<PAGE>

                                                                   EXHIBIT 10.43

May 10, 2000



Mr. Gordon M. Binder
130 Delfern Drive
Los Angeles, CA  90077


Re:  Agreement Regarding Part-Time Special Assignment Position
     ---------------------------------------------------------

Dear Gordon:

On behalf of Amgen Inc. ("Amgen" or the "Company"), I am pleased to confirm in
this letter agreement (the "Agreement") the terms and conditions under which you
will continue to be employed by Amgen from and after the date upon which you
cease to serve as Amgen's Chief Executive Officer which will occur on May 11,
2000 (the "Effective Date").  You will remain in your current position and
receive all compensation and benefits of that position between now and the
Effective Date.  This Agreement also provides for the termination of your
employment with Amgen on or before December 31, 2002, as set forth below.

1.   POSITION AND DUTIES
     -------------------

     On the Effective Date, you will retire and resign from all offices you hold
     in Amgen and its subsidiaries, except that, if elected by the stockholders
     of the Company at the Annual Meeting of Stockholders to be held on May 11,
     2000, then you will remain as a member of the Board of Directors until
     December 31, 2000, and if appointed by the Board of Directors to be
     Chairman of the Board of Directors, then you will remain as Chairman of the
     Board of Directors until December 31, 2000.  In connection with resigning
     your offices, you agree to execute and return to Amgen with this Agreement
     a signed original resignation letter (the "Resignation Letter") on your
     Amgen letterhead in the form provided in Appendix A to this Agreement.
     Appendix A is hereby incorporated into and made part of the Agreement by
     reference.

     On the Effective Date you will cease to be a regular full-time employee of
     Amgen and you will also continue to be employed by Amgen as an employee in
     a part-time special assignment position, as Special Advisor to the Chief
     Executive Officer.  As Special Advisor to the Chief Executive Officer, you
     will assist Kevin Sharer or his successor or designee (collectively "Your
     Supervisor").  You will assist Your Supervisor in monitoring and evaluating
     various federal government developments as they relate to Amgen's current
     products, products which Amgen is in the process of developing and
     potential future products, including those which Amgen may acquire by
     corporate or other acquisitions.  You will also advise Your Supervisor on
     certain arbitration and litigation matters, such as those involving Johnson
     & Johnson and Transkaryotic Therapies, Inc. and such other matters as you
     and Your Supervisor mutually agree upon.
<PAGE>

Mr. Gordon M. Binder
May 10, 2000
Page 2

     Upon Your Supervisor's reasonable request, you will be required to provide
     Your Supervisor with written or oral reports and/or copies of other written
     materials with regard to the foregoing.  Your Supervisor will evaluate your
     performance.

     You will be a member of the Executive Department and as such, Your
     Supervisor will control and direct the manner in which you perform the
     services under this Agreement, including the details and means by which you
     provide your services.

     You will be an employee of Amgen for all purposes during the term of this
     Agreement and will not be an independent contractor.

     As we have discussed, the position of Special Advisor to the Chief
     Executive Officer is a part-time special assignment position in which you
     will be expected to work a minimum of ten (10) hours per month; however,
     you also agree that, to the extent that Your Supervisor requests, you will
     work up to twenty (20) hours per month.  In the event that Amgen requests,
     and you agree, to work more than twenty (20) hours per month, then you will
     receive no additional compensation or benefits for such additional work.
     Your time spent traveling pursuant to this Agreement shall count toward
     your hours worked under this Agreement.  For any month in which Amgen does
     not specially assign you a sufficient amount of work to meet your minimum
     hour requirement, you should satisfy your minimum by independently
     identifying, researching, and evaluating issues and developments in your
     areas of responsibility, as set forth above, and reporting on your findings
     to Your Supervisor.

     If requested by Your Supervisor, you agree to attend certain meetings or
     programs related to your area of expertise so long as such meeting or
     program does not unreasonably interfere with your other activities.

     You will maintain a log showing the time you have spent performing the
     foregoing services and this log shall be deemed conclusive evidence of the
     time spent.  Amgen, at any time, may request a copy of your log and you
     agree to provide such a copy within a reasonable period of time after the
     request is made.  Furthermore, from time to time, your duties may require
     you to travel and attend meetings at various locations, including Amgen's
     Thousand Oaks facility, and you agree that no reasonable request by Your
     Supervisor for travel or attendance at meetings will be refused.  Your
     Supervisor will work with you in scheduling any such business trips or
     meetings so that they do not unreasonably interfere with your other
     activities and Amgen will reimburse you for your reasonable travel expenses
     pursuant to the reimbursement policy(ies) in place at Amgen for corporate
     officers at the time you incur such expenses.  In the event that you fly on
     Amgen business on a private aircraft that you own (in whole or in part),
     then Amgen will reimburse you for the cost of such a trip in the amount of
     the applicable first-class commercial airfare rate for such a trip.
<PAGE>

Mr. Gordon M. Binder
May 10, 2000
Page 3

     We have agreed that your part-time special assignment will continue until
     December 31, 2002, subject to extension as you and Amgen may agree in
     writing or to earlier termination by you or Amgen as set forth in Paragraph
     8 of this Agreement. As long as you are employed by Amgen, you will
     continue to be subject to Amgen's policies and procedures, including but
     not limited to those relating to the non-disclosure of proprietary and
     confidential information and you will continue to be subject to the Amgen
     Inc. Proprietary Information and Inventions Agreement, executed by you on
     or about June 1, 1982 (the "Proprietary Agreement") (which also contains
     obligations that survive the termination of your employment with Amgen).
     However, notwithstanding the foregoing, you will not be required to comply
     with Procedures 3, 10 and 11 of the Company's Corporate Policy Number 230
     ("Conflict of Interest/Insider Information"), a copy of which is attached
     hereto as Appendix B, commencing on the opening of business on the third
     full business day following the Company's public release detailing the
     Company's full financial results for the fiscal year ended December 31,
     2000.

     During the term of your part-time special assignment, except as set forth
     herein, you may not be employed by any person or company other than Amgen,
     without Amgen's prior approval. You may be self-employed, an independent
     contractor, a partner, a consultant, or a member of a venture capital or
     private equity firm. You may only join the board of directors of any
     company within the fields of biotechnology, human therapeutics, or
     pharmaceutics with Amgen's advance written permission, but you may join the
     board of directors of any other company without Amgen's permission. You may
     also engage in teaching, charitable, civic, or political activities. You
     may engage in the activities described in the preceding three sentences
     provided that such activity: (1) does not interfere with your duties under
     this Agreement and (2) does not violate the terms of the Proprietary
     Agreement. You also agree that during the term of this Agreement, you will
     not solicit for employment or affiliation, including as independent
     contractor, any officer, director, or employee of Amgen or its
     subsidiaries.

2.   COMPENSATION AND BENEFITS
     -------------------------

     Following is a brief description of the compensation and benefits you will
     receive under this Agreement during your part-time special assignment.  The
     terms and conditions of all of your benefits are subject to the terms and
     conditions of each of the applicable plans, policies or arrangements, as
     they may be amended or terminated by Amgen from time to time.

     2.1  Compensation:  Your compensation will be $80,000 per month from the
          ------------
          Effective Date through December 31, 2000, and $40,000 per month from
          December 31, 2000 through December 31, 2002, subject to applicable
          income tax and employment tax withholding requirements.  In addition,
          Amgen will reimburse you for any reasonable business expenses you
          incur in performing your duties, subject to Amgen's standard employee
          expense reimbursement policies.
<PAGE>

Mr. Gordon M. Binder
May 10, 2000
Page 4

     2.2  Administrative Support and Office Space: Amgen will provide you with
          ---------------------------------------
          an office and secretarial assistance for any work that you perform
          while at Amgen's Thousand Oaks headquarters. You will also be provided
          any office equipment and supplies you may need to perform your duties
          under this Agreement at Amgen's Thousand Oaks headquarters and you
          will have access to the services of Amgen's travel department.

          If you maintain an office where you will perform some of the services
          required by this Agreement and this office is located more than 15
          miles from Amgen's Thousand Oaks headquarters, then Amgen will
          reimburse you for the actual amount of rental expenses for such an
          office and the charge for up to two (2) parking spaces at the office
          building complex where your office is located up to a maximum amount
          of $6,000 per month. Amgen will supply you with office furniture for
          this office and at the end of your special assignment period, you must
          either return this furniture to Amgen or purchase the furniture from
          Amgen at its then depreciated value as determined by Amgen. Amgen will
          supply you with a secretary through a temporary employment agency
          utilized by Amgen. All other reasonable business expenses incurred by
          you in connection with such an office will be paid by you and
          reimbursed by Amgen.

     2.3  Management Incentive Plan:  You will not be eligible to participate in
          -------------------------
          Amgen's Management Incentive Plan (the "MIP") for any year after the
          1999 calendar year.

     2.4  Special Bonus for 2000 Calendar Year: As part of the transition to
          ------------------------------------
          your part-time special assignment position, you will be entitled to a
          special bonus in the amount of 37% of the MIP payment that you would
          have received for the calendar year 2000 based on what would have been
          your MIP rating for the calendar year 2000, if you had been eligible
          for that MIP payment and if you had been deemed to have been a regular
          full-time employee for the entire year for the purposes of MIP. This
          special bonus will be paid to you at the same time that MIP
          distributions are made to the participants in the MIP in 2001.

     2.5  Supplemental Retirement Plan: As an employee in a part-time special
          ----------------------------
          assignment position, you will no longer be eligible to receive
          additional credits in your supplemental retirement plan account,
          although you will continue to maintain an account and receive earnings
          on the balance in your account until the termination of your
          employment.

     2.6  Retirement and Savings Plan: Pursuant to Section 3.3 of the 401(k)
          ---------------------------
          Plan, employees that are eligible to participate in the 401(k) Plan
          are those that are classified as "regular full-time" or "regular part-
          time" employees. By signing below, you expressly acknowledge and agree
          that Amgen is not classifying you as a
<PAGE>

Mr. Gordon M. Binder
May 10, 2000
Page 5


          regular full-time or regular part-time employee and therefore, as of
          the Effective Date, you will not be eligible to make contributions or
          to have contributions made on your behalf to the 401(k) Plan. This
          letter qualifies as an agreement pursuant to Section 3.3(c)(2) of the
          401(k) Plan. You will, however, be able to maintain your 401(k)
          account in the Amgen plan to the extent allowed by law.

     2.7  Change of Control Severance Plan:  You will continue to be eligible to
          --------------------------------
          participate in the Amgen Inc. Change of Control Severance Plan (the
          "CIC Plan"). However, on the Effective Date you will cease to be a
          Group I Participant and will become a Group II Participant in the CIC
          Plan by virtue of your ceasing to be a member of Amgen's Operating
          Committee. Notwithstanding the foregoing, in the event that the
          aggregate benefits provided for in this Agreement are greater than
          those provided in the CIC Plan upon a termination of employment for
          which you would be eligible to receive benefits under the terms and
          conditions of the CIC Plan, this Agreement, rather than the CIC Plan
          shall govern and control your rights upon a termination of employment;
          provided, that, in such event, and if applicable, you shall also
          receive the 280G tax gross-up benefit provided in Section 4.1(G) of
          the CIC Plan.

     2.8  Stock Options:
          -------------

          2.8.1  No New Grants: As an employee in a part-time special assignment
                 -------------
                 position, you will not be eligible to receive additional stock
                 option grants after the Effective Date.

          2.8.2  Vesting During Special Assignment: To the extent that you
                 ---------------------------------
                 continue in your part-time special assignment, you will be
                 eligible to continue to vest in all unvested options that have
                 previously been granted to you by Amgen on the dates and in the
                 manner provided in your stock option grant agreements and
                 applicable stock option plans. No stock options will vest
                 following the Termination Date as defined in Paragraph 8 of
                 this Agreement.

          2.8.3  Voluntary Retirement: Nothing in this Agreement shall be
                 --------------------
                 construed as limiting (i) your right to voluntarily retire from
                 Amgen during or at the end of the special assignment or (ii)
                 the applicability of Paragraph I of the Grants of Stock Options
                 listed on Appendix C to this Agreement to any termination of
                 your employment.

          2.8.4  Cooperation To Restructure: As we have discussed, it is our
                 --------------------------
                 intention that your ability to continue to vest in and exercise
                 options while in your part-time special assignment position
                 will not result in any additional compensation charges to Amgen
                 in accordance with U.S. generally accepted
<PAGE>

Mr. Gordon M. Binder
May 10, 2000
Page 6

                 accounting principles. Accordingly, if at any time Amgen
                 determines that it is reasonably likely that Amgen will incur a
                 compensation charge as a result of your vesting or exercising
                 options in your part-time special assignment position then you
                 agree that you will use your reasonable best efforts to
                 cooperate with Amgen to restructure this Agreement and your
                 position as Amgen reasonably determines is necessary for you to
                 continue to be able to vest and exercise your options without
                 creating a compensation charge to Amgen in accordance with U.S.
                 generally accepted accounting principles and without causing
                 you to lose any of the benefits of this Agreement. It is
                 expressly understood that your "reasonable best efforts to
                 cooperate with Amgen" shall not require that you take or
                 forbear from taking any action that would result in any loss of
                 value of the options.

          2.8.5  No Amendment to Stock Option Grant Agreements or Stock Option
                 -------------------------------------------------------------
                 Plans: Nothing in this Agreement shall be deemed to alter,
                 -----
                 amend, or otherwise modify the terms of your stock option grant
                 agreements or the terms of the applicable stock option plans.

     2.9  Medical, Dental, and Vision Insurance and COBRA: Your medical, dental,
          -----------------------------------------------
          and vision insurance coverage will terminate on the Effective Date. If
          after the Effective Date, you or your eligible dependents should elect
          to continue coverage under Amgen's group health plan(s) under the
          Consolidated Omnibus Budget Reconciliation Act ("COBRA") continuation
          rights, and you or your eligible dependents timely take the required
          steps to initiate such coverage, then Amgen will pay the cost of COBRA
          coverage for you and your eligible dependents until the earlier of
          December 31, 2002, or until you and/or your eligible dependents no
          longer qualify for COBRA continuation rights or in the case of your
          dependents, the date on which such dependents cease to be eligible
          dependents on your Amgen group health plan(s), which ever comes first.
          If you and/or your eligible dependents qualify for COBRA benefits on
          or after December 31, 2002, then you and/or your eligible dependents
          will have the option of continuing coverage under Amgen's group health
          plan(s), under COBRA and at your own expense. If you and/or your
          eligible dependents lose COBRA eligibility prior to December 31, 2002,
          and you obtain health insurance coverage for you and/or your eligible
          dependents for the period between the time you and your eligible
          dependents lose such coverage and December 31, 2002, then Amgen will
          reimburse you for the full cost of such insurance premiums. To receive
          reimbursement, submit copies of the health insurance premium invoices
          and other applicable information on a monthly basis to Amgen. For a
          complete description of the rights and responsibilities you and your
          eligible dependents have under COBRA, you must refer to the COBRA
          documents that will be sent to you by Amgen or its designee under
          separate cover.

     2.10 Basic Life Insurance:  Your Basic Life Insurance coverage will
          --------------------
          terminate on the Effective Date. If you are interested in converting
          this insurance to an individual policy, please contact Jean Ellis at
          Aetna (860) 273-7252 within thirty (30) days
<PAGE>

Mr. Gordon M. Binder
May 10, 2000
Page 7



          after the Effective Date.

     2.11 Long-Term Disability Insurance:  Your Long-Term Disability Plan
          ------------------------------
          coverage will terminate on the Effective Date and there is no
          conversion policy or plan available for this coverage.

     2.12 Amgen Foundation Matching Funds:  During the term of your special
          -------------------------------
          assignment, contributions you make to qualified organizations will
          continue to be eligible for matching funds from the Amgen Foundation,
          subject to the same terms, conditions, and limitations that apply to
          contributions made by regular, full-time employees of Amgen.

     2.13 Other Benefits:  As an employee in a part-time special assignment
          --------------
          position, you will not be eligible to participate in the following
          Amgen benefit plans and programs as well as any other benefits not
          specifically listed in this letter: Dependent Care Assistance Program;
          Medical Flexible Spending Account; Employee Stock Purchase Plan;
          Voluntary and Dependent Life Insurance coverage; Accidental Death and
          Dismemberment benefit; use of Amgen Fitness Center facilities; use of
          Amgen Child Care Center facilities; personal illness;
          vacation/optional holiday pay; family illness/personal time;
          bereavement leave or holidays. Your accrued and unused vacation hours
          and optional holiday pay will be paid to you on the next regularly
          scheduled payroll date following the Effective Date.

3.   TRANSFER OF COMPANY PROPERTY
     ----------------------------

     Except as provided in the remainder of this Subparagraph, you promise that
     on or before the Termination Date, as defined in Paragraph 8 of this
     Agreement, you will return to Amgen all files, memoranda, documents,
     records, copies of the foregoing, credit cards, keys, and any other Amgen
     property in your possession or under your control.  As an employee in a
     part-time special assignment position, you will continue to have access to
     and use of the cellular telephone and telefax machines that Amgen
     previously provided to you.  As of the termination of your employment with
     Amgen, you will be entitled to retain the equipment referenced in the
     preceding sentence.

4.   OFFICERS AND DIRECTORS INSURANCE
     --------------------------------

     During your part-time special assignment and for six (6) years following
     the Termination Date, you will be covered by such officers and directors
     insurance coverage that Amgen provides to its senior executive officers at
     your salary grade level during that time period.  In addition, Amgen shall
     indemnify and hold you and your estate harmless both during and after the
     entire term of your employment (including your service hereunder) to the
     fullest extent permitted by law with regards to actions or inactions in
     relation to your duties performed at Amgen, both before and after the date
     of this Agreement.  In the
<PAGE>

Mr. Gordon M. Binder
May 10, 2000
Page 8

     event that you are being indemnified pursuant to this Paragraph 4, then you
     will be entitled to the advancement of expenses to the same extent as Amgen
     corporate officers would then be entitled to such advancement of expenses.
     Furthermore, you will be entitled to reimbursement of expenses incurred in
     accordance with your rights under California Labor Code Section 2802.

5.   LEGAL FEE AND FINANCIAL/TAX CONSULTING REIMBURSEMENT
     ----------------------------------------------------

     Amgen will reimburse you for the legal expenses reasonably incurred by you
     in connection with the review of this Agreement up to a maximum amount of
     $10,000.  Amgen will also reimburse you for financial and/or tax counseling
     expenses that you reasonably incur, up to a maximum amount of $3,000 per
     year, for each year of this Agreement.

6.   REFERENCE
     ---------

     Amgen will provide you with a positive written factual reference.  I should
     be listed as your work reference.  You agree to confer with me on the form
     and nature of the reference to be provided to third parties concerning the
     work that you have performed at Amgen.  If, by sixty (60) days after the
     Effective Date, you are unable to reach agreement with me on the written
     reference to be provided, then Amgen's only obligation will be to respond
     to inquiries by confirming to third parties the dates of your employment at
     Amgen and the last position you held as an Amgen employee.

7.   RELOCATION
     ----------

     If you decide to relocate outside of the fifty (50) mile radius of your
     Residence (as defined below) during the period of your part-time special
     assignment or immediately at the termination thereof for any reason other
     than for a Stated Reason, as defined below, and sell your current, local,
     primary residence located in Los Angeles, California (the "Residence") so
     that the sale escrow closes no later than December 31, 2002, then Amgen
     will provide you with the following:

     7.1  If your new employer, if any, provides for part of the following
          expenses, then Amgen would pay normal and customary amounts beyond
          those which such new employer paid, up to the amounts that Amgen would
          normally pay, as of the date your employment with Amgen terminated, to
          newly hired Amgen employees in your job: normal and customary costs
          for the packing, shipping, delivery, storage (for up to ninety (90)
          days) and unpacking of your common household goods and furnishings.

     7.2  If you shall sell your Residence so that the close of escrow on the
          sale occurs prior to December 31, 2002, then in such event, Amgen will
          reimburse you for those
<PAGE>

Mr. Gordon M. Binder
May 10, 2000
Page 9

          normal and non-recurring customary sales costs associated with the
          sale of such residence, subject to the following terms and conditions:

          7.2.1  Amgen's obligation will be limited to that amount which, as of
                 the day immediately prior to the date of this Agreement, Amgen
                 would pay to reimburse other employees of your then salary
                 grade level;

          7.2.2  to the extent that your new employer, if any, reimburses you
                 for, or pays any of, such non-recurring customary sales costs,
                 then Amgen will only reimburse you for that portion of the non-
                 recurring customary sales costs that exceed the amount paid for
                 by such new employer; and

          7.2.3  you provide all documentation requested by Amgen in connection
                 with this Subparagraph 7.2, upon the request of Amgen.

     7.3  If you meet the above conditions and so elect, Amgen will grant you
          the opportunity to place your Residence in the "Amgen Marketing
          Assistance and Homesale Program" (the "Program"). For a description of
          the Program, please contact Christine Swinburne of the Amgen Human
          Resources Department. In order to participate in the Program, you must
          notify Ms. Swinburne in writing, of your election to participate in
          the Program no later than June 30, 2002, in order to complete the home
          sale process by December 31, 2002. In order for Amgen to provide you
          with the assistance provided for in this Subparagraph 7.3 in
          connection with the sale of your Residence, you must give Amgen
          control over the disposition of the property, must provide such
          documentation as Amgen may request and must cooperate with Amgen in
          the sale of the Residence.

8.   EARLY TERMINATION OF SPECIAL ASSIGNMENT
     ---------------------------------------

     We have agreed that you will continue in your part-time special assignment
     position until December 31, 2002, at which time your employment with Amgen
     will terminate, provided however, that Amgen may terminate your employment
     prior to December 31, 2002 and you may terminate your employment prior to
     December 31, 2002 upon thirty (30) days prior written notice to Amgen.

     For purposes of this Paragraph 8, a "Stated Reason" means (i) your
     conviction of a felony related to the business of Amgen; (ii) the engaging
     by you in conduct that constitutes willful gross neglect or willful gross
     misconduct in carrying out your duties set forth in Paragraph 1 of this
     Agreement, resulting, in either case, in material economic harm to Amgen,
     unless you believed in good faith that such conduct was in, or not contrary
     to, the best interests of Amgen; or (iii) your material breach of any of
     the terms of this Agreement. In order for an event described in clauses
     (ii) and (iii) of the preceding sentence to qualify as a Stated Reason,
     Amgen must give written notice of the event to you and you must fail to
     cure the event within 60 days of receipt of that written notice.
<PAGE>

Mr. Gordon M. Binder
May 10, 2000
Page 10

     For purposes hereof, no act, or failure to act, on your part shall be
     deemed "willful" unless done, or omitted to be done, by you not in good
     faith.

     For purposes of this Paragraph 8, a "Covered Breach" means a breach by
     Amgen of its obligations under this Agreement in the following manner only
     (i) any reduction in your salary or benefits provided for in this Agreement
     or (ii) the assignment of duties to you that are inconsistent with, or
     greater in scope than, those set forth in Paragraph 1 of this Agreement or
     (iii) a reduction in your title or position or (iv) a material breach of
     Paragraphs 4, 6, or 12 of this Agreement by Amgen or (v) a failure by Amgen
     to have any successor expressly assume this Agreement in accordance with
     Paragraph 16 of this Agreement.  In order for an event described in the
     preceding sentence to qualify as a Covered Breach, you must give written
     notice of the event to Amgen and Amgen must fail to cure the event within
     60 days of receipt of that written notice.

     In the event your employment is terminated by Amgen for a Stated Reason or
     if you terminate your employment for any reason other than a Covered Breach
     then your payments and benefits from Amgen under this Agreement, including
     but not limited to the vesting of your stock options, will cease as of the
     effective date of the termination of your employment.

     In the event your employment is terminated by Amgen not for a Stated Reason
     or if you terminate your employment for a Covered Breach, then (i) you
     shall be paid in a cash lump-sum all of the remaining cash payments due to
     you under this Agreement from the date of your termination through December
     31, 2002, (ii) you shall continue to be provided the benefits set forth in
     Paragraph 2.9 of this Agreement through December 31, 2002 and (iii) Amgen
     shall take the necessary corporate action to accelerate the vesting of all
     of your outstanding and then unvested stock options so that they shall vest
     and become immediately exercisable in full as of the Termination Date; such
     stock options, as so accelerated shall be exercisable as provided in your
     stock option grant agreements and applicable stock option plans.  Amgen
     shall provide you with a copy of the resolutions taking the action
     described in clause (iii) of the preceding sentence.

     The date of the termination of your employment for any of the foregoing
     reasons, or upon your death, is hereinafter referred to as the "Termination
     Date".

9.   DEATH AND DISABILITY
     --------------------

     In the event of the termination of your employment hereunder by reason of
     your death or disability (within the meaning of Title II or XVI of the
     Social Security Act and as determined by the Social Security
     Administration) prior to December 31, 2002, all of the remaining payments
     pursuant to Paragraphs 2.1 and 2.4 of this Agreement will be payable to
     you, or in the event of your death, to the beneficiary or beneficiaries
     that you designate in writing to Amgen (if you make no such written
     designation, then such amounts would be payable to the beneficiary or
     beneficiaries you have designated for purposes of Amgen's 401(k) Plan).
     If, on your death, your spouse qualifies for coverage
<PAGE>

Mr. Gordon M. Binder
May 10, 2000
Page 11

     under Amgen's group health plan(s) pursuant to COBRA continuation rights,
     or if your spouse does not qualify for COBRA continuation rights but
     obtains health insurance coverage, then Amgen will continue to either pay
     the cost of COBRA coverage for your spouse, or reimburse your spouse for
     the full cost of such insurance premiums, whichever applies, through
     December 31, 2002, pursuant to the procedures set forth in Paragraph 2.9 of
     this Agreement. Your other remaining benefits will be treated according to
     their specific terms concerning such death or disability. For purposes of
     Paragraph 8(a) of the Amgen Inc. Amended and Restated 1988 Stock Option
     Plan and Paragraph 10(a) of the Amgen Inc. Amended and Restated 1991 Equity
     Incentive Plan, your employment with Amgen shall be deemed to have
     commenced in 1982, when you first became an employee at Amgen.

10.  INTERPRETATION
     --------------

     This Agreement and Appendix A and Appendix B attached hereto shall be
     construed as a whole according to their fair meaning, and not strictly for
     or against any of the parties.

     Unless the context indicates otherwise, the term "or" shall be deemed to
     include the term "and" and the singular or plural number shall be deemed to
     include the other.  Paragraph headings used in this Agreement are intended
     solely for convenience of reference and shall not be used in the
     interpretation of any of this Agreement.

11.  NOTICES
     -------

     For the purposes of this Agreement, notices, demands and all other
     communications provided for in this Agreement shall be in writing and shall
     be deemed to have been duly given when delivered either personally or by
     United States certified or registered mail, return receipt requested,
     postage prepaid, addressed, if to you, to the last address on file with
     Amgen and if to Amgen, to its executive offices or to such other address as
     any party may have furnished to the others in writing in accordance
     herewith, except that notices of change of address shall be effective only
     upon receipt.

12.  LEGAL FEES; ARBITRATION
     -----------------------

     12.1 Agreement to Arbitrate:  Any dispute (an "Arbitrable Dispute")
          ----------------------
          arising between the parties, including but not limited to those
          concerning the formation, validity, interpretation, effect, or alleged
          violations of this Agreement, must be submitted to binding arbitration
          for resolution in Los Angeles, California in accordance with the rules
          and procedures of the Employment Dispute Resolution Rules of the
          American Arbitration Association then in effect. The decision of the
          arbitrator shall be final and binding on both parties, and any court
          of competent jurisdiction may enter judgment upon the award. Except
          for an action taken outside of arbitration pursuant to Subparagraph
          12.4 of this Agreement, should either party pursue any other legal or
          administrative action against the other, the responding party shall be
          entitled to the return of any payments that party made under the
<PAGE>

Mr. Gordon M. Binder
May 10, 2000
Page 12

          Agreement and shall be entitled to recover all costs, expenses and
          attorneys' fees the responding party incurs as a result of such
          action. The arbitrator may not modify or change this Agreement in any
          way.

     12.2 Costs of Arbitration:  Each party shall pay the fees of their
          --------------------
          respective attorneys, the expenses of their witnesses and any other
          expenses connected with the arbitration, but all other costs of the
          arbitration, including the fees of the arbitrator, cost of any record
          or transcript of the arbitration, administrative fees and other fees
          and costs shall be paid in equal shares by you and Amgen. The party
          losing the arbitration shall reimburse the party who prevailed for all
          fees and expenses the prevailing party paid pursuant to the preceding
          sentence, and (where a prevailing-party attorney's fees provision
          exists) shall also reimburse the prevailing party for attorney's fees
          paid.

     12.3 Exclusive Remedy:  Arbitration in this manner shall be the
          ----------------
          exclusive remedy for any Arbitrable Dispute. The arbitrator's decision
          or award shall be fully enforceable and subject to an entry of
          judgment by a court of competent jurisdiction. Except for an action
          taken outside of arbitration pursuant to Subparagraph 12.4 of this
          Agreement, should you or Amgen, without the consent of the other
          party, attempt to resolve an Arbitrable Dispute by any method other
          than arbitration pursuant to this Paragraph 12, the responding party
          shall be entitled to recover from the initiating party all damages,
          expenses and attorneys' fees incurred as a result.

     12.4 Sole Exception:  Notwithstanding the foregoing, a dispute relating
          --------------
          to the alleged use or disclosure of information which is prohibited by
          the Proprietary Agreement, and/or the criticism, denigration or
          disparagement of Amgen or any of Amgen's products, processes,
          experiments, policies, practices, standards of business conduct, or
          areas or techniques of research may be resolved through a means other
          than arbitration, at Amgen's sole option.

13.  GOVERNING LAW
     -------------

     This Agreement is governed by, and is to be construed and enforced in
     accordance with, the laws of the State of California, without regard to
     principles of conflicts of laws.

14.  TAXES
     -----

     You acknowledge and agree that all payments made pursuant to this Agreement
     shall be made less applicable tax withholdings and/or other withholdings as
     required by law.  You acknowledge and agree that you, and not Amgen, shall
     be solely responsible for any taxes imposed upon you as a result of the
     payments and benefits you receive under the Agreement with the sole
     exception of the potential 280G tax gross-up as provided in Subparagraph
     2.7 of this Agreement.  This paragraph shall not be construed to require
<PAGE>

Mr. Gordon M. Binder
May 10, 2000
Page 13

     you to pay Amgen's portion of any employment tax withholding, such as
     Amgen's portion of FICA or FUTA.

15.  NO ASSIGNMENT OR DELEGATION
     ---------------------------

     Amgen has selected you for this part-time special assignment because it has
     judged that your unique experience and skills are those Amgen required for
     the job.  Accordingly, you may not assign or delegate any of your duties or
     responsibilities under this Agreement.

16.  SUCCESSORS; BINDING AGREEMENT
     -----------------------------

     16.1  Amgen's Successors:  No rights or obligations of Amgen under this
           ------------------
           Agreement may be assigned or transferred except that Amgen will
           require any successor (whether direct or indirect, by purchase,
           merger, consolidation or otherwise) to all or substantially all of
           the business and/or assets of Amgen to expressly assume and agree to
           perform this Agreement in the same manner and to the same extent that
           Amgen would be required to perform it if no such succession had taken
           place. As used in this Agreement, "Amgen" shall mean Amgen as herein
           before defined and any successor to its business and/or assets (by
           merger, purchase or otherwise) which executes and delivers the
           agreement provided for in this Paragraph 16 or which otherwise
           becomes bound by all the terms and provisions of this Agreement by
           operation of law.

     16.2  Your Successors:  No rights or obligations of you under this
           ---------------
           Agreement may be assigned or transferred by you other than your
           rights to payments or benefits hereunder, which may be transferred
           only by will or the laws of descent and distribution. Upon your
           death, this Agreement and all rights of you hereunder shall inure to
           the benefit of and be enforceable by your beneficiary or
           beneficiaries, personal or legal representatives, or estate, to the
           extent any such person succeeds to your interests under this
           Agreement. You shall be entitled to select and change a beneficiary
           or beneficiaries to receive any benefit or compensation payable
           hereunder following your death by giving Amgen written notice
           thereof. In the event of your death or a judicial determination of
           your incompetence, reference in this Agreement to you shall be
           deemed, where appropriate, to refer to your beneficiary (ies), estate
           or other legal representative(s). If your should die following your
           Termination Date while any amounts would still be payable to you
           hereunder if you had continued to live, all such amounts unless
           otherwise provided herein shall be paid in accordance with the terms
           of this Agreement to such person or persons so appointed in writing
           by you, or otherwise to your legal representatives or estate.
<PAGE>

Mr. Gordon M. Binder
May 10, 2000
Page 14

17.  ENTIRE AGREEMENT
     ----------------

     The Proprietary Agreement, your stock option agreements, this Agreement and
     Appendices A, B and C attached hereto, constitute the entire agreement,
     arrangement and understanding between you and Amgen; they may not be
     modified or canceled in any manner except by a writing signed by both you
     and Amgen.  This Agreement supersedes any prior or contemporaneous
     agreement, arrangement or understanding on this subject matter.  By
     executing this Agreement, you expressly acknowledge the termination of any
     such prior agreement, arrangement or understanding.  Also, by executing
     this Agreement, you affirm that no one has made any written or verbal
     statement that contradicts the provisions of this Agreement.

                                    Sincerely yours,


                                    /s/ Edward F. Garnett
                                    ---------------------
                                    Amgen Inc.
                                    By: Edward F. Garnett
                                    Vice President, Human Resources



     Acknowledged and Agreed:


     /s/ Gordon M. Binder
     --------------------
     Gordon M. Binder

     Dated: 5/10/00
            -------
<PAGE>

                                  APPENDIX A
<PAGE>

                                  RESIGNATION
                                  -----------

The undersigned hereby retires and resigns as Chief Executive Officer of Amgen
Inc. and as a Director of the Amgen Foundation effective May 11, 2000.  The
undersigned also agrees to resign from the Board of Directors and as Chairman of
the Board of Directors of Amgen Inc. effective December 31, 2000.



                                    /s/ Gordon M. Binder
                                    --------------------
                                    Gordon M. Binder


<PAGE>

                                  APPENDIX B


                    AMGEN -- Corporate Policy and Procedure

SUBJECT: Conflict of Interest/Inside Information

POLICY:

  Amgen staff members may receive important information that is not yet publicly
     available ("inside information") about Amgen or about other publicly-traded
     companies with which Amgen does business.  Because of access to this
     information, staff members may be in a position to profit financially by
     buying or selling or in some other way dealing in Amgen stock or stock of
     another publicly-traded company.  Staff members may also be in a position
     to benefit financially or otherwise by passing this information on to some
     other person.

  "Inside information" is non-public information that would be important to
     anyone who may trade in Amgen stock, or other publicly-traded companies
     with which Amgen does business.  As a general rule, if the non-public
     information would lead a staff member to consider buying or selling a
     company's stock, it would likely have the same effect on others.

  For anyone to use such information, or to disclose it to someone else, in
     order to gain personal benefit is illegal.  Any sale or purchase of stock
     based on such information is illegal, regardless of the amount of stock
     involved.  Furthermore, both for the protection of staff members and Amgen,
     it is important to avoid the appearance as well as the fact of insider
     trading or disclosure of inside information.

  It is the policy of Amgen to prohibit its staff members from engaging in any
     activity or practice in conflict with the interests of the Company, or
     which could be viewed as insider trading or disclosure of inside
     information.

APPLICABILITY: All Amgen staff members

PROCEDURE:

     1.   Amgen staff members should not allow themselves to be placed in a
          position where a conflict of personal interest and company interest
          may exist, or appear to exist. Amgen staff members must use care to
          avoid even the appearance of impropriety. When in doubt

                                                                             B-1
<PAGE>

          as to whether a certain activity represents a conflict of interest the
          staff member should contact the Law Department.

     2.   Amgen staff members are prohibited from buying or selling shares of
          Amgen stock while in possession of material confidential information
          that has not become generally known to the public.

     3.   In order to avoid any implication that any Amgen staff member might be
          inadvertently engaging in insider trading, Amgen staff members are
          prohibited from engaging in trades of puts, calls, options (whether
          "covered" or not), short sales and similar transactions in the
          Company's stock.

     4.   Staff members who possess "inside information" are prohibited from
          trading in a company's stock, advising anyone else to do so, or
          disclosing or otherwise communicating the information to anyone else,
          including, but not limited to: family members, friends, brokers, etc.,
          until the information has been widely circulated to the public.

     5.   Amgen staff members should deal with all suppliers, customers and all
          other persons doing business with Amgen in a completely fair and
          objective manner without favor or preference based upon personal
          financial or familial considerations.

     6.   Amgen staff members should neither seek nor accept, directly or
          indirectly, any payment, fees, loans, or services from any person or
          firm as a condition or result of their doing business with Amgen or
          any of its subsidiaries.

     7.   Amgen staff members should not accept gifts from any person or firm
          doing or seeking to do business with the Company under circumstances
          from which it might reasonably be inferred that the purpose of the
          gift is to influence the staff member in the conduct of Company
          business with the donor. Such gifts should be returned with a note of
          explanation. Staff members are not prohibited from accepting gifts of
          nominal value when circumstances clearly show that the gifts are
          offered for reasons of personal esteem and affection, or in accordance
          with normal business practices.

     8.   Amgen staff members should not do business with a relative on behalf
          of Amgen or any of its subsidiaries. If a situation should arise where
          a related family member is negotiating to do business with Amgen, then
          the staff member must disclose their relationship with the family
          member to his or her supervisor or others involved in the
          negotiations.

     9.   Amgen staff members should not hold any financial interest in any firm
          or corporation which is a competitor of or which does or seeks to do
          business with Amgen or its subsidiaries if such interest may influence
          any decision that person might make in the performance of their Amgen
          responsibilities.

     10.  Amgen staff members should not make investments in any securities of
          any corporation with which Amgen has entered into any type of research
          collaboration or joint venture ("Partner"). This prohibition applies
          to investments in the Common or Preferred Stock of

                                                                             B-2
<PAGE>

          such Partner, investments in limited partnerships sponsored by the
          Partner or investments in any puts, calls or convertible securities of
          the Partner. This policy does not require divestiture of investments
          made before this policy took effect, or made before the staff member
          joined Amgen or before Amgen entered into the research collaboration
          or joint venture. This policy does not prohibit investments in
          publicly traded mutual funds that invest in any Partner.

     11.  Amgen staff members have the affirmative duty to disclose to their
          responsible corporate officer the existence of any personal or
          material financial interest in any firm or corporation which is a
          competitor of or which seeks to do or does business with Amgen or any
          of its subsidiaries. Corporate officers should review each case with
          the General Counsel or Corporate Counsel, to determine whether there
          is a violation of this policy.

   Individuals who fail to comply with the requirements of this policy may be
     subject to disciplinary action, up to, and including, termination of
     employment.

Policy Number: 230
Effective Date: June, 1992

                                                                             B-3
<PAGE>

                                  APPENDIX C


                -----------------------------------------------
                    Grant Number               Date of Grant
                    ------------               -------------
                -----------------------------------------------

                -----------------------------------------------
                      927796                     07/01/97
                -----------------------------------------------
                      931893                     07/01/97
                -----------------------------------------------
                      933504                     07/01/98
                -----------------------------------------------
                      938857                     07/01/98
                -----------------------------------------------