Agreement with Sigma-Aldrich

Oxford Biomedica PLC
20 October 2005



FOR IMMEDIATE RELEASE                                           20 OCTOBER 2005


        OXFORD BIOMEDICA AND SIGMA-ALDRICH ENTER STRATEGIC ALLIANCE FOR 
                 COMMERCIALISATION OF LENTIVECTOR(R) TECHNOLOGY

Oxford, UK and St Louis, Missouri, USA: 20 October 2005 - Oxford BioMedica (LSE:
OXB), the leading gene therapy company, and Sigma-Aldrich (NASDAQ: SIAL), a
leading life science and high technology company, today announced an agreement
for Sigma-Aldrich to commercialise Oxford BioMedica's LentiVector technology for
the reagent and research tool market. The announcement was made at the Cambridge
Healthtech Institute's Third Annual 'Discovery on Target' conference, being held
in Boston from 18 - 21 October, where both Companies are sponsoring sessions and
presenting data.

This strategic alliance identifies Sigma-Aldrich as Oxford BioMedica's exclusive
global partner in the development and marketing of research products based on
the LentiVector technology. Sigma-Aldrich plans to develop a range of high value
LentiVector research products for its extensive customer base in the
pharmaceutical, biotechnology and academic sectors.

Under the agreement, which gives Sigma-Aldrich the exclusive right to sublicense
the technology for research purposes, Oxford BioMedica will receive an upfront
payment, annual minimum payments and royalties on sales. In addition
Sigma-Aldrich has first rights to negotiate for a license to develop a new range
of products based on Oxford BioMedica's EIAV-based LentiVector technology.
Furthermore, Sigma-Aldrich has committed to an equity investment of $5 million
in Oxford BioMedica, to be completed before 31 January, 2006. Other financial
terms were not disclosed.

Oxford BioMedica's lentivirus-based gene delivery technology, known as
LentiVector, is one of the most powerful technologies for the delivery of genes
to a wide range of cell and tissue types. The LentiVector technology has
applications both in therapeutic products and as a drug discovery tool for
target validation and the creation of targeted disease models. Oxford BioMedica
has a comprehensive portfolio of US and European patents that cover the
technology. Existing licensees and partners for the LentiVector technology
include Biogen Idec, Merck & Co, Pfizer and Viragen.

Commenting on today's announcement, Peter Nolan, Senior Vice President of Oxford
BioMedica said:  'We are delighted to work with Sigma-Aldrich as our chosen
partner for commercialisation of the LentiVector technology in the research
reagent market. Through its broad scientific customer base and membership of the
internationally renowned RNAi Consortium, Sigma is a clear leader in this area.
This partnership will allow Oxford BioMedica to derive maximum benefit from
research applications of the technology, while keeping the primary business
development focus on the commercialisation of our therapeutic product pipeline'.

Shaf Yousaf, President of the Sigma-Aldrich Research Biotechnology business unit
stated:

'Over the course of the last 12 months Sigma has made a number of strategic
moves, including formation of a research collaboration with The RNAi Consortium
(TRC), acquisition of Proligo, and the licensing of key intellectual property
from MIT and Alnylam, designed to enable us to become a dominant player in the
area of RNA Interference. The addition of the Oxford BioMedica patents to the
Sigma RNAi intellectual property portfolio further solidifies our position in
this important field of research. Additionally, the equity stake in Oxford
BioMedica ensures our ability to capitalise on their extensive knowledge in this
area and clears the way for a collaborative effort that we expect to result in
even more innovative tools for the biopharmaceutical industry.'


                                     -Ends-


For further information, please contact:
Oxford BioMedica plc:

Professor Alan Kingsman, Chief Executive               Tel: [phone]

Peter Nolan, SVP Commercial Development
Sigma-Aldrich:

Christina Shasserre                                        Tel: [phone]

Joan Suda                                                  Tel: [phone]
City/Financial Enquiries:

Lisa Baderoon/ Mark Court/ Mary-Jane Johnson Buchanan  Tel: [phone]
Communications
Scientific/Trade Press Enquiries:

Sue Charles/ Katja Stout/ Ashley Lilly                 Tel: [phone]

Northbank Communications



Notes to editors:


1. Oxford BioMedica

Oxford BioMedica (LSE: OXB) is a biopharmaceutical company specialising in the
development of novel gene-based therapeutics with a focus on the areas of
oncology and neurotherapy. The Company was established in 1995 as a spin out
from Oxford University, and is listed on the London Stock Exchange.

Oxford BioMedica has core expertise in gene delivery, as well as in-house
clinical, regulatory and manufacturing know-how. In oncology, the pipeline
includes an immunotherapy and a gene therapy in multiple Phase II trials, and a
preclinical targeted antibody therapy in collaboration with Wyeth. In
neurotherapy, the Company's lead product is a gene therapy for Parkinson's
disease, which is expected to enter clinical trials in 2006, and four further
preclinical candidates. The Company is underpinned by over 80 patent families,
which represent one of the broadest patent estates in the field.

The Company has a staff of approximately 70 split between its main facilities in
Oxford and its wholly owned subsidiary, BioMedica Inc, in San Diego, California.
Oxford BioMedica has corporate collaborations with Wyeth, Intervet, Viragen,
MolMed and Kiadis; and has licensed technology to a number of companies
including Merck & Co, Biogen Idec and Pfizer.

Further information is available at www.oxfordbiomedica.co.uk


2. LentiVector technology

Oxford BioMedica's LentiVector gene delivery technology, based on lentiviruses,
is arguably the most potent system currently available for treating a range of
diseases, particularly those of the central nervous system. Oxford BioMedica has
shown that its lentiviral vectors are able to deliver genes with high efficiency
to a variety of both dividing and non-dividing cells, including neurons in the
brain.

Oxford BioMedica has three issued US patents and a European patent for its
LentiVector technology. These include broad composition of matter claims and
methods of production claims for lentiviral vector gene delivery systems of both
human and non-human origin. The patents also cover derivatives of lentiviral
vector systems that, unlike many versions of lentiviral vectors, have real
clinical utility because of their safety.

The Company has established a neurotherapy pipeline of product candidates based
on its LentiVector technology, which includes ProSavin(R) for Parkinson's
disease, RetinoStat(R) for retinopathy, MoNudin(R) for motor neuron disease,
SMN1-G for spinal muscular atrophy and Innurex(R) for nerve repair.


3. Sigma-Aldrich

Sigma-Aldrich is a leading Life Science and High Technology company. The
Company's biochemical and organic chemical products and kits are used in
scientific and genomic research, biotechnology, pharmaceutical development, the
diagnosis of disease and as key components in pharmaceutical and other high
technology manufacturing. It has customers in life science companies, university
and government institutions, hospitals, and in industry. Over one million
scientists and technologists use its products. Sigma-Aldrich operates in 35
countries and has over 6,800 employees providing excellent service worldwide.
The Company is committed to the Accelerating the success of its Customers
through leadership in Life Science, High Technology and Service.

For more information about Sigma-Aldrich, please visit its award- winning
website at www.sigma-aldrich.com

This release contains forward-looking statements relating to future performance,
goals, strategic actions and initiatives, and similar intentions and beliefs and
other statements regarding the Company's expectations, goals, beliefs,
intentions and the like, which involve assumptions regarding Company operations
and conditions in the markets the Company serves. The Company does not undertake
any obligation to update these forward-looking statements.


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