Xenova Group PLC — Tariquidar Phase I Paediatric Study Data Presented at ASCO

Abstract on XR5944 Also Presented

SLOUGH, U.K., June, 7 2004 (PRIMEZONE) — Xenova Group plc (LSE:XEN)
(Nasdaq:XNVA) announced today that the Paediatric Oncology Branch of the
National Cancer Institute (NCI) in Bethesda, U.S., yesterday presented a
poster at the American Society of Clinical Oncology (ASCO) conference in
New Orleans, Louisiana on the paediatric Phase I clinical trial of tariquidar
in children with solid tumours.
The primary objectives of this trial were to assess the toxicity, optimal
dose and pharmacokinetics of tariquidar in children with solid tumours and
to assess the toxicity and pharmacokinetics of the anti cancer drugs in combination
with tariquidar. A total of 18 children have been enrolled into the study
to date, between the ages of 2 and 18 with a range of tumours including Ewing's
Sarcoma, osteosarcoma and adrenocortical carcinoma amongst others.
Tariquidar was administered intravenously over 30 minutes with a starting
dose of 1mg/kg in four patients and then escalated to 1.5mg/kg in six patients
and then to 2.0mg/kg in the eight remaining patients. This was followed by
administration of the anti-cancer drug which was chosen on the basis of tumour
type and prior therapy. Doxorubicin was administered to 11 patients at 50mg/m2,
docetaxel was administered to four patients at 75mg/m2 and vinorelbine was
administered to two patients at 20mg/m2 on days one and eight. Fligrastim
was administered to all patients during the 21 day cycle.
The results of the study showed that tariquidar was well tolerated in
children. Of the 18 subjects enrolled, one patient had a complete response,
one had a partial response and five had stable disease for one to eight cycles
of therapy. Doxorubicin clearance was comparable to previously published
results indicating the clearance of doxorubicin was not altered by pre-treatment
with tariquidar. The future development of tariquidar by Xenova is currently
under review.
Commenting on these results, David Oxlade, Chief Executive Officer of
Xenova, said, “It is encouraging to see these results in children with solid
tumours. The NCI is undertaking a number of exploratory clinical trials with
tariquidar in both adults and children and we look forward to further results
from these studies.”
In addition to this poster, Xenova and Millennium have an abstract published
relating to the on-going Phase I study of XR5944 at the same meeting.

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

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
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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.

CONTACT: Xenova Group plc
David A. Oxlade, Chief Executive Officer Daniel Abrams, Finance
Director Veronica Cefis Sellar, Head of Corporate Communications +44
(0)1753 706600 UK Financial Dynamics David Yates Ben Atwell +44 (0)20
7831 3113 US Trout Group/BMC Communications Media: Brad Miles
Investors: Lee Stern (212) 477-9007