Research Update

RNS Number:5470K
Antisoma PLC
30 April 2003


Positive data from NIH highlight broad potential in Antisoma's targeted
apoptosis programme

London, UK: 30 April 2003 Data showing powerful anti-tumour effects for
Antisoma's drug AS1406 (formerly Theranase) in both breast cancer and lymphoma
are presented today at the Recombinant Antibodies meeting in Munich, Germany.
These are the first animal data from Antisoma's 'targeted apoptosis' programme,
which combines antibodies that specifically target tumour cells with enzymes
that trigger apoptosis or 'programmed cell death'.

AS1406 significantly slowed the growth of primary breast tumours in a mouse
model. It also inhibited the spread of breast cancer to other organs: 66% fewer
secondary tumours were formed in the lungs with AS1406 than with a control. In
another model, where breast cancer cells were administered into the circulation,
AS1406 was associated with an 85% reduction in the number of lung tumours.
AS1406 also significantly prolonged survival in a mouse model of lymphoma, a
form of blood cancer. The studies were carried out by Professor Susanna Rybak at
the United States National Cancer Institute under a Collaborative Research and
Development Agreement between Antisoma and the US National Institutes of Health.

AS1406 is the antibody humanised HMFG1 linked to the enzyme RNase. HMFG1 is an
antibody that targets and binds to a protein found on the surface of cells in
many solid tumours and also on lymphomas. Previous experiments have shown that
when the antibody binds to this target protein, it releases the RNase enzyme
into the cancer cell, prompting the cell to 'commit suicide' by apoptosis.
Healthy cells do not show the protein targeted by HMFG1 on their surfaces; they
are therefore not exposed to the apoptosis enzyme and remain unharmed.

Professor Susanna Rybak, the lead researcher on the RNase programme, said:
"Tests have shown that AS1406 reproducibly reduces tumour burden in numerous
different cancer models spanning diverse forms of the disease, providing us with
a compelling case to move forwards into human clinical trials."

Glyn Edwards, Chief Executive Officer of Antisoma, added:
"We see targeted apoptosis as a potential magic bullet for cancer, whereby we
could hit cancer cells with a lethal drug whilst leaving healthy tissues
unscathed. The positive data presented in Munich validate the whole concept of
targeted apoptosis as a new approach to cancer therapy, one in which Antisoma
has a leading position."


Enquiries:

Antisoma plc
Glyn Edwards, Chief Executive Officer           Tel: [phone]

Financial Dynamics
Jonathan Birt                                   Tel: [phone]


Notes to Editors

RNase and targeted apoptosis
AS1406 is the antibody humanised HMFG1 linked to the enzyme recombinant
cytotoxic RNase. Antisoma has exclusive worldwide rights to use of this enzyme
in combination with monoclonal antibodies that target MUC1 and mCEA (membrane
bound carcino-embryonic antigen) - protein targets found on certain cancer
cells. These rights were acquired through an in-licensing agreement with the US
National Institutes of Health (NIH) announced in September 2001. Rights have
recently been extended to cover use in lymphoma and myeloma as well as solid
tumours. The technology is covered by three granted and two pending US patents
and their non-US equivalents.

Antisoma has been funding research into the combined use of antibodies and RNase
by Prof Rybak at the Frederick Cancer Research and Development Center, National
Cancer Institute, in Maryland, USA, since 1999. The combination showed potential
to kill isolated tumour cells, leading to Antisoma's decision to acquire the
relevant intellectual property rights.

About Antisoma
Based in London, UK, Antisoma is a biopharmaceutical company that develops novel
products for the treatment of cancer. The Company fills its development pipeline
by acquiring promising new product candidates from internationally recognised
academic or cancer research institutions. Its core activity is the pre-clinical
and clinical development of these drug candidates. Antisoma forms partnerships
with pharmaceutical companies to bring its products to market. In November 2002,
Antisoma signed a ground-breaking collaboration agreement with Roche to develop
and commercialise products from Antisoma's pipeline. Visit www.antisoma.com for
further information about Antisoma.


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