<PAGE>

                                                                    EXHIBIT 10.1

                             ENBREL SUPPLY AGREEMENT

THIS ENBREL SUPPLY AGREEMENT ("Agreement") is made effective as of April 12,
                               ---------
2002, by and between Immunex Corporation, a Washington corporation, having its
principal place of business at 51 University Street, Seattle, Washington 98101
("Immunex"), and Genentech, Inc., a Delaware corporation, having its principal
  -------
place of business at One DNA Way, South San Francisco, California 94080
("Genentech").
  ---------

                                   BACKGROUND
                                   ----------

Immunex markets and sells a certain proprietary biological pharmaceutical
product known as ENBREL(R) (etanercept). Immunex desires to obtain additional
supply of commercial quantities of ENBREL bulk drug substance. Genentech has the
experience and expertise necessary to perform the manufacturing and related
services needed to supply ENBREL bulk drug substance, and Genentech owns a
facility that, with some modifications, could be suitable for production of
commercial quantities of ENBREL bulk drug substance.

Immunex desires to retain Genentech as a nonexclusive manufacturer of commercial
quantities of ENBREL bulk drug substance and purchase commercial quantities of
such product from Genentech, and Genentech desires to perform such services and
sell commercial quantities of such product to Immunex, all on the terms and
conditions set forth in this Agreement.

                                    AGREEMENT
                                    ---------

NOW, THEREFORE, IN CONSIDERATION OF the mutual covenants set forth in this
Agreement, and for other good and valuable consideration, the receipt and
sufficiency of which are hereby acknowledged, the Parties hereby agree as
follows:

                             ARTICLE 1. DEFINITIONS
                             ----------------------

The following terms, whether used in the singular or plural, shall have the
meanings assigned to them below for purposes of this Agreement.

1.1  "Acquisition Cost" means the actual invoiced price paid by Genentech to any
      ----------------
     Third Party for acquiring any materials used in the manufacture of the
     Product under this Agreement, including, but not limited to, shipping and
     handling costs and customs duties incurred and paid by Genentech in
     connection with the acquisition of such materials, and also including [*]
     percent ([*]%) of the above amounts to cover such

* Portions of this exhibit have been omitted pursuant to a request for
confidential treatment filed with the Securities and Exchange Commission. The
omitted portions of this exhibit have been filed separately with the SEC.

<PAGE>

     Party's storage and overhead costs. This definition, including the [*]
     percent ([*]%) markup, shall only apply in the circumstances set forth in
     Section 6.2(a)(5) and Section 19.3(d)(1) hereof.
     -----------------     ------------------

1.2  "Affiliate" means, with respect to any Party, any other corporation or
      ---------
     business entity that directly, or indirectly through one or more
     intermediaries, controls, is controlled by or is under common control with
     such Party. For purposes of this definition, the term "control" means
     direct or indirect ownership of fifty percent (50%) or more of the
     securities or other ownership interests representing the equity voting
     stock or general partnership or membership interest of such entity or the
     power to direct or cause the direction of the management or policies of
     such entity, whether through the ownership of voting securities, by
     contract, resolution or otherwise.

1.3  "Batch" or "Lot" means the quantity of Bulk Drug produced from a single
      -----      ---
     Run, and refers to a Commercial Batch or Lot, a Development Batch or Lot,
     and/or a Qualification Batch or Lot, as the context requires. A Run may
     result in more than one subbatch or sublot due to splitting into tanks
     downstream in the Manufacturing Process.

1.4  "Batch Records" shall have the meaning set forth in the Quality Agreement.
      -------------

1.5  "BIP" means Boehringer Ingelheim Pharma KG.
      ---

1.6  "BIP Confidential Information" means Immunex Confidential Information that
      ----------------------------
     has been identified in writing as confidential information of BIP, and is
     referred to in Section 17.6 hereof.
                    ------------

1.7  "Bulk Drug" means the bulk form of the Product which has been manufactured
      ---------
     by Genentech pursuant to this Agreement, which has been purified to a
     concentrated form from one or more Batches and can be stored in a liquid or
     frozen form under appropriate conditions, and, except with respect to
     Non-Conforming Bulk Drug, which has been manufactured in compliance with
     cGMP and conforms to the Bulk Drug Specifications.

1.8  "Bulk Drug Commitment" refers to the first [*] months of each binding
      --------------------
     rolling Product Manufacturing Forecast (including all amendments thereto),
     and means a commitment by Genentech to comply with and perform the number
     of Runs set forth therein. The Bulk Drug Commitment is a rolling [*] month
     commitment, and is described with more particularity in Section 4.2 hereof.
                                                             -----------

1.9. "Bulk Drug Specifications" means specifications developed by Immunex for
      ------------------------
     Bulk Drug as set forth in the Product sBLA, including, without limitation,
     testing methods and acceptance criteria for each Batch generated, a summary
     of which is attached to the Quality Agreement, as such specifications may
     be amended from time to time in accordance with Section 6.2 hereof,
                                                     -----------
     including, without limitation, such amendments as

* Portions of this exhibit have been omitted pursuant to a request for
confidential treatment filed with the Securities and Exchange Commission. The
omitted portions of this exhibit have been filed separately with the SEC.

                                     Page 2

<PAGE>

     may be required to obtain approval from the FDA and other applicable
     regulatory authorities in the United States.

1.10 "cGMP" means the regulatory requirements for current good manufacturing
      ----
     practices promulgated by the FDA under the FD&C Act, 21 C.F.R.(S)(S)210,
     211 and 600 et seq. and under the PHS Act, 21 C.F.R.(S)(S)600-610, as the
     same may be amended from time to time.

1.11 "Cell Line" means a proprietary Immunex Chinese Hamster Ovary cell line
      ---------
     that expresses the Product.

1.12 "Certificate of Analysis" means, for each Batch, a document prepared by
      -----------------------
     Immunex: (a) listing tests performed by Immunex, specifications, test
     date(s), and test results, and certifying the accuracy of the foregoing;
     (b) referring to the related Certificate of Compliance prepared by
     Genentech, listing the manufacturing date, unique Batch number, and
     quantity of Bulk Drug in such Batch, as certified by Genentech in such
     Certificate of Compliance; and (c) referring to the related Certificate of
     Testing prepared by Genentech, listing tests performed by Genentech,
     specifications, test date(s), and test results, as certified by Genentech.
     The Parties shall from time to time agree upon a format or formats for the
     Certificate of Analysis to be used under this Agreement.

1.13 "Certificate of Compliance" means, for each Batch, a document prepared by
      -------------------------
     Genentech: (a) listing the manufacturing date, unique Batch number, and
     quantity of Bulk Drug in such Batch, and (b) certifying that such Batch was
     manufactured in accordance with the Bulk Drug Specifications and cGMP. The
     Parties shall from time to time agree upon a format or formats for the
     Certificate of Compliance to be used under this Agreement.

1.14 "Certificate of Testing" means, for each Batch, a document prepared by
      ----------------------
     Genentech: (a) listing tests performed by Genentech, specifications, and
     test results, and (b) certifying the accuracy of the foregoing. The Parties
     shall from time to time agree upon a format or formats for the Certificate
     of Testing to be used under this Agreement.

1.15 "Change of Control" means the merger, acquisition or consolidation of
      -----------------
     Immunex with or into Amgen Inc. or a subsidiary of Amgen Inc.

1.16 "Commercial Batch" or "Commercial Lot" means a Batch or Lot produced from a
      ------------------------------------
     Commercial Run.

1.17 "Commercial Run" means a Run that is initiated following the commencement
      --------------
     of Commercial Production and is used to manufacture commercial Bulk Drug.

1.18 "Commercially Reasonable Efforts" means [*].
      -------------------------------

* Portions of this exhibit have been omitted pursuant to a request for
confidential treatment filed with the Securities and Exchange Commission. The
omitted portions of this exhibit have been filed separately with the SEC.

                                     Page 3

<PAGE>

1.19 "Commercially Reasonable Best Efforts" means: for Immunex, [*]; and for
      ------------------------------------
     Genentech, [*].

1.20 "Confidential Information" means Immunex Confidential Information and/or
      ------------------------
     Genentech Confidential Information, as the context requires.

1.21 "Development Batch" means a Batch or Lot produced from a Development Run.
      -----------------

1.22 "Development Run" means a Run used for process demonstration and
      ---------------
     confirmation of some or all of the Manufacturing Process steps, and is
     described in Section 3.7(a) hereof.
                  --------------

1.23 "Effective Date" means April 12, 2002, which is the date set forth in the
      --------------
     first paragraph of this Agreement and shall be the effective date of this
     Agreement.

1.24 "EMEA" means the European Medicines Evaluation Agency, or any successor
      ----
     agency.

1.25 "Enbrel License Agreement" means that certain License Agreement for
      ------------------------
     Etanercept between Immunex and Genentech dated [*].

1.26 "Facility Modifications and Services Costs" means the actual invoiced price
      -----------------------------------------
     paid by Genentech to any Third Party for acquiring services, including,
     without limitation, design and engineering services, and necessary
     equipment, for modifications to the Genentech Facility needed to implement
     the Manufacturing Process at the Genentech Facility, all to the extent
     incurred in accordance with the Tech Transfer Agreement, and including,
     without limitation, such amounts incurred in accordance with the Letter of
     Intent (and also including, without limitation, such amounts incurred in
     accordance with the Letter of Intent after expiration of the Letter of
     Intent and prior to or on the Effective Date of this Agreement, as if the
     Letter of Intent had been extended through and including the Effective Date
     of this Agreement).

1.27 "Facility Validation" shall have the meaning ascribed to it in the Tech
      -------------------
     Transfer Agreement.

1.28 "FD&C Act" means the United States Federal Food, Drug and Cosmetic Act, as
      --------
     the same may be amended from time to time.

1.29 "FDA" means the United States Food and Drug Administration, or any
      ---
     successor agency thereto.

1.30 "Field" shall mean the manufacture of Product utilizing the manufacturing
      -----
     process in actual use as of the Effective Date, as well as any
     modifications to such manufacturing process that are implemented in
     accordance with this Agreement into the manufacturing process actually used
     by Genentech in manufacturing Product pursuant to this Agreement, as well
     as any other modifications to such manufacturing process

* Portions of this exhibit have been omitted pursuant to a request for
confidential treatment filed with the Securities and Exchange Commission. The
omitted portions of this exhibit have been filed separately with the SEC.

                                     Page 4

<PAGE>

     that are implemented by Immunex, its Affiliates, Product licensees or
     contract manufacturers for Product either during or, with respect to [*].

1.31 "Finished Product" means Bulk Drug which has been formulated, compounded,
      ----------------
     filled into containers, and labeled, and placed in final commercial
     packaging.

1.32 "For Cause Audit" shall have the meaning set forth in the Quality
      ---------------
     Agreement.

1.33 "Genentech Confidential Information" means all technical and other
      ----------------------------------
     information, whether patented or unpatented, relating to the Genentech
     Facility and/or Genentech processes, methods, operations, technologies,
     forecasts and business information that are disclosed or supplied to, or
     used on behalf of Immunex by Genentech pursuant to this Agreement, the Tech
     Transfer Agreement and/or the Quality Agreement, or of which Immunex may
     become aware of through the presence of their employees or agents at
     Genentech offices or at the Genentech Facility, including, without
     limitation, trade secrets, know-how, processes, concepts, experimental
     methods and results and business and scientific plans and information and
     facility layout and schematics.

1.34 "Genentech Facility" means Genentech's commercial manufacturing facility
      ------------------
     located at One DNA Way in South San Francisco, California. In addition, in
     the event Genentech, in its sole discretion, utilizes storage capacity in
     its Vacaville, California facility to store Bulk Drug, then the term
     "Genentech Facility" includes, when and as the context requires,
      ------------------
     Genentech's facility located in Vacaville, California, but only to the
     extent that, and with respect to those portions of, the Vacaville facility
     that is used by Genentech to perform Genentech's obligations hereunder.

1.35 [*]

1.36 "Genentech Patents" shall have the same definition as set forth in the
      -----------------
     Enbrel License Agreement.

1.37 "Genentech [*] Patents" shall mean Patents containing claims covering [*],
      ---------------------
     in each case which were [*].

1.38 "Immunex Confidential Information" means the Cell Line, Master Cell Bank,
      --------------------------------
     Working Cell Bank, Manufacturing Documentation, Manufacturing Process, and
     Product, and all technical and other information, whether patented or
     unpatented, relating thereto and/or to Immunex processes, methods,
     operations, technologies, forecasts and business information that are
     disclosed or supplied to Genentech by or on behalf of Immunex pursuant to
     this Agreement, the Tech Transfer Agreement and/or the Quality Agreement,
     or of which Genentech may become aware of through the presence of its
     employees or agents at Immunex offices or facilities or at other facilities
     that manufacture the Product, including, without limitation, trade secrets,
     know-how, processes, concepts, experimental methods and results and
     business and scientific plans and information and facility layout and
     schematics. All portions of documents

* Portions of this exhibit have been omitted pursuant to a request for
confidential treatment filed with the Securities and Exchange Commission. The
omitted portions of this exhibit have been filed separately with the SEC.

                                     Page 5

<PAGE>

     and records describing or to the extent relating to the Manufacturing
     Process at the Genentech Facility, including, without limitation, process
     trend and variability data related to the Product, shall be deemed to be
     Immunex Confidential Information.

1.39 "Letter of Intent" means that certain letter of intent and authorization to
      ----------------
     proceed between the Parties dated February 4, 2002, as amended on March 22,
     2002, regarding the intent of the Parties to negotiate in good faith and
     execute this Agreement, and which letter is superceded in accordance with
     its terms by this Agreement.

1.40 "Manufacturing Documentation" means all documents and records describing or
      ---------------------------
     otherwise related to the Manufacturing Process or any part of the
     Manufacturing Process provided to Genentech by or on behalf of Immunex
     under this Agreement, the Tech Transfer Agreement or the Quality Agreement,
     including, without limitation, documents and records consisting of or
     containing piping and instrumentation diagrams, software logic and
     descriptions, batch records, standard operating procedures, including,
     without limitation, standard operating procedures for in-process quality
     control testing, facility layout schematics, equipment and instrumentation
     specifications and process trend and variability data.

1.41 "Manufacturing Process" means the [*] production process for the
      ---------------------
     manufacture of Bulk Drug pursuant to this Agreement, as summarily described
     in the Quality Agreement and as described in the Tech Transfer Agreement,
     as such process may be changed from time to time in accordance with this
     Agreement. [*]

1.42 "Master Cell Bank" means Immunex's reference deposit or collection of vials
      ----------------
     of the Cell Line, from which the Working Cell Bank is derived.

1.43 "Milestone I" means [*], and is referred to in Section 5.2(a) hereof.
      -----------                                   --------------

1.44 "Milestone II" means [*] referred to in Section 5.2(b) hereof.
      ------------                           --------------

1.45 "Milestone III" means [*] or, if earlier, [*], and is referred to in
      -------------
      Section 5.2(c) hereof.
      --------------

1.46 "Milestone IV" means [*], and is referred to in Section 5.2(d) hereof.
      ------------                                   --------------

1.47 "Net Sales" shall have the same definition as set forth in the Enbrel
      ---------
     License Agreement.

1.48 "Non-Conforming Bulk Drug" means Bulk Drug that fails to conform to any of
      ------------------------
      the warranties set forth in Section 6.1(a) hereof.
                                  --------------

1.49 "Non-Portable Equipment" means the Equipment (as defined in Section 14.2
      ----------------------                                     ------------
     hereof), excluding any Portable Equipment. Components of the Non-Portable
     Equipment, such as valves, pumps and agitators, shall also be deemed
     Non-Portable Equipment. Non-Portable Equipment includes the related
     documentation regarding the design,

* Portions of this exhibit have been omitted pursuant to a request for
confidential treatment filed with the Securities and Exchange Commission. The
omitted portions of this exhibit have been filed separately with the SEC.

                                     Page 6

<PAGE>

     validation, operation, calibration and maintenance of such equipment.

1.50 "PHS Act" means the Public Health Service Act, Biological Products, as
      -------
     amended, as the same may be amended from time to time.

1.51 "Party" or "Parties" means Genentech and/or Immunex, as the context
      -----      -------
     requires.

1.52 "Patents" shall mean, with respect to an invention, any patent or patent
      -------
     application, and any patent issuing therefrom, together with any
     extensions, reissues, reexaminations, substitutions, renewals, divisions,
     continuations and continuations-in-part thereof, and any patent or patent
     application claiming priority to any application in common with any such
     patent containing a disclosure substantially similar to any such patent,
     all to the extent the foregoing contain claims covering such invention.

1.53 "Portable Equipment" means the portable equipment described with
      ------------------
     particularity in the Tech Transfer Agreement and referred to in Section 5.1
                                                                     -----------
     hereof, including, without limitation, the related documentation regarding
     the design, validation, operation, calibration, and maintenance of such
     equipment. The Portable Equipment is a part of the Equipment, as defined in
     Section 14.2 hereof. Components of the Portable Equipment, such as valves,
     ------------
     pumps and agitators, shall also be deemed Portable Equipment.

1.54 [*]

1.55 "Product" means the proprietary biological pharmaceutical product known as
      -------
     ENBREL(R)(etanercept), which is a [*].

1.56 "Purchase Price" means the purchase price to be paid by Immunex to
      --------------
     Genentech for Bulk Drug as determined in accordance with the terms of this
     Agreement.

1.57 "Qualification Batch" or "Qualification Lot" means a Batch or Lot produced
      -------------------      -----------------
     from a Qualification Run.

1.58 "Qualification Run" means a Run used to document the operability and
      -----------------
     reproducibility of the Manufacturing Process at the Genentech Facility, and
     is described in Section 3.7(b) hereof.
                     --------------

1.59 "Quality Agreement" means the quality agreement between the Parties of even
      -----------------
     date herewith which refers to this Agreement.

1.60 "Roche" means Roche Holdings, Inc., a Delaware corporation, and its
      -----
     "Affiliates" (as hereinafter defined) other than Genentech and Genentech's
     subsidiaries. With respect to Roche, "Affiliates" means any other
                                           ----------
     corporation or business entity that directly, or indirectly through one or
     more intermediaries, controls, is controlled by or is under common control
     with Roche Holdings, Inc.; and, for purposes of this definition, the

* Portions of this exhibit have been omitted pursuant to a request for
confidential treatment filed with the Securities and Exchange Commission. The
omitted portions of this exhibit have been filed separately with the SEC.

                                     Page 7

<PAGE>

     term "control" means direct or indirect ownership of fifty percent (50%) or
     more of the securities or other ownership interests representing the equity
     voting stock or general partnership or membership interest of such entity
     or the power to direct or cause the direction of the management or policies
     of such entity, whether through the ownership of voting securities, by
     contract, resolution or otherwise.

1.61 "Run" means a single fermentation start or run of the Manufacturing Process
      ---
     at the [*] liter fermentation scale at the Genentech Facility, and refers
     to a Commercial Run, Development Run and/or Qualification Run, as the
     context requires. A fermentation start for the Product shall be deemed to
     be a Run if such fermentation start proceeds to the [*] at the [*] liter
     scale or later in the Manufacturing Process.

1.62 "sBLA" means a biologics license application for the Product, any
      ----
     equivalent successor filing thereto with the FDA, and any supplements or
     amendments to any of the foregoing.

1.63 "Specialized Raw Materials" means the specialized raw materials described
      -------------------------
     with particularity in the Tech Transfer Agreement and referred to in
     Section 3.6 hereof.

1.64 [*]

1.65 "Tech Transfer Agreement" means the technology transfer agreement and
      -----------------------
     process implementation plan between the Parties of even date herewith which
     refers to this Agreement, and which describes the agreement of the Parties
     regarding the transfer of technology and implementation of the
     Manufacturing Process at the Genentech Facility, and the modifications to
     the Genentech Facility needed to implement the Manufacturing Process at the
     Genentech Facility, including a timeline, budget and statement of work
     jointly developed by the Parties, as the same may be amended from time to
     time by mutual written agreement of the Parties.

1.66 "Territory" means the entire world.
      ---------

1.67 "Third Party" means any party other than Immunex, Genentech and their
      -----------
     respective Affiliates.

1.68 "United States" or "U.S." means the United States of America, its
     -------------       ----
     territories and possessions, and the Commonwealth of Puerto Rico.

1.69 [*]

1.70 "Working Cell Bank" means a vialed collection of serially subcultivated
      -----------------
     cells generated by Immunex that is derived from the Master Cell Bank. The
     Working Cell Bank is used to establish seed cultures of the Cell Line to
     initiate the Manufacturing Process.

* Portions of this exhibit have been omitted pursuant to a request for
confidential treatment filed with the Securities and Exchange Commission. The
omitted portions of this exhibit have been filed separately with the SEC.

                                     Page 8

<PAGE>

1.71 Each of the following definitions are found in the body of this Agreement,
     or elsewhere, as indicated below:

<TABLE>
<CAPTION>
     Defined Term                                           Section
     ------------                                           -------
     <S>                                                    <C>
     "Acceptance Date"                                      4.3(e)
     [*]                                                    13.2(b)(2)(A)
     "Allocable Overhead"                                   3.9
     "Annual Maximum"                                       4.1
     "Annual Minimum"                                       4.1
     "Approved Suppliers"                                   3.6(a)
     "Assigned Inventions"                                  14.1(d)
     "Batch Record"                                         Quality Agreement
     "BIP ENBREL Supply Agreement"                          17.6
     "Commercial Production"                                6.3
     "Delivery Schedule"                                    4.3(a)
     "Delivery Date"                                        4.3(b)
     "Designated Carrier"                                   4.4
     "Designated Purchaser"                                 3.6(a)
     "Disclosing Party"                                     13.2(c)
     "Equipment"                                            14.2
     "FDA Approval"                                         3.4(d)
     "Finance Contact"                                      3.2(b)
     "Force Majeure Event"                                  20.1
     "Genentech Improvements"                               14.1(c)
     "Immunex IP Rights"                                    13.1
     "Indemnitee"                                           16.3(a)
     "Indemnitor"                                           16.3(a)
     "Internal Costs"                                       3.9
     "JPT"                                                  3.3(a)
     "Liabilities"                                          16.1(a)
     "Non-Requesting Party"                                 22.2(b)
     "Notified Party"                                       17.4(a)
     "Notifying Party"                                      17.4(a)
     "Operations Team"                                      6.3
     "Product Manufacturing Forecast"                       4.2(a)
     "Project Team Leader"                                  3.2
     "Recipient"                                            13.2(c)
     "Records"                                              5.4
     "Term"                                                 19.1
     "Warning Letter"                                       Quality Agreement
</TABLE>

* Portions of this exhibit have been omitted pursuant to a request for
confidential treatment filed with the Securities and Exchange Commission. The
omitted portions of this exhibit have been filed separately with the SEC.

                                     Page 9

<PAGE>

                 ARTICLE 2. COMMITMENT TO MANUFACTURE; PURCHASE
                 ----------------------------------------------

2.1  Commitment to Manufacture; Purchase.  Subject to the terms and conditions
     -----------------------------------
     set forth in this Agreement, during the Term, Immunex shall retain
     Genentech as a non- exclusive manufacturer of Bulk Drug, Genentech shall
     manufacture Bulk Drug exclusively for the benefit of Immunex and sell Bulk
     Drug exclusively to Immunex, and Immunex shall purchase such Bulk Drug from
     Genentech.

            ARTICLE 3. TECHNOLOGY TRANSFER AND PROCESS IMPLEMENTATION
            ---------------------------------------------------------

3.1  Technology Transfer and Manufacturing Process Implementation.
     ------------------------------------------------------------

     (a)  Process Description and Tech Transfer Agreement. The Parties
          -----------------------------------------------
          acknowledge that in order to enable them to fulfill their respective
          obligations under this Agreement, they have entered into the Tech
          Transfer Agreement and, pursuant thereto, jointly developed a plan for
          the transfer of technology and implementation of the Manufacturing
          Process at the Genentech Facility. Pursuant to this Agreement and the
          Tech Transfer Agreement, Immunex shall promptly disclose to Genentech
          the Manufacturing Process for the Bulk Drug and the Bulk Drug
          Specifications and other specifications related thereto, in order to
          enable Genentech to fulfill its obligations under this Agreement. The
          Tech Transfer Agreement sets forth the specific responsibilities of
          the Parties in connection with technology transfer and implementation
          of the Manufacturing Process at the Genentech Facility, and the
          modifications to the Genentech facility needed to implement the
          Manufacturing Process at the Genentech Facility, including a timeline,
          budget and statement of work jointly developed by the Parties, as the
          same may be amended from time to time by mutual written agreement of
          the Parties. The Tech Transfer Agreement includes milestones for the
          transfer of technology, exchange of information, and implementation of
          the project, reasonable timelines for achieving such milestones, and
          criteria for assessing the progress and success of the project as it
          progresses.


     (b)  Commercially Reasonable Best Efforts; Cooperation; Tech Transfer
          ----------------------------------------------------------------
          Agreement. The Parties shall use Commercially Reasonable Best Efforts
          ---------
          to complete their respective responsibilities in a timely manner under
          and in accordance with the Tech Transfer Agreement and Section 3.1 of
                                                                 -----------
          this Agreement. In addition, each Party agrees to use Commercially
          Reasonable Best Efforts to cooperate with and assist the other Party
          in its efforts to perform its obligations under the Tech Transfer
          Agreement and Section 3.1 of this Agreement; and, notwithstanding
                        -----------
          anything in this Agreement to the contrary, a Party shall not be
          deemed to have failed to use Commercially Reasonable Best Efforts to
          the extent the failure or delay in such Party's performance of its
          obligations is caused by a Force Majeure Event (as defined in Section
                                                                        -------
          20.1 below), or the failure or delay on the part of the other Party in
          ----
          performance of such other Party's obligations under this Agreement,
          the Tech Transfer Agreement and/or the Quality Agreement.

     (c)  On-Site Participation. Pursuant to and as set forth in greater detail
          ---------------------
          in the Tech Transfer Agreement and Quality Agreement, in order to
          expedite the

                                    Page 10

<PAGE>

          implementation of the Tech Transfer Agreement, Immunex may have its
          personnel on-site at the Genentech Facility, in such numbers as may be
          agreed to by the Parties but in no event less than a reasonable number
          of personnel. All such personnel will coordinate closely with
          Genentech in order to minimize impact on other Genentech operations.
          Unless otherwise agreed by Genentech: (i) such Immunex personnel shall
          have access only to those portions of the Genentech Facility
          reasonably related to the technology transfer and implementation of
          the Manufacturing Process, and (ii) while at the Genentech Facility,
          such Immunex personnel shall, at Genentech's option, be accompanied by
          a Genentech employee, in which case Genentech will make good faith
          efforts to have such Genentech employee available. Employees or agents
          of one Party who will be at the other Party's site may be required by
          the other Party to sign confidentiality agreements protecting the
          other Party's information, using a form of confidentiality agreement
          mutually agreed to by the Parties in writing in advance in order to
          give effect to the confidentiality provisions set forth in this
          Agreement. In addition, all Parties' personnel shall have executed a
          confidentiality agreement with their employer, which shall include an
          obligation of maintaining the confidentiality that would cover the
          other Party's confidential information.

     (d)  Delivery of Working Cell Bank. By not later than the applicable
          -----------------------------
          delivery deadline set forth in the Tech Transfer Agreement, Immunex
          shall deliver to Genentech the Working Cell Bank, which shall conform
          to Immunex's applicable release criteria, as set forth in Immunex's
          Working Cell Bank specifications.

3.2  Appointment of Project Team Leaders and Finance Contacts.
     --------------------------------------------------------

(a)  Appointment of Project Team Leader. Immunex and Genentech shall each
     ----------------------------------
     appoint a Project Team Leader (each, a "Project Team Leader") to act as the
                                             -------------------
     primary contact for such Party in connection with matters related to the
     implementation of the Manufacturing Process and in connection with
     activities to be performed under the Tech Transfer Agreement. The initial
     Project Team Leaders are:

          [*]

          A Party may replace its Project Team Leader at any time and from time
          to time for any reason by providing written notice of the change to
          the other Party.

     (b)  Appointment of Finance Contacts. In addition, Immunex and Genentech
          -------------------------------
          shall each appoint a Finance Contact (each, a "Finance Contact") to
                                                         ---------------
          act as the primary contact for such Party in connection with matters
          related to financial activities and issues arising hereunder.

          The initial Finance Contacts are:

* Portions of this exhibit have been omitted pursuant to a request for
confidential treatment filed with the Securities and Exchange Commission. The
omitted portions of this exhibit have been filed separately with the SEC.

                                    Page 11

<PAGE>

               [*]

          A Party may replace its Finance Contact at any time and from time to
          time for any reason by providing written notice of the change to the
          other Party.

3.3  Joint Project Team.
     ------------------

     (a)  Role and Authority Generally. The Parties will form a Joint Project
          ----------------------------
          Team ("JPT") to facilitate the activities under the Tech Transfer
                 ---
          Agreement and to resolve issues that may arise in connection with such
          activities or in connection with the other matters described in
          Section 3.3(b) below. The JPT will be composed of an appropriate equal
          --------------
          number of representatives from each Party, to be determined by mutual
          agreement, and will include the Project Team Leaders. The membership
          in the JPT, and the role and authority generally of the JPT, may
          change after commencement of Commercial Production of Bulk Drug under
          this Agreement (see Section 6.3 below).
                              -----------

     (b)  Scope of Authority Prior to Commercial Production; Changes to Tech
          ------------------------------------------------------------------
          Transfer Agreement; Changes to the Manufacturing Process.
          --------------------------------------------------------


          (1)  Prior to the commencement of Commercial Production of Bulk Drug
               under this Agreement (see Section 6.3 below), and subject to
                                         -----------
               Section 3.3(c) hereof, the JPT shall have the authority to modify
               --------------
               or supplement the Tech Transfer Agreement (to the extent
               permitted in the Tech Transfer Agreement, which provides therein
               that the JPT shall have the authority to amend the attachments
               and exhibits attached to the Tech Transfer Agreement but shall
               not have authority to amend the body of the Tech Transfer
               Agreement) or the Manufacturing Process as necessary or useful to
               ensure implementation of the Manufacturing Process in the
               Genentech Facility in a timely manner. If the JPT is considering
               a modification or supplement to the Tech Transfer Agreement or
               the Manufacturing Process that would require Genentech to perform
               additional or repeat work under the Tech Transfer Agreement, or
               which would delay Genentech's performance, or ability to perform,
               under the Tech Transfer Agreement or this Agreement, or would
               result in additional capital expenditures that would not be
               subject to reimbursement under this Agreement or the Tech
               Transfer Agreement, then a Project Team Leader may request that
               Genentech provide to the JPT (with Immunex's assistance, if
               reasonably requested by Genentech) an estimate of the increased
               cost of or delay to Genentech's performance caused by such
               amendment or supplement. The JPT's formal written approval of
               such modification or supplement shall constitute Immunex's
               agreement to pay Genentech's costs and expenses for such
               increased work or additional capital expenditures as set forth in
               such estimate and agreed to in a writing signed by the Project
               Team Leaders (or other authorized representatives of the
               Parties), and/or to extend the time for performance as set forth
               in such estimate and agreed to in a writing signed by the Project
               Team Leaders (or other authorized representatives of the
               Parties).

* Portions of this exhibit have been omitted pursuant to a request
for confidential treatment filed with the Securities and Exchange Commission.
The omitted portions of this exhibit have been filed separately with the SEC.

                                    Page 12

<PAGE>

          (2)  Similarly, the JPT shall be empowered, as and when appropriate,
               acting in good faith, to adjust the reimbursement trigger dates
               set forth in Section 3.4(d) hereof, to adjust the milestone dates
                            --------------
               set forth in Section 5.2 hereof, to adjust the date set forth in
                            -----------
               Section 19.2(c)(ii) hereof, and to reduce, extend or otherwise
               -------------------
               adjust the budget, timeline and scope of work in the Tech
               Transfer Agreement; provided, however, that adjustments should be
               made only on account of events that have a material adverse
               effect on the critical path to completing the related goal. The
               Parties acknowledge that there are various amounts of float time
               included in the schedules, dates and deadlines set forth in the
               Tech Transfer Agreement, the reimbursement trigger dates set
               forth in Section 3.4(d) hereof, the milestone dates set forth in
                        --------------
               Section 5.2 hereof, and the date set forth in Section 19.2(c)(ii)
               -----------                                   -------------------
               hereof. Float time should be considered by the JPT in determining
               whether to make any such adjustments, and the Parties understand
               that a certain amount of float time may be appropriate for the
               remainder of the schedule. Notwithstanding the foregoing, the
               JPT's authority shall be subject to Section 3.3(c) below.
                                                   --------------

          (3)  The members of the JPT shall operate in good faith and shall act
               reasonably in exercising their authority and in approving or
               rejecting proposals.

          (4)  After Commercial Production of Bulk Drug has commenced (see
               Section 6.3 hereof), the JPT shall operate in accordance with
               -----------
               Section 6 hereof, and all other changes to the Manufacturing
               ---------
               Process shall be made as set forth in Section 6.2 hereof and the
                                                     -----------
               Quality Agreement or as the Parties may otherwise agree in
               writing.

          (c) Decision-making. All decisions of the JPT shall be made by the
              ---------------
          unanimous agreement of all of its members or their designated
          representatives, and shall be reflected in written meeting minutes of
          the JPT, which shall be signed by the Project Team Leaders (or other
          authorized representatives of the Parties). In addition, any decision
          by the JPT to adjust the reimbursement trigger dates set forth in
          Section 3.4(d) hereof, to adjust the milestone dates set forth in
          --------------
          Section 5.2 hereof, to adjust the date set forth in Section
          -----------                                         -------
          19.2(c)(ii) hereof, shall only be effective upon the written approval
          -----------
          of, at Immunex, the Senior Vice President of Supply Operations, and,
          at Genentech, the Senior Vice President of Product Operations, or
          other individuals having the same or substantially similar positions,
          which approval and execution shall not be unreasonably withheld. The
          JPT may amend the Tech Transfer Agreement in accordance with the terms
          thereof. In the event that the JPT is unable, despite the good faith
          efforts of all members, to resolve within [*] business days a disputed
          issue that is within the purview of the JPT, the disputed issue shall
          be referred immediately by the JPT to the Project Team Leaders. In the
          event the Project Team Leaders are unable to resolve the disputed
          issue within an additional [*] business days, the disputed issue will
          be referred to, at Immunex, the Senior Vice President of Supply
          Operations and, at Genentech, the Senior Vice President of Product
          Operations or their successor in

* Portions of this exhibit have been omitted pursuant to a request for
confidential treatment filed with the Securities and Exchange Commission. The
omitted portions of this exhibit have been filed separately with the SEC.

                                    Page 13

<PAGE>

         an equivalent position. If the dispute cannot be resolved by Immunex's
         and Genentech's senior management as designated above within an
         additional [*] business days, it shall be referred to, at Immunex, the
         Chief Operating Officer, and, at Genentech, the Executive Vice
         President of Development and Product Operations, or their respective
         successors in interest. If the dispute is still unresolved within an
         additional [*] business days, the matter will be handled in accordance
         with Section 22.2 hereof. Notwithstanding the foregoing, issues
              ------------
         relating to quality shall be resolved in accordance with the Quality
         Agreement, and disputes relating to whether Bulk Drug is Non-Conforming
         Bulk Drug shall be governed by Article 8 herein.
                                        ---------

3.4  Regulatory Matters.
     ------------------

     (a) Regulatory Approach. As set forth in greater detail below, Immunex
         -------------------
         shall use Commercially Reasonable Best Efforts to timely file, and
         Commercially Reasonable Efforts to maintain, the sBLA for the
         manufacture of Bulk Drug at the Genentech Facility, and Genentech shall
         use Commercially Reasonable Best Efforts to timely file, and
         Commercially Reasonable Efforts to maintain, supplements to its
         existing FDA licenses for the manufacture of Bulk Drug at the Genentech
         Facility.

     (b) Immunex Obligations. Except with respect to obligations of Genentech
         -------------------
         under Section 3.4(c) below, Immunex shall use Commercially Reasonable
               --------------
         Best Efforts to timely prepare and obtain, and Commercially Reasonable
         Efforts to maintain, all regulatory approvals that are required to
         market and sell in the United States the Product resulting from the
         Manufacturing Process as carried out at the Genentech Facility,
         including, without limitation, the preparation, filing and maintenance
         of the sBLA for the manufacture of Bulk Drug at the Genentech Facility,
         and Immunex shall reasonably assist Genentech in meeting its
         obligations under this Section 3.4.
                                -----------

     (c) Genentech Obligations. Except with respect to obligations of Immunex
         ---------------------
         under Section 3.4(b) above, Genentech shall use Commercially Reasonable
               --------------
         Best Efforts to timely prepare and obtain, and Commercially Reasonable
         Efforts to maintain, all regulatory approvals that are required to
         manufacture Bulk Drug at the Genentech Facility in South San Francisco,
         California, including, without limitation, the preparation, filing and
         maintenance of supplements to Genentech's existing FDA licenses (and
         drug master file), and Genentech shall reasonably assist Immunex in
         meeting its obligations under this Section 3.4, including, without
                                            -----------
         limitation, reasonably assisting with the preparation and review of the
         drafts of the chemistry, manufacturing and controls sections of the
         sBLA to be filed by Immunex with FDA. Genentech shall also reasonably
         assist Immunex in responding to requests and inquiries from the FDA
         prior to, during and after regulatory review periods and by attending
         meetings with such regulatory authorities to the extent it is essential
         for Genentech to participate given its unique

* Portions of this exhibit have been omitted pursuant to a request for
confidential treatment filed with the Securities and Exchange Commission. The
omitted portions of this exhibit have been filed separately with the SEC.

                                    Page 14

<PAGE>

          knowledge or its status as manufacturer of Bulk Drug under this
          Agreement. Genentech personnel shall also facilitate pre-approval
          inspection of the Genentech Facility conducted by such regulatory
          authorities. The assistance to be provided by Genentech under this
          Section 3.4(c) shall be provided at no additional cost to Immunex,
          --------------
          except as otherwise provided in Sections 3.9 and 4.5 hereof.
                                          --------------------

     (d)  Target Date for FDA Approval. Each Party agrees to use Commercially
          ----------------------------
          Reasonable Best Efforts to obtain by [*], FDA approval for the
          manufacture of Bulk Drug at the Genentech Facility ("FDA Approval").
                                                               ------------
          [*]. In accordance with Section 3.3(b), [*] may be extended for delays
                                  --------------
          that are caused by a Force Majeure Event (as defined in Section 20.1
                                                                  ------------
          below) affecting Genentech which, for purposes of this Section 3.4(d),
                                                                 --------------
          may include, without limitation, [*] all to the extent beyond the
          control and without the fault or negligence of the Party affected
          thereby, to the extent that such delays have a material adverse effect
          on the critical path for obtaining FDA Approval. Each Party agrees to
          give the other Party prompt written notice of any such potential Force
          Majeure Event, the nature thereof, and the extent to which FDA
          Approval is likely to be delayed. Each Party further agrees to use
          Commercially Reasonable Best Efforts to cure the Force Majeure Event
          as quickly as practicable. The JPT shall determine, in accordance with
          Section 3.3 hereof, whether the above dates in this Section 3.4(d)
          -----------                                         --------------
          that trigger Genentech's reimbursement obligations shall be extended,
          and, if so, the appropriate length of time for the extension, and to
          approve or adopt standards, requirements or actions intended to
          correct the Force Majeure Event as quickly as practicable, and each
          Party shall act in good faith and exercise reasonable judgment in
          connection therewith. Notwithstanding anything in this Agreement
          seemingly to the contrary, Immunex agrees that Immunex's sole
          compensation under this Agreement as a result of failure to obtain FDA
          Approval shall be limited to [*]. The Parties further agree that
          Immunex shall use its Commercially Reasonable Efforts to [*], and, if
          Immunex does not do so and the failure to do so has a material adverse
          effect on the critical path to [*], then the JPT shall be empowered to
          adjust the FDA Approval termination date set forth in Section
                                                                -------
          19.2(c)(ii) hereof. The JPT shall determine, in accordance with
          -----------
          Section 3.3 hereof, whether such date shall be extended, and, if so,
          -----------
          the appropriate length of time for the extension, and each Party shall
          act in good faith and exercise reasonable judgment in connection
          therewith.

3.5  Facility Modifications and Improvements. Genentech shall use Commercially
     ---------------------------------------
     Reasonable Efforts to: (a) make facility modifications as required to
     conduct the Manufacturing Process at the Genentech Facility; and (b)
     procure, engineer, install, scale-up, test and validate the equipment and
     systems necessary to conduct the Manufacturing Process at the Genentech
     Facility; in each case as described in, and in accordance with, the Tech
     Transfer Agreement.

* Portions of this exhibit have been omitted pursuant to a request for
confidential treatment filed with the Securities and Exchange Commission. The
omitted portions of this exhibit have been filed separately with the SEC.

                                    Page 15

<PAGE>

3.6  Raw Materials and Suppliers.
     ---------------------------

     (a) Raw Materials. Immunex has developed specifications for the raw
         -------------
         materials, including, without limitation, Specialized Raw Materials,
         used in the Manufacturing Process. The raw materials specifications and
         a list of certain "Approved Suppliers" for raw materials will be
                            ------------------
         included in the Tech Transfer Agreement. Immunex has entered into
         supply contracts with the Approved Suppliers of raw materials. During
         the Term, Immunex shall provide Genentech with access to the favorable
         pricing and services provided under Immunex's contracts with those
         Approved Suppliers and Genentech shall become a "Designated Purchaser"
         under those contracts and Immunex shall provide Genentech with a true
         and correct copy of each such contract; and, if Immunex enters into new
         supply contracts for raw materials used in the manufacture of the Bulk
         Drug, then, during the Term, Immunex shall provide Genentech with
         access to the favorable pricing and services provided thereunder and
         Genentech shall become a "Designated Purchaser" thereunder, and Immunex
         shall provide Genentech with a true and correct copy of each such
         contract. Immunex shall provide oversight and coordination of
         inventories of Specialized Raw Materials. Immunex further agrees that
         to the extent Immunex controls or influences the allocation of
         Specialized Raw Materials provided to Immunex for the manufacture of
         Product in Rhode Island and to Genentech as a Designated Purchaser
         under Immunex's supply contracts with the Approved Suppliers for the
         manufacture of Bulk Drug hereunder, Immunex will use its Commercially
         Reasonable Efforts to ensure that, in the event a shortage of
         Specialized Raw Materials exists, or is anticipated, each shall receive
         a pro rata amount of available Specialized Raw Materials under such
         supply contracts based on an allocation of [*] percent ([*] %) to
         Genentech for its forecasted production at the Genentech Facility with
         respect to the then-current Bulk Drug Commitment, and [*] percent
         ([*]%) to Immunex for its forecasted production in Rhode Island with
         respect to the same time period, until such shortage is abated. If any
         such shortage continues beyond such period, the allocation will
         continue in accordance with the foregoing sentence, on a rolling basis
         for subsequent then-current Bulk Drug Commitments, until such shortage
         is abated.

     (b) Raw Materials for Development Runs and Qualification Runs.
         ---------------------------------------------------------
         Notwithstanding anything seemingly to the contrary herein, Immunex
         shall timely procure, at [*]'s sole cost and expense, and timely
         provide to Genentech, sufficient quantities of all Specialized Raw
         Materials as required for the Development Runs and Qualification Runs
         described in Section 3.7 below. The Parties shall in good faith
                      -----------
         determine the amount and value of usable Specialized Raw Materials
         remaining after the Development Runs and Qualification Runs, [*], upon
         the expiration or termination of this Agreement, Immunex shall pay
         Genentech the amounts payable under Section 19.3(d)(1) of this
                                             ------------------
         Agreement.

     (c) Raw Materials Management. Genentech shall procure, at [*]'s sole cost
         ------------------------
         and expense (except for Specialized Raw Materials [*]), maintain and
         store such amounts of raw materials and components as required for the
         Development Runs

* Portions of this exhibit have been omitted pursuant to a request for
confidential treatment filed with the Securities and Exchange Commission. The
omitted portions of this exhibit have been filed separately with the SEC.

                                    Page 16

<PAGE>

         and Qualification Runs described in Section 3.7 below and the
                                             -----------
         Commercial Runs. Except as set forth in Section 6.2(a)(5) or 19.3(d)(1)
                                                 -----------------    ----------
         hereof, Genentech will provide such raw materials and components and
         such procurement and management services [*].

     (d) Raw Materials Testing. Genentech shall perform testing and evaluation
         ---------------------
         of the raw materials (including, without limitation, the Specialized
         Raw Materials procured by Immunex and provided to Genentech pursuant to
         Section 3.6(b) above) as required by the applicable raw material
         --------------
         specifications or Bulk Drug Specifications and cGMP, and otherwise in
         accordance with the Quality Agreement and standard operating procedures
         to be agreed upon in writing by the Parties.

3.7  Initial Runs and Batches.
     ------------------------

     (a) Development Runs. Genentech shall perform Development Runs and
         ----------------
         manufacture Development Batches at such size and in such number as is
         set forth in the Tech Transfer Agreement. Genentech will provide the
         Product resulting from such Development Runs and Development Batches
         to Immunex, [*], in accordance with the delivery terms set forth in
         Section 4.4 hereof. Immunex may make whatever further use of such
         -----------
         Product as it shall determine; provided, however, that Immunex agrees
         that (i) such Product shall not be used in humans, (ii) the warranties
         provided in Section 6.1(a) of this Agreement shall not apply to such
                     --------------
         Product, (iii) the disclaimer of warranties set forth in Section
                                                                  -------
         6.1(c) of this Agreement shall apply to such Product, and (iv) this
         ------
         Section 3.7(a) shall survive termination or expiration of this
         --------------
         Agreement.

     (b) Validation and Qualification Batches. Once scale-up of the
         ------------------------------------
         Manufacturing Process is completed at the Genentech Facility, Genentech
         shall perform all required process validation and shall perform
         Qualification Runs and manufacture Qualification Batches at commercial
         scale as set forth in the Tech Transfer Agreement in order to document
         the operability and reproducibility of the Manufacturing Process and
         permit the Parties to complete and file the regulatory documents
         described in Section 3.4 hereof. Genentech shall provide the Product
                      -----------
         and Bulk Drug resulting from such Qualification Runs and Qualification
         Batches to Immunex, [*], in accordance with the delivery terms set
         forth in Section 4.4 hereof.
                  -----------

3.8  Manufacturing Documentation. In accordance with the terms of the Tech
     ---------------------------
     Transfer Agreement, Immunex shall, by the relevant date that is set forth
     in the Tech Transfer Agreement as such date may be modified by the JPT,
     provide to Genentech the items listed within exhibits and schedules to the
     Tech Transfer Agreement, and shall, thereafter, from time to time and in
     accordance with the timeline set forth in the Tech Transfer Agreement,
     provide to Genentech such additional Manufacturing Documentation as
     Genentech shall reasonably require in order to implement the

* Portions of this exhibit have been omitted pursuant to a request for
confidential treatment filed with the Securities and Exchange Commission. The
omitted portions of this exhibit have been filed separately with the SEC.

                                    Page 17

<PAGE>

     Tech Transfer Agreement and the Manufacturing Process and otherwise perform
     its obligations under this Agreement. In accordance with the terms of the
     Tech Transfer Agreement, Genentech shall provide certain information to
     Immunex, including, without limitation, the process trend and variability
     data. Both Parties' obligations under this Section 3.8 shall be subject to
                                                -----------
     obligations to Third Parties as set forth in written agreements in effect
     prior to the Effective Date of this Agreement. In the event an obligation
     to a Third Party prohibits a Party from rendering such assistance, that
     Party shall promptly seek from such Third Party permission to render such
     assistance.

3.9  [*] At Immunex's request prior to [*], Genentech agrees to discuss in good
     faith with Immunex and give serious consideration to [*]. The determination
     as to whether Genentech could accept such a [*] would be made by Genentech,
     in its sole discretion, after good faith discussion with Immunex, and after
     a good-faith and serious evaluation of the following factors: [*]. If such
     a [*] were acceptable to Genentech, in its sole discretion, Immunex would
     be responsible for any additional costs to be agreed upon by the Parties,
     including but not limited to [*] (as defined below) associated with [*],
     and the Parties would agree upon new dates and deadlines set forth in this
     Agreement to the extent impacted by such [*]. The Bulk Drug Commitment
     outstanding at the time Immunex issues a request for [*] shall remain
     binding upon the Parties; provided, however, that Immunex shall,
     notwithstanding such request for [*], unless and until such [*] occurs,
     purchase Bulk Drug in accordance with this Agreement up to the applicable
     Annual Minimum set forth in Exhibit A hereto. [*]. For purposes of this
     Agreement, the term [*]. For purposes of this Agreement, the term [*].

                     ARTICLE 4. RUNS; PRODUCTION AND SUPPLY;
                     ---------------------------------------
                                   DELIVERIES
                                   ----------

4.1  Minimum and Maximum Runs. Notwithstanding anything seemingly to the
     ------------------------
     contrary in this Article 4, but subject to the other terms of this
                      ---------
     Agreement, in each calendar year during the Term, Genentech shall perform
     at least the number of Runs identified as the "Annual Minimum" for such
                                                    --------------
     calendar year on Exhibit A attached hereto and incorporated herein, and
                      ---------
     may in its sole discretion perform up to the number of Runs identified as
     the "Annual Maximum" for such calendar year on said Exhibit A. Subject to
          --------------                                 ---------
     Section 3.9 and Section 4.5 hereof, Genentech shall have sole discretion
     -----------     -----------
     to determine the actual number of Runs in any calendar year, within the
     ranges set forth in Exhibit A hereto, and subject to the Product
                         ---------
     Manufacturing Forecast and applicable Bulk Drug Commitment. For purposes
     of this Article 4, the term "Runs" refers to Commercial Runs, and does
                                  ----
     not refer to Qualification Runs or Development Runs.

4.2  Production and Supply
     ---------------------

     (a)  Product Manufacturing Forecast. By not later than the Effective Date
          ------------------------------
          of this Agreement and thereafter on the [*] business day of each
          month, beginning [*], for

* Portions of this exhibit have been omitted pursuant to a request for
confidential treatment filed with the Securities and Exchange Commission. The
omitted portions of this exhibit have been filed separately with the SEC.

                                    Page 18

<PAGE>

          the remainder of the Term, the Parties shall issue a rolling "Product
                                                                        -------
          Manufacturing Forecast" which shall establish, on a monthly basis, for
          ----------------------
          the remainder of the Term, the number of Runs to be performed and the
          quantity of Bulk Drug reasonably expected to be manufactured, released
          and supplied to Immunex, within the ranges set forth in Exhibit A
                                                                  ---------
          hereto. The Product Manufacturing Forecast shall be used for joint
          planning purposes and shall be nonbinding unless otherwise specified
          herein, and may be amended by the Parties from time to time as the
          Parties deem appropriate. Beginning [*] or such other date as agreed
          upon by the Parties in writing, each Product Manufacturing Forecast
          shall be binding for the first [*] months, and non-binding for the
          remainder of the Term, as further described below. Beginning with the
          initial binding Product Manufacturing Forecast, the forecasts for Bulk
          Drug within the first [*] months of each such rolling Product
          Manufacturing Forecast shall constitute a Bulk Drug Commitment and
          shall be binding upon the Parties and cannot be changed except upon
          mutual written consent of the Parties (or except upon mutual agreement
          of the Parties under Section 3.9 or Section 4.5 hereof, which
                               -----------    -----------
          agreement shall not, without the consent of Genentech, affect any Runs
          that are in process [*]), and the [*]-month period shall be that
          period which commences on the first day of the month immediately
          following the month in which the Product Manufacturing Forecast is
          issued. By way of example only, when the rolling Product Manufacturing
          Forecast for [*], is issued, the [*]-month period covered by such
          forecast shall commence on [*], and shall end on [*]. The Bulk Drug
          Commitment shall include approximate harvest dates for each Commercial
          Run.

     (b)  Weekly Meetings. The Parties shall participate in a weekly meeting, in
          ---------------
          person or via telephone, to review and discuss production, supply and
          logistics operations for the next [*]-month period, including: (i)
          dates or approximate dates on which Runs will occur; (ii) dates or
          approximate dates for Genentech's and Immunex's release of Bulk Drug;
          (iii) size or approximate size of Batches; (iv) dates or approximate
          dates for delivery of Batches; (v) destination for shipment of
          Batches; and (vi) status of Batches undergoing investigation, and
          related matters, and to issue and, as appropriate, update the Product
          Manufacturing Forecast.

4.3  Management of Product Manufacturing Forecast.
     --------------------------------------------

     (a)  Delivery. Immunex and Genentech will work together in good faith to
          --------
          determine delivery dates and a shipping schedule for deliveries of
          Bulk Drug under this Agreement, and shall establish a written
          "Delivery Schedule" as a part of the Product Manufacturing Forecast
           -----------------
          and the related Bulk Drug Commitment.

     (b)  Delivery Dates. For each Run, the delivery date respectively set forth
          --------------
          in the Delivery Schedule will be the "Delivery Date" for such Run,
                                                -------------
          unless the Parties agree on an alternative delivery date; provided,
          however, that for purposes of Section 8.1(a)(ii) hereof, the "Delivery
                                        ------------------
          Date" for any particular Bulk Drug shall be the actual date on which
          such Bulk Drug is delivered to Immunex's Designated

* Portions of this exhibit have been omitted pursuant to a request for
confidential treatment filed with the Securities and Exchange Commission. The
omitted portions of this exhibit have been filed separately with the SEC.

                                    Page 19

<PAGE>

          Carrier at Genentech's Facility in accordance with Section 4.4 hereof.
                                                             -----------

     (c)  Purchase Quantities. Except as otherwise set forth in this Agreement
          -------------------
          (including, without limitation, upon mutual agreement of the Parties
          under Section 3.9 or Section 4.5 hereof, which agreement shall not,
                -----------    -----------
          without the consent of Genentech, affect any Runs that are in process
          [*]), Immunex shall purchase all Bulk Drug that complies with the
          warranties set forth in Section 6.1(a), up to the applicable Annual
                                  --------------
          Maximum set forth in Exhibit A hereto.
                               ---------

     (d)  Shortages; Shortfalls; Delivery Delays. If at any time during the
          --------------------------------------
          Term, Genentech is unable to fulfill the Bulk Drug Commitments on the
          related Delivery Date(s), and which inability results from other than
          a Force Majeure Event, then Genentech shall (1) immediately notify
          Immunex in writing as to the reason for the shortfall, shortage and/or
          delay, and provide an indication of the likely duration of the
          shortfall, shortage and/or delay, and (2) unless and except to the
          extent such inability to fulfill the Bulk Drug Commitment is caused by
          an Immunex material breach, use Commercially Reasonable Efforts to
          provide Immunex with additional Commercial Runs to meet outstanding
          Bulk Drug Commitments under this Agreement, to the extent that
          Genentech has excess capacity and/or can reasonably revise its
          production schedule without material adverse impact to itself or its
          obligations to Third Parties and/or Affiliates. In addition, Genentech
          shall also promptly notify Immunex in writing when any such shortfall,
          shortage and/or delay is over. Unless otherwise directed in writing by
          Immunex, after Immunex's receipt of notice from Genentech that a
          shortfall, shortage and/or delay as described above is over, Genentech
          shall use Commercially Reasonable Efforts to make up shortfalls in
          delivery as promptly as practicable, to the extent that Genentech has
          excess capacity and/or can reasonably revise its production schedule
          without material adverse impact to itself or its obligations to Third
          Parties and/or Affiliates, and shall promptly supply Bulk Drug to
          Immunex and/or their respective designee, as appropriate, to meet such
          Bulk Drug Commitments. Notwithstanding the foregoing, any shortfalls,
          shortages and/or delays resulting from a Force Majeure Event shall be
          governed by Article 18 below.
                      ----------

     (e)  Acceptance of Bulk Drug. Genentech shall deliver to Immunex samples of
          ------------------------
          all Batches manufactured under this Agreement, as and when Batches are
          manufactured, and otherwise in accordance with the Quality Agreement
          and applicable standard operating procedures approved by both Parties,
          to enable Immunex to perform release testing on the Bulk Drug as
          required by Article 11 of this Agreement and the Quality Agreement.
                      ----------
          Genentech shall also provide the related Batch Record and other Batch
          documentation described in the Quality Agreement for each Batch of
          Bulk Drug as soon as practicable after each such Batch is
          manufactured. Upon receipt of samples of a particular Batch of Bulk
          Drug together with the related Batch Record and other Batch
          documentation, Immunex shall perform release testing and review the
          Batch Record and other

* Portions of this exhibit have been omitted pursuant to a request for
confidential treatment filed with the Securities and Exchange Commission. The
omitted portions of this exhibit have been filed separately with the SEC.

                                    Page 20

<PAGE>

          Batch documentation for each Batch, in good faith and as soon as
          reasonably practicable, and, in the absence of an investigation for
          said Batch pursuant to the Quality Agreement or Section 8.1 hereof,
                                                          -----------
          such testing and review shall be completed within [*] days after
          Immunex's receipt of samples of such Batch together with the related
          Batch Record and other Batch documentation. Any investigation shall be
          initiated and conducted in accordance with Immunex's applicable
          standard operating procedure. Subject to Immunex's rights to make
          claims under Article 8 hereof, a Batch shall be deemed to have been
                       ---------
          accepted by Immunex on the date (the "Acceptance Date") on which the
                                                ---------------
          first of the following events occurs: (i) the receipt by Genentech of
          written notice from Immunex that such Batch has been released by
          Immunex pursuant to applicable release testing standard operating
          protocols as described in the Quality Agreement, (ii) the failure of
          Immunex to issue a notice of investigation or rejection within [*]
          days after Immunex's receipt of samples of such Batch together with
          the related Batch Record and other Batch documentation, and (iii) the
          determination under Section 8.1(b) below that Genentech has no
                              --------------
          liability for such non-conforming Batch. The Parties agree that,
          subject to prior written approval by Immunex on a Batch by Batch
          basis, Genentech may deliver Batches of Bulk Drug prior to the
          Acceptance Date, provided, however, that the procedures set forth in
          this Agreement for acceptance of such Batches under this Section 4.3
                                                                   -----------
          and payment for such Batches under Section 5.3 hereof shall
                                             -----------
          nevertheless apply to such Batches, and provided, further, that, for
          the avoidance of doubt, Genentech shall have no liability to Immunex
          for costs and expenses incurred by Immunex for filling and finishing
          Bulk Drug that is delivered prior to the Acceptance Date in accordance
          with this Section 4.3.
                    -----------

4.4  Delivery Terms. Genentech shall deliver Bulk Drug to Immunex's "Designated
     --------------                                                  ----------
     Carrier" at Genentech's Facility, and Immunex shall arrange for shipment of
     -------
     Bulk Drug from Genentech's Facility to Immunex via Immunex's Designated
     Carrier at the expense of Immunex. Immunex shall arrange for shipment and
     take delivery of Bulk Drug within [*] days after the Acceptance Date
     related thereto. Genentech shall provide storage for such Bulk Drug at no
     charge during this period. Title to and risk of loss of Bulk Drug shall be
     and remain with Genentech until the earlier of (i) the date on which such
     Bulk Drug is delivered to Immunex's Designated Carrier at Genentech's
     Facility and (ii) the expiration of such [*]-day period, at which time
     title to and risk of loss for the Bulk Drug shall transfer to Immunex.
     Genentech shall not be required to deliver Bulk Drug to Immunex's
     Designated Carrier until Immunex's Designated Carrier informs Genentech
     that it has obtained all appropriate approvals and consents of any
     governmental authority necessary for the transportation or shipment of such
     Bulk Drug. Genentech shall comply with all applicable laws and regulations
     regarding the packaging of Bulk Drug for shipment. Product resulting from
     Development Runs and Qualification Runs (see Sections 3.7(a) and (b)
                                                  -----------------------
     hereof), and Non-Conforming Bulk Drug (see Section 8.1(d)) shall also be
                                                --------------
     subject to the delivery terms set forth in this Section 4.4. Immunex shall
                                                     -----------
     procure, at Immunex's sole cost and expense, and provide to Genentech
     sufficient quantities of freeze tanks for shipment of Bulk Drug from

* Portions of this exhibit have been omitted pursuant to a request for
confidential treatment filed with the Securities and Exchange Commission. The
omitted portions of this exhibit have been filed separately with the SEC.

                                    Page 21

<PAGE>

     Genentech's Facility to Immunex via Immunex's Designated Carrier. Title to
     and risk of loss of such freeze tanks shall transfer to Genentech upon
     initial delivery of such freeze tanks to Genentech; such freeze tanks shall
     be deemed to be "Portable Equipment" and shall be subject to transfer to
                      ------------------
     Immunex pursuant to Sections 14.2 and 19.3 of this Agreement.
                         ----------------------

4.5  [*] Any time following the completion of Milestone III, Immunex may request
     that Genentech [*]. Upon such request, the JPT will meet to discuss
     timelines, costs, activities and responsibilities necessary to [*], and
     Immunex shall reimburse Genentech for such costs as agreed upon by the JPT.
     [*] The supply, purchase and payment provisions of this Agreement would not
     be affected by a decision to [*] hereunder unless otherwise agreed to in
     writing by the Parties, and Immunex would continue to purchase the Bulk
     Drug Commitment in accordance with the terms of this Agreement, at least up
     to the applicable Annual Minimum set forth in Exhibit A hereto. The Parties
                                                   ---------
     would negotiate in good faith to amend the Agreement as appropriate to
     address [*].

                               ARTICLE 5. PAYMENTS
                               -------------------

5.1  Reimbursement for Facility Modifications and Services Costs. Immunex shall
     -----------------------------------------------------------
     reimburse Genentech for Facility Modifications and Services Costs, in
     accordance with the Tech Transfer Agreement, including, without limitation,
     the acquisition of Portable Equipment (provided, however, that Immunex
     shall not be required to reimburse Genentech for the costs of acquiring
     Portable Equipment under the Tech Transfer Agreement or this Agreement if
     Immunex paid for such Portable Equipment directly or if Immunex has already
     reimbursed Genentech for such costs),and Genentech shall bear all of
     Genentech's internal costs and expenses (including, without limitation,
     Genentech's internal labor and material costs) for the modifications needed
     to implement the Manufacturing Process at the Genentech Facility, except as
     otherwise provided in Section 3.9 or Section 4.5 hereof. All Portable
                           -----------    -----------
     Equipment acquired by Genentech under this Agreement (including, without
     limitation, the freeze tanks referred to in Section 4.4 above) or the Tech
                                                 -----------
     Transfer Agreement shall be subject to Sections 14.2 and 19.3 of this
                                            ----------------------
     Agreement.

5.2  Milestone Payments. For each Milestone that is completed by the deadline
     ------------------
     respectively described below, Immunex shall pay the related milestone,
     within [*] days of receipt of a correct invoice, which may be delivered
     on or after the date earned:

     (a)  Completion of Milestone I: [*]: Immunex shall pay Genentech [*]
          ------------------------------
          Dollars ($[*]) upon the completion of Milestone I.

     (b)  Completion of Milestone II: [*]: Immunex shall pay Genentech [*]
          -------------------------------
          Dollars ($[*]) upon the completion of Milestone II, provided that [*];
          and, in addition, Genentech shall also be entitled to receive
          additional payments of [*] Dollars

* Portions of this exhibit have been omitted pursuant to a request for
confidential treatment filed with the Securities and Exchange Commission. The
omitted portions of this exhibit have been filed separately with the SEC.

                                    Page 22

<PAGE>

          $([*]) [*], which such additional payment amounts shall be payable
          upon [*].

     (c)  Completion of Milestone III: [*]: Immunex shall pay Genentech [*]
          --------------------------------
          Dollars ($[*]) upon the completion of Milestone III, provided that
          this milestone has been completed by not later than [*].

     (d)  Completion of Milestone IV: [*]: If Milestone IV is completed by not
          -------------------------------
          later than [*], then Immunex shall pay Genentech [*] Dollars ($[*]).

     (e)  Adjustment of Milestone Dates. In accordance with Section 3.3(b)
          -----------------------------                     --------------
          hereof, the dates in Sections 5.2(b), (c) and (d) above may be
                               ----------------------------
          extended for delays occasioned by a Force Majeure Event (as defined in
          Section 20.1 below), which, for purposes of this Section 5.2(e), may
          ------------                                     --------------
          include, without limitation, [*], all to the extent beyond the control
          and without the fault or negligence of the Party affected thereby, and
          to the extent that such delays have a material adverse effect on the
          critical path for completing the related milestone. Each Party agrees
          to give the other Party prompt written notice of any such potential
          Force Majeure Event, the nature thereof, and the extent to which
          completion of the related milestone is likely to be delayed. Each
          Party further agrees to use Commercially Reasonable Best Efforts to
          cure the Force Majeure Event as quickly as practicable. The JPT shall
          determine, in accordance with Section 3.3 hereof, whether the date(s)
                                        -----------
          in this Section 5.2(b), (c) or (d) that trigger the related milestone
                  --------------------------
          payment shall be extended, and, if so, the appropriate length of time
          for the extension, and to approve or adopt standards, requirements or
          actions intended to correct the Force Majeure Event as quickly as
          practicable, and each Party shall act in good faith and exercise
          reasonable judgment in connection therewith.

5.3  Bulk Drug Pricing; Invoicing.
     ----------------------------

     (a)  Bulk Drug Pricing. Except as otherwise expressly set forth in this
          -----------------
          Agreement, including, without limitation, in Sections 3.7, 6.2, and
                                                       ------------  ---
          8.1 hereof, Immunex shall pay Genentech [*] Dollars ($[*]) per gram
          ---
          for all Bulk Drug manufactured in compliance with this Agreement and
          cGMP that conforms with the Bulk Drug Specifications and the
          warranties provided in Section 6.1(a) hereof, and such amount shall be
                                 --------------
          the Purchase Price for such Bulk Drug. The Purchase Price may be
          adjusted in accordance with Section 5.3(d) below. Notwithstanding
                                      --------------
          anything in this Section 5.3(a) seemingly to the contrary, the
                           --------------
          Purchase Price for Bulk Drug [*].

     (b)  Invoicing Immunex for Bulk Drug. Invoices may be issued on or after
          -------------------------------
          the related Acceptance Date, and amounts due thereunder shall be due
          and payable in U.S. currency within [*] days after receipt of invoice.
          Such invoices shall reference the Acceptance Date, the quantity
          delivered and the total Purchase Price. Payments shall be made by wire
          transfer. Past due amounts shall bear interest at a floating rate
          equal to [*] percent ([*]%) per annum above the rate of interest set
          forth from

* Portions of this exhibit have been omitted pursuant to a request for
confidential treatment filed with the Securities and Exchange Commission. The
omitted portions of this exhibit have been filed separately with the SEC.

                                    Page 23

<PAGE>

          time to time in the Wall Street Journal and identified therein as the
          prime rate of interest. Invoices may be issued prior to the completion
          of [*].

     (c)  Changes in Cost of Raw Materials. In case the net average cost of raw
          --------------------------------
          materials or components used for a Batch in the Manufacturing Process
          for producing Bulk Drug increases or decreases by more than [*]
          percent ([*]%) with respect to production of Bulk Drug for a Calendar
          Year, as compared to the net average cost of raw materials or
          components used for a Batch in the Manufacturing Process for producing
          Bulk Drug (including both Immunex's and Genentech's combined costs for
          such raw materials or components) in Calendar Year [*], which change
          must be reasonably substantiated, the Parties shall, acting reasonably
          and in good faith, within [*] days agree upon the direct amount of
          such increase or decrease, for each Batch that is manufactured after
          the date of the Parties' agreement to the change, and the effective
          date for such increase or decrease, based on good faith negotiations.
          In the event of an increase, if Immunex can reasonably demonstrate to
          Genentech that any equivalent materials or components used for
          producing Bulk Drug can be purchased at a lower price than Genentech's
          cost of such materials, and that such materials or components can be
          supplied on a reasonably consistent and reliable basis, then Genentech
          shall accept such lower price for purposes of this Section 5.3(c). The
                                                             --------------
          Purchase Price shall not be adjusted as a result of any such increase
          or decrease; instead, the direct amount of any such increase or
          decrease as agreed upon shall be payable to the other Party by Immunex
          or Genentech, as appropriate, pursuant to a separate invoice within
          [*] days after receipt thereof.

     (d)  Adjustment to Purchase Price. The Purchase Price shall be adjusted
          ----------------------------
          prior to the first Commercial Run to a price equal to:

          [*]

5.4  Commercial Audit. For at least three (3) years after final payment under
     ----------------
     this Agreement (or for such longer period of time as may be required by
     applicable laws and regulations), Genentech shall maintain complete and
     accurate books, records, documents, and other evidence of costs, expenses
     and allowances pertaining to this Agreement and/or the Tech Transfer
     Agreement and the Facility Modifications and Services Costs (for purposes
     of this Section 5.4, hereinafter collectively called "Records") to the
             -----------                                   -------
     extent and in such detail as will properly reflect all costs and expenses
     incurred by Genentech in connection with this Agreement and/or the Tech
     Transfer Agreement. Immunex, acting through its independent public
     accountants of recognized national standing selected by Immunex and
     reasonably acceptable to Genentech, shall have a right to examine and audit
     Genentech's Records once annually, upon at least [*] days' prior written
     notice, but only in the event that Immunex makes payments under either
     Section 6.2(a)(5) hereof (Specification and Process Changes) or Section
     -----------------                                               -------
     19.3(d)(1) hereof, or under the Letter of Intent or the Tech Transfer
     ----------
     Agreement, and only to the extent that such Records are applicable to
     determining the accuracy of such payments.

* Portions of this exhibit have been omitted pursuant to a request for
confidential treatment filed with the Securities and Exchange Commission. The
omitted portions of this exhibit have been filed separately with the SEC.

                                    Page 24

<PAGE>

             ARTICLE 6. GENENTECH PRODUCT WARRANTIES; SPECIFICATIONS
             -------------------------------------------------------

6.1  Warranties by Genentech.
       -----------------------

     (a)  Product Warranties. Genentech hereby warrants to Immunex that the Bulk
          ------------------
          Drug, at the time of Delivery to Immunex's Designated Carrier, shall:

          (1)  conform to the Bulk Drug Specifications; provided, however, that
               solely with respect to Bulk Drug that is delivered prior to the
               Acceptance Date, Genentech hereby warrants to Immunex, effective
               as of the Acceptance Date for such Bulk Drug, that, as of the
               time of Delivery to Immunex's Designated Carrier, such Bulk Drug
               shall conform to the Bulk Drug Specifications;

          (2)  be manufactured in compliance with the requirements of cGMP;

          (3)  be manufactured in compliance with the requirements of all
               applicable material national, state and local laws, ordinances
               and governmental rules and regulations of the U.S. [*]; and

          (4)  be transferred free and clear of any liens or encumbrances of any
               kind to the extent arising through or as a result of the acts or
               omissions of Genentech, its Affiliates or their respective
               agents.

     (b)  Genentech Facility. Genentech hereby warrants that it owns or lawfully
          ------------------
          controls the Genentech Facility, and that, provided the Manufacturing
          Process is successfully implemented in accordance with the Tech
          Transfer Agreement, and provided no Force Majeure Event shall occur,
          it has sufficient manufacturing capacity to enable Genentech to
          manufacture Bulk Drug throughout the Term in quantities sufficient to
          fulfill, in each calendar year, the minimum Runs for such year as set
          forth in Exhibit A hereto, in accordance with this Agreement.
                   ---------
          Genentech hereby covenants that it will use Commercially Reasonable
          Efforts to ensure that the Genentech Facility shall be maintained in
          accordance with cGMP and in such condition as will allow Genentech to
          manufacture the Bulk Drug in compliance with cGMP and in conformance
          with the Bulk Drug Specifications.

     (c)  Disclaimer by Genentech. OTHER THAN AS SET FORTH IN THIS SECTION 6.1
          -----------------------                                  -----------
          AND SECTION 15.2 HEREOF, ALL OTHER WARRANTIES, BOTH EXPRESS AND
          ----------------
          IMPLIED, ARE HEREBY EXPRESSLY DISCLAIMED, INCLUDING, WITHOUT
          LIMITATION, ANY WARRANTY OF MERCHANTABILITY, OR FITNESS FOR A
          PARTICULAR PURPOSE.

* Portions of this exhibit have been omitted pursuant to a request for
confidential treatment filed with the Securities and Exchange Commission. The
omitted portions of this exhibit have been filed separately with the SEC.

                                    Page 25

<PAGE>

6.2  Specification and Manufacturing Process Changes. Except as otherwise
     -----------------------------------------------
     expressly set forth to the contrary in the Quality Agreement, the Parties
     agree as follows:

     (a)  Specification and Process Changes. In the event that (i) Immunex is
          ---------------------------------
          required to change the Bulk Drug Specifications or the Manufacturing
          Process pursuant to applicable law, rule or regulation or in response
          to the order or request of a governmental authority or in response to
          the order or request of a governmental authority or regulatory body,
          or (ii) Immunex requests the change pursuant to its strategy for
          global synchronization and worldwide consistency of Product, or (iii)
          Immunex wishes to change the Bulk Drug Specifications or the
          Manufacturing Process after commencement of Commercial Production
          hereunder, the following provisions will apply:

          (1)  Immunex shall promptly advise Genentech in writing of any such
               change(s), and provide information reasonably necessary for
               Genentech to evaluate the effect of such change(s), and Genentech
               shall promptly advise Immunex as to scheduling and/or Purchase
               Price adjustments, if any, which may result from such change(s).
               The notification and approval procedure shall be in accordance
               with standard operating procedures (i.e., change control
               procedures) agreed upon by the Parties from time to time. The
               Parties shall hold a JPT meeting in a timely manner with
               appropriate advisors invited to discuss such changes as
               appropriate.

          (2)  Prior to implementation of such change(s) to the Bulk Drug
               Specifications or Manufacturing Process, the Parties agree to
               negotiate in good faith in an attempt to reach agreement on (i)
               the new Purchase Price for any Bulk Drug manufactured under this
               Agreement by Genentech which embodies such change, giving due
               consideration to the effect of such change on Genentech's direct
               manufacturing costs for Bulk Drug, and (ii) any other amendments
               to this Agreement which may be necessitated by such changes.

          (3)  Prior to implementation of such change(s), Genentech will provide
               Immunex with an estimate of the reasonable and necessary expenses
               that would be incurred by Genentech as a result of the
               implementation of any such change(s) to the Bulk Drug
               Specifications or Manufacturing Process, including, but not
               limited to, its validation and analytical development costs,
               capital expenditure costs, and [*], as defined in Section 3.9
                                                                 -----------
               above. If such change(s) are implemented, Immunex will reimburse
               Genentech for the reasonable and necessary expenses as agreed
               upon in advance and incurred by Genentech as a result of any such
               change(s) to the Bulk Drug Specifications or Manufacturing
               Process, including, but not limited to, reimbursing Genentech for
               its validation and analytical development costs, capital
               expenditure costs, and Internal Costs.

* Portions of this exhibit have been omitted pursuant to a request for
confidential treatment filed with the Securities and Exchange Commission. The
omitted portions of this exhibit have been filed separately with the SEC.

                                    Page 26

<PAGE>

          (4)  Genentech shall use Commercially Reasonable Best Efforts to
               accommodate changes described in Section 6.2(a)(i) hereof as soon
                                                -----------------
               as practicable after notice thereof, but in any event within [*]
               days' lead time, unless otherwise agreed upon by the Parties or
               required by an applicable regulatory authority. Immunex shall not
               unreasonably require Genentech to implement changes to the
               Manufacturing Process or Bulk Drug Specifications within such
               [*]-day period if such changes would typically require Genentech
               a longer period of time to implement, or that would have a
               material adverse effect on Genentech's then current operations.
               Genentech shall use Commercially Reasonable Efforts to
               accommodate changes described in Section 6.2(a)(ii) and (iii)
                                                ----------------------------
               hereof in light of, among other considerations, Genentech's
               facilities and resource constraints, current operations and
               commercial goals; and notwithstanding the foregoing, Genentech
               shall not be required to implement any changes to the
               Manufacturing Process or Bulk Drug Specifications if such changes
               would have a material adverse effect on Genentech's then current
               operations. Genentech shall cooperate with Immunex in good faith
               to implement all agreed upon changes to the Bulk Drug
               Specifications or Manufacturing Process in accordance with the
               agreed upon schedule. During the pendency of Genentech
               implementing any such changes to the Manufacturing Process or
               Bulk Drug Specifications, Genentech shall produce and Immunex
               shall purchase Bulk Drug in accordance with the terms of the
               Agreement.

          (5)  If any such changes to the Bulk Drug Specifications or
               Manufacturing Process renders obsolete or unusable any raw
               materials (including, without limitation, Specialized Raw
               Materials), components or supplies used to manufacture the Bulk
               Drug, and to the extent such materials may not be either returned
               to the appropriate vendor for a credit or utilized by Genentech
               for its other manufacturing operations, Immunex shall purchase
               from Genentech, at Genentech's Acquisition Cost, that amount of
               inventory of such raw materials, components or supplies, as the
               case may be, so rendered obsolete or unusable, not to exceed the
               amount of such raw materials, components or supplies which would
               have been required for Genentech to manufacture and supply the
               total quantity of Bulk Drug specified in Bulk Drug Commitments
               outstanding under this Agreement.

          (6)  The notification and formal approval procedure for those changes
               to the Bulk Drug Specifications or Manufacturing Process approved
               by the Parties under this Section shall be in accordance with the
               Quality Agreement and standard operating procedures (i.e., change
                                                                    ----
               control procedures) agreed upon in writing by Immunex and
               Genentech from time to time.

     (b)  Procedure for Specification or Manufacturing Process Changes by
          ---------------------------------------------------------------
          Genentech. Genentech shall not change the Bulk Drug Specifications or
          ---------
          the Manufacturing Process except as set forth in Section 6.2(a)
                                                           --------------
          hereof, or in the Quality Agreement

* Portions of this exhibit have been omitted pursuant to a request for
confidential treatment filed with the Securities and Exchange Commission. The
omitted portions of this exhibit have been filed separately with the SEC.

                                    Page 27

<PAGE>

          and standard operating procedures to be agreed upon by Immunex and
          Genentech from time to time.

     (c)  Vendor or Supplier Changes. Genentech shall not change any vendor or
          --------------------------
          supplier of raw materials or analytical reagents used in the
          manufacture or testing of Bulk Drug except as set forth in the Quality
          Agreement and standard operating procedures to be agreed upon by
          Immunex and Genentech from time to time or with the prior written
          consent of Immunex.

     (d)  Ongoing Process Improvement Obligations. Immunex agrees to provide
          ---------------------------------------
          assistance to Genentech [*] in "trouble-shooting" and optimizing the
          Manufacturing Process, at such times and to such extent as Genentech
          may reasonably request, given Immunex's unique expertise and
          understanding of the Product and the Manufacturing Process.

6.3  JPT as Commercial Operations Team. Following [*], "Commercial Production"
     ---------------------------------                  ---------------------
     of Bulk Drug will commence under this Agreement, with the first Commercial
     Run performed after the completion of [*]. After commencement of Commercial
     Production under this Agreement, the membership in the JPT may change to
     reflect the changing nature of the project. During Commercial Production,
     the JPT shall meet (i) in person or by telephone in accordance with Section
                                                                         -------
     4.2(b) hereof to review the Bulk Drug Commitment and Product Manufacturing
     ------
     Forecast, and (ii) at least twice a year to review the overall results of
     the manufacturing operations, and (iii) at such additional times as
     appropriate and as may be requested by either Party. Issues relating to
     quality of Product shall be resolved in accordance with the Quality
     Agreement.

                              ARTICLE 7. PACKAGING
                              --------------------

7.1  In General. Genentech shall package and label the Bulk Drug according to
     the Bulk Drug Specifications and according to packaging procedures
     mutually agreed upon by Immunex and Genentech in writing.

                                ARTICLE 8. CLAIMS
                                -----------------

8.1  Claims.
     ------

     (a)  Notice of Claims. In the event that any Bulk Drug is Non-Conforming
          ----------------
          Bulk Drug, Immunex may reject the same by giving written notice
          thereof to Genentech (1) within the later of (i) [*] after the
          applicable Acceptance Date for such Bulk Drug, and (ii) [*] days after
          the applicable Delivery Date for such Bulk Drug, based on an
          inspection of such Bulk Drug and related freeze tanks and packing and
          shipping materials and components, for matters that were not readily
          ascertainable by the release testing of the related samples and review
          of the related Batch Record and other Batch documentation described in
          Section 4.3(e) hereof, or, (2) in the case of a latent defect, within
          --------------
          [*] days after discovery of such latent defect,

* Portions of this exhibit have been omitted pursuant to a request for
confidential treatment filed with the Securities and Exchange Commission. The
omitted portions of this exhibit have been filed separately with the SEC.

                                    Page 28

<PAGE>

          but in no event later than [*] after delivery to Immunex's Designated
          Carrier at the Genentech Facility), which notice shall specify the
          manner in which such Bulk Drug fails to conform to any warranty and
          shall be accompanied by any test results or reports evidencing such
          non-conformity. Alternatively, rather than initially issuing a notice
          of rejection, Immunex may give written notice to Genentech within the
          applicable time period set forth in this Section 8.1(a) of an Immunex
                                                   --------------
          decision to investigate whether a potentially Non-Conforming shipment
          should be rejected, which investigation shall, unless otherwise agreed
          by Immunex and Genentech, be completed within the applicable time
          period set forth in this Section 8.1(a), and in accordance with the
                                   --------------
          procedures set forth in the Quality Agreement.

     (b)  No Genentech Liability. If it is determined by agreement of the
          ----------------------
          Parties (or in the absence of such agreement, by a mutually acceptable
          qualified independent Third Party whose fees shall be paid by the
          non-prevailing Party) that either (1) there is no nonconformity, in
          which case Immunex shall pay to Genentech the Purchase Price for such
          Bulk Drug, or (2) there is nonconformity but the nonconformity was not
          caused by Genentech's failure to perform its obligations under the
          Agreement, in which case Genentech shall have no liability to Immunex
          with respect thereto, and Immunex shall pay to Genentech the Purchase
          Price for such Bulk Drug and the Bulk Drug shall be treated in all
          other respects under this Agreement as though it conformed with all of
          the warranties set forth in Section 6.1(a) of this Agreement.
                                      --------------

     (c)  Genentech Liability; Replacement of Product. If it is determined by
          -------------------------------------------
          agreement of the Parties (or in the absence of such agreement, by a
          mutually acceptable qualified independent Third Party whose fees shall
          be paid by the non-prevailing Party) that the nonconformity was caused
          by Genentech, Genentech shall as soon as practicable use Commercially
          Reasonable Efforts to replace such Non-Conforming Bulk Drug with
          conforming Bulk Drug, to the extent that Genentech has excess capacity
          and/or can reasonably revise its production schedule without adverse
          impact to itself or its obligations to Third Parties and/or
          Affiliates, at no additional cost to Immunex except for payment of the
          Purchase Price for the replacement conforming Bulk Drug, which shall
          be payable as follows: if Immunex previously paid the Purchase Price
          for the Non-Conforming Bulk Drug, then Genentech shall promptly and in
          any event within [*] days credit such amount to Immunex on the next
          invoice (or, at Immunex's option, Immunex may set off such amount
          against amounts owed to Genentech under this Agreement), and Immunex
          shall pay the Purchase Price for the replacement conforming Bulk Drug;
          and, if Immunex did not previously pay the Purchase Price for the
          Non-Conforming Bulk Drug, then Immunex shall pay the Purchase Price
          for the replacement conforming Bulk Drug. In addition, if, despite its
          use of Commercially Reasonable Efforts, to the extent that Genentech
          has excess capacity and/or can reasonably revise its production
          schedule without adverse impact to itself or its obligations to Third
          Parties and/or Affiliates, Genentech

* Portions of this exhibit have been omitted pursuant to a request for
confidential treatment filed with the Securities and Exchange Commission. The
omitted portions of this exhibit have been filed separately with the SEC.

                                    Page 29

<PAGE>

          cannot replace Non-Conforming Bulk Drug with conforming Bulk Drug by a
          date that is acceptable to Immunex, then Genentech shall upon demand
          by Immunex reimburse Immunex for any amount of the applicable Purchase
          Price that Immunex paid to Genentech for such Non-Conforming Bulk
          Drug. Notwithstanding anything herein seemingly to the contrary, with
          respect to latent defects only, if it is determined by agreement of
          the Parties (or in the absence of such agreement, by a mutually
          acceptable qualified independent Third Party, whose fees shall be paid
          by the non-prevailing Party) that the nonconformity was caused by both
          Genentech and Immunex, Genentech's obligation to reimburse Immunex for
          any amount of the applicable Purchase Price that Immunex paid to
          Genentech for such Non-Conforming Bulk Drug shall be measured in terms
          of proportionate liability and shall be diminished in proportion to
          the amount of causation attributable to Immunex.

     (d)  Cooperation in Investigations; Disposition of Non-Conforming Bulk
          -----------------------------------------------------------------
          Drug. If Immunex desires to make a claim against Genentech with
          -----
          respect to and reject a Batch of Non-Conforming Bulk Drug pursuant to
          Section 8.1(c), Immunex agrees that it shall not dispose of or allow
          --------------
          such Bulk Drug to be disposed of without written authorization and
          instructions from Genentech either to dispose of or return to
          Genentech such Non-Conforming Bulk Drug. Upon written request by
          Immunex, Genentech agrees promptly to give Immunex such authorization
          and instructions within a reasonable period of time. Each Party shall
          act in good faith and shall cooperate with the other Party and with
          any mutually acceptable qualified independent Third Party in
          connection with an investigation as to the existence of or source of
          any nonconformity of Bulk Drug supplied under this Agreement. At the
          request of Immunex, Genentech will provide all Non-Conforming Bulk
          Drug to Immunex, at no cost to Immunex (except for shipping and
          delivery expenses payable under Section 4.4 hereof), in accordance
                                          -----------
          with the delivery terms set forth in Section 4.4 hereof, and Immunex
                                               -----------
          may make whatever further use of such Product as it shall determine;
          provided, however, that Immunex agrees that (i) such Product shall not
          be used in humans, (ii) the warranties provided in Section 6.1(a) of
                                                             --------------
          this Agreement shall not apply to such Product, and (iii) the
          disclaimer of warranties set forth in Section 6.1(c) of this Agreement
                                                --------------
          shall apply to such Product.

                 ARTICLE 9. MANUFACTURING AUDITS; CERTIFICATE OF
                 -----------------------------------------------
                         COMPLIANCE; REGULATORY MATTERS
                         ------------------------------

9.1  Manufacturing Audits. Immunex shall have the right to perform, directly or
     --------------------
     through its representatives, one annual standard cGMP compliance audit, and
     additional For Cause Audits, all in accordance with the audit provisions
     set forth in the Quality Agreement. During the standard audits, personnel
     of Immunex or its representatives shall have access only to those areas
     that are directly related to the performance of Genentech's obligations
     under this Agreement, including the manufacture, testing, storage and
     shipping of Bulk Drug. No more than a reasonable number of representatives
     shall be permitted on Genentech's premises for any such audit and, at
     Genentech's option, each representative shall be accompanied by a Genentech
     employee at all times while on Genentech's premises.

                                    Page 30

<PAGE>

9.2  Certificates; Manufacturing Issues; Records.
     -------------------------------------------

     (a)  Certificates; Manufacturing Issues. As soon as possible after
          ----------------------------------
          manufacture and, unless otherwise agreed by Immunex, in any event by
          not later than the date of each shipment of Bulk Drug, Genentech shall
          furnish to Immunex the Batch Records and Manufacturer's Release
          Documentation described in the Quality Agreement, including, without
          limitation, a Certificate of Testing, a Certificate of Compliance and
          a summary (in a format to be agreed upon by Immunex and Genentech) of
          any deviations or investigations that occurred during the
          manufacturing or testing of the Bulk Drug that is part of such
          shipment. The provisions set forth in the Quality Agreement regarding
          deviations shall control whether a deviation results in Non-Conforming
          Bulk Drug.

     (b)  Records. Genentech shall maintain all of its manufacturing and
          -------
          analytical records, all records of shipments of Bulk Drug and all
          validation data relating to Bulk Drug for the time periods required by
          applicable laws and regulations of the FDA. Genentech agrees that, in
          response to any complaint, or in the defense by Immunex of any
          litigation, hearing, regulatory proceeding or investigation relating
          to Bulk Drug, Genentech shall use reasonable efforts to make available
          to Immunex during normal business hours and upon reasonable prior
          written notice, such Genentech employees and records reasonably
          necessary to permit the effective response to, defense of, or
          investigation of such matters, subject to appropriate confidentiality
          protections. Immunex shall reimburse Genentech for all reasonable
          costs and expenses incurred by Genentech in connection with the
          performance of Genentech's obligations under the immediately preceding
          sentence.

9.3  Complaints. Immunex shall have responsibility for reporting any
     ----------
     complaints relating to the Product to the FDA and any other regulatory
     authorities, including, but not limited to, complaints relating to the
     manufacture of the Product and adverse drug experience reports. Immunex
     shall maintain complaint files in accordance with cGMP. Genentech shall
     provide Immunex with a copy of any complaints received by Genentech with
     respect to the Product in accordance with the Quality Agreement and
     standard operating procedures to be agreed upon by Immunex and Genentech
     from time to time. Immunex shall have responsibility for responding to all
     complaints, and for promptly providing Genentech with a copy of any
     responses to complaints relating to the manufacture of the Product.
     Genentech shall use Commercially Reasonable Efforts to respond to requests
     from Immunex for information in Genentech's possession that is necessary
     for Immunex to respond to complaints arising out of the manufacture of the
     Bulk Drug.

9.4  Regulatory Correspondence.
     -------------------------

     (a) Notification to Other Parties of Regulatory Correspondence. Each
         ----------------------------------------------------------
         Party shall immediately and within at least [*] business days
         notify the other Party in writing

* Portions of this exhibit have been omitted pursuant to a request for
confidential treatment filed with the Securities and Exchange Commission. The
omitted portions of this exhibit have been filed separately with the SEC.

                                   Page 31

<PAGE>

          of, and shall provide the other Party with copies of, any
          correspondence and other documentation received or prepared by such
          Party in connection with any of the following events: (1) receipt of a
          regulatory letter, Warning Letter, or similar item, from the FDA or
          any other regulatory authority directed to the manufacture, packaging,
          and storage of Bulk Drug, or in connection with any general cGMP
          inspections applicable to any Genentech Facility to the extent
          associated with Genentech's activities under this Agreement; (2) any
          recall, market withdrawal or correction of any Batch of Bulk Drug or
          resulting Finished Product; and (3) any regulatory comments related to
          the manufacture of Bulk Drug or resulting Finished Product requiring a
          response or action by a Party.

     (b)  Regulatory Correspondence Requiring a Genentech Response. In the event
          --------------------------------------------------------
          Genentech receives any regulatory letter or comments from any federal,
          state or local regulatory authority directed to its manufacture of
          Bulk Drug requiring a response or action by Genentech, including, but
          not limited to, receipt of a Form 483 (Inspectional Observations) or a
          Warning Letter, Immunex promptly will provide Genentech with any data
          or information required by Genentech in preparing any response related
          to Genentech's manufacture of Bulk Drug and will cooperate fully with
          Genentech in preparing such response. Genentech shall provide Immunex
          with a copy of each such response (redacted to remove information not
          related to the manufacture of Bulk Drug or Genentech's other
          obligations under this Agreement) for Immunex's review and comment
          prior to Genentech's submission of its detailed written response.
          Genentech shall give all due consideration to any Immunex comments to
          each such proposed Genentech response provided Immunex timely
          responds. Likewise, in the event Immunex receives any regulatory
          letter or comments from any federal, state or local regulatory
          authority directed to the manufacture of Bulk Drug at the Genentech
          Facility requiring a response or action by Immunex, including, but not
          limited to, receipt of a Form 483 (Inspectional Observations) or a
          Warning Letter, Genentech will, to the extent within its control or
          possession, promptly provide Immunex with relevant data or information
          sufficient for Immunex to prepare any response related to the
          manufacture of Bulk Drug and will cooperate fully with Immunex in
          preparing such response. Immunex shall provide Genentech with a copy
          of each such response (redacted to remove information not related to
          the manufacture of Bulk Drug at Genentech's Facility or Immunex's
          obligations under this Agreement) for Genentech's review and comment
          prior to Immunex's submission of its detailed written response.
          Immunex shall give all due consideration to any Genentech comments to
          each such proposed Immunex response provided Genentech timely
          responds.

9.5  Inspections; Non-Compliance; Failure to Manufacture.
     ---------------------------------------------------

     (a) Inspections. In the event the Genentech Facility is inspected, or
         -----------
         Genentech is notified that the Genentech Facility will be inspected, by
         representatives of any federal, state or local regulatory agency
         directed to Genentech's manufacture of Bulk Drug, Genentech shall
         notify Immunex promptly after receipt of notice of such inspection, and
         shall supply Immunex with copies of any correspondence or portions of
         correspondence which relate to Bulk Drug. Immunex may send, and

                                    Page 32

<PAGE>

         upon the request of Genentech shall send, representatives to the
         Genentech Facility to participate in any portion of such inspection
         directed to Bulk Drug.

     (b) Non-Compliance; Failure to Manufacture. In the event that the FDA shall
         --------------------------------------
         determine, as a result of an inspection described in Section 9.5(a)
                                                              --------------
         above, that Genentech is not in compliance with applicable laws or
         regulations or otherwise not in compliance with cGMP with respect to
         the manufacture of Bulk Drug, Genentech shall at its expense use
         Commercially Reasonable Best Efforts to cure any such non-compliance
         with cGMP, and use Commercially Reasonable Efforts to cure any other
         such non-compliance as soon as practicable. In the event that any
         regulatory agency other than the FDA shall determine that Genentech is
         not in material compliance with applicable laws and regulations
         relating to the manufacture of Bulk Drug, the Parties shall discuss any
         potential Genentech curative efforts in good faith. In the event
         Genentech receives a Warning Letter from the FDA and as a result
         Genentech is unable to manufacture Bulk Drug for a particular period,
         then, except in the event of Genentech's gross negligence or willful
         misconduct, the provisions of Sections 20.3, 20.4 and 20.5 hereof shall
                                       ----------------------------
         apply, it being understood that Genentech's inability to manufacture
         Bulk Drug for the reasons set forth in this Section 9.5 shall be deemed
                                                     -----------
         to be a Force Majeure Event unless Genentech's inability to manufacture
         was caused by Genentech's gross negligence or willful misconduct.

                               ARTICLE 10. RECALLS
                               -------------------

10.1 Recalls. Immunex shall notify Genentech promptly (and in any event within
     -------
     [*] business days of receipt of written notice) if any batch of Bulk Drug
     or resulting Finished Product is the subject of a recall, market withdrawal
     or correction. Immunex shall (i) bear the cost of and be responsible for
     conducting all recalls, market withdrawals or corrections of Bulk Drug or
     Finished Product, (ii) remain obligated to pay Genentech the Purchase Price
     for the Bulk Drug recalled or used to make such recalled Finished Product
     and (iii) reimburse Genentech for its out-of-pocket expenses related to the
     recall, if any. Notwithstanding the foregoing, [*] recall, market
     withdrawal or correction was caused by Genentech's breach of any of its
     warranties set forth in Section 6.1 hereof, [*] Genentech shall credit
                             -----------
     Immunex for all or a portion of the Purchase Price for the Bulk Drug
     recalled or used to make such recalled Finished Product and shall reimburse
     Immunex for [*] Immunex's out-of-pocket expenses related to the recall, if
     any, [*]. Immunex or its agent shall in all events be responsible for
     conducting any recalls, market withdrawals or corrections with respect to
     the Product in the Territory.

* Portions of this exhibit have been omitted pursuant to a request for
confidential treatment filed with the Securities and Exchange Commission. The
omitted portions of this exhibit have been filed separately with the SEC.

                                  Page 33

<PAGE>

     ARTICLE 11. QUALITY ASSURANCE; QUALITY CONTROL; VALIDATION; STABILITY
     ---------------------------------------------------------------------

11.1 Responsibility for Quality Assurance and Quality Control. Responsibility
     --------------------------------------------------------
     for quality assurance and quality control of Bulk Drug shall be allocated
     between Immunex and Genentech as set forth in the Quality Agreement and in
     standard operating procedures agreed upon in writing by Immunex and
     Genentech from time to time. In general, (a) Genentech shall be responsible
     for performing certain in-process testing and selected acceptance testing
     on the Bulk Drug as set forth in the Tech Transfer Agreement and the
     Quality Agreement, and (b) Immunex shall be responsible for all final
     acceptance testing and authorizing final release of all Bulk Drug. In the
     event the Parties disagree on whether a Batch shall be released, the
     dispute shall be resolved in compliance with the provisions set forth in
     Section 8.1 hereof.
     ------------------

11.2 Validation of Genentech Facility; Utilities and Equipment. Genentech shall
     ---------------------------------------------------------
     maintain cGMP validation status of the Genentech Facility, as well as the
     utilities and equipment used in the manufacture of Bulk Drug at the
     Genentech Facility, and shall make relevant validation reports applicable
     thereto (redacted to remove information not related to the manufacture of
     Bulk Drug) available to Immunex for review at Genentech's Facility, at
     Immunex's reasonable request.

11.3 Validation of Bulk Manufacturing Process. In accordance with the
     ----------------------------------------
     requirements of and timelines set forth in the Tech Transfer Agreement,
     Immunex shall provide Genentech with Manufacturing Documentation related to
     the validation of the Manufacturing Process, as further described therein,
     including, without limitation, drafts of the product comparability protocol
     and the process validation protocol related to the Manufacturing Process.
     Immunex is responsible for Process Validation. A Process Qualification plan
     to be developed by Genentech and approved by Immunex will identify
     additional process validation related to the technology transfer to
     Genentech, if required, at commercial scale. Genentech shall provide
     Immunex with copies of documentation related to the validation of the
     Manufacturing Process, as implemented by Genentech, and validation reports
     applicable thereto, to Immunex, at Immunex's reasonable request, on a
     frequency and in a format to be agreed upon by Genentech and Immunex.

11.4 Change Control. Any changes to the Genentech Facility, utilities, equipment
     --------------
     or processes used by Genentech in its performance under this Agreement,
     including those relating to the manufacturing, storage, testing, shipping
     and cleaning procedures that are used by Genentech in the manufacture of
     Bulk Drug under this Agreement, shall occur pursuant to change control
     procedures agreed upon by Genentech and Immunex and as set forth in the
     Quality Agreement.

11.5 Stability. Immunex shall conduct all necessary stability testing to comply
     ---------
     with cGMP and other applicable regulatory guidelines. Such stability
     testing shall include testing to validate the lead times for shipment, the
     shelf life of Bulk Drug and the Bulk Drug Specifications applicable to
     shipment, storage and handling of Bulk Drug. Genentech shall prepare all
     stability samples, and shall sublot stability samples and package and ship
     stability samples to Immunex, all in accordance with timelines, protocols
     and procedures agreed upon by Genentech and Immunex and set forth in the
     Quality Agreement.

                                      Page 34

<PAGE>

11.6 Person in the Plant. As further described in the Quality Agreement, Immunex
     -------------------
     shall have the right to designate one employee of Immunex to be present in
     the Genentech Facility in South San Francisco during normal business hours
     during the Term of this Agreement to observe the Runs and observe
     Genentech's performance of its obligations under this Agreement. Such
     person shall have sufficient technical expertise and delegated corporate
     authority to, at a minimum, approve change control authorizations and
     deviations. While at the Facility, such representative of Immunex shall be
     restricted to such areas as are directly relevant to the manufacture of the
     Bulk Product, or as otherwise authorized by Genentech, and shall comply
     with all applicable Genentech policies and procedures and may, at
     Genentech's option, be escorted by Genentech personnel. Such representative
     shall have no right to direct or supervise Genentech personnel.

               ARTICLE 12. GENENTECH'S OBLIGATIONS AS MANUFACTURER
               ---------------------------------------------------

12.1 Control of Working Cell Bank. Genentech shall maintain all portions of the
     ----------------------------
     Working Cell Bank that it receives in safe and secure storage under its
     control in the Genentech Facility at One DNA Way in South San Francisco,
     California, and shall not permit the transfer of the Working Cell Bank to
     any Genentech Affiliate or any Third Party that is not specifically
     authorized in advance and in writing by Immunex. Genentech shall comply
     with all applicable FDA regulatory requirements relating to general safety
     in handling the Working Cell Bank and any raw materials and components used
     in manufacturing Product and Bulk Drug.

12.2 Manufacturing Capabilities. Genentech shall at all relevant times
     --------------------------
     throughout the Term use Commercially Reasonable Efforts consistent with the
     terms of this Agreement to (a) own or lawfully control all the necessary
     plant, equipment and facilities, and (b) have sufficient numbers of
     appropriately qualified personnel, in each case to enable Genentech to
     manufacture Bulk Drug in accordance with the Bulk Drug Specifications and
     in quantities sufficient to fulfill its obligations to supply Bulk Drug
     under this Agreement.

12.3 Compliance with Law. Genentech shall perform all work and services under
     -------------------
     this Agreement in conformance with cGMP and in conformance with the
     substantive requirements of all applicable material national, state and
     local laws, ordinances and governmental rules or regulations of the United
     States, the noncompliance with which would materially adversely affect the
     marketability of the Bulk Drug, and shall have all applicable licenses and
     permits required to perform the work and services hereunder, the absence of
     which would materially adversely affect the marketability of the Bulk Drug.

12.4 Genentech Facility. Genentech will use Commercially Reasonable Efforts to
     ------------------
     ensure that the Genentech Facility shall be maintained in accordance with
     cGMP and in such condition as will allow Genentech to manufacture the Bulk
     Drug in accordance with the Bulk Drug Specifications.

12.5 Storage Facilities. Subject to Section 4.4, Genentech shall provide
     ------------------             -----------
     sufficient and suitable storage facilities that meet the Bulk Drug
     Specifications for Bulk Drug and raw

                                  Page 35

<PAGE>

      materials.

12.6  Regulatory Documentation.
      ------------------------

     (a)  Genentech shall provide Immunex in a timely manner with a copy of any
          Genentech manufacturing and control records for Bulk Drug which are
          required for any Immunex regulatory filings with respect to the
          Product, which records shall be in Genentech's standard formats unless
          otherwise agreed upon by the Parties.

     (b)  Genentech shall provide Immunex promptly after the end of each annual
          reporting period for the Product (as calculated consistent with
          appropriate regulations and guidelines) with such information as is
          reasonably requested in writing by Immunex for the preparation of the
          annual report with respect to the manufacturing and control of the
          Product for such annual reporting period. Thereafter, Immunex shall
          provide to Genentech at least [*] days prior to Immunex's filing with
          the respective regulatory authorities a copy of such Immunex annual
          report, and Immunex shall take into consideration any Genentech
          comments to such annual report with respect to the manufacture of
          Product.

12.7 Manufacturing Data. Genentech shall collect data on the yield from each
     ------------------
     Batch, as well as the date of manufacture of each such Batch and make
     reports of the same available to Immunex in the form of a monthly
     manufacturing status report in Genentech's standard format or in such other
     format as may be agreed by the Parties. Genentech shall retain such
     manufacturing data in accordance with the requirements of applicable laws,
     rules and regulations.

12.8 Retention and Reserve Samples. Genentech shall isolate, identify and,
     -----------------------------
     subject to Section 19.3 hereof, retain retention and reserve samples of all
                ------------
     raw materials and in-process production steps used in the production of
     Bulk Drug as may be required by standard operating procedures to be agreed
     upon in writing by Genentech and Immunex from time to time.

12.9 Analytical Testing. Except as otherwise contemplated by this Agreement or
     ------------------
     expressly set forth in the Quality Agreement, Genentech shall not perform
     any analytical testing on Bulk Drug unless agreed to by Genentech and
     Immunex.

12.10 Accurate Documentation. Each Party shall use diligent efforts to ensure
      ----------------------
      all records and documentation provided to the other Party in connection
      with the manufacture of Bulk Drug shall be accurate in all material
      respects.


* Portions of this exhibit have been omitted pursuant to a request for
confidential treatment filed with the Securities and Exchange Commission. The
omitted portions of this exhibit have been filed separately with the SEC.

                                    Page 36

<PAGE>

                           ARTICLE 13. LICENSE GRANTS
                           --------------------------

13.1 License to Genentech. During the Term (subject to early termination in
     --------------------
     accordance with Article 19 hereof), Immunex hereby grants to Genentech a
                     ----------
     royalty-free, non-exclusive license under any and all intellectual property
     rights owned or controlled by Immunex (including, without limitation, such
     rights as are licensed to Immunex by a Third Party and which may be
     sublicensed to Genentech in accordance with the terms set forth herein) and
     which are necessary for Genentech to perform its obligations under this
     Agreement, including, without limitation, all rights necessary to the use
     of the Cell Line, the Manufacturing Process, and/or the Immunex
     Confidential Information (such rights are collectively the "Immunex IP
                                                                 ----------
     Rights") for the sole and limited purpose of Genentech's performance of its
     ------
     obligations under this Agreement, including, without limitation, to
     manufacture and supply Bulk Drug to Immunex.

13.2 [*].

    (a)  [*] Expressly conditioned on Immunex' representation and warranty
         under Section 15.1(e) hereof, Genentech, for itself and its
               --------------
         subsidiaries, hereby [*]. The terms of this Section 13.2(a) shall [*],
                                                     --------------
         and shall survive expiration or termination of this Agreement, and
         shall be binding upon and inure to the benefit of the successors and
         assigns of the Parties. In the event that Genentech [*]; provided,
         however, that Genentech's good faith and inadvertent failure to do so
         shall not be considered a material breach of this Agreement.

     (b) [*].

          (1) License to [*]. Except for Genentech Improvements assigned to
              --------------
          Immunex pursuant to Section 14.1(c) hereof, Genentech hereby grants
                              ---------------
          Immunex [*] to make, have made, use, market, distribute, import, offer
          for sale and sell Product within the Territory within the Field. The
          license granted under this Section 13.2(b)(1) is also subject to the
                                     ------------------
          last sentence of [*].

         (2) [*]

             (A) [*].

             (B) [*]

     (3) [*]

 (c) [*] Subject to the exceptions below in this Section 13.2(c)(1), the [*]
                                                 ------------------
     provisions of this Section 13.2(c) shall apply to the Confidential
                        ---------------
     Information of a Party ("Disclosing Party") disclosed to or received by the
     other Party ("Recipient") in the course of performance of this Agreement,
     the Tech Transfer Agreement or the Quality Agreement, or in the course of
     negotiating said agreements, or effecting

* Portions of this exhibit have been omitted pursuant to a request for
confidential treatment filed with the Securities and Exchange Commission. The
omitted portions of this exhibit have been filed separately with the SEC.

                                    Page 37

<PAGE>

          the technology transfer of the Product manufacturing process in effect
          as of the Effective Date or the Manufacturing Process, or information
          relating to the Product or to the manufacture thereof disclosed to a
          Party by the other Party or received by a Party from the other Party
          pursuant to the Confidentiality Agreements between the Parties dated
          August 16, 2000, December 13, 2001 and March 29, 2002 (collectively,
          the "CDAs"). The obligations of this Section 13.2(c) shall cease to
                                               --------------
          apply to Confidential Information of a Party, as well as to knowledge
          and information obtained by Recipient from access to said Confidential
          Information, upon said Confidential Information becoming subject to
          the exclusions listed in Section 17.3 hereof. Neither Party shall
                                   ------------
          disclose its ) confidential information to other Party that is not
          reasonably necessary or appropriate for the performance of its
          obligations under this Agreement, the Tech Transfer Agreement or the
          Quality Agreement, and this Section 13.2(c) shall not apply to the
                                      --------------
          Disclosing Party's Confidential Information that is not reasonably
          necessary or appropriate to be disclosed by the Disclosing Party for
          purposes of the Recipient's performance of its obligations under this
          Agreement, the Tech Transfer Agreement or the Quality Agreement,
          including, without limitation, any information on manufacturing
          processes for other products. Notwithstanding the foregoing, the
          Disclosing Party's Confidential Information of which the Recipient
          becomes aware due to the presence of its employees, agents or
          contractors at the Disclosing Party's facilities, either through
          inadvertent good faith disclosures or through misappropriation, shall
          be subject to the provisions of this Section 13.2(c). Each Party shall
                                               --------------
          use good faith efforts to provide the Disclosing Party's Confidential
          Information to the Recipient through the Disclosing Party's employees
          having responsibility for the performance of the Disclosing Party's
          obligations under this Agreement, the Tech Transfer Agreement or the
          Quality Agreement, but inadvertent failures to do so shall not limit
          the applicability of this Section 13.2(c).
                                    --------------

         (1)  [*]

         (2)  [*]

     (d)  Survival. The obligations of the Parties set forth in this Section
          --------                                                   -------
          13.2 shall survive the expiration or termination of this Agreement.
          ----

     ARTICLE 14. OWNERSHIP OF INTELLECTUAL PROPERTY, MATERIALS AND EQUIPMENT
     -----------------------------------------------------------------------

     14.1 Ownership of Intellectual Property, Confidential Information,
          -------------------------------------------------------------
          Biological Materials and Manufacturing Documentation.
          ----------------------------------------------------

     (a)  Intellectual Property. In accordance with the rules of inventorship of
          ---------------------
          the United States of America, each Party shall solely own any and all
          inventions or discoveries that are conceived or reduced to practice in
          the course of or resulting

* Portions of this exhibit have been omitted pursuant to a request for
confidential treatment filed with the Securities and Exchange Commission. The
omitted portions of this exhibit have been filed separately with the SEC.

                                    Page 38

<PAGE>

          from this Agreement, the Tech Transfer Agreement and/or the Quality
          Agreement by the Party or its employees or agents, and the Parties
          shall jointly own inventions or discoveries that are conceived or
          reduced to practice in the course of or resulting from this Agreement,
          the Tech Transfer Agreement and/or the Quality Agreement with an
          inventive contribution by employees or agents of both Parties.
          Licenses to the foregoing are described in Article 13 above. The
                                                     ----------
          Parties hereby agree that neither Party shall be considered an
          "employee or agent" of the other Party.

     (b)  Confidential Information. As between the Parties, Immunex shall own
          ------------------------
          all Immunex Confidential Information, and Genentech shall own all
          Genentech Confidential Information; provided, however, that the
          foregoing shall not limit Immunex' ownership of, or ability to use,
          the Cell Line, Master Cell Bank, Working Cell Bank, and/or the
          Product, including, without limitation, aspects of Genentech
          Confidential Information that result in or contribute to modifications
          to said Cell Line, Master Cell Bank, Working Cell Bank, and/or the
          Product in the course of or resulting from this Agreement, the Tech
          Transfer Agreement and/or the Quality Agreement, either by Immunex in
          an authorized manner under said agreements or by Genentech.

     (c)  Biological Materials. As between the Parties, Immunex shall own all
          --------------------
          rights in and title to the biological materials described as the Cell
          Line, Master Cell Bank, Working Cell Bank, and/or the Product, and any
          and all improved or enhanced versions of the foregoing that are
          created by either Party in the course of or resulting from this
          Agreement, the Tech Transfer Agreement and/or the Quality Agreement,
          including, without limitation, any derivatives or variants of the
          foregoing created by either Party in the course of or resulting from
          this Agreement, the Tech Transfer Agreement and/or the Quality
          Agreement. Genentech hereby assigns to Immunex any Genentech
          Improvements that relate solely to the Cell Line, Master Cell Bank,
          Working Cell Bank, and/or the Product. For purposes of this provision,
          "Genentech Improvements" shall mean any and all patentable inventions
          made in the course of or resulting from this Agreement, the Tech
          Transfer Agreement and/or the Quality Agreement, solely by Genentech
          or its employees or agents, or jointly by the employees and/or agents
          of each Party, and all intellectual property rights therein. [*].

     (d)  Manufacturing Documentation. As between the Parties, Immunex shall own
          ---------------------------
          the Manufacturing Documentation.

     (e)  Survival. The terms of this Section 14.1 shall survive the expiration
          --------                    ------------
          or termination of this Agreement, and shall be binding upon and inure
          to the benefit of the successors and assigns of the Parties. The
          Parties will continue to reasonably cooperate with each other to
          perfect the rights granted in this Section 14.1.
                                             ------------

* Portions of this exhibit have been omitted pursuant to a request for
confidential treatment filed with the Securities and Exchange Commission. The
omitted portions of this exhibit have been filed separately with the SEC.

                                    Page 39

<PAGE>

14.2 Ownership of Equipment. Genentech shall own all right, title and interest
     ----------------------
     in and to any and all equipment, materials, facilities improvements and
     other assets purchased by Genentech and which are required to be reimbursed
     by Immunex under the Tech Transfer Agreement, including, without
     limitation, the Portable Equipment and the Non-Portable Equipment
     (collectively, the "Equipment"), free and clear of any right or claim of
                         ---------
     Immunex and anyone claiming through Immunex. All Equipment shall be
     maintained in good repair. Notwithstanding the foregoing, however, at the
     expiration or termination of this Agreement, Immunex may, at its option,
     take title to and possession of some or all of the Portable Equipment (at
     no charge but with Immunex paying reasonable costs and expenses to remove
     such equipment from Genentech's facilities and ship and deliver it to
     Immunex's facilities), and Genentech may, at no cost, retain all other
     portions of the Equipment. The freeze tanks described in Section 4.7 hereof
                                                              -----------
     shall be deemed to be "Portable Equipment" and shall be subject to transfer
     to Immunex pursuant to the terms of this Section 14.2. In addition, all of
                                              ------------
     the Equipment shall also be subject to the provisions of Section 19.3
                                                              ------------
     below. If Genentech fails to timely arrange for the removal of the Portable
     Equipment from the Genentech Facility, Immunex shall send written notice
     requesting such removal. If such removal has not occurred within [*] days
     of such notice, then Immunex shall be entitled to hire a qualified Third
     Party at Genentech's reasonable expense to enter the Genentech Facility
     with written notice at least [*] business days in advance and remove the
     Portable Equipment, which shall be removed in a reasonable manner without
     damage to the Genentech Facility. For clarification purposes, removal of
     the Portable Equipment shall not in and of itself be considered damage to
     the Genentech Facility.

                   ARTICLE 15. REPRESENTATIONS AND WARRANTIES
                   ------------------------------------------

15.1 Immunex.  Immunex hereby represents and warrants to Genentech that:
     -------

     (a)  To the best of Immunex's knowledge, after reasonable inquiry, Immunex
          is free to supply to Genentech the Working Cell Bank, Immunex
          Confidential Information (including, without limitation, the
          Manufacturing Documentation), and all information to be supplied by
          Immunex to Genentech under the Tech Transfer Agreement; and Immunex's
          supply to Genentech of the Working Cell Bank and Immunex Confidential
          Information (including, without limitation, the Manufacturing
          Documentation), and all information supplied by Immunex to Genentech
          under the Tech Transfer Agreement, and Genentech's use thereof in
          accordance with the terms of and in performance of its obligations
          under this Agreement, does not, to the best of Immunex's knowledge,
          after reasonable inquiry, infringe any valid claim of any Third Party
          patent; and, to the best of Immunex's knowledge, after reasonable
          inquiry, except for the pending suit brought by ZymoGenetics, Inc.,
          there is no suit pending against Immunex or Wyeth in the U.S. that
          alleges patent infringement by the manufacture or sale of the Product;
          and to the best of Immunex's knowledge, after reasonable inquiry,
          Immunex has not received written notice alleging infringement of a
          Third Party

* Portions of this exhibit have been omitted pursuant to a request for
confidential treatment filed with the Securities and Exchange Commission. The
omitted portions of this exhibit have been filed separately with the SEC.

                                    Page 40

<PAGE>

          patent by the manufacture or sale of the Product;

     (b)  Immunex has made Genentech aware of any known hazards involved in
          handling the Cell Line, Working Cell Bank, the Specialized Raw
          Materials and the Bulk Drug, and will continue to make Genentech aware
          of such matters in the future;

     (c)  Immunex has the corporate power and authority and consents and the
          legal right to enter into this Agreement and to perform its
          obligations under this Agreement, including, but not limited to,
          consents of [*], Immunex's Board of Directors, and Amgen Inc.;

     (d)  Immunex has taken all necessary corporate action on its part to
          authorize the execution and delivery of this Agreement and the
          performance of its respective obligations under this Agreement. This
          Agreement has been duly executed and delivered on behalf of Immunex,
          and constitutes a legal, valid, binding obligation, enforceable
          against Immunex and its successors and assigns in accordance with its
          terms;

     (e)  [*]; and

     (f)  To the best of Immunex' knowledge after reasonable inquiry, Immunex
          has the legal right to [*] set forth in [*] above and the [*] set
          forth in [*] above.

15.2 Genentech.  Genentech hereby represents and warrants to Immunex that:
     ---------

     (a)  To the best of Genentech's knowledge, after reasonable inquiry,
          Genentech is free to supply the Genentech Confidential Information to
          Immunex;

     (b)  Genentech has the corporate power and authority and the legal right to
          enter into this Agreement and to perform its obligations under this
          Agreement;

     (c)  Genentech has taken all necessary corporate action on its part to
          authorize the execution and delivery of this Agreement and the
          performance of its obligations under this Agreement. This Agreement
          has been duly executed and delivered on behalf of Genentech, and
          constitutes a legal, valid, binding obligation, enforceable against
          Genentech in accordance with its terms;

     (d)  Genentech owns or lawfully controls the Genentech Facility, and, to
          the best of its knowledge after reasonable inquiry, has a sufficient
          number of employees with such expertise and experience as is necessary
          or appropriate to produce Bulk Drug in accordance with the terms
          hereof and in quantities sufficient to fulfill the Annual Minimums set
          forth in Exhibit A hereof; and
                   ---------

     (e)  To the best of Genentech's knowledge after reasonable inquiry,
          Genentech has the legal right to [*] above and to [*]; as of the
          Effective Date, Genentech has not [*].

* Portions of this exhibit have been omitted pursuant to a request for
confidential treatment filed with the Securities and Exchange Commission. The
omitted portions of this exhibit have been filed separately with the SEC.

                                    Page 41

<PAGE>

                           ARTICLE 16. INDEMNIFICATION
                           ---------------------------

16.1 Indemnification by Immunex.
     --------------------------

     (a)  Indemnification by Immunex. Subject to and except to the extent of any
          --------------------------
          indemnification from Genentech pursuant to Section 16.2 below, Immunex
                                                     ------------
          shall indemnify, defend and hold Genentech, its Affiliates, and their
          respective directors, officers, employees and agents harmless from and
          against all losses, damages, liabilities, settlements, penalties,
          fines, costs and expenses (including, without limitation, reasonable
          attorneys' fees and expenses), (collectively, the "Liabilities") to
                                                             -----------
          the extent such Liabilities arise out of or result from (1) any claim,
          lawsuit or other action or threat by a Third Party arising out of the
          manufacture, use, handling, distribution, marketing or sale of the
          Product, in any form, (2) any material breach of the representations,
          warranties and covenants made by Immunex under this Agreement, (3)
          Immunex's grossly negligent acts or omissions or willful misconduct,
          and/or (4) any recall of the Product, except and to the extent arising
          out of or resulting from any material breach of the representations,
          warranties and covenants made by Genentech under this Agreement, or
          Genentech's grossly negligent acts or omissions or willful misconduct.

     (b)  Additional Indemnification by Immunex. Immunex shall indemnify, defend
          -------------------------------------
          and hold Genentech, its Affiliates, and their respective directors,
          officers, employees and agents harmless from and against all
          Liabilities to the extent such Liabilities arise out of or result from
          any claim by a Third Party that Genentech's manufacture of Bulk Drug
          for Immunex hereunder, to the extent such manufacture of Bulk Drug
          hereunder is in compliance with the Manufacturing Documentation,
          Manufacturing Process and Bulk Drug Specifications, infringes the
          intellectual property rights of such Third Party. [*]

16.2 Indemnification by Genentech. Subject to and except to the extent of any
     ----------------------------
     indemnification from Immunex pursuant to Section 16.1(a) and (b) above,
                                              -----------------------
     Genentech shall indemnify, defend and hold Immunex, and its Affiliates,
     directors, officers, employees and agents harmless from and against all
     Liabilities to the extent such Liabilities arise out of or result from (a)
     any material breach of the representations and warranties made by Genentech
     under this Agreement or any material breach of any of the covenants made by
     Genentech [*], or (b) Genentech's grossly negligent acts or omissions or
     willful misconduct. For the purposes of this Section 16.2, "willful
                                                  ------------
     misconduct" shall not include [*].

16.3 Indemnification Procedures.
     --------------------------

     (a)  Identification of Indemnitor and Indemnitee. An "Indemnitor" means
          -------------------------------------------      ----------
          Immunex with respect to Section 16.1(a) and (b) hereof, and Genentech
                                  ---------------     ---
          with respect to

* Portions of this exhibit have been omitted pursuant to a request for
confidential treatment filed with the Securities and Exchange Commission. The
omitted portions of this exhibit have been filed separately with the SEC.

                                    Page 42

<PAGE>

          Section 16.2 hereof. An "Indemnitee" means any of Genentech, its
          ------------             ----------
          Affiliates, and their respective directors, officers, employees and
          agents with respect to Section 16.1(a) and (b) hereof, and any of
                                 --------------      ---
          Immunex, and its respective Affiliates, directors, officers, employees
          and agents with respect to Section 16.2 hereof.
                                     ------------

     (b)  Indemnification Procedures. An Indemnitee which intends to claim
          --------------------------
          indemnification under Section 16.1 or 16.2 hereof shall promptly
                                ------------    ----
          notify the Indemnitor in writing of any claim, lawsuit or other action
          in respect of which the Indemnitee, its Affiliates, or any of their
          respective directors, officers, employees and agents intend to claim
          such indemnification. The Indemnitee shall permit, and shall cause its
          Affiliates and their respective directors, officers, employees and
          agents to permit, the Indemnitor, at its discretion, to settle any
          such claim, lawsuit or other action and agrees to the complete control
          of such defense or settlement by the Indemnitor; provided, however,
          such settlement does not adversely affect the Indemnitee's rights
          under this Agreement or impose any obligations on the Indemnitee in
          addition to those set forth herein in order for the Indemnitor to
          exercise such rights. No such claim, lawsuit or other action shall be
          settled without the prior written consent of the Indemnitor and the
          Indemnitor shall not be responsible for any legal fees or other costs
          incurred other than as provided herein. The Indemnitee, its Affiliates
          and their respective directors, officers, employees and agents shall
          cooperate fully with the Indemnitor and its legal representatives in
          the investigation and defense of any claim, lawsuit or other action
          covered by this indemnification, all at the reasonable expense of the
          Indemnitor. The Indemnitee shall have the right, but not the
          obligation, to be represented by counsel of its own selection and
          expense.

16.4 Survival of Indemnification Obligations. The provisions of this Article 16
     ---------------------------------------                         ----------
     shall survive the termination or expiration of this Agreement.

16.5 Disclaimer of Consequential Damages. Except for claims arising from [*], in
     -----------------------------------
     no event shall either Party be liable to the other Party for incidental,
     indirect, special, punitive or consequential damages arising from or
     related to breach of this Agreement, including, without limitation, any
     claims for damages based upon lost profits [*].

                           ARTICLE 17. CONFIDENTIALITY
                           ---------------------------

17.1 Confidentiality Obligations.
     ---------------------------

     (a)  Genentech Confidentiality Obligations. Genentech shall not disclose
          -------------------------------------
          Immunex Confidential Information to any third party other than

          (1)  its employees or employees of its subsidiaries who have a need to
               know such information in order to perform their duties in
               carrying out Genentech's obligations under this Agreement, the
               Tech Transfer Agreement and/or the Quality Agreement,

* Portions of this exhibit have been omitted pursuant to a request for
confidential treatment filed with the Securities and Exchange Commission. The
omitted portions of this exhibit have been filed separately with the SEC.

                                    Page 43

<PAGE>

          (2)  contractors who are bound by similar obligations of
               confidentiality and nonuse and who have a need to know such
               information in order to provide direction to Genentech or Immunex
               regarding their respective obligations under this Agreement, the
               Tech Transfer Agreement and/or the Quality Agreement, or

          (3)  regulatory authorities, for example, the FDA, that require such
               information in order to review a BLA or sBLA for the Product or
               other regulatory filing.

          For purposes of clarity, Genentech shall not be authorized to disclose
          any Immunex Confidential Information to Roche without Immunex' prior
          written consent. Further, Genentech shall not disclose any
          confidential information of Roche to Immunex.

     (b)  Immunex Confidentiality Obligations. Immunex shall not disclose any
          -----------------------------------
          Genentech Confidential Information to any third party (including,
          without limitation, Amgen, prior to the effective date of the Change
          of Control, if any) other than

          (1)  employees, consultants, agents or contractors of Immunex or
               Immunex's Affiliates who are bound by similar obligations of
               confidentiality and nonuse and who have a need to know such
               information in order to perform their duties in carrying out
               Immunex's obligations under this Agreement, the Tech Transfer
               Agreement and/or the Quality Agreement, or in order to provide
               direction to Immunex regarding production, testing, storage or
               quality of the Product or regulatory or compliance issues related
               to the Product, or

          (2)  regulatory authorities, for example, the FDA, that require such
               information in order to review a BLA or sBLA for the Product or
               other regulatory filing.

          For purposes of this Section 17.1(b), American Home Products
                               ---------------
          Corporation, now known as Wyeth, and its Affiliates shall not be
          deemed to be affiliates of Immunex [*].

     (c)  Responsibility for Compliance with Confidentiality and Nonuse
          -------------------------------------------------------------
          Obligations. Each Party shall be responsible for any intentional
          -----------
          misuse or misappropriation, by such Party, its Affiliates, or the
          employees, consultants, agents or contractors of such Party or such
          Party's Affiliates, of the other Party's Confidential Information.

17.2 Terms of Agreement. Subject to Sections 17.4 and 18.1 hereof, and except
     ------------------             -------------     ----
     for any disclosure as is deemed necessary, in the reasonable judgment of
     the responsible Party, to comply with national, federal or state laws or
     regulations (including the rules and regulations of any national stock
     exchange on which such Party's securities are traded),

* Portions of this exhibit have been omitted pursuant to a request for
confidential treatment filed with the Securities and Exchange Commission. The
omitted portions of this exhibit have been filed separately with the SEC.

                                    Page 44

<PAGE>

     neither Party shall, without the prior written consent of the other Party,
     disclose in any manner to any Third Party the terms and conditions of this
     Agreement; provided that this Section 17.2 shall not prohibit the
                                   ------------
     disclosure of this Agreement by Immunex to Amgen Inc., and shall not
     prohibit the disclosure of this Agreement by Genentech to Roche.

17.3 Exclusions. The obligations of confidentiality and nonuse applicable
     ----------
     hereunder to Genentech with respect to Immunex Confidential Information and
     to Immunex with respect to Genentech Confidential Information shall not
     apply to any information which:

     (a)  at the time of disclosure, is known publicly or thereafter becomes
          known publicly through no fault of the recipient, its Affiliates or
          agents;

     (b)  becomes available to the recipient from a Third Party which is not
          legally prohibited from disclosing such information, provided such
          information was not acquired directly or indirectly from the
          disclosing Party;

     (c)  was developed by the recipient independently of information obtained
          from the disclosing Party as evidenced by written records;

     (d)  was already known to the recipient before receipt from the disclosing
          Party, as shown by its prior written records, provided that such
          information was not acquired directly or indirectly from the
          disclosing Party; or

     (e)  is released with the prior written consent of the Party that had
          originally disclosed such information to the other Party hereunder.

     In determining whether or not the disclosing Party's Confidential
     Information has entered the public domain, the obligations of
     confidentiality shall no longer apply to only that portion of said
     Confidential Information that has become public, and portions remaining
     confidential shall retain their status as Confidential Information.

17.4 Notification of Mandatory Disclosure.
     ------------------------------------

     (a)  Notification and Consultation. In the event that a Party (in such
          -----------------------------
          case, the "Notifying Party") believes it is required by applicable
                     ---------------
          statute or regulation (including the rules and regulations of any
          national stock exchange on which such Party's securities are traded),
          or by judicial or administrative process to disclose any part of the
          other Party's (in such case, the "Notified Party") Confidential
                                            --------------
          Information which is disclosed to it under this Agreement, the
          Notifying Party shall (1) promptly notify the Notified Party of each
          such requirement and identify the documents so required thereby, so
          that the Notified Party may seek an appropriate protective order or
          other remedy and/or waive compliance by the Notifying Party with the
          provisions of this Agreement, and (2) consult with the Notified Party
          on the advisability of taking legally available steps to resist or
          narrow the scope of such requirement.

                                    Page 45

<PAGE>

     (b)  Limited Disclosure. If, in the absence of such a protective order or
          ------------------
          such a waiver by the Notified Party of the provisions of this
          Agreement, the Notifying Party is nonetheless required by mandatory
          applicable law to disclose any part of the Notified Party's
          Confidential Information which is disclosed to it under this
          Agreement, the Notifying Party may disclose such Confidential
          Information without liability under this Agreement, except that the
          Notifying Party shall furnish only that portion of the Confidential
          Information which is legally required.

17.5 No Licenses; Maintenance of Confidentiality; Nonuse Obligations.
     ---------------------------------------------------------------

     (a)  No Licenses. Except as expressly provided in [*], no right or license,
          -----------
          either express or implied, under any intellectual property right is
          granted under this Agreement, the Tech Transfer Agreement, or the
          Quality Agreement, by virtue of the disclosure of Confidential
          Information under this Agreement, the Tech Transfer Agreement, or the
          Quality Agreement, or otherwise.

     (b)  Maintenance of Confidentiality. Each Party shall use reasonable and
          ------------------------------
          customary precautions to safeguard the other Party's Confidential
          Information, including ensuring that all employees, consultants,
          agents or contractors who are provided access to such Confidential
          Information are informed of the confidential and proprietary nature of
          such Confidential Information and have contractual confidentiality and
          nonuse obligations that are at least as restrictive as those contained
          in this Agreement.

     (c)  Nonuse Obligations. Immunex Confidential Information shall not be
          ------------------
          utilized by Genentech for any purpose other than performing its
          obligations under this Agreement, the Tech Transfer Agreement, or the
          Quality Agreement, without first obtaining Immunex's prior written
          consent to each such utilization. Genentech Confidential Information
          shall not be utilized by Immunex except as set forth in this
          Agreement, the Tech Transfer Agreement, or the Quality Agreement, or
          except for the limited purpose of production, testing, storage or
          quality of the Product or regulatory or compliance issues related to
          the Product, without first obtaining Genentech's prior written consent
          to each such utilization.

     (d)  Equitable Relief. Each Party agrees that the other Party and their
          ----------------
          respective Affiliates would be irreparably injured by a material
          breach of the confidentiality and nonuse provisions of this Agreement
          by the breaching Party or by its employees or the employees of its
          Affiliates, consultants, agents or contractors, that monetary remedies
          would be inadequate to protect the other Party against any actual or
          threatened material breach of the provisions of this Article 17 by the
                                                               ----------
          breaching Party or by its employees or the employees of its
          Affiliates, consultants, agents or contractors, and, without prejudice
          to any other rights and remedies otherwise available to the other
          Party, the breaching Party agrees, upon proof of any such actual or
          threatened material breach, to the granting of equitable relief,
          including injunctive relief and specific performance, in the other
          Party's favor

* Portions of this exhibit have been omitted pursuant to a request for
confidential treatment filed with the Securities and Exchange Commission. The
omitted portions of this exhibit have been filed separately with the SEC.

                                    Page 46

<PAGE>

         without proof of actual damages. It is further understood and agreed
         that no failure or delay by either Party in exercising any right, power
         or privilege hereunder shall operate as a waiver thereof, nor shall any
         single or partial exercise thereof preclude any other or further
         exercise thereof or the exercise of any other right, power or privilege
         hereunder.

17.6 Survival of Confidentiality Obligations. The provisions of this Article 17
     ---------------------------------------                         ----------
     shall survive the termination or expiration of this Agreement for a period
     of [*] years; provided, however, that with respect to Immunex Confidential
     Information that is identified by Immunex as "BIP Confidential
                                                   ----------------
     Information," the provisions of this Article 17 shall survive for the
     -----------                          ----------
     longer of the following time periods: [*] years after the termination or
     expiration of the ENBREL supply agreement among BIP, American Home Products
     Corporation, and Immunex dated November 5, 1998, as amended (the "BIP
                                                                       ---
     ENBREL Supply Agreement"); and (b) [*] years after the termination or
     -----------------------
     expiration of this Agreement.

17.7 Termination of Certain Prior Agreements and Letter of Intent. This
     ------------------------------------------------------------
     Agreement supersedes (a) the Confidentiality Agreements between the Parties
     dated August 16, 2000 and December 13, 2001, (b) the Letter of Intent, and
     (c) the Confidential Disclosure Agreement between the Parties dated March
     29, 2002. All Confidential Information (as defined in such Confidentiality
     Agreements, Letter of Intent and Confidential Disclosure Agreement),
     exchanged between the Parties under such Confidentiality Agreements, Letter
     of Intent and Confidential Disclosure Agreement shall be deemed
     Confidential Information under this Agreement (either Immunex Confidential
     Information or Genentech Confidential Information, as the context requires)
     and shall be subject to the terms of this Agreement.

17.8 No Disclosure of Unrelated Information. Neither Party shall disclose
     --------------------------------------
     confidential information to the other Party that is not reasonably
     necessary for performance of a Party's obligations under this Agreement,
     the Tech Transfer Agreement and/or the Quality Agreement, including but not
     limited to manufacturing processes for other products, marketing plans and
     clinical development plans. Notwithstanding the foregoing, nothing in this
     provision shall limit the confidentiality and non-use obligations and
     rights herein.

                    ARTICLE 18. PRESS RELEASES; USE OF NAMES
                    ----------------------------------------

18.1 Press Releases. The Parties agree that the public announcement of the
     --------------
     execution of this Agreement shall be in the form of a draft press release
     to be agreed upon by the Parties, and, after the press release is
     published, each Party shall be entitled to make or publish any public
     statement consistent with the contents thereof. Except as set forth in the
     preceding sentence, no press release, publicity or other form of public
     written disclosure related to this Agreement shall be permitted by either
     Party unless the other Party has indicated its consent to the form of the
     release in writing. This Section shall not apply

* Portions of this exhibit have been omitted pursuant to a request for
confidential treatment filed with the Securities and Exchange Commission. The
omitted portions of this exhibit have been filed separately with the SEC.

                                    Page 47

<PAGE>

     to any disclosure as is deemed necessary, in the reasonable judgment of the
     responsible Party, to comply with national, federal or state laws or
     regulations (including the rules and regulations of any national stock
     exchange on which such Party's securities are traded).

18.2 Use of Names. No Party shall make use of the name of any other Party in any
     ------------
     advertising or promotional material, or otherwise, in connection with this
     Agreement or any related agreements, without the prior written consent of
     such other Party; provided, however, either Party may include the other
     Party on a general list of business partners or collaborations.

                          ARTICLE 19. TERM; TERMINATION
                          -----------------------------

19.1 Term; Option to Extend. Unless sooner terminated pursuant to the terms of
     ----------------------
     this Agreement, the term of this Agreement (the "Term") shall commence on
                                                      ----
     the Effective Date and shall continue until December 31, 2005. The Parties
     may, by mutual written agreement, extend the Term of this Agreement for an
     additional year, and, in such case, the Term would be extended through
     December 31, 2006.

19.2 Termination. This Agreement may be terminated prior to the end of the Term
     -----------
     as follows:

     (a)  Material Breach.
          ---------------

          (1)  Genentech Material Breach. This Agreement may be terminated in
               -------------------------
               its entirety by Immunex upon written notice thereof to Genentech
               in the event of a material breach by Genentech which is not cured
               within [*] days after receipt of written notice from Immunex to
               Genentech, specifying in reasonable detail the nature of such
               breach, or such longer period of time if Genentech delivers a
               certificate that such material breach is not reasonably capable
               of being cured within [*] days and that Genentech is working
               diligently to cure such breach, but in no event shall the time
               for curing such breach exceed an additional [*] days. In the
               event such breach is not cured within such cure period, this
               Agreement shall terminate as set forth in Immunex's notice of
               breach and in accordance with the terms of this Article;
               provided, however, that this Agreement shall not be terminated
               prior to the end of such cure period.

          (2)  Immunex Material Breach. This Agreement may be terminated by
               -----------------------
               Genentech upon written notice thereof to Immunex in the event of
               a material breach by Immunex which is not cured within [*] days
               from written notice to Immunex specifying in reasonable detail
               the nature of such breach or longer if Immunex delivers a
               certificate that such material breach is not reasonably capable
               of being cured within [*] days and that

* Portions of this exhibit have been omitted pursuant to a request for
confidential treatment filed with the Securities and Exchange Commission. The
omitted portions of this exhibit have been filed separately with the SEC.

                                    Page 48

<PAGE>

               Immunex is working diligently to cure such breach, but in no
               event shall the time for curing such breach exceed an additional
               [*] days. Notwithstanding the foregoing, if the material breach
               referred to in this Section 19.2(a)(2) arises out of or consists
                                   ------------------
               of the failure to pay Genentech amounts due under this Agreement
               in accordance with the terms hereof, there shall be a single
               period of [*] days after notice of breach within which Immunex
               shall have the right to cure such default by making payment in
               full of the amount then due and payable. In the event such breach
               is not cured within such cure period, this Agreement shall
               terminate as set forth in Genentech's notice of breach and in
               accordance with the terms of this Article; provided, however,
               that this Agreement shall not be terminated prior to the end of
               such cure period.

     (b)  Force Majeure; No Fault Termination. This Agreement may be terminated
          -----------------------------------
          as follows: If, as a result of a Force Majeure Event, a Party is
          unable fully to perform its obligations under this Agreement for any
          consecutive period of [*] days, unless the Parties mutually agree in
          writing upon a shorter time period, Immunex (in the case of a Force
          Majeure Event affecting Genentech) or Genentech (in the case of a
          Force Majeure Event affecting Immunex) shall have the right to
          terminate this Agreement, upon providing written notice thereof to the
          other Party, such termination to be effective [*] days from the
          effective date of such notice.

     (c)  Failure to Obtain FDA Approval for Genentech Facility. This Agreement
          -----------------------------------------------------
          may be terminated as follows: (i) in the event FDA Approval for the
          manufacture of Bulk Drug at the Genentech Facility is not received by
          [*], or if at any time either Party receives information which
          indicates that FDA approval by [*] would be highly unlikely, the
          Parties agree to enter into good faith discussions to determine
          whether this Agreement should be terminated and, upon agreement of the
          Parties, this Agreement shall be terminated on the date agreed to by
          the Parties; and (ii) in the event FDA Approval for the manufacture of
          Bulk Drug at the Genentech Facility is not received by [*], Immunex
          may, in its sole discretion, terminate this Agreement in its entirety
          upon at least [*] days' prior written notice to Genentech; provided,
          however, that Immunex may not issue a termination notice pursuant to
          this Section 19.2(c)(ii) after FDA Approval for the manufacture of
               -------------------
          Bulk Drug at the Genentech Facility has been received. The date set
          forth in Section 19.2(c)(ii) hereof may be adjusted by the JPT in
                   -------------------
          accordance with Section 3.4(d). Immunex may exercise its termination
                          --------------
          rights under Section 19.2(c)(ii) hereof so long as Immunex has not
                       -------------------
          acted in bad faith to materially and adversely affect the critical
          path to FDA Approval.

     (d)  Withdrawal of Product. This Agreement may be terminated by Immunex, in
          ---------------------
          its sole discretion, upon at least [*] days' prior written notice to
          Genentech, in the event the BLA for the Product is irrevocably
          withdrawn by Immunex.

* Portions of this exhibit have been omitted pursuant to a request for
confidential treatment filed with the Securities and Exchange Commission. The
omitted portions of this exhibit have been filed separately with the SEC.

                                Page 49

<PAGE>

19.3 Consequences of Termination.
     ---------------------------

     (a)  Payment of Amounts Due; Cumulative Remedies. Expiration or termination
          -------------------------------------------
          of this Agreement for any reason shall not exempt any Party from
          paying to any other Party any amounts owing to such Party at the time
          of such expiration or termination. Except as expressly stated
          otherwise herein, remedies under this Agreement are cumulative, and
          nothing in this Agreement shall prevent any Party, in the case of a
          material breach (after expiration of applicable cure period and notice
          periods), from terminating this Agreement and seeking to enforce its
          rights under this Agreement.

     (b) [intentionally omitted]
         -----------------------

     (c) Termination of Bulk Drug Commitment.
         -----------------------------------

          (1)  Upon termination of this Agreement in its entirety by Immunex
               pursuant to Section 19.2(a(1)(Genentech Material Breach),
                           -----------------
               Immunex may, in its discretion, cancel, in whole or in part, any
               Runs that were scheduled to be initiated on or after the
               effective date of such termination. Likewise, upon termination of
               this Agreement in its entirety by Genentech pursuant to
               Section 19.2(a(2)(Immunex Material Breach), Genentech may, in
               -----------------
               its discretion, cancel, in whole or in part, any Runs that were
               scheduled to be initiated on or after the effective date of such
               termination. Runs that are in process and [*] as of the effective
               date of any such termination shall not be cancelled without the
               mutual agreement of the Parties, and the Agreement shall continue
               to survive with respect to those in-process Runs.

          (2)  Upon the issuance of a notice of termination of this Agreement
               pursuant to Section 19.2(b)(Force Majeure; No Fault Termination)
                           ---------------
               hereof, all Runs which were scheduled to be initiated after the
               date on which the notice of termination was issued shall be
               automatically cancelled. Runs that are in process and [*] on the
               date on which the notice of termination was issued shall not be
               cancelled without the mutual agreement of the Parties, and the
               Agreement shall continue to survive with respect to those
               in-process Runs.

          (3)  Upon the termination of this Agreement pursuant to
               Section 19.2(c) (Failure to Obtain FDA Approval for Genentech
               ---------------
               Facility), Genentech shall immediately stop all Bulk Drug
               manufacturing hereunder, other than completing testing and
               release of Bulk Drug that has been fully-manufactured as of the
               date of termination. Bulk Drug that has been fully-manufactured
               as of the date of termination but for which testing and release
               has not been completed shall remain subject to the terms of this
               Agreement, and the Agreement shall continue to survive with
               respect to such Bulk Drug.

* Portions of this exhibit have been omitted pursuant to a request for
confidential treatment filed with the Securities and Exchange Commission. The
omitted portions of this exhibit have been filed separately with the SEC.

                                 Page 50

<PAGE>

          (4)  Upon the issuance by Immunex of a notice of termination of this
               Agreement pursuant to Section 19.2(d) (Withdrawal of Product),
                                     ---------------
               Genentech shall immediately stop all Bulk Drug manufacturing
               hereunder, other than completing testing and release of Bulk Drug
               that has been fully manufactured as of the date on which the
               notice of termination was issued. Bulk Drug that has been
               fully-manufactured as of the date on which the notice of
               termination was issued but for which testing and release has not
               been completed shall remain subject to the terms of this
               Agreement, and the Agreement shall continue to survive with
               respect to such Bulk Drug. In lieu of termination, it shall be
               Immunex's option to request that Genentech [*].

     (d) Other Financial Obligations.
         ---------------------------

          (1)  Raw Materials. Upon expiration of this Agreement or termination
               -------------
               of this Agreement pursuant to Section 19.2(a(2) (Immunex
                                             -----------------
               Material Breach), Immunex shall purchase from Genentech, at the
               request of Genentech, at Genentech's Acquisition Cost, all
               remaining usable raw materials, intermediates and packaging
               components acquired and paid for by Genentech for the manufacture
               and packaging of Bulk Drug under this Agreement, and, upon
               termination of this Agreement pursuant to Section 19.2(b) (Force
                                                         ---------------
               Majeure; No Fault Termination), Section 19.2(c) (Failure to
                                               ---------------
               Obtain FDA Approval for Genentech Facility), or Section 19.2(d)
                                                               ---------------
               (Withdrawal of Product) hereof, Immunex shall purchase from
               Genentech, at the request of Genentech, at Genentech's
               Acquisition Cost, all remaining usable Specialized Raw Materials,
               and Immunex may purchase from Genentech, at the request of
               Genentech, at Genentech's Acquisition Cost, all remaining usable
               raw materials (other than Specialized Raw Materials),
               intermediates and packaging components acquired and paid for by
               Genentech for the manufacture and packaging of Bulk Drug under
               this Agreement; provided, however, that Immunex shall not be
               obligated to purchase an amount of such raw materials,
               intermediates and packaging components in excess of the amount
               reasonably necessary to fulfill the outstanding Bulk Drug
               Commitment for Bulk Drug that are outstanding at the time of such
               termination plus a reasonable safety stock; and provided,
               further, that Genentech shall have an obligation upon receipt of
               a notice of termination to place no further orders for raw
               materials, intermediates or packaging components except as may be
               necessary for completion of any portion of Genentech's services
               hereunder that are not immediately terminated. Upon expiration of
               this Agreement, Immunex shall purchase from Genentech, at the
               request of Genentech, at Genentech's Acquisition Cost, all
               remaining usable raw materials, intermediates and packaging
               components acquired and paid for by Genentech for the manufacture
               and packaging of Bulk Drug under this Agreement; provided,
               however, that Immunex shall not be obligated to purchase an
               amount of such raw materials, intermediates and packaging
               components in excess of the amount

* Portions of this exhibit have been omitted pursuant to a request for
confidential treatment filed with the Securities and Exchange Commission. The
omitted portions of this exhibit have been filed separately with the SEC.

                                Page 51

<PAGE>

               reasonably necessary to fulfill the outstanding Bulk Drug
               Commitment for Bulk Drug that are outstanding at the time of such
               expiration plus a reasonable safety stock; and provided, further,
               that Genentech shall have an obligation to place no orders for
               raw materials, intermediates or packaging components except as
               may be necessary for completion of any portion of Genentech's
               services hereunder prior to expiration.

          (2)  Termination Fee for Withdrawal of Product. Upon termination of
               -----------------------------------------
               this Agreement pursuant to Section 19.2(d) (Withdrawal of
                                          ---------------
               Product), Genentech shall be entitled to payment by Immunex of an
               amount which shall be equal to and calculated as of the notice of
               termination is received, as follows: [*]

     (e)  Return of Materials and of Immunex Confidential Information; Transfer
          ---------------------------------------------------------------------
          of Portable Equipment. Upon expiration or termination of this
          ---------------------
          Agreement, unless otherwise directed by Immunex, Genentech shall
          promptly (1) return or, at Immunex's election, destroy all quantities
          of the Cell Line, Master Cell Bank, and Working Cell Bank received by
          Genentech under this Agreement, the Tech Transfer Agreement or the
          Quality Agreement, with any such destruction to be certified in
          writing to Immunex by an authorized Genentech officer, (2) return all
          Immunex Confidential Information to Immunex, except for a single copy
          and/or sample which may be retained for documentation purposes only
          and which shall remain subject to the obligations of nonuse and
          confidentiality set forth in this Agreement, and (3) return to Immunex
          all retention and reserve samples being held by Genentech pursuant to
          Section 12.8 hereof, provided that Genentech may retain one set of
          ------------
          such samples for documentation purposes only. In addition, if
          requested by Immunex, Genentech shall transfer the Equipment to
          Immunex in accordance with Section 14.2 hereof.
                                     ------------

     (f)  Return of Genentech Confidential Information. Upon expiration or
          --------------------------------------------
          termination of this Agreement, and at Genentech's written request,
          Immunex shall promptly return all Genentech Confidential Information
          to Genentech, except for a single copy and/or sample to be retained by
          Immunex and Immunex for documentation purposes only and which shall
          remain subject to the obligations of nonuse and confidentiality set
          forth in this Agreement.

     (g)  Accrued Rights. Except as otherwise expressly set forth herein, any
          --------------
          termination or expiration of this Agreement shall be without prejudice
          to any right which shall have accrued to the benefit of either Party
          and shall not relieve either Party of any obligation which has accrued
          prior to the effective date of such termination or expiration, which
          obligations shall remain in full force and effect for the period
          provided therein or, if no period is provided therein, then such
          obligations shall remain in full force and effect indefinitely.

* Portions of this exhibit have been omitted pursuant to a request for
confidential treatment filed with the Securities and Exchange Commission. The
omitted portions of this exhibit have been filed separately with the SEC.

                                 Page 52

<PAGE>

                            ARTICLE 20. FORCE MAJEURE
                            -------------------------

20.1 Effects of Force Majeure. No Party shall be in breach of this Agreement if
     ------------------------

     there is any failure of performance under this Agreement (except for
     payment of any amounts due under this Agreement) occasioned by any reason
     beyond the control and without the fault or negligence of the Party
     affected thereby, including, without limitation, an act of God, fire, act
     of government or state, war, civil commotion, insurrection, embargo, [*],
     prevention from or hindrance in obtaining energy or other utilities, a
     market shortage of raw materials or necessary components, labor disputes of
     whatever nature, or any other reason beyond the control and without the
     fault or negligence of the Party affected thereby (a "Force Majeure
                                                           -------------
     Event"). Such excuse shall continue as long as the Force Majeure Event
     -----
     continues. Upon cessation of such Force Majeure Event, the affected Party
     shall promptly resume performance under this Agreement.

20.2 Notice of Force Majeure. Each Party agrees to give the other Party prompt
     -----------------------
     written notice of the occurrence of any Force Majeure Event, the nature
     thereof, and the extent to which the affected Party will be unable fully to
     perform its obligations under this Agreement. Each Party further agrees to
     use Commercially Reasonable Efforts to correct the Force Majeure Event as
     quickly as practicable and to give the other Party prompt written notice
     when it is again fully able to perform such obligations.

20.3 Allocation of Capacity. If, as a result of a Force Majeure Event, Genentech
     ----------------------
     at any time is unable fully to supply outstanding Bulk Drug Commitments for
     Bulk Drug, Genentech shall use reasonable efforts to equitably allocate its
     available resources and production capacity among Genentech, Immunex and
     Genentech's other Third Party customers, as the case may be, taking into
     consideration the respective requirements of each during a reasonable time
     period prior to the allocation, as well as such requirements during the
     allocation period. Genentech shall not grant a higher priority to itself or
     any Third Party than to Immunex with respect to manufacture or shipment of
     products from the Genentech Facility except as required by contractual
     obligations pre-dating this Agreement and except and to the extent such
     Force Majeure Event affects only the manufacture or shipment of Bulk Drug
     and does not affect the manufacture or shipment of other products.

20.4 Termination. This Agreement may be terminated as a result of a Force
     -----------
     Majeure Event in accordance with Section 19.2(b) hereof.
                                      ---------------

20.5 Reduction in Annual Maximum Amount and Annual Minimum Amount. If a Force
     ------------------------------------------------------------
     Majeure Event prevents Genentech from manufacturing Bulk Drug under this
     Agreement in any calendar year, the parties shall in good faith discuss and
     Genentech shall use Commercially Reasonable Efforts to increase
     proportionately the Annual Maximum and Annual Minimum in the subsequent
     calendar year, if Genentech has excess capacity or can reasonably revise
     its production schedule without adversely impacting itself or its
     obligations to Third Parties and/or Affiliates.

* Portions of this exhibit have been omitted pursuant to a request for
confidential treatment filed with the Securities and Exchange Commission. The
omitted portions of this exhibit have been filed separately with the SEC.

                                  Page 53

<PAGE>

                             ARTICLE 21. ASSIGNMENT
                             ----------------------

21.1 Assignment. This Agreement shall be binding upon the successors and assigns
     ----------
     of the Parties and the name of a Party appearing herein shall be deemed to
     include the names of its successors and assigns. Neither Party may assign
     its interest under this Agreement without the prior written consent of the
     other Party, such consent not to be unreasonably withheld; provided,
     however, either Party may assign its interest under this Agreement, without
     the prior written consent of the other Party, (a) to an Affiliate, so long
     as the assigning Party unconditionally guarantees the obligations of such
     Affiliate or (b) to a successor of the assigning Party's business by reason
     of merger, sale of all or substantially all of its assets or other form of
     acquisition. Any purported assignment without a required consent shall be
     void. No assignment shall relieve any Party of responsibility for the
     performance of any obligation that accrued prior to the effective date of
     such assignment.

                         ARTICLE 22. DISPUTE RESOLUTION
                         ------------------------------

22.1 Exclusions. Section 22.2 below shall not apply to any disputes arising
     ----------  ------------
     under Article 17 (Confidentiality) or Section 23.9 [*].
           ----------                      ------------

22.2 Dispute Resolution.
     ------------------

     (a) Disputes. The Parties recognize that a bona fide dispute as to certain
         ---------                              ---------
         matters may from time to time arise during the term of this Agreement
         that relates to a Party's rights and/or obligations under this
         Agreement. In the event of the occurrence of such a dispute, any Party
         may, by written notice to the other Parties, have such dispute referred
         to their respective officers designated below, or their respective
         designees, for attempted resolution by good faith negotiations within
         [*] days after such notice is received. Such designated officers are as
         follows:

                For Immunex - Chief Executive Officer

                For Genentech - Chief Executive Officer

         In the event the designated officers, or their respective designees,
         are not able to resolve such dispute within such [*]-day period, or
         such other period of time as the Parties may mutually agree in writing,
         either Party may, by written notice to the other, invoke the following
         provisions of this Section 22.2 hereinafter.
                            ------------

     (b)  Mediation and Arbitration. The Parties agree that, except as otherwise
          -------------------------
          set forth in Section 22.1 above or Section 22.2(d) below, any dispute,
                       ------------          ---------------
          controversy or claim arising out of or relating to this Agreement, the
          Tech Transfer Agreement, or the Quality Agreement, or the breach,
          termination, or invalidity thereof, shall be resolved

* Portions of this exhibit have been omitted pursuant to a request for
confidential treatment filed with the Securities and Exchange Commission. The
omitted portions of this exhibit have been filed separately with the SEC.

                                   Page 54

<PAGE>

          through mediation and binding arbitration. If a dispute arises between
          the Parties, and if such dispute cannot be resolved pursuant to
          Section 22.2(a) above, the Parties agree to try in good faith to
          ---------------
          resolve such dispute by mediation administered by the American
          Arbitration Association (unless otherwise agreed in writing by the
          Parties) in accordance with its Commercial Mediation Rules (unless
          otherwise agreed in writing by the Parties). If efforts at mediation
          are unsuccessful within [*] days, any unresolved controversy or claim
          between the Parties shall be resolved by binding arbitration
          administered by the American Arbitration Association (unless otherwise
          agreed in writing by the Parties) in accordance with its Commercial
          Arbitration Rules (unless otherwise agreed in writing by the Parties),
          except as modified herein. Each Party shall select one arbitrator and
          the two (2) arbitrators so selected shall choose a third arbitrator to
          resolve the dispute. A reasoned arbitration decision shall be rendered
          in writing within [*] months of the conclusion of arbitration and
          shall be binding and not be appealable to any court in any
          jurisdiction. The prevailing Party may enter such decision in any
          court having competent jurisdiction. Unless otherwise mutually agreed
          upon by the Parties, the mediation and arbitration proceedings shall
          be conducted at the location of the Party not originally requesting
          the resolution of the dispute (the "Non-Requesting Party"), and, if
                                              --------------------
          the Non-Requesting Party is Immunex, then the location shall be, at
          Immunex's option, Seattle, Washington, or Los Angeles, California, or
          such other location as may be agreed in writing by the Parties and, if
          the Non-Requesting Party is Genentech, then the location shall be, at
          Genentech's option, San Francisco, California, or such other location
          as may be agreed in writing by the Parties. The Parties agree that
          they shall share equally the cost of the mediation and arbitration
          filing and hearing fees, and the cost of the mediator/arbitrator. Each
          Party must bear its own attorneys' fees and associated costs and
          expenses.

     (c) Jurisdiction. For the purposes of this Article 22, the Parties agree to
         ------------
         accept the jurisdiction of the federal courts located in (a) the
         Northern District of California for the purposes of enforcing awards
         entered on behalf of Genentech pursuant to this Article 22 and for
         enforcing the agreements reflected in this Article, or to a state court
         in such jurisdiction if the applicable rules of civil procedure
         preclude federal court jurisdiction, and (b) the Western District of
         Washington, or the Southern District of California, for the purposes of
         enforcing awards entered on behalf of Immunex pursuant to this Article
         22 and for enforcing the agreements reflected in this Article, or to a
         state court in such jurisdiction if the applicable rules of civil
         procedure preclude federal court jurisdiction, and the Parties hereby
         consent to the jurisdiction and venue of such courts.

     (d)  Determination of Patents and Other Intellectual Property.
          --------------------------------------------------------
          Notwithstanding the foregoing, any dispute relating to the
          determination of validity of a Party's patents or other issues
          relating to a Party's intellectual property shall be submitted
          exclusively to the federal court located in the jurisdiction of the
          defendant, or to a state court in such jurisdiction if the applicable
          rules of civil procedure preclude federal court jurisdiction, and the
          Parties hereby consent to the jurisdiction and venue of such courts.

* Portions of this exhibit have been omitted pursuant to a request for
confidential treatment filed with the Securities and Exchange Commission. The
omitted portions of this exhibit have been filed separately with the SEC.

                                    Page 55

<PAGE>

                            ARTICLE 23. MISCELLANEOUS
                            -------------------------

23.1 Notices. Other than notices within the jurisdiction of the respective
     -------
     Project Team Leaders, which shall be given to those individuals, any notice
     required or permitted to be given under this Agreement by any Party shall
     be in writing and shall be (a) delivered personally, (b) sent by registered
     mail, return receipt requested, postage prepaid, (c) sent by a
     nationally-recognized courier service guaranteeing next-day or second day
     delivery, charges prepaid, or (d) delivered by facsimile (with the original
     promptly sent by any of the foregoing manners), to the addresses or
     facsimile numbers of the other Parties set forth below, or at such other
     addresses as may from time to time be furnished by similar notice by any
     Party. The effective date of any notice under this Agreement shall be the
     date of receipt by the receiving Party.

     If to Genentech:       Corporate Secretary
                            Genentech, Inc.
                            1 DNA Way
                            South San Francisco, CA  94080
                            Fax:     (650) 952-9881
                            Phone: (650) 225-1672

     with a copy to:        Senior Vice President of Product Operations
                            Genentech, Inc.
                            1 DNA Way, MS 53
                            South San Francisco, CA  94080
                            Fax: (650) 225-5007
                            Phone: (650) 225-3978

     with a copy to:        Vice President of Business & Commercial Development
                            Genentech, Inc.
                            1 DNA Way
                            South San Francisco, CA  94080
                            Phone: (650) 225-3009
                            Fax: (650) 225-3705

     If to Immunex:         Immunex Corporation
                            51 University Street
                            Seattle, Washington  98101
                            Attention:  Senior Vice President, Supply Operations
                            Fax: (206) 682-9927
                            Phone: (206) 389-4016

     with a copy to:        Immunex Corporation
                            51 University Street
                            Seattle, Washington 98101
                            Attention:  General Counsel
                            Fax: (206) 292-9271
                            Phone: (206) 587-0430

                                    Page 56

<PAGE>

23.2 Applicable Law. This Agreement shall be construed, interpreted and enforced
     --------------
     in accordance with the internal substantive laws of the State of [*],
     without reference to the choice of law doctrine of such state.

23.3 Headings. The table of contents and all headings in this Agreement are for
     --------
     convenience of reference only and shall not affect the interpretation of
     this Agreement.

23.4 Exhibits. All exhibits referred to herein form an integral part of this
     --------
     Agreement and are incorporated into this Agreement by such reference.

23.5 Severability. Each Party hereby expressly agrees that it has no intention
     ------------
     to violate any public policy, statutory or common laws, rules, regulations,
     treaty or decision of any government agency or executive body thereof of
     any country or community or association of countries; that if any word,
     sentence, paragraph, clause or combination thereof in this Agreement is
     found by a court or executive body with judicial powers having jurisdiction
     over this Agreement or any Party hereto, in a final unappealed order, to be
     in violation of any such provisions in any country or community or
     association of countries, such words, sentences, paragraphs, clauses or
     combination shall be inoperative in such country or community or
     association of countries and the remainder of this Agreement shall remain
     binding upon the Parties, so long as enforcement of the remainder does not
     violate the Parties' overall intentions in this transaction.

23.6 Independent Contractors. Each of the Parties is an independent contractor
     -----------------------
     and nothing herein contained shall be deemed to constitute the relationship
     of partners, joint venturers, nor of principal and agent between the
     Parties. Neither Party shall hold itself out to Third Parties as purporting
     to act on behalf of, or serving as the agent of, the other Party.

23.7 Waiver. No waiver of any term, provision or condition of this Agreement
     ------
     whether by conduct or otherwise in any one or more instances shall be
     deemed to be or construed as a further or continuing waiver of any such
     term, provision or condition or of any other term, provision or condition
     of this Agreement.

23.8 Counterparts. This Agreement and any amendment hereto may be executed in
     ------------
     any number of counterparts, each of which shall for all purposes be deemed
     an original and all of which shall constitute the same instrument. This
     Agreement shall be effective upon full execution by facsimile or original,
     and a facsimile signature shall be deemed to be and shall be as effective
     as an original signature.

23.9 [*]

* Portions of this exhibit have been omitted pursuant to a request for
confidential treatment filed with the Securities and Exchange Commission. The
omitted portions of this exhibit have been filed separately with the SEC.

                                    Page 57

<PAGE>

23.10 Entirety; Amendments. This Agreement, including any exhibits attached
      --------------------
      hereto and referenced herein, constitutes the full understanding of the
      Parties and a complete and exclusive statement of the terms of their
      agreement with respect to the specific subject matter hereof (i.e.,
                                                                    ----
      purchase and supply of Bulk Drug), and no terms, conditions,
      understandings or agreements purporting to modify or vary the terms
      thereof shall be binding unless it is hereafter made in writing and signed
      by each of the Parties. No modification to this Agreement shall be
      effected by the acknowledgment or acceptance of any purchase order or
      shipping instruction forms or similar documents containing terms or
      conditions at variance with or in addition to those set forth herein. In
      the event of a conflict between this Agreement and the exhibits hereto,
      the terms of this Agreement shall control. This Agreement may be amended
      and supplemented only by a written instrument signed by each of the
      Parties.

23.11 Preference. Unless otherwise specifically provided for in the Quality
      ----------
      Agreement and/or Tech Transfer Agreement, the terms of this Agreement
      shall prevail in the event of a conflict between this Agreement and any
      of the aforementioned agreements.

                [the remainder of this page intentionally blank]

                                    Page 58

<PAGE>

IN WITNESS WHEREOF, the Parties have caused this Agreement to be executed as of
the Effective Date.

Immunex Corporation

By:        /s/ Efraim Cohen-Arazi
         --------------------------------------------
         Efraim Cohen-Arazi
         Senior Vice President, Supply Operations

Genentech, Inc.

By:        /s/ David Ebersman
         --------------------------------------------
         David Ebersman
         Senior Vice President of Product Operations




* Portions of this exhibit have been omitted pursuant to a request for
confidential treatment filed with the Securities and Exchange Commission. The
omitted portions of this exhibit have been filed separately with the SEC.

                                    Page 59

<PAGE>

                                    Exhibit A

                            Minimum and Maximum Runs*

Calendar Year                Minimum Runs               Maximum Runs
--------------------------------------------------------------------

     [*]                         [*]                        [*]

     [*]                         [*]                        [*]

     [*]                         [*]                        [*]



*When used in this Exhibit, the term "Runs" is a defined term, and it shall have
the meaning given in the Agreement.


* Portions of this exhibit have been omitted pursuant to a request for
confidential treatment filed with the Securities and Exchange Commission. The
omitted portions of this exhibit have been filed separately with the SEC.

                                     Page 60