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 a planned acquisition (the "Acquisition") between Amgen
Inc. ("Amgen") and 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 sent an email message to all of its staff regarding
the Acquisition. The text of the email message follows.

Memorandum  [AMGEN LOGO]

To:    All Amgen Staff

From:  Kevin Sharer

Date:  December 17, 2001

Re:    Acquisition of Immunex

I am pleased to tell you that we have agreed to acquire Seattle-based Immunex,
one of the biotech industry's fastest-growing and most-respected companies.
Strategically, this acquisition is great for Amgen. The company has a product we
think is terrific-Enbrel(R), for rheumatoid arthritis patients. Enbrel(R)
changes patient's lives in a dramatic way. It is a market-leading product with
nearly $1 billion in sales expected in 2002 and potential for $3 billion or more
in subsequent years.

Enbrel(R) is the fastest-growing biologic drug ever. Our core competencies in
bringing successful drugs to market and optimizing their potential will help
Enbrel(R) achieve its full promise. We'll add this additional blockbuster to our
portfolio. We'll also become an instant leader in a new therapeutic area,
inflammation, enhancing our already strong leadership position in oncology and
nephrology. Inflammation is a very large and opportunity-rich area for us and
very underserved from a patient perspective. It complements the pipeline
products and research we already have in inflammation.

Immunex is a great company with a lot of great people. They have a culture that
is very much like ours. They share our values, our biotechnology heritage and
they are located on the West Coast.




Financially, the acquisition is attractive to our shareowners. It is very
modestly dilutive, less than 5 percent in 2003. Adding Immunex, we expect to
increase our long-term product sales growth rate to the low-30s and our cash
earnings per share growth rate to the mid-20s for the 2001-2005 period.

While the acquisition of Immunex isn't expected to close until mid-2002, pending
customary regulatory approvals and shareholder votes, we are already planning
how best to integrate Immunex into Amgen so that all of our goals with this
transaction will be met. I will be CEO of the combined company, and the CEO of
Immunex, Ed Fritzky, will join Amgen's Board of Directors. We also are fortunate
to have two executives from Immunex join Amgen's Executive Committee. Peggy
Phillips will be an Executive Vice President, reporting to me. Doug Williams,
who now runs discovery research at Immunex, will be a Senior Vice President,
reporting to Roger Perlmutter and overseeing discovery research in Seattle.

On behalf of the Executive Committee, I couldn't be more excited about this new
chapter in Amgen's development and the opportunity it represents for our
company, staff, shareholders and the millions of patients around the world and
others who look to us to create the medicines of the future.

WEBSITE AND WEBCAST ANNOUNCEMENT
- --------------------------------

For more information on the acquisition announcement, go to
http://amgen.acquisitioninformation.com
- ---------------------------------------

There will be a conference call with the investment community on Monday,
December 17, 2001, at 6:00 a.m. PST/9:00 a.m. EST. To access the conference
call, dial (877) 817-2450 or (706) 634-7548. Live audio of the conference call
and slides that will be used to facilitate discussion can be accessed on the
Internet by going to http://amgen.acquisitioninformation.com and following the
appropriate links.

Replays will be available for 30 days beginning about four hours after the
call's conclusion. To access the replay on the Internet, go to
http://amgen.acquisitioninformation.com and follow the appropriate links. For
staff to replay the call from your telephone, dial (800) 642-1687 or (706)
645-9291. The pass code is 271-2097.

For Thousand Oaks staff, the video replay will be available Tuesday, December 18
- - Friday, December 21, from noon to 1:00 p.m. in the Bistro, Oasis and Terrace
cafeterias.

Additional Information and Where to Find It
- -------------------------------------------

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.