Teriflunomide Significantly Reduced Annualized Relapse Rate and was Well Tolerated in MS Patients

First Results From the TEMSO Phase III Trial to be Presented During the ECTRIMS Congress in October 2010

PARIS, August 30, 2010 - Sanofi-aventis (EURONEXT: SAN and NYSE: SNY) announced today
that the investigational once-daily oral drug teriflunomide significantly
reduced annualized relapse rate (ARR) at 2 years versus placebo in patients
with relapsing multiple sclerosis (RMS), thus achieving the primary endpoint
in the TEMSO phase III trial. Both the 7mg and 14mg doses of teriflunomide
were well tolerated with a similar number of patients reporting either
treatment-emergent adverse events (TEAEs) or TEAEs leading to treatment
discontinuation in the treatment arms versus placebo.

Effects on other clinical and MRI related outcomes further
support the primary outcome. The safety profile was in line with previous
clinical experience.

The TEMSO trial is the first study of a large phase III
clinical development program to produce results on teriflunomide as
monotherapy. Study findings from TEMSO will be presented during the platform
presentation scheduled for October 15, 2010, starting at 9:15 a.m. CET at the
26th Annual Meeting of the European Committee for Treatment and Research in
Multiple Sclerosis (ECTRIMS) in Gothenburg, Sweden. The TEMSO study results
are embargoed until this oral presentation.

About Teriflunomide

Teriflunomide is a new oral disease modifier for RMS that
blocks de novo pyrimidine synthesis thus reducing T- and B-cells
proliferation with no cytotoxicity. A comprehensive clinical development
program for teriflunomide has been launched in monotherapy. First Phase II
study results of the safety and efficacy of teriflunomide monotherapy in MS
were published in Neurology in 2006. In addition to the TEMSO trial, two
other Phase III trials, TOWER and TENERE, are ongoing in RMS. A Phase III
study, TOPIC, is also underway in early MS or Clinically Isolated Syndrome
(CIS). Teriflunomide has also been evaluated as an adjunct therapy to either
interferon 1-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 meeting (ACTRIMS) congress,
and the American Academy of Neurology (AAN) meeting respectively. Phase II
studies with teriflunomide (7mg and 14mg) in adjunct with interferon 1-beta
demonstrated an improvement in outcomes, with a consistent safety profile in
patients treated with the adjunct treatment compared with patients treated
with IFN-beta and receiving placebo. In the other 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.

About TEMSO Study

TEMSO is a 2-year randomized, double-blind, placebo controlled
study including 1088 RMS patients worldwide, aged 18-55 years, with an
Expanded Disability Status Scale (EDSS) <= 5.5 and at least one relapse over
the previous year or at least 2 relapses over the preceding 2 years. Patients
were randomized to placebo or teriflunomide, 7mg or 14mg, once daily. The
primary endpoint was annualized relapse rate defined as the number of
confirmed relapses per patients-year. The key secondary endpoint was the time
to disability progression measured by EDSS. Safety and tolerability
evaluations were based on treatment emergent adverse events, physical
examinations, vital signs and laboratory investigations.

About Multiple Sclerosis

Multiple sclerosis (MS) is a chronic, unpredictable and
progressively disabling disease. Patients with MS 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 an acceptable benefit/risk profile.

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