Document:

PRODUCT SUPPLY AGREEMENT

                                     BETWEEN

                           INEX PHARMACEUTICALS, INC.

                                       AND

                           ENZON PHARMACEUTICALS, INC.

                                January 19, 2004

*** Indicates the omission of confidential material pursuant to a request for
confidential treatment made in accordance with Rule 24b-2 under the Securities
Exchange Act of 1934, as amended. The Confidential material is being filed
separately with the Secretary to the Securities and Exchange Commission.

<PAGE>

                                     - ii -

                                TABLE OF CONTENTS

Article 1 Interpretation......................................................6
     1.1    Definitions.......................................................6
     1.2    Entire Agreement; Conflicts......................................15
     1.3    Governing Law....................................................15
     1.4    Headings.........................................................15
     1.5    Severability.....................................................15

Article 2 Purchasing and Price...............................................15
     2.1    Purchase Price of Product........................................15
     2.2    Terms of Payment for Manufacturing Cost Plus.....................16
     2.3    Terms of Payment for Deferred Sales Payments.....................17
     2.4    Remuneration respecting Sublicensees.............................17
     2.5    Third Party Payments.............................................17
     2.6    Commercial Sales of Development Stock............................17
     2.7    Reports and Payment..............................................18
     2.8    Withholding Taxes................................................18
     2.9    Foreign Payments.................................................19
     2.10   Method of Payment................................................19
     2.11   Late Payments....................................................19
     2.12   Records..........................................................19
     2.13   Audits...........................................................19

Article 3 Forecasting and Purchase Orders....................................20
     3.1    Sales and Operations Plan........................................20
     3.2    Purchase Orders Issued Before First FDA Approval.................21
     3.3    Purchase Orders Issued After First FDA Approval..................22

Article 4 Manufacturing......................................................22
     4.1    Technical Activities to Support Manufacturing....................22
     4.2    Manufacturing in Compliance......................................22
     4.3    Subcontractors...................................................22
     4.4    Technical Transfer to and Manufacture by Enzon...................22
     4.5    Material Change to Financial Terms...............................23
     4.6    Quality/Technical Agreement......................................23

Article 5 Supply and Shipment................................................24
     5.1    Shipping Notification............................................24
     5.2    Shipment of Product..............................................24
     5.3    Shipment of Released Product.....................................24
     5.4    Risk of Loss and Shipping Expenses...............................24
     5.5    Rejection of Delivered Product...................................24
     5.6    Obsolescence and Returns.........................................25
     5.7    Disposal and Destruction.........................................25

Article 6 Product Receipt and Distribution...................................25
     6.1    Receipt..........................................................25
     6.2    Storage and Handling.............................................25
     6.3    Distribution.....................................................25

*** Indicates the omission of confidential material pursuant to a request for
confidential treatment made in accordance with Rule 24b-2 under the Securities
Exchange Act of 1934, as amended. The Confidential material is being filed
separately with the Secretary to the Securities and Exchange Commission.

<PAGE>

                                     - iii -

     6.4    Records for Traceability.........................................25

Article 7 Shipments for Launch...............................................25
     7.1    Consequence of Launch Supply Failure.............................25
     7.2    Enzon's First Option to Terminate................................26
     7.3    Enzon's Second Option to Terminate...............................26
     7.4    Cure by Inex.....................................................26

Article 8 Changes............................................................27
     8.1    Enzon's Right to Notice of and Consent to Changes................27
     8.2    New Regulatory Requirements......................................27
     8.3    Reservation......................................................27

Article 9 Commercialization..................................................27
     9.1    Regulatory Compliance............................................27
     9.2    Assignment of Trademarks.........................................28
     9.3    Use of Inex Trademarks in Labelling..............................28
     9.4    Patent Marking...................................................28
     9.5    Commercialization Efforts........................................28
     9.6    Commercial Diligence in accordance with Commercialization Plan...28
     9.7    Overview of Commercialization....................................29
     9.8    Subcontractors...................................................29
     9.9    Commercialization Plans..........................................29
     9.10   Funding of Commercialization Costs...............................30
     9.11   Consequence of No Sales..........................................30
     9.12   Reports..........................................................30
     9.13   Launch of Competitive Product by Enzon...........................31

Article 10 Joint Steering Committee..........................................31
     10.1   Joint Steering Committee.........................................31
     10.2   Meetings of the Joint Steering Committee.........................32
     10.3   Working Committees...............................................32

Article 11 Pharmacovigilance, DDMAC and Recalls..............................32
     11.1   Regulatory Responsibilities......................................32
     11.2   Pharmacovigilance Agent..........................................33
     11.3   Agency for DDMAC Activities and the Like.........................33
     11.4   Agent for Regulatory Authorities Generally.......................34
     11.5   Recalls and Withdrawals of Product...............................34
     11.6   Replacement Shipments............................................35

Article 12 Restrictive Covenants; Title......................................35
     12.1   Injunctive Relief................................................35
     12.2   Ownership of Pre-Existing Intellectual Property Rights...........35
     12.3   Ownership of Intellectual Property Rights in the Product.........35
     12.4   Ownership of Regulatory Approvals and Regulatory Submissions.....36
     12.5   Ownership of Intellectual Property Rights Outside the
            Commercialization and Co-Promotion...............................36
     12.6   Co-operation.....................................................36
     12.7   Prosecution and Maintenance of Licensed Patents..................36
     12.8   Notice of Inventions.............................................37

*** Indicates the omission of confidential material pursuant to a request for
confidential treatment made in accordance with Rule 24b-2 under the Securities
Exchange Act of 1934, as amended. The Confidential material is being filed
separately with the Secretary to the Securities and Exchange Commission.

<PAGE>

                                     - iv -

     12.9   Restriction on Attacks on Intellectual Property..................37
     12.10  Elan a Third Party Beneficiary...................................37

Article 13 Allocation of Risk................................................37
     13.1   Limits...........................................................37
     13.2   Conduct of Infringement Proceedings..............................38
     13.3   Defense of Infringement Proceedings..............................38
     13.4   Co-operation with Other Licensees................................38

Article 14 Indemnification and Liability Limitations.........................38
     14.1   Indemnification by Enzon.........................................38
     14.2   Indemnification by Inex..........................................39
     14.3   Notice of Claims.................................................40
     14.4   Consequential Losses.............................................40
     14.5   Actions Between the Parties......................................41
     14.6   Insurance........................................................41

Article 15 Confidential Information and Publication..........................41
     15.1   Treatment of Confidential Information............................41
     15.2   Permitted Disclosures............................................41
     15.3   Publications Generally...........................................42
     15.4   No Limitation on Regulatory Compliance...........................42

Article 16 Dispute Resolution................................................42
     16.1   Negotiation......................................................42
     16.2   Arbitration......................................................43
     16.3   Consent to Jurisdiction..........................................43

Article 17 Termination.......................................................43
     17.1   Term of Agreement................................................43
     17.2   Renewal..........................................................44
     17.3   Termination for Breach...........................................44
     17.4   Termination upon Bankruptcy......................................44
     17.5   Termination of Related Agreements................................44
     17.6   Effect of Termination............................................45
     17.7   Consequences of Termination in Certain Circumstances.............45
     17.8   Additional Consequences of Termination...........................46
     17.9   Survival of Obligations; Return of Confidential Information......46

Article 18 Miscellaneous.....................................................47
     18.1   Assignment.......................................................47
     18.2   Counterparts.....................................................47
     18.3   Exhibits and Appendices..........................................47
     18.4   Force Majeure....................................................47
     18.5   Further Assurances...............................................48
     18.6   International Sale of Goods Act..................................48
     18.7   Modification.....................................................48
     18.8   No Agency........................................................48
     18.9   No Solicitation or Hiring of Employees...........................48
     18.10  Non-Use of Names.................................................48
     18.11  Notices..........................................................48
     18.12  Parallel Imports.................................................50
     18.13  Publicity........................................................50
     18.14  No Third Party Beneficiaries.....................................51
     18.15  Waiver...........................................................51
     18.16  Cross Default....................................................51

*** Indicates the omission of confidential material pursuant to a request for
confidential treatment made in accordance with Rule 24b-2 under the Securities
Exchange Act of 1934, as amended. The Confidential material is being filed
separately with the Secretary to the Securities and Exchange Commission.

<PAGE>
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                            PRODUCT SUPPLY AGREEMENT

This PRODUCT SUPPLY AGREEMENT dated as of the 19th day of January, 2004 between
Inex Pharmaceuticals, Inc., a corporation duly incorporated pursuant to the laws
of Delaware, USA, having a registered office at Corporation Trust Center, 1209
Orange Street, Wilmington, DE 19801 (hereinafter referred to as "Inex"), and
Enzon Pharmaceuticals, Inc., a corporation duly incorporated pursuant to the
laws of Delaware, having a principal place of business at 685 Route 202/206,
Bridgewater, New Jersey 08807 (hereinafter referred to as "Enzon").

INTRODUCTION

A. Enzon is a pharmaceutical company with operations in research and
development, import, export, manufacture and sale of pharmaceutical products;

B. Inex is in the business of developing, manufacturing and selling certain
pharmaceutical products, including Vincristine Sulfate Liposomes Injection (as
further defined in this Agreement);

C. Of even date hereof, the Parties have entered into a Development Agreement
for the development of Vincristine Sulfate Liposomes Injection and for the
purpose of enabling Enzon to acquire rights to develop, market, distribute and
sell Inex's Vincristine Sulfate Liposomes Injection product;

D. Subject to the terms and conditions set forth in this Agreement, Enzon wishes
to have Inex supply to Enzon Vincristine Sulfate Liposomes Injection; and

E. Inex wishes to supply same to Enzon;

NOW, THEREFORE, the Parties, intending to be legally bound, hereby agree as
follows:

                            Article 1 Interpretation

1.1   Definitions

Unless otherwise defined in this Agreement, capitalized terms used in this
Agreement shall have the meaning set out therefor in the Development Agreement
and the Co-Promotion Agreement. In the event of a conflict between the
definitions set out for capitalized terms in this Agreement and the capitalized
terms set out in any other Related Agreement, the priority set out in Section
1.2 shall govern. For purposes of this Agreement, the following terms will have
the meanings set forth below:

      1.1.1   "Adverse Drug Event" will have the meaning set forth in Exhibit
              1.1.1.

      1.1.2   "Affiliate" means any corporation, company, partnership, joint
              venture or other person or entity which controls, is controlled by
              or is under common control with a Party. For purposes of this
              Section 1.1.2, "control" shall mean (a) in the case of corporate
              entities,

*** Indicates the omission of confidential material pursuant to a request for
confidential treatment made in accordance with Rule 24b-2 under the Securities
Exchange Act of 1934, as amended. The Confidential material is being filed
separately with the Secretary to the Securities and Exchange Commission.

<PAGE>
                                     - 7 -

              direct or indirect ownership of at least 50% of the stock or
              shares (or such lesser percentage which is the maximum allowed to
              be owned by a foreign corporation in a particular jurisdiction)
              entitled to vote for the election of directors or otherwise having
              the power to vote on or direct the affairs of such Party; and (b)
              in the case of non-corporate entities, direct or indirect
              ownership of at least 50% of the equity interest or the power to
              direct the management and policies of such non-corporate entities.

      1.1.3   "Agreement" means this Product Supply Agreement including all
              exhibits attached to this Agreement.

      1.1.4   "Applicable Laws" means all applicable federal, provincial, state
              and local laws, ordinances, rules and regulations of any kind
              whatsoever in the Territory, including, without limitation,
              pharmaceutical and environmental rules and regulations, including
              cGMP Requirements, GCP Requirements, GLP Requirements and the
              General Biological Products Standards of the FDA, and the Federal
              Food, Drug and Cosmetic Act, as amended, or any successor act
              thereto ("FDCA").

      1.1.5   "Approved S&OP" has the meaning set out in Section 3.1.4.

      1.1.6   "Business Day" means any day other than a day which is a Saturday,
              a Sunday or a statutory holiday in New York City, New York, USA.

      1.1.7   "Calendar Quarter" means the three-month period ending on March
              31, June 30, September 30 or December 31.

      1.1.8   "cGMP Requirements" shall mean the current Good Manufacturing
              Practices standards required by the FDA, the Therapeutic Products
              Directorate Organization of Health Canada ("TPD") and the
              equivalent Regulatory Authority(ies) elsewhere in the Territory,
              and the applicable regulations, policies or guidelines of each of
              them in effect for the manufacture and testing of pharmaceutical
              materials, active ingredients, or excipients, as applicable.

      1.1.9   "Code" or "Codes" means the Code on Interactions with Healthcare
              Professionals promulgated by the Pharmaceutical Research and
              Manufacturers of America (PhRMA) and the American Medical
              Association (AMA) Guidelines on Gifts to Physicians from Industry,
              as either of the foregoing may be amended from time to time.

      1.1.10  "Commercial Quarter" means a Calendar Quarter during which Net
              Sales are recorded.

      1.1.11  "Commercial Year" means a period of four consecutive Calendar
              Quarters commencing with the Initial Commercial Quarter.

      1.1.12  "Commercialization" means the activities customarily associated
              with sales of pharmaceutical products including without
              limitation, DDMAC Activities, price and reimbursement
              negotiations, pre-launch and launch activities, marketing, sales,
              distribution, Post-Approval Clinical Activities, the development,
              prosecution, registration and maintenance of trademarks, trade
              names and domain names, and Pharmacovigilance in each country in
              the Territory.

      1.1.13  "Commercialization Costs" means the cost of Commercialization of
              the Product, including the Commercialization FTE Costs and
              Out-of-Pocket Costs utilized or incurred by a Party in fulfilling
              its obligations under the then-current Commercialization Plan and

*** Indicates the omission of confidential material pursuant to a request for
confidential treatment made in accordance with Rule 24b-2 under the Securities
Exchange Act of 1934, as amended. The Confidential material is being filed
separately with the Secretary to the Securities and Exchange Commission.

<PAGE>
                                     - 8 -

              all Commercialization FTE Costs and Out of Pocket Costs incurred
              in excess of the Budget in the then-current Commercialization
              Plan, provided that any such excess costs have been approved in
              advance by the Joint Steering Committee. For greater certainty,
              "Commercialization Costs" do not include Development Costs as
              defined in the Development Agreement.

      1.1.14  "Commercialization FTE" means a scientific or technical person
              employed by a Party or a Party's Affiliates and assigned to work
              on Commercialization with such time and effort to constitute one
              person working on Commercialization on a full time basis
              consistent with normal business and scientific practice (e.g.,
              having appropriate education, training and experience and working
              *** hours per year of dedicated effort).

      1.1.15  "Commercialization FTE Costs" means the price of Commercialization
              FTEs to be used for the purposes of determining the costs incurred
              with respect to personnel performing work on the Commercialization
              in accordance with the then-approved Commercialization Plan. The
              price per Commercialization FTE shall initially be *** per
              Commercialization FTE year or pro-rata portion thereof incurred on
              the Commercialization. The Commercialization FTE rate includes all
              the fully burdened cost of salary, employee benefits, incidental
              materials, travel, lodging and other expenses including support
              staff and direct and indirect overhead for or associated with a
              Commercialization FTE. On each anniversary of the Effective Date,
              the FTE rate shall be raised by a percentage equal to the
              percentage increase in the Index (defined below) for the twelve
              (12) month period ending with December of the calendar year
              immediately preceding such anniversary date (such increase, the
              "CPI Increase"). For purposes of this Agreement, the term "Index"
              shall mean the Consumer Price Index for all Urban Consumers
              (CPI-U) - - U.S. City Average. All Items (1982-1984 = 100), as
              published by the United States Bureau of Labor Statistics, or if
              such index is no longer published, then the index most comparable
              thereto.

      1.1.16  "Commercialization Plan" means the Commercialization Plan for
              Commercializing the Product, together with a corresponding budget
              accounting for the anticipated Commercialization Costs to be
              expended or incurred by each Party in conducting the
              Commercialization. The Parties will adopt a definitive
              Commercialization Plan in accordance with Section 9.9, which
              Commercialization Plan will form a part of this Agreement.

      1.1.17  "Commercially Reasonable Efforts" means efforts which are not less
              than those efforts a Party makes with respect to other
              pharmaceutical products in its portfolio (but, in any event, not
              less than the efforts that would be exerted by a reasonably
              prudent and diligent pharmaceutical company similarly situated and
              seeking to accomplish similar objectives), taking into account the
              product's market potential, level of competition, number of
              prescribers and other relevant factors.

      1.1.18  "Competitive Product" means any liposomal medicinal products where
              such liposomal medicinal products incorporate Vincristine.

      1.1.19  "Confidential Information" means:

              (a)       all proprietary information and materials, patentable or
                        otherwise, of a Party which is disclosed in writing by
                        or on behalf of such Party to the other Party and marked
                        as confidential or proprietary, including DNA sequences,
                        vectors, cells, substances, formulations, techniques,
                        methodology, equipment, data, reports,

*** Indicates the omission of confidential material pursuant to a request for
confidential treatment made in accordance with Rule 24b-2 under the Securities
Exchange Act of 1934, as amended. The Confidential material is being filed
separately with the Secretary to the Securities and Exchange Commission.

<PAGE>
                                     - 9 -

                        Inex Technology, preclinical and clinical trials and the
                        results thereof, sources of supply, patent positioning,
                        marketing plans and business plans, including any
                        negative developments;

              (b)       any other information, oral or written, designated in
                        writing by the disclosing Party to the other Party as
                        confidential or proprietary within ten (10) days after
                        such disclosure, whether or not related to the making,
                        use, importing or selling of the Product; and

              (c)       the Data, the Inex Technology, the Regulatory Approvals
                        and Regulatory Submissions, and the Licensed Patents
                        (all of which are deemed to be Confidential Information
                        of Inex);

              provided that Confidential Information shall not include such
              information which:

              (d)       was known or used by the receiving Party or its
                        Affiliates prior to its date of disclosure to the
                        receiving Party, as evidenced by the prior written
                        records of the receiving Party or its Affiliates; or

              (e)       either before or after the date of the disclosure to the
                        receiving Party is lawfully disclosed to the receiving
                        Party or its Affiliates by an independent, unaffiliated
                        Third Party rightfully in possession of the Confidential
                        Information; or

              (f)       either before or after the date of the disclosure to the
                        receiving Party becomes published or generally known to
                        the public through no fault or omission on the part of
                        the receiving Party or its Affiliates; or

              (g)       the receiving Party can verify, by written
                        documentation, results from research and development by
                        the receiving Party or any of its Affiliates independent
                        of disclosure by the other Party thereof.

      1.1.20  "Co-Promotion" has the meaning set out in the Co-Promotion
              Agreement.

      1.1.21  "Co-Promotion Agreement" means the Co-Promotion Agreement between
              Inex and Enzon of even date herewith.

      1.1.22  "DDMAC Activities" mean all jointly agreed-to activities performed
              or to be performed by one or both Parties in accordance with the
              requirements of the Division of Drug Marketing, Advertising and
              Communications, Center for Drug Evaluation and Research of the
              FDA, and the Office of the Inspector General of the Department of
              Health and Human Services of the United States.

      1.1.23  "Deferred Sales Price" and "Deferred Sales Payment" shall have the
              meaning set forth in Exhibit 2.1.1(b).

      1.1.24  "Development Agreement" shall mean the Development Agreement
              between Inex and Enzon entered into as of the Effective Date.

      1.1.25  "DMF" means each drug master file, as defined by the FDA, held by
              Inex or Inex's contract manufacturers.

      1.1.26  "Dollar" and "$" means United States Dollars.

*** Indicates the omission of confidential material pursuant to a request for
confidential treatment made in accordance with Rule 24b-2 under the Securities
Exchange Act of 1934, as amended. The Confidential material is being filed
separately with the Secretary to the Securities and Exchange Commission.

<PAGE>
                                     - 10 -

      1.1.27  "Effective Date" means the date shown on page one of this
              Agreement.

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

      1.1.29  "First Commercial Sale" means (a) with respect to a country in the
              Territory, the first sale by Enzon, its sublicensees or its
              Affiliates for use, consumption or resale of the Product in such
              country (excluding any sales for clinical trials, compassionate
              uses or other non-commercial purposes) and (b) with respect to the
              Territory, the First Commercial Sale in any country within the
              Territory. A sale to a sublicensee or an Affiliate shall not
              constitute a First Commercial Sale unless the sublicensee or
              Affiliate is the end user of the Product.

      1.1.30  "Forecast" shall have the meaning set out in Section 3.1.2.

      1.1.31  "GCP Requirements" or "Good Clinical Practices" means the then
              current standards for clinical trials for pharmaceuticals as
              required by the FDA, the TPD and the equivalent Regulatory
              Authority(ies) elsewhere in the Territory, and as applicable, the
              policies and guidelines of the International Conference on
              Harmonization in effect for the clinical testing of pharmaceutical
              materials.

      1.1.32  "GLP Requirements" or "Good Laboratory Practices" means the
              current Good Laboratory Practices standards required by the FDA
              and the TPD and the equivalent Regulatory Authority(ies) elsewhere
              in the Territory in effect for the testing of pharmaceutical
              materials as applied to raw materials and finished products.

      1.1.33  "include" and "including" (and the like) means "including, without
              limitation".

      1.1.34  "Indemnitee" shall have the meaning set out in Section 14.3.

      1.1.35  "Indemnitor" shall have the meaning set out in Section 14.3.

      1.1.36  "Inex Technology" means all technical information and know-how
              owned or controlled by Inex which relates to the Product and is
              necessary or useful for the development and commercialization of
              the Product and shall include:

              (a)       as of the Effective Date, all biological, chemical,
                        pharmacological, toxicological, clinical, assay, control
                        and manufacturing data and any other information owned
                        or controlled by Inex and necessary or useful for the
                        development and commercialization of the Product;

              (b)       any Data referred to in Section 10.3 of the Development
                        Agreement; and

              (c)       any Data referred to in Section 12.3.

      1.1.37  "Intellectual Property Rights" means any rights to any Patents and
              copyright rights and registrations and applications for
              registration of the foregoing rights, and trade secrets and moral
              rights. "Intellectual Property Rights" do not include trademark,
              domain name or trade name rights.

      1.1.38  "Initial Commercial Quarter" means the Calendar Quarter during
              which the First Commercial Sale is recorded.

*** Indicates the omission of confidential material pursuant to a request for
confidential treatment made in accordance with Rule 24b-2 under the Securities
Exchange Act of 1934, as amended. The Confidential material is being filed
separately with the Secretary to the Securities and Exchange Commission.

<PAGE>
                                     - 11 -

      1.1.39  "Joint Steering Committee" or "JSC" means the committee formed
              pursuant to Section 10.1 and having the duties and
              responsibilities set forth in Exhibit 10.1. The Joint Steering
              Committee formed under this Agreement shall be the same as the
              Joint Steering Committee formed under the Development Agreement.

      1.1.40  "Licensed Patents" means the Patents owned or controlled by Inex
              relating to VSLI and necessary or useful for the development and
              commercialization of the Product, and shall include:

              (a)       as of the Effective Date, the Inex Patents, the ***;

              (b)       any Patents on inventions referred to in Section 10.3 of
                        the Development Agreement;

              (c)       any Patents on inventions referred to in Section 12.3;

              (d)       any Patents to which Inex acquires a right to grant a
                        sublicense to Enzon pursuant to Section 2.5.2 or 14.2.

      1.1.41  "Losses" has the meaning set out in Section 14.1.1.

      1.1.42  "Manufacture" shall mean the performance of all activities or a
              portion thereof for the manufacture of Product and Product
              Components, including the shipping, receipt, handling, testing,
              and storage of starting materials, the bulk manufacture, filling,
              packaging, labelling, testing, storage, shipping or receiving of
              the Product and Product Components, and all associated activities,
              including quality control and quality assurance. "Manufacturing",
              and "Manufactured" shall have comparable meanings.

      1.1.43  "Manufacturing Cost" shall mean, with respect to Manufacture of
              the Product the costs described in Exhibit 2.1.1(a).

      1.1.44  "Manufacturing FTE" means a person employed by Inex or its
              Affiliates and assigned to work, at least as a portion of his or
              her responsibilities, on Manufacturing with such time and effort
              to constitute one person working on Manufacturing on a full time
              basis consistent with normal business and pharmaceutical practice
              (e.g., having appropriate education, training and experience and
              working 1800 hours per year of dedicated effort).

      1.1.45  "Manufacturing FTE Cost" means the price of Manufacturing FTEs to
              be used for the purposes of determining the costs incurred with
              respect to personnel performing work on the Manufacturing. The
              price per Manufacturing FTE shall be *** per Manufacturing FTE
              year or pro-rata portion thereof incurred on the Manufacturing.
              The Manufacturing FTE rate includes all the fully burdened cost of
              salary, employee benefits, incidental materials, travel, lodging
              and other expenses including support staff and direct and indirect
              overhead for or associated with a Manufacturing FTE. On each
              anniversary of the Effective Date, the Manufacturing FTE rate
              shall be raised by a percentage equal to the percentage increase
              in the Index (defined below) for the twelve (12) month period
              ending with December of the calendar year immediately preceding
              such anniversary date (such increase, the "CPI Increase"). For
              purposes of this Agreement, the term "Index" shall mean the
              Consumer Price Index for all Urban Consumers (CPI-U) - - U.S. City
              Average. All Items (1982-1984 = 100), as published by the United
              States Bureau of Labor Statistics, or if such index is no longer
              published, then the index most comparable thereto.

*** Indicates the omission of confidential material pursuant to a request for
confidential treatment made in accordance with Rule 24b-2 under the Securities
Exchange Act of 1934, as amended. The Confidential material is being filed
separately with the Secretary to the Securities and Exchange Commission.

<PAGE>
                                     - 12 -

      1.1.46  "Master Production Record" shall mean Inex's complete detailed
              manufacturing and control instructions and specifications for the
              manufacture of the Product, as defined by Regulatory Requirements,
              as amended from time to time by mutual agreement of the Parties.
              The current Master Production Record is identified as set out in
              Exhibit 1.1.44.

      1.1.47  "NDA" means a New Drug Application in accordance with the rules
              and regulations of the FDA.

      1.1.48  "Net Sales" means the aggregate United States dollar equivalent of
              gross revenues invoiced by Enzon and its Affiliates and its
              Sublicensees from or on account of the sale of the Product to
              Third Parties, less deductions allowed to customers by Enzon, its
              Affiliates or Sublicensees as the case may be, to sell the Product
              using generally accepted accounting principles and reasonable
              practices with respect to sales of all Enzon's products,
              consistently applied, for the following:

              ***

              (collectively, the "Permitted Deductions"). No deduction shall be
              made for any item of cost incurred by Enzon, its Affiliates or
              Sublicensees in preparing, shipping or selling the Product except
              as permitted pursuant to Sections 1.1.48Error! Reference source
              not found. through 1.1.48(g) inclusive. Net Sales shall not
              include any transfer between any of Enzon and any of its
              Affiliates or Sublicensees for resale, but Net Sales shall include
              the subsequent final sales to Third Parties by such Affiliates or
              Sublicensees. Fair market value shall be assigned to any and all
              non-cash consideration such as but not limited to any credit,
              barter, benefit, advantage or concession received by Enzon or its
              Affiliates or Sublicensees in payment for sale of the Product. As
              used in this definition, a "sale" shall have occurred on the
              earlier of when the Products are invoiced or shipped.
              Notwithstanding anything herein to the contrary, the following
              shall not be considered a sale of a Product under this Agreement:
              (i) the transfer of a Product to a Third Party without
              consideration to Enzon in connection with the development or
              testing of a Product; or (ii) the transfer of a Product to a Third
              Party without consideration in connection with the marketing or
              promotion of the Product (e.g., pharmaceutical samples).
              Notwithstanding the foregoing, in calculating Net Sales, no
              deductions from gross revenues that are not permitted by U.S. GAAP
              from being deducted for the purposes of such calculation shall be
              deducted.

      1.1.49  "not to be unreasonably withheld" and the like means not to be
              unreasonably withheld or delayed.

      1.1.50  "Notice of Rejection" shall have the meaning set out in Section
              5.5.1.

      1.1.51  "Out-of-Pocket Cost" means an out-of-pocket payment made by a
              Party to a Third Party but only to the extent such payment relates
              to costs which are incurred by such Party with respect to
              fulfilling its obligations with respect to Commercialization,
              Manufacturing, or Co-Promotion.

      1.1.52  "Party" means Inex or Enzon and "Parties" means Inex and Enzon.

      1.1.53  "Person" means and includes any individual, corporation,
              partnership, firm, joint venture, syndicate, association, trust,
              government body, and any other form of entity or organization.

*** Indicates the omission of confidential material pursuant to a request for
confidential treatment made in accordance with Rule 24b-2 under the Securities
Exchange Act of 1934, as amended. The Confidential material is being filed
separately with the Secretary to the Securities and Exchange Commission.

<PAGE>
                                     - 13 -

      1.1.54  "Pharmacovigilance" means all the activities associated with
              maintaining an effective drug safety monitoring system and adverse
              events reporting system in compliance with the requirements of
              Regulatory Authorities.

      1.1.55  "Prime Rate" means the prime or equivalent rate quoted by
              Citibank, N.A. from time to time.

      1.1.56  "Product" means VSLI.

      1.1.57  "Product Components" means all components of Products, including
              Sodium Phosphate Injection, Sphingomyelin Cholesterol Liposome
              Injection, and Vincristine Sulfate Injection.

      1.1.58  "Purchase Order" means a purchase order from Enzon to Inex for the
              Product issued in accordance with the provisions herein.

      1.1.59  "Purchase Price" shall have the meaning set forth in Section 2.1.

      1.1.60  "QA" means Quality Assurance, being that part of each management
              system, within Inex and Enzon separately, having responsibility
              for assuring the quality of the Product in respect of compliance
              with Regulatory Requirements.

      1.1.61  "Quality/Technical Agreement" shall have the meaning set forth in
              Section 4.6.

      1.1.62  "Reference Price" has the meaning given it in Section 2.2.1.

      1.1.63  "Regulatory Approvals" means all necessary and appropriate
              regulatory approvals which must be obtained before placing the
              Product on the market in the Field in any country in the Territory
              in which such approval is required, including without limitation,
              INDs, NDAs, and any other comparable terms as applicable with
              regard to any such approvals in any other country in the
              Territory.

      1.1.64  "Regulatory Authority" or "Regulatory Authorities" means:

              (a)       the FDA, the TPD and the equivalent Regulatory
                        Authority(ies) elsewhere in the Territory, whether
                        federal, provincial, state or municipal, regulating the
                        importation, distribution, marketing and/or sale of
                        therapeutic substances in the Territory; and

              (b)       the corresponding governmental authorities, whether
                        federal, provincial, state or municipal, of each other
                        applicable jurisdiction outside the Territory in which
                        the Product will be developed, used or sold.

      1.1.65  "Regulatory Requirements" means:

              (a)       Applicable Laws, rules, regulations, guidances, and the
                        Codes and Standards in respect of all activities of the
                        Parties and their permitted Representatives under the
                        Related Agreements, including guidances in respect of
                        quality control and QA procedures and processes,
                        manufacturing and production batch records (including
                        the Master Production Record), packaging, handling,
                        storage, delivery and retention of raw material and
                        Product samples and associated support data, and all
                        licenses, certificates, authorizations or requirements
                        from Regulatory Authorities; and

*** Indicates the omission of confidential material pursuant to a request for
confidential treatment made in accordance with Rule 24b-2 under the Securities
Exchange Act of 1934, as amended. The Confidential material is being filed
separately with the Secretary to the Securities and Exchange Commission.

<PAGE>
                                     - 14 -

              (b)       the corresponding laws, rules, regulations and guidances
                        of each other applicable jurisdiction outside the
                        Territory in which such activities take place.

      1.1.66  "Regulatory Submissions" means all submissions and filings made in
              furtherance of obtaining and maintaining any Regulatory Approvals.

      1.1.67  "Related Agreements" means, collectively, this Agreement, the
              Quality/Technical Agreement, the Development Agreement and the
              Co-Promotion Agreement.

      1.1.68  "Representatives" means, in respect of a Party, that Party's
              Affiliates and their respective directors, officers, employees,
              consultants, subcontractors, sublicensees, agents, representatives
              and other persons acting under their authority.

      1.1.69  "S&OP" has the meaning set out in Section 3.1.1.

      1.1.70  "SOP" means the duly authorized and documented standard operating
              procedure practised by each of Enzon and Inex in the performance
              of a specified process.

      1.1.71  "Specifications" means the specifications for Manufacturing the
              Product and the related methods and stability protocols and
              procedures as set forth in the approved NDA and any supplements
              and amendments thereto, together with the specifications for raw
              materials, packaging, sampling, shipping and storage of Product.
              The Specifications are set forth at Exhibit 1.1.71 attached
              hereto.

      1.1.72  "Standards" means the Accreditation Council for Continuing Medical
              Education (ACCME) Standards for Commercial Support of Continuing
              Medical Education, as they may be amended from time to time.

      1.1.73  "Sublicensee" means a Third Party which is not an Affiliate of
              Enzon and to whom Enzon has granted a sublicense for the purpose
              of developing, using, selling, having sold, distributing or
              importing the Product in one or more countries of the Territory.

      1.1.74  "Term" shall have the meaning set out in Section 17.1.

      1.1.75  "Territory" means Mexico, Canada and the USA.

      1.1.76  "Third Party" means any Person other than a Party or an Affiliate
              of a Party.

      1.1.77  "Trademarks" means trademarks, trade names, and domain names
              identified in Exhibit 1.1.77 and all alternate trademarks adopted
              and used by Enzon for the Product and all applications and
              registrations therefor in the Territory.

      1.1.78  "USA" means the United States of America, including its
              territories, possessions and the Commonwealth of Puerto Rico.

      1.1.79  "Vincristine" means the chemical compound known as vincristine
              sulfate.

      1.1.80  "Vincristine Sulfate Liposomes Injection" or "VSLI" means
              Vincristine encapsulated in sphingomyelin/cholesterol liposomes or
              a kit for production of same.

*** Indicates the omission of confidential material pursuant to a request for
confidential treatment made in accordance with Rule 24b-2 under the Securities
Exchange Act of 1934, as amended. The Confidential material is being filed
separately with the Secretary to the Securities and Exchange Commission.

<PAGE>
                                     - 15 -

1.2   Entire Agreement; Conflicts

This Agreement, together with the other Related Agreements, constitutes the
entire agreement between the Parties concerning the subject matter hereof. In
the event of a conflict between the terms and conditions set out in any of the
Related Agreements, the following agreement shall govern in the following
priority:

      1.2.1   this Agreement; then

      1.2.2   the Quality/Technical Agreement; then

      1.2.3   the Development Agreement; and then

      1.2.4   the Co-Promotion Agreement.

1.3   Governing Law

This Agreement shall be governed by and construed in accordance with the laws of
Delaware in force therein without regard to its conflict of law rules.

1.4   Headings

The headings contained in this Agreement are for convenience of reference only
and shall not be considered in construing this Agreement. References to Articles
are references to Articles of this Agreement and the Sections contained therein,
and references to Sections are references to Sections of this Agreement.

1.5   Severability

If a court or other tribunal of competent jurisdiction should hold any term or
provision of this agreement to be excessive, invalid, void or unenforceable, the
offending term or provision shall be deemed inoperative to the extent it
conflicts with such holding and shall be deemed to be modified to the extent
necessary to conform with such statute or rule of law, while still preserving,
to the extent practicable, the legitimate aims of the Parties, provided that the
remaining portions hereof shall remain in full force and effect. In the event
that the terms and conditions of this Agreement are materially altered as a
result of the above, the Parties will renegotiate the terms and conditions of
this Agreement to resolve any inequities.

                         Article 2 Purchasing and Price

2.1   Purchase Price of Product

      2.1.1   Subject to the terms of this Agreement, Enzon will purchase
              Product from Inex for commercial resale at the Purchase Price
              comprised of the sums set forth in this Section 2.1.1 ("Purchase
              Price") below:

              (a)       Manufacturing Cost for the units delivered as set forth
                        in Exhibit 2.1.1(a) plus five percent (5%)

              (b)       Deferred Sales Payments as set forth in Exhibit
                        2.1.1(b); and

              (c)       Sales Threshold Bonuses ("Sales Threshold Bonuses") as
                        follows:

                        (i)   Ten Million Dollars ($10,000,000) payable when
                              cumulative Net Sales first exceeds One Hundred
                              Twenty-five Million Dollars ($125,000,000) in any
                              rolling four (4) Commercial Quarter period; and

*** Indicates the omission of confidential material pursuant to a request for
confidential treatment made in accordance with Rule 24b-2 under the Securities
Exchange Act of 1934, as amended. The Confidential material is being filed
separately with the Secretary to the Securities and Exchange Commission.

<PAGE>
                                     - 16 -

                        (ii)  Fifteen Million Dollars ($15,000,000) payable when
                              cumulative Net Sales first exceeds Two Hundred
                              Fifty Million Dollars ($250,000,000) in any
                              rolling four (4) Commercial Quarter period.

      2.1.2   Subject to the terms of this Agreement, Enzon will purchase
              Product from Inex for use in Post-Approval Clinical Activities at
              a purchase price equal to the Manufacturing Cost.

      2.1.3   The Parties shall cooperate in good faith to establish a mechanism
              to share on a 50/50 basis the per unit financial benefit
              associated with any reduction in the Manufacturing Cost derived
              from the Technical and Manufacturing Support Activities described
              in Section 5.6.2 of the Development Agreement and/or the transfer
              of Manufacturing to Enzon (if any) pursuant to Section 4.4. If the
              Parties cannot agree, either Party may refer the matter to
              resolution pursuant to Article 16.

2.2   Terms of Payment for Manufacturing Cost Plus

With respect to payments pursuant to Section 2.1:

      2.2.1   On or before Enzon issues its first pre-launch Purchase Order
              pursuant to Section 3.2.1, but in any event on or before the
              earlier of: 45 days of the Effective Date; and the date of the
              first Purchase Order, the Parties will agree on their best
              estimate of the Manufacturing Cost for a unit of Product for 2004
              plus five percent (the "Reference Price"). If the Parties are
              unable to agree on such price, either Party may refer the matter
              for resolution pursuant to Article 16.

      2.2.2   Upon shipment of Product and complete QA documentation related
              thereto, including Certificate(s) of Analysis, to Enzon, Inex
              shall deliver an invoice to Enzon for the Product included in such
              shipment, which invoice shall be based on the Reference Price for
              the units of Product shipped. Provided the Product has not been
              rejected pursuant to Section 5.5.1, Enzon agrees to pay each such
              invoice within thirty (30) days after its receipt of the shipment,
              complete QA documentation for such shipment and the applicable
              invoice.

      2.2.3   Within twelve (12) Business Days after the end of each Calendar
              Quarter, Inex shall calculate the actual Manufacturing Cost for
              the units of Product shipped to Enzon during such Calendar Quarter
              and deliver a report setting forth such actual Manufacturing Cost
              (with amounts broken out for the line items reflected in Exhibit
              2.1.1(a)). Any Manufacturing Cost for the units of Product shipped
              to Enzon during any Calendar Quarter and not captured in the
              calculation delivered in the report referred to in this Section
              shall be captured in subsequent reports.

      2.2.4   If the aggregate actual Manufacturing Cost for all the units of
              Product shipped to Enzon (and for which Enzon owed or owes payment
              to Inex pursuant to Section 2.2.2) during such Calendar Quarter
              exceeds the aggregate Reference Price paid or payable by Enzon
              pursuant to Section 2.2.2 for the units of Product so shipped,
              then Inex will deliver an invoice to Enzon (contemporaneous with
              the report described in Section 2.2.3) for the amount of such
              excess. Enzon shall pay such invoice within thirty (30) days from
              the receipt of such invoice.

      2.2.5   If the aggregate actual Manufacturing Cost for all the units of
              Product shipped to Enzon (and for which Enzon owed or owes payment
              to Inex pursuant to Section 2.2.2) during such Calendar Quarter is
              less than the aggregate Reference Price paid or payable by

*** Indicates the omission of confidential material pursuant to a request for
confidential treatment made in accordance with Rule 24b-2 under the Securities
Exchange Act of 1934, as amended. The Confidential material is being filed
separately with the Secretary to the Securities and Exchange Commission.

<PAGE>
                                     - 17 -

              Enzon pursuant to Section 2.2.2 for the units of Product so
              shipped, then Inex will deliver a credit statement to Enzon
              (contemporaneous with the report described in Section 2.2.3) for
              the amount of such deficiency. The amount of the deficiency shall
              be credited against future amounts owed by Enzon to Inex under
              Section 2.2.2.

      2.2.6   At least once annually, or as more frequently as the Parties may
              agree, the Parties will agree on their best estimate of a revised
              Reference Price, and thereafter use the revised Reference Price
              for the purposes of invoices issued pursuant to Section 2.2.2. If
              the Parties are unable to agree on such price, either Party may
              refer the matter for resolution pursuant to Article 16.

2.3   Terms of Payment for Deferred Sales Payments

With respect to the Deferred Sales Payment as set forth in Section 2.1.1(b), on
a quarterly basis, Enzon shall make a Deferred Sales Payment in accordance with
Exhibit 2.1.1(b) on each unit of Product in every country in the Territory until
the expiry of the Term in such country.

2.4   Remuneration respecting Sublicensees

In the event Enzon grants sublicenses to others to sell the Product, such
sublicenses shall include an obligation for the Sublicensee to account for and
report its sales of the Product on the same basis as if such sales were sales of
Enzon, and Inex shall receive compensation in the same amounts as if the sales
of the Sublicensee were sales of Enzon.

2.5   Third Party Payments

      2.5.1   Inex shall pay all royalties or other remuneration owing to Third
              Parties pursuant to agreements between Inex and such Third Parties
              in effect as of the Effective Date which result from the exercise
              by Enzon of the rights granted in Section 2.1 of the Development
              Agreement.

      2.5.2   If, during the term of this Agreement, Enzon and Inex mutually
              agree that it is necessary to seek a license from any Third Party
              in the Territory in order to avoid infringement during the
              exercise of the rights herein granted or if a court of competent
              jurisdiction determines that such a license is required, or if an
              independent, mutually acceptable Third Party patent attorney
              determines that such a license is required (in accordance with the
              procedure outlined in this Section 2.5.2), ***. In the event that
              the Parties are unable to agree on whether any such license is
              needed or on the terms of such license, the Parties shall submit
              such dispute to an independent, mutually acceptable Third Party
              patent attorney for a final and binding determination of such
              dispute, and the Parties shall equally share the cost of engaging
              such patent attorney.

      2.5.3   Notwithstanding the provisions of Section 2.5.2, if the license
              from the Third Party or the royalty or other fee payable to such
              Third Party gives rise to an indemnification obligation under the
              Related Agreements in favour of Enzon on the part of Inex, then
              such royalty or other fee shall be paid by Inex as Losses in
              accordance therewith.

2.6   Commercial Sales of Development Stock

Any Product produced for Development which, by agreement of the Parties, is
converted to commercial stock for resale, will be sold by Inex to Enzon for
commercial sale pursuant to this Agreement, and any

*** Indicates the omission of confidential material pursuant to a request for
confidential treatment made in accordance with Rule 24b-2 under the Securities
Exchange Act of 1934, as amended. The Confidential material is being filed
separately with the Secretary to the Securities and Exchange Commission.

<PAGE>
                                     - 18 -

contribution of Development Costs already paid by Enzon in respect of such stock
will be credited against Enzon's purchase of such stock.

2.7   Reports and Payment

Enzon shall deliver to Inex within thirty (30) days after the end of each
Commercial Quarter a written report showing its computation of Deferred Sales
Payments and Sales Threshold Bonuses, if any, due under this Agreement in
respect of such Commercial Quarter, and setting out:

      2.7.1   Net Sales segmented in each such report according to sales by
              Enzon, each Affiliate and each Sublicensee, as well as on a
              country-by-country and month-by-month basis.

      2.7.2   Deductions from gross revenues by the categories for same set out
              in the definition of Net Sales.

      2.7.3   The rates of exchange used to convert such Deferred Sales Payments
              to United States dollars from the currency in which such sales
              were made. For purposes hereof, such conversion calculations are
              to be made on a monthly basis and the rate of exchange to be used
              for converting Deferred Sales Price payments hereunder from a
              foreign currency to United States dollars in any month shall be
              equal to the average of: (i) the daily foreign mid-range rate as
              published in the Wall Street Journal (or any rate replaced
              thereby) in respect of the first Business Day of the relevant
              month; and (ii) the same rate in respect of the last Business Day
              of the relevant month.

Enzon, simultaneously with the delivery of each such report, shall tender
payment in United States dollars all Deferred Sales Payments and Sales Threshold
Bonuses, if any, shown to be due thereon.

2.8   Withholding Taxes

The Parties contemplate that there will be no payment or withholding by Enzon of
taxes on any payments made by Enzon to Inex pursuant to this Agreement. In the
event that either Party takes any action, or if the circumstances applicable to
either Party change with the result that taxes must be paid or withheld on the
payments due pursuant to this Agreement, then such taxes shall be borne by such
Party. Without limiting the generality of the foregoing:

      2.8.1   if Enzon assigns or sublicenses its rights hereunder, undergoes a
              reorganization or otherwise changes its structure, or changes its
              domicile, and thereafter taxes must be paid or withheld on the
              payments hereunder, such payments shall be grossed up so that Inex
              receives the actual amounts set out in this Agreement; and

      2.8.2   if Inex assigns or sublicenses its rights hereunder, undergoes a
              reorganization or otherwise changes its structure, or changes its
              domicile, and thereafter taxes must be paid or withheld on the
              payments hereunder, then such tax or withholding payments shall be
              deducted from the amounts set forth herein, and Enzon shall assist
              Inex as may be reasonably required, including providing proof of
              such payment of such tax payment, in order to allow Inex to claim
              the benefit of, exemption from or repayment such tax payment, as
              may be applicable; and

      2.8.3   in the event that payment or withholding by Enzon of taxes becomes
              necessary on any payments made by Enzon to Inex pursuant to this
              Agreement when neither Section 2.8.1 nor Section 2.8.2 applies,
              then such tax or withholding payments shall be deducted from the
              amounts set forth herein, and Enzon shall assist Inex as may be
              reasonably required,

*** Indicates the omission of confidential material pursuant to a request for
confidential treatment made in accordance with Rule 24b-2 under the Securities
Exchange Act of 1934, as amended. The Confidential material is being filed
separately with the Secretary to the Securities and Exchange Commission.

<PAGE>
                                     - 19 -

              including providing proof of such payment of such tax payment, in
              order to allow Inex to claim the benefit of, exemption from or
              repayment such tax payment, as may be applicable.

Notwithstanding the foregoing, if Inex is able to credit the grossed up portion
of any payment made by Enzon pursuant to Section 2.8.1 against taxes payable by
Inex, or gain exemption from or repayment of such tax payment, Inex will
promptly pay the equivalent of the benefit received by Inex to Enzon.

2.9   Foreign Payments

Where payments are due Inex hereunder for sales of the Product in a country in
the Territory where, by reason of currency regulations or taxes of any kind, it
is impossible or illegal for Enzon, any Affiliate or Sublicensee to transfer
such payments to Inex, such payments shall be deposited in whatever currency is
allowable by the Person not able to make the transfer for the benefit or credit
of Inex in an accredited bank in that country in the Territory that is
reasonably acceptable to Inex.

2.10  Method of Payment

Enzon shall make all payments due under this Agreement in U.S. Dollars by wire
transfer of funds via the Federal Reserve Wire Transfer System to Inex's account
as designated in writing by Inex to Enzon.

2.11  Late Payments

Any payment by Enzon or Inex that is not paid on or before the date such payment
is due under this Agreement shall bear interest at a rate equal to the lesser
of:

      2.11.1  Prime Rate plus *** per year, or

      2.11.2  the maximum rate permitted by law;

calculated based on the number of days that payment is delinquent.

2.12  Records

Both Parties shall keep full, true and accurate books of accounts and other
records containing all information and data which may be necessary to ascertain
and verify:

      2.12.1  the Commercialization Costs incurred by each Party and their
              respective Representatives hereunder for a period of three (3)
              years after the completion of the Commercialization; and

      2.12.2  any other amount payable hereunder for a period of three (3) years
              after the completion of the Term.

2.13  Audits

During the Term and for a period of three years thereafter, each Party shall
have the right from time to time (not to exceed once during each calendar year)
to have either its internal financial audit personnel or an independent firm of
accountants (i.e., a certified public accountant or like person reasonably
acceptable to the Party being audited) inspect the books, records and supporting
data of the other Party referred to in Section 2.12. Such independent firm of
accountants shall perform these audits at the requesting Party's expense upon
reasonable prior notice and during the other Party's regular business hours, and
shall agree as a condition to such audit to maintain the confidentiality of all
information disclosed or observed in connection

*** Indicates the omission of confidential material pursuant to a request for
confidential treatment made in accordance with Rule 24b-2 under the Securities
Exchange Act of 1934, as amended. The Confidential material is being filed
separately with the Secretary to the Securities and Exchange Commission.

<PAGE>
                                     - 20 -

with such audit and to disclose to the requesting Party only whether the other
Party has complied with its obligations under this Agreement with respect to the
calculation and payment of Commercialization Costs and any other money owing
pursuant to this Agreement. If the result of such audit demonstrates an
overpayment or underpayment, there shall be a prompt (but in no event more than
60 days after completion of the audit) accounting between the parties to
reconcile such overpayment or underpayment. If the results of such audit
demonstrates a discrepancy and the discrepancy represents *** or more of the
actual value, then the party that has to pay to settle the discrepancy shall pay
the reasonable costs of the audit.

                   Article 3 Forecasting and Purchase Orders

3.1   Sales and Operations Plan

      3.1.1   The Parties will confer monthly as contemplated by this Section to
              review and update a rolling eighteen (18) month Sales and
              Operation Plan (the "S&OP") to govern activities related to
              forecasting, production capacity, inventory management, risk
              management and other activities related to the timely and
              efficient management of the supply and distribution of the
              Product.

      3.1.2   Initially, within 30 days after the Effective Date, and on or
              before the last Business Day of each month thereafter, Enzon will
              provide Inex by electronic mail a rolling, eighteen (18) month
              forecast ("Forecast") estimating Enzon's requirements for Product
              for the following eighteen (18) months. The Forecast will be made
              in good faith to assist Inex in developing the S&OP and, except as
              otherwise set forth in this Agreement, shall be non-binding. Each
              Forecast will contain:

              (a)       in respect of Forecasts provided by Enzon subsequent to
                        Inex's first shipment to Enzon, an inventory status of
                        Products on hand; and

              (b)       in respect of the first nine (9) months of each
                        Forecast, the quantities of Product to be purchased
                        broken down both by:

                        (i)   the use for the Product, designated as either for
                              clinical use or commercial use; and

                        (ii)  the jurisdiction in which the Product will be
                              used.

      3.1.3   Promptly (but in any event within two (2) Business Days after
              becoming aware of same) Inex will notify Enzon of any difficulties
              that are likely to cause a delay in meeting or a failure to meet
              Enzon's requirements during the Forecast period. Inex shall
              present detailed descriptions of such difficulties for discussion
              during the monthly S&OP planning meeting or teleconference.

      3.1.4   Within one week of Inex's receipt of Enzon's Forecast for each
              Forecast period, Inex will provide Enzon a draft S&OP setting out
              the quantity of Product scheduled to be Manufactured during the
              Forecast period, and the Parties will jointly review and make
              reasonable efforts to agree upon such changes as may be required
              to develop an S&OP approved by both Parties (the "Approved S&OP").
              In the absence of express agreement of the Parties to the
              contrary, if the Parties fail to agree on any Approved S&OP, Inex
              will continue to operate using the most recently Approved S&OP. In
              the absence of express agreement of the Parties to the contrary,
              in no event will the total and monthly quantities of Product set
              out in the Approved S&OP exceed the capacity of Inex's
              Representatives.

*** Indicates the omission of confidential material pursuant to a request for
confidential treatment made in accordance with Rule 24b-2 under the Securities
Exchange Act of 1934, as amended. The Confidential material is being filed
separately with the Secretary to the Securities and Exchange Commission.

<PAGE>
                                     - 21 -

      3.1.5   Inex's commitment to Manufacture, and Enzon's commitment to
              Purchase such quantities of Product as set forth in the first nine
              (9) months of each Approved S&OP shall be binding upon the
              parties.

      3.1.6   The parties acknowledge and confirm that Inex shall rely upon the
              Forecasts provided by Enzon in determining its Manufacturing
              schedules and acquiring the necessary raw materials in advance
              thereof, and notwithstanding the non-binding nature of the
              remaining nine (9) months of the Approved S&OP, Enzon shall use
              Commercially Reasonable Efforts to project accurately its
              requirements.

3.2   Purchase Orders Issued Before First FDA Approval

      3.2.1   Prior to the FDA's grant of Regulatory Approval for the Product,
              and pursuant to each Approved S&OP, Enzon will provide Inex
              binding Purchase Orders by facsimile or electronic mail at least
              nine (9) months prior to each proposed delivery date, specifying

              (a)       delivery date specified as "the week of;"

              (b)       delivery location; and

              (c)       mode of delivery (default transportation will be by
                        surface in the USA);

              and shall pay to Inex within five Business Days of issuing each
              such Purchase Order, a pre-payment of *** of the Reference Price
              of the quantity of Product specified in each Purchase Order,
              creditable against Enzon's future payment of the Purchase Price of
              the Product.

      3.2.2   Inex or its designee will respond by facsimile or electronic mail
              within three (3) Business Days of receipt of Enzon's Purchase
              Orders with a confirmed delivery date that is within two (2) weeks
              of that specified in the Purchase Order.

      3.2.3   Notwithstanding anything else herein to the contrary, except for
              the payment of *** of the Reference Price under Section 3.2.1,
              Enzon shall not be obligated to purchase any shipment of Product
              for commercial use prior to Regulatory Approval of the Product by
              the FDA.

      3.2.4   Provided the batch or batches of Product Manufactured pursuant to
              Enzon's Purchase Orders under Section 3.2.1 meets the minimum
              shelf life set forth in Section 5.2.2 or such other shelf life as
              agreed between the Parties acting reasonably and provided Enzon
              shall not have rejected the Product pursuant to Section 5.5.1,
              Enzon shall purchase such batch or batches of Product at the
              Purchase Price less the pre-payment already made in respect of
              such batch or batches of Product as set out in Section 3.2.1.
              Inex's right to receive payment hereunder is in addition to and
              not in lieu of Inex's right to quarterly reconciliations of
              payment pursuant to Article 2.

      3.2.5   If any batch of Product Manufactured pursuant to Enzon's Purchase
              Orders under Section 3.2.1 does not meet the minimum shelf life
              set forth in Section 5.2.2 or such other shelf life as agreed
              between the Parties acting reasonably, Enzon shall not be required
              to purchase such batch of Product, but shall not be entitled to a
              refund of any prepayment made in respect of such batch of Product
              pursuant to Section 3.2.1.

*** Indicates the omission of confidential material pursuant to a request for
confidential treatment made in accordance with Rule 24b-2 under the Securities
Exchange Act of 1934, as amended. The Confidential material is being filed
separately with the Secretary to the Securities and Exchange Commission.

<PAGE>
                                     - 22 -

3.3   Purchase Orders Issued After First FDA Approval

      3.3.1   In accordance with the most recently Approved S&OP, Enzon will
              provide Inex a binding Purchase Order at least nine (9) months
              prior to each proposed delivery date, specifying:

              (a)       quantity of Product to be purchased as provided in the
                        Approved S&OP, broken down both by:

                        (i)   the use for the Product, designated as either for
                              clinical use or commercial use; and

                        (ii)  the jurisdiction in which the Product will be
                              used;

              (b)       delivery date specified as "the week of" as provided in
                        the Approved S&OP;

              (c)       delivery location; and

              (d)       mode of delivery (default transportation will be by
                        surface in the USA).

      3.3.2   Enzon will send all Purchase Orders to Inex by facsimile or
              electronic mail.

      3.3.3   Inex or its designee will respond by facsimile or electronic mail
              within three (3) Business Days of receipt of Enzon's Purchase
              Order with a confirmed delivery date that is within two (2) weeks
              of that specified in the Purchase Order.

                            Article 4 Manufacturing

4.1   Technical Activities to Support Manufacturing

Subject to Section 4.4 and unless otherwise agreed between the Parties, Inex
will oversee all Manufacturing activities required to:

      4.1.1   obtain and maintain Regulatory Approvals; and

      4.1.2   provide Product for Clinical Activities and commercial sale.

4.2   Manufacturing in Compliance

Inex shall Manufacture the Product in compliance with the Regulatory
Requirements, the Specifications and the Master Production Record.

4.3   Subcontractors

Except for contracts executed prior to the Effective Date, Inex may not
subcontract to any Third Party the Manufacture of the Product without the
consent of Enzon, which consent shall not be withheld unreasonably. Inex shall
be responsible to Enzon for the performance of and all activities undertaken by
Inex's subcontractors.

4.4   Technical Transfer to and Manufacture by Enzon

If the Parties' mutually agree that Inex will subcontract some or all of the
Manufacture of Product to Enzon, upon completion by Inex of manufacturing due
diligence with Enzon to Inex's satisfaction:

*** Indicates the omission of confidential material pursuant to a request for
confidential treatment made in accordance with Rule 24b-2 under the Securities
Exchange Act of 1934, as amended. The Confidential material is being filed
separately with the Secretary to the Securities and Exchange Commission.

<PAGE>
                                     - 23 -

      4.4.1   the Parties will amend the Commercialization Plan to establish the
              respective responsibilities of the Parties in respect of such
              subcontracting;

      4.4.2   Enzon will effect such transfer and ensure validation of Enzon's
              processes and facility by no later than a date to be mutually
              agreed upon by the Parties;

      4.4.3   Enzon will fund *** and Inex will fund *** of all costs of such
              transfer, including FTE Costs and Out of Pocket Costs;

      4.4.4   the Manufacture of Product by Enzon will cover clinical and
              commercial requirements both inside and outside the Territory;

      4.4.5   for Product supplied by Enzon to Inex for commercial purposes
              outside the Territory, Product will be supplied at the cost of
              goods per unit of Product ***;

      4.4.6   for Product supplied by Enzon to Inex for clinical development,
              Product will be supplied at Manufacturing Cost; and

      4.4.7   the Parties will amend this Agreement or enter into a new Product
              Supply Agreement to provide for such transfer.

The matters set forth in this Section 4.4 constitute merely an expression of the
desire of the Parties to negotiate with each other regarding the terms of an
agreement regarding the subject matter of this Section 4.4, and nothing in this
Section 4.4 will have any legal or binding effect unless set out in writing in a
separate agreement and signed by the duly authorized representatives of the
Parties.

4.5   Material Change to Financial Terms

Unless otherwise agreed in writing by the Parties, in the event of:

      4.5.1   any material amendment to any of the Related Agreements;

      4.5.2   any termination of any of the Related Agreements that does not
              result in termination of all of the Related Agreements;

the Parties will review and renegotiate financial terms under the amended or
remaining Related Agreements so that the financial compensation received by Inex
as a result of the amended or remaining Related Agreements is no less favourable
to Inex than the financial terms of the Related Agreements would have been
without such amendment or termination. If the Parties are unable to agree to
such terms, either Party may refer the matter for resolution pursuant to Article
16.

4.6   Quality/Technical Agreement

Upon execution of this Agreement, the Parties will commence good faith
negotiations of a Quality/Technical Agreement setting forth in greater detail
the regulatory and quality assurance responsibilities of the Parties with regard
to the Manufacture of Product and further providing for compliance with
Regulatory Requirements. Each of the Parties will exercise Commercially
Reasonable Efforts to finalize and execute such agreement within 90 days after
the Effective Date.

*** Indicates the omission of confidential material pursuant to a request for
confidential treatment made in accordance with Rule 24b-2 under the Securities
Exchange Act of 1934, as amended. The Confidential material is being filed
separately with the Secretary to the Securities and Exchange Commission.

<PAGE>
                                     - 24 -

                         Article 5 Supply and Shipment

5.1   Shipping Notification

      5.1.1   No later than five (5) Business Days prior to Product shipment,
              Inex will provide Enzon with shipping details that include lot
              number, quantity, shipping date, transport mode, and destination.

      5.1.2   Inex will send all shipping notices to Enzon by facsimile or
              electronic mail.

5.2   Shipment of Product

      5.2.1   In respect of each shipment of Product, Inex shall:

              (a)       ensure the Product is properly stored in validated
                        transport containers;

              (b)       prepare and ship Product in accordance with approved
                        shipping SOPs;

              (c)       provide tracking information to Enzon upon shipment from
                        Inex's or Inex's subcontractors' facilities at the time
                        of shipment.

      5.2.2   All Product shipped by Inex or its designees shall have a expiry
              date no less than eight (8) months from the date of shipment,
              provided that Enzon purchases the entire batch or batches of
              Product Manufactured for shipment, except as mutually agreed upon
              between the Parties, acting reasonably. The Parties will use
              Commercially Reasonable Efforts to increase the Product shelf life
              to at least twelve (12) months.

      5.2.3   Unless otherwise agreed between the Parties, Inex shall not ship
              any Product to Enzon except pursuant to a Purchase Order.

5.3   Shipment of Released Product

Inex will ship Product to Enzon or Enzon's designees only after Product has been
released by Inex's QA representatives. Enzon shall not be responsible for QA
release of the Product.

5.4   Risk of Loss and Shipping Expenses

The Product will be shipped F.A.S. Enzon's designated location.

5.5   Rejection of Delivered Product

      5.5.1   After receipt by Enzon of the Product or of the sample of the
              Product and complete QA documentation corresponding thereto,
              including Certificate(s) of Analysis, if Enzon rejects the Product
              delivered to it by reason of any shortage in quantity of the
              shipment, damage to the Product or packaging, including the
              shipping container, or any obvious defect detectable by the naked
              eye, Enzon will notify Inex within 10 Business Days.

      5.5.2   Product not rejected in accordance with these terms within such
              period will be deemed accepted.

      5.5.3   Inex will use Commercially Reasonable Efforts to make up any
              shortage of Product.

*** Indicates the omission of confidential material pursuant to a request for
confidential treatment made in accordance with Rule 24b-2 under the Securities
Exchange Act of 1934, as amended. The Confidential material is being filed
separately with the Secretary to the Securities and Exchange Commission.

<PAGE>
                                     - 25 -

5.6      Obsolescence and Returns

If Enzon has not rejected the Product in accordance with Section 5.5, Inex will
not accept return of any Product from Enzon or its Representatives regardless of
the reason(s) therefor.

5.7   Disposal and Destruction

Unless otherwise agreed in writing between the Parties, unsold Product in
Enzon's possession or control will be destroyed or disposed by Enzon in
accordance with Regulatory Requirements at Enzon's sole expense.

                   Article 6 Product Receipt and Distribution

6.1   Receipt

Unless otherwise agreed upon in advance between the Parties, Enzon shall
practice receipt procedures in accordance with agreed SOPs or written
instructions agreed between the Parties.

6.2   Storage and Handling

If Enzon or its Representatives' receipt, storage or handling of Product is not
done in accordance with the Specifications or Regulatory Requirements and the
whole or part of a shipment of Product is rendered unsuitable for its purpose,
Enzon shall remain liable for the Purchase Price of any compromised Product and
for any shipping costs associated with such purchase.

6.3   Distribution

In respect of each shipment of Product from Enzon to its Representatives or any
Third Parties, Enzon shall, and shall cause its Representatives to:

      6.3.1   ensure the Product is properly stored in validated transport
              containers; and

      6.3.2   prepare and ship Product in accordance with approved shipping
              SOPs.

6.4   Records for Traceability

Enzon shall maintain and shall require its Representatives who receive, handle,
store, ship, or distribute Product to maintain a record retention policy
consistent with cGMP and Regulatory Requirements, and to maintain records with
sufficient detail to facilitate traceability in the event of recalls or
voluntary withdrawals of Product.

                         Article 7 Shipments for Launch

7.1   Consequence of Launch Supply Failure

      7.1.1   If Inex fails to deliver to Enzon at least *** of the quantity of
              Product (that satisfies all material, applicable requirements of
              this Agreement) ordered by Enzon in its initial pre-Regulatory
              Approval Purchase Order (as contemplated in Section 3.2) (such ***
              the "Minimum Launch Quantity") within six months after the: the
              delivery date specified in such Purchase Order; and the date of
              Regulatory Approval; whichever is later, and such failure has not
              been caused by any act or omission of Enzon (such failure to
              deliver within six months shall be a "Launch Supply Failure"),
              Inex shall, within 10 Business Days after the Launch Supply
              Failure, make a cash payment to Enzon in the amount set out in
              Section 7.1.2 to compensate Enzon for the loss in value associated
              with a delayed

*** Indicates the omission of confidential material pursuant to a request for
confidential treatment made in accordance with Rule 24b-2 under the Securities
Exchange Act of 1934, as amended. The Confidential material is being filed
separately with the Secretary to the Securities and Exchange Commission.

<PAGE>
                                     - 26 -

              launch. For greater clarity, in the event of a Launch Supply
              Failure, the date of the Launch Supply Failure will be the date
              six months from the later of: the delivery date specified in such
              Purchase Order; and the date of Regulatory Approval.

      7.1.2   The amount to compensate for the loss in value shall be:

              (a)       if the Launch Supply Failure is before April 15, 2006,
                        then the amount shall be ***; and

              (b)       if the Launch Supply Failure is on or after April 15,
                        2006 and before April 15, 2007, then the amount shall be
                        ***; and

              (c)       if the Launch Supply Failure is on or after April 15,
                        2007, then the amount shall be ***.

7.2   Enzon's First Option to Terminate

      7.2.1   Upon the occurrence of a Launch Supply Failure, Enzon shall have
              the right, which right must be exercised within ten Business Days
              after the date of occurrence of the Launch Supply Failure, to
              terminate this Agreement immediately upon notice to Inex.
              Termination by Enzon under this Section 7.2 shall not relieve Inex
              of its liability under Section 7.1.

      7.2.2   If Enzon fails to exercise its termination right pursuant to
              Section 7.2.1, then it may not terminate this Agreement for a
              period of six months after the date of occurrence of the Launch
              Supply Failure, provided Inex does not commit any non-supply
              related material breach of this Agreement that would otherwise
              provide a basis for termination by Enzon.

7.3   Enzon's Second Option to Terminate

If Enzon elects not to exercise its termination right pursuant to Section 7.2.1,
but Inex fails to deliver the Minimum Launch Quantity within six months after
the Launch Supply Failure, Enzon shall be entitled to terminate this Agreement
immediately upon notice to Inex, which right must be exercised within ten
Business Days after the expiry of six months after the Launch Supply Failure.
Any such termination by Enzon shall be deemed to be pursuant to Section 17.3.

7.4   Cure by Inex

If a Launch Supply Failure occurs and Enzon has not exercised its termination
right pursuant to Section 7.2.1 or 7.3, and Inex delivers the Minimum Launch
Quantity, then Enzon shall, within 10 Business Days after such delivery
(provided such shipment is not rejected under Section 5.5.1) make a cash payment
to Inex in an amount determined by the following formula:

***

where X is equal to the amount of the payment to be made by Enzon, A is equal to
the amount paid by Inex to Enzon pursuant to Section 7.1.2, Y is equal to the
number of full months elapsed between the date of occurrence of the Launch
Supply Failure and the date of the delivery of the Minimum Launch Quantity and Z
is equal to a fraction that expresses the pro rata portion of the last month
elapsed prior to the delivery.

*** Indicates the omission of confidential material pursuant to a request for
confidential treatment made in accordance with Rule 24b-2 under the Securities
Exchange Act of 1934, as amended. The Confidential material is being filed
separately with the Secretary to the Securities and Exchange Commission.

<PAGE>
                                     - 27 -

                               Article 8 Changes

8.1   Enzon's Right to Notice of and Consent to Changes

      8.1.1   In respect of changes to the Specifications, Master Production
              Records, procedures, processes, materials, facilities, equipment
              or any matter contained or referenced in the NDA or DMFs
              pertaining to the Product, Inex shall notify Enzon and/or seek
              Enzon's prior approval in accordance with the Quality/Technical
              Agreement.

      8.1.2   The Quality/Technical Agreement will provide that Inex will:

              (a)       inform Enzon of all notices received by Inex in respect
                        of changes described in Section 8.1.1 provided to Inex
                        by its Representatives; and

              (b)       cooperate with Enzon to resolve all requests for changes
                        described in Section 8.1.1;

              so that all notice and consent obligations between Inex and Enzon
              take into consideration those now in effect between Inex and its
              Representatives.

8.2   New Regulatory Requirements

Inex and Enzon will use Commercially Reasonable Efforts to make such changes as
reasonably necessary to the Master Production Record, the Specifications or
procedures, processes, materials, facilities, equipment or any matter utilized
by Inex under this Agreement or contained or referenced in Inex's NDA or DMF
controlled by Inex to meet new Regulatory Requirements and guidelines in the
Territory. Upon agreement by the Parties to proceed with such changes, Enzon
shall be responsible for ***, and Inex ***, of all costs incurred by the
Parties, including Development FTE costs, in respect of any changes made by
either Party pursuant to this Section 8.2.

8.3   Reservation

Except as set out in this Article 8, as between Inex and Enzon, Inex retains the
sole right and authority to make all decisions with respect to the Manufacture
of the Product and Inex's performance under this Agreement.

                          Article 9 Commercialization

9.1   Regulatory Compliance

      9.1.1   Each of the Parties, directly and through its permitted
              Representatives, shall perform the Commercialization activities in
              compliance with Regulatory Requirements.

      9.1.2   Each Party shall ensure none of its Representatives who
              participate in any Commercialization and/or Co-Promotion:

              (a)       is or has been suspended, debarred or disqualified by
                        the FDA;

              (b)       has been convicted of any offence that would form the
                        basis for any debarment; or

              (c)       is or has been subject to any proceedings for the
                        suspension, disqualification or debarment of such Party
                        or any Representative of such Party.

*** Indicates the omission of confidential material pursuant to a request for
confidential treatment made in accordance with Rule 24b-2 under the Securities
Exchange Act of 1934, as amended. The Confidential material is being filed
separately with the Secretary to the Securities and Exchange Commission.

<PAGE>
                                     - 28 -

9.2   Assignment of Trademarks

Inex shall assign to Enzon the Trademarks identified in Exhibit 1.1.77 in the
Territory as soon as reasonably possible after such Trademark(s) may be legally
transferred. Inex shall own and have the right to use all Trademarks outside the
Territory.

9.3   Use of Inex Trademarks in Labelling

      9.3.1   The parties agree that Enzon shall affix to the outer packaging of
              and shall include on the package insert for the Product, and in
              addition to its own trademarks and names, one or more labels
              displaying with equal prominence to the Enzon trademarks or names,
              the Inex name and corporate logo, or such other trademark or
              statement as Inex shall reasonably request. Inex shall also have
              the right to review and approve all claims relating to the
              intended use of Product contained in package inserts and other
              promotional materials, which approval shall not be unreasonably
              delayed or withheld.

      9.3.2   Inex hereby grants to Enzon a non-exclusive license, sublicensable
              in accordance with the terms of this Agreement, to use such
              name(s) or trademark(s) accordingly and in substantially the same
              manner as used by its owner; provided, however, that each such use
              of such trademark(s) be accompanied by a printed notice
              identifying Inex as the owner thereof. In the event that any
              Products do not meet the specifications or quality standards
              required under this Agreement, Inex may cause Enzon to remove all
              trademarks of Inex from such Product and shall have the right to
              cancel the foregoing grant of license to use such trademarks,
              unless Enzon promptly meets such specifications or quality
              standards. Inex shall have the right to receive and approve the
              use of its marks in any proposed product literature, advertising
              material or material for publication.

9.4   Patent Marking

Enzon shall mark all Product made, used or sold under the terms of the Related
Agreements, or their containers in compliance with the applicable patent marking
laws. Inex shall have the right to review and approve all patent marking, such
approval not to be unreasonably withheld.

9.5   Commercialization Efforts

Subject to the terms of the Co-Promotion Agreement, in each country in the
Territory in which the Product has received Regulatory Approval, Enzon, directly
and through its permitted Representatives, shall use Commercially Reasonable
Efforts to Commercialize the Product. Enzon's Commercially Reasonable Efforts to
Commercialize the Product shall include the obligation to Manufacture the
Product only if the Manufacture of same is transferred to Enzon pursuant to
Section 4.4.

9.6   Commercial Diligence in accordance with Commercialization Plan

Subject to the terms of the Co-Promotion Agreement, without limiting Enzon's
obligations set out in Section 9.5:

      9.6.1   Enzon will undertake the Commercialization as set out in the
              Commercialization Plan and as amended from time to time by the
              Parties in accordance with this Article 9.

      9.6.2   Enzon shall:

              (a)       conduct pre-launch marketing activities in respect of
                        the Product;

*** Indicates the omission of confidential material pursuant to a request for
confidential treatment made in accordance with Rule 24b-2 under the Securities
Exchange Act of 1934, as amended. The Confidential material is being filed
separately with the Secretary to the Securities and Exchange Commission.

<PAGE>
                                     - 29 -

              (b)       market and launch the Product and sell the Product in
                        each country in the Territory where Regulatory Approval
                        have been granted;

              (c)       pay *** of the costs of Commercializing the Product,
                        including the costs referred to in this Section;

              (d)       Enzon will maintain a minimum effort of an aggregate of
                        *** Sales Representatives and Medical Science Liaisons
                        to Promote the Product in the Territory; and

              (e)       diligently prosecute and maintain the Trademarks and use
                        the Trademarks for the Product.

9.7   Overview of Commercialization

The Parties intend to work cooperatively to pursue the Commercialization in
accordance with the terms of this Agreement and the Co-Promotion Agreement.
Unless otherwise agreed by the Joint Steering Committee or otherwise set out in
this Agreement, Enzon will conduct the Commercialization monitored by the Joint
Steering Committee and under the oversight of the Parties in conformance with
the Commercialization Plan.

9.8   Subcontractors

Either Party may subcontract to any of its Representatives any of its
obligations in respect of the Commercialization with the consent of the other
Party, such consent not to be unreasonably withheld or delayed; provided
however, that the subcontracting Party shall be responsible for the performance
of its Representatives and shall remain fully responsible and obligated to the
other Party for all activities undertaken by its Representatives.

9.9   Commercialization Plans

      9.9.1   Within ninety (90) days after the Effective Date, Enzon shall
              prepare, review and submit to the Parties for approval a detailed
              Commercialization Plan for the Commercialization of the Product
              and the Parties shall reasonably promptly thereafter agree on a
              reasonable, detailed Commercialization Plan. The Commercialization
              Plan shall reflect Enzon's covenant set forth in Section 9.5.

      9.9.2   Commercialization of the Product shall be conducted by Enzon in
              conformance with the Commercialization Plan.

      9.9.3   The Commercialization Plan may be updated by Enzon for review and
              approval by the Parties as provided herein.

      9.9.4   At a minimum, the Commercialization Plan as amended from time to
              time shall describe the specific activities to be performed for a
              twelve (12) month period, with a summary of Commercialization
              Activities to be performed thereafter. The Commercialization Plan
              will be reviewed on at least a semi-annual basis by the Joint
              Steering Committee to update the specific activities to be
              performed for the rolling twelve (12) month period, as well as to
              reflect the revised Commercialization Plan as the Joint Steering
              Committee reasonably determines to be necessary or useful.
              Notwithstanding the above, no amendment to any Commercialization
              Plan shall be construed to be final unless it has been made in
              accordance with the provisions of this Article 9.

*** Indicates the omission of confidential material pursuant to a request for
confidential treatment made in accordance with Rule 24b-2 under the Securities
Exchange Act of 1934, as amended. The Confidential material is being filed
separately with the Secretary to the Securities and Exchange Commission.

<PAGE>
                                     - 30 -

      9.9.5   The JSC shall review progress against the Commercialization Plan
              on a quarterly basis.

9.10  Funding of Commercialization Costs

From and after the Effective Date until the definitive Commercialization Plan is
approved by the Parties, Enzon shall fund 100% of the cost of Commercialization
activities and shall pay Inex for any Commercialization Costs incurred by Inex
in accordance with the interim budget set out as Exhibit 9.10 (the "Interim
Budget"). After the Effective Date, in the absence of a definitive
Commercialization Plan agreed upon by the Parties, no commitment not in effect
as of the Effective date with a price exceeding $5,000 in Commercialization
Costs will be incurred without the agreement of the Parties. If the Parties fail
to agree on the terms of the definitive Commercialization Plan within 90 days of
the Effective Date, until the terms of the definitive Commercialization Plan are
determined, Enzon shall fund 100% of Commercialization Costs incurred by the
Parties acting reasonably, in pursuit of Commercialization of the Product during
this transition period. After the definitive Commercialization Plan is approved
by the Parties, Enzon shall fund 100% of the cost of Commercialization
activities and shall pay Inex for any Commercialization Costs incurred by Inex
in its performance of activities in accordance with the Commercialization Plan
as amended from time to time, without deduction or set off, except as otherwise
expressly set forth in this Agreement. On a quarterly basis, Inex shall send
Enzon invoices accompanied by the appropriate documentation, including a listing
of expenditures in reasonably specific detail within twelve (12) Business Days
after the end of each Calendar Quarter. Enzon shall pay such invoices within
thirty (30) days after receipt of same. Any Commercialization Costs arising in
any Calendar Quarter and not captured in the calculation delivered in the report
referred to in this Section shall be captured in subsequent reports. The costs
incurred by Inex in pursuing Co-Promotion activities under the Co-Promotion
Agreement shall not be included in the Commercialization Costs referenced above
in this Section 9.10 or reimbursed by Enzon. The Co-Promotion Agreement
describes the manner in which Enzon will make payments to Inex in respect of
such Co-Promotion activities.

9.11  Consequence of No Sales

In addition to the terms of Section 9.6, Enzon shall be deemed to have breached
its obligation to use Commercially Reasonable Efforts in conducting marketing of
a Product in any country in the Territory if, for a continuous period of *** at
any time following launch of commercial sales of the Product in any such
country, no sales of the Product are made in the ordinary course of business in
such country by Enzon, an Affiliate or a Sublicensee, unless Enzon is prevented,
restricted, interfered with or delayed in making such sales by reason of a cause
beyond Enzon's reasonable control and can demonstrate same to Inex, in which
event such period shall be extended by the period of Enzon's inability, provided
that Enzon uses Commercially Reasonable Efforts to avoid or remove the cause of
such inability.

9.12  Reports

Enzon shall report to Inex on the status and progress of Enzon's efforts under
this Article 9 as follows:

      9.12.1  Enzon shall deliver to Inex within thirty (30) days after the end
              of each Calendar Quarter reports setting forth in general terms,
              reasonably sufficient for evaluation of the diligence obligations
              contained herein, the efforts Enzon made to commercialize the
              Product during the such year, including the achievement of any
              Sales Threshold Bonuses, any significant adverse developments, and
              any plans for or occurrences of any commercial sales of the
              Product in any jurisdiction and a summary of the efforts it
              intends to make in the upcoming year(s) on these matters. Enzon
              agrees to appropriately consider any Inex input and comments
              related to Enzon's plan for the upcoming year(s), provided that it
              is understood that Enzon shall have final decision making
              responsibility for such plans.

*** Indicates the omission of confidential material pursuant to a request for
confidential treatment made in accordance with Rule 24b-2 under the Securities
Exchange Act of 1934, as amended. The Confidential material is being filed
separately with the Secretary to the Securities and Exchange Commission.

<PAGE>
                                     - 31 -

      9.12.2  To the extent that such could not be appropriately communicated to
              Inex in accordance with Section 9.12.1, Enzon shall keep Inex
              informed in a timely manner of significant developments in Enzon's
              (and its Affiliates and Sublicensees where relevant) progress of
              its efforts to Commercialize the Product, including without
              limitation, the achievement of any Sales Threshold Bonuses, any
              significant adverse developments, and any plans for or occurrences
              of any commercial sales of the Product in any jurisdiction.

9.13  Launch of Competitive Product by Enzon

Enzon hereby agrees that in the event Enzon or its Affiliates, either alone or
in partnership, in collaboration or in conjunction with any Person other than
Inex or Inex's Affiliate(s), whether as principal, agent, employee, director,
officer, shareholder, licensor or in any capacity or manner whatsoever, whether
directly or indirectly, develops, manufactures or commercializes any Competitive
Product during the Term in the Territory, this Agreement shall terminate and
Enzon's rights hereunder shall revert to Inex. No termination pursuant to this
Section shall terminate this Agreement with respect to any other country in the
Territory. Notwithstanding the foregoing, if Enzon or an Affiliate acquires an
entity or all or substantially all of the assets of an entity during such period
of time and such entity distributes or such assets include a Competitive
Product, Enzon, or its Affiliate(s), shall have two hundred seventy (270) days
in which to either (a) divest itself of such Competitive Product or to otherwise
cease distribution of such Competitive Product, and Enzon shall not be in
violation of this Section 9.13 if it so divests or ceases distribution within
such two hundred seventy (270) day period, or (b) terminate this Agreement and
Related Agreements. The Parties mutually agree that Enzon's (or Affiliates')
commercialization, as described above, of any Competitive Product shall not be
deemed a breach of this Agreement, and Inex's sole recourse for such an event
shall be that as described in this Section 9.13 only.

                      Article 10 Joint Steering Committee

10.1  Joint Steering Committee

      10.1.1  As of the Effective Date of this Agreement, the Joint Steering
              Committee shall be formed and shall be constituted of four
              representatives from each Party. The members of the Joint Steering
              Committee as of the Effective Date are as set forth on Exhibit
              10.1. The Chairperson of the Joint Steering Committee at the first
              meeting of the Joint Steering Committee shall be an Enzon member
              of the Joint Steering Committee, and thereafter, the Chairperson
              will alternate at each meeting between a representative of Inex
              and a representative of Enzon. The Chairperson shall be
              responsible for issuing an agenda for the meeting, conducting and
              chairing the meeting and preparing the minutes for the meeting,
              and such other tasks as assigned by the committee. The Joint
              Steering Committee shall meet regularly:

              (a)       at least quarterly during the period when
                        Commercialization is occurring, or more frequently if
                        necessary; and

              (b)       at such periods to be determined by the Joint Steering
                        Committee.

      10.1.2  Each Party shall bear its own expenses associated with its
              participation in the Joint Steering Committee and its
              administration and oversight of the activities contemplated by
              this Agreement. Such expenses shall not be included in
              Commercialization Costs.

*** Indicates the omission of confidential material pursuant to a request for
confidential treatment made in accordance with Rule 24b-2 under the Securities
Exchange Act of 1934, as amended. The Confidential material is being filed
separately with the Secretary to the Securities and Exchange Commission.

<PAGE>
                                     - 32 -

10.2  Meetings of the Joint Steering Committee

      10.2.1  The Joint Steering Committee should meet at least once per year at
              the location of Inex or an Affiliate of Inex, and once per year at
              a location of Enzon or an Affiliate of Enzon. All other meetings
              of the Joint Steering Committee may occur by telephone, video
              conference or other acceptable means if requested by a Party. The
              Joint Steering Committee shall oversee all Commercialization
              activities of the Parties under this Agreement, including
              coordinating the overall strategy for Commercialization. The Joint
              Steering Committee shall have the responsibilities as set forth
              generally in Exhibit 10.1. Each Party may appoint its
              representatives to the Joint Steering Committee and other members
              of its project team at its discretion. The Joint Steering
              Committee shall act only as a body making recommendations to the
              Parties, and neither Party is bound by any recommendation of the
              Joint Steering Committee. The members of the Joint Steering
              Committee shall attempt, in good faith, to reach consensus on all
              matters before the committee and make a consensus recommendation
              to the Parties. In the event that the Joint Steering Committee
              cannot make a consensus recommendation to the Parties which is
              acceptable to the Parties, either Party may refer the matter for
              resolution in accordance with the terms of Article 16.

      10.2.2  The Joint Steering Committee shall cause there to be recorded
              reasonably detailed minutes of its meetings. The Party providing
              the chairperson of each meeting shall be responsible for preparing
              draft minutes of such meeting and distributing same to the other
              members of the committee within five Business Days after such
              meeting. If the other Party desires to revise the draft minutes it
              will provide comments on such minutes within ten Business Days
              after receiving the minutes. If such comments are provided,
              members of the Joint Steering Committee designated by each Party
              shall confer promptly and in good faith to resolve such comments
              and finalize the minutes. If the members of the Joint Steering
              Committee are unable to finalize the minutes within 30 days after
              the date of the meeting, either Party may refer the matter for
              resolution in accordance with the terms of Article 16.

10.3  Working Committees

The Joint Steering Committee may establish working committees to oversee the
Commercialization. Such working committees will conduct at a minimum quarterly
planning and review meetings as well as ad hoc meetings as necessary. The
primary method of meeting will be teleconference. Responsibilities of the
working committees may include overseeing the planning and monitoring of the
manufacturing and supply issues arising under this Agreement.

                Article 11 Pharmacovigilance, DDMAC and Recalls

11.1  Regulatory Responsibilities

Inex will be responsible for maintaining and fulfilling all Regulatory
Requirements with respect to the Product that are imposed upon Inex as the
manufacturer and holder of the Regulatory Approvals. Subject to the other
express terms of the Related Agreements, Enzon and its designees will have sole
responsibility for the advertising and other promotion of the Product and for
maintaining and fulfilling all Regulatory Requirements with respect to the
Product that are imposed upon Enzon as the advertiser, marketer and distributor
thereof.

*** Indicates the omission of confidential material pursuant to a request for
confidential treatment made in accordance with Rule 24b-2 under the Securities
Exchange Act of 1934, as amended. The Confidential material is being filed
separately with the Secretary to the Securities and Exchange Commission.

<PAGE>
                                     - 33 -

11.2  Pharmacovigilance Agent

      11.2.1  Unless the Parties agree to establish the agency referred to in
              Section 11.2.2 on an accelerated basis, Inex shall be responsible
              for performing Pharmacovigilance in respect of all pre-Regulatory
              Approval Clinical Activities (in addition to all other Regulatory
              Activities for which Inex is responsible). Until this agency is
              established, if Enzon receives any information of any type
              whatsoever that may constitute a complaint regarding the Product
              or indicates that the Product in any way relates to an Adverse
              Drug Event, then it will record the information set forth on
              Exhibit 1.1.1 and transmit the completed form to Inex as soon as
              possible, and in any event at least in time to allow Inex to meet
              its reporting obligations under Regulatory Requirements. Inex will
              then report the Adverse Drug Event in accordance with Regulatory
              Requirements, and provide Enzon with a copy(ies) of all
              documentation provided to Regulatory Authorities in respect of
              such complaint or Adverse Drug Event. Further, until this agency
              is established, if Inex receives any information of any type
              whatsoever that may constitute a complaint regarding the Product
              or indicates that the Product in any way relates to an Adverse
              Drug Event, then it will record the information set forth on
              Exhibit 1.1.1, provide a copy of the completed form to Enzon (if
              possible, prior to submitting it to Regulatory Authorities) and
              report the Adverse Drug Event in accordance with Regulatory
              Requirements.

      11.2.2  After Regulatory Approval of the Products by a Regulatory
              Authority (or sooner if and to the extent agreed to by the
              Parties), Enzon shall be appointed by Inex as Inex's agent with
              respect to the regulatory dossier for the Product in the Field in
              the Territory for the sole purpose of conducting
              Pharmacovigilance. After this agency has been established, Enzon
              shall manage and carry out on behalf of Inex all relevant
              communications and relations with Regulatory Authorities to the
              extent related to Pharmacovigilance with respect to the Product.
              Inex shall be entitled to participate in all negotiations and
              discussions between Enzon and Regulatory Authorities relating to
              Pharmacovigilance with respect to the Product. Without limiting
              the generality of the foregoing, after this agency has been
              established, if Inex receives any information of any type
              whatsoever that may constitute a complaint regarding the Product
              or indicates that the Product in any way relates to an Adverse
              Drug Event, then it will record the information set forth on
              Exhibit 1.1.1 and transmit the completed form to Enzon as soon as
              possible, and in any event at least in time to allow Enzon to meet
              its reporting obligations under Regulatory Requirements. Enzon
              will then report the Adverse Drug Event in accordance with
              Regulatory Requirements, and provide Inex with a copy(ies) of all
              documentation provided to Regulatory Authorities in respect of
              such complaint or Adverse Drug Event. Further, after this agency
              has been established, if Enzon receives any information of any
              type whatsoever that may constitute a complaint regarding the
              Product or indicates that the Product in any way relates to an
              Adverse Drug Event, then it will record the information set forth
              on Exhibit 1.1.1, provide a copy of the completed form to Inex (if
              possible, prior to submitting it to Regulatory Authorities) and
              report the Adverse Drug Event in accordance with Regulatory
              Requirements.

11.3  Agency for DDMAC Activities and the Like

      11.3.1  Inex hereby appoints Enzon as its agent for the Product in the
              Field in the Territory for the sole purpose of conducting all
              DDMAC Activities in the USA and the foreign equivalents in the
              remainder of the Territory.

      11.3.2  Enzon shall perform the DDMAC Activities in the USA and the
              foreign equivalents in the remainder of the Territory in
              compliance with Regulatory Requirements.

*** Indicates the omission of confidential material pursuant to a request for
confidential treatment made in accordance with Rule 24b-2 under the Securities
Exchange Act of 1934, as amended. The Confidential material is being filed
separately with the Secretary to the Securities and Exchange Commission.

<PAGE>
                                     - 34 -

      11.3.3  Enzon will perform all DDMAC Activities in the USA and the foreign
              equivalents in the remainder of the Territory and subject to
              Section 11.2, be responsible for all post-approval
              Pharmacovigilance activities, and assume all the costs associated
              therewith.

      11.3.4  In each country for which Inex is the holder of the Regulatory
              Approval, Enzon shall regularly inform Inex of Enzon's DDMAC
              Activities and foreign equivalents and obtain Inex's prior consent
              to Enzon's DDMAC Activities and foreign equivalents and plans
              respecting any of them. In the event Enzon informs Inex of its
              DDMAC Activities, foreign equivalents and plans, and does not
              receive a written objection from Inex within 10 Business Days,
              Inex shall be deemed to have consented to such activities and
              plans.

11.4  Agent for Regulatory Authorities Generally

      11.4.1  Nothing in Sections 11.2, 11.3 or this Section 11.4 precludes Inex
              from appointing an agent for Regulatory Authorities for products
              other than the Product, or for territories outside the Territory.

      11.4.2  All activities, communications and relations as well as Enzon's
              role as agent for Regulatory Authorities shall be performed by
              Enzon in close coordination with Inex, as holder of the Regulatory
              Approvals.

      11.4.3  In respect of all of the foregoing under Sections 11.2, 11.3 or
              this Section 11.4, except as required by Regulatory Requirements
              and except for those reporting requirements which have timeliness
              requirements that make it impossible to seek and obtain Inex's
              consent prior to making such report, any communications with
              Regulatory Authorities by Enzon under Sections 11.2, 11.3 or this
              Section 11.4 are subject to the consent of the Inex, such consent
              not to be unreasonably withheld.

11.5  Recalls and Withdrawals of Product

      11.5.1  If Inex or Enzon will be required or requested by any Regulatory
              Authority to recall any Product for any reason, or should Enzon
              decide voluntarily to withdraw any Product:

              (a)       Enzon will be responsible for co-ordinating such recall
                        or withdrawal;

              (b)       Enzon shall pay the costs and expenses of such recall or
                        withdrawal, subject to recovery of some or all of same
                        in accordance with the terms of Section 11.5.2;

              (c)       unless Inex is liable for such costs and expenses in
                        accordance with the terms of Section 11.5.2, Enzon will
                        remain responsible to Inex for the Purchase Price for
                        such Product and will reimburse Inex for all of the
                        reasonable costs and expenses actually incurred by Inex
                        in connection with such recall or withdrawal including,
                        but not limited to, administration of the recall or
                        withdrawal and such other reasonable costs as may be
                        reasonably related to the recall or withdrawal; and

              (d)       both Parties will cooperate fully with one another in
                        connection with any such recall or withdrawal.

      11.5.2  If a recall or withdrawal is due to Inex's negligence, wilful
              misconduct or breach of this Agreement or Inex's failure to
              Manufacture the Product in conformity with the Specifications or
              the provisions of this Agreement or the Quality/Technical
              Agreement referred to in Section 4.6, Inex will reimburse Enzon
              for all of Enzon's reasonable costs

*** Indicates the omission of confidential material pursuant to a request for
confidential treatment made in accordance with Rule 24b-2 under the Securities
Exchange Act of 1934, as amended. The Confidential material is being filed
separately with the Secretary to the Securities and Exchange Commission.

<PAGE>
                                     - 35 -

              and expenses actually incurred by Enzon in connection with the
              recall or withdrawal, including the Purchase Price for the
              recalled or withdrawn Product, costs of retrieving Product already
              delivered to customers, costs and expenses Enzon is required to
              pay for notification, shipping and handling charges, destruction
              or return of the defective Product or Product and such other
              reasonable costs as may be reasonably related to the recall or
              withdrawal.

      11.5.3  If the Parties are unable to agree on whether or not a recall or
              withdrawal is due to Inex's negligence, wilful misconduct or
              breach of this Agreement, either Party may refer the matter for
              resolution pursuant to Article 16.

11.6  Replacement Shipments

In the event of a recall or withdrawal of Product, and upon Enzon's request,
Inex shall use Commercially Reasonable Efforts to deliver replacement Product as
soon as reasonably possible.

                    Article 12 Restrictive Covenants; Title

12.1  Injunctive Relief

Each Party acknowledges the competitive and technical value and the sensitive
and confidential nature of the Confidential Information and agrees that monetary
damages alone will be inadequate to protect the other Party's interests against
any actual or threatened material breach of this Agreement. Accordingly, each
Party consents to the granting of specific performance and injunctive or other
equitable relief to the other Party in respect of any actual or threatened
breach of this Agreement, without proof of actual damages.

12.2  Ownership of Pre-Existing Intellectual Property Rights

Any Intellectual Property Rights or trademark rights owned by either Party prior
to the Effective Date shall remain solely owned by such Party.

12.3  Ownership of Intellectual Property Rights in the Product

All Intellectual Property Rights arising from and during the course of the
Commercialization or Co-Promotion, including all Intellectual Property Rights:

      12.3.1  to all inventions arising from and during the course of the
              Commercialization or Co-Promotion;

      12.3.2  to all data, information, know-how and results and the like
              created as part of the Commercialization or Co-Promotion (the
              "Data"); and

      12.3.3  relating to the Product or improvements thereto or the process for
              manufacturing the Product;

shall be solely owned by Inex or its designee, regardless of:

      12.3.4  which Party(ies) created or invented the same; and

      12.3.5  whether or not such Intellectual Property Rights are required to
              obtain and maintain Regulatory Approvals;

*** Indicates the omission of confidential material pursuant to a request for
confidential treatment made in accordance with Rule 24b-2 under the Securities
Exchange Act of 1934, as amended. The Confidential material is being filed
separately with the Secretary to the Securities and Exchange Commission.

<PAGE>
                                     - 36 -

and shall be licensed to Enzon hereunder as Licensed Patents and Inex Technology
without additional consideration or formality during the Term. Without limiting
the generality of the foregoing, any Elan Improvements made by Enzon, or its
Representatives, regardless of whether or not arising from and during the course
of the Commercialization or Co-Promotion, shall be solely owned by Elan and
sublicensed (within the Field and within the Territory) without additional
consideration to Enzon through Inex on the terms set out in this Section. Enzon
shall cooperate, and shall cause its Representatives to cooperate, with Inex and
Elan, at Inex's expense, in perfecting Elan's ownership and other proprietary
rights in respect of any Elan Improvements and shall execute and deliver, and
cause its Representatives to execute and deliver, to Elan any documents that
Elan may reasonably require with respect thereto. If at any time Elan does not
exercise its rights under this Section, such rights may be exercised by Inex as
if Inex were Elan under this Section.

12.4  Ownership of Regulatory Approvals and Regulatory Submissions

Notwithstanding the terms of Section 12.3:

      12.4.1  Inex or an Affiliate of Inex will own all Regulatory Approvals and
              Regulatory Submissions made as part of the Commercialization or
              Co-Promotion in respect of the Product in the Territory and all
              Intellectual Property Rights in same; and

      12.4.2  Inex may use all Data and Regulatory Approvals and Regulatory
              Submissions without further consideration, in Inex's efforts to
              register and commercialize the Product outside the Territory and
              inside the Territory but outside the Field.

12.5  Ownership of Intellectual Property Rights Outside the Commercialization
      and Co-Promotion

Except as otherwise provided in Sections 12.3 and 12.4, and subject to
provisions of the Development Agreement, each Party shall have and retain sole
and exclusive title to all inventions, discoveries and know-how which are made,
conceived, reduced to practice or generated by its Representatives. For greater
certainty, Intellectual Property Rights or inventions or creations generated
outside the Commercialization and Co-Promotion and without access to the other
Party's Confidential Information shall not be licensed hereunder as or included
in the Licensed Patents or Inex Technology.

12.6  Co-operation

Enzon shall make available to Inex or Inex's authorized attorneys any Enzon
Representatives whom Inex in its reasonable judgment deems necessary in order to
assist it in obtaining patent protection of the Licensed Patents and any
applications therefor. Enzon shall execute all legal documents reasonably
necessary to support the filing, prosecution and maintenance of said Patents.
Enzon shall, at the request of Inex, enter into such further agreements and
execute any and all documents as may reasonably be required to ensure that
ownership of the Licensed Patents remains with Inex.

12.7  Prosecution and Maintenance of Licensed Patents

      12.7.1  Inex shall be responsible for and pay all future costs of
              prosecuting and maintaining the Licensed Patents.

      12.7.2  Subject to Inex's obligations to its licensors, if Inex decides to
              abandon prosecution or maintenance of a particular Licensed Patent
              whose claims relate directly to the Field, Inex will notify Enzon
              of such decision as soon as reasonably possible, and in any event
              no less than 30 days prior to the effective abandonment date. As
              for patent applications, upon receiving such notice, Enzon may
              request that Enzon have the right to continue such prosecution of
              such patent application, which request Inex will reasonably
              consider,

*** Indicates the omission of confidential material pursuant to a request for
confidential treatment made in accordance with Rule 24b-2 under the Securities
Exchange Act of 1934, as amended. The Confidential material is being filed
separately with the Secretary to the Securities and Exchange Commission.

<PAGE>
                                     - 37 -

              but Inex need not grant such request in any event if Inex has a
              strategic reason, with respect to its prosecution strategy for its
              Patents, for abandoning such patent applications. As for issued
              patents, upon receiving such notice, Enzon will have the right at
              its sole discretion, to direct Inex to continue payment of
              maintenance fees of any such issued patents, at Enzon's expense.

12.8  Notice of Inventions

Each Party will report promptly any inventions or anything giving rise to
Intellectual Property Rights arising in the course of and in connection with the
Development, Commercialization or Co-Promotion to the other Party. Without
limiting the generality of the foregoing, Enzon shall promptly notify Inex of
any Elan Improvements, and Inex will notify Elan of such Elan Improvements.

12.9  ***

12.10 Elan a Third Party Beneficiary

The Parties agree that Elan is a third party beneficiary under this Agreement
and shall have the right (at its option) to directly enforce any obligations for
the benefit of Elan contained in this Agreement.

                         Article 13 Allocation of Risk

13.1  Limits

Except as expressly set out in the Related Agreements, nothing in the Related
Agreements shall be construed as:

      13.1.1  a warranty or representation by Inex as to title to the Licensed
              Patents and Inex Technology or that anything made, used, sold or
              otherwise disposed of under the license granted in the Related
              Agreements is or will be free from infringement of patents,
              copyrights, trade-marks, industrial design or other intellectual
              property rights;

      13.1.2  a warranty or representation by Inex that any patents covered by
              the Related Agreements are valid or enforceable;

      13.1.3  an obligation by Inex to bring or prosecute or defend actions or
              suits against Third Parties for infringement of patents,
              copyrights, trade-marks, industrial designs or other intellectual
              property or contractual rights;

      13.1.4  the conferring by Inex of the right to use in advertising or
              publicity the name of Inex or its trade marks;

      13.1.5  a warranty or representation by Enzon that anything made, used,
              sold or otherwise disposed of under the license granted in the
              Related Agreements is or will be free from infringement of
              patents, copyrights, trade-marks, industrial design or other
              intellectual property rights; or

      13.1.6  the conferring by Enzon of the right to use in advertising or
              publicity the name of Enzon or its trade marks.

*** Indicates the omission of confidential material pursuant to a request for
confidential treatment made in accordance with Rule 24b-2 under the Securities
Exchange Act of 1934, as amended. The Confidential material is being filed
separately with the Secretary to the Securities and Exchange Commission.

<PAGE>
                                     - 38 -

13.2  ***

13.3  ***

13.4  Co-operation with Other Licensees

Enzon acknowledges that Inex or its Affiliates have granted rights:

      13.4.1  in the Territory in respect of fields outside the Field, and

      13.4.2  outside the Territory,

and may grant to other sublicensees rights:

      13.4.3  in the Territory in respect of fields outside of the Field, or

      13.4.4  outside the Territory,

similar to those granted to Enzon under Sections 13.2, 13.3 and this Section
13.4. In the event of any litigation of the kind described in Sections 13.2 and
13.3:

      13.4.5  inside the Territory in fields outside of the Field, or outside
              the Territory, that may reasonably affect Enzon's use in the
              Territory of the Licensed Patents or Inex Technology in the Field
              or the use or sale of the Product; or

      13.4.6  in respect of the Field that may reasonably affect Inex or one or
              more of Inex's or its Affiliates' sublicensee's use of the
              Licensed Patents or Inex Technology outside the Field or outside
              the Territory or the manufacture, use or sale of products outside
              the Field or outside the Territory by Inex, its Affiliates, or one
              or more other such sublicensee(s);

then Inex, Enzon and such other sublicensees will use good faith efforts to
consult with each other and consider the interests of the other parties in
determining the course of action, if any, necessary or appropriate to prosecute
or defend the litigation. Inex will use Commercially Reasonable Efforts to
include in its sublicense agreements, provisions that allow the participation of
Enzon as contemplated herein.

              Article 14 Indemnification and Liability Limitations

14.1  Indemnification by Enzon

      14.1.1  Enzon hereby agrees that it shall be responsible for, indemnify,
              hold harmless and defend Inex and its Affiliates, and their
              respective shareholders, partners, Representatives, and their
              respective heirs, successors and assigns (collectively, the "Inex
              Indemnitees") from and against any and all claims, demands,
              losses, liabilities, damages, Development Costs and expenses
              (including reasonable legal fees) (collectively, "Losses")
              suffered or incurred by any Inex Indemnitee arising out of,
              relating to, resulting from or in connection with:

              (a)       any claim by Enzon's employees arising out of the
                        employment by Enzon of such employees and related to the
                        employment relationship or termination thereof; or

              (b)       any Third Party claims arising out of or relating to:

*** Indicates the omission of confidential material pursuant to a request for
confidential treatment made in accordance with Rule 24b-2 under the Securities
Exchange Act of 1934, as amended. The Confidential material is being filed
separately with the Secretary to the Securities and Exchange Commission.

<PAGE>
                                     - 39 -

                        (i)   the breach of any representation or warranty made
                              by Enzon in any of the Related Agreements;

                        (ii)  the default by Enzon in the performance or
                              observance of any of its obligations to be
                              performed or observed under any of the Related
                              Agreements;

                        (iii) the breach by Enzon, its Affiliates or
                              Sublicensees of any Regulatory Requirements in
                              connection with the Product or in the performance
                              or observance of any of its obligations to be
                              performed or observed under any Related Agreement;
                              or

                        (iv)  the negligence or wilful misconduct of Enzon or
                              its Representatives.

      14.1.2  The foregoing shall not apply to the extent that such Losses are
              due to:

              (a)       the breach of any representation or warranty made by
                        Inex in the Related Agreements;

              (b)       the default by Inex in the performance or observance of
                        any of its obligations to be performed or observed under
                        the Related Agreements;

              (c)       the breach by Inex of any Regulatory Requirements in
                        connection with the Product or in the performance or
                        observance of any of its obligations to be performed or
                        observed under the Related Agreements; or

              (d)       the negligence or wilful misconduct of Inex or its
                        Representatives.

14.2  Indemnification by Inex

      14.2.1  Inex hereby agrees that it shall be responsible for, indemnify,
              hold harmless and defend Enzon and Enzon's Affiliates and
              Sublicensees, and their respective shareholders, partners,
              Representatives, and their respective heirs, successors and
              assigns (collectively, the "Enzon Indemnitees"), from and against
              any and all Losses suffered or incurred by any Enzon Indemnitee
              arising out of, relating to, resulting from or in connection with:

              (a)       any claim by Inex's employees arising out of the
                        employment by Inex of such employees and related to the
                        employment relationship or termination thereof; or

              (b)       any Third Party claims arising out of or relating to:

                        (i)   the breach of any representation or warranty made
                              by Inex in any Related Agreement;

                        (ii)  Inex's failure to convey to Enzon Intellectual
                              Property Rights under the Regents' Patents at
                              least co-extensive (within the Field and within
                              the Territory as defined in the Related
                              Agreements) with the scope of the Intellectual
                              Property Rights under the Regents' Patents
                              purported to be granted by Elan to IE pursuant to
                              the Elan License;

                        (iii) the default by Inex in the performance or
                              observance of any of its obligations to be
                              performed or observed under any Related Agreement;

*** Indicates the omission of confidential material pursuant to a request for
confidential treatment made in accordance with Rule 24b-2 under the Securities
Exchange Act of 1934, as amended. The Confidential material is being filed
separately with the Secretary to the Securities and Exchange Commission.

<PAGE>
                                     - 40 -

                        (iv)  the breach by Inex of any Regulatory Requirements
                              in connection with the Product or in the
                              performance or observance of any of its
                              obligations to be performed or observed under any
                              Related Agreement; or

                        (v)   the negligence or wilful misconduct of Inex or its
                              Representatives.

      14.2.2  The foregoing shall not apply to the extent that such Losses are
              due to:

              (a)       the breach of any representation or warranty made by
                        Enzon in the Related Agreements;

              (b)       the default by Enzon in the performance or observance of
                        any of its obligations to be performed or observed under
                        the Related Agreements;

              (c)       the breach by Enzon, its Affiliates or Sublicensees of
                        any Regulatory Requirements in connection with the
                        Product or in the performance or observance of any of
                        its obligations to be performed or observed under the
                        Related Agreements; or

              (d)       the negligence or wilful misconduct of Enzon or its
                        Representatives.

14.3  Notice of Claims

In the event that a claim is made pursuant to Section 14.1 or 14.2 above against
any person or entity which seeks indemnification hereunder (the "Indemnitee"),
the Indemnitee shall give the indemnifying Party (the "Indemnitor") prompt
notice of any claim or lawsuit or other action for which it seeks to be
indemnified under this Agreement and agrees that the Indemnitor shall not have
any obligation under the relevant Section unless:

      14.3.1  the Indemnitor is granted, subject to the provisions of this
              Section 14.3 and the relevant provisions of Article 13, full
              authority and control over the defense, including settlement,
              against such claim or law suit or other action, and

      14.3.2  the Indemnitee cooperates fully with the Indemnitor and its agents
              in defense of the claims or law suit or other action.

The Indemnitee shall have the right to participate in the defense of any such
claim, complaint, suit, proceeding or cause of action referred to in this
Section utilizing attorneys of its choice, at its own expense, provided however,
that the Indemnitor shall, subject to the provisions of this Section 14.3 and
the relevant provisions of Article 13, have full authority and control to handle
any such claim, complaint, suit proceeding, or cause of action, including any
settlement or other disposition thereof, for which the Indemnitee seeks
indemnification under this Section, provided however, subject to the following
sentence, that no settlement or consent judgment or other voluntary final
disposition may be entered into without the consent of the Indemnitee if such
settlement would require the Indemnitee to be subject to an injunction or to
make a monetary payment or would restrict the claims in or admit any invalidity
of any Licensed Patent(s) or significantly adversely affect the rights of the
Indemnitee.

14.4  Consequential Losses

NO PARTY WILL BE LIABLE FOR CONSEQUENTIAL OR INCIDENTAL DAMAGES OF ANY NATURE
ARISING FROM SUCH PARTY'S ACTIVITIES UNDER THE RELATED AGREEMENTS; PROVIDED,
HOWEVER, THAT THIS LIMITATION SHALL NOT LIMIT THE INDEMNIFICATION

*** Indicates the omission of confidential material pursuant to a request for
confidential treatment made in accordance with Rule 24b-2 under the Securities
Exchange Act of 1934, as amended. The Confidential material is being filed
separately with the Secretary to the Securities and Exchange Commission.

<PAGE>
                                     - 41 -

OBLIGATION OF SUCH PARTY UNDER SECTIONS 14.1 OR 14.2 FOR CONSEQUENTIAL OR
INCIDENTAL DAMAGES RECOVERED BY A THIRD PARTY.

14.5  Actions Between the Parties

For the avoidance of doubt, in connection with actions brought by one Party
hereto against the other (whether for breach of any provisions hereof, any
representation or warranty made herein or otherwise), each Party expressly
reserves all of its rights and remedies under Applicable Law, including, without
limitation, the right to sue for breach of contract.

14.6  Insurance

Except as provided for below, for the term of this Agreement and for a period of
five years after the expiration of this Agreement or the earlier termination
thereof, each of the Parties shall obtain and maintain, and shall cause their
respective Affiliates and any Sublicensees to obtain and maintain, at their
respective sole cost and expense, comprehensive general liability insurance,
including product liability insurance on the Products, in amounts, which are
reasonable and customary in the USA pharmaceutical industry for companies of
comparable size and activities, but in no event less than ***. To the extent
reasonably practicable, this insurance shall include the other Party and their
respective Representatives as additional insureds. Each Party shall provide
written proof of the existence of such insurance to the other Party upon
request. If a Party maintains clinical trial insurance separate from its product
liability insurance, which clinical trial insurance is in an amount that is
reasonable and customary in the US pharmaceutical industry for companies of
comparable size and activities, then the product liability insurance need not
commence until FDA approval.

              Article 15 Confidential Information and Publication

15.1  Treatment of Confidential Information

Each Party hereto shall maintain the Confidential Information of the other Party
in confidence, and shall not disclose, divulge or otherwise communicate such
Confidential Information to others, or use it for any purpose, except pursuant
to, and in order to carry out, the terms and objectives of the Related
Agreements, and hereby agrees to exercise every reasonable precaution to prevent
and restrain the unauthorized disclosure of such Confidential Information by any
of its Representatives.

15.2  Permitted Disclosures

      15.2.1  Either Party may disclose the Confidential Information of the
              other Party to its permitted Representatives to facilitate or
              carry out the activities under the Related Agreements, provided
              that such Third Parties enter into an agreement with such Party
              which contains confidentiality provisions substantially the same
              as those set forth herein, and such Party remains liable to the
              other Party for the breach of such terms by such Party's
              Representatives.

      15.2.2  Either Party may disclose the Confidential Information of the
              other Party to its attorneys, accountants or other advisors, or
              actual or potential lenders, investors or purchasers, each of whom
              is subject to confidentiality restrictions similar to those set
              forth herein and such Party remains liable to the other Party for
              the breach of such terms by such persons.

      15.2.3  Either Party may disclose the Confidential Information of the
              other Party to the extent such disclosure is required to be
              disclosed by the receiving Party to comply with Applicable Laws,
              to defend or prosecute litigation or to comply with governmental

*** Indicates the omission of confidential material pursuant to a request for
confidential treatment made in accordance with Rule 24b-2 under the Securities
Exchange Act of 1934, as amended. The Confidential material is being filed
separately with the Secretary to the Securities and Exchange Commission.

<PAGE>
                                     - 42 -

              regulations, provided that the receiving Party provides prior
              written notice of such disclosure to the other Party and takes
              reasonable and lawful actions to avoid and/or minimize the degree
              of such disclosure, and provided further that disclosure of such
              Confidential Information pursuant to this Section shall not
              relieve the receiving Party of continued adherence to Section 15.1
              with respect to such Confidential Information.

15.3  Publications Generally

The following restrictions shall apply with respect to the disclosure in
scientific journals or publications or speeches by any Party or any employee or
consultant of any Party relating to the inventions contained in the Licensed
Patents and the Inex Technology or to the activities or results of the
Development, Manufacture or Commercialization:

      15.3.1  a Party (the "Publishing Party") shall provide the other Party
              with an advance copy of any proposed publication and such other
              Party shall have a reasonable opportunity to recommend any changes
              it reasonably believes are necessary to preserve Intellectual
              Property Rights or Confidential Information belonging in whole or
              in part to Inex or Enzon, and the incorporation of such
              recommended changes shall not be unreasonably refused; and

      15.3.2  if such other Party informs the Publishing Party, within fifteen
              (15) Business Days after receipt of an advance copy of a proposed
              publication, that such publication in its reasonable judgment
              could be expected to have a material adverse effect on any
              Intellectual Property Rights or Confidential Information belonging
              in whole or in part to Inex or Enzon, the Publishing Party shall
              delay or prevent such publication as proposed. In the case of
              inventions, the delay shall be sufficiently long to permit the
              timely preparation and filing of a patent application(s) or
              application(s) for a certificate of invention on the information
              involved but not less than ninety (90) days or more than 120 days.

Nothing in this Section 15.3 shall apply to Promotional Materials approved for
use in accordance with the Co-Promotion Agreement.

15.4  No Limitation on Regulatory Compliance

Nothing in the Related Agreements shall be construed as preventing or in any way
inhibiting either Party from complying with Regulatory Requirements governing
the development, manufacture, use and sale or other distribution of Product in
the Territory in any manner which it reasonably deems appropriate, including,
for example, by disclosing to Regulatory Authorities confidential or other
information received from the other Party.

                         Article 16 Dispute Resolution

16.1  Negotiation

Subject to Section 12.1 of this Agreement:

      16.1.1  If a dispute or controversy regarding any right or obligation
              under the Related Agreements arises between the Parties and cannot
              be resolved within fifteen (15) days of the dispute or
              controversy, or within such other period as may be agreed by the
              Parties, the Parties will seek to resolve such dispute or
              controversy or failure to agree by good

*** Indicates the omission of confidential material pursuant to a request for
confidential treatment made in accordance with Rule 24b-2 under the Securities
Exchange Act of 1934, as amended. The Confidential material is being filed
separately with the Secretary to the Securities and Exchange Commission.

<PAGE>
                                     - 43 -

              faith negotiation between senior management representatives of the
              Parties, to be commenced promptly after such dispute or
              controversy or failure to agree arises.

      16.1.2  If such dispute or controversy or failure to agree is not resolved
              by such negotiation within thirty (30) days after written notice
              by one Party to the other, and at least one Party requires such
              resolution, then the Parties shall proceed as follows: any
              unresolved dispute, controversy, action, claim or proceeding
              initiated by either Party (other than a Third Party action, claim
              or other proceeding in a bona fide action, claim or other
              proceeding initiated by a Third Party against a Party) relating
              to, arising out of or resulting from any Related Agreement, or the
              performance by either Party of its obligations under any Related
              Agreement, or any alleged breach, termination or invalidity of any
              Related Agreement, whether before or after termination or
              expiration of any Related Agreement, shall be finally resolved by
              binding arbitration pursuant to Section 16.2.

16.2  Arbitration

Subject to Section 12.1 of this Agreement, in the event of any unresolvable
dispute, difference, or question arising between the Parties in connection with
the Related Agreements or any clause or the construction thereof, or the rights,
duties or liabilities of either Party, or the scope or validity of any patent
licensed hereunder, the matter shall be submitted for arbitration in accordance
with the rules of the American Arbitration Association. Such arbitration shall
take place in Chicago, Illinois or as otherwise agreed by the Parties. A single
arbitrator shall be appointed by agreement of the Parties to resolve all such
disputes, differences or questions. The arbitrator shall be guided by the
contents of the Related Agreements in arriving at a decision to resolve the
dispute, but may rely on extrinsic evidence where appropriate and/or necessary.
The arbitrator's resolution must be pursuant to and consistent with the laws of
Delaware. The Parties shall share the cost of the arbitration unless, in the
arbitrator's opinion, the position advanced by one of the Parties, or the nature
or manner of presenting it, is such that it would be unfair to so apportion such
expenses, in which case the arbitrator may apportion such expenses differently.

16.3  Consent to Jurisdiction

Subject to Section 12.1 of this Agreement, the parties hereto irrevocably
consent to the non-exclusive personal jurisdiction of any state or federal court
in the Northern District of Illinois for the enforcement of any arbitration
award arising under the Related Agreements.

                             Article 17 Termination

17.1  Term of Agreement

This Agreement shall become effective on the Effective Date and, unless earlier
terminated as provided for herein, shall expire, on a country-by-country basis,
upon the later of:

      17.1.1  expiration of the last to expire of the Licensed Patents
              containing Valid Claims covering the Product in such country in
              the Territory; and

      17.1.2  fifteen years from the date of the First Commercial Sale in that
              country;

and such period shall be the "Term" under this Agreement.

*** Indicates the omission of confidential material pursuant to a request for
confidential treatment made in accordance with Rule 24b-2 under the Securities
Exchange Act of 1934, as amended. The Confidential material is being filed
separately with the Secretary to the Securities and Exchange Commission.

<PAGE>
                                     - 44 -

17.2  Renewal

On or before six months before the expiration of this Agreement in accordance
with its terms in any country in the Territory, Enzon may notify Inex in writing
that Enzon wishes to renew this Agreement. In the event that Enzon so notifies
Inex, the Parties will negotiate in good faith for the extension of the Term. If
the Parties have not reached agreement in writing to extend the Term on or
before the expiry of the Term in such country, this Section 17.2 shall be of no
further force or effect.

17.3  Termination for Breach

Each Party shall be entitled to terminate this Agreement by written notice to
the other Party in the event that the other Party shall be in material default
of any of its obligations hereunder, and shall fail to remedy any such default
within ninety (90) days after notice thereof by the non-breaching Party. Any
such notice shall specifically state that the non-breaching Party intends to
terminate this Agreement in the event that the breaching Party shall fail to
remedy the default. Any such notice shall set out expressly the actions required
of the breaching Party to remedy the default. If such default is not corrected,
the non-breaching Party shall have the right to terminate this Agreement by
giving written notice to the Party in default provided the notice of termination
is given within six (6) months of the default and prior to correction of the
default.

17.4  Termination upon Bankruptcy

      17.4.1  This Agreement may be terminated by a Party by providing written
              notice to the other Party upon:

              (a)       the bankruptcy, liquidation or dissolution of the other
                        Party;

              (b)       the filing of any voluntary petition for bankruptcy,
                        dissolution, liquidation or winding-up of the affairs of
                        the other Party; or

              (c)       the filing of any involuntary petition for bankruptcy,
                        dissolution, liquidation or winding-up of the affairs of
                        the other Party which is not dismissed within one
                        hundred twenty (120) days after the date on which it is
                        filed or commenced.

      17.4.2  Notwithstanding the foregoing, either Party may seek the waiver of
              the operation of Section 17.4.1 in advance of any event giving
              rise to a right of termination under Section 17.4.1(b), and,
              provided that:

              (a)       the requesting Party is in good standing and not in
                        breach of any of the terms of the Related Agreements;

              (b)       the requesting Party is in reasonable financial
                        condition; and

              (c)       the Party whose consent is sought will not be prejudiced
                        by granting such waiver,

              the Party whose consent is sought will not unreasonably withhold
              its consent to such waiver. Such waiver may be revocable in the
              event of a material adverse change in circumstances related to the
              requesting Party not contemplated at the time of granting the
              waiver.

17.5  Termination of Related Agreements

In the event of termination of this Agreement, the Related Agreements shall
terminate with immediate effect, subject to any continuing or surviving
obligations as set forth in each such Related Agreement.

*** Indicates the omission of confidential material pursuant to a request for
confidential treatment made in accordance with Rule 24b-2 under the Securities
Exchange Act of 1934, as amended. The Confidential material is being filed
separately with the Secretary to the Securities and Exchange Commission.

<PAGE>
                                     - 45 -

17.6  Effect of Termination

The termination of this Agreement for any reason will be without prejudice to:

      17.6.1  at Enzon's option and request, and subject to the terms of this
              Agreement, Inex shall continue to perform its obligations
              hereunder in respect of any Purchase Orders delivered to Inex
              prior to the effective date of such termination, and Enzon will
              pay Inex for any such Product received in accordance with such
              Purchase Order(s);

      17.6.2  Inex's right to receive all payments accrued from Enzon as of the
              effective date of such termination including, but not limited to,
              payment for all Product for which a Purchase Order has been
              received as of the effective date of such termination and for
              which Enzon has elected to have Inex perform its obligations
              hereunder pursuant to Section 17.6.1;

      17.6.3  Inex's right to receive reimbursement for all costs and
              liabilities incurred by Inex as of the date of Inex's receipt of
              Enzon's notice of termination, which cost and liabilities Inex has
              properly and reasonably incurred in exercising good supply chain
              management practices in response to Enzon's Forecast. For greater
              certainty, such costs and liabilities shall include all reasonable
              and necessary non-cancellable obligations entered into prior to
              Inex's receipt of Enzon's notice of termination, but arising after
              Inex's receipt of Enzon's notice of termination; and

      17.6.4  any other legal, equitable or administrative remedies as to which
              either Party may then or thereafter become entitled.

17.7  Consequences of Termination in Certain Circumstances

      17.7.1  In the event of:

              (a)       the termination of this Agreement by Enzon pursuant to
                        Sections 17.3 or 17.4:

                        (i)   Inex hereby provides Enzon permission to provide
                              the FDA and any foreign equivalent of the FDA in
                              the Territory with reference access to Inex's NDA
                              filed or to be filed in the United States, Canada
                              and elsewhere and such other Regulatory
                              Submissions as Enzon may request. In countries in
                              the Territory where required by Regulatory
                              Requirements, Enzon may incorporate Inex's NDA and
                              Regulatory Submissions into Enzon's own
                              submissions;

                        (ii)  Inex will use Commercially Reasonable Efforts, at
                              Enzon's expense, to transfer the Inex Technology
                              then in the possession of Inex to the extent
                              necessary to permit Enzon or its designee to
                              Manufacture the Product. Where the Manufacturing
                              is performed by Third Parties, Inex shall use
                              Commercially Reasonable Efforts to assist Enzon,
                              at Enzon's expense, in dealing with such Third
                              Parties; and

                        (iii) Enzon will buy Inex's raw materials, work in
                              progress and inventory of Product at Inex's cost
                              of same; and

                        (iv)  For up to three years after the effective date of
                              such termination, Inex shall use Commercially
                              Reasonable Efforts to ensure that Enzon has a
                              continuous and uninterrupted supply of Product, on
                              commercially

*** Indicates the omission of confidential material pursuant to a request for
confidential treatment made in accordance with Rule 24b-2 under the Securities
Exchange Act of 1934, as amended. The Confidential material is being filed
separately with the Secretary to the Securities and Exchange Commission.

<PAGE>
                                     - 46 -

                              reasonable terms to the extent under Inex's
                              reasonable control, until Enzon has a reasonably
                              secure alternative source of supply for the
                              Product, provided that Enzon is using Commercially
                              Reasonable Efforts to obtain such an alternative
                              source of supply.

              (b)       termination of this Agreement by Inex pursuant to
                        Sections 17.3 or 17.4, Inex may, on notice in writing to
                        Enzon, do any or all of the following:

                        (i)   cause Enzon to buy Inex's raw materials, work in
                              progress and inventory of Product at Inex's cost
                              of same;

                        (ii)  cause Enzon to assign to Inex any Trademarks and
                              all registrations and applications therefor
                              without additional consideration; and

                        (iii) terminate the license to certain Inex Trademarks
                              set out in Section 9.3.

      17.7.2  Enzon shall within thirty (30) days after the effective date of a
              termination pursuant to this Article 17, notify Inex in writing of
              the amount of the Product which Enzon, its Affiliates and
              Sublicensees then have on hand, the sale of which would, but for
              the termination, be subject to payments to Inex in accordance with
              this Agreement, and Enzon, its Affiliates and Sublicensees shall
              thereupon be permitted during the six (6) month period following
              such termination to sell that amount of the Product, provided that
              Enzon shall pay the aggregate sums owed to Inex pursuant to this
              Agreement thereon at the conclusion of the earlier of the last
              such sale or such period.

17.8  Additional Consequences of Termination

      17.8.1  On or before the effective date of termination of this Agreement,
              Enzon shall promptly deliver to Inex a copy of all Data and such
              other information, materials (including biological materials) and
              documents in Enzon's possession or control arising from the
              development of the Product under this Agreement, including,
              without limitation, the Development, provided that Inex shall be
              responsible for any reasonable associated Out-of-Pocket Costs
              associated with transferring same;

      17.8.2  In the event that termination occurs before the payment of all
              Manufacturing Costs referred to in Article 2, then, concurrently
              with such termination, Enzon shall pay to Inex such payment on the
              effective date of such termination.

17.9  Survival of Obligations; Return of Confidential Information

      17.9.1  Upon any termination of this Agreement pursuant to this Article
              17, neither Party shall be relieved of any obligations incurred
              prior to such termination.

      17.9.2  Notwithstanding any termination of this Agreement, the obligations
              of the Parties under Article 1, Sections 2.8, 2.9, 2.11, 2.12,
              2.13, 5.6, 5.7, 6.2, 6.3, 6.4, 9.12 and 11.5, Article 12, Article
              13, Article 14, Article 15, Article 16, Article 17 and Article 18,
              as well as under any other provisions which by their nature are
              intended to survive any such termination, shall survive and
              continue to be enforceable.

      17.9.3  Upon any termination of this Agreement pursuant to Article 17,
              except as contemplated hereby, each Party shall promptly return to
              the other Party all Manufactured materials, written Confidential
              Information, and all copies thereof (except for one archival copy
              to

*** Indicates the omission of confidential material pursuant to a request for
confidential treatment made in accordance with Rule 24b-2 under the Securities
Exchange Act of 1934, as amended. The Confidential material is being filed
separately with the Secretary to the Securities and Exchange Commission.

<PAGE>
                                     - 47 -

              be retained by a person designated by such Party (who shall not
              make such Confidential Information generally available to
              employees or other representatives of such Party) for the purpose
              of confirming which information to hold in confidence hereunder),
              of the other Party which is not covered by a license surviving
              such termination.

                            Article 18 Miscellaneous

18.1  Assignment

      18.1.1  The rights and obligations set out in this Agreement are personal
              to each Party and for this reason, except as expressly set out in
              this Agreement, this Agreement will not be assignable by either
              Party in whole or in part, nor will either Party subcontract any
              of its obligations hereunder without the prior written consent of
              the other Party, which consent shall not be withheld or delayed
              unreasonably; provided, however, that the restriction contained
              herein will in no way limit the rights of either Party to:

              (a)       assign or subcontract any right or obligation hereunder
                        to any of its Affiliates; or

              (b)       appoint as its agent for any purpose of this Agreement
                        any such Affiliate; or

              (c)       assign any right or obligation hereunder to any person
                        or entity that:

                        (i)   purchases all or substantially all of its assets
                              to which this Agreement relates or

                        (ii)  purchases all or substantially all of the stock of
                              either Party; or

                        (iii) acquires or is combined with either Party in a
                              merger or some other form of business combination.

      18.1.2  This Agreement will be binding upon and will enure to the benefit
              of the parties hereto and to any permitted assignee or successor
              of either party.

      18.1.3  Subject to other provisions of this Section 18.1, if one Party
              validly assigns or subcontracts any or all of its obligations
              hereunder, such assigning or subcontracting Party agrees to remain
              bound by all of its responsibilities and obligations hereunder.

      18.1.4  Any and all assignments of this Agreement or any interest herein
              not made in accordance with this Section 18.1 will be void ab
              initio.

18.2  Counterparts

This Agreement may be executed in any number of counterparts, each of which
shall be deemed an original but all of which together shall constitute one and
the same instrument.

18.3  Exhibits and Appendices

Each exhibit hereto is incorporated by reference and made a part of this
Agreement.

18.4  Force Majeure

In the event that either Party is prevented from performing or is unable to
perform any of its obligations under this Agreement due to any act of God; fire;
casualty; flood; war; strike; lockout; failure of public

*** Indicates the omission of confidential material pursuant to a request for
confidential treatment made in accordance with Rule 24b-2 under the Securities
Exchange Act of 1934, as amended. The Confidential material is being filed
separately with the Secretary to the Securities and Exchange Commission.

<PAGE>
                                     - 48 -

utilities; injunction or any act, exercise, assertion or requirement of
governmental authority; epidemic; destruction of production facilities; riots;
insurrection; failure of transportation; inability to procure or use materials,
or any other cause beyond the reasonable control of the Party invoking this
Section 18.4 if such Party shall have used its reasonable efforts to avoid such
occurrence, such Party shall give notice to the other Party in writing promptly,
and thereupon the affected Party's performance shall be excused and the time for
performance shall be extended for the period of delay or inability to perform
due to such occurrence.

18.5  Further Assurances

Each Party hereto agrees to execute, acknowledge and deliver such further
instruments and do all such further acts as may be necessary or appropriate to
carry out the purposes and intent of this Agreement.

18.6  International Sale of Goods Act

The Parties acknowledge and agree that the International Sale of Goods Act and
the United Nations Convention on Contracts for the International Sale of Goods
have no application to this Agreement.

18.7  Modification

No waiver, alteration or modification of any of the provisions hereof shall be
binding unless made in writing and signed by the Parties by their respective
officers thereunto duly authorized.

18.8  No Agency

Except as explicitly set forth herein, nothing herein shall be deemed to
constitute either Party as the agent or representative of the other Party, or
both Parties as joint venturers or partners for any purpose. Inex shall be an
independent contractor, not an employee of Enzon, and the manner in which Inex
renders its services under this Agreement shall be within Inex's sole
discretion. Neither Party shall be responsible for the acts or omissions of the
other Party, and neither Party will have authority to speak for, represent or
obligate the other Party in any way without prior written authority from the
other Party.

18.9  No Solicitation or Hiring of Employees

During the Term and for one year thereafter, neither Inex nor Enzon shall,
without the prior consent of the other Party, solicit the employment of or hire
any person who during the course of employment with the other Party was involved
with activities under the Commercialization Plan and who when solicited or to be
hired is a current employee of the other Party.

18.10 Non-Use of Names

Except as otherwise expressly set out in this Agreement, neither Party shall use
the name of the other Party, nor any adaptation thereof, in any advertising,
promotional or sales literature without prior written consent obtained from such
other Party in each case (which consent shall not be unreasonably withheld or
delayed).

18.11 Notices

Any notice or other communication in connection with this Agreement must be in
writing and if by mail, by registered mail, return receipt requested, and shall
be effective when delivered to the addressee at the address listed below or such
other address as the addressee shall have specified in a notice actually
received by the addressor.

If to Inex:

*** Indicates the omission of confidential material pursuant to a request for
confidential treatment made in accordance with Rule 24b-2 under the Securities
Exchange Act of 1934, as amended. The Confidential material is being filed
separately with the Secretary to the Securities and Exchange Commission.

<PAGE>
                                     - 49 -

      Inex Pharmaceuticals, Inc.
      c/o Corporation Trust Center
      1209 Orange Street
      Wilmington, DE 19801

      Attention: President and CEO

      With copies to:

      Inex Pharmaceuticals Corporation
      100-8900 Glenlyon Parkway
      Burnaby, British Columbia
      Canada V5J 5J8
      Fax: 604-419-3202
      Attention: Sr. V.P. Commercial Operations;

      With a copy to:

      Inex Pharmaceuticals Corporation
      100-8900 Glenlyon Parkway
      Burnaby, British Columbia
      Canada V5J 5J8
      Fax: 604-419-3202
      Attention:  Business Development

      and:

      Lang Michener
      1500-1055 West Georgia Street
      Vancouver, British Columbia
      Canada V6E 4N7
      Fax: 604-685-7084
      Attention: Leo Raffin

      and:

      Farris, Vaughan, Wills & Murphy
      2600 - 700 West Georgia Street
      Vancouver, British Columbia
      Canada V7Y 1B3
      Fax: 604-661-9349
      Attention: James Hatton

*** Indicates the omission of confidential material pursuant to a request for
confidential treatment made in accordance with Rule 24b-2 under the Securities
Exchange Act of 1934, as amended. The Confidential material is being filed
separately with the Secretary to the Securities and Exchange Commission.

<PAGE>
                                     - 50 -

      If to Enzon:

      ENZON PHARMACEUTICALS, INC.
      685 Route 202/206
      Bridgewater, New Jersey
      08807
      Fax: 908.541.8680
      Attention: Vice President, Business Development

      with a copy to:

      Enzon Pharmaceuticals, Inc.
      685 Route 202/206
      Bridgewater, NJ  08807
      Fax: 908.541.8838
      Attention: General Counsel

18.12 Parallel Imports

Enzon and Inex shall each use its Commercially Reasonable Efforts to provide
that each Party's sublicensees, distributors or dealers to whom each Party or
its Affiliates or sublicensees sells the Products for resale shall not sell any
Product to any customer located outside any country or region of the Territory
where each Party may exercise its rights.

18.13 Publicity

Except as required by law, stock exchange or Regulatory Authority:

      18.13.1 neither Party, nor any of its Affiliates, shall originate any
              publicity, news release or other public announcement, written or
              oral, relating to this Agreement or the existence of an
              arrangement between the Parties, without the prior written
              approval of the other Party and agreement upon the nature and text
              of such announcement or disclosure, which approval shall not be
              unreasonably withheld;

      18.13.2 the Party desiring to make any such public announcement or other
              disclosure shall inform the other Party of the proposed
              announcement or disclosure in reasonably sufficient time prior to
              public release, and shall provide the other Party with a written
              copy thereof, in order to allow such other Party to comment upon
              such announcement or disclosure; and

*** Indicates the omission of confidential material pursuant to a request for
confidential treatment made in accordance with Rule 24b-2 under the Securities
Exchange Act of 1934, as amended. The Confidential material is being filed
separately with the Secretary to the Securities and Exchange Commission.

<PAGE>
                                     - 51 -

      18.13.3 notwithstanding the foregoing, the Parties agree that the press
              release set out in Exhibit 18.13.3 shall be released by the
              Parties upon execution and delivery of this Agreement by both
              Parties.

18.14 No Third Party Beneficiaries

Except as expressly set out in this Agreement, nothing in this Agreement is
intended to or shall confer upon any Third Part any legal or equitable right,
benefit or remedy of any nature whatsoever.

18.15 Waiver

The waiver by either Party of a breach or a default of any provision of this
Agreement by the other Party shall not be construed as a waiver of any
succeeding breach of the same or any other provision, nor shall any delay or
omission on the part of either Party to exercise or avail itself of any right,
power or privilege that it has or may have hereunder operate as a waiver of any
right, power or privilege by such Party.

18.16 Cross Default

A breach of or default under any of the Related Agreements other than the
Co-Promotion Agreement shall constitute a breach of and default under all the
Related Agreements.

IN WITNESS WHEREOF, the Parties have executed this Product Supply Agreement as
of the date first above written.

Inex Pharmaceuticals, Inc.

By: /s/ David J. Main
    ---------------------------
Name:  David J. Main
Title: President & CEO

Enzon Pharmaceuticals, Inc.

By: /s/ Arthur J. Higgins
    ---------------------------
Name:  Arthur J. Higgins
Title: Chairman & CEO

*** Indicates the omission of confidential material pursuant to a request for
confidential treatment made in accordance with Rule 24b-2 under the Securities
Exchange Act of 1934, as amended. The Confidential material is being filed
separately with the Secretary to the Securities and Exchange Commission.

<PAGE>
                                     - 52 -

Exhibit 1.1.1: Adverse Drug Event

                             ADVERSE DRUG EVENT FORM

      An Adverse Drug Event shall mean any noxious, unintended, or untoward
      medical occurrence in a patient or clinical investigation subject
      associated with the use of a medicinal or investigational product, whether
      or not related to the medicinal or investigational product.

      This Form must be completed and faxed to the Regulatory Authorities (with
      a copy provided to the other Party):

a)    Immediately, or not later than 24 hours following receipt of any
      information relating to an Adverse Drug Event; and

b)    No later than two (2) business days following receipt of any information
      relating to a product complaint.

      Complaint Date:__________________________

      Complaint received by:___________________      Title:_____________________

      Manner complaint received in:    Oral |_|    Written |_|    Faxed |_|

                                       Other:___________________________________

      Complainant's name:_________________   Phone:_______________ Fax: ________

      Clinic's name:_________________ Phone:___________________  Fax:___________

      Clinic's Address:_________________________________________________________

      Product Name: ____________ Lot number: __________ Expiry Date:____________

      Description of Product Complaint or Adverse Drug Event:___________________

________________________________________________________________________________

________________________________________________________________________________

________________________________________________________________________________

________________________________________________________________________________

________________________________________________________________________________

________________________________________________________________________________

________________________________________________________________________________

________________________________________________________________________________

*** Indicates the omission of confidential material pursuant to a request for
confidential treatment made in accordance with Rule 24b-2 under the Securities
Exchange Act of 1934, as amended. The Confidential material is being filed
separately with the Secretary to the Securities and Exchange Commission.

<PAGE>
                                     - 53 -

Exhibit 1.1.44: Master Production Record

Inex SOP 1202.28-RO Manufacturing of Vincristine Sulfate Liposomes Injection
(14.2 mg/mL) (incorporated by reference)

*** Indicates the omission of confidential material pursuant to a request for
confidential treatment made in accordance with Rule 24b-2 under the Securities
Exchange Act of 1934, as amended. The Confidential material is being filed
separately with the Secretary to the Securities and Exchange Commission.

<PAGE>
                                     - 54 -

Exhibit 1.1.71: Specifications

Specifications as set forth in the approved NDA will be inserted upon FDA
approval

*** Indicates the omission of confidential material pursuant to a request for
confidential treatment made in accordance with Rule 24b-2 under the Securities
Exchange Act of 1934, as amended. The Confidential material is being filed
separately with the Secretary to the Securities and Exchange Commission.

<PAGE>
                                     - 55 -

Exhibit 1.1.77: Trademarks in the Territory

The trademark which the FDA approves for use in association with the Product in
the USA and its Canadian counterpart.

*** Indicates the omission of confidential material pursuant to a request for
confidential treatment made in accordance with Rule 24b-2 under the Securities
Exchange Act of 1934, as amended. The Confidential material is being filed
separately with the Secretary to the Securities and Exchange Commission.

<PAGE>
                                     - 56 -

Exhibit 2.1.1(a): Manufacturing Cost

***

*** Indicates the omission of confidential material pursuant to a request for
confidential treatment made in accordance with Rule 24b-2 under the Securities
Exchange Act of 1934, as amended. The Confidential material is being filed
separately with the Secretary to the Securities and Exchange Commission.

<PAGE>
                                     - 57 -

Exhibit 2.1.1(b): Deferred Sales Price and Deferred Sales Payments

In partial consideration for the purchase of Product, Enzon shall pay Inex
Deferred Sales Payments based on all Net Sales in the Territory of the Product
by Enzon, its Affiliates and Sublicensees at the following rates, calculated in
the manner set out below and in Article 2:

--------------------------------------------------------------------------------
                                                                   Deferred
         Annual Net Sales of Product in Territory ($)            Sales Price
================================================================================

***

*** Indicates the omission of confidential material pursuant to a request for
confidential treatment made in accordance with Rule 24b-2 under the Securities
Exchange Act of 1934, as amended. The Confidential material is being filed
separately with the Secretary to the Securities and Exchange Commission.

<PAGE>
                                     - 58 -

Exhibit 9.10: Interim Budget

***

*** Indicates the omission of confidential material pursuant to a request for
confidential treatment made in accordance with Rule 24b-2 under the Securities
Exchange Act of 1934, as amended. The Confidential material is being filed
separately with the Secretary to the Securities and Exchange Commission.

<PAGE>
                                     - 59 -

Exhibit10.1: Joint Steering Committee Responsibilities and Initial Constituency

The members of the Joint Steering Committee as of the Effective Date are:

For Enzon:

Eddy Anglade, VP - Clinical

      Clarke Atwell, VP - Sales & Marketing

      Katherine Bishburg, VP - Regulatory

      Eric Liebler, VP - Business Development

For Inex:

      Tom MacRury, Senior VP, Commercial Operations

      Alexandra Mancini, Senior VP, Clinical and Regulatory Affairs

      Jeff Charpentier, VP Finance and CFO

      Linda Diano, Director, Project Management

The Joint Steering Committee shall have the following responsibilities:

1.    review amendments to the Commercialization Plan and submit same to the
      Parties for review and approval;

2.    establish working committees to conduct work under the Commercialization
      Plan;

3.    assign responsibility for conducting all needed Commercialization work
      appropriately between the Parties, including providing for subcontractors
      to perform certain tasks if desirable;

4.    oversee all Commercialization activities;

5.    coordinate between the Parties with respect to the overall strategy for
      Commercialization;

6.    review the reports of Commercialization Costs;

7.    review the reports of Net Sales against sales targets;

8.    be the primary contact point between the Parties regarding the transfer of
      information and the discussion of each Party's efforts to conduct
      Commercialization;

9.    such other duties and responsibilities as may be agreed upon by the
      Parties; and

10.   be the primary contact point between the Parties regarding the transfer of
      information and the discussion of each Party's efforts to conduct
      Commercialization.

*** Indicates the omission of confidential material pursuant to a request for
confidential treatment made in accordance with Rule 24b-2 under the Securities
Exchange Act of 1934, as amended. The Confidential material is being filed
separately with the Secretary to the Securities and Exchange Commission.

<PAGE>
                                     - 60 -

Exhibit 18.13.3: Press Release

  ENZON AND INEX SIGN COMMERCIALIZATION PARTNERSHIP FOR ONCOLOGY DRUG ONCO TCS

Bridgewater, NJ, and Vancouver, Canada - January XX, 2004 - Enzon
Pharmaceuticals, Inc. ("Enzon"; NASDAQ: ENZN) and Inex Pharmaceuticals
Corporation ("INEX"; TSX: IEX) today announced a strategic partnership to
develop and commercialize INEX's proprietary oncology product Onco TCS.

Under the terms of the agreement, Enzon receives the exclusive North American
commercialization rights for Onco TCS for all indications. The lead indication
is relapsed aggressive non-Hodgkin's lymphoma (NHL) for which INEX is in the
process of submitting a "rolling" New Drug Application (NDA) to the United
States Food and Drug Administration (FDA), which is expected to be completed
during the first quarter of calendar year 2004. The product is also in numerous
phase II clinical trials for several other cancer indications, including
first-line NHL.

INEX receives a US$12 million up-front payment and will receive up to a US$20
million payment upon Onco TCS receiving approval from the FDA. Additional
development milestones and sales based bonus payments could total US$43.75
million, of which US$10 million is payable upon annual sales first reaching
US$125 million and US$15 million is payable upon annual sales first reaching
US$250 million. INEX will also receive a percentage of commercial sales of Onco
TCS and this percentage will increase as sales reach certain predetermined
thresholds.

INEX has the option of complementing Enzon's sales efforts by co-promoting Onco
TCS through the formation of a dedicated North American sales and medical
science liaison force. The costs of building INEX's co-promotion force would be
shared equally by both companies and Enzon will record all sales in the licensed
territories.

Arthur Higgins, Enzon's chairman and chief executive officer, said, "This
transaction is highly complementary to our R&D and manufacturing infrastructure,
is an excellent fit with the therapeutic focus of our field force and most
importantly, offers the potential to significantly increase Enzon's product
revenues beginning as soon as fiscal 2005."

David Main, INEX's president and chief executive officer, said the agreement
meets INEX's objectives for a commercialization partnership. "It rewards our
company for successfully taking Onco TCS through clinical trials and through to
an NDA, it gives us a strong partner dedicated to oncology with which to share
costs of commercializing Onco TCS and expanding its potential uses. It also lets
us benefit from future sales with a formula for capturing an increasing share of
commercial sales."

"Enzon has expertise in the development, manufacturing and marketing of
liposomal drugs and has the motivation to make Onco TCS sales an important part
of its future," Main said. "This deal also provides a cost-effective means for
us to build our own commercial infrastructure to work alongside Enzon's, which
is important for our future growth strategy and pipeline activities."

Enzon and INEX will share equally the future development costs designed to
obtain and maintain marketing approvals in North America for Onco TCS, while
Enzon will pay all sales and marketing costs and certain other post-approval
clinical development costs typically associated with commercialization
activities. Enzon plans to market Onco TCS through its entire North American

*** Indicates the omission of confidential material pursuant to a request for
confidential treatment made in accordance with Rule 24b-2 under the Securities
Exchange Act of 1934, as amended. The Confidential material is being filed
separately with the Secretary to the Securities and Exchange Commission.

<PAGE>
                                     - 61 -

sales force of approximately 60 people, which currently markets ABELCET(R),
ONCASPAR(R), and DEPOCYT(R) to the oncology market.

INEX retains manufacturing rights and will initially manufacture and supply the
drug and be reimbursed by Enzon. INEX and Enzon are discussing the potential of
transferring manufacturing to Enzon's sterile injectable manufacturing facility
in Indianapolis, Indiana where Enzon manufacturers its commercial drug
ABELCET(R) (Amphotericin B Lipid Complex Injection) and where MYOCETTM (liposome
encapsulated doxorubicin citrate complex) is manufactured for Elan Corporation,
plc.

The companies will also explore the acquisition and joint development of other
cancer drugs.

About Onco TCS

Onco TCS is a proprietary drug comprised of the widely used off-patent cancer
drug vincristine encapsulated in INEX's TCS (liposomal) drug delivery
technology. The TCS technology provides prolonged blood circulation, tumor
accumulation and extended drug release at the cancer site. These characteristics
are designed to increase the effectiveness and reduce the side effects of the
encapsulated drug.

INEX has completed a pivotal phase II/III clinical trial treating relapsed
aggressive NHL with Onco TCS. Currently, there is no effective treatment for
patients with aggressive NHL that have relapsed following first-line and
second-line treatment.

INEX's multi-center pivotal phase II/III trial treated 119 NHL patients who had
not responded to their previous therapy or had responded and subsequently
relapsed. After treatment with Onco TCS, an overall response rate of 25% was
attained. The results of this pivotal trial were released in June 2003 and
presented in December 2003 at the American Society of Hematology annual
conference along with interim results from two ongoing phase II trials in
relapsed Hodgkin's disease and relapsed B-cell lymphoma.

INEX has submitted two major sections of its "rolling" NDA to the FDA seeking
marketing approval for Onco TCS as a treatment for relapsed aggressive NHL. The
first section was submitted September 30, 2003 and included nonclinical, safety
and pharmacology data. The second section was submitted December 3, 2003 and
included data on manufacturing process, stability of the drug, composition of
the drug and other chemistry and related information. INEX expects the third and
final section, containing data from clinical trials, to be submitted during the
first quarter of calendar year 2004.

A "rolling" NDA is a process used by the FDA to expedite the review of a drug
intended for the treatment of a serious or life threatening condition and that
demonstrates the potential to address an unmet medical need. This allows the FDA
to begin to review sections of the NDA as they are submitted, as opposed to the
normal approval process, which requires the entire NDA to be submitted at one
time. In order to be eligible to submit a rolling NDA, a company will usually
have been granted Fast Track designation by the FDA, which INEX received in
August 2000.

Subject to acceptance of the full NDA for review, INEX expects to have a
response from the FDA within six months. If approved, it is anticipated that
Onco TCS could be introduced to the marketplace before the end of calendar year
2004 or early in 2005.

Although INEX has chosen to file an NDA for relapsed aggressive NHL as the first
route to approval for Onco TCS, Enzon and INEX intend to develop Onco TCS for
use as a stand-alone

*** Indicates the omission of confidential material pursuant to a request for
confidential treatment made in accordance with Rule 24b-2 under the Securities
Exchange Act of 1934, as amended. The Confidential material is being filed
separately with the Secretary to the Securities and Exchange Commission.

<PAGE>
                                     - 62 -

drug and/or in combination therapy for several cancers in which vincristine is
now used. Onco TCS is being evaluated in several phase II clinical trials as a
treatment for first-line NHL, relapsed small cell lung cancer, relapsed
Hodgkin's disease, relapsed acute lymphoblastic leukemia, relapsed pediatric
malignancies, relapsed NHL in combination with the approved cancer drug
Rituxan(R) (rituximab), and relapsed NHL in combination with the approved cancer
drug etoposide.

About Non-Hodgkin's Lymphoma (NHL)

NHL is the fifth-leading cause of cancer deaths in the United States (23,400
estimated in 2003) and the sixth-leading cause of cancer deaths in Canada (2,800
estimated in 2003), according to estimates of the American Cancer Society and
the Canadian Cancer Society. Approximately 53,400 and 6,400 new cases were
diagnosed in the U.S. and Canada respectively in 2003.

Enzon Conference Call

Company management of Enzon will be hosting a conference call on Wednesday,
January 14, 2004 at 7:30 AM EST regarding the agreement. All interested parties
can access the call using the following information:

            Domestic dial-in number          888-423-3274

            International dial-in number     612-332-0345

            Access Code                      717232

Enzon's conference call will also be webcast in a "listen only" mode via the
internet at http://www.vcall.com. Additionally, for those parties unable to
listen at the time of Enzon's conference call, a rebroadcast will be available
following the call from Wednesday, January 14, 2004 at approximately 11:00 AM.
This rebroadcast will end on Wednesday, January 21, 2004 at 11:59PM. The
rebroadcast may be accessed using the following information:

             Domestic Dial-In Number:           800-475-6701

             International Dial-In Number:      320-365-3844

             Access Code:                       717232

INEX Conference Call

Company management of INEX will be hosting a conference call on Wednesday,
January 14, 2004 at 8:30 AM EST regarding the formation of the partnership. All
interested parties can access the call using the following information:

             Dial-In Number:                    416-405-9328

             North American toll free access:   800-387-6216

INEX's conference call will also be webcast via the internet at
www.inexpharm.com.

Additionally, for those parties unable to listen at the time of INEX's
conference call, a replay will be available shortly following the completion of
the call. This rebroadcast will end on January 20, 2004 at 11:59 PM. The
rebroadcast may be accessed using the following information:

*** Indicates the omission of confidential material pursuant to a request for
confidential treatment made in accordance with Rule 24b-2 under the Securities
Exchange Act of 1934, as amended. The Confidential material is being filed
separately with the Secretary to the Securities and Exchange Commission.

<PAGE>
                                     - 63 -

             Dial-In Number:                    416-695-5800

             North American toll free access:   800-408-3053

             Access Code:                       1520395

About INEX

INEX is a Canadian biopharmaceutical company developing and commercializing
proprietary drugs and drug delivery systems to improve the treatment of cancer.

INEX entered into the partnership with Enzon through agreements entered into by
its wholly owned U.S. subsidiary, Inex Pharmaceuticals, Inc.

About Enzon

Enzon Pharmaceuticals is a biopharmaceutical company dedicated to the discovery,
development and commercialization of therapeutics to treat life-threatening
diseases. The company has developed or acquired a number of marketed products,
including PEG-INTRON(R), marketed by Schering-Plough, and ABELCET(R),
ONCASPAR(R), ADAGEN(R), and DEPOCYT(R), which are all marketed in North America
by Enzon's hospital and oncology sales forces. Enzon's science-focused strategy
includes an extensive drug development program that leverages the Company's
macromolecular engineering technology platforms, including PEG modification and
single-chain antibody (SCA(R)) technologies Internal research and development
efforts are complemented by strategic transactions that provide access to
additional products, projects, and technologies. Enzon has several drug
candidates in various stages of development, independently and with partners.

      There are forward-looking statements contained herein that are not based
      on historical fact, including without limitation statements containing the
      words "believes," "may," "plans," "will," "estimate," "continue,"
      "anticipates," "intends," "expects," and similar expressions. Such
      forward-looking statements involve known and unknown risks, uncertainties
      and other factors that may cause the actual results, events or
      developments to be materially different from actual future results, events
      or developments. Such factors include the risk that Onco-TCS may not
      receive regulatory approval from the FDA, as well as those described in
      Enzon's Form 10-K and Forms 10-Q on file with the SEC and INEX's publicly
      filed periodic reports and others, such as, (i) as to Enzon, Enzon's
      ability to successfully launch and market Onco-TCS, Enzon's ability to
      sustain profitability, and positive cash flow; risks in obtaining and
      maintaining regulatory approval for indications and expanded indications
      for Enzon's products; market acceptance of and continuing demand for
      Enzon's products; timing and results of clinical trials and the impact of
      competitive products and pricing and (ii) as to INEX, INEX's stage of
      development, lack of product revenues, additional capital requirements,
      risks associated with the completion of clinical trials and obtaining
      regulatory approval to market INEX's products, risks associated with the
      failure to secure all necessary intellectual property from third parties,
      the ability to protect its intellectual property and dependence on
      collaborative partners. These factors should be considered carefully and
      readers are cautioned not to place undue reliance on such forward-looking
      statements. All information in this press release is as of January __,
      2004, and Enzon and INEX undertake no duty to update this information.

      This release is also available at http://www.enzon.com and
      http://www.inexpharm.com

*** Indicates the omission of confidential material pursuant to a request for
confidential treatment made in accordance with Rule 24b-2 under the Securities
Exchange Act of 1934, as amended. The Confidential material is being filed
separately with the Secretary to the Securities and Exchange Commission.

<PAGE>
                                     - 2 -

Contacts for Enzon Pharmaceuticals, Inc.     Contacts for Inex Pharmaceuticals
                                             Corporation

Investors                                    Investors
---------                                    ---------

Susan M. Mesco                               Ian Mortimer
Director, Investor Relations                 Senior Director, Investor Relations
Phone: 908-541-8678                          Phone: 604-419-3200

Media                                        Media
-----                                        -----

Euro RSCG Life NRP                           James Hoggan & Associates Inc.
Mark Vincent                                 Karen Cook Boas
Phone : 212-845-4239                         Phone: 604-739-7500

Enzon's common shares are traded on NASDAQ under the trading symbol "ENZN".

INEX's common shares are traded on the Toronto Stock Exchange under the trading
symbol "IEX".- i -

                             CO-PROMOTION AGREEMENT

                                     BETWEEN

                           INEX PHARMACEUTICALS, INC.

                                       AND

                           ENZON PHARMACEUTICALS, INC.

                                January 19, 2004

*** Indicates the omission of confidential material pursuant to a request for
confidential treatment made in accordance with Rule 24b-2 under the Securities
Exchange Act of 1934, as amended. The Confidential material is being filed
separately with the Secretary to the Securities and Exchange Commission.

<PAGE>

                                     - ii -

                                TABLE OF CONTENTS

Article 1 Interpretation.......................................................1
    1.1   Definitions..........................................................1

Article 2 Co-Promotion.........................................................3
    2.1   Co-Promotion Rights..................................................3
    2.2   Use by Inex of Representatives.......................................4
    2.3   Enzon's Back Office Responsibilities.................................4

Article 3 Coordination.........................................................4
    3.1   Coordination of Activities...........................................4
    3.2   Reporting Relationships..............................................4
    3.3   Supervision and Management of Personnel..............................4
    3.4   Training.............................................................5
    3.5   Communication........................................................5
    3.6   Marketing  Subcommittee..............................................5

Article 4 Promotional Material.................................................5
    4.1   Approved Promotional Materials.......................................5
    4.2   Provision of Enzon's Promotional Materials...........................5
    4.3   Approval of Inex's Promotional Material..............................5
    4.4   Use of Promotional Materials.........................................6
    4.5   Corporate Logos......................................................6
    4.6   Website..............................................................6

Article 5 Compliance...........................................................7
    5.1   Consistent Statements................................................7
    5.2   Medical Science Liaisons.............................................7
    5.3   Communications to Sales Representatives and
          Medical Science Liaisons.............................................7
    5.4   Standards............................................................7

Article 6 Payments by Enzon....................................................8
    6.1   Reporting and Payment of Co-Promotion Commercialization Costs........8
    6.2   Additional Sales Representatives and Medical Science Liaisons........8
    6.3   Payment of Co-Promotion Costs........................................8
    6.4   Notice of Other Promotional Activities...............................9
    6.5   Taxes; Indemnification...............................................9

Article 7 Termination..........................................................9
    7.1   Term of Agreement....................................................9
    7.2   Termination for Breach...............................................9
    7.3   Termination upon Bankruptcy.........................................10
    7.4   Effect of Termination...............................................10
    7.5   Survival of Obligations; Return of Confidential Information.........11

*** Indicates the omission of confidential material pursuant to a request for
confidential treatment made in accordance with Rule 24b-2 under the Securities
Exchange Act of 1934, as amended. The Confidential material is being filed
separately with the Secretary to the Securities and Exchange Commission.

<PAGE>
                                     - iii -

Article 8 Miscellaneous.......................................................11
    8.1   Assignment..........................................................11
    8.2   Counterparts........................................................12
    8.3   Exhibits and Appendices.............................................12
    8.4   Force Majeure.......................................................12
    8.5   Further Assurances..................................................12
    8.6   Modification........................................................12
    8.7   No Agency...........................................................12
    8.8   No Solicitation or Hiring of Employees..............................13
    8.9   Non-Use of Names....................................................13
    8.10  Notices.............................................................13
    8.11  Publicity...........................................................14
    8.12  No Third Party Beneficiaries........................................15
    8.13  Waiver..............................................................15

*** Indicates the omission of confidential material pursuant to a request for
confidential treatment made in accordance with Rule 24b-2 under the Securities
Exchange Act of 1934, as amended. The Confidential material is being filed
separately with the Secretary to the Securities and Exchange Commission.

<PAGE>
                                     - 1 -

                             CO-PROMOTION AGREEMENT

This CO-PROMOTION AGREEMENT dated as of the 19th day of January, 2004 between
Inex Pharmaceuticals, Inc., a corporation duly incorporated pursuant to the laws
of Delaware, USA, having a registered office at Corporation Trust Center, 1209
Orange Street, Wilmington, DE 19801 (hereinafter referred to as "Inex"), and
Enzon Pharmaceuticals, Inc., a corporation duly incorporated pursuant to the
laws of Delaware, having a principal place of business at 685 Route 202/206,
Bridgewater, New Jersey 08807 (hereinafter referred to as "Enzon").

INTRODUCTION

A. Enzon is a pharmaceutical company with operations in research and
development, import, manufacture and sale of pharmaceutical products;

B. Inex is in the business of developing, manufacturing and selling certain
pharmaceutical products, including Vincristine Sulfate Liposomes Injection (as
further defined in this Agreement);

C. Of even date hereof, the Parties have entered into a Product Supply Agreement
pursuant to which Inex will supply to Enzon Vincristine Sulfate Liposomes
Injection (the "Product Supply Agreement");

D. Of even date hereof, the Parties also have entered into a Development
Agreement for the development of Vincristine Sulfate Liposomes Injection and for
the purpose of providing for the Regulatory Approval of, and conveying certain
rights to Enzon with respect to, Inex's Vincristine Sulfate Liposomes Injection
product in the Territory (the "Development Agreement"); and

E. Subject to the terms and conditions set forth in this Agreement, the Parties
wish to set out certain co-promotion rights for Inex and Enzon in the Territory.

*** Indicates the omission of confidential material pursuant to a request for
confidential treatment made in accordance with Rule 24b-2 under the Securities
Exchange Act of 1934, as amended. The Confidential material is being filed
separately with the Secretary to the Securities and Exchange Commission.

<PAGE>
                                      - 2 -

NOW, THEREFORE, the Parties, intending to be legally bound, hereby agree as
follows:

                            Article 1 Interpretation

1.1   Definitions

Unless otherwise defined in this Agreement, capitalized terms used in this
Agreement shall have the meaning set out therefor in the Product Supply
Agreement or the Development Agreement (in the event of a conflict, the Product
Supply Agreement shall prevail). For purposes of this Agreement, the following
terms will have the meanings set forth below:

      1.1.1   "Code" or "Codes" means the Code on Interactions with Healthcare
              Professionals promulgated by the Pharmaceutical Research and
              Manufacturers of America (PhRMA) and the American Medical
              Association (AMA) Guidelines on Gifts to Physicians from Industry,
              as either of the foregoing may be amended from time to time.

      1.1.2   "Commercialization" means the activities customarily associated
              with sales of pharmaceutical products including without
              limitation, Manufacturing, DDMAC Activities, price and
              reimbursement negotiations, pre-launch and launch activities,
              marketing, sales, distribution, Co-Promotion, Post-Approval
              Clinical Activities, the development, prosecution, registration
              and maintenance of trademarks, trade names and domain names, and
              pharmaco-vigilance in each country in the Territory.

      1.1.3   "Co-Promotion" or "Promotion" means:

              (a)       Detailing and/or other related activities, including the
                        provision of medical information services or medical
                        liaison support, and

              (b)       market research, journal advertising, direct mail
                        programs, participation in trade shows, symposia,
                        congresses and other medical meetings; and

              (c)       MSL Activities;

              undertaken by Enzon, or by Inex in concert with Enzon's marketing
              personnel and sales force to augment Enzon's marketing and sale of
              VSLI. When used as a verb, "Co-Promote" or "Promote" means to
              engage in such activities.

      1.1.4   "Co-Promotion Costs" means, with respect to Co-Promotion of the
              Product by Inex or its Representatives, Inex's personnel cost of
              Sales Representatives and Medical Science Liaisons including ***.
              For greater certainty, "Co-Promotion Costs" are not included in
              Commercialization Costs as defined in the Product Supply
              Agreement.

      1.1.5   "Detail" means a face-to-face meeting (including live video
              presentation) with a physician; other medical professional with
              prescribing authority; or office nurse or medical paraprofessional
              with influence over pharmaceutical

*** Indicates the omission of confidential material pursuant to a request for
confidential treatment made in accordance with Rule 24b-2 under the Securities
Exchange Act of 1934, as amended. The Confidential material is being filed
separately with the Secretary to the Securities and Exchange Commission.

<PAGE>
                                      - 3 -

              prescribing or treatment regimes for patients in the Territory
              during which scientific and/or medical information about the
              Product is discussed. When used as a verb, the term "Detailing"
              means to engage in the activity of a Detail.

      1.1.6   "Medical Science Liaison" means an individual employed by either
              Party to perform MSL Activities.

      1.1.7   "MSL Activities" means through the use of Medical Science Liaisons
              the maintenance of effective relationships with clinical
              investigators with respect to the Product in the Territory. MSL
              Activities would also include responding to physicians' requests
              for medical information with respect to the Field.

      1.1.8   "Pharmacovigilance" means all the activities associated with
              maintaining an effective drug safety monitoring system and adverse
              events reporting system in compliance with the requirements of
              Regulatory Authorities.

      1.1.9   "Product Labeling" means:

              (a)       the full prescribing information for the Product,
                        including any required patient information, as approved
                        by Regulatory Authorities; and

              (b)       all labels and other written, printed, or graphic matter
                        upon any container, wrapper, or any package insert,
                        utilized with or for the Product.

      1.1.10  "Promotional Materials" means all written, printed, graphic,
              electronic, audio or video matter, including journal
              advertisements, sales visual aids, direct mail, direct-to-consumer
              advertising, web pages, web links, Internet postings, broadcast
              advertisements, sales reminder aids (e.g., scratch pads, pens and
              other such items) and reprints intended for use or used by the
              Parties in connection with any Promotion, except the Product
              Labeling.

      1.1.11  "Sales Representative" means an individual employed by either
              Party or whose services are contracted for by either Party and who
              engages in Co-Promotion.

      1.1.12  "Standards" means the Accreditation Council for Continuing Medical
              Education (ACCME) Standards for Commercial Support of Continuing
              Medical Education, as they may be amended from time to time.

      1.1.13  "Term" shall have the meaning set out in Section 7.1.

                             Article 2 Co-Promotion

2.1   Co-Promotion Rights

Inex shall have the right to engage in Co-Promotion activities with respect to
VSLI in the Territory pursuant to and in accordance with the provisions of this
Agreement.

*** Indicates the omission of confidential material pursuant to a request for
confidential treatment made in accordance with Rule 24b-2 under the Securities
Exchange Act of 1934, as amended. The Confidential material is being filed
separately with the Secretary to the Securities and Exchange Commission.

<PAGE>
                                      - 4 -

2.2   Use by Inex of Representatives

To the extent Inex does engage in Co-Promotion activities, it will do so through
its own employees or, subject to the approval of Enzon, not to be unreasonably
withheld, through its Representatives, such Representatives to include a
contract sales force.

2.3   Enzon's Back Office Responsibilities

Notwithstanding any Co-Promotion activities engaged in by the Parties, Enzon
shall remain responsible to book all sales of VSLI, conduct reimbursement
negotiations, conduct Pharmacovigilance, handle returns/recalls and order
processing, invoicing and collection, distribution, warehousing, inventory and
receivables, collection of sales data from hospitals and other end users and all
other customer service related functions and the like.

                             Article 3 Coordination

3.1   Coordination of Activities

Enzon and Inex shall cooperate on the determination of activities to be
undertaken by Inex employees and its Representatives engaged in Co-Promotion on
both a geographic and physician base basis. Due consideration will be given to
ensure that Inex employees and its Representatives have no lesser economic
opportunity than Enzon employees for their respective geographic and physician
assignments.

3.2   Reporting Relationships

To the extent they are engaged in Co-Promotion, Inex employees and its
Representatives shall be subject to the control and direction of Enzon. For the
purposes of conducting Co-Promotion, such Inex employees and Representatives
shall have reporting responsibilities and be subordinate to the Enzon managers
to whom their peer level Enzon employees report and are subordinate. Enzon
managers will work cooperatively with their peer level Inex employees and Inex's
Vice President, Sales & Marketing or such other executive officer as Inex
designates in the management of such Inex employees and Representatives. To the
extent the same Inex employees and its Representatives are engaged in
promotional activities related to products other than VSLI, they shall not be
subject to the control and direction of Enzon.

3.3   Supervision and Management of Personnel

Inex shall cooperate with Enzon promptly and reasonably with respect to the
supervision and management of its employees and its Representatives engaged in
Co-Promotion. Subject to Section 3.1, Inex shall consider in good faith and give
due weight to and, to the extent practicable, accommodate the recommendations of
Enzon with respect to the management of Inex's employees and its Representatives
engaged in Co-Promotion, including such matters as territorial assignments,
performance improvement and disciplinary actions, promotions, demotions,
terminations, etc. In addition, to the extent practical, the Parties will employ
similar compensation systems to foster strategic alignment and to foster
positive relations between each Party's personnel engaged in Co-Promotion.

*** Indicates the omission of confidential material pursuant to a request for
confidential treatment made in accordance with Rule 24b-2 under the Securities
Exchange Act of 1934, as amended. The Confidential material is being filed
separately with the Secretary to the Securities and Exchange Commission.

<PAGE>
                                      - 5 -

3.4   Training

Inex shall have the opportunity to review all training materials prior to their
use. Inex employees and its Representatives engaged in Co-Promotion shall be
subject to the same training, knowledge and performance requirements to which
their peer level Enzon employees are subject. They shall attend the same
training sessions and the same sales and other meetings that Enzon employees are
required to attend. Enzon shall bear all costs of organizing and conducting any
training sessions, except for travel and out-of-pocket costs incurred by Inex
personnel which shall be shared by Inex and Enzon pursuant to Section 6.1.

3.5   Communication

Each Party shall have the right to arrange for its employees and Representatives
directly involved in Co-Promotion of the Product to visit the other Party at the
other Party's offices, and to discuss related activities with the technical and
business personnel and consultants of such Party, provided that such visits
shall be upon reasonable prior notice and during normal business hours and shall
not unreasonably interrupt the operations of such Party.

3.6   Marketing Subcommittee

The Joint Steering Committee shall create a subcommittee, to be called the
Marketing Subcommittee, which will be constituted of such persons and engage in
such activities regarding Co-Promotion as shall be determined by the Joint
Steering Committee.

                         Article 4 Promotional Material

4.1   Approved Promotional Materials

In its Co-Promotion, Inex shall use only the Promotional Materials approved by
Enzon in writing and the trademarks, tradenames and domain names maintained by
Enzon and Inex for VSLI. Enzon shall bear all costs related to the preparation
and production of promotional materials for use by Inex employees and its
Representatives.

4.2   Provision of Enzon's Promotional Materials

Enzon shall provide Inex with sufficient final copies of all Promotional
Materials concurrently with Enzon's finalization of the form of same, and in any
event, prior to any public dissemination of same.

4.3   Approval of Inex's Promotional Material

Enzon shall have absolute discretion to approve all Promotional Materials
prepared by Inex prior to their use by Inex in Co-Promoting the Product. Enzon
shall designate an employee contact to whom Inex shall send for approval all
Promotional Materials.

*** Indicates the omission of confidential material pursuant to a request for
confidential treatment made in accordance with Rule 24b-2 under the Securities
Exchange Act of 1934, as amended. The Confidential material is being filed
separately with the Secretary to the Securities and Exchange Commission.

<PAGE>
                                      - 6 -

4.4   Use of Promotional Materials

      4.4.1   Each Party shall own all Intellectual Property Rights in any
              Promotional Materials created or developed by such Party.

      4.4.2   Inex will provide to Enzon prior to their use Promotional
              Materials that Inex creates for use outside the Territory. Inex
              will consider in good faith any comments or suggestions made by
              Enzon concerning such Promotional Materials.

      4.4.3   Inex reserves the right to use outside the Territory all
              Promotional Material created by Inex and approved by Enzon for use
              inside the Territory.

      4.4.4   Inex shall have the opportunity to review Promotional Materials
              created by Enzon.

      4.4.5   Enzon and Inex will cooperate in good faith with Inex's
              Representatives, and Inex will use Commercially Reasonable Efforts
              to cause its Representatives to cooperate in good faith with Enzon
              and Inex, with respect to the preparation of Promotional Materials
              for, and the use of such materials in, different geographic
              markets on a global basis.

4.5   Corporate Logos

All training materials and Promotional Materials shall bear both Parties'
corporate logos in equal prominence. During the Term, each Party grants to the
other, the non-exclusive right to use its corporate logo in the Territory solely
for the purpose of the Promotion of the Product in accordance with the terms of
this Agreement. Each Party will use commercially reasonable efforts to protect
the other Party's corporate name, logo and symbol. Each Party acknowledges that
the other Party owns all right, title and interest in such other Party's
corporate name, logo and symbols and all good will associated therewith and that
any and all use of corporate name, logo or symbols under the Related Agreements,
and any good will associated with such use, shall inure exclusively to the
benefit of the owner of such name, logo or symbol.

4.6   Website

On any website relating solely to the Product that is owned or controlled by, or
operated on behalf of, Enzon to promote the Product (the "Websites"), Enzon
shall place (or cause to have placed) the Inex logo and accompanying text
provided by Inex, or such other Inex logo and accompanying text as Inex may
designate from time to time in writing to Enzon, subject to review and approval
of any such text by Enzon. Any such logo and accompanying text shall be given
appropriate placement on such websites and shall link to a uniform resource
locator ("URL") address designated by Inex, which URL address may be changed by
Inex from time to time upon reasonable notice to Enzon; provided, however, that
before providing any such link to a URL address, Enzon shall have the right to
review and approve the contents thereof. Inex grants Enzon the right to
establish a link to the Websites or other websites designated by Enzon and
approved by Inex from specific websites relating solely to the Product owed or
controlled by, or operated on behalf of, Inex. Enzon also grants Inex the right
to place (or cause to have

*** Indicates the omission of confidential material pursuant to a request for
confidential treatment made in accordance with Rule 24b-2 under the Securities
Exchange Act of 1934, as amended. The Confidential material is being filed
separately with the Secretary to the Securities and Exchange Commission.

<PAGE>
                                     - 7 -

placed) the Enzon logo and accompanying text provided by Enzon, or such other
Enzon logo and accompanying text as Enzon may designate from time to time in
writing to Inex, on such Inex websites, subject to review and approval of any
such text by Inex. The content of the websites owned or controlled by Inex
relating solely to the Product and accessible in the Territory, and the portions
of other websites owned or controlled by Inex that relate to the Product and are
directed at Commercializing the Product shall be subject to the review and
approval of Enzon, which approval shall not be unreasonably withheld.

                              Article 5 Compliance

5.1   Consistent Statements

In connection with each Party's Promotion and Detailing of the Product, neither
Party shall make, nor permit its Sales Representatives to make, any statement,
representation or warranty, oral or written, to any person that is inconsistent
with the Product Labeling or the Promotional Materials. Each Party shall
promptly notify the other Party of and provide the other Party with a copy of
any correspondence or other reports or complaints received by a Party from any
Regulatory Authority, or any third party claiming that any Promotional Materials
are inconsistent with the Product Labeling or are otherwise in violation of
Regulatory Requirements.

5.2   Medical Science Liaisons

Each Party shall conduct MSL Activities using only Medical Science Liaisons who
have sufficient technical training and experience to perform such activities in
a manner consistent with the practice by leading pharmaceutical and
biotechnology companies of such activities within the Field. Each Party shall
require each Medical Science Liaison to attend training before such Medical
Science Liaison is permitted to conduct MSL Activities.

5.3   Communications to Sales Representatives and Medical Science Liaisons

Enzon shall provide Inex with copies of general communications (including
communications sent electronically or by voice mail) disseminated by Enzon to
the Sales Representatives and Medical Science Liaisons and relating to
strategies for the Promotion or Detailing of the Product or the conduct of MSL
Activities, as applicable.

5.4   Standards

In addition to its obligations to comply with Regulatory Requirements, each
Party shall:

      5.4.1   Promote the Product in conformity with the practices and
              procedures relating to the education of the medical community set
              forth in the Standards; and

      5.4.2   promptly notify the other Party of and provide the other Party
              with a copy of any correspondence or other reports with respect to
              the Promotion of the Product or the conduct of the MSL Activities
              that a Party receives from:

              (a)       the Accreditation Council for Continuing Medical
                        Education (ACCME) relating to either Party's compliance
                        with the Standards;

*** Indicates the omission of confidential material pursuant to a request for
confidential treatment made in accordance with Rule 24b-2 under the Securities
Exchange Act of 1934, as amended. The Confidential material is being filed
separately with the Secretary to the Securities and Exchange Commission.

<PAGE>
                                     - 8 -

              (b)       the PhRMA and the AMA relating to either Party's
                        compliance with the Codes; and

              (c)       the Division of Drug Marketing, Advertising and
                        Communications (DDMAC), of the FDA in relation to either
                        Party's compliance with Applicable Laws.

                          Article 6 Payments by Enzon

6.1   Reporting and Payment of Co-Promotion Costs

Enzon shall reimburse Inex for 50% of the Co-Promotion Costs of Inex's
Co-Promotion to augment Enzon's efforts up to a maximum of 30 sales persons and
medical science liaisons in accordance with the following:

      6.1.1   after launch of the Product and until Enzon has achieved Net Sales
              of the Product of at least $*** in any rolling four Commercial
              Quarter period, the number of Sales Representatives and Medical
              Science Liaisons shall not exceed ***;

      6.1.2   after Enzon has achieved Net Sales of the Product of at least $***
              in any rolling four Commercial Quarter period, but before it has
              achieved annual Net Sales of the Product of at least $*** in any
              rolling four Commercial Quarter period, the number of Sales
              Representatives and Medical Science Liaisons shall not exceed ***;
              and

      6.1.3   after Enzon has achieved Net Sales of the Product of at least $***
              in any rolling four Commercial Quarter period:, the number of
              Sales Representatives and Medical Science Liaisons may increase to
              *** or such number of Sales Representatives and Medical Science
              Liaisons above *** as mutually agreed to by the Parties in writing
              (and in accordance with such agreement).

6.2   Additional Sales Representatives and Medical Science Liaisons

Notwithstanding the foregoing, Inex may at any time utilize Sales
Representatives and Medical Science Liaisons in excess of the numbers set out in
Sections 6.1.1, 6.1.2 and 6.1.3 at Inex's expense, provided that such Sales
Representatives and Medical Science Liaisons comply with the terms of this
Agreement and Inex bears any incremental costs of Enzon associated with such
Sales Representatives and Medical Science Liaisons.

6.3   Payment of Co-Promotion Costs

On a quarterly basis, within 12 Business Days after the end of each Calendar
Quarter, Inex shall send Enzon invoices for 50% of its Co-Promotion Costs
accompanied by the appropriate documentation, including a listing of
expenditures in reasonably specific detail. Enzon shall pay such invoices within
thirty (30) days after receipt of same. Any Co-Promotion Costs incurred by Inex
or its Representatives in a particular quarter and not reflected in the invoice
delivered pursuant to the foregoing sentence shall be captured in subsequent
invoice(s).

*** Indicates the omission of confidential material pursuant to a request for
confidential treatment made in accordance with Rule 24b-2 under the Securities
Exchange Act of 1934, as amended. The Confidential material is being filed
separately with the Secretary to the Securities and Exchange Commission.

<PAGE>
                                     - 9 -

6.4   Notice of Other Promotional Activities

If any Inex employee or Representative engaged in Co-Promotion is to commence
promotional activities with respect to any other product, Inex will provide
written notice thereof to Enzon at least 60 days prior to the commencement of
such other promotional activities. Enzon shall not be obligated to reimburse
Inex with respect to any promotional activities related to other products. For
purposes of determining Enzon's reimbursement obligations, the Commercialization
Costs for any employee engaged in such other promotional efforts shall be
allocated between VSLI and the other products on an equitable basis.

6.5   Taxes; Indemnification

The Inex employees and Representatives engaged in the Co-Promotion shall not be
deemed to be employees of Enzon. Inex shall be responsible for all income tax
withholding and similar obligations to all relevant taxing and other authorities
associated with all personnel engaged in Co-Promotion. Enzon's sole financial
obligations shall be to make the reimbursement payments directly to Inex as set
forth in this Agreement. Inex hereby does indemnify and shall defend Enzon
against and hold it harmless from any and all claims and/or liabilities that may
arise out of any characterization of, or attempt to characterize, any person
engaged in the Co-Promotion as an employee of Enzon.

                             Article 7 Termination

7.1   Term of Agreement

This Agreement shall become effective on the Effective Date and, unless earlier
terminated as provided for herein, shall expire, on a country-by-country basis,
upon the expiration of any of the Related Agreements and such period shall be
the "Term" under this Agreement.

7.2   Termination for Breach

Each Party shall be entitled to terminate this Agreement by written notice to
the other Party in the event that the other Party shall be in material default
of any of its obligations hereunder, and shall fail to remedy any such default
within sixty (60) days after notice thereof by the non-breaching Party. Any such
notice shall specifically state that the non-breaching Party intends to
terminate this Agreement in the event that the breaching Party shall fail to
remedy the default. Any such notice shall set out expressly the actions required
of the breaching Party to remedy the default. If such default is not corrected,
the non-breaching Party shall have the right to terminate this Agreement by
giving written notice to the Party in default provided the notice of termination
is given within six (6) months of the default and prior to correction of the
default.

7.3   Termination upon Bankruptcy

      7.3.1   This Agreement may be terminated by a Party by providing written
              notice to the other Party upon:

*** Indicates the omission of confidential material pursuant to a request for
confidential treatment made in accordance with Rule 24b-2 under the Securities
Exchange Act of 1934, as amended. The Confidential material is being filed
separately with the Secretary to the Securities and Exchange Commission.

<PAGE>
                                     - 10 -

              (a)       the bankruptcy, liquidation or dissolution of the other
                        Party;

              (b)       the filing of any voluntary petition for bankruptcy,
                        dissolution, liquidation or winding-up of the affairs of
                        the other Party; or

              (c)       the filing of any involuntary petition for bankruptcy,
                        dissolution, liquidation or winding-up of the affairs of
                        the other Party which is not dismissed within one
                        hundred twenty (120) days after the date on which it is
                        filed or commenced.

      7.3.2   Notwithstanding the foregoing, either Party may seek the waiver of
              the operation of Section 7.3.1 in advance of any event giving rise
              to a right of termination under Section 7.3.1(b), and, provided
              that:

              (a)       the requesting Party is in good standing and not in
                        breach of any of the terms of the Related Agreements;

              (b)       the requesting Party is in reasonable financial
                        condition; and

              (c)       the Party whose consent is sought will not be prejudiced
                        by granting such waiver,

              the Party whose consent is sought will not unreasonably withhold
              its consent to such waiver. Such waiver may be revocable in the
              event of a material adverse change in circumstances related to the
              requesting Party not contemplated at the time of granting the
              waiver.

7.4   Effect of Termination

The termination of this Agreement for any reason will be without prejudice to:

      7.4.1   Inex's right to receive all payments accrued from Enzon as of the
              effective date of such termination;

      7.4.2   Inex's right to receive reimbursement for all costs and
              liabilities incurred by Inex as of the date of Inex's receipt of
              Enzon's notice of termination, which cost and liabilities Inex has
              properly and reasonably incurred in its obligations hereunder. For
              greater certainty, such costs and liabilities shall include all
              reasonable and necessary non-cancellable obligations entered into
              prior to Inex's receipt of Enzon's notice of termination, but
              arising after Inex's receipt of Enzon's notice of termination; and

      7.4.3   any other legal, equitable or administrative remedies as to which
              either Party may then or thereafter become entitled.

*** Indicates the omission of confidential material pursuant to a request for
confidential treatment made in accordance with Rule 24b-2 under the Securities
Exchange Act of 1934, as amended. The Confidential material is being filed
separately with the Secretary to the Securities and Exchange Commission.

<PAGE>
                                     - 11 -

7.5   Survival of Obligations; Return of Confidential Information

      7.5.1   The provisions of Article 1, Sections 4.4.1, 4.4.3, 4.4.5, Article
              5, Section 6.5, Article 7 and Article 8 will survive any
              expiration or termination of this Agreement in accordance with
              their terms.

      7.5.2   Upon any termination of this Agreement pursuant to Article 7,
              except as contemplated hereby, each Party shall promptly return to
              the other Party all written Confidential Information, and all
              copies thereof (except for one archival copy to be retained by a
              person designated by such Party (who shall not make such
              Confidential Information generally available to employees or other
              representatives of such Party) for the purpose of confirming which
              information to hold in confidence hereunder), of the other Party
              which is not covered by a license surviving such termination.

                            Article 8 Miscellaneous

8.1   Assignment

      8.1.1   The rights and obligations set out in this Agreement are personal
              to each Party and for this reason, except as expressly set out in
              this Agreement, this Agreement will not be assignable by either
              Party in whole or in part, nor will either Party subcontract any
              of its obligations hereunder without the prior written consent of
              the other Party, which consent shall not be withheld or delayed
              unreasonably; provided, however, that the restriction contained
              herein will in no way limit the rights of either Party to:

              (a)       assign or subcontract any right or obligation hereunder
                        to any of its Affiliates; or

              (b)       appoint as its agent for any purpose of this Agreement
                        any such Affiliate; or

              (c)       assign any right or obligation hereunder to any person
                        or entity that:

                        (i)   purchases all or substantially all of its assets
                              to which this Agreement relates or

                        (ii)  purchases all or substantially all of the stock of
                              either Party; or

                        (iii) acquires or is combined with either Party in a
                              merger or some other form of business combination.

      8.1.2   This Agreement will be binding upon and will enure to the benefit
              of the parties hereto and to any permitted assignee or successor
              of either party.

      8.1.3   Subject to other provisions of this Section 8.1, if one Party
              validly assigns or subcontracts any or all of its obligations
              hereunder, such assigning or

<PAGE>
                                     - 12 -

              subcontracting Party agrees to remain bound by all of its
              responsibilities and obligations hereunder.

      8.1.4   Any and all assignments of this Agreement or any interest herein
              not made in accordance with this Section 8.1 will be void ab
              initio.

8.2   Counterparts

This Agreement may be executed in any number of counterparts, each of which
shall be deemed an original but all of which together shall constitute one and
the same instrument.

8.3   Exhibits and Appendices

Each exhibit hereto is incorporated by reference and made a part of this
Agreement.

8.4   Force Majeure

In the event that either Party is prevented from performing or is unable to
perform any of its obligations under this Agreement due to any act of God; fire;
casualty; flood; war; strike; lockout; failure of public utilities; injunction
or any act, exercise, assertion or requirement of governmental authority;
epidemic; destruction of production facilities; riots; insurrection; failure of
transportation; inability to procure or use materials, or any other cause beyond
the reasonable control of the Party invoking this Section 8.4 if such Party
shall have used its reasonable efforts to avoid such occurrence, such Party
shall give notice to the other Party in writing promptly, and thereupon the
affected Party's performance shall be excused and the time for performance shall
be extended for the period of delay or inability to perform due to such
occurrence.

8.5   Further Assurances

Each Party hereto agrees to execute, acknowledge and deliver such further
instruments and do all such further acts as may be necessary or appropriate to
carry out the purposes and intent of this Agreement.

8.6   Modification

No waiver, alteration or modification of any of the provisions hereof shall be
binding unless made in writing and signed by the Parties by their respective
officers thereunto duly authorized.

8.7   No Agency

Except as explicitly set forth herein, nothing herein shall be deemed to
constitute either Party as the agent or representative of the other Party, or
both Parties as joint venturers or partners for any purpose. Inex shall be an
independent contractor, not an employee of Enzon, and the manner in which Inex
renders its services under this Agreement shall be within Inex's sole
discretion. Neither Party shall be responsible for the acts or omissions of the
other Party, and neither Party will have authority to speak for, represent or
obligate the other Party in any way without prior written authority from the
other Party.

*** Indicates the omission of confidential material pursuant to a request for
confidential treatment made in accordance with Rule 24b-2 under the Securities
Exchange Act of 1934, as amended. The Confidential material is being filed
separately with the Secretary to the Securities and Exchange Commission.

<PAGE>
                                     - 13 -

8.8   No Solicitation or Hiring of Employees

During the Term and for one year thereafter, neither Inex nor Enzon shall,
without the prior consent of the other Party, solicit the employment of or hire
any person who during the course of employment with the other Party was involved
with activities under the Commercialization Plan and who when solicited or to be
hired is a current employee of the other Party.

8.9   Non-Use of Names

Except as otherwise expressly set out in this Agreement, neither Party shall use
the name of the other Party, nor any adaptation thereof, in any advertising,
promotional or sales literature without prior written consent obtained from such
other Party in each case (which consent shall not be unreasonably withheld or
delayed).

8.10  Notices

Any notice or other communication in connection with this Agreement must be in
writing and if by mail, by registered mail, return receipt requested, and shall
be effective when delivered to the addressee at the address listed below or such
other address as the addressee shall have specified in a notice actually
received by the addressor.

If to Inex:

       Inex Pharmaceuticals, Inc.
       c/o Corporation Trust Center
       1209 Orange Street
       Wilmington, DE 19801

       Attention: President and CEO

       With copies to:

       Inex Pharmaceuticals Corporation
       100-8900 Glenlyon Parkway
       Burnaby, British Columbia
       Canada V5J 5J8
       Fax: 604-419-3202
       Attention: Sr. V.P. Commercial Operations;

       With a copy to:

       Inex Pharmaceuticals Corporation
       100-8900 Glenlyon Parkway
       Burnaby, British Columbia
       Canada V5J 5J8
       Fax: 604-419-3202
       Attention:  Business Development

       and:

*** Indicates the omission of confidential material pursuant to a request for
confidential treatment made in accordance with Rule 24b-2 under the Securities
Exchange Act of 1934, as amended. The Confidential material is being filed
separately with the Secretary to the Securities and Exchange Commission.

<PAGE>
                                     - 14 -

      Lang Michener
      1500-1055 West Georgia Street
      Vancouver, British Columbia
      Canada V6E 4N7
      Fax: 604-685-7084
      Attention: Leo Raffin

      and:

      Farris, Vaughan, Wills & Murphy
      2600 - 700 West Georgia Street
      Vancouver, British Columbia
      Canada V7Y 1B3
      Fax: 604-661-9349
      Attention: James Hatton

      If to Enzon:

      ENZON PHARMACEUTICALS, INC.
      685 Route 202/206
      Bridgewater, New Jersey
      08807
      Fax: 908.541.8680
      Attention: Vice President, Business Development

      with a copy to:

      Enzon Pharmaceuticals, Inc.
      685 Route 202/206
      Bridgewater, NJ 08807
      Fax: 908.541.8838
      Attention: General Counsel

8.11  Publicity

Except as required by law, stock exchange or Regulatory Authority:

      8.11.1  neither Party, nor any of its Affiliates, shall originate any
              publicity, news release or other public announcement, written or
              oral, relating to this Agreement or the existence of an
              arrangement between the Parties, without the prior written
              approval of the other Party and agreement upon the nature and text
              of such announcement or disclosure, which approval shall not be
              unreasonably withheld;

      8.11.2  the Party desiring to make any such public announcement or other
              disclosure shall inform the other Party of the proposed
              announcement or disclosure in reasonably sufficient time prior to
              public release, and shall provide the other Party with a written
              copy thereof, in order to allow such other Party to comment upon
              such announcement or disclosure; and

*** Indicates the omission of confidential material pursuant to a request for
confidential treatment made in accordance with Rule 24b-2 under the Securities
Exchange Act of 1934, as amended. The Confidential material is being filed
separately with the Secretary to the Securities and Exchange Commission.

<PAGE>
                                     - 15 -

      8.11.3  notwithstanding the foregoing, the Parties agree that the press
              release set out as an Exhibit to the Product Supply Agreement
              shall be released by the Parties upon execution and delivery of
              this Agreement by both Parties.

8.12  No Third Party Beneficiaries

Except as expressly set out in this Agreement, nothing in this Agreement is
intended to or shall confer upon any Third Part any legal or equitable right,
benefit or remedy of any nature whatsoever.

8.13  Waiver

The waiver by either Party of a breach or a default of any provision of this
Agreement by the other Party shall not be construed as a waiver of any
succeeding breach of the same or any other provision, nor shall any delay or
omission on the part of either Party to exercise or avail itself of any right,
power or privilege that it has or may have hereunder operate as a waiver of any
right, power or privilege by such Party.

IN WITNESS WHEREOF, the Parties have executed this Co-Promotion Agreement as of
the date first above written.

Inex Pharmaceuticals, Inc.

By: /s/ David J. Main
    ---------------------------
Name:  David J. Main
Title: President & CEO

Enzon Pharmaceuticals, Inc.

By: /s/ Arthur J. Higgins
    ---------------------------
Name:  Arthur J. Higgins
Title: Chairman & CEO

*** Indicates the omission of confidential material pursuant to a request for
confidential treatment made in accordance with Rule 24b-2 under the Securities
Exchange Act of 1934, as amended. The Confidential material is being filed
separately with the Secretary to the Securities and Exchange Commission.

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