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

Business Editors/Health/Medical Writers

BRIDGEWATER, N.J.--(BUSINESS WIRE)--Sept. 3, 2003

Cambridge Antibody Technology (LSE:CAT; NASDAQ:CATG), Micromet AG, and Enzon Pharmaceuticals, Inc. (NASDAQ:ENZN)

Expanded Opportunities for the Development of

Novel Antibody Therapeutic Products

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."

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.

-- 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 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 GBP41m in its IPO in March 1997 and

GBP93m 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

HUMIRA(TM).

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 BiTE(TM) 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 science-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 September 3 , 2003, and the Company undertakes no duty to update this information.

This release is also available at http://www.enzon.com