Document:

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                                                                    EXHIBIT 10.3

                        AMENDMENT TO EMPLOYMENT AGREEMENT

            This Amendment to Employment Agreement (this "Amendment"), made as
      of the 10th day of July, 2001, is entered into by The Medicines Company, a
      Delaware corporation with its principal place of business at One Cambridge
      Center, Cambridge, Massachusetts 02142 (the "Company"), and David Stack,
      residing at One Robin Drive, Oak Ridge, New Jersey 07438 (the "Employee").

            WHEREAS, the Company and the Employee are parties to an Employment
      Agreement dated as of April 1, 2000, as amended (the "Employment
      Agreement"); and

            WHEREAS, the Company and the Employee desire to make certain
      amendments to the terms of the Employment Agreement to reflect the
      Employee's agreement to devote his full business time to the Company;

            NOW THEREFORE, in consideration of these premises, the mutual
      covenants and promises contained herein, and other good and valuable
      consideration, the receipt and sufficiency of which are acknowledged, the
      parties hereto agree as follows:

I.    Employment Agreement

1.    Defined Terms.  The capitalized terms used herein but not otherwise
defined shall have the meanings assigned to them in the Employment Agreement.

2.    Title; Capacity.  The Employment Agreement is hereby amended by
deleting Section 2 of the Employment Agreement in its entirety and inserting
in lieu thereof the following:

            "2. Title; Capacity. The Employee shall serve as Senior Vice
            President or in such other position as the Company or its Board of
            Directors (the "Board") may determine from time to time. The
            Employee shall be based at the Company's principal offices in New
            Jersey, unless otherwise agreed by the parties. The Employee shall
            be subject to the supervision of, and shall have such authority as
            is delegated to him by Clive Meanwell (or if Dr. Meanwell shall have
            ceased to serve as Chief Executive Officer or Chairman of the
            Company, the Board or such officer of the Company as may be
            designated by the Board).

            The Employee hereby accepts such employment on a full-time basis and
            agrees to undertake the duties and responsibilities inherent in such
            position and/or such other duties and responsibilities as Dr.
            Meanwell (or the Board or its designee) shall from time to time
            reasonably assign to him. The Company acknowledges and agrees that
            during the Employment Period, the Employee may continue to serve on
            the board of directors of the companies listed on Exhibit A attached
            hereto (as amended from time
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            to time upon the written agreement of the Company and the Employee,
            the "Permitted Boards"). The Company also acknowledges and agrees
            that the Employee may devote a portion of his business time to the
            winding down and termination of operations of Stack Pharmaceuticals,
            Inc. ("SPI"), provided that the Employee is working in good faith to
            wind down and terminate the operations of SPI as promptly as
            possible, consistent with good business judgment and SPI's
            obligations under contracts to which SPI is currently a party. The
            Employee agrees to abide by the rules, regulations, instructions,
            personnel practices and policies of the Company and any changes
            therein which may be adopted from time to time by the Company except
            as provided in these agreements. The Employee acknowledges receipt
            of copies of all such rules and policies committed to writing as of
            the date of this Agreement."

3.    Salary; Vacation.  The annual base salary payable to the Employee shall
be $265,000 commencing on August 1, 2001.  The Employee shall be entitled to
four weeks paid vacation per year, to be taken at such times as may be
approved by Dr. Meanwell (or the Board or its designee).

4.    Termination for Cause.  The Employment Agreement is hereby amended by
deleting paragraphs (e) and (f) of Section 4.2 of the Employment Agreement in
their entirety and inserting in lieu thereof the following:

            "(e) the Employee's excessive use of alcohol and/or drugs which is
            judged by the Board to materially interfere with the performance of
            his duties;

            "(f)  any misconduct by the Employee which in the
            reasonable judgment of the Board would jeopardize the
            success of the Company; or

            "(g) the Employee's breach of the Invention and Non-Disclosure
            Agreement dated as of July 10, 2001 between the Company and the
            Employee."

5.    Non-Compete.

      (a) The Employment Agreement is hereby amended by deleting the last
      sentence of Section 6.1 of the Employment Agreement in its entirety and
      inserting in lieu thereof the following:

            "For this purpose, "Competitive Products" shall mean a product with
            chemical or commercial characteristics of the kind or type developed
            or being developed, produced, marketed or sold by the Company during
            the Employment Period.";

      provided that this amendment shall not be effective with respect to the
      activities and business conducted by SPI under contracts to which SPI is
      currently a party until such time as the operations of SPI are wound down
      and terminated.

                                     - 2 -
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      (b) The Employment Agreement is hereby amended by adding the following
      sentence to the end of Section 6.2 of the Employment Agreement:

             "The Company also agrees that a directorship by the Employee on a
            Permitted Board shall not be considered a violation of Section 6.1,
            so long as the Employee notifies the Company in writing of any
            potential violation of Section 6.1 as a result of such directorship
            and Dr. Meanwell (or the Board or its designee) agrees in writing
            that such directorship shall not be considered a violation of
            Section 6.1."

6.    Inventions and Proprietary Information.

      (a) The Employment Agreement is hereby amended by deleting Section 8 in
      its entirety. This amendment shall only be effective from and after the
      date hereof and shall have no retroactive effect on the Employee.

      (b) On or prior to the date hereof, the Employee shall have executed an
      Invention and Non-Disclosure Agreement (the "Invention Agreement") with
      the Company, which shall be effective from and after the date hereof. The
      Employee hereby confirms and ratifies his obligation thereunder.

II.   Stock Options

            Upon the date hereof, the Company shall grant to the Employee
      non-statutory stock options to purchase 200,000 shares of Common Stock on
      the terms and in the form of Non-statutory Stock Option Agreement attached
      hereto as Exhibit B (the "Option Agreement"). Such options shall vest in
      equal monthly installments in arrears over the four-year period commencing
      on the date hereof in accordance with the Option Agreement; provided,
      however, that, subject to the express terms set forth in the Option
      Agreement,

(a)   if a Change in Control Event (as defined in the Option Agreement) occurs
      prior to the date, if any, on which the Employee is first elected as Chief
      Executive Officer of the Company, upon such Change in Control Event such
      options shall become immediately exercisable in full, and

(b)   if a Change in Control Event occurs on or after the date, if any, on which
      the Employee is first elected as Chief Executive Officer of the Company,
      then following such Change in Control Event such options shall become
      immediately exercisable in full if, on or prior to the first anniversary
      of the date of the consummation of the Change in Control Event, a
      Termination Event (as defined in the Option Agreement) occurs.

III.  Winding Down of Stack Pharmaceuticals, Inc.

            The Company and the Employee agree that promptly following the
      execution of this Agreement, the Company and the Employee shall discuss in
      good faith the Company's role in the winding down and termination of the
      operations of Stack Pharmaceuticals, Inc. ("SPI"), including without
      limitation the proposed transition to the

                                     - 3 -
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      Company of certain activities currently being undertaken by SPI, the
      proposed acquisition by the Company of certain assets of SPI and the
      proposed assumption by the Company of certain obligations and liabilities
      of SPI (it being understood that neither SPI nor the Company shall be
      obligated hereunder to consummate any transaction with respect to the
      winding down and termination of the operations of SPI until such time as
      definitive agreements are entered into between SPI and the Company).

IV.   Miscellaneous Provisions

1. The captions of the sections of this Amendment are for convenience of
reference only and in no way define, limit, or affect the scope or substance of
any section of this Amendment.

2. This Amendment shall be construed, interpreted, and enforced in accordance
with the laws of the Commonwealth of Massachusetts, without giving effect to
conflict of laws provisions.

3. This Amendment, together with the Employment Agreement, the Invention
Agreement and the Option Agreement, constitute the entire agreement between the
parties and supersedes all prior agreements and understandings, whether written
or oral, relating to the subject matter hereof.

4. In all respects other than as specifically provided in this Amendment, the
Employment Agreement is hereby ratified and affirmed.

            IN WITNESS WHEREOF, the parties hereto have executed this Amendment
      as of the day and year set forth above.

                                         THE MEDICINES COMPANY

                                         By:  /s/ Clive Meanwell
                                              --------------------------
                                              Clive A. Meanwell

                                              Chief Executive Officer

                                                        EMPLOYEE

                                                        /s/ David Stack
                                                --------------------------------
                                                            David Stack

                                     - 4 -
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                                                                       EXHIBIT B

                              THE MEDICINES COMPANY

                       Nonstatutory Stock Option Agreement
                     Granted Under 1998 Stock Incentive Plan

1.      Grant of Option.

        This agreement evidences the grant by The Medicines Company, a Delaware
corporation (the "Company") on July 10, 2001 (the "Grant Date") to David Stack,
an employee of the Company (the "Participant"), of an option to purchase, in
whole or in part, on the terms provided herein and in the Company's 1998 Stock
Incentive Plan (the "Plan"), a total of 200,000 shares (the "Shares") of common
stock, $0.001 par value per share ("Common Stock"), of the Company at a price of
$18.10 per Share. Unless earlier terminated, this option shall expire on the
tenth anniversary of the Grant Date (the "Final Exercise Date").

        It is intended that the option evidenced by this agreement shall not be
an incentive stock option as defined in Section 422 of the Internal Revenue Code
of 1986, as amended and any regulations promulgated thereunder (the "Code").
Except as otherwise indicated by the context, the term "Participant", as used in
this option, shall be deemed to include any person who acquires the right to
exercise this option validly under its terms.

2.      Vesting Schedule.

         (a) The options will vest in equal monthly installments in arrears over
the four-year period commencing on the Grant Date as determined by multiplying
the original number of Shares by a fraction, the numerator of which shall equal
the total number of months elapsed from the Grant Date and the denominator shall
be 48. This option shall expire upon, and will not be exercisable after, the
Final Exercise Date.

         (b) The right of exercise shall be cumulative so that to the extent the
option is not exercised in any period to the maximum extent permissible it shall
continue to be exercisable, in whole or in part, with respect to all shares for
which it is vested until the earlier of the Final Exercise Date or the
termination of this option under Section 3 hereof or the Plan.

         (c) Upon the occurrence of an Acquisition Event (as defined below)
(regardless of whether such event also constitutes a Change in Control Event (as
defined below)), or the execution by the Company of any agreement with respect
to an Acquisition Event (regardless of whether such event will result in a
Change in Control Event), the Board shall provide that this option shall be
assumed, or equivalent options shall be substituted, by the acquiring or
succeeding corporation (or an affiliate thereof); provided that if such
Acquisition Event also constitutes a Change in Control Event, except to the
extent specifically provided to the contrary in this agreement or any other
agreement between the Participant and the Company,

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         (i) if such Change in Control Event occurs prior to the date, if any,
         on which the Participant is first elected as Chief Executive Officer of
         the Company, such assumed or substituted options shall become
         immediately exercisable in full, and

         (ii) if such Change in Control Event occurs on or after the date, if
         any, on which the Participant is first elected as Chief Executive
         Officer of the Company, such assumed or substituted options shall
         become immediately exercisable in full if, on or prior to the first
         anniversary of the date of the consummation of the Change in Control
         Event, a Termination Event (as defined below) occurs.

         Notwithstanding the foregoing, if the acquiring or succeeding
corporation (or an affiliate thereof) does not agree to assume, or substitute
for, this option, then the Board shall (x) upon written notice to the
Participant, provide that all then unexercised portion of this option will
become exercisable in full as of a specified time (the "Acceleration Time")
prior to the Acquisition Event and will terminate immediately prior to the
consummation of such Acquisition Event, except to the extent exercised by the
Participant before the consummation of such Acquisition Event, and/or (y) in the
event of an Acquisition Event under the terms of which holders of Common Stock
will receive upon consummation thereof a cash payment for each share of Common
Stock surrendered pursuant to such Acquisition Event (the "Acquisition Price"),
provide that this option shall terminate upon consummation of such Acquisition
Event and the Participant shall receive, in exchange therefor, a cash payment
equal to the amount (if any) by which (A) the Acquisition Price multiplied by
the number of shares of Common Stock subject to this option (whether or not then
exercisable), exceeds (B) the aggregate exercise price of this option.

         (d) Following the occurrence of a Change in Control Event that does not
also constitute an Acquisition Event, except to the extent specifically provided
to the contrary in this agreement or any other agreement between the Participant
and the Company,

         (i) if such Change in Control Event occurs prior to the date, if any,
         on which the Participant is first elected as Chief Executive Officer of
         the Company, this option shall become immediately exercisable in full,
         and

         (ii) if such Change in Control Event occurs on or after the date, if
         any, on which the Participant is first elected as Chief Executive
         Officer of the Company, this option shall become immediately
         exercisable in full if, on or prior to the first anniversary of the
         date of the consummation of the Change in Control Event, a Termination
         Event occurs.

         (e) With the consent of the Board, which may be withheld, the
Participant may at any time exercise this option as to all or any part of the
Shares, including then unvested Shares, provided, that the Participant as a
condition to such exercise executes and delivers an Agreement Covering Shares
Acquired Upon Exercise of Unvested Options (and escrow agreement), upon terms
satisfactory to the Company, pursuant to which the Company shall have the right
to purchase, upon termination of the Participant's employment, all Shares that
would not then have been vested under the terms set forth in this agreement or
the Plan.

<PAGE>
         (f) Notwithstanding anything in this option to the contrary, in the
event that the Participant's relationship with the Company is terminated by
reason of death or disability (within the meaning of Section 22(e)(3) of the
Code), then, in addition to the Shares as to which this option is exercisable as
of such termination date pursuant to the terms hereof, this option shall also
become exercisable for an additional number of Shares equal to 50% of the Shares
covered by this option which were not otherwise exercisable as of such
termination date. For example, if as of the termination date, 6,000 shares of a
10,000 share stock option had vested and no shares covered by such option had
been exercised, upon such termination date, the option would become exercisable
for an additional 2,000 shares (50% of (10,000 - 6,000)) or total of 8,000
shares.

         (g) For purposes of this Section 2, the following terms shall have the
definitions set forth below:

         (1)      An "Acquisition Event" shall mean:

                  (A)      any merger or consolidation of the Company with or
                           into another entity as a result of which the Common
                           Stock is converted into or exchanged for the right to
                           receive cash, securities or other property; or

                  (B)      any exchange of shares of the Company for cash,
                           securities or other property pursuant to a statutory
                           share exchange transaction.

         (2)      A "Change in Control Event" shall mean:

                  (A)      any sale or transfer of all or substantially all of
                           the assets of the Company to another corporation or
                           entity, any merger, consolidation or reorganization
                           of the Company into or with another corporation or
                           entity, with the result that, upon conclusion of the
                           transaction, the voting securities of the Company
                           immediately prior thereto do not represent (either by
                           remaining outstanding or by being converted into
                           voting securities of the surviving entity) more than
                           50% of the combined voting power of the voting
                           securities of the continuing or surviving entity of
                           such consolidation, merger or reorganization; or

                  (B)      following the date on which the Company becomes
                           subject to the periodic reporting requirements under
                           Section 13 of the Securities Exchange Act of 1934, as
                           amended (the "Exchange Act"), a disclosure that any
                           person (as the term "person" is used in Section
                           13(d)(3) or Section 14(d)(2) of the Exchange Act),
                           other than (i) any shareholder who, prior to the
                           Company becoming subject to such reporting
                           requirements of Section 13 of the Exchange Act,
                           previously held at least 30% of the combined voting
                           power of outstanding voting securities of the
                           Company, (ii) the Company or (iii) any corporation
                           owned directly or indirectly by the

<PAGE>
                           stockholders of the Company in substantially the same
                           proportion as their ownership of stock of the
                           Company, becomes the beneficial owner as the term
                           "beneficial owner" is defined under Rule 13d-3 or any
                           successor rule or regulation thereto under the
                           Exchange Act) of securities representing 30% or more
                           of the combined voting power of the then outstanding
                           voting securities of the Company; or

                  (C)      such time as individuals who as of the date of the
                           initial adoption of the Plan constitute the Board of
                           Directors of the Company, and any new director (other
                           than a director designated by a person who has
                           entered into an agreement with the Company to effect
                           any transaction described in clause (A) or (B) of
                           this section) whose election by the Board or
                           nomination for election by the Company's stockholders
                           was approved by a vote of at least two-thirds of the
                           directors then still in office who were either
                           directors at the beginning of the period or whose
                           election or whose nomination for election was
                           previously so approved, cease for any reason to
                           constitute a majority of the Board of Directors.

         (3)      "Termination Event" shall mean the termination of the
                  Participant's employment by (i) by the Company or the
                  acquiring or succeeding corporation without Cause (as defined
                  in the Employment Agreement dated as of April 1, 2000, as
                  amended, between the Company and the Participant, as amended
                  from time to time); (ii) as a result of his death or
                  disability (within the meaning of Section 22(4)(3) of the
                  Code); or (iii) by the Participant upon written notice given
                  promptly after the Company's or the acquiring or succeeding
                  corporation's taking any of the following actions, which
                  actions shall not have been cured within a 30-day period
                  following such notice: (w) the principal place of the
                  performance of the Participant's responsibilities (the
                  "Principal Location") is changed to a location outside of a 30
                  mile radius from the Principal Location immediately prior to
                  the Change in Control Event; (x) there is a material reduction
                  in the Participant's responsibilities without Cause; (y) there
                  is a material reduction in the Participant's salary; or (z)
                  there is a significant diminution in the scope of the
                  Participant's responsibilities without the Participant's
                  agreement (excluding increases in responsibility and sideways
                  moves to jobs with similar descriptions).

3.       Exercise of Option.

                  Form of Exercise. Each election to exercise this option shall
be in writing, signed by the Participant, and received by the Company at its
principal office, accompanied by this agreement, and payment in full in the
manner provided in the Plan. The Participant may purchase less than the number
of shares covered hereby, provided that no partial exercise of this option may
be for any fractional share or for fewer than ten whole shares.

<PAGE>
                  Continuous Relationship with the Company Required. Except as
otherwise provided in this Section 3, this option may not be exercised unless
the Participant, at the time he or she exercises this option, is, and has been
at all times since the date of grant of this option, an employee, officer or
director of, or consultant or advisor to, the Company or any parent or
subsidiary of the Company as defined in Section 424(e) or (f) of the Code (an
"Eligible Participant").

                  Termination of Relationship with the Company. If the
Participant ceases to be an Eligible Participant for any reason, then, except as
provided in paragraphs (d) and (e) below, the right to exercise this option
shall terminate three months after such cessation (but in no event after the
Final Exercise Date), provided that this option shall be exercisable only to the
extent that the Participant was entitled to exercise this option on the date of
such cessation. Notwithstanding the foregoing, if the Participant, prior to the
Final Exercise Date, violates the non-competition or confidentiality provisions
of any employment contract, confidentiality and nondisclosure agreement or other
agreement between the Participant and the Company, the right to exercise this
option shall terminate immediately upon written notice to the Participant from
the Company describing such violation.

                  Exercise Period Upon Death or Disability. If the Participant
dies or becomes disabled (within the meaning of Section 22(e)(3) of the Code)
prior to the Final Exercise Date while he or she is an Eligible Participant and
the Company has not terminated such relationship for "cause" as specified in
paragraph (e) below, this option shall be exercisable, within the period of one
year following the date of death or disability of the Participant, by the
Participant, provided that this option shall be exercisable only to the extent
that this option was exercisable by the Participant on the date of his or her
death or disability, and further provided that this option shall not be
exercisable after the Final Exercise Date.

                  Discharge for Cause. If the Participant, prior to the Final
Exercise Date, is discharged by the Company for Cause, the right to exercise
this option shall terminate immediately upon the effective date of such
discharge. "Cause" shall mean: (i) conviction of any felony or any crime
involving moral turpitude or dishonesty; (ii) participation in a fraud or act of
dishonesty against the Company; (iii) willful and material breach of the
Company's policies; (iv) intentional and material damage to the Company's
property; or (v) material breach of such Participant's non-disclosure,
non-competition or other similar agreement with the company.

4.       Withholding.

         No Shares will be issued pursuant to the exercise of this option unless
and until the Participant pays to the Company, or makes provision satisfactory
to the Company for payment of, any federal, state or local withholding taxes
required by law to be withheld in respect of this option.

<PAGE>
5.      Nontransferability of Option.

        This option may not be sold, assigned, transferred, pledged or otherwise
encumbered by the Participant, either voluntarily or by operation of law, except
by will or the laws of descent and distribution, and, during the lifetime of the
Participant, this option shall be exercisable only by the Participant.

6.      Provisions of the Plan.

        This option is subject to the provisions of the Plan, a copy of which is
furnished to the Participant with this option.

<PAGE>
        IN WITNESS WHEREOF, the Company has caused this option to be executed
under its corporate seal by its duly authorized officer. This option shall take
effect as a sealed instrument.

                                            The Medicines Company

Dated: __________                           By:  _________________________
                                                   Clive Meanwell
                                                   Chief Executive Officer

<PAGE>
                            PARTICIPANT'S ACCEPTANCE

        The undersigned hereby accepts the foregoing option and agrees to the
terms and conditions thereof. The undersigned hereby acknowledges receipt of a
copy of the Company's 1998 Stock Incentive Plan.

               PARTICIPANT: ____________________________

               Address: ___________________________________

                        __________________________________<PAGE>
                                                                    EXHIBIT 10.4

                    AMENDED AND RESTATED EMPLOYMENT AGREEMENT

        THIS EMPLOYMENT AGREEMENT (the "Agreement"), made this 1st day of
November, 2001, is entered into by The Medicines Company, a Delaware corporation
with its principal place of business at One Cambridge Center, Cambridge,
Massachusetts 02142 (the "Company"), and David Stack, residing at One Robin
Drive, Oak Ridge, New Jersey 07438 (the "Employee").

        WHEREAS, the Company and the Employee are parties to an Employment
Agreement dated April 1, 2000 (the "April 2000 Employment Agreement"), which was
amended by an Amendment to Employment Agreement dated July 10, 2001 ("Amendment
No. 1", with the April 2000 Employment Agreement, as amended by Amendment No. 1,
being referred to as the "Former Employment Agreement");

         WHEREAS, on September 24, 2001, the Board of Directors of the Company
elected the Employee as President and Chief Executive Officer and a Director of
the Company; and

         WHEREAS, the Company and the Employee wish to amend and restate the
Former Employment Agreement to, among other things, reflect the Employee's new
positions with the Company;

         NOW THEREFORE, in consideration of the mutual covenants and promises
contained herein, and other good and valuable consideration, the receipt and
sufficiency of which are hereby acknowledged by the parties hereto, the parties
agree as follows:

         1. Term of Employment. The Company hereby agrees to employ the
Employee, and the Employee hereby accepts employment with the Company, upon the
terms set forth in this Agreement, for the period commencing on November 1, 2001
(the "Commencement Date") and ending on November 1, 2002 (such period, as it may
be renewed as provided in the following sentence, the "Employment Period"),
unless sooner terminated in accordance with the provisions

<PAGE>
of Section 4. The Employment Period shall automatically be renewed for
successive one (1) year periods unless either the Employee or the Company
provide written notice of non-renewal to the other party at least ninety (90)
days prior to the expiration of the then current term.

        2. Title; Capacity. The Employee shall serve as President and Chief
Executive Officer or in such other position or positions as the Company or its
Board of Directors (the "Board") may determine from time to time. The Employee
shall be based at the Company's principal offices in New Jersey, unless
otherwise agreed by the parties. The Employee shall be subject to the
supervision of, and shall have such authority as is delegated to him by Clive
Meanwell (or if Dr. Meanwell shall have ceased to serve as Chairman of the
Company, the Board or such officer of the Company as may be designated by the
Board.)

        The Employee hereby accepts such employment on a full-time basis and
agrees to undertake the duties and responsibilities inherent in such position
and/or such other duties and responsibilities as Dr. Meanwell (or the Board or
its designee) shall from time to time reasonably assign to him. The Company
acknowledges and agrees that during the Employment Period, the Employee may
continue to serve on the board of directors of the companies listed on Exhibit A
attached hereto (as amended from time to time upon the written agreement of the
Company and the Employee, the "Permitted Boards"). The Company also acknowledges
and agrees that the Employee may devote a portion of his business time to the
winding down and termination of operations of Stack Pharmaceuticals, Inc.
("SPI"), provided that the Employee is working in good faith to wind down and
terminate the operations of SPI as promptly as possible, consistent with good
business judgment and SPI's obligations under contracts to which SPI is
currently a party. The Employee agrees to abide by the rules, regulations,
instructions, personnel practices and policies of the Company and any changes
therein which may be adopted from time to time by the Company except as provided
in these agreements. The Employee acknowledges receipt of copies of all such
rules and policies committed to writing as of the date of this Agreement.

                                      -2-
<PAGE>
        3.     Compensation and Benefits.

               3.1 Salary. The Company shall pay the Employee, in semi-monthly
installments, an annual base salary of $265,000 for the one-year period
commencing on the Commencement Date. Such salary shall be subject to adjustment
thereafter as determined by the Board, but shall not be reduced below the amount
set forth above without the Employee's consent.

               3.2 Bonus. The Employee shall be eligible to receive a bonus of
up to 40% of his base salary upon the achievement of annual objectives to be
approved by the Chairman of the Company after discussion with the Employee. The
Board shall review the Employee's performance and determine the amount of the
bonus, if any, to be paid to the Employee.

               3.3 Reimbursement of Expenses. The Company shall reimburse the
Employee for all reasonable travel, entertainment and other expenses incurred or
paid by the Employee in connection with, or related to, the performance of his
duties, responsibilities or services under this Agreement, upon presentation by
the Employee of documentation, expense statements, vouchers and/or such other
supporting information as the Company may request.

               3.4 Fringe Benefits. The Employee shall be entitled to
participate in all other bonus and stock incentive programs that the Company
establishes and makes available to its other employees at the same level as the
Employee to the extent that Employee's position, tenure, salary, age, health and
other qualifications make him eligible to participate. The Employee shall be
entitled to four weeks paid vacation per year, to be taken at such times as may
be approved by Dr. Meanwell (or the Board or its designee).

         4.    Employment Termination. The employment of the Employee by the
Company pursuant to this Agreement shall terminate upon the occurrence of any of
the following:

               4.1 Expiration of Employment Period. Expiration of the Employment
Period in accordance with Section 1.

                                      -3-
<PAGE>
            4.2 Termination for Cause. At the election of the Company,
immediately upon written notice by the Company to the Employee, for "cause" as
determined by the Board. For purposes of this Section 4.2, "cause" for
termination shall be deemed to exist only if any of the following shall have
occurred:

                (a) the Employee's conviction of any crime (whether or not
involving the Company) which constitutes a felony in the jurisdiction involved
(other than unintentional motor vehicle felonies);

                (b) any act of theft, fraud, misappropriation of funds or
embezzlement by the Employee, in connection with his work with the Company, or
any other act or acts of dishonesty on the part of the Employee resulting or
intended to result directly or indirectly in personal gain or enrichment of the
Employee at the expense of the Company;

                (c) the Employee's failure to perform in all material respects
the services required to be performed pursuant to Section 2 of this Agreement,
provided that if such failure is capable of being corrected, such failure
continues uncorrected for a period of thirty (30) days after the Employee shall
have received written notice from the Company stating with reasonably
specificity the nature of such failure;

                (d) the Employee's breach of Sections 6 or 7 of this Agreement;

                (e) the Employee's excessive use of alcohol and/or drugs which
is judged by the Board to materially interfere with the performance of his
duties;

                (f) any misconduct by the Employee which in the reasonable
judgment of the Board would jeopardize the success of the Company; or

                (g) the Employee's breach of the Invention and Non-Disclosure
Agreement dated as of July 10, 2001 between the Company and the Employee (the
"Invention Agreement").

                                      -4-
<PAGE>
                4.3 Death or Disability. Thirty (30) days after the death or
disability of the Employee. As used in this Agreement, the term "disability"
shall mean the inability of the Employee, due to a physical or mental
disability, for a period of ninety (90) days, whether or not consecutive, during
any 360-day period to perform the services contemplated under this Agreement. A
determination of disability shall be made by a physician satisfactory to both
the Employee and the Company, provided that if the Employee and the Company do
not agree on a physician, the Employee and the Company shall each select a
physician and these two together shall select a third physician, whose
determination as to disability shall be binding on all parties.

                4.4 Voluntary Termination. At the election of either party, upon
written notice of termination given at least ninety (90) days prior to the
effective date of termination.

                4.5 Voluntary Termination for "Good Reason." At the election of
the Employee, upon at least 30 days prior written notice to the Company, for
"Good Reason," which shall be deemed to exist only if:

                    (i) if the Company fails to comply in any material respect
with the provisions of Section 3, other than an isolated, insubstantial and
inadvertent failure which is remedied by the Company promptly after receipt of
notice thereof given by the Employee; or

                    (ii) the Company shall require the Employee to be based at a
location that is more than 50 miles from Parsippany, New Jersey.

        5.     Effect of Termination.

               5.1 Termination for Cause or at Election of Employee. In the
event the Employee's employment is terminated for cause pursuant to Section 4.2,
at the election of the Employee pursuant to Section 4.4, or at the election of
either party pursuant to Section 4.6, the Company shall pay to the Employee all
sums otherwise payable to him under Section 3 through the last day of his actual
employment by the Company.

                                      -5-
<PAGE>
                  5.2      Termination for Death or Disability. If the
Employee's employment is terminated by death or because of disability pursuant
to Section 4.3, the Company shall pay to the estate of the Employee or to the
Employee, as the case may be, all sums which would otherwise be payable to the
Employee under Section 3 up to the end of the month in which the termination of
his employment because of death or disability occurs.

                  5.3      Termination for Good Reason or at Election of
Company. In the event that Employee's employment is terminated by the Employee
for "Good Reason" pursuant to Section 4.5, or at the election of the Company
pursuant to Section 4.4, the Company shall continue to pay to the Employee the
salary set forth in Section 3.1, and shall continue to make available to the
Employee the benefits set forth in Section 3.3, excluding vacation days and
bonus sums under said Section 3.3 accrued during this period, until the date
three (3) months after the date of termination, but in no event later than such
date as the Employee shall have commenced full-time employment with a new
employer.

                  5.4      Survival. The provisions of Sections 6 and 7 shall
survive the termination of this Agreement.

        6.     Non-Compete.

                  6.1      Non-Compete Restrictions During the Employment Period
and for a period of one (1) year after the termination or expiration thereof
(such one (1) year period being inapplicable in the event of a termination
pursuant to Section 4.4 at the election of the Company or by the Employee
pursuant to Section 4.5), the Employee will not directly or indirectly as an
individual proprietor, partner, officer, consultant, employee, director, joint
venturer, or in any other similar capacity engage in the business of developing,
producing, marketing or selling (or assist any other person engaging in the
business of developing, producing, marketing or selling)

                                      -6-
<PAGE>
any Competitive Products. For this purpose, "Competitive Products" shall mean a
product with chemical or commercial characteristics of the kind or type
developed or being developed, produced, marketed or sold by the Company during
the Employment Period. Notwithstanding the foregoing, the Employee shall not be
prohibited from engaging in the activities and business conducted by SPI under
contracts to which SPI is currently a party until such time as the operations of
SPI are wound down and terminated.

                  6.2      Limitations. Notwithstanding the provisions of
Section 6.1, it is recognized that the Employee's primary experience is in the
pharmaceutical industry, and that his ability to earn a livelihood is likely to
be dependent on future employment in such industry. Accordingly, the Company
agrees that the employment of the Employee by a pharmaceutical company in a
position in which he assumes responsibility for multiple products, most of which
are not Competitive Products, shall not be considered a violation of Section
6.1, so long as (i) the Employee's responsibilities in such position are not
directed principally to Competitive Products, (ii) the portfolio of the
pharmaceutical company which hires the Employee must contain the Competitive
Products prior to the hiring of the Employee, and (iii) the pharmaceutical
company which hires the Employee has been in existence for at least five (5)
years prior to hiring the Employee. The Company also agrees that a directorship
by the Employee on a Permitted Board shall not be considered a violation of
Section 6.1, so long as the Employee notifies the Company in writing of any
potential violation of Section 6.1 as a result of such directorship and Dr.
Meanwell (or the Board or its designee) agrees in writing that such directorship
shall not be considered a violation of Section 6.1.

                                      -7-
<PAGE>
                  6.3      Extension. If the Employee violates the provisions of
Section 6.1, the Employee shall continue to be bound by the restrictions set
forth in this Section 6 until a period of one year has expired without any
violation of such provision.

                  6.4      Cutback Clause. If any restriction set forth in this
Section 6 is found by any court of competent jurisdiction to be unenforceable
because it extends for too long a period of time or over too great a range of
activities or in too broad a geographic area, it shall be interpreted to extend
only over the maximum period of time, range of activities or geographic area as
to which it may be enforceable.

                  6.5      Equitable Remedies. The restrictions contained in
this Section 6 are necessary for the protection of the business and goodwill of
the Company and are considered by the Employee to be reasonable for such
purpose. The Employee agrees that any breach of Section 6.1 is likely to cause
the Company substantial and irrevocable damage and therefore, in the event of
any such breach, the Employee agrees that the Company, in addition to such other
remedies which may be available, shall be entitled to specific performance and
other injunctive relief.

         7.       Non-solicitation.

                  7.1      Non-solicitation Restrictions. While the Employee is
employed by the Company and for a period of one (1) year after the termination
or cessation of such employment for any reason, the Employee will not directly
or indirectly recruit, solicit or hire any employee of the Company, or induce or
attempt to induce any employee of the Company to terminate his/her employment
with, or otherwise cease his/her relationship with, the Company (other than
Thomas Quinn, Fred Ryan, or Melinda Popolla). If the Employee violates the
provisions of this Section 7.1, the Employee shall continue to be bound by the
restrictions set forth in this Section 7.1 until a period of one (1) year has
expired without any violation of such provisions.

                                      -8-
<PAGE>
                  7.2      Cutback Clause. If any restriction set forth in
Section 7.1 is found by any court of competent jurisdiction to be unenforceable
because it extends for too long a period of time or over too great a range of
activities or in too broad a geographic area, it shall be interpreted to extend
only over the maximum period of time or range of activities as to which it may
be enforceable.

                  7.3      Equitable Remedies. The restrictions contained in
Section 7.1 are necessary for the protection of the business and goodwill of the
Company and are considered by the Employee to be reasonable for such purpose.
The Employee agrees that any breach of Section 7 is likely to cause the Company
substantial and irrevocable damage and therefore, in the event of any such
breach, the Employee agrees that the Company, in addition to such other remedies
which may be available, shall be entitled to specific performance and other
injunctive relief.

         8.       Inventions and Proprietary Information. On July 10, 2001, the
Employee executed the Invention Agreement with the Company. The Employee hereby
confirms and ratifies his obligation thereunder.

         9.       Other Agreements. Employee hereby represents that he is not
bound by the terms of any agreement with any previous employer or other party to
refrain from using or disclosing any trade secret or confidential or proprietary
information in the course of his employment with the Company or to refrain from
competing, directly or indirectly, with the business of such previous employer
or any other party. Employee further represents that his performance of all the
terms of this Agreement and as an employee of the Company does not and will not
breach any agreement to keep in confidence proprietary information, knowledge or
data acquired by him in confidence or in trust prior to his employment with the
Company.

         10.      Notices. All notices required or permitted under this
Agreement shall be in writing and shall be deemed effective upon personal
delivery or upon deposit in the United

                                      -9-
<PAGE>
States Post Office, by registered or certified mail, postage prepaid, addressed
to the other party at the address shown above, or at such other address or
addresses as either party shall designate to the other in accordance with this
Section 10.

         11.      Pronouns. Whenever the context may require, any pronouns used
in this Agreement shall include the corresponding masculine, feminine or neuter
forms, and the singular forms of nouns and pronouns shall include the plural,
and vice versa.

         12.      Entire Agreement. This Agreement, together with the Invention
Agreement, constitutes the entire agreement between the parties and supersedes
all prior agreements and understandings, whether written or oral, relating to
the subject matter of this Agreement, including without limitation the Former
Employment Agreement, which this Agreement amends and restates and which shall
be of no further force or effect after the date hereof.

         13.      Amendment. This Agreement may be amended or modified only by a
written instrument executed by both the Company and the Employee.

         14.      Governing Law. This Agreement shall be construed, interpreted
and enforced in accordance with the laws of the State of New Jersey.

         15.      Successors and Assigns. This Agreement shall be binding upon
and inure to the benefit of both parties and their respective successors and
assigns, including any entity with which or into which the Company may be merged
or which may succeed to its assets or business, provided, however, that the
obligations of the Employee are personal and shall not be assigned by him.

         16.      Miscellaneous.

                  16.1     No Waiver. No delay or omission by the Company in
exercising any right under this Agreement shall operate as a waiver of that or
any other right. A waiver or consent given by the Company on any one occasion
shall be effective only in that instance and shall not be construed as a bar or
waiver of any right on any other occasion.

                                      -10-
<PAGE>
                  16.2     Captions. The captions of the sections of this
Agreement are for convenience of reference only and in no way define, limit or
affect the scope or substance of any section of this Agreement.

                  16.3     Enforceability. In case any provision of this
Agreement shall be invalid, illegal or otherwise unenforceable, the validity,
legality and enforceability of the remaining provisions shall in no way be
affected or impaired thereby.

                  16.4     Counterparts. This Agreement may be executed in one
or more counterparts, each of which shall be deemed to be an original, but all
of which shall be one and the same document.

                    [Remainder of page intentionally omitted]

                                      -11-
<PAGE>
        IN WITNESS WHEREOF, the parties hereto have executed this Agreement as
of the day and year set forth above.

                                            THE MEDICINES COMPANY

                                            By:    /s/ Clive Meanwell
                                                   ------------------
                                                   Clive A. Meanwell
                                                   Chairman

                                           /s/David Stack
                                           --------------
                                            David Stack

                                      -12-
<PAGE>
                                                                       Exhibit A

Bio-Imaging Technologies, Inc.
Medsite, Inc.

                                      -13-

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