Document:

EX-10.20

 

Exhibit 10.20

STOCK PURCHASE AGREEMENT

By and Among

SANOFI-AVENTIS AMÉRIQUE DU NORD,

SANOFI-AVENTIS US LLC

AND

REGENERON PHARMACEUTICALS, INC.

Dated as of November 28, 2007

 

 

TABLE OF CONTENTS

	 	 	 	 	 
	 	 	Page	 
	1. DEFINITIONS
	 	 	1	 
	1.1 Defined Terms
	 	 	1	 
	1.2 Additional Defined Terms
	 	 	4	 
	2. PURCHASE AND SALE OF COMMON STOCK
	 	 	4	 
	3. CLOSING DATE; DELIVERIES
	 	 	5	 
	3.1 Closing Date
	 	 	5	 
	3.2 Deliveries
	 	 	5	 
	4. REPRESENTATIONS AND WARRANTIES OF THE COMPANY
	 	 	6	 
	4.1 Organization, Good Standing and Qualification
	 	 	6	 
	4.2 Capitalization and Voting Rights
	 	 	6	 
	4.3 Subsidiaries
	 	 	7	 
	4.4 Authorization
	 	 	7	 
	4.5 No Defaults
	 	 	7	 
	4.6 No Conflicts
	 	 	7	 
	4.7 No Governmental Authority or Third Party Consents
	 	 	8	 
	4.8 Valid Issuance of Shares
	 	 	8	 
	4.9 Litigation
	 	 	8	 
	4.10 Licenses and Other Rights; Compliance with Laws
	 	 	8	 
	4.11 Company SEC Documents; Financial Statements; Nasdaq Stock Market
	 	 	8	 
	4.12 Absence of Certain Changes
	 	 	9	 
	4.13 Internal Controls; Disclosure Controls and Procedures
	 	 	9	 
	4.14 Intellectual Property
	 	 	10	 
	4.15 Offering
	 	 	10	 
	4.16 No Integration
	 	 	10	 
	4.17 Brokers’ or Finders’ Fees
	 	 	10	 
	4.18 Not Investment Company
	 	 	10	 
	5. REPRESENTATIONS AND WARRANTIES OF THE INVESTOR
	 	 	10	 
	5.1 Organization; Good Standing
	 	 	10	 
	5.2 Authorization
	 	 	11	 

i 

 

	 	 	 	 	 
	5.3 No Conflicts
	 	 	11	 
	5.4 No Governmental Authority or Third Party Consents
	 	 	11	 
	5.5 Purchase Entirely for Own Account
	 	 	11	 
	5.6 Disclosure of Information
	 	 	12	 
	5.7 Investment Experience and Accredited Investor Status
	 	 	12	 
	5.8 Acquiring Person
	 	 	12	 
	5.9 Restricted Securities
	 	 	12	 
	5.10 Legends
	 	 	12	 
	5.11 Financial Assurances
	 	 	13	 
	6. COVENANTS OF THE COMPANY
	 	 	13	 
	6.1 Conduct of the Business Pending Closing
	 	 	13	 
	6.2 Use of Proceeds
	 	 	13	 
	7. INVESTOR’S CONDITIONS TO CLOSING
	 	 	13	 
	7.1 Representations and Warranties
	 	 	13	 
	7.2 Covenants
	 	 	14	 
	7.3 Investor Agreement
	 	 	14	 
	7.4 Discovery Agreement; Sanofi License and Collaboration Agreement
	 	 	14	 
	7.5 No Material Adverse Effect
	 	 	14	 
	8. COMPANY’S CONDITIONS TO CLOSING
	 	 	14	 
	8.1 Representations and Warranties
	 	 	14	 
	8.2 Covenants
	 	 	14	 
	8.3 Investor Agreement
	 	 	14	 
	8.4 Discovery Agreement; Sanofi License and Collaboration Agreement
	 	 	14	 
	9. MUTUAL CONDITIONS TO CLOSING
	 	 	15	 
	9.1 HSR Act and Other Qualifications
	 	 	15	 
	9.2 Absence of Litigation
	 	 	15	 
	9.3 No Prohibition
	 	 	15	 
	10. TERMINATION
	 	 	15	 
	10.1 Ability to Terminate
	 	 	15	 
	10.2 Effect of Termination
	 	 	16	 
	11. ADDITIONAL COVENANTS AND AGREEMENTS
	 	 	17	 
	11.1 Legending of Existing Shares
	 	 	17	 
	11.2 Amendment of Aventis Agreement
	 	 	17	 

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	11.3 Market Listing
	 	 	18	 
	11.4 Notification under the HSR Act
	 	 	18	 
	11.5 Assistance and Cooperation
	 	 	18	 
	11.6 Effect of Waiver of Condition to Closing
	 	 	19	 
	12. MISCELLANEOUS
	 	 	19	 
	12.1 Governing Law; Submission to Jurisdiction
	 	 	19	 
	12.2 Waiver
	 	 	19	 
	12.3 Notices
	 	 	20	 
	12.4 Entire Agreement
	 	 	20	 
	12.5 Amendments
	 	 	20	 
	12.6 Headings; Nouns and Pronouns; Section References
	 	 	20	 
	12.7 Severability
	 	 	20	 
	12.8 Assignment
	 	 	20	 
	12.9 Successors and Assigns
	 	 	21	 
	12.10 Counterparts
	 	 	21	 
	12.11 Third Party Beneficiaries
	 	 	21	 
	12.12 No Strict Construction
	 	 	21	 
	12.13 Survival of Warranties
	 	 	21	 
	12.14 Remedies
	 	 	21	 
	12.15 Expenses
	 	 	21	 
	 
	 	 	 	 
	Exhibit A – Form of Cross Receipt
	 	 	 	 
	Exhibit B
– Form of Investor Agreement
	 	 	 	 
	Exhibit C – Conduct of the Business Pending Closing
	 	 	 	 
	Exhibit D – Notices
	 	 	 	 

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Exhibit 10.20

STOCK PURCHASE AGREEMENT

     THIS STOCK PURCHASE AGREEMENT (this “Agreement”), dated as of November 28, 2007, by
and among sanofi-aventis Amérique du Nord (the “Investor”), a société en nom collectif
organized under the laws of France and wholly owned by sanofi-aventis, a company organized under
the laws of France (“sanofi-aventis”), with its principal headquarters at 174, avenue de
France, 75013 Paris, France, sanofi-aventis US LLC (solely for purposes of Sections 5.11, 8.2, 8.3,
11.2 and 12.13), a Delaware limited liability company indirectly wholly owned by the Investor
(“Sanofi US”) and the successor in interest to Aventis Pharmaceuticals Inc., a Delaware
corporation indirectly wholly owned by the Investor (“Aventis”), with respect to the
Aventis Collaboration Agreement, with its headquarters at 55 Corporate Drive, Bridgewater, New
Jersey 00807, and Regeneron Pharmaceuticals, Inc. (the “Company”), a New York corporation
with its principal place of business at 777 Old Saw Mill River Road, Tarrytown, New York 10591.

     WHEREAS, pursuant to the terms and subject to the conditions set forth in this Agreement, the
Company desires to issue and sell to the Investor, and the Investor desires to subscribe for and
purchase from the Company, certain shares of common stock, par value $0.001 per share, of the
Company (the “Common Stock”).

     NOW, THEREFORE, in consideration of the following mutual promises and obligations, and for
good and valuable consideration, the adequacy and sufficiency of which are hereby acknowledged, the
Investor, Sanofi US and the Company agree as follows:

1. Definitions.

     1.1 Defined Terms. When used in this Agreement, the following terms shall have the respective
meanings specified therefor below:

     “Affiliate” shall mean, with respect to any Person, another Person which controls, is
controlled by or is under common control with such Person. A Person shall be deemed to control
another Person if such Person possesses, directly or indirectly, the power to direct or cause the
direction of the management and policies of such Person, whether through the ownership of voting
securities, by contract or otherwise. Without limiting the generality of the foregoing, a Person
shall be deemed to control another Person if any of the following conditions is met: (i) in the
case of corporate entities, direct or indirect ownership of more than fifty percent (50%) of the
stock or shares having the right to vote for the election of directors, and (ii) in the case of
non-corporate entities, direct or indirect ownership of more than fifty percent (50%) of the equity
interest with the power to direct the management and policies of such non-corporate entities. The
parties acknowledge that in the case of certain entities organized under the Laws of certain
countries outside of the United States, the maximum percentage ownership permitted by Law for a
foreign investor may be less than fifty percent (50%), and that in such case such lower percentage
shall be substituted in the preceding sentence, provided that such foreign investor has the power
to direct the management and policies of such entity. For the purposes of this Agreement, in no
event shall the Investor or any of its Affiliates be deemed Affiliates of the

 

 

Company or any of its Affiliates, nor shall the Company or any of its Affiliates be deemed
Affiliates of the Investor or any of its Affiliates.

     “Agreement” shall have the meaning set forth in the Preamble, including all Exhibits
attached hereto.

     “Aventis Collaboration Agreement” shall mean the Collaboration Agreement, dated as of
September 5, 2003, by and between Sanofi US (as successor in interest to Aventis) and the Company,
as amended by the First Amendment, dated as of December 31, 2004, the Second Amendment, dated as of
January 7, 2005, the Third Amendment, dated as of December 21, 2005, the Fourth Amendment, dated as
of January 31, 2006, Section 11.2 of this Agreement, and as further amended from time to time.

     “Business Day” shall mean a day on which commercial banking institutions in New York,
New York are open for business.

     “Collaboration Agreements” means, collectively, the Aventis Collaboration Agreement,
the Discovery Agreement and the Sanofi License and Collaboration Agreement.

     “Cross Receipt” shall mean an executed document signed by each of the Company and the
Investor, in substantially the form of Exhibit A attached hereto.

     “Discovery Agreement” shall mean that certain Discovery and Preclinical Development
Agreement between the Company and Aventis dated as of the date hereof, as the same may be amended
from time to time.

     “Effect” shall have the meaning set forth in the definition of “Material Adverse
Effect.”

     “Governmental Authority” shall mean any court, agency, authority, department or other
instrumentality of any government or country or of any national, federal, state, provincial,
regional, county, city or other political subdivision of any such government or country or any
supranational organization of which any such country is a member.

     “Intellectual Property” shall mean shall mean trademarks, trade names, trade dress,
service marks, copyrights, and similar rights (including registrations and applications to register
or renew the registration of any of the foregoing), patents and patent applications, trade secrets,
and any other similar intellectual property rights.

     “Intellectual Property License” shall mean any license, permit, authorization,
approval, contract or consent granted, issued by or with any Person relating to the use of
Intellectual Property.

     “Investor Agreement” shall mean that certain Investor Agreement among sanofi-aventis,
Sanofi US, Aventis, the Investor and the Company, to be dated as of the Closing Date, in
substantially the form of Exhibit B attached hereto, as the same may be amended from time
to time.

2

 

     “Law” or “Laws” shall mean all laws, statutes, rules, regulations, orders,
judgments, injunctions and/or ordinances of any Governmental Authority.

     “Material Adverse Effect” shall mean any change, event or occurrence (each, an
“Effect”) that, individually or when taken together with all other Effects, has (i) a
material adverse effect on the business, financial condition, results of operations or prospects of
the Company and its subsidiaries, taken as a whole, or (ii) a material adverse effect on the
Company’s ability to perform its obligations, or consummate the Transaction, in accordance with the
terms of this Agreement, except in the case of (i) or (ii) to the extent that any such Effect
results from or arises out of: (A) changes in conditions in the United States or global economy or
capital or financial markets generally, including changes in interest or exchange rates, (B)
changes in general legal, regulatory, political, economic or business conditions or changes in
generally accepted accounting principles in the United States or interpretations thereof that, in
each case, generally affect the biotechnology or biopharmaceutical industries, (C) the
announcement, pendency or performance of this Agreement, the Discovery Agreement or the Sanofi
License and Collaboration Agreement, or the consummation of the Transaction or the identity of the
Investor, (D) any change in the trading prices or trading volume of the Common Stock (it being
understood that the facts giving rise to or contributing to any such change may be deemed to
constitute, or be taken into account when determining whether there has been or will be, a Material
Adverse Effect, except to the extent any of such facts is an Effect referred in clauses (A) through
(J) of this definition), (E) acts of war, sabotage or terrorism, or any escalation or worsening of
any such acts of war, sabotage or terrorism, (F) earthquakes, hurricanes, floods or other natural
disasters, (G) any action taken by the Company contemplated by this Agreement or in accordance with
any of the Collaboration Agreements or with the Investor’s written consent, (H) any breach,
violation or non-performance by the Investor or any of its Affiliates under any of the
Collaboration Agreements, or (I) shareholder litigation arising out of or in connection with the
execution, delivery or performance of the Transaction Agreements, the Discovery Agreement or the
Sanofi License and Collaboration Agreement; provided, that with respect to clauses (A),
(B), (E) and (F) such Effect does not have a materially disproportionate and adverse effect on the
Company relative to most other comparable companies and their respective subsidiaries, taken as a
whole, in the biotechnology or biopharmaceutical industries.

     “Organizational Documents” shall mean (i) the Restated Certificate of Incorporation of
the Company as of June 21, 1991, as amended through the date of this Agreement and (ii) the By-Laws
of the Company, as amended through the date of this Agreement.

     “Person” shall mean any individual, partnership, limited liability company, firm,
corporation, trust, unincorporated organization, government or any department or agency thereof or
other entity, as well as any syndicate or group that would be deemed to be a Person under Section
13(d)(3) of the Exchange Act.

     “Sanofi License and Collaboration Agreement” shall mean that certain License and
Collaboration Agreement between the Company, the Investor and Aventis dated as of the date hereof.

     “Third Party” shall mean any Person (other than a Governmental Authority) other than
the Investor, the Company or any Affiliate of the Investor or the Company.

3

 

     “Transaction” means the issuance and sale of the Shares by the Company, and the
purchase of the Shares by the Investor, in accordance with the terms hereof.

     “Transaction Agreements” shall mean this Agreement and the Investor Agreement.

     1.2 Additional Defined Terms. In addition to the terms defined in Section 1.1, the following terms
shall have the respective meanings assigned thereto in the sections indicated below:

	 	 	 	 	 
	 	 	Defined Term	 	Section
	 
	 	 	 	 
	 

	 	Aggregate Purchase Price
	 	Section 2
	 

	 	Aventis
	 	Preamble
	 

	 	Class A Stock
	 	Section 4.2(a).
	 

	 	Closing
	 	Section 3.1
	 

	 	Closing Date
	 	Section 3.1
	 

	 	Common Stock
	 	Preamble
	 

	 	Company
	 	Preamble
	 

	 	Company SEC Documents
	 	Section 4.11(a)
	 

	 	Exchange Act
	 	Section 4.11(a)
	 

	 	Final Termination Date
	 	Section 10.1(b)
	 

	 	HSR Act
	 	Section 4.7
	 

	 	Investor
	 	Preamble
	 

	 	LAS
	 	Section 4.7
	 

	 	Modified Clause
	 	Section 12.7
	 

	 	Permits
	 	Section 4.10
	 

	 	Original Termination Date
	 	Section 10.1(b)
	 

	 	Sanofi US
	 	Preamble
	 

	 	sanofi-aventis
	 	Preamble
	 

	 	SEC
	 	Section 4.7
	 

	 	Securities Act
	 	Section 4.11(a)
	 

	 	Share Amount
	 	Section 2
	 

	 	Shares
	 	Section 2

2. Purchase and Sale of Common Stock. Subject to the terms and conditions of this Agreement, at
the Closing, the Company shall issue and sell to the Investor, free and clear of all liens, other
than any liens arising as a result of any action by the Investor, and the Investor shall purchase
from the Company, a number of shares of Common Stock equal to the Share Amount (the
“Shares”), for an aggregate purchase price of US $312,000,000.00. (the “Aggregate
Purchase Price”). The “Share Amount” shall equal 12,000,000; provided,
however, that in the event of any stock dividend, stock split, combination of shares,
recapitalization or other similar change in the capital structure of the Company after the date
hereof and on or prior to the Closing which affects or relates to the Common Stock, the Share
Amount shall be adjusted proportionately.

4

 

3. Closing Date; Deliveries.

     3.1 Closing Date. Subject to the satisfaction or waiver of all the conditions to the Closing set
forth in Sections 7, 8 and 9 hereof, the closing of the purchase and sale of the Shares hereunder
(the “Closing”) shall be held on the third (3rd) Business Day after the
satisfaction of the conditions to Closing set forth in Sections 7, 8 and 9 (other than those
conditions that by their nature are to be satisfied at the Closing), at 10:00 a.m. New York City
time, at the offices of Skadden, Arps, Slate, Meagher & Flom LLP, 4 Times Square, New York, New
York 10036, or at such other time, date and location as the parties may agree in writing. The date
the Closing occurs is hereinafter referred to as the “Closing Date.”

     3.2 Deliveries.

          (a) Deliveries by the Company. At the Closing, the Company shall deliver to the
Investor a stock certificate, registered in the name of the Investor, representing the Shares, and
the Company shall instruct its transfer agent to register such issuance at the time of such
issuance. The Company shall also deliver at the Closing: (i) a duly executed Cross Receipt; (ii) a
certificate in form and substance reasonably satisfactory to the Investor and duly executed on
behalf of the Company by an authorized executive officer of the Company, certifying that the
conditions to Closing set forth in Sections 7 and 9.3(b) of this Agreement have been fulfilled;
(iii) a duly executed Investor Agreement; and (iv) a certificate of the secretary of the Company
dated as of the Closing Date certifying (A) that attached thereto is a true and complete copy of
the By-Laws of the Company as in effect on the Closing Date; (B) that attached thereto is a true
and complete copy of all resolutions adopted by the Board of Directors of the Company authorizing
the execution, delivery and performance of the Transaction Agreements and the Transaction and that
all such resolutions are in full force and effect and are all the resolutions adopted in connection
with the transactions contemplated hereby as of the Closing Date; (C) that attached thereto is a
true and complete copy of the Company’s Restated Certificate of Incorporation as in effect on the
Closing Date; and (D) as to the incumbency and specimen signature of any officer of the Company
executing a Transaction Agreement on behalf of the Company.

          (b) Deliveries by the Investor. At the Closing, the Investor shall deliver to the
Company the Aggregate Purchase Price by wire transfer of immediately available United States funds
to an account designated by the Company. The Company shall notify the Investor in writing of the
wiring instructions for such account not less than three (3) Business Days before the Closing Date.
The Investor shall also deliver, or cause to be delivered, at the Closing: (i) a duly executed
Cross Receipt; (ii) a certificate in form and substance reasonably satisfactory to the Company duly
executed by an authorized executive officer of the Investor certifying that the conditions to
Closing set forth in Section 8 of this Agreement have been fulfilled; (iii) an Investor Agreement,
duly executed by sanofi-aventis, Sanofi US, Aventis and the Investor; and (iv) a certificate of the
secretaries of sanofi-aventis, Sanofi US, Aventis and the Investor dated as of the Closing Date
certifying (A) that attached thereto are true and complete copies of any and all organizational
documents (including any articles or memoranda of organization or association, charter, bylaws or
similar documents) of each of sanofi-aventis, Sanofi US, Aventis and the Investor, as applicable,
as in effect on the Closing Date; and (B) as to the incumbency and specimen signature of any
officer executing a Transaction Agreement on behalf of sanofi-aventis, Sanofi US, Aventis or the
Investor, as applicable.

5

 

4. Representations and Warranties of the Company. The Company hereby represents and warrants to
the Investor that:

     4.1 Organization, Good Standing and Qualification.

          (a) The Company is a corporation duly organized, validly existing and in good standing under
the laws of the State of New York. The Company has all requisite corporate power and corporate
authority to own, lease and operate its properties and assets, to carry on its business as now
conducted, and as proposed to be conducted as described in the Company SEC Documents, to enter into
the Transaction Agreements to issue and sell the Shares and to carry out the other transactions
contemplated by the Transaction Agreements.

          (b) The Company is qualified to transact business and is in good standing in each jurisdiction
in which the character of the properties owned, leased or operated by the Company or the nature of
the business conducted by the Company makes such qualification necessary, except where the failure
to be so qualified would not have a Material Adverse Effect.

     4.2 Capitalization and Voting Rights.

          (a) The authorized capital of the Company as of the date hereof consists of: (i) 160,000,000
shares of Common Stock of which, as of the date of this Agreement, (w) 63,932,731 shares are issued
and outstanding, (x) 2,260,266 shares are reserved for issuance upon conversion of the Company’s
Class A Stock, par value $0.001 per share (the “Class A Stock”), each share of Class A
Stock being convertible into one (1) share of Common Stock, (y) 18,843,943 shares are reserved for
issuance pursuant to the Company’s 2000 Long-Term Incentive Plan, of which 15,244,146 shares are
issuable upon the exercise of stock options outstanding on the date hereof, and (z) 6,611,300
shares are reserved for issuance upon conversion of the Company’s 51/2% Convertible Senior
Subordinated Notes due 2008; (ii) 40,000,000 shares of Class A Stock of which, as of the date of
this Agreement, 2,260,266 shares are issued and outstanding and 44,246 shares are reserved for
issuance pursuant to the Company’s 1989 Executive Stock Purchase Plan; and (iii) 30,000,000 shares
of preferred stock, par value $0.01 per share, of which no shares are issued and outstanding as of
the date of this Agreement. All of the issued and outstanding shares of Common Stock and Class A
Stock (A) have been duly authorized and validly issued, (B) are fully paid and non-assessable and
(C) were issued in compliance with all applicable federal and state securities Laws and not in
violation of any preemptive rights.

          (b) All of the authorized shares of Common Stock are entitled to one (1) vote per share. All
of the authorized shares of Class A Stock are entitled to ten (10) votes per share.

          (c) Except as described or referred to in Section 4.2(a) above, as of the date hereof, there
are not: (i) any outstanding equity securities, options, warrants, rights (including conversion or
preemptive rights) or other agreements pursuant to which the Company is or may become obligated to
issue, sell or repurchase any shares of its capital stock or any other securities of the Company or
(ii) except as set forth in the Investor Agreement, any restrictions on the transfer of capital
stock of the Company other than pursuant to state and federal securities Laws.

6

 

          (d) Except as provided in the Investor Agreement, the Company is not a party to or subject to
any agreement or understanding relating to the voting of shares of capital stock of the Company or
the giving of written consents by a stockholder or director of the Company.

     4.3 Subsidiaries. The Company does not have any subsidiaries required to be disclosed in an
exhibit to its Annual Report on Form 10-K pursuant to Item 601(b)(21) of Regulation S-K.

     4.4 Authorization.

          (a) All requisite corporate action on the part of the Company, its directors and stockholders
required by applicable Law or, assuming the accuracy of the Investor’s representation in Section
5.8, The NASDAQ Stock Market LLC for the authorization, execution and delivery by the Company of
the Transaction Agreements and the performance of all obligations of the Company hereunder and
thereunder, including the authorization, issuance and delivery of the Shares, has been taken.

          (b) This Agreement has been, and upon the execution and delivery of the Investor Agreement by
the Company at the Closing, the Investor Agreement will be, duly executed and delivered by the
Company, and upon the due execution and delivery of this Agreement by the Investor and Sanofi US,
this Agreement will constitute, and upon the due execution and delivery of the Investor Agreement
by sanofi-aventis, Sanofi US, Aventis and the Investor, the Investor Agreement will constitute,
valid and legally binding obligations of the Company, enforceable against the Company in accordance
with their respective terms (except as such enforceability may be limited by (i) applicable
bankruptcy, insolvency, reorganization, moratorium or other Laws of general application relating to
or affecting enforcement of creditors’ rights and (ii) rules of Law governing specific performance,
injunctive relief or other equitable remedies and limitations of public policy).

     4.5 No Defaults. The Company is not in default under or in violation of (a) its Organizational
Documents, (b) any provision of applicable Law or any ruling, writ, injunction, order, Permit,
judgment or decree of any Governmental Authority or (c) any agreement, arrangement or instrument,
whether written or oral, by which the Company or any of its assets are bound, except, in the case
of subsections (b) and (c), as would not have a Material Adverse Effect. To the knowledge of the
Company, there exists no condition, event or act which after notice, lapse of time, or both, would
constitute a default or violation by the Company under any of the foregoing, except, in the case of
subsections (b) and (c), as would not have a Material Adverse Effect.

     4.6 No Conflicts. The execution, delivery and performance of the Transaction Agreements and
compliance with the provisions thereof by the Company do not and shall not: (a) violate any
provision of applicable Law or any ruling, writ, injunction, order, permit, judgment or decree of
any Governmental Authority, (b) constitute a breach of, or default under (or an event which, with
notice or lapse of time or both, would become a default under) or conflict with, or give rise to
any right of termination, cancellation or acceleration of, any agreement, arrangement or
instrument, whether written or oral, by which the Company or any of its assets are bound or (c)

7

 

violate or conflict with any of the provisions of the Company’s Organizational Documents, except,
in the case of subsections (a) and (b), as would not have a Material Adverse Effect.

     4.7 No Governmental Authority or Third Party Consents. No consent, approval, authorization or
other order of, or filing with, or notice to, any Governmental Authority or other Third Party is
required to be obtained or made by the Company in connection with the authorization, execution and
delivery by the Company of any of the Transaction Agreements or with the authorization, issue and
sale by the Company of the Shares, except (i) such filings as may be required to be made with the
Securities and Exchange Commission (the “SEC”) and with any state blue sky or securities
regulatory authority, which filings shall be made in a timely manner in accordance with all
applicable Laws, (ii) as required pursuant to the Hart-Scott-Rodino Antitrust Improvements Act, as
amended (the “HSR Act”) and (iii) with respect to the Shares, the filing with The NASDAQ
Stock Market LLC of, and the absence of unresolved issues with respect to, a Notification Form:
Listing of Additional Shares (the “LAS”).

     4.8 Valid Issuance of Shares. When issued, sold and delivered at the Closing in accordance with
the terms hereof for the Aggregate Purchase Price, the Shares shall be duly authorized, validly
issued, fully paid and nonassessable, free from any liens, encumbrances or restrictions on
transfer, including preemptive rights, rights of first refusal or other similar rights, other than
as arising pursuant to the Transaction Agreements, as a result of any action by the Investor or
under federal or state securities Laws.

     4.9 Litigation. Except as set forth in the Company SEC Documents filed prior to the date of this
Agreement, there is no action, suit, proceeding or investigation pending (of which the Company has
received notice or otherwise has knowledge) or, to the Company’s knowledge, threatened, against the
Company or which the Company intends to initiate which has had or is reasonably likely to have a
Material Adverse Effect.

     4.10 Licenses and Other Rights; Compliance with Laws. The Company has all franchises, permits,
licenses and other rights and privileges (“Permits”) necessary to permit it to own its
properties and to conduct its business as presently conducted and is in compliance thereunder,
except where the failure to be in compliance does not and would not have a Material Adverse Effect.
To the Company’s knowledge, it has not taken any action that would interfere with the Company’s
ability to renew all such Permit(s), except where the failure to renew such Permit(s) would not
have a Material Adverse Effect. The Company is and has been in compliance with all Laws applicable
to its business, properties and assets, and to the products and services sold by it, except where
the failure to be in compliance does not and would not have a Material Adverse Effect.

     4.11 Company SEC Documents; Financial Statements; Nasdaq Stock Market.

          (a) Since December 31, 2006, the Company has timely filed all required reports, schedules,
forms, statements and other documents (including exhibits and all other information incorporated
therein), and any required amendments to any of the foregoing, with the SEC (the “Company SEC
Documents”). As of their respective filing dates, each of the Company SEC Documents complied
in all material respects with the requirements of the Securities Act of 1933, as amended (the
“Securities Act”), and the Securities Exchange Act of

8

 

1934, as amended (the “Exchange Act”), and the rules and regulations of the SEC
promulgated thereunder applicable to such Company SEC Documents, and no Company SEC Documents when
filed, declared effective or mailed, as applicable, contained any untrue statement of a material
fact or omitted to state a material fact required to be stated therein or necessary in order to
make the statements therein, in light of the circumstances under which they were made, not
misleading.

          (b) The financial statements of the Company included in its Annual Report on Form 10-K for the
fiscal year ended December 31, 2006 and in its quarterly reports on Form 10-Q for the quarterly
periods ended September 30, 2007, June 30, 2007, and March 31, 2007 comply as to form in all
material respects with applicable accounting requirements and the published rules and regulations
of the SEC with respect thereto, have been prepared in accordance with United States generally
accepted accounting principles applied on a consistent basis during the periods involved (except as
may be indicated in the notes thereto) and fairly present in all material respects the financial
position of the Company as of the dates thereof and the results of its operations and cash flows
for the periods then ended. Except (i) as set forth in the Company SEC Documents or (ii) for
liabilities incurred in the ordinary course of business subsequent to the date of the most recent
balance sheet contained in the Company SEC Documents, the Company has no liabilities, whether
absolute or accrued, contingent or otherwise, other than those that would not, individually or in
the aggregate, have a Material Adverse Effect.

          (c) As of the date of this Agreement, the Common Stock is listed on The Nasdaq Global Market,
and the Company has taken no action designed to, or which to its knowledge is likely to have the
effect of, terminating the registration of the Common Stock under the Exchange Act or delisting the
Common Stock from The Nasdaq Global Market. As of the date of this Agreement, the Company has not
received any notification that, and has no knowledge that, the SEC or The NASDAQ Stock Market LLC
is contemplating terminating such listing or registration.

     4.12 Absence of Certain Changes. Except as disclosed in the Company SEC Documents, since December
31, 2006, there has not occurred any event that has caused or would reasonably be expected to cause
a Material Adverse Effect.

     4.13 Internal Controls; Disclosure Controls and Procedures. The Company maintains internal control
over financial reporting as defined in Rule 13a-15(f) under the Exchange Act. The Company has
implemented the “disclosure controls and procedures” (as defined in Rules 13a-15(e) and 15d-15(e)
under the Exchange Act) required in order for the Chief Executive Officer and Chief Financial
Officer of the Company to engage in the review and evaluation process mandated by the Exchange Act,
and is in compliance with such disclosure controls and procedures in all material respects. Each
of the Chief Executive Officer and the Chief Financial Officer of the Company (or each former Chief
Executive Officer of the Company and each former Chief Financial Officer of the Company, as
applicable) has made all certifications required by Sections 302 and 906 of the Sarbanes-Oxley Act
of 2002 with respect to all reports, schedules, forms, statements and other documents required to
be filed by the Company with the SEC.

9

 

     4.14 Intellectual Property. The Intellectual Property that is owned by the Company is owned free
from any liens or restrictions, and all of the Company’s material Intellectual Property Licenses
are in full force and effect in accordance with their terms, and are free of any liens or
restrictions, except (a) where the failure to be free from such liens or restrictions would not
have a Material Adverse Effect or (b) as set forth in any such Intellectual Property License.
Except as set forth in the Company SEC Documents, there is no legal claim or demand of any Person
pertaining to, or any proceeding which is pending (of which the Company has received notice or
otherwise has knowledge) or, to the knowledge of the Company, threatened, (i) challenging the right
of the Company in respect of any Company Intellectual Property, or (ii) that claims that any
default exists under any Intellectual Property License, except, in the case of (i) and (ii) above,
where any such claim, demand or proceeding would not have a Material Adverse Effect.

     4.15 Offering. Subject to the accuracy of the Investor’s representations set forth in Sections
5.5, 5.6, 5.7, 5.9 and 5.10, the offer, sale and issuance of the Shares to be issued in conformity
with the terms of this Agreement constitute transactions which are exempt from the registration
requirements of the Securities Act and from all applicable state registration or qualification
requirements. Neither the Company nor any Person acting on its behalf will take any action that
would cause the loss of such exemption.

     4.16 No Integration. The Company has not, directly or through any agent, sold, offered for sale,
solicited offers to buy or otherwise negotiated in respect of, any security (as defined in the
Securities Act) which is or will be integrated with the Shares sold pursuant to this Agreement in a
manner that would require the registration of the Shares under the Securities Act.

     4.17 Brokers’ or Finders’ Fees. No broker, finder, investment banker or other Person is entitled
to any brokerage, finder’s or other fee or commission from the Company in connection with the
transactions contemplated by the Transaction Agreements.

     4.18 Not Investment Company. The Company is not, and solely after receipt of the Aggregate
Purchase Price and application of such proceeds in substantially the manner described under “Use of
Proceeds” in the Company’s prospectus supplement filed November 15, 2006 with the SEC, will not be,
an “investment company” as defined in the Investment Company Act of 1940, as amended.

5. Representations and Warranties of the Investor. The Investor hereby represents and warrants to
the Company as set forth in Sections 5.1 through 5.10 (on behalf of itself, Sanofi US, Aventis and
sanofi-aventis), and the Investor and Sanofi US hereby jointly and severally represent and warrant
to the Company as set forth in Section 5.11, that:

     5.1 Organization; Good Standing. The Investor is a partnership duly organized, validly existing
and in good standing under the laws of France. Sanofi US is a limited liability company duly
organized, validly existing and in good standing under the laws of the State of Delaware. Aventis
is a corporation duly organized, validly existing and in good standing under the laws of the State
of Delaware. sanofi-aventis is a company duly organized, validly existing and in good standing
under the laws of France. Each of the Investor and Sanofi US has, and Aventis and sanofi-aventis
will have, all requisite power and authority to enter into the

10

 

Transaction Agreements to which it is or will be a party, in the case of the Investor to purchase
the Shares and, in the case of the Investor, Sanofi US, Aventis and sanofi-aventis, to perform its
respective obligations under and to carry out the other transactions contemplated by the
Transaction Agreements to which it is or will be a party.

     5.2 Authorization. All requisite action on the part of the Investor, Sanofi US, Aventis,
sanofi-aventis and their respective directors and stockholders, required by applicable Law for the
authorization, execution and delivery by the Investor, Sanofi US, Aventis and sanofi-aventis of the
Transaction Agreements to which they are a party, and the performance of all of their respective
obligations thereunder, including the subscription for and purchase of the Shares, has been taken
or, in the case of Aventis and sanofi-aventis, will be taken prior to the Closing. This Agreement,
and upon the execution and delivery of the Investor Agreement at the Closing by the Investor,
Sanofi US, Aventis and sanofi-aventis, the Investor Agreement will be, duly executed and delivered
by, as applicable, the Investor, Sanofi US, Aventis and sanofi-aventis and upon the due execution
and delivery thereof by the Company, will constitute valid and legally binding obligations of, as
applicable, the Investor, Sanofi US, Aventis and sanofi-aventis, enforceable against, as
applicable, the Investor, Sanofi US, Aventis and sanofi-aventis in accordance with their respective
terms (except as such enforceability may be limited by (a) applicable bankruptcy, insolvency,
reorganization, moratorium or other Laws of general application relating to or affecting
enforcement of creditors’ rights and (b) rules of Law governing specific performance, injunctive
relief or other equitable remedies and limitations of public policy).

     5.3 No Conflicts. The execution, delivery and performance of the Transaction Agreements and
compliance with the provisions thereof by the Investor, Sanofi US, Aventis and sanofi-aventis, do
not and shall not: (a) violate any provision of applicable Law or any ruling, writ, injunction,
order, permit, judgment or decree of any Governmental Authority, (b) constitute a breach of, or
default under (or an event which, with notice or lapse of time or both, would become a default
under) or conflict with, or give rise to any right of termination, cancellation or acceleration of,
any agreement, arrangement or instrument, whether written or oral, by which the Investor, Sanofi
US, Aventis or sanofi-aventis or any of their respective assets, are bound, or (c) violate or
conflict with any of the provisions of the Investor’s, Sanofi US’, Aventis’ or sanofi-aventis’
organizational documents (including any articles or memoranda of organization or association,
charter, bylaws or similar documents), except as would not impair or adversely affect the ability
of the Investor, Sanofi US, Aventis or sanofi-aventis, as applicable, to consummate the
Transactions and perform their respective obligations under the Transaction Agreements and except,
in the case of subsections (a) and (b) as would not have a material adverse effect on the Investor,
Sanofi US, Aventis or sanofi-aventis.

     5.4 No Governmental Authority or Third Party Consents. No consent, approval, authorization or
other order of any Governmental Authority or other Third Party is required to be obtained by the
Investor, Sanofi US, Aventis or sanofi-aventis in connection with the authorization, execution and
delivery of any of the Transaction Agreements or with the subscription for and purchase of the
Shares, except as required pursuant to the HSR Act.

     5.5 Purchase Entirely for Own Account. The Shares shall be acquired for investment for the
Investor’s own account, not as a nominee or agent, and not with a view to the

11

 

resale or distribution of any part thereof, and the Investor has no present intention of selling,
granting any participation or otherwise distributing the Shares. The Investor does not have and
will not have as of the Closing any contract, undertaking, agreement or arrangement with any Person
to sell, transfer or grant participation to a Person any of the Shares.

     5.6 Disclosure of Information. The Investor has received all the information from the Company and
its management that the Investor considers necessary or appropriate for deciding whether to
purchase the Shares hereunder. The Investor further represents that it has had an opportunity to
ask questions and receive answers from the Company regarding the Company, its financial condition,
results of operations and prospects and the terms and conditions of the offering of the Shares
sufficient to enable it to evaluate its investment.

     5.7 Investment Experience and Accredited Investor Status. The Investor is an “accredited investor”
(as defined in Regulation D under the Securities Act). The Investor has such knowledge and
experience in financial or business matters that it is capable of evaluating the merits and risks
of the investment in the Shares to be purchased hereunder.

     5.8 Acquiring Person. As of the date of this Agreement and immediately prior to the Closing, (a)
sanofi-aventis together with its Affiliates, beneficially own and will beneficially own (as
determined pursuant to Rule 13d-3 under the Exchange Act without regard for the number of days in
which a Person has the right to acquire such beneficial ownership) 2,799,552 shares of Common
Stock, and (b) neither sanofi-aventis nor any of its Affiliates beneficially owns, or will
beneficially own (as determined pursuant to Rule 13d-3 under the Exchange Act without regard for
the number of days in which a Person has the right to acquire such beneficial ownership), any other
securities of the Company.

     5.9 Restricted Securities. The Investor understands that the Shares, when issued, shall be
“restricted securities” under the federal securities Laws inasmuch as they are being acquired from
the Company in a transaction not involving a public offering and that under such Laws the Shares
may be resold without registration under the Securities Act only in certain limited circumstances.
In this connection, the Investor represents that it is familiar with Rule 144 of the Securities
Act, as presently in effect.

     5.10 Legends. The Investor understands that the certificates representing the Shares shall bear
the following legends:

          (a) “These securities have not been registered under the Securities Act of 1933. They may not
be sold, offered for sale, pledged or hypothecated in the absence of a registration statement in
effect with respect to the securities under the Securities Act or an opinion of counsel (which
counsel shall be reasonably satisfactory to Regeneron Pharmaceuticals, Inc.) that such registration
is not required or unless sold pursuant to Rule 144 of the Securities Act.”;

          (b) any legend required by applicable state securities Laws; and

          (c) “The securities represented by this certificate are subject to and shall be transferable
only upon the terms and conditions of an Investor Agreement dated as of [   ], 2007,

12

 

by and among Regeneron Pharmaceuticals, Inc. and the other parties signatory thereto, a copy
of which is on file with the Secretary of Regeneron Pharmaceuticals, Inc.”

     5.11 Financial Assurances. As of the date hereof and as of the Closing Date, the Investor has and
will have access to cash in an amount sufficient to pay to the Company the Aggregate Purchase
Price.

6. Covenants of the Company.

     6.1 Conduct of the Business Pending Closing. During the period from the date hereof until the
Closing, except as (a) set forth on Exhibit C attached hereto, (b) consented to in writing
by the Investor (which consent shall not be unreasonably withheld, conditioned or delayed) or (c)
otherwise contemplated by this Agreement or any of the Collaboration Agreements, the Company shall
(i) operate its business only in the ordinary course, (ii) maintain its existence under applicable
Law, (iii) use commercially reasonable efforts to maintain and enforce its material Intellectual
Property, (iv) pay all applicable material taxes when due and payable and (v) (A) not declare, set
aside or pay any dividend or make any other distribution or payment (whether in cash, stock or
property or any combination thereof) in respect of its capital stock, (B) not make any other
actual, constructive or deemed distribution in respect of any shares of its capital stock or
otherwise make any payments to stockholders in their capacity as such and (C) not redeem,
repurchase or otherwise acquire any securities of the Company or any of its subsidiaries.

     6.2 Use of Proceeds. From and after the Closing Date, the Company shall use the Aggregate Purchase
Price in substantially the manner described under “Use of Proceeds” in the Company’s prospectus
supplement filed November 15, 2006 with the SEC.

7. Investor’s Conditions to Closing. The Investor’s obligation to purchase the Shares at the
Closing is subject to the fulfillment as of such Closing of the following conditions (unless waived
in writing by the Investor):

     7.1 Representations and Warranties. (a) The representations and warranties made by the Company in
Section 4 hereof shall be true and correct as of the date of this Agreement and as of the Closing
Date as though made on and as of such Closing Date; (b) the representations and warranties made by
the Company in Article 8 of the Discovery Agreement (other than Section 8.1(a) thereof) shall be
true and correct as of the date of the Discovery Agreement and as of the Closing Date as though
made on and as of such Closing Date; and (c) the representations and warranties made by the Company
in Article XV of the Sanofi License and Collaboration Agreement (other than Section 15.1(a)
thereof) shall be true and correct as of the date of the Sanofi License and Collaboration Agreement
and as of the Closing Date as though made on and as of such Closing Date, except in the case of
subsections (a), (b) and (c) to the extent such representations and warranties are specifically
made as of a particular date, in which case such representations and warranties shall be true and
correct as of such date; provided, however, that for purposes of this Section 7.1,
all such representations and warranties of the Company (other than Sections 4.1(a), 4.2, 4.3,
4.4(a) and 4.8 of this Agreement, Section 8.1(b) of the Discovery Agreement and Section 15.1(b) of
the Sanofi License and Collaboration Agreement) shall be deemed to be true and correct for purposes
of this Section 7.1 unless the

13

 

failure or failures of such representations and warranties to be so true and correct, without
regard to any “material,” “materiality” or “Material Adverse Effect” qualifiers set forth therein
(other than any reference to “material” in Sections 4.11(a) and 4.11(b)), individually or in the
aggregate, has had or would reasonably be expected to have a Material Adverse Effect.

     7.2 Covenants. All covenants and agreements contained in this Agreement to be performed or
complied with by the Company on or prior to the Closing Date shall have been performed or complied
with in all material respects.

     7.3 Investor Agreement. The Company shall have duly executed and delivered to the Investor,
pursuant to Section 3.2(a) of this Agreement, the Investor Agreement, and (subject to execution by
sanofi-aventis, Sanofi US, Aventis and the Investor) such agreement shall be in full force and
effect.

     7.4 Discovery Agreement; Sanofi License and Collaboration Agreement. The Company shall have duly
executed and delivered to the Investor the Discovery Agreement and the Sanofi License and
Collaboration Agreement, and there shall have been no termination of either of the Discovery
Agreement or the Sanofi License and Collaboration Agreement that, as of the Closing, is effective.

     7.5 No Material Adverse Effect. From and after the date of this Agreement until the Closing Date,
there shall have occurred no event that has caused or would reasonably be expected to cause a
Material Adverse Effect.

8. Company’s Conditions to Closing. The Company’s obligation to issue and sell the Shares at the
Closing is subject to the fulfillment as of such Closing of the following conditions (unless waived
in writing by the Company):

     8.1 Representations and Warranties. The representations and warranties made by the Investor (on
its own behalf and on behalf of Sanofi US, Aventis and sanofi-aventis) and by Sanofi US (a) in
Section 5 hereof (other than Sections 5.4 and 5.6 hereof) shall be true and correct and (b) in
Sections 5.4 and 5.6 hereof shall be true and correct in all material respects, in each case as of
the date of this Agreement and as of the Closing Date as though made on and as of such Closing Date
(except to the extent such representations and warranties are specifically made as of a particular
date, in which case such representations and warranties shall be true and correct as of such date).

     8.2 Covenants. All covenants and agreements contained in this Agreement to be performed or
complied with by the Investor or Sanofi US as applicable, on or prior to the Closing Date shall
have been performed or complied with in all material respects.

     8.3 Investor Agreement. sanofi-aventis, Sanofi US, Aventis and Investor shall have duly executed
and delivered to the Company, pursuant to Section 4.2(b) of this Agreement, the Investor Agreement,
and (subject to execution by the Company) such agreement shall be in full force and effect.

     8.4 Discovery Agreement; Sanofi License and Collaboration Agreement. Sanofi US, Aventis and the
Investor, as applicable, shall have duly executed and delivered to the

14

 

Company the Discovery Agreement and the Sanofi License and Collaboration Agreement, and there shall
have been no termination of either of the Discovery Agreement or the Sanofi License and
Collaboration Agreement that, as of the Closing, is effective. The Company shall have received
from Aventis the payment required by Section 4.1 of the Discovery Agreement.

9. Mutual Conditions to Closing. The obligations of the Investor and the Company to consummate the
Closing is subject to the fulfillment as of the Closing Date of the following conditions:

     9.1 HSR Act and Other Qualifications. The filings required under the HSR Act in connection with
this Agreement shall have been made and the required waiting period shall have expired or been
terminated as of the Closing Date, and all other authorizations, consents, waivers, permits,
approvals, qualifications and registrations to be obtained or effected with any Governmental
Authority, including, without limitation, necessary blue sky permits and qualifications required by
any state for the offer and sale to the Investor of the Shares, shall have been duly obtained and
shall be in effect as of the Closing Date.

     9.2 Absence of Litigation. There shall be no action, suit, proceeding or investigation by a
Governmental Authority pending or currently threatened in writing against the Company, the
Investor, Sanofi US, Aventis or sanofi-aventis which questions the validity of any of the
Transaction Agreements, the right of the Company, the Investor, Sanofi US, Aventis or
sanofi-aventis to enter into any Transaction Agreement or to consummate the transactions
contemplated hereby or thereby or which, if determined adversely, would impose substantial monetary
damages on the Company, the Investor, Sanofi US, Aventis or sanofi-aventis as a result of the
consummation of the transactions contemplated by any Transaction Agreement.

     9.3 No Prohibition. (a) No provision of any applicable Law and no judgment, injunction
(preliminary or permanent), order or decree that prohibits, makes illegal or enjoins the
consummation of the Transaction shall be in effect; and (b) there shall be no unresolved issues
with The NASDAQ Stock Market LLC with respect to the LAS.

10. Termination.

     10.1 Ability to Terminate. This Agreement may be terminated at any time prior to the Closing by:

          (a) mutual written consent of the Company and the Investor;

          (b) either the Company or the Investor, upon written notice to the other no earlier than three
(3) Business Days after January 31, 2008 (the “Original Termination Date”), if the Original
Termination Date cannot be or has not been validly extended pursuant to this Section 10.1(b), and
if the Transaction shall not have been consummated by the Original Termination Date;
provided, however, that the Original Termination Date may be extended to March 31,
2008 (the “Final Termination Date”) by either the Company or the Investor, upon written
notice to the other on or within two (2) Business Days after the Original Termination Date, if the
Transaction shall not have been consummated by the Original Termination Date solely as the result
of a failure to satisfy the condition set forth in Section 9.1 as of the Original Termination Date;
provided further, however, that the right to terminate this Agreement under

15

 

this Section 10.1(b) shall not be available to any party whose failure to fulfill any
obligation under this Agreement has been the cause of, or resulted in, the failure to consummate
the transactions contemplated hereby prior to the Original Termination Date or the Final
Termination Date, as applicable;

          (c) either the Company or the Investor, upon written notice to the other, if any of the mutual
conditions to the Closing set forth in Section 9 shall have become incapable of fulfillment by the
Original Termination Date or, if the Original Termination Date has been validly extended pursuant
to Section 10.1(b), the Final Termination Date, and shall not have been waived in writing by the
other party; provided, however, that the right to terminate this Agreement under
this Section 10.1(c) shall not be available to any party whose failure to fulfill any obligation
under this Agreement has been the cause of, or resulted in, the failure to consummate the
transactions contemplated hereby prior to the Original Termination Date or the Final Termination
Date, as applicable;

          (d) the Company, upon written notice to the Investor, so long as the Company is not then in
breach of its representations, warranties, covenants or agreements under this Agreement such that
any of the conditions set forth in Section 7.1 or 7.2, as applicable, could not be satisfied by the
Closing Date, (i) upon a breach of any covenant or agreement on the part of the Investor set forth
in this Agreement, or (ii) if any representation or warranty of the Investor or Sanofi US shall
have been or become untrue, in each case such that any of the conditions set forth in Section 8.1,
8.2, 8.3 or 8.4, as applicable, could not be satisfied by the Closing Date;

          (e) the Company, upon written notice to the Investor, if the Investor or any of its Affiliates
has breached Section 20.16 of the Aventis Collaboration Agreement (for avoidance of doubt, the
Company shall not have the right to terminate this Agreement as a result of a de minimis breach of
Section 20.16(a) of the Aventis Collaboration Agreement or an inadvertent breach of Section
20.16(g) of the Aventis Collaboration Agreement arising from informal discussions covering general
corporate or other business matters the purpose of which is not intended to effectuate or lead to
any of the actions referred to in paragraphs (a) through (e) of Section 20.16 of the Aventis
Collaboration Agreement); provided that any action taken in connection with the Transaction
shall not be deemed to be a violation of Section 20.16 of the Aventis Collaboration Agreement; and

          (f) the Investor, upon written notice to the Company, so long as the Investor and Sanofi US
are not then in breach of their representations, warranties, covenants or agreements under this
Agreement such that any of the conditions set forth in Section 8.1 or 8.2, as applicable, could not
be satisfied by the Closing Date, upon a breach of any covenant or agreement on the part of the
Company set forth in this Agreement, or if any representation or warranty of the Company shall have
been or become untrue, in each case such that any of the conditions set forth in Section 7.1, 7.2,
7.3 or 7.4, as applicable, could not be satisfied by the Closing Date.

     10.2 Effect of Termination. In the event of the termination of this Agreement pursuant to Section
10.1 hereof, (a) this Agreement (except for this Section 10.2 and Article XII (other than Section
12.13), and any definitions set forth in this Agreement and used in such sections) shall forthwith
become void and have no effect, without any liability on the part of any

16

 

party hereto or its Affiliates, and (b) all filings, applications and other submissions made
pursuant to this Agreement, to the extent practicable, shall be withdrawn from the agency or other
Person to which they were made or appropriately amended to reflect the termination of the
transactions contemplated hereby; provided, however, that nothing contained in this
Section 10.2 shall relieve any party from liability for fraud or any intentional or willful breach
of this Agreement.

11. Additional Covenants and Agreements.

     11.1 Legending of Existing Shares. At the Closing, the Investor shall cause Aventis to deliver to
the Company the certificate(s) representing 2,799,552 shares of Common Stock issued to Aventis, and
the Company shall (or shall cause its transfer agent to) promptly cancel such certificate and issue
to Aventis a replacement certificate representing 2,799,552 shares of Common Stock and containing
the legends set forth in Section 5.10 hereof.

     11.2 Amendment of Aventis Agreement. Effective as of the date of this Agreement, the Investor
hereby acknowledges and agrees that it shall be bound by (and shall cause its Affiliates to comply
with) the restrictions applicable to Sanofi US (as successor to Aventis) under Section 20.16 of the
Aventis Collaboration Agreement, and the Investor, Sanofi US and the Company acknowledge and agree
that for purposes of Section 19.5 of the Aventis Collaboration Agreement, references to “Aventis”
in such section include the Investor and its other Affiliates. The Investor, Sanofi US and the
Company agree that, subject to clause (c) below, effective as of the date of this Agreement:

          (a) The first clause of Section 20.16 of the Aventis Collaboration Agreement is hereby amended
and restated in its entirety to read:

“From and after the Effective Date until the later of (A) the fifth (5th)
anniversary of the expiration or earlier termination of the Term and (B) the fifth
(5th) anniversary of the expiration or earlier termination of the “Term” (as such
term is defined in the License and Collaboration Agreement among the Company, sanofi-aventis
Amérique du Nord and Aventis dated as of November 28, 2007), neither Aventis nor any of its
Affiliates (for purposes of this Section 20.16, Aventis, together with such Affiliates,
being referred to as the “Investor”) shall:”

          (b) Section 20.16(a) of the Aventis Collaboration Agreement is hereby amended and restated in
its entirety to read:

"(a) directly or indirectly, acquire beneficial ownership of Shares of Then Outstanding
Capital Stock and/or Common Stock Equivalents, or make a tender, exchange or other offer to
acquire Shares of Then Outstanding Capital Stock and/or Common Stock Equivalents, if after
giving effect to such acquisition (and assuming the full conversion into, and exercise and
exchange for, shares of Common Stock of all Common Stock Equivalents beneficially owned by
the Investor), the Investor would beneficially own (as defined in Rule 13d-3 under the
Securities Exchange Act) more than the Standstill Limit; provided, however,
that notwithstanding the provisions of this Section 20.16, if the number of shares
constituting Shares of Then Outstanding Capital Stock is reduced or if

17

 

the aggregate ownership of the Investor is increased as a result of a recapitalization of
Regeneron, the Investor shall not be required to dispose of any of its holdings of Shares of
Then Outstanding Capital Stock even though such action resulted in Investor’s ownership
totaling more than the Standstill Limit; as used in this Section 20.16(a):

(i) “Common Stock Equivalents” shall mean any options, warrants or other securities
or rights convertible into or exercisable or exchangeable for, whether directly or following
conversion into or exercise or exchange for other options, warrants or other securities or
rights, shares of Class A Stock or Common Stock; and

(ii) “Standstill Limit” shall mean (i) from November 28, 2007 until December 31,
2011, the lesser of (A) twenty-one percent (21%) of the Shares of Then Outstanding Capital
Stock, in the case of this clause (A) only, calculated on a fully diluted basis assuming the
full conversion into, or exercise or exchange for, shares of Common Stock of all Common
Stock Equivalents outstanding (as such Common Stock Equivalents outstanding are calculated
from Regeneron’s most recent Form 10-Q or Form 10-K, as applicable, filed with the SEC), and
(B) twenty-five percent (25%) of the Shares of Then Outstanding Capital Stock, and (ii) from
and after January 1, 2012, thirty percent (30%) of the Shares of Then Outstanding Capital
Stock;”

          (c) Notwithstanding the foregoing, if this Agreement is terminated in accordance with Section
10 hereof, the amendments to Section 20.16 of the Aventis Collaboration Agreement set forth above
shall be of no further force or effect, and the provisions of Section 20.16 of the Aventis
Collaboration Agreement in effect immediately prior to the execution and delivery of this Agreement
shall again be in full force and effect.

     11.3 Market Listing. From the date hereof through the Closing Date, Company shall use all
reasonable efforts to (a) maintain the listing and trading of the Common Stock on The NASDAQ Global
Market and (b) effect the listing of the Shares on The NASDAQ Global Market, including submitting a
notice of listing of additional shares with respect to the Shares to The NASDAQ Stock Market LLC no
later than fifteen (15) calendar days prior to the Closing Date.

     11.4 Notification under the HSR Act. The parties shall, as soon as practicable, and, in any event,
no later than ten (10) days after the date of this Agreement, file or cause to be filed with the
Federal Trade Commission and the Department of Justice the notifications required to be filed under
the HSR Act and the rules and regulations promulgated thereunder with respect to the transactions
contemplated by this Agreement. The parties will use all reasonable efforts to respond on a timely
basis to any requests for additional information made by either of such agencies.

     11.5 Assistance and Cooperation. Prior to the Closing, upon the terms and subject to the
conditions set forth in this Agreement, each of the parties agrees to use all reasonable efforts to
take, or cause to be taken, all actions and to do, or cause to be done, and to assist and cooperate
with the other party in doing, all things necessary, proper or advisable to consummate and make
effective, in the most expeditious manner practicable, the transactions contemplated by this
Agreement, including using all reasonable efforts to accomplish the following: (a) taking all

18

 

reasonable acts necessary to cause the conditions precedent set forth in Sections 7, 8 and 9 to be
satisfied (including, in the case of the Company, promptly notifying the Investor of any notice
from The NASDAQ Stock Market LLC with respect to the LAS); (b) obtaining all necessary actions or
non-actions, waivers, consents, approvals, orders and authorizations from Governmental Authorities
and the making of all necessary registrations, declarations and filings (including registrations,
declarations and filings with Governmental Authorities, if any) and taking all reasonable steps as
may be necessary to avoid any suit, claim, action, investigation or proceeding by any Governmental
Authority; (c) obtaining all necessary consents, approvals or waivers from Third Parties; and (d)
defending any suits, claims, actions, investigations or proceedings, whether judicial or
administrative, challenging this Agreement or the consummation of the transactions contemplated
hereby, including seeking to have any stay or temporary restraining order entered by any court or
other Governmental Authority vacated or reversed. In addition, each of the Company and the
Investor will promptly take any and all steps necessary to obtain any consent or to vacate or lift
any order, writ, judgment, injunction, decree, stipulation, determination or award entered by or
with any Governmental Authority relating to antitrust matters that would have the effect of making
any of the transactions contemplated by this Agreement illegal or otherwise prohibiting or
materially delaying their consummation. Notwithstanding anything to the contrary in this Section
11.5, nothing in this Section 11.5 will require the Investor to dispose of or hold separate any
portion of its business or assets if such action, in the reasonable business judgment of the
Investor, would impair, or be reasonably expected to impair, in any significant manner (i) the
benefits to the Investor of the transactions contemplated by this Agreement, the Discovery
Agreement or the Collaboration Agreements or (ii) the business, financial condition, results of
operations or prospects of the Investor and its subsidiaries, taken as a whole.

     11.6 Effect of Waiver of Condition to Closing. In the event that, as of the Closing, the Investor
waives the condition regarding a Material Adverse Effect set forth in Section 7.5 of this
Agreement, the Investor shall be deemed to have waived any right of recourse against the Company
for, and agreed not to sue the Company in respect of, any and all events or inaccuracies in any
representations or warranties of the Company (a) that, as of the Closing, have caused or would
reasonably be expected to cause such Material Adverse Effect and (b) of which the Investor had
notice in writing from the Company immediately prior to the Closing.

12. Miscellaneous.

     12.1 Governing Law; Submission to Jurisdiction. This Agreement shall be governed by and construed
in accordance with the Laws of the State of New York, without regard to the conflict of laws
principles thereof that would require the application of the Law of any other jurisdiction. The
parties irrevocably and unconditionally submit to the exclusive jurisdiction of the United States
District Court for the Southern District of New York solely and specifically for the purposes of
any action or proceeding arising out of or in connection with this Agreement.

     12.2 Waiver. Waiver by a party of a breach hereunder by the other party shall not be construed as
a waiver of any subsequent breach of the same or any other provision. No delay or omission by a
party in exercising or availing itself of any right, power or privilege hereunder shall preclude
the later exercise of any such right, power or privilege by such party. No waiver

19

 

shall be effective unless made in writing with specific reference to the relevant provision(s) of
this Agreement and signed by a duly authorized representative of the party granting the waiver.

     12.3 Notices. All notices, instructions and other communications hereunder or in connection
herewith shall be in writing, shall be sent to the address of the relevant party set forth on
Exhibit D attached hereto and shall be (a) delivered personally, (b) sent by registered or
certified mail, return receipt requested, postage prepaid, (c) sent via a reputable nationwide
overnight courier service or (d) sent by facsimile transmission, with a confirmation copy to be
sent by registered or certified mail, return receipt requested, postage prepaid. Any such notice,
instruction or communication shall be deemed to have been delivered upon receipt if delivered by
hand, three (3) Business Days after it is sent by registered or certified mail, return receipt
requested, postage prepaid, one (1) Business Day after it is sent via a reputable nationwide
overnight courier service or when transmitted with electronic confirmation of receipt, if
transmitted by facsimile (if such transmission is made during regular business hours of the
recipient on a Business Day; or otherwise, on the next Business Day following such transmission).
Either party may change its address by giving notice to the other party in the manner provided
above.

     12.4 Entire Agreement. This Agreement and the Investor Agreement (once executed), contain the
entire agreement among the parties with respect to the subject matter hereof and thereof and
supersede all prior and contemporaneous arrangements or understandings, whether written or oral,
with respect hereto and thereto.

     12.5 Amendments. No provision in this Agreement shall be supplemented, deleted or amended except
in a writing executed by an authorized representative of each of the Investor and the Company.

     12.6 Headings; Nouns and Pronouns; Section References. Headings in this Agreement are for
convenience of reference only and shall not be considered in construing this Agreement. Whenever
the context may require, any pronouns used herein shall include the corresponding masculine,
feminine or neuter forms, and the singular form of names and pronouns shall include the plural and
vice-versa. References in this Agreement to a section or subsection shall be deemed to refer to a
section or subsection of this Agreement unless otherwise expressly stated.

     12.7 Severability. If, under applicable Laws, any provision hereof is invalid or unenforceable, or
otherwise directly or indirectly affects the validity of any other material provision(s) of this
Agreement in any jurisdiction (“Modified Clause”), then, it is mutually agreed that this
Agreement shall endure and that the Modified Clause shall be enforced in such jurisdiction to the
maximum extent permitted under applicable Laws in such jurisdiction; provided that the parties
shall consult and use all reasonable efforts to agree upon, and hereby consent to, any valid and
enforceable modification of this Agreement as may be necessary to avoid any unjust enrichment of
either party and to match the intent of this Agreement as closely as possible, including the
economic benefits and rights contemplated herein.

     12.8 Assignment. Neither this Agreement nor any of the rights or obligations hereunder may be
assigned by either the Investor or the Company without (a) the prior written

20

 

consent of Company in the case of any assignment by the Investor or (b) the prior written consent
of the Investor in the case of an assignment by the Company.

     12.9 Successors and Assigns. This Agreement shall be binding upon and inure to the benefit of the
parties hereto and their respective successors and permitted assigns.

     12.10 Counterparts. This Agreement may be executed in counterparts, each of which shall be deemed
an original but which together shall constitute one and the same instrument.

     12.11 Third Party Beneficiaries. None of the provisions of this Agreement shall be for the benefit
of or enforceable by any Third Party, including any creditor of any party hereto. No Third Party
shall obtain any right under any provision of this Agreement or shall by reason of any such
provision make any claim in respect of any debt, liability or obligation (or otherwise) against any
party hereto.

     12.12 No Strict Construction. This Agreement has been prepared jointly and will not be construed
against either party.

     12.13 Survival of Warranties. The representations and warranties of the Company and the Investor
contained in this Agreement shall survive the Closing for eighteen (18) months, except for (a) the
representations and warranties set forth in Sections 4.1, 4.2, 4.4, 4.8, 4.15, 4.16, 4.17, 4.18,
5.1, 5.2, 5.5, 5.7, 5.8, 5.9 and 5.10, which shall survive forever and (b) the representation and
warranty of the Investor and Sanofi US in Section 5.11, which shall not survive the Closing. The
parties hereby acknowledge and agree that the rights of the parties hereunder are special, unique
and of extraordinary character, and that if any party refuses or otherwise fails to act, or to
cause its Affiliates to act, in accordance with the provisions of this Agreement, such refusal or
failure would result in irreparable injury to the Company or the Investor as the case may be, the
exact amount of which would be difficult to ascertain or estimate and the remedies at law for which
would not be reasonable or adequate compensation. Accordingly, if any party refuses or otherwise
fails to act, or to cause its Affiliates to act, in accordance with the provisions of this
Agreement, then, in addition to any other remedy which may be available to any damaged party at law
or in equity, such damaged party will be entitled to seek specific performance and injunctive
relief, without posting bond or other security, and without the necessity of proving actual or
threatened damages, which remedy such damaged party will be entitled to seek in any court of
competent jurisdiction.

     12.14 Remedies. The rights, powers and remedies of the parties under this Agreement are cumulative
and not exclusive of any other right, power or remedy which such parties may have under any other
agreement or Law. No single or partial assertion or exercise of any right, power or remedy of a
party hereunder shall preclude any other or further assertion or exercise thereof.

     12.15 Expenses. Each party shall pay its own fees and expenses in connection with the preparation,
negotiation, execution and delivery of the Transaction Agreements.

(Signature Page Follows)

21

 

Exhibit 10.20

     IN WITNESS WHEREOF, the parties have executed and delivered this Agreement as of the date
first above written.

	 	 	 	 	 
	 	SANOFI-AVENTIS AMÉRIQUE DU NORD

 	 
	 	By:  	/s/ Jean-Luc Renard
 	 
	 	 	Name:  	Jean-Luc Renard 	 
	 	 	Title:  	Authorized Signatory 	 
	 
	 	 	 
	 	By:  	               /s/ Karen Linehan
 	 
	 	 	Name:  	Karen Linehan 	 
	 	 	Title:  	Authorized Signatory 	 
	 

	 	 	 	 	 
	 	SANOFI-AVENTIS US LLC

(Solely for purposes of

Sections 5.11, 8.2, 8.3, 11.2 and 12.13)

 	 
	 	By:  	/s/ Karen Linehan
 	 
	 	 	Name:  	Karen Linehan 	 
	 	 	Title:  	Authorized Signatory 	 
	 
	 	 	 
	 	By:  	             /s/ Robin White
 	 
	 	 	Name:  	Robin White 	 
	 	 	Title:  	Authorized Signatory 	 
	 

	 	 	 	 	 
	 	REGENERON PHARMACEUTICALS, INC.

 	 
	 	By:  	/s/ Leonard Schleifer
 	 
	 	 	Name:  	Leonard S. Schleifer, M.D., Ph.D. 	 
	 	 	Title:  	President & CEO 	 
	 

Signature Page to Stock Purchase Agreement,

 

 

Exhibit 10.20

EXHIBIT A

FORM OF CROSS RECEIPT

CROSS RECEIPT

     Regeneron Pharmaceuticals, Inc. hereby acknowledges receipt from sanofi-aventis Amérique du
Nord on [                    ], 2007 of US$312,000,000.00, representing the purchase price for 12,000,000
shares of Common Stock, par value $0.001 per share, of Regeneron Pharmaceuticals, Inc., pursuant to
that certain Stock Purchase Agreement, dated as of November 28, 2007, by and among sanofi-aventis
Amérique du Nord, sanofi-aventis US LLC and Regeneron Pharmaceuticals, Inc.

	 	 	 	 	 
	 	REGENERON PHARMACEUTICALS, INC.

 	 
	 	By:  	 	 
	 	 	Name:  	 	 
	 	 	Title:  	 	 
	 

     sanofi-aventis Amérique du Nord hereby acknowledges receipt from Regeneron Pharmaceuticals,
Inc. on [                    ], 2007 of 12,000,000 shares of Common Stock, par value $0.001 per share, of
Regeneron Pharmaceuticals, Inc., delivered pursuant to that certain Stock Purchase Agreement, dated
as of November 28, 2007, by and among sanofi-aventis Amérique du Nord, sanofi-aventis US LLC and
Regeneron Pharmaceuticals, Inc.

	 	 	 	 	 
	 	SANOFI-AVENTIS AMÉRIQUE DU NORD

 	 
	 	By:  	 	 
	 	 	Name:  	 	 
	 	 	Title:  	 	 
	 
	 	 	 
	 	By:  	
 	 
	 	 	Name:  	 	 
	 	 	Title:  	 	 

 

 

	 	 	 	 	 

EXHIBIT B

FORM OF INVESTOR AGREEMENT

[See the Investor Agreement, dated as of December 20, 2007, filed as Exhibit 10.21]

 

 

EXHIBIT C

CONDUCT OF THE BUSINESS PENDING CLOSING

The Company may refinance its 51/2% Convertible Senior Subordinated Notes due 2008.

The Company, in its sole discretion, shall be entitled to make equity-based or phantom equity
incentive and other compensation awards, pursuant to equity-based or phantom equity incentive and
other compensation plans in effect on the date of this Agreement.

 

 

EXHIBIT D

NOTICES

	 	 	 
	(a)

	 	If to the Investor or Sanofi US:
	 
	 	 
	 

	 	sanofi-aventis
	 

	 	174, avenue de France
	 

	 	75013 Paris
	 

	 	France
	 

	 	Attention: General Counsel
	 
	 	 
	 

	 	with a copy to:
	 
	 	 
	 

	 	Jones Day
	 

	 	222 East 41st Street
	 

	 	New York, New York 10017
	 

	 	Attention: Jere R. Thomson
	 
	 	 
	(b)

	 	If to the Company:
	 
	 	 
	 

	 	Regeneron Pharmaceuticals, Inc.
	 

	 	777 Old Saw Mill River Road
	 

	 	Tarrytown, New York 10591
	 

	 	U.S.A.
	 

	 	Attention: President
	 

	 	Copy: General Counsel
	 
	 	 
	 

	 	with a copy to:
	 
	 	 
	 

	 	Skadden, Arps, Slate, Meagher & Flom LLP
	 

	 	One Beacon Street, 31st Floor
	 

	 	Boston, MA 02108
	 

	 	Attention: Kent A. CoitEX-10.21

 

Exhibit 10.21

INVESTOR AGREEMENT

By and Among

SANOFI-AVENTIS,

SANOFI-AVENTIS US LLC,

AVENTIS PHARMACEUTICALS INC.,

SANOFI-AVENTIS AMÉRIQUE DU NORD

AND

REGENERON PHARMACEUTICALS, INC.

Dated as of December 20, 2007

 

 

TABLE OF CONTENTS

	 	 	 	 	 
	 	 	Page	 
	1. DEFINITIONS
	 	 	1	 
	 
	 	 	 	 
	2. REGISTRATION RIGHTS
	 	 	7	 
	 
	 	 	 	 
	2.1 Required Registration
	 	 	7	 
	2.2 Underwritten Required Registration Required; Priority in Underwritten
Offering
	 	 	9	 
	2.3 Priority in Required Registration
	 	 	9	 
	2.4 Revocation of Required Registration
	 	 	10	 
	2.5 Effective Required Registrations
	 	 	10	 
	2.6 Continuous Effectiveness of Registration Statement
	 	 	.       11	 
	2.7 Obligations of the Company
	 	 	11	 
	2.8 Furnish Information
	 	 	14	 
	2.9 Expenses
	 	 	14	 
	2.10 Indemnification
	 	 	14	 
	2.11 SEC Reports
	 	 	16	 
	2.12 Assignment of Registration Rights
	 	 	16	 
	 
	 	 	 	 
	3. RESTRICTIONS ON BENEFICIAL OWNERSHIP
	 	 	17	 
	 
	 	 	 	 
	3.1 Standstill
	 	 	17	 
	3.2 Amendment to Aventis Collaboration Agreement
	 	 	18	 
	 
	 	 	 	 
	4. RESTRICTIONS ON DISPOSITIONS
	 	 	18	 
	 
	 	 	 	 
	4.1 Lock-Up
	 	 	18	 
	4.2 Limitations Following Lock-Up Term
	 	 	19	 
	4.3 Certain Tender Offers
	 	 	20	 
	4.4 Offering Lock-Up
	 	 	20	 
	 
	 	 	 	 
	5. VOTING AGREEMENT
	 	 	20	 
	 
	 	 	 	 
	5.1 Voting of Securities
	 	 	20	 
	5.2 Certain Extraordinary Matters
	 	 	21	 
	5.3 Quorum
	 	 	21	 
	 
	 	 	 	 
	6. TERMINATION OF CERTAIN RIGHTS AND OBLIGATIONS
	 	 	22	 
	 
	 	 	 	 
	6.1 Termination of Registration Rights
	 	 	22	 
	6.2 Termination of Standstill Agreement
	 	 	22	 
	6.3 Termination of Restrictions on Dispositions
	 	 	23	 
	6.4 Termination of Voting Agreement
	 	 	23	 
	6.5 Effect of Termination
	 	 	23	 
	 
	 	 	 	 
	7. MISCELLANEOUS
	 	 	23	 
	 
	 	 	 	 
	7.1 Governing Law; Submission to Jurisdiction
	 	 	23	 
	7.2 Waiver
	 	 	23	 
	7.3 Notices
	 	 	24	 

i 

 

	 	 	 	 	 
	 	 	Page	 
	7.4 Entire Agreement
	 	 	24	 
	7.5 Amendments
	 	 	24	 
	7.6 Headings; Nouns and Pronouns; Section References
	 	 	24	 
	7.7 Severability
	 	 	24	 
	7.8 Assignment
	 	 	25	 
	7.9 Successors and Assigns
	 	 	25	 
	7.10 Counterparts
	 	 	25	 
	7.11 Third Party Beneficiaries
	 	 	25	 
	7.12 No Strict Construction
	 	 	25	 
	7.13 Remedies
	 	 	25	 
	7.14 Specific Performance
	 	 	25	 
	7.15 No Conflicting Agreements
	 	 	25	 
	 
	 	 	 	 
	Exhibit A – Form of Irrevocable Proxy
	Exhibit B – Notices
	 	 	 	 

ii 

 

INVESTOR AGREEMENT

     THIS INVESTOR AGREEMENT (this “Agreement”) is made as of December 20, 2007, by and
among sanofi-aventis, a company organized under the laws of France, with its principal headquarters
at 174, avenue de France, 75013 Paris, France (“sanofi-aventis”), sanofi-aventis US LLC, a
Delaware limited liability company indirectly wholly owned by sanofi-aventis (“Sanofi US”)
and the successor-in-interest to Aventis Pharmaceuticals Inc. (“Aventis”) with respect to
the Aventis Collaboration Agreement, with its headquarters at 55 Corporate Drive, Bridgewater, New
Jersey 00807, Aventis, a Delaware corporation and an indirect wholly owned subsidiary of the
Investor with its headquarters at 55 Corporate Drive, Bridgewater, New Jersey 00807, sanofi-aventis
Amérique du Nord, a société en nom collectif organized under the laws of France wholly owned by
sanofi-aventis with its principal headquarters at 174, avenue de France, 75013 Paris, France (the
“Investor”, and, together with sanofi-aventis, Sanofi US and Aventis, the “Purchaser
Parties”), and Regeneron Pharmaceuticals, Inc. (the “Company”), a New York corporation
with its principal place of business at 777 Old Saw Mill River Road, Tarrytown, New York 10591.

     WHEREAS, the Stock Purchase Agreement, dated as of November 28, 2007, by and among the
Investor, sanofi-aventis US and the Company (the “Purchase Agreement”) provides for the
issuance and sale by the Company to the Investor, and the purchase by the Investor, of a number of
shares of the Company’s common stock, par value $0.001 per share (the “Common Stock”),
equal to the Share Amount (as defined in the Purchase Agreement) (the “Purchased Shares”);
and

     WHEREAS, as a condition to consummating the transactions contemplated by the Purchase
Agreement, the Purchaser Parties and the Company have agreed upon certain rights and restrictions
as set forth herein with respect to the Purchased Shares and other securities of the Company
beneficially owned by the Purchaser Parties and their respective Affiliates, and it is a condition
to the closing under the Purchase Agreement that this Agreement be executed and delivered by the
Purchaser Parties and the Company.

     NOW, THEREFORE, in consideration of the premises and mutual agreements hereinafter set forth,
and for other valuable consideration, the receipt and sufficiency of which are hereby acknowledged,
the parties hereto agree as follows:

     1.
Definitions. As used in this Agreement, the following terms shall have the following meanings:

          (a) “Acquisition Proposal” shall have the meaning set forth in Section 3.1(c).

          (b) “Affiliate” shall mean, with respect to any Person, another Person which controls,
is controlled by or is under common control with such Person. A Person shall be deemed to control
another Person if such Person possesses, directly or indirectly, the power to direct or cause the
direction of the management and policies of such Person, whether through the ownership of voting
securities, by contract or otherwise. Without limiting the generality of the foregoing, a Person
shall be deemed to control another Person if any of the following conditions is met: (i) in the
case of corporate entities, direct or indirect ownership of more than fifty percent

 

 

(50%) of the stock or shares having the right to vote for the election of directors, and (ii)
in the case of non-corporate entities, direct or indirect ownership of more than fifty percent
(50%) of the equity interest with the power to direct the management and policies of such
non-corporate entities. The parties acknowledge that in the case of certain entities organized
under the Laws of certain countries outside the United States, the maximum percentage ownership
permitted by Law for a foreign investor may be less than fifty percent (50%), and that in such case
such lower percentage shall be substituted in the preceding sentence, provided that such foreign
investor has the power to direct the management and policies of such entity. For the purposes of
this Agreement, in no event shall the Investor or any of its Affiliates be deemed Affiliates of the
Company or any of its Affiliates, nor shall the Company or any of its Affiliates be deemed
Affiliates of the Investor or any of its Affiliates.

          (c) “Agreement” shall have the meaning set forth in the Preamble to this Agreement,
including all Exhibits attached hereto.

          (d) “Aventis” shall have the meaning set forth in the Preamble to this Agreement.

          (e) “Aventis Collaboration Agreement” shall mean the Collaboration Agreement, dated as
of September 5, 2003, by and between Sanofi US and the Company, as amended by the First Amendment,
dated as of December 31, 2004, the Second Amendment, dated as of January 7, 2005, the Third
Amendment, dated as of December 21, 2005, the Fourth Amendment, dated as of January 31, 2006, and
Section 11.2 of the Purchase Agreement, as the same may be further amended from time to time.

          (f) “Aventis Stock Purchase Agreement” shall mean the Stock Purchase Agreement, dated
as of September 5, 2003, by and between Aventis and the Company.

          (g) “beneficial owner,” “beneficially owns,” “beneficial ownership”
and terms of similar import used in this Agreement shall, with respect to a Person, have the
meaning set forth in Rule 13d-3 under the Exchange Act (i) assuming the full conversion into, and
exercise and exchange for, shares of Common Stock of all Common Stock Equivalents beneficially
owned by such Person and (ii) determined without regard for the number of days in which such Person
has the right to acquire such beneficial ownership.

          (h) “Business Day” shall mean a day on which commercial banking institutions in New
York, New York are open for business.

          (i) “Change of Control” shall mean, with respect to the Company, any of the following
events: (i) any Person is or becomes the beneficial owner (except that a Person shall be deemed to
have beneficial ownership of all shares that any such Person has the right to acquire, whether such
right which may be exercised immediately or only after the passage of time), directly or
indirectly, of a majority of the total voting power represented by all Shares of Then Outstanding
Common Stock; (ii) the Company consolidates with or merges into another corporation or entity, or
any corporation or entity consolidates with or merges into the Company, other than (A) a merger or
consolidation which would result in the voting securities of the Company outstanding immediately
prior to such merger or consolidation continuing to represent

2

 

(either by remaining outstanding or by being converted into voting securities of the surviving
entity or any parent thereof) a majority of the combined voting power of the voting securities of
the Company or such surviving entity or any parent thereof outstanding immediately after such
merger or consolidation, or (B) a merger or consolidation effected to implement a recapitalization
of the Company (or similar transaction) in which no Person becomes the beneficial owner, directly
or indirectly, of a majority of the total voting power of all Shares of Then Outstanding Common
Stock or (iii) the Company conveys, transfers or leases all or substantially all of its assets to
any Person other than a wholly owned Affiliate of the Company.

          (j) “Class A Stock” shall mean the Class A Stock, par value $0.001 per share, of the
Company.

          (k) “Closing Date” shall have the meaning set forth in the Purchase Agreement.

          (l) “Common Stock” shall have the meaning set forth in the Preamble to this Agreement.

          (m) “Common Stock Equivalents” shall mean any options, warrants or other securities
(including Class A Stock) or rights convertible into or exercisable or exchangeable for, whether
directly or following conversion into or exercise or exchange for other options, warrants or other
securities or rights, shares of Common Stock.

          (n) “Company” shall have the meaning set forth in the Preamble to this Agreement.

          (o) “Demand Request” shall have the meaning set forth in Section 2.1.

          (p) “Disposition” or “Dispose of” shall mean any (i) offer, pledge, sale,
contract to sell, sale of any option or contract to purchase, purchase of any option or contract to
sell, grant of any option, right or warrant for the sale of, or other disposition of or transfer of
any shares of Class A Stock or Common Stock, or any Common Stock Equivalents, including, without
limitation, any “short sale” or similar arrangement, or (ii) swap or any other agreement or any
transaction that transfers, in whole or in part, directly or indirectly, the economic consequence
of ownership of shares of Class A Stock or Common Stock, whether any such swap or transaction is to
be settled by delivery of securities, in cash or otherwise.

          (q) “Exchange Act” shall mean the Securities Exchange Act of 1934, as amended, and the
rules and regulations of the SEC promulgated thereunder.

          (r) “Extraordinary Matter” shall have the meaning set forth in Section 5.2.

          (s) “Filing Date” shall mean (i) with respect to any Registration Statement to be
filed on Form S-1 (or any applicable successor form), ninety (90) days after receipt by the Company
of a Demand Request for such Registration Statement and (ii) with respect to any Registration
Statement to be filed on Form S-3 (or any applicable successor form), forty-five (45) days after
receipt by the Company of a Demand Request for such Registration Statement.

3

 

          (t) “Governmental Authority” shall mean any court, agency, authority, department,
regulatory body or other instrumentality of any government or country or of any national, federal,
state, provincial, regional, county, city or other political subdivision of any such government or
country or any supranational organization of which any such country is a member.

          (u) “Holders” shall mean (but, in each case, only for so long as such Person remains
an Affiliate of sanofi-aventis) the Investor, Aventis and any Permitted Transferee thereof, if any,
in accordance with Section 2.12.

          (v) “Initiating Holder” shall have the meaning set forth in Section 2.2.

          (w) “Interference” shall have the meaning set forth in Section 2.5.

          (x) “Investor” shall have the meaning set forth in the Preamble to this Agreement.

          (y) “Law” or “Laws” shall mean all laws, statutes, rules, regulations, orders,
judgments, injunctions and/or ordinances of any Governmental Authority.

          (z) “Lock-Up Term” shall have the meaning set forth in Section 4.1.

          (aa) “Modified Clause” shall have the meaning set forth in Section 7.7.

(bb) “Offeror” shall have the meaning set forth in Section 3.1(c).

          (cc) “Other Holders” shall mean any Person having rights to participate in a
registration of the Company’s securities.

          (dd) “Permitted Transferee” shall mean a controlled Affiliate of sanofi-aventis that
is wholly owned, directly or indirectly, by sanofi-aventis; it being understood that for purposes
of this definition “wholly owned” shall mean an Affiliate in which sanofi-aventis owns, directly or
indirectly, at least ninety-nine percent (99%) of the outstanding capital stock of such Affiliate.

          (ee) “Person” shall mean any individual, partnership, firm, corporation, association,
trust, unincorporated organization, government or any department or agency thereof or other entity,
as well as any syndicate or group that would be deemed to be a Person under Section 13(d)(3) of the
Exchange Act.

          (ff) “Prospectus” shall mean the prospectus forming a part of any Registration
Statement, as supplemented by any and all prospectus supplements and as amended by any and all
amendments (including post-effective amendments) and including all material incorporated by
reference or explicitly deemed to be incorporated by reference in such prospectus.

          (gg) “Purchase Agreement” shall have the meaning set forth in the Preamble to this
Agreement, and shall include all Exhibits attached thereto.

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          (hh) “Purchased Shares” shall have the meaning set forth in the Preamble to this
Agreement, and shall be adjusted for (i) any stock split, stock dividend, share exchange, merger,
consolidation or similar recapitalization and (ii) any Common Stock issued as (or issuable upon the
exercise of any warrant, right or other security that is issued as) a dividend or other
distribution with respect to, or in exchange or in replacement of, the Purchased Shares.

          (ii) “Purchaser Parties” shall have the meaning set forth in the Preamble to this
Agreement.

          (jj) “registers,” “registered,” and “registration” refer to a
registration effected by preparing and filing a Registration Statement or similar document in
compliance with the Securities Act, and the declaration or ordering of effectiveness of such
Registration Statement or document by the SEC.

          (kk) “Registrable Securities” shall mean (i) the Purchased Shares and any shares of
Common Stock owned of record by Aventis as of the date of this Agreement, together with any shares
of Common Stock issued in respect thereof as a result of any stock split, stock dividend, share
exchange, merger, consolidation or similar recapitalization and (ii) any Common Stock issued as (or
issuable upon the exercise of any warrant, right or other security that is issued as) a dividend or
other distribution with respect to, or in exchange or in replacement of, the shares of Common Stock
described in clause (i) of this definition, excluding in all cases, however, (A) any Registrable
Securities if and after they have been transferred to a Permitted Transferee in a transaction in
connection with which registration rights granted hereunder are not assigned, (B) any Registrable
Securities sold to or through a broker or dealer or underwriter in a public distribution or a
public securities transaction or (C) Registrable Securities eligible for resale pursuant to Rule
144(k) under the Securities Act.

          (ll) “Registration Expenses” shall mean all expenses incurred by the Company in
connection with any Required Registration pursuant to Section 2.1 or the Company’s compliance with
Section 2.7 (excluding clauses (m), (n) and (r) thereof), including, without limitation, all
registration and filing fees, fees and expenses of compliance with securities or blue sky Laws
(including reasonable fees and disbursements of counsel in connection with blue sky qualifications
of any Registrable Securities), expenses of printing (i) certificates for any Registrable
Securities in a form eligible for deposit with the Depository Trust Company or (ii) Prospectuses if
the printing of Prospectuses is requested by Holders, messenger and delivery expenses, fees and
disbursements of counsel for the Company and its independent certified public accountants
(including the expenses of any management review, cold comfort letters or any special audits
required by or incident to such performance and compliance), Securities Act liability insurance (if
the Company elects to obtain such insurance), the reasonable fees and expenses of any special
experts retained by the Company in connection with such registration, fees and expenses of other
Persons retained by the Company and the reasonable fees and expenses of one (1) counsel for the
Holders of Registrable Securities in each Required Registration, selected by the Holders of a
majority of the Registrable Securities to be included in such Required Registration. In addition,
the Company will pay its internal expenses (including, without limitation, all salaries and
expenses of its officers and employees performing legal or accounting duties), the expense of any
annual audit and the fees and expenses incurred in connection with the listing of the Purchased
Shares to be registered on each securities exchange,

5

 

if any, on which equity securities issued by the Company are then listed or the quotation of
such securities on any national securities exchange on which equity securities issued by the
Company are then quoted.

          (mm) “Registration Rights Term” shall have the meaning set forth in Section 2.1.

          (nn) “Registration Statement” shall mean any registration statement of the Company
under the Securities Act that covers any of the Registrable Securities pursuant to the provisions
of this Agreement, including the related Prospectus, all amendments and supplements to such
registration statement (including post-effective amendments), and all exhibits and all materials
incorporated by reference or explicitly deemed to be incorporated by reference in such Registration
Statement.

          (oo) “Required Period” with respect to a Required Registration shall mean the earlier
of (i) the date on which all Registrable Securities covered by such Required Registration are sold
pursuant thereto and (ii) one-hundred twenty (120) days following the first day of effectiveness of
the Registration Statement for such Required Registration, in each case subject to extension as set
forth herein; provided, however, that in no event will the Required Period expire
prior to the expiration of the applicable period referred to in Section 4(3) of the Securities Act
and Rule 174 promulgated thereunder.

          (pp) “Required Registration” shall have the meaning set forth in Section 2.1.

          (qq) “Sanofi License and Collaboration Agreement” shall mean that certain License and
Collaboration Agreement between the Company, the Investor and Aventis dated as of November 28,
2007, as the same may be amended from time to time.

          (rr) “sanofi-aventis” shall have the meaning set forth in the Preamble to this
Agreement.

          (ss) “Sanofi US” shall have the meaning set forth in the Preamble to this Agreement.

          (tt) “SEC” shall mean the United States Securities and Exchange Commission.

          (uu) “Securities Act” shall mean the Securities Act of 1933, as amended, and the rules
and regulations of the SEC promulgated thereunder.

          (vv) “Selling Expenses” shall mean all underwriting discounts and selling commissions
applicable to the sale of Registrable Securities pursuant to this Agreement.

          (ww) “Shares of Then Outstanding Common Stock” shall mean, at any time, the issued and
outstanding shares of Class A Stock and Common Stock at such time, as well as all capital stock
issued and outstanding as a result of any stock split, stock dividend, or reclassification of Class
A Stock or Common Stock distributable, on a pro rata basis, to all holders of Class A Stock and
Common Stock, as applicable.

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          (xx) “Standstill Limit” shall mean (i) from the Closing Date until the fourth
(4th) anniversary of the Closing Date, the lesser of (A) twenty-one percent (21%) of the
Shares of Then Outstanding Common Stock, in the case of this clause (A) only, calculated on a fully
diluted basis assuming the full conversion into, or exercise or exchange for, shares of Common
Stock of all Common Stock Equivalents outstanding (as such Common Stock Equivalents outstanding are
calculated from the Company’s most recent Form 10-Q or Form 10-K, as applicable, filed with the
SEC), and (B) twenty-five percent (25%) of the Shares of Then Outstanding Common Stock, and (ii)
from the fourth (4th) anniversary of the Closing Date until the expiration of the
Standstill Term, thirty percent (30%) of the Shares of Then Outstanding Common Stock.

          (yy) “Standstill Parties” shall have the meaning set forth in Section 3.1.

(zz) “Standstill Term” shall have the meaning set forth in Section 3.1.

          (aaa) “Third Party” shall mean any Person other than the Purchaser Parties, the
Company or any of their respective Affiliates.

          (bbb) “Underwritten Registration” or “Underwritten Offering” shall mean a
registration in which Registrable Securities are sold to an underwriter for reoffering to the
public.

          (ccc) “Violation” shall have the meaning set forth in Section 2.10(a).

2. Registration Rights.

     2.1 Required Registration. If, at any time after the expiration of the Lock-Up Term but no later than
the tenth (10th) anniversary of such expiration (the “Registration Rights
Term”), the Company receives from any Holder or Holders a written request or requests (each, a
“Demand Request”) that the Company file a Registration Statement under the Securities Act
to effect the registration (a “Required Registration”) of Registrable Securities, the
Company shall use all reasonable efforts to file a Registration Statement covering such Holders’
Registrable Securities as soon as practicable (and by the applicable Filing Date) and shall use all
reasonable efforts to, as soon as practicable thereafter, effect the registration of the
Registrable Securities to permit or facilitate the sale and distribution in an Underwritten
Offering of all or such portion of such Holder’s or Holders’ Registrable Securities as are
specified in such Demand Request, subject however, to the conditions and limitations set forth
herein; provided, however, that the Company shall not be obligated to effect any
registration of Registrable Securities upon receipt of a Demand Request pursuant to this Section
2.1 if:

          (i) the Company has already completed three (3) Required Registrations;

          (ii) (A) in the event that the market value of all Registrable Securities
outstanding is equal to or greater than $50,000,000, the market value of the
Registrable Securities proposed to be included in the registration, based on the
average closing price during the ten (10) consecutive trading days period prior to
the making of the Demand Request, is less than $50,000,000 or (B) in the event that
the market value of all Registrable Securities outstanding is less than

7

 

$50,000,000, (i) less than all such Registrable Securities are proposed to be
included in the registration, or (ii) the market value of all such Registrable
Securities is less than $25,000,000;

          (iii) the Company shall furnish to the Holders a certificate signed by an
authorized officer of the Company stating that (A) within ninety (90) days of
receipt of the Demand Request under this Section 2.1, the Company shall file a
registration statement for the public offering of securities for the account of the
Company (other than a registration of securities (x) issuable pursuant to an
employee stock option, stock purchase or similar plan, (y) issuable pursuant to a
merger, exchange offer or a transaction of the type specified in Rule 145(a) under
the Securities Act or (z) in which the only securities being registered are
securities issuable upon conversion of debt securities which are also being
registered), or (B) the Company is engaged in a material transaction or has an
undisclosed material corporate development, in either case, which would be required
to be disclosed in the Registration Statement, and in the good faith judgment of the
Company’s Board of Directors, such disclosure would be seriously detrimental to the
Company and its stockholders at such time (in which case, the Company shall disclose
the matter as promptly as reasonably practicable and thereafter file the
Registration Statement, and each Holder agrees not to disclose any information about
such material transaction to Third Parties until such disclosure has occurred or
such information has entered the public domain other than through breach of this
provision by such Holder), provided, however, that the Company shall
have the right to only defer the filing of the Registration Statement pursuant to
this subsection once in any twelve (12) month period and, such deferral may not
exceed a period of more than one-hundred twenty (120) days after receipt of a Demand
Request;

          (iv) the Company has, within the twelve (12) month period preceding the date of
the Demand Request, already effected one (1) Required Registration for any Holder
pursuant to this Section 2.1; or

          (v) at any time during the period between the Company’s receipt of the Demand
Request and the completion of the Required Registration, any Holder is in breach of
or has failed to cause its Affiliates to comply with the obligations and
restrictions of Sections 3, 4 or 5 of this Agreement, and such breach or failure is
ongoing and has not been remedied; it being understood that (A) a one-time,
inadvertent and de minimis breach of Section 4 shall not be deemed to be a breach of
the obligations and restrictions under Section 4 for purposes of this Section 2.1(v)
and (B) a de minimis breach of Section 3.1(a) hereof, or an inadvertent breach of
Section 3.1(g) hereof arising from informal discussions covering general corporate
or other business matters the purpose of which is not intended to effectuate or lead
to any of the actions referred to in paragraphs (a) through (e) of Section 3.1,
shall not be deemed to be a breach of the obligations and restrictions under Section
3.1 for purposes of this Section 2.1(v).

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     2.2 Underwritten Required Registration Required; Priority in Underwritten Offering. The underwriter
for any Underwritten Offering requested pursuant to Section 2.1 shall be selected by a majority in
interest of the Holders initiating the Required Registration hereunder (such Holder(s) initiating
the registration request, the “Initiating Holders”) and shall be acceptable to the Company.
The right of any Holder to include its Registrable Securities in the Underwritten Offering shall
be conditioned upon such Holder’s participation in such Underwritten Offering and the inclusion of
such Holder’s Registrable Securities to the extent provided herein. All Holders requesting the
inclusion of their Registrable Securities in such Underwritten Offering shall (together with the
Company as provided in Section 2.7(h)) enter into an underwriting agreement in customary form with
the underwriter or underwriters selected for such Underwritten Offering. Notwithstanding any other
provision of this Section 2, if the managing underwriter for the Underwritten Offering determines
in good faith that marketing factors require a limitation of the number of shares of Registrable
Securities to be included in such Underwritten Offering, then the Company shall so advise all
Holders which requested inclusion of their Registrable Securities in such Underwritten Offering,
and the number of shares of Registrable Securities that may be included in such Underwritten
Offering shall be allocated among the Holders in proportion (as nearly as practicable) to the
amount of Registrable Securities of the Company owned by each Holder; provided,
however, that the number of shares of Registrable Securities to be included in such
Underwritten Offering shall not be reduced unless all other securities are first entirely excluded
from such Underwritten Offering. In the event the Company advises the Holders of its intent to
decrease the total number of Registrable Securities that may be included by the Holders in such
Required Registration such that the number of Registrable Securities included in such Required
Registration would be less than seventy-five percent (75%) of all Registrable Securities which the
Holders requested be included in such Required Registration, then Holders representing a majority
of the Registrable Securities requested to be included in such Required Registration will have the
right to withdraw, on behalf of all Holders of all Registrable Securities requested to be so
included, such Required Registration, in which case, such Required Registration will not count as a
Required Registration for the purposes of Section 2.1(i), and the Company shall bear all
Registration Expenses in connection therewith; provided, that, the right to
withdraw a registration and have it not count as a Required Registration may only be exercised once
by the Holders (taken collectively).

     2.3 Priority in Required Registration. With respect to any Required Registration of Registrable
Securities requested pursuant to Section 2.1, the Company may also (i) propose to sell shares of
Common Stock on its own behalf and (ii) provide written notice of such Required Registration to
Other Holders and permit all such Other Holders who request to be included in the Required
Registration to include any or all Company securities held by such Other Holders in such Required
Registration on the same terms and conditions as the Registrable Securities. Notwithstanding the
foregoing, if the managing underwriter or underwriters of the Underwritten Offering to which any
Required Registration relates advise the Company and the Holders of Registrable Securities that, in
its good faith determination, the total amount of securities that such Holders, Other Holders, and
the Company intend to include in such Required Registration is in an amount in the aggregate which
would adversely affect the success of such Underwritten Offering, then such Required Registration
shall include (i) first, all Registrable Securities of the Holders allocated, if the amount is less
than all the Registrable Securities requested to be sold, pro rata on the basis of the total number
of Registrable Securities held by such Holders; and (ii) second, as many other securities proposed
to be included in the Required Registration by the

9

 

Company and any Other Holders, allocated pro rata among the Company and such Other Holders, on the
basis of the amount of securities requested to be included therein by the Company and each such
Other Holder so that the total amount of securities to be included in such Underwritten Offering is
the full amount that, in the written opinion of such managing underwriter, can be sold without
materially and adversely affecting the success of such Underwritten Offering.

     2.4 Revocation of Required Registration. With respect to one (1) Required Registration only, the
Holders of at least a majority of the Registrable Securities to be included in a Registration
Statement with respect to such Required Registration may, at any time prior to the effective date
of such Registration Statement, on behalf of all Holders of all Registrable Securities requested to
be included therein, revoke the request to have Registrable Securities included therein and revoke
the request for such Required Registration by providing a written notice to the Company, in which
case such Required Registration that has been revoked will be deemed not to have been effected and
will not count as a Required Registration for purposes of Section 2.1(i) if, and only if, the
Holders of Registrable Securities which had requested inclusion of Registrable Securities in such
Required Registration promptly reimburse the Company for all Registration Expenses incurred by the
Company in connection with such Required Registration. Notwithstanding the foregoing sentence, the
parties agree and acknowledge that the Holders may revoke any Required Registration (without any
obligation to reimburse the Company for Registration Expenses incurred in connection therewith) if
such revocation is based on (i) a material adverse change in circumstances with respect to the
Company and its subsidiaries, taken as a whole, caused by an act or failure to act by the Company
or any of its subsidiaries and not known to any Holder at the time the Required Registration was
first made or (ii) the Company’s failure to comply in any material respect with its obligations
hereunder, and any such revocation based on an event described in (i) or (ii) above shall be
exercisable at any time and shall not be counted as the one (1) revocation of a Required
Registration permitted by the first sentence of this Section 2.4.

     2.5 Effective Required Registrations. A Required Registration will not be deemed to be effected for
purposes of Section 2.1(i) if the Registration Statement for such Required Registration has not
been declared effective by the SEC or become effective in accordance with the Securities Act and
the rules and regulations thereunder and kept effective for the Required Period. In addition, if
after such Registration Statement has been declared or becomes effective, (i) the offering of
Registrable Securities pursuant to such Registration Statement is interfered with by any stop
order, injunction, or other order or requirement of the SEC or other governmental agency or court
such that the continued offer and sale of Registrable Securities being offered pursuant to such
Registration Statement would violate applicable Law and such stop order, injunction or other order
or requirement of the SEC or other governmental agency or court does not result from any act or
omission of any Holder whose Registrable Securities are registered pursuant to such Registration
Statement (an “Interference”) and (ii) any such Interference is not cured within sixty (60)
days thereof, such Required Registration will be deemed not to have been effected and will not
count as a Required Registration. In the event such Interference occurs and is cured, the Required
Period relating to such Registration Statement will be extended by the number of days of such
Interference, including the date such Interference is cured.

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     2.6 Continuous Effectiveness of Registration Statement. The Company will use all reasonable efforts to
cause each Registration Statement filed pursuant to this Section 2 to be declared effective by the
SEC or to become effective under the Securities Act as promptly as practicable and to keep each
such Registration Statement that has been declared or becomes effective continuously effective for
the Required Period.

     2.7 Obligations of the Company. Whenever required under Section 2.1 to effect the registration of any
Registrable Securities, the Company shall, as expeditiously as reasonably possible:

          (a) prepare and file with the SEC a Registration Statement with respect to such Registrable
Securities sought to be included therein; provided that at least five (5) Business Days prior to
filing any Registration Statement or Prospectus or any amendments or supplements thereto, the
Company shall furnish to the Holders of the Registrable Securities covered by such Registration
Statement, their counsel and the managing underwriter copies of all such documents proposed to be
filed, and any such Holder shall have the opportunity to comment on any information pertaining
solely to such Holder and its plan of distribution that is contained therein and the Company shall
make the corrections reasonably requested by such Holder or the managing underwriter with respect
to such information prior to filing any such Registration Statement or amendment;

          (b) prepare and file with the SEC such amendments and post-effective amendments to any
Registration Statement and any Prospectus used in connection therewith as may be necessary to keep
such Registration Statement effective for the Required Period, and cause the Prospectus to be
supplemented by any required prospectus supplement, and as so supplemented to be filed pursuant to
Rule 424 under the Securities Act, to comply with the provisions of the Securities Act with respect
to the disposition of all Registrable Securities covered by such registration statement for the
Required Period; provided that at least five (5) Business Days prior to filing any such amendments
and post effective amendments or supplements thereto, the Company shall furnish to the Holders of
the Registrable Securities covered by such Registration Statement, their counsel and the managing
underwriter copies of all such documents proposed to be filed, and any such Holder or managing
underwriter shall have the opportunity to comment on any information pertaining solely to such
Holder and its plan of distribution that is contained therein and the Company shall make the
corrections reasonably requested by such Holder and the managing underwriter with respect to such
information prior to filing any such Registration Statement or amendment;

          (c) furnish to the Holders of Registrable Securities covered by such Registration Statement
and the managing underwriter such numbers of copies of such Registration Statement, each amendment
and supplement thereto, the Prospectus included in such Registration Statement (including each
preliminary prospectus or free writing prospectus) in conformity with the requirements of the
Securities Act, and such other documents as they may reasonably request in order to facilitate the
disposition of Registrable Securities owned by them;

          (d) notify the Holders of Registrable Securities covered by such Registration Statement,
promptly after the Company shall receive notice thereof, of the time when such

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Registration Statement becomes or is declared effective or when any amendment or supplement or
any Prospectus forming a part of such Registration Statement has been filed;

          (e) notify the Holders of Registrable Securities covered by such Registration Statement
promptly of any request by the SEC for the amending or supplementing of such Registration Statement
or Prospectus or for additional information and promptly deliver to such Holders copies of any
comments received from the SEC;

          (f) notify the Holders promptly of any stop order suspending the effectiveness of such
Registration Statement or Prospectus or the initiation of any proceedings for that purpose, and use
all reasonable efforts to obtain the withdrawal of any such order or the termination of such
proceedings;

          (g) use all reasonable efforts to register and qualify the Registrable Securities covered by
such Registration Statement under such other securities or blue sky Laws of such jurisdictions as
shall be reasonably requested by the Holders, use all reasonable efforts to keep each such
registration or qualification effective, including through new filings, or amendments or renewals,
during the Required Period, and notify the Holders of Registrable Securities covered by such
Registration Statement of the receipt of any written notification with respect to any suspension of
any such qualification; provided, however, that the Company shall not be required
in connection therewith or as a condition thereto to qualify to do business or to file a general
consent to service of process in any such states or jurisdictions;

          (h) enter into and perform its obligations under an underwriting agreement, in usual and
customary form, with the managing underwriter of the Underwritten Offering pursuant to which such
Registrable Securities are being offered;

          (i) use all reasonable efforts to obtain: (A) at the time of effectiveness of the Registration
Statement covering such Registrable Securities, a “cold comfort letter” from the Company’s
independent certified public accountants covering such matters of the type customarily covered by
“cold comfort letters” as the underwriters may reasonably request; and (B) at the time of any
underwritten sale pursuant to such Registration Statement, a “bring-down comfort letter,” dated as
of the date of such sale, from the Company’s independent certified public accountants covering such
matters of the type customarily covered by “bring-down comfort letters” as the underwriters may
reasonably request.

          (j) promptly notify each Holder of Registrable Securities covered by such Registration
Statement at any time when a Prospectus relating thereto is required to be delivered under the
Securities Act of the happening of any event as a result of which the Prospectus included in such
Registration Statement or any offering memorandum or other offering document includes an untrue
statement of a material fact or omits to state any material fact required to be stated therein or
necessary to make the statements therein not misleading in the light of the circumstances then
existing, and promptly prepare a supplement or amendment to such Prospectus or file any other
required document so that, as thereafter delivered to the purchasers of such Registrable
Securities, such Prospectus will not contain an untrue statement of material fact or omit to state
any fact necessary to make the statements therein not misleading;

12

 

          (k) permit any Holder of Registrable Securities covered by such Registration Statement, which
Holder in its reasonable judgment could reasonably be deemed to be an underwriter with respect to
the Underwritten Offering pursuant to which such Registrable Securities are being offered, or to be
a controlling Person of the Company, to reasonably participate in the preparation of such
Registration Statement and to require the insertion therein of information to the extent concerning
such Holder, furnished to the Company in writing, which in the reasonable judgment of such Holder
and its counsel should be included;

          (l) in connection with any Underwritten Offering, use all reasonable efforts to obtain an
opinion or opinions addressed to the underwriter or underwriters in customary form and scope from
counsel for the Company;

          (m) upon reasonable notice and during normal business hours, subject to the Company receiving
customary confidentiality undertakings or agreements from any Holder of Registrable Securities
covered by such Registration Statement or other person obtaining access to Company records,
documents, properties or other information pursuant to this subsection (m), make available for
inspection by a representative of such Holder and any underwriter participating in any disposition
of such Registrable Securities and any attorneys or accountants retained by any such Holder or
underwriter, relevant financial and other records, pertinent corporate documents and properties of
the Company, and use all reasonable efforts to cause the officers, directors and employees of the
Company to supply all information reasonably requested by any such representative, underwriter,
attorneys or accountants in connection with the Registration Statement;

          (n) with respect to one (1) Required Registration which includes Registrable Securities the
market value of which is at least one hundred million United States dollars ($100,000,000),
participate, to the extent requested by the managing underwriter, in efforts extending for no more
than five (5) days scheduled by such managing underwriter and reasonably acceptable to the
Company’s senior management, to sell the Registrable Securities being offered pursuant to such
Required Registration (including participating during such period in customary “roadshow” meetings
with prospective investors);

          (o) use all reasonable efforts to comply with all applicable rules and regulations of the SEC
relating to such registration and make generally available to its security holders earning
statements satisfying the provisions of Section 11(a) of the Securities Act, provided that the
Company will be deemed to have complied with this Section 2.7(o) with respect to such earning
statements if it has satisfied the provisions of Rule 158;

          (p) if requested by the managing underwriter or any selling Holder, promptly incorporate in a
prospectus supplement or post-effective amendment such information as the managing underwriter or
any selling Holder reasonably requests to be included therein, with respect to the Registrable
Securities being sold by such selling Holder, including, without limitation, the purchase price
being paid therefor by the underwriters and with respect to any other terms of the Underwritten
Offering of Registrable Securities to be sold in such offering, and promptly make all required
filings of such prospectus supplement or post-effective amendment;

13

 

          (q) cause the Registrable Securities covered by such Registration Statement to be listed on
each securities exchange, if any, on which equity securities issued by the Company are then listed;
and

          (r) reasonably cooperate with each selling Holder and each underwriter participating in the
disposition of such Registrable Securities and their respective counsel in connection with filings
required to be made with the Financial Industry Regulatory Authority, Inc., if any.

     2.8 Furnish Information. It shall be a condition precedent to the obligations of the Company to take
any action pursuant to this Section 2 with respect to the Registrable Securities of any selling
Holder that such Holder shall furnish to the Company such information regarding itself and the
Registrable Securities held by it as shall be reasonably necessary to effect the registration of
such Holder’s Registrable Securities.

     2.9 Expenses. Except as specifically provided herein, all Registration Expenses shall be borne by the
Company. All Selling Expenses incurred in connection with any registration hereunder shall be
borne by the Holders of Registrable Securities covered by a Registration Statement, pro rata on the
basis of the number of Registrable Securities registered on their behalf in such Registration
Statement.

     2.10 Indemnification. In the event any Registrable Securities are included in a Registration Statement
under this Agreement:

          (a) The Company shall indemnify and hold harmless each Holder including Registrable Securities
in any such Registration Statement, any underwriter (as defined in the Securities Act) for such
Holder and each Person, if any, who controls such Holder or underwriter within the meaning of
Section 15 of the Securities Act or Section 20 of Exchange Act and the officers, directors, owners,
agents and employees of such controlling Persons, against any and all losses, claims, damages or
liabilities (joint or several) to which they may become subject under any securities Laws
including, without limitation, the Securities Act, the Exchange Act, or any other statute or common
law of the United States or any other country or political subdivision thereof, or otherwise,
including the amount paid in settlement of any litigation commenced or threatened (including any
amounts paid pursuant to or in settlement of claims made under the indemnification or contribution
provisions of any underwriting or similar agreement entered into by such Holder in connection with
any offering or sale of securities covered by this Agreement), and shall promptly reimburse them,
as and when incurred, for any legal or other expenses incurred by them in connection with
investigating any claims and defending any actions, insofar as any such losses, claims, damages or
liabilities (or actions in respect thereof) arise out of or are based upon any of the following
statements, omissions or violations (each, a “Violation”): (i) any untrue statement or
alleged untrue statement of a material fact contained in or incorporated by reference into such
Registration Statement, including any preliminary prospectus or final prospectus contained therein
or any free writing prospectus or any amendments or supplements thereto, or in any offering
memorandum or other offering document relating to the offering and sale of such securities or (ii)
the omission or alleged omission to state therein a material fact required to be stated therein, or
necessary to make the statements therein not misleading; provided, however, the
Company shall not be liable in any such case for any such loss, claim,

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damage, liability or action to the extent that it (A) arises out of or is based upon a
Violation which occurs solely in reliance upon and in conformity with written information furnished
expressly for use in connection with such registration by such Holder; or (B) is caused by such
Holder’s disposition of Registrable Shares during any period during which such Holder is obligated
to discontinue any disposition of Registrable Shares as a result of any stop order suspending the
effectiveness of any registration statement or prospectus with respect to Registrable Securities.

          (b) Each Holder including Registrable Securities in a registration statement shall indemnify
and hold harmless the Company, each of its directors, each of its officers who has signed the
registration statement, each Person, if any, who controls the Company within the meaning of Section
15 of the Securities Act or Section 20 of the Exchange Act and the officers, directors, owners,
agents and employees of such controlling Persons, any underwriter, any other Holder selling
securities in such registration statement and any controlling Person of any such underwriter or
other Holder, against any losses, claims, damages or liabilities (joint or several) to which any of
the foregoing Persons may become subject, under liabilities (or actions in respect thereto) which
arise out of or are based upon any Violation, in each case to the extent (and only to the extent)
that such Violation: (i) arises out of or is based upon a Violation which occurs solely in reliance
upon and in conformity with written information furnished expressly for use in connection with such
registration by such Holder; or (ii) is caused by such Holder’s disposition of Registrable Shares
during any period during which such Holder is obligated to discontinue any disposition of
Registrable Shares as a result of any stop order suspending the effectiveness of any registration
statement or prospectus with respect to Registrable Securities. Each such Holder shall pay, as
incurred, any legal or other expenses reasonably incurred by any Person intended to be indemnified
pursuant to this Section 2.10(b), in connection with investigating or defending any such loss,
claim, damage, liability or action; provided, however, that the indemnity agreement
contained in this Section 2.10(b) shall not apply to amounts paid in settlement of any such loss,
claim, damage, liability or action if such settlement is effected without consent of the Holder,
which consent shall not be unreasonably withheld.

          (c) Promptly after receipt by an indemnified party under this Section 2.10 of notice of the
commencement of any action (including any action by a Governmental Authority), such indemnified
party shall, if a claim in respect thereof is to be made against any indemnifying party under this
Section 2.10, deliver to the indemnifying party a written notice of the commencement thereof and
the indemnifying party shall have the right to participate in, and, to the extent the indemnifying
party so desires, jointly with any other indemnifying party similarly noticed, to assume the
defense thereof with counsel mutually satisfactory to the parties; provided,
however, that an indemnified party shall have the right to retain its own counsel, with the
reasonable fees and expenses to be paid by the indemnifying party, if representation of such
indemnified party by the counsel retained by the indemnifying party would be inappropriate due to
actual or potential differing interests between such indemnified party and any other party
represented by such counsel in such proceeding. The failure to deliver written notice to the
indemnifying party within a reasonable time of the commencement of any such action, if prejudicial
to its ability to defend such action, shall relieve such indemnifying party of any liability to the
indemnified party under this Section 2.10, but the omission so to deliver written notice to the
indemnifying party shall not relieve it of any liability that it may have to any indemnified party
otherwise than under this Section 2.10.

15

 

          (d) In order to provide for just and equitable contribution to joint liability in any case in
which a claim for indemnification is made pursuant to this Section 2.10 but it is judicially
determined (by the entry of a final judgment or decree by a court of competent jurisdiction and the
expiration of time to appeal or the denial of the last right of appeal) that such indemnification
may not be enforced in such case notwithstanding the fact that this Section 2.10 provided for
indemnification in such case, the Company and each Holder of Registrable Securities shall
contribute to the aggregate losses, claims, damages or liabilities to which they may be subject
(after contribution from others) in proportion to the relative fault of the Company, on the one
hand, and such Holder, severally, on the other hand; provided, however, that in any
such case, no Person guilty of fraudulent misrepresentation (within the meaning of Section 11(f) of
the Securities Act) shall be entitled to contribution from any Person who was not guilty of such
fraudulent misrepresentation; provided further, however, that in no event
shall any contribution under this Section 2.10(d) on the part of any Holder exceed the net proceeds
received by such Holder from the sale of Registrable Securities giving rise to such contribution
obligation.

          (e) The obligations of the Company and the Holders under this Section 2.10 shall survive the
completion of any offering of Registrable Securities in a registration statement under this
Agreement and otherwise.

     2.11 SEC Reports. With a view to making available to the Holders the benefits of Rule 144 under the
Securities Act and any other rule or regulation of the SEC that may at any time permit a Holder to
sell Registrable Securities of the Company to the public without registration, the Company agrees
to at any time that it is a reporting company under Section 13 or 15(d) of the Exchange Act:

          (a) file with the SEC in a timely manner all reports and other documents required of the
Company under the Exchange Act; and

          (b) furnish to any Holder, so long as such Holder owns any Registrable Securities, forthwith
upon request (i) a written statement by the Company that it has complied with the reporting
requirements of the Exchange Act, (ii) a copy of the most recent annual or quarterly report of the
Company and such other reports and documents so filed by the Company, and (iii) such other
information as may be reasonably requested in availing any Holder of any rule or regulation of the
SEC (exclusive of Rule 144A) which permits the selling of any Registrable Securities without
registration.

     2.12 Assignment of Registration Rights. The rights to cause the Company to register any Registrable
Securities pursuant to this Agreement may be assigned in whole or in part (but only with all
restrictions and obligations set forth in this Agreement) by a Holder to a Permitted Transferee
which acquires Registrable Securities from such Holder; provided, however, (a) such
Holder shall, within five (5) days prior to such transfer, furnish to the Company written notice of
the name and address of such Permitted Transferee, details of its status as a Permitted Transferee
and details of the Registrable Securities with respect to which such registration rights are being
assigned, (b) the Permitted Transferee, prior to or simultaneously with such transfer or
assignment, shall agree in writing to be subject to and bound by all restrictions and obligations
set forth in this Agreement, (c) the Purchaser Parties shall continue to be bound by all
restrictions

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and obligations set forth in this Agreement and (d) such transfer or assignment shall be effective
only if immediately following such transfer or assignment the further disposition of such
Registrable Securities by the Permitted Transferee is restricted under the Securities Act and other
applicable securities Law.

3. Restrictions on Beneficial Ownership.

     3.1 Standstill. During the period (such period, the “Standstill Term”) from and after the date
of this Agreement until the later of (A) the fifth (5th) anniversary of the expiration
or earlier termination of the “Term” (as such term is defined in the Aventis Collaboration
Agreement) and (B) the fifth (5th) anniversary of the expiration or earlier termination
of the “Term” (as such term is defined in the Sanofi License and Collaboration Agreement), neither
the Purchaser Parties nor any of their respective Affiliates (collectively, the “Standstill
Parties”) shall (and the Purchaser Parties shall cause their respective Affiliates not to),
except as expressly approved or invited in writing by the Company:

          (a) directly or indirectly, acquire beneficial ownership of Shares of Then Outstanding Common
Stock and/or Common Stock Equivalents, or make a tender, exchange or other offer to acquire Shares
of Then Outstanding Common Stock and/or Common Stock Equivalents, if after giving effect to such
acquisition, the Standstill Parties would beneficially own more than the Standstill Limit;
provided, however, that notwithstanding the provisions of this Section 3.1(a), if
the number of shares constituting Shares of Then Outstanding Common Stock is reduced or if the
aggregate ownership of the Standstill Parties is increased as a result of a repurchase of Shares of
Then Outstanding Common Stock, stock split, stock dividend or a recapitalization of the Company,
the Standstill Parties shall not be required to dispose of any of their holdings of Shares of Then
Outstanding Common Stock even though such action resulted in the Standstill Parties’ beneficial
ownership totaling more than the Standstill Limit;

          (b) directly or indirectly, seek to have called any meeting of the stockholders of the
Company, propose or nominate for election to the Company’s Board of Directors any person whose
nomination has not been approved by a majority of the Company’s Board of Directors or cause to be
voted in favor of such person for election to the Company’s Board of Directors any Shares of Then
Outstanding Common Stock;

          (c) directly or indirectly, encourage or support a tender, exchange or other offer or proposal
by any other Person or group (an “Offeror”) the consummation of which would result in a
Change of Control of the Company (an “Acquisition Proposal”);

          (d) directly or indirectly, solicit proxies or consents or become a participant in a
solicitation (as such terms are defined in Regulation 14A under the Exchange Act) in opposition to
the recommendation of a majority of the Company’s Board of Directors with respect to any matter, or
seek to advise or influence any Person, with respect to voting of any Shares of Then Outstanding
Common Stock of the Company;

          (e) deposit any Shares of Then Outstanding Common Stock in a voting trust or subject any
Shares of Then Outstanding Common Stock to any arrangement or agreement with respect to the voting
of such Shares of Then Outstanding Common Stock;

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          (f) act in concert with any Third Party to take any action in clauses (a) through (e) above,
or form, join or in any way participate in a “partnership, limited partnership, syndicate, or other
group” within the meaning of Section 13(d)(3) of the Exchange Act.

          (g) enter into discussions, negotiations, arrangements or agreements with any Person relating
to the foregoing actions referred to in (a) through (e) above; or

          (h) request or propose in writing to the Company’s Board of Directors, any member(s) thereof
or any officer of the Company that the Company amend, waive, or consider the amendment or waiver
of, any provisions set forth in this Section 3.1;

provided, however, that the mere voting in accordance with Section 5 hereof of any
voting securities of the Company held by the Purchaser Parties or their Affiliates shall not
constitute a violation of any of clauses (a) through (h) above.

     3.2 Amendment to Aventis Collaboration Agreement. Sections 3.1 and 6.2 of this Agreement shall,
effective as of the date of this Agreement, supersede and replace Sections 20.16 and 20.17 of the
Aventis Collaboration Agreement. The foregoing sentence shall not impair the rights of the Company
or constitute a waiver by the Company of any breach or default by Aventis, Sanofi US or any of
their Affiliates under Sections 20.16 and 20.17 of the Aventis Collaboration Agreement.
sanofi-aventis, the Investor, Sanofi US and the Company agree that Section 19.5 of the Aventis
Collaboration Agreement is hereby amended and restated in its entirety to read:

“Notwithstanding anything to the contrary herein, Regeneron will have the unilateral right
to terminate this Agreement in its entirety, upon written notice to Aventis, if any of the
Standstill Parties (as defined in the Investor Agreement, dated as of [                    ], 2007 (the
“Investor Agreement”), by and among sanofi-aventis, sanofi-aventis US LLC, Aventis,
sanofi-aventis Amérique du Nord and Regeneron) shall have breached Section 3.1 of the
Investor Agreement. For the avoidance of doubt, Regeneron shall not have the right to
terminate this Agreement as a result of a de minimis breach of Section 3.1(a) of the
Investor Agreement or an inadvertent breach of Section 3.1(g) of the Investor Agreement
arising from informal discussions covering general corporate or other business matters the
purpose of which is not intended to effectuate or lead to any of the actions referred to in
paragraphs (a) through (e) of Section 3.1 of the Investor Agreement.”

4. Restrictions on Dispositions.

     4.1 Lock-Up. From and after the date of this Agreement and until the earlier of (i) the fifth
(5th) anniversary of the date of this Agreement and (ii) the expiration, or earlier
valid termination by Aventis in its entirety pursuant to Section 19.3 or 19.4 thereof, of the
Sanofi License and Collaboration Agreement (the “Lock-Up Term”), without the prior approval
of a majority of the Company’s Board of Directors, the Purchaser Parties shall not, and shall cause
their respective Affiliates not to, Dispose of (x) any of the Purchased Shares or any shares of
Common Stock beneficially owned by any Standstill Party as of the date of this Agreement, together
with any shares of Common Stock issued in respect thereof as a result of any stock split,

18

 

stock dividend, share exchange, merger, consolidation or similar recapitalization, and (y) any
Common Stock issued as (or issuable upon the exercise of any warrant, right or other security that
is issued as) a dividend or other distribution with respect to, or in exchange or in replacement
of, the shares of Common Stock described in clause (x) of this sentence; provided,
however, that the foregoing shall not prohibit the Investor or Aventis from (A)
transferring Registrable Securities to a Permitted Transferee in accordance with and subject to the
terms of Section 2.12, or (B) Disposing of any Shares of Then Outstanding Common Stock as they may
hold from time to time in order to reduce the beneficial ownership of the Standstill Parties to
19.9% of the Shares of Then Outstanding Common Stock, provided that any such Disposition referred
to in this clause (B), whether occurring before or after the expiration of the Lock-Up Term, shall
be subject to the restrictions and requirements set forth in paragraphs (a), (b) and (c) of Section
4.2.

     4.2 Limitations Following Lock-Up Term. The Purchaser Parties agree that, except for any transfer of
Registrable Securities by the Investor or Aventis to a Permitted Transferee in accordance with and
subject to the terms of Sections 2.12 and 4.1, they shall not, and shall cause their respective
Affiliates not to, Dispose of any Shares of Then Outstanding Common Stock and/or Common Stock
Equivalents at any time after the expiration of the Lock-Up Term except (i) pursuant to a
registered underwritten public offering in accordance with Section 2, (ii) pursuant to Rule 144
under the Securities Act or (iii) pursuant to privately negotiated sales in transactions exempt
from the registration requirements under the Securities Act; provided, however,
that:

          (a) In any Underwritten Offering in accordance with Section 2, the Holders whose Registrable
Securities are included in such Underwritten Offering shall request that the underwriter for such
Underwritten Offering, and shall require that the underwriter for such Underwritten Offering shall
agree in writing to, use all reasonable efforts to make as broad a distribution as reasonably
practical and to prevent any Person, or Affiliates of such Person, from purchasing in such offering
Registrable Securities which would constitute, or result in such Person, together with such
Person’s Affiliates, having beneficial ownership of, five percent (5%) or more of the total shares
of Common Stock then outstanding.

          (b) The Purchaser Parties shall not (and shall cause their respective Affiliates not to),
without the prior approval of a majority of the Company’s Board of Directors, Dispose of any Shares
of Then Outstanding Common Stock and/or Common Stock Equivalents if such Disposition, together with
any Disposition(s) by any Standstill Parties during the immediately preceding three (3) months,
would exceed one million (1,000,000) Shares of Then Outstanding Common Stock of the Company
(assuming the full conversion into, and exercise and exchange for, shares of Common Stock of all
Common Stock Equivalents Disposed of by the Standstill Parties): provided, however,
that, without limitation of Section 4.2(a), the foregoing limitations in this Section 4.2(b) shall
not prohibit or limit any Disposition of Registrable Securities by a Holder as part of an
Underwritten Offering with respect to such Registrable Securities in accordance with Section 2
hereof. This Section 4.2(b) shall, effective as of the date of this Agreement, supersede and
replace Section 5.3(a) of the Aventis Stock Purchase Agreement. The foregoing sentence shall not
impair the rights of the Company or constitute a waiver by the Company of any breach or default by
Aventis or any of its Affiliates under such Section 5.3(a) with respect to events or circumstances
occurring or existing prior to the date of this Agreement.

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          (c) The Purchasing Parties shall not (and shall cause their respective Affiliates not to),
without the prior approval of a majority of the Company’s Board of Directors, Dispose of any Shares
of Then Outstanding Common Stock and/or Common Stock Equivalents to any Person if such Person is,
or such Disposition would (in the case of a Disposition pursuant to Rule 144 under the Securities
Act, to the knowledge of any Standstill Party) result in such Person becoming, after giving effect
to such Disposition, the beneficial owner of five percent (5%) or more of the total shares of
Common Stock then outstanding; provided, however, that, without limitation of
Section 4.2(a), the foregoing limitation in this Section 4.2(c) shall not prohibit or limit any
Disposition of Registrable Securities by a Holder as part of a registered offering with respect to
such Registrable Securities in accordance with Section 2 hereof.

     4.3 Certain Tender Offers. Notwithstanding any other provision of this Section 4, this Section 4 shall
not prohibit or restrict any Disposition of Shares of Then Outstanding Common Stock and/or Common
Stock Equivalents by the Standstill Parties into (a) a tender offer by a Third Party which is not
opposed by the Company’s Board of Directors (but only after the Company’s filing of a Schedule
14D-9, or any amendment thereto, with the SEC disclosing the recommendation of the Company’s Board
of Directors with respect to such tender offer) or (b) an issuer tender offer by the Company.

     4.4 Offering Lock-Up. The Holders shall, if requested by the Company and an underwriter of Common
Stock of the Company, agree not to Dispose of any Shares of Then Outstanding Common Stock and/or
Common Stock Equivalents for a specified period of time, such period of time not to exceed ninety
(90) days. Such agreement shall be in writing in a form satisfactory to the Company and the
underwriter(s) in such offering. The Company may impose stop transfer instructions with respect to
the Shares of Then Outstanding Common Stock and/or Common Stock Equivalents subject to the
foregoing restrictions until the end of the specified period of time. This Section 4.4 shall,
effective as of the date of this Agreement, supersede and replace Section 5.3(c) of the Aventis
Stock Purchase Agreement.

5. Voting Agreement.

     5.1 Voting of Securities. From and after the date of this Agreement, other than as permitted by
Section 5.2 with respect to Extraordinary Matters, in any vote or action by written consent of the
stockholders of the Company (including, without limitation, with respect to the election of
directors), the Purchaser Parties shall, and shall cause their respective Affiliates to, vote or
execute a written consent with respect to all voting securities of the Company as to which they are
entitled to vote or execute a written consent, in the sole discretion of the Purchaser Parties,
either (a) in accordance with the recommendation of the Company’s Board of Directors or (b) if such
Purchaser Party or Affiliate of a Purchaser Party has delivered written notice to the Company at
any time prior to the vote on any given matter or the effective time of an action to be taken by
written consent, setting forth its intent to vote pursuant to this Section 5.1(b), in the same
proportion as the votes cast by all other holders of all classes of voting securities of the
Company (as estimated by the inspector of election immediately prior to the closing of the polls
with respect to the vote on any given matter, subject to adjustment for the inspector of election’s
final tabulation of votes cast). In the event that a Purchaser Party or Affiliate of a Purchaser
Party does not deliver written notice to the
Company as provided in Section 5.1(b), such Person shall be deemed to have elected to vote all
voting securities of the Company as to which it is

20

 

entitled to vote as provided in Section 5.1(a).
In furtherance of this Section 5.1, the Purchaser Parties shall, and shall cause their respective
Affiliates to, if and when requested by the Company from time to time, promptly execute and deliver
to the Company an irrevocable proxy, substantially in the form of Exhibit A attached hereto, and
irrevocably appoint the Company or its designees, with full power of substitution, its attorney,
agent and proxy to vote (or cause to be voted) or to give consent with respect to, all of the
voting securities of the Company as to which such Purchaser Party or Affiliate of a Purchaser Party
is entitled to vote, in the manner and with respect to the matters set forth in this Section 5.1.
The Purchaser Parties acknowledge, and shall cause their Affiliates to acknowledge, that any such
proxy executed and delivered shall be coupled with an interest, shall constitute, among other
things, an inducement for the Company to enter into this Agreement, shall be irrevocable and
binding on any successor in interest of such Purchaser Party or Affiliate of such Purchaser Party,
as applicable, and shall not be terminated by operation of Law upon the occurrence of any event.
Such proxy shall operate to revoke and render void any prior proxy as to any voting securities of
the Company heretofore granted by such Purchaser Party or Affiliate of such Purchaser Party, as
applicable, to the extent it is inconsistent herewith. Such proxy shall terminate upon the earlier
of the expiration or termination of this Section 5.1.

     5.2 Certain Extraordinary Matters. The Purchaser Parties and their Affiliates may vote, or execute a
written consent with respect to, any or all of the voting securities of the Company as to which
they are entitled to vote or execute a written consent, as they may determine in their sole
discretion, with respect to the following matters (each such matter being an “Extraordinary
Matter”):

          (a) any transaction which would result in a Change of Control;

          (b) any vote of the Company’s stockholders with respect to any stock option or stock purchase
plan, or any material amendment thereto, or other equity compensation arrangement or material
amendment thereto, which has been approved by the Company’s Compensation Committee and taken as a
whole is not generally and materially consistent with the Company’s equity compensation historical
practices;

          (c) any other issuance of shares of Common Stock or Common Stock Equivalents voted upon by
stockholders of the Company that equals or exceeds ten percent (10%) of, or ten percent (10%) of
the voting power of, the Shares of Then Outstanding Common Stock, as of immediately prior to such
issuance; and

          (d) any liquidation or dissolution of the Company.

     5.3
Quorum. In furtherance of Section 5.1, the Purchaser Parties shall be, and shall cause each of
their Affiliates to be, present in person or represented by proxy at all meetings of stockholders
to the extent necessary so that all voting securities of the Company as to which they are entitled
to vote shall be counted as present for the purpose of determining the presence of a quorum at such
meeting.

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6. Termination of Certain Rights and Obligations.

     6.1 Termination of Registration Rights. Except for Section 2.10, which shall survive until the
expiration of any applicable statutes of limitation, Section 2 shall terminate automatically and
have no further force or effect upon the earliest to occur of:

          (a) the expiration of the Registration Rights Term;

          (b) the date on which the Common Stock ceases to be registered pursuant to Section 12 of the
Exchange Act; and

          (c) a liquidation or dissolution of the Company.

     6.2 Termination of Standstill Agreement. Provided that none of the Standstill Parties has violated
Section 3.1(c), (d) or (f) with respect to the Offeror referred to in this Section 6.2, Section 3
(except for Section 3.2, but only to the extent such Section 3.2 amends Section 19.5 of the Aventis
Collaboration Agreement) shall terminate and have no further force or effect, upon the earliest to
occur of:

          (a) the public announcement by an Offeror of an Acquisition Proposal for the Company;

          (b) the public announcement by the Company or any Offeror of any definitive agreement
providing for a Change of Control of the Company;

          (c) the expiration of the Standstill Term;

          (d) the date of any issuance by the Company to a Third Party of shares of Common Stock, which,
when combined with all other Shares of Then Outstanding Common Stock beneficially owned by such
Third Party immediately prior to such issuance, represents more than ten percent (10%) of the
voting power represented by all Shares of Then Outstanding Common Stock outstanding immediately
after giving effect to such issuance, if the Company does not enter into a standstill agreement
with such Third Party having material terms substantially similar (i) with respect to restrictions
on such Third Party, to the restrictions on the Standstill Parties set forth in Section 3.1 of this
Agreement and (ii) with respect to the termination of such restrictions, to the provisions of this
Section 6.2; provided, however, that any collaborative or other commercial
arrangements between the Company and such Third Party entered into connection with such issuance of
Common Stock to such Third Party shall be taken into consideration in determining whether the terms
of the standstill agreement entered into with such Third Party are materially similar to the terms
of Section 3.1 of this Agreement;

          (e) the date on which the Common Stock ceases to be registered pursuant to Section 12 of the
Exchange Act; and

          (f) a liquidation or dissolution of the Company;

provided, however, that if any of the transactions referred to in (a) or (b) above
terminates and the Company has not made a public announcement of its intent to solicit or engage in
a

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transaction (or has announced its decision to discontinue pursuing such a transaction) the
consummation of which would result in a Change of Control of the Company, then the restrictions
contained in Section 3 shall again be applicable, unless a Standstill Party has announced a
bona-fide Acquisition Proposal for the Company prior to such termination.

     6.3 Termination of Restrictions on Dispositions. Section 4 shall terminate and have no further force
or effect upon the earliest to occur of:

          (a) the consummation by an Offeror of a Change of Control of the Company;

          (b) a liquidation or dissolution of the Company; and

          (c) the date on which the Common Stock ceases to be registered pursuant to Section 12 of the
Exchange Act.

     6.4 Termination of Voting Agreement. Section 5 shall terminate and have no further force or effect
upon the earliest to occur of:

          (a) the consummation by an Offeror of a Change of Control of the Company;

          (b) a liquidation or dissolution of the Company;

          (c) the date on which the Standstill Parties beneficially own voting securities representing
less than five percent (5%) of the voting power of the Shares of Then Outstanding Common Stock; and

          (d) the date on which the Common Stock ceases to be registered pursuant to Section 12 of the
Exchange Act.

     6.5 Effect of Termination. No termination pursuant to any of Sections 6.1, 6.2 or 6.3 or 6.4 shall
relieve any of the parties (or the Permitted Transferee, if any) for liability for breach of or
default under any of their respective obligations or restrictions under any terminated provision of
this Agreement, which breach or default arose out of events or circumstances occurring or existing
prior to the date of such termination.

7. Miscellaneous.

     7.1 Governing Law; Submission to Jurisdiction. This Agreement shall be governed by and construed in
accordance with the Laws of the State of New York, without regard to the conflict of laws
principles thereof that would require the application of the Law of any other jurisdiction. The
parties irrevocably and unconditionally submit to the exclusive jurisdiction of the United States
District Court for the Southern District of New York solely and specifically for the purposes of
any action or proceeding arising out of or in connection with this Agreement.

     7.2 Waiver. Waiver by a party of a breach hereunder by another party shall not be construed as a
waiver of any subsequent breach of the same or any other provision. No delay or omission by a
party in exercising or availing itself of any right, power or privilege hereunder

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shall preclude the later exercise of any such right, power or privilege by such party. No waiver
shall be effective unless made in writing with specific reference to the relevant provision(s) of
this Agreement and signed by a duly authorized representative of the party granting the waiver.

     7.3 Notices. All notices, instructions and other communications hereunder or in connection herewith
shall be in writing, shall be sent to the address of the relevant party set forth on Exhibit
B attached hereto and shall be (a) delivered personally, (b) sent by registered or certified
mail, return receipt requested, postage prepaid, (c) sent via a reputable nationwide overnight
courier service or (d) sent by facsimile transmission, with a confirmation copy to be sent by
registered or certified mail, return receipt requested, postage prepaid. Any such notice,
instruction or communication shall be deemed to have been delivered upon receipt if delivered by
hand, three (3) Business Days after it is sent by registered or certified mail, return receipt
requested, postage prepaid, one (1) Business Day after it is sent via a reputable nationwide
overnight courier service or when transmitted with electronic confirmation of receipt, if
transmitted by facsimile (if such transmission is made during regular business hours of the
recipient on a Business Day; or otherwise, on the next Business Day following such transmission).
Any party may change its address by giving notice to the other parties in the manner provided
above.

     7.4 Entire Agreement. This Agreement and the Purchase Agreement contain the entire agreement among the
parties with respect to the subject matter hereof and thereof and supersede all prior and
contemporaneous arrangements or understandings, whether written or oral, with respect hereto and
thereto.

     7.5 Amendments. No provision in this Agreement shall be supplemented, deleted or amended except in a
writing executed by an authorized representative of each of the parties hereto.

     7.6 Headings; Nouns and Pronouns; Section References. Headings in this Agreement are for convenience
of reference only and shall not be considered in construing this Agreement. Whenever the context
may require, any pronouns used herein shall include the corresponding masculine, feminine or neuter
forms, and the singular form of names and pronouns shall include the plural and vice-versa.
References in this Agreement to a section or subsection shall be deemed to refer to a section or
subsection of this Agreement unless otherwise expressly stated.

     7.7 Severability. If, under applicable Laws, any provision hereof is invalid or unenforceable, or
otherwise directly or indirectly affects the validity of any other material provision(s) of this
Agreement in any jurisdiction (“Modified Clause”), then, it is mutually agreed that this
Agreement shall endure and that the Modified Clause shall be enforced in such jurisdiction to the
maximum extent permitted under applicable Laws in such jurisdiction; provided that the parties
shall consult and use all reasonable efforts to agree upon, and hereby consent to, any valid and
enforceable modification of this Agreement as may be necessary to avoid any unjust enrichment of
either party and to match the intent of this Agreement as closely as possible, including the
economic benefits and rights contemplated herein.

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     7.8 Assignment. Neither this Agreement nor any rights or duties of a party hereto may be assigned by
such party, in whole or in part, without (a) the prior written consent of the Company in the case
of any assignment by the Purchaser Parties, except as provided by Section 2.12 with respect to the
Investor’s or Aventis’ assignment to a Permitted Transferee; or (b) the prior written consent of
the Purchaser Parties in the case of an assignment by the Company.

     7.9 Successors and Assigns. This Agreement shall be binding upon and inure to the benefit of the
parties hereto and their respective successors and permitted assigns.

     7.10 Counterparts. This Agreement may be executed in counterparts, each of which shall be deemed an
original but which together shall constitute one and the same instrument.

     7.11 Third Party Beneficiaries. None of the provisions of this Agreement shall be for the benefit of or
enforceable by any Third Party. No Third Party shall obtain any right under any provision of this
Agreement or shall by reason of any such provision make any claim in respect of any debt, liability
or obligation (or otherwise) against any party hereto.

     7.12 No Strict Construction. This Agreement has been prepared jointly and will not be construed against
any party.

     7.13 Remedies. The rights, powers and remedies of the parties under this Agreement are cumulative and
not exclusive of any other right, power or remedy which such parties may have under any other
agreement or Law. No single or partial assertion or exercise of any right, power or remedy of a
party hereunder shall preclude any other or further assertion or exercise thereof.

     7.14 Specific Performance. The Purchaser Parties hereby acknowledge and agree that the rights of the
parties hereunder are special, unique and of extraordinary character, and that if any party refuses
or otherwise fails to act, or to cause its Affiliates to act, in accordance with the provisions of
this Agreement, such refusal or failure would result in irreparable injury to the Company or the
Purchaser Parties, as the case may be, the exact amount of which would be difficult to ascertain or
estimate and the remedies at law for which would not be reasonable or adequate compensation.
Accordingly, if any party refuses or otherwise fails to act, or to cause its Affiliates to act, in
accordance with the provisions of this Agreement, then, in addition to any other remedy which may
be available to any damaged party at law or in equity, such damaged party will be entitled to seek
specific performance and injunctive relief, without posting bond or other security, and without the
necessity of proving actual or threatened damages, which remedy such damaged party will be entitled
to seek in any court of competent jurisdiction.

     7.15 No Conflicting Agreements. Each of the Purchaser Parties hereby represents and warrants to the
Company that neither it nor any of its Affiliates is, as of the date of this Agreement, a party to,
and agrees that neither it nor any of its Affiliates shall, on or after the date of this Agreement,
enter into any agreement that conflicts with the rights granted to the Company in this Agreement.
The Company hereby represents and warrants to each Holder that it is not, as of the date of this
Agreement, a party to, and agrees that it shall not, on or after the date of this Agreement, enter
into, any agreement or approve any amendment to its Organizational Documents (as defined in the
Purchase Agreement) with respect to its securities that conflicts

25

 

with the rights granted to the Holders in this Agreement. The Company further represents and
warrants that the rights granted to the Holders hereunder do not in any way conflict with the
rights granted to any other holder of the Company’s securities under any other agreements.

(Signature Page Follows)

26

 

     IN WITNESS WHEREOF, the parties have executed and delivered this Agreement as of the date
first above written.

	 	 	 	 	 
	 	SANOFI-AVENTIS

 	 
	 	By:  	/s/ Jean-Michel Levy
 	 
	 	 	Name:  	Jean-Michel Levy 	 
	 	 	Title:  	Senior Vice President, Business Development 	 
	 

	 	 	 	 	 
	 	 	 
	 	By:  	       /s/ Laurence Debroux
 	 
	 	 	Name:  	Laurence Debroux 	 
	 	 	Title:  	Senior Vice President, Chief Financial Officer 	 
	 

	 	 	 	 	 
	 	SANOFI-AVENTIS US LLC

 	 
	 	By:  	/s/ Karen Linehan
 	 
	 	 	Name:  	Karen Linehan 	 
	 	 	Title:  	Authorized Representative 	 
	 

	 	 	 	 	 
	 	 	 
	 	By:  	               /s/ Robin White
 	 
	 	 	Name:  	Robin White 	 
	 	 	Title:  	Authorized Representative 	 
	 

	 	 	 	 	 
	 	AVENTIS PHARMACEUTICALS INC.

 	 
	 	By:  	/s/ Karen Linehan
 	 
	 	 	Name:  	Karen Linehan 	 
	 	 	Title:  	Authorized Representative 	 
	 

	 	 	 	 	 
	 	 	 
	 	By:  	             /s/ Robin White
 	 
	 	 	Name:  	Robin White 	 
	 	 	Title:  	Authorized Representative 	 
	 

 

 

	 	 	 	 	 
	 	SANOFI-AVENTIS AMÉRIQUE DU NORD

 	 
	 	By:  	/s/ Karen Linehan
 	 
	 	 	Name:  	Karen Linehan 	 
	 	 	Title:  	Authorized Representative 	 
	 

	 	 	 	 	 
	 	 	 
	 	By:  	            /s/ Jean-Luc Renard
 	 
	 	 	Name:  	Jean-Luc Renard 	 
	 	 	Title:  	Authorized Representative 	 
	 

	 	 	 	 	 
	 	REGENERON PHARMACEUTICALS, INC.

 	 
	 	By:  	/s/ Leonard Schleifer
 	 
	 	 	Name:  	Leonard Schleifer 	 
	 	 	Title:  	President & CEO 	 

 

 

EXHIBIT A — FORM OF IRREVOCABLE PROXY

     In order to secure the performance of the duties of the undersigned pursuant to Section 5.1 of
the Investor Agreement, dated as of [___], 2007 (the “Agreement”), by and among
sanofi-aventis, sanofi-aventis US LLC, Aventis Pharmaceuticals Inc., sanofi-aventis Amérique du
Nord and Regeneron Pharmaceuticals, Inc. (the “Company”), the undersigned hereby
irrevocably appoints [___] and [___], and each of them, the attorneys, agents and
proxies, with full power of substitution in each of them, for the undersigned, and in the name,
place and stead of the undersigned, to vote (or cause to be voted) or, if applicable, to give
consent, in such manners as each such attorney, agent and proxy or his substitute shall in his sole
discretion deem proper to record such vote (or consent) in the manners, and with respect to such
matters as set forth in Section 5.1 of the Agreement (but in any case, in accordance with any
written instruction from the undersigned, properly delivered under Section 5.1 of the Agreement, to
vote or give consent as contemplated by Section 5.1(b) of the Agreement) with respect to all voting
securities (whether taking the form of shares of Common Stock, par value $0.001 per share, or other
voting securities of the Company), which the undersigned is or may be entitled to vote at any
meeting of the Company held after the date hereof, whether annual or special and whether or not an
adjourned meeting or, if applicable, to give written consent with respect thereto. This proxy is
coupled with an interest, shall be irrevocable and binding on any successor in interest of the
undersigned and shall not be terminated by operation of law upon the occurrence of any event. This
proxy shall operate to revoke and render void any prior proxy as to voting securities heretofore
granted by the undersigned which is inconsistent herewith. This proxy shall terminate upon the
earlier of the expiration or termination of the voting agreement set forth in Section 5.1 of the
Agreement.

	 	 	 	 	 	 	 	 
	 	 	[	 
	]	 	 
	 	 	 By: 	 	 
	 	 	 
	 	 
	 	 	 Name:	 	 	 
	 	 	 Title:	 	 	 

 

 

EXHIBIT B

NOTICES

	 	 	 
	(a)

	 	If to sanofi-aventis, the Investor, Aventis or Sanofi US:
	 
	 	 
	 

	 	sanofi-aventis
	 

	 	174, avenue de France
	 

	 	75013 Paris
	 

	 	France
	 

	 	Attention: Chief Financial Officer
	 
	 	 
	 

	 	with a copy to:
	 
	 	 
	 

	 	sanofi-aventis
	 

	 	174, avenue de France
	 

	 	75013 Paris
	 

	 	France
	 

	 	Attention: General Counsel
	 
	 	 
	(b)

	 	If to the Company:
	 
	 	 
	 

	 	Regeneron Pharmaceuticals, Inc.
	 

	 	777 Old Saw Mill River Road
	 

	 	Tarrytown, New York 10591
	 

	 	U.S.A.
	 

	 	Attention: President
	 

	 	Copy: General Counsel
	 
	 	 
	 

	 	with a copy to:
	 
	 	 
	 

	 	Skadden, Arps, Slate, Meagher & Flom LLP
	 

	 	One Beacon Street, 31st Floor
	 

	 	Boston, MA 02108
	 

	 	Attention: Kent A. Coit

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