IMMUNEX CORP /DE/
8-K, 1996-07-24
BIOLOGICAL PRODUCTS, (NO DIAGNOSTIC SUBSTANCES)
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<PAGE>

                          SECURITIES AND EXCHANGE COMMISSION

                               WASHINGTON, D.C.  20549

                                       FORM 8-K

                                    CURRENT REPORT

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

           Date of report (Date of earliest event reported):  July 1, 1996



                                  IMMUNEX CORPORATION
             (Exact name of each registrant as specified in its charter)


                                       WASHINGTON
                    (State or other jurisdiction of incorporation)


                                         0-12406
                               (Commission File Number)


                                        51-0346580
                          (IRS Employer Identification No.)

                       51 UNIVERSITY STREET, SEATTLE, WA  98101
                (Address of principal executive offices and zip code)

                                    (206) 587-0430
                 (Registrant's telephone number, including area code)

                                         NONE
            (Former name or former address, if changed since last report)

                           Exhibit Index appears on page 6.

<PAGE>

 ITEM 5.  OTHER EVENTS

    On July 17, 1996, the Board of Directors of Immunex Corporation ("Immunex")
approved the terms of revised and amended research agreements among Immunex,
American Cyanamid Company ("Cyanamid") and American Home Products Corporation
("AHP") relating to oncology products and tumor necrosis factor receptor
("TNFR").  Following such approval, Immunex, Cyanamid and AHP entered into a new
Research Agreement effective July 1, 1996, which terminates and replaces the
Research and Development Agreement between Immunex and Cyanamid dated as of
June 1, 1993.  Immunex and AHP also (i) entered into a new TNFR License and
Development Agreement effective as of July 1, 1996, and (ii) amended the Immunex
New Oncology Product License Agreement between Immunex and Cyanamid dated
June 1, 1993 effective as of July 1, 1996 (the "INOP Amendment").

    Under the terms of the new and amended agreements, Immunex retains North
American marketing rights to TNFR and those oncology products resulting from its
own research.  AHP retains ex-North American rights to oncology products
discovered by Immunex.  Immunex's 1996 funding commitment to support oncology
research and development at AHP will decrease from a $26 million to a $16
million annual rate, plus shared expenses of collaborative development.
Immunex's obligation to contribute to AHP oncology discovery research will
continue at this level in subsequent years, with certain annual adjustments.

    Immunex's rights with respect to AHP oncology products are converted into
an option to obtain North American marketing rights to oncology products arising
from certain discovery research activities conducted by the Wyeth-Ayerst
Research Division ("Wyeth") of AHP that are supported by Immunex contributions.
Immunex's product rights do not extend to any products resulting from third
party collaborations of AHP, products or technology acquired by AHP from third
parties, or certain non-small molecule products developed by AHP.

    The option held by Immunex will be exercisable for a period of 90 days
following receipt by Immunex of notice from Wyeth that a product has been
selected by Wyeth for preclinical and clinical development, together with
certain relevant information concerning such product.  If Immunex exercises its
option, the parties will negotiate and develop the terms of a product license
and development agreement under which Immunex will be granted exclusive
marketing rights in the United States and Canada.  If Immunex elects not to
exercise its option, all rights in the product will revert to Wyeth and AHP
without further obligations of any kind on Immunex.  Immunex will also be
entitled to discontinue its support of the development process at certain
decision events coordinated with the product development cycle.  If its decision
to discontinue development occurs following the completion of Phase II or
Phase III studies, Immunex will be entitled to a

<PAGE>

royalty or revenue sharing if AHP continues to develop the product or licenses
the product to a third party in North America.

    Under the terms of the INOP Amendment, Immunex will provide notice to
Cyanamid if an Immunex product is selected by Immunex for preclinical and
clinical development, together with certain relevant information concerning such
product.  Following receipt of such notice and information, Cyanamid will have
90 days in which to notify Immunex that it intends to retain its rights in such
product.  If Cyanamid elects to retain its rights, the parties will negotiate
and develop the terms of a product development agreement governing the ongoing
development and commercialization of the retained product.  If Cyanamid does not
elect to retain its rights, all rights in the product will revert to Immunex
without further obligations of any kind to Cyanamid or AHP.

    The right of first refusal (the "ROFR") previously held by Cyanamid that
applies to Immunex products and technology was transferred to AHP under the new
Research Agreement and amended to address the diversity of technologies and
opportunities that may result from Immunex research, as well as the data needed
by Wyeth to make a decision regarding exercise of the ROFR.  The ROFR was
extended to include TNFR and Immunex oncology products.  However, a 90-day,
rather than 180-day, decision period will apply to these products.  At Immunex's
request, AHP will review any product prior to completion of Phase I clinical
studies to exclude products of no interest to AHP.

    Immunex and AHP entered into a new TNFR License and Development Agreement
(the "TNFR Agreement") which restates AHP's exclusive rights to TNFR outside of
North America and addresses joint project management, cost sharing,
manufacturing responsibilities, intellectual property protection and disposition
of rights upon relinquishment or termination of product development.
Previously, AHP's rights in TNFR had been stated in the Research and Development
Agreement between Immunex and Cyanamid.  This has been terminated and replaced
by the new Research Agreement discussed above.  Pursuant to the TNFR Agreement,
Immunex and AHP have also agreed to negotiate the terms of a manufacturing
agreement for the commercial supply of TNFR to AHP.


<PAGE>

 ITEM 7.  FINANCIAL STATEMENTS AND EXHIBITS

    The following exhibits are filed with this report:


Exhibit Number   Description
- --------------   -----------
10.1             Research Agreement by and among the Wyeth-Ayerst Research
                 division of American Home Products Corporation, the Lederle
                 Pharmaceutical division of American Cyanamid Company and
                 Immunex Corporation dated as of July 1, 1996.

10.2             TNFR License and Development Agreement by and between the
                 Wyeth-Ayerst Laboratories division of American Home Products
                 Corporation and Immunex Corporation dated as of July 1, 1996.

10.3             Amendment No. 1 to Immunex New Oncology Product License
                 Agreement by and between Immunex Corporation and American
                 Cyanamid Company dated as of July 1, 1996.

99.1             Press release issued on July 17, 1996 with respect to the
                 Research Agreement.

<PAGE>

                                      SIGNATURE

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

                                       IMMUNEX CORPORATION

                                       By:  /s/ Scott G. Hallquist
                                            ----------------------
                                       Name:  Scott G. Hallquist
                                       Title:  Senior Vice President; General
                                               Counsel; Secretary

Dated:  July 24, 1996


<PAGE>

                                     EXHIBIT INDEX

Number   Description
- ------   -----------
10.1     Research Agreement by and among the Wyeth-Ayerst Research division of
         American Home Products Corporation, the Lederle Pharmaceutical
         division of American Cyanamid Company and Immunex Corporation dated as
         of July 1, 1996.

10.2     TNFR License and Development Agreement by and between the Wyeth-Ayerst
         Laboratories division of American Home Products Corporation and
         Immunex Corporation dated as of July 1, 1996.

10.3     Amendment No. 1 to Immunex New Oncology Product License Agreement by
         and between  Immunex Corporation and American Cyanamid Company dated
         as of July 1, 1996.

99.1     Press release issued on July 17, 1996 with respect to the Research
         Agreement.



<PAGE>




                                                               REDACTED VERSION


                                     EXHIBIT 10.1

                                          TO

                                IMMUNEX CORPORATION'S

                                       FORM 8-K

                                        DATED

                                    JULY 24, 1996





    "[*]" = omitted, confidential material, which material has been
separately filed with the Securities and Exchange Commission pursuant to a
report for confidential treatment.

<PAGE>
 
                                                                   EXHIBIT 10.1










                                  RESEARCH AGREEMENT

                                     BY AND AMONG

                        THE WYETH-AYERST RESEARCH DIVISION OF

                         AMERICAN HOME PRODUCTS CORPORATION,

                        THE LEDERLE PHARMACEUTICAL DIVISION OF

                              AMERICAN CYANAMID COMPANY

                                         AND

                                 IMMUNEX CORPORATION
<PAGE>

                                                                   EXHIBIT 10.1


                                   RESEARCH AGREEMENT

    THIS AGREEMENT is made as of this 1st day of July, 1996 ("Effective Date")
by and among AMERICAN HOME PRODUCTS CORPORATION, a corporation organized and
existing under the laws of the State of Delaware ("AHPC"), acting through its
Wyeth-Ayerst Research Division ("W-AR"), AMERICAN CYANAMID COMPANY, a
corporation organized and existing under the laws of Maine and a wholly-owned
subsidiary of AHPC ("ACY"), acting through its Lederle Pharmaceutical (formerly
Lederle Laboratories) division ("Lederle"), and IMMUNEX CORPORATION, a
corporation organized and existing under the laws of the State of Washington,
together with its Affiliates ("Immunex").

    WHEREAS, Immunex and ACY entered into that certain Research and Development
Agreement dated as of June 1, 1993 (the "Research and Development Agreement")
providing for, among other things, the financial support by Immunex of oncology
research and development by ACY and the collaboration of the parties in oncology
research and development as set forth in said agreement; and

    WHEREAS, the oncology research and development activities of ACY are
currently being conducted by W-AR and Lederle (collectively, "Wyeth");
    WHEREAS, the parties hereto desire to terminate the Research and
Development Agreement and to replace it with this Agreement on the terms and
conditions set forth herein and the TNFR Agreement (as defined herein).

    NOW THEREFORE, in consideration of the premises, representations and
warranties set forth herein, the parties hereto agree as follows:

                               ARTICLE 1.  DEFINITIONS

    1.01  "Affiliate" shall mean any corporation or business entity of which a
party owns directly or indirectly, fifty percent (50%) or more of the assets or
outstanding stock, or any corporation which a party directly or indirectly
controls, or any parent corporation that owns, directly or indirectly, fifty
percent (50%) or more of the assets or outstanding stock of a party or directly
or indirectly controls a party.  For purposes of this Agreement, the parties and
their Affiliates shall not be deemed to be Affiliates of each other.

    1.02  "AHPC/ACY Patent(s)" shall mean all AHPC/ACY Granted Patents and
patent applications relating to WNOP(s), Joint Patents, or third-party patents
or patent applications in which AHPC/ACY has a licensable interest, that are
necessary or useful in order to research, develop, make, have made, market, use,
import, offer for


<PAGE>

sale, or sell WNOP(s), and any reissues, re-examinations, continuations,
continuations-in-part, divisions, renewals, extensions, patents of addition, and
any extension of the term of the patent or supplementary protection certificate
or other means by which greater effective patent protection is extended that
exist as of the Effective Date or are issued or filed at any time during the
term of this Agreement.

    1.03  "Amended INOP Agreement" shall mean the Immunex New Oncology Product
License Agreement, dated June 1, 1993, between Immunex and ACY, as amended by
Amendment No. 1 dated the date hereof.

    1.04  "Combination Product(s)" shall mean any pharmaceutical or biological
preparation in finished form that contains Relinquished WNOP(s) in combination
with one or more other active ingredients.

    1.05  "Distributor" shall mean any unaffiliated third party that purchases
Products in finished form (in final packaged form bearing Immunex tradedress)
for resale in a particular part of the Territory.

    1.06  "Field" shall mean the diagnosis or treatment of cancerous or
precancerous transitional or neoplastic diseases or conditions in human beings.

    1.07  "Governance Agreement" shall mean the Amended and Restated Governance
Agreement among American Cyanamid Company, Lederle Oncology Corporation and
Immunex Corporation dated as of December 15, 1992.

    1.08  "Granted Patent(s)" shall mean any claims of an issued and unexpired
Patent that has not been revoked or held unenforceable or invalid by a decision
of a court or other governmental agency of competent jurisdiction, or that
remains unappealable or unappealed within the time allowed for appeal, or that
has not been disclaimed, denied or admitted to be invalid or unenforceable
through reissue, re-examination, disclaimer or otherwise, and shall refer to
patents owned solely by Immunex ("Immunex Granted Patents"), patents owned
solely by AHPC and/or ACY ("AHPC/ACY Granted Patents"), or patents owned jointly
by the parties ("Joint Granted Patents"), however appropriate.

    1.09  "Health Care Market" shall mean end users of health care products,
health care professionals or treatment providers, hospitals, clinics, health
maintenance organizations, wholesalers, Distributors, manufacturers of systems
or equipment that incorporate Products or Technology as enabling technology,
operating components or reagents, and third parties who assist in the sale,
marketing or distribution of Products or Technology other than by co-promotion
or co-marketing arrangements.

                                         -2-

<PAGE>

    1.10  "Immunex Patent(s)" shall mean all Immunex Granted Patents and patent
applications and any third party patents and patent applications in which
Immunex has a licensable interest, that are necessary or useful in order to
research, develop, make, have made, market, use, import, offer for sale, sell,
or have sold Product(s), and any reissues, re-examinations, continuations,
continuations-in-part, divisions, renewals, extensions, patents of addition, and
any extension of the term of the patent or supplementary protection certificate
or other means by which greater effective patent protection is extended that
exist as of the Effective Date of or are issued or filed at any time during the
term of this Agreement.

    1.11  "Intellectual Property" shall mean Patent(s) and Technology and where
appropriate may specifically refer to Intellectual Property solely owned or
controlled by Immunex (the "Immunex Intellectual Property"), solely owned or
controlled by AHPC/ACY (the "AHPC/ACY Intellectual Property"), or jointly owned
or controlled by the parties hereto (the "Joint Intellectual Property").

    1.12  "Immunex New Oncology Product" or "INOP" shall have the meaning
accorded thereto in the Amended INOP Agreement.

    1.13  "Immunex Territory" shall mean North America (as defined herein).

    1.14  "Joint Patent(s)" shall mean all Granted Patents and patent
applications of which AHPC and/or ACY is a joint owner with Immunex, as
determined by the patent laws of the United States or as otherwise expressly
provided for by the parties.

    1.15  "Manufacturing Cost" shall mean, for each quantity of an Elected
WNOP, the cost to the manufacturing party or its Affiliate(s) for raw materials,
energy, labor (salary and benefits), and reasonable overhead charges relating to
the manufacture, quality control testing and delivery of such Product, and other
direct and allocable indirect costs to manufacture such Product, including but
not limited to royalties to an unaffiliated third party on licensed technology,
manufacturing charges for inventory adjustments, for offgrade or defective
material, handling losses, physical adjustments, salvage and start-up, all such
costs and charges to be calculated on a basis consistent with then current
methods and practices applied to all other products manufactured by the
manufacturing party, as the case may be, at the facility or facilities used for
production.  If such Product is manufactured by a party that is not an Affiliate
of a party to this Agreement, the Manufacturing Cost shall be the amount payable
to the unaffiliated third party on arm's-length dealing with such manufacturer
plus any costs needed to complete manufacture quality control testing and
delivery of such Products.  Manufacturing Cost shall not include capital costs,
other than depreciation, or opportunity costs for contract manufacturing.

                                         -3-

<PAGE>


    1.16  "Market Launch" shall mean on a country by country basis, the first
commercial sale of a Product(s) in that country.

    1.17  "Materials" shall mean any and all compounds, culture media, assay
systems, DNA, RNA, and fragments thereof, genes and other nucleotide constructs,
plasmids, vectors, development strains, expression systems, cell lines,
antibodies, hybridomas, clones, peptides, protein compositions, colonies, animal
models, promoters, epitopes, microorganisms and any other biological or chemical
materials, as well as the information embodied therein, that are necessary or
useful in developing, manufacturing, using, marketing, or selling Product(s).

    1.18  "Net Sales" shall mean the gross invoice price of Relinquished
WNOP(s) sold by Wyeth, its Affiliates, sublicensees, distributors or other
designees to an independent third party after deducting, if not already deducted
in the amount invoiced:
        (i)   the standard inventory cost (actual acquisition cost) of devices
used for dispensing or administering such Product(s) and that accompany such
Product(s) as they are sold;
        (ii)  then normal or customary trade, cash, and/or quantity discounts;
        (iii) returns, rebates and allowances;
        (iv)  retroactive price reductions applicable to sales of such
Product(s);
        (v)   sales commissions paid to distributors and selling agents;
        (vi)  sales taxes, excise taxes, tariffs and duties; and
        (vii) two percent (2%) of the amount invoiced to cover bad debt,
freight or other transportation costs, insurance charges, additional special
packaging, and other governmental charges.

     1.19  "North America" shall mean the United States, its territories and
possessions (including Puerto Rico) and Canada.

     1.20  "Oncology Products" shall have the meaning accorded thereto in the
Amended INOP Agreement.

     1.21  "Other Product(s)" shall mean all products heretofore or hereafter
discovered or developed by Immunex other than Immunex New Oncology Product(s) in
the Field.  Other Product(s) shall exclude any product to the extent that
Immunex cannot

                                         -4-

<PAGE>

grant license rights to Wyeth due to preexisting agreements entered into prior
to December 15, 1992.  However, should Immunex have any such rights returned to
it, Immunex shall notify Wyeth of the extent to which the returned rights allow
that product to be deemed an Other Product.

     1.22  "Patents" shall mean Immunex Patents, AHPC/ACY Patents, and Joint
Patents.

     1.23  "Product(s)" shall mean individually and/or collectively, depending
on the context, the WNOPs, INOPs, Other Products and Oncology Products.

     1.24  "Technology" shall mean all technical data, and business and other
commercial information relating to Products that are owned or controlled by a
party and for which such party has a right to disclose or license to the other
hereunder, excluding Wyeth data and information relating to Third Party
Projects, but including techniques, discoveries, inventions, processes,
know-how, Materials, regulatory data and information of any kind including
pre-clinical and clinical experimental results, and any other information
reasonably necessary to permit a party to develop, manufacture, test, use,
market, sell and distribute a Product, in whatever form kept and whether or not
such information is patentable, copyrightable, or subject to trademark
protection, and whether or not such aforementioned intellectual property
protection has been sought.  As appropriate, Technology may be referred to as
that solely owned or controlled by Immunex ("Immunex Technology"), that solely
owned or controlled by AHPC and/or ACY ("Wyeth Technology"), and that owned or
controlled jointly by the parties ("Joint Technology").

     1.25  "Third Party Projects" shall mean each AHPC and/or ACY substance of
any kind heretofore or hereafter acquired pursuant to a merger or acquisition or
acquired or discovered pursuant to a license, joint venture, collaboration or
other third party transaction, and including without limitation any future
derivations of, new or additional oncology uses for, or modifications to such
substance by internal Wyeth efforts or otherwise.

     1.26  "TNFR" shall mean tumor necrosis factor receptor (p80) and all
derivatives and analogues thereof.

     1.27  "TNFR Agreement" shall mean the TNFR License and Development
Agreement, dated the date hereof, between Immunex and Wyeth, regarding the
global development of TNFR.

     1.28  "Wyeth Internal Oncology Discovery" shall mean the research
activities undertaken by Wyeth's oncology discovery research group at the
oncology research

                                         -5-

<PAGE>

facility at Pearl River, New York, and at additional or successor locations to
such Pearl River research facility, at which such activities may be conducted in
the future, to discover and develop products in the Field that are chemically
derived, small molecules or peptido mimetic molecules, excluding activities
relating to Third Party Projects.

     1.29  "Wyeth New Oncology Products" or "WNOPs" shall mean all products
useful (to the extent useful) in the Field resulting from Wyeth Internal
Oncology Discovery, including, without limitation:
          -cytotoxics (including photosensitizers) and cytotoxic modulators;
          -small molecule hematopoietic stimulators;
          -receptor antagonists
          -signal transduction pathway inhibitors
          -nuclear receptors
          provided, however, that a product shall be deemed to have resulted
from Wyeth Internal Oncology Discovery if either (i) the initial identification
of the structure of the compound is made by Wyeth Internal Oncology Discovery;
or (ii) the initial identification of the structure of a compound is made by
Wyeth outside of Wyeth Internal Oncology Discovery, and such compound is (x)
subsequently determined by Wyeth Internal Oncology Discovery to be useful in the
Field and (y) developed by Wyeth primarily for use in the Field.

     1.30  "Wyeth Territory" shall mean all of the countries of the world except
North America.

     1.31  Each of the following definitions are found in the body of the
Agreement as indicated:
                                                                     PARAGRAPH
                                                                     ---------
"Covered Product"                                                       4.01

"Elected Wyeth Oncology Product" or "Elected WNOP"                      2.05

"Exercise Period"                                                       2.04

"Global Development Plan"                                               2.07(b)

"Information"                                                           5.10

                                         -6-

<PAGE>

"Joint Project Development Team"                                        2.07(c)

"License Right"                                                         2.01

"Product Agreement"                                                     2.07

"Product Development Steering Committee"                                2.02

"Registration and Positioning Strategy Document"                     2.07(i)(ii)

"Relinquished Wyeth Oncology Product" or "Relinquished WNOP"            2.07(i)

"Research Strategy Document"                                            2.07(b)

"ROC"                                                                   2.03

"Shared Costs"                                                      2.07(a)(iii)

"Wyeth IND Track Proposal Document"                                     2.04

              ARTICLE 2.  IMMUNEX RIGHTS TO WYETH NEW ONCOLOGY PRODUCTS

     2.01  Right to Obtain Exclusive License:  In consideration for payments
made by Immunex in support of Wyeth Internal Discovery prior to the Effective
Date and the payments to be made pursuant to Paragraph 3.01 hereof, Wyeth hereby
grants and agrees to grant to Immunex the right as set forth in this Article 2
to obtain an exclusive license on the terms set forth in Paragraph 2.07(a) below
with respect to each WNOP in the Immunex Territory (a "License Right").  It is
expressly understood and agreed that no Third Party Projects shall be subject to
a License Right.

     2.02  Steering Committee.
          (a)  Formation.  As soon as practicable after the Effective Date, an
omnibus committee (the "Product Development Steering Committee") shall be formed
comprising an equal number of senior representatives of each party to supervise
and monitor the implementation activities of all Joint Project Development
Teams.  The Product Development Steering Committee shall, among other things,
review draft research strategies, forecast and endorse projected budgets and
manage the flow of funds.  Decisions shall be reached through majority vote.
          (b)  Dispute Resolution.  The Product Development Steering Committee
shall endeavor to resolve as soon as practicable all matters in dispute in
                                         -7-

<PAGE>


connection with the development of Elected WNOPs, including any matters referred
to it as contemplated by Paragraph 2.07(d).  If, after a period of thirty (30)
days (or earlier at the election of either party), any such matter is not
resolved, the matter shall be referred to the CEO of Immunex and the Executive
Officer of AHPC responsible for global pharmaceutical operations, or their
designees, to resolve in a period of thirty (30) days through good faith
discussions, or if still unresolved, to promptly agree upon a binding
independent third party dispute resolution mechanism intended to promptly and
fairly resolve the matter in dispute.

     2.03  Informational Reports to Immunex:  Wyeth shall keep Immunex informed
of all current and planned Wyeth Internal Discovery activities by providing
Immunex with a written annual report detailing the status of such discovery
activities for the previous year and a summary of the activities planned for
each item so detailed, as well as any new items for the year immediately
following the year reported on.  Wyeth shall also provide Immunex with summary
semi-annual reports of such activities in a form that is acceptable to each
party.  From time to time, Wyeth shall also provide oral updates of significant
developments with regard to Wyeth Internal Discovery efforts.  Immunex
representative(s) shall also be invited to Wyeth Discovery Council and Research
Operating Committee ("ROC") meetings to discuss select oncology discovery
projects and IND track candidates that are the subject of Immunex's License
Rights hereunder.

     2.04  Commencement of Exercise Period:  In the event that the ROC formally
accords any WNOP "IND-track status," Wyeth shall, as soon as reasonably
practicable thereafter, provide to Immunex written notice thereof, together with
a Wyeth IND Track Proposal Document and Immunex shall have a period of ninety
(90) days from the date of such written notice (the "Exercise Period") in which
to exercise its License Right with respect to such WNOP.  The "Wyeth IND Track
Proposal Document" means a proprietary Wyeth research management document that
(i) outlines the background data accumulated on a candidate product that
supports the designation by Wyeth research management that such candidate
product should be accorded IND track status, and (ii) contains a pre-clinical
development plan and a description of potential indications for such IND track
candidate product, together with preliminary timelines and budgets through the
anticipated IND filing.

     2.05  Exercise of License Right:  In order to exercise the License Right
with respect to a WNOP, Immunex shall provide written notice of its election to
so exercise to Wyeth, on or before the expiration of the Exercise Period and
such product shall thereupon be deemed to be an "Elected Wyeth New Oncology
Product" or "Elected WNOP."

     2.06  Expiration of Exercise Period:  If Immunex has not exercised its
License Right with respect to any WNOP within the applicable Exercise Period, no
rights with

                                         -8-

<PAGE>

respect thereto shall vest in Immunex and Wyeth shall retain all rights to such
WNOP to exploit in its sole discretion (including without limitation, North
American development activities), with no further obligations of any kind to
Immunex.

     2.07  Exercise of Rights/Preparation of Product Agreement:  Promptly after
the exercise by Immunex of the License Right with respect to an Elected WNOP,
the parties shall negotiate and develop the terms and conditions of a license
and product development agreement to be entered into by AHPC or an AHPC
Affiliate and Immunex (a "Product Agreement") granting an exclusive license to
Immunex and governing the ongoing development and commercialization of such
Elected WNOP, which shall, unless otherwise agreed, include the following
principles:
          (a)  Grant of Exclusive License:  The Product Agreement shall contain
a grant of an exclusive license under AHPC/ACY Intellectual Property, including
AHPC/ACY's interest in any Joint Intellectual Property, to make, have made, use,
offer for sale, sell, have sold, and import the Elected WNOPs in the Field in
the Immunex Territory, such license to be subject to Wyeth's retained right to
make, have made and use such Elected WNOPs in North America, including the right
to sell for export to the Wyeth Territory.
          (b)  Research Strategy Document and Global Development Plan:  The
Product Agreement shall provide for the joint preparation, prior to IND filing,
of (i) a "Research Strategy Document" outlining the general indications and
approaches to be taken by the parties to gain the initial and each subsequent
market approval; and (ii) a "Global Development Plan" outlining and specifying
the duties and responsibilities of each party in completing the preclinical and
clinical development of the product and including and identifying the studies
anticipated to be required to obtain marketing approvals as well as the required
manufacturing investments and responsibilities.  The Global Development Plan
shall also specify the criteria for continuation of clinical studies at mutual
and synchronized decision points.
          (c)  Joint Project Development Team.  A team ("Joint Project
Development Team") shall be formed to prepare the Research Strategy Document and
Global Development Plan for each Elected WNOP, and to manage the implementation
of the Global Development Plan.  The Joint Project Development Team shall be
comprised of representatives designated by each party on the basis of specific
areas of expertise and ability to contribute to the development of the Elected
WNOP.  Decisions of the Joint Project Development Team shall be made by
consensus (i.e., a majority of the members designated by the representatives
designated by each party).  In the implementation of the Global Development
Plan, the Joint Project Development Team shall utilize either party's personnel
or other resources in any Territory, subject
                                         -9-

<PAGE>

to prior mutual agreement, and shall base all resource allocation decisions on
factors such as personnel availability, expertise and overall efficiency.
          (d)  Dispute/Deadlock Resolution.  The Joint Project Development Team
shall endeavor to reach a consensus on all matters in dispute within a period of
thirty (30) days.  If such a resolution cannot be reached in that time period
(or earlier at the election of either party), the matter shall be referred to
the Product Development Steering Committee which shall endeavor to resolve the
matter as soon as practicable in accordance with the provisions of Paragraph
2.02(b).
          (e)  Sharing of Development Expenses.
               (i)  The costs of all development activities authorized by the
Product Development Steering Committee for an Elected WNOP for the North
American and European markets incurred from the commencement of the
corresponding Exercise Period shall be shared on an equal basis between the
parties, such costs to include, without limitation:
     -    direct out-of-pocket costs (E.G. grants, materials, animals, and costs
of similar nature)
     -    costs of chemical or process development, excluding capital costs;
     -    direct labor costs (salary plus benefits); and
     -    overhead factors (standardized to an appropriate add-on factor
( E.G. [ * ] ) to the direct labor costs),
          with all costs to be determined by allocation principles established
by mutual agreement of the parties which shall be in accordance with generally
accepted accounting principles, consistently applied.
               (ii)  Territory specific activities intended to support unique
regulatory and marketing approvals in territories other than North America and
Europe (E.G., Japan, Latin America) shall be excluded from equal basis sharing
between the parties, and shall be borne solely by Wyeth.  Each party shall be
responsible for funding and management of any Phase IV studies performed in its
respective Territory.
               (iii)  The Joint Project Development Team shall prepare annual
workplans and budgets designating planned activities and estimated costs subject
to cost sharing ("Shared Costs") pursuant to subparagraph (i) above, which
workplans and budgets shall be reviewed by the Product Development Steering
Committee and such budgets shall be combined by the Steering Committee with
similar budgets, if any, relating to other Product Agreements.  Based upon such
budgets, the party

                                         -10-

<PAGE>

projected to be required to reimburse the other to equally balance Shared Costs
shall pay to the other, in advance of each calendar month, 1/12 of the
difference between (a) its budgeted annual Shared Costs, and (b) one-half of the
total annual budgeted Shared Costs to be incurred by both parties.  Each party
shall report to the other, within ten (10) days following the end of each
calendar month, its actual Shared Costs for such month.  The parties shall
adjust the budgeted monthly payments on a quarterly basis to reflect actual
Shared Costs incurred in previous calendar quarters.
          (f)  Supply Provisions:  The Product Agreement shall provide that, if
an Elected WNOP (or an ingredient or component thereof) is to be manufactured by
either Wyeth or Immunex for supply to the other, then the manufacturing party
shall supply the other party's reasonable clinical and commercial requirements
for such Elected WNOP at the manufacturing party's Manufacturing Cost plus, in
the case of reasonable commercial requirements, a reasonable profit pursuant to
an appropriate supply and manufacturing agreement specifying the quantity and
quality of such Wyeth Elected New Oncology Product, delivery schedule,
termination and other material terms.
          (g)  Publication:  The Product Agreement shall establish a publication
policy related to the results of the product development, taking into account
the existing publication approval policies of the parties, the right of the
parties to file for appropriate patent protection, and the confidentiality
provisions of this Article 5.  Such policy shall provide that each party shall
inform the other party if it contemplates publication or disclosure of any
technical data or other scientific information obtained in the product
development process prior to submission to unaffiliated third parties in order
to avoid potential loss of international patent rights.
          (h)  Joint Intellectual Property:  The Product Agreement shall include
appropriate provisions for the joint ownership and use of Joint Intellectual
Property.
          (i)  Release of Rights:  The Product Agreement covering each Elected
WNOP shall provide Immunex with the right, in its sole discretion, to terminate
such Product Agreement and the sharing of costs thereunder with respect to such
Elected WNOP (a "Relinquished Wyeth New Oncology Product" or "Relinquished
WNOP") by providing written notice thereof to Wyeth within the following time
periods:
               (i)  Time Period I:  Within thirty (30) days following the
written notification to Immunex of the results obtained from preliminary safety
studies (i.e., following completion of Phase I clinical trials);

                                         -11-


<PAGE>

               (ii)  Time Period II:  Within thirty (30) days following the end
of Phase II clinical trials and receipt by Immunex of a "Registration and
Positioning Strategy Document."  The "Registration and Positioning Strategy
Document" means a document which updates the Global Development Plan and which
is prepared by the Joint Project Development Team prior to the initiation of
Phase III studies; and
               (iii)  Time Period III:   Within thirty (30) days of receipt by
Immunex of the results of that portion of the Phase III clinical trial data to
be utilized for the regulatory filings in the Immunex Territory together with
any other relevant scientific data that is then available to Wyeth and is useful
or necessary in evaluating the safety or efficacy of the Product.
          Upon receipt by Wyeth of such notice, all rights to such Relinquished
WNOP shall revert to Wyeth to exploit in Wyeth's sole discretion, with no
further obligations of any kind to Immunex except for Immunex's right to receive
payments in accordance with subparagraph (j) below.  The Product Agreement shall
not otherwise be terminable, transferable or assignable by Immunex.
          (j)  Royalties:  The Product Agreement shall provide that, subject to
Wyeth's right to recoup its incremental development costs pursuant to
subparagraph (o) below, if Wyeth or any Wyeth Affiliate, sublicensee, or other
designee sells a Relinquished WNOP which has been relinquished pursuant to
Paragraph 2.07(i)(ii) or (iii) (but not 2.07(i)(i), Wyeth shall pay or cause to
be paid to Immunex an earned royalty on their respective quarterly Net Sales in
North America to begin on the date of Market Launch of such Relinquished WNOP in
a specific country within North America and continue until the later of
(i) expiration of the last Granted Patent(s) in such country that specifically
claims such Relinquished WNOP being sold in such country, or (ii) ten (10) years
from the date of such Market Launch of the Relinquished WNOP in such country,
all in accordance with the following:
               (A)  if such Relinquished WNOP has been relinquished pursuant to
Paragraph 2.07(i)(ii) above and is not claimed by a Granted Patent(s), Wyeth
shall pay or cause to be paid to Immunex (i) an earned royalty of [ * ] on Net
Sales thereof by Wyeth, its Affiliates, or designees, and (ii) if rights thereto
are licensed by Wyeth to an unaffiliated third party, Wyeth shall pay or cause
to be paid to Immunex [ * ] of revenues received by Wyeth with respect to Net
Sales thereof by such third party;
               (B)  if such Relinquished WNOP has been relinquished pursuant to
Paragraph 2.07(i)(ii) above and is claimed by a Granted Patent(s), Wyeth shall
pay or cause to be paid to Immunex (i) an earned royalty of [ * ] on Net Sales
thereof by Wyeth, its Affiliates, or other designees, and (ii) if rights thereto
are

                                         -12-

<PAGE>

licensed by Wyeth to an unaffiliated third party, Wyeth shall pay or cause to be
paid to Immunex [ * ] of revenues received by Wyeth with respect to Net Sales
thereof by such third party;
               (C)  if such Relinquished WNOP has been relinquished pursuant to
Paragraph 2.07(i)(iii) above and is not claimed by a Granted Patent(s), Wyeth
shall pay or cause to be paid to Immunex (i) an earned royalty of [ * ] on Net
Sales thereof by Wyeth, its Affiliates, or other designees; and (ii) if rights
thereto are licensed by Wyeth to an unaffiliated third party, Wyeth shall pay or
cause to be paid to Immunex [ * ] of revenues received by Wyeth with respect to
Net Sales thereof by such third party;
               (D)  if such Relinquished WNOP has been relinquished pursuant to
Paragraph 2.07(i)(iii) above and is claimed by a Granted Patent(s), Wyeth shall
pay or cause to be paid to Immunex (i) an earned royalty of [ * ] on Net Sales
thereof by Wyeth, its Affiliates, or other designees, and (ii) if rights thereto
are licensed by Wyeth to an unaffiliated third party, Wyeth shall pay or cause
to be paid to Immunex [ * ] of revenues received by Wyeth with respect to Net
Sales thereof by such third party.
          (k)  Combination Products:  The Product Agreement shall provide, with
respect to Relinquished WNOPs relinquished pursuant to Paragraphs 2.07(i)(ii) or
2.07(i)(iii), that:
               (i)  with respect to Combination Products,
                    (A)  Royalties due on sales of Combination Product(s) shall
be calculated by multiplying actual Net Sales of such Combination Products by
the fraction A/(A+B) where A is the invoice price of the Relinquished WNOP if
sold separately, and B is the total invoice price of any other active component
or components in the combination, if sold separately by Wyeth.
                    (B)  If the other active component or components in the
combination are not sold separately by Wyeth, Net Sales, for the purpose of
determining royalties on the Combination Products shall be calculated by
multiplying actual Net Sales of such Combination Products by the fraction A/C
where A is the invoice price of the Relinquished WNOP if sold separately and C
is the invoice price of the Combination Product.
                    (C)  If neither the Relinquished WNOP nor the Combination
Product is sold separately by Wyeth, Net Sales for purposes of determining
royalties on the Combination Products shall be calculated as above except


                                         -13-

<PAGE>

that Immunex and Wyeth shall allocate values to the components A and B based
upon a good-faith determination of the respective contributions of such
components to the market value of the Combination Product.
          (l)  Internal Sales.  Sales between Wyeth and its Affiliates,
sublicensees, or other designees or among its Affiliates and sublicensees, or
other designees shall not be subject to royalties, but in such cases royalties
shall be calculated upon Wyeth's, its sublicensees', Affiliates', or other
designees' quarterly Net Sales to an unaffiliated third party.
          (m)  One Royalty.  The obligation to pay royalties shall be imposed
only once with respect to the same unit of  Relinquished WNOP.
          (n)  Samples.  No royalties shall accrue on disposition of reasonable
quantities of Relinquished WNOP(s) for no charge as samples or donations to
independent third parties.
          (o)  Recoupment:  The Product Agreement shall provide that,
notwithstanding the principles set forth in Paragraphs 2.07(j)-(o), no earned
royalties shall be due Immunex with respect to Net Sales of a Relinquished WNOP
made prior to the date that Wyeth has fully recouped its development costs in
the Immunex Territory with respect to such WNOP accrued from the date that
Immunex relinquished its rights under Paragraph 2.07(i), as such costs are
substantiated in accordance with applicable Wyeth accounting records which are
in accordance with GAAP, consistently applied, in conjunction with allocation
principles established by mutual agreement of the parties; and as such costs
have been offset by any amounts received from third parties as non-refundable
and non-creditable license fees or other non-offsetting consideration for the
grant of marketing rights in the Immunex or Wyeth Territories or the use of data
obtained in development activities in the Immunex or Wyeth Territories.
          (p)  Additional Indications.  The Product Agreement shall provide
that, if a party elects to develop an additional or secondary indication for an
Elected WNOP that the other party chooses not to support, the developing party
shall retain all rights to the data it obtains in such independent development
activities, subject to the non-developing party's right to acquire rights to use
such data to prepare regulatory approval filings in its Territory upon payment
to the developing party of a fee equal to [ * ]  of the developing party's costs
of conducting clinical studies and other activities related to such additional
or secondary indication, such right to expire twelve (12) months from the date
of the initial submission of a regulatory approval filing or registration
package with respect to such indication.

                                         -14-

<PAGE>

                                ARTICLE 3.  PAYMENTS:

     3.01  Immunex Annual Payments to Wyeth:
          (a)  In consideration of the annual grant of rights pursuant to
Paragraph 2.01 hereof, Immunex shall pay to Wyeth an annual amount equal to:
               (i) [*] for the remainder of 1996; and
               (ii) for each year thereafter, $16 million adjusted by an amount
based upon the percentage increase or decrease in the U.S. Consumer Price Index
for the preceding year, as published by the U.S. Department of Commerce;
provided however, that in no event shall the amount payable by Immunex for any
year exceed 50% of Wyeth's actual expenditures on Wyeth Internal Discovery
during such year.
          (b)  Immunex shall satisfy its payment obligations under subparagraph
(a) above by making payments in advance of each month.  An annual reconciliation
of  Wyeth's actual expenditures on Wyeth Internal Discovery to Immunex's
payments hereunder will be provided by Wyeth to Immunex within sixty (60) days
following the end of each calendar year.

                     ARTICLE 4.  WYETH RIGHTS TO IMMUNEX PRODUCTS

     4.01  Wyeth Rights:  The Board of Directors of Immunex shall determine, on
a case by case basis, whether Immunex will market itself to the Health Care
Market any Other Products, INOPs, Oncology Products, Elected WNOPs or Technology
that it develops or acquires (the "Covered Products") in any country or
countries in which Immunex has or acquires marketing rights.  If the Board of
Directors of Immunex determines that Immunex will not so market or will cease to
so market any such Covered Product in any one or more such countries, Immunex
shall offer Wyeth all such marketing rights to such Covered Product.
     4.02  Delivery of Notice:
          (a)  Immunex shall provide prompt written notice to Wyeth of any such
determination under Section 4.01, provided, however, that:
               (i)  for Covered Products that are pharmaceutical or biological
products having potential utility in treating human disease or conditions, such
notice shall not be provided to Wyeth prior to the time that sufficient data is
available to enable Wyeth to reasonably evaluate the safety and efficacy of such
Covered Product

                                         -15-

<PAGE>

for its intended use, which data shall include, at a minimum, preliminary
clinical evidence of safety (I.E., completion of Phase I studies); and
               (ii) for Technology, such notice shall not be provided to Wyeth
prior to the time that the criteria set forth in ANNEX I has been satisfied.
          (b)  The notice provided pursuant to subparagraph (a) shall be
accompanied by all pertinent data and other information available to Immunex,
which shall be updated from time to time as appropriate during the period set
forth in Paragraph 4.03.

     4.03  Commencement of Time Period:  Upon the receipt of notice pursuant to
Paragraph 4.02, the parties shall have a period of one hundred and eighty (180)
days in which to establish mutually acceptable terms and conditions under which
Wyeth shall acquire such marketing rights provided, however, that in the case of
Oncology Products or INOPS such period shall be reduced to ninety (90) days.  At
the end of such period, if the parties are unable to establish such mutually
acceptable terms and conditions, Immunex shall have the right to license such
Covered Product to an unaffiliated third party on terms which, taken as a whole,
are no less favorable to Immunex than those offered to Wyeth.  If Immunex
desires to enter into a license with an unaffiliated third party on terms that,
taken as a whole, are more favorable to such third party than the terms offered
to Wyeth, then Immunex shall not enter into an agreement with such third party
unless it first offers such new terms to Wyeth.  Wyeth shall have thirty (30)
days from receipt of such additional offer to accept such new terms.

     4.04  Waiver of Rights:  If the Board of Directors of Immunex makes the
determination set forth in Paragraph 4.01 prior to the time that notice may be
given pursuant to Paragraph 4.02, then, at the request of Immunex, Wyeth shall
undertake to review all pertinent information available to Immunex, which shall
be provided by Immunex to Wyeth, regarding any Covered Product and shall exempt
from this Article 4 any such Covered Product that, in Wyeth's good faith
determination, does not fit within its then current or anticipated product
profile.
                             ARTICLE 5.  CONFIDENTIALITY

     5.01  Confidentiality:  All information of whatever kind, in whatever form
kept, relating to or developed during the term of this Agreement, including
without limitation, all oral, written, electronic or other communications and
other information, including any and all analyses or conclusions drawn or
derived regarding the Materials, Field, Product(s), Intellectual Property,
research programs, know-how, workplans, compounds, or either party's marketing,
financial or other business plans or data, personnel, processes, formulations,
analytical procedures, clinical procedures, methodologies, products,

                                         -16-

<PAGE>


samples, specimens or functions (selectively and collectively "Information")
that is owned or licensed to a party shall be possessed and used by the parties
hereto, subject to the following terms and conditions:
          (a)  Each party shall keep all Information in confidence and shall use
Information solely in accordance with the terms and conditions of this
Agreement.  Absent prior written consent of the other party, neither party shall
disclose any Information to any person or entity, except those of its officers,
employees, clinical investigators, and consultants who require said Information
to enable such party to perform obligations under this Agreement. The officers,
employees, clinical investigators and consultants to whom Information is to be
disclosed shall be advised by such party of, and bound directly and separately
by the terms of this Agreement, wherever reasonably practicable.
          (b)  The obligations of confidentiality and non-use set forth herein
shall not apply to any Information that is (or subsequently becomes):
               (i)  published or available to the general public otherwise than
through a breach of this Agreement; or
               (ii) previously known to or independently developed by a party
prior to entering into this Agreement; or
               (iii)     disclosed to the receiving party by a third-party who
has no obligation to the disclosing party of non-disclosure, or
               (iv) required by operation of law or regulation to be disclosed,
including, without limitation, patent application filings.
          (c)  In the event that either party is required by judicial or
administrative process to disclose any Information, it shall promptly notify the
other party and allow the other party a reasonable time to oppose such process
before disclosing any Information, and to redact any portion of Information as
may be permissibly redacted in accordance with such aforementioned process.

     5.02  Return of Information:  Subject to a party's rights set forth herein,
and upon termination of this Agreement as set forth in Article 8 hereof, a party
that has received Information from the other party shall immediately return to
the disclosing party all Information that it has received from the disclosing
party, all notes that may have been made regarding said Information, and all
copies thereof.  The receiving party may retain one copy of each item of
Information and notes regarding same, provided that said copy shall be retained
and used solely for compliance purposes and shall be held in the

                                         -17-

<PAGE>

receiving party's confidential files. For purposes of this Paragraph, Wyeth and
Immunex shall each be considered the disclosing parties with respect to any
Joint Intellectual Property.

     5.03  Survival:  The confidentiality and non-use provisions contained
herein shall remain effective during the term of this Agreement and for five (5)
years thereafter.
                          ARTICLE 6. ACCOUNTING AND REPORTS

     6.01  True Accounts:  Wyeth and/or its Affiliates, sublicensees, or other
designees, as applicable, shall keep true accounts of Net Sales, third party
revenues received from unaffiliated third parties, and of all sums payable under
Article 2 hereof and deliver to Immunex, within forty-five (45) calendar days
after the end of each calendar quarter a written account, including quantities,
of its such Net Sales that are subject to earned royalty payments together with
the amount of the payment due for said calendar quarter.

     6.02  Payments:  With each accounting required by this Article, Wyeth
and/or its Affiliates, as applicable, shall also provide to Immunex, without
deduction except where expressly permitted by this Agreement, all earned royalty
payments due for the calendar quarter for which the accounting is made.

     6.03  Access to Records:  Wyeth and/or its Affiliates, sublicensees, or
other designees as applicable, shall keep accurate records in sufficient detail
to enable the amounts due to Immunex to be determined.  Upon request, Wyeth
shall permit an independent, certified public accountant selected by Immunex,
except one to whom Wyeth has a reasonable objection, to have access, on
reasonable advance notice and during regular business hours, to records
necessary to determine the correctness of any report or payment made in respect
to any calendar quarter and obtain information as to the amount of royalties
payable for any such period. Such examination shall be at the requesting party's
sole expense, shall be under conditions of strict confidentiality and shall not
take place more than once each calendar year. These rights with respect to any
calendar quarter shall terminate two (2) years after the end of any such
quarter.

     6.04  Research Expenditures:  Wyeth shall each keep true and detailed
accounts of all expenditures in furtherance of Wyeth Internal Research, in
accordance with allocation principles established by mutual agreement of the
parties which shall be in accordance with generally accepted accounting
principles, consistently applied.

                                         -18-



<PAGE>

                                 ARTICLE 7.  CURRENCY

     7.01  U.S. Currency:  All payments to be made under this Agreement shall be
made in United States dollars by bank wire transfer in immediately available
funds to a bank account designated by the party receiving the funds.

                               ARTICLE 8.  TERMINATION

     8.01  Term:  This Agreement shall commence as of the Effective Date and
shall continue in effect unless terminated as provided hereinbelow.

     8.02  Insolvency or Bankruptcy:  Either party may, in addition to any other
remedies available to it by law or in equity, terminate this Agreement by
written notice to the other party (the "insolvent party") in the event such
other party shall have become insolvent or bankrupt, or shall have made an
assignment for the benefit of its creditors, or there shall have been appointed
a trustee or receiver of the insolvent party or for all or a substantial part of
its property, or any case or proceeding shall have been commenced or other
action taken by or against the insolvent party in bankruptcy or seeking
reorganization, liquidation, dissolution, winding-up arrangement, composition or
readjustment of its debts or any other relief under any bankruptcy, insolvency,
reorganization or other similar act or law of any jurisdiction now or hereafter
in effect, or there shall have been issued a warrant of attachment, execution or
similar process against any substantial part of the property of the insolvent
party, and any such event shall have continued for sixty (60) days undismissed,
unbonded and undischarged.

     8.03  Rights in Bankruptcy:  All rights and licenses under or pursuant to
this Agreement by the parties are, and shall otherwise be deemed to be, for
purposes of Section 365(n) of the U.S. Bankruptcy Code, licenses of rights to
"intellectual property" as defined under Section 101 of the U.S. Bankruptcy
Code.  The parties agree that, as licensees of such rights under this Agreement,
each shall retain and may fully exercise all of their rights and elections under
the U.S. Bankruptcy Code.  The parties further agree that, in the event of the
commencement of a bankruptcy proceeding by or against Wyeth or Immunex under the
U.S. Bankruptcy Code, the party which is not the bankrupt or insolvent entity
shall be entitled to a complete duplicate of (or complete access to, as
appropriate) any such intellectual property and all embodiments of such
intellectual property, and the same, if not already in its possession, shall be
promptly delivered to it (a) upon any such commencement of a bankruptcy
proceeding upon its written request therefor, unless the party subject to such
proceeding elects to continue to perform all of its obligations under this
Agreement or (b) if not delivered under (a) above, upon the rejection of this
Agreement by or on behalf of the party subject to such proceeding upon written
request therefor by any non-insolvent party.

                                         -19-

<PAGE>


     8.04  Material Breach:  Notwithstanding any other provision of this Article
8, failure by either party (the "defaulting party") to comply with any of the
material obligations contained in this Agreement shall entitle the other party
(the "nondefaulting party") to give to the defaulting party notice specifying
the nature of the default and requiring it to cure such default.  If the
defaulting party disagrees with the existence, extent or nature of the default,
the parties shall use good faith efforts to resolve the dispute.  If (i) such
default is not cured within sixty (60) days after the receipt of such notice or
the date of such determination, as applicable, or (ii) if such default cannot be
cured within such sixty (60) day period and if the defaulting party does not
commence and diligently continue actions to cure such default or (iii) the
parties have not otherwise resolved the dispute during such period, the
nondefaulting party shall be entitled, except as otherwise specifically provided
in this Agreement, without prejudice to any of its other rights conferred on it
by this Agreement, to terminate this Agreement.

     8.05  Wyeth's Rights:  If AHPC ceases to be a majority owner of Immunex,
Wyeth may terminate this Agreement upon sixty (60) days' notice to Immunex.

     8.06  Accrued Rights, Surviving Obligations:  Termination of this Agreement
for any reason stated above shall be without prejudice to any rights which shall
have accrued to the benefit of either party prior to such termination.  Such
termination shall not relieve either party from obligations which are expressly
indicated to survive termination of this Agreement.

                           ARTICLE 9.  PUBLIC ANNOUNCEMENTS

     9.01  Advance Notice:  If either party desires to, or is required by law
to, make a public announcement concerning this Agreement or the subject matter
hereof, such party shall give reasonable advance notice of the proposed text of
such announcement to the other party for its review and approval.  All written
publications and other public announcements such as regulatory filings and
approvals shall include the names of the parties, where appropriate.

                           ARTICLE 10.  INDEPENDENT PARTIES

     10.01  Obligations of the Parties:  At all times during the term of this
Agreement, Immunex, on the one hand, and Wyeth and Lederle, on the other hand,
shall be deemed and shall in fact be independent of one another and neither
shall be authorized or empowered hereby to act as the agent for the other party
for any purpose whatsoever or, on behalf of the other, enter into any contract,
warranty or representation as to any matter.

     10.02  AHPC, Wyeth and ACY shall not exercise or cause to be exercised any
of ACY's rights set forth under Section 4.04 or 4.05 of the Governance Agreement
to prevent

                                         -20-

<PAGE>

or interfere with the exercise by Immunex of any rights provided to it under
this Agreement.
                             ARTICLE 11.  EXPORT CONTROLS

     11.01  Legal Compliance:  The parties acknowledge that both are subject to
laws and regulations of the United States of America governing exportation of
technical information, computer software, laboratory prototypes and other
commodities and that the rights hereunder are contingent on compliance with all
such laws and regulations.  The transfer of certain technical data and
commodities may require a license from the appropriate agency of the United
States Government and neither party shall export such technical data or
commodities to certain foreign countries to which export restrictions apply
without the prior approval of such agency.

                           ARTICLE 12.  TRANSITION MATTERS

     12.01  Termination of Research and Development Agreement:
          (a)  As of the Effective Date, (i) the Research and Development
Agreement and all licenses and other rights granted or conveyed therein shall
terminate and be of no further force or effect; (ii) except as provided in this
Agreement or contemplated by subparagraph (c) below, Immunex shall cease funding
of all oncology research and development by ACY and its Affiliates thereunder.
The parties to the Research and Development Agreement hereby release each other
and their respective Affiliates from and against all claims arising out of or
claimed to arise out of the Research and Development Agreement.
          (b)  Any notice given prior to the Effective Date by Immunex to ACY
pursuant to Section 3.2 of the Research and Development Agreement shall be
deemed to be null and void except to the extent that ACY has, prior to the
Effective Date, expressly exercised or relinquished its rights thereunder.
          (c)  The parties shall negotiate and set forth definitively the terms
and conditions of license and product development agreement(s) suitable to
govern the continued development of the Products in the Field listed on
Schedule 12.01.  To the extent appropriate, the principles set forth in
Paragraph 2.07(a)-(o) shall apply to such license and product development
agreements.
                              ARTICLE 13.  MISCELLANEOUS

     13.01  Waivers:  Any term or condition of this Agreement may be waived or
qualified at any time by the party entitled to the benefit thereof by a written
instrument that specifically identifies this Agreement and the term or condition
to be waived or

                                         -21-

<PAGE>

qualified and is executed by a duly authorized officer of said party. No delay
or failure on the part of either party in exercising any rights hereunder, and
no partial or single exercise thereof, shall constitute a waiver of such rights
or of any other rights hereunder.

     13.02  Governing Law:  With the exception of patent matters which shall be
governed by application of national patent laws, this Agreement shall be
construed and the respective rights of the parties hereto determined in
accordance with the laws of the State of New Jersey and of the United States.

     13.04  Assignment:  Neither party may assign this Agreement in whole or in
part without the prior written consent of the other, provided that in the event
of any purchase, reorganization, merger or consolidation involving a party, such
party may assign its rights and obligations under this Agreement to any person
or entity that is the purchaser of or successor in interest to all or
substantially all of its business and assets. Any assignment in violation of
this provision shall be void. Subject to the foregoing, any reference to Immunex
or Wyeth in this Article shall be deemed to include the successors thereto and
assigns thereof.

     13.06  Severance:  If any provision of this Agreement is held to be invalid
or unenforceable by a court of competent jurisdiction, all other provisions
shall continue in full force and effect.

     13.07  Notices:
           (a) Notices to AHPC, Wyeth, ACY or Lederle shall be addressed to:

               Wyeth-Ayerst Research
               555 E. Lancaster
               St. Davids, PA  19087
               Attention:  Senior Vice President-Global Business Development

     Copy to:  AMERICAN HOME PRODUCTS CORPORATION

               Five Giralda Farms
               Madison, New Jersey 07940
               Attention:  Senior Vice President and General Counsel

     Notices to Immunex shall be addressed to:

               IMMUNEX CORPORATION
               51 University Street
               Seattle, Washington  98101
               Attention:  President

                                         -22-

<PAGE>

     Copy to:  General Counsel at the same address.
          (b)  Any notice required or provided for by the terms of this
Agreement shall be in writing, addressed in accordance with this Paragraph, and
sent by registered or certified mail, return receipt requested, postage prepaid
or by express courier services providing evidence of delivery. The effective
date of any notice shall be the date of receipt by the receiving party.

     13.08  Force Majeure:  No failure or omission by the parties hereto in the
performance of any obligation under this Agreement shall be deemed a breach
hereof or create any liability if the same arises from any cause beyond the
control of the parties including, but not limited to, the following: act of God;
acts or omissions of any government; any rule, regulation or order issued by any
governmental authority or by any officer, department, agency or instrumentality
thereof; fire; storm; flood; earthquake; accident; war; rebellion; insurrection;
riot; invasion; or strike, lockout or other work stoppage provided that such
failure or omission is cured as soon as is practicable after the occurrence of
the force majeure.

     13.09  Entire Agreement:  This Agreement, together with any Annexes and
Schedules attached hereto and expressly incorporated herein constitutes the
entire agreement between the parties relative to the subject matter hereof and
supersedes all previous arrangements whether written or oral. Any amendment or
modification to this Agreement shall be of no effect unless made in a writing
that specifically references this Agreement and signed by both parties.   
                                         -23-

<PAGE>

IN WITNESS WHEREOF the parties, intending to be bound hereby, have caused their
duly authorized representatives to execute this Agreement.

                                             AMERICAN HOME PRODUCTS CORPORATION


                                             By:  /s/ Joseph J. Carr
                                                  ---------------------
                                             Its  Senior Vice President
                                                  ---------------------

                                             AMERICAN CYANAMID COMPANY



                                             By:  /s/ Joseph J. Carr
                                                  ---------------------
                                             Its  Senior Vice President
                                                  ---------------------

                                             IMMUNEX CORPORATION



                                             By:  /s/ Edward V. Fritzky
                                                  ---------------------
                                                  Edward V. Fritzky
                                                  Chairman and Chief Executive
                                                  Officer

                                         -24-

<PAGE>

                                                                        ANNEX I
                        CRITERIA FOR TRIGGERING AHP'S ROFR TO
                                     "TECHNOLOGY"

When TECHNOLOGY is a SUBSTANCE (but not a Product, in which case the Product
ROFR criteria obtains), such as a protein:

     -    STRUCTURE

          FOR PROTEINS OTHER THAN ANTIBODIES, THIS SHALL MEAN THE NATURAL
          PROTEIN HAS BEEN ISOLATED AND PURIFIED AND IMMUNEX IS WORKING ON
          ELUCIDATING THE AMINO ACID SEQUENCE AND CLONING THE DNA

          FOR POLYCLONAL ANTIBODIES, THIS SHALL MEAN THAT THE ANTIGEN BOUND BY
          THE ANTIBODIES HAS BEEN IDENTIFIED AND IMMUNEX HAS ISOLATED THE
          ANTIGEN IN A FORM SUFFICIENTLY PURE TO BE USED TO RAISE ADDITIONAL
          POLYCLONAL ANTIBODIES


          FOR A MONOCLONAL ANTIBODY, THIS SHALL MEAN THAT THE ANTIGEN BOUND BY
          THE ANTIBODY HAS BEEN IDENTIFIED AND IMMUNEX HAS ISOLATED A HYBRIDOMA
          SUITABLE FOR SUSTAINED PRODUCTION OF THE MONOCLONAL ANTIBODY

     -    SCIENTIFICALLY ACCEPTABLE EVIDENCE THAT SUBSTANCE FUNCTIONALLY RELATES
          TO DISEASE STATE OR BIOLOGICAL PROCESS

          E.G.,  FOR GENES AND THE PROTEINS THEY ENCODE, THIS SHALL INCLUDE
          SCIENTIFIC EVIDENCE SUCH AS THAT PROVIDED BY A KNOCK-OUT MOUSE MODEL,
          ANTISENSE INHIBITION, ANTIBODY INHIBITION OR DOMINANT NEGATIVE
          MUTATIONS THAT ARE CAPABLE OF DEMONSTRATING THE BIOLOGICAL EFFECT OF
          ALTERING OR ABLATING PROTEIN FUNCTION, IN VITRO DEMONSTRATION THAT
          CERTAIN SUBSTANCES SPECIFICALLY MODULATE THE ACTIVITY OF THE GENE OR
          PROTEIN IT ENCODES, AND THE LIKE, AS APPROPRIATE; FOR SMALL MOLECULES
          THIS SHALL INCLUDE STRUCTURE-FUNCTIONAL ACTIVITY DATA, POTENCY
          INFORMATION, AND THE LIKE, AS APPROPRIATE; AND FOR POLYCLONAL OR
          MONOCLONAL ANTIBODIES, SCIENTIFIC EVIDENCE THAT A DIAGNOSTIC ASSAY
          USING THE

                                         -25-

<PAGE>

          ANTIBODIES CAN BE USED TO DETECT A DISEASE STATE OR OTHER BIOLOGICAL
          CONDITION DESIRED TO BE DETECTED
Criteria to also include the following when entity to be developed is a
RECOMBINANT PROTEIN:

               -    INDICIA THAT PROTEIN WILL BE CAPABLE OF SUCCESSFUL
                    RECOMBINANT EXPRESSION

               -    IN VITRO PROFILE COMPARISON OF RECOMBINANT PROTEIN TO NATIVE
                    PROTEIN (E.G., BINDING ACTIVITY AND SPECIFICITY AND OTHER
                    PARAMETERS AS APPROPRIATE)

               -    IF PURIFIED NATURAL PROTEIN IS NOT PRACTICALLY AVAILABLE
                    (E.G., TPO) OTHER EVIDENCE THAT THE RECOMBINANT PROTEIN IS
                    BIOLOGICALLY ACTIVE MAY BE EMPLOYED
     -    PATENT APPLICATION FILED

When TECHNOLOGY is a METHODOLOGY:

     -    SCIENTIFICALLY ACCEPTABLE EVIDENCE THAT METHODOLOGY HAS COMMERCIAL
          AND/OR RESEARCH TOOL SIGNIFICANCE

          E.G.,  FOR EXPRESSION SYSTEMS, PURIFICATION SYSTEMS AND THE LIKE, THIS
          SHALL INCLUDE DATA SUPPORTING ENHANCED YIELDS OF EXPRESSION OR
          PURIFICATION OR DEMONSTRATION OF EXPRESSION OR PURIFICATION THAT HAD
          NOT BEEN PREVIOUSLY OBTAINABLE, AND THE LIKE, AS APPROPRIATE

          FOR MOLECULAR SCREENING TARGETS, E.G., TACE, THIS SHALL INCLUDE
          MEANINGFUL DATA SHOWING THAT INHIBITION OR POTENTIATION OF THE
          BIOLOGICAL FUNCTION OF THE TARGET WILL HAVE A POTENTIALLY USEFUL
          EFFECT IN MODULATING A DISEASE STATE OR BIOLOGICAL PROCESS, FOR
          EXAMPLE, GROWTH, DEVELOPMENT OR REPRODUCTION

     -    PATENT APPLICATION FILED

          UNLESS INAPPROPRIATE BECAUSE STRATEGY IS TO MAINTAIN SUCH PROPRIETARY
          METHODOLOGY AS A TRADE SECRET

                                         -26-

<PAGE>


                                    SCHEDULE 12.01

     .    Leucovorin Liquid

     .    Flt 3 Ligand

     -    Thioplex II

     -    L-Leucovorin

     -    Mitomycin

     -    Etoposide

     -    Thioplex

     -    Novantrone (new indications such as prostate cancer, NHL)

                                         -27-




<PAGE>

                                                                    EXHIBIT 10.2






                                                                REDACTED VERSION


                                     EXHIBIT 10.2

                                          To

                                Immunex Corporation's

                                       Form 8-K

                                        Dated

                                    July 24, 1996





    "[ * ]" = omitted, confidential material, which material has been 
separately filed with the Securities and Exchange Commission pursuant to a 
report for confidential treatment.
<PAGE>
                                                                   EXHIBIT 10.2

 
                        TNFR LICENSE AND DEVELOPMENT AGREEMENT

    AGREEMENT made as of this 1st day of July, 1996 ("Effective Date") by and
between American Home Products Corporation, a Delaware corporation, acting
through its Wyeth-Ayerst Laboratories Division, ("AHP") and Immunex Corporation,
a Washington corporation, together with its Affiliates ("Immunex").

         A.   Immunex and American Cyanamid Corporation, a wholly-owned
subsidiary of AHP ("ACY"), entered into a Research and Development Agreement
dated as of June 1, 1993 (the "R&D Agreement") providing for, among other
things, the collaboration of the parties in oncology research and development
and the granting by Immunex to ACY of certain license rights to TNFR.

         B.   Immunex, AHP and ACY have determined to terminate the R&D
Agreement and replace it with the Research Agreement dated the date hereof
relating to oncology research and development and this Agreement relating to the
development and commercialization of TNFR on the terms and conditions set forth
herein.
                               ARTICLE 1.  DEFINITIONS

    1.01  "Affiliate" shall mean any corporation or business entity of which a
party owns directly or indirectly, fifty percent (50%) or more of the assets or
outstanding stock, or any corporation which a party directly or indirectly
controls, or any parent corporation that owns, directly or indirectly, fifty
percent (50%) or more of the assets or outstanding stock of a party or directly
or indirectly controls a party.  For purposes of this Agreement, the parties and
their respective Affiliates shall not be deemed to be Affiliates of each other.

    1.02  "AHP Patent(s)" shall mean any and all AHP Granted Patents and patent
applications relating to TNFR, or third-party patents or patent applications in
which AHP and/or its Affiliates has a licensable interest, that are necessary or
useful in order to research, develop, make, have made, market, use, import,
offer for sale, or sell TNFR, and any reissues, re-examinations, continuations,
continuations-in-part, divisions, renewals, extensions,  patents of addition,
and any extension of the term of the patent or supplementary protection
certificate or other means by which greater effective patent protection is
extended that exist as of the Effective Date or are issued or filed at any time
during the term of this Agreement.

    1.03  "AHP Territory" shall mean all of the countries of the world except
North America.
<PAGE>


    1.04  "Combination Product(s)" shall mean any pharmaceutical or biological
preparation in finished form that contains TNFR in combination with one or more
other active ingredients.

    1.05  "Distributor" shall mean any third party that purchases TNFR in
finished form (in final packaged form bearing Immunex tradedress) for resale in
a particular part of the Immunex Territory.

    1.06  "FDA" shall mean the Federal Food and Drug Administration of the
United States Department of Health and Human Services or successor agencies.

    1.07  "Global Development Plan" shall have the meaning accorded thereto in
Article 3.01.

    1.08  "GMP" shall mean good manufacturing practices as established from
time to time by the FDA.

    1.09  "Governance Agreement" shall mean the Amended and Restated Governance
Agreement among American Cyanamid Company, Lederle Oncology Corporation and
Immunex Corporation dated as of December 15, 1992.

    1.10  "Governmental Approvals" shall mean any marketing or pricing
approvals, health licenses, registrations or authorizations, however called, of
any country or international regulatory agency, department, bureau or other
government entity, including the FDA and its foreign counterparts, necessary for
the manufacture, use, storage, transport or sale of TNFR.

    1.11  "Granted Patent(s)" shall mean any claims of an issued and unexpired
Patent that has not been revoked or held unenforceable or invalid by a decision
of a court or other governmental agency of competent jurisdiction, or that
remains unappealable or unappealed within the time allowed for appeal, or that
has not been disclaimed, denied or admitted to be invalid or unenforceable
through reissue, re-examination, disclaimer or otherwise, and shall refer to
patents owned solely by Immunex ("Immunex Granted Patents"), patents owned
solely by AHP and/or its Affiliates ("AHP Granted Patents"), or patents owned
jointly by the parties ("Joint Granted Patents"), however appropriate.

    1.12  "Health Care Market" shall mean end users of health care products,
health care professionals or treatment providers, hospitals, clinics, health
maintenance organizations, wholesalers, Distributors, manufacturers of systems
or equipment that incorporate TNFR or Technology as enabling technology,
operating components or reagents, and third parties who assist in the sale,
marketing or distribution of TNFR or Technology other than by co-promotion or
co-marketing arrangements.


                                          2

<PAGE>


    1.13  "Immunex Patent(s)" shall mean all Immunex Granted patents and patent
applications and any third party patents and patent applications in which
Immunex has a licensable interest, that are necessary or useful in order to
research, develop, make, have made, market, use, import, offer for sale, sell,
or have sold TNFR, and any reissues, re-examinations, continuations,
continuations-in-part, divisions, renewals, extensions, patents of addition, and
any extension of the term of the patent or supplementary protection certificate
or other means by which greater effective patent protection is extended that
exist as of the Effective Date of or are issued or filed at any time during the
term of this Agreement.

    1.14  "Intellectual Property" shall mean Patent(s) and Technology and where
appropriate may specifically refer to Intellectual Property solely owned or
controlled by Immunex (the "Immunex Intellectual Property"), solely owned or
controlled by AHP and/or its Affiliates (the "AHP Intellectual Property"), or
jointly owned or controlled by the parties hereto (the "Joint Intellectual
Property").

    1.15  "Immunex Territory" shall mean North America (as hereinafter
defined).

    1.16  "Joint Patent(s)" shall mean all Granted Patents and patent
applications of which AHP and/or its Affiliates is a joint owner with Immunex,
as determined by the patent laws of the United States or as otherwise expressly
provided for by the parties.

    1.17  "Joint Project Development Team" shall have the meaning accorded
thereto in Article 3.02.

    1.18  "Manufacturing Agreement" shall have the meaning accorded thereto in
Article 2.01.

    1.19  "Manufacturing Cost" shall mean, for each quantity of TNFR, the cost
to the manufacturing party or its Affiliate(s) for raw materials, energy, labor
(salary and benefits), and reasonable overhead charges relating to the
manufacture, quality control testing and delivery of such TNFR, and other direct
and allocable indirect costs to manufacture such TNFR, including but not limited
to royalties to an unaffiliated third party on licensed technology, to
manufacturing charges for inventory adjustments, for offgrade or defective
material, handling losses, physical adjustments, salvage and start-up, all such
costs and charges to be calculated on a basis consistent with then current
methods and practices applied to all other products manufactured by the
manufacturing party, as the case may be, at the facility or facilities used for
production plus appropriately allocated manufacturing general and administrative
costs determined by allocation principles established by mutual agreement of the
parties which shall be in accordance with generally accepted accounting
principles, consistently applied.  If TNFR is manufactured by a party that is
not an Affiliate of a party to this Agreement, the Manufacturing Cost shall be
the amount payable to the unaffiliated third party on arm's-length dealing with
such manufacturer plus any costs needed to complete manufacture


                                          3

<PAGE>

quality control testing and delivery of such TNFR.  Manufacturing Cost shall not
include capital costs, other than depreciation, or opportunity costs for
contract manufacturing.

    1.20  "Market Launch" shall mean on a country-by-country basis, the first
commercial sale of a product containing TNFR in that country.

    1.21  "Materials" shall mean any and all compounds, culture media, assay
systems, DNA, RNA, and fragments thereof, genes and other nucleotide constructs,
plasmids, vectors, development strains, expression systems, cell lines,
antibodies, hybridomas, clones, peptides, protein compositions, colonies, animal
models, promoters, epitopes, microorganisms and any other biological or chemical
materials, as well as the information embodied therein, that are necessary or
useful in developing, manufacturing, using, marketing, or selling TNFR.

    1.22  "Net Sales" shall mean the gross invoice price of TNFR sold by a
party, its Affiliates, sublicensees, distributors or other designees to an
independent third party after deducting, if not already deducted in the amount
invoiced:

         (i)    the standard inventory cost (actual acquisition cost) of
devices used for dispensing or administering TNFR and that accompany such TNFR
as they are sold;

         (ii)   then normal or customary trade, cash, and/or quantity
discounts;

         (iii)  returns, rebates and allowances;

         (iv)   retroactive price reductions applicable to sales of TNFR;

         (v)    sales commissions paid to distributors and selling agents;

         (vi)   sales taxes, excise taxes, tariffs and duties; and

         (vii)  two percent (2%) of the amount invoiced to cover bad debt,
freight or other transportation costs, insurance charges, additional special
packaging, and other governmental charges.

    1.23  "North America" shall mean the United States, its territories and
possessions (including Puerto Rico) and Canada.

    1.24  "Patents" shall mean Immunex Patents, AHP Patents, and Joint Patents.

    1.25  "Product Development Steering Committee" or "Steering Committee"
shall mean the Committee created in Article 3.03 of this Agreement.

    1.26  "Technology" shall mean all technical data, and business and other
commercial information relating to TNFR that are owned or controlled by a party
and for


                                          4

<PAGE>


which such party has a right to disclose or license to the other hereunder,
including techniques, discoveries, inventions, processes, know-how, Materials,
regulatory data and information of any kind including pre-clinical and clinical
experimental results and any other information reasonably necessary to permit a
party to develop, manufacture, test, use, market, sell and distribute TNFR, in
whatever form kept and whether or not such information is patentable,
copyrightable, or subject to trademark protection, and whether or not such
aforementioned intellectual property protection has been sought.  As
appropriate, Technology may be referred to as that solely owned or controlled by
Immunex ("Immunex Technology"), that solely owned or controlled by AHP ("AHP
Technology"), and that owned or controlled jointly by the parties ("Joint
Technology").

    1.27  "TNFR" shall mean tumor necrosis factor receptor (p75 to p80) and all
derivatives and analogues thereof.

                              ARTICLE 2.  LICENSE GRANTS

    2.01  Immunex hereby grants AHP a royalty-free, exclusive license,
including the right to sublicense others, under Immunex Intellectual Property,
and Immunex's portion of the Joint Technology, to research, develop, use,
distribute, offer for sale, import and sell TNFR manufactured by Immunex in the
AHP Territory.  It is contemplated by the parties that Immunex shall retain the
rights to manufacture TNFR for itself and AHP.  Should Immunex do so, it is the
parties' intention that Immunex enter into a manufacturing agreement with AHP to
manufacture and supply TNFR to AHP under a "Manufacturing Agreement" as more
fully defined in Article 4.  In the event Immunex cannot or will not manufacture
TNFR on behalf of AHP, the license to AHP shall include the right to make and
have made.  Furthermore, to the extent that AHP or its Affiliates needs to sell
TNFR in North America for export and final sale in the AHP Territory, the
license to AHP includes such right to sell for export to the AHP Territory.

    2.02  Immunex shall determine whether it will exclusively market TNFR
itself to the Health Care Market in any country or countries in the Immunex
Territory.  If Immunex determines that it will not so market or will cease to so
market TNFR in any one or more such countries, Immunex shall offer AHP all such
marketing rights to TNFR.  If Immunex and AHP are unable to establish mutually
acceptable terms within 90 days following such offer, Immunex shall have the
right to license TNFR to a third party on terms which are no less favorable to
Immunex than those offered to AHP.  If Immunex desires to enter into a license
with an unaffiliated third party on terms that, taken as a whole, are more
favorable to such third party than the terms offered to AHP, then Immunex shall
not enter into an agreement with such third party unless it first offers such
new terms to AHP.  AHP shall have thirty (30) days from receipt of such
additional offer to accept such terms.


                                          5

<PAGE>

    2.03  AHP hereby grants Immunex a royalty-free exclusive license
(including, subject to Article 2.02, the right to sublicense others) under AHP
Intellectual Property, and AHP's portion of the Joint Technology, to research,
develop, make, have made, use, distribute, offer for sale, import and sell TNFR
itself to health care professionals and/or providers in the Immunex Territory.
This exclusive license, however, is subject to AHP's retained right to make and
have made TNFR in North America if the Manufacturing Agreement is not entered
into, and AHP's right to sell for export to the AHP Territory.

    2.04  Joint Technology shall be jointly owned by the parties, with each
holding an undivided one-half (1/2) interest in such Joint Technology.  Joint
Technology shall not be assignable or otherwise conveyed to third parties
without the express written consent of both parties to this Agreement, said
consent not to be unreasonably withheld or delayed.  The parties each shall
execute and deliver any instrument and take such other actions as may be
required to assign, convey or transfer to such other party its undivided one-
half (1/2) interest in such Joint Technology.

                           ARTICLE 3.  DEVELOPMENT OF TNFR

    3.01  Promptly after the Effective Date, the parties shall negotiate in
good faith and jointly prepare a Research Strategy Document and a Global
Development Plan to be implemented jointly.  The Research Strategy Document
shall outline the general indications and approaches to be taken to gain
initial/subsequent market approval.  The Global Development Plan shall specify
the duties and responsibilities of each party in completing the preclinical and
clinical development of TNFR, and shall include and identify the studies needed
to obtain Governmental Approvals.  The plan shall also specify the criteria for
continuation of clinical studies at mutual and synchronized decision points.
The parties shall have access to all TNFR clinical data (raw data and finished
reports)  generated by each other.  AHP shall have the right to participate in
FDA advisory board presentations and Immunex shall have the right to participate
in equivalent presentations sponsored by AHP in the AHP Territory.

    3.02  The parties hereby establish a Joint Project Development Team to
devise the Research Strategy Document and Global Development Plan, and to manage
the implementation of the Global Development Plan.  The Joint Project
Development Team shall be comprised of members designated by each party on the
basis of specific areas of expertise and ability to contribute to the
development of TNFR. The parties shall be free to change or equally increase the
number of their respective representatives upon reasonable notice to the other
party.  Decisions of the Joint Project Development Team shall be made by
consensus (i.e., a majority of the members designated by the representatives
designated by each party).  In the implementation of the Global Development
Plan, the Joint Project Development Team may utilize either party's personnel or
other resources in any Territory, subject to prior mutual agreement. The


                                          6

<PAGE>

Joint Project Development Team shall take into account factors such as personnel
availability, expertise and overall efficiency in allocating responsibilities to
the parties.

    3.03  The parties hereby establish a Product Development Steering 
Committee, or Steering Committee, comprising five senior representatives of 
each party to supervise and monitor the implementation activities of each of 
the Joint Product Development Teams.   Co-chairpersons of the Steering 
Committee shall be designated annually by AHP and Immunex.  The initial 
members and Co-chairpersons of the Steering Committee are listed on Schedule 
A attached hereto.  The parties shall be free to change or equally increase 
the number of their respective representatives upon reasonable notice to the 
other party. Expansion of the Steering Committee shall require the consent of 
each party. The Steering Committee shall, among other things, review draft 
research strategies, forecast and endorse projected budgets and manage the 
flow of funds. The Steering Committee shall meet once each calendar quarter 
and may meet at additional times, as the parties shall agree.  The 
Co-chairpersons shall send notices and agendas for all regular meetings to 
all Steering Committee members. The location of regularly scheduled meetings 
shall alternate between the offices of the parties, unless otherwise agreed 
by the parties.   Meetings may be held telephonically.  Members of the 
Steering Committee shall have the right to participate in and vote at 
meetings by telephone or proxy.  The party hosting any meeting shall appoint 
a secretary to the meeting who shall record the minutes of the meeting; such 
minutes shall be circulated to the parties promptly following the meeting for 
review, comment, ratification and distribution.

    3.04  The Joint Project Development Team shall endeavor to reach a
consensus on all matters in dispute within a period of thirty (30) days.  If
such a resolution cannot be reached in that time period (or earlier at the
election of either party), the matter shall be referred to the Steering
Committee which shall endeavor to resolve the matter as soon as practicable.
Decisions of the Steering Committee shall be made by simple majority vote of the
members of the Steering Committee.  If, after a period of thirty (30) days (or
earlier at the election of either party), the matter is still not resolved, it
shall be referred to the CEO of Immunex and the Executive Officer of AHP
responsible for its global pharmaceutical operations, or their designees, to
resolve in a period of thirty (30) days through good faith discussions, or if
still unresolved, to promptly agree upon a binding third party dispute
resolution mechanism intended to promptly and fairly resolve the matter in
dispute.

    3.05  All development costs incurred with respect to development activities
authorized by the Joint Project Development Team for the North American and
European markets incurred from the Effective Date shall be shared on an equal
basis between the parties, such costs to include, without limitation:

         -direct out-of-pocket costs (e.g. grants, Materials, animals, and
costs of similar nature);


                                          7

<PAGE>

         -costs of chemical or process development, excluding capital costs
other than depreciation;

         -direct labor costs (salary plus benefits);

         -an overhead factor of [ * ], added to the direct labor costs; and

         -TNFR clinical materials, which shall be manufactured by Immunex in
compliance with GMP.

         All costs shall be determined in accordance with allocation principles
established by mutual agreement of the parties which shall be in accordance with
generally accepted accounting principles, consistently applied.  The Joint
Project Development Team shall prepare annual workplans and budgets designating
planned activities and estimated costs subject to cost sharing ("Shared Costs")
pursuant to this Article 3.05, which workplans and budgets shall be reviewed by
the Steering Committee and such budgets shall be combined by the Steering
Committee with similar budgets, if any, relating to other product development
agreements between the parties.  Based upon such budgets, the party projected to
be required to reimburse the other to equally balance Shared Costs shall pay to
the other, in advance of each calendar month, 1/12 of the difference between
(a) its budgeted annual Shared Costs, and (b) one-half of the total annual
budgeted Shared Costs to be incurred by both parties.  Each party shall report
to the other, within ten (10) days following the end of each calendar month, its
actual Shared Costs for such month.  The parties shall adjust the budgeted
monthly payments on a quarterly basis to reflect actual Shared Costs incurred in
previous calendar quarters.   Each report shall detail the costs outlined above.
In reporting labor costs, each party shall report (a) the project or project
involved; (b) the number of hours expended by each of its employees during such
quarter, (c) a general indication of the activity or activities in which such
hours were expended; and (d) the direct labor cost rate (salary and benefits)
and overhead rate applicable to such employee.  AHP shall have a [ * ] credit
towards its obligations to Immunex hereunder.

    3.06  Territory specific activities intended to support unique regulatory
and marketing approvals in territories other than North America and Europe
(e.g., Japan, Latin America) shall be excluded from sharing and shall be borne
solely by AHP.  Each party shall be responsible for funding and management of
any Phase IV studies performed in its respective Territory.

    3.07  Either party may, in its sole discretion, relinquish its rights to
TNFR, and the sharing of costs hereunder, by providing written notice thereof to
the other party within the following time periods:

         (A)  TIME PERIOD I:  Within thirty (30) days following the end of
Phase II clinical trials and receipt by each party of a "Registration and
Positioning Strategy


                                          8

<PAGE>

Document".  The "Registration and Positioning Strategy Document" means a
document which updates the Global Development Plan and which is prepared by the
Joint Project Development Team prior to the initiation of Phase III studies; and

         (B)  TIME PERIOD II:  Within thirty (30) days of receipt of the
results of that portion of the Phase III clinical trial data to be utilized for
the regulatory filings in its Territory together with any other relevant data
that is then available to the parties and is useful or necessary in evaluating
the safety or efficacy of TNFR.

         Upon receipt by the non-relinquishing party of such notice, all rights
to TNFR shall be transferred to the non-relinquishing party to exploit in its
sole discretion, with no further obligations of any kind to the relinquishing
party except for the right to receive payments in accordance with Article 3.08
below.

    3.08  Subject to the non-relinquishing party's right to recoup its
development costs accrued from the date that the other party relinquished its
rights to TNFR pursuant to Article 3.09 below, if the non-relinquishing party or
its Affiliate, distributor, sublicensee, or other designee sells product(s)
containing TNFR after receipt of notification of relinquishment of rights to
TNFR from the other party pursuant to Article 3.07 (A) or (B), such other party
shall pay or cause to be paid to the relinquishing party an earned royalty on
their respective quarterly Net Sales in the relinquishing party's former
Territory to begin on the date of Market Launch of TNFR in a specific country
within such Territory and continue until the later of (i) expiration of the last
Granted Patent(s) in such country that specifically claims product containing
TNFR being sold in such country, or (ii) ten (10) years from the date of such
Market Launch of product in such country, all in accordance with the following:

         (A)  If TNFR has been relinquished pursuant to Article 3.07 (A) 
above and is not claimed by a Granted Patent(s), the non-relinquishing party 
shall pay or cause to be paid to the other party (i) an earned royalty of 
[ * ] on its, its Affiliates', or other designees' Net Sales thereof and (ii) 
[ * ] of revenues received by the non-relinquishing party with respect to Net 
Sales thereof by a third party if rights thereto are licensed by the 
non-relinquishing party to an unaffiliated third party;

         (B)  If TNFR has been relinquished pursuant to Article 3.07(A) above
and is claimed by a Granted patent(s), the non-relinquishing party shall pay or
cause to be paid to the other party (i) an earned royalty of [ * ] on its, its
Affiliates' or other designees' Net Sales thereof and (ii) if rights thereto are
licensed by the non-relinquishing party to an unaffiliated third party, [ * ] of
revenues received by the non-relinquishing party with respect to Net Sales
thereof by such third party;

         (C)  If TNFR has been relinquished pursuant to Article 3.07 (B) 
above and is not claimed by a Granted Patent(s), the non-relinquishing party 
shall pay or cause to be paid to the other party (i) an earned royalty of 
[ * ] on its, its Affiliates', or other


                                          9

<PAGE>

designees' Net Sales thereof and (ii) [ * ] of revenues received by the
non-relinquishing party with respect to Net Sales thereof by a third party
if rights thereto are licensed by the non-relinquishing party to an
unaffiliated third party; and

         (D)  If TNFR has been relinquished pursuant to Article 3.07 (B) 
above and is claimed by a Granted Patent(s), the non-relinquishing party 
shall pay or cause to be paid to the other party (i) an earned royalty of 
[ * ] on its, its Affiliates', or other designees' Net Sales thereof and (ii) 
if rights thereto are licensed by the non-relinquishing party to an 
unaffiliated third party, [ * ]of revenues received by the non-relinquishing 
party with respect to Net Sales thereof by such third party;

         provided, however, that if no Granted Patent(s) exist with respect to
TNFR, earned royalties or third-party revenues shall be due in accordance with
subparagraph (A) and (C) above on a country-by-country basis for a period of ten
(10) years beginning on the date of Market Launch of TNFR in each such country
within the relinquishing party's former Territory.

         (E)  Royalties due on sales of Combination Product(s) would be
calculated by multiplying actual Net Sales of such Combination Products by the
fraction A/(A+B) where A is the invoice price of TNFR if sold separately, and B
is the total invoice price of any other active component or components in the
combination, if sold separately.

         (F)  If the other active component or components in the combination
are not sold separately, Net Sales, for the purpose of determining royalties on
Combination Products would be calculated by multiplying actual Net Sales of such
Combination Products by the fraction A/C where A is the invoice price of TNFR if
sold separately and C is the invoice price of the Combination Product.

         (G)  If neither TNFR nor the Combination Product is sold separately,
Net Sales for purposes of determining royalties on the Combination Products
would be calculated as above except that Immunex and AHP would allocate values
to the components A and B based upon a good-faith determination of the
respective contributions of such components to the market value of the
Combination Product.

         (H)  Sales between a party and its Affiliates, sublicensees or other
designees or among its Affiliates and sublicensees or other designees, shall not
be subject to royalties, but in such cases royalties shall be calculated upon
the party's, its sublicensees', Affiliates' or other designees' annual Net Sales
to an independent third party.  Only one royalty payment shall accrue with
respect to the same unit of TNFR.  No royalties shall accrue on disposition of
reasonable quantities of TNFR and Combination Products for no charge as samples
or donations to independent third parties.


                                          10

<PAGE>


    3.09  Notwithstanding the foregoing, no earned royalties would be due with
respect to Net Sales made prior to the date that the non-relinquishing party has
fully recouped its development costs in the relinquishing party's former
Territory with respect thereto accrued from the date that the other party
relinquished its rights to TNFR under Article 3.07, as such costs are
substantiated in accordance with allocation principles established by mutual
agreement of the parties, which shall be in accordance with generally accepted
accounting principles, consistently applied, and offset by any amounts received
from third parties as license fees or other consideration for the grant of
marketing rights in the relinquishing party's former Territory or the use of
data obtained in development activities in such Territory.

    3.10  If a party elects to develop an additional or secondary indication
for TNFR, that the other party chooses not to support, the developing party
shall retain all rights to the data it obtains in such independent development
activities, subject to the non-developing party's right to acquire rights to use
such data to prepare regulatory approval filings in its Territory upon payment
to the developing party of a fee equal to [ * ] of the developing party's costs
of conducting clinical studies and other activities related to such additional
or secondary indication, such right to expire twelve (12) months from the date
of the initial submission of a regulatory approval filing or registration
package with respect to such indication.

                         ARTICLE 4.  MANUFACTURING AGREEMENT

    4.01  No later than two (2) years prior to AHP's estimated first Market
Launch in any country in the AHP Territory, the parties shall enter into a
definitive Manufacturing Agreement for supply of TNFR to AHP, unless Immunex
cannot or will not manufacture TNFR for AHP.  TNFR shall not be manufactured by
a party that is not an Affiliate of a party to this Agreement without the prior
written consent of both parties.

    4.02  The Manufacturing Agreement shall contain terms and conditions
customary in such agreements, including but not limited to the following:

         (A)  AHP shall pay to Immunex the following sums for TNFR manufactured
by Immunex:
              (i)    All third party royalty obligations to be paid only once
either separately or as part of TNFR Manufacturing Cost;

              (ii)   Immunex Manufacturing Cost of TNFR; plus

              (iii)  A reasonable profit equal to [ * ] of Immunex Manufacturing
Cost (excluding for these purposes any third party royalty obligation included
in Manufacturing Cost) of TNFR;



                                          11

<PAGE>

         provided, however, that the parties shall negotiate in good faith an 
appropriate reduction in such amount to be paid to Immunex with respect to 
TNFR to be sold in any country in the AHP Territory in which such amount 
(plus any other royalty obligations paid directly to third parties) on a per 
unit basis exceeds [ * ] of the net selling price (determined in accordance 
with Article 1.22) per unit of TNFR to be sold by Wyeth, its Affiliates, 
sublicensees, distributors or other designees, such reduction to take into 
account all relevant facts and circumstances with respect to the marketing of 
TNFR in such country.

    4.03  Prior to the start of manufacture of TNFR, the parties shall
establish guidelines upon which the Immunex Manufacturing Cost of TNFR will be
based.  These guidelines will be in accordance with allocation principles
established by mutual agreement of the parties, which shall be in accordance
with generally accepted accounting principles, consistently applied.  The
Immunex Manufacturing Cost of TNFR shall be recalculated annually based upon
these guidelines.

                  ARTICLE 5.  PATENT AND TECHNOLOGY REPRESENTATIONS
                                    AND WARRANTIES

    5.01  Immunex represents and warrants to AHP that:

         A.   it has, and at all times during the term of the license granted
to AHP herein will maintain the right to grant to AHP the rights set forth in
this Agreement and to provide to AHP the Immunex Technology and Immunex Patents
rights set forth in this Agreement;

         B.   the existing Immunex Patent(s) and Immunex Intellectual Property
are owned by or licensed to Immunex exclusively with the right to license and/or
sublicense to AHP;

         C.   it is not aware of any claims by any third parties to an
ownership interest in the Immunex Intellectual Property licensed to AHP under
this Agreement;

         D.   it shall immediately notify AHP in writing in the event it
receives notice of any claims as referenced in C above, becomes in default under
any license agreement, or becomes aware of patent, trade secret, or other right
as referenced in C above.

         E.   to the best of its knowledge, all, and only, the true inventors
of the subject matter claimed are named in the existing Immunex Patent(s), and
no part of Immunex Intellectual Property has been unlawfully derived from a
third party.

         F.   it has and shall continue to disclose all information material to
the examination of Immunex Patent(s), within the meaning of 37 C.F.R. 1.56, in
writing to


                                        12

<PAGE>

the U.S.P.T.O.; and further, is not aware of any anticipatory disclosures within
the meaning of 35 U.S.C. 102 that would be prejudicial to the patentability of
the subject matter of existing patent applications within Immunex Patent(s).

    5.02  AHP represents and warrants to Immunex that:

         A.   it has, and at all times during the term of the license granted
to Immunex herein will maintain the right to grant to Immunex the rights set
forth in this Agreement and to provide to Immunex the AHP Intellectual Property
rights set forth in this Agreement;

         B.   the existing AHP Intellectual Property are owned by or licensed
to AHP exclusively with the right to license and/or sublicense to Immunex;

         C.   it is not aware of any claims by any third parties to an
ownership interest in the AHP Intellectual Property licensed to Immunex under
this Agreement;

         D.   it shall immediately notify Immunex in writing in the event it
receives notice of any claims as referenced in C above, becomes in default under
any license agreement, or becomes aware of a patent, trade secret, or other
right as referenced in C above.

         E.   to the best of its knowledge, all, and only, the true inventors
of the subject matter claimed are named in the existing AHP Patent(s), and no
part of AHP Intellectual Property has been unlawfully derived from a third
party.

         F.   it has and shall continue to disclose all information material to
the examination of AHP Patent(s), within the meaning of 37 C.F.R. 1.56, in
writing to the U.S.P.T.O.; and further, is not aware of any anticipatory
disclosures within the meaning of 35 U.S.C. 102 that would be prejudicial to the
patentability of the subject matter of existing patent applications within AHP
Patent(s).

    5.03  During the term of this Agreement, Immunex shall promptly inform AHP
concerning all Intellectual Property relating to TNFR that is conceived, made,
developed or reduced to practice solely by Immunex personnel, or by Immunex
personnel jointly with employees of AHP.  During the term of this Agreement, AHP
shall inform Immunex concerning all Intellectual Property relating to TNFR that
is conceived, made, developed or reduced to practice solely by AHP personnel, or
by AHP personnel jointly with employees of Immunex.

    5.04  Immunex shall be responsible, at its sole expense, for the
preparation, filing, prosecution and maintenance of all Immunex Patent(s) in a
commercially reasonable manner. Immunex shall consult with AHP in advance, and
consider AHP's timely given reasonable comments and advice with respect to the
prosecution and


                                          13

<PAGE>

maintenance of Immunex Patent(s), and shall give due credence to AHP's comments
with respect to appropriate countries in which a foreign filing campaign should
be conducted.

    5.05  AHP shall prepare, file, prosecute and maintain, in a commercially
reasonable manner, all AHP Patent(s) owned or controlled solely by AHP, and all
Joint Patent(s).  All preparation, filing, prosecution and maintenance of Joint
Patent(s) and AHP Patent(s) will be handled by AHP, with AHP paying all costs
related thereto. If, in AHP's sole discretion, it is deemed necessary to use
outside counsel or an agent to prepare, file, prosecute or maintain AHP
Patent(s) or Joint Patent(s), AHP shall engage such counsel or agent. Fifty
percent (50%) of all reasonable expenses paid to outside counsel with respect to
Joint Patent(s) shall be paid by AHP and fifty percent (50%) by Immunex.  AHP
shall be solely responsible for any and all expenses paid to outside counsel
with respect to AHP Patent(s). AHP may, upon sixty (60) calendar days prior
written notice, advise Immunex that AHP no longer wishes to prosecute or
maintain any patents or patent applications, as solely owned by AHP and within
AHP Patent(s), or Joint Patent(s). If AHP so notifies Immunex, Immunex may take
over the prosecution or maintenance of Joint Patent(s) or allow the Joint
Patent(s) to become abandoned or lapse.  Immunex shall have no right to take
over the prosecution, but may take over, at its sole expense, the maintenance of
any such aforementioned AHP Patent(s).

    5.06  Immunex shall inform AHP of all substantive developments with respect
to the filing, prosecution and maintenance of Immunex Patent(s), including
without limitation, interference, opposition, nullification, and revocation
matters.  AHP shall inform Immunex of all substantive developments with respect
to the filing, prosecution and maintenance of AHP Patent(s) and Joint Patent(s),
including without limitation, interference, opposition, nullification, and
revocation matters. With respect to said activities, each shall provide to the
other copies of all office actions and other communications concerning any
Immunex Patent(s), AHP Patent(s) and/or Joint Patent(s), and consider the timely
given, reasonable comments and advice of the other party with respect to the
strategy employed and submissions made relative thereto.

    5.07  Each party shall give notice to the other of any decision to cease
prosecution and/or maintenance of AHP Patent(s), Immunex Patent(s) or Joint
Patent(s) and, in such case, shall permit the other, at its sole discretion, to
continue prosecution or maintenance, at its own expense. If either party elects
to continue prosecution or maintenance upon notice from the other that it will
cease such activities, the party giving notice shall execute such documents and
perform such acts at its expense as may be reasonably necessary for the other
party to perform such prosecution or maintenance.  Fifty percent (50%) of the
expenses and costs incurred by a party to continue prosecution and maintenance
of Patent(s) abandoned by the other party shall be fully creditable against
royalties due under Article 3 herein; however, no royalty payment when due,
regardless of the number of such credits available to a party in accordance with
the terms of this Agreement, shall be reduced by more than fifty percent (50%)
in any calendar


                                          14

<PAGE>

year.  Unused credits may be carried over into subsequent royalty periods 
until fully exhausted. In the event that either party continues prosecution 
and/or maintenance of any Joint Patent(s), it shall do so at its sole expense.

    5.08  Immunex shall enforce and/or protect the Immunex Patent(s) and
Immunex Intellectual Property licensed to AHP under this Agreement against any
third party who infringes or wrongfully uses same in any manner.  With the
reasonable assistance and cooperation of Immunex in all material respects, AHP
shall have the right but not the obligation to enforce and/or protect the Joint
Patent(s) and Joint Intellectual Property, in its sole discretion, against any
third party who infringes or wrongfully uses same in any manner.  AHP shall, at
its sole discretion, enforce and/or protect the AHP Patent(s) and AHP
Intellectual Property against any third party who infringes or wrongfully uses
same in any manner.  The party enforcing the aforementioned Patent and/or
Intellectual Property rights shall bear all costs of suit and shall retain all
damages or other monies awarded or received in settlement of such suit.

    5.09
         a)   In the event that there is infringement on a substantial
commercial scale by a third party of any Immunex Patent(s) or misuse of Immunex
Intellectual Property, the party first receiving notification thereof shall
notify the other party in writing to that effect, including with said written
notice evidence establishing a prima facie case of such infringement or misuse
by such third party.  If, prior to the expiration of one hundred and twenty
(120) days from the date of said notice, Immunex obtains a discontinuance of
such infringement or brings suit against the third party infringer, then the
obligation of AHP to pay royalties hereunder shall continue unabated.  Immunex
shall bear all the expenses of any suit brought by it and shall retain all
damages or other monies awarded or received in settlement of such suit.  AHP
will cooperate with Immunex in any such suit and shall have the right to consult
with Immunex and be represented by its own counsel at its own expense.  Immunex
shall not settle any such suit without the consent of AHP as to the terms and
conditions of such settlement.

         b)   In addition, AHP shall have the right after such one hundred
twenty (120) day notice period, but not the obligation, to bring suit against
such infringer and join Immunex as a party plaintiff, provided that AHP shall
bear all the expenses of such suit.  Immunex will cooperate with AHP in any such
suit brought by AHP against a third party, and shall have the right to consult
with AHP and to participate in and be represented by independent counsel in such
litigation at its own expense.  AHP shall incur no liability to Immunex as a
consequence of such litigation or any unfavorable decision resulting therefrom,
including any decision holding an Immunex Patent invalid or unenforceable.


                                          15

<PAGE>

    5.10  Each party shall promptly give notice to the other of the grant,
lapse, revocation, surrender, invalidation or abandonment of any Immunex
Patent(s), Joint Patent(s) or AHP Patent(s) for which it has the responsibility
of filing, prosecution and maintenance.

    5.11  The parties hereto shall cooperate with each other in seeking to gain
patent term restoration or similar extensions or continuations of rights under
the Immunex Patent(s), AHP Patent(s) or Joint Patent(s).

    5.12  The parties shall cooperate to obtain such license(s) under any third
party patent(s) as necessary or desirable to manufacture, use and sell TNFR in
any Territory.  Any such license shall only be entered into if both Immunex and
AHP give their prior written consent.

                             ARTICLE 6.  CONFIDENTIALITY

    6.01  All information of whatever kind relating to or developed hereunder,
including without limitation, all oral, written, electronic or other
communications and other information, including any and all analysis or
conclusions drawn or derived regarding the, Materials, Field, Intellectual
Property, TNFR, Immunex Patent(s), AHP Patent(s), Joint Patent(s), or either
party's marketing, financial or other business plans or data, personnel,
processes, formulations, analytical procedures, clinical procedures,
methodologies, products, samples, specimens or functions ("Information") that is
owned or provided by either party or licensed or otherwise provided to the other
party hereunder shall be possessed and used subject to the following terms and
conditions:

         A.   Each party shall keep all Information in confidence and shall use
Information solely in accordance with the terms and conditions of this
Agreement.  Absent prior written consent of the other party, neither party shall
disclose any Information to any person or entity, except those of its officers,
employees, in the case of Immunex, employees of AHP and its Affiliates, in the
case of AHP and its Affiliates, employees of Immunex, clinical investigators and
consultants of the parties who require said Information to enable such party to
perform obligations under this Agreement. The officers, employees, clinical
investigators and consultants to whom Information is to be disclosed shall be
advised by such party of, and bound by the terms of this Agreement, wherever
reasonably practicable.

         B.   The obligations of confidentiality and non-use set forth herein
shall not apply to any Information that is (or subsequently becomes):

              (i)    not owned or otherwise controlled by, or provided by AHP
or Immunex or licensed hereunder; or


                                          16

<PAGE>

              (ii)   published or available to the general public otherwise
than through a breach of this Agreement; or

              (iii)  previously known to or independently developed by AHP
prior to entering into this Agreement.

         C.   In the event that either party is required by judicial or
administrative process to disclose any or all of the Information, it shall
promptly notify the other party and allow the other party a reasonable time to
oppose such process before disclosing any Information, and to redact any portion
of Information as may be permissibly redacted in accordance with such
aforementioned process.

    6.02  Subject to Sections 12.01 and 12.02 hereof, each party shall be free
to disclose and use such Information in any manner that reasonably advances the
research, development, manufacturing, marketing and/or sale of TNFR.  Nothing
herein shall limit either party's disclosure or use of any of its Intellectual
Property or other Information in which the other party does not have an
ownership interest or that is not exclusively licensed to the other party.

    6.03  Subject to the license rights set forth in Article 2 herein and the
parties' rights upon termination set forth in Article 9 herein, upon expiration
or termination of this Agreement, a party that has received Information from the
other party shall immediately return to the disclosing party all Information
that it has received from the disclosing party, all notes that may have been
made regarding said Information, and all copies thereof. The receiving party may
retain one copy of each item of Information and notes regarding same, provided
that said copy shall be retained and used solely for compliance purposes and
shall be held in the receiving party's confidential files. For purposes of this
Paragraph, AHP and Immunex shall each be considered the disclosing parties with
respect to any Joint Intellectual Property.

    6.04  The confidentiality and non-use provisions contained herein shall
remain effective during the term of this Agreement and for five (5) years
thereafter.
                          ARTICLE 7. ACCOUNTING AND REPORTS

    7.01  Each party and/or its Affiliates, as applicable, shall keep true
accounts of Net Sales and of all sums payable under Article 3 hereof and deliver
to the other party, within forty five (45) calendar days after the end of each
calendar quarter year after relinquishment of the other party's rights to TNFR,
a written account, including quantities, of its and its sublicensees' Net Sales
of TNFR subject to royalty payments together with the amount of the payment due
for said calendar quarter year.

    7.02  With each accounting required by this Article, the reporting party
and/or its Affiliates, as applicable, shall also provide to the other party,
without deduction except


                                          17

<PAGE>

where expressly permitted by this Agreement, all royalty payments due for the
calendar quarter year for which the accounting is made.

    7.03  Each party and/or its Affiliates, as applicable, shall keep accurate
records in sufficient detail to enable the amounts due to the other party to be
determined.  Upon request, the reporting party shall permit an independent,
certified public accountant selected by the other party, except one to whom the
reporting party has a reasonable objection, to have access, on reasonable
advance notice and during regular business hours, to records necessary to
determine the correctness of any report or payment made in respect to any
calendar year and obtain information as to the amount of royalties payable for
any such period. Such examination shall be at the requesting party's sole
expense and shall not take place more than once each calendar year. These rights
with respect to any calendar year shall terminate two (2) years after the end of
any such year.

    7.04  Each party shall keep true and detailed accounts of all expenditures
in furtherance of the research and development collaboration hereunder.  During
the term of this Agreement and for one (1) year thereafter, at the requesting
party's sole expense and no more than once per calendar year, the other party
shall permit an audit of such records by an independent, certified public
accountant.  Such accountant shall be selected by the requesting party but shall
be one to whom the other party has no reasonable objection, and shall access, on
reasonable advance notice and during regular business hours, the records
necessary to determine the correctness of the aforementioned report and
accounting.  These rights with respect to any calendar year shall terminate two
(2) years after the end of any such year.

                                 ARTICLE 8. CURRENCY

    8.01  All payments to be made under this Agreement shall be made in United
States dollars by bank wire transfer in immediately available funds to a bank
account designated by the party receiving the funds.

                                ARTICLE 9. TERMINATION

    9.01  Upon any material breach by either party under this Agreement, in
addition to any other remedy it may have, the non-breaching party may terminate
this Agreement by sixty (60) calendar days written notice to the breaching
party, specifying the material breach, default or other defect.  If the
breaching party has proposed a course of action to cure the breach and is acting
in good faith to cure the breach, but has not cured the breach by the sixtieth
(60th) day, the said period shall be extended by such period as is reasonably
necessary to permit the breach to be cured.

    9.02  Either party may terminate this Agreement and any licenses granted
hereunder with notice if the other party becomes insolvent, makes an assignment
for the benefit of creditors, is the subject of proceedings in voluntary or
involuntary bankruptcy


                                          18

<PAGE>

instituted on behalf of or against such party, or has a receiver or trustee
appointed for all or substantially all of its property, provided that in the
case of an involuntary bankruptcy proceeding such right to terminate shall only
become effective if the party consents to the involuntary bankruptcy or such
proceeding is not dismissed within ninety (90) calendar days after the filing
thereof.

    9.03  Any expiration or early termination of this Agreement shall be
without prejudice to the rights of either party against the other accrued or
accruing under this Agreement prior to the effective date of such termination
including the obligation to pay royalties for TNFR sold prior to the effective
date of such termination.

                         ARTICLE 10. RIGHTS UPON TERMINATION

    10.01  If this Agreement is terminated by either party pursuant to Article
9.01 or 9.02, on the effective date of said termination, both party's
obligations under this Agreement shall terminate. However, notwithstanding such
termination, the terminating party shall retain a fully paid up, fee free,
worldwide, exclusive license under the Joint Intellectual Property and the
non-terminating party's Intellectual Property to research, develop, make, have
made, use, import, offer for sale, and sell TNFR in accordance with the license
grant set forth in Article 2 herein.

                                ARTICLE 11. INDEMNITY

    11.01  Except as is set forth in Article 11.02 herein and the Manufacturing
Agreement if entered into by the parties, and, except to the extent caused by
Immunex's negligent or more culpable acts or omissions, AHP shall defend,
indemnify and hold Immunex harmless from and against any and all claims,
settlements of claims or other liabilities, including reasonable attorneys fees,
that Immunex incurs as a result of exercise by AHP of any rights licensed or
otherwise accruing to it under this Agreement.  Immunex agrees that AHP shall
select counsel reasonably satisfactory to Immunex to undertake the defense of
any claim against Immunex covered by AHP's indemnity, Immunex further agrees
that AHP, by and through said counsel and with Immunex's participation, shall
control the course of such legal representation including, but not limited to,
settlements or other resolutions of claims. AHP shall pay the fees of such
counsel as they are incurred.

    11.02  Except as is set forth in Article 11.01 herein and the Manufacturing
Agreement if entered into by the parties, and, except to the extent caused by
AHP's negligent or more culpable acts or omissions, Immunex shall defend,
indemnify and hold AHP harmless from and against any and all claims, settlements
of claims or other liabilities, including reasonable attorneys fees, that AHP
incurs as a result of exercise by Immunex of any rights licensed or otherwise
accruing to it under this Agreement.  AHP agrees that Immunex shall select
counsel reasonably satisfactory to AHP to undertake the defense of any claim
against AHP covered by Immunex's indemnity.  AHP further agrees


                                          19

<PAGE>

that Immunex, by and through said counsel and with AHP's participation, shall
control the course of such legal representation including, but not limited to,
settlements or other resolutions of claims.  Immunex shall pay the fees of such
counsel as they are incurred.

    11.03  Except to the extent caused by the other party's negligent or more
culpable acts or omissions, each party shall defend, indemnify and hold the
other party harmless from and against any and all claims, settlements of claims
or other liabilities, including reasonable attorneys fees, that the indemnified
party incurs as a result of failure or breach of any warranty made by the other
party herein or the other party's exercise of any rights or obligations accruing
to it under this Agreement. The indemnifying party shall select counsel
reasonably satisfactory to the other party to undertake the defense of any claim
covered by an indemnity.  The indemnifying party by and through said counsel and
with the other party's participation, shall control the course of such legal
representation including, but not limited to, settlements or other resolutions
of claims.  The indemnifying party shall pay the fees of such counsel as they
are incurred. It is understood and agreed that the obligations set forth in this
Article 11.03 are in addition to any remedies for breach of contract that either
party may have.
                   ARTICLE 12. PUBLIC ANNOUNCEMENT AND PUBLICATION

    12.01  If either party desires to, or is required by law to, make a public
announcement concerning this Agreement or the subject matter hereof, such party
shall give reasonable advance notice of the proposed text of such announcement
to the other party for its review and approval.  All written publication and
other public announcements such as regulatory filings and approvals shall
include the names of the parties, where appropriate.

    12.02  In the event that either party wishes to publicly disclose, any
research performed hereunder under or the results thereof, or any Information
(as defined in Article 6.01 herein), it shall provide a copy of any such
proposed public disclosure to the non-disclosing party at least sixty (60)
calendar days prior to any planned issuance of the same. The non-disclosing
party shall have sixty (60) calendar days from the receipt of the proposed
public disclosure to object to the proposed disclosure on the basis that it
contains or references unprotected patentable subject matter and/or violates the
confidentiality provisions hereof.  Notwithstanding the foregoing sentence, each
party shall use reasonable efforts to review and respond to any proposed
disclosures as quickly as possible within said sixty (60) calendar days. If the
non-disclosing party objects solely on the basis that the disclosure contains
unprotected patentable subject matter, the party that has proposed the
disclosure shall refrain from making the disclosure for one hundred twenty (120)
calendar days from the date of the non-disclosing party objection in order to
allow the parties an opportunity to obtain proper legal protection for the
subject matter contained in the proposed public disclosure. In the event that
the non-disclosing party objects to any proposed public disclosure on the basis
that some or all of said disclosure


                                          20

<PAGE>

violates the confidentiality terms of this Agreement or any third party
confidentiality agreement, said disclosure shall not be made.

    12.03     In the event that either party submits any manuscript relating to
TNFR for scientific publication, it will consider and acknowledge the
contributions of the other party, including, as appropriate, co-authorship.

                           ARTICLE 13. INDEPENDENT PARTIES

    13.01  At all times during the term of this Agreement, Immunex and AHP
shall be deemed and shall in fact be independent of one another and neither
shall be authorized or empowered hereby to act as the agent for the other party
for any purpose whatsoever or, on behalf of the other, enter into any contract,
warranty or representation as to any matter.

    13.02  AHPC and ACY shall not exercise or cause to be exercised any of
ACY's rights set forth under Section 4.04 or 4.05 of the Governance Agreement to
prevent or interfere with the exercise by Immunex of any rights provided to it
under this Agreement.

                ARTICLE 14. ADDITIONAL REPRESENTATIONS AND WARRANTIES

    Each party hereby represents and warrants to the other party as follows:

    14.01  Such party (a) is a corporation duly organized, validly existing and
in good standing under the laws of the state in which it is incorporated, (b)
has the corporate power and authority and the legal right to own and operate its
property and assets, to lease the property and assets it operates under lease,
and to carry on its business as it is now being conducted, and (c) is in
compliance with all requirements of applicable law, except to the extent that
any noncompliance would not have a material adverse effect on the properties,
business, financial or other condition of such party and would not materially
adversely affect such party's ability to perform its obligations under this
Agreement.

    14.02  Such party (a) has the corporate power and authority and the legal
right to enter into this Agreement and to perform its obligations hereunder, and
(b) has taken all necessary corporate action on its part to authorize the
execution and delivery of this Agreement and the performance of its obligations
hereunder.  This Agreement has been duly executed and delivered on behalf of
such party, and constitutes a legal, valid, binding obligation, enforceable
against such party in accordance with its terms.

    14.03  All necessary consents, approvals and authorizations of all
governmental authorities and other persons required to be obtained by such party
in connection with the execution, delivery and performance of this Agreement
have been and shall be obtained.


                                          21

<PAGE>

    14.04  Notwithstanding anything to the contrary in this Agreement, the
execution and delivery of this Agreement and the performance of such party's
obligations hereunder (a) do not conflict with or violate any requirement of
applicable laws or regulations and (b) do not and shall not conflict with,
violate or breach or constitute a default or require any consent under, any
contractual obligation of such party.

    14.05  THE PARTIES MAKE NO REPRESENTATIONS AND EXTEND NO WARRANTIES OF ANY
KIND, EITHER EXPRESS OR IMPLIED, AND PARTICULARLY THAT COMPOUNDS AND/OR PRODUCTS
WILL BE DEVELOPED HEREUNDER, WILL HAVE COMMERCIAL UTILITY OR MERCHANTABILITY OR
FITNESS FOR A PARTICULAR PURPOSE.

                             ARTICLE 15.  EXPORT CONTROLS

    15.01  The parties acknowledge that both are subject to laws and
regulations of the United States of America governing exportation of technical
information, computer software, laboratory prototypes and other commodities and
that the rights hereunder are contingent on compliance with all such laws and
regulations.  The transfer of certain technical data and commodities may require
a license from the appropriate agency of the United States Government and
neither party shall export such technical data or commodities to certain foreign
countries to which export restrictions apply without the prior approval of such
agency.

                          ARTICLE 16.  SURVIVAL AND WAIVERS

    16.01  The covenants of the parties that by their terms or express intent
are to be performed after the termination or expiration of this Agreement shall
survive the termination or expiration of this Agreement.

    16.02  Any term or condition of this Agreement may be waived or qualified
at any time by the party entitled to the benefit thereof by a written instrument
that specifically identifies this Agreement and the term or condition to be
waived or qualified and is executed by a duly authorized officer of said party.
No delay or failure on the part of either party in exercising any rights
hereunder, and no partial or single exercise thereof, shall constitute a waiver
of such rights or of any other rights hereunder.

                              ARTICLE 17. GOVERNING LAW

    17.01  With the exception of patent matters which shall be governed by
application of national patent laws, this Agreement shall be construed and the
respective rights of the parties hereto determined in accordance with the laws
of the State of New Jersey and of the United States, and the parties shall
submit to the jurisdiction of the district and state courts of New Jersey,
however applicable.


                                          22

<PAGE>

                                ARTICLE 18. ASSIGNMENT

    18.01  Neither party may directly or indirectly assign or otherwise
transfer this Agreement in whole or in part without the prior written consent of
the other.  Any assignment or other transfer in violation of this provision
shall be void.

                           ARTICLE 19. SUBSIDIARY AGREEMENT

    19.01  AHP may, from time to time, request and Immunex agrees to execute,
upon request, separate license agreements (hereinafter called "Subsidiary
Agreements") separately granting directly to any Affiliate equivalent rights as
granted to AHP herein, within the AHP Territory.  Any such Subsidiary Agreement
entering into force under this Paragraph shall be prepared by AHP and shall
contain terms and conditions consistent with those of this Agreement.

                                ARTICLE 20. SEVERANCE

    20.01  If any provision of this Agreement is held to be invalid or
unenforceable by a court of competent jurisdiction, all other provisions shall
continue in full force and effect.

                                 ARTICLE 21. NOTICE

    21.01     Notices to AHP shall be addressed to:

                   AMERICAN HOME PRODUCTS CORPORATION
                   Five Giralda Farms
                   Madison, New Jersey 07940
                   Attention:     Office of the Senior Vice President and
                                  General Counsel

    Copy to:       Senior Vice President, Global Business Development
                   Wyeth-Ayerst
                   555 E. Lancaster
                   St. Davids, PA  19087

    Notices to Immunex shall be addressed to:

                   IMMUNEX CORPORATION
                   51 University Street
                   Seattle, Washington   98101
                   Attention:  General Counsel

    21.02    Any notice required or provided for by the terms of this Agreement
shall be in writing, addressed in accordance with this Paragraph, and sent by
registered or certified mail, return receipt requested, postage prepaid or by
express courier services

                                          23

<PAGE>

providing evidence of delivery. The effective date of any notice shall be the 
date of receipt by the receiving party.

                              ARTICLE 22. FORCE MAJEURE

    22.01  No failure or omission by the parties hereto in the performance of
any obligation under this Agreement shall be deemed a breach hereof or create
any liability if the same arises from any cause beyond the control of the
parties including, but not limited to, the following: act of God; acts or
omissions of any government; any rule, regulation or order issued by any
governmental authority or by any officer, department, agency or instrumentality
thereof; fire; storm; flood; earthquake; accident; war; rebellion; insurrection;
riot; invasion; or strike, lockout or other work stoppage provided that such
failure or omission is cured as soon as is practicable after the occurrence of
the force majeure.
                             ARTICLE 23. ENTIRE AGREEMENT

    23.01  This Agreement, together with any Schedules attached hereto and
expressly incorporated herein, and the Manufacturing Agreement if entered into
by the parties, constitute the entire agreement between the parties relative to
the subject matter hereof and supersede all previous arrangements whether
written or oral. Any amendment or modification to this Agreement shall be of no
effect unless made in a writing that specifically references this Agreement and
signed by both parties.

    IN WITNESS WHEREOF the parties, intending to be bound hereby, have caused
their duly authorized representatives to execute this Agreement.

AMERICAN HOME PRODUCTS CORPORATION
NAME: /s/ Joseph J. Carr
    -------------------------

DATE:  July 17, 1996
    -------------------------

IMMUNEX CORPORATION
NAME: /s/ Edward V. Fritzky
    -------------------------
    Edward V. Fritzky
    Chairman and Chief Executive Officer

DATE:  July 17, 1996
    -------------------------


                                          24

<PAGE>
                                      SCHEDULE A

                                  STEERING COMMITTEE

AHP Members:

    Bruce Schneider

    Joseph Pittelli

    Mahdi Fawzi

    Gerald Fisher

    Justin Victoria

Immunex members:

    Peggy Phillips

    Kenneth Seamon

    F. Ann Hayes

    Helmut Sassenfeld

    Andrew Lewis


<PAGE>

                                                                    EXHIBIT 10.3









                                    EXHIBIT 10.3

<PAGE>

                                                                    EXHIBIT 10.3

                       AMENDMENT NO. 1 TO IMMUNEX NEW ONCOLOGY
                              PRODUCT LICENSE AGREEMENT

    This Amendment No. 1 (this "Amendment") to the Immunex Oncology Product
License Agreement, dated as of June 1, 1993 (the "INOP Agreement") is made as of
the lst day of July, 1996 by and between Immunex Corporation, a Washington
corporation and American Cyanamid Company, a Maine Corporation and a
wholly-owned subsidiary of American Home Products Corporation, a Delaware
Corporation ("AHPC").  Capitalized terms used herein without definition have the
meanings set forth in the INOP Agreement.

    WHEREAS, the parties to the INOP Agreement desire to amend the INOP
Agreement as set forth herein.

    NOW, THEREFORE, in consideration of the premises, representations and
warranties set forth herein, the parties hereto agree as follows:

                            ARTICLE I.  GLOBAL DEVELOPMENT

    1.01:     When Immunex formally accords any INOP "IND Track Status",
Immunex shall, as soon as reasonably practicable thereafter, provide to Cyanamid
written notice thereof, together with an "Immunex IND Track Proposal Document"
and Cyanamid shall have a period of ninety (90) days from the date of such
written notice (the "Exercise Period") in which to provide written notice to
Immunex (a "Retention Notice") of Cyanamid's intention to retain its exclusive
license pursuant to Paragraph 2.01 of the INOP Agreement with respect to such
INOP (an "Elected INOP").  The "Immunex IND Track Proposal Document" means a
proprietary Immunex research management document that (i) outlines the
background data accumulated on a candidate product that supports the designation
by Immunex management that such candidate product should be accorded IND track
status, and (ii) contains a pre-clinical development plan and a description of
potential indications for such IND track candidate product, together with
preliminary timelines and budgets through the anticipated IND filing.

    1.02:     Cyanamid shall keep Immunex informed of all current and planned
research and development activities related to INOPs by providing Cyanamid with
a written annual report detailing the status of such activities for the previous
year and a summary of the activities planned for each item so detailed, as well
as any new items for the year immediately following the year reported on.
Immunex shall also provide Cyanamid or its designee with summary semi-annual
reports of such activities in a form that is acceptable to each party.  From
time to time, Immunex shall also provide oral updates of significant
developments with regard to Immunex research and development efforts related to
INOPs.   Cyanamid representative(s) shall also be invited to Immunex Trimester
Project


<PAGE>

Review Meetings to discuss select oncology discovery projects and product
candidates that are the subject of Cyanamid's rights under the INOP Agreement.

    1:03:     If Cyanamid has not provided to Immunex a retention notice with
respect to an INOP within the applicable Exercise Period, the license granted
pursuant to Paragraph 2.01 of the INOP Agreement with respect to such INOP shall
terminate and be of no further force or effect and Immunex shall thereupon have
all rights to such INOP to exploit in its sole discretion, with no further
obligations of any kind to Cyanamid or AHPC.

    1:04:     Promptly after the delivery of a Retention Notice with respect to
an Elected INOP, the parties shall negotiate and develop the terms and
conditions of a product development agreement governing the ongoing development
and commercialization of such Elected INOP, such agreement, to the extent
appropriate, to include on a reciprocal basis the principles set forth in
Paragraphs 2.07(b)-(p) of the Research Agreement, dated as of the date hereof
(the "Research Agreement"), among AHPC, Cyanamid and Immunex.

                              ARTICLE II.  MISCELLANEOUS

    2.01:     Except as otherwise set forth in this Amendment, the INOP
Agreement shall remain in full force and effect.
























                                         -2-

<PAGE>

    IN WITNESS WHEREOF, the parties, intending to be bound hereby, have caused
their duly authorized representatives to execute this Amendment.

                                            IMMUNEX CORPORATION



                                            By:/s/ Edward V. Fritzky
                                               ---------------------
                                            Name:  Edward V. Fritzky
                                            Title: Chairman and Chief
                                                    Executive Officer

                                            AMERICAN CYANAMID COMPANY

                                            By:  /s/ Joseph J. Carr
                                                 --------------------
                                            Name:  Joseph J. Carr
                                            Title: Senior Vice President


AGREED TO AND ACCEPTED BY:

AMERICAN HOME PRODUCTS CORPORATION

By: /s/ Joseph J. Carr
    ---------------------
Name:  Joseph J. Carr
Title: Senior Vice President


                                      -3-

<PAGE>

                                                                    EXHIBIT 99.1



                                     Exhibit 99.1


<PAGE>

                                                                    EXHIBIT 99.1


                         IMMUNEX AND AMERICAN HOME PRODUCTS
                              REVISE RESEARCH AGREEMENTS

    SEATTLE -- July 17, 1996 -- Immunex Corporation (NASDAQ:IMNX) and American
Home Products Corporation (NYSE:AHP) today announced that they have agreed to
revise and amend research agreements related to joint development of new
oncology products and the TNF receptor (TNFR).

    Under the prior oncology research agreement, Immunex was obligated to
contribute $26.1 million in 1996, up to $38.3 million in 1997, and 50 percent of
the AHP oncology discovery research budget for years after 1997.  The revised
agreements, to be made effective July 1, provide for Immunex to contribute $16
million per year (adjusted for inflation in the years after 1996) to support AHP
discovery research in oncology, plus 50 percent of shared development costs if
an AHP oncology product is selected for clinical testing.  For comparison
purposes, the Immunex contribution specified under these agreements totaled $13
million in the first half of 1996 and will decrease in the second half to $8
million for discovery, plus additional cost for development programs, when
specific plans are established.

    "Today, the Board approved new agreements between Immunex and AHP," said Ed
Fritzky, Immunex chairman and CEO.  "Immunex's financial support of AHP oncology
research will be focused on discovery of small molecule cancer products, which
will complement Immunex's biological research efforts.  The projected cost
savings from the amended agreements will allow the company to accelerate
investment in Immunex products with nearer-term potential, such as TNFR for
rheumatoid arthritis, Leukine-Registered Trademark- GM-CSF in fungal infections,
Novantrone-Registered Trademark- for prostate cancer, and to investigate the
utility of FLT3 ligand as an immunomodulator and IL-4 receptor as an asthma
therapy."

    Under the terms of the new agreements, Immunex will retain North American
marketing rights on oncology products resulting from its own research.  AHP
retains ex-North American rights to oncology products discovered by Immunex.
Immunex's rights with respect to AHP oncology products will be converted into an
option to obtain North American marketing rights to products resulting from AHP
oncology research supported by Immunex.  Once an oncology product is selected
for collaborative development, the companies will share costs on a 50/50 basis.

    In addition, the companies entered into a new agreement on TNFR.  Global
marketing rights are allocated as in the original agreement, with Immunex
retaining rights in North America, and AHP with exclusive rights for territories
outside North America.  The companies have established joint project management
systems and will

<PAGE>

share the costs of developing TNFR in North America and Europe.  The prior
agreement called for AHP to contribute $4 million per year in the years 1994
through 1997 to support TNFR development.

    Immunex is a biopharmaceutical company dedicated to developing immune
system science to protect human health.  The company's products offer hope to
patients with cancer, inflammatory and infectious diseases.

    American Home Products owns a majority interest in Immunex.  AHP is one of
the world's largest research-based pharmaceutical and health care products
companies and is a leading developer, manufacturer and marketer of prescription
drugs and over-the-counter medications.  It is also a leader in vaccines,
generic pharmaceuticals, biotechnology, agricultural products, animal health
care, medical devices and food products.


                                      -2-


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