Document:

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                                                                   Exhibit 10.17

                              EMPLOYMENT AGREEMENT
                              --------------------

         THIS EMPLOYMENT AGREEMENT (the "Agreement"), made this 30th day of
March, 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").

         The Company desires to employ the Employee, and the Employee desires to
be employed by the Company. 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 April 1, 2000
(the "Commencement Date") and ending on April 1, 2001 (such period, as it may be
renewed as provided in the following sentence, the "Employment Period"), unless
sooner terminated in accordance with the provisions 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 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 5 Sylvan Way,
Parsippany, New Jersey. The Employee shall be subject to the supervision of, and
shall have such

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authority as is delegated to him by, the Board or such officer of the Company as
may be designated by the Board.
The Employee hereby accepts such employment and agrees to undertake the duties
and responsibilities inherent in such position and/or such other duties and
responsibilities as the Board or its designee shall from time to time reasonably
assign to him. The Employee agrees to devote twelve (12) working days per month
to the business and interests of the Company during the Employment Period. 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. The Employee acknowledges receipt of
copies of all such rules and policies committed to writing as of the date of
this Agreement.

         3. COMPENSATION AND BENEFITS.

                  3.1 SALARY. The Company shall pay the Employee, in
semi-monthly installments, an annual base salary of $150,000 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 CEO 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,

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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.

         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.

                  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;

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(d) the Employee's breach of Sections 6 or 7 of this Agreement or any material
breach of the Invention and Nondisclosure Agreement dated of even date herewith
between the Employee and the Company (the "Nondisclosure Agreement"); (e) the
Employee's excessive use of alcohol and/or drugs which is judged by the CEO and
the Board to materially interfere with the performance of his duties; or (f) any
misconduct by the Employee which in the reasonable judgment of the CEO and the
Board would jeopardize the success of the Company.

                  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
end of the then current Employment Period.

                  4.5 VOLUNTARY TERMINATION FOR "GOOD REASON." At the election
of the Employee, for "Good Reason," which shall be deemed to exist only 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.

         5. EFFECT OF TERMINATION.

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                  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,
or at the election of the Employee pursuant to Section 4.4, 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.

                  5.2 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 later of (a) the first
anniversary of the Commencement Date of this Agreement, or (b) 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.

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                  6.1 NON-COMPETE RESTRICTIONS  During the Employment Period and
for a period of one (1) year after the termination or expiration thereof for any
reason, the Employee will not directly or indirectly:

(a)  as an individual proprietor, partner, stockholder, officer, employee,
     director, joint venturer, investor, lender, or in any other capacity
     whatsoever (other than as the holder of not more than an one percent (1%)
     equity interest in any publicly held company), 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)
     any Competitive Products. For this purpose, "Competitive Products" shall
     mean any drugs or devices used to diagnose, prevent or treat arterial or
     venous thrombosis [To Be Discussed]; or

(b)  solicit, divert or take away, or attempt to divert or to take away, the
     business or patronage of any of the clients, customers or accounts, or
     prospective clients, customers or accounts, of the Company.

                  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.

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                  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

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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.

                  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. 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.

         9. 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

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United 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 9.

         10. 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.

         11. ENTIRE AGREEMENT. This 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.
Reference is made to the following separate agreements between the Employee and
the Company dated of even date herewith which cover additional agreements
between the parties: the Nonstatutory Stock Option Agreement, the Noncompetition
and Nonsolicitation Agreement and the Invention and Nondisclosure Agreement.

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

         13. GOVERNING LAW. This Agreement shall be construed, interpreted and
enforced in accordance with the laws of the Commonwealth of Massachusetts.

         14. 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.

         15. MISCELLANEOUS.

                  15.1 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

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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.

                  15.2 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.

                  15.3 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.

         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 A. Meanwell
                                               ---------------------------------

                                            Title: CEO
                                                  ------------------------------

                                            /s/ David M. Stack
                                            ------------------------------------
                                            Name

                                       10<PAGE>   1
                                                                   Exhibit 10.18

                             I N D E X T O L E A S E

                                      FROM

                     TRUSTEES OF ONE CAMBRIDGE CENTER TRUST

                                       TO

                              THE MEDICINES COMPANY

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

ARTICLE
NUMBER                CAPTION                                               PAGE
-------               -------                                               ----

ARTICLE I             BASIC LEASE PROVISIONS AND
                      ENUMERATIONS OF EXHIBITS                                 1

ARTICLE II            PREMISES                                                 4

ARTICLE III           LEASE TERM                                               4

ARTICLE IV            DELIVERY                                                 5

ARTICLE V             ANNUAL FIXED RENT AND ELECTRICITY                        5

ARTICLE VI            TAXES                                                    6

ARTICLE VII           LANDLORD'S REPAIRS AND SERVICES AND  TENANT'S
                      ESCALATION PAYMENTS                                      8

ARTICLE VIII          TENANT'S REPAIRS                                        13

ARTICLE IX            ALTERATIONS                                             14

ARTICLE X             PARKING                                                 16

ARTICLE XI            CERTAW TENANT COVENANTS                                 18

ARTICLE XII           ASSIGNMENT AND SUBLETTING                               20

ARTICLE XIII          INDEMNITY AND COMMERCIAL GENERAL LIABILITY
                      INSURANCE                                               22

ARTICLE XIV           FIRE, CASUALTY AND TAKING                               23

ARTICLE XV            DEFAULT                                                 26

<PAGE>   2

ARTICLE XVI           BANKRUPTCY OR INSOLVENCY                                29

ARTICLE XVII          MISCELLANEOUS PROVISIONS                                31

                     Section 17.1        Waiver
                     Section 17.2        Cumulative Remedies
                     Section 17.3        Quiet Enjoyment
                     Section 17.4        Surrender
                     Section 17.5        Brokerage
                     Section 17.6        Invalidity of Particular Provisions
                     Section 17.7        Provisions Binding, Etc.
                     Section 17.8        Recording
                     Section 17.9        Notices and Time for Action
                     Section 17.10       When Lease Becomes Binding
                     Section 17.11       Paragraph Headings
                     Section 17.12       Rights of Mortgagee
                     Section 17.13       Rights of Ground Lessor
                     Section 17.14       Notice to Mortgagee and Ground Lessor
                     Section 17.15       Assignment of Rents
                     Section 17.16       Status Report and Financial Statements
                     Section 17.17       Self-Help
                     Section 17.18       Holding Over
                     Section 17.19       Entry by Landlord
                     Section 17.20       Tenant's Payments
                     Section 17.21       Late Payment
                     Section 17.22       Counterparts
                     Section 17.23       Entire Agreement
                     Section 17.24       Landlord Liability
                     Section 17.25       No Partnership
                     Section 17.26       Security Deposit
                     Section 17.27       Governing Law

EXHIBIT A-1   --    Description Of Site

EXHIBIT A-2   --    Loading Dock Plan

EXHIBIT B     --    Intentionally Omitted

EXHIBIT C     --    Intentionally Omitted

EXHIBIT D     --    Landlord's Services

EXHIBIT E     --    Floor Plan

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EXHIBIT F     --    Development Area Map

EXHIBIT G     --    Intentionally Omitted

EXHIBIT H     --    Memorandum Re: Procedure For Adjustment Of Electricity Costs

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         THIS INSTRUMENT IS AN INDENTURE OF LEASE in which the Landlord and the
Tenant are the parties hereinafter named, and which relates to space in the
building (the "Building") known as, and having an address at, One Cambridge
Center, Cambridge, Massachusetts.

         The parties to this instrument hereby agree with each other as follows:

                                   ARTICLE I

               BASIC LEASE PROVISIONS AND ENUMERATIONS OF EXHIBITS

1.1      INTRODUCTION. The following sets forth the basic data and identifying
         Exhibits elsewhere hereinafter referred to in this Lease, and, where
         appropriate, constitute definitions of the terms hereinafter listed.

1.2      BASIC DATA.

<TABLE>
<S>                                                        <C>
         Date:                                             March 15, 1997

         Landlord:                                         MORTIMER B. ZUCKERMAN, EDWARD H.
                                                           LINDE AND DAVID BARRETT, AS
                                                           TRUSTEES OF ONE CAMBRIDGE CENTER
                                                           TRUST under Declaration of Trust
                                                           dated May 14, 1985, recorded with
                                                           the Middlesex South District
                                                           Registry of Deeds in Book 16221,
                                                           Page 413, as amended by instrument
                                                           dated July 31, 1986 and recorded
                                                           with said Registry of Deeds in Book
                                                           17438, Page 23, but not
                                                           individually.

         Present Mailing Address of Landlord:              c/o Boston Properties, Inc.
                                                           8 Arlington Street
                                                           Boston, Massachusetts 02116

         Landlord's Construction Representative:           Michael A. Cantalupa

         Tenant:                                           The Medicines Company, a Delaware corporation
         Present Mailing Address:                          One Cambridge Center
                                                           Cambridge, Massachusetts 02142

         Tenant's Construction Representative:             Clive Meanwell

         Lease Term: (sometimes called the                 Fifteen (15) calendar months commencing on
</TABLE>

<PAGE>   5

<TABLE>
<S>                                                        <C>
         "Original Lease Term")                            April 1, 1997 and expiring June 30, 1998,
                                                           unless sooner terminated as hereinafter
                                                           provided.

         Lease Year:                                       A period of twelve (12) consecutive calendar
                                                           months, commencing on the first day of
                                                           January in each year, except that the first Lease
                                                           Year of the Lease Term hereof shall be the
                                                           period commencing on the Commencement Date and
                                                           ending on the succeeding December 3 1, and the
                                                           last Lease Year of the Lease Term hereof shall
                                                           be the period commencing on January I of the
                                                           calendar year in which the Lease Term ends, and
                                                           ending with the date on which the Lease Term ends.

         Commencement Date:                                April 1, 1997, subject to the terms of Section
                                                           3.1 hereof.

         Premises:                                         A portion of the fourth floor of the Building,
                                                           in accordance with the floor plan annexed
                                                           hereto as Exhibit E and incorporated herein by
                                                           reference, as further defined and limited in
                                                           Section 2.1 hereof.

         Rentable Floor Area of the Premises:              4,063 square feet, including a proportionate
                                                           share of common areas of the Building outside
                                                           of the Premises'.

         Annual Fixed Rent:                                During the Original Lease Term at the annual
                                                           rate of $113,764.00, being the product of (i)
                                                           $28.00 and (ii) the "Rentable Floor Area of
                                                           the Premises" (hereinabove defined in this
                                                           Section 1.2).

         Tenant Electricity:                               Initially as provided in Section 5.1 hereof,
                                                           subject to adjustment as provided in Section
                                                           5.2 and Section 7.5 hereof.

         Additional Rent:                                  All charges and other sums payable to Tenant
                                                           as set forth in this Lease, in addition to
                                                           Annual Fixed Rent.

         Initial Minimum Limits of Tenant's Commercial     $5,000,000 combined single limit per
         General Liability Insurance:                      occurrence on a per location basis.

         Total Rentable Floor Area of the Building:        215,686 square feet.
</TABLE>

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<TABLE>
<S>                                                        <C>
         Lot or Site:                                      All, and also any part of, the property
                                                           described in Exhibit A-1, plus any
                                                           additions or reductions thereto resulting
                                                           from the change of any abutting street line.
                                                           The terms Lot and Site are used interchangeably
                                                           in this instrument.

         Property:                                         The Building and Lot or Site.

         Loading Dock:                                     The service dock and related driveway providing
                                                           vehicular service access for the Building as
                                                           shown on Exhibit A-2.

         Development Area:                                 The area of the Cambridge Center development, as
                                                           shown on Exhibit F.

         Permitted Use:                                    General Office use.

         Broker:                                           Whittier Partners Group Company
                                                           155 Federal Street
                                                           Boston, Massachusetts 02110

         Security Deposit:                                 $9,480.34
</TABLE>

1.3      ENUMERATION OF EXHIBITS.****PARAGRAPH ON ORIGINAL DOCUMENT IS
         ILLEGIBLE ****

         Exhibit A-1       Description of the Site.

         Exhibit A-2       Loading Dock Plan.

         Exhibit B         Intentionally Omitted.

         Exhibit C         Intentionally Omitted.

         Exhibit D         Landlord's Services.

         Exhibit E         Floor Plan.

         Exhibit F         Development Area Map.

         Exhibit G         Intentionally Omitted.

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         Exhibit H         Memorandum Re: Procedure for Adjustment of
                           Electricity Costs.

                                   ARTICLE II

                                    PREMISES

2.1      DEMISE AND LEASE OF PREMISES. Landlord hereby demises and leases to
         Tenant, and Tenant hereby hires and accepts from Landlord, the Premises
         in the Building, excluding exterior faces of exterior walls, the common
         stairways and stairwells, elevators and elevator walls, mechanical
         rooms, electric and telephone closets, janitor closets, and pipes,
         ducts, shafts, conduits, wires and appurtenant fixtures serving
         exclusively or in common other parts of the Building, and if the
         Premises includes less than the entire rentable area of any floor,
         excluding the common corridors, elevator lobbies and toilets located on
         such floor.

2.2      APPURTENANT RIGHTS AND RESERVATIONS. Tenant shall have, as appurtenant
         to the Premises, the non-exclusive right to use in common with others,
         but not in a manner or extent that would interfere with the normal
         operation and use of the Building as a multi-tenant office building and
         subject to reasonable rules of general applicability to tenants of the
         Building from time to time made by Landlord of which Tenant is given
         notice: (a) the common lobbies, corridors, stairways, and elevators of
         the Building, and the pipes, ducts, shafts, conduits, wires and
         appurtenant meters and equipment serving the Premises in common with
         others, (b) the Loading Dock and the common walkways and driveways
         necessary for access to the Building, (c) if the Premises include less
         than the entire rentable floor area of any floor, the common toilets,
         corridors and elevator lobby of such floor and (d) common areas within
         Parcel 4 of the Development Area. Landlord reserves the right from time
         to time, without unreasonable interference with Tenant's use: (a) to
         install, use, maintain, repair, replace and relocate for service to the
         Premises and other parts of the Building, or either, pipes, ducts,
         conduits, wires and appurtenant fixtures, wherever located in the
         Premises or the Building, and (b) to alter or relocate any other common
         facility, provided that substitutions are substantially equivalent or
         better. Installations, replacements and relocations referred to in
         clause (a) above shall be located so far as practicable in the central
         core area of the Building, above ceiling surfaces, below floor surfaces
         or within perimeter walls of the Premises. Except in the case of
         emergencies, Landlord agrees to use its best efforts to give Tenant
         reasonable advance notice of any of the foregoing activities which
         require work in the Premises and to use reasonable efforts not cause
         unreasonable interference with Tenant's use of and access to the
         Premises.

                                  ARTICLE III

                                   LEASE TERM

3.1      TERM. The Term of this Lease shall be the period specified in Section
         1.2 hereof as the "Lease Term", unless sooner terminated as herein
         provided. The Commencement Date of the Lease Term shall be the date set
         forth in Section 1.2 hereof as the "Commencement Date", unless Landlord
         is unable to deliver the Premises to Tenant in accordance with the

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         provisions of Section 4.1 hereinbelow as of such date, in which event
         the Commencement Date shall be the date the Premises are so delivered.

                                   ARTICLE IV

                                    DELIVERY

4.1      DELIVER . Landlord shall deliver the Premises to Tenant broom-clean and
         free from all occupants but otherwise in "as is" condition and Landlord
         shall have no obligation to perform any additions, alterations or
         demolition in the Premises nor shall Landlord be responsible for the
         installation or connection of Tenant's telephone or other
         communications systems or equipment. If the occupant of the Premises as
         of the Date of this Lease (the "Existing Tenant") fails to deliver
         possession of the Premises at the time when its tenancy is scheduled to
         expire (being March 31, 1997), Landlord shall use reasonable efforts
         and due diligence (which shall be limited to the commencement and
         prosecution thereafter of eviction proceedings but shall not require
         the taking of any appeal) to evict such occupant from such space and to
         deliver possession of the Premises to Tenant. If Landlord is unable to
         deliver possession of the Premises to Tenant by May 15, 1997, Tenant
         may terminate this Lease without recourse to either party by written
         notice given by Tenant to Landlord prior to the first to occur of (i)
         the date Landlord delivers the Premises to Tenant or (ii) June 1,
         1997.. Commencement of the term of Tenant's occupancy and lease of the
         Premises shall, in the event of such holding over by such occupant, be
         deferred until possession of the Premises is delivered to Tenant.
         Tenant's right of termination contained in this paragraph shall be
         Tenant's sole and exclusive remedy for the failure of the Existing
         Tenant to so vacate the Premises.

                                   ARTICLE V

                        ANNUAL FIXED RENT AND ELECTRICITY

5.1      FIXED RENT AND ELECTRICITY CHARGES. Tenant agrees to pay to Landlord,
         or as directed by Landlord, at Landlord's Present Mailing Address
         specified in Section 1.2 hereof, or at such other place as Landlord
         shall from time to time designate by notice, (a) on the Commencement
         Date, and thereafter monthly, in advance, on the first day of each and
         every calendar month during the Original Lease Term, a sum equal to
         one-twelfth (1/12) of the Annual Fixed Rent specified in Section 1.2
         hereof and (b) on the Commencement Date and thereafter monthly, in
         advance, on the first day of each and every calendar month during the
         Original Lease Term, a sum equal to one-twelfth (1/12) of $1.00 per
         annum for each square foot of Rentable Floor Area of the Premises for
         Tenant Electricity subject to adjustment as provided in Section 5.2 and
         Section 7.5 hereof. Until notice of some other designation is given,
         Annual Fixed Rent and all other charges for which provision is herein
         made shall be paid by remittance to or to the order of BOSTON
         PROPERTIES, INC., Agents at 8 Arlington Street, Boston, Massachusetts
         02116, and all remittances received by BOSTON PROPERTIES, INC., as
         Agents as aforesaid, or by any subsequently designated recipient, shall
         be treated as a payment to Landlord.

                                       5
<PAGE>   9

Annual Fixed Rent for any partial month shall be paid by Tenant to Landlord at
such rate on a pro rata basis, and, if the Commencement Date shall be other than
the first day of a calendar month, the first payment which Tenant shall make to
Landlord shall be a payment equal to a proportionate part of such monthly Annual
Fixed Rent for the partial month from the Commencement Date to the first day of
the succeeding calendar month.

Other charges payable by Tenant on a monthly basis, as elsewhere provided in
this Lease, likewise shall be prorated, and the first payment on account thereof
shall be determined in similar fashion and shall commence on the Commencement
Date and other provisions of this Lease calling for monthly payments shall be
read as incorporating this undertaking by Tenant.

The Annual Fixed Rent and all other charges for which provision is made in this
Lease shall be paid by Tenant to Landlord without setoff, deduction or
abatement.

5.2      REALLOCATION OF ELECTRICITY CHARGES. Notwithstanding the provisions of
         Section 5.1 relating to the payment by Tenant for the cost of
         electricity, if and to the extent that Landlord is permitted from time
         to time by then applicable law, ordinance, rule, regulation and utility
         company policy, Landlord may reallocate the cost of electricity to
         tenants of the Building (including, but not limited to, Tenant herein)
         in accordance with the procedure contained in Exhibit H, and Tenant
         shall pay for electricity as provided in said Exhibit H. If Landlord
         does not so reallocate the cost of electricity as aforesaid, Tenant
         shall pay the charge for electricity as specified in Section 5.1 hereof
         and additional adjustment payments shall be made in the manner
         specified in Section 7.5 hereof.

                                   ARTICLE VI

                                      TAXES

6.1      DEFINITIONS. With reference to the real estate taxes referred to in
         this Article VI, it is agreed that terms used herein are defined as
         follows:

         (a)      "Tax Year" means the 12-month period beginning July I each
                  year during the Lease Term or if the appropriate Governmental
                  tax fiscal period shall begin on any date other than July 1,
                  such other date.

         (b)      "Landlord's Tax Expenses Allocable to the Premises" means the
                  same proportion of Landlord's Tax Expenses as Rentable Floor
                  Area of Tenant's Premises bears to 95% of the Total Rentable
                  Floor Area of the Building.

         (c)      "Landlord's Tax Expenses" with respect to any Tax Year means
                  the aggregate "real estate taxes" (hereinafter defined) with
                  respect to that Tax Year, reduced by any net abatement
                  receipts with respect to that Tax Year; provided, however,
                  that if in any Tax Year an abatement has been obtained on
                  account of vacancies in the Building, or if the real estate
                  taxes had initially been assessed in an amount to reflect such
                  vacancies then Landlord's Tax Expenses shall be determined to
                  be an amount equal to the taxes which would

                                       6
<PAGE>   10

                  normally be expected to have been assessed had occupancy been
                  ninety-five percent (95%) as of the reference date or period
                  on which or in relation to which such assessment was made. For
                  this purpose, taxes on properties comparable to the Property
                  may be used as a reference (specifically including the
                  buildings known as Four and Five Cambridge Center) if such
                  properties were occupied at ninety-five percent (95%) more or
                  less during the relevant period.

         (d)      "Real estate taxes" means all taxes and special assessments of
                  every kind and nature assessed by any Governmental authority
                  on the Site or the Building or the Property which the Landlord
                  shall be obligated to pay because of or in connection with the
                  ownership, leasing and operation of the Site and the Building
                  and reasonable expenses of any proceedings for abatement of
                  taxes. The amount of special taxes or special assessments to
                  be included shall be limited to the amount of the installment
                  (plus any interest other than penalty interest payable
                  thereon) of such special tax or special assessment required to
                  be paid during the year in respect of which such taxes are
                  being determined. There shall be excluded from such taxes all
                  income, estate, succession, inheritance and transfer taxes;
                  provided, however, that if at any time during the Lease Term
                  the present system of ad valorem taxation of real property
                  shall be changed so that in lieu of, or in addition to, the
                  whole or any part of the ad valorem tax on real property,
                  there shall be assessed on Landlord a capital levy or other
                  tax on the gross rents received with respect to the Site or
                  Building, or a Federal, State, County, Municipal, or other
                  local income, franchise, excise or similar tax, assessment,
                  levy or charge (distinct from any now in effect in the
                  jurisdiction in which the Property is located) measured by or
                  based, in whole or in part, upon any such gross rents, then
                  any and all of such taxes, assessments, levies or charges, to
                  the extent so measured or based, shall be deemed to be
                  included within the term "real estate taxes" but only to the
                  extent that the same would be payable if the Site or Building
                  were the only property of Landlord.

         (e)      "Base Taxes" means Landlord's Tax Expenses (hereinbefore
                  defined) for fiscal tax year 1997 (that is the period
                  beginning July 1, 1996 and ending June 30, 1997).

         (f)      "Base Taxes Allocable to the Premises" means the same
                  proportion of Base Taxes as the Rentable Floor Area of
                  Tenant's Premises bears to 95% of the Total Rentable Floor
                  Area of the Building.

6.2      TENANT'S SHARE OF REAL ESTATE TAXES. If with respect to any full Tax
         Year or fraction of a Tax Year falling within the Lease Term Landlord's
         Tax Expenses Allocable to the Premises for a full Tax Year exceed Base
         Taxes Allocable to the Premises or for any such fraction of a Tax Year
         exceed the corresponding fraction of Base Taxes Allocable to the
         Premises (such amount being hereinafter referred to as the "Tax
         Excess"), then Tenant shall pay to Landlord, as additional rent, the
         amount of such Tax Excess. Payments by Tenant on account of the Tax
         Excess shall be made monthly at the time and in the fashion herein
         provided for the payment of Annual Fixed Rent. The

                                       7
<PAGE>   11

         amount so to be paid to Landlord shall be an amount from time to time
         reasonably estimated by Landlord to be sufficient to provide Landlord,
         in the aggregate, a sum equal to the Tax Excess, ten (10) days at least
         before the day on which tax payments by Landlord would become
         delinquent. Not later than ninety (90) days after Landlord's Tax
         Expenses Allocable to the Premises are determinable for the first such
         Tax Year or fraction thereof and for each succeeding Tax Year or
         fraction thereof during the Lease Term, Landlord shall render Tenant a
         statement in reasonable detail certified by a representative of
         Landlord showing for the preceding year or fraction thereof, as the
         case may be, real estate taxes on the Building and Lot, abatements and
         reftinds, if any, of any such taxes and assessments, expenditures
         incurred in obtaining such abatement or reftind, the amount of the Tax
         Excess, the amount thereof already paid by Tenant and the amount
         thereof overpaid by, or remaining due from Tenant for the period
         covered by such statement. Within thirty (30) days after the receipt of
         such statement, Tenant shall pay any sum remaining due. Any balance
         shown as due to Tenant shall be credited against Annual Fixed Rent next
         due, or refunded to Tenant if the Lease Term has then expired and
         Tenant has no further obligation to Landlord. Expenditures for legal
         fees and for other expenses incurred in obtaining an abatement or
         refund may be charged against the abatement or refund before the
         adjustments are made for the Tax Year.

To the extent that real estate taxes shall be payable to the taxing authority in
installments with respect to periods less than a Tax Year, the statement to be
furnished by Landlord shall be rendered and payments made on account of such
installments.

                                  ARTICLE VII

                       LANDLORD'S REPAIRS AND.SERVICES AND
                          TENANT'S ESCALATION PAYMENTS

7.1      STRUCTURAL REPAIRS. Except for (a) normal and reasonable wear and use
         and (b) damage caused by fire or other casualty and by eminent domain,
         Landlord shall, throughout the Lease Term, at Landlord's sole cost and
         expense, keep and maintain in good order, condition and repair the
         following portions of the Building: the structural portions of the
         roof, the exterior and load bearing walls, the foundation, the
         structural columns and floor slabs and other structural elements of the
         Building; provided however, that Tenant shall pay to Landlord, as
         Additional Rent, the cost of any and all such repairs which may be
         required as a result of repairs, alterations, or installations made by
         Tenant or any subtenant, assignee, licensee or concessionaire of Tenant
         or any agent, servant, employee or contractor of any of them or to the
         extent of any loss, destruction or damage caused by the omission or
         negligence of Tenant, any assignee or subtenant or any agent, servant,
         employee, customer, visitor or contractor of any of them.

7.2      OTHER REPAIRS TO BE MADE BY LANDLORD. Except as otherwise provided in
         this Lease and subject to provisions for reimbursement by Tenant as
         contained in Section 7.5, Landlord agrees to keep and maintain in good
         order, condition and repair the common areas and facilities of the
         Building, including heating, ventilating, air conditioning, plumbing
         and other Building systems equipment servicing the Premises, except
         that Landlord shall in no event be responsible to Tenant for (a) the
         condition of glass in and about the Premises (other than for glass in
         exterior walls for which Landlord shall be responsible unless the
         damage thereto is attributable to Tenant's negligence or

                                       8
<PAGE>   12

         misuse, in which event the responsibility therefor shall be Tenant's),
         or (b) for any condition in the Premises or the Building caused by any
         act or neglect of Tenant or any agent, employee, contractor, assignee,
         subtenant or invitee of Tenant. Without limitation, Landlord shall not
         be responsible to make any improvements or repairs to the Building or
         the Premises other than as expressly provided in Section 7.1 or in this
         Section 7.2, unless expressly otherwise provided in this Lease.

7.3      SERVICES TO BE PROVIDED BY LANDLORD. In addition, and except as
         otherwise provided in this Lease and subject to provisions for
         reimbursement by Tenant as contained in Section 7.5 and Tenant's
         responsibilities in regard to electricity as provided in Section 5.2,
         Landlord agrees to furnish services, utilities, facilities and supplies
         set forth in Exhibit D hereto equal in quality comparable to those
         customarily provided by landlords in high quality buildings in
         Cambridge. In addition, Landlord agrees to furnish, at Tenant's
         expense, reasonable additional Building operation services which are
         usual and customary in similar buildings in Cambridge, and such
         additional special services as may be mutually agreed upon by Landlord
         and Tenant, upon reasonable and equitable rates from time to time
         established by Landlord.

7.4      OPERATING COSTS DEFINED. "Operating Expenses Allocable to the Premises"
         means the same proportion of the Operating Expenses for the Property as
         Rentable Floor Area of the Premises bears to 95% of the Total Rentable
         Floor Area of the Building. "Base Operating Expenses" means Operating
         Expenses for the Property (as hereinafter defined) for calendar year
         1997 (that is the period beginning January 1, 1997 and ending December
         31, 1997). "Base Operating Expenses Allocable to the Premises" means
         the same proportion of Base Operating Expenses as the Rentable Floor
         Area of Tenant's Premises bears to 95% of the Total Rentable Floor Area
         of the Building. "Operating Expenses for the Property" means the cost
         of operation of the Property incurred by Landlord, including those
         incurred in discharging Landlord's obligations under Sections 7.2 and
         7.3. Such costs shall exclude (i) payments of debt service and any
         other mortgage charges, including, principal, interest and points (ii)
         brokerage corrimissions and legal fees incurred in the leasing of space
         in the Building, (iii) salaries of executives and owners not directly
         employed in the management or operation of the Building, (iv) the
         general overhead and administrative expenses of the home office of
         Landlord or Landlord's managing agent, (v) costs of special services
         rendered to tenants (including Tenant) for which a separate charge is
         made, (vi) the cost of any item or service to the extent to which
         Landlord is actually reimbursed or compensated by insurance, any tenant
         or any third party, (vii) real estate taxes, provided that real estate
         taxes are payable as provided in Section 6.2, (viii) penalties,
         interest and legal expenses for late payment of any obligation of
         Landlord, including, without limitation, taxes, insurance, and
         equipment leases, (ix) costs incurred in performing tenant improvements
         for any tenant, (x) all capital expendituies, except as otherwise
         explicitly provided in this Section 7.4, (xi) the cost of testing,
         remediation or removal of "Hazardous Materials" (as defined in Section
         11.2) in the Building or on the Site as required by "Hazardous
         Materials Laws" (as defined in Section 11.2), (xii) legal fees and
         other costs associated with the enforcement of any lease of space in
         the Building, (xiii) the cost of any service or materials provided by
         Landlord or its affiliates, to the extent such costs exceed the
         reasonable cost for such services or materials absent such relationship
         in buildings similar to the Building in the vicinity of the Building,
         and (xiv)

                                       9
<PAGE>   13

         advertising and promotional expenses incurred in connection with
         leasing space in the Building, but shall include, without limitation:

         (a)      compensation, wages and all fringe benefits, workmen's
                  compensation insurance premiums and payroll taxes paid to, for
                  or with respect to all persons for their services in the
                  operating, maintaining or cleaning of the Building or the
                  Site;

         (b)      payments under service contracts with independent contractors
                  for operating, maintaining or cleaning of the Building or the
                  Site;

         (c)      steam, water, sewer, gas, oil, electricity and telephone
                  charges (excluding such utility charges separately chargeable
                  to tenants for additional or separate services and electricity
                  charges paid by Tenant in the manner set forth in Section 5.2)
                  and costs of maintaining letters of credit or other security
                  as may be required by utility companies as a condition of
                  providing such services;

         (d)      cost of maintenance, cleaning and repairs (other than repairs
                  not properly chargeable against income or reimbursed from
                  contractors under guarantees);

         (e)      cost of snow removal and care of landscaping;

         (f)      cost of building and cleaning supplies and equipment;

         (g)      premiums for insurance carried with respect to the Property
                  (including, without limitation, liability insurance, insurance
                  against loss in case of fire or casualty and of monthly
                  installments of Annual Fixed Rent and any Additional Rent
                  which may be due under this Lease and other leases of space in
                  the Building for not more than twelve (12) months in the case
                  of both Annual Fixed Rent and Additional Rent and, if there be
                  any first mortgage on the Property, including such insurance
                  as may be required by the holder of such first mortgage);

         (h)      management fees at reasonable rates consistent with the type
                  of occupancy and the services rendered;

         (i)      the Building's share of operating expenses (as herein defined
                  in this Section 7.4) related to the maintenance and repair of
                  the Loading Dock and of other common areas and facilities
                  within Parcel 4 of the Development Area for use of tenants of
                  the Building in common with tenants of other buildings in the
                  Development Area;

         (j)      depreciation for capital expenditures made by Landlord (x) to
                  reduce operating expenses if Landlord reasonably shall have
                  determined that the annual reduction in operating expenses
                  shall exceed depreciation therefor or (y) to comply with
                  applicable laws, rules, regulations, requirements, statutes,
                  ordinances, by-laws and court decisions of all public
                  authorities which are

                                       10
<PAGE>   14

                  enacted after the Date of this Lease (herein collectively
                  called "Legal Requirements"), (plus, in the case of both (x)
                  and (y), an interest factor, reasonably determined by
                  Landlord, as being the interest rate then charged for long
                  term mortgages by institutional lenders on like properties
                  within the general locality in which the Building is located),
                  and in the case of both (x) and (y) depreciation shall be
                  determined by dividing the original cost of such capital
                  expenditure by the number of years of useful life of the
                  capital item acquired, which useful life shall be determined
                  reasonably by Landlord in accordance with generally accepted
                  accounting principles and practices in effect at the time of
                  acquisition of the capital item; and

         (k)      all other reasonable and necessary expenses paid in connection
                  with the operating, cleaning and maintenance of the Building,
                  the Site and said common areas and facilities and properly
                  chargeable against income.

Notwithstanding the foregoing, in determining the amount of Operating Expenses
for the Property for any calendar year or portion thereof falling within the
Lease Term, no decrease in Operating Expenses Allocable to the Property shall
result in a reduction in the amount otherwise payable by Tenant if and to the
extent said decrease is attributable to vacancy in the Building rather than to
any other causes.

7.5      TENANT'S ESCALATION PAYMENTS. (A) If with respect to any calendar year
         falling within the Lease Term, or fraction of a calendar year falling
         within the Lease Term at the beginning or end thereof, the Operating
         Expenses Allocable to the Premises (as defined in Section 7.4) for a
         full calendar year exceed Base Operating Expenses Allocable to the
         Premises (as defined in Section 7.4) or for any such fraction of a
         calendar year exceed the corresponding fraction of Base Operating
         Expenses Allocable to the Premises (such amount being hereinafter
         referred to as the "Operating Cost Excess"), then Tenant shall pay to
         Landlord, as Additional Rent, on or before the thirtieth (30th) day
         following receipt by Tenant of the statement referred to below in this
         Section 7.5, the amount of such excess. Base Operating Expenses (as
         defined in Section 7.4) DO NOT include the $ 1.00 for tenant
         electricity to be paid by Tenant as part of the Annual Fixed Rent.
         However, if and so long as Landlord is NOT allocating the cost of
         electricity among tenants of the Building in accordance with Exhibit H,
         then the Base Operating Expenses shall be increased by $ 1.00 per
         square foot of the Total Rentable Floor Area of the Building.

(B) Payments by Tenant on account of the Operating Cost Excess shall be made
monthly at the time and in the fashion herein provided for the payment of Annual
Fixed Rent. The amount so to be paid to Landlord shall be an amount from time to
time reasonably estimated by Landlord to be sufficient to cover, in the
aggregate, a sum equal to the Operating Cost Excess for each calendar year
during the Lease Term.

(C) No later than ninety (90) days after the end of the first calendar year or
fraction thereof ending December 31 and of each succeeding calendar year during
the Lease Term or fraction thereof at the end of the Lease Term, Landlord shall
render Tenant a statement in reasonable detail and according to usual accounting
practices certified by a representative of Landlord, showing for the preceding
calendar year or fraction thereof, as the case may be, the Operating Expenses
for the

                                       11
<PAGE>   15

Property and the Operating Expenses Allocable to the Premises. Said statement to
be rendered to Tenant also shall show for the preceding year or fraction
thereof, as the case may be, the amounts already paid by Tenant on account of
Operating Cost Excess and the amount of Operating Cost Excess remaining due
from, or overpaid by, Tenant for the year or other period covered by the
statement.

If such statement shows a balance remaining due to Landlord, Tenant shall pay
same to Landlord on or before the thirtieth (30th) day following receipt by
Tenant of said statement. Any balance shown as due to Tenant shall be credited
against Annual. Fixed Rent next due, or refunded to Tenant if the Lease Term has
then expired and Tenant has no further obligation to Landlord. Upon notice to
Landlord given within ninety (90) days after Tenant's receipt of such statement,
Tenant, at Tenant's expense, may examine Landlord's books and records regarding
such statement at any reasonable time specified by Landlord during Landlord's
business hours at a place designated by Landlord. Tenant shall hold such books
and records in confidence and not disclose the same to any other party,
including, without limitation, any other tenant in the Building. If such
examination reveals that Landlord's Operating Expenses for a calendar year have
been (a) overstated by Landlord, then an equitable adjustment shall be made in
the amount paid or payable pursuant to this Section 7.5 for such calendar year,
and appropriate credit shall be made against (i) monthly installments of Annual
Fixed Rent next thereafter coming due or (ii) any other sums due from Tenant to
Landlord under this Lease (or refund such amount if the Term has ended and
Tenant has no further obligation to Landlord other than an indemnification
obligation for which no claim has been made) or (b) understated by Landlord,
then an equitable adjustment shall be made in the amount paid or payable
pursuant to this Section 7.5 for such calendar year and an appropriate payment
shall be made by Tenant to Landlord within thirty (30) days after Landlord bills
Tenant therefor.

Any payment by Tenant for the Operating Cost Excess shall not be deemed to waive
any rights of Tenant to claim that the amount thereof was not determined in
accordance with the provisions of this Lease.

7.6      NO DAMAGE. Landlord shall not be liable to Tenant for any compensation
         or reduction of rent by reason of inconvenience or annoyance or for
         loss of business arising from the necessity of Landlord or its agents
         entering the Premises for any purposes in this Lease authorized, or for
         repairing the Premises or any portion of the Building however the
         necessity may occur. In case Landlord is prevented or delayed from
         making any repairs, alterations or improvements, or furnishing any
         services or performing any other covenant or duty to be performed on
         Landlord's part, by reason of any cause reasonably beyond Landlord's
         control, including, without limitation, strike, lockout, breakdown,
         accident, order or regulation of or by any Governmental authority, or
         failure of supply, or inability by the exercise of reasonable diligence
         to obtain supplies, parts or employees necessary to furnish such
         services, or because of war or other emergency, or for any cause due to
         any act or neglect of Tenant or Tenant' s servants, agents, employees,
         licensees or any person claiming by, through or under Tenant, Landlord
         shall not be liable to Tenant therefor, nor, except as expressly
         otherwise provided in this Lease, shall Tenant be entitled to any
         abatement or reduction of rent by reason thereof, nor shall the same
         give rise to a claim in Tenant's favor that such failure constitutes
         actual or constructive, total or partial, eviction from the Premises.
         Subject to the foregoing terms of this Section 7.6,

                                       12
<PAGE>   16

         Landlord shall use reasonable efforts to remedy as soon as practicable
         any delay referenced above.

Landlord reserves the right to stop any service or utility system, when
necessary by reason of accident or emergency, or until necessary repairs have
been completed; provided, however, that in each instance of stoppage, Landlord
shall exercise reasonable diligence to eliminate the cause thereof. Except in
case of emergency repairs, Landlord will give Tenant reasonable advance notice
of any contemplated stoppage and will use diligent efforts to avoid unnecessary
inconvenience to Tenant by reason thereof.

                                  ARTICLE VIII

                                TENANT'S REPAIRS

8.1      TENANT'S REPAIRS AND MAINTENANCE. Tenant covenants and agrees that,
         from and after the date that possession of the Premises is delivered to
         Tenant and until the end of the Lease Term, Tenant will keep neat and
         clean and maintain in good order, condition and repair the Premises and
         every part thereof, excepting only for those repairs for which Landlord
         is responsible under the terms of Article VII of this Lease and damage
         by fire or other casualty and as a consequence of the exercise of the
         power of eminent domain. Tenant shall not permit or commit any waste,
         and Tenant shall be responsible for the cost of repairs which may be
         made necessary by reason of damages to common areas in the Building by
         Tenant, Tenant's agents, employees, contractors, or invitees.

If repairs are required to be made by Tenant pursuant to the terms hereof,
Landlord may demand in writing (except in the event of an emergency, when no
prior notice is required, provided that Landlord shall give verbal or written
notice to Tenant as soon as practicable after making repairs) that Tenant make
the same forthwith, and if Tenant refuses or neglects to commence such repairs
and complete the same with reasonable dispatch within thirty (30) days after
such demand (except in the event of an emergency, when Landlord may make such
repairs immediately), Landlord may (but shall not be required to do so) make or
cause such repairs to be made and shall not be responsible to Tenant for any
loss or damage that may accrue to Tenant's stock or business by reason thereof
If Landlord makes or causes such repairs to be made, Tenant agrees that Tenant
will forthwith on demand, pay to Landlord as Additional Rent the cost thereof,
and if Tenant shall default in such payment, Landlord shall have the remedies
provided for nonpayment of rent or other charges payable hereunder.

                                       13
<PAGE>   17

                                   ARTICLE IX

                                   ALTERATIONS

9.1      LANDLORD'S APPROVAL. Tenant covenants and agrees not to make
         alterations, additions or improvements to the Premises, whether before
         or during the Lease Term, except in accordance with plans and
         specifications therefor first approved by Landlord in writing, which
         approval shall not be unreasonably withheld or delayed. Landlord shall
         not be deemed unreasonable:

         (a)      for withholding approval of any alterations, additions or
                  improvements which (i) in Landlord's opinion might adversely
                  affect any structural or exterior element of the Building, any
                  area or element outside of the Premises or any facility
                  serving any area of the Building outside of the Premises, or
                  (ii) involve or affect the exterior design, size, height or
                  other exterior dimensions of the Building, or (iii) enlarge
                  the Rentable Floor Area of the Premises; or

         (b)      for making its approval conditional on Tenant's agreement to
                  restore the Premises to its condition prior to such
                  alteration, addition, or improvement at the expiration or
                  earlier termination of the Lease Term.

Landlord's review and approval of any such plans and specifications and consent
to perform work described therein shall not be deemed an agreement by Landlord
that such plans, specifications and work conform with applicable Legal
Requirements and requirements of insurers of the Building (herein called
"Insurance Requirements") nor deemed a waiver of Tenant's obligations under this
Lease with respect to applicable Legal Requirements and Insurance Requirements
nor impose any liability or obligation upon Landlord with respect to the
completeness, design sufficiency or compliance of such plans, specifications and
work with applicable Legal Requirements and Insurance Requirements.

9.2      CONFORMITY OF WORK. Tenant covenants and agrees that any alterations,
         additions, improvements or installations made by it to or upon the
         Premises shall be done in a good and workmanlike manner and in
         compliance with all applicable Legal Requirements and Insurance
         Requirements now or hereafter in force, that materials of first and
         otherwise good quality shall be employed therein, that the structure of
         the Building shall not be endangered or impaired thereby and that the
         Premises shall not be diminished in value thereby.

9.3      PERFORMANCE OF WORK, GOVERNMENTAL PERMITS AND INSURANCE. All of
         Tenant's alterations and additions and installation of furnishings
         shall be coordinated with any work being performed by or for Landlord
         and in such manner as to maintain harmonious labor relations and not to
         damage the Building or Site or interfere with Building construction or
         operation and, except for installation of furnishings, shall be
         performed by Landlord's general contractor or by contractors or workmen
         first approved by Landlord. Except for work by Landlord's general
         contractor, Tenant shall procure all necessary governmental permits
         before making any repairs, alterations, other

                                       14
<PAGE>   18

         improvements or installations. Tenant agrees to save harmless and
         indemnify Landlord from any and all injury, loss, claims or damage to
         any person or property occasioned by or arising out of the doing of any
         such work whether the same be performed prior to or during the Term of
         this Lease. In addition, Tenant shall cause each contractor to carry
         workmen's compensation insurance in statutory amounts covering the
         employees of all contractors and subcontractors, and commercial general
         liability insurance or comprehensive general liability insurance with a
         broad form comprehensive liability endorsement with such limits as
         Landlord may require reasonably from time to time during the Term of
         this Lease, but in no event less than the minimum amount of commercial
         general liability insurance or comprehensive general liability
         insurance Tenant is required to maintain as set forth in Section 1.2
         hereof and as the same may be modified as provided in Section 13.2
         hereof (all such insurance to be written in companies approved
         reasonably by Landlord and insuring Landlord, Landlord's managing agent
         and Tenant as well as contractors) and to deliver to Landlord
         certificates of all such insurance.

9.4      LIENS. Tenant covenants and agrees to pay promptly when due the entire
         cost of any work done on the Premises by Tenant, its agents, employees
         or contractors, and not to cause or permit any liens for labor or
         materials performed or furnished in connection therewith to attach to
         the Premises or the Building or the Site and immediately to discharge
         any such liens which may so attach.

9.5      NATURE OF ALTERATIONS. All work, construction, repairs, alterations,
         other improvements or installations made to or upon the Premises
         (including, but not limited to, the construction performed by Landlord
         under Article IV), shall become part of the Premises and shall become
         the property of Landlord and remain upon and be surrendered with the
         Premises as a part thereof upon the expiration or earlier termination
         of the Lease Term, except as follows:

         (a)      All trade fixtures whether by law deemed to be a part of the
                  realty or not, installed at any time or times by Tenant or any
                  person claiming under Tenant shall remain the property of
                  Tenant or persons claiming under Tenant and may be removed by
                  Tenant or any person claiming under Tenant at any time or
                  times during the Lease Term or any occupancy by Tenant
                  thereafter and shall be removed by Tenant at the expiration or
                  earlier termination of the Lease Term if so requested by
                  Landlord. Tenant shall repair any damage to the Premises
                  occasioned by the removal by Tenant or any person claiming
                  under Tenant of any such property from the Premises.

         (b)      At the expiration or earlier termination of the Lease Term,
                  unless otherwise agreed in writing by Landlord, Tenant shall
                  remove any wiring for Tenant's computer, telephone and other
                  communication systems and equipment and any alterations,
                  additions and improvements made with Landlord's consent during
                  the Lease Term for which such removal was made a condition of
                  such consent under Section 9.1 (b). Upon such removal Tenant
                  shall restore the Premises to their condition prior to such
                  alterations, additions and improvements and repair any damage
                  occasioned by such removal and restoration.

                                       15
<PAGE>   19

         (c)      If Tenant shall make any alterations, additions or
                  improvements to the Premises for which Landlord's approval is
                  required under Section 9.1 without obtaining such approval,
                  then at Landlord's request at any time during the Lease Term,
                  and at any event at the expiration or earlier termination of
                  the Lease Term, Tenant shall remove such alterations,
                  additions and improvements and restore the Premises to their
                  condition prior to same and repair any damage occasioned by
                  such removal and restoration. Nothing herein shall be deemed
                  to be a consent to Tenant to make any such alterations,
                  additions or improvements, the provisions of Section 9.1 being
                  applicable to any such work.

9.6      INCREASES IN TAXES. Tenant shall pay, as additional rent, one hundred
         percent (100%) of any increase in real estate taxes on the Property
         which shall, at any time after the Commencement Date, result from
         alterations, additions or improvements to the Premises made by Tenant
         if the taxing authority specifically determines such increase results
         from such alterations, additions or improvements made by Tenant.

                                    ARTICLE X

                                     PARKING

10.1     PARKING PRIVILEGES. Reference is made to the fact that affiliates of
         Landlord have constructed two (2) parking garages and propose to
         construct one or more additional parking garages (hereinafter the
         "Garage" or the "Garages") within the Development Area shown on Exhibit
         F to serve the Building and other buildings constructed or to be
         constructed by Landlord or affiliates of Landlord within the
         Development Area. The existing Garage, with vehicular entrances from
         the south side of Broadway and the east side of Ames Street, is also
         sometimes hereinafter referred to as the "East Garage". The existing
         Garage, located on Parcel 2 of the Development Area with vehicular
         entrances from the north side of Broadway and the south side of Binney
         Street is also sometimes hereinafter referred to as the "North Garage".
         Landlord shall provide to Tenant monthly parking privileges in one or
         more of the Garages in number not to exceed parking for two (2)
         passenger automobiles for each 1,000 square feet of Rentable Floor Area
         of the Premises for the parking of motor vehicles in unreserved stalls
         in one or more of the Garages by Tenant's employees commencing on the
         Commencement Date of the Lease Term. Such parking privileges may be
         shifted from time to time among the Garages by notice from Landlord;
         provided however that parking shall be provided in the East Garage for
         no less than one-half (Y2) of the total number of automobiles for which
         Tenant elects to have parking privileges pursuant to this Section 10.
         1. Within thirty (3 0) days after the date of execution of this Lease,
         Tenant shall notify Landlord of the number of parking spaces which
         Tenant desires be made available in the Garage(s) for its use in
         accordance with this Section.

10.2     PARKING CHARGES. Tenant shall pay for parking privileges in Garages at
         prevailing monthly rates from time to time charged by the operator or
         operators of Garages, whether or not such operator is an affiliate of
         Landlord. Such monthly parking charges for parking privileges in the
         Garage or Garages shall constitute Additional Rent and shall be payable

                                       16
<PAGE>   20

         monthly as directed by Landlord upon billing therefor by Landlord.
         Tenant acknowledges that said monthly charges to be paid under this
         Section are for the use by the Tenant of the parking privileges
         referred to herein, and not for any other service.

10.3     GARAGE OPERATION. Unless otherwise determined by Landlord, each Garage
         is to be operated on a self-parking basis, and Tenant shall be
         obligated to park and remove its own automobiles. Tenant's parking
         shall be on an unreserved basis, Tenant having the right to park in any
         available stalls. Tenant's access and use privileges with respect to
         the Garage shall be in accordance with regulations of uniform
         applicability to the users of the Garage from time to time established
         by the operator of the Garage. Tenant shall receive one (1)
         identification sticker or pass and one (1) magnetic card so-called, or
         other suitable device providing access to the Garage, for each vehicle
         paid for by Tenant. Tenant shall supply Landlord with an identification
         roster listing, for each identification sticker or pass, the name of
         the employee and the make, color and registration number of the vehicle
         to which it has been assigned, and shall provide a revised roster to
         Landlord monthly indicating changes thereto. Any automobile found
         parked in the Garage during normal business hours without appropriate
         identification will be subject to being towed at said automobile
         owner's expense. The parking privileges granted herein are
         nontransferable. The door of the Garage will be open during normal
         business hours except during periods of severe inclement or cold
         weather. For periods during which an attendant is not on duty at the
         Garage entrance or when the door to the Garage is closed, or at any
         other periods as may from time to time be stipulated by the Garage
         Operator in accordance with its regulations, including normal business
         hours, the magnetic cards furnished to Tenant shall be used by Tenant
         to gain access to and egress from the Garage for motor vehicles.

10.4     LIMITATIONS. Tenant agrees that it and all persons claiming by, through
         and under it, shall at all times abide by all reasonable rules and
         regulations promulgated by Landlord or the operator of the parking
         facilities with respect to the use of the Garage or such ongrade
         parking facilities as may be provided by Landlord within the
         Development Area. Except to the extent of gross negligence or willful
         acts, neither the Landlord nor the operator of such parking facilities
         assumes any responsibility whatsoever for loss or damage due to fire or
         theft or otherwise to any automobile or to any personal property
         therein, however caused, and Tenant agrees, upon request from the
         Landlord, from time to time, to notify its officers, employees and
         agents then using any of the parking privileges provided for herein, of
         such limitation of liability. Tenant further acknowledges and agrees
         that a license only is hereby granted, and no bailment is intended or
         shall be created.

10.5     INTERIM ON-GRADE PARKING. Notwithstanding the references to Garages in
         this Article X, Tenant acknowledges that, from time to time, Landlord
         may satisfy the requirements of providing Tenant with parking hereunder
         (except for parking called for as to be provided in the East Garage) by
         providing such parking in on-grade parking lots within the Development
         Area, in which case such parking shall be paid for in accordance with
         the prevailing monthly rate from time to time charged by the operator
         or operators of such lots, whether or not such operator is an affiliate
         of Landlord, and in all other respects in accordance with the terms and
         conditions of this Article X.

                                       17
<PAGE>   21

                                   ARTICLE XI

                            CERTAIN TENANT COVENANTS

Tenant covenants during the Lease Term and for such further time as Tenant
occupies any part of the Premises:

                                       18
<PAGE>   22

11.1     To pay when due all Annual Fixed Rent and Additional Rent and all
         charges for utility services rendered to the Premises and service
         inspections therefor (except as is otherwise provided in Exhibit D)
         and, as further Additional Rent, all charges for additional and special
         services rendered pursuant to Section 7.3.

11.2     To use and occupy the Premises for the Permitted Uses only, and not to
         injure or deface the Premises or the Property, not to permit in the
         Premises any auction sale, vending machine or flammable fluids or
         chemicals, or nuisance, or the emission from the Premises of any
         objectionable noise or odor, nor to use or devote the Premises or any
         part thereof for any purpose other than the Permitted Uses, nor any use
         thereof which is inconsistent with the maintenance of the Building as
         an office building of the first-class in the quality of its
         maintenance, use and occupancy, or which is improper, offensive,
         contrary to law or ordinance or liable to invalidate or increase the
         premiums for any insurance on the Building or its contents or liable to
         render necessary any alteration or addition to the Building. Further,
         (i) Tenant shall not, nor shall Tenant permit its employees, invitees,
         agents, independent contractors, contractors, assignees or subtenants
         to, keep, maintain, store or dispose of (into the sewage or waste
         disposal system or otherwise) or engage in any activity which might
         produce or generate any substance which is or may hereafter be
         classified as a hazardous material, waste or substance (collectively
         "Hazardous Materials"), under federal, state or local laws, rules and
         regulations, including, without limitation, 42 U.S.C. Section 6901 et
         seq., 42 U.S.C. Section 9601 et seq., 42 U.S.C. Section 2601 et seq.,
         49 U.S.C. Section 1802 et seq. and Massachusetts General Laws, Chapter
         2 1 E and the rules and regulations promulgated under any of the
         foregoing, as such laws, rules and regulations may be amended from time
         to time (collectively "Hazardous Materials Laws"), (ii) Tenant shall
         immediately notify Landlord of any incident in, on or about the
         Premises, the Building or the Site that would require the filing of a
         notice under any Hazardous Materials Laws, (iii) Tenant shall comply
         and shall cause its employees, invitees, agents, independent
         contractors, contractors, assignees and subtenants to comply with each
         of the foregoing and (iv) Landlord shall have the right to make such
         inspections (including testing) as Landlord shall elect from time to
         time to determine that Tenant is complying with the foregoing.

11.3     Not to obstruct in any manner any portion of the Building not hereby
         leased or any portion thereof or of the Site used by Tenant in common
         with others; not without prior consent of Landlord to permit the
         painting or placing of any signs, curtains, blinds, shades, awnings,
         aerials or flagpoles, or the like, visible from outside the Premises;
         and to comply with all reasonable rules and regulations now or
         hereafter made by Landlord, of which Tenant has been given notice, for
         the care and use of the Building and the Site and their facilities and
         approaches, but Landlord shall not be liable to Tenant for the failure
         of other occupants of the Building to conform to such rules and
         regulations.

11.4     To keep the Premises equipped with all safety appliances required by
         law or ordinance or any other regulation of any public authority
         because of any use made by Tenant other than normal office use, and to
         procure all licenses and permits so required because of any use made by
         Tenant other than normal office use, and to procure all licenses and
         permits so required because of such use and, if requested by Landlord,
         to do any work so required

                                       19
<PAGE>   23

         because of such use, it being understood that the foregoing provisions
         shall not be construed to broaden in any way Tenant's Permitted Uses.

11.5     Not to place a load upon any floor in the Premises exceeding an average
         rate of 70 pounds of live load (including partitions) per square foot
         of floor area; and not to move any safe, vault or other heavy equipment
         in, about or out of the Premises except in such manner and at such time
         as Landlord shall in each instance authorize. Tenant's business
         machines and mechanical equipment shall be placed and maintained by
         Tenant at Tenant's expense in settings sufficient to absorb and prevent
         vibration or noise that may be transmitted to the Building structure or
         to any other space in the Building.

11.6     To pay promptly when due all taxes which may be imposed upon personal
         property (including, without limitation, fixtures and equipment) in the
         Premises to whomever assessed.

11.7     To pay, as Additional Rent, all reasonable costs, counsel and other
         fees incurred by Landlord in connection with the successful enforcement
         by Landlord of any, obligations of Tenant under this Lease.

11.8     Not to do or permit anything to be done in or upon the Premises, or
         bring in anything or keep anything therein, which shall increase the
         rate of insurance on the Premises or on the Building above the standard
         rate applicable to premises being occupied for the use to which Tenant
         has agreed to devote the Premises; and Tenant further agrees that, in
         the event that Tenant shall do any of the foregoing, Tenant will
         promptly pay to Landlord, on demand, any such increase resulting
         therefrom, which shall be due and payable as Additional Rent hereunder.

11.9     To comply with all applicable Legal Requirements now or hereafter in
         force which shall impose a duty on Landlord or Tenant relating to or as
         a result of the use or occupancy of the Premises; provided that Tenant
         shall not be required to make any alterations or additions to the
         structure, roof, exterior and load bearing walls, foundation,
         structural floor slabs and other structural elements of the Building
         unless the same are required by such Legal Requirements as a result of
         or in connection with Tenant's use or occupancy of the Premises beyond
         normal use of space of this kind, Tenant shall promptly pay all fines,
         penalties and damages that may arise out of or be imposed because of
         its failure to comply with the provisions of this Section 11.9.

                                  ARTICLE XII

                            ASSIGNMENT AND SUBLETTING

12.1     PROHIBITION. Tenant covenants and agrees that it shall not assign,
         mortgage, pledge, hypothecate or otherwise transfer this Lease and/or
         Tenant's interest in this Lease or sublet (which term, without
         limitation, shall include granting of concessions, licenses or the
         like) the whole or any part of the Premises, or to permit occupancy of
         the Premises or any part thereof by anyone other than the Tenant. Any
         assignment, mortgage, pledge, occupancy arrangement, hypothecation,
         transfer or subletting shall be void, ab initio; shall be of no force
         and effect; and shall confer no rights on or in favor of third parties;

                                       20
<PAGE>   24

         and, at Landlord's sole option, shall constitute a default of Tenant
         entitling Landlord to exercise its remedies in the event of default
         hereunder by Tenant. In addition, Landlord shall be entitled to seek
         specific performance by Tenant and or the equitable relief with respect
         to the provisions of this Article XII.

12.2     EXCEPTIONS FOR PARENT OR SUBSIDIAR. Notwithstanding the foregoing
         provisions of Section 12.1 above, but subject to the provisions of
         Sections 12.3 and 12.4 below, Tenant shall have the right to assign
         this Lease or to sublet the Premises (in whole or in part) to (i) any
         entity that controls, is controlled by or is under common control with
         Tenant or (ii) any corporation into which Tenant may be converted or
         with which it may merge, provided that the entity to which this Lease
         is so assigned or which so sublets the Premises has a credit worthiness
         (e.g. assets on a pro forma basis using generally accepted accounting
         principles consistently applied and using the most recent financial
         statements) which is the same or better than the Tenant as of the Date
         of this Lease.

12.3     TENANT'S NOTICE. Tenant shall give Landlord notice of any proposed
         sublease or assignment, and said notice shall specify the provisions of
         the proposed assignment or subletting, including (a) the name and
         address of the proposed assignee or subtenant, (b) all of the terms and
         provisions upon which the proposed assignment or subletting is to be
         made, and (c) such information as may be reasonably required by
         Landlord to determine that such proposed assignment or subletting
         complies with the requirements of said Section 12.2.

12.4     ADDITIONAL CONDITIONS. (A) It shall be a condition of the validity of
         any assignment or subletting of right under Section 12.2 above that
         both Tenant and the assignee or sublessee agree directly with Landlord
         in a separate written instrument reasonably satisfactory to Landlord
         which contains terms and provisions reasonably required by Landlord,
         including, without limitation, the agreement of the assignee or
         sublessee to be bound by all the obligations of the Tenant hereunder,
         including, without limitation, the obligation to pay the Annual Fixed
         Rent, Additional Rent, and other amounts provided for under this Lease
         (but in the case of a partial subletting, such subtenant shall agree on
         a pro rata basis to be so bound), including the provisions of Section
         12.1 through 12.4 hereof, but such assignment or subletting shall not
         relieve the Tenant named herein of any of the obligations of the Tenant
         hereunder, Tenant shall remain fully and primarily liable therefor and
         the liability of Tenant and such assignee (or subtenant, as the case
         may be) shall be joint and several. Further, and notwithstanding the
         foregoing, the provisions hereof shall not constitute a recognition of
         the assignment or the assignee thereunder or the sublease or the
         subtenant thereunder, as the case may be, and at Landlord's option,
         upon the termination of the Lease, the assignment or sublease shall be
         terminated.

(B) If this Lease be assigned, or if the Premises or any part thereof be sublet
or occupied by anyone other than Tenant, Landlord may upon prior notice to
Tenant, at any time and from time to time, collect Annual Fixed Rent, Additional
Rent, and other chargesfrom the assignee, sublessee or occupant and apply the
net amount collected to the Annual Fixed Rent, Additional Rent and other charges
herein reserved, but no such assignment, subletting, occupancy or collection
shall be deemed a waiver of this covenant, or a waiver of the provisions of
Sections 12.1 through 12.4 hereof, or the

                                       21
<PAGE>   25

acceptance of the assignee, sublessee or occupant as a tenant or a release of
Tenant from the further performance by Tenant of covenants on the part of Tenant
herein contained, the Tenant herein named to remain primarily liable under this
Lease.

(C) As Additional Rent, Tenant shall reimburse Landlord promptly for out of
pocket legal and other expenses incurred by Landlord in connection with any
assignment or subletting.

                                  ARTICLE XIII

              INDEMNITY AND COMMERCIAL GENERAL LIABILITY INSURANCE

13.1     TENANT'S INDEMNITY. To the maximum extent this agreement may be made
         effective according to law, Tenant agrees to indemnify and save
         harmless Landlord from. and against all claims of whatever nature
         arising from or claimed to have arisen from: any act, omission or
         negligence of Tenant, or Tenant's contractors, licensees, invitees,
         agents, servants, independent contractors or employees; any accident,
         injury or damage whatsoever caused to any person, or to the property of
         any person, occurring in or about the Premises after the date that
         possession of the Premises is first delivered to Tenant and until the
         end of the Lease Term and thereafter, provided that during any such
         period after the Lease Term Tenant or anyone acting by, through or
         under Tenant is in occupancy of the Premises or any portion thereof, or
         any accident, injury or damage occurring outside the Premises but
         within the Building, the Garage or on the Site, where such accident,
         injury or damage results, or is claimed to have resulted, from an act,
         omission or negligence on the part of Tenant or Tenant's contractors,
         licensees, invitees, agents, servants, independent contractors or
         employees.

This indemnity and hold harmless agreement shall include indemnity against all
costs, expenses and liabilities incurred in or in connection with any such claim
or proceeding brought thereon, and the defense thereof.

13.2     COMMERCIAL GENERAL LIABILITY INSURANCE. Tenant agrees to maintain in
         full force from the date upon which Tenant first enters the Premises
         for any reason, throughout the Lease Term of this Lease, and
         thereafter, so long as Tenant is in occupancy of any part of the
         Premises, a policy of commercial general liability or comprehensive
         general liability insurance written on an occurrence basis with a broad
         form comprehensive liability endorsement under which Landlord and
         Landlord's managing agent (and such other persons as are in privity of
         estate with Landlord and Landlord's managing agent as may be set out in
         notice from time to time) and Tenant are named as insureds, and under
         which the insurer agrees to indemnify and hold Landlord and Landlord's
         managing agent, and those in privity of estate with Landlord and
         Landlord's managing agent, harmless from and against all cost, expense
         and/or liability arising out of or based upon any and all claims,
         accidents, injuries and damages mentioned in Section 13.1 of this
         Article XIII, in the broadest form of such, coverage from time to time
         available in the jurisdiction in which the Premises are located. Each
         such policy shall be non-cancelable and non-amendable with respect to
         Landlord and Landlord's said designees without thirty (30) days' prior
         notice to Landlord, and a duplicate original or certificate thereof
         shall be delivered to Landlord. As of the

                                       22
<PAGE>   26

         Commencement Date hereof, the minimum limits of liability of such
         insurance shall be as specified in Section 1.2 and from time to time
         during the Lease Term for such higher limits, if any, as are carried
         customarily in the Greater Boston Area with respect to similar
         properties. All insurance required to be maintained by Tenant pursuant
         to this Lease shall be maintained with responsible companies qualified
         to do business, and in good standing, in the Commonwealth of
         Massachusetts and which have a rating of at least "A2' and are within a
         financial size category of not less than "Class VIII" in the most
         current Best's Key Rating Guide or such similar rating as may be
         reasonably selected by Landlord if such Guide is no longer published.

13.3     TENANT'S PROPERTY INSURANCE. Tenant, at Tenant's expense, shall
         maintain at all times during the Term of the Lease insurance against
         loss or damage covered by the so-called "all risk" type insurance
         coverage with respect to Tenant's fixtures, equipment, goods, wares and
         merchandise, tenant improvements made by or paid for by Tenant, and
         other property of Tenant (collectively "Tenants Property"). Such
         insurance shall be in an amount at least equal to the full replacement
         cost of Tenant's Property.

13.4     NON-SUBROGATION. Any insurance carried by either party with respect to
         the Premises or property therein or occurrences thereon shall, if it
         can be so written without additional premium or with an additional
         premium which the other party agrees to pay, include a clause or
         endorsement denying to the insurer rights of subrogation against the
         other party to the extent rights have been waived by the insured prior
         to occurrence of injury or loss. Each party, notwithstanding any
         provisions of this Lease to the contrary, hereby waives any rights of
         recovery against the other for injury or loss due to hazards covered by
         such insurance to the extent of the indemnification received
         thereunder.

13.5     TENANTS RISK. To the maximum extent that this agreement may be made
         effective according to law, Tenant agrees to use and occupy the
         Premises and to use such other portions of the Building, the Garage or
         Garages, the Site and the Development Area as Tenant is herein given
         the right to use at Tenant's own risk; and Undlord shall have no
         responsibility or liability for any loss of or damage to fixtures or
         other personal property of Tenant.

                                  ARTICLE XIV

                            FIRE, CASUALTY AND TAKING

14.1     DAMAGE RESULTING FROM CASUALTY. In case during the Lease Term the
         Building or the Site are damaged by fire or other casualty, and such
         fire or casualty damage cannot, in the ordinary course, reasonably be
         expected to be repaired within one hundred twenty (120) days from the
         time that repair work would commence, Landlord may, at its election,
         terminate this Lease by notice given to Tenant within sixty (60) days
         after the date of such fire or other casualty, specifying the effective
         date of termination. The effective date of termination specified by
         Landlord shall not be less than thirty (30) days nor more than
         forty-five (45) days after the date of notice of such termination.
         Unless terminated pursuant to the foregoing provisions, this Lease
         shall remain in full force and effect following any such damage
         subject, however, to the following provisions.

                                       23
<PAGE>   27

If during the last fifteen (15) months of the Lease Term, the Building shall be
damaged by fire or casualty and such fire or casualty damage to the Premises
cannot reasonably be expected to be repaired or restored within one hundred
twenty (120) days from the time that repair or restoration work would commence,
then Tenant shall have the right, by giving notice to Landlord not later than
thirty (30) days after such damage, to terminate this Lease, whereupon this
Lease shall terminate as of the date of such notice with the same force and
effect as if such date were the date originally established as the expiration
date hereof

If the Building or the Site or any part thereof are damaged by fire or other
casualty and this Lease is not so terminated, or Landlord has no right to
terminate this Lease, and in either such case the holder of any mortgage which
includes the Building as a part of the mortgaged premises or any ground lessor
of any ground lease which includes the Site as part of the demised premises
allows the net insurance proceeds to be applied to the restoration of the
Building (and/or the Site), Landlord, promptly after such damage and the
determination of the net amount of insurance proceeds available shall use due
diligence to restore the Premises and the Building in the event of damage
thereto (excluding Tenant's Property ) into proper condition for use and
occupation and a just proportion of the Annual Fixed Rent, the Operating Cost
Excess and Tenant's share of real estate taxes according to the nature and
extent of the injury to the Premises shall be abated from the date of casualty
until the Premises shall have been put by Landlord substantially into such
condition. Notwithstanding the foregoing, Landlord shall not be obligated to
expend for such repairs and restoration any amount in excess of the net
insurance proceeds.

Where Landlord is obligated or otherwise elects to effect restoration of the
Premises, unless such restoration is completed within one (1) year from the date
of the casualty or taking, such period to be subject, however, to extension
where the delay in completion of such work is due to causes beyond Landlord's
reasonable control (but in no event beyond eighteen (18) months from the date of
the casualty or taking), Tenant shall have the right to terminate this Lease at
any time after the expiration of such one-year (as extended) period until the
restoration is substantially completed, such termination to take effect as of
the thirtieth (30th) day after the date of receipt by Landlord of Tenant's
notice, with the same force and effect as if such date were the date originally
established as the expiration date hereof unless, within such thirty (30) day
period such restoration is substantially completed, in which case Tenant's
notice of termination shall be of no force and effect and this Lease and the
Lease Term shall continue in full force and effect.

14.2     UNINSURED CASUALTY. Notwithstanding anything to the contrary contained
         in this Lease, if the Building or the Premises shall be substantially
         damaged by fire or casualty as the result of a risk not covered by the
         forms of casualty insurance at the time maintained by Landlord and such
         fire or casualty damage cannot, in the ordinary course, reasonably be
         expected to be repaired within ninety (90) days from the time that
         repair work would commence, Landlord may, at its election, terminate
         the Term of this Lease by notice to Tenant given within thirty (30)
         days after such loss. If Landlord shall give such notice, then this
         Lease shall terminate as of the date of such notice with the same force
         and effect as if such date were the date originally established as the
         expiration date hereof.

14.3     RIGHTS OF TERMINATION FOR TAKING. Except as hereinafter provided in
         Section 14.4 hereof, if the Building, or such portion thereof as to
         render the balance (if reconstructed to the maximum extent practicable
         in the circumstances) unsuitable for

                                       24
<PAGE>   28

         Tenant's purposes, shall be taken by condemnation or right of eminent
         domain, Landlord or Tenant shall have the right to terminate this Lease
         by notice to the other of its desire to do so, provided that such
         notice is given not later than thirty (30) days after Tenant has been
         deprived of possession. If either party shall give such notice, then
         this Lease shall terminate as of the date of such notice with the same
         force and effect as if such date were the date originally established
         as the expiration date hereof.

Further, if so much of the Building shall be so taken that continued operation
of the Building would be uneconomic, Landlord shall have the right to terminate
this Lease by giving notice to Tenant of Landlord's desire to do so not later
than thirty (30) days after Tenant has been deprived of possession of the
Premises (or such portion thereof as may be taken). If Landlord shall give such
notice, then this Lease shall terminate as of the date of such notice with the
same force and effect as if such date were the date originally established as
the expiration date hereof.

Should any part of the Premises be so taken or condemned during the Lease Term
hereof, and should this Lease not be terminated in accordance with the foregoing
provisions, and the holder of any mortgage which includes the Premises as part
of the mortgaged premises or any ground lessor of any ground lease which
includes the Site as part of the demised premises allows the net condemnation
proceeds to be applied to the restoration of the Building, Landlord agrees that
after the determination of the net amount of condemnation proceeds available to
Landlord, Landlord shall * use due diligence to put what may remain of the
Premises into proper condition for use and occupation as nearly like the
condition of the Premises prior to such taking as shall be practicable
(excluding Tenant's Property). Notwithstanding the foregoing, Landlord shall not
be obligated to expend for such repair and restoration any amount in excess of
the net condemnation proceeds.

If the Premises shall be affected by any exercise of the power of eminent domain
and neither Landlord nor Tenant shall terminate this Lease as provided above,
then the Annual Fixed Rent, the Operating Cost Excess and Tenant's share of real
estate taxes shall be justly and equitably abated and reduced according to the
nature and extent of the loss of use thereof suffered by Tenant; and in case of
a taking which permanently reduces the Rentable Floor Area of the Premises, a
just proportion of the Annual Fixed Rent, the Operating Cost Excess and Tenant's
share of real estate taxes shall be abated for the remainder of the Lease Term.

14.4     AWARD. Except as otherwise provided in Section 14.4, Landlord shall
         have and hereby reserves and excepts, and Tenant hereby grants and
         assigns to Landlord, all rights to recover for damages to the Building,
         the Site and the Garage or Garages and the leasehold interest hereby
         created, and compensation accrued or hereafter to accrue by reason of
         such taking, damage or destruction, as aforesaid, and by way of
         confirming the foregoing, Tenant hereby grants and assigns, and
         covenants with Landlord to grant and assign to Landlord, all rights to
         such damages or compensation.

However, nothing contained herein shall be construed to prevent Tenant from
prosecuting in any such proceedings a claim for its trade fixtures so taken or
relocation, moving and other dislocation expenses, provided that such action
shall not affect the amount of compensation otherwise recoverable by Landlord
from the taking authority.

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<PAGE>   29

                                   ARTICLE XV

                                     DEFAULT

15.1     TENANT'S DEFAULT. This Lease and the term of this Lease are subject to
         the limitation that Tenant shall be in default if, at any time during
         the Lease Term, any one or more of the following events (herein called
         an "Event of Default" a "default of Tenant" or similar reference) shall
         occur and not be cured prior to the expiration of the grace period (if
         any) herein provided, as follows:

         (a)      Tenant shall fail to pay any installment of the Annual Fixed
                  Rent, or any Additional Rent or any other monetary amount due
                  under this Lease on or before the date on which the same
                  becomes due and payable, and such failure continues for five
                  (5) days after notice from Landlord thereof, or

         (b)      Landlord having rightfully given the notice specified in (a)
                  above to Tenant twice in any twelve (12) month period, Tenant
                  shall fail thereafter to pay the Annual Fixed Rent, Additional
                  Rent or any other monetary amount due under this Lease on or
                  before the date on which the same becomes due and payable; or

         (c)      Tenant shall fail to perform or observe some term or condition
                  of this Lease which, because of its character, would
                  immediately jeopardize Landlord's interest (such as, but
                  without limitation, failure to maintain general liability
                  insurance, or the employment of labor and contractors within
                  the Premises which interfere with Landlord's work, in
                  violation of Section 4.3 or Section 9.3), and such failure
                  continues for three (3) days after notice from Landlord to
                  Tenant thereof; or

         (d)      Tenant shall fail to perform or observe any other requirement,
                  term, covenant or condition of this Lease (not hereinabove in
                  this Section 15.1 specifically referred to) on the part of
                  Tenant to be performed or observed and such failure shall
                  continue for thirty (30) days after notice thereof from
                  Landlord to Tenant, or if said default shall reasonably
                  require longer than thirty (30) days to cure, if Tenant shall
                  fail to commence to cure said default within thirty (30) days
                  after notice thereof and/or fail to continuously prosecute the
                  curing of the same to completion with due diligence; or

         (e)      The estate hereby created shall be taken on execution or by
                  other process of law; or

         (f)      Tenant shall make an assignment or trust mortgage arrangement,
                  so-called, for the benefit of its creditors; or

         (g)      Tenant shall judicially be declared bankrupt or insolvent
                  according to law; or

                                       26
<PAGE>   30

         (h)      a receiver, guardian, conservator, trustee in involuntary
                  bankruptcy or other similar officer is appointed to take
                  charge of all or any substantial part of Tenant's property by
                  a court of competent jurisdiction; or

         (i)      any petition shall be filed against Tenant in any court,
                  whether or not pursuant to any statute of the United States or
                  of any State, in any bankruptcy, reorganization, composition,
                  extension, arrangement or insolvency proceeding, and such
                  proceedings shall not be fully and finally dismissed within
                  sixty (60) days after the institution of the same; or

         (j)      Tenant shall file any petition in any court, whether or not
                  pursuant to any statute of the United States or any State, in
                  any bankruptcy, reorganization, composition, extension,
                  arrangement or insolvency proceeding.

15.2     TERMINATION; RE-ENTRY. Upon the happening of any one or more of the
         aforementioned Events of Default (notwithstanding any license of a
         former breach of covenant or waiver of the benefit hereof or consent in
         a former instance), Landlord or Landlord's agents or servants may give
         to Tenant a notice (hereinafter called "notice of termination")
         terminating this Lease on a date specified in such notice of
         termination (which shall be not less than five (5) days after the date
         of the mailing of such notice of termination), and this Lease and the
         Lease Term, as well as any and all of the right, title and interest of
         the Tenant hereunder, shall wholly cease and expire on the date set
         forth in such notice of termination (Tenant hereby waiving any rights
         of redemption) in the same manner and with the same force and effect as
         if such date were the date originally specified herein for the
         expiration of the Lease Term, and Tenant shall then quit and surrender
         the Premises to Landlord.

In addition or as an alternative to the giving of such notice of termination,
Landlord or Landlord's agents or servants may, by any suitable action or
proceeding at law, immediately or at any time thereafter re-enter the Premises
and remove therefrom Tenant, its agents, employees, servants, licensees, and any
subtenants and other persons, and all or any of its or their property therefrom,
and repossess and enjoy the Premises, together with all additions, alterations
and improvements thereto; but, in any event under this Section 15.2, Tenant
shall remain liable as hereinafter provided.

The words "re-enter" and "re-entry" as used throughout this Article XV are not
restricted to their technical legal meanings.

15.3     CONTINUED LIABILITY. RE-LETTING. If this Lease is terminated or if
         Landlord shall re-enter the Premises as aforesaid, or in the event of
         the termination of this Lease, or of re- entry, by or under any
         proceeding or action or any provision of law by reason of an Event of
         Default hereunder on the part of Tenant, Tenant covenants and agrees
         forthwith to pay and be liable for, on the days originally fixed herein
         for the payment thereof, amounts equal to the several installments of
         Annual Fixed Rent, all Additional Rent and other charges reserved as
         they would, under the terms of this Lease, become due if this Lease had
         not been terminated or if Landlord had not entered or re-entered, as
         aforesaid,

                                       27
<PAGE>   31

         and whether the Premises be relet or remain vacant, in whole or in
         part, or for a period less than the remainder of the Lease Term, or for
         the whole thereof, but, in the event the Premises be relet by Landlord,
         Tenant shall be entitled to a credit in the net amount of rent and
         other charges received by Landlord in reletting, after deduction of all
         reasonable expenses incur-red in reletting the Premises (including,
         without limitation, remodeling costs, brokerage fees and the like), and
         in collecting the rent in connection therewith, in the following
         manner:

Amounts received by Landlord after reletting shall first be applied against such
Landlord's expenses, until the same are recovered, and until such recovery,
Tenant shall pay, as of each day when a payment would fall due under this Lease,
the amount which Tenant is obligated to pay under the terms of this Lease
(Tenant's liability prior to any such reletting and such recovery not in any way
to be diminished as a result of the fact that such reletting might be for a rent
higher than the rent provided for in this Lease); when and if such expenses have
been completely recovered, the amounts received from reletting by Landlord as
have not previously been applied shall be credited against Tenant's obligations
as of each day when a payment would fall due under this Lease, and only the net
amount thereof shall be payable by Tenant. Further, Tenant shall not be entitled
to any credit of any kind for any period after the date when the term of this
Lease is scheduled to expire according to its terms.

15.4     LIQUIDATED DAMAGES. Landlord may elect, as an alternative, to have
         Tenant pay liquidated damages, which election may be made by notice
         given to Tenant at any time after the termination of this Lease under
         Section 15.2, above, and whether or not Landlord shall have collected
         any damages as hereinbefore provided in this Article XV, and in lieu of
         all other such damages beyond the date of such notice. Upon such
         notice, Tenant shall promptly pay to Landlord, as liquidated damages,
         in addition to any damages collected or due from Tenant from any period
         prior to such notice, such a sum as at the time of such notice
         represents the amount of the excess, if any, of (a) the discounted
         present value, at a discount rate of 6%, of the Annual Fixed Rent,
         Additional Rent and other charges which would have been payable by
         Tenant under this Lease for the remainder of the Lease Term if the
         Lease terms had been fully complied with by Tenant, over and above (b)
         the discounted present value, at a discount rate of 6%, of the Annual
         Fixed Rent, Additional Rent and other charges that would be received by
         Landlord if the Premises were re- leased at the time of such notice for
         the remainder of the Lease Term at the fair market value (including
         provisions regarding periodic increases in Annual Fixed Rent if such
         are applicable) prevailing at the time of such notice.

For the purposes of this Article, if Landlord elects to require Tenant to pay
liquidated damages in accordance with this Section 15.4, the total rent shall be
computed by assuming the Tenant's share of real estate taxes under Section 6.1
and the Operating Cost Excess under Section 7.4 to be the same as were payable
for the twelve (12) calendar months (or if less than twelve (12) calendar months
have been elapsed since the date hereof, the partial year) immediately preceding
such termination of re-entry.

Nothing contained in this Lease shall limit or prejudice the right of Landlord
to prove for and obtain in proceedings for bankruptcy or insolvency by reason of
the termination of this Lease, an amount

                                       28
<PAGE>   32

equal to the maximum allowed by any statute or rule of law in effect at the time
when, and governing the proceeds in which, the damages are to be proved, whether
or not the amount be greater, equal to, or less than the amount of the loss or
damages referred to above.

15.5     WAIVER OF REDEMPTION. Tenant, for itself and any and all persons
         claiming through or under Tenant, including its creditors, upon the
         termination of this Lease and of the term of this Lease in accordance
         with the terms hereof, or in the event of entry of judgment for the
         recovery of the possession of the Premises in any action or proceeding,
         or if Landlord shall enter the Premises by process of law or otherwise,
         hereby waives any right of redemption provided or permitted by any
         statute, law or decision now or hereafter in force, and does hereby
         waive, surrender and give up all rights or privileges which it or they
         may or might have under and by reason of any present or future law or
         decision, to redeem the Premises or for a continuation of this Lease
         for the term of this Lease hereby demised after having been
         dispossessed or ejected therefrom by process of law, or otherwise.

15.6     LANDLORDS DEFAULT. Landlord shall in no event be in default in the
         performance of any of Landlord's obligations hereunder unless and until
         Landlord shall have failed to perform such obligations within thirty
         (30) days, or such additional time as is reasonably required to correct
         any such default, after notice by Tenant to Landlord properly
         specifying wherein Landlord has failed to perform any such obligation.

                                  ARTICLE XVI

                            BANKRUPTCY OR INSOLVENCY

16.1     CHAPTER 7 PROCEEDINGS. If the Tenant shall become a debtor under
         Chapter 7 of the Bankruptcy Code and Tenant's trustee or Tenant shall
         elect to assume this Lease for the purpose of assigning the same or
         otherwise, such election and assignment may be made only if all of the
         provisions of Sections 16.2 and 16.4 of this Article XVI are satisfied.
         If Tenant or Tenant's trustee shall fail to elect to assume this Lease
         within sixty (60) days after the filing of a petition, or such
         additional time as provided by the court within such 60- day period,
         this Lease shall be deemed to have been rejected. Immediately
         thereupon, Landlord shall be entitled to possession of the Premises
         without further obligation to Tenant or Tenant's trustee and this Lease
         shall terminate, but Landlord's right to be compensated for damages
         (including, without limitation, damages pursuant to Article XV), in any
         such proceeding shall survive.

16.2     CHAPTER 11 PROCEEDINGS. If a petition for reorganization or adjustment
         of debts is filed concerning Tenant under Chapter I I of the Bankruptcy
         Code, or a proceeding is filed under Chapter 7 of the Bankruptcy Code
         and is transferred to Chapter 11, Tenant's trustee or Tenant, as
         debtor-in- possession, must elect to assume this Lease within the
         earlier of (i) confirmation of the plan and (ii) one hundred twenty
         (120) days from the date of the filing of the petition under Chapter 11
         or such transfer thereto or Tenant's trustee or Tenant, as
         debtor-in-possession, shall be deemed to have rejected this Lease. If
         Tenant's trustee or Tenant, as debtor-in-possession, has failed to
         perform all of Tenant's obligations under this Lease within the time
         periods (excluding grace periods) required

                                       29
<PAGE>   33

         for such performance, no election by Tenant's trustee or by Tenant, as
         debtor-in-possession, to assume this Lease, whether under Chapter 7 or
         Chapter 11, shall be effective unless each of the following conditions
         has been satisfied:

         (a)      Tenant's trustee or Tenant, as debtor-in- possession, has
                  cured, or has provided Landlord with Assurance (hereinafter
                  defined) that it will cure (i) all monetary defaults under
                  this lease within ten (10) days from the date of such
                  assumption, and (ii) all nonmonetary defaults under this lease
                  within thirty (30) days from the date of such assumption; and

         (b)      Tenant's trustee or Tenant, as debtor-in-possession, has
                  provided Landlord with Assurance of the future performance of
                  each of the obligations under this Lease of Tenant, Tenant's
                  trustee or Tenant, as debtor-in-possession, and has (i)
                  deposited with Landlord, as security for the timely payment of
                  rent hereunder, an amount equal to one annual installment of
                  Annual Fixed Rent which Tenant was obligated to pay to
                  Landlord under this Lease during the Lease Year in which such
                  default occurred, and (ii) paid in advance to Landlord
                  Tenant's annual obligations for Additional Rent and all other
                  monetary charges payable by Tenant under this Lease. The
                  obligations imposed upon Tenant's trustee or Tenant, as
                  debtor-in-possession, shall continue with respect to Tenant or
                  any assignee of Tenant's interests in this Lease after the
                  completion of bankruptcy proceedings.

For purposes of this Section 16.2, Landlord and Tenant acknowledge that
"Assurance" shall mean no less than: (i) Tenant's trustee or Tenant, as
debtor-in-possession, has and will continue to have sufficient unencumbered
assets after the payment of all secured obligations and administration expenses
to assure Landlord that sufficient funds will be available to fulfill the
obligations of Tenant under this Lease, and (ii) the Bankruptcy Court shall have
entered an order segregating sufficient cash payment to Landlord, or Tenant's
trustee or Tenant, as debtor-in-possession, or shall have granted a valid and
perfected first lien and security interest and mortgage in property of Tenant,
acceptable as to value and kind to Landlord, to secure to Landlord the
obligation of Tenant's trustee or Tenant, as debtor-in- possession, to cure
defaults under this Lease, both monetary and nonmonetary, within the time period
set forth above.

16.3     BANKRUPTCY EVENT FOLLOWING LEASE ASSUMPTION. If this Lease is assumed
         in accordance with the provisions of Section 16.2 and thereafter Tenant
         is liquidated or files or has filed against it a subsequent petition
         for reorganization or adjustment of debts under Chapter I I of the
         Bankruptcy Code, Landlord may, at its option, terminate this Lease and
         all rights of Tenant hereunder, by giving Tenant notice of its election
         to so terminate within thirty (30) days after the occurrence of either
         of such events.

16.4     LEASE ASSIGNMENT FOLLOWING LEASE ASSUMPTION. If Tenant's trustee or
         Tenant, as debtor-in-possession, has assumed this Lease pursuant to the
         terms and provisions of Sections 16.1 and 16.2 of this Article for the
         purpose of assigning (or elects to assign) this Lease, this Lease may
         be so assigned only if the proposed assignee has provided adequate
         assurance of future performance of all of the terms, covenants and
         conditions of this Lease to be performed by Tenant. Landlord shall be
         entitled to receive

                                       30
<PAGE>   34

         all cash proceeds of any such assignment. As used herein, "adequate
         assurance of future performance" shall mean that all of the following
         conditions have been satisfied:

         (a)      the proposed assignee has furnished Landlord with either (i) a
                  current financial statement audited by a certified public
                  accountant indicating a net worth and working capital in
                  amounts which Landlord reasonably determines to be sufficient
                  to assure the future performance by such assignee of Tenant's
                  obligations under this Lease, or (ii) a guaranty or guaranties
                  in form and substance satisfactory to Landlord from one or
                  more persons or entities with aggregate net worth which
                  Landlord reasonably determines to be sufficient to assure the
                  future performance by such assignee of Tenant's obligations
                  under this Lease; and

         (b)      Landlord has obtained all consents or waivers from others
                  required under any lease, mortgage, financing agreement or
                  other agreement by which Landlord is bound to permit Landlord
                  to consent to such assignment.

16.5     USE AND OCCUPANCY CHARGES. When, pursuant to the Bankruptcy Code,
         Tenant's trustee or Tenant, as debtor-in-possession, shall be obliged
         to pay reasonable use and occupancy charges for the use of the
         Premises, such charges shall not be less than the Annual Fixed Rent
         which Tenant is obligated to pay to Landlord under this Lease, plus all
         Additional Rent and all other monetary charges payable by Tenant under
         this Lease.

16.6     FURTHER PROVISIONS. Neither the whole nor any portion of Tenant's
         interest in this Lease or its estate in the Premises shall pass to any
         United States trustee, receiver, assignee for the benefit of creditors,
         or any other person or entity, or otherwise by operation of law under
         the laws of any state having jurisdiction of the person of property of
         Tenant, unless Landlord shall have consented to such transfer in
         writing. No acceptance by Landlord of rent or any other payments from
         any United States trustee, receiver, assignee, person or other entity
         shall be deemed to constitute such consent by Landlord, nor shall it be
         deemed a waiver of Landlord's right to terminate this Lease for any
         transfer of Tenant's interest under this Lease without such consent.

                                  ARTICLE XVII

                            MISCELLANEOUS PROVISIONS

17.1     WAIVER. Failure on the part of Landlord or Tenant to complain of any
         action or nonaction on the part of the other, no matter how long the
         same may continue, shall never be a waiver by Tenant or Landlord,
         respectively, of any of its rights hereunder.

Further, no waiver at any time of any of the provisions hereof by Landlord or
Tenant shall be construed as a waiver of any of the other provisions hereof, and
a waiver at any time of any of the provisions hereof shall not be construed as a
waiver at any subsequent time of the same provisions. The consent or approval of
Landlord or Tenant to or of any action by the other requiring such consent or
approval shall not be construed to waive or render unnecessary Landlord's or
Tenant's consent or approval to or of any subsequent similar act by the other.

                                       31
<PAGE>   35

No payment by Tenant, or acceptance by Landlord, of a lesser amount than shall
be due from Tenant to Landlord shall be treated otherwise than as a payment on
account. The acceptance by Landlord of a check for a lesser amount with an
endorsement or statement thereon, or upon any letter accompanying such check,
that such lesser amount is payment in full, shall be given no effect, and
Landlord may accept such check without prejudice to any other rights or remedies
which Landlord may have against Tenant. Further, the acceptance by Landlord of
Annual Fixed Rent, Additional Rent or any other charges paid by Tenant under
this Lease shall not be or be deemed to be a waiver by Landlord of any default
by Tenant, whether or not Landlord knows of such default, except for such
defaults as to which such payment relates.

17.2     CUMULATIVE REMEDIES. The specific remedies to which Landlord and Tenant
         may resort under the terms of this Lease are cumulative and are not
         intended to be exclusive of any other remedies or means of redress
         which they may be lawfully entitled to seek in case of any breach or
         threatened breach of any provisions of this Lease. In addition to the
         other remedies provided in this Lease, Landlord shall be entitled to
         the restraint by injunction of the violation or attempted or threatened
         violation of any of the covenants, conditions or provisions of this
         Lease or to seek specific performance of any such covenants, conditions
         or provisions, provided, however, that the foregoing shall not be
         construed as a confession ofjudgment by Tenant.

17.3     QUIET ENJOYMENT. Landlord agrees that, upon Tenant's paying the Annual
         Fixed Rent, Additional Rent and other charges herein reserved, and
         performing and observing the covenants, conditions and agreements
         hereof upon the part of Tenant to be performed and observed, Tenant
         shall and may peaceably hold and enjoy the Premises during the term of
         this Lease, without interruption or disturbance from Landlord or
         persons claiming through or under Landlord, subject, however, to the
         terms of this Lease. This covenant shall be construed as running with
         the land to and against subsequent owners and successors in interest,
         and is not, nor shall it operate or be construed as, a personal
         covenant of Landlord, except to the extent of the Landlord's interest
         in the Premises, and this covenant and any and all other covenants of
         Landlord contained in this Lease shall be binding upon Landlord and
         upon such subsequent owners and successors in interest of Landlord's
         interest under this Lease, to the extent of their respective interests,
         as and when they shall acquire same and then only for so long as they
         shall retain such interest.

17.4     SURRENDER. (A) No act or thing done by Landlord during the Lease Term
         shall be deemed an acceptance of a surrender of the Premises, and no
         agreement to accept such surrender shall be valid, unless in writing
         signed by Landlord. No employee of Landlord or of Landlord's agents
         shall have any power to accept the keys of the Premises as an
         acceptance of a surrender of the Premises prior to the termination of
         this Lease; provided, however, that the foregoing shall not apply to
         the delivery of keys to Landlord or its agents in its (or their)
         capacity as managing agent or for purpose of emergency access. In any
         event, however, the delivery of keys to any employee of Landlord or of
         Landlord's agents shall not operate as a termination of the Lease or a
         surrender of the Premises.

(B) Upon the expiration or earlier termination of the Lease Term, Tenant shall
surrender the Premises to Landlord in the condition as required by Sections 8.1
and 9.5, first removing all goods and effects of Tenant and completing such
other removals as may be permitted or required pursuant to Section 9.5.

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<PAGE>   36

17.5     BROKERAGE. Tenant warrants and represents that Tenant has not dealt
         with any broker in connection with the consummation of this Lease other
         than the broker, person or firm designated in Section 1.2 hereof; and
         in the event any claim is made against the Landlord relative to
         dealings with brokers other than the broker designated in Section 1.2
         hereof, Tenant shall defend the claim against Landlord with counsel of
         Landlord's selection and save harmless and indemnify Landlord on
         account of loss, cost or damage which may arise by reason of such
         claim. Landlord agrees that it shall be solely responsible for the
         payment of brokerage commissions to the broker, person or firm
         designated in Section 1.2 hereof.

17.6     INVALIDITY OF PARTICULAR PROVISIONS. If any term or provision of this
         Lease, or the application thereof to any person or circumstance shall,
         to any extent, be invalid or unenforceable, the remainder of this
         Lease, or the application of such term or provision to persons or
         circumstances other than those as to which it is held invalid or
         unenforceable, shall not be affected thereby, and each term and
         provision of this Lease shall be valid and be enforced to the fullest
         extent permitted by law.

17.7     PROVISIONS BINDING, ETC. The obligations of this Lease shall run with
         the land, and except as herein otherwise provided, the terms hereof
         shall be binding upon and shall inure to the benefit of the successors
         and assigns, respectively, of Landlord and Tenant and, if Tenant shall
         be an individual, upon and to his heirs, executors, administrators,
         successors and assigns. Each term and each provision of this Lease to
         be performed by Tenant shall be construed to be both a covenant and a
         condition. The reference contained to successors and assigns of Tenant
         is not intended to constitute a consent to assignment by Tenant.

17.8     RECORDING. Each of Landlord and Tenant agree not to record the within
         Lease, but each party hereto agrees, on the request of the other, to
         execute a so-called Notice of Lease or short form lease in form
         recordable and complying with applicable law and reasonably
         satisfactory to Landlord's and Tenant's attorneys. In no event shall
         such document set forth the rent or other charges payable by Tenant
         under this Lease; and any such document shall expressly state that it
         is executed pursuant to the provisions contained in this Lease, and is
         not intended to vary the terms and conditions of this Lease.

17.9     NOTICES AND TIME FOR ACTION. Whenever, by the terms of this Lease,
         notice shall or may be given either to Landlord or to Tenant, such
         notices shall be in writing and shall be sent by hand, registered or
         certified mail, or overnight or other commercial courier, postage or
         delivery charges, as the case may be, prepaid as follows:

                  If intended for Landlord, addressed to Landlord at the address
                  set forth on the first page of this Lease (or to such other
                  address or addresses as may from time to time hereafter be
                  designated by Landlord by like notice).

                  If intended for Tenant, addressed to Tenant at the address set
                  forth on the first page of this Lease except that from and
                  after the Commencement Date the address of Tenant shall be the
                  Premises (or

                                       33
<PAGE>   37

                  to such other address or addresses as may from time to time
                  hereafter be designated by Tenant by like notice).

Except as otherwise provided herein, all such notices shall be effective when
received; provided, that (i) if receipt is refused, notice shall be effective
upon the first occasion that such receipt is refused or (ii) if the notice is
unable to be delivered due to a change of address of which no notice was given,
notice shall be effective upon the date such delivery was attempted.

Where provision is made for the attention of an individual or department, the
notice shall be effective only if the wrapper in which such notice is sent is
addressed to the attention of such individual or department.

Time is of the essence with respect to any and all notices and periods for
giving of notice or taking any action thereto under this Lease.

17.10    WHEN LEASE BECOMES BINDING. Employees or agents of Landlord have no
         authority to make or agree to make a lease or any other agreement or
         undertaking in connection herewith. The submission of this document for
         examination and negotiation does not constitute an offer to lease, or a
         reservation of, or option for, the Premises, and this document shall
         become effective and binding only upon the execution and delivery
         hereof by both Landlord and Tenant. All negotiations, considerations,
         representations and understandings between Landlord and Tenant are
         incorporated herein and may be modified or altered only by written
         agreement between Landlord and Tenant, and no act or omission of any
         employee or agent of Landlord shall alter, change or modify any of the
         provisions hereof

17.11    PARAGRAPH HEADINGS. The paragraph headings throughout this instrument
         are for convenience and reference only, and the words contained therein
         shall in no way be held to explain, modify, amplify or aid in the
         interpretation, construction or meaning of the provisions of this
         Lease.

17.12    RIGHTS OF MORTGAGEE. This Lease shall be subject and subordinate to any
         mortgage now or hereafter on the Site or the Building, or both, and to
         all renewals, modifications, consolidations, replacements and
         extensions thereof and all substitutions therefor, provided that the
         holder of such mortgage agrees to recognize the right of Tenant to use
         and occupy the Premises upon the payment of rent and other charges
         payable by Tenant under this Lease and the performance by Tenant of
         Tenant's obligations hereunder. In confirmation of such subordination
         and recognition, Tenant shall execute and deliver promptly such
         instruments of subordination as such mortgagee may reasonably request,
         subject to receipt of such instruments of recognition from such
         mortgagee as Tenant may reasonably request. In the event that any
         mortgagee or its respective successor in title shall succeed to the
         interest of Landlord, then this Lease shall nevertheless continue in
         full force and effect and Tenant shall and does hereby agree to attorn
         to such mortgagee or successor and to recognize such mortgagee or
         successor as its landlord. If any holder of a mortgage which includes
         the Premises, executed and recorded prior to the Date of this Lease,
         shall so elect, this Lease, and the rights of Tenant hereunder, shall
         be superior in right to the rights of such holder, with the same force
         and effect as if this Lease had been executed, delivered and recorded,
         or a statutory Notice

                                       34
<PAGE>   38

         hereof recorded, prior to the execution, delivery and recording of any
         such mortgage. The election of any such holder shall become effective
         upon either notice from such holder to Tenant in the same fashion as
         notices from Landlord to Tenant are to be given hereunder or by the
         recording in the appropriate registry or recorder's office of an
         instrument in which such holder subordinates its rights under such
         mortgage to this Lease.

If in connection with obtaining financing for the Demised Premises a bank,
insurance company, pension trust or other institutional lender shall request
reasonable modifications in this Lease as a condition to such financing, Tenant
will not unreasonably withhold, delay or condition its consent thereto, provided
that such modifications do not increase the monetary obligations of Tenant
hereunder or materially adversely affect the leasehold interest hereby created
or Tenant's rights hereunder.

17.13    RIGHTS OF GROUND LESSOR. If Landlord's interest in property (whether
         land only or land and buildings) which includes the Premises is
         acquired by another party and simultaneously leased back to Landlord
         herein, the holder of the ground lessor's interest in such lease shall
         enter into a recognition agreement with Tenant simultaneously with the
         sale and leaseback, wherein the ground lessor will agree to recognize
         the right of Tenant to use and occupy the Premises upon the payment of
         Annual Fixed Rent, Additional Rent and other charges payable by Tenant
         under this Lease and the performance by Tenant of Tenant's obligations
         hereunder, and wherein Tenant shall agree to attorn to such ground
         lessor as its Landlord and to perform and observe all of the tenant
         obligations hereunder, in the event such ground lessor succeeds to the
         interest of Landlord hereunder under such ground lease.

17.14    NOTICE TO MORTGAGEE AND GROUND LESSOR. After receiving notice from any
         person, finn or other entity that it holds a mortgage which includes
         the Premises as part of the mortgaged premises, or that it is the
         ground lessor under a lease with Landlord as ground lessee, which
         includes the Premises as a part of the Premises, no notice from Tenant
         to Landlord shall be effective unless and until a copy of the same is
         given to such holder or ground lessor at the address as specified in
         said notice (as it may from time to time be changed), and the curing of
         any of Landlord's defaults by such holder or ground lessor within a
         reasonable time after such notice (including a reasonable time to
         obtain possession of the premises if the mortgagee or ground lessor
         elects to do so) shall be treated as performance by Landlord. For the
         purposes of this Section 17.14, the term "mortgage" includes a mortgage
         on a leasehold interest of Landlord (but not one on Tenant's leasehold
         interest).

17.15    ASSIGNMENT OF RENTS. With reference to any assignment by Landlord of
         Landlord's interest in this Lease, or the rents payable hereunder,
         conditional in nature or otherwise, which assignment is made to the
         holder of a mortgage or ground lease on property which includes the
         Premises, Tenant agrees:

         (a)      That the execution thereof by Landlord, and the acceptance
                  thereof by the holder of such mortgage, or the ground lessor,
                  shall never be treated as an assumption by such holder or
                  ground lessor of any of the obligations of

                                       35
<PAGE>   39

                  Landlord hereunder, unless such holder, or ground lessor,
                  shall, by notice sent to Tenant, specifically otherwise elect;
                  and

         (b)      That, except as aforesaid, such holder or ground lessor shall
                  be treated as having assumed Landlord's obligations hereunder
                  only upon foreclosure of such holder's mortgage and the taking
                  of possession of the Premises, or, in the case of a ground
                  lessor, the assumption of Landlord's position hereunder by
                  such ground lessor. In no event shall the acquisition of title
                  to the Building and the land on which the same is located by a
                  purchaser which, simultaneously therewith, leases the entire
                  Building or such land back to the Seller thereof be treated as
                  an assumption, by operation of law or otherwise, of Landlord's
                  obligations hereunder, but Tenant shall look solely to such
                  seller-lessee, and its successors from time to time in title,
                  for performance of Landlord's obligations hereunder. In any
                  such event, this Lease shall be subject and subordinate to the
                  lease to such purchaser provided that such purchaser-lessor
                  agrees to recognize the right of Tenant to use and occupy the
                  Demised Premises upon the payment of rent and all other
                  charges payable by Tenant under this Lease and the performance
                  by Tenant of Tenant's obligations under this Lease. For all
                  purposes, such seller-lessee, and its successors in title,
                  shall be the landlord hereunder unless and until Landlord's
                  position shall have been assumed by such purchaser-lessor.

17.16    STATUS REPORT AND FINANCIAL STATEMENTS. Recognizing that Landlord may
         find it necessary to establish to third parties, such as accountants,
         banks, potential or existing mortgagees, potential purchasers or the
         like, the then current status of performance hereunder, Tenant on the
         request of Landlord made from time to time, will promptly furnish to
         Landlord, or any existing or potential holder of any mortgage
         encumbering the Premises, the Building, the Site and/or the Complex or
         any potential purchaser of the Premises, the Building, the Site and/or
         the Complex (each an "Interested Party") a statement of the status of
         any matter pertaining to this Lease, including, without limitation,
         acknowledgments that (or the extent to which) each party is in
         compliance with its obligations under the terms of this Lease. In
         addition, Tenant shall deliver to Landlord, or any Interested Party
         designated by Landlord, financial statements of Tenant, and any
         guarantor of Tenant's obligations under this Lease, as reasonably
         requested by Landlord (but in no event more frequently than on three
         (3) occasions during the Lease Term) including, but not limited to,
         financial statements for the past three (3) years. Landlord agrees that
         it shall execute an instrument in a form reasonably acceptable to
         Landlord, wherein Landlord agrees to keep any information contained in
         such status statement or financial statement confidential, except that
         Landlord may provide the same to any Interested Party. Any such status
         statement or financial statement delivered by Tenant or Landlord
         pursuant to this Section 17.16 may be relied upon by any Interested
         Party.

17.17    SELF-HELP. If Tenant shall at any time fail to make any payment or
         perform any act which Tenant is obligated to make or perform under this
         Lease and (except in the case of emergency) if the same continues
         unpaid or unperformed beyond applicable grace periods, then Landlord
         may, but shall not be obligated so to do, after ten (10) days' notice
         to and demand upon Tenant, or with notice as soon as may be practicable
         in the case of

                                       36
<PAGE>   40

         any emergency (which notice may be before or after the exercise by
         Landlord of its rights hereunder), and without waiving, or releasing
         Tenant from, any obligations of Tenant in this Lease contained, make
         such payment or perform such act which Tenant is obligated to perform
         under this Lease in such manner and to such extent as may be reasonably
         necessary, and, in exercising any such rights, pay any costs and
         expenses, employ counsel and incur and pay reasonable attorneys' fees.
         All sums so paid by Landlord and all reasonable and necessary costs and
         expenses of Landlord incidental thereto, together with interest thereon
         at the annual rate equal to the sum of (a) the Base Rate from time to
         time announced by Bank of Boston as its Base Rate and (b) two percent
         (2%), from the date of the making of such expenditures by Landlord,
         shall be deemed to be Additional Rent and, except as otherwise in this
         Lease expressly provided, shall be payable to the Landlord on demand,
         and if not promptly paid shall be added to any rent then due or
         thereafter becoming due under this Lease, and Tenant covenants to pay
         any such sum or sums with interest as aforesaid, and Landlord shall
         have (in addition to any other right or remedy of Landlord) the same
         rights and remedies in the event of the non-payment thereof by Tenant
         as in the case of default by Tenant in the payment of Annual Fixed
         Rent.

17.18    HOLDING OVER. Any holding over by Tenant after the expiration of the
         term of this Lease shall be treated as a tenancy at sufferance at one
         and one-half (I V2) the rents and other charges herein (prorated on a
         daily basis) and shall otherwise be on the terms and conditions set
         forth in this Lease, as far as applicable; provided, however, that
         neither the foregoing nor any other term or provision of this Lease
         shall be deemed to permit Tenant to retain possession of the Premises
         or hold over in the Premises after the expiration or earlier
         termination of the Lease Term.

17.19    ENTRY BY LANDLORD. Landlord, and its duly authorized representatives,
         shall, upon reasonable prior notice (except in the case of emergency),
         have the right to enter the Premises at all reasonable times (except at
         any time in the case of emergency) for the purposes of inspecting the
         condition of same and making such repairs, alterations, additions or
         improvements thereto as may be necessary if Tenant fails to do so as
         required hereunder (but the Landlord shall have no duty whatsoever to
         make any such inspections, repairs, alterations, additions or
         improvements except as otherwise provided in Sections 4.2, 4.3, 7.1 and
         7.2), and to show the Premises to prospective tenants during the six
         (6) months preceding expiration of the term of this Lease as it may
         have been extended and at any reasonable time during the Lease Term to
         show the Premises to prospective purchasers and mortgagees.

17.20    TENANT'S PAYMENTS. Each and every payment and expenditure, other than
         Annual Fixed Rent, shall be deemed to be Additional Rent hereunder,
         whether or not the provisions requiring payment of such amounts
         specifically so state, and shall be payable, unless otherwise provided
         in this Lease, within ten (10) days after written demand by Landlord,
         and in the case of the non-payment of any such amount, Landlord shall
         have, in addition to all of its other rights and remedies, all the
         rights and remedies available to Landlord hereunder or by law in the
         case of non-payment of Annual Fixed Rent. Unless expressly otherwise
         provided in this Lease, the performance and observance by Tenant of all
         the terms, covenants and conditions of this Lease to be performed and
         observed by Tenant shall be at Tenant's sole cost and expense.

                                       37
<PAGE>   41

17.21    LATE PAYMENT. If Landlord shall not have received any payment or
         installment of rent on or before the date (the "Due Date") on which the
         same first becomes payable under this Lease, the amount of such payment
         or installment shall bear interest from the Due Date through and
         including the date such payment or installment is received by Landlord,
         at a rate equal to the lesser of (i) the rate announced by The First
         National Bank of Boston from time to time as its prime or base rate (or
         if such rate is no longer available, a comparable rate reasonably
         selected by Landlord), plus two percent (2%), or (ii) the maximum
         applicable legal rate, if any. Such interest shall be deemed Additional
         Rent and shall be paid by Tenant to Landlord upon demand.

17.22    COUNTERPARTS. This Lease may be executed in several counterparts, each
         of which shall be deemed an original, and such counterparts shall
         constitute but one and the same instrument.

17.23    ENTIRE AGREEMENT. This Lease constitutes the entire agreement between
         the parties hereto, Landlord's managing agent and their respective
         affiliates with respect to the subject matter hereof and thereof and
         supersedes all prior dealings between them with respect to such subject
         matter, and there are no verbal or collateral understandings,
         agreements, representations or warranties not expressly set forth in
         this Lease and such Agreement to Lease. No subsequent alteration,
         amendment, change or addition to this Lease shall be binding upon
         Landlord or Tenant, unless reduced to writing and signed by the party
         or parties to be charged therewith.

17.24    LANDLORD LIABILITY. Tenant shall neither assert nor seek to enforce any
         claim for breach of this Lease against any of Landlord's assets other
         than Landlord's interest in the Building, and Tenant agrees to look
         solely to such interest for the satisfaction of any liability of
         Landlord under this Lease, it being specifically agreed that neither
         Landlord, nor any successor holder of Landlord's interest hereunder,
         nor any beneficiary of any Trust of which any person from time to time
         holding Landlord's interest is Trustee, nor any such Trustee, shall
         ever be personally liable for any such liability. This paragraph shall
         not limit any right that Tenant might otherwise have to obtain
         injunctive relief against Landlord or Landlord's
         successors-in-interest, or to take any other action which shall not
         involve the personal liability of Landlord, or of any successor holder
         of Landlord's interest hereunder, or of any beneficiary of any trust of
         which any person from time to time holding Landlord's interest is
         Trustee, or of any such Trustee, to respond in monetary damages from
         Landlord's assets other than Landlord's interest in said Building, as
         aforesaid. In no event shall Landlord ever be liable for any indirect
         or consequential damages.

17.25    NO PARTNERSHIP. The relationship of the parties hereto is that of
         landlord and tenant and no partnership, joint venture or participation
         is hereby created.

17.26    SECURITY DEPOSIT. IF, in Section 1.2 hereof, a security deposit is
         specified, Tenant agrees that the same will be paid upon execution and
         delivery of this Lease and that Landlord shall hold the same,
         throughout the term of this Lease (including any extension thereof), as
         security for the performance by Tenant of all obligations on the part
         of Tenant to be performed. Landlord shall have the right from time to
         time without

                                       38
<PAGE>   42

         prejudice to any other remedy Landlord may have on account thereof, to
         apply such deposit, or any part thereof, to Landlord's damages arising
         from any default on the part of Tenant. If Landlord so applies all or
         any portion of such deposit, Tenant shall within seven (7) days after
         notice from Landlord deliver cash to Landlord in an amount sufficient
         to restore such deposit to the full amount stated in Section 1.2.
         Tenant not then being in default and having performed all of its
         obligations under this Lease, including the payment of all Annual Fixed
         Rent, Landlord shall return the deposit, or so much thereof as shall
         not have theretofore been applied in accordance with the terms of this
         Section 17.26, to Tenant on the expiration or earlier termination of
         the Lease Tenn and surrender of possession of the Premises by Tenant to
         Landlord in the condition required in the Lease at such time. While
         Landlord holds such deposit, Landlord shall have no obligation to pay
         interest on the same and shall have the right to commingle the same
         with Landlord's other fimds. If Landlord conveys Landlord's interest
         under this Lease, the deposit, or any part thereof not previously
         applied, shall be turned over by Landlord to Landlord's grantee for
         proper application of the deposit in accordance with the terms of this
         Section 17.26, and the return thereof in accordance herewith.

Neither the holder of a mortgage nor the landlord in a ground lease on property
which includes the Premises shall ever be responsible to Tenant for the return
or application of any such deposit, whether or not it succeeds to the position
of Landlord hereunder, unless such deposit shall have been received in hand by
such holder or ground lessor.

17.27    GOVERNING LAW. This Lease shall be governed exclusively by the
         provisions hereof and by the law of The Commonwealth of Massachusetts,
         as the same may from time to time exist.

                             (HERE ENDS THIS PAGE.)

                                       39
<PAGE>   43

         EXECUTED as a sealed instrument in two or more counterparts by persons
or officers hereunto duly authorized on the Date set forth in Section 1.2 above.

WITNESS:                                LANDORD:

                                        /s/ David Barrett
                                        ----------------------------------------
--------------------------------------  DAVID BARRETT AS TRUSTEE OF ONE
                                        CAMBRIDGE CENTER TRUST FOR HIMSELF
                                        AND CO-TRUSTEES, BUT NOT INDIVIDUALLY

                                        Tenant:

Witness:                                THE MEDICINES COMPANY

/s/ Helmut Giersiefen                   By /s/ Clive Meanwell
--------------------------------------    --------------------------------------
                                        Name Clive Meanwell
                                            ------------------------------------
                                        Title Chief Executive Officer
                                             -----------------------------------

                                        ----------------------------------------
                                                HEREUNTO DULY AUTHORIZED

                                        By
--------------------------------------    --------------------------------------
                                        Name
                                            ------------------------------------
                                        Title
                                             -----------------------------------

                                        ----------------------------------------
                                                HEREUNTO DULY AUTHORIZED

                                                   (CORPORATE SEAL)

<PAGE>   44

                                   EXHIBIT A-1

                               DESCRIPTION OF SITE

A certain tract of land situated on the southerly side of Broadway in the City F
Cambridge, in the County of Middlesex, Commonwealth of Massachusetts, bounded
and described as follows:

Beginning at a point in the southerly line of Broadway at the northwesterly
corner of the Premises S 60(0)-30'-18"E a distance of Six Hundred Sixty-Six and
Eighty-One Hundredths feet (666.8l') from the point of curvature of the
southerly sideline of Broadway and the easterly line of Sixth Street; thence

S 60 degrees-301-18" E         a distance of Two Hundred Six and EightyThree
                               Hundredths feet (206.83' ) bounding on the
                               southerly line of Broadway to a point; thence

Along the arc of a curve, curving to the right with a radius of Five Hundred
Eighty-One and Eighty-Eight Hundredths feet (581.88'), a distance of Fifty-Five
and Fifty Hundredths (55.50') to a point; thence

S49 degrees-201-28" E          a distance of Seventy and No Hundredths feet
                               (70.00') along a certain parcel of land, now or
                               formerly owned by the Cambridge Redevelopment
                               Authority for the next four (4) courses to a
                               point; thence

S 34 degrees-35'-57" W         a distance of Thirty-Four and Fifty-Five
                               Hundredths feet (34.55') to a point; thence

N 81 degrees-44'-36" W         a distance of One Hundred Ten and No

N 05 degrees-30'-53" E         a distance of Forty-Four and Fifty-Nine

N 84 degrees-29'-07" W         a distance of One Hundred Seventy-Six and
                               Forty-One Hundredths feet (176.4l') to a
                               point; thence

N 05 degrees-34'-07" E         a distance of Twenty-Four and Five Hundredths
                               feet (24.05') along the outside face of a
                               brick building for the next four (4) courses
                               to a point; thence

N 84 degrees-151-14" W         a distance of Nine and Ninety-Five Hundredths
                               feet (9.95') to a point; thence

N 05 degrees-29'-37" E         a distance of Fifty-Six and Ninety-Two
                               Hundredths feet (56.92') to a point; thence

S 84 degrees-25'-46" E         a distance of Twenty and Two Hundredths feet
                               (20.021) to a point; thence

N 05 degrees-27'-58" E         a-distance of Fifty-Three-and Forty-Four
                               Hundredths feet (53.44') to the point of
                               beginning.

The above-described tract of land contains 26,325 square feet, more or less, as
shown on a plan entitled "Kendall Sq. Urban Renewal Area, Cambridge, Mass.";
Dated November 19, 1985, Revised August 19, 1986; Prepared by Allen & Demurjian,
Inc., Scale 1"=40'. (Sheet 1 of 4).

The Site has appurtenant thereto and. is, subject -to. all rights, easements and
restrictions of record, whether currently existing or to be hereafter created.

<PAGE>   45

                                    EXHIBIT D

                              ONE CAMBRIDGE CENTER

                               LANDLORD'S SERVICES

I. CLEANING

A.       OFFICE AREA

         Daily: (Monday through Friday, inclusive, holidays excepted)

         1.       Empty all waste-receptacles and ash trays and remove waste
                  material from the Premises; clean ash trays daily and wash
                  receptacles as necessary.

         2.       Sweep and dust mop all uncarpeted areas using a dust-treated
                  mop.

         3.       Vacuum all rugs and carpeted areas.

         4.       Hand dust and wipe clean with treated cloths all horizontal
                  surfaces including furniture, office equipment, window sills,
                  door ledges, chair rails, and convector tops, within normal
                  reach.

         5.       Wash clean all water fountains.

         6.       Remove and dust under all telephones and other furnishings
                  (but not computer terminals or other specialized equipment)
                  and replace same.

         7.       Wipe clean all brass and other bright-work.

         8.       Hand dust all grill work within normal reach.

         9.       Upon completion of cleaning, turn off all lights, lock main
                  entry doors and any other doors found locked, and leave the
                  Premises in an orderly condition.

         Weekly:

         1.       Dust coat racks, and the like.

         2.       Remove all fingermarks from private entrance doors, light
                  switches and doorways.

         Quarterly:

         Render high dusting not reached in daily cleaning to include:

         1.       Dusting all pictures, frames, charts, graphs and similar wall
                  hangings.

                              Exhibit D Page 1 of 5
<PAGE>   46

         2.       Dusting of all vertical surfaces, such as walls, partitions,
                  doors and ducts.

         3.       Dusting of all pipes, ducts and high moldings.

         4.       Dusting of all venetian blinds.

B.       LAVATORIES

         Daily: (Monday through Friday, inclusive, holidays excepted.)

         1.       Sweep and damp mop floors.

         2.       Clean all mirrors, powder shelves, dispensers and receptacles,
                  bright work, flushometers, piping and toilet seat hinges.

         3.       Wash both sides of all toilet seats.

         4.       Wash all basins,.-bowls and urinals.

         5.       Dust and clean all powder room fixtures.

         6.       Empty and clean paper towel and sanitary disposal receptacles.

         7.       Remove waste paper and refuse.

         8.       Refill tissue holders, soap dispensers, towel dispensers and
                  vending sanitary dispensers as required, materials to be
                  furnished by Landlord;

         9.       A sanitizing solution will be used in all lavatory cleaning.

         Monthly:

         1.       Machine scrub lavatory floors.

         2.       Wash all partitions and tile walls in lavatories.

C.       MAIN LOBBY, ELEVATORS, BUILDING EXTERIOR AND CORRIDORS

         Daily: (Monday through Friday, inclusive, holidays excepted.)

         1.       Sweep and wash all floors.

         2.       Wash all rubber mats.

         3.       Clean elevators, wash or vacuum floors, wipe down walls and
                  doors.

         4.       Spot clean any metal work inside lobby.

         5.       Spot clean any metal work surrounding Building entrance doors.

                              Exhibit D Page 2 of 5
<PAGE>   47

                  Monthly:

         All resilient tile floors in public areas to be treated equivalent to
         spray buffing.

D.       WINDOW CLEANING

         Windows of exterior walls will be washed on the inside and outside no
         less than three (3) times per year.

E.       Tenant requiring services in excess of those described above shall
         request same through Landlord, and any such excess services provided
         shall be at Tenant's expense.

II. HEATING, VENTILATING, AIR CONDITIONING

A.       Landlord shall furnish space heating and cooling as normal seasonal
         changes may require to provide reasonably comfortable space temperature
         and ventilation for occupants of the Premises under normal business
         operation, daily from 8:00 AM to 6:00 PM. Saturdays from 8:00 AM to
         1:00 PM, Sundays and holidays excepted.

         If Tenant shall require air conditioning or heating or ventilation
         outside the hours and days above specified, Landlord shall furnish such
         service at Tenant's expense.

B.       The air conditioning system is based upon an occupancy of not more than
         one person per 150 square feet of useable floor area, and upon a
         combined lighting and standard electrical load not to exceed 3.0 watts
         per square foot of useable floor area. In the event Tenant exceeds this
         condition or introduces onto the Premises equipment which overloads the
         systems, and/oroin'any other way causes,the system not adequately to
         perform their proper functions, supplementary systems may at Landlord's
         option be provided by Landlord at Tenant's expense.

III. WATER

         Cold water at temperatures supplied by the City of Cambridge water
         mains for drinking. lavatory, toilet and (if the same have been
         approved by Landlord for installation in the Premises), kitchen and
         restaurant purposes and hot water for lavatory purposes only from
         regular building supply at prevailing temperatures; provided, however,
         that Landlord may require Tenant at Tenant's expense, to install a
         meter or meters to measure the water supplied to any kitchen (including
         dishwashing) and restaurant areas in the Premises, in which case Tenant
         shall upon Landlord's request reimburse Landlord for the cost of the
         water (including heating thereof) consumed in such areas and the sewer
         use charges resulting therefrom.

IV. ELEVATORS

                              Exhibit D Page 3 of 5
<PAGE>   48

         The passenger elevator system shall be in automatic operation and
         available to Tenant at all times except when necessary repairs or
         inspections are being rendered. The use of the service elevator will
         have to be scheduled with the Landlord and coordinated with the needs
         of the other tenants.

V.       ELECTRICAL SERVICE

A.       Landlord shall cause to be provided electric power for up to 1.5 watts
         per square foot of useable floor area for lighting plus 1.0 watts per
         square foot of useable floor area for office machines through standard
         receptacles for the typical office space.

B.       Landlord, at its option, may require separate metering and direct
         billing to Tenant for the electric power required for any special
         equipment (such as computers and reproduction equipment) that requires
         either 3phase electric power or any voltage other than 120. Landlord
         will furnish and install at Tenant's expense all replacement lighting
         tubes,-lamps,znd ballasts required by Tenant. Landlord will clean
         lighting fixtures on a regularly scheduled basis at Tenant's expense.

         Useable floor area as used herein means the area between the central
         building core and the interior face of the exterior walls, unless
         Tenant's space includes less than the entire rentable floor area of any
         floor, in which case the useable floor area shall mean the area within
         the demising walls but shall excludes any common area on the floor.

C.       Notwithstanding anything else in this Exhibit D to the contrary, Tenant
         shall pay for all electrical service provided for lights, power,
         ..HVAC, -,etc. , pursuant to the terms of the Lease to which this
         Exhibit D is attached.

                              Exhibit D Page 4 of 5
<PAGE>   49

                                    EXHIBIT H

                              ONE CAMBRIDGE CENTER

                        PROCEDURE FOR ADJUSTMENT OF COSTS

                       OF ELECTRIC POWER USAGE BY TENANTS

         This memo outlines the procedure for adjusting charges for electric
power to tenants at the office building to be known as One Cambridge Center.

         1.       Main electric service to this building will be provided by the
                  local util ` ity company (currently Cambridge Electric Light
                  Company) to a single main meter. All charges by the utility
                  will be read from. this meter and billed to and paid by
                  Landlord at rates established by the utility company.

         2.       All office tenants shall pay for electricity as- part of their
                  rental payments, including electricity for both common areas
                  of the building and for tenant occupied areas. Each lease
                  shall also contain a provision making such tenant responsible
                  for its proportionate share of any increases in the cost of
                  electricity used in the building over the base year amounts
                  established in the Lease.

         3.       In order to assure that charges for electric service are
                  apportioned fairly among tenants in - relation. to the
                  relative amounts of electricity used-by each tenant,
                  additional meters (known as "check meters") will be installed
                  by Landlord to permit periodic evaluations of electric usage
                  to be made. On each office floor there will be one meter
                  serving all of the floor.

         4.       Each meter shall be installed so that it will measure all of
                  the electricity provided to the floor governed by that meter,
                  including all lights and power in both tenant and common core
                  areas (restrooms, corridors, HVAC equipment room etc.). This
                  shall not, however, include the following, which `Shall be
                  wired from the main building service and not through the check
                  meters stairwell and emergency lights; elevators; lighting and
                  HVAC in the building lobby and main service areas; exterior
                  lighting; and all main building mechanical systems. (Common
                  areas on each floor, including the elevator lobby, corridors,
                  and bathrooms will have service through and check meters on
                  each floor.) In addition, further modification to the
                  number-and location of check meters may-be made by Landlord if
                  required to improve the quality of information obtained
                  thereby.

         5.       The Landlord will cause the check meters to be read
                  periodically by its employees and will perform an analysis of
                  information for the purpose of determining whether any
                  adjustments are required to achieve an equitable allocation of
                  the costs of electric service among the tenants in the
                  building in relation to the respective amounts of usage of
                  electricity for those tenants. For this purpose, the Landlord
                  shall, as far as possible in each case, read the meters to
                  determine usage

                              Exhibit H Page 1 of 3
<PAGE>   50

                  for periods that include one or more entire periods used by
                  the utility company for the reading of the main building meter
                  (so that the Landlord may, in its discretion, choose periods
                  that are longer than those used by the utility company --for
                  example, quarterly, semi-annual or annual periods).

         6.       A rent adjustment shall be made by Landlord on the following
                  basis:

                  a.       The total kilowatt hour usage for the period under
                           evaluation shall be established for each check meter
                           and for each floor.andalso.for the building as a
                           whole by a reading of the main building meter for
                           that period.

                  b.       The cost of the total amount of electricity supplied
                           for usage by tenants during the period (herein called
                           "Tenant Electricity") shall be determined by
                           multiplying the total cost of electricity as invoiced
                           by the utility company for the same period by a
                           fraction, the numerator of which is the total amount
                           of kilowatt hour usage as measured by all of the
                           check meters in the building .(Tenant Electricity)
                           and the denominator of which is the total amount of
                           kilowatt hour usage for the entire building as
                           measured by the main building electric meter.

                  c.       Where one or more floors is occupied entirely by one
                           tenant, its allocable share of Tenant `Electricity
                           cost for the period shall be determined by
                           multiplying the total costs of Tenant Electricity by
                           a fraction, the numerator of which is the kilowatt
                           hour usage of tenant electricity by said tenant
                           (calculated as the sum of kilowatt hour usage during
                           the period measured by all check meters serving its
                           premises) and the denominator of which is the total
                           kilowatt hour usage of Tenant Electricity for the
                           same period.

                  d.       Where a floor is occupied by more than one tenant,
                           the cost of Tenant Electricity for that floor shall
                           first be determined by the same procedure as set
                           forth in paragraph (c) above, and then the allocable
                           share of each tenant on that floor shall be
                           determined by multiplying the cost of Tenant
                           Electricity for that floor by a fraction, the
                           numerator of which is the rentable area leased to
                           each tenant (respectively for each tenant) and the
                           denominator of which is the total rentable area under
                           lease to tenants on said floor.

                  e.       Where part or all of the rentable area on a floor has
                           been occupied for less than all of the period for
                           which adjustments are being made, appropriate and
                           equitable modifications shall be made to the
                           allocation formula so that each tenant's allocable
                           share of costs equitable reflects its period of
                           occupancy, provided that in no event shall the total
                           of all costs as allocated to tenants be less than the
                           total cost of Tenant Electricity for said period.

         7.       The results of the cost adjustment analysis made by

                              Exhibit H Page 2 of 3
<PAGE>   51

                  Landlord under paragraph (6) above shall be compared to the
                  schedule of amounts due from tenants in regard to Tenant
                  Electricity in accordance with the leases in effect during the
                  period in question. Where the .payment due pursuant to the
                  lease is less than the cost as determined by the cost
                  adjustment analysis, each tenant shall be billed for the
                  difference by Landlord. Where the payment due pursuant to the
                  lease is greater than the cost as determined by the cost
                  adjustment analysis, the tenant shall be provided with a
                  credit in the amount of such difference applicable to the
                  rental payment next due (or in the case of tenants no longer
                  in occupancy, Landlord shall refund such amount to such
                  tenants).

                  In addition, where the leases call for tenants to make
                  periodic payments to Landlord based on estimates by .Landlord
                  of their allocable share of Tenant Electricity, such estimates
                  by Landlord shall, so far as possible, be based on the
                  effective distribution of costs among tenants during prior
                  periods, resulting from the application of the cost adjustment
                  procedures established herein.

         8.       All costs of electricity billed to Landlord through the main
                  electric meter for use in and around the building other than
                  the costs of Tenant Electricity allocated pursuant to the
                  procedures established herein, shall be treated as part of the
                  Operating Expenses for the Property for purposes of
                  determining the allocation of those costs.

                              Exhibit H Page 3 of 3

<PAGE>   52

                            FIRST AMENDMENT TO LEASE

         FIRST AMENDMENT TO LEASE dated as of this 17th day of July, 1998, by
and between MORTIMER B. ZUCKERMAN, EDWARD H. LINDE and DAVID BARRETT, the
TRUSTEES of ONE CAMBRIDGE CENTER TRUST under Declaration of Trust dated May 14,
1985, recorded with the Middlesex South District Registry of Deeds in Book
16221, Page 413 as amended by instrument dated July 31, 1986 and recorded with
said Registry of Deeds in Book 17438, Page 23, but not individually,
("Landlord") and THE MEDICINES COMPANY, a Delaware corporation ("Tenant").

                                    RECITALS

         By Lease dated March 15, 1997 (the "Lease"), Landlord did lease to
Tenant and Tenant did hire and lease from Landlord certain premises containing
4,063 square feet of rentable floor area located on the fourth (4th) floor in
the building (the "Building") known as and numbered One Cambridge Center,
Cambridge, Massachusetts. Said premises is referred to in the Lease as the
"Premises" and is hereinafter sometimes referred to as the "Initial Premises."

         By letter agreement between Landlord and Tenant dated June 26, 1998
(the "Letter Agreement") Landlord and Tenant extended the term of the Lease for
one (1) period of one (1) month (the "First Extended Term") upon the terms set
forth in such Letter Agreement.

         Landlord and Tenant have agreed to terminate the Lease with regard to
the entire Initial Premises and Tenant has determined to lease from Landlord the
8,811 square feet of rentable floor area (the "Rentable Floor Area of the New
Premises") located on the third (3rd) floor of the Building (the "New Premises")
shown on Exhibit A attached hereto, upon the terms and conditions contained in
this First Amendment to Lease (the "First Amendment").

         In addition, the Lease, as amended, provides for a Term which is
scheduled to expire on July 31, 1998. Landlord and Tenant desire to further
extend the Term of the Lease upon the terms contained in this First Amendment.

         Landlord and Tenant are entering into this instrument to set forth said
agreements and to further amend the Lease.

         NOW THEREFORE, in consideration of One Dollar ($1.00) and other good
and valuable consideration in hand this date paid by each of the parties to the
other, the receipt and sufficiency of which are hereby severally acknowledged,
and in further consideration of the mutual promises herein contained, Landlord
and Tenant, hereby agree to and with each other as follows:

1.       As of the "New Premises Commencement Date" (as defined in Section 2
         hereinbelow), the New Premises shall constitute the "Premises" demised
         to Tenant under the Lease and the Initial Premises shall no longer be
         deemed to be and shall be deleted and removed from the "Premises"
         demised to Tenant under the Lease.

2.       The following definitions are hereby added to Section 1.2 and the Lease
         immediately after the definition of "Commencement Date":

<PAGE>   53

          NEW PREMISES COMMENCEMENT DATE:    The later to occur of (a) August
                                             15, 1998 or (b) the earlier to
                                             occur of (i) the date on which the
                                             New Premises are "Substantially
                                             Complete" as provided in Section 8
                                             of this First Amendment, which day
                                             shall in no event be less than five
                                             (5) days subsequent to the date
                                             Landlord gives Tenant notice
                                             ("Landlord's Completion Notice") of
                                             the day Landlord expects the New
                                             Premises to be Substantially
                                             Complete or (ii) the date which
                                             Tenant commences beneficial use of
                                             the New Premises.

         NEW PREMISES SCHEDULED TERM
         COMMENCEMENT DATE:                  August 15, 1998.

3.       On or prior to the New Premises Commencement Date, (or the "Carpet
         Delivery Date" in the event of a "Carpet Delivery Delay" (as such terms
         are defined in Section 9 hereinbelow)) Tenant shall quit and vacate the
         Initial Premises and surrender the same in the condition required by
         the Lease upon the expiration or earlier termination of the Lease Tenn.

4.       The Lease Term, which but for this First Amendment is scheduled to
         expire on July 31, 1998, is hereby extended for the period commencing
         on August 1, 1998 and expiring on the date which is sixty (60) months
         subsequent to the New Premises Commencement Date (plus the partial
         month, if any, immediately following the New Premises Commencement
         Date) (the "Second Extended Term") unless sooner terminated in
         accordance with the provisions of the Lease as herein amended, such
         extension to be upon all the same terms and conditions set forth in the
         Lease except as otherwise provided in this First Amendment.

5.       (A)    For the period prior to July 1, 1998, Annual Fixed Rent at
                the annual rate of $113,764.00 (being the product of (i) $28.00
                and (ii) the Rentable Floor Area of the Initial Premises (being
                4,063 square feet)) shall continue to be paid as provided in the
                Lease.

         (B)     Notwithstanding the rental set forth in the Letter
                Agreement, for the period from July 1, 1998 until the New
                Premises Commencement Date, Annual Fixed Rent shall be payable
                for the Initial Premises at the annual rate of $113,764.00
                (being the product of (i) $28.00 and (ii) the Rentable Floor
                Area of the Initial Premises).

         (C)    For the period from the New Premises Commencement Date
                through July 31, 1999, Annual Fixed Rent for the New Premises
                shall be payable at the annual rate of $290,763.00 (being the
                product of (i) $33.00 and (ii) the Rentable Floor Area of the
                New Premises (being 8,811 square feet)).

                                       2
<PAGE>   54
        (D)     For the period from August 1, 1999 through July 31, 2000,
                Annual Fixed Rent for the New Premises shall be payable at the
                annual rate of $295,168.50 (being the product of (i) $33.50 and
                (ii) the Rentable Floor Area of the New Premises).

        (E)     For the period from August 1, 2000 through July 31, 2001,
                Annual Fixed Rent for the New Premises shall be payable at the
                annual rate of $303,979.50 (being the product of (i) $34.50 and
                (ii) the Rentable Floor Area of the New Premises).

        (F)     For the period from August 1, 2001 through July 31, 2002,
                Annual Fixed Rent for the New Premises shall be payable at the
                annual rate of $310,587.75 (being the product of (i) $35.25 and
                (ii) the Rentable Floor Area of the New Premises).

        (G)     For the period from August 1, 2002 through the expiration of
                the Second Extended Term, Annual Fixed Rent for the New Premises
                shall be payable at the annual rate of $314,993.25 (being the
                product of (i) $35.75 and (ii) the Rentable Floor Area of the
                New Premises).

6.       For the purposes of computing the "Tax Excess" (as defined in Section
         6.2 of the Lease), the "Operating Cost Excess" (as defined in Section
         7.5 of the Lease), and Tenant payments for electricity (as determined
         pursuant to Sections 5.1, 5.2 and 7.5 of the Lease), for the portion of
         the Lease Term on and after the New Premises Commencement Date, the
         "Rentable Floor Area of the Premises" shall be 8,811 square feet. For
         the portion of the Lease Term prior to the New Premises Commencement
         Date, the rentable floor area of the Premises shall continue to be the
         rentable floor area of the Initial Premises for such purposes.

7.       (A) For the purposes of computing Tenant's payments for the "Operating
         Cost Excess" (as defined in Section 7.5 of the Lease) for the portion
         of the Lease Term on and after the New Premises Commencement Date, the
         definition of "Base Operating Expenses" contained in Section 7.4 of the
         Lease shall be deleted in its entirety and replaced with the following:

         "Base Operating Expenses" means Landlord's Operating Expenses
         (hereinafter defined) for calendar year 1998, being the period from
         January 1, 1998 through December 31, 1998.

For the portion of the Lease Term prior to the New Premises Commencement Date,
such definition shall remain unchanged for such purposes.

         (B)    For the purposes of computing Tenant's payments for the "Tax
                Excess" (as defined in Section 6.2 of the Lease) for the portion
                of the Lease Term on and after the New Premise's Commencement
                Date, the definition of "Base Taxes" contained in Section 6.1 of
                the Lease shall be deleted in its entirety and replaced with the
                following:

                "Base Taxes" means Landlord's Tax Expenses (hereinbefore
                defined) for calendar year 1998 (that is the second half of
                fiscal tax year 1997 (being January 1, 1998 to June 30, 1998)
                and the first

                                        3
<PAGE>   55
                  half of fiscal tax year 1998 (being July 1, 1998 to December
                  31, 1998))

For the portion of the Lease Term prior to the New Premises Commencement Date,
such definition shall remain unchanged for such purposes.

8.       (A)      Landlord agrees to use due diligence to complete the work for
                  and respecting the New Premises described in Exhibit B
                  attached hereto by the New Premises Scheduled Term
                  Commencement Date, however, the failure of Landlord to
                  complete such work prior to any particular date shall not
                  entitle Tenant to any reduction or abatement of Annual Fixed
                  Rent or Additional Rent or the right to withhold or set off
                  against Annual Fixed Rent or Additional Rent nor give rise to
                  any right to terminate Lease or this First Amendment. Landlord
                  shall have no responsibility for the installation or
                  connection of Tenant's telephone or other communications
                  equipment or systems.

         Landlord's completion of the work shown on Exhibit B shall be subject
         to delays due to governmental regulation, unusual scarcity of or
         inability to obtain labor or materials, labor difficulties, casualty or
         other causes reasonably beyond Landlord's control ("Landlord's Force
         Majeure"). The New Premises shall be "Substantially Complete" on the
         date on which the work described in Exhibit B attached hereto together
         with common facilities for access and service, has been completed
         except for (i) items of work and adjustment of equipment and fixtures
         which can be completed after occupancy thereof has been taken without
         causing substantial interference with Tenant's use of the New Premises
         (i.e. so-called "punch list" items) and (ii) items of work described in
         Exhibit B for which there is a long lead time in obtaining the
         materials therefor or which are specially or specifically manufactured,
         produced or milled for the work in or to the New Premises and require
         additional time for receipt or installation ("long lead" items).
         Landlord shall use due diligence to complete all items and work
         excepted above along with the work described in Exhibit C attached
         hereto and Tenant shall not use the New Premises in such manner as will
         increase the cost of completion. Landlord shall permit Tenant access
         for installing furnishings in portions of the New Premises when it can
         be done without material interference with construction of the work
         described in Exhibit B. Landlord shall use diligent efforts to avoid or
         minimize disruption to, or interference with, Tenant's use and
         occupancy of the new Premises during completion of the work.

         Landlord and Tenant acknowledge and agree that Tenant is ordering the
         carpet for the New Premises described in Exhibit B and in the event
         that such carpet has not been delivered to Landlord on or before August
         11, 1998 (the "Carpet Delivery Delay"), Landlord shall not be required
         to install the carpet and the electrical data floor mounted monument
         style recepticals (the "Carpet Work") prior to the New Premises
         Commencement Date and the definition of "Substantially Complete" shall
         not be deemed to include completion of such work. In the event of a
         Carpet Delivery Delay, Tenant shall be permitted to hold over in the
         Initial Premises until the Carpet Work is Substantially Complete (the
         "Carpet Work Completion Date") and during the period form the New
         Premises Commencement Date through the Carpet Work Completion Date the
         Lease shall remain in full force and effect with respect to the Initial
         Premises and in

                                       4
<PAGE>   56

         addition to Tenant's payments for Annual Fixed Rent, operating costs,
         real estate taxes and electricity and all other amounts for the New
         Premises as provided in this First Amendment, Tenant shall continue to
         make payments for Annual Fixed Rent, operating costs, real estate taxes
         and electricity and all other amounts payable under the Lease for the
         Initial Premises as provided in the Lease prior to this First
         Amendment.

         Landlord and Tenant acknowledge that Landlord and Simon, Kucher &
         Partners, Strategy & Marketing Consultants, LLC ("Simon Kucher") are
         endeavoring to execute a lease with respect to the Initial Premises. In
         the event that Landlord and Simon Kucher have not executed a lease for
         the Initial Premises as of the date on which the work described in
         Exhibit B is Substantially Complete, Landlord shall promptly commence
         and use due diligence to complete the work for and respecting the New
         Premises described in Exhibit C attached hereto and the definition of
         "Substantially Complete" shall be deemed to include the completion of
         the work described in Exhibit C, including the Carpet Work, except for
         punch list items and long lead items as defined hereinabove.

         Landlord and Tenant acknowledge and agree that upon the expiration or
         earlier termination of the Lease (i) Tenant shall not be required to
         remove any of the additions, alterations or improvements described in
         Exhibits B and C attached hereto and (ii) Tenant may remove the glass
         modular petitions installed by Tenant in the New Premises provided that
         Tenant restores the New Premises as required by the Lease.

         (B)      Landlord shall provide Tenant with a special allowance in the
                  amount of $88,110.00 to be applied towards the cost of the
                  work to be performed by Landlord in the New Premises upon
                  notice from Tenant given to Landlord. Tenant shall pay
                  Landlord, as Additional Rent, any cost of performing such work
                  in excess of said special allowance within thirty (30) days
                  after being billed therefor. In the event that the cost of any
                  such work is less than the special allowance, Tenant shall not
                  be entitled to any payment or credit nor shall there be any
                  application towards Annual Fixed Rent or Additional Rent or
                  other amounts owed by Tenant.

9.       Landlord and Tenant acknowledge that Landlord is holding a security
         deposit in the amount of $9,480.34 as provided in Section 1.2 of the
         Lease. Upon the execution of this First Amendment by Tenant, Tenant
         shall deposit with Landlord good funds in an amount equal to
         $142,068.66 as additional security for the performance by Tenant of its
         obligations under the Lease. The total security deposit in the amount
         of $151,549.00 shall be held by Landlord in accordance with Section
         17.26 of the Lease; provided, however, that upon the first day of the
         thirty first (31st) month of the Second Extended Term, Landlord shall
         return a portion of such deposit in the amount of $75,774.50, provided
         that (i) there exists no Event of Default (as defined in Section 15.1
         of the Lease) and (ii) no portion of said deposit has been applied to
         Landlord's damages arising from any Event of Default on the part of
         Tenant whether or not Tenant has restored the amount so applied by
         Landlord.

10.      In the event Tenant executes a Lease (the "New Lease") with Landlord or
         any affiliate of Landlord for contiguous space in a building owned by
         Landlord located within the

                                       5
<PAGE>   57

         Development Area, which has a rentable floor area greater than or equal
         to 15,000 square feet, Landlord agrees to terminate the Lease as of the
         commencement of the term of the New Lease (the "Early Termination
         Date") and Tenant shall be relieved of all obligations under the Lease
         subsequent to the date of such termination, provided however that any
         such termination of the Lease shall be conditioned upon (i) Tenant
         actually occupying the space demised under the New Lease (ii) Tenant
         commencing rental payments under the New Lease (iii) there being no
         "Event of Default" under the Lease and the New Lease (as defined in
         Section 15.1 of both the Lease and the New Lease) as of the Early
         Termination Date (iv) Tenant having paid all Annual Fixed Rent and
         Additional Rent due under the Lease through the Early Termination Date
         (v) Tenant having surrendered and vacated the Premises in the condition
         required in the Lease upon the expiration or earlier termination of the
         Lease Term and (vi) Tenant having paid to Landlord good funds in an
         amount equal to (the "Applicable Termination Payment') (as defined
         hereinbelow) as of the date of execution of the New Lease. The
         "Applicable Termination Payment" shall be equal to the product of (a)
         the "Fixed Monthly Amortization Amount" as defined hereinbelow and (b)
         the number of months remaining and any fractions thereof in the Second
         Extended Term as of the Early Termination Date if Tenant had not
         exercised its right under this Section 10 to terminate this Lease. The
         "Fixed Monthly Amortization Amount" shall equal the monthly payment on
         a direct reduction loan basis amortized monthly where (i) the principal
         amount is equal to the sum of (a) the amount of the special allowance
         (referred to in Section 8(B) hereinabove) utilized by Tenant and (b)
         the brokerage commission in the amount of $35,244.00 payable to CB
         Commercial/Whittier Partners in connection with the consummation of
         this First Amendment, (collectively the "Transaction Costs") (ii) the
         term is sixty (60) calendar months and (iii) the monthly interest rate
         is 0.8333%. For example, if Tenant utilizes the full work allowance,
         the amount of the Transaction Costs will be $123,354.00 and if Tenant
         elected an Early Termination Date which is twenty (20) months prior to
         the expiration of the Term then the Applicable Termination Payment
         would be $48,098.95, being a principal amount of $123,354.00 amortized
         monthly over sixty (60) months at a monthly interest rate of 0.8333%.
         Notwithstanding the foregoing provisions of this Section 10, Landlord
         shall not be under any obligation to enter into a New Lease with Tenant
         and any New Lease shall be upon terms and conditions satisfactory to
         both Landlord and Tenant; provided, however, that if Landlord and
         Tenant do not execute a New Lease for whatever reason this Lease shall
         remain in full force and effect.

11.      Landlord shall provide to Tenant monthly parking privileges in one or
         more of the Garages in a number not to exceed parking for two (2)
         passenger automobiles for each 1,000 square feet of Rentable Floor Area
         of the New Premises in accordance with the terms of Article X of the
         Lease. Prior to the New Premises Commencement Date, Tenant shall notify
         Landlord of the number of parking spaces which Tenant desires to be
         made available in the Garage(s) for its use as of the New Premises
         Commencement Date. Landlord and Tenant acknowledge that Tenant's
         parking privileges with respect to the New Premises are in lieu of
         those parking privileges provided with respect to the Initial Premises
         and that the total number of spaces elected by Tenant shall not exceed
         two (2) spaces for each 1,000 square feet of Rentable Floor Area of the
         New Premises.

12.      Article MI of the Lease is hereby deleted in its entirety and replaced
         with the following:

                                       6
<PAGE>   58

12.1     RESTRICTIONS ON TRANSFER. Except as otherwise expressly provided
         herein, Tenant covenants and agrees that it shall not assign, mortgage,
         pledge, hypothecate or otherwise transfer this Lease and/or Tenant's
         interest in this Lease or sublet (which term, without limitation, shall
         include granting of concessions, licenses or the like) the whole or any
         part of the Premises. Any assignment, mortgage, pledge, hypothecation,
         transfer or subletting not expressly permitted in or consented to by
         Landlord under this Article XII shall be void, ab initio; shall be of
         no force and effect; and shall confer no rights on or in favor of third
         parties. In addition, Landlord shall be entitled to seek specific
         performance of or other equitable relief with respect to the provisions
         hereof.

12.2     EXCEPTIONS FOR PARENT OR SUBSIDIARY. Notwithstanding the foregoing
         provisions of Section 12.1 above and the provisions of Section 12.4
         below, but subject to the provisions of Sections 12.5, 12.6 and 12.7
         below, Tenant shall have the right to assign this Lease or to sublet
         the Premises (in whole or in part) to (i) any entity that controls, is
         controlled by or is under common control with Tenant, (ii) any entity
         which acquires substantially all of the assets of Tenant or (iii) any
         corporation into which Tenant may be converted or with which it may
         merge, provided that the entity to which this Lease is so assigned or
         which so sublets the Premises has a credit worthiness (e.g. assets on a
         pro forma basis using generally accepted accounting principles
         consistently applied and using the most recent financial statements)
         which is the same or better than the Tenant as of the Date of this
         Lease.

12.3     LANDLORD'S TERMINATION RIGHT. Notwithstanding the provisions of Section
         12.1 above, in the event Tenant desires to assign this Lease or to
         sublet the whole or part or part of the Premises, Tenant shall notify
         Landlord thereof in writing and Landlord shall have the right at its
         sole option, to be exercised within thirty (30) days after receipt of
         Tenants notice, to terminate this Lease as of a date specified in a
         notice to Tenant, which date shall not be earlier than sixty (60) days
         nor later than one hundred and twenty (120) days after Landlord's
         notice to Tenant; provided, however, that upon the termination date as
         set forth in Landlord's notice, all obligations relating to the period
         after such termination date (but not those relating to the period
         before such termination date) shall cease and promptly upon being
         billed therefor by Landlord, Tenant shall make final payment of all
         rent and additional rent due from Tenant through the termination date.
         In the event that Landlord shall not exercise its termination rights as
         aforesaid, or shall fail to give any or timely notice pursuant to this
         Section the provisions of Sections 12.4-12.7 shall be applicable. This
         Section 12.3 shall not be applicable to an assignment or sublease
         pursuant to Section 12.2.

12.4     CONSENT OF LANDLORD. Notwithstanding the provisions of Section 12.1
         above, but subject to the provisions of this Section 12.4 and the
         provisions of Sections 12.5, 12.6 and 12.7 below, in the event that
         Landlord shall not have exercised the termination right as set forth in
         Section 12.3, or shall have failed to give any or timely notice under
         Section 12.3, then for a period of ninety (90) days (i) after the
         receipt of Landlord's notice stating that Landlord does not elect the

                                       7
<PAGE>   59

         termination right, or (ii) after the expiration of the thirty (30) day
         period referred to in Section 12.3, in the event Landlord shall not
         give any or timely notice under Section 12.3 as the case may be, Tenant
         shall have the right to assign this Lease or sublet the whole (but not
         part) of the Premises in accordance with Tenants notice to Landlord
         given as provided in Section 12.5 provided that, in each instance,
         Tenant first obtains the express prior written consent of Landlord,
         which consent shall not be unreasonably withheld or delayed. Landlord
         shall not be deemed to be unreasonably withholding its consent to such
         a proposed assignment or subleasing if:

         (a)      the proposed assignee or subtenant is not of a character
                  consistent with the operation of a first class office building
                  (by way of example Landlord shall not be deemed to be
                  unreasonably withholding its consent to an assignment or
                  subleasing to any governmental agency), or

         (b)      the proposed assignee or subtenant is not of good character
                  and reputation, or

         (c)      the proposed assignee or subtenant does not possess adequate
                  financial capability to perform the Tenant obligations as and
                  when due or required, or

         (d)      the assignee or subtenant proposes to use the Premises (or
                  part thereof) for a purpose other than the purpose for which
                  the Premises may be used as stated in Section 1.2 hereof, or

         (e)      the character of the business to be conducted or the proposed
                  use of the Premises by the proposed subtenant or assignee
                  shall (i) be likely to increase Operating Expenses for the
                  Property beyond that which Landlord now incurs for use by
                  Tenant; (ii) be likely to increase the burden on elevators or
                  other Building systems or equipment over the burden prior to
                  such proposed subletting or assignment; or (iii) violate or be
                  likely to violate any provisions or restrictions contained
                  herein relating to the use or occupancy of the Premises, or

         (f)      there shall be existing an Event of Default (defined in
                  Section 15.1).

12.5     TENANTS NOTICE. Tenant shall give Landlord notice of any proposed
         sublease or assignment, and said notice shall specify the provisions of
         the proposed assignment or subletting, including (a) the name and
         address of the proposed assignee or subtenant, (b) in the case of a
         proposed assignment or subletting pursuant to Section 12.4, such
         information as to the proposed assignee's or proposed subtenant's net
         worth and financial capability and standing as may reasonably be
         required for Landlord to make the determination referred to in Section
         12.4 above (provided, however, that Landlord shall hold such
         information confidential having the right to release same to its
         officers, accountants, attorneys and mortgage lenders on a confidential
         basis), (c) all of the

                                       8
<PAGE>   60

         terms and provisions upon which the proposed assignment or subletting
         is to be made, (d) in the case of a proposed assignment or subletting
         pursuant to Section 12.4, all other information necessary to make the
         determination referred to in Section 12.4 above and (e) in the case of
         a proposed assignment or subletting pursuant to Section 12.2 above,
         such information as may be reasonably required by Landlord to determine
         that such proposed assignment or subletting complies with the
         requirements of said Section 12.2.

         If Landlord shall consent to the proposed assignment or subletting, as
         the case may be then, in such event, Tenant may thereafter sublease
         (the whole or part of the Premises) or assign pursuant to Tenants
         notice, as given hereunder; provided, however, that if such assignment
         or sublease shall not be executed and delivered to Landlord within
         ninety (90) days after the date of Landlord's consent the consent shall
         be deemed null and void and the provisions of Section 12.3 shall be
         applicable.

12.6     PROFIT ON SUBLEASING OR ASSIGNMENT. In addition, in the case of any
         assignment or subleasing as to which Landlord may consent (other than
         an assignment or subletting permitted under Section 12.2 hereof) such
         consent shall be upon the express and further condition, covenant and
         agreement, and Tenant hereby covenants and agrees that, in addition to
         the Annual Fixed Rent, Additional Rent and other charges to be paid
         pursuant to this Lease, fifty percent (50%) of the "Assignment/Sublease
         Profits" (hereinafter defined), if any shall be paid to Landlord.

         The "Assignment/Sublease Profits" shall be the excess, if any, of (a)
         the "Assignment/Sublease Net Revenues" as hereinafter defined over (b)
         the Annual Fixed Rent, Additional Rent and other charges provided in
         this Lease (provided, however, that for the purpose of calculating the
         Assignment/Sublease Profits in the case of a sublease, appropriate
         proportions in the applicable Annual Fixed Rent, Additional Rent and
         other charges under this Lease shall be made based on the percentage of
         the Premises subleased and on the terms of the sublease). The
         "Assignment/Sublease Net Revenues" shall be the fixed rent, Additional
         Rent and all other charges and sums payable either initially or over
         the term of the sublease or assignment plus all other profits and
         increases to be derived by Tenant as a result of such subletting or
         assignment, less the reasonable costs of Tenant incurred in such
         subleasing or assignment (the definition of which shall include but not
         necessarily be limited to rent concessions, brokerage commissions,
         reasonable legal fees and alteration allowances) amortized over the
         term of the sublease or assignment.

         All payments of the Assignment/Sublease Profits due Landlord shall be
         made within ten (10) days of receipt of same by Tenant.

12.7     ADDITIONAL CONDITIONS. (A) It shall be a condition of the validity of
         any assignment or subletting of right under Section 12.2 above, or
         consented to under Section 12.4 above, that both Tenant and the
         assignee or sublessee agree directly

                                       9
<PAGE>   61

         with Landlord in a separate written instrument reasonably satisfactory
         to Landlord which contains terms and provisions reasonably required by
         Landlord, including, without limitation, the agreement of the assignee
         or sublessee to be bound by all the obligations of the Tenant
         hereunder, including, without limitation, the obligation to pay the
         Annual Fixed Rent, Additional Rent, and other amounts provided for
         under this Lease (but in the case of a partial subletting, such
         subtenant shall agree on a pro rata basis to be so bound) including the
         provisions of Sections 12.1 through 12.7 hereof, but such assignment or
         subletting shall not relieve the Tenant named herein of any of the
         obligations of the Tenant hereunder, Tenant shall remain fully and
         primarily liable therefor and the liability of Tenant and such assignee
         (or subtenant, as the case may be) shall be joint and several. Further,
         and notwithstanding the foregoing, the provisions hereof shall not
         constitute a recognition of the assignment or the assignee thereunder
         or the sublease or the subtenant thereunder, as the case may be, and at
         Landlord's option, upon the termination of the Lease, the assignment or
         sublease shall be terminated.

         (B)      As Additional Rent, Tenant shall reimburse Landlord promptly
                  for reasonable out of pocket legal and other expenses incurred
                  by Landlord in connection with any request by Tenant for
                  consent to assignment or subletting.

         (C)      If this Lease be assigned, or if the Premises or any part
                  thereof be sublet or occupied by anyone other than Tenant,
                  Landlord may upon prior notice to Tenant, at any time and from
                  time to time, collect Annual Fixed Rent, Additional Rent, and
                  other charges from the assignee, sublessee or occupant and
                  apply the net amount collected to the Annual Fixed Rent,
                  Additional Rent and other charges herein reserved, but no such
                  assignment, subletting, occupancy or collection shall be
                  deemed a waiver of this covenant, or a waiver of the
                  provisions of Sections 12.1 through 12.7 hereof, or the
                  acceptance of the assignee, sublessee or occupant as a tenant
                  or a release of Tenant from the further performance by Tenant
                  of covenants on the part of Tenant herein contained, the
                  Tenant herein named to remain primarily liable under this
                  Lease.

         (D)      The consent by Landlord to an assignment or subletting under
                  any of the provisions of Sections 12.2 or 12.4 shall in no
                  wise be construed to relieve Tenant from obtaining the express
                  consent in writing of Landlord to any further assignment or
                  subletting.

         (E)      In addition to the other requirements set forth in this Lease
                  and notwithstanding any other provision of this Lease, partial
                  sublettings of the Premises shall only be permitted under the
                  following terms and conditions: (i) the layout of both the
                  subleased premises and the remainder of the Premises must
                  comply with applicable laws, ordinances, rules and/or
                  regulations and be approved by Landlord, including, without
                  limitation, all requirements concerning access and egress;
                  (ii), in the event

                                       10
<PAGE>   62
                  the subleased premises are separately physically demised from
                  the remainder of the Premises, Tenant shall pay all costs of
                  separately physically demising the subleased premises; and
                  (iii) Tenant, at Landlord's option, shall restore the Premises
                  and the subleased premises to their original condition upon
                  the expiration or earlier termination of this Lease.

13.     (A)       Tenant warrants and represents that Tenant has not dealt
                  with any broker in connection with the consummation of this
                  First Amendment other than CB Commercial/Whittier Partners
                  CCB/Whittier); and in the event any claim is made against
                  Landlord relative to dealings by Tenant with brokers other
                  than CB/Whittier, Tenant shall defend the claim against
                  Landlord with counsel of Tenant's selection first approved by
                  Landlord (which approval will not be unreasonably withheld)
                  and save harmless and indemnify Landlord on account of loss,
                  cost or damage which may arise by reason of such claim.

        (B)       Landlord warrants and represents that Landlord has not
                  dealt with any broker in connection with the consummation of
                  this First Amendment other than CB/Whittier and in the event
                  any claim is made against Tenant relative to dealings by
                  Landlord with brokers, Landlord shall defend the claim against
                  Tenant with counsel of Landlord's selection and save harmless
                  and indemnify Tenant on account of loss, cost or damage which
                  may arise by reason of such claim.

14.      Except as otherwise expressly provided herein, all capitalized terms
         used herein without definition shall have the same meanings as are set
         forth in the Lease.

15.      Except as herein amended the Lease shall remain unchanged and in full
         force and effect. All references to the "Lease" shall be deemed to be
         references to the Lease as amended by the Letter Agreement and as
         herein amended.

         EXECUTED as a sealed instrument as of the date and year first above
written.

WITNESSES:                               LANDLORD:

                                         /s/ Michael A. Cantalupa
-------------------------------------    ---------------------------------------
                                         MICHAEL A. CANTALUPA, FOR THE
                                         TRUSTEES OF ONE CAMBRIDGE
                                         CENTER TRUST PURSUANT TO
                                         WRITTEN DELEGATION, BUT NOT
                                         INDIVIDUALLY

                                       11
<PAGE>   63

ATTEST:                                  TENANT:

By: /s/ Steve Roper                      THE MEDICINES COMPANY
   ----------------------------------
Name: Steve Roper
     --------------------------------
Title: Business Manager                     By: /s/ Peyton J. Marshall
      -------------------------------       ------------------------------------
                                         Name: Peyton J. Marshall
                                              ----------------------------------
                                         Title: Vice President, Treasurer
                                               ---------------------------------

                                         HERETO DULY AUTHORIZED

                                         By:
                                            ------------------------------------
                                         Name:
                                              ----------------------------------
                                         Title:
                                               ---------------------------------

                                         HERETO DULY AUTHORIZED

                                         (CORPORATE SEAL)

                                       12

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