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 asExhibit Ahereto, 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 onExhibit Aas 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 asExhibit A-1and which plan shall
be attached hereto asExhibit 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. § 12101et 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 Ahereto.

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 inExhibit Bhereto.

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

6

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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
|            |  | 1.2
|            |  | 1.3
|ARTICLE II  |  | 12 
|            |  | 2.1
|            |  | 2.2
|            |  | 2.3
|ARTICLE III |  | 14 
|            |  | 3.1
|            |  |    
|            |  |    
|            |  |    
|            |  |    
|            |  | 3.2
|            |  |    
|            |  | 3.3
|            |  | 3.4
|            |  | 3.5
|ARTICLE IV  |  | 29 
|            |  | 4.1
|            |  | 4.2
|            |  |    
|            |  |    
|            |  |    
|            |  |    
|            |  |    
|            |  |    
|            |  |    
|            |  |    
|            |  |    
|            |  |    
|            |  | 4.3
|            |  |    

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|ARTICLE V    |  | 40 
|------------ |  | ---
|             |  | 5.1
|             |  |    
|             |  |    
|             |  |    
|             |  |    
|             |  |    
|             |  |    
|             |  |    
|             |  |    
|             |  |    
|             |  |    
|             |  |    
|             |  |    
|             |  |    
|             |  |    
|             |  |    
|             |  | 5.2
|             |  |    
|             |  |    
|             |  |    
|ARTICLE VI   |  | 47 
|             |  | 6.1
|             |  | 6.2
|             |  | 6.3
|ARTICLE VII  |  | 51 
|             |  | 7.1
|             |  | 7.2
|             |  | 7.3
|             |  | 7.4
|             |  | 7.5
|             |  | 7.6
|ARTICLE VIII |  | 53 
|             |  | 8.1
|             |  | 8.2
|             |  | 8.3
|ARTICLE IX   |  | 56 
|             |  | 9.1
|             |  |    
|             |  |    
|             |  |    
|             |  |    
|             |  |    
|             |  |    
|             |  |    

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|ARTICLE X |  | 57   
|--------- |  | -----
|          |  | 10.1 
|          |  | 10.2 
|          |  | 10.3 
|          |  | 10.4 
|          |  | 10.5 
|          |  | 10.6 
|          |  | 10.7 
|          |  | 10.8 
|          |  | 10.9 
|          |  | 10.10
|          |  | 10.11
|          |  | 10.12
|          |  | 10.13
|          |  | 10.14
|          |  | 10.15
|          |  | 10.16
|          |  | 10.17
|          |  | 10.18
|          |  | 10.19
|          |  | 10.20
|          |  | 10.21

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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.



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.



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.



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(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.



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.



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 40.0000et 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.



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. § 12101et
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".



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.



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



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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.



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.



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.



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.



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.



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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.



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:



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.



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.



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.



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
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.



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.



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.



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.



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.



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.



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.



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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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.



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.



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.



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:



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.



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.



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:



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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:



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).



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.



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.



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.



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.



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 inExhibit B-2hereto 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

63

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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 onExhibit Ahereto (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

64

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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

65

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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 onExhibit Ahereto (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

66

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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
| |  | -----------------------------
| |  |                              
| |  |                              
| |  | TENANT:                      
| |  |                              

68

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EXHIBIT APlan Showing Complex  (attached)

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EXHIBIT A-1Legal Description of Lot  (to be provided by Landlord)

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EXHIBIT A-2Plan Showing Lot  (to be provided by Landlord)

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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:                

|Title: |  | 
|------ |  | 

|Date of Execution:  |  | , 2001
|------------------- |  | ------
|KENDALL SQUARE, LLC

|By: |  | 
|--- |  | 

|Title: |  | 
|------ |  | 

|Date of Execution: |  | , 2001
|------------------ |  | ------

|Date of Execution: |  | , 2001
|------------------ |  | ------

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EXHIBIT A-4CONFIRMATION 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                                                                                                                                         |  | COMPLETION DATE                   
|-- |  | -------------------------------------------------------------------------------------------------------------------------------------------- |  | ----------------------------------
|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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EXHIBIT B-1

Project Budget Form

|                                 |                                                  | Budget           |     | Actual Project Cost
|-------------------------------- | ------------------------------------------------ | ---------------- | --- | -------------------
|Land & Environmental Remediation |                                                  | $                |     | $60.00 per r.s.f.  
|Hard Costs                       |                                                  |                  |     |                    
|                                 | Base Building                                    |                  |     |                    
|                                 | Tenant Improvement Allowance                     |                  | -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                         |                  |     |                    
|                                 | 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                                  |                  |     |                    
|                                 | Brokerage Fee                                    |                  |     |                    
|                                 |                                                  | Total Soft Costs |     |                    
|Total Project Cost               |                                                  |                  |     |                    

2

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EXHIBIT B-2

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

|                       |                                                                      | Budget for Building
Common Areas |                                    | Budget for Complex
Common Areas
|---------------------- | -------------------------------------------------------------------- | -------------------------------- | ---------------------------------- | -------------------------------
|
|Cleaning:              |                                                                      |                                  |                                    |                                
|                       | Daily Cleaning Service                                               |                                  | 0.71                               |                                
|                       | Window Cleaning                                                      |                                  | 0.02                               |                                
|                       | Trash RemovalRoutine                                                |                                  | 0.09                               |                                
|                       | Trash RemovalOther                                                  |                                  | 0.01                               |                                
|                       | Exterminating                                                        |                                  | 0.01                               |                                
|                       | Other Cleaning                                                       |                                  | 0.00                               |                                
|                       |                                                                      |                                  | Total Cleaning                     |                                
|Repairs & Maintenance: |                                                                      |                                  |                                    |                                
|                       | Maintenance Salaries                                                 |                                  | 0.54                               |                                
|                       | Elevator Service Contracts                                           |                                  | 0.14                               |                                
|                       | Elevator Repairs                                                     |                                  | 0.03                               |                                
|                       | HVACSystem Contracts                                                |                                  | 0.39                               |                                
|                       | HVACExtra Repairs                                                   |                                  | 0.14                               |                                
|                       | Electrical Repairs                                                   |                                  | 0.08                               |                                
|                       | Plumbing Repairs                                                     |                                  | 0.05                               |                                
|                       | Roofing Repairs                                                      |                                  | 0.03                               |                                
|                       | Alarm Systems Maintenance                                            |                                  | 0.05                               |                                
|                       | Alarm Systems Inspections                                            |                                  | 0.02                               |                                
|                       | Other Maintenance &                                                  |                                  | 0.11                               |                                
|                       | Supplies (including architectural repairs, finishes, hardware, etc.) |                                  |                                    |                                
|                       |                                                                      |                                  | Total Mechanical Systems           |                                
|Utilities:             |                                                                      |                                  |                                    |                                
|                       | Electricity                                                          |                                  | 0.00                               |                                
|                       | Gas                                                                  |                                  | 0.68                               |                                
|                       | Water & Sewer                                                        |                                  | 0.16                               |                                
|                       | Steam                                                                |                                  | 0.00                               |                                
|                       | Telephone                                                            |                                  | 0.00                               |                                
|                       | Data                                                                 |                                  | 0.00                               |                                
|                       | Other                                                                |                                  | 0.00                               |                                
|                       |                                                                      |                                  | Total Utilities net of Tenant Elec |                                
|Roads/Grounds/Security |                                                                      |                                  |                                    |                                
|                       | Landscaping Contracts                                                |                                  | 0.11                               |                                
|                       | Snowplowing Contracts                                                |                                  | 0.07                               |                                
|                       | Other Roads/Grounds Expenses                                         |                                  | 0.00                               |                                
|                       | Skating Rink Expenses                                                |                                  | 0.00                               |                                
|                       | Small Boat Ramp Expenses                                             |                                  | 0.00                               |                                
|                       | Security Payroll                                                     |                                  | 0.00                               |                                
|                       | Security Contracts                                                   |                                  | 0.24                               |                                
|                       | Total Roads/Grounds/Security                                         |                                  | 0.42                               |                                
|Administrative:        |                                                                      |                                  |                                    |                                
|                       | Admin Salaries                                                       |                                  | 0.24                               |                                
|                       | Management Fee                                                       |                                  | 0.97                               |                                
|                       | Monitoring Fee                                                       |                                  | 0.07                               |                                
|                       |                                                                      |                                  |                                    |                                

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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   
|                       |                           |  | Total Expenses Before Taxes |  | 5.67      |  | 1,332,450 |  | 0.95   
|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   

2

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EXHIBIT C

Rules and Regulations

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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 inExhibit "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:



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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                 
| |  | Name:              
| |  | Title:             
| |  | TENANT:            
| |  | GENZYME CORPORATION
| |  | By                 
| |  | Name:              
| |  | Title:             

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: |  | 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.



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, anyHazardous 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 Materialsas 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 40.0000et
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 anyHazardous Materialson, 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:



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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:



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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:                 |  | David E. Clem, Member                                                       |  | 
|GENZYME CORPORATION |  |                                                                            
|By:                 |  | Name: Henri A. Termeer
Title: President and Chief Executive Officer         |  | 

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EXHIBIT E-1

List of Remediation Documents



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