and uncertainties. Actual results may vary significantly based upon a
    number of factors, which are described in the Company's Form 10-K, Form
    10-Q's and Form 8-K's on file with the SEC, including without limitation,
    Enzon's ability to clinically advance its PEG-Camptothecin and ATG-Fresenius
    programs, Enzon's dependence on Schering-Plough's effective marketing of
    PEG-INTRON; Enzon's ability to sustain profitability; risks in obtaining and
    maintaining regulatory approval for indications and expanded indications for
    Enzon's products; market acceptance of and continuing demand for Enzon's
    products; timing and results of clinical trials and the impact of
    competitive products and pricing, All information in this press release is
    as of 3 September , 2003, and the Company undertakes no duty to update this
    information.





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