Exhibit 10.24

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                            STOCK PURCHASE AGREEMENT

                                 By and Between

                               NOVARTIS PHARMA AG

                                       AND

                         REGENERON PHARMACEUTICALS, INC.

                           Dated as of March 28, 2003

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                            STOCK PURCHASE AGREEMENT

                  THIS STOCK PURCHASE AGREEMENT ("Agreement"), dated as of March
28, 2003, by and between NOVARTIS PHARMA AG (the "Investor"), a corporation
organized under the laws of Switzerland, with its principal place of business at
Lichtstrasse 35, 4056 Basel, Switzerland, and REGENERON PHARMACEUTICALS, INC.
(the "Company"), a corporation organized under the laws of New York with its
principal place of business at 777 Old Saw Mill Road, Tarrytown, New York,
U.S.A.

                  WHEREAS, concurrently with the execution of this Agreement,
the Investor and the Company have entered into a Collaboration, License and
Option Agreement (the "Collaboration Agreement") and a Registration Rights
Agreement (the "Registration Rights Agreement, and together with the
Collaboration Agreement, the "Transaction Agreements"); and

                  WHEREAS, it is contemplated by the Collaboration Agreement
that the Investor purchases, and the Company issues and sells to the Investor,
shares of common stock of the Company pursuant to the terms and conditions of
this Agreement.

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

                                    ARTICLE I

                                   DEFINITIONS

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

                  "Adjustment Period Termination Date" shall mean the thirtieth
trading day immediately succeeding the date hereof.

                  "Business Day" shall mean any day other than a Saturday or
Sunday or a day on which banks located in New York, New York or Basel,
Switzerland are authorized or required by law to close.

                  "Draft Form 10-K" shall mean the draft of the Company's Form
10-K, dated March 4, 2003, for the year ended December 31, 2002, provided to the
Investor by the Company as amended by the substitution of page 14 thereof by a
document delivered to the Investor on March 26, 2003.

                  "Governmental Authority" shall mean any federal, state,
municipal, local, provincial, regional governmental authority in the United
States or other political subdivision thereof and any Person exercising
executive, legislative, judicial regulatory or administrative functions of or
pertaining to government.



                  "Material Adverse Effect" shall mean any events, occurrences
or circumstances which give rise to or would reasonably be expected to give rise
to, individually or in the aggregate, a material adverse effect on (i) the
business, properties, financial condition or results of operations of the
Company, or (ii) the ability of the Company to comply with its obligations under
the Transaction Agreements.

                  "Per Share Price" shall mean the average closing price per
share of the Company's common stock as quoted in the Wall Street Journal on each
trading day during the period commencing on the eleventh trading day immediately
succeeding the date hereof and ending on (and including) the Adjustment Period
Termination Date.

                  "Person" shall mean and include an individual, a partnership,
a joint venture, a corporation, a limited liability company, a limited liability
partnership, a trust, an incorporated organization and a Governmental Authority.

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



         Defined Term              Section             Defined Term             Section
         ------------              -------             ------------             -------
                                                                      
Agreement                        Preamble      Indemnified Parties             6.2
ANDA                             3.16(a)       Indemnifying Party              6.2
Axokine Press Release            6.13(b)       Intellectual Property           3.14(a)(i)
BLA                              3.16(a)       IND                             3.16(a)
Closing                          2.2           Investor                        Preamble
Closing Date Stock               2.1           NDA                             3.16(a)
Collaboration Agreement          Preamble      Organizational Documents        3.1
Company                          Preamble      Purchase Price                  2.1
Company Intellectual Property    3.14(a)(ii)   Purchased Stock                 2.4(a)
Company SEC Documents            3.11          Registration Rights Agreement   Preamble
FDA                              3.16(b)       Securities Act                  3.2(b)
GCP                              3.16(b)       Severed Clause                  6.12
GLP                              3.16(c)       Transaction Agreements          Preamble


                  Section 1.3       Construction. In this Agreement, unless the
context otherwise requires:

                  (a)      any reference in this Agreement to "writing" or
comparable expressions includes a reference to facsimile transmission or
comparable means of communication;

                  (b)      words expressed in the singular number shall include
the plural and vice versa, words expressed in the masculine shall include the
feminine and neuter gender and vice versa;

                  (c)      references to Articles and Sections are references to
articles and sections of this Agreement;



                  (d)      reference to "day" or "days" are to calendar days;

                  (e)      this "Agreement" or any other agreement or document
shall be construed as a reference to this Agreement or, as the case may be, such
other agreement or document as the same may have been, or may from time to time
be, amended, varied, novated or supplemented; and

                  (f)      "include," "includes," and "including" are deemed to
be followed by "without limitation" whether or not they are in fact followed by
such words or words of similar import.

                  Section 1.4       Knowledge. Where any representation or
warranty contained in this Agreement is expressly qualified by reference to the
knowledge of the Company, the Company confirms that it has made due and diligent
inquiry as to the matters that are the subject of such representations and
warranty.

                                   ARTICLE II

                        PURCHASE AND SALE OF COMMON STOCK

                  Section 2.1       Issuance of Common Stock. Subject to the
terms and conditions hereof, on the date hereof, the Company agrees to issue and
sell to the Investor, and the Investor agrees to purchase, 2,400,000 shares of
its common stock (the "Closing Date Stock") for an aggregate purchase price of
$48,000,000 (the "Purchase Price"), such number of shares of its common stock to
be adjusted pursuant to Section 2.4

                  Section 2.2       Closing. The purchase and sale of the
Purchased Stock (the "Closing") shall occur on the date hereof at the Company's
offices at 777 Old Saw Mill Road, Tarrytown, New York.

                  Section 2.3       Delivery. The Company shall deliver to the
Investor a stock certificate, registered in the Investor's name, representing
the Purchased Stock, against payment of the Purchase Price by certified or
cashier's check payable to the Company, or by wire transfer of same day funds to
the Company's bank account as follows:

                  Beneficiary Name:              [*  *  *  *]
                  Beneficiary Address:           [*  *  *  *]

                  Account Number:                [*  *  *  *]
                  Bank Name:                     [*  *  *  *]
                  Bank Address:                  [*  *  *  *]

                  Bank Clearing Number:          [*  *  *  *]

                  Section 2.4       Determination of Purchased Stock.



                  (a)      In the event that the number of shares of common
stock of the Company which is equal to the nearest whole number that is obtained
by dividing $48,000,000 by the Per Share Price is (x) less than the number of
shares of Closing Date Stock, the Investor shall promptly, but in no event later
than the thirty-fifth trading day immediately succeeding the date hereof,
deliver to the Company an amount of shares of common stock of the Company that
is equal to such deficiency, or (y) greater than the number of shares of Closing
Date Stock, the Company shall promptly, but in no event later than the
thirty-fifth trading day immediately succeeding the date hereof, issue and
deliver to the Investor, an amount of shares of common stock of the Company that
is equal to such excess, provided, however that the aggregate amount of the
Company's common stock issued to the Investor pursuant to Section 2.1 and this
subsection (y) shall in no event exceed 19.9% of the issued and outstanding
common stock of the Company as of the date hereof. The Closing Date Stock, as
adjusted pursuant to this Section 2.4, is referred to herein as the "Purchased
Stock").

                  (b)      For the purposes of determining the number of shares
of Purchased Stock required to be delivered pursuant to Section 2.4(a),
adjustment shall be made in the event of any stock split, stock dividend,
reverse stock split, recapitalization or the like that occurs between the
Closing and the Adjustment Period Termination Date.

                                  ARTICLE III

                  REPRESENTATIONS AND WARRANTIES OF THE COMPANY

                  The Company hereby represents and warrants to the Investor as
follows:

                  Section 3.1       Organization, Good Standing and
Qualification. The Company is a corporation duly organized, validly existing and
in good standing under the laws of the State of New York. The Company has all
requisite corporate power and corporate authority to own and operate its
properties and assets, to carry on its business as now conducted, to enter into
the Transaction Agreements, to issue and sell the Purchased Stock and to carry
out the other transactions contemplated under the Transaction Agreements. The
Company is qualified to transact business and is in good standing in each
jurisdiction in which the character of the properties owned, leased or operated
by the Company or the nature of the business conducted by the Company makes such
qualification necessary, except where the failure to be so qualified would not
have a Material Adverse Effect. The Company has delivered to the Investor true,
correct and complete copies of the Company's Restated Certificate of
Incorporation and the Company's By-laws (together, the "Organizational
Documents") as in effect on the date hereof.

                  Section 3.2       Capitalization and Voting Rights.

                  (a)      The authorized capital of the Company as of March 26,
2003 consists of: (i) 160,000,000 shares of common stock, par value $0.001 per
share, of which (x) 42,021,013 shares are issued and outstanding, (y) 2,486,181
shares are reserved for issuance upon conversion of the class A common stock,
each share of class A common stock being convertible into one share of common
stock, and (z) 11,401,366 shares are reserved for issuance pursuant to the
Company's 1990 Long-Term Incentive Plan and 2000 Long-Term Incentive Plan, (ii)
40,000,000 shares of class A common stock, par value $0.001 per share, of which
2,486,181



shares are issued and outstanding, and (iii) 30,000,000 shares of preferred
stock, par value $0.01 per share, of which no shares are issued and outstanding.
All of the issued and outstanding shares of common stock and class A common
stock have been duly authorized, and all of the issued and outstanding shares of
common stock and class A common stock have been validly issued, are fully paid
and non-assessable, and were issued in compliance with all applicable federal
and state securities laws.

                  (b)      Except as set forth in the Company SEC Documents
filed prior to the date of this Agreement or in the Draft Form 10-K, or as
provided in the Transaction Agreements, there are not, nor upon the consummation
of the transactions contemplated hereby, shall there be: (i) any outstanding
options, warrants, rights (including conversion or preemptive rights) or
agreements pursuant to which the Company is or may become obligated to issue,
sell or repurchase any shares of its capital stock or any other securities of
the Company; (ii) any restrictions on the transfer of capital stock of the
Company imposed by the Organizational Documents, or any agreement to which the
Company is a party, any order of any court or any Governmental Authority to
which the Company is subject, or any law other than state and federal securities
laws; and (iii) any registration rights (including piggy-back rights) under the
Securities Act of 1933, as amended (the "Securities Act") with respect to shares
of the Company's capital stock.

                  (c)      Except as set forth in the Company SEC Documents
filed prior to the date of this Agreement or in the Draft Form 10-K, the Company
is not a party to or subject to any agreement or understanding relating to the
voting of shares of capital stock of the Company or the giving of written
consents by a shareholder or director of the Company.

                  (d)      Since December 31, 2002, the Company has only issued
stock options to its or subsidiaries' employees in the ordinary course of
business, consistent with past practice.

                  Section 3.3       Subsidiaries. The Company does not have
any subsidiaries required to be disclosed in Exhibit 21 to the Draft Form 10-K.

                  Section 3.4       Authorization. All corporate action on the
part of the Company, its directors and stockholders necessary for the
authorization, execution and delivery of the Transaction Agreements, the
performance of all obligations of the Company thereunder, including the
authorization, issuance and delivery of the Purchased Stock, has been taken. The
Transaction Agreements have been duly executed and delivered by the Company and
constitute valid and legally binding obligations of the Company, enforceable
against the Company in accordance with their respective terms (except as such
enforceability may be limited by applicable bankruptcy, insolvency,
reorganization, moratorium or other laws of general application relating to or
affecting enforcement of creditors' rights).

                  Section 3.5       No Conflicts. The execution, delivery and
performance of the Transaction Agreements and compliance with the provisions
thereof by the Company, does not and shall not: (a) violate any provision of
law, statute, ordinance, rule or regulation or any ruling, writ, injunction,
order, judgment or decree of any Governmental Authority, (b) conflict with or
result in any breach of any of the terms, conditions or provisions of, or
constitute (whether or not with due notice or lapse of time, or both) a default
(or give rise to any right of termination,



cancellation or acceleration) or result in the creation of any lien, security
interest, charge or encumbrance upon any of the properties or assets of the
Company pursuant to any agreement, document, instrument, contract,
understanding, arrangement, note, indenture, mortgage, lease or permit to which
the Company is a party, or under which the Company or any of its assets is bound
or affected, or (c) violate or conflict with any of the provisions of the
Organizational Documents; except, in the case of subsections (a) and (b) as
would not have a Material Adverse Effect.

                  Section 3.6       Valid Issuance of Purchased Stock. When
issued, sold and delivered in accordance with the terms hereof for the
consideration expressed herein, the Purchased Stock shall be validly issued and
outstanding, fully paid and nonassessable, free from any encumbrances or
restrictions on transfer, including preemptive rights, rights of first refusal
or other similar rights, other than restrictions on transfer under the
Transaction Agreements and under federal and state securities laws.

                  Section 3.7       Governmental Consents. No consent, approval,
order or authorization of, or registration, qualification, designation,
declaration or filing with, any Governmental Authority is required in connection
with the consummation of the transactions contemplated by the Transaction
Agreements, except for registration or qualification, or taking such action to
secure exemption from such registration or qualification, of the Purchased Stock
under applicable state or federal securities laws, which actions shall be taken,
by and at the expense of the Company, on a timely basis as may be required.

                  Section 3.8       Litigation. Except as set forth in the
Company SEC Documents filed prior to the date of this Agreement or in the Draft
Form 10-K, there is no action, suit, proceeding or investigation pending or
threatened against the Company or which the Company intends to initiate which
questions the validity of the Transaction Agreements or the right of the Company
to enter into them, or to consummate the transactions contemplated thereby, or
which have a Material Adverse Effect, or result in any material change in the
current equity ownership of the Company.

                  Section 3.9       Licenses and Other Rights; Compliance with
Laws. The Company has all franchises, permits, licenses and other rights and
privileges necessary to permit it to own its properties and to conduct its
business as presently conducted and is in compliance thereunder except where the
failure to be in compliance does not have a Material Adverse Effect. The Company
is and has been in compliance with all laws and governmental rules and
regulations applicable to its business, properties and assets, and to the
products and services sold by it, including, without limitation, all such rules,
laws and regulations relating to fair employment practices, occupational safety
and health and public safety, except where the failure to be in compliance does
not have a Material Adverse Effect.

                  Section 3.10      Compliance with Other Instruments; Action.
The Company has neither received written notice nor otherwise has knowledge of
any violation or default of (a) any of the terms, conditions or provisions of
any agreement, document, instrument, contract, understanding, arrangement, note,
indenture, mortgage, lease or permit to which the Company is a party, or under
which the Company or any of its assets is bound or affected, or (b) the



Organizational Documents; except, in the case of subsection (a) as would not
have a Material Adverse Effect.

                  Section 3.11      Company SEC Documents; Financial Statements.

                  (a)      Since December 31, 2001, the Company has filed all
required reports, schedules, forms, statements and other documents (including
exhibits and all other information incorporated therein) with the SEC ("Company
SEC Documents"). As of their respective dates, each of the Company SEC Documents
complied, and the Draft Form 10-K complies, in all material respects with the
requirements of the Securities Act or the Securities Exchange Act of 1934, as
amended, and the rules and regulations of the SEC promulgated thereunder
applicable to such Company SEC Documents and the Draft Form 10-K, and no Company
SEC Documents when filed contained, and the Draft Form 10-K does not contain,
any untrue statement of a material fact or omitted to state a material fact
required to be stated therein or necessary in order to make the statements
therein, in light of the circumstances under which they were made, not
misleading.

                  (b)      The financial statements of the Company included in
the Draft Form 10-K comply as to form in all material respects with applicable
accounting requirements and the published rules and regulations of the SEC with
respect thereto, have been prepared in accordance with United States generally
accepted accounting principles applied on a consistent basis during the periods
involved (except as may be indicated in the notes thereto) and fairly present
the financial position of the company as of the dates thereof and the results of
its operations and cash flows for the periods then ended.

                  Section 3.12      Liabilities. The Company does not have any
liabilities, whether absolute, accrued, contingent or otherwise, except for
liabilities (i) set forth in the audited balance sheet for the year ended
December 31, 2002 included in the Draft Form 10-K, or specifically disclosed in
the footnotes thereto or (ii) incurred in the ordinary course of business since
December 31, 2002, that do not have a Material Adverse Effect.

                  Section 3.13      Absence of Changes. Since December 31, 2002,
there has not been a Material Adverse Effect.

                  Section 3.14      Intellectual Property.

                  (a)      For purposes of this Agreement, (i) "Intellectual
Property" shall mean any of the following: (u) patents and patent applications;
(v) registered and unregistered trademarks, service marks and other indicia of
origin, pending trademark and service mark registration applications, and
intent-to-use registrations or similar reservations of marks; (w) registered and
unregistered copyrights and applications therefor; (x) internet domain names,
applications and reservations therefor, uniform resource locators and the
corresponding Internet sites; (y) trade secrets and proprietary information not
otherwise listed in (u) through (x) above, including, without limitation,
unpatented inventions, invention disclosures, confidential information,
technical data, customer lists, corporate and business names, trade names, trade
dress, brand names, know-how, formulae, methods (whether or not patentable),
designs, processes, procedures, technology, source codes, object codes, computer
software programs, databases, data



collections and other proprietary information or material of any type, and all
derivatives, improvements and refinements thereof, howsoever recorded, or
unrecorded; and (6) any good will associated with any of the foregoing; and (ii)
"Company Intellectual Property" shall mean any Intellectual Property or rights
thereto, owned by or licensed to the Company for use in connection with the
business of the Company.

                  (b)      Except as does not have a Material Adverse Effect,
except as set forth in the Company SEC Documents filed prior to the date of this
Agreement or in the Draft Form 10-K, and except with respect to the Trap-1 (as
such term is defined in the Collaboration Agreement):

                           (i)      each item of Company Intellectual Property
which is registered, filed, issued or applied for, has been duly and validly
registered in, filed in or issued by, the official governmental registrars
and/or issuers (or officially recognized issuers) of patents, trademarks,
copyrights or Internet domain names, in their respective jurisdictions of use
and intended use, and each such registration, filing and/or issuance (x) has not
been abandoned, canceled or otherwise compromised, (y) has been maintained
effective by all requisite filings, renewals and payments, and (z) remains in
full force and effect;

                           (ii)     the Company has the exclusive right to file,
prosecute and maintain all applications and registrations with respect to the
Company Intellectual Property;

                           (iii)    the Company owns or is licensed to use the
Company Intellectual Property free and clear of any Liens, other than Permitted
Liens without, with respect to Company-owned Intellectual Property, obligation
to pay any royalty or any other fees with respect thereto; and

                           (iv)     the Company has not received any notice of
any claim, or a threat of any claim, from any third party, and no third party
claims are pending, (i) challenging the right of the Company to use any
Intellectual Property or alleging any violation, infringement, misuse or
misappropriation by the Company of any Intellectual Property or indicating that
the failure to take a license would result in any such claim, or (ii)
challenging the ownership rights of the Company in any Company Intellectual
Property or asserting any opposition, interference, invalidity, termination,
abandonment, unenforceability, or other infirmity of any Company Intellectual
Property.

                  Section 3.15      Environmental Matters.

                  (a)      For purposes of this Agreement:

                           (i)      "Environmental Claim" means any claim,
action, cause of action, investigation or written notice by any person or entity
alleging potential liability (including, without limitation, potential liability
for investigatory costs, cleanup costs, governmental response costs, natural
resources damages, property damages, personal injuries, or penalties) arising
out of, based on or resulting from (a) the presence or Release of any Hazardous
Materials at any location, whether or not owned or operated by the Company, or
(b) circumstances forming the basis of any violation of any Environmental Law.



                           (ii)     "Environmental Laws" means all federal,
state, local and foreign laws and regulations relating to pollution or
protection of human health or the environment, including without limitation,
laws relating to Releases or threatened Releases of Hazardous Materials or
otherwise relating to the manufacture, processing, distribution, use, treatment,
storage, transport or handling of Hazardous Materials.

                           (iii)    "Hazardous Materials" means all substances
defined as Hazardous Substances, Oils, Pollutants or Contaminants in the Natural
Oil and Hazardous Substances Pollution Contingency Plan, 40 C.F.R. Section
300.5, or defined as such by, or regulated as such under, any Environmental Law.

                           (iv)     "Release" means any release, spill,
emission, discharge, leaking, pumping, injection, deposit, disposal, dispersal,
leaching or migration into the environment (including, without limitation,
ambient air, surface water, groundwater and surface or subsurface strata) or
into or out of any property, including the movement of Hazardous Materials
through or in the air, soil, surface water, groundwater or property.

                  (b)      Except as set forth in the Company SEC Documents and
the Draft Form 10-K:

                           (i)      the Company is in compliance with all
applicable Environmental Laws (which compliance includes, but is not limited to,
the possession by the Company of all permits and other governmental
authorizations required under applicable Environmental Laws, and compliance with
the terms and conditions thereof), except where failure to so comply would not
have a Material Adverse Effect; and

                           (ii)     there is no Environmental Claim pending or
threatened against the Company which would have a Material Adverse Effect

                  Section 3.16      FDA Matters.

                  (a)      No director, officer or, to the Company's knowledge,
employee of the Company directly involved in clinical trials has ever been
convicted of a felony under law for conduct relating to the development, testing
or approval of any drug, biological product or device, or the preparation or
submission of an Investigational New Drug Application ("IND"), a New Drug
Application ("NDA"), an Abbreviated New Drug Application ("ANDA"), or a
Biologics License Application ("BLA").

                  (b)      All clinical trials conducted, supervised or
monitored by or on behalf of the Company have been conducted in compliance with
all applicable federal, state and local laws, regulations, rules and
requirements, including, but not limited to, current Good Clinical Practices
("GCPs") and the requirements of the regulations of the Food and Drug
Administration ("FDA") at, where applicable, 21 C.F.R. Part 312, and 21 C.F.R.
Part 50, and the Company has not been cited for failure to comply with GCPs,
except where any failure to so comply would not have a Material Adverse Effect.



                  (c)      All nonclinical studies conducted by or on behalf of
the Company are and have been conducted in accordance with current Good
Laboratory Practices ("GLPs") and the requirements of the regulations of the FDA
at, where applicable, in 21 C.F.R. Part 58, and the Company has not been cited
for failure to comply with GLPs, except where the failure to so conduct such
studies or to so comply would not have a Material Adverse Effect.

                  (d)      Neither the Company nor, to the Company's knowledge,
any of its agents or employees directly involved in clinical trials have been
disqualified or debarred by the FDA under 21 U.S.C. Section 335a, nor has the
Company, to its knowledge, used in any capacity the services of any Person who,
at the time that the services were rendered, was debarred by the FDA under 21
U.S.C. Section 335a, except where such disqualification or debarrment would not
have a Material Adverse Effect.

                  (e)      The Company is in compliance with the applicable
provisions, if any, of the Clinical Laboratories Improvement Act of 1967, as
amended, except where any failure to so comply would not have a Material Adverse
Effect.

                  Section 3.17      Offering. Subject to the accuracy of the
Investor's representations set forth in Section 4.3 and 4.4, the offer, sale and
issuance of the Purchased Stock to be issued in conformity with the terms of
this Agreement constitute transactions which are exempt from the registration
requirements of the Securities Act and from all applicable state registration or
qualification requirements, other than those with which the Company has
complied.

                  Section 3.18      Brokers' or Finders' Fees. No broker,
finder, investment banker or other Person is entitled to any brokerage, finder's
or other fee or commission in connection with the transactions contemplated by
this Agreement.

                                   ARTICLE IV

                 REPRESENTATIONS AND WARRANTIES OF THE INVESTOR

         The Investor hereby represents and warrants as follows:

                  Section 4.1       Organization; Good Standing. The Investor is
a corporation duly organized, validly existing and in good standing under the
laws of Switzerland. The Investor has all requisite corporate power and
corporate authority to enter into the Transaction Agreements, to purchase the
Purchased Stock and to carry out the other transactions contemplated under the
Transaction Documents.

                  Section 4.2       Authorization. All corporate action on the
part of the Investor, and its directors and stockholders necessary for the
authorization, execution and delivery of the Transaction Agreements, the
performance of all obligations of the Investor thereunder, including the
subscription and purchase of the Purchased Stock, has been taken. This Agreement
has been duly executed and delivered by the Investor and constitutes a valid and
legally binding obligation of the Investor, enforceable against the Investor in
accordance with its terms (except as such



enforceability may be limited by applicable bankruptcy, insolvency,
reorganization, moratorium or other laws of general application relating to or
affecting enforcement of creditors' rights).

                  Section 4.3       Purchase Entirely for Own Account. The
Purchased Stock shall be acquired for investment for the Investor's own account,
not as a nominee or agent, and not with a view to the resale or distribution of
any part thereof, and the Investor has no present intention of selling, granting
any participation, or otherwise distributing the Purchased Stock. The Investor
does not have any contract, undertaking, agreement or arrangement with any
Person to sell, transfer or grant participation to such Person any of the
Purchased Stock.

                  Section 4.4       Investment Experience and Accredited
Investor Status. The Investor either (i) is an "accredited investor" (as defined
in Regulation D under the Securities Act) or (ii) is a "non-U.S. person" (as
defined in Regulation S under the Securities Act) and is not acquiring the
Purchased Stock for the account or benefit of any U.S. Person.

                                   ARTICLE V

                   FURTHER ASSURANCES; SECURITIES LAW MATTERS

                  Section 5.1       Further Assurances. The parties agree to
take such reasonable steps and execute such other and further documents as may
be necessary or appropriate to cause the terms and conditions contained herein
to be carried into effect.

                  Section 5.2       Restricted Securities. The Investor
understands that the Purchased Stock, when issued, shall be restricted
securities under the federal securities laws inasmuch as they are being acquired
from the Company in a transaction not involving a public offering and that under
such laws and applicable regulations such securities may be resold without
registration under the Securities Act only in certain limited circumstances. In
this connection, the Investor represents that it is familiar with Rule 144, as
presently in effect, and understands the resale limitations imposed thereby and
by the Securities Act.

                  Section 5.3       Limitations on Disposition. The Investor
shall not make any disposition of all or any portion of the Purchased Stock,
except to a subsidiary, unless such disposition is in compliance with Article II
of the Registration Rights Agreement and:

                  (a)      there is then in effect a Registration Statement
under the Securities Act covering such proposed disposition and such disposition
is made in accordance with such Registration Statement;

                  (b)      the disposition is made pursuant to Rule 144 or
similar provisions of federal securities laws as in effect from time to time; or

                  (c)      (i) the Investor has notified the Company of the
proposed disposition, and (ii) if requested by the Company, the Investor shall
have furnished the Company with an opinion of counsel (which counsel shall be
reasonably satisfactory to the Company) that such disposition will not require
registration of such shares of the Purchased Stock under the Securities Act. The
Company agrees and acknowledges that for the purpose of any opinion required
pursuant to this



Section 5.3(c), White & Case LLP shall be considered counsel reasonably
satisfactory to the Company without any further action or request on the part of
the Investor.

                  Section 5.4       Legends. It is understood that the
certificates representing the Purchased Stock shall bear the following legends:

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

                  (b)      any legend required by applicable state securities
laws.

                                   ARTICLE VI

                                  MISCELLANEOUS

                  Section 6.1       Survival of Warranties.

                  (a)      Except as set forth in subsection (b) below, the
respective representations and warranties of the Company and the Investor
contained in this Agreement shall survive the Closing until the thirtieth (30th)
day after the expiration of the applicable statute of limitations (after giving
effect to any waivers and extensions thereto) without regard to any
investigation made by any of the parties hereto

                  (b)      The representations and warranties set forth in
Section 3.15 (Environmental Matters) shall survive indefinitely without regard
to any investigation made by any of the parties hereto.

                  Section 6.2       Indemnification. Each party (an
"Indemnifying Party") shall indemnify, defend and hold the other party and the
other party's directors, officers, employees, agents and affiliates
(collectively, the "Indemnified Parties") harmless against any and all
liabilities, loss, cost or damage, together with all reasonable costs and
expenses related thereto (including legal and accounting fees and expenses),
arising from, relating to, or connected with the untruth or inaccuracy of any
representations or warranties (which untruth or inaccuracy shall, in the case of
the representations and warranties set forth in Section 3.15, be determined
without regard to any reference to "material" "in all material respects,"
"Material Adverse Effect" or other materiality qualifier) as of the date hereof,
or any breach of any covenants of the Indemnifying Party contained herein. The
foregoing indemnification shall survive the termination of this Agreement for
any reason.

                  Section 6.3       Remedies. In case any one or more of the
covenants or agreements set forth in this Agreement shall have been breached by
any party hereto, the party or parties entitled to the benefit of such covenants
or agreements may proceed to protect and enforce their rights either by suit in
equity or action at law, including, but not limited to, an action for damages



as a result of any such breach or an action for specific performance of any such
covenant or agreement contained in this Agreement. The rights, powers and
remedies of the parties under this Agreement are cumulative and not exclusive of
any other right, power or remedy which such parties may have under any other
agreement or law. No single or partial assertion or exercise of any right, power
or remedy of a party hereunder shall preclude any other or further assertion or
exercise thereof.

                  Section 6.4       Successors and Assigns. Except as otherwise
expressly provided herein, the terms and conditions of this Agreement shall
inure to the benefit of and be binding upon the respective successors and
assigns of the parties. This Agreement and the rights and duties of the Company
set forth herein may not be assigned, in whole or in part, by the Company. The
Investor may assign the right and obligation to purchase the Purchased Stock for
the Purchase Price, and all of its other rights and obligations under the
Transaction Agreements, to any of its subsidiaries, provided that the Investor
shall remain liable for the performance of the obligations such subsidiary
hereunder and thereunder.

                  Section 6.5       Entire Agreement. This Agreement (including
exhibits hereto), together with the Registration Rights Agreement, contains the
complete understanding of the Parties with respect to the subject matter hereof
and thereof and supersedes all prior understandings and writings relating to the
subject matter hereof and thereof. The exhibits to this Agreement are
incorporated into and form an integral part hereof. If an exhibit is a form of
agreement, such agreement, when executed and delivered by the Parties, shall
constitute a document independent of this Agreement.

                  Section 6.6       Governing Law; Submission to Jurisdiction.
This Agreement shall be governed by and construed in accordance with the laws of
the State of New York, without regard to conflict of laws principles. Each of
the parties irrevocably submits to the exclusive jurisdiction of (a) the Supreme
Court of the State of New York, and (b) the United States District Court for the
Southern District of New York, for the purposes of any suit, action or other
proceeding arising out of this Agreement or any transaction contemplated hereby.
Each of the parties agrees to commence any action, suit or proceeding relating
hereto in the United States District Court for the Southern District of New York
or if such suit, action or other proceeding may not be brought in such court for
jurisdictional purposes, in the Supreme Court of the State of New York.

                  Section 6.7       Counterparts. This Agreement may be executed
in counterparts, each of which shall be deemed an original but which together
shall constitute one and the same instrument.

                  Section 6.8       Titles and Subtitles. The titles and
subtitles used in this Agreement are used for convenience only and are not to be
considered in construing or interpreting this Agreement.

                  Section 6.9       Notices. All notices, instructions and other
communications hereunder or in connection herewith shall be in writing, shall be
sent to the address of the relevant party set forth below and shall be (a)
delivered personally, (b) sent by registered or certified mail, return receipt
requested, postage prepaid, (c) sent via a reputable nationwide



overnight courier service, or (d) sent by facsimile transmission, with a
confirmation copy to be sent by registered or certified mail, return receipt
requested, postage prepaid. Any such notice, instruction or communication shall
be deemed to have been delivered upon receipt if delivered by hand, three (3)
Business Days after it is sent by registered or certified mail, return receipt
requested, postage prepaid, one (1) Business Day after it is sent via a
reputable nationwide overnight courier service, or when transmitted with
electronic confirmation of receipt, if transmitted by facsimile (if such
transmission is on a Business Day; or otherwise, on the next Business Day
following such transmission). Either party may change its address by giving
notice to the other party in the manner provided above.

         To the Company:         Regeneron Pharmaceuticals, Inc.
                                 777 Old Saw Mill Road
                                 Tarrytown, New York 10591
                                 Attention: General Counsel

         With a copy (which      Skadden, Arps, Slate, Meagher & Flom LLP
         shall not constitute    4 Time Square
         notice) to:             New York, NY 10036
                                 Attention: David J. Goldschmidt, Esq.

         To the Investor:        Novartis Pharma AG
                                 Lichtstrasse 35
                                 CH-4002 Basel
                                 Switzerland
                                 Attention: General Counsel

         With a copy to (which:  Novartis Corporation
         shall not constitute    608 Fifth Avenue
         notice) to              New York, New York 10020
                                 Attention: General Counsel and Deputy
                                 General Counsel

                  Section 6.10      Expenses. Each party shall pay its own fees
and expenses with respect to this Agreement. If any action at law or in equity
is necessary to enforce or interpret the terms of this Agreement or the
Articles, the prevailing party shall be entitled to reasonable attorney's fees,
costs and necessary disbursements in addition to any other relief to which such
party may be entitled.

                  Section 6.11      Amendments and Waivers. Any term of this
Agreement may be amended and the observance of any term of this Agreement may be
waived (either generally or in a particular instance and either retroactively or
prospectively), only with the written consent of the Company and the Investor.

                  Section 6.12      Severability. If, under applicable laws, any
provision hereof is invalid or unenforceable, or otherwise directly or
indirectly affects the validity of any other material provision(s) of this
Agreement ("Severed Clause"), then, it is mutually agreed that this Agreement
shall endure except for the Severed Clause. The Parties shall consult and use
their



reasonable best efforts to agree upon a valid and enforceable provision which
shall be a reasonable substitute for such Severed Clause in light of the intent
of this Agreement.

                  Section 6.13      Confidentiality and Publicity.

                  (a)      Neither the Company nor the Investor shall disclose
to any person (other than its attorneys, accountants, employees, officers, and
directors) the existence or terms of this Agreement or any of the transactions
contemplated hereby without the prior written consent of the other party, except
as may, in the reasonable opinion of such party's counsel, be required by law
(in which event the disclosing party shall first consult with the other party
with respect to such disclosure). If the Company is required to provide a copy
of this Agreement or any related document to any third party, the Company shall
ensure that such document is redacted, to the extent permitted by law, to
eliminate all confidential information. The Investor shall have the right to
review and approve each such document prior to its submission to a third party.
A period of five (5) Business Days shall be provided for such review unless not
permitted by law, in which case the maximum period allowable shall be provided.
The Company and the Investor shall consult and reach agreement with one another
as to the form and substance of any press release or any other public disclosure
of the existence or terms of this Agreement or the transactions contemplated
hereby prior to issuing any such press release or making any such public
disclosure.

                  (b)      The Company shall not later than April 5, 2003, issue
a press release (the "Axokine Press Release") announcing the results of the
initial Phase 3 clinical study for Axokine.

                    [Remainder of page intentionally blank.]



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

                                    NOVARTIS PHARMA AG

                                    By: /s/ Joseph E. Mamie
                                       -----------------------------------------
                                     Name: Joseph E. Mamie
                                     Title: Head Operational Treasury

                                    By: /s/ Kim Urdahl
                                       -----------------------------------------
                                     Name: Kim Urdahl
                                     Title: Head of Legal, Primary Care

                                    REGENERON PHARMACEUTICALS, INC.

                                    By: /s/ Stuart Kolinski
                                       -----------------------------------------
                                     Name: Stuart Kolinski
                                     Title: Vice President & General Counsel