<PAGE>
                                                                   EXHIBIT 10.23



[CONFIDENTIAL TREATMENT REQUESTED]/*/ INDICATES MATERIAL THAT HAS BEEN OMITTED
AND FOR WHICH CONFIDENTIAL TREATMENT HAS BEEN REQUESTED. ALL SUCH OMITTED
MATERIAL HAS BEEN FILED WITH THE SECURITIES AND EXCHANGE COMMISSION PURSUANT TO
RULE 406 PROMULGATED UNDER THE SECURITIES ACT OF 1933, AS AMENDED.

                                                                  EXECUTION COPY






                                LICENSE AGREEMENT


                                  BY AND AMONG


                              ELAN CORPORATION, PLC
         (ACTING THROUGH ITS DIVISION ELAN PHARMACEUTICAL TECHNOLOGIES)

                                       AND

                        ELAN PHARMA INTERNATIONAL LIMITED


                                       AND


                              ACUSPHERE NEWCO, LTD.








<PAGE>



                                TABLE OF CONTENTS



1        DEFINITIONS

2        ELAN LICENSE TO NEWCO

3        INTELLECTUAL PROPERTY

4        [CONFIDENTIAL TREATMENT REQUESTED]/*/

5        FINANCIAL PROVISIONS

6        RIGHT OF INSPECTION AND AUDIT

7        REPRESENTATIONS AND WARRANTIES

8        TERM AND TERMINATION

9        CONFIDENTIAL INFORMATION

10       GOVERNING LAW AND JURISDICTION

11       IMPOSSIBILITY OF PERFORMANCE - FORCE MAJEURE

12       ASSIGNMENT

13       NOTICES

14       MISCELLANEOUS




<PAGE>


THIS AGREEMENT made this 30th day of June 2000

BETWEEN:

(1)      ELAN CORPORATION, PLC, a public limited company, acting through its
         division ELAN PHARMACEUTICAL TECHNOLOGIES and having its registered
         office at Lincoln House, Lincoln Place, Dublin 2, Ireland; and ELAN
         PHARMA INTERNATIONAL LIMITED a private limited company incorporated
         under the laws of Ireland, and having its registered office at WIL
         House, Shannon Business Park, Shannon, County Clare, Ireland; and

(2)      ACUSPHERE NEWCO, LTD., an exempted limited liability company
         incorporated under the laws of Bermuda and having its registered office
         at Clarendon House, 2 Church St., Hamilton, Bermuda;


RECITALS:

A.       Simultaneously herewith, Acusphere, Elan, EIS, and Newco (capitalized
         terms used herein are defined below) are entering into the JDOA for the
         purpose of recording the terms and conditions of the joint venture and
         of regulating their relationship with each other and certain aspects of
         the affairs of, and their dealings with Newco.

B.       Newco desires to enter into this Agreement with Elan so as to permit
         Newco to utilize the Elan Intellectual Property in making, having made,
         importing, using, offering for sale and selling the Products in the
         Field in the Territory.

C.       Simultaneously herewith Newco and Acusphere are entering into the
         Acusphere License Agreement relating to Newco's use of the Acusphere
         Intellectual Property.


1        DEFINITIONS

1.1      In this Agreement unless the context otherwise requires:

         "ACUSPHERE" shall mean Acusphere, Inc., a Delaware corporation and its
         Affiliates.

         "ACUSPHERE IMPROVEMENTS" shall have the meaning set forth in the
         Acusphere License Agreement.

         "ACUSPHERE INTELLECTUAL PROPERTY" shall mean the Acusphere Know-How,
         the Acusphere Patents and the Acusphere Improvements.

         "ACUSPHERE JV" shall have the meaning set forth in the Acusphere
         License Agreement.

         "ACUSPHERE KNOW-HOW" shall have the meaning set forth in the Acusphere
         License Agreement.



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<PAGE>

         "ACUSPHERE LICENSE" shall mean have the meaning set forth in the
         Acusphere License Agreement.

         "ACUSPHERE LICENSE AGREEMENT" shall mean that certain license
         agreement, of even date herewith, entered into between Acusphere and
         Newco.

         "ACUSPHERE PATENTS" shall have the meaning set forth in the Acusphere
         License Agreement.

         "AFFILIATE" shall mean any corporation or entity controlling,
         controlled or under the common control of Elan or Acusphere, as the
         case may be, excluding an Elan JV or an Acusphere JV. For the purpose
         of this definition, "control" shall mean direct or indirect ownership
         of [CONFIDENTIAL TREATMENT REQUESTED]/*/ or more of the stock or shares
         entitled to vote for the election of directors. For purposes of this
         Agreement, Newco is not an Affiliate of Elan or EIS.

         "AGREEMENT" shall mean this license agreement (which expression shall
         be deemed to include the Recitals and Schedules hereto).

         "BUSINESS PLAN" shall have the meaning set forth in the JDOA.

         "CHANGE OF CONTROL OF ACUSPHERE/NEWCO" shall mean circumstances where:

         (i)      a Technological Competitor of Elan shall, directly or through
                  an Affiliate or subsidiary, (a) acquire [CONFIDENTIAL
                  TREATMENT REQUESTED]/*/ or more of the voting stock of
                  Acusphere or Newco, or (b) obtain the ability to control the
                  management of Acusphere or Newco; or

         (ii)     any person or entity shall, directly or indirectly, acquire
                  [CONFIDENTIAL TREATMENT REQUESTED]/*/ or more of the then
                  voting stock of Acusphere or Newco, or otherwise merge,
                  consolidate or enter into any similar transaction (or binding
                  agreement in respect thereof) with Acusphere or Newco.

         "COMMERCIALIZATION" shall mean the manufacture, have manufactured,
         promotion, distribution, import, use, market, offer for sale and sale
         of the Products.

         "COMPOUNDS" shall mean [CONFIDENTIAL TREATMENT REQUESTED]/*/ and such
         other active ingredients for the Products as may be nominated by the
         Management Committee in accordance with Clause 2 of the JDOA.

         "CONFIDENTIAL INFORMATION" shall have the meaning set forth in Clause
         9.

         "DEFINITIVE DOCUMENTS" shall mean the definitive agreements relating to
         the transaction including finance, stock purchase, research and license
         agreements.




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<PAGE>

         "EFFECTIVE DATE" shall mean the date of this Agreement.

         "EIS" shall mean Elan International Services, Ltd., a Bermuda exempted
         limited liability company having its registered office at Clarendon
         House, 2 Church St., Hamilton, Bermuda.

         "ELAN" shall mean EPIL and Elan Corporation, plc carrying on business
         as Elan Pharmaceutical Technologies. For purposes of this Agreement,
         Elan shall exclude The Liposome Company, Inc. and its subsidiaries,
         Axogen Limited and Neuralab Limited and all Affiliates and subsidiaries
         (present or future) of Elan Corporation, plc within the division of
         Elan Corporation, plc carrying on business as Elan Pharmaceuticals
         which incorporates, inter alia, Athena Neurosciences, Inc., Elan
         Pharmaceuticals, Inc., Elan Diagnostics, Carnrick Laboratories, and
         Elan Europe Limited.

         "ELAN IMPROVEMENTS" shall mean improvements relating to the Elan
         Patents and/or the Elan Know-How, developed (i) by Elan whether or not
         pursuant to the Project, (ii) by Newco or Acusphere or by a third party
         (under contract with Newco) pursuant to the Project, and/or (iii)
         jointly by any combination of Elan, Acusphere or Newco pursuant to the
         Project, except as limited by agreements with third parties.

         Subject to third party agreements, Elan Improvements shall constitute
         part of Elan Intellectual Property and be included in the license of
         the Elan Intellectual Property pursuant to Clause 2.1 solely for the
         purposes set forth therein. If the inclusion of a Elan Improvement in
         the license of Elan Intellectual Property is restricted or limited by a
         third party agreement, Elan shall use reasonable commercial efforts to
         minimize any such restriction or limitation.

         "ELAN INTELLECTUAL PROPERTY" shall mean the Elan Know-How, the Elan
         Patents and the Elan Improvements.

         For the avoidance of doubt, Elan Intellectual Property shall exclude
         inventions, patents and know-how owned, licensed or controlled by The
         Liposome Company, Inc. and its subsidiaries, Axogen Limited and
         Neuralab Limited and by all Affiliates or subsidiaries (present or
         future) of Elan Corporation, plc within the Elan Pharmaceuticals
         division which incorporates, inter alia, EPIL (ONLY to the extent that
         EPIL owns, licenses or controls inventions, patents and know-how
         invented and/or developed within the Elan Pharmaceuticals division of
         Elan Corporation, plc but, for the avoidance of doubt, not to the
         extent that it is the owner of inventions, patents or know-how
         expressly licensed or sub-licensed hereunder pursuant to the Elan
         License), Athena Neurosciences, Inc., Elan Pharmaceuticals, Inc., Elan
         Diagnostics, Carnrick Laboratories, and Elan Europe Limited.

         "ELAN JV" shall mean an entity that Elan and a third party (i)
         establish or has established, (ii) take shareholdings in or have a
         right to take shareholdings in, and (iii) grant certain licenses in and
         to certain intellectual property rights for the purpose of implementing
         a strategic alliance.


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<PAGE>
         "ELAN KNOW-HOW" shall, subject to Clause 4.2, mean any and all rights
         owned, licensed or controlled by Elan to any discovery, invention
         (whether patentable or not), know-how, substances, data, techniques,
         processes, systems, formulations, designs, expertise and information
         owned by Elan relating to Pharmazome(R) and NanoCrystal(TM) Technology.

         "ELAN LICENSE" shall have the meaning set forth in Clause 2.1.

         "ELAN PATENTS" shall, subject to Clause 4.2, mean any and all rights
         under any and all patent applications and/or patents, now existing,
         currently pending or hereafter filed or obtained or licensed by Elan
         relating to Pharmazome(R) and NanoCrystal(TM) Technology as set forth
         in Schedule 1, which list is not exhaustive, and any foreign
         counterparts thereof and all divisionals, continuations,
         continuations-in-part, any foreign counterparts thereof and all patents
         issuing on, any of the foregoing, together with all registrations,
         reissues, re-examinations or extensions thereof.

         "EPIL" shall mean Elan Pharma International Limited, a private limited
         company incorporated under the laws of Ireland.

         "EPIL PATENTS" shall mean the Elan Patents owned by EPIL.

         "FIELD" shall mean the delivery of a specified Compound by a specific
         Mode of Administration in a specific device to treat a specific medical
         condition, as set forth in Clause 2.3 of the JDOA with respect to
         [CONFIDENTIAL TREATMENT REQUESTED]/*/ and as further determined by the
         unanimous vote of the Management Committee in accordance with Clause 2
         of the JDOA.

         "FINANCIAL YEAR" shall mean each year commencing on 1 January (or in
         the case of the first Financial Year, the Effective Date) and expiring
         on 31 December of each year.

         "IN MARKET" shall mean the sale of the Product in the Territory by
         Newco or its Affiliates, or where applicable by a permitted
         sub-licensee, to an unaffiliated third party, such as (i) the end-user
         consumer of the Product (ii) a wholesaler, managed care organization,
         hospital or pharmacy or other third party who effects the final
         commercial sale to the end-user consumer of the Product, and shall
         exclude the transfer pricing of the Product(s) by Newco to an Affiliate
         or a sub-licensee.

         "JDOA" shall mean that certain subscription, joint development and
         operating agreement, of even date herewith, by and between Elan,
         Acusphere, EIS and Newco.

         "LICENSES" shall mean the Elan License and the Acusphere License.

         "MANAGEMENT COMMITTEE" shall have the meaning set forth in the JDOA.

         "MODE OF ADMINISTRATION" shall mean administration via the pulmonary
         route (a) for local or systemic effect, and (b) by immediate or
         controlled release.



                                       4
<PAGE>

         "NANOCRYSTAL(TM)TECHNOLOGY" shall mean [CONFIDENTIAL TREATMENT
         REQUESTED]/*/

         "NET SALES" shall mean that sum determined by deducting the following
         deductions from the aggregate gross In Market sales proceeds billed for
         the Products by Newco or its Affiliate or a permitted sub-licensee, as
         the case may be:

         (i)      transportation charges or allowances, if any, included in such
                  price;

         (ii)     trade, quantity or cash discounts, broker's or agent's
                  commissions, if any, allowed or paid;

         (iii)    credits or allowances, if any, given or made on account of
                  price adjustments, returns, promotional discounts, rebates and
                  any and all federal, state or local government rebates whether
                  in existence now or enacted at any time during the term of the
                  Licenses; and

         (iv)     any tax, excise or governmental charge upon or measured by the
                  sale, transportation, delivery or use of the Products.

         "NEWCO" shall mean, Acusphere Newco, Ltd. a new company established by
         Acusphere and EIS, in Bermuda.

         "NEWCO INTELLECTUAL PROPERTY" shall mean all rights to patents,
         know-how and other intellectual property arising out of the conduct of
         the Project by any person, including any technology acquired by Newco
         from a third party, that relates to the Products and which is not (in
         the case of the Compound) or which cannot be segregated into (nor does
         it constitute) Elan Intellectual Property or Acusphere Intellectual
         Property.

         "PARTY" shall mean Elan or Newco, as the case may be, and "PARTIES"
         shall mean Elan and Newco.

         "PHARMAZOME(R)" shall mean [CONFIDENTIAL TREATMENT REQUESTED]/*/

         "PRODUCTS" shall mean formulations of the Compound(s) for use as a
         human therapeutic for a specified medical condition.

         "PROJECT" shall mean all activities as undertaken by Elan, Acusphere
         and Newco in order to develop the Products.

         "TECHNOLOGICAL COMPETITOR OF ELAN" shall mean a company, corporation or
         person listed in Schedule 2 and successors thereof or any additional
         broad-based technological competitor of Elan added to such Schedule
         from time to time upon mutual agreement of the Parties

         "TERM" shall have the meaning set forth in Clause 8.

         "TERRITORY" shall mean all the countries of the world.


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<PAGE>

         "UNITED STATES DOLLAR" and "US$" shall mean the lawful currency for the
         time being of the United States of America.

1.2      In this Agreement:

         1.2.1    The singular includes the plural and vice versa, and the
                  masculine includes the feminine and vice versa and the neuter
                  includes the masculine and the feminine.

         1.2.2    Any reference to a Clause or Schedule shall, unless otherwise
                  specifically provided, be to a Clause or Schedule of this
                  Agreement.

         1.2.3    The headings of this Agreement are for ease of reference only
                  and shall not affect its construction or interpretation.


2        ELAN LICENSE TO NEWCO

2.1      Elan hereby grants to Newco for the Term [CONFIDENTIAL TREATMENT
         REQUESTED]/*/ license (the "ELAN LICENSE") of the Elan Intellectual
         Property solely in the Field to make, have made, import, use, offer for
         sale and sell the Products in the Field in the Territory, subject to
         any contractual obligations that Elan has as of the Effective Date,
         including but not limited to [CONFIDENTIAL TREATMENT REQUESTED]/*/.

2.2      [CONFIDENTIAL TREATMENT REQUESTED]/*/ shall be responsible for payments
         related to the financial provisions and obligations of any third party
         agreement with respect to [CONFIDENTIAL TREATMENT REQUESTED]/*/ to
         which it is a party on the Effective Date (including amendments
         thereto) including without limitation, any royalty or other
         compensation obligations triggered thereunder on the Effective Date, or
         triggered thereunder after the Effective Date.

2.3      Acusphere shall be a third party beneficiary under this Agreement and
         shall have the right to cause Newco to enforce Newco's rights under
         this Agreement against Elan.

2.4      Notwithstanding anything contained in this Agreement to the contrary,
         Elan shall have the right outside the Field and subject to the
         non-competition provisions of Clause 4 to exploit and grant licenses
         and sublicenses of the Elan Intellectual Property.

         For the avoidance of doubt, Newco shall have no right to use the Elan
         Intellectual Property outside the Field.

2.5      Except as provided in Clause 11 of the JDOA, Newco shall not be
         permitted to assign, license or sublicense any of its rights under the
         Elan Intellectual Property without the prior consent in writing of
         Elan.


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<PAGE>
2.6      Any agreement between Newco and any permitted third party for the
         development or exploitation of the Elan Intellectual Property shall
         require such third party to maintain the confidentiality of all
         information concerning the Elan Intellectual Property.

         Insofar as the obligations owed by Newco to Elan are concerned, Newco
         shall remain responsible for all acts and omissions of any permitted
         sub-licensee, including Acusphere, as if they were acts and omissions
         by Newco.


3        INTELLECTUAL PROPERTY

3.1      Ownership of Intellectual Property:

         3.1.1    Newco shall own the Newco Intellectual Property.

         3.1.2    Elan shall own the Elan Intellectual Property.


4        [CONFIDENTIAL TREATMENT REQUESTED]/*/

5        FINANCIAL PROVISIONS

5.1      LICENSE FEE:

         In consideration of (a) the license by Elan Corporation, plc to Newco
         of the Elan Patents under Clause 2 (other than the EPIL Patents), Newco
         is paying to Elan Corporation, plc a non-refundable license fee of
         [CONFIDENTIAL TREATMENT REQUESTED]/*/ in cash, and (b) the license by
         EPIL to Newco of the EPIL Patents under Clause 2, Newco is paying to
         EPIL a non-refundable license fee of [CONFIDENTIAL TREATMENT
         REQUESTED]/*/ in cash (collectively, the "LICENSE FEE"), the receipt of
         which is hereby acknowledged by Elan Corporation, plc and EPIL.

         The License Fee is not subject to future performance obligations of
         Elan to Newco or Acusphere and is not applicable against future
         services provided by Elan to Newco or Acusphere.

         The payment of the license fee to Elan Corporation, plc shall
         constitute a full discharge of Newco's obligations to pay the license
         fee to EPIL.

         The terms of this Clause 5.1 relating to the License Fee are
         independent and distinct from the other terms of this Agreement.


5.2      ROYALTIES:

         Prior to the Commercialization of the Products, the Management
         Committee shall consider and if appropriate, determine reasonable
         royalties with respect to the Commercialization of the Products by
         Newco that shall be payable by Newco to Elan and Acusphere[CONFIDENTIAL
         TREATMENT REQUESTED]/*/.



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<PAGE>


5.3      Payment of royalties pursuant to Clause 5.2 shall be made quarterly in
         arrears during each Financial Year within 30 days after the expiry of
         the calendar quarter. The method of payment shall be by wire transfer
         to an account specified by Elan. Each payment made to Elan shall be
         accompanied by a true accounting of all Products sold by Newco's
         permitted sublicensees, if any, during such quarter.

         Such accounting shall show, on a country-by-country and
         Product-by-Product basis, Net Sales (and the calculation thereof) and
         each calculation of royalties with respect thereto, including the
         calculation of all adjustments and currency conversions.

5.4      Newco shall maintain and keep clear, detailed, complete, accurate and
         separate records for a period of 3 years:

         5.4.1    to enable any royalties on Net Sales that shall have accrued
                  hereunder to be determined; and

         5.4.2    to enable any deductions made in the Net Sales calculation to
                  be determined.

5.5      All payments due hereunder shall be made in United States Dollars.
         Payments due on Net Sales of any Product for each calendar quarter made
         in a currency other than United States Dollars shall first be
         calculated in the foreign currency and then converted to United States
         Dollars on the basis of the exchange rate in effect on the last working
         day for such quarter for the purchase of United States Dollars with
         such foreign currency quoted in the Wall Street Journal (or comparable
         publication if not quoted in the Wall Street Journal) with respect to
         the currency of the country of origin of such payment, determined by
         averaging the rates so quoted on each business day of such quarter.

5.6      If, at any time, legal restrictions in the Territory prevent the prompt
         payment when due of royalties or any portion thereof, the Parties shall
         meet to discuss suitable and reasonable alternative methods of paying
         Elan the amount of such royalties. In the event that Newco is prevented
         from making any payment under this Agreement by virtue of the statutes,
         laws, codes or government regulations of the country from which the
         payment is to be made, then such payments may be paid by depositing
         them in the currency in which they accrue to Elan's account in a bank
         acceptable to Elan in the country the currency of which is involved or
         as otherwise agreed by the Parties.

5.7      Elan and Newco agree to co-operate in all respects necessary to take
         advantage of any double taxation agreements or similar agreements as
         may, from time to time, be available.

5.8      Any taxes payable by Elan on any payment made to Elan pursuant to this
         Agreement shall be for the account of Elan. If so required by
         applicable law, any payment made pursuant to this Agreement shall be
         made by Newco after deduction of the appropriate




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<PAGE>

         withholding tax, in which event the Parties shall co-operate to obtain
         the appropriate tax clearance as soon as is practicable. On receipt of
         such clearance, Newco shall forthwith arrange payment to Elan of the
         amount so withheld.

5.9      Royalties and other payments payable to Elan under the terms of this
         Agreement shall be apportioned, where applicable, on an arm's length
         basis among Affiliates of Elan.


6        RIGHT OF INSPECTION AND AUDIT

6.1      Once during each Financial Year, or more often not to exceed quarterly
         as reasonably requested by Elan, Newco shall permit Elan or its duly
         authorized representatives, upon reasonable notice and at any
         reasonable time during normal business hours, to have access to inspect
         and audit the accounts and records of Newco and any other book, record,
         voucher, receipt or invoice relating to the calculation of the royalty
         payments on Net Sales submitted to Elan.

         Any such inspection of Newco's records shall be at the expense of Elan,
         except that if any such inspection reveals a deficiency in the amount
         of the royalty actually paid to Elan hereunder in any Financial Year
         quarter of [CONFIDENTIAL TREATMENT REQUESTED]/*/ or more of the amount
         of any royalty actually due to Elan hereunder, then the expense of such
         inspection shall be borne solely by Newco. Any amount of deficiency
         shall be paid promptly to Elan by Newco.

         If such inspection reveals a surplus in the amount of royalties
         actually paid to Elan by Newco, Elan shall reimburse Newco the surplus
         within [CONFIDENTIAL TREATMENT REQUESTED]/*/ after determination.

6.2      In the event of any unresolved dispute regarding any alleged deficiency
         or overpayment of royalty payments hereunder, the matter will be
         referred to an independent firm of chartered accountants chosen by
         agreement of Acusphere and Elan for a resolution of such dispute. Any
         decision by the said firm of chartered accountants shall be binding on
         the Parties.


7        REPRESENTATIONS AND WARRANTIES

7.1      Upon the selection of the Compound by the Management Committee in
         accordance with Clause 2.3 of the JDOA Elan represents and warrants to
         Newco and Acusphere as of such selection date with respect to the Elan
         Intellectual Property as it relates to such Compound, as follows:

         7.1.1    Elan has the right to grant the Elan License;

         7.1.2    There are no agreements between Elan and any third party that
                  conflict with the Elan License; and

         7.1.3    [CONFIDENTIAL TREATMENT REQUESTED]/*/



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<PAGE>

7.2      In addition to any other indemnities provided for herein, Elan shall
         indemnify and hold harmless Newco and its Affiliates and their
         respective employees, agents, officers and directors from and against
         any claims, losses, liabilities or damages (including reasonable
         attorney's fees and expenses) incurred or sustained by Newco arising
         out of or in connection with any:

         7.2.1    breach of any representation, covenant, warranty or obligation
                  by Elan hereunder; or

         7.2.2    act or omission on the part of Elan or any of its respective
                  employees, agents, officers and directors in the performance
                  of this Agreement.

7.3      In addition to any other indemnities provided for herein, Newco shall
         indemnify and hold harmless Elan and its Affiliates and their
         respective employees, agents, officers and directors from and against
         any claims, losses, liabilities or damages (including reasonable
         attorney's fees and expenses) incurred or sustained by Elan arising out
         of or in connection with any:

         7.3.1    breach of any representation, covenant, warranty or obligation
                  by Newco hereunder; or

         7.3.2    act or omission on the part of Newco or any of its agents or
                  employees in the performance of this Agreement.

7.4      The Party seeking an indemnity shall:

         7.4.1    fully and promptly notify the other Party of any claim or
                  proceeding, or threatened claim or proceeding;

         7.4.2    permit the indemnifying Party to take full care and control of
                  such claim or proceeding;

         7.4.3    co-operate in the investigation and defense of such claim or
                  proceeding;

         7.4.4    not compromise or otherwise settle any such claim or
                  proceeding without the prior written consent of the other
                  Party, which consent shall not be unreasonably withheld
                  conditioned or delayed; and

         7.4.5    take all reasonable steps to mitigate any loss or liability in
                  respect of any such claim or proceeding.

7.5      [CONFIDENTIAL TREATMENT REQUESTED]/*/ ELAN IS GRANTING THE ELAN LICENSE
         HEREUNDER ON AN "AS IS" BASIS WITHOUT REPRESENTATION OR WARRANTY
         WHETHER EXPRESS OR IMPLIED INCLUDING WARRANTIES OF MERCHANTABILITY OR
         FITNESS FOR A PARTICULAR PURPOSE, OR INFRINGEMENT OF THIRD PARTY
         RIGHTS, AND ALL SUCH WARRANTIES ARE EXPRESSLY DISCLAIMED.


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<PAGE>
7.6      NOTWITHSTANDING ANYTHING TO THE CONTRARY IN THIS AGREEMENT, ELAN AND
         NEWCO SHALL NOT BE LIABLE TO THE OTHER BY REASON OF ANY REPRESENTATION
         OR WARRANTY, CONDITION OR OTHER TERM OR ANY DUTY OF COMMON LAW, OR
         UNDER THE EXPRESS TERMS OF THIS AGREEMENT, FOR ANY CONSEQUENTIAL,
         SPECIAL OR INCIDENTAL OR PUNITIVE LOSS OR DAMAGE (WHETHER FOR LOSS OF
         PROFITS OR OTHERWISE) AND WHETHER OCCASIONED BY THE NEGLIGENCE OF THE
         RESPECTIVE PARTIES, THEIR EMPLOYEES OR AGENTS OR OTHERWISE.


8.       TERM AND TERMINATION

8.1      The term of this Agreement shall commence as of the Effective Date and
         shall, subject to the rights of termination outlined in this Clause 8,
         expire on a Product-by-Product basis and on a country-by-country basis
         on the last to occur of:

         8.1.1    [CONFIDENTIAL TREATMENT REQUESTED]/*/ starting from the date
                  of the first commercial sale of the Product in the country
                  concerned; or

         8.1.2    the date of expiration of the last to expire of the patents
                  included in the Elan Patents and the Elan Improvements and/or
                  the Acusphere Patents and the Acusphere Improvements

         ("THE TERM").

8.2      If either Party commits a Relevant Event, the other Party shall have,
         in addition to all other legal and equitable rights and remedies
         hereunder, the right to terminate this Agreement upon 30 days' prior
         written notice to the defaulting Party.

8.3      For the purpose of this Clause 8, a "RELEVANT EVENT" is committed or
         suffered by a Party if:

         8.3.1    it commits a material breach of its obligations under this
                  Agreement or the JDOA and fails to cure it within 60 days of
                  being specifically required in writing to do so by the other
                  Party; provided, that if the breaching Party has proposed a
                  course of action to cure the breach and is acting in good
                  faith to cure same but has not cured the breach by the 60th
                  day, such period shall be extended by such period as is
                  reasonably necessary to permit the breach to be cured,
                  provided that such period shall not be extended by more than
                  90 days, unless otherwise agreed in writing by the Parties;

         8.3.2    a distress, execution, sequestration or other process is
                  levied or enforced upon or sued out against a material part of
                  its property, which is not discharged or challenged within 30
                  days;

         8.3.3    it is unable to pay its debts in the normal course of
                  business;


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<PAGE>

         8.3.4    it ceases wholly or substantially to carry on its business,
                  otherwise than for the purpose of a reconstruction or
                  amalgamation, without the prior written consent of the other
                  Party (such consent not to be unreasonably withheld);

         8.3.5    the appointment of a liquidator, receiver, administrator,
                  examiner, trustee or similar officer of such Party or over all
                  or substantially all of its assets under the law of any
                  applicable jurisdiction, including without limitation, the
                  United States of America, Bermuda or Ireland;

         8.3.6    an application or petition for bankruptcy, corporate
                  re-organization, composition, administration, examination,
                  arrangement or any other procedure similar to any of the
                  foregoing under the law of any applicable jurisdiction,
                  including without limitation, the United States of America,
                  Bermuda or Ireland, is filed, and is not discharged within 60
                  days, or a Party applies for or consents to the appointment of
                  a receiver, administrator, examiner or similar officer of it
                  or of all or a material part of its assets, rights or revenues
                  or the assets and/or the business of a Party are for any
                  reason seized, confiscated or condemned.

8.4      Acusphere shall promptly provide Elan written notice in the event a
         Change of Control of Acusphere/Newco has occurred. Elan, at its option,
         shall have the right, excisable within 120 days of Elan's receipt of
         such written notice from Acusphere, to terminate the Elan License by
         notice in writing to Acusphere.

8.5      Upon expiration or termination of the Agreement:

         8.5.1.   any sums that were due from Newco to Elan on Net Sales in the
                  Territory or in such particular country or countries in the
                  Territory (as the case may be) prior to the expiration or
                  termination of this Agreement as set forth herein shall be
                  paid in full within 60 days after the expiration or
                  termination of this Agreement for the Territory or for such
                  particular country or countries in the Territory (as the case
                  may be);

         8.5.2    any provisions that expressly survive termination or
                  expiration of this Agreement, including without limitation
                  this Clause 8, shall remain in full force and effect;

         8.5.3    all representations, warranties and indemnities shall insofar
                  as are appropriate remain in full force and effect;

         8.5.4    the rights of inspection and audit set out in Clause 6 shall
                  continue in force for a period of one year; and

         8.5.5    subject to Clause 8.5.7, all rights and licenses granted to
                  Newco pursuant to this Agreement and to the Elan Intellectual
                  Property pursuant to the JDOA (including the rights of Newco
                  pursuant to Clause 10 of the JDOA with respect to patent
                  prosecution and maintenance) shall cease for the Territory or



                                       12
<PAGE>

                  for such particular country or countries in the Territory (as
                  the case may be) and shall revert to or be transferred to
                  Elan, and Newco shall not thereafter use in the Territory or
                  in such particular country or countries in the Territory (as
                  the case may be) any rights covered by this Agreement;

         8.5.6    subject to such license, if any, granted by Newco to Elan
                  pursuant to the provisions of Clause 11.3 of the JDOA, all
                  rights to Newco Intellectual Property shall be transferred to
                  and jointly owned by Acusphere and Elan and may be exploited
                  by both Elan and Acusphere separately provided that nothing
                  hereunder shall grant, or be construed to grant, a license to
                  the other party under the Elan Intellectual Property or the
                  Acusphere Intellectual Property;

         8.5.7    the rights of permitted third party sub-licensees in and to
                  the Elan Intellectual Property shall survive the termination
                  of the license and sublicense agreements granting said
                  intellectual property rights to Newco; and Newco, Elan and
                  Acusphere shall in good faith agree upon the form most
                  advantageous to Elan and Acusphere in which the rights of
                  Newco under any such licenses and sublicenses are to be held
                  (which form may include continuation of Newco solely as the
                  holder of such licenses or assignment of such rights to a
                  third party or parties, including an assignment to both Elan
                  and Acusphere).

                  Any sublicense agreement between Newco and such permitted
                  sublicensee shall permit an assignment of rights by Newco and
                  shall contain appropriate confidentiality provisions.


9        CONFIDENTIAL INFORMATION

9.1      The Parties agree that it will be necessary, from time to time, to
         disclose to each other confidential and proprietary information,
         including without limitation, inventions, works of authorship, trade
         secrets, specifications, designs, data, know-how and other proprietary
         information relating to the Field, the Products, processes, services
         and business of the disclosing Party.

         The foregoing shall be referred to collectively as "CONFIDENTIAL
         INFORMATION".

9.2      Any Confidential Information disclosed by one Party to another Party
         shall be used by the receiving Party exclusively for the purposes of
         fulfilling the receiving Party's obligations under this Agreement and
         the JDOA and for no other purpose.

9.3      Save as otherwise specifically provided herein, each Party shall
         disclose Confidential Information of the other Party only to those
         employees, representatives and agents requiring knowledge thereof in
         connection with fulfilling the Party's obligations under this
         Agreement. Each Party further agrees to inform all such employees,
         representatives and agents of the confidentiality terms and provisions
         of this Agreement and their duties hereunder and to obtain their
         agreement hereto as a condition of receiving Confidential Information.
         Each Party shall exercise the same


                                       13
<PAGE>
         standard of care as it would itself exercise in relation to its own
         confidential information (but in no event less than a reasonable
         standard of care) to protect and preserve the proprietary and
         confidential nature of the Confidential Information disclosed to it by
         the other Party. Each Party shall, upon request of the other Party,
         return all documents and any copies thereof containing Confidential
         Information belonging to, or disclosed by, such other Party.

9.4      Any breach of this Clause 9 by any person informed by one of the
         Parties is considered a breach by the Party itself.

9.5      Confidential Information shall not be deemed to include:

         9.5.1    information that is in the public domain;

         9.5.2    information which is made public through no breach of this
                  Agreement;

         9.5.3    information which is independently developed by a Party as
                  evidenced by such Party's records;

         9.5.4    information that becomes available to a Party on a
                  non-confidential basis, whether directly or indirectly, from a
                  source other than a Party, which source did not acquire this
                  information on a confidential basis; or

9.6      The receiving Party will be entitled to disclose Confidential
         Information which the receiving Party is required to disclose pursuant
         to:

         9.6.1    a valid order of a court or other governmental body; or

         9.6.2    any other requirement of law;

         provided that if the receiving Party becomes legally required to
         disclose any Confidential Information, the receiving Party shall give
         the disclosing Party prompt notice of such fact so that the disclosing
         Party may obtain a protective order or other appropriate remedy
         concerning any such disclosure. The receiving Party shall fully
         co-operate with the disclosing Party in connection with the disclosing
         Party's efforts to obtain any such order or other remedy. If any such
         order or other remedy does not fully preclude disclosure, the receiving
         Party shall make such disclosure only to the extent that such
         disclosure is legally required.

9.7      The provisions relating to confidentiality in this Clause 9 shall
         remain in effect during the term of this Agreement, and for a period of
         7 years following the expiration or earlier termination of this
         Agreement.

9.8      The Parties agree that the obligations of this Clause 9 are necessary
         and reasonable in order to protect the Parties' respective businesses,
         and each Party agrees that monetary damages would be inadequate to
         compensate a Party for any breach by the other Party of its covenants
         and agreements set forth herein. Accordingly, the Parties agree that
         any such violation or threatened violation shall cause irreparable
         injury to a

                                       14
<PAGE>

         Party and that, in addition to any other remedies that may be
         available, in law and equity or otherwise, each Party shall be entitled
         to obtain injunctive relief against the threatened breach of the
         provisions of this Clause 9, or a continuation of any such breach by
         the other Party, specific performance and other equitable relief to
         redress such breach together with its damages and reasonable counsel
         fees and expenses to enforce its rights hereunder, without the
         necessity of proving actual or express damages.

9.9      For the avoidance of doubt, all Confidential Information of Newco
         received by Elan hereunder shall not be disclosed by Elan to Affiliates
         and/or subsidiaries (present or future) of Elan Corporation, plc.
         within the division of Elan Corporation, plc. carrying on business as
         Elan Pharmaceuticals which incorporates, inter alia, Athena
         Neurosciences, Inc., Elan Pharmaceuticals, Inc., Elan Diagnostics,
         Carnrick Laboratories, The Liposome Company, Inc. and Elan Europe
         Limited.


10       GOVERNING LAW AND JURISDICTION

10.1     This Agreement shall be governed by and construed in accordance with
         the laws of the State of New York.

10.2     The Parties will attempt in good faith to resolve any dispute arising
         out of or relating to this Agreement promptly by negotiation between
         executives of the Parties. In the event that such negotiations do not
         result in a mutually acceptable resolution, the Parties agree to
         consider other dispute resolution mechanisms including mediation.

         In the event that the Parties fail to agree on a mutually acceptable
         dispute resolution mechanism, any such dispute shall be finally settled
         by the courts of competent jurisdiction. For the purposes of this
         Agreement the parties submit to the non-exclusive jurisdiction of the
         courts of the State of New York.


11       IMPOSSIBILITY OF PERFORMANCE - FORCE MAJEURE

         Neither Elan nor Newco shall be liable for delay in the performance of
         any of its obligations hereunder if such delay results from causes
         beyond its reasonable control, including, without limitation, acts of
         God, fires, strikes, acts of war, intervention of a government
         authority, but any such delay or failure shall be remedied by such
         Party as soon as practicable.


12       ASSIGNMENT

         This Agreement may not be assigned by either Party without the prior
         written consent of the other, save that either Party may assign this
         Agreement to its Affiliates or subsidiaries without such prior written
         consent; provided that such assignment does not have any adverse tax
         consequences on the other Party.


                                       15
<PAGE>
13       NOTICES

13.1     Any notice to be given under this Agreement shall be sent in writing in
         English by registered airmail or telefaxed to the following addresses:

         If to Newco at:

         Clarendon House,
         2 Church St.,
         Hamilton,
         Bermuda
         Attention:        Secretary
         Telephone:        441 292 9169
         Fax:              441 292 2224

         with a copy to Acusphere at:

         38 Sidney Street
         Cambridge, MA 02139-4169

         Attn:             Chief Executive Officer
         Telephone         617-577-8800
         Fax:              617-577-0233


         If to Acusphere at:

         38 Sidney Street
         Cambridge, MA 02139-4169

         Attn:             Chief Executive Officer
         Telephone         617-577-8800
         Fax:              617-577-0233

         with a copy to:

         Testa, Hurwitz & Thibeault, LLP
         125 High Street
         Boston, MA 02110

         Attention:        Lawrence S. Wittenberg
         Telephone:        617-248-7000
         Fax:              617-248-7100



                                       16
<PAGE>
         If to Elan at:

         Elan Corporation, plc
         102 St. James Court
         Flatts, Smiths FL04
         Bermuda

         Attention:        President
         Telephone:        441-292-9169
         Fax:              441-292-2224

         or to such other address(es) and telefax numbers as may from time to
         time be notified by either Party to the other hereunder.

13.2     Any notice sent by mail shall be deemed to have been delivered within 7
         working days after dispatch and any notice sent by telex or telefax
         shall be deemed to have been delivered within 24 hours of the time of
         the dispatch. Notice of change of address shall be effective upon
         receipt.


14       MISCELLANEOUS

14.1     WAIVER:

         No waiver of any right under this Agreement shall be deemed effective
         unless contained in a written document signed by the Party charged with
         such waiver, and no waiver of any breach or failure to perform shall be
         deemed to be a waiver of any other breach or failure to perform or of
         any other right arising under this Agreement.

14.2     SEVERABILITY:

         If any provision in this Agreement is agreed by the Parties to be, or
         is deemed to be, or becomes invalid, illegal, void or unenforceable
         under any law that is applicable hereto:

         14.2.1   such provision will be deemed amended to conform to applicable
                  laws so as to be valid and enforceable; or

         14.2.2   if it cannot be so amended without materially altering the
                  intention of the Parties, it will be deleted, with effect from
                  the date of such agreement or such earlier date as the Parties
                  may agree, and the validity, legality and enforceability of
                  the remaining provisions of this Agreement shall not be
                  impaired or affected in any way.

14.3     FURTHER ASSURANCES:

         At the request of any of the Parties, the other Party or Parties shall
         (and shall use reasonable efforts to procure that any other necessary
         parties shall) execute and perform all such documents, acts and things
         as may reasonably be required subsequent to the signing of this
         Agreement for assuring to or vesting in the requesting Party the full
         benefit of the terms hereof.


                                       17
<PAGE>
14.4     SUCCESSORS:

         This Agreement shall be binding upon and enure to the benefit of the
         Parties hereto, their successors and permitted assigns.

14.5     NO EFFECT ON OTHER AGREEMENTS/CONFLICT:

         No provision of this Agreement shall be construed so as to negate,
         modify or affect in any way the provisions of any other agreement
         between the Parties unless specifically referred to, and solely to the
         extent provided herein.

         In the event of a conflict between the provisions of this Agreement and
         the provisions of the JDOA, the terms of the JDOA shall prevail unless
         this Agreement specifically provides otherwise.

14.6     AMENDMENTS:

         No amendment, modification or addition hereto shall be effective or
         binding on any Party unless set forth in writing and executed by a duly
         authorized representative of each Party.

14.7     COUNTERPARTS:

         This Agreement may be executed in any number of counterparts, each of
         which when so executed shall be deemed to be an original and all of
         which when taken together shall constitute this Agreement.

14.8     GOOD FAITH:

         Each Party undertakes to do all things reasonably within its power
         which are necessary or desirable to give effect to the spirit and
         intent of this Agreement.

14.9     NO RELIANCE:

         Each Party hereby acknowledges that in entering into this Agreement it
         has not relied on any representation or warranty save as expressly set
         out herein or in any document referred to herein.



14.10    RELATIONSHIP OF THE PARTIES:

         Nothing contained in this Agreement is intended or is to be construed
         to constitute Elan and Newco as partners, or Elan as an employee of
         Newco, or Newco as an employee of Elan.

         Neither Party hereto shall have any express or implied right or
         authority to assume or create any obligations on behalf of or in the
         name of the other Party or to bind the other Party to any contract,
         agreement or undertaking with any third party.


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<PAGE>


IN WITNESS WHEREOF the Parties hereto have executed this Agreement.

SIGNED

BY: /s/ illegible signature
-------------------------------------------
for and on behalf of ELAN CORPORATION, PLC,
ACTING THROUGH ITS DIVISION ELAN
PHARMACEUTICAL TECHNOLOGIES


SIGNED

BY: /s/ illegible signature
-------------------------------------------
for and behalf of ELAN PHARMA
INTERNATIONAL LIMITED


SIGNED

BY: /s/ illegible signature
-------------------------------------------
For and on behalf of ACUSPHERE NEWCO, LTD.


AGREED TO AND ACCEPTED:

SIGNED

BY: /s/ Sherri C. Oberg
-------------------------------------------
For and behalf of ACUSPHERE, INC.



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<PAGE>

                                   SCHEDULE 1


                           REPRESENTATIVE ELAN PATENTS

                      [CONFIDENTIAL TREATMENT REQUESTED]/*/




















<PAGE>

                                   SCHEDULE 2

                        TECHNOLOGICAL COMPETITORS OF ELAN

                      [CONFIDENTIAL TREATMENT REQUESTED]/*/