BARCLAYS HEALTHCARE CONFERENCE David Meeker, Chief Executive Officer, Genzyme

March 14, 2012

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Forward Looking Statements

This presentation contains forward-looking statements as defined in the Private Securities Litigation Reform Act of 1995, as amended. Forward-looking statements are statements that are not historical facts. These statements include projections and estimates and their underlying assumptions, statements regarding plans, objectives, intentions and expectations with respect to future financial results, events, operations, services, product development and potential, and statements regarding future performance. Forward-looking statements are generally identified by the words "expects", "anticipates", "believes", "intends", "estimates", "plans" and similar expressions. Although Sanofi's management believes that the expectations reflected in such forward-looking statements are reasonable, investors are cautioned that forward-looking information and statements are subject to various risks and uncertainties, many of which are difficult to predict and generally beyond the control of Sanofi, that could cause actual results and developments to differ materially from those expressed in, or implied or projected by, the forward-looking information and statements. These risks and uncertainties include among other things, the uncertainties inherent in research and development, future clinical data and analysis, including post marketing, decisions by regulatory authorities, such as the FDA or the EMA, regarding whether and when to approve any drug, device or biological application that may be filed for any such product candidates as well as their decisions regarding labeling and other matters that could affect the availability or commercial potential of such product candidates, the absence of guarantee that the product candidates if approved will be commercially successful, the future approval and commercial success of therapeutic alternatives, the Group's ability to benefit from external growth opportunities, trends in exchange rates and prevailing interest rates, the impact of cost containment policies and subsequent changes thereto, the average number of shares outstanding as well as those discussed or identified in the public filings with the SEC and the AMF made by Sanofi, including those listed under "Risk Factors" and "Cautionary Statement Regarding Forward-Looking Statements" in Sanofi's annual report on Form 20-F for the year ended December 31, 2011. Other than as required by applicable law, Sanofi does not undertake any obligation to update or revise any forward-looking information or statements.

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Highlights of key achievements to date

Rare diseases opportunity

Agenda

Multiple sclerosis opportunity

Rare diseases and Genzyme

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Sanofi Grew Sales in 2011 due to Genzyme Acquisition and Growth Platforms

2011

€33,389m

2010

€32,367m

2009

€29,306m

2008

€27,568m

Sales

+5.3% at CER

4 (1) In 2008 and 2009, Merial Joint Venture sales were not consolidated by Sanofi (2) In 2010, excluding non-consolidated sales from Merial, Sanofi reported sales of €30,384m

(1) (1) (2)

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2009 2011 2010 2008

% of Total

42.7% 65.0%

Sales of Growth Platforms(1) & Genzyme

Sanofi Boosted Sales of its Growth Platforms and Significantly Reduced its Patent Cliff Exposure in 2011

(1) 2010 include sales of Merial. In 2008 and 2009, Merial Joint Venture sales were not consolidated by Sanofi (2) Lovenox® U.S., Plavix® Western EU, Taxotere® Western EU & U.S., Eloxatin® U.S., Ambien CR® U.S., Allegra® U.S., Aprovel® Western EU, Xyzal® U.S., Xatral® U.S., Nasacort® U.S. Eloxatin® U.S. market exclusivity expected through August 9, 2012.

2011 2009 2010 2008

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% of Total

27.4% 9.4%

Sales of Key Genericized Products(2)

€21,703m

€11,783m

€3,152m

€7,565m

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€6.61

2011

€6.65

2010

€7.06

2009 2008

€5.59

Patent Cliff Impact on EPS Mitigated in 2011

Business EPS

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-3.8% at CER

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Successful Acquisition of Genzyme in 2011

Strong management team in place Focus on Rare Diseases and Multiple Sclerosis

Completing the integration

Ensuring manufacturing recovery

Creating synergies Achieved synergies of $230m in 2011

Advancing R&D pipeline Strong Phase III results with LemtradaTM

Oral eliglustat tartrate Phase III program fully recruited Cambridge positioned as primary U.S. research site

A SANOFI COMPANY

FDA and EMA approvals granted for Framingham plant to supply Fabrazyme®

Progress towards focusing Allston plant on Cerezyme® Target inventory increase of Cerezyme® and Fabrazyme®

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2

3

4

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Q2 2011 Q3 2011 Q4 2011

Genzyme Recovery On Track

Quarterly Sales(1) (€m)

&

● FY 2011 Genzyme consolidated sales reached €2,395m, +7.7%(1,2)

● Q4 2011 sales of €831m, +0.8%(2) ● Rare Diseases sales of €346m

• Solid performance of Myozyme®/ Lumizyme® of €108m, +15.9%

• Cerezyme® and Fabrazyme® sales constrained by supply

● Good performance of Renagel®/ Renvela® and Synvisc® franchise

● EMA and FDA approvals granted for Framingham plant in Jan 2012 ● Complete return to normal supply

levels of Fabrazyme® to begin in Q2 2012

& Others

(1) Genzyme sales are consolidated since April 1, 2011 (2) Change on a constant structure basis and at constant exchange rates

€796m €768m €831m

Others

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Highlights of key achievements to date

Rare diseases opportunity

Agenda

Multiple sclerosis opportunity

Rare diseases and Genzyme

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Orphan Drug Market

Orphan Drug Market is Attractive and Offers Growth Potential Due to Significant Unmet Needs

● Significant unmet needs create strong growth potential ● Under-served patient population

● Drugs available for only ~200 out of >6,000 orphan diseases(1)

● 85% orphan diseases are life threatening and 50% are pediatric(2)

● Several attractive market characteristics ● Unique development challenges

● Regulatory exclusivity period

● >$10bn sales for orphan-only drugs growing at high single digit since 2000 ● Expected to reach $18bn in 2015(3)

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(1) BioWorld Today, 2011 (2) Food and Drug Administration, "Office of Orphan Products Development," Budget 2010 (3) EvaluatePharma; internal analysis

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Unleashing the Full Potential of Genzyme within Sanofi

Develop MS

franchise

Escalate existing

R&D programs

Broaden biologics

experience

Leverage global

scope and manufacturing

expertise

Create R&D hub in Boston

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Highlights of key achievements to date

Rare diseases opportunity

Agenda

Multiple sclerosis opportunity

Rare diseases and Genzyme

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1983

2001

Cerezyme® is the Foundation of the Genzyme Model

Transformative Therapy

2011 Sales Split

Ensure Market Access Extensive Global Reach

● Increase awareness

● Enable access to diagnostic testing

● Identify and train experts

● Support patient advocacy

● Partner with healthcare systems

EU

U.S. ROW

47%

28% 25%

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Untapped Cerezyme® Opportunity in Gaucher Disease

(1) Symptomatic prevalence and diagnosed patient estimates from 2010 rare disease Market Models / Epidemiology Database. (2) Sims K, Pastores G, Weinreb N, Barranger J, Rosenbloom B, Packman S, et al. Improvement of bone disease by imiglucerase (Cerezyme®) therapy

in patients with skeletal manifestations of type 1 Gaucher disease: results of a 48-month longitudinal cohort study. Clin Genet 2008; 73:430-40.

● Focus is on supplying patients ● Expect improving supply outlook

from February 2012 forward

● Differentiated profile: ● 20 years of proven safety and

efficacy ● Demonstrated bone benefits(2)

● Significant additional opportunity exists with undiagnosed patients

Total treated Diagnosed

~7,000 ~6,400

CZ treated

~4,600

Large population of undiagnosed

patients(1) 9% of diagnosed

patients not treated

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Myozyme®/Lumizyme®: Only Approved Treatment for Pompe

15 (1) Symptomatic Prevalence based on 2011 Pompe Epi Model in 92 countries (excluding China and India). (2) Identified and treated patient numbers from regional patient trackers and LSD WW Report as of December 2010

MZ/LZ treated

~1,600

Total treated

~1,600

Diagnosed

~2,000

Large population of undiagnosed

patients(1)

19% of diagnosed

patients not treated(2)

● Long-term potential commercial opportunity similar to Cerezyme®

● Documented clinical benefit across disease spectrum

● Focus is on:

● Driving disease awareness

● Partnering with physicians to increase early diagnosis

050

100150200250300350400450500550600

0 1 year 2 year 3 year 4 year 5 year

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Myozyme®: Genzyme’s Most Successful Launch

(1) Reflects the first full fiscal year after launch

Ceredase®/Cerezyme®

Fabrazyme®

Aldurazyme®

Myozyme®/Lumizyme®

(1)

$m Sales

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Fabrazyme® Potential Unleashed when Supply is Restored

(1) Symptomatic prevalence and diagnosed patient estimates from 2010 rare disease Market Models / Epidemiology Database.

Total treated

~4,200

FZ treated

~6,000

Diagnosed

Large population of undiagnosed

patients(1)

30% of diagnosed

patients not treated

~1,600

● Efficacy demonstrated at 1mg/kg ● Regain significant market share by:

● Restoring supply ● Driving importance of dose in

clinical outcomes ● Growing patient awareness

● Framingham plant received regulatory approval from FDA and EMA January 2012 ● Begins the process of

returning patients to full dosing levels

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Fabrazyme® – Treating the Family

Finding 1 new index patient leads, on average, to diagnosis of another 5 patients in that family

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Expanding Manufacturing Capacity is Key to Future Growth

Sites 2011 2012e 2015e Capacity

12,000L

20,000L

Framingham, MA new plant

8,000L

Allston, MA

Geel, Belgium

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Creation of the Genzyme

R&D Center

Leveraging Genzyme’s Innovative Capabilities

● Strong expertise in rare diseases and multiple sclerosis

● Unique biologics platform

● Commitment to open innovation

● Integrated innovation hub in the Boston area

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Eliglustat tartrate: a Novel Oral Therapy in Gaucher Disease(1)

● Potent, novel substrate inhibitor

● Convenience of oral therapy ● Eliminating challenges of

infusing patients

● Clinical profile expected to be similar to Cerezyme®

● 4-year Phase II data at WORLD congress in February 2012

● Phase III trials fully recruited

(1) Investigational drug (2) Patient from Phase II clinical trial WORLD – World Organization of Research on Lysosomal Diseases

December 2006 pre-treatment (18 years)

December 2009 3 years post treatment (21 years)(2)

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Phase 2: Eliglustat tartrate Clinical Data Comparable to Cerezyme®(1)

Platelets +95%

Hemoglobin +2.3 g/dL

-4

-2

0

2

4

Hb Change from Baseline

(g/dL)

-100%

-50%

0%

50%

100%

Mean % Change

from Baseline

Liver -28%

Spleen -63%

Year 1

Year 2 Year 3 Year 4 Baseline

(1) Cerezyme® Registry Data on File – Upper and Lower 95% Confidence Interval around Mean

Study Results: Treatment Changes to 4 Years

Cerezyme® Range

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Kynamro™: Targeting Rare Familial Hypercholesterolemias

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(1) Patients for hoFH and Severe FH in US and EU markets hoFH – Homozygous Familial Hypercholesterolemia Severe FH – Severe Familial Hypercholesterolemia = treated LDL-C CHD – Coronary Heart Disease heFH – Heterozygous familial hypercholesterolemia

● Four Phase III trials conducted in severe forms of hypercholesterolemia ● Sustained reduction in apo B production

resulting in significant decreases in LDL-C and Lp(a) when added to a regimen of maximally tolerated statin dose and other lipid lowering therapies

● Adverse reactions include ISRs, FLS, and elevations in liver transaminases and fat ● Liver fat stabilized or decreased in some

patients with treatment beyond 12 months

HeFH: 1 million patients

HoFH Severe FH

Understanding Rarity

~40,000 patients(1)

On statins: 60 million patients

ISR – Injection Site Reactions FLS – Flu Like Symptoms

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Highlights of key achievements to date

Rare diseases opportunity

Agenda

Multiple sclerosis opportunity

Rare diseases and Genzyme

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Global MS Market Expected to Continue to Grow

MS Market Sales(1) Key Facts about MS

● ~2.1m patients worldwide

● Prevalent in young women (~2:1 female/male ratio)

● Life expectancy 5-10 years lower than unaffected people

● A major impact on family, social and professional life

● Symptoms include fatigue, weakness, walking and balance difficulties, vision problems

Multiple Sclerosis CAGR

~6%

(1) Evaluate Pharma

2010 2015e

U.S.

ROW

$11.2bn

~$15.3bn

53%

57%

47% 43%

Efficacy with manageable safety

Convenience, safety & efficacy

Early MS/CIS(1) RRMS(2) and early active MS

RMS(3) severe/ highly active

Emergence of a Franchise Addressing the Full Spectrum of Patient Needs in Multiple Sclerosis

Lemtrada™

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Aubagio®

Convenience & safety

Rebif®

Lemtrada™

Aubagio™

(1) CIS – Clinically Isolated Syndrome, TOPIC Phase III study presently ongoing (2) RRMS – Relapse Remitting Multiple Sclerosis (3) RMS – Relapsing Multiple Sclerosis 26

A Unique Value Proposition: Superior Efficacy with Convenient Annual Dosing

CARE-MS I CARE-MS II

Patients 581 840

Study Duration 2 years 2 years

Patient Population

Treatment naïve

Relapsed on prior treatment

Treatment Arms

Alemtuzumab vs. IFNβ 1a

Alemtuzumab vs. IFNβ 1a

Relapse Rate Reduction at 2 Years(1)

55% (p<0.0001)

49% (p<0.0001)

Sustained Accumulation of Disability Reduction in

6 Months(1) (ns) 42%

(p=0.0084)

● Superior efficacy in Phase III vs. Rebif®

● Manageable safety:

● Well-characterized and consistent across studies

● Effective risk management when events identified early

(1) Co-primary endpoints in CARE-MS I and CARE-MS II 27

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Aubagi A Once-Daily Oral Therapy with Comparable Efficacy to Injectable Interferon

● Efficacy demonstrated in TEMSO on both Relapse Rate and Disability Progression at 14mg

● No superiority vs. Rebif® in TENERE but lower rate of TEAE-related discontinuation

● Manageable safety profile with up to 10 years of follow-up

(1) Aubagio™ is a registered trade name submitted to health authorities for teriflunomide, an investigational agent. (2) Adjusted for Expanded Disability Status Scale score strata at baseline and takes duration of treatment into account. TEAE – Treatment Emergent Adverse Events, ARR – Annualized Relapse Rate, RRR – Relative risk reduction, HRR – Hazard ratio reduction

0 0,1 0,2 0,3 0,4 0,5 0,6

T. 14 mg

T. 7 mg

Placebo

TEMSO: Reduction in Adjusted(2) ARR

RRR: 31.2% p=0.0002

RRR: 31.5% p=0.0005

0 12 24 36 48 60 72 84 96 1080%

20%

10%

HRR: 23.7% p=ns

HRR: 29.8% p=0.0279

30% Placebo T. 7 mg T. 14 mg

Week

TEMSO: Reduction in Disability Progression (%)

1

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2012-2015: Genzyme Key Growth Drivers

● Maximize market opportunity for rare disease business

● Increase manufacturing capabilities for Cerezyme® & Fabrazyme®

● Increase Pompe disease awareness/diagnosis

● Launch eliglustat tartrate and Kynamro™

● Further expand rare diseases business through internal and external opportunities

● Establish leading MS franchise

● Launch Aubagio™ and Lemtrada™

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