Presentation of AS1403 data

RNS Number:9502O
Antisoma PLC
22 August 2003


Results presented from AS1403 phase I biodistribution study


22 August 2003, London, UK plc (LSE:ASM, NASD-E:ASOM): Antisoma announces that
results from its phase I biodistribution study of AS1403 (formerly TheraFab)
will be presented this weekend to the European Association of Nuclear Medicine
meeting in Amsterdam by Dr Michael Garkavij, a leading investigator in the
trial.

AS1403 is a fragment of the monoclonal antibody HMFG1 linked to a radioactive
isotope with cell-killing ability. The biodistribution study examined the
ability of AS1403 to deliver a targeted dose of radiation to tumours in patients
with non-small cell lung cancer. For this study, the therapeutic isotope in
AS1403 was replaced by an imaging isotope, allowing the investigators to
evaluate the distribution of radioactivity in the body. Imaging showed that
radioactivity accumulated in tumours after administration of AS1403. This
confirms the targeting ability of the antibody fragment, in line with earlier
studies using HMFG1 antibody fragments. However, dosimetry findings suggested
that quantities of radioactivity delivered to other tissues such as the kidneys
could be such that they would produce unacceptable levels of toxicity if a
therapeutic isotope were used. Significant targeting of the kidneys is a
well-documented property of antibody fragments that is not shared by whole
antibodies. Work to overcome this issue would require significant investment,
and Antisoma has therefore decided not to continue the development of AS1403 at
this time.

Glyn Edwards, CEO of Antisoma, said, 'We have many promising drug candidates in
our pipeline and can therefore move quickly to discontinue programmes when trial
results show that resources would be more usefully allocated elsewhere.'



Notes to editors

AS1403

AS1403 is a F(ab')2 fragment of the mouse monoclonal antibody HMFG1 linked to
the radioactive isotope yttrium-90. In the phase I biodistribution study, the
yttrium was replaced with the imaging isotope, indium-111. Previous
biodistribution studies on radiolabelled HMFG1 antibodies include Kalofonos et
al. (HMFG1 F(ab')2 fragment; 1988, Cancer Research 48: 1977-1984), Kalofonos et
al. (HMFG1 and  HMFG1 F(ab')2 fragment; 1989, Br J Cancer 59: 939-942) and
Al-Yasi et al. (humanised HMFG1; 2002, Br J Cancer 18: 870-878).



Enquiries:

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

Financial Dynamics
Jonathan Birt                                    Tel: [phone]



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