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                                                                    Exhibit 10.5

                          REGISTRATION RIGHTS AGREEMENT

            THIS REGISTRATION RIGHTS AGREEMENT (this "Agreement") is made as of
this 29th day of March, 2005, by and among:

            Molecular Insight Pharmaceuticals, Inc., a Massachusetts corporation
            (the "Company"), the holders (the "Series A Holders") of the Series
            A Convertible Preferred Stock, par value $0.01 per share, of the
            Company (the "Series A Preferred Stock") set forth on Schedule A
            attached hereto;

            The holders (the "Series B Holders") of the Series B Convertible
            Preferred Stock, par value $0.01 per share, of the Company (the
            "Series B Preferred Stock") set forth on Schedule B attached hereto;

            The holders (the "Series C Holders" and together with the Series A
            Holders and the Series B Holders, the "Preferred Holders") of the
            Series C Convertible Preferred Stock, par value $0.01 per share, of
            the Company (the "Series C Preferred Stock") set forth on Schedule C
            attached hereto; and

            The holders (the "Common Holders" and together with the Series A
            Holders, the Series B Holders and the Series C Holders, each, an
            "Investor" and collectively, the "Investors") of the common stock of
            the Company, par value $0.01 per share (the "Common Stock").

                                    RECITALS:

            A. Pursuant to the terms of a certain Stock Purchase Agreement, of
even date herewith, by and among the Company, Cerberus Partners, L.P. and Medcap
Partners, L.P., as the lead investors, and the other Series C Holders signatory
thereto (as may be amended, restated, supplemented or otherwise modified from
time to time, the "Purchase Agreement"), the Company is issuing to the Series C
Holders an aggregate of up to 148,515 shares (the "Series C Preferred Shares")
of the newly created Series C Preferred Stock; and

            B. As a condition to the Initial Closing (and each Follow-on
Closing, if any) under the Purchase Agreement, the parties hereto desire to
enter into this Agreement to set forth, among other things, the rights of the
Investors with respect to the registration of shares of Common Stock held by and
issuable to the Preferred Holders upon conversion of the Series A Preferred
Stock, Series B Preferred Stock and Series C Preferred Stock (the "Preferred
Stock");

            NOW, THEREFORE, in consideration of the foregoing and the respective
covenants hereinafter set forth, and for other good and valuable consideration,
the receipt and sufficiency of which are hereby acknowledged, the Company and
each Preferred Holder, severally and not jointly, hereby agree as follows:

ARTICLE I   DEFINITIONS.

      1.1   General Definitions. All capitalized terms used but not defined
herein shall have the meanings ascribed thereto in the Purchase Agreement. As
used in this Agreement, unless the context otherwise requires, the following
terms shall have the respective meanings set forth below:

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            "Affiliate" means, with respect to any Person, any other Person
which directly or indirectly Controls, is Controlled by, or is under common
Control with, such Person. Notwithstanding the foregoing, none of the Company,
its owners, officers, directors, employees, agents or advisors (or any of their
family members) shall be deemed an "Affiliate" of a Preferred Holder, unless any
such Person is otherwise (i.e., independent of the Company) an Affiliate of such
Preferred Holder.

            "Agreement" shall have the meaning ascribed to it in the preamble to
this Agreement.

            "Board" means the Board of Directors of the Company.

            "Business Day" means a day, other than a Saturday or Sunday, on
which banks in New York, New York are open for the general transaction of
business.

            "Cerberus" means Cerberus Capital Management, L.P., for itself
and/or one or more of its Affiliates and/or accounts managed by Cerberus Capital
Management, L.P., including, without limitation, Cerberus Partners, L.P.

            "Control" means the possession, direct or indirect, of the power to
direct or cause the direction of the management and policies of a Person,
whether through the ownership of voting securities, by contract or otherwise.

            "Co-Lead Investors" means Cerberus Partners, L.P. and MedCap
Partners, L.P.

            "Commission" means the U.S. Securities and Exchange Commission or
any other successor federal agency then administering the Securities Act and
other federal securities laws.

            "Common Stock" means the common stock, par value $.01 per share, of
the Company, and any other securities into which or for which such Common Stock
may be converted or exchanged pursuant to a plan of recapitalization,
reorganization, merger, consolidation, sale of assets or other similar
transaction.

            "Company" shall have the meaning ascribed to it in the preamble to
this Agreement.

            "Conversion Shares" means the shares of Common Stock issuable upon
conversion of the Series C Preferred Stock.

            "Exchange Act" means the Securities Exchange Act of 1934, as
amended, or any successor federal statute, and the rules and regulations of the
Commission issued under such Act, as they each may, from time to time, be in
effect.

            "Initial Public Offering" means the first underwritten public
offering of the Common Stock by the Company pursuant to an effective
Registration Statement.

            "Initiating Stockholders" means the Investor(s) who cause a Demand
Notice to be delivered pursuant to Section 2.1.

            "Investor(s)" shall have the meaning ascribed to it in the preamble
to this Agreement.

            "Other Stockholders" shall have the meaning ascribed to it in
Section 2.1(d).

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            "Person" means an individual, corporation, partnership, limited
liability company, trust, business trust, association, joint stock company,
joint venture, sole proprietorship, unincorporated organization, governmental
authority or any other form of entity not specifically listed herein..

            "Preferred Holders" shall have the meaning ascribed to it in the
recitals to this Agreement.

            "Preferred Stock" shall have the meaning ascribed to it in the
recitals to this Agreement.

            "Prospectus" shall mean the prospectus included in any Registration
Statement, as amended or supplemented by any prospectus supplement, with respect
to the terms of the offering of any portion of the Registrable Securities
covered by such Registration Statement and by all other amendments and
supplements to the prospectus, including post-effective amendments and all
material incorporated by reference in such prospectus.

            "Purchase Agreement" shall have the meaning ascribed to it in the
recitals to this Agreement.

            "Register," "registered" and "registration" refer to a registration
made by preparing and filing a Registration Statement or similar document in
compliance with the Securities Act, and the declaration or ordering of
effectiveness of such Registration Statement or document.

            "Registrable Securities" means: (i) the Preferred Stock; (ii) any
and all shares of Common Stock issued or issuable in respect of the Preferred
Stock upon any stock split, reverse stock split, stock dividend,
recapitalization, reorganization, merger, consolidation, sale of assets or
similar event; (iii) the shares of Common Stock issuable as payment-in-kind
dividends on the Preferred Stock in accordance with the terms thereof; and (iv)
any other shares of Common Stock acquired by any of the Investors at any time.
Notwithstanding the foregoing, the term "Registrable Securities" shall not
include any shares which have been (i) sold to or through a broker or dealer or
underwriter in a public distribution or a public securities transaction, (ii)
sold in a transaction exempt from the registration and prospectus delivery
requirements of the Securities Act under Section 4(1) thereof so that all
transfer restrictions and restrictive legends with respect thereto are removed
upon the consummation of such sale, (iii) registered under the Securities Act
pursuant to an effective Registration Statement filed thereunder or (iv)
publicly sold pursuant to Rule 144 under the Securities Act.

            "Registration Statement" means a Registration Statement filed by the
Company with the Commission for a public offering and sale of securities of the
Company (other than a Registration Statement on Form S-8 or Form S-4, or their
successors, or any other form for a similar limited purpose, or any Registration
Statement covering only securities proposed to be issued in exchange for
securities or assets of another corporation).

            "Requisite Series AB Holders" means (i) the holders of at least a
majority of the Common Stock then issued and outstanding but not registered,
which were issued upon conversion of the Series A Preferred Stock and Series B
Preferred Stock, or (ii) holders holding at least a majority of the Common Stock
issuable upon conversion of the then issued and outstanding shares of Series A
Preferred Stock and Series B Preferred Stock.

            "Requisite Series C Holders" means Cerberus and (i) Series C Holders
holding at least a majority of the Common Stock then issued and outstanding but
not registered, which were issued upon conversion of the Series C Preferred
Stock, or (ii) Series C Holders holding at least a majority of the Common Stock
issuable upon conversion of the then issued and outstanding shares of Series C
Preferred Stock.

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            "Securities Act" means the Securities Act of 1933, as amended, or
any successor federal statute, and the rules and regulations of the Commission
issued under such Act, as they each may, from time to time, be in effect.

            "Series A Holders" shall have the meaning ascribed to it in the
preamble to this Agreement.

            "Series A Preferred Stock" shall have the meaning ascribed to it in
the preamble to this Agreement.

            "Series AB Demand Registration" shall have the meaning ascribed to
it in Section 2.1(a)(ii).

            "Series AB Holders" means the Series A Holders and the Series B
Holders.

            "Series B Holders" shall have the meaning ascribed to it in the
preamble to this Agreement.

            "Series B Preferred Stock" shall have the meaning ascribed to it in
the preamble to this Agreement.

            "Series C Demand Registration" shall have the meaning ascribed to it
in Section 2.1(a)(i).

            "Series C Holders" shall have the meaning ascribed to it in the
recitals to this Agreement.

            "Series C Preferred Stock" shall have the meaning ascribed to it in
the recitals to this Agreement.

ARTICLE II  REGISTRATION RIGHTS.

      2.1   Demand Registration.

            (a)   At any time after the sooner of (x) the closing of an Initial
Public Offering (but not within 180 days after the effective date of the
Registration Statement filed in respect of that Initial Public Offering) and (y)
March 29, 2012, by delivery of written notice to the Company (a "Demand
Notice"):

                  (i) the Requisite Series C Holders may require the Company to
register for sale under the Securities Act all or any portion of the Registrable
Securities held by the Series C Holders for sale in the manner specified in such
Demand Notice (a "Series C Demand Registration"). The Requisite Series C Holders
shall be entitled to only two (2) Series C Demand Registrations pursuant to this
Section 2.1(a)(i); provided, that, they may only make demand for one such Series
C Demand Registration in any twelve month period, unless any of them shall have
had any Registrable Securities excluded from a Registration Statement that was
filed during such twelve month period; and

                  (ii) the Requisite Series AB Holders may require the Company
to register for sale under the Securities Act all or any portion of the
Registrable Securities held by the Series AB Holders for sale in the manner
specified in such Demand Notice; provided, that (i) the portion of the
Registrable Securities required to be so registered equals at least 25% of the
shares of Common Stock issuable upon

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conversion of the shares of Series A Preferred Stock and Series B Preferred
Stock then outstanding and (ii) the aggregate proceeds from the sale of the
shares so registered is reasonably expected to exceed $30,000,000 (a "Series AB
Demand Registration"). The Requisite Series AB Holders shall be entitled to only
two (2) Series AB Demand Registrations pursuant to this Section 2.1(a)(ii);
provided, that, they may only make demand for one such Series AB Demand
Registration in any twelve month period, unless any of them shall have had any
Registrable Securities excluded from a Registration Statement that was filed
during such twelve month period; and

                  (iii) following a change in the "Series C Conversion Price"
(as that term is defined in the Articles of Amendment), such that additional
shares of Common Stock become issuable upon conversion of the outstanding Series
C Preferred Stock, the Requisite Series C Holders may require the Company to
register for sale under the Securities Act such additional shares of Common
Stock (the "Additional Shares"), but only to the extent the Additional Shares
are not at the time covered by an effective Registration Statement or such
Additional Shares cannot be added by pre-effective amendment to an existing
Registration Statement. Such Registration Statement shall include the plan of
distribution specified in the Demand Notice delivered by the Requisite Series C
Holders pursuant to this Section 2.1(a)(iii). Such Registration Statement also
shall cover, to the extent allowable under the Securities Act (including without
limitation Rule 416), such indeterminate number of additional shares of Common
Stock resulting from stock splits, stock dividends or similar transactions with
respect to the Additional Shares. The Registration Statement (and each amendment
or supplement thereto, and each request for acceleration of effectiveness
thereof) shall be furnished for review in accordance with Section 2.4(a) prior
to its filing or other submission. Notwithstanding anything in this Agreement to
the contrary, no demand made pursuant to this Section 2.1(a)(iii) shall be
deemed a Series C Demand Registration that reduces the number of such Series C
Demand Registrations to which the Series C Holders are entitled hereunder; and

                  (iv) if the Company is then a registrant entitled to use Form
S-3 or any successor form thereto to effect the distribution of such Registrable
Securities for public sale or re-sale (as the case may be), (aa) the Requisite
Series C Holders may require the Company to register for sale or re-sale under
the Securities Act by filing a Registration Statement on Form S-3 or any
comparable or successor form thereto for a public offering of all or any portion
of the Registrable Securities held by them, or (bb) the Requisite Series AB
Holders may require the Company to register for sale or re-sale under the
Securities Act by filing a Registration Statement on Form S-3 or any comparable
or successor form thereto for a public offering of all or any portion of the of
Registrable Securities held by them, in each case, in accordance with the method
of disposition specified in the Demand Notice. Whenever the Company is required
by this Section 2.1(a)(iv) to effect the registration of Registrable Securities,
each of the procedures and requirements of Sections 2.1 and 2.4 shall apply to
such registration, and the Company shall cause such Registration Statement to be
declared effective within one hundred eighty (180) days after the Company's
receipt of the request for such registration. There shall be no limitation on
the number of registrations on Form S-3 which may be requested and obtained
under this Section 2.1, and such requests and registrations shall not reduce the
number of Series C Demand Registrations or Series AB Demand Registrations, as
the case may be, to which the Series C Holders or Series AB Holders, as the case
may be, are entitled hereunder.

            (b)   Following receipt of any Demand Notice under this Section 2.1,
the Company shall file a Registration Statement including the securities covered
by such Demand Notice within thirty (30) days after receipt of such Demand
Notice (the "Filing Deadline"), and the Company shall use its best efforts to
effect the registration under the Securities Act as soon as practicable, and in
any event within one hundred eighty (180) days after receipt of such Demand
Notice (the "Effectiveness Deadline"), for public sale or re-sale in accordance
with the method of disposition specified in such Demand Notice of the number of
Registrable Securities specified in such Demand Notice. If a Registration
Statement including the Registrable Securities referenced in the Demand Notice
is not (i) filed with the Commission on or

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prior to the applicable Filing Deadline, or (ii) declared effective by the
applicable Effectiveness Deadline, then the Company shall make pro rata payments
to each Investor whose securities are to be included in such Registration
Statement, as liquidated damages (and not as a penalty, as damages are
impossible to forecast or predict and these amounts are deemed reasonable in all
respects), in an amount equal to 1.5% of the aggregate Market Price (as defined
in the Articles of Amendment) (as of the Filing Deadline) of the Investor's
securities to be included in such Registration Statement for each 30-day period
or pro rata for any portion thereof following the date by which such
Registration Statement should have been filed or declared effective, as the case
may be, for which no Registration Statement is filed or has not been declared
effective, as the case may be, with respect to the Registrable Securities. Such
payments shall be in partial compensation to the Investors, and shall not
constitute the Investors' exclusive remedy for such events. Such payments shall
be made to each Investor in cash. The amounts payable as liquidated damages
pursuant to this Section 2.1(b) shall be payable in lawful money of the United
States, and amounts payable as liquidated damages shall be paid within two (2)
Business Days of the last day of each such 30-day period during which the
Registration Statement should have been filed or been declared effective, as the
case may be, for which no Registration Statement was filed or had not yet been
declared effective, as the case may be, with respect to the Registrable
Securities.

            (c) If the Initiating Stockholders intend to distribute the
Registrable Securities covered by their Demand Notice by means of an
underwriting, the Initiating Stockholders shall so advise the Company in their
Demand Notice. If the method of disposition is an underwritten public offering,
the Initiating Stockholders may designate the managing underwriter of such
offering, which designation shall be subject to the Company's approval, not to
be unreasonably withheld. The Initiating Stockholders may elect to include in
such underwriting all or any part of the Registrable Securities it holds,
subject to the limitations required by the managing underwriter as provided for
in Section 2.1(d).

            (d) A Registration Statement filed pursuant to this Section 2.1 may,
subject to the following provisions and in addition to the Registrable
Securities, include (i) shares of Common Stock for sale by the Company for its
own account and (ii) shares of Common Stock held by persons other than the
Company and the Preferred Holders (the "Other Shareholders"), in each case for
sale in accordance with the method of disposition specified by the Initiating
Stockholders and subject to the exclusions provided herein. If such registration
shall be underwritten, the Company, the Preferred Holders and the Other
Shareholders proposing to distribute their shares through such underwriting
shall enter into an underwriting agreement in customary form with the
representative of the underwriter or underwriters selected for such
underwriting; the terms of which shall not be more favorable to the Company and
such Other Shareholders than the terms afforded therein to the Initiating
Stockholders. If and to the extent that the managing underwriter determines that
marketing factors require a limitation on the number of shares to be included in
such registration, then the shares of Common Stock sought to be registered by
the Preferred Holders and the Other Shareholders and shares of Common Stock to
be sold by the Company for its own account shall be excluded from such
registration to the extent so required by such managing underwriter in the
following order of priority: (1st) and unless the Other Shareholders and the
Company have otherwise agreed in writing, such exclusion shall be applied first
to the shares sought to be registered by the Other Shareholders to the extent
any such reduction is required by the managing underwriter; (2nd) then to the
shares of Common Stock of the Company to be included for its own account to the
extent any such reduction is required by the managing underwriter; (3rd) then
the shares sought to be registered by the Series AB Holders to the extent any
such reduction is required by the managing underwriter; and (4th) then to the
shares sought to be registered by the Series C Holders to the extent any such
reduction is required by the managing underwriter. In any event, all securities
to be sold other than Registrable Securities of the Series C Holders shall be
excluded prior to any exclusion of Registrable Securities of the Series C
Holders, if they are participating in such registration, whether or not they are
the Initiating Stockholders with respect to such registration. No Registrable
Securities or other securities, in either case, excluded from the underwriting
by reason of the underwriter's marketing limitation shall be included

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in such registration. If any of the Preferred Holders or any of the Other
Shareholders who has requested inclusion in such registration as provided above,
disapproves of the terms of the underwriting, then such Preferred Holder(s) or
such Other Shareholder(s) may elect to withdraw therefrom by written notice to
the Company and the managing underwriter. The securities so withdrawn shall
thereupon be withdrawn from registration.

            (e)   The Company may delay or postpone for up to 45 consecutive
days effecting a Series AB or Series C Demand Registration if the Company has
delivered a written certificate to each Investor stating that the Board, acting
in good faith, has resolved that pursuit of such Demand Registration during such
45-day period would be detrimental to the Company and its shareholders;
provided, however, that in the event of any such postponement, the Initiating
Stockholders shall be entitled to withdraw the request for such Demand
Registration and, if such request is withdrawn, such request shall not count as
a Demand Registration hereunder; and provided, further, that the Company may not
exercise its rights under this Section 2.1(e) for more than a total 60 days in
any eighteen month period.

      2.2   Piggy-Back Registration.

            (a)   If the Company at any time (other than pursuant to Section
2.1) proposes to register any of its securities under the Securities Act for
sale to the public, whether for its own account or for the account of other
shareholders of the Company or both (except with respect to (i) an Initial
Public Offering, (ii) Registration Statements on Forms S-4, S-8 or any successor
to such forms, (iii) any Registration Statement including only securities issued
pursuant to a dividend reinvestment plan, (iv) a Registration Statement in which
the only securities to be registered are securities issuable upon conversion of
debt securities or other convertible securities which are also being registered
or (v) another form of Registration Statement not available for registering the
Registrable Securities for sale to the public), each such time the Company shall
promptly give written notice to the Preferred Holders of its intention to do so
(each, a "Piggy-Back Notice"). Upon the written request of the Requisite Series
C Holders, received by the Company within twenty (20) days after the date of
delivery of a Piggy-Back Notice, in accordance with Section 3.4, to register any
or all of the Registrable Securities held by the Series C Holders as stated in
such request, the Company shall use its best efforts to cause the Registrable
Securities as to which registration shall have been so requested to be included
in such Registration Statement. If the Registration Statement relates to an
underwritten public offering, the Company shall so advise the Preferred Holders
as a part of a Piggy-Back Notice. In such event, the Preferred Holders' right to
include Registrable Securities in such registration shall be conditioned upon
its participation in such underwriting to the extent provided herein. The
Preferred Holders, if participating in such distribution, shall enter into an
underwriting agreement in customary form with the underwriter or underwriters
selected for underwriting by the Company; the terms of which shall be no less
favorable to the Preferred Holders than the terms afforded therein to the
Company.

            (b)   Notwithstanding any other provision of this Section 2.2, if
the managing underwriter or underwriters in the registration giving rise to the
Piggy-Back Notice determine(s) that the number of shares to be included in such
registration (including any securities that the Company and the Other
Shareholders propose to be included that are not Registrable Securities) exceeds
the largest number of shares that can be sold without having an adverse effect
on such offering (the "Maximum Offering Size"), the Company will include in such
registration, in the following priority, up to the Maximum Offering Size:

                  (i) first, that number of securities held by the Person(s)
(other than the Company and the Series AB Holders) who demanded such
registration, if any, as would not cause the offering to exceed the Maximum
Offering Size; and

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                  (ii) second, if the Maximum Offering Size has not then been
exceeded, that number of securities proposed to be registered for the account of
the Series C Holders;

                  (iii) third, if the Maximum Offering Size has not then been
exceeded, that number of securities proposed to be registered for the account of
the holders of the Series A and Series B Preferred Stock, ratably between them
treating them as one series for the purpose of this clause (iii);

                  (iv) fourth, if the Maximum Offering Size has not then been
exceeded, that number of securities proposed to be registered by the Company for
its own account; and

                  (v) fifth, if the Maximum Offering Size has not then been
exceeded, any securities proposed to be registered for the account of any other
Persons (other than the Company and those Persons described in clauses (i), (ii)
and (iii) immediately above) with such priorities among them as the Company
shall determine.

            (c)   Any request by a Preferred Holder for inclusion in any
registration may be withdrawn, in whole or in part, at any time prior to the
effective date of the Registration Statement for such offering. No request for
inclusion of, nor the inclusion of, Registrable Securities by a Series C Holder
shall be deemed a Series C Demand Registration that reduces the number of such
Series C Demand Registrations to which the Series C Holders are entitled
hereunder.

            (d)   The Company shall have the right to terminate or withdraw any
registration contemplated under this Section 2.2 prior to the effectiveness of
such registration, whether or not the Series C Holders have elected to include
securities in such registration.

            (e)   There shall be no limitation on the number of registrations a
Preferred Holder may participate in under this Section 2.2, and any such
participation shall not reduce the number of Series C Demand Registrations to
which the Series C Holders are entitled hereunder.

      2.3   Limitation on Registration. Notwithstanding anything herein to the
contrary, the Company shall not be required to file a Registration Statement
pursuant to Section 2.1 that would: (i) require the Company to execute a general
consent to service of process in any jurisdiction in order to effect such
registration if the Company is not already subject to service in such
jurisdiction, or (ii) subject the Company to taxation in a jurisdiction where
the Company is not otherwise subject to taxation.

      2.4   Registration Procedures. If and whenever the Company is required by
the provisions of Section 2.1 or 2.2 to effect the registration of any
Registrable Securities under the Securities Act, the Company shall, as
expeditiously as possible:

            (a)   Prepare and file with the Commission a Registration Statement
on the applicable form with respect to such securities and use its best efforts
to cause such Registration Statement to become and remain effective until the
earlier of (i) the sale of all of the Registrable Securities covered thereby and
(ii) the first date when all Registrable Securities covered thereby are eligible
for sale under Rule 144(k) without regard to any volume or manner of sale
limitations; provided, however, that, as soon as practicable but in no event
later than five (5) Business Days before filing such Registration Statement, any
related prospectus or any amendment or supplement thereto (other than any
amendment or supplement made solely as a result of incorporation by reference of
documents filed with the Commission subsequent to the filing of such
Registration Statement), the Company shall furnish to the Preferred Holders and
the underwriters, if any, copies of all such documents proposed to be filed,
which documents shall be subject to review by the Preferred Holders and any such
underwriters; the Company shall not file

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any Registration Statement or amendment thereto or any prospectus or any
supplement thereto (other than any amendment or supplement made solely as a
result of incorporation by reference of documents filed with the Commission
subsequent to the filing of such Registration Statement) to which the managing
underwriters of the applicable offering, if any, or either of the Co-Lead
Investors shall have reasonably objected in writing, within four (4) Business
Days after receipt of such documents, to the effect that such Registration
Statement or amendment thereto or prospectus or supplement thereto does not
comply in all material respects with the requirements of the Securities Act and
specifying in reasonable detail the reasons therefor (provided that the
foregoing shall not limit the a Preferred Holder's right to reasonably object,
within four (4) Business Days after receipt of such documents, to any particular
information that is to be contained in such Registration Statement, amendment,
prospectus or supplement and relates specifically to such Preferred Holder,
including without limitation any information describing the manner in which the
Preferred Holder acquired Such Registrable Securities and the intended method of
distribution of such Registrable Securities), and if the Company is unable to
file any such document due to the objections of such underwriters or either of
the Co-Lead Investors, the Company shall use its best efforts to cooperate with
such underwriters and either of the Co-Lead Investors to prepare, as soon as
practicable, a document that is responsive in all material respects to the
reasonable objections of either of the Co-Lead Investors;

            (b)   Permit a single law firm designated by the Co-Lead Investors
to represent all of the Series C Holders, and a single law firm designated by
the Requisite Series AB Holders to represent the Series AB Holders, to review
and comment on the Registration Statement which includes their respective
Registrable Securities and all amendments and supplements for a reasonable
period prior to filing and to respond to any reasonable objections raised by
such counsel.

            (c)   Prepare and file with the Commission such amendments and
supplements to such Registration Statement and the prospectus used in connection
therewith as may be necessary to keep such Registration Statement effective for
the period specified herein and comply with the provisions of the Securities Act
with respect to the disposition of all Registrable Securities covered by such
Registration Statement in accordance with the intended method of disposition set
forth in such Registration Statement for such period; provided, that, the
Company shall comply with the provisions of Section 2.4(a) above;

            (d)   Furnish to the Preferred Holders and to each underwriter
copies of the Registration Statement and each such amendment and supplement
thereto (together with all exhibits thereto) and the prospectus included therein
and any other prospectus filed under Rule 424 or Rule 434 under the Securities
Act as the Preferred Holders and such underwriter reasonably may request in
order to facilitate the disposition of the Registrable Securities covered by
such Registration Statement;

            (e)   Use its best efforts to register or qualify the Registrable
Securities covered by such Registration Statement under the securities or "blue
sky" laws of such jurisdictions as the sellers of the Registrable Securities or,
in the case of an underwritten public offering, the managing underwriter
reasonably shall request; provided, however, that the Company shall not be
required to (i) qualify to transact business as a foreign corporation in any
jurisdiction where it is not so qualified, (ii) consent to general service of
process or (iii) submit to taxation in any such jurisdiction, unless the Company
is already subject to service or subject to taxation in such jurisdiction;

            (f)   Use its best efforts to list or qualify the Registrable
Securities covered by such Registration Statement on any securities exchange or
quotation system on which the Common Stock is then listed;

            (g)   Comply in all material respects with all applicable rules and
regulations under the Securities Act and Exchange Act;

                                       9
<PAGE>

            (h)   Immediately notify the Preferred Holders and each underwriter
under such Registration Statement, at any time when a prospectus relating
thereto is required to be delivered under the Securities Act, of the happening
of any event which has resulted or would result in the prospectus contained in
such Registration Statement, as then in effect, to include an untrue statement
of a material fact or omit to state a material fact required to be stated
therein or necessary to make the statements therein, in light of the
circumstances under which they were made, not misleading, and promptly prepare
and furnish to such Investor and underwriter an updated prospectus;

            (i)   If the offering is underwritten, and at each Preferred
Holder's request, use its best efforts to furnish on the date that Registrable
Securities are delivered to the underwriters for sale pursuant to such
registration (i) an opinion, dated such date, of counsel to the Company,
addressed to the underwriters and the Preferred Holder, to such effect as
reasonably may be requested by the underwriters, and (ii) a letter, dated such
date, from the independent public accountants retained by the Company, addressed
to the underwriters and, if applicable, the Preferred Holder, stating that they
are independent public accountants within the meaning of the Securities Act and
that, in the opinion of such accountants, the financial statements of the
Company included in the Registration Statement or the prospectus, or any
amendment or supplement thereof, comply as to form in all material respects with
the applicable accounting requirements of the Securities Act, and such letter
shall additionally cover such other financial matters (including information as
to the period ending no more than five (5) Business Days prior to the date of
such letter) with respect to such registration as such underwriters reasonably
may request, and deliver copies of such letter to the Investor;

            (j)   For the purpose of participating in any Registration
Statement, upon reasonable notice and at reasonable times during normal business
hours, make available for inspection by the Preferred Holder, any underwriter
participating in any distribution pursuant to such Registration Statement, and
any attorney, accountant or other agent retained by the Preferred Holder or such
underwriter, reasonable access to all financial and other records, pertinent
corporate documents and properties of the Company, as such parties may
reasonably request, and cause the Company's officers, directors and employees to
supply all information reasonably requested by any of the Preferred Holder, such
underwriter, attorney, accountant or agent in connection with such Registration
Statement; provided, however, the Company shall neither disclose the existence
or content of any material, non-public information concerning the Company at a
time when possession of such information by the Preferred Holder would, under
applicable law, prohibit the Preferred Holder from trading in the Company's
securities;

            (k)   Notify the Preferred Holders (i) when the prospectus or any
prospectus supplement or post-effective amendment has been filed, and, with
respect to such Registration Statement or any post-effective amendment, when the
same has become effective, such notice to be given no later than 9:00 a.m. (New
York time) of the morning on the Business Day immediately after the declaration
of effectiveness by the Commission, (ii) immediately of any request by the
Commission for amendments or supplements to such Registration Statement or to
amend or supplement such prospectus or for additional information, (iii)
immediately of the issuance by the Commission of any stop order suspending the
effectiveness of such Registration Statement or the initiation of any proceeding
for that purpose and (iv) immediately of the suspension of the qualification of
securities covered by such registration for offering or sale in any
jurisdiction, or of the initiation of any proceeding for any of such purposes;

            (k)   Take such other actions as the Preferred Holders or the
underwriters reasonably request in order to expedite or facilitate the
disposition of the Registrable Securities, including, without limitation,
preparing for, and participating in, such number of "road shows" and all such
other customary selling efforts as the underwriters reasonably request in order
to expedite or facilitate such disposition;

                                       10
<PAGE>

            (l)   use its reasonable best efforts to prevent the issuance of any
stop order or other suspension of effectiveness and, if such order is issued,
obtain the withdrawal of any such order at the earliest possible moment; and

            (m)   otherwise use its reasonable best efforts to comply with all
applicable rules and regulations of the Commission under the Securities Act and
the Exchange Act and take such other actions as may be reasonably necessary to
facilitate the registration of the Registrable Securities hereunder; and make
available to its security holders, as soon as reasonably practicable, but not
later than the Availability Date (as defined below), an earnings statement
covering a period of at least twelve (12) months, beginning after the effective
date of each Registration Statement, which earnings statement shall satisfy the
provisions of Section 11(a) of the Securities Act (for the purpose of this
Section 2.4(m), "Availability Date" means the 45th day following the end of the
fourth fiscal quarter that includes the effective date of such Registration
Statement, except that, if such fourth fiscal quarter is the last quarter of the
Company's fiscal year, "Availability Date" means the 90th day after the end of
such fourth fiscal quarter).

      2.5   Expenses. The Company shall bear all reasonable expenses incurred in
complying with Sections 2.1, 2.2 and 2.4, including, without limitation, all
registration and filing fees, printing expenses, fees and disbursements of
counsel and independent public accountants for the Company, fees and expenses
(including counsel fees) incurred in connection with complying with state
securities or "blue sky" laws, reasonable fees and disbursements of one law firm
designated by the Co-Lead Investors and one law firm designated by the Series AB
Holders, of transfer agents and registrars and costs of any insurance which
might be obtained by the Company with respect to the offering by the Company.

      2.6   Indemnification and Contribution.

            (a)   The Company shall indemnify and hold harmless, to the fullest
extent permitted by law, each Preferred Holder and its Affiliates and the
directors, officers, employees, investors, partners and agents of each Preferred
Holder and its Affiliates, from and against any and all losses, claims, damages,
liabilities and expenses (including without limitation reasonable attorney fees
and disbursements and other expenses incurred in connection with investigating,
preparing or defending any action, claim or proceeding, pending or threatened
and the costs of enforcement hereof) (collectively, "Losses") to which any such
Person may become subject, arising out of or based upon any untrue statement or
alleged untrue statement of a material fact contained in any Registration
Statement covering any Registrable Securities, any related prospectus or
preliminary prospectus, or any amendment or supplement thereto, or any omission
or alleged omission to state in any thereof a material fact required to be
stated therein or necessary to make the statements therein (in the case of a
prospectus or prospectus supplement, in light of the circumstances under which
they were made) not misleading; provided, however, that the Company will not be
liable in any such case to the extent any Losses arise out of or are based upon
an untrue statement of a material fact or an omission to state a material fact
in such Registration Statement, prospectus, preliminary prospectus, amendment or
supplement, as the case may be, made or omitted, as the case may be, in express
reliance upon and in strict conformity with written information furnished to the
Company by a Preferred Holder expressly for use therein. This indemnity is in
addition to any liability that the Company may otherwise have. The Company shall
also indemnify any underwriters of the Registrable Securities, selling brokers,
dealer managers and similar securities industry professionals participating in
the distribution and their officers and directors and each Person who controls
such underwriters or other Persons (within the meaning of the Securities Act) to
the same extent as provided above with respect to the indemnification of the
Preferred Holder and its Affiliates as described above, if so required by the
underwriting agreement entered into in connection with the registration of such
Registrable Securities

                                       11
<PAGE>

            (b)   In connection with any Registration Statement covering
Registrable Securities, each Preferred Holder whose Registrable Securities were
included in such Registration Statement shall furnish to the Company in writing
such information with respect to the Preferred Holder as the Company reasonably
requests for use in connection with such Registration Statement, any related
Prospectus or preliminary prospectus, or any amendment or supplement thereto,
and shall indemnify, to the fullest extent permitted by law, the Company, the
Company's directors, officers, employees and agents, each Person who controls
the Company (within the meaning of the Securities Act), against all Losses
arising out of or based upon any untrue statement of a material fact contained
in any Registration Statement covering any Registrable Securities, any related
Prospectus or preliminary prospectus, or any amendment or supplement thereto, or
any omission to state in any such prospectus, amendment or supplement, a
material fact required to be stated therein or necessary to make the statements
therein (in the case of a prospectus or prospectus supplement, in light of the
circumstances under which they were made) not misleading, in each case to the
extent, and only to the extent, that the Losses arise out of or are based upon
an untrue statement of a material fact or an omission to state a material fact
in such Registration Statement or in such related Prospectus, preliminary
prospectus, amendment or supplement, as the case may be, made or omitted, as the
case may be, in express reliance upon and in strict conformity with written
information furnished to the Company by the Preferred Holder expressly for use
therein. Notwithstanding anything in this Agreement to the contrary, in no event
shall the Preferred Holder's indemnification obligation exceed the dollar amount
of the proceeds actually received by such Preferred Holder from the sale of the
Registrable Securities under the Registration Statement giving rise to such
obligation.

            (c)   Promptly after receipt by any Person (the "Indemnified
Person") of notice of any demand, claim or circumstances which would or might
give rise to a claim or the commencement of any action, proceeding or
investigation in respect of which indemnity may be sought pursuant to Section
2.7, such Indemnified Person shall promptly notify the party obligated to
provide indemnification under this Section 2.7 in respect thereof (an
"Indemnifying Party") and the Indemnifying Party shall assume the control and
defense thereof, including the employment of counsel reasonably satisfactory to
such Indemnified Person, and shall assume the payment of all fees and expenses
in connection with such defense and such counsel; provided, however, that the
failure of any Indemnified Person to so notify the Indemnifying Party shall not
relieve the Indemnifying Party of its obligations hereunder except to the extent
that the Indemnifying Party is actually and materially prejudiced by such
failure to notify. In any such proceeding, any Indemnified Person shall have the
right to retain its own counsel, but the fees and expenses of such counsel shall
be at the expense of such Indemnified Person unless: (i) the Indemnifying Party
and the Indemnified Person shall have mutually agreed to the retention of such
counsel; or (ii) in the reasonable judgment of counsel to such Indemnified
Person (x) representation of both parties by the same counsel would be
inappropriate due to actual or potential differing interests between them or (y)
if there are one or more defenses available to such Indemnified Person that
is/are not available to the Indemnifying Party. Without the prior written
consent of the Indemnified Person, which consent shall not be unreasonably
withheld, delayed or conditioned, the Indemnifying Party shall not effect any
settlement of any pending or threatened action, claim or proceeding with respect
to any Indemnified Person, unless such settlement includes an unconditional
release of such Indemnified Person from all liability arising out of such
proceeding.

            (d)   (i) If the indemnification provided for in this Section 2.7
from the Indemnifying Party is unavailable to an Indemnified Person hereunder or
is inadequate in respect of any Losses for which indemnification is provided
under this Section 2.7, then the Indemnifying Party, in lieu of indemnifying
such Indemnified Person, shall contribute to the amount paid or payable by such
Indemnified Person as a result of such Losses in such proportion as is
appropriate to reflect the relative fault of the Indemnifying Party, on the one
hand, and Indemnified Person(s), on the other hand, in connection with the
actions that resulted in such Losses, as well as any other relevant equitable
considerations. The relative fault of such Indemnifying Party and Indemnified
Person shall be determined

                                       12
<PAGE>

by reference to, among other things, whether any action in question, including
any untrue or alleged untrue statement of a material fact or omission or alleged
omission to state a material fact, has been made by, or relates to information
supplied by, such Indemnifying Party or Indemnified Persons, and the parties'
relative intent, knowledge, access to information and opportunity to correct or
prevent such action. The amount paid or payable by a party as a result of the
Losses referred to above shall be deemed to include, subject to the limitations
set forth in Section 2.7(c), any legal or other fees or expenses reasonably
incurred by such party in connection with any investigation or proceeding.

                  (ii) The parties hereto agree that it would not be just and
equitable if contribution pursuant to this Section 2.7(d) were determined by pro
rata allocation or by any other method of allocation that does not take account
of the equitable considerations referred to in Section 2.7(d)(i).
Notwithstanding any other provision hereof, in no event shall the Investor's
contribution obligation exceed the excess of (A) the dollar amount of the
proceeds received by the Investor upon the sale of the Registrable Securities
giving rise to such contribution obligation over (B) the dollar amount of any
damages that the Preferred Holder has otherwise been required to pay by reason
of the untrue or alleged untrue statement or omission or alleged omission giving
rise to such obligation. No Person guilty of fraudulent misrepresentation
(within the meaning of Section 11(f) of the Securities Act) shall be entitled to
contribution from any Person who was not guilty of such fraudulent
misrepresentation.

                  (iii) If indemnification is available under this Section 2.7,
the Indemnifying Parties shall indemnify each Indemnified Person to the fullest
extent provided in Section 2.7(a) and Section 2.7(b) without regard to the
relative fault of said Indemnifying Party or Indemnified Person or any other
equitable consideration provided for in this Section 2.7(d).

                  (iv) If any provision of an indemnification or contribution
clause in an underwriting agreement or agency agreement executed by or on behalf
of the Investor differs from a provision in this Section 2.7, such provision in
the underwriting agreement shall determine the Investor's rights in respect
thereof.

            (e)   Notwithstanding anything in this Agreement to the contrary,
the indemnities and obligations provided in this Section 2.7 shall survive the
transfer of any Registrable Securities by the Preferred Holder.

      2.7   Reporting. With a view to making available the benefits of certain
rules and regulations of the Commission which may at any time permit the sale of
the Registrable Securities to the public without registration, so long as the
Company is subject to the reporting requirements of the Exchange Act, the
Company shall:

            (a)   make and keep public information available, as contemplated in
Rule 144(c) under the Securities Act (or any successor rule); and

            (b)   use its best efforts to file with the Commission in a timely
manner all reports and other documents required of the Company under the
Securities Act and the Exchange Act to, among other things, remain eligible to
use Form S-3 (or any successor thereto).

      2.8   Furnishing Information.

                  (a) The Company shall make available, during normal business
hours, for inspection and review by each of the Investors whose Registrable
Securities are to be included in a Registration Statement, and their respective
advisors and representatives (who may or may not be Affiliated with such
Investor), and any underwriter participating in any disposition of Common Stock
on

                                       13
<PAGE>

behalf of the such Investors pursuant to a Registration Statement or amendments
or supplements thereto or any blue sky, NASD or other filing, all financial and
other records, all filings with the Commission, and all other corporate
documents and properties of the Company as may be reasonably necessary for the
purpose of such review, and cause the Company's officers, directors and
employees, within a reasonable time period, to supply all such information
reasonably requested by such Investors or any such representative, advisor or
underwriter in connection with such Registration Statement (including, without
limitation, in response to all questions and other inquiries reasonably made or
submitted by any of them), prior to the filing and effectiveness of the
Registration Statement for the sole purpose of enabling such Investors and such
representatives, advisors and underwriters and their respective accountants and
attorneys to conduct initial due diligence with respect to the Company and the
accuracy of such Registration Statement. Notwithstanding the foregoing, the
Company shall not disclose material nonpublic information to the Investors, or
to advisors to or representatives of the Investors, unless prior to disclosure
of such information the Company identifies such information as being material
nonpublic information and provides the Investors, such advisors and
representatives with the opportunity to accept or refuse to accept such material
nonpublic information for review.

                  (b) It shall be a condition precedent to the obligations of
the Company to take any action pursuant to this Article II that each Preferred
Holder furnish to the Company in writing such information regarding such
Preferred Holder, the Registrable Securities held by it and the intended method
of disposition of such securities as shall be required to effect the
registration thereof.

      2.9   Additional Registration Rights. As of the date hereof, neither the
Company nor any of its security holders (other than as set forth on Schedule
2.10 attached hereto) has any right to include securities of the Company in a
Registration Statement other than the Registrable Securities, and the Company
shall not, after the date hereof, enter into any agreement providing any rights
to be included with a Registration Statement to any of its security holders or
potential security holders, without the prior written consent of the Requisite
Series C Holders. Until after the effective date of a Registration Statement
which includes Registrable Securities owned by Series C Holders, the Company
shall not file any other Registration Statement solely with respect to shares to
be offered by the Company or any Series AB Holder, including, without
limitation, a Registration Statement on Form S-1, S-3, S-4 or S-8 or any
successor form to any of the foregoing, without the consent of the Requisite
Series C Holders.

      2.10  Lock Up. Each Series AB Holder shall, in connection with any
registration of the Company's securities, upon the request of the Company or the
underwriters managing any underwritten offering of the Company's securities,
agree in writing not to effect any sale, transfer, disposition or distribution
of any of its Registrable Securities (other than that included in such
registration) without the prior written consent of the Company or such
underwriters, as the case may be, for such period of time not to exceed one
hundred eighty (180) days from the effective date of such registration as the
Company or the underwriters may specify.

ARTICLE III MISCELLANEOUS.

      3.1   Successors and Assigns. This Agreement may not be assigned by a
party hereto without the prior written consent of the Company or Cerberus, as
applicable, and, if such assignment materially adversely affects the Series AB
Holders, the Requisite Series AB Holders; provided, however, that a Preferred
Holder may assign its rights and delegate its duties hereunder in whole or in
part, without the prior written consent of any other party, to an Affiliate and
to any Person to whom such Preferred Holder transfers any of the Registrable
Securities, provided, that, no such assignment shall be effective or confer any
right on any such assignee unless, prior to such assignment, the assignee agrees
in writing that such assignee will be bound by all provisions binding on such
Preferred Holder. The provisions of this

                                       14
<PAGE>

Agreement shall inure to the benefit of and be binding upon the respective
permitted successors and assigns of the parties. Except for any other provisions
of this Agreement expressly to the contrary, nothing in this Agreement, express
or implied, is intended to confer upon any party other than the parties hereto
or their respective successors and assigns any rights, remedies, obligations, or
liabilities under or by reason of this Agreement.

      3.2   Counterparts; Faxes. This Agreement may be executed in two or more
counterparts, each of which shall be deemed an original, but all of which
together shall constitute one and the same instrument. This Agreement may also
be executed via facsimile, which shall be deemed an original.

      3.3   Titles and Subtitles. The titles and subtitles used in this
Agreement are used for convenience only and are not to be considered in
construing or interpreting this Agreement.

      3.4   Notices. Unless otherwise provided, any notice required or permitted
under this Agreement shall be given in writing and shall be deemed effectively
given as hereinafter described: (i) if given by personal delivery, then such
notice shall be deemed given upon such delivery; (ii) if given by telex or
telecopier, then such notice shall be deemed given upon receipt of confirmation
of complete transmittal with a confirming copy to be sent by first class mail;
(iii) if given by mail, then such notice shall be deemed given upon the earlier
of (A) receipt of such notice by the recipient or (B) three (3) days after such
notice is deposited in first class mail, postage prepaid; and (iv) if given by
an internationally recognized overnight air courier, then such notice shall be
deemed given one (1) Business Day after delivery to such carrier. All notices
shall be addressed to the party to be notified at the address as follows, or at
such other address as such party may designate by ten (10) days' advance written
notice to the other party:

                     If to the Company:

                     Molecular Insight Pharmaceuticals, Inc.
                     160 Second Street
                     Cambridge, Massachusetts 02142
                     Attn: David Barlow
                     Fax: (617) 492-5664

                     With a copy to:

                     Foley & Lardner LLP
                     111 Huntington Avenue
                     26th Floor
                     Boston, Massachusetts 02199
                     Attn: Gabor Garai, Esq.
                     Fax: (617) 342-4001

                     If to any of the Investors:

                     to the addresses set forth on the signature pages attached
                     hereto.

                     If to any Series AB Holder:

                     to the addresses set forth on Schedule A attached hereto.

                                       15
<PAGE>

or to such other address as any party hereto shall notify the other parties
hereto (as provided above) from time to time.

      3.5   Expenses. In the event that legal proceedings are commenced by any
party to this Agreement against another party to this Agreement in connection
with this Agreement, the party or parties which do not prevail in such
proceedings shall severally, but not jointly, pay their pro rata share of the
reasonable attorneys' fees and other reasonable out-of-pocket costs and expenses
incurred by the prevailing party in such proceedings.

      3.6   Amendments and Waivers. This Agreement shall not be amended without
the prior written consent of (i) the Requisite Series C Holders and (ii) if such
amendment materially adversely affects the Series AB Holders, the Requisite
Series AB Holders. The Company may take any action herein prohibited, or omit to
perform any act herein required to be performed by it, only if the Company shall
have obtained the written consent to such amendment, action or omission to act,
of (i) the Requisite Series C Holders and (ii) if such amendment, action or
omission to act materially adversely affects the Series AB Holders, the
Requisite Series AB Holders.

      3.7   Publicity. No public release or announcement concerning the
transactions contemplated by this Agreement shall be issued by the Company or
any of the Preferred Holders without, in the case of a release or announcement
by any of the Preferred Holders, the prior written consent of the Company, and,
in the case of a release or announcement by the Company, prior written consent
of the Requisite Series C Holders, which in each case, shall not be unreasonably
withheld; provided, however, in the case of any release or announcement that may
be required by law, such release or announcement may be made without prior
consent, but the Company or the Requisite Series C Holders, as the case may be,
shall allow the other, to the extent reasonably practicable in the
circumstances, reasonable time to comment on such release or announcement in
advance of its dissemination.

      3.8   Severability. Any provision of this Agreement that is prohibited or
unenforceable in any jurisdiction shall, as to such jurisdiction, be ineffective
to the extent of such prohibition or unenforceability without invalidating the
remaining provisions hereof but shall be interpreted as if it were written so as
to be enforceable to the maximum extent permitted by applicable law, and any
such prohibition or unenforceability in any jurisdiction shall not invalidate or
render unenforceable such provision in any other jurisdiction. To the extent
permitted by applicable law, the parties hereby waive any provision of law which
renders any provision hereof prohibited or unenforceable in any respect.

      3.9   Entire Agreement. This Agreement, including Schedules, constitutes
the entire agreement among the parties hereof with respect to the subject matter
hereof and thereof and supersede all prior agreements and understandings, both
oral and written, between the parties with respect to the subject matter hereof
and thereof.

      3.10  Further Assurances. The parties shall execute and deliver all such
further instruments and documents and take all such other actions as may
reasonably be required to carry out the transactions contemplated hereby and to
evidence the fulfillment of the agreements herein contained.

      3.11  Governing Law; Consent to Jurisdiction. This Agreement shall be
governed by, and construed in accordance with, the internal laws of the State of
New York without regard to the choice of law principles thereof. Each of the
parties hereto irrevocably submits to the jurisdiction of the courts of the
State of New York located in New York County and the United States District
Court for the Southern District of New York for the purpose of any suit, action,
proceeding or judgment relating to or arising out of this Agreement and the
transactions contemplated hereby. Service of process in connection with any such
suit, action or proceeding may be served on each party hereto anywhere in the
world by the same

                                       16
<PAGE>

methods as are specified for the giving of notices under this Agreement. Each of
the parties hereto irrevocably consents to the jurisdiction of any such court in
any such suit, action or proceeding and to the laying of venue in such court.
Each party hereto irrevocably waives any objection to the laying of venue of any
such suit, action or proceeding brought in such courts and irrevocably waives
any claim that any such suit, action or proceeding brought in any such court has
been brought in an inconvenient forum. THE COMPANY AND EACH OF THE INVESTORS,
SERIES A HOLDERS AND SERIES B HOLDERS HEREBY IRREVOCABLY WAIVES ANY AND ALL
RIGHT TO TRIAL BY JURY IN ANY LEGAL PROCEEDING RELATING TO OR ARISING OUT OF
THIS AGREEMENT OR ANY OTHER TRANSACTION DOCUMENT AND THE TRANSACTIONS
CONTEMPLATED HEREBY AND THEREBY.

      3.12  Independent Nature of Investors' Obligations and Rights. Except as
expressly provided herein and therein, the obligations of each Investor under
this Agreement are several and not joint with the obligations of any other
Investor, and no Investor shall be responsible in any way for the performance of
the obligations of any other Investor under this Agreement. Nothing contained
herein, and no action taken by any Investor (including, without limitation, any
of the Co-Lead Investors) pursuant hereto or thereto, shall be deemed to
constitute the Investors as a partnership, an association, a joint venture or
any other kind of entity, or create a presumption that the Investors are in any
way acting in concert or as a group with respect to such obligations or the
transactions contemplated by this Agreement. Each Investor acknowledges that no
other Investor (including, without limitation, any of the Co-Lead Investors) has
acted as agent for such Investor in connection with this Agreement or in making
its investment in the Company and that no Investor (including, without
limitation, any of the Co-Lead Investors) will be acting as agent of such
Investor in connection with monitoring its investment in the Company or
enforcing its rights under this Agreement. Each Investor shall be entitled to
independently protect and enforce its rights, including, without limitation, the
rights arising out of this Agreement, and it shall not be necessary for any
other Investor to be joined as an additional party in any proceeding for such
purpose. Notwithstanding anything contained in this Agreement to the contrary,
neither of the Co-Lead Investors shall have any duty, fiduciary or otherwise, to
any other Investor by virtue of such Investor serving as a Co-Lead Investor or
otherwise.

      3.13  Injunctive Relief. It is acknowledged that it will be impossible to
measure the damages that would be suffered by an Investor if the Company fails
to comply with the provisions of this Agreement and that in the event of any
such failure, the Investor will not have an adequate remedy at law. The Investor
shall, therefore, be entitled to obtain specific performance of any of the
Company's obligations hereunder and to obtain immediate injunctive relief. The
Company shall not argue, as a defense to any proceeding for such specific
performance or injunctive relief, that the Investor has an adequate remedy at
law.

                  [REMAINDER OF PAGE INTENTIONALLY LEFT BLANK]

                                       17
<PAGE>

                            [COMPANY SIGNATURE PAGE]

      IN WITNESS WHEREOF, the parties hereto have executed this Agreement or
caused this Agreement to be executed by their duly authorized representatives,
as of the date first written above.

                                     THE COMPANY:

                                     MOLECULAR INSIGHT PHARMACEUTICALS, INC.

                                     By: /s/ David S. Barlow
                                         -------------------------------
                                     Name:
                                     Title:

                                       18
<PAGE>

                        [SERIES C HOLDER SIGNATURE PAGE]

      IN WITNESS WHEREOF, the undersigned has executed this Agreement as of the
date first above written.

                                     NAME OF SERIES C HOLDER:

                                     CERBERUS PARTNERS, L.P.

                                     By: Cerberus Associates, LLC,
                                         its General Partner

                                     By: /s/ Seth Plattus
                                         -----------------
                                         Seth Plattus
                                         Managing Director

                                     Address: 299 Park Avenue
                                              22nd Floor
                                              New York, NY 10171

                                     With a copy to (which shall not be deemed
                                     notice for purposes of the Agreement):

                                     Lowenstein Sandler PC
                                     65 Livingston Avenue
                                     Roseland, NJ 07068
                                     Attn: Robert G. Minion, Esq.
                                     Fax: (973) 597-2400

                                       19
<PAGE>

                        [SERIES C HOLDER SIGNATURE PAGE]

      IN WITNESS WHEREOF, the undersigned has executed this Agreement as of the
date first above written.

                                     NAME OF SERIES C HOLDER:

                                     Andrew R Midler Family Trust 5/99

                                     By: /s/ Andrew R Midler
                                         ----------------------------------
                                         Name: Andrew R Midler
                                         Title: Trustee

                                     Address: 283 Summit Ave
                                              Mill Valley Ca 94941

                                     With a copy to (which shall not be deemed
                                     notice for purposes of the Agreement):

                                     ________________________________
                                     ________________________________
                                     ________________________________

                                       20
<PAGE>

                        [SERIES C HOLDER SIGNATURE PAGE]

      IN WITNESS WHEREOF, the undersigned has executed this Agreement as of the
date first above written.

                                     NAME OF SERIES C HOLDER:

                                     John D. Singer, Esq.

                                     By: /s/ John D. Singer, Esq.
                                         --------------------------------
                                         Name: John D. Singer, Esq.
                                         Title:

                                     Address: 200 East 69th Street
                                              Apartment #18-E
                                              New York, NY 10021

                                     With a copy to (which shall not be deemed
                                     notice for purposes of the Agreement):

                                     ________________________________
                                     ________________________________
                                     ________________________________

                                       21
<PAGE>

                        [SERIES C HOLDER SIGNATURE PAGE]

      IN WITNESS WHEREOF, the undersigned has executed this Agreement as of the
date first above written.

                                     NAME OF SERIES C HOLDER:

                                     Michael C. Deutsch

                                     By: /s/ Michael C. Deutsch
                                         ----------------------------------
                                     Name: Michael C. Deutsch
                                     Title:

                                     Address: 331 Madison Ave., 3rd Floor
                                              New York, NY 10017

                                     With a copy to (which shall not be deemed
                                     notice for purposes of the Agreement):

                                     ________________________________
                                     ________________________________
                                     ________________________________

                                       22
<PAGE>

                       [COMMON STOCKHOLDER SIGNATURE PAGE]

      IN WITNESS WHEREOF, the undersigned has executed this Agreement as of the
date first above written.

                                      NAME OF COMMON STOCKHOLDER:

                                      POITRAS, JAMES W. & PATRICIA T., JTWROS

                                      By: /s/ James W. Poitras
                                          --------------------
                                          Name: James W. Poitras
                                          Title:

                                           /s/ Patricia T. Poitras
                                           ------------------------
                                           Patricia T. Poitras

                                          BOTH AS INDIVIDUALS AND AS
                                          TRUSTEES OF THEIR RESPECTIVE
                                          REVOCABLE TRUST

                                      Address:   M/M JAMES W. POITRAS
                                                3100 SPRINGHEAD COURT
                                               NARCOOSSEE FL 34771-8554

                                      With a copy to (which shall not be deemed
                                      notice for purposes of the Agreement):

                                      _____________________________
                                      _____________________________
                                      _____________________________

                                       23
<PAGE>

                        [SERIES C HOLDER SIGNATURE PAGE]

      IN WITNESS WHEREOF, the undersigned has executed this Agreement as of the
date first above written.

                                      NAME OF SERIES C HOLDER:

                                      Carol Frank

                                      By: __________________________________
                                          Name:
                                          Title:

                                      Address: 11529 Conway Rd.
                                               St. Louis MO 63131

                                      With a copy to (which shall not be deemed
                                      notice for purposes of the Agreement):

                                      ______________________________________
                                      ______________________________________
                                      ______________________________________

                                       24
<PAGE>

                        [SERIES C HOLDER SIGNATURE PAGE]

      IN WITNESS WHEREOF, the undersigned has executed this Agreement as of the
date first above written.

                                      NAME OF SERIES C HOLDER:

                                      Benjamin M. Frank Trust

                                      By: /s/ Benjamin M. Frank
                                          ---------------------
                                          Name: Benjamin M. Frank
                                          Title: Trustee

                                      Address: 106 Breckenwood Way
                                               Sacramento, CA 95864

                                      With a copy to (which shall not be deemed
                                      notice for purposes of the Agreement):

                                      ___________________________________
                                      ___________________________________
                                      ___________________________________

                                       25
<PAGE>

                        [SERIES C HOLDER SIGNATURE PAGE]

      IN WITNESS WHEREOF, the undersigned has executed this Agreement as of the
date first above written.

                                      NAME OF SERIES C HOLDER:

                                      [ILLEGIBLE]

                                      By: ______________________________
                                          Name:
                                          Title:

                                      Address: 16413 NE 135th St
                                               Redmond, WA 98052

                                      With a copy to (which shall not be deemed
                                      notice for purposes of the Agreement):

                                      Kristine Davy
                                      16413 NE 135 St
                                      Redmond WA 98052

                                       26
<PAGE>

                        [SERIES C HOLDER SIGNATURE PAGE]

      IN WITNESS WHEREOF, the undersigned has executed this Agreement as of the
date first above written.

                                      NAME OF SERIES C HOLDER:

                                      Rajpal Sandhu

                                      By: /s/ Mary C Henry
                                          ----------------
                                          Name: RAJPAL SANDHU &  MARY HENRY
                                          Title:

                                      Address: 420 FAMILY FARM ROAD
                                               WOOD SIDE, CA-94062
                                               650-529-0606
                                               Raj@RajSandhu.com

                                      With a copy to (which shall not be deemed
                                      notice for purposes of the Agreement):

                                      ____________________
                                      ____________________
                                      ____________________

                                       27
<PAGE>

                        [SERIES C HOLDER SIGNATURE PAGE]

      IN WITNESS WHEREOF, the undersigned has executed this Agreement as of the
date first above written.

                                      NAME OF SERIES C HOLDER:

                                      ___________________________________

                                      By: /s/ James T. Lenehan
                                          -------------------------------
                                          Name: JAMES T. LENEHAN
                                          Title:

                                      Address: 1586 HAMPTON RD
                                               RYDAL, PA
                                               19046

                                      With a copy to (which shall not be deemed
                                      notice for purposes of the Agreement):

                                      _____________________________________
                                      _____________________________________
                                      _____________________________________

                                       28
<PAGE>

                        [SERIES B HOLDER SIGNATURE PAGE]

      IN WITNESS WHEREOF, the undersigned has executed this Agreement as of the
date first above written.

                                      NAME OF SERIES B HOLDER:

                                      LIONEL N. STERLING REVOCABLE TRUST

                                      By: /s/ Lionel N. Sterling
                                          ------------------------------
                                          Name: LIONEL N. STERLING
                                          Title: TRUSTEE

                                      Address: 631 WEST RD.
                                               NEW CANAAN CT.
                                               06940

                                      With a copy to (which shall not be deemed
                                      notice for purposes of the Agreement):

                                      LIONEL N. STERLING
                                      c/o EQUITY RESOURCES INC 4th FL
                                      5 GREENWICH OFFICE PARK
                                      GREENWICH CT. 06831

                                       29

<PAGE>

                        [SERIES C HOLDER SIGNATURE PAGE]

      IN WITNESS WHEREOF, the undersigned has executed this Agreement as of the
date first above written.

                                      NAME OF SERIES C HOLDER:

                                      America Durham, L.P.

                                      By: /s/ T. K. Duggan
                                          ----------------
                                          Name: T. K. DUGGAN
                                          Title: MANAGING PRINCIPAL

                                      Address: 680 SF Ave
                                               22nd Floor
                                               N.Y., N.Y. 10019

                                      With a copy to (which shall not be deemed
                                      notice for purposes of the Agreement):

                                      _____________________
                                      _____________________
                                      _____________________

                                       30
<PAGE>

                        [SERIES C HOLDER SIGNATURE PAGE]

      IN WITNESS WHEREOF, the undersigned has executed this Agreement as of the
date first above written.

                                      NAME OF SERIES C HOLDER:

                                      International Durham, L.P.

                                      By: /s/ T. K. Duggan
                                          ----------------
                                          Name: T. K. Duggan
                                          Title: MANAGING PRINCIPAL

                                      Address: 680 SF Ave
                                               22nd Floor
                                               N.Y., N.Y. 10019

                                      With a copy to (which shall not be deemed
                                      notice for purposes of the Agreement):

                                      ____________________
                                      ____________________
                                      ____________________

                                       31
<PAGE>

                        [SERIES C HOLDER SIGNATURE PAGE]

      IN WITNESS WHEREOF, the undersigned has executed this Agreement as of the
date first above written.

                                      NAME OF SERIES C HOLDER:

                                      Institutional Benchmarks Master Fund

                                      By: Garry Crowder
                                          ----------------------------------
                                          Name: Garry Crowder
                                          Title: Director

                                      Address: _____________________________
                                               _____________________________
                                               _____________________________

                                      With a copy to (which shall not be deemed
                                      notice for purposes of the Agreement):

                                      ______________________________________
                                      ______________________________________
                                      ______________________________________

                                       32
<PAGE>

                        [SERIES C HOLDER SIGNATURE PAGE]

      IN WITNESS WHEREOF, the undersigned has executed this Agreement as of the
date first above written.

                                      NAME OF SERIES C HOLDER:

                                      RICHARD SIMON

                                      By: /s/ Richard Simon
                                          -----------------
                                          Name:
                                          Title:

                                      Address: 219 LAKE AVENUE
                                               NEWTON, MA 02461

                                      With a copy to (which shall not be deemed
                                      notice for purposes of the Agreement):

                                      _____________________________________
                                      _____________________________________
                                      _____________________________________

                                       33
<PAGE>

                        [SERIES C HOLDER SIGNATURE PAGE]

      IN WITNESS WHEREOF, the undersigned has executed this Agreement as of the
date first above written.

                                      NAME OF SERIES C HOLDER:

                                      ___________________________________

                                      By: /s/ William R. Ebsworth
                                          --------------------------------
                                          Name: WILLIAM R. EBSWORTH
                                          Title:

                                      Address: 17 [ILLEGIBLE] RD
                                               WESTON MA 02493

                                      With a copy to (which shall not be deemed
                                      notice for purposes of the Agreement):

                                      _____________________________________
                                      _____________________________________
                                      _____________________________________

                                       34

<PAGE>

                        [SERIES C HOLDER SIGNATURE PAGE]

      IN WITNESS WHEREOF, the undersigned has executed this Agreement as of the
date first above written.

                                NAME OF SERIES C HOLDER:

                                Alan N. Berro

                                By: /s/ Alan N. Berro
                                    -------------------
                                    Name:
                                    Title:

                                Address: P.O. BOX 15155
                                         BEVERLY HILLS, CA
                                         90209

                                With a copy to (which shall not be deemed
                                notice for purposes of the Agreement):

                                _____________________________________
                                _____________________________________
                                _____________________________________

                                       35
<PAGE>

                        [SERIES C HOLDER SIGNATURE PAGE]

      IN WITNESS WHEREOF, the undersigned has executed this Agreement as of the
date first above written.

                                        NAME OF SERIES C HOLDER:

                                        Renee M Noto

                                        By: /s/ Renee M Noto
                                            ----------------
                                            Name:
                                            Title:

                                        Address: 275 Stanwich Road
                                                 Greenwich, CT 06830

                                        With a copy to (which shall not be
                                        deemed notice for purposes of the
                                        Agreement):
                                        ________________________________
                                        ________________________________
                                        ________________________________

                                       36
<PAGE>

                        [SERIES C HOLDER SIGNATURE PAGE]

      IN WITNESS WHEREOF, the undersigned has executed this Agreement as of the
date first above written.

                                       NAME OF SERIES C HOLDER:

                                       THE RAPTOR GLOBAL PORTFOLIO LTD.

                                       By: Tudor Investment Corporation,
                                           Investment Advisor

                                       By: /s/ William T. Flaherty
                                           -------------------------
                                           Name: William T. Flaherty
                                           Title: Managing Director

                                       Address: c/o Tudor Investment Corporation
                                                50 Rowes Wharf, 6th Floor
                                                Boston, MA 02110

                                       With a copy to (which shall not be
                                       deemed notice for purposes of the
                                       Agreement):
                                       ________________________________
                                       ________________________________
                                       ________________________________

                                       37
<PAGE>

                        [SERIES C HOLDER SIGNATURE PAGE]

      IN WITNESS WHEREOF, the undersigned has executed this Agreement as of the
date first above written.

                                     NAME OF SERIES C HOLDER:

                                     THE TUDOR BVI GLOBAL PORTFOLIO LTD.

                                     By: Tudor Investment Corporation,
                                         Trading Advisor

                                     By: /s/ William T. Flaherty
                                         -------------------------
                                         Name: William T. Flaherty
                                         Title: Managing Director

                                     Address: c/o Tudor Investment Corporation
                                              50 Rowes Wharf, 6th Floor
                                              Boston, MA 02110

                                     With a copy to (which shall not be deemed
                                     notice for purposes of the Agreement):
                                     ________________________________
                                     ________________________________
                                     ________________________________

                                       38
<PAGE>

                        [SERIES C HOLDER SIGNATURE PAGE]

      IN WITNESS WHEREOF, the undersigned has executed this Agreement as of the
date first above written.

                                       NAME OF SERIES C HOLDER:

                                       TUDOR PROPRIETARY TRADING, L.L.C.

                                       By: /s/ William T. Flaherty
                                           -------------------------
                                           Name: William T. Flaherty
                                           Title: Managing Director

                                       Address: 50 Rowes Wharf, 6th Floor
                                                Boston, MA 02110
                                                ______________________

                                       With a copy to (which shall not be
                                       deemed notice for purposes of the
                                       Agreement):
                                       ________________________________
                                       ________________________________
                                       ________________________________

                                       39
<PAGE>

                        [SERIES C HOLDER SIGNATURE PAGE]

      IN WITNESS WHEREOF, the undersigned has executed this Agreement as of the
date first above written.

                                    NAME OF SERIES C HOLDER:

                                    /s/ William C Smith
                                        ---------------------------------------
                                        William C Smith

                                    /s/ Dana Davis Smith
                                        ---------------------------------------
                                        Dana Davis Smith

                                    By: _______________________________________
                                        JOINT TENANTS WITH RIGHT OF SURVIVORSHIP

                                    Address: 218 RIVER PARK DRIVE
                                             GREAT FALLS, VA
                                             22066

                                    With a copy to (which shall not be
                                    deemed notice for purposes of the
                                    Agreement):
                                    ________________________________
                                    ________________________________
                                    ________________________________

                                       40
<PAGE>

                        [SERIES C HOLDER SIGNATURE PAGE]

      IN WITNESS WHEREOF, the undersigned has executed this Agreement as of the
date first above written.

                                   NAME OF SERIES C HOLDER:

                                   THE ALTAR ROCK FUND L.P.

                                   By: Tudor Investment Corporation,
                                       General Partner

                                   By: /s/ William T. Flaherty
                                       -------------------------
                                       Name: William T. Flaherty
                                       Title: Managing Director

                                   Address: c/o Tudor Investment Corporation
                                            50 Rowes Wharf, 6th Floor
                                            Boston, MA 02110

                                   With a copy to (which shall not be deemed
                                   notice for purposes of the Agreement):
                                   ________________________________
                                   ________________________________
                                   ________________________________

                                       41
<PAGE>

                        [SERIES C HOLDER SIGNATURE PAGE]

      IN WITNESS WHEREOF, the undersigned has executed this Agreement as of the
date first above written.

                                   NAME OF SERIES C HOLDER:

                                   Julie R Frank, Trustee

                                   By: /s/ Julie R Frank Revocable Trust
                                       ---------------------------------
                                       Dated August 13, 2001
                                       Name:
                                       Title:

                                   Address: 3 Roclare Lane
                                            St. Louis MO 63131
                                            ___________________

                                   With a copy to (which shall not be deemed
                                   notice for purposes of the Agreement):
                                   _____________________________________
                                   _____________________________________
                                   _____________________________________

                                       42
<PAGE>

                        [SERIES C HOLDER SIGNATURE PAGE]

      IN WITNESS WHEREOF, the undersigned has executed this Agreement as of the
date first above written.

                                   NAME OF SERIES C HOLDER
                                   _______________________

                                   By: /s/ John C. Otsuki
                                       ____________________________
                                       Name: John C. Otsuki
                                       Title:

                                   Address: 4718 MERIVALE RD.
                                            CHEVY CHASE, MARYLAND 21815

                                   With a copy to (which shall not be deemed
                                   notice for purposes of the Agreement):
                                   ________________________________
                                   ________________________________
                                   ________________________________

                                       43
<PAGE>

                        [SERIES C HOLDER SIGNATURE PAGE]

      IN WITNESS WHEREOF, the undersigned has executed this Agreement as of the
date first above written.

                                         NAME OF SERIES C HOLDER:

                                         MedCap Partners L.P.

                                         By: /s/ [ILLEGIBLE]
                                             -------------------------
                                             Name: [ILLEGIBLE]
                                             Title: Managing Member

                                         Address: 500 Third Street, Suite 535
                                                  San Francisco, CA 94107

                                         With a copy to (which shall not be
                                         deemed notice for purposes of the
                                         Agreement):

                                         _____________________________
                                         _____________________________
                                         _____________________________

                                       44

<PAGE>

                        [SERIES C HOLDER SIGNATURE PAGE]

      IN WITNESS WHEREOF, the undersigned has executed this Agreement as of the
date first above written.

                                         NAME OF SERIES C HOLDER:

                                         MedCap Master Fund, L.P.

                                         By: /s/ [ILLEGIBLE]
                                             ----------------------------
                                             Name: [ILLEGIBLE]
                                             Title: Managing Member of the GP

                                         Address: ATC Trustees (Cayman) Limited
                                                  [ILLEGIBLE]
                                                  George Town,
                                                  Grand Cayman,
                                                  Cayman Islands

                                         With a copy to (which shall not be
                                         deemed notice for purposes of the
                                         Agreement):

                                         500 Third Street Suite 535
                                         San Francisco CA 94107

                                       45

<PAGE>

                        [SERIES C HOLDER SIGNATURE PAGE]

      IN WITNESS WHEREOF, the undersigned has executed this Agreement as of the
date first above written.

                                         NAME OF SERIES C HOLDER:

                                         Kenneth Rubin

                                         By: /s/ Kenneth Rubin
                                             ------------------
                                             Name: Individually
                                             Title:

                                         Address: 68 Barbers Point Road
                                                  Sands Point, NY 11050

                                         With a copy to (which shall not be
                                         deemed notice for purposes of the
                                         Agreement):

                                         _________________________
                                         _________________________
                                         _________________________

                                       46

<PAGE>

                        [SERIES C HOLDER SIGNATURE PAGE]

      IN WITNESS WHEREOF, the undersigned has executed this Agreement as of the
date first above written.

                                         NAME OF SERIES C HOLDER:

                                         ________________________

                                         By: /s/ William P. Rice
                                             -------------------------
                                             Name: William P. Rice
                                             Title:

                                         Address: P.O. BOX 1599
                                                  DUXBURY, MA
                                                  02331

                                         With a copy to (which shall not be
                                         deemed notice for purposes of the
                                         Agreement):

                                         _________________________
                                         _________________________
                                         _________________________

                                       47

<PAGE>

                        [SERIES C HOLDER SIGNATURE PAGE]

      IN WITNESS WHEREOF, the undersigned has executed this Agreement as of the
date first above written.

                                         NAME OF SERIES C HOLDER:

                                         JAMES J. GOLL

                                         By: /s/ James J. Goll
                                             -------------------------
                                             Name: JAMES J. GOLL
                                             Title:

                                         Address: 32 Three Wells Lane
                                                  DARIEN, CT 06820
                                                  (203) 656-0228
                                                  jjcg@SBCGLOBAL.NET

                                         With a copy to (which shall not be
                                         deemed notice for purposes of the
                                         Agreement):

                                         _________________________
                                         _________________________
                                         _________________________

                                       48

<PAGE>

                        [SERIES C HOLDER SIGNATURE PAGE]

      IN WITNESS WHEREOF, the undersigned has executed this Agreement as of the
date first above written.

                                         NAME OF SERIES C HOLDER:

                                         _________________________

                                         By: /s/ James M. Hirshberg
                                             -------------------------
                                             Name: JAMES M. HIRSHBERG
                                             Title:

                                         Address: 62 PRINCE ST
                                                  WEST NEWTON, WA 02465

                                         With a copy to (which shall not be
                                         deemed notice for purposes of the
                                         Agreement):

                                         _________________________
                                         _________________________
                                         _________________________

                                       49

<PAGE>

                        [SERIES C HOLDER SIGNATURE PAGE]

      IN WITNESS WHEREOF, the undersigned has executed this Agreement as of the
date first above written.

                                         NAME OF SERIES C HOLDER:

                                         Dana Doe

                                         By: /s/ Dana Doe
                                             -------------------------
                                             Name:
                                             Title:

                                         Address: 12 McCall Rd
                                                  Winchester, MA 01890

                                         With a copy to (which shall not be
                                         deemed notice for purposes of the
                                         Agreement):

                                         _________________________
                                         _________________________
                                         _________________________

                                       50

<PAGE>

                        [SERIES C HOLDER SIGNATURE PAGE]

      IN WITNESS WHEREOF, the undersigned has executed this Agreement as of the
date first above written.

                                         NAME OF SERIES C HOLDER:

                                         _____________________________

                                         By: /s/ Daniel Frank
                                             -------------------------
                                             Name: DANIEL FRANK
                                             Title:

                                         Address: 19 WHALING ROAD
                                                  DARIEN CT
                                                  06820

                                         With a copy to (which shall not be
                                         deemed notice for purposes of the
                                         Agreement):

                                         _________________________
                                         _________________________
                                         _________________________

                                       51

<PAGE>

                        [SERIES B HOLDER SIGNATURE PAGE]

      IN WITNESS WHEREOF, the undersigned has executed this Agreement as of the
date first above written.

                                         NAME OF SERIES B HOLDER:

                                         CERBERUS PARTNERS, L.P.
                                         ------------------------------------
                                         By: Cerberus Associates, LLC,
                                             its General Partner

                                         By: /s/ [ILLEGIBLE]
                                             --------------------------------
                                             Name: [ILLEGIBLE]
                                             Title: Managing Director

                                         Address: 299 Park Avenue, 22nd floor
                                                  ----------------------------
                                                  New York, NY 10171
                                                  ----------------------------

                                                  ----------------------------

                                         With a copy to (which shall not be
                                         deemed notice for purposes of the
                                         Agreement):

                                         Lowenstein Sandler PC
                                         -------------------------------------
                                         65 Livingston Avenue
                                         -------------------------------------
                                         Roseland, NJ 07068
                                         -------------------------------------
                                         Attn: Robert G. Miman, Esq.
                                         -------------------------------------
                                         Fax: (973)597-2400
                                         -------------------------------------

                                       52
<PAGE>

                        [SERIES B HOLDER SIGNATURE PAGE]

      IN WITNESS WHEREOF, the undersigned has executed this Agreement as of the
date first above written.

                                         NAME OF SERIES B HOLDER:

                                         FREDERICK FRANK

                                         By: /s/ Frederick Frank
                                             -------------------------
                                             Name:
                                             Title:

                                         Address: 109 East 91st Street
                                                  New York, New York 10128

                                          With a copy to (which shall not be
                                          deemed notice for purposes of the
                                          Agreement):

                                          _________________________
                                          _________________________
                                          _________________________

                                       53
<PAGE>

                        [SERIES B HOLDER SIGNATURE PAGE]

      IN WITNESS WHEREOF, The undersigned has executed this Agreement as of the
date first above written.

                                          NAME OF SERIES B HOLDER:

                                          MEYTHALER INVESTMENT PARTNERS, LLC

                                          By: /s/ L. Charles Meythaler
                                              --------------------------------
                                              Name: L. Charles Meythaler
                                              Title: Managing Shareholder

                                          Address: 399 Wahackme  Road
                                                   New Canaan ,CT 06840

                                          With a copy to (which shall not be
                                          deemed notice for purposes of the
                                          Agreement):

                                          ____________________________________
                                          ____________________________________
                                          ____________________________________

                                       54
<PAGE>

                        [SERIES B HOLDER SIGNATURE PAGE]

      IN WITNESS WHEREOF, THE undersigned has executed this Agreement as of the
date first above written.

                                          NAME OF SERIES B HOLDER:

                                          ____________________________________

                                          By: /s/ Gerald Izzi MD
                                              --------------------------------
                                              Name: Gerald Izzi
                                              Title:

                                          Address: 156 Ivy ST
                                                   BROOKLING MA 02446

                                          With a copy to (which shall not be
                                          deemed notice for purposes of the
                                          Agreement):

                                          ____________________________________
                                          ____________________________________
                                          ____________________________________

                                       55
<PAGE>

                        [SERIES B HOLDER SIGNATURE PAGE]

      IN WITNESS WHEREOF, the undersigned has executed this Agreement as of the
date first above written.

                                          NAME OF SERIES B HOLDER:

                                          ____________________________________

                                          By: /s/ Ines Capelli
                                              --------------------------------
                                              Name:
                                              Title:

                                          Address: 104 Marlborough St
                                                   Boston, MA 02116

                                          With a copy to (which shall not be
                                          deemed notice for purposes of the
                                          Agreement):

                                          ____________________________________
                                          ____________________________________
                                          ____________________________________

                                       56
<PAGE>

                        [SERIES B HOLDER SIGNATURE PAGE]

      IN WITNESS WHEREOF, the undersigned has executed this Agreement as of the
date first above written.

                                          NAME OF SERIES B HOLDER:

                                          ____________________________________

                                          By: /s/ John C. Otsuki
                                              --------------------------------
                                              Name: JOHN C Otsuki
                                              Title:

                                          Address: 4718 MERIVALE RD.
                                                   CHEVY CHASE, MD 20815

                                          With a copy to (which shall not be
                                          deemed notice for purposes of the
                                          Agreement):

                                          ____________________________________
                                          ____________________________________
                                          ____________________________________

                                       57
<PAGE>

                        [SERIES A HOLDER SIGNATURE PAGE]

      IN WITNESS WHEREOF, the undersigned has executed this Agreement as of the
date first above written.

                                          NAME OF SERIES A HOLDER:

                                          ____________________________________

                                          By: /s/ Kevin Maresca
                                              --------------------------------
                                              Name: Kevin Maresca
                                              Title:

                                          Address: 13 Bailey Rd
                                                   Tewksbury, MA 01876

                                          With a copy to (which shall not be
                                          deemed notice for purposes of the
                                          Agreement):
                                          ____________________________________
                                          ____________________________________
                                          ____________________________________

                                       58

<PAGE>

                        [SERIES A HOLDER SIGNATURE PAGE]

      IN WITNESS WHEREOF, the undersigned has executed this Agreement as of the
date first above written.

                                          NAME OF SERIES A HOLDER:

                                          ____________________________________

                                          By: /s/ John C. Otsuki
                                              --------------------------------
                                              Name: JOHN C. OTSUKI
                                              Title:

                                          Address: 4718 MERIVALE RD.
                                                   CHEVY CHASE, MD 20815

                                          With a copy to (which shall not be
                                          deemed notice for purposes of the
                                          Agreement):

                                          ____________________________________
                                          ____________________________________
                                          ____________________________________

                                       59
<PAGE>

                        [SERIES A HOLDER SIGNATURE PAGE]

      IN WITNESS WHEREOF, the undersigned has executed this Agreement as of the
first date above written.

                                          NAME OF SERIES A HOLDER:

                                          MEYTHALER INVESTMENT PARTNERS, LLC

                                          By: /s/ L. Charles Meythaler
                                              --------------------------------
                                              Name: L. Charles Meythaler
                                              Title: Managing Shareholder

                                          Address: 399 Wahackme Road
                                                   New Canaan, CT 06840

                                          With a copy to (which shall not be
                                          deemed notice for purposes of the
                                          Agreement):

                                          ____________________________________
                                          ____________________________________
                                          ____________________________________

                                       60
<PAGE>

                        [SERIES A HOLDER SIGNATURE PAGE]

      IN WITNESS WHEREOF, the undersigned has executed this Agreement as of
the date first above written.

                                          NAME OF SERIES A HOLDER:

                                          OKJIN KIM

                                          By: /s/ Okjin Kim
                                              --------------------------------
                                              Name:
                                              Title:

                                          Address:____________________________
                                                  ____________________________
                                                  ____________________________

                                          With a copy to (which shall not be
                                          deemed notice for purposes of the
                                          Agreement):

                                          ____________________________________
                                          ____________________________________
                                          ____________________________________

                                       61
<PAGE>

                        [SERIES A HOLDER SIGNATURE PAGE]

      IN WITNESS WHEREOF, the undersigned has executed this Agreement as of
the date first above written.

                                          NAME OF SERIES A HOLDER:

                                          ANN BARLOW

                                          By: /s/ Ann Barlow
                                              --------------------------------
                                              Name:
                                              Title:

                                          Address:____________________________
                                                  ____________________________
                                                  ____________________________

                                          With a copy to (which shall not be
                                          deemed notice for purposes of the
                                          Agreement):

                                          ____________________________________
                                          ____________________________________
                                          ____________________________________

                                       62
<PAGE>

                        [SERIES A HOLDER SIGNATURE PAGE]

      IN WITNESS WHEREOF, the undersigned has executed this Agreement as of the
date first above written.

                                          NAME OF SERIES A HOLDER:

                                          ____________________________________

                                          By: /s/ John F. Brennan
                                                  Deborah L. Brennan
                                              --------------------------------
                                              Name: John F. Brennan or
                                                    Deborah L. Brennan
                                              Title: [ILLEGIBLE]

                                          Address:  477 Far Reach Rd.
                                                    Westwood, MA 02090

                                          With a copy to (which shall not be
                                          deemed notice for purposes of the
                                          Agreement):

                                          ____________________________________
                                          ____________________________________
                                          ____________________________________

                                       63
<PAGE>

                        [SERIES A HOLDER SIGNATURE PAGE]

     IN WITNESS WHEREOF, the undersigned has executed this Agreement as of the
date first above written.

                                         NAME OF SERIES A HOLDER:
                                         ____________________________

                                         By: Jack L. Barlow
                                             ------------------------
                                             Name:  Jack L. Barlow
                                             Title: Stockholder

                                         Address: 48 COVE ST.
                                                  -------------------
                                                  DUXBURY, MA 02332
                                                  -------------------

                                         With a copy to (which shall not be
                                         deemed notice for purposes of the
                                         Agreement):

                                         ____________________________
                                         ____________________________
                                         ____________________________

                                       64

<PAGE>

                        [SERIES A HOLDER SIGNATURE PAGE]

     IN WITNESS WHEREOF, the undersigned has executed this Agreement as of the
date first above written.

                                         NAME OF SERIES A HOLDER:

                                         POITRAS, JAMES W. & PATRICIA
                                         T., JTWROS

/s/ [ILLEGIBLE]                          By: /s/ James W. Poitras
---------------------------                  ------------------------
Patricia T. Poitras                          Name: James W. Poitras
                                             Title:

BOTH AS INDIVIDUALS AND AS
TRUSTEES OF THEIR RESPECTIVE             Address:   M/M JAMES W. POITRAS
REVOCABLE TRUST                                     --------------------------
                                                    3100 SPRINGHEAD COURT
                                                    --------------------------
                                                    NARCOOSSEE FL 34771-8554
                                                    --------------------------

                                         With a copy to (which shall not be
                                         deemed notice for purposes of the
                                         Agreement):

                                         ____________________________
                                         ____________________________
                                         ____________________________

                                      65

<PAGE>

                       [COMMON STOCKHOLDER SIGNATURE PAGE]

     IN WITNESS WHEREOF, the undersigned has executed this Agreement as of the
date first above written.

                                         NAME OF COMMON STOCKHOLDER:

                                         MICHAEL C. DEUTSCH

                                         By: /s/ MICHAEL C. DEUTSCH
                                             ------------------------
                                             Name: MICHAEL C. DEUTSCH
                                             Title:

                                         Address: 331 MADISON AVE., Fl. 3
                                                  ________________________
                                                  NEW YORK, NY 10017
                                                  ________________________

                                                  ________________________

                                         With a copy to (which shall not be
                                         deemed notice for purposes of the
                                         Agreement):

                                         ____________________________
                                         ____________________________
                                         ____________________________

                                       66

<PAGE>

                       [COMMON STOCKHOLDER SIGNATURE PAGE]

     IN WITNESS WHEREOF, the undersigned has executed this Agreement as of the
date first above written.

                                         NAME OF COMMON STOCKHOLDER:

                                         JOHN D. SINGER
                                         ----------------------------

                                         By: /s/ John D. Singer
                                             ------------------------
                                             Name: JOHN D. SINGER
                                             Title:

                                         Address:  331 Madison Ave., F1. 3
                                                   -----------------------
                                                   New York, NY 10017
                                                   -----------------------
                                                   -----------------------

                                         With a copy to (which shall not be
                                         deemed notice for purposes of the
                                         Agreement):

                                         ---------------------------------
                                         ---------------------------------
                                         ---------------------------------

                                       67

<PAGE>

                       [COMMON STOCKHOLDER SIGNATURE PAGE]

     IN WITNESS WHEREOF, the undersigned has executed this Agreement as of the
date first above written.

                                         NAME OF COMMON STOCKHOLDER:

                                         POITRAS, JAMES W. & PATRICIA
                                         T., JTWROS

/s/ Patricia T. Poitras                  By: /s/ James W. Poitras
--------------------------                   ------------------------
Patricia T. Poitras                          Name: James W. Poitras
                                             Title:

BOTH AS INDIVIDUALS AND AS               Address:  M/M JAMES W. POITRAS
TRUSTEES OF THEIR RESPECTIVE                       ------------------------
REVOCABLE TRUST                                    3100 SPRINGHEAD COURT
                                                   ------------------------
                                                   NARCOOSSEE FL 34771-8554
                                                   ------------------------

                                         With a copy to (which shall not be
                                         deemed notice for purposes of the
                                         Agreement):

                                         ----------------------------------
                                         ----------------------------------
                                         ----------------------------------

                                       68

<PAGE>

                       [COMMON STOCKHOLDER SIGNATURE PAGE]

     IN WITNESS WHEREOF, the undersigned has executed this Agreement as of the
date first above written.

                                         NAME OF COMMON STOCKHOLDER:

                                         ANN BARLOW

                                         By: /s/ Ann Barlow
                                             ------------------------
                                             Name:
                                             Title:

                                         Address:____________________
                                                 ____________________
                                                 ____________________

                                         With a copy to (which shall not be
                                         deemed notice for purposes of the
                                         Agreement):

                                         ____________________________
                                         ____________________________
                                         ____________________________

                                       69

<PAGE>

                       [COMMON STOCKHOLDER SIGNATURE PAGE)

     IN WITNESS WHEREOF, the undersigned has executed this Agreement as of the
date first above written.

                                         NAME OF COMMON STOCKHOLDER:

                                         PHILLIP S. MAGIERA

                                         By: /s/ Phillip S. Magiera
                                             ------------------------
                                             Name: Phillip S. Magiera
                                             Title: Shareholder

                                         Address: 20 Strawberry Hill St.
                                                  ------------------------
                                                  Dover, MA 02030
                                                  ------------------------

                                                  ------------------------

                                         With a copy to (which shall not be
                                         deemed notice for purposes of the
                                         Agreement):

                                         ____________________________
                                         ____________________________
                                         ____________________________

                                       70
<PAGE>

                       [COMMON STOCKHOLDER SIGNATURE PAGE]

     IN WITNESS WHEREOF, the undersigned has executed this Agreement as of the
date first above written.

                                         NAME OF COMMON STOCKHOLDER:

                                         MEYTHALER INVESTORS, LLC

                                         By: /s/ L. Charles Meythaler
                                             ------------------------
                                             Name: L. Charles Meythaler
                                             Title: Manager

                                         ADDRESS: 399 Wahackme Road
                                                  New Canaan, CT 06840

                                         With a copy to (which shall not be
                                         deemed notice for purposes of the
                                         Agreement):

                                         ____________________________
                                         ____________________________
                                         ____________________________

                                       71

<PAGE>

                       [COMMON STOCKHOLDER SIGNATURE PAGE)

     IN WITNESS WHEREOF, the undersigned has executed this Agreement as of the
date first above written.

                                         NAME OF COMMON STOCKHOLDER:

                                         ____________________________

                                         By: /s/ Jack Barlow
                                             ------------------------
                                              Name: Jack Barlow
                                              Title: Stockholder

                                         Address: 48 COVE St.
                                                  DUXBURY, MA 02332

                                         With a copy to (which shall not be
                                         deemed notice for purposes of the
                                         Agreement);

                                         ____________________________
                                         ____________________________
                                         ____________________________

                                       72<PAGE>
                                                                    Exhibit 10.6

               GREENWORKS MOLECULAR INSIGHT PHARMACEUTICALS LEASE

1.   DATE OF LEASE: June 19, 2003

2.   LANDLORD: RayJoe Limited Partnership, a Massachusetts limited partnership,
     which expression shall include its heirs, executors, administrators,
     successors and assigns.

2A.  LANDLORD'S ADDRESS: c/o Gravestar, Inc., One Broadway, Cambridge, MA 02142

3.   TENANT: MOLECULAR INSIGHT PHARMACEUTICALS, INC., which expression shall
     include its heirs, executors, administrators, successors and assigns.
     Please note that Tenant was formerly known as Biostream, Inc.

3A.  TENANT'S ADDRESS: Greenworks Building, 160 Second Street, Cambridge,
     Massachusetts 02142

4.   DEMISED PREMISES: Landlord hereby leases to Tenant and Tenant hereby leases
     from Landlord, upon and subject to the terms and provisions of this Lease,
     Office Space containing approximately 3,064 rentable square feet of floor
     area, and Laboratory Space containing approximately 1,481 rentable square
     feet of floor area all as more fully shown on EXHIBIT E, attached hereto,
     located in the Greenworks Building, 160 Second Street, Cambridge,
     Massachusetts ("Property"), together with the right to use in common with
     others entitled thereto, the hallways, stairways and elevator (if any)
     necessary for access to the Demised Premises, and lavatories nearest
     thereto, if there is no lavatory within the Demised Premises.

4A.  ACCEPTANCE OF DEMISED PREMISES: Tenant agrees that no representations or
     warranties respecting the condition of the Demised Premises and no promises
     to alter, repair or improve the Demised Premises have been made by
     Landlord, except as expressly provided for in this Lease. Tenant occupies
     office and laboratory space at the Greenworks Building under previous
     leases for office and laboratory spaces dated May 15, 1998, as amended,
     scheduled to terminate on June 30, 2003.

4B.  LABORATORY RELOCATION WORK: Landlord and Tenant agree to relocate Tenant's
     Third Floor laboratory space located in Unit #28 and Second Floor
     laboratory space located in Unit #20 to the New Laboratory Space on the
     Second Floor, Units #14, #15 and #20 pursuant to the Biostream Relocation
     Project Scope Summary, Design Build Specification, Electrical
     Specification, Equipment List, and Cavanaugh Tocci and Plumbing Permit
     Letters shown on EXHIBIT B, and Plans D.1.1, A.1.1 and A.6.1, dated May
     6, 2003 shown on EXHIBIT C, known in the aggregate as the Laboratory
     Relocation Work.

4C.  LABORATORY RELOCATION SCHEDULE: Landlord and Tenant agree to the proposed
     Laboratory Relocation Schedule provided by Marc Truant and Associates,
     dated May 2, 2003 as shown on EXHIBIT D. Landlord and Tenant agree that the
     attached Laboratory Relocation Schedule is provided as the most current and
     viable estimate for the Laboratory Relocation Work. Landlord and Tenant
     agree that neither Landlord, Gravestar, Inc., Marc Truant and Associates as
     Landlord's Contractor, nor Jennifer Pinck as Landlord's

                                                      GREENWORKS MOLECULAR LEASE

                                      -1-

<PAGE>

     Project Manager will assume any responsibility, financial or otherwise, for
     any delays in the Laboratory Relocation Schedule. Good faith efforts will
     be used to accommodate Tenant's needs in the event of unforeseen delays to
     the Laboratory Relocation Schedule. Biostream Inc, as Tenant is solely
     responsible for obtaining any and all permits and approvals for the
     operation of its laboratory(ies). Marc Truant and Associates, under
     contractual obligation with Landlord to provide pre-construction and
     construction services, is responsible for obtaining the local building
     permit required to execute the Laboratory Relocation Work and providing the
     local certificate of occupancy.

4D.  LABORATORY RELOCATION COST: Landlord and Tenant agree to share the cost of
     the Laboratory Relocation Work as shown on EXHIBIT A, as follows:

     1.   The GMP Contract between Landlord and Marc Truant and Associates
          estimates the cost of the Laboratory Relocation Work at $327,426. The
          GMP Contract Summary includes an itemized list of additional work to
          be performed for the benefit of Tenant in the amount of $19,800, which
          falls outside of the scope of the original agreed-upon relocation
          work.

     2.   Landlord agrees to pay 66.7% (2/3) of the final cost of the Laboratory
          Relocation Work minus the additional work to be performed for the
          benefit of Tenant (($327,426 - $19,800) x 0.667). Thus, Landlord's
          contribution is estimated at $205,186.54.

     3.   Tenant agrees to pay 33.3% (1/3) of the final cost of the original
          agreed-upon relocation work plus the additional work to be performed
          for the benefit of Tenant (($307,626 x 0.333) + $19,800). Thus,
          Tenant's contribution is estimated at $122,239.46.

     4.   Landlord and Tenant agree to share any net cost savings that may
          accrue from the GMP Contract estimate proportionately. Thus, Landlord
          will receive 66.7% and Tenant will receive 33.3% of any resulting net
          cost savings.

5.   LEASE TERM: Five (5) Lease Years.

5A.  COMMENCEMENT DATE: July 1, 2003, subject to the following exception:
     Pursuant to the New Laboratory Space on the Second Floor, if the Laboratory
     Relocation Work is completed prior to July 1, 2003 and Tenant is in
     physical possession of the New Laboratory Space on the Second Floor, all
     provisions of this Lease will apply to said New Laboratory Space on the
     Second Floor, except for the payment of rent, tax and operating expenses
     charges, which shall be governed by the provisions of the previous
     laboratory Lease (dated May 15, 1998, as amended), until June 30, 2003.

5B.  TERMINATION DATE: June 30, 2008

6.   PERMITTED USE: Tenant shall use the portions of the Demised Premises listed
     under Exhibit E, as Office Space solely and exclusively for the purpose of
     general offices and Laboratory Space solely and exclusively for the purpose
     of laboratory uses in conformance with the provisions of this Lease and in
     compliance with all applicable laws and regulations, including
     environmental laws, regulations, ordinances, orders and standards.

                                                      GREENWORKS MOLECULAR LEASE

                                      -2-

<PAGE>

7. RENT:

<TABLE>
<CAPTION>
                             Dates:          Yearly Rent:   Monthly Rent:      Rent psf.
                             ------          ------------   -------------      ---------
<S>                   <C>                    <C>            <C>                <C>
Office Space:         7/1/03 to 6/30/08       $79,668.00      $6,639.00         $26.00
Laboratory Space:     7/1/03 to 6/30/08       $44,430.00      $3,702.50         $30.00
</TABLE>

     Tenant agrees to pay rent to Landlord in monthly installments, in advance,
     on the first day of each and every month during the Lease Term.

7A.  PARKING CHARGE: Tenant agrees to pay $500.00 per month for the use of Five
     (5) assigned parking space(s) within the Property. Landlord, at its sole
     discretion, reserves the right to increase its parking charges in the
     future to adjust to market conditions. Said increase becomes effective upon
     30-day advance written notice to Tenant.

8.   SECURITY DEPOSIT: A Security Deposit in the amount of $5,248.75 is
     currently held by Landlord under the previous Lease, as security for the
     punctual performance of each and every obligation under the Lease. The
     Security Deposit will be refunded to Tenant within sixty (60) days after
     the end of the Lease Term without interest, subject to the Tenant's
     satisfactory compliance with the terms of the Lease.

9.   TAX CHARGE: Tenant shall pay to Landlord as additional rent hereunder,
     21.5% of real estate taxes charged to the land and buildings of which the
     Demised Premises are a part of, for each Lease Year. Tenant's Tax charge of
     14.5% in relation to the Office Space will be computed in excess of real
     estate taxes assessed for fiscal year 2003. Tenant's Tax Charge of 7% in
     relation to the Laboratory Space will be computed by multiplying the real
     estate taxes by 7%, without any initial tax base. Tenant shall make
     estimated monthly payments based upon reasonable projections made by
     Landlord, adjusted as needed. When the actual annual Tax liability is
     known, Landlord will promptly issue a written statement and refund any
     overpayment to Tenant or request Tenant to pay any underpayment balance.
     Tenant will pay any underpayment within 30 days after receipt of Landlord's
     statement.

10.  OPERATING EXPENSES CHARGE: Tenant shall pay to Landlord as additional rent
     hereunder, 21.5% of all costs and expenses incurred by Landlord for each
     Lease Year in connection with the operation and maintenance of the land and
     buildings of which the Demised Premises are a part of. Tenant's Operating
     Expenses Charge of 14.5% in relation to the Office Space will be computed
     in excess of actual operating expenses for the calendar year 2003. Tenant's
     Operating Expenses Charge of 7% in relation to the Laboratory Space will be
     computed by multiplying the actual operating expenses by 7%, without any
     initial operating expenses base. Tenant shall make estimated monthly
     payments based upon reasonable projections made by Landlord, adjusted as
     needed. Within 90 days after the end of each calendar year during the Lease
     Term, Landlord will issue a written statement of actual annual operating
     expenses and refund any overpayment to Tenant or request Tenant to pay any
     underpayment balance. Tenant will pay any underpayment within 30 days after
     receipt of Landlord's statement.

11.  LATE PAYMENTS: Any installment of Rent, additional rent and any other
     required payment not paid by Tenant within ten (10) days after the due
     date, shall bear a late charge until paid, equal to the lesser of 1.5% of
     the amount due for each month or the highest rate permitted by law.

                                                      GREENWORKS MOLECULAR LEASE

                                       -3-

<PAGE>

12.  TENANT'S WORK: Upon the prior written consent of Landlord, Tenant shall, at
     its own expense, complete any work in and to the Demised Premises, in a
     good and workmanlike manner with materials of the highest quality, without
     interference to other work or businesses within the Greenworks Building,
     and in compliance with the terms of this Lease and all applicable laws,
     codes, ordinances and regulations. Landlord reserves the right, upon
     twenty-four (24) hours written notice to Tenant, to order Tenant to cease
     any and all Tenant's Work, if such work appears to cause disharmony, does
     not comply with union work rules applicable at the Property or interferes
     with the orderly operation of the other Tenants within the Property.
     Tenant's Work shall be performed only in accordance with applicable rules
     and regulations contained in the Greenworks Policy Manual and complete
     plans and specifications submitted to and approved in advance by Landlord.

13.  TENANT COVENANTS & OBLIGATIONS: Tenant agrees to conform to the following
     provisions during the Lease Term:

     (a) Tenant will conform and abide to the rules and regulations contained in
     the Greenworks Policy Manual, attached as EXHIBIT F. Landlord may, from
     time to time, amend the Greenworks Policy Manual, effective upon advance
     written notice to Tenant.

     (b) Tenant will not make any alterations, improvements and/or additions to
     the Demised Premises without the advance written consent of Landlord, not
     to be unreasonably withheld. Any consent request will include such plans,
     specifications and details as Landlord may reasonably request.

     (c) Tenant agrees to maintain the Demised Premises in a clean, safe and
     sanitary condition in accordance with all applicable federal, state and
     local laws, codes, ordinances and regulations. Tenant shall not permit or
     commit any waste.

     (d) Tenant agrees to reimburse Landlord for the cost of replacement light
     bulbs and ballasts for fluorescent light fixtures within the Demised
     Premises.

     (e) Tenant agrees to obtain prior written consent from Landlord before the
     installation of any signage visible from the outside of the Demised
     Premises.

     (f) Tenant agrees not to perform or conduct any act or practice which may
     injure the Demised Premises or the property, or which is unlawful,
     improper, noisy, offensive or in any manner contrary to all applicable
     federal, state and local laws, codes, ordinances and regulations.

     (g) Tenant agrees not to do any spray painting within the Demised Premises.

     (h) Tenant agrees not to allow any mechanics' liens or other similar liens
     to be placed upon the Property, as a result of any work related to Tenant
     or its Demised Premises. Tenant will immediately cause any such liens to be
     released of record, at its sole expense.

     (i) Tenant agrees to periodically shampoo and/or wax any carpeting and/or
     tiled flooring within the Demised Premises, as needed to maintain them in a
     clean and good operating condition.

14.  LANDLORD'S RIGHT TO CHANGE THE PROPERTY: Landlord reserves the right (but
     not any obligation), from time to time, to alter, replace, construct, raze
     or otherwise modify any buildings, structures, improvements, systems,
     equipment, signs, or any other features within the Property, provided it
     does not permanently interfere with Tenant's right to use the Demised
     Premises.

                                                      GREENWORKS MOLECULAR LEASE

                                      -4-
<PAGE>

15.  LANDLORD'S ACCESS: Landlord and its designees, shall have the right (but
     not any obligation) at all times, upon reasonable advance notice to Tenant,
     to enter upon the Demised Premises for the purpose of inspecting or
     performing routine maintenance or repairs, or for any other reasonable
     purpose, as determined by Landlord. No advance notice will be required in
     the event of emergencies.

16.  LANDLORD'S MAINTENANCE & REPAIR OBLIGATIONS: Landlord agrees to keep in the
     same good order, condition and repair, as at present, less reasonable wear
     and tear, the roof, and the exterior face and structural portions of the
     Demised Premises. Landlord's obligations do not apply to damage caused by
     fire, other insured casualty or condemnation. Landlord shall not be
     responsible to repair or restore any damage caused by any act, omission or
     negligence of Tenant, its employees, agents, licensees, invitees or
     contractors, and Tenant shall bear the entire cost of such damage.

16A. CLEANING: Landlord agrees to empty customary office-type waste baskets on
     each business day, vacuum at least once per week and clean windows twice
     per year.

17.  TENANT'S INSURANCE: Tenant agrees to pay for and maintain in full force
     during the Lease Term, a policy of comprehensive general liability
     insurance for personal injury and property damage on an occurrence basis,
     under which the Landlord or others as may be set out in written notice by
     landlord to Tenant, from time to time, are named as additional insureds.
     Each policy will be written by a company(ies) licensed to do business in
     Massachusetts and rated A-VIII or higher by A.M. Best's Rating Agency and
     will be non-cancelable without at least thirty (30) days' prior written
     notice to Landlord. The minimum limits of liability of such insurance shall
     be not less than $1,000,000, combined single limit for personal injury and
     death, and for property damage arising out of any one incident or disaster.
     Tenant shall provide Landlord with evidence of full coverage prior to
     Tenant's occupancy. Tenant will provide Landlord with a renewed Certificate
     of Insurance, thirty (30) days prior to the expiration of the current
     policy.

17A. TENANT'S PROPERTY INSURANCE: Tenant shall keep its fixtures, equipment,
     furniture and other personal property insured against loss or damage by
     fire with the usual extended coverage endorsements. Tenant assumes all risk
     of damage or loss to its own property arising from any cause, including
     theft.

17B. INCREASE IN INSURANCE RATES: Tenant agrees that it will not use, do or
     permit anything to be done in or upon the Demised Premises, which makes
     voidable or increases the rate of insurance on the property or any part
     thereof, and agrees to pay for any increase which may arise from such use
     or action.

17C. INDEMNIFICATION: Tenant agrees to indemnify and save harmless Landlord from
     and against all claims, actions or damages of whatever nature arising from
     any act, omission or negligence of the Tenant or Tenant's contractors,
     licensees, invitees, agents, servants or employees, on or about the Demised
     Premises or Property, during the Lease Term. Landlord agrees to indemnify
     and save harmless Tenant from and against all claims, actions or damages of
     whatever nature arising from any act, omission or negligence of the
     Landlord or Landlord's contractors, licensees, invitees, agents, servants
     or employees, on or about the Demised Premises, during the Lease Term.

                                                      GREENWORKS MOLECULAR LEASE

                                      -5-
<PAGE>

18.  UTILITIES: Landlord will provide and maintain all utilities serving the
     Demised Premises. Landlord reserves the right to place and maintain within
     the Demised Premises utility lines, pipes, fixtures, conduits and the like
     to serve the Demised Premises and other premises. Landlord shall not be
     liable to Tenant in damages or otherwise for any interruption, curtailment
     or suspension of any utility services. Tenant agrees to install, maintain
     and pay for all expenses associated with telephone and internet services.

19.  ASSIGNMENT AND SUBLETTING: Tenant may not assign this Lease or sublet the
     Demised Premises without Landlord's prior written approval, not to be
     unreasonably withheld. Notwithstanding any consent, Tenant shall remain
     liable to Landlord for the payment of all rents and for the full
     performance of the terms of this Lease.

20.  FIRE, CASUALTY AND EMINENT DOMAIN: Landlord may elect to terminate this
     Lease if the Demised Premises or the Property are substantially damaged by
     fire, other casualty or taken by condemnation or the right to eminent
     domain. Landlord's obligation to repair and restore in the event of partial
     damage by fire or other casualty is limited by the actual net amount of
     insurance proceeds. Tenant may elect to terminate this Lease if Landlord
     fails to give written notice within thirty (30) days after the event, of
     its intention to restore the Demised Premises or Landlord fails to restore
     the Demised Premises to a condition reasonably suited for its intended use
     within ninety (90) days after said event. Landlord will provide Tenant with
     a just and proportionate abatement of rent during the time the Demised
     Premises remain substantially unsuitable for their intended use. Landlord
     reserves and Tenant assigns to Landlord all rights which Tenant may have
     for damages or injury to the Demised Premises for any condemnations or
     takings by eminent domain.

21.  SURRENDER OF PREMISES: Upon the expiration or sooner termination of this
     Lease, Tenant shall remove all Tenant's equipment, furniture and other
     personal property and surrender the Demised Premises in good and tenantable
     order and repair and in good operating condition, except for ordinary wear
     and tear. If Tenant fails to surrender the premises as required, Landlord
     may retain or dispose of Tenant's property or restore the premises, all at
     Tenant's expense. Any fixtures or other improvements installed by Landlord
     or Tenant remain Landlord's property and should not be removed by Tenant
     without Landlord's prior written consent.

21A. HOLDOVER BY TENANT: If Tenant remains in possession, after the expiration
     or sooner termination of this Lease without an executed renewal, this Lease
     becomes a month to month tenancy, at a monthly rental equal to two hundred
     (200%) percent of the rent payable during the last month of the Lease Term,
     subject to all other charges and terms contained in this Lease.

22.  ENVIRONMENTAL MATTERS: Tenant agrees not to use, store, generate,
     manufacture, process or dispose of (or suffer or permit the use, storage,
     generating, manufacturing, processing or disposal of) oil, grease,
     chemical, hazardous, toxic or dangerous materials, substances or waste at
     or around the Demised Premises, Property or within any pipes, conduits,
     drains, mains or ducts or into any septic, sewer, drainage or other
     systems, except for materials used in Tenant's Laboratory Space solely and
     exclusively for the purpose of

                                                      GREENWORKS MOLECULAR LEASE

                                      -6-
<PAGE>

     laboratory uses in conformance with the provisions of this Lease and
     stored, used and disposed in strict compliance with all applicable laws and
     regulations, including environmental laws, regulations, ordinances, orders
     and standards. Tenant shall at all times comply with all applicable
     federal, state and local environmental laws, ordinances, orders or
     regulations now or hereafter affecting or applicable to the Demised
     Premises or Property. Tenant agrees to indemnify, defend, save and hold
     harmless Landlord from all claims, actions, liens, demands, costs,
     expenses, fines and judgments resulting from any spills or contamination of
     any kind caused by the acts or omissions of Tenant or its agents,
     employees, licensees, servants or contractors or any other violation of
     applicable environmental laws or this Provision of this Lease. Tenant
     agrees to pay all costs associated with the evaluation and remediation of
     any environmental matter and enforcement of this Environmental Provision
     including any reasonable engineering, consulting or legal fees and
     expenses. Landlord reserves the right to request Tenant to provide data,
     specifications and professional opinions in connection with any
     environmental concern related to Tenant or the Demised Premises.

23.  SUBORDINATION: Tenant's rights under this Lease shall be subject and
     subordinate to any mortgages or deeds of trust or other instruments in the
     nature of a mortgage or lien on the Property and Tenant, upon request,
     shall promptly execute and deliver any written instrument necessary to show
     the subordination of this Lease.

24.  EVENTS OF DEFAULT: In the event that: (a) Tenant shall default in the
     payment of rent or any other payments and such default shall continue for
     ten (10) days; or (b) Tenant shall default in the performance of any
     covenant or obligation under the terms of this Lease and such default shall
     not be corrected within fifteen (15) days after written notice thereof; or
     (c) Tenant shall be declared bankrupt or insolvent according to law, or, if
     any assignment shall be made of Tenant's property for the benefit of
     creditors, then:

     Landlord shall have the right at any time thereafter, while such default
     continues, to re-enter the Demised Premises and take complete possession,
     to declare the term of this Lease ended, and remove the Tenant's effects,
     without prejudice to any other remedies that might be otherwise used for
     unpaid rents or other defaults. Tenant shall indemnify Landlord against
     loss of rent and other payments that the Landlord may incur by reason of
     such termination during the remainder of the Lease Term.

     In the event that Tenant shall default in the performance of any covenant
     or obligation under the terms of this Lease, excluding non-payment of rent
     or other charges, and such default shall not be corrected within fifteen
     (15) days after written notice thereof, Landlord may (but is not obligated
     to do so) remedy such default at the expense of Tenant, to be paid as
     additional rent.

     Failure by Landlord to complain of any action or non-action on the part of
     Tenant, no matter how long or frequent the same may continue, shall never
     be deemed to be a waiver by Landlord of any rights hereunder.

25.  NO BROKERAGE: Landlord and Tenant warrant and represent that they have had
     no contact or dealings with any broker or any person or entity intending to
     claim a commission, in connection with this Lease or the Demised Premises.

                                                      GREENWORKS MOLECULAR LEASE

                                      -7-
<PAGE>

26.  LIMITATION OF LIABILITY: Landlord shall not be liable to Tenant for any
     failure to perform its obligations under the terms of this Lease due to any
     cause beyond Landlord's reasonable control or caused by an act or neglect
     of Tenant or its servants, agents, employees or licensees. Landlord shall
     never be liable to Tenant for any indirect or consequential damages. No
     trustee, beneficiary, agent, employee, officer or partner of Landlord, nor
     any person, firm or entity having an interest in Landlord, shall ever be
     personally liable for any performance of Landlord's obligations under this
     Lease or any related judgments. Landlord's obligations are limited to the
     provisions of this Lease, during its ownership interest in the Property and
     are not binding upon any other assets held by Landlord.

27.  NOTICES: Any notice required under the terms of this Lease shall be in
     writing and shall be hand-delivered or sent to Landlord at Landlord's
     Address and to Tenant at Tenant's Address. Notice shall be sent by
     registered or certified mail, return receipt requested, postage prepaid or
     by a recognized national courier that maintains records of delivery, such
     as Federal Express. Notice shall be deemed given when received, refused or
     tendered for delivery, provided it is correctly addressed.

28.  AUTHORIZATION: The person signing this Lease on behalf of Tenant by virtue
     of his or her signature hereon personally represents and warrants to
     Landlord that Tenant has taken all necessary actions to authorize his or
     her signature hereon on behalf of such Tenant and that upon the signing and
     delivery hereof to the Landlord by him or her, this Lease will be binding
     upon Tenant.

     WITNESS the execution hereof, under seal, in any number of counterpart
     copies, each which shall be deemed to be an original for all purposes as of
     the day and year first above written.

   LANDLORD:                                 TENANT:

   RAYJOE LIMITED PARTNERSHIP                MOLECULAR INSIGHT
   By: KDO Real Estate Holdings, Inc.        PHARMACEUTICALS, INC.

   By: /s/ Deborah A. Ciolfi                 By: /s/ John E. McCray
       ------------------------                  ------------------------
   Deborah A. Ciolfi                         Name: John E. McCray
   Treasurer, duly authorized.               Title: COO, duly authorized

                                             ATTEST By:

                                             /s/ Wendy Graham Coco
                                             ------------------------------
                                             Name: Wendy Graham Coco
                                             Title: Dir. Business Development &
                                                    Operations

                                                      GREENWORKS MOLECULAR LEASE

                                      -8-
<PAGE>

     FIRST AMENDMENT TO MOLECULAR INSIGHT PHARMACEUTICALS, INC., GREENWORKS
     OFFICE LEASE

     For good and valuable consideration, the receipt and sufficiency of which
is hereby acknowledged, RayJoe Limited Partnership ("Landlord") and Molecular
InSight Pharmaceuticals, Inc., ("Tenant"), confirm the following facts and their
agreement as follows:

     1. RECITALS. Landlord and Tenant are parties to a Lease Agreement dated
June 19, 2003 ("Lease"). By mutual agreement, the parties hereby agree to lease
two (2) additional office spaces until the expiration date of the Lease on June
30, 2008. The spaces are shown under attached EXHIBIT A.

The purpose of this writing is to set forth the entire agreement of the parties
with respect thereto.

     2. AMENDMENT. The Lease is hereby amended as follows:

     A. ADDITIONAL SPACE #1: Tenant shall lease Unit # 18, the Pioneer Financial
     office space, as is, containing approximately 198 rsf, for a term of five
     (5) years, commencing on September 1, 2003 until June 30, 2008 ("Additional
     Space #1"). Tenant agrees that Landlord has made no representations or
     warranties respecting the condition of the Additional Space #1.

     B. FIXED RENT FOR ADDITIONAL SPACE #1: Provided Landlord has delivered the
     Additional Space #1, Tenant shall pay Fixed Rent ("Rent"), commencing on
     September 1, 2003, as follows:

<TABLE>
<CAPTION>
    Dates:                     Yearly Rent:                  Monthly Rent:
    ------                     ------------                  -------------
<S>                            <C>                           <C>
9/1/03 - 6/30/08               $ 5,148.00                      $ 429.00
</TABLE>

     C. ADDITIONAL SPACE #1 AVAILABILITY CONTINGENCY: In the event that,
     Additional Space #1 is not delivered to Tenant as of December 1, 2003, the
     portions of this Amendment relating to Additional Space #1 will become void
     and unenforceable, unless Landlord and Tenant mutually agree to extend the
     delivery date for said unavailable space.

     D. ADDITIONAL SPACE #2: Tenant shall lease Unit #16, currently occupied by
     Stella Tarnay, as is, containing approximately 170 rsf, for a term of five
     (5) years, commencing on October 1, 2003 until June 30, 2008 ("Additional
     Space #2"). Tenant agrees that Landlord has made no representations or
     warranties respecting the condition of the Additional Space #2.

     E. FIXED RENT FOR ADDITIONAL SPACE #2: Provided Landlord has delivered the
     Additional Space #2, Tenant shall pay Fixed Rent ("Rent"), commencing on
     October 1, 2003, as follows:

<TABLE>
<CAPTION>
    Dates:                      Yearly Rent:                 Monthly Rent:
    ------                      ------------                 -------------
<S>                             <C>                          <C>
10/1/03 - 6/30/08               $ 4,416.00                    $ 368.00
</TABLE>

                                               MOLECULAR INSIGHT FIRST AMENDMENT

                                      -1-
<PAGE>

     F. ADDITIONAL SPACE #2 AVAILABILITY CONTINGENCY: In the event that,
     Additional Space #2 is not delivered to Tenant as of December 1, 2003, the
     portions of this Amendment relating to Additional Space #2 will become void
     and unenforceable, unless Landlord and Tenant mutually agree to extend the
     delivery date for said unavailable space.

     G.   ADDITIONAL RENT ADJUSTMENT PERCENTAGES:

     1.   TAX CHARGE: Tenant shall pay 16 % of real estate taxes for the
          Property over the 2003 fiscal year tax base, as additional rent in
          relation to its office space.

     2.   OPERATING COST: Tenant shall pay 16 % of operating expenses for the
          Property over the 2003 calendar year base operating expenses, as
          additional rent in relation to its office space.

     H. BASEMENT STORAGE: Tenant shall pay a charge of $110.00 per month for its
     lease of a wire cage in the basement, containing approximately 110 square
     feet for storage purposes only, commencing on July 1, 2003 until June 30,
     2008. Landlord shall not be liable for any damage or losses incurred by
     Tenant due to theft, fire or any other cause. Tenant agrees to insure the
     personal property stored in said wire cage and assumes full responsibility
     for its security.

     3. GENERAL. The individual signing this writing on behalf of Tenant
personally represents and warrants to Landlord that all necessary corporate
action authorizing the same has been duly taken and that upon the execution and
delivery hereof, this writing shall be binding upon the Tenant and enforceable
in accordance with its terms. Landlord and Tenant confirm that, as except as
modified hereby, the Lease remains in full force and effect upon all the other
terms and provisions.

EXECUTED as a sealed instrument_____________________________, 2003.

LANDLORD:                               TENANT:
RAYJOE LIMITED PARTNERSHIP              MOLECULAR INSIGHT
By: KDO Real Estate Holdings, Inc.      PHARMACEUTICALS, INC.

By: _____________________________       By: /s/ John E. McCray
    Deborah A. Ciolfi                       ------------------
    Treasurer, duly authorized          Name: John E. McCray
                                        Title: COO, as duly authorized.

                                        ATTEST By:

                                        /s/ John W. Babich
                                        --------------------
                                        Name: JOHN W. BABICH
                                        Title: PRESIDENT & CSO

                                        MOLECULAR INSIGHT FIRST AMENDMENT

                                      -2-
<PAGE>

                                                                       EXHIBIT A

                                  [FLOOR PLAN]

Source: [{"source": "alea-institute/alea-institute/kl3m-data-edgar-agreements/train-00093-of-00352.parquet"}, [{"source": "alea-institute/alea-institute/kl3m-data-edgar-agreements/train-00093-of-00352.parquet"}]]