Exhibit
4.6  EXECUTION COPY    REGISTRATION RIGHTS AGREEMENT   by and among   IMCLONE SYSTEMS INCORPORATED  as Issuer,  and  MORGAN STANLEY & CO. INCORPORATED  and  UBS
SECURITIES LLC  as the Initial Purchasers       Dated as of
May 7, 2004 
   THIS REGISTRATION
RIGHTS AGREEMENT is made and entered into as ofMay 7, 2004, by andamong ImClone Systems Incorporated, a
Delaware corporation (the Company), and Morgan Stanley & Co.
Incorporatedand UBS Securities LLC (together, theInitial Purchasers), pursuant to the
Purchase Agreement datedMay 3, 2004(the Purchase Agreement) among 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, (i) for their benefit as Initial Purchasers and
(ii) for the benefit of the beneficial owners (including the Initial
Purchasers) from time to time of the Notes (as defined herein) and the
beneficial owners from time to time of the Underlying Common Stock (as defined
herein) issued upon conversion of the Notes (each of the foregoing a Holder
and together the Holders), as follows: Section1. 
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: Additional Interest has the
meaning set forth in Section 2(e) hereof. Additional Interest Accrual Period
has the meaning set forth in Section 2(e) hereof. Additional Interest Payment Date
means each May 15 and November 15. 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 set forth in Section
2(d) hereof. Applicable
Conversion Price  as of any
date of determination means the Conversion Price in effect as of such date of
determination or, if no Notes are then outstanding, the Conversion Price that
would be in effect were Notes then outstanding. 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 the shares of common stock, par value $.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 such term in the Indenture. Deferral
Notice has the meaning set forth in Section 3(i) hereof. Deferral
Period has the meaning set forth in Section 3(i) hereof. Effectiveness
Deadline Date has the meaning set forth in Section 2(a) hereof. Effectiveness
Period means the period commencing on the date hereof and ending on
the date that all Registrable Securities have ceased to be Registrable
Securities.  2 
   Event
has the meaning set forth in Section 2(e) hereof. Event Date
has the meaning set forth in Section 2(e) hereof. Event
Termination Date has the meaning set forth 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 set forth in Section 2(a) hereof. Holder
has the meaning set forth in the second paragraph of this Agreement. Indenture
means the Indenture, dated as of the Closing Date, between the Company and The
Bank of New York, as trustee, pursuant to which the Notes are being issued. Initial
Purchasers means Morgan Stanley & Co. Incorporated and UBS
Securities LLC. Initial
Shelf Registration Statement has the meaning set forth in Section
2(a) hereof. Issue Date
means the first date of original issuance of the Notes. Losses
has the meaning set forth in Section 6 hereof. Material
Event has the meaning set forth in Section 3(i) hereof. Notes
means the 1-3/8%
Convertible Notes due 2024 of the Company to be purchased pursuant to the
Purchase Agreement. 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 dated May 3, 2004relating to the Notes. Notice
Holder means, on any date, any Holder that has delivered a Notice
and Questionnaire to the Company on or prior to such date. 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 430A 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 set forth in the preamble hereof. Record
Holder means (i) with respect to any Additional Interest Payment
Date relating to any Notes as to which any Additional Interest has accrued, the
holder of record of such Note on the record date with respect to the interest
payment date under the Indenture on which such Additional Interest Payment Date
shall occur and (ii) with respect to any Additional Interest Payment Date
relating to the Underlying Common Stock as to which any such Additional
Interest has accrued, the registered holder of such Underlying Common Stock
fifteen (15) days prior to such Additional Interest Payment Date. Registrable
Securities means the Notes until such Notes have been converted
into or exchanged for the Underlying Common Stock and, at all times subsequent
to any such  3 
   conversion or
exchange the Underlying Common Stock and any securities into or for which such
Underlying Common Stock has 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, (A) 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) or (iii) its sale to the public
pursuant to Rule 144 (or any similar provision then in force, but not Rule
144A) under the Securities Act, and (B) as a result of the event or
circumstance described in any of the foregoing clauses (i) through (iii), the
legend with respect to transfer restrictions required under the Indenture are
removed or removable in accordance with the terms of the Indenture or such
legend, as the case may be. Registration
Expenses has the meaning set forth 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 means Restricted Securities as defined 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 Securities and Exchange Commission. Securities
Act means the Securities Act of 1933, as amended, and the rules and
regulations promulgated by the SEC thereunder. Shelf
Registration Statement has the meaning set forth in Section 2(a)
hereof. Special
Counsel means Cravath, Swaine & Moore LLP or such other
successor counsel as shall be specified by the Holders of a majority of the
Registrable Securities, but which may, with 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, the reasonable fees and expenses of which will be paid by the Company
pursuant to Section 5 hereof.Throughout this
Agreement, for purposes of determining the holders of a majority of Registrable
Securities in this definition, Holders of Notes shall be deemed to be the
Holders of the number of shares of Underlying Common Stock into which such
Notes are or would be convertible as of the date the consent is requested. Subsequent
Shelf Registration Statement has the meaning set forth in Section
2(b) hereof. TIA
means the Trust Indenture Act of 1939, as amended. Trustee
means The Bank of New York, the Trustee under the Indenture. Underlying
Common Stock means the Common Stock into which the Notes are
convertible or issued upon any such conversion.  4 
   Section2. 
Shelf
Registration.(a)The Company shall use its reasonable
efforts to 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, which term shall include the Initial Shelf
Registration Statement and each Subsequent 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, as defined below) continuously
effective under the Securities Act until the expiration of the Effectiveness
Period.  At the time the Initial Shelf
Registration Statement is declared effective, each Holder that became a Notice
Holder on or prior to the date ten (10) Business Days prior to such time of
effectiveness shall be named as a selling securityholder in the Initial Shelf
Registration Statement and the related Prospectus in such a manner as to permit
such Holder to deliver such Prospectus to purchasers of Registrable Securities
in accordance with applicable law. Except for the piggyback registration rights
granted to (i) Merck KGaA under its Development and License Agreement dated
December 14, 1998 with the Company and (ii) Bristol-Myers Squibb Company (BMS)
under its Stockholder Agreement dated September 19, 2001 with the Company, for
each of which the Company will use its reasonable efforts to obtain a waiver or
offer to each of Merck KGaA and BMS a separate shelf registration statement,
none of the Companys security holders (other than the Holders of Registrable
Securities) shall have the right to include the Companys securities  in the Shelf Registration Statement. (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 resold pursuant thereto or shall have
otherwise ceased to be Registrable Securities), the Company shall use its
reasonable 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
Registrable Securities (a Subsequent Shelf Registration Statement).  If a Subsequent Shelf Registration Statement
is filed, the Company shall use its reasonable efforts to cause the Subsequent
Shelf Registration Statement to become effective as promptly as is practicable
after such filing and to keep such 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 as  5 
   reasonably
requested by the Initial Purchasers or by the Trustee on behalf of the Holders
of the Registrable Securities covered by such Shelf Registration Statement. (d)  Each Holder of Registrable Securities 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 of Registrable Securities 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 three (3) 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 (x) at the end of each calendar quarter or (y) if a Deferral
Period is in effect at the end of such calendar quarter, no later than fifteen
(15) Business Days after the expiration of such Deferral Period, (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
(including a Subsequent Shelf Registration Statement) so that the Holder
delivering a Notice and Questionnaire during such calendar quarter is named as
a selling securityholder 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 or shall file a Subsequent Shelf Registration Statement,
use its reasonable efforts to cause such post-effective amendment or Subsequent
Shelf Registration Statement 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).  Notwithstanding
anything contained herein to the contrary, (i) the Company shall be under no
obligation to name any Holder that is not a Notice Holder as a selling
securityholder in any Registration Statement or related Prospectus and (ii) the
Amendment Effectiveness Deadline Date shall be extended by up to ten (10)
Business Days from the expiration of a Deferral Period (and the Company shall
incur no obligation to pay Additional Interest during such extension) if such
Deferral Period shall be in effect on the Amendment Effectiveness Deadline
Date. (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) within the time period required therein, (iv) any post-effective
amendment to a Shelf Registration Statement or any Subsequent Shelf
Registration Statement filed pursuant to Section 2(d)(i) has not become
effective under the Securities Act on or prior to the Amendment Effectiveness
Deadline Date, (v) the aggregate  6 
   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 (vi) the number of Deferral
Periods in any period exceeds the number permitted in respect of such period
pursuant to Section 3(i) hereof (each of the events of a type described in any
of the foregoing clauses (i) through (vi) 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), the Amendment Effectiveness Deadline Date in the case of clause
(iv), 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 (v), 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 (vi), 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 is declared 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) the date the
applicable post-effective amendment to a Shelf Registration Statement or
Subsequent Shelf Registration Statement becomes effective under the Securities
Act in the case of an Event of the type described in clause (iv), 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 (v), 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 (vi). Accordingly,
commencing on (and including) any Event Date and ending on (but excluding) the
next date on which there are no Events that have occurred and are continuing
(an Additional
Interest Accrual Period), the Company agrees to pay, as additional
interest and not as a penalty, an amount (the Additional Interest),
payable on the Additional Interest Payment Dates to Record Holders of Notes
that are Registrable Securities and of shares of Underlying Common Stock issued
upon conversion of Notes that are Registrable Securities, as the case may be,
accruing, for each portion of such Additional Interest Accrual Period beginning
on and including an Additional Interest Payment Date (or, in respect of the
first time that the Additional Interest is to be paid to Holders on an
Additional Interest Payment Date as a result of the occurrence of any
particular Event, from the Event Date) and ending on but excluding the first to
occur of (A) the date of the end of the Additional Interest Accrual Period or
(B) the next Additional Interest Payment Date, at a rate per annum equal to
one-quarter of one percent (0.25%) of the outstanding principal amount of such
Notes for the first 90 days after the occurrence of the event and one-half of
one percent (0.5%) of the outstanding principal amount of such Notes after the
first 90 days or, in the case of Notes that have been converted into or exchanged
for Underlying Common Stock, the Applicable Conversion Price of such shares of
Underlying Common Stock, as the case may be, in each case determined as of the
Business Day immediately preceding the next Additional Interest Payment Date; provided,
that in the case of an Additional Interest 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 Additional Interest shall be paid only to
the Holders that have delivered Notice and Questionnaires that caused the  7 
   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
Additional Interest accrued with respect to any Note or portion thereof called
for redemption on a redemption date or converted into Underlying Common Stock
on a conversion date prior to the Additional Interest Payment Date, shall, in
any such event, be paid instead to the Holder who submitted such Note 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).In calculating the Additional Interest on any date on which no Notes
are outstanding, the Conversion Price and the Additional Interest payable with
respect to shares of Common Stock which are Registrable Securities, shall be
calculated as if the Notes were still outstanding.Notwithstanding the foregoing, no Additional Interest 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 Additional Interest with respect to any period shall not exceed
the rate provided for in this paragraph notwithstanding the occurrence of
multiple concurrent Events.  Following
the cure of all Events requiring the payment by the Company of Additional
Interest to the Holders of Registrable Securities pursuant to this Section, the
accrual of Additional Interest will cease (without in any way limiting the
effect of any subsequent Event requiring the payment of Additional Interest by
the Company). The Trustee shall
be entitled, on behalf of Holders of Notes or Underlying Common Stock, to seek
any available remedy for the enforcement of this Agreement, including for the
payment of any Additional Interest.  Notwithstanding
the foregoing, the parties agree that the sole damages payable for a violation
of the terms of this Agreement with respect to which Additional Interest is
expressly provided shall be such Additional Interest.  Nothing shall preclude a Notice Holder or Holder of Registrable
Securities 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 Additional Interest 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. Section3. 
Registration
Procedures.In connection with the registration
obligations of the Company under Section 2 hereof, the Company shall: (a)           Prepare and file with the SEC a
Registration Statement or Registration Statements on any appropriate form under
the Securities Act available for the sale of the Registrable Securities by the
Holders thereof in accordance with the intended method or methods of
distribution thereof, and use its reasonable efforts to cause each such
Registration Statement to become effective and remain effective as provided
herein; provided,
that before filing any Registration Statement or Prospectus or any amendments
or supplements thereto with the SEC, furnish to the Initial Purchasers and the
Special Counsel copies of all such documents proposed to be filed and use its
reasonable efforts to reflect in each such document when so filed with the  8 
   SEC such comments
as the Special Counsel reasonably shall propose within five (5) Business Days
of the delivery of such copies to the Initial Purchasers and the Special
Counsel. (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 use its
reasonable efforts to 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, the Initial Purchasers and the Special Counsel (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 been declared 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 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 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 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 reasonable efforts to 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, in either case at the
earliest possible moment, and provide prompt notice to each Notice Holder and
the Initial Purchasers of the withdrawal of any such order. (e)           If reasonably requested by an Initial
Purchaser or any Notice Holder, as promptly as practicable incorporate in a
Prospectus supplement or post-effective amendment to a Registration Statement
such information as the Initial Purchaser, the Special Counsel or such Notice
Holder shall, on the basis of a written 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. (f)            As promptly as practicable furnish to
each Notice Holder, the Special Counsel and the Initial Purchasers, without
charge, at least one (1) conformed copy of the Registration   9 
   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,
Special Counsel, counsel or Initial Purchaser). (g)           During the Effectiveness Period,
deliver to each Notice Holder, the Special Counsel and the Initial Purchasers,
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, 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 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 reasonable 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, as promptly as practicable prepare and file, if necessary pursuant to
applicable law, 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  10 
   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 (except for any such untrue statement or omission made
in reliance on and in conformity with information relating to any Notice Holder
furnished to the Company in writing by such Notice Holder expressly for use
therein), 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 (except for any such untrue
statement or omission made in reliance on and in conformity with information
relating to any Notice Holder furnished to the Company in writing by such
Notice Holder expressly for use therein), 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 efforts to cause it to be declared effective
as promptly as is practicable, and (ii) give notice to the Notice Holders, and
the Special Counsel, if any, 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 all reasonable 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 practicable thereafter and (z) in the case of
clause (C) above, as soon as, in the discretion of the Company, such suspension
is no longer appropriate.  The Company
shall be entitled to exercise its right under this Section 3(i) to suspend the
availability of the Shelf Registration Statement or any Prospectus, without
incurring or accruing any obligation to pay Additional Interest pursuant to
Section 2(e), no more than one (1) time in any three month period or three (3)
times in any twelve month period, and any such period during which the
availability of the Registration Statement and any Prospectus is suspended (the
Deferral
Period) shall, without incurring any obligation to pay Additional
Interest pursuant to Section 2(e), not exceed 30 days; provided, that in the case
of a Material Event relating to an acquisition or a probable acquisition or
financing, recapitalization, business combination or other similar transaction,
the Company may, without incurring any obligation to pay Additional Interest
pursuant to Section 2(e), deliver to Notice Holders a second notice to the effect
set forth above, which shall have the effect of extending the Deferral Period
by up to an additional 30 days, or such shorter period of time as is specified
in such second notice, provided, that the aggregate duration of
any Deferral Periods shall not, without incurring any obligation to pay
Additional Interest pursuant to Section 2(e), exceed 30 days in any three month
period (or 60 days in any three month period in the event of a Material Event
pursuant to which the Company has delivered a second notice as required above)
or 90 days in any twelve (12) month period. (j)            If requested in writing in connection
with a disposition of Registrable Securities pursuant to a Registration
Statement, make reasonably available for inspection during normal business
hours by a representative for the Notice Holders of such Registrable
Securities, and any  11 
   managing
underwriter, broker-dealers, attorneys and accountants retained by such Notice
Holders, all relevant financial and other records and pertinent corporate
documents and properties of the Company and its subsidiaries, and cause the
appropriate officers, directors and employees of the Company and its
subsidiaries to make reasonably available for inspection during normal business
hours on reasonable notice all relevant information reasonably requested by
such representative for the Notice Holders, or any such managing underwriter,
broker-dealers, attorneys or accountants in connection with such disposition,
in each case as is customary for similar due diligence 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,
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 and provided
further, that the Company shall not be required to disclose any
information subject to the attorney-client or attorney work product privilege
if and to the extent such disclosure would constitute a waiver of such
privilege. (k)           Use all reasonable efforts to 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) no later
than 45 days after the end of any 3-month period (or 90 days after the end of
any 12-month period if such period is a fiscal year) commencing on the first
day of the first fiscal quarter of the Company commencing after the effective
date of a Registration Statement, which statements shall cover said periods. (l)    Cooperate
with each Notice Holder to facilitate the timely preparation and delivery of
certificates representing Registrable Securities sold or to be sold pursuant to
a Registration Statement, which certificates shall not bear any restrictive
legends, 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 (2) 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 and the transfer agent for the Common Stock with printed
certificates for the Registrable Securities that are in a form eligible for
deposit with The Depository Trust Company. (n)    Cooperate
and assist in any filings required to be made with the National Association of
Securities Dealers, Inc.  12 
    (o)    Upon
(i) the filing of the Initial Shelf Registration Statement and (ii) the
effectiveness of the Initial Shelf Registration Statement and any Subsequent
Shelf Registration Statement, announce the same, in each case by release to
Reuters Economic Services and Bloomberg Business News. Section 4. 
Holders
Obligations.Each Holder agrees, by acquisition of the
Registrable Securities, that no Holder of Registrable Securities 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 the Company may from
time to time reasonably request.  Any
sale of any Registrable Securities by any Holder shall constitute a
representation and warranty by such Holder that the information relating to
such Holder and its plan of distribution is as set forth in the Prospectus
delivered by such Holder in connection with such disposition, that such
Prospectus does not as of the time of such sale contain any untrue statement of
a material fact relating to or provided by such Holder or its plan of
distribution and that such Prospectus does not as of the time of such sale omit
to state any material fact relating to or provided by such Holder or its plan
of distribution necessary to make the statements in such Prospectus, in the
light of the circumstances under which they were made, not misleading. 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
Registration Statement is 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, reasonable fees and
disbursements of the Special Counsel 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 and the Special Counsel in connection with the Shelf
Registration Statement (provided that the Company shall not be liable for the
fees and expenses of more than one separate firm for all parties participating
in any transaction hereunder), (v) reasonable fees and disbursements of the
Trustee and its counsel and of the registrar and transfer agent for the Common
Stock and (vi) any Securities Act liability insurance obtained by the Company
in its sole discretion.  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 by the Company 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.  13 
   Notwithstanding
the provisions of this Section 5, each seller of Registrable Securities shall
pay selling expenses and all registration expenses to the extent required by
applicable law. Section6. 
Indemnification. (a)    Indemnification
by the Company.  The Company
shall indemnify and hold harmless each Notice Holder and each person, if any,
who controls any Notice Holder (within the meaning of either Section 15 of the
Securities Act or Section 20 of the Exchange Act) from and against any losses,
liabilities, claims, damages and expenses (including, without limitation, any
legal or other expenses reasonably incurred in connection with defending or
investigating any such action or claim) (collectively, Losses), arising out of or
based upon any untrue statement or alleged untrue statement of a material fact
contained in any Registration Statement or Prospectus or in any amendment or
supplement thereto or in any preliminary prospectus, or arising out of or based
upon any omission or alleged omission to state therein a material fact required
to be stated therein or necessary to make the statements therein not
misleading, provided,
however, that the Company shall not be liable in any such case to
the extent that any such Losses arise out of or are based upon an untrue
statement or alleged untrue statement contained in or omission or alleged
omission from any of such documents in reliance upon and conformity with any of
the information relating to the Holders furnished to the Company in writing by
a Holder expressly for use therein; provided further,that the indemnification
contained in this paragraph shall not inure to the benefit of any Holder of
Registrable Securities (or to the benefit of any person controlling such
Holder) on account of any such Losses arising out of or based upon an untrue
statement or alleged untrue statement or omission or alleged omission made in
any preliminary prospectus provided in each case the Company has performed its
obligations under Section 3(a) hereof if either (A) (i) such Holder failed to
send or deliver a copy of the Prospectus with or prior to the delivery of
written confirmation of the sale by such Holder to the person asserting the
claim from which such Losses arise and (ii) the Prospectus would have corrected
such untrue statement or alleged untrue statement or such omission or alleged omission,
or (B) (x) such untrue statement or alleged untrue statement, omission or
alleged omission is corrected in an amendment or supplement to the Prospectus
and (y) having previously been furnished by or on behalf of the Company with
copies of the Prospectus as so amended or supplemented, such Holder thereafter
fails to deliver such Prospectus as so amended or supplemented, with or prior
to the delivery of written confirmation of the sale of a Registrable Security
to the person asserting the claim from which such Losses arise. (b)  Indemnification by Holders of Registrable Securities.  Each Holder agrees severally and not jointly
to indemnify and hold harmless the Company and its respective directors and
officers, and each person, if any, who controls the Company (within the meaning
of either Section 15 of the Securities Act or Section 20 of the Exchange Act)
or any other Holder, from and against all Losses arising out of or based upon
any untrue statement or alleged untrue statement of a material fact contained
in any Registration Statement or Prospectus or in any amendment or supplement
thereto or in any preliminary prospectus, or arising out of or based upon any
omission or alleged omission to state therein a material fact required to be
stated therein or necessary to make the statements therein not misleading, to
the extent, but only to the extent, that such untrue statement or alleged
untrue statement or omission or alleged omission was made in reliance upon and
in conformity with information furnished to the Company by such Holder
expressly for use in such Registration Statement or Prospectus or amendment or
supplement thereto.  In no event shall
the liability of any selling Holder of Registrable Securities  14 
   hereunder be
greater in amount than the dollar amount of the proceeds received by such
Holder upon the sale of the Registrable Securities pursuant to the Registration
Statement giving rise to such indemnification obligation. (c)  Conduct of Indemnification Proceedings.  In case any proceeding (including any
governmental investigation) shall be instituted involving any person in respect
of which indemnity may be sought pursuant to either of the two preceding
paragraphs, such person (the indemnified party) shall promptly notify
the person against whom such indemnity may be sought (the indemnifying party) in
writing and the indemnifying party, upon request of the indemnified party,
shall retain counsel reasonably satisfactory to the indemnified party to
represent the indemnified party and any others the indemnifying party may
designate in such proceeding and shall pay the reasonable fees and
disbursements of such counsel related to such proceeding.  In any such proceeding, any indemnified
party shall have the right to retain its own counsel, but the fees and expenses
of such counsel shall be at the expense of such indemnified party unless (i)
the indemnifying party and the indemnified party shall have mutually agreed to
the retention of such counsel or (ii) the named parties to any such proceeding
(including any impleaded parties) include both the indemnifying party and the
indemnified party and representation of both parties by the same counsel would
be inappropriate due to actual or potential differing interests between
them.  It is understood that the
indemnifying party shall not, in respect of the legal expenses of any
indemnified party in connection with any proceeding or related proceedings in
the same jurisdiction, be liable for the fees and expenses of more than one
separate firm (in addition to any local counsel) for all indemnified parties,
and that all such fees and expenses shall be reimbursed as they are
incurred.  Such separate firm shall be
designated in writing by, in the case of parties indemnified pursuant to
Section 6(a), the Holders of a majority (with Holders of Notes deemed to be the
Holders, for purposes of determining such majority, of the number of shares of
Underlying Common Stock into which such Notes are or would be convertible or
exchangeable as of the date on which such designation is made) of the
Registrable Securities covered by the Registration Statement held by Holders
that are indemnified parties pursuant to Section 6(a) and, in the case of
parties indemnified pursuant to Section 6(b), the Company.  The indemnifying party shall not be liable
for any settlement of any proceeding effected without its written consent, but
if settled with such consent or if there be a final judgment for the plaintiff,
the indemnifying party agrees to indemnify the indemnified party from and
against any loss or liability by reason of such settlement or judgment.  No indemnifying party shall, without the
prior written consent of the indemnified party, effect any settlement of any
pending or threatened proceeding in respect of which any indemnified party is
or could have been a party and indemnity could have been sought hereunder by
such indemnified party, unless such settlement includes an unconditional
release of such indemnified party from all liability on claims that are the
subject matter of such proceeding. (d)  Contribution.  To the
extent that the indemnification provided for in this Section 6 is unavailable
to an indemnified party under Section 6(a) or 6(b) hereof in respect of any
Losses or is insufficient to hold such indemnified party harmless, then each
applicable indemnifying party, in lieu of indemnifying such indemnified party,
shall contribute to the amount paid or payable by such indemnified party as a
result of such Losses (i) in such proportion as is appropriate to reflect the
relative benefits received by the indemnifying party or parties on the one hand
and the indemnified party or parties on the other hand or (ii) if the
allocation provided by clause (i) above is not permitted by applicable law, in
such proportion as is appropriate to reflect not only the relative benefits
referred to in clause (i) above but also the relative fault of the indemnifying  15 
   party or parties
on the one hand and of the indemnified party or parties on the other hand in
connection with the statements or omissions that resulted in such Losses, as
well as any other relevant equitable considerations.  Benefits received by the Company shall be deemed to be equal to
the total net proceeds from the initial placement pursuant to the Purchase
Agreement (before deducting expenses) of the Registrable Securities to which
such Losses relate.  Benefits received
by any Holder shall be deemed to be equal to the value of receiving Registrable
Securities that are registered under the Securities Act.  The relative fault of the Holders on the one
hand and the Company on the other hand shall be determined by reference to,
among other things, whether the untrue or alleged untrue statement of a
material fact or the omission or alleged omission to state a material fact
relates to information supplied by the Holders or by the Company, and the
parties relative intent, knowledge, access to information and opportunity to
correct or prevent such statement or omission. 
The Holders respective obligations to contribute pursuant to this
Section 6(d) are several in proportion to the respective number of Registrable
Securities they have sold pursuant to a Registration Statement, and not joint. The parties hereto
agree that it would not be just and equitable if contribution pursuant to this
Section 6(d) were determined by pro  rata allocation or by any
other method or allocation that does not take into account the equitable
considerations referred to in the immediately preceding paragraph.  The amount paid or payable by an indemnified
party as a result of the Losses referred to in the immediately preceding
paragraph shall be deemed to include, subject to the limitations set forth
above, any legal or other expenses reasonably incurred by such indemnified
party in connection with investigating or defending any such action or
claim.  Notwithstanding this Section
6(d), an indemnifying party that is a selling Holder of Registrable Securities
shall not be required to contribute any amount in excess of the amount by which
the total price at which the Registrable Securities sold by such indemnifying
party and distributed to the public were offered to the public exceeds the
amount of any damages that such indemnifying party 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. (e)  The indemnity, contribution and expense reimbursement obligations
of the parties hereunder shall be in addition to any liability any indemnified
party may otherwise have hereunder, under the Purchase Agreement or otherwise. (f)  The indemnity and contribution provisions contained in this
Section 6 shall remain operative and in full force and effect regardless of (i)
any termination of this Agreement, (ii) any investigation made by or on behalf
of any Holder or any person controlling any Holder, or the Company, or the
Companys officers or directors or any person controlling the Company and (iii)
the sale of any Registrable Securities by any Holder. Section7. 
Information
Requirements.  (a)  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
of Registrable Securities and take such further reasonable action as any Holder
of Registrable Securities 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  16 
   customarily taken
in connection with sales pursuant to such exemptions.  Upon the written request of any Holder of Registrable Securities,
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 filed pursuant to Section 13 or
Section 15(d) of Exchange Act. 
Notwithstanding the foregoing, nothing in this Section 7 shall be deemed
to require the Company to register any of its securities (other than the Common
Stock) under any section of the Exchange Act. (b)  The Company shall file the reports required to be filed by it
under the Exchange Act and shall comply with all other requirements set forth
in the instructions to Form S-3 in order to allow the Company to be eligible to
file registration statements on Form S-3. Section8. 
Miscellaneous. (a)  No Conflicting Agreements. 
Except for the piggyback registration rights granted to (i) Merck
KGaA under its Development and License Agreement dated December 14, 1998 with
the Company and (ii) BMS under its Stockholder Agreement dated September
19, 2001 with the Company, for each of which the Company will use its
reasonable efforts to obtain a waiver or offer to each of Merck KGaA and BMS a
separate shelf registration statement: (i)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. (ii)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 Notes deemed
to be the Holders, for purposes of this Section, of the number of outstanding
shares of Underlying Common Stock into which such Notes 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 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.Notwithstanding the
foregoing sentence, (i) this Agreement may be amended by written agreement
signed by the Company and the Initial Purchasers, without the consent of the
Holders of Registrable Securities, to cure any ambiguity or to correct or
supplement any provision contained herein that may be defective or inconsistent
with any other provision contained herein, or to make such other provisions in
regard to matters or questions arising under this Agreement that shall not
adversely affect the interests of the  17 
   Holders of Registrable Securities.Each Holder of
Registrable Securities outstanding at the time of any such amendment,
modification, supplement, waiver or consent or thereafter 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 of Registrable Securities, 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:ImClone Systems 
  Incorporated180 Varick Street, 7th FloorNew York, NY 10014Attention: 
  General CounselTelecopy No.: 
  (212) 645-2054andDavis Polk & Wardwell450 Lexington AvenueNew York, NY 10017Attention:  Richard A. Drucker, Esq.Telecopy No.: (212) 450-4800(y)
  
  if to the Initial Purchasers, to:Morgan Stanley & Co. Incorporated1585 BroadwayNew York, New YorkAttention: 
  Equity Capital MarketsTelecopy No.: (212) 761-0538  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.  18 
   (d)  Approval of Holders. 
Whenever the consent or approval of Holders of a specified percentage of
Registrable Securities is required hereunder, Registrable Securities held by
the Company or its affiliates (as such term is defined in Rule 405 under the
Securities Act) (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 of any Registrable Securities,provided that nothing herein
shall be deemed to permit any assignment, transfer or other disposition of
Registrable Securities in violation of the terms of the Indenture.  If any transferee of any Holder shall
acquire Registrable Securities, in any manner, whether by operation of law or
otherwise, such Registrable Securities shall be held subject to all of the
terms of this Agreement, and by taking and holding such Registrable Securities,
such person shall be conclusively deemed to have agreed to be bound by and to
perform all of the terms and provisions of this Agreement and such person shall
be entitled to receive the benefits hereof. (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, WITHOUT REGARD TO CONFLICTS OF LAWS PRINCIPLES THEREOF. (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.  No party hereto shall have any rights, duties or obligations
other than those specifically set forth in this Agreement.  In no event will such methods of distribution
take the  19 
    form of an underwritten
offering of the Registrable Securities without the prior agreement of the
Company. (k)  Termination.This
Agreement and the obligations of the parties hereunder shall terminate upon the
end of the Effectiveness Period, except for any liabilities or obligations
under Section 4, 5 or 6 hereof and the obligations to make payments of and
provide for Additional Interest 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.        20 
    IN WITNESS
WHEREOF, the parties have executed this Agreement as of the date first written
above.  IMCLONE SYSTEMS INCORPORATEDByName:Title:Confirmed and accepted as of the 
  date first above written:MORGAN STANLEY & CO. INCORPORATEDUBS SECURITIES LLCBy:  Morgan
  Stanley & Co. IncorporatedByName:Title:   21