Sanofi-aventis Initiates 10,000 Patient Study With Multaq(R) in Permanent Atrial Fibrillation

For non-U.S. media only

PARIS, May 12, 2010 - Sanofi-aventis (EURONEXT: SAN and NYSE: SNY) announced today
the initiation of a multinational, randomized, double-blind Phase IIIb trial,
PALLAS, to assess the potential clinical benefit of Multaq(R) (dronedarone)
in over 10,000 patients with permanent atrial fibrillation (AF) to reduce
major adverse cardiovascular events. The announcement was made during Heart
Rhythm 2010, the Heart Rhythm Society's 31st Annual Scientific Sessions.

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Permanent AF afflicts 50% of patients suffering from AF and
these patients are at high risk of major adverse cardiovascular events. The
trial rationale was based on post-hoc findings from the landmark ATHENA
trial, in which a trend towards reduction of CV hospitalization and death was
seen in patients classified as "permanent" (i.e. with AF/AFL at each ECG
recording).

"This is a trial of major significance since no
anti-arrhythmic drug has ever been shown to reduce major morbidity and
mortality in permanent AF patients in a large-scale clinical trial," said
Stuart Connolly, MD, Division of Cardiology, McMaster University, Hamilton,
Canada, one of the trial's principal investigators. "We designed the PALLAS
trial to further assess the role of Multaq(R) to reduce cardiovascular
outcomes in patients with AF."

The primary objective of the PALLAS trial is to demonstrate a
reduction in either or both of two composite outcomes which are 1. major
cardiovascular events (stroke, systemic arterial embolism, myocardial
infarction or cardiovascular death) or 2. cardiovascular hospitalization or
death from any cause among patients with permanent atrial fibrillation and
additional risk factors. The secondary objectives are to evaluate the
efficacy of Multaq(R) in preventing cardiovascular death and whether the drug
is well-tolerated in this patient population.

"The initiation of the PALLAS trial confirms our strong belief
in Multaq(R) and our commitment to improve AF patient well-being and overall
cardiovascular health," said Marc Cluzel, MD, Executive Vice President,
Research and Development, sanofi-aventis. "We are looking forward to first
patient enrolment of PALLAS in the third-quarter 2010."

About PALLAS

PALLAS* is a multinational, randomized, double-blind,
parallel-group, placebo-controlled, multicenter Phase IIIb trial comparing
the efficacy of Multaq(R) 400mg twice-daily with placebo in permanent AF
patients. All patients will receive standard treatment to control heart rate
and prevent blood clots (antithrombotic therapy); patients will be randomized
to receive additional treatment with either Multaq(R) 400mg BID or placebo.

Required risk factors include age above 65 years with at least
one of the following major risk factors: systemic arterial embolism,
myocardial infarction, documented coronary artery disease, prior stroke,
symptomatic heart failure, or the combination of age above 75 years,
hypertension and diabetes mellitus. Exclusion criteria include patients with
New York Heart Association (NYHA) Class IV heart failure or unstable NYHA
Class III heart failure.

The trial has two composite co-primary endpoints: 1. Major
cardiovascular events (stroke, systemic arterial embolism, myocardial
infarction or cardiovascular death). 2. Cardiovascular hospitalization or
death from any cause.

There will be 10,800 patients enrolled in 43 countries at 700
sites. The trial is event-driven with a fixed Common Study End Date, meaning
that the study duration will depend upon the occurrence of a statistically
required number of outcome events.

*Permanent Atrial fibriLLAtion outcome Study using Dronedarone on top of
standard therapy (PALLAS)

About Permanent Atrial Fibrillation

The incidence of atrial fibrillation is growing worldwide in
relation to aging populations. It is emerging as a public health concern,
affects about 4.5 million people in Europe and represents one-third of
hospitalizations for arrhythmia in the European Union. Atrial fibrillation
leads to potential life-threatening complications. AF increases the risk of
stroke up to five-fold, worsens the prognosis of patients with cardiovascular
risk factors, and doubles the risk of mortality with significant burden on
patients, health care providers and payers. Seventy percent of AF management
costs are driven by hospital care and interventional procedures in the
European Union.

According to ACC/AHA/ESC guidelines, permanent AF is the
designation given when sinus rhythm cannot be sustained after cardioversion
of AF (medical intervention designed to restore sinus rhythm) or when the
patient and physician have decided to allow AF to continue without further
efforts to restore sinus rhythm.[i] In the Euro Heart Survey one year
follow-up, one year mortality in patients suffering from AF was high and the
risk continuously present. Mortality (5.3%) was comparable with results of
previous studies, which is also the case for the observed higher mortality in
permanent AF than in other AF types.[ii]

About Multaq(R)

Multaq(R), discovered and developed by sanofi-aventis, has
been studied in a clinical development program, including seven
international, multicenter, randomized clinical trials involving more than
7000 patients with almost 4000 patients receiving Multaq(R). The landmark
ATHENA trial was the largest anti-arrhythmic drug trial conducted in patients
with AF/AFL, involving 4,628 patients with a follow-up of 30 months. In this
trial, Multaq(R), on top of standard cardiovascular therapy, significantly
reduced cardiovascular hospitalization or death by 24 percent (p<0.001) when
compared to placebo, meeting the study's primary endpoint. This result was
entirely attributable to a reduction in cardiovascular hospitalization.

Multaq(R) has a fixed dose regimen of twice daily 400 mg
tablets to be taken with morning and evening meals. Treatment with Multaq(R)
does not require a loading dose and can be initiated in an outpatient
setting. Most common adverse reactions are diarrhea, nausea, vomiting,
abdominal pain, asthenia (weakness) and skin rash.

The European Commission granted marketing authorization for
Multaq(R) in November 2009. Multaq(R) is indicated in the EU in adult
clinically stable patients with a history of, or current non-permanent atrial
fibrillation (AF) to prevent recurrence of AF or to lower ventricular rate.
The use of Multaq(R) in unstable patients with NYHA class III and IV heart
failure is contraindicated. Because of limited experience in stable patients
with recent (1 to 3 months) NYHA class III heart failure or with Left
Ventricular Ejection Fraction (LVEF) <35%, the use of Multaq(R) is not
recommended in these patients[iii].

In the U.S., Multaq(R) is indicated to reduce the risk of
cardiovascular hospitalization in patients with paroxysmal or persistent
atrial fibrillation (AF) or atrial flutter (AFL), with a recent episode of
AF/AFL and associated cardiovascular risk factors (i.e., age >70,
hypertension, diabetes, prior cerebrovascular accident, left atrial diameter
greater-than-or-equal-to 50 mm or left ventricular ejection fraction [LVEF]
<40%), who are in sinus rhythm or who will be cardioverted.[iv] Multaq(R) is
contraindicated in patients with NYHA Class IV heart failure, or NYHA Class
II-III heart failure with a recent decompensation requiring hospitalization
or referral to a specialized heart failure clinic.

Multaq(R) is currently available in the U.S., Canada,
Switzerland, Germany, Denmark, Ireland, Norway, Finland and the UK and is
being launched in most European countries in 2010.

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). For more information, please visit:
www.sanofi-aventis.com.

Forward-Looking Statement

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 projections and estimates and their underlying assumptions,
statements regarding plans, objectives, intentions and expectations with
respect to future financial results, events, operations, services, product
development and potential 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 EMA, 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, the Group's ability to benefit from external growth
opportunities 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, 2009. Other than as required by applicable law, sanofi-aventis
does not undertake any obligation to update or revise any forward-looking
information or statements.

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[i] Fuster V, Ryden LE, Cannom DS, et al. ACC/AHA/ESC 2006 Guidelines for
the Management of Patients with Atrial Fibrillation: a report of the American
College of Cardiology/American Heart Association Task Force on Practice
Guidelines and the European Society of Cardiology Committee for Practice
Guidelines (Writing Committee to Revise the 2001 Guidelines for the
Management of Patients With Atrial Fibrillation): developed in collaboration
with the European Heart Rhythm Association and the Heart Rhythm Society.
Circulation 2006;114(7):e257-354.

[ii] Nieuwlaat R, Prins MH, Le Heuzey JY, et al. Prognosis, disease
progression, and treatment of atrial fibrillation patients during 1 year:
follow-up of the Euro Heart Survey on atrial fibrillation. Eur Heart J
2008;29(9):1181-9.

[iii] European Medicines Agency. European Public Assessment Report. Doc.
Ref.: EMA/625172/2009; EMEA/H/C/1043

[iv] MULTAQ U.S. Prescribing information
products.sanofi-aventis.us/Multaq/Multaq.pdf

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Media Contact: Ingrid Gorg-Armbrecht, +33-1-53-77-46-25 or +33-6-38-10-50-87, ingrid.goerg-armbrecht at sanofi-aventis.com