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As filed with the Securities and Exchange Commission on October 7, 2003

Registration No. 333-107639

SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

AMENDMENT NO. 1
TO
FORM S-3
REGISTRATION STATEMENT
UNDER THE SECURITIES ACT OF 1933

AMGEN INC.
(Exact name of registrant as specified in its charter)

Delaware
(State or other jurisdiction of incorporation or organization)		 95-3540776
(I.R.S. Employer Identification Number)

One Amgen Center Drive
Thousand Oaks, California 91320-1799
(805) 447-1000
(Address, including zip code, and telephone number, including area code, of each registrant's principal executive offices)

Steven M. Odre, Esq.
Senior Vice President, General Counsel and Secretary
One Amgen Center Drive
Thousand Oaks, California 91320-1799
(805) 447-1000
(Name, address, including zip code, and telephone number, including area code, of agent for service)

Copies to:
Gary Olson, Esq.
Brian Cartwright, Esq.
Latham & Watkins LLP
633 West Fifth Street, Suite 4000
Los Angeles, California 90071-2007
(213) 485-1234

        APPROXIMATE DATE OF COMMENCEMENT OF PROPOSED SALE TO THE PUBLIC: From time to time after the effective date of this registration statement.

        If the only securities being registered on this Form are being offered pursuant to dividend or interest reinvestment plans, please check the following box.  o

        If any of the securities being registered on this Form are to be offered on a delayed or continuous basis pursuant to Rule 415 under the Securities Act of 1933, other than securities offered only in connection with dividend or interest reinvestment plans, check the following box.  ý

        If this Form is filed to register additional securities for an offering pursuant to Rule 462(b) under the Securities Act, please check the following box and list the Securities Act registration statement number of the earlier effective registration statement for the same offering.  o

        If this Form is a post-effective amendment filed pursuant to Rule 462(c) under the Securities Act, check the following box and list the Securities Act registration statement number of the earlier effective registration statement for the same offering.  o

        If delivery of the prospectus is expected to be made pursuant to Rule 434, please check the following box.  o

        The registrant hereby amends this registration statement on such date or dates as may be necessary to delay its effective date until the registrant shall file a further amendment which specifically states that this registration statement shall thereafter become effective in accordance with Section 8(a) of the Securities Act of 1933 or until this registration statement shall become effective on such date as the Securities and Exchange Commission, acting pursuant to said Section 8(a), may determine.

Subject to Completion, Dated October 7, 2003.

The information in this preliminary prospectus is not complete and may be changed. We may not sell these securities until the registration statement filed with the Securities and Exchange Commission is effective. This preliminary prospectus is not an offer to sell these securities and it is not soliciting an offer to buy these securities in any state where the offer or sale is not permitted.

PRELIMINARY PROSPECTUS

$1,000,000,000
AMGEN INC.
Debt Securities
Common Stock
Preferred Stock
Warrants to Purchase Debt Securities, Common Stock and Preferred Stock
Securities Purchase Contracts
Securities Purchase Units
Depositary Shares

        We may offer and sell the securities from time to time in one or more offerings. This prospectus provides you with a general description of the securities we may offer.

        Each time we sell securities, we will provide a supplement to this prospectus that contains specific information about the offering and the terms of the securities. The supplement may also add, update or change information contained in this prospectus. You should carefully read this prospectus and the accompanying prospectus supplement before you invest in any of our securities.

        We may offer and sell the following securities:


        Our common stock is traded on the Nasdaq National Market under the symbol "AMGN."

        See "RISK FACTORS" on page 5 for information you should consider before buying these securities.

        Neither the Securities and Exchange Commission nor any state securities commission has approved or disapproved of these securities or passed upon the adequacy or accuracy of this prospectus. Any representation to the contrary is a criminal offense.

        We will sell these securities directly to our stockholders or to purchasers or through agents on our behalf or through underwriters or dealers as designated from time to time. If any agents or underwriters are involved in the sale of any of these securities, the applicable prospectus supplement will provide the names of the agents or underwriters and any applicable fees, commissions or discounts.

The date of this prospectus is            , 2003.


TABLE OF CONTENTS

 
   Page
About this Prospectus   3
Forward-Looking Statements   3
Where You Can Find More Information   3
Amgen   5
Risk Factors   5
Use of Proceeds   5
Ratio of Earnings to Fixed Charges   5
Description of Securities   6
Description of Debt Securities   6
Description of Capital Stock   14
Description of Warrants   16
Description of Securities Purchase Contracts and Securities Purchase Units   19
Description of Depositary Shares   20
Global Securities   23
Plan of Distribution   26
Experts   27
Validity of the Securities   27

        You should rely only on the information contained or incorporated by reference in this prospectus and in any supplement to this prospectus. We have not authorized any other person to provide you with different information. If anyone provides you with different or inconsistent information, you should not rely on it. You should assume that the information appearing in this prospectus and the accompanying prospectus supplement is accurate as of the date on their respective covers. Our business, financial condition, results of operations and prospects may have changed since that date.

        When used in this prospectus, the terms "Amgen," "we," "our" and "us" refer to Amgen Inc. and its consolidated subsidiaries, unless otherwise specified.

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ABOUT THIS PROSPECTUS

        This prospectus is part of a "shelf" registration statement that we filed with the Securities and Exchange Commission, or SEC. By using a shelf registration statement, we may sell up to $1,000,000,000 offering price of any combination of the securities described in this prospectus from time to time and in one or more offerings. This prospectus only provides you with a general description of the securities that we may offer. Each time we sell securities, we will provide a supplement to this prospectus that contains specific information about the terms of the securities. The supplement may also add, update or change information contained in this prospectus. Before purchasing any securities, you should carefully read both this prospectus and the accompanying prospectus supplement, together with the additional information described under the heading, "Where You Can Find More Information."


FORWARD-LOOKING STATEMENTS

        This prospectus, any accompanying prospectus supplement and the documents they incorporate by reference contain forward-looking statements that are based on current expectations, estimates, forecasts and projections about us, our future performance, our business or others on our behalf, our beliefs and our management's assumptions. Words such as "expect," "anticipate," "outlook," "could," "target," "project," "intend," "plan," "believe," "seek," "estimate," "should," "may," "assume," "continue," variations of such words and similar expressions are intended to identify such forward-looking statements. These statements are not guarantees of future performance and involve certain risks, uncertainties and assumptions that are difficult to predict. We have based our forward-looking statements on our management's beliefs and assumptions based on information available to our management at the time the statements are made. We caution you that actual outcomes and results may differ materially from what is expressed, implied or forecast by our forward-looking statements. Reference is made in particular to forward-looking statements regarding product sales, expenses, earnings per share, liquidity and capital resources and trends. Except as required under the federal securities laws and the rules and regulations of the SEC, we do not have any intention or obligation to update publicly any forward-looking statements after the distribution of this prospectus, whether as a result of new information, future events, changes in assumptions or otherwise.

        You are cautioned not to rely unduly on any forward-looking statements. These risks and uncertainties are discussed in more detail under "Business" and "Management's Discussion and Analysis of Financial Condition and Results of Operations" in our Annual Report on Form 10-K for the year ended December 31, 2002, our Quarterly Report on Form 10-Q for the quarterly period ended March 31, 2003, our Quarterly Report on Form 10-Q for the quarterly period ended June 30, 2003 and other documents on file with the SEC. You may obtain copies of these documents as described under "Where You Can Find More Information" below.


WHERE YOU CAN FIND MORE INFORMATION

Available Information

        We have filed and will file reports and other information with the SEC under the Securities Exchange Act of 1934, as amended. You may read and copy this information at the following SEC public reference room:

Public Reference Room
450 Fifth Street, N.W.
Room 1024
Washington, D.C. 20549

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        You may also obtain copies of this information by mail from the Public Reference Section of the SEC, 450 Fifth Street, N.W., Room 1024, Washington, D.C. 20549, at prescribed rates. Please call the SEC at 1-800-SEC-0330 for further information on the public reference room.

        The SEC also maintains a web site that contains reports, proxy statements and other information about issuers, including Amgen Inc., who file electronically with the SEC. The address of that site is www.sec.gov.

        You can also inspect reports and other information about us at the offices of Nasdaq, 1735 K Street, N.W., Washington, D.C., 20006.

Incorporation by Reference

        We are incorporating by reference into this prospectus some information filed by us with the SEC. We are disclosing important information to you by referring you to those documents. The information incorporated by reference is considered part of this prospectus, except to the extent modified or superseded, as described below.

        We incorporate by reference the following documents we have filed with the SEC:

Those documents contain important information about us and our finances.

        All documents filed by us with the SEC under Sections 13(a), 13(c), 14 and 15(d) of the Exchange Act from the date of this prospectus to the end of the offering of the common stock under this document (other than current reports deemed furnished and not filed) shall also be deemed to be incorporated by reference and will automatically update information in this prospectus.

        Any statements made in this prospectus or in a document incorporated or deemed to be incorporated by reference in this prospectus will be deemed to be modified or superseded for purposes of this prospectus to the extent that a statement contained in this prospectus or in any other subsequently filed document that is also incorporated or deemed to be incorporated by reference in this prospectus modifies or supersedes the statement. Any statement so modified or superseded will not be deemed, except as so modified or superseded, to constitute a part of this prospectus.

        You may request a copy of these filings, at no cost, by writing or calling us at the following address or telephone number:

Manager of Investor Relations
Amgen Inc.
One Amgen Center Drive
Thousand Oaks, California 91320-1799
(805) 447-1000

Exhibits to the filings will not be sent, however, unless those exhibits have specifically been incorporated by reference in this document.

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AMGEN

        We are a global biotechnology company that discovers, develops, manufactures and markets human therapeutics based on advances in cellular and molecular biology.

        We were incorporated in California in 1980 and merged into a Delaware corporation in 1987. Our principal executive offices are located at One Amgen Center Drive, Thousand Oaks, California 91320-1799.


RISK FACTORS

        You should carefully consider the specific risks set forth under the caption "Risk Factors" in the applicable prospectus supplement and under the caption "Management's Discussion and Analysis of Financial Condition and Results of Operation—Financial Outlook—Forward looking statements and factors that may affect Amgen" in our Annual Report on Form 10-K, as updated in our Quarterly Reports on Form 10-Q, which are incorporated by reference in this prospectus, before making an investment decision.


USE OF PROCEEDS

        We intend to use the net proceeds from the sale of the securities under this prospectus for general corporate purposes, including repaying, redeeming or repurchasing debt, acquisitions, share repurchases, capital expenditures and working capital. When a particular series of securities is offered, the prospectus supplement relating thereto will set forth our intended use for the net proceeds we receive from the sale of the securities. Pending the application of the net proceeds, we may invest the proceeds in short-term, interest-bearing instruments or other investment-grade securities.


RATIO OF EARNINGS TO FIXED CHARGES

        Our ratio of earnings to fixed charges are as follows for the periods indicated:

 
   Six Months Ended
June 30,
   Year Ended December 31,
 
   2003
   2002
   2002
   2001
   2000
   1999
   1998
Ratio of Earnings to Fixed Charges   41.7x   38.4x   (a)   46.3x   46.5x   45.3x   34.8x
(a)
Earnings are approximately $716.3 million lower than the amount needed to cover fixed charges in this year, as earnings were impacted by a write-off of acquired in-process research and development of approximately $3.0 billion related to the acquisition of Immunex Corporation.

        Fixed charges consist of interest expense, including capitalized interest, amortized premiums, discounts and capitalized expenses related to indebtedness and estimated interest included in rental expense.

        For the periods indicated above, we had no outstanding shares of preferred stock with required dividend payments. Therefore, the ratios of earnings to combined fixed charges and preferred stock dividends are identical to the ratios presented in the table above.

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DESCRIPTION OF SECURITIES

        The following is a general description of the terms and provisions of the securities we may offer and sell by this prospectus. These summaries are not meant to be a complete description of each security. This prospectus and any accompanying prospectus supplement will contain the material terms and conditions for each security. The accompanying prospectus supplement may add, update or change the terms and conditions of the securities as described in this prospectus.


DESCRIPTION OF DEBT SECURITIES

        This prospectus describes the general terms and provisions of our debt securities. When we offer to sell a particular series of debt securities, we will describe the specific terms of the series in a supplement to this prospectus. We will also indicate in the supplement whether the general terms and provisions described in this prospectus apply to a particular series of debt securities.

        We may offer under this prospectus up to $1,000,000,000 in aggregate principal amount of debt securities, or if debt securities are issued at a discount, or in a foreign currency or composite currency, such principal amount as may be sold for an initial public offering price of up to $1,000,000,000. We may offer debt securities in the form of either senior debt securities or subordinated debt securities. The senior debt securities and the subordinated debt securities are together referred to in this prospectus as the "debt securities." Unless otherwise specified in a supplement to this prospectus, the senior debt securities will be our direct, unsecured obligations and will rank equally with all of our other unsecured and unsubordinated indebtedness. The subordinated debt securities generally will be entitled to payment only after payment of our senior debt. See "—Subordination" below.

        The debt securities will be issued under an indenture between us and a trustee. We have summarized the general features of the debt securities to be governed by the indenture. The summary is not complete. The indenture has been filed as an exhibit to the registration statement that we have filed with the SEC, of which this prospectus forms a part. We encourage you to read the indenture. Capitalized terms used in the summary have the meanings specified in the indenture.

General

        The terms of each series of debt securities will be established by or pursuant to a resolution of our board of directors, or a committee thereof, and set forth or determined in the manner provided in an officers' certificate or by a supplemental indenture. The particular terms of each series of debt securities will be described in a prospectus supplement relating to such series, including any pricing supplement.

        We can issue an unlimited amount of debt securities under the indenture that may be in one or more series with the same or various maturities, at par, at a premium or at a discount. We will set forth in a prospectus supplement, including any pricing supplement, relating to any series of debt securities being offered, the aggregate principal amount and the following terms of the debt securities:

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        We may issue debt securities that provide for an amount less than their stated principal amount to be due and payable upon declaration of acceleration of their maturity pursuant to the terms of the indenture. We will provide you with information on the federal income tax considerations and other special considerations applicable to any of these debt securities in the applicable prospectus supplement.

        If we denominate the purchase price of any of the debt securities in a foreign currency or currencies or a foreign currency unit or units, or if the principal of, and premium and interest on, any series of debt securities is payable in a foreign currency or currencies or a foreign currency unit or units, we will provide you with information on the restrictions, elections, general tax considerations, specific terms and other information with respect to that issue of debt securities and such foreign currency or currencies or foreign currency unit or units in the applicable prospectus supplement.

Transfer and Exchange

        Each debt security will be represented by either one or more global securities registered in the name of The Depository Trust Company, as Depositary, or a nominee (we will refer to any debt security represented by a global debt security as a "book-entry debt security"), or a certificate issued in definitive registered form (we will refer to any debt security represented by a certificated security as a "certificated debt security") as set forth in the applicable prospectus supplement. Except as set forth under the heading "Global Securities" below, book-entry securities will not be issuable in certificated form.

        You may transfer or exchange certificated debt securities at any office we maintain for this purpose in accordance with the terms of the indenture. No service charge will be made for any transfer or exchange of certificated debt securities, but we may require payment of a sum sufficient to cover any tax or other governmental charge payable in connection with a transfer or exchange.

        You may effect the transfer of certificated debt securities and the right to receive the principal of, and any premium and interest on, certificated debt securities only by surrendering the certificate representing those certificated debt securities and either reissuance by us or the trustee of the certificate to the new holder or the issuance by us or the trustee of a new certificate to the new holder.

No Protection in the Event of a Change of Control

        Unless we state otherwise in the applicable prospectus supplement, the debt securities will not contain any provisions which may afford holders of the debt securities protection in the event we have a change in control or in the event of a highly leveraged transaction (whether or not such transaction results in a change in control) which could adversely affect holders of debt securities.

Covenants

        We will set forth in the applicable prospectus supplement any restrictive covenants applicable to any issue of debt securities.

Consolidation, Merger and Sale of Assets

        We may not consolidate with or merge with or into, or convey, transfer or lease all or substantially all of our properties and assets to, any person, which we refer to as a successor person, unless:

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Events of Default

        Event of default means, with respect to any series of debt securities, any of the following:

        No event of default with respect to a particular series of debt securities (except as to certain events of bankruptcy, insolvency or reorganization) necessarily constitutes an event of default with respect to any other series of debt securities. The occurrence of an event of default may constitute an event of default under our bank credit agreements in existence from time to time. In addition, the occurrence of certain events of default or an acceleration under the indenture may constitute an event of default under certain of our other indebtedness outstanding from time to time.

        If an event of default with respect to debt securities of any series at the time outstanding occurs and is continuing, then the trustee or the holders of not less than a majority in principal amount of the outstanding debt securities of that series may, by a notice in writing to us (and to the trustee if given by the holders), declare to be due and payable immediately the principal (or, if the debt securities of that series are discount securities, that portion of the principal amount as may be specified in the terms of that series) of, and accrued and unpaid interest, if any, on all debt securities of that series. In the case of an event of default resulting from certain events of bankruptcy, insolvency or reorganization, the principal (or such specified amount) of and accrued and unpaid interest, if any, on all outstanding debt securities will become and be immediately due and payable without any declaration or other act on the part of the trustee or any holder of outstanding debt securities. At any time after a declaration of acceleration with respect to debt securities of any series has been made, but before a judgment or decree for payment of the money due has been obtained by the trustee, the holders of a majority in principal amount of the outstanding debt securities of that series may rescind and annul the acceleration if all events of default, other than the non-payment of accelerated principal and interest, if any, with respect to debt securities of that series, have been cured or waived as provided in the indenture. We refer you to the prospectus supplement relating to any series of debt securities that are

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discount securities for the particular provisions relating to acceleration of a portion of the principal amount of such discount securities upon the occurrence of an event of default.

        The indenture provides that the trustee will be under no obligation to exercise any of its rights or powers under the indenture at the request of any holder of outstanding debt securities, unless the trustee receives indemnity satisfactory to it against any loss, liability or expense. Subject to certain rights of the trustee, the holders of a majority in principal amount of the outstanding debt securities of any series will have the right to direct the time, method and place of conducting any proceeding for any remedy available to the trustee or exercising any trust or power conferred on the trustee with respect to the debt securities of that series.

        No holder of any debt security of any series will have any right to institute any proceeding, judicial or otherwise, with respect to the indenture or for the appointment of a receiver or trustee, or for any remedy under the indenture, unless:

        Notwithstanding the foregoing, the holder of any debt security will have an absolute and unconditional right to receive payment of the principal of, and any premium and interest on, that debt security on or after the due dates expressed in that debt security and to institute suit for the enforcement of payment.

        If any securities are outstanding under the indenture, the indenture requires us, within 120 days after the end of our fiscal year, to furnish to the trustee a statement as to compliance with the indenture. The indenture provides that the trustee may withhold notice to the holders of debt securities of any series of any default or event of default (except in payment on any debt securities of that series) with respect to debt securities of that series if it in good faith determines that withholding notice is in the interest of the holders of those debt securities.

Modification and Waiver

        We may modify and amend the indenture with the consent of the holders of at least a majority in principal amount of the outstanding debt securities of each series affected by the modifications or amendments. We may not make any modification or amendment without the consent of the holders of each affected debt security then outstanding if that amendment will:

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        Except for certain specified provisions, the holders of at least a majority in principal amount of the outstanding debt securities of any series may on behalf of the holders of all debt securities of that series waive our compliance with provisions of the indenture. The holders of a majority in principal amount of the outstanding debt securities of any series may on behalf of the holders of all the debt securities of such series waive any past default under the indenture with respect to that series and its consequences, except a default in the payment of the principal of, or any premium or interest on, any debt security of that series or in respect of a covenant or provision, which cannot be modified or amended without the consent of the holder of each outstanding debt security of the series affected; provided, however, that the holders of a majority in principal amount of the outstanding debt securities of any series may rescind an acceleration and its consequences, including any related payment default that resulted from the acceleration.

Defeasance of Debt Securities and Certain Covenants in Certain Circumstances

        Legal Defeasance.    The indenture provides that, unless otherwise provided by the terms of the applicable series of debt securities, we may be discharged from any and all obligations in respect of the debt securities of any series (except for certain obligations to register the transfer or exchange of debt securities of such series, to replace stolen, lost or mutilated debt securities of such series, and to maintain paying agencies and certain provisions relating to the treatment of funds held by paying agents). We will be so discharged upon the deposit with the trustee, in trust, of money and/or U.S. government obligations or, in the case of debt securities denominated in a single currency other than U.S. dollars, foreign government obligations, that, through the payment of interest and principal in accordance with their terms, will provide money in an amount sufficient in the opinion of a nationally recognized firm of independent public accountants to pay and discharge each installment of principal of, premium and interest on and any mandatory sinking fund payments in respect of the debt securities of that series on the stated maturity of those payments in accordance with the terms of the indenture and those debt securities.

        This discharge may occur only if, among other things, we have delivered to the trustee an opinion of counsel stating that we have received from, or there has been published by, the United States Internal Revenue Service a ruling or, since the date of execution of the indenture, there has been a change in the applicable United States federal income tax law, in either case to the effect that, and based thereon such opinion shall confirm that, the holders of the debt securities of that series will not recognize income, gain or loss for United States federal income tax purposes as a result of the deposit, defeasance and discharge and will be subject to United States federal income tax on the same amounts and in the same manner and at the same times as would have been the case if the deposit, defeasance and discharge had not occurred.

        Defeasance of Certain Covenants.    The indenture provides that, unless otherwise provided by the terms of the applicable series of debt securities, upon compliance with certain conditions:

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The conditions include:

        Covenant Defeasance and Events of Default.    In the event we exercise our option to effect covenant defeasance with respect to any series of debt securities and the debt securities of that series are declared due and payable because of the occurrence of any event of default, the amount of money and/or U.S. government obligations or foreign government obligations on deposit with the trustee will be sufficient to pay amounts due on the debt securities of that series at the time of their stated maturity but may not be sufficient to pay amounts due on the debt securities of that series at the time of the acceleration resulting from the event of default. In such a case, we would remain liable for those payments.

        "Foreign Government Obligations" means, with respect to debt securities of any series that are denominated in a currency other than U.S. dollars:

Subordination

        Unless indicated differently in a prospectus supplement, our subordinated debt securities will be subordinated in right of payment to the prior payment in full of all our senior debt. This means that upon:

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        the holders of all of our senior debt will be entitled to receive:

before the holders of any of the subordinated debt securities are entitled to receive any payment. So long as any of the events in clauses (a), (b), (c) or (d) above has occurred and is continuing, any amounts payable on the subordinated debt securities will instead be paid directly to the holders of all senior debt to the extent necessary to pay the senior debt in full and, if any payment is received by the subordinated indenture trustee under the subordinated indenture or the holders of any of the subordinated debt securities before all senior debt is paid in full, the payment or distribution must be paid over to the holders of the unpaid senior debt. Subject to paying the senior debt in full, the holders of the subordinated debt securities will be subrogated to the rights of the holders of the senior debt to the extent that payments are made to the holders of senior debt out of the distributive share of the subordinated debt securities.

        "senior debt" means with respect to the subordinated debt securities, the principal of, premium, if any, and interest, if any, on and any other payment in respect of indebtedness due pursuant to any of the following, whether outstanding on the date the subordinated debt securities are issued or thereafter incurred, created or assumed:

unless, in the case of any particular indebtedness, renewal, extension or refunding, the instrument creating or evidencing the same or the assumption or guarantee of the same by its terms provides that such indebtedness, renewal, extension or refunding is not superior in right of payment to or is pari passu with such securities.

        Due to the subordination, if our assets are distributed upon insolvency, certain of our general creditors may recover more, ratably, than holders of subordinated debt securities. The subordination provisions will not apply to money and securities held in trust under the satisfaction and discharge and the defeasance provisions of the applicable subordinated indenture.

        The subordinated debt securities and the subordinated indenture do not limit our ability to incur additional indebtedness, including indebtedness that will rank senior to subordinated debt securities. We may incur substantial additional amounts of indebtedness in the future.

Governing Law

        The indenture and the debt securities will be governed by, and construed in accordance with, the internal laws of the State of New York.

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DESCRIPTION OF CAPITAL STOCK

        The following description of our capital stock is summarized from, and qualified in its entirety by reference to, Amgen's certificate of incorporation, as amended, which has been publicly filed with the SEC. See "Where You Can Find More Information."

        Our authorized capital stock consists of:

        The only equity securities currently outstanding are shares of common stock. As of July 18, 2003, there were 1,290,780,772 shares of common stock issued and outstanding.

Common Stock

        Each holder of our common stock is entitled to one vote per share on all matters to be voted upon by our stockholders. Upon any liquidation, dissolution or winding up of our business, the holders of our common stock are entitled to share equally in all assets available for distribution after payment of all liabilities, subject to the liquidation preference of shares of preferred stock, if any, then outstanding. Our common stock has no preemptive or conversion rights. All outstanding shares of common stock are fully paid and non-assessable. Our common stock is listed on the Nasdaq National Market System under the symbol "AMGN."

Preferred Stock

        Pursuant to our certificate of incorporation, our board of directors may, by resolution and without further action or vote by our stockholders, provide for the issuance of up to 5,000,000 shares of preferred stock from time to time in one or more series having such voting powers, and such designations, preferences, and relative, participating, optional, or other special rights and qualifications, limitations, or restrictions thereof, as the board of directors may determine.

        The issuance of preferred stock may have the effect of delaying or preventing a change in control of us without further action by our stockholders. The issuance of shares of preferred stock with voting and conversion rights may adversely affect the voting power of the holders of our common stock.

Rights Agreement and Series A Junior Participating Preferred Stock

        Each share of our common stock carries with it one preferred share purchase right. If the rights become exercisable, each right entitles the registered holder to purchase from us one four-thousandth of a share of Series A Junior Participating Preferred Stock at a fixed price, subject to adjustment. Until a right is exercised, the holder of the right has no right to vote or receive dividends or any other rights as a stockholder as a result of holding the right. The rights trade automatically with shares of our common stock, and may only be exercised in connection with certain attempts to take over our company. The rights are designed to protect the interests of our company and our stockholders against coercive takeover tactics and encourage potential acquirors to negotiate with our board of directors before attempting a takeover. The rights may, but are not intended to, deter takeover proposals that may be in the interests of our stockholders. The description and terms of the rights are set forth in an amended and restated rights agreement, dated as of December 12, 2000, as the same may be amended from time to time, between us and the American Stock Transfer & Trust Company, as rights agent.

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Dividends

        Subject to preferences that may be applicable to any outstanding preferred stock, the holders of common stock are entitled ratably to receive dividends, if any, declared by our board of directors out of funds legally available for the payment of dividends. We have not paid cash dividends to date and do not expect to pay any cash dividends in the foreseeable future.

Anti-Takeover Effects of Delaware Law

        We are subject to the provisions of Section 203 of the Delaware General Corporation Law. Under Section 203, we would generally be prohibited from engaging in any business combination with any interested stockholder for a period of three years following the time that this stockholder became an interested stockholder unless:

        Under Section 203, a "business combination" includes:

        In general, Section 203 defines an interested stockholder as an entity or person beneficially owning 15% or more of the outstanding voting stock of the Corporation and any entity or person affiliated with or controlling or controlled by such entity or person.

Transfer Agent

        The transfer agent and registrar for our common stock is the American Stock Transfer & Trust Company.

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DESCRIPTION OF WARRANTS

        This section describes the general terms of the warrants that we may offer and sell by this prospectus. This prospectus and any accompanying prospectus supplement will contain the material terms and conditions for each warrant. The accompanying prospectus supplement may add, update or change the terms and conditions of the warrants as described in this prospectus.

General

        We may issue warrants to purchase debt securities, preferred stock or common stock. Warrants may be issued independently or together with any securities and may be attached to or separate from those securities. The warrants will be issued under warrant agreements to be entered into between us and a bank or trust company, as warrant agent, all of which will be described in the prospectus supplement relating to the warrants we are offering. The warrant agent will act solely as our agent in connection with the warrants and will not have any obligation or relationship of agency or trust for or with any holders or beneficial owners of warrants. A copy of the warrant agreement will be filed with the SEC in connection with the offering of the warrants.

Debt Warrants

        We may issue warrants for the purchase of our debt securities. As explained below, each debt warrant will entitle its holder to purchase debt securities at an exercise price set forth in, or to be determinable as set forth in, the related prospectus supplement. Debt warrants may be issued separately or together with debt securities.

        The debt warrants are to be issued under debt warrant agreements to be entered into between us, and one or more banks or trust companies, as debt warrant agent, as will be set forth in the prospectus supplement relating to the debt warrants being offered by the prospectus supplement and this prospectus. A copy of the debt warrant agreement, including a form of the debt warrant certificate representing the debt warrants, will be filed with the SEC in connection with the offering of the debt warrants.

        The particular terms of each issue of debt warrants, the debt warrant agreement relating to the debt warrants and the debt warrant certificates representing debt warrants will be described in the applicable prospectus supplement, including, as applicable:

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        Debt warrant certificates will be exchangeable for new debt warrant certificates of different denominations and, if in registered form, may be presented for registration of transfer, and debt warrants may be exercised at the corporate trust office of the debt warrant agent or any other office indicated in the related prospectus supplement. Before the exercise of debt warrants, holders of debt warrants will not be entitled to payments of principal of, premium, if any, or interest, if any, on the debt securities purchasable upon exercise of the debt warrants, or to enforce any of the covenants in the indenture.

Equity Warrants

        We may issue warrants for the purchase of our equity securities, such as our preferred stock or common stock. As explained below, each equity warrant will entitle its holder to purchase equity securities at an exercise price set forth in, or to be determinable as set forth in, the related prospectus supplement. Equity warrants may be issued separately or together with equity securities.

        The equity warrants are to be issued under equity warrant agreements to be entered into between us and one or more banks or trust companies, as equity warrant agent, as will be set forth in the prospectus supplement relating to the equity warrants being offered by the prospectus supplement and this prospectus. A copy of the equity warrant agreement, including a form of the equity warrant certificate representing the equity warranty, will be filed with the SEC in connection with the offering of the equity warrants.

        The particular terms of each issue of equity warrants, the equity warrant agreement relating to the equity warrants and the equity warrant certificates representing equity warrants will be described in the applicable prospectus supplement, including, as applicable:

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        Holders of equity warrants will not be entitled, solely by virtue of being holders, to vote, to consent, to receive dividends, to receive notice as shareholders with respect to any meeting of shareholders for the election of directors or any other matter, or to exercise any rights whatsoever as a holder of the equity securities purchasable upon exercise of the equity warrants.

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DESCRIPTION OF SECURITIES PURCHASE CONTRACTS AND SECURITIES PURCHASE UNITS

        This section describes the general terms of the securities purchase contracts and securities purchase units that we may offer and sell by this prospectus. This prospectus and any accompanying prospectus supplement will contain the material terms and conditions for each securities purchase contract and securities purchase unit. The accompanying prospectus supplement may add, update or change the terms and conditions of the securities purchase contracts and securities purchase units as described in this prospectus.

Stock Purchase Contract and Stock Purchase Units

        We may issue stock purchase contracts, representing contracts obligating holders to purchase from us, and obligating us to sell to the holders, a specified number of shares of common stock or preferred stock at a future date or dates, or a variable number of shares of common stock or preferred stock for a stated amount of consideration. The price per share and the number of shares of common stock or preferred stock may be fixed at the time the stock purchase contracts are issued or may be determined by reference to a specific formula set forth in the stock purchase contracts. Any such formula may include anti-dilution provisions to adjust the number of shares of common stock or preferred stock issuable pursuant to the stock purchase contracts upon certain events.

        The stock purchase contracts may be issued separately or as part of units consisting of a stock purchase contract and, as security for the holder's obligations to purchase the shares under the stock purchase contracts, either (a) our senior debt securities or subordinated debt securities, (b) our debt obligations of third parties, including U.S. Treasury securities, or (c) preferred securities of a trust. The stock purchase contracts may require us to make periodic payments to the holders of the stock purchase units or vice versa, and such payments may be unsecured or prefunded on some basis. The stock purchase contracts may require holders to secure their obligations in a specified manner, and in certain circumstances, we may deliver newly issued prepaid stock purchase contracts upon release to a holder of any collateral securing such holder's obligations under the original stock purchase contract.

Debt Purchase Contracts and Debt Purchase Units

        We may issue debt purchase contracts, representing contracts obligating holders to purchase from us, and obligating us to sell to the holders, a specified principal amount of debt securities at a future date or dates. The purchase price and the interest rate may be fixed at the time the debt purchase contracts are issued or may be determined by reference to a specific formula set forth in the debt purchase contracts.

        The debt purchase contracts may be issued separately or as part of units consisting of a debt purchase contract and, as security for the holder's obligations to purchase the securities under the debt purchase contracts, either (a) our senior debt securities or subordinated debt securities, (b) our debt obligations of third parties, including U.S. Treasury securities, or (c) preferred securities of a trust. The debt purchase contracts may require us to make periodic payments to the holders of the debt purchase units or vice versa, and such payments may be unsecured or prefunded on some basis. The debt purchase contracts may require holders to secure their obligations in a specified manner, and in certain circumstances, we may deliver newly issued prepaid debt purchase contracts upon release to a holder of any collateral securing such holder's obligations under the original debt purchase contract.

        The applicable prospectus supplement will describe the general terms of any purchase contracts or purchase units and, if applicable, prepaid purchase contracts. The description in the prospectus supplement will not purport to be complete and will be qualified in its entirety by reference to (a) the purchase contracts, (b) the collateral arrangements and depositary arrangements, if applicable, relating to such purchase contracts or purchase units and (c) if applicable, the prepaid purchase contracts and the document pursuant to which such prepaid purchase contracts will be issued. Material United States federal income tax considerations applicable to the purchase contracts and the purchase units will also be discussed in the applicable prospectus supplement.

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DESCRIPTION OF DEPOSITARY SHARES

        This section describes the general terms of the depositary shares we may offer and sell by this prospectus. This prospectus and any accompanying prospectus supplement will contain the material terms and conditions for the depositary shares. The accompanying prospectus supplement may add, update, or change the terms and conditions of the depositary shares as described in this prospectus.

General

        We may, at our option, elect to offer depositary shares, each representing a fraction (to be set forth in the prospectus supplement relating to a particular series of preferred stock) of a share of a particular class or series of preferred stock as described below. In the event we elect to do so, depositary receipts evidencing depositary shares will be issued to the public.

        The shares of any class or series of preferred stock represented by depositary shares will be deposited under a deposit agreement among us, a depositary selected by us, and the holders of the depositary receipts. The depositary will be a bank or trust company having its principal office in the United States and having a combined capital and surplus of at least $50,000,000. Subject to the terms of the deposit agreement, each owner of a depositary share will be entitled, in proportion to the applicable fraction of a share of preferred stock represented by such depositary share, to all the rights and preferences of the shares of preferred stock represented by the depositary share, including dividend, voting, redemption and liquidation rights.

        The depositary shares will be evidenced by depositary receipts issued pursuant to the deposit agreement. Depositary receipts will be distributed to those persons purchasing the fractional shares of the related class or series of preferred shares in accordance with the terms of the offering described in the related prospectus supplement.

        Pending the preparation of definitive depositary receipts, the depositary may, upon our written order, issue temporary depositary receipts substantially identical to, and entitling the holders thereof to all the rights pertaining to, the definitive depositary receipts but not in definitive form. Definitive depositary receipts will be prepared without unreasonable delay, and temporary depositary receipts will be exchangeable for definitive depositary receipts without charge to the holder.

Dividends and Other Distributions

        The depositary will distribute all cash dividends or other cash distributions received for the preferred stock to the entitled record holders of depositary shares in proportion to the number of depositary shares that the holder owns on the relevant record date; provided, however, that if we or the depositary is required by law to withhold an amount on account of taxes, then the amount distributed to the holders of depositary shares shall be reduced accordingly. The depositary will distribute only an amount that can be distributed without attributing to any holder of depositary shares a fraction of one cent. The depositary will add the undistributed balance to and treat it as part of the next sum received by the depositary for distribution to holders of the depositary shares.

        If there is a non-cash distribution, the depositary will distribute property received by it to the entitled record holders of depositary shares, in proportion, insofar as possible, to the number of depositary shares owned by the holders, unless the depositary determines, after consultation with us, that it is not feasible to make such distribution. If this occurs, the depositary may, with our approval, sell such property and distribute the net proceeds from such sale to the holders. The deposit agreement also will contain provisions relating to how any subscription or similar rights that we may offer to holders of the preferred stock will be available to the holders of the depositary shares.

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Withdrawal of Shares

        Upon surrender of the depositary receipts at the corporate trust office of the depositary, unless the related depositary shares have previously been called for redemption, converted or exchanged into our other securities, the holder of the depositary shares evidenced thereby is entitled to delivery of the number of whole shares of the related class or series of preferred stock and any money or other property represented by such depositary shares. Holders of depositary receipts will be entitled to receive whole shares of the related class or series of preferred stock on the basis set forth in the prospectus supplement for such class or series of preferred stock, but holders of such whole shares of preferred stock will not thereafter be entitled to exchange them for depositary shares. If the depositary receipts delivered by the holder evidence a number of depositary shares in excess of the number of depositary shares representing the number of whole shares of preferred stock to be withdrawn, the depositary will deliver to such holder at the same time a new depositary receipt evidencing such excess number of depositary shares. In no event will fractional shares of preferred stock be delivered upon surrender of depositary receipts to the depositary.

Conversion, Exchange and Redemption

        If any class or series of preferred stock underlying the depositary shares may be converted or exchanged, each record holder of depositary receipts representing the shares of preferred stock being converted or exchanged will have the right or obligation to convert or exchange the depositary shares represented by the depositary receipts.

        Whenever we redeem or convert shares of preferred stock held by the depositary, the depositary will redeem or convert, at the same time, the number of depositary shares representing the preferred stock to be redeemed or converted. The depositary will redeem the depositary shares from the proceeds it receives from the corresponding redemption of the applicable series of preferred stock. The depositary will mail notice of redemption or conversion to the record holders of the depositary shares that are to be redeemed between 30 and 60 days before the date fixed for redemption or conversion, The redemption price per depositary share will be equal to the applicable fraction of the redemption price per share on the applicable class or series of preferred stock. If less than all the depositary shares are to be redeemed, the depositary will select which shares are to be redeemed by lot on a pro rata basis or by any other equitable method as the depositary may decide.

        After the redemption or conversion date, the depositary shares called for redemption or conversion will no longer be outstanding. When the depositary shares are no longer outstanding, all rights of the holders will end, except the right to receive money, securities or other property payable upon redemption or conversion of the depositary shares.

Voting the Preferred Stock

        When the depositary receives notice of a meeting at which the holders of the particular class or series of preferred stock are entitled to vote, the depositary will mail the particulars of the meeting to the record holders of the depositary shares. Each record holder of depositary shares on the record date may instruct the depositary on how to vote the shares of preferred stock underlying the holder's depositary shares. The depositary will try, if practical, to vote the number of shares of preferred stock underlying the depositary shares according to the instructions. We will agree to take all reasonable action requested by the depositary to enable it to vote as instructed.

Amendment and Termination of the Deposit Agreement

        We and the depositary may agree at any time to amend the deposit agreement and the depositary receipt evidencing the depositary shares. Any amendment that (a) imposes or increases certain fees, taxes or other charges payable by the holders of the depositary shares as described in the deposit

21


agreement or (b) otherwise materially adversely affects any substantial existing rights of holders of depositary shares, will not take effect until such amendment is approved by the holders of at least a majority of the depositary shares then outstanding. Any holder of depositary shares that continues to hold its shares after such amendment has become effective will be deemed to have agreed to the amendment.

        We may direct the depositary to terminate the deposit agreement by mailing a notice of termination to holders of depositary shares at least 30 days before termination. The depositary may terminate the deposit agreement if 90 days have elapsed after the depositary delivered written notice of its election to resign and a successor depositary is not appointed. In addition, the deposit agreement will automatically terminate if:

Reports and Obligations

        The depositary will forward to the holders of depositary shares all reports and communications from us that are delivered to the depositary and that we are required by law, the rules of an applicable securities exchange or our amended and restated certificate of incorporation to furnish to the holders of the preferred stock. Neither we nor the depositary will be liable if the depositary is prevented or delayed by law or any circumstances beyond its control in performing its obligations under the deposit agreement. The deposit agreement limits our obligations to performance in good faith of the duties stated in the deposit agreement. The depositary assumes no obligation and will not be subject to liability under the deposit agreement except to perform such obligations as are set forth in the deposit agreement without negligence or bad faith. Neither we nor the depositary will be obligated to prosecute or defend any legal proceeding connected with any depositary shares or class or series of preferred stock unless the holders of depositary shares requesting us to do so furnish us with a satisfactory indemnity. In performing our obligations, we and the depositary may rely and act upon the advice of our counsel or accountants, on any information provided to us by a person presenting shares for deposit, any holder of a receipt, or any other document believed by us or the depositary to be genuine and to have been signed or presented by the proper party or parties.

Payment of Fees and Expenses

        We will pay all fees, charges and expenses of the depositary, including the initial deposit of the preferred stock and any redemption of the preferred stock. Holders of depositary shares will pay taxes and governmental charges and any other charges as are stated in the deposit agreement for their accounts.

Resignation and Removal of Depositary

        At any time, the depositary may resign by delivering notice to us, and we may remove the depositary at any time. Resignations or removals will take effect upon the appointment of a successor depositary and its acceptance of the appointment. The successor depositary must be appointed within 90 days after the delivery of the notice of resignation or removal and must be a bank or trust company having its principal office in the United States and having a combined capital and surplus of at least $50,000,000.

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GLOBAL SECURITIES

Book-Entry, Delivery and Form

        Unless we indicate differently in a supplemental prospectus, the securities initially will be issued in book-entry form and represented by one or more global notes or global securities (collectively, "global securities"). The global securities will be deposited with, or on behalf of, The Depositary Trust Company, New York, New York, as depositary ("DTC"), and registered in the name of Cede & Co., the nominee of DTC. Unless and until it is exchanged for individual certificates evidencing securities under the limited circumstances described below, a global security may not be transferred except as a whole by the depositary to its nominee or by the nominee to the depositary, or by the depositary or its nominee to a successor depositary or to a nominee of the successor depositary.

        DTC has advised us that it is:

        DTC holds securities that its participants deposit with DTC. DTC also facilitates the settlement among its participants of securities transactions, such as transfers and pledges, in deposited securities through electronic computerized book-entry changes in participants' accounts, thereby eliminating the need for physical movement of securities certificates. "Direct participants" in DTC include securities brokers and dealers, including underwriters, banks, trust companies, clearing corporations and other organizations. DTC is owned by a number of its direct participants and by the New York Stock Exchange, Inc., the American Stock Exchange LLC and the National Association of Securities Dealers, Inc. Access to the DTC system is also available to others, which we sometimes refer to as "indirect participants," that clear through or maintain a custodial relationship with a direct participant, either directly or indirectly. The rules applicable to DTC and its participants are on file with the SEC.

        Purchases of securities under the DTC system must be made by or through direct participants, which will receive a credit for the securities on DTC's records. The ownership interest of the actual purchaser of a security, which we sometimes refer to as a "beneficial owner," is in turn recorded on the direct and indirect participants' records. Beneficial owners of securities will not receive written confirmation from DTC of their purchases. However, beneficial owners are expected to receive written confirmations providing details of their transactions, as well as periodic statements of their holdings, from the direct or indirect participants through which they purchased securities. Transfers of ownership interests in global securities are to be accomplished by entries made on the books of participants acting on behalf of beneficial owners. Beneficial owners will not receive certificates representing their ownership interests in the global securities, except under the limited circumstances described below.

        To facilitate subsequent transfers, all global securities deposited by direct participants with DTC will be registered in the name of DTC's partnership nominee, Cede & Co., or such other name as may be requested by an authorized representative of DTC. The deposit of securities with DTC and their registration in the name of Cede & Co. or such other nominee will not change the beneficial ownership of the securities. DTC has no knowledge of the actual beneficial owners of the securities. DTC's records reflect only the identity of the direct participants to whose accounts the securities are credited, which may or may not be the beneficial owners. The participants are responsible for keeping account of their holdings on behalf of their customers.

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        So long as the securities are in book-entry form, you will receive payments and may transfer securities only through the facilities of the depositary and its direct and indirect participants. We will maintain an office or agency in the Borough of Manhattan, the City of New York, where notices and demands in respect of the securities and the indenture may be delivered to us and where certificated securities may be surrendered for payment, registration of transfer or exchange.

        Conveyance of notices and other communications by DTC to direct participants, by direct participants to indirect participants and by direct participants and indirect participants to beneficial owners will be governed by arrangements among them, subject to any legal requirements in effect from time to time.

        Redemption notices will be sent to DTC. If less than all of the securities of a particular series are being redeemed, DTC's practice is to determine by lot the amount of the interest of each direct participant in the securities of such series to be redeemed.

        Neither DTC nor Cede & Co. (or such other DTC nominee) will consent or vote with respect to the securities. Under its usual procedures, DTC will mail an omnibus proxy to us as soon as possible after the record date. The omnibus proxy assigns the consenting or voting rights of Cede & Co. to those direct participants to whose accounts the securities of such series are credited on the record date, identified in a listing attached to the omnibus proxy.

        So long as securities are in book-entry form, we will make payments on those securities to the depositary or its nominee, as the registered owner of such securities, by wire transfer of immediately available funds. If securities are issued in definitive certificated form under the limited circumstances described below, we will have the option of paying interest by check mailed to the addresses of the persons entitled to payment or by wire transfer to bank accounts in the United States designated in writing to the applicable trustee at least 15 days before the applicable payment date by the persons entitled to payment.

        Redemption proceeds, distributions and dividend payments on the securities will be made to Cede & Co., or such other nominee as may be requested by an authorized representative of DTC. DTC's practice is to credit direct participants' accounts upon DTC's receipt of funds and corresponding detail information from us on the payment date in accordance with their respective holdings shown on DTC records. Payments by participants to beneficial owners will be governed by standing instructions and customary practices, as is the case with securities held for the account of customers in bearer form or registered in "street name." Those payments will be the responsibility of participants and not of DTC or us, subject to any statutory or regulatory requirements in effect from time to time. Payment of redemption proceeds, distributions and dividend payments to Cede & Co., or such other nominee as may be requested by an authorized representative of DTC, is our responsibility, disbursement of payments to direct participants is the responsibility of DTC, and disbursement of payments to the beneficial owners is the responsibility of direct and indirect participants.

        Except under the limited circumstances described below, purchasers of securities will not be entitled to have securities registered in their names and will not receive physical delivery of securities. Accordingly, each beneficial owner must rely on the procedures of DTC and its participants to exercise any rights under the securities and the indenture.

        The laws of some jurisdictions may require that some purchasers of securities take physical delivery of securities in definitive form. Those laws may impair the ability to transfer or pledge beneficial interests in securities.

        DTC may discontinue providing its services as securities depository with respect to the securities at any time by giving reasonable notice to us. Under such circumstances, in the event that a successor depository is not obtained, securities certificates are required to be printed and delivered.

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        As noted above, beneficial owners of a particular series of securities generally will not receive certificates representing their ownership interests in those securities. However, if:

we will prepare and deliver certificates for such securities in exchange for beneficial interests in the global securities. Any beneficial interest in a global security that is exchangeable under the circumstances described in the preceding sentence will be exchangeable for securities in definitive certificated form registered in the names that the depositary directs. It is expected that these directions will be based upon directions received by the depositary from its participants with respect to ownership of beneficial interests in the global securities.

        We have obtained the information in this section and elsewhere in this prospectus concerning DTC and DTC's book-entry system from sources that are believed to be reliable, but we take no responsibility for the accuracy of this information.

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PLAN OF DISTRIBUTION

        We may sell the securities described in this prospectus from time to time in one or more transactions

        We may distribute the securities from time to time in one or more transactions at:

Direct Sales

        We may sell the securities directly to institutional investors or others. A prospectus supplement will describe the terms of any sale of securities we are offering hereunder.

To Underwriters

        The applicable prospectus supplement will name any underwriter involved in a sale of securities. Underwriters may offer and sell securities at a fixed price or prices, which may be changed, or from time to time at market prices or at negotiated prices. Underwriters may be deemed to have received compensation from us from sales of securities in the form of underwriting discounts or commissions and may also receive commissions from purchasers of securities for whom they may act as agent.

        Underwriters may sell securities to or through dealers, and such dealers may receive compensation in the form of discounts, concessions or commissions from the underwriters and/or commissions (which may be changed from time to time) from the purchasers for whom they may act as agent.

        Unless otherwise provided in a prospectus supplement, the obligations of any underwriters to purchase securities or any series of securities will be subject to certain conditions precedent, and the underwriters will be obligated to purchase all such securities if any are purchased.

Through Agents and Dealers

        We will name any agent involved in a sale of securities, as well as any commissions payable by us to such agent, in a prospectus supplement. Unless we indicate differently in the prospectus supplement, any such agent will be acting on a reasonable efforts basis for the period of its appointment.

        If we utilize a dealer in the sale of the securities being offered pursuant to this prospectus, we will sell the securities to the dealer, as principal. The dealer may then resell the securities to the public at varying prices to be determined by the dealer at the time of resale.

Delayed Delivery Contracts

        If we so specify in the applicable prospectus supplement, we will authorize underwriters, dealers and agents to solicit offers by certain institutions to purchase securities pursuant to contracts providing

26


for payment and delivery on future dates. Such contracts will be subject to only those conditions set forth in the applicable prospectus supplement.

        The underwriters, dealers and agents will not be responsible for the validity or performance of the contracts. We will set forth in the prospectus supplement relating to the contracts the price to be paid for the securities, the commissions payable for solicitation of the contracts and the date in the future for delivery of the securities.

General Information

        Underwriters, dealers and agents participating in a sale of the securities may be deemed to be underwriters as defined in the Securities Act, and any discounts and commissions received by them and any profit realized by them on resale of the securities may be deemed to be underwriting discounts and commissions, under the Securities Act. We may have agreements with underwriters, dealers and agents to indemnify them against certain civil liabilities, including liabilities under the Securities Act, and to reimburse them for certain expenses.

        Underwriters or agents and their associates may be customers of, engage in transactions with or perform services for us or our affiliates in the ordinary course of business.

        Unless we indicate differently in a prospectus supplement, we will not list the securities on any securities exchange, other than shares of our common stock. The securities, except for our common stock, will be a new issue of securities with no established trading market. Any underwriters that purchase securities for public offering and sale may make a market in such securities, but such underwriters will not be obligated to do so and may discontinue any market making at any time without notice. We make no assurance as to the liquidity of or the trading markets for any securities.


EXPERTS

        The consolidated financial statements of Amgen Inc. appearing in Amgen Inc.'s Annual Report (Form 10-K) for the year ended December 31, 2002, have been audited by Ernst & Young LLP, independent auditors, as set forth in their report thereon included therein and incorporated herein by reference. Such consolidated financial statements are incorporated herein by reference in reliance upon such report given on the authority of such firm as experts in accounting and auditing.


VALIDITY OF THE SECURITIES

        Latham & Watkins LLP, Los Angeles, California, will pass upon certain legal matters relating to the issuance and sale of the securities on behalf of Amgen Inc.

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PART II.
INFORMATION NOT REQUIRED IN PROSPECTUS

Item 14. Other Expenses of Issuance and Distribution.

Securities and Exchange Commission registration fee   $ 80,900
Printing expenses     50,000
Trustee fees and expenses     5,000
Legal fees and expenses     100,000
Accounting fees and expenses     100,000
Miscellaneous     100,000
   
  Total   $ 435,900
   

All of the above except the Securities and Exchange Commission registration fee are estimated.

Item 15. Indemnification of Directors and Officers.

        Section 145 of the Delaware General Corporation Law, the Restated Certificate of Incorporation, as amended, and the Amended and Restated Bylaws of Amgen contain provisions covering indemnification of corporate directors and officers against certain liabilities and expenses incurred as a result of proceedings involving such persons in their capacities as directors and officers, including proceedings under the Securities Act of 1933, as amended (the "Securities Act") and the Securities Exchange Act of 1934, as amended (the "Exchange Act").

        The Registrant has authorized the entering into of indemnity contracts and provides indemnity insurance pursuant to which officers and directors are indemnified or insured against liability or loss under certain circumstances which may include liabilities or related loss under the Securities Act and the Exchange Act.

Item 16. Exhibits.

        See the Exhibit Index attached to this Registration Statement and incorporated herein by reference.

Item 17. Undertakings.

        (a)   The undersigned registrant hereby undertakes:

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provided, however, that (a)(1)(i) and (a)(1)(ii) above do not apply if the information required to be included in a post-effective amendment by those paragraphs is contained in periodic reports filed with or furnished to the Securities and Exchange Commission by the registrant pursuant to Section 13 or Section 15(d) of the Exchange Act that are incorporated by reference in the Registration Statement.


        (b)   The undersigned registrant hereby undertakes that, for purposes of determining any liability under the Securities Act, each filing of the registrant's annual report pursuant to Section 13(a) or Section 15(d) of the Exchange Act that is incorporated by reference in this Registration Statement shall be deemed to be a new registration statement relating to the securities offered herein, and the offering of such securities at that time shall be deemed to be the initial bona fide offering thereof.

        (c)   Insofar as indemnification for liabilities arising under the Securities Act may be permitted to directors, officers and controlling persons of the registrant pursuant to the foregoing provisions or otherwise, the registrant have been advised that in the opinion of the Securities and Exchange Commission such indemnification is against public policy as expressed in the Securities Act and is, therefore, unenforceable. In the event that a claim for indemnification against such liabilities (other than the payment by a registrant of expenses incurred or paid by a director, officer or controlling person in the successful defense of any action, suit or proceeding) is asserted by such director, officer or controlling person in connection with the securities being registered, such registrant will, unless in the opinion of its counsel the matter has been settled by controlling precedent, submit to a court of appropriate jurisdiction the question whether such indemnification by it is against public policy as expressed in the Securities Act and will be governed by the final adjudication of such issue.

        (d)   The undersigned registrant hereby undertakes to file an application for the purpose of determining the eligibility of the trustees to act under subsection (a) of Section 310 of the Trust Indenture Act in accordance with the rules and regulations prescribed by the Securities and Exchange Commission under Section 305(b) (2) of the Securities Act.

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SIGNATURES

        Pursuant to the requirements of the Securities Act of 1933, as amended, Amgen Inc. certifies that it has reasonable grounds to believe that it meets all of the requirements for filing on Form S-3 and has duly caused this Amendment No. 1 to the registration statement to be signed on its behalf by the undersigned, thereunto duly authorized, in the City of Thousand Oaks, State of California, on October 7, 2003.

    AMGEN INC.

 
 
By
*
Kevin W. Sharer
 Chairman of the Board, Chief Executive Officer,
President and Director

        Pursuant to the requirements of the Securities Act of 1933, as amended, this Amendment No. 1 to the registration statement has been signed by the following persons in the capacities and on the dates indicated.

Signature
   Title
   Date

 
 
 
 
 
*
Kevin W. Sharer		   Principal Executive Officer; Chairman of the Board, Chief Executive Officer, President and Director   October 7, 2003

*
Richard D. Nanula
 
Principal Financial Officer; Executive Vice President, Finance, Strategy and Communications and Chief Financial Officer
 
October 7, 2003

*
Barry D. Schehr
 
Principal Accounting Officer; Vice President, Financial Operations
 
October 7, 2003

*
David Baltimore
 
Director
 
October 7, 2003

*
Frank J. Biondi, Jr.
 
Director
 
October 7, 2003
         

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*
Jerry D. Choate
 
Director
 
October 7, 2003

*
Edward V. Fritzky
 
Director
 
October 7, 2003

*
Frederick W. Gluck
 
Director
 
October 7, 2003

*
Franklin P. Johnson, Jr.
 
Director
 
October 7, 2003

*
Steven Lazarus
 
Director
 
October 7, 2003

*
Gilbert S. Omenn
 
Director
 
October 7, 2003

*
Judith C. Pelham
 
Director
 
October 7, 2003

*
J. Paul Reason
 
Director
 
October 7, 2003

*
Donald B. Rice
 
Director
 
October 7, 2003

*
Patricia C. Sueltz
 
Director
 
October 7, 2003
*By:   /s/  STEVEN M. ODRE      
Steven M. Odre
 Attorney-in-Fact		  

II-4


AMGEN INC. REGISTRATION STATEMENT ON FORM S-3
EXHIBIT INDEX

Exhibit No.
   Description
1.1*   Underwriting Agreement.
3.1(1)   Restated Certificate of Incorporation as amended.
3.2(2)   Amended and Restated Bylaws of Amgen Inc. (as amended May 14, 2003).
3.3(3)   Certificate of Amendment of Restated Certificate of Incorporation.
3.4(4)   Certificate of Designations of Series A Junior Participating Preferred Stock.
4.1***   Indenture, dated as of August 4, 2003, between Amgen Inc. and JPMorgan Chase Bank, as Trustee.
4.2*   Form of Note.
4.5(1)   Form of stock certificate for the common stock, par value $.0001 per share, of the Company.
4.6(5)   Amended and Restated Rights Agreement, dated as of December 12, 2000, between Amgen Inc. and American Stock Transfer & Trust Company, as Rights Agent.
4.7*   Form of Warrant Agreement.
4.8   Form of Warrant Certificate. (to be included in Exhibit 4.7).
4.9*   Form of Deposit Agreement.
4.10   Form of Depositary Receipt. (to be included in Exhibit 4.9).
4.11*   Form of Purchase Contract.
4.12*   Form of Purchase Unit.
5.1***   Opinion of Latham & Watkins LLP.
12.1***   Statement Regarding the Computation of Ratio of Earnings to Fixed Charges.
23.1   Consent of Independent Auditors (Ernst & Young LLP).
23.2   Consent of Latham & Watkins LLP (included in Exhibit 5.1).
24.1***   Power of Attorney.
25.1**   Statement of Eligibility on Form T-1 under the Trust Indenture Act of 1939, as amended, of JPMorgan Chase Bank, as Trustee under the Indenture.
*
To be filed by amendment or as an exhibit to a report filed under the Securities Exchange Act of 1934, as amended, and incorporated herein by reference.

**
Previously filed pursuant to Section 305(b)(2) of the Trust Indenture Act of 1939, as amended, and incorporated herein by reference.

***
Previously filed.

(1)
Filed as an exhibit to the Quarterly Report on Form 10-Q for the quarter ended March 31, 1997 on May 13, 1997 and incorporated herein by reference.

(2)
Filed as an exhibit to the Quarterly Report on Form 10-Q for the quarter ended June 30, 2003 on July 30, 2003 and incorporated herein by reference.

(3)
Filed as an exhibit to the Quarterly Report on Form 10-Q for the quarter ended June 30, 2000 on August 1, 2000 and incorporated herein by reference.

(4)
Filed as an exhibit to the Annual Report on Form 10-K for the year ended December 31, 2000 on March 7, 2001 and incorporated herein by reference.

(5)
Filed as an exhibit to the Current Report on Form 8-K dated December 13, 2000 on December 18, 2000 and incorporated herein by reference.


QuickLinks

TABLE OF CONTENTS
ABOUT THIS PROSPECTUS
FORWARD-LOOKING STATEMENTS
WHERE YOU CAN FIND MORE INFORMATION
AMGEN
RISK FACTORS
USE OF PROCEEDS
RATIO OF EARNINGS TO FIXED CHARGES
DESCRIPTION OF SECURITIES
DESCRIPTION OF DEBT SECURITIES
DESCRIPTION OF CAPITAL STOCK
DESCRIPTION OF WARRANTS
DESCRIPTION OF SECURITIES PURCHASE CONTRACTS AND SECURITIES PURCHASE UNITS
DESCRIPTION OF DEPOSITARY SHARES
GLOBAL SECURITIES
PLAN OF DISTRIBUTION
EXPERTS
VALIDITY OF THE SECURITIES
PART II. INFORMATION NOT REQUIRED IN PROSPECTUS
SIGNATURES
AMGEN INC. REGISTRATION STATEMENT ON FORM S-3 EXHIBIT INDEX

Exhibit 23.1

Consent of Ernst & Young LLP, Independent Auditors

        We consent to the reference to our firm under the caption "Experts" in the Registration Statement (Form S-3) and related Prospectus of Amgen Inc. for the registration of debt securities, common stock, associated preferred share purchase rights, preferred stock, warrants to purchase debt securities, common stock or preferred stock, securities purchase contracts, securities purchase units and depositary shares of Amgen Inc. and to the incorporation by reference therein of our report dated January 24, 2003, with respect to the consolidated financial statements and schedule of Amgen Inc. included in its Annual Report (Form 10-K) for the year ended December 31, 2002, filed with the Securities and Exchange Commission.


 
 
 
/s/ ERNST & YOUNG LLP    

 
 
 
Los Angeles, CA
October 6, 2003