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                                                                     EXHIBIT 4.4

                                                                  EXECUTION COPY

                          REGISTRATION RIGHTS AGREEMENT

            THIS REGISTRATION RIGHTS AGREEMENT is made and entered into as of
October 17, 2001 by and between Regeneron Pharmaceuticals, Inc., a New York
corporation (the "Company"), and Merrill Lynch & Co., Merrill Lynch, Pierce,
Fenner & Smith Incorporated and Robertson Stephens, Inc. (collectively, the
"Initial Purchasers") pursuant to the Purchase Agreement, dated as of October
12, 2001 (the "Purchase Agreement"), between the Company and the Initial
Purchasers. In order to induce the Initial Purchasers to enter into the Purchase
Agreement, the Company has agreed to provide the registration rights set forth
in this Agreement. The execution of this Agreement is a condition to the closing
under the Purchase Agreement.

            The Company agrees with the Initial Purchasers for the benefit of
the Initial Purchasers and for the benefit of the beneficial owners (including
the Initial Purchasers) from time to time of the Registrable Securities (as
defined herein) (each of the foregoing a "Holder" and together the "Holders"),
as follows:

Section 1. Definitions. Capitalized terms used herein without definition shall
have their respective meanings set forth in the Purchase Agreement. As used in
this Agreement, the following terms shall have the following meanings:

            "Affiliate" means, with respect to any specified person, an
"affiliate," as defined in Rule 144, of such person.

            "Amendment Effectiveness Deadline Date" has the meaning specified in
Section 2(d) hereof.

            "Business Day" means each Monday, Tuesday, Wednesday, Thursday and
Friday that is not a day on which banking institutions in The City of New York
are authorized or obligated by law or executive order to close.

            "Common Stock" means any shares of Common Stock, par value $0.001
per share, of the Company and any other shares of common stock as may constitute
"Common Stock" for purposes of the Indenture, including the Underlying Common
Stock.

            "Conversion Price" has the meaning assigned to that term in the
Indenture.

            "Damages Accrual Period" has the meaning specified in Section 2(e)
hereof.

            "Damages Payment Date" means each October 17 and April 17 in the
case of Securities and the Underlying Common Stock.

            "Deferral Notice" has the meaning specified in Section 3(i) hereof.

            "Deferral Period" has the meaning specified in Section 3(i) hereof.
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            "Effectiveness Deadline Date" has the meaning specified in Section
2(a) hereof.

            "Effectiveness Period" means the period of two years from the Issue
Date or such shorter period that will terminate upon the earliest of the
following: (A) when all the Securities covered by the Shelf Registration
Statement have been sold pursuant to the Shelf Registration Statement or when
all shares of Underlying Common Stock have been sold pursuant to the Shelf
Registration Statement and (B) when, in the written opinion of counsel to the
Company, all outstanding Registrable Securities held by persons which are not
affiliates of the Company may be resold without registration under the
Securities Act pursuant to Rule 144(k) under the Securities Act or any successor
provision thereto.

            "Event" has the meaning specified in Section 2(e) hereof.

            "Event Termination Date" has the meaning specified in Section 2(e)
hereof.

            "Event Date" has the meaning specified in Section 2(e) hereof.

            "Exchange Act" means the Securities Exchange Act of 1934, as
amended, and the rules and regulations of the SEC promulgated thereunder.

            "Filing Deadline Date" has the meaning specified in Section 2(a)
hereof.

            "Holder" has the meaning specified in the second paragraph of this
Agreement.

            "Indenture" means the Indenture dated as of the date hereof between
the Company and the Trustee, pursuant to which the Securities are being issued.

            "Initial Purchasers" has the meaning specified in the first
paragraph of this Agreement.

            "Initial Shelf Registration Statement" has the meaning specified in
Section 2(a) hereof.

            "Issue Date" means October 17, 2001.

            "Liquidated Damages Amount" has the meaning specified in Section
2(e) hereof.

             "Material Event" has the meaning specified in Section 3(i) hereof.

            "Notice and Questionnaire" means a written notice delivered to the
Company containing substantially the information called for by the Selling
Securityholder Notice and Questionnaire attached as Annex A to the Offering
Memorandum of the Company issued October 12, 2001 relating to the Securities.

            "Notice Holder" means, on any date, any Holder that has delivered a
Notice and Questionnaire to the Company on or prior to such date.

            "Principal Amount" means, with the respect to the Securities, the
principal amount due on the maturity date as shown on such Securities.


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            "Prospectus" means the prospectus included in any Registration
Statement (including, without limitation, a prospectus that discloses
information previously omitted from a prospectus filed as part of an effective
registration statement in reliance upon Rule 415 promulgated under the
Securities Act), as amended or supplemented by any amendment or prospectus
supplement, including post-effective amendments, and all materials incorporated
by reference or explicitly deemed to be incorporated by reference in such
Prospectus.

            "Purchase Agreement" has the meaning specified in the first
paragraph of this Agreement.

            "Record Holder" means, with respect to any Damages Payment Date
relating to any Securities or Underlying Common Stock as to which any Liquidated
Damages Amount has accrued, the registered Holder of such Securities or
Underlying Common Stock, as the case may be, 15 days prior to the next
succeeding Damages Payment Date.

            "Registrable Securities" means the Securities, until such Securities
have been converted or exchanged, and the Underlying Common Stock and any
securities into or for which such securities have been converted or exchanged,
and any security issued with respect thereto upon any stock dividend, split or
similar event until, in the case of any such security, the earliest of (i) its
effective registration under the Securities Act and resale in accordance with
the Registration Statement covering it, (ii) expiration of the holding period
that would be applicable thereto under Rule 144(k) were it not held by an
Affiliate of the Company or (iii) its sale to the public pursuant to Rule 144.

            "Registration Expenses" means the expenses described in Section 5
hereof.

            "Registration Statement" means any registration statement of the
Company that covers any of the Registrable Securities pursuant to the provisions
of this Agreement, including the Prospectus, amendments and supplements to such
registration statement, including post-effective amendments, all exhibits, and
all materials incorporated by reference or explicitly deemed to be incorporated
by reference in such registration statement.

            "Restricted Securities" has the meaning assigned to that term in
Rule 144.

            "Rule 144" means Rule 144 under the Securities Act, as such Rule may
be amended from time to time, or any similar rule or regulation hereafter
adopted by the SEC.

            "Rule 144A" means Rule 144A under the Securities Act, as such Rule
may be amended from time to time, or any similar rule or regulation hereafter
adopted by the SEC.

            "SEC" means the U.S. Securities and Exchange Commission and any
successor agency.

            "Securities" means the 5-1/2% Convertible Senior Subordinated Notes
due 2008 of the Company to be purchased pursuant to the Purchase Agreement.

            "Securities Act" means the Securities Act of 1933, as amended, and
the rules and regulations promulgated by the SEC thereunder.


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            "Shelf Registration Statement" has the meaning specified in Section
2(a) hereof.

            "Subsequent Shelf Registration Statement" has the meaning specified
in Section 2(b) hereof.

            "TIA" means the Trust Indenture Act of 1939, as amended.

            "Trustee" means American Stock Transfer & Trust Company (or any
successor entity), the Trustee under the Indenture.

            "Underlying Common Stock" means the Common Stock into which the
Securities are convertible or issued upon any such conversion.

         Section 2. Shelf Registration. (a) The Company shall prepare and file
or cause to be prepared and filed with the SEC, as soon as practicable but in
any event by the date (the "Filing Deadline Date") ninety (90) days after the
Issue Date, a Registration Statement for an offering to be made on a delayed or
continuous basis pursuant to Rule 415 of the Securities Act (a "Shelf
Registration Statement") registering the resale from time to time by Holders
thereof of all of the Registrable Securities (the "Initial Shelf Registration
Statement"). The Initial Shelf Registration Statement shall be on Form S-3 or
another appropriate form permitting registration of such Registrable Securities
for resale by such Holders in accordance with the methods of distribution
elected by the Holders and set forth in the Initial Shelf Registration
Statement. The Company shall use its reasonable best efforts to cause the
Initial Shelf Registration Statement to be declared effective under the
Securities Act as promptly as is practicable but in any event by the date (the
"Effectiveness Deadline Date") that is one hundred and eighty (180) days after
the Issue Date, and to keep the Initial Shelf Registration Statement (or any
Subsequent Shelf Registration Statement) continuously effective under the
Securities Act until the expiration of the Effectiveness Period; provided,
however, that no Holder shall be entitled to have the Registrable Securities
held by it covered by such Shelf Registration Statement unless such Holder shall
have provided a Notice and Questionnaire in accordance with Section 2(d) and is
in compliance with Section 4. From and after the date hereof, the Company will
not grant any existing or future holders of the Company's securities the right
to include any of the Company's securities in the Shelf Registration Statement.
The Company will use its reasonable best efforts to seek and obtain waivers from
its security holders with pre-existing registration rights to effectively waive
any such rights with respect to the Shelf Registration Statement; provided that
no assurance can be given that any such third-parties shall waive their rights.

         (b) If the Initial Shelf Registration Statement or any Subsequent Shelf
Registration Statement ceases to be effective for any reason at any time during
the Effectiveness Period (other than because all Registrable Securities
registered thereunder shall have been sold pursuant thereto or shall have
otherwise ceased to be Registrable Securities), the Company shall use its
reasonable best efforts to obtain the prompt withdrawal of any order suspending
the effectiveness thereof, and in any event shall within thirty (30) days of
such cessation of effectiveness amend the Shelf Registration Statement in a
manner reasonably expected to obtain the withdrawal of the order suspending the
effectiveness thereof, or file an additional Shelf Registration Statement
covering all of the securities that as of the date of such filing are


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Registrable Securities (a "Subsequent Shelf Registration Statement"). If a
Subsequent Shelf Registration Statement is filed, the Company shall use its
reasonable best efforts to cause the Subsequent Shelf Registration Statement to
become effective as promptly as is practicable after such filing and to keep
such Registration Statement (or another Subsequent Shelf Registration Statement)
continuously effective until the end of the Effectiveness Period.

         (c) The Company shall supplement and amend the Shelf Registration
Statement if required by the rules, regulations or instructions applicable to
the registration form used by the Company for such Shelf Registration Statement,
if required by the Securities Act or, to the extent to which the Company does
not reasonably object, as reasonably requested by the Initial Purchasers or by
the Trustee on behalf of the registered Holders.

         (d) Each Holder agrees that if such Holder wishes to sell Registrable
Securities pursuant to a Shelf Registration Statement and related Prospectus, it
will do so only in accordance with this Section 2(d) and Section 3(i). Each
Holder wishing to sell Registrable Securities pursuant to a Shelf Registration
Statement and related Prospectus agrees to deliver a Notice and Questionnaire to
the Company at least five (5) Business Days prior to any intended distribution
of Registrable Securities under the Shelf Registration Statement. From and after
the date the Initial Shelf Registration Statement is declared effective, the
Company shall, as promptly as is practicable after the date a Notice and
Questionnaire is delivered, and in any event within five (5) Business Days after
such date, (i) if required by applicable law, file with the SEC a post-effective
amendment to the Shelf Registration Statement or prepare and, if required by
applicable law, file a supplement to the related Prospectus or a supplement or
amendment to any document incorporated therein by reference or file any other
required document so that the Holder delivering such Notice and Questionnaire is
named as a selling security holder in the Shelf Registration Statement and the
related Prospectus in such a manner as to permit such Holder to deliver such
Prospectus to purchasers of the Registrable Securities in accordance with
applicable law and, if the Company shall file a post-effective amendment to the
Shelf Registration Statement, use its reasonable best efforts to cause such
post-effective amendment to be declared effective under the Securities Act as
promptly as is practicable, but in any event by the date (the "Amendment
Effectiveness Deadline Date") that is forty-five (45) days after the date such
post-effective amendment is required by this clause to be filed; (ii) provide
such Holder copies of any documents filed pursuant to Section 2(d)(i); and (iii)
notify such Holder as promptly as practicable after the effectiveness under the
Securities Act of any post-effective amendment filed pursuant to Section
2(d)(i); provided, that if such Notice and Questionnaire is delivered during a
Deferral Period, the Company shall so inform the Holder delivering such Notice
and Questionnaire and shall take the actions set forth in clauses (i), (ii) and
(iii) above upon expiration of the Deferral Period in accordance with Section
3(i), provided, further, that if under applicable law the Company has more than
one option as to the type or manner of making any such filing, it will make the
required filing or filings in the manner or of a type that is reasonably
expected to result in the earliest availability of the Prospectus for effecting
resales of Registrable Securities. Notwithstanding anything contained herein to
the contrary, the Company shall be under no obligation to name any Holder that
is not a Notice Holder as a selling security holder in any Registration
Statement or related Prospectus; provided, however, that any Holder that becomes
a Notice Holder pursuant to the provisions of this Section 2(d) (whether or not
such Holder was a Notice Holder at the time the Registration Statement was
declared effective) shall


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be named as a selling security holder in the Registration Statement or related
Prospectus in accordance with the requirements of this Section 2(d).

         (e) The parties hereto agree that the Holders of Registrable Securities
will suffer damages, and that it would not be feasible to ascertain the extent
of such damages with precision, if (i) the Initial Shelf Registration Statement
has not been filed on or prior to the Filing Deadline Date, (ii) the Initial
Shelf Registration Statement has not been declared effective under the
Securities Act on or prior to the Effectiveness Deadline Date, (iii) the Company
has failed to perform its obligations set forth in Section 2(d) hereof within
the time period required therein, (iv) the aggregate duration of Deferral
Periods in any period exceeds the number of days permitted in respect of such
period pursuant to Section 3(i) hereof or (v) the number of Deferral Periods in
any period exceeds the number permitted in respect of such periods pursuant to
Section 3(i) (each of the events of a type described in any of the foregoing
clauses (i) through (v) are individually referred to herein as an "Event," and
the Filing Deadline Date in the case of clause (i), the Effectiveness Deadline
Date in the case of clause (ii), the date by which the Company is required to
perform its obligations set forth in Section 2(d) in the case of clause (iii)
(including the filing of any post-effective amendment prior to the Amendment
Effectiveness Deadline Date), the date on which the aggregate duration of
Deferral Periods in any period exceeds the number of days permitted by Section
3(i) hereof in the case of clause (iv), and the date of the commencement of a
Deferral Period that causes the limit on the number of Deferral Periods in any
period under Section 3(i) hereof to be exceeded in the case of clause (v), being
referred to herein as an "Event Date"). Events shall be deemed to continue until
the "Event Termination Date," which shall be the following dates with respect to
the respective types of Events: the date the Initial Shelf Registration
Statement is filed in the case of an Event of the type described in clause (i),
the date the Initial Shelf Registration Statement becomes effective under the
Securities Act in the case of an Event of the type described in clause (ii), the
date the Company performs its obligations set forth in Section 2(d) in the case
of an Event of the type described in clause (iii) (including, without
limitation, the date the relevant post-effective amendment to the Shelf
Registration Statement is declared effective under the Securities Act),
termination of the Deferral Period that caused the limit on the aggregate
duration of Deferral Periods in a period set forth in Section 3(i) to be
exceeded in the case of the commencement of an Event of the type described in
clause (iv), and termination of the Deferral Period the commencement of which
caused the number of Deferral Periods in a period permitted by Section 3(i) to
be exceeded in the case of an Event of the type described in clause (v).

            Accordingly, commencing on (and including) any Event Date and ending
on (but excluding) the relevant Event Termination Date (a "Damages Accrual
Period"), the Company agrees to pay, as liquidated damages and not as a penalty,
an amount (the "Liquidated Damages Amount"), payable on the Damages Payment
Dates to Record Holders, accruing for each portion of such Damages Accrual
Period beginning on and including a Damages Payment Date (or, in respect of the
first time that the Liquidation Damages Amount is to be paid to Holders on a
Damages Payment Date as a result of the occurrence of any particular Event, from
and including the Event Date) and ending on but excluding the first to occur of
(A) the date of the end of the Damages Accrual Period or (B) the next Damages
Payment Date, at a rate per annum equal to one-quarter of one percent (0.25%)
for the first 90-day period from the Event Date, and thereafter at a rate per
annum equal to one-half of one percent (0.5%), of the aggregate Principal Amount
of such Securities or, if the Holder has converted such Securities into
Underlying


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Common Stock and such shares of Common Stock then constitute Registrable
Securities, the Conversion Price of such Securities in effect at the time of
such conversion, in each case, determined as of the Business Day immediately
preceding the next Damages Payment Date; provided, that in the case of a Damages
Accrual Period that is in effect solely as a result of an Event of the type
described in clause (iii) of the immediately preceding paragraph, such
Liquidated Damages Amount shall be paid only to the Holders that have delivered
Notice and Questionnaires that caused the Company to incur the obligations set
forth in Section 2(d) the non-performance of which is the basis of such Event;
provided further, that any Liquidated Damages Amount accrued with respect to any
Securities or portion thereof called for redemption on a redemption date or
converted into Underlying Common Stock on a conversion date prior to the Damages
Payment Date, shall, in any such event, be paid instead to the Holder who
submitted such Securities or portion thereof for redemption or conversion on the
applicable redemption date or conversion date, as the case may be, on such date
(or promptly following the conversion date, in the case of conversion).
Notwithstanding the foregoing, no Liquidated Damages Amounts shall accrue as to
any Registrable Security from and after the earlier of (x) the date such
security is no longer a Registrable Security and (y) expiration of the
Effectiveness Period. The rate of accrual of the Liquidated Damages Amount with
respect to any period shall not exceed the applicable rate provided for in this
paragraph and shall not exceed one-half of one percent (0.5%), notwithstanding
the occurrence of multiple concurrent Events. Following the relevant Event
Termination Date, the accrual of Liquidated Damages Amounts will cease (without
in any way limiting the effect of any subsequent Event requiring the payment of
Liquidated Damages Amount by the Company).

            The Trustee shall be entitled, on behalf of Holders of Securities or
Underlying Common Stock, to seek any available remedy for the enforcement of
this Agreement, including for the payment of any Liquidated Damages Amount.
Notwithstanding the foregoing, the parties agree that the sole monetary damages
payable for a violation of the terms of this Agreement with respect to which
liquidated damages are expressly provided shall be such liquidated damages.
Nothing shall preclude a Notice Holder or Holder from pursuing or obtaining
specific performance or other equitable relief with respect to this Agreement.

            All of the Company's obligations set forth in this Section 2(e) that
are outstanding with respect to any Registrable Security at the time such
security ceases to be a Registrable Security shall survive until such time as
all such obligations with respect to such security have been satisfied in full
(notwithstanding termination of this Agreement pursuant to Section 8(k)).

            The parties hereto agree that the liquidated damages provided for in
this Section 2(e) constitute a reasonable estimate of the damages that may be
incurred by Holders of Registrable Securities by reason of the failure of the
Shelf Registration Statement to be filed or declared effective or available for
effecting resales of Registrable Securities in accordance with the provisions
hereof.

         Section 3. Registration Procedures. In connection with the registration
obligations of the Company under Section 2 hereof, the Company shall:

         (a) Before filing any Registration Statement or Prospectus or any
amendments or supplements thereto with the SEC, furnish to the Initial
Purchasers copies of all such


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documents proposed to be filed and use its reasonable best efforts to reflect in
each such document when so filed with the SEC such comments as the Initial
Purchasers reasonably shall propose within three (3) Business Days of the
delivery of such copies to the Initial Purchasers.

         (b) Prepare and file with the SEC such amendments and post-effective
amendments to each Registration Statement as may be necessary to keep such
Registration Statement continuously effective for the applicable period
specified in Section 2(a); cause the related Prospectus to be supplemented by
any required Prospectus supplement, and as so supplemented to be filed pursuant
to Rule 424 (or any similar provisions then in force) under the Securities Act;
and comply with the provisions of the Securities Act applicable to it with
respect to the disposition of all securities covered by such Registration
Statement during the Effectiveness Period in accordance with the intended
methods of disposition by the sellers thereof set forth in such Registration
Statement as so amended or such Prospectus as so supplemented.

         (c) As promptly as practicable give notice to the Notice Holders and
the Initial Purchasers (i) when any Prospectus, Prospectus supplement,
Registration Statement or post-effective amendment to a Registration Statement
has been filed with the SEC and, with respect to a Registration Statement or any
post-effective amendment, when the same has become effective, (ii) of any
request, following the effectiveness of the Initial Shelf Registration Statement
under the Securities Act, by the SEC or any other federal or state governmental
authority for amendments or supplements to any Registration Statement or related
Prospectus or for additional information, (iii) of the issuance by the SEC or
any other federal or state governmental authority of any stop order suspending
the effectiveness of any Registration Statement or, to the Company's knowledge,
the initiation or threatening of any proceedings for that purpose, (iv) of the
receipt by the Company of any notification with respect to the suspension of the
qualification or exemption from qualification of any of the Registrable
Securities for sale in any jurisdiction or, to the Company's knowledge, the
initiation or threatening of any proceeding for such purpose, (v) of the
occurrence of (but not the nature of or details concerning) a Material Event
(provided, however, that no notice by the Company shall be required pursuant to
this clause (v) in the event that the Company either promptly files a Prospectus
supplement to update the Prospectus or a Form 8-K or other appropriate Exchange
Act report that is incorporated by reference into the Registration Statement,
which, in either case, contains the requisite information with respect to such
Material Event that results in such Registration Statement no longer containing
any untrue statement of material fact or omitting to state a material fact
necessary to make the statements contained therein not misleading) and (vi) of
the determination by the Company that a post-effective amendment to a
Registration Statement will be filed with the SEC, which notice may, at the
discretion of the Company (or as required pursuant to Section 3(i)), state that
it constitutes a Deferral Notice, in which event the provisions of Section 3(i)
shall apply.

         (d) Use its reasonable best efforts to prevent the issuance, and if
issued to promptly obtain the withdrawal of any order suspending the
effectiveness of a Registration Statement or the lifting of any suspension of
the qualification (or exemption from qualification) of any of the Registrable
Securities for sale in any jurisdiction in which they have been qualified for
sale.


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         (e) If reasonably requested by the Initial Purchasers or any Notice
Holder, promptly incorporate in a Prospectus supplement or post-effective
amendment to a Registration Statement such information as the Initial Purchasers
or such Notice Holder shall, on the basis of an opinion of nationally-recognized
counsel experienced in such matters, determine to be required to be included
therein by applicable law and make any required filings of such Prospectus
supplement or such post-effective amendment; provided, that the Company shall
not be required to take any actions under this Section 3(e) that are not, in the
reasonable opinion of counsel for the Company, in compliance with applicable
law.

         (f) Furnish to each Notice Holder and the Initial Purchasers, upon
their request and without charge, at least one (1) conformed copy of the
Registration Statement and any amendment thereto, including financial statements
but excluding schedules, all documents incorporated or deemed to be incorporated
therein by reference and all exhibits (unless requested in writing to the
Company by such Notice Holder or the Initial Purchasers, as the case may be).

         (g) During the Effectiveness Period, deliver to each Notice Holder in
connection with any sale of Registrable Securities pursuant to a Registration
Statement, without charge, as many copies of the Prospectus or Prospectuses
relating to such Registrable Securities (including each preliminary prospectus)
and any amendment or supplement thereto as such Notice Holder may reasonably
request; and the Company hereby consents (except during such periods that a
Deferral Notice is outstanding and has not been revoked) to the use of such
Prospectus or each amendment or supplement thereto by each Notice Holder in
connection with any offering and sale of the Registrable Securities covered by
such Prospectus or any amendment or supplement thereto in the manner set forth
therein.

         (h) Prior to any public offering of the Registrable Securities pursuant
to the Shelf Registration Statement, register or qualify or cooperate with the
Notice Holders in connection with the registration or qualification (or
exemption from such registration or qualification) of such Registrable
Securities for offer and sale under the securities or Blue Sky laws of such
jurisdictions within the United States as any Notice Holder reasonably requests
in writing (which request may be included in the Notice and Questionnaire);
prior to any public offering of the Registrable Securities pursuant to the Shelf
Registration Statement, use its reasonable best efforts to keep each such
registration or qualification (or exemption therefrom) effective during the
Effectiveness Period in connection with such Notice Holder's offer and sale of
Registrable Securities pursuant to such registration or qualification (or
exemption therefrom) and do any and all other acts or things reasonably
necessary or advisable to enable the disposition in such jurisdictions of such
Registrable Securities in the manner set forth in the relevant Registration
Statement and the related Prospectus; provided, that the Company will not be
required to (i) qualify as a foreign corporation or as a dealer in securities in
any jurisdiction where it would not otherwise be required to qualify but for
this Agreement or (ii) take any action that would subject it to general service
of process in suits or to taxation in any such jurisdiction where it is not then
so subject.

         (i) Upon (A) the issuance by the SEC of a stop order suspending the
effectiveness of the Shelf Registration Statement or the initiation of
proceedings with respect to the Shelf Registration Statement under Section 8(d)
or 8(e) of the Securities Act, (B) the occurrence of any event or the existence
of any fact (a "Material Event") as a result of which any


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Registration Statement shall contain any untrue statement of a material fact or
omit to state any material fact required to be stated therein or necessary to
make the statements therein not misleading, or any Prospectus shall contain any
untrue statement of a material fact or omit to state any material fact required
to be stated therein or necessary to make the statements therein, in the light
of the circumstances under which they were made, not misleading, or (C) the
occurrence or existence of any pending corporate development that, in the
discretion of the Company, makes it appropriate to suspend the availability of
the Shelf Registration Statement and the related Prospectus, (i) in the case of
clause (B) above, subject to the next sentence, promptly prepare and file a
post-effective amendment to such Registration Statement or a supplement to the
related Prospectus or any document incorporated therein by reference or file any
other required document that would be incorporated by reference into such
Registration Statement and Prospectus so that such Registration Statement does
not contain any untrue statement of a material fact or omit to state any
material fact required to be stated therein or necessary to make the statements
therein not misleading, and such Prospectus does not contain any untrue
statement of a material fact or omit to state any material fact required to be
stated therein or necessary to make the statements therein, in the light of the
circumstances under which they were made, not misleading, as thereafter
delivered to the purchasers of the Registrable Securities being sold thereunder,
and, in the case of a post-effective amendment to a Registration Statement,
subject to the next sentence, use its reasonable best efforts to cause it to be
declared effective as promptly as is reasonably practicable, and (ii) give
notice to the Notice Holders that the availability of the Shelf Registration
Statement is suspended (a "Deferral Notice") and, upon receipt of any Deferral
Notice, each Notice Holder agrees not to sell any Registrable Securities
pursuant to the Registration Statement until such Notice Holder's receipt of
copies of the supplemented or amended Prospectus provided for in clause (i)
above, or until it is advised in writing by the Company that the Prospectus may
be used, and has received copies of any additional or supplemental filings that
are incorporated or deemed incorporated by reference in such Prospectus. The
Company will use its reasonable best efforts to ensure that the use of the
Prospectus may be resumed (x) in the case of clause (A) above, as promptly as is
practicable, (y) in the case of clause (B) above, as soon as, in the sole
judgment of the Company, public disclosure of such Material Event would not be
prejudicial to or contrary to the interests of the Company or, if necessary to
avoid unreasonable burden or expense, as soon as reasonably practicable
thereafter and (z) in the case of clause (C) above, as soon as, in the sole
judgment of the Company, such suspension is no longer appropriate. The period
during which the availability of the Registration Statement and any Prospectus
is suspended (the "Deferral Period") without the Company incurring any
obligation to pay liquidated damages pursuant to Section 2(e) shall not exceed
forty-five (45) days in any three (3) month period and one-hundred twenty (120)
days in any twelve (12) month period.

         (j) In the event of a Qualified Underwritten Offering, make available
for inspection during normal business hours by a representative for the Notice
Holders of such Registrable Securities and any broker-dealers, attorneys and
accountants retained by such Notice Holders, all relevant financial and other
records, pertinent corporate documents and properties of the Company and its
subsidiaries, and cause the appropriate executive officers, directors and
designated employees of the Company and its subsidiaries to make available for
inspection during normal business hours all relevant information reasonably
requested by such representative for the Notice Holders or any such
broker-dealers, attorneys or accountants in connection with such disposition, in
each case as is customary for similar "due diligence"


                                       10
<PAGE>
examinations; provided, however, that such persons shall first agree in writing
with the Company that any information that is reasonably and in good faith
designated by the Company in writing as confidential at the time of delivery of
such information shall be kept confidential by such persons and shall be used
solely for the purposes of exercising rights under this Agreement, unless (i)
disclosure of such information is required by court or administrative order or
is necessary to respond to inquiries of regulatory authorities, (ii) disclosure
of such information is required by law (including any disclosure requirements
pursuant to federal securities laws in connection with the filing of any
Registration Statement or the use of any Prospectus referred to in this
Agreement), (iii) such information becomes generally available to the public
other than as a result of a disclosure or failure to safeguard by any such
person or (iv) such information becomes available to any such person from a
source other than the Company and such source is not bound by a confidentiality
agreement; and provided further that the foregoing inspection and information
gathering shall, to the greatest extent possible, be coordinated on behalf of
all the Notice Holders and the other parties entitled thereto by the counsel
referred to in Section 5. For the purposes of this paragraph, "Qualified
Underwritten Offering" shall mean an underwritten public offering of Registrable
Securities in an aggregate amount of at least $25 million.

         (k) Comply with all applicable rules and regulations of the SEC and
make generally available to its securityholders earning statements (which need
not be audited) satisfying the provisions of Section 11(a) of the Securities Act
and Rule 158 thereunder (or any similar rule promulgated under the Securities
Act) commencing on the first day of the first fiscal quarter of the Company
commencing after the effective date of a Registration Statement.

         (l) Cooperate with each Notice Holder to facilitate the timely
preparation and delivery of certificates representing Registrable Securities
sold pursuant to a Registration Statement, and cause such Registrable Securities
to be in such denominations as are permitted by the Indenture and registered in
such names as such Notice Holder may request in writing at least two Business
Days prior to any sale of such Registrable Securities.

         (m) Provide a CUSIP number for all Registrable Securities covered by
each Registration Statement not later than the effective date of such
Registration Statement and provide the Trustee for the Securities and the
transfer agent for the Underlying Common Stock the with printed certificates for
the Registrable Securities that are in a form eligible for deposit with The
Depository Trust Company.

         (n) Use its reasonable best efforts to provide such information as is
required for any filings required to be made with the National Association of
Securities Dealers, Inc.

         (o) Upon (i) the filing of the Initial Shelf Registration Statement and
(ii) the effectiveness of the Initial Shelf Registration Statement, announce the
same, in each case by release to Reuters Economic Services and Bloomberg
Business News.

         (p) Enter into such customary agreements and take all such other
reasonably necessary actions in connection therewith (including those requested
by the holders of a majority of the Registrable Securities being sold) in order
to expedite or facilitate disposition of such Registrable Securities.


                                       11
<PAGE>
         (q) Cause the Indenture to be qualified under the TIA not later than
the effective date of any Registration Statement; and in connection therewith,
cooperate with the Trustee to effect such changes to the Indenture as may be
required for the Indenture to be so qualified in accordance with the terms of
the TIA and execute, and use its reasonable best efforts to cause the Trustee to
execute, all documents as may be required to effect such changes, and all other
forms and documents required to be filed with the SEC to enable the Indenture to
be so qualified in a timely manner.

         Section 4. Holder's Obligations. Each Holder agrees, by acquisition of
the Registrable Securities, that no Holder shall be entitled to sell any of such
Registrable Securities pursuant to a Registration Statement or to receive a
Prospectus relating thereto, unless such Holder has furnished the Company with a
Notice and Questionnaire as required pursuant to Section 2(d) hereof (including
the information required to be included in such Notice and Questionnaire) and
the information set forth in the next sentence. Each Notice Holder agrees
promptly to furnish to the Company all information required to be disclosed in
order to make the information previously furnished to the Company by such Notice
Holder not misleading and any other information regarding such Notice Holder and
the distribution of such Registrable Securities as may be required to be
disclosed in the Registration Statement under applicable law.

         Section 5. Registration Expenses. The Company shall bear all fees and
expenses incurred in connection with the performance by the Company of its
obligations under Sections 2 and 3 of this Agreement whether or not any of the
Registration Statements are declared effective. Such fees and expenses shall
include, without limitation, (i) all registration and filing fees (including,
without limitation, fees and expenses (x) with respect to filings required to be
made with the National Association of Securities Dealers, Inc. and (y) of
compliance with federal and state securities or Blue Sky laws (including,
without limitation, fees and disbursements of the counsel specified in the next
sentence in connection with Blue Sky qualifications of the Registrable
Securities under the laws of such jurisdictions as the Notice Holders of a
majority of the Registrable Securities being sold pursuant to a Registration
Statement may designate), (ii) printing expenses (including, without limitation,
expenses of printing certificates for Registrable Securities in a form eligible
for deposit with The Depository Trust Company), (iii) duplication expenses
relating to copies of any Registration Statement or Prospectus delivered to any
Holders hereunder, (iv) fees and disbursements of counsel for the Company in
connection with the Shelf Registration Statement and (v) fees and disbursements
of the Trustee and its counsel and of the registrar and transfer agent for the
Common Stock. In addition, the Company shall bear or reimburse the Notice
Holders for the fees and disbursements of one firm of legal counsel for the
Holders, which shall initially be Shearman & Sterling, but which may, upon the
written consent of the Initial Purchasers (which shall not be unreasonably
withheld), be another nationally recognized law firm experienced in securities
law matters designated by the Company. In addition, the Company shall pay the
internal expenses of the Company (including, without limitation, all salaries
and expenses of officers and employees performing legal or accounting duties),
the expense of any annual audit, the fees and expenses incurred in connection
with the listing of the Registrable Securities on any securities exchange on
which similar securities of the Company are then listed and the fees and
expenses of any person, including special experts, retained by the Company.


                                       12
<PAGE>
         Section 6. Indemnification; Contribution. (a) The Company agrees to
indemnify and hold harmless the Initial Purchasers and each Holder and each
person, if any, who controls the Initial Purchasers or any Holder within the
meaning of either Section 15 of the Securities Act or Section 20 of the Exchange
Act, as follows:

            (i) against any and all loss, liability, claim, damage and expense
      whatsoever, as incurred, arising out of any untrue statement or alleged
      untrue statement of a material fact contained in the Registration
      Statement (or any amendment thereto), or the omission or alleged omission
      therefrom of a material fact necessary in order to make the statements
      therein, in light of the circumstances under which they were made, not
      misleading or arising out of any untrue statement or alleged untrue
      statement of a material fact included in any preliminary prospectus or the
      Prospectus (or any amendment or supplement thereto), or the omission or
      alleged omission therefrom of a material fact necessary in order to make
      the statements therein, in the light of the circumstances under which they
      were made, not misleading;

            (ii) against any and all loss, liability, claim, damage and expense
      whatsoever, as incurred, to the extent of the aggregate amount paid in
      settlement of any litigation, or any investigation or proceeding by any
      governmental agency or body, commenced or threatened, or of any claim
      whatsoever based upon any such untrue statement or omission, or any such
      alleged untrue statement or omission, provided that (subject to Section
      6(d) below) any such settlement is effected with the prior written consent
      of the Company; and

            (iii) against any and all expense whatsoever, as incurred (including
      the fees and disbursements of counsel), reasonably incurred in
      investigating, preparing or defending against any litigation, or any
      investigation or proceeding by any governmental agency or body, commenced
      or threatened, or any claim whatsoever based upon any such untrue
      statement or omission, or any such alleged untrue statement or omission,
      to the extent that any such expense is not paid under (i) or (ii) above;

provided, however, that this indemnity shall not apply to any loss, liability,
claim, damage or expense to the extent arising out of any untrue statement or
omission or alleged untrue statement or omission made in reliance upon and in
conformity with written information furnished to the Company by the Initial
Purchasers or such Holder (which also acknowledges the indemnity provisions
herein) and each person, if any, who controls the Initial Purchasers or any such
Holder expressly for use in the Registration Statement (or any amendment
thereto), or any preliminary prospectus or the Prospectus (or any amendment or
supplement thereto), and provided further that any amounts payable by the
Company to the Initial Purchasers or the Holders shall be net of any insurance
proceeds actually recovered by the Initial Purchasers or the Holders in
connection therewith.

            (b) In connection with any Shelf Registration in which a Holder,
including, without limitation, the Initial Purchasers, is participating, in
furnishing information relating to such Holder to the Company in writing
expressly for use in such Registration Statement, any preliminary prospectus,
the Prospectus or any amendments or supplements thereto, such Holders agree,
severally and not jointly, to indemnify and hold harmless the Initial Purchasers
and each


                                       13
<PAGE>
person, if any, who controls the Initial Purchasers within the meaning of either
Section 15 of the Securities Act or Section 20 of the Exchange Act and the
Company, and each person, if any, who controls the Company within the meaning of
either such Section, against any and all loss, liability, claim, damage and
expense described in the indemnity contained in subsection (a) of this Section,
as incurred, but only with respect to untrue statements or omissions, or alleged
untrue statements or omissions, made in the Registration Statement (or any
amendment thereto), or any preliminary prospectus or the Prospectus (or any
amendment or supplement thereto) in reliance upon and in conformity with written
information furnished to the Company by such Holder (which also acknowledges the
indemnity provisions herein) and each person, if any, who controls any such
Holder expressly for use in the Registration Statement (or any amendment
thereto) or such preliminary prospectus or the Prospectus (or any amendment or
supplement thereto).

         Each of the Initial Purchasers agrees to indemnify and hold harmless
the Company, the Holders, and each person, if any, who controls the Company or
any Holder within the meaning of either Section 15 of the Securities Act or
Section 20 of the Exchange Act against any and all loss, liability, claim,
damage and expense described in the indemnity contained in subsection (a) of
this Section, as incurred, but only with respect to untrue statements or
omissions, or alleged untrue statements or omissions, made in the Registration
Statement (or any amendment thereto), or any preliminary prospectus or the
Prospectus (or any amendment or supplement thereto) in reliance upon and in
conformity with written information furnished to the Company by the Initial
Purchasers expressly for use in the Registration Statement (or any amendment
thereto) or such preliminary prospectus or the Prospectus (or any amendment or
supplement thereto).

         (c) Each indemnified party shall give notice as promptly as reasonably
practicable to each indemnifying party of any action commenced against it in
respect of which indemnity may be sought hereunder, but failure to so notify an
indemnifying party shall not relieve such indemnifying party from any liability
hereunder to the extent it is not materially prejudiced as a result thereof and
in any event shall not relieve it from any liability which it may have otherwise
than on account of this indemnity agreement. An indemnifying party may
participate at its own expense in the defense of any such action; provided,
however, that counsel to the indemnifying party shall not (except with the
consent of the indemnified party) also be counsel to the indemnified party. In
no event shall the indemnifying parties be liable for fees and expenses of more
than one counsel (in addition to any local counsel) separate from their own
counsel for all indemnified parties in connection with any one action or
separate but similar or related actions in the same jurisdiction arising out of
the same general allegations or circumstances. Counsel for the indemnified party
shall be legal counsel acceptable to the indemnifying party; provided that the
indemnifying party shall not unreasonably object to the legal counsel selected
by the indemnified party. With respect to any action commenced, the parties
hereto agree that it shall not be deemed to be an "unreasonable objection" if
the indemnifying party objects to the choice of legal counsel selected by the
indemnified party if such legal counsel is unable, for any reason, to also act
as legal counsel to the indemnifying party; provided that the indemnifying party
shall not raise such objection with respect to more than two legal counsels
selected by the indemnified party. No indemnifying party shall, without the
prior written consent of the indemnified parties, settle or compromise or
consent to the entry of any judgment with respect to any litigation, or any
investigation or proceeding by any


                                       14
<PAGE>
governmental agency or body, commenced or threatened, or any claim whatsoever in
respect of which indemnification or contribution could be sought under this
Section 6 hereof (whether or not the indemnified parties are actual or potential
parties thereto), unless such settlement, compromise or consent (i) includes an
unconditional release of each indemnified party from all liability arising out
of such litigation, investigation, proceeding or claim and (ii) does not include
a statement as to or an admission of fault, culpability or a failure to act by
or on behalf of any indemnified party.

         (d) If at any time an indemnified party shall have requested an
indemnifying party to reimburse the indemnified party for fees and expenses of
counsel, such indemnifying party agrees that it shall be liable for any
settlement of the nature contemplated by Section 6(a)(ii) effected without its
written consent if (i) such settlement is entered into more than 45 days after
receipt by such indemnifying party of aforesaid request, (ii) such indemnifying
party shall have received notice of the terms of such settlement at least 30
days prior to such settlement being entered into and (iii) such indemnifying
party shall not have reimbursed such indemnified party in accordance with such
request prior to the date of such settlement.

         (e) If the indemnification provided for in this Section 6 is for any
reason unavailable to or insufficient to hold harmless an indemnified party in
respect of any losses, liabilities, claims, damages or expenses referred to
therein, then each indemnifying party shall contribute to the aggregate amount
of such losses, liabilities, claims, damages and expenses incurred by such
indemnified party, as incurred, in such proportion as is appropriate to reflect
the relative fault of the indemnifying party or parties on the one hand and of
the indemnified party on the other hand in connection with the statements or
omissions which resulted in such losses, liabilities, claims, damages or
expenses, as well as any other relevant equitable considerations.

         The relative fault of the Company on the one hand and the holders of
the Registrable Securities or the Initial Purchasers on the other hand shall be
determined by reference to, among other things, whether any such untrue or
alleged untrue statement of a material fact or omission or alleged omission to
state a material fact relates to information supplied by the Company or by the
Holder, including without limitation the Initial Purchasers and the parties'
relative intent, knowledge, access to information and opportunity to correct or
prevent such statement or omission.

         The parties hereto agree that it would not be just and equitable if
contribution pursuant to this Section 6(e) were determined by pro rata
allocation or by any other method of allocation which does not take account of
the equitable considerations referred to above in this Section 6(e). The
aggregate amount of losses, liabilities, claims, damages, and expenses incurred
by an indemnified party and referred to above in this Section 6(e) shall be
deemed to include any legal or other expenses reasonably incurred by such
indemnified party in investigating, preparing or defending against any
litigation, or any investigation or proceeding by any governmental agency or
body, commenced or threatened, or any claim whatsoever based upon any such
untrue or alleged untrue statement or omission or alleged omission.

         Notwithstanding the provisions of this Section 6, neither the Holders
nor the Initial Purchasers, shall be required to indemnify or contribute any
amount in excess of the amount by which the total price at which the Registrable
Securities sold by such Holder or


                                       15
<PAGE>
underwritten by the Initial Purchasers, as the case may be, and distributed to
the public were offered to the public exceeds the amount of any damages that
such Holder or the Initial Purchasers has otherwise been required to pay by
reason of such untrue or alleged untrue statement or omission or alleged
omission.

         No person guilty of fraudulent misrepresentation (within the meaning of
Section 11(f) of the Securities Act) shall be entitled to contribution from any
person who was not guilty of such fraudulent misrepresentation.

         For purposes of this Section 6(e), each person, if any, who controls
the Initial Purchasers or any Holder within the meaning of Section 15 of the
Securities Act or Section 20 of the Exchange Act shall have the same rights to
contribution as the Initial Purchasers or such holder, and each person, if any,
who controls the Company within the meaning of Section 15 of the Securities Act
or Section 20 of the Exchange Act shall have the same rights to contribution as
the Company.

         Section 7. Information Requirements. The Company covenants that, if at
any time before the end of the Effectiveness Period the Company is not subject
to the reporting requirements of the Exchange Act, it will cooperate with any
Holder and take such further reasonable action as any Holder may reasonably
request in writing (including, without limitation, making such reasonable
representations as any such Holder may reasonably request), all to the extent
required from time to time to enable such Holder to sell Registrable Securities
without registration under the Securities Act within the limitation of the
exemptions provided by Rule 144 and Rule 144A under the Securities Act and
customarily taken in connection with sales pursuant to such exemptions. Upon the
written request of any Holder, the Company shall deliver to such Holder a
written statement as to whether it has complied with such filing requirements,
unless such a statement has been included in the Company's most recent report
required to be filed and filed pursuant to Section 13 or Section 15(d) of
Exchange Act.

         Section 8. Miscellaneous.

         (a) No Conflicting Agreements. The Company is not, as of the date
hereof, a party to, nor shall it, on or after the date of this Agreement, enter
into, any agreement with respect to its securities that conflicts with the
rights granted to the Holders of Registrable Securities in this Agreement. The
Company represents and warrants that the rights granted to the Holders of
Registrable Securities hereunder do not in any way conflict with the rights
granted to the holders of the Company's securities under any other agreements.

         (b) Amendments and Waivers. The provisions of this Agreement, including
the provisions of this sentence, may not be amended, modified or supplemented,
and waivers or consents to departures from the provisions hereof may not be
given, unless the Company has obtained the written consent of Holders of a
majority of the then outstanding Underlying Common Stock constituting
Registrable Securities (with Holders of Securities deemed to be the Holders, for
purposes of this Section, of the number of outstanding shares of Underlying
Common Stock into which such Securities are or would be convertible or
exchangeable as of the date on which such consent is requested). Notwithstanding
the foregoing, a waiver or consent to depart from the provisions hereof with
respect to a matter that relates exclusively to the rights of


                                       16
<PAGE>
Holders of Registrable Securities whose securities are being sold pursuant to a
Registration Statement and that does not directly or indirectly affect the
rights of other Holders of Registrable Securities may be given by Holders of at
least a majority of the Registrable Securities being sold by such Holders
pursuant to such Registration Statement; provided, that the provisions of this
sentence may not be amended, modified, or supplemented except in accordance with
the provisions of the immediately preceding sentence. Each Holder shall be bound
by any such amendment, modification, supplement, waiver or consent effected
pursuant to this Section 8(b), whether or not any notice, writing or marking
indicating such amendment, modification, supplement, waiver or consent appears
on the Registrable Securities or is delivered to such Holder.

         (c) Notices. All notices and other communications provided for or
permitted hereunder shall be made in writing by hand delivery, by telecopier, by
courier guaranteeing overnight delivery or by first-class mail, return receipt
requested, and shall be deemed given (i) when made, if made by hand delivery,
(ii) upon confirmation, if made by telecopier, (iii) one (1) Business Day after
being deposited with such courier, if made by overnight courier or (iv) on the
date indicated on the notice of receipt, if made by first-class mail, to the
parties as follows:

         (w) if to a Holder, at the most current address given by such Holder to
the Company in a Notice and Questionnaire or any amendment thereto;

         (x) if to the Company, to:

             Regeneron Pharmaceuticals, Inc.
             777 Old Saw Mill River Road
             Tarrytown, New York 10591-607
             Attention: General Counsel
             Telecopy No.:  (914) 345-7721

             with a copy to:

             Skadden, Arps, Slate, Meagher & Flom LLP
             4 Times Square
             New York, NY10036-6522
             Attention: David J. Goldschmidt

             and

         (y) if to the Initial Purchasers, to:

             Merrill Lynch & Co., Merrill Lynch, Pierce, Fenner & Smith
             Incorporated
             World Financial Center
             North Tower
             250 Vesey Street
             New York, New York 10281
             Attention:  Syndicate Department
             Telecopy No.:  (212) 738-1069


                                       17
<PAGE>
or to such other address as such person may have furnished to the other persons
identified in this Section 8(c) in writing in accordance herewith.

         (d) Approval of Holders. Whenever the consent or approval of Holders of
a specified percentage of Registrable Securities is required hereunder, the
Registrable Securities held by the Company or its Affiliates (other than the
Initial Purchasers or subsequent Holders of Registrable Securities if such
subsequent Holders are deemed to be such affiliates solely by reason of their
holdings of such Registrable Securities) shall not be counted in determining
whether such consent or approval was given by the Holders of such required
percentage.

         (e) Successors and Assigns. Any person who purchases any Registrable
Securities from the Initial Purchasers shall be deemed, for purposes of this
Agreement, to be an assignee of the Initial Purchasers. This Agreement shall
inure to the benefit of and be binding upon the successors and assigns of each
of the parties and shall inure to the benefit of and be binding upon each
Holder.

         (f) Counterparts. This Agreement may be executed in any number of
counterparts and by the parties hereto in separate counterparts, each of which
when so executed shall be deemed to be original and all of which taken together
shall constitute one and the same agreement.

         (g) Headings. The headings in this Agreement are for convenience of
reference only and shall not limit or otherwise affect the meaning hereof.

         (h) Governing Law. THIS AGREEMENT SHALL BE GOVERNED BY AND CONSTRUED IN
ACCORDANCE WITH THE LAWS OF THE STATE OF NEW YORK.

         (i) Severability. If any term, provision, covenant or restriction of
this Agreement is held to be invalid, illegal, void or unenforceable, the
remainder of the terms, provisions, covenants and restrictions set forth herein
shall remain in full force and effect and shall in no way be affected, impaired
or invalidated thereby, and the parties hereto shall use their best efforts to
find and employ an alternative means to achieve the same or substantially the
same result as that contemplated by such term, provision, covenant or
restriction, it being intended that all of the rights and privileges of the
parties shall be enforceable to the fullest extent permitted by law.

         (j) Entire Agreement. This Agreement is intended by the parties as a
final expression of their agreement and is intended to be a complete and
exclusive statement of the agreement and understanding of the parties hereto in
respect of the subject matter contained herein and the registration rights
granted by the Company with respect to the Registrable Securities. Except as
provided in the Purchase Agreement, there are no restrictions, promises,
warranties or undertakings, other than those set forth or referred to herein,
with respect to the registration rights granted by the Company with respect to
the Registrable Securities. This Agreement supersedes all prior agreements and
undertakings among the parties with respect to such registration rights.


                                       18
<PAGE>
         (k) Termination. This Agreement and the obligations of the parties
hereunder shall terminate upon the expiration of the Effectiveness Period,
except for any liabilities or obligations under Sections 4, 5 or 6 hereof and
the obligations to make payments of and provide for liquidated damages under
Section 2(e) hereof to the extent such damages accrue prior to the end of the
Effectiveness Period, each of which shall remain in effect in accordance with
its terms.

                               * * * * * * * *


                                       19
<PAGE>
            IN WITNESS WHEREOF, the parties have executed this Registration
Rights Agreement as of the date first written above.


                                    REGENERON PHARMACEUTICALS, INC.



                                    By:   __________________________________
                                          Name:
                                          Title:


Confirmed and accepted as of the date first above written:

MERRILL LYNCH & CO.
   MERRILL LYNCH, PIERCE, FENNER & SMITH
                  INCORPORATED
ROBERTSON STEPHENS, INC.

By:   MERRILL LYNCH & CO.
         MERRILL LYNCH, PIERCE, FENNER & SMITH
                        INCORPORATED


By:   _________________________________
      Name:
      Title: