Filed by Amgen Inc. Pursuant to Rule 425
                                                under the Securities Act of 1933
                                        and deemed filed pursuant to Rule 14a-12
                                       under the Securities Exchange Act of 1934

                                            Subject Company: Immunex Corporation
                                                     Commission File No. 0-12406


This filing relates to the proposed acquisition ("Acquisition") by Amgen Inc.
("Amgen") of Immunex Corporation ("Immunex") pursuant to the terms of an
Agreement and Plan of Merger, dated as of December 16, 2001 (the "Merger
Agreement"), by and among Amgen, AMS Acquisition Inc. and Immunex. The Merger
Agreement is on file with the Securities and Exchange Commission as an exhibit
to the Current Report on Form 8-K, as amended, filed by Amgen today, December
17, 2001, and is incorporated by reference into this filing.

On December 17, 2001, Amgen made the following information regarding the
Acquisition available at http://amgen.acquisitioninformation.com and, by
                         ---------------------------------------
following the appropriate links, on its website at www.amgen.com:
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                           Combined Company Fact Sheet

AMGEN                                                                    IMMUNEX

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Strategic Rationale
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[_]  Amgen's acquisition of Immunex brings together two of the world's fastest
     growing biotech companies, significantly accelerating Amgen's long-term
     growth.
[_]  The new Amgen will have an unparalleled, diversified portfolio of 3
     blockbuster drugs with long patent lives, including Amgen's EPOGEN(R) and
     NEUPOGEN(R) and Immunex's ENBREL(R), along with Amgen's potential
     blockbuster Aranesp(TM).
[_]  The new Amgen will have leadership in three targeted therapeutic areas -
     nephrology, oncology, and inflammation - with a rich pipeline and R&D focus
     in proteins and antibodies.
[_]  Acquisition of Immunex will increase Amgen's long-term product sales growth
     rate to the low 30s and cash EPS growth rate to the mid-20s, driven by
     potential ENBREL(R) sales of $3 billion or more by 2005.

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Transaction Summary
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Structure        Tax-free reorganization (Immunex shareholders will not be taxed
                 to the extent that they exchange their Immunex stock for Amgen
                 stock)

Terms            Immunex shareholders receive 0.44 shares of Amgen common stock
                 and cash of $4.50 for each Immunex share






Total value                Approximately $16 billion
Ownership                  Amgen shareholders 81%; Immunex shareholders 19%
                           Amgen will purchase AHP's 41% stake in Immunex,
                           giving AHP an 8% stake in the new company, which is
                           expected to be reduced over time
Accounting                 Purchase
Expected Closing           Second Half 2002

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Key Product Lineup
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Marketed Products                      Pipeline
- -----------------                      --------
Oncology-NEUPOGEN(R), Thioplex(R)      Oncology-Aranesp(TM), KGF, Pegfilgrastim,
Inflammation-ENBREL(R), Kineret(TM)    Epratuzumab, Novantrone(R), ABX-EGF
Nephrology - EPOGEN(R), Aranesp(TM)    Inflammation-sTNF-RI, IL-1 r2
                                       Nephrology-Calcimimetics

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Key Financials
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                    Amgen LTM*          Immunex LTM*           Pro Forma 2002**
                    ---------           -----------            --------------
Annual Revenues     $3.8 Billion        $861 Million           $5.5 Billion
Net Income          $1.1 Billion        $154 Million           $1.5 Billion

Cost Synergies      Estimated cost synergies are expected to total more than
                    $200 million in 2003, and more than $250 million in 2004.

 * Last Twelve Months as of September 30, 2001
** Based on H2 2002 close

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Management
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Chairman & CEO         Kevin Sharer      EVP, Sales & Marketing   George Morrow
EVP, R&D               Roger Perlmutter  EVP, Operations          Dennis Fenton
EVP, Finance/Strategy  Richard Nanula    EVP                      Peggy Phillips

This document contains forward-looking statements which are based on
management's current expectations and beliefs and are subject to a number of
risks, uncertainties and assumptions that could cause actual results to differ
materially from those described in the forward-looking statements. Risks,
uncertainties and assumptions include those risks that are described in the
Important Notice contained on this website and in the Securities and Exchange
Commission reports filed by Amgen and Immunex, including their most recent
filings on Form 10-Q. Amgen and Immunex assume no obligation and expressly
disclaim any duty to update information contained in this document except as
required by law.

Additional Information and Where to Find It
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In connection with Amgen's proposed acquisition of Immunex, Amgen and Immunex
intend to file with the SEC a joint proxy statement/prospectus and other
relevant materials. INVESTORS AND SECURITY HOLDERS OF AMGEN AND IMMUNEX ARE
URGED TO READ THE JOINT PROXY STATEMENT/PROSPECTUS AND THE OTHER RELEVANT
MATERIALS WHEN THEY BECOME AVAILABLE BECAUSE THEY WILL CONTAIN IMPORTANT
INFORMATION ABOUT AMGEN, IMMUNEX AND THE ACQUISITION. The joint proxy
statement/prospectus and other relevant materials (when they become available),
and any other documents filed by Amgen or Immunex with the SEC, may be obtained
free of charge at the SEC's web site at www.sec.gov. In addition, investors and
security holders may obtain free copies of the documents filed with the SEC by
Amgen by directing a request to: Amgen Inc., One Amgen Center Drive, Thousand
Oaks, CA 91320-1799, Attn: Investor Relations. Investors and security holders
may obtain free copies of the documents filed with the SEC by Immunex by
contacting Immunex's Investor Relations department at 51 University Street,
Seattle, WA 98101. Investors and security holders are urged to read the joint
proxy statement/prospectus and the other



relevant materials when they become available before making any voting or
investment decision with respect to the acquisition.

Amgen, Immunex and their respective executive officers and directors may be
deemed to be participants in the solicitation of proxies from the stockholders
of Amgen and Immunex in favor of the acquisition. Information about the
executive officers and directors of Amgen and their ownership of Amgen common
stock is set forth in the proxy statement for Amgen's 2001 Annual Meeting of
Shareholders, which was filed with the SEC on April 4, 2001. Information about
the executive officers and directors of Immunex and their ownership of Immunex
common stock is set forth in the proxy statement for Immunex's 2001 Annual
Meeting of Shareholders, which was filed with the SEC on March 16, 2001.
Investors and security holders may obtain more detailed information regarding
the direct and indirect interests of Amgen, Immunex and their respective
executive officers and directors in the acquisition by reading the joint proxy
statement/prospectus regarding the acquisition when it becomes available.

Forward-Looking Statements
This document contains forward-looking statements within the meaning of the
"safe harbor" provisions of the Private Securities Litigation Reform Act of
1995, including statements about future financial and operating results and
Amgen's anticipated acquisition of Immunex. These statements are based on
management's current expectations and beliefs and are subject to a number of
risks, uncertainties and assumptions that could cause actual results to differ
materially from those described in the forward-looking statements. All
statements other than statements of historical fact are statements that could be
deemed forward-looking statements. For example, statements of expected
synergies, accretion, timing of closing, industry ranking, execution of
integration plans and management and organizational structure are all
forward-looking statements. Risks, uncertainties and assumptions include the
possibility that the market for the sale of certain products and services may
not develop as expected; that development of these products and services may not
proceed as planned; the Immunex acquisition does not close or that the companies
may be required to modify aspects of the transaction to achieve regulatory
approval; that prior to the closing of the proposed acquisition, the businesses
of the companies suffer due to uncertainty; that the parties are unable to
successfully execute their integration strategies, or achieve planned synergies;
and other risks that are described in the Securities and Exchange Commission
reports filed by Amgen, including its most recent Form 10-Q. Amgen conducts
research in the biotechnology/pharmaceutical field where movement from concept
to product is uncertain; consequently, there can be no guarantee that any
particular product candidate will be successful and become a commercial product.

Furthermore, Amgen's research, testing, pricing, marketing and other operations
are subject to extensive regulation by domestic and foreign government
regulatory authorities. In addition, sales of Amgen's products are affected by
reimbursement policies imposed by third party payors, including governments,
private insurance plans and managed-care providers. These government regulations
and reimbursement policies may affect the development, usage and pricing of
Amgen's products.

In addition, while Amgen routinely obtains patents for Amgen's products and
technology, the protection offered by Amgen's patents and patent applications
may be challenged, invalidated or circumvented by our competitors.

Because forward-looking statements involve risks and uncertainties, actual
results and events may differ materially from results and events currently
expected by Amgen and Immunex. Amgen and Immunex assume no obligation and
expressly disclaim any duty to update information contained in this document
except as required by law.

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