CAS Granted Patent in US

Cambridge Antibody Tech Group PLC
15 January 2001


For further information contact:

Cambridge Antibody Technology        
Tel: [phone]
Diane Mellett, General Counsel
John Aston, Finance Director       
Rowena Gardner, Head of Corporate Communications       

HCC De Facto (Europe)
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Adam Michael
David Speechley
                                                                              
BMC Communications/The Trout Group (USA)
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Brad Miles, ext.17 (media)
Brandon Lewis, ext.15 (investors)



CAMBRIDGE ANTIBODY TECHNOLOGY GRANTED FURTHER KEY PATENT IN US


Melbourn, UK Cambridge Antibody Technology (LSE: CAT) has announced that it
has been granted another US patent, US 6,172,197, entitled 'Methods for
Producing Members of Specific Binding Pairs'. 

The patent provides protection for libraries of phage displaying functional
protein binding domains derived from natural repertoires of nucleic acids,
wherein each phage particle contains a phagemid genome. Dependent claims cover
display of antibodies, and of scFv or Fab antibody fragments.

Dr David Chiswell, CAT's CEO, commented, 'This patent further extends CAT's
growing US patent estate covering the phage display of antibodies and antibody
fragments. It is particularly noteworthy that this new patent includes not
just scFv antibody fragments but also Fab antibody fragments as well as other
non-antibody proteins. Taken together with CAT's other patents granted
worldwide, the granting of 

this patent reinforces the strength of  CAT's patent position and confirms
CAT's leadership in the development of human antibodies.'


Notes to Editors:

Cambridge Antibody Technology (LSE: CAT) 
CAT is a UK biotechnology company using its proprietary technologies in human
monoclonal antibodies for drug discovery and drug development.  Based in
Melbourn, 10 miles south of Cambridge, England, CAT currently employs nearly
200 people.  
CAT is listed on the London Stock Exchange, having raised £41m in its IPO in
March 1997. A secondary offering in March 2000 raised £93m.  
CAT has a world-leading platform technology for rapidly isolating human
monoclonal antibodies using phage display systems.  CAT has an extensive phage
display antibody library, currently incorporating around 100 billion distinct
antibodies. This library forms the basis for the company's strategy to develop
a portfolio of clinical development programs and for discovering new drug
leads using functional genomics.  Four fully human therapeutic antibodies
developed by CAT are at various stages of clinical trials.  
CAT works in partnership with other companies at all stages of the drug
discovery and development process. CAT's collaborations, past and present,
include: AstraZeneca, BASF Pharma, Eli Lilly, Genentech, Genetics Institute,
Genzyme, Human Genome Sciences, Immunex, Oxford GlycoSciences, Pharmacia
Corporation, Pfizer, Wyeth-Ayerst 

CAT's patent portfolio 
CAT's patent portfolio broadly covers the field of phage display of antibodies
and, along with the licences CAT has (particularly with The MRC, Dyax, Scripps
and Stratagene), gives CAT the freedom to operate its technology. 
CAT currently has two main patent families covering antibody libraries (Winter
II) and phage display (McCafferty). CAT's Winter II and McCafferty patents
have both been granted in Europe (9 April 1994 and 13 November 1996
respectively). The granted US McCafferty continuation is entitled to a term
expiring on 19 October 2016. 
The Griffiths et al patent (US 5,885,793) was granted on 23 March 1999. It
refers to the isolation of human antibodies to human proteins by phage display
and to methods for producing human antibodies. 

Phagemids 
A phagemid is a plasmid containing a bacterial origin of replication and a
phage origin of replication. Use of a phagemid containing a geneIII-antibody
fusion, together with a helper phage, allows a mixture of wild-type pIII and
fusion pIII to be displayed on the surface of the phage particle. If phagemids
are not used, several antibody molecules are displayed on each phage
(multivalent display). Phagemids allow display of a single antibody molecule
per phage (monovalent display) enabling selection for higher affinity
antibodies by avoidance of avidity effects. The phagemid system is widely used
by antibody phage display companies.

Fab
A Fab fragment is a two chain fragment of an antibody molecule containing the
binding site for antigens, such as human proteins. It consists of two chains,
the light chain and the part of the heavy chain including the antigen binding
region. Fab fragments are widely used by phage display companies.

scFv
A scFv fragment is a single chain molecule containing the binding site of an
antibody molecule for antigens such as human proteins. It consists of part of
the light chain and part of the heavy chain including the antigen binding
region, linked together into a single molecule. ScFv molecules are widely used
by phage display companies.