Exhibit 10.18

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                                LICENSE AGREEMENT

                                     between

                           ELAN PHARMACEUTICALS, INC.

                                       and

                                   ENZON, INC.

                             Dated November 22, 2002

================================================================================

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            THIS LICENSE AGREEMENT (this "Agreement"), effective November 22,
2002 (the "Effective Date"), is between Elan Pharmaceuticals, Inc., a Delaware
corporation ("Elan"), and Enzon, Inc., a Delaware corporation ("Enzon").

                                    RECITALS

            Enzon, Elan and certain Affiliates of Elan entered into an Asset
Purchase Agreement, dated as of October 1, 2002 (the "Asset Purchase
Agreement"), pursuant to which Elan and certain of its Affiliates will sell to
Enzon, and Enzon will purchase from Elan and certain of its Affiliates, on the
Effective Date, any rights, title and interests related to the "Product" and
"Product Improvements" (each as defined in the Asset Purchase Agreement); this
license serves to convey certain of those rights to Enzon and return certain of
those rights that are assigned to Enzon pursuant to the Asset Purchase Agreement
and certain Related Agreements to Elan to the extent that they are not related
to the Product or Product Improvements.

            In consideration of the premises and the mutual covenants and
promises contained herein, and for other good and valuable consideration, the
receipt and sufficiency of which are hereby acknowledged, the parties hereby
agree as follows:

                                    ARTICLE I

                                   DEFINITIONS

            Section 1.01. Definitions. Capitalized terms not defined in this
Section 1.01 shall have their corresponding meanings as set forth in the Asset
Purchase Agreement. For purposes of this Agreement:

            "Elan Improvements" shall mean Product Improvements developed by the
Elan Companies or its Affiliates for use, having used, distribution, marketing,
selling, offering to sell, having sold and promotion solely outside the
Territory.

            "Excluded Technology" shall mean any proprietary Know-How or Patent
Rights owned or Controlled by Elan or its Affiliates that are unrelated to: (a)
lipid or liposomal combinations or formulations, (b) other combinations or
formulations of Amphotericin B, or any chemical derivatives thereof, with
respect to which Elan or its Affiliates are conducting or have conducted
clinical or pre-clinical research prior to the Effective Date (including any
aerosol formulations of or combination products with Amphotericin B), and/or (c)
the making, having made, using, selling, offering for sale or importing of
compositions of matter or articles of manufacture constituting any of the
foregoing. Notwithstanding the foregoing, included within this definition shall
be the NanoCrystal Technology and PROMDAS.

            "Know-How" shall mean any proprietary or nonproprietary information
directly related to the manufacture, preparation, development (both research and
clinical), or commercialization of a product, including, without limitation,
product specifications, processes, product designs, plans,

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trade secrets, ideas, concepts, inventions, formulae, chemical, pharmacological,
toxicological, pharmaceutical, physical, analytical, stability, safety, quality
assurance, quality control and clinical information, technical information,
research information, and all other confidential or proprietary technical and
business information, whether or not embodied in any documentation or other
tangible materials, but in no event shall the definition of "Know-How" include
information properly in the public domain as of the Effective Date.

            "NanoCrystal Technology" means that certain nanoparticle milling and
stabilization technology that the Elan Companies or their Affiliates acquired
from or by reason of their acquisition of NanoSystems, Inc.

            "Patent Rights" shall mean rights conferred or represented by a
granted or issued patent in force, or such like rights related to a patent
application and any divisionals, continuations, continuations-in-part,
provisionals, substitutions, patents of addition, reissues, extensions,
reexaminations or renewal applications related to, or claiming priority to, the
foregoing (including any supplemental patent certificates) or any confirmation
patent or registration patent and all patents issuing and all foreign
counterparts of any of the foregoing.

            "Product Know-How" shall mean the Product Related Know-How and the
Product Specific Know-How.

            "Product Patent Rights" shall mean the Product Related Patent Rights
and the Product Specific Patent Rights.

            "Product Related Intellectual Property" shall mean the Product
Related Know-How and the Product Related Patent Rights.

            "Product Related Know-How" shall mean that Know-How owned or
Controlled by Elan or its Affiliates that relates to the Product or Current
Product Improvement and shall exclude the Product Specific Know-How. For the
sake of clarity, Know-How claimed in an issued patent or published patent
application within the Product Related Patent Rights shall not be included in
the definition of Product Related Know-How.

            "Product Related Patent Rights" shall mean those Patent Rights
listed on Exhibit A of this Agreement and any other Patents Rights that are
owned or Controlled by Elan or its Affiliates, the practice of which during the
making, having made, use, having used, marketing, sale, having sold, offering to
sell and importation of the Product or any Product Improvement in the Territory
would result in the infringement thereof, and shall exclude the Product Specific
Patent Rights.

            "Product Specific Intellectual Property" shall mean the Product
Specific Know-How and the Product Specific Patent Rights.

            "Product Specific Know-How" shall mean that Know-How Controlled by
Elan or its Affiliates that relates specifically and exclusively to the Product
or any Current Product improvement. For the sake of clarity, Know-How claimed in
an issued patent or published patent application within


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the Product Specific Patent Rights shall not be included in the definition of
Product Specific Know-How.

            "Product Specific Patent Rights" shall mean those Patent Rights
listed on Exhibit B of this Agreement.

            "PROMDAS" shall mean those solid oral dosage forms and medium chain
fatty acid enhancers as claimed and particularly described in the PCT
application WO 00/50012.

            "Third Party Intellectual Property" shall mean any Know-How or
Patent Rights that are owned or controlled by any party other than a party to
this Agreement (a "Third Party").

                                    ARTICLE 2

                                 LICENSE GRANTS

            Section 2.01. Assignments by Elan. In accordance with the Asset
Purchase Agreement and the Patent Assignment Agreement, Elan has assigned to
Enzon all right, title and interest in the Product Specific Intellectual
Property.

            Section 2,02. License Grants.

            (a) Elan Grant to Enzon.

            Elan grants to Enzon, its Affiliates and their respective assigns,
successors, and Enzon accepts, a royalty-free, fully-paid up, irrevocable
exclusive license, or as applicable, sub-license, (exclusive even as to Elan) in
the Territory to the Product Related Intellectual Property to the extent
reasonably necessary or useful to develop, make, have made, use, have used,
market, sell, have sold, offer to sell and import the Product and any Product
Improvements. Elan shall retain and have the exclusive right and license under
the Product Related Intellectual Property, both within and without the
Territory, for all other purposes. The parties also acknowledge that Elan shall
retain the right to the Product Related Intellectual Property only to the extent
reasonably necessary or useful to make or have made the Product solely within
the Territory, or any improvements to the products developed by the Elan
Companies or its Affiliates, for use, having used, distribution, marketing,
selling, offering to sell, having sold and promotion solely outside the
Territory.

            For the avoidance of doubt, and subject to the terms of the Asset
Purchase Agreement and Section 2.02(c) below, Enzon and its Affiliates and their
respective assigns and successors, shall have rights to use and have used the
Product and any Product Improvements outside the Territory in connection with
(A) clinical trials participated in or undertaken by Enzon and/or its Affiliates
in accordance with the terms of the Asset Purchase Agreement and the Related
Agreements; and (B) development and research activities undertaken or to be
undertaken by Enzon, its Affiliates and their respective assigns, successors
which are related to the Product or any Product Improvements in the Territory
(the foregoing collectively, "Enzon R&D Activities").


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            (b) Enzon Grant to Elan.

            Subject to Section 8.14 of the Asset Purchase Agreement, Enzon
grants to Elan and its Affiliates, their respective assigns and successors, and
Elan accepts, a royalty-free, fully-paid up, irrevocable exclusive license
(exclusive even as to Enzon) to the Product Specific Intellectual Property to
the extent reasonably necessary or useful to develop, make, have made, use, have
used, market, sell, have sold, offer to sell and import any composition of
matter or article of manufacture other than the Product or any Product
Improvements. Enzon further grants to Elan and its Affiliates, their respective
assigns, successors, and Elan accepts a royalty-free, fully-paid up co-exclusive
license in the Territory (with Enzon) to the Product Specific Intellectual
Property only to the extent reasonably necessary or useful to make or have made
the Product, or any Elan Improvement, for use, having used, distribution,
marketing, selling, offering to sell, having sold and promotion solely outside
the Territory.

            For the avoidance of doubt, and subject to the terms of the Asset
Purchase Agreement and Section 2.02(c) below, Elan and its Affiliates and their
respective assigns and successors, shall have rights to use and have used the
Product and any Elan Improvements in the Territory in connection with (A)
clinical trials participated in or undertaken by Elan and/or its Affiliates in
accordance with the terms of the Asset Purchase Agreement and the Related
Agreements; and (B) development and research activities undertaken or to be
undertaken by Elan, its Affiliates and their respective assigns and successors
which are related to use, having used, distribution, marketing, selling,
offering to sell, having sold and promotion of the Product or any Elan
Improvements outside the Territory (the foregoing collectively, "Elan R&D
Activities").

            (c) Trademark License and Quality Control

            Each party grants to the other and its Affiliates, their respective
assigns and successors and each party accepts free of royalty, a fully-paid up
co-exclusive license to use such party's corporate name, logo or symbol on
Labeling and packaging for the Product outside the applicable territory solely
to the extent legally required to implement the rights afforded by this
Agreement and the Asset Purchase Agreement. Each party will use commercially
reasonable efforts to protect the other party's corporate name, logo and symbol.
Each party will have prior approval of each form of use of its corporate name,
logo or symbol on Labeling and packaging by the other party. Each party
acknowledges that the other party owns all right, title and interest in such
other party's corporate name, logo or symbols and the goodwill associated with
same, and that any and all use of corporate names, logos and symbols under this
Agreement, and any goodwill associated with such use, shall inure exclusively to
the benefit of the respective trademark owner.

            Enzon further grants to Elan and its Affiliates a limited license to
use the ABELCET and ABCL marks (the "Marks") in the Territory only in connection
with Elan R&D Activities. Elan further grants to Enzon and its Affiliates a
limited license to use the Marks outside of the Territory only in connection
with Enzon R&D Activities. The parties agree and acknowledge that Enzon owns all
right, title and interest in the Marks in the Territory and that Elan owns all
right, title and interest in the Marks outside of the Territory. Any goodwill
associated with any and all use of the Marks in the Territory shall inure
exclusively to the benefit of Enzon, and any goodwill associated with any and


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all use of the Marks outside of the Territory shall inure exclusively to the
benefit of Elan. With respect to the activities undertaken in connection with
this limited license of the Marks, each party shall have the right, in its
discretion and prior to use or distribution in its territory, to request, review
and approve, in its reasonable discretion, samples of the other party's Products
bearing the Marks, as well as any related packaging, promotional or advertising
materials bearing the trademark(s) in any form, including (without limitation)
web site pages featuring the Marks (with a username and/or password to permit
access to restricted areas, as necessary).

            In the event that actual confusion should arise, or either party
believes that a likelihood of confusion may arise, in connection with the
parties' use of the Marks, the parties will fully cooperate in an effort to
eliminate such confusion and to avoid the possibility of such a likelihood of
confusion.

            (d) Copyright License.

            Elan grants to Enzon a fully-paid up, irrevocable royalty-free
license in the Territory to the copyrights or equivalent statutory rights
relating specifically to the Product, including, without limitation, a right to
create derivative works or compilations thereof.

            Section 2.03. Covenant Not to Enforce. During the term of this
Agreement, Elan and its Affiliates will not enforce any intellectual property
rights they own or Control, or support an action of a Third Party to enforce any
such intellectual property rights, that would block, prevent or frustrate
commercialization of the Product or any Product Improvement by Enzon, its
Affiliates or their sublicensees in the Territory. During the term of this
Agreement, Enzon and its Affiliates will not enforce any intellectual property
rights they own or Control in relation to the Product, or any Product
Improvement transferred to Enzon under the Asset Purchase Agreement, or support
an action of a Third Party to enforce any such intellectual property rights,
that would block, prevent or frustrate commercialization of the Product or any
Elan Improvements by Elan, its Affiliates or their sublicensees outside of the
Territory, or the manufacture of the Product within the Territory solely for
sale by Elan, its Affiliates or their sublicensees outside of the Territory. For
purposes of clarity, nothing in this Section 2.03 shall apply to Patent Rights
or Know-How of a Third Party that is either licensed to or purchased by, but not
issued to, a party or its Affiliates after the Effective Date or that is owned
or Controlled by a Third Party who, after the Effective Date, acquires or merges
with the ultimate parent entity of either party.

            Section 2.04. Third Party Intellectual Property. Except as otherwise
provided for by the Asset Purchase Agreement or the Supply Agreement, Enzon
shall be responsible for obtaining any rights or licenses to Third Party
Intellectual Property required for the manufacture, sale, offer for sale, use,
promotion, import or export of the Product or Product Improvement thereto in the
Territory (such as, for example, any activity which may be considered by a
competent court to infringe a Patent Right owned by a Third Party), and Elan
shall be responsible for obtaining any rights or licenses to Third Party
Intellectual Property required for the manufacture, sale, offer for sale, use,
promotion, import or export of the Product or any Elan Improvement outside of
the Territory. Each of Enzon and Elan shall provide prompt written notice to the
other of the particulars of any Third Party Intellectual


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Property in the Territory that Enzon or Elan, as applicable, reasonably believes
may be asserted or that has been asserted to be Third Party Intellectual
Property.

            Section 2.05. Sublicenses. All of the rights and licenses reserved
by or granted hereunder shall be freely sublicensable by the licensee, its
Affiliates and their respective licensees, sublicensees or contracting parties
without approval of the other party. All of the terms and conditions of this
Agreement shall apply to any such sublicenses. Enzon and Elan hereby guarantee
and assume responsibility for the performance of all obligations so imposed on
any sublicensee by reason of operation of the applicable sublicense.

            Section 2.06. Delivery Obligations. To the extent not precluded by
confidentiality obligations owed to a Third Party, each party shall promptly,
upon the other party's reasonable request, deliver to such other party any
copies of any reasonably available tangible embodiments of the Product Patent
Rights and/or the Product Know-How licensed under this Agreement.

            Section 2.07. Transfer of Product Know-How. Within ten (10) business
days following the Closing Date, the parties shall agree on a schedule for the
comprehensive disclosure by Elan to Enzon of all Product Know-How. Elan shall
for a period not to exceed one (1) year (the "Transfer Period") make available
qualified and knowledgeable personnel to promptly respond to reasonable
questions pertaining to Product Know-How. Elan will make its personnel available
for up to 100 hours without additional charge, and for up to an additional two
hundred (200) hours at an hourly rate agreed upon by the parties. Upon the
expiration of the Transfer Period, Elan shall have no further transfer
obligations.

            Section 2.08. Exclusions. Notwithstanding any provision herein, none
of the obligations, covenants or license grants contained within this Agreement
shall extend to or encompass Excluded Technology.

                                    ARTICLE 3

                           MAINTENANCE AND ENFORCEMENT
                         OF INTELLECTUAL PROPERTY RIGHTS

            Section 3.01. Prosecution and Maintenance of Patent Rights.

            (a) Decisions as to whether to file, prosecute and maintain, the
Product Specific Patent Rights, along with other strategic decisions relating to
patent prosecution thereof in the Territory, shall be made by Enzon, at Enzon's
sole expense and discretion. Elan shall coordinate and cooperate in the filing,
maintenance or prosecution of the Product Specific Patent Rights with the person
or persons designated in writing by Enzon. Enzon shall reasonably advise Elan of
the status and prosecution strategy of the actual and prospective patent
filings. Enzon shall not materially prejudice any foreign counterparts of the
Product Specific Patent Rights. Elan shall be permitted to comment on the
prosecution of the Patent Rights subject to this Section 3.01(a) and may, at
its own expense and


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discretion, submit such comments to Enzon. Enzon shall consider such comments in
good faith, but shall not be obligated to implement them.

            (b) Decisions as to whether to file, prosecute and maintain, the
Product Related Patent Rights or the foreign counterparts of the Product Patent
Rights, along with other strategic decisions relating to patent prosecution
thereof, shall be made by Elan, at Elan's sole expense and discretion. Enzon
shall coordinate and cooperate in the filing, maintenance or prosecution of the
Product Related Patent Rights with the person or persons designated in writing
by Elan; provided, however, that to the extent such activities are unrelated to
the Product or any Product Improvement, Enzon shall be reimbursed for its
reasonable out-of-pocket costs relating thereto. Elan shall reasonably advise
Enzon of the status and prosecution strategy of the actual and prospective
patent filings in the Territory. Elan shall not materially prejudice the Product
Patent Rights. Enzon shall be permitted to comment on the prosecution of the
Patent Rights subject to this Section 3.01(b) and may, at its own expense and
discretion, submit such comments to Elan. Elan shall consider such comments in
good faith, but shall not be obligated to implement them.

            (c) Immediately upon the decision of either party not to file,
maintain or continue the prosecution of any Product Patent Rights or foreign
counterparts thereof, and at least sixty (60) days before ceasing prosecution
and/or maintenance of any such Patent Rights, if a party elects not to file a
patent application or ceases the diligent prosecution and/or maintenance of any
such Patent Right, the other party at its sole discretion, may elect to file
and/or continue prosecution and/or maintenance or assume control of the
prosecution of such Patent Rights at its own cost and expense.

            (d) The parties shall cooperate, if necessary and appropriate, with
each other in gaining patent term extensions that are now available or become
available in the future wherever applicable to the Product, a Product
Improvement or an Elan Improvement. The parties shall, if necessary and
appropriate, use reasonable efforts to agree upon a joint strategy relating to
patent term extensions, but, in the absence of mutual agreement with respect to
any extension issue, a patent shall be extended if either party elects to extend
such patent. All filings for such extension shall be made by the party to whom
the patent is assigned; provided, however, such party shall (i) inform the other
party of its intention not to file and (ii) grant the other party the right to
file for such extension.

            (e) Except as otherwise provided for by the Asset Purchase Agreement
or the Supply Agreement, the parties shall bear their own costs and expenses of
filing, prosecuting, maintaining and extending any Patent Rights subject to this
Agreement.

            Section 3.02. Infringement of Licensed Property.

            (a) Enzon shall, with respect to infringement claims maturing after
the Effective Date, within the Territory, have the sole and exclusive right to
enforce, even as to acts or products unrelated to the Product or any Product
Improvement (a "Non-Product Claim"), the Patent Specific Product Rights. Elan
shall, within and without the Territory, have and retain the sole and exclusive
right to enforce, even as to acts or products related to the Product or any
Product Improvement (a "Product Related Claim") of the Patent Related Product
Rights and the foreign counterparts of the Product Patent Rights. In
prosecuting, as applicable, the enforcement rights retained or granted under


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this Section 3.02(a), neither party may materially prejudice the other party's
rights, as applicable, in the Product Patent Rights or their foreign
counterparts. The parties agree to cooperate in the enforcement of the Product
Patent Rights. If one party brings any action or proceeding to enforce the
Product Patent Rights, the second party may be joined as a party plaintiff if
necessary for the action or proceeding to proceed and, in case of joining, the
second party agrees to give the first party reasonable assistance and authority
to file and to prosecute such suit. Each party agrees to provide the party that
is seeking to prevent or enjoin any such infringement with all reasonable
assistance, information and authority to perform the foregoing. The
non-prosecuting party shall have the right, but not the obligation at its own
expense, to be represented in such action by its own counsel. Each party shall
keep the other party reasonably informed as to the status and conduct of the
litigation and shall, at the other party's sole cost and expense, accept and
reasonably consider the other party's comments relating thereto. A party having
knowledge that any of the Product Patent Rights are subject to infringement, or
having knowledge of a reasonable probability of such infringement, shall
promptly notify the other in writing, but in any event within thirty (30) days
of receipt of written notice of such infringement. The notice shall set forth
the facts of such infringement in reasonable detail.

            (b) Upon receiving notice of infringement or suspected infringement
of the Product Specific Patent Rights, including, without limitation, a
Non-Product Claim, Enzon shall have the sole right and discretion, but not the
obligation, to institute, prosecute, and control with its own counsel at its own
expense any action or proceeding with respect to infringement of the Product
Specific Patents and Elan shall have the right, but not the obligation at its
own expense, to be represented in such action by its own counsel. Enzon shall be
entitled to retain all awards, damages and settlement amounts arising out of any
action initiated pursuant to this Section 3.02(b); provided, however, Elan shall
be entitled to receive fifty percent (50%) of any amount directly attributable
to any Non-Product Claim less Enzon's reasonable attorneys' fees and expenses
relating to prosecuting such Non-Product Claim. Elan shall have no right to
institute or prosecute such an infringement action if Enzon declines to do so.

            (c) Upon receiving notice of infringement or suspected infringement
of the Product Related Patent Rights or the foreign counterparts of the Product
Patent Rights, including, without limitation, a Product Related Claim, Elan
shall have the sole right and discretion, but not the obligation, to institute,
prosecute, and control with its own counsel at its own expense any action or
proceeding with respect to infringement of the Product Related Patent Rights or
the foreign counterparts of the Product Patent Rights and Enzon shall have the
right, but not the obligation at its own expense, to be represented in such
action by its own counsel. Elan shall be entitled to retain all awards, damages
and settlement amounts arising out of any action initiated pursuant to this
Section 3.02(b); provided, however, Enzon shall be entitled to receive fifty
percent (50%) of any amount directly attributable to any Product Related Claim
arising out of the Product Related Patent Rights less Elan's reasonable
attorneys' fees and expenses relating to prosecuting such Product Related Claim.
Enzon shall have no right to institute such an infringement action if Elan to do
so.

            Section 3.03. Challenge of Patents. Neither party or its Affiliates,
nor their respective sublicensees, will challenge (other than in defense of an
action for infringement of a Product Patent Right or in an action for breach of
contract) any of the Patent Rights owned or Controlled by the other party or its
Affiliates that are related to the Product, or to any Product Improvement in the


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case of Enzon and any Elan Improvement in the case of Elan, or support an action
of its Affiliate or a Third Party challenging the validity of any such Patent
Rights.

                                    ARTICLE 4

                              TERM AND TERMINATION

            Section 4.01. Term and Expiration. This Agreement shall become
effective as of the Effective Date and shall continue in perpetuity unless and
until all licenses under Section 2 have terminated by mutual written agreement
of the parties.

            Section 4.02. Accrued Rights; Surviving Obligations. Termination of
this Agreement shall be without prejudice to any rights that shall have accrued
to the benefit of any party prior to such termination. Such termination shall
not relieve any party from obligations that are expressly indicated to survive
termination of this Agreement.

                                    ARTICLE 5

                                  MISCELLANEOUS

            Section 5.01. Assignment, Binding Effect. Neither Elan nor Enzon may
assign this agreement, or any of their respective right or obligations
hereunder, without the prior written consent of the other party, which consent
shall not be unreasonably withheld; provided, however, that (i) either party may
assign this Agreement to an Affiliate without the prior written consent of the
other party, and (ii) either party may assign or transfer this Agreement without
consent to any entity into or with which such party merges or consolidates, or
to whom such party transfers all or substantially all of its business or assets
to which this Agreement relates, subject in either case to the assignee or
transferee agreeing in advance and in writing to assume all of the assignor's or
transferor's obligations under this Agreement. Notwithstanding the foregoing,
the Product Patent Rights may not be assigned to an Affiliate or a Third Party
without the concomitant assignment of this Agreement or all of the obligations
hereunder to the assignee and any attempt to do so will be null and void. This
Agreement is binding upon, inures to the benefit of and is enforceable by the
parties hereto and each of their respective successors and permitted assigns.
The covenants, licenses and obligations contained herein are appurtenant to and
shall run with transfer, assignment, sale or other disposition of the Patent
Rights subject to this Agreement. Each party, at the request of the other party,
shall take such reasonable steps, including, without limitation, filings with
the applicable patent office, as are necessary to perfect the other party's
rights with respect to such Patent Rights under this Agreement.

            Section 5.02. Insolvency. All rights and licenses granted under or
pursuant to this Agreement by either party are, and shall otherwise be deemed to
be, for purposes of Section 365(n) of the U.S. Bankruptcy Code and other similar
foreign laws, licenses of rights to "intellectual property" as defined under
Section 101 of the U.S. Bankruptcy Code or such foreign laws. Each party


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agrees that the other party, as a licensee of such rights under this Agreement,
shall retain and may fully exercise all of its rights and elections under
Section 365(n) of the U.S. Bankruptcy Code and other similar foreign laws, and
neither party shall claim that this Agreement does not fall within the scope
thereof. Each party further agrees that, upon the commencement of a bankruptcy
proceeding by or against such party under the U.S. Bankruptcy Code, the other
party shall be immediately entitled to a complete duplicate of (or complete
access to, as appropriate) any such intellectual property and all embodiments of
such intellectual property, and the same, if not already in such other party's
possession, shall be promptly delivered to the other party if such party rejects
this Agreement, fails to promptly elect in writing to continue to perform all of
its obligations under this Agreement, and/or fails to take all steps necessary
to protect such intellectual property.

            Section 5.03. Tax Matters. Elan agrees that it will deliver to Enzon
two (2) duly completed, appropriate and valid Withholding Certificates (as
defined under ss. 1.1441-1(c)(16) of the U.S. Income Tax Regulations)
certifying its status (i.e., U.S. or foreign person).

            Section 5.04. Affiliates. Each party guarantees that its Affiliates
shall comply with the terms and conditions of this Agreement relating thereto,
including, without limitation, the terms and conditions of this Agreement
applicable to the license of any rights hereunder.

            Section 5.05. Miscellaneous Terms. For the sake of brevity, this
Agreement incorporates by reference the provisions of the Asset Purchase
Agreement where this Agreement is silent. By way of example, such incorporation
includes but is not limited to Choice of Law, Indemnification, Confidentiality,
Public Announcements, Descriptive Headings, Injunctive Relief, Non-Waiver,
Relationship of the Parties, Severability, and Counterparts, as they appear in
the Asset Purchase Agreement.

                         [SIGNATURES ON FOLLOWING PAGE]


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            IN WITNESS WHEREOF, the parties have executed this Agreement as of
the day and year first above written.

                                        ELAN PHARMACEUTICALS, INC.

                                        By: /s/ Lisabeth F. Murphy
                                           -------------------------------------
                                           Name: Lisabeth F. murphy
                                           Title: Vice President & Secretary


                                        ENZON, INC.

                                        By:
                                           -------------------------------------
                                           Name:
                                           Title:


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            IN WITNESS WHEREOF, the parties have executed this Agreement as of
the day and year first above written.


                                        ELAN PHARMACEUTICALS, INC.

                                        By:
                                           -------------------------------------
                                           Name:
                                           Title:


                                        ENZON, INC.

                                        By: [SIGNATURE ILLEGIBLE]
                                           -------------------------------------
                                           Name: [NAME ILLEGIBLE]
                                           Title:VP & GC


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