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.

The following is the text of questions and answers that Amgen has prepared for
its directors and officers to use in responding to questions regarding the
Acquisition:

For Internal Use Only

                               IMMUNEX ACQUISITION

                         INTERNAL QUESTIONS AND ANSWERS

Strategic Rationale/Transaction

What is driving this deal?

This transaction is a strategically compelling combination of two of the world's
most successful and fastest growing biotechnology companies. It represents a key
step in accelerating Amgen's long-term growth program, will establish immediate
leadership in Inflammation, and should enable ENBREL(R) to achieve its full
potential.

Why does this transaction make sense for Amgen?  For Immunex?

For Amgen, it will add ENBREL(R) to the company's already impressive portfolio
of blockbuster and near-blockbuster drugs; will make it the leader in
inflammation, adding to its leadership in oncology and nephrology; and will
substantially enhance the company's discovery research capabilities in proteins
and antibodies. It will increase Amgen's compound annual growth rate from the
low 20s to the mid-20s and increases its financial strength. For Immunex, it
will bring Amgen's core competencies in bringing successful drugs to market and
optimizing their success, ensuring that ENBREL(R) can reach its full potential.

Does this acquisition signal a change in strategy for Amgen?

No. This acquisition simply accelerates our growth plan. It is a reaffirmation
of our longstanding commitment to biotech, and to achieving a leadership
position in each of the therapeutic areas we've targeted.



For Internal Use Only

To what extent was there any prior relationship between Amgen and Immunex? Amgen
and American Home Products?

None.

Did Amgen explore other companies as potential acquisition targets? Has Immunex
had discussions with other potential acquirers?

Amgen maintains an active M & A department that screens and analyzes numerous
companies. While we would prefer not to reveal other explorations we have
undertaken, we can say that Immunex meets most of the requirements that we have
for the ideal acquisition candidate.

Do you anticipate any Hart-Scott-Rodino or other regulatory problems?

We will need to make a filing with the regulatory authorities and we cannot
predict the outcome of that process.

What other regulatory approvals are required?

None.

Can Immunex consider other offers?

It can't solicit other offers but the Immunex Board has the ability to exercise
their fiduciary duties. This transaction has the unanimous support of their
board and the commitment of their largest shareholder (41%) to support this
deal. We fully expect this deal to go through.

Operations/Integration

Who will have primary responsibility for the integration process? Do you have an
integration plan laid out? Have integration teams been formed?

We are committed to integrating the two companies as smoothly and quickly as
possible after the closing. Peggy Phillips, COO at Immunex, will be working with
Amgen's Fabrizio Bonanni, Senior VP for Quality and Compliance, to head up the
integration team to plan this process. Until the transaction is actually closed,
we have a limited ability to take specific integration actions.

How will patients be affected?

Patients will be better served by the integration of these two companies through
greater potential for the development of new drugs. In particular, ENBREL(R)
users should benefit from the acquisition as Amgen's protein manufacturing
expertise will help increase supply of that drug in the longer term.

What will happen to Immunex's Seattle headquarters? What are your plans for the
new facility under production in Rhode Island?

We currently intend to make Seattle our Inflammation headquarters and complete
Immunex's second facility in Rhode Island. Payments for the first phase of the
BioNext manufacturing building project in Rhode Island are already completed,
and we anticipate it will take about $400-$500M to get the next building phase
up and running.

Why did you decide to place the inflammation headquarters in Seattle, not in
Thousand Oaks?

Immunex's expertise in inflammation is significant.

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For Internal Use Only

Will the Immunex name be retained in any form?

No.

Who will fill the top operating positions?

There won't be any significant changes in Amgen's operating leadership. Peggy
Phillips is expected to become Executive Vice President and Doug Williams is
expected to become Senior Vice President. Phillips will report to Kevin Sharer,
and Williams to Roger Perlmutter.

What will Amgen's board makeup be?

Ed Fritzky, currently Chairman and Chief Executive Officer of Immunex, will
relinquish that title and join Amgen's board. That is the only change as a
result of this deal.

This news seems to be adding an enormous amount of stress to an already
overworked organization.

The stress is relatively short term. To smooth the process, we will have a
highly capable integration team.

What impact will this acquisition have on our Alignment Initiative activities?

The alignment initiative efforts will continue to unfold as planned.

Human Resources

How will this acquisition affect Amgen's inflammation team?

Amgen plans to base its inflammation research activities in Seattle.

Are the cultures of Amgen and Immunex compatible?

Amgen and Immunex have a strong cultural fit. Both companies are science-based,
entrepreneurial in spirit, and have an unwavering commitment to biotech.

If a staff member wants to move from one business unit or geographic location to
another, will there be opportunities to do so?

This will be resolved on a case-by-case basis.

Should we hold off on planned purchases or contract negotiations, etc., until we
hear more?

Each business leader will be making those decisions.

Should we put current work/purchasing/hiring plans on hold? What about
promotions or new hires now under way? Are these frozen or should we move
forward as planned?

Each business leader will be making those decisions.

How many layoffs do you expect as a result of this deal, and where will they
come from?

Keep in mind that this acquisition is about growing the company. We'll be taking
a look at what we will have in Seattle and what our development plans are there,
and what overlaps there are, and making sure we grow efficiently following the
closing.

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For Internal Use Only

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

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For Internal Use Only

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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