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Exhibit 10.4

LEASE
by and between
KENDALL SQUARE, LLC
LANDLORD,
and
GENZYME CORPORATION,
TENANT

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ARTICLE I

REFERENCE DATA

1.1    SUBJECTS REFERRED TO

ANNUAL FIXED RENT RATE PER RENTABLE SQUARE FOOTAGE OF PREMISES:   Subject to
Sections 4.1(b), 10.11 and 10.12 hereof, an amount determined by (a) dividing
(i) the Project Cost by (ii) the Rentable Square Footage of Building and
(b) multiplying the result thereof by twelve percent (12%).
APPROXIMATE TERM:
 
Subject to Section 10.12 hereof, fifteen (15) years.
BUILDING:
 
The building now known as Building D, Cambridge Research Park, Cambridge,
Massachusetts, to be constructed by Landlord and containing approximately
300,000 rentable square feet ("r.s.f."), of which approximately 15,000 r.s.f.
shall be ground floor retail space (the "Retail Space"). Tenant shall have the
right to name the Building "The Genzyme Building," "Genzyme Center" or a similar
name, but in each case including the street address of the Building.
COMPLEX:
 
An approximately ten acre parcel of land, including the Lot and all buildings
thereon and improvements thereto hereafter constructed by Landlord or by an
Affiliate of Landlord (as such term is defined below in this Section 1.1), in
Cambridge, Massachusetts currently owned by Landlord and shown on a plan
entitled "Master Plan" dated June 1, 1999, Scale 1"=50', a reduced copy of which
is attached as Exhibit A hereto, but excluding any portion of the Complex which
is not hereafter owned by Landlord or an Affiliate of Landlord.
EXPANSION SPACES:
 
As determined and defined in Section 10.11 hereof.
INITIAL ESTIMATED ANNUAL ADDITIONAL RENT FOR BUILDING:
 
$2,467,500.00 based upon $10.50/r.s.f.
INITIAL ESTIMATED ANNUAL ADDITIONAL RENT FOR COMPLEX:
 
$352,500.00 based upon $1.50/r.s.f.
LANDLORD:
 
Kendall Square, LLC, formerly known as Cambridge Research Park, LLC, a Delaware
limited liability company.
LANDLORD'S ARCHITECT:
 
As determined pursuant to Section 3.1.1 hereof.
LANDLORD'S ADDRESS:
 
c/o Lyme Properties, LLC
101 Main Street
Cambridge, Massachusetts 02142      

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LANDLORD'S CONTRACTOR:
 
As determined pursuant to Section 3.1.1 hereof.
LANDLORD'S REPRESENTATIVE:
 
Each of David E. Clem and Robert L. Green
LEASE YEAR:
 
Each consecutive period of twelve (12) calendar months commencing on the
Commencement Date if it occurs on the first day of a calendar month and
otherwise commencing on the first day of the month immediately following the
month in which the Commencement Date occurs, and each anniversary of such date.
LOT:
 
The land on which the Building is to be constructed and shown on Exhibit A as
being generally bounded by Atheneum Street, Kendall Street, Easement, and land
of others, the legal description of which (and a plan for which) shall be
prepared by Landlord prior to the commencement of construction of the Base
Building Improvements by Landlord and attached hereto as Exhibit A-1 and which
plan shall be attached hereto as Exhibit A-2.
MANAGING AGENT:
 
To be determined by Landlord based upon a list of managing agents proposed from
time to time by Landlord and approved by Tenant, such approval not to be
unreasonably withheld, conditioned or delayed.
OPTIONS TO EXTEND:
 
Two (2) Options to Extend the Term of this Lease for successive periods of ten
(10) years each, in accordance with Section 10.12 hereof.
PERMITTED USES:
 
General office uses and accessory uses customarily incidental to general office
uses.
PREMISES:
 
Those portions of the Building demised to Tenant under this Lease from time to
time, as such portions are determined pursuant to Section 3.1.1 hereof and
subject to Sections 5.1.2 and 10.11 hereof.
PROJECT COST:
 
As determined pursuant to Section 3.1.1 hereof.
COMMERCIAL LIABILITY INSURANCE LIMITS:
 
Bodily Injury: $10,000,000
Property Damage: $10,000,000
RENTABLE SQUARE
FOOTAGE OF BUILDING:
 
As determined pursuant to Section 2.3 hereof, but the Building is currently
estimated to consist of 300,000 r.s.f. of space.      

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RENTABLE SQUARE
FOOTAGE OF PREMISES:
 
As determined pursuant to Section 2.3 hereof, but the Premises are currently
estimated to consist initially of approximately 235,000 r.s.f. of space in the
Building to be constructed by Landlord on the Lot; and the Rentable Square
Footage of Premises shall be increased at such time as each Expansion Space is
demised to Tenant; and the Expansion Spaces are currently estimated to consist
of approximately 50,000 r.s.f. of space, in the aggregate, in the Building to be
constructed by Landlord on the Lot, subject to Sections 5.1.2 and 10.11 hereof.
SCHEDULED SUBSTANTIAL COMPLETION DATE:
 
September 1, 2002
SCHEDULED TERM COMMENCEMENT DATE:
 
December 1, 2002
TENANT:
 
Genzyme Corporation, a Massachusetts corporation.
TENANT'S ADDRESS (For Notice and Billing):
 
One Kendall Square
Building 1400
Cambridge, Massachusetts 02139
TENANT'S ARCHITECT:
 
To be determined by Tenant.
TENANT'S PROPORTIONATE FRACTION FOR BUILDING:
 
As determined and as the same may be adjusted pursuant to Sections 2.3 and 10.11
hereof.
TENANT'S PROPORTIONATE FRACTION FOR COMPLEX:
 
As determined and as the same may be adjusted pursuant to Sections 2.3 and 10.11
hereof.
TENANT'S CONSTRUCTION REPRESENTATIVE:
 
To be identified by Tenant by notice to Landlord.
TENANT'S LEASE REPRESENTATIVE:
 
Evan M. Lebson
TERM COMMENCEMENT DATE:
 
The earlier of (a) the date that is ninety-one (91) days after the Substantial
Completion Date or (b) the date on which Tenant's personnel occupy all or any
portion of the Premises for the conduct of any aspect of Tenant's business (as
opposed to the conduct by Tenant of any of Tenant's Work or the installation in
the Premises of fixtures, furnishings, equipment or personal property);
provided, however, if Tenant only occupies a portion of the Premises for the
conduct of its business prior to the date determined by the preceding
clause (a), Tenant shall only be obligated to pay Rent calculated with respect
to such portion of the Premises so occupied.
TERM EXPIRATION DATE:
 
The last day of the fifteenth Lease Year, subject to two (2) Options to Extend
for successive periods of ten (10) years each, in accordance with Section 10.12.

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        The following capitalized terms shall have the respective meanings set
forth below or as referenced in this Lease:

ADA Requirements: The Americans with Disabilities Act (42 U.S.C. § 12101 et
seq.) and the regulations and Accessibility Guidelines for Buildings and
Facilities issued pursuant thereto.

Additional Rent Adjustment Date: As defined in Section 4.2.4

Additional Rent: All rent, charges and other sums, other than Fixed Rent, due
Landlord pursuant to this Lease.

Affiliate of Landlord: A person or entity controlled by, controlling or under
common control with Landlord.

Affiliate of Tenant: Any entity controlled by, controlling or under common
control with Tenant.

Annual Building Maintenance and Operation Charge: As defined in Section 4.2.4

Annual Complex Maintenance and Operation Charge: As defined in Section 4.2.4.

Annual Maintenance Charge: The sum of the Annual Building Maintenance and
Operation Charge, the Annual Complex Maintenance and Operation Charge and the
Nonstandard Charge.

Annual Tax, Insurance and Utility Charge: The sum of the Initial Tax Charge, the
Initial Insurance Charge and the Initial Utility Charge.

Appraiser: A commercial real estate broker having at least ten (10) years
experience in the commercial leasing market in the City of Cambridge,
Massachusetts.

Approved Contractor: As defined in Section 3.2.1.

Arbitrator: As defined in Section 10.13.

Architect's Contract: As defined in Section 3.1.1.

Availability Notice: As defined in Section 10.18

Base Building Improvements: As defined in Section 3.1.1.

Brokers: Trammel Crow Company and Insignia/ESG.

Building Common Areas: Interior and exterior common areas and facilities of the
Building and the Lot.

Casualty Restoration Completion Date: As defined in Section 6.1.

CDD: Community Development Department of the City of Cambridge, Massachusetts.

Change Orders: As defined in Section 3.1.2.

Chapter 91 Determination: As defined in Section 3.1.4.

Commencement Date: As defined and determined pursuant to Section 2.2.

Complex Common Areas: Interior and exterior common areas and facilities of the
Complex.

Confidential Information: Any and all knowledge, information, data, materials,
trade secrets, and other work product of a confidential nature gained, obtained,
derived, produced, generated or otherwise acquired by Landlord with respect to
Tenant's business.

Construction Contract: As defined in Section 3.1.1.

Construction Documents: As defined in Section 3.2.1.

Design Development Documents: As defined in Section 3.1.1.

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Design Process Letter: Letter dated January 17, 2000 from David Clem of Lyme
Properties, LLC to Henri Termeer, President and CEO of Tenant.

Developer's Fee: As defined in Section 3.1.1.

Development Approvals: As defined in Section 3.1.4.

Early Occupancy Space: As defined in Section 10.11.

Environmental Agreement: The Environmental Agreement between Landlord and Tenant
in the form of Exhibit E hereto.

Environmental Remediation: As defined in Section 3.1.3.

Estimated Annual Additional Rent: Landlord's estimate of the total amount of
Additional Rent which may be due from Tenant for any particular Lease Year with
respect to the Building, Lot and Complex.

Estimated Annual Maintenance Charge: Landlord's reasonable estimate of the
Annual Maintenance Charge.

Estimated Annual Tax, Insurance and Utility Charge: Landlord's reasonable
estimate of the Annual Tax, Insurance and Utility Charge.

Event of Default: As defined in Section 7.1.

Excluded Taxes: Any income taxes, excess profits taxes, excise taxes, franchise
taxes, or any taxes or assessments with respect to the Garage and other
buildings leased or available for lease (and the parcels of land upon which such
buildings are situated), other than the Building, the Lot and any building or
portion of a building in the Complex which is not available for lease (and the
parcel(s) of land on which the same may be located), in the Complex.

Exercise Notice: As defined in Section 10.12.

Expansion Spaces: As defined in Section 10.11.

Extension Periods: As defined in Section 10.12.

Extension Rent: As defined in Section 10.12.

Fair Market Rent: As defined in Section 10.12.

Final Design Documents: As defined in Section 3.1.1.

Final Project Budget: All hard costs and soft costs incurred by Landlord in
connection with the construction of the Base Building Improvements as reflected
in a final project budget to be mutually approved by Landlord and Tenant, as
provided in Section 3.1.1.

First Expansion Space: As defined in Section 10.11.

Fixed Rent: As defined in Section 4.1.

Garage Owner: The owner of the Garage.

Garage Parking Spaces: Tenant's Parking Spaces and the Valet Parking Spaces.

Garage: The underground parking structure to be constructed and/or owned by
Landlord or an Affiliate of Landlord south of Kendall Street, as shown on
Exhibit A hereto.

Holder: As defined in Section 8.1.

Impositions: As defined in Section 4.2.4(1)(a).

Indemnified Parties: As defined in Section 5.1.6.

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Initial Estimated Annual Additional Rent for Building: As defined in
Section 4.2.

Inquiry Notice: As defined in Section 10.12.

Labor Unrest: As defined in Section 3.2.1.

Landlord Milestone Date: As defined in Section 3.2.

Landlord's Statement: As defined in Section 4.2.4.

Landlord's Work: The construction of the Base Building Improvements in
accordance with the Final Design Documents as affected by Change Orders.

MCP: Massachusetts Contingency Plan, 310 CMR 40.0000 et seq., as amended.

MEPA Certificate: Certificate of the Secretary of Environmental Affairs on the
Final Environmental Impact Report dated April 15, 1999.

Minor Alteration: As defined in Section 3.2.1.

Mitigation Expenses: As defined in Section 3.1.1.

Mortgage: Mortgages, deeds of trust or other similar instruments evidencing
other voluntary liens or encumbrances, and modifications, consolidations,
extensions, renewals, replacements and substitutes thereof.

Nonstandard Charge: As defined in Section 4.2.4.

Nonstandard Costs: As defined in Section 4.2.4.

Option to Lease: The option to lease with respect to Building B executed by
Landlord and Tenant simultaneously with the execution hereof.

Options to Extend: As defined in Section 10.12.

Order of Conditions: Order of Conditions issued July 12, 1999 by the City of
Cambridge Conservation Commission.

Outside Completion Date: As defined in Section 3.2.

Parking Fee: As defined in Section 10.14.

Preliminary Design Concept: As defined in Section 3.1.1.

Progress Schedule: As set forth in Exhibit B hereto.

PTDM Approval: The PTDM Decision, the PTDM Letter and PTDM Plan.

PTDM Decision: PTDM Ordinance Final Decision issued April 20, 1999 by the CDD.

PTDM Letter: The Letter dated April 20, 1999 to Robert L. Green of Lyme
Properties from Susanne Rasmussen of the CDD attached to the PTDM Decision.

PTDM Plan: Landlord's Parking Transportation Demand Management Plan dated
April 9, 1999.

PUD Approval: The PUD Permit and the Settlement Agreement.

PUD Permit: A Special Permit issued by the City of Cambridge Planning Board,
Case No. PB #141 filed April 7, 1999 (the "PUD Permit"), recorded with the
Middlesex South District Registry of Deeds (the "Registry") in Book 31137, Page
89.

Punch List Items: Minor items which can be fully completed by Landlord within
thirty (30) days without material interference with Tenant and other items which
because of the season or weather or the

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nature of the item are not practicable to do at the time, provided that none of
said items is necessary to perform Tenant's Work.

Relevant Market: As defined in Section 10.12(b).

Remediation Documents: The documents set forth on Exhibit E-1 hereto.

Rentable Square Feet, Rentable Square Footage or r.s.f.: The rentable square
footage of the space in question as measured in accordance with the standard set
forth in Section 2.3.

Response Action Outcome: As such term is defined in the MCP.

ROFR Notice: As defined in Section 10.18.

ROFR Space: As defined in Section 10.18.

ROFR: As defined in Section 10.18.

Schematic Design Documents: As defined in Section 3.1.1.

Settlement Agreement: A Settlement Agreement dated May 24, 1999 among Barbara
Broussard, Mary DeFreitas, the East Cambridge Planning Team and Landlord.

SNDA: Subordination, Non-disturbance and Attornment Agreement.

Subdivision: As defined in Section 9.1.6.

Sublease Costs: As defined in Section 5.2.1.

Sublease Profits: As defined in Section 5.2.1.

Subsequent Approvals: As defined in Section 3.1.4.

Substantial Completion Date: As defined in Section 3.2.

Substitute Taxes: As defined in Section 4.2.1.

Tenant Delay: As defined in Section 3.1.1.

Tenant's Property: All of the furnishings, fixtures, equipment, effects and
property of every kind, nature and description owned or leased by Tenant or by
any person claiming by, through or under Tenant which, during the continuance of
this Lease or any occupancy of the Premises by Tenant or anyone claiming under
Tenant, may be on the Premises.

Tenant's Proportionate Fraction for Building: As defined in Section 2.3

Tenant's Proportionate Fraction for Complex: As defined in Section 2.3.

Tenant's Work: As defined in Section 3.2.1.

TI Factor: As defined in Section 10.11.

Title Exceptions: Item Nos. 2 through 12, inclusive set forth in Schedule B,
Part 1 of the Title Policy.

Title Policy: Owner's Policy No. 136-00-336684 dated August 19, 1998, issued by
Lawyer's Title Insurance Corporation.

TMA: The Charles River Transportation Management Association or any other
transportation management association of which Landlord is a member.

Transfer: As defined in Section 9.1.6.

Utilities: As defined in Section 4.2.3.

Utility Service Provider or Utility Service Providers: As defined in
Section 4.2.3.

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Utility Services: As defined in Section 4.2.3.

Valet Parking Fee: As defined in Section 10.14.

Valet Parking Spaces: As defined in Section 10.14.

1.2    EXHIBITS.

        The Exhibits listed below in this section are incorporated in this Lease
by reference and are to be construed as a part of this Lease:

EXHIBIT A   Plan showing Complex EXHIBIT A-1   Legal Description EXHIBIT A-2  
Plan showing Lot EXHIBIT A-3   Confirmation of Commencement Date and Rentable
Square Footage EXHIBIT A-4   Confirmation of Location of Expansion Spaces
EXHIBIT B   Progress Schedule EXHIBIT B-1   Project Budget Form EXHIBIT B-2  
Annual Maintenance Charge Categories EXHIBIT C   Rules and Regulations EXHIBIT D
  SNDA Form EXHIBIT E   Environmental Agreement EXHIBIT E-1   Remediation
Documents

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1.3    TABLE OF CONTENTS

ARTICLE I   1     1.1   SUBJECTS REFERRED TO   1     1.2   EXHIBITS.   8     1.3
  TABLE OF CONTENTS   9 ARTICLE II   12     2.1   PREMISES   12     2.2   TERM.
  13     2.3   MODIFICATION OF CERTAIN DEFINITIONS; CERTIFICATE REGARDING   13
ARTICLE III   14     3.1   INITIAL DESIGN AND CONSTRUCTION.   14         3.1.1  
Architect Selection Process, Development of Design Documents, Landlord's
Contractor and Project Cost.   14         3.1.2   Change Orders   20        
3.1.3   Environmental Remediation   21         3.1.4   Development Approvals and
Title Exceptions.   21     3.2   PREPARATION OF PREMISES FOR PERFORMANCE OF
TENANT'S WORK   23         3.2.1.   Performance of Tenant's Work.   25     3.3  
GENERAL PROVISIONS APPLICABLE TO CONSTRUCTION   29     3.4   REPRESENTATIVES  
29     3.5   LANDLORD INDEMNITY AND CORRECTION OF LANDLORD'S WORK   29 ARTICLE
IV   29     4.1   FIXED RENT   29     4.2   ADDITIONAL RENT   30         4.2.1  
Real Estate Taxes   30         4.2.2   Insurance   32             4.2.2.1  
Insurance Taken Out by Tenant   32             4.2.2.2   Insurance Taken Out by
Landlord   32             4.2.2.3   Tenant Reimbursement of Insurance Taken Out
by Landlord   33             4.2.2.4   Certain Requirements Applicable to
Insurance Policies   33             4.2.2.5   Waiver of Subrogation   33        
4.2.3   Utilities for Premises   34         4.2.4   Common Area Maintenance and
Expenses   34         4.2.5   Payments on Account of Taxes, Insurance and
Utilities   38     4.3   LATE PAYMENT OF RENT   39                      

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ARTICLE V   40     5.1   AFFIRMATIVE COVENANTS   40         5.1.1   Perform
Obligations   40         5.1.2   Occupancy and Use   40         5.1.3   Repair
and Maintenance   41         5.1.4   Compliance with Law   41         5.1.5  
Tenant's Work   42         5.1.6   Indemnity   43         5.1.7   Landlord's
Right to Enter   43         5.1.8   Personal Property at Tenant's Risk   43    
    5.1.9   Payment of Landlord's Cost of Enforcement   44         5.1.10  
Yield Up   44         5.1.11   Estoppel Certificate   44         5.1.12  
Landlord's Expenses Re: Consents   45         5.1.13   Rules and Regulations  
45         5.1.14   Loading   45         5.1.15   Holdover   45     5.2  
NEGATIVE COVENANTS   45         5.2.1   Assignment and Subletting   45        
5.2.2   Nuisance   47         5.2.3   Installation, Alterations or Additions  
47 ARTICLE VI   47     6.1   DAMAGE BY FIRE   47     6.2   CONDEMNATION   50    
6.3   AWARD   51 ARTICLE VII   51     7.1   EVENTS OF DEFAULT   51     7.2  
REMEDIES   52     7.3   REMEDIES CUMULATIVE   53     7.4   LANDLORD'S RIGHT TO
CURE DEFAULTS   53     7.5   EFFECT OF WAIVERS OF DEFAULT   53     7.6   NO
ACCORD AND SATISFACTION   53 ARTICLE VIII   53     8.1   RIGHTS OF MORTGAGE
HOLDERS   53     8.2   SUPERIORITY OF LEASE; OPTION TO SUBORDINATE   54     8.3
  LEASE AMENDMENTS   55 ARTICLE IX   56     9.1   AFFIRMATIVE COVENANTS   56    
    9.1.1   Perform Obligations   56         9.1.2   Repairs   56         9.1.3
  Compliance with Law   56         9.1.4   Indemnity   56         9.1.5  
Estoppel Certificate   57         9.1.6   Subdivision   57                      

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ARTICLE X   57     10.1   NOTICES FROM ONE PARTY TO THE OTHER   57     10.2  
QUIET ENJOYMENT   57     10.3   EASEMENTS; CHANGES TO LOT LINES   58     10.4  
LEASE NOT TO BE RECORDED   58     10.5   BIND AND INURE; LIMITATION OF
LANDLORD'S LIABILITY   58     10.6   ACTS OF GOD   58     10.7   LANDLORD'S
DEFAULT   59     10.8   BROKERAGE   59     10.9   APPLICABLE LAW AND
CONSTRUCTION   60     10.10   SUBMISSION NOT AN OFFER   60     10.11   EXPANSION
OF PREMISES   60     10.12   OPTIONS TO EXTEND   62     10.13   ARBITRATION   63
    10.14   PARKING   64     10.15   CONFIDENTIAL INFORMATION   65     10.16  
SIGNAGE   65     10.17   BUILDING B LEASE   66     10.18   RIGHT OF FIRST
REFUSAL   66     10.19   RETAIL TENANTS   67     10.20   ACCESS   67     10.21  
COOPERATION   67

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ARTICLE II

PREMISES AND TERM

2.1    PREMISES.

        Landlord hereby leases and demises to Tenant and Tenant hereby leases
from Landlord, subject to and with the benefit of the terms, covenants,
conditions and provisions of this Lease, the Premises. Tenant shall have, as
appurtenant to the Premises, the right to use in common with others, if any,
entitled thereto (i) the common areas and common facilities, if any, included in
the Building, on the Lot or in the Complex, (ii) the building service fixtures
and equipment serving the Premises, and (iii) subject to Section 10.14 hereof,
(a) the right to use that number of nonreserved parking spaces determined by
dividing the Rentable Square Footage (as the same shall be determined pursuant
to Section 2.3 hereof and as the same may be increased pursuant to Section 10.11
hereof) by 500 ("Tenant's Parking Spaces") in the underground parking garage
located south of Kendall Street as shown on Exhibit A hereto (the "Garage") and
(b) the right to use that number of nonreserved Valet Parking Spaces, as such
term is defined and such number is determined pursuant to Section 10.14 hereof.
To the extent that the Premises includes all of the rentable square footage on a
particular floor of the Building, Tenant shall have exclusive use of the common
areas on such floors, but Landlord shall have the rights set forth in the next
paragraph hereof.

        Landlord reserves the right from time to time, without unreasonable
interference with Tenant's use, (a) to install, repair, replace, use, maintain
and relocate for service to the Premises and to other parts of the Building, or
either, building service fixtures and equipment wherever located in the
Building, including the perimeter walls of the Premises, on the roof of the
Building, in mechanical penthouses and in any space in or adjacent to the
Premises used for shafts, stacks, pipes, conduits, wires and appurtenant
fixtures, ducts, electric or other utilities, telecommunications equipment or
other Building facilities, as well as the right of access (which right of access
shall be at reasonable times and upon reasonable notice, except in the case of
emergency) through the Premises for the purpose of operation, maintenance and
repair, provided, however, that the Annual Fixed Rent, Additional Rent (as
defined in Section 4.2 hereof) and other charges payable hereunder by Tenant
shall be proportionally reduced in the event that any such installation or
relocation of service materially reduces the usable floor area of the Premises
(other than a temporary reduction to accommodate installation, repair,
replacement, maintenance and relocation of such service); notwithstanding the
foregoing provisions of this clause (a), to the extent that the Premises include
all of the rentable square footage on a particular floor of the Building,
Landlord's right to install, repair, replace, use, maintain and relocate such
building service fixtures and equipment on such floor of the Building shall be
limited to placing or installing such building service fixtures and equipment in
shafts, pipes, stacks, conduits, chases and risers located within the central
core common area of such floor or in such other locations on such floor as may
be set forth in the Final Design Documents; (b) to construct, alter or relocate
any Building Common Areas and/or Complex Common Areas (provided that, except for
any construction, alteration or relocation of Complex Common Areas required or
permitted by the Development Approvals or Subsequent Approvals, no such
construction, alteration or relocation of any such Complex Common Areas shall
substantially or materially increase any payments due from Tenant under this
Lease and any such construction, alteration or relocation shall be substantially
similar in quality and utility to Complex Common Areas being altered or
relocated or substantially similar to common areas of first-class, mixed use
projects in the Relevant Market); and (c) after construction of the Building to
construct, alter or relocate any Building Common Areas, subject to approval by
Tenant, such approval not to be unreasonably withheld, delayed or conditioned.

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2.2    TERM.

        To have and to hold for a period (the "Term") commencing on the Term
Commencement Date (as such term is defined in Section 1.1 hereof) (the
"Commencement Date") and continuing until the Term Expiration Date, unless
sooner terminated as provided herein, including Section 3.2 and Article VII
hereof, and subject to extension in accordance with the terms of Section 10.12
hereof.

2.3    MODIFICATION OF CERTAIN DEFINITIONS; CERTIFICATE REGARDING COMMENCEMENT
DATE.

        Landlord and Tenant acknowledge that the actual rentable square footage
of the Premises, the Expansion Spaces (as such term is defined in Section 10.11
hereof) and the Building may, upon completion of construction of the Base
Building Improvements (as hereinafter defined), be different than the estimates
as set forth in Article I hereof. Accordingly, after completion of construction
of the Base Building Improvements, Landlord will notify Tenant of the Rentable
Square Footage of the Premises, the Expansion Spaces and the Building, all of
which shall be measured by Landlord's Architect in accordance with the ANSI/BOMA
Z65.1-1996 Standard Method for Measuring Building Rentable Area, approved
June 7, 1996 for a single tenant building. Landlord's Architect's measurement
shall be subject to review and approval by Tenant's Architect for conformity to
the foregoing standard. If necessary, Landlord and Tenant will execute an
amendment to this Lease modifying the definitions of Rentable Square Footage of
Premises, Rentable Square Footage of Building, the location in the Building of
the Premises and the Expansion Spaces, Tenant's Proportionate Fraction for
Building, Tenant's Proportionate Fraction for Complex, Initial Estimated Annual
Additional Rent for Building, Initial Estimated Annual Additional Rent for
Complex, and such other terms and provisions, if any, of this Lease as may be
necessary to reflect such actual measurements. Landlord and Tenant will also
execute, upon request of either, a certificate, substantially in the form of
Exhibit A-3 hereto, acknowledging, inter alia, the Commencement Date of this
Lease as provided for in Section 2.2 hereof, after such Commencement Date has
occurred (as described in Section 3.2 hereof), and the Rentable Square Footage
of the Building, the Premises and the Expansion Spaces. After such measurement
by Landlord's Architect, the Premises, the Expansion Spaces and the Building
shall not be subject to remeasurement without the consent of Landlord and
Tenant. Anything in this Lease to the contrary notwithstanding, the Premises, as
initially demised, shall include all of the Rentable Square Footage in the
Building other than the Expansion Spaces and the Retail Space. "Tenant's
Proportionate Fraction for Building" shall be the ratio, expressed as a
percentage, of the Rentable Square Footage of Premises, including the Expansion
Spaces and any ROFR Space (from and after the dates on which each of the
Expansion Spaces or any ROFR Space is demised to Tenant), to the Rentable Square
Footage of Building. "Tenant's Proportionate Fraction for Complex" shall be the
ratio, expressed as a percentage, of the Rentable Square Footage of the
Premises, including the Expansion Spaces and any ROFR Space, when applicable, to
the Rentable Square Footage of all buildings (other than any garages in the
Complex and any building or portion thereof which is not available for lease
such as an information kiosk), including the Building, which Landlord is
permitted to develop in the Complex pursuant to the PUD Approval. Landlord shall
have the right to estimate on a good faith basis, from time to time, the
Rentable Square Footage of all such buildings prior to the construction thereof.
From time to time after construction of each building in the Complex, Landlord
shall notify Tenant of the Rentable Square Footage of such buildings and shall
provide to Tenant, upon Tenant's request, such information as Tenant may
reasonably request with respect to the calculation thereof. Within thirty
(30) days after notice of such Rentable Square Footage, Tenant shall pay to
Landlord or Landlord shall credit to Additional Rent next due from Tenant, as
applicable, any underpayment owed or overpayment made, as applicable, by Tenant
based upon the estimated Rentable Square Footage of such buildings, on account
of Tenant's Proportionate Fraction for Complex of taxes and assessments and
Tenant's Proportionate Fraction for Complex of the Annual Complex Maintenance
and Operation Charge and the actual Rentable Square Footage of such buildings.

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ARTICLE III

BASE BUILDING IMPROVEMENTS

3.1    INITIAL DESIGN AND CONSTRUCTION.

3.1.1    Architect Selection Process, Development of Design Documents,
Landlord's Contractor and Project Cost.

        Landlord has initiated a design competition for the Building as more
fully set forth in a letter dated January 17, 2000 from David Clem of Lyme
Properties, LLC to Henri Termeer, President and CEO of Tenant (the "Design
Process Letter"), which is incorporated herein by reference thereto. Landlord
and Tenant agree to cooperate in connection with the design competition as set
forth in the Design Process Letter. Upon completion of such design competition,
Landlord and Tenant shall mutually select Landlord's Architect (for purposes of
this Lease the term "Landlord's Design Team" shall be deemed to refer not only
to Landlord's Architect but also to the principal engineers, architects and
other design consultants employed by Landlord or Landlord's Architect for the
design and construction of the Building) and Landlord's Design Team (to the
extent then identified). Landlord and Tenant shall also mutually establish and
agree upon (i) a preliminary design concept for the Building (the "Preliminary
Design Concept"), which shall be based upon Tenant's program, outline building
specifications, schedule requirements, and (ii) a preliminary hard and soft cost
budget for the Base Building Improvements (the "preliminary Project Cost
budget"). Such selection of Tenant's Architect and Landlord's Design Team (to
the extent then identified), the establishment and agreement upon the
Preliminary Design Concept and the establishment and agreement upon such
preliminary Project Cost budget shall be made by the respective dates for each
set forth in the progress schedule attached as Exhibit B hereto (the "Progress
Schedule"). Landlord and Tenant acknowledge and agree that the Progress Schedule
represents a good faith estimate of the respective dates upon which the items
set forth in the Progress Schedule are to occur but that the Progress Schedule
is subject to finalization by Landlord and Tenant upon selection of Landlord's
Architect and Landlord's Contractor. Accordingly, references in this Lease to
the Progress Schedule shall mean the Progress Schedule attached hereto as
Exhibit B as the same may be finalized. The Preliminary Design Concept shall
describe the general scope and quality of the Building and shall identify those
portions of the Building which will constitute the Premises initially leased to
Tenant and the Expansion Spaces. If despite the diligent and good faith efforts
of Landlord and Tenant the parties are unable to mutually select Landlord's
Architect, to establish a mutually acceptable Preliminary Design Concept and/or
a mutually acceptable preliminary Project Cost budget by the applicable dates
set forth in the Progress Schedule, either Landlord or Tenant may terminate this
Lease upon thirty (30) days' prior written notice to the other party. During
such thirty (30) day period Landlord and Tenant shall use diligent and good
faith efforts to select such Architect, establish such Preliminary Design
Concept and/or preliminary Project Cost budget, as applicable, failing which
this Lease shall terminate on the date set forth in such notice. In the event of
such termination, all third party, out-of-pocket costs incurred by Landlord in
connection with the design competition and design process solely for the
Building shall be shared equally by Landlord and Tenant.

        Landlord and Tenant also agree to cooperate in good faith in connection
with the design of the Building and the Base Building Improvements and the
development of a mutually acceptable Final Project Budget (as defined below).
Neither Landlord nor Tenant shall be required to approve any Design Documents
unless the Building includes at least 285,000 r.s.f. of office space and at
least 15,000 r.s.f. of ground floor retail space and each Expansion Space
includes approximately 25,000 r.s.f. of contiguous space on a single floor of
the Building. The size, layout, design and base building fit-up of the Building
and Base Building Improvements and the Final Project Budget shall be mutually
agreed

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upon by Landlord and Tenant. Landlord and Tenant acknowledge and agree that
during design development process contemplated hereby, Tenant, with Landlord's
approval, which approval shall not be unreasonably withheld, conditioned or
delayed, shall have the right to approve and/or design base building electrical,
mechanical, HVAC and other systems and design specifications (such as, by way of
example, entranceway and lobby design, internal stair location, elevator size
and finish, location of electrical and telecom rooms and equipment, location of
mechanical shaftways and equipment, structural bay spaces, window mullions
spacing and sill depth and height, floor to floor heights and the like),
provided that the specifications for such base building elements are equal or
better than the quality of the specifications therefor in a newly constructed,
first-class office tower in Cambridge.

        Each party acknowledges and agrees that it is in its best interest for
the Substantial Completion Date to occur on or before the Scheduled Substantial
Completion Date and that the Final Project Budget be substantially consistent
with the preliminary Project Cost budget and the updates thereto. Accordingly,
each party hereby agrees that it shall keep the other party informed of the
progress and status of its efforts to achieve the various milestones and other
scheduled completion dates set forth on the Progress Schedule; and that if
either party concludes that a milestone or other scheduled completion date will
not be met, such party shall use reasonable efforts to notify the other party of
the occurrence of any act, event, condition, omission or circumstance which
could have a substantial or material impact on: (i) the ability to achieve the
various milestone and other scheduled completion dates set forth on the Progress
Schedule; (ii) the cost or financial viability of the construction of the
Building or Complex; or (iii) Tenant's use and occupancy of the Premises.

        After Landlord's Architect and the Landlord's Design Team have been
selected and Landlord and Tenant have mutually established the Preliminary
Design Concept, Landlord shall enter into a contract (the "Architect's
Contract") with Landlord's Architect. The Architect's Contract shall be subject
to Tenant's prior approval, which approval shall not be unreasonably withheld,
conditioned or delayed. The Architect's Contract shall include provisions
requiring Landlord's Architect to submit all Design Documents (as hereinafter
defined) for each stage in the design process simultaneously to both Landlord
and Tenant sufficiently prior to the applicable Design Document completion date
for such design stage set forth in the Progress Schedule, in order to provide
Landlord and Tenant with reasonably sufficient time (in any event not less than
ten (10) business days for initial review of the applicable Design Document)
following receipt of such submission to review, comment on and approve such
submission prior to such completion date, to be responsible for the adequacy,
accuracy and completeness of the Final Design Documents approved by Landlord and
Tenant, and to cause the Final Design Documents to comply with all applicable
laws, regulations, building codes, building design standards, the Development
Approvals, Subsequent Approvals, agreed upon floor loading limits, and with
respect to all materials, equipment and special designs, processes or products,
that the same do not infringe any patent or other proprietary rights of others.
Contemporaneously with the selection of Landlord's Architect, Landlord shall
retain a construction manager or similar consultant (the "Construction Cost
Estimator"), reasonably satisfactory to the Tenant, to work with and provide
pre-construction services for Landlord, Tenant and Landlord's Architect to
develop, and provide value engineering services to control, a preliminary
Project Cost budget and updates thereto during the Schematic Design Documents
phase and the Design Development Documents phase. The parties acknowledge that
Landlord may, subject to Tenant's reasonable approval, elect, at any time, to
hire such Construction Cost Estimator as Construction Manager/General Contractor
for the Building. Subject to the limitations hereafter set forth with respect to
Tenant's right to disapprove bids with respect to the Construction Contract,
each of Landlord and Tenant shall have the right to approve such preliminary
Project Cost budget and updates thereto, which approvals shall not be
unreasonably withheld, conditioned or delayed.

        Landlord shall cause Landlord's Architect to prepare schematic
architectural plans, structural and engineering plans, elevations and building
sections, and site plans for the Building based upon the

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Preliminary Design Concept ("Schematic Design Documents"), which shall mean a
conceptual design of the Base Building Improvements illustrating the scale and
relationship of the components of the Base Building Improvements and calculating
the gross floor area and Rentable Square Footage of the Building. Additionally,
the Construction Cost Estimator shall prepare an updated budget for the Base
Building Improvements for approval by Landlord and Tenant. The Schematic Design
Documents shall show walkways and plazas for the Building and Lot, major
landscape features, hardscaping, scale and relationship of other major
components of the Building and Lot, pedestrian and vehicular (including service)
access and flow through the Lot, lighting, survey information such as existing
elevations, benchmarks and utilities, and any known construction limits. The
Schematic Design Documents shall also include models, color renderings and
outline specifications indicating all basic materials and systems of the
proposed Base Building Improvements. The Schematic Design Documents and all
subsequent Design Documents shall be prepared and distributed by Landlord's
Architect in both hard copy and electronic format.

        During the development of the Schematic Design Documents, Landlord and
Tenant shall meet with representatives of the CDD (as defined in Section 3.1.4
hereof) and their respective consultants to review and refine the design of the
Building and the Lot. Thereafter, Landlord shall seek approval of the Schematic
Design Documents by the Planning Board (as defined in Section 3.1.4 hereof), and
Tenant shall cooperate with Landlord in connection therewith. If despite the
good faith efforts of Landlord and Tenant the Planning Board rejects the design
reflected in the Schematic Design Documents or insists upon major changes to the
Schematic Design Documents which are unacceptable to either Landlord or Tenant
and if as a result thereof Landlord is unable to obtain approval of the
Schematic Design Documents by the Planning Board by the date set forth in the
Progress Schedule, as the same may be changed by any Tenant Delay, either
Landlord or Tenant may terminate this Lease upon thirty (30) days prior written
notice. If Planning Board approval of the Schematic Design Documents is not
obtained by the end of such thirty-day period, this Lease shall thereupon
terminate. In the event of such termination, all third party, out-of-pocket
costs incurred by Landlord in connection with the design competition and design
process solely for the Building and Lot shall be shared equally by Landlord and
Tenant. Planning Board approval of the Schematic Design Documents shall be a
Subsequent Approval (as defined in Section 3.1.4 hereof). Landlord and Tenant
agree to cooperate in connection with any conditions imposed by the Planning
Board in connection with the Planning Board's approval of the Schematic Design
Documents, such as further review of the Design Documents by the CDD.

        At such time as the Schematic Design Documents have been approved by
Landlord and Tenant (and by the Planning Board, if Landlord elects to have the
Schematic Design Documents approved by the Planning Board), Landlord shall cause
(i) Landlord's Architect to prepare further details and development of the
Schematic Design Documents (the "Design Development Documents") for the Building
and the Base Building Improvements, which shall mean plans, sections and
elevations, typical construction details, and equipment layouts showing the
scope, relationships, forms, size and appearance of the Base Building
Improvements and calculating the gross floor area and the Rentable Square
Footage of the Building and (ii) the Construction Cost Estimator, based upon
such Design Development Documents, to prepare an updated budget for the Base
Building Improvements, each for approval by Landlord and Tenant. Design
Development Documents shall include architectural, mechanical and electrical
drawings and details of the Building, exterior materials to be incorporated in
the Building, walkways and other plaza areas on the Lot, a site and landscape
plan for the Lot showing all site development and landscape detail for lighting,
paving, landscaping, utilities, grading, drainage, access and service areas. The
Design Development Documents shall also include outline specifications
indicating all basic materials and mechanical and electrical systems of the
proposed Base Building Improvements. As with the Schematic Development
Documents, the Design Development Documents shall be prepared and distributed in
both hard copy and electronic format.

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        At such time as the Design Development Documents have been approved by
Landlord and Tenant, Landlord shall cause (i) Landlord's Architect to prepare
detailed construction drawings and specifications ("Final Design Documents")
which shall set forth in detail the requirements for construction of Landlord's
Work (including all architectural, mechanical, electrical and structural
drawings and detailed specifications), shall be fully coordinated with one
another and with field conditions as they exist on the Lot, shall show all work
necessary to complete Landlord's Work, including all cutting, fitting, and
patching and all connections to the mechanical and electrical systems and
components of the Base Building Improvements, and shall include calculations of
the gross floor area and the Rentable Square Footage of the Base Building
Improvements and (ii) the Construction Cost Estimator, based upon such Final
Design Documents, to prepare an updated budget for the Base Building
Improvements, each for approval by Landlord and Tenant. The Final Design
Documents shall be used for the construction of the Base Building Improvements
and shall be based upon the Design Development Documents and other information
which is relevant to the design and construction of the Base Building
Improvements. The Final Design Documents shall be prepared and stamped by
Landlord's Architect. The Preliminary Design Concept, the Schematic Design
Documents and the Final Design Documents (collectively, the "Design Documents")
shall not include any of Tenant's Work (as hereinafter defined). As used herein,
the term "Base Building Improvements" shall mean the items of work and materials
to be performed and supplied by Landlord in accordance with the Final Design
Documents as affected by Change Orders (as such term is hereafter defined) and
the term "Landlord's Work" shall mean the construction of the Base Building
Improvements in accordance with the Final Design Documents as affected by Change
Orders.

        The preliminary and final Schematic Design Documents, the preliminary
and final Design Development Documents, and the Final Design Documents shall be
submitted to both Landlord and Tenant for review and comment in accordance with
the dates and requirements included in the Progress Schedule, which shall be
incorporated, to the extent applicable, in the Architect's Contract. In each
instance both parties shall have until the respective completion dates set forth
in the Progress Schedule to review each submission and to notify the other party
of approval or disapproval. Tenant may disapprove any new items shown on a
submission which are not in compliance with (i) the Preliminary Design Concept
with regard to the Schematic Design Documents, (ii) the Schematic Design
Documents with regard to the Design Development Documents, or (iii) the Design
Development Documents with regard to the Final Design Documents, specifying and
detailing in each case such objections. To the extent that any such submission
is consistent with prior submissions approved by Tenant, such submission shall
be approved by Tenant, provided however, that Tenant shall have the right, with
Landlord's approval, to make modifications as set forth in the next sentence
hereof. Tenant, with the approval of Landlord, which approval shall not be
unreasonably withheld, conditioned or delayed, shall have the right to modify
the design of the Base Building Improvements at any time during the design
process contemplated hereby, provided that if as a result of any such design
change (a) any particular Design Document submission is not approved by the
applicable completion date set forth on the Progress Schedule, or (b) any such
design change delays the Substantial Completion Date, such lack of approval or
design change shall constitute a Tenant Delay for purposes of Section 3.2. In
the event Tenant shall fail to object to any Design Documents submissions by the
applicable completion date for such submission set forth in the Progress
Schedule, provided that Tenant had received such submission not less than five
(5) business days prior to the applicable completion date, such failure shall
constitute a Tenant Delay for purposes of Section 3.2. If Tenant objects to any
such submission because such submission is inconsistent with the prior
submission approved by Tenant, Landlord shall cause Landlord's Architect to
modify such submission to respond to Tenant's objection and submit such modified
submission to Tenant within five (5) business days after receipt of Tenant's
objections for approval by Tenant in the same manner as with regard to the prior
submission. Rejection of new items included in any submission that are
inconsistent with the approvals given for prior design phases shall not give
rise to a Tenant Delay so long as the initial rejection was delivered within the
dates established

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in the Progress Schedule, as modified. Landlord and Tenant agree to cooperate
with one another diligently and in good faith so as to complete the review and
approval of all Design Document submission by the applicable completion dates
set forth in the Progress Schedule.

        Upon approval of the Final Design Documents, Landlord shall solicit bids
from general contractors or construction managers mutually identified by
Landlord and Tenant by the date set forth in the Progress Schedule. Landlord and
Tenant shall mutually determine whether such bids shall be submitted on the
basis of a guaranteed maximum or fixed price contract basis. Upon receipt of
bids from such general contractors or construction managers, Landlord and Tenant
shall mutually select Landlord's Contractor from among such bidders and
thereupon Landlord shall enter into a contract (the "Construction Contract")
with Landlord's Contractor for construction of the Base Building Improvements.
The parties acknowledge that if Landlord and Tenant have agreed to hire the
Construction Cost Estimator to serve as Construction Manager/General Contractor
for the Building, instead of soliciting bids from general contractors or
construction managers as described above, such Construction Manager shall
instead be required to solicit bids from all subcontractors, and in such case
Landlord and Tenant shall be entitled to approve the subcontractors selected by
the Construction Manager and require Landlord's Contractor to enter into such
subcontracts. The Construction Contract shall be subject to Tenant's prior
approval, which approval shall not be unreasonably withheld, conditioned or
delayed. If, after such bids are received, none of such bids is acceptable to
Tenant and/or Tenant seeks any change in previously approved Design Documents,
and as a result thereof Tenant fails or refuses to approve the Final Project
Budget (as hereinafter defined) by the date set forth in the Project Schedule,
such failure or refusal shall constitute a Tenant Delay. Additionally, Tenant
shall have no right to withhold approval of any general contractor bid or any
subcontractor bid if the total amount of all such bids does not exceed by more
than fifteen percent (15%) the estimated amount thereof set forth in the
preliminary budget for Project Cost or the updated budget for Project Cost, as
the case may be, then most recently approved by Landlord and Tenant.

        As used in this Lease, the term "Project Cost" shall mean (i) all hard
costs and soft costs incurred by Landlord in connection with the construction of
the Base Building Improvements as reflected in a final project budget (the
"Final Project Budget") to be mutually approved by Landlord and Tenant based
upon, inter alia, all amounts payable by Landlord pursuant to the Architect's
Contract and the Construction Contract, and including all liabilities and
expenses of all architectural and engineering services relating to Landlord's
Work, appropriate amounts for the other line item categories set forth on the
Project Budget form attached hereto as Exhibit B-1 (the "Project Budget Form"),
(ii) the net amount of all Change Orders (as hereinafter defined), (iii) a
pro-rata portion of all "Mitigation Expenses" (as such term is hereafter
defined) incurred by Landlord or any Affiliate of Landlord pursuant to the
Development Approvals and the Subsequent Approvals (as such terms are defined in
Section 3.1.4 hereof), which pro-rata portion shall be equal to the ratio of the
gross floor area of the Building (as such gross floor area is determined
pursuant to the Cambridge Zoning Ordinance) to 1,313,000 square feet (being the
maximum amount of gross floor area, determined pursuant to the Cambridge Zoning
Ordinance, permitted to be developed in the Complex pursuant to the PUD Approval
(as such term is defined in Section 3.1.4 hereof) except as hereinafter set
forth and (iv) taxes and assessments for the Building and Lot, utility and
insurance costs for the Building and Lot and all other operating and maintenance
costs for the Building and Lot, in each case incurred by Landlord for the period
from the Substantial Completion Date through the Term Commencement Date. The
term "Mitigation Expenses" shall mean all capital expenses for housing linkage
payments and public open space linkage payments required pursuant to the PUD
Approval with respect to the Building, costs of traffic mitigation required by
the Development Approvals and Subsequent Approvals and infrastructure
improvements for the Complex required by the Development Approvals and
Subsequent Approvals. Tenant's pro-rata share of capital expenses for housing
linkage payments and public open space linkage payments required pursuant to the
PUD Approval with respect to the Building shall be equal to the ratio of the
Rentable Square Footage of Premises to the Rentable Square Footage of Building.
For

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purposes of determining Project Cost, the line item amount for Land and
Environmental Remediation shall be fixed at $60.00 per r.s.f. regardless of the
actual cost of such line item; Project Cost shall not include any amount for
construction of the Garage (as hereinafter defined) or for the leasing of (or
the making of any tenant improvements to) the Expansion Spaces to tenants; the
developer's fee shall be fixed at five percent (5%) of Project Cost (exclusive,
however, of the line item amounts for Land and Environmental Remediation,
Development Fee/Supervision (the "Developer's Fee") and Interest on Landlord's
Equity (as such term is hereinafter defined)); the broker's fee shall not exceed
$7.50 per r.s.f. and no amount shall be included in Project Cost for general or
administrative expenses of Landlord or for improvements to the Retail Space in
excess of the cost of Base Building Improvements related thereto, and no amount
shall be included in Project Cost for any interest, charges or fees paid or
payable by Landlord with respect to any construction loan financing for the
Project. Project Cost shall include an amount determined by multiplying all
components of the Project Cost (exclusive, however, of the line item for the
Developer's Fee) by twelve percent (12%) per annum for the period commencing as
of the date the cost of each such component is incurred through and including
the Term Commencement Date (as so determined, "Interest on Landlord's Equity"),
it being understood and agreed by Landlord and Tenant that Interest on
Landlord's Equity with respect to any component of Project Cost that Landlord
has acquired, purchased or incurred prior to the date of execution of this
Lease, such as the cost of the Land & Environmental component of the Project
Cost, shall be deemed to begin to accrue, not as of the date that the cost was
actually incurred, but rather as of the execution date of this Lease. Landlord
shall account for all Project Costs on a so-called "open book" basis. Within
ninety (90) days after the Substantial Completion Date, Landlord shall deliver
to Tenant a full accounting of the Project Cost incurred as of the Substantial
Completion Date; Tenant, from the date hereof through the date which is twelve
(12) months after receipt of such full accounting of Project Cost, may review
all of Landlord's books and records relating to the incurrence and payment of
the Project Cost in order to verify and confirm the accuracy thereof. If
Landlord incurs any cost or expense properly includable in Project Cost after
the Substantial Completion Date (including, without limitation, any Mitigation
Expenses) which is not included in the full accounting, Landlord shall notify
Tenant thereof and Landlord shall provide Tenant with such documentation with
respect thereto as Tenant reasonably may request. Landlord and Tenant
acknowledge and agree that the incurrence of additional costs and expenses by
Landlord after the Substantial Completion Date which are properly includable in
Project Cost will result in an increase in the Annual Fixed Rent Rate, which
increase shall be effective as of the date of incurrence thereof.

        Tenant shall have the right (but not the obligation) to offer to finance
up to twenty percent (20%) of the Project Cost as hereinafter provided ("Tenant
Financing"). If Tenant shall desire to offer Tenant Financing, Tenant shall give
Landlord written notice ("Financing Notice") of such offer not later than thirty
(30) days after Landlord and Tenant have agreed upon the first preliminary
Project Budget; such Financing Notice shall specify the amount (the "Tenant
Financing Amount") and other financial terms of such Tenant Financing described
below. Delivery by Tenant of a Financing Notice shall constitute a
representation by Tenant that it has the capacity to provide such Tenant
Financing.

        If Tenant offers to provide Tenant Financing and all of the terms and
conditions thereof, including without limitation, all documents evidencing and
securing Tenant Financing, are acceptable to Landlord and its construction
and/or permanent lenders, in their respective sole discretion, Tenant shall make
a loan to Landlord for an amount equal to the Tenant Financing Amount. The
Financing Notice shall specify the interest rate per annum payable on such
Tenant Financing loan and the repayment schedule (interest only until maturity;
or payments of principal and interest based upon the amortization period
specified by Tenant in the Financing Notice), which interest rate and repayment
schedule shall be subject to Landlord acceptance or rejection. Such Tenant
Financing loan shall be due and payable not later than the scheduled expiration
date of the initial Term of the Lease, and shall be secured by a mortgage on the
Lot and Building, which mortgage shall be subject and subordinate to the lien of
any mortgage granted to any lender now or hereafter providing Landlord with
construction and/or

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permanent financing ("Landlord's Project Financing"). The amount by which the
Project Cost exceeds the Tenant Financing Amount is herein referred to as the
"Landlord Project Cost Portion". Tenant agrees that upon any uncured Event of
Default hereunder, Landlord shall be entitled to offset against any payments due
under the Tenant Financing loan any amount owed by Tenant to Landlord pursuant
to this Lease. In addition, Tenant agrees that it will enter into any
intercreditor agreement (which may include typical subordinate lender standstill
agreements) requested by any lender providing Landlord's Project Financing.
Tenant shall disburse the proceeds of such Tenant Financing loan to Landlord on
the Commencement Date, and Landlord shall apply such proceeds to pay down
Landlord's Project Financing by the Tenant Financing Amount.

        If Tenant provides Tenant Financing as aforesaid, the definition of
Annual Fixed Rent Rate set forth in Section 1.1 shall be deemed to be revised to
read as follows:

        Subject to Sections 4.1(b), 10.11 and 10.12 thereof, an amount equal to
(a) the sum of (i) the product of (x) the Landlord Project Cost Portion
multiplied by (y) twelve percent (12%) plus (ii) the product of (x) the Tenant
Financing Amount multiplied by (y) the Tenant Financing interest rate per annum
payable on the Tenant Financing (or debt service constant if Tenant elects to
have the Tenant Financing amortized), divided by (b) the Rentable Square Footage
of the Building.

3.1.2    Change Orders.

        Tenant and Landlord recognize that it may be necessary or advisable to
make certain changes to the Final Design Documents or the Base Building
Improvements from time to time. Any changes shall be made in accordance with
this Lease.

        (a)   In the event that Tenant shall request or authorize any Change
Order (as hereinafter defined) or additional services from Landlord with respect
to the Base Building Improvements for the purpose of upgrading or changing the
scope, manner of performance, or quality of the Base Building Improvements,
including any change of design, subcontractor, supplier or materials made at the
request of Tenant, such Change Order when implemented by Landlord may result in
a change in the Progress Schedule and/or the Project Cost. As used herein, the
term "Change Order" shall mean (A) a written order from Landlord which Landlord
determines is necessary to carry out the approved design and construction of the
Base Building Improvements, whether due to any mistake or omission in, or
clarification of, the Design Documents, or (B) a written order to Landlord from
Tenant requesting or authorizing a Change in Landlord's Work or an adjustment of
the Project Cost or the Progress Schedule. Landlord shall provide Tenant with
copies of all proposed and final Change Orders. In addition: subject to the last
sentence of this Subparagraph (a), (i) with respect to additive Change Orders,
the Project Cost shall be increased by an amount equal to the change in the cost
of Landlord's Work (as determined pursuant to the Construction Contract and/or
the Architect's Contract) attributable to such Change Order, and (ii) with
respect to deductive Change Orders, the Project Cost shall be reduced by the
change in the cost of Landlord's Work (as determined pursuant to the
Construction Contract and/or the Architect's Contract) attributable to such
Change Order. Additive or deductive Change Orders shall result in an increase or
decrease, respectively, in the Developer's Fee (but not in any change of the
percentage thereof), and Landlord shall be reimbursed by Tenant, either directly
or through an increase or decrease, as applicable, in the Project Cost, for the
actual cost of overhead and profit, if any, which Landlord is required to pay to
Landlord's Contractor on account of any additive Change Order as set forth in
the Construction Contract approved by Tenant and Landlord. Anything herein to
the contrary notwithstanding, Tenant's approval of a Change Order shall be

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required for each of the following, which approval shall not be unreasonably
withheld, conditioned or delayed:

        (1)   A change in the rentable square footage of the Premises by more
than four percent (4%) in the aggregate;

        (2)   A change in the rentable square footage of any floor included
within the Premises by more than five percent (5%) in the aggregate;

        (3)   Any material change in the elevator systems or mechanical or
electrical systems serving the Premises with the result that such systems would
be significantly different than those shown on the Final Design Documents;

        (4)   Any material change in standard structural floor load capacities
from those shown on the Final Design Documents;

        (5)   Any material change in the quality of materials and fixtures used
in the lobby of the Building, passenger elevator cabs serving the Premises, or
washrooms serving the Premises with the result that the same would be
significantly different from to those shown on the Final Design Documents;

        (6)   Any change in the exterior design or appearance of the Building;
or

        (7)   Any individual Change Order which increases the Project Cost by
more than $500,000.00.

        (b)   If Tenant requests or requires any Change Order for the Base
Building Improvements, Landlord shall submit all such Change Orders with plans,
specifications, pricing and a schedule of values if appropriate to Tenant for
its review and approval, which approval shall not be unreasonably withheld,
delayed or conditioned. No Change Order for the Base Building Improvements
requested by Tenant shall be effective unless approved by Landlord's
Representative and Tenant's Construction Representative in writing, such
approval not to be unreasonably withheld, delayed or conditioned. Tenant may
withdraw any Change Order requested by Tenant at any time prior to Tenant's
Construction Representative having given its approval to such Change Order.
Promptly, but not later than ninety (90) days after the Term Commencement Date,
Landlord shall deliver a set of as built plans and operating and maintenance
manuals for the Base Building Improvements to Tenant.

3.1.3    Environmental Remediation.

        Landlord shall be responsible for undertaking and completing
environmental remediation of the Lot ("Environmental Remediation") pursuant to
an Environmental Agreement (the "Environmental Agreement") between Landlord and
Tenant in the form of Exhibit E hereto. Landlord has delivered to Tenant the
documents set forth on Exhibit E-1 hereto (the "Remediation Documents") and
Landlord will provide Tenant with such additional information pertaining to
Environmental Remediation and hazardous substances present on other portions of
the Lot as Tenant reasonably may request, including correspondence with
regulatory authorities and other governmental bodies with respect to the
Environmental Remediation. Landlord will provide Tenant with notice of any
circumstances relating to the Environmental Remediation which could delay the
Substantial Completion Date, as affected by any Tenant Delay, by more than
thirty (30) days.

3.1.4    Development Approvals and Title Exceptions.

        Reference is hereby made to (i) a Special Permit issued by the City of
Cambridge Planning Board (the "Planning Board"), Case No. PB #141 filed April 7,
1999 (the "PUD Permit"), recorded with the Middlesex South District Registry of
Deeds (the "Registry") in Book 31137, Page 89 as affected by a Settlement
Agreement dated May 24, 1999 among Barbara Broussard, Mary DeFreitas, the East
Cambridge Planning Team and Landlord (the "Settlement Agreement") (the PUD
Permit and the

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Settlement Agreement are herein collectively referred to herein as the "PUD
Approval"), (ii) PTDM Ordinance Final Decision issued April 20, 1999 by the
Community Development Department ("CDD") of the City of Cambridge (the "PTDM
Decision"), the Letter dated April 20, 1999 to Robert L. Green of Lyme
Properties from Susanne Rasmussen of the CDD (the "PTDM Letter") attached to the
PTDM Decision, and Landlord's Parking Transportation Demand Management Plan
dated April 9, 1999 (the "PTDM Plan") (the PTDM Decision, the PTDM Letter and
PTDM Plan are collectively referred to herein as the "PTDM Approval"), (iii) a
Certificate of the Secretary of Environmental Affairs on the Final Environmental
Impact Report dated April 15, 1999 (the "MEPA Certificate"), (iv) an Order of
Conditions issued July 12, 1999 by the City of Cambridge Conservation Commission
(the "Order of Conditions") and (v) a Determination for Issuance of a Waterways
License Amendment dated December 8, 1999, issued by the Executive Office of
Environmental Affairs of the Commonwealth of Massachusetts (the "Chapter 91
Determination"), (collectively, the "Development Approvals"). Reference is also
hereby made to Item Nos. 2 through 12, inclusive (the "Title Exceptions") set
forth in Schedule B, Part 1 of Owner's Policy No. 136-00-336684 dated August 19,
1998, issued by Lawyer's Title Insurance Corporation (the "Title Policy").
Tenant acknowledges that Landlord has delivered to Tenant copies of the
Development Approvals, the Title Exceptions and the Title Policy. This Lease,
and the development, construction and operation of the Building, the Lot and the
Complex, shall be subject to the Development Approvals, the license to be issued
pursuant to the Chapter 91 Determination, the Title Exceptions and all other
determinations, approvals, decisions and actions of governmental authorities
having jurisdiction of the Complex hereafter issued pursuant to or contemplated
by the Development Approvals and delivered to Tenant ("Subsequent Approvals").
Each of Landlord and Tenant, in the exercise of their respective rights and the
performance of their respective obligations pursuant to this Lease, shall
observe and comply with all requirements of the Development Approvals and
Subsequent Approvals. Landlord, however, shall not enter into any Subsequent
Approval which will materially and adversely decrease the amount of parking
spaces available at the Complex.

        Without limiting the generality of the foregoing, to the extent required
for compliance with the PUD Permit and the PTDM Approval, as the same may be
affected by Subsequent Approvals (but only for so long as the same remain in
force and effect from time to time), Tenant shall comply with the following:
(a) Tenant shall comply with the obligations of the PTDM Approval applicable to
tenants, employers and/or employees in the Complex, (b) Tenant shall cooperate
with Landlord in the implementation of the Additional Recommendations set forth
in the PTDM Letter if the mode split goal of the PTDM Approval is not achieved,
(c) Tenant shall cooperate with Landlord and/or the Charles River Transportation
Management Association or any other transportation management association of
which Landlord is a member (a "TMA") in implementing the PTDM Approval and TMA
programs (and Tenant is hereby encouraged to participate in all TMA programs),
(d) Tenant shall establish a guaranteed ride home program for Tenant's employees
as provided in the PUD Approval and the PTDM Approval, as the same may be
affected by Subsequent Approvals, (e) Tenant shall, either directly or through a
program established by Landlord or a TMA for tenants of the Complex, complete
surveys pursuant to Section III D of the PTDM Plan, (f) as required by the PUD
Approval and PTDM Approval, as the same may be affected by Subsequent Approvals,
Tenant shall contract with the MBTA and subsidize transit passes and commuter
rail passes in an amount not less than 60% of the cost thereof or such higher
percentage as Landlord may require if mode split commitments are not achieved,
(g) as provided in the PTDM Approval, as the same may be affected by Subsequent
Approvals, Tenant shall cooperate with Landlord in connection with surveys
concerning attitudes of employees and customers of Tenant in order to refine and
develop transportation demand management programs, (h) Tenant shall provide
Tenant's employees with information provided to Tenant by or on behalf of
Landlord pursuant to the PTDM Plan, including information on the advantages and
benefits of telecommuting, flexible time, compressed work week programs, the
materials to be provided pursuant to Section VII A of the PTDM Plan and other
programs recommended by the City of

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Cambridge, (i) as provided in the PTDM Approval, as the same may be affected by
Subsequent Approvals, Tenant is hereby encouraged to use a commuter choice
program which allows qualifying employees the option of receiving the cash value
of a Tenant's Parking Space, (j) Tenant shall participate in and pay a
reasonable share (which shall not be less than Tenant's Proportionate Fraction
for Complex) of the cost of any TMA shuttle bus service serving the Complex, as
contemplated by the PTDM Approvals, and (k) Tenant shall cooperate with Landlord
with respect to all other aspects of the PTDM Approval.

3.2    PREPARATION OF PREMISES FOR PERFORMANCE OF TENANT'S WORK.

        During the course of performance of Landlord's Work, Landlord and Tenant
shall meet on not less than a monthly basis to review the progress of Landlord's
Work. Landlord agrees to use reasonable and diligent efforts to have the
Premises ready for the performance of Tenant's Work on or before the Scheduled
Substantial Completion Date which Substantial Completion Date shall, however, be
extended for a period equal to that of (a) any delays due to Acts of God, labor
disputes or unrest, riots, fire, unusual delays in deliveries, casualties or
other causes beyond Landlord's reasonable control (collectively, "Force Majeure
Events") and (b) any delays due to (i) any Change Order, (ii) any act, omission
or neglect of Tenant, or of any employee, agent, or separate contractor of
Tenant, (iii) the concurrent performance of the Base Building Improvements and
Tenant's Work, (iv) Tenant's failure to furnish information or approve any of
the Design Documents, the Architect's Contract, the Construction Contract or the
Project Cost by the applicable dates set forth in the Progress Schedule or to
respond to any request by Landlord for information or approval within the time
period required by the Progress Schedule, or if no time period is required by
the Progress Schedule, within five (5) business days of Landlord's request, or
(v) any breach or default by Tenant in the performance of Tenant's obligations
pursuant to this Lease, even if such breach or default is cured (collectively,
"Tenant Delay"). In the event of any such Force Majeure Event, Landlord shall
use reasonable efforts to eliminate the cause of such delays or to secure
alternate supplies. If any one or more Force Majeure Events shall delay the
Substantial Completion Date by more than one hundred eighty (180) days, either
Landlord or Tenant may terminate this Lease upon not less than fifteen (15) days
prior written notice to the other. A Tenant Delay shall not affect the
Substantial Completion Date unless Landlord has given Tenant notice thereof and
Tenant fails to cure the same within two (2) business days, provided, however,
that Landlord shall not be required to provide Tenant with any notice or
opportunity to cure with respect to any date set forth in the Progress Schedule
by which Tenant must take any action, and any failure or refusal by Tenant to
take such action by any such date set forth in the Progress Schedule, which
failure or refusal in fact results in a delay, shall constitute a Tenant Delay.
As used herein, the term "Substantial Completion Date" shall mean and refer to
the date on which: (i) the Base Building Improvements have been substantially
completed in accordance with the Final Design Documents, as affected by Change
Orders, without material deviation therefrom as certified by Landlord's
Architect and confirmed by Tenant's Architect, which confirmation shall not be
unreasonably withheld, delayed or conditioned, with the exception of minor items
which can be fully completed by Landlord within thirty (30) days without
material interference with Tenant and other items which because of the season or
weather or the nature of the item are not practicable to do at the time,
provided that none of said items is necessary to perform Tenant's Work
(collectively "Punch List Items"), (ii) if Tenant's Work has not then commenced,
a Certificate of Occupancy from the City of Cambridge (or a Temporary
Certificate of Occupancy with conditions which can be satisfied without material
interference with the performance of Tenant's Work) shall have been obtained,
(iii) the Premises are broom clean and free of debris except to the extent, if
any, resulting from Tenant's Work, and (iv) all utilities required for the use
of the Premises have been brought by Landlord to the location(s) shown on the
Final Design Documents, as the same may be affected by Change Orders; provided,
however, that if the Substantial Completion Date does not occur on or before the
Scheduled Substantial Completion Date due to any Tenant Delay, then solely for
purposes of determining the Commencement Date under Section 2.2 and

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other applicable provisions of this Lease, the Base Building Improvements shall
be deemed to be substantially completed, and the Substantial Completion Date
shall be deemed to have occurred, on the date on which the Substantial
Completion Date would have occurred taking into account any Force Majeure Events
but without taking into account any Tenant Delay. If Landlord's Architect has
certified that the Base Building Improvements are substantially complete but
Tenant's Architect does not confirm the same within five (5) business days
thereafter, Landlord's Architect and Tenant's Architect shall immediately select
a third independent architect who shall conclusively determine whether the Base
Building Improvements are substantially complete. Landlord and Tenant shall
share equally the costs of such third architect. Landlord's Work shall be deemed
to have been performed as of the date on which the Base Building Improvements
are substantially complete (as certified by Landlord's Architect and confirmed
by Tenant's Architect or such independent architect) except for latent defects,
Punch List Items and items which do not conform with the requirements of the
Final Design Documents, as affected by Change Orders, and as to which Tenant or
Tenant's Architect shall have given written notice to Landlord prior to such
date. If Tenant or Tenant's Architect does not provide such written notice prior
to the date on which the Base Building Improvements are substantially complete,
a certificate of substantial completion by a licensed architect or registered
engineer shall be conclusive evidence that Landlord has performed all such
obligations except for latent defects, Punch List Items and items stated in such
certificate to be incomplete or not in conformity with such requirements.
Landlord shall use reasonable and diligent efforts to complete Punch List Items
within thirty (30) days after the Substantial Completion Date and in a manner
which will not unreasonably interfere with the performance of Tenant's Work (as
defined in Section 3.2.1 hereof). Landlord represents that Landlord has the
capacity to effect financial arrangements to enable Landlord to complete
Landlord's Work, and to otherwise enable Landlord to fulfill all of its
obligations under this Lease. After the commencement of construction of
Landlord's Work, Landlord shall furnish to Tenant, at Tenant's request, a copy
of the portions of Landlord's financing commitment for construction of the
Building confirming the availability of construction financing therefor. Tenant
agrees to observe any reasonable limitations on dissemination thereof to others
that Landlord may impose.

        Notwithstanding the foregoing, (A) if Landlord has not commenced the
Environmental Remediation of the Lot by the date set forth in the Progress
Schedule, (B) if Landlord has not filed a Response Action Outcome Statement (as
such term is defined in the Massachusetts Contingency Plan, 310 CMR 40.0000 et
seq., as amended ("MCP")) for the Lot by the date set forth in the Progress
Schedule, (C) if a building permit for the Base Building Improvements has not
been issued by the date set forth in the Progress Schedule, (D) if construction
of the Base Building Improvements has not commenced by the date set forth in the
Progress Schedule (each of the foregoing being referred to as a "Landlord
Milestone Date"), Tenant shall have the right to terminate this Lease as
hereinafter set forth. Upon request of Tenant, Landlord shall provide such
evidence as Tenant reasonably may request to evidence achievement of each
Landlord Milestone Date. Each of the Landlord Milestone Dates shall be extended
by one business day for each day of Tenant Delay occurring before a respective
Landlord Milestone Date. If Landlord is in default with respect to any Landlord
Milestone Date, as extended as aforesaid by any Tenant Delay, Tenant shall
notify Landlord within five (5) business days thereof. If Landlord does not cure
the default or alleged default within thirty (30) business days after receipt of
such notice, Tenant, upon written notice, may thereupon terminate this Lease.

        If the Garage and the streets and roadways of the Complex necessary for
access to the Building and Garage are not substantially complete by the date of
substantial completion of Tenant's Work to be performed in connection with
Tenant's initial occupancy of the Premises then Tenant, as Tenant's sole remedy,
shall receive a credit against the initial and succeeding payments of the
Parking Fee due hereunder, until such credit is fully exhausted, equal to two
day's Parking Fee (for all of Tenant's Garage Parking Spaces or for such number
of Tenant's Garage Parking Spaces as may be unavailable, as applicable) for each
day from substantial completion of Tenant's Work until the Garage and such
street and roadway work are substantially complete.

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        In the event Landlord's Work shall not be substantially completed by the
Scheduled Substantial Completion Date specified in Section 1.1 (as and to the
extent such Scheduled Substantial Completion Date may be extended by Tenant
Delays and delays caused by Force Majeure Events), then after the Term does
commence, Tenant, as Tenant's sole remedy, shall receive a credit against the
initial and succeeding payments of Annual Fixed Rent due hereunder, until such
credit is fully exhausted, equal to one day's Annual Fixed Rent for each day
from the Scheduled Substantial Completion Date (as so extended) until the date
that Landlord's Work is substantially completed.

        In the event Landlord's Work shall not be substantially completed within
one hundred eighty (180) days after the Scheduled Substantial Completion Date
(as and to the extent such Scheduled Substantial Completion Date may be extended
by Tenant Delays and delays caused by Force Majeure Events) (such 180th day is
referred to herein as the "Outside Completion Date"), Tenant may at any time
thereafter, but prior to Landlord's Work being substantially completed, notify
Landlord of Tenant's election to terminate this Lease. Tenant shall give
Landlord no less than thirty (30) days' prior notice of Tenant's intention to
terminate this Lease before notifying Landlord of Tenant's election to terminate
this Lease; it being understood and agreed, however, that Tenant may give notice
of such intention as early as thirty (30) days prior to the Outside Completion
Date.

3.2.1.    Performance of Tenant's Work.

        Except for the Base Building Improvements to be performed by Landlord in
accordance with the Design Documents, all of Tenant's initial interior
improvements, fixtures, finishes, furnishings, furniture, telephones, movable
equipment and signs (collectively, "Tenant's Work"), shall be performed and
provided at the sole cost and expense of Tenant. Tenant's performance of
Tenant's Work shall be coordinated with any work being performed by Landlord
and/or by any Affiliate of Landlord in the Building, on the Lot or in the
Complex in such manner as to maintain harmonious labor relations during the
performance of Landlord's Work (which Landlord expects will be performed by
union contractors) and thereafter and not to damage the Building or Lot or
interfere with Building or Lot operations or with any work being performed by or
on behalf of Landlord or any Affiliate of Landlord in the Complex. All work
described in Tenant's Work shall be performed by an Approved Contractor. For
purposes of this Lease, an "Approved Contractor" shall mean a contractor or
mechanic identified by Tenant in writing, who has been approved by Landlord in
writing (such approval not to be unreasonably withheld, delayed or conditioned).
Contractors may be approved in one of two ways. First, Tenant may submit to
Landlord in writing from time to time a list (or a revised list) of contractors
that Tenant anticipates using from time to time to perform Tenant's Work. If
Landlord fails to object to any of the contractors identified on such list
within ten (10) days after receipt of such list from Tenant, all contractors
identified on such list shall be deemed "Approved Contractors". Second, Tenant
may submit to Landlord from time to time requests for Landlord to approve
specific contractors (not already on the list of Approved Contractors) to
perform Tenant's Work. Landlord shall have the right, upon written notice to
Tenant to withdraw its approval of any previously Approved Contractors at any
time for any cause as determined in Landlord's reasonable judgment. A
contractor's failure to provide or maintain adequate insurance levels shall be a
reasonable basis for Landlord to withhold or withdraw approval unless Tenant
notifies Landlord in writing that such contractor shall be covered by insurance
then being maintained by Tenant and if Tenant provides documentary evidence that
said Contractor is covered and of the amount of coverage. Additionally, Landlord
may withhold or withdraw approval of any contractor proposed by Tenant or
previously approved by Landlord to perform any Tenant's Work if Landlord
determines, in Landlord's sole but reasonable discretion, that any contractor
proposed or previously approved by Landlord by Tenant for the performance of any
Tenant's Work does not have a sufficient bonding capacity or may cause
picketing, labor unrest, strikes, protests or similar activities (collectively
"Labor Unrest"). If after approval of an Approved Contractor by Landlord, any
Labor Unrest shall occur or be threatened on account of any Tenant's Work,
Landlord shall have the right to require cessation of Tenant's Work until
resolution of such Labor Unrest. Except

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as set forth in Sections 3.2.1 and 5.1.10 hereof, all initial Tenant's Work
which may constitute a fixture, part of the real estate, a part of a Building
system or Building utilities shall become a part of the Premises and upon
termination of this Lease shall be considered to be the property of the
Landlord.

        Unless Tenant agrees to readapt the Premises for a typical general
office layout prior to the expiration or termination of the Lease, Tenant shall
not effect any Tenant's Work (or any alterations or additions to the Premises
after performance of the initial Tenant's Work) that might require any unusual
expense to reuse the Premises for any general office use.

        Tenant's Work shall be performed in accordance with complete,
consistent, final construction drawings and specifications ("Construction
Documents") approved by Landlord in writing, which approval shall not be
unreasonably withheld, conditioned or delayed. The Construction Documents shall
be prepared and stamped by Tenant's Architect. Landlord reserves the right to
reject, in whole or in part, any or all of the Construction Documents which in
its reasonable opinion fail to comply with Sections 3.2.1, 3.3 and 5.1.5 of this
Lease within fifteen (15) business days of its receipt thereof (the "Review
Period"). The Review Period shall not commence unless and until Tenant delivers
a complete set of Construction Documents. If Landlord shall disapprove the
Construction Documents, it shall state specifically the reasons therefor, and
Tenant shall promptly revise and resubmit the Construction Documents. If
Landlord fails to respond to Tenant's request for approval of the Construction
Documents within the Review Period, then the Construction Documents shall be
deemed approved. Upon completion of Tenant's Work to prepare the Premises for
Tenant's initial occupancy, Tenant shall provide Landlord with a set of as-built
plans, and operating and maintenance manuals therefor.

        Tenant shall be solely responsible for the liabilities of and expenses
of all architectural and engineering services relating to Tenant's Work and for
the adequacy, accuracy, and completeness of the Construction Documents approved
by Landlord. The Construction Documents (i) shall set forth in detail the
requirements for construction of the Tenant's Work (including all architectural,
mechanical, electrical and structural drawings and detailed specifications),
(ii) shall be fully coordinated with one another and with field conditions as
they exist in the Premises and elsewhere in the Building, and (iii) shall show
all work necessary to complete the Tenant's Work including all cutting, fitting,
and patching and all connections to the mechanical and electrical systems and
components of the Building. Tenant agrees to indemnify and hold Landlord
harmless if any Tenant's Work described in the Construction Documents (a) fails
to comply with all applicable laws, regulations, building codes, building design
standards, the Development Approvals and Subsequent Approvals, (b) in any manner
affects any structural component of the Building (including, without limitation,
exterior walls, exterior windows, core walls, roofs or floor slabs), (c) in any
respect is incompatible with the electrical and mechanical components and
systems of the Building, (d) affects the exterior of the Building, (e) fails to
conform to floor loading limits, and (f) with respect to all materials,
equipment and special designs, processes or products, infringes any patent or
other proprietary rights of others. Landlord's approval or deemed approval of
the Construction Documents and the performance of Tenant's Work pursuant to the
Construction Documents shall not result in any liability of Landlord, and
Landlord's approval of Construction Documents shall signify only Landlord's
consent to Tenant's Work shown thereon and shall not result in any
responsibility of Landlord concerning compliance of Tenant's Work with laws,
regulations, or codes, coordination of any aspect of Tenant's Work with any
other aspect of Tenant's Work, or the feasibility of constructing Tenant's Work
without material damage or harm to the Building, all of which shall be the sole
responsibility of Tenant.

        If Tenant enters into a contract with Landlord's Contractor for the
performance of Tenant's Work to prepare the Premises for Tenant's initial
occupancy, Landlord agrees that Tenant shall have a license to enter the
Premises at such time or times prior to the Term Commencement Date as Landlord,
in its sole but reasonable discretion, may permit to enable Tenant to carry out
Tenant's Work. Upon any such entry by Tenant prior to the Term Commencement
Date, Tenant shall be subject to, and perform all of

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its obligations under this Lease except for the obligation to pay Rent, which
obligation shall not arise until the Term Commencement Date occurs.

        An Approved Contractor may be used by Tenant until Landlord notifies
Tenant that an Approved Contractor is no longer approved due to such Approved
Contractor's failure to comply in any material respect with the requirements of
the Construction Documents and/or this Lease. Tenant shall procure all necessary
governmental permits, licenses and approvals before undertaking any Tenant's
Work. When any Tenant's Work is in progress, Tenant shall cause to be maintained
insurance as may be required by Landlord covering any additional hazards due to
such Tenant Work, for the benefit of Landlord. It shall be a condition of
Landlord's approval of any Tenant's Work that certificates of such insurance
issued by a responsible insurance company qualified to do business in
Massachusetts and having a Best's Insurance Rating of A- or better, shall have
been deposited with Landlord, that Tenant has provided Tenant's certification of
the insurable value of the work in question for casualty insurance purposes, and
that all of the other conditions of the Lease have been satisfied. Tenant shall
reimburse Landlord for up to $25,000 of the reasonable, out-of-pocket, third
party costs of reviewing proposed Construction Documents and Tenant's Work and
inspecting installation of the same. At all times while performing Tenant's
Work, Tenant shall require each Approved Contractor performing Tenant's Work to
comply with all applicable laws, regulations, permits and policies relating to
such work. In performing Tenant's Work, each Approved Contractor shall comply
with Landlord's requirements set forth in Section 3.2.1, Section 3.3,
Section 5.1.5 and Section 5.2.3 hereof relating to the time and methods for such
work, use of delivery elevators and other Building facilities and each Approved
Contractor shall not interfere with or disrupt Landlord's Contractor. Each
Approved Contractor shall in all events work on the Premises without causing
labor disharmony, coordination difficulties, or delay or impairment of any
guaranties, warranties or obligations of any contractors of Landlord and without
causing unreasonable interference with the rights of other tenants in the
Building. If any Approved Contractor uses any Building services or facilities
prior to the Commencement Date, such Contractor, jointly and severally with
Tenant, shall agree to reimburse Landlord for the cost thereof based on
Landlord's schedule of charges established from time to time (and if no such
charges have been established, then based on Landlord's reasonable charge
established at the time). Tenant shall include a provision in each contract with
each Approved Contractor whereby such Approved Contractor shall, by entry into
the Building or onto the Lot or Complex, agree to indemnify and hold Landlord
harmless from any claim, loss or expense arising in whole or in part out of any
act or neglect committed by such person while in the Building or on the Lot or
Complex, to the same extent as Tenant has so agreed in this Lease, which
indemnities of Tenant and Approved Contractor shall be joint and several.

        Subject to Tenant's right to contest amounts due to any Approved
Contractor, Tenant shall pay on or prior to date when any such payment is due
the entire cost of all Tenant's Work so that the Premises shall always be free
of liens for labor or materials. If any mechanic's lien (which term shall
include all similar liens relating to the furnishing of labor and materials) is
filed against the Premises, the Building, the Lot or the Complex or any part
thereof (regardless of whether Tenant contests the same) which is claimed to be
attributable to Tenant, its agents, employees or contractors, Tenant shall
promptly discharge the same by payment or filing any necessary bond within
thirty (30) days after Tenant has notice (from any source) of such mechanic's
lien. Tenant shall prepare and complete not less than seventy-five percent (75%)
of the Rentable Square Footage of Premises for Tenant's occupancy within nine
(9) months after the Substantial Completion Date. If Tenant does not prepare and
complete the entire Premises for Tenant's occupancy within nine (9) months after
the Substantial Completion Date, Tenant shall deposit with Landlord on or before
the end of such nine-month period a completion bond, letter of credit or similar
security in the amount of Landlord's reasonable estimate of the cost to so
complete the Premises. The form and substance of such bond, letter of credit or
similar security shall be subject to Landlord's approval, which approval shall
not be unreasonably withheld, conditioned or delayed.

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        After the performance of Tenant's Work to prepare the Premises for
Tenant's initial occupancy, (i) all Tenant's Work shall be subject to all
provisions of this Lease relating to Tenant's Work to prepare the Premises for
Tenant's initial occupancy, except as expressly set forth herein, and
(ii) Landlord and Tenant shall agree in writing, at the time Landlord approves
any alteration or addition, whether Tenant will be required to, permitted to or
forbidden to, at Tenant's sole cost and expense, remove any such alteration or
addition and/or to readapt, repair or restore the Premises to substantially the
condition the same were in prior to such alteration or addition upon the
expiration or termination of this Lease. Landlord's approval of any alteration
or addition which is not a Minor Alteration (as hereinafter defined in this
Section 3.2) shall be deemed to have been given if Landlord fails to notify
Tenant of its objection thereto within fifteen (15) business days after Tenant's
request for such approval. In circumstances in which Tenant desires the right to
remove additions or alterations at the expiration or termination of this Lease,
Landlord shall reasonably agree, and such agreement shall not be unreasonably
withheld, conditioned or delayed (and shall be deemed to have been given if
Landlord fails to notify Tenant of its objection thereto within fifteen
(15) business days after Tenant's request for such agreement), to permit such
removal where items installed by Tenant are in the nature of equipment, but are
so affixed to Building that such items may be construed as fixtures. Tenant's
rights to remove additions or alterations hereunder shall not apply to
replacement of items included in Tenant's Work that are replaced due to the fact
that such items have worn out or become substantially obsolete. After the
performance of Tenant's Work, all changes and additions shall be part of the
Building except such items as by writing at the time of approval the parties
agree either shall be removed or left by Tenant on termination of this Lease, or
shall be removed or left at Tenant's election.

        Notwithstanding the foregoing, the parties hereby agree that for any
non-structural alterations or additions to the Premises which do not involve
modifications to the Building operating systems and for which the cost may be
reasonably estimated to be less than $100,000 (each a "Minor Alteration"):
(i) Landlord's prior written consent shall not be required unless such Minor
Alteration requires a building permit from the City of Cambridge, in which case
Landlord's reasonable consent shall be required, provided that such consent
shall be deemed to have been given if Landlord fails to notify Tenant of its
objection to such Minor Alteration within five (5) days after Tenant's request
for Landlord's consent with respect thereto, and (ii) if Landlord's consent was
not obtained therefor, upon the expiration or termination of this Lease, Tenant
shall readapt, repair and restore the affected portion of the Premises to
substantially the condition the same were in prior to such Minor Alteration.
Additionally, Tenant shall give prior written notice to Landlord of any Minor
Alteration for which the cost may be reasonably estimated to be less than
$100,000 but greater than $25,000 and regardless of whether Landlord's consent
is required.

        The parties further agree that after the performance of Tenant's Work to
prepare the Premises for Tenant's initial occupancy (a) any request for
Landlord's consent to any alteration or addition (including, without limitation,
any Minor Alteration) shall be accompanied by drawings and specifications in
reasonable detail given the size and scope of the proposed alteration or
addition, and (b) Tenant shall furnish Landlord as-built drawings showing any
and all alterations or additions (including, without limitation, any and all
Minor Alterations) made by Tenant or any assignee, sublessee or licensee of
Tenant within 30 days after completion of the same.

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3.3    GENERAL PROVISIONS APPLICABLE TO CONSTRUCTION.

        All construction work required or permitted by this Lease, whether by
Landlord or by Tenant, shall be done at the sole risk of the party performing
such work, in a good and workmanlike manner employing new materials of good
quality, and in compliance with all Development Approvals, Subsequent Approvals,
applicable laws, codes, ordinances, regulations and orders of any governmental
authority or insurer of the Building, including the Americans with Disabilities
Act (42 U.S.C. § 12101 et seq.) and the regulations and Accessibility Guidelines
for Buildings and Facilities issued pursuant thereto (collectively, the "ADA
Requirements"). Either party may inspect the work of the other at reasonable
times and shall give notice of observed defects. Landlord shall not be
responsible for any loss, damage, or injury resulting from the installation of
any components, fixtures, or equipment provided they were appropriately
specified and installed in accordance with the manufacturer's or supplier's
instructions; provided, however, that Landlord shall assign any and all
contractor's, manufacturer's and supplier's warranties with respect to the Base
Building Improvements, including, without limitation, Landlord's Contractor's
warranty as set forth in the Construction Contract, to Tenant for the Term of
this Lease, upon the expiration or sooner termination of which such warranties
shall automatically revert to Landlord.

3.4    REPRESENTATIVES.

        Each party authorizes the other to rely in connection with their
respective rights and obligations under this Article III upon approval and other
actions on the party's behalf by Landlord's Representative in the case of
Landlord and Tenant's Lease Representative in the case of Tenant lease matters
and Tenant's Construction Representative, in the case of Tenant design and
construction matters, or by any person hereafter designated in substitution or
addition by notice to the party relying.

3.5    LANDLORD INDEMNITY AND CORRECTION OF LANDLORD'S WORK.

        Landlord agrees to indemnify and hold Tenant harmless if any of
Landlord's Work described in the Final Design Documents (a) fails to comply with
all applicable laws, regulations, building codes, building design standards, the
Development Approvals and Subsequent Approvals and (b) with respect to all
materials, equipment and special designs, processes or products, infringes any
patent or other proprietary rights of others. If within one year after the
Substantial Completion Date (i) any item of Base Building Improvements does not
conform with the Final Design Documents or (ii) there is any latent defect or
any other defect in the Base Building Improvements caused by faulty workmanship
performed on behalf of Landlord or materials installed on behalf of Landlord,
Landlord, upon written notice thereof from Tenant prior to the expiration of
such one-year period, shall forthwith cause such nonconformity or defect to be
corrected without cost or expense to Tenant.

ARTICLE IV

RENT

4.1    FIXED RENT.

        (a)    Monthly Installments; Definitions.    Commencing on the
Commencement Date, Tenant covenants and agrees to pay Fixed Rent (as hereinafter
defined) for the Premises to Landlord by wire transfer as Landlord may from time
to time direct in writing, without any offset or reduction whatsoever (except as
may be made in accordance with the express provisions of this Lease), or in the
absence of wire transfer instructions from Landlord, at the Original Address of
Landlord or at such other place or to such other person or entity as Landlord
may by notice to Tenant from time to time direct, in the amount of (x) the
Annual Fixed Rent Rate set forth in Article I multiplied by (y) the Rentable
Square Footage of the Premises, and subject to adjustment as set forth in
Sections 4.1(b),

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5.1.2, 10.11 and 10.12 hereof (collectively "Fixed Rent" or "Annual Fixed
Rent"), in equal installments equal to 1/12th of the Fixed Rent in advance on
the first day of each calendar month included in the Term; and for any portion
of a calendar month at the beginning or end of the Term, at that rate payable in
advance for such portion.

        (b)    Adjustment of Annual Fixed Rent.    On the tenth anniversary of
the Commencement Date, each of the Annual Fixed Rent for the Premises (as
initially demised to Tenant) determined pursuant to Section 1.1 hereof, and the
Annual Fixed Rent for the Expansion Spaces as determined pursuant to
Section 10.11 hereof, shall be increased by an amount determined by multiplying
the Annual Fixed Rent for the first Lease Year by twenty-one and nine tenths
percent (21.9%). For example, if for the first Lease Year the Annual Fixed Rent
for the Premises (as initially demised to Tenant) is $5,877,350.00, such
increase shall equal $1,287,139.65 and if the Annual Fixed Rent (including the
TI Factor) for both the Expansion Spaces as determined pursuant to
Section 10.11(c) is $1,520,500.00, such increase shall equal $332,989.50. The
respective Annual Fixed Rent for the Premises (as initially demised to Tenant)
and the Expansion Spaces, increased as aforesaid, shall be effective from the
tenth anniversary of the Commencement Date through the end of the fifteenth
Lease Year.

        (c)   Landlord shall send advance written notice to Tenant on a monthly
basis of the amount of Fixed Rent and Additional Rent due pursuant to this
Lease; such advance written notice shall be given not later than five
(5) business days prior to the first day of each calendar month.

4.2    ADDITIONAL RENT.

        As used herein, the term "Additional Rent" shall mean all rent, charges
and other sums, other than Fixed Rent, due Landlord pursuant to this Lease. All
regularly recurring items of Additional Rent, such as the Annual Maintenance
Charge, shall be paid by Tenant to Landlord by wire transfer as Landlord may
from time to time direct in writing, or in the absence of wire transfer
instructions from Landlord, at the Original Address of Landlord. Nonrecurring
items of Additional Rent shall be paid by Tenant to Landlord by check or wire
transfer as Tenant may from time to time elect. In order that the Fixed Rent
shall be absolutely net to Landlord, commencing on the Commencement Date, Tenant
covenants and agrees to pay, as Additional Rent, without any offset or reduction
whatsoever except as expressly set forth in this Lease, taxes, municipal or
state betterment assessments, insurance costs, utility charges and the Annual
Maintenance Charge with respect to the Premises as provided in this Section 4.2
as follows:

        As used herein, the term "Estimated Annual Additional Rent" shall mean
and refer to Landlord's estimate of the total amount of Additional Rent which
may be due from Tenant for any particular Lease Year with respect to the
Building, Lot and Complex. Landlord shall furnish Tenant with a statement within
sixty (60) days after the commencement of each Lease Year setting forth the
amount of Landlord's Estimated Annual Additional Rent for such Lease Year.
Landlord's good faith estimate of the Estimated Annual Additional Rent for the
first "fiscal year" (as such term is defined in Section 4.2.4 hereof) of the
Term is set forth in Section 1.1 as the "Initial Estimated Annual Additional
Rent for Building" and "Initial Estimated Annual Additional Rent for Complex".

4.2.1    Real Estate Taxes.

        Tenant shall pay directly to the Landlord: (i) Tenant's Proportionate
Fraction for Building and Tenant's Proportionate Fraction for Complex,
respectively, of all taxes, assessments (special or otherwise), levies, fees,
water and sewer rents and charges, and all other government levies and charges,
general and special, ordinary and extraordinary, foreseen and unforeseen, which
are, at any time during the Term hereof, imposed or levied upon or assessed
against the Premises, the Building, the Lot or the Complex, and (ii) the full
amount of any tax or assessment imposed or levied upon or against (A) any Fixed
Rent, Additional Rent or other sum payable hereunder, (B) this Lease, or the

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leasehold estate hereby created, or which arise in respect of the operation,
possession or use of the Premises; (C) all gross receipts or similar taxes
imposed or levied upon, assessed against or measured by any Fixed Rent,
Additional Rent or other sum payable hereunder; and (D) all sales, value added,
use and similar taxes at any time levied, assessed or payable on account of the
acquisition, leasing or use of the Premises (and Tenant's Proportionate Fraction
for Building and Tenant's Proportionate Fraction for Complex, respectively, of
any such taxes if they are levied, assessed or payable on account of the
acquisition, leasing or use of the entire Building Lot or the Complex) which may
become a lien on the Building, the Lot, the Premises or the Complex
(collectively "taxes and assessments" or if singular "tax or assessment"). For
each tax or assessment period, or installment period thereof, wholly included in
the Term, all such payments shall be made by Tenant not more than twenty
(20) days after receipt of an invoice therefor. For any fraction of a tax or
assessment period, or installment period thereof, included in the Term at the
beginning or end thereof, Tenant shall pay to Landlord, within twenty 20 days
after receipt of an invoice therefor, Tenant's Proportionate Fraction for
Building and Tenant's Proportionate Fraction for Complex, as applicable, of
taxes and assessments so levied or assessed or becoming payable which is
allocable to such included period. At Landlord's option, Tenant shall pay taxes
and assessments in accordance with Section 4.2.5 hereof. Subject to Tenant's
payment to Landlord of taxes and assessments as and when required by this
Section 4.2.1, Landlord agrees to pay such tax and assessments to the proper
authorities prior to delinquency and to provide Tenant with evidence of such
payment upon request therefor. Anything herein to the contrary notwithstanding,
if and to the extent that the Lot is not a separately assessed parcel, Landlord
shall make reasonable allocation of any taxes and assessments between the Lot
and the Building and the Complex of which the Lot is a part.

        Tenant may apply for any abatement of, or otherwise contest, any tax or
assessment, provided that the expenses of such proceedings, including, without
limitation, any penalties, interest, late fees or charges, and attorneys' fees
incurred as a result thereof, shall be paid by Tenant. Landlord and Tenant shall
discuss and may mutually agree upon any other tax initiatives available for the
Lot or Building.

        Nothing contained in this Lease shall, however, require Tenant to pay
any income taxes, excess profits taxes, excise taxes, franchise taxes, or any
taxes or assessments with respect to the Garage and other buildings leased or
available for lease (and the parcels of land upon which such buildings are
situated), other than the Building, the Lot and any building or portion of a
building in the Complex which is not designed and available for lease to third
parties (and the parcel(s) of land on which the same may be located) in the
Complex ("Excluded Taxes"), estate, succession, inheritance or transfer taxes,
provided, however, that if at any time during the Term the present system of ad
valorem taxation of real property shall be changed so that in lieu of 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 Building, the Lot, or the Complex or all of them, 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) measured by or
based, in whole or in part, upon gross rents, then any and all of such taxes,
assessments, levies or charges, to the extent so measured or based ("Substitute
Taxes"), Tenant's Proportionate Fraction for Building and Tenant's Proportionate
Fraction for Complex, respectively, of Substitute Taxes shall be payable by
Tenant; provided, however, that (i) Tenant's obligation with respect to the
aforesaid Substitute Taxes shall be limited to the amount thereof as computed at
the rates that would be payable if the Building and Lot and buildings not
available for lease (and the parcel(s) of land on which the same may be located)
were the only property of Landlord, and (ii) only that portion of the Substitute
Taxes in excess of the Excluded Taxes shall be payable by Tenant. Landlord shall
furnish to Tenant a copy of any notice of any public, special or betterment
assessment received by Landlord concerning the Building and Lot.

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4.2.2    Insurance.

4.2.2.1    Insurance Taken Out by Tenant.

        Tenant shall take out and maintain throughout the Term of this Lease the
following insurance:

        (a)   Comprehensive general liability insurance indemnifying Landlord
and Tenant against all claims and demands for (i) injury to or death of any
person or damage to or loss of property, on the Premises, in the Building or on
the Lot or adjoining walks, streets or ways, or connected with the use,
condition or occupancy of any thereof unless caused by the negligence of
Landlord or its servants or agents, (ii) violation of this Lease, or (iii) any
act, fault or omission, or other misconduct of Tenant or its agents,
contractors, licensees, sublessees or invitees, in amounts which shall, at the
beginning of the Term, be at least equal to the limits set forth in Section 1.1,
and, from time to time during the Term, shall be for such higher limits, if any,
as are customarily carried in the area in which the Premises, Building and Lot
are located for property similar to the Premises, Building and Lot and used for
similar purposes, provided, however, Landlord shall not require an increase in
such limits more frequently than once every three years, and in no event shall
such limits exceed the limits required for buildings in Cambridge similar to the
Building, and shall be written on the "Occurrence Basis"; and

        (b)   Worker's compensation insurance with statutory limits covering all
of the Tenant's employees working on the Premises.

All insurance required to be carried by Tenant pursuant to this Lease may be
provided under one or more "blanket" insurance policies covering other locations
and facilities operated by Tenant or any Affiliate of Tenant, provided that such
blanket policies otherwise comply with the provisions of this Section. In
addition, Tenant may satisfy the $10,000,000 per occurrence liability insurance
coverage, as the same may be increased pursuant to Section 4.2.2.1(a) hereof,
with excess liability (so-called "umbrella") coverage, so long as Tenant
maintains primary liability coverage of not less than $5,000,000, as the same
may be increased pursuant to Section 4.2.2.1(a) hereof.

        (c)   Landlord acknowledges that Tenant shall have the right, at its
sole election, and at Tenant's sole expense, independently to obtain all risk
fire and casualty and boiler/sprinkler damage insurance similar to that
described in Sections 4.2.2.2(b) and (c) below for the purpose of providing
Tenant with insurance proceeds to fund any Tenant's Restoration Fund described
in Section 6.1(h) below. However, Tenant shall not be obligated to file any
claim or use any proceeds from such insurance for the benefit of Landlord.

4.2.2.2    Insurance Taken Out by Landlord.

        Landlord shall take out and maintain throughout the Term of this Lease
the following insurance:

        (a)   Comprehensive general liability insurance for the Building, the
Lot and the Complex of the same nature and type as described in
Section 4.2.2.1(a) of this Lease, and with the same policy limits or such higher
policy limits as Landlord may reasonably determine; and

        (b)   All risk, fire and casualty insurance on a one hundred percent
(100%) replacement cost basis, together with rental loss coverage and, if the
Building is located in a flood zone, flood coverage to the extent the same is
available, insuring the Building and its rental value, and Complex Common Areas;
and

        (c)   Insurance against loss or damage from sprinklers and from leakage
or explosions or cracking of boilers, pipes carrying steam or water, or both,
pressure vessels or similar apparatus, in the so-called "broad form", in such
amounts as are customary and commercially reasonable for

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buildings in the Cambridge, Massachusetts area which are of like kind and
quality to the Building and have office uses, and insurance against such other
hazards and in such amounts as may from time to time be required by any bank,
insurance company or other lending institution holding a first mortgage on the
Building, the Lot or the Complex.

Landlord shall have no obligation to insure Tenant's personal property or
chattels, including without limitation, Tenant's trade fixtures.

4.2.2.3    Tenant Reimbursement of Insurance Taken Out by Landlord.

        Tenant shall from time to time reimburse Landlord within thirty
(30) days of Landlord's invoice for Tenant's Proportionate Fraction for Building
and Tenant's Proportionate Fraction for Complex of Landlord's costs incurred in
providing the insurance provided pursuant to Section 4.2.2.2 of this Lease,
equitably prorated in the case of blanket policies to reflect the insurance
coverage reasonably attributable to the Premises, the Building, the Lot, other
buildings in the Complex, and Complex Common Areas, and provided further that
Tenant shall reimburse Landlord for all of Landlord's costs incurred in
providing such insurance which is attributable to any special endorsement or
increase in premium resulting from the business or operations of Tenant, and any
special or extraordinary risks or hazards resulting therefrom. At Landlord's
option, Tenant shall reimburse Landlord for insurance costs in accordance with
Section 4.2.5 hereof.

4.2.2.4    Certain Requirements Applicable to Insurance Policies.

        Policies for insurance provided for under the provisions of Sections
4.2.2.2(b) and 4.2.2.2(c) shall, in case of loss, be first payable to the
holders of any mortgages on the Building, the Lot or the Complex under a
standard mortgagee's clause, and shall be deposited with the holder of any
mortgage or with Landlord, as Landlord may elect. All policies for insurance
required to be obtained by either party under the provisions of Section 4.2.2
shall be obtained from responsible companies qualified to do business in the
Commonwealth of Massachusetts and in good standing therein, which companies and
the amount of insurance allocated thereto shall be subject to Landlord's
approval. Each party agrees to furnish the other with certificates of all such
insurance which such party is obligated to obtain pursuant to Section 4.2.2
prior to the beginning of the Term hereof and with renewal certificates at least
thirty (30) days prior to the expiration of the policy they renew. In addition,
Tenant agrees to furnish Landlord with any policies of insurance which Tenant is
obligated to obtain hereunder, including any renewal policies, upon request of
any of Landlord's mortgagees (provided that Tenant may redact from such policies
any Confidential Information, as defined in Section 10.15 hereof). Each such
policy required to be maintained by Tenant shall name Landlord and Landlord's
Managing Agent (and such mortgagees of Landlord and members or shareholders of
Landlord if such mortgagees, members and/or shareholders may be named as
additional insureds without additional premium charges to Tenant or, if
additional premium charges are required, if Landlord reimburses Tenant for such
additional premium charges) as additional insureds and shall be noncancellable
with respect to the interest of Landlord, Landlord's Managing Agent and such
additional insureds without at least thirty (30) days' prior written notice
thereto.

4.2.2.5    Waiver of Subrogation.

        All insurance which is carried by either party with respect to the
Premises, the Building, the Lot or the Complex or with respect to furniture,
furnishings, fixtures or equipment therein or alterations or improvements
thereto, whether or not required, shall include provisions which either
designate the other party as one of the insured or deny to the insurer
acquisition by subrogation of rights of recovery against the other party to the
extent such rights have been waived by the insured party prior to occurrence of
loss or injury, insofar as, and to the extent that such provisions may be
effective without

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making it impossible to obtain insurance coverage from responsible companies
qualified to do business in the state in which the Premises are located (even
though extra premium may result therefrom) and without voiding the insurance
coverage in force between the insurer and the insured party. In the event that
extra premium is payable by either party as a result of this provision, the
other party shall reimburse the party paying such premium the amount of such
extra premium. If at the request of one party, this non-subrogation provision is
waived, then the obligation of reimbursement shall cease for such period of time
as such waiver shall be effective, but nothing contained in this Section 4.2.2.5
shall derogate from or otherwise affect releases elsewhere herein contained of
either party for claims. Each party hereby waives all rights of recovery against
the other for loss or injury against which the waiving party is protected by
insurance containing said provisions, reserving, however, any rights with
respect to any excess of loss or injury over the amount recovered from such
insurance. Tenant shall not acquire as insured under any insurance carried by
Landlord on the Premises, the Building, the Lot or the Complex under the
provisions of this Section 4.2.2 any right to participate in the adjustment of
loss or to receive insurance proceeds and agrees upon request promptly to
endorse and deliver to Landlord any checks or other instruments in payment of
loss in which Tenant is named as payee.

4.2.3    Utilities for Premises.

        Landlord and Tenant agree that the Design Documents shall include
separate metering or submetering of all or certain Utility Services (as
hereinafter defined) for the Premises and the Expansion Spaces. Accordingly, to
the extent such Utility Services are separately metered or submetered, Tenant
shall pay directly to the proper authorities charged with the collection thereof
all charges for water, sewer, gas, electricity, telephone and other utilities or
services (singularly, "Utility Service" and collectively, "Utility Services")
used or consumed on the Premises, whether called charge, tax, assessment, fee or
otherwise, including, without limitation, water and sewer use charges and taxes,
if any, all such charges to be paid as the same from time to time become due.
Landlord shall be under no obligation to furnish any utilities to the Premises
except as may be shown on the Final Design Documents and Landlord shall not be
liable for any interruption or failure in the supply of any such Utility
Services to the Premises; provided, however, that in the event such loss or
failure is due to Landlord's negligence or willful misconduct, Landlord shall be
responsible for restoring the supply of such Utility Services to the Premises
but otherwise shall have no liability to Tenant.

        To the extent permitted by law, Landlord shall have the right at any
time and from time to time during the Term to contract for or purchase one or
more Utility Services from any company or third party, including without
limitation, electricity, steam, chilled water and natural gas (collectively
"Utilities") providing Utilities (the "Utility Service Provider" or "Utility
Service Providers"), which contracts or purchases, in Landlord's reasonable
opinion, are likely to result in a reduction in costs for Utility Services to
the occupants of the Building or of the Complex taken as a whole. Tenant, at no
cost to Tenant, agrees to reasonably cooperate with Landlord and the Utility
Service Providers and at all times and, as reasonably necessary, and on
reasonable advance notice, shall allow Landlord and the Utility Service
Providers reasonable access to any utility lines, equipment, feeders, risers,
fixtures, wiring and any other such machinery or personal property within the
Premises and associated with the delivery of Utility Services. Tenant may, but
shall not be required to, purchase Utilities from respective Utility Service
Providers.

4.2.4    Common Area Maintenance and Expenses.

        Landlord shall maintain the interior and exterior common areas and
facilities of the Building and the Lot (collectively, "Building Common Areas")
and interior and exterior common areas and facilities of the Complex
(collectively, "Complex Common Areas") in the same quality and condition as
other comparable first class office buildings in Cambridge, including without
limitation, keeping the Building Common Areas and the Complex Common Areas clean
and free of debris, keeping the sidewalks,

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driveways and parking areas reasonably clear of snow and ice, maintaining the
exterior landscaping, lighting, parking areas and sidewalks of the Lot and
Complex, maintaining passenger elevator service, providing Utility Services to
the Premises (if any of such Utility Services are not separately metered or
submetered), Building Common Areas and Complex Common Areas, including hot water
for lavatory purposes and cold water (at temperatures supplied by the provider
thereof) for drinking, lavatory and toilet purposes, providing cleaning and
janitorial services to the Premises on Monday through Friday, excluding
holidays, provided the same are kept in order by Tenant in accordance with
cleaning standards from time to time agreed upon by Landlord and Tenant, and
providing security services for the Building, Lot and Complex to a standard
comparable to security services provided at other first class office buildings
in Cambridge. Landlord's obligations with respect to the foregoing shall be
subject to Tenant's right to self-manage the Building as set forth in
Section 10.11(h) hereof. Tenant shall maintain the interior of the Premises,
including the mechanical, electrical and plumbing systems of the Premises in
good order, repair and condition (provided that if Tenant shall fail to effect
such repairs or maintenance or Tenant shall elect to have Landlord perform such
repairs or maintenance, Landlord may or shall, as applicable, effect such
repairs or maintenance and charge the entire cost thereof to Tenant as
Additional Rent). Notwithstanding the foregoing, it is expressly understood and
agreed that Landlord shall have no liability or responsibility for the storage,
containment or disposal of any hazardous or medical waste generated, stored or
contained by Tenant, Tenant hereby agreeing to store, contain and dispose of any
and all such hazardous or medical waste at Tenant's sole cost and expense in
accordance with the provisions of Article V hereof.

        Tenant shall pay to Landlord as Additional Rent the Annual Maintenance
Charge computed and payable as follows:

        (1)   The Annual Maintenance Charge shall be equal to the sum of the
"Annual Building Maintenance and Operation Charge", the "Annual Complex
Maintenance and Operation Charge" and the "Nonstandard Charge" as hereinafter
defined.

        (a)   The "Annual Building Maintenance and Operation Charge" shall be
equal to Tenant's Proportionate Fraction for Building on account of all costs
incurred by Landlord during the then current fiscal year in operating the
Building and Lot and providing maintenance, including without limitation
maintenance, operation and repair of the Lot and the Building and all heating,
plumbing, electrical, air conditioning and mechanical fixtures and equipment
serving Building Common Areas, Utility Services for Building Common Areas,
maintenance of Lot and Building signage, elevators, landscaping, snow removal,
trash dumpster rental, trash removal, management fees (which management fees
shall have a commercially reasonably relationship to the scope of services to be
provided by such manager and which may be based upon a percentage of rent
payable by tenants of the Building), amortization of equipment to the extent
used for Building or Lot operation and maintenance, and all costs incurred by
Landlord in order for Landlord to comply with the Development Approvals and
Subsequent Approvals and which are recurring or properly categorized as
operating or maintenance costs ("Impositions") and equitably attributable or
allocated to the Building or Lot.

        (b)   The "Annual Complex Maintenance and Operation Charge" shall be
equal to Tenant's Proportionate Fraction for Complex on account of all costs
incurred by Landlord during the then current fiscal year in operating the
Complex Common Areas and providing Complex Common Areas maintenance, including
without limitation, maintenance, operation and repair of all heating, plumbing,
electrical, air conditioning and mechanical fixtures and equipment serving
Complex Common Areas, Utility Services for Complex Common Areas, maintenance of
Complex Common Area signage, elevators, landscaping, snow removal, trash
dumpster rental, trash removal, management fees (which management fee shall have
a commercially reasonable relationship to the scope of services to be provided
by such manager

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and which may be based upon a percentage of rent payable by tenants of the
Complex), amortization of equipment to the extent used for Complex Common Areas
operation and maintenance and all Impositions equitably attributable to or
allocated to the Complex.

        (c)   Anything herein to the contrary notwithstanding, the Annual
Maintenance Charge shall not include (1) leasing and sales commissions for the
Building or any portion thereof or any other building in the Complex, (2) fees
paid in connection with any tenant improvement costs for the Building or any
other building in the Complex, (3) such other fees and commissions paid in
connection with the leasing, re-leasing, extension or renewal of leases for the
Building or any other building in the Complex, (4) costs incurred with respect
to the operation and maintenance of any other building in the Complex which is
leased or available for lease, any rentable space therein or any common areas or
facilities in such buildings (except to the extent that Landlord maintains a
management office therein or in the Building, in which event Tenant shall pay
Tenant's Proportionate Fraction for Complex of the fair market rental value
thereof as equitably determined by Landlord), (5) any cost or expense
attributable to the underground garage(s) within the Complex, (6) costs and
expenses which are properly attributable to a particular building (other than
the Building) or a particular tenant thereof, (7) third party management fees
for the Building and Complex included in the Annual Maintenance Charge to the
extent such fees exceed market rate fees, (8) any management or supervisory fee
of Landlord if a third party is managing the Building or Complex (but if
Landlord is self-managing the Building or Complex, Landlord shall be entitled to
reimbursement of its reasonable costs for managing the Building and Complex
provided that in no event may Landlord's costs and fees for self-managing the
Building or Complex exceed the costs and fees that a market-rate third party
management company would charge for providing comparable services), (9) in the
event that any capital repair, improvement or replacement to the Building Common
Areas or the Complex Common Areas made by Landlord has a useful life of over one
year (as determined in accordance with generally accepted accounting practices
consistently applied), then only the amortized cost of such repair, improvement
or replacement over said useful life shall be included in the Annual Building
Maintenance and Operation Charge or Annual Complex Maintenance and Operation
Charge, as applicable, provided that replacement of a capital item shall be of
substantially the same quality and/or usefulness as the capital item being
replaced or shall be expected to reduce the Annual Maintenance Charge or
otherwise provide some other economic benefit to the operation of the Premises,
Building, Lot or Complex, as applicable, such as conserving energy or
environmental resources, or if such capital item is required by any law enacted
after the date hereof, (10) wages, salaries, or other compensation or benefits
paid to any persons above the grade of Building manager and Complex manager (or
equivalent position), (11) debt service, (12) capital expenditures (except to
the extent expressly permitted under this Section), (13) depreciation and
amortization (except to the extent expressly permitted under this Section),
(14) legal and accounting fees relating to (A) disputes with occupants of the
Building or Complex, or (B) disputes with purchasers, prospective purchasers,
mortgages or prospective mortgagees, (15) any rent under any ground or
underlying lease, (16) any fines or penalties incurred due to violations of law
by Landlord or any tenant or other occupant of the Building or Complex, (17) any
amount incurred to any entity affiliated with Landlord to the extent the same
exceeds the amount which would have been incurred on an arm's length basis in
the absence of such affiliation, (18) any interest, fines or penalties incurred
or resulting from late payment by Landlord of any operating expense, (19) costs
incurred in connection with the Environmental Remediation, (20) any amounts
incurred for repairs or other work occasioned by fire, windstorm or other
casualty to the extent Landlord is reimbursed by insurance or would have been
reimbursed by insurance had Landlord maintained the insurance it is required to
maintain under this Lease, (21) costs incurred in connection with

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the permitting, financing or construction of the Building and Complex, and
(22) any so-called asset management fees.

        (d)   Notwithstanding anything herein to the contrary, if Landlord
furnishes or makes available any service, utility or facility to less than all
of the tenants of the Building or Complex, as applicable, Landlord shall
allocate all costs incurred by Landlord on account of such services, utilities
or facilities to the tenants of the Building or Complex, as applicable, to whom
or to which such services, utilities or facilities are furnished or made
available (all such costs being herein referred to as the "Nonstandard Costs").
The "Nonstandard Charge" shall be equal to Tenant's share of Nonstandard Costs
equitably allocated to Tenant by Landlord. By way of example, if Landlord
furnishes trash services and/or cleaning services to office tenants of the
Building, but not to retail tenants, Landlord shall allocate the cost thereof to
office tenants and Tenant shall pay Tenant's share thereof as equitably
allocated by Landlord. In no event shall any cost incurred by Landlord and
payable by Tenant for insurance, Utility Services for the Premises which are
separately metered or submetered, and taxes and assessments be included in the
Annual Maintenance Charge payable by Tenant.

        Attached hereto as Exhibit B-2 is a list of the Annual Maintenance
Charge categories for the Building Common Areas and the Complex Common Areas,
insurance, Mitigation Expenses and taxes and assessments. Landlord shall not
make any change in the categories set forth thereon without obtaining Tenant's
prior consent thereto, which consent shall not be unreasonably withheld, delayed
or conditioned. Tenant, however, shall have no right to approve the amount of
any costs which may be incurred by Landlord with respect to such categories,
except to the extent set forth in Section 10.11(h) hereof. At the beginning of
every fiscal year, Landlord shall deliver to Tenant its reasonable estimate of
the Annual Maintenance Charge (the "Estimated Annual Maintenance Charge") for
the said fiscal year, which estimate may include a reasonable contingency of up
to five percent (5%), and Tenant shall make payments on account of the Annual
Maintenance Charge monthly in advance on the first day of each calendar month
during the Term in the amount of one-twelfth of the Estimated Annual Maintenance
Charge. Landlord reserves the right to reasonably re-estimate and modify the
Estimated Annual Maintenance Charge by notice to Tenant once annually in each
Lease Year (the "Additional Rent Adjustment Date"), and Tenant's payments shall
thereupon be adjusted accordingly. Not later than ninety (90) days after the end
of each fiscal year during the Term and after Lease termination, Landlord shall
render a statement ("Landlord's Statement"), in reasonable detail and according
to usual accounting practices, certified by Landlord and showing for the
preceding fiscal year or fraction thereof, as the case may be, the actual Annual
Maintenance Charge for the said fiscal year or fraction thereof, and thereupon
any balance owed by Tenant shall be paid to Landlord within twenty (20) days
after Tenant receives written notice thereof, and any excess paid by Tenant
under this Section shall be paid to Landlord, or credited to Tenant, on the next
rent payment date. Tenant shall have the right for a period of one (1) year
following its receipt of Landlord's Statement to examine Landlord's books and
records concerning the Annual Maintenance Charge. Such examination may be made
only by an independent certified public accounting firm approved by Landlord,
which approval shall not be unreasonably withheld, conditioned or delayed.
Landlord may withhold its approval of any examiner of Tenant who or which is
being paid by Tenant, in whole or in part, on a contingent fee basis. As a
condition to performing any such examination, Tenant and its examiner shall be
required to execute and deliver to Landlord an agreement, in form acceptable to
Landlord, agreeing to keep confidential any information which it discovers about
Landlord, the Building or the Complex in connection with such examination. If
the Annual Maintenance Charge due was less than the Annual Maintenance Charge
paid by Tenant, Landlord shall either promptly refund to Tenant the difference
or credit same against rent next due from Tenant. If the Annual Maintenance
Charge due was less than ninety-five percent (95%) of the Annual Maintenance
Charge paid by Tenant, Landlord shall reimburse Tenant for the reasonable
third-party costs of reviewing Landlord's books and records.

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        For purposes of this Lease, the first "fiscal year" shall be the annual
period commencing on the Commencement Date and ending on December 31 of the year
in which the Commencement Date occurs; subsequently, the term "fiscal year,
shall mean each consecutive annual period thereafter, commencing on the day
following the end of the preceding fiscal year. Landlord shall have the right
from time to time to change the periods of accounting under this Section 4.2.4
to any annual period other than a fiscal year, and upon any such change all
items referred to in this Section shall be appropriately apportioned, provided
that any such change in the fiscal year shall not result in any inequitable
shifting of, or increase in, amounts payable to Landlord by Tenant. In all
Landlord's Statements rendered under this Section, amounts for periods partially
within and partially without the accounting periods shall be appropriately
apportioned, and any items which are not determinable at the time of a
Landlord's Statement shall be included therein on the basis of Landlord's
estimate, and with respect thereto Landlord shall render promptly after
determination a supplemental Landlord's Statement, and appropriate adjustment
shall be made according thereto. All of Landlord's Statements shall be prepared
on an accrual basis of accounting.

        Notwithstanding any other provision of this Section 4.2.4, if the Term
expires or is terminated as of a date other than the last day of a fiscal year,
then for such fraction of a fiscal year at the end of the Term, Tenant's last
payment to Landlord under this Section 4.2.4 shall be made on the basis of
Landlord's best estimate of the items otherwise includable in Landlord's
Statement and shall be made on or before twenty (20) days after Landlord
delivers such estimate to Tenant. Landlord shall thereafter prepare a Landlord's
Statement showing the actual Annual Maintenance Charge for such fiscal year, as
hereinabove provided, and an appropriate payment or refund shall thereafter
promptly be made upon submission of such Landlord's Statement to Tenant.

4.2.5    Payments on Account of Taxes, Insurance and Utilities.

        Tenant shall make payments on account of the Annual Tax, Insurance and
Utility Charge (as hereinafter defined) monthly in advance on the first day of
each calendar month during the Term, which payments shall initially be in the
amount of the sum of the Initial Tax Charge, the Initial Insurance Charge and
the Initial Utility Charge (the "Estimated Initial Tax, Insurance and Utility
Charges"). At the beginning of every fiscal year, Landlord shall deliver to
Tenant its reasonable estimate of the Annual Tax, Insurance and Utility Charge
("the Estimated Annual Tax, Insurance and Utility Charge") for said fiscal year,
and, in lieu of payments of one twelfth of the Estimated Initial Tax, Insurance
and Utility Charge, Tenant shall make payments on account of the Annual Tax,
Insurance and Utility Charge monthly in advance on the first day of each
calendar month during the Term in the amount of one-twelfth of the Estimated
Annual Tax, Insurance and Utility Charge. Landlord reserves the right to
reasonably re-estimate and modify the Estimated Annual Tax, Insurance and
Utility Charge by notice to Tenant once annually on the Additional Rent
Adjustment Date (as defined in Section 4.2.4 hereof), and Tenant's payments
shall thereupon be adjusted accordingly.

        Not later than ninety (90) days after the end of each fiscal year during
the Term and after Lease termination, Landlord shall render a statement in
reasonable detail and according to usual accounting practices certified by
Landlord and showing for the preceding fiscal year or fraction thereof, as the
case may be, the actual Annual Tax, Insurance and Utility Charge for the said
fiscal year or fraction thereof, and thereupon any balance owed by Tenant or
excess paid by Tenant under this Section shall be paid to Landlord, or credited
to Tenant, as the case may be, within twenty (20) days thereafter. As used
herein, the term "Annual Tax, Insurance and Utility Charge" shall mean and refer
to the amount of funds paid by Tenant pursuant to Section 4.2.1, 4.2.2 and 4.2.3
for the fiscal year in question for costs actually incurred by Landlord (without
any mark-up for Landlord's overhead or profit). All payments under this Section
shall to the extent thereof relieve Tenant of its obligations under said
Sections 4.2.1, 4.2.2 and 4.2.3 hereof.

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        Landlord shall have the right from time to time to change the periods of
accounting under this Section 4.2.5 to any annual period other than a fiscal
year (but not more frequently than once every three years), and upon any such
change all items referred to in this Section shall be appropriately apportioned,
provided that any such change in accounting periods shall not result in any
inequitable shifting of, or increase in, amounts payable to Landlord by Tenant.
In all Landlord's annual statements rendered under this Section, amounts for
periods partially within and partially without the accounting periods shall be
appropriately apportioned, and any items which are not determinable at the time
of such a statement shall be included therein on the basis of Landlord's
estimate, and with respect thereto Landlord shall render promptly after
determination a supplemental statement, and an appropriate adjustment shall be
made according thereto. All of landlord's statements under this Section shall be
prepared on an accrual basis of accounting.

        Notwithstanding any other provision of this Section 4.2.5, if the Term
expires or is terminated as of a date other than the last day of a fiscal year,
then for such fraction of a fiscal year at the end of the Term, Tenant's last
payment to Landlord under this Section 4.2.5 shall be made on the basis of
Landlord's best estimate of the items otherwise includable in the annual
statement rendered by Landlord under this Section and shall be made on or before
the later of (a) twenty (20) days after Landlord delivers such estimate to
Tenant or (b) the last day of the Term, with an appropriate payment or refund to
be made upon submission of Landlord's statement.

4.3    LATE PAYMENT OF RENT.

        If any installment of rent is paid after the date the same was due (or
if such due date is not a business day, on the first business day after such due
date), at Landlord's election it shall bear interest from the due date (or if
such due date is not a business day, from the first business day after such due
date) at the higher of (a)(i) the annual rate of interest payable by Landlord to
its mortgagee(s) or (ii) the prime commercial rate of Fleet National Bank or its
successor(s), as it may be adjusted from time to time, plus (b) four percent
(4%) per annum, but in no event more than the highest rate of interest allowed
by applicable law. Any amounts due under this Section 4.3 shall be Additional
Rent.

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ARTICLE V

TENANT'S ADDITIONAL COVENANTS

5.1   AFFIRMATIVE COVENANTS.

        Tenant covenants at its expense at all times during the Term and for
such further time as Tenant occupies the Premises or any part thereof:

5.1.1    Perform Obligations.

        To perform promptly all of the obligations of Tenant set forth in this
Lease; and to pay when due the Fixed Rent and Additional Rent and all charges,
rates and other sums which by the terms of this Lease are to be paid by Tenant.

5.1.2    Occupancy and Use.

        Except for (i) the period of time permitted by this Lease for Tenant to
perform Tenant's Work to prepare the Premises for Tenant's initial occupancy as
set forth in Section 3.2.1 and (ii) a period of six (6) months at the end of the
Term, and (iii) temporary vacancies of not more than forty percent (40%) of the
Premises at any one time, continuously from the Commencement Date, to use and
occupy the Premises only for the Permitted Uses, and from time to time, to
procure all licenses and permits necessary therefor at Tenant's sole expense,
and to the extent set forth in Section 10.21 hereof, with Landlord's
cooperation. Without limitation, Tenant shall comply in all material respects
with all federal, state, and municipal laws, ordinances, and regulations
governing, and all Development Approvals, Subsequent Approvals and Title
Exceptions applicable to, Tenant's particular use or manner of use of the
Premises. Tenant shall be solely responsible for procuring and complying at all
times with any and all necessary permits directly relating or incident to: the
conduct of its office activities on the Premises; its, transportation, storage,
handling, use and disposal of any chemical or radioactive or bacteriological or
pathological substances or organisms or other hazardous wastes or
environmentally dangerous substances or materials or medical waste. Within
thirty (30) days of a request by Landlord, which request shall be made not more
than once during each period of twelve (12) consecutive months during the Term
hereof, unless otherwise requested by any mortgagee of Landlord, Tenant shall
furnish Landlord with copies of all such permits which Tenant possesses or has
obtained together with a certificate certifying that such permits are all of the
permits which Tenant possesses or has obtained with respect to the Premises.
Tenant shall be entitled to redact any Confidential Information from the copies
of such permits and accompanying certificates of Tenant. Tenant shall promptly
give notice to Landlord of any warnings or violations relative to the matters
described in this Section 5.1.2 received from any federal, state, or municipal
agency or by any court of law and shall promptly cure the conditions causing any
such violations. Tenant shall not be deemed to be in default of its obligations
under the preceding sentence to promptly cure any condition causing any such
violation in the event that, in lieu of such cure, Tenant shall contest the
validity of such violation by appellate or other proceedings permitted under
applicable law, provided that: (i) any such contest is made reasonably and in
good faith, (ii) Tenant makes provisions, including, without limitation, posting
bond(s) or giving other security, acceptable to Landlord to protect Landlord,
the Building, the Lot and the Complex from any liability, costs, damages or
expenses arising in connection with such violation and failure to cure,
(iii) Tenant shall agree to indemnify, defend (with counsel reasonably
acceptable to Landlord) and hold Landlord harmless from and against any and all
liability, costs, damages, or expenses arising in connection with such condition
and/or violation, (iv) Tenant shall promptly cure any violation in the event
that its appeal of such violation is overruled or rejected, and (v) Tenant shall
certify to Landlord's satisfaction that Tenant's decision to delay such cure
shall not result in any actual or threatened bodily injury or property damage to
Landlord, any tenant or occupant of the Building, the Lot or the Complex, or any
other person or entity. Landlord agrees that any Confidential Information gained
or

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obtained by Landlord pursuant to this Section 5.1.2 shall be kept confidential
in accordance with Section 10.15 hereof.

5.1.3    Repair and Maintenance.

        Except as otherwise provided in Article VI, to keep the Premises
including, without limitation, all fixtures and equipment now or hereafter on
the Premises, or exclusively serving the Premises, but excluding the exterior
(exclusive of glass and doors) and structural elements of the Building and the
grounds of the Lot, which Landlord shall maintain and repair unless such repairs
are required because of Tenant's willful misconduct or negligence, in good
order, condition and repair and at least as good order, condition and repair as
they are in on the Commencement Date or may be put in during the Term,
reasonable use and wear, damages by fire or other insurable casualty or eminent
domain, and any damage directly caused by failure of Landlord to perform any of
its obligations only excepted; to keep in a safe, secure and sanitary condition
all trash and rubbish temporarily stored at the Premises; and to make all
repairs and replacements and to do all other work necessary for the foregoing
purposes whether the same may be ordinary or extraordinary, foreseen or
unforeseen. Unless otherwise agreed to by Landlord and Tenant, Tenant shall be
responsible for Utility Services systems serving the Premises to the extent that
such systems are not a part of Base Building Improvements, and Tenant shall
secure, pay for and keep in force contracts with appropriate and reputable
service companies providing for the regular maintenance of the heating, air
conditioning and other utility systems exclusively serving the Premises to the
extent that such systems are not a part of Base Building Improvements, and
copies of such contracts shall be furnished to Landlord. It is further agreed
that the exception of reasonable use and wear shall not apply so as to permit
Tenant to keep the Premises in anything less than suitable, tenantlike, and
efficient and usable condition considering the nature of the Premises and the
use reasonably made thereof, or in less than good and tenantlike repair.

5.1.4    Compliance with Law.

        To make all repairs, alterations, additions or replacements to the
Premises required by any law or ordinance or any order or regulation of any
public authority other than major capital repairs, alterations, additions or
replacements to the foundations and structural elements of the Building which
are the responsibility of Landlord pursuant to the terms of this Lease and
unless required because of Tenant's failure to comply with the provisions of
Section 5.1.3 hereof; to keep the Premises equipped with all safety appliances
so required; to pay all municipal, county, or state taxes assessed against the
leasehold interest hereunder, or against Tenant's personal property of any kind
on or about the Premises; and to comply with the orders and regulations of all
governmental authorities with respect to zoning, building, fire, health and
other codes, regulations, ordinances or laws applicable to the Premises. To the
extent that applicable law requires Tenant to make any capital repair,
alteration, addition or replacement to the Premises, Tenant may implement such
capital repair, alteration, addition or replacement over the longest period
provided by applicable law.

        Except for typical office operating and cleaning supplies which are
stored, used and disposed of in compliance with all applicable laws, Tenant
shall not use, generate, manufacture, produce, handle, store, release, discharge
or dispose of in, on, under or about the Premises or transport to or from the
Premises, or allow its employees, agents, contractors, invitees or any other
person or entity to do so, any oil, hazardous or toxic materials or hazardous or
toxic wastes or medical waste (collectively, "hazardous materials") except to
the extent that the following conditions regarding the use, generation,
manufacture, production, handling, storing, releasing, discharging, disposal or
transport (individually or collectively, the "Use") of hazardous materials shall
be satisfied: (i) the Use shall be directly related to the operation of Tenant's
business as permitted herein, (ii) Tenant shall first provide Landlord with the
list of the types and quantities of such proposed hazardous materials which
Tenant is required to furnish to the applicable governmental authorities for
purposes of compliance with the Resource

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Conservation and Recovery Act, as amended (42 U.S.C. § 9601, et seq.) (the "RCRA
List") (or, in the event that the RCRA List ceases to be required to be filed
under such law, a list containing the same information required to be listed on
the RCRA List as of the date hereof), and shall update such list as necessary
for continuing accuracy, and such other information reasonably satisfactory to
Landlord as Landlord may reasonably require concerning such Use, and (iii) such
Use shall be in strict compliance (at Tenant's expense) with all applicable
laws, regulations, licenses and permits. Landlord hereby covenants and agrees
that the information contained in any list, or update thereof, referred to in
the foregoing clause (ii) shall be kept confidential in accordance with
Section 10.15 hereof. Notwithstanding the foregoing, Tenant hereby agrees to
consult and coordinate with Landlord prior to transporting any hazardous
materials to or from the Premises whenever (i) such transportation is not of the
kind regularly made during the ordinary course of business by a person or entity
operating a facility for the storage or disposal of such hazardous materials or
(ii) Tenant has reason to believe that such transportation may result in a
public demonstration, protest or other similar disturbance at the Building, the
Lot or the Complex. If the use of any hazardous materials anywhere on the
Premises in connection with the Tenant's use of the Premises results in
(1) contamination of the soil, surface or ground water or (2) injury, loss or
damage to person(s) or property, then Tenant agrees to respond in accordance
with the following paragraph:

Tenant agrees (i) to notify Landlord immediately of any contamination, claim of
contamination, injury, loss or damage, (ii) after consultation and approval by
Landlord, to clean up the contamination in full compliance with all applicable
statutes, regulations and standards, and (iii) to indemnify, defend (with
counsel acceptable to Landlord) and hold Landlord harmless from and against any
claims, suits, causes of action, costs and fees, including attorneys' fees,
arising from or connected with any such contamination, claim of contamination,
injury, loss or damage. No consent or approval of Landlord shall in any way be
construed as imposing upon Landlord any liability for the means, methods, or
manner of removal, containment or other compliance with applicable law for and
with respect to the foregoing.

        Tenant shall promptly notify Landlord upon Tenant's receipt of any
inquiry, notice, or threat to give notice by any government authority or any
other third party with respect to any hazardous materials. Notwithstanding the
foregoing, Tenant shall not be liable to Landlord hereunder for any
contamination, claim of contamination, injury, loss or damage arising in
connection with hazardous materials to the extent the same is the result of
(A) hazardous materials existing in the Building or on or under the Lot or
Complex prior to the date hereof, (B) migration of hazardous materials from any
site onto or under the Lot or Complex not caused by Tenant, (C) the use of any
hazardous materials at the Building, the Lot or Complex by Landlord, any other
tenant or occupant, or any so-called "midnight dumpers" or (D) the Use by any
party other than Tenant of hazardous materials at the Building, the Lot or
Complex after the date upon which Tenant has completely vacated the same,
including removal of all of its property (to the extent permitted herein) and
hazardous materials. Tenant's indemnification obligations under this Section
shall survive the expiration or earlier termination of this Lease.

        Nothing herein contained shall be construed to limit or impair Tenant's
obligation to comply with any law, code, rule or regulation which requires
Tenant to notify any governmental authority or any other person concerning the
Use of hazardous materials by Tenant at the Premises.

5.1.5    Tenant's Work.

        To procure at Tenant's sole expense all necessary permits and licenses
(but subject to Section 10.21 hereof) before Tenant undertakes any work on the
Premises; to do all such work in compliance with the applicable provisions of
Sections 3.2.1, 3.3 and 5.2.3 hereof; to do all such work in a good and
workmanlike manner employing new materials of good quality and so as to conform
with all applicable

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zoning, environmental, building, fire, health and other codes, regulations,
ordinances and laws and the ADA Requirements; to keep the Premises at all times
free of liens for labor and materials; to employ for such work one or more
responsible contractors whose labor will work without interference with other
labor working on the Premises, in the Building, on the Lot or in the Complex; to
require such contractors employed by Tenant to carry worker's compensation
insurance in accordance with statutory requirements and comprehensive public
liability insurance covering any general contractors on or about the Premises in
amounts that at least equal the limits agreed to by Landlord for an Approved
Contractor and to submit certificates evidencing such coverage to Landlord prior
to the commencement of such work; and to save Landlord harmless and indemnified
from all injury, loss, claims or damage to any person or property occasioned by
or growing out of such work.

5.1.6    Indemnity.

        To defend, with counsel reasonably approved by Landlord, all actions
against Landlord, any officer, director, member, manager or stockholder of
Landlord, or a partner, trustee, stockholder, officer, director, employee, agent
or beneficiary of any member of Landlord, holders of mortgages secured by the
Premises, the Building or Lot and any other party having an interest in the
Premises ("Indemnified Parties") with respect to, and to pay, protect, indemnify
and save harmless, to the extent permitted by law, all Indemnified Parties from
and against, any and all liabilities, losses, damages, costs, (including
reasonable attorneys' fees and expenses), causes of action, suits, claims,
demands or judgments of any nature arising from (i) injury to or death of any
person, or damage to or loss of property, on the Premises, the Lot or Complex or
on adjoining streets or ways connected with the use or occupancy thereof by
Tenant or its agents, contractors, licensees, employees, sublessees or invitees,
unless and to the extent caused by the negligence of Landlord or its servants or
agents, (ii) violation of this Lease by Tenant or its agents, contractors,
licensees, employees, sublessees or invitees, or (iii) any act, fault, omission,
or other misconduct of Tenant or its agents, contractors, licensees, employees,
sublessees or invitees.

5.1.7    Landlord's Right to Enter.

        To permit Landlord and its agents to enter into the Premises at
reasonable times and upon at least twenty-four (24) hours advance notice (except
in case of emergency in which event no prior notice shall be required) to
examine the Premises, make such repairs and replacements as Landlord may be
authorized or required to perform pursuant to this Lease, and show the Premises
to prospective purchasers and lenders, and, during the last eighteen (18) months
of the Term, to show the Premises to prospective tenants and to keep affixed in
suitable places notices of availability of the Premises. Landlord's right to
enter the Premises in accordance with the foregoing shall be subject to
Landlord's obligations pursuant to Section 10.15 hereof. Notwithstanding the
foregoing, Landlord agrees that in the event that Landlord shows the Premises to
any prospective purchaser or tenant, Landlord shall: (i) provide at least three
(3) days' notice to Tenant identifying the prospective purchaser or tenant,
(ii) only show the Premises to such purchaser or tenant if Landlord believes in
good faith that such person or entity is a bona fide prospective purchaser or
tenant, and (iii) conduct such showing in compliance with such reasonable
requests and instructions as Tenant may make for purposes of protecting Tenant's
Confidential Information.

5.1.8    Personal Property at Tenant's Risk.

        All of the furnishings, fixtures, equipment, effects and property of
every kind, nature and description owned or leased by Tenant or by any person
claiming by, through or under Tenant which, during the continuance of this Lease
or any occupancy of the Premises by Tenant or anyone claiming under Tenant, may
be on the Premises (collectively, "Tenant's Property"), shall, as between the
parties, be at the sole risk and hazard of Tenant and if the whole or any part
thereof shall be destroyed or

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damaged by fire, water or otherwise, or by the leakage or bursting of water
pipes, steam pipes, or other pipes, by theft or from any other cause, no part of
said loss or damage is to be charged to or to be borne by Landlord, except that
Landlord shall in no event be indemnified or held harmless or exonerated from
any liability to Tenant or to any other person, for any injury, loss, damage or
liability to the extent (i) such injury, loss, damage or liability is the result
of the negligence or willful misconduct of Landlord, its contractors, agents or
employees, or (ii) such indemnification, agreement to hold harmless or
exoneration is prohibited by law.

5.1.9    Payment of Landlord's Cost of Enforcement.

        To pay on demand Landlord's expenses, including reasonable attorney's
fees, incurred in enforcing any obligation of Tenant under this Lease or in
curing any default by Tenant under this Lease as provided in Section 7.4.

5.1.10    Yield Up.

        Subject to Section 3.2.1 hereof, at the expiration of the Term or
earlier termination of this Lease: to surrender all keys to the Premises; to
remove all of its trade fixtures and personal property in the Premises; to
remove such installations and improvements made by Tenant as Landlord may
request at the time of Landlord's approval of such installation (but excluding
any Tenant's Work performed to prepare the Premises for Tenant's initial
occupancy) and all Tenant's signs wherever located; to repair all damage caused
by such removal; and to yield up the Premises (including all installations and
improvements made by Tenant except for trade fixtures and such of said
installations or improvements as Landlord shall request Tenant to remove),
broom-clean and in the same good order and repair in which Tenant is obliged to
keep and maintain the Premises by the provisions of this Lease, reasonable wear
and tear, damage by fire or other insured casualty or eminent domain, and damage
directly caused by failure of Landlord to perform any of its obligations only
excepted. Subject to Section 3.2.1 hereof, any property not so removed shall be
deemed abandoned and may be removed and disposed of by Landlord in such manner
as Landlord shall determine and Tenant shall pay Landlord the entire cost and
expense incurred by Landlord in effecting such removal and disposition and in
making any incidental repairs and replacements to the Premises and for use and
occupancy during the period after the expiration of the Term and prior to
Tenant's performance of its obligations under this Section 5.1.10. Tenant shall
further indemnify Landlord against all loss, cost and damage resulting from
Tenant's failure and delay in surrendering the Premises as above provided.

5.1.11    Estoppel Certificate.

        Upon not less than fifteen (15) days' prior notice by Landlord, to
execute, acknowledge and deliver to Landlord, any prospective purchaser or
mortgagee of the Premises, Building, Lot or Complex a statement in writing
certifying that this Lease is unmodified and in full force and effect and that
except as stated therein Tenant has no knowledge of any defenses, offsets or
counterclaims against its obligations to pay the Fixed Rent and Additional Rent
and any other charges and to perform its other covenants under this Lease (or,
if there have been any modifications that the Lease is in full force and effect
as modified and stating the modifications and, if there are any defenses,
offsets or counterclaims, setting them forth in reasonable detail), the dates to
which the Fixed Rent and Additional Rent and other charges have been paid and a
statement that, to the best of Tenant's knowledge, Landlord is not in default
hereunder (or if in default, the nature of such default, in reasonable detail)
and such other matters reasonably required by Landlord or any prospective
purchaser or mortgagee of the Premises, the Building, Lot or Complex. Any such
statement delivered pursuant to this Section 5.1.11 may be relied upon by any
such prospective purchaser or mortgagee of the Premises, or any prospective
assignee of any such mortgage.

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5.1.12    Landlord's Expenses Re: Consents

        To reimburse Landlord promptly on demand for all reasonable legal
expenses incurred by Landlord in connection with all requests by Tenant for
consent or approval under this Lease. Notwithstanding the foregoing, except for
consents or approvals pursuant to Section 5.2.1 hereof, Tenant shall not be
liable for any reasonable legal expenses incurred by Landlord for the first two
(2) such requests made by Tenant during each period of twelve (12) consecutive
calendar months during the Term.

5.1.13    Rules and Regulations.

        To comply with the Rules and Regulations set forth in Exhibit C, as the
same may be amended from time to time by Landlord to provide for the beneficial
operation of the Building, Lot and or the Complex, provided that such amendments
do not materially interfere with Tenant's right of use and enjoyment of the
Premises, the Lot or the Complex pursuant to this Lease. So long as Tenant and
Tenant's Affiliates are occupying at least sixty percent (60%) of the r.s.f. in
the Building or Tenant, Tenant's Affiliates or Tenant's subtenants are occupying
all of the r.s.f. in the Building, in each case excluding the Retail Space, all
such amendments shall be subject to Tenant's prior approval, which shall not be
unreasonably withheld, conditioned or delayed.

5.1.14    Loading.

        Not to place Tenant's Property, as defined in Section 5.1.8, upon the
Premises so as to exceed the floor load limits to be set forth in the Design
Documents 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 times as Landlord shall in
each instance approve; Tenant's business machines and mechanical equipment which
cause vibration or noise that may be detectable outside of the Premises shall be
placed or maintained by Tenant in settings of cork, rubber, spring, or other
types of vibration or noise eliminators sufficient to reduce such vibration or
noise to a level reasonably acceptable to Landlord.

5.1.15    Holdover.

        To pay to Landlord (i) the greater of twice (a) the then fair market
rent as reasonably determined by Landlord or (b) the total of the Fixed Rent,
Additional Rent, and all other payments then payable hereunder, for each month
or portion thereof Tenant shall retain possession of the Premises or any part
thereof after the termination of this Lease, whether by lapse of time or
otherwise, and (ii) all damages sustained by Landlord on account thereof;
provided, however, that any payments made by Tenant under the foregoing
clause (i) in excess of the then fair market rent for the Premises as so
reasonably determined by Landlord shall be applied against any damages under the
foregoing clause (ii). The provisions of this subsection shall not operate as a
waiver by Landlord of the right of re-entry provided in this Lease.

5.2    NEGATIVE COVENANTS.

        Tenant covenants at all times during the Term and for such further time
as Tenant occupies the Premises or any part thereof:

5.2.1    Assignment and Subletting.

        Not without the prior written consent of Landlord to assign this Lease,
to make any sublease, or to permit occupancy of the Premises or any part thereof
by anyone other than Tenant, voluntarily or by operation of law, except as
hereinafter provided; as Additional Rent, to reimburse Landlord promptly for
reasonable legal and other expenses incurred by Landlord in connection with any
request by Tenant for consent to assignment or subletting; no assignment or
subletting (including any assignment or

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sublease not requiring Landlord's consent) shall affect the continuing primary
liability of Tenant (which, following assignment, shall be joint and several
with the assignee); and no consent to any of the foregoing in a specific
instance shall operate as a waiver in any subsequent instance. Landlord's
consent to any proposed assignment or subletting is required both as to the
terms and conditions thereof and as to the consistency of the proposed
assignee's or subtenant's business with other uses and tenants in the Building
and Complex. Tenant shall not assign this Lease or sublease any portion of the
Premises to any other tenant in the Complex (unless such assignee or subtenant
is an Affiliate of Tenant) if Landlord has or expects to have (within two years
of the date of the proposed assignment or sublease) vacant space in the Complex
for the Permitted Uses or if the proposed assignee or subtenant (other than an
Affiliate of Tenant) has been shown space in the Complex within six months prior
to the date of the proposed assignment or sublease. In addition, as to any
assignee or subtenant of all or substantially all of the Premises, Landlord's
consent shall be required as to the creditworthiness of the proposed assignee or
subtenant in view of market conditions then prevailing for leases having terms
and conditions comparable to this Lease and the obligations of such assignee or
subtenant pursuant to this Lease.

        If Tenant requests Landlord's consent to (i) assign this Lease or sublet
any portion of the Premises to any entity which is not an Affiliate of Tenant
(as herein defined) for the remainder of the Term or substantially all of the
remainder of the Term or (ii) sublease more than twenty-five percent (25%) of
the r.s.f. of the Premises for a sublease term of more than five years, Landlord
shall have the option, exercisable by written notice to Tenant given within
thirty (30) days after receipt of such request, to terminate this Lease (in the
event of a proposed assignment of the Lease) or to terminate this Lease only as
to the portion of the Premises proposed to be subleased (in the event of a
sublease), in each case as of the date of commencement of the proposed sublease
or assignment. If Landlord does not exercise such right to terminate this Lease
as to, and recapture, the portion of the Premises affected by such assignment or
sublease, Tenant shall have the right to consummate the assignment or sublease
at such rent as Tenant may determine, provided however, that Tenant shall pay to
Landlord fifty percent (50%) of Sublease Profits (as herein defined) on account
thereof.

        Provided that Tenant is not then in default under this Lease beyond any
applicable notice, grace or cure period, Tenant shall have the right, without
Landlord's consent, to sublease up to twenty-five percent (25%) of the r.s.f of
the Premises, in the aggregate, to subtenants, provided that no such sublease
shall be for a term greater than the lesser of (x) five (5) years (including any
extensions provided for in such sublease) and (y) the remaining term of this
Lease (including any Extension Term previously exercised), and provided further
that in such case Tenant shall pay to Landlord fifty percent (50%) of the
Sublease Profits (as herein defined) with respect to all such subleases. All
other subleases by Tenant shall require Landlord's consent.

        In the event that any assignee or subtenant pays to Tenant any amounts
in excess of the Fixed Rent, Additional Rent, and all other payments then
payable hereunder, or pro rata portion thereof on a square footage basis for any
portion of the Premises (such excess being hereinafter referred to as "Sublease
Profits"), Tenant shall promptly pay fifty percent (50%) of said Sublease
Profits to Landlord as and when received by Tenant after deduction of Tenant's
Sublease Costs (as hereinafter defined). The term "Sublease Costs" shall mean
and refer to Tenant's reasonable legal, brokerage and construction costs and
expenses incurred in good faith in view of the size and expected term of any
applicable sublease or assignment and the then unamortized costs of Tenant's
Work incurred by Tenant to prepare the Premises for Tenant's initial occupancy
of the Premises. Sublease Costs shall be amortized on a straight line basis over
the term of the applicable sublease or assignment, except that the costs of
Tenant's Work incurred by Tenant to prepare the Premises for Tenant's initial
occupancy of the Premises shall be amortized on a straight line basis over the
initial Term of this Lease.

        Notwithstanding the foregoing provisions of this Section 5.2.1, Tenant
may assign this Lease or sublet any portion of the Premises without Landlord's
consent and without payment of Sublease Profits

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to Landlord to (i) any successor of Tenant resulting from an acquisition of all
or substantially all of Tenant's assets or a merger or consolidation of Tenant
and (ii) any Affiliate of Tenant (as hereinafter defined), provided that Tenant
provides Landlord at least thirty (30) days prior notice of such assignment or
subletting pursuant to either of the foregoing clauses (i) or (ii) and the
assignee or sublessee executes an assignment and assumption agreement reasonably
satisfactory to Landlord prior to taking occupancy. From and after any sublease
or assignment, Genzyme Corporation shall continue to be primarily liable
pursuant to this Lease. As used herein, the term "Affiliate of Tenant" shall
mean and refer to any entity controlled by, controlling or under common control
with Tenant.

5.2.2    Nuisance.

        Not to injure, deface or otherwise harm the Premises; nor commit any
nuisance; nor permit the emission of any noise, vibration or odor which is
contrary to any law or ordinance; nor make, allow or suffer any waste; nor make
any use of the Premises which is improper, offensive or contrary to any law or
ordinance or which will invalidate any of Landlord's insurance; nor to serve or
allow the consumption of alcoholic beverages in the Premises unless Tenant
maintains Host Liquor liability insurance with an insurance company and with
limits of coverage satisfactory to Landlord.

5.2.3    Installation, Alterations or Additions.

        Except for Tenant's Work approved or deemed approved by Landlord
pursuant to this Lease or any Minor Alteration, not to make any installations,
alterations, or additions in, to or on the Premises nor to permit the making of
any openings in the walls, partitions, ceilings or floors of the Premises.

ARTICLE VI

CASUALTY OR TAKING

6.1   DAMAGE BY FIRE.

        In the event of loss of, or damage to, the Premises or the Building or
the Garage by fire or other casualty, the rights and obligations of the parties
hereto shall be as follows:

        (a)(i) If the Premises, or any part thereof, shall be damaged by fire or
other casualty, Tenant shall give prompt notice thereof to Landlord, and
Landlord, upon receiving such notice, shall proceed promptly and with due
diligence, subject to Force Majeure Events, to repair, or cause to be repaired,
such damage except as otherwise provided herein. With respect to portions of the
Building or Lot outside of the Premises that shall be damaged by fire or other
casualty, Landlord shall proceed promptly and with due diligence, subject to
Force Majeure Events, to repair, or to cause to be repaired, such damage after
such damage occurs except as otherwise provided herein; and (ii) if the Garage,
or any part thereof, shall be damaged by fire or other casualty and if the
Garage is then owned by Landlord or an Affiliate of Landlord (as defined in
Section 10.14 hereof) Landlord shall cause the Garage Owner to proceed promptly
and with due diligence, subject to Force Majeure Events, to repair or cause to
be repaired, such damage except as otherwise provided herein. If Landlord or an
Affiliate of Landlord is not the Garage Owner at the time of such damage by fire
or other casualty, Landlord shall use all reasonable efforts to cause the Garage
Owner to proceed promptly to repair such damage.

        (b)(i) If the Premises, or any part thereof, shall be rendered
untenantable by reason of such damage, whether to the Premises or to the
Building or if such damage materially interferes with Tenant's access to the
Premises, Annual Fixed Rent and Additional Rent shall proportionately (i.e.,
based on rentable square footage) abate for that portion of the Premises which
is untenantable for the period from the date of such damage or from the date
when material interference with Tenant's access due to such damage commences to
the date when such damage shall have been

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repaired or such access shall have been restored, as applicable; and (ii) if the
Garage or any part thereof shall be rendered untenantable by reason of such
damage or if such damage prevents Tenant's access to the Garage then to the
extent that Landlord does not provide Tenant with substitute parking spaces in
the Complex or within a reasonable walking distance of the Premises ("Substitute
Parking Spaces"), the Parking Fee (as defined in Section 10.14) and/or the Valet
Parking Fee (as defined in Section 10.14), as applicable, shall proportionately
abate (based upon the number of Tenant's Parking Spaces or Valet Parking Spaces)
for each of the Garage Parking Spaces (as defined in Section 10.14) in excess of
the Substitute Parking Spaces which are unavailable to Tenant for the period
from the date of such damage or from the date when access to the Garage ceases
due to such damage to the date when such damage shall have been repaired or such
access shall have been restored, as applicable.

        (c)(i) If, as a result of fire or other casualty, the whole or a
substantial part of the Building is rendered untenantable, Landlord, within
ninety (90) days from the date of such fire or casualty, may terminate this
Lease by notice to Tenant, specifying a date not less than twenty (20) nor more
than forty (40) days after the giving of such notice on which the Term of this
Lease shall terminate. If Landlord does not so elect to terminate this Lease,
then Landlord shall proceed with diligence to repair the damage to the Building
and Premises and all facilities serving the same, and the Annual Fixed Rent and
Additional Rent shall meanwhile proportionately abate, all as provided in
Paragraph (b)(i) of this Section 6.1. Landlord within one hundred twenty
(120) days after the fire or other casualty shall notify Tenant in writing
whether or not, in its reasonable judgment, the Building and the Premises can be
restored to substantially their condition prior to such damage and Utility
Services restored within twelve (12) months of the date of the casualty. If such
notification shall state that such restoration cannot be so accomplished, then
Tenant may terminate this Lease within thirty (30) days from Tenant's receipt of
such notification. Furthermore, if Tenant does not so terminate this Lease and
if such damage is not repaired, Utility Services are not restored and the
Premises and the remainder of the Building are not restored to substantially the
same condition as they were prior to such damage within twelve (12) months from
the date of such damage, Tenant within thirty (30) days from the expiration of
such twelve (12) month period or from the expiration of any extension thereof by
reason of Force Majeure Events (the "Casualty Restoration Completion Date"), may
terminate this Lease by notice to Landlord, specifying a date not more than
forty-five (45) days after the giving of such notice on which the term of this
Lease shall terminate. The period within which the required repairs may be
accomplished shall be extended by the number of days lost as a result of Force
Majeure Events, provided however that such period shall in no event be extended
beyond six (6) months from the Casualty Restoration Completion Date. Substantial
part for purposes of this Section 6.1(c)(i) and section 6.1(d) shall mean
thirty-three and one-third percent (331/3%) or more of the Building; and (ii) if
as a result of fire or other casualty, the whole or a substantial part of the
Garage is rendered untenantable, Landlord, within ninety (90) days from the date
of such fire or casualty, shall notify Tenant whether the Garage Owner will
repair the damage to the Garage. If the Garage Owner is unwilling to repair such
damage and Landlord does not provide substitute parking in the Complex or within
reasonable walking distance of the Premises, then Tenant may terminate this
Lease by notice to Landlord, specifying a date not less than twenty (20) nor
more than forty (40) days after the giving of such notice on which the Term of
this Lease shall terminate. "Substantial part" for this Section 6.1(c)(ii) shall
mean thirty-three and one-third percent (331/3%) or more of Tenant's Parking
Spaces.

If Tenant fails to terminate in accordance within the foregoing time periods set
forth in this Section 6.1, Tenant shall have waived its right to terminate.

        (d)   If a substantial part of the Premises shall be rendered
untenantable by fire or other casualty during the last eighteen (18) months of
the then current Term of this Lease and Tenant

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has not exercised an Option to Extend (as set forth in Section 10.12 hereof),
Landlord may terminate this Lease effective as of the date of such fire or other
casualty upon notice to Tenant given within sixty (60) days after such fire or
other casualty.

        (e)   With respect to Sections 6.1 and 6.2 hereof, Landlord shall not be
required to repair or replace any of Tenant's trade fixtures, business
machinery, equipment, cabinet work, furniture, personal property or other
installations or improvements not originally installed by Landlord or otherwise
required to be insured by Tenant under the terms of this Lease, or any damage to
the Premises or Building caused by Tenant, or any damage to the Premises or
Building not covered by insurance proceeds or condemnation proceeds, or any
damage or destruction which Landlord is unable to restore due to Landlord's
inability, after exercising reasonable and diligent efforts, to obtain final
approval therefor from applicable governmental authorities, and no damages,
compensation or claim shall be payable by Landlord for inconvenience, loss of
business or annoyance arising from any repair or restoration of any portion of
the Premises or of the Building.

        (f)    The provisions of this Section 6.1 shall be considered an express
agreement governing any instance of damage or destruction of the Building, the
Premises or the Garage by fire or other casualty, and any law now or hereafter
in force providing for such contingency in the absence of express agreement
shall have no application.

        (g)   In the event of any termination of this Lease pursuant to this
Section 6.1, the Term of this Lease shall expire as of the effective termination
date as fully and completely as if such date were the date herein originally
scheduled as the Term Expiration Date; provided that Landlord shall within
thirty (30) days thereafter refund any prepaid Rent.

        (h)   If less than fifty percent (50%) of the Building shall be rendered
untenantable by fire or other casualty and Landlord reasonably determines that
the net proceeds of insurance recovered for such damage are not adequate to
restore the Building (or Premises or Utility Service) to substantially their
condition immediate prior to the damage or Landlord's mortgagee refuses to
release to Landlord sufficient insurance proceeds to restore the Building (or
Premises or Utility Service) to such condition, Landlord shall so notify Tenant
within ninety (90) days following such fire or other casualty (the "Insurance
Shortfall Notice"). Within thirty (30) days after Tenant's receipt of an
Insurance Shortfall Notice, Tenant may elect to (i) terminate this Lease or
(ii) (x) to require Landlord to restore the Building (or Premises or Utility
Service) to substantially their condition immediately prior to the occurrence of
such fire or other casualty and (y) to pay the difference between the net
proceeds of insurance recovered and the total cost of restoration (the "Tenant
Deficiency Election"). If Tenant does not give Landlord notice of Tenant's
Deficiency Election within such thirty (30) day period, Landlord may terminate
this Lease or Landlord may elect to restore the Building, in each case pursuant
to Section 6.1(c)(i) of this Lease. For purposes of this Lease, the phrase
"restored to substantially their condition immediately prior to the occurrence
of such fire or casualty" shall mean Landlord's Base Building Improvements
without the restoration of the improvements to the Premises that constitute
Tenant's Work, in respect to which Tenant acknowledges that Tenant, and not
Landlord, bears the risk of loss in respect to such fire or other casualty.

If Tenant makes Tenant's Deficiency Election, Tenant shall promptly deposit with
Landlord's mortgagee (or another "restoration trustee" mutually acceptable to
Landlord and Tenant) the amount reasonably estimated by Landlord's architect to
fund the estimated cost of the total restoration of the Building (or Premises or
Utility Service) to substantially their condition immediately prior to the
occurrence of the fire or other casualty after application of the net proceeds
of insurance recovered (the "Reconstruction Fund"); all amounts so deposited by
Tenant into the Reconstruction Fund shall be referred to herein as "Tenant's
Restoration Funds". Tenant shall have the right to approve the construction cost
for the restoration of the Building (or

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Premises or Utility Service), which approval shall not be unreasonably withheld,
conditioned or delayed. Landlord's mortgagee (or another "restoration trustee"
mutually acceptable to Landlord and Tenant) shall advance proceeds from the
Reconstruction Fund, as needed, to prosecute the restoration as herein provided,
and any funds remaining in the Reconstruction Fund after final completion and
payment in full of all of the costs of restoration shall be repaid to Tenant. If
there is a shortfall in the funding of such restoration, Tenant shall promptly
deposit the required additional funds in the Reconstruction Fund after Tenant's
receipt of notice from Landlord or Landlord's mortgagee (or another "restoration
trustee" mutually acceptable to Landlord and Tenant) stating the amount of the
required additional funds and a description of the restoration work related
thereto. Landlord shall have no obligation to repay to Tenant any portion of the
Reconstruction Fund. During the period of such restoration, Fixed Rent and
Additional Rent shall proportionately abate as set forth in
Section 6.1(b)(i) hereof.

        (i)    Landlord's architect's certificate, given in good faith, shall be
deemed conclusive of the statements therein contained and binding upon Tenant
with respect to the extent of the damage to the Building and the performance and
completion of any repair or restoration work undertaken by Landlord pursuant to
Sections 6.1 or 6.2 hereof.

6.2   CONDEMNATION.

        In the event that the whole or any substantial part of the Building
shall be taken or appropriated by eminent domain or shall be condemned for any
public or quasi-public use, or (by virtue of any such taking, appropriation or
condemnation) shall suffer any damage (direct, indirect or consequential) for
which Landlord or Tenant shall be entitled to compensation, then (and in any
such event) this Lease and the Term hereof may be terminated at the election of
Landlord by a notice in writing of its election so to terminate which shall be
given by Landlord to Tenant within ninety (90) days following the date on which
Landlord shall have received notice of such taking, appropriation or
condemnation. In the event that a substantial part of the Premises or of the
means of access thereto or of the Garage Parking Spaces (as such term is defined
in Section 10.14 hereof) (unless replaced without undue delay by substitute
facilities within a reasonable walking distance from the Building) shall be so
taken, appropriated or condemned so as to substantially interfere with the
Permitted Uses of the Premises, then this Lease and the Term hereof may be
terminated at the election of Tenant by a notice in writing of its election so
to terminate which shall be given by Tenant to Landlord within sixty (60) days
following the date on which Tenant shall have received notice of such taking,
appropriation or condemnation. Substantial part for purposes of this Section 6.2
shall mean thirty-three and one-third percent (331/3%) or more of the Premises
or thirty-three and one-third percent (331/3%) or more of the Garage Parking
Spaces, as applicable.

        Upon giving of any such notice of termination (either by Landlord or
Tenant), this Lease and the Term hereof shall terminate as of the date on which
Tenant shall be required to vacate any part of the Premises or shall be deprived
of a substantial part of the means of access thereto. In the event of any such
termination, this Lease and the Term hereof shall expire as of the effective
termination date as fully and completely as if such date were the date herein
originally scheduled as the Term Expiration Date. If neither party elects to
terminate, Landlord will with reasonable diligence and at Landlord's expense,
restore the remainder of the Premises and Building, or the remainder of the
means of access and Garage Parking Spaces, to substantially the same condition
as practicable as existed prior to such taking, appropriation or condemnation in
which event a just proportion of the Annual Fixed Rent and Additional Rent,
according to the nature and extent of the taking, appropriation or condemnation
and the resultant injury sustained by the Premises and the means of access
thereto, shall be abated until what remains of the Premises and the means of
access thereto shall have been restored as fully as may be for permanent use and
occupancy by Tenant hereunder. In the event of any taking of the Premises or any
part thereof for temporary use, (i) this Lease shall be and remain unaffected
thereby, and

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(ii) Tenant shall be entitled to receive for itself any award made for such use,
provided, that if any taking is for a period extending beyond the Term of this
Lease, such award shall be apportioned between Landlord and Tenant as of the
Term Expiration Date.

6.3   AWARD.

        Irrespective of the form in which recovery may be had by law, all rights
to damages or compensation payable pursuant to Section 6.2 hereof shall belong
to Landlord in all cases except as set forth below in this Section 6.3 or in
Section 6.2 hereof. Tenant hereby grants to Landlord all of Tenant's rights to
such damages and compensation and covenants to deliver such further assignments
thereof as Landlord may from time to time request. It is agreed and understood,
however, that Landlord does not reserve to itself, and Tenant does not assign to
Landlord, any damages payable for (i) movable trade fixtures installed by Tenant
or anybody claiming under Tenant, at Tenant's cost and expense, (ii) relocation
expenses or damages for loss of business (in excess of any such damages
attributable to the value of this lease) and (iii) the then unamortized cost of
Tenant's Work, in each case recoverable by Tenant from such authority in a
separate action.

ARTICLE VII

DEFAULTS

7.1   EVENTS OF DEFAULT.

        (a)  If Tenant shall default in the performance of any of its
obligations to pay the Fixed Rent or Additional Rent hereunder and, in the case
of the Fixed Rent or regularly recurring items of Additional Rent, such as
monthly payments of the Annual Maintenance Charge, if such default shall
continue for five (5) days after written notice from Landlord to Tenant or, in
the case of nonrecurring items of Additional Rent, such as self-help costs
incurred by Landlord or amounts due as the result of the annual reconciliation
of Annual Maintenance Charge, if such default shall continue for twenty
(20) days after written notice from Landlord to Tenant (provided, however, that
in all cases Landlord shall not be required to provide such notice more than two
(2) times in any period of twelve (12) consecutive calendar months) or if within
30 days after written notice from Landlord to Tenant specifying any other
default or defaults Tenant has not commenced diligently to correct the default
or defaults so specified or has not thereafter diligently pursued such
correction to completion, or (b) if any assignment for the benefit of creditors
shall be made by Tenant, or by any guarantor of Tenant, or (c) if Tenant's
leasehold interest shall be taken on execution or other process of law in any
action against Tenant, or (d) if a lien or other involuntary encumbrance is
filed against Tenant's leasehold interest, and is not discharged within thirty
(30) days thereafter, or (e) if a petition is filed by Tenant or any guarantor
of Tenant for liquidation, or for reorganization or an arrangement or any other
relief under any provision of the Bankruptcy Code as then in force and effect,
or (f) if an involuntary petition under any of the provisions of said Bankruptcy
Code is filed against Tenant or any guarantor of Tenant and such involuntary
petition is not dismissed within ninety (90) days thereafter, or (g) if Tenant
fails to maintain the insurance required under Section 4.2.2.1 hereof,
(individually, an "Event of Default" and collectively, "Events of Default")
then, and in any of such cases, Landlord and the agents and servants of Landlord
lawfully may, in addition to and not in derogation of any remedies for any
preceding breach of covenant, immediately or at any time thereafter prior to
such time, if any, as Landlord has accepted a cure of such Event of Default and
without demand or notice, at Landlord's election, do any one or more of the
following: (1) give Tenant written notice stating that the Lease is terminated,
effective upon the giving of such notice or upon a date stated in such notice,
as Landlord may elect, in which event the Lease shall be irrevocably
extinguished and terminated as stated in such notice without any further action,
or (2) with or without process of law, in a lawful manner and without illegal
force, enter and repossess the Premises as of Landlord's former estate, and
expel Tenant and those claiming through or under Tenant, and remove its and
their effects, without being guilty of

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trespass, in which event the Lease shall be irrevocably extinguished and
terminated at the time of such entry, or (3) pursue any other rights or remedies
permitted by law. Any such termination of the Lease shall be without prejudice
to any remedies which might otherwise be used for arrears of rent or prior
breach of covenant, and in the event of such termination Tenant shall remain
liable under this Lease as hereinafter provided. Tenant hereby waives all
statutory rights of redemption and Landlord, without notice to Tenant, may store
Tenant's effects, and those of any person claiming through or under Tenant, at
the expense and risk of Tenant, and, if Landlord so elects, may sell such
effects at public auction or private sale and apply the net proceeds to the
payment of all sums due to Landlord from Tenant, if any, and pay over the
balance, if any, to Tenant.

7.2   REMEDIES.

        In the event that this Lease is terminated under any of the provisions
contained in Section 7.1 or shall be otherwise terminated for breach of any
obligation of Tenant, Tenant covenants to pay forthwith to Landlord, as
compensation, the excess of the total rent reserved for the residue of the Term
over the fair market rental value of the Premises for said residue of the Term.
In calculating the rent reserved there shall be included, in addition to the
Fixed Rent and Additional Rent, the value of all other considerations agreed to
be paid or performed by Tenant during said residue. Tenant further covenants (as
additional and cumulative obligations) after any such termination to pay
punctually to Landlord all the sums and to perform all the obligations which
Tenant covenants in this Lease to pay and to perform in the same manner and to
the same extent and at the same time as if this Lease had not been terminated.
In calculating the amounts to be paid by Tenant pursuant to the next preceding
sentence Tenant shall be credited with any amount paid to Landlord as
compensation as in this Section 7.2 provided and also with the net proceeds of
any rent obtained by Landlord by reletting the Premises, after deducting all of
the Landlord's reasonable expenses in connection with such reletting, including,
without limitation, all repossession costs, brokerage commissions, fees for
legal services and expenses of preparing the Premises for such reletting, it
being agreed by Tenant that Landlord may (i) relet the Premises or any part or
parts thereof, for a term or terms which may at Landlord's option be equal to or
less than or exceed the period which would otherwise have constituted the
balance of the Term and may grant such concessions and free rent as Landlord in
its reasonable judgment considers advisable or necessary to relet the same and
(ii) make such alterations, repairs and decorations in the Premises as Landlord
in its reasonable judgment considers commercially advisable or necessary to
relet the same, and no action of Landlord in accordance with the foregoing or
failure to relet or to collect rent under reletting shall operate or be
construed to release or reduce Tenant's liability as aforesaid.

        In lieu of any other damages or indemnity and in lieu of full recovery
by Landlord of all sums payable under all the foregoing provisions of this
Section 7.2, Landlord may by notice to Tenant, at any time after this Lease is
terminated under any of the provisions contained in Section 7.1 or is otherwise
terminated for breach of any obligation of Tenant and before such full recovery,
elect to recover, and Tenant shall thereupon pay, as liquidated damages, an
amount equal to the aggregate of the Fixed Rent and Additional Rent for the
twelve (12) months ended next prior to such termination, plus the amount of rent
of any kind accrued and unpaid at the time of termination and less the amount of
any recovery from Tenant by Landlord under the foregoing provisions of this
Section 7.2 up to the time of payment of such liquidated damages.

        Nothing contained in this Lease shall, however, 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 equal to the
maximum allowed by any statute or rule of law in effect at the time when, and
governing the proceedings in which, the damages are to be proved, whether the
amount be greater than, equal to, or less than the amount of the loss or damages
referred to above.

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7.3   REMEDIES CUMULATIVE.

        Any and all rights and remedies which either Landlord or Tenant may have
under this Lease, and at law and equity, shall be cumulative and shall not be
deemed inconsistent with each other, and any two or more of all such rights and
remedies may be exercised at the same time insofar as permitted by law.

7.4   LANDLORD'S RIGHT TO CURE DEFAULTS.

        Landlord may, but shall not be obligated to, cure, at any time,
following ten (10) days' prior notice to Tenant, except in cases of emergency
when no notice shall be required, any default by Tenant under this Lease; and
whenever Landlord so elects, all costs and expenses incurred by Landlord,
including reasonable attorneys' fees, in curing a default shall be paid by
Tenant to Landlord as Additional Rent within twenty (20) days after Tenant's
receipt of a written demand therefor, together with interest thereon at the rate
provided in Section 4.3 from the date of payment by Landlord to the date of
payment by Tenant.

7.5   EFFECT OF WAIVERS OF DEFAULT.

        Any consent or permission by Landlord or Tenant to any act or omission
by the other party which otherwise would be a breach of any covenant or
condition herein, or any waiver by Landlord or Tenant of the breach of any
covenant or condition herein by the other party, shall not in any way be held or
construed (unless expressly so declared) to operate so as to impair the
continuing obligation of any covenant or condition herein, or otherwise, except
as to the specific instance, operate to permit similar acts or omissions.

        The failure of Landlord or Tenant to seek redress for violation of, or
to insist upon the strict performance of, any covenant or condition of this
Lease by the other party shall not be deemed a waiver of such violation nor
prevent a subsequent act, which would have originally constituted a violation,
from having all the force and effect of an original violation. The receipt by
Landlord, or the payment by Tenant, as the case may be, of rent with knowledge
of the breach of any covenant of this Lease shall not be deemed to have been a
waiver of such breach by Landlord or Tenant, as the case may be. No consent or
waiver, express or implied, by Landlord or Tenant, as the case may be, to or of
any breach of any agreement or duty shall be construed as a waiver or consent to
or of any other breach of the same or any other agreement or duty.

7.6   NO ACCORD AND SATISFACTION.

        No acceptance by Landlord of a lesser sum than the Fixed Rent,
Additional Rent or any other charge then due shall be deemed to be other than on
account of the earliest installment of such rent or charge due, unless Landlord
elects by notice to Tenant to credit such sum against the most recent
installment due, nor shall any endorsement or statement on any check or any
letter accompanying any check or payment as rent or other charge be deemed an
accord and satisfaction, and Landlord may accept such check or payment without
prejudice to Landlord's right to recover the balance of such installment or
pursue any other remedy in this Lease provided.

ARTICLE VIII

MORTGAGES

8.1   RIGHTS OF MORTGAGE HOLDERS.

        The word "mortgage" as used herein includes mortgages, deeds of trust or
other similar instruments evidencing other voluntary liens or encumbrances, and
modifications, consolidations, extensions, renewals, replacements and
substitutes thereof. The word "holder" shall mean a mortgagee,

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and any subsequent holder or holders of a mortgage. Until the holder of a
mortgage shall enter and take possession of the Premises for the purpose of
foreclosure, such holder shall have only such rights of Landlord as are
necessary to preserve the integrity of this Lease as security. Upon entry and
taking possession of the Premises for the purpose of foreclosure, such holder
shall have all the rights of Landlord. Notwithstanding any other provision of
this Lease to the contrary, including without limitation Section 10.5, no such
holder of a mortgage shall be liable either as mortgagee or as assignee to
perform, or be liable in damages for failure to perform, any of the obligations
of Landlord unless and until such holder shall enter and take possession of the
Premises for the purpose of foreclosure or is otherwise deemed to be a
mortgagee-in-possession under applicable law, and such holder shall not in any
event be liable to perform or for failure to perform the obligations of Landlord
under Article III. Upon entry for the purpose of foreclosure, such holder shall
be liable to perform all of the obligations of Landlord (except for the
obligations under Article III), subject to and with the benefit of the
provisions of Section 10.5, provided that a discontinuance of any foreclosure
proceeding shall be deemed a conveyance under said provisions to the owner of
the equity of the Premises. No Fixed Rent, Additional Rent or any other charge
shall be paid more than 10 days prior to the due dates thereof and payments made
in violation of this provision shall (except to the extent that such payments
are actually received by a mortgagee in possession or in the process of
foreclosing its mortgage) be a nullity as against such mortgagee and Tenant
shall be liable for the amount of such payments to such mortgagee.

        The covenants and agreements contained in this Lease with respect to the
rights, powers and benefits of a holder of a mortgage (including, without
limitation, the covenants and agreements contained in this Section 8.1)
constitute a continuing offer to any person, corporation or other entity, which
by accepting a mortgage subject to this Lease, assumes the obligations herein
set forth with respect to such holder; such holder is hereby constituted a party
of this Lease as an obligee hereunder to the same extent as though its name were
written hereon as such; and such holder shall be entitled to enforce such
provisions in its own name. Tenant agrees on request of Landlord to execute and
deliver from time to time a Subordination, Non-disturbance and Attornment
Agreement ("SNDA"), substantially in the form of Exhibit D hereto or any other
reasonable agreement which may be necessary to implement the provisions of this
Section 8.1 and Section 8.2 hereof.

8.2   SUPERIORITY OF LEASE; OPTION TO SUBORDINATE.

        This Lease shall be superior to and shall not be subordinate to any
future mortgage or other voluntary lien or other encumbrance of the Lot, the
Building or the Complex; provided, however, that Landlord shall have the option
to subordinate this Lease to any such mortgage of the Lot, the Building or the
Complex provided that Landlord obtains from the holder of record of any existing
or future mortgage an SNDA substantially in the form of Exhibit D hereto or
another form of agreement with Tenant and reasonably acceptable to Tenant by the
terms of which such holder will agree (a) to recognize the rights of Tenant
under this Lease, (b) to perform Landlord's obligations hereunder arising after
the date of such holder's acquisition of title as hereinafter described,
expressly excluding, however, Landlord's obligations under Article III of this
Lease, and (c) to accept Tenant as tenant of the Premises under the terms and
conditions of this Lease in the event of acquisition of title by such holder
through foreclosure proceedings or otherwise, provided that Tenant will agree to
recognize the holder of such mortgage as Landlord in such event, which agreement
shall be made expressly to bind and inure to the benefit of the successors and
assigns of Tenant and of the holder and upon anyone purchasing said Premises at
any foreclosure sale. Tenant and Landlord agree to execute and deliver any
appropriate instruments necessary to carry out the agreements contained in this
Section 8.2. Any such mortgage to which this Lease shall be subordinate may
contain such terms, provisions and conditions as the holder deems usual or
customary.

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8.3   LEASE AMENDMENTS.

        Tenant agrees to make such changes in this Lease as may be reasonably
required by the holder of any mortgage of which the Premises are a part, or any
institution which may purchase all or a substantial part of Landlord's interest
in the Premises, provided that such changes may not increase the Fixed Rent or
other payments due hereunder or otherwise materially affect the obligations of
Tenant hereunder, and provided further that such changes do not (i) materially
interfere with Tenant's right of use and enjoyment of the Premises pursuant to
this Lease, (ii) limit, impair or delay Tenant's rights to sublease or assign
all or portion of this Lease pursuant to Section 5.2.1 hereof, (iii) limit,
impair or delay Tenant's right to obtain a reduction or abatement of rent
pursuant to Section 6.2, (iv) limit, impair or delay Tenant's right to terminate
this Lease pursuant to Section 3.2 or Section 6.2 or (v) otherwise unreasonably
limit, impair or delay Tenant's rights hereunder. Tenant's failure or refusal to
make any such changes shall not constitute an Event of Default by Tenant
pursuant to this Lease.

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ARTICLE IX

LANDLORD'S ADDITIONAL COVENANTS

9.1   AFFIRMATIVE COVENANTS.

        Landlord covenants at all times during the Term:

9.1.1    Perform Obligations.

        To perform promptly all of the obligations of Landlord set forth in this
Lease, including, without limitation, furnishing, through Landlord's employees
or independent contractors, the services required to be furnished by Landlord
pursuant to this Lease (the cost of which is to be included in the Annual
Maintenance Charge).

9.1.2    Repairs.

        Except as otherwise provided in Article VI, to make such repairs (the
cost of which is to be included in the Annual Maintenance Charge) to the
foundations, roof, exterior walls, exterior windows and waterproofing, floor
slabs, other structural columns, beams and other components, parking areas,
walks, landscaping, courtyard and any other Building Common Areas and Complex
Common Areas as may be necessary to keep them in the condition required by
Section 4.2.4 hereof. Landlord shall be responsible for the maintenance and
repair of the Utility Services systems and the components thereof serving the
Building to the extent that such systems and components are included in Base
Building Improvements.

9.1.3    Compliance with Law.

        To make all repairs, alterations, additions or replacements to the
Building, the Lot and the Complex (the appropriate costs of which are to be
included in the Annual Maintenance Charge) required by any law, ordinance or
order or regulation of any public authority including repairs, alterations,
additions or replacements to the foundations and structural elements of the
Building, except as required because of Tenant's failure to comply with the
provisions of Section 5.1.3 hereof; to keep the Building equipped with all
safety appliances so required (the costs of which are to be included in the
Annual Maintenance Charge); subject to Section 4.2.1, to pay all municipal,
county, or state taxes assessed against the Building or the Lot, or against
Landlord's personal property of any kind on or about the Building or the Lot;
and to comply with the orders and regulations of all governmental authorities
with respect to zoning, building, fire, health and other codes, regulations,
ordinances or laws applicable to the Building or the Lot, including the ADA
Requirements (as defined in Section 3.3 hereof) and any codes, regulations,
ordinances or laws relating to hazardous materials (as defined in
Section 5.1.4), subject to, and without limitation of, Tenant's obligations with
respect to such codes, regulations, ordinances or laws. The appropriate costs
incurred by Landlord in connection with the foregoing compliance obligations
shall be included in the Annual Maintenance Charge. All of the foregoing
covenants and obligations are subject to, and without limitation of, all of
Tenant's obligations under this Lease, including, without limitation, those set
forth in Sections 4.2 and 5.1.4.

9.1.4    Indemnity

        To defend, with counsel reasonably approved by Tenant, all actions
against Tenant, any partner, trustee, stockholder, officer, director, employee
or beneficiary of Tenant ("Tenant's Indemnified Parties") with respect to, and
to pay, protect, indemnify and save harmless, to the extent permitted by law,
all Tenant's Indemnified Parties from and against any and all liabilities,
losses, damages, costs, expenses (including reasonable attorneys' fees and
expenses), causes of action, suits, claims, demands or

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judgments of any nature to which any of Tenant's Indemnified Parties is subject
arising from and to the extent of any negligent or willful act, fault, omission,
or other misconduct of Landlord or its agents, contractors or employees.

9.1.5    Estoppel Certificate.

        Upon not less than fifteen (15) days' prior notice from Tenant, to
execute, acknowledge and deliver to Tenant a statement in writing certifying
that this Lease is unmodified and in full force and effect and that except as
stated therein Landlord has no knowledge of any defenses, offsets or
counterclaims against its obligations under this Lease (or, if there have been
any modifications that the Lease is in full force and effect as modified and
stating the modifications and, if there are any defenses, offsets or
counterclaims, setting them forth in reasonable detail), the dates to which the
Fixed Rent and Additional Rent and other charges have been paid and a statement
that, to the best of Landlord's knowledge, Tenant is not in default hereunder
(or if in default, the nature of such default, in reasonable detail) and such
other matters reasonably required by Tenant or any prospective assignee of
Tenant. Any such statement delivered pursuant to this Section 9.1.5 may be
relied upon by any prospective assignee.

9.1.6    Subdivision.

        The Lot is currently a portion of the Complex and Landlord may subdivide
the Complex so as to, inter alia, establish the Lot as a separate taxable parcel
and establish easements which benefit and/or burden the Lot and remaining
portions of the Complex (collectively, the "Subdivision"). Upon or after the
Subdivision, Landlord may convey the Lot and assign this Lease to an Affiliate
of Landlord (the "Transfer"). Tenant agrees to cooperate with Landlord in
connection with such Subdivision and Transfer, including without limitation, the
execution, acknowledgment and delivery of an instrument pursuant to which this
Lease shall be subordinated to easements reasonably established in connection
with the Subdivision and Transfer and such other documents as Landlord
reasonably may request so long as such Subdivision and Transfer do not
materially interfere with Tenant's use of the Premises or any of Tenant's rights
under this Lease to other portions of the Complex. After the Substantial
Completion Date, Landlord may convey the Lot and the Building and assign this
Lease to any person or entity.

ARTICLE X

MISCELLANEOUS PROVISIONS

10.1    NOTICES FROM ONE PARTY TO THE OTHER.

        All notices required or permitted hereunder shall be in writing and
addressed, if to the Tenant, at the Original Address of Tenant or such other
address as Tenant shall have last designated by notice in writing to Landlord,
with a copy to Genzyme Corporation, One Kendall Square, Building 1400,
Cambridge, Massachusetts 02139, Attention: General Counsel, and, if to Landlord,
at Landlord's Address or such other address as Landlord shall have last
designated by notice in writing to Tenant, with a copy to Patrick C. Toomey,
Esquire, Gadsby Hannah LLP, 225 Franklin Street, Boston, Massachusetts 02110.
Any notice shall be deemed duly given if mailed to such address postage prepaid,
registered or certified mail, return receipt requested, when deposited with the
U.S. Postal Service, or if delivered by a recognized courier service (e.g.
Federal Express) when deposited with such courier service, or if delivered to
such address by hand, when so delivered.

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10.2    QUIET ENJOYMENT.

        Landlord agrees that upon Tenant's paying the rent and performing and
observing the terms, covenants, conditions and provisions on its part to be
performed and observed, Tenant shall and may peaceably and quietly have, hold
and enjoy the Premises during the Term without any manner of hindrance or
molestation from Landlord or anyone claiming under Landlord, subject, however,
to the terms of this Lease.

10.3    EASEMENTS; CHANGES TO LOT LINES.

        Landlord reserves the right, from time to time, to grant easements
affecting the Building, the Lot or the Complex and to change or alter existing
boundaries of the Lot or Complex for purpose of developing and using the Lot and
the Complex so long as such easements or such changes or alterations to existing
boundaries of the Lot or the Complex do not materially interfere with Tenant's
use of the Premises or any of Tenant's rights under this Lease to other portions
of the Complex.

10.4    LEASE NOT TO BE RECORDED.

        Neither party shall record this Lease. Both parties shall execute and
deliver a notice of this Lease in such form, as may be permitted by applicable
statute. If this Lease is terminated before the Term Expiration Date the parties
shall execute, deliver and record an instrument acknowledging such fact and the
actual date of termination of this Lease, and Tenant hereby appoints Landlord
its attorney-in-fact, coupled with an interest, with full power of substitution
to execute such instrument in the event that Tenant fails to do so within five
(5) days after Landlord's request therefor.

10.5    BIND AND INURE; LIMITATION OF LANDLORD'S LIABILITY.

        The obligations of this Lease shall run with the land, and this Lease
shall be binding upon and inure to the benefit of the parties hereto and their
respective successors and assigns. No owner of the Premises shall be liable
under this Lease except for breaches of Landlord's obligations occurring while
owner of the Premises. The obligations of Landlord shall be binding upon the
assets of Landlord which comprise the Premises, Building and Lot, but not upon
other assets of Landlord. Without limiting the generality of the foregoing, upon
any assignment of this Lease by Kendall Square, LLC to an Affiliate of Landlord,
Kendall Square, LLC shall have no further liability or obligation pursuant to
this Lease. No member, partner, trustee, stockholder, officer, director,
employee or beneficiary (or the members, partners, trustees, stockholders,
officers, directors or employees of any such beneficiary) of Landlord shall be
personally liable under this Lease and Tenant shall look solely to Landlord's
interest in the Building and Lot, including insurance proceeds and eminent
domain awards and the proceeds of any sale of the Building or Lot, and any rents
and profits from the Building in pursuit of its remedies upon an event of
default hereunder, and the general assets of the members, partners, trustees,
stockholders, officers, employees or beneficiaries (and the members, partners,
trustees, stockholders, officers, directors or employees of any such
beneficiary) of Landlord shall not be subject to levy, execution or other
enforcement procedure for the satisfaction of the remedies of Tenant; provided
that the foregoing provisions of this sentence shall not constitute a waiver of
any obligation evidenced by this Lease and provided further that the foregoing
provisions of this sentence shall not limit the right of Tenant to name Landlord
or any individual partner or trustee thereof as party defendant in any action or
suit in connection with this Lease so long as no personal money judgment shall
be asked for or taken against any individual partner, trustee, stockholder,
officer, employee or beneficiary of Landlord.

10.6    ACTS OF GOD.

        In any case where either party hereto is required to do any act (other
than the payment of money), delays caused by or resulting from the occurrence of
one or more Force Majeure Events shall

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not be counted in determining the time during which work shall be completed,
whether such time be designated by a fixed date, a fixed time or a "reasonable
time", and such time shall be deemed to be extended by the period of such delay.

10.7    LANDLORD'S DEFAULT.

        Landlord shall not be deemed to be in default in the performance of any
of its obligations hereunder unless it shall fail to perform such obligations
and such failure shall continue for a period of thirty (30) days following
receipt of written notice from Tenant or such additional time as is reasonably
required to correct any such default, or such other time as may be set forth in
Section 3.2 hereof, after written notice has been given by Tenant to Landlord
specifying the nature of Landlord's alleged default. Landlord shall not be
liable in any event for incidental or consequential damages to Tenant by reason
of any default by Landlord hereunder, whether Landlord is notified that such
damages may occur. Except as expressly set forth in Section 3.2 and Section 6.2
hereof, Tenant shall have no right to terminate this Lease for any default by
Landlord hereunder and no right, for any such default, to offset or counterclaim
against any rent due hereunder.

        Notwithstanding the foregoing, if any repairs to the Premises required
by this Lease, or any maintenance, cleaning, or lighting of the common areas of
the Building or the Lot, are not performed by Landlord within thirty (30) days
after notice from Tenant (or such longer period as may be reasonably required in
the event that any such repair, maintenance, cleaning or lighting cannot be
completed within said thirty (30) day period), Tenant shall have the right to
perform such obligation of Landlord. If Tenant performs any such obligation of
Landlord, Landlord shall pay to Tenant the reasonable cost thereof within thirty
(30) days after notice from Tenant, provided, however, that in no event shall
Tenant have the right to offset or deduct the amount thereof against any payment
of rent due hereunder.

        If an emergency occurs where a repair is required to be done immediately
in order to avoid imminent danger to persons or material damage to the Premises,
Tenant shall have the right to self-help consistent with the immediately
preceding paragraph of this Section 10.7 after giving Landlord only such notice
as is reasonable under the circumstances, provided, however, that formal notice
shall be promptly given thereafter. However, the right of self-help afforded to
Tenant in this Section 10.7 shall be carefully and judiciously exercised by
Tenant, it being understood and agreed that except in the case of an emergency,
Landlord shall be given sufficient opportunity to take the action required of
Landlord to avoid such default, in order to avoid any conflict with respect to
whether self-help should have been availed of by Tenant, or with respect to the
reasonableness of the expenses incurred by Tenant.

        Subject to the foregoing provisions of this Section 10.7, Landlord
agrees to pay on demand Tenant's expenses, including reasonable attorneys' fees,
incurred by Tenant in enforcing any obligation of Landlord under this Lease or
in curing any default by Landlord.

10.8    BROKERAGE.

        Each party warrants and represents to the other party that it has had no
dealings with any broker or agent in connection with this Lease other than
Trammel Crow Company and Insignia/ESG (the "Brokers") and covenants to defend
with counsel reasonably approved by such other party, hold harmless and
indemnify such other party from and against any and all cost, expense or
liability arising from any breach of the foregoing warranty and representation.
Landlord shall pay to the Brokers the real estate commission or fee due such
Brokers with respect to the transactions contemplated herein as and when due
pursuant to separate agreement(s) between Landlord and the Brokers.

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10.9    APPLICABLE LAW AND CONSTRUCTION.

        This Lease shall be governed by and construed in accordance with the
laws of the Commonwealth of Massachusetts. If any term, covenant, condition or
provision of this Lease or the application thereof to any person or
circumstances shall be declared invalid, or unenforceable by the final ruling of
a court of competent jurisdiction having final review, the remaining terms,
covenants, conditions and provisions of this Lease and their application to
persons or circumstances shall not be affected thereby and shall continue to be
enforced and recognized as valid agreements of the parties, and in the place of
such invalid or unenforceable provision, there shall be substituted a like, but
valid and enforceable provision which comports to the findings of the aforesaid
court and most nearly accomplishes the original intention of the parties.

        There are no prior oral or written agreements between Landlord and
Tenant affecting this Lease. The Letter of Intent dated January 5, 2000 from
Tenant to Mr. David Clem of Lyme Properties, LLC shall be of no further force or
effect. This Lease may be amended, and the provisions hereof may be waived or
modified, only by instruments in writing executed by Landlord and Tenant. The
titles of the several Articles and Sections contained herein are for convenience
only and shall not be considered in construing this Lease. Unless repugnant to
the context, the words "Landlord" and "Tenant" appearing in this Lease shall be
construed to mean those named in Article I above and their successors and
assigns, and those claiming through or under them respectively. If there be more
than one tenant the obligations imposed by this Lease upon Tenant shall be joint
and several.

10.10    SUBMISSION NOT AN OFFER.

        The submission of a draft of this Lease or a summary of some or all of
its provisions does not constitute an offer to lease or demise the Premises, it
being understood and agreed that neither Landlord nor Tenant shall be legally
bound with respect to the leasing of the Premises unless and until this Lease
has been executed by both Landlord and Tenant and a fully executed copy
delivered to each of them.

10.11    EXPANSION OF PREMISES.

        (a)   On the condition that this Lease is in full force and effect as of
the commencement of the fourth Lease Year, then, effective as of the
commencement of the fourth Lease Year, Landlord hereby leases to Tenant and
Tenant hereby leases from Landlord, subject to and with the benefit of the
terms, covenants, conditions and provisions of this Lease, approximately 25,000
r.s.f. in the Building (the "First Expansion Space") in its then "AS IS"
condition but subject to Section 10.11(e) hereof, and on the condition that this
Lease is in full force and effect as of the commencement of the sixth Lease
Year, then effective as of the commencement of the sixth Lease Year, Landlord
hereby leases to Tenant and Tenant hereby leases from Landlord, subject to and
with the benefit of the terms, covenants, conditions and provisions of this
Lease, approximately 25,000 r.s.f. in the Building (the "Second Expansion
Space") in its then "AS IS" condition but subject to Section 10.11(e) hereof.
Landlord and Tenant agree that the Premises initially demised to Tenant by
Landlord pursuant to this Lease, together with the First Expansion Space and the
Second Expansion Space, will constitute all of the Rentable Square Footage in
the Building except for the Retail Space.

        (b)   On or prior to the date upon which Tenant is required to approve
the Schematic Design Documents, Landlord and Tenant shall mutually agree on the
location in the Building of the Premises initially demised to Tenant pursuant to
this Lease and the location in the Building of the First Expansion Space and the
Second Expansion Space (the "Expansion Spaces"). At such time as the parties
have agreed upon the location of the Expansion Spaces, the parties shall attach
hereto as Exhibit A-4 a plan showing such locations. The actual Rentable Square
Footage of the Expansion Spaces shall be determined pursuant to Section 2.3
hereof.

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        (c)   The Annual Fixed Rent Rate for each of the First Expansion Space
and the Second Expansion Space shall be calculated separately for each Expansion
Space and shall be (i) the Annual Fixed Rent Rate for the Premises initially
demised to Tenant plus (ii) the TI Factor (as hereinafter defined) and shall be
payable in each instance starting on the later of the date on which possession
of the First Expansion Space or the Second Expansion Space, as applicable, is
delivered to Tenant or the commencement of the Term with respect thereto as set
forth in Section 10.11(a) hereof. The "TI Factor" shall mean the product of
(1) the lesser of (A) all hard and soft costs, determined on a Rentable Square
Footage basis, incurred by Landlord for tenant improvements to the First
Expansion Space or the Second Expansion Space, as applicable, or (B) $45.00 per
r.s.f., multiplied by (2) twelve percent (12%). For example, if Landlord incurs
$45.00 per r.s.f. for tenant improvements to the First Expansion Space, the TI
Factor will be $5.40 per r.s.f. ($45.00 per r.s.f. × .12 = $5.40 per r.s.f.).
Except as set forth in Section 10.11(e) hereof, Landlord shall have no
obligation to make any tenant improvements to the Expansion Spaces for Tenant.
Notwithstanding any other provision of this Lease, Tenant shall not be required
to pay rent on either of the Expansion Spaces prior to the respective dates
determined above in this Section 10.11(c).

        (d)   Commencing as of the tenth anniversary of the Commencement Date,
the Annual Fixed Rent (including the TI Factor) for the First Expansion Space
and the Second Expansion Space shall be increased by an amount determined by
multiplying such Annual Fixed Rent by twenty-one and nine tenths percent
(21.9%), as provided in Section 4.1(b) hereof.

        (e)   Tenant improvements made to the Expansion Spaces by Landlord for
the initial tenants thereof shall be consistent with first class office space
and not overly partitioned with small or large offices and conference/training
rooms. Tenant may make alterations to the Expansion Spaces after the respective
commencement of the Term with respect thereto, but only in accordance with the
provisions of this Lease applicable to Tenant's Work, and Tenant shall occupy
the Expansion Spaces within six (6) months after the respective commencement of
the Term with respect thereto.

        (f)    The term of this Lease with respect to the Expansion Spaces shall
be coterminous with the Term Expiration Date, such that the Lease of the
Expansion Spaces will terminate as of the Term Expiration Date.

        (g)   Upon commencement of the Term with respect to the First Expansion
Space and the Second Expansion Space, as applicable, (i) the term "Premises" as
used herein shall mean the Premises initially demised to Tenant and the First
Expansion Space and Second Expansion Space, as applicable, and (ii) Tenant's
Proportionate Fraction for Building and Tenant's Proportionate Fraction for
Complex shall be recalculated as set forth in Section 2.3 hereof.

        (h)   If upon commencement of the Term with respect to the Second
Expansion Space, and so long thereafter as Genzyme Corporation, Affiliate(s) of
Tenant or subtenants of Tenant occupy all of the r.s.f. of the Building, other
than the Retail Space, (i) Tenant shall have line item approval rights, not to
be unreasonably withheld, delayed or conditioned, with respect to major
operating expense categories for the Building set forth in Exhibit B-2 hereto or
(ii) Tenant may self-manage the Building, including the Retail Space, provided,
however, that during any period of self-management, Tenant shall be obligated to
manage, maintain and repair the Building in the same condition and to the same
extent required of Landlord pursuant to Section 4.2.4 and 9.1.2 hereof and
provided further, that Landlord shall have the right to approve any and all
contracts and contractors to be retained by Tenant, such approval not to be
unreasonably withheld, delayed or conditioned.

        (i)    Notwithstanding Section 10.11(a) hereof, Tenant shall have the
option to (i) lease the First Expansion Space as of the Commencement Date or
(ii) both Expansion Spaces as of the Commencement Date (as so determined, the
"Early Occupancy Space") by giving Landlord written notice thereof on or prior
to that date which is one (1) year prior to the Scheduled Substantial Completion
Date. In such event, (a) the Annual Fixed Rent for the Early Occupancy Space
shall be

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determined on the basis of the Annual Fixed Rent Rate set forth in Section 1.1
and not pursuant to Section 10.11(c) hereof and (b) Landlord shall have no
obligation to make any tenant improvements to the Early Occupancy Space.

10.12    OPTIONS TO EXTEND.

        (a)   Tenant shall have two (2) options to extend the Term of this Lease
(the "Options to Extend") for successive periods of ten (10) years each (the
"Extension Periods"), subject to and on the terms set forth herein. Tenant may
only exercise the Options to Extend with respect to the entire Premises
(including the Expansion Spaces). If Tenant shall desire to exercise either
Option to Extend, it shall give Landlord a notice (the "Inquiry Notice") of such
desire not later than twenty-one (21) months prior to the expiration of the
Initial Term of this Lease or the preceding Extension Period, as the case may
be. Thereafter, the Fair Market Rent (as defined in Subsection (b) below) for
the applicable Extension Period shall be determined in accordance with
Subsection (e) below. After the applicable Fair Market Rent has been so
determined, Tenant may exercise each Option to Extend by giving Landlord written
notice (the "Exercise Notice") of its election to do so not later than (x) the
date by which Fair Market Rent has been determined pursuant to this
Section 10.12 or (y) eighteen (18) months prior to the expiration of the Initial
Term of this Lease, or the preceding Extension Period, as the case may be,
whichever is earlier. If Tenant fails to timely give either the Inquiry Notice
or the Exercise Notice to Landlord with respect to any Option to Extend, at the
sole election of Landlord, Tenant shall be conclusively deemed to have waived
such Option to Extend hereunder.

        (b)   For purposes of this Section 10.12, "Fair Market Rent" shall mean
the average of (1) ninety-five percent (95%) of the fair market rental value for
unfinished, shell office space in a comparable office building in the Kendall
Square, Cambridge, Massachusetts office market area (the "Relevant Market") and
(2) ninety-five percent (95%) of the fair market rental value for the Premises,
including the Expansion Spaces, and shall take into account all other relevant
factors in the Relevant Market, including the ten (10) year term of the
applicable Extension Period. In no event shall the Fair Market Rent for the
first Extension Period be less than the Annual Fixed Rent for the Premises,
including the Expansion Spaces, for the fifteenth Lease Year and in no event
shall the Fair Market Rent for the second Extension Period be less than the
Annual Fixed Rent for the Premises, including the Expansion Spaces, for the
twenty-fifth Lease Year.

        (c)   Notwithstanding any contrary provision of this Lease, each Option
to Extend and any exercise by Tenant thereof shall be void and of no force or
effect unless on the dates Tenant gives Landlord its Inquiry Notice and Exercise
Notice for each Option to Extend and on the date of commencement of each
Extension Period (i) this Lease is in full force and effect, (ii) there is no
uncured Event of Default of Tenant under this Lease, (iii) Tenant has not
assigned this Lease (or agreed to assign this Lease) or subleased (or agreed to
sublease) more than forty percent (40%) of the Rentable Floor Area of the
Premises, in either case to any person or entity other than an Affiliate of
Tenant.

        (d)   All of the terms, provisions, covenants, and conditions of this
Lease shall continue to apply during each Extension Period, except that (i) the
Annual Fixed Rent during each Extension Period (the "Extension Rent") shall be
equal to the Fair Market Rent for the Premises determined in accordance with
Subsection (b) above and the procedure set forth in Subsection (e) below and
(ii) Tenant shall not have any other Options to Extend.

        (e)   The Fair Market Rent for each Extension Period shall be determined
as follows: Within five (5) days after Tenant gives Landlord its Inquiry Notice
with respect to either Option to Extend, Landlord shall give Tenant notice of
Landlord's determination of the Fair Market Rent for the applicable Extension
Period. Such determination shall separately identify the two factors used to
calculate Fair Market Rent. Within ten (10) days after Tenant receives such
notice, Tenant shall notify Landlord of its agreement with or objection to
Landlord's determination of the Fair Market Rent. If

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Tenant shall notify Landlord of Tenant's objection to Landlord's determination
of Fair Market Rent, the Fair Market Rent shall be determined by appraisal in
the manner set forth below. If Tenant does not notify Landlord within such ten
(10) day period of Tenant's agreement with or objection to Landlord's
determination of the Fair Market Rent, then the Fair Market Rent for the
applicable Extension Period shall be deemed to be Landlord's determination of
the Fair Market Rent as set forth in the notice from Landlord described in this
subsection.

        If Tenant notifies Landlord of Tenant's objection to Landlord's
determination of Fair Market Rent under the preceding subsection, such notice
shall also set forth a request for appraisal and Tenant's appointment of a
commercial real estate broker having at least ten (10) years experience in the
commercial leasing market in the City of Cambridge, Massachusetts (an
"Appraiser"). Within five (5) days thereafter, Landlord shall by notice to
Tenant appoint a second Appraiser. In determining the Fair Market Rent, each of
the Appraisers appointed by Landlord and Tenant shall separately identify the
two separate factors used to calculate Fair Market Rent. Each Appraiser shall
determine the Fair Market Rent for the applicable Extension Period within thirty
(30) days after Landlord's appointment of the second Appraiser. On or before the
expiration of such thirty (30) day period, the two Appraisers shall confer to
compare their respective determinations of the Fair Market Rent. If the
difference between the amounts so determined by the two Appraisers is less than
or equal to ten percent (10%) of the lower of said amounts, then the final
determination of the Fair Market Rent shall be equal to the average of said
amounts. If such difference between said amounts is greater than ten percent
(10%), then the two Appraisers shall have ten (10) days thereafter to appoint a
third Appraiser (the "Third Appraiser"), who shall be instructed to determine
the Fair Market Rent for the applicable Extension Period within ten (10) days
after its appointment by selecting one of the amounts determined by the other
two Appraisers. If the two Appraisers are unable to agree upon the Third
Appraiser within such ten (10) day period, such Third Appraiser shall be
appointed by the then President of the Greater Boston Real Estate Board upon
request of either Landlord or Tenant. Each party shall bear the cost of the
Appraiser selected by such party. The cost for the Third Appraiser, if any,
shall be shared equally by Landlord and Tenant. Each Appraiser and Landlord
shall be given reasonable access to the Premises for purposes of determining
Fair Market Rent.

10.13    ARBITRATION.

        All disputes arising from or related to the performance of Landlord's
Work or the interpretation of the Design Documents shall be submitted to and
resolved in arbitration under the Construction Industry Rules of the American
Arbitration Association, before the Arbitrator (as hereinafter defined), in
Boston, Massachusetts. Any award entered by the Arbitrator shall be final and
binding upon the parties thereto. Judgment upon any award rendered by the
Arbitrator may be entered in any court having competent jurisdiction.

        Notwithstanding the foregoing, disputes with respect to whether (i) the
Schematic Design Documents are in compliance with the Preliminary Design
Concept, (ii) the Design Development Documents are in compliance with the
Schematic Design Development Documents, or (iii) the Final Design Documents are
in compliance with the Design Development Documents, shall be summarily decided
by the Arbitrator and disputes concerning the achievement of the Substantial
Completion Date shall be determined by the Arbitrator, in each case without
resort to formal arbitration under the Construction Industry Rules of the
American Arbitration Association, and the Arbitrator's decision thereon shall be
binding on the parties. Otherwise, such disputes shall be resolved in
arbitration as set forth herein.

        Arbitration proceedings under this Section 10.13 shall, upon motion of
any party, be consolidated with arbitration proceedings pending between other
parties relating to the Landlord's Work, the same transaction, the same subject
matter, and/or involving related substantive rights. All parties hereby consent
to such consolidation. In addition to the foregoing, any party to any agreement,
whose rights or

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performance is involved in an arbitration proceeding hereunder, may be joined as
a party in any arbitration proceeding instituted hereunder. Consolidation and
joinder hereunder shall be by order of the Arbitrator. If the Arbitrator shall
fail, upon motion, to make such an order, any party may apply to the Superior
Court for Middlesex County, Massachusetts for such an order. Neither party nor
the Arbitrator may disclose the existence, content or results of any arbitration
hereunder without the prior written consent of both parties. All administrative
fees and expenses of the arbitration shall be borne equally by the parties. Each
party shall bear the expense of its own counsel, experts, witnesses, and
preparation and presentation of proofs.

        There shall be a single arbitrator, who shall be experienced as an
arbitrator and who shall be either a registered engineer, architect, or general
contractor engaged in business in Massachusetts, for at least ten (10) years,
and familiar with issues generally similar to those in dispute, and who shall
not have had any dealings with either party within the five-year period
immediately preceding such dispute (the "Arbitrator"). If Landlord and Tenant
are unable to agree upon the Arbitrator within ten (10) days after submission of
a dispute to arbitration, then either Landlord or Tenant may request that the
then President of the Boston Bar Association select the Arbitrator. Each party
shall bear half the cost of the Arbitrator. The right to arbitrate shall not be
deemed to be a limitation of the rights or remedies of either party in aid of
arbitration under any and all applicable laws, unless expressly waived, by such
party hereto. All arbitration proceedings shall be conducted in Boston,
Massachusetts.

10.14    PARKING.

        Tenant shall pay monthly, in advance, as Additional Rent the then fair
market value (the "Parking Fee") (adjusted no more frequently than annually) for
each of Tenant's Parking Spaces to be leased to Tenant. In no event shall the
Parking Fee exceed the lowest monthly rate being charged to tenants of the
Complex by Landlord or any Affiliate of Landlord for parking in the Garage.
After the Commencement Date, all of Tenant's Parking Spaces leased hereby may
only be utilized by Tenant's employees, visitors, sublessees of the Premises or
assignees of the Lease, visiting or working at the Premises. All of Tenant's
Parking Spaces and Valet Parking Spaces (as hereinafter defined) shall be
located in the underground parking structure to be constructed and/or owned by
Landlord or an Affiliate of Landlord (as hereinafter defined) south of Kendall
Street, as shown on Exhibit A hereto (the "Garage"). As used herein, the term
"Affiliate of Landlord" shall mean a person or entity controlled by, controlling
or under common control with Landlord. The owner of the Garage from time to time
is herein referred to as the "Garage Owner", and the Tenant's Parking Spaces and
the Valet Parking Spaces are herein referred to collectively as the "Garage
Parking Spaces." Landlord covenants and agrees that if the Garage is conveyed by
Landlord to any other person or entity, including an Affiliate of Landlord, such
conveyance shall be subject to a lease, permanent easement or similar instrument
by and between Landlord and the Garage Owner so that the Tenant shall have,
throughout the Term, the right to use the Garage Parking Spaces, subject to the
terms of this Lease.

        Landlord shall also lease to Tenant and Tenant shall lease from Landlord
one valet parking space per 1,000 r.s.f. of the Rentable Square Footage as
determined from time to time (the "Valet Parking Spaces") at a rate per space
equal to (i) the Parking Fee plus (ii) the incremental costs associated with
valet parking services for the Garage, which incremental costs shall be
pro-rated if valet parking spaces are provided to other tenants of the Complex
(as so determined, the "Valet Parking Fee"). Tenant shall pay monthly, in
advance, as Additional Rent the Valet Parking Fee for each Valet Parking Space.
Employees of Tenant visiting the Complex from other facilities may use the
Garage, subject to availability, at the daily rate charged by the Garage Owner,
provided, however, Landlord and Tenant agree to implement a parking ticket
validation system so that employees of Tenant visiting the Complex from other
facilities of Tenant may use any unused Valet Parking Spaces. The Garage Owner
shall have the right, from time to time but not more often than every six
(6) months, to relocate, on a temporary basis as may be necessary to effect
repairs and improvements to the Garage or for other business

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reasons, parking spaces located in the Garage to another location within 1000
feet of the Lot, provided that in each instance such other location may be
lawfully used for accessory parking, and provided further that the monthly rent
to be paid by Tenant for each temporarily relocated parking space shall be an
amount equal to the fair market value thereof but in no event more than the rent
then being paid by Tenant for a parking space in the Garage. Anything herein to
the contrary notwithstanding, Landlord shall have the right to relocate all or
any number of the Garage Parking Spaces to a garage which may be constructed by
Landlord or an Affiliate of Landlord in the northerly portion of the Complex
provided that access from the Building to such other garage is substantially as
convenient as access between the Building and the Garage, whereupon provisions
of this Lease applicable to the Garage, the Garage Owner and the Garage Parking
Spaces shall apply, mutatis mutandis, to such garage, garage owner and the
Garage Parking Spaces located therein.

        Neither Landlord nor the Garage Owner shall be responsible for money,
jewelry, automobiles or other personal property lost in or stolen from the
Garage, regardless of whether such loss or theft occurs when the Garage or other
areas therein are locked or otherwise secured against entry, or liable for any
loss, injury or damage to persons using the Garage or automobiles or other
property therein, it being agreed that the use of the Garage and the Garage
Parking Spaces shall be at the sole risk of Tenant and its employees, visitors
and guests. Landlord and the Garage Owner shall have the right from time to time
to promulgate reasonable rules and regulations regarding the Garage, the Garage
Parking Spaces and the use thereof, including, but not limited to, rules and
regulations controlling the flow of traffic to and from various parking areas,
the angle and direction of parking and the like, which rules and regulations and
any additions and amendments thereto Garage Owner shall use reasonable efforts
to consistently apply to all users of the Garage. Tenant shall comply with and
cause its employees, visitors and guests to comply with all such rules and
regulations as well as all reasonable additions and amendments thereto.

        Except for emergency repairs using authorized repair services, no person
using the Garage Parking Spaces shall perform any work on any automobiles while
located in the Garage. Except in connection with an approved assignment of the
Lease or an approved subletting of all or a portion of the Premises in
accordance with the terms hereof, Tenant shall not assign or sublease any of the
Garage Parking Spaces. Landlord shall have the right to terminate this Lease
with respect to any Garage Parking Spaces that Tenant sublets or assigns in
violation of the foregoing sentence. Landlord or the Garage Owner may elect to
provide parking cards or keys to control access to the Garage. In such event,
Landlord or the Garage Owner shall provide Tenant with one card or key for each
Garage Parking Space that Tenant is leasing hereunder, provided that Landlord or
the Garage Owner shall have the right to require Tenant or its employees to
place a reasonable deposit on such access cards or keys and to pay a reasonable
fee for any lost or damaged cards or keys. Tenant, at its sole cost and expense,
may obtain extra cards and keys from Landlord or the Garage Owner if any cards
are lost, stolen or destroyed.

10.15    CONFIDENTIAL INFORMATION.

        Landlord hereby agrees that any and all knowledge, information, data,
materials, trade secrets, and other work product of a confidential nature
gained, obtained, derived, produced, generated or otherwise acquired by Landlord
with respect to Tenant's business (collectively "Confidential Information")
shall be kept confidential. Landlord shall use diligent efforts to ensure that
no Confidential Information is revealed, divulged, communicated, related, or
described to any person or entity without the written consent of Tenant, except
as may be required by applicable law.

10.16    SIGNAGE.

        Landlord shall provide a standard building directory in the office lobby
of the Building listing Tenant as a tenant of the Building. Tenant shall have
the exclusive right, at its sole cost and expense, to

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install and maintain signs on the exterior of the Building provided that:
(i) the size, location, quality, color and style of such signs shall be subject
to Landlord's approval, such approval not to be unreasonably withheld or
delayed, and (ii) such signs shall be subject to limitations of applicable law,
including, without limitation, the Cambridge Zoning Ordinance, as amended from
time to time and the PUD Permit. Tenant shall secure all permits necessary for
the installation of such signs at its sole cost and expense. Upon the expiration
or sooner termination of the Term of this Lease, Tenant shall remove such signs
and repair any damage resulting therefrom at Tenant's sole cost and expense.
Notwithstanding the foregoing, Landlord shall have the right to install, and to
allow tenants of the Retail Space to install, signage on the windows and doors
of the Retail Space and additional signage on the exterior of the Building at a
height of up to fifteen (15) feet above ground level, subject to limitations of
applicable law, including, without limitation, the Cambridge Zoning Ordinance
and the Permits and Approvals.

10.17    BUILDING B LEASE.

        Simultaneously with the execution hereof, Landlord and Tenant shall
enter into an option to lease approximately 150,000 r.s.f in a building to be
constructed by Landlord now known as Building B in the area of the Complex
approximately shown on Exhibit A hereto (the "Option to Lease") in accordance
with and subject to the terms of the Option to Lease.

10.18    RIGHT OF FIRST REFUSAL.

        Provided that at the time Tenant exercises its rights under this
Section 10.18: (i) this Lease remains in full force and effect, (ii) there is
not then outstanding an uncured Event of Default of Tenant under this Lease, and
(iii) Tenant and/or Tenant's Affiliates are occupying at least seventy-five
percent (75%) of the r.s.f of the Premises, then Tenant shall have a continuing
right of first refusal ("ROFR") to lease any office, research or laboratory
space in the Complex then owned by Landlord or Landlord's Affiliate
(collectively, the "ROFR Space"), (a) which may become available for lease after
the initial term of any lease(s) for the ROFR Space, as any of such lease(s) may
be extended or renewed pursuant to the terms of the initial lease(s) thereof or
(b) which may become available for lease upon the expiration or termination of
lease(s), including extensions and renewals thereof, entered into by Landlord
after Tenant has failed or declined to enter into a lease of such ROFR Space.
Landlord shall notify Tenant in writing (the "Availability Notice") at least ten
(10) months in advance of the expected date upon which the ROFR Space will
become available, provided however, that if ROFR Space becomes available due to
a termination of a lease for ROFR Space prior to the stated termination of a
lease for ROFR Space, Landlord's Availability Notice shall be sent to Tenant
promptly after Landlord becomes aware of the expected date of availability of
such ROFR Space. Upon receipt by Tenant of an Availability Notice, Tenant shall
have ten (10) business days within which to send to Landlord notice of the
exercise of Tenant's ROFR (the "ROFR Notice"), in which event Landlord and
Tenant shall negotiate in good faith for a period of fifteen (15) days (the
"ROFR Negotiation Period") after the date of such ROFR Notice with respect to
the terms by which Tenant would lease the ROFR Space from Landlord. If Tenant
fails or refuses to send the ROFR Notice or if Landlord and Tenant are unable to
agree on the lease terms for the ROFR Space within such fifteen (15) day period,
thereupon Landlord may, at any time during the one hundred eighty (180) day
period following the expiration of the ROFR Negotiation Period, lease all or any
portion of the ROFR Space which was the subject of the Availability Notice to
any third party on terms and conditions no more favorable to such third party
than the final terms offered by Landlord to Tenant during the ROFR Negotiation
Period. If Landlord has not leased the ROFR Space to a third party within such
180-day period, or if Landlord proposes to offer the ROFR Space for lease to a
third party on terms and conditions more favorable to such third party than the
final terms offered to Tenant during the ROFR Negotiation Period, Landlord shall
first re-offer the ROFR Space to Tenant hereunder before Landlord may offer the
ROFR Space to any third party, and Tenant shall have five (5) business days
within which to accept such offer. Any person

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dealing with ROFR Space may without further inquiry conclusively rely upon a
representation in a certificate of Landlord or Landlord's Affiliate as to
whether the provisions of this Section have been satisfied.

10.19    RETAIL TENANTS.

        Provided that Tenant or an Affiliate of Tenant is occupying at least
sixty percent (60%) of the Rentable Square Footage of the Premises, Tenant shall
have the right to approve tenant(s) of the Retail Space, which approval shall
not be unreasonably conditioned, withheld or delayed.

10.20    ACCESS

        Commencing on the Commencement Date, Tenant shall have access to the
Building twenty-four (24) hours per day, 365/366 days per year and during those
hours that the Building is not accessible to the general public, via a security
card system provided by Landlord. Tenant agrees to use and comply with any
security systems including the security card systems employed by Landlord from
time to time during the Term. Landlord may provide a manned security desk within
the lobby of the Building comparable to that of other buildings in the Complex,
it being understood by Tenant that the provision of a security desk and security
card systems are no warranty, representation or guaranty by Landlord as to the
safety or security of persons and property within the Building or the Premises.
Notwithstanding the foregoing sentence, Tenant shall be solely responsible for
the security of all persons and property within the Premises and for access to
the Premises including any security card system serving the Premises. Landlord
and Tenant agree to use good faith efforts to coordinate any security card
system from time to time implemented by Landlord for the Building and/or Complex
and any security card system implemented from time to time by Tenant for the
Premises and other premises of Tenant outside of the Complex.

10.21    COOPERATION.

        Landlord agrees that it shall, at Tenant's expense, cooperate with,
support, consult with, and provide information in its possession to Tenant in
seeking, applying for and obtaining any and all consents, permits, licenses,
certificates, waivers, special permits, approvals and the like required, or
deemed necessary or appropriate by Tenant, in connection with (a) Tenant's use
and occupancy of the Premises for the Permitted Use and/or (b) Tenant's exercise
of its rights and/or performance of its obligations under this Lease. Landlord
agrees that such cooperation shall include, without limitation, the co-signing
of applications, the providing of support and information that can reasonably be
made available by the record owner of the Premises but not by other parties;
providing letters of support or other supporting information or evidence for
submission to hearings or proceedings before any zoning, planning, land use, or
regulatory board or authority, or any license or permit-granting or permitting
office, board or authority. Notwithstanding the foregoing, Landlord shall not be
required to take any action (and Landlord may oppose any action proposed by
Tenant) if Landlord determines, in its sole discretion, that any action or
series of actions proposed by Tenant could have an adverse impact on the
Building, Lot or Complex or any of the Development Approvals, Subsequent
Approvals or any rights or obligations of Landlord thereunder or under this
Lease.

[THE REMAINDER OF THIS PAGE IS INTENTIONALLY LEFT BLANK]

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        WITNESS the execution hereof under seal as of the 28th day of August,
2000.

    LANDLORD: KENDALL SQUARE, LLC
 
 
 
 
By:
Lyme Properties LLC, a New Hampshire limited liability company, its Manager
 
 
 
 
By:
/s/  DAVID E. CLEM      

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David E. Clem, Member
 
 
TENANT:
 
GENZYME CORPORATION
 
 
 
 
By:
/s/  HENRI TERMEER      

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Henri Termeer, President and
Chief Executive Officer

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EXHIBIT A

Plan Showing Complex
(attached)

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EXHIBIT A-1

Legal Description of Lot
(to be provided by Landlord)

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

EXHIBIT A-2

Plan Showing Lot
(to be provided by Landlord)

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

EXHIBIT A-3

CONFIRMATION OF COMMENCEMENT DATE AND RENTABLE SQUARE FOOTAGE

        Reference is made to that certain Lease dated February    , 2000 (the
"Lease") by and between KENDALL SQUARE, LLC ("Landlord"), a Delaware limited
liability company, and GENZYME CORPORATION ("Tenant"), a Massachusetts
corporation, for certain space in Building D located at Cambridge Research Park,
Cambridge, Massachusetts (the "Premises").

        In accordance with the terms and provisions of the above-referenced
Lease, Landlord and Tenant hereby confirm the following as of the date hereof:

        The Commencement Date of the Lease
is                                    , 2001.

        A.    The rentable square footage of the Premises is            square
feet.

        B.    The rentable square footage of the Building is            square
feet.

        C.    The rentable square footage of the First Expansion Space
is            square feet.

        D.    The rentable square footage of the Second Expansion Space
is            square feet.

        E.    Tenant's Proportionate Fraction for Building is    %.

        F.     Tenant's Proportionate Fraction for Complex is    %.

        Agreed and Accepted as of the Commencement Date:

GENZYME CORPORATION
By:
 

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Title:
 

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Date of Execution:
 
        

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                    , 2001

KENDALL SQUARE, LLC

By:
 
 

Title:
 

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Date of Execution:
 
        

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                    , 2001

Date of Execution:
 
        

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                    , 2001

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EXHIBIT A-4

CONFIRMATION OF LOCATION OF EXPANSION SPACES

(to be agreed upon by Landlord and Tenant as provided in Section 10.11)

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EXHIBIT B

Progress Schedule

 
  ITEM

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  COMPLETION DATE

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1.   Selection of Landlord's Architect and agreement upon Preliminary Design
Concept   Completed prior to Lease execution 2.   Execution of Contract for
Landlord's Architect and selection of Landlord's Design Team, to the extent then
identified   Completed prior to Lease execution 3.   Selection of Landlord's
Contractor   Completed prior to Lease Execution 4.   Execution of Construction
Contract   July 14, 2000 5.   Plans         Preliminary Schematic Design
Documents delivered To Tenant and Landlord   July 17, 2000     Tenant's Response
to Preliminary Schematic Design Documents   July 21, 2000     Final Schematic
Design Documents and gross floor area and r.s.f. calculations delivered to
Tenant and Landlord   August 11, 2000     Planning Board Design Review Hearing  
August 1, 2000     Planning Board Design Review Approval   August 15, 2000    
Tenant's Approval of Final Schematic Design Documents   August 25, 2000    
Preliminary Project Cost Budget delivered to Tenant and Landlord   September 11,
2000     Preliminary Design Development Documents and gross floor area and
r.s.f. calculations delivered to Tenant and Landlord   October 16, 2000    
Tenant's Response to Preliminary Design Development Documents   October 20, 2000
    Final Design Development Documents and gross floor area and r.s.f.
calculations delivered to Tenant and Landlord   November 10, 2000     Tenant's
Approval of Final Design Development Documents and gross floor area and r.s.f.
calculations   November 17, 2000     Updated Preliminary Project Budget
delivered to Tenant (Proposed GMP)   December 11, 2000     Final Design
Documents delivered to Tenant and Landlord   February 19, 2001     Tenant's
Approval of Final Design Documents and gross floor area and r.s.f. calculations
  February 26, 2001     Solicitation of Bids from general contractors or
construction managers   March 2, 2001     Tenant's Approval of final GMP and
Project Budget   March 9, 2001     Building Permit Issued   March 23, 2001*    
Commencement of Construction of Base Building Improvements   March 26, 2001    
Substantial Completion of Base Building Improvements   September 1, 2002* 4.  
Environmental Remediation         Commencement of Environmental Remediation of
Lot   June 26, 2000*     File Response Action Outcome Statement for Lot pursuant
to MCP   January 1, 2002*     Indemnity Expiration Date (as defined in Release
and Indemnity Agreement)   June 1, 2002     Certification of Landlord's LSP and
Estoppel Certificates of COM/Energy (as required under Paragraphs 2(b) and 3 of
Environmental Agreement)   July 1, 2002

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*indicates Landlord Milestone Date

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EXHIBIT B-1

Project Budget Form

 
  Budget

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  Actual Project Cost

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Land & Environmental Remediation   $   $60.00 per r.s.f. Hard Costs          
Base Building           Tenant Improvement Allowance   -0-   -0-   Sitework    
      Contingency             Total Hard Costs        
Soft Costs
 
 
 
    Architecture & Engineering           Civil Engineering          
Architectural Phase I           MEPFP Engineering Phase I           Structural
Engineering Phase I           Legal           General & Administrative       -0-
  Title Insurance & Recording           Permits & Fees (including permitting
consultant)           Impact Fees           Interest on Landlord's Equity      
    Construction Insurance & Taxes           Operating Expenses           Survey
& Appraisal Fees           Contingency           Developer's Fee       not to
exceed 5% of Project Cost exclusive of this line item and the Land +
Environmental Remediation line item   Brokerage Fee       not to exceed $7.50
per r.s.f.     Total Soft Costs         Total Project Cost        

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EXHIBIT B-2

Annual Maintenance Charge, Insurance, Mitigation Expenses
and Taxes and Assessments Categories

 
  Budget for Building
Common Areas

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  Budget for Complex
Common Areas

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  $ p.s.f.

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  $ Total

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  $ p.s.f.

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  $ Total

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Cleaning:                   Daily Cleaning Service   0.71   166,850   0.00   —  
Window Cleaning   0.02   4,700   0.00   —   Trash Removal—Routine   0.09  
21,150   0.00   —   Trash Removal—Other   0.01   2,350   0.00   —  
Exterminating   0.01   2,350           Other Cleaning   0.00   —   0.00   —    
  Total Cleaning   0.84   197,400   0.00   —
Repairs & Maintenance:
 
 
 
 
 
 
 
    Maintenance Salaries   0.54   126,900   0.00   —   Elevator Service
Contracts   0.14   32,900   0.00   —   Elevator Repairs   0.03   7,050   0.00  
—   HVAC—System Contracts   0.39   91,650   0.00   —   HVAC—Extra Repairs   0.14
  32,900   0.00   —   Electrical Repairs   0.08   18,800   0.00   —   Plumbing
Repairs   0.05   11,750   0.00   —   Roofing Repairs   0.03   7,050   0.00   —  
Alarm Systems Maintenance   0.05   11,750   0.00   —   Alarm Systems Inspections
  0.02   4,700   0.00   —   Other Maintenance &   0.11   25,850   0.00   —  
Supplies (including architectural repairs, finishes, hardware, etc.)            
          Total Mechanical Systems   1.58   371,300   0.00   —
Utilities:
 
 
 
 
 
 
 
    Electricity   0.00   —   0.00   —   Gas   0.68   159,800   0.00   —   Water
& Sewer   0.16   37,600   0.00   —   Steam   0.00   —   0.00   —   Telephone  
0.00   —   0.00   —   Data   0.00   —   0.00   —   Other   0.00   —   0.00   —  
    Total Utilities net of Tenant Elec   0.84   197,400   0.00   —
Roads/Grounds/Security                   Landscaping Contracts   0.11   25,850  
0.30   393,900   Snowplowing Contracts   0.07   16,450   0.40   525,200   Other
Roads/Grounds Expenses   0.00   —   0.00   —   Skating Rink Expenses   0.00   —
  0.10   131,300   Small Boat Ramp Expenses   0.00   —   0.05   65,650  
Security Payroll   0.00   —   0.00   —   Security Contracts   0.24   56,400  
0.00   —   Total Roads/Grounds/Security   0.42   98,700   0.85   1,116,050
Administrative:
 
 
 
 
 
 
 
    Admin Salaries   0.24   56,400   0.00   —   Management Fee   0.97   227,950
  0.00   —   Monitoring Fee   0.07   16,450   0.00   —                  

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  Legal Expense   0.03   7,050   0.00   —   Office Supplies   0.04   9,400  
0.00   —   Postage & Delivery   0.01   2,350   0.00   —   Telephone Expense  
0.03   7,050   0.00   —   Office Rent   0.25   58,750   0.00   —   Other Admin
Expenses   0.01   2,350   0.00   —       Total Admin Expenses   1.65   387,750  
0.00   —
Mitigation Expenses:
 
 
 
 
 
 
 
    PTDM Fees   0.03   7,050   0.00   —   Other Mitigation Expenses   0.00   —  
0.00   —       Total Mitigation Expenses   0.03   7,050   0.00   —
Insurance:
 
 
 
 
 
 
 
    General Liability   0.11   25,850   0.05   65,650   Property Insurance  
0.18   42,300   0.05   65,650   Rental Interruption   0.02   4,700   0.00   —  
Other Insurance   0.00   —   0.00   —       Total Insurance   0.31   72,850  
0.10   131,300      
Total Expenses Before Taxes
 
5.67
 
1,332,450
 
0.95
 
1,247,350 Taxes and Assessments:                   Real Estate Taxes   4.83  
1,135,050   0.55   722,150   Other Taxes   0.00   —   0.00   —       TOTAL
EXPENSES   10.50   2,467,500   1.50   1,969,500

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EXHIBIT C

Rules and Regulations

1.The common entrances, lobbies, elevators, sidewalks, and stairways of the
Building, the Lot and the Complex shall not be encumbered or obstructed by
Tenant, Tenant's agents, servants, employees, licensees or visitors or used by
them for any purposes other than ingress or egress to and from the Building.

2.Landlord reserves the right to have Landlord's structural engineer review
Tenant's floor loads on the Building at Tenant's expense.

3.Tenant, or the employees, agents, servants, visitors or licensees of Tenant
shall not at any time place, leave or discard any rubbish, paper, articles, or
objects of any kind whatsoever outside of the Building. Bicycles shall not be
permitted in the Building unless Landlord provides for the parking thereof in
the Building.

4.Tenant shall not place objects against glass partitions or doors or windows or
adjacent to any common space which would be unsightly from the exterior of the
Building and will promptly remove the same upon notice from Landlord.

5.Tenant shall not make noises, cause disturbances, create vibrations, odors or
noxious fumes or use or operate any electric or electrical devices or other
devices that emit sound waves or that would interfere with the operation of any
device or equipment or radio or television broadcasting or reception from or
within the Building or elsewhere, or with the operation of roads or highways in
the vicinity of the Building and shall not place or install any projections,
antennae, receivers, transmitters, aerials, or similar devices inside or outside
of the Building, without the prior written approval of Landlord.

6.Tenant shall not: (a) use the Building for lodging, or for any immoral or
illegal purposes; (b) use the Building to engage in the manufacture or sale of
spirituous, fermented, intoxicating or alcoholic beverages; (c) use the Building
to engage in the manufacture or sale of, or permit the use of, any illegal
drugs.

7.No awning or other projections shall be attached to the outside walls or
windows. No curtains, blinds, shades, screens or signs, other than those, if
any, furnished by Landlord, shall be attached to, hung in, or used in connection
with any exterior window or door of the Building without the prior written
consent of Landlord, which consent shall not be unreasonably withheld,
conditioned or delayed. No sign, advertisement, object, notice or other
lettering shall be exhibited, inscribed, painted or affixed on any part of the
outside or inside of the Building if visible from outside of the Building
without the prior written consent of Landlord, which consent shall not be
unreasonably withheld, conditioned or delayed.

8.Door keys, pass cards or similar devices for doors in the Building will be
furnished by Landlord or Tenant, based upon the agreements reached between the
parties regarding Building security systems. If Tenant shall affix additional
locks on doors then Tenant shall furnish Landlord with copies of keys for pass
cards or similar devices said locks.

10.Tenant shall cooperate and participate in all reasonable security programs
affecting the Building and the Complex.

11.Tenant assumes full responsibility for protecting its space from theft,
robbery and pilferage, which includes keeping doors locked and other means of
entry to its space in the Building closed and secured.

12.The water and wash closets and other plumbing fixtures shall not be used for
any purposes other than those for which they were constructed, and no sweepings,
rubbish, rags, or other substances shall be thrown therein.

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13.Discharge of industrial sewage shall only be permitted if Tenant, at its sole
expense, shall have obtained all necessary permits and licenses therefor,
including without limitation permits from state and local authorities having
jurisdiction thereof.

14.The use of asbestos containing cement or other similar asbestos containing
adhesive material is expressly prohibited.

15.In the event of any conflict between the provisions of this Exhibit C and the
provisions of the Lease, the provisions of the Lease shall govern.

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EXHIBIT D

Form of SNDA
(attached)

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SUBORDINATION, NON-DISTURBANCE AND
ATTORNMENT AGREEMENT

        THIS SUBORDINATION, NON-DISTURBANCE AND ATTORNMENT AGREEMENT
("Agreement") is entered into this            day of                        ,
200    , between                        ("Lender"), and Genzyme Corporation, a
Massachusetts corporation ("Tenant").

R E C I T A L S:

        A.    Lender is the owner and the holder of a Promissory Note (the
"Note") dated                        , 200    , in the face amount of
$                        payable to the order of Lender. The Note is secured by
a Mortgage, Security Agreement and Fixture Filing with Assignment of Leases and
Rents (hereinafter called the "Mortgage") dated of even date with said Note,
secured by the real property described in Exhibit "A" attached hereto and by
reference made part hereof (the "Property").

        B.    Tenant is the tenant under that certain Lease
dated                        , 2000 (the "Lease"), between Tenant, as tenant,
and Kendall Square, LLC, a Delaware limited liability company, as landlord (said
landlord and its successors and assigns under the Lease hereinafter called
"Landlord"), covering all or part of the Property as set forth in the Lease (the
"Demised Premises").

        C.    Tenant and Lender desire to confirm their understanding with
respect to the Lease and the Mortgage.

        NOW, THEREFORE, in consideration of the mutual covenants and agreements
herein contained and other good valuable consideration, the receipt and
sufficiency of which are hereby acknowledged by all parties, Lender and Tenant
hereby agree and covenant as follows:

        1.    Subordination.    The Lease now is, and shall at all times and for
all purposes continue to be, subject and subordinate, in each and every respect,
to the Mortgage, with the provisions of the Mortgage (including but not limited
to the provisions of the Mortgage pertaining to the application of insurance
proceeds and condemnation awards) controlling in all respects over the
provisions of the Lease; moreover the Lease is subordinate and subject, in each
and every respect, to any and all increases, renewals, modifications,
extensions, and/or consolidations of the Mortgage, and all other loan documents
securing the Note, provided that any and all such increases, renewals,
modifications, extensions and/or consolidations shall nevertheless be subject to
the terms of this Agreement.

        2.    Non-Disturbance.    So long as Tenant is not in default (beyond
any period given Tenant to cure such default in the Lease) in the payment of
rent or additional rent or in the performance of any of the terms, covenants or
conditions of the Lease on Tenant' s part to be performed, (i) Tenant' s
possession, occupancy, use and quiet enjoyment of the Demised Premises and
Tenant's other rights and options under the Lease, or any extensions or renewals
thereof or acquisition of additional space, which may be effected in accordance
with any option therefor in the Lease, shall not be terminated or interfered
with by Lender in the exercise of any of its rights under the Mortgage, or as
may otherwise be provided for at law or in equity and (ii) Lender will not join
Tenant as a party defendant in any action or proceeding for the purpose of
terminating Tenant' s interest and estate under the Lease because of any default
under the Mortgage.

        3.    Attornment.    If any proceedings are brought for the foreclosure
of the Mortgage or if the Property is sold pursuant to a power of sale under the
Mortgage, or Lender shall succeed to the interest of Landlord under the Lease in
any manner, Tenant shall attorn and be bound to such party (whether Lender or
another party) upon any such succession in interest or foreclosure sale and
shall recognize such party as the Landlord under the Lease. Such attornment
shall be effective and self-operative without the execution of any further
instrument on the part of any of the parties hereto. Tenant agrees, however, to
execute and deliver at any time and from time to time, upon the request of
Lender or of any holder(s) of any of the indebtedness or other obligations
secured by the Mortgage or any purchaser of the Property at a foreclosure sale,
any instrument or certificate which may be necessary or appropriate (in any such
foreclosure proceeding or

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otherwise) to evidence such attornment. In the event of any such attornment,
Tenant further waives the provisions of any statute or rule of law, now or
hereafter in effect, which may give or purport to give Tenant any right or
election to terminate or otherwise adversely affect the Lease and the obligation
of Tenant thereunder as a result of any such foreclosure proceeding.

        4.    Obligations of Lender.    If Lender shall succeed to the interest
of the Landlord under the Lease, or if any purchaser acquires the Property, upon
any foreclosure of the Mortgage, Lender or such purchaser, as the case may be,
shall have the same remedies by entry, action or otherwise in the event of any
default by Tenant (beyond any period given Tenant to cure such default) in the
payment of rent or additional rent by Tenant or in the performance of any of the
terms, covenants and conditions of the Lease on Tenant's part to be performed
that the Landlord under the Lease had or would have had if Lender or such
purchaser had not succeeded to the interest of Landlord. From and after any such
attornment, Lender or such purchaser shall be bound to Tenant under all of the
terms, covenants, and conditions of the Lease, and Tenant shall, from and after
the succession to the interest of Landlord under the Lease by Lender or such
purchaser, have the same remedies against Lender or such purchaser for the
breach of any agreement contained in the Lease that Tenant might have had under
the Lease against the Landlord if Lender or such purchaser had not succeeded to
the interest of Landlord; provided further, however, that Lender or such
purchaser shall not be liable or bound to Tenant as follows:

        (a)   for any act or omission of any prior landlord (including Landlord)
provided, however, that nothing in this clause (a) shall release Lender or any
such purchaser, after such attornment, from any obligation of a prior landlord
to: (i) reconstruct or repair the Property following any fire, casualty or
condemnation which may have occurred prior to such attornment, to the extent
that insurance proceeds or condemnation awards are available and otherwise as
required under Article VI of the Lease; or (ii) perform any on-going
maintenance, repair and/or Building operation obligations of the prior landlord
under the Lease even if the need for such item of repair, maintenance or
Building operation arose prior to such attornment; and provided further, nothing
in this clause (a) shall affect or limit Tenant's express rights to terminate
the Lease under Sections 3.1.1, 3.2 and 6.1 of the Lease under the applicable
circumstances set forth in each such section; or

        (b)   for any offsets or defenses which Tenant might have against any
landlord (including Landlord); or

        (c)   for or by any rent or additional rent which Tenant has paid for
more than the current month or the next succeeding month to any prior landlord
(including Landlord) unless such rent payment is actually paid or credited to
Lender or such purchaser by the prior landlord; or

        (d)   by any amendment or modification of the Lease made without
Lender's written consent, which consent shall not be unreasonably withheld,
conditioned or delayed if Lender determines that such amendment or modification
will not materially and adversely affect the value of the Lease as collateral
security for the Note; or

        (e)   for any security deposit, rental deposit or other deposit paid by
Tenant to a prior landlord (including Landlord) unless such deposit is actually
paid over or credited to Lender or such purchaser by the prior landlord;

        (f)    by any notice of a landlord default given by Tenant to a prior
landlord (including Landlord) unless a copy thereof was also then given to
Lender in accordance with this Agreement; or

        (g)   under any indemnification provisions set forth in the lease or for
any damages Tenant may suffer as a result of any false representation set forth
in the Lease, the breach of any warranty

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set forth in the Lease, or any act of, or failure to act by any party other than
Lender or such purchaser, as applicable.

        Further, in such event any insurance proceeds or condemnation awards
relating to the Property shall be applied in accordance with the terms of the
Mortgage and not the Lease.

        The person or entity to whom Tenant attorns shall be liable to Tenant
under the Lease only to the extent of the interest of such person or entity in
the Premises, the Building and the Lot (as such terms are defined in the Lease)
and only for matters arising during such person's or entity's period of
ownership, and such liability shall terminate upon the transfer by such person
or entity of its interest in the Lease and the Property and the assumption of
such liability by the transferee.

        Lender hereby agrees that if at the time of such attornment (x) Landlord
has commenced but not substantially completed Landlord's Work and (y) Tenant has
commenced Tenant's Work, then in order to complete Landlord's Work, (i) Lender
may elect to complete Landlord's Work, (ii) Lender may elect to advance to
Tenant, in accordance with the terms of the Mortgage or the other loan documents
executed in connection therewith, the then undisbursed proceeds of Lender's loan
evidenced by the Note, in which event such loan proceeds shall be included in
Project Cost (as such term is defined in the Lease) for purposes of calculating
Annual Fixed Rent (as such term is defined in the Lease) payable by Tenant, or
(iii) if Lender does not elect to substantially complete Landlord's Work or
advance such loan proceeds, Tenant may advance funds to complete Landlord's
Work, in which event Tenant shall receive an abatement of Annual Fixed Rent,
commencing on the Rent Commencement Date, in an amount equal to the funds so
advanced from time to time by Tenant with interest thereon at the non-default
rate of interest set forth in the Note on the outstanding amount of such
advances and continuing until such abatement is exhausted. If Lender does not
elect to complete Landlord's Work or if Lender elects to complete Landlord's
Work but fails to substantially complete Landlord's Work by the Outside
Completion Date, Tenant, shall have the right to terminate the Lease in
accordance with the last paragraph of Section 3.2 of the Lease. If, however,
Lender elects to advance to Tenant the then undisbursed proceeds of Lender's
loan in accordance with clause (ii) hereof or Tenant advances funds to complete
Landlord's Work in accordance with clause (iii) hereof, Tenant shall have no
right to terminate this Lease pursuant to the last paragraph of Section 3.2 of
the Lease if Landlord's Work is not substantially complete by the Outside
Completion Date.

        5.    Rent Payment.    Tenant agrees to pay all rents directly to Lender
in accordance with the Lease immediately upon receipt of written notice of
Lender's succeeding to the Landlord's interest under the Lease or upon receipt
of written notice that Lender is exercising its rights under the Mortgage or any
other loan documents which secure the Note following a default by Landlord or
other applicable party. Tenant shall be entitled to full credit under the Lease
to the extent of all rents paid to Lender pursuant to this paragraph of this
Agreement. By its signature to and consent to this Agreement, Landlord agrees to
this paragraph and releases Tenant from any liability to Landlord to the extent
of the payment of all rents delivered to Lender under this provision.

        6.    Notice of Mortgage.    To the extent that the Lease shall entitle
the Tenant to notice of any mortgage or security agreement, this Agreement shall
constitute such notice to the Tenant with respect to the Mortgage.

        7.    Successor of Lender.    The term "Lender" as used throughout this
Agreement includes any successor, assigns or holder(s) in interest of the
indebtedness secured by the Mortgage.

        8.    Landlord Defaults.    Tenant agrees with Lender that effective as
of the date of this Agreement: (i) that Tenant shall not take any steps to
terminate the Lease for any default by Landlord or any succeeding owner of the
Property until after giving Lender written notice of such default, stating the
nature of the default and giving Lender thirty (30) days from receipt of such

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notice to effect a cure of the same, or if a cure cannot be effected within said
thirty (30) days due to the nature of the default, Lender shall have a
reasonable time to cure provided that it commences to cure within said thirty
(30) day period of time and diligently pursues such cure to completion; and
(ii) that notice to the Landlord under the Lease (oral or written) shall not
constitute notice to Lender. Notwithstanding any provisions in this Section 8 to
the contrary: (x) Tenant shall be entitled to exercise its express rights to
terminate the Lease under Section 3.1.1 and its express rights to terminate the
Lease under Section 3.2 on account of the failure of the Landlord to have
achieved any of the Landlord Milestone Dates, as the same may be extended by any
Tenant Delay (as such term is defined in the Lease), upon giving Lender the same
notice and right to cure as Tenant is required to give to Landlord pursuant to
Sections 3.1.1 and 3.2 of the Lease; and (y) with respect to Tenant's other
express rights to terminate the Lease under Section 3.2, the period of time
specified above in this Section during which Lender may diligently seek to cure
shall in no event extend beyond the Outside Completion Date.

        9.    No Abridgment.    Nothing herein contained is intended, nor shall
it be, construed to abridge or adversely affect any right or remedy of the
Landlord under the Lease in the event of any default by Tenant (beyond any
period given Tenant to cure such default) in the payment of rent or additional
rent or in the performance of any of the terms, covenants or conditions of the
Lease on Tenant's part to be performed.

        10.    No Amendment or Termination of Lease.    Lender and Tenant agree
that Tenant's interest in and obligations under the Lease shall not be
(i) altered or modified without the prior written consent of Lender, which
consent shall not be unreasonably withheld, delayed or conditioned if Lender
determines that such amendment or modification will not materially and adversely
affect the value of the Lease as collateral security for the Note or
(ii) terminated (other than in accordance with the express terms of the Lease
and this Agreement) without the prior written consent of Lender. Lender and
Tenant also agree that Tenant shall neither assign the Lease or allow it to be
assigned in any manner nor sublet the Demised Premises or any part thereof
without the prior written consent of Lender in any situation where Landlord' s
consent to any such action is required under the Lease. Lender agrees that its
consent to any such assignment or subletting shall not be unreasonably withheld,
conditioned or delayed if Lender determines that such assignment or subletting
will not materially and adversely affect the value of the Lease as collateral
security for the Note.

        11.    Interpretation.    This Agreement may not be modified orally or
in any manner other than by an agreement in writing signed by the parties hereto
or their respective successors in interest. This Agreement shall inure to the
benefit of and be binding upon the parties hereto, their successors and assigns,
and any purchaser or purchasers at foreclosure of the Property, and their
respective heirs, personal representatives, successors and assigns. This
Agreement is subject to the laws of the Commonwealth of Massachusetts.

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        IN WITNESS WHEREOF, the parties hereto have hereunto caused this
Agreement to be duly executed as of the day and year first above written.

    LENDER:
 
 
By
 

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    Name:  

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    Title:  

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TENANT:
 
 
GENZYME CORPORATION
 
 
By
 

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    Name:  

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    Title:  

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LANDLORD:

Landlord consents to this Agreement and Landlord's
obligations under Paragraph 5 hereof,
as of                        , 200    .

KENDALL SQUARE, LLC

By:   Lyme Properties LLC, a New Hampshire
limited liability company, its Manager    
By:
 

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David E. Clem, Member

 
 

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EXHIBIT A

DESCRIPTION OF PROPERTY
(to be provided)

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EXHIBIT E

Environmental Agreement
(attached)

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ENVIRONMENTAL AGREEMENT

        THIS ENVIRONMENTAL AGREEMENT, ("Agreement"), is entered into as of
the            day of                        , 2000 by and between KENDALL
SQUARE, LLC a Delaware limited liability company, having an address at 101 Main
Street, 18th Floor, Cambridge, Massachusetts 02142 ("Landlord"), and GENZYME
CORPORATION, a Massachusetts corporation having an address of One Kendall
Square, Building 1400, Cambridge, Massachusetts 02139 ("Tenant"), and is made in
conjunction with a Lease dated the date hereof (the "Lease") by and between
Landlord and Tenant, regarding the Lot, as described and defined in the Lease,
located in Cambridge, Middlesex County, Massachusetts (the Lot is hereinafter
referred to as the "Property").

        RECITALS

        A.    Landlord is the current owner of the Property, having acquired the
right, title and interest of Com/Energy Research Park Realty ("Com/Energy") in
the Property, together with certain other real property (approximately ten acres
of land, including the Property, hereinafter the "Cambridge Research Park
Site"). In connection with the acquisition of the Cambridge Research Park Site
by Landlord, Landlord entered into a Release and Indemnity Agreement and a
Remediation Agreement, both of which are by and between Com/Energy and CRP and
dated August 18, 1998 (hereinafter the "Release and Indemnity Agreement"and the
"Remediation Agreement"), which govern certain rights, responsibilities,
releases, indemnities and remediation obligations with respect to the Cambridge
Research Park Site, including the Property.

        B.    Landlord and Com/Energy have made commitments to each other
pursuant to the Release and Indemnity Agreement and the Remediation Agreement,
including commitments with respect to the Property. These commitments include,
among others, (1) the commitment by Landlord to release and indemnify Com/Energy
for certain matters relating to the environmental condition of the Cambridge
Research Park Site, including the Property, and the remediation thereof, and
(2) the commitment by Landlord to require its lessees to agree to be bound by
certain terms of the Release and Indemnity Agreement and the Remediation
Agreement.

        In consideration of the Recitals stated above and for other good and
valuable consideration, the receipt and sufficiency of which are hereby
acknowledged, and solely with respect to the Property (and no other properties),
the parties agree as follows:

        1.     Definitions. All terms not otherwise defined herein shall have
the definitions set forth in the Release and Indemnity Agreement and the
Remediation Agreement, as indicated herein.

        2.     Release and Indemnity Agreement. A copy of the Release and
Indemnity Agreement is attached hereto as Exhibit A.

        (a)    Release.    Tenant acknowledges that it is a Releasing Party as
that term is defined in the Release and Indemnity Agreement and expressly
understands and agrees that the Release and Indemnity Agreement runs with the
land, which includes the Property, and is binding upon Tenant, except as
otherwise provided herein.

        (b)    Indemnity.    The parties acknowledge that Paragraph 5 of the
Release and Indemnity Agreement provides in part that Landlord may perform
remediation and subsequent development at the Cambridge Research Park Site,
including the Property, on a phased-basis and that for each such phase, the
Indemnity Expiration Date (as that term is defined in the Release and Indemnity
Agreement) with respect to Releasing Parties (as that term is defined in the
Release and Indemnity Agreement) which are owners, successors or assigns to such
remediated phases of the Cambridge Research Park Site shall occur on the later
to occur of the RAO Date or the Foundation Date (as those terms are defined in
the Release and Indemnity Agreement), for claims made thereafter.

        Prior to the Substantial Completion Date (as such term is defined in the
Lease) Landlord will deliver to Tenant (i) the certification of Landlord's
Licensed Site Professional certifying that the RAO has been completed in
accordance with the MCP with respect to the Property and (ii) an estoppel

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certificate of COM/Energy pursuant to Paragraph 15 of the Release and Indemnity
Agreement certifying, to the best of COM/Energy's knowledge, there is no default
on the part of Landlord under the Release and Indemnity Agreement and further
stating that the Indemnity Expiration Date has occurred with respect to the
Property.

        3.     Remediation Agreement. A copy of the Remediation Agreement is
attached hereto as Exhibit B.

        The parties acknowledge that the Remediation Agreement provides in part
that: The Remediation Agreement shall be binding upon Landlord, its successors,
heirs, administrators and assigns and with respect to the remediation
obligations set forth therein, the Remediation Agreement shall run with the
land, consisting of all or any portion of the Cambridge Research Park Site,
including the Property, be binding upon any and all subsequent owners, ground
tenants, and mortgagees of the Cambridge Research Park Site, including the
Property, or any portion thereof or interest therein. The Remediation Agreement
further provides that notwithstanding the preceding sentence, that (a) Landlord
may, at its election, perform its remediation and development obligations under
the Remediation Agreement in phases and (b) with respect to any subsequent
owner, ground tenant or mortgagee of any such phase or any portion thereof, the
remediation obligation set forth in the Remediation Agreement shall not be
binding upon any such subsequent owner, ground tenant or mortgagee, provided the
obligations under the Remediation Agreement have been satisfied with respect to
such phase. Prior to the Substantial Completion Date Landlord shall deliver to
Tenant (i) the certification of Landlord's Licensed Site Professional certifying
that the RAO has been completed in accordance with the MCP with respect to the
Property and (ii) an estoppel certificate of COM/Energy pursuant to Paragraph 14
of the Remediation Agreement certifying, to the best of COM/Energy's knowledge,
there is no default on the part of Landlord under the Remediation Agreement and
further stating that COM/Energy has approved the RAO and that Landlord has
satisfied Landlord's obligations under the Remediation Agreement with respect to
the Property.

        4.     Landlord Indemnity of Tenant. Effective as of the date hereof,
Landlord agrees to defend, hold harmless and indemnify Tenant from and against
any and all claims, fees, costs, disbursements and expenses that may be imposed
upon, incurred by or asserted or awarded against Tenant that relate to or arise
from the presence, release or threatened release of, or the mitigation or
remediation of, any Hazardous Materials (as defined herein) on, at or below the
Property, including migration onto the Property from the Cambridge Research Park
Site, for which Landlord is responsible or liable pursuant to the terms and
provisions of the Remediation Agreement or the Release and Indemnity Agreement
or for which Landlord is responsible or liable pursuant to the operation of the
Massachusetts Oil and Hazardous Materials Release Prevention and Response Act,
Massachusetts General Laws Chapter 21E, as amended ("Chapter 21E"). Hazardous
Materials as used herein shall mean "hazardous materials" and "oils" as defined
in Chapter 21E and regulations adopted pursuant to said act, including, but not
limited to, the Massachusetts Contingency Plan, 310 CMR 40.0000 et seq. as
amended (the "MCP") and "hazardous substances" shall mean "hazardous substances"
as defined in the Comprehensive Environmental Response Compensation and
Liability Act of 1980, as amended, and regulations adopted pursuant to said act;
and "hazardous wastes" as defined in the Resource Conservation and Recovery Act,
as amended, the Massachusetts Hazardous Waste Management Act, Massachusetts
General Laws Chapter 21C, as amended, and regulations adopted pursuant to said
acts.

        Landlord's obligation to indemnify Tenant as set forth in this Section 4
shall not include indemnification for any claims, fees, costs, disbursements or
expenses that relate to the release or threatened release of Hazardous Materials
on, at or from the Property which release or threatened release first occurs on
or after the date hereof.

        5.     Tenant Indemnity of Landlord. Tenant, for itself and for each of
the other Transferring Parties (as hereinafter defined), jointly and severally,
agrees to defend, hold harmless and indemnify Landlord

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from and against any and all claims, fees, costs, disbursements and expenses
that may be imposed upon, incurred by or asserted or awarded against Tenant that
relate to or arise from the presence, release or threatened release of any
Hazardous Materials on, at or from the Property which release or threatened
release is due to the act, omission or neglect of Tenant.

        6.     Site Access Upon MADEP Audit of RAO. The parties acknowledge that
pursuant to Chapter 21E and the MCP, the Massachusetts Department of
Environmental Protection ("MADEP") may perform an audit of the RAO documentation
submitted to MADEP for the Property. It is the intention of the parties that in
the event that such audit occurs, Landlord shall be solely responsible for
providing response to such audit and shall be solely responsible for providing
response to any inquiries raised by MADEP in such audit and curing any
deficiencies or defects which may be revealed during such audit. Tenant hereby
agrees to cooperate with Landlord to the extent reasonably necessary to respond
to any audit by MADEP.

        7.     Exhibits. The Exhibits to this Agreement are incorporated by
reference as if fully set forth in this Agreement.

        8.     Notices. All notices and other communications given or made
pursuant hereto shall be in writing and shall be deemed to have been duly given
or made as of the date delivered or mailed if delivered personally or mailed by
registered or certified mail (postage prepaid, return receipt requested), or
sent by facsimile transmission, (confirmation received) to the parties at the
following addresses and facsimile transmission numbers (or at such other number
for a party as shall be specified by like notice), except that notices after the
giving of which there is a designated period within which to perform an act and
notices of changes of address or number shall be effective only upon receipt:

i.    if to Landlord:

Kendall Square, LLC
101 Main Street, 18th Floor
Cambridge, MA 02142
Attention: Robert L. Green
Fax No. (617) 225-2133

with copies to:

Lyme Properties LLC
16 On The Common
Post Office Box 266
Lyme, NH 03678
Attention: David E. Clem
Fax No. (603) 795-4789

Gadsby Hannah LLP
225 Franklin Street
Boston, MA 02110
Attention: Leigh A. Gilligan, Esq.
                  Patrick C. Toomey, Esq.
Fax No. (617) 345-7050

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ii. if to Tenant:

Genzyme Corporation
One Kendall Square
Building 1400
Cambridge, MA 02139
Attention: General Counsel
Fax No. (617) 374-7368

with a copy to:

Palmer & Dodge LLP
One Beacon Street
Boston, MA 02108
Attention: Thomas G. Schnorr, Esquire
Fax No. (617) 227-4420

        9.     Successors and Permitted Assigns. This Agreement shall be binding
upon and shall inure to the benefit of the parties to this Agreement and their
successors and permitted assigns; provided, however, that this Agreement may not
be assigned by Tenant without Landlord's express written consent, which shall
not be unreasonably withheld if this Agreement is to be assigned in connection
with an assignment of the Lease. Tenant shall further require that any party to
whom Tenant assigns this Agreement acknowledge its acceptance of this Agreement
(as well as said Assignee's agreement to enter into and be bound by this
Agreement) in writing to Landlord. Tenant shall further require any party to
whom Tenant subleases all or any portion of the Premises (as such term is
defined in the Lease) to enter into and be bound by this Agreement or a similar
agreement acceptable to Landlord. Tenant, its successors and assigns, and all
other parties referred to in this Paragraph 9 (specifically excluding Landlord
and its successors and assigns) shall be referred to herein as the "Transferring
Parties".

        10.   No Third Party Beneficiaries. This Agreement is for the sole
benefit of the parties hereto, and their permitted assigns and nothing herein
expressed or implied shall give or be construed to give any person or entity,
other than the parties hereto, and their permitted assigns, any legal or
equitable rights hereunder.

        11.   Amendment or Modification. This Agreement may not be amended or
modified except by an instrument in writing signed by Landlord and Tenant.

        12.   Drafting of Agreement. This Agreement is the joint product of the
parties and each provision hereof has been subject to the mutual consultation,
negotiation and agreement of those parties and shall not be construed for or
against any party hereto.

        13.   Governing Law. This Agreement shall be governed by, and construed
in accordance with, the laws of the Commonwealth of Massachusetts (without
giving effect to its choice of law principles).

        14.   Dispute Resolution. Any dispute, controversy or claim between the
parties relating to, arising out of or in connection with this Agreement (or any
subsequent agreements or amendments thereto), including as to its existence,
enforceability, validity, interpretation, performance, breach or damages,
including claims in tort, whether arising before or after the termination of
this Agreement, shall be settled only by binding arbitration pursuant to the
Commercial Arbitration Rules, as then amended and in effect, of the American
Arbitration Association (the "Rules"), subject to the following:

            i.  The arbitration shall take place in Boston, Massachusetts.

           ii.  There shall be three arbitrators, who shall be selected under
the normal procedures prescribed in the Rules, except that one such arbitrator
shall be a certified public accountant

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and one arbitrator (who shall chair the arbitration panel) shall be a member of
the American Board of Trial Advocates or the American College of Trial Lawyers.
The arbitrator so designated shall not be an employee, consultant, officer,
director or stockholder of any party hereto or any affiliate of any party to
this Agreement.

          iii.  Subject to legal privileges, each party shall be entitled to
discovery in accordance with the Federal Rules of Civil Procedure.

          iv.  At the arbitration hearing, each party may make written and oral
presentations to the arbitrator, present testimony and written evidence and
examine witnesses.

           v.  The arbitrators' decision shall be in writing, shall be binding
and final and may be entered and enforced in any court of competent
jurisdiction.

          vi.  The arbitrators shall have the authority to grant injunctive
relief and order specific performance.

         vii.  No party shall be eligible to receive, and the arbitrators shall
not have the authority to award, exemplary or punitive damages.

        viii.  The arbitrators shall have the authority to allocate the fees and
expenses of the arbitrators and the American Arbitration Association as well as
the fees and expenses of the parties based upon the arbitrators' determination
as to the merits of the parties' respective position in the arbitration. If the
arbitrators fail to make a specific determination as to fees and expenses, then
such fees and expenses of the arbitrators and the American Arbitration
Association shall be paid by the parties in equal amounts and the parties shall
each bear their own fees and expenses.

          ix.  The arbitrators shall adhere to paragraph 13. Within 15 days
after the designation of the arbitrators, the arbitrators (or chair of the
arbitration panel), Tenant and Landlord shall meet, at which time Landlord and
Tenant shall be required to set forth in writing all disputes, controversies or
claims under and a proposed ruling on each such dispute, controversy or claim.
The arbitrators (or chair of the arbitration panel) shall set a date for the
arbitration hearing to discuss each dispute, controversy or claim identified by
the Tenant and Landlord, which hearing shall commence no later than 30 days
after the submittal of written proposals pursuant to the immediately preceding
sentence. The arbitrators shall use best efforts to rule on each dispute,
controversy or claim within 30 days after the completion of the arbitration
hearing described in the immediately preceding sentence.

        15.   Counterparts. This Agreement may be executed in one or more
counterparts, and by the different parties hereto in separate counterparts, each
of which when executed shall be deemed to be an original but all of which taken
together shall constitute one and the same agreement.

        16.   Integration. This Agreement, together with Exhibits hereto, and
the documents and instruments and other agreements among the parties delivered
pursuant hereto, constitute the entire agreement and supersede all prior
agreements and undertakings, both written and oral, among Landlord and Tenant
with respect to the subject matter hereof and are not intended to confer upon
any other Person any rights or remedies hereunder, except as otherwise expressly
provided herein. Without limiting the foregoing, the parties acknowledge that
this Agreement shall survive the termination or expiration of the Lease. The
terms of this Agreement may not be terminated, modified or waived except by a
written agreement signed by Landlord and Tenant.

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        IN WITNESS WHEREOF, the Parties have caused this Agreement to be
executed under seal.

KENDALL SQUARE, LLC

By:   Lyme Properties LLC, a New Hampshire
limited liability company, its Manager    
By:
 

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David E. Clem, Member
 
 
GENZYME CORPORATION
 
 
By:
 

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Name: Henri A. Termeer
Title: President and Chief Executive Officer
 
 

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EXHIBIT E-1

List of Remediation Documents

•Draft Release Abatement Measure Plan, NAPL Stabilization, Cambridge Research
Park, 364 Third Street, Cambridge, prepared by ThermoRetec Consulting
Corporation ("ThermoRetec") and dated February, 2000;

•Draft Phase II—Comprehensive Site Assessment, Buildings C and D Area, Cambridge
Research Park, 364 Third Street, Cambridge, prepared by ThermoRetec and dated
February, 2000;

•Draft Phase III—Remedial Action Plan, Buildings C and D Area, Cambridge
Research Park, 364 Third Street, Cambridge, prepared by ThermoRetec and dated
January, 2000; and

•Environmental Response, Compensation and Liability Insurance Policy issued by
Kemper Environmental, Ltd. to Cambridge Research Park, LLC and The Lyme Timber
Company (Policy No. 4LY000169).

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QuickLinks

Exhibit 10.4

ARTICLE I REFERENCE DATA
ARTICLE II PREMISES AND TERM
ARTICLE III BASE BUILDING IMPROVEMENTS
ARTICLE IV RENT
EXHIBIT A Plan Showing Complex (attached)
EXHIBIT A-1 Legal Description of Lot (to be provided by Landlord)
EXHIBIT A-2 Plan Showing Lot (to be provided by Landlord)
EXHIBIT A-3
EXHIBIT A-4 CONFIRMATION OF LOCATION OF EXPANSION SPACES
EXHIBIT B