1998 Non-Qualified Stock Option Plan - ImClone Systems Inc.


                          IMCLONE SYSTEMS INCORPORATED

               1998 NON-QUALIFIED STOCK OPTION PLAN, AS AMENDED(1)

                                    ARTICLE I

                                 Purpose of Plan

      1.1   General Purpose. The purpose of this Non-Qualified Stock Option Plan
(the 'Plan') is to promote the interests of ImClone Systems Incorporated (the
'Company') by affording key consultants, advisors, and non-officer employees an
opportunity to acquire a proprietary interest in the Company pursuant to stock
options issued by the Company, and thus to create in such persons increased
personal interest in its continued success.

      1.2   Statutory Stock Option. Options granted under the Plan are intended
to be 'non-qualified' stock options under the Internal Revenue Code of 1986, as
amended (the 'Code'). 

                                   ARTICLE II

                             Shares Subject to Plan

      2.1   Description of Shares. Subject to Article VII hereof, the stock to
which the Plan applies is shares of the Company's common stock, $.001 par value
('Common Stock'), either authorized but unissued or Treasury shares. The number
of shares of Common Stock to be issued or sold pursuant to options granted
hereunder shall not exceed 1,000,000 shares.

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(1)  Amended by the Board of Directors on July 7, 1998.


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      2.2   Restoration of Unpurchased Shares. Any shares subject to an option
granted hereunder that, for any reason, expires or is terminated unexercised as
to such shares may again be subject to an option to be granted hereunder.

                                   ARTICLE III

                     Administration; Committees; Amendments

      3.1   Administration. The Plan shall be administered by any of the
Compensation and Stock Option Committee (the 'Committee') or the Board of
Directors of the Company (the 'Board'). The Committee shall be comprised of not
less than two persons who shall be appointed by the Board from among the members
of the Board.

      3.2   Duration; Removal; Etc. The members of the Committee shall serve at
the pleasure of the Board, which shall have the power at all times to remove
members from the Committee or to add members thereto. Vacancies in the
Committee, however caused, shall be filled by action of the Board.

      3.3   Meetings; Actions of Committee. The Committee may select one of its
members as its Chairman and shall hold meetings at such times and places as it
may determine. All decisions or determinations of the Committee and the Board
shall be made by the majority vote or decision of all of its members, whether
present at a meeting or not; provided, however, that any decision or
determination reduced to writing and signed by all of the members shall be as
fully effective as if this had been made at a meeting duly called and held. The
Committee and the Board may make such rules and regulations for the conduct of
its business not inconsistent herewith as it may deem advisable.


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      3.4   Interpretation. The interpretation and construction by the Committee
or the Board of the provisions of the Plan or of the options granted hereunder
shall be final, unless in the case of the Committee otherwise determined by the
Board. No member of the Board or of the Committee shall be liable for an action
taken or determination made in good faith.

      3.5   Amendments or Discontinuation. The Board may make such amendments,
changes, and additions to the Plan, or may discontinue and terminate the Plan,
as it may deem advisable from time to time; provided, however, that no action
shall affect or impair any options theretofore granted under the Plan.

                                   ARTICLE IV

            Participants; Participation Guidelines; Duration of Plan

      4.1   Eligibility and Participation. Options shall be granted only to
persons ('Participants') who at the time of granting are key consultants,
advisors, or non-officer employees of the Company or a subsidiary. The Committee
or the Board shall determine the key consultants, advisors, and non-officer
employees to be granted options hereunder, the number of shares of Common Stock
subject to such options, the exercise prices of options, the terms thereof and
any other provisions not inconsistent with the Plan. Persons who are disabled
within the meaning of the Code shall not be eligible for the grant of options.

      4.2   Guidelines for Participation. In selecting Participants and
determining the numbers of shares of Common Stock for which options are to be
granted, either the Committee or the Board shall consult with officers and
directors of the Company, and shall take into account the duties of the
respective persons, their present and potential contributions to the success of
the Company, and such other factors of the Committee or the Board shall deem
relevant.


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      4.3   Duration of Plan. All options under the Plan shall be granted within
ten years from the date the Plan is approved by the Committee and the Board.

                                    ARTICLE V

                         Terms and Conditions of Options

      5.1   Individual Stock Option Agreements. All stock options granted
pursuant to the Plan shall be evidenced by stock option agreements ('Stock
Option Agreements'), which need not be identical, between the Company and the
Participant in such form as any of the Committee or the Board shall from time to
time approve, subject to the terms of the Plan.

      5.2   Number of Shares. Each Stock Option Agreement shall state the total
number of shares of Common Stock with respect to which the option is granted,
the terms and conditions of the option, and the exercise price or prices
thereof, it being understood that the Committee or the Board shall have
authority to prescribe in any Stock Option Agreement that the option evidenced
thereby may be exercisable in full or in part, as to any number of shares
subject thereto, at any time or from time to time during said term as the
Committee or the Board may determine; provided that no option granted pursuant
to the Plan shall be exercisable after the expiration of ten years from the date
such option is granted. Except as otherwise provided in any Stock Option
Agreement, an option may be exercised at any time or from time to time during
the term of the option as to any or all full (but no fractional) shares which
have become purchasable under such option. The Committee or the Board shall have
the right to accelerate, in whole or in part, from time to time, conditionally
or unconditionally, the right to exercise any option granted hereunder.

      5.3   Option Price. The price at which the shares of Common Stock subject
to each option granted under this Plan may be purchased (the 'option price' or
'exercise price') shall be 


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determined by any of the Committee or the Board, which shall have the authority
at the time the option is granted to prescribe in any Stock Option Agreement
that the price per share, with the passage of pre-determined periods of time,
shall increase from the original price to higher prices.

      5.4   Method of Exercising Option; Full Payment. Subject to the terms of
Section 6.1 and Section 6.2 hereof, options granted pursuant to the Plan may be
exercised only if the Participant was, at all times during the period beginning
on the date the option was granted and ending on the date of such exercise, a
key consultant, advisor or a non-officer employee of the Company or a
subsidiary. Options shall be exercised by written notice to the Company,
addressed to the Company at its principal place of business. Such notice shall
state the Participant's election to exercise the option and the number of shares
of Common Stock in respect of which it is being exercised, and shall be signed
by the Participant so exercising the option. Such notice shall be accompanied by
(a) the Stock Option Agreement (which, if not exercised for all the shares
subject thereto, shall be appropriately endorsed and returned to the
Participant); (b) payment of the full purchase price of such shares, which
payment shall be by wire transfer, certified or bank check or in stock of the
Company that has been owned by the Participant for at least six months, or as
agreed to by the Board, other consideration; and such written representations
and other documents as may be desirable, in the opinion of the Company's legal
counsel, for purposes of compliance with state or Federal securities or other
laws. In the case of payment made in stock of the Company, the stock shall be
valued at its Fair Market Value (as hereinafter defined) on the last business
day prior to the date of exercise. The term 'Fair Market Value' for the Common
Stock on any particular date shall mean the last reported sale price of the
Common Stock on the principal market on which the Common Stock trades on such
date or, if no trades of Common Stock are made or reported on such date, then on
the next 


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preceding date on which the Common Stock traded. The Company shall deliver a
certificate or certificates representing shares of Common Stock purchased
pursuant to such notice to the purchaser as soon as practicable after receipt of
such notice, subject to Article VIII hereof. Either the Committee or the Board
may amend an already outstanding Stock Option Agreement to add a provision
permitted by clause (b) of this Section 5.4, and no such amendment, by itself,
shall be deemed to constitute the grant of a new option for purposes of this
Plan.

      5.5   Rights as a Shareholder. No Participant shall have any rights as a
shareholder with respect to shares of Common Stock subject to an option granted
under the Plan until the date of the issuance to such Participant of a stock
certificate in respect of such shares. No adjustment shall be made for dividends
or other rights for which the record date is prior to the date such stock
certificate is issued.

      5.6   Other Provisions. Stock Option Agreements entered into pursuant to
the Plan may contain such other provisions (not inconsistent with the Plan) as
each of the Committee or the Board may deem necessary or desirable, including,
but not limited to, covenants on the part of the Participant not to compete, not
to sell Common Stock obtained from the exercise of options for specified periods
of time, and remedies available to the Company in the event of the breach of any
such covenant.

                                   ARTICLE VI

                          Termination; Transferability

      6.1   Termination. Except as otherwise provided in connection with the
grant of any option or the termination of any Participant, the right to exercise
any unexercised portion of any option granted under the Plan shall terminate on
the date of termination of the relationship


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between the Participant and the Company or a subsidiary, for any reason, without
regard to cause, other than by reason of death or disability. The option may not
be exercised thereafter, and the shares of Common Stock subject to the
unexercised portion of such option may again be subject to new options under the
Plan.

      6.2   Death or Disability of Participant. Except as otherwise permitted in
connection with the grant of any option or the death or disability of a
Participant, in the event a Participant dies or is disabled while he is a
consultant, advisor or non-officer employee of the Company or a subsidiary, any
options theretofore granted to him shall be exercisable only within the next 12
months immediately succeeding such death or disability and then only (a) in the
case of death, by the person or persons to whom the Participants rights under
the option shall pass by will or the laws of descent and distribution, and in
the case of disability, by such Participant or his legal representative, and (b)
if and to the extent that he was entitled to exercise the option at the date of
his death or disability.

      6.3   Transferability. Options granted to a Participant under the Plan
shall not be transferable otherwise than by will, by the laws of descent and
distribution, or (if authorized in the applicable Stock Option Agreement)
pursuant to a qualified domestic relations order ('QDRO') as defined by the
Internal Revenue Code of 1986, as amended, or Title I of the Employee Retirement
Income Security Act of 1974, as amended, or the rules thereunder. During the
Participant's lifetime, options shall be exercised only by such Participant,
such Participant's guardian or legal representative, or (if authorized in the
applicable Stock Option Agreement) such Participant's transferee pursuant to a
QDRO.


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                                   ARTICLE VII

                               Capital Adjustments

      7.1   Capital Adjustments. If any change is made in the shares of Common
Stock subject to the Plan or subject to any option granted under the Plan
(through merger, consolidation, reorganization, recapitalization, stock
dividend, split-up, combination of shares, exchange of shares, issuance of
rights to subscribe, or change in capital structure), appropriate adjustments
shall be made by either the Committee or the Board as to the maximum number of
shares subject to the Plan and the number of shares and price per share subject
to outstanding options as shall be equitable to prevent dilution or enlargement
of option rights. Any determination made by either the Committee or the Board
under this Article VII shall be final, binding and conclusive upon each
Participant.

                                  ARTICLE VIII

                            Legal Requirements, Etc.

      8.1   Revenue Stamps. The Company shall be responsible and shall pay for
any transfer, revenue, or documentary stamps with respect to shares issued upon
the exercise of options granted under the Plan.

      8.2   Legal Requirements. The Company shall not be required to issue
certificates for shares upon the exercise of any option unless and until, in the
opinion of the Company's legal counsel, such issuance would not result in a
violation of any state or Federal securities or other law. Certificates for
shares, when issued, shall have, if required in the opinion of the Company's
legal counsel, the following legend, or statements of other restrictions,
endorsed thereon, and may not immediately be transferable:


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      The shares of Common Stock evidenced by this certificate have been issued
      to the registered owner in reliance upon written representations that
      these shares have been purchased for investment. These shares may not be
      sold, transferred, or assigned unless, in the opinion of the Company and
      its legal counsel, such sale, transfer, or assignment will not be in
      violation of the Securities Act of 1933, as amended, applicable rules and
      regulations of the Securities and Exchange Commission and any applicable
      state securities laws.

      8.3   Private Offering. The options to be granted under the Plan are
available only to a limited number of present and future key consultants,
advisors and non-officer employees of the Company who have knowledge of the
Company's financial condition, management, and affairs. Such options are not
intended to provide additional capital for the Company, but are to encourage
stock ownership by the Company's key personnel. By the act of accepting an
option, in the absence of an effective registration statement under the
Securities Act of 1933, as amended, Participants shall agree that upon exercise
of such option, they will acquire the shares of Common Stock that are the
subject thereof for investment and not with any intention at such time to resell
or redistribute the same, and they shall confirm such agreement at the time of
exercise, but the neglect or failure to confirm the same in writing shall not be
a limitation of such agreement.

                                   ARTICLE IX

                                     General

      9.1   Application of Funds. The proceeds received by the Company from the
sale of shares of Common Stock pursuant to the exercise of options therefor
shall be used for general corporate purposes.

      9.2   Right of the Company to Terminate Relationship. Nothing contained in
the Plan or in a Stock Option Agreement shall confer upon any Participant any
right to be continued as a consultant, advisor or non-officer employee of the
Company, or interfere in any way with the


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right of the Company to terminate such relationship for any reason whatsoever,
with or without cause, at any time.

      9.3   No Obligation to Exercise. The granting of an option hereunder shall
impose no obligation upon the Participant to exercise such option.

      9.4   Effectiveness of Plan. The Plan shall become effective upon its
adoption by the Committee and ratification of the Board. Options may be granted
under the Plan prior to the ratification of the Plan by the Board, but no such
option may be exercised prior to such approval.

      9.5   Other Benefits. Participation in the Plan shall not preclude a
Participant from eligibility in any other stock benefit plan of the Company or
any old age benefit, insurance, pension, profit sharing, retirement, bonus or
other plan which the Company has adopted, or may, at any time, adopt.

      9.6   Tax Requirements. The exercise or surrender of any option under this
Plan shall constitute a Participant's full and complete consent to whatever
action the Committee or the Board elect to satisfy the Federal and state
withholding requirements, if any, which the Committee in its discretion deems
applicable to such exercise.

      9.7   Interpretations and Adjustments. To the extent permitted by Law, an
interpretation of the Plan and a decision on any matter within either the
Committee or the Board's discretion made in good faith is binding on all
persons. A misstatement or other mistake of fact shall be corrected when it
becomes known, and the person responsible shall make such adjustment on account
thereof as he considers equitable and practicable.

      9.8   Information. The Company shall, upon request or as may be
specifically required hereunder, furnish or cause to be furnished, all of the
information or documentation which is 


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necessary or required by either the Committee or the Board to perform its duties
and functions under the Plan.

      9.9   Governing Law. The Plan and any and all options granted thereunder
shall be governed by, and construed and enforced in accordance with, the laws of
the State of New York from time to time in effect.

      9.10  Certain Definitions.

      9.10.1 'Parent'. The term 'parent' shall mean a 'parent corporation' as
defined in Section 424(e) of the Code.

      9.10.2 'Subsidiary'. The term 'subsidiary' shall mean a 'subsidiary
corporation' as defined in Section 424(f) of the Code.

      9.10.3 'Disabled'. The term 'disabled' shall have the definition set forth
in Section 22(a) (3) of the Code.