Sanofi-aventis Initiates Phase III Study with Teriflunomide as Adjunct Therapy with Interferon Beta to Further Explore Clinical Benefits in Multiple Sclerosis

TERACLES is the First Phase III Study of an Oral Drug as an Add-On to Standard Therapy in Relapsing Multiple Sclerosis

PARIS, October 26, 2010 - Sanofi-aventis (EURONEXT: SAN and NYSE: SNY) announced today
the initiation of a multinational Phase III study evaluating the efficacy and
safety of two doses of once daily teriflunomide (7mg or 14mg) versus placebo
in patients with relapsing multiple sclerosis (RMS) treated with interferon
beta (IFN beta). Teriflunomide is a novel oral disease modifier developed by
sanofi-aventis which is being investigated in a large Phase III clinical
development program. It includes studies of teriflunomide in monotherapy for
the treatment of RMS and in clinically isolated syndrome as well as adjunct
therapy.

"Initiation of the TERACLES study is a tremendous milestone as
it is the first ever Phase III study of an oral drug in adjunct therapy to be
launched in multiple sclerosis," said Marc Cluzel, M.D., Ph.D., Executive
Vice President, Research & Development, sanofi-aventis. "We are confident
that teriflunomide is an excellent candidate for assessing innovative adjunct
therapy in multiple sclerosis considering the positive effect observed when
it was used in adjunct with interferon beta in the Phase II study."

Specifically, the TERACLES study will evaluate whether once
daily oral teriflunomide 14 or 7mg, in patients treated for at least 6 months
on a stable dose of IFN beta prior to randomization, can reduce the
annualized relapse rate (primary endpoint) compared to IFN beta plus oral
placebo tablets. The main secondary endpoints of the study are to document
the disease activity measured by MRI, the time to disability progression
and overall safety.

"The purpose of the TERACLES study is to assess the clinical
benefits of teriflunomide as an adjunct therapy in patients with relapsing
multiple sclerosis," said Mark S. Freedman, HBSc, MSc, M.D., Professor of
Neurology, Department of Medicine, and University of Ottawa, Ontario, Canada.
"We hope that this study will replicate the additional efficacy and safety
profile we observed in the Phase II trial with teriflunomide in adjunct with
interferon beta, and bring an innovative therapeutic approach to this patient
population."

The Phase II study results presented this year during the
ACTRIMS congress showed that teriflunomide in adjunct with IFN beta
significantly improved disease control (evaluated by MRI activity) beyond IFN
beta plus oral placebo at one year, with a trend towards fewer clinical
relapses and with a consistent safety profile with the data from a Phase II
monotherapy study.

Approximately 240 study sites in 28 countries are targeted for
participation in the TERACLES study which will involve 1455 RMS patients. The
first patient is expected to be enrolled before the end of this year and the
trial will end once the last patient recruited has received at least 48 weeks
of treatment.

About Teriflunomide

Teriflunomide is a new chemical entity being studied in a far-reaching
and ambitious clinical program including more than 3,500 patients in 36
countries. Teriflunomide has previously been evaluated as an adjunct therapy
to either interferon beta or glatiramer acetate in two Phase II
studies. Results of these studies were presented earlier this year during the
American Committee for Treatment and Research in Multiple Sclerosis (ACTRIMS)
and American Academy of Neurology (AAN) meetings respectively. In one of this
Phase II study, teriflunomide in adjunct to glatiramer acetate (GA) was
well-tolerated compared to patients receiving GA and placebo. Although there
was a numerical trend for the reduction in number and volume of gadolinium
enhancing T-1 brain MRI lesions in the adjunct arm compared to placebo with
GA, the relative effect was not as robust as that observed for teriflunomide
with IFN beta. Teriflunomide is also being investigated in a monotherapy
clinical development program. TEMSO Phase III trial positive results have
been presented during the last European Committee for Treatment and Research
in Multiple Sclerosis (ECTRIMS) congress and showed that teriflunomide
successfully reduces annualized relapses rate (primary study endpoint) vs
placebo and was well tolerated in MS patients. Two other Phase III trials,
TOWER and TENERE, are also ongoing in RMS patients. A Phase III study, TOPIC,
completes the clinical development in early MS or CIS (Clinically isolated
syndrome).

About Multiple Sclerosis

Multiple sclerosis (MS) is a chronic, unpredictable and
progressively disabling disease with a substantial burden on patients. MS
patients typically are diagnosed at a young age and they face a lifetime of
uncertainty with gradually declining health. Today, over two million people
around the world suffer from MS. MS is the result of damage to myelin, a
protective sheath surrounding nerve fibres of the central nervous system.
When myelin is damaged, this interferes with messages between the brain and
other parts of the body. Multiple sclerosis is a very variable condition and
the symptoms depend on which areas of the central nervous system have been
affected. There is no definite pattern to MS and everyone with MS has a
different set of symptoms, which vary from time to time and can change in
severity and duration, even in the same person. Management of MS is complex;
early intervention in the pathological process is recommended in order to
delay disease progression or at least, slow it down. A complex support system
is required for the care of MS patients, including health and social
services, as well as various healthcare professionals. Although there is no
known cure for multiple sclerosis, several therapies are proven to be helpful
but there remains an unmet need for new oral therapies with proven efficacy
and good tolerability as well as good long term safety.

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).

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MEDIA CONTACT: Philippe BARQUET, Tel: +33(0)6-70-48-61-28, Email: philippe.barquet at sanofi-aventis.com