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Antisoma plc (SRC)

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Monday 02 June, 2008

Antisoma plc

Positive data on Antisoma's ASA404 presented at...





London, UK, and Chicago, IL, 1 June 2008 - Antisoma (LSE:ASM;
USOTC:ATSMY) announces that two presentations supporting ASA404 are
being made at this year's American Society of Clinical Oncology
(ASCO) meeting in Chicago. ASA404 is a Tumour-Vascular Disrupting
Agent for which worldwide rights were licensed to Novartis in April
2007.

Broad potential in lung cancer
A poster presentation to be given today shows that patients with both
squamous and non-squamous types of non-small cell lung cancer
experienced a survival benefit in phase II trials with ASA404.
Addition of ASA404 to chemotherapy was generally well tolerated in
both groups, with no evidence for bleeding related side-effects that
have been seen with some other drugs in squamous patients. Around 30%
of patients with non-small cell lung cancer have squamous disease.

The ASCO presentation is a retrospective analysis of data from phase
II trials in which ASA404 was added to carboplatin and paclitaxel
chemotherapy. Patients who received two different doses of ASA404
with their chemotherapy were pooled and compared with patients who
received chemotherapy alone. Median survival data showed an extension
of 4.7 months in squamous patients (10.2 vs 5.5 months) and of 3.9
months in non-squamous patients (14.9 vs 11.0 months). Response rates
and time to tumour progression were also superior in both groups with
ASA404.

The data will be presented by Dr Mark McKeage of the Auckland Cancer
Centre, New Zealand, a leading investigator in phase II trials of
ASA404 who is now participating in Novartis' ATTRACT-1 phase III
trial of ASA404 in non-small cell lung cancer. Dr McKeage said "These
data suggest that ASA404 could provide benefits for a wide range of
lung cancer patients and support the broad inclusion criteria of the
phase III ATTRACT-1 study."

The ATTRACT-1 phase III trial started in April 2008 and includes both
squamous and non-squamous patients. Patients are being randomised to
receive carboplatin and paclitaxel plus either ASA404 or a placebo.
The primary endpoint in the trial is overall survival, and key
secondary endpoints are overall survival in the squamous and
non-squamous subgroups. If the ATTRACT-1 trial yields positive
results, it is expected that filings for marketing authorisations
will take place in 2011.

Glyn Edwards, CEO of Antisoma, added: "The phase II trial data in
lung cancer have provided remarkably consistent support for ASA404
across different measures of efficacy, with different doses, and now
in patients with different types of the disease."

The poster presentation will be available from 8pm today UK time (2pm
Chicago time) on Antisoma's website (www.antisoma.com).

Supportive interim data in prostate cancer
An oral presentation on ASA404 will be given tomorrow in the Clinical
Science Symposium 'Novel anti-angiogenic mechanisms' by Prof Roberto
Pili of Johns Hopkins University. This presentation will include
details of interim findings from the phase II trial of ASA404 in
prostate cancer, which were announced in headline form in October, as
well as a new analysis of ASA404's effects on the prostate cancer
biomarker PSA.

In the prostate cancer trial, patients were randomised to receive
either 1200 mg/m2 ASA404 plus docetaxel or docetaxel alone. Several
different measures now suggest better results with the
ASA404-docetaxel combination than with docetaxel alone:

  * PSA response rates were 59% with ASA404 plus docetaxel and 37%
    with docetaxel alone. A new analysis considers the proportion of
    patients showing a 30% decline in PSA levels in the 3 months
    after the start of treatment. This was the PSA measure most
    predictive of survival in a major prostate cancer study.
    Proportions of patients with such a PSA decline were 63% with
    ASA404 plus docetaxel and 47% with docetaxel alone

  * Tumour response rates in patients assessable by RECIST were 23%
    in patients who received ASA404 plus docetaxel versus 9% in
    patients who received docetaxel alone

  * Time to disease progression was 7.3 months in patients who
    received ASA404 plus docetaxel and 6.9 months in patients who
    received docetaxel alone, according to investigators' assessment;
    an independent assessment showed a similar pattern (8.7 vs 8.4
    months)

  * Safety findings from the trial showed that addition of ASA404 to
    chemotherapy was generally well tolerated.

Overall, interim findings from the trial are encouraging. A decision
on next steps in prostate cancer will be made once median survival
data are available. These are expected during the second half of this
year.

Prof Pili's presentation will be available from 5.30pm UK time
tomorrow (11.30am Chicago time) on Antisoma's website at
www.antisoma.com.


Enquiries:
Glyn Edwards, CEO
Daniel Elger, Director of Communications              +44 (0)7909 915
Antisoma plc                                          068

Mark Court/Lisa Baderoon/Rebecca Skye                 +44 (0)20 7466
Dietrich                                              5000
Buchanan Communications

Brian Korb                                            +1 646 378 2923
The Trout Group


Certain matters discussed in this statement are forward looking
statements that are subject to a number of risks and uncertainties
that could cause actual results to differ materially from results,
performance or achievements expressed or implied by such statements.
These risks and uncertainties may be associated with product
discovery and development or licensing activities, including
statements regarding the clinical development programmes, the
expected timing of clinical trials and regulatory filings,
out-licensing opportunities, and funding requirements. Such
statements are based on management's current expectations, but actual
results may differ materially.

Notes for Editors:

PSA and PSA responses
PSA is a protein, prostate-specific antigen. Levels of PSA in the
blood are used in the diagnosis of prostate cancer and the tracking
of responses to its treatment. PSA is one of the most widely
recognised disease markers in oncology. In the ASA404 phase II trial,
PSA response was defined as a 50% or greater reduction in PSA level
from baseline. This is in accordance with the Bubley criteria
(Eligibility and response guidelines for phase II clinical trials in
androgen-independent prostate cancer: recommendations from the
Prostate-Specific Antigen Working Group. Journal of Clinical Oncology
1999, 17:3461-3467).

Data supporting the importance of a 30% decline in PSA within three
months of the start of treatment are reported in 'Prostate-Specific
Antigen and Pain Surrogacy Analysis in Metastatic Hormone-Refractory
Prostate Cancer'; Andrew J. Armstrong, Elizabeth Garrett-Mayer,
Yi-Chun Ou Yang, Michael A. Carducci, Ian Tannock, Ronald de Wit, and
Mario Eisenberger; Journal of Clinical Oncology 2007, 25:3965-3970.

RECIST
Tumour responses (reflecting the growth or shrinkage or tumours after
treatment) are often assessed according to RECIST (Response
Evaluation Criteria In Solid Tumours). In prostate cancer, modified
RECIST criteria are used because of the need to assess bone
metastases, which cannot be assessed using the standard criteria.

Time to tumour/time to disease progression
Time to tumour progression is the time from the start of treatment
(of a solid tumour) until disease progression is shown according to
RECIST. As with the evaluation of response, this assessment is
modified in prostate cancer. In the phase II ASA404 prostate cancer
trial, investigators' assessment of time to disease progression
included RECIST data, PSA data and clinical observations. Independent
assessment of time to disease progression used RECIST and PSA data.

Background on ASA404
ASA404 (DMXAA) is a small-molecule Tumour-Vascular Disrupting
Agent (Tumour-VDA) which targets the blood vessels that nourish
tumours. The drug was discovered by Professors Bruce Baguley and
William Denny and their teams at the Auckland Cancer Society Research
Centre, University of Auckland, New Zealand. It was in-licensed by
Antisoma from Cancer Research Ventures Limited (now Cancer Research
Technology), the development and commercialisation company of the
Cancer Research Campaign (now Cancer Research UK), in August 2001.
Antisoma has conducted a number of phase II trials, including a
randomised trial in non-small cell lung cancer. In this trial,
patients who received ASA404 in addition to chemotherapy had a median
survival of 14.0 months while patients who received chemotherapy
alone had a median survival of 8.8 months. Additional details of
phase II findings are available on Antisoma's website at
www.antisoma.com. Worldwide rights to ASA404 were licensed to
Novartis AG in April 2007. A phase III trial (ATTRACT-1) is
evaluating ASA404 in combination with carboplatin and paclitaxel in
the first-line treatment of non-small cell lung cancer.

Background on Antisoma
Headquartered in London, UK, Antisoma is a biopharmaceutical company
that develops novel products for the treatment of cancer. Antisoma
fills its development pipeline by acquiring promising new product
candidates from internationally recognised academic or cancer
research institutions. Its core activity is the preclinical and
clinical development of these drug candidates. Please visit
www.antisoma.com for further information about Antisoma.

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