Collaboration with Valentis

Oxford Biomedica PLC
13 December 2000

COLLABORATION WITH VALENTIS



For further information, please contact:       
Oxford BioMedica plc       
Professor Alan Kingsman, Chief Executive       Tel: [phone]
City/Financial Enquiries:
David Simonson/Melanie Toyne Sewell
Merlin Financial Communications                Tel: [phone]
Scientific/Trade Press Enquiries:
Sue Charles/Chris Gardner, HCC.De Facto Group  Tel:  [phone]
PolyMASC Pharmaceuticals plc
James Green, Commercial Director               Tel:  [phone] 

OXFORD BIOMEDICA ANNOUNCES COLLABORATION AGREEMENT WITH VALENTIS ON ITS CANCER
THERAPEUTIC, METXIA(R).

Oxford, UK and Burlingame, CA; 13 December, 2000 - Oxford BioMedica announced
today that it has signed a collaborative agreement with PolyMASC
Pharmaceuticals plc, a wholly-owned subsidiary of the major US gene therapy
company, Valentis Inc. (NASDAQ:VLTS) to jointly develop an enhanced version of
BioMedica's cancer therapeutic MetXia(R). MetXia(R) represents a platform
technology for increasing tumour cell death via the local activation of the
established anti-cancer prodrug, cyclophosphamide.

On 6 November 2000 Oxford BioMedica announced the first clinical trial results
from the MetXia(R) programme. A total of eight breast cancer and melanoma
patients were treated, by direct administration to the tumour, with three
doses of MetXia(R). Gene transfer was achieved in all patients and MetXia(R)
appeared to be safe and well tolerated throughout the dose range. 

The use of MetXia(R) can be expanded in a number ways, thereby broadening the
commercial potential of the product. One example of this is through the
collaboration announced today. PolyMASC and BioMedica will co-develop a
version of MetXia(R) that is designed to selectively target tumours following
systemic administration of the product. This is to be achieved by coating
MetXia(R) using PolyMASCs' proprietary viraMASC(TM) PEGylation technology. The
PEGylation process, which uses polyethylene glycol (PEG), leads to selective
accumulation of the gene therapy vector at tumour sites. PolyMASC is a world
leader in this technology.  Financial terms of the collaboration were not
disclosed.  

Commenting on the announcement, Chief Executive, Prof. Alan Kingsman said;
'We are delighted with the signing of this agreement with PolyMASC.  The
potential value of MetXia(R) is high, and this has been recognised by Valentis
in their commitment to our collaboration and their enthusiasm for putting
their PEG technology alongside our gene therapy systems. This is a very
exciting combination of technologies.'

Dr Gillian Francis, Managing Director of PolyMASC, said:
'The collaboration with Oxford BioMedica is an example of how PolyMASC's
viraMASC(TM) technology may open up new commercial opportunities through the
intravenous administration of viral vectors in cancer therapy. PolyMASC's
PEGylation technologies can be applied to a number of biopharmaceuticals
including replicating and non-replicating viruses, proteins and antibodies to
improve the safety and efficacy of these emerging products.  PolyMASC welcomes
this collaboration as an excellent opportunity to combine Oxford BioMedica's
vector technology with the benefits of our proprietary viraMASC(TM) delivery
system.'


Notes to Editors

1. Oxford BioMedica plc
Established in 1995, the Company specialises in the development and
application of gene-based therapeutics and immunotherapeutics for the
treatment of disease in the areas of Oncology, Viral Infection, and
Neurobiology and in Gene Discovery. Oxford BioMedica plc was floated on the
Alternative Investment Market of the London Stock Exchange in December 1996.
Currently Oxford BioMedica has corporate collaborations with Aventis,
AstraZeneca, IDM, Modex Therapeutics, Nycomed Amersham and Virbac. BioMedica's
first clinical product, MetXia(R) is in Phase I/II clinical trials for
late-stage breast cancer (BC1) and ovarian cancer (OC1). Recently it received
ethical approval form the UK Gene Therapy Advisory Committee for a Phase I/II
clinical trial of its cancer vaccine TroVax(TM) in colorectal cancer. The
TroVax(TM) clinical programme is expected to commence shortly.

2. MetXia(R) gene therapy for cancer
A common strategy for the treatment of cancer is to administer cytotoxic (or
cell killing) drugs in an attempt to destroy the tumour. Cyclophosphamide is
one of a group of drugs that is taken by the patient in the form of an
inactive prodrug. The prodrug travels through the body to the liver where
enzymes convert it to the active, cytotoxic form. This approach affects the
whole body and leads to the familiar adverse side effects of cancer
chemotherapy because the cytotoxic drug destroys normal cells on its way from
the liver to the tumour. In addition, because the activating enzymes are
present only in the liver, high doses of prodrug must be given to achieve
therapeutic levels of the cytotoxic drug at the tumour site. Often the
therapeutic effect is compromised by the toxicity.

Oxford BioMedica's MetXia(R) addresses these problems by delivering the gene
(CYP2B6) directly to the tumour. Once incorporated into the genetic material
of the tumour cells, this gene produces the liver enzyme that converts the
cyclophosphamide pro-drug to its active form within the tumour. The aim is to
achieve high concentrations of activated cyclophosphamide locally in the
tumour while minimising circulating levels of the drug. It is anticipated that
this will lead to substantially increased sensitivity of the tumour to the
drug and to an ability to reduce the dose of cyclophosphamide, thereby
reducing adverse side effects. 

In a variety of preclinical models, BioMedica has shown that delivery of the
human CYP2B6 gene to tumours, using MetXia(R), does indeed increase their
sensitivity to cyclophosphamide and leads to enhanced tumour cell killing. The
Company is now engaged in Phase I/II clinical trials in breast cancer (BC1)
and ovarian cancer (OC1). The results reported on 6 November 2000 confirm that
the gene transfer achieved in preclinical models also occurs in the cancer
patients in the BC1 trial. The implication for the efficacy of the product of
this level of gene transfer will be evaluated in further studies. 

MetXia(R) represents a platform technology which can be developed in a number
of ways; firstly as a product in its own right, secondly as a component of a
combination product that induces the immune system to destroy tumours and
finally, in selected formulations to achieve tumour targeting. The
collaborative agreement signed today with Valentis, is an example of the third
of these options.

3. Valentis, Inc.
Valentis, Inc. is a leader in the field of biopharmaceutical delivery.
Valentis develops proprietary technologies and applies its preclinical and
early clinical development expertise to create novel therapeutics. The
company's core technologies include multiple gene delivery and gene expression
systems and PEGylation technologies designed to improve the safety, efficacy
and dosing characteristics of genes, proteins, peptides, peptidomimetics,
antibodies and replicating and non-replicating viruses.

These technologies are covered by a broad patent portfolio that includes
issued U.S. and European claims. Valentis' commercial strategy is to enter
into corporate collaborations for full-scale clinical development and
marketing and sales of products. Together, Valentis and its wholly-owned
subsidiary PolyMASC Pharmaceuticals currently have corporate collaborations
with Roche Holdings, Eli Lilly, Glaxo Wellcome, Boehringer Ingelheim, Heska
Corporation, Transkaryotic Therapies, Onyx Pharmaceuticals and Bayer
International, and a manufacturing partnership (the pAlliance) with DSM
Biologics and Qiagen N.V.

Additional information about Valentis can be found at www.valentis.com

Statements in this press release that are not strictly historical are 'forward
looking' statements as defined in the Private Securities Litigation Reform Act
of 1995. The words 'believes,' 'expects,' 'intends,' 'anticipates,' variations
of such words, and similar expressions identify forward-looking statements,
but their absence does not mean that the statement is not forward-looking.
These statements are not guarantees of future performance and are subject to
certain risks, uncertainties and assumptions that are difficult to predict.
Factors that could affect the Company's actual results include the need for
additional capital, the early stage of product development, uncertainties
related to clinical trials, and uncertainties related to patent position.
There can be no assurance that Valentis will be able to develop commercially
viable gene-based therapeutics or PEGylated products, that any of its programs
will be partnered with a pharmaceutical partner, that necessary regulatory
approvals will be obtained, or that any clinical trial will be successful. The
actual results may differ from those projected in the forward-looking
statement due to risks and uncertainties that exist in the Company's
operations and business environment. These are described more fully in the
Valentis Annual Report on Form 10-K for the period ended June 30, 2000 as
filed with the Securities and Exchange Commission.

4. World Wide Web
This release is also available on the World Wide Web at
http://www.oxfordbiomedica.co.uk