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                                                                     Exhibit 4.3

                                                                  EXECUTION COPY


                                PLEDGE AGREEMENT


                  This PLEDGE AGREEMENT (the "Pledge Agreement") is made and
entered into as of October 17, 2001 by Regeneron Pharmaceuticals, Inc., a New
York corporation (the "Pledgor"), having its principal office at 777 Old Saw
Mill River Road, Tarrytown, New York 10591, in favor of American Stock Transfer
& Trust Company, a New York corporation with trust power, in its capacity as
trustee (the "Trustee") for the holders from time to time (the "Holders") of the
Notes (as defined herein), issued by the Pledgor under the Indenture referred to
below. Capitalized terms used and not defined in this Pledge Agreement have the
meanings set forth or referred to in the Indenture.

                               W I T N E S S E T H

                  WHEREAS, the Pledgor and Merrill Lynch & Co., Merrill Lynch,
Pierce, Fenner & Smith Incorporated and Robertson Stephens, Inc. (collectively,
the "Initial Purchasers") are parties to a Purchase Agreement dated October 12,
2001 (the "Purchase Agreement"), pursuant to which the Pledgor will issue and
sell to the Initial Purchasers $200,000,000 aggregate principal amount of 5-1/2%
Convertible Senior Subordinated Notes due 2008 (the "Initial Notes") and
pursuant to which the Pledgor has granted to the Initial Purchasers options to
purchase all or any part of an additional $50,000,000 aggregate principal amount
of the Notes (the "Option Notes" and together with the Initial Notes, the
"Notes");

                  WHEREAS, the Pledgor and the Trustee have entered into that
certain indenture dated as of the date hereof (as amended, restated,
supplemented or otherwise modified from time to time, the "Indenture"), pursuant
to which the Pledgor is issuing the Initial Notes on the date hereof;

                  WHEREAS, the Pledgor is the beneficial owner of security
entitlements (the "Pledged Security Entitlements") with respect to (i) the
United States Treasury securities identified by CUSIP number in Schedule I
hereto, and credited to the Pledgor's account with The Bank of New York (the
"Account Holder"), ABA No. 021000018, Account No. 303640 at its office at 101
Barclay Street, New York, New York 10286, in the name of "American Stock
Transfer & Trust Company, as Trustee for the benefit of the holders of the
5-1/2% Convertible Senior Subordinated Notes due 2008 of Regeneron
Pharmaceuticals Collateral Pledge Account" (the "Pledged Account") and (ii) all
other financial assets credited from time to time to the Pledged Account
(collectively with the assets described in clause (i) above, the "Pledged
Financial Assets");

                  WHEREAS, to secure the obligation of the Pledgor under the
Indenture and the Notes to pay in full each of the first six scheduled interest
payments on the Notes when due and to secure repayment of a portion of the
principal, premium (if any) and interest on the Notes in the event that the
Notes become due and payable prior to such time as the first six scheduled
interest payments thereon shall have been paid in full (collectively, the
"Obligations"), the
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Pledgor has agreed (i) to pledge to the Trustee for its benefit and the ratable
benefit of the Holders of the Notes, a security interest in the Collateral (as
defined herein) securing the payment and performance by the Pledgor of all of
the Obligations and (ii) to execute and deliver this Pledge Agreement;

                  WHEREAS, it is a condition precedent to the initial purchase
of the Notes by the initial Holders thereof that the Pledgor shall have executed
and delivered this Pledge Agreement; and

                  WHEREAS, unless otherwise defined herein or in the Indenture,
terms used in Article 8 or 9 of the Uniform Commercial Code as in effect in the
State of New York ("UCC") and/or in the Federal Book Entry Regulations (as
defined below) are used in this Pledge Agreement as such terms are defined in
such Article 8 or 9 and/or the Federal Book Entry Regulations. The term "Federal
Book Entry Regulations" means (a) the federal regulations contained in Subpart B
("Treasury/Reserve Automated Debt Entry System (TRADES)") governing book-entry
securities consisting of U.S. Treasury bonds, notes and bills and Subpart D
("Additional Provisions") of 31 C.F.R. Part 357, 31 C.F.R. Section 357.2,
Section 357.10 through Section 357.14 and Section 357.41 through Section 357.44
and (b) to the extent substantially identical to the federal regulations
referred to in clause (a) above (as in effect from time to time), the federal
regulations governing other book-entry securities.

                                    AGREEMENT

                  NOW, THEREFORE, in consideration of the premises herein
contained, and in order to induce the initial Holders of the Notes to purchase
the Notes, the Pledgor hereby agrees with the Trustee, for the benefit of the
Trustee and for the ratable benefit of the Holders of the Notes, as follows:

                  SECTION 1. Pledge and Grant of Security Interest. The Pledgor
hereby pledges to the Trustee, for its benefit and for the ratable benefit of
the Holders of the Notes, and hereby grants to the Trustee, a security interest
and continuing lien in, the Pledgor's right, title and interest in and to the
following, in each case, whether now owned or hereafter acquired by the Pledgor,
wherever located and whether now or hereafter existing or arising (hereinafter
collectively referred to as the "Collateral"):

                  (a) the Pledged Financial Assets and the certificates, if any,
         representing the Pledged Financial Assets, and all dividends, interest,
         money (as defined in the UCC), instruments (as defined in the UCC, the
         "Instruments") and other property from time to time received,
         receivable or otherwise distributed or distributable in respect of or
         in exchange for any or all of such Pledged Financial Assets;

                  (b) the Pledged Account and all security entitlements with
         respect thereto, all Pledged Security Entitlements with respect to all
         Pledged Financial Assets from time to time credited to the Pledged
         Account, any and all securities accounts in which the Pledged Security
         Entitlements are carried, and all dividends, interest, cash,
         instruments and other property from time to time received, receivable
         or otherwise distributed or

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         distributable in respect of or in exchange for any or all of such
         Pledged Security Entitlements;

                  (c) all other securities, securities entitlements and other
         financial assets hereafter acquired by the Pledgor pursuant to Article
         12 of the Indenture; and

                  (d) all proceeds of any and all of the foregoing Collateral
         (including, without limitation, proceeds that constitute property of
         the types described in clauses (a), (b) and (c) of this Section 1) and,
         to the extent not otherwise included, all cash.

                  SECTION 2. Security for Obligations. This Pledge Agreement
secures, and the Collateral is collateral security for, the prompt and complete
payment and performance when due (whether at stated maturity, by acceleration or
otherwise) of all the Obligations or other obligations of the Pledgor, whether
for principal, interest, fees or otherwise, now or hereafter existing, under
this Pledge Agreement, the Notes or the Indenture (all such obligations being
the "Secured Obligations"). Without limiting the generality of the foregoing,
this Pledge Agreement secures, and the Collateral is collateral security for,
the payment of all amounts that constitute part of the Secured Obligations and
would be owed by the Pledgor to the Trustee or the Holders under the Notes or
the Indenture but for the fact that they are unenforceable or not allowable due
to the existence of a bankruptcy, reorganization or similar proceeding involving
the Pledgor.

                  SECTION 3. Maintaining the Pledged Account. So long as any
Secured Obligation shall remain outstanding:

                  (a) The Pledgor will maintain separately the Pledged Account
         with The Bank of New York.

                  (b) It shall be a term and condition of the Pledged Agreement,
         notwithstanding any term or condition to the contrary in any other
         agreement relating to the Pledged Account, and except as otherwise
         provided by the provisions of Section 5 and Section 18 hereof, that no
         funds shall be paid or released to or for the account of, or withdrawn
         by or for the account of, the Pledgor or any other Person from the
         Pledged Account.

                  The Pledged Account shall be subject to such applicable laws,
         and such applicable regulations of the Board of Governors of the
         Federal Reserve System and of any other appropriate banking or
         governmental authority, as may now or hereafter be in effect.

                  SECTION 4. Delivery of Collateral. (a) All cash, certificates
or instruments representing or evidencing the Pledged Financial Assets, the
Pledged Security Entitlements or the Pledged Account shall be delivered to and
held by or on behalf of the Trustee pursuant hereto and shall be in suitable
form for transfer by delivery, or shall be accompanied by duly executed
instruments of transfer or assignment in blank, all in form and substance
satisfactory to the Trustee. The Trustee shall have the right, at any time in
its discretion and without notice to the Pledgor, to transfer to or to register
in the name of the Trustee or any of its nominees any or all of the Collateral.
In addition, the Trustee shall have the right at any time to exchange
certificates or instruments representing or evidencing any or all of the
Collateral for certificates or instruments of smaller or larger denominations.
Also, the Trustee shall have the right at any time

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to convert Collateral consisting of financial assets credited to the Pledged
Account to Collateral consisting of financial assets held directly by the
Trustee, and to convert Collateral consisting of financial assets held directly
by the Trustee to Collateral consisting of financial assets credited to the
Pledged Account.

                  (b) With respect to any Collateral in which the Pledgor has
any right, title or interest and that constitutes an uncertificated security,
the Pledgor shall cause the issuer thereof either (i) to register the Trustee as
the registered owner of such security or (ii) to agree in writing with the
Pledgor and the Trustee that such issuer will comply with instructions with
respect to such security originated by the Trustee without further consent of
the Pledgor, such agreement to be in form and substance satisfactory to the
Trustee.

                  (c) With respect to any Collateral in which the Pledgor has
any right, title or interest and that constitutes a security entitlement, the
Pledgor shall cause the securities intermediary with respect to such security
entitlement either (i) to identify in its records the Trustee as the entitlement
holder of such security entitlement against such securities intermediary or (ii)
to agree in writing with the Pledgor and the Trustee that such securities
intermediary will comply with entitlement orders (that is, notifications
communicated to such securities intermediary directing transfer or redemption of
the financial asset to which the Pledgor has a security entitlement) originated
by the Trustee without further consent of the Pledgor, such agreement to be in
substantially the form of Annex A hereto or otherwise in form and substance
satisfactory to the Trustee.

                  (d) With respect to any Collateral that constitutes a
securities account, the Pledgor will comply with subsection (c) of this Section
4 with respect to all security entitlements carried in such securities account.

                  (e) Prior to or concurrently with the execution and delivery
hereof and prior to the transfer to the Trustee of the Pledged Security
Entitlements, as provided in subsections (a) through (c) of this Section 4, the
Trustee shall establish the Pledged Account with The Bank of New York. Upon
transfer of the Pledged Financial Assets to the Trustee, as confirmed to the
Trustee by the securities intermediary, the Trustee shall make appropriate book
entries indicating that the Pledged Financial Assets have been credited to and
are held in the Pledged Account. Subject to the other terms and conditions of
this Pledge Agreement, all funds or other property held by the Trustee pursuant
to this Pledge Agreement shall be held in the Pledged Account subject (except as
expressly provided in Sections 5(a), (b) and (c) hereof) to the exclusive
dominion and control of the Trustee and exclusively for the benefit of the
Trustee and for the ratable benefit of the Holders of the Notes and segregated
from all other funds or other property otherwise held by the Trustee.

                  (f) All Collateral shall be retained in the appropriate
Pledged Account pending disbursement pursuant to the terms hereof.

                  (g) Concurrently with the execution and delivery of this
Pledge Agreement, the Trustee is delivering to the Pledgor a duly executed
Control Agreement (the "Control Agreement"), in the form of Annex A hereto.

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                  (h) Concurrently with the execution and delivery of this
Pledge Agreement, the Pledgor is delivering to the Trustee acknowledgment copies
or stamped receipt copies of proper financing statements, duly filed on or
before the Closing Date under the UCC, covering the Collateral described in this
Pledge Agreement.

                  SECTION 5. Disbursements. (a) Three business days prior to the
due date of any of the first six scheduled interest payments on the Notes, the
Pledgor may, pursuant to written instructions given by the Pledgor to the
Trustee (an "Issuer Order"), direct the Trustee to release from the Pledged
Account and pay to the Holders of the Notes proceeds sufficient to provide for
payment in full of such interest then due on the Notes. Upon receipt of an
Issuer Order, the Trustee will (i) issue a Payment Order (as defined in the
Control Agreement) to the Account Holder for the release from the Pledged
Account funds to the Trustee in an amount sufficient to provide for the payment
of the interest on the Notes in accordance with such Issuer Order and (ii) pay
such funds to the Holders of the Notes in accordance with the Indenture and the
Notes. Nothing in this Section 5 shall affect the Trustee's rights to apply the
Collateral to the payments of amounts due on the Notes upon acceleration
thereof.

                  (b) If the Pledgor makes any of the first six scheduled
interest payments on the Notes or portion of such an interest payment from a
source of funds other than the Pledged Account ("Pledgor Funds"), the Pledgor
may, after payment in full of such interest payment, direct the Trustee pursuant
to an Issuer Order to issue a Payment Order (as defined in the Control
Agreement) to the Account Holder for the release to the Pledgor or to another
party at the direction of the Pledgor (the "Pledgor's Designee") proceeds from
the Pledged Account in an amount less than or equal to the amount of Pledgor
Funds applied to such interest payment. Upon receipt by the Trustee of such
Issuer Order and provided the Trustee has received such interest payment, the
Trustee shall direct the Account Holder pursuant to a Payment Order to pay over
to the Pledgor or the Pledgor's Designee, as the case may be, the requested
amount from proceeds in the Pledged Account as soon as practicable.

                  (c) At least three Business Days prior to the due date of each
of the first six scheduled interest payments on the Notes, the Pledgor shall
give the Trustee notice (by Issuer Order) as to whether such interest payment
will be made pursuant to Section 5(a) or 5(b) above and the respective amounts
of interest that will be paid from the Pledged Account and from Pledgor Funds.
Any Pledgor Funds to be used to make any interest payment shall be delivered to
the Trustee, in immediately available funds, prior to 10:00 a.m. (New York City
time) on such interest payment date. If no such notice is given or such Pledgor
Funds have not been so delivered, the Trustee will act pursuant to Section 5(a)
above as if it had received an Issuer Order pursuant thereto for the payment in
full of the interest then due from the Pledged Account.

                  (d) The Trustee shall instruct the Account Holder to liquidate
Collateral in the Pledged Account (pursuant to written instructions from
Pledgor) in order to make any of the scheduled payments of interest on the
Notes, unless there are sufficient funds in the Pledged Account on such interest
payment date. The Trustee shall be entitled to instruct the Account Holder to
sell any Collateral as contemplated hereunder prior to the maturity of such
Collateral and shall not be responsible for any costs and expenses of such sale.

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                  (e) Nothing contained in this Pledge Agreement shall (i)
afford the Pledgor any right to issue entitlement orders with respect to any of
the Pledged Security Entitlements or any securities account in which any such
security entitlement may be carried, or otherwise afford the Pledgor control of
any Pledged Security Entitlement or (ii) otherwise give rise to any rights of
Pledgor with respect to the Pledged Financial Assets or any securities account
in which any such security entitlement may be carried, other than the Pledgor's
rights under this Pledge Agreement as the beneficial owner of collateral pledged
to and subject to the exclusive dominion and control (except as expressly
provided in Sections 5(a) and (b) hereof) of the Trustee in its capacity as such
(and not as a securities intermediary) before the payment in full, when due, of
the first six scheduled interest payments on the Notes. The Pledgor
acknowledges, confirms and agrees that the Trustee is an entitlement holder of
the Pledged Security Entitlements solely as Trustee for the Holders of the Notes
and not as a securities intermediary.

                  SECTION 6. Investing of Amounts in the Pledged Account. If
requested and as directed by the Pledgor, the Trustee will, subject to the
provisions of Sections 3, 5 and 13 of this Pledge Agreement, from time to time,
instruct the Account Holder to invest interest paid on the Pledged Financial
Assets and reinvest other proceeds of any Pledged Financial Assets that may
mature or be sold, in each case, in (i) identified United States Treasury
securities or (ii) selected shares of a money market fund registered under the
Investment Company Act of 1940, as amended, the portfolio of which consists of
United States Treasury securities, in each case credited to the Pledged Account.

                  SECTION 7. Representations and Warranties. The Pledgor hereby
represents and warrants that:

                  (a) This Pledge Agreement has been duly authorized, validly
         executed and delivered by the Pledgor and constitutes a valid and
         binding agreement of the Pledgor, enforceable against the Pledgor in
         accordance with its terms, except as (i) the enforceability hereof may
         be limited by bankruptcy, insolvency, fraudulent conveyance,
         preference, reorganization, moratorium or similar laws now or hereafter
         in effect relating to or affecting creditors' rights or remedies
         generally, (ii) the availability of equitable remedies may be limited
         by equitable principles of general applicability, (iii) the exculpation
         provisions and rights to indemnification hereunder may be limited by
         U.S. federal and state securities laws and public policy considerations
         and (iv) the waiver of rights and defenses contained in Section 13(b),
         Section 19.8 and Section 19.12 hereof may be limited by applicable law.

                  (b) The Pledgor's exact legal name, as defined in Section
         9-503(a) of the UCC, is Regeneron Pharmaceuticals, Inc. The Pledgor is
         located (within the meaning of Section 9-307 of the UCC) and has its
         chief executive office in the State of New York.

                  (c) The Pledgor is the legal and beneficial owner of the
         Collateral free and clear of any Lien, claim, option or right of others
         (except for the security interests created by this Pledge Agreement).
         No effective financing statement or instrument similar in effect
         covering all or any part of the Collateral or listing the Pledgor or
         any trade name of the Pledgor is on file in any public or recording
         office, other than the financing statements filed pursuant to this
         Pledge Agreement.

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                  (d) All filings and other actions (including, without
         limitation, (A) actions necessary to obtain control of the Collateral
         as provided in Sections 9-104, 9-105, 9-106 and 9-107 of the UCC and
         (B) actions necessary to perfect the Trustee's security interest with
         respect to the Collateral evidenced by a certificate of ownership)
         necessary to perfect the security interest in the Collateral created
         under this Pledge Agreement have been duly made or taken and are in
         full force and effect, and this Pledge Agreement creates in favor of
         the Trustee for its benefit and the ratable benefit of the Holders of
         the Notes a valid and, together with such filings and other actions,
         perfected first priority security interest in the Collateral, securing
         the payment of the Secured Obligations.

                  (e) The execution and delivery by the Pledgor of, and the
         performance by the Pledgor of its obligations under, this Pledge
         Agreement will not contravene any provision of applicable law or the
         Certificate of Incorporation of the Pledgor or any material agreement
         or other material instrument binding upon the Pledgor or
         Amgen-Regeneron Partners or any judgment, order or decree of any
         governmental body, agency or court having jurisdiction over the Pledgor
         or Amgen-Regeneron Partners, or result in the creation or imposition of
         any Lien on any assets of the Pledgor, except for the security
         interests granted under this Pledge Agreement.

                  (f) No consent of any other person and no approval,
         authorization, order of, action by notice to, filing or qualification
         with, any governmental authority, regulatory body, agency or other
         third party is required for (i) the grant by the Pledgor of the
         assignment, pledge and security interest granted under this Pledge
         Agreement, (ii) the execution or delivery by the Pledgor of, or the
         performance by the Pledgor of its obligations under, this Pledge
         Agreement, (iii) the perfection or maintenance of the assignment,
         pledge and security interest created hereunder (including the first
         priority nature of such assignment, pledge or security interest),
         except for the filing of financing and contribution statements under
         the UCC, which financing statements have been duly filed and are in
         full force and effect, or (iv) for the exercise by the Trustee of its
         voting or other rights provided for in this Pledge Agreement or the
         remedies in respect of the Collateral pursuant to this Pledge
         Agreement, except as may be required in connection with the disposition
         of any portion of the Collateral by laws affecting the offering and
         sale of securities generally.

                  (g) The Pledgor covenants and agrees with the Trustee and the
         Holders of the Notes that in the event of a Registration Default, as
         defined in the Registration Rights Agreement, and the interest rate on
         the Notes is increased as provided in Section 2(e) of the Registration
         Rights Agreement, the Company shall purchase and deliver free to the
         Trustee additional Pledged Security Entitlements in such amount as will
         be sufficient upon receipt of scheduled interest and/or principal
         payments of all Pledged Security Entitlements thereafter held in the
         Pledged Account, in the opinion of a nationally recognized firm of
         independent public accountants selected by the Pledgor, to provide
         payment for the first six scheduled interest payments due on the Notes
         (assuming the additional interest requirement remains in effect for the
         entire period). The additional Pledged Security Entitlements shall be
         pledged by the Pledgor to the Trustee for the benefit of the Holders
         and shall be held by the Trustee in the Pledged Account.

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                  (h) There are no legal or governmental proceedings pending or,
         to the best of the Pledgor's knowledge, threatened to which the Pledgor
         or Amgen-Regeneron Partners is a party or to which any of the
         properties of the Pledgor or Amgen-Regeneron Partners is subject that
         would materially adversely affect the power or ability of the Pledgor
         to perform its obligations under this Pledge Agreement or to consummate
         the transactions contemplated hereby.

                  (i) The pledge of the Collateral pursuant to this Pledge
         Agreement is not prohibited by law or governmental regulation
         (including, without limitation, Regulations G, T, U and X of the Board
         of Governors of the Federal Reserve System) applicable to the Pledgor.

                  (j) No Event of Default (as defined below) exists.

                  (k) The jurisdiction (for purposes of Section 8-110(e) of the
         UCC) of the securities intermediary that maintains the Pledged Account
         and all securities accounts carrying the Pledged Securities
         Entitlements is New York.

                  SECTION 8. Further Assurances. (a) The Pledgor agrees that
from time to time, at the expense of the Pledgor, the Pledgor will promptly
execute and deliver all further instruments and documents, and take all further
action, that may be necessary or desirable, or that the Trustee may reasonably
request, in order to perfect and protect any pledge or security interest granted
or purported to be granted hereunder or to enable the Trustee to exercise and
enforce its rights and remedies hereunder with respect to any Collateral.
Without limiting the generality of the foregoing, the Pledgor will: (i) if any
Collateral shall be evidenced by a promissory note or other instrument, deliver
and pledge to the Trustee hereunder such note or instrument, duly indorsed and
accompanied by duly executed instruments of transfer or assignment, all in form
and substance satisfactory to the Trustee; (ii) execute and file such financing
or continuation statements, or amendments thereto, and such other instruments or
notices, as may be necessary or desirable, or as the Trustee may reasonably
request, in order to perfect and preserve the pledge and security interest
granted or purported to be granted hereby; (iii) deliver and pledge to the
Trustee for its benefit and the ratable benefit of the Holders of the Notes
certificates representing Collateral that constitutes certificated securities,
accompanied by undated stock or bond powers executed in blank; and (iv) deliver
to the Trustee evidence that all other action that the Trustee may deem
reasonably necessary or desirable in order to perfect and protect the security
interest created by Pledgor under this Pledge Agreement has been taken.

                  (b) The Pledgor hereby authorizes the Trustee to file one or
more financing or continuation statements, and amendments thereto, including,
without limitation, one or more financing statements indicating that such
financing statements cover all assets or all personal property (or words of
similar effect), in each case without the signature of the Pledgor, and
regardless of whether any particular asset described in such financing
statements falls within the scope of UCC or the granting clause of this Pledge
Agreement. A photocopy or other reproduction of this Pledge Agreement or any
financing statement covering the Collateral or any part thereof shall be
sufficient as a financing statement where permitted by law. The Pledgor ratifies
its authorization for the Trustee to have filed such financing statements,
continuation statements or amendments filed prior to the date hereof.

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                  (c) The Pledgor will furnish to the Trustee from time to time
statements and schedules further identifying and describing the Collateral and
such other reports in connection with the Collateral as the Trustee may
reasonably request, all in reasonable detail.

                  (d) The Pledgor will promptly pay all reasonable costs
incurred in connection with any of the foregoing within 45 days of receipt of an
invoice therefor. The Pledgor also agrees, whether or not requested by the
Trustee, to take all actions that are necessary to perfect or continue the
perfection of, or to protect the first priority of, the Trustee's security
interest in and to the Collateral, including the filing of all necessary
financing and continuation statements, and to protect the Collateral against the
rights, claims or interests of third persons (other than any such rights, claims
or interests created by or arising through the Trustee).

                  SECTION 9. Covenants. (a) The Pledgor covenants and agrees
with the Trustee and the Holders of the Notes that from and after the date of
this Pledge Agreement until the earlier of payment in full in cash of (x) each
of the first six scheduled interest payments on the Notes when due under the
terms of the Indentures or (y) all obligations due and owing under the Indenture
and the Notes in the event such obligations become due and payable prior to the
payment of the first six scheduled interest payments on the Notes:

                  (i) that (A) it will not (and will not purport to) sell,
         assign or otherwise dispose of, or grant any option or warrant with
         respect to, any of the Collateral or its beneficial interest therein,
         and (B) it will not create or suffer to exist any Lien or other adverse
         interest upon or with respect to any of the Collateral or its
         beneficial interest therein (except for the security interests granted
         under this Pledge Agreement); and

                  (ii) that it will not (A) enter into any agreement or
         understanding that restricts or inhibits or purports to restrict or
         inhibit the Trustee's rights or remedies hereunder, including, without
         limitation, the Trustee's right to sell or otherwise dispose of the
         Collateral or (B) fail to pay or discharge any tax, assessment or levy
         of any nature with respect to its beneficial interest in the Collateral
         not later than five days prior to the date of any proposed sale under
         any judgment, writ or warrant of attachment with respect to such
         beneficial interest;

                  (iii) that it will not change its name, type of organization,
         jurisdiction of organization, organizational identification number or
         location from those set forth in Section 7(b) hereof without first
         giving at least 30 days' prior written notice to the Trustee and taking
         all action required by the Trustee for the purpose of perfecting or
         protecting the security interest granted by this Pledge Agreement; and

                  (iv) that it will, and cause the Trustee and the Account
         Holder to, execute and deliver on or prior to any Date of Delivery (as
         defined in Section 2(b) of the Purchase Agreement) a supplement to this
         Pledge Agreement, reasonably satisfactory to the Initial Purchasers,
         providing for the pledge of additional Collateral to secure all
         Obligations in respect of the Option Notes.

                  SECTION 10. Power of Attorney. In addition to all of the
powers granted to the Trustee pursuant to the Indenture, the Pledgor hereby
irrevocably appoints the Trustee as the

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Pledgor's attorney-in-fact (with full power of substitution), with full
authority in the place and stead of the Pledgor and in the name of the Pledgor
or otherwise, from time to time in the Trustee's discretion, to take any action
and to execute any instrument that is necessary or advisable or as the Trustee
may deem necessary or advisable to accomplish the purposes of this Pledge
Agreement, including, without limitation:

                  (a) to ask for, demand, collect, sue for, recover, compromise,
         receive and give acquittance and receipts for moneys due and to become
         due under or in respect of any of the Collateral,

                  (b) to receive, indorse and collect any drafts or other
         instruments, documents and chattel paper, in connection with clause (a)
         above,

                  (c) to file any claims or take any action or institute any
         proceedings that the Trustee may deem necessary or desirable for the
         collection of any of the Collateral or otherwise to enforce the rights
         of the Trustee with respect to any of the Collateral, and

                  (d) to pay or discharge taxes or Liens levied or placed upon
         the Collateral that the Pledgor has failed to pay or discharge in
         accordance herewith, the legality or validity thereof and the amounts
         necessary to discharge the same to be determined by the Trustee in its
         sole reasonable discretion, and such payments made by the Trustee to
         become part of the Obligations of the Pledgor to the Trustee, due and
         payable immediately upon demand;

provided, however, that the Trustee shall have no obligation to perform any of
the foregoing actions. The Trustee's authority under this Section 10 shall
include, without limitation, the authority to endorse and negotiate any checks
or instruments representing proceeds of Collateral in the name of the Pledgor,
execute and give receipt for any certificate of ownership or any document
constituting Collateral, transfer title to any item of Collateral, sign the
Pledgor's name on all financing statements (to the extent permitted by
applicable law) or any other documents deemed necessary or appropriate by the
Trustee to preserve, protect or perfect the security interest in the Collateral
granted hereunder and to file the same, prepare, file and sign the Pledgor's
name on any notice of Lien, and to take any other actions arising from or
incident to the powers granted to the Trustee in this Pledge Agreement. This
power of attorney is coupled with an interest and is irrevocable by the Pledgor.

                  SECTION 11. No Assumption of Duties; Reasonable Care. The
powers conferred on the Trustee hereunder are solely to protect the security
interest of the Trustee for its benefit and the ratable benefit of the Holders
of the Notes in the Collateral and shall not impose any duty on the Trustee to
exercise any such powers. Except for the safe custody of any Collateral in its
possession and the accounting for moneys actually received by it hereunder, the
Trustee shall have no duty as to any Collateral as to (i) ascertaining or taking
action with respect to calls, conversions, exchanges, maturities, tenders or
other matters relative to any Collateral, whether or not the Trustee has or is
deemed to have knowledge of such matters, (ii) taking of any necessary steps to
preserve rights against any parties or any other rights pertaining to any
Collateral or (c) investing or reinvesting any of the Collateral or any loss on
any investment. The Trustee shall be deemed to have exercised reasonable care in
the custody and preservation of any

                                       10
<PAGE>
Collateral in its possession if such Collateral is accorded treatment
substantially equal to that which it accords its own property. The Trustee shall
be entitled to all the rights, benefits, privileges and immunities accorded to
it under the Indenture.

                  SECTION 12. Indemnity and Expenses. (a) The Pledgor agrees to
indemnify, defend and save and hold harmless the Trustee and its officers,
directors, employees, agents and advisors (each, an "Indemnified Party") from
and against, and shall pay on demand, any and all claims, damages, losses,
liabilities and expenses (including, without limitation, reasonable fees and
expenses of counsel) that may be incurred by or asserted or awarded against any
Indemnified Party, in each case arising out of or in connection with or
resulting from this Pledge Agreement (including, without limitation, enforcement
of this Pledge Agreement), except to the extent such claim, damage, loss,
liability or expense is found in a final, non-appealable judgment by a court of
competent jurisdiction to have resulted from such Indemnified Party's gross
negligence or willful misconduct.

                  (b) The Pledgor will upon demand pay to the Trustee the amount
of any and all reasonable expenses, including, without limitation, the
reasonable fees and expenses of its counsel and of any experts and agents, that
the Trustee may incur in connection with (i) the review, negotiation and
administration of this Pledge Agreement, (ii) the custody or preservation of, or
the sale of, collection from or other realization upon, any of the Collateral,
(iii) the exercise or enforcement of any of the rights of the Trustee or the
Holders of the Notes hereunder or (iv) the failure by the Pledgor to perform or
observe any of the provisions hereof.

                  SECTION 13. Remedies. If any Event of Default under the
Indenture or default hereunder (any such Event of Default or default being
referred to in this Pledge Agreement as an "Event of Default") shall have
occurred and be continuing:

                  (a) The Trustee and the Holders of the Notes may exercise in
         respect of the Collateral, in addition to all other rights and remedies
         given by law or by this Pledge Agreement or the Indenture, all of the
         rights and remedies of a secured party under the UCC (whether or not
         the UCC applies to the affected Collateral) and also may: (i) require
         the Pledgor to, and the Pledgor hereby agrees that it will at its
         expense and upon request of the Trustee forthwith, assemble all or part
         of the Collateral as directed by the Trustee and make it available to
         the Trustee at a place and time to be designated by the Trustee that is
         reasonably convenient to both parties and (ii) without notice except as
         specified below, sell the Collateral or any part thereof in one or more
         parcels at any broker's board or at public or private sale, in one or
         more sales or lots, at any of the Trustee's offices or elsewhere, for
         cash, on credit or for future delivery, and upon such other terms as
         the Trustee may deem commercially reasonable. The Pledgor agrees that,
         to the extent notice of sale shall be required by law, at least ten
         days' notice to the Pledgor of the time and place of any public sale or
         the time after which any private sale is to be made shall constitute
         reasonable notification. The Trustee shall not be obligated to make any
         sale of Collateral regardless of notice of sale having been given. The
         Trustee may adjourn any public or private sale from time to time by
         announcement at the time and place fixed therefor, and such sale may,
         without further notice, be made at the time and place to which it was
         so adjourned. The purchaser of any or all Collateral so sold shall
         thereafter hold the same absolutely, free from any claim, encumbrance
         or right of any kind

                                       11
<PAGE>
         whatsoever created by or through the Pledgor. Any sale of the
         Collateral conducted in conformity with reasonable commercial practices
         of banks, insurance companies, commercial finance companies, or other
         financial institutions disposing of property similar to the Collateral
         shall be deemed to be commercially reasonable. The Trustee or any
         Holder of Notes may, in its own name or in the name of a designee or
         nominee, buy any of the Collateral at any public sale and, if permitted
         by applicable law, at any private sale. All expenses (including court
         costs and reasonable attorneys' fees, expenses and disbursements) of,
         or incident to, the enforcement of any of the provisions hereof shall
         be recoverable from the proceeds of the sale or other disposition of
         the Collateral.

                  (b) Any cash held by or on behalf of the Trustee and all cash
         proceeds received by or on behalf of the Trustee in respect of any sale
         of, collection from, or other realization upon all or any part of the
         Collateral may, in the discretion of the Trustee, be held by the
         Trustee as collateral for, and/or then or at any time thereafter
         applied (after payment of any amounts payable to the Trustee pursuant
         to Section 12(b) of this Pledge Agreement) in whole or in part by the
         Trustee for the ratable benefit of the Holders of the Notes against,
         all or any part of the Secured Obligations in such order as the Trustee
         shall elect. Any surplus of such cash or cash proceeds held by or on
         behalf of the Trustee and remaining after payment in full of all the
         Secured Obligations shall be paid over to the Pledgor or to whomsoever
         may be lawfully entitled to receive such surplus.

                  (c) The Trustee may, without notice to the Pledgor except as
         required by law and at any time or from time to time, charge, set-off
         and otherwise apply all or any part of the Secured Obligations against
         the Pledged Account or any part thereof.

                  (d) The Pledgor agrees to (i) provide the Trustee with such
         information as may be necessary, or in the opinion of the Trustee,
         advisable to enable the Trustee to effect the sale of the Collateral
         and (ii) use its reasonable best efforts to do or cause to be done all
         such other acts and things as may be necessary to make such sale or
         sales of all or any portion of the Collateral pursuant to this Section
         13 valid and binding and in compliance with any and all other
         applicable requirements of law. The Pledgor further agrees that a
         breach of any of the covenants contained in this Section 13(d) will
         cause irreparable injury to the Trustee and the Holders of the Notes,
         that the Trustee and the Holders of the Notes have no adequate remedy
         at law in respect of such breach and, as a consequence, that each and
         every covenant contained in this Section 13(d) shall be specifically
         enforceable against the Pledgor, and the Pledgor hereby waives and
         agrees not to assert any defenses against an action for specific
         performance of such covenants except for a defense that no Event of
         Default has occurred and is continuing.

                  (e) The Pledgor acknowledges the impossibility of ascertaining
         the amount of damages that would be suffered by the Trustee or any
         Holders of the Notes by reason of the failure by the Pledgor to perform
         any of the covenants contained in Section 13(d) above and,
         consequently, agrees that, if the Pledgor shall fail to perform any of
         such covenants, it will pay, as liquidated damages and not as a
         penalty, an amount equal to the value of the Collateral on the date the
         Trustee shall demand compliance with Section 13(d) above.

<PAGE>

         SECTION 14. Security Interest Absolute. All rights of the Trustee and
the Holders of the Notes and the pledges, assignments and security interests
hereunder, and all obligations of the Pledgor hereunder, shall be irrevocable,
absolute and unconditional irrespective of, and the Pledgor hereby irrevocably
waives (to the maximum extent permitted by applicable law) any defenses it may
now have or may hereafter acquire in any way relating to, any or all of the
following:

                  (a) any lack of validity or enforceability of the Indenture or
         Notes or any other agreement or instrument relating thereto;

                  (b) any change in the time, manner or place of payment of, or
         in any other term of, all or any of the Secured Obligations, or any
         other amendment or waiver of or any consent to any departure from the
         Indenture or Notes or any other agreement or instrument relating
         thereto;

                  (c) any taking, exchange or release of, or non-perfection of
         any Liens on, any Collateral or any other collateral for all or any of
         the Secured Obligations;

                  (d) any manner of application of any Collateral or any other
         collateral, or proceeds thereof, to all or any of the Secured
         Obligations, or any manner of sale or other disposition of any
         Collateral or any other collateral for all or any of the Secured
         Obligations or any other assets of the Pledgor;

                  (e) any change, restructuring or termination of the corporate
         structure or existence of the Pledgor; or

                  (f) to the extent permitted by applicable law, any other
         circumstance (including, without limitation, any statute of
         limitations) or any existence of or reliance on any representation by
         the Trustee or any Holder of the Notes, which might otherwise
         constitute a defense available to, or a discharge of, the Pledgor in
         respect of the Secured Obligations or of this Pledge Agreement.

This Pledge Agreement shall continue to be effective or be reinstated, as the
case may be, if at any time any payment of any of the Secured Obligations is
rescinded or must otherwise be returned by the Trustee or any Holder of the
Notes or by any other Person upon the insolvency, bankruptcy or reorganization
of the Pledgor or otherwise, all as though such payment had not been made.

         SECTION 15. Amendments, Waivers and Consents. (a) No amendment or
waiver of any provision of this Pledge Agreement, and no consent to any
departure by the Pledgor from any provision of this Pledge Agreement, shall in
any event be effective unless the same shall be in writing and signed by the
Trustee, and then such waiver or consent shall be effective only in the specific
instance and for the specific purpose for which given. No failure on the part of
the Trustee or any Holder of the Notes to exercise, and no delay in exercising
any right hereunder, shall operate as a waiver thereof; nor shall any single or
partial exercise of any such right preclude any other or further exercise
thereof or the exercise of any other right.


                                       13
<PAGE>
         SECTION 16. Notices. Any notice or communication given hereunder shall
be sufficiently given if in writing and delivered in person or mailed by first
class mail, commercial courier service or telecopier communication, addressed as
follows; or, as to any party, at such other address as shall be designated by
such party in a written notice to the other parties:

            if to the Pledgor:

                  Regeneron Pharmaceuticals, Inc.
                  777 Old Saw Mill River Road
                  Tarrytown, New York  10591
                  Fax:  (914) 345-7721
                  Attention:  Stuart Kolinski

                  with a copy to:

                  Skadden, Arps, Slate, Meagher & Flom LLP
                  Four Times Square
                  New York, New York 10036
                  Fax:  (212) 735-2000
                  Attention:  Matthew J. Mallow

            if to the Trustee:

                  American Stock Transfer & Trust Company
                  59 Maiden Lane
                  New York, New York  10038
                  Attn: Corporate Trust Department
                  Fax:  (718) 331-1852

All such notices and other communications shall, when mailed, delivered or
telecopied, respectively, be effective when deposited in the mails, delivered or
telecopied, respectively, addressed as aforesaid.

         SECTION 17. Continuing Security Interest. This Pledge Agreement shall
create a continuing security interest in the Collateral and (a) shall, unless
otherwise provided in this Pledge Agreement, remain in full force and effect
until the payment in full in cash of the Secured Obligations, (b) be binding
upon the Pledgor, its successors and assigns and (c) inure, together with the
rights and remedies of the Trustee hereunder, to the benefit of the Trustee and
the Holders of the Notes and their respective successors, transferees and
assigns.

         SECTION 18. Termination. So long as no Event of Default shall have
occurred and be continuing, this Pledge Agreement (other than Pledgor's
obligations under Section 12 hereof) shall terminate upon the earlier of (i) the
redemption of the Notes in whole, (ii) the payment in full of each of the first
six scheduled interest payments on the Notes when due, or (iii) the discharge of
the Indenture. Upon any such termination, without any necessary action on the
part of the Pledgor, (i) the Control Agreement(s) will terminate and control of
the Pledged Account and the Pledged Security Entitlements shall revert to the
Pledgor, (ii) the Trustee shall


                                       14
<PAGE>
promptly obtain from the Account Holder and deliver to the Pledgor all
certificates and instruments representing any portion of the Pledged Financial
Assets constituting certificated securities and (iii) the Trustee shall no
longer have any rights in any of the Collateral.

         SECTION 19. Miscellaneous Provisions.

         Section 19.1. No Adverse Interpretation of Other Agreements. This
Pledge Agreement may not be used to interpret another pledge, security or debt
agreement of the Pledgor or any subsidiary thereof. No such pledge, security or
debt agreement (other than the Indenture) may be used to interpret this Pledge
Agreement.

         Section 19.2. Severability. The provisions of this Pledge Agreement are
severable, and if any clause or provision shall be held invalid, illegal or
unenforceable in whole or in part in any jurisdiction, then such invalidity or
unenforceability shall affect in that jurisdiction only such clause or
provision, or part thereof, and shall not in any manner affect such clause or
provision in any other jurisdiction or any other clause or provision of this
Pledge Agreement in any jurisdiction.

         Section 19.3. Headings. The headings in this Pledge Agreement have been
inserted for convenience of reference only, are not to be considered a part
hereof and shall in no way modify or restrict any of the terms or provisions
hereof.

         Section 19.4. Counterpart Originals. This Pledge Agreement may be
signed in two or more counterparts, each of which shall be deemed an original,
but all of which shall together constitute one and the same agreement. Delivery
of an executed counterpart of a signature page to this Pledge Agreement by
telecopier shall be effective as delivery of an original executed counterpart of
this Pledge Agreement.

         Section 19.5. Benefits of Pledge Agreement. Nothing in this Pledge
Agreement, express or implied, shall give to any person, other than the parties
hereto and their successors hereunder, and the Holders of the Notes and the
Account Holder, any benefit or any legal or equitable right, remedy or claim
under this Pledge Agreement.

         Section 19.6. Interpretation of Agreement. To the extent a term or
provision of this Pledge Agreement conflicts with the Indenture, the Indenture
shall control with respect to the subject matter of such term or provision.
Acceptance of or acquiescence in a course of performance rendered under this
Pledge Agreement shall not be relevant to determine the meaning of this Pledge
Agreement even though the accepting or acquiescing party had knowledge of the
nature of the performance and opportunity for objection.

         Section 19.7. Survival of Representations and Covenants. All
representations, warranties and covenants of the Pledgor contained herein shall
survive the execution and delivery of this Pledge Agreement, and shall terminate
only upon the termination of this Pledge Agreement, except as otherwise
specified in such representatives, warranties and covenants.

         Section 19.8. Waivers. The Pledgor waives presentment and demand for
payment of any of the Obligations, protest and notice of dishonor or default
with respect to any


                                       15
<PAGE>
of the Obligations, and all other notices to which the Pledgor might otherwise
be entitled, except as otherwise expressly provided herein or in the Indenture.

         Section 19.9. Authority of the Trustee. (a) The Trustee shall have and
be entitled to exercise all powers hereunder that are specifically granted to
the Trustee by the terms hereof, together with such powers as are reasonably
incident thereto. The Trustee may perform any of its duties hereunder or in
connection with the Collateral by or through agents or employees and shall be
entitled to retain counsel and to act in reliance upon the advice of counsel
concerning all such matters. Except as otherwise expressly provided in this
Pledge Agreement or the Indenture, neither the Trustee nor any director,
officer, employee, attorney or agent of the Trustee shall be liable to the
Pledgor for any action taken or omitted to be taken by the Trustee, in its
capacity as Trustee, hereunder, except for its own bad faith, gross negligence
or willful misconduct, and the Trustee shall not be responsible for the
validity, effectiveness or sufficiency hereof or of any document or security
furnished pursuant hereto. The Trustee and its directors, officers, employees,
attorneys and agents shall be entitled to rely on any communication, instrument
or document believed by it or them to be genuine and correct and to have been
signed or sent by the proper person or persons.

         (b) The Pledgor acknowledges that the rights and responsibilities of
the Trustee under this Pledge Agreement with respect to any action taken by the
Trustee or the exercise or non-exercise by the Trustee of any option, right,
request, judgment or other right or remedy provided for herein or resulting or
arising out of this Pledge Agreement shall, as between the Trustee and the
Holders of the Notes, be governed by the Indenture and by such other agreements
with respect thereto as may exist from time to time among them, but, as between
the Trustee and the Pledgor, the Trustee shall be conclusively presumed to be
acting as agent for the Holders of the Notes with full and valid authority so to
act or refrain from acting, and the Pledgor shall not be obligated or entitled
to make any inquiry respecting such authority.

         Section 19.10. Final Expression. This Pledge Agreement, together with
the Indenture and any other agreement executed in connection herewith, is
intended by the parties as a final expression of this Pledge Agreement and is
intended as a complete and exclusive statement of the terms and conditions
thereof.

         Section 19.11. Rights of Holders of the Notes. No Holder of Notes shall
have any independent rights hereunder other than those rights granted to
individual Holders of the Notes pursuant to Section 6.06 of the Indenture;
provided that nothing in this subsection shall limit any rights granted to the
Trustee under the Notes or the Indenture.

         Section 19.12. Governing Law; Submission to Jurisdiction; Waiver of
Jury Trial; Waiver of Damages. (a) This pledge agreement shall be governed by,
and construed in accordance with, the laws of the state of New York.

         (b) The Pledgor agrees that the Trustee shall, in its capacity as
trustee or in the name and on behalf of any Holder of Notes, have the right, to
the extent permitted by applicable law, to proceed against the Pledgor or the
Collateral in a court in any location reasonably selected in good faith (and
having personal or in rem jurisdiction over the Pledgor or the Collateral, as
the case may be) to enable the Trustee to realize on the Collateral, or to
enforce a


                                       16
<PAGE>
judgment or other court order entered in favor of the Trustee. The Pledgor
agrees that it will not assert any counterclaims, setoffs or crossclaims in any
proceeding brought by the Trustee to realize on such property or to enforce a
judgment or other court order in favor of the Trustee, except for such
counterclaims, setoffs or crossclaims which, if not asserted in any such
proceeding, could not otherwise be brought or asserted. The Pledgor waives any
objection that it may have to the location of the court in the city of New York
once the Trustee has commenced a proceeding described in this paragraph
including, without limitation, any objection to the laying of venue or based on
the grounds of forum non conveniens.

         (c) The Pledgor agrees that neither any Holder of Notes nor (except as
otherwise provided in this Pledge Agreement or the Indenture) the Trustee in its
capacity as trustee shall have any liability to the Pledgor (whether arising in
tort, contract or otherwise) for losses suffered by the Pledgor in connection
with, arising out of, or in any way related to, the transactions contemplated
and the relationship established by this Pledge Agreement, or any act, omission
or event occurring in connection therewith, unless it is determined by a final
and nonappealable judgment of a court that is binding on the Trustee or such
Holder of Notes, as the case may be, that such losses were the result of acts or
omissions on the part of the Trustee or such Holders of Notes, as the case may
be, constituting bad faith, gross negligence or willful misconduct.

         (d) To the extent permitted by applicable law, the Pledgor waives the
posting of any bond otherwise required of the Trustee or any Holder of Notes in
connection with any judicial process or proceeding to enforce any judgment or
other court order pertaining to this Pledge Agreement or any related agreement
or document entered in favor of the Trustee or any Holder of Notes, or to
enforce by specific performance, temporary restraining order or preliminary or
permanent injunction, this Pledge Agreement or any related agreement or document
between the Pledgor on the one hand and the Trustee and/or the Holders of the
Notes on the other hand.

            [The remainder of this page intentionally left blank.]


                                       17
<PAGE>
            IN WITNESS WHEREOF, the Pledgor and the Trustee have each caused
this Pledge Agreement to be duly executed and delivered as of the date first
above written.

                                    Pledgor:

                                    REGENERON PHARMACEUTICALS, INC.



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



                                    Trustee:

                                    AMERICAN STOCK TRANSFER & TRUST
                                       COMPANY, as Trustee



                                    By:
                                          ------------------------------------
                                       Name:
                                       Title:
<PAGE>
                                   SCHEDULE I

                            Pledged Financial Assets



<TABLE>
<CAPTION>
        Security                Coupon Date                  CUSIP No.
        --------                -----------                  ---------
<S>                             <C>                          <C>
       B 4/11/02                 04/17/2002                  912795JP7
      SP 08/15/02                10/17/2002                  912820BE6
      SP 02/15/03                04/17/2003                  912820BF3
      SP 08/15/03                10/17/2003                  912820BG1
      SP 02/15/04                04/17/2003                  912820BH9
      SP 08/15/04                10/17/2004                  912820BK2
</TABLE>
<PAGE>
                                                                         ANNEX A

                                CONTROL AGREEMENT


            This CONTROL AGREEMENT (the "Agreement") dated as of October 17,
2001 by and among Regeneron Pharmaceuticals, Inc. (the "Pledgor") and American
Stock Transfer & Trust Company, a New York corporation with trust power, in its
capacity as trustee (the "Trustee") and The Bank of New York, a New York banking
corporation, in its capacity as securities intermediary and depository bank (the
"Account Holder").

PRELIMINARY STATEMENTS:

         (1) The Pledgor has granted the Trustee a security interest (the
"Security Interest") in certain security entitlements (the "Pledged Security
Entitlements") with respect to certain U.S. Treasury securities (the "Pledged
Financial Assets") identified on Schedule I attached hereto maintained by the
Trustee with the Account Holder and carried from time to time in an account with
the Account Holder, ABA No. 021000018, Account No. 303640 at its office at 101
Barclay Street, New York, New York 10286, in the name of "American Stock
Transfer and Trust Company, as Trustee for the benefit of the holders of the
5-1/2% Convertible Senior Subordinated Notes due 2008 of Regeneron
Pharmaceuticals, Inc., Collateral Pledge Account" (the "Pledged Account") and
all additions thereto and substitutions and proceeds thereof (collectively, the
"Collateral"), pursuant to, and as more particularly described in, a Pledge
Agreement dated as of October 17, 2001, among the Pledgor and the Trustee (as
the same may hereafter be amended, supplemented or otherwise modified from time
to time, the "Pledge Agreement"; terms defined in the Pledge Agreement and not
otherwise defined herein are used herein as therein defined). The Pledgor
acknowledges having received value for such pledge of the Collateral.

         (2) Terms defined in Article 8 or 9 of the Uniform Commercial Code as
in effect in the State of New York (the "UCC") are used in this Agreement
(including, without limitation, paragraph (1) above) as such terms are defined
in such Article 8 or 9.

         (3) The Pledgor, the Trustee and the Account Holder are delivering this
Agreement pursuant to the terms of the Pledge Agreement.

         NOW, THEREFORE, in consideration of the premises and mutual agreements
contained herein, the parties hereto hereby agree as follows:

         SECTION 1. Notice of Exclusive Control. The Pledgor and Trustee are
entering into this Agreement to perfect, and confirm the first priority lien of,
the Trustee's security interest in the Collateral. The Account Holder agrees to
promptly make all necessary entries or notations in its books and records to
reflect the Trustee's security interest in the Collateral and to apply any value
distributed on account of any Pledged Financial Assets as directed in writing by
the Trustee without further consent from the Pledgor. The Account Holder
acknowledges that the Trustee has exclusive control over the Pledged Account and
all Pledged Security Entitlements contained therein from time to time.
<PAGE>
         SECTION 2. The Account. The Account Holder represents and warrants to,
and agrees with, the Pledgor and the Trustee and the Holders of the Notes that:

                  (a) The Account Holder has established the Pledged Account and
         shall not change the name or account number of the Pledged Account
         without the prior written consent of the Trustee.

                  (b) The Account Holder maintains the Pledged Account for the
         Trustee, and all property (including, without limitation, all funds and
         financial assets) held by the Account Holder for the account of the
         Trustee is, and will continue to be, credited to the Pledged Account.

                  (c) To the extent that funds are credited to the Pledged
         Account, the Pledged Account is a deposit account; and to the extent
         that financial assets are credited to the Pledged Account, the Pledged
         Account is a securities account. The Account Holder is (i) the bank
         with which the Pledged Account is maintained and (ii) the securities
         intermediary with respect to financial assets held in the Pledged
         Account. The Trustee is (x) the Account Holder's customer with respect
         to the Pledged Account and (y) the entitlement holder with respect to
         financial assets credited from time to time to the Pledged Account.

                  (d) All financial assets in registered form or payable to or
         to the order of and credited to the Pledged Account shall be registered
         in the name of, payable to or to the order of, or endorsed to, the
         Account Holder and in no case during the term of the Pledge Agreement
         will any financial asset credited to the Pledged Account be registered
         in the name of, payable to or to the order of, or endorsed to, the
         Pledgor, except to the extent the foregoing have been subsequently
         endorsed by the Pledgor to the Account Holder or in blank.

                  (e) Notwithstanding any other agreement to the contrary, the
         Account Holder's jurisdiction with respect to the Pledged Account for
         purposes of the UCC is, and will continue to be for so long as the
         Security Interest shall be in effect, the State of New York.

                  (f) The Account Holder does not know of any claim to or
         interest in the Pledged Account or any property (including, without
         limitation, all funds and financial assets) credited to the Pledged
         Account, except for claims and interests of the parties referred to in
         this Agreement.

         SECTION 3. Control by Trustee. (a) The Account Holder will comply with
(A) all written instructions directing disposition of the funds in the Pledged
Account (such instructions, a "Payment Order"), (B) all notifications and
entitlement orders that the Account Holder receives directing it to transfer or
redeem any financial asset in the Pledged Account and (C) all other directions
concerning the Collateral, including, without limitation, directions to
distribute to the Trustee proceeds of any such transfer or redemption or
interest on any property in the Pledged Account (any such instruction,
notification or direction referred to in clause (A),
<PAGE>
(B) or (C) above being an "Account Direction"), in each case of clauses (A), (B)
and (C) above originated by the Trustee without further consent by the Pledgor
or any other person.

         (b) The Trustee hereby acknowledges that it shall maintain and exercise
control of the Pledged Account on behalf of the Holders of the Notes.

         (c) The Account Holder will not (i) comply with Account Directions or
other directions concerning the Collateral originated by the Pledgor or (ii)
distribute to the Pledgor interest or other distributions on or in respect of
the Collateral.

         SECTION 4. Priority of Trustee's Security Interest. (a) The Account
Holder (i) subordinates to the Security Interest and in favor of the Trustee any
security interest, lien, or right of setoff the Account Holder may have, now or
in the future, against the Pledged Account or property in the Pledged Account,
and (ii) agrees that it will not exercise any right in respect of any such
security interest or lien or any such right of setoff until the Security
Interest is terminated, except that the Account Holder will retain its prior
lien on property in the Pledged Account to secure payment for property purchased
for the Pledged Account and normal commissions and fees for the Pledged Account.

         (b) The Account Holder will not enter into any other agreement with any
Person relating to Account Directions or other directions with respect to the
Pledged Account.

         SECTION 5. Statements, Confirmations, and Notices of Adverse Claims.
(a) The Account Holder will send copies of all statements and confirmations for
the Pledged Account simultaneously to the Pledgor and the Trustee.

         (b) When the Account Holder knows of any claim or interest in the
Pledged Account or any property credited to the Pledged Account other than the
claims and interests of the parties referred to in this Agreement, the Account
Holder will promptly notify the Trustee and the Pledgor of such claim or
interest.

         SECTION 6. The Account Holder's Responsibility. (a) The Account Holder
will not be liable to the Pledgor or the Trustee or the Holders of the Notes for
complying with an Account Direction or other direction concerning the Collateral
originated by the Trustee, even if the Pledgor notifies the Account Holder that
the Trustee is not legally entitled to issue the Account Direction or such other
direction unless the Account Holder takes the action after it is served with an
injunction, restraining order, or other legal process enjoining it from doing
so, issued by a court of competent jurisdiction, and had a reasonable
opportunity to act on the injunction, restraining order or other legal process.

         (b) This Agreement does not create any obligation of the Account Holder
except for those expressly set forth in this Agreement and in Part 5 of Article
8 of the UCC and in Article 4 of the UCC. In particular, the Account Holder need
not investigate whether the Trustee is entitled under the Trustee's agreements
with the Pledgor to give an Account Direction or other direction concerning the
Pledged Account. The Account Holder may conclusively rely on notices and
communications it believes given by the appropriate party.
<PAGE>
         (c) In no event shall the Account Holder or any of its affiliates,
shareholders, directors, officers, employees or agents be liable for indirect,
special, punitive, incidental or consequential damages of any kind whatsoever
even if advised of the possibility of such damages, other than such damages
caused by its own bad faith, gross negligence or willful misconduct.

         (d) Without limiting the foregoing, and notwithstanding any provision
to the contrary elsewhere, the Account Holder and its affiliates, shareholders,
directors, officers, employees or agents:

                  (i) shall have no responsibilities, obligations or duties in
         respect of the subject matter hereof other than those expressly set
         forth in this Agreement, and no implied duties, responsibilities,
         covenants or obligations shall be read into this Agreement against the
         Account Holder. Without limiting the foregoing, the Account Holder
         shall have no duty or authority to determine and/or investigate whether
         or not an event of default exists under any agreement between the
         Pledgor and the Trustee, or to determine and/or investigate whether or
         not the Trustee is entitled to give any Account Direction with respect
         to the Collateral;

                  (ii) may in any instance where the Account Holder determines
         that it lacks or is uncertain as to its authority to take or refrain
         from taking certain action hereunder, or as to any of the requirements
         of this Agreement under the circumstance before it, delay or refrain
         from taking any action unless and until it shall have received
         appropriate written instructions from the Trustee or advice from legal
         counsel selected by it (or other appropriate advisor), as the case may
         be, detailing the action required to be taken hereunder and the Account
         Holder may rely conclusively on any such instructions or advice;

                  (iii) so long as it and they shall have acted (or refrained
         from acting) in good faith and within the reasonable belief that such
         action or omission is duly authorized or within the discretion or
         powers granted to it hereunder, shall not be responsible or liable for
         any error of judgment in any action taken, suffered or omitted by it or
         them, or for any act done or step taken or omitted, or for any mistake
         of fact or law, unless such action constitutes gross negligence or
         willful misconduct as finally determined by a non-appealable judgment
         of a court of competent jurisdiction on its (or their) part;

                  (iv) will not be responsible or liable to the Pledgor, the
         Trustee, or any other person or entity whatsoever for the due
         execution, legality, validity, enforceability, genuineness,
         effectiveness or sufficiency of this Agreement (provided, however, that
         the Account Holder warrants that the Account Holder has legal capacity
         and has been duly authorized to enter into this Agreement) or for any
         statement, warranty or representation made by any other party in
         connection with this Agreement;

                  (v) will not incur any responsibility or liability by acting
         or not acting in reliance upon advice of counsel, or upon any notice,
         consent, certificate, instruction, Account Direction, statement, wire
         instruction, telecopy or other writing reasonably and
<PAGE>
         in good faith believed by it or them to be genuine and in conformance
         with this Agreement and signed or sent by the proper party or parties
         and contemplated herein;

                  (vi) shall not be required to expend or risk its or their own
         funds, or to take any action (including the institution or defense of
         legal proceedings) which in its or their reasonable judgment may cause
         it or them to incur or suffer any expense or liability, unless the
         Account Holder shall have been provided with security or indemnity,
         acceptable to Account Holder in its sole discretion, for the payment of
         the costs, expenses (including reasonable attorneys' fees) and
         liabilities which may be incurred therein or thereby.

         (e) If any Collateral subject to this Agreement is at any time attached
or levied upon, or in case the transfer or delivery of any such Collateral shall
be stayed or enjoined, or in the case of any other legal process or judicial
order affecting such Collateral, the Account Holder is authorized to comply with
any such order in any manner as the Account Holder or its legal counsel
reasonably deems appropriate. The Account Holder shall give prompt written
notice to the Pledgor and the Trustee of any such attachment, levy, stay,
injunction or legal process. If the Account Holder complies with any process,
order, writ, judgment or decree relating to the Collateral subject to this
Agreement, then the Account Holder shall not be liable or responsible to the
Pledgor, the Trustee, or any other person or entity whatsoever even if such
order, writ, judgment, decree or process is subsequently modified, vacated or
otherwise determined to have been without legal force or effect.

         (f) The Account Holder shall not be liable or responsible for any
delays or failures in performance of any of its duties hereunder which result
from events or conditions beyond its reasonable control and so long as the same
exist or continue and cannot reasonably be remedied by the Account Holder in
accordance with its normal business practices. Such events or conditions shall
include, but shall not be limited to, acts of God, strikes, lockouts, riots,
acts of war or terrorism, epidemics, nationalization, expropriation, currency
restrictions, governmental regulations superimposed after the fact, fire,
communication line failures (including the unavailability of the Federal Reserve
Bank wire or telex or other wire or communication facility), power failures,
earthquakes or other disasters.


         SECTION 7. Indemnity. The Pledgor will indemnify the Account Holder,
its officers, directors, employees and agents against claims, liabilities and
expenses arising out of this Agreement (including, without limitation,
reasonable attorney's fees and disbursements), except to the extent the claims,
liabilities or expenses are caused by the Account Holder's gross negligence or
willful misconduct as found by a court of competent jurisdiction in a final,
non-appealable judgment.

         SECTION 8. Termination; Survival. (a) This Agreement shall terminate
automatically upon receipt by the Account Holder of written notice executed by
two officers of the Trustee that (i) all of the Secured Obligations have been
paid in full in cash or otherwise satisfied or (ii) all of the Collateral has
been released, which ever is earlier, and the Account Holder shall thereafter be
relieved of all duties and obligations hereunder. The Account Holder may
terminate this Agreement on 60 days' prior notice to the Trustee and the
Pledgor, provided
<PAGE>
that before such termination the Account Holder and the Pledgor shall make
arrangements to transfer the property in the Pledged Account to another
securities intermediary that shall have executed, together with the Trustee and
the Pledgor, a control agreement in favor of the Trustee and the Holders of the
Notes in respect of such property in substantially the form of this Agreement or
otherwise in form and substance satisfactory to the Trustee.

         (b) In the event that the Trustee no longer serves as Trustee for the
Collateral, the Trustee, the Account Holder and the Pledgor shall make
arrangements for another Person to assume the rights and obligations of the
Trustee hereunder, and such Person shall have executed, together with the
Account Holder and the Pledgor, a control agreement in favor of such Person and
the Holders of the Notes in substantially the form of this Agreement or
otherwise in form and substance satisfactory to the Trustee.

         (c) Sections 7 and 8 will survive termination of this Agreement.

         SECTION 9. Conflict with Other Agreements. (a) In the event of any
conflict between this Agreement (or any portion thereof) and any other agreement
now existing or hereafter entered into, the terms of this Agreement shall
prevail;

            (b) No amendment or modification of this Agreement or waiver of any
right hereunder shall be binding on any party hereto unless it is in writing and
is signed by all of the parties hereto;

            (c)  The Account Holder hereby confirms and agrees that:

                  (i) There are no other agreements entered into between the
         Account Holder and the Pledgor with respect to the Pledged Account;

                  (ii) It has not entered into, and until the termination of the
         this Agreement will not enter into, any agreement with any other person
         relating to the Pledged Account and/or any financial assets credited
         thereto pursuant to which it has agreed to comply with entitlement
         orders (as defined in Section 8-102(a)(8) of the UCC) of such other
         person; and

                  (iii) It has not entered into, and until the termination of
         this Agreement will not enter into, any agreement with the Pledgor or
         the Trustee purporting to limit or condition the obligation of the
         Account Holder to comply with Account Directions as set forth in
         Section 3 hereof.


         SECTION 10. Permitted Investments. In accordance with the Pledge
Agreement, the Trustee shall direct the Account Holder with respect to the
selection of investments to be made with the funds in the Pledged Account.

         SECTION 11. Entire Agreement. This Agreement is the entire agreement,
and supersedes any prior agreements, and contemporaneous oral agreements, of the
parties
<PAGE>
concerning its subject matter. The Trustee and the Account Holder shall be
entitled to all the rights, benefits, privileges and immunities accorded to the
Trustee under the Indenture.

         SECTION 12. Amendments. No modification, amendment or waiver of, nor
consent to any departure by any party from, any provision of this Agreement will
be effective unless made in writing signed by the parties hereto, and then such
waiver or consent shall be effective only in the specific instance and for the
purpose for which given.

         SECTION 13. Financial Assets. The Account Holder agrees with Trustee
and the Pledgor that, to the fullest extent permitted by applicable law, all
property credited from time to time to the Pledged Account will be treated as
financial assets under Article 8 of the UCC.

         SECTION 14. Notices. All notices, demands, requests, consents,
approvals and other communications required or permitted hereunder must be in
writing and will be effective upon receipt if delivered personally, or if sent
by facsimile transmission with confirmation of delivery, or by nationally
recognized overnight courier service, to the Pledgor's and the Trustee's
addresses as set forth in the Pledge Agreement, and to the Account Holder's
address as set forth below, or to such other address as any party may give to
the others in writing for such purpose.

         SECTION 15. Binding Effect. This Agreement shall become effective when
it shall have been executed by the Pledgor, the Trustee and the Account Holder,
and thereafter shall be binding upon and inure to the benefit of the Pledgor,
the Trustee and the Account Holder and their respective successors and assigns.

         SECTION 16. Execution in Counterparts. This Agreement may be executed
in any number of counterparts and by different parties hereto in separate
counterparts, each of which when so executed shall be deemed to be an original
and all of which taken together shall constitute one and the same agreement.
Delivery of an executed counterpart of a signature page to this Agreement by
telecopier shall be effective as delivery of an original executed counterpart of
this Agreement.

         SECTION 17. Governing Law and Jurisdiction. THIS AGREEMENT WILL BE
GOVERNED BY, AND CONSTRUED IN ACCORDANCE WITH, THE LAWS OF THE STATE OF NEW
YORK. Each of the parties hereby irrevocably submits for itself and its property
in any legal action or proceeding relating to this Agreement, or for recognition
and enforcement of any judgment in respect thereof, to the non-exclusive general
jurisdiction and venue of the courts of the State of New York, the courts of the
United States of America in New York, and appellate courts from any thereof.

         SECTION 18. WAIVER OF JURY TRIAL. EACH OF THE PARTIES HERETO
IRREVOCABLY WAIVES ANY AND ALL RIGHT IT MAY HAVE TO A TRIAL BY JURY IN ANY
ACTION, PROCEEDING OR CLAIM (WHETHER BASED ON CONTRACT, TORT OR OTHERWISE) OF
ANY NATURE RELATING TO THIS AGREEMENT, ANY DOCUMENTS EXECUTED IN CONNECTION WITH
THIS AGREEMENT OR ANY TRANSACTION CONTEMPLATED IN ANY OF SUCH DOCUMENTS. EACH
PARTY HERETO ACKNOWLEDGES THAT THE FOREGOING WAIVER IS KNOWING AND VOLUNTARY.
<PAGE>
            IN WITNESS WHEREOF, the parties hereto have caused this Agreement to
be executed by their respective officers thereunto duly authorized, as of the
date first above written.

                                    Pledgor:

                                    REGENERON PHARMACEUTICALS, INC.



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



                                    Trustee:

                                    AMERICAN STOCK TRANSFER & TRUST
                                       COMPANY, as Trustee



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


                                    Account Holder:

                                    THE BANK OF NEW YORK,
                                       as Account Holder


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

                                    Address:
                                    101 Barclay Street
                                    New York, New York 10286
                                    Attn:  Ming Shiang
                                    Fax:  (212) 896-7298
<PAGE>
                                   SCHEDULE I

                            Pledged Financial Assets


<TABLE>
<CAPTION>
        Security                Coupon Date                  CUSIP No.
        --------                -----------                  ---------
<S>                             <C>                          <C>
       B 4/11/02                 04/17/2002                  912795JP7
      SP 08/15/02                10/17/2002                  912820BE6
      SP 02/15/03                04/17/2003                  912820BF3
      SP 08/15/03                10/17/2003                  912820BG1
      SP 02/15/04                04/17/2003                  912820BH9
      SP 08/15/04                10/17/2004                  912820BK2
</TABLE>