Teriflunomide Successfully Reduces Relapses and is Well Tolerated in Multiple Sclerosis Patients

Phase III TEMSO Study Meets Goals Including Delayed Disability Progression for Teriflunomide 14mg

PARIS, October 15, 2010 - Sanofi-aventis (EURONEXT: SAN and NYSE: SNY) announced today the results
from the two year phase III TEMSO study of teriflunomide, a novel oral
disease modifier investigated for the treatment of relapsing multiple
sclerosis (RMS). In this study, both doses of teriflunomide (7 and 14mg)
significantly reduced annualized relapse rate (primary study endpoint) by 31%
vs. placebo (p is less than or equal to 0.0005). The risk of disability
progression (sustained for 12 weeks) was also significantly reduced by 30%
for the 14mg dose (p=0.02) and numerically reduced by 24% for the 7mg dose
(p=0.08). Both doses of teriflunomide were well tolerated with a similar
number of patients reporting either treatment-emergent adverse events
(TEAEs) including serious adverse events or TEAEs leading to treatment
discontinuation in the treatment vs. placebo arms.

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"We are very pleased with the successful results of the TEMSO
study which are an important step forward in multiple sclerosis clinical
research," said Marc Cluzel, M.D., Ph.D., Executive Vice President, Research
& Development, sanofi-aventis. "These exciting results with
teriflunomide represent a new real hope to delivering an oral therapy to
patients who live with this serious condition and are eager for new treatment
options, and more convenient product forms in-line with our sanofi-aventis
commitment to multiple sclerosis."

The results of the TEMSO trial are the first study findings
from a large phase III clinical development program on teriflunomide. These
results were presented today during the European Committee for Treatment and
Research in Multiple Sclerosis (ECTRIMS) congress, in Gothenburg, Sweden.

"Multiple sclerosis is a complex disease, and it often has an
unpredictable and highly disabling disease course, therefore leading to
important health care needs in this relatively young patient group ", said
Dr. Paul O'Connor, Director of the MS Clinic at St Michael's Hospital,
Toronto, Canada and principal investigator of the TEMSO study. "We were very
satisfied to see how TEMSO demonstrated that teriflunomide successfully
reduced relapse rate but also reduced the time to disability progression for
the highest dose with a favorable safety profile for multiple sclerosis
patients with relapses and emerges as a potential new first-line treatment
option in this patient population."

Teriflunomide also significantly reduced the brain disease
activity on a range of magnetic resonance imaging (MRI) measures including a
significant reduction of the burden of disease (total lesion volume), by 39%
(p=0.03) and 67% (p=0.0003) at the 7 and 14mg doses relative to placebo,
respectively.

Teriflunomide was well tolerated with no major safety
concerns. Adverse events occurring at a higher rate in the teriflunomide
groups were diarrhea, nausea, alanine transferase increases that were mainly
mild and asymptomatic with no dose effect and mild hair thinning and hair
loss which rarely led to treatment discontinuation. No serious opportunistic
infections occurred in patients treated with teriflunomide.

In addition to the TEMSO results, data on long-term safety of
RMS patients, from eight years of follow-up of the open-label extension of a
phase II study were also presented at the ECTRIMS congress. These data showed
that teriflunomide was well tolerated during eight years of continuous use
with a safety profile consistent with that reported during the first 36
double-blind phase weeks of the study.

About Teriflunomide

Teriflunomide is a new disease modifying drug being
investigated for the treatment of multiple sclerosis with a comprehensive
clinical development program which 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
patients. A Phase III study, TOPIC, is also underway in early MS or CIS
(Clinically isolated syndrome). Teriflunomide has also 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.
Phase II studies with teriflunomide (7 and 14mg) in adjunct with IFNbeta
demonstrated an improvement in MRI outcomes, with a consistent safety profile
in patients treated with the adjunct therapy compared to patients treated
with IFNbeta 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 and showed a numerical trend
for the reduction in number and volume of gadolinium enhancing T-1 brain MRI
lesions in the adjunct arm compared to the placebo with GA arm.

About the TEMSO Study

TEMSO is a 2-year randomized, double-blind, placebo-controlled
multinational study including 1,088 RMS patients aged 18-55 years from 21
countries, with an Expanded Disability Status Scale (EDSS) is less than or
equal to 5.5 and at least one relapse in the previous year or at least 2
relapses in the preceding 2 years. Patients were randomized to placebo or
teriflunomide, 7 or 14mg, once daily and followed for 108 weeks. The primary
endpoint was annualized relapse rate defined as the number of confirmed
relapses per patient-year. The key secondary endpoint was the time to
sustained disability progression measured by the 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 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 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 .