<PAGE>



                                                                   EXHIBIT 10.38




                         EXCLUSIVE SUB-LICENSE AGREEMENT


                            Dated: September 21, 2001


                                 by and between


                                  UR LABS, INC.


                                       and


                         PROGENICS PHARMACEUTICALS, INC.













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                                TABLE OF CONTENTS

                                                                           Page
                                                                           ----
PREAMBLE              ........................................................1

ARTICLE I -           DEFINITIONS.............................................1

ARTICLE II -          GRANT...................................................5

ARTICLE III -         CERTAIN COVENANTS.......................................6

ARTICLE IV -          COMMERCIAL DILIGENCE....................................6

ARTICLE V -           PAYMENTS................................................8

ARTICLE VI -          REPORTS AND RECORDS....................................12

ARTICLE VII -         PATENT PROSECUTION, INFRINGEMENT AND
                      MISAPPROPRIATION.......................................12

ARTICLE VIII -        REPRESENTATIONS AND WARRANTIES.........................14

ARTICLE IX -          CONFIDENTIALITY........................................17

ARTICLE X -           INDEMNIFICATION........................................18

ARTICLE XI -          PUBLICITY; NON-USE OF NAMES............................19

ARTICLE XII -         ASSIGNMENT.............................................19

ARTICLE XIII -        TERM AND TERMINATION...................................19

ARTICLE XIV -         EXPORT MATTERS.........................................22

ARTICLE XV -          NOTICES AND OTHER COMMUNICATIONS.......................22

ARTICLE XVI -         MISCELLANEOUS PROVISIONS...............................22

EXHIBIT A -           PATENTS................................................24

EXHIBIT B -           FORM OF ACKNOWLEDGEMENT AND UNDERTAKING
                      OF THE UNIVERSITY OF CHICAGO...........................27


<PAGE>

                         EXCLUSIVE SUB-LICENSE AGREEMENT

                  This Exclusive Sub-License Agreement (this "Agreement"), dated
as of September 21, 2001 (the "Effective Date"), by and between UR Labs, Inc., a
Nevada corporation with principal offices located at 2015 Emily Court, Carson
City, Nevada 89703 ("Licensor"), and Progenics Pharmaceuticals, Inc., a Delaware
corporation with principal offices located at 777 Old Saw Mill River Road,
Tarrytown, New York 10591 ("Licensee").

                                   WITNESSETH

                  WHEREAS, Licensor is the owner or exclusive licensee of the
Compound, Patents and of the related Know How, each as defined below; and

                  WHEREAS, Licensee seeks to commercially develop products based
on the Compound, Patents and Know How; and

                  NOW, THEREFORE, in consideration of the premises and the
mutual covenants contained herein, the parties hereto agree as follows:


                                   ARTICLE I
                                   DEFINITIONS

                  For the purpose of this Agreement, the following words and
phrases shall have the following meanings:

                  1.1 "Affiliate" shall mean any person, corporation, company,
partnership, joint venture, firm, individual or other entity controlling,
controlled by or under common control with a party hereto. For purposes of this
definition, the term "control" shall mean ownership, directly or indirectly, of
50% or more of the equity capital or voting interest. Any corporation, company,
partnership, joint venture, firm, individual or other entity which does not come
within this definition shall be a third party for purposes of this Agreement.

                  1.2 "Compound" shall mean [*] having the chemical structure
[*], in each instance claimed in a Patent.

                  1.3 "Confidential Information" shall mean, with respect to a
party, all information (and all tangible and intangible embodiments thereof),
which is owned or controlled by such party, is disclosed by such party to the
other party pursuant to this Agreement or the binding Term Sheet, dated June 26,
2001, and (if disclosed in writing or other tangible medium) is marked or
identified as confidential at the time of disclosure to the receiving party or
(if otherwise disclosed) is identified as confidential at the time of disclosure
to the receiving party or described as such in writing within thirty (30) days
after such disclosure. Notwithstanding the foregoing, Confidential Information
of a party shall not include information which, and only to the extent, the
receiving party can establish by written documentation (a) was known by the
receiving party prior to disclosure of such information by the disclosing party
to the receiving party; (b) was or becomes generally available in the public
domain, without the fault of the receiving party; (c) has been received by the
receiving party at any time from a source, other than the disclosing party,
rightfully having possession of and the right to disclose such information free
of confidentiality obligations; (d) becomes otherwise known by the receiving
party free of confidentiality obligations prior to disclosure of such
information by the disclosing party to the receiving party; or (e) has been
independently developed by employees or others on behalf of the receiving party
without access to or use of such information disclosed by the disclosing party
to the receiving party (each of the foregoing exceptions being referred to
herein as a "Confidentiality Exception").

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                  1.4 "FDA" shall mean the Food and Drug Administration of the
United States, or the successor thereto.

                  1.5 "Field of Use" shall mean [*].

                  1.6 "First Commercial Sale" shall mean when a Licensed Product
is first billed or invoiced to a third party who is not an Affiliate or
Sublicensee of Licensee, unless such Affiliate or Sublicensee is the end user,
after all applicable marketing and pricing approvals (if any) have been granted
by the applicable governing health authority of the country in which the sale
takes place.

                  1.7 "IND" shall mean an Investigational New Drug application
filed with the FDA, or any corresponding filing or submission with any foreign
regulatory authority required to commence human clinical testing of any product.

                  1.8 "Know How" shall mean all technology and information,
including without limitation methods, processes, techniques, compounds,
drawings, indications, data, results of tests or studies (including clinical
studies previously performed with respect to the Compound, whether performed by
or under the auspices of Licensor or University), expertise and trade secrets,
whether patentable or not, relating to the Compound or necessary or useful for
the commercialization of Licensed Products, existing on the date hereof or at
any time during the term of this Agreement, which is owned or controlled by
Licensor or in which Licensor has a licensed right at any time during the term
of this Agreement.

                  1.9 "Licensed Product" shall mean any article, composition,
substance, material, method, process, product, use or service containing or
consisting of the Compound or using the Patents or Know How.

                  1.10 "Major European Counties" shall mean, collectively, [*].

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                  1.11 NDA" shall mean a New Drug Application, Product License
Application, or similar application for marketing approval of a product for use
in the Field of Use submitted to the FDA, or its foreign equivalent.

                  1.12 "Net Sales" shall mean the amount billed or invoiced for
sales of Licensed Products produced hereunder less the sum of the following [*].

                  Net Sales shall not include [*].

                  1.13 "Patents" shall mean those patents and patent
applications listed on Appendix A; and any patents and patent applications
related thereto which claim [*], as well as all continuations,
continuations-in-part, divisions, patents of addition, reissues, renewals or
extensions thereof, which, at any time during the term of this Agreement, are
owned, controlled or exclusively licensed by Licensor, or to which Licensor has
any right of use or right of exploitation or which are subject to assignment or
license, in whole or in part, to Licensor.

                  1.14 "Phase II Clinical Trial" shall mean a human clinical
trial in any country that is intended to initially evaluate the effectiveness of
a Product for a particular indication or indications in patients with the
disease or indication under study or that would otherwise satisfy requirements
of 21 CFR 312.21(b), or its foreign equivalent.

                  1.15 "Phase III Clinical Trial" shall mean a human clinical
trial in any country the results of which could be used to establish safety and
efficacy of a Product as a basis for a NDA or that would otherwise satisfy
requirements of 21 CFR 312.21(c), or its foreign equivalent.

                  1.16 "Rights" shall mean, collectively, any and all rights of
the Licensor in or to the Compound, the Patents and the Know How, whether owned,
controlled or held as an exclusive licensee as of the date of this Agreement or
hereafter acquired.

                  1.17 "Royalty Period" shall mean the period starting with the
date of the First Commercial Sale of a Licensed Product by Licensee or any
Affiliate or sublicensee hereunder of the Licensee and ending [*].

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                  1.18 "Royalty Year" shall mean each twelve month period
commencing January 1 and ending December 31 during the term of this Agreement.
For the first year of the Royalty Period under this Agreement, the Royalty Year
shall be the period of time between the date of the First Commercial Sale and
December 31.

                  1.19 "Term Sheet" shall mean that certain binding Term Sheet
executed by Licensor and Licensee on June 26, 2001

                  1.20 "University" shall mean the University of Chicago and its
affiliate, ARCH Development Corporation.

                  1.21 "University Agreement" shall mean that certain Option and
License Agreement entered into between the University and Licensor on May 8,
1985, as amended.

                  1.22 "Valid Patent" shall mean either (a) an allowed and
issued Patent which has not been held permanently revoked, unenforceable or
invalid by a decision of a court or other governmental agency of competent
jurisdiction, unappealable or unappealed within the time allowed for appeal, and
which has not been admitted to be invalid or unenforceable through reissue or
disclaimer or otherwise, or (b) a pending patent application included in the
Patents which application was filed in good faith and has not been abandoned or
finally disallowed without the possibility of appeal or refiling of such
application.


                                   ARTICLE II
                                      GRANT

                  2.1 Licensor hereby grants to Licensee and its Affiliates in
the Field of Use an exclusive, worldwide right and sub-license in and to the
Rights, including the right to sublicense, use, lease, develop, manufacture and
sell the Compound, the Patents and the Know How including, without limitation,
the right to make, have made, use, lease, develop, import, offer for sale, sell
and have sold Licensed Products and to make, have made, offer for sale or sell
Know How in connection therewith.

                  2.2 (a) The license rights granted under this Agreement shall
specifically include the right for Licensee to grant sublicenses, subject to the
further provisions of this Agreement.

                      (b) Within [*] days after the execution of a sublicense
agreement, Licensee shall notify Licensor of such sublicense agreement and
provide Licensor with the name and address of the sublicensee and a copy of the
executed sublicense. Upon taking such action, such sublicensee shall be deemed
to be a sublicensee of record for purposes of this Agreement.

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                      (c) All sublicensees of Licensee shall agree in writing to
abide by the terms of this Agreement.

                      (d) No sublicense agreement shall relieve Licensee of its
obligations under this Agreement, including the obligation of Licensee to pay
Licensor royalties on the Net Sales of Licensed Products and to be responsible
for the performance of its sublicensees.

                      (e) In connection with the grant of any sublicense by
Licensee, Licensor shall provide to Licensee and such sublicensee (or
prospective sublicensee), at the request of Licensee, Licensor's written
confirmation of Licensee's ongoing rights under this Agreement, including the
right to grant sublicenses.

                  2.3 The license granted hereunder shall not be construed to
confer any rights upon Licensee by implication, estoppel or otherwise, other
than those expressly granted hereby. Licensor agrees that it will negotiate with
Licensee in good faith for a period of not less than 60 days, such period being
subject to extension by mutual agreement between the parties which agreement may
not be unreasonably withheld or delayed, a license to any patent or other
Licensor intellectual property rights, not included within the Rights, which are
conceived after the date of this Agreement in which Licensor obtains a
licensable right and which would be necessary for, or would assist Licensee or
its Affiliates or sublicensees in, exercising the rights granted to them under
this Agreement or otherwise in commercializing Licensed Products.

                                   ARTICLE III
                                CERTAIN COVENANTS

                  3.1 Subject to Section 4.1 below, Licensee shall [*], in
accordance with Licensee's [*], to bring Licensed Products to market through a
program for exploitation of the Rights.

                  3.2 Licensee shall be responsible for taking all reasonable
steps to secure all necessary governmental approvals to sell, exploit or market
Licensed Products in accordance with Licensee's reasonable commercial judgment.

                  3.3 Without the prior written consent of Licensee, Licensor
shall not voluntarily (i) amend or modify, or consent to any action that may be
taken under, the University Agreement, the effect of which would adversely
affect Licensee's rights hereunder or (ii) terminate or engage in any act or
omission that constitutes or would constitute, with or without the giving of
notice or the passage of time, an event which would permit the University to
terminate the University Agreement. Licensor shall immediately notify Licensee
and promptly confirm such notification in writing, of any such termination event
or of the receipt by Licensor of any notice of breach or termination of the
University Agreement. When and if necessary, Licensor, at Licensee's expense,
shall take all reasonable actions necessary, or permit such actions to be taken
in its name by Licensee, to enforce Licensor's rights under the University
Agreement in a manner consistent with the terms of this Agreement, provided,
however, that all expenses incurred by Licensee with respect to such actions
shall be deducted from future royalties paid to Licensor.

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                                   ARTICLE IV
                              COMMERCIAL DILIGENCE

                  4.1 Licensee (alone or with its Affiliates and/or
sublicensees) will [*].

                  4.2 Without limiting the generality of the obligations set
forth in Section 4.1 above, Licensee, its sublicensees or their respective
Affiliates, shall:

                      (a) within [*] days of each anniversary date of this
Agreement deliver to Licensor an updated Development Plan which shall detail
Licensee's efforts in advancing the development, registration and approval for
marketing of Licensed Products, such Development Plan shall include pertinent
information relating to activities of Licensee in the areas of [*], provided,
however, that any mid-year updates to the Development Plan shall also be
provided to Licensor as and when they are available,

                      (b) [*],

                      (c) [*], and

                      (d) [*].

                  4.3 In the event that, despite the use of reasonable diligent
efforts on the part of Licensee, [*], Licensee and Licensor agree to discuss and
agree in good faith on or before the fulfillment date for the involved
Development Milestone any appropriate revisions to such Development Milestone,
which agreement on the part of Licensor shall not be unreasonably withheld or
delayed provided Licensee can demonstrate its use of reasonable diligent efforts
in its development program. Licensee shall notify Licensor as soon as it becomes
aware of an issue that will prevent Licensee from meeting a Development
Milestone, but in no event later than [*] prior to the fulfillment date of the
Development Milestone, unless such issue or event giving rise to the delay
arises within the [*] period.

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                  4.4 Licensee shall be conclusively deemed to have fulfilled
its commercialization diligence requirements under this Article IV, including
without limitation its obligation to continue providing updated Development
Plans under Section 4.2(a), [*]. The immediately preceding sentence
notwithstanding, Licensee will continue to use reasonable commercial efforts and
will maintain, or cause to be maintained, and so report to Licensor as set forth
in Section 4.2(d) [*].


                                    ARTICLE V
                                    PAYMENTS

                  5.1 For the rights, privileges and license granted hereunder,
in addition to the initial fee paid upon the execution of the Term Sheet,
Licensee shall make the following license fee and milestone payments to Licensor
in the manner hereinafter provided:

                      (a) Within 30 days of the Effective Date, Licensee shall
pay a nonrefundable and non-creditable license fee of $[*].

                      (b) Licensee shall pay the following nonrefundable and
non-creditable amounts for the purposes stated below on or before the dates
specified, unless, as to any such payment, this Agreement shall have been
terminated prior to the applicable payment date:

                      (i)     [*];

                      (ii)    [*]; and

                      (iii)   [*].

                      (c) Upon the achievement of each of the following
milestones Licensee shall give written notice to Licensor and shall pay to
Licensor the corresponding nonrefundable and non-creditable milestone payments
described below:

                      (i)     [*];

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                      (ii)    $[*];

                      (iii)   $[*];

                      (iv)    $[*]; and

                      (v)     $[*].

                  Each of the foregoing milestone payments shall be payable only
once and shall be due within 30 days after the achievement of the related
milestone.

                  5.2 Within 30 days following the First Commercial Sale of each
Licensed Product in each country, Licensee shall give written notice to Licensor
thereof. Then, for the rights, privileges and license granted hereunder,
Licensee shall pay running royalties to Licensor in each of the following
instances for the applicable Royalty Period, in the manner hereinafter provided:

                      (a) In countries where the sale of a Licensed Product
would [*] of the Licensed Product in each such country by Licensee, any
Affiliate of Licensee or any sublicensee of Licensee; or

                      (b) In countries where a Valid Patent is [*] of a Licensed
Product in each such country by Licensee, any Affiliate of Licensee or any
sublicensee of Licensee.

                  5.3 Commencing upon [*], such payment being calculated and any
balance due being payable [*]. The [*] obligation will lapse upon expiration of
the term of this Agreement.

                  5.4 On or before the [*] anniversary of the Effective Date,
provided Licensee has not [*], Licensee, at its sole option, may elect to [*].
In the event Licensee is desirous of obtaining [*]. Absent such an agreement
between Licensee and Licensor, [*], except as set forth in this Section 5.4 or
as otherwise specifically set forth in this Agreement.

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                  5.5 (a) In the event Licensee [*]

                  (i) if such [*] is entered into prior to
the initiation of [*], then Licensee shall pay to Licensor [*]% of all
Sub-license Fees (as defined hereinafter) received by Licensee from such
sublicensee pursuant to such sub-license of the Rights; or

                  (ii) if such [*] is entered into after [*],
then Licensee shall pay to Licensor [*]% of all Sub-license Fees (as defined
hereinafter) received by Licensee from such sublicensee pursuant to such
sub-license of the Rights.

                  As used herein, "Sub-license Fees" shall mean [*].

         (b) For all sublicenses which are not [*], regardless of when they are
entered into, excluding, however, [*], Licensee shall pay to Licensor [*].

                  5.6 Sales of Licensed Product by Licensee, any Affiliate of
Licensee or any sublicensee of Licensee solely for research or clinical testing
or for indigent or similar public support or compassionate use programs which
sales are made at or below the cost of goods of such Licensed Product or at or
below the cost of purchasing such Licensed Product from a third party
manufacturer if such Licensed Product is so purchased by Licensee (plus, in each
case, the costs of shipping and administration of such clinical, indigent or
compassionate use program) shall be excluded from the computation of Net Sales,
provided such indigent and compassionate use sales are within normal and
customary levels for the pharmaceutical industry and do not exceed [*] of Net
Sales.

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                  5.7 Sales between and among Licensee and its Affiliates and
sublicensees of Licensed Products which are subsequently resold or to be resold
by such Affiliates or sublicenses shall not be subject to royalty, but in such
cases royalties shall accrue upon the occurrence of and be calculated based on
any subsequent sale of such Licensed Products to a non-Affiliate or
non-sublicensee. In the event such subsequent sale to a non-Affiliate or
non-sublicensee does not occur within [*] of Licensee's invoice date to such
Affiliate or sublicensee, then the sale from Licensee to the Affiliate or
sublicensee shall be subject to royalty. In any event, no provision of this
Agreement shall be construed as requiring the payment of more than a single
royalty for each Net Sale of a Licensed Product.

                  5.8 In the event that Licensee, any Affiliate of Licensee or
any sublicensee of Licensee is required to pay royalties to third parties as a
result of sales of Licensed Products and the total accumulated royalties being
paid by Licensee exceeds [*] provided that in no event in those countries where
the royalty paid by Licensee is calculated under Section 5.2(a) hereof shall
[*].

                  5.9 After expiration of the applicable Royalty Period in each
country, Licensee's rights hereunder shall be fully paid and royalty-free.

                  5.10 Licensee may withhold from royalties due to Licensor
amounts for payment of any withholding tax that Licensee has paid to any taxing
authority with respect to royalties paid or to be paid to Licensor under this
Agreement on the manufacture or sale of Licensed Products. Licensee agrees to
cooperate in all reasonable respects with Licensor in obtaining a foreign tax
credit in the United States with respect to taxes withheld on royalties due to
Licensor on the manufacture or sale of Licensed Products.

                  5.11 Royalty payments shall be paid in United States dollars
and sent to an address which Licensor may reasonably designate consistent with
the laws and regulations controlling in any foreign country, but not in any
other currency. If any currency conversion shall be required in connection with
the payment of royalties hereunder, such conversion shall be made by using the
exchange rate prevailing at the Chase Manhattan Bank (N.A.) on the last business
day of the calendar quarterly reporting period to which such royalty payments
relate.

                  5.12 Except as expressly stated in the first sentence of
Section 13.6, no unaccrued royalties or payments shall be due and payable to
Licensor hereunder with respect to Net Sales of Licensed Products after
termination of this Agreement.

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                                   ARTICLE VI
                               REPORTS AND RECORDS

                  6.1 Within [*] of the close of each calendar quarter of a
Royalty Year, Licensee shall deliver to Licensor a written report, giving such
particulars of the business conducted by Licensee and reported to Licensee by
its sublicenses during the preceding calendar quarter as shall be pertinent to a
royalty accounting hereunder. With each such report submitted, Licensee shall
pay to Licensor the royalties due and payable under this Agreement for such
calendar quarter. If no royalties shall be due, Licensee shall so report. The
written report for the final calendar quarter of each Royalty Year shall also
provide summary of the royalties paid during the subject Royalty Year and
calculate whether there is any balance due on the Minimum Royalty set forth in
Section 5.3 hereof.

                  6.2 Licensee shall keep full, true and accurate books of
account containing all particulars that may be necessary for the purpose of
showing the amounts payable to Licensor hereunder. Such records and books of
account shall be maintained for a period of no less than three years following
the period to which they pertain. For the term of this Agreement, upon receipt
of 30 days' prior written notice, Licensee shall permit an independent
accounting firm of national standing chosen by Licensor and reasonably
satisfactory to Licensee to inspect such books and records only for the purpose
of verifying the correctness of any report relating to a payment required under
this Agreement. Any such inspection shall be subject to such accounting firm
making such customary confidentiality undertakings to the Licensee as Licensee
shall reasonably request. Such accounting firm shall report to Licensee only
whether Licensee has complied with its obligations hereunder. Should such
inspection lead to the discovery of a greater than 10% discrepancy in reporting
of royalties Licensor's detriment, Licensee agrees to pay the full cost of such
inspection and interest on any amounts found to be owed to Licensor.


                                   ARTICLE VII
              PATENT PROSECUTION, INFRINGEMENT AND MISAPPROPRIATION

                  7.1 On and after the Effective Date, Licensee, using patent
counsel of its choosing and reasonably acceptable to Licensor, shall assume the
responsibility for the prosecution and maintenance of the Patents, shall
diligently prosecute and maintain the Patents and pay for all costs of such
prosecution and maintenance. Licensee shall promptly provide or cause to be
provided to Licensor copies of all relevant documentation received from and
transmitted to each patent office so that Licensor may be informed and appraised
of the continuing prosecution and be provided a reasonable opportunity to
comment upon any documents prior to submission to any patent office. Licensee
shall not abandon any of the Patents with out first consulting Licensor. In the
event Licensee elects to abandon a Patent, all rights in and to such abandoned
Patent shall revert to Licensor and Licensor may elect to assume the prosecution
and maintenance of such Patent.

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                  7.2 Within 60 days of regulatory approval of each Licensed
Product or Combination Product, or other time as allowed by statute, Licensee
will cause to be filed an application for extension of patent term under 35 USC
ss.156(c) of a Patent owned or controlled by Licensor and sublicensed to
Licensee under this Agreement, if such extension is possible under the statute.
Should an option exist to extend the term of more than one such Patent of
Licensor for a given Product, the parties will mutually select the Patent whose
term shall be extended. Should the parties be unable to agree upon a Patent for
term extension, Licensor's selection shall prevail. The term of as many Patents
of Licensor as possible shall be so extended under 35 USC ss.156(c). Licensor
shall cooperate in all respects with Licensee's efforts to obtain such
extensions.

                  7.3 Licensee, as the exclusive commercial user of the Rights,
shall assume primary responsibility for enforcing the Rights within the Field of
Use. Licensor as owner of the Rights shall be entitled to participate in the
enforcement of the Rights. In enforcing the Rights, Licensee, if it deems it
appropriate in its reasonable commercial judgment, shall contact any third party
who may have misappropriated and/or may be infringing the Rights and take all
reasonable steps to persuade such third party to desist from using or infringing
the Rights, including initiating and prosecuting a legal proceeding if
necessary, or defending a challenge to the validity of the Rights. Licensee also
shall notify Licensor of any alleged misappropriation or infringement and shall
keep Licensor reasonably informed of all stages of Rights enforcement. Licensee
may use the name of Licensor as party plaintiff. All costs of any action to
enforce the Rights taken by Licensee shall be borne by Licensee, and Licensee
shall keep any recovery of damages derived therefrom, subject, after the
reimbursement of costs and expenses incurred by Licensee, to royalties due under
Sections 5.2 (a) and 5.2(b) to the extent that damages are awarded for lost
sales or lost profits from the sale of Licensed Products. No settlement, consent
judgment or other voluntary final disposition of the suit that materially and
adversely affects Licensor's rights hereunder or as the owner of the Rights may
be entered into without the consent of Licensor, which consent shall not
unreasonably be withheld.

                  7.4 If Licensee has not taken legal action to recover the
embodiment of any of the Rights or to obtain the cessation of any such
misappropriation or infringement within 90 days of written notification from
Licensor of such circumstances, or if Licensee elects not to continue
prosecuting any legal action against such third party, Licensor shall have the
right, but shall not be obligated, to prosecute at its own expense any such
legal proceeding. In any such legal proceeding by Licensor, all expenses of
first Licensor and then Licensee shall be reimbursed by any recovery, and the
excess of such recovery then shall be awarded to Licensor. No settlement,
consent judgment or other voluntary final disposition of a suit that materially
and adversely affects Licensee's rights hereunder may be entered into without
the consent of Licensee, which consent shall not unreasonably be withheld.

                  7.5 By mutual agreement, Licensee and Licensor may agree to
institute suit jointly, the suit being brought in both their names. Such
agreement shall cover such matters as the sharing of recovery, reimbursement of
costs and expenses, exercise of control, and other relevant matter.

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                  7.6 Licensee, during the period of this Agreement, shall have
the sole right in accordance with the terms and conditions of Section 2.2 to
sublicense any third party alleged to have misappropriated or to be infringing
the Rights in the Field of Use for future use of the Rights.

                  7.7 Each party shall promptly notify the other in writing in
the event that a third party shall bring a claim of misappropriation or
infringement against Licensor or Licensee.

                  7.8 In any misappropriation or infringement suit that either
party may institute to enforce the Rights against third parties pursuant to this
Agreement, or in any misappropriation or infringement action brought against
either party by a third party, each party hereto shall, at the request and
expense of the other party, cooperate in all respects (including by joining such
action in the case of an action commenced to enforce the Rights) and, to the
extent possible, have its employees testify when requested and make available
relevant records, papers, information, samples, specimens, and the like.


                                  ARTCILE VIII
                         REPRESENTATIONS AND WARRANTIES

                  8.1 Licensor hereby represents and warrants as follows:

                           (a) Licensor is the owner or exclusive licensee,
through the University Agreement, of, has sole and exclusive possession of and
has good and valid title to, all of the Rights, free and clear of any liens,
security interests, licenses (other than the University Agreement), charges,
encumbrances, equities, claims or restrictions. The Rights include all rights,
property, assets, information and knowledge owned by or in the possession of
Licensor useful or necessary to enable Licensee to manufacture, use, and sell
Licensed Products.

                           (b) The license granted to Licensor by the University
under the University Agreement, insofar as it relates to any of the Rights, is
and continues in full force and effect. No event has occurred or omission made,
and no circumstances exist, which, with or without the giving of notice and/or
the passage of time, would permit University to terminate the University
Agreement as it relates to any of the Rights.

                           (c) Licensor has not filed or submitted, and will not
file or submit, and has no interest in or rights to, and to Licensor's knowledge
after reasonable inquiry neither University or any other person has filed or
submitted, or has any interest in or to, any patent, patent application or
similar document, filing or right relating to the Compound, the Patents or the
Know How, other than patent applications, filings and similar documents related
to the Patents. Licensor, and to Licensor's knowledge after reasonable inquiry
University, has complied in all material respects with their respective duty of
disclosure with respect to the Patents.

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                           (d) To the best of Licensor's knowledge: (i) the use
or practice of the Patents or the Know How does not infringe or conflict with
any proprietary right of any other person, and neither the use of any of the
Rights nor the manufacture, use, or sale of the Compound will infringe or
conflict with any proprietary or other right of any other person; and (ii) there
is no existing or potential infringement of any of the Rights. There is no claim
pending or, to Licensor's knowledge, threatened against Licensor alleging that
any of the Rights, or the use of any of the Rights, or the manufacture, use or
sale of the Compound infringes or conflicts with, or will infringe or conflict
with, any proprietary or other right of any person, and to Licensor's knowledge
there is no such claim pending or threatened against any other person.

                           (e) All documentation relating to the Know How
previously furnished or furnished after the date hereof to Licensee is or will
be, to the best of Licensor's knowledge, current, accurate, complete and
sufficient in detail and content to explain all aspects of the Know How and to
allow its full use without reliance on the memory of others.

                           (f) Licensor has not transferred, disclosed or made
available to any person, other than Licensee, the Compound, Patents or Know How,
except pursuant to enforceable material transfer agreements or confidentiality
agreements, which in each case prohibited such person from further transferring,
disclosing or making available such materials and from using such materials
other than for evaluation purposes. To Licensor's knowledge all samples of
Compound, and all written or electronic embodiments of the Patents and Know How,
previously furnished by Licensor to any such persons, and any copies thereof,
have been returned to Licensor or destroyed. With respect to that portion of the
technology or information, including the materials and information described on
Exhibit A hereto, purported to be proprietary to Licensor or otherwise intended
to be Know How licensed to Licensee hereunder that is not part of the public
knowledge or literature, Licensor has taken all measures and precautions
necessary to protect the secrecy, confidentiality and value of such technology,
information and Know How.

                           (g) Licensor has all rights and powers necessary to
execute and deliver this Agreement, to grant the licenses provided herein and to
perform its obligations hereunder. This Agreement, and each obligation of
Licensor hereunder, constitutes a valid and binding obligation of Licensor. This
Agreement is enforceable against Licensor in accordance with its terms.

                           (h) Neither the execution and delivery of this
Agreement nor the performance of this Agreement will result (with or without
notice and/or lapse of time) in (i) a violation of any law, rule, regulation,
judgment, order, or decree to which Licensor is subject; (ii) a breach or
violation of any agreement or understanding (whether oral, written, express or
implied) to which Licensor is a party or by which Licensor is bound, including
the University Agreement; or (iii) the termination of, or the imposition of any
lien, security interest, license, charge, encumbrance, equity, claim,
restriction, tax or assessment on or with respect to, any of the Rights.

                           (i) Licensor has not (i) made a general assignment
for the benefit of creditors; (ii) filed any voluntary bankruptcy petition;
(iii) suffered the filing of any involuntary bankruptcy petition by any of his
creditors; (iv) suffered the appointment of a receiver to take possession of all
or any substantial portion of its assets; (v) suffered the attachment or other
judicial seizure of all or any substantial portion of its assets; or (vi)
admitted in writing its inability to pay any of his debts.

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                           (j) Licensor is not a party to any agreement,
understanding or arrangement that does or could impair, restrict or render
conditional the free enjoyment by Licensee of, the rights and privileges granted
to Licensee hereunder or does or could impair, restrict or render conditional
Licensee's ability to make, use or sell, or otherwise commercialize, Licensed
Products.

                           (k) Attached hereto as Exhibit B is an
Acknowledgement and Undertaking of University. To the knowledge of the Licensor,
all statements made in such certificate are true and correct.

                           (l) Neither this Agreement nor any of the documents
delivered to Licensee in connection herewith contains an untrue statement of a
material fact or omits to state any material fact necessary to make any of the
representations or any of the other statements or information contained herein
or therein not misleading. Without limiting the generality of the foregoing,
there are not facts known to Licensor that may have an adverse effect on any of
the Rights or Licensees' ability to use or sublicense any of the Rights, or
Licensee's ability to manufacture, use or sell Licensed Products.

                  8.1.1 Licensee hereby represents and warrants as follows:

                           (a) Neither the execution and delivery of this
Agreement nor the performance of this Agreement will result (with or without
notice and/or lapse of time) in (i) a violation of any law, rule, regulation,
judgment, order or decree to which Licensee is subject; (ii) a breach or
violation of any agreement or understanding (whether oral, written, express or
implied) to which Licensee is a party or by which Licensee is bound; or (iii)
the imposition of any lien, security interest, license, charge, encumbrance,
equity, claim, restriction, tax or assessment on or with respect to, any of the
Rights.

                           (b) Licensee has not (i) made a general assignment
for the benefit of creditors; (ii) filed any voluntary bankruptcy petition;
(iii) suffered the filing of any involuntary bankruptcy petition by any of its
creditors; (iv) suffered the appointment of a receiver to take possession of all
or any substantial portion of its assets; (v) suffered the attachment or other
judicial seizure of all or any substantial portion of its assets; or (vi)
admitted in writing its inability to pay any of its debts.

                           (c) Licensee has all rights and powers necessary to
execute and deliver this Agreement and to perform its obligations hereunder.
This Agreement, and each obligation of Licensee hereunder, constitutes a valid
and binding obligation of Licensee. This Agreement is enforceable against
Licensee in accordance with its terms.

                           (d) Neither this Agreement nor any of the documents
delivered to Licensor in connection herewith contains an untrue statement of a
material fact or omits to state any material fact necessary to make any of the
representations or any of the other statements or information contained herein
or therein not misleading.

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                                   ARTICLE IX
                                 CONFIDENTIALITY

                  9.1 During the term of this Agreement, the parties may
disclose to each other proprietary and confidential technology, inventions,
technical information, material, reagents, biological materials and similar
items which are owned or controlled by the party providing such information or
which that party is obligated to maintain in confidence and which is designated
by the party providing such information as confidential ("Confidential
Information"). Subject to the provisions hereof, each party agrees to retain
such Confidential Information in confidence and not to disclose any such
Confidential Information to a third party without the prior written consent of
the party providing such information and to use such Confidential Information
only for the purposes contemplated by this Agreement.

                  9.2 The obligations of confidentiality set forth in Section
9.1 will not apply to Confidential Information which:

                           (i) was known to the receiving party or generally
known by the public prior to its disclosure hereunder;

                           (ii) subsequently becomes known to the public by some
means other than a breach of this Agreement;

                           (iii) is subsequently disclosed to the receiving
party by a third party having a lawful right to make such disclosure;

                           (iv) is demonstrated by written records to have been
developed by the receiving party independent of disclosures by the disclosing
party;

                           (v) is required by law, rule, regulation or legal
process to be disclosed, provided that the receiving party making such
disclosure shall take all reasonable steps to restrict, and maintain to the
extent possible confidentiality of, such disclosure, and shall provide
reasonable notice to the other party whose Confidential Information is involved
in order that such other party may take reasonable steps to oppose the
requirement of disclosure; or

                           (vi) is approved for release by the disclosing party.

                  9.3 Notwithstanding anything herein to the contrary, Licensee
shall have the right to transfer or disclose Licensor's Confidential Information
included within the Know How to its Affiliates or sublicensees pursuant to
Section 2.2, or to third parties for any valid purpose in connection with
research, development, manufacturing and/or marketing activities contemplated
hereby, including without limitation potential sublicensees or other
collaborative partners and in connection with obtaining or seeking to obtain
financing; provided that such Affiliates, Sublicensees or third parties agree to
obligations of confidentiality similar to those contained in this Article IX.

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                  9.4 Licensee shall be free to publish scientific data relating
to the research and development program contemplated hereby; provided that such
publications or presentations shall not contain Confidential Information of the
Licensor.


                                    ARTICLE X
                                 INDEMNIFICATION

                  10.1 Licensee shall at all times during the term of this
Agreement and thereafter, indemnify, defend and hold Licensor, its directors,
officers, employees and Affiliates harmless against all claims and expenses,
including legal expenses and reasonable attorneys' fees, arising out of (i) any
breach of Licensee's representations or warranties contained herein or (ii) 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, sale, use, lease,
consumption or advertisement of Licensed Products by Licensee or its Affiliates
or sublicensees.

                  10.2 Licensor shall at all times during the term of this
Agreement and thereafter, indemnify, defend and hold Licensee, its directors,
officers, employees and Affiliates harmless against all claims and expenses,
including legal expenses and reasonable attorneys' fees, arising out of any
breach of Licensor's covenants, representations or warranties contained herein.

                  10.3 EXCEPT AS OTHERWISE EXPRESSLY SET FORTH IN THIS
AGREEMENT, LICENSOR AND LICENSEE MAKE NO REPRESENTATIONS AND EXTEND NO
WARRANTIES OF ANY KIND, EITHER EXPRESS OR IMPLIED, INCLUDING, BUT NOT LIMITED
TO, WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.


                                   ARTICLE XI
                           PUBLICITY; NON-USE OF NAMES

                  11.1 In the absence of prior written approval of the other
party hereto, neither party hereto shall originate any publicity, news release
or other public announcement, written or oral, whether to the public press, to
stockholders or otherwise, as to the contents or execution of this Agreement.
The above prohibition shall not apply to Licensee to the extent that Licensee,
in the reasonable opinion of such its counsel, is required to disclose
information by applicable law, regulation or order of a governmental agency or a
court of competent jurisdiction, including without limitation, a disclosure in
connection with Licensee filing of a registration statement or other filing with
the United States Securities and Exchange Commission. Except as required by law,
neither party shall use the name of the other party, nor any adaptation thereof,
in any advertising, promotional or sales literature without prior written
consent obtained from the other party.


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                                   ARTICLE XII
                                   ASSIGNMENT

                  12.1 This Agreement may be assigned by Licensee with notice to
Licensor no less than thirty (30) days prior to the effective date for such
assignment. Licensor shall not assign this Agreement without the prior written
consent of the Licensee, which consent shall not be unreasonably withheld or
delayed. Notwithstanding the foregoing, either party hereto may assign this
Agreement without the other party's consent in connection with a merger into, a
consolidation with, or a transfer of all or substantially all of its assets to
which this Agreement pertains as an entirety to any corporation, partnership or
other person or entity, so long as the successor surviving person or entity in
any such merger, consolidation, partnership or other person or entity transfer
or reorganization assumes in writing the obligations of this Agreement. Such
merger, consolidation, transfer or reorganization shall not in any way be a
breach of this Article XII, nor be any default under this Agreement.


                                  ARTICLE XIII
                              TERM AND TERMINATION

                  13.1 The term of this Agreement shall commence on the
Effective Date and thereafter remain in effect until the expiration of the
applicable Royalty Period, unless terminated in accordance with the terms of
this Agreement. After expiration of the applicable Royalty Period in each
country, Licensee's rights hereunder shall be fully paid and royalty-free.

                  13.2 Should Licensee fail to pay Licensor license fees,
milestones fees or royalties due and payable hereunder for more than 90 days
after the due date hereunder, Licensor shall have the right to terminate this
Agreement on 60 days' written notice to Licensee, unless Licensee or any
Affiliate or sublicensee shall pay Licensor within the 60 day period all such
license fees, royalties and patent expenses due and payable plus interest from
the date such payment was first due. Upon the expiration of the 60 day period,
if Licensee or its Affiliates or sublicensees shall not have paid all such
amount, the rights, privileges and licenses granted hereunder shall terminate,
unless Licensee's failure to pay arises from a bona fide dispute concerning
fees, royalties or expenses due, in which case either of the parties may elect
to pursue the alternative dispute resolution provided by Section 13.7 below.

                  13.3 Upon any material breach of this Agreement by Licensee,
other than those occurrences set out in Section 13.2, which shall always take
precedence over any material breach or default referred to in this Section 13.3,
Licensor shall have the right to terminate this Agreement and the rights,
privileges and license granted hereunder on 90 days' written notice to Licensee.
Such termination shall become effective unless Licensee or an Affiliate or
sublicensee thereof shall have cured any such breach prior to the expiration of
the 90 day period or unless Licensee disputes the breach in which case either of
the parties may elect to pursue the alternative disputes resolution provided by
Section 13.7 below.

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                  13.4 Upon any material breach of this Agreement by Licensor,
Licensee shall have the right by 60 days' written notice to Licensor to render
the rights of Licensee hereunder royalty-free. Such notice shall become
effective unless Licensor or an Affiliate thereof shall have cured any such
breach prior to the expiration of the 60 day period or unless Licensor disputes
the breach in which case either of the parties may elect to pursue the
alternative disputes resolution provided by Section 13.7 below.

                  13.5 Licensee shall be entitled to terminate this Agreement
for cause or convenience, in its sole discretion, upon 60 days' written notice
to Licensor.

                  13.6 Upon termination of this Agreement by Licensor due to
Licensee's breach pursuant to Section 13.2, or 13.3 hereof or a termination by
Licensee pursuant to Section 13.5 hereof, Licensee and its Affiliates and
sublicensees shall have the right for one year thereafter to dispose of all
Licensed Products then in their respective inventories, and shall pay royalties
thereon, in accordance with the provisions of Article V and shall submit the
related reports as required by Article VI, as though this Agreement had not
terminated. Upon termination of this Agreement by Licensee due to Licensor's
breach pursuant to Section 13.4, Licensee and its Affiliates and sublicensees
shall have a perpetual, fully paid license to the Rights. Nothing herein shall
be construed to release either party from any obligation that matured prior to
the effective date of such termination.

                  13.7 (a) Any controversy or bona fide disputed claim arising
between the parties to this Agreement, which dispute cannot be resolved by
mutual agreement, shall by the election of either party be resolved by
submitting to non-binding dispute resolution before a fact-finding mediation
body composed of one or more experts in the field, selected by mutual agreement
of the parties within 30 days of written request by either party. Said dispute
resolution shall be held at such place as shall be mutually agreed upon in
writing by the parties.

                           (b) If the parties are unable to resolve any dispute
through mediation, the parties shall resort to arbitration. The arbitration
shall be held in accordance with the Commercial Arbitration Rules (the
"Arbitration Rules") of the American Arbitration Association (the "Association")
as the Arbitration Rules then exist, in the selected forum, with the following
deviations from the Arbitration Rules. Commercially reasonable pre-hearing
discovery shall be permitted. The arbitrators shall consist of one Licensor
nominee, one Licensee nominee, and a third person jointly selected by those two
nominees. The party requesting arbitration shall designate its nominee in the
request, which shall be addressed to the Association with a simultaneous copy to
the other party. If the other party shall fail within 30 days of the request for
arbitration to nominate the second arbitrator or if the two arbitrators are
unable to agree upon the third arbitrator within 30 days after selection of the
second arbitrator, then in either case the arbitration panel will be completed
according to the Arbitration Rules. Both legal and equitable remedies shall be
available to the arbitrators. The award of a majority of the arbitration panel
shall be final and binding on the parties hereto and shall be enforceable in any
court having jurisdiction. Licensor and Licensee each irrevocably consent and
submit to the jurisdiction of the state and federal courts of the selected
forum.

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                           (c) Each party shall pay 50% of the mediation or
arbitration filing fees, mediators' fees and the like, but shall bear its own
attorneys' fees and other costs in such mediation or arbitration.

                  13.8 Sublicenses shall survive the termination of this
Agreement. Upon termination of this Agreement for any reason, Licensor shall
recognize and be bound by the terms and conditions of any sublicenses granted by
Licensee under the Rights in accordance with Article II of this Agreement;
provided that that Licensor shall have the right to receive any payments or
other consideration payable to Licensee thereunder, and shall have the right to
terminate the sublicense under the same termination provisions applicable to
Licensee in this Agreement; provided, further, that Licensor shall not assume,
and shall not be responsible to any sublicensee for any representations,
warranties or obligations of Licensee to any sublicensee other than the licenses
under Rights as authorized herein.

                  13.9 Upon the termination of this Agreement by Licensor
pursuant to Sections 13.2 or 13.3 or any termination for convenience by Licensee
pursuant to 13.5, Licensee shall provide to Licensor, and Licensor shall have
the option to assume Licensee's rights and responsibilities with respect
thereto, copies of all information and materials developed by Licensee during
the term of this Agreement relating to Licensee's efforts to complete the
development and commercialize the Licensed Products (including, without
limitation, all data resulting from research and clinical trials, improvements
and additions to the Know-How, data contained in regulatory filings,
communications with regulatory agencies and manufacturing and formulation
methods, techniques and data for all dosage forms) (the "Licensee Material"),
provided there does not exist a regulatory or legal prohibition from doing so.
In such an event, Licensor's assumption of Licensee's rights and
responsibilities with respect to the Licensee Material and Licensor's use of the
Licensee Material shall be subject to the rights of any sublicensee of record
that continues to validly exist. Licensor shall indemnify and hold Licensee
harmless from any and all liabilities or claims that may arise from Licensor's
use of the Licensee Material at any time after the termination of this Agreement
as set forth immediately above. Licensee shall have the right to retain one copy
of all such tangible information so delivered to Licensor for archival purposes.

                  13.10 The provisions of Sections 7.6 and 7.7, Articles IX and
Article X, Sections 13.6, 13.7, 13.8, 13.9 and 13.10 and Articles XIV, XV and
XVI shall survive termination of this Agreement for any reason.


                                   ARTICLE XIV
                                 EXPORT MATTERS

                  14.1 This Agreement is subject to any restrictions concerning
the export of products or technical information from the United States which may
be imposed by the United States. Accordingly, each party agrees that it will not
export, directly or indirectly, any technical information acquired under this
Agreement or any products utilizing any such technical information to any
country for which the United States Government or any agency thereof at the time
of export requires an export license or other governmental approval, without
first obtaining the written consent to do so from the Department of Commerce or
other agency of the United States Government when required by an applicable
statute or regulation.

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                                   ARTICLE XV
                        NOTICES AND OTHER COMMUNICATIONS

                  15.1 All notices and other communications provided for
hereunder shall be in writing and shall be mailed or delivered to the business
address of the respective parties set forth below, or to such other address or
addresses as either party shall designate in writing to the others. All such
notices and communications shall be considered given and/or delivered: (i) when
given if delivered in person or sent by facsimile and acknowledged by a
responsible person at the office of the recipient; (ii) one day after being sent
by a major overnight courier; or (iii) four days after being mailed by
registered mail, return receipt requested, at the business address of the
respective parties as specified below.

In the case of Licensor:                         In the case of Licensee:

UR Labs, Inc.                                    Progenics Pharmaceuticals, Inc.
c/o Eric Drell, Secretary                        777 Old Saw Mill River Road
2015 Emily Court                                 Tarrytown, NY 10591
Carson City, Nevada 89703                        Attention: President
Attention:  Eliot Drell, M.D., President

                                   ARTICLE XVI
                            MISCELLANEOUS PROVISIONS

                  16.1 This Agreement shall be construed, governed, interpreted
and applied in accordance with the laws of the State of Delaware without regard
to the choice of laws principles thereof.

                  16.2 All rights and licenses granted under or pursuant to this
Agreement by Licensor are, and shall be deemed to be, for purposes of Section
365(n) of the U.S. Bankruptcy Code, licenses of rights to "intellectual
property" as defined under Section 101(52) of the U.S. Bankruptcy Code. The
parties agree that Licensee, as a licensee of such rights under this Agreement,
shall retain and may fully exercise all of its rights and elections under the
U.S. Bankruptcy Code. The parties further agree that, in the event of the
commencement of a bankruptcy proceeding by or against Licensor under the U.S.
Bankruptcy Code, Licensee shall be entitled to a complete duplicate of (or
complete access to, as appropriate) any such intellectual property and all
embodiments of such intellectual property upon written request therefor by
Licensee. Such intellectual property and all embodiments thereof shall be
promptly delivered to Licensee (i) upon any such commencement of a bankruptcy
proceeding upon written request therefor by Licensee, unless Licensor elects to
continue to perform all of its obligations under this Agreement, or (ii) if not
delivered under (i) above, upon the rejection of this Agreement by or on behalf
of Licensor, upon written request therefor by Licensee. Licensor shall not
interfere with the rights of Licensee as provided in this Agreement, or any
agreement supplementary hereto, to such intellectual property (including all
such embodiments thereof), including any right of Licensee to obtain such
intellectual property (or such embodiment) from any other entity.

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                  16.3 The parties hereto acknowledge that this Agreement sets
forth the entire Agreement and understanding of the parties hereto as to the
subject matter hereof, and shall not be subject to any change or modification
except by the execution of a written instrument subscribed to by the parties
hereto.

                  16.4 The provisions of this Agreement are severable, and in
the event that any provisions of this Agreement shall be determined to be
invalid or unenforceable under any controlling body of the law, such invalidity
or unenforceability shall not in any way affect the validity or enforceability
of the remaining provisions hereof.

                  16.5 The failure of either party to assert a right hereunder
or to insist upon compliance with any term or condition of this Agreement shall
not constitute a waiver of that right or excuse a similar subsequent failure to
perform any such term or condition by the other party.

                  16.6 This Agreement may be executed in any number of
counterparts and each of such counterparts shall for all purposes be an original
and all such counterparts shall together constitute but one and the same
agreement.

                  16.7 The headings in this Agreement are intended solely for
convenience of reference and shall be given no effect in the construction or
interpretation of this Agreement.

         IN WITNESS WHEREOF, the parties have hereunto set their hands and seals
and duly executed this Agreement the day and year last set forth below.

UR LABS INC.                            PROGENICS PHARMACEUTICALS, INC.


By: _____________________________       By: ___________________________
    Eliot Drell                             Ronald J. Prentki
    President                               President

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                                    EXHIBIT A
                                       to
                         EXCLUSIVE SUB-LICENSE AGREEMENT

                   Materials and Information to be Transferred
            to Licensee by Licensor Pursuant to Section 2.1(b) hereof

Patents:   [*]




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                                    EXHIBIT B

                                       to

                         EXCLUSIVE SUB-LICENSE AGREEMENT

                     Form of Acknowledgement and Undertaking
              of the University of Chicago ("The Letter Agreement")

                                                       Date: September 20, 2001


Ronald J. Prentki
President
Progenics Pharmaceuticals, Inc.
777 Old Saw Mill River Road
Tarrytown, New York 10591

                  Re:      Exclusive Sublicense Agreement, dated as of
                           September 21, 2001, between UR Labs, Inc. ("URL")
                           and Progenics Pharmaceuticals, Inc. ("Progenics")
                           (the "Exclusive Sub-License")

Dear Sirs:

In order to facilitate the creation and existence of the above referenced
relationship between URL and Progenics, the University of Chicago, on behalf of
itself and its affiliate ARCH Development Corporation (the "University")
acknowledges, undertakes and agrees as set forth below.

Unless otherwise specifically defined within the text hereof, all capitalized
terms used herein, shall have the same meaning ascribed thereto as set forth on
Schedule 1 hereto.

         1.       In making this acknowledgement, undertaking and agreement,
                  University reaffirms, and where appropriate each provision
                  shall be read to be subject to, its reservation to itself,
                  subject to the rights granted pursuant to the University
                  Agreement (as defined in paragraph 3 below), of the worldwide
                  right to (i) practice the inventions claimed in the Patents,
                  and make, have made, use, import, offer to sell and sell,
                  transfer and disclose Compound solely for educational and
                  non-commercial research purposes which it may choose in its
                  own discretion and without payment to any party therefor.

         2.       University owns, either individually or jointly with URL, free
                  and clear all rights in the Field of Use to the Compound,
                  Patents and University Know How, subject only to the exclusive
                  license granted to URL and described in paragraph 3 below. If
                  any license to the Patents, Compound or University Know How
                  previously existed within the Field of Use, other than the
                  University Agreement, University shall promptly disclose to
                  Progenics the terms of such previously granted license in or
                  to the Compound, Patents or University Know How. Other than
                  the University Agreement, any previously granted license in
                  the Field of Use has been terminated.


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         3.       University acknowledges and agrees that pursuant the
                  University Agreement, University has granted an exclusive
                  license to URL in the Field of Use of all rights to the
                  Compound and Patents, including, without limitation, any and
                  all improvements, inventions and new uses thereof as described
                  in the University Agreement. University additionally
                  acknowledges that as of this date, it does not own any patent
                  or other intellectual property rights that would be infringed
                  by the commercialization of the Compound and Patents licensed
                  by University to URL that is not included in the rights
                  granted URL under the University Agreement. University further
                  acknowledges and agrees that the exclusive license to URL
                  pursuant to the University Agreement includes within such
                  exclusive license any patent application filed by it or URL
                  with respect to other or new uses of the Compound within the
                  Field of Use and all corresponding foreign patents issued to
                  date. With respect to inventions arising within the Field
                  after this date during the term of any sublicense to
                  Progenics, if the University has not licensed such
                  invention(s) to URL, the University shall give Progenics a
                  right of first refusal to negotiate a license to such
                  invention provided it is not obligated to license such
                  invention(s) to any third party. If a license is not executed
                  three months after the date University first discloses such
                  invention to Progenics, then such right of first refusal
                  expires and University shall be free to license said
                  invention(s) to any third party(s). With respect to any
                  invention conceived or first reduced to practice in the
                  performance of a federal grant, contract, or cooperative
                  agreement: such invention shall be subject to the requirements
                  of 35 U.S.C. Section 200 et seq., as amended, and the
                  implementing regulations and policies pertaining thereto.

         4.       The University Agreement is in full force and effect.
                  University will notify Progenics of any breach of the
                  University Agreement by URL or other termination event or
                  termination of which University has knowledge. If the
                  University Agreement terminates or expires during the term of
                  the Exclusive Sub-License, University will promptly notify
                  Progenics of such termination or expiration and license
                  Progenics directly on the terms identical to those set forth
                  in the University Agreement and Letter Agreement.

         5.       The Exclusive Sub-License is permitted under the University
                  Agreement; no consent of University is required except as has
                  been given. There is no agreement, arrangement or undertaking
                  between University and URL or, to the best of University's
                  knowledge, any other third party, that restricts, impairs or
                  renders conditional the rights granted in the University
                  Agreement, and University will not enter into any such
                  arrangement, except as permitted pursuant to paragraph 1
                  hereof.

         6.       Subject to paragraph 1 hereof, University shall not transfer
                  or disclose the Compound or Patents to third parties.
                  University will not make any subsequent transfer or disclosure
                  thereof without Progenics' prior written consent, except as
                  permitted pursuant to paragraph 1 hereof.


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         7.       (a) [*]

                  (b) University is dedicated to the free scholarly exchange and
                  public dissemination of the results and data derived from its
                  scholarly activities. Subject to the obligations set forth
                  herein, nothing in this acknowledgement, undertaking and
                  agreement or in the University Agreement or Exclusive
                  Sub-License shall restrict the right of University and its
                  faculty to publish, disseminate or otherwise disclose its
                  research, results of research and data relating to the
                  Compound. At University's discretion, it may submit drafts of
                  scientific articles, papers, abstracts or the like arising
                  from research projects not sponsored by Progenics, proposed
                  for publication or distribution ("Proposed Publications") to
                  Progenics for its review. In the event a Proposed Publication
                  or a portion thereof contains information of concern to
                  Progenics, University and Progenics agree to discuss in good
                  faith a mutually acceptable appropriate disposition of the
                  matter that addresses the concerns and interests of both
                  parties. However, nothing in this Agreement shall require
                  University to neither delay publication of any Proposed
                  Publications nor alter any Proposed Publications or
                  presentations of any kind.

         8.       With respect to any future clinical and/or research studies to
                  be conducted by University, University shall consider
                  proposals made by Progenics. If the parties agree to pursue
                  clinical and/or basic research studies conducted at the
                  University and sponsored by Progenics, the appropriate
                  agreements shall be negotiated to cover these activities.
                  Clinical trials shall be addressed through a separate clinical
                  trial agreement. Sponsored research shall be addressed through
                  a separate sponsored research agreement.

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         9.       University is willing to permit Progenics to engage its
                  faculty members as consultants in order to assist Progenics in
                  its completion of the development, registration and
                  commercialization effort on the Compound, provided, however,
                  that such duties shall not conflict with such faculty member's
                  responsibilities or obligations as a member of the faculty of
                  the University.

The University of Chicago has caused this Letter Agreement to be executed by its
authorized representatives as of the day and year first written above.

                                   Very truly yours,
                                   THE UNIVERSITY OF CHICAGO



                                   By: /S/ ALAN THOMAS
                                       -----------------------------------
                                   Name: Alan Thomas
                                   Title:   Director,
                                            Technology Commercialization



Acknowledged, Agreed and Accepted

PROGENICS PHARMACEUTICALS, INC.


By: /S/ RONALD J. PRENTKI
    ---------------------------------
    Ronald J. Prentki
    President


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                                   Schedule 1

            Definition of Capitalized Terms as Used in this Exhibit B


"Compound" shall mean N-methylnaltrexone having the chemical structure [*].

"Field of Use" shall mean [*].

"University Know How" shall mean all technology and information, including
without limitation methods, processes, techniques, compounds, drawings,
indications, data, results of tests or studies (including clinical studies
previously performed with respect to the Compound, expertise and trade secrets,
whether patentable or not, relating to the Compound or necessary or useful for
the commercialization of Licensed Products, existing on the date hereof or at
any time during the term of this Agreement, which is owned or controlled by
University.

"Licensed Product" shall mean any article, composition, substance, material,
method, process, product, use or service containing, consisting of the Compound
or using the Patents.

"Patents" shall mean those patents and patent applications listed on Appendix A;
and any patents and patent applications which claim [*], as well as all
continuations, continuations-in-part, divisions, patents of addition, reissues,
renewals or extensions thereof, which, as of the date of the term of this
Agreement, are exclusively licensed by Licensor.

 "University" shall mean the University of Chicago and its affiliate, ARCH
Development Corporation. .

"University Agreement" shall mean that certain Option and License Agreement
entered into between the University and Licensor on May 8, 1985, as amended.


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