<PAGE>
[*] = CERTAIN CONFIDENTIAL INFORMATION CONTAINED IN THIS DOCUMENT, MARKED BY
BRACKETS, HAS BEEN OMITTED AND FILED SEPARATELY WITH THE SECURITIES AND
EXCHANGE COMMISSION PURSUANT TO RULE 406 OF THE SECURITIES ACT OF 1933, AS
AMENDED.



                                                                   Exhibit 10.15

                           EXCLUSIVE LICENSE AGREEMENT

     Effective as of 1 March 2000, GEORGETOWN UNIVERSITY, a not-for-profit
corporation of the District of Columbia, having a principal address at 37th & O
Streets, N.W., Washington, D C. 20057 ("LICENSOR"), and ZEBRA PHARMACEUTICALS, a
Massachusetts corporation, having a principal place of business at 160 Second
St., Cambridge, Massachusetts 02142 ("LICENSEE"), agree as follows:

                                 1. BACKGROUND

      1.1 LICENSOR is the owner by assignment or obligation of assignment to
certain Technology directed generally to Ligands for Metatrobic Glutamate
Receptors and Inhibitors of NAALADase (as further defined herein).

      1.2 LICENSOR wishes to have the Technology developed and marketed at the
earliest possible time in order that products resulting therefrom may be
available for public use and benefit.

      1.3 LICENSEE wishes to acquire a license under said Technology for the
purpose of undertaking development, to manufacture, use and sell Licensed
Product(s) in the Licensed Field of Use.

                                 2. DEFINITIONS

      2.1 "Patent Rights" refers to LICENSOR's rights arising from U.S.
Provisional Patent Applications Serial No. 60/166,915, filed 22 November 1999
"Ligands for Metatrobic Glutamate Receptors and Inhibitors of NAALADase" and
Serial No. 60/131,627 filed 28 April 1999 entitled "Ligands for Metatrobic
Glutamate Receptors and Inhibitors of NAALADase" and naming as inventors Alan P.
Kozikowski, Jarda T. Wroblewski and Fajun Nan including any foreign patent
applications corresponding thereto, any United States divisions, continuations,
reissues, or reexaminations thereof, and any United States or foreign patent(s)
issued or granted therefrom and any United States or foreign patents or patent
applications claiming Technology. Such patent application(s) are the "Licensed
Application(s)" and any resulting issued patents are the "Licensed Patent(s)."

      2.2 "Technology" means any technical data, know-how, material, research
results and other information provided to LICENSEE by LICENSOR or its employees
or contractors relating "Ligands for Metatrobic Glutamate Receptors and
Inhibitors of NAALADase" including, without limitation, any biochemical,
preclinical, clinical, manufacturing, formulation, and scientific research
information of a confidential nature whether patentable or unpatentable.

      2.3 "Licensed Product(s)" means any compound, product or part thereof,
device, method or service, the manufacture, use, or sale of which:

<PAGE>

Page 2

            (a) is covered by a valid claim of an issued, unexpired Licensed
Patent(s). A claim of an issued, unexpired Licensed Patent(s) shall be presumed
to be valid unless and until it has been held to be invalid by a final judgment
of a court of competent jurisdiction from which no appeal can be or is taken;

            (b) is covered by any claim being prosecuted in Licensed
Application(s).

      2.4 "Net Sales" means the gross revenue generated by sale of the Licensed
Product(s) or use of the Licensed Process(es) in the form in which it is sold or
used, whether or not assembled (and without excluding therefrom any components
or subassemblies thereof, whatever their origin and whether or not patent
impacted) less the following items:

            (a) Import, export, excise, value added and sales taxes, plus custom
duties;

            (b) Costs of insurance, packing and transportation from the place of
manufacture to the customer's premises or point of installation;

            (c) Normal and customary quantity and cash discounts; and

            (d) Credit for returns, allowances, or trades actually given.

      2.5 "Licensed Field of Use" means any diagnostic or therapeutic use
concerning "Ligands for Metatrobic Glutamate Receptors and Inhibitors of
NAALADase".

      2.6 "Exclusive" means LICENSOR has not granted and shall not grant further
licenses in the Licensed Field of Use, so long as this Agreement is in effect.

      2.7 "Regulatory Approval" means any approval or clearance by any
governmental agency or agencies having authority to regulate the use or sale of
any Licensed Product(s) in the pertinent jurisdiction or territory.

      2.8 "LICENSEE" is understood to include Zebra and any and all of its
Affiliates. An Affiliate of LICENSEE shall mean any corporation or other
business entity controlled by, controlling, or under common control with
LICENSEE during the term of this Agreement. For this purpose, "control" means
direct or indirect beneficial ownership:

            (a) of at least fifty percent (50%) of the voting stock; or

            (b) of at least fifty percent (50%) interest in the income of such
corporation or other business.

      2.9 "First Commercial Sale" means the first sale of a Licensed Product at
an arms length transaction with a third party un-Affiliated with any party to
this Agreement.

<PAGE>
[*] = CERTAIN CONFIDENTIAL INFORMATION CONTAINED IN THIS DOCUMENT, MARKED BY
BRACKETS, HAS BEEN OMITTED AND FILED SEPARATELY WITH THE SECURITIES AND
EXCHANGE COMMISSION PURSUANT TO RULE 406 OF THE SECURITIES ACT OF 1933, AS
AMENDED.



Page 3

                                    3. GRANT

      3.1 LICENSOR hereby grants and LICENSEE hereby accepts a worldwide license
in the Licensed Field of Use to make, have made, use, sell, and have sold
Licensed Product(s) and to use Technology.

      3.2 Said license, which includes the right to sublicense, shall be
Exclusive in the Licensed Field of Use.

                     4. ROYALTIES, PAYMENTS AND MILESTONES

      4.1 During the term of this Agreement, LICENSEE agrees to assume
responsibility for future patent prosecution and maintenance costs as provided
in the following Article 8.1.

      4.2 LICENSEE shall use good faith efforts to develop, obtain clinical
approval for, manufacture, market and promote Licensed Products.

      4.3 LICENSOR shall have the right to terminate or render this license
nonexclusive at any time after two (2) years from the date of the license if, in
LICENSOR's reasonable judgment, LICENSEE:

            (i) has not put the licensed subject matter into commercial use in
the country or countries where licensed, directly or through a sublicense, and
is not keeping the licensed subject matter reasonably available to the public,
or

            (ii) is not demonstrably engaged in research, development,
manufacturing, marketing or licensing program, as appropriate, directed toward
this end.

In making this determination, LICENSEE shall take into account the normal course
of such programs conducted with sound and reasonable business practices and
judgment and shall take into account the reports provided hereunder by LICENSEE.

      4.4 (a) LICENSEE shall pay to LICENSOR benchmark royalties relating to
each Licensed Product as follows:

                  (1) $[******] within thirty (30) days after the IND approval;

                  (2) $[*******] within thirty (30) days after approval of Phase
II tests

<PAGE>

Page 4

                  (3) $[*******] within thirty (30) days after approval of Phase
III tests; and

                  (4) $[*******] within thirty (30) days after the approval of
the NDA.

LICENSEE may investigate more than one Licensed Product through Phase II tests,
without paying more than one set of benchmark royalties. If LICENSEE should
choose to submit multiple NDAs or an NDA covering more than one Licensed
Product, then the benchmark royalties relating to additional Licensed Products
as set forth in 4.3 (3) and (4) above shall be reduced by fifty percent (50%).
If, after obtaining approval of an NDA, LICENSEE attempts to develop additional
Licensed Products, benchmark royalties relating to such products will be reduced
by 50%.

      4.5 Fifty percent ([**]%) of the total milestone fees paid to Licensor by
Licensee as provided in 4.4 above, shall be creditable against earned royalties
as provided in 4.6 up to a maximum of fifty percent ([**]%) of such royalties
until such credit is fully consumed.

      4.6 In addition, LICENSEE shall pay LICENSOR earned royalties of two
percent ([*]%) on Net Sales of any diagnostic Licensed Product and three
percent ([*]%) on Net Sales of any therapeutic Licensed Product in the country
in which the Licensed Product is made, used or sold. LICENSEE shall pay to
LICENSOR, as royalties relating to any sublicense, the greater of (a) the
applicable royalty as set forth above or (b) twenty percent ([**]%) of any
compensation LICENSEE receives from the sublicensee.

      4.7 The royalty on sales in currencies other than U.S. Dollars shall be
calculated using the appropriate foreign exchange rate for such currency quoted
by the Wall Street Journal, on the close of business on the last banking day of
each calendar quarter. Royalty payments to LICENSOR shall be in U.S. Dollars.

      4.8 In the event that the Patent Rights relating to a particular Licensed
Product are finally rejected as being unpatentable by the U.S. Patent and
Trademark Office or as being invalid by a court of competent jurisdiction, or
upon the expiration of the last patent covering such Licensed Product, LICENSEE
shall be entitled to a [*****] percent ([**]%) reduction in all royalties
related to such Licensed Product accruing pursuant to this Article 4.6,
commencing on the effective date of such determination, judgment or expiration.

                        5.REPORTS.PAYMENTS AND ACCOUNTING

      5.1 Quarterly Royalty Payment and Report. LICENSEE shall make written
reports and royalty payments to LICENSOR within ninety (90) days after the end
of each calendar quarter following the First Commercial Sale. This report shall
state the number, description, and aggregate Net Sales of Licensed Product(s)
during such completed calendar quarter, and resulting calculation of earned
royalty payment due LICENSOR for

<PAGE>

Page 5

such completed calendar quarter. Concurrent with the making of each such report,
LICENSEE shall include payment due LICENSOR of royalties for the calendar
quarter covered by such report.

      5.2 Annual Progress Reports. LICENSEE shall provide annual written
progress reports within sixty (60) days after the anniversary date of the
effective date of this agreement. The reports shall include sufficient detail to
allow LICENSEE to determine progress on research and development, manufacturing,
sublicensing, marketing and sales during the previous twelve (12) months as well
as plans for the coming year.

      5.3 Accounting. LICENSEE agrees to keep records for a period of two (2)
years showing the manufacturing, sales, use, and other disposition of products
sold or otherwise disposed of under the license herein granted in sufficient
detail to enable the royalties payable hereunder by LICENSEE to be determined,
and further agrees to permit its books and records to be examined from time to
time by a certified public accountant of a nationally recognized accounting
firm, who is selected and paid for by LICENSOR, but no more than once per
calendar year, to the extent necessary to verify reports provided for in
Paragraph 5.1. Such examination is to be made by LICENSOR, at its expense and
all such information obtained shall be treated as confidential information
pursuant to Article 10. If LICENSOR determines that LICENSEE has, for any
reason, failed to pay adequate royalties, LICENSEE shall immediately upon notice
thereof pay to LICENSOR any owed royalties plus interest at the rate of eleven
percent (11%) per annum, compounded daily, calculated from the date upon which
such royalties should have been paid to the date of actual payment of LICENSOR.

                                  6. WARRANTY

      LICENSOR represents and warrants that it has the right to grant LICENSEE
the license granted herein and that it has not granted the Patent Rights or any
rights in any Licensed Product(s) to any third party, except for United States
government rights which may have been required by law. LICENSOR also represents
and warrants that, to the best of LICENSOR's knowledge, information and belief,
the Invention(s) are novel.

                                7. INFRINGEMENT

      7.1 LICENSOR and LICENSEE shall promptly give notice to the other in
writing of any alleged infringement of Patent Rights. The parties shall
thereupon confer as to what steps are to be taken to stop or prevent such
infringement.

      7.2 LICENSEE shall have the first right to defend Patent Rights against
any infringer at LICENSEE's cost and expense including by bringing any legal
action for infringement or defending any counterclaim of invalidity or action of
a third party for declaratory judgment of non-infringement, which LICENSEE, in
its sole discretion,

<PAGE>

Page 6

decides is reasonable and necessary for it to undertake. LICENSEE shall bring or
defend or may settle any such actions solely at its own expense and through
counsel of its selection and will be entitled to retain any settlement or damage
award received except as provided for in Article 7.5; provided, however, that
LICENSOR shall be entitled in each instance to participate through counsel of
its own selection and its own expense. LICENSEE and LICENSOR acknowledge and
agree that, although LICENSOR shall have the right at LICENSOR's option to
prosecute infringers as provided in the following Article 7.3, LICENSOR is not
desirous of being a party to any such infringement suit. LICENSEE shall not join
LICENSOR as a party-plaintiff in any suit which LICENSEE may institute unless
necessary for the maintenance of said suit, and then only with the prior
knowledge and written consent of LICENSOR. In such event, LICENSOR shall not be
chargeable for any costs or expenses. LICENSOR shall execute all documents
necessary for the prosecution of any infringement suit brought by LICENSEE and
provide other such support as LICENSEE may require including having its
employees testify when requested and make available relevant records, papers,
information, samples, specimens and the like, all however at the expense, with
respect to travel and the like, of LICENSEE.

      7.3 LICENSOR shall have the right to defend the Patent Rights against
infringement in the event that LICENSEE declines to exercise its rights to
defend Patent Rights under Article 7.2 and shall have sole discretion to file
and prosecute, defend or settle such infringement and declaratory judgment
action at its own expense through counsel of its own selection and will be
entitled to retain any settlement or damage award received; provided, however,
that LICENSEE shall be entitled in each instance to participate through counsel
of its own selection and at its own expense. LICENSEE shall have no
responsibility or financial obligation with respect to any such infringement
action except to provide reasonable assistance to LICENSOR as requested and
LICENSOR shall reimburse LICENSEE for LICENSEE's out-of-pocket expenses in
connection with any such assistance. LICENSEE shall execute all documents
necessary for the prosecution of any infringement suit brought by LICENSOR and
provide other such support as LICENSOR may require, including having its
employees testify when requested and make available relevant records, papers,
information, samples, specimens and the like, all however at the expense, with
respect to travel and the like, of LICENSOR.

      7.4 In the event that LICENSOR decides to institute suit, LICENSOR shall
be entitled to retain the entire amount of any recovery or settlement.
Furthermore, at its option, LICENSOR may join LICENSEE as plaintiff.

<PAGE>

Page 7

      7.5 LICENSOR shall be entitled to the percentage of any recovery obtained
in any infringement suit brought by LICENSEE equal to the amount to which
LICENSOR would be entitled under the sublicensee royalty provision of this
Agreement had said recovery been paid to LICENSEE as sublicense royalties by the
defendant in said infringement suit. LICENSEE may deduct its reasonable costs
and attorneys' fees incurred in prosecuting such suit, to the extent such costs
and fees are not otherwise recovered, prior to calculating the share owing to
LICENSOR pursuant to this provision.

      7.6 Should either LICENSOR or LICENSEE commence a suit under the
provisions of Paragraphs 7.2 or 7.3 and thereafter elect to abandon the same, it
shall give timely notice to the other party which may, if it so desires,
continue prosecution of such suit; provided, however, that the sharing of
expenses and any recovery in such suit shall be agreed upon between LICENSOR and
LICENSEE.

      7.7 LICENSEE during the period of this Agreement, shall have the sole
right in accordance with the terms and conditions herein to sublicense any
alleged infringer, and LICENSOR shall be entitled to royalties therefrom as
specified in Article 4.6.

                       8. PROSECUTION OF LICENSED PATENTS

      8.1 LICENSEE agrees to accept liaison and financial responsibilities, as
hereinafter set forth, for the prosecution, by a patent lawyer in independent
practice, who shall be nominated by LICENSEE and approved by LICENSOR, of the
Licensed Applications. Said financial responsibilities shall not only include
the costs of prosecution but also the payment of maintenance fees, where
required, to maintain said patent applications and patents, if issued, in force
and effect for as long as possible. It is further agreed that the patent lawyer
selected by LICENSEE and approved by LICENSOR shall be required, if so desired
by LICENSOR, to keep a patent lawyer selected by LICENSOR informed of all steps
in the prosecution and maintenance of said Patent Rights. Written approval will
be required from LICENSOR to the patent lawyer selected by LICENSEE for actions
concerning this patent.

      8.2 Within two (2) weeks of notification to LICENSOR by LICENSEE of the
identity of the patent lawyer, LICENSOR will request that its counsel furnish to
the patent lawyer nominated in accordance with Paragraph 8.1 above:

            (a) Complete file histories of all of the patent applications
constituting said Licensed Applications; and

            (b) An executed power of attorney or powers of attorney appointing
such patent lawyer as attorney of record in connection with all of said Licensed
Applications.

<PAGE>

Page 8

      8.3 LICENSOR shall have the right at any time, by notice in writing and
sent to LICENSEE by registered mail, to assume and continue at its own expense,
direction of the prosecution of any of said Licensed Applications. Upon receipt
by LICENSEE of any such notice from LICENSOR, LICENSEE and the patent lawyer
nominated in accordance herewith shall provide in two weeks from the time of
notice an executed power of attorney and all the file histories of the patent
applications constituting said Licensed Applications. Upon receipt of this
documentation, LICENSEE and the patent attorney nominated by LICENSEE shall be
relieved of all future responsibilities to prosecute the Licensed Applications
to which the notice is directed. In which event, LICENSOR agrees to use its good
faith efforts to apply for, seek prompt issuance of, and maintain during the
term of this Agreement, Patent Rights to the extent necessary to cover both
broadly and specifically Licensed Products. LICENSEE shall have reasonable
opportunity to advise LICENSOR and shall cooperate with LICENSOR in such filing,
prosecution and maintenance. LICENSOR shall use its good faith efforts to
furnish LICENSEE with copies of any patent application sufficiently in advance
of its anticipated filing date to give LICENSEE a reasonable opportunity to
review and comment thereon.

LICENSOR also agrees to furnish LICENSEE with copies of all substantive
communications to and from U. S. and foreign patent offices regarding Licensed
Applications and in good faith shall consider the reasonable comments of
LICENSEE regarding all communications and filings to and from the respective
patent office. If, for any reason, prosecution or maintenance of a particular
patent application or patent in a particular country is to be abandoned by
LICENSEE, LICENSOR will be notified in sufficient time to assume prosecution.
LICENSEE shall bear all cost to maintain the patent prosecution until such time
that LICENSOR can assume patent prosecution.

                            9. TERM AND TERMINATION

      9.1 The Term of this Agreement shall be for a period beginning with the
Effective Date and extending until the later often (10) years after the First
Commercial Sale or the last to expire valid claim of Patent Rights covering a
Licensed Product, unless sooner terminated as herein provided. Thereafter,
LICENSEE'S license granted in 3.1 shall be a fully paid up, non-exclusive
license. Surviving any termination are: (a) LICENSEE's obligation to pay
royalties accrued or accruable; and (b) Any cause of action or claim of LICENSEE
or LICENSOR, accrued or to accrue, because of any breach or default by the other
party.

      9.2 Upon any material breach or default under this Agreement by LICENSEE,
LICENSOR may give written notice thereof to LICENSEE, and LICENSEE, shall have
thirty (30) days thereafter to cure such breach or default. If such breach or
default is not so cured, LICENSOR, may then in its sole discretion and option
(a) terminate this Agreement and the licenses granted herein or (b) seek such
other relief as may be provided by law in such circumstances by giving written
notice thereof to LICENSEE.

<PAGE>

Page 9

      9.3 LICENSEE shall have the right to terminate this Agreement at any time
upon ninety (90) days written notice to LICENSOR and payment of all amounts due
LICENSOR through the effective date of termination.

      9.4 Upon termination of this Agreement under any provision, all further
obligations of the parties under this Agreement shall terminate without further
liability of any party to another; provided, however, that the publicity and
confidentiality obligations of the parties contained in Section 10 hereof, shall
survive any such termination for the periods set forth therein. Termination
shall not relieve any party of any obligation occurring prior to such
termination, of any liability for a breach of, or for any misrepresentation
under this Agreement or be deemed to constitute a waiver of any available remedy
(including specific performance if available) for any such breach or
misrepresentation, provided, however, that neither party shall be liable for
consequential, punitive or special damages including without limitation, lost
profits. LICENSEE and any sublicensee thereof may, however, after the effective
date of such termination, sell all Licensed Products, and complete Licensed
Products in the process of manufacture and fulfill all orders for Licensed
Products at the time of such termination and sell the same, provided that
LICENSEE shall pay to LICENSOR the royalties thereon as required by Article 4 of
this Agreement and shall submit the reports required by Article 5 hereof on the
sales of such Licensed Products.

      9.5 In the event of termination of this Agreement for any reason, any and
all rights granted LICENSEE hereunder, including any rights granted by LICENSEE
to any sublicensee, shall cease and terminate, and all such rights shall revert
to LICENSOR. LICENSEE shall diligently thereafter return to LICENSOR, or to
LICENSOR's designated attorneys, any files or other documents in its possession
or in the possession of its attorneys, agents or sublicensees, relating to
pending or issued Licensed Patent(s), except that one copy of each such document
may be retained by LICENSEE's attorney for the purpose of ensuring compliance
hereunder. LICENSEE and shall also execute any and all documents necessary to
return control of said Licensed Patent(s) until such time as control has
properly been transferred to LICENSOR. Further, LICENSEE shall immediately
return to LICENSOR all research data, biological and other material (including
but not limited to licensed cell lines), prototypes, process information,
clinical data and the like of LICENSOR in its possession or in the possession of
its sublicensees.

                       10. PUBLICITY AND CONFIDENTIALITY

      10.1 Neither party shall use the name of the other in any form of
advertising or promotion without the prior written approval of the other. The
parties may, however, acknowledge Sponsor's support for, and subject to the
obligations of confidentiality set forth in 10.3, the nature of the
investigations being pursued under this Agreement. In any such statement, the
relationship of the parties shall be accurately and appropriately described.

<PAGE>

Page 10

      10.2 Confidential Items. Confidential Items shall mean any proprietary
information or materials belonging to the disclosing party clearly marked
CONFIDENTIAL (whether or not patentable) including, but not limited to,
formulations, techniques, methodology, equipment, data, reports, know-how,
sources of supply, patent positioning, consultants and business plans, including
any negative developments, which are communicated to, learned by, or otherwise
acquired by the party receiving such information or materials during or in the
course of this Agreement, further including information concerning the
existence, scope or activities of any research and development project of the
disclosing party.

      10.3 Each party shall hold in confidence for a period of three (3) years,
and shall not disclose to any person outside its respective organization, any
Confidential Items disclosed to it by the other party to this Agreement. The
party receiving such Confidential Items shall use such Confidential Items only
for the limited purpose for which it was disclosed and shall not exploit such
Confidential Items for its own benefit or the benefit of another without the
prior written consent of the disclosing party. Each party shall disclose
Confidential Items of the other party under this Agreement only to persons
within its organization and to consultants who have a need to know such
Confidential Items in the course of the performance of their duties and who are
bound to protect the confidentiality of such Confidential Items.

      10.4 The confidentiality and non-use obligations of the receiving party
shall not apply to any Confidential Item(s) which is received by one party from
the other party and which:

(i) is disclosed in a printed publication available to the public, is described
in an issued patent anywhere in the world, is otherwise in the public domain at
the time of disclosure, or becomes publicly known through no breach of this
Agreement by the receiving party;

(ii) becomes known to the receiving party through disclosure by sources other
than the disclosing party having the right to disclose such Confidential Items;

(iii) is disclosed pursuant to the requirements of a governmental agency or any
law requiring disclosure thereof, provided that the disclosing party is provided
with prior written notice of any such disclosure;

(iv) is generally disclosed to third parties by the disclosing party without
similar restrictions on such third parties;

(v) is approved for release by written authorization of an officer of the
disclosing party; or

(vi) is already known by the receiving party as evidenced by its prior written
records;

<PAGE>

Page 11

provided, however, that a breach of the foregoing obligations shall not be
absolved by the subsequent occurrence of any of the above exceptions.

                                11. PUBLICATION

      Subject to all other terms of this Agreement, including those concerning
confidentiality, LICENSOR's investigators have the right to publish or otherwise
publicly disclose information. However, LICENSOR will provide LICENSEE with
copies of articles reporting on research involving the TECHNOLOGY prior to their
submission for publication in order to provide LICENSOR an opportunity to
determine if patentable inventions or Confidential Items are disclosed. LICENSEE
shall inform LICENSOR and LICENSOR'S author(s) within thirty (30) days after
receipt of the material whether in its judgment the material contains
information on which patent applications may or should be filed and the
identification of any LICENSEE Confidential Items to be removed therefrom.
Submission then may be delayed up to an additional sixty (60) days to allow
filing of appropriate patent applications.

                                 12. ASSIGNMENT

      This Agreement shall not be assignable by either party without the prior
written consent of the other party, except that LICENSEE may assign this
Agreement to an entity, which acquires all or substantially all of the assets to
which this Agreement pertains without the prior written consent of LICENSOR.

                              13. INDEMNIFICATION

      13.1 LICENSEE agrees that during the term of this Agreement and
thereafter, it will indemnify, defend and hold LICENSOR, its trustees, officers,
employees and affiliates, harmless against all claims and expenses, including
legal expenses and attorneys' fees, arising out of the death of or injury to any
person or persons, or out of any damage to property, and against any other
claim, proceeding, demand, expense and liability of any kind whatsoever
resulting from the production, manufacture, sales, use, consumption or
advertisement of Licensed Products by LICENSEE.

                                  14. NOTICES

      All notices under this Agreement shall be deemed to have been fully given
when done in writing and deposited in the United States mail, registered or
certified, and addressed as follows:

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Page 12

            TO LICENSOR:

                      William J. Hartman
                      Director of Research and Technology Development Services
                      Georgetown University Medical Center
                      Suite 177, Bldg. D.
                      4000 Reservoir Road, N.W.
                      Washington, D.C. 20007

            TO LICENSEE:

                      ZEBRA PHARMACEUTICALS
                      Attn: John Babich
                      160 Second St.
                      Cambridge, MA 02142

      Either party may change its address upon notice to the other party as
provided herein.

                             15. DISPUTE RESOLUTION

      Should the parties hereafter have any dispute as to their obligations
pursuant to this Agreement, they shall first attempt to resolve such dispute
among themselves. If such efforts are not successful, the exclusive method for
resolving such a dispute shall be arbitration as described herein.

      Either party may elect to submit the issue to arbitration by giving
written notice to the other party and naming an arbitrator. The other party will
then have thirty (30) days to select its own arbitrator. Once both arbitrators
have been selected they shall meet within thirty (30) days of the appointment of
the second arbitrator and select a third arbitrator mutually agreeable to them.

      Once the panel of arbitrators have been chosen, they shall conduct an
arbitration on the disputed issue or issues in accordance with the Commercial
Arbitration Rules of the American Arbitration Association. The third arbitrator
shall serve as the presiding arbitrator, although, in the event of dispute among
the arbitrators, the majority decision of the arbitration panel shall be
binding. The decision of the arbitrators shall be final and either party may
apply to a court located in the District of Columbia to enter judgment based on
the arbitrator's decision. All costs of the arbitrators and arbitration, other
than the respective parties' attorneys' fees and costs, shall be borne equally
by the parties.
<PAGE>

Page 13

                                   16. WAIVER

      None of the terms, covenants and conditions of this Agreement can be
waived except by the written consent of the party waiving compliance.

                               17. APPLICABLE LAW

      This Agreement shall be construed, interpreted and applied in accordance
with the laws of the District of Columbia and applicable federal laws.

                              18. ENTIRE AGREEMENT

      This writing constitutes the entire agreement of the parties and there are
no promises, understandings or agreements of any kind pertaining to this
Agreement other than those written in this Agreement.

      IN WITNESS WHEREOF, the parties thereto have executed this Agreement in
duplicate originals by their duly authorized officers or representatives.

For LICENSOR                                   For LICENSEE:

By: /s/ Robert J. Halonen                      /s/ John W. Babich
    ---------------------------                ----------------------------
    Robert J. Halonen, Ph.D.                   John W. Babich
    Chief Financial Officer                    President and CEO

         2-23-00                                       3/3/00
    ---------------------------                ----------------------------
    Date                                       Date

    /s/ William J. Hartman
    ----------------------------
    William J. Hartman, Director
    Research & Technology Development Services

            2/23/00
    --------------------------
    Date

<PAGE>


                    AMENDMENT TO EXCLUSIVE LICENSE AGREEMENT

                              Dated March 1, 2000


    Between BioStream Inc. (formerly designated Zebra Pharmaceuticals in the
             above-referenced Agreement) and Georgetown University



     This amendment serves to modify the original agreement entered into March
1, 2000, for Patent Rights and Technology related to US Patent Application
Serial Nos. 60/131,627 filed April 28, 1999, and 60/166,195 filed November 22,
1999, both entitled "Ligands for Metabotropic Glutamate Receptors and
Inhibitors of NAALADase", foreign applications corresponding thereto, and any
divisions, continuations, or reexaminations thereof, and will be enforceable on
the date of the last signature of this Amendment.

BIOSTREAM and GEORGETOWN UNIVERSITY agree that the following provisions of the
above-referenced agreement shall be modified as follows:


                                 2. DEFINITIONS

SECTION 2.5

Section 2.5 formerly;

2.5 "Licensed Field of Use" means any diagnostic or therapeutic use concerning
"Ligands for Metabotropic Glutamate Receptors and Inhibitors of NAALADase".

Shall be replaced by:

2.5 "Licensed Field of Use" means use of "Ligands for Metabotropic Glutamate
Receptors and Inhibitors of NAALADase" under "Patent Rights" for imaging
applications only. Use of said compounds for development or sale of therapeutic
compounds is specifically precluded.


                       8. PROSECUTION OF LICENSED PATENTS


SECTION 8.4 SHALL BE ADDED;



<PAGE>
8.4 In the event that LICENSOR exclusively licenses "Patent Rights" for fields
of use other than specified in Section 2.5, LICENSOR shall compensate LICENSEE,
from licensing revenue received from said license, for 50% of patent costs
incurred by LICENSOR according to section 4.1. LICENSOR and LICENSEE shall each
pay 50% of any and all patent costs incurred after the effective date of any
such exclusive license.

In witness thereof, the parties have executed the Amendment on the dates
indicated.



BIOSTREAM                              GEORGETOWN UNIVERSITY

By: /s/ John W. Babich                 By: /s/ Martin A. Mullins
   ____________________________            ______________________________

Name: John W. Babich                   Name: Martin Mullins
     __________________________             _____________________________

Title: President                       Title: Vice President
      _________________________               Office of Technology Transfer
                                              _____________________________

Date: 02/14/03                         Date: 1/27/2003
     __________________________             _____________________________



<PAGE>
                SECOND AMENDMENT TO EXCLUSIVE LICENSE AGREEMENT

                             Dated October 27, 2005

Between Molecular Insight Pharmaceuticals, Inc. (formerly designated in the
above referenced Agreement as BioStream Inc., and prior to that, Zebra
Pharmaceuticals) and Georgetown University.

     This Second Amendment serves to modify the Agreement entered into March 1,
2000 and Amended February 14, 2003, for Patent Rights and Technology related to
US Patent Application Serial Nos. 60/131,627 (filed April 28, 1999) and
60/166,195 (filed November 22, 1999), both entitled "Ligands for Metabotropic
Glutamate Receptors and Inhibitors of NAALDase", as well as any foreign
applications corresponding thereto, and any divisions, continuations, or any
reexaminations thereof, and will be enforceable on the date of the last
signature of this Second Amendment.

     Molecular Insight Pharmaceuticals, Inc. and Georgetown University agree
that the following provisions in the above referenced agreement shall be
modified as follows:

                                    PREAMBLE

The Agreement preamble formerly reciting:

     Effective as of 1 March, 2000, GEORGETOWN UNIVERSITY, a not-for-profit
corporation of the District of Columbia, having a principal address at 37th & O
Streets, N.W., Washington, D.C. 20057 ("LICENSOR") and ZEBRA PHARMACEUTICALS, a
Massachusetts corporation, having a principal place of business at 160 Second
St. Cambridge, Massachusetts 02142 ("LICENSEE"), agree as follows:

Shall be replaced by:

     Effective as of 1 March, 2000, GEORGETOWN UNIVERSITY, a not-for-profit
corporation of the District of Columbia, having a principal address at 37th & O
Streets, N.W., Washington, D.C. 20057 ("LICENSOR") and MOLECULAR INSIGHT
PHARMACEUTICALS, a Massachusetts corporation, having a principal place of
business at 160 Second St., Cambridge, Massachusetts 02142 ("LICENSEE"), agree
as follows:

                                 2. DEFINITIONS

Section 2.1 formerly reciting:

     2.1 "Patent Rights" refers to LICENSOR's rights arising from U.S.
Provisional Patent Applications Serial No. 60/166,195, filed November 22, 1999
"Ligands for Metabotropic Glutamate Receptors and Inhibitors of NAALDase", and
Serial No. 60/131,627 filed April 28, 1999, entitled "Ligands for Metabotropic
Glutamate Receptors and Inhibitors of NAALDase", and naming as inventors Alan P.
Kozikowski, Jarda T Wroblewski and Fajun Nan, including any
<PAGE>
foreign patent applications corresponding thereto, any United States divisions,
continuations, reissues, or reexaminations thereof, and any United States or
foreign patent(s) issued or granted therefrom and any United States or foreign
patents or patent applications claiming Technology. Such patent application(s)
are the "Licensed Application(s)" and any resulting patents are the "Licensed
Patents(s)."

Shall be replaced by:

     2.1 "Patent Rights" refers to LICENSOR's rights arising from U.S.
Provisional Patent Applications Serial No. 60/166,195, filed November 22, 1999
"Ligands for Metabotropic Glutamate Receptors and Inhibitors of NAALADase", and
Serial No. 60/131,627 filed April 28, 1999, entitled "Ligands for Metabotropic
Glutamate Receptors and Inhibitors of NAALADase", originally converted as
U.S.S.N. 09/559,978, and which are now U.S.S.N., 10/374,765 and U.S. Patent
6,528,499, and further including any foreign patent applications corresponding
thereto, any United States divisions, continuations, continuations in-part to
the extent the claims are directed to subject matter specifically described in
USSN 09/559,978, reissues, or reexaminations thereof and any United States or
foreign patent(s) issued or granted therefrom and any United States or foreign
patents or patent applications corresponding thereto all to the extent owned or
controlled by Georgetown. Such patent application(s) are the "Licensed
Application(s)" and any resulting patents are the "Licensed Patents(s)."

In witness thereof, the parties have executed this Second Amendment on the
dates indicated.


MOLECULAR INSIGHT                      GEORGETOWN UNIVERSITY
PHARMACEUTICALS, INC.


By:                                    By: /s/ Martin Mullins
   ____________________________            ______________________________

Name: John W. Babich                   Name: Martin Mullins

Title: President and CSO               Title: Vice President
                                              Office of Technology Transfer

Date:                                  Date: 10/28/05
   ____________________________            ______________________________






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