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Antisoma plc (SRC)

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Sunday 06 June, 2010

Antisoma plc

Antisoma announces presentation at ASCO of new ...






London, UK, Cambridge, MA, and Chicago, IL: 5 June 2010 - Antisoma plc (LSE:
ASM; USOTC: ATSMY) announces the presentation of new data supporting AS1413 and
AS1411 at the American Society of Clinical Oncology (ASCO) Annual Meeting being
held in Chicago from June 4-8.

Glyn Edwards, CEO of Antisoma, said: "We're delighted to share a wealth of new
data on AS1413 and AS1411 at the ASCO meeting. Both drugs are approaching
important milestones, with phase III data on AS1413 and phase IIb data on AS1411
due in the next 12 months. The latest findings provide further evidence of the
unique potential of these novel approaches to cancer therapy."

Highlights of data presented:

·         Meta-analysis of published acute myeloid leukemia (AML) trials shows
significant link between failure to respond to standard therapy and presence of
the multi-drug resistance mechanism P-glycoprotein, underlining the opportunity
for AS1413, which bypasses multi-drug resistance

·         Analysis of phase II data shows comparable activity with AS1413 plus
cytarabine in the two subgroups of secondary AML patients being studied in the
ongoing AS1413 phase III trial (patients with prior myelodysplastic syndrome
(MDS) and patients previously treated for other cancers)

·         Follow up of AS1411 phase II trial in relapsed/refractory AML shows
durable remissions among patients who responded to AS1411 plus cytarabine,
supporting ongoing development of AS1411 in AML

·         Phase II trial of AS1411 in renal cancer provides further evidence of
anti-cancer activity, suggesting that AS1411 could have application in a variety
of cancer settings

P-glycoprotein (Pgp) is a cell-membrane pump that removes chemotherapy drugs
from cells. It is a key contributor to multi-drug resistance (MDR) and is common
in cancer cells of patients with AML. Today's Leukemia poster session includes a
meta-analysis evaluating the impact of Pgp on remission rates in AML. Presented
by Professor J.-P. Marie of the Hôpital Dieu, Paris, France, it includes 74
published studies with over 4,500 evaluable patients, all of whom were treated
with currently available therapies for AML.

The meta-analysis shows that the presence of Pgp significantly reduces the
likelihood of achieving complete remission with currently available therapies
(overall remission rates were 74% in patients with Pgp-negative disease and 46%
in patients with Pgp-positive disease). This highlights the need for new
treatments unaffected by Pgp. Antisoma's AS1413 (amonafide L-malate) is known to
evade Pgp and other MDR mechanisms. It is therefore being developed as a
potential alternative to anthracyclines and related AML treatments that are
susceptible to MDR. A 450-patient randomised phase III trial, ACCEDE, is
comparing AS1413 with the anthracycline daunorubicin in patients with secondary
AML, where MDR is particularly common and outcomes with current therapies are
poor.

Prof Marie said: "This meta-analysis underlines the importance of multi-drug
resistance as a factor compromising the results of current treatments for AML
and highlights the need for new treatments that can bypass multi-drug resistance
mechanisms."

The Leukemia poster session also includes a new evaluation of data from
Antisoma's phase II trial of AS1413 in secondary AML. Performed by Dr Mikkael
Sekeres, Director of the Leukemia Program at the Cleveland Clinic, and
colleagues, this compares outcomes in the two groups of patients that together
comprise secondary AML: those with prior MDS and those with a history of
treatment with radiotherapy or chemotherapy for other cancers. Response rates
and longer term outcomes in the two patient types were comparable, reinforcing
the validity of secondary AML as a grouping when considering treatment options
for these patients.

A third presentation in the Leukemia session reports updated findings from
Antisoma's randomised phase II trial of AS1411 in relapsed and refractory AML.
This trial previously reported a higher remission rate in patients receiving
AS1411 plus high-dose cytarabine (~20%) compared with patients receiving
cytarabine alone (~5%).  The new data, presented by Dr Robert Stuart of the
Medical University of South Carolina, show that a number of the patients who
responded to the AS1411-based regimen appeared to derive longer term benefit,
with substantial survival durations (12-20 months plus) in five of the eight
responding patients.

Monday's Genitourinary Cancer poster session includes the findings from a
35-patient phase II study of AS1411 as monotherapy in advanced renal cancer
refractory to at least one tyrosine kinase inhibitor. While Antisoma has decided
not to pursue this indication for commercial reasons, the data provide further
evidence that AS1411 has activity in a variety of cancer settings. The
presentation, given by Dr Jonathan Rosenberg of the Dana-Farber/Harvard Cancer
Center, shows that one patient had a sustained partial response, with tumour
shrinkage exceeding 80%. Twenty-one patients (60%) showed disease stabilisation
according to independent assessment, which indicated that median
progression-free survival was 3.9 months, comparable with values reported for
active agents in the same setting.

The new 'Trials in Progress' session on Monday includes poster presentations on
both AS1413 and AS1411. One details an ongoing phase IIa pharmacokinetic and
efficacy study of AS1413, which includes a broader range of AML patients than
the current phase III study. The other describes the randomised phase IIb study
of AS1411 in relapsed and refractory AML, which is expected to report headline
data in the first half of 2011.

Details of the presentations at the meeting are provided below. The posters will
be made available at www.antisoma.com <

http://www.antisoma.com/> when they have
been presented.

Enquiries:

 Antisoma plc:

 Glyn Edwards, CEO

 (In London)                                   +44 (0)20 3249 2100

 Daniel Elger, VP Marketing & Communications

 (In Chicago)                                  +44 (0)7909 915 068

 Mark Court/Lisa Baderoon/Catherine Breen      +44 (0)20 7466 5000

 Buchanan Communications


Except for the historical information presented, certain matters discussed in
this announcement 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, including statements regarding the company's clinical
development programmes, the expected timing of clinical trials and regulatory
filings. Such statements are based on management's current expectations, but
actual results may differ materially.

Details of the presentations at ASCO

General poster session: Leukemia, Myelodysplasia, and Transplantation;

Saturday, June 5, 8am-12pm, S Hall A2

  * #6557; Board 14G:  Long-term outcomes of responders in a randomized,
    controlled phase II trial of aptamer AS1411 in AML. Rizzieri et al.
  * #6582; Board 17H: Treatment-related AML and AML evolving from MDS: Similar
    outcomes following treatment with amonafide plus cytarabine. Sekeres et al.
  * #6586; Board 18D: Effect of the presence of P-glycoprotein (MDR1) on the
    ability of AML patients to achieve complete remission: Results of a
    meta-analysis of the literature. Marie et al.

Trials in Progress Poster Session (Special Session, Clinical Trials); Monday,
June 7, 8am-12pm, S Hall A2

  * #TPS278; Board 48A: A phase IIa pharmacokinetic and efficacy study of
    amonafide (AS1413) in combination with cytarabine in patients with acute
    myeloid leukemia. Lundberg et al.
  * #TPS279; Board 48B: A multicenter dose-finding randomized controlled phase
    IIb study of the aptamer AS1411 in patients with primary refractory or
    relapsed AML. Stuart et al.

General poster session: Genitourinary Cancer; Monday, June 7, 1pm-5pm, S Hall A2

  * #4590; Board 4A: A phase II, single-arm study of AS1411 in metastatic renal
    cell carcinoma (RCC). Rosenberg et al.

About AML (acute myeloid leukaemia)

AML is a type of cancer in which the bone marrow makes abnormal and immature
blood cells, eventually leading to bone marrow failure. The American Cancer
Society estimates that there will be over 13,000 new cases of AML diagnosed this
year in the US alone.

About AS1413 (amonafide L-malate)

AS1413 (amonafide L-malate) was added to Antisoma's pipeline through the
acquisition of Xanthus Pharmaceuticals, Inc. in June 2008. AS1413 is a novel DNA
intercalator that induces apoptotic signalling by blocking topoisomerase II
binding to DNA. This differs from the action of classical topoisomerase II
inhibitors, which induce apoptosis by causing extensive DNA damage. A further
distinctive feature of AS1413 is its ability to evade Pgp and related
transporters responsible for multi-drug resistance (MDR). A pivotal phase III
trial (ACCEDE) is evaluating AS1413 as a treatment for secondary AML, a
condition often associated with MDR and in which outcomes with currently
available treatments are poor. Earlier this month, the US Food and Drug
Administration granted AS1413 Fast Track status for the treatment of secondary
AML.

About AS1411

AS1411 was originally developed by Dr Paula Bates, Dr John Trent and Prof.
Donald Miller at the University of Alabama and later at the University of
Louisville. Antisoma added AS1411 to its pipeline when it acquired the
Louisville-based company Aptamera Inc. in 2005.  AS1411 belongs to a new type of
drugs called aptamers. These are short pieces of DNA or RNA that fold into
three-dimensional structures capable of targeting particular proteins. AS1411 is
a DNA aptamer that binds to nucleolin, a protein expressed in the nucleus of all
cells but which in cancer cells is also exposed on the cell surface, providing a
basis for specific targeting by AS1411. When AS1411 binds to nucleolin on cancer
cells, it is internalised and causes apoptosis through interference with various
functions of nucleolin. AS1411 is being evaluated in a phase IIb trial in
patients with relapsed and refractory AML.

About Antisoma

Antisoma is a London Stock Exchange-listed biopharmaceutical company that
develops novel products for the treatment of cancer. The Company has operations
in the UK and the US. Please visit www.antisoma.com <

http://www.antisoma.com/>
for further information about Antisoma.



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