1

ENTREMED, INC.
EXHIBIT 10.28

["..." INDICATES MATERIAL HAS BEEN OMITTED PURSUANT TO A CONFIDENTIAL TREATMENT
REQUEST, WHICH THE COMPANY HAS FILED SEPARATELY WITH THE SECURITIES AND EXCHANGE
COMMISSION]




                                    AGREEMENT


                                 by and between


                                 ENTREMED, INC.


                                       and


                               CELGENE CORPORATION


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                                TABLE OF CONTENTS


                                                                                                 PAGE
                                                                                                 ----
                                                                                               
SECTION 1 - DEFINITIONS............................................................................1
    1.1     "AFFILIATE"............................................................................2
    1.2     "CALENDAR QUARTER".....................................................................2
    1.3     "CELGENE DEVELOPED INTELLECTUAL PROPERTY"..............................................2
    1.4     "CELGENE DEVELOPED PATENT RIGHTS"......................................................2
    1.5     "CELGENE DEVELOPED TECHNOLOGY RIGHTS"..................................................2
    1.6     "CELGENE EXISTING INTELLECTUAL PROPERTY"...............................................3
    1.7     "CELGENE EXISTING PATENT RIGHTS".......................................................3
    1.8     "CELGENE EXISTING TECHNOLOGY RIGHTS"...................................................3
    1.9     "CMCC AGREEMENT".......................................................................3
    1.10    "ENTREMED DEVELOPED PATENT RIGHTS".....................................................3
    1.11    "ENTREMED DEVELOPED TECHNOLOGY RIGHTS".................................................4
    1.12    "ENTREMED EXISTING PATENT RIGHTS"......................................................4
    1.13    "ENTREMED EXISTING TECHNOLOGY RIGHTS"..................................................4
    1.14    "ENTREMED INTELLECTUAL PROPERTY".......................................................4
    1.15    "FIELD"................................................................................5
    1.16    "FIRST COMMERCIAL SALE"................................................................5
    1.17    "NCI AGREEMENT"........................................................................5
    1.18    "NDA"..................................................................................5
    1.19    "NET SALES"............................................................................5
    1.20    "PATENT RIGHT(s)"......................................................................6
    1.21    "PRODUCT"..............................................................................7
    1.22    "SUBLICENSEE"..........................................................................7
    1.23    "TECHNOLOGY RIGHTS"....................................................................7
    1.24    "TERRITORY"............................................................................8
    1.25    "THALIDOMIDE"..........................................................................8
    1.26    "THIRD PARTY(IES)".....................................................................8
    1.27    "VALID CLAIM"..........................................................................8

SECTION 2 - GRANT..................................................................................8
    2.1     Grant of ENTREMED EXISTING PATENT RIGHTS
            and ENTREMED EXISTING TECHNOLOGY RIGHTS................................................8
    2.2     Grant of ENTREMED DEVELOPED PATENT RIGHTS and ENTREMED DEVELOPED TECHNOLOGY RIGHTS.....9
    2.3     CELGENE'S Right To Sublicense..........................................................9
    2.4     Assignment Of Investigational New Drug and Orphan Drug
            Status Applications...................................................................10
    2.5     Assignment Of Agreements..............................................................10
    2.6     Technology Transfer...................................................................11
    2.7     Understanding Regarding CMCC AGREEMENT................................................11


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SECTION 3 - DUE DILIGENCE.........................................................................13
    3.1     In the United States..................................................................13
    3.2     Outside the United States.............................................................15
    3.3     For PRODUCTS For Use In Animals.......................................................16
    3.4     No Other ENTREMED Rights..............................................................17
    3.5     Co-Promotion By CELGENE And ENTREMED..................................................17
    3.6     Establishment Of A Scientific Committee...............................................19

SECTION 4 - ROYALTIES.............................................................................21
    4.1     Royalty Payments......................................................................21
    4.2     Sublicensing Payments and Royalties...................................................22
    4.3     Later-Issued VALID CLAIM..............................................................23
    4.4     "...".................................................................................23
    4.5     THIRD PARTY Sales.....................................................................23
    4.6     Recordkeeping.........................................................................24
    4.7     Quarterly Payments and Reports........................................................25
    4.8     Accounting Reports....................................................................25

SECTION 5 - CONFIDENTIALITY.......................................................................26
    5.1     Confidential Information..............................................................26
    5.2     Non-Confidential Information..........................................................26
    5.3     Disclosure To THIRD PARTIES...........................................................27
    5.4     Disclosure To Sublicensees............................................................28
    5.5     Public Statements.....................................................................28

SECTION 6 - ADVERSE MEDICAL EXPERIENCES...........................................................28
    6.1     Adverse Medical Experience Reporting..................................................28

SECTION 7 - PATENTS...............................................................................28
    7.1     Patent Prosecution....................................................................28
    7.2     Cooperation In Prosecution............................................................29
    7.3     Infringement and Declaratory Judgment Actions.........................................29

SECTION 8 - REPRESENTATIONS AND WARRANTIES........................................................32
    8.1     By Both Parties.......................................................................32
    8.2     By ENTREMED...........................................................................32

SECTION 9 - INDEMNIFICATION AND INSURANCE.........................................................34
    9.1     By CELGENE............................................................................34
    9.2     By ENTREMED...........................................................................35
    9.3     Conditions to Indemnification.........................................................36


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SECTION 10 - ASSIGNMENT AND SUCCESSORS.............................................................36
    10.1     By Either Party.......................................................................36
    10.2     By CELGENE............................................................................37
    10.3     CELGENE As Guarantor..................................................................37
    10.4     Binding Effect........................................................................37

SECTION 11 - FORCE MAJEURE.........................................................................37

SECTION 12 - TERMINATION...........................................................................38
    12.1     Term..................................................................................38
    12.2     By Reason Of FDA Action...............................................................38
    12.3     Termination Of Royalty Obligations....................................................38
    12.4     Breach................................................................................38
    12.5     Insolvency............................................................................40
    12.6     Work-In-Progress......................................................................41
    12.7     Survival..............................................................................41
    12.8     Reversion of Rights...................................................................41

SECTION 13 - GENERAL PROVISIONS....................................................................41
    13.1     Relationship of Parties...............................................................41
    13.2     Entire Understanding..................................................................42
    13.3     Governing Law.........................................................................42
    13.4     Headings..............................................................................42
    13.5     No Waiver.............................................................................42
    13.6     Export Controls.......................................................................42
    13.7     Notices...............................................................................42
    13.8     Original Counterparts.................................................................43


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                                    AGREEMENT

      This Agreement is effective this 9th day of December, 1998 (the "EFFECTIVE
DATE") by and between CELGENE CORPORATION, a Delaware corporation located at 6
Powder Horn Drive, Warren, New Jersey 07059 ("CELGENE"), and ENTREMED, INC., a
Delaware Corporation located at 9610 Medical Center Drive, Rockville, Maryland
20850 ("ENTREMED").

      WHEREAS, CELGENE is a company that develops, manufactures, markets and
sells pharmaceutical products for healthcare, and that has developed and owns
certain patents, patent applications, proprietary technology, know-how, and
United States Food and Drug Administration ("FDA") filings relating to PRODUCTS,
as hereinafter defined; and

      WHEREAS, ENTREMED is the owner or exclusive licensee of certain PATENT
RIGHTS as hereinafter defined, TECHNOLOGY RIGHTS, as hereinafter defined, and
FDA filings related to PRODUCTS, and has certain rights and obligations relating
to PRODUCTS pursuant to agreements with THIRD PARTIES, as hereinafter defined;
and

      WHEREAS, CELGENE desires to obtain assignments and/or exclusive rights in
the TERRITORY in and to all of ENTREMED's PATENT RIGHTS, TECHNOLOGY RIGHTS,
rights by agreement, and FDA filings, whether presently existing or subsequently
developed, for the commercial development, use, and sale of PRODUCTS; and

      WHEREAS, ENTREMED is willing to grant the assignments and/or exclusive
rights desired by CELGENE, as set forth herein, in order to transfer its entire
present and future right, title and interest in PRODUCTS to CELGENE.

      NOW, THEREFORE, in consideration of the mutual promises and other good and
valuable consideration, the parties agree as follows:

                            SECTION 1 - DEFINITIONS

         The terms used in this Agreement have the following meaning:


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      1.1   The term "AFFILIATE" as applied to either party shall mean any
            company or other legal entity other than the party in question in
            whatever country organized, controlling controlled by or under
            common control with that party. The term "control" means ownership
            or control, directly or indirectly, of at least fifty percent (50%)
            of the outstanding stock or voting rights entitled to elect
            directors.

      1.2   The term "CALENDAR QUARTER" shall mean the period of three (3)
            consecutive calendar months ending on March 31, June 30, September
            30 or December 31, as the case may be.

      1.3   The term "CELGENE DEVELOPED INTELLECTUAL PROPERTY" shall mean
            CELGENE DEVELOPED PATENT RIGHTS and CELGENE DEVELOPED TECHNOLOGY
            RIGHTS.

      1.4   The term "CELGENE DEVELOPED PATENT RIGHTS" shall mean any United
            States or foreign patents or patent applications filed by CELGENE,
            or an AFFILIATE, successor or assign thereof at any time subsequent
            to the EFFECTIVE DATE, in which CELGENE has a transferrable
            interest, relating to a modification of a PRODUCT described in any
            ENTREMED INTELLECTUAL PROPERTY or a method of using such PRODUCT,
            which modification is (a) necessary for the manufacture, use, or
            sale of such PRODUCT, and (b) then currently in use by CELGENE at
            the time ENTREMED exercises its rights under Section 12.4(b), for
            the manufacture, use, or sale of such PRODUCT.

      1.5   The term "CELGENE DEVELOPED TECHNOLOGY RIGHTS" shall mean any
            TECHNOLOGY RIGHTS developed, obtained, or acquired by CELGENE or an
            AFFILIATE, successor or assign thereof at any time subsequent to the
            EFFECTIVE DATE, in which CELGENE has a transferrable interest,
            relating to a modification of a PRODUCT described in any ENTREMED
            INTELLECTUAL PROPERTY or a method of using or use of such PRODUCT,
            which modification is (a) necessary for the



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            manufacture, use, or sale of such PRODUCT, and (b) then currently in
            use by CELGENE at the time ENTREMED exercises its rights under
            Section 12.4(b), for the manufacture, use, or sale of such PRODUCT.

      1.6   The term "CELGENE EXISTING INTELLECTUAL PROPERTY" shall mean CELGENE
            EXISTING PATENT RIGHTS and CELGENE EXISTING TECHNOLOGY RIGHTS.

      1.7   The term "CELGENE EXISTING PATENT RIGHTS" shall mean the United
            States and foreign patents and patent applications relating to
            PRODUCTS in which CELGENE has an interest, jointly or solely, as
            owner, assignee, or licensee, whether exclusive or nonexclusive, as
            of the EFFECTIVE DATE.

      1.8   The term "CELGENE EXISTING TECHNOLOGY RIGHTS" shall mean any
            TECHNOLOGY RIGHTS developed, obtained, or acquired, solely or
            jointly, exclusively or non-exclusively, by CELGENE or an AFFILIATE,
            successor or assign thereof as of the EFFECTIVE DATE.

      1.9   The term "CMCC AGREEMENT" shall mean that certain License Agreement
            entered into by and between ENTREMED and Children's Medical Center
            Corporation ("CMCC"), dated May 26, 1994, as amended to the date
            hereof, attached hereto as Exhibit A.

      1.10  The term "ENTREMED DEVELOPED PATENT RIGHTS" shall mean any United
            States or foreign patent applications relating to PRODUCTS assigned
            to, licensed to or filed, solely or jointly, by ENTREMED, or an
            AFFILIATE, successor or assign thereof at any time subsequent to the
            EFFECTIVE DATE, including any United States or foreign patent
            applications filed pursuant to the CMCC AGREEMENT or NCI AGREEMENT,
            and the patents issuing therefrom, which patent applications and
            patents shall be added to Appendix A and shall be


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            included in this Agreement as PATENT RIGHTS and licensed to CELGENE
            in accordance with Section 2 of this Agreement.

      1.11  The term "ENTREMED DEVELOPED TECHNOLOGY RIGHTS" shall mean any
            TECHNOLOGY RIGHTS developed, obtained, or acquired, solely or
            jointly, exclusively or non-exclusively, by ENTREMED, or an
            AFFILIATE, successor or assign thereof at any time subsequent to the
            EFFECTIVE DATE, including any TECHNOLOGY RIGHTS developed or
            obtained pursuant to the CMCC AGREEMENT or NCI AGREEMENT, which
            TECHNOLOGY RIGHTS shall be included in this Agreement and licensed
            to CELGENE in accordance with Section 2 of this Agreement.

      1.12  The term "ENTREMED EXISTING PATENT RIGHTS" shall mean the PATENT
            RIGHTS in which ENTREMED has an interest, jointly or solely, as
            owner, assignee, or licensee, whether exclusive or nonexclusive, as
            of the EFFECTIVE DATE.

      1.13  The term "ENTREMED EXISTING TECHNOLOGY RIGHTS" shall mean any
            TECHNOLOGY RIGHTS developed, obtained, or acquired, solely or
            jointly, exclusively or non-exclusively, by ENTREMED, or an
            AFFILIATE, successor or assign thereof as of the EFFECTIVE DATE,
            including without limitation any TECHNOLOGY RIGHTS developed or
            obtained pursuant to the CMCC AGREEMENT or NCI AGREEMENT. ENTREMED
            EXISTING TECHNOLOGY RIGHTS expressly includes any regulatory data
            and filings, including without limitation all FDA Investigational
            New Drug and Orphan Drug Status applications, as set forth in
            Appendix C.

      1.14  The term "ENTREMED INTELLECTUAL PROPERTY" shall mean and include
            ENTREMED DEVELOPED PATENT RIGHTS, ENTREMED DEVELOPED TECHNOLOGY
            RIGHTS, ENTREMED EXISTING PATENT RIGHTS, and ENTREMED EXISTING
            TECHNOLOGY RIGHTS.



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      1.15  The term "FIELD" shall mean the use of THALIDOMIDE in humans and
            animals, including without limitation any and all diagnostic,
            prophylactic, therapeutic, and research and development uses.

      1.16  The term "FIRST COMMERCIAL SALE" shall mean, in each country of the
            TERRITORY, the first sale after the EFFECTIVE DATE in such country
            to a THIRD PARTY in connection with the nationwide introduction of
            any PRODUCT by CELGENE, its AFFILIATES or SUBLICENSEES following
            marketing and/or pricing approval by the appropriate governmental
            agency for the country in which the sale is to be made and, when
            governmental approval is not required, the first sale in that
            country in connection with the nationwide introduction of a PRODUCT
            in that country.

      1.17  The term "NCI AGREEMENT" shall mean that certain Agreement by and
            between the Division of Cancer Treatment at the National Cancer
            Institute ("NCI") and ENTREMED, dated November 16, 1994, and
            executed on behalf of ENTREMED on November 23, 1994, and on behalf
            of NCI on November 18, 1994, attached hereto as Exhibit B.

      1.18  The term "NDA" shall mean a New Drug Application filed with the
            United States Food and Drug Administration.

      1.19  The term "NET SALES" means the gross amount received by CELGENE or
            its AFFILIATES or SUBLICENSEES for sale of PRODUCT to THIRD PARTIES,
            less: (i) cost of freight, postage, and freight insurance, (if paid
            by seller); (ii) sales taxes, value added taxes, excise taxes, and
            customs duties; (iii) cost of export licenses and any taxes, fees or
            other charges associated with the exportation or importation of
            PRODUCTS; (iv) rebates accrued, incurred or paid to Federal Medicaid
            and State Medicare and any other price reductions required by a
            governmental agency; (v) rejected shipments, returns, and
            retroactive deductions; (vi) the amount received for sales which
            become the subject of a subsequent temporary or partial recall


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            by a regulatory agency for safety or efficacy reasons outside the
            control of CELGENE; and (vii) customary cash, quantity, and trade
            discounts; provided, however, that a sale or transfer to an
            AFFILIATE or SUBLICENSEE for re-sale by such AFFILIATE or
            SUBLICENSEE shall not be considered a sale for the purpose of this
            provision but the resale by such AFFILIATE or SUBLICENSEE shall be a
            sale for such purposes. A "sale" shall also include a transfer or
            other disposition for consideration, but not such transfers or
            dispositions, without consideration, for pre-clinical, clinical,
            regulatory or governmental purposes prior to receiving marketing
            approval for the specific indication for which such transfer is
            made. In the event that consideration in addition to or in lieu of
            money is received for PRODUCT, such consideration shall be added to
            the NET SALES as valued on the day of receipt thereof by CELGENE. To
            the extent that a PRODUCT is sold in other than an arms length
            transaction, NET SALES shall be the fair market value of such
            PRODUCT if sold in an arms length transaction, less the costs
            identified in subsections (i)-(vi) of this Section 1.19. PRODUCT
            shall be considered "sold" at the earlier of (a) the transfer of
            title in such PRODUCT to a person other than an AFFILIATE or
            SUBLICENSEE of CELGENE or (b) the shipment of such PRODUCT from the
            manufacturing or warehouse facilities of CELGENE or its AFFILIATE or
            SUBLICENSEE to a THIRD PARTY.

      1.20  The term "PATENT RIGHT(s)" shall mean:

            (a)   the United States patent applications and patents listed in
                  Appendix A;

            (b)   the United States and foreign patents issued from applications
                  listed in Appendix A and from divisionals and continuations of
                  such applications;

            (c)   claims of United States continuation-in-part applications and
                  of equivalent foreign applications, and of the resulting
                  patent(s), that


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                  are directed to subject matter described in the United States
                  and foreign applications listed in Appendix A;

            (d)   claims of all later-filed foreign patent applications, and of
                  the resulting patents, that are directed to subject matter
                  described in the United States patents and/or patent
                  applications described in the foregoing subsections of this
                  Section 1.20;

            (e)   any reissues, re-examinations or extension of United States
                  patents described in the foregoing subsections of this Section
                  1.20; and

            (f)   ENTREMED DEVELOPED PATENT RIGHTS, when assigned to, licensed
                  to or filed, solely or jointly, by ENTREMED, or an AFFILIATE,
                  successor or assign thereof, pursuant to Section 1.10 of this
                  Agreement.

      1.21  The term "PRODUCT" shall mean any article of manufacture, substance,
            material, chemical, formulation or composition for use in the FIELD
            which is or includes THALIDOMIDE as an active ingredient, including,
            without limitation, a composition that comprises THALIDOMIDE and a
            non-steroidal anti-inflammatory compound(s). PRODUCT expressly
            excludes THALIDOMIDE analogs.

      1.22  The term "SUBLICENSEE" shall mean any THIRD PARTY licensed by
            CELGENE to make, have made, use, offer to sell, sell or import any
            PRODUCT.

      1.23  The term "TECHNOLOGY RIGHTS" shall mean any information relating to
            PRODUCTS that is not covered by a patent or patent application,
            including without limitation technical and non-technical
            information, know-how, methods, processes, procedures, compositions,
            devices, formulae, protocols, techniques, software, designs,
            drawings, plans, diagrams, specifications, data, the results of
            tests or assays, and all other information relating to PRODUCTS.



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      1.24  The term "TERRITORY" shall mean all countries of the world.

      1.25  The term "THALIDOMIDE" shall mean a compound with the chemical
            structure described as
            2-(2,6-Dioxo-3-piperidinyl)-1H-isoindole-1,3(2H)-dione, or as
            otherwise defined in the Merck Index, entry 9390, 12th ed., and
            pharmaceutically acceptable salts thereof.

      1.26  The term "THIRD PARTY(IES)" shall mean a person or entity who or
            which is neither a party hereto nor an AFFILIATE of a party hereto.

      1.27  The term "VALID CLAIM" shall mean an issued claim of an unexpired
            patent ("ISSUED VALID CLAIM") or a claim of a pending patent
            application, which shall not have been withdrawn, canceled or
            disclaimed, or held invalid or unenforceable by a court of competent
            jurisdiction in an unappealed or unappealable decision.
            Notwithstanding the foregoing to the contrary, a claim of a pending
            patent application, divisional application or continuation-in-part
            shall cease to be a VALID CLAIM if no patent has issued on such
            claim on or prior to the fifth (5th) anniversary of the EFFECTIVE
            DATE of this Agreement, provided that such claim shall once again
            become a VALID CLAIM on the issue date of a patent that subsequently
            issues and covers such claim.

      1.28  The use herein of the plural shall include the singular, and the use
            of the masculine shall include the feminine.

                               SECTION 2 - GRANT

      2.1   Grant of ENTREMED EXISTING PATENT RIGHTS and ENTREMED EXISTING
            TECHNOLOGY RIGHTS. ENTREMED hereby grants to CELGENE and CELGENE
            hereby accepts from ENTREMED an exclusive, royalty bearing right and
            license or sublicense, as the case may be, under the ENTREMED
            EXISTING PATENT RIGHTS and the



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                  ENTREMED EXISTING TECHNOLOGY RIGHTS to make, have made, use,
                  offer to sell, sell, and import PRODUCTS in the TERRITORY.

            2.2   Grant of ENTREMED DEVELOPED PATENT RIGHTS and ENTREMED
                  DEVELOPED TECHNOLOGY RIGHTS. ENTREMED hereby grants to
                  CELGENE, to the extent not prohibited by the United States
                  Government or by prior contractual obligations to any THIRD
                  PARTY, and CELGENE hereby accepts from ENTREMED:

                  (a)   an exclusive, royalty bearing right and license under
                        the ENTREMED DEVELOPED PATENT RIGHTS and the ENTREMED
                        DEVELOPED TECHNOLOGY RIGHTS to make, have made, use,
                        offer to sell, sell, and import PRODUCTS in the
                        TERRITORY; and

                  (b)   to the extent an exclusive license is not available to
                        CELGENE in a country under a particular ENTREMED
                        DEVELOPED PATENT RIGHT or ENTREMED DEVELOPED TECHNOLOGY
                        RIGHT, but a non-exclusive license would be available,
                        ENTREMED hereby grants CELGENE a nonexclusive, royalty
                        bearing right and license under such ENTREMED DEVELOPED
                        PATENT RIGHT(s) and ENTREMED DEVELOPED TECHNOLOGY
                        RIGHT(s) to make, have made, use, offer to sell, sell,
                        and import PRODUCTS in the TERRITORY.

            2.3   CELGENE'S Right To Sublicense.

                  (a)   In the United States. ENTREMED hereby grants to CELGENE
                        the right to sublicense ENTREMED INTELLECTUAL PROPERTY
                        in the United States with the consent of ENTREMED, to be
                        exercised in ENTREMED's sole discretion.

                  (b)   Outside the United States. ENTREMED hereby grants to
                        CELGENE the right to sublicense ENTREMED INTELLECTUAL



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                        PROPERTY outside the United States with the written
                        consent of ENTREMED, which consent shall not be
                        unreasonably withheld. Outside the United States,
                        CELGENE shall use reasonable efforts to negotiate
                        sublicensing agreements that are commercially reasonable
                        according to contemporaneous prevailing standards within
                        the pharmaceutical industry.

            2.4   Assignment Of Investigational New Drug and Orphan Drug Status
                  Applications. Within ten (10) days of the EFFECTIVE DATE,
                  ENTREMED and CELGENE shall notify the Food and Drug
                  Administration ("FDA") of the transfer of ENTREMED's rights in
                  PRODUCTS to CELGENE by submitting to the FDA letters
                  substantially in the form attached hereto as Exhibit C, and
                  ENTREMED shall notify CELGENE of its compliance with this
                  Section 2.4 by copies of such letters. ENTREMED shall take all
                  further steps necessary or helpful to assign to CELGENE all
                  Orphan Drug Status and Investigational New Drug applications
                  filed by ENTREMED as of the EFFECTIVE DATE, as set forth in
                  Appendix C. If the FDA declines to allow the assignment of any
                  of ENTREMED's Investigational New Drug and/or Orphan Drug
                  Status application(s) to CELGENE, for whatever reason, then
                  ENTREMED's rights under such application(s) will be included
                  in this Agreement as ENTREMED EXISTING TECHNOLOGY RIGHTS and
                  will be licensed to CELGENE in accordance with Section 2 of
                  this Agreement.

            2.5   Assignment Of Agreements. Within ten (10) days of the
                  EFFECTIVE DATE, ENTREMED shall notify CMCC and NCI of the
                  sublicense and transfer, respectively, of its rights in
                  PRODUCTS to CELGENE, and shall take all steps necessary or
                  helpful to assign to CELGENE the NCI AGREEMENT, including
                  without limitation requesting consent to assign ENTREMED's
                  obligations and entire right, title, and interest, under such
                  agreement to CELGENE, and upon receipt of the consent of NCI
                  to assign the NCI AGREEMENT, CELGENE will expressly assume all
                  of



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                  ENTREMED's duties and obligations thereunder. In the event
                  that ENTREMED is not permitted to assign its rights under the
                  NCI AGREEMENT to CELGENE, ENTREMED's rights in any PATENT
                  RIGHTS or TECHNOLOGY RIGHTS resulting from the NCI AGREEMENT
                  will be included in this Agreement as ENTREMED DEVELOPED
                  PATENT RIGHTS and ENTREMED DEVELOPED TECHNOLOGY RIGHTS,
                  respectively, and will be licensed to CELGENE in accordance
                  with Section 2.2 of this Agreement.

            2.6   Technology Transfer. As soon as reasonably possible following
                  the EFFECTIVE DATE, but in no event later than one (1) month
                  after such date, ENTREMED shall transfer to CELGENE all
                  ENTREMED EXISTING TECHNOLOGY RIGHTS and ENTREMED DEVELOPED
                  TECHNOLOGY RIGHTS not already in CELGENE's possession.
                  ENTREMED agrees to disclose and transfer all ENTREMED
                  DEVELOPED TECHNOLOGY RIGHTS to CELGENE promptly, as they are
                  obtained or developed. ENTREMED also agrees to provide, upon
                  reasonable notice from CELGENE, any technical, scientific,
                  statistical, and/or regulatory support necessary or useful to
                  CELGENE's understanding and/or use of ENTREMED EXISTING
                  TECHNOLOGY RIGHTS and ENTREMED DEVELOPED TECHNOLOGY RIGHTS.

            2.7   Understanding Regarding CMCC AGREEMENT. To the extent
                  TECHNOLOGY RIGHTS and/or PATENT RIGHTS licensed to CELGENE
                  under this Agreement are rights which ENTREMED has licensed
                  from CMCC under the CMCC AGREEMENT, CELGENE and ENTREMED
                  understand and agree as follows:

                  (a)   The rights licensed to CELGENE by ENTREMED are subject
                        to the terms, limitations, restrictions and obligations
                        of the CMCC AGREEMENT.



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                  (b)   CELGENE will comply with the terms, obligations,
                        limitations and restrictions of sublicensees under
                        Articles II, V, VII, VIII, IX, X, XII, XIII, and XV of
                        the CMCC AGREEMENT.

                  (c)   ENTREMED will, at its own expense, timely pay the
                        milestone payment of "..." due to CMCC upon completion
                        of a Phase II clinical trial for any indication,
                        pursuant to Section 4.1.3 of the CMCC AGREEMENT.
                        ENTREMED shall promptly provide written notice to
                        CELGENE of such payment.

                  (d)   CELGENE will, at its own expense, timely pay the
                        milestone payment of "..." due to CMCC upon completion
                        of a Product License Application for any indication,
                        pursuant to Section 4.1.4 of the CMCC AGREEMENT, which
                        payment shall be made to ENTREMED and timely forwarded
                        by ENTREMED to CMCC; provided, however, that if (i) such
                        payment becomes due prior to January 1, 2000, and (ii)
                        CELGENE's annual sales in the year such payment becomes
                        due are less than "...", CELGENE may notify ENTREMED, in
                        writing, that it wishes ENTREMED to pay such amount to
                        CMCC directly, which ENTREMED hereby agrees to do, and,
                        by June 30, 2000 CELGENE shall reimburse ENTREMED the
                        amount paid to CMCC, plus interest calculated at the
                        annual rate of the sum of one percent (1%) plus the
                        prime interest rate quoted by Citibank, N.A. on the date
                        said payment is due. ENTREMED shall promptly provide
                        written notice to CELGENE of all payments under this
                        Section 2.7(d).

                  (e)   ENTREMED will comply with the terms, obligations,
                        limitations and restrictions of the CMCC AGREEMENT,
                        including, without limitation, any provisions relating
                        to due diligence, notification with respect to
                        sublicenses, and milestone payments, subject to Sections
                        2.7(c) and (d) of this Agreement.


                                      -12-
   17

                  (f)   The CMCC AGREEMENT and ENTREMED's rights thereunder
                        shall remain in full force and effect for the life of
                        the last to expire patent issued under the Patent
                        Rights, as defined therein, unless earlier terminated
                        pursuant to Article XIII of the CMCC AGREEMENT.

                           SECTION 3 - DUE DILIGENCE

            3.1   In the United States.

                  (a)   CELGENE shall initiate and diligently use reasonable
                        efforts to develop, or to file for regulatory approval
                        of or register, and to market and sell PRODUCTS in the
                        United States. Reasonable efforts with respect to the
                        development and/or pursuit of regulatory approval or
                        registration for PRODUCTS in the United States shall be
                        demonstrated by CELGENE (i) developing and pursuing
                        regulatory approval for PRODUCTS for those uses CELGENE,
                        in good faith, determines to be commercially and
                        scientifically reasonable, including but not limited to
                        (a) one (1) "...", (b) one (1) "...", and (c) one (1)
                        "..."; and (ii) funding and conducting clinical trials
                        for PRODUCTS for other uses in order to enhance
                        scientific knowledge with regard to such PRODUCTS,
                        including for the publication of data and results in
                        scientific journals, whether or not such clinical trials
                        result in or facilitate the pursuit of regulatory
                        approval.

                  (b)   ENTREMED agrees that, subject to Section 3.6 of this
                        Agreement, (i) the decision regarding which uses to
                        pursue regulatory approval of PRODUCTS for, and/or to
                        fund and conduct clinical trials of PRODUCTS for,
                        pursuant to Section 3.1(a) of this Agreement, shall be
                        made by and in the sole discretion of CELGENE; and (ii)
                        with respect to the manner in which regulatory approval
                        is sought and/or clinical trials are funded and
                        conducted, CELGENE shall



                                      -13-
   18

                        have sole discretion, including, without limitation,
                        complete control over all regulatory submissions of
                        PRODUCTS to the appropriate regulatory agencies
                        worldwide, including whether, when, and how to file,
                        maintain, withdraw, or abandon an application for
                        regulatory approval of PRODUCTS.

                  (c)   Within 90 days after the EFFECTIVE DATE, CELGENE shall
                        draft a Development Plan outlining CELGENE'S development
                        objectives for PRODUCTS, in accordance with Sections
                        3.1(a)(i) and (b) of this Agreement. CELGENE shall
                        consult with ENTREMED concerning the Development Plan.
                        The Development Plan shall include suitable clinical
                        milestones which are reasonably intended to lead to
                        regulatory approval of PRODUCTS, in accordance with
                        Sections 3.1(a)(i) and (b) of this Agreement.

                  (d)   CELGENE shall provide a written summary report to
                        ENTREMED within thirty (30) days after June 30th and
                        December 31st of each calendar year concerning the
                        efforts being made in accordance with this Section 3.1
                        with respect to PRODUCTS. CELGENE shall provide ENTREMED
                        with any additional information reasonably requested by
                        ENTREMED in this respect.

                  (e)   At ENTREMED'S reasonable request, CELGENE shall provide
                        ENTREMED access to all clinical trial data for PRODUCTS
                        conducted by CELGENE in accordance with the Development
                        Plan set forth in this Section 3.1. In the event that
                        rights are returned to ENTREMED under Section 3.1(f) of
                        this Agreement, ENTREMED shall have the right to review
                        and use the clinical trial data in its own clinical
                        program.

                  (f)   In the event that CELGENE fails to meet any of its
                        obligations under this Section 3.1 with respect to
                        PRODUCTS in the United


                                      -14-
   19

                        States, and such failure is not cured within sixty (60)
                        days after written notice thereof is received by CELGENE
                        from ENTREMED, then ENTREMED shall have the right and
                        option to terminate the license granted in this
                        Agreement and this Agreement by giving CELGENE sixty
                        (60) days prior written notice thereof.

            3.2   Outside the United States.

                  (a)   Diligence. CELGENE shall initiate and diligently use
                        reasonable efforts to develop, or to file for regulatory
                        approval of or register, and to market and sell PRODUCTS
                        in Europe, in Canada, and in the Pacific Rim, Japan, and
                        Australia (collectively, the "PACIFIC RIM"). Reasonable
                        efforts with respect to the development and/or pursuit
                        of regulatory approval or registration for PRODUCTS in
                        Europe, Canada, and the PACIFIC RIM shall be
                        demonstrated by CELGENE, or a sublicensee thereof,
                        pursuing regulatory approval for PRODUCTS (i) in Italy,
                        France, the United Kingdom, and Germany (in the case of
                        Europe), and in Japan and one other country of the
                        PACIFIC RIM (in the case of the PACIFIC RIM), within
                        "..." from the date of the first FDA approval of a
                        PRODUCT for an oncology indication or Crohn's disease,
                        whichever occurs earlier; and (ii) in Canada, within
                        "..." from the date of the first FDA approval of a
                        PRODUCT for an oncology indication or Crohn's disease,
                        whichever occurs earlier.

                  (b)   CELGENE's Discretion. ENTREMED agrees that, subject to
                        Section 3.6 of this Agreement, (i) the decision
                        regarding which uses to pursue regulatory approval of
                        PRODUCTS for, and/or to fund and conduct clinical trials
                        of PRODUCTS for, pursuant to Section 3.2(a) of this
                        Agreement, shall be made by and in the sole discretion
                        of CELGENE; and (ii) with respect to the manner in



                                      -15-
   20

                        which regulatory approval is sought and/or clinical
                        trials are funded and conducted, CELGENE shall have sole
                        discretion, including, without limitation, complete
                        control over all regulatory submissions of PRODUCTS to
                        the appropriate regulatory agencies worldwide, including
                        whether, when, and how to file, maintain, withdraw, or
                        abandon an application for regulatory approval of
                        PRODUCTS.

                  (c)   Cooperation. If CELGENE fails to use reasonable efforts
                        in Europe, Canada, or the PACIFIC RIM, as set forth in
                        Section 3.2(a) of this Agreement, or to sublicense its
                        rights to a THIRD PARTY, then ENTREMED shall have the
                        right and option to either (i) terminate the licenses
                        granted in the region where such failure has occurred,
                        i.e., Europe, Canada, or the PACIFIC RIM, respectively,
                        by giving CELGENE sixty (60) days prior written notice
                        thereof, or (ii) cooperate with CELGENE to find an
                        appropriate SUBLICENSEE for such rights.

            3.3   For PRODUCTS For Use In Animals.

                  (a)   Diligence. CELGENE shall initiate and diligently use
                        reasonable efforts to develop, or to file for regulatory
                        approval of or register, and to market and sell PRODUCTS
                        for use in animals. Such reasonable efforts shall be
                        demonstrated by CELGENE obtaining regulatory approval
                        for the sale of a PRODUCT for use in animals within four
                        (4) years of the EFFECTIVE DATE in the United States
                        and, outside the United States, in one of the following
                        countries: Italy, France, the United Kingdom, or
                        Germany.

                  (b)   Cooperation. If CELGENE fails to use reasonable efforts
                        either in the United States or outside the United
                        States, as set forth in Section 3.3(a) of this
                        Agreement, or to sublicense its rights in such regions
                        to a THIRD PARTY, then ENTREMED shall have the


                                      -16-
   21

                        right and option to either (i) terminate CELGENE's
                        rights in the region where such failure has occurred,
                        i.e., in the United States or outside the United States,
                        respectively, in and to such PRODUCTS for use in animals
                        by giving CELGENE sixty (60) days prior written notice
                        thereof, or (ii) cooperate with CELGENE to find an
                        appropriate SUBLICENSEE for such rights.

            3.4   No Other ENTREMED Rights. Except as otherwise expressly
                  provided in this Agreement, ENTREMED agrees that it has not
                  retained any rights under ENTREMED INTELLECTUAL PROPERTY to
                  PRODUCTS, and that is shall not (i) make, use, offer to sell,
                  sell, or import PRODUCTS in the TERRITORY, or (ii)
                  collaborate, negotiate, or deal with THIRD PARTIES with
                  respect to PRODUCTS.

            3.5   Co-Promotion By CELGENE And ENTREMED.

                  (a)   With Regard To PRODUCTS. If CELGENE, in its sole
                        discretion, decides to co-promote any PRODUCT or to seek
                        sales assistance in promoting any PRODUCT, including,
                        but not limited to, sales assistance for indications not
                        then promoted by CELGENE sales personnel, CELGENE shall,
                        in good faith, consider ENTREMED for the opportunity to
                        co-promote such PRODUCT(S) for such indications in the
                        United States.

                        (i)   CELGENE will give ENTREMED due consideration for
                              the opportunity to co-promote such PRODUCT(S) as
                              set forth herein, provided that ENTREMED has a
                              sales force capable of providing the required
                              details to the targeted physician audience, or is
                              capable of assembling such a sales force within
                              six (6) months, and agrees to do so. If and only
                              if ENTREMED either has a sales force capable of
                              providing the required details to the targeted
                              physician audience, or commits to assembling such
                              a sales force



                                      -17-
   22

                              within six (6) months, the decision to offer
                              ENTREMED the opportunity to co-promote such
                              PRODUCT(s) for such indications in the United
                              States shall be made, in good faith, by CELGENE,
                              and CELGENE shall notify ENTREMED of its decision
                              in writing.

                        (ii)  If CELGENE offers ENTREMED the opportunity to
                              co-promote, pursuant to Section 3.5(a)(i) of this
                              Agreement, ENTREMED shall have thirty (30) days to
                              accept such offer by written notice to CELGENE. If
                              ENTREMED accepts such offer to co-promote
                              PRODUCTS, then the parties will negotiate, in good
                              faith, a co-promotion agreement setting forth the
                              substance of this Section 3.5 and other normal and
                              customary conditions within six (6) months of
                              CELGENE's receipt of ENTREMED's acceptance
                              pursuant to this Section 3.5(a)(ii).

                        (iii) ENTREMED's co-promotion efforts will focus on
                              detailing (product presentations) the PRODUCT to
                              the targeted physician audience. In such case,
                              ENTREMED's sales representatives will also have
                              the opportunity, from time to time, to participate
                              in seminars, in-service training, group
                              presentations, and other educational and
                              promotional activities initiated by CELGENE in
                              consultations with ENTREMED. In addition, ENTREMED
                              will assign a product manager to participate with
                              the CELGENE marketing team to provide input as
                              appropriate and to be the operational liaison
                              between CELGENE and ENTREMED's sales force.

                  (b)   With Regard To Anti-angiogenic Compounds. If ENTREMED,
                        in its sole discretion, decides to co-promote an
                        anti-angiogenic compound or a composition containing, as
                        an active ingredient, such a compound, or to seek sales
                        assistance in promoting any



                                      -18-
   23

                        such anti-angiogenic compound or composition, including,
                        but not limited to, sales assistance for indications not
                        then promoted by ENTREMED sales personnel, ENTREMED
                        shall, in good faith, consider CELGENE for the
                        opportunity to co-promote such anti-angiogenic compounds
                        and/or compositions. The decision to offer CELGENE the
                        opportunity to co-promote such anti-angiogenic compounds
                        and/or compositions shall be made in the sole discretion
                        of ENTREMED, and be subject, mutatis mutandis, to the
                        terms and conditions set forth in Sections 3.5(a)(ii)
                        and (iii) of this Agreement.

            3.6   Establishment Of A Scientific Committee. CELGENE agrees to
                  conduct and fund a development program designed to obtain
                  approval to market PRODUCTS, in accordance with its
                  obligations under Section 3.1(a)(i) and 3.1(b) of this
                  Agreement (the "PROGRAM"). To ensure the continued
                  participation of ENTREMED in these development activities, the
                  PROGRAM will be monitored by a Scientific Committee as
                  described herein (the "COMMITTEE").

                  (a)   Members. Within ten (10) days of the date hereof,
                        ENTREMED and CELGENE shall each appoint two (2) persons
                        to serve on the COMMITTEE. Each party will have the
                        right to change its representation on the COMMITTEE upon
                        written notice to the other.

                  (b)   Chairperson. The COMMITTEE will be chaired by one
                        representative of CELGENE, who shall be chosen in the
                        sole discretion of CELGENE.

                  (c)   Responsibilities. The COMMITTEE will have authority to:

                        (i)   act in an advisory role and provide information,
                              including without limitation technical and
                              regulatory information and


                                      -19-
   24

                              marketing and sales information, helpful in
                              connection with the PROGRAM;

                        (ii)  make recommendations regarding the performance of
                              the PROGRAM and the conduct of the work pursuant
                              thereto, and monitor performance thereunder;

                        (iii) propose modifications to the PROGRAM;

                        (iv)  review any and all proposed publication(s)
                              relating to the PROGRAM and the results therefrom;
                              and

                        (v)   review all information and data resulting from the
                              PROGRAM.

                  (d)   Meetings. The COMMITTEE will meet not less than four (4)
                        times a year during the term of the PROGRAM, at such
                        dates and times as agreed to by the parties. The
                        COMMITTEE will prepare written minutes of each meeting
                        and a written record of all decisions whether made at a
                        formal meeting or not. All decisions made and actions
                        taken by the COMMITTEE will be made or taken in the sole
                        discretion of CELGENE after good faith consideration of
                        the position or opinion of the ENTREMED members.

                  (e)   Term and Termination. The PROGRAM will continue until
                        there are no longer any ongoing activities in pursuit of
                        regulatory approval, or any pending applications for
                        regulatory approval, for PRODUCTS, pursuant to Sections
                        3.1(a)(i) and (b) of this Agreement. Once all such
                        activities have been completed and all such regulatory
                        approvals have been obtained, CELGENE may, in its sole
                        discretion, extend the term of the PROGRAM to include
                        PRODUCTS in clinical trials for other uses, as set forth
                        in Sections 3.1(a)(ii) and (b) of this Agreement, in
                        which case the PROGRAM will continue until such clinical
                        trials have been completed or otherwise terminated or,
                        if applicable, until regulatory approval has


                                      -20-
   25

                        been obtained, unless the PROGRAM is sooner terminated
                        by CELGENE.

                             SECTION 4 - ROYALTIES

            4.1   Royalty Payments.

                  (a)   First Twelve Years. CELGENE shall pay to ENTREMED the
                        following royalties on the NET SALES of PRODUCTS sold by
                        CELGENE or its AFFILIATES in each country of the
                        TERRITORY (i) for the first consecutive twelve (12)
                        years from the date of the FIRST COMMERCIAL SALE of a
                        PRODUCT in each country of the TERRITORY, and,
                        separately and independently, (ii) for the first
                        consecutive twelve (12) years from the date of the FIRST
                        COMMERCIAL SALE of each PRODUCT that contains, as a
                        second active ingredient, a compound other than
                        THALIDOMIDE, in each country of the TERRITORY:

                        (i)   "..." of NET SALES up to "..." dollars of such
                              sales;

                        (ii)  "..." of NET SALES between "..." dollars and "..."
                              dollars of such sales;

                        (iii) "..." of NET SALES between "..." and "..." dollars
                              of such sales; and

                        (iv)  "..." of NET SALES over "..." dollars of such
                              sales.

                  (b)   After Twelve Years. For each PRODUCT in each country in
                        the TERRITORY in which the twelve (12) year period
                        provided for in Section 4.1(a) of this Agreement shall
                        have terminated, CELGENE shall pay to ENTREMED the
                        following royalties on the NET SALES of such PRODUCT
                        covered by an ISSUED VALID CLAIM of the PATENT RIGHTS
                        that are sold by CELGENE or its AFFILIATES in such
                        country:

                        (i)   "..." of NET SALES up to "..." dollars of such
                              sales;


                                      -21-
   26

                        (ii)  "..." of NET SALES between "..." dollars and "..."
                              dollars of such sales;

                        (iii) "..." of NET SALES between "..." and "..." dollars
                              of such sales; and

                        (iv)  "..." of NET SALES over "..." dollars of such 
                              sales;

                  and such royalties under this Section 4.1(b) shall be
                  payable until the last to expire PATENT RIGHT containing an
                  ISSUED VALID CLAIM covering such PRODUCT sold by CELGENE or
                  its AFFILIATES in such country.

            4.2   Sublicensing Payments and Royalties.

                  (a)   Under CELGENE's Rights. If CELGENE grants a sublicense
                        of its exclusive rights under this Agreement, pursuant
                        to Section 2.3 of this Agreement, in any country(ies) of
                        the TERRITORY, CELGENE shall pay to ENTREMED (i) "..."
                        of any non-royalty consideration, including but not
                        limited to any sublicensing and/or milestone payments
                        received by CELGENE pursuant to such sublicense and (ii)
                        "..." of the royalty income paid by SUBLICENSEES to
                        CELGENE on NET SALES of PRODUCTS.

                  (b)   CELGENE-ENTREMED Cooperation. If CELGENE grants a
                        sublicense of any of its rights under this Agreement in
                        any area of the FIELD or any country of the TERRITORY
                        with respect to which ENTREMED and CELGENE are
                        cooperating pursuant to Sections 3.2 or 3.3 of this
                        Agreement, CELGENE shall pay to ENTREMED "..." of any
                        non-royalty consideration, including but not limited to
                        any sublicensing and/or milestone payments received by
                        CELGENE pursuant to such sublicense. CELGENE shall also
                        pay to ENTREMED, as applicable, the following: (i) if
                        CELGENE and ENTREMED are cooperating in any country(ies)
                        pursuant to Section 3.2 of this Agreement, "..." of the
                        royalty income paid by SUBLICENSEES to CELGENE on NET
                        SALES, in such country(ies), of PRODUCTS; and (ii) if
                        CELGENE and



                                      -22-
   27

                        ENTREMED are cooperating in any country(ies) with regard
                        to PRODUCTS for use in animals pursuant to Section 3.3
                        of this Agreement, "..." of the royalty income paid by
                        SUBLICENSEES to CELGENE on NET SALES in such
                        country(ies) of such PRODUCTS.

            4.3   Later-Issued VALID CLAIM. In the event that there is no ISSUED
                  VALID CLAIM of a PATENT RIGHT in a country within the
                  TERRITORY on the date the twelve (12) year period provided for
                  in Section 4.1(a) of this Agreement expires, no royalties
                  shall be owed by CELGENE to ENTREMED under Sections 4.1(b) and
                  4.2 of this Agreement on PRODUCTS sold by CELGENE or its
                  AFFILIATES in such country, provided, however, that if a VALID
                  CLAIM of a PATENT RIGHT thereafter issues in such country,
                  CELGENE shall pay ENTREMED royalties on the NET SALES in such
                  country of PRODUCTS covered by an ISSUED VALID CLAIM of the
                  PATENT RIGHTS that are sold by CELGENE or its AFFILIATES,
                  according to the royalty rates set forth in Sections 4.1(b)
                  and 4.2 of this Agreement, and such royalties under this
                  Section 4.3 shall be payable until the last to expire PATENT
                  RIGHT containing an ISSUED VALID CLAIM covering the PRODUCTS
                  sold by CELGENE, its AFFILIATES or SUBLICENSEE in such
                  country.

            4.4   "..."

            4.5   THIRD PARTY Sales. In any country where sales by a THIRD PARTY
                  of a PRODUCT(s) for a similar dosage form and/or route of
                  administration:

                  (a)   are equal to or greater than "..." of the dollar market
                        share for such PRODUCT in such country ("MARKET SHARE"),
                        but less than "..." of the MARKET SHARE, then the
                        royalty payable to


                                      -23-
   28

                        ENTREMED pursuant to Sections 4.1 and 4.3 of this
                        Agreement shall be reduced by "...";

                  (b)   are equal to or greater than "..." of the MARKET SHARE,
                        but less than "..." of the MARKET SHARE, then the
                        royalty payable to ENTREMED pursuant to Sections 4.1 and
                        4.3 of this Agreement shall be reduced by "...";

                  (c)   are equal to or greater than "..." of the MARKET SHARE,
                        but less than "..." of the MARKET SHARE, then the
                        royalty payable to ENTREMED pursuant to set Sections 4.1
                        and 4.3 of this Agreement shall be reduced by "..."; and

                  (d)   are equal to or greater than "..." of the MARKET SHARE,
                        then the royalty payable to ENTREMED pursuant to
                        Sections 4.1 and 4.3 of this Agreement shall be reduced
                        by "...";

                  provided that royalties payable to ENTREMED shall never be
                  reduced below "..." of NET SALES in each royalty bracket. For
                  purposes of this Section 4.5, oral dosage forms shall include,
                  without limitation, all capsule, caplet, tablet, and liquid
                  formulations for oral administration.

            4.6   Recordkeeping. CELGENE shall keep, and shall cause each of its
                  AFFILIATES and SUBLICENSEES to keep, full and accurate books
                  of account containing all particulars relevant to its sales of
                  PRODUCTS that may be necessary for the purpose of calculating
                  all royalties payable to ENTREMED. Such books of account shall
                  be kept at their principal place of business and, with all
                  necessary supporting data shall, for the three (3) years next
                  following the end of the calendar year to which each shall
                  pertain, be open for inspection by an independent certified
                  public accountant reasonably acceptable to CELGENE, upon
                  reasonable notice during normal business hours at ENTREMED'S
                  expense for the sole purpose of verifying royalty statements
                  or compliance with this Agreement. In the event the inspection
                  determines that royalties due


                                      -24-
   29

                  ENTREMED for any period have been underpaid by five percent
                  (5%) or more, then CELGENE shall pay for all costs of the
                  inspection. In all cases, CELGENE shall pay to ENTREMED any
                  underpaid royalties promptly and with interest at the prime
                  rate available to ENTREMED from its bank plus two percent
                  (2%). All information and data reviewed in the inspection
                  shall be used only for the purpose of verifying royalties and
                  shall be treated as CELGENE CONFIDENTIAL INFORMATION subject
                  to the obligations of this Agreement. No audit by an agent of
                  ENTREMED shall occur more frequently than once during any
                  twelve (12) month period.

            4.7   Quarterly Payments and Reports. In each year the amount of
                  royalty due shall be calculated quarterly as of the end of
                  each CALENDAR QUARTER and shall be paid quarterly within the
                  forty-five (45) days next following such date. Every such
                  payment shall be supported by the accounting described in
                  Section 4.8 of this Agreement. All royalties due ENTREMED are
                  payable in United States dollars. When PRODUCTS are sold for
                  currency other than United States dollars, the earned
                  royalties will first be determined in the foreign currency of
                  the country in which such PRODUCTS were sold and then
                  converted into equivalent United States funds. The exchange
                  rate will be that rate quoted in the Wall Street Journal on
                  the last business day of the CALENDAR QUARTER in which such
                  sales were made.

            4.8   Accounting Reports. With each quarterly payment, CELGENE shall
                  deliver to ENTREMED a full and accurate accounting to include
                  at least the following information:

                  (a)   Quantity of PRODUCT subject to royalty sold, by country,
                        by CELGENE, its AFFILIATES or SUBLICENSEES;

                  (b)   Total receipts for each PRODUCT subject to royalty, by
                        country and, to the extent used in any royalty
                        calculations during such


                                      -25-
   30

                        quarter, the exchange rate set forth in Section 4.7 of
                        this Agreement; 

                  (c)   Compensation on PRODUCTS received from SUBLICENSEES
                        pursuant to a sublicense of CELGENE's rights under this
                        Agreement; and

                  (c)   Total royalties and/or compensation payable to ENTREMED.

                          SECTION 5 - CONFIDENTIALITY

            5.1   Confidential Information. During the term of this Agreement,
                  it is contemplated that each party may disclose to the other,
                  proprietary and confidential technology, inventions, technical
                  information, material, reagents, biological materials and the
                  like which are owned or controlled by the party providing such
                  information or which that party is obligated to maintain in
                  confidence and which is designated by the party providing such
                  information as confidential ("CONFIDENTIAL INFORMATION"). Each
                  party agrees not to disclose the CONFIDENTIAL INFORMATION and
                  to maintain the CONFIDENTIAL INFORMATION in strict confidence,
                  to cause all of its agents, representatives and employees to
                  maintain the disclosing party's CONFIDENTIAL INFORMATION in
                  confidence and not to disclose any such CONFIDENTIAL
                  INFORMATION to a THIRD PARTY without the prior written consent
                  of the disclosing party, and not to use such CONFIDENTIAL
                  INFORMATION for any purpose other than as provided under this
                  Agreement. The secrecy obligations of the parties with respect
                  to CONFIDENTIAL INFORMATION shall continue for a period ending
                  ten (10) years from the termination of this Agreement.

            5.2   Non-Confidential Information. The obligations of
                  confidentiality will not apply to information that:



                                      -26-
   31

                  (a)   was known to the receiving party or generally known to
                        the public prior to its disclosure hereunder through no
                        fault of the disclosing party or any agent,
                        representative or employee thereof; or

                  (b)   subsequently becomes known to the public by some means
                        other than a breach of this Agreement, including
                        publication and/or laying open to inspection of any
                        patent applications or patents;

                  (c)   is subsequently disclosed to the receiving party by a
                        THIRD PARTY having a lawful right to make such
                        disclosure and who is not under an obligation of
                        confidentiality to the disclosing party;

                  (d)   is required by law, rule, regulation or bona fide legal
                        process to be disclosed, provided that the disclosing
                        party takes all reasonable stem to restrict and maintain
                        confidentiality of such disclosure and provides
                        reasonable notice to the non-disclosing party; or

                  (e)   is approved for release by the parties.

            5.3   Disclosure To THIRD PARTIES. The obligations of Section 5.1
                  notwithstanding, CELGENE or ENTREMED, as the case may be, may
                  disclose the CONFIDENTIAL INFORMATION licensed hereunder to
                  THIRD PARTIES

                  (a)   who need to know the same in order to obtain regulatory
                        approval for a PRODUCT under this Agreement, provided
                        that the actions of such THIRD PARTY are not in conflict
                        with CELGENE's rights under this Agreement,

                  (b)   who need to know the same in order to work towards the
                        commercial development of PRODUCT on behalf of CELGENE,
                        or

                  (c)   for whom the non-disclosing party, ENTREMED or CELGENE,
                        as the case may be, has given prior written approval



                                      -27-
   32

                        provided that such THIRD PARTIES are bound by
                        obligations of confidentiality and non-use at least as
                        stringent as those set forth herein.

                  5.4   Disclosure To Sublicensees. CELGENE may disclose
                        ENTREMED's CONFIDENTIAL INFORMATION to a SUBLICENSEE
                        without ENTREMED's approval, provided that such
                        SUBLICENSEES are bound by obligations of confidentiality
                        and non-use at least as stringent as those set forth
                        herein.

                  5.5   Public Statements. Neither CELGENE nor ENTREMED may
                        issue a public statement, including without limitation a
                        press release, with regard to this Agreement without the
                        prior written consent of the other party, which consent
                        shall not be unreasonably withheld. In accordance with
                        the rules and regulations promulgated by the Securities
                        and Exchange Commission, the parties will request that
                        this Agreement be treated as confidential.

                        SECTION 6 - ADVERSE MEDICAL EXPERIENCES

                  6.1   Adverse Medical Experience Reporting. CELGENE shall
                        comply fully with all applicable medical/adverse
                        experience reporting requirements in all countries where
                        CELGENE intends to carry out clinical trials and/or
                        market PRODUCT.

                              SECTION 7 - PATENTS

                  7.1   Patent Prosecution.

                        (a)   ENTREMED shall use reasonable efforts to prepare,
                              file, prosecute and maintain patent applications
                              and patents directed to PATENT RIGHTS and PRODUCTS
                              through patent counsel selected by ENTREMED and
                              reasonably acceptable to CELGENE, who shall
                              consult with and keep CELGENE advised with respect
                              thereto.



                                      -28-
   33

                        (b)   CELGENE shall reimburse ENTREMED for all
                              reasonable costs and expenses incurred after the
                              EFFECTIVE DATE for the filing, prosecution and
                              maintenance of PATENT RIGHTS.

                  7.2   Cooperation In Prosecution.

                        (a)   With respect to any PATENT RIGHTS, each patent
                              application, office action, response to office
                              action, request for terminal disclaimer, petition,
                              and request for reissue or reexamination of any
                              patent issuing from such application shall be
                              provided to CELGENE sufficiently prior to the
                              filing of such application, response, petition, or
                              request to allow for review and comment by
                              CELGENE. ENTREMED shall have the right to take any
                              action that, in its judgement, is necessary to
                              preserve such PATENT RIGHTS.

                        (b)   Within a reasonable time from the EFFECTIVE DATE,
                              CELGENE and ENTREMED will discuss each party's
                              patent portfolio with regard to PRODUCTS, in
                              accordance with prior obligations of
                              confidentiality owed by each party to any THIRD
                              PARTY, and will use reasonable efforts to
                              coordinate their respective patent portfolio, to
                              the extent possible, so as to maximize the patent
                              protection for PRODUCTS.

                  7.3   Infringement and Declaratory Judgment Actions.

                        (a)   Notification. In the event that either party
                              learns of the infringement of any PATENT RIGHT, or
                              the filing of a Declaratory Judgement action
                              alleging the invalidity, unenforceability, or
                              noninfringement of any PATENT RIGHT ("DJ ACTION"),
                              that party must promptly notify the other party of
                              the infringement or DJ ACTION, as the case may be,
                              in writing, and must provide reasonable evidence
                              of the infringement. Neither


                                      -29-
   34

                        party will notify a THIRD PARTY of the infringement of
                        any PATENT RIGHT or of the filing of a DJ ACTION
                        directed to any PATENT RIGHT without first obtaining
                        consent of the other party, which consent shall not be
                        unreasonably withheld.

                  (b)   CELGENE's Right To File Infringement Actions. To the
                        extent ENTREMED has the right to bring a suit or action
                        to compel the termination of infringement of the PATENT
                        RIGHTS, including to the extent provided in Article 7 of
                        the CMCC AGREEMENT, ENTREMED hereby grants CELGENE the
                        right and option, but not the obligation, to bring an
                        action for infringement or to defend against a DJ
                        action, at its sole expense, in the name of ENTREMED
                        and/or in the name of CELGENE, and to join ENTREMED as a
                        party plaintiff if required. No settlement, consent
                        judgment or other voluntary final disposition of a suit
                        that adversely affects PATENT RIGHTS may be entered into
                        without the consent of ENTREMED, which consent shall not
                        be unreasonably withheld.

                  (c)   CELGENE's Right To Defend DJ ACTIONS. In the event that
                        a DJ ACTION is brought naming CELGENE as a defendant,
                        CELGENE shall have the right to proceed with the
                        litigation or settle such action provided, however, that
                        no settlement, consent judgment or other voluntary final
                        disposition of a suit that adversely affects PATENT
                        RIGHTS may be entered into without the consent of
                        ENTREMED, which consent shall not be unreasonably
                        withheld.

                  (d)   CELGENE's Recovery. In the event that CELGENE shall
                        undertake the enforcement and/or defense of the PATENT
                        RIGHTS by litigation, any recovery of damages by CELGENE
                        for any such litigation shall be applied first in
                        satisfaction of any


                                      -30-
   35

                        unreimbursed expenses and legal fees of CELGENE relating
                        to the suit. The balance remaining from any such
                        recovery shall, after ENTREMED receives its royalties
                        from lost sales, belong to CELGENE.

                  (e)   ENTREMED's Right To Litigate. In the event that CELGENE
                        elects not to pursue an action for infringement or to
                        defend against a DJ action, as the case may be, CELGENE
                        shall notify ENTREMED in writing of such election and
                        ENTREMED shall have the right and option, but not the
                        obligation, at its cost and expense, to initiate
                        infringement litigation and to retain any recovered
                        damages.

                  (f)   Cooperation. In any infringement suit either party may
                        institute to enforce or defend the PATENT RIGHTS
                        pursuant to this Agreement, the other party hereto
                        shall, at the request of the party initiating such suit,
                        cooperate in all respects and, to the extent possible,
                        have its employees testify when requested and make
                        available relevant records, papers, information,
                        samples, specimens, and the like. All reasonable
                        out-of-pocket costs incurred in connection with
                        rendering cooperation requested hereunder shall be paid
                        by the party requesting cooperation.

                  (g)   THIRD PARTY Royalty Reduction. In the event that an
                        infringement action is brought by a THIRD PARTY against
                        CELGENE alleging that CELGENE's making, using, offering
                        to sell, selling, or importing of PRODUCTS under the
                        PATENT RIGHTS infringes a THIRD PARTY patent, and
                        results in a judgment or settlement requiring royalties
                        to be paid by CELGENE to such THIRD PARTY, the royalties
                        owed by CELGENE to ENTREMED under Section 4 of this
                        Agreement shall be reduced by an amount equal to "..."
                        of the royalties owed


                                      -31-
   36

                        to such THIRD PARTY, provided that the royalties owed to
                        ENTREMED shall not be reduced under this Section 7.3(f)
                        to less than "..." of NET SALES, nor shall any specific
                        royalty payment be reduced under this Section 7.3(g) by
                        more than "...".

               SECTION 8 - REPRESENTATIONS AND WARRANTIES.

            8.1   By Both Parties. Each party hereby represents and warrants
                  that each has the full right and authority to enter into this
                  Agreement and that the entry into this Agreement does not
                  require the consent of a THIRD PARTY whose consent has not
                  been obtained.

            8.2   By ENTREMED. ENTREMED represents and warrants as follows:

                  (a)   that ENTREMED has not received any notice of
                        infringement of THIRD PARTY patents or notice of
                        interfering subject matter; that, without having made
                        any special investigation, ENTREMED is not aware of any
                        THIRD PARTY patents or patent applications that contain
                        any interfering subject matter, or any issued THIRD
                        PARTY patents that would be infringed by the making,
                        using, selling, offering for sale, or importing by
                        CELGENE of PRODUCTS covered by the ENTREMED EXISTING
                        PATENT RIGHTS or the ENTREMED EXISTING TECHNOLOGY RIGHTS
                        in any country in the TERRITORY, or by the exercise by
                        CELGENE of any right granted to it under this Agreement,
                        aside from those set forth in Appendix D;

                  (b)   that the PATENT RIGHTS set forth in Appendix A and the
                        TECHNOLOGY RIGHTS transferred to CELGENE under this
                        Agreement, constitute the entirety of ENTREMED EXISTING
                        PATENT RIGHTS and ENTREMED EXISTING TECHNOLOGY RIGHTS;


                                      -32-
   37

                  (c)   that ENTREMED presently has no rights in PRODUCTS, nor
                        any option in or expectation of any rights in PRODUCTS,
                        apart from those identified in this Agreement and set
                        forth in the agreements listed in Appendix B, and that
                        ENTREMED is not in material breach or default of any of
                        the agreements set forth in Appendix B, and that if
                        ENTREMED acquires any such rights after the EFFECTIVE
                        DATE, the agreements setting forth those rights,
                        including all licenses and assignments for ENTREMED
                        DEVELOPED PATENT RIGHTS and ENTREMED DEVELOPED
                        TECHNOLOGY RIGHTS, shall be redacted to the extent they
                        do not relate to CELGENE's rights under this Agreement,
                        and attached hereto as independent Exhibits and
                        incorporated herein;

                  (d)   that, with regard to PRODUCTS, ENTREMED has no
                        applications filed or pending with the FDA as of the
                        EFFECTIVE DATE, including without limitation any
                        Investigational New Drug or Orphan Drug Status
                        applications, apart from those set forth in Appendix C;

                  (e)   that ENTREMED will comply with all obligations and
                        duties with regard to PRODUCTS under the CMCC AGREEMENT
                        and, unless and until it is assigned to CELGENE pursuant
                        to Section 2.5 of this Agreement, the NCI AGREEMENT,
                        including, without limitation, any notification
                        provisions necessary to maintain in effect this
                        Agreement or preserve CELGENE's exclusive or
                        non-exclusive rights under this Agreement, including
                        without limitation the preservation of CELGENE's rights
                        hereunder in the event that ENTREMED shall breach or
                        default on its obligations under the CMCC AGREEMENT or
                        the NCI AGREEMENT;



                                      -33-
   38

                  (f)   that ENTREMED understands and agrees that it has not
                        retained any rights under the ENTREMED INTELLECTUAL
                        PROPERTY to PRODUCTS in the TERRITORY, and that the
                        licenses and assignments granted in Sections 2.1, 2.2,
                        2.4, and 2.5 of this Agreement are exclusive of any
                        continuing right of ENTREMED, except as otherwise
                        provided herein; and

                  (g)   that ENTREMED will not collaborate, negotiate, or deal
                        with THIRD PARTIES with respect to PRODUCTS, except as
                        expressly provided herein. 

            8.3   EXCEPT AS OTHERWISE EXPRESSLY SET FORTH HEREIN, ENTREMED MAKES
                  NO REPRESENTATIONS OR EXTENDS ANY WARRANTIES OF ANY KIND
                  EITHER EXPRESS OR IMPLIED, INCLUDING, BUT NOT LIMITED TO,
                  WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR
                  PURPOSE, NON-INFRINGEMENT OR VALIDITY OF ANY ENTREMED PATENT
                  OR OTHER INTELLECTUAL PROPERTY RIGHTS.

                  SECTION 9 - INDEMNIFICATION AND INSURANCE

            9.1   By CELGENE. CELGENE will defend, indemnify and hold harmless
                  ENTREMED, its successors, AFFILIATES and licensors and their
                  employees, agents, officers, trustees, shareholders and
                  directors and each of them (the "ENTREMED Indemnified
                  Parties") from and against any and all THIRD PARTY claims,
                  causes of action and costs (including reasonable attorney's
                  fees) of any nature made or lawsuits or other proceedings
                  filed or otherwise instituted against the ENTREMED Indemnified
                  Parties in connection with any claims, suits or judgments
                  arising out of any theory of product liability concerning the
                  development, testing, manufacture, sale or use of any PRODUCT
                  by CELGENE, its AFFILIATES or its SUBLICENSEES.



                                      -34-
   39

                  9.1.1        CELGENE's indemnification under this Section 9.1
                               shall not apply to any liability, damage, loss or
                               expense to the extent that it is directly
                               attributable to the negligent activity, reckless
                               misconduct or intentional misconduct of ENTREMED.

                  9.1.2        Commencing not later than the date of FIRST
                               COMMERCIAL SALE of a PRODUCT, CELGENE shall
                               obtain and carry in full force and effect product
                               liability insurance against any claims,
                               judgments, liabilities and expenses for which it
                               is obligated to indemnify ENTREMED and others
                               under Section 9.1 of this Agreement, in such
                               amounts and with such deductibles as are
                               customary at the time for companies engaged in a
                               similar business, and shall provide ENTREMED with
                               written evidence of such insurance upon request.

            9.2   By ENTREMED. ENTREMED will defend, indemnify and hold harmless
                  CELGENE, its successors, AFFILIATES and licensors and their
                  employees, agents, officers, trustees, shareholders and
                  directors and each of them (the "CELGENE Indemnified Parties")
                  from and against any and all THIRD PARTY claims, causes of
                  action and costs (including reasonable attorney's fees) of any
                  nature made or lawsuits or other proceedings filed or
                  otherwise instituted against the CELGENE Indemnified Parties
                  in connection with any claims, suits or judgments arising out
                  of any theory of product liability concerning the development,
                  testing, manufacture, sale or use of any PRODUCT by ENTREMED,
                  its AFFILIATES or its SUBLICENSEES prior to the EFFECTIVE
                  DATE.

                  9.2.1 ENTREMED's represents and warrants that it presently
                        carries, in full force and effect, and will continue to
                        carry, product liability insurance against any claims,
                        judgments, liabilities and expenses incurred in
                        connection with the use of THALIDOMIDE in clinical
                        trials by or on behalf of 


                                      -35-
   40

                        ENTREMED, and shall provide CELGENE with written 
                        evidence of such insurance upon request.

            9.3   Conditions to Indemnification. A person or entity that intends
                  to claim indemnification under this Section 9 (the
                  "Indemnitee") shall promptly notify the party from whom
                  indemnification is sought (the "Indemnitor"), of any loss,
                  claim, damage, liability or action in respect of which the
                  Indemnitee intends to claim such indemnification, and the
                  Indemnitor shall assume the defense thereof with counsel
                  mutually satisfactory to the Indemnitee whether or not such
                  claim is rightfully brought; provided, however, that an
                  Indemnitee shall have the right to retain its own counsel,
                  with the fees and expenses to be paid by the Indemnitor if
                  Indemnitor does not assume the defense, or if representation
                  of such Indemnitee by the counsel retained by the Indemnitor
                  would be inappropriate due to actual or potential differing
                  interests between such Indemnitee and any other person
                  represented by such counsel in such proceedings. The failure
                  to deliver notice to the Indemnitor within a reasonable time
                  after the commencement of any such action, only if prejudicial
                  to its ability to defend such action, shall relieve such
                  Indemnitor of any liability to the Indemnitee under this
                  Section 9, but the omission so to deliver notice to the
                  Indemnitor will not relieve it of any liability that it may
                  have to any Indemnitee otherwise than under this Section 9.
                  The Indemnitee under this Section 9, its employees and agents,
                  shall cooperate fully with the Indemnitor and its legal
                  representatives in the investigations of any action, claim or
                  liability covered by this indemnification.

                   SECTION 10 - ASSIGNMENT AND SUCCESSORS

            10.1  By Either Party. This Agreement shall not be assignable by
                  either party without the written consent of the other party,
                  except that either party may assign this Agreement to an
                  AFFILIATE, successor in interest or 



                                      -36-
   41

                  transferee of all or substantially all of the portion of the 
                  business to which this Agreement relates without the consent 
                  of the other party.

            10.2  By CELGENE. If CELGENE assigns or licenses its rights under
                  this Agreement to a SUBLICENSEE or an AFFILIATE, such
                  SUBLICENSEE or AFFILIATE shall be bound by the terms and
                  conditions of this Agreement. CELGENE shall advise ENTREMED of
                  any such assignment or license and provide ENTREMED with a
                  copy of any sublicense within thirty (30) days of execution of
                  such sublicense.

            10.3  CELGENE As Guarantor. CELGENE shall guarantee and be
                  responsible for the payment of all royalties due and the
                  making of reports under this Agreement by reason of the
                  development and sales of any PRODUCTS by CELGENE, its
                  AFFILIATES and SUBLICENSEES and their compliance with all
                  applicable terms of this Agreement. Performance or
                  satisfaction of any obligations of CELGENE under this
                  Agreement by any of its AFFILIATES or SUBLICENSEES shall be
                  deemed performance or satisfaction of such obligation by
                  CELGENE.

            10.4  Binding Effect. This agreement shall be binding upon and inure
                  to the benefit of said successors in interest and assignees to
                  the parties. Any such successor or assignee of a party's
                  interest shall expressly assume in writing the performance of
                  all the terms and conditions of this Agreement to be performed
                  by said party and such Assignment shall not relieve the
                  Assignor of any of its obligations under this Agreement.

                           SECTION 11 - FORCE MAJEURE

            11.1  Neither party shall be liable to the other party for damages
                  or loss occasioned by failure of performance by the defaulting
                  party if the failure is occasioned by war, fire, explosion,
                  flood, strike or lockout, embargo, or any similar cause beyond
                  the control of the defaulting party, provided that the party
                  claiming this exception has exerted all reasonable efforts to



                                      -37-
   42

                  avoid or remedy such event and provided such event does not
                  extend for more than six (6) months.

                            SECTION 12 - TERMINATION

            12.1  Term. Unless earlier terminated as hereinafter provided, this
                  Agreement shall remain in full force and effect until
                  CELGENE's obligations to pay royalties or other compensation
                  under Section 4 of this Agreement, either directly or pursuant
                  to a sublicense, terminate.

            12.2  By Reason Of FDA Action. If the FDA withdraws or recalls
                  THALIDOMIDE from the market permanently, or in any other way
                  revokes or terminates CELGENE's regulatory approval to market
                  and sell THALIDOMIDE and/or PRODUCTS, CELGENE shall promptly
                  notify ENTREMED in writing, and this Agreement and all of
                  CELGENE's and ENTREMED's rights and obligations hereunder
                  shall terminate upon receipt by ENTREMED of such notice.

            12.3  Termination Of Royalty Obligations. Upon termination of
                  CELGENE's obligation to pay royalties and other compensation
                  hereunder with respect to a specific country and specific
                  PRODUCT as to which CELGENE's license is then in effect, the
                  license granted to CELGENE with respect to such country and
                  such PRODUCT pursuant to Section 2 shall be deemed to be fully
                  paid and CELGENE shall thereafter have a royalty free,
                  exclusive right to use the PATENT RIGHTS to make, have made,
                  use, offer to sell, sell and import such PRODUCT in such
                  country.

            12.4  Breach.

                  (a)   By Either Party. This Agreement shall be terminable upon
                        the material breach or default of either party. In the
                        event of a material breach or default by a party
                        ("Defaulting Party"), the other party ("Non-Defaulting
                        Party") shall give the Defaulting Party written 



                                      -38-
   43

                        notice of the default. The Defaulting Party will then 
                        have sixty (60) days to cure the breach. If cure has 
                        not been affected within said sixty (60) days, the 
                        Non-Defaulting Party shall have the right to terminate 
                        this Agreement.

                  (b)   By CELGENE.

                        (i)   Payments. If and only if CELGENE materially
                              breaches this Agreement by failure to pay
                              royalties and/or sublicensing or milestone
                              payments due under Section 4 of this Agreement,
                              and fails to cure such material breach within
                              sixty (60) days of receiving written notice
                              thereof pursuant to Section 12.4(a) of this
                              Agreement then: 

                              a)    CELGENE's rights under this Agreement to 
                                    ENTREMED INTELLECTUAL PROPERTY shall 
                                    terminate; and

                              b)    CELGENE shall grant to ENTREMED, to the 
                                    extent not prohibited by the United States 
                                    Government or by prior contractual 
                                    obligations to any THIRD PARTY, an 
                                    exclusive, worldwide, royalty-free license, 
                                    with the right to sublicense, under CELGENE
                                    DEVELOPED INTELLECTUAL PROPERTY to make,
                                    use, offer to sell, sell, and import
                                    PRODUCTS in the TERRITORY.

                        (ii)  Diligence. If and only if ENTREMED exercises its
                              right and option to terminate the license granted
                              to CELGENE in the entire TERRITORY, pursuant to
                              Section 3.1(f) of this Agreement, or ENTREMED
                              exercises its right and option to terminate the
                              license granted to CELGENE in Europe, Canada, or
                              the PACIFIC RIM, pursuant to Section 3.2(c)(i) of
                              this Agreement, then, either in the entire
                              TERRITORY



                                      -39-
   44

                              or in the region in which such termination has
                              occurred, i.e., Europe, Canada, or the PACIFIC
                              RIM, as applicable:

                              a)    CELGENE's rights under this Agreement to
                                    ENTREMED INTELLECTUAL PROPERTY shall
                                    terminate; and

                              b)    CELGENE shall grant to ENTREMED, to the
                                    extent not prohibited by the United States
                                    Government or by prior contractual
                                    obligations to any THIRD PARTY, an
                                    exclusive, worldwide, royalty-free license,
                                    with the right to sublicense, under CELGENE
                                    DEVELOPED INTELLECTUAL PROPERTY to make,
                                    use, offer to sell, sell, and import
                                    PRODUCTS.

                        The grant of rights by CELGENE to ENTREMED under this
                        Section 12.4 expressly excludes rights in any CELGENE
                        EXISTING INTELLECTUAL PROPERTY.

                  (c)   Termination under this Section 12.4 will be effective
                        upon the date specified in the written notice. All
                        termination rights shall be in addition to and not in
                        substitution for any other remedies that may be
                        available to the Non-Defaulting Party. Termination
                        pursuant to this Section 12.4 shall not relieve the
                        Defaulting Party from liability and damages to the
                        Non-Defaulting Party for default. Waiver by either party
                        of a single default or a succession of defaults shall
                        not deprive such party of any right to terminate or
                        convert this Agreement arising by reason of any
                        subsequent default.

            12.5  Insolvency. Either party to this Agreement may terminate this
                  Agreement upon receipt of notice that the other party has
                  become insolvent or has suspended business in all material
                  respects hereof, or has consented to an involuntary petition
                  purporting to be pursuant to any reorganization or insolvency
                  law of any jurisdiction, or has made an assignment for the
                  benefit of creditors or has applied for or consented to the
                  appointment of a



                                      -40-
   45

                  receiver or trustee for a substantial part of its property, by
                  giving written notice to the other party, and termination of
                  this Agreement will be effective upon receipt of such notice.

            12.6  Work-In-Progress. Upon termination of this Agreement, CELGENE
                  shall be entitled to, but shall not be obligated to finish any
                  work-in-progress at the time of termination and sell the same
                  as well as all completed inventory of PRODUCTS which remains
                  on hand as of the date of the termination, so long as CELGENE
                  pays to ENTREMED the royalties applicable to said subsequent
                  sales in accordance with the same terms and conditions as set
                  forth in this Agreement.

            12.7  Survival. The obligations of Sections 5 and 9, as well as
                  Sections 12.6, 12.7, 12.8, and 13.3, shall survive any
                  termination of this Agreement.

            12.8  Reversion of Rights. Upon termination of this Agreement or of
                  the rights and licenses granted to CELGENE in any country of
                  the TERRITORY, CELGENE agrees not to use the TECHNOLOGY RIGHTS
                  or PATENT RIGHTS or information or technology derived
                  therefrom for the manufacture, use or sale of PRODUCTS in any
                  country other than those countries in which CELGENE retains a
                  license under this Agreement. In addition, all rights to the
                  TECHNOLOGY RIGHTS and PATENT RIGHTS in such country shall
                  revert to ENTREMED and may be used by ENTREMED without
                  restriction in any country other than those countries in which
                  CELGENE retains a license under this Agreement.

                        SECTION 13 - GENERAL PROVISIONS

            13.1  Relationship of Parties. The relationship between ENTREMED and
                  CELGENE is that of independent contractors. ENTREMED and
                  CELGENE are not joint venturers, partners, principal and
                  agent, master and servant, employer or employee, and have no
                  relationship other than as independent contracting parties.
                  ENTREMED shall have no power to bind


                                      -41-
   46

                  or obligate CELGENE in any manner. Likewise, CELGENE shall
                  have no power to bind or obligate ENTREMED in any manner.

            13.2  Entire Understanding. This Agreement sets forth the entire
                  agreement and understanding between the parties as to the
                  subject matter thereof and supersedes all prior agreements in
                  this respect. There shall be no amendments or modifications to
                  these Agreements, except by a written document which is signed
                  by both parties.

            13.3  Governing Law. This Agreement shall be construed and enforced
                  in accordance with the laws of the State of Delaware, U.S.A.
                  without reference to its choice of law principles.

            13.4  Headings. The headings in this Agreement have been inserted
                  for the convenience of reference only and are not intended to
                  limit or expand on the meaning of the language contained in
                  the particular or section or paragraph.

            13.5  No Waiver. Any delay in enforcing a party's rights under this
                  Agreement or any waiver as to a particular default or other
                  matter shall not constitute a waiver of a party's right to the
                  future enforcement of its rights under this Agreement,
                  excepting only as to an expressed written and signed waiver as
                  to a particular matter for a particular period of time.

            13.6  Export Controls. In conducting any activities under this
                  Agreement or in connection with the manufacture use or sale of
                  PRODUCT, CELGENE shall comply with all applicable laws and
                  regulations including, but not limited to, all Export
                  Administration Regulations of the United States Department of
                  Commerce.

            13.7  Notices. Any notices given pursuant to this Agreement shall be
                  in writing and shall be deemed delivered upon the earlier of
                  (i) when received at the address set forth below, or (ii)
                  three (3) business days after mailed by certified or
                  registered mail postage prepaid and properly addressed, with



                                      -42-
   47

                  return receipt requested, or (iii) when sent, if sent by
                  facsimile, as confirmed by certified or registered mail.
                  Notices shall be delivered to the respective parties as
                  indicated below:

                  If To ENTREMED          EntreMed, Inc.
                                          9610 Medical Center Drive
                                          Rockville, MD 20850
                                          Attn:  CEO
                                          Fax:  (301) 217-9594

                  If To CELGENE:          Celgene Corporation
                                          6 Powder Horn Drive
                                          Warren, NJ 07059
                                          Attn:  President
                                          Fax:  (732) 805-3931

            13.8  Original Counterparts. This Agreement may be executed in any
                  number of separate counterpart, each of which shall be deemed
                  to be an original, but which together shall constitute one and
                  the same instrument.




                                      -43-
   48

      IN WITNESS WHEREOF, the parties have executed this Agreement as of the
date set forth above.

ENTREMED, INC.                                  CELGENE CORPORATION


By:   /s/  Edward R. Gubish                     By:   /s/  John W. Jackson
      -------------------------------                 --------------------------
Name:      Edward R. Gubish                     Name:      John W. Jackson
     --------------------------------                ---------------------------
Title:     Sr. V.P. R & D                       Title:     Chairman & CEO
      -------------------------------                 --------------------------





                                      -44-
   49

                                   APPENDIX A

United States Patent No. 5,629,327
United States Patent No. 5,593,990
United States Patent Application Serial No. 08/025,046
United States Patent Application Serial No. 08/168,817
United States Patent Application Serial No. 08/371,987
United States Patent Application Serial No. 08/468,792
United States Patent Application Serial No. 08/918,610
United States Patent Application Serial No. 08/955,638
United States Patent Provisional Application Serial No. 60/028,708
United States Patent Application Serial No. 08/963,058
United States Patent Application Serial No. 09/107,578
United States Patent Application Serial No. 09/126,542





                                      -45-
   50

                                   APPENDIX B

1.       That certain License Agreement entered into by and between ENTREMED and
         Children's Medical Center Corporation ("CMCC"), dated May 26, 1994, as
         amended to the date hereof, attached as Exhibit A to this Agreement.

2.       That certain Agreement by and between the Division of Cancer Treatment
         at the National Cancer Institute ("NCI") and ENTREMED, dated November
         16, 1994, and executed on behalf of ENTREMED on November 23, 1994, and
         on behalf of NCI on November 18, 1994, attached as Exhibit C to this
         Agreement.





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                                   APPENDIX C


Orphan Drug Designation Application (ODA) 97-1011     Primary Brain Malignancies
Orphan Drug Designation Application (ODA) 98-1149     Kaposis Sarcoma
Orphan Drug Designation Application (ODA) 98-1143     Prostate Cancer

Investigational New Drug Application 46,591           Ophthalmology
Investigational New Drug Application 55,966           Oncology






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   52

                                   APPENDIX D

United States Patent No. 5,605,684 to Piacquadio
United States Patent No. 5,443,824 to Piacquadio
United States Patent No. 5,731,325 to Andrulis, Jr. et al.
United States Patent No. 5,654,312 to Andrulis, Jr. et al.
United States Patent No. 5,643,915 to Andrulis, Jr. et al.
United States Patent No. 5,434,170 to Andrulis, Jr.





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   53

                                    EXHIBIT A
                                 CMCC AGREEMENT





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   54

                                    EXHIBIT B
                                  NCI AGREEMENT





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                                    EXHIBIT C
                      LETTER TO FDA INDICATING TRANSFER OF
                       RIGHTS IN INVESTIGATIONAL NEW DRUG
                     AND ORPHAN DRUG APPLICATIONS TO CELGENE







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