UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM 20-F

(Mark One)

OR

For the fiscal year ended December 31, 20092011

OR

OR

Date of event requiring this shell company report . . . . . . . . . . . . . . . . . . .

For the transition period from              to             

Commission File Number: 001-31368

Sanofi-AventisSanofi

(Exact name of registrant as specified in its charter)

N/A

(Translation of registrant’s name into English)

France

(Jurisdiction of incorporation or organization)

174, avenue de France, 7501354, Rue La Boétie, 75008 Paris, France

(Address of principal executive offices)

Karen Linehan, Senior Vice President Legal Affairs and General Counsel

174, avenue de France, 7501354, Rue La Boétie, 75008 Paris, France. Fax: 011 + 33 1 53 77 43 0303. Tel: 011 + 33 1 53 77 40 00

(Name, Telephone, E-mail and/or Facsimile number and Address of Company Contact Person)

Securities registered or to be registered pursuant to Section 12(b) of the Act:

Securities registered pursuant to Section 12(g) of the Act:None

American Depositary Shares, each representing one quarter of a Participating Share Series A, par value €70.89 per share (removed from listing and registration on the New York Stock Exchange effective July 31, 1995).

The number of outstanding shares of each of the issuer’s classes of capital or

common stock as of December 31, 20092011 was:

Ordinary shares:    1,318,479,0521,340,918,811

Indicate by check mark if the registrant is a well-known seasoned issuer, as defined in Rule 405

of the Securities Act.

YES  x    NO  ¨.

If this report is an annual or transition report, indicate by check mark if the registrant is not

required to file reports pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934.

YES  ¨    NO  x.

Note — Checking the box above will not relieve any registrant required to file reports pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 from their obligations under those Sections.

Indicate by check mark whether the registrant (1) has filed all reports required to be filed by Section 13 or 15(d) of the Securities Exchange Act of 1934 during the preceding 12 months (or for such shorter period that the registrant was required to file such reports), and (2) has been subject to such filing requirements for the past 90 days.

Yes  x    No  ¨

Indicate by check mark whether the registrant has submitted electronically and posted on its corporate Web site, if any, every Interactive Data File required to be submitted and posted pursuant to Rule 405 of Regulation S-T (§232.405 of this chapter) during the preceding 12 months (or for such shorter period that the registrant was required to submit and post such files).

Yes  x    No  ¨

Indicate by check mark whether the registrant is a large accelerated filer, an accelerated filer, or a non-accelerated filer. See definition of “accelerated filer and large accelerated filer” in Rule 12b-2 of the Exchange Act. (Check one):

Indicate by check mark which basis of accounting the registrant has used to prepare the financial statements included in this filing:

U.S. GAAP  ¨    International Financial Reporting Standards as issued by the International Accounting Standards Board  x        Other  ¨

If “Other” has been checked in response to the previous question, indicate by check mark which financial statement item the registrant has elected to follow.

Item 17  ¨        Item 18   ¨

If this is an annual report, indicate by check mark whether the registrant is a shell company (as defined in Rule 12b-2 of the Exchange Act).

YES  ¨        NO  x.

PRESENTATION OF FINANCIAL AND OTHER INFORMATION

The consolidated financial statements contained in this annual report on Form 20-F have been prepared in accordance with International Financial Reporting Standards (IFRS) as issued by the International Accounting Standards Board (IASB) and with IFRS as adopted by the European Union, as of December 31, 2009.2011.

Unless the context requires otherwise, the terms “sanofi-aventis,“Sanofi,” the “Company,” the “Group,” “we,” “our” or “us” refer to sanofi-aventisSanofi and its consolidated subsidiaries.

All references herein to “United States” or “U.S.” are to the United States of America, references to “dollars” or “$” are to the currency of the United States, references to “France” are to the Republic of France, and references to “euro” and “€” are to the currency of the European Union member states (including France) participating in the European Monetary Union.

Brand names appearing in this annual report are trademarks of sanofi-aventisSanofi and/or its affiliates, with the exception of:

Not all trademarks related to investigational agents have been authorized as of the date of this annual report by the relevant health authorities; for instance Lyxumia^® and Aubagio^™ trade names have not been approved by the FDA.

The data relative to market shares and ranking information for pharmaceutical products presented in particular in “Item 4. Information on the Company — B. Business Overview — Markets — Marketing and distribution” are based on sales data from IMS Health MIDAS (IMS), retail and hospital, for calendar year 2009,2011, in constant euros (unless otherwise indicated).

While we believe that the IMS sales data we present below are generally useful comparative indicators for our industry, they may not precisely match the sales figures published by the companies that sell the products (including our company and other pharmaceutical companies). In particular, the rules used by IMS to attribute the sales of a product covered by an alliance or license agreement do not always exactly match the rules of the agreement.

In order to allow a reconciliation with our basis of consolidation as defined in “Item 5. Operating and Financial Review and Prospects — Presentation of Net Sales,” IMS data shown in the present document have been adjusted and include:

Data relative to market shares and ranking information presented herein for our vaccines business are based on internal estimates unless stated otherwise.

Product indications described in this annual report are composite summaries of the major indications approved in the product’s principal markets. Not all indications are necessarily available in each of the markets in which the products are approved. The summaries presented herein for the purpose of financial reporting do not substitute for careful consideration of the full labeling approved in each market.

CAUTIONARY STATEMENT REGARDING FORWARD-LOOKING STATEMENTS

This annual report contains forward-looking statements. We may also make written or oral forward-looking statements in our periodic reports to the Securities and Exchange Commission on Form 6-K, in our annual report to shareholders, in our offering circulars and prospectuses, in press releases and other written materials and in oral statements made by our officers, directors or employees to third parties. Examples of such forward-looking statements include:

Words such as “believe,” “anticipate,” “plan,” “expect,” “intend,” “target,” “estimate,” “project,” “predict,” “forecast,” “guideline,” “should” and similar expressions are intended to identify forward-looking statements but are not the exclusive means of identifying such statements.

Forward-looking statements involve inherent, known and unknown, risks and uncertainties. uncertainties associated with the regulatory, economic, financial and competitive environment, and other factors that could cause future results and objectives to differ materially from those expressed or implied in the forward-looking statements. The list below indicates some of the risk factors faced by the Company:

We caution you that the foregoing list of risk factors is not exclusive and a number of important factors, discussed under “Item 3. Key Information — D. Risk Factors” below, could affect the future results and cause actual results to differ materially from those contained in any forward-looking statements. Such factors, some of which are discussed under “Item 3. Key Information — D. Risk Factors” below, include but areAdditional risks, not limited to:

We caution you that the foregoing list of factors is not exclusive and that other risks and uncertainties may cause actual results to differ materially from those in forward-looking statements.investment.

Forward-looking statements speak only as of the date they are made. Other than required by law, we do not undertake any obligation to update them in light of new information or future developments.

TABLE OF CONTENTS

PART I

Item 1. Identity of Directors, Senior Management and Advisers

N/A

Item 2. Offer Statistics and Expected Timetable

N/A

Item 3. Key Information

A. Selected Financial Data

SUMMARY OF SELECTED FINANCIAL DATA

The tables below set forth selected consolidated financial data for sanofi-aventis.Sanofi. These financial data are derived from the sanofi-aventisSanofi consolidated financial statements. The sanofi-aventisSanofi consolidated financial statements for the years ended December 31, 2009, 20082011, 2010 and 20072009 are included in Item 18 of this annual report.

The consolidated financial statements of sanofi-aventisSanofi for the years ended December 31, 2009, 20082011, 2010 and 20072009 have been prepared in compliance with IFRS issued by the International Accounting Standards Board (IASB) and with IFRS adopted by the European Union.Union as of December 31, 2011. The term “IFRS” refers collectively to international accounting and financial reporting standards (IAS and IFRS) and to interpretations of the interpretations committees (SIC and IFRIC). mandatorily applicable as of December 31, 2011.

Sanofi-aventisSanofi reports its financial results in euros.

SELECTED CONDENSED FINANCIAL INFORMATION

SELECTED EXCHANGE RATE INFORMATION

The following table sets forth, for the periods and dates indicated, certain information concerning the exchange rates for the euro from 20052007 through February 2010March 2012 expressed in U.S. dollardollars per euro. The information concerning the U.S. dollar exchange rate is based on the noon buying rate in New York City for cable transfers in foreign currencies as certified for customs purposes by the Federal Reserve Bank of New York (the “Noon Buying Rate”). We provide the exchange rates below solely for your convenience. We do not represent that euros were, could have been, or could be, converted into U.S. dollars at these rates or at any other rate. For information regarding the effect of currency fluctuations on our results of operations, see “Item 5. Operating and Financial Review and Prospects” and “Item 11. Quantitative and Qualitative Disclosures about Market Risk.”

On March 10, 20105, 2012 the European Central Bank Rate was 1.36101.3220 per euro.

B. Capitalization and Indebtedness

N/A

C. Reasons for Offer and Use of Proceeds

N/A

D. Risk Factors

Important factors that could cause actual financial, business, research or operating results to differ materially from expectations are disclosed in this annual report, including without limitation the following risk factors and the factors described under “Cautionary Statement Regarding Forward-Looking Statements.”Statements”. In addition to the risks listed below, we may be subject to other material risks that as of the date of this report are not currently known to us or that we deem immaterial at this time.

Risks Relating to Legal Matters

Generic versions of someWe rely on our patents and proprietary rights to provide exclusive rights to market certain of our products, may be approved for sale in oneand if such patents and other rights were limited or more of their major markets.

Competitors may file marketing authorization requests for generic versions ofcircumvented, our products. Approval and market entry of a generic product would reduce the price that we receive for these products and/or the volume of the product that we would be able to sell, and could materially adversely affect our business,financial results of operations and financial condition. The market for our products could also be affected if a competitor’s innovative drug in the same market were to become available as a generic. Additionally, a number of our products acquired through business combinations have substantial balance sheet carrying values, as disclosed at Note D.4. to our consolidated financial statements, which could be substantially impaired by the introduction of a generic competitor, with adverse effects on our financial conditionmaterially and the value of our assets.adversely affected.

Through patent and other proprietary rights such as supplementary protection certificate in Europe for instance, we hold exclusivity rights for a number of our research-based products. However, the patent protection that we are able to obtain varies from product to product and country to country and may not be sufficient including to maintain effective product exclusivity. Furthermore weexclusivity because of local variations in the patents, differences in national law or legal systems, development in law or jurisprudence, or inconsistent judgments. We are involved in litigation worldwide to enforce certain of these patent rights against generics and proposed generics (see Note D.22.b) to our consolidated financial statements included in this annual report at Item 18“Item 8. Financial Information — A. Consolidated Financial Statements and Other Financial Information — Information on Legal or Arbitration Proceedings” for additional information). Moreover, patent rights are limited in time and do not always provide effective protection for our products: competitors may successfully avoid patents through design innovation, we may not hold sufficient evidence of infringement to bring suit, or our infringement claim may not result in a decision that our rights are valid, enforceable or infringed. Moreover, a number of countries are increasingly easing the introduction of generic drugs or biosimilar products through accelerated approval procedures.

Moreover, evenEven in cases where we do ultimately prevail in our infringement claim, legal remedies available for harm caused to us by infringing products may be inadequate to make us whole. A competitor may launch a generic product “at risk” before the initiation or completion of the court proceedings, and the court may decline to grant us a preliminary injunction to halt further “at risk” sales and remove the infringing product from the market. Additionally, while we would be entitled to obtain damages in such a case, the amount that we may ultimately be awarded and able to collect may be insufficient to compensate all harm caused to us.

Finally,Further, our successful assertion of a given patent against one competing product is not necessarily predictive of our future success or failure in asserting the same patent against a second competing product because of such factors as possible differences in the formulations of the competing products, intervening developments in law or jurisprudence, or inconsistent judgments. Moreover, patents differ from country to country andformulations. Also a successful result in one country may not predict success in another country because of local variations in the patents and differences in national law or legal systems.patents.

A numberTo the extent valid third-party patent rights cover our products, we or our partners may be required to obtain licenses from the holders of these patents in order to manufacture, use or sell these products, and payments under these licenses may reduce our profits from these products. We may not be able to obtain these licenses on favorable terms, or at all. If we fail to obtain a required license or are unable to alter the Group’sdesign of our technology to fall outside the scope of a third-party patent, we may be unable to market some of our products, are already subject to aggressive generic competition (in particular, in the United States where legislative initiatives to further facilitate the introduction of generic drugs or comparable biologic products through accelerated approval procedureswhich may create further challenges) and additional products of the Group could become subject to generic competition in the future. A few particularly significant products sold by the Group that may face the risk of generic competition in a major market as early as 2010 are described below:limit our profitability.

•

If we do not obtain pediatric exclusivity, Taxotere® may face generic competition in the United States starting in May 2010 (upon expiration of the patent protecting the active ingredient). Furthermore, even though we have secondary formulation patents with later expiration dates, it is not certain that we would be successful in asserting them against a competing product (see Note D.22.b) to the consolidated financial statements included at Item 18 of this annual report).

Product liability claims could adversely affect our business, results of operations and financial condition.

Product liability is a significant business risk for us, notably inany pharmaceutical company, and the United States where product liability claims can be particularly costly. The Group’s recent acquisitions mayongoing diversification could increase our product liability exposure (see “Thenotably “— The diversification of the Group’s business exposes us to additional risks” below). Substantial damage awards and/or settlements have been made — notably in certainthe United States and other common law jurisdictions — against pharmaceutical companies based uponon claims for injuries allegedly caused by the use of their products. Not all possibleSuch claims can also be accompanied by consumer fraud claims by customers or third-party payers seeking reimbursement of the cost of the product. Often the side effectseffect profile of a product canpharmaceutical drugs cannot be anticipatedfully established based on preapproval clinical studies involving only several hundred to several thousand patients. Routine review and analysis of the continually growing body of post-marketing safety surveillance and clinical trials provide additional information — for example, potential evidence of rare, population-specific or long-term adverse reactions or of drug

interactions that were not observed in preapproval clinical studies — and may cause product labeling to evolve, restrictionincluding restrictions of therapeutic indications, new contraindications, warnings or precautions, and potentiallyoccasionally even the suspension or withdrawal of a product. See “Item 19. Exhibits — 99.1 Report of the Chairman of the Board of Directors for 2009” for further discussion of these issues.product marketing authorization. Several pharmaceutical companies have recalled or withdrawn products from the market because of actualnewly detected or suspected adverse reactions to their products, and currentlyas a result of such withdrawal now face significant product liability claims. We are currently defending a number of product liability claims (see Note D.22.a) to the consolidated financial statements included at Item 18 of this annual report) and there can be no assurance that the Group will be successful in defending against each of these claims or will not face additional claims in the future. Also our risk exposure also increased due to the fact that we are now commercializing some devices using new technologies which, in case of malfunction, could cause unexpected damages and trigger our liability (see “— We are increasingly dependent on information technologies and networks.” below).

Although we continue to insure parta portion of our product liability with third-party carriers, product liability coverage is increasingly difficult and costly to obtain, particularly in the United States, and in the future it is possible that self-insurance may become the sole commercially reasonable means available for managing the product liability financial risk of our pharmaceutical and vaccines businesses. The availability ofbusinesses (see “Item 4. Information on the Company — B. Business Overview — Insurance and Risk Coverage”). Due to insurance capacityconditions, even when the Group has insurance coverage, recoveries from insurers may also suffer from the possible effects of the global financial crisis on insurers that remain active in this market.not be totally successful. Moreover the insolvency of a carrier could negatively affect our ability to achieve the practical recovery of the coverage for which we have already paid a premium.

Product liability claims, regardless of their merits or the ultimate success of the Group’s defense, are costly, divert management attention, and may harm our reputation and can impact the demand for our products. Substantial product liability claims, if successful, could adversely affect our business, results of operations and financial condition.

Claims and investigations relating to competition law, marketing practices and competition lawpricing could adversely affect our business, results of operations and financial condition.

The marketing of our products is heavily regulated, and alleged failures to comply fully with applicable regulations could subject us to substantial fines, penalties and injunctive or administrative remedies, potentially leading to the imposition of additional regulatory controls or exclusion from government reimbursement programs. Sanofi-aventisSanofi and certain of its subsidiaries are under investigation by various government entities and are defending a number of lawsuits relating to antitrust and/or pricing and marketing practices, including, for example in the United States, class action lawsuits and whistle blower litigation. See Note D.22.c) to our consolidated financial statements included at Item 18 of this annual report.

Because many of these cases allege substantial unquantified damages, may be subject to treble damages and frequently seek significant punitive damages and penalties, it is possible that any final determination of liability or settlement of these claims or investigations could have a material adverse effect on our business, results of operations or financial condition.

There are other legal matters in which adverse outcomes could have a material adverse effect on our business, results of operations and financial condition.

The Group faces significant litigation and government investigations or audits, including allegations of securities law violations, claims related to employment matters, patent and intellectual property disputes, consumer law claims and tax audits.

Unfavorable outcomes in these matters, or in similar matters to be faced in the future, could preclude the commercialization of products, negatively affect the profitability of existing products and subject us to substantial fines, penalties and injunctive or administrative remedies, potentially leading to the imposition of additional regulatory controls or exclusion from government reimbursement programs. Any such result could materially and adversely affect our results of operations, financial condition, or business. See “Item 8. Financial Information — A. Consolidated Financial Statements and Other Financial Information — Information on Legal or Arbitration Proceedings” and Note D.22. to our consolidated financial statements included at Item 18 of this annual report.

Changes in the laws or regulations that apply to us could affect the Group’s business, results of operations and financial condition.

Governmental authorities are increasingly looking to facilitate generic and biosimilar competition to existing products through new regulatory proposals intended to, or resulting in, within the major markets, changes to the scope of patent rights or data exclusivity rules.rights and use of accelerated regulatory pathways for generic and biosimilar drug approvals. Such regulatory proposals, if enacted, could make prosecution of patents for new products more difficult and time consuming or could adversely affect the exclusivity period for our products, thereby materially and adversely affecting our financial results.

This new competitive environment and potential regulatory changes may further limit the exclusivity enjoyed by innovative products on the market and directly impact pricing and reimbursement levels, which may adversely affect our business and future results. See “Item 4. Information on the Company — B. Business Overview — Competition” and “—“Item 4. Information on the Company — B. Business Overview — Regulation”.

In addition, changes in tax laws or in their application with respect to matters such as tax rates, transfer pricing, dividends, controlled companies or a restriction in certain forms of tax relief, could affect our effective tax rate and our future results.

For more information regarding risks related to changes in environmental rules and regulations, see “— Environmental Risks of our Industrial Activities — Environmental liabilities and compliance costs may have a significant adverse effect on our results of operations” below.

Risks Relating to Our Business

Generic versions of some of our products may be approved for sale in one or more of their major markets.

Many of our products are subject to aggressive generic competition, and additional products of the Group could become subject to generic competition in the future as product patents and/or exclusivities for several of our products have recently expired, or are about to expire. For example pediatric exclusivity for Aprovel^® and Plavix^® which contribute significantly to our net income will expire in the United States in March 2012 and May 2012, respectively, and the compound patent of Aprovel^® will expire in most of the European Union in August 2012. Also, the U.S. market exclusivity of Eloxatin^® will expire in August 2012, pursuant to settlement agreements. We expect this generic competition to continue and to implicate drug products with even relatively modest revenues.

The introduction of a generic version of a branded medicine typically results in a significant and rapid reduction in net sales for the branded product because generic manufacturers typically offer their unbranded versions at sharply lower prices. Accordingly, approval and market entry of a generic product often reduces the price that we receive for these products and/or the volume of the product that we would be able to sell and could materially and adversely affect our business, results of operations and financial condition. The extent of sales erosion also depends on the number of generic versions of our products that are actually marketed. For instance in 2011, there was only one generic product of enoxaparin sodium (Lovenox^®) marketed in the United States. The introduction of a second generic on the U.S. market in early 2012 is likely to decrease our sales and revenues on this product.

Our long-term objectives may not be fully realized.

We have established a strategy focused on three pillars: increased innovation in R&D, adaptation of our structure for future opportunities and challenges and pursuit of external growth opportunities. We may not be able to fully realize our strategic objectives and, even if we are able to do so, these strategic objectives may not deliver the expected benefits.

For example, our strategy involves concentrating efforts around identified growth platforms and meeting significant growth objectives over 2012-2015. There is no guarantee that we will meet these objectives or that these platforms will grow in line with anticipated growth rates. A failure to continue to expand our business in targeted growth platforms could affect our business, results of operations or financial condition.

As a further example, we are implementing a cost savings program across the Group and expect this new initiative, together with expected synergies from our recent acquisition of Genzyme, to generate additional incremental cost savings by 2015. We may fail to realize all the expected cost savings, which could materially and adversely affect our financial results.

We may fail to adequately renew our product portfolio whether through our own research and development or through the making of acquisitions orand strategic alliances.

To be successful in the highly competitive pharmaceutical industry, we must commit substantial resources each year to research and development in order to develop new products to take the place of products facing expiration of patent and regulatory data exclusivity or competition from new products that are perceived as being superior. In 2009,2011, we spent €4,583€4,811 million on research and development, amounting to approximately 15.6%14.4% of our net sales.

Developing a product is a costly, lengthy and uncertain process. Also we may not be investing in the right technology platforms, leading therapeutic area, and products classes in order to build a robust pipeline and fulfill unmet medical needs. Fields of discovery and especially biotechnology are highly competitive and characterized by significant and rapid technological changes. Numerous companies are working on the same targets and a product considered as promising at the very beginning may become less attractive if a competitor showing the same mechanism of action reaches earlier the market.

The research and development process typically takes from 10 to 15 years from discovery to commercial product launch. This process is conducted in various stages in order to test, along with other features, the effectiveness and safety of a product. There can be no assurance that any of these compounds will be proven safe or effective. See “Item 4. Information on the Company — B. Business Overview — Pharmaceutical Research & Development” and “—“Item 4. Information on the Company — B. Business Overview — Vaccines Research and Development”. Accordingly, there is a substantial risk at each stage of development that we will not achieve our goals of safety and/or effectiveness including during the course of a development trial and that we will have to abandon a product in which we have invested substantial amounts and human resources, including in late stage development (Phase III). Decisions concerning the studies to be carried out can have a significant impact on the marketing strategy for a given product. Multiple in-depth studies can demonstrate that a product has additional benefits, facilitating the product’s marketing, but such studies are expensive and time consuming and may delay the product’s submission to health authorities for approval.

Our ongoing investments in new product launches and research and development for future products could therefore result in increased costs without a proportionate increase in revenues. Furthermore eachrevenues which may negatively affect our operating results. Each regulatory authority may also impose its own requirements in order to grant a license to market the product, including requiring local clinical studies, and may delay or refuse to grant approval, even though a product has already been approved in another country. Finally, obtaining regulatory marketing approval is not a guarantee that the product will achieve commercial success.

Also our success depends on our ability to educate patients and healthcare providers and provide them with innovative data about our products and their uses. If these education efforts are not effective, then we may not be able to increase the sales of our new products to the market.

On the same topic, for the research and development of drugs in rare diseases, we produce relatively small amounts of material at early stages. Even if a product candidate receives all necessary approvals for commercialization, we may not be able to successfully scale-up production of the product material at a reasonable cost or at all and we may not receive additional approvals in sufficient time to meet product demand.

As a complement to itsour portfolio of products, sanofi-aventis pursueswe pursue a strategy of selective acquisitions, in-licensing and partnerships in order to develop new growth opportunities. The implementation of this strategy depends on our ability to identify business development opportunities at a reasonable cost and under acceptable conditions of

financing. Moreover, entering into these in-licensing or partnership agreements generally requires the payment of significant “milestones” well before the relevant products are possibly placed on the market without any assurance that such investments will ultimately become profitable in the long term.

Because of the active competition among pharmaceutical groups for such business development opportunities, there can be no assurance of our success in completing these transactions when such opportunities are identified.

A substantial share of the revenue and income of sanofi-aventis dependsthe Group continues to depend on the performance of certain flagship productsproducts.

Sanofi-aventis generatesWe generate a substantial share of itsour revenues from the sale of certain key products (see “Item 5. Operating and Financial Review and Prospects — Results of Operations — Year ended December 31, 2011 compared with year ended December 31, 2010 — Net Sales by Product — Pharmaceuticals”), which represented 45.3%37.6% of the Group’s consolidated revenues in 2009.2011. Among these products is Lantus^®, which in 2009, becamewas the Group’s leading product with revenues of €3,080€3,916 million in 2011, representing 10.5%11.7% of the Group’s consolidated revenues.revenues for the year. Lantus^® is a flagship product of the Diabetes division, one of the Group’s recognized growth platforms. A reduction in

Sales of Cerezyme^®, our enzyme-replacement product for patients with Gaucher disease which is also amongst our flagship products, totaled €441 million for the year ended December 31, 2011, below the usual level of sales due to important production disruptions since 2009 (see “— The manufacture of our products is technically complex, and supply interruptions, product recalls or inventory losses caused by unforeseen events may reduce sales, adversely affect our operating results and financial condition and delay the launch of new products.” below). In addition the patient population with Gaucher disease is limited. Furthermore, changes in the methods for treating patients with such disease could limit growth, ofor result in a decline, in Cerezyme^® sales.

In general, a reduction in sales of one or more of theseour flagship products (in particular sales of Lantus^®)or in their growth could affect theour business, the results of operations and the financial condition of sanofi-aventis.condition.

We may lose market share to competing low-cost remedies or generic brands if they are perceived to be equivalent or superior products.

We are faced with intense competition from generic products and brand-name drugs. Doctors or patients may choose these products over ours if they perceive them to be safer, more reliable, more effective, easier to administer or less expensive, which could cause our revenues to decline and affect our results of operations.

For example, Cerezyme^® and Fabrazyme^® shortages due to manufacturing issues at our facility in Allston, Massachusetts (United-States) (see “— The manufacture of our products is technically complex, and supply interruptions, product recalls or inventory losses caused by unforeseen events may reduce sales, adversely affect our operating results and financial condition and delay the launch of new products.” below) created, and continue to create, opportunities for our competitors and have resulted in a decrease in the number of patients using these products and a loss of our overall market share of Gaucher and Fabry patients, respectively. Even if we are able again to provide a full, sustainable product supply, there is no guarantee these patients will return to using our products.

Additionally, the market for our products could also be affected if a competitor’s innovative drug in the same market were to become available as generic because a certain number of patients can be expected to switch to a lower-cost alternative therapy.

The diversification of the Group’s business exposes us to additional risks.

We have undertaken to transform our Group byare implementing a strategy that includes pursuing external growth opportunities to meet the challenges that we have identified for the future. The inability to quickly or efficiently integrate newly acquired activities or businesses, such as Genzyme, the loss of key employees or integration costs that are higher than anticipated, could delay our growth objectives and prevent us from achieving expected synergies. For instance, challenges that we may face in our efforts to integrate Genzyme include, among others:

If we fail to effectively integrate Genzyme or the integration takes longer than expected, we may not achieve the expected benefits of the transaction.

Moreover, we may miscalculate the risks associated with these entitiesnewly acquired activities or businesses at the time they are acquired or not have the means to evaluate them properly. It may take a considerable amount of time and be difficult to implement a risk analysis after the acquisition is completed due to lack of historical data. As a result, risk management and the coverage of such risks, particularly through insurance policies, may prove to be insufficient or ill-adapted.

In addition toWhile pursuing our objective to become a global and diversified leader within the health industry, we are exposed to a number of new risks inherent in sectors in which, in the past, we have been either less active or entirely inactive.not present at all. As an example, we have increased exposure to the animal health business. The contribution of our animal health business to the Group’s income may be adversely affected by a number of risks including some which are specific to this business: i.e., the outbreak of an epidemic or pandemic that could kill large numbers of animals, and the effect of reduced veterinary expenditures during an economic crisis. In some of these sectors example:

Moreover, losses that may be sustained or caused by these new businesses may differ, with regards to their nature, scope and level, from the types of product liability claims that we have handled in the past (See(see “— Product liability claims could adversely affect our business, results of operations and financial condition” above), and thus our current risk management and insurance coverage may not be adapted to such losses. These risks could affect our business, results of operations or financial condition.

The globalization of the Group’s business exposes us to increased risks.

Emerging markets have been identified as one of our growth platforms and are among the pillars of our overall strategy. Any difficulties in adapting to emerging markets and/or a significant decline in the anticipated growth rate in these regions could impair our ability to take advantage of these growth opportunities and could affect our business, results of operations or financial condition.

There is no guarantee that our efforts to expand sales in emerging markets will succeed. The significant expansion of our activities in emerging markets may further expose us to more volatile economic conditions, political instability, competition from companies that are already well established in these

markets, the inability to adequately respond to the unique characteristics of these markets, particularly with respect to their regulatory frameworks, difficulties in recruiting qualified personnel, potential exchange controls, weaker intellectual

property protection, higher crime levels (particularly with respect to counterfeit products (see “— Risks Relating to Our Business — Counterfeit versions of our products could harm our business”business,” below)), corruption and fraud. Any difficultiesfraud, as we operate in adaptingmany parts of the world where corruption exists to some degree.

Our existing policies and procedures, which are designed to help ensure that we, our employees and our agents comply with the U.S. Foreign Corrupt Practices Act ( FCPA), the UK Bribery Act, and other anti-bribery laws, may not adequately protect us against liability under these marketslaws for actions taken by our employees, agents and intermediaries with respect to our business. Failure to comply with domestic or international laws could impair our abilityresult in various adverse consequences, including possible delay in the approval or refusal to take advantageapprove a product, recalls, seizures, withdrawal of these growth opportunities and could affect our business, resultsan approved product from the market, or the imposition of operationscriminal or financial condition.civil sanctions, including substantial monetary penalties.

The regulatory environment is increasingly challenging forOur products and manufacturing facilities are subject to significant government regulations and approvals, which are often costly and could result in adverse consequences to our business if we fail to comply with the pharmaceutical industry.regulations or maintain the approvals.

The industry in which we operate faces a changing regulatory environment and heightened public scrutiny worldwide, which simultaneously require greater assurances than ever as to the safety and efficacy of medications and health products on the one hand, and effectively provide reduced incentives for innovative pharmaceutical research on the other hand.

Health authorities, inare increasingly focusing on product safety and on the risk/benefit profile of pharmaceuticals products. In particular, the U.S. Food and Drug Administration (FDA)FDA and the European Medicines Agency (EMA) have imposed increasingly burdensome requirements on pharmaceutical companies, particularly in terms of the volume of data needed to demonstrate a product’s efficacy and safety. MarketedFor the same reasons, the marketed products are also subject to continual review, risk evaluations or comparative effectiveness studies even after regulatory approval. See “Item 19. Exhibit — 99.1 Report ofThese requirements have resulted in increasing the Chairman of the Board of Directorscosts associated with maintaining regulatory approvals and achieving reimbursement for 2009” for a further discussion of these issues. our products.

Later discovery of previously undetected problems may result in marketing restrictions or the suspension or withdrawal of the product, as well as an increased risk of litigation for both pharmaceutical and animal health products. These post-regulatory approval reviews and data analyses can lead to the issuance of recommendations by government agencies, health professional and patient organizations or other specialized organizations regarding the use of products, which may result in a reduction in sales volume, such as, for example, a recommendation to limit the patient scope of a drug’s indication. For instance in September 2011, the EMA defined a more restrictive indication for Multaq^®, one of our cardiovascular products. Such reviews may result in the discovery of significant problems with respect to a competing product that is similar to one sold by the Group, which may in turn cast suspicion on the entire class to which these products belong and ultimately diminish the sales of the relevant product of the Group. When such issues arise, the contemplative nature of evidence-based health care and restrictions on what pharmaceutical manufacturers may say about their products are not always well suited to rapidly defending the Group or the public’s legitimate interests in the face of the political and market pressures generated by social media and rapid news cycles, and this may result in unnecessary commercial harm, overly restrictive regulatory actions and erratic share price performance.

ToIn addition, to the extent that new regulations raise the costs of obtaining and maintaining product authorization, or limit the economic value of a new product to its inventor, the growth prospects of our industry and of our Companythe Group are diminished. Also about 50% of our current research and development portfolio is constituted by biological products, that may bring in the future new therapeutic responses to current unmet medical needs but which may also lead to more technical constraints and costly investments from an industrial standpoint.

Moreover, we and certain of our third-party suppliers are also required to comply with applicable regulations, known as good manufacturing practices, which govern the manufacture of pharmaceutical products. To monitor our compliance with those applicable regulations, the FDA, the EMA and comparable agencies in other jurisdictions routinely conduct inspections of our facilities and may identify potential deficiencies which might be expensive and time consuming to address. If we fail to adequately respond to a warning letter

identifying a deficiency, or otherwise fail to comply with applicable regulatory requirements, we could be subject to enforcement, remedial and/or punitive actions by the FDA, the EMA or other regulatory authorities.

For example, in May 2010, Genzyme entered into a consent decree with the FDA relating to its Allston facility (see “Item 4. Information on the Company — B. Business Overview — Production and Raw Materials.”). Pursuant to the consent decree, in November 2010, Genzyme paid $175.0 million to the U.S. Federal Governement disgorgement of past profits. The consent decree also requires Genzyme to implement a plan to bring the Allston facility into compliance with applicable laws and regulations. Genzyme submitted a comprehensive remediation plan to FDA in April 2011. Remediation of the Allston facility in accordance with that plan is underway and is currently expected to continue for four more years, however, there is no guarantee that this timeframe will be respected.

We incurred substantial debt in connection with the acquisition of Genzyme which may limit our business flexibility compared to some of our peers

Our consolidated debt increased substantially in connection with our acquisition of Genzyme because we incurred debt to finance the acquisition price, and because our consolidated debt includes the debt incurred by Genzyme prior to the acquisition. Although we already achieved a partial deleverage by the end of 2011 (as of December 31, 2011, our debt, net of cash and cash equivalents amounted to €10.9 billion), we make significant debt service payments to our lenders and this could limit our ability to engage in new transactions which could have been part of our strategy.

We face uncertainties over the pricing and reimbursement of pharmaceutical products.

The commercial success of our existing products and our products candidates depends in part on the conditions under which our products are reimbursed. Pressure on pricing and reimbursement is strong due to:

In addition to the pricing pressures they exert, stategovernmental and private third-party payers and purchasers of pharmaceutical products may reduce volumes of sales by restricting access to formularies or otherwise discouraging physician prescriptions of our products. In the United States, the Democrats, who currently hold the majority in Congress and the presidency, have introduced ahealth care reform proposal designed to increaselaw is increasing the government’s role in determining thewith respect to price, reimbursement and the coverage levels for healthcare-related expenses. This proposal includes notably provisions seeking to expandexpenses for the large government health care sector, imposed cost containment measures and increaseimposed drug companies’ rebates to create an independent body to reduce expenditures,the government. Implementation of health care reform has affected and to reinforce the authority of the government agency responsible for regulating and funding Medicaid and Medicare in particular to experiment with various payments schemes. Since this reform is currently under discussion, its scope and practical implications, in particular for the pharmaceutical industry, are uncertain. Nevertheless, its purpose, which is to reduce healthcare-related expenses and to prevent them from increasing, could result in a decrease instill affect our revenues and/or margins of sanofi-aventis, which could in turn affect its business, operating results, and financial condition (for further details concerning this reform projectlaw and a description of certain regulatory pricing systems that affect our Group see “Item 4. Information on the Company — B. Business Overview — Markets — Pricing & Reimbursement”). Some states are also considering legislation that would control the prices of and access to drugs and we believe that federal and state legislatures and health agencies will continue to focus on healthcare reform implementation in the future.

We encounter similar cost containment issues in countries outside the United States. In certain countries, including countries in the EU and Canada, the coverage of prescription drugs, pricing and levels of reimbursement are subject to governmental control. For example, in Spain, recent direct price-related measures include price discount to all products launched more than 10 years ago, all genericized products needing to be at a minor (lower) price, and no more gradualism in price reductions of originator post generics introduction. Additionally, measures such as INN prescriptions, have been implemented. Another example, in Turkey Government has accelerated enforcement of drugs costs containment measures which include increased institutional discount applied on reimbursement prices and lower reference prices for reimbursement of Generics and originals with Generics as well as 20-year old drugs without Generics.

Due to the ongoing cost containment policies being pursued in many jurisdiction in which we operate, we are unable to predict the availability or amount of reimbursement for our product candidates.

In addition, our operating results may also be affected by parallel imports, particularly within the European Union, whereby distributors engage in arbitrage based on national price differences to buy product on low cost markets for resale on higher cost markets.

AThe ongoing slowdown of global economic growth and the financial crisis could have negative consequences for our business.business⁽¹⁾¹.

Over the past several years, growth of the global pharmaceutical market has become increasingly tied to global economic growth. In this context, a substantial and lasting slowdown of the global economy or major national economies could negatively affect growth in the global pharmaceutical market and, as a result, adversely affect our business. This effect may be expected to be particularly strong in markets having significant co-pays or lacking a developed third-party payer system, as individual patients may delay or decrease out-of-pocket healthcare expenditures. Such a slowdown could also reduce the sources of funding for national social security systems, leading to heightened pressure on drug prices, increased substitution of generic drugs, and the exclusion of certain products from formularies.

Additionally, to the extent the slowing economic environment, as well as ongoing sovereign debt crisis affecting several European countries, may lead to financial difficulties or even the default or failure of major players including wholesalers or public sector buyers financed by insolvent States, the Group could experience disruptions in the distribution of its products as well as the adverse effects described below at “— We“We are subject to the risk of non-payment by our customers.customers”. Moreover, to the extent that the economic and financial crisis is directly affecting business, it may also lead to a disruption or delay in the performance of third parties on which we rely for parts of our business, including collaboration partners and suppliers (for more information see “Item 5. Operating and Financial Review and Prospects — Liquidity.”

). Such disruptions or delays could have a material and adverse effect on our business and results of operations. See “— We rely on third parties for the manufacture and supply of a substantial portion of our raw materials, active ingredients and medical devices; supply disruptions and/or quality concerns could adversely affect our operating results and financial condition”, “We rely on third parties for the marketing of some of our products.products” and “ Fluctuations in currency exchange rates could adversely affect our results of operations and financial condition” below.

We marketFurther, we believe our net sales may be negatively impacted by the continuing challenging global economic environment, as high unemployment levels and increases in co-pays may lead some of ourpatients to switch to generic products, in collaboration with other pharmaceutical companies. For example, we currently have major collaborative arrangements with Bristol-Myers Squibb (BMS) for the marketing of Plavix^® and Aprovel^®delay treatments, skip doses or use less effective treatments to reduce their costs. Moreover, current economic conditions in the United States and several other countries, with Warner Chilcott forhave resulted in an increase in the osteoporosis treatment Actonel^®, with Teva for Copaxone^®, and with Merck & Co., Inc. fornumber of patients in the distributionMedicaid program, under which sales of vaccines in Europe. See “Item 4. Information on the Company — B. Business Overview”; our major alliances are detailed under “— Main pharmaceutical products”. When we market our products through collaboration arrangements, wepharmaceuticals are subject to substantial rebates and, in many U.S. states, to formulary restrictions limiting access to brand-name drugs, including ours.

Our animal health business may also be negatively affected by the risk that certain decisions, such ascurrent slowdown in global economic growth (for instance tight credit conditions may limit the establishmentborrowing power of budgets and promotion strategies, are subjectlivestock producers, causing some to the control of our collaboration partners, and that deadlocks may adversely affect the activities conducted through the collaboration arrangements. For example, our alliances with BMS are subjectswitch to the operational management of BMS in some countries, including the United States. Any conflicts that we may have with our partners may affect the marketing of certain of our products. Such difficulties may cause a decline in our revenues and affect our results of operations.lower-priced products).

The manufacture of our products is technically complex, and supply interruptions, product recalls or inventory losses caused by unforeseen events may reduce sales, delay the launch of new products and adversely affect our operating results and financial condition.condition and delay the launch of new products.

Many of our products are manufactured using technically complex processes requiring specialized facilities, highly specific raw materials and other production constraints. We must also be able to produce sufficient quantities of the products to satisfy demand. Our vaccinebiologic products (including vaccines) in particular are subject to the risk of manufacturing stoppages or the risk of loss of inventory because of the difficulties inherent to the sterile processing of biological materials and the potential unavailability of adequate amounts of raw materials meeting our standards. Additionally, specific conditions must be respected both by the Group and itsour customers for the storage and distribution of many of our products,e.g., cold storage for certain vaccines and insulin-based products. The complexity of these processes, as well as strict internal and government standards for the manufacture of our products, subject us to risks. The occurrence or suspected occurrence of out-of-specification

production or storage can lead to lost inventories, and in some cases product recalls, with consequential reputational damage and the risk of product liability (See(see “— Risks Relating to Legal Matters — Product liability claims could adversely affect our business, results of operations and financial condition”condition,” above). The investigation and remediation of any identified problems can cause production delays, substantial expense, lost sales and the delay of new product launches and can adversely affect our operating results and financial condition.

Like many of our competitors, we have faced, and to a certain extent continue to face, significant manufacturing issues, most notably in our Genzyme subsidiary for the production of Cerezyme^® and Fabrazyme^®. In June 2009, Genzyme announced it had detected a virus that impairs cell growth in one of the bioreactors used in the Allston, Massachusetts facility to produce Cerezyme^®. This contamination has had a material adverse effect on Cerezyme^® and Fabrazyme^® revenues. We will continue to work with minimal levels of inventory for Cerezyme^® and Fabrazyme^® until we are able to build inventory. However, there can be no guarantee that we will be able to return to pre-contamination supply levels of such products, nor can there be any guarantee that we will not face similar issues in the future or that we will successfully manage such issues when they arise.

We rely on third parties for the manufacture and supply of a substantial portion of our raw materials, active ingredients and medical devices.devices; supply disruptions and/or quality concerns could adversely affect our operating results and financial condition.

Third parties supply us with a substantial portion of our raw materials, active ingredients and medical devices, which exposes us to the risk of a supply interruption in the event that these suppliers experience financial difficulties or are unable to manufacture a sufficient supply of our products meeting Group quality standards. It also increases the risk of quality issues, even with the most scrupulously selected suppliers. For example, in 2008 we recalled a limited number of batches of Lovenox

^® and wrote down significant unused inventory following the discovery of quality issues at a Chinese supplier of raw materials. If disruptions or quality concerns were to arise in the third-party supply of raw materials, active ingredients or medical devices, this could adversely affect our ability to sell our products in the quantities demanded by the market and could damage our reputation and relationships with our customers. See also “— The manufacture of our products is technically complex, and supply interruptions, product recalls or inventory losses caused by unforeseen events may reduce sales, delay the launch of new products and adversely affect our operating results and financial condition”condition and delay the launch of new products” above. We may not have redundant manufacturing capacity for certain products particularly biologic products. For instance in summer 2011 a technical incident occurred in the filling line used for Apidra 3mL cartridges at our manufacturing site in Frankfurt and this has caused temporary shortages for Apidra 3mL cartridges. Also all of our bulk Cerezyme^® products are produced solely at our Allston, Massachusetts facility. Even though we aim to have backup sources of supply whenever possible, including by manufacturing backup supplies of our principal active ingredients at a second or third facility when practicable, we cannot be certain they will be sufficient if our principal sources become unavailable. Switching sources and manufacturing facilities may require significant time. Some

Further, some raw materials essential to the manufacture of our products are not widely available from sources we consider reliable; for example, we have approved only a limited number of suppliers of heparins for use in the manufacture of Lovenox^®. Heparin purchase prices can also fluctuate. See “Item 4. Information on the Company — B. Business Overview — Production and Raw Materials” for a description of these outsourcing arrangements. Any of these factors could adversely affect our business, operating results or financial condition.

We rely on third parties for the marketing of some of our products.

We market some of our products in collaboration with other pharmaceutical companies. For example, we currently have major collaborative arrangements with Bristol-Myers Squibb (BMS) for the marketing of Plavix^® and Aprovel^® in the United States and several other countries, with Warner Chilcott for the osteoporosis treatment Actonel^®, and with Merck & Co., Inc. for the distribution of vaccines in Europe. See “Item 4. Information on the Company — B. Business Overview — Pharmaceutical Products — Main pharmaceutical products” and “Item 4. Information on the Company — B. Business Overview — Vaccine Products” for more information on our major alliances. When we market our products through collaboration arrangements, we are subject to the risk that certain decisions, such as the establishment of budgets and promotion strategies, are subject to the control of our collaboration partners, and that deadlocks may adversely affect the activities conducted through the collaboration arrangements. For example, our alliances with BMS are subject to the operational management of BMS in some countries, including the United States. Any conflicts that

we may have with our partners during the course of these agreements or at the time of their renewal or renegotiation may affect the marketing of certain of our products and may cause a decline in our revenues and affect our results of operations.

Counterfeit versions of the Group’sour products could harm our business.

The drug supply has been increasingly challenged by the vulnerability of distribution channels to illegal counterfeiting and the presence of counterfeit products in a growing number of markets and over the Internet. Counterfeit products are frequently unsafe or ineffective, and can be potentially life-threatening. To distributors and users, counterfeit products may be visually indistinguishable from the authentic version. Reports of adverse reactions to counterfeit drugs or increased levels of counterfeiting could materially affect patient confidence in the authentic product, and could harm the business of companies such as sanofi-aventis.Sanofi. Additionally, it is possible that adverse events caused by unsafe counterfeit products will mistakenly be attributed to the authentic product. If a Group product werewas the subject of counterfeits, the Group could incur substantial reputational and financial harm. See “Item 4. Information on the Company — B. Business Overview — Competition.”

Use of biologically derived ingredients may face resistance from patients or the purchasers of these products, which could adversely affect sales and cause us to incur substantial costs.

In line with industry practice, we manufacture our vaccines and many of our prescription pharmaceutical products with ingredients derived from animal or plant tissue. We subject our products incorporating these ingredients to extensive tests and believe them to be safe. There have been instances in the past where the use of biologically derived ingredients by sanofi-aventis or its competitors has been alleged to be an actual or theoretical source of harm, including infection or allergic reaction, or instances where production facilities have been subject to prolonged periods of closure because of possible contamination. Such allegations have on occasion led to damage claims and increased resistance on the part of patients to such ingredients. A substantial claim of harm caused by a product incorporating biologically derived ingredients or a contamination event could lead us to incur potentially substantial costs as a result of, among other things, litigation of claims, product recalls, adoption of additional safety measures, manufacturing delays, investment in patient education, and development of synthetic substitutes for ingredients of biological origin. Such claims could also generate patient resistance, with a corresponding adverse effect on sales and results of operations.

We are subject to the risk of non-payment by our customers.⁽¹⁾¹

We run the risk of delayed payments or even non-payment by our customers, which consist principally of wholesalers, distributors, pharmacies, hospitals, clinics and government agencies. This risk is accentuated by the current worldwide financial crisis. The United States which is our largest market in terms of sales, poses particular client credit risk issues, because of the concentrated distribution system in which approximately 78%62% of our consolidated U.S. pharmaceutical sales wereare accounted for by just three wholesalers. In addition, the Group’s three main customers represent 22%17.4% of our gross total revenues. We are also exposed to large wholesalers in other markets, particularly in Europe. An inability of one or more of these wholesalers to honor their debts to us could adversely affect our financial condition (see Note D.34. to our consolidated financial statements included at Item 18 of this annual report).

Since the beginning of 2010, financial difficulties in some countries of southern Europe have increased especially in Greece and Portugal. Part of our customers in these countries are public or subsidized health systems. The deteriorating economic and credit conditions in these countries has led to longer payment terms. This trend may continue and we may need to reassess the recoverable amount of our debts in these countries during the coming financial years (for more information see “Item 5. Operating and Financial Review and Prospects — Liquidity.”).

Our pension liabilities are affected by factors such as the performance of plan assets, interest rates, actuarial data and experience and changes in laws and regulations.

Our future funding obligations for our main defined-benefit pension plans depend on changes in the future performance of assets held in trust for these plans, the interest rates used to determine funding levels (or company liabilities), actuarial data and experience, inflation trends, the level of benefits provided for by the plans, as well as changes in laws and regulations. Adverse changes in those factors could increase our unfunded obligations under such plans, which would require more funds to be contributed and hence negatively affect our cash flow and results (see Note D.18.1D.19.1 to our consolidated financial statements included at Item 18 of this annual report).

Impairment charges or write downs in our books and changes in accounting standards could have a significant adverse effect on the Group’s results of operations and financial results.

New or revised accounting standards, rules and interpretations issued from time to time by the IASB (International Accounting Standards Board) could result in changes to the recognition of income and expense that may materially and adversely affect the Group’s financial results.

In addition, substantial value is allocated to intangible assets and goodwill resulting from business combinations, as disclosed at Note D.4. to our consolidated financial statements included in this annual report at Item 18, which could be substantially impaired upon indications of impairment (primarily relating to pharmacovigilance, patent litigation and the launch of competing products), with adverse effects on our financial condition and the value of our assets.

Also if any of our strategic equity investments decline in value and remain below cost for an extended duration, we may be required to write down our investment.

In addition the global financial crisis and in particular the ongoing sovereign debt crisis affecting certain European countries could also negatively affect the value of our assets (see “— Fluctuations in currency exchange rates could adversely affect our results of operations and financial condition” below and “— The ongoing slowdown of global economic growth and the financial crisis could have negative consequences for our business” above). For example, given the current level of investor confidence in the ability of the Greek State to avoid default, as a result of mark to market accounting standards, we recognized an impairment of €49 million on certain Greek bonds held by us in 2011.

We are increasingly dependent on information technologies and networks.

Our business depends on the use of information technologies, which means that certain key areas such as research and development, production and sales are to a large extent dependent on our information technology capabilities. We are commercializing some devices using new technologies which, in case of malfunctions could lead to a misuse causing a risk of damages to patients (see “— Product liability claims could adversely affect our business, results of operations and financial condition” above). Our inability or the inability of our third-party service providers (for instance the accounting of some of our subsidiaries has been externalized) to implement adequate security and quality measures for data processing could lead to data deterioration or loss in the event of a system malfunction, or allow data to be stolen or corrupted in the event of a security breach, which could have a material adverse effect on our business, operating results and financial condition.

Natural disasters prevalent in certain regions in which we do business could affect our operations

Some of our production sites are located in areas exposed to natural disasters, such as earthquakes (in North Africa, Middle East, Asia, Pacific, Europe, Central and Latin Americas), floods (in Africa, Asia Pacific and Europe) and hurricanes. In the event of a major disaster we could experience severe destruction or interruption of our operations and production capacity. As a result, our operations could suffer serious harm which could have a material adverse effect on our business, financial condition and results of operations.

Environmental Risks of Our Industrial Activities

Risks from the handling of hazardous materials could adversely affect our results of operations.

Manufacturing activities, such as the chemical manufacturing of the active ingredients in our products and the related storage and transportation of raw materials, products and wastes, expose us to various risks, including:

These operating risks can cause personal injury, property damage and environmental contamination, and may result in:

The occurrence of any of these events may significantly reduce the productivity and profitability of a particular manufacturing facility and adversely affect our operating results.

Although we maintain property, business interruption and casualty insurance that we believe is in accordance with customary industry practices, we cannot assure you that this insurance will be adequate to cover fully all potential hazards incidental to our business.

Environmental liabilities and compliance costs may have a significant adverse effect on our results of operations.

The environmental laws of various jurisdictions impose actual and potential obligations on our Group to remediate contaminated sites. These obligations may relate to sites:

These environmental remediation obligations could significantly reduce our operating results. Sanofi-aventisSanofi accrues provisions for remediation when our management believes the need is probable and that it is reasonably possible to estimate the cost. See “Item 4. Information on the Company — B. Business Overview — Health, Safety and Environment (HSE)” for additional information regarding our environmental policies. In particular, our provisions for these obligations may be insufficient if the assumptions underlying these provisions prove incorrect or if we are held responsible for additional, currently undiscovered contamination. These judgments and estimates may later prove inaccurate, and any shortfalls could have a material adverse effect on our results of operations and financial condition.

Furthermore, we are or may become involved in claims, lawsuits and administrative proceedings relating to environmental matters. Some current and former sanofi-aventisSanofi’s subsidiaries have been named as “potentially responsible parties” or the equivalent under the U.S. Comprehensive Environmental Response, Compensation and Liability Act of 1980, as amended (also known as “Superfund”), and similar statutes in France, Germany, Italy, Brazil and elsewhere. As a matter of statutory or contractual obligation, we and/or our subsidiaries may retain responsibility for environmental liabilities at some of the sites of our predecessor companies, or our subsidiaries that we demerged, divested or may divest. We have disputes outstanding for example, with Rhodia, over costs related to environmental liabilities regarding certain sites no longer owned by the Group. An adverse outcome in such disputes might have a significant adverse effect on our operating results. See Note D.22.e) to the consolidated financial statements included at Item 18 of this annual report.

Environmental regulations are evolving (i.e.(i.e., in Europe, REACH, CLP/GHS, SEVESO, IPPC, the Waste Framework Directive, the Emission Trading Scheme Directive, the Water Framework Directive and the Directive on Taxation of Energy Products and Electricity and several other regulations aiming at preventing global warming). Stricter environmental, safety and health laws and enforcement policies could result in substantial costs and liabilities to our Group and could subject our handling, manufacture, use, reuse or disposal of substances or pollutants, site restoration and compliance costs to more rigorous scrutiny than is currently the case. Consequently, compliance with these laws could result in significant capital expenditures as well as other costs and liabilities, thereby adversely affecting our business, results of operations or financial condition. For more detailed information on environmental issues, see “Item 4. Information on the Company — B. Business Overview — Health, Safety and Environment (HSE).”

Risks Related to Financial Markets⁽¹⁾¹

Fluctuations in currency exchange rates could adversely affect our results of operations and financial condition.

Because we sell our products in numerous countries, our results of operations and financial condition could be adversely affected by fluctuations in currency exchange rates. We are particularly sensitive to movements in exchange rates between the euro and the U.S. dollar, the British pound, the Japanese yen, and to currencies in emerging countries. In 2009, approximately 32%2011, 29.8% of our net sales were realized in the United States. While we incur expenses in those currencies, the impact of currency exchange rates on these expenses does not fully offset the impact of currency exchange rates on our revenues. As a result, currency exchange rate movements can have a considerable impact on our earnings. When deemed appropriate and when technically feasible, we enter into transactions to hedge our exposure to foreign exchange risks. These efforts, when undertaken, may fail to offset the effect of

adverse currency exchange rate fluctuations on our results of operations or financial condition. In addition, in the specific context of the sovereign debt crisis affecting certain European countries, the alleged or actual disruption in the use of the euro as currency in one or more European Monetary Union countries and the associated fluctuations in currency exchange rates could have a material effect on our financial condition and earnings, the magnitude and consequences of which are unpredictable. For more information concerning our exchange rate exposure, see “Item 11. Quantitative and Qualitative Disclosures about Market Risk.”

In the context of the worldwide financial crisis, our liquidity may be constrained.

As of December 31, 2009,2011, the Group’s net debt amounted approximately to €4.1 billion.€10.9 billion, an amount which increased substantially with the acquisition of Genzyme in 2011. In addition to debt outstanding, the Group has contracted a number of credit lines and put into place commercial paper and medium term note programs with the aim of providing liquidity. See “Item 11. Quantitative and Qualitative Disclosures about Market Risk.” In the event of a market-wide liquidity crisis, the Group might be faced with reduced access to

sources of financing, including under programs currently in place, or less favorable conditions. While liquidity conditions in the financial markets have improved somewhat in recent months, they could deteriorate once again, in which case our sources of financing could be substantially reduced, and we might find it difficult to refinance existing debt or to incur new debt on terms that we would consider to be commercially reasonable.

Risks Relating to an Investment in our Shares or ADSs

Foreign exchange fluctuations may adversely affect the U.S. dollar value of our ADSs and dividends (if any).

Holders of ADSs face exchange rate risk. Our ADSs trade in U.S. dollars and our shares trade in euros. The value of the ADSs and our shares could fluctuate as the exchange rates between these currencies fluctuate. If and when we do pay dividends, they would be denominated in euros. Fluctuations in the exchange rate between the euro and the U.S. dollar will affect the U.S. dollar amounts received by owners of ADSs upon conversion by the depositary of cash dividends, if any. Moreover, these fluctuations may affect the U.S. dollar price of the ADSs on the New York Stock Exchange (NYSE), whether or not we pay dividends in addition to the amounts, if any, that a holder would receive upon our liquidation or upon the sale of assets, merger, tender offer or similar transactions denominated in euros or any foreign currency other than U.S. dollars.

Persons holding ADSs rather than shares may have difficulty exercising certain rights as a shareholder.

Holders of ADSs may have more difficulty exercising their rights as a shareholder than if they directly held shares. For example, if we offer new shares and they have the right to subscribe for a portion of them, the depositary is allowed, at its own discretion, to sell for their benefit that right to subscribe for new shares instead of making it available to them. Also, to exercise their voting rights, as holders of ADSs, they must instruct the depositary how to vote their shares. Because of this extra procedural step involving the depositary, the process for exercising voting rights will take longer for holders of ADSs than for holders of shares. ADSs for which the depositary does not receive timely voting instructions will not be voted at any meeting.

Our two largest shareholders own a significant percentage of the share capital and voting rights of sanofi-aventis.Sanofi.

As of December 31, 2009, Total and2011, L’Oréal our two largest shareholders,and Total held approximately 7.33%8.82% and 8.97%3.22% of our issued share capital, respectively, accounting for approximately 12.36%15.69% and approximately 15.32%5.52%, respectively, of the voting rights (excluding treasury shares) of sanofi-aventis.Sanofi. See “Item 7. Major Shareholders and Related Party Transactions — A. Major Shareholders.” Affiliates of each of these shareholders are currently serving on our Board of Directors. To the extent these shareholders continue to hold a large percentage of our share capital and voting rights, TotalL’Oréal and L’OréalTotal will remain in a position to exert heightened influence in the election of the directors and officers of sanofi-aventisSanofi and in other corporate actions that require shareholders’ approval.

Sales of our shares may cause the market price of our shares or ADSs to decline.

Neither TotalL’Oréal nor L’OréalTotal is, to our knowledge, subject to any contractual restrictions on the sale of the shares each holds in our Company. Both of these shareholders have announced their intent to sell all or part ofthat they do not consider their stakes in our company,Company as strategic to them, and have recently liquidated a significant partTotal makes regular sales of their respective holdings.its holdings on the financial market. Sales of large numbers of our shares, or a perception that such sales may occur, could adversely affect the market price for our shares and ADSs.

Risks Relating to our Contingent Value Rights (CVRs)

In addition to the risks relating to our shares, CVR holders are subject to additional risks.

In connection with our acquisition of Genzyme, we issued CVRs under a CVR agreement entered into by and between us and American Stock Transfer & Trust Company, the trustee. A copy of the form of the CVR agreement is attached as exhibit 4.1 to our Registration Statement on Form F-4 (Registration No. 333-172638), as amended. Pursuant to the CVR agreement, each holder of a CVR is entitled to receive cash payments upon the achievement of certain milestones, based on U.S. regulatory approval of Lemtrada™ (alemtuzumab for treatment of multiple sclerosis), and on achievement of certain aggregate net sales thresholds. See “Item 10. Additional Information — C. Material Contracts — The Contingent Value Rights Agreement.”

CVR holders are subject to additional risks, including:

Item 4. Information on the Company

Introduction

We are a global pharmaceutical group engaged in the research, development, manufacture and marketing of healthcare products. In 2009,2011, our net sales amounted to €29,306€33,389 million. Based on 2009 sales, weWe are the fourthfifth largest pharmaceutical group in the world and the secondthird largest pharmaceutical group in Europe (source: IMS sales 2009)2011). Sanofi-aventisSanofi is the parent of a consolidated group of companies. A list of the principal subsidiaries included in this consolidation is shown at Note F. to our consolidated financial statements included at Item 18 of this annual report.

Our business includes twothree main activities: pharmaceuticals,Pharmaceuticals, Human Vaccines through Sanofi Pasteur and human vaccines through sanofi pasteur. The Group is also present in animal healthAnimal Health products through Merial Limited (“Merial”)(Merial).

In our pharmaceuticalPharmaceuticals activity, which generated net sales of €25,823€27,890 million in 2009, we specialize in the following therapeutic areas:2011, our major product categories are:

The global pharmaceutical portfolio of sanofi-aventisSanofi also comprises a wide range of other pharmaceutical products in Consumer Health Care (“CHC”)(CHC) and other prescription drugs including generics.

We are a world leader in the vaccines industry. Our net sales amounted to €3,483€3,469 million in 2009,2011, with leading vaccines in five areas:

•

Adult and adolescent booster vaccines protecting against pertussis, tetanus, diphtheria and polio. Our main products include: Adacel® (the first trivalent booster against pertussis, tetanus and diphtheria for adolescents and adults, launched in the U.S. in 2005), Adacel Polio®, Decavac®, Repevax® and Revaxis®;

In 2009, our vaccines, activity was favorably influenced by the continued uptake of Pentacel^® sales following its U.S. launch in 2008,influenza vaccines, adult and by the sales growth of Pentaxim^® in the international⁽¹⁾ region. Sanofi Pasteur also strengthened its leadership position in both seasonaladolescent booster vaccines, meningitis vaccines, and pandemic influenza.travel and endemics vaccines.

Our animal healthAnimal Health activity is managedcarried out through Merial, formerly a joint venture in which we and Merck & Co., Inc. (“Merck”) each held 50%. On September 17, 2009 we acquired Merck’s interest in Merial. On March 8, 2010, sanofi-aventis exercised its contractual right to combine the Intervet/Schering-Plough Animal Health business with Merial to form an animal health joint venture that would be equally owned by the new Merck and sanofi-aventis. In addition to execution of final agreements, formation of the new animal health joint venture remains subject to approval by the relevant competition authorities and other closing conditions (for more information see “Item 8 — B. Significant Changes — Merial” and Notes D.1 and D.8.1 to our consolidated financial statements included at Item 18 of this annual report). Merial is one of the world’s leading animal healthcare companies, dedicated to the research, development, manufacture and delivery of innovative pharmaceuticals and vaccines used by veterinarians, farmers and pet owners. Itsowners providing a comprehensive range of products to enhance the health, well-being and performance of a wide range of animals (production and companion animals). Our net sales for 2009 (which are not included in the Group’s 2009 net sales) amounted to $2,554 million. The company’s top-selling products include Frontline^®, a topical anti-parasitic flea and tick brand for dogs and cats, Heartgard^®, a parasiticide for control of heartworm€2,030 million in companion animals as well as Ivomec^®, a parasiticide for the control of internal and external parasites in livestock.2011.

In the description below, the following should be kept in mind:

A. History and Development of the Company

Sanofi-aventisSanofi was incorporated under the laws of France in 1994 as asociété anonyme, a form of limited liability company, for a term of 99 years. We operate under the commercial name “sanofi-aventis”“Sanofi” (formerly sanofi-aventis). Our registered office is located at 174, avenue de France, 7501354, rue La Boétie, 75008 Paris, France, and our main telephone number is +33 1 53 77 40 00. Our principal U.S. subsidiary’s office is located at 55 Corporate Drive, Bridgewater, NJ 08807; Telephone:telephone: +1 (908) 981-5000.

We are present in approximately 110100 countries on five continents with about 105,000113,719 employees at year end 2009, not including an additional 5,600 employees of Merial.2011. Our legacy companies, Sanofi-Synthélabo (formed by athe 1999 merger betweenof Sanofi and Synthélabo in 1999)into the current holding company) and Aventis (formed by the combination of Rhône-Poulenc and Hoechst also in 1999), bring to the Group more than a century of experience in the pharmaceutical industry.

Sanofi was founded in 1973 by Elf Aquitaine, a French oil company, when it took control of the Labaz group, a pharmaceutical company. Its first significant venture into the U.S. market was the acquisition of the prescription pharmaceuticals business of Sterling Winthrop — an affiliate of Eastman Kodak — in 1994.

Synthélabo was founded in 1970 through the merger of two French pharmaceutical laboratories, Laboratoires Dausse (founded in 1834) and Laboratoires Robert & Carrière (founded in 1899). In 1973, the French cosmetics group L’Oréal acquired the majority of its share capital.

Hoechst traces its origins to the second half of the 19th century, withto the time of the German industrial revolution and the emergence of the chemical industry. Traditionally active in pharmaceuticals, Hoechst strengthened its position in that industry by taking a controlling interest in Roussel-Uclaf in 1974 and the U.S. pharmaceutical company Marion Merrell in 1995.

Rhône-Poulenc was formed in 1928 from the merger of two French companies: a chemical company created by the Poulenc brothers and the Société Chimique des Usines du Rhône, which was founded in 1895. The company’s activities in the first half of the 20th century focused on producing chemicals, textiles and pharmaceuticals. Rhône-Poulenc began to focus its activities on life sciences in the 1990s, which led to the successive purchases of Rorer, a U.S. pharmaceutical company acquired in two stages in 1990 and 1997, the remaining 49% of shares of Pasteur Mérieux Connaught in the area of vaccinesSerums & Vaccins S.A. in 1994, and the U.K.-based pharmaceuticals company Fisons in 1995.

Sanofi-Synthélabo took control of Aventis in August 2004 and changed its registered name to “sanofi-aventis”. On December 31, 2004, Aventis merged with and into sanofi-aventis, with sanofi-aventis as the surviving company.

In 1994, Pasteur Mérieux Serums & Vaccins, the Group’s vaccines division, together with the vaccines division of Merck & Co., Inc. formed Sanofi Pasteur MSD, creating the only European firm entirely dedicated to vaccines.

Merial was founded in 1997 as a combination of the animal health activities of Rhône-Poulenc and Merck. Merial was a joint venture in which we and Merck each held 50%. On September 17, 2009, sanofi-aventiswe acquired Merck’s 50%entire interest in Merial. Merial and Merial is now a wholly-owned subsidiary of sanofi-aventis. On March 8, 2010, sanofi-aventis exercised its contractual right to combine the Intervet/Schering-Plough Animal Health business with Merial to form anbecame Sanofi’s dedicated animal health division following the joint venture that would be equally ownedstatement issued by the new Merck and sanofi-aventis. FormationSanofi in March 2011 announcing the end of thetheir agreement to create a new animal health joint venture remains subject to approval by the relevant competition authorities and other closing conditions (for more information see “Item 8 — B. Significant Changes — Merial” and Notes D.1 and D.8.1combining their respective animal health segments. See Note D.2. to our consolidated financial statements included at Item 18 of this annual report).report.

Starting in 2009, Sanofi made a series of acquisitions to create or strengthen our regional CHC and generics platforms including:

On April 4, 2011, we acquired Genzyme Corporation, a leading biotechnology group headquartered in Cambridge, Massachusetts and specialized in the treatment of rare diseases, renal diseases, endocrinology, oncology and biosurgery. Immediately following the tender offer, Sanofi held over 90% of Genzyme’s outstanding shares, and acquired the remaining shares in a “short form” merger on April 8, 2011. The agreement is described at “Item 10. Additional Information — C. Material Contracts”.

As of the May 2011 General Meeting of Shareholders, the Group changed its name to “Sanofi”.

B. Business Overview

Strategy

Sanofi-aventisSanofi is a diversified, global healthcare leader with a numberoffering solutions across areas of core strengths:historical strength and multiple growth platforms. Like other pharmaceutical companies, we have been facing competition from generics for several of our major products, in an environment subject to cost containment pressures from both third party payers and healthcare authorities. Starting in 2009, we have responded to these major challenges by implementing a strongnew strategy with the objective of repositioning Sanofi for more stable and long-established presencesustainable revenue and earnings growth. During that time we have transformed the Company by decreasing our reliance on existing “blockbuster” medicines (medicines with over $1 billion in emerging markets global sales), optimizing our approach to Research & Development (R&D), increasing our diversification, and investing in 6 growth platforms (Emerging Markets⁽¹⁾, Diabetes Solutions, Human Vaccines, Consumer Health Care, Animal Health, and Innovative Products). Additionally, we became a global leader in rare genetic diseases through our acquisition of Genzyme in 2011.

We regularly review our strategy and are continuing to execute on this strategy along three prongs:

We have conducted a complete review of our research and development portfolio since 2009, in order to improve the allocation of diabetes drugsour resources. This review has led to a rationalization of our portfolio, focusing on high-value projects and reallocating part of our resources from internal infrastructure to partnerships and collaborations. We also redefined our decision-making processes so that commercial potential and the scope for value creation are better integrated into our development choices. We also redesigned our R&D footprint including the biggest selling insulinincreasing our presence in the world: Lantus^®,Boston, MA area with its concentration of universities and innovative biotechnology companies. R&D is now based on an organizational structure focused on patient needs and encouraging entrepreneurship. This network-based organization, open to external opportunities, enables our R&D portfolio to more effectively capitalize on innovation, from a market-leading position in vaccines, a broadwide range of consumer health care products and research that is increasingly focused on biological products, allied with a track record of adapting cost structures and a solid financial position.sources.

Like most pharmaceutical companies, we are facing competition from generics for several of our major products, in an environment subject to cost containment pressures from both third party payers and healthcare authorities as well as tougher regulatory hurdles. We have decided to respond to these major challenges by developing our platforms for growth.

Throughout 2009, we have been engaged in a wide-ranging transformation program designed to secure sources of sustainable growth. Our strategy focuses on three key themes:

We conducted a complete and objective review of our research portfolio in 2009, in order to reassess the allocation of resources. This review led to a rationalization of our portfolio, targeting the most promising projects. In February 2010, 60% of our development portfolio consisted of biological products and vaccines. We also redefined our decision-making processes so that new commercial potential and the scope for value creation are better integrated into our development choices. The ongoing reorganization of our R&D is intended to help us become more flexible and innovative, with some of our existing resources being reallocated to external collaborations. In line with this policy, we have signed a number ofnew alliance and licensing agreements with partners including Kyowa Hakko Kirin Co. Ltd (“Kyowa Hakko Kirin”), Exelixis, Inc. (“Exelixis”), Merrimack Pharmaceuticals, Inc. (“Merrimack”), Wellstat Therapeutics Corporation (“Wellstat”), Micromet, Inc. (“Micromet”), and Alopexx Pharmaceuticals LLC (“Alopexx”). These agreements arein 2011 designed to give us access to new technologies, and/or to broaden or strengthen our existing fields of research. We have also signed additional agreements with Regeneron Pharmaceuticals, Inc. to broadenresearch (including diabetes, oncology and extend our existing collaboration on the research, development and commercialization of fully human therapeutic monoclonal antibodies. In February 2010, 55% of our development portfolio consisted of projects originated by external R&D.vaccines). Finally, we have made progress on our objective of offering more products that add value for patients: for example Multaq^®, whichpatients, with five New Molecular Entities (NMEs) submitted to regulatory agencies in 2009 was launched in2011, and 18 potential new product launches possible before the United States and approved in the European Union.end of 2015.

DuringSince 2009, we have adapted our operating model, previously toofrom being focused on the most importantbest-selling prescription drugs in our traditionally importanttraditional markets, to reflecta broader set of products and services reflecting the diversity of our activities and our geographical reach. In particular, we tailored our strategy, structure and offering to each region’s needs, so as to deliver the most appropriate solution to each patient. 25%The result is a dramatic shift in business mix from Top 15 products to key growth platforms. In 2008, 61 % of our 2009sales originated from our top 15 products while in 2011, 65 % of our sales originated from Genzyme and our growth platforms. Moreover, 30 % of our 2011 sales were in emerging markets. We strengthenedmarkets where we have enhanced our presenceofferings in vaccineshigh growth market segments such as Generics and expanded our consumer health care operations, so as to address our customers’ needs more thoroughlyConsumer Health Care by completing 17 transactions and take better advantageinvesting a total of growth opportunities. approximately €3.7 billion in acquisitions over the last three years.

We also realigned our industrial capacity to reflect our anticipationexpectation of changes in volumes and our analysisanalyses of growth opportunities. Combined with the opportunities for growth. Streamliningstreamlining of our R&D structures and our operating model have also enabledkeeping a tight control on SG&A expenses, this has helped enable us to further improve our operating ratios. In 2009, the initial resultssuccessfully navigate through a period where multiple of our leading products faced the loss of patent exclusivity protection, despite an often tougher economic environment with new healthcare cost control program fed into a one percentage point reductioncontainment measures in each of the ratios of our research and development expenses and our selling and general expenses to our net sales. Sanofi-aventis generated €480 million of savings in 2009 compared to 2008 cost structures.many markets.

Business development is wholly integrated intoremains an integral and disciplined pillar of our overall strategy, and translates into disciplinedtargeting acquisitions and alliances that create and/or strengthen platforms for long-term growth and create value for our shareholders. DuringSince January 2009, we conducted an active andhave invested a total of approximately €23 billion in external growth accounting for approximately 20% increase in 2011 consolidated sales. During 2011, we pursued this targeted policy ofactively, announcing 30 new transactions, including three acquisitions and 27 R&D alliances. We successfully completed our offer for Zentiva N.V. (“Zentiva”), a branded generics group with products tailored to the Eastern and Central European markets, and we also acquired Laboratorios Kendrick (“Kendrick”), one of Mexico’s leading generics manufacturers, and Medley, a leading generics company in Brazil. In R&D, we acquired two companies: BiPar Sciences, Inc. (“BiPar”), an American biopharmaceutical company developing novel tumor-selective approaches for the treatment of different types of cancers, and Fovea Pharmaceuticals SA (“Fovea”), a French biopharmaceutical R&D company specializing in ophthalmology. In consumer health care, we finalized the acquisition of Laboratoire Oenobiol (“Oenobiol”), one of France’s leading playersGenzyme, a global leader in healthrare genetic diseases and beauty dietary supplements. At the end of the year, we finalized an agreement to acquire Chattem, Inc. (“Chattem”), one of the leading manufacturers and distributors of branded consumer health products, toiletries and dietary supplementsemerging leader in the United States. In human vaccines, we took control of Shantha Biotechnics (“Shantha”), an Indian biotechnology company that develops, produces and markets vaccines to international

standards.multiple sclerosis. We also strengthened our animal health interests by acquiringEmerging Markets growth platform with the remaining 50%acquisition of Merial not previously held by usUniversal Medicare, advancing our sustainable growth strategy in India and subsequently exercised on March 8, 2010,facilitating the creation of a Consumer Health Care platform in that country. Our U.S. vaccines operations were reinforced with the acquisition of Topaz Pharmaceuticals, which complements our contractual right to combine the Intervet/Schering-Plough Animal Health business with Merial to form an animal health joint venture that would be equally owned by the new Merck and sanofi-aventis. In addition to execution of final agreements, formation of the new animal health joint venture remains subject to approval by the relevant competition authorities and other closing conditions (for more information see “Item 8 — B. Significant Changes — Merial” and Notes D.1 and D.8.1 to our consolidated financial statements included at Item 18 of this annual report).pediatric offering.

OurIn the years to come, we expect our sound financial position should giveto provide us significantthe potential to create value via external growth opportunities and to strengthen our diversification and growth platforms through new acquisitions and partnerships. We will remain financially disciplined with the aim of securingour business development activities to execute strategically important transactions and partnerships that secure a return on investment in excess of our cost of capital.

Pharmaceutical Products

Main Pharmaceutical Products

Within our Pharmaceuticals business, we focus on the following therapeutic areas:categories: diabetes, rare diseases, oncology, thrombosis &and other flagship products in anti-thrombotics, cardiovascular, central nervous systemrenal and internal medicine.biosurgery fields.

The sections that follow provide additional information on the indications and market position of these products in their principal markets. The Group’sour key products. Our intellectual property relating to itsrights over our pharmaceutical products isare material to our operations and isare described at “— Patents, Intellectual Property and otherOther Rights” below. As disclosed in Note D.22.b to our consolidated financial statements included at Item 18“Item 8. Financial Information — A. Consolidated Financial Statements and Other Financial Information — Patents” of this annual report, we are involved in significant litigation concerning the patent protection of a number of these products.

The following table sets forth the net sales of our best sellingbest-selling pharmaceutical products for the year ended December 31, 2009.2011. These products are major contributors to public health.

Therapeutic Area / Product Name		2011 Net Sales (€ million)				Drug Category / Main Areas of Use
Renagel® (sevelamer hydrochloride) / Renvala® (sevelamer carbonate)			415	(1)		Oral phosphate binders
						• High phosphorus levels in patients with chronic kidney disease, or CKD, on dialysis
Synvisc® / Synvisc-One® (hylan G-F 20)			256	(1)		Viscosupplements
						• Pain associated with osteoarthritis of the knee
Others
Stilnox® /Ambien®/Myslee® (zolpidem tartrate)			490			Hypnotic
						• Sleep disorders
Allegra® (fexofenadine hydrochloride)			580	(2)		Anti-histamine
						• Allergic rhinitis • Urticaria
Copaxone® (glatiramer acetate)			436			Non-interferon immunomodulating agent
						• Multiple sclerosis
Tritace® (ramipril)		429	375			Angiotensin Converting Enzyme Inhibitorinhibitor
						• Hypertension • Congestive heart failure • Nephropathy
Multaq® (dronedarone)		25		Anti-arrhythmic drug
				• Atrial Fibrillation
Others
Central Nervous System
Stilnox®/Ambien®/Myslee® (zolpidem tartrate)		873		Hypnotic
				• Sleep disorders
of which Ambien® CR		506
Copaxone® (glatiramer acetate)		467		Non-interferon immunomodulating agent
				• Multiple sclerosis
Depakine® (sodium valproate)		329	388			Anti-epileptic
				• Epilepsy
Internal Medicine
Allegra® (fexofenadine hydrochloride)		731		Anti-histamine
				• Allergic rhinitis • Urticaria
Nasacort® (triamcinolone acetonide)		220		Local corticosteroid
				• Allergic rhinitisEpilepsy
Xatral® (alfuzosin hydrochloride)		296	200			Uroselective alpha1-blocker
						• Benign prostatic hypertrophy
Actonel® (risedronate sodium)		264	167			Biphosphonate
						• Osteoporosis • Paget’s Diseasedisease
Nasacort® (triamcinolone acetonide)			106			Local corticosteroid
						• Allergic rhinitis

(1)	Since date of acquisition

(2)	Excluding Allegra® OTC sales.

Diabetes

The prevalence of diabetes is expected to increase significantly over the next 20 years, as a direct result ofreflecting multiple socio-economic factors including sedentary lifestyle, excessivelifestyles, excess weight and obesity, unhealthy diet and an aging population. Our principal diabetes products are Lantus^®, a long-acting analog of human insulin,insulin; Apidra^®, a rapid-acting analog of human insulininsulin; Insuman^®, a human insulin; and Amaryl^®, a sulfonylurea. In 2011, in some European markets, we launched the BGStar^® solution range of blood glucose meters for patients with diabetes, whether they are treated with insulin or not.

Lantus^®

Lantus^® (insulin glargine) is a long-acting analog of human insulin, offering improved pharmacokinetic and pharmacodynamic profiles compared to other basal insulins. Lantus^® is indicated for once-daily subcutaneous administration in the treatment of adult patients with type 2 diabetes mellitus who require basal insulin for the control of hyperglycemia, and for adult and pediatric patients aged six years and above with type 1 diabetes mellitus.

Lantus^® is a well establishedwell-established treatment with 24over 38 million patient-years exposure since 2000. Over 70,000 patients throughout the world have been involved inThe clinical trial experience with Lantus^® clinical trials.covers over 100,000 patients.

Lantus^® can be administered subcutaneously using syringes or specific pens including the Lantus^® SoloSTAR^® disposable pen and the new ClikSTAR^® reusable pen:including:

New meta-analyses and new studies have investigated the efficacy and safety of Lantus^® in type 2 diabetes mellitus:

In JuneSeptember 2009, following four highly publicized but methodologically limited registry analyses, discussingsome of which created concern over a potential link between the use of Lantus^® and an increased risk of breast cancer, were published inDiabetologia based on a retrospective follow-up of diabetic patients. Clinical studies have not indicated an association between insulin glargine and cancer, and no conclusion can be drawn from these analyses regarding a possible causal relationship between Lantus^® use and the occurrence of malignancies, as their authors pointed out.

Patient safety being the primary concern of sanofi-aventis, we convened a group of fourteen internationally-recognized experts in the fields of endocrinology, oncology and epidemiology to review the findings of the registry analyses. On July 15, 2009, they published a statement concluding that all four manuscripts had significant methodological limitations and shortcomings, and that they provided inconsistent and inconclusive results. This statement followed cautionary statements by the European Medicines Agency (“EMA”), the U.S. FDA as well as patient and scientific organizations such as the American Diabetes Association, the American Association of Clinical Endocrinologists, and the International Diabetes Federation warning against over-interpretation of and over reaction to these data.

On July 23, 2009, the EMA’s Committee for Medicinal Products for Human Use (“CHMP”) re-confirmed its initial assessment of Lantus^®, based on a review of existing evidence and of the recent publications of registry analyses inDiabetologia, and concluded that the available data does not provide a cause for concern and that changes to the prescribing advice were therefore not necessary. All four registry analyses were found to have methodological limitations and to provide inconsistent and inconclusive results regarding a potential link between Lantus^® use and an increased risk of cancer.

In September 2009, we announced an action plan to provide methodologically robust research that will contribute to the scientific resolution of the debate over insulin safety, including insulin analogs and Lantus^®. The research program encompasses both pre-clinicalpreclinical and clinical programs involving human insulin and insulin glargine andanalogues, including insulin glargine; it is designed to generate more information on whether there is any association between cancer and insulin use, and to assess ifwhether there is any difference in risk between insulin glargine and otherdifferent types of insulins. The plan is structured to yield short-term and longer-term results. Three epidemiological studies are planned (two retrospectivesretrospective cohort studies and one case-control study) have been launched:

The ADA/ACS (American Diabetes Association / American Cancer Society) Consensus Report published on June 16, 2010 reasserted the inconclusiveness of any link between insulin and cancer.

In January 2011, the FDA updated its ongoing safety review of Lantus^®. We expectIn addition to complete the two retrospectives cohort studies and analyze theiranalysis of the four registry analyses published in 2009, the FDA also reviewed results from a five-year diabetic retinopathy clinical trial in patients with type 2 Diabetes. Based on these data, the FDA has not concluded at this time for scientific presentations at medical conferences in 2012. We aim to presentthat Lantus^® increases the risk of cancer. FDA review remains ongoing.

In December 2011, results of new meta-analysis were presented at the World Diabetes Congress. This new meta-analysis of all published studies—observational studies derived from databases as well as randomized controlled clinical trials and one case-control studystudy—has demonstrated no increased risk in 2013. We are also conducting pre-clinical studies that for which we expectpeople using Lantus^® when compared to have results in 2010 and in 2011.the users of human insulin.

The American Diabetes Association (“ADA”)ADA and European Association for the Study of Diabetes (“EASD”)(EASD) have maintained their 2008 treatment recommendations for type 2 diabetes. As a reminder, theseThese guidelines further established basal insulins such as Lantus^®, or a sulfonylurea such as Amaryl^®, as two preferred second-line treatment options for people with diabetes who are unable to achieve glycemic control targets with lifestyle intervention and metformin alone. These treatment recommendations reinforce the timely use of basal insulin as a core therapy for type 2 diabetes.

Lantus^® is the world number-one soldselling insulin brand in the world interms of both sales and units (source: IMS, 20092011 sales) and is available in over 70 countries worldwide. The three leading countries for sales of Lantus^® arein 2011 were the United States, France and Germany.Japan.

Apidra^®

Apidra^® (insulin glulisine) is a rapid-acting analog of human insulin. Apidra^® is indicated for the treatment of adults with type 1 anddiabetes, or in type 2 diabetes for supplementary glycemic control. Apidra^® has a more rapid onset and shorter duration of action than fast-acting human insulin and can be associated with long-acting insulins such as Lantus^® for supplementary glycemic control at mealtime.

In addition, Apidra^® is equally effective in adult diabetics ranging from lean to obese and offers patients greater flexibility of administration, either before or just after mealtime.

Apidra^® can be administered subcutaneously using syringes or specific pens including the Apidra^® SoloSTAR^® disposable pen and the new ClikSTAR^® reusable pen:pen.

Apidra^® was launchedis available in Germany in 2004, in other Europeanover 60 countries in 2005, in the United States in 2006, and in Canada and Japan in 2009.worldwide.

Due to a technical incident on a manufacturing line, Apidra^® is now available in over 26 countries worldwide. The top three countries contributing to salesfaced a temporary shortage of Apidra^® are3mL cartridges (including Apidra^® SoloSTAR^®) which impacted supplies in some markets. The production of Apidra^® 3mL cartridges is expected to return to full capacity in the United States, Germanyfirst half of 2012. Apidra^® vials were not impacted.

Insuman^®

Insuman^® (human insulin) is a range of insulin solutions and Italy.suspensions for injection and is indicated for diabetes patients where treatment with insulin is required. Human insulin is produced by recombinant DNA technology inEscherichia coli strains.

Insuman^® is supplied in vials, cartridges, pre-filled disposable pens (OptiSet^® and SoloStar^®) or reusable pens (ClickSTAR^®) containing the active substance human insulin. The Insuman^® range is comprised of rapid-acting insulin solutions (Insuman^® Rapid and Insuman^® Infusat) that contain soluble insulin, an intermediate-acting insulin suspension (Insuman^® Basal) that contains isophane insulin, and combinations of fast- and intermediate-acting insulins in various proportions (Insuman^® Comb). Insuman^® is mostly sold in Germany.

Amaryl^®/Amarel^®/Solosa^®

Amaryl^® (glimepiride) is a latest-generation, orally administered once-daily sulfonylurea (a glucose-lowering agent) indicated as an adjunct to diet and exercise to improve glycemic control in patients with type 2 diabetes. Amaryl^® reduces the body’s blood sugar level in two ways: by helping the body to produce more insulin both at mealtime and between meals, and by decreasing insulin resistance. Amaryl^® has a more rapid onset and longer duration of action than first-generation agents, allowing patients to achieve a very good level of control with a lower risk of hypoglycemia.

Amaryl^® was the first oral diabetes drug in its class to receive approval for administration in one of three ways: either as a monotherapy or in combination with insulin or metformin.

The combination of metformin (which reduces hepatic glucose production and improvesdecreases insulin resistance) with a sulfonylurea such as Amaryl^® is the rational combination for counteractingeffective in combating the two defects seen incauses of type 2 diabetes. It is one of the most prescribed combinationcombinations of diabetes drugs worldwide. Amaryl M^®, a fixed-dose combination of Amaryl^® plus metformin in a single presentation, was launched in 2007. The fixed dose treatment is more effective than either agent alone in patients with type 2 diabetes and has equal efficacy and better compliance than the free combination of glimepiride and metformin. In 2009, Amaryl M^® was launched in Chile and in the United Arab Emirates.

Our leading market for Amaryl^® is Japan, where it is the leadingbest-selling oral anti-diabetes product by volume (source: IMS 20092011 sales). A number of generics have received marketing authorization and have been launched in Europe and the United States. Generic became available in Japan in November 2010 but the impact on Amaryl^® sales compared to the impact of generic sales generally observed in the U.S. or the EU has been more moderate.

BGStar^® / iBGStar™

Sanofi and its partner AgaMatrix are co-developing innovative solutions in diabetes care with the aim of simplifying the diabetes management experience for patients and healthcare providers. The blood glucose monitoring solutions will be exclusive to Sanofi and are designed to be synergistic with our Diabetes portfolio, with a positive effect on sales of Lantus^® and other products expected.

BGStar^® and iBGStar™ are blood glucose meters that feature Dynamic Electrochemistry^®, an innovative technology that extracts a spectrum of information from blood that is inaccessible to traditional electrochemical methods and compensates for many interfering factors that often distort blood glucose results.

These monitoring devices are an important step towards our vision of becoming the global leader in diabetes care by integrating innovative monitoring technology, therapeutic innovations, personalized services and support solutions. During 2011, the BGStar^® and iBGStar™ were made commercially available in Germany, France, Switzerland, Spain, the Netherlands and Italy.

In December 2011, the FDA approved the iBGStar™ the first blood glucose meter that connects to the iPhone^® allowing patients to view and analyze accurate, reliable information in “real time”.

The main compounds currently in Phase II or III clinical development in the DiabetesDiabetes/Other Metabolic Disorders field are:

Phase I studies on combination of lixisenatide and Lantus^® have been successfully finalized. A proof-of-concept study to compare insulin glargine/ lixisenatide fixed ratio combination versus insulin glargine on glycemic control over 24 weeks has begun.

Oncology

Sanofi-aventisSanofi is a leaderpresent in the oncology field, primarily in chemotherapy, with twothree major agents:products: Taxotere^® and, Eloxatine^®., and Jevtana^®, which was launched commercially in the United States in 2010 and in the second quarter of 2011 in Europe.

Taxotere^®

Taxotere^® (docetaxel), a taxoid class derivative, inhibits cancer cell division by essentially “freezing” the cell’s internal skeleton, which is comprised of microtubules. Microtubules assemble and disassemble during a cell cycle. Taxotere^® promotes their assembly and blocks their disassembly, thereby preventing many cancer cells from dividing and resulting in death in somemany cancer cells.

Taxotere^® is available in more than 100 countries as an injectable solution. The single vial formulation (one vial IV route 20-80mg) was launched in the U.S. and in the European Union in 2010. It has gained approval for use in eleven indications in five different tumor types (breast, prostate, gastric, lung, and head and neck). Taxotere^® is indicated for early stage and metastatic breast cancer, first-line and second-line metastatic Non-Small Cell Lung Cancer (“NSCLC”)(NSCLC), androgen-independent (hormone-refractory) metastatic prostate cancer, advanced gastric adenocarcinoma including(including adenocarcinoma of the gastroesophageal junctionjunction), and for the induction treatment of patients with locally advanced squamous cell carcinoma of the head and neck.

In June 2009, the Committee for Medicinal Products for Human Use (“CHMP”) of the EMA issued a positive opinion on Roche’s Avastin^® (bevacizumab) in combination with Taxotere^® as a first line treatment for women with metastatic breast cancer, based on the results of the AVADO study. This combination, which presents a better efficacy (significantly better Progression Free Survival — PFS) than the Taxotere^® monotherapy, allows a larger number of patients to be treated with Taxotere^®. In the United States, a Taxotere^®-bevacizumab combination is being reviewed by the FDA for an expected approval in the second quarter of 2010.

Based on the GEICAM 9805 trial results, which showed significant survival benefit in favor of the Taxotere^®-based regimen compared to a fluorouracil-based regimen in 1,100 patients with node negative early stage breast cancer, sanofi-aventis filed a dossier with the EMA in November 2009 for a new indication of Taxotere^® in association with doxorubicin and cyclophosphamide for the treatment of patients with node negative early stage breast cancer. In the United States, this Taxotere^® regimen is already considered as a standard treatment in this indication.

For patients with androgen-independent (hormone-refractory) metastatic prostate cancer, Taxotere^® remains the standard of care for a first-line treatment and new clinical studies on Taxotere^® in combination with targeted therapies could lead to more frequent use of Taxotere^®.

In November 2009, the European Commission approved a new single vial formulation of Taxotere^® in Europe. This new formulation was also filed for approval in the United States in December 2008. A pediatric data dossier on Taxotere^® was submitted for regulatory approval in the United States in November 2009, in response to the FDA’s prior written request.

The top four countries contributing to sales of Taxotere^® in 2009 are2011 were the United States, Japan, France, Germany and Japan.China. Generics of docetaxel were launched at the end of 2010 in Europe and in April 2011 in the U.S. Exclusivity for Taxotere^® in Japan will be maintained through November 2013 (see “— Patents, Intellectual Property and Other Rights” below).

EloxatineEloxatin^®

EloxatineEloxatin^® (oxaliplatin) is a platinum-based cytotoxic agent. EloxatineEloxatin^® combined with infusional (given(delivered through the bloodstream) administration of two other chemotherapy drugs, 5-fluorouracil/leucovorin (the FOLFOX regimen), is approved by the FDA for adjuvant treatment of people with stage III colon cancer who have had their primary (original) tumors surgically removed. This approval was based on evidence of an improvement in disease-free survival after four years.

In clinical studies of patients with stage III colon cancer who had their primary tumors surgically removed, EloxatineEloxatin^® is in-licensed from Debiopharm and is marketed in the FOLFOX regimen has been shown to:more than 70 countries worldwide.

For patients with stage IV colorectal cancer, the FOLFOX regimen is approved by the FDA for the treatment of advanced colorectal cancer (cancer of the colon and/or rectum). The FOLFOX regimen showed the following benefits in clinical trials of patients with advanced colorectal cancer:

Following the end of the EloxatineEloxatin^® European regulatory data exclusivity in April 2006, a number of oxaliplatin generics have received marketing authorization and have been launched throughout Europe. With regard to the United StatesU.S. market, in August and September 2009, a number of oxaliplatin generics received final marketing authorization from the FDA and have since been launched.were marketed until June 30, 2010, when their manufacturers were ordered by the U.S. District Court for the District of New Jersey to cease selling their unauthorized Eloxatin^® generic in the United States. Eloxatin U.S. market exclusivity is expected to be maintained through August 9, 2012. See “Item 8. Financial Information — A. Consolidated Financial Statements and other Financial Information — Patents”.

EloxatineJevtana^®

Jevtana^® (cabazitaxel) is a new taxane derivative approved in combination with prednisone for the treatment of patients with hormone-refractory metastatic prostate cancer previously treated with a docetaxel-containing treatment regimen. Jevtana^® was the result of a 14-year research and development program to address the significant unmet medical need after taxane-based treatment progression.

The results of the TROPIC Phase III study demonstrated that cabazitaxel plus prednisone/prednisolone significantly improved overall survival versus the standard regimen of mitoxantrone plus prednisone/prednisolone in patients with metastatic hormone-refractory prostate cancer whose disease progressed following treatment with docetaxel-based chemotherapy. A combination of cabazitaxel and prednisone/prednisolone significantly reduced the risk of death by 28% with an improvement in median overall survival of 15.1 months vs. 12.7 months in the mitoxantrone combination arm.

Jevtana^® was launched in the United States in July 2010. Jevtana^® therapy is now covered by CMS (Committee for Medicare and Medicaid Services), and by most of the private insurance companies that pay for oncology care. In addition, the safety profile seen in clinical practice has been consistent with that seen in the pivotal TROPIC study.

In March 2011, Jevtana^® received marketing authorization from the European Commission and was launched during the second quarter of 2011 in Germany and France. Jevtana^® is in-licensed from Debiopharm andnow approved in 53 countries.

Sanofi has initiated a broad development program with Jevtana^®. The clinical program is marketed in more than 70 countries worldwide. The top countries contributingprojected to the sales of Eloxatineevaluate Jevtana^® in 2009first- and second-line treatment of prostate cancer patients, second-line treatment of small-cell lung cancer patients, and patients with advanced gastric cancer.

The top four countries contributing to sales of Jevtana^® in 2011 were the United States, Canada, ChinaGermany, Brazil and South Korea.France.

The main compounds currently in Phase II or III clinical development in the Oncology field are:

in the treatment of patients with advanced cancers, including cancers where bevacizumab has not demonstrated efficacy. Patients who had previously received bevacizumab were also included in the clinical trials for certain second-line treatment settings. In June 2011, Sanofi announced the positive results from VELOUR, a multinational, randomized, double-blind trial comparing the FOLFIRI (irinotecan-5-fluorouracil-leucovorin) chemotherapy regimen in combination with either Zaltrap or placebo in the treatment of patients with mCRC. The study randomized 1,226 patients with mCRC who previously had been treated with an oxaliplatin-based regimen. About one-third of the participants received bevacizumab as part of their first-line therapy. The primary endpoint was an improvement in overall survival. Secondary endpoints included progression-free survival, response to treatment and safety. Results were first presented at the ESMO World Congress on Gastrointestinal Cancer on June 25, 2011. The abstract (#0-0024) was published in the June 2011 supplement to Annals of Oncology. The current development program also explores Zaltrap for the treatment of metastatic prostate cancer with VENICE: First-line treatment for androgen-independent (hormone-refractory) metastatic prostate cancer in combination with docetaxel and prednisone (Phase III). Final results are anticipated in 2012. The aflibercept dossier was accepted for review by the EMA at the end of 2011. A NDA was filed in February 2012.

the treatment of advanced or recurrent endometrial cancer. Combinations with paclitaxel/carboplatin, letrozole and trastuzumab are also being evaluated. Phase I trials of novel combinations with MSC1936369B (under a collaboration with Merck Serono, a division of Merck KGaA, Darmstadt, Germany) and MM121 (see below) have been initiated.

In May 2009, two compounds were in-licensed from Exelixis:XL147 (PI3K inhibitor) andXL765 (PI3K/mTOR dual inhibitor). Multiple Phase I studies as single agent or in combination are ongoing with both compounds. Besides the license, under an exclusive discovery collaboration, sanofi-aventis and Exelixis will combine research efforts to establish several preclinical programs related to isoform-selective inhibitors of P13K (phosphoinositide-3 kinase).

An exclusive worldwide licence and collaboration agreement has been signedCollaborations with the U.S. biotechnology company Merrimack relating toMM-121, currently in Phase I for solid malignancies.

A collaboration and worldwide license agreement was announced in October 2009 between Micromet and sanofi-aventis for the development of a BiTE^® antibody, directed against an antigen present on the surface of tumor cells. BiTE^® antibodies are novel therapeutic antibodies that activate T-cells so that they will identify and destroy tumor cells.

Thrombosis and CardiovascularRegeneron

Thrombosis occurs when a thrombus, or blood clot, forms inside an artery or a vein. Left untreated, a thrombus can eventually grow large enough to blockWe and Regeneron globally collaborate on the blood vessel, preventing blooddevelopment and oxygen from reaching the organ being supplied. Our principal products for the treatment and preventioncommercialization of thrombosis are LovenoxZaltrap^®/Clexane. Under the terms of our September 2003 collaboration agreement, as amended, we and Regeneron will share co-promotion rights and profits on sales, if any, of Zaltrap^® outside of Japan for disease indications included in our collaboration. In Japan, Sanofi will develop and Plavixcommercialize Zaltrap^®/ Iscover, with Regeneron entitled to a royalty payment. Under the terms of the agreement, Sanofi is responsible for funding 100% of the development costs of Zaltrap^®. Once Zaltrap^® starts to be marketed, Regeneron will repay 50% of the development costs (originally paid by Sanofi) in accordance with a formula based on Regeneron’s share of the profits. Sanofi may also be responsible for making milestone payments upon receipt of specified marketing approvals for Zaltrap^® in the United States or the European Union and in Japan.

WithinIn November 2007, Sanofi signed additional agreements with Regeneron to discover, develop and commercialize fully-human therapeutic antibodies. These agreements were broadened, and their term extended, on November 10, 2009. Under the cardiovascular market, hypertension remains the most prevalent disease. Hypertension is defined as blood pressure above the normal level and is oneterms of the main causesdiscovery agreement, Sanofi committed to fund the costs of severe heart, brain, blood vesselRegeneron’s antibody research program until 2017. Sanofi has an option to license for further development those antibodies discovered by Regeneron which advance to IND. Upon exercise of the option, Sanofi is primarily responsible for funding the development and eye complications. co-developing the antibody with Regeneron. Sanofi and Regeneron would also share co-promotion rights and profits on sales. Once a product begins to be marketed, Regeneron will repay out of its profits (provided they are sufficient) 50% of the development costs borne by Sanofi for all antibodies licensed by Sanofi. Sanofi may also be responsible for making milestone payments based upon aggregate sales of antibodies under the collaboration.

Rare Diseases

The acquisition of Genzyme in April 2011 brought to the Group specific expertise in rare diseases, a sector where there are still many unmet needs, and expanded Sanofi’s presence in the biotechnology sector.

Our principalRare Disease business is focused on products for the treatment of cardiovascularrare genetic diseases and other chronic debilitating diseases, including lysosomal storage disorders, or LSDs, a group of metabolic disorders caused by enzyme deficiencies. Our principle rare disease products are Aprovel^®/Avapro^®/Karveaenzyme replacement therapies: Cerezyme^® and Tritace(imiglucerase for injection) to treat Gaucher disease; Fabrazyme^®/Triatec (agalsidase beta) to treat Fabry disease and Myozyme^®/Delix Lumizyme^®/Altace^®. (alglucosidase alfa) to treat Pompe disease.

The incidence of atrial fibrillation (“AF”) is growing worldwide in relation to aging populations. It is emerging as a public health concern and affects about 4.5 million people in Europe and 2.5 million people in the United States. AF leads to potential life-threatening complications, and increases the risk of stroke up to five-fold, worsens the prognosis of patients with cardiovascular risk factors, and doubles the risk of mortality and the risk of hospitalization with significant burden on patients, health care providers and payers. 70% of AF management costs are driven by hospital care and interventional procedures in the European Union. In July 2009, we launched MultaqCerezyme^®

Cerezyme^® (dronedarone) in the United States. Multaq(imiglucerase for injection) is an enzyme replacement therapy that is used to treat Gaucher disease, an inherited, potentially life-threatening LSD. It is estimated that there are approximately 10,000 Gaucher patients worldwide.

Cerezyme^® is the only therapy with a 17-year history of reducing, relieving and reversing many of the symptoms and risks of Type 1 Gaucher disease. Cerezyme^® is administered by intravenous infusion over 1-2 hours.

In June 2009, Genzyme interrupted production of Cerezyme^® and Fabrazyme^® at its Allston facility after identifying a virus in a bioreactor used for Cerezyme^® production. Genzyme resumed Cerezyme^® shipments in the fourth quarter of 2009. This interruption was followed by a second one in March 2010 resulting from a municipal electrical power failure that compounded issues with the facility’s water system.

Genzyme communicated at the end of 2011 that, given current productivity and progress in the manufacturing recovery, we expect an improving supply outlook as the year progresses. We have begun communicating with the U.S. Gaucher community to inform them that, beginning in February 2012, current patients in the U.S. can be returned to normal dosing. Genzyme will also begin the process of returning additional regions globally back to normal supply. This process will begin in the second quarter of 2012 and continue gradually through the remainder of the year, to ensure that a ramp-up can be sustained. Regions outside of the U.S. will be maintained at their current allocation of Cerezyme^®, as Genzyme assesses the timing of the return of additional regions to full supply. No regional allocation will be decreased to accommodate the U.S. ramp-up. We continue to make Cerezyme^® available to patients as it is produced. However, since we have minimal inventory, any change to our manufacturing plans can have an immediate impact on our ability to provide product.

The principal markets for Cerezyme^® are the United States, Latin America and Europe.

Fabrazyme^®

Fabrazyme^® (agalsidase beta) is an enzyme replacement therapy that is used to treat Fabry disease, an inherited, progressive and potentially life-threatening LSD. Fabry disease is estimated to affect between 5,000 and 10,000 people worldwide. Fabrazyme^® is administered by intravenous infusion.

Fabrazyme^® is available in over 30 countries, including the United States and Europe, and has been used in hundreds of patients.

Due to the June 2009 production interruption and low manufacturing productivity upon re-start of production, Fabrazyme^® shipments decreased in the fourth quarter of 2009 and Genzyme began shipping Fabrazyme^® at a rate equal to 30% of estimated product demand. Throughout 2011, Genzyme has maintained consistent supply of Fabrazyme^® to current patients at a reduced dose. To return to normal supply levels of Fabrazyme^® for existing and new patients, it will be necessary to utilize the additional capacity from Genzyme’s new manufacturing facility in Framingham, Massachusetts, that was approved in January 2012 by the FDA and the EMA. Genzyme will begin the process of moving the most severely affected patients in Europe to full dose of Fabrazyme^® during the first quarter of 2012. Beginning in March 2012 in the U.S., all patients currently on therapy are expected to be able to return to full dosing (1mg/kg). In addition, Genzyme will begin to transition

new patients in the U.S. onto Fabrazyme^® at full dosing (1mg/kg) levels. Beginning of March, Genzyme started shipping Fabrazyme^® from Framingham. Globally, the return to normal supply levels of Fabrazyme^® is expected to begin in the second quarter of 2012 and only anti-arrhythmic drugcontinue throughout the year as planned, as Genzyme works to have shown a significant reductionobtain all global regulatory approvals throughout the year and to build inventory.

The principal markets for Fabrazyme^® are the United States and Europe.

Myozyme^® / Lumizyme^®

Myozyme^®/ Lumizyme^® (alglucosidase alfa) are enzyme replacement therapies used to treat Pompe disease, an inherited, progressive and often fatal LSD. We estimate that there are approximately 10,000 Pompe patients worldwide.

Myozyme^® has been marketed since 2006 in cardiovascular hospitalization or deaththe United States and the EU and is currently available in 48 markets worldwide. Lumizyme^® is the first treatment approved in the United States specifically to treat patients with late-onset Pompe disease: Lumizyme^® has been marketed since June 2010. Myozyme^®and Lumizyme^®are administered by intravenous infusion. Lumizyme^® is used to treat Pompe disease in patients with AF/ Atrial flutter (“AFL”).over 8 years of age without evidence of cardiac hypertrophy.

Both products are a recombinant form of the same human enzyme but are manufactured using different sized bioreactors.

The main compounds currently in Phase II or III clinical development in the Rare Diseases field are:

Other Flagship Products

Lovenox^®/Clexane^®

Lovenox^® (enoxaparin sodium) is the most widely studied and used low molecular weight heparin (“LMWH”)available in the world. Itover 100 countries, it has been used to treat an estimated 200over 350 million patients in 100 countries since its launch and is approved for more clinicallaunch.

Lovenox^® has the broadest range of indications than any other LMWH.amongst low molecular weight heparins (LMWH). A comprehensive dossier of clinical studiesdevelopment plan has demonstrated the benefitsefficacy and safety of Lovenox^® in the prophylaxisprevention and treatment of deep vein thrombosisvenous thrombo-embolism (VTE) and in treatmentthe management of the full spectrum of acute coronary syndromes (“ACS”)(ACS). It has become the product of reference in clinical trials for the development of new anti-coagulants in both venous and arterial indications.

In the field of venous thromboembolism (“VTE”) prevention,VTE management, Lovenox^® use continuesis continuing to grow especiallyas a treatment for the prevention of VTE, mainly in hospitalizedacutely ill patients not undergoing surgery.

In 2009, two publications from the ENDORSE survey further highlighted the prevalence of patients at risk of VTE after undergoing surgery other than orthopedic surgery and the underuse of prophylaxis in those patients. It showed that the use of prophylaxis is even lower across different types of hospitalized patients not undergoing surgery and at risk of VTE, prompting the need to further improve the use of effective prophylaxis, as recommended by international guidelines.

After approval2008, new oral anticoagulants were launched for the prevention of VTE in patients undergoing orthopedic surgery and were approved in 2011 for stroke prevention in patients with atrial fibrillation, with the objective to replace vitamin K antagonists (e.g. warfarin). However, the impact has been limited on Lovenox^® usage as prevention of VTE in orthopedic surgery is a small segment of Lovenox^® usage and as stroke prevention in atrial fibrillation is not a Lovenox^® approved indication.

In VTE prophylaxis in acutely ill medical patients, a major market segment for Lovenox^®, two large clinical trials have compared new oral anti-coagulants to Lovenox^®: extended prophylaxis using new oral anti-coagulants has not shown added benefit compared to short term prophylaxis using Lovenox^®.

Competing generics of enoxaparin were launched respectively in July 2010 and in February 2012 in the lower limbs such as total hip replacement, total knee replacementU.S. An authorized generic is available in the U.S.. See “Item 5. Operating and hip fracture surgery in Japan (January 2008),Financial Review and Prospects — Impacts from generic competition”.

In 2011, Lovenox^® was approved for VTE preventionthe leading anti-thrombotic in patients undergoing abdominal surgery in February 2009.

In the cardiovascular area, Lovenox^® was approved in 2007 in the United States for the treatment of patients with ST-segment elevation myocardial infarction, and since then has been approved in more than 40 countries worldwide for this indication.

Lovenox^® is the leader in anti-thrombotics in the United States, Germany, France, Italy, Spain, and the United Kingdom (source: IMS 20092011 sales).

Plavix^®/Iscover^®