5,500,000 SHARES REGENERON PHARMACEUTICALS, INC. COMMON STOCK, $0.001 PAR VALUE PER SHARE UNDERWRITING AGREEMENT

Exhibit 1.1

5,500,000 SHARES

REGENERON PHARMACEUTICALS, INC.

COMMON STOCK, $0.001 PAR VALUE PER SHARE

October 7, 2010

Citigroup Global Markets Inc.
000 Xxxxxxxxx Xxxxxx
Xxx Xxxx, Xxx Xxxx 00000

Ladies and Gentlemen:

REGENERON PHARMACEUTICALS, INC., a New York corporation (the “Company”), proposes to issue and sell to you (the “Underwriter”) the number of shares of its common stock, $0.001 par value per share, set forth in Schedule I hereto (the “Firm Shares”). The Company also proposes to issue and sell to the Underwriter not more than the number of additional shares of its common stock, $0.001 par value per share, set forth in Schedule I hereto (the “Additional Shares”) if and to the extent that you, shall have determined to exercise the right to purchase such shares of common stock granted to the Underwriter in Section 2 hereof. The Firm Shares and the Additional Shares are hereinafter collectively referred to as the “Shares.” The shares of common stock, $0.001 par value per share, of the Company to be outstanding after giving effect to the sales contemplated hereby are hereinafter referred to as the “Common Stock.”

The Company has filed with the Securities and Exchange Commission (the “Commission”) a registration statement, including a prospectus on Form S-3 (the file number of which is set forth in Schedule I hereto), relating to the securities (the “Shelf Securities”), including the Shares, to be issued from time to time by the Company. The registration statement as amended to the date of this Agreement, including the information (if any) deemed to be part of the registration statement at the time of effectiveness pursuant to Rule 430A or Rule 430B under the Securities Act of 1933, as amended (the “Securities Act”), is hereinafter referred to as the “Registration Statement,” and the related prospectus covering the Shelf Securities dated October 6, 2010 in the form first used to confirm sales of the Shares (or in the form first made available to the Underwriter by the Company to meet requests of purchasers pursuant to Rule 173 under the Securities Act) is hereinafter referred to as the “Basic Prospectus.” The Basic Prospectus, as supplemented by the prospectus supplement specifically relating to the Shares in the form first used to confirm sales of the Shares (or in the form first made available to the Underwriter by the Company to meet requests of purchasers pursuant to Rule 173 under the Securities Act) is hereinafter referred to as the “Prospectus,” and the term “preliminary prospectus” means any preliminary form of the Prospectus. For purposes of this Agreement, “free writing prospectus” has the meaning set forth in Rule 405 under the Securities Act, “Time of Sale Prospectus” means the Basic Prospectus and the preliminary prospectus together with the final term sheet identified in Schedule I hereto, and “broadly available road show” means a “bona fide electronic road show” as defined in Rule 433(h)(5) under the Securities Act that has been made available without restriction to any person. As used herein, the terms “Registration Statement,” “Basic Prospectus,” “preliminary prospectus,” “Time of Sale Prospectus” and “Prospectus” shall include the documents, if any, incorporated by reference therein. The terms “supplement,” “amendment,” and “amend” as used herein with respect to the Registration Statement, the Basic Prospectus, the Time of Sale Prospectus, any preliminary prospectus or free writing prospectus, if any, shall include all documents subsequently filed by the Company with the Commission pursuant to the Securities Exchange Act of 1934, as amended (the “Exchange Act”), that are deemed to be incorporated by reference therein.

1. Representations and Warranties. The Company represents and warrants to and agrees with the Underwriter that:

(a) Registration Statement Effective; Eligibility. The Registration Statement has become effective; no stop order suspending the effectiveness of the Registration Statement is in effect, and no proceedings for such purpose are pending before or threatened by the Commission. If the Registration Statement is an automatic shelf registration statement as defined in Rule 405 under the Securities Act, the Company is a well-known seasoned issuer (as defined in Rule 405 under the Securities Act) eligible to use the Registration Statement as an automatic shelf registration statement and the Company has not received notice that the Commission objects to the use of the Registration Statement as an automatic shelf registration statement.

(b) Compliance with Form; Disclosure. (i) Each document, if any, filed or to be filed pursuant to the Exchange Act and incorporated by reference in the Time of Sale Prospectus or the Prospectus complied or will comply when so filed in all material respects with the Exchange Act and the applicable rules and regulations of the Commission thereunder, (ii) each part of the Registration Statement, when such part became effective, did not contain, and each such part, as amended or supplemented, if applicable, will not contain any untrue statement of a material fact or omit to state a material fact required to be stated therein or necessary to make the statements therein not misleading, (iii) the Registration Statement as of the date hereof does not contain any untrue statement of a material fact or omit to state a material fact required to be stated therein or necessary to make the statements therein not misleading, (iv) the Registration Statement, the Time of Sale Prospectus and the Prospectus comply, and as amended or supplemented, if applicable, will comply in all material respects with the Securities Act and the applicable rules and regulations of the Commission thereunder, (v) the Time of Sale Prospectus does not, and at the time of each sale of the Shares in connection with the offering when the Prospectus is not yet available to prospective purchasers and at the Closing Date (as defined in Section 4), the Time of Sale Prospectus, as then amended or supplemented by the Company, if applicable, will not, contain any untrue statement of a material fact or omit to state a material fact necessary to make the statements therein, in the light of the circumstances under which they were made, not misleading, (vi) each broadly available road show, if any, when considered together with the Time of Sale Prospectus, does not contain any untrue statement of a material fact or omit to state a material fact necessary to make the statements therein, in the light of the circumstances under which they were made, not misleading and (vii) the Prospectus does not contain and, as amended or supplemented, if applicable, will not contain any untrue statement of a material fact or omit to state a material fact necessary to make the statements therein, in the light of the circumstances under which they were made, not misleading, except that the representations and warranties set forth in this paragraph do not apply to statements or omissions in the Registration Statement, the Time of Sale Prospectus or the Prospectus based upon information relating to the Underwriter furnished to the Company in writing by such Underwriter expressly for use therein.

(c) Free Writing Prospectuses. The Company is not an “ineligible issuer” pursuant to Rules 164, 405 and 433 under the Securities Act in connection with the offering. Any free writing prospectus that the Company is required to file pursuant to Rule 433(d) under the Securities Act has been, or will be, filed with the Commission in accordance with the requirements of the Securities Act and the applicable rules and regulations of the Commission thereunder. Each free writing prospectus that the Company has filed, or is required to file, pursuant to Rule 433(d) under the Securities Act or that was prepared by or behalf of or used or referred to by the Company complies or will comply in all material respects with the requirements of the Securities Act and the applicable rules and regulations of the Commission thereunder. Except for the free writing prospectuses, if any, identified in Schedule I hereto forming part of the Time of Sale Prospectus, and electronic road shows, if any, each furnished to you before first use, the Company has not prepared, used or referred to, and will not, without your prior consent, prepare, use or refer to, any free writing prospectus.

(d) Incorporated Documents. The documents incorporated or deemed to be incorporated by reference in the Registration Statement, the Time of Sale Prospectus and the Prospectus, at the time they were or hereafter are filed with the Commission (or, in the case of the Time of Sale Prospectus, first used, and, in the case of the Prospectus, for so long as a prospectus is required to be delivered in connection with the sale of the Shares), complied and will comply in all material respects with the requirements of the 1934 Act and the rules and regulations of the Commission thereunder (the “1934 Act Regulations”) and, when read together with the other information in (i) the Time of Sale Prospectus, at the time the Registration Statement became effective and at the time of each sale of Shares in the offering when the Prospectus is not yet available to prospective purchasers, and (ii) the Prospectus at the time the Prospectus was issued and at the Closing Time, in each case, did not and will not contain an untrue statement of a material fact or omit to state a material fact required to be stated therein or necessary to make the statements therein not misleading.

(e) Independent Accountants. The accountants who certified the financial statements and supporting schedules included in the Registration Statement are independent public accountants as required by the 1933 Act and the rules and regulations of the Commission under the Securities Act (the “1933 Act Regulations”).

(f) Financial Statements. The financial statements included in the Registration Statement, the Time of Sale Prospectus and the Prospectus, together with the related schedules and notes, present fairly the respective financial positions of the Company at the dates indicated and the statement of operations, stockholders’ equity and cash flows of the Company for the periods specified; said financial statements have been prepared in conformity with generally accepted accounting principles (“GAAP”) applied on a consistent basis throughout the periods involved. The supporting schedules, if any, included in the Registration Statement present fairly in accordance with GAAP the information required to be stated therein. The selected financial data included in the Prospectus present fairly the information shown therein and have been compiled on a basis consistent with that of the audited financial statements included in the Registration Statement. All disclosures in the Registration Statement, the Time of Sale Prospectus or the Prospectus regarding “non-GAAP financial measures” (as such term is defined by the rules and regulations of the Commission) comply with Regulation G under the Exchange Act and Item 10(e) of Regulation S-K of the 1933 Act Regulations, to the extent applicable.

(g) No Material Adverse Change in Business. Since the respective dates as of which information is given in the Registration Statement and the Prospectus, except as otherwise stated therein, (A) there has been no material adverse change or a development known to the Company involving a prospective material adverse change, in the condition, financial or otherwise, or in the earnings or business affairs of the Company, whether or not arising in the ordinary course of business (a “Material Adverse Effect”), (B) there have been no transactions entered into by the Company, other than those in the ordinary course of business, which are material with respect to the Company, and (C) there has been no dividend or distribution of any kind declared, paid or made by the Company on any class of its capital stock.

(h) Good Standing of the Company. The Company has been duly organized and is validly existing as a corporation in good standing under the laws of the State of New York and has corporate power and authority to own, lease and operate its properties and to conduct its business as described in the Time of Sale Prospectus and the Prospectus and to enter into and perform its obligations under this Agreement; and the Company is duly qualified as a foreign corporation to transact business and is in good standing in each jurisdiction in which such qualification is required, whether by reason of ownership or leasing of property or the conduct of business, except where the failure so to qualify or be in good standing would not result in a Material Adverse Effect.

(i) Subsidiaries. Other than Regeneron UK Limited, which has no operations, employees, assets requiring disclosure in the Company’s financial statements, or obligations or liabilities (contingent or otherwise), the Company has no subsidiaries.

(j) Capitalization. The authorized, issued and outstanding capital stock of the Company is as set forth in the condensed balance sheet at June 30, 2010 of the Company included in the Time of Sale Prospectus and the Prospectus (except for subsequent issuances, if any, pursuant to this Agreement, pursuant to reservations, agreements or employee benefit plans referred to in the Time of Sale Prospectus and the Prospectus or pursuant to the exercise of convertible securities or options referred to in the Time of Sale Prospectus and the Prospectus). The shares of issued and outstanding capital stock of the Company have been duly authorized and validly issued and are fully paid and non-assessable; none of the outstanding shares of capital stock of the Company was issued in violation of the preemptive or other similar rights of any securityholder of the Company.

(k) Authorization of Agreement. This Agreement has been duly authorized, executed and delivered by the Company.

(l) Authorization and Description of Securities. The Shares to be purchased by the Underwriter from the Company have been duly authorized for issuance and sale to the Underwriter pursuant to this Agreement and, when issued and delivered by the Company pursuant to this Agreement against payment of the consideration set forth herein, will be validly issued, fully paid and non-assessable; the Common Stock conforms to all statements relating thereto contained in the Time of Sale Prospectus and the Prospectus and such description conforms to the rights set forth in the instruments defining the same; and no holder of the Shares will be subject to personal liability by reason of being such a holder; and the issuance of the Shares are not subject to the preemptive or other similar rights of any securityholder of the Company.

(m) Absence of Defaults and Conflicts. The Company is not in violation of its charter or by-laws or in default in the performance or observance of any obligation, agreement, covenant or condition contained in any contract, indenture, mortgage, deed of trust, loan or credit agreement, note, lease or other agreement or instrument to which the Company is a party or by which it may be bound, or to which any of the property or assets of the Company is subject (collectively, “Agreements and Instruments”) except for such defaults that would not result in a Material Adverse Effect; and the execution, delivery and performance of this Agreement by the Company and the consummation by the Company of the transactions contemplated herein and in the Prospectus (including the issuance and sale of the Shares and the use of the proceeds from the sale of the Shares as described in the Time of Sale Prospectus and the Prospectus under the caption “Use of Proceeds”) and compliance by the Company with its obligations hereunder have been duly authorized by all necessary corporate action and do not and will not, whether with or without the giving of notice or passage of time or both, conflict with or constitute a breach of, or default or Repayment Event (as defined below) under, or result in the creation or imposition of any lien, charge or encumbrance upon any property or assets of the Company pursuant to, the Agreements and Instruments (except for such conflicts, breaches or defaults or liens, charges or encumbrances that would not result in a Material Adverse Effect), nor will such action result in any violation of the provisions of the charter or by-laws of the Company, or any applicable law, statute, rule, regulation, judgment, order, writ or decree of any government, government instrumentality or court, domestic or foreign, having jurisdiction over the Company or any of its assets, properties or operations except for any such violation that could not be expected to result in a Material Adverse Effect. As used herein, a “Repayment Event” means any event or condition which gives the holder of any note, debenture or other evidence of indebtedness (or any person acting on such holder’s behalf) the right to require the repurchase, redemption or repayment of all or a portion of such indebtedness by the Company.

(n) Absence of Labor Dispute. No labor dispute with the employees of the Company exists or, to the knowledge of the Company, is imminent, and the Company is not aware of any existing or imminent labor disturbance by the employees of any of its principal suppliers, manufacturers, customers or contractors, which, in any case, may reasonably be expected to result in a Material Adverse Effect.

(o) Absence of Proceedings. Other than as disclosed in the Registration Statement, the Time of Sale Prospectus and the Prospectus, there is no action, suit, proceeding, inquiry or investigation before or brought by any court or governmental agency or body, domestic or foreign, now pending, or, to the knowledge of the Company, threatened, against or affecting the Company, which is required to be disclosed in the Registration Statement, the Time of Sale Prospectus and the Prospectus, or which might reasonably be expected to result in a Material Adverse Effect, or which might reasonably be expected to materially and adversely affect the properties or assets thereof or the consummation of the transactions contemplated in this Agreement or the performance by the Company of its obligations hereunder; the aggregate of all pending legal or governmental proceedings to which the Company is a party or of which any of its property or assets is the subject which are not described in the Registration Statement, the Time of Sale Prospectus and the Prospectus including ordinary routine litigation incidental to the business, could not reasonably be expected to result in a Material Adverse Effect.

(p) Foreign Corrupt Practices Act. Neither the Company nor any of its affiliates, nor any director, officer, or employee, nor any agent or representative of the Company or of any of its affiliates, in each case, to the Company’s knowledge, has taken any action in furtherance of an offer, payment, promise to pay, or authorization or approval of the payment or giving of money, property, gifts or anything else of value, directly or indirectly, to any “government official” (including any officer or employee of a government or government-owned or controlled entity or of a public international organization, or any person acting in an official capacity for or on behalf of any of the foregoing, or any political party or party official or candidate for political office) to influence official action or secure an improper advantage; and, to the Company’s knowledge, the Company and its affiliates have conducted their businesses in compliance with applicable anti-corruption laws.

(q) Anti-Money Laundering Laws. The operations of the Company are and have been conducted at all times in material compliance with all applicable financial recordkeeping and reporting requirements, including those of the Bank Secrecy Act, as amended by Title III of the Uniting and Strengthening America by Providing Appropriate Tools Required to Intercept and Obstruct Terrorism Act of 2001 (USA PATRIOT Act), and the applicable anti-money laundering statutes of jurisdictions where the Company conducts business, the rules and regulations thereunder and any related or similar rules, regulations or guidelines, issued, administered or enforced by any governmental agency (collectively, the “Anti-Money Laundering Laws”), and no action, suit or proceeding by or before any court or governmental agency, authority or body or any arbitrator involving the Company with respect to the Anti-Money Laundering Laws is pending or, to the knowledge of the Company, threatened.

(r) Foreign Asset Control Compliance. (i) The Company represents that neither the Company nor, to the Company’s knowledge, any director, officer, employee, agent, affiliate or representative of the Company, is an individual or entity (each, a “Person”) that is, or is owned or controlled by a Person that is:

(A) the subject of any sanctions administered or enforced by the U.S. Department of Treasury’s Office of Foreign Assets Control (“OFAC”), the United Nations Security Council (“UNSC”), the European Union (“EU”), Her Majesty’s Treasury (“HMT”), or other relevant sanctions authority (collectively, “Sanctions”), or

(B) located, organized or resident in a country or territory that is the subject of Sanctions (including, without limitation, Burma/Myanmar, Cuba, Iran, North Korea, Sudan and Syria).

(ii) The Company represents that it will use the proceeds from the sale of the Shares as described in the Time of Sale Prospectus and the Prospectus under the caption “Use of Proceeds.”

(iii) The Company represents that it is not knowingly engaged in any dealings or transactions with any Person, or in any country or territory, that at the time of the dealing or transaction is or was the subject of Sanctions.

(s) Accuracy of Exhibits. There are no contracts or documents which are required to be described in the Registration Statement, the Time of Sale Prospectus and the Prospectus or the documents incorporated by reference therein or to be filed as exhibits thereto which have not been so described and filed as required.

(t) Possession of Intellectual Property. The Company owns or possesses, or will use its best efforts to acquire on reasonable terms, adequate patents, patent rights, licenses, inventions, copyrights, know-how (including trade secrets and other unpatented and/or unpatentable proprietary or confidential information, systems or procedures), trademarks, service marks, trade names or other intellectual property (collectively, “Intellectual Property”) necessary to carry on the business now operated by them. Except as disclosed in the Time of Sale Prospectus and the Prospectus, (i) there is no litigation or other proceeding pending or, to the Company’s knowledge, threatened and no claims are presently being asserted by any third party challenging or questioning the ownership, validity, enforceability of the Company’s right to use or own any Intellectual Property or asserting that the use of any Intellectual Property by the Company or the operation of the business of the Company infringes upon or misappropriates the Intellectual Property of any third party, other than infringements which would not be reasonably likely to have a Material Adverse Effect, and (ii) the Company is not otherwise aware of any infringement of or conflict with asserted rights of others with respect to any Intellectual Property or of any facts or circumstances which would render any Intellectual Property invalid or inadequate to protect the interest of the Company therein, and which infringement or conflict (if the subject of any unfavorable decision, ruling or finding) or invalidity or inadequacy, singly or in the aggregate, would result in a Material Adverse Effect.

(u) Absence of Further Requirements. No filing with, or authorization, approval, consent, license, order, registration, qualification or decree of, any court or governmental authority or agency is necessary or required for the performance by the Company of its obligations hereunder, in connection with the offering, issuance or sale of the Shares hereunder or the consummation of the transactions contemplated by this Agreement, except such as have been already obtained or as may be required under the Securities Act or state securities laws.

(v) Possession of Licenses and Permits. The Company possesses such permits, licenses, approvals, consents and other authorizations (collectively, “Governmental Licenses”) issued by the appropriate federal, state, local or foreign regulatory agencies or bodies necessary to conduct the business now operated by them; the Company is in compliance with the terms and conditions of all such Governmental Licenses, except where the failure so to comply would not, singly or in the aggregate, have a Material Adverse Effect; all of the Governmental Licenses are valid and in full force and effect, except when the invalidity of such Governmental Licenses or the failure of such Governmental Licenses to be in full force and effect would not have a Material Adverse Effect; and the Company has not received any notice of proceedings relating to the revocation or modification of any such Governmental Licenses which, singly or in the aggregate, if the subject of an unfavorable decision, ruling or finding, would result in a Material Adverse Effect.

(w) Title to Property. The Company has good and marketable title to all real property owned by the Company and good title to all other properties owned by it, in each case, free and clear of all mortgages, pledges, liens, security interests, claims, restrictions or encumbrances of any kind except such as (a) are described in the Time of Sale Prospectus and the Prospectus or (b) do not, singly or in the aggregate, materially affect the value of such property and do not interfere with the use made and proposed to be made of such property by the Company; and all of the leases and subleases material to the business of the Company considered as one enterprise, and under which the Company holds properties described in the Time of Sale Prospectus and the Prospectus, are in full force and effect, and the Company has no notice of any material claim of any sort that has been asserted by anyone adverse to the rights of the Company any of the leases or subleases mentioned above, or affecting or questioning the rights of the Company to the continued possession of the leased or subleased premises under any such lease or sublease.

(x) Environmental Laws. Except as described in the Registration Statement, the Time of Sale Prospectus and the Prospectus and except as would not, singly or in the aggregate, result in a Material Adverse Effect, (A) the Company is not in violation of any federal, state, local or foreign statute, law, rule, regulation, ordinance, code, policy or rule of common law or any judicial or administrative interpretation thereof, including any judicial or administrative order, consent, decree or judgment, relating to pollution or protection of human health, the environment (including, without limitation, ambient air, surface water, groundwater, land surface or subsurface strata) or wildlife, including, without limitation, laws and regulations relating to the release or threatened release of chemicals, pollutants, contaminants, wastes, toxic substances, hazardous substances, petroleum or petroleum products (collectively, “Hazardous Materials”) or to the manufacture, processing, distribution, use, treatment, storage, disposal, transport or handling of Hazardous Materials (collectively, “Environmental Laws”), (B) the Company has all permits, authorizations and approvals required under any applicable Environmental Laws and are each in compliance with their requirements, (C) there are no pending or threatened administrative, regulatory or judicial actions, suits, demands, demand letters, claims, liens, notices of noncompliance or violation, investigation or proceedings relating to any Environmental Law against the Company and (D) there are no events or circumstances that might reasonably be expected to form the basis of an order for clean-up or remediation, or an action, suit or proceeding by any private party or governmental body.

(y) Investment Company Act. The Company is not, and upon the issuance and sale of the Shares as herein contemplated and the application of the net proceeds therefrom as described in the Time of Sale Prospectus and the Prospectus will not be, an “investment company” or an entity controlled by an “investment company” as such terms are defined in the Investment Company Act of 1940, as amended (the “1940 Act”).

(z) FDA and PTO Proceedings. To the Company’s knowledge, except as disclosed in the Time of Sale Prospectus and the Prospectus, there are no rulemaking or similar proceedings before the U.S. Food and Drug Administration, the U.S. Patent and Trademark Office or the European Patent Office which affect or involve the Company or any of the processes or products which the Time of Sale Prospectus and the Prospectus disclose the Company to have developed, to be developing or to propose to develop or use or propose to use which, if the subject of an action unfavorable to the Company, would have a Material Adverse Effect.

2. Agreements to Sell and Purchase. The Company hereby agrees to sell to the Underwriter, and the Underwriter, upon the basis of the representations and warranties herein contained, but subject to the conditions hereinafter stated, agrees to purchase from the Company the number of Shares set forth in Schedule II hereto opposite its name at the purchase price set forth in Schedule I hereto (the “Purchase Price”).

On the basis of the representations and warranties contained in this Agreement, and subject to its terms and conditions, the Company agrees to sell to the Underwriter the Additional Shares, and the Underwriter shall have the right to purchase up to the number of Additional Shares set forth in Schedule I hereto at the Purchase Price, provided, however, that the amount paid by the Underwriter for any Additional Shares shall be reduced by an amount per share equal to any dividends declared by the Company and payable on the Firm Shares but not payable on such Additional Shares. You may exercise this right on behalf of the Underwriter in whole or from time to time in part by giving written notice not later than 30 days after the date of the Prospectus. Any exercise notice shall specify the number of Additional Shares to be purchased by the Underwriter and the date on which such shares are to be purchased (an “Option Closing Date”). Each Option Closing Date must be at least one business day after the written notice is given and may not be earlier than the closing date for the Firm Shares nor later than ten business days after the date of such notice. Additional Shares may be purchased as provided in Section 4 hereof solely for the purpose of covering over-allotments made in connection with the offering of the Firm Shares.

3. Public Offering. The Company is advised by you that the Underwriter proposes to make a public offering of the Shares as soon after the Registration Statement and this Agreement have become effective as in your judgment is advisable. The Company is further advised by you that the Shares are to be offered to the public upon the terms set forth in the Prospectus.

4. Payment and Delivery. Payment for the Shares shall be made to the Company in Federal or other funds immediately available in New York City on the closing date and time set forth in Schedule I hereto, or at such other time on the same or such other date, not later than the fifth business day thereafter, as may be designated in writing by you. The time and date of such payment are hereinafter referred to as the “Closing Date.”

Payment for any Additional Shares shall be made to the Company in Federal or other funds immediately available in New York City on the date specified in the corresponding notice described in Section 2 or at such other time on the same or on such other date, in any event not later than the tenth business day thereafter, as may be designated in writing by you.

The Firm Shares and the Additional Shares shall be registered in such names and in such denominations as you shall request in writing not later than one full business day prior to the Closing Date or applicable Option Closing Date, as the case may be, for the account of the Underwriter, with any transfer taxes payable in connection with the transfer of the Shares to the Underwriter duly paid, against payment of the Purchase Price therefor.

5. Conditions to the Underwriter’s Obligations. The obligations of the Underwriter are subject to the following conditions:

(a) Subsequent to the execution and delivery of this Agreement and prior to the Closing Date:

(i) there shall not have occurred any downgrading, nor shall any notice have been given of any intended or potential downgrading or of any review for a possible change that does not indicate the direction of the possible change, in the rating accorded any of the securities of the Company by any “nationally recognized statistical rating organization,” as such term is defined for purposes of Rule 436(g)(2) under the Securities Act; and

(ii) there shall not have occurred any change, or any development involving a prospective change, in the condition, financial or otherwise, or in the earnings, business or operations of the Company from that set forth in the Time of Sale Prospectus as of the date of this Agreement that, in your judgment, is material and adverse and that makes it, in your judgment, impracticable to market the Shares on the terms and in the manner contemplated in the Time of Sale Prospectus.

(b) The Underwriter shall have received on the Closing Date a certificate, dated the Closing Date and signed by an executive officer of the Company, to the effect set forth in Section 5(a)(i) above and to the effect that the representations and warranties of the Company contained in this Agreement are true and correct as of the Closing Date and that the Company has complied with all of the agreements and satisfied all of the conditions on its part to be performed or satisfied hereunder on or before the Closing Date.

The officer signing and delivering such certificate may rely upon the best of his or her knowledge as to proceedings threatened.

(c) The Underwriter shall have received on the Closing Date (i) the favorable opinion of Skadden, Arps, Slate, Xxxxxxx & Xxxx LLP, outside counsel for the Company, dated the Closing Date, (ii) the favorable opinion of Xxxxxx X. Xxxxxxxx, Esq., General Counsel of the Company, dated the Closing Date, and (iii) the favorable opinion of Xxxxxx Xxxxx, in-house intellectual property counsel for the Company, dated the Closing Date, in each case, in form and substance satisfactory to the Underwriter. The opinions of counsel for the Company referred to in this Section 5(c) shall be rendered to the Underwriter at the request of the Company and shall so state therein.

(d) The Underwriter shall have received on the Closing Date an opinion of Ropes & Xxxx LLP, counsel for the Underwriter, dated the Closing Date, in form and substance satisfactory to the Underwriter.

(e) The Underwriter shall have received on the Closing Date a letter dated the date of the Closing Date, in form and substance satisfactory to the Underwriter, from PricewaterhouseCoopers LLP, independent public accountants, containing statements and information of the type ordinarily included in accountants’ “comfort letters” to underwriters with respect to the financial statements and certain financial information contained in the Registration Statement, the Time of Sale Prospectus and the Prospectus; provided that the letter delivered on the Closing Date shall use a “cut-off date” not earlier than the date hereof.

6. Covenants of the Company. The Company covenants with the Underwriter as follows:

(a) To furnish to you, without charge, a signed copy of the Registration Statement (including exhibits thereto and documents incorporated by reference therein) and to deliver to you during the period mentioned in Section 6(e) or 6(f) below, as many copies of the Time of Sale Prospectus, the Prospectus, any documents incorporated by reference therein and any supplements and amendments thereto or to the Registration Statement as you may reasonably request.

(b) Before amending or supplementing the Registration Statement, the Time of Sale Prospectus or the Prospectus, to furnish to you a copy of each such proposed amendment or supplement and not to file any such proposed amendment or supplement to which you reasonably object.

(c) To furnish to you a copy of each proposed free writing prospectus to be prepared by or on behalf of, used by, or referred to by the Company and not to use or refer to any proposed free writing prospectus to which you reasonably object.

(d) Not to take any action that would result in the Underwriter or the Company being required to file with the Commission pursuant to Rule 433(d) under the Securities Act a free writing prospectus prepared by or on behalf of the Underwriter that the Underwriter otherwise would not have been required to file thereunder.

(e) If the Time of Sale Prospectus is being used to solicit offers to buy the Shares at a time when the Prospectus is not yet available to prospective purchasers and any event shall occur or condition exist as a result of which it is necessary to amend or supplement the Time of Sale Prospectus in order to make the statements therein, in the light of the circumstances, not misleading, or if any event shall occur or condition exist as a result of which the Time of Sale Prospectus conflicts with the information contained in the Registration Statement then on file, or if, in the opinion of counsel for the Underwriter, it is necessary to amend or supplement the Time of Sale Prospectus to comply with applicable law, forthwith to prepare, file with the Commission and furnish, at its own expense, to the Underwriter and to any dealer upon request, either amendments or supplements to the Time of Sale Prospectus so that the statements in the Time of Sale Prospectus as so amended or supplemented will not, in the light of the circumstances when delivered to a prospective purchaser, be misleading or so that the Time of Sale Prospectus, as amended or supplemented, will no longer conflict with the Registration Statement, or so that the Time of Sale Prospectus, as amended or supplemented, will comply with applicable law.

(f) If, during such period after the first date of the public offering of the Shares as in the opinion of counsel for the Underwriter the Prospectus (or in lieu thereof the notice referred to in Rule 173(a) under the Securities Act) is required by law to be delivered in connection with sales by the Underwriter or dealer, any event shall occur or condition exist as a result of which it is necessary to amend or supplement the Prospectus in order to make the statements therein, in the light of the circumstances when the Prospectus (or in lieu thereof the notice referred to in Rule 173(a) under the Securities Act) is delivered to a purchaser, not misleading, or if, in the opinion of counsel for the Underwriter, it is necessary to amend or supplement the Prospectus to comply with applicable law, forthwith to prepare, file with the Commission and furnish, at its own expense, to the Underwriter and to the dealers (whose names and addresses you will furnish to the Company) to which Shares may have been sold by you on behalf of the Underwriter and to any other dealers upon request, either amendments or supplements to the Prospectus so that the statements in the Prospectus as so amended or supplemented will not, in the light of the circumstances when the Prospectus (or in lieu thereof the notice referred to in Rule 173(a) under the Securities Act) is delivered to a purchaser, be misleading or so that the Prospectus, as amended or supplemented, will comply with applicable law.

(g) To endeavor to qualify the Shares for offer and sale under the securities or Blue Sky laws of such jurisdictions as you shall reasonably request.

(h) To make generally available to the Company’s security holders and to you as soon as practicable an earning statement which shall satisfy the provisions of Section 11(a) of the Securities Act and the rules and regulations of the Commission thereunder.

(i) Whether or not the transactions contemplated in this Agreement are consummated or this Agreement is terminated, to pay or cause to be paid all expenses incident to the performance of its obligations under this Agreement, including: (i) the fees, disbursements and expenses of the Company’s counsel and the Company’s accountants in connection with the registration and delivery of the Shares under the Securities Act and all other fees or expenses in connection with the preparation and filing of the Registration Statement, any preliminary prospectus, the Time of Sale Prospectus, the Prospectus, any free writing prospectus prepared by or on behalf of, used by, or referred to by the Company and amendments and supplements to any of the foregoing, including the filing fees payable to the Commission relating to the Shares (within the time required by Rule 456(b)(1), if applicable), all printing costs associated therewith, and the mailing and delivering of copies thereof to the Underwriter and dealers, in the quantities hereinabove specified, (ii) all costs and expenses related to the transfer and delivery of the Shares to the Underwriter, including any transfer or other taxes payable thereon, (iii) the cost of printing or producing any Blue Sky or Legal Investment memorandum in connection with the offer and sale of the Shares under state securities laws and all expenses in connection with the qualification of the Shares for offer and sale under state securities laws as provided in Section 6(g) hereof, including filing fees and the reasonable fees and disbursements of counsel for the Underwriter in connection with such qualification and in connection with the Blue Sky or Legal Investment memorandum, (iv) all filing fees and the reasonable fees and disbursements of counsel to the Underwriter incurred in connection with the review and qualification of the offering of the Shares by the Financial Industry Regulatory Authority, if required, (v) the cost of printing certificates representing the Shares, (vi) the costs and charges of any transfer agent, registrar or depositary, (vii) the costs and expenses of the Company relating to investor presentations on any “road show” undertaken in connection with the marketing of the offering of the Shares, including, without limitation, expenses associated with the preparation or dissemination of any electronic road show, expenses associated with the production of road show slides and graphics, fees and expenses of any consultants engaged in connection with the road show presentations with the prior approval of the Company, travel and lodging expenses of the representatives and officers of the Company and any such consultants, and the cost of any aircraft chartered in connection with the road show, (viii) the document production charges and expenses associated with printing this Agreement and (ix) all other costs and expenses incident to the performance of the obligations of the Company hereunder for which provision is not otherwise made in this Section. It is understood, however, that except as provided in this Section, Section 8 entitled “Indemnity and Contribution” and the last paragraph of Section 10 below, the Underwriter will pay all of its costs and expenses, including fees and disbursements of its counsel, stock transfer taxes payable on resale of any of the Shares by them and any advertising expenses connected with any offers they may make.

(j) If the third anniversary of the initial effective date of the Registration Statement occurs before all the Shares have been sold by the Underwriter, prior to the third anniversary to file a new shelf registration statement and to take any other action necessary to permit the public offering of the Shares to continue without interruption; references herein to the Registration Statement shall include the new registration statement declared effective by the Commission;

The Company also covenants with the Underwriter that, without the prior written consent of the Underwriter, it will not, during the restricted period set forth in Schedule I hereto, (1) offer, pledge, sell, contract to sell, sell any option or contract to purchase, purchase any option or contract to sell, grant any option, right or warrant to purchase, lend, or otherwise transfer or dispose of, directly or indirectly, any shares of Common Stock or any securities convertible into or exercisable or exchangeable for Common Stock or (2) enter into any swap or other arrangement that transfers to another, in whole or in part, any of the economic consequences of ownership of the Common Stock, whether any such transaction described in clause (1) or (2) above is to be settled by delivery of Common Stock or such other securities, in cash or otherwise or (3) file any registration statement with the Commission relating to the offering of any shares of Common Stock or any securities convertible into or exercisable or exchangeable for Common Stock. The foregoing sentence shall not apply to (a) the Shares to be sold hereunder, (b) the issuance by the Company of shares of Common Stock upon the exercise of an option or warrant or the conversion of a security outstanding on the date hereof of which the Underwriter has been advised in writing or which is described in the Time of Sale Prospectus, (c) the issuance of any shares of Common Stock in connection with acquisition, licensing, collaboration or similar strategic arrangements, provided that the Company first causes any such recipient of shares under this clause (c) to execute and deliver to you a "lock-up" agreement substantially in the form of Exhibit A, (d) the issuance of shares of Common Stock as matching contributions under the Company's 401(k) plan, or (e) the grant of options or the issuance of shares of restricted Common Stock to employees, officers, directors, advisors or consultants pursuant to the Company's employee benefit plans. In addition, the Company will not, during the period commencing on the date hereof and ending 30 days after the date of the Prospectus, (i) clear or otherwise allow for any executive officer or director to sell or otherwise transfer shares of Common Stock or any security convertible into or exercisable or exchangeable for Common Stock under the Company’s xxxxxxx xxxxxxx policy and will not open the “trading window” under such policy for any executive officer or director, except, for the avoidance of doubt, the foregoing restrictions shall not apply to sales or transfers pursuant to any written trading plans under Rule 10b5-1 of the Exchange Act that exist as of the date of the Prospectus or (ii) waive the lockup provisions of any agreement to which the Company is a party as of the date of the Prospectus.

7. Covenants of the Underwriter. The Underwriter covenants with the Company not to take any action that would result in the Company being required to file with the Commission under Rule 433(d) a free writing prospectus prepared by or on behalf of such Underwriter that otherwise would not be required to be filed by the Company thereunder, but for the action of the Underwriter.

8. Indemnity and Contribution. (a) The Company agrees to indemnify and hold harmless the Underwriter, each person, if any, who controls the Underwriter within the meaning of either Section 15 of the Securities Act or Section 20 of the Exchange Act and each agent and each affiliate of the Underwriter within the meaning of Rule 405 under the Securities Act from and against any and all losses, claims, damages and liabilities (including, without limitation, any legal or other expenses reasonably incurred in connection with defending or investigating any such action or claim) caused by any untrue statement or alleged untrue statement of a material fact contained in the Registration Statement or any amendment thereof, any preliminary prospectus, the Time of Sale Prospectus, any issuer free writing prospectus as defined in Rule 433(h) under the Securities Act, any Company information that the Company has filed, or is required to file, pursuant to Rule 433(d) under the Securities Act, or the Prospectus or any amendment or supplement thereto, or caused by any omission or alleged omission to state therein a material fact required to be stated therein or necessary to make the statements therein not misleading, except insofar as such losses, claims, damages or liabilities are caused by any such untrue statement or omission or alleged untrue statement or omission based upon information relating to the Underwriter furnished to the Company in writing by the Underwriter expressly for use therein.

(b) The Underwriter agrees to indemnify and hold harmless the Company, its directors, its officers who sign the Registration Statement and each person, if any, who controls the Company within the meaning of either Section 15 of the Securities Act or Section 20 of the Exchange Act to the same extent as the foregoing indemnity from the Company to the Underwriter, but only with reference to information relating to such Underwriter furnished to the Company in writing by such Underwriter expressly for use in the Registration Statement, any preliminary prospectus, the Time of Sale Prospectus, any issuer free writing prospectus or the Prospectus or any amendment or supplement thereto.

(c) In case any proceeding (including any governmental investigation) shall be instituted involving any person in respect of which indemnity may be sought pursuant to Section 8(a) or 8(b), such person (the “indemnified party”) shall promptly notify the person against whom such indemnity may be sought (the “indemnifying party”) in writing and the indemnifying party, upon request of the indemnified party, shall retain counsel reasonably satisfactory to the indemnified party to represent the indemnified party and any others the indemnifying party may designate in such proceeding and shall pay the fees and disbursements of such counsel related to such proceeding. In any such proceeding, any indemnified party shall have the right to retain its own counsel, but the fees and expenses of such counsel shall be at the expense of such indemnified party unless (i) the indemnifying party and the indemnified party shall have mutually agreed to the retention of such counsel or (ii) the named parties to any such proceeding (including any impleaded parties) include both the indemnifying party and the indemnified party and representation of both parties by the same counsel would be inappropriate due to actual or potential differing interests between them. It is understood that the indemnifying party shall not, in respect of the legal expenses of any indemnified party in connection with any proceeding or related proceedings in the same jurisdiction, be liable for the fees and expenses of more than one separate firm (in addition to any local counsel) for all such indemnified parties and that all such fees and expenses shall be reimbursed as they are incurred. Such firm shall be designated in writing by the Underwriter, in the case of parties indemnified pursuant to Section 8(a), and by the Company, in the case of parties indemnified pursuant to Section 8(b). The indemnifying party shall not be liable for any settlement of any proceeding effected without its written consent, but if settled with such consent or if there be a final judgment for the plaintiff, the indemnifying party agrees to indemnify the indemnified party from and against any loss or liability by reason of such settlement or judgment. Notwithstanding the foregoing sentence, if at any time an indemnified party shall have requested an indemnifying party to reimburse the indemnified party for fees and expenses of counsel as contemplated by the second and third sentences of this paragraph, the indemnifying party agrees that it shall be liable for any settlement of any proceeding effected without its written consent if (i) such settlement is entered into more than 30 days after receipt by such indemnifying party of the aforesaid request and (ii) such indemnifying party shall not have reimbursed the indemnified party in accordance with such request prior to the date of such settlement. No indemnifying party shall, without the prior written consent of the indemnified party, effect any settlement of any pending or threatened proceeding in respect of which any indemnified party is or could have been a party and indemnity could have been sought hereunder by such indemnified party, unless such settlement includes an unconditional release of such indemnified party from all liability on claims that are the subject matter of such proceeding.

(d) To the extent the indemnification provided for in Section 8(a) or 8(b) is unavailable to an indemnified party or insufficient in respect of any losses, claims, damages or liabilities referred to therein, then each indemnifying party under such paragraph, in lieu of indemnifying such indemnified party thereunder, shall contribute to the amount paid or payable by such indemnified party as a result of such losses, claims, damages or liabilities (i) in such proportion as is appropriate to reflect the relative benefits received by the Company on the one hand and the Underwriter on the other hand from the offering of the Shares or (ii) if the allocation provided by clause 8(d)(i) above is not permitted by applicable law, in such proportion as is appropriate to reflect not only the relative benefits referred to in clause 8(d)(i) above but also the relative fault of the Company on the one hand and of the Underwriter on the other hand in connection with the statements or omissions that resulted in such losses, claims, damages or liabilities, as well as any other relevant equitable considerations. The relative benefits received by the Company on the one hand and the Underwriter on the other hand in connection with the offering of the Shares shall be deemed to be in the same respective proportions as (i) the total net proceeds from the offering of the Shares (before deducting expenses) received by the Company and (ii) the total underwriting discounts and commissions received by the Underwriter bear to the aggregate public offering price of the Shares. The relative fault of the Company on the one hand and the Underwriter on the other hand shall be determined by reference to, among other things, whether the untrue or alleged untrue statement of a material fact or the omission or alleged omission to state a material fact relates to information supplied by the Company or by the Underwriter and the parties’ relative intent, knowledge, access to information and opportunity to correct or prevent such statement or omission.

(e) The Company and the Underwriter agree that it would not be just or equitable if contribution pursuant to this Section 8 were determined by pro rata allocation or by any other method of allocation that does not take account of the equitable considerations referred to in Section 8(d). The amount paid or payable by an indemnified party as a result of the losses, claims, damages and liabilities referred to in Section 8(d) shall be deemed to include, subject to the limitations set forth above, any legal or other expenses reasonably incurred by such indemnified party in connection with investigating or defending any such action or claim. Notwithstanding the provisions of this Section 8, the Underwriter shall not be required to provide indemnity for or contribute any amount in excess of the amount by which the total price at which the Shares underwritten by it are sold to the public exceeds the amount of any damages that such Underwriter has otherwise been required to pay by reason of such untrue or alleged untrue statement or omission or alleged omission. 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. The remedies provided for in this Section 8 are not exclusive and shall not limit any rights or remedies which may otherwise be available to any indemnified party at law or in equity.

(f) The indemnity and contribution provisions contained in this Section 8 and the representations, warranties and other statements of the Company contained in this Agreement shall remain operative and in full force and effect regardless of (i) any termination of this Agreement, (ii) any investigation made by or on behalf of the Underwriter, any person controlling the Underwriter or any affiliate of the Underwriter or by or on behalf of the Company, its officers or directors or any person controlling the Company and (iii) acceptance of and payment for any of the Shares.

9. Termination. The Underwriter may terminate this Agreement by notice given by you to the Company if, after the execution and delivery of this Agreement and prior to the Closing Date (i) trading generally shall have been suspended or materially limited on, or by, as the case may be, any of the New York Stock Exchange, the American Stock Exchange, the NASDAQ Global Market, the Chicago Board of Options Exchange, the Chicago Mercantile Exchange or the Chicago Board of Trade, (ii) trading of any securities of the Company shall have been suspended on any exchange or in any over-the-counter market, (iii) a material disruption in securities settlement, payment or clearance services in the United States shall have occurred, (iv) any moratorium on commercial banking activities shall have been declared by Federal or New York State authorities or (v) there shall have occurred any outbreak or escalation of hostilities, or any change in financial markets or any calamity or crisis that, in your judgment, is material and adverse and which, singly or together with any other event specified in this clause (v), makes it, in your judgment, impracticable or inadvisable to proceed with the offer, sale or delivery of the Shares on the terms and in the manner contemplated in the Time of Sale Prospectus or the Prospectus.

10. Effectiveness. This Agreement shall become effective upon the execution and delivery hereof by the parties hereto.

If this Agreement shall be terminated by the Underwriter because of any failure or refusal on the part of the Company to comply with the terms or to fulfill any of the conditions of this Agreement, or if for any reason the Company shall be unable to perform its obligations under this Agreement, the Company will reimburse the Underwriter for all out-of-pocket expenses (including the fees and disbursements of its counsel) reasonably incurred by the Underwriter in connection with this Agreement or the offering contemplated hereunder.

11. Entire Agreement. (a) This Agreement, together with any contemporaneous written agreements and any prior written agreements (to the extent not superseded by this Agreement) that relate to the offering of the Shares, represents the entire agreement between the Company and the Underwriter with respect to the preparation of any preliminary prospectus, the Time of Sale Prospectus, the Prospectus, the conduct of the offering, and the purchase and sale of the Shares.

(b) The Company acknowledges that in connection with the offering of the Shares: (i) the Underwriter has acted at arms length, is not an agent of, and owes no fiduciary duties to, the Company or any other person, (ii) the Underwriter owes the Company only those duties and obligations set forth in this Agreement and prior written agreements (to the extent not superseded by this Agreement), if any, and (iii) the Underwriter may have interests that differ from those of the Company. The Company waives to the full extent permitted by applicable law any claims it may have against the Underwriter arising from an alleged breach of fiduciary duty in connection with the offering of the Shares.

12. Counterparts. This Agreement may be signed in two or more counterparts, each of which shall be an original, with the same effect as if the signatures thereto and hereto were upon the same instrument.

13. Applicable Law. This Agreement shall be governed by and construed in accordance with the internal laws of the State of New York.

14. Headings. The headings of the sections of this Agreement have been inserted for convenience of reference only and shall not be deemed a part of this Agreement.

15. Notices. All communications hereunder shall be in writing and effective only upon receipt and if to the Underwriter shall be delivered, mailed or sent to you at the address set forth in Schedule I hereto; and if to the Company shall be delivered, mailed or sent to the address set forth in Schedule I hereto.

[Remainder of page intentionally left blank; signature page follows.]

			Very truly yours,

			REGENERON PHARMACEUTICALS, INC.


			By:	/s/ Xxxxxx Xxxxxxxx
				Name:	Xxxxxx X. Xxxxxxxx
				Title:	Senior Vice President, Finance
					and Administration and Chief
					Financial Officer


Accepted as of the date hereof

CITIGROUP GLOBAL MARKETS INC.





By:	/s/ Xxxxx Xxxxxxx
	Name:	Xxxxx Xxxxxxx
	Title:	Vice President

[Signature page to Underwriting Agreement]

	SCHEDULE I

Registration Statement File No.:	333-169786

Time of Sale Prospectus	99	Basic Prospectus

	100	Preliminary prospectus

	101	Term sheet attached as Exhibit B

Lock-up Restricted Period:	45 days

Title of Shares to be purchased:	Common Stock, $0.001 par value per share

Number of Firm Shares:	5,500,000

Number of Additional Shares:	825,000

Purchase Price:	$27.69 per share

Public Offering Price	The price per share in each trade executed pursuant to the Registration Statement and this Agreement.

Closing Date and Time:	October 13, 2010, 10 a.m.

Closing Location:	Xxxxxxx Xxxx, Slate, Xxxxxxx & Xxxx LLP
	Xxxx Xxxxx Xxxxxx
	Xxx Xxxx, Xxx Xxxx 00000

Address for Notices to Underwriter:	Citigroup Global Markets Inc.
	000 Xxxxxxxxx Xx.
	Xxx Xxxx, Xxx Xxxx 00000
	Attention: General Counsel

Address for Notices to the Company:	Regeneron Pharmaceuticals, Inc.
	000 Xxx Xxx Xxxx Xxxxx Xxxx
	Xxxxxxxxx, Xxx Xxxx 00000-0000
	Attention:	Xxxxxx X. Xxxxxxxx, Esq.

		SCHEDULE II

		Number of Firm
		Shares To Be
Underwriter		Purchased
Citigroup Global Markets Inc.		5,500,000
Total:		5,500,000

EXHIBIT A

[●], 2010

Citigroup Global Markets Inc.
000 Xxxxxxxxx Xxxxxx
Xxx Xxxx, Xxx Xxxx 00000

Ladies and Gentlemen:

The undersigned understands that Citigroup Global Markets Inc. (“Citi”) has entered into an Underwriting Agreement (the “Underwriting Agreement”) with Regeneron Pharmaceuticals, Inc., a New York corporation (the “Company”), providing for the public offering (the “Public Offering”) by Citi as underwriter (the “Underwriter”) of 5,500,000 firm shares and 825,000 additional shares (collectively, the “Shares”) of the Common Stock ($0.001 par value per share) of the Company (the “Common Stock”).

The undersigned hereby agrees that, without the prior written consent of Citi, it will not, during the period commencing on the date hereof and ending on the earlier to occur of (a) 45 days after the date of the final prospectus supplement relating to the Public Offering, and (b) 5 days after the date of such final prospectus supplement if the sale of the Shares to the Underwriter has not closed, (1) offer, pledge, sell, contract to sell, sell any option or contract to purchase, purchase any option or contract to sell, grant any option, right or warrant to purchase, lend, or otherwise transfer or dispose of, directly or indirectly, any shares of Common Stock or any securities convertible into or exercisable or exchangeable for Common Stock or (2) enter into any swap or other arrangement that transfers to another, in whole or in part, any of the economic consequences of ownership of the Common Stock, whether any such transaction described in clause (1) or (2) above is to be settled by delivery of Common Stock or such other securities, in cash or otherwise. The foregoing sentence shall not apply to (a) transactions relating to shares of Common Stock or other securities acquired in open market transactions after the completion of the Public Offering; (b) transfers of shares of Common Stock or any security convertible into Common Stock as a bona fide gift; (c) distributions or transfers to family members, trusts, and/or controlled entities in connection with estate planning, provided that each transferee shall sign and deliver a lock-up letter substantially in the form of this letter; (d) the sale of Common Stock in the public market pursuant to a written trading plan in existence prior to the date hereof designed to comply with Rule 10b5-1 under the Securities Exchange Act of 1934, as amended; or (e) the exercise of a stock option for, or the conversion of any convertible security into, shares of common stock, including, without limitation, by transferring or submitting for cancellation aged shares or shares otherwise issued or issuable upon the exercise of a stock option to the Company to satisfy the exercise price of a stock option under the Company’s long-term incentive plans (or to satisfy the minimum withholding tax required in connection with such option exercise). In addition, the undersigned agrees that, without the prior written consent of Citi, it will not, during the period commencing on the date hereof and ending 45 days after the date of the final prospectus supplement, make any demand for or exercise any right with respect to, the registration of any shares of Common Stock or any security convertible into or exercisable or exchangeable for Common Stock. The undersigned agrees and consents to the entry of stop transfer instructions with the Company’s transfer agent and registrar against the transfer of the undersigned’s shares of Common Stock except in compliance with the foregoing restrictions.

The undersigned understands that the Company and the Underwriter are relying upon this agreement. The undersigned further understands that this agreement is irrevocable and shall be binding upon the undersigned’s heirs, legal representatives, successors and assigns.

(continued on next page)

Very truly yours,


(Signature)

(Printed Name)

(Address)

EXHIBIT B

Regeneron Pharmaceuticals, Inc. (the “Company”) is offering 5,500,000 shares of its common stock (the “Shares”) in a variable price offering. Citi’s indicative price for the Shares is $28.00 per share, plus a commission equivalent of up to 5 cents per share. The Company has granted Citi an option to purchase up to an additional 825,000 shares of common stock solely to cover over-allotments, if any.

The Shares are being offered under the Company’s existing effective shelf registration statement. Copies of the prospectus supplement and accompanying prospectus related to this offering may be obtained from Citi, Brooklyn Army Terminal, 000 00xx Xxxxxx, 0xx Xxxxx, Xxxxxxxx, Xxx Xxxx 00000 (tel: (000) 000-0000).

This notice shall not constitute an offer to sell or the solicitation of an offer to buy nor shall there be any sales of these securities in any jurisdiction in which such offer, solicitation or sale would be unlawful prior to registration or qualification under the securities laws of such jurisdiction.

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5,500,000 SHARES REGENERON PHARMACEUTICALS, INC. COMMON STOCK, $0.001 PAR VALUE PER SHARE UNDERWRITING AGREEMENT

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