Sanofi's Investigational Semuloparin in Cancer Patients Initiating Chemotherapy Shows a 64 % Risk Reduction in Life-Threatening Venous Thrombo-Embolism

PARIS, June 4, 2011 -

- Results of Phase III SAVE-ONCO Study Selected for "Best of ASCO 2011" -

- Venous Thrombo-embolism Affects Up to 1 in 5 Cancer Patients And
Chemotherapy Further Increases this Risk

Sanofi (EURONEXT: SAN and NYSE: SNY) announced today results
of the pivotal SAVE-ONCO study which demonstrated that, in cancer patients
initiating a chemotherapy regimen, investigational semuloparin significantly
reduced the risk of the composite of symptomatic-deep vein thromboembolism
(DVT), non-fatal pulmonary embolism (PE) or venous thromboembolism
(VTE)-related death by 64%[i], meeting the study primary endpoint
(respectively 1.2% and 3.4% for semuloparin and placebo HR 0.36 95% CI
(0.21-0.60)), p< 0.0001). Semuloparin reduced the risk of this type of blood
clots without increasing the incidence of major bleeding over placebo (1.2%
vs. 1.1%) [i]. The SAVE-ONCO study results will be presented on June 6, 2011
in an oral presentation at the 47th Annual Meeting of the American Society of
Clinical Oncology (ASCO) in Chicago, and are selected for the Best of ASCO*.

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In VTE, blood clots usually form in deep veins (commonly
referred as thrombo-phlebitis) and can migrate and potentially block blood
flow in the blood vessels of the lungs (pulmonary embolism), which may result
in sudden death [ii]. Often clinically silent, VTE is a life-threatening
complication of cancer affecting up to one in five patients[iii], [iv], and
initiating chemotherapy further increases the risk by more than 60%[v],[vi].

"For cancer patients initiating chemotherapy, there is
currently no approved treatment for the primary prevention of venous
thrombo-embolism risk," said Giancarlo Agnelli, Professor of Internal
Medicine at the University of Perugia, Italy and SAVE-ONCO principal study
investigator. "Therefore, we are encouraged by the 64% risk reduction of
Life-Threatening Venous Blood Clots demonstrated in this randomized trial".

"In many patients affected by cancer, preventing venous
thromboembolism is an important clinical management issue", said Dr. Elias
Zerhouni, President, Global Research & Development, Sanofi. "We are pleased
with the results achieved in this study of our selectively engineered
semuloparin as shown by the SAVE-ONCO trial. Based on these results of
SAVE-ONCO we plan to submit semuloparin for regulatory filing in Q3 2011".

SAVE-ONCO, the international randomized phase 3 study enrolled
3,212 patients initiating a chemotherapy regimen for locally advanced or
metastatic solid tumor (lung, colon-rectum, stomach, ovary, pancreas or
bladder cancer). Patients received either a daily 20 mg subcutaneous
administration of semuloparin or placebo for at least three months or until
change in the chemotherapy regimen. The primary endpoint of the study was the
composite of any symptomatic-DVT, non-fatal PE and VTE-related deathi.
Clinically relevant bleeding (bleedings requiring medical attention) was
respectively 2.8% and 2.0% for semuloparin and placeboi . Consistent with
previous findings, there was no case of reported HIT (heparin induced
thrombocytopenia) in the 3,212 studied patients. SAVE-ONCO study median
treatment duration with semuloparin was approximately 3.5 monthsi.

* The 2011 Best of ASCO Meetings feature the most relevant and
cutting-edge science in oncology research.

About Semuloparin

Semuloparin is an investigational selectively engineered
Ultra-LMWH (low molecular weight heparin) with enriched anti-thrombin binding
sites, leading to anticoagulant activity mainly directed towards coagulation
Factor Xa, with a minimal effect on Factor IIa. Selectively engineered
semuloparin, in addition to a specific anti-Factor Xa/IIa ratio, retains
biological activities that are relevant in cancer biology such as effects on
TFPI (tissue factor pathway inhibitor)[vii]. A large Phase III clinical study
(SAVE-ONCO) investigating semuloparin benefit in cancer patients with locally
advanced or metastatic solid tumor initiating chemotherapy has been
completed. The SAVE-ONCO study assessed the efficacy and safety of
semuloparin for the prevention of symptomatic- DVT, non-fatal Pulmonary
Embolism and VTE-related death in cancer patients initiating a chemotherapy
regimen.

About Sanofi Oncology

Based in Cambridge, Massachusetts, and Vitry, France, Sanofi
Oncology is dedicated to translating science into effective cancer
therapeutics to address unmet medical needs for patients with cancer.
Starting with a deep understanding of the mechanisms by which cancer
develops, grows and spreads, the company employs innovative approaches in
drug discovery, clinical development and partnerships to bring the right
medicines to the right patients with the goal of helping cancer patients live
healthier and longer lives.

Sanofi Oncology is committed to the pursuit of science and
innovative cancer therapies. We believe in partnership with leading experts,
and combining that expertise with our own internal scientific strength and
heritage. There are currently more than 10 investigational compounds in
clinical development including small molecules and biological agents.

About Sanofi

Sanofi, a global and diversified healthcare leader, discovers,
develops and distributes therapeutic solutions focused on patients' needs.
Sanofi has core strengths in the field of healthcare with seven growth
platforms: diabetes solutions, human vaccines, innovative drugs, rare
diseases, consumer healthcare, emerging markets and animal health. Sanofi is
listed in Paris (EURONEXT: SAN) and in New York (NYSE: SNY).

Forward Looking Statements

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defined in the Private Securities Litigation Reform Act of 1995, as amended.
Forward-looking statements are statements that are not historical facts.
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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
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well as their decisions regarding labeling and other matters that could
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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, including those listed under "Risk
Factors" and "Cautionary Statement Regarding Forward-Looking Statements" in
Sanofi's annual report on Form 20-F for the year ended December 31, 2010.
Other than as required by applicable law, Sanofi does not undertake any
obligation to update or revise any forward-looking information or statements.

[i] Agnelli G et al. ASCO June 3-7, 2011 Chicago. Oral Abstract #LBA9014.

[ii] Heit AJ. Risk factors for venous thromboembolism. Clin Chest Med.
2003 Mar; 24 (1): 1-12.

[iii] Lyman GH. Venous Thromboembolism in the Patient With Cancer. Cancer
2011; 1334-50.

[iv] Khorana AA et al. Thromboembolism is a leading cause of death in
cancer patients receiving outpatient chemotherapy . J Thromb Haemost
2007;5:632-4.

[v] Heit JA. Cancer and Venous Thromboembolism: Scope of the Problem.
Cancer Control. September 2005; 12: 5-10.

[vi] Heit JA et al. Risk Factors for Deep Vein Thrombosis and Pulmonary
Embolism. Arch Intern Med 2000 ;160:809-15.

[vii] Gómez-Outes A et al. New parenteral anticoagulants in development.
Ther Adv Cardiovasc Dis 2011 5: 33-59.

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Contacts: Product Communications, Salah Mahyaoui, Tel: +33-(0)1-53-77-40-31, Mobile: +33(0)6-73-68-78-88, E-mail: salah.mahyaoui at sanofi-aventis.com. Corporate Media Relations, Marisol Peron, Tel: +33-(0)1-53-77-45-02, Mobile: +33-(0)6-08-18-94-78, E-mail: marisol.peron at sanofi-aventis.com. US Product Communications, Jeanne Longo, Tel: +1-(908)-981-6576, E-mail: jeanne.longo at sanofi-aventis.com