Sanofi Pasteur Starts a Phase II Study of a Vaccine Against Clostridium Difficile

Lyon, France (ots/PRNewswire) -

- Novel Vaccine Approach Tested in the UK Against One of the Most
Common Causes of Hospital-Acquired Infection in Europe and North
America

Sanofi Pasteur, the vaccines division of sanofi-aventis Group
(EURONEXT : SAN et NYSE : SNY), announced today that it is sponsoring
a phase II clinical study of a vaccine against Clostridium difficile,
which is among the most common causes of hospital-acquired infection
in Europe and North America.

The trial currently conducted in the United Kingdom is
investigating the safety and efficacy of sanofi pasteur's C.
difficile candidate vaccine. While the target indication for the
vaccine is primary prevention of C. difficile infection (CDI), this
trial in infected patients aims at providing early proof of concept
of the vaccine approach.

"Treatment of C. difficile infection includes the use of one of
two antibiotics. Non-antibiotic approaches for managing C. difficile
infection are badly needed since the alteration of the gut flora
associated with antibiotics triggers the infection in the first
place. There is also considerable concern about the emergence of
antibiotic-resistance in C. difficile and other bacteria. Vaccination
has the potential to be a very effective strategy to combat
gastrointestinal pathologies caused by C. diff. along with better
antibiotic stewardship and infection control practices," said Barry
Cookson, Director, Laboratory of Healthcare Associated Infections,
Centre for Infections, Health Protection Agency and the lead
investigator of the trial.

Sanofi Pasteur's candidate vaccine uses a toxoid-based approach,
which has been used extensively in sanofi pasteur's licensed vaccines
against tetanus, diphtheria and pertussis (whooping cough). This
candidate vaccine has successfully completed phase I clinical trials
in more than 200 participants to evaluate its safety and
immunogenicity.

The incidence of CDI has increased significantly in recent years
in both North America and Europe. CDI-related treatments in these two
regions of the world are estimated to be costing more than US$7bn a
year. The emergence of a hyper-virulent strain of C. difficile in
2002 further highlighted the importance of tackling CDI.

About the Clinical Trial

The phase IIb trial involves about 600 participants with acute
CDI at about 30 centers across the United Kingdom. Participants will
be randomized to 4 study groups, where three groups will receive
vaccine, while the fourth group will be given a placebo vaccine. All
subjects will receive standard of care antibiotics.

About C. difficile

C. difficile is an anaerobic spore-forming bacterium, present
asymptomatically in approximately 60% of infants but only about 3% of
healthy adults. It belongs to the Clostridium family of bacteria,
which also includes C. tetani (tetanus) and C. botulinum (botulism).
The C. difficile bacteria produce two potent toxins: A and B. When
the natural microbial flora of the gut is disturbed, usually as a
result of antibiotic treatment, and a patient ingests C. difficile
spores, the bacteria can multiply and release the two toxins, which
cause gastrointestinal pathologies in humans known collectively as
CDI.

Hospital-acquired infections caused by C. difficile bacteria are
a considerable problem in many industrialized countries, including
the U.S., Canada, and Europe. It is estimated that C. difficile
causes about 500,000 cases in the US alone(1) with annual costs to
the healthcare system of US$3.2bn.(2) In the EU, assuming a
population of about 460 million people, the healthcare costs of CDI
are estimated to be around US$4.4bn per year.(3) Additional
information is available at the UK Health Protection Agency C.
difficile information page (4) and at
http://www.sanofipasteur.com/cdiff

About sanofi-aventis

Sanofi-aventis, a leading global pharmaceutical company,
discovers, develops and distributes therapeutic solutions to improve
the lives of everyone. Sanofi-aventis is listed in Paris (EURONEXT:
SAN) and in New York (NYSE: SNY).

Sanofi Pasteur, the vaccines division of sanofi-aventis Group,
provided more than 1.6 billion doses of vaccine in 2008, making it
possible to immunize more than 500 million people across the globe. A
world leader in the vaccine industry, sanofi pasteur offers the
broadest range of vaccines protecting against 20 infectious diseases.
The company's heritage, to create vaccines that protect life, dates
back more than a century. Sanofi Pasteur is the largest company
entirely dedicated to vaccines. Every day, the company invests more
than EUR1 million in research and development. For more information,
please visit: http://www.sanofipasteur.com or
http://www.sanofipasteur.us

References:

1. CDC: http://www.cdc.gov/ncidod/dhqp/id_Cdiff.html

2. O'Brien et al, The Emerging Infectious Challenge of
Clostridium difficile-Associated Disease in Massachusetts Hospitals:
Clinical and Economic Consequences. Infection Control and Hospital
Epidemiology, 2007; 28(11):1219-1227

3. European Centre for Disease Prevention and Control, Emergence
of Clostridium difficile-associated disease in North America and
Europe, Clinical Microbiology and Infectious Diseases, 2006; 12
(Suppl. 6): 2-18

4. HPA: http://www.hpa.nhs.uk/webw/HPAweb&Page&HPAwebAutoListName
/Page/1179744911867

Forward Looking Statements

This press release contains forward-looking statements as defined
in the Private Securities Litigation Reform Act of 1995, as amended.
Forward-looking statements are statements that are not historical
facts. These statements include product development, product
potential projections and estimates and their underlying assumptions,
statements regarding plans, objectives, intentions and expectations
with respect to future events, operations, products and services, and
statements regarding future performance. Forward-looking statements
are generally identified by the words "expects," "anticipates,"
"believes," "intends," "estimates," "plans" and similar expressions.
Although sanofi-aventis' management believes that the expectations
reflected in such forward-looking statements are reasonable,
investors are cautioned that forward-looking information and
statements are subject to various risks and uncertainties, many of
which are difficult to predict and generally beyond the control of
sanofi-aventis, that could cause actual results and developments to
differ materially from those expressed in, or implied or projected
by, the forward-looking information and statements. These risks and
uncertainties include among other things, the uncertainties inherent
in research and development, future clinical data and analysis,
including post marketing, decisions by regulatory authorities, such
as the FDA or the EMEA, regarding whether and when to approve any
drug, device or biological application that may be filed for any such
product candidates as well as their decisions regarding labelling and
other matters that could affect the availability or commercial
potential of such products candidates, the absence of guarantee that
the products candidates if approved will be commercially successful,
the future approval and commercial success of therapeutic
alternatives as well as those discussed or identified in the public
filings with the SEC and the AMF made by sanofi-aventis, including
those listed under "Risk Factors" and "Cautionary Statement Regarding
Forward-Looking Statements" in sanofi-aventis' annual report on Form
20-F for the year ended December 31, 2007. Other than as required by
applicable law, sanofi-aventis does not undertake any obligation to
update or revise any forward-looking information or statements.

http://www.sanofipasteur.com

http://www.sanofipasteur.us

ots Originaltext: sanofi-aventis Group
Im Internet recherchierbar: http://www.presseportal.de

Contact:
Contacts: Global Media Relations, Pascal Barollier, T.
+33(0)4-37-37-50-38, pascal.barollier@sanofipasteur.com; US Media
Relations, Len Lavenda, T. +1-570-957-4446,
len.lavenda@sanofipasteur.com