RNS Number:8971M
Antisoma PLC
30 June 2003

Antisoma starts new trial of R1550 (formerly Therex) in breast cancer



London, UK: 30 June 2003 Antisoma, the UK-based biopharmaceutical company, today
announces that it is starting patient recruitment into a phase I trial of its
drug R1550 (formerly Therex), a novel cancer therapy that it is co-developing
with pharmaceutical company Roche. The trial is enrolling patients with locally
advanced or metastatic (spreading) breast cancer, with recruitment taking place
initially at the UCLA's Jonsson Comprehensive Cancer Center USA.  An earlier
phase I study, conducted in the UK by the Imperial Cancer Research Fund, showed
that R1550 was well tolerated in breast cancer patients.



Antisoma licensed the worldwide marketing rights for the product to Roche as
part of the alliance agreement signed by the two companies in November 2002.
Since that agreement Roche has been funding the development of R1550 in full.
Antisoma will conduct the current phase I study in breast cancer, but Roche
plans to conduct future studies, which are expected to evaluate the potential of
the drug in a variety of cancer indications.



R1550 is an antibody  (humanised HMFG1) that targets and binds to a protein
called MUC1. This protein is exposed only on the surface of cancer cells, so the
antibody binds specifically to tumours. Evidence suggests that the antibody then
recruits components of the immune system called 'natural killer cells' to attack
the cancer cells. R1550 has broad potential because the MUC1 protein that it
targets is made by many different types of cancer.



Dr Miroslav Ravic, Chief Clinical Officer of Antisoma, said: 'Breast cancer
accounts for 30% of all cancers that affect women, and there is a profound need
for improved treatment. Our new trial of R1550 will define the doses to be used
in phase II trials in breast and other cancers'.



Enquiries:


Antisoma plc
Glyn Edwards, Chief Executive Officer                Tel: +44 (0)20 8799 8200

Financial Dynamics

Jonathan Birt                                        Tel: +44 (0)7884 238952





Notes to Editors



HMFG1 and R1550

HMFG1 is a mouse monoclonal antibody that forms the basis for a number of
Antisoma's drugs in development. R1550 (huHMFG1) is a humanised form of the
antibody suitable for repeat administration into the systemic circulation.  The
drug is a naked antibody thought to attack cancer cells by recruiting the
patient's immune system, particularly natural killer cells. This is the process
of antibody-dependent cell-mediated cytotoxicity (ADCC), which has been
demonstrated during in-vitro experiments with the R1550 antibody.



A growing body of evidence links the MUC1 protein targeted by HMFG1 antibodies
with cancer progression and metastasis. In particular, MUC1 has been implicated
in changes in intracellular signalling and altered interactions with
extracellular matrix components such as ICAM-1. These findings reinforce the
relevance of MUC1 as a target for anti-cancer treatments and open up the
possibility that, in addition to mediating ADCC, naked anti-MUC1 antibodies such
as R1550 could exert effects on cancer cells by altering the interactions of
MUC1 with other proteins.




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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