AMGEN INC
8-K, 1997-04-08
BIOLOGICAL PRODUCTS, (NO DIAGNOSTIC SUBSTANCES)
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<PAGE>
 
================================================================================

                       SECURITIES AND EXCHANGE COMMISSION

                             WASHINGTON, D.C. 20549



                                    FORM 8-K

                                 CURRENT REPORT
                     PURSUANT TO SECTION 13 OR 15(D) OF THE
                        SECURITIES EXCHANGE ACT OF 1934



        Date of Report (Date of earliest event reported):  APRIL 8, 1997



                                   AMGEN INC.
               (Exact Name of Registrant as Specified in Charter)


         DELAWARE                    0-12477              95-3540776
(State or Other Jurisdiction       (Commission         (I.R.S. Employer
     of Incorporation)             File Number)       Identification No.)


1840 DEHAVILLAND DRIVE
THOUSAND OAKS, CALIFORNIA                     91320-1789
(Address of Principal Executive Offices)      (Zip Code)


      Registrant's telephone number, including area code:  (805) 447-1000



                                 NOT APPLICABLE
         (Former Name or Former Address, if Changed Since Last Report)

================================================================================
<PAGE>
 
ITEM 5.  OTHER EVENTS.

      On December 19, 1991, Amgen Inc. (the "Company") filed with the Securities
and Exchange Commission (the "Commission") a registration statement on Form S-3
(File No. 33-44454) (the "Registration Statement") under the Securities Act of
1933, as amended (the "Securities Act"), relating to the public offering from
time to time of up to $200,000,000 in aggregate initial offering price of debt
securities of the Company.  On January 17, 1997, the Company filed a
registration statement on Form S-3 (File No. 333-19931) with the Commission
pursuant to Rule 462(b) under the Securities Act relating to the public offering
of up to $13,000,000 in initial offering price of debt securities.

      On April 3, 1997, the Company entered into an underwriting agreement (the
"Underwriting Agreement") with Merrill Lynch, Pierce Fenner & Smith Incorporated
and Morgan Stanley & Co. Incorporated relating to the sale of the Company's 8
1/8% Debentures due April 1, 2097. The Underwriting Agreement is attached
hereto.

ITEM 7.  FINANCIAL STATEMENTS, PRO FORMA FINANCIAL INFORMATION AND EXHIBITS.

(c)   Exhibits.

1.1   Underwriting Agreement dated April 3, 1997, among Merrill Lynch, Pierce,
      Fenner & Smith Incorporated, Morgan Stanley & Co. Incorporated and the
      Company.

4.1   Officer's Certificate pursuant to Sections 2.1 and 2.3 of the Indenture,
      dated as of January 1, 1992, as supplemented by the First Supplemental
      Indenture, dated as of February 26, 1997, each between the Company and
      Citibank, N.A., as Trustee, establishing a series of securities entitled
      "8 1/8% Debentures due April 1, 2097."

4.2   8 1/8% Debentures due April 1, 2097 described in Exhibit 4.1.

                                       2
<PAGE>
 
                                   SIGNATURES

   Pursuant to the requirements of the Securities Exchange Act of 1934, the
registrant has duly caused this report to be signed on its behalf by the
undersigned thereto duly authorized.


                                 Amgen Inc.



Dated: April 8, 1997             By /s/ Robert S. Attiyeh
                                   -------------------------------------------
                                        Robert S. Attiyeh
                                        Senior Vice President, Finance
                                        and Corporate Development and
                                        Chief Financial Officer
<PAGE>
 
                                 EXHIBIT INDEX
<TABLE>
<CAPTION>
 
 EXHIBIT
  NUMBER                                      DESCRIPTION
- ---------                                     -----------
<S>          <C>
1.1          Underwriting Agreement dated April 3, 1997, among Merrill Lynch, Pierce, Fenner & Smith
             Incorporated, Morgan Stanley & Co Incorporated and the Company.

4.1          Officer's Certificate pursuant to Sections 2.1 and 2.3 of the Indenture, dated as
             of January 1, 1992, as supplemented by the First Supplemental Indenture, dated as of
             February 26, 1997, each between the Company and Citibank, N.A., as Trustee,
             establishing a series of securities entitled "8 1/8% Debentures due April 1, 2097."

4.2          8 1/8% Debentures due April 1, 2097 described in Exhibit 4.1.
</TABLE>


<PAGE>

                                                                     EXHIBIT 1.2

                            UNDERWRITING AGREEMENT


                                           April 3, 1997



AMGEN INC.
1840 DeHavilland Drive
Thousand Oaks, California  91320-1789

Ladies and Gentlemen:

          We, the underwriters named below (collectively, the "Underwriters"),
understand that Amgen Inc., a Delaware corporation (the "Company"), proposes to
issue and sell $100,000,000 aggregate principal amount of its 8 1/8% Debentures
due April 1, 2097 (the "Offered Securities").

          A.   Subject to the terms and conditions set forth or incorporated by
reference herein, the Company hereby agrees to sell and the Underwriters agree
to purchase, severally and not jointly, the principal amount of the Offered
Securities set forth below opposite their names at a purchase price of 98.333%
of the principal amount of the Offered Securities, plus accrued interest, if
any, from April 1, 1997 to the Closing Date (as defined below):
<TABLE> 
<CAPTION> 
                                     Principal Amount of
      Name                           Offered Securities
      ----                           ------------------
<S>                                     <C> 
Merrill Lynch, Pierce,
 Fenner & Smith Incorporated.......     $ 50,000,000
Morgan Stanley & Co.
 Incorporated......................     $ 50,000,000
 
       Total.......................     $100,000,000
                                        ============
</TABLE>

The Underwriters will pay for the Offered Securities upon delivery thereof at
10:00 a.m. (New York time) on April 8, 1997, at such place as the Underwriters
shall designate.  Such date and location of delivery of and payment for the
Offered Securities may be varied by agreement between the Company and the
<PAGE>
 
Underwriters.  The time and date of such payment and delivery are hereinafter
referred to as the Closing Date.

          B.   The Offered Securities are to be issued pursuant to the
provisions of an Indenture, dated as of January 1, 1992, as supplemented by a
First Supplemental Indenture dated as of February 26, 1997 (as so supplemented,
and including any instrument establishing the form and terms of the Offered
Securities, the "Indenture"), between the Company and Citibank, N.A., as
trustee.

          C.   The Offered Securities shall have the terms set forth in the
Basic Prospectus dated March 28, 1997, and the Prospectus Supplement dated April
3, 1997, relating to the Offered Securities.

          D.   The Company will pay all expenses incident to the performance of
its obligations under this Agreement, including, without limitation, (i) the
preparation, printing (or reproduction) and filing with the Commission of the
Registration Statement, any preliminary prospectus and the Prospectus and of
each amendment and supplement thereto, (ii) the printing (or reproduction) and
delivery to the Underwriters of this Agreement and such other documents as may
be required in connection with the offering, purchase, sale and delivery of the
Offered Securities, (iii) the preparation, issuance and delivery of the
certificates for the Offered Securities to the Underwriters, including any
transfer taxes or duties payable upon the sale of the Offered Securities to the
Underwriters, (iv) the fees and disbursements of the Company's counsel,
accountants and other advisors, (v) the expenses described in Section 5(d)
hereof, and (vi) the printing (or reproduction) and delivery to the
Underwriters of any blue sky survey and any supplement thereto.

          E.   All provisions contained in the document entitled Amgen Inc.
Underwriting Agreement Standard Provisions (Debt Securities), a copy of which is
attached hereto, are herein incorporated by reference in their entirety and
shall be deemed to be a part of this Agreement to the same extent as if such
provisions had been set forth in full herein, except that (i) if any term
defined in such document is otherwise defined herein, the definition set forth
herein shall control and (ii) all references in such document to a type of
security that is not an Offered Security shall not be deemed to be a part of
this Agreement.

                                       2
<PAGE>
 
          Please confirm your agreement by having an authorized officer sign a
copy of this Agreement in the space set forth below.

                    Very truly yours,

                    MERRILL LYNCH, PIERCE, FENNER & SMITH
                      INCORPORATED
                    MORGAN STANLEY & CO. INCORPORATED
                         As the Underwriters named herein


               By:  MERRILL LYNCH, PIERCE, FENNER & SMITH
                      INCORPORATED


                    By:         /s/ Matt Pendo
                         ----------------------------------
                         Name:  Matt Pendo
                         Title: Managing Director


               By:  MORGAN STANLEY & CO. INCORPORATED


                    By:         /s/ Harold J. Hendershot III
                         ----------------------------------
                         Name:  Harold J. Hendershot III
                         Title:  Vice President


Accepted:

AMGEN INC.


By:       /s/ Robert S. Attiyeh
     -----------------------------------
     Name:  Robert S. Attiyeh
     Title: Senior Vice President
            Finance and Corporate Development,
            and Chief Financial Officer

                                       3
<PAGE>
 
                                   AMGEN INC.

                             UNDERWRITING AGREEMENT

                              STANDARD PROVISIONS
                               (DEBT SECURITIES)



          From time to time, Amgen Inc., a Delaware corporation (the "Company"),
may enter into one or more underwriting agreements that provide for the sale of
designated securities to the several underwriters named therein.  The standard
provisions set forth herein may be incorporated by reference in any such
underwriting agreement (each, an "Underwriting Agreement").  Any such
Underwriting Agreement, including the provisions incorporated therein by
reference, is herein referred to as this Agreement.  Terms defined in any such
Underwriting Agreement are used herein as therein defined.

          The Company has filed with the Securities and Exchange Commission (the
"Commission") a registration statement (Registration No. 33-44454) including a
prospectus relating to the Offered Securities and has filed with, or transmitted
for filing to, or shall promptly hereafter file with or transmit for filing to,
the Commission a prospectus supplement (the "Prospectus Supplement")
specifically relating to the Offered Securities pursuant to Rule 424 under the
Securities Act of 1933, as amended (the "Securities Act").  The term "Regis-
tration Statement" means the registration statement (Registration No. 33-44454)
as amended to the date of this Agreement, and the registration statement
(Registration No. 333-19931) relating to the Offered Securities filed by the
Company with the Commission on January 17, 1997 pursuant to Rule 462(b) under
the Securities Act.  The term "Basic Prospectus" means the basic prospectus
included in the Registration Statement, as amended by the final basic prospectus
relating to the offering and sale of debt securities, filed with the Commission
on March 28, 1997 pursuant to Rule 424 under the Securities Act.  The term
"Prospectus" means the Basic Prospectus together with the Prospectus Supplement.
The term "preliminary prospectus" means the preliminary prospectus supplement
specifically relating to the Offered Securities, filed with the Commission on
March 28, 1997 pursuant to Rule 424 under the Securities Act, together with the
Basic Prospectus.  As used herein, the terms "Basic Prospectus," "Prospectus,"
"preliminary prospectus," "supplement" and "amendment" or "amend" shall include,
in each case, all documents that are incorporated or (as required by paragraph
(b) of Item 12 of Form S-3) deemed to be incorporated by reference in the
Prospectus that are filed subsequent to the date of the Basic Prospectus by the
Company with the Commission pursuant to the Securities Exchange Act of 1934, as
amended (the "Exchange Act").
<PAGE>
 
          The term "Significant Subsidiary" shall be used herein as such term is
defined in Rule 1-02 of Regulation S-X.

          The term "Subsidiary" as used herein shall mean any corporation the
outstanding securities of which having ordinary voting power to elect a
majority of the board of directors of such corporation (whether or not any other
class of securities has or might have voting power by reason of the happening of
a contingency) are at the time owned or controlled directly or indirectly by
the Company or one or more Subsidiaries or by the Company and one or more
Subsidiaries.

          1.   Representations and Warranties.  The Company represents and
               ------------------------------                             
warrants to each of the Underwriters and agrees with each Underwriter that:

               (a) The Registration Statement has become effective; no stop
     order suspending the effectiveness of the Registration Statement is in
     effect, and no proceedings for such purpose are pending before or to the
     Company's knowledge threatened by the Commission.

               (b) (i) Each document, if any, filed or to be filed pursuant to
     the Exchange Act and incorporated by reference in the Prospectus complied
     or will comply when so filed in all material respects with the Exchange Act
     and the applicable rules and regulations of the Commission thereunder, (ii)
     each part of the Registration Statement, when such part became effective,
     did not contain, and each such part, as amended or supplemented, if
     applicable, will not contain, any untrue statement of a material fact or
     omit to state a material fact required to be stated therein or necessary to
     make the statements therein not misleading, (iii) the Registration
     Statement and the Prospectus comply, and, as amended or supplemented, if
     applicable, will comply, in all material respects with the Securities Act
     and the applicable rules and regulations of the Commission thereunder and
     (iv) the Prospectus does not contain and, as amended or supplemented, if
     applicable, will not contain any untrue statement of a material fact or
     omit to state a material fact necessary to make the statements therein, in
     the light of the circumstances under which they were made, not misleading,
     except that the representations and warranties set forth in this Section
     1(b) do not apply (A) to statements or omissions in the Registration
     Statement or the Prospectus based upon information concerning any
     Underwriter furnished to the Company in writing by such Underwriter
     expressly for use therein or (B) to that part of the Registration Statement
     that constitutes the Statement of Eligibility and Qualification (Form T-1)
     under the Trust Indenture Act of 1939, as amended (the "Trust Indenture
     Act"), of the trustee referred to in the Registration Statement.

                                       2
<PAGE>
 
               (c) The Company has been duly incorporated, is validly existing
     as a corporation in good standing under the laws of the State of Delaware,
     has the corporate power and authority to own its property and to conduct
     its business as described in the Prospectus and is duly qualified to
     transact business and is in good standing in each jurisdiction in which the
     conduct of its business or its ownership or leasing of property requires
     such qualification, except to the extent that the failure to be so
     qualified or be in good standing would not have a material adverse effect
     on the financial condition of the Company and its Subsidiaries, taken as a
     whole.

               (d) The Company has no Significant Subsidiaries.

               (e) Kirin-Amgen, Inc. has been duly incorporated, is validly
     existing as a corporation in good standing under the laws of the
     jurisdiction of its incorporation, has the power and authority to own its
     property and to conduct its business as described in the Prospectus and is
     duly qualified to transact business and is in good standing in each
     jurisdiction in which the conduct of its business or its ownership or
     leasing of property requires such qualification, except to the extent that
     the failure to be so qualified or be in good standing would not have a
     material adverse effect on the financial condition of the Company and its
     Subsidiaries, taken as a whole.

               (f) This Agreement has been duly authorized, executed and deliv-
     ered by the Company.

               (g) The Indenture has been duly authorized, executed and
     delivered by the Company and (assuming the due execution and delivery
     thereof by the trustee thereunder) is a valid and binding agreement of the
     Company, enforceable in accordance with its terms except (i) to the extent
     that a waiver of rights under any usury laws may be unenforceable and as
     the enforceability thereof may be limited by bankruptcy, insolvency,
     fraudulent conveyance, moratorium or other similar laws now or hereafter in
     effect relating to or affecting the enforcement of creditors' rights and
     remedies generally and (ii) as rights of acceleration and the availability
     of equitable remedies may be limited by equitable principles of general
     applicability, whether or not enforcement is sought at law or in equity.

               (h) The Offered Securities have been duly authorized and, when
     executed and authenticated in accordance with the provisions of the
     Indenture and delivered to and paid for by the Underwriters in accordance
     with the terms of this Agreement, will be entitled to the benefits of the
     Indenture and will be valid and legally binding obligations of the Company,
     enforceable in accordance with their terms except (i) to the extent that a
     waiver of rights under any usury laws may be unenforce-

                                       3
<PAGE>
 
     able and as the enforceability thereof may be limited by bankruptcy,
     insolvency, fraudulent conveyance, moratorium or other similar laws now or
     hereafter in effect relating to or affecting the enforcement of creditors'
     rights and remedies generally and (ii) as rights of acceleration and the
     availability of equitable remedies may be limited by equitable principles
     of general applicability, whether or not enforcement is sought at law or in
     equity.

               (i) The execution and delivery by the Company of, and the perfor-
     mance by the Company of its obligations under, this Agreement, the
     Indenture and the Offered Securities (A) will not contravene any provision
     of (i) the certificate of incorporation or by-laws of the Company, (ii) any
     agreement or other instrument binding upon the Company, Kirin-Amgen, Inc.
     or their respective business or assets that is material to the financial
     condition of the Company and its Subsidiaries, taken as a whole, (iii)
     applicable law and (iv) any judgment, order or decree of any governmental
     body, agency or court having jurisdiction over the Company, Kirin-Amgen,
     Inc. or their respective business or assets, and (B) no consent, approval
     or authorization or order of or qualification with any governmental body
     or agency is required for the performance by the Company of its obligations
     under this Agreement, the Indenture or the Offered Securities except such
     as may be required by the securities or Blue Sky laws of the various states
     in connection with the offer and sale of the Offered Securities.

               (j) There has not been any material adverse change or any 
     prospective material adverse change in the financial condition or in the
     earnings of the Company and its Subsidiaries, taken as a whole, from that
     set forth in the Prospectus.

               (k) There are no legal or governmental proceedings pending or to
     the Company's knowledge threatened to which the Company or Kirin-Amgen,
     Inc. is a party or to which any of their respective properties is subject
     that are required to be described in the Registration Statement or the
     Prospectus and are not so described or any contracts or other documents
     that are required to be filed as exhibits to the Registration Statement
     that are not filed as required.

               (l) Each of the Company and Kirin-Amgen, Inc. has all necessary
     consents, authorizations, approvals, orders, certificates and permits of
     and from, and has made all declarations and filings with, all federal,
     state, local and other governmental authorities, all self-regulatory
     organizations and all courts and other tribunals, to own, lease, license
     and use its properties and assets and to conduct its business in the manner
     described in the Prospectus, except to the extent that the failure to
     obtain

                                       4
<PAGE>
 
     or file would not have a material adverse effect on the financial condition
     of the Company and its Subsidiaries, taken as a whole.

               (m) The Company is not an "investment company" or an entity "con-
     trolled by" an "investment company," as such terms are defined in the
     Investment Company Act of 1940, as amended.

               (n) To the Company's knowledge, each of the Company and Kirin-
     Amgen, Inc. owns or possesses, or can acquire on reasonable terms, all
     patents, licenses, inventions, copyrights, know-how (including trade
     secrets and other unpatented and/or unpatentable proprietary or
     confidential information, systems or procedures), trademarks, service marks
     and trade names which are currently employed by them in connection with the
     business now operated by them and which, in each case, are material to the
     financial condition of the Company and its Subsidiaries, taken as a whole,
     and, except as described in the Registration Statement or the Prospectus,
     neither the Company nor Kirin-Amgen, Inc. has received any notice of
     infringement with respect to any of the foregoing which, singly or in the
     aggregate, if the subject of an unfavorable decision, ruling or finding,
     would result in any material adverse change in the financial condition of
     the Company and its Subsidiaries, taken as a whole.

               (o) Neither the Company nor Kirin-Amgen, Inc. is in violation of
     any federal or state law or regulation relating to occupational safety and
     health or to the storage, handling or transportation of hazardous or toxic
     materials and each of the Company and Kirin-Amgen, Inc. has received all
     permits, licenses or other approvals required of them under applicable
     federal and state occupational safety and health and environmental laws and
     regulations to conduct their respective businesses, and each of the Company
     and Kirin-Amgen, Inc. is in compliance with all terms and conditions of any
     such permit, license or approval, except any such violation of law or
     regulation, failure to receive required permits, licenses or other
     approvals or failure to comply with the terms and conditions of such
     permits, licenses or approvals which would not, singly or in the aggregate,
     result in a material adverse change in the financial condition of the
     Company and its Subsidiaries, taken as a whole, except as described in or
     contemplated by the Prospectus.

          2.   Public Offering.  The Company is advised by the Underwriters that
               ---------------                                                  
the Underwriters propose to make a public offering of their respective portions
of the Offered Securities as soon after this Agreement has been entered into as
in the Underwriters' judgment is advisable.  The terms of the public offering of
the Offered Securities are set forth in the Prospectus.

                                       5
<PAGE>
 
          3.  Purchase and Delivery.  Except as otherwise provided in this
              ---------------------                                       
Section 3, payment for the Offered Securities shall be made by wire transfer of
same day funds at the time and place set forth in this Agreement, upon delivery
to the respective accounts of the several Underwriters of the Offered
Securities, represented by a fully registered global security and registered in
the name of The Depository Trust Company or its nominee, with any transfer taxes
payable in connection with the transfer of the Offered Securities to the Un-
derwriters duly paid.

          4.   Conditions to Closing.  The several obligations of the
               ---------------------                                 
Underwriters hereunder are subject to the following conditions:

               (a)  (i)   subsequent to the execution and delivery of this
          Agreement and prior to the Closing Date, there shall not have occurred
          any downgrading, nor shall any notice have been given of any intended
          or potential downgrading or of any review for a possible change that
          does not indicate the direction of the possible change, in the rating
          accorded any of the Company's securities by any "nationally recognized
          statistical rating organization," as such term is defined for purposes
          of Rule 436(g)(2) under the Securities Act;

                    (ii) there shall not have occurred any change in the
          financial condition or in the earnings of the Company and its
          Subsidiaries, taken as a whole, from that set forth in the Prospectus,
          that, in the judgment of the Underwriters, is material and adverse and
          that makes it, in the judgment of the Underwriters, impracticable to
          market the Offered Securities on the terms and in the manner
          contemplated in the Prospectus; and

                    (iii) the Underwriters shall have received on the Closing
          Date a certificate, dated the Closing Date and signed by an executive
          officer of the Company, to the effect set forth in clause (i) above
          and to the effect that the representations and warranties of the
          Company contained in this Agreement are true and correct in all
          material respects as of the Closing Date and that the Company has
          complied in all material respects with all of the agreements and
          satisfied all of the conditions on its part to be performed or
          satisfied on or before the Closing Date.

               The officer signing and delivering such certificate may rely upon
     the best of his knowledge as to proceedings threatened.

                                       6
<PAGE>
 
               (b) The Underwriters shall have received on the Closing Date an
     opinion of counsel for the Company (who may be an employee of the Company),
     dated the Closing Date, to the effect set forth in Exhibit A.

               (c) The Underwriters shall have received on the Closing Date an
     opinion of Latham & Watkins, special counsel for the Company, dated the
     Closing Date, to the effect set forth in Exhibit B.

               (d) The Underwriters shall have received on the Closing Date an
     opinion of Skadden, Arps, Slate, Meagher & Flom LLP, special counsel for
     the Underwriters, dated the Closing Date, to the effect set forth in
     Exhibit C.

               (e) The Underwriters shall have received on the Closing Date an
     opinion of Hogan & Hartson L.L.P., special counsel for the Company, dated
     the Closing Date, in form and substance reasonably acceptable to Skadden,
     Arps, Slate, Meagher & Flom LLP, special counsel for the Underwriters, with
     respect to the disclosure contained in the Prospectus relating to the False
     Claims Act Matter (as defined in Exhibit B hereto).

               (f) The Underwriters shall have received at the time of the
     execution of this Agreement a letter, dated the date hereof, in form and
     substance satisfactory to the Underwriters, from Ernst & Young LLP, the
     Company's independent public accountants, containing statements and
     information of the type ordinarily included in accountants' "comfort
     letters" to underwriters with respect to the financial statements and
     certain financial information contained in or incorporated by reference
     into the Prospectus.

               (g) The Registration Statement shall have become effective and on
     the Closing Date no stop order suspending the effectiveness of the
     Registration Statement shall have been issued under the Securities Act or
     proceedings therefor initiated or, to the knowledge of the Company or the
     Underwriters, threatened by the Commission.

               (h) The Underwriters shall have received on the Closing Date a
     letter, dated the Closing Date, in form and substance satisfactory to the
     Underwriters, from Ernst & Young LLP, to the effect that they reaffirm the
     statements made in the letter furnished pursuant to paragraph (f) of this
     Section, except that the specified date referred to shall be a date not
     more than two business days prior to the Closing Date.

                                       7
<PAGE>
 
          5.  Covenants of the Company.  In further consideration of the
              ------------------------                                  
agreements of the Underwriters contained herein, the Company covenants as
follows:

               (a) To furnish the Underwriters, without charge, a signed copy of
     the Registration Statement (including exhibits thereto) and, during the
     period mentioned in paragraph (c) below, as many copies of the Prospectus,
     any documents incorporated by reference therein and any supplements and
     amendments thereto or to the Registration Statement as the Underwriters may
     reasonably request.

               (b) Before amending or supplementing the Registration Statement
     or the Prospectus with respect to the Offered Securities, to furnish to the
     Underwriters a copy of each such proposed amendment or supplement and not
     to file any such proposed amendment or supplement to which the Underwriters
     reasonably object.

               (c) If, during such period after the first date of the public
     offering of the Offered Securities as in the written opinion of counsel for
     the Underwriters the Prospectus is required by law to be delivered in
     connection with sales by an Underwriter or dealer, any event shall occur
     as a result of which it is necessary to amend or supplement the Prospectus
     in order to make the statements therein not misleading in the light of the
     circumstances when the Prospectus is delivered to a purchaser, or if it is
     necessary to amend or supplement the Prospectus to comply with law,
     forthwith to prepare and furnish, at its own expense, to the Underwriters
     and to the dealers (whose names and addresses the Underwriters will furnish
     to the Company) to which Offered Securities may have been sold by the
     Underwriters and to any other dealer upon request, either amendments or
     supplements to the Prospectus so that the statements in the Prospectus as
     so amended or supplemented will not be misleading in the light of the
     circumstances when the Prospectus is delivered to a purchaser, or so that
     the Prospectus, as so amended or supplemented, will comply with law.

               (d) To endeavor to qualify the Offered Securities for offer and
     sale under the securities or Blue Sky laws of such jurisdictions as the
     Underwriters shall reasonably request and to pay all expenses (including
     reasonable fees and disburse ments of counsel) in connection with such
     qualification.

               (e) To make generally available to the Company's security holders
     and to the Underwriters as soon as practicable an earning statement
     covering a 12-month period beginning on the first day of the first full
     fiscal quarter after the date of this Agreement, which earning statement
     shall satisfy the provisions of Section 11(a) of the Securities Act and the
     rules and regulations of the Commission thereunder.


                                       8
<PAGE>
 
               (f) During the period beginning on the date of this Agreement and
     continuing to and including the Closing Date, not to offer, sell, contract
     to sell or otherwise dispose of any debt securities of the Company
     substantially similar to the Offered Securities (other than (i) the Offered
     Securities and (ii) commercial paper issued in the ordinary course of
     business), without the prior written consent of the Underwriters.

          6.   Indemnification and Contribution.  The Company agrees to
               --------------------------------                        
indemnify and hold harmless each Underwriter and each person, if any, who
controls such Underwriter within the meaning of either Section 15 of the
Securities Act or Section 20 of the Exchange Act from and against any and all
losses, claims, damages and liabilities caused by any untrue statement or
alleged untrue statement of a material fact contained in the Registration State-
ment (as amended if the Company shall have furnished any amendments thereto), or
the omission or alleged omission to state therein a material fact required to be
stated therein or necessary to make the statements therein not misleading or
caused by any untrue statement of material fact contained in any preliminary
prospectus or the Prospectus (as amended or supplemented if the Company shall
have furnished any amendments or supplements thereto), or the omission or
alleged omission to state therein a material fact necessary in order to make the
statements therein, in the light of the circumstances under which they were
made, not misleading, except insofar as such losses, claims, damages or
liabilities are caused by any such untrue statement or omission or alleged
untrue statement or omission based upon information relating to any Underwriter
furnished to the Company in writing by such Underwriter expressly for use
therein; provided, however, that the foregoing indemnity agreement with respect
         --------  -------                                                     
to any preliminary prospectus shall not inure to the benefit of any Underwriter
from whom the person asserting any such losses, claims, damages or liabilities
purchased Offered Securities, or any person controlling such Underwriter, if a
copy of the Prospectus (as then amended or supplemented if the Company shall
have furnished any amendments or supplements thereto) was not sent or given by
or on behalf of such Underwriter to such person, if required by law so to have
been delivered, at or prior to the written confirmation of the sale of the
Offered Securities to such person, and if the Prospectus (as so amended or
supplemented) would have cured the defect giving rise to such losses, claims,
damages or liabilities.

          Each Underwriter agrees, severally and not jointly, to indemnify and
hold harmless the Company, its directors, its officers who sign the Registration
Statement and each person, if any, who controls the Company within the meaning
of either Section 15 of the Securities Act or Section 20 of the Exchange Act to
the same extent as the foregoing indemnity from the Company to each Underwriter,
but only with reference to information relating to such Underwriter furnished to
the Company by such Underwriter in writing expressly for use in the Registration
Statement, any preliminary prospectus, the Prospectus or any amendments or
supplements thereto.

                                       9
<PAGE>
 
          In case any proceeding (including any governmental investigation)
shall be instituted involving any person in respect of which indemnity may be
sought pursuant to either of the two preceding paragraphs, such person (the
"indemnified party") shall promptly notify the person against whom such
indemnity may be sought (the "indemnifying party") in writing and the
indemnifying party, upon request of the indemnified party, shall retain counsel
reasonably satisfactory to the indemnified party to represent the indemnified
party and any others the indemnifying party may designate in such proceeding and
shall pay the reasonable fees and disbursements of such counsel related to such
proceeding.  In any such proceeding, any indemnified party shall have the right
to retain its own counsel, but the fees and expenses of such counsel shall be at
the expense of such indemnified party unless (i) the indemnifying party and the
indemnified party shall have mutually agreed to the retention of such counsel or
(ii) the named parties to any such proceeding (including any impleaded parties)
include both the indemnifying party and the indemnified party and representation
of both parties by the same counsel would, in the written opinion of independent
legal counsel, be inappropriate due to actual or potential differing interests
between them.  It is understood that the indemnifying party shall not, in
connection with any proceeding or related proceedings in the same jurisdiction,
be liable for the fees and expenses of more than one separate firm (in addition
to any local counsel) for all such indemnified parties and that all such fees
and expenses shall be reimbursed as they are incurred.  Such firm shall be
designated in writing by Merrill Lynch, Pierce, Fenner & Smith Incorporated, in
the case of parties indemnified pursuant to the second preceding paragraph, and
by the Company, in the case of parties indemnified pursuant to the first
preceding paragraph.  The indemnifying party shall not be liable for any
settlement of any proceeding effected without its written consent, but if
settled with such consent or if there be a final judgment for the plaintiff, the
indemnifying party agrees to indemnify the indemnified party from and against
any loss or liability by reason of such settlement or judgment.  No indemnifying
party shall, without the prior written consent of the indemnified party, effect
any settlement of any pending or threatened proceeding in respect of which any
indemnified party is or could have been a party and indemnity could have been
sought hereunder by such indemnified party, unless such settlement includes an
unconditional release of such indemnified party from all liability on claims
that are the subject matter of such proceeding.

          If the indemnification provided for in the first or second paragraph
in this Section 6 is unavailable to an indemnified party or insufficient in
respect of any losses, claims, damages or liabilities referred to therein, then
each indemnifying party under such paragraph, in lieu of indemnifying such
indemnified party thereunder, shall contribute to the amount paid or payable by
such indemnified party as a result of such losses, claims, damages or
liabilities (i) in such proportion as is appropriate to reflect the relative
benefits received by the Company and the Underwriters from the offering of the
Offered Securities or (ii) if the allocation provided by clause (i) above is not
permitted by applicable law, in such proportion

                                      10
<PAGE>
 
as is appropriate to reflect not only the relative benefits referred to in
clause (i) above but also the relative fault of the Company and of the
Underwriters in connection with the statements or omissions that resulted in
such losses, claims, damages or liabilities, as well as any other relevant
equitable considerations.  The relative benefits received by the Company and the
Underwriters in connection with the offering of the Offered Securities shall be
deemed to be in the same respective proportions as the net proceeds from the
offering of such Offered Securities (before deducting expenses) received by the
Company and the total underwriting discounts and commissions received by the
Underwriters, in each case as set forth in the table on the cover of the
Prospectus Supplement, bear to the aggregate public offering price of the
Offered Securities.  The relative fault of the Company and of the Underwriters
shall be determined by reference to, among other things, whether the untrue or
alleged untrue statement of a material fact or the omission or alleged omission
to state a material fact relates to information supplied by the Company or by
the Underwriters and the parties' relative intent, knowledge, access to
information and opportunity to correct or prevent such statement or omission.

          The Company and the Underwriters agree that it would not be just or
equitable if contribution pursuant to this Section 6 were determined by pro rata
allocation (even if the Underwriters were treated as one entity for such
purpose) or by any other method of allocation that does not take account of the
equitable considerations referred to in the immediately preceding paragraph.
The amount paid or payable by an indemnified party as a result of the losses,
claims, damages and liabilities referred to in the immediately preceding
paragraph shall be deemed to include, subject to the limitations set forth
above, any legal or other expenses reasonably incurred by such indemnified party
in connection with investigating or defending any such action or claim.
Notwithstanding the provisions of this Section 6, no Underwriter shall be
required to contribute any amount in excess of the amount by which the total
price at which the Offered Securities underwritten by it and distributed to the
public were offered to the public exceeds the amount of any damages that such
Underwriter has otherwise been required to pay by reason of such untrue or
allegedly untrue statement or omission or alleged omission.  No person guilty of
fraudulent misrepresentation (within the meaning of Section 11(f) of the
Securities Act) shall be entitled to contribution from any person who was not
guilty of such fraudulent misrepresentation.  The Underwriters' respective
obligations to contribute pursuant to this Section 6 are several in proportion
to the respective principal amount of Offered Securities purchased by each of
such Underwriters and not joint.  The remedies provided for in this Section 6
are not exclusive and shall not limit any rights or remedies which may otherwise
be available to any indemnified party at law or in equity.

          The indemnity and contribution provisions contained in this Section 6
and the representations and warranties of the Company contained herein shall
remain operative and in full force and effect regardless of (i) any termination
of this Agreement, (ii) any investigation

                                      11
<PAGE>
 
made by or on behalf of any Underwriter or any person controlling any
Underwriter or by or on behalf of the Company, its directors or officers or any
person controlling the Company and (iii) delivery of the Offered Securities to
the Underwriters.

          7.   Termination.  This Agreement shall be subject to termination in
               -----------                                                    
the Underwriters' absolute discretion, by notice given to the Company, if (a)
after the execution and delivery of this Agreement and prior to the Closing Date
(i) trading generally shall have been suspended or materially limited on or by,
as the case may be, any of the New York Stock Exchange, the American Stock
Exchange or the National Association of Securities Dealers, Inc., (ii) trading
of any securities of the Company shall have been suspended on any exchange or in
any over-the-counter  market, (iii) a general moratorium on commercial banking
activities in New York shall have been declared by either Federal or New York
State authorities, or (iv) there shall have occurred any outbreak or escalation
of hostilities or any change in financial markets or any calamity or crisis
that, in the judgment of the Underwriters, is material and adverse and (b) in
the case of any of the events specified in clauses (a)(i) through (iv), such
event, singly or together with any other such event, makes it, in the judgment
of the Underwriters, impracticable to market the Offered Securities on the terms
and in the manner contemplated in the Prospectus.

          8.   Defaulting Underwriters.  If on the Closing Date any one or more
               -----------------------                                         
of the Underwriters shall fail or refuse to purchase Offered Securities that it
has or they have agreed to purchase on such date, and the aggregate amount of
Offered Securities which such defaulting Underwriter or Underwriters agreed but
failed or refused to purchase is not more than one-tenth of the aggregate amount
of the Offered Securities to be purchased on such date, the other Underwriters
shall be obligated severally in the proportions that the amount of Offered
Securities set forth opposite their respective names above bears to the
aggregate amount of Offered Securities set forth opposite the names of all such
non-defaulting Underwriters, or in such other proportions as the Underwriters
may specify, to purchase the Offered Securities which such defaulting
Underwriter or Underwriters agreed but failed or refused to purchase on such
date; provided that in no event shall the amount of Offered Securities that any
      --------                                                                 
Underwriter has agreed to purchase pursuant to this Agreement be increased
pursuant to this Section 8 by an amount in excess of one-ninth of such amount of
Offered Securities without the written consent of such Underwriter.  If on the
Closing Date any Underwriter or Underwriters shall fail or refuse to purchase
Offered Securities and the aggregate amount of Offered Securities with respect
to which such default occurs is more than one-tenth of the aggregate amount of
Offered Securities to be purchased on such date, and arrangements satisfactory
to the Underwriters and the Company for the purchase of such Offered Securities
are not made within 36 hours after such default, this Agreement shall terminate
without liability on the part of any non-defaulting Underwriter or the Company.
In any such case either the Underwriters or the Company shall have the right to
postpone the Closing Date but

                                      12
<PAGE>
 
in no event for longer than seven days, in order that the required changes, if
any, in the Registration Statement and in the Prospectus or in any other
documents or arrangements may be effected.  Any action taken under this
paragraph shall not relieve any defaulting Underwriter from liability in
respect of any default of such Underwriter under this Agreement.

          If this Agreement shall be terminated by the Underwriters, or any of
them, because of any failure or refusal on the part of the Company to comply
with the terms or to fulfill any of the conditions of this Agreement, or if for
any reason the Company shall be unable to perform its obligations under this
Agreement, the Company will reimburse the Underwriters or such Underwriters as
have so terminated this Agreement with respect to themselves, severally, for all
out-of-pocket expenses (including the reasonable fees and disbursements of their
counsel) reasonably incurred by such Underwriters in connection with the Offered
Securities.

          9.   Miscellaneous.  This Agreement may be signed in any number of
               -------------                                                
counterparts, each of which shall be an original, with the same effect as if the
signatures thereto and hereto were upon the same instrument.

          This Agreement shall be governed by and construed in accordance with
the internal laws of the State of New York.

          10.  Headings.  The headings of the sections of this Agreement have
               --------                                                      
been inserted for convenience of reference only and shall not be deemed a part
of this Agreement.

                                      13
<PAGE>
 
                                                                       Exhibit A


                         Opinion of George A. Vandeman,
                        General Counsel for the Company



          The opinion of George A. Vandeman, General Counsel for the Company, to
be delivered pursuant to Section 4(b) of the Underwriting Agreement, shall be to
the effect that:

               (i) the Company has been duly incorporated and is validly
     existing and in good standing under the laws of the State of Delaware, with
     corporate power and authority to own, lease and operate its properties and
     to conduct its business as described in the Registration Statement and the
     Prospectus.  Based solely on certificates from public officials, such
     counsel shall confirm that the Company is qualified to do business in the
     states set forth on Annex A;

               (ii) based solely on certificates from public officials, such
     counsel shall confirm that Kirin-Amgen, Inc. has been duly incorporated and
     is validly existing and in good standing under the laws of the State of
     Delaware, and, based solely on the Certificate of Incorporation of Kirin-
     Amgen, Inc., has the corporate power and authority to own, lease and
     operate its properties and to conduct its business as described in the
     Registration Statement and the Prospectus;

               (iii)  the Underwriting Agreement has been duly authorized,
     executed and delivered by the Company;

               (iv) the execution and delivery by the Company of, and the
     issuance and sale of the Offered Securities pursuant to, the Underwriting
     Agreement (A) will not contravene (i) the certificate of incorporation or
     by-laws of the Company or (ii) any agreement or other instrument identified
     as an exhibit to the Company's most recent annual report on Form 10-K, and
     (B) to such counsel's knowledge (i) will not contravene any provision of
     applicable law, (ii) will not contravene any judgment, order or decree of
     any governmental body, agency or court having jurisdiction over the
     Company, Kirin-Amgen, Inc. or their respective business or assets, and
     (iii) no consent, approval or authorization or order of or qualification
     with any governmental body or agency is required for the issuance and sale
     of the Offered Securities by the Company under the Underwriting Agreement,
     except such as are specified and have

                                      A-1
<PAGE>
 
     been obtained and as may be required by the securities or Blue Sky laws of
     the various states in connection with the offer and sale of the Offered
     Securities;

               (v) to such counsel's knowledge, the statements in "Item 3 -
     Legal Proceedings" of the Company's most recent annual report on Form 10-K
     incorporated by reference in the Prospectus, insofar as such statements
     constitute summaries of the legal matters, documents or proceedings
     referred to therein, are accurate in all material respects;

               (vi) such counsel does not know of any legal or governmental
     proceedings pending or threatened to which the Company is a party or to
     which any of the properties of the Company is subject that are required to
     be described in the Registration Statement or the Prospectus and are not so
     described or of any contracts or other documents that are required to be
     filed as exhibits to the Registration Statement that are not filed as
     required; and

               (vii) each document filed pursuant to the Exchange Act and
     incorporated by reference in the Prospectus (except for financial
     statements, schedules and other financial data included or incorporated
     therein as to which such counsel need not express any opinion) complied
     when so filed as to form in all material respects with the Exchange Act and
     the applicable rules and regulations of the Commission thereunder.

          In addition, such counsel shall state that he has participated in
conferences with officers and other representatives of the Company,
representatives of the independent public accountants for the Company and
representatives of the Underwriters, at which the contents of the Registration
Statement and the Prospectus and related matters were discussed and, although
such counsel does not pass upon, and does not assume any responsibility for, the
accuracy, completeness or fairness of the statements contained in the
Registration Statement and the Prospectus and has not made any independent check
or verification thereof, during the course of such participation (relying as to
materiality to a large extent upon the statements of officers and other
representatives of the Company), no facts came to such counsel's attention that
caused such counsel to believe that the Registration Statement, at the time it
became effective, contained an untrue statement of a material fact or omitted to
state a material fact required to be stated therein or necessary to make the
statements therein not misleading, or that the Prospectus, as of its date and as
of the date hereof, contained an untrue statement of a material fact or omitted
to state a material fact necessary to make the statements therein, in light of
the circumstances under which they were made, not misleading; it being
understood that such counsel need not express any belief with respect to the
financial statements,

                                      A-2
<PAGE>
 
schedules and other financial data included in the Registration Statement or the
Prospectus or incorporated therein by reference or with respect to the Form T-1.

          Counsel for the Company may limit his opinion to the laws of the
States of Delaware and California, and the federal laws of the United States;
provided, that with respect to the laws of the State of California such counsel
- --------                                                                       
may either (A) rely upon an opinion or opinions (in the form and substance
reasonably satisfactory to Underwriters' counsel) of other counsel or counsels
admitted to practice law in the State of California or (B) state in his opinion
that his opinion is based on the advice of counsel or counsels who are admitted
to practice law in the State of California; provided, further, that such counsel
                                            --------  -------                   
or counsels may be employees of the Company.  If such counsel shall rely on the
opinion of another counsel with regard to the laws of the State of California,
the opinion of such counsel for the Company shall state that the opinion or
opinions, as the case may be, of any other such counsel or counsels is or are in
form satisfactory to such counsel and, in such counsel's opinion, the
Underwriters and they are justified in relying thereon.

                                      A-3
<PAGE>
 
                              ANNEX A
                              -------

          California                     North Carolina
          Florida                        Ohio
          Massachusetts                  Pennsylvania
          Michigan                       Tennessee
          Missouri                       Texas
          New Jersey                     Virginia
          New York                       Wisconsin
          

                                      A-4
<PAGE>
 
                                                                       Exhibit B


                          Opinion of Latham & Watkins,
                        Special Counsel for the Company


          The opinion of counsel to the Company, to be delivered pursuant to
Section 4(c) of the Underwriting Agreement shall be to the effect that:

          (i) the Indenture has been duly authorized, executed and delivered by
     the Company and (assuming due authorization, execution and delivery by the
     Trustee) is the legally valid and binding agreement of the Company,
     enforceable against the Company in accordance with its terms;

          (ii) the Offered Securities have been duly authorized and, when
     executed and authenticated in accordance with the provisions of the
     Indenture and delivered to and paid for by the Underwriters in accordance
     with the terms of the Underwriting Agreement, will be entitled to the
     benefits provided by the Indenture and will be a legally valid and binding
     obligation of the Company, enforceable against the Company in accordance
     with their terms;

          (iii)  the statements in the Prospectus Supplement under the caption
     "Description of the Debentures" and in the Basic Prospectus under the
     caption "Description of Debt Securities" insofar as such statements
     constitute summaries of the legal matters or documents referred to therein,
     are accurate in all material respects; and

          (iv) the Registration Statement and Prospectus (except for financial
     statements, schedules and other financial data included or incorporated
     herein as to which such counsel need not express any opinion), comply as to
     form in all material respects with the Securities Act and the applicable
     rules and regulations of the Commission thereunder.

          In addition, we have participated in conferences with officers and
other representatives of the Company, representatives of the independent public
accountants for the Company and representatives of the Underwriters, at which
the litigation matter filed under the qui tam provisions of the Federal False
Claims Act (the "False Claims Act Matter") set forth in "Item 3 - Legal
Proceedings" of the Company's Annual Report on Form 10-K for the year ended
December 31, 1996 filed with the Commission on March 24, 1997 (the "Form 10-K")
were discussed and, although we are not passing upon, and do not assume any
responsi-

                                      B-1
<PAGE>
 
bility for, the accuracy, completeness or fairness of the statements contained
in the Form 10-K with respect to the False Claims Act Matter and have not made
any independent check or verification thereof, during the course of such
participation (relying as to materiality to the extent we deemed appropriate
upon the statements of officers and other representatives of the Company), no
facts came to our attention that caused us to believe that the description of 
the False Claims Act Matter included in Item 3 of the Form 10-K, as of the date
of the Prospectus Supplement and as of the date hereof, contained an untrue
statement of a material fact or omitted to state a material fact required to be
stated therein or necessary to make the statements therein, in light of the
circumstances under which they were made, not misleading; it being understood,
except with respect to the False Claims Act Matter set forth in the Form 10-K
and incorporated by reference in the Prospectus, that we express no belief with
respect to the Registration Statement or the Prospectus.

          Counsel for the Company may limit their opinion to the laws of the
States of Delaware, California and New York and the federal laws of the United
States.  Such counsel's opinion shall be subject to the following exceptions,
limitations and qualifications: (A) the effect of bankruptcy, insolvency,
reorganization, moratorium, fraudulent conveyance or other similar laws now or
hereafter in effect relating to or affecting the rights and remedies of
creditors; (B) the effect of general principles of equity, whether enforcement
is considered in a proceeding in equity or law, and the discretion of the court
before which any proceeding therefor may be brought; (C) the unenforceability
under certain circumstances under law or court decisions of provisions providing
for the indemnification of or contribution to a party with respect to a
liability where such indemnification or contribution is contrary to public
policy; (D) we express no opinion concerning the enforceability of the waiver of
rights or defenses contained in the Indenture; and (E) we express no opinion
with respect to whether the acceleration of the Offered Securities may affect
the collectibility of that portion of the stated principal amount thereof which
might be determined to constitute unearned interest thereon.  With respect to
paragraph (iv) above, such counsel may state that such counsel's opinion assumes
that the statements made and incorporated by reference in the Prospectus and
Registration Statement are correct and complete.

                                      B-2
<PAGE>
 
                                                                       Exhibit C


              Opinion of Skadden, Arps, Slate, Meagher & Flom LLP,
                          Counsel for the Underwriters


          The opinion of Skadden, Arps, Slate, Meagher & Flom LLP, counsel for
the Underwriters, to be delivered pursuant to Section 4(d) of the Underwriting
Agreement shall be to the effect that:

          (i)  the Underwriting Agreement has been duly authorized, executed and
     delivered by the Company;

          (ii) the Indenture has been qualified under the Trust Indenture Act of
     1939, as amended, and has been duly authorized, executed and delivered by
     the Company and is a valid and binding agreement of the Company,
     enforceable in accordance with its terms except to the extent that
     enforcement thereof may be limited by (i) bankruptcy, insolvency,
     reorganization, moratorium or other similar laws now or hereafter in effect
     relating to creditors' rights generally and (ii) general principles of
     equity (regardless of whether enforceability is considered in a proceeding
     at law or in equity);

          (iii) the issuance and sale of the Offered Securities have been duly
     authorized by the Company, and the Offered Securities, when executed and
     authenticated in accordance with the provisions of the Indenture and
     delivered to and paid for by the Underwriters in accordance with the terms
     of the Underwriting Agreement, will be entitled to the benefits of the
     Indenture and will be valid and binding obligations of the Company
     enforceable in accordance with their terms except to the extent that
     enforcement thereof may be limited by (i) bankruptcy, insolvency,
     reorganization, moratorium or other similar laws now or hereafter in effect
     relating to creditors' rights generally and (ii) general principles of
     equity (regardless of whether enforceability is considered in a proceeding
     at law or in equity);

          (iv) The Registration Statement, as of its effective date, and the
     Prospectus, as of its date, appeared on their face to be appropriately
     responsive in all material respects to the requirements of the Act and the
     Rules and Regulations, except that in each case (A) we express no opinion
     as to (i) the financial statements, schedules and other financial data
     included or incorporated by reference therein or excluded therefrom, (ii)
     the documents incorporated by reference therein or (iii) the exhibits to
     the Registration Statement, including the Form T-1, (B) and we do not
     assume any

                                      C-1
<PAGE>
 
     responsibility for the accuracy, completeness or fairness of the statements
     contained in the Registration Statement and the Prospectus.

        In addition, we have participated in conferences with officers and
representatives of the Company, counsel for the Company, representatives of the
independent accountants of the Company and you at which the contents of the
Registration Statement and the Prospectus and related matters were discussed
and, although we are not passing upon, and do not assume any responsibility for,
the accuracy, completeness or fairness of the statements contained in the
Registration Statement or the Prospectus and have made no independent check or
verification thereof, on the basis of the foregoing, no facts have come to our
attention that have led us to believe that the Registration Statement, at the
time it became effective, contained an untrue statement of a material fact or
omitted to state any material fact required to be stated therein or necessary to
make the statements therein not misleading or that the Prospectus, as of its
date and as of the date hereof, contained or contains an untrue statement of a
material fact or omitted or omits to state a material fact necessary in order to
make the statements therein, in light of the circumstances under which they were
made, not misleading, except that we express no opinion or belief with respect
to (i) the financial statements, schedules and other financial data included
therein or excluded therefrom, (ii) the documents incorporated by reference
therein or (iii) the exhibits to the Registration Statement, including the Form
T-1.


                                      C-2

<PAGE>
 
                                                                     EXHIBIT 4.1

                             OFFICER'S CERTIFICATE

                                       OF

                                   AMGEN INC.


          Pursuant to Sections 2.1 and 2.3 of the Indenture, dated as of January
1, 1992, as supplemented by a First Supplemental Indenture, dated as of February
26, 1997 (as so supplemented, the "Indenture") each between Amgen Inc., a
Delaware corporation (the "Company"), and Citibank, N.A., as trustee, the
undersigned officer of the Company hereby certifies as follows in connection
with the issuance of the Company's 8 1/8% Debentures due April 1, 2097, under 
the Indenture:

          (i) the Debentures shall constitute a series of Securities having the
     title "8 1/8% Debentures due April 1, 2097" (referred to herein as the
     "Debentures");

          (ii) the form of the Debentures is attached hereto as Exhibit A;

          (iii)  the Debentures, which may be authenticated and delivered under
     the Indenture, shall be limited to $100,000,000 aggregate principal amount
     (except for Debentures authenticated and delivered upon registration of
     transfer of, in exchange for, or in lieu of, other Debentures pursuant to
     Section 2.8, 2.9, 2.11, 8.5 or 12.3 of the Indenture);

          (iv) the Debentures shall be issued as Registered Global Securities
     only, without coupons, and beneficial interests in the Debentures may be
     acquired, or subsequently transferred, only in denominations of $1,000 and
     any integral multiple thereof;

          (v) the principal amount of the Debentures shall be payable on April
     1, 2097;

          (vi) interest on the Debentures shall accrue at a fixed rate of 8 1/8%
     per annum; the Debentures will bear interest from April 1, 1997, and such
     interest will be payable semi-annually on April 1 and October 1 of each
     year, commencing on October 1, 1997 (each, an "Interest Payment Date"); the
     record date with respect to the Debentures shall be the 15th day
     immediately preceding such Interest Payment Date, whether or not a Business
     Day; and interest on the Debentures will be calculated on the basis of a
     360-day year of twelve 30-day months;

          (vii)  principal and interest payable with respect to the Debentures
     shall be payable by Citibank, N.A., as paying agent;
<PAGE>
 
          (viii)  the Company, upon the occurrence of a Tax Event (as defined in
     the Debenture), will have the right to shorten the maturity of the
     Debentures to the extent required, in the opinion of a nationally
     recognized independent tax counsel experienced in such matters, such that,
     after the shortening of the maturity, interest paid on the Debentures will
     be deductible for Federal income tax purposes;

          (ix) the Debentures are subject to redemption in whole or in part, at
     the option of the Company at any time, at a redemption price equal to the
     greater of (i) 100% of the principal amount to be redeemed or (ii) the sum
     of the present values of the Remaining Scheduled Payments (as defined in
     the Debentures) on the redemption date discounted to maturity on a
     semiannual basis (assuming a 360-day year consisting of twelve 30-day
     months) at the Treasury Yield (as defined in the Debentures) plus 20 basis
     points, plus in each case accrued interest to the date of redemption;

          (x) the Debentures are not subject to any sinking fund;

          (xi) if a Tax Event occurs and in the opinion of a nationally
     recognized independent tax counsel experienced in such matters there would,
     notwithstanding any shortening of the maturity of the Debentures, be more
     than an insubstantial risk that interest paid by the Company on the
     Debentures is not, or will not be, deductible, in whole or in part, for
     purposes of Federal income tax, the Company will have the right, within 90
     days following the occurrence of such Tax Event, to redeem the Debentures
     in whole (but not in part) at a redemption price equal to the greater of
     (i) 100% of the principal amount of the Debentures or (ii) the sum of the
     present values of the Remaining Scheduled Payments on the redemption date
     discounted to maturity on a semiannual basis (assuming a 360-day year
     consisting of twelve 30-day months) at the Treasury Yield plus 35 basis
     points, plus in each case accrued interest to the date of redemption;

          (xii)  Section 3.8 of the Indenture, "Limitation on Indebtedness of
     Subsidiaries" shall not apply to the Debentures; and

          (xiii)  the Debentures shall be issued in the form of a Registered
     Global Security, the trustee for such Debentures shall be Citibank, N.A.
     and the Depositary for such Debentures shall be The Depository Trust
     Company.

     The undersigned further certifies, having read the Indenture and certain
other corporate documents and records, and having made such examination or
investigation as I have deemed necessary to enable us to express an informed
opinion, that all conditions precedent to the authentication and delivery of the
Debentures have been complied with,

                                       2
<PAGE>
 
and that the Debentures delivered to the Trustee for authentication have been
duly executed and conform to the terms set forth herein and in the Indenture.

     Unless otherwise indicated, capitalized terms used herein that are not
otherwise defined shall have the meanings ascribed thereto in the Indenture.

                                       3
<PAGE>
 
     IN WITNESS WHEREOF, the undersigned has executed this Officer's Certificate
as of this 8th day of April, 1997.


                              /s/ Robert S. Attiyeh
                              ------------------------------------------ 
                              Robert S. Attiyeh
                              Senior Vice President,
                              Finance and Corporate Development, and
                              Chief Financial Officer

                                      S-1
<PAGE>
 
                                                                       EXHIBIT A

REGISTERED                                                      PRINCIPAL AMOUNT
NO. R-1                                                             $100,000,000

CUSIP NO. 03116 2AA 8


                                   AMGEN INC.
                       8-1/8% DEBENTURE DUE APRIL 1, 2097

          UNLESS THIS DEBENTURE IS PRESENTED BY AN AUTHORIZED REPRESENTATIVE OF
THE DEPOSITORY TRUST COMPANY ("DTC"), 55 WATER STREET, NEW YORK, NEW YORK TO THE
COMPANY OR ITS AGENT FOR REGISTRATION OF TRANSFER, EXCHANGE OR PAYMENT, AND SUCH
DEBENTURE ISSUED IS REGISTERED IN THE NAME OF CEDE & CO., OR SUCH OTHER NAME AS
IS REQUESTED BY AN AUTHORIZED REPRESENTATIVE OF DTC (AND ANY PAYMENT IS MADE TO
CEDE & CO. OR TO SUCH OTHER ENTITY AS IS REQUESTED BY AN AUTHORIZED
REPRESENTATIVE OF DTC), ANY TRANSFER, PLEDGE OR OTHER USE HEREOF FOR VALUE OR
OTHERWISE BY OR TO ANY PERSON IS WRONGFUL INASMUCH AS THE REGISTERED OWNER
HEREOF, CEDE & CO., HAS AN INTEREST HEREIN.

          UNLESS AND UNTIL THIS DEBENTURE IS EXCHANGED IN WHOLE OR IN PART FOR
SECURITIES IN DEFINITIVE REGISTERED FORM, THIS DEBENTURE MAY NOT BE TRANSFERRED
EXCEPT AS A WHOLE BY DTC TO THE NOMINEE OF DTC OR BY A NOMINEE OF DTC TO DTC OR
ANOTHER NOMINEE OF DTC OR BY DTC OR ANY SUCH NOMINEE TO A SUCCESSOR OF DTC OR A
NOMINEE OF SUCH SUCCESSOR.

          AMGEN INC., a Delaware corporation (the "Company," which term shall
include any successor under the Indenture hereinafter referred to), for value
received, hereby promises to pay to CEDE & CO., or registered assigns, the
principal sum of One Hundred Million Dollars ($100,000,000) on April 1, 2097,
and to pay interest thereon at the rate of 8-1/8% per annum, until the entire
principal amount hereof is paid or duly provided for.  This Debenture is one of
a duly authorized series issued by the Company and designated as the "8-1/8%
Debentures due April 1, 2097" (referred to herein as the "Debentures").

          Unless otherwise indicated, capitalized terms used herein that are not
otherwise defined shall have the meanings ascribed thereto in the Indenture (as
defined below).

1.  Definitions.

          "Comparable Treasury Issue" means the United States Treasury security
selected by an Independent Investment Banker as having a maturity comparable to
the remaining terms of the Debentures.  If no such security exists, a security
that would be utilized, at the time of selection and in accordance with
customary financial practice, in pricing new issues of corporate debt securities
of comparable maturity to the remaining term of the Debentures will be used.
"Independent Investment Banker" means Merrill Lynch, Pierce, Fenner & Smith
Incorporated or Morgan Stanley & Co. Incorporated or, if either firm is
unwilling or unable to select the
<PAGE>
 
Comparable Treasury Issue, an independent investment banking institution of
national standing appointed by the Trustee (as defined herein).

          "Comparable Treasury Price" means, with respect to any redemption
date, (i) the average of the bid and asked prices for the Comparable Treasury
Issue (expressed in each case as a percentage of its principal amount) on the
third business day preceding such redemption date, as set forth in the daily
statistical release (or any successor release) published by the Federal Reserve
Bank of New York and designated "Composite 3:30 p.m. Quotations for U.S.
Government Securities" or (ii) if such release (or any successor release) is not
published or does not contain such prices on such business day, the average of
the Reference Treasury Dealer Quotations for such redemption date.  "Reference
Treasury Dealer Quotations" means, with respect to each Reference Treasury
Dealer and any redemption date, the average of the bid and asked prices for the
Comparable Treasury Issue (expressed in each case as a percentage of its
principal amount) quoted in writing to the Trustee by such Reference Treasury
Dealer at 5:00 p.m. on the third business day preceding such redemption date.

          "Reference Treasury Dealer" means each of Merrill Lynch, Pierce,
Fenner & Smith Incorporated and Morgan Stanley & Co. Incorporated, and their
respective successors; provided, however, that if any of the foregoing shall
cease to be a primary U.S. Government securities dealer in New York City (a
"Primary Treasury Dealer"), the Company shall substitute therefor another
Primary Treasury Dealer.

          "Remaining Scheduled Payments" means, with respect to any Debenture,
the remaining scheduled payments of the principal thereof to be redeemed and
interest thereon that would be due after the related redemption date but for
such redemption; provided, however, that, if such redemption date is not an
interest payment date with respect to such Debenture, the amount of the next
succeeding scheduled interest payment thereon will be reduced by the amount of
interest accrued thereon to such redemption date.

          "Tax Event" means that the Company shall have received an opinion of a
nationally recognized independent tax counsel experienced in such matters to the
effect that on or after April 8, 1997, as a result of (a) any amendment to,
clarification of, or change (including any announced prospective change) in
laws, or any regulations thereunder, of the United States, (b) any judicial
decision, official administrative pronouncement, ruling, regulatory procedure,
notice or announcement, including any notice or announcement of intent to adopt
such procedures or regulations (an "Administrative Action"), or (c) any
amendment to, clarification of, or change in the official position or the
interpretation of such Administrative Action or judicial decision that differs
from the theretofore generally accepted position, in each case, on or after
April 8, 1997, such change in tax law creates a more than insubstantial risk
that interest paid by the Company on the Debentures is not, or will not be,
deductible, in whole or in part, by the Company for purposes of Federal income
tax.

          "Treasury Yield" means, with respect to any redemption date, the rate
per annum equal to the semiannual equivalent yield to maturity of the Comparable
Treasury Issue, assuming a price for the Comparable Treasury Issue (expressed as
a percentage of its principal amount) equal to the Comparable Treasury Price for
such redemption date.

                                       2
<PAGE>
 
2.  Interest.

          The Company will pay interest semiannually on April 1 and October 1 of
each year (each an "Interest Payment Date"), commencing on October 1, 1997.
Interest on the Debentures will accrue from the most recent date to which
interest has been paid, unless the date hereof is a date to which interest has
been paid, in which case from the date of the Debenture, or, if no interest has
been paid, from April 1, 1997.  Notwithstanding the foregoing, when there is no
existing default in the payment of interest on the Debentures, if the date
hereof is after a record date, as that term is defined below, and before the
next succeeding Interest Payment Date, this Debenture shall bear interest from
such Interest Payment Date; provided, however, that if the Company shall default
in the payment of interest due on such Interest Payment Date, then this
Debenture shall bear interest from the next preceding Interest Payment Date to
which interest has been paid, or, if no interest has been paid on the
Debentures, from April 1, 1997.  Interest will be computed on the basis of a
360-day year of twelve 30-day months.

3.  Method of Payment.

          The Company will pay interest on the Debentures (except defaulted
interest) to the persons who are registered Holders of Debentures at the close
of business on the 15th day immediately preceding such Interest Payment Date
whether or not a Business Day (a "record date").  Holders must surrender
Debentures to the paying agent prior to collecting principal payments.  The
Company will pay principal and interest in money of the United States that at
the time of payment is legal tender for payment of public and private debts.
However, the Company may pay principal and any interest by its check payable in
such money.  It may mail an interest check to a Holder's registered address.

4.  Paying Agent and Registrar.

          Initially, the Trustee will act as paying agent and registrar.  The
Company may change any paying agent, registrar or co-registrar without notice.
The Company or any of its subsidiaries may, subject to certain exceptions, act
as paying agent, registrar or co-registrar.

5.  Indenture.

          The Company issued the Debentures under an Indenture, dated as of
January 1, 1992, as supplemented by a First Supplemental Indenture, dated as of
February 26, 1997 (as so supplemented, and including the Officer's Certificate
dated April 8, 1997 (the "Officer's Certificate") establishing the form and
terms of the Debentures, the "Indenture"), each between the Company and
Citibank, N.A., as trustee (the "Trustee").  The terms of the Debentures include
those stated in the Indenture and those made part of the Indenture by reference
to the Trust Indenture Act of 1939 (15 U.S.  Code (S)(S) 77aaa-77bbbb) as in
effect on the date of the Indenture.  The Debentures are subject to all such
terms and Holders are referred to the Indenture and such Act for a statement of
them.

                                       3
<PAGE>
 
6.  Conditional Right to Shorten Maturity.

          Upon the occurrence of a Tax Event, the Company will have the right to
shorten the maturity of the Debentures to the extent required, in the opinion of
a nationally recognized independent tax counsel experienced in such matters,
such that, after the shortening of the maturity, interest paid on the Debentures
will be deductible for Federal income tax purposes.

          In the event that the Company elects to exercise its right to shorten
the maturity of the Debentures on the occurrence of a Tax Event, the Company
will mail a notice of shortened maturity to each Holder of record of the
Debentures by first-class mail not more than 60 days after the occurrence of
such Tax Event, stating the new maturity date of the Debentures.  Such notice
shall be effective immediately upon mailing.

7.  Redemption at the Option of the Company.

          The Debentures will be redeemable as a whole or in part, at the option
of the Company at any time, at a redemption price equal to the greater of (i)
100% of the principal amount to be redeemed or (ii) the sum of the present
values of the Remaining Scheduled Payments on the redemption date discounted to
maturity on a semiannual basis (assuming a 360-day year consisting of twelve 30-
day months) at the Treasury Yield plus 20 basis points, plus in each case
accrued interest to the date of redemption.

          In addition, if a Tax Event occurs and in the opinion of a nationally
recognized independent tax counsel experienced in such matters there would,
notwithstanding any shortening of the maturity of the Debentures, be more than
an insubstantial risk that interest paid by the Company on the Debentures is
not, or will not be, deductible, in whole or in part, for purposes of Federal
income tax, the Company will have the right, within 90 days following the
occurrence of such Tax Event, to redeem the Debentures in whole (but not in
part) at a redemption price equal to the greater of (i) 100% of the principal
amount of the Debentures and (ii) the sum of the present values of the Remaining
Scheduled Payments on the redemption date discounted to maturity on a semiannual
basis (assuming a 360-day year consisting of twelve 30-day months) at the
Treasury Yield plus 35 basis points, plus in each case accrued interest to the
date of redemption.

          Holders of Debentures to be redeemed will receive notice thereof by
first-class mail at least 30 and not more than 60 days prior to the date fixed
for redemption.

          Unless the Company defaults in payment of the redemption price, on and
after the redemption date interest will cease to accrue on the Debentures or
portions thereof called for redemption.

8.  Denominations, Transfer, Exchange.

          The Debentures are in registered form only.  The registrar may require
a Holder, among other things, to furnish appropriate endorsements and transfer
documents and to pay any taxes and fees required by law or permitted by the
Indenture.

                                       4
<PAGE>
 
9.  Persons Deemed Owners.

          The Holder of a Debenture may be treated as the owner of it for all
purposes.

10.  Unclaimed Money.

          If money for the payment of principal or interest remains unclaimed
for two years, the Trustee or any paying agent will pay the money back to the
Company at its written request.  After that, Holders entitled to the money must
look to the Company for payment unless an abandoned or unclaimed property law
designates another person, and all liability of the Trustee or any such paying
agent with respect to such money shall cease.

11.  Discharge Prior to Maturity.

          Subject to certain conditions, if the Company deposits with the
Trustee money or U.S. Government Obligations sufficient to pay principal of and
accrued interest on the Debentures to maturity, the Company will be discharged
(to the extent provided in the Indenture) from the Indenture and the Debentures.

12.  Amendment, Supplement, Waiver.

          Subject to certain exceptions requiring the consent of the Holders of
each of the affected Securities, at such time as the Debentures are the only
Securities then outstanding under the Indenture, the Indenture or the Debentures
may be amended or supplemented with the consent of the Holders of not less than
a majority in principal amount of the Debentures then outstanding affected by
such amendment or supplement.  Any past default or compliance with any provision
as to the Debentures may be waived with the consent of the Holders of a majority
in principal amount of the Debentures then outstanding.  Without the consent of
any Holder, the Company and the Trustee may amend or supplement the Indenture or
the Debentures to, among other things, cure any ambiguity, defect or
inconsistency or to make any change that does not materially adversely affect
the rights of any Holder.

13.  Restrictive Covenants.

          The Debentures are general unsecured obligations of the Company
limited to the aggregate principal amount of $100,000,000.  The Indenture does
not limit the Company from incurring unsecured Indebtedness other than the
aggregate principal amount of indebtedness to be issued pursuant to the
Officer's Certificate.  It does limit the ability of the Company and its
subsidiaries to grant certain security interests in their property without
equally and ratably securing the Debentures and to engage in certain sale and
leaseback transactions, subject to certain important exceptions described
therein.  Once a year the Company must report to the Trustee with respect to its
compliance with such limitations.

                                       5
<PAGE>
 
14.  Successor Corporation.

          When a successor corporation assumes all the obligations of its
predecessor under the Debentures and the Indenture, the predecessor corporation
will be released from those obligations.

15.  Defaults and Remedies.

          An Event of Default is:  default for 30 days in payment of interest on
any of the Debentures; default in payment of principal of any of the Debentures
due and payable at maturity or otherwise; failure by the Company for 90 days
after written notice to it to comply with any of its other agreements in the
Indenture or in the Debentures; failure by the Company to make any payment at
maturity in respect of Indebtedness in an amount in excess of $10,000,000 and
continuance of such failure for a period of 30 days after notice to the Company
by the Trustee or to the Company and the Trustee by Holders of not less than 25%
in aggregate principal amount of the Securities issued under the Indenture
(treated as one class) then outstanding; the happening of an event of default
under other Indebtedness of the Company which default results in the
acceleration of Indebtedness in an amount in excess of $10,000,000, unless cured
or waived in accordance with the provisions of the applicable instrument, or
discharged within 30 days after notice to the Company by the Trustee or to the
Company and the Trustee by Holders of not less than 25% in aggregate principal
amount of the Securities issued under the Indenture (treated as one class) then
outstanding; and certain events of bankruptcy or insolvency.  If an Event of
Default occurs and is continuing (other than an Event of Default relating to
certain events of bankruptcy or insolvency and certain Events of Default
relating to all outstanding Securities issued under the Indenture), the Trustee
or the Holders of not less than 25% in aggregate principal amount of the
Debentures then outstanding may declare all the Debentures to be due and payable
immediately in accordance with Section 5.1 of the Indenture.  Holders may not
enforce the Indenture or the Debentures except as provided in the Indenture.
The Trustee may require security and indemnity satisfactory to it before it
enforces the Indenture or the Debentures.  Subject to certain limitations,
Holders of a majority in aggregate principal amount of all of the Securities
(treated as one class) then outstanding may direct the Trustee in its exercise
of any trust or power.  The Trustee may withhold from Holders notice of any
continuing default (except a default in payment of principal or interest) if it
determines that withholding notice is in their interests.

16.  Trustee Dealings with Company.

          Citibank, N.A., the Trustee under the Indenture, in its individual or
any other capacity, may make loans to, accept deposits from, and perform
services for the Company, and may otherwise deal with the Company, as if it were
not the Trustee.

17.  No Recourse Against Others.

          A past, present or future director, officer, employee, stockholder or
incorporator, as such, of the Company or successor corporation shall not have
any liability for any obligations of the Company under the Debentures or the
Indenture or for any claim based on, in respect of,

                                       6
<PAGE>
 
or by reason of such obligations or their creation.  Each Holder by accepting a
Debenture waives and releases all such liability.  The waiver and release are
part of the consideration for the issue of the Debentures.

18.  Authentication.

          This Debenture shall not be valid until the Trustee signs the
certificate of authentication at the end of this Debenture.

19.  Copies of the Indenture.

          The Company will furnish to any Holder upon written request and
without charge a copy of the Indenture.  Requests may be made to:
 
                                 Amgen Inc.
                                 1840 DeHavilland Drive
                                 Thousand Oaks, California 91320
                                 Attention:  General Counsel

20.  Abbreviations and Defined Terms.

          Customary abbreviations may be used in the name of a Holder of a
Debenture or an assignee, such as: TEN COM (= tenants in common), TEN ENT 
(= tenants by the entireties), JT TEN (= joint tenants with right of
survivorship and not as tenants in common), CUST (= Custodian), and U/G/M/A 
(= Uniform Gifts to Minors Act).

21.  CUSIP Numbers.

          Pursuant to a recommendation promulgated by the Committee on Uniform
Security Identification Procedures, the Company will cause CUSIP numbers to be
printed on the Debentures as a convenience to the Holders of the Debentures.  No
representation is made as to the accuracy of such numbers as printed on the
Debentures and reliance may be placed only on the other identification numbers
printed hereon.

                           [Signature Page To Follow]

                                       7
<PAGE>
 
          IN WITNESS WHEREOF, the Company has caused this instrument to be duly
executed under its corporate seal this __th day of April, 1997.


  
                                          By:
                                             -----------------------------------
                                             Name:
                                             Title:



     (SEAL)



TRUSTEE'S CERTIFICATE OF AUTHENTICATION:

          This is one of the Securities referred to in the within-mentioned
Indenture.


Citibank, N.A.,
as Trustee


By:
   ----------------------------
     Authorized Signatory

                                      S-1
<PAGE>
 
                                ASSIGNMENT FORM

                   FOR VALUE RECEIVED, THE UNDERSIGNED HEREBY
                        SELLS, ASSIGNS AND TRANSFERS TO

PLEASE INSERT SOCIAL
SECURITY OR OTHER IDENTIFYING
NUMBER OF ASSIGNEE


- --------------------------------------------------------------------------------

- --------------------------------------------------------------------------------

                  (Please Print or Typewrite Name and Address
                        including Zip Code of Assignee)


- --------------------------------------------------------------------------------

the within Debenture of __________________________________ and ______________
hereby does irrevocably constitute and appoint


- --------------------------------------------------------------------------------

Attorney to transfer said Debenture on the books of the within-named Company
with full power of substitution in the premises.


Dated:
       --------------------         --------------------------------------------
 
                                    --------------------------------------------

NOTICE:  The signature to this assignment must correspond with the name as it
appears on the first page of the within Debenture in every particular, without
alteration or enlargement or any change whatever.


Signature Guaranteed:



- ------------------------------ 
     Authorized Signature

Signature guarantee should be 
made by a guarantor institution 
participating in the Securities 
Transfer Agents Medallion Program 
or in such guarantee program
acceptable to the Trustee.

                                      A-1

<PAGE>
 
                                                                     EXHIBIT 4.2

REGISTERED                                                      PRINCIPAL AMOUNT
NO. R-1                                                             $100,000,000

CUSIP NO. 03116 2AA 8


                                   AMGEN INC.
                       8-1/8% DEBENTURE DUE APRIL 1, 2097

          UNLESS THIS DEBENTURE IS PRESENTED BY AN AUTHORIZED REPRESENTATIVE OF
THE DEPOSITORY TRUST COMPANY ("DTC"), 55 WATER STREET, NEW YORK, NEW YORK TO THE
COMPANY OR ITS AGENT FOR REGISTRATION OF TRANSFER, EXCHANGE OR PAYMENT, AND SUCH
DEBENTURE ISSUED IS REGISTERED IN THE NAME OF CEDE & CO., OR SUCH OTHER NAME AS
IS REQUESTED BY AN AUTHORIZED REPRESENTATIVE OF DTC (AND ANY PAYMENT IS MADE TO
CEDE & CO. OR TO SUCH OTHER ENTITY AS IS REQUESTED BY AN AUTHORIZED
REPRESENTATIVE OF DTC), ANY TRANSFER, PLEDGE OR OTHER USE HEREOF FOR VALUE OR
OTHERWISE BY OR TO ANY PERSON IS WRONGFUL INASMUCH AS THE REGISTERED OWNER
HEREOF, CEDE & CO., HAS AN INTEREST HEREIN.

          UNLESS AND UNTIL THIS DEBENTURE IS EXCHANGED IN WHOLE OR IN PART FOR
SECURITIES IN DEFINITIVE REGISTERED FORM, THIS DEBENTURE MAY NOT BE TRANSFERRED
EXCEPT AS A WHOLE BY DTC TO THE NOMINEE OF DTC OR BY A NOMINEE OF DTC TO DTC OR
ANOTHER NOMINEE OF DTC OR BY DTC OR ANY SUCH NOMINEE TO A SUCCESSOR OF DTC OR A
NOMINEE OF SUCH SUCCESSOR.

          AMGEN INC., a Delaware corporation (the "Company," which term shall
include any successor under the Indenture hereinafter referred to), for value
received, hereby promises to pay to CEDE & CO., or registered assigns, the
principal sum of One Hundred Million Dollars ($100,000,000) on April 1, 2097,
and to pay interest thereon at the rate of 8-1/8% per annum, until the entire
principal amount hereof is paid or duly provided for.  This Debenture is one of
a duly authorized series issued by the Company and designated as the "8-1/8%
Debentures due April 1, 2097" (referred to herein as the "Debentures").

          Unless otherwise indicated, capitalized terms used herein that are not
otherwise defined shall have the meanings ascribed thereto in the Indenture (as
defined below).

1.  Definitions.

          "Comparable Treasury Issue" means the United States Treasury security
selected by an Independent Investment Banker as having a maturity comparable to
the remaining terms of the Debentures.  If no such security exists, a security
that would be utilized, at the time of selection and in accordance with
customary financial practice, in pricing new issues of corporate debt securities
of comparable maturity to the remaining term of the Debentures will be used.
"Independent Investment Banker" means Merrill Lynch, Pierce, Fenner & Smith
Incorporated or Morgan Stanley & Co. Incorporated or, if either firm is
unwilling or unable to select the
<PAGE>
 
Comparable Treasury Issue, an independent investment banking institution of
national standing appointed by the Trustee (as defined herein).

          "Comparable Treasury Price" means, with respect to any redemption
date, (i) the average of the bid and asked prices for the Comparable Treasury
Issue (expressed in each case as a percentage of its principal amount) on the
third business day preceding such redemption date, as set forth in the daily
statistical release (or any successor release) published by the Federal Reserve
Bank of New York and designated "Composite 3:30 p.m. Quotations for U.S.
Government Securities" or (ii) if such release (or any successor release) is not
published or does not contain such prices on such business day, the average of
the Reference Treasury Dealer Quotations for such redemption date.  "Reference
Treasury Dealer Quotations" means, with respect to each Reference Treasury
Dealer and any redemption date, the average of the bid and asked prices for the
Comparable Treasury Issue (expressed in each case as a percentage of its
principal amount) quoted in writing to the Trustee by such Reference Treasury
Dealer at 5:00 p.m. on the third business day preceding such redemption date.

          "Reference Treasury Dealer" means each of Merrill Lynch, Pierce,
Fenner & Smith Incorporated and Morgan Stanley & Co. Incorporated, and their
respective successors; provided, however, that if any of the foregoing shall
cease to be a primary U.S. Government securities dealer in New York City (a
"Primary Treasury Dealer"), the Company shall substitute therefor another
Primary Treasury Dealer.

          "Remaining Scheduled Payments" means, with respect to any Debenture,
the remaining scheduled payments of the principal thereof to be redeemed and
interest thereon that would be due after the related redemption date but for
such redemption; provided, however, that, if such redemption date is not an
interest payment date with respect to such Debenture, the amount of the next
succeeding scheduled interest payment thereon will be reduced by the amount of
interest accrued thereon to such redemption date.

          "Tax Event" means that the Company shall have received an opinion of a
nationally recognized independent tax counsel experienced in such matters to the
effect that on or after April 8, 1997, as a result of (a) any amendment to,
clarification of, or change (including any announced prospective change) in
laws, or any regulations thereunder, of the United States, (b) any judicial
decision, official administrative pronouncement, ruling, regulatory procedure,
notice or announcement, including any notice or announcement of intent to adopt
such procedures or regulations (an "Administrative Action"), or (c) any
amendment to, clarification of, or change in the official position or the
interpretation of such Administrative Action or judicial decision that differs
from the theretofore generally accepted position, in each case, on or after
April 8, 1997, such change in tax law creates a more than insubstantial risk
that interest paid by the Company on the Debentures is not, or will not be,
deductible, in whole or in part, by the Company for purposes of Federal income
tax.

          "Treasury Yield" means, with respect to any redemption date, the rate
per annum equal to the semiannual equivalent yield to maturity of the Comparable
Treasury Issue, assuming a price for the Comparable Treasury Issue (expressed as
a percentage of its principal amount) equal to the Comparable Treasury Price for
such redemption date.

                                       2
<PAGE>
 
2.  Interest.

          The Company will pay interest semiannually on April 1 and October 1 of
each year (each an "Interest Payment Date"), commencing on October 1, 1997.
Interest on the Debentures will accrue from the most recent date to which
interest has been paid, unless the date hereof is a date to which interest has
been paid, in which case from the date of the Debenture, or, if no interest has
been paid, from April 1, 1997.  Notwithstanding the foregoing, when there is no
existing default in the payment of interest on the Debentures, if the date
hereof is after a record date, as that term is defined below, and before the
next succeeding Interest Payment Date, this Debenture shall bear interest from
such Interest Payment Date; provided, however, that if the Company shall default
in the payment of interest due on such Interest Payment Date, then this
Debenture shall bear interest from the next preceding Interest Payment Date to
which interest has been paid, or, if no interest has been paid on the
Debentures, from April 1, 1997.  Interest will be computed on the basis of a
360-day year of twelve 30-day months.

3.  Method of Payment.

          The Company will pay interest on the Debentures (except defaulted
interest) to the persons who are registered Holders of Debentures at the close
of business on the 15th day immediately preceding such Interest Payment Date
whether or not a Business Day (a "record date").  Holders must surrender
Debentures to the paying agent prior to collecting principal payments.  The
Company will pay principal and interest in money of the United States that at
the time of payment is legal tender for payment of public and private debts.
However, the Company may pay principal and any interest by its check payable in
such money.  It may mail an interest check to a Holder's registered address.

4.  Paying Agent and Registrar.

          Initially, the Trustee will act as paying agent and registrar.  The
Company may change any paying agent, registrar or co-registrar without notice.
The Company or any of its subsidiaries may, subject to certain exceptions, act
as paying agent, registrar or co-registrar.

5.  Indenture.

          The Company issued the Debentures under an Indenture, dated as of
January 1, 1992, as supplemented by a First Supplemental Indenture, dated as of
February 26, 1997 (as so supplemented, and including the Officer's Certificate
dated April 8, 1997 (the "Officer's Certificate") establishing the form and
terms of the Debentures, the "Indenture"), each between the Company and
Citibank, N.A., as trustee (the "Trustee").  The terms of the Debentures include
those stated in the Indenture and those made part of the Indenture by reference
to the Trust Indenture Act of 1939 (15 U.S.  Code (S)(S) 77aaa-77bbbb) as in
effect on the date of the Indenture.  The Debentures are subject to all such
terms and Holders are referred to the Indenture and such Act for a statement of
them.

                                       3
<PAGE>
 
6.  Conditional Right to Shorten Maturity.

          Upon the occurrence of a Tax Event, the Company will have the right to
shorten the maturity of the Debentures to the extent required, in the opinion of
a nationally recognized independent tax counsel experienced in such matters,
such that, after the shortening of the maturity, interest paid on the Debentures
will be deductible for Federal income tax purposes.

          In the event that the Company elects to exercise its right to shorten
the maturity of the Debentures on the occurrence of a Tax Event, the Company
will mail a notice of shortened maturity to each Holder of record of the
Debentures by first-class mail not more than 60 days after the occurrence of
such Tax Event, stating the new maturity date of the Debentures.  Such notice
shall be effective immediately upon mailing.

7.  Redemption at the Option of the Company.

          The Debentures will be redeemable as a whole or in part, at the option
of the Company at any time, at a redemption price equal to the greater of (i)
100% of the principal amount to be redeemed or (ii) the sum of the present
values of the Remaining Scheduled Payments on the redemption date discounted to
maturity on a semiannual basis (assuming a 360-day year consisting of twelve 30-
day months) at the Treasury Yield plus 20 basis points, plus in each case
accrued interest to the date of redemption.

          In addition, if a Tax Event occurs and in the opinion of a nationally
recognized independent tax counsel experienced in such matters there would,
notwithstanding any shortening of the maturity of the Debentures, be more than
an insubstantial risk that interest paid by the Company on the Debentures is
not, or will not be, deductible, in whole or in part, for purposes of Federal
income tax, the Company will have the right, within 90 days following the
occurrence of such Tax Event, to redeem the Debentures in whole (but not in
part) at a redemption price equal to the greater of (i) 100% of the principal
amount of the Debentures and (ii) the sum of the present values of the Remaining
Scheduled Payments on the redemption date discounted to maturity on a semiannual
basis (assuming a 360-day year consisting of twelve 30-day months) at the
Treasury Yield plus 35 basis points, plus in each case accrued interest to the
date of redemption.

          Holders of Debentures to be redeemed will receive notice thereof by
first-class mail at least 30 and not more than 60 days prior to the date fixed
for redemption.

          Unless the Company defaults in payment of the redemption price, on and
after the redemption date interest will cease to accrue on the Debentures or
portions thereof called for redemption.

8.  Denominations, Transfer, Exchange.

          The Debentures are in registered form only.  The registrar may require
a Holder, among other things, to furnish appropriate endorsements and transfer
documents and to pay any taxes and fees required by law or permitted by the
Indenture.

                                       4
<PAGE>
 
9.  Persons Deemed Owners.

          The Holder of a Debenture may be treated as the owner of it for all
purposes.

10.  Unclaimed Money.

          If money for the payment of principal or interest remains unclaimed
for two years, the Trustee or any paying agent will pay the money back to the
Company at its written request.  After that, Holders entitled to the money must
look to the Company for payment unless an abandoned or unclaimed property law
designates another person, and all liability of the Trustee or any such paying
agent with respect to such money shall cease.

11.  Discharge Prior to Maturity.

          Subject to certain conditions, if the Company deposits with the
Trustee money or U.S. Government Obligations sufficient to pay principal of and
accrued interest on the Debentures to maturity, the Company will be discharged
(to the extent provided in the Indenture) from the Indenture and the Debentures.

12.  Amendment, Supplement, Waiver.

          Subject to certain exceptions requiring the consent of the Holders of
each of the affected Securities, at such time as the Debentures are the only
Securities then outstanding under the Indenture, the Indenture or the Debentures
may be amended or supplemented with the consent of the Holders of not less than
a majority in principal amount of the Debentures then outstanding affected by
such amendment or supplement.  Any past default or compliance with any provision
as to the Debentures may be waived with the consent of the Holders of a majority
in principal amount of the Debentures then outstanding.  Without the consent of
any Holder, the Company and the Trustee may amend or supplement the Indenture or
the Debentures to, among other things, cure any ambiguity, defect or
inconsistency or to make any change that does not materially adversely affect
the rights of any Holder.

13.  Restrictive Covenants.

          The Debentures are general unsecured obligations of the Company
limited to the aggregate principal amount of $100,000,000.  The Indenture does
not limit the Company from incurring unsecured Indebtedness other than the
aggregate principal amount of indebtedness to be issued pursuant to the
Officer's Certificate.  It does limit the ability of the Company and its
subsidiaries to grant certain security interests in their property without
equally and ratably securing the Debentures and to engage in certain sale and
leaseback transactions, subject to certain important exceptions described
therein.  Once a year the Company must report to the Trustee with respect to its
compliance with such limitations.

                                       5
<PAGE>
 
14.  Successor Corporation.

          When a successor corporation assumes all the obligations of its
predecessor under the Debentures and the Indenture, the predecessor corporation
will be released from those obligations.

15.  Defaults and Remedies.

          An Event of Default is:  default for 30 days in payment of interest on
any of the Debentures; default in payment of principal of any of the Debentures
due and payable at maturity or otherwise; failure by the Company for 90 days
after written notice to it to comply with any of its other agreements in the
Indenture or in the Debentures; failure by the Company to make any payment at
maturity in respect of Indebtedness in an amount in excess of $10,000,000 and
continuance of such failure for a period of 30 days after notice to the Company
by the Trustee or to the Company and the Trustee by Holders of not less than 25%
in aggregate principal amount of the Securities issued under the Indenture
(treated as one class) then outstanding; the happening of an event of default
under other Indebtedness of the Company which default results in the
acceleration of Indebtedness in an amount in excess of $10,000,000, unless cured
or waived in accordance with the provisions of the applicable instrument, or
discharged within 30 days after notice to the Company by the Trustee or to the
Company and the Trustee by Holders of not less than 25% in aggregate principal
amount of the Securities issued under the Indenture (treated as one class) then
outstanding; and certain events of bankruptcy or insolvency.  If an Event of
Default occurs and is continuing (other than an Event of Default relating to
certain events of bankruptcy or insolvency and certain Events of Default
relating to all outstanding Securities issued under the Indenture), the Trustee
or the Holders of not less than 25% in aggregate principal amount of the
Debentures then outstanding may declare all the Debentures to be due and payable
immediately in accordance with Section 5.1 of the Indenture.  Holders may not
enforce the Indenture or the Debentures except as provided in the Indenture.
The Trustee may require security and indemnity satisfactory to it before it
enforces the Indenture or the Debentures.  Subject to certain limitations,
Holders of a majority in aggregate principal amount of all of the Securities
(treated as one class) then outstanding may direct the Trustee in its exercise
of any trust or power.  The Trustee may withhold from Holders notice of any
continuing default (except a default in payment of principal or interest) if it
determines that withholding notice is in their interests.

16.  Trustee Dealings with Company.

          Citibank, N.A., the Trustee under the Indenture, in its individual or
any other capacity, may make loans to, accept deposits from, and perform
services for the Company, and may otherwise deal with the Company, as if it were
not the Trustee.

17.  No Recourse Against Others.

          A past, present or future director, officer, employee, stockholder or
incorporator, as such, of the Company or successor corporation shall not have
any liability for any obligations of the Company under the Debentures or the
Indenture or for any claim based on, in respect of,

                                       6
<PAGE>
 
or by reason of such obligations or their creation.  Each Holder by accepting a
Debenture waives and releases all such liability.  The waiver and release are
part of the consideration for the issue of the Debentures.

18.  Authentication.

          This Debenture shall not be valid until the Trustee signs the
certificate of authentication at the end of this Debenture.

19.  Copies of the Indenture.

          The Company will furnish to any Holder upon written request and
without charge a copy of the Indenture.  Requests may be made to:
 
                                 Amgen Inc.
                                 1840 DeHavilland Drive
                                 Thousand Oaks, California 91320
                                 Attention:  General Counsel

20.  Abbreviations and Defined Terms.

          Customary abbreviations may be used in the name of a Holder of a
Debenture or an assignee, such as: TEN COM (= tenants in common), TEN ENT 
(= tenants by the entireties), JT TEN (= joint tenants with right of
survivorship and not as tenants in common), CUST (= Custodian), and U/G/M/A 
(= Uniform Gifts to Minors Act).

21.  CUSIP Numbers.

          Pursuant to a recommendation promulgated by the Committee on Uniform
Security Identification Procedures, the Company will cause CUSIP numbers to be
printed on the Debentures as a convenience to the Holders of the Debentures.  No
representation is made as to the accuracy of such numbers as printed on the
Debentures and reliance may be placed only on the other identification numbers
printed hereon.

                           [Signature Page To Follow]

                                       7
<PAGE>
 
          IN WITNESS WHEREOF, the Company has caused this instrument to be duly
executed under its corporate seal this 8th day of April, 1997.


  
                                          By: /s/ Robert S. Attiyeh
                                             -----------------------------------
                                             Name:  Robert S. Attiyeh
                                             Title: Senior Vice President,
                                                    Finance and Corporate
                                                    Development; Chief
                                                    Financial Officer


     (SEAL)



TRUSTEE'S CERTIFICATE OF AUTHENTICATION:

          This is one of the Securities referred to in the within-mentioned
Indenture.


Citibank, N.A.,
as Trustee


By: /s/ Reynaldo L. Duma
   ----------------------------
     Authorized Signatory

                                      S-1
<PAGE>
 
                                ASSIGNMENT FORM

                   FOR VALUE RECEIVED, THE UNDERSIGNED HEREBY
                        SELLS, ASSIGNS AND TRANSFERS TO

PLEASE INSERT SOCIAL
SECURITY OR OTHER IDENTIFYING
NUMBER OF ASSIGNEE


- --------------------------------------------------------------------------------

- --------------------------------------------------------------------------------

                  (Please Print or Typewrite Name and Address
                        including Zip Code of Assignee)


- --------------------------------------------------------------------------------

the within Debenture of __________________________________ and ______________
hereby does irrevocably constitute and appoint


- --------------------------------------------------------------------------------

Attorney to transfer said Debenture on the books of the within-named Company
with full power of substitution in the premises.


Dated:
       --------------------         --------------------------------------------
 
                                    --------------------------------------------

NOTICE:  The signature to this assignment must correspond with the name as it
appears on the first page of the within Debenture in every particular, without
alteration or enlargement or any change whatever.


Signature Guaranteed:



- ------------------------------ 
     Authorized Signature

Signature guarantee should be 
made by a guarantor institution 
participating in the Securities 
Transfer Agents Medallion Program 
or in such guarantee program
acceptable to the Trustee.

                                      A-1


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