Dear Shareholders,News flow was strong in the secondquarter of 2011. For the first time, weconsolidated Genzyme’s net sales.Our previous blockbusters sufferedfurther damage from genericcompetition and were in decline, whileour new growth platforms continuedto make headway. Over the first half as a whole, thegrowth platforms achieved an excellent performance. Our Diabetesbusiness returned to double-digit growth in the first half thanks tonew promotional effort implemented from mid-2010. The dynamismof Emerging Markets, where we are well ahead of our competitors,continues unabated. In Consumer Health Care, we have seenthe hugely successful launch of Allegra® over the counter in theUnited States and sales were more than 28% higher (at constantexchange rates). In Animal Health, a very solid business, saleswere up nearly 7% in the first half (at constant exchange rates).Net sales from our Vaccines business reached €1.3 billion onrecord sales of seasonal influenza vaccines in the southernhemisphere. Finally, our Innovative Products, Multaq® andJevtana®, added €227 million to net sales. In the field of innovation, we are planning to submit filings forapproval of six new products in only 9 months. Given that R&Dproductivity is one of our priorities, we are proud to be making goodprogress.

As regards Genzyme, its performance in the second quarter wasgood, and integration is progressing well. Its Personalized GeneticHealth and Multiple Sclerosis divisions, in which Genzyme hasdeveloped solid expertise, will continue to be part of Genzymebecause they are integral to its unique patient care approach. Wehave decided to integrate its Renal Medicine, Biosurgery andOncology divisions with Sanofi’s existing activities because theyare closer to our business model. This should lead to substantialsynergies. If we look at what has been achieved since the end of 2008, Sanofihas accomplished an impressive transformation and the patentcliff for a number of our products is now almost behind us. After2012, which will be marked by the loss of exclusivity of Plavix® andAvapro® in the United States, Sanofi is on course for a period ofsolid sustainable growth thanks to the soundness of our growthplatforms, the contribution from Genzyme and our continuingfinancial discipline. Our objective of lifting the dividend payoutratio to 50% reflects Sanofi’s improved prospects and ourcommitment to create value for our shareholders. Thank you for your confidence,

Christopher A. ViehbacherChief Executive Officer

SANOFI � SEPTEMBER 2011

Letter to ShareholdersDear Shareholders,Though competition from generics hitthe second quarter particularly hard,there were good performances fromthe growth platforms and Genzyme,the acquisition of which was finalizedin April. We expect that these growth platformswill account for 80% of our sales in2015. Acquisitions carried out sinceJanuary 2009 are expected to represent around 30% of our salesin 2015. As regards generic competition, by mid 2012 we will beone of the companies least exposed to the patent cliff.

In light of this outlook, and ensuring that we have the necessaryresources to pursue our investments for growth, we decided toincrease the dividend payout ratio, aiming to reach 50% for the2013 dividend paid in 2014. This decision clearly shows ourconfidence in the future of our company.Thank you for your continuing loyalty.

Serge WeinbergChairman of the Board of Directors

Sanofi Shareholder Relations: 174, avenue de France – 75013 Paris – FranceTel. Europe: +33 800 075 876, toll-free number U.S.: +1 888 516 3002Individualshareholders@sanofi.com

N°. 27

NEWS

SANOFI ANNOUNCES NEW LONG TERMOBJECTIVES On the occasion of the Thematic Investor Relations Seminar dedicated to ourstrategy and outlook, Sanofi management highlighted the company’s impressivetransformation since end 2008 and presented growth perspectives for the 2012-2015 period.For further information, please go to pages 3 and 4 of this Letter.

DIVESTMENT OF THE DERMIKDERMATOLOGY UNIT TO VALEANTIn July 2011, Sanofi decided on the strategic divestiture of its dermatologybusiness, Dermik, to Valeant Pharmaceuticals International Inc.*, for a totalcash consideration of U.S. $425 million. Valeant is a pharmaceutical companyfocused on the neurology and dermatology therapeutic areas, based in Canada.Dermik has a significant presence in the medical dermatology market in theUnited States and Canada with a portfolio including leading therapeutic andaesthetic dermatology brands. Sanofi decided to divest its dermatology business with the intention to furtherconcentrate on its growth platforms.

*The closing of the transaction is subject to customary conditions, including clearance by certainantitrust authorities.

PROGRESS IN RESEARCH & DEVELOPMENT Sanofi expects to submit filings to health authorities for 6 new products overthe next 9 months:

� Kynamro™ (mipomersen) - licensed from Isis Pharmaceuticals Inc - U.S.filing for the homozygous familial hypercholesterolemia (hoFH) indicationis expected in the fourth quarter of this year. In Europe, a MarketingAuthorization Application was submitted in July for the treatment of patientswith hoFH and severe heterozygous familial hypercholesterolemia (heFH).

� Visamerin® / Mulsevo® (semuloparin) - filing in Europe and the U.S. inSeptember 2011 for the prevention of Venous Thrombo-Embolism eventsin cancer patients initiating a chemotherapy regimen.

� Aubagio™ (teriflunomide) should be filed in Europe in the first quarter of2012. In the U.S. it was filed for the treatment of relapsing multiple sclerosisin August.

� Zaltrap™ (aflibercept) - alliance with Regeneron – filing in the U.S. inSeptember/October 2011 and in Europe in the fourth quarter of 2011 insecond line metastatic colorectal cancer.

� Lyxumia® (lixisenatide) - licensed from Zealand Pharma – is expected tobe filed in Europe in the fourth quarter of 2011 for the treatment of type 2diabetes.

� Lemtrada™ (alemtuzumab) is expected to be filed in the U.S. and Europein the first quarter of 2012 for relapsing remitting multiple sclerosis. Theproduct has been granted fast track designation by the FDA.

CONCLUSION OF NEWRESEARCHCOLLABORATIONS

HEARING LOSS

In June 2011, Sanofi entered into a two-year researchcollaboration with the biopharmaceutical companyAudion Therapeutics to develop potential treatmentsfor hearing loss through the optimization of smallmolecules by using a regenerative medicineapproach. Over 500 million patients suffer from hearing lossworldwide with no currently available disease-modifying treatments.

TUBERCULOSIS

In June 2011, Sanofi entered into a researchcollaboration with Weill Cornell Medical College toidentify new antiinfectives that aim to shorten thecourse of treatment of tuberculosis and could provideeffective therapies against drug-susceptible anddrug-resistant strains of tuberculosis. Every year, more than 1.7 million people worldwidedie from tuberculosis. Today’s drugs are more than40 years old and have long and demanding treatmentschedules. They prove too much for many patientsand the resulting erratic or inconsistent treatmentcan lead to drug resistance, treatment failure ordeath.

ANTIBIOTICS

Sanofi signed an exclusive worldwide researchcollaboration agreement and option for license withRib-X Pharmaceuticals, Inc. in July 2011. Thecollaboration focuses on a novel technology thattargets bacterial ribosomes to create entirely newclasses of antibiotic therapeutics for the treatmentof infections caused by resistant pathogens.

Further information: en.sanofi.com

2

EVENT 3

2008-2011: TRANSFORMING SANOFI

Since the end of 2008, Sanofi has led an impressive transformation by executinga new strategy focused on three pillars: increase innovation in R&D, pursueexternal growth opportunities, adapt structure for future challenges andopportunities. Over this period, the Group has centered its activities around six growth platformsincluding Emerging Markets(1), Human Vaccines, Diabetes Solutions, ConsumerHealth Care, Innovative Products and Animal Health. These platforms havebeen strengthened through the reallocation of resources and acquisitions. SinceJanuary 2009, the Group has invested €23 billion in 23 acquisitions, includingGenzyme, to develop and support its growth platforms. The acquisition ofGenzyme adds a global center for excellence in rare diseases and multiplesclerosis. In parallel, Sanofi has built a leaner Pharma R&D organization. A comprehensiveand rigorous review of the R&D portfolio was performed and enabled the Groupto refocus on high-value projects and to reallocate resources to externalpartnerships. At the same time, Sanofi signed 61 in-licensing agreements toenrich its R&D portfolio. The management team has also been enhanced by adding senior executiveswith solid international experience.

2011-2012: MITIGATING THE IMPACT OF THE PATENT CLIFF

In 2011, sales of key genericized products(2) are expected to decline to about€3 billion vs. €7.6 billion in 2008. In parallel, consolidated sales generated bygrowth platforms and Genzyme should exceed €22 billion this year vs.€11.8 billion in 2008. The last significant headwind remains the impact on profitcontribution from Plavix® and Avapro® in the U.S. following the end of exclusivityin May 2012 and March 2012, respectively. This impact on the business netincome(3) is estimated to be around €1.4 billion (net of tax) in 2012. Given thisimpact, the Group’s business operating(4) margin is expected to be around 31%in 2012.

STRATEGY & OUTLOOKINVESTOR RELATIONS THEMATIC SEMINAR

On September 6, 2011, the Investor Relations team organized its 4th thematic seminar for the financial community. The 2011 editionfocused on the execution of the Group’s strategy and its longterm objectives. More than 500 people followed it, either on site orby connecting to the live audio webcast on en.sanofi.com: therecorded webcast is still available there.

At the event, Christopher A. Viehbacher, Chief Executive Officer,Jérôme Contamine, Executive Vice President, Chief FinancialOfficer, Hanspeter Spek, President Global Operations, PierreChancel, Senior Vice President, Diabetes, Olivier Charmeil, SeniorVice President, Vaccines, Dr. David Meeker, Chief OperatingOfficer Genzyme and José Barella, Chief Executive Officer Merialhighlighted the key achievements between 2008 and 2011 andpresented the perspectives for 2012-2015, in terms of evolution ofour growth platforms, capital allocation and growth objectivesbeyond the patent cliff.

2008-2011From Top 15 Products...Sales split in 2008

...to Key Growth Platforms & GenzymeSales split in 2011

Basebusiness29%

Top 1561%

Vaccines10%

Other25%

Growth platforms & Genzyme~ 66%

Key genericized products(2)

9%

Genzyme

4

(1) See note (3) on page 5(2) Lovenox® U.S., Plavix® Western Europe, Taxotere® Western Europe

& U.S., Eloxatin® U.S., Ambien CR® U.S., Allegra® U.S., Aprovel® WesternEurope, Xyzal® U.S., Xatral® U.S., Nasacort® U.S. - Generic makers ofoxaliplatin (Teva, Fresenius Kabi (formerly Dabur), Sandoz,Mayne/Hospira, MN/Par, Actavis and Sun) required to cease selling inthe U.S. since June 30, 2010 but litigation continues.

(3) See note (2) on page 5.(4) See the definition of business operating income in the press release

from September 6, 2011.(5) At CER before inflation and tax and on a constant structure basis

compared to 2008.(6) At CER before inflation and tax and on a constant structure basis.(7) Compound annual growth rate (CAGR).

2012-2015: GENERATING CONSISTENT AND SUSTAINABLEGROWTH

Growth platforms - The growth platforms and Genzyme are expected togenerate approximately 66% of Group sales in 2011 and to contribute morethan 80% of Group sales in 2015. Sanofi expects to extend its leadership inEmerging Markets(1) which are expected to account for 38% to 40% of its salesin 2015 compared to 29% in 2010. This objective implies double digit salesgrowth in Emerging Markets over 2012-2015.Tight cost control - As previously announced, the €2 billion(5) cost savingsprogram initiated in 2009 will be reached in 2011, two years ahead of target.Furthermore, Sanofi now expects that new initiatives combined with the previouslyannounced $700 million savings expected from the acquisition of Genzymewill generate additional incremental cost savings of €2 billion(6) by 2015.R&D objectives - The R&D transformation initiated in 2009 should start todeliver results during 2012-2015 with 19 potential projects to be launched. Ofthese 19 projects, 6 are scheduled to be filed between July 2011 and March2012. 2013 objective - In July 2009, Sanofi announced its objective to achieve atleast the same level of sales and a comparable business net income(3) level in2013 vs. 2008. In February 2011, Sanofi announced the expected accretionfrom the acquisition of Genzyme in 2013. Despite recent healthcare reformsin the U.S. and austerity measures in EU, Sanofi confirms both its originalobjective for 2013 and the incremental contribution from Genzyme.Sales and business EPS(3) growth - Sanofi announces its prospects for longterm growth and its objective to deliver average sales growth of at least 5%per year(7) over 2012-2015. Sanofi targets average business EPS(3) growth peryear(7) to be superior to sales growth over the same period. As a result ofleverage of growth platforms, synergies from Genzyme and Merial and newcost savings program, Sanofi expects to improve the business operating(4)

margin over 2012-2015. Capital allocation - Given its commitment to shareholder value creation andits improved outlook, Sanofi has decided to progressively increase the dividendpayout to 50% for the dividend paid in 2014 compared to 35% for the dividendpaid in 2011. The company also confirms its current practice of opportunisticshare buy back.

€2.50

€2.20 €2.40

2009 2010 2011 2014

Payout35%

Payout50%

2012-2015Sustaining Higher Shareholder Returns

Progressive increase of the dividend payout target

A STRONG SCORECARD FOR 2012-2015

2012-2015 sales CAGR At least 5%

Diversified sources of growth �

Scale in businesses with significant barriers to entry �

Low small molecule patent exposure in mature markets* ~6%

Large presence in Emerging Markets in 2015 (estimated value) 38-40%

Potential new product launches 2012-2015 19

Operating margin evolution Rebounding

2012-2015 business EPS CAGR Superior to sales CAGR

Increased dividend payout 50% by 2014

* 2012 sales from chemical products exposed to patent expiry in the U.S., Japan and Western Europe over 2012-2015

FINANCIAL NEWS 5

Q2 2011 Change on a Change at H1 2011 Change on a Change atreported basis CER reported basis CER

Net sales €8,349m +0.5% +6.9% €16,128m -0.5% +1.0%

Business net income(2) €2,150m -13.2% -7.0% €4,320m -11.9% -11.5%

Business EPS(2) €1.64 -13.7% -7.4% €3.30 -12.2% -11.7%

SALES GROWTH DESPITE IMPACT FROM GENERICCOMPETITION

In the second quarter of 2011, Sanofi generated net sales of €8,349 million, up 0.5% on a reported basis. Exchange ratemovements had a negative effect of 6.4 percentage points, of whichmore than 70% was due to the weakening of the U.S. dollar versusthe Euro. At constant exchange rates, and including changes instructure (primarily the consolidation of Genzyme from April 1, 2011),net sales increased by 6.9%. Excluding Genzyme, sales were down4.0% reflecting €778 million of sales lost due to generic competitionvs. Q2 2010.Second-quarter net sales for the pharmaceuticals business were€7,147 million (up 7.7%), which reflects the positive impact (€796 million) from the consolidation of Genzyme from April 1st aswell as generic competition and the impact of the U.S. healthcarereform and EU austerity measures.The generics business recorded sales of €434 million in the secondquarter, an increase of 17.6%, notably led by sales of authorizedgenerics of Taxotere® and Ambien®CR in the U.S. Sales in EmergingMarkets reached €279 million, up 13.8% supported by the roll out ofMedley products in additional countries in Latin America.The Group’s growth platforms grew by 9.5% and including Genzymeaccounted for 65.2% of total consolidated sales in the second quarterof 2011, which is up from 54.9% in the second quarter of 2010.

SOLID PERFORMANCE OF GROWTH PLATFORMS ANDGENZYME

� Emerging Markets(3): Sales of €2,533 million, up12.3% (+7.1% excluding Genzyme and A/H1N1vaccines sales / +6.9% excluding Genzyme).

� Diabetes Solutions: Sales of €1,168 million, up 12.4%led by double-digit growth of Lantus®, notably in theU.S. and Emerging Markets.

� Human Vaccines: Sales of €706 million, up 2.5% or3.4% excluding A/H1N1 sales.

� Consumer Health Care: Sales of €644 million, up17.6%, reflecting the success of the launch of Allegra®

OTC in the U.S. and the positive impact fromacquisitions (mainly BMP Sunstone in China).

� Innovative Products: Sales of €116 million, of which€48 million for Jevtana® and €68 million for Multaq®.

� Animal Health: Sales of €496 million, up 1.1%,reflecting a slight decrease of 0.3% of the companionanimals segment and a 3.7% growth of the productionanimals segment.

� Genzyme: Sales of €796 million, up 16.0% at constantstructure and exchange rates.

SECOND QUARTER 2011 RESULTS� Total sales grew(1) 6.9% to €8,349m thanks to the acquisition of Genzyme and the performance of growth

platforms. � Growth platforms grew 9.5% and accounted for 65.2% of total sales including Genzyme. � Business EPS(2) down 7.4% at constant exchange rates (CER) to €1.64.� As a result of the Genzyme acquisition, net debt was €13.2bn at the end of Q2 2011.

UPDATE OF 2011 GUIDANCE(4)

The Group expects 2011 business EPS(2) to be 2% to 5% lowerthan 2010 business EPS(5) at CER, barring major unforeseenadverse events.

(1) Unless otherwise indicated, sales growth figures are stated at constant exchangerates.

(2) Business net income is defined as net income attributable to equity holders of theCompany excluding: amortization of intangible assets, impairment of intangible assets,other impacts associated with acquisitions (including impacts of acquisitions onassociates), restructuring costs*, gains and losses on disposals of non-current assets*,costs or provisions associated with litigation*, tax effect related to the items listedabove as well as effects of major tax disputes.*Reported in the line items: Restructuring costs and Gains and losses on disposals,and litigationBusiness EPS: Business earnings per share is defined as business net incomedivided by the weighted average number of shares outstanding.

(3) World excluding United States and Canada, Western Europe, Japan, Australia andNew Zealand.

(4) See forward-looking statement on page 6.(5) €7.06

CALENDAROctober 4, 2011Shareholder meeting in Nantes, France

November 3, 2011Third quarter 2011 results

November 18-19, 2011Shareholding fair ActionariaPalais des Congrès in Paris,France

November 18, 2011Shareholder meeting at Actionaria in Paris, France

November 22, 2011Shareholder meeting in Bordeaux, France

December 8, 2011Shareholder meeting in Biarritz, France

Forward-looking statement:This letter contains projections and otherforward-looking statements that are nothistorical facts. Although the management ofSanofi believes that these projections andforward- looking statements, and theirunderlying assumptions, are reasonable as ofthe date of this letter, investors are cautionedthat such projections, assumptions, intentionsand forward-looking statements are subject tovarious risks and uncertainties (many of whichare difficult to predict and generally beyond thecontrol of Sanofi) that could cause actualresults and developments to differ materiallyfrom those expressed or implied. These risksand uncertainties include those discussedelsewhere in this letter, as well as in the filingsof Sanof i wi th the U.S. Secur i t ies andExchange Commission (SEC) and the FrenchAutorité des marchés financiers (AMF), notablyunder the caption “Risk Factors” in thecompany’s annual report on Form 20-F. Otherthan as required by applicable law, Sanofi doesnot undertake any obligation to update anystatement that is not a historical fact.

Design and production: Signature Graphique Photographs: Page 1: Nicolas Dohr, Marthe LemellePage 2 and 3: Romain Baltz

The Letter to Shareholders is published by Sanofi Investor Relations / Shareholder Relations 174 Avenue de France – 75013 Paris – France www.sanofi.com/shareholders Status: September 8, 2011

SHARE PERFORMANCE 6

Listed on Euronext Paris: member code SAN / ISIN code FR 0000120578 Listed on the New York Stock Exchange in the form of American Depositary Shares (1 ADS = 0.5 share): ticker SNY / CUSIP 80105N105000

SHARE PRICE TREND SINCE SEPTEMBER 1, 2010 - PARIS60

55

50

45

40

35

SANOFI CAC 40

09/1/10 10/1/10 11/1/10 12/1/10 01/1/11 02/1/11 03/1/11 04/1/11 05/1/11 06/1/11 07/1/11 08/1/11 09/1/11

Between September 1, 2010 and September 8, 2011, Sanofi shares were up by 5.7%. During thisperiod, the CAC 40 was down 14.8%.CAC 40 rebased on the Sanofi share price - Source: Bloomberg

VISIT OUR NEW WEB SITE WWW.SANOFI.COM

The relaunch of our corporate Website takes into account the latest trends in Web Communicationsto emphasize our strategy and our focus on patients. It illustrates the company’s overall commitmentof becoming a diversified healthcare company, focused on patients’ needs. The site’s design is alsomore modern and integrates Sanofi’s new visual identity.

The website’s ergonomics were simplified and divided into two main navigation principles: � One set of menu options provides access to information about the company, its strategy, research

and development, products and commitment to patients; � A second menu provides access to targeted sections of the site for investors and shareholders,

journalists, partners and job seekers.

The Individual Shareholders section is still accessible via the direct link: www.sanofi.com/shareholders

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