EXHIBIT 10.5

                               IMMUNEX CORPORATION

                      PROFIT SHARING 401(k) PLAN AND TRUST







               (As Amended and Restated Effective January 1, 2000)



                                    CONTENTS


                                                                         
I.   NAME AND EFFECTIVE DATE............................................... I-1
     1.1    Name........................................................... I-1
     1.2    Effective Date................................................. I-1

II.  DEFINITIONS........................................................... II-1
     2.1    Accounts....................................................... II-1
     2.2    Accrued Benefit................................................ II-1
     2.3    Affiliate...................................................... II-1
     2.4    Allocable Income............................................... II-1
     2.5    Beneficiary.................................................... II-1
     2.6    Board.......................................................... II-2
     2.6    Code........................................................... II-2
     2.7    Compensation................................................... II-2
     2.8    Computation Period............................................. II-3
     2.9    Employee....................................................... II-3
     2.10   Employer....................................................... II-4
     2.11   Enrollment Date................................................ II-4
     2.12   ERISA.......................................................... II-4
     2.13   Highly Compensated Employee.................................... II-4
     2.14   Hour of Service................................................ II-5
     2.15   Investment Fund................................................ II-7
     2.16   Investment Manager............................................. II-7
     2.17   Limitation Year................................................ II-7
     2.18   Nonhighly Compensated Employee................................. II-7
     2.19   Normal Retirement Age.......................................... II-8
     2.20   One-Year Break in Service...................................... II-8
     2.21   Participant.................................................... II-8


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      2.22  Participant Elected Contribution.............................  II-8
      2.23  Plan or Trust................................................  II-8
      2.24  Plan Administrator or Committee..............................  II-8
      2.25  Plan Year....................................................  II-8
      2.26  Required Beginning Date......................................  II-8
      2.27  Salary Deferral Agreement....................................  II-9
      2.28  Section 402(g) Limit.........................................  II-9
      2.29  Spouse.......................................................  II-9
      2.30  Surviving Spouse.............................................  II-10
      2.31  Trust Fund or Fund...........................................  II-10
      2.32  Trustee......................................................  II-10
      2.33  Trust Fund or Fund...........................................  II-10
      2.34  Valuation Date...............................................  II-10
      2.35  Year of Service..............................................  II-10

III.  ELIGIBLE EMPLOYEES.................................................  III-1
      3.1   Participation................................................  III-1
      3.2   Participation on Reemployment................................  III-1
      3.3   Ineligible Employees.........................................  III-2
      3.4   Inactive Participants........................................  III-2
      3.5   End of Participation.........................................  III-3
      3.6   Qualified Military Service...................................  III-3

IV.   CONTRIBUTIONS......................................................  IV-1
      4.1   Participant Elected Contributions............................  IV-1
      4.2.  Employer Matching Contributions..............................  IV-5
      4.3.  Employer's Profit Sharing Contribution.......................  IV-6
      4.4   Employee Contributions.......................................  IV-6
      4.5   Nondiscrimination Test:  Matching Contributions
            and Employee Contributions...................................  IV-6
      4.6   Rollover Contributions.......................................  IV-8


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V.     PARTICIPANT ACCOUNTS AND CREDITING OF CONTRIBUTIONS......................  V-1
       5.1  Accounts............................................................  V-1
       5.2  Allocation and Crediting of Contributions...........................  V-1
       5.3  Valuation of Assets.................................................  V-2
       5.4  Adjustment of Participants' Accounts................................  V-2
       5.5  Limitation on Allocations...........................................  V-3
       5.6  Controlled Groups...................................................  V-5
       5.7  Protection of Accrued Benefits......................................  V-5
       5.8  Title to Assets in Trustee..........................................  V-5

VI.    INVESTMENT FUNDS.........................................................  VI-1
       6.1  Separate Funds......................................................  VI-1
       6.2  Participant Direction...............................................  VI-1
       6.3  Investment Results..................................................  VI-1
       6.4  Voting of Stock Held in Investment Funds............................  VI-1
       6.5  Voting of Employer Stock............................................  VI-1
       6.6  Tender of Employer Stock............................................  VI-2

VII.   PARTICIPANT LOANS........................................................  VII-1
       7.1  Loans to Participants...............................................  VII-1
       7.2  Accounting for Loans................................................  VII-4

VIII.  NONFORFEITABLE BENEFITS..................................................  VIII-1
       8.1  Nonforfeitable Interest.............................................  VIII-1
       8.2  Years of Service....................................................  VIII-1
       8.3  No Increase in Pre-break Vesting....................................  VIII-2
       8.4  Forfeitable Interests...............................................  VIII-2
       8.5  Distribution to Separated Participants..............................  VIII-4

IX.    RETIREMENT...............................................................  IX-1
       9.1  Retirement Age and Benefit..........................................  IX-1


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X.     DEATH BENEFIT............................................................  X-1
       10.1  Death of Participant...............................................  X-1
       10.2  Payments Upon Failure to Designate Beneficiary.....................  X-1

XI.    DISABILITY BENEFIT.......................................................  XI-1
       11.1  Payment Due........................................................  XI-1
       11.2  "Permanently Disabled".............................................  XI-1

XII.   DISTRIBUTIONS AND WITHDRAWALS............................................  XII-1
       12.1  Distribution of Benefits...........................................  XII-1
       12.2  Required Distributions.............................................  XII-2
       12.3  Distributions to Minors and Incompetents...........................  XII-4
       12.4  Qualified Domestic Relations Orders................................  XII-4
       12.5  Hardship Distributions.............................................  XII-6
       12.6  Direct Rollover Distributions......................................  XII-8
       12.7  Waiver of 30-Day Election Period...................................  XII-9

XIII.  TOP HEAVY PROVISIONS.....................................................  XIII-1
       13.1  Applicability......................................................  XIII-1
       13.2  Definitions........................................................  XIII-1
       13.3  Minimum Contributions..............................................  XIII-4
       13.5  Benefits Under Different Plans.....................................  XIII-5

XIV.   PROVISION AGAINST ANTICIPATION...........................................  XIV-1

XV.    ADMINISTRATIVE COMMITTEE - NAMED FIDUCIARY AND ADMINISTRATOR.............  XV-1
       15.1  Appointment of Committee...........................................  XV-1
       15.2  Committee Action...................................................  XV-1
       15.3  Rights and Duties..................................................  XV-1
       15.4  Investments........................................................  XV-3
       15.5  Information, Reporting and Disclosure..............................  XV-3
       15.6  Independent Qualified Accountant...................................  XV-3


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         15.7   Standard of Care Imposed Upon the Committee.....................  XV-4
         15.8   Allocation and Delegation of Responsibility.....................  XV-4
         15.9   Bonding.........................................................  XV-5
         15.10  Claims Procedure................................................  XV-5
         15.11  Unclaimed Account Procedures....................................  XV-9
         15.12  Funding Policy..................................................  XV-10
         15.13  Indemnification.................................................  XV-10

XVI.     APPOINTMENT OF INVESTMENT MANAGER......................................  XVI-1
         16.1   Authority for Appointment.......................................  XVI-1
         16.2   Investment Manager Discretion...................................  XVI-1

XVII.    INVESTMENT OF TRUST FUNDS BY TRUSTEE...................................  XVII-1

XVIII.   POWERS AND DUTIES OF TRUSTEE...........................................  XVIII-1
         18.1   Powers of Trustee...............................................  XVIII-1
         18.2   Annual Accounts.................................................  XVIII-3
         18.3   Notices and Directions..........................................  XVIII-3
         18.4   Standard of Care Imposed Upon Trustee...........................  XVIII-4
         18.5   Trustee's Acknowledgment of Responsibility......................  XVIII-5

XIX.     CONSTRUCTION...........................................................  XIX-1

XX.      LIABILITY OF TRUSTEE...................................................  XX-1
         20.1   Actions of Trustee Conclusive...................................  XX-1
         20.2   Distributions by Trustee........................................  XX-1
         20.3   Expenses of Administration......................................  XX-1
         20.4   Indemnity of Trustee............................................  XX-1

XXI.     RESIGNATION OR REMOVAL OF TRUSTEE......................................  XXI-1
         21.1   Resignation.....................................................  XXI-1
         21.2   Removal.........................................................  XXI-1
         21.3   Settlement of Account...........................................  XXI-1


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XXII.    SUITS....................................................................  XXII-1

XXIII.   MERGERS AND CONSOLIDATIONS...............................................  XXIII-1

XXIV.    AMENDMENT AND TERMINATION OF PLAN........................................  XXIV-1
         24.1   Right to Amend and Terminate......................................  XXIV-1
         24.2   No Revesting......................................................  XXIV-1
         24.3   Exclusive Benefit of Participants.................................  XXIV-1
         24.4   Termination and Discontinuance of Contributions...................  XXIV-1

XXV.     RIGHT TO DISCHARGE EMPLOYEES.............................................  XXV-1

XXVI.    RETURN OF CONTRIBUTIONS..................................................  XXVI-1
         26.1   Mistake of Fact...................................................  XXVI-1
         26.2   Allowance of Deductibility........................................  XXVI-1

XXVII.   PUERTO RICO..............................................................  XXVII-2


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                               IMMUNEX CORPORATION

                      PROFIT SHARING 401(k) PLAN AND TRUST

     THIS DOCUMENT, made and executed by Immunex Corporation, a Washington
corporation, hereinafter referred to as the "Employer":

                                   WITNESSETH

     WHEREAS, the Employer established its profit sharing plan effective as of
January 1, 1987 and to conform the plan to applicable law, the Employer intends
to amend the plan by complete restatement; and

     WHEREAS, the Employer intends that the plan and trust established hereunder
be qualified under Sections 401(a) and 401(k) of the Internal Revenue Code (the
"Code") and be exempt from federal income taxation under Section 501(a) of the
Code; and

     WHEREAS, the form of this plan and trust has been approved by the Employer;

     NOW, THEREFORE, it is agreed:

Immunex Corporation Profit Sharing 401(k) Plan and Trust



                           I.  NAME AND EFFECTIVE DATE

1.1  Name

     This Plan shall be known as the Immunex Corporation Profit Sharing 401(k)
     Plan and Trust.

1.2  Effective Date

     The original effective date of the Plan was January 1, 1987. Unless
     specifically provided otherwise, the effective date of this Agreement (and
     the amended and restated Plan set forth herein) shall be January 1, 2000.
     The benefit payable to or on behalf of a Participant included under the
     Plan in accordance with the following provisions shall not be affected by
     the terms of any amendment to the Plan adopted after such Participant's
     service with the Employer terminates, unless the amendment expressly
     provides otherwise.

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                                II.  DEFINITIONS

Whenever used herein, unless the context clearly indicates otherwise, masculine,
feminine, and neuter words may be used interchangeably, singular shall mean the
plural and vice versa, and the following words and phrases shall have the
following meanings:

2.1  Accounts

     "Accounts" means the individual separate Accounts established by the Plan
     Administrator in the name of each Participant in accordance with the Plan.

2.2  Accrued Benefit

     "Accrued Benefit" means the balance of a Participant's Accounts including
     investment experience, as of the most recent Valuation Date, plus
     accumulated contributions since such date and less any distributions since
     such date.

2.3  Affiliate

     "Affiliate" means any member of a controlled group of corporations (within
     the meaning of Code Section 414(b), as modified in accordance with Code
     Section 415(h) for purposes of Sections 5.5 and 5.6), a group of trades or
     businesses under common control (within the meaning of Code Section 414(c),
     as modified in accordance with Code Section 415(h) for purposes of Sections
     5.5 and 5.6) or an affiliated service group (within the meaning of Code
     Section 414(m) or (o)) of which the Employer is a member.

2.4  Allocable Income

     "Allocable Income" means net income or net loss. To calculate Allocable
     Income for the Plan Year, the Plan Administrator will use a uniform
     nondiscriminatory method that reasonably reflects the manner used by the
     Plan to allocate income to the Participant's Accounts. Allocable Income
     will not be determined for the period between the end of the Plan Year and
     the date of distribution.

2.5  Beneficiary

     "Beneficiary" means the person or persons designated as such by a
     Participant in accordance with Article X.

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2.6  Board

     "Board" means the Board of Directors of Immunex Corporation.

2.6  Code

     "Code" means the Internal Revenue Code of 1986, as amended.

2.7  Compensation

     Except as otherwise expressly modified by other provisions of the Plan,
     "Compensation" means an Employee's wages, salary, fees for professional
     services and other amounts received during the Plan Year (without regard to
     whether or not an amount is paid in cash) for personal services actually
     rendered in the course of employment with the Employer to the extent that
     such amounts are includible in gross income, including, but not limited to,
     overtime, bonuses and commissions, but excluding fringe benefits and
     reimbursements or other expense allowances under a nonaccountable plan (as
     defined in Treasury Regulation (S) 1.62-2(c)). Compensation shall not
     include Employer contributions to a plan of deferred compensation to the
     extent that, before the application of the Section 415 limitations to that
     plan, the contributions are not includible in the employee's gross income
     for the taxable year in which contributed; deductible Employer
     contributions to a simplified employee pension plan described in Code
     Section 408(k); distribution from a plan of deferred compensation,
     regardless of whether such amounts are includible in the employee's gross
     income when distributed; amounts realized from the exercise of a
     non-qualified stock option or when restricted stock (or property) held by
     an employee becomes freely transferable or is no longer subject to a
     substantial risk of forfeiture; amounts realized from the sale, exchange or
     other disposition of stock acquired under a qualified stock option; or any
     other amounts which receive special tax benefits. Notwithstanding the
     foregoing, (i) Compensation shall include amounts excludable from the
     Employee's gross income by reason of Code Section 125, 402(e)(3), 402(h) or
     403(b), and (ii) solely for purposes of Sections 2.27, 4.1A, 4.1E, 4.2A and
     5.2A, Compensation shall not include commissions or, effective March 1,
     2002, retention bonuses. Effective on and after January 1, 2001,
     Compensation shall also include amounts excludable from the Employee's
     gross income for qualified taxable fringe benefits pursuant to Code Section
     132(f)(4).

     A Participant's Compensation for any Plan Year shall not exceed the
     Compensation Limit in effect under Code Section 401(a)(17), as adjusted for
     increases in the cost-of-living in accordance with Code

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     Section 401(a)(17)(B) for such Plan Year. The Compensation Limit in effect
     for any Plan Year is the Compensation Limit in effect at the beginning of
     that Plan Year. For a Plan Year of less than 12 months, the Compensation
     Limit is a prorated dollar amount, determined by multiplying the
     Compensation Limit by a fraction, the numerator of which equals the number
     of months in the short period and the denominator of which equals 12.

2.8  Computation Period

     "Computation Period" shall mean a twelve (12) consecutive month period
     designated for purposes of determining an Employee's Years of Service and
     One-Year Breaks in Service for benefit accrual and vesting as follows:

          Eligibility Computation Period shall mean the twelve (12) consecutive
          month period beginning on the date on which the Employee first
          completes an Hour of Service. The second and subsequent Eligibility
          Computation Periods shall be the Plan Year, beginning with the Plan
          Year that includes the first anniversary of the date on which the
          Employee first completed an Hour of Service. In the case of an
          Employee who incurs a One-Year Break in Service prior to becoming a
          Participant, a new Eligibility Computation Period shall begin on the
          date on which the Employee first completes an Hour of Service
          following such One-Year Break in Service. The second and subsequent
          Eligibility Computation Periods for such Employee shall be the Plan
          Year, beginning with the Plan Year that includes the first anniversary
          of the date on which the Employee first completed an Hour of Service
          following his reemployment.

          Accrual Computation Period shall mean the Plan Year.

          Vesting Computation Period shall mean the Plan Year.

2.9  Employee

     "Employee" means any person, including officers, in the service of the
     Employer. Employee shall not mean an independent contractor. Employee shall
     also mean any leased employee, within the meaning of Code Section 414(n),
     unless such leased employee is covered by a plan maintained by the leasing
     organization that meets the requirements of Code Section 414(n)(5)(B) and
     leased employees do not constitute more than 20 percent of the Employer's
     Nonhighly Compensated Employee work force.

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2.10 Employer

     "Employer" means Immunex Corporation and any Affiliate that, with the
     consent of the Board, elects to adopt the Plan and any organization that
     acquires the Employer's business and adopts the Plan; provided, that for
     purposes of Article XV (Administrative Committee) and Article XXIV
     (Amendment and Termination of Plan), Employer means Immunex Corporation.

2.11 Enrollment Date

     "Enrollment Date" means the first day of any month and shall be the date on
     which the Employee commences participation in the Plan.

2.12 ERISA

     "ERISA" means the Employee Retirement Income Security Act of 1974, as
     amended.

2.13 Highly Compensated Employee

     A.   Effective for Plan Years beginning on and after January 1, 1997,
          "Highly Compensated Employee" means an Employee who:

          1.   Was a more than 5% owner of an Employer (applying the
               constructive ownership rules of Code Section 318) during the Plan
               Year or during the preceding 12-month period; or

          2.   For the preceding Plan Year (i) had Compensation in excess of
               $80,000 (as adjusted by the Commissioner of Internal Revenue for
               the relevant year); and (ii) if the Employer so elects, was in
               the top-paid group of Employees (i.e., the group consisting of
               the top 20% of the Employees when ranked on the basis of
               Compensation paid during such Plan Year).

     B.   A Highly Compensated Employee also includes a former Employee who must
          be treated as a Highly Compensated Employee for the relevant Plan Year
          pursuant to Regulation Section 1.414(q)-1T Q&A-4 and Notice 97-45.

     C.   The Employer and its Affiliates shall be treated as a single Employer
          for purposes of determining the number and identity of Highly
          Compensated Employees.

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2.14 Hour of Service

     "Hour of Service" means the following:

     A.   Each hour for which an Employee is paid, or entitled to payment, for
          the performance of duties for the Employer during the applicable
          Computation Period.

     B.   Each hour for which an Employee is paid, or entitled to payment, by
          the Employer on account of a period of time during which no duties are
          performed (irrespective of whether the employment relationship has
          terminated) due to vacation, holiday, illness, incapacity (including
          disability), layoff, jury duty, military duty or leave of absence.

          Notwithstanding the preceding sentence,

          1.   No more than 501 Hours of Service shall be credited under this
               paragraph to an Employee on account of any single continuous
               period during which the Employee performs no duties (whether or
               not such period occurs in a single Computation Period);

          2.   An hour for which an Employee is directly or indirectly paid, or
               entitled to payment, on account of a period during which no
               duties are performed is not required to be credited to the
               Employee if such payment is made or due under an insured
               disability plan or a plan maintained solely for the purposes of
               complying with applicable worker's compensation, unemployment
               compensation, or disability insurance laws;

          3.   Hours of Service are not required to be credited for a payment
               that solely reimburses an Employee for medically related expenses
               incurred by the Employee; and

          4.   For purposes of this paragraph, a payment shall be deemed to be
               made by or due from the Employer, regardless of whether such
               payment is made by or due from the Employer directly or
               indirectly through a trust fund or insurer to which the Employer
               contributes or pays premiums, and, regardless of whether
               contributions made or due to the trust fund, insurer or other
               entity are for the benefit of particular Employees or are on
               behalf of a group of Employees in the aggregate.

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     C.   Each hour for which back pay, irrespective of mitigation of damages,
          is either awarded or agreed to by the Employer. The same Hours of
          Service shall not be credited both under paragraph A or paragraph B,
          as the case may be, and under this paragraph C.

     D.   Each hour with which an Employee would normally be credited (or eight
          hours per normal working day if the Plan is unable to determine the
          Employee's hours) during the Employee's absence from work if the
          Employee's absence commences in a Plan Year beginning after December
          31, 1984, and the absence is because of the Employee's pregnancy, the
          birth of the Employee's child, or the placement of a child with the
          Employee in connection with the Employee's adoption of the child, or
          for the purpose of caring for such child for a period beginning
          immediately after the child's birth or placement. An Employee shall be
          credited with the Employee's Hours of Service determined under this
          paragraph D only for the purpose of determining whether the Employee
          has incurred a One-Year Break in Service and the number of Hours of
          Service credited to an Employee in connection with such pregnancy or
          placement shall not exceed 501. Hours of Service credited under this
          paragraph D shall be credited in the Computation Period in which the
          Employee's absence begins or in the next following Computation Period
          if the Hours of Service credited under this paragraph are not needed
          to prevent the Employee from incurring a One-Year Break in Service in
          the earlier Computation Period. The Plan Administrator may establish
          reasonable requirements for information to be furnished by the
          Employee to show that the Employee's absence is for a reason referred
          to under this paragraph and the number of days of such absence. The
          Employee shall be credited with the Employee's Hours of Service under
          this paragraph only if the Employee provides the required information
          on a timely basis.

     E.   Other than as specifically required under this Section, the
          determination of Hours of Service for reasons other than the
          performance of duties and the crediting of Hours of Service to
          Computation Periods shall be in accordance with Department of Labor
          Regulations (S) 2530.200b-2(b) and (c), and such rules are hereby
          incorporated by reference.

     F.   For purposes of eligibility and vesting, service with an Affiliate
          (while it is an Affiliate) shall be considered service with the
          Employer and Hours of Service shall be credited, in accordance with
          this Section, for such service. In addition, effective January 1,
          2002, for purposes of

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          eligibility and vesting, individuals who are Employees of Greenwich
          Holdings Inc. on January 1, 2002 (or who transfer from service covered
          by the American Home Products Corporation Savings Plan to an Employer
          as a result of, and by the first September 30 following, Immunex
          Corporation's acquisition of Greenwich Holdings Inc.) will be credited
          with the service they had accrued as of December 31, 2001 (or, if
          later, as of the date they transfer to an Employer) under the American
          Home Products Corporation Savings Plan.

     G.   Hours of Service shall also be credited for all purposes under the
          Plan to a leased employee, as defined in Code Section 414(n), for such
          employee's service to the Employer as a leased employee.

2.15 Investment Fund

     "Investment Fund" means a separate portion of the Trust Fund established at
     the direction of the Plan Administrator to provide investment options for
     Participants.

2.16 Investment Manager

     "Investment Manager" means a person, insurance company, corporation,
     partnership or association which is appointed by the Plan Administrator to
     direct the investment and reinvestment of all or any portion of the Trust
     Fund and which qualifies as an "investment manager" under the provisions of
     Section 3(38) of ERISA.

2.17 Limitation Year

     "Limitation Year" shall mean the 12 consecutive month period corresponding
     to the Plan Year and shall be the 12 month period under which the limits of
     Code Section 415 are applied.

2.18 Nonhighly Compensated Employee

     "Nonhighly Compensated Employee" shall mean an Employee who is not a Highly
     Compensated Employee.

2.19 Normal Retirement Age

     "Normal Retirement Age" means age 65.

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2.20 One-Year Break in Service

     "One-Year Break in Service" means a Vesting Computation Period during which
     an Employee fails to complete more than 500 Hours of Service.

2.21 Participant

     "Participant" means an Employee who satisfies the eligibility requirements
     of Article III and who commences participation in the Plan.

2.22 Participant Elected Contribution

     "Participant Elected Contribution" means the amounts designated by a
     Participant pursuant to Section 4.1 and contributed to the Plan by the
     Employer in lieu of payment of an equal amount directly to the Participant
     as compensation.

2.23 Plan or Trust

     "Plan" or "Trust" means this Profit Sharing 401(k) Plan and Trust Agreement
     and all subsequent amendments thereto.

2.24 Plan Administrator or Committee

     "Plan Administrator" or "Committee" means the Administrative Committee as
     appointed by Employer pursuant to Section 15.1.

2.25 Plan Year

     "Plan Year" means the twelve (12) consecutive month period ending on the
     last day of December. The Plan Year shall be the year on which the records
     of the Plan are kept.

2.26 Required Beginning Date

     Effective for Plan Years beginning on and after January 1, 1997, "Required
     Beginning Date" means April 1 of the calendar year following the later of
     the calendar year in which the Participant's Service terminates or the
     calendar year in which the Participant attains age 70 1/2; provided,
     however, that if a Participant is a 5% owner (as defined in Code Section
     416) with respect to the calendar year in which such Participant attains
     age 70 1/2, the Participant's Required Beginning Date is April 1 of the
     calendar year following such calendar year.

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     (a)  Any Participant (other than a 5% owner) who attained age 70 1/2 in
          years after 1995 and before January 1, 2002 may elect by April 1 of
          the calendar year following the year in which the Participant attained
          age 70 1/2 (or by December 31, 1997, in the case of a Participant
          attaining age 70 1/2 in 1996) to defer distributions until April 1 of
          the calendar year following the calendar year in which the Participant
          retires. If no such election is made, the Participant will begin
          receiving distributions by the April 1 of the calendar year following
          the calendar year in which the Participant attained age 70 1/2 (or by
          December 31, 1997, in the case of a Participant attaining age 70 1/2
          in 1996.)

     (b)  Any Participant (other than a 5% owner) who attained age 70 1/2 in a
          year prior to 1997 may elect to stop distributions and recommence
          benefit payments by April 1 of the calendar year following the
          calendar year in which the Participant retires.

     A Participant shall be considered a 5% owner for the purpose of this
     Section 2.26 if such Participant is a 5% owner as defined in Code Section
     416(i) at any time during the Plan Year ending with or within the calendar
     year in which such owner attains age 70 1/2. Once minimum required
     distributions begin to a 5% owner, they must continue to be distributed
     even if the Participant ceased to be a 5% owner in a subsequent year.

2.27 Salary Deferral Agreement

     "Salary Deferral Agreement" means the written authorization of a
     Participant to the Employer to deduct from the Participant's Compensation
     an amount or percentage to be deferred as a Participant Elected
     Contribution in accordance with this Plan.

2.28 Section 402(g) Limit

     "Section 402(g) Limit" means the limitation in effect under Code Section
     402(g) for such calendar year.

2.29 Spouse

     "Spouse" means the lawful husband or wife of the Participant.

Immunex Corporation Profit Sharing 401(k) Plan and Trust               Page II-9



2.30 Surviving Spouse

     "Surviving Spouse" means the Participant's Spouse surviving at the date of
     the Participant's death.

2.31 Trust Fund or Fund

     "Trust Fund" or "Fund" means all contributions received by the Trustee for
     purposes of the Plan, the investment thereof, and the earnings and
     appreciation thereon, less payments made to carry out the Plan.

2.32 Trustee

     "Trustee" means Security Trust Company or such other person(s) or
     entity(ies) designated by the Board to serve as trustee of the Trust Fund.

2.33 Trust Fund or Fund

     "Trust Fund" or "Fund" means all property held in the Trust.

2.34 Valuation Date

     "Valuation Date" means the last day of each Plan Year and such other date
     or dates as may be designated by the Plan Administrator.

2.35 Year of Service

     "Year of Service" means:

     A.   Eligibility Service

          For purposes of determining an Employee's eligibility to participate
          in the Plan, Year of Service shall mean the completion of 1,000 or
          more Hours of Service during an Eligibility Computation Period.

     B.   Benefit Accrual Service

          For purposes of determining an Employee's benefit accrual, Year of
          Service shall mean the completion of 1,000 or more Hours of Service
          during an Accrual Computation Period while a Participant.

     C.   Vesting Service

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          For purposes of determining an Employee's nonforfeitable interest in
          the Employee's Accrued Benefit, Year of Service shall mean the
          completion of 1,000 or more Hours of Service during a Vesting
          Computation Period.

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                            III.  ELIGIBLE EMPLOYEES

3.1  Participation

     A.   Subject to the provisions of Sections 3.1B, 3.1C and 3.3, an Employee
          shall participate in this Plan on the Enrollment Date that coincides
          with or immediately follows the date on which the Employee first
          performs one Hour of Service with the Employer.

     B.   An Employee who is regularly scheduled to work less than twenty (20)
          hours per week shall participate in this Plan on the Enrollment Date
          that coincides with or immediately follows the date on which such
          Employee completes one Year of Eligibility Service or attains age
          twenty-one (21), whichever occurs later.

     C.   An Employee who is classified by the Employer as a temporary employee
          shall participate in this Plan on the Enrollment Date that coincides
          with or immediately follows the date on which such Employee completes
          one Year of Eligibility Service or attains age twenty-one (21),
          whichever occurs later.

     D.   An Employee who is participating in the Plan immediately prior to the
          effective date of this Agreement shall continue to participate in the
          Plan subject to the provisions hereunder.

3.2  Participation on Reemployment

     A.   Subject to the provisions of Section 3.3, a former Participant shall
          resume participation in the Plan upon the date of the Participant's
          reemployment by the Employer if the Participant had a nonforfeitable
          interest under the Plan to any Accrued Benefit derived from Employer
          contributions at the time of the Participant's earlier separation from
          service or the number of the Employee's consecutive One-Year Breaks in
          Service is fewer than the greater of five (5) or the aggregate number
          of the Employee's Years of Service prior to such Break.

     B.   A former Participant who does not resume participation under paragraph
          A of this Section shall be required to again complete the eligibility
          requirement of Section 3.1 before participating in the Plan.

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3.3  Ineligible Employees

     Notwithstanding the provisions of Section 3.1 and Section 3.2, the
     following classes of Employees shall not participate in the Plan:

     A.   An Employee who is covered by a collective bargaining agreement
          between employee representatives and the Employer, unless the
          collective bargaining agreement specifically requires participation in
          this Plan. In applying the preceding sentence, the term "employee
          representatives" shall not include an organization of which more than
          one-half of the members are owners, officers, or executives of the
          Employer.

     B.   A leased employee, within the meaning of Code Section 414(n).

     C.   A non-resident alien with no U.S.-source income (within the meaning of
          Code Section 911(d)(2)) from the Employer.

     D.   A summer intern.

     E.   An individual who is not treated by the Employer as an employee for
          payroll tax purposes, but who is subsequently determined by a
          government agency, by the conclusion or settlement of threatened or
          pending litigation, or otherwise to be (or to have been) an Employee,
          unless and until the Plan Administrator provides that such individual
          is eligible to participate in the Plan (which eligibility shall be on
          a prospective basis only).

3.4  Inactive Participants

     In the event a Participant transfers to an ineligible class of employees,
     such Employee's participation in the Plan for purposes of benefit accrual
     shall cease as of the date of such transfer.

     In the event an ineligible Employee transfers to the eligible class, such
     Employee shall participate in the Plan immediately if the Employee is a
     former Participant or the Employee has previously satisfied the
     requirements of Section 3.1 and would have previously been admitted to
     participation if the Employee had been in the eligible class.

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3.5  End of Participation

     Active participation ends upon suspension of contributions or termination
     of employment. Participation ends when the individual has no further
     account balances under the Plan.

3.6  Qualified Military Service

     Effective December 12, 1994, notwithstanding anything herein to the
     contrary, contributions, benefits and service credit with respect to
     qualified military service will be provided in accordance with Code Section
     414(u).

Immunex Corporation Profit Sharing 401(k) Plan and Trust              Page III-3



                                IV.  CONTRIBUTIONS

4.1  Participant Elected Contributions

     A.   Election to Defer Compensation

          Each Participant may elect, effective as of the first day of any month
          coincident with or following the Participant's Enrollment Date, by
          filing a Salary Deferral Agreement with the Plan Administrator within
          such time as the Plan Administrator may determine, to defer any whole
          percentage of the Participant's Compensation not to exceed 15% (20%
          for Plan Years beginning on or after January 1, 2002), but in any
          event, the amount of deferral shall not exceed the Section 402(g)
          Limit. Such deferred amounts shall be contributed to the Plan by the
          Employer and designated for such Participant's Deferral Account.
          Contributions shall be made by payroll deduction as authorized by the
          Participant on the Participant's Salary Deferral Agreement. The
          Participant may, in accordance with rules established by the Plan
          Administrator, increase or decrease his elective deferrals effective
          as of the first day of any month; provided, however, a Participant
          shall only be entitled to defer those amounts of Compensation that are
          not currently available to the Participant.

     B.   Payment to Trustee

          The Employer shall transmit the Participant Elected Contributions to
          the Trustee as soon as such Participant Elected Contributions can
          reasonably be segregated from the Employers' general assets, but in
          any event not later than the 15th business day of the month following
          the month in which such amounts would otherwise have been payable to
          the Participant in cash.

     C.   Limitation on Deferral of Compensation

          Effective for Plan Years beginning on and after January 1, 1997, the
          Participant Elected Contributions (together with any qualified
          nonelective contributions that the Plan Administrator may, under
          applicable Treasury Regulations, elect (and does elect) to include in
          the calculation) for a Plan Year shall satisfy one of the following
          tests:

Immunex Corporation Profit Sharing 401(k) Plan and Trust               Page IV-1



          1.   The Average Actual Deferral Percentage of the eligible Highly
               Compensated Employees for the current Plan Year may not be
               greater than the Average Actual Deferral Percentage of the
               eligible Nonhighly Compensated Employees for the prior Plan Year
               multiplied by 1.25; or

          2.   The Average Actual Deferral Percentage of the eligible Highly
               Compensated Employees for the current Plan Year may not be
               greater than the Average Actual Deferral Percentage of the
               eligible Nonhighly Compensated Employees for the prior Plan Year
               multiplied by 2. However, the excess of the Average Actual
               Deferral Percentage of the eligible Highly Compensated Employees
               for the current Plan Year over that of the eligible Nonhighly
               Compensated Employees for the prior Plan Year may not be greater
               than two (2.0) percentage points.

          The "Average Actual Deferral Percentage" for a specified group of
          Employees for a Plan Year shall be the average of the ratios
          (calculated separately for each Employee in such group) of the sum of
          the Participant Elected Contributions (and qualified nonelective
          contributions, if applicable) to the Employee's compensation, as
          defined under Code Section 414(s), for the entire Plan Year or
          compensation while the Participant was eligible to participate. The
          Plan Administrator shall select the Code Section 414(s) definition of
          compensation and the method to be used for the Plan Year and the same
          definition of compensation and method shall be applied to each
          Participant for that year.

          The Plan is subject to Code Section 401(k) and the regulations
          thereunder, which are hereby incorporated in this Document by
          reference. The above tests (and any necessary correction pursuant to
          Section 4.1D) shall be performed in accordance with such Code Section
          and regulations. In order to satisfy the above requirements, the Plan
          Administrator may, in its sole discretion, require the Employer to
          reduce future deferrals elected by the Highly Compensated Employees
          and/or return a portion of the amounts deferred by the Highly
          Compensated Employees in accordance with Section 4.1D.

          A Participant's Participant Elected Contribution shall be taken into
          account for a Plan Year for purposes of the foregoing tests only if it
          is considered allocated as of a date within that Plan Year. A
          Participant's

Immunex Corporation Profit Sharing 401(k) Plan and Trust               Page IV-2



          Participant Elected Contribution is considered allocated as of a date
          within the Plan Year only if:

          1.   The allocation is not contingent upon the Participant's
               participation in the Plan or performance of services on any date
               subsequent to that date; and

          2.   The elective contribution is actually paid to the Trust no later
               than the end of the twelve-month period immediately following the
               Plan Year to which the contribution relates.

          Likewise, a Participant's Participant Elected Contribution shall be
          taken into account for a Plan Year for purposes of the foregoing tests
          only if it relates to compensation that either:

          1.   Would have been received by the Participant in the Plan Year but
               for the Participant's election to defer; or

          2.   Is attributable to services performed by the Participant in the
               Plan Year and, but for the Participant's election to defer, would
               have been received by the Participant within two and one-half
               months after the close of the Plan Year.

          If an amount is returned to an Employee because the Employee's
          elective deferrals for the calendar year exceed the Section 402(g)
          Limit (other than excess elective deferrals of Nonhighly Compensated
          Employees that arise solely from elective deferrals made under the
          Plan or plans of the Employers), such excess deferrals shall
          nevertheless be counted in determining the Employee's actual deferral
          percentage for the Plan Year in which such excess deferrals were made.

          If two or more cash or deferred arrangements (as determined under Code
          Section 401(k)) are treated as a single plan for purposes of Code
          Sections 401(a)(4) or 410(b), such arrangements shall be treated as a
          single plan for purposes of the limitations of this Section.

     D.   Return of Excess Deferrals

          1.   Nondiscrimination Test

               If amounts contributed by the Employer for the Highly Compensated
               Employees cause the Plan to fail to meet the

Immunex Corporation Profit Sharing 401(k) Plan and Trust               Page IV-3



               requirements of Section 4.1C and Code Section 401(k) for a Plan
               Year, then, to the extent that such amounts are in excess of such
               limitations, the excess amounts (called excess contributions)
               shall be returned to the Highly Compensated Employees, together
               with Allocable Income, no later than the close of the following
               Plan Year. Excess contributions shall mean, with respect to any
               Plan Year, the excess of (a) the aggregate amount of Participant
               Elected Contributions (and qualified nonelective contributions,
               if applicable) actually taken into account in computing the
               Average Actual Deferral Percentage of the Highly Compensated
               Employees for such Plan Year, over (b) the maximum amount of such
               contributions permitted by the Average Actual Deferral Percentage
               test (determined by hypothetically reducing contributions made on
               behalf of Highly Compensated Employees in order of the actual
               deferral percentages, beginning with the highest of such
               percentages).

               The excess contributions are then allocated to the Highly
               Compensated Employees with the largest amounts of Participant
               Elected Contributions (and qualified nonelective contributions,
               if applicable) taken into account in calculating the Average
               Actual Deferral Percentage test for the Plan Year in which the
               excess arose, beginning with the Highly Compensated Employee with
               the largest amount of such contributions and continuing in
               descending order until all the excess contributions have been
               allocated. For purposes of the preceding sentence, the "largest
               amount" is determined after distribution of any excess
               contributions. The amount of excess contributions to be returned
               with respect to any Participant for a Plan Year shall be reduced
               by any excess deferrals previously distributed to such
               Participant for the Participant's taxable year ending with or
               within such Plan Year. The amount of excess deferrals that must
               be returned to a Participant for a taxable year shall be reduced
               by any excess contributions previously distributed with respect
               to such Participant for the Plan Year beginning with or within
               such taxable year of the Employer.

Immunex Corporation Profit Sharing 401(k) Plan and Trust               Page IV-4



          2.   Section 402(g) Limit

               If a Participant's elective deferrals (e.g., Participant Elected
               Contributions) under Code Section 401(k) exceed the Section
               402(g) Limit for a calendar year (such excess being called excess
               deferrals), the Plan Administrator shall distribute such excess
               deferrals, together with Allocable Income for the calendar year
               in which the excess deferrals were made, no later than April 15
               of the following calendar year. If a Participant makes elective
               deferrals under the Plan and under any other plan or arrangement
               described in Code Section 402(g)(3) for a Plan Year, and the
               total of such elective deferrals exceeds the Section 402(g)
               Limit, such Participant shall notify the Plan Administrator in
               writing on the prescribed form by March 1 of the succeeding Plan
               Year of the portion of the excess deferrals that he has allocated
               to the Plan and the Plan Administrator shall distribute the
               amount of excess deferrals allocated to this Plan, together with
               Allocable Income, to the Participant no later than April 15 of
               the calendar year following calendar year for which the excess
               deferrals were made.

     E.   Suspension of Deferrals

          A Participant may, upon thirty (30) days' prior written notice filed
          with the Plan Administrator, suspend the Participant's election under
          Section 4.1A to have a portion of the Participant's Compensation
          deferred. In the event of such a suspension, a Participant shall not
          be entitled to again elect to have Participant Elected Contributions
          made hereunder until the first day of the next month. The Participant
          shall, nevertheless, be considered a Participant hereunder for all
          other purposes during such period of time if the Participant's service
          with the Employer continues during that time.

4.2. Employer Matching Contributions

     A.   Basic Matching Contribution

          As soon as practicable following each pay period, the Employer shall
          make a contribution for each Participant who has Compensation deferred
          during that period and who is otherwise eligible, as provided in the
          following sentence, for such contributions. A Participant shall become
          eligible for contributions under this Section 4.2A as of the

Immunex Corporation Profit Sharing 401(k) Plan and Trust               Page IV-5



          January 1 or July 1 coincident with or next following the
          Participant's Enrollment Date. The contribution shall be equal to 100%
          of the first 2% of Compensation deferred by the Participant, plus, for
          Employees with less than five Years of Service, 50% of the amount
          deferred by the Participant that is between 2% and 6% of Compensation,
          and for Employees with five or more Years of Service, 75% of the
          amount deferred by the Participant that is between 2% and 6% of
          Compensation.

     B.   Forfeitures

          Forfeited amounts derived from the Employer Matching Account of a
          Participant who separates from the Employer's service shall be used to
          reduce the Employer's matching contribution for the Plan Year in which
          the forfeited amount becomes available and in subsequent years, if
          necessary.

4.3. Employer's Profit Sharing Contribution

     A.   Discretionary Contribution

          For any Plan Year, the Employer shall have the right to contribute an
          amount that the Employer, in its sole discretion, shall determine. The
          Employer's determination of its discretionary contribution shall be
          binding on all Participants, the Plan Administrator and the Employer.
          In making a discretionary contribution, the Employer shall have the
          discretionary authority to declare that a portion or all of the
          contribution for the Plan Year shall be a qualified nonelective
          contribution as defined in Code Section 401(m)(4)(C), which will be
          allocated as provided in Section 5.2C.

     B.   Date of Payment

          The Employer shall pay its discretionary contribution to the Trustee
          no later than the due date (including extensions thereof) for the
          filing of its federal income tax return for the fiscal year for which
          such contribution is made.

4.4  Employee Contributions

     Other than wage or salary deferrals allowed under Section 4.1A,
     contributions by an Employee under the Plan are not permitted.

Immunex Corporation Profit Sharing 401(k) Plan and Trust               Page IV-6



4.5  Nondiscrimination Test: Matching Contributions and Employee Contributions

     Effective for Plan Years beginning on and after January 1, 1997, in the
     case of Employer Matching Contributions and any other contributions that
     the Employer may elect to include as permitted under Treasury Regulations,
     such contributions shall satisfy one of the following tests:

     A.   The Average Contribution Percentage of the eligible Highly Compensated
          Employees for the current Plan Year shall be not greater than the
          Average Contribution Percentage of the eligible Nonhighly Compensated
          Employees for the prior Plan Year multiplied by 1.25; or

     B.   The Average Contribution Percentage of the eligible Highly Compensated
          Employees for the current Plan Year shall be not greater than the
          Average Contribution Percentage of the eligible Nonhighly Compensated
          Employees for the prior Plan Year multiplied by 2. However, the excess
          of the Contribution Percentage of the eligible Highly Compensated
          Employees for the current Plan Year over that of the eligible
          Nonhighly Compensated Employees for the prior Plan Year shall be not
          greater than two (2.0) percentage points.

     If a Highly Compensated Employee participates in a plan or plans maintained
     by the Employer or an Affiliate under which the Highly Compensated Employee
     is eligible to make elective contributions subject to the requirements of
     Code Section 401(k) and one or more of such plans is also subject to Code
     Section 401(m), the tests applied to the contributions for the Highly
     Compensated Employee shall be performed in accordance with Code Section
     401(m) and the regulations thereunder to prevent the multiple use of the
     alternative limitation as provided in Code Section 401(m).

     If two or more plans are aggregated for purposes of Code Section 410(b) or
     a Highly Compensated Employee participates in two or more plans of the
     Employer and its Affiliates to which matching contributions or employee
     after-tax contributions are made, all such contributions shall be
     aggregated to the extent required under Treasury Regulation (S)
     1.401(m)-1(f)(1)(ii)(B) to apply the requirements of this Section.

     The "Average Contribution Percentage" for a specified group of Employees
     for a Plan Year shall be the average of the ratios (calculated separately
     for each Employee in such group) of the sum of the Employer Matching
     Contributions (and such other contributions as permitted (or required) to
     be included in the

Immunex Corporation Profit Sharing 401(k) Plan and Trust              Page  IV-7



     calculation under Treasury Regulations) to the Employee's compensation, as
     defined under Code Section 414(s), for the entire Plan Year or compensation
     while the Participant was eligible to participate. The Plan Administrator
     shall select the Code Section 414(s) definition of compensation and the
     method to be used for the Plan Year and the same definition of compensation
     and method shall be applied to each Participant for that year.

     Contributions that cause the Average Contribution Percentage of the
     eligible Highly Compensated Employees to exceed the limits of this Section
     4.5 shall be distributed to the applicable Participant if vested, or
     forfeited if forfeitable, together with Allocable Income, before the close
     of the following Plan Year. Such excess contributions shall be called
     excess aggregate contributions. (The Employer will incur an excise tax
     equal to 10 percent of the amount of the excess aggregate contributions for
     a Plan Year that are not returned to the appropriate Highly Compensated
     Employees during the first 2-1/2 months of the following Plan Year.) Excess
     aggregate contributions shall mean, with respect to any Plan Year, the
     excess of (i) the aggregate amount of Employer Matching Contributions (and
     such other contributions as permitted (or required) to be included in the
     calculation under Treasury Regulations) actually taken into account in
     computing the Average Contribution Percentage of the Highly Compensated
     Employees for such Plan Year, over (ii) the maximum amount of such
     contributions permitted by the Average Contribution Percentage test
     (determined by hypothetically reducing contributions made on behalf of
     Highly Compensated Employees in order of the contribution percentages,
     beginning with the highest of such percentages). The excess aggregate
     contributions are then allocated to the Highly Compensated Employees with
     the largest amounts of Employer Matching Contributions (and such other
     contributions as permitted (or required) to be included in the calculation
     under Treasury Regulations) taken into account in calculating the Average
     Contribution Percentage test for the Plan Year in which the excess arose,
     beginning with the Highly Compensated Employee with the largest amount of
     such contributions and continuing in descending order until all the excess
     aggregate contributions have been allocated. For purposes of the preceding
     sentence, the "largest amount" is determined after distribution of any
     excess contributions. Forfeited amounts may not be reallocated to a Highly
     Compensated Employee whose contributions for such Plan Year are reduced by
     reason of this Section.

     Code Section 401(m) and the regulations thereunder are hereby incorporated
     in this Plan by reference and the limitations of this Section shall be
     carried out in accordance with such law and regulations.

Immunex Corporation Profit Sharing 401(k) Plan and Trust              Page  IV-8




4.6  Rollover Contributions

     A.   Subject to the approval of the Plan Administrator, the Plan may accept
          an "eligible rollover distribution," as defined in Section 12.6A, with
          respect to an Employee who is a Participant, or who is expected to
          become a Participant, provided, that the contribution is received on
          or before the 60th day following its distribution from the prior
          qualified plan or individual retirement account or as a direct
          rollover from the prior qualified plan.

     B.   Any rollover contribution accepted by the Plan shall be separately
          accounted for and the Participant shall have a nonforfeitable interest
          in such account called the Participant's Rollover Account at all
          times. The Participant's Rollover Account shall be adjusted with its
          pro rata share of net earnings, losses, appreciation, or depreciation
          as of each Valuation Date. If not earlier withdrawn, the total amount
          of a Participant's Rollover Account shall be paid to the Participant
          in the same form and at the same time as the Participant's
          Employer-derived Accrued Benefit.

     C.   If an Employee has not yet become a Participant at the time he makes a
          rollover contribution to the Plan, he shall be deemed to be a
          Participant only for purposes of the investment and distribution of
          such contribution. He shall not be permitted to make Participant
          Elected Contributions or share in Employer Matching Contributions or
          Employer Profit Sharing Contributions until he has become an active
          Participant pursuant to Article III.

Immunex Corporation Profit Sharing 401(k) Plan and Trust              Page  IV-9




             V. PARTICIPANT ACCOUNTS AND CREDITING OF CONTRIBUTIONS

5.1  Accounts

     The Plan Administrator shall establish in the name of each Participant such
     Accounts as are necessary to properly account for the types of
     contributions made on behalf of a Participant.

5.2  Allocation and Crediting of Contributions

     A.   Crediting of Participant Elected Contributions

          Employer contributions arising from a Participant's election to defer
          Compensation shall be credited to the Participant's Employee Deferral
          Account.

     B.   Crediting of Employer Matching Contributions

          Employer Matching Contributions shall be credited to the Employer
          Matching Account of the Participant for whom the Employer Matching
          Contribution is made in accordance with Section 4.2.

     C.   Allocation of the Employer's Profit Sharing Contribution

          A share of the Employer's Profit Sharing Contribution shall be
          allocated to the Employer Profit Sharing Account of a Participant who
          is in the service of the Employer on the last day of the Plan Year for
          which such contribution is made, who completes 1,000 or more Hours of
          Service during such Plan Year and who is otherwise eligible to share
          in such contribution, provided, that a Participant who retires after
          attaining Normal Retirement Age, dies, or becomes Permanently
          Disabled, as defined in Section 11.2, during the Plan Year shall share
          in the Employer's Profit Sharing Contribution for such Plan Year to
          the extent provided herein on the basis of the amount of the
          Participant's Compensation during such Plan Year prior to the
          Participant's termination of service. A Participant shall become
          eligible to share in the Employer's Profit Sharing Contributions as of
          the January 1 or July 1 coincident with or immediately following the
          Participant's Enrollment Date. In the case of a Participant who

Immunex Corporation Profit Sharing 401(k) Plan and Trust               Page  V-1



          otherwise qualifies for a Profit Sharing Contribution but who enters
          an ineligible class of Employees during the Plan Year, or in the case
          of a Participant who first becomes eligible to share in Profit Sharing
          Contributions during such Plan Year, such Participant shall share in
          the contributions for such Plan Year to the extent of the amount of
          the Participant's Compensation paid or accrued during the time the
          Participant was in an eligible class of employees and was eligible to
          share in the Employer's Profit Sharing Contribution for such Plan
          Year.

          The amount allocated to the Employer Profit Sharing Account of a
          Participant shall be a sum as shall bear the same ratio to the total
          contribution as the ratio such Participant's Compensation bears to the
          Compensation of all Participants eligible to share in the Profit
          Sharing Contribution.

          Forfeitable amounts derived from the Employer Profit Sharing Account
          of a Participant who separates from the Employer's service shall be
          used to reduce future Employer Matching Contributions.

          If the Employer designates some portion or all of its Profit Sharing
          Contribution as a qualified nonelective contribution, the qualified
          nonelective contribution shall be allocated among the Participants who
          are Nonhighly Compensated Employees based on the ratio that each such
          Participant's Compensation for the Plan Year bears to the Compensation
          of all such Participants for the Plan Year.

5.3  Valuation of Assets

     As of each Valuation Date, the Trustee shall value the assets of the Trust
     at the then current fair market value.

5.4  Adjustment of Participants' Accounts

     As of each Valuation Date, the net income (or loss) of the Trust since the
     immediately preceding Valuation Date shall be determined. Net income (or
     loss) of the Trust includes the increase (or decrease) in the fair market
     value of Trust Fund assets, interest income, dividends and other income and
     gains (or losses) attributable to Trust Fund assets since the immediately
     preceding Valuation Date, reduced by any expenses charged to the Trust Fund
     for the period since the immediately preceding Valuation Date.

Immunex Corporation Profit Sharing 401(k) Plan and Trust               Page  V-2




      The net income (or loss) of the Trust will be determined separately for
      each Investment Fund and allocated among the Accounts of the Participants
      in proportion to the respective balances of such Accounts invested in each
      such Investment Fund.

5.5   Limitation on Allocations

      Notwithstanding any other provision of the Plan, the annual addition to a
      Participant's Accounts for a Limitation Year shall not exceed an amount
      equal to:

      A.   Limitation. The lesser of:

           1.   $30,000, as adjusted pursuant to Code Section 415(d) for Plan
                Years beginning on and after January 1, 1995, or

           2.   Twenty-five percent (25%) of the compensation paid by the
                Employer to the Participant during the Limitation Year.
                Effective January 1, 1998, for purposes of this Section 5.5,
                compensation means Compensation as defined in Section 2.7.

      B.   Additions

           For purposes of imposing the limitations of Code Section 415, "annual
           additions" shall mean the sum of the following credited to the
           Participant for the Limitation Year:

           1.   Employer contributions;

           2.   The Participant's contributions other than a rollover
                contribution;

           3.   Forfeitures;

           4.   Amounts allocated to a separate account under a pension or
                annuity plan for a key employee (as defined under Code Section
                416(i)) in Plan Years beginning after March 31, 1984, to provide
                post-retirement medical benefits to such Participant and the
                Participant's spouse and dependents, and amounts paid after
                December 31, 1985, in tax years ending after that date to a
                separate account under a welfare benefit plan (as defined under
                Code Section 419(e)) of the Employer for a Participant who is or
                was a key employee (as defined under Code Section 416(i)) to
                provide post-retirement medical benefits to such Participant;
                and

Immunex Corporation Profit Sharing 401(k) Plan and Trust                Page V-3



           5.   Amounts allocated to a separate account under a pension or
                annuity plan for a Participant and the Participant's spouse and
                dependents, under which benefits described in Code Section
                401(h) are payable.

      C.   Aggregation of Plans

           All defined contribution plans maintained by the Employer, including
           voluntary employee contribution accounts in a defined benefit plan,
           Key employee accounts under a welfare benefit plan described in Code
           Section 419, and any Employer contributions allocated to an
           individual retirement account, shall be treated as a single plan for
           purposes of the limitations of this Section.

      D.   Excess Addition

           If the annual addition to the Account of a Participant exceeds the
           limitation of this Section 5.5 during a Plan Year, then such excess
           amount shall be eliminated first by returning, to the extent
           necessary to satisfy these limitations, the Participant's Participant
           Elected Contributions for such Plan Year, as adjusted for allocable
           income (together with forfeiting any related Matching Contribution),
           and then (if the limitations of this Section are still not satisfied)
           by reducing, to the extent necessary to satisfy these limitations,
           the Employer's contribution to the Participant's Account made for any
           other reason. The amount of the reduction (hereafter called the
           excess amount) shall be used to reduce the Employer's contribution
           for the next Plan Year, and each succeeding Plan Year, for that
           Participant if covered by the Plan as of the end of such Plan Year.
           If the Participant is not covered by the Plan as of the end of the
           Plan Year, then the excess amount shall be held unallocated in a
           suspense account for the Plan Year and allocated and reallocated in
           the next Plan Year, to the extent possible, to reduce the Employer's
           contribution for such Plan Year. If a suspense account is in
           existence during a Plan Year, other than the Plan Year in which it is
           established, the Employer shall make no contribution to the Plan
           until all amounts in the suspense account have been allocated and
           reallocated to Participants. No investment gains or losses or other
           income or expense shall be allocated to a suspense account. In the
           event a suspense account is in existence at the time the Plan
           terminates, any amount in the suspense account that cannot then be
           allocated to Participants shall be returned to the Employer.

Immunex Corporation Profit Sharing 401(k) Plan and Trust                Page V-4



5.6   Controlled Groups

      In applying the limitations of Section 5.5, the Employer and its
      Affiliates shall be treated as a single employer.

5.7   Protection of Accrued Benefits

      With the exception of an amendment described under Code Section 412(c)(8),
      no amendment to the Plan shall reduce the Accrued Benefit of a Participant
      determined as of the date immediately preceding the adoption of the
      amendment. In the event that an amendment either directly or indirectly
      reduces or restricts a protected benefit under Code Section 411(d)(6),
      such benefit for a Participant is presumed as of the later of the adoption
      date or the effective date of the amendment. In the case of an amendment
      adopted after July 30, 1984 that, with respect to benefits attributable to
      service before the amendment, eliminates or reduces an early retirement
      benefit or a retirement-type subsidy (as defined by the Secretary of the
      Treasury), such amendment shall not reduce the Accrued Benefit of a
      Participant, determined immediately prior to the adoption of the amendment
      and determined without regard to the amendment, if the Participant, either
      before or after the amendment but before termination of service, satisfies
      the preamendment requirements for the benefit. An amendment described in
      the preceding sentence shall not eliminate optional benefit forms (except
      as permitted by the Secretary of the Treasury) with respect to the Accrued
      Benefit of a Participant accrued as of the date immediately preceding the
      adoption of the amendment. The availability of any protected benefit of a
      Participant provided under the Plan, as defined in Code Section 411(d)(6),
      shall not be subject to the Employer's consent or discretion.

5.8   Title to Assets in Trustee

      Title to all assets under the Plan shall be vested in the Trustee which
      shall hold the Trust Fund and the income as a part thereof and make
      payments therefrom as provided in the Plan.

Immunex Corporation Profit Sharing 401(k) Plan and Trust                Page V-5



                              VI. INVESTMENT FUNDS

6.1   Separate Funds

      The Plan Administrator, in its discretion, shall select Investment Funds
      to be offered to Participants for investment of their Accounts, and the
      Plan Administrator shall direct the Trustee to establish accounts for the
      Investment Funds as determined by the Plan Administrator.

6.2   Participant Direction

      In the event that the Plan Administrator authorizes the use of more than
      one Investment Fund, each Participant shall designate the percentage of
      the future contributions to be allocated to his Accounts that will be
      invested in each of the Investment Funds available under the Plan. Any
      such designation shall be made in such increments, in such manner and
      pursuant to such other rules and limitations as the Plan Administrator
      shall prescribe. A Participant's investment designation shall remain in
      effect until changed by the Participant (or the Beneficiary, if
      applicable). A Participant (or Beneficiary, as applicable) may change his
      investment designation with respect to the future contributions to be
      allocated to, and/or the existing balances in, his Accounts at such times,
      in such increments and pursuant to such other rules and limitations as the
      Plan Administrator shall prescribe.

6.3   Investment Results

      As of each Valuation Date, the investment results obtained in the
Investment Funds shall be allocated only to the Account balances of Participants
who have invested in the fund.

6.4   Voting of Stock Held in Investment Funds

      With respect to each Participant's investment in any Investment Fund,
other than the Immunex Corporation Common Stock Fund, the Trustee shall vote the
number of shares credited to each Participant's Account, in each case, in a
manner that the Trustee believes to be consistent with its fiduciary duties
under section 404 of ERISA.

6.5   Voting of Employer Stock

      With respect to each Participant's investment in the Immunex Corporation
Common Stock Fund, before each annual or special meeting of the stockholders of
the

Immunex Corporation Profit Sharing 401(k) Plan and Trust               Page VI-1



Employer, the Employer will furnish such Participant with a copy of the proxy
solicitation material for such meeting, together with a form addressed to the
Trustee requesting the Participant's confidential instructions on how the shares
of Immunex Corporation common stock ("Shares") allocated to the Participant's
Account should be voted on each matter to come before the meeting. The number of
Shares allocated to a Participant's Account will be determined by multiplying
the number of Shares held in the Immunex Corporation Common Stock Fund as of the
applicable record date by a fraction, the numerator of which is the number of
units of such Fund held in the Participant's Account as of the applicable record
date and the denominator of which is the total number of outstanding units of
such Fund as of such date. Upon receipt of such instructions, the Trustee shall
vote Shares allocated to each Participant's Account (including fractional as
well as whole Shares) in accordance with timely directions of such Participant;
provided, that a failure of a Participant to timely and affirmatively direct the
manner in which Shares allocated to the Participant's Account are to be voted
shall be deemed for purposes of this Section to be an affirmative direction to
abstain from voting.

6.6   Tender of Employer Stock

      The Trustee shall, with respect to Shares allocated to that portion of
each Participant's Account invested in the Immunex Corporation Common Stock
Fund, act in response to any tender offer or exchange offer for Shares commenced
by a person or persons, including, but not limited to, a tender offer or
exchange offer within the meaning of the Securities Exchange Act of 1934, as
amended from time to time (all such tender or exchange offers collectively, a
"tender offer"), in accordance with timely directions of such Participant;
provided, that a failure of a Participant to timely and affirmatively direct the
manner in which the Trustee is to act in response to a tender offer with respect
to Shares allocated to the Participant's Account shall be deemed for purposes of
this Section to be an affirmative direction not to take action with respect to
such Shares. For purposes of determining the number of Shares to be the subject
of any particular response to a tender offer, the Trustee shall use the nearest
practicable date as determined by the Trustee. The number of Shares allocated to
a Participant's Account will be determined by multiplying the number of Shares
held in the Immunex Corporation Common Stock Fund as of the relevant date by a
fraction, the numerator of which is the number of units of such Fund held in the
Participant's Account as of such date and the denominator of which is the total
number of outstanding units of such Fund as of such date. The Employer and the
Trustee each shall use its best efforts to timely distribute or to cause to be
distributed to each Participant such information as is being distributed to
other stockholders of the Employer in connection with any such tender offer.

Immunex Corporation Profit Sharing 401(k) Plan and Trust              Page VI-2



                             VII. PARTICIPANT LOANS

The Plan Administrator, upon the application of a Participant, may direct the
Trustee to make a loan or loans to such Participant. The Plan Administrator
shall follow a uniform and nondiscriminatory policy in approving such loans and
loans shall be made available to Participants on a reasonably equivalent basis.

7.1   Loans to Participants

      A.  Availability of Loans

          Upon application by a Participant, the Plan Administrator may direct
          the Trustee to make a loan to the Participant from the vested balances
          in the Participant's Employee Deferral Account, Rollover Account and
          Employer Matching Account. Such borrowing rules must be formulated and
          administered so that the requirements of Code Section 72(p) for
          non-taxable loans, the applicable Department of Labor regulations on
          plan loans, and the following provisions of this Section 7.1 are
          satisfied. Any loan hereunder will bear a reasonable rate of interest
          and will be evidenced by a promissory note signed by the Participant
          in such form as the Plan Administrator may require. The amount of any
          such loan will be withdrawn from the vested balances in the
          Participant's Employee Deferral Account, Rollover Account and Employer
          Matching Account and from the Investment Fund or Funds in which such
          Accounts are invested in the manner specified in the Plan
          Administrator's borrowing rules.

      B.  Plan Administrator's Borrowing Rules

          The Plan Administrator may adopt borrowing rules for loans hereunder
          and may revise such rules from time to time. The rules may contain
          such requirements pertaining to loans as the Plan Administrator deems
          necessary or desirable and that are not specified herein. The
          borrowing rules may govern the procedures and cut-off dates for
          applying for loans hereunder and the terms of such loans, including
          (i) the number of loans that a Participant may request in any year and
          the number of loans that may be outstanding at any time to a
          Participant, (ii) any restrictions on reborrowing not stated in this
          Section 7.1, (iii) the interest rate in effect from time to time for
          loans or the method of ascertaining such interest rate, and (iv) the
          repayment schedule for loans or the method for determining the
          repayment schedule.

Immunex Corporation Profit Sharing 401(k) Plan and Trust              Page VII-1



      C.  Amount of Loans

          The minimum loan amount is $1,000 or such lesser amount as the Plan
          Administrator may from time to time set forth in its borrowing rules.
          The maximum aggregate loan amount is based upon the vested balances in
          the Participant's Accounts. No Participant loan will exceed the
          smallest of (i) the amount of the vested balances in the Participant's
          Employee Deferral Account, Rollover Account and Employer Matching
          Account, (ii) one-half of the Participant's vested Account balances,
          or (iii) $50,000 (reduced by the highest outstanding loan balance to
          the Participant during the 12 months preceding the loan). For purposes
          of applying such limits, Account values as the Valuation Date
          coincident with or immediately preceding the date on which the loan is
          made will be used.

      D.  Maximum Repayment Period

          1.   Other Than Residential Loans

               Except as provided in paragraph 2 immediately below, the maximum
               term of a loan will be 5 years (provided that the Plan
               Administrator may establish a shorter repayment period for small
               loans).

          2.   Residential Loans

               If a Participant requests a loan for the acquisition or
               construction of the Participant's principal residence, the
               repayment period will be determined by reference to bank loans
               for the same purpose but may not exceed 10 years; provided,
               however, that effective January 1, 2002, loans described in this
               paragraph 2 that are transferred (or rolled over) to this Plan
               from another plan shall retain the original term of such loan,
               even if it exceeds 10 years.

      E.  Security for Repayment

               Each loan hereunder will be a Participant-directed investment for
               the benefit of the Participant requesting such loan; accordingly,
               any default in the repayment of principal or interest of any loan
               hereunder will reduce the amount available for distribution to
               such Participant (or the Participant's Beneficiary). Thus, any
               loan hereunder will be secured by up to 50 percent of the vested
               amount in the Participant's Accounts. The

Immunex Corporation Profit Sharing 401(k) Plan and Trust              Page VII-2



          Plan Administrator acting under its borrowing rules may require other
          security for repayment of a loan in any instance. A Participant
          receiving a loan must execute such instruments as the Plan
          Administrator requests and must pay any fees for filings required by
          the Plan Administrator to perfect any security interest in the
          Participant's Accounts or other security.

      F.  Repayment

          The Plan Administrator may require a Participant to execute an
          agreement to repay the principal and interest of a loan through
          regular payroll deduction payments from the Participant's
          compensation. The Plan Administrator may establish back-up repayment
          procedures for Participants who do not make payroll deduction
          repayment. Except as otherwise may be permitted under Treasury
          regulations, any repayment procedure must provide for substantially
          level amortization payments made quarterly or more frequently. Any
          loan hereunder may be prepaid, in whole or in part, at any time
          without penalty. If a Participant's service as an Employee is
          terminated for any reason, the entire unpaid principal and interest of
          any loan then outstanding to such Participant will become immediately
          due and payable.

      G.  Action Upon Default

          If a Participant defaults on any payment of interest or principal of a
          loan hereunder or defaults upon any other obligation relating to such
          loan, the Plan Administrator may take (or direct the Trustee to take)
          such action or actions as it determines to be necessary to protect the
          interests of the Plan. Such actions may include commencing legal
          proceedings against the Participant, or foreclosing on any security
          interest in the Participant's Accounts or other security given in
          connection with a loan hereunder; however, the Plan Administrator will
          not direct foreclosure on the Participant's Employee Deferral Account
          at a time when the Participant would not be entitled to receive a
          distribution or withdrawal from such Account.

      H.  Distribution to Participant With Loan

          In the case of any Participant with a loan outstanding hereunder, the
          amount available for distribution to such Participant (or such
          Participant's Beneficiary) will consist of the portion of his Accounts
          invested in the Investment Funds of the Trust Fund. In addition, the

Immunex Corporation Profit Sharing 401(k) Plan and Trust              Page VII-3



          Participant's note will be distributed to the Participant (or the
          Participant's Beneficiary), and the Trustee will report the value of
          the note for income tax purposes as the amount of unpaid principal and
          interest due thereon at the date of distribution.

7.2   Accounting for Loans

      A.  Source of Loan

          The Plan Administrator will establish procedures and ordering rules
          for liquidating the Participant's Accounts to make a loan to him.

      B.  Loan Account

          The Plan Administrator will establish and maintain a loan account for
          each borrowing Participant. The unpaid principal and accrued but
          unpaid interest on the loans to a Participant will be reflected for
          Plan accounting purposes in the Participant's loan account. Repayments
          by the Participant will be credited to the Participant's loan account.
          The Plan Administrator will establish uniform procedures for
          transferring repayment amounts from his loan account to the
          Participant's other accounts.

Immunex Corporation Profit Sharing 401(k) Plan and Trust              Page VII-4



                          VIII. NONFORFEITABLE BENEFITS

8.1   Nonforfeitable Interest

      A Participant shall have a nonforfeitable interest in the Participant's
      Accounts based on the Participant's Years of Service for vesting. The
      Participant's Years of Service shall be determined in accordance with
      Section 8.2, and the Participant's nonforfeitable interest shall be
      determined as follows:

      A.  Employee Deferral Account and Rollover Account

          A Participant shall have a nonforfeitable interest in the
          Participant's Employee Deferral Account and Rollover Account at all
          times.

      B.  Employer Matching Account and Employer Profit Sharing Account

          A Participant's nonforfeitable interest in the Participant's Employer
          Matching Account and Employer Profit Sharing Account shall be
          determined under the following schedule:

         Completed Years                           Nonforfeitable
           of Service                                Percentage

          Less than 1                                     0
        1 but less than 2                                20
        2 but less than 3                                40
        3 but less than 4                                60
        4 but less than 5                                80
          5 or more                                     100

          In the event the Employer designates some part or all of a Profit
          Sharing Contribution for a Plan Year as a qualified nonelective
          contribution, a Participant to whom such a contribution is allocated
          shall have nonforfeitable interest in such contribution at all times.

8.2   Years of Service

      The following rules shall be applied in determining the number of a
      Participant's Years of Service using the Vesting Computation Period to
      credit Years of Service and One-Year Breaks in Service. All of an
      Employee's Years

Immunex Corporation Profit Sharing 401(k) Plan and Trust             Page VIII-1



     of Service with the Employer shall be counted except the following Years of
     Service shall be disregarded:

     A.   Years of Service prior to a One-Year Break in Service until the
          Employee completes a Year of Service following the Participant's
          return to the service of the Employer.

     B.   Years of Service completed prior to a One-Year Break in Service if the
          Employee does not have any nonforfeitable interest under the Plan to
          an Accrued Benefit derived from Employer contributions and the number
          of the Employee's consecutive One-Year Breaks in Service equals or
          exceeds the greater of five (5) or the aggregate number of the
          Employee's Years of Service prior to such Break; provided, that in the
          case of Plan Years beginning prior to January 1, 1985, a nonvested
          Employee's Years of Service prior to a One-Year Break in Service
          (incurred in a Plan Year beginning prior to 1985) shall not be counted
          if the number of the Employee's consecutive One-Year Breaks in Service
          equals or exceeds the aggregate number of the Employee's Years of
          Service prior to such Break. In applying the rules of this paragraph,
          if any Years of Service are disregarded by reason of any earlier
          One-Year Break in Service, such Years of Service shall not be
          aggregated when determining whether Years of Service are to be
          disregarded by reason of a subsequent One-Year Break in Service.

8.3  No Increase in Pre-break Vesting

     In the case of a Participant who incurs five (5) consecutive One-Year
     Breaks in Service, Years of Service completed by such Participant after
     such Break period shall not be counted to increase the Participant's
     nonforfeitable interest in the Participant's Accounts as determined prior
     to such Break period.

8.4  Forfeitable Interests

     Upon separation from the Employer's service for any reason, a Participant's
     forfeitable interest in the Participant's Accrued Benefit shall be
     forfeited in accordance with the following rules, whichever is applicable.

Immunex Corporation Profit Sharing 401(k) Plan and Trust             Page VIII-2



     A.   Zero Percent Vested

          In the event a Participant's service with the Employer terminates and
          such Participant does not have any nonforfeitable interest in the
          Participant's Accrued Benefit, the Participant shall be deemed to have
          received a distribution of such nonforfeitable Accrued Benefit on his
          termination date and the forfeitable portion of the Accrued Benefit
          shall be forfeited at the time of the Participant's separation from
          service. A Participant who has no vested interest will be deemed
          cashed out from the Plan. If a Participant is deemed to receive a
          distribution in accordance with this paragraph and the Participant
          resumes service with the Employer or an Affiliate before the date on
          which the Participant incurs five consecutive One-Year Breaks in
          Service, the amount of the forfeited Accrued Benefit shall be
          restored.

     B.   Partially Vested

          1.   Five-Year Break in Service

               In the event a Participant's service with the Employer and its
               Affiliates terminates and such Participant has a nonforfeitable
               interest in the Participant's Accrued Benefit but is not paid the
               entire nonforfeitable portion of the Participant's Account, a
               separate account shall be established for the Participant's
               remaining Accrued Benefit and the forfeitable interest the
               Participant shall be forfeited as of the end of the Plan Year in
               which the Participant incurs five (5) consecutive One-Year Breaks
               in Service. The Participant's nonforfeitable interest in the
               Participant's separate Account at any time prior to incurring 5
               consecutive One-Year Breaks in Service shall be an amount "X"
               determined under the formula X = P(AB + (R x D)) - (R x D), where
               P is the vested percentage at the relevant time; AB is the
               Account balance at the relevant time; D is the amount of the
               distribution; R is the ratio of the Account balance at the
               relevant time to the Account balance after distribution; and the
               relevant time is the time at which, under the Plan, the vested
               percentage in the Account cannot increase.

          2.   Cash Out Rule

               In the event a Participant's service with the Employer and its
               Affiliates terminates and such Participant is paid the
               Participant's

Immunex Corporation Profit Sharing 401(k) Plan and Trust             Page VIII-3



               entire nonforfeitable interest prior to incurring 5 consecutive
               One-Year Breaks in Service, the forfeitable interest of the
               Participant shall be forfeited at the time the payment is made.
               If the Participant returns to the Employer's (or an Affiliate's)
               service before incurring 5 consecutive One-Year Breaks in Service
               and repays to the Plan the full amount of the earlier
               distribution, the forfeited amount, unadjusted by any investment
               increases or decreases, shall be restored to the Participant's
               Account. To obtain a restoration of a forfeited amount, the
               Participant's repayment must be made before the earlier of the
               date on which the Participant incurs five consecutive One-Year
               Breaks in Service or the end of the five year period beginning
               with the date on which the Participant resumes employment with
               the Employer or an Affiliate. If the Participant's earlier
               distribution was made for any reason other than separation of
               service with the Employer and its Affiliates, the forfeited
               amount shall be restored only if the Participant repays the
               earlier distribution before the date five years after the date of
               the distribution. A Participant whose entire nonforfeitable
               interest has been distributed from the Plan will be deemed cashed
               out from the Plan.

8.5  Distribution to Separated Participants

     In the case of a Participant who separates from the service of the Employer
     and its Affiliates, the Participant's nonforfeitable interest in the
     Participant's Accounts shall be payable in accordance with the provisions
     of Article XII.

Immunex Corporation Profit Sharing 401(k) Plan and Trust             Page VIII-4



                                 IX. RETIREMENT

9.1   Retirement Age and Benefit

      A.  Normal Retirement

          A Participant shall have a nonforfeitable interest in the
          Participant's Accrued Benefit upon attaining Normal Retirement Age.
          Payment of the Participant's Accounts shall be made in accordance with
          the provisions of Article XII.

      B.  Postponed Retirement

          A Participant may not be required to retire involuntarily under this
          Plan simply because the Participant attains Normal Retirement Age.
          Subject to Section 12.2A, no payment of a Participant's Accounts shall
          be made under the Plan until a Participant actually retires and ceases
          employment. Upon actual retirement, payment of the Participant's
          Accounts shall be made in accordance with the provisions of Article
          XII.


Immunex Corporation Profit Sharing 401(k) Plan and Trust               Page IX-1



                                X. DEATH BENEFIT

10.1      Death of Participant

          A Participant who dies while in the service of the Employer shall be
          100 percent vested in the Participant's Accounts upon the
          Participant's death. Upon a Participant's death, the nonforfeitable
          portion of the Participant's Accounts shall be payable to the
          Participant's Surviving Spouse, or the Participant's designated
          Beneficiary if the Participant has no Surviving Spouse at the time of
          death or the Spouse consents to the designation of a Beneficiary other
          than the Surviving Spouse. The designation of a Beneficiary to whom
          the Spouse has consented shall not be changed without the Spouse's
          consent to such change unless the Spouse's earlier consent expressly
          permits designations by the Participant without any requirement of
          further consent by the Spouse. A Spouse's consent must be in writing,
          it must acknowledge the effect of the Beneficiary designation and it
          must be witnessed by a notary public or a Plan representative. A
          Spouse's consent to a Beneficiary designation as provided for under
          this Section is effective only with respect to that Spouse. Payment of
          the death benefit shall be made in accordance with the provisions of
          Article XII, provided that the Surviving Spouse may require that the
          payment be made within a reasonable time following the Participant's
          death.

10.2      Payments Upon Failure to Designate Beneficiary

          Any portion of the amount payable that is undisposed of because of the
          failure to designate a Beneficiary or the failure of the Beneficiary
          to survive the Participant shall be paid in order of survivorship to:

          A.   The Participant's Surviving Spouse;

          B.   The Participant's descendants, per stirpes; and

          C.   If none are surviving, the Participant's estate.

          Notwithstanding the above, if the Plan Administrator is unable to
          locate any of the persons listed in (A) or (B) within three (3)
          months, the Plan Administrator may pay the death benefits to the
          Participant's estate.


Immunex Corporation Profit Sharing 401(k) Plan and Trust                Page X-1





                             XI.  DISABILITY BENEFIT

11.1 Payment Due

     If a Participant becomes Permanently Disabled while in the service of the
     Employer, the Participant shall be 100 percent vested in the Participant's
     Accounts as of the date of the Participant's disability. Payment of the
     Participant's entire interest shall be made in accordance with the
     provisions of Article XII.

11.2 "Permanently Disabled"

     "Permanently Disabled" means that the Participant is unable by reason of
     any medically determinable physical or mental impairment to substantially
     perform the regular material duties of the same occupations for which the
     Participant has been employed by the Employer, and such disability is
     expected to be of long, continued and indefinite duration. Permanent
     disability shall be established by the certification of a physician,
     selected by the Participant and approved by the Plan Administrator that the
     Participant has suffered a permanent disability, or if the physician
     selected by the Participant shall not be approved by the Plan
     Administrator, by a majority of three physicians, one selected by the
     Participant (or the Participant's Spouse, child, parent or legal
     representative in the event of the Participant's inability to select a
     physician), one by the Plan Administrator, and the third by the two
     physicians selected by the Participant and the Plan Administrator. The
     decision of the majority of such three physicians shall be final and
     conclusive.

Immunex Corporation Profit Sharing 401(k) Plan and Trust               Page XI-1



                       XII.  DISTRIBUTIONS AND WITHDRAWALS

12.1 Distribution of Benefits

     A.   Forms of Distribution

          Subject to subsection C below, any amounts payable under the terms of
          the Plan with respect to a Participant who retires after attaining
          Normal Retirement Age, becomes Permanently Disabled or dies shall, at
          the election of the Participant or Beneficiary (as applicable), be
          paid as a single-sum distribution of cash, or in a series of payments
          over a period not to extend beyond the life expectancy of the
          Participant (or the Beneficiary, as applicable) or the joint life
          expectancy of the Participant and the Participant's Beneficiary. Any
          amounts payable under the terms of the Plan with respect to a
          Participant who separates from service for any other reason shall be
          paid as a single-sum distribution of cash. No annuities shall be
          payable from the Plan. Each optional form of benefit offered under the
          Plan shall be available to all Participants on a nondiscriminatory
          basis. Notwithstanding the foregoing, if the Plan Administrator
          establishes an Investment Fund that is designed to invest primarily in
          the common stock of Immunex Corporation, a Participant (or
          Beneficiary, as applicable) may elect to receive such whole shares of
          Immunex Corporation common stock as are allocated to that portion of
          the Participant's vested Accounts that is invested in such Investment
          Fund (with cash for any fractional shares), in lieu of receiving cash
          for such portion of the Participant's Accounts.

     B.   Time of Distribution

          1.   Distribution Dates

               Subject to paragraph 2 of this subsection B, subsection C below
               and Section 12.2, benefits due to a Participant or Beneficiary,
               as applicable, shall be paid or commence to be paid within an
               administratively reasonable time following the Valuation Date
               elected by the Participant or Beneficiary, as applicable. A
               Participant or Beneficiary may elect to commence distributions as
               of any Valuation Date coinciding with or following the
               Participant's separation from service with the Employer and its
               Affiliates. In the case of a payment to a Participant, the
               payment shall not be made without the consent of the Participant,
               to the

Immunex Corporation Profit Sharing 401(k) Plan and Trust              Page XII-1



               extent required by law, if the value of the Participant's
               nonforfeitable interest in the Participant's Accounts exceeds
               $5,000 as of the date of distribution.

          2.   Consent to Distribution

               Unless a Participant elects in writing to receive the
               Participant's benefit at a later date, payment to a Participant
               shall be made no later than sixty (60) days after the close of
               the Plan Year in which the latest of the following events occurs:

               a.   The Participant attains age sixty-five (65);

               b.   The 10th anniversary of the date on which the Participant
                    first became a Participant; or

               c.   The termination of the Participant's service with the
                    Employer.

     C.   Small Benefit Cash-Out

          If the Participant's nonforfeitable interest in his Accounts does not
          exceed $5,000 as of the date of distribution, that interest shall be
          distributed as a lump sum within an administratively reasonable time
          following the Valuation Date coinciding with or immediately following
          the Participant's separation from service with the Employer and its
          Affiliates.

     D.   Valuation of Accounts for Distribution

          For purposes of determining the value of a Participant's Accounts
          under this Section, the value shall be determined as of the Valuation
          Date immediately preceding the date of distribution.

12.2 Required Distributions

     Notwithstanding any other provision of this Plan to the contrary, effective
     for Plan Years beginning on and after January 1, 1997, the following shall
     apply:

     A.   The entire interest of a Participant shall be distributed commencing
          no later than the Participant's Required Beginning Date.

Immunex Corporation Profit Sharing 401(k) Plan and Trust              Page XII-2



     B.   The Participant's interest shall be distributed over a period that
          does not exceed the life expectancy of the Participant (or the
          Beneficiary) or the life expectancy of the Participant and the
          Participant's designated Beneficiary, provided, that if the
          distributions are for a period measured by the life expectancy of the
          Participant or the joint life expectancy of the Participant and the
          Participant's Spouse, if applicable, such life expectancies shall be
          recalculated annually, if the Participant so elects. If the
          Participant's designated Beneficiary is someone other than his Spouse,
          then the Participant's life expectancy may be recalculated, but the
          Beneficiary's may not. Distributions to the Participant or the
          Participant and the Participant's designated Beneficiary shall meet
          the minimum annual distribution requirements and the incidental death
          benefit rules of Code Section 401(a)(9) and the regulations
          thereunder, including Treasury Regulation (S) 1.401(a)(9)-2, which are
          incorporated herein by reference.

          Notwithstanding any provision of the Plan to the contrary, with
          respect to distributions under the Plan made for calendar years
          beginning on or after January 1, 2001, the Plan will apply the minimum
          distribution requirements of Code Section 401(a)(9) in accordance with
          the regulations under Code Section 401(a)(9) that were proposed on
          January 17, 2001, notwithstanding any provision of the Plan to the
          contrary. This amendment shall continue in effect until the end of the
          last calendar year beginning before the effective date of final
          regulations under Code Section 401(a)(9) or such other date as may be
          specified in guidance published by the Internal Revenue Service.

     C.   If payments have commenced to the Participant and the Participant dies
          before the Participant's entire interest is distributed, the
          Participant's remaining interest shall be distributed to the
          Participant's Beneficiary at least as rapidly as under the method of
          distribution to the Participant as of the date of the Participant's
          death.

     D.   If a Participant dies before distribution of the Participant's
          interest has commenced, the Participant's entire interest shall be
          distributed by December 31 of the calendar year containing the fifth
          anniversary of the Participant's death, provided, that if the
          Participant has designated a Beneficiary to receive a part or all of
          the Participant's interest and if payment to the Beneficiary commences
          no later than December 31 of the calendar year following the year of
          the Participant's death, the portion payable to such Beneficiary may
          be paid over a period that does

Immunex Corporation Profit Sharing 401(k) Plan and Trust              Page XII-3



          not exceed the Beneficiary's life expectancy. In the event the
          Participant's designated Beneficiary is the Participant's Spouse,
          payment to the Spouse need not commence earlier than the later of
          December 31 of the year in which the Participant would have attained
          age seventy and one-half (70-1/2) or December 31 of the year following
          the year of the Participant's death. If a deceased Participant's
          designated Beneficiary is the Participant's Spouse and the Spouse dies
          before payments commence, the Participant's entire interest shall be
          distributed by applying the rules of this paragraph as though the
          deceased Spouse were the Participant.

12.3 Distributions to Minors and Incompetents

     If any Participant or Beneficiary entitled to receive benefits hereunder is
     a minor or, in the judgment of the Plan Administrator, unable to take care
     of his affairs because of mental condition, illness or accident, any
     payment due such person may, in the sole discretion of the Plan
     Administrator (unless prior claim therefor shall have been made by a
     qualified guardian or other legal representative), be paid for the benefit
     of such Participant or Beneficiary: (a) to such person's legal
     representative appointed by proceedings satisfactory to the Plan
     Administrator; (b) to such person (other than a minor) directly even though
     he is not then able to exercise control over such payment; and/or (c) to
     any custodian under the Uniform Gifts to Minors Act or similar statutes or
     guardian of such person or of his property with whom such person is making
     his home. Neither the Trustee, the Plan Administrator nor the Employer
     shall be required to see to the application of any such distribution so
     made to any of said persons, but said person's receipt shall be a full
     discharge of the Trustee's, the Plan Administrator's and the Employer's
     duties.

12.4 Qualified Domestic Relations Orders

     A.   Distributions

          In the event a person (hereafter called the "alternate payee") is
          designated by a qualified domestic relations order, as defined under
          Code Section 414(p), as having a right to receive all, or a portion
          of, the benefits payable under the Plan to a Participant, payment to
          the alternate payee may, to the extent provided by such order, begin
          at a time not permitted for distributions to the Participant. Payment
          to the alternate payee may be made as though the Participant had
          retired on the date on which the order requires payment to begin
          considering the present value

Immunex Corporation Profit Sharing 401(k) Plan and Trust              Page XII-4



          of benefits accrued by the Participant up to such date (but
          disregarding an Employer subsidy for early retirement). Payment may be
          made in any form permitted by the Plan other than in the form of a
          joint and survivor annuity with respect to the alternate payee and the
          alternate payee's spouse.

     B.   Separate Account Period

          If it is being determined whether a domestic relations order received
          in connection with a Participant is a qualified domestic relations
          order, the Plan Administrator shall separately account for the amounts
          that would have been paid to the alternate payee during the period of
          determination if the order was a qualified one. If the order is
          determined to be a qualified order at any time during the eighteen
          (18) month period beginning on the date on which the first payment
          would be required to be made under the qualified domestic relations
          order, the Plan Administrator shall pay the segregated amounts,
          including interest thereon, to the persons entitled to the amounts
          under the order. If it is determined that the order is not a qualified
          order or if at the end of the eighteen (18) month period it is still
          undetermined whether the order is a qualified order, the segregated
          amounts, including interest thereon, shall be paid to the persons who
          would have been entitled to the payments had there been no order. In
          the event it is determined that the order is a qualified order only
          after the eighteen (18) month period has elapsed, the application of
          the order shall be applied prospectively only, beginning as of such
          determination date.

     C.   Suspension of Benefits

          Notwithstanding any provision of the Plan to the contrary, in
          accordance with procedures established by the Plan Administrator, the
          Plan Administrator may temporarily suspend a Participant's right to
          borrow or withdraw from his Account or obtain a distribution from his
          Account, if (i) the Plan Administrator receives a domestic relations
          order and the Participant's Account is a source of the payment for
          such domestic relations order, or (ii) if the Plan Administrator
          receives notice that a domestic relations order is being sought by the
          Participant, his spouse, former spouse, child or other dependent (as
          defined in Code Section 152) and the Participant's Account is a source
          of the payment for such domestic relations order. Such suspension may
          continue for a reasonable period of time (as determined by the
          Administrator) which

Immunex Corporation Profit Sharing 401(k) Plan and Trust              Page XII-5



            may include the period of time the Plan Administrator, a court of
            competent jurisdiction or other appropriate person is determining
            whether the domestic relations order qualifies as a QDRO.

12.5   Hardship Distributions

       The Plan will allow hardship distributions. A distribution of all or a
       portion of the Participant's Elected Contributions Account (other than
       earnings credited thereto after December 31, 1988) and the Participant's
       Rollover Account may be made to a Participant upon the Participant's
       request if it is established that the Participant has an immediate and
       heavy financial need and the distribution is necessary to satisfy such
       need. The Plan Administrator shall establish the existence of the
       Participant's immediate and heavy financial need and the Participant's
       necessity for a distribution to satisfy such need by applying the
       following standards:

       A.   Immediate and Heavy Financial Need

            A need will be deemed to be an immediate and heavy financial need if
            it is to pay for one or more of the following:

            1.   Uninsured medical expenses described in Code Section 213(d)
                 incurred by the Participant, the Participant's Spouse, or any
                 dependent of the Participant (a dependent shall be determined
                 under Code Section 152) or necessary for such persons to
                 receive medical care, as defined in Code Section 213(d);

            2.   Purchase (excluding mortgage payments) of a principal residence
                 for the Participant;

            3.   Payment of tuition and related educational fees for the next 12
                 months of post-secondary education for the Participant or the
                 Participant's Spouse, children or dependents;

            4.   The need to prevent the eviction of the Participant from the
                 Participant's principal residence or foreclosure on the
                 mortgage of the Participant's principal residence; or

            5.   Any other reason recognized to constitute an immediate and
                 heavy financial need by the Commissioner of the Internal
                 Revenue Service in a revenue ruling, notice or other document
                 of general applicability. A need otherwise determined to
                 constitute

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            an immediate and heavy financial need will not fail to be such a
            need merely because the need is foreseeable or voluntarily incurred
            by the Participant.

B.     Distribution Necessary to Satisfy the Financial Need

       A distribution will be necessary to satisfy the immediate and heavy
       financial need only if all of the following requirements are satisfied:

       1.   The amount distributed does not exceed the amount of the heavy and
            immediate financial need, increased by any amounts necessary to pay
            any federal, state or local income taxes or penalties reasonably
            anticipated to result from the distribution;

       2.   The Participant has obtained all distributions (other than hardship
            distributions) and all nontaxable loans currently available to the
            Participant under the Plan and under all other qualified plans
            maintained by the Employer; and

       3.   The requirements of subsection C immediately below are satisfied.

C.     Restrictions

       The following restrictions will apply to a Member who receives a hardship
       withdrawal:

       1.   Upon receiving a distribution under this Section 12.5, the
            Participant's elective contributions (e.g., Participant Elected
            Contributions) and employee contributions under this Plan and all
            other plans maintained by the Employer or an Affiliate will be
            suspended for at least 12 consecutive months; and

       2.   A Participant who receives a distribution under this Section may not
            make elective contributions (e.g., Participant Elected
            Contributions) under the Plan or any other plans maintained by the
            Employer or an Affiliate for the Participant's taxable year
            (immediately following the taxable year of the hardship
            distribution) in excess of the Section 402(g) Limit for such taxable
            year less the amount of the Participant's elective contributions for
            the taxable year of the hardship distribution.

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       D.   Additional Rules

            The following rules shall apply to each request for a hardship
            distribution by a Participant.

            1.   The Participant's request for a hardship distribution shall be
                 made on such forms as are provided by the Plan Administrator
                 from time to time and the Participant shall furnish the Plan
                 Administrator with such information as the Plan Administrator
                 requests in its evaluation of the Participant's request;

            2.   The amount distributed, if any, shall in no event exceed the
                 balance of the Participant's Employee Deferral Contributions
                 Account (excluding earnings credited thereto after December 31,
                 1988) and Rollover Account; and

            3.   A Participant's request for a hardship distribution shall not
                 be honored to the extent it requires the distribution of an
                 amount serving as security for a loan to the Participant

12.6   Direct Rollover Distributions

       Notwithstanding any provision of the Plan to the contrary that would
       otherwise limit a distributee's election under this Section, a
       distributee may elect, at the time and in the manner prescribed by the
       Plan Administrator, to have any portion of an eligible rollover
       distribution paid directly to an eligible retirement plan specified by
       the distributee in a direct rollover.

       A.   Eligible Rollover Distribution

            An eligible rollover distribution is any distribution of all or any
            portion of the balance to the credit of the distributee, except that
            an eligible rollover distribution does not include: any distribution
            that is one of a series of substantially equal periodic payments
            (not less frequently than annually) made for the life (or life
            expectancy) of the distributee or the joint lives (or joint life
            expectancies) of the distributee and the distributee's designated
            beneficiary, or for a specified period of ten years or more; any
            distribution to the extent such a distribution is required under
            Code Section 401(a)(9); the portion of any distribution that is not
            includible in gross income (determined without regard to the
            exclusion for net unrealized appreciation with respect to employer
            securities); and any portion of a hardship withdrawal pursuant to
            Section 12.5 made

Immunex Corporation Profit Sharing 401(k) Plan and Trust              Page XII-8



            from a Participant's Employee Deferral Account after December 31,
            1998.

       B.   Eligible Retirement Plan

            An eligible retirement plan is an individual retirement account
            described in Code Section 408(a), an individual retirement annuity
            described in Code Section 408(b), an annuity plan described in Code
            Section 403(a), or a qualified trust described in Code Section
            401(a), that accepts the distributee's eligible rollover
            distribution. However, in the case of an eligible rollover
            distribution to the surviving spouse, an eligible retirement plan is
            an individual retirement account or individual retirement annuity.

       C.   Distributee

            A distributee includes an employee or former employee. In addition,
            the employee's or former employee's surviving spouse and the
            employee's or former employee's spouse or former spouse who is the
            alternate payee under a qualified domestic relations order, as
            defined in Code Section 414(p), are distributees with regard to the
            interest of the spouse or former spouse.

       D.   Direct Rollover

            A direct rollover is a payment by the Plan to the eligible
            retirement plan specified by the distributee.

12.7   Waiver of 30-Day Election Period

       If a distribution is one to which Code Sections 401(a)(11) and 417 do not
       apply, such distribution may commence less than 30 days after the notice
       required by Income Tax Regulation (S) Section 1.411(a)-11(c) is given
       provided (i) the Committee clearly informs the Participant that the
       Participant has a right to a period of at least 30 days after receiving
       the notice to consider the decision of whether or not to elect a
       distribution or a direct rollover, and (ii) the Participant, after
       receiving the notice, affirmatively elects a distribution or a direct
       rollover.

Immunex Corporation Profit Sharing 401(k) Plan and Trust              Page XII-9



                           XIII. TOP HEAVY PROVISIONS

13.1  Applicability

      Notwithstanding any other provision of the Plan to the contrary, the
      provisions of this Article shall apply for any Plan Year, beginning after
      December 31, 1983, in which the Plan is a Top-Heavy Plan as defined in
      Code Section 416(g).

13.2  Definitions

      A.   Aggregation Group

           Aggregation Group includes each plan maintained by the Employer or an
           Affiliate in which a Key Employee participates and each other plan
           maintained by the Employer or an Affiliate which enables any plan in
           which a Key Employee participates to meet the requirements of Code
           Section 401(a)(4) or 410. In addition, the Employer may elect to
           include other plans in the Aggregation Group which satisfy the
           requirements of Code Sections 401(a)(4) and 410 when considered
           together with the plans that are required to be aggregated. Any plan,
           however, that is or may be permissively included in the Aggregation
           Group upon an election by the Employer shall not be subject to the
           provisions of this Article.

      B.   Determination Date

           Determination Date shall be the last day of the preceding Plan Year
           or, if such Plan Year is the first Plan Year of the Plan, the last
           day of such Plan Year. In the case of plans included in an
           Aggregation Group, the present value of accrued benefits or accounts
           shall be combined for all aggregated plans that have a Determination
           Date that falls in the same calendar year.

      C.   Key Employee

           Key Employee means an Employee or a former Employee (or the
           beneficiary of such an Employee) who during the Plan Year ending on
           the Determination Date or during the four (4) preceding Plan Years
           is, as determined under Code Section 416(i):

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      1.   An officer of the Employer having an annual compensation greater than
           50 percent of the amount in effect under Code Section 415(b)(1)(A);

      2.   One of the ten Employees having annual compensation from the Employer
           greater than the amount in effect under Code Section 415(c)(1)(A) and
           owning (or considered as owning within the meaning of Code Section
           318) the largest interest in the Employer;

      3.   A five (5) percent owner; or

      4.   A one (1) percent owner who has annual compensation from the Employer
           in excess of $150,000.

      Code Section 416(i) is hereby incorporated in the Plan by reference for
      the purpose of determining whether an Employee is a Key Employee, a former
      Key Employee, or a Non-Key Employee.

D.    Non-Key Employee

      Non-Key Employee means an Employee or a former Employee (or the
      beneficiary of such an Employee) who during the Plan Year ending on the
      Determination Date or during the four (4) preceding Plan Years is not a
      Key Employee or former Key Employee as defined under Code Section 416(i).

E.    Super Top-Heavy

      A plan or plans required to be included in the Aggregation Group shall be
      Super Top-Heavy for a Plan Year if on the Determination Date for such Plan
      Year the Top-Heavy Ratio exceeds ninety percent (90%).

F.    Top-Heavy

      A plan or plans required to be included in the Aggregation Group shall be
      Top-Heavy for a Plan Year if on the Determination Date for such Plan Year
      the Top-Heavy Ratio exceeds sixty percent (60%).

G.    Top-Heavy Ratio

      Top-Heavy Ratio means the ratio determined from dividing the present value
      of accrued benefits and accounts for Key Employees by the total

Immunex Corporation Profit Sharing 401(k) Plan and Trust             Page XIII-2



           value of accrued benefits and accounts for Key Employees and Non-Key
           Employees. The value of accrued benefits and accounts shall be
           determined as prescribed under paragraph H below.

     H.    Valuation of Accrued Benefit

           1.   Defined Contribution Plan

                The present value of an accrued benefit under a defined
                contribution plan is the account balance derived from Employer
                and nondeductible Employee contributions as of the most recent
                valuation date within the twelve (12) month period ending on the
                Determination Date, plus any contributions actually made since
                such date or, in the case of a plan subject to minimum funding
                requirements, contributions required to be made as of the
                Determination Date. All defined contribution plans required to
                be included or permissively included in the Aggregation Group
                shall be treated as a single plan.

           2.   Defined Benefit Plan

                The present value of an accrued benefit under a defined benefit
                plan is the value of the monthly retirement benefit derived from
                Employer or nondeductible Employee contributions, determined as
                of the most recent valuation date within the twelve (12) month
                period ending on the Determination Date, and determined as
                though the individual terminated service as of such valuation
                date. The benefit of Employee, other than a Key Employee, shall
                be treated as accruing under the method that is used for accrual
                purposes for all plans of the Employer and its Affiliates or, if
                there is no such method, as if such benefit accrued not more
                rapidly than the slowest accrual rate permitted under Code
                Section 411(b)(1)(C). Reasonable actuarial assumptions shall be
                used to determine the value of the benefit under the plan;
                provided, that assumptions as to future withdrawal or future
                salary increases shall not be used. All defined benefit plans
                required to be included or permissively included in the
                Aggregation Group shall be treated as a single plan and the same
                actuarial assumptions shall be used to value benefits under each
                of the plans included in the Aggregation Group.

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           3.   Distributions Included

                In determining the present value of any accrued benefits and the
                amount of any account to be used to determine the Top-Heavy
                Ratio, distributions within the period of five (5) consecutive
                Plan Years ending on the Determination Date, and such rollover
                accounts as prescribed by regulation by the Secretary of the
                Treasury, shall be added to the value of accrued benefits as of
                such Determination Date. The accrued benefits of a former Key
                Employee and the accrued benefits of an individual who has not
                performed any services for the Employer maintaining the Plan at
                any time during the five (5) year period ending on the
                Determination Date shall, however, be disregarded.

13.3  Minimum Contributions

      For any Plan Year in which the Plan's Aggregation Group is Top-Heavy, the
      Employer contribution and forfeitures allocated to a Participant who is a
      Non-Key Employee in the employ of the Employer on the last day of the Plan
      Year shall be not less than the lesser of:

           A.   Three percent (3%) of the Participant's Compensation; or

           B.   The percentage at which contributions are made under the Plan
                for the Key Employee for whom such percentage is the highest for
                the Plan Year. In determining the contribution rate for a Key
                Employee, Employee elective contributions under a plan qualified
                under Code Section 401(k) shall be included.

                If the Plan is required to be included in an Aggregation Group
                and the Plan allows a defined benefit plan required to be in
                such Group to meet the requirements of Code Section 401(a)(4) or
                410, the minimum contribution, in such circumstances, shall be
                not less than three (3) percent of the Participant's
                Compensation for the Plan Year. All defined contribution plans
                required to be included in the Aggregation Group shall be
                treated as a single plan.

Immunex Corporation Profit Sharing 401(k) Plan and Trust             Page XIII-4



13.5  Benefits Under Different Plans

      If the Employer maintains one or more defined contribution plans (which
      shall be treated as a single defined contribution plan for purposes of
      this Article) in addition to a defined benefit plan and a Non-Key Employee
      participates in both types of plans, the Employer shall provide such
      Participant with the minimum benefit required under the defined benefit
      pension plan, offset, however, by any benefit provided under the
      Employer's defined contribution plan.

Immunex Corporation Profit Sharing 401(k) Plan and Trust             Page XIII-5



                       XIV. PROVISION AGAINST ANTICIPATION

Until distribution pursuant to the terms hereof, no Participant shall have the
right or power to alienate, anticipate, commute, pledge, encumber or assign any
of the benefits, proceeds or avails set aside for him under the terms of the
Plan, and no such benefits, proceeds or avails shall be subject to seizure by
any creditor of the Participant or the Employer under any writ or proceedings at
law or in equity, provided, that the terms of this Section shall not prohibit
the creation, assignment or recognition of a right to any benefit payable with
respect to a Participant if such creation, assignment or recognition of a right
is made under a qualified domestic relations order as defined under Code Section
414(p), a judgment, order, decree or settlement agreement described in Code
Section 401(a)(13) issued or entered into after August 4, 1997, or as security
for a loan from the Plan which is permitted pursuant to Code Section 4975.

Immunex Corporation Profit Sharing 401(k) Plan and Trust              Page XIV-1



XV.    ADMINISTRATIVE COMMITTEE - NAMED FIDUCIARY AND ADMINISTRATOR

15.1   Appointment of Committee

       The Employer shall appoint an Administrative Committee comprised of one
       or more persons (herein referred to as the Committee) to serve for such
       terms as the Employer may designate or until a successor has been
       appointed or until removal by the Employer. The Employer shall advise the
       Trustee in writing of the names of the members of the Committee and any
       changes thereafter made in the membership of the Committee. Vacancies due
       to resignation, death, removal or other causes shall be filled by the
       Employer. Members shall be bonded except as may otherwise be allowed by
       law. A member of the Committee may be paid reasonable compensation for
       the member's service, provided, that a member who is a full-time employee
       of the Employer shall serve without compensation. All reasonable expenses
       of the Committee shall be paid by the Employer. The number of the
       Committee may be changed by the Employer at any time.

15.2   Committee Action

       The Committee shall appoint a secretary who shall keep minutes of the
       Committee's proceedings and all data, records and documents pertaining to
       the Committee's administration of the Plan. The Committee shall act by
       majority vote of its members in office at that time, such vote to be
       taken at a meeting or, in writing, without a meeting. The Committee may,
       by such majority action, authorize its secretary or any one or more of
       its members to execute any document or documents on behalf of the
       Committee, in which event the Committee shall notify the Trustee in
       writing of such action and the name or names of those so designated. The
       Trustee shall accept and rely conclusively upon any direction or document
       executed by such secretary, member or members as representing action by
       the Committee until the Committee shall file with the Trustee a written
       revocation of such designation. A member of the Committee who is also a
       Participant hereunder shall not vote or act upon any matter relating
       solely to such member.

15.3   Rights and Duties

       The Committee shall be the Plan Administrator and Named Fiduciary of the
       Plan within the meaning of ERISA. The Committee, on behalf of the
       Participants and their Beneficiaries, shall have the authority to control
       and

Immunex Corporation Profit Sharing 401(k) Plan and Trust               Page XV-1



       manage the operation and administration of the Plan and shall have all
       powers and discretionary authority necessary to accomplish those
       purposes. It will interpret and apply all Plan provisions and may correct
       any defect, supply any omission or reconcile any inconsistency or
       ambiguity in such manner as it deems advisable. It will make all final
       determinations concerning eligibility, benefits and rights hereunder, and
       all other matters concerning plan administration and interpretation. All
       determinations and actions of the Committee will be conclusive and
       binding upon all persons, except as otherwise provided herein or by law,
       and except that the Committee may revoke or modify a determination or
       action previously made in error. Any action or omission by the Committee
       will be subject to review (by a court or otherwise) only for an abuse of
       discretion. The Committee will exercise all powers and authority given to
       it in a nondiscriminatory manner, and will apply uniform administrative
       rules of general application in order to assure similar treatment of
       persons in similar circumstances. The responsibility and authority of the
       Committee shall include, but shall not be limited to, the following:

       A.   Construing and interpreting the terms and provisions of the Plan;

       B.   Determining the eligibility of any person for benefits under the
            Plan, the amount of any such benefits and all other questions
            pertaining to the rights of Participants, their Spouses and their
            Beneficiaries hereunder;

       C.   Authorizing all disbursements by the Trustee from the Trust;

       D.   Maintaining all necessary records for the administration of the Plan
            other than those that the Trustee has specifically agreed to
            maintain;

       E.   Interpreting the provisions of the Plan and publishing such rules
            for the regulation of the Plan as are deemed necessary and not
            inconsistent with the terms of the Plan;

       F.   Establishing reasonable procedures to determine the qualified status
            of domestic relations orders and to administer distributions under
            such qualified orders;

       G.   Notifying the Participant and any other alternate payee, as defined
            under Code Section 414(p)(8), of the receipt of a domestic relations
            order, the Plan's procedures for determining the qualified status of
            such an order, and the determination made in connection with such
            order;

Immunex Corporation Profit Sharing 401(k) Plan and Trust               Page XV-2



       H.   Directing the Trustee to make distributions from the Trust Fund to
            Participants, former Participants, and beneficiaries of the Trust in
            accordance with the provisions of the Plan. The Trustee shall
            withhold from such distributions any amount required to be withheld
            pursuant to Code Section 3405 unless the recipient of such
            distributions has made an appropriate election under Code Section
            3405(a)(2) or 3405(b)(3).

15.4   Investments

       The Committee may appoint, in writing, an Investment Manager or Managers
       to manage and control all or part of the investments of the Plan. No
       appointment of an Investment Manager shall be effective until the
       Investment Manager has acknowledged in writing that the Investment
       Manager is a fiduciary of the Plan, and that the Investment Manager has
       complied with the bonding requirements of ERISA.

15.5   Information, Reporting and Disclosure

       To enable the Committee to perform its functions, the Employer shall
       supply full and timely information to the Committee on all matters
       relating to the Compensation of all Participants; their continuous,
       regular employment; their retirement, death or cause for termination of
       employment; and such other pertinent facts as the Committee may require,
       and the Committee shall furnish the Trustee such information as may be
       pertinent to the Trustee's administration of the Trust. The Committee, as
       Plan Administrator, shall have the responsibility of complying with the
       reporting and disclosure requirements of ERISA and, to the extent
       applicable, any other federal or state law.

15.6   Independent Qualified Accountant

       Unless the Plan is exempt from the requirement by applicable law or
       regulation, the Committee shall engage, on behalf of all Participants, an
       independent qualified public accountant who shall conduct such
       examinations of the financial statements of the Plan and of other books
       and records of the Plan as the accountant may deem necessary to enable
       the accountant to form an opinion as to whether the financial statements
       and schedules required by law to be included in any reports are presented
       fairly and in conformity with generally accepted accounting principles
       applied on a basis consistent with that of any preceding year.

Immunex Corporation Profit Sharing 401(k) Plan and Trust               Page XV-3



15.7   Standard of Care Imposed Upon the Committee

       The Committee shall discharge its duties with respect to the Plan solely
       in the interest of the Participants and Beneficiaries; and

       A.   For the exclusive purpose of providing benefits to Participants and
            their Beneficiaries and defraying reasonable expenses of the Plan;

       B.   With the care, skill, prudence and diligence under the circumstances
            then prevailing that a prudent person, acting in a like capacity and
            familiar with such matters, would use in the conduct of an
            enterprise of like character and with like aims; and

       C.   In accordance with the Plan provisions insofar as such provisions
            are consistent with the provisions of ERISA.

15.8   Allocation and Delegation of Responsibility

       The Committee may, by written rule promulgated under Section 15.3 above,
       allocate fiduciary responsibilities among Committee members and may
       delegate to persons other than Committee members the authority to carry
       out fiduciary responsibilities under the Plan, provided that no such
       responsibility shall be allocated or delegated to the Trustee without its
       written consent. As used in this part, the term "fiduciary
       responsibility" shall not include any responsibility provided in the
       Trust Agreement to manage or control the assets of the Plan.

       The Committee, in making the above allocation of fiduciary
       responsibilities, may provide that a person or group of persons may
       serve, with respect to the Plan, in more than one fiduciary capacity. The
       Committee or, so long as the Committee shall have made written approval,
       persons to whom fiduciary responsibilities have been delegated by the
       Committee may employ one or more persons to render advice with regard to
       any responsibility such fiduciary has under the Plan.

       In the event a fiduciary responsibility is allocated to a Committee
       member, no other Committee member shall be liable for any such act or
       omission of the person to whom the responsibility is allocated except as
       may be otherwise required by law. If a fiduciary responsibility is
       delegated to a person other than a Committee member, the Committee shall
       not be responsible or liable for an

Immunex Corporation Profit Sharing 401(k) Plan and Trust               Page XV-4



       act or omission of such person in carrying out such responsibility except
       as may otherwise be required by law.

15.9   Bonding

       Each fiduciary of the Plan and every person handling Plan funds shall be
       bonded unless exempt from such requirement by law. It shall be the
       obligation of the Committee to assure compliance with applicable bonding
       requirements. The Trustee shall not be responsible for assuring that
       bonding requirements are complied with and such responsibility is
       specifically allocated to the Committee.

15.10  Claims Procedure

       A.    Effective Date

             The claims procedure set forth below applies to claims decided on
             or after January 1, 2002. Claims decided prior to January 1, 2002,
             shall be decided under the claims procedure in effect at the time
             of such decision.

       B.    Filing Claim

             A Participant or a Beneficiary, or the authorized representative of
             either (the "Claimant"), who believes that he is then entitled to
             benefits hereunder may file a written claim for such benefits with
             the Secretary of the Administrative Committee. The Administrative
             Committee may prescribe a form for filing such claims, and, if it
             does so, a claim will not be deemed properly filed unless such form
             is used, but the Secretary of the Administrative Committee shall
             provide a copy of such form to any person whose claim for benefits
             is improper solely for this reason.

       C.    Claim Review

             Claims that are properly filed will be reviewed by the
             Administrative Committee, which will make its decision with respect
             to such claim and notify the Claimant in writing of such decision
             within 90 days (45 days in the case of a claim related to permanent
             disability (within the meaning of Section 11.2)) after the
             Secretary of the Administrative Committee's receipt of the written
             claim; provided that the 90-day period (45-day period in the case
             of a claim related to permanent disability (within the meaning of
             Section 11.2)) can be extended for up

Immunex Corporation Profit Sharing 401(k) Plan and Trust               Page XV-5



             to an additional 90 days (30 days in the case of a claim related to
             permanent disability (within the meaning of Section 11.2)) if the
             Administrative Committee determines that special circumstances
             require an extension of time to process the claim and the Claimant
             is notified of the extension, the reasons therefor, and the date by
             which the Administrative Committee expects to render a decision
             prior to the commencement of the extension. If the claim is wholly
             or partially denied, the written response to the Claimant shall
             include:

             1.   the specific reason or reasons for the adverse determination;

             2.   references to the specific provisions of the Plan document on
                  which the determination is based;

             3.   a description of any additional information necessary for the
                  Claimant to perfect his claim and an explanation why such
                  information is necessary;

             4.   a description of the Plan's review procedures (and the time
                  limits applicable thereto), as set forth in subsection (D)
                  immediately below;

             5.   a statement of the Claimant's right to bring a civil action
                  under ERISA Section 502(a) following an adverse benefit
                  determination on appeal; and

             6.   in the case of an adverse benefit determination related to
                  permanent disability (within the meaning of Section 11.2):

                  a.   if an internal rule, guideline, protocol or other similar
                       criterion was relied upon in making the adverse
                       determination, either the specific rule, guideline,
                       protocol or other similar criterion; or a statement that
                       such a rule, guideline, protocol or similar criterion was
                       relied upon in making the adverse determination and that
                       a copy of such rule, guideline, protocol or other
                       criterion will be provided free of charge to the Claimant
                       upon request; or

                  b.   if the adverse benefit determination is based on a
                       medical necessity or experimental treatment or similar
                       exclusion or limit, either an explanation of the
                       scientific or clinical judgment for the determination,
                       applying the terms of the

Immunex Corporation Profit Sharing 401(k) Plan and Trust               Page XV-6



                       Plan to the Claimant's medical circumstances, or a
                       statement that such explanation will be provided free of
                       charge upon request.

       D.    Appeal

             If the claim is denied in whole or in part, the Claimant may appeal
             such denial by filing a written request for appeal with the
             Secretary of the Administrative Committee within 60 days (180 days
             in the case of a claim related to permanent disability (within the
             meaning of Section 11.2)) of receiving written notice that the
             claim has been denied. Such written request for appeal should
             include:

             1.   a statement of the grounds on which the appeal is based;

             2.   reference to the specific provisions in the Plan document
                  which support the claim;

             3.   the reason or argument why the Claimant believes the claim
                  should be granted and evidence supporting each reason or
                  argument; and

             4.   any other relevant documents or comments that the Claimant
                  wishes to include.

             Appeals will be considered by the Administrative Committee, which
             will take into account all comments, documents, records and other
             information submitted by the Claimant relating to the claim,
             without regard to whether such information was submitted or
             considered in the initial determination. The Administrative
             Committee will make its decision with respect to any appeal, and
             notify the Claimant in writing of such decision, within 60 days (45
             days in the case of a claim related to permanent disability (within
             the meaning of Section 11.2)) after the Administrative Committee's
             receipt of the written request for appeal; provided that the 60-day
             period (45-day period in the case of a claim related to permanent
             disability (within the meaning of Section 11.2)) can be extended
             for up to an additional 60 days (45 days in the case of a claim
             related to permanent disability (within the meaning of Section
             11.2)) if the Administrative Committee determines that special
             circumstances require an extension of time to process the appeal
             and the Claimant is notified of the extension, and the reasons
             therefor, prior to

Immunex Corporation Profit Sharing 401(k) Plan and Trust               Page XV-7



             the commencement of the extension.  In the event the claim is
             denied on appeal, the written denial will include:

             1.   the specific reason or reasons for the adverse determination;

             2.   references to the specific provisions of the Plan document on
                  which the benefit determination is based;

             3.   a statement that the Claimant is entitled to receive, upon
                  request and free of charge, reasonable access to, and copies
                  of, documents, records, and other information relevant to the
                  Claimant's claim for benefits;

             4.   a statement of the Claimant's right to bring a civil action
                  under ERISA Section 502(a);

             5.   in the case of an adverse benefit determination related to
                  permanent disability (within the meaning of Section 11.2):

                  a.   if an internal rule, guideline, protocol or other similar
                       criterion was relied upon in making the adverse
                       determination, either the specific rule, guideline,
                       protocol or other similar criterion; or a statement that
                       such a rule, guideline, protocol or similar criterion was
                       relied upon in making the adverse determination and that
                       a copy of such rule, guideline, protocol or other
                       criterion will be provided free of charge to the Claimant
                       upon request;

                  b.   if the adverse benefit determination is based on a
                       medical necessity or experimental treatment or similar
                       exclusion or limit, either an explanation of the
                       scientific or clinical judgment for the determination,
                       applying the terms of the Plan to the Claimant's medical
                       circumstances, or a statement that such explanation will
                       be provided free of charge upon request; and

                  c.   the following statement: "You and your Plan may have
                       other voluntary alternative dispute resolution options,
                       such as mediation. One way to find out what may be
                       available is to contact your local U.S. Department of
                       Labor Office or your State insurance regulatory agency."

Immunex Corporation Profit Sharing 401(k) Plan and Trust               Page XV-8



       E.    Provision of Documents, Records and Other Information

             During the appeal period, the Claimant will be provided, upon
             request and free of charge, reasonable access to, and copies of,
             documents, records and other information relevant to his claim. A
             document, record or other information will be considered "relevant"
             to a Claimant's claim, if such document, record or other
             information:

             (1)  Was relied upon by the Administrative Committee in reaching
                  its decision on the claim;

             (2)  Was submitted, considered or generated in the course of
                  deciding the claim, without regard to whether the document,
                  record or other information was relied upon by the
                  Administrative Committee in reaching its decision on the
                  claim; or

             (3)  Demonstrates compliance with the administrative processes and
                  safeguards required under Department of Labor regulations in
                  making the benefit determination.

       F.    Standard of Review

             Any further review, judicial or otherwise, of the Administrative
             Committee's decision on the Claimant's claim will be limited to
             whether, in the particular instance, the Administrative Committee
             abused its discretion. In no event will such further review,
             judicial or otherwise, be on a de novo basis, as the Administrative
             Committee has discretionary authority to determine eligibility for
             benefits and to construe and interpret the terms of the Plan.

15.11  Unclaimed Account Procedures

       If a Participant or the Participant's Surviving Spouse or Beneficiary,
       if applicable, does not claim the Participant's vested Accrued Benefit,
       the Participant's vested Accrued Benefit shall be forfeited and applied
       in accordance with the provisions of Section 4.1B.3 or 5.2, as
       applicable. An unclaimed vested Accrued Benefit shall be forfeited on the
       later of the date that is 6 months after the date the Plan Administrator
       notifies the Participant, Surviving Spouse or Beneficiary, as applicable,
       by certified or registered mail addressed to his last known address, that
       he is entitled to a benefit or the date on which occurs the earlier of
       the Participant's attainment of Normal

Immunex Corporation Profit Sharing 401(k) Plan and Trust               Page XV-9



        Retirement Age or death, provided that the Participant, Surviving Spouse
        or Beneficiary has not made his whereabouts known prior to such date.

        If a Participant's vested Accrued Benefit is forfeited pursuant to this
        Section 15.11 and the Participant, Surviving Spouse or Beneficiary, as
        applicable, subsequently makes a claim for benefits, the forfeited
        Accrued Benefit shall be restored to the same dollar amount as was
        forfeited, unadjusted for any gains or losses occurring after the date
        on which it was forfeited. Such restoration shall be made first from the
        amount, if any, of Participant forfeitures occurring during the year of
        reinstatement. If such forfeitures are insufficient, restoration will be
        made from a special Employer contribution earmarked for that purpose.
        The reinstated vested Accrued Benefit shall be distribute to the
        Participant, Surviving Spouse or Beneficiary in accordance with the
        preceding provisions of the Plan.

15.12   Funding Policy

        The Committee shall be responsible for establishing and carrying out a
        funding policy for the Plan. In establishing such a policy, the
        short-term liquidity needs of the Plan shall be determined, to the
        extent possible, by considering, among other factors, the anticipated
        retirement date of Participants, turnover and contributions to be made
        by the Employer. In addition, all or a portion of the Plan's assets can
        be invested in "qualifying employer securities," within the meaning of
        Section 407(d)(5) of ERISA, including, but not limited to, common stock
        of Immunex Corporation. The funding policy and method so established
        shall be considered by the Committee in selecting Investment Funds
        pursuant to Section 6.1 and communicated by the Committee to any other
        fiduciary responsible for investment, including the Trustee and any
        Investment Manager, as applicable.

15.13   Indemnification

        The Employer does hereby indemnify and hold harmless each Committee
        member from any loss, claim or suit arising out of the performance of
        obligations imposed hereunder and not arising from said Committee
        member's willful neglect, misconduct or gross negligence.

Immunex Corporation Profit Sharing 401(k) Plan and Trust              Page XV-10



                     XVI. APPOINTMENT OF INVESTMENT MANAGER

16.1    Authority for Appointment

        The Plan Administrator shall have the authority prescribed in ERISA
        Section 402(c)(3) to appoint one or more Investment Managers and
        contract with each for management of any part of the Fund. Selection and
        retention of an Investment Manager shall be in the Plan Administrator's
        discretion. Each Investment Manager shall have the power to manage,
        acquire and dispose of that part of the Fund designated by the Plan
        Administrator. The Investment Manager has no responsibility for Plan
        operation or administration.

16.2    Investment Manager Discretion

        Without limitation of the foregoing and if an Investment Manager is
        appointed:

        A.   The Trustee, on Plan Administrator direction, shall segregate the
             Fund or any part thereof into one or more Investment Manager
             accounts. The Plan Administrator shall appoint an Investment
             Manager for each account and designate to the Trustee the part of
             the Fund to be managed by each Investment Manager. The Trustee
             shall send directly to the Investment Manager the proxies under the
             direction of the Investment Manager, who shall then vote such
             proxies at their discretion.

        B.   Upon request, the Plan Administrator shall advise others that the
             Investment Manager is authorized to enter orders for such
             Investment Manager's account, but the Trustee shall always have
             custody of account assets. The Trustee shall give the Investment
             Manager copies of, or extracts from, such portions of its records
             relating to such accounts as are necessary for the exercise of such
             Investment Manager's functions.

        C.   The Trustee shall neither question nor inquire about any action,
             direction or failure to give directions of any Investment Manager
             and shall not review the securities held in any Investment Manager
             account nor make any suggestions to the Investment Manager with
             respect to investment of, or disposition of, investments in any
             Investment Manager account. The Trustee shall not be liable for any
             act or omission of an Investment Manager or be under any obligation
             to invest or otherwise manage any asset of the Fund that is subject
             to the management of an Investment Manager. The Trustee shall not
             be liable for loss due to action or

Immunex Corporation Profit Sharing 401(k) Plan and Trust              Page XVI-1



             inaction complying with or in the absence of the Investment
             Manager's directions.

        D.   The Plan Administrator, by notice to the Trustee and the Investment
             Manager, may terminate at any time the authority of an Investment
             Manager to manage the account. In such event or upon resignation of
             an Investment Manager, the Plan Administrator shall either appoint
             a successor Investment Manager for the account or, with the
             Trustee's consent, direct the Trustee to assume responsibility for
             the investment management of the assets in the account, in which
             case such assets shall no longer be segregated from the other
             assets of the Fund. Until receipt of notice of such termination or
             resignation, the Trustee shall rely on the latest prior notice of
             the appointment of an Investment Manager.

        E.   Each Investment Manager to whom any fiduciary responsibility with
             respect to the Plan or Trust Fund is delegated shall discharge such
             responsibility in accordance with the standards set forth in ERISA
             Section 404(a).

        F.   Upon written direction of an Investment Manager received by the
             Trustee, the Trustee is authorized to purchase or sell stock,
             bonds, commercial paper, mortgages, or other securities or
             indebtedness of the Trustee or any of its affiliates.

Immunex Corporation Profit Sharing 401(k) Plan and Trust              Page XVI-2



                   XVII. INVESTMENT OF TRUST FUNDS BY TRUSTEE

The Trustee shall exercise authority or discretion in the management and control
of the assets of the Plan, except to the extent the selection of Investment
Funds for investment by Participants is made by the Committee and except to the
extent the management of any part of the Trust Fund has been delegated to any
Investment Manager pursuant to Article XVI. Without limiting the generality of
the foregoing, the Trustee shall invest and reinvest the principal and income of
the Trust Fund in common Investment Funds, real estate, real estate contracts,
government, municipal or corporation bonds, debentures or notes, including notes
secured by deeds of trust, common and preferred stocks, or other forms of
property whether real, personal or mixed, including investments for which
interest is guaranteed by a bank, insurance company or other financial
institution. In the event the Trustee invests any assets of the Plan in a common
Investment Fund maintained by the Trustee or any bank affiliated with the
Trustee (within the meaning of Section 1504 of the Code), the terms of such
common fund are hereby adopted as part of the Plan and such terms are, by this
reference, incorporated as part of this Document.

Immunex Corporation Profit Sharing 401(k) Plan and Trust             Page XVII-1



                       XVIII. POWERS AND DUTIES OF TRUSTEE

18.1    Powers of Trustee

        The Trustee shall have the following powers with regard to Trust assets.
        If investment discretion is exercised by a fiduciary or fiduciaries
        other than the Trustee, to the extent any of the following powers
        involve the exercise of investment discretion, the Trustee shall
        exercise such power at the direction of the investment fiduciary or
        fiduciaries.

        A.   To sell, convey, transfer, mortgage, pledge, lease or otherwise
             dispose of Trust assets without the approval of any court and
             without obligation upon any person dealing with the Trustee to see
             to the application of any money or other property delivered to it;

        B.   To exchange property or securities for other property or
             securities;

        C.   To keep any or all securities or other property in the name of a
             nominee, to deposit securities in a securities depository and hold
             them in the name of its nominee, and to hold securities in book
             entry form at a Federal Reserve Bank;

        D.   To vote, either in person or by proxy, any shares of stock or other
             securities held as part of the assets of the Trust, provided the
             Trustee shall forward proxies to the appropriate investment
             fiduciary, if the Trustee does not exercise investment discretion
             with respect to the security to be voted;

        E.   To collect, as the same shall become due and payable, the principal
             or income of the Trust and, if necessary, to take such legal
             proceedings as may deem advisable in the best interest of the Trust
             to collect any sum of money due the Trust. The Trustee shall be
             under no obligation to commence suit unless it shall have been
             first indemnified by the Trust Fund or the Employer with respect to
             expenses or losses to which it may be subjected through taking such
             action;

        F.   To borrow money for purposes of the Trust and to have power to
             execute and deliver notes, mortgages, pledges or other instruments
             as may be necessary in connection therewith;

Immunex Corporation Profit Sharing 401(k) Plan and Trust            Page XVIII-1



      G.   To pay the expenses of the Trust out of the Fund, including any taxes
           and reasonable compensation for its services as Trustee, if and to
           the extent that the Employer does not pay such expenses and
           compensation;

      H.   To receive and hold in safekeeping the assets of the Trust, provided
           assets invested in a registered mutual fund or in any similar pooled
           fund for which the Trustee is not the custodian shall be held in
           safekeeping by the custodian of such fund, and the Trustee shall not
           be responsible for their safekeeping;

      I.   To employ agents and to utilize the services of affiliates in
           performing its duties hereunder;

      J.   To deposit Trust funds in an interest-bearing account with a bank or
           similar financial institution, including the Trustee, provided such
           deposits shall bear a reasonable rate of interest;

      K.   To determine the fair market value of the Trust assets on an annual
           and other periodic basis. The Trustee shall perform such valuation in
           a reasonable and consistent manner in accordance with generally
           accepted accounting principles. The Trustee may utilize and shall be
           entitled to rely upon published quotation and pricing services that
           it considers reliable. In the event that the Committee or an
           Investment Manager directs investment into assets for which no
           published pricing information is available, the Trustee may obtain
           their fair market value from the Committee, the Investment Manager,
           or an appraiser selected by them, and shall be entitled to rely
           completely upon the value provided. If the Committee or Investment
           Manager is unable to unwilling to provide such valuation, the Trustee
           may engage an appraiser or other expert to determine the fair market
           value, and the fee for such service shall be an administrative
           expense of the Trust; and

      L.   Upon direction of the Committee or an Investment Manager,
           acquire and maintain deposit administration contracts,
           insurance company investment contracts, individual annuities,
           or group annuity policies ("Contracts"). The Trustee shall
           execute the application for a Contract and a Contract in such
           form as the investment fiduciary and the Trustee shall agree.
           The Trustee shall be the legal owner of all Contracts held in
           the Trust. Upon the direction of the investment fiduciary, the
           Trustee shall pay from the Trust the premiums, assessments,
           charges, or other costs to acquire and maintain Contracts. The
           Trustee shall have no duty

Immunex Corporation Profit Sharing 401(k) Plan and Trust            Page XVIII-2



           to make such payment unless the Trustee receives such direction. If
           the cash available in the Trust is not sufficient to pay all the sums
           the investment fiduciary has directed the Trustee to pay, the Trustee
           shall promptly notify the investment fiduciary of the deficiency, and
           the Trustee shall have no duty to make any such payment until it
           receives sufficient cash to make the payment. Upon direction of the
           investment fiduciary, the Trustee shall collect and receive dividends
           or other income of the Contract or leave the income with the issuing
           company; convert from one form of Contract to another; designate a
           mode of settlement of the proceeds of a Contract; sell or assign a
           Contract; surrender a Contract for cash; agree with the issuing
           company to any release, modification, reduction, or amendment
           thereof; and without limitation exercise any other right, option, or
           privilege that belongs to the legal owner of a Contract. The Trustee
           shall have no discretion with respect to the exercise of any of the
           foregoing powers or any other action permitted by a Contract held in
           the Trust, but it shall exercise such powers or take such action only
           upon the direction of the investment fiduciary.

      M.   Generally, with relation to the assets of the Trust, to do all such
           acts, execute all such instruments, take all such proceedings and
           exercise all such rights and privileges as it deems necessary to
           carry out its obligations hereunder to the extent consistent with the
           rights of Participants and Beneficiaries and the standard of care
           imposed by Section 18.4;

18.2  Annual Accounts

      The Trustee, within a reasonable period following the close of each Plan
      Year (not to exceed 120 days), shall render to the Plan Administrator a
      certified account of its administration of the Trust during the preceding
      year, which shall include such information maintained by the Trustee
      necessary to enable the Plan Administrator to comply with the reporting
      requirements of federal law. The Plan Administrator shall promptly review
      the Trustee's accountings and shall file any exceptions within 120 days of
      receipt. In the event it files no exception within such 120-day period,
      the accounting shall be deemed settled for the period covered by it.

Immunex Corporation Profit Sharing 401(k) Plan and Trust            Page XVIII-3



18.3  Notices and Directions

      Whenever a notice or direction is given to the Trustee, the instrument
      shall be signed by a person or persons duly authorized by resolution,
      minutes, or similar action to act on behalf of the Employer, the Plan
      Administrator, an Investment Manager, or any other person or agent with
      authority to direct the Trustee ("Authorized Person"). The Trustee shall
      be protected in acting upon any such notice, resolution, order,
      certificate, opinion, telegram, letter or other document believed to be
      genuine and to have been signed by the proper party or parties, and may
      act thereon without notice to any Participant and without considering the
      rights of any Participant.

      An Authorized Person may give, and the Trustee may rely upon, facsimile
      instructions. An Authorized Person is responsible to verify that facsimile
      instructions delivered to the Trustee are legible in form, clear in
      content, and properly executed. The Trustee shall not be liable for the
      security measures followed by an Authorized Person with respect to
      transmission of facsimile instructions. Should any person request
      disbursement by wire, the Trustee may require as a condition to such
      disbursement that such person conform to Trustee's standard policies and
      procedures for funds transfer and execute Trustee's standard funds
      transfer agreement.

      The Trustee shall not be required to determine or make any investigation
      to determine' the identity or mailing address of any person entitled to
      benefits under the Plan and shall send checks and other papers to such
      persons at addresses as may be furnished it by the Plan Administrator.

18.4  Standard of Care Imposed Upon Trustee

      The Trustee shall discharge its responsibilities under the Plan and Trust
      solely in the interests of the Participants and Beneficiaries; and

      A.   For the exclusive purpose of providing benefits to Participants and
           their Beneficiaries and defraying reasonable expenses of
           administering the Plan;

      B.   With care, skill, prudence and diligence under the circumstances then
           prevailing that a prudent person, acting in a like capacity and
           familiar with such matters, would use in the conduct of an enterprise
           of a like character and with like aims;

Immunex Corporation Profit Sharing 401(k) Plan and Trust            Page XVIII-4



      C.   To the extent it exercises investment discretion, by diversifying the
           investments of the Plan so as to minimize the risk of large losses,
           unless under the circumstances it is clearly prudent not to do so;
           and

      D.   In accordance with the terms of this Plan and Trust Agreement insofar
           as such provisions are consistent with the provisions of ERISA.

18.5  Trustee's Acknowledgment of Responsibility

      The Trustee appointed under the Plan and Trust shall acknowledge and
      accept its appointment by signing this Document or by signing a separate
      document of acceptance which incorporates the Plan and Trust by reference.
      The Trustee's acknowledgment or acceptance of any modification of this
      Document shall be necessary if such modification changes the duties of the
      Trustee in any way.

Immunex Corporation Profit Sharing 401(k) Plan and Trust            Page XVIII-5



                                XIX. CONSTRUCTION

This Agreement shall be construed in accordance with the Code, ERISA and
regulations issued thereunder and, to the extent not superseded thereby, the
laws of the State of Washington.

Immunex Corporation Profit Sharing 401(k) Plan and Trust              Page XIX-1



                            XX. LIABILITY OF TRUSTEE

20.1   Actions of Trustee Conclusive

       In the performance of its duties under the Trust, the Trustee shall
       exercise good faith and comply with the standard of care imposed upon it
       and with the terms of this Agreement. The Trustee shall have the
       authority to interpret its responsibilities hereunder, and, in the
       absence of fraud or breach of fiduciary responsibility, the Trustee's
       interpretation shall be conclusive. In case any dispute or doubt arises
       as to the Trustee's rights, liabilities or duties hereunder, the Trustee
       may employ counsel and take the advice of such counsel as it may select
       and shall be fully protected in acting upon and following such advice,
       except to the extent otherwise provided by law. The Trustee shall be
       entitled to reimburse itself from the Trust Fund for reasonable expenses
       thereby incurred, to the extent such expenses are not paid by the
       Employer.

20.2   Distributions by Trustee

       Until the Trustee receives written notice of any agreement or occurrence
       having effect upon any rights hereunder, including but not limited to
       birth, marriage, divorce, death and/or agreements between Spouses, the
       Trustee shall incur no liability for distributions made.

20.3   Expenses of Administration

       In the event the Employer files for reorganization or protection from
       creditors under the bankruptcy laws, or files a petition in bankruptcy,
       or an assignment of assets for creditors, the Trustee shall pay from
       Trust assets any unpaid expenses for services rendered to the Plan,
       including but not limited to administration, actuarial and consulting
       services.

20.4   Indemnity of Trustee

       The Employer shall indemnify and hold harmless the Trustee from any loss
       or liability (including reasonable attorneys' fees) incurred as a result
       of (a) following any direction (or not acting in the absence of
       direction) from the Employer, the Plan Administrator, an Investment
       Manager, or any other person authorized by the Employer to issue
       direction to the Trustee; and (b) its good faith performance of its
       duties hereunder, except for its own negligence, breach of fiduciary
       duty, or willful misconduct.

Immunex Corporation Profit Sharing 401(k) Plan and Trust               Page XX-1



                     XXI. RESIGNATION OR REMOVAL OF TRUSTEE

21.1   Resignation

       The Trustee may resign at any time by giving the Employer at least sixty
       (60) days written notice of such resignation sent by registered mail. In
       such event, the Employer shall designate a successor Trustee within sixty
       (60) days, and failing in which, the Trustee may petition an appropriate
       court to designate a successor Trustee, which successor Trustee may be a
       corporate Trustee or an individual Trustee.

21.2   Removal

       The Employer may remove a Trustee with or without cause by giving the
       Trustee at least sixty (60) days' written notice and by appointing a
       successor Trustee, Trustees, corporate or individual, or any combination
       of Trustees.

21.3   Settlement of Account

       Upon the resignation or removal of the Trustee, all right, title and
       interest of such Trustee in the assets of the Trust and all rights and
       privileges under this Agreement theretofore vested in such Trustee, shall
       vest in the successor Trustee, and thereupon, all future liability of
       such Trustee shall terminate; provided, however, that the Trustee shall
       execute, acknowledge and deliver all documents and written instruments
       which are necessary to transfer and convey the right, title and interest
       in the Trust assets and all rights and privileges to the successor
       Trustee.

Immunex Corporation Profit Sharing 401(k) Plan and Trust              Page XXI-1



                                   XXII. SUITS

If any person or party to this Agreement shall request the Trustee to bring any
action at law or suit in equity to determine any of the provisions or rights
arising out of this Agreement, the Trustee shall not be obligated to bring such
suit unless the Trustee is fully indemnified for all costs of such action,
including a reasonable sum for attorneys' fees.

Immunex Corporation Profit Sharing 401(k) Plan and Trust             Page XXII-1



                        XXIII. MERGERS AND CONSOLIDATIONS

In the case of any merger or consolidation with any other plan or a transfer of
assets or liabilities to any other plan, each Participant shall be entitled to
be credited with a benefit immediately after such merger, consolidation or
transfer which is equal to the benefit to which he would have been entitled
immediately before such merger or consolidation had the Plan then terminated.

Immunex Corporation Profit Sharing 401(k) Plan and Trust            Page XXIII-1



                     XXIV AMENDMENT AND TERMINATION OF PLAN

24.1   Right to Amend and Terminate

       The Employer represents that the Plan is intended to be a continuing and
       permanent program for Participants but reserves the right to terminate
       the Plan at any time. The Employer may modify, alter or amend the Plan in
       whole or in part, at any time and for any reason.

24.2   No Revesting

       No termination, modification, alteration or amendment shall have the
       effect of revesting in the Employer any of its contributions or the
       income derived therefrom.

24.3   Exclusive Benefit of Participants

       At no time during the existence hereof or at its termination may the Plan
       assets be used for or directed to purposes other than for the exclusive
       benefit of Participants or their Beneficiaries.

24.4   Termination and Discontinuance of Contributions

       The Employer shall have the right, at any time, to discontinue its
       contributions hereunder and to terminate, or partially terminate, this
       Agreement (and the Plan and Trust established hereunder). Upon complete
       discontinuance of the Employer's contributions or full or partial
       termination of the Plan, the Accounts and rights to benefits of all
       affected Participants shall become fully vested and shall not thereafter
       be subject to forfeiture, except to the extent that law or regulations
       may preclude such vesting in order to prevent discrimination in favor of
       Highly Compensated Employees. Upon final termination of the Plan, the
       Plan Administrator shall direct the Trustee to distribute to the
       Participants all assets remaining in the Trust after payment of any
       expenses properly chargeable against the Trust in accordance with the
       value credited to such Participants, as of the date of such termination,
       in cash or in kind and in such manner as the Plan Administrator shall
       determine.

Immunex Corporation Profit Sharing 401(k) Plan and Trust             Page XXIV-1



                        XXV. RIGHT TO DISCHARGE EMPLOYEES

Neither the establishment of the Plan, nor any modification thereof, nor the
payment of any benefit shall be construed as giving any Participant or any other
person any legal or equitable right against the Employer or the Trustee, unless
the same shall be specifically provided for in the Plan, nor as giving any
Employee or Participant the right to be retained in the employ of the Employer.
All Employees shall remain subject to discharge by the Employer to the same
extent as if the Plan had never been adopted.

Immunex Corporation Profit Sharing 401(k) Plan and Trust              Page XXV-1



                          XXVI. RETURN OF CONTRIBUTIONS

26.1  Mistake of Fact

      In the event a contribution is made by reason of a mistake of fact, the
      amount that would not have been contributed had the mistake not occurred
      may be returned to the Employer if the amount is returned within one year
      of the mistaken contribution.

26.2  Allowance of Deductibility

      All contributions to the Plan are conditioned upon their deductibility
      under Code Section 404. Notwithstanding any provision herein to the
      contrary, to the extent a deduction is disallowed, the deduction shall be
      returned to the Employer if the Employer so requests and the amount is
      returned within one year of the disallowance.

Immunex Corporation Profit Sharing 401(k) Plan and Trust             Page XXVI-1



                               XXVII. PUERTO RICO

To the extent Puerto Rican law imposes different limits or requirements than
those set forth above for plan qualification, the terms and provisions of the
Plan shall be deemed to have been modified to reflect those limits and
requirements with respect to any Eligible Employees employed in Puerto Rico.

Immunex Corporation Profit Sharing 401(k) Plan and Trust            Page XXVII-2



      IN WITNESS WHEREOF, the parties hereto have caused this Document to be
executed this 25th day of February, 2002.

                                            IMMUNEX CORPORATION

                                            By: /s/ David A. Mann
                                                --------------------------------
                                               Title Executive Vice President
                                                     ---------------------------
                                                     and Chief Financial Officer
                                                     ---------------------------

                                            SECURITY TRUST COMPANY, as Trustee

                                            By: /s/ Nicole McDermott
                                                --------------------------------
                                               Title Vice President
                                                     ---------------------------

Immunex Corporation Profit Sharing 401(k) Plan and Trust            Page XXVII-3



                                 AMENDMENT NO. 1
                                       TO
                               IMMUNEX CORPORATION
                      PROFIT SHARING 401(k) PLAN AND TRUST

     This Amendment No. 1 is made to the Immunex Corporation Profit Sharing
401(k) Plan and Trust (the "Plan"), which was originally effective January 1,
1987, and most recently amended and restated effective January 1, 2000. All
terms defined in the Plan shall have the same meaning when used herein. All
provisions of the Plan not amended by this Amendment No. 1 shall remain in full
force and effect.

     Effective March 1, 2002, the first sentence of Section 4.1A is amended to
read as follows:

          Each Participant may elect, effective as of the first day of any
     month coincident with or following the Participant's Enrollment Date, by
     filing a Salary Deferral Agreement with the Plan Administrator within
     such time as the Plan Administrator may determine, to defer any whole
     percentage of the Participant's Compensation not to exceed 30%, but in
     any event, the amount of deferral shall not exceed the Section 402(g)
     Limit.

     The Employer has caused this Amendment to be executed on the date indicated
below.

                                              IMMUNEX CORPORATION


Dated: February 28, 2002                      By: /s/ Philip Laub
                                                 -------------------------------
                                                 Its: VP, HR
                                                     ---------------------------



                                 AMENDMENT NO. 2
                                       TO
                               IMMUNEX CORPORATION
                      PROFIT SHARING 401(K) PLAN AND TRUST

     This Amendment No. 2 is made to the Immunex Corporation Profit Sharing
401(k) Plan and Trust (the "Plan"), which was originally effective January 1,
1987, and most recently amended and restated effective January 1, 2000. All
terms defined in the Plan shall have the same meaning when used herein. This
Amendment shall be effective as of the effective date of Amgen Inc.'s
acquisition of Immunex Corporation. All provisions of the Plan not amended by
this Amendment No. 2 shall remain in full force and effect.

     1.  The name of the Plan is hereby changed to the Amgen Inc. Profit Sharing
401(k) Plan and Trust, and all references in the Plan thereto are hereby revised
accordingly. To that end, Section 1.1 is amended to read as follows:

         1.1  Name

              This Plan shall be known as the Amgen Inc. Profit Sharing 401(k)
              Plan and Trust.

     2.  Section 2.6 is amended to read as follows:

         2.6  Board

              "Board" means the Board of Directors of Amgen Inc.

     3.  Sections 2.6 (Code) through 2.35 (Year of Service) are renumbered as
Sections 2.7 through 2.36, respectively, and all references thereto in the Plan
are revised accordingly.

     4.  Effective March 1, 2002, the third sentence of the first paragraph of
Section 2.8 (as renumbered) is amended to read as follows:

         Notwithstanding the foregoing, (i) Compensation shall include
         amounts excludable from the Employee's gross income by reason of
         Code Section 125, 402(e)(3), 402(h) or 403(b), and (ii) solely
         for purposes of Sections 2.27, 4.1A, 4.1E, 4.2A and 5.2A,
         Compensation shall not include commissions or, effective March 1,
         2002, any amounts paid pursuant to the Immunex Corporation
         Retention Plan or the Immunex Corporation Employee Severance
         Plan.

     5.  Section 2.11 (as renumbered) is amended to read as follows:

         2.11 Employer



          "Employer" means Immunex Corporation (or any successor thereof) and
          any Affiliate that, with the consent of the Board, elects to adopt the
          Plan; provided, that for purposes of Article XV (Administrative
          Committee), Article XXI (Resignation or Removal of Trustee) and
          Article XXIV (Amendment and Termination of Plan), Employer means Amgen
          Inc.

6.   Sections 6.4, 6.5 and 6.6 are amended to read as follows:

     6.4  Voting of Stock Held in Investment Funds

          With respect to each Participant's investment in any Investment Fund,
          other than the Amgen Inc. Common Stock Fund, the Trustee shall vote
          the number of shares credited to each Participant's Account, in each
          case, in a manner that the Trustee believes to be consistent with its
          fiduciary duties under Section 404 of ERISA.

     6.5  Voting of Amgen Stock

          With respect to each Participant's investment in the Amgen Inc. Common
          Stock Fund, before each annual or special meeting of the stockholders
          of Amgen Inc., Amgen Inc. will furnish such Participant with a copy of
          the proxy solicitation material for such meeting, together with a form
          addressed to the Trustee requesting the Participant's confidential
          instructions on how the shares of Amgen Inc. common stock ("Shares")
          allocated to the Participant's Account should be voted on each matter
          to come before the meeting. The number of Shares allocated to a
          Participant's Account will be determined by multiplying the number of
          Shares held in the Amgen Inc. Common Stock Fund as of the applicable
          record date by a fraction, the numerator of which is the number of
          units of such Fund held in the Participant's Account as of the
          applicable record date and the denominator of which is the total
          number of outstanding units of such Fund as of such date. Upon receipt
          of such instructions, the Trustee shall vote Shares allocated to each
          Participant's Account (including fractional as well as whole Shares)
          in accordance with timely directions of such Participant; provided,
          that a failure of a Participant to timely and affirmatively direct the
          manner in which Shares allocated to the Participant's Account are to
          be voted shall be deemed for purposes of this Section to be an
          affirmative direction to abstain from voting.

     6.6  Tender of Amgen Stock

          The Trustee shall, with respect to Shares allocated to that portion of
          each Participant's Account invested in the Amgen Inc. Common Stock

                                     Page 2



               Fund, act in response to any tender offer or exchange offer for
               Shares commenced by a person or persons, including, but not
               limited to, a tender offer or exchange offer within the meaning
               of the Securities Exchange Act of 1934, as amended from time to
               time (all such tender or exchange offers collectively, a "tender
               offer"), in accordance with timely directions of such
               Participant; provided, that a failure of a Participant to timely
               and affirmatively direct the manner in which the Trustee is to
               act in response to a tender offer with respect to Shares
               allocated to the Participant's Account shall be deemed for
               purposes of this Section to be an affirmative direction not to
               take action with respect to such Shares. For purposes of
               determining the number of Shares to be the subject of any
               particular response to a tender offer, the Trustee shall use the
               nearest practicable date as determined by the Trustee. The number
               of Shares allocated to a Participant's Account will be determined
               by multiplying the number of Shares held in the Amgen Inc. Common
               Stock Fund as of the relevant date by a fraction, the numerator
               of which is the number of units of such Fund held in the
               Participant's Account as of such date and the denominator of
               which is the total number of outstanding units of such Fund as of
               such date. Amgen Inc. and the Trustee each shall use its best
               efforts to timely distribute or to cause to be distributed to
               each Participant such information as is being distributed to
               other stockholders of Amgen Inc. in connection with any such
               tender offer.

     7.   The last sentence of Section 12.1(A) is amended to read as follows:

          Notwithstanding the foregoing, if the Plan Administrator establishes
          an Investment Fund that is designed to invest primarily in the common
          stock of Amgen Inc., a Participant (or Beneficiary, as applicable) may
          elect to receive such whole shares of Amgen Inc. common stock as are
          allocated to that portion of the Participant's vested Accounts that is
          invested in such Investment Fund (with cash for any fractional
          shares), in lieu of receiving cash for such portion of the
          Participant's Accounts.

     8.   The third sentence of Section 15.12 is amended to read as follows:

          In addition, all or a portion of the Plan's assets can be invested in
          "qualifying employer securities," within the meaning of Section
          407(d)(5) of ERISA, including, but not limited to, common stock of
          Amgen Inc.

     The Employer has caused this Amendment No. 2 to be executed on the date
indicated below.

                               IMMUNEX CORPORATION

                                     Page 3



Dated:   July 12, 2002                      By:   /s/ Edward Fritzky
       -------------------------                --------------------------------
                                                  Its:  Chief Executive Officer
                                                       -------------------------

Accepted:

                                            SECURITY TRUST COMPANY, as Trustee

                                            By:  /s/ Nicole McDermott
                                                --------------------------------
Dated:   July 15, 2002                            Its:  Vice President
       -------------------------                       -------------------------

                                     Page 4