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Xenova Group PLC (XEN)

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Wednesday 14 July, 2004

Xenova Group PLC

results second clinical trial

Xenova Group PLC
14 July 2004

                                  News Release

                                Xenova Group plc

                 Successful Results from Second Clinical Trial

                        of Anti-Smoking Vaccine, TA-NIC



Slough, UK, 14 July 2004 - Xenova Group plc (London Stock Exchange: XEN; NASDAQ:
XNVA) announced today initial results from the second clinical trial of TA-NIC,
the Company's therapeutic vaccine being developed for the treatment of nicotine
addiction.



60 smokers, divided into three cohorts of 20 subjects, have been recruited into
this double-blind, randomised, placebo-controlled study.  The objectives of this
second Phase I clinical study were to explore the safety, tolerability and level
of anti-nicotine antibody response to increasing doses of the vaccine TA-NIC,
and to select a dose for Phase II/III evaluation.



Key findings from the study were:



•         No drug-related serious adverse events were seen in any cohort

•         Minimal injection-site effects were seen at the dose selected for
          Phase II/III studies

•         Anti-nicotine antibody responses were dose dependent

•         The selected dose showed an improved anti-nicotine antibody response
          profile compared to the lowest dose tested:

     o        Approximately twice the level of anti-nicotine antibodies were 
              observed

     o        Faster and more rapid onset of anti-nicotine antibody response was
              achieved

•         Although not designed to test the effect of the TA-NIC vaccine on
          smoker's quit rates, there was a clear reduction across all groups 
          receiving TA-NIC compared to those with the placebo group, in terms of 
          those smokers who voluntarily quit during the 12-week period or self-
          reported a reduction in smoking pleasure

     o        At week six, 19 out of the 44 (43%) subjects receiving TA-NIC
              voluntarily gave up smoking or reported reduced pleasure when 
              smoking compared to only 1 out of 11 (9%) receiving the placebo

On the basis of these results, a Phase II/III dose has been selected for further
clinical evaluation.  The final data from this Phase I study is expected at the
end of this year (2004) with Phase II trials commencing shortly thereafter.



David Oxlade, Chief Executive Officer of Xenova said, 'We are most encouraged by
these results.  The next stage of trials will test TA-NIC's ability to help
smokers break the habit and thereby reduce the serious consequences to health
caused by smoking.'



Contacts:


Xenova Group plc                                        +44 (0)1753 706600
David A. Oxlade, Chief Executive Officer
Daniel Abrams, Finance Director
Veronica Cefis Sellar, Head of Corporate Communications

UK - Financial Dynamics                                 +44 (0)20 7831 3113
David Yates
Ben Atwell

US - Trout Group/BMC Communications                     +1 212 477 9007
Media: Brad Miles
Investors: Lee Stern



Xenova Group plc is a UK-based biopharmaceutical company focused on the
development of novel drugs to treat cancer and addiction with a secondary focus
in immunotherapy.  The Company has a broad pipeline of products in clinical
development, including three cancer programmes:  its lead product TransMID(TM),
for the treatment of high-grade glioma, is in Phase III trials, and its novel
DNA targeting agents and XR303 are both in Phase I for cancer indications.
Xenova is also developing two therapeutic vaccines for cocaine and nicotine
addiction, which are in Phase II and Phase I trials respectively.  Quoted on the
London Stock Exchange (XEN) and on NASDAQ (XNVA), Xenova employs approximately
112 people throughout its sites in the UK and North America. (Reuters XEN.L;
Bloomberg XEN LN)

For further information about Xenova and its products please visit the Xenova
website at www.xenova.co.uk.



Notes to Editors



Clinical Data

The first Phase I placebo controlled clinical trial was completed in 60 smokers
and non-smokers in June 2002.  The vaccine was well tolerated locally and
systemically up to a course of 5 vaccinations of 50 mcg over 8-20 weeks and a
booster vaccine given at 9 months after the initial injection.
Nicotine-specific antibodies capable of binding free nicotine were generated,
unaffected by smoking status, during the initial primary vaccination course.
These antibody levels declined over 3-6 months, but a further significant
increase in antibody levels was seen rapidly after the single booster injection.



Smoking Statistics

The World Health Organisation (WHO) notes that the tobacco epidemic is still
expanding, especially in developing countries where currently 84% of smokers
live.  Tobacco use kills 4.9 million people each year and this toll is expected
to double in the next 20 years.  At current rates, the total number of tobacco
users is expected to rise to 1.7 billion by 2025 from 1.3 billion now (May
2004).



Smoking cessation in the UK

Long term (and short term) success rates in terms of smokers reducing or
stopping smoking remain low, with only approximately 5% of smokers being able to
stop smoking after receiving advice from their doctor; a maximum of
approximately 18% succeed when intensive support from specialists as well as
nicotine replacement therapy are provided in addition.



Of the 1.3 billion smokers globally, it is estimated that some 4 million smokers
each year in the UK attempt to quit, but that only 3-6% (or 1-2% of all smokers)
are successful in giving up tobacco.  Conventional treatment of nicotine
addiction concentrates on psychosocial interventions (counselling, smoking
cessation clinics) together with pharmacotherapy, including nicotine replacement
therapy (NRT) and bupropion (Zyban(R), GlaxoSmithKline).  Even with effective
behavioural and pharmacological therapies, many individuals dependant on
nicotine fail in their attempts to remain abstinent, with smoking cessation
rates of only approximately 10-20% at 1 year.  Long term cessation rates are
even lower with 40% of ex-smokers relapsing after 12 months abstinence.



Inhaled nicotine is highly addictive.  Absorption of nicotine from cigarette
smoke through the lung is rapid, producing with each inhalation a high
concentration arterial bolus of nicotine that reaches the brain within 10-16
seconds, faster than by intravenous injection.  Nicotine is able to cross the
blood brain barrier where it binds to acetyl-choline receptors, triggering the
release of neurotransmitters, such as dopamine and serotonin.  These give rise
to positive feelings (pleasure, relaxation, lack of anxiety, suppressed
appetite, improved concentration) which are reinforced with each cigarette.
Nicotine has a distribution half life of 15-20 minutes and a terminal half life
in the blood of two hours. Smokers therefore experience a pattern of repetitive
and transient high blood nicotine concentrations from each cigarette, with
regular hourly cigarettes needed to maintain raised concentrations, and
overnight blood levels dropping near to those of non-smokers.  Smoking cessation
is difficult to achieve due to the addictive properties of nicotine and the
unpleasant withdrawal symptoms (irritability, lack of concentration, weight
gain, nicotine craving).



TA-NIC mode of action

TA-NIC is a therapeutic vaccine in development for the treatment of nicotine
addiction.  Nicotine is a small molecule which, by itself, does not trigger an
immune response.  However, when nicotine is carried by an immunogenic protein it
can prime the immune system to produce anti-nicotine antibodies.  The active
ingredient of TA-NIC vaccine is a protein conjugate: nicotine butyric acid (NBA)
covalently linked to recombinant cholera toxin B (rCTB).  rCTB was chosen as the
carrier protein because it is known to be highly immunogenic and has been used
for many years as a component of cholera vaccine.  rCTB has been approved by the
Swedish Medical Products Agency for use in an oral cholera vaccine that is
marketed in Sweden and Norway and in 2003 was approved by the CPMP.



Nicotine is bound by the induced circulating anti-nicotine antibodies in the
bloodstream and the resulting antigen-antibody complex is too large to cross the
blood-brain barrier, so the pleasurable stimulus which usually accompanies
smoking will be absent or reduced. Without this reward, the motivation to smoke
again is reduced, preventing the reinforcement which is required to maintain the
nicotine addiction.



References:

NICE Guidance on the use of nicotine replacement therapy (NRT) and bupropion for
smoking cessation. March 2002



For Xenova: Disclaimer to take advantage of the 'Safe Harbor' provisions of the
US Private Securities Litigation Reform Act of 1995. This press release contains
'forward-looking statements,' including statements about development and
commercialization of products. Various risks may cause Xenova's actual results
to differ materially from those expressed or implied by the forward looking
statements, including: unexpected costs and delays, adverse results in our drug
discovery and clinical development programs; failure to obtain patent protection
for our discoveries; commercial limitations imposed by patents owned or
controlled by third parties; our dependence upon strategic alliance partners to
develop and commercialize products and services; difficulties or delays in
obtaining regulatory approvals to market products and services resulting from
our development efforts; the requirement for substantial funding to conduct
research and development and to expand commercialization activities; and product
initiatives by competitors.  For a further list and description of the risks and
uncertainties we face, see the reports we have filed with the Securities and
Exchange Commission.  We disclaim any intention or obligation to update or
revise any forward-looking statements, whether as a result of new information,
future events or otherwise.










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