<PAGE>   1


                                                                    Exhibit 10.1







                                      LEASE

                                 BY AND BETWEEN

                         270 ALBANY STREET REALTY TRUST,

                                    LANDLORD,

                                       AND

                        MILLENNIUM PHARMACEUTICALS, INC.,

                                     TENANT


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                                    ARTICLE I

                                 REFERENCE DATA

1.1     SUBJECTS REFERRED TO.

APPROXIMATE TERM:          Fifteen (15) full years from the Term Commencement 
                           Date.

BUILDING:                  The entire Building at the Premises known and 
                           numbered as 270 Albany Street, Cambridge,
                           Massachusetts, containing approximately 73,347 r.s.f.
                           as shown in Exhibit A-1 attached hereto

BUILDING ADDRESS:          270 Albany Street
                           Cambridge, Massachusetts

BUILDING FLOOR AREA:       73,347 rentable square feet

ANNUAL FIXED RENT RATE:    Commencing on the Term Commencement Date and 
                           continuing until the Phase II Substantial Completion
                           Date, $35.62 per rentable square foot, and after the
                           Phase II Substantial Completion Date, $38.75 per
                           rentable square foot, subject to adjustment as set
                           forth in Section 3.1(b) and Section 4.1(b) hereof.

INITIAL ESTIMATED
ANNUAL ADDITIONAL RENT     $5.50 p.r.s.f.

LANDLORD:                  David E. Clem and David M. Roby, Trustees, 270 Albany
                           Street Realty Trust, u/d/t dated June 18, 1997
                           recorded with the Middlesex South District Registry
                           of Deeds in Book 27406, Page 83

LANDLORD'S ARCHITECT:      DTS Shaw Associates
                           153 Milk Street
                           Boston, MA 02109

LANDLORD'S & MANAGING
AGENT'S ADDRESS:           McNeil Management, Inc.
                           320 Norwood Park South
                           Norwood, MA 02062

LANDLORD'S REPRESENTATIVE: David Clem

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, except that the first Lease Year shall
                           also include the period from the Commencement Date
                           until the first day of the following month in the
                           event that




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                           the Commencement Date does not occur on the first day
                           of a calendar month.

LOT:                       The land shown on EXHIBIT A-l and more particularly 
                           described on EXHIBIT A-2 attached hereto.

MANAGING AGENT:            McNeil Management, Inc.

OPTIONS TO EXTEND:         Two (2) terms of five (5) years each

PERMITTED USES:            General office, research and development, laboratory
                           and light manufacturing.

PREMISES:                  Approximately 73,347 r.s.f. of space in the Building,
                           as shown on EXHIBIT A.

PUBLIC LIABILITY
INSURANCE LIMITS:          Bodily Injury: $5,000,000
                           Property Damage: $5,000,000

SCHEDULED SUBSTANTIAL
COMPLETION DATE:           September 1, 1998

SCHEDULED
PHASE II SUBSTANTIAL
COMPLETION DATE:           September 1, 1999

SCHEDULED TERM
COMMENCEMENT DATE:         September 1, 1998

SECURITY DEPOSIT:          $3,150,000 subject to the provisions of Section 10.11
                           hereto

TENANT:                    Millennium Pharmaceuticals, Inc.

TENANT'S ADDRESS           238 Main Street
(For Notice and Billing):  Cambridge, MA 02139
                           Attention: Janet Bush, Vice President of Finance

TENANT ALLOWANCE:          $5,000,000.00 for the Phase I Leasehold Improvements 
                           and $1,000,000.00 for the Phase II Leasehold
                           Improvements, subject in each case to the provisions
                           of Section 3.1 hereof.

TENANT'S ARCHITECT         To be selected by Tenant subject to Landlord's 
                           approval, which approval shall not be unreasonably
                           withheld

TENANT'S PROPORTIONATE
FRACTION:                  100% of the Building in which the Premises is 
                           situated and the ratio of the total area of the
                           Building to the total area of the buildings on the
                           Lot is currently 98.4%.



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TENANT'S REPRESENTATIVE:   Janet Bush, Vice President of Finance

TERM EXPIRATION DATE:      Fifteen (15) years after the Commencement Date


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 the Premises
        EXHIBIT A-l.   Plan showing the Lot
        EXHIBIT A-2.   Legal Description of Lot
        EXHIBIT B.     Base Building Improvements
        EXHIBIT C.     Rules and Regulations
        EXHIBIT D.     Description Of Phase I Plans
        EXHIBIT E.     Plan Submission and Construction Schedule
        EXHIBIT F.     INTENTIONALLY OMITTED
        EXHIBIT G.     Refer to Exhibit B
        EXHIBIT H.     Schedule of Floor Load Limits
        EXHIBIT I.     Landlord's Services


1.3     TABLE OF CONTENTS

                                                                           Page
                                                                           ----

ARTICLE I - REFERENCE DATA .................................................. 1

     Section 1.1       Subjects Referred To ................................. 1
     Section 1.2       Exhibits.............................................. 3
     Section 1.3       Table of Contents..................................... 3

ARTICLE II - PREMISES AND TERM .............................................. 5

     Section 2.1       Premises ............................................. 5
     Section 2.2       Term ................................................. 6

ARTICLE III - IMPROVEMENTS .................................................. 6

     Section 3.1       Initial Construction ................................. 6
     Section 3.2       Preparation of Premises for Occupancy................. 8
     Section 3.3       General Provisions Applicable to Construction ........ 9
     Section 3.4       Representatives ......................................10

ARTICLE IV - RENT............................................................11

     Section 4.1       The Fixed Rent .......................................11
     Section 4.2       Additional Rent ......................................11
            4.2.1      Real Estate Taxes ....................................12
            4.2.2      Insurance ............................................13
            4.2.2.1    Insurance Taken Out by Tenant ........................13
            4.2.2.2    Insurance Taken Out by Landlord ......................13
            4.2.2.3    Tenant Reimbursement of Insurance Taken Out by 
                        Landlord ............................................13
            4.2.2.4    Certain Requirements Applicable to Insurance 
                        Policies ............................................14
            4.2.2.5    Waiver of Subrogation ................................14


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            4.2.3      Utilities ............................................15
            4.2.4      Common Area Maintenance and Expenses..................15
            4.2.5      Payments on Account of Taxes, Insurance and 
                        Utilities ...........................................17
     Section 4.3       Late Payment of Rent .................................18

ARTICLE V - TENANT'S ADDITIONAL COVENANTS ...................................18

     Section 5.1       Affirmative Covenants ................................18
            5.1.1      Perform Obligations ..................................18
            5.1.2      Occupancy and Use ....................................19
            5.1.3      Repair and Maintenance ...............................19
            5.1.4      Compliance with Law ..................................20
            5.1.5      Tenant's Work ........................................22
            5.1.6      Indemnity ............................................22
            5.1.7      Landlord's Right to Enter ............................22
            5.1.8      Personal Property at Tenant's Risk ...................23
            5.1.9      Payment of Landlord's Cost of Enforcement ............23
            5.1.10     Yield Up .............................................23
            5.1.11     Estoppel Certificate .................................24
            5.1.12     Landlord's Expenses Re: Consents .....................24
            5.1.13     Rules and Regulations ................................24
            5.1.14     Loading ..............................................24
            5.1.15     Holdover .............................................24

     Section 5.2       Negative Covenants ...................................25
            5.2.1      Assignment and Subletting ............................25
            5.2.2      Nuisance .............................................26
            5.2.3      Installation, Alterations or Additions................26

ARTICLE VI - CASUALTY OR TAKING .............................................26

     Section 6.1       Termination ..........................................26
     Section 6.2       Restoration ..........................................27
     Section 6.3       Award ................................................27

ARTICLE VII - DEFAULTS ......................................................27

     Section 7.1       Events of Default ....................................27
     Section 7.2       Remedies .............................................28
     Section 7.3       Remedies Cumulative ..................................29
     Section 7.4       Landlord's Right to Cure Defaults ....................29
     Section 7.5       Effect of Waivers of Default .........................29
     Section 7.6       No Accord and Satisfaction ...........................29

ARTICLE VIII - MORTGAGES ....................................................30

     Section 8.1       Rights of Mortgage Holders ...........................30
     Section 8.2       Subordination     ....................................30
     Section 8.3       Lease Amendments .....................................31

ARTICLE IX - LANDLORD'S ADDITIONAL COVENANTS ................................31

     Section 9.1       Affirmative Covenants ................................31
     Section 9.1.1     Perform Obligations ..................................31


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     Section 9.1.2     Repairs...............................................31
     Section 9.1.3     Compliance with Law ..................................32
     Section 9.1.4     Indemnity.............................................32
     Section 9.1.5     Estoppel Certificate .................................32
     Section 9.1.6     Landlord's Title......................................33
     Section 9.1.7     Utilities.............................................33
     Section 9.1.8     Payment of Tenant's Cost of Enforcement ..............33

ARTICLE X - MISCELLANEOUS PROVISIONS ........................................33

     Section 10.1      Notices from One Party to the Other ..................33
     Section 10.2      Quiet Enjoyment.......................................33
     Section 10.3      Easements; Changes to Lot Lines ......................33
     Section 10.4      Leases Not To Be Recorded ............................34
     Section 10.5      Bind and Inure; Limitation of Landlord's 
                        Liability ...........................................34
     Section 10.6      Acts of God ..........................................34
     Section 10.7      Landlord's Default ...................................34
     Section 10.8      Brokerage ............................................35
     Section 10.9      Applicable Law and Construction ......................35
     Section 10.10     Submission Not an Offer ..............................36
     Section 10.11     Security Deposit .....................................36
     Section 10.12     Options to Extend.....................................36
     Section 10.13     Confidential Information .............................38
     Section 10.14     Parking ..............................................38
     Section 10.15     Signage ..............................................38
     Section 10.16     Access ...............................................38



                                   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 entitled
thereto (i) the common facilities on the Lot, (ii) the building service fixtures
and equipment serving the Premises, and (iii) the right to lease seventy-five
(75) parking spaces ("Tenant's Parking Spaces") at the garage at 47 Erie Street,
Cambridge, Massachusetts, upon the terms and conditions set forth in Section
10.14 hereof.

        Landlord reserves the right from time to time, without material
interference with Tenant's use, (a) to install, repair, replace, use, maintain
and relocate for service to the Premises , building service fixtures and
equipment wherever located in the Building, 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);
and (b) to alter or relocate any common facilities, provided that in all events
(1) substitutions are in compliance with applicable zoning laws, and (2)
substitutions are substantially equivalent. 


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2.2     TERM.

        To have and to hold for a period (the "Term") commencing on the earlier
of (a) the date which is the later of the Scheduled Term Commencement Date or
the Phase I Substantial Completion Date and (b) the date on which Tenant
occupies all or any part of the Premises for the Permitted Uses (whichever of
said dates is appropriate being hereafter referred to as the "Commencement
Date"), and continuing until the Term Expiration Date, unless sooner terminated
as provided in Section 3.2 or in Article VI or Article VII. Tenant shall have
the right to access the Premises prior to the Commencement Date for purposes of
installing equipment and furnishings in accordance with and subject to the
provisions of Section 3.2.

                                   ARTICLE III

                                  IMPROVEMENTS

3.1     INITIAL CONSTRUCTION.

        (a) PLANS. Landlord and Tenant have developed and approved construction
drawings and specifications specified in Exhibit D hereto (the "Phase I Complete
Plans") showing all work to be performed by Landlord for the amount specified as
the Tenant Allowance for Phase I Leasehold Improvements, except for installation
of furnishings and the installation of telephone and data outlets (which must be
performed by a qualified installer at the Tenant's direction and expense).
Landlord and Tenant shall proceed to develop and approve construction drawings
and specifications for the Phase II Leasehold Improvements (as hereinafter
defined) for the Premises (the "Phase II Complete Plans") in accordance with the
procedure set forth in Exhibit E attached hereto.

        Landlord and Tenant shall initial the Phase II Complete Plans after the
same have been approved by Landlord and Tenant in accordance with said Exhibit
E. Tenant's interior furnishings, i.e., specification, coordination, supply and
installation of furniture, furnishings, telephones and movable equipment, will
be the responsibility of Tenant. Tenant's installation of furnishings shall be
coordinated with any work being performed by Landlord in such manner as to
maintain harmonious labor relations during the performance of the Phase I
Leasehold Improvements and the Phase II Leasehold Improvements, respectively,
and not to damage the Building or Lot or interfere with Building or Lot
operations. Except for installation of furnishings and the installation of
telephone and data outlets (which must be performed by a qualified installer at
the Tenant's direction and expense) all work described in the Phase I Complete
Plans and the Phase II Complete Plans (the "Phase I Leasehold Improvements" and
the "Phase II Leasehold Improvements," as applicable, and collectively, the
"Leasehold Improvements") shall be performed by Siena Construction or another
contractor designated by Landlord and reasonably approved by Tenant ("Landlord's
Contractor"). Except as set forth in Sections 3.3 and 5.1.10 hereof, all
Leasehold Improvements shall become a part of the Premises and shall be
considered to be the property of the Landlord. Notwithstanding the foregoing, at
the expiration or earlier termination of this Lease, Tenant shall be permitted
to remove all removable equipment paid for by Tenant and installed by Tenant at
Tenant's sole cost and expense.

        (b) PHASE I CHANGE ORDER COSTS AND PHASE II LEASEHOLD IMPROVEMENTS
COSTS. Landlord hereby agrees to furnish Tenant with a copy of the contract for
the Phase II Leasehold Improvements for the Premises, by and between Landlord
and Landlord's Contractor, within ten (10) days after execution thereof. On or
before fifteen (15) days after Landlord and Tenant initial the Phase II Complete
Plans, Landlord shall give Tenant a notice (the "Proposed GMP Notice") setting
forth the guaranteed maximum price ("GMP") of Landlord's Contractor and
estimated cost of the work for the Phase II Leasehold Improvements, inclusive of
Landlord's Contractor's 



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<PAGE>   8

Fee and architectural and engineering fees, including fees incurred for Tenant's
Architect (the "Estimated Cost of the Work"). Tenant shall thereafter have the
right to approve or reject such proposed GMP by notice given to Landlord. In the
event the Tenant rejects the GMP the Tenant and the Landlord shall equally share
all costs for work of the Architect in order to make such changes to the Phase
II Complete Plans as shall be required to produce a revised GMP acceptable to
Tenant. Landlord shall neither commence, nor be required to commence, any Phase
II Leasehold Improvements until the parties have agreed upon the GMP. In the
event that Landlord and Tenant have not agreed upon the GMP for the Phase II
Leasehold Improvements on or before the date which is thirty (30) days after the
Proposed GMP Notice and Tenant does not agree in writing to compensate Landlord
for the delay in constructing the Phase II Leasehold Improvements as set forth
in this paragraph, Landlord shall have the right to withdraw the Tenant
Allowance for the Phase II Leasehold Improvements upon notice to Tenant.

        If Tenant requests any change order for the Leasehold Improvements,
Landlord shall submit all such change orders with pricing to Tenant for its
review and approval. No change order for the Leasehold Improvements requested by
Tenant shall be effective unless approved by Tenant in writing, such approval
not to be unreasonably withheld or delayed. Notwithstanding the foregoing,
Tenant's review and approval shall not be required for change orders for the
Base Building Improvements (as defined in Exhibit G hereof) and such change
orders will not materially change the Base Building Improvement defined in
Exhibit G. If prior to the Commencement Date Tenant requests and approves any
change order for Phase I Leasehold Improvements and as a result thereof the cost
of the Phase I Leasehold Improvements will exceed the Tenant Allowance for Phase
I Leasehold Improvements specified herein (the "Excess Phase I Costs"), Tenant
shall elect in writing at the time of approval of any such change order to have
the Excess Phase I Costs paid from the remaining balance, if any, of the Tenant
Allowance for Phase II Leasehold Improvements or to pay the Excess Phase I Costs
in the same manner and at the same times as the TIR (as hereinafter defined). If
Tenant elects to have the Excess Phase I Costs paid from the remaining balance,
if any, of the Tenant Allowance for Phase II Leasehold Improvements (an "Excess
Cost Election"), the Tenant Allowance for Phase II Leasehold Improvements
specified herein shall be automatically reduced on a dollar-for-dollar basis and
the Annual Fixed Rent Rate shall be increased by an amount which equals (i) the
ratio of the amount of Excess Phase I Costs related to such change orders
approved by Tenant to $1,000,000.00 multiplied (ii) by $3.13. For example, if
the Excess Phase I Costs are $500,000.00, the Annual Fixed Rent Rate would
increase by $1.57 [($500,000.00 / $1,000,000.00) x $3.13] = $1.57. Any increase
in the Annual Fixed Rent Rate due to Excess Phase I Costs shall be effective on
the Commencement Date.

        Tenant shall pay to Landlord as Additional Rent a sum equal to all
additional costs incurred by Landlord on account of the Excess Phase I Costs (if
Tenant does not make an Excess Cost Election) and on account of the Phase II
Leasehold Improvements (excluding, however, the Tenant Allowance for the Phase
II Leasehold Improvements but including in the costs so incurred the cost to
Landlord of Landlord's Contractor's overhead and profit equal to 10% of costs of
work not covered by the Tenant Allowance for the Phase II Leasehold
Improvements), hereinafter called "Tenant Improvement Reimbursement to Landlord"
or "TIR". Tenant shall pay to Landlord Landlord's Estimated TIR (as hereinafter
defined) as construction of the Phase II Leasehold Improvements progresses, less
retainage of 10%, within ten (10) days after submission by Landlord to Tenant of
a statement on or about the first day of each month showing construction,
engineering and design costs incurred. As used herein with respect to the Phase
II Leasehold Improvements, the term "Estimated TIR" shall mean and refer to the
difference between the Estimated Cost of the Work and the Tenant Allowance for
the Phase II Leasehold Improvements. The portion of Estimated TIR invoiced on
each monthly statement shall be equal to the product of (a) a fraction, the
numerator of which is Landlord's Estimated TIR and the denominator of which is
the Estimated Cost of the Work, multiplied by (b) the total construction,
engineering and design costs shown on each such statement. Each monthly
statement shall be 


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<PAGE>   9

accompanied by a certificate of Landlord's Contractor that all payments then due
to laborers, materialmen and subcontractors, less required retainage, have been
made. Landlord shall not be required to continue construction if Tenant fails to
pay timely Estimated TIR and any delay in the preparation of the Premises shall
be deemed to be a Tenant Delay for which Landlord shall have no liability. On
the Phase II Substantial Completion Date (as defined in Section 3.2 hereof)
Tenant shall pay to Landlord a sum sufficient to increase the total payments to
Landlord on account of TIR to ninety-five percent (95%) of TIR (it being
understood that actual TIR may be more or less than the Estimated TIR). The
remaining five percent (5%) retainage withheld by Tenant shall be paid by Tenant
within ten (10) days after delivery to Tenant of (i) a permanent Certificate of
Occupancy from the City of Cambridge for the Phase II Leasehold Improvements and
(ii) a certificate of Landlord's Architect and Tenant's Architect certifying
that all Punch List Items (as defined in Section 3.2 hereof) for the Phase II
Leasehold Improvements have been reasonably satisfied after consultation between
Landlord's Architect and Tenant. Landlord shall withhold from Landlord's
Contractor retainage the amount of five percent (5%) of the cost of the work
until such time as Landlord's Architect, after consultation with Tenant's
Architect, shall have delivered said certificate to Tenant (provided, however,
that Landlord may release any retainage held with respect to any supplier or
subcontractor which is finally and fully completed for the portion of the work
for which it was responsible prior to the delivery of said certificate.) All
change orders or cost overruns shall first be subject to reasonable approval by
Tenant within two (2) business days of receipt of said change order.

        In addition to paying TIR as above provided, for Excess Phase I Costs
(if Tenant does not make an Excess Cost Election) and the Phase II Leasehold
Improvements Tenant shall pay an amount equal to all costs incurred by Landlord
as a result of any change orders requested by Tenant and signed by Tenant and
Landlord affecting the Complete Plans, including the cost to Landlord of
Landlord's Contractor's overhead and profit equal to 10% of those costs
exclusive of overhead and profit, but only to the extent that such change order
costs, together with all other costs incurred on account of the Phase I
Leasehold Improvements or the Phase II Leasehold Improvements, as applicable,
exceed the applicable Tenant Allowance. Amounts due and payable on account of
such change orders shall be included in the monthly statements relating to TIR
provided for above, and Tenant shall pay therefor in accordance with each such
statement within ten (10) days, and in all events by the Phase I Substantial
Completion Date or Phase II Substantial Completion Date, as applicable.
Notwithstanding the foregoing, Tenant shall not be liable for any costs incurred
by Landlord as a result of change orders relating solely to Base Building
Improvements (as defined in Exhibit G).

        Notwithstanding the foregoing, Landlord shall be liable for completion
of all Base Building Improvements as set forth in Exhibit G. Landlord agrees to
consult with Tenant with respect to the design of the lobby area except with
respect to requirements to the Cambridge Historical Commission, and will
cooperate with Tenant in good faith to accommodate Tenant's reasonable comments.

        Landlord shall deliver to Tenant a copy of each monthly requisition for
the Phase II Leasehold Improvements from Landlord's Contractor promptly after
Landlord's receipt of the same.

3.2     PREPARATION OF PREMISES FOR OCCUPANCY.

        Landlord agrees to use reasonable efforts to have the Phase I Leasehold
Improvements, including completion of the Base Building Improvements described
in Exhibit B hereto, completed so that the Premises are ready for occupancy on
or before the Scheduled Substantial Completion Date and to have the Phase II
Leasehold Improvements completed by the Scheduled Phase II Substantial
Completion Date, which Dates shall, however, be extended for a period equal to
that of any delays due to Acts of God, or by changes ordered by Tenant in the
work, or 


                                      -8-



<PAGE>   10

by labor disputes, fire, unusual delays in deliveries, unavoidable casualties or
other causes beyond Landlord's reasonable control (collectively, "Force Majeure
Events") and by delays due to any act or neglect of Tenant, or of any employee,
agent, or separate contractor of Tenant. The Premises shall be deemed ready for
occupancy on the Phase I Substantial Completion Date (as hereinafter defined).
In no event shall the Phase I Substantial Completion Date be later than January
1, 1999 (the "Outside Completion Date"), in which case Tenant shall have the
right to terminate this Lease. As used herein, the term "Phase I Substantial
Completion Date" and "Phase II Substantial Completion Date," as applicable,
shall mean and refer to the date on which: (i) the Phase I Leasehold
Improvements or the Phase II Leasehold Improvements, as applicable, as specified
in the Phase I Complete Plans or the Phase II Complete Plans, as applicable, are
ready for occupancy as certified by Landlord's Architect and Tenant's Architect
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
make the Premises tenantable for the Permitted Uses (collectively "Punch List
Items"), (ii) a Certificate of Occupancy from the City of Cambridge (or a
Temporary Certificate of Occupancy permitting Tenant to occupy the Premises with
conditions which can be satisfied without material interference with Tenant's
use and occupancy of the Premises) shall have been obtained, (iii) the Premises
is broom clean and free of debris, and (iv) all utilities required for the use
of the Premises have been brought by Landlord to the Premises as specified in
Exhibit B; provided, however, that if Landlord is unable to complete
construction of the Premises in accordance with the foregoing on or before the
Phase I Scheduled Substantial Completion Date or the Scheduled Phase II
Substantial Completion Date, as applicable, due to delay in Tenant's compliance
with the provisions of Section 3.1 or the respective schedule set forth in
Exhibit E of this Lease, then the Premises shall be deemed ready for occupancy
no later than the date which would have been the Substantial Completion Date but
for such non-compliance.

        Landlord shall permit Tenant and Tenant's contractors access for
installing equipment and furnishings in the Premises prior to the Commencement
Date if it can be done without material interference with completion of the
Phase I Leasehold Improvements.

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 in a good and workmanlike manner and in
compliance with all applicable laws and all lawful ordinances, regulations and
orders of any governmental authority or insurer of the Building. 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 all components, fixtures, or equipment, including, without
limitation, Landlord's Contractor's warranty (which shall be for a period of at
lease one [1] year) as to construction completed in connection with the Tenant
Improvements, to Tenant for the Term of this Lease, upon the expiration or
sooner termination of which such warranties shall automatically revert to
Landlord. Landlord's obligations under Section 3.1 and 3.2 shall be deemed to
have been performed on the Phase I Substantial Completion Date or the Phase II
Substantial Completion Date, as applicable, except for items which are
incomplete or do not conform with the requirements of Sections 3.1 and 3.2 and
as to which Tenant shall in either case have given written notice to Landlord
prior to such date. If Tenant does not provide such written notice prior to the
Phase I Substantial Completion Date or the Phase II Substantial Completion Date,
as applicable, a certificate of completion by a licensed architect or registered
engineer shall be conclusive evidence (exclusive of latent defects) that
Landlord has performed 



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<PAGE>   11

all such obligations except for items stated in such certificate to be
incomplete or not in conformity with such requirements.

        Tenant will not make any alterations or additions to the Premises (other
than initial improvements made in accordance with the Complete Plans and any
other improvements consistent therewith) without Landlord's approval which
consent shall not be unreasonably withheld, conditioned or delayed. Landlord
will disapprove any alterations or additions requested by Tenant which will
delay completion of the Premises, the Building or the Leasehold Improvements,
unless Tenant shall agree (a) to pay all costs associated with such alterations,
additions and delay, (b) to extend the Scheduled Substantial Completion Date or
the Scheduled Phase II Substantial Completion Date, as applicable, for the
period of such delay, and (c) that the Annual Fixed Rent and Additional Rent
shall nonetheless begin to accrue from the date the Phase I Leasehold
Improvements or the Phase II Leasehold Improvements, as applicable, would have
been completed but for such delay. All changes and additions shall be part of
the Building except Tenant's equipment (a list of which shall be provided to
Landlord upon Commencement of the Lease) and except such items as by writing at
the time of approval the parties agree either shall be removed 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 $50,000 and shall be generic in form (each
a "Minor Alteration") (generic meaning that such space will be easily usable for
other tenants): (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, and
(ii) upon the expiration or termination of this Lease, Tenant shall readapt,
repair and restore the Premises to the condition the same were in prior to such
Minor Alteration, regardless of whether Landlord's consent was required or
obtained with respect thereto.

        The parties further agree that (a) any request for 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 both in printed form
and on diskette in CAD format compatible and consistent with existing as-built
plans for the Building, 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.

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 Representative in the case of Tenant or by any person
hereafter designated in substitution or addition by notice to the party relying.



                                      -10-



<PAGE>   12

                                   ARTICLE IV

                                      RENT

4.1     FIXED RENT.

        (a) MONTHLY INSTALLMENTS; DEFINITIONS. Beginning on the Commencement
Date (and beginning on the Phase II Substantial Completion Date), Tenant
covenants and agrees to pay rent to Landlord, without any offset or reduction
whatsoever (except as may be made in accordance with the express provisions of
this Lease), 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, at the respective Annual Fixed Rent Rate set forth in Article I
(and subject to adjustment in the event of an Excess Cost Election), in equal
installments equal to 1/12th of the Annual Fixed Rent Rate 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 FOR CPI. On the later of September 1, 2003 or the
Commencement of the Sixth Lease Year and on the later of September 1, 2008 or
the Commencement of the Eleventh Lease Year (the "Adjustment Date"), the Annual
Fixed Rent Rate shall be increased by multiplying said rate by a fraction, the
numerator of which shall be the Price Index (as hereinafter defined) most
recently established prior to the Adjustment Date, and the denominator of which
shall be the Base Price Index (as hereinafter defined). As used herein, the term
"Price Index" shall mean and refer to the "Consumer Price Index for Urban Wage
Earners and Clerical Workers, for the Boston, Massachusetts area, All Items
(1982-84=100)" published by the Bureau of Labor Statistics of the United States
Department of Labor or successor or substitute index appropriately adjusted, and
the term "Base Price Index" shall mean and refer to the Price Index most
recently established prior to September 1, 1998. In the event the Price Index
(or a successor or substitute index) shall not be published for the City of
Boston, or for the months indicated above, the corresponding index for the
United States City Average (and if this is not available, a reliable
governmental or other nonpartisan publication evaluating similar or equivalent
information as used in the Price Index) shall be used. In the event the Price
Index ceases to use the 1982-84 average of 100 as the basis of calculation, or
if a substantial change is made in the terms or numbers of items contained in
the Price Index, then the Price Index shall be adjusted to the figure using the
replacement method of calculation utilized by the United States Department of
Labor. Notwithstanding the foregoing, any such increase shall not exceed four
percent (4%) per year compounded annually.

          By way of example on September 1, 2003 the Monthly Base Rent
$229,209.38 x CPI @ August 1, 2003/CPI @ August 1, 1998 but in no event more
than $278,947.82 (i.e., $229,209.38 plus 4% per year compounded for five (5)
years or $229,209.38 x 1.217).

4.2     ADDITIONAL RENT.

        In order that the Annual Rent Rate shall be absolutely net to Landlord
(except to the extent herein otherwise provided), Tenant covenants and agrees to
pay, as Additional Rent, without any offset or reduction whatsoever, taxes,
municipal or state betterment assessments, insurance costs, utility charges and
Annual Maintenance Charges 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. Landlord shall furnish
Tenant with a statement as soon as reasonably practicable after the commencement
of each Lease Year setting forth the amount of Landlord's 


                                      -11-



<PAGE>   13

Estimated Annual Additional Rent for such Lease Year. Landlord's good faith
estimate of the Estimated Annual Additional Rent for the first fiscal year of
the Term is set forth in Section 1.1 as the "Initial Estimated Annual Additional
Rent".

        4.2.1  REAL ESTATE TAXES.

               Tenant shall pay directly to the Landlord: (i) all taxes,
assessments to the extent due and payable (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 prior to or during the Term hereof, imposed or levied upon or
assessed against (A) the Premises or the Building or a fraction of the Lot, (B)
any Fixed Rent, Additional Rent or other sum payable hereunder or (C) this
Lease, or the leasehold estate hereby created, or which arise in respect of the
operation, possession or use of the Premises or the Building or the Lot; (ii)
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;
(iii) all sales, value added, use and similar taxes at any time levied, assessed
or payable on account of the leasing or use of the Premises (and any such taxes
if they are levied, assessed or payable on account of the acquisition, leasing
or use of the entire Building or Tenant's Proportionate Share of Lot); and (iv)
all charges for utilities furnished to the Premises (and all charges for
utilities furnished to the entire Building or Tenant's Proportionate Share of
the Lot) which may become a lien on the Building or the Lot or the Premises
(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 less than five (5) days
prior to the last date on which the same may be paid without interest or
penalty, provided that Tenant receives any such invoice for payment at least
thirty (30) days before said amount is due. 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 20 days after
receipt of invoice therefor, the fraction 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.

        In the event that Tenant requests that Landlord apply for any abatement
of, or otherwise contest, any tax or assessment, Landlord shall file such
abatement or otherwise contest such tax or assessment and shall diligently
pursue the same to completion, provided that (i) Landlord receives notice of
such request from Tenant at least 30 days prior to the last day on which such
abatement or contest may validly be made under applicable law, and (ii) 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 included in the Annual Maintenance Charge of the then current
fiscal year.

        Nothing contained in this Lease shall, however, require Tenant to pay
any income taxes, excess profits taxes, excise taxes, franchise taxes ("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 Premises, the
Building and the Lot, 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"), 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 Premises 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 



                                      -12-


<PAGE>   14

notice of any public, special or betterment assessment received by Landlord
concerning the Premises.

        4.2.2  INSURANCE.

               4.2.2.1     INSURANCE TAKEN OUT BY TENANT.

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

                           (a)    Comprehensive liability insurance indemnifying
Landlord and Tenant against all claims and demands for (i) injury to or death of
any person or damage to or loss of property, on the Premises or walks, streets
or ways appurtenant to the Premises, or connected with the use, condition or
occupancy of any thereof unless caused by the negligence or willful misconduct
of Landlord or its servants or agents, (ii) violation of this Lease, or (iii)
any act, fault or omission, or other misconduct of Tenant or its agents,
contractors, licensees, sublessees or invitees, in amounts which shall, at the
beginning of the Term, be at least equal to the limits set forth in Section 1.1,
and, from time to time during the Term, shall be for such higher limits, if any,
as are customarily carried in the area in which the Premises are located on
property similar to the Premises and used for similar purposes; and shall be
written on the "Occurrence Basis" and include Host Liquor liability insurance;
and

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

               4.2.2.2     INSURANCE TAKEN OUT BY LANDLORD.

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

                           (a)    Comprehensive liability insurance for the
Building and Lot of the same nature and type as described in Section 4.2.2.1(a)
of this Lease, and with the same policy limits; and

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

                           (c)    Insurance against loss or damage from
sprinklers and from leakage or explosions or cracking of boilers, pipes carrying
steam, or water, or both, and pipes carrying other liquids and gases, pressure
vessels or similar apparatus, in the so-called "broad form", in such amounts as
are customary and commercially reasonable for buildings in the Cambridge,
Massachusetts area which are of like kind and quality to the Building and have
laboratory uses, and insurance against such other hazards and in such amounts as
may from time to time be reasonably required by any bank, insurance company or
other lending institution holding a first mortgage on the Building and Lot.

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

               4.2.2.3     TENANT REIMBURSEMENT OF INSURANCE TAKEN OUT BY 
LANDLORD.

                           Tenant shall from time to time reimburse Landlord
within thirty days of Landlord's invoice for Landlord's costs incurred in
providing the insurance provided pursuant 



                                      -13-


<PAGE>   15

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 and the Lot (only to the extent of Tenant's Proportionate Fraction with
respect to the Lot), 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, including without limitation, any risks or hazards
associated with the generation, storage and disposal of medical waste provided
the same is attributable to Tenant's use and that the same is not necessarily
due to other tenant's use. At Landlord's option, Tenant shall reimburse Landlord
for insurance costs in accordance with Section 4.2.5 hereof.

               4.2.2.4     CERTAIN REQUIREMENTS APPLICABLE TO INSURANCE 
POLICIES.

                           Policies for insurance provided for under the 
provisions of Sections 4.2.2.2(b) and 4.2.2.2(c) shall, in case of loss, be
first payable to the holders of any mortgages on the Building and Lot 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
state in which the Premises are located and in good standing therein, which
companies and the amount of insurance allocated thereto shall be subject to
Landlord's reasonable 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 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 10.13 hereof). Each such policy required to be maintained by Tenant
shall name Landlord and Landlord's Managing Agent as additional insureds and
shall be noncancellable with respect to the interest of Landlord, Landlord's
Managing Agent and such mortgagees without at least 30 days' prior written
notice thereto.

               4.2.2.5     WAIVER OF SUBROGATION.

                           All insurance which is carried by either party with 
respect to the Premises or 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 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 shall
be entitled to have duplicates or certificates of any policies containing such
provisions. 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 by such insurance. Tenant
shall not acquire as insured under any insurance carried on the Premises under
the provisions of this 


                                      -14-



<PAGE>   16

Section 4.2.2 any right to participate in the adjustment of loss or to receive
insurance proceeds and agrees upon request promptly to endorse and deliver to
Landlord any checks or other instruments in payment of loss in which Tenant is
named as payee.

        4.2.3  UTILITIES.

               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 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. Upon Tenant's request, Landlord shall install
separate meters to measure Tenant's consumption of any utility servicing the
Premises. If Tenant is not charged directly by the respective utility for any of
such utilities or services, Tenant shall from time to time, within 20 days of
receipt of Landlord's invoice therefor, pay to Landlord the total of such
charges for the Building and Lot, provided that if said utilities or services
are provided to less than all of the rentable space on the Lot , Tenant shall
pay its share of said charges based upon the actual consumption shown on any
separate meter for such utility or service, and, in the event there is no such
separate meter, based upon the area of the Premises relative to the area of the
entire space to which utilities are provided, or such greater or lesser amount
required, in Landlord's reasonable judgment, by Tenant's disproportionate use of
utilities, and provided further that, at Landlord's option, all such charges
shall be payable by Tenant in accordance with Section 4.2.5. Without limitation
of the foregoing, in the event of a Casualty or Taking, if Landlord's Architect
and Tenant's Architect reasonably determines that the Base Building utilities as
shown in Exhibit B hereto will not be repaired or restored so as to be available
within ninety (90) days after the occurrence of such Casualty or Taking, then
Tenant shall have the right to terminate this Lease by notice given within 30
days after the date of such determination. All of the utilities shall be
installed in the Building and the Premises in accordance with Exhibit B attached
hereto.

        4.2.4  COMMON AREA MAINTENANCE AND EXPENSES.

               Landlord shall use reasonable efforts to maintain the common
areas of the Lot and (Landlord and Tenant will cooperate to determine who will
be responsible for providing services required to operate the Building or to
maintain the Lot , as contemplated in Exhibit I, except to the extent repairs or
maintenance are required due to Tenant's negligence or willful misconduct (in
which case Tenant shall promptly effect such repairs or maintenance or, at
Landlord's option, Landlord may 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 Lot Maintenance Charge and the Annual Building
               Maintenance and Operation Charge as hereinafter defined.

                       (a) The Annual Lot Maintenance Charge shall be equal to
               the product obtained by multiplying (x) the costs incurred by
               Landlord during the fiscal year (as hereinafter defined) for
               which the Annual Maintenance Charge is being computed (the
               "Current Fiscal Year") in providing Lot maintenance, including
               without limitation landscaping, street lighting, security (if
               required, in Landlord's judgment), maintenance and snow plowing,
               maintenance of Lot signage, 


                                      -15-


<PAGE>   17

               maintenance of utilities, commercially reasonable management fees
               and reasonable amortization of equipment to the extent used for
               Lot maintenance, by (y) a fraction whose numerator is the
               Premises Floor Area, as built, and whose denominator is the gross
               floor area of the buildings located on the Lot at the end of the
               Current Fiscal Year.

                       (b) The Annual Building Maintenance and Operation Charge
               shall be equal to Tenant's Proportionate Fraction of the
               reasonable costs incurred by Landlord during the Current Fiscal
               Year in providing Building maintenance, including without
               limitation repair, maintenance and cleaning of common facilities
               in the Building, and maintenance and repairing of all common
               heating, plumbing, electrical, air conditioning and mechanical
               fixtures and equipment serving the Building or the Premises and
               not for other tenant's use, elevators, trash dumpster rental,
               trash removal, recycling, performance of such other tasks as
               Tenant shall request and Landlord shall agree to perform,
               commercially reasonable management fees (exclusive of leasing and
               sale commissions, fees paid in connection with tenant improvement
               costs, and such other fees or commissions paid in connection with
               the leasing, releasing, extension or renewal of leases for the
               Building or the Lot) and reasonable amortization of equipment to
               the extent used for the Building maintenance.

               Notwithstanding the foregoing, in the event that any capital
repair, improvement or replacement to the common areas and facilities of the
Building and the Lot has a useful life of over one year (as determined in
accordance with generally accepted accounting practices consistently applied),
then only the amortized cost of such repair, improvement or replacement over
said useful life shall be included in the Annual Lot Maintenance Charge or the
Annual Building Maintenance Charge, as applicable.

               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. 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 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 on or about July 1 of each Lease Year (the "Additional Rent Adjustment
Date"), and Tenant's payments shall thereupon be adjusted accordingly. Not later
than sixty (60) 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 generally accepted accounting practices
certified by Landlord and showing for the preceding fiscal year or fraction
thereof, as the case may be, the actual Annual Maintenance Charges 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, on the next rent payment date or refunded if the
Term has ended and Tenant is not then in default (or if Tenant is in default,
then any excess over that necessary to cure said default shall be returned to
Tenant). Landlord shall furnish Tenant with copies of all reasonable
documentation and records for the Annual Maintenance Charges for any fiscal year
upon Tenant's request for the same; provided, however, that Landlord shall not
be required to furnish such copies for any fiscal year if Tenant has not
requested such copies within two (2) years after the expiration of such fiscal
year.



                                      -16-



<PAGE>   18

        Tenant shall have the right to conduct an audit of Landlord's records
relating to Maintenance Charges. If the Tenant's audit indicates that there is
an error greater than five percent (5%), then Landlord shall reimburse Tenant
for the cost of said audit.

               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. 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 the later of (a) 10 days after Landlord
delivers such estimate to Tenant or (b) the last day of the Term. Landlord shall
thereafter prepare a Landlord's Statement showing the actual Annual Maintenance
Charge for such fiscal year, as herein above provided, and an appropriate
payment or refund shall thereafter promptly be made upon submission of such
Landlord's Statement to Tenant.

               Notwithstanding the foregoing, Landlord hereby agrees that access
to the Premises, HVAC service and all other utilities shall be available to
Tenant 24 hours per day, seven (7) days per week, subject to the provisions
hereof with respect to loss or interruption of utilities and other services.

        4.2.5  PAYMENTS ON ACCOUNT OF TAXES, INSURANCE AND UTILITIES.

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

               Not later than sixty (60) 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 generally accepted 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 


                                      -17-


<PAGE>   19

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, on the next rent payment
date or refunded if the Term has ended and provided Tenant is not then in
default, or if Tenant is in default, then any excess over that necessary to cure
the default shall be returned to Tenant. 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.

               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, and upon any such change all items referred to in this Section
shall be appropriately apportioned. 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) 10 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 after
applicable grace and cure periods, it shall bear interest from the due date at
the prime commercial rate of BankBoston, as it may be adjusted from time to
time, plus 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.

                                    ARTICLE V

                          TENANT'S ADDITIONAL COVENANTS

5.1     AFFIRMATIVE COVENANTS.

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

        5.1.1  PERFORM OBLIGATIONS.

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




                                      -18-


<PAGE>   20

        5.1.2  OCCUPANCY AND USE.

               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. Landlord covenants to Tenant that as of the date of
execution of this Lease, the Building is in compliance with the City of
Cambridge zoning laws and state and local building laws, ordinances and
regulations, and that the Permitted Use is an allowed use under the City of
Cambridge zoning laws.

               Without limitation, Tenant shall strictly comply with all
federal, state, and municipal laws, ordinances, and regulations governing the
use of Tenant's laboratory, scientific experimentation and the generation,
storage, containment and disposal of medical waste. 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 and research
activities on the demised premises; its scientific experimentation,
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 ten (10) 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 above 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, reasonably acceptable to Landlord to protect
Landlord, the Building and the Lot 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 without further appeal
permitted, 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 or
the Lot, or any other person or entity. Landlord agrees that any Confidential
Information gained or obtained by Landlord pursuant to this Section 5.1.2 shall
be kept confidential in accordance with Section 10.13 hereof.

        5.1.3  REPAIR AND MAINTENANCE.

               Except as otherwise provided in Article VI, to keep the Premises
including, without limitation, all fixtures and equipment now or hereafter on
the Premises, or exclusively serving the Premises, but excluding the exterior
(exclusive of glass and doors) and structural elements of the Building, the
Building's systems and the grounds and parking 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 only excepted; to keep in a
safe, secure and sanitary condition all 



                                      -19-


<PAGE>   21

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.
Tenant shall secure, pay for and keep in force contracts with appropriate and
reputable service companies providing for regular and emergency maintenance of
the heating and air-conditioning systems and copies of such contracts shall be
furnished to Landlord; provided, however, that it is agreed that Tenant shall be
responsible only for the repair and maintenance of the heating and
air-conditioning systems and the components thereof located within or
exclusively serving the Premises. Notwithstanding the foregoing, Landlord and
Tenant shall cooperate with one another to determine which party will be
responsible for services required to operate the Building. It is further agreed
that the exception of reasonable use and wear shall not apply so as to permit
Tenant to keep the Premises in anything less than suitable, tenantlike, and
efficient and usable condition considering the nature of the Premises and the
use reasonably made thereof, or in less than good and tenantlike repair.

        5.1.4  COMPLIANCE WITH LAW.

               To make all repairs, alterations, additions or replacements to
the Premises required by any law or ordinance or any order or regulation of any
public authority other than major capital repairs, alterations, additions or
replacements to the foundations and structural elements of the Building which
are not required because of Tenant's failure to comply with the Provisions of
Article 5.1.3 hereof; to keep the Premises equipped with all safety appliances
necessary for Tenant's use of the Premises; to pay all municipal, county, or
state taxes assessed against the leasehold interest hereunder, or against
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.

               The 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
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
10.13 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
laboratory facility for the Permitted Uses or (ii) Tenant has reason to believe
that such transportation may result in a public demonstration, protest or other
similar disturbance at the Building or the Lot. If the transportation,
generation, manufacture, production, handling, release, storage, use or disposal
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, 



                                      -20-


<PAGE>   22

surface or ground water or (2) loss or damage to person(s) or property, then
Tenant agrees to respond in accordance with the following paragraph:

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

               Tenant shall promptly notify Landlord upon Tenant's receipt of
any inquiry, notice, or threat to give notice by any government authority or any
other third party with respect to any hazardous materials. Notwithstanding the
foregoing, Tenant shall not be liable to Landlord hereunder for any
contamination, claim of contamination, 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 and the Lot prior to Tenant's use or
occupancy of the Premises, (B) migration of hazardous materials from any site
onto the Lot not caused by Tenant, (C) the generation, manufacture, production,
handling, release, storage, use or disposal of any hazardous materials at the
Building or the Lot by Landlord, any other tenant or occupant, or any so-called
"midnight dumpers" or (D) the Use (as defined above in this Section) by any
party other than Tenant of hazardous materials at the Building or the Lot.
Tenant's indemnification obligations under this Section shall survive the
expiration or earlier termination of this lease.

               Prior to vacating the Premises at the expiration of the term
hereof, Tenant at its sole cost and expense shall provide Landlord with an
environmental audit with respect to Tenant's actions at the Premises by a
qualified environmental engineering firm reasonably satisfactory to Landlord,
which audit shall include reasonable subsurface testing if a preliminary review
suggests Tenant may have contaminated the same. The aforesaid environmental
audit shall affirmatively certify that the Premises are free from any and all
contaminants, pollutants, radioactive materials, hazardous wastes or materials,
medical waste, bacteriological agents or organisms which would render the
Premises in violation of M.G.L. c. 21E, the Comprehensive Environmental
Response, Compensation, and Liability Act of 1980, as amended, 42 U.S.C. Section
9602 et seq., or any other applicable laws, rules, regulations or orders, as
they may be amended or supplemented by administrative regulations, from time to
time. Landlord has delivered to Tenant at Tenant's request, a Phase I
Environmental Site Assessment for the Building and the Lot prepared by Haley &
Aldrich dated June, 1997 , which Landlord obtained in connection with Landlord's
acquisition of the Building and the Lot. Landlord makes no representations
regarding the content of the information contained in the report and has agreed
to provide the same to Tenant as a courtesy only.

               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 (as defined above in this Section) of hazardous materials by
Tenant at the Premises.

               Tenant agrees that, with respect to improvements to the Premises
subsequent to the Initial Tenant Improvements, it shall be responsible for
compliance with the Americans with 



                                      -21-


<PAGE>   23

Disabilities Act (42 U.S.C. 12101 et seq.) and the regulations and Accessibility
Guidelines for Buildings and Facilities issued pursuant thereto (collectively,
the "ADA Requirements"). Landlord shall be responsible for compliance of the
Initial Tenant Improvements and the Building with the ADA Requirements.

               Tenant covenants and agrees that its use of the Premises shall
not cause a discharge of more than 5,250 gallons per day from the Premises of
sanitary (non-industrial) sewage. Discharges in excess of that amount, and any
discharge of industrial sewage or waste, shall only be permitted if Tenant, at
its sole expense, shall have obtained all necessary permits and licenses
therefor, including without limitation permits from state and local authorities
having jurisdiction thereof.

        5.1.5  TENANT'S WORK.

               To procure at Tenant's sole expense all necessary permits and
licenses before undertaking any work on the Premises; to do all such work in
compliance with the applicable provisions of Sections 3.3 and 5.2.3 hereof; to
do all such work in a good and workmanlike manner employing materials of good
quality and so as to conform with all applicable zoning, environmental,
building, fire, health and other codes, regulations, ordinances and laws and the
ADA Requirements; to furnish to Landlord prior to the commencement of any work
for which the cost may reasonably be estimated to exceed $750,000.00, a bond or
other security acceptable to Landlord assuring that any work commenced or
continued by Tenant will be completed in accordance with specifications approved
in advance in writing by Landlord; 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; 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 set forth in
Section 1.1 and to submit certificates evidencing such coverage to Landlord
prior to the commencement of such work and to save Landlord harmless and
indemnified from all injury, loss, claims or damage to any person or property
occasioned by or growing out of such work.

        5.1.6  INDEMNITY.

               To defend, with counsel approved by Landlord, all actions against
Landlord, any partner, trustee, stockholder, officer, director, employee or
beneficiary of Landlord, holders of mortgages secured by the Premises or the
Building and 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, expenses (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 or on adjoining
sidewalks, streets or ways appurtenant to the Premises and 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 or willful misconduct of Landlord or its servants or agents, (ii)
violation of this Lease by Tenant or its agents, contractors, licensees,
employees, sublessees or invitees, or (iii) any act, fault, omission, or other
misconduct of Tenant or its agents, contractors, licensees, employees,
sublessees or invitees.

        5.1.7  LANDLORD'S RIGHT TO ENTER.

               To permit Landlord and its agents to enter into the Premises at
reasonable times and upon at least 24 hours advance notice (except in case of
emergency in which event no prior 


                                      -22-


<PAGE>   24

notice shall be required) to examine the Premises, make such repairs and
replacements as Landlord may elect, without however, any obligation to do so
except as may be otherwise expressly set forth in this Lease, and show the
Premises to prospective purchasers and lenders, and, during the last twelve
months of the Term, to show the Premises to prospective tenants. Landlord's
right to enter the Premises in accordance with the foregoing shall be subject to
Landlord's obligations pursuant to Section 10.13 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,
(iii) conduct such showing in compliance with such reasonable requests and
instructions as Tenant may make for purposes of protecting Tenant's Confidential
Information.

        5.1.8  PERSONAL PROPERTY AT TENANT'S RISK.

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

        5.1.9  PAYMENT OF LANDLORD'S COST OF ENFORCEMENT.

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

        5.1.10 YIELD UP.

               Subject to Article III 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 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. Subject to
Section 3.3 hereof, any property required to be removed and 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.



                                      -23-



<PAGE>   25

        5.1.11 ESTOPPEL CERTIFICATE.

               Upon not less than 10 days' prior notice by Landlord, to execute,
acknowledge and deliver to Landlord 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. Any such statement delivered pursuant to this Section
5.1.11 may be relied upon by any prospective purchaser or mortgagee of the
Premises, or any prospective assignee of any such mortgage.

        5.1.12 LANDLORD'S EXPENSES RE: CONSENTS.

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

        5.1.13 RULES AND REGULATIONS.

               To comply with the Rules and Regulations set forth in Exhibit C,
as the same may be reasonably amended from time to time by Landlord to provide
for the beneficial operation of the Building and/or Lot, provided that such
amendments do not materially interfere with Tenant's right of use and enjoyment
of the Premises pursuant to this Lease, it being understood that, subject to the
provisions of Section 10.2 hereof, Landlord shall not be liable to Tenant for
the failure of other tenants of the Building or the Lot to conform to such Rules
and Regulations.

        5.1.14 LOADING.

               Not to place Tenant's Property, as defined in Section 5.1.8, upon
the Premises so as to exceed the floor load limits set forth in EXHIBIT H
attached hereto 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 transmitted to the Building
structure or to any other leased space in the Building shall be placed or
maintained by Tenant in settings of cork, rubber, spring, or other types of
vibration eliminators sufficient to reduce such vibration or noise to a level
reasonably acceptable to Landlord.

        5.1.15 HOLDOVER.

               To pay to Landlord (i) the greater of twice (a) the then fair
market rent as reasonably determined by Landlord or (b) the total of the Fixed
Rent, Additional Rent, and all other payments then payable hereunder, for the
period that 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 


                                      -24-


<PAGE>   26

any damages under the foregoing clause (ii). The provisions of this subsection
shall not operate as a waiver by Landlord of the right of re-entry provided in
this Lease.

5.2     NEGATIVE COVENANTS.

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

        5.2.1  ASSIGNMENT AND SUBLETTING.

               Not without the prior written consent of Landlord to assign this
Lease, to make any sublease, or to permit occupancy of the Premises or any part
thereof by anyone other than Tenant, voluntarily or by operation of law, except
as hereinafter provided; as Additional Rent, to reimburse Landlord promptly for
reasonable legal and other expenses incurred by Landlord in connection with any
request by Tenant for consent to assignment or subletting (subject to the
provisions of Section 5.1.12 hereof); no assignment or subletting shall affect
the continuing primary liability of Tenant (which, following assignment, shall
be joint and several with the assignee); 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 as to
the terms and conditions thereof. In addition, as to any assignee (but not as to
any sublessee) Landlord's consent shall be required as to the reasonable
creditworthiness of the proposed assignee in view of market conditions then
prevailing for leases having terms and conditions comparable to this Lease.
Landlord's consent to any assignment or subletting by Tenant shall not be
unreasonably withheld, provided that Tenant is not then in default beyond
applicable grace and cure periods under this Lease. If Tenant requests
Landlord's consent to assign this Lease or to sublet the entire Premises for
substantially all of the then remaining Term, Landlord shall have the option,
exercisable by written notice to Tenant given within 10 days after receipt of
such request, to terminate this Lease as of the date of commencement the
proposed sublease or assignment; provided, however, that Tenant shall have the
right to rescind any such request in the event Landlord elects to so terminate
this Lease by notice given to Landlord within five (5) days after the date of
such termination notice from Landlord, in which event such termination notice
shall be of no further force or effect.

               If, at any time during the Term of this Lease, Tenant is:

                (i) a corporation or a trust (whether or not having shares of
beneficial interest) and there shall occur any change in the identity of any of
the persons then having power to participate in the election or appointment of
the directors, trustees or other persons exercising like functions and managing
the affairs of Tenant; or

               (ii) a partnership or association or otherwise not a natural
person (and is not a corporation or a trust) and there shall occur any change in
the identity of any of the persons who then are members of such partnership or
association or who comprise Tenant;

Tenant shall so notify Landlord and Landlord may terminate this Lease by notice
to Tenant given within 90 days thereafter if, in Landlord's reasonable judgment,
the credit of Tenant is thereby impaired. This paragraph shall not apply if the
initial Tenant named herein is a corporation and the outstanding voting stock
thereof is listed on a recognized securities exchange.

               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 to (i) any successor of Tenant resulting from a merger or
consolidation of Tenant s (ii) any Affiliate of Tenant (as hereinafter defined)
whose net worth is equal to or greater than the net worth of Tenant as of the
date hereof, or (iii) sublet any portion of the Premises to any subsidiary of
Tenant provided that 


                                      -25-


<PAGE>   27

tenant holds the majority of the Controlling Shares of such subsidiary and
Tenant remains primarily liable under this Lease, provided that Tenant provides
Landlord notice within thirty (30) days after such assignment or subletting
pursuant to any of the foregoing clauses (i), (ii) or (iii). As used herein, the
term "Affiliate of Tenant" shall mean and refer to any entity controlled by,
controlling or under common control with Tenant.

               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, construction costs
and expenses incurred in good faith in view of the size and expected term of any
applicable sublease or assignment and the unamortized cost of Tenant's build out
expenses and the financing of such construction. Sublease Costs shall be
amortized over the term of the applicable sublease or assignment.

        5.2.2  NUISANCE.

               Not to injure, deface or otherwise harm the Premises; nor commit
any nuisance; nor permit the emission of any noise, vibration or odor which is
contrary to any law or ordinance; nor make, allow or suffer any waste; nor make
any use of the Premises which is improper, offensive or contrary to any law or
ordinance or which will invalidate any of Landlord's insurance.

        5.2.3  INSTALLATION, ALTERATIONS OR ADDITIONS.

               Subject to the provisions of Section 3.3 and Section 5.1.5
hereof, not to make any installations, alterations, or additions in, to or on
the Premises (including, without limitation, buildings, lawns, planted areas,
walks, roadways, parking and loading areas, but expressly excluding the initial
improvements made in accordance with Complete Plans approved by Landlord and
Tenant, and any other improvements consistent therewith, provided the same are
approved by Landlord, such approval not to be unreasonably withheld or delayed)
nor to permit the making of any apertures in the walls, partitions, ceilings or
floors without on each occasion obtaining the prior written consent of Landlord
and then only pursuant to plans and specifications approved by Landlord in
advance in each instance. Notwithstanding the foregoing, Tenant may make
non-structural improvements, installations, alterations or additions to the
Premises which do not exceed the sum of $50,000.00 without the prior approval or
Consent of the Landlord.

                                   ARTICLE VI

                               CASUALTY OR TAKING

6.1     TERMINATION.

        In case during the period which is two (2) years prior to the expiration
of the Term all or any substantial part of the Premises or of the Building or of
the Lot or any one or more of them shall be taken by any public authority or for
any public use, or shall be destroyed or damaged by fire or casualty, or by the
action of any public authority, or Landlord receives compensable damage by
reason of anything lawfully done in pursuance of public or other authority,
(hereinafter referred to as the "Casualty or Taking"), then this Lease may be
terminated at the election of Landlord or Tenant. Such election, which may be
made notwithstanding the fact that 


                                      -26-


<PAGE>   28

Landlord's entire interest may have been divested, shall be made by the giving
of notice by Landlord to Tenant or Tenant to Landlord within 30 days after the
Casualty or Taking.

6.2     RESTORATION.

        If either party does not exercise said election (or is not entitled to
exercise said election in the case of a Casualty or Taking occurring more than
two (2) years prior to the expiration of the Term of this Lease), this Lease
shall continue in force and a just proportion of the rent reserved, according to
the nature and extent of the damages sustained by the Premises, shall be abated
from the date of the Casualty or Taking until the Premises, or what may remain
thereof, shall be put by Landlord in proper condition for the Permitted Uses
subject to zoning and building laws or ordinances then in existence, which,
unless Landlord has exercised its option to terminate pursuant to Section 6.1,
Landlord covenants to do with reasonable diligence at Landlord's expense.

        Notwithstanding the foregoing, in the event that Landlord's Architect
reasonably determines that the Premises will not be repaired or restored (to the
extent permitted by the net proceeds of insurance recovered or damages awarded
from such Casualty or Taking) within one year after the occurrence of such
Casualty or Taking then Tenant shall have the right to terminate this Lease by
notice given within thirty (30) days after the date of such determination.

6.3     AWARD.

        Irrespective of the form in which recovery may be had by law, all rights
to damages or compensation shall belong to Landlord in all cases except as set
forth below in this Section 6.3. 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 its own cost
and expense, or other personal property of Tenant, or (ii) relocation expenses
or damages for loss of business (in excess of any such damages attributable to
the value of this lease) 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 for more than five (5)
business days after notice thereof twice during any twelve (12) month period, or
if within 30 days after notice from Landlord to Tenant specifying any other
default or defaults Tenant has not commenced to cure the default or defaults so
specified or has not thereafter diligently pursued such cure 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 or bonded over 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 



                                      -27-


<PAGE>   29

required under Section 4.2.2.1 hereof, 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 the curing of such 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 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 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. Landlord shall be required to use
reasonable efforts to relet the Premises.

        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, at its sole election, 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 accrued in the 


                                      -28-


<PAGE>   30

three (3) 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 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 or not
the amount be greater than, equal to, or less than the amount of the loss or
damages referred to above.

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 thirty (30) 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 on demand, 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 



                                      -29-


<PAGE>   31

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, 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. 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 any agreement which may be necessary to implement the
provisions of this Section 8.1.

8.2     SUBORDINATION.

        This Lease is subject and subordinate to any mortgage now on the
Building, if any, and shall be, at the mortgagee's election, subject and
subordinate to any mortgage hereafter on the Building and to each advance made
or hereafter to be made under any mortgage, and to all renewals, modifications,
consolidations, replacements and extensions thereof and all substitutions
therefor; provided, however, such mortgagee shall not disturb Tenant's
possession hereunder or rights hereunder in the event of a foreclosure by
Mortgagee except to the extent permitted hereunder pursuant to an Event of
Default by Tenant. This Section 8.2 shall be self-operative and no further
instrument of subordination shall be required, but if such subordination 



                                      -30-


<PAGE>   32

is in writing, then such mortgagee shall execute a non-disturbance and
attornment agreement in favor of Tenant in form acceptable to such mortgagee. In
confirmation of such subordination, Tenant shall execute and deliver promptly an
estoppel certificate concerning this Lease and Tenant's tenancy in form
reasonably acceptable to such mortgagee. Tenant hereby irrevocably appoints
Landlord as attorney-in-fact for Tenant (such appointment being coupled with an
interest) with full power and authority to execute and deliver in the name and
on behalf of Tenant any such certificate which Tenant fails so to execute and
deliver within ten (10) business days after written request and presentation by
Landlord or such mortgagee. Landlord represents that as of the date hereof,
there is no mortgage, ground lease or superior lien on the Building or the
Premises.

8.3     LEASE AMENDMENTS.

        Tenant agrees not to unreasonably withhold its agreement 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 or rights 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 any 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 3.2 or
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.

                                   ARTICLE IX

                         LANDLORD'S ADDITIONAL COVENANTS

9.1     AFFIRMATIVE COVENANTS.

        Landlord covenants at all times during the Term:

        9.1.1  PERFORM OBLIGATIONS.

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

        9.1.2  REPAIRS.

               Except as otherwise provided in Article VI, to make such repairs
(the cost of which is to be included in the Annual Maintenance Charge) to the
roof, exterior walls, exterior windows and waterproofing, floor slabs, other
structural components and common areas and facilities of the Building as may be
necessary to keep them in good, serviceable condition. Without limitation of the
foregoing, Landlord shall be responsible for the maintenance and repair of the
heating and air-conditioning systems and the components thereof serving the
Building, except for such systems and the components thereof as are located
within the Premises or exclusively serve the Premises (as provided in 
Section 5.1.3 hereof).



                                      -31-



<PAGE>   33

               Notwithstanding the foregoing, Landlord shall only be responsible
for maintenance, service and repair of Base Building utilities and services as
shown on Exhibit B hereto.

        9.1.3  COMPLIANCE WITH LAW.

               To make all repairs, alterations, additions or replacements to
the Building or the Lot (the 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 5.1.4
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 costs incurred by Landlord in connection with the foregoing compliance
obligations (to the extent required due to a change in law) shall be included in
the Annual Maintenance Charge. All of the foregoing covenants and obligations
are subject to, and without limitation of, all of Tenant's obligations under
this Lease, including, without limitation, those set forth in Sections 4.2 and
5.1.4.

        9.1.4  INDEMNITY.

               To defend, with counsel reasonably approved by Tenant, all
actions against Tenant, any partner, trustee, stockholder, officer, director,
employee or beneficiary of Tenant ("Tenant's Indemnified Parties") with respect
to, and to pay, protect, indemnify and save harmless, to the extent permitted by
law, all Tenant's Indemnified Parties from and against, any and all liabilities,
losses, damages, costs, expenses (including reasonable attorneys' fees and
expenses), causes of action, suits, claims, demands or judgments of any nature
arising from (i) injury to or death of any person, or damage to or loss of
property, on the Premises or on adjoining sidewalks, streets or ways appurtenant
to the Premises and not 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 or willful misconduct of Tenant or
its servants or agents, (ii) violation of this Lease by Landlord or its agents,
contractors, licensees, employees, sublessees or invitees, or (iii) any act,
fault, omission, or other misconduct of Landlord or its agents, contractors,
licensees, employees, sublessees or invitees.

        9.1.5  ESTOPPEL CERTIFICATE.

               Upon not less than 10 days' prior notice by 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 



                                      -32-



<PAGE>   34

prospective assignee of Tenant. Any such statement delivered pursuant to this
Section 9.1.5 may be relied upon by any prospective assignee.

        9.1.6  LANDLORD'S TITLE.

               Landlord has delivered to Tenant a copy of Landlord's owner's
policy of title insurance (the "Policy") with respect to the Lot. Landlord has
no knowledge of any changes in the status of the title since the date of the
Policy.

        9.1.7  UTILITIES.

               Utilities shall be installed in the Building and the Premises in
accordance with Exhibit B hereto.

        9.1.8  PAYMENT OF TENANT'S COST OF ENFORCEMENT.

               To pay on demand Tenant's expenses, including reasonable
attorney's fees, incurred in enforcing any obligation of Landlord under this
Lease.

                                    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
and, if to Landlord, at Landlord's Address or such other address as Landlord
shall have last designated by notice in writing to Tenant. Any notice shall be
deemed duly given if mailed to such address postage prepaid, registered or
certified mail, return receipt requested, two (2) days after deposit with the
U.S. Postal Service, or if delivered by a recognized courier service (e.g.
Federal Express) when delivered by such courier service, or if delivered to such
address by hand, when so delivered.

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 Premises or the Building or the Lot and to change or alter
existing boundaries of the Lot for purpose of developing and using the Lot so
long as such easements or such changes or alterations to existing boundaries of
the Lot do not materially interfere with Tenant's use of the Premises, and to
enter upon the Premises for purposes of constructing and maintaining any pipes,
wires and other facilities serving any portion of the Lot or of the Building,
subject to the terms of Section 5.1.7 and Section 10.13 hereof.



                                      -33-


<PAGE>   35

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, if any, 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.

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 except to the extent (i) disclosed on an estoppel
certificate or (ii) the acquiror did not seek an estoppel certificate. The
obligations of Landlord shall be binding upon the assets of Landlord which
comprise the Building and the Lot but not upon other assets of Landlord. 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 the Lot in pursuit of its remedies upon an event of default
hereunder, and the general assets of the partners, trustees, stockholders,
officers, employees or beneficiaries (and the 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 a 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, delays
caused by or resulting from the occurrence of one or more Force Majeure Events
shall not be counted in determining the time during which work shall be
completed, except for the Outside Completion Date, 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 notice from Tenant or such additional time as is reasonably required
to correct any such default after notice has been given by Tenant to Landlord
specifying the nature of Landlord's alleged default provided Landlord commences
such cure within thirty (30) days and proceeds diligently thereafter until such
cure is completed. Landlord shall not be liable in any event for incidental or
consequential damages to Tenant by reason of any default by Landlord hereunder,
whether or not 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.



                                      -34-



<PAGE>   36

        Notwithstanding the foregoing, if any repairs to the Premises or any
maintenance, cleaning, or lighting of the common areas of the Building or the
Lot, are not performed by Landlord or the Premises any time after the
Substantial Completion Date and 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 grammatical 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 or not self-help should have been availed of by
Tenant, or with respect to the reasonableness of the expenses incurred by
Tenant.

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 Lynch
Murphy Walsh & Partners ("Broker") 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 all such
fees to the Broker.

10.9    APPLICABLE LAW AND CONSTRUCTION.

        This Lease shall be governed by and construed in accordance with the
laws of the state in which the Premises are located. 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. 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 above and their
respective heirs, executors, administrators, successors and assigns, and those
claiming through or under them respectively. If 



                                      -35-


<PAGE>   37

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          SECURITY DEPOSIT.

        Within seven (7) days of execution by Tenant of this Lease, Tenant shall
deliver to Landlord an irrevocable and unconditional standby letter of credit
(the "Letter of Credit") naming Landlord as beneficiary thereof in the full
amount of the Security Deposit set forth in Article I hereof in a form
reasonably acceptable to Landlord, which shall secure the performance by Tenant
of all obligations on the part of Tenant hereunder. The issuer of the Letter of
Credit shall be a banking institution with at least a rating of A and otherwise
reasonably acceptable to Landlord. Although Landlord shall only have the right
to draw under the Letter of Credit in the event of a default as set forth
herein, under the terms of the Letter of Credit, the sole condition to
Landlord's draw upon the Letter of Credit shall be presentment to the issuer
thereof, prior to or on the expiration date of the Letter of Credit, of a demand
for payment. The Letter of Credit shall be self-renewing from year to year
during the term of this Lease so as to expire no earlier than thirty (30) days
following the Lease expiration date and shall contain such other customary terms
as Landlord requires in its reasonable discretion, including, but not limited
to, a provision that the Letter of Credit is transferable to Landlord's
successors and assigns and a provision which allows the Landlord to make
multiple draws on the Letter of Credit, up to the stated amount thereof. If
Landlord receives any draw on the Letter of Credit, Tenant, within fifteen (15)
days after the date of such draw, shall cause the issuer of the Letter of Credit
to restore the amount which may be drawn on the Letter of Credit to the full
amount of the Security Deposit. For and during the Term, Landlord shall have the
irrevocable right, without further notice or approval of Tenant but not the
obligation from time to time without prejudice to any other remedy Landlord may
have on account thereof, to apply the Security Deposit or any portion thereof or
interest thereon, to Landlord's damage resulting from any default after
applicable grace and cure periods by Tenant. On termination of the Term, the
Security Deposit, or the portion thereof then held by Landlord shall be returned
to Tenant, beyond the amount necessary to cure the breach of any provision of
this Lease by Tenant. If all or any part of the Security Deposit is applied to
an obligation of Tenant hereunder, Tenant shall immediately upon request by
Landlord restore the Security Deposit to its original amount. Tenant shall not
have the right to call upon Landlord to apply all or any part of the Security
Deposit to cure any default or fulfill any obligation of Tenant, but such use
shall be solely in the discretion of Landlord. Upon any conveyance by Landlord
of its interest under this Lease, the Security Deposit shall be delivered by
Landlord to Landlord's grantee or transferee. Upon any such delivery, Tenant
hereby releases Landlord herein named of any and all liability with respect to
the Security Deposit, its application and return, and Tenant agrees to look
solely to such grantee or transferee. It is further understood that this
provision shall also apply to subsequent grantees and transferees.

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 five (5) 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. If
Tenant shall desire to exercise any Option to Extend, it shall give Landlord a



                                      -36-



<PAGE>   38

notice (the "Inquiry Notice") of such desire not later than twelve (12) 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 (c) below) for the applicable Extension Period shall be
determined in accordance with Subsection (d) below. After the applicable Fair
Market Rent has been so determined, Tenant shall exercise each Option to Extend
by giving Landlord notice (the "Exercise Notice") of its election to do so not
later than nine (9) months prior to the expiration of the Initial Term of this
Lease, or the preceding Extension Period, as the case may be. If Tenant fails to
timely give either the Inquiry Notice or the Exercise Notice to Landlord with
respect to any Option to Extend, Tenant shall be conclusively deemed to have
waived such Option to Extend hereunder.

        (b) Notwithstanding any contrary provision of this Lease, at the sole
election of Landlord, 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 the each Extension Period (i) this Lease is in full
force and effect, and (ii) there is no Event of Default of Tenant under this
Lease.

        (c) All of the terms, provisions, covenants, and conditions of this
Lease shall continue to apply during each Extension Period, except that the
Annual Fixed Rent Rate during each Extension Period (the "Extension Rent") shall
be equal to the fair market rent for the Premises determined as of the date
twelve (12) months prior to expiration of the Initial Term or the preceding
Extension Period, as the case may be, in accordance with the procedure set forth
in Subsection (d) below (the "Fair Market Rent").

        (d) 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 any Option to Extend, Landlord shall give Tenant notice of
Landlord's determination of the Fair Market Rent for the applicable Extension
Period. 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, whereupon the Fair Market Rent shall be determined by
arbitration conducted 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.

        (e) 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 arbitration 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 and MAI
approved (an "Arbitrator"). Within five (5) days thereafter, Landlord shall by
notice to Tenant appoint a second Arbitrator. Each Arbitrator shall be advised
to determine the Fair Market Rent for the applicable Extension Period within
thirty (30) days after Landlord's appointment of the second Arbitrator. On or
before the expiration of such thirty (30) day period, the two Arbitrators shall
confer to compare their respective determinations of the Fair Market Rent. If
the difference between the amounts so determined by the two Arbitrators 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 arbitrators shall have ten (10) days thereafter to appoint a
third Arbitrator (the "Third Arbitrator"), 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 Arbitrators. Each party shall bear the cost of the Arbitrator selected by
such party. The cost for the Third Arbitrator, if any, shall be shared equally
by Landlord and Tenant.



                                      -37-



<PAGE>   39

10.13   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.

10.14   PARKING.

        Tenant shall be obligated to pay as Additional Rent monthly, the then
fair market value (estimated to be $140.00 per space per month in calendar year
1998) for each of the 75 parking spaces to be leased to Tenant located at the
garage (the "Garage") at 47 Erie Street, Cambridge, Massachusetts, to be owned
or controlled by Landlord or an affiliate of Landlord, which parking spaces may
only be utilized by Tenant's employees, visitors, sublesees or assignees,
visiting or working at the Premises. In the event Landlord is unable to provide
said parking spaces in the Garage, Landlord shall be required to provide
alternate parking spaces in a location acceptable to Tenant in its reasonable
discretion. Failure by Landlord to provide said parking spaces shall be a
Landlord's Default.

10.15   SIGNAGE.

        Tenant shall be permitted, at its sole cost and expense, to 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 By-Law, as amended from time to time. 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.

10.16   ACCESS.

        Tenant shall have exclusive access to the Building and the Premises
shown on Exhibit A attached hereto. Tenant shall have access to the Building 24
hours a day, 7 days per week and 365 days a year. Normal hours of operation of
the Building are Monday through Friday, 8:00 a.m. to 6:00 p.m.




                                      -38-
<PAGE>   40


        WITNESS the execution hereof under seal as of this 12th day of June,
1998.

               LANDLORD:

                                         /s/ David E. Clem 
                                     ___________________________________________
                                     David E. Clem, Trustee and not individually


                                         /s/ David M. Roby
                                     ___________________________________________
                                     David M. Roby, Trustee and not individually


               TENANT:               MILLENNIUM PHARMACEUTICALS, INC.


                                     By: 
                                         /s/ Janet C. Bush
                                         _______________________________________
                                         Janet C. Bush
                                         Vice President, Finance
                                          
                                     Its:
                                             hereunto duly authorized




                                      -39-
<PAGE>   41



                                    EXHIBIT B

                           BASE BUILDING IMPROVEMENTS


GENERAL

The base building is designed to provide services for seven tenants, four
tenants at ground floor, two at first floor, and one on second floor.

FIRE PROTECTION

The tenant space is completely sprinklered, the system is based on ordinary
hazard and a 10' x 10' grid with upright sprinklers. The tenant shall
reconfigure sprinklers in order to meet their space and requirements.

PLUMBING

The domestic water and non-potable water system varies from 80 psi at ground
floor to 55 psi at penthouse level.

Tenant plumbing provisions have been made in (6 ) equally spaced shafts.

Provisions made at each shaft location on each floor as follows:

         -      4" acid waste capped connection 
         -      4" vent waste capped connection.

Provisions made at (3) shafts per floor are as follows:

         -      4" acid waste capped connection 
         -      4" vent waste capped connection
         -      2" natural gas valved and capped connection 
         -      2" cold water valved and capped connection 
         -      2" non-potable cold water valved and capped.

Seven independent acid waste and vent systems have been designed. These systems
shall terminate in the Ground Floor Mechanical Room. 300 SF of this Ground Floor
Mechanical Room space has been allocated for seven PH neutralization systems.

HVAC

(3) 24,000 CFM air handling units, (2) 150 ton chillers, (2) 3000 MBH boilers
all located in Penthouse which serve (5) equally spaced shafts.

Provisions made at each shaft are as follows:

At Ground Floor

         -   6600 CFM ducted supply
         -   6600 CFM ducted return
         -   (2) 900 CFM, 12" diameter ducts for fume hood exhaust with capped 
             connections at roof and floor served


<PAGE>   42
                                   EXHIBIT B                            Page 2


         -   1-1/2" chilled water supply and return for supplemental cooling 
             (13 gpm) with valved and capped connections
         -   1" hot water supply and return (2 GPM) valved and capped 
             connections.

At First Floor:

         -   4000 CFM ducted supply.
         -   2200 CFM ducted return.
         -   (2) 900 CFM, 12" diameter ducts for fume hood exhaust with capped
             connections at roof and floor served.
         -   1" hot water and return (2 GPM) valved and capped connections.

At Second Floor:

         -   4000 CFM ducted supply.
         -   2200 CFM ducted return.
         -   (2) 900 CFM, 12" diameter fume hood exhaust with capped connections
             at roof and floor served.
         -   1" hot water and return (2 GPM) valved and capped connections.

At each floor, perimeter fin tube heating is provided.

At Penthouse level, approximately 1500 SF is allocated for tenant use (i.e for
additional air handling unit, chiller, or similar equipment).

ELECTRICAL

At each floor, the tenant shall be provided with (2) electrical closets and (1)
telephone closet. Each electrical closet has (1) 400 AMP main circuit breaker,
277/480 volt, 3 phase, 4 wire distribution panelboard. Space is allocated for
two 112.5kVA transformers and two 400 amp main circuit breaker, 120/208 volt, 3
phase, 4 wire panelboards within each closet. The telephone closet has been
provided with one backboard.


<PAGE>   43


                                   EXHIBIT C

                              RULES AND REGULATIONS

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

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

3.      Tenant, or the employees, agents, servants, visitors or licensees of
        Tenant shall not at any time place, leave or discard any rubbish, paper,
        articles, or objects of any kind whatsoever outside of the Building.
        Bicycles shall not be permitted in the Building except in designated
        areas.

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

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

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

7.      No awning or other projections shall be attached to the outside walls or
        windows. No curtains, blinds, shades, screens or signs other than those
        furnished by Landlord shall be attached to, hung in, or used in
        connection with any exterior window or door of the Building without
        prior written consent of Landlord, such consent not to be unreasonably
        withheld.

8.      No sign, advertisement, object, notice or other lettering, except as set
        forth in Section 10.15 of the Lease, shall be exhibited, inscribed,
        painted or affixed on any part of the outside or inside of the Building
        if visible from outside of the Building.

9.      Door keys for doors in the Building will be furnished on the
        Commencement Date by Landlord. If Tenant shall affix additional locks on
        doors then Tenant shall furnish Landlord with copies of keys for said
        locks.

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



<PAGE>   44
                                   EXHIBIT C                            Page 2


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

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

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

14.     Except as permitted under Article III of the Lease, Tenant shall not
        mark, paint, drill into, or in any way deface any part of the Building
        or Premises. No boring, driving of nails or screws, cutting or stringing
        of wires shall be permitted except with the prior written consent of
        Landlord not to be unreasonably withheld, and as Landlord may direct.
        Tenant shall not install any resilient tile or similar floor covering in
        the Premises except with the prior written approval of Landlord not to
        be unreasonably withheld. The use of cement or other similar adhesive
        material is expressly prohibited.

15.     Building employees shall not be required to perform, and shall not be
        requested by any tenant or occupant to perform, any work outside of
        their regular duties, unless under specific instructions from the office
        of the Managing Agent of the Building.

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




<PAGE>   45



                                    EXHIBIT D

                                  PHASE I PLANS

The plans and specifications described in the three-page attachment hereto
prepared by Siena Construction Corporation entitled "Project #09757 270 Albany
Street Fitout."




<PAGE>   46


                                    EXHIBIT E

                BRIEF OUTLINE OF DESIGN AND CONSTRUCTION PROCESS

                                    PHASE II

Receive final space program*                 ____________, 1998
Initial layout review with MPI*              ____________, 199__
Receive equipment listing*                   ____________, 199__
Schematic sign-off approval*                 ____________, 199__
CAD shells to consultants*                   ____________, 199__
Early release package*                       ____________, 199__
Design development approval*                 ____________, 199__
Full construction documents*                 ____________, 199__
Occupancy Permit                             September 1, 1999

*Tenant shall provide to Landlord proposed dates with respect to these items for
Landlord's approval, which approval shall not be unreasonably withheld.




<PAGE>   47



                                    EXHIBIT F

                              INTENTIONALLY OMITTED




<PAGE>   48



                                    EXHIBIT G

                        REFER TO EXHIBIT B OF THIS LEASE.




<PAGE>   49

                                    EXHIBIT H

                          SCHEDULE OF FLOOR LOAD LIMITS

Lower Level: 100 pounds per square feet (psf).

First Floor (including new entry and loading dock areas): 100 psf.

Second Floor: 100 psf.

Penthouse Floor: 70 psf.




<PAGE>   50

                                    EXHIBIT I

                               LANDLORD'S SERVICES

I.      EXTERIOR MAINTENANCE

        Landlord shall keep the Lot and Common Areas of the Building clean and
        free of debris.

        Landlord shall keep the sidewalks, driveways and parking areas
        reasonably clear of snow and ice.

        Landlord shall maintain the exterior landscaping, lighting, parking
        areas, exterior roof, slab, foundation, exterior doors and windows, and
        sidewalks of the Building and the Lot in good repair and condition
        consistent with facilities of the size and quality of the Building and
        the Lot in the Cambridge, Massachusetts area.

II.     MECHANICAL, ELECTRICAL AND PLUMBING

        Subject to the provisions of Section 5.1.3 of the Lease, Landlord shall
        maintain in good repair and condition the mechanical, electrical and
        plumbing systems for the Building.

III.    PRIORITY

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

IV.     PARKING LOT SECURITY

        Landlord agrees to provide security for the parking lot should be the
        same become necessary in its reasonable discretion.

V.      CLEANING

        Landlord shall keep clean and neat the public areas of the Building and
        Lot, including, without limitation, the restrooms.