<PAGE>   1
                                                                   Exhibit 10.28

                               EXHIBIT 1, SHEET 1
                                Building No. 600
                                TECHNOLOGY SQUARE
                         Cambridge, Massachusetts 02139

                                   LEASE DATA

Execution Date:     NOVEMBER 28, 2000

Tenant:             AKAMAI TECHNOLOGIES, INC.
                    a Delaware corporation

Mailing Address:    Akamai Technologies, Inc.
                    500 Technology Square
                    Cambridge, Massachusetts 02139-3539

Landlord:           TECHNOLOGY SQUARE LLC, a Delaware limited liability company
                    (the sole manager of which is Beacon Capital Partners L.P.,
                    a Delaware limited partnership d/b/a Beacon Capital Partners
                    Limited Partnership; the sole general partner of which is
                    Beacon Capital Partners, Inc., a Maryland corporation)

Mailing Address:    c/o Beacon Capital Partners, One Federal Street, Boston,
                    Massachusetts 02110, Attention: General Counsel

Complex:            The land, buildings and other improvements thereon, from
                    time to time, located off Main Street in the City of
                    Cambridge, Middlesex County, Commonwealth of Massachusetts
                    known as Technology Square. The Complex is initially
                    substantially as shown on Exhibit 6, Sheet 1, and the legal
                    description of the Complex is set forth on Exhibit 6, Sheets
                    2, 3, and 4; however, the Complex may change from time to
                    time as set forth herein. Without limiting the foregoing,
                    the parties acknowledge that the Complex presently consists
                    of Buildings 200, 400 and 500. The parties anticipate that
                    Building 300 will be added to the Complex in May 2001;
                    Building 600 will be added to the Complex on or before the
                    Full Rent Commencement Date and Building 700 will be added
                    to the Complex one month after Building 600. There is no
                    current estimate of when Building 100 will be added to the
                    Complex.

Building:           600 Technology Square, Cambridge, Massachusetts

Premises:           A PORTION OF THE FIRST (1ST) AND THE ENTIRETY OF THE
                    SECOND (2ND), THIRD (3RD), FOURTH (4TH) AND FIFTH
                    (5TH) FLOORS OF THE BUILDING, SUBSTANTIALLY AS SHOWN
                    ON LEASE PLAN, EXHIBIT 2, SHEETS 1, 2, 3, 4 AND 5.

Art. 3.1            Specified Commencement Date:         May 1, 2001

<PAGE>   2

                               EXHIBIT 1, SHEET 2
                                Building No. 600
                                TECHNOLOGY SQUARE
                         Cambridge, Massachusetts 02139

                        Tenant: AKAMAI TECHNOLOGIES, INC.
                        Execution Date: NOVEMBER 28, 2000


                    Term Commencement Date: Substantial Completion Date

                    Estimated Full Rent Commencement Date:      October 1, 2001

Art. 3.2            Termination Date:  TWELVE (12) YEARS AFTER THE FULL RENT
                                       COMMENCEMENT DATE

Art. 4.3            Landlord's Construction Representative: Greg Walsh

                    Tenant's Construction Representative: Skip Hartwell

Art. 5              Use of Premises: GENERAL BUSINESS OFFICE USE

Art. 6              Yearly Rent:

                    RENT YEAR            YEARLY RENT      MONTHLY PAYMENT

                     1 - 6:(1)          $6,818,760.00      $568,230.00

                      7-12:             $7,386,990.00      $615,582.50

Art. 7              Total Rentable Area of the Premises:    113,646 square feet

                    Total Rentable Area of the Building:    127,150 square feet

                    Total Rentable Non-Retail Area of
                        the Building                        113,646 square feet

                    Initial Total Rentable Area of the Complex:

                    Buildings 200, 400 and 500              532,279 square feet
                    Building 300                            175,226 square feet
                    Building 600                            127,150 square feet

----------------------------
(1) For the purposes of this Lease, "Rent Year 1" shall be defined as the
twelve-(12)-month period commencing as of the Rent Commencement Date and ending
on the last day of the month in which the first (1st) anniversary of the Rent
Commencement Date occurs. Thereafter, "Rent Year" shall be defined as any twelve
(12) month period during the term of the Lease commencing as of the first (1st)
day of the month following the month in which any anniversary of the Rent
Commencement Date occurs.

                                       -2-
<PAGE>   3

                               EXHIBIT 1, SHEET 3
                                Building No. 600
                                TECHNOLOGY SQUARE
                         Cambridge, Massachusetts 02139

                        Tenant: AKAMAI TECHNOLOGIES, INC.
                        Execution Date: NOVEMBER 28, 2000

                    Building 700                             49,508 square feet

Art. 8              Electricity:     Electric current will be metered and paid
                                     for by Tenant in accordance with Article
                                     8.1 of the Lease.

Art. 9              Operating and Tax Escalation:

                         Operating Cost Base: $681,876.00 (i.e. $6.00 per square
                                              foot of Total Rentable Area of the
                                              Non-Retail Area of the Building)

                         Tax Base:            $397,761.00 (i.e. $3.50 per square
                                              foot of the Total Rentable Area of
                                              the Premises)

                         Tenant's Building Operating Cost Percentage:  100%

                         Tenant's Building Tax Percentage: 89.38%

                         Tenant's Complex Tax Percentage: The Total Rentable
                         Area of the Premises divided by the Total Rentable Area
                         of the Complex, as the same may change from time to
                         time.

Art. 29.3           Co-Brokers:    INSIGNIA/ESG AND SPAULDING & SLYE

Art. 29.5           Arbitration:   SUPERIOR COURT; MIDDLESEX COUNTY

                    Exhibit Date:  LEASE PLAN, EXHIBIT 2, SHEETS 1, 2, 3, 4 AND
                                   5 DATED NOVEMBER 28, 2000

                                      -3-
<PAGE>   4

                               EXHIBIT 1, SHEET 4
                                Building No. 600
                                TECHNOLOGY SQUARE
                         Cambridge, Massachusetts 02139

                        Tenant: AKAMAI TECHNOLOGIES, INC.
                        Execution Date: NOVEMBER 28, 2000

LANDLORD:                               TENANT:

TECHNOLOGY SQUARE LLC,                  AKAMAI TECHNOLOGIES, INC.
a Delaware limited liability company    a Delaware corporation

By: Beacon Capital Partners L.P.,
    a Delaware limited partnership
    d/b/a Beacon Capital Partners
    Limited Partnership, its manager

    By: Beacon Capital Partners, Inc., a
        Maryland corporation, its general
        partner

        By: /s/ Thomas Ragno            By: /s/ Kathryn L. Jorden
            -----------------------         ----------------------------
        Name: Thomas Ragno              Name: /s/ Kathryn L. Jorden
                                              --------------------------
        Title: Senior Vice President    Title: VP, General Counsel
                                               -------------------------
Date Signed: 12/05/00                   Date Signed: 12/05/00
             ----------------------                  -------------------


                                      -4-
<PAGE>   5

                                TABLE OF CONTENTS



<TABLE>
<S>                                                                          <C>
1.       REFERENCE DATA                                                       1


2.       DESCRIPTION OF DEMISED PREMISES                                      1
         2.1      DEMISED PREMISES............................................1
         2.2      APPURTENANT RIGHTS..........................................1
         2.3      PARKING.....................................................1
         2.4      EXCLUSIONS AND RESERVATIONS.................................2


3.       TERM OF LEASE                                                        2
         3.1      DEFINITIONS.................................................2
         3.2      HABENDUM....................................................3
         3.3      DECLARATION FIXING TERM COMMENCEMENT DATE...................3


4.       CONSTRUCTION                                                         3
         4.0      LANDLORD'S WORK.............................................3
         4.1      TENANT'S REMEDIES BASED ON DELAYS IN LANDLORD'S WORK........9
         4.2      TENANT'S WORK..............................................11
         4.3      QUALITY AND PERFORMANCE OF WORK............................13


5.       USE OF PREMISES                                                     13
         5.1      PERMITTED USE..............................................13
         5.2      PROHIBITED USES............................................14
         5.3      LICENSES AND PERMITS.......................................14


6.       RENT AND SPECIAL ALLOWANCE                                          14
         6.1.     RENT.......................................................14
         6.2      LANDLORD'S CONTRIBUTION....................................15


7.       RENTABLE AREA                                                       17


8.       SERVICES FURNISHED BY LANDLORD                                      17
         8.1      ELECTRIC CURRENT...........................................17
         8.2      WATER......................................................18
         8.3      ELEVATORS, HEAT, CLEANING..................................18
         8.4      AIR CONDITIONING...........................................19
         8.5      ADDITIONAL HEAT, CLEANING AND AIR CONDITIONING SERVICES....19
         8.6      ADDITIONAL AIR CONDITIONING EQUIPMENT......................19
         8.7      REPAIRS....................................................20
         8.8      INTERRUPTION OF CURTAILMENT OF SERVICES....................20
</TABLE>

                                      -i-
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<TABLE>
<S>                                                                          <C>
         8.9      ENERGY CONSERVATION........................................21
         8.10     MISCELLANEOUS..............................................21


9.       ESCALATION                                                          21
         9.1      DEFINITIONS................................................21
         9.2      TAX EXCESS.................................................29
         9.3      OPERATING EXPENSE EXCESS...................................30
         9.4      PART YEARS.................................................30
         9.5      EFFECT OF TAKING...........................................30
         9.6      ADJUSTMENT OF OPERATING COSTS BASED UPON OCCUPANCY.........31
         9.7      EFFECT OF CONVERSION OF COMPLEX TO A CONDOMINIUM...........31
         9.8      DISPUTES, ETC..............................................31
         9.9      TENANT'S AUDIT RIGHTS......................................31


10.      CHANGES OR ALTERATIONS BY LANDLORD                                  35


11.      FIXTURES, EQUIPMENT AND IMPROVEMENTS--REMOVAL BY TENANT             35


12.      ALTERATIONS AND IMPROVEMENTS BY TENANT                              36


13.      TENANT'S CONTRACTORS--MECHANICS' AND OTHER LIENS--
         STANDARD OF TENANT'S PERFORMANCE--COMPLIANCE WITH LAWS              37


14.      REPAIRS BY TENANT--FLOOR LOAD                                       39
         14.1     REPAIRS BY TENANT..........................................39
         14.2     FLOOR LOAD--HEAVY MACHINERY................................39


15.      INSURANCE, INDEMNIFICATION, EXONERATION AND EXCULPATION             39
         15.1     GENERAL LIABILITY INSURANCE................................39
         15.2     CERTIFICATES OF INSURANCE..................................40
         15.3     GENERAL....................................................40
         15.4     PROPERTY OF TENANT.........................................41
         15.5     BURSTING OF PIPES, ETC.....................................41
         15.6     REPAIRS AND ALTERATIONS--NO DIMINUTION OF RENTAL VALUE.....42


16.      ASSIGNMENT, MORTGAGING AND SUBLETTING                               42


17.      MISCELLANEOUS COVENANTS                                             46
         17.1     RULES AND REGULATIONS......................................46
         17.2     ACCESS TO PREMISES--SHORING................................47
         17.3     ACCIDENTS TO SANITARY AND OTHER SYSTEMS....................47
</TABLE>

                                      -ii-
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<TABLE>
<S>                                                                          <C>
         17.4     SIGNS, BLINDS AND DRAPES...................................48
         17.5     ESTOPPEL CERTIFICATE.......................................49
         17.6     PROHIBITED MATERIALS AND PROPERTY..........................49
         17.7     REQUIREMENTS OF LAW--FINES AND PENALTIES...................49
         17.8     TENANT'S ACTS--EFFECT ON INSURANCE.........................50
         17.9     MISCELLANEOUS..............................................50


18.      DAMAGE BY FIRE, ETC.                                                50


19.      WAIVER OF SUBROGATION                                               53


20.      CONDEMNATION - EMINENT DOMAIN                                       53


21.      DEFAULT                                                             55
         21.1     CONDITIONS OF LIMITATION - RE-ENTRY - TERMINATION..........55
         21.2     INTENTIONALLY OMITTED......................................56
         21.3     DAMAGES - TERMINATION......................................56
         21.4     FEES AND EXPENSES..........................................57
         21.5     WAIVER OF REDEMPTION.......................................57
         21.6     LANDLORD'S REMEDIES NOT EXCLUSIVE..........................58
         21.7     GRACE PERIOD...............................................58


22.      END OF TERM - ABANDONED PROPERTY                                    58


23.      SUBORDINATION                                                       59


24.      QUIET ENJOYMENT                                                     61


25.      ENTIRE AGREEMENT -- WAIVER -- SURRENDER                             62
         25.1     ENTIRE AGREEMENT...........................................62
         25.2     WAIVER.....................................................62
         25.3     SURRENDER..................................................62


26.      INABILITY TO PERFORM - EXCULPATORY CLAUSE                           63


27.      BILLS AND NOTICES                                                   63


28.      PARTIES BOUND -- SEIZIN OF TITLE                                    64
</TABLE>

                                     -iii-
<PAGE>   8

<TABLE>
<S>                                                                          <C>
29.      MISCELLANEOUS                                                       64
         29.1     SEPARABILITY...............................................64
         29.2     CAPTIONS, ETC..............................................64
         29.3     BROKER.....................................................65
         29.4     MODIFICATIONS..............................................65
         29.5     ARBITRATION................................................65
         29.6     GOVERNING LAW..............................................66
         29.7     ASSIGNMENT OF RENTS........................................66
         29.8     REPRESENTATION OF AUTHORITY................................66
         29.9     EXPENSES INCURRED BY LANDLORD UPON TENANT REQUESTS.........66
         29.10    RETAIL AREA................................................67
         29.11    SURVIVAL...................................................67


EXHIBIT 2  Lease Plan                                                        69


EXHIBIT 2-1  Plan of Complex                                                 70


EXHIBIT 3  Requirements for Tenant's Plans                                   71


EXHIBIT 4  Building Services                                                 72


EXHIBIT 5  Form of Letter of Credit                                          75


EXHIBIT 6  Base Building Specifications                                      77


EXHIBIT 7  Exterior Signage                                                  78


EXHIBIT 8  Tenant's Removable Property                                       79



RIDER TO LEASE                                                               80
</TABLE>

                                      -iv-
<PAGE>   9

     THIS INDENTURE OF LEASE made and entered into on the Execution Date as
stated in Exhibit 1 and between the Landlord and the Tenant named in Exhibit 1.

Landlord does hereby demise and lease to Tenant, and Tenant does hereby hire and
take from Landlord, the Premises hereinafter mentioned and described
(hereinafter referred to as "Premises"), upon and subject to the covenants,
agreements, terms, provisions and conditions of this Lease for the term
hereinafter stated:

1.   REFERENCE DATA

     Each reference in this Lease to any of the terms and titles contained in
any Exhibit attached to this Lease shall be deemed and construed to incorporate
the data stated under that term or title in such Exhibit.

2.   DESCRIPTION OF DEMISED PREMISES

     2.1  DEMISED PREMISES. The Premises are that portion of the Building as
described in Exhibit 1 and is hereinafter referred to as "Building",
substantially as shown hatched or outlined on the Lease Plan (Exhibit 2) hereto
attached and incorporated by reference as a part hereof.

     2.2  APPURTENANT RIGHTS. Tenant shall have, as appurtenant to the Premises,
rights to use in common, with others entitled thereto, subject to reasonable
rules from time to time made by Landlord of which Tenant is given notice; (a)
the common lobbies, hallways, stairways and elevators of the Building, serving
the Premises in common with others, (b) common walkways necessary for access to
the Building, and (c) if the Premises include less than the entire rentable area
of any floor, the common toilets and other common facilities of such floor; and
no other appurtenant rights or easements. Landlord shall allow Tenant's
telecommunication service provider to have access to the Building and to
Tenant's Premises, provided however, that Landlord shall have the right to
charge Tenant's provider fees in connection with the services being performed by
such provider. Notwithstanding the foregoing, so long as Tenant's
telecommunications service provider ("Provider") does not provide
telecommunications service to any other tenant of the Building, Landlord shall
not require such Provider to pay any fees for such access.

     2.3  PARKING. During the term of the Lease, commencing on the Rent
Commencement Date (and, if there is more than one Rent Commencement Date
pursuant to Article 3.1 hereof commencing on a pro rata basis with each such
Rent Commencement Date), the Landlord will make available, at Tenant's written
request, which request must be made on or before the Full Rent Commencement
Date, up to one and one-half (1.5) monthly parking passes per 1,000 square feet
of Total Rentable Area leased by Tenant (the "Parking Space Cap") for use in the
garage of the Complex or surface parking areas in the Building, as the same may
change from time to time ("Parking Areas"). If Tenant fails timely to make such
request for any such parking passes, Tenant shall have no right to obtain such
parking passes under this Article 2.3, except to the extent thereafter
available, as more specifically set forth herein. If Tenant requests fewer
passes than the Parking Space Cap prior to the Full Rent Commencement Date,
Tenant shall have the right, from time to time during the term of the Lease, to
request additional parking passes up to the Parking Space Cap. If Landlord has
such passes available, Landlord will provide the same to Tenant (but in no event
more than the Parking Space Cap), provided

                                      -1-
<PAGE>   10

however, that, if such passes are not available, Landlord shall have no
obligation to provide additional passes to Tenant. Tenant shall have no right to
sublet, assign, or otherwise transfer said parking passes, other than to an
Assignee or a Qualified Transferee pursuant to an approved assignment or
sublease under Article 16 of the Lease. Said parking passes shall be paid for by
Tenant at the then current prevailing rate in the Parking Areas, as such rate
may vary from time to time. If, for any reason, Tenant shall fail timely to pay
the charge for said parking passes, and if such default continues for ten (10)
days after written notice, Tenant shall have no further right to the parking
passes for which Tenant failed to pay the charge under this Article 2.3. Said
parking passes will be on an unassigned, non-reserved basis, and shall be
subject to such reasonable and uniform rules and regulations as may be in effect
for the use of said Parking Areas (including, without limitation, Landlord's
right, without additional charge to Tenant above the prevailing rate for parking
passes, to institute a valet or attendant-managed parking system), from time to
time in force.

     2.4  EXCLUSIONS AND RESERVATIONS. All the perimeter walls of the Premises
except the inner surfaces thereof, any balconies (except to the extent same are
shown as part of the Premises on the Lease Plan (Exhibit 2)), terraces or roofs
adjacent to the Premises, and any space in or adjacent to the Premises used for
shafts, stacks, pipes, conduits, wires and appurtenant fixtures, fan rooms,
ducts, electric or other utilities, sinks or other Building facilities, and the
use thereof, as well as the right of access through the Premises for the
purposes of operation, maintenance, decoration and repair, are expressly
excluded from the Premises and reserved to Landlord.

3.   TERM OF LEASE.

     3.1  DEFINITIONS. As used in this Lease the words and terms which follow
mean and include the following:

          (a)  "SPECIFIED COMMENCEMENT DATE" - The "Specified Commencement Date"
is the date (as stated in Exhibit 1) on which it is estimated that Landlord's
Work Necessary to Trigger Term Commencement Date will be substantially
completed.

          (b)  "TERM COMMENCEMENT DATE" - The "Term Commencement Date" is the
date on which the First Substantial Completion Date, as defined in Article
4.0(b), occurs.

          (c)  "RENT COMMENCEMENT DATE" - Subject to the provisions of this
Article 3.1(c), the "Rent Commencement Date" is the earlier of (i) the Outside
Rent Commencement Date, as defined in Article 3.1(d), or (ii) the date Tenant
takes possession of the whole of the Premises for use and operation of Tenant's
business as set forth in Exhibit 1. If Tenant takes earlier possession of any
portion of any floor on which the Premises are located prior to the Outside Rent
Commencement Date for use as set forth in Exhibit 1, then the Rent Commencement
Date for the entirety of the portion of the Premises located on such floor shall
occur as of the date that Tenant first takes such possession. As used herein,
the term "FULL RENT COMMENCEMENT DATE" shall mean the date on which the Rent
Commencement Date has occurred for the entirety of the Premises.

          (d)  "OUTSIDE RENT COMMENCEMENT DATE" - Subject to the provisions of
this Article 3.1(d), the "Outside Rent Commencement Date" shall be later of: (i)
one hundred fifty (150) days after the Term Commencement Date, or (ii) one
hundred twenty (120) days after

                                      -2-
<PAGE>   11

the Third and Fourth Floor Substantial Completion Date, as hereinafter defined,
or (iii) ninety (90) days after the First and Second Floor Substantial
Completion Date, as hereinafter defined, or (iv) sixty (60) days after the
Permanent Power Turn-On Date, as hereinafter defined, or (v) the Base Building
Substantial Completion Date, as hereinafter defined, or (vi) five (5) days after
the HVAC Operational Date, as hereinafter defined. Notwithstanding the
foregoing, if Tenant does not, in fact, substantially complete Tenant's Work
prior to the Outside Rent Commencement Date, as determined pursuant to the first
sentence of this Article 3.1(d), and if any Landlord Delays occur, then the
Outside Rent Commencement Date shall be extended by the number of days that any
Landlord Delay actually delays the substantial completion of Tenant's Work
beyond the Outside Rent Commencement Date, as determined pursuant to the first
sentence of this Article 3.1(d).

     3.2  HABENDUM. TO HAVE AND TO HOLD the Premises for a term of years
commencing on the Term Commencement Date and ending on the Termination Date as
stated in Exhibit 1 or on such earlier date upon which said term may expire or
be terminated pursuant to any of the conditions of limitation or other
provisions of this Lease or pursuant to law (which date for the termination of
the terms hereof will hereafter be called "Termination Date"). Notwithstanding
the foregoing, if the Termination Date as stated in Exhibit 1 shall fall on
other than the last day of a calendar month, said Termination Date shall be
deemed to be the last day of the calendar month in which said Termination Date
occurs.

     3.3  DECLARATION FIXING TERM COMMENCEMENT DATE, RENT COMMENCEMENT DATE, AND
TERMINATION DATE. As soon as may be after the execution date hereof, each of the
parties hereto agrees, upon demand of the other party to join in the execution,
in recordable form, of a statutory notice, memorandum, etc. of lease and/or
written declaration in which shall be stated the Term Commencement Date, the
Rent Commencement Date(s), and (if need be) the Termination Date. If this Lease
is terminated before the term expires, then upon Landlord's request the parties
shall execute, deliver and record an instrument acknowledging such fact and the
date of termination of this Lease, and Tenant hereby appoints Landlord its
attorney-in-fact in its name and behalf to execute such instrument if Tenant
shall fail to execute and deliver such instrument after Landlord's request
therefor within ten (10) days.

4.   CONSTRUCTION

     4.0  LANDLORD'S WORK.

     (a)  Landlord, at Landlord's sole cost and expense, shall perform the base
building work ("LANDLORD'S WORK") as defined in the Base Building Specifications
attached hereto as Exhibit 6. Landlord shall not make any material change in the
Base Building Specifications without obtaining the prior written approval of
Tenant (which approval shall not be unreasonably withheld, conditioned, or
delayed). Without limiting the foregoing, Landlord shall not make any material
changes in the finishes of the lobby of the Building without obtaining the prior
written approval of Tenant (which approval shall not be unreasonably withheld,
conditioned, or delayed). Notwithstanding the foregoing, Tenant hereby agrees
that: (i) with respect to the glasswall finish adjacent to the retail areas in
the lobby, Landlord may use an alternate wall finish in lieu of the materials
specified in the Base Building Specifications (which alternate finish shall be
at least equal in quality to the finishes contained in the lobby at 500
Technology Square as of the date hereof) and Landlord shall perform, as part of
the Landlord's Work, whatever sprinkler work is required by applicable codes in
connection with such wall finish, and

                                      -3-
<PAGE>   12

(ii) with respect to the lobby walls, Landlord may use an alternate finish in
lieu of the finish specified in the Base Building Specifications, provided that
such alternate finish is at least equal in quality to the finishes contained in
the lobby at 500 Technology Square as of the date hereof. Subject to delays due
to governmental regulation, unusual scarcity of or inability to obtain labor or
materials, labor difficulties, casualty or other causes reasonably beyond
Landlord's control (collectively "Landlord's Force Majeure"), Landlord shall use
reasonable speed and diligence in the construction of Landlord Work Necessary to
Trigger Term Commencement Date (as defined in Article 4.0(g) below) so as to
have the same substantially completed on or before the Specified Commencement
Date set forth in Exhibit 1, but Tenant shall have no claim against Landlord for
failure to complete construction of Landlord's Work, except as expressly set
forth in Article 4.1. In each such instance of Landlord's Force Majeure,
Landlord shall exercise reasonable diligence to eliminate the cause of such
inability to perform.

     (b)  The "FIRST SUBSTANTIAL COMPLETION DATE" shall be defined as the date
on which the Landlord's Work Necessary to Trigger Term Commencement Date, as
defined in Article 4.0(g), has been substantially completed, so that any
remaining Landlord's Work can be performed with a minimum of interference or
delay in the progress of Tenant's Work on the fifth floor, Tenant acknowledging,
however, the priority of Landlord's Work, as set forth in Article 4.2(c).

     (c)  The "THIRD AND FOURTH FLOOR SUBSTANTIAL COMPLETION DATE" shall be
defined as the date on which Landlord's Work Necessary to Trigger Third and
Fourth Floor Substantial Completion Date, as defined in Article 4.0(h), has been
substantially completed, so that any remaining Landlord's Work can be performed
with a minimum of interference or delay in the progress of Tenant's Work on the
third and fourth floors, Tenant acknowledging, however, the priority of
Landlord's Work, as set forth in Article 4.2(c). Notwithstanding the foregoing,
in the event of any Tenant Delays which actually delay the performance of
Landlord's Work Necessary to Trigger Third and Fourth Floor Substantial
Completion Date, the Third and Fourth Floor Substantial Completion Date shall be
defined as the date on which Landlord's Work Necessary to Trigger Third and
Fourth Floor Substantial Completion Date would have been substantially completed
but for such Tenant Delays.

     (d)  The "FIRST AND SECOND FLOOR SUBSTANTIAL COMPLETION DATE" shall be
defined as the date on which Landlord's Work Necessary to Trigger First and
Second Floor Substantial Completion Date, as defined in Article 4.0(i), has been
substantially completed, so that any remaining Landlord's Work can be performed
with a minimum of interference or delay in the progress of Tenant's Work on the
first and second floors, Tenant acknowledging, however, the priority of
Landlord's Work, as set forth in Article 4.2(c). Notwithstanding the foregoing,
in the event of any Tenant Delays which actually delay the performance of
Landlord's Work Necessary to Trigger First and Second Floor Substantial
Completion Date, the First and Second Floor Substantial Completion Date shall be
defined as the date on which Landlord's Work Necessary to Trigger First and
Second Floor Substantial Completion Date would have been substantially completed
but for such Tenant Delays.

     (e)  The "PERMANENT POWER TURN-ON DATE" shall be defined as the date on
which Landlord has made permanent electric power and the base building heating
and air conditioning system operational for the entire Premises, except that in
the event of any Tenant Delays which actually delay Landlord's ability to
achieve the Permanent Power Turn-On Date, the Permanent Power Turn-On Date shall
be defined as the date on which Landlord would have been able to

                                      -4-
<PAGE>   13

make permanent electric power and the base building heating and air conditioning
system operational for the entire Premises but for such Tenant Delays.

     (f)  The "BASE BUILDING SUBSTANTIAL COMPLETION DATE" shall be defined as
the date on which Landlord's Work Necessary to Trigger Rent Commencement Date,
as defined in Article 4.0(j), has been substantially completed, except that in
the event of any Tenant Delays which actually delay the performance of
Landlord's Work Necessary to Trigger Rent Commencement Date, the Base Building
Substantial Completion Date shall be defined as the date on which Landlord's
Work Necessary to Trigger Rent Commencement Date would have been substantially
completed but for such Tenant Delays.

     (g)  The "LANDLORD WORK NECESSARY TO TRIGGER TERM COMMENCEMENT DATE" shall
be defined as the following items of work:

          i.)       Site utilities serving the Building;
          ii.)      Foundation piles, grade beams, and structural slab on grade;
          iii.)     Under slab drainage and utilities;
          iv.)      Structural steel erected and set;
          v.)       Composite concrete decks;
          vi.)      Spray fireproofing;
          vii.)     Precast concrete Building exterior panels;
          viii.)    The fifth floor is Building Tight, as defined in Article
                    4.0(k), and
          ix.)      Any other portions of Landlord's Work necessary to enable
                    Tenant and its contractor to commence the Tenant's Work (as
                    defined in Article 4.2) on the fifth floor.

     (h)  The "LANDLORD WORK NECESSARY TO TRIGGER THIRD AND FOURTH FLOOR
SUBSTANTIAL COMPLETION DATE" shall be defined as the following items of work:

          i.)       The Landlord Work Necessary to Trigger Term Commencement
                    Date;
          ii)       Both the third and fourth floors are Building Tight, as
                    defined in Article 4.0(k); and
          iii)      Any other portions of Landlord's Work necessary to enable
                    Tenant and its contractor to commence the Tenant's Work on
                    both the third and fourth floors.

     (i)  The "LANDLORD WORK NECESSARY TO TRIGGER FIRST AND SECOND FLOOR
SUBSTANTIAL COMPLETION DATE" shall be defined as the following items of work:

          i.)       The Landlord Work Necessary to Trigger Term Commencement
                    Date;
          ii.)      The Landlord Work Necessary to Trigger Third and Fourth
                    Floor Substantial Completion Date;
          iii.)     Both the first and second floors are Building Tight, as
                    defined in Article 4.0(k); and
          iv.)      Any other portions of Landlord's Work necessary to enable
                    Tenant and its contractor to commence the Tenant's Work on

                                      -5-
<PAGE>   14

                    the second floor and in the portion of the first floor in
                    which the Premises are located.

     (j)  The Landlord Work necessary to trigger the "BASE BUILDING SUBSTANTIAL
COMPLETION DATE" shall be defined as the following items of work:

          i.)       The Landlord Work Necessary to Trigger Term Commencement
                    Date;
          ii.)      The Landlord Work Necessary to Trigger Third and Fourth
                    Floor Substantial Completion Date;
          iii.)     The Landlord Work Necessary to Trigger First and Second
                    Floor Substantial Completion Date;
          iv.)      The following items of Landlord's Work, to the extent not
                    included in clauses (i), (ii), and (iii) of this Article
                    4.0(j):

                    (a)  Curtainwall;
                    (b)  Roofing;
                    (c)  Windows;
                    (d)  Elevators;
                    (e)  Mechanical, Electrical & Plumbing Systems for Building
                         Core & Shell;
                    (f)  Building Cores including bathroom, mechanical,
                         electrical, and telephone/data rooms;
                    (g)  Building Lobby and Lobby interior finishes to the
                         extent which would be necessary to satisfy the
                         Certificate of Occupancy Test, as defined in Article
                         4.0(l);
                    (h)  Mechanical/Electrical & Plumbing finishes;
                    (i)  Base Building Fire Alarm Panels & Life Safety Systems;
                    (j)  Exterior walkways at least five (5) feet wide and
                         sufficient to permit access to and egress from the
                         Premises and adjacent public streets and parking areas,
                         as well as around the perimeter of the Building; and
                    (k)  All elements of Landlord's Work necessary to satisfy
                         the Certificate of Occupancy Test, as further defined
                         in Article 4.0(l).

Any portion of Landlord's Work which is not completed on or before the Base
Building Substantial Completion Date which affects a particular portion of the
Premises, or the access thereto, shall be completed within thirty (30) days
after a Certificate of Occupancy has been issued for such portion of the
Premises, except for (x) items of Landlord Work which are not complete due to
delays caused by weather (for those items which are weather-sensitive), and (y)
items of Landlord Work which are not complete due to delays caused by long lead
time items and causes beyond Landlord's reasonable control (provided, however,
that items of Landlord Work which are not complete due to delays caused by long
lead time items and causes beyond Landlord's reasonable control shall in any
event be completed within ninety (90) days after the issuance of the Certificate
of Occupancy for the portion of the Premises in question). Without limiting the
foregoing, the final balancing of mechanical systems need not be completed as of
the Rent Commencement Date, however, the air handling units serving the Premises
shall be

                                      -6-
<PAGE>   15

operational (the date such units are made operational being herein referred to
as the "HVAC Operational Date").

     (k)  BUILDING TIGHT. Any floor shall be deemed to be "Building Tight" if
all of the following have been achieved:

          i.)       The roof of the Building has been installed and is
                    weather-tight;
          ii.)      The windows on such floor have been installed and are
                    weather-tight;
          iii.)     The precast concrete on such floor has been installed and
                    is weather-tight;
          iv.)      All core walls facing the tenanted areas of such floor have
                    been substantially completed;
          v.)       The perimeter wall of the Building on such floor has been
                    installed, is weather tight and has interior drywall ready
                    for finish treatment;
          vi.)      Temporary power is available to Tenant on such floor;
          vii.)     All base building mechanical systems which are to be
                    provided to such floor have been stubbed to such floor.

     (l)  CERTIFICATE OF OCCUPANCY TEST.

          i.)  As a Condition to the Base Building Substantial Completion Date.
Reference is made to clauses (g) and (j) of Article 4.0(j)(iv), which provide
that, as a condition to achieving the Base Building Substantial Completion Date,
Landlord's Work must have been completed to the extent necessary to enable
Tenant to obtain a Certificate of Occupancy for the Premises (hereinafter
referred to as the "Certificate of Occupancy Test"). Landlord shall apply to the
Building Inspector of the City of Cambridge ("Building Inspector") for a
Certificate of Occupancy with respect to Landlord's Work ("Base Building") in
order to assist the parties in determining whether the Base Building Substantial
Completion Date has occurred. If the Building Inspector issues a Base Building
Certificate of Occupancy, the Certificate of Occupancy Test shall be
conclusively deemed to have been satisfied. The parties acknowledge that: (a) if
Tenant's Work has not progressed to the point where Tenant is able to apply for
a Certificate of Occupancy with respect to at least a portion of the Premises,
the Building Inspector may not be willing to perform such inspection, (b) given
that Tenant's Work includes a portion of the sprinkler system, the Building
Inspector may not be able to issue a Base Building Certificate of Occupancy if
Tenant's Work is not complete, and (c) other incomplete portions of Tenant's
Work may prevent Landlord from obtaining a Base Building Certificate of
Occupancy. If the Building Inspector is willing to perform such inspection and
if the Building Inspector denies the issuance of the Base Building Certificate
of Occupancy based solely on deficiencies identified by the Building Inspector
in Landlord's Work, then the Certificate of Occupancy Test shall not be deemed
satisfied until Landlord corrects such deficiencies to the satisfaction of the
Building Inspector. If, despite Landlord's application for a Base Building
Certificate of Occupancy, the Building Inspector does not perform such
inspection, or if the Building Inspector performs such inspection, but does not
identify any deficiencies in Landlord's Work and does not issue a Base Building
Certificate of Occupancy, then the Certificate of Occupancy Test may still be
satisfied as follows: Landlord shall notify Tenant when it believes that all of
Landlord's Work necessary for Tenant to obtain a Certificate of Occupancy has
been substantially completed ("Landlord's Completion Notice"). If Tenant
disputes Landlord's assertion of substantial

                                      -7-
<PAGE>   16

completion, it shall so notify Landlord within ten (10) days after receipt of
Landlord's Completion Notice, whereupon such dispute shall be immediately
submitted to arbitration in accordance with the provisions of Article 29.5. The
parties hereby acknowledge that Tenant, and not Landlord, is responsible for all
items of Tenant's Work which must be completed in order to enable Tenant to
obtain a Certificate of Occupancy for the Premises and in no event shall
Landlord be deemed to have failed to satisfy the Certificate of Occupancy Test
based upon any deficiency or lack of completion of Tenant's Work.

          ii.) Tenant's Inability to Obtain a Certificate of Occupancy after the
Occurrence of the Base Building Substantial Completion Date. If the Base
Building Substantial Completion Date (i.e. and the Rent Commencement Date)
occurs prior to the issuance of a Certificate of Occupancy with respect to any
portion of the Premises, and if, subsequently Tenant is denied a Certificate of
Occupancy with respect to any portion of the Premises, solely by reason of any
deficiency in Landlord's Work, then: (x) Landlord shall, as promptly as
possible, remedy such deficiency so as to remove such impediment to Tenant's
obtaining such Certificate of Occupancy, and (y) Tenant's obligation to pay
Yearly Rent and other charges due under the Lease in respect of the portion of
the Premises which Tenant is unable to occupy because it cannot obtain such
Certificate of Occupancy shall be fully abated during the period of time
commencing as of the date that Tenant is denied such Certificate of Occupancy
until Landlord cures such deficiency in Landlord's Work so that it is no longer
prevents Tenant from obtaining such Certificate of Occupancy.

     (m)  TENANT DELAY. A "Tenant Delay" shall be defined as any act or omission
by Tenant, or any agent, employee, consultant, contractor, or subcontractor of
Tenant, which causes an actual delay in the performance of Landlord's Work
Necessary to Trigger Full Rent Commencement Date. Notwithstanding the foregoing,
no event shall be deemed to be a Tenant Delay until and unless Landlord has
given Tenant written notice ("Tenant Delay Notice") advising Tenant: (i) that a
Tenant Delay is occurring, (ii) of the basis on which Landlord has determined
that a Tenant Delay is occurring, and (iii) the actions which Landlord believes
that Tenant must take to eliminate such Tenant Delay. No period of time prior to
the time that Tenant receives a Tenant Delay Notice shall be included in the
period of time charged to Tenant pursuant to such Tenant Delay Notice.

     (n)  LANDLORD DELAY. A "Landlord Delay" shall be defined as any act or
omission by Landlord or any agent, employee, consultant, contractor or
subcontractor of Landlord which: (i) is not a result of the priority granted to
Landlord's Work as set forth in Article 4.2(c) hereof, and (ii) causes an actual
delay in the performance of Tenant's Work. Notwithstanding the foregoing, except
as set forth in Article 4.2(e), no event shall be deemed to be a Landlord Delay
until and unless Tenant has given Landlord written notice ("Landlord Delay
Notice") advising Landlord: (i) that a Landlord Delay is occurring, (ii) of the
basis on which Tenant has determined that a Landlord Delay is occurring, and
(iii) the actions which Tenant believes that Landlord must take to eliminate
such Landlord Delay. No period of time prior to the time that Landlord receives
a Landlord Delay Notice shall be included in the period of time charged to
Landlord pursuant to such Landlord Delay Notice.

     (o)  LANDLORD'S WARRANTY; SATISFACTION OF LANDLORD'S OBLIGATIONS UNDER
ARTICLE 4.

                                      -8-
<PAGE>   17

     i.)  Landlord's Warranty. Landlord warrants to Tenant that: (x) materials
and equipment furnished in the performance of Landlord's Work will be of good
quality and new unless otherwise required or permitted by the Base Building
Specifications, (y) Landlord's Work will be free from defects not inherent in
the quality required or permitted under the Base Building Specifications, and
(z) Landlord's Work will conform the requirements of the Base Building
Specifications. Any portion of Landlord's Work not conforming to the
requirements of this clause (i), including substitutions not properly approved
and authorized, may be considered defective. Landlord's warranty excludes remedy
for damage or defect caused by abuse, modifications not executed by Landlord,
improper or insufficient maintenance (other than by Landlord, where Landlord is
required to perform maintenance on the item or system in question), improper
operation (other than by Landlord, where Landlord operates the item or system in
question), or normal wear and tear and normal usage.

     ii.) Warranty Period. Landlord shall be deemed to have satisfied all of its
obligations under this Article 4 (including, without limitation, Landlord's
warranty obligations under this Article 4.0(o) and under Article 4.3) except to
the extent that, on or before the Warranty Expiration Date, as hereinafter
defined, Tenant gives written notice to Landlord in accordance with the
provisions of Article 27 setting forth with specificity the manner in which
Tenant believes that Landlord has failed to comply with its obligations under
this Article 4. The "Warranty Expiration Date" shall be defined as the date
three hundred fifty-eight (358) days after the Full Rent Commencement Date.

     iii.) Repair of Defective Work. Landlord agrees that it shall, without cost
to Tenant, correct any portion of Landlord's Work which is found not to be in
accordance with the requirements of the warranties set forth in this Article
4.0(o) and in Article 4.3, unless Tenant has previously given Landlord a written
acceptance of such condition, provided that: Tenant gives Landlord written
notice of such condition in accordance with the provisions of Article 27
promptly after it becomes aware of such condition, and in any event on or before
the Warranty Expiration Date. The provisions of this Article 4.0(o) shall not
relieve Landlord of any obligation which Landlord has to make repairs or to
perform maintenance pursuant to Article 8 of the Lease.

     (p)  Any dispute between the parties with respect to the provisions of this
Article 4 shall be submitted to arbitration in accordance with Article 29.5.

     4.1  TENANT'S REMEDIES BASED ON DELAYS IN LANDLORD'S WORK.

     (a)  If the Term Commencement Date shall not have occurred on or before
October 1, 2001 ("INITIAL OUTSIDE COMPLETION DATE") (which date shall be
extended for up to ninety (90) days on account of any Force Majeure Delays, as
hereinafter defined), Tenant shall have the right to terminate this Lease by
giving notice to Landlord of Tenant's desire to do so before such completion and
within the time period from the Initial Outside Completion Date (as so extended)
until the date which is thirty (30) days subsequent to the Initial Outside
Completion Date (as so extended); and, upon the giving of such notice, the Term
of this Lease shall cease and come to an end without further liability or
obligation on the part of either party unless, within thirty (30) days after
receipt of such notice, the Term Commencement Date occurs. If Tenant terminates
the Lease pursuant to this Paragraph (a), Landlord shall return to Tenant any
Letter of Credit given by Tenant to Landlord within fifteen (15) business days
after Landlord's receipt written request for such return from Tenant, and
Landlord shall reimburse Tenant an amount equal to the

                                      -9-
<PAGE>   18

lesser of: (x) Five Hundred Sixty-Eight Thousand Two Hundred Thirty
($568,230.00) Dollars, or (y) the actual cost incurred by Tenant through the
Effective Termination Date in preparing the plans and specifications for
Tenant's Work. Landlord shall make such payment to Tenant within thirty (30)
days after Tenant delivers to Landlord evidence reasonably satisfactory to
Landlord of the amount such costs. Landlord shall have the right to audit
Tenant's books and records with respect to Tenant's costs.

     (b)  If the Base Building Substantial Completion Date does not occur on or
before March 1, 2002 ("INTERIM OUTSIDE COMPLETION DATE") (which date shall be
extended (i) for the period of any Tenant Delays, and (ii) for up to ninety (90)
days on account of any Force Majeure Delays), Tenant shall have the right to
terminate this Lease by giving notice to Landlord of Tenant's desire to do so
before such completion and within the time period from the Interim Outside
Completion Date (as so extended) until the date which is thirty (30) days
subsequent to the Interim Outside Completion Date (as so extended); and, upon
the giving of such notice ("Effective Termination Date"), the Term of this Lease
shall cease and come to an end without further liability or obligation on the
part of either party unless the Base Building Substantial Completion Date occurs
on or before the date thirty (30) days after receipt of such notice (as so
extended). If Tenant has occupied part of the Premises for the Permitted Use
prior to such termination, then the Effective Termination Date with respect to
the part of the Premises so occupied shall be ninety (90) days subsequent to the
Interim Outside Completion Date (as so extended). If Tenant terminates the Lease
pursuant to this Paragraph (b), Landlord shall return to Tenant any Letter of
Credit given by Tenant to Landlord within fifteen (15) business days after
Landlord's receipt written request for such return from Tenant, and Landlord
shall reimburse Tenant an amount equal to the actual cost incurred by Tenant
through the Effective Termination Date in performing and designing the Tenant's
Work to the extent that such amount exceeds any portion of Landlord's
Contribution theretofore paid to or for the account of Tenant. Landlord shall
make such payment to Tenant within thirty (30) days after Tenant delivers to
Landlord evidence reasonably satisfactory to Landlord of the amount such costs.
Landlord shall have the right to audit Tenant's books and records with respect
to Tenant's costs.

     (c)  If the Base Building Substantial Completion Date does not occur on or
before June 1, 2002 ("FINAL OUTSIDE COMPLETION DATE") (which date shall be
extended for the period of any Tenant Delays), Tenant shall have the right to
terminate this Lease by giving notice to Landlord of Tenant's desire to do so
before such completion and within the time period from the Final Outside
Completion Date until the date which is thirty (30) days subsequent to the Final
Outside Completion Date; and, upon the giving of such notice ("Effective
Termination Date"), the Term of this Lease shall cease and come to an end
without further liability or obligation on the part of either party unless the
Base Building Substantial Completion Date occurs on or before the date thirty
(30) days after receipt of such notice. If Tenant has occupied part of the
Premises for the Permitted Use prior to such termination, then the Effective
Termination Date with respect to the part of the Premises so occupied shall be
ninety (90) days subsequent to the Final Outside Completion Date. If Tenant
terminates the Lease pursuant to this Paragraph (c), Landlord shall return to
Tenant any Letter of Credit given by Tenant to Landlord within fifteen (15)
business days after Landlord's receipt written request for such return from
Tenant, and Landlord shall reimburse Tenant an amount equal to the actual cost
incurred by Tenant through the Effective Termination Date in performing and
designing the Tenant's Work to the extent that such amount exceeds any portion
of Landlord's Contribution theretofore paid to or for the account of Tenant.
Landlord shall make such payment to Tenant within thirty (30) days after Tenant
delivers to

                                      -10-
<PAGE>   19

Landlord evidence reasonably satisfactory to Landlord of the amount such costs.
Landlord shall have the right to audit Tenant's books and records with respect
to Tenant's costs.

     (d)  FORCE MAJEURE DELAYS. For the purposes of this Article 4.1, "Force
Majeure Delays" shall be defined as any delays in the performance of Landlord's
Work to the extent arising from causes beyond Landlord's reasonable control
other than Tenant Delays, provided however, that no delay shall be deemed to be
a Force Majeure Delay unless Landlord advises Tenant in writing of such delay on
or before the date thirty (30) days after Landlord first becomes aware of such
delay.

     (e)  RENT CREDIT. If the Full Rent Commencement Date has not occurred for
all or a portion of the Premises on or before the Liquidated Damage Date, as
hereinafter defined, then with respect to those portion(s) of the Premises with
respect to which the Rent Commencement Date has not occurred, Tenant shall be
entitled to a credit against the Yearly Rent on a day-for-day basis for the
lesser of (i) the number of days from the Liquidated Damage Date to but not
including the Rent Commencement Date with respect to such portion(s) of the
Premises, and (ii) one hundred eighty (180) days. The "Liquidated Damage Date"
shall be defined as December 1, 2001.

     (f)  The remedies set forth in this Article 4.1 are Tenant's sole and
exclusive rights and remedies based upon any delay in the performance of
Landlord's Work. If Tenant terminates this Lease pursuant to this Article 4.1,
then the Third Amendment to the Building 500 Lease (as defined in Article 21.1
hereof) shall also thereby be automatically terminated and of no further force
and effect.

     4.2  TENANT'S WORK.

     (a)  Tenant shall, on or before the Outside Tenant Work Commencement Date,
commence the performance of the work ("Tenant's Work") necessary to prepare the
Premises for Tenant's occupancy, and Tenant shall thereafter diligently
prosecute the Tenant's Work to completion. The "OUTSIDE TENANT WORK COMMENCEMENT
DATE" shall be defined as the date nine (9) months after the Term Commencement
Date, provided that if Tenant is delayed in the commencement of Tenant's Work by
reason of causes beyond Tenant's reasonable control, the Outside Tenant Work
Commencement Date shall be extended by the lesser of: (i) the period of time
which Tenant is so delayed, or (ii) three (3) additional months (i.e. in no
event shall the Outside Tenant Work Commencement Date occur later than the date
one (1) year after the Term Commencement Date).

     (b)  Tenant shall substantially complete Tenant's Work on or before the
Outside Tenant Work Completion Date. The "OUTSIDE TENANT WORK COMPLETION DATE"
shall be defined as the date fifteen (15) months after the Full Rent
Commencement Date, provided that if Tenant is delayed in the performance of
Tenant's Work by reason of causes beyond Tenant's reasonable control, the
Outside Tenant Work Completion Date shall be extended by the lesser of: (i) the
period of time which Tenant is so delayed, or (ii) three (3) additional months
(i.e. in no event shall the Outside Tenant Work Completion Date occur later than
the date eighteen (18) months after the Full Rent Commencement Date).

     (c)  COST OF TENANT'S WORK; PRIORITY OF WORK. Except for Landlord's
Contribution, as set forth in Article 6.2, all of the Tenant's Work shall be
performed at Tenant's

                                      -11-
<PAGE>   20

sole cost and expense, and shall be performed in accordance with the provisions
of this Lease (including, without limitation, Articles 11 and 12). Tenant and
Landlord shall each take necessary reasonable measures to the end that Tenant's
contractors and Landlord's contractors shall cooperate in all ways with
Landlord's contractors to avoid any delay in either Landlord's Work or Tenant's
Work or any conflict with the performance of either Landlord's Work or Tenant's
Work, Tenant acknowledging, however, that in the case of conflict that is not
reasonably avoidable, the performance of Landlord's Work shall have priority.
Tenant shall pay to Landlord, as additional rent, within ten (10) days of
billing therefor, charges (which shall be reasonably based on Tenant's usage)
for the use of elevators and/or hoisting in connection with the performance of
Tenant's Work. Tenant shall have access to the Premises and the Building on a
24-hour a day, 365-day a year basis in order to perform Tenant's Work. Landlord
and Tenant recognize that to the extent Tenant elects to perform some or all of
Tenant's Work during times other than normal construction hours, Landlord will
need to make arrangements to have supervisory personnel on site. Accordingly,
Landlord and Tenant agree as follows: Tenant shall give Landlord at least five
(5) days' written notice of any time outside of normal construction hours (i.e.,
Monday-Friday, 7 a.m. to 3 p.m., excluding holidays) when Tenant intends to
perform portions of Tenant's Work (the "After Hours Work"). Landlord shall pay
the cost of the first one hundred hours, in the aggregate, of Landlord's
supervisory personnel overseeing the After Hours Work. Tenant shall reimburse
Landlord, within thirty (30) days after demand therefor, for the cost of all
additional hours of Landlord's supervisory personnel overseeing the After Hours
Work. Landlord shall notify Tenant of the after hours hourly rates (which shall
be normal and customary) for such supervisory personnel from time to time upon
written request.

     (d)  TENANT'S PLANS. In connection with the performance of Tenant's Work,
Tenant shall submit to Landlord for Landlord's reasonable approval an initial
set of plans ("Initial Plans"), progress plans from time to time ("Interim
Plans") and a full set of construction drawings ("Final Plans") for Tenant's
Work (collectively "the Plans"). The Final Plans shall contain at least the
information required by, and shall conform to the requirements of, Exhibit 3.
Landlord's approval of the Initial Plans and the Interim Plans (and the Final
Plans, provided that the Final Plans are consistent with the Initial Plans and
the Interim Plans and contain at least the information required by, and conform
to the requirements of, said Exhibit 3), shall not be unreasonably withheld,
conditioned or delayed and shall comply with the requirements to avoid aesthetic
or other conflicts with the design and function of the balance of the Building.
Landlord's approval is solely given for the benefit of Landlord under this
Article 4.2 and neither Tenant nor any third party shall have the right to rely
upon Landlord's approval of Tenant's Plans for any other purpose whatsoever.
Without limiting the foregoing, Tenant shall be responsible for all elements of
the design of Tenant's plans (including, without limitation, compliance with
law, functionality of design, the structural integrity of the design, the
configuration of the Premises and the placement of Tenant's furniture,
appliances and equipment), and Landlord's approval of Tenant's Plans shall in no
event relieve Tenant of the responsibility for such design.

     (e)  TIME PERIODS FOR LANDLORD'S RESPONSE TO TENANT'S PLANS. Landlord
agrees to respond to any Initial Plans within ten (10) days of receipt thereof
and to Interim Plans and the Final Plans within fifteen (15) days of receipt
thereof. If Landlord has not responded to any submission of Tenant's Plans
within the ten (10) or fifteen (15) day, as applicable, time period set forth
above, then Tenant may send Landlord a notice of such failure to respond, which
notice ("Second Notice") shall contain the following language in bold face and
all capital letters: "SECOND NOTICE. FAILURE TO RESPOND TO THIS NOTICE WITHIN
FIVE (5)

                                      -12-
<PAGE>   21

DAYS SHALL CONSTITUTE A LANDLORD DELAY UNDER THE LEASE, WHICH MAY ENTITLE TENANT
TO A RENT ABATEMENT." If Landlord does not respond to the submission of Tenant's
Plans within five (5) days after receipt of the Second Notice, then each
additional day after five (5) days before Landlord responds to such submission
shall constitute a Landlord Delay.

     (f)  TENANT'S HOIST. Subject to Landlord's prior written approval of
Tenant's plans and specifications therefor (which approval shall not be
unreasonably withheld, conditioned, or delayed), Tenant shall have the right,
during the performance of Tenant's Work, to install a hoist at the Building in
order to enable Tenant's contractor to perform Tenant's Work. Tenant shall
maintain such hoist in good condition and in a manner which does not interfere
with the performance of Landlord's Work. The initial location of such hoist
shall be as reasonably approved by Tenant, recognizing the priority given to
Landlord's Work in Article 4.2(c) hereof. Once such hoist is installed, Tenant
shall not be required to relocate such hoist, except that Tenant shall remove
such hoist from the Building at the time that Landlord makes available to Tenant
an elevator for Tenant's exclusive use. Tenant shall repair any damage to the
Building caused by the installation or removal of such hoist.

     (g)  GAS LINE. Subject to (i) Landlord's prior written approval of Tenant's
plans and specifications therefor (which approval shall not be unreasonably
withheld, conditioned, or delayed), and (ii) Tenant having obtained all
necessary governmental approvals therefor, Landlord shall bring natural gas to
the perimeter of the Building at Landlord's expense and Tenant shall have the
right to tie into the same at its expense for the purpose of serving Tenant's
back-up generator.

     4.3  QUALITY AND PERFORMANCE OF WORK. All construction work required or
permitted by this Lease (whether constituting part of Landlord's Work or
Tenant's Work) shall be done in a good and workmanlike manner and in compliance
with all applicable laws, ordinances, rules, regulations, statutes, by-laws,
court decisions, and orders and requirements of all public authorities ("Legal
Requirements") and all insurance requirements of this Lease. All of Tenant's
Work shall be coordinated with any work being performed by, or for, Landlord,
and in such manner as to maintain harmonious labor relations. Each party
authorizes the other to rely in connection with design and construction upon the
written approval or other written authorizations on the party's behalf by any
Construction Representative of the party designated by the party. Each party's
initial Construction Representative is designated on Exhibit 1.

5.   USE OF PREMISES

     5.1  PERMITTED USE. Tenant shall continuously during the term hereof occupy
and use the Premises only for the purposes as stated in Exhibit 1 and for no
other purposes. Service and utility areas (whether or not a part of the
Premises) shall be used only for the particular purpose for which they were
designed. Without limiting the generality of the foregoing, Tenant agrees that
it shall not use the Premises or any part thereof, or permit the Premises or any
part thereof to be used for the preparation or dispensing of food, whether by
vending machines or otherwise. Notwithstanding the foregoing, but subject to the
other terms and provisions of this Lease, Tenant may, with Landlord's prior
written consent, which consent shall not be unreasonably withheld, install at
its own cost and expense so-called hot-cold water fountains, coffee makers and
refrigerator-sink-stove combinations for the preparation of beverages and foods,
provided that no cooking, frying, etc., are carried on in the Premises to such
extent as

                                      -13-
<PAGE>   22

requires special exhaust venting, Tenant hereby acknowledging that the Building
is not engineered to provide any such special venting. Landlord hereby agrees
that any equipment shown on Tenant's final approved plans and equivalent
equipment in substitution of such equipment shall not, if maintained in good
operating order, be deemed to violate the provisions of this Article 5.1.

     5.2  PROHIBITED USES. Notwithstanding any other provision of this Lease,
Tenant shall not use, or suffer or permit the use or occupancy of, or suffer or
permit anything to be done in or anything to be brought into or kept in or about
the Premises or the Building or any part thereof (including, without limitation,
any materials appliances or equipment used in the construction or other
preparation of the Premises and furniture and carpeting): (i) which would
violate any of the covenants, agreements, terms, provisions and conditions of
this Lease or otherwise applicable to or binding upon the Premises; (ii) for any
unlawful purposes or in any unlawful manner; (iii) which, in the reasonable
judgment of Landlord shall in any way (a) impair the appearance or reputation of
the Building; or (b) impair, interfere with or otherwise diminish the quality of
any of the Building services or the proper and economic heating, cleaning,
ventilating, air conditioning or other servicing of the Building; or Premises,
or with the use or occupancy of any of the other areas of the Building, or
occasion discomfort, inconvenience or annoyance, or injury or damage to any
occupants of the Premises or other tenants or occupants of the Building; or (iv)
which is inconsistent with the maintenance of the Building as an office building
of the first class in the quality of its maintenance, use, or occupancy. Tenant
shall not install or use any electrical or other equipment of any kind which, in
the reasonable judgment of Landlord, might cause any such impairment,
interference, discomfort, inconvenience, annoyance or injury.

     5.3  LICENSES AND PERMITS. If any governmental license or permit shall be
required for the proper and lawful conduct of Tenant's business, and if the
failure to secure such license or permit would in any way affect Landlord, the
Premises, the Building or Tenant's ability to perform any of its obligations
under this Lease, Tenant, at Tenant's expense, shall duly procure and thereafter
maintain such license and submit the same to inspection by Landlord. Tenant, at
Tenant's expense, shall at all times comply with the terms and conditions of
each such license or permit. Tenant shall furnish all data and information to
governmental authorities and Landlord as required in accordance with legal,
regulatory, licensing or other similar requirements as they relate to Tenant's
use or occupancy of the Premises or the Building.

6.   RENT AND SPECIAL ALLOWANCE

     6.1. RENT.

     (a)  During the term of this Lease the Yearly Rent and other charges, at
the rate stated in Exhibit 1, shall be payable by Tenant to Landlord by monthly
payments, as stated in Exhibit 1, in advance and without demand on the first day
of each month for and in respect of such month. The rent and other charges
reserved and covenanted to be paid under this Lease in respect of the Premises
shall commence on the Rent Commencement Date. If, by reason of any provisions of
this Lease, the rent reserved hereunder shall commence or terminate on any day
other than the first day of a calendar month, the rent for such calendar month
shall be prorated. The rent shall be payable to Landlord or, if Landlord shall
so direct in writing, to Landlord's agent or nominee, in lawful money of the
United States which shall be legal tender for payment of all debts and dues,
public and private, at the time of payment, at the office of the Landlord or

                                      -14-
<PAGE>   23

such place as Landlord may designate, and the rent and other charges in all
circumstances shall be payable without any setoff or deduction whatsoever.
Rental and any other sums due hereunder not paid on or before the date which is
five (5) business days after the date due shall bear interest for each month or
fraction thereof from the due date until paid computed at the annual rate of
three percentage points over the so-called prime rate then currently from time
to time charged to its most favored corporate customers by the largest national
bank (N.A.) located in the city in which the Building is located ("National
Bank"), or at any applicable lesser maximum legally permissible rate for debts
of this nature. In lieu of requiring Tenant to pay monthly installments of
Yearly Rent and other fixed monthly charges in the manner described above,
Tenant shall have the right to pay such amounts by means of an automated debit
system (the "Automatic Debit System") whereby any or all such payments shall be
debited from Tenant's account in a bank or financial institution designated by
Tenant and credited to Landlord's account in a bank or financial institution
designated by Landlord. In the event Tenant elects to pay monthly installments
of Yearly Rent and other fixed monthly charges by means of the Automatic Debit
System, Tenant, within thirty (30) days after written request by Landlord, shall
execute and deliver to Landlord any authorizations, certificates or other
documentation as may be required to establish and give effect to the Automatic
Debit System. Either party shall have the right to change its bank or financial
institution from time to time, provided that Tenant, no less than thirty (30)
days prior to the effective date of any such change, shall provide Landlord with
written notice of such change and any and all authorizations, certificates or
other documentation as may be required to establish and give effect to the
Automatic Debit System at Tenant's new bank or financial institution if Tenant
elects to continue to use such Automatic Debit System. Tenant shall promptly pay
all service fees and other charges imposed upon Tenant in connection with the
Automatic Debit System, and Tenant shall promptly reimburse Landlord for any
charges resulting from insufficient funds in Tenant's bank account (provided
however, that Tenant shall have the right to discontinue the use of the
Automatic Debit System at any time upon at least thirty (30) days' prior written
notice to Landlord). In the event that any Yearly Rent or other fixed monthly
charges are not paid on time as a result of insufficient funds in Tenant's
account, Tenant shall be liable for any interest in accordance with this
Article. Tenant shall remain liable to Landlord for all payments of Rent due
hereunder regardless of whether Tenant's account is incorrectly debited in any
given month, it being agreed that a debit of less than the full amount due shall
not be construed as a waiver by Landlord of its right to receive any unpaid
balance.

     (b)  Rentable Area. Landlord and Tenant acknowledge the Total Rentable Area
of the Premises, the Building and of the other buildings initially in the
Complex have been determined by agreement, and that the figures set forth in
Exhibit 1 shall be conclusive and binding on Landlord and Tenant with regard to
the Complex. In the event that Landlord alters any of the buildings in, or adds
other buildings to, the Complex, the Total Rentable Area of any such buildings
shall be included in the Total Rentable Area of the Complex when first occupied.

     6.2  LANDLORD'S CONTRIBUTION.

     (a)  As an inducement to Tenant's entering into this Lease, Landlord shall
provide to Tenant a special allowance equal to up to Thirty and 00/100 Dollars
($30.00) per square foot of Rentable Floor Area of the Premises initially
demised to Tenant (i.e. Three Million Four Hundred Nine Thousand Three Hundred
Eighty and 00/100 Dollars ($3,409,380.00)) ("Landlord's Contribution") to be
used by Tenant to pay for the cost of the Tenant's Work. For

                                      -15-
<PAGE>   24

the purposes hereof, the cost to be so reimbursed by Landlord shall include the
cost of leasehold improvements but not the cost of any of Tenant's personal
property, trade fixtures or trade equipment or any so-called soft costs.
Furthermore, in the event that Tenant does not build out all of the Premises,
Landlord's Contribution shall be limited to a maximum of Thirty and 00/100
Dollars ($30.00) per square foot of Rentable Floor Area of the Premises actually
built out by Tenant (the "Finished Area").

     (b)  Landlord shall pay Landlord's Proportion (as hereinafter defined) of
the cost shown on each requisition (as hereinafter defined) submitted by Tenant
to Landlord within twenty (20) days of submission thereof by Tenant to Landlord
until the entirety of Landlord's Contribution has been exhausted. For purposes
hereof, "Landlord's Proportion" shall be a fraction, the numerator of which is
Landlord's Contribution and the denominator of which is the total contract price
for Tenant's Work, and a "requisition" shall mean written documentation
(including, without limitation, invoices from Tenant's contractors, vendors,
service providers and consultants, lien waivers, and such other documentation as
Landlord or Landlord's mortgagee may reasonably request) showing in reasonable
detail the costs of the item in question or of the improvements installed to
date in the Premises, accompanied by certifications from Tenant that the amount
of the requisition in question does not exceed the cost of the items, services
and work covered by such requisition. Each requisition shall be accompanied by
evidence reasonably satisfactory to Landlord that items, services and work
covered by such requisition has been fully paid by Tenant and that the work has
been performed. Landlord shall have the right, upon reasonable advance notice to
Tenant, to inspect Tenant's books and records relating to each requisition in
order to verify the amount thereof. Tenant shall submit requisition(s) no more
often than monthly.

     (c)  Notwithstanding anything to the contrary herein contained:

          (i)  Landlord shall have no obligation to advance funds on account of
               Landlord's Contribution unless and until Landlord has received
               the requisition in question.

          (ii) Except with respect to work and/or materials previously paid for
               by Tenant, as evidenced by paid invoices and written lien waivers
               provided to Landlord, Landlord shall have the right to have
               Landlord's Contribution paid to directly to Tenant's
               contractor(s), consultants, service providers, and vendor(s). In
               no event shall Landlord's Contribution be applied to any fees
               paid to Tenant or any affiliate of Tenant.

          (iii) Landlord shall have no obligation to pay any portion of
               Landlord's Contribution in respect of any requisition submitted
               after the date ("Outside Requisition Date") which is the earlier
               of: (a) three (3) months after the completion of Tenant's Work,
               or (b) twenty-one (21) months after the Full Rent Commencement
               Date (provided, however, that if Tenant certifies to Landlord
               that it is engaged in a good faith dispute with its contractor,
               such Outside Requisition Date shall be extended while such
               dispute is ongoing, so long as Tenant is diligently prosecuting
               the resolution of such dispute). Tenant shall not be entitled to
               receive any portion of Landlord's Contribution except to the
               extent

                                      -16-
<PAGE>   25

               that it has submitted requisitions and/or made demand therefor,
               on or before the Outside Requisition Date.

          (iv) Tenant shall not be entitled to any unused portion of Landlord's
               Contribution.

          (v)  Landlord's obligation to pay any portion of Landlord's
               Contribution shall be conditioned upon there existing no default
               beyond the expiration of any applicable grace periods by Tenant
               in its obligations under the Lease at the time that Landlord
               would otherwise be required to make such payment.

7.   RENTABLE AREA

     Total Rentable Area of the Premises, the Building and the Complex have, as
of the Execution Date, been agreed to be the amounts set forth on Exhibit 1.

8.   SERVICES FURNISHED BY LANDLORD

     8.1  ELECTRIC CURRENT.

          (a)  As stated in Exhibit 1, Landlord will require Tenant to contract
directly with the company supplying electric current for the purchase and
obtaining by Tenant of electric current directly from such company to be billed
directly to, and paid for by, Tenant. Tenant shall have the right to choose
among companies supplying electric current to the Premises if there is more than
one such company available. Tenant acknowledges that such electric current
purchased directly by Tenant shall include the current used to operate the HVAC
equipment serving the Premises.

          (b)  Landlord shall (i) permit its risers, conduits and feeders to the
extent available, suitable and safely capable, to be used for the purpose of
enabling Tenant to purchase and obtain electric current directly from such
company, (ii) without cost or charge to Tenant, make such alterations and
additions to the electrical equipment and/or appliances in the Building as such
company shall specify for the purpose of enabling Tenant to purchase and obtain
electric current directly from such company, and (iii) at Landlord's expense,
furnish and install in or near the Premises any necessary metering equipment
used in connection with measuring Tenant's consumption of electric current and
Tenant, at Tenant's expense, shall maintain and keep in repair such metering
equipment.

          (c)  If Tenant shall require electric current for use in the Premises
in excess of the capacity available at the commencement of the term of this
Lease and if (i) in Landlord's reasonable judgment, Landlord's facilities are
inadequate for such excess requirements or (ii) such excess use shall result in
an additional burden on the Building air conditioning system and additional cost
to Landlord on account thereof then, as the case may be, (x) Landlord upon
written request and at the sole cost and expense of Tenant, will furnish and
install such additional wire, conduits, feeders, switchboards and appurtenances
as reasonably may be required to supply such additional requirements of Tenant
if current therefor be available to Landlord, provided that the same shall be
permitted by applicable laws and insurance regulations and shall not cause
damage to the Building or the Premises or cause or create a dangerous or
hazardous condition or

                                      -17-
<PAGE>   26

entail excessive or unreasonable alterations or repairs or interfere with or
disturb other tenants or occupants of the Building or (y) Tenant shall reimburse
Landlord for such additional cost, as aforesaid.

          (e)  Landlord, at Tenant's expense and upon Tenant's request, shall
purchase and install all replacement lamps of types generally commercially
available (including, but not limited to, incandescent and fluorescent) used in
the Premises.

          (f)  Subject to Article 8.8(b), Landlord shall not in any way be
liable or responsible to Tenant for any loss, damage or expense which Tenant may
sustain or incur if the quantity, character, or supply of electrical energy is
changed or is no longer available or suitable for Tenant's requirements.

          (g)  Tenant agrees that it will not make any material alteration or
material addition to the electrical equipment and/or appliances in the Premises
without the prior written consent of Landlord in each instance first obtained,
which consent will not be unreasonably withheld, and will promptly advise
Landlord of any other alteration or addition to such electrical equipment and/or
appliances.

     8.2  WATER. Landlord shall furnish hot and cold water for ordinary premises
cleaning, toilet, lavatory and drinking purposes. If Tenant requires, uses or
consumes water for any purpose other than for the aforementioned purposes,
Landlord may (i) assess a reasonable charge for the additional water so used or
consumed by Tenant or (ii) install a water meter and thereby measure Tenant's
water consumption for all purposes. In the latter event, Landlord shall pay the
cost of the meter and the cost of installation thereof and shall keep said meter
and installation equipment in good working order and repair. Tenant agrees to
pay for water consumed, as shown on said meter, together with the sewer charge
based on said meter charges, as and when bills are rendered, and on default in
making such payment Landlord may pay such charges and collect the same from
Tenant, but only to the extent that the charges shown on the meter exceed the
consumption reasonably expected for ordinary premises cleaning, toilet, lavatory
and drinking purposes. All piping and other equipment and facilities for use of
water outside the building core will be installed and maintained by Landlord at
Tenant's sole cost and expense.

     8.3  ELEVATORS, HEAT, CLEANING.

          (a)  Landlord at its expense shall: (i) provide necessary elevator
facilities (which may be manually or automatically operated, either or both, as
Landlord may from time to time elect) on Mondays through Fridays, excepting
legal holidays, from 8:00 a.m. to 6:00 p.m. and on Saturdays, excepting legal
holidays, from 8:00 a.m. to 1:00 p.m. (called "business days") and have one
elevator in operation available for Tenant's use, non-exclusively, together with
others having business in the Building, at all other times; (ii) furnish heat
(substantially equivalent to that being furnished in comparably aged similarly
equipped office buildings in the same city) to the Premises during the normal
heating season on business days; and (iii) cause the office areas and the
network operations center of the Premises to be cleaned on business days (except
on Saturdays) provided the same are kept in order by Tenant. Either Exhibit 4
(if annexed hereto) or, otherwise, the cleaning standards generally prevailing
in first-class office buildings in the city or town where the Building is
located, shall represent substantially the extent and scope of the cleaning by
Landlord referred to in this Article 8.3.

                                      -18-
<PAGE>   27

          (b)  The parties agree and acknowledge that, despite reasonable
precautions in selecting cleaning and maintenance contractors and personnel, any
property or equipment in the Premises of a delicate, fragile or vulnerable
nature may nevertheless be damaged in the course of cleaning and maintenance
services being performed. Accordingly, Tenant shall take reasonable protective
precautions with such property and equipment (including, without limitation,
computers or other data processing components or equipment and optical or
electronic equipment, etc.), e.g., housing the property and equipment in a
separate, locked room, so as to render it inaccessible to the Building's
cleaning personnel.

     8.4  AIR CONDITIONING. Landlord shall through the air conditioning
equipment of the Building furnish to and distribute in the Premises air
conditioning as normal seasonal changes may require on business days during the
hours as aforesaid in Article 8.3 when air conditioning may reasonably be
required for the comfortable occupancy of the Premises by Tenant. Tenant agrees
to use reasonable efforts to lower and close the blinds or drapes when necessary
because of the sun's position, whenever the air conditioning system is in
operation, and to cooperate fully with Landlord with regard to, and to abide by
all the reasonable regulations and requirements which Landlord may prescribe for
the proper functioning and protection of the air conditioning system. The air
conditioning system referred to in this Article 8.4 shall be capable of
maintaining the following: the air conditioning system referred to in this
Article 8.4 shall be capable of providing 75(Degree)F dry bulb and 55% of
relative humidity with outside conditions of 91(Degree)F dry bulb and
73(Degree)F wet bulb.

     8.5  ADDITIONAL HEAT, CLEANING AND AIR CONDITIONING SERVICES.

          (a)  Landlord will use reasonable efforts upon reasonable advance
written notice from Tenant of its requirements in that regard, to furnish
additional heat, cleaning or air conditioning services to the Premises on days
and at times other than as above provided.

          (b)  There shall be no charge for additional heat or air conditioning,
as Tenant pays the cost of electricity therefor directly pursuant to Article
8.1. Tenant will pay to Landlord a reasonable charge (i) for any such additional
cleaning service required by Tenant, (ii) for any extra cleaning of the Premises
required because of the carelessness or indifference of Tenant or because of the
nature of Tenant's business, and (iii) for any cleaning done at the request of
Tenant of any portions of the Premises which may be used for storage, shipping
room or other non-office purposes. If the cost to Landlord for cleaning the
Premises shall be increased due to the installation in the Premises, at Tenant's
request, of any materials or finish other than those which are building
standard, Tenant shall pay to Landlord an amount equal to such increase in cost.

     8.6  ADDITIONAL AIR CONDITIONING EQUIPMENT. In the event Tenant requires
additional air conditioning for business machines, meeting rooms or other
special purposes, or because of occupancy or excess electrical loads, any
additional air conditioning units, chillers, condensers, compressors, ducts,
piping and other equipment, such additional air conditioning equipment will be
installed and maintained by Landlord at Tenant's sole cost and expense, but only
if, in Landlord's reasonable judgment, the same will not cause damage or injury
to the Building or create a dangerous or hazardous condition or entail excessive
or unreasonable alterations, repairs or expense or interfere with or disturb
other tenants; and Tenant shall

                                      -19-
<PAGE>   28

reimburse Landlord in such an amount as will compensate it for the cost incurred
by it in operating such additional air conditioning equipment.

     8.7  REPAIRS. Except as otherwise provided in Articles 18 and 20, and
subject to Tenant's obligations in Article 14, Landlord shall keep and maintain
the roof, exterior walls, structural floor slabs, columns, elevators, public
stairways and corridors, lavatories, equipment (including, without limitation,
sanitary, electrical, heating, air conditioning, or other systems) and other
common facilities of the Building in good condition and repair.

     8.8  INTERRUPTION OR CURTAILMENT OF SERVICES.

          (a)  When necessary by reason of accident or emergency, or for
repairs, alterations, replacements or improvements which in the reasonable
judgment of Landlord are desirable or necessary to be made, or of difficulty or
inability in securing supplies or labor, or of strikes, or of any other cause
beyond the reasonable control of Landlord, whether such other cause be similar
or dissimilar to those hereinabove specifically mentioned until said cause has
been removed, Landlord reserves the right to interrupt, curtail, stop or suspend
(i) the furnishing of heating, elevator, air conditioning, and cleaning services
and (ii) the operation of the plumbing and electric systems. Landlord shall
exercise reasonable diligence to eliminate the cause of any such interruption,
curtailment, stoppage or suspension, but there shall be no diminution or
abatement of rent or other compensation due from Landlord to Tenant hereunder,
nor shall this Lease be affected or any of the Tenant's obligations hereunder
reduced, and the Landlord shall have no responsibility or liability for any such
interruption, curtailment, stoppage, or suspension of services or systems.

          (b)  Notwithstanding anything to the contrary in this Lease contained,
if the Premises shall lack any service which Landlord is required to provide
hereunder, or if Tenant's use and occupancy of the Premises shall be disturbed
in violation of Article 10 hereof (thereby rendering the Premises or a portion
thereof substantially untenantable) so that, for the Landlord Service
Interruption Cure Period, as hereinafter defined, the continued operation in the
ordinary course of Tenant's business is materially adversely affected and if
Tenant ceases to use the affected portion of the Premises during the period of
untenantability as the direct result of such lack of service or disturbance,
then, provided that Tenant ceases to use the affected portion of the Premises
during the entirety of the Landlord Service Interruption Cure Period and that
such untenantability and Landlord's inability to cure such condition is not
caused by the fault or neglect of Tenant or Tenant's agents, employees or
contractors, Yearly Rent, Operating Expense Excess and Tax Excess shall
thereafter be abated in proportion to such untenantability until the day such
condition is completely corrected. For the purposes hereof, the "Landlord
Service Interruption Cure Period" shall be defined as five (5) consecutive
business days after Landlord's receipt of written notice from Tenant of the
condition causing untenantability in the Premises, provided however, that the
Landlord Service Interruption Cure Period shall be ten (10) consecutive business
days after Landlord's receipt of written notice from Tenant of such condition
causing untenantability in the Premises if either the condition was caused by
causes beyond Landlord's control or Landlord is unable to cure such condition as
the result of causes beyond Landlord's control.

          (c)  The provisions of Paragraph (b) of this Article 8.8 shall not
apply in the event of untenantability caused by fire or other casualty, or
taking (see Articles 18 and 20).

                                      -20-
<PAGE>   29

     8.9  ENERGY CONSERVATION. Notwithstanding anything to the contrary in this
Article 8 or in this Lease contained, Landlord may institute, and Tenant shall
comply with, such policies, programs and measures as may be necessary, required,
or expedient for the conservation and/or preservation of energy or energy
services, provided however, that Landlord does not, by reason of such policies,
programs and measures, reduce the level of energy or energy services being
provided to the premises below the level of energy or energy services then being
provided in comparably aged, first-class office buildings in the greater Boston
area, or as may be necessary or required to comply with applicable codes, rules
regulations or standards.

     8.10 MISCELLANEOUS. Other than air conditioning, all services provided by
Landlord to Tenant are based upon an assumed maximum Premises population of one
person per one hundred fifty (150) square feet of Total Rentable Area. Tenant
acknowledges that if it exceeds the foregoing limitation, Landlord may incur
costs including, without limitation, additional costs due to the additional load
on building systems. Tenant agrees to reimburse Landlord for the amount of such
costs (if any), as reasonably determined by Landlord, due to a Premises
population in excess of the foregoing maximum.

9.   ESCALATION

     9.1  DEFINITIONS. As used in this Article 9, the words and terms which
follow mean and include the following:

     (a)  "Operating Year" shall mean a calendar year in which occurs any part
of the term of this Lease.

     (b)  "Operating Cost Base" shall be the amount as stated in Exhibit 1.

     (c)  Subject to the provisions of Article 6(b),"Tenant's Building
Percentage" and "Tenant's Complex Percentage" shall be the respective figures as
stated in Exhibit 1.

     (d)  "Taxes":

          Subject to Article 9.7:

          (d1) "Building Taxes" shall mean the real estate taxes and other
     taxes, levies and assessments imposed upon the Building and that portion of
     the land of the Complex comprised of the Building's footprint and an area
     surrounding the Building as shown on Exhibit 2-1, and upon any personal
     property of Landlord used in the operation of the Building, or on
     Landlord's interest in the Building or such personal property (provided
     that to the extent such taxes, levies, and assessments are also allocable
     to property other than the Building, such amounts shall be allocated among
     all real estate which is so jointly assessed based on the assessor's
     records or, if the records do not provide a separate allocation, based on
     square footage of the buildings in question); charges, fees and assessments
     for transit, housing, police, fire or other services or purported benefits
     to the Building; service or user payments in lieu of taxes; and any and all
     other taxes, levies, betterments, assessments and charges arising from the
     ownership, leasing, operating, use or occupancy of the Building or based
     upon rentals derived therefrom, which are or shall be imposed by federal,
     state, county, municipal or other governmental authorities. Notwithstanding
     anything to the contrary herein contained, with respect to

                                      -21-
<PAGE>   30

     betterments or other extraordinary or special assessments, Tenant's
     obligations shall apply only to the extent such assessments are payable
     during and in respect of the term of the Lease if paid over the longest
     period permitted by law. The definition of Building Taxes is subject to the
     provisions of Article 9.1(d4)

          (d2) "Land" shall mean all of the land of the Complex (but not any
     improvements thereon which are separately assessed, except for common
     facilities as set forth in Paragraph (d3) below), excluding, however, the
     land on which the Garage and all other parking areas are located and the
     portions of land under each building in the Complex and an area surrounding
     each such building as shown on Exhibit 2-1, and reasonable similar areas
     designated by Landlord in connection with new buildings added to the
     Complex from time to time. Real estate taxes with respect to such parking
     areas are included in the parking fees charged to users and real estate
     taxes attributable to the land comprised of the footprint and such
     perimeter area of each building in the Complex shall be allocated on a
     building-by-building basis.

          (d3) "Land Taxes" shall mean the real estate taxes and other taxes,
     levies and assessments imposed upon the Land, upon any common facilities
     separately assessed as such by the tax assessor, and upon any personal
     property of Landlord used in connection with the Land, or on Landlord's
     interest in the Land or such personal property (provided that to the extent
     such taxes, levies, and assessments are also allocable to property other
     than the Land, such amounts shall be equitably allocated among all real
     estate which is so jointly assessed); charges, fees and assessments for
     transit, housing, police, fire or other governmental services or purported
     benefits to the Land; service or user payments in lieu of taxes; and any
     and all other taxes, levies, betterments, assessments and charges arising
     from the ownership, leasing, operation, or use of the Land or based upon
     rentals derived therefrom, which are or shall be imposed by federal, state,
     county, municipal or other governmental authorities. Land Taxes shall
     exclude any taxes on any parking garage located on the Land or which are
     otherwise assessed as part of Building Taxes. The definition of Land Taxes
     is subject to the provisions of Article 9.1(d4).

          (d4) As of the Execution Date, neither Building Taxes nor Land Taxes
     shall include any inheritance, estate, succession, gift, franchise, rental,
     income or profit tax, capital stock tax, capital levy or excise, or any
     income taxes arising out of or related to the ownership and operation of
     the Building or Complex, provided, however, that any of the same and any
     other tax, excise, fee, levy, charge or assessment, however described, that
     may in the future be levied or assessed as a substitute for or an addition
     to, in whole or in part, any tax, levy or assessment which would otherwise
     constitute "Taxes," whether or not now customary or in the contemplation of
     the parties on the Execution Date of this Lease, shall constitute "Taxes,"
     but only to the extent calculated as if the Complex were the only real
     estate owned by Landlord. "Taxes" shall also include reasonable expenses of
     tax abatement or other proceedings contesting assessments or levies.

     (e)  "Tax Base" shall be the amount stated in Exhibit 1 and shall apply to
a Tax Period of twelve (12) months. The Tax Base shall be reduced pro rata if
and to the extent that the Tax Period contains fewer than twelve (12) months.

                                      -22-
<PAGE>   31

     (f)  "Tax Period" shall be any fiscal/tax period in respect of which Taxes
are due and payable to the appropriate governmental taxing authority (i.e., as
mandated by the governmental taxing authority), any portion of which period
occurs during the term of this Lease, the first such Period being the one in
which the Rent Commencement Date (or, if there is more than one Rent
Commencement Date hereunder, the first such date) occurs.

     (g)  "Operating Costs":

          Subject to Article 9.7:

          (g1) Definition of Building Operating Costs. "Building Operating
     Costs" shall mean all costs incurred and expenditures of whatever nature
     made by Landlord in the operation and management, for repair and
     replacements, cleaning and maintenance of the non-retail portion of the
     Building, including, without limitation, vehicular and pedestrian
     passageways serving the Building, related equipment, facilities and
     appurtenances and cooling and heating equipment. For costs and expenditures
     made by Landlord in connection with the Building as a whole, Landlord shall
     make a reasonable allocation thereof between the retail and non-retail
     portions of the Building. A portion of Complex Operating Costs shall be
     included in Building Operating Costs in accordance with Subparagraphs g(3)
     and g(6).

          (g2) Definition of Complex Operating Costs. "Complex Operating Costs"
     shall mean all costs incurred and expenditures made by Landlord in the
     operation and management, repair and replacement, cleaning and maintenance
     of the common areas of the Complex, exclusive of the Garage, the Parking
     Areas, the Building, and the other buildings in the Complex. Any expenses
     incurred by Landlord that can be allocated on a building-by-building basis
     shall be so allocated in accordance with Subparagraph (g3). To the extent
     that a cost included in Complex Operating Costs is also allocable to
     property other than the Complex, such cost shall be equitably allocated to
     each parcel of property which benefits from such cost.

          (g3) The allocation of costs and expenditures among the various
     buildings in the Complex shall be on the basis of the ratio of the Total
     Rentable Area of each building in the Complex to the Total Rentable Area of
     the Complex, unless such allocation would result in a disproportionate
     charge based upon the relative usage of the service on which such cost is
     based, in which case such allocation shall be based upon such relative
     usage. Building Operating Costs and Complex Operating Costs shall include,
     without limitation, those categories of "Specifically Included Operating
     Costs", as set forth below, but shall not include "Excluded Costs", as
     hereinafter defined.

          (g4) Definition of Excluded Costs. "Excluded Costs" shall be defined
     as:

               (i)       mortgage charges (including interest, principal, points
                         and fees);

               (ii)      brokerage commissions;

                                      -23-
<PAGE>   32

               (iii)     salaries of executives and owners not directly
                         employed in the management/operation of the Complex;

               (iv)      the cost of work done by Landlord for a particular
                         tenant for which Landlord has the right to be
                         reimbursed by such tenant;

               (v)       subject to Subparagraph (g5) below, such portion of
                         expenditures as are not properly chargeable against
                         income;

               (vi)      any ground or underlying lease rental;

               (vii)     bad debt expenses;

               (viii)    costs incurred by Landlord to the extent that
                         Landlord is reimbursed by insurance proceeds or is
                         otherwise reimbursed, other than through the payment of
                         Operating Costs;

               (ix)      depreciation, amortization and interest payments,
                         except as expressly set forth in subparagraph (g5)
                         below and except on equipment, materials, tools,
                         supplies and vendor-type equipment purchased by
                         Landlord to enable Landlord to supply services Landlord
                         might otherwise contract for with a third party where
                         such depreciation, amortization and interest payments
                         would otherwise have been included in the charge for
                         such third party's services, all as determined in
                         accordance with generally accepted accounting
                         principles, consistently applied, and when depreciation
                         or amortization is permitted or required, the item
                         shall be amortized over its reasonably anticipated
                         useful life;

               (x)       advertising and promotional expenditures, and costs of
                         acquisition and maintenance of one-party signs in or on
                         the Building identifying the owner of the Building or
                         other tenants;

               (xi)      marketing costs, including leasing commissions,
                         attorneys' fees (in connection with the negotiation and
                         preparation of letters, deal memos, letters of intent,
                         leases, subleases and/or assignments), space planning
                         costs and other costs and expenses incurred in
                         connection with lease, sublease and/or assignment
                         negotiations and transactions with present or
                         prospective tenants or other occupants of the Building;

                                      -24-
<PAGE>   33

               (xii)     costs, including permit, license and inspection costs,
                         incurred with respect to the installation of tenants'
                         or other occupants' improvements or incurred in
                         renovating or otherwise improving, decorating, painting
                         or redecorating vacant space for tenants or other
                         occupants of the Building;

               (xiii)    expenses in connection with services or other
                         benefits which are offered to other tenants of the
                         Building or Complex but not to Tenant or for which
                         Tenant is charged directly, other than through
                         Operating Costs;

               (xiv)     fines, interest and penalties incurred by Landlord due
                         to the violation by Landlord or any tenant of the terms
                         and conditions of any lease of space in the Building;

               (xv)      management fees paid or charged by Landlord in
                         connection with the management of the Building to the
                         extent such management fee is in excess of the market
                         rate.

               (xvi)     salaries and other benefits paid to any executive
                         employees above the level of senior property manager of
                         the Complex;

               (xvii)    amounts paid to Landlord or to subsidiaries or
                         affiliates of Landlord for goods and/or services in the
                         Building to the extent the same exceeds the costs of
                         such goods and/or services rendered by unaffiliated
                         third parties on a competitive basis;

               (xviii)   Landlord's general corporate overhead and general
                         administrative expenses;

               (xix)     any compensation paid to clerks, attendants or other
                         persons in commercial concessions operated by Landlord;

               (xx)      services provided, taxes, attributable to, and costs
                         incurred in connection with the operation (as opposed
                         to the repair and maintenance thereof which shall be
                         included in Operating Costs) of any garage for the
                         Building, and any replacement garages or parking
                         facilities;

               (xxi)     costs incurred in connection with upgrading the
                         Building to comply with laws, rules, regulations and
                         codes in effect prior to the Term Commencement Date;

                                      -25-
<PAGE>   34

               (xxii)    fines, interest and penalties arising from the
                         negligence or willful misconduct of Landlord or other
                         tenants or occupants of the Building or their
                         respective agents, employees, licensees, vendors,
                         contractors or providers of materials or services;

               (xxiii)   costs arising from Landlord's political
                         contributions;

               (xxiv)    costs for sculpture, paintings or other objects of
                         art;

               (xxv)     costs associated with the operation of the business of
                         the entity which constitutes Landlord as the same are
                         distinguished from the costs of operation of the
                         Building, including accounting and legal matters, costs
                         of defending any lawsuits with any mortgagee (except as
                         the actions of Tenant may be in issue), costs of
                         selling, syndicating, financing, mortgaging or
                         hypothecating any of Landlord's interest in the
                         Building, costs incurred in connection with any
                         disputes between Landlord and its employees, between
                         Landlord and Building management, or between Landlord
                         and other tenants or occupants;

               (xxvi)    rentals for items which, if purchased rather than
                         rented, would constitute a capital cost, to the extent
                         that the rental payments exceed the costs which could
                         be included pursuant to paragraph (g5) below;

               (xxvii)   costs of electricity for plugs and lights provided
                         to other tenants' demised premises;

               (xxviii)  repair and replacement costs in connection with
                         defects in Landlord's Work which are incurred by
                         Landlord prior to the third (3rd) anniversary of the
                         Full Rent Commencement Date; and

               (xxix)    any costs related to any development, demolition or
                         construction activity in the Building or the Complex,
                         and any and all costs of construction mitigation
                         measures, including, without limitation, dust control,
                         cleaning, maintenance, debris removal, traffic control
                         and noise control, but the foregoing shall have no
                         effect on the inclusion of the cost of normal cleaning
                         services for the Complex.

          (g5) Capital Expenditures.

               (i)  REPLACEMENTS. If, during the term of this Lease, Landlord
          shall replace any capital items or make any capital expenditures

                                      -26-
<PAGE>   35

          (collectively called "Capital Expenditures") the total amount of which
          is not properly includable in Operating Costs for the Operating Year
          in which they were made, in accordance with generally accepted
          accounting principles and practices in effect at the time of such
          replacement, there shall nevertheless be included in such Operating
          Costs and in Operating Costs for each succeeding Operating Year the
          amount, if any, by which the Annual Charge-Off (determined as
          hereinafter provided) of such Capital Expenditure (less insurance
          proceeds, if any, collected by Landlord by reason of damage to, or
          destruction of the capital item being replaced) exceeds the Annual
          Charge-Off of the Capital Expenditure for the item being replaced.

               (ii) NEW CAPITAL ITEMS. If a new capital item is acquired which
          does not replace another capital item which was worn out, has become
          obsolete, etc., and such new capital item being acquired is either (i)
          required by law or (ii) reasonably projected to reduce Operating
          Costs, then there shall be included in Operating Costs for each
          Operating Year in which and after such capital expenditure is made the
          Annual Charge-Off of such capital expenditure.

               (iii) ANNUAL CHARGE-OFF. "Annual Charge-Off" shall be defined as
          the annual amount of principal and interest payments which would be
          required to repay a loan ("Capital Loan") in equal monthly
          installments over the Useful Life, as hereinafter defined, of the
          capital item in question on a direct reduction basis at an annual
          interest rate equal to the Capital Interest Rate, as hereinafter
          defined, where the initial principal balance is the cost of the
          capital item in question.

               (iv) USEFUL LIFE. "Useful Life" shall be reasonably determined by
          Landlord in accordance with generally accepted accounting principles
          and practices in effect at the time of acquisition of the capital
          item. Notwithstanding the foregoing, if Landlord reasonably concludes
          on the basis of engineering estimates that a particular capital
          expenditure will effect savings in Complex operating expenses
          including, without limitation, energy-related costs, and that such
          annual projected savings will exceed the Annual Charge-Off of Capital
          Expenditures computed as aforesaid, then and in such events, the
          Annual Charge-Off shall be determined based upon a Useful Life which
          would cause the principal and interest payments in a full repayment of
          the Capital Loan in question to equal the amount of projected savings
          of such Useful Life.

               (v)  CAPITAL INTEREST RATE. "Capital Interest Rate" shall be
          defined as an annual rate of either one percentage point over the AA
          Bond rate (Standard & Poor's corporate composite or, if unavailable,
          its equivalent) as reported in the financial press at the time the
          capital expenditure is made or, if the capital item is acquired
          through third-party financing, then the actual (including fluctuating)
          rate paid by Landlord in financing the acquisition of such capital
          item.

          (g6) Specifically Included Categories of Operating Costs. Subject to
     the Excluded Costs definition, the qualifications on reimbursable Building
     Operating Costs and Complex Operating Costs set forth in Articles 9.1(g1)
     9.1(g2) and 9.1(g3), and

                                      -27-
<PAGE>   36

     except as otherwise expressly excluded from the definition of Building
     Operating Costs and Complex Operating Costs pursuant to the provisions of
     this Lease, Building Operating Costs and Complex Operating Costs shall
     include, but not be limited to, the following, provided that if such costs
     are attributable to the Building and to other buildings in the Complex,
     then such costs shall be equitably apportioned among the Building and such
     other buildings in accordance with Article 9.1(g3), and if such costs are
     attributable to common areas of the Complex and to other property which is
     not part of the Complex, then such costs shall be equitably apportioned
     among the Complex and such other property.

     TAXES (other than Real Estate Taxes): Sales taxes and Federal Social
     Security, Unemployment and Old Age Taxes and contributions and State
     Unemployment taxes and contributions accruing to and paid by the Landlord
     on account of all employees of Landlord and/or Landlord's managing agent,
     who are employed in, about or on account of the Premises (to the extent
     that the underlying wages or salaries are included in Building Operating
     Costs or Complex Operating Costs, as the case may be), except that taxes
     levied upon the net income of the Landlord and taxes withheld from
     employees, and "Taxes" as defined in Article 9.1(d) shall not be included
     herein.

     WATER: All charges and rates connected with water supplied to the Premises,
     the Building and/or the common areas of the Complex and related sewer use
     charges.

     HEAT AND AIR CONDITIONING: The cost of electricity connected with heat and
     air conditioning supplied to the common areas of the Building and/or
     Complex, and all other charges connected with heat and air conditioning
     supplied to the Premises, Building and/or Complex.

     WAGES: Wages and cost of all employee benefits of all employees of the
     Landlord and/or Landlord's managing agent who are employed in, about or on
     account of the Premises and/or Complex provided that wages and costs for
     employees who also work on other properties shall be allocated to the
     Complex based upon the proportion of their time spent working on the
     Complex and then allocated to the Premises on a square foot basis.

     CLEANING: The cost of labor and material for cleaning the Premises and/or
     Complex, surrounding areaways and windows in the Premises and/or Complex,
     including, without limitation, the services listed on Exhibit 4.

     ELEVATOR MAINTENANCE: All expenses for or on account of the upkeep and
     maintenance of all elevators in the Premises, Building and/or the Complex
     (if any).

     ELECTRICITY: The cost of all electric current for the operation of any
     machine, appliance or device used for the operation of the Premises and the
     Building and/or Complex, including the cost of electric current for the
     elevators, lights, air conditioning and heating, but not including electric
     current which is paid for directly to the utility by the user/tenant in the
     Premises and/or Complex. (If and so long as Tenant is billed directly by
     the electric utility for its own consumption of electricity for lights and
     plugs as determined by its separate meter or by submeter, then Operating
     Costs shall include only public area electric current consumption and
     electricity for base building HVAC and not any demised Premises electric
     current consumption for lights and plugs.) Wherever

                                      -28-
<PAGE>   37

     separate metering is unlawful, prohibited by utility company regulation or
     tariff or is otherwise impracticable, relevant consumption figures for the
     purposes of this Article 9 shall be determined by fair and reasonable
     allocations and engineering estimates made by Landlord.

     INSURANCE, ETC.: Fire, casualty, liability and such other insurance as may
     from time to time be reasonably required by lending institutions on
     first-class office buildings in the City or Town wherein the Building is
     located and all other expenses customarily incurred in connection with the
     operation and maintenance of first-class suburban office/research and
     development buildings in the Market Area.

     MANAGEMENT SPACE: Market rate rental costs associated with the Complex's
     management office.

     COMPLEX AMENITIES: The cost of operating any amenities in the Complex
     available to all tenants of the Complex including, without limitation, any
     cafeteria. The costs to be included in Complex Operating Costs shall
     include any subsidy, including lower than market rate rent, provided by
     Landlord for or with respect to such amenity. In the event that the costs
     of a Complex amenity are included in an Operating Year but such costs were
     not included in the Complex Operating Costs Base, then the Complex
     Operating Costs Base shall be adjusted to reflect what would have been the
     costs for such amenity in the Complex Operating Costs Base if such amenity
     had been operated during calendar year 2000.

     9.2  TAX EXCESS.

          (a)  IN GENERAL. Commencing as of the Rent Commencement Date (or, if
there is more than one Rent Commencement Date hereunder, the first such date),
and continuing thereafter throughout the term of this Lease, if with respect to
any Tax Period, the sum ("Tenant's Tax Share") of (i) Tenant's Building Tax
Percentage of Building Taxes plus (ii) Tenant's Complex Tax Percentage of Land
Taxes exceeds the Tax Base, Tenant shall, subject to Article 9.10, pay such
excess to Landlord, such amount being hereinafter referred to as "Tax Excess."
Tax Excess shall be due within thirty (30) days of Tenant's receipt of
Landlord's bill therefor. In implementation and not in limitation of the
foregoing, Tenant shall remit to Landlord pro rata monthly installments on
account of projected Tax Excess, calculated by Landlord on the basis of the most
recent Tax data available. If the total of such monthly remittances on account
of any Tax Period is greater than the actual Tax Excess for such Tax Period,
Tenant may credit the difference against the next installment of rental or other
charges due to Landlord hereunder, except that if such difference is determined
after the end of the term of this Lease, Landlord shall refund such difference
to Tenant within thirty (30) days after such determination to the extent that
such difference exceeds any amounts then due from Tenant to Landlord. If the
total of such remittances is less than the actual Tax Excess for such Tax
Period, Tenant shall pay the difference to Landlord within thirty (30) days of
Tenant's receipt of the bill.

          (b)  EFFECT OF ABATEMENTS. Appropriate credit against Tax Excess shall
be given for any refund obtained by reason of a reduction in any Taxes by the
Assessors or the administrative, judicial or other governmental agency
responsible therefor. The original computations, as well as reimbursement or
payments of additional charges, if any, or allowances, if any, under the
provisions of this Article 9.2 shall be based on the original assessed
valuations

                                      -29-
<PAGE>   38

with adjustments to be made at a later date when the tax refund, if any, shall
be paid to Landlord by the taxing authorities. Expenditures for reasonable legal
fees and for other reasonable similar or dissimilar expenses incurred in
obtaining the tax refund may be charged against the tax refund before the
adjustments are made for the Tax Period.

     9.3  OPERATING EXPENSE EXCESS.

     Commencing as of the Rent Commencement Date (or, if there is more than one
Rent Commencement Date hereunder, the first such date), and continuing
thereafter throughout the term of the Lease, if with respect to any Operating
Year, the Building Operating Costs exceed the Operating Cost Base, Tenant shall,
subject to Article 9.10, pay Tenant's Building Operating Cost Percentage of such
excess to Landlord, such amount being hereinafter referred to as "Operating
Expense Excess." Operating Expense Excess shall be due within thirty (30) days
of the Tenant's receipt of the Landlord's bill therefor. In implementation and
not in limitation of the foregoing, Tenant shall remit to Landlord pro rata
monthly installments on account of projected Operating Expense Excess,
calculated by Landlord on the basis of the most recent Operating Costs data or
budget available. Landlord shall, within one hundred twenty (120) days after the
end of each Operating Year, deliver to Tenant a reasonably detailed statement
("Year End Statement") of the actual amount of Operating Costs for such
Operating Year. If the total of such monthly remittances on account of any
Operating Year is greater than the actual Operating Expense Excess for such
Operating Year, Tenant may credit the difference against the next installment of
rent or other charges due to Landlord hereunder, except that if such difference
is determined after the end of the term of this Lease, Landlord shall refund
such difference to Tenant within thirty (30) days after such determination to
the extent that such difference exceeds any amounts then due from Tenant to
Landlord. If the total of such remittances is less than actual Operating Expense
Excess for such Operating Year, Tenant shall pay the difference to Landlord
within thirty (30) days of Tenant's receipt of Landlord's bill therefor.

     9.4  PART YEARS. If any Rent Commencement Date or if the Termination Date
occurs in the middle of an Operating Year or Tax Period, Tenant shall be liable
for only that portion of the Operating Expense or Tax Excess, as the case may
be, in respect of such Operating Year or Tax Period represented by a fraction
the numerator of which is the number of days of the herein term (commencing as
of the applicable Rent Commencement Date) which falls within the Operating Year
or Tax Period and the denominator of which is three hundred sixty-five (365), or
the number of days in said Tax Period, as the case may be. Any credit pursuant
to Article 9.10 for the years in which any Rent Commencement Date or the
Termination Date occur shall be similarly pro-rated.

     9.5  EFFECT OF TAKING. In the event of any taking of a portion of the
Complex, the Building or the land upon which it stands under circumstances
whereby this Lease shall not terminate under the provisions of Article 20 then,
for the purposes of determining Tax Excess, there shall be substituted for the
Tax Base originally provided for herein a fraction of such Tax Base, the
numerator of which fraction shall be the Taxes for the first Tax Period
subsequent to the condemnation or taking which takes into account such
condemnation or taking, and the denominator of which shall be the Taxes for the
last Tax Period prior to the condemnation or taking, which did not take into
account such condemnation or taking. Tenant's Building Tax Percentage shall be
adjusted appropriately to reflect the proportion of the Premises and the
Building remaining after such taking.

                                      -30-
<PAGE>   39

     9.6  ADJUSTMENT OF OPERATING COSTS BASED UPON OCCUPANCY. If less than
ninety-five percent (95%) of the rentable area of the Building shall have been
occupied by tenants at any time during any Operating Year (including the Base
Year), or if services, for any other reason, are not provided by Landlord to at
least ninety-five (95%) percent of the rentable area of the Building, then, at
Landlord's election, Building Operating Costs for such Operating Year shall be
adjusted to equal the amount which Landlord reasonably determines is the amount
Building Operating Costs would have been for such period had occupancy been
ninety-five percent (95%) throughout such period, or if such services had been
provided to ninety-five (95%) percent of the Building throughout such period, as
the case may be.

     9.7  EFFECT OF CONVERSION OF COMPLEX TO A CONDOMINIUM. Landlord reserves
the right to create a condominium encompassing some or all of the Complex,
including the Building. In the event that such a condominium is created, then
(i) if the Building shall constitute a separately assessed unit in the
condominium, Building Taxes shall thereafter be defined as the amount of Taxes
assessed against such unit, and if the Building does not constitute a separately
assessed unit, Landlord shall thereafter equitably allocate Taxes to the
Building and the Land on a reasonable basis; and (ii) Landlord shall include any
condominium fees assessed against the unit containing the premises in Building
Operating Costs and Complex Operating Costs, as the case may be, to the extent
such fees represent costs which would otherwise be included in Building
Operating Costs or Complex Operating Costs. The allocation of any such
condominium fees between Building Operating Costs and Complex Operating Costs
shall be based on square footage of Total Rentable Area of the premises
benefiting from the cost in question, unless Landlord reasonably determines that
such allocation should be made on another reasonable basis.

     9.8  DISPUTES, ETC. Any disputes arising under this Article 9 may, at the
election of either party, be submitted to arbitration as hereinafter provided.
Any obligations under this Article 9 which shall not have been paid at the
expiration or sooner termination of the term of this Lease shall survive such
expiration and shall be paid when and as the amount of same shall be determined
and be due.

     9.9  TENANT'S AUDIT RIGHTS. Subject to the provisions of this paragraph,
Tenant shall have the right, at Tenant's cost and expense, to examine all
documentation and calculations prepared in the determination of Operating
Expense Excess:

          1.   Such documentation and calculation shall be made available to
               Tenant at the offices where Landlord keeps such records during
               normal business hours within a reasonable time after Landlord
               receives a written request from Tenant to make such examination.

          2.   Tenant shall have the right to make such examination no more than
               once in respect of any period in which Landlord has given Tenant
               a statement of the actual amount of Operating Costs.

          3.   Any request for examination in respect of any Operating Year may
               be made no more than sixty (60) days after Landlord advises
               Tenant of the actual amount of Operating Costs in respect of such
               period.

          4.   Such examination may be made only by a nationally recognized
               independent certified public accounting firm approved by
               Landlord, such

                                      -31-
<PAGE>   40

               approval not to be unreasonably withheld or delayed. Without
               limiting Landlord's approval rights, Landlord may withhold its
               approval of any examiner of Tenant who is being paid by Tenant on
               a contingent fee basis.

          5.   As a condition to performing any such examination, Tenant and its
               examiners shall be required to execute and deliver to Landlord an
               agreement, in form reasonably acceptable to Landlord, agreeing to
               keep confidential any information which it discovers about
               Landlord or the Building or the Complex in connection with such
               examination.

          6.   If such audit reveals an overcharge of more than five percent
               (5%), Landlord shall reimburse Tenant the reasonable cost of such
               audit within thirty (30) days after written demand therefor.

     9.10 CREDIT IF OPERATING COSTS AND TAXES ARE LESS THAN THEIR RESPECTIVE
BASES.

     (a)  The provisions of this Article 9.10(a) shall only apply if, with
respect to any Operating Year, Tenant is required to pay Operating Expense
Excess, but the amount of Tenant's Tax Share for such Operating Year is less
than the Tax Base. In such instance, the amount of Operating Expense Excess
payable by Tenant for such Operating Year shall be reduced by an amount equal to
the amount by which the Tax Base exceeds Tenant's Tax Share for such Operating
Year. Since, as of the Execution Date, the method for determining Tenant's Tax
Share is determined based upon a fiscal Tax Period commencing as of each July 1
and ending as of the following June 30, Tenant's Tax Share for any Operating
Year shall, for the purposes of this Article 9.10(a), be determined based upon
the pro-rata portion of the actual amount of Taxes payable in respect of each
Tax Period which overlaps such Operating Year. Following are three examples of
this calculation:

     EXAMPLE 1

     (1)  For calendar year 2002, the Operating Expense Excess payable by Tenant
     would be $1,000.00, but for the provisions of this Article 9.10(a), and

     (2)  For fiscal year 2002 (i.e. July 1, 2001-June 30, 2002), the Tenant's
     Tax Share is $500.00 LESS than the Tax Base, and

     (3)  For fiscal year 2003 (i.e. July 1, 2002-June 30, 2003), the Tenant's
     Tax Share is $200.00 MORE than the Tax Base, then,

     (4)  The amount of Operating Expense Excess payable by Tenant for calendar
     year 2002 shall be reduced by $150.00 pursuant to this Article 9.10(a) (the
     reduction amount being equal to 50% of the amount by which Tenant's Tax
     Share is LESS than the Tax Base for fiscal year 2002 [$250.00] MINUS 50% of
     the amount by which Tenant's Tax Share for fiscal year 2003 is MORE than
     the Tax Base [$100.00]).

     EXAMPLE 2

                                      -32-
<PAGE>   41

     (1)  For calendar year 2002, the Operating Expense Excess payable by Tenant
     would be $1,000.00, but for the provisions of this Article 9.10(a), and

     (2)  For fiscal year 2002 (i.e. July 1, 2001-June 30, 2002), the Tenant's
     Tax Share is $400.00 LESS than the Tax Base, and

     (3)  For fiscal year 2003 (i.e. July 1, 2002-June 30, 2003), the Tenant's
     Tax Share is $300.00 LESS than the Tax Base, then,

     (4)  The amount of Operating Expense Excess payable by Tenant for calendar
     year 2002 shall be reduced by $350.00 pursuant to this Article 9.10(a) (the
     reduction amount being equal to 50% of the amount by which Tenant's Tax
     Share is LESS than the Tax Base for fiscal year 2002 [$200.00] PLUS 50% of
     the amount by which Tenant's Tax Share for fiscal year 2003 is LESS than
     the Tax Base [$150.00]).

     EXAMPLE 3

     (1)  For calendar year 2002, the Operating Expense Excess payable by Tenant
     would be $1,000.00, but for the provisions of this Article 9.10(a), and

     (2)  For fiscal year 2002 (i.e. July 1, 2001-June 30, 2002), the Tenant's
     Tax Share is $300.00 LESS than the Tax Base, and

     (3)  For fiscal year 2003 (i.e. July 1, 2002-June 30, 2003), the Tenant's
     Tax Share is $600.00 MORE than the Tax Base, then,

     (4)  The amount of Operating Expense Excess payable by Tenant for calendar
     year 2002 shall not be reduced pursuant to this Article 9.10(a) (the
     reduction amount being equal to 50% of the amount by which Tenant's Tax
     Share is LESS than the Tax Base for fiscal year 2002 [$150.00] MINUS 50% of
     the amount by which Tenant's Tax Share for fiscal year 2003 is MORE than
     the Tax Base [$300.00], but never less than zero).

     (b)  The provisions of this Article 9.10(b) shall only apply if, with
respect to any Tax Period, Tenant is required to pay Tax Excess, but the amount
of Tenant's Building Operating Cost Percentage of Building Operating Costs
("Tenant's Operating Share") for such Tax Period is less than the Operating Cost
Base. In such event, the amount of Tax Excess payable by Tenant for such Tax
Period shall be reduced by an amount equal to the amount by which the Operating
Cost Base exceeds Tenant's Operating Share for such Tax Period. Since, as of the
Execution Date, the method for determining Tenant's Tax Share is determined
based upon a fiscal Tax Period commencing as of each July 1 and ending as of the
following June 30, Tenant's Operating Share for any Tax Period shall, for the
purposes of this Article 9.10(b), be determined based upon the pro-rata portion
of the actual amount of Tenant's Operating Share payable in respect of each
Operating Year which overlaps such Tax Period Year. Following are three examples
of this calculation:

     EXAMPLE 1

     (1)  For fiscal year 2003 (i.e. July 1, 2002-June 30, 2003), the Tax Excess
     payable by Tenant would be $1,000.00, but for the provisions of this
     Article 9.10(b), and

                                      -33-
<PAGE>   42

     (2)  For calendar year 2002, the Tenant's Operating Share is $500.00 LESS
     than the Operating Cost Base, and

     (3)  For calendar year 2003, the Tenant's Operating Share is $200.00 MORE
     than the Operating Cost Base, then,

     (4)  The amount of Tax Excess payable by Tenant for fiscal year 2003 shall
     be reduced by $150.00 pursuant to this Article 9.10(b) (the reduction
     amount being equal to 50% of the amount by which Tenant's Operating Share
     is LESS than the Operating Cost Base for calendar year 2002 [$250.00] MINUS
     50% of the amount by which Tenant's Operating Share for calendar year 2003
     is MORE than the Operating Cost Base [$100.00]).

     EXAMPLE 2

     (1)  For fiscal year 2003 (i.e. July 1, 2002-June 30, 2003), the Tax Excess
     payable by Tenant would be $1,000.00, but for the provisions of this
     Article 9.10(b), and

     (2)  For calendar year 2002, the Tenant's Operating Share is $400.00 LESS
     than the Operating Cost Base, and

     (3)  For calendar year 2003, the Tenant's Operating Share is $300.00 LESS
     than the Operating Cost Base, then,

     (4)  The amount of Tax Excess payable by Tenant for fiscal year 2003 shall
     be reduced by $350.00 pursuant to this Article 9.10(b) (the reduction
     amount being equal to 50% of the amount by which Tenant's Operating Share
     is LESS than the Operating Cost Base for calendar year 2002 [$200.00] PLUS
     50% of the amount by which Tenant's Operating Share for calendar year 2003
     is LESS than the Operating Cost Base [$150.00]).

     EXAMPLE 3

     (1)  For fiscal year 2003 (i.e. July 1, 2002-June 30, 2003), the Tax Excess
     payable by Tenant would be $1,000.00, but for the provisions of this
     Article 9.10(b), and

     (2)  For calendar year 2002, the Tenant's Operating Share is $300.00 LESS
     than the Operating Cost Base, and

     (3)  For calendar year 2003, the Tenant's Operating Share is $600.00 MORE
     than the Operating Cost Base, then,

     (4)  The amount of Tax Excess payable by Tenant for fiscal year 2003 shall
     not be reduced pursuant to this Article 9.10(b) (the reduction amount being
     equal to 50% of the amount by which Tenant's Operating Share is LESS than
     the Operating Cost Base for calendar year 2002 [$150.00] MINUS 50% of the
     amount by which Tenant's Operating Share for calendar year 2003 is MORE
     than the Operating Cost Base [$300.00], but never less than zero).

                                      -34-
<PAGE>   43

10.  CHANGES OR ALTERATIONS BY LANDLORD

     Landlord reserves the right, exercisable by itself or its nominee, at any
time and from time to time without the same constituting an actual or
constructive eviction and without incurring any liability to Tenant therefor or
otherwise affecting Tenant's obligations under this Lease, to make such changes,
alterations, additions, improvements, repairs or replacements in or to the
Building (including the Premises) and the fixtures and equipment thereof, as
well as in or to the street entrances, halls, passages, elevators, escalators,
and stairways thereof, as it may deem necessary or desirable, and to change the
arrangement and/or location of entrances or passageways, doors and doorways, and
corridors, elevators, stairs, toilets, or other public parts of the Building,
provided, however, that there be no unreasonable obstruction of the right of
access to, or unreasonable interference with the use and enjoyment of, the
Premises by Tenant. Nothing contained in this Article 10 shall be deemed to
relieve Tenant of any duty, obligation or liability of Tenant with respect to
making any repair, replacement or improvement or complying with any law, order
or requirement of any governmental or other authority. Landlord reserves the
right to adopt and at any time and from time to time to change the name or
address of the Building. After the initial change of the name and address of the
Building, Landlord shall provide to Tenant at least six (6) months' prior
written notice of any subsequent change of the name or address of the Building.
Neither this Lease nor any use by Tenant shall give Tenant any right or easement
for the use of any door or any passage or any concourse connecting with any
other building or to any public convenience, and the use of such doors, passages
and concourses and of such conveniences may be regulated or discontinued at any
time and from time to time by Landlord without notice to Tenant and without
affecting the obligation of Tenant hereunder or incurring any liability to
Tenant therefor, provided, however, that there be no unreasonable obstruction of
the right of access to, or unreasonable interference with the use of the
Premises by Tenant.

     If at any time any windows of the Premises are temporarily closed or
darkened for any reason whatsoever including but not limited to, Landlord's own
acts, Landlord shall not be liable for any damage Tenant may sustain thereby and
Tenant shall not be entitled to any compensation therefor nor abatements of rent
nor shall the same release Tenant from its obligations hereunder nor constitute
an eviction.

     Subject to the provisions of Article 8.8(b) hereof, during the performance
of demolition or renovation of existing buildings and construction of new
buildings by Landlord in the Complex, Landlord, its agents, employees and
contractors shall use reasonable efforts to minimize any interference with
Tenant's use and occupancy of the Premises.

11.  FIXTURES, EQUIPMENT AND IMPROVEMENTS--REMOVAL BY TENANT

     All fixtures, equipment, improvements and appurtenances attached to or
built into the Premises prior to or during the term, whether by Landlord at its
expense or at the expense of Tenant (either or both) or by Tenant shall be and
remain part of the Premises and shall not be removed by Tenant during or at the
end of the term unless Landlord otherwise elects to require Tenant to remove
such fixtures, equipment, improvements and appurtenances, in accordance with
Articles 12 and/or 22 of the Lease; provided, however, that Tenant shall have
the right to remove (at Tenant's expense) the items of Tenant's Removable
Property listed on Exhibit 8, attached hereto, provided that such removal shall
not materially damage the Premises or the

                                      -35-
<PAGE>   44

Building and that the cost of repairing any damage to the Premises or the
Building arising from installation or such removal shall be paid by Tenant. All
electric, plumbing, heating and sprinkling systems, fixtures and outlets,
vaults, paneling, molding, shelving, radiator enclosures, cork, rubber, linoleum
and composition floors, ventilating, silencing, air conditioning and cooling
equipment, shall be deemed to be included in such fixtures, equipment,
improvements and appurtenances, whether or not attached to or built into the
Premises. Where not built into the Premises, all removable electric fixtures,
carpets, drinking or tap water facilities, furniture, or trade fixtures or
business equipment or Tenant's inventory or stock in trade shall not be deemed
to be included in such fixtures, equipment, improvements and appurtenances and
may be, and upon the request of Landlord will be, removed by Tenant upon the
condition that such removal shall not materially damage the Premises or the
Building and that the cost of repairing any damage to the Premises or the
Building arising from installation or such removal shall be paid by Tenant. If
this Lease shall be terminated by reason of Tenant's breach or default, then,
notwithstanding anything to the contrary in this Lease contained, Landlord shall
have a lien against all Tenant's property in the Premises or elsewhere in the
Building at the time of such termination to secure Landlord's rights under
Article 21 hereof. Tenant shall, within ten (10) days of Landlord's written
request, from time to time, execute and deliver to Landlord such documentation
(e.g., UCC statements) as may be necessary to enable Landlord to perfect such
lien.

12.  ALTERATIONS AND IMPROVEMENTS BY TENANT

     Tenant shall make no alterations, decorations, installations, removals,
additions or improvements in or to the Premises without Landlord's prior written
consent and then only those made by contractors or mechanics approved by
Landlord. No installations or work shall be undertaken or begun by Tenant until:
(i) Landlord has approved written plans and specifications and a time schedule
for such work; (ii) Tenant has made provision for either written waivers of
liens from all contractors, laborers and suppliers of materials for such
installations or work, the filing of lien bonds on behalf of such contractors,
laborers and suppliers, or other appropriate protective measures approved by
Landlord and reasonably and customarily required by other landlords of first
class office buildings in Cambridge, Massachusetts for work of the type being
performed; and (iii) where the cost of such work exceeds $300,000.00 in any one
instance, Tenant has procured appropriate surety payment and performance bonds.
No amendments or additions to such plans and specifications shall be made
without the prior written consent of Landlord. Landlord's consent and approval
required under this Article 12 shall not be unreasonably withheld. Landlord's
approval is solely given for the benefit of Landlord and neither Tenant nor any
third party shall have the right to rely upon Landlord's approval of Tenant's
plans for any purpose whatsoever. Without limiting the foregoing, Tenant shall
be responsible for all elements of the design of Tenant's plans (including,
without limitation, compliance with law, functionality of design, the structural
integrity of the design, the configuration of the Premises and the placement of
Tenant's furniture, appliances and equipment), and Landlord's approval of
Tenant's plans shall in no event relieve Tenant of the responsibility for such
design. Landlord shall have no liability or responsibility for any claim, injury
or damage alleged to have been caused by the particular materials, whether
building standard or non-building standard, appliances or equipment selected by
Tenant in connection with any work performed by or on behalf of Tenant in the
Premises including, without limitation, furniture, carpeting, copiers, laser
printers, computers and refrigerators. Any such work, alterations, decorations,
installations, removals, additions and improvements shall be done at Tenant's
sole expense and at such times and in such manner as Landlord may from time to
time

                                      -36-
<PAGE>   45

designate. If Tenant shall make any alterations, decorations, installations,
removals, additions or improvements to the Premises, then Landlord may elect to
require the Tenant at the expiration or sooner termination of the term of this
Lease to restore the Premises to substantially the same condition as existed at
the Full Rent Commencement Date. Landlord agrees to make such election at the
time that Landlord approves Tenant's plans for any such alterations, etc., if
Tenant requests in writing that Landlord make such election at the time that
Tenant requests Landlord's approval of such alterations, etc.

     Tenant shall have the right, during the term of the Lease, to use the
internal stairwells of the Building to provide access for Tenant's employees
between the floors of the Premises provided that (i) such use is permitted by
applicable law, (ii) Landlord shall, if required by applicable laws, rules,
orders and regulations, install a card key access system for the doors to and
from such stairwells, and (iii) Tenant shall reimburse Landlord, as additional
rent, or shall use a portion of the Landlord Allowance, for the costs incurred
by Landlord to install such card key access system.

     Notwithstanding anything to the contrary herein contained, Tenant shall
have the right, without obtaining Landlord's consent, to make interior
nonstructural alterations, additions, or improvements, provided however that
Tenant:

          (i)   shall give prior written notice to Landlord of such alterations,
                additions or improvements;

          (ii)  Tenant shall submit to Landlord plans for such alterations,
                additions or improvements if Tenant utilizes plans for such
                alterations, additions or improvements, and

          (iii) that such alterations, additions or improvements shall not
                materially, adversely affect any of the Building's systems, or
                the ceiling of the Premises.

13.  TENANT'S CONTRACTORS--MECHANICS' AND OTHER LIENS--STANDARD OF TENANT'S
     PERFORMANCE--COMPLIANCE WITH LAWS

     Whenever Tenant shall make any alterations, decorations, installations,
removals, additions or improvements in or to the Premises--whether such work be
done prior to or after the Term Commencement Date--Tenant will strictly observe
the following covenants and agreements:

          (a)  Tenant agrees that it will not, either directly or indirectly,
use any contractors and/or materials if their use will create any difficulty,
whether in the nature of a labor dispute or otherwise, with other contractors
and/or labor engaged by Tenant or Landlord or others in the construction,
maintenance and/or operation of the Building or any part thereof.

          (b)  In no event shall any material or equipment be incorporated in or
added to the Premises, so as to become a fixture or otherwise a part of the
Building, in connection with any such alteration, decoration, installation,
addition or improvement which is subject to any lien, charge, mortgage or other
encumbrance of any kind whatsoever or is subject to any security interest or any
form of title retention agreement. No installations or work shall be undertaken
or

                                      -37-
<PAGE>   46

begun by Tenant until (i) Tenant has made provision for written waiver of liens
from all contractors, laborers and suppliers of materials for such installations
or work, and taken other appropriate protective measures approved by Landlord;
and (ii) Tenant has procured appropriate surety payment and performance bonds
which shall name Landlord as an additional obligee and has filed lien bond(s)
(in jurisdictions where available) on behalf of such contractors, laborers and
suppliers. Any mechanic's lien filed against the Premises or the Building for
work claimed to have been done for, or materials claimed to have been furnished
to, Tenant shall be discharged by Tenant within ten (10) days thereafter, at
Tenant's expense by filing the bond required by law or otherwise. If Tenant
fails so to discharge any lien, Landlord may do so at Tenant's expense and
Tenant shall reimburse Landlord for any expense or cost incurred by Landlord in
so doing within fifteen (15) days after rendition of a bill therefor.
Notwithstanding the foregoing, Tenant shall have the right to grant security
interests and/or to lease its business equipment and personal property in the
Premises which were not paid for in whole or in part by the Landlord Allowance,
provided that such lessor or secured party agrees:

               1.   That it will repair any damage to the Building or the
                    Premises caused by the installation or removal of any such
                    equipment or personal property;

               2.   That it will give Landlord not less than five (5) days
                    advance written notice prior to making any entry into the
                    Premises;

               3.   That it will not hold any auction or foreclosure sale on the
                    Premises; and

               4.   That it will have the right to remove such equipment or
                    property only during the term of this Lease.

          (c)  All installations or work done by Tenant shall be at its own
expense and shall at all times comply with (i) laws, rules, orders and
regulations of governmental authorities having jurisdiction thereof; (ii)
orders, rules and regulations of any Board of Fire Underwriters, or any other
body hereafter constituted exercising similar functions, and governing insurance
rating bureaus; (iii) Rules and Regulations of Landlord; and (iv) plans and
specifications prepared by and at the expense of Tenant theretofore submitted to
and approved by Landlord. Notwithstanding any other provision of this Lease,
Tenant shall not be responsible for compliance with any laws, regulations, or
the like requiring (i) structural repairs or modifications or (ii) repairs or
modifications to the utility or building service equipment or (iii) installation
of new building service equipment, such as fire detection or suppression
equipment, unless such repairs, modifications, or installations shall be (a) due
to Tenant's particular use or manner of use of the Premises (as opposed to
office use generally), (b) due to the negligence or willful misconduct of Tenant
or any agent, employee, or contractor of Tenant, or (c) due to alterations,
additions or installations by or on behalf of Tenant.

          (d)  Tenant shall procure all necessary permits before undertaking any
work in the Premises; do all of such work in a good and workmanlike manner,
employing materials of good quality and complying with all governmental
requirements; and defend, save harmless, exonerate and indemnify Landlord from
all injury, loss or damage to any person or property occasioned by or growing
out of such work. Tenant shall cause contractors employed by Tenant to carry
Worker's Compensation Insurance in accordance with statutory requirements,

                                      -38-
<PAGE>   47

Automobile Liability Insurance and, naming Landlord as an additional insured,
Commercial General Liability Insurance covering such contractors on or about the
Premises in the amounts stated in Article 15 hereof or in such other reasonable
amounts as Landlord shall require and to submit certificates evidencing such
coverage to Landlord prior to the commencement of such work.

14.  REPAIRS BY TENANT--FLOOR LOAD

     14.1 REPAIRS BY TENANT. Tenant shall keep all and singular the Premises
neat and clean (including periodic rug shampoo and waxing of tiled floors and
cleaning of blinds and drapes) and in such repair, order and condition as the
same are in on the Term Commencement Date or may be put in during the term
hereof, reasonable use and wearing thereof and damage by fire or by other
casualty excepted. Tenant shall be solely responsible for the proper maintenance
of all equipment and appliances operated by Tenant, including, without
limitation, copiers, laser printers, computers and refrigerators. Tenant shall
make, as and when needed as a result of misuse by, or neglect or improper
conduct of, Tenant or Tenant's servants, employees, agents, contractors,
invitees, or licensees or otherwise, all repairs in and about the Premises
necessary to preserve them in such repair, order and condition, which repairs
shall be in quality and class equal to the original work. Landlord may elect, at
the expense of Tenant, to make any such repairs or to repair any damage or
injury to the Building or the Premises caused by moving property of Tenant in or
out of the Building, or by installation or removal of furniture or other
property, or by misuse by, or neglect, or improper conduct of, Tenant or
Tenant's servants, employees, agents, contractors, or licensees.

     14.2 FLOOR LOAD--HEAVY MACHINERY. Tenant shall not place a load upon any
floor of the Premises exceeding the floor load per square foot of area which
such floor was designed to carry and which is allowed by law. Landlord reserves
the right to prescribe the weight and position of all business machines and
mechanical equipment, including safes, which shall be placed so as to distribute
the weight. Business machines and mechanical equipment shall be placed and
maintained by Tenant at Tenant's expense in settings sufficient in Landlord's
judgment to absorb and prevent vibration, noise and annoyance. Tenant shall not
move any safe, heavy machinery, heavy equipment, freight, bulky matter, or
fixtures into or out of the Building without Landlord's prior written consent.
If such safe, machinery, equipment, freight, bulky matter or fixtures requires
special handling, Tenant agrees to employ only persons holding a Master Rigger's
License to do said work, and that all work in connection therewith shall comply
with applicable laws and regulations. Any such moving shall be at the sole risk
and hazard of Tenant and Tenant will defend, indemnify and save Landlord
harmless against and from any liability, loss, injury, claim or suit resulting
directly or indirectly from such moving. Proper placement of all such business
machines, etc., in the Premises shall be Tenant's responsibility.

15.  INSURANCE, INDEMNIFICATION, EXONERATION AND EXCULPATION

     15.1 GENERAL LIABILITY INSURANCE. Tenant shall procure, and keep in force
and pay for Commercial General Liability Insurance insuring Tenant on an
occurrence basis against all claims and demands for personal injury liability
(including, without limitation, bodily injury, sickness, disease, and death) or
damage to property which may be claimed to have occurred from and after the time
Tenant and/or its contractors enter the Premises in accordance with Article 4 of
this Lease, of not less than Two Million ($2,000,000) Dollars in the event of
personal injury to any number of persons or damage to property, arising out of
any one occurrence, and from time

                                      -39-
<PAGE>   48

to time thereafter shall be not less than such higher amounts, if procurable, as
may be reasonably required by Landlord and are customarily carried by
responsible similar tenants in the City or Town wherein the Building is located.

     15.2 CERTIFICATES OF INSURANCE. Such insurance shall be effected with
insurers approved by Landlord, authorized to do business in the State wherein
the Building is situated under valid and enforceable policies wherein Tenant
names Landlord and Landlord's managing agent as additional insureds. Such
insurance shall provide that it shall not be canceled or modified without at
least thirty (30) days' prior written notice to each insured named therein. On
or before the time Tenant and/or its contractors enter the Premises in
accordance with Articles 4 and 14 of this Lease and thereafter not less than
fifteen (15) days prior to the expiration date of each expiring policy, original
copies of the policies provided for in Article 15.1 issued by the respective
insurers, or certificates of such policies setting forth in full the provisions
thereof and issued by such insurers together with evidence satisfactory to
Landlord of the payment of all premiums for such policies, shall be delivered by
Tenant to Landlord and certificates as aforesaid of such policies shall upon
request of Landlord, be delivered by Tenant to the holder of any mortgage
affecting the Premises.

     15.3 GENERAL. Tenant will save Landlord, its agents and employees, harmless
and will exonerate, defend and indemnify Landlord, its agents and employees,
from and against any and all claims, liabilities or penalties asserted by or on
behalf of any person, firm, corporation or public authority arising from the
Tenant's breach of the Lease or:

          (a)  On account of or based upon any injury to person, or loss of or
damage to property, sustained or occurring on the Premises on account of or
based upon the act, omission, fault, negligence or misconduct of any person
whomsoever (except to the extent the same is caused by Landlord, its agents,
contractors or employees);

          (b)  On account of or based upon any injury to person, or loss of or
damage to property, sustained or occurring elsewhere (other than on the
Premises) in or about the Building (and, in particular, without limiting the
generality of the foregoing, on or about the elevators, stairways, public
corridors, sidewalks, concourses, arcades, malls, galleries, vehicular tunnels,
approaches, areaways, roof, or other appurtenances and facilities used in
connection with the Building or Premises) to the extent arising out of the use
or occupancy of the Building or Premises by the Tenant, or by any person
claiming by, through or under Tenant, to the extent on account of or based upon
the fault, negligence or misconduct of Tenant, its agents, employees or
contractors; and

          (c)  On account of or based upon (including monies due on account of)
any work or thing whatsoever done (other than by Landlord or its contractors, or
agents or employees of either) on the Premises during the term of this Lease and
during the period of time, if any, prior to the Term Commencement Date that
Tenant may have been given access to the Premises.

          (d)  Tenant's obligations under this Article 15.3 shall be insured
either under the Commercial General Liability Insurance required under Article
15.1, above, or by a contractual insurance rider or other coverage; and
certificates of insurance in respect thereof shall be provided by Tenant to
Landlord upon request.

                                      -40-
<PAGE>   49

          (e)  Except as set forth in this Article 15.3(e), Tenant shall not be
liable to Landlord for consequential damages. Notwithstanding the foregoing, in
the event that Tenant is required to indemnify Landlord against the claim of a
third party pursuant to this Article 15.3, and if such third party recovers a
judgment against Landlord for consequential damages based upon the negligence or
willful misconduct of Tenant, its contractors, agents or employees, Tenant shall
be liable for such consequential damages suffered by such third party. The
foregoing shall not limit Landlord's right to recover damages in accordance with
Article 21.3 (x) or (y) or to recover damages in accordance with the last
paragraph of Article 22 as the result of a holdover by Tenant in the premises
beyond the term of the Lease.

     15.4 PROPERTY OF TENANT. In addition to and not in limitation of the
foregoing, Tenant covenants and agrees that, to the maximum extent permitted by
law, all merchandise, furniture, fixtures and property of every kind, nature and
description related or arising out of Tenant's leasehold estate hereunder, which
may be in or upon the Premises or Building, in the public corridors, or on the
sidewalks, areaways and approaches adjacent thereto, shall be at the sole risk
and hazard of Tenant, and that if the whole or any part thereof shall be
damaged, destroyed, stolen or removed from any cause or reason whatsoever no
part of said damage or loss shall be charged to, or borne by, Landlord, except,
subject to Article 19 hereof, to the extent such damage or loss is due to the
negligence or willful misconduct of Landlord or Landlord's agents, employees or
contractors, in which case Landlord shall bear loss or damage only to "ordinary
office property" (as hereinafter defined). For the purpose of this Article 15.4,
"ordinary office property" shall mean merchandise, furniture, and other tangible
personal property of the kind and quantity which may customarily be expected to
be found within comparable business offices in the greater Cambridge area, and
excluding any unusually valuable or exotic property, works of art, and the like.

     15.5 BURSTING OF PIPES, ETC. Landlord shall not be liable for any injury or
damage to persons or property resulting from fire, explosion, falling plaster,
steam, gas, air contaminants or emissions, electricity, electrical or electronic
emanations or disturbance, water, rain or snow or leaks from any part of the
Building or from the pipes, appliances, equipment or plumbing works or from the
roof, street or sub-surface or from any other place or caused by dampness,
vandalism, malicious mischief or by any other cause of whatever nature, unless
caused by or due to the negligence of Landlord, its agents, servants or
employees, and then, where notice and an opportunity to cure are appropriate
(i.e., where Tenant has an opportunity to know or should have known of such
condition sufficiently in advance of the occurrence of any such injury or damage
resulting therefrom as would have enabled Landlord to prevent such damage or
loss had Tenant notified Landlord of such condition) only after (i) notice to
Landlord of the condition claimed to constitute negligence and (ii) the
expiration of a reasonable time after such notice has been received by Landlord
without Landlord having taken all reasonable and practicable means to cure or
correct such condition; and pending such cure or correction by Landlord, Tenant
shall take all reasonably prudent temporary measures and safeguards to prevent
any injury, loss or damage to persons or property. In no event shall Landlord be
liable for any loss, the risk of which is covered by Tenant's insurance or is
required to be so covered by this Lease; nor shall Landlord or its agents be
liable for any such damage caused by other tenants or persons in the Building or
caused by operations in construction of any private, public, or quasi-public
work; nor shall Landlord be liable for any latent defect in the Premises or in
the Building; provided however, that: (i) the foregoing shall not limit
Landlord's obligation to repair any latent defect in Landlord's Work of which
Tenant gives Landlord written notice within the time period required pursuant to
Article 4.8, and (ii) the foregoing shall not relieve Landlord of its obligation
to

                                      -41-
<PAGE>   50

perform maintenance and repairs pursuant to Article 8.7. Landlord shall
cooperate with Tenant in such manner as Tenant shall reasonably request in the
event that Tenant suffers any loss or damage by reason of any such latent defect
so that Tenant shall be able to prosecute any claim which it may have against
the contractor and/or material supplier responsible for such latent defect.
Without limiting the foregoing, Landlord shall assign its right to Tenant
against any such contractor and/or material supplier, if necessary to enable
Tenant to prosecute its claim against any such contractor and/or material
supplier.

     15.6 REPAIRS AND ALTERATIONS--NO DIMINUTION OF RENTAL VALUE. Except as
otherwise provided in Article 18, there shall be no allowance to Tenant for
diminution of rental value and no liability on the part of Landlord by reason of
inconvenience, annoyance or injury to Tenant arising from any repairs,
alterations, additions, replacements or improvements made by Landlord, or any
related work, Tenant or others in or to any portion of the Building or Premises
or any property adjoining the Building, or in or to fixtures, appurtenances, or
equipment thereof, or for failure of Landlord or others to make any repairs,
alterations, additions or improvements in or to any portion of the Building, or
of the Premises, or in or to the fixtures, appurtenances or equipment thereof.

16.  ASSIGNMENT, MORTGAGING AND SUBLETTING

     A.   Tenant covenants and agrees that neither this Lease nor the term and
estate hereby granted, nor any interest herein or therein, will be assigned,
mortgaged, pledged, encumbered or otherwise transferred, voluntarily, by
operation of law or otherwise, and that neither the Premises, nor any part
thereof will be encumbered in any manner by reason of any act or omission on the
part of Tenant, or used or occupied, or permitted to be used or occupied, or
utilized for desk space or for mailing privileges, by anyone other than Tenant,
or for any use or purpose other than as stated in Exhibit 1, or be sublet, or
offered or advertised for subletting.

     B.   Notwithstanding anything to the contrary in the Lease contained,
except to the extent set forth in Paragraph C below:

               1.   Tenant shall, prior to offering or advertising the Premises,
                    or any portion thereof for sublease or assignment give
                    Landlord a Recapture Offer, as hereinafter defined.

               2.   For the purposes hereof a "Recapture Offer" shall be defined
                    as a notice in writing from Tenant to Landlord which:

                    (a)  States that Tenant desires to sublet the Premises, or a
                         portion thereof, or to assign its interest in this
                         Lease.

                    (b)  Identifies the affected portion of the Premises
                         ("Recapture Premises").

                    (c)  Identifies the period of time ("Recapture Period")
                         during which Tenant proposes to sublet the Recapture
                         Premises or to assign its interest in the Lease.

                                      -42-
<PAGE>   51

                    (d)  Offers to Landlord to terminate the Lease in respect of
                         the Recapture Premises (in the case of a proposed
                         assignment of Tenant's interest in the Lease or a
                         subletting for the remainder of the term of the Lease)
                         or to suspend the term of the Lease PRO TANTO in
                         respect of the Recapture Period (i.e. the term of the
                         Lease in respect of the Recapture Premises shall be
                         terminated during the Recapture Period and Tenant's
                         rental obligations shall be reduced in proportion to
                         the ratio of the Total Rentable Area of the Recapture
                         Premises to the Total Rentable Area of the Premises
                         then demised to Tenant).

               3.   Landlord shall have twenty-one (21) business days to accept
                    a Recapture Offer. If Landlord does not timely give written
                    notice to Tenant accepting a Recapture Offer, then Landlord
                    agrees that, subject to Subparagraph 5 of this Paragraph B,
                    it will not unreasonably withhold or delay its consent to a
                    sublease of the Recapture Premises for the Recapture Period,
                    or an assignment of Tenant's interest in the Lease, as the
                    case may be, to a Qualified Transferee, as hereinafter
                    defined.

               4.   For the purposes hereof, a "Qualified Transferee" shall be
                    defined as a person, firm or corporation which, in
                    Landlord's reasonable opinion:

                    (a)  is financially responsible and of good reputation
                         (recognizing that Akamai Technologies, Inc. remains
                         liable hereunder); and

                    (b)  is engaged in a business, the functional aspects of
                         which, with respect to the Premises, are similar to the
                         use of other Premises made by other office space
                         tenants in the Building.

               5.   In the event that the proposed assignee or sublessee is then
                    a tenant or subtenant of other premises in the Building or
                    the Complex (an "Existing Tenant"), then Tenant's written
                    request for Landlord's consent to a sublease or assignment
                    to such entity shall be deemed to constitute a second
                    Recapture Offer to Landlord with respect to such proposed
                    sublease or assignment, except that Landlord shall have
                    seven (7) calendar days from the receipt of Tenant's written
                    request for consent to such proposed sublease or assignment
                    in which to give Tenant written notice that Landlord accepts
                    such Recapture Offer.

               6.   Notwithstanding anything to the contrary in this Paragraph B
                    contained:

                                      -43-
<PAGE>   52

                    (a)  If Tenant is in default of its obligations under the
                         Lease at the time that it makes the aforesaid offer to
                         Landlord, such default shall be deemed to be a
                         "reasonable" reason for Landlord withholding its
                         consent to any proposed subletting or assignment; and

                    (b)  If Tenant does not enter into a sublease with a
                         subtenant (or an assignment to an assignee, as the case
                         may be) approved by Landlord, as aforesaid, on or
                         before the date which is one hundred eighty (180) days
                         after the earlier of: (x) the expiration of said
                         twenty-one (21) business day period, or (y) the date
                         that Landlord notifies Tenant that Landlord will not
                         accept Tenant's offer to terminate or suspend the
                         Lease, then Landlord shall have the right arbitrarily
                         to withhold its consent to any subletting or assignment
                         proposed to be entered into by Tenant after the
                         expiration of said one hundred eighty (180) day period
                         unless Tenant again offers, in accordance with this
                         Paragraph B, either to terminate or to suspend the
                         Lease in respect of the portion of the Premises
                         proposed to be sublet (or in respect of the entirety of
                         the Premises in the event of a proposed assignment, as
                         the case may be). If Tenant shall make any subsequent
                         offers to terminate or suspend the Lease pursuant to
                         this Paragraph B, any such subsequent offers shall be
                         treated in all respects as if it is Tenant's first
                         offer to suspend or terminate the Lease pursuant to
                         this Paragraph B, provided that the period of time
                         Landlord shall have in which to accept or reject such
                         subsequent offer shall be fourteen (14) business days.

               7.   Notwithstanding anything to the contrary herein contained,
                    except in connection with a Protected Sublease, as defined
                    in Subparagraph 8 of this Paragraph B, Tenant shall have no
                    right, under this Paragraph B hereof, prior to the date that
                    is the earlier of (i) one (1) year after the Full Rent
                    Commencement Date, and (ii) the date when Buildings 100, 300
                    and 700 are one hundred percent (100%) leased.

               8.   Notwithstanding the foregoing, Tenant shall have the right
                    to sublease up to 35,696 square feet of Rentable Floor Area,
                    in the aggregate, of the Premises for a term not in excess
                    of forty-two months (a "Protected Sublease") without the
                    requirement of giving Landlord a Recapture Notice with
                    respect thereto, and without being subject to the provisions
                    of Paragraph (7) above. Such Protected Sublease shall,
                    however, require Landlord's consent, which shall not be
                    unreasonably withheld, conditioned or delayed for a sublease
                    to a Qualified Transferee, as defined in Paragraph (4)
                    above, and shall be subject to the provisions of

                                      -44-
<PAGE>   53

                    Paragraph (5) above allowing Landlord to recapture the
                    relevant portion of the Premises in connection with
                    subleases or assignments to Existing Tenants. Tenant shall
                    pay Landlord 50% of the net (i.e., net of the reasonable and
                    customary brokerage, legal, design and construction costs
                    incurred by Tenant in connection with such Protected
                    Sublease) amount of all rent and other consideration which
                    Tenant receives as a result of a Protected Sublease that is
                    in excess of the rent payable to Landlord for the portion of
                    the Premises and Term covered by the Transfer. Tenant shall
                    pay Landlord for Landlord's share of any excess within ten
                    (10) days after Tenant's receipt of such excess
                    consideration.

               9.   No subletting or assignment shall relieve Tenant of its
                    primary obligation as party-Tenant hereunder, nor shall it
                    reduce or increase Landlord's obligations under the Lease.

     C.   Notwithstanding anything to the contrary herein contained, Tenant
shall have the right, without obtaining Landlord's consent and without giving
Landlord a Recapture Offer, to assign its interest in this Lease and to sublease
the premises, or any portion thereof, to an Affiliated Entity, as hereinafter
defined, so long as such entity remains in such relationship to Tenant, and
provided that prior to or simultaneously with such assignment or sublease, such
Affiliated Entity executes and delivers to Landlord an Assumption Agreement, as
hereinabove defined. For the purposes hereof, an "Affiliated Entity" shall be
defined as any entity which is controlled by, is under common control with, or
which controls Tenant. Notwithstanding anything to the contrary herein
contained, it is hereby expressly understood and agreed, however, that if Tenant
is a corporation, that the assignment or transfer of this Lease, and the term
and estate hereby granted, to any corporation into which Tenant is merged or
with which Tenant is consolidated or which acquires all or substantially all of
its stock or assets which corporation shall have a net worth at least equal to
that of Tenant immediately prior to such merger or consolidation (such
corporation being hereinafter called "Assignee"), shall not be deemed to be
prohibited hereby, or to require Landlord's consent, or to require the
furnishing of a Recapture Offer, if, and upon the express condition that
Assignee and Tenant shall promptly execute, acknowledge and deliver to Landlord
an agreement in form and substance satisfactory to Landlord whereby Assignee
shall agree to be independently bound by and upon all the covenants, agreements,
terms, provisions and conditions set forth in this Lease on the part of Tenant
to be performed, and whereby Assignee shall expressly agree that the provisions
of this Article 16 shall, notwithstanding such assignment or transfer, continue
to be binding upon it with respect to all future assignments and transfers.

     D.   If Tenant is an individual who uses and/or occupies the Premises with
partners, or if Tenant is a partnership, then:

          (i)  Each present and future partner shall be personally bound by and
upon all of the covenants, agreements, terms, provisions and conditions set
forth in this Lease on the part of Tenant to be performed; and

                                      -45-
<PAGE>   54

          (ii) In confirmation of the foregoing, Landlord may (but without being
required to do so) request (and Tenant shall duly comply) that Tenant, at the
time that Tenant admits any new partner to its partnership, shall require each
such new partner to execute an agreement in form and substance satisfactory to
Landlord whereby such new partner shall agree to be personally bound by and upon
all of the covenants, agreements, terms, provisions and conditions of this Lease
on the part of Tenant to be performed, without regard to the time when such new
partner is admitted to partnership or when any obligations under any such
covenants, etc., accrue.

     E.   The listing of any name other than that of Tenant, whether on the
doors of the Premises or on the Building directory, or otherwise, shall not
operate to vest in any such other person, firm or corporation any right or
interest in this Lease or in the Premises or be deemed to effect or evidence any
consent of Landlord, it being expressly understood that any such listing is a
privilege extended by Landlord revocable at will by written notice to Tenant.

     F.   If this Lease be assigned, or if the Premises or any part thereof be
sublet or occupied by anybody other than Tenant, Landlord may, at any time and
from time to time, collect rent and other charges from the assignee, subtenant
or occupant, and apply the net amount collected to the rent and other charges
herein reserved then due and thereafter becoming due, but no such assignment,
subletting, occupancy or collection shall be deemed a waiver of this covenant,
or the acceptance of the assignee, subtenant or occupant as a tenant, or a
release of Tenant from the further performance by Tenant of covenants on the
part of Tenant herein contained. Any consent by Landlord to a particular
assignment or subletting shall not in any way diminish the prohibition stated in
the first sentence of this Article 16 or the continuing liability of the Tenant
named on Exhibit 1 as the party Tenant under this Lease. No assignment or
subletting shall affect the purpose for which the Premises may be used as stated
in Exhibit 1.

     G.   Tenant agrees that in no event shall this Lease be assigned, or all or
any portion of the Premises be sublet, to any of the following entities: Gardner
Group, Inc.; META Group, Inc.; GIGA Information Group, Inc.; Jupiter
Communications; The Yankee Group, a subsidiary of Primark Corporation; Odyssey
Research; and Mainspring Communications, Inc.

17.  MISCELLANEOUS COVENANTS

     Tenant covenants and agrees as follows:

     17.1 RULES AND REGULATIONS. Tenant will faithfully observe and comply with
the Rules and Regulations, if any, annexed hereto and such other and further
reasonable Rules and Regulations as Landlord hereafter at any time or from time
to time may make and may communicate in writing to Tenant, which in the
reasonable judgment of Landlord shall be necessary for the reputation, safety,
care or appearance of the Building, or the preservation of good order therein,
or the operation or maintenance of the Building, or the equipment thereof, or
the comfort of tenants or others in the Building, provided, however, that in the
case of any conflict between the provisions of this Lease and any such
regulations, the provisions of this Lease shall control, and provided further
that nothing contained in this Lease shall be construed to impose upon Landlord
any duty or obligation to enforce the Rules and Regulations or the terms,
covenants or conditions in any other lease as against any other tenant and
Landlord shall not be liable to Tenant for violation of the same by any other
tenant, its servants, employees, agents, contractors, visitors, invitees or
licensees. Notwithstanding anything to the contrary in

                                      -46-
<PAGE>   55

this Lease contained, Landlord agrees that it will not enforce said Rules and
Regulations against Tenant in a discriminatory or arbitrary manner.

     17.2 ACCESS TO PREMISES--SHORING. Tenant shall: (i) permit Landlord to
erect, use and maintain pipes, ducts and conduits in and through the Premises,
provided the same do not materially reduce the floor area or materially
adversely affect the appearance thereof; (ii) upon reasonable prior oral notice
(except that no notice shall be required in emergency situations), permit
Landlord and any mortgagee of the Building or the Building and land or of the
interest of Landlord therein, and any lessor under any ground or underlying
lease, and their representatives, to have free and unrestricted access to and to
enter upon the Premises at all reasonable hours for the purposes of inspection
or of making repairs, replacements or improvements in or to the Premises or the
Building or equipment (including, without limitation, sanitary, electrical,
heating, air conditioning or other systems) or of complying with all laws,
orders and requirements of governmental or other authority or of exercising any
right reserved to Landlord by this Lease (including the right during the
progress of any such repairs, replacements or improvements or while performing
work and furnishing materials in connection with compliance with any such laws,
orders or requirements to take upon or through, or to keep and store within, the
Premises all necessary materials, tools and equipment); and (iii) permit
Landlord, at reasonable times, upon reasonable advance notice, to show the
Premises during ordinary business hours to any existing or prospective
mortgagee, ground lessor, space lessee, purchaser, or assignee of any mortgage,
of the Building or of the Building and the land or of the interest of Landlord
therein, and during the period of 12 months next preceding the Termination Date
to any person contemplating the leasing of the Premises or any part thereof. If,
during the last month of the term, Tenant shall have removed all or
substantially all of Tenant's property therefrom, Landlord may immediately enter
and alter, renovate and redecorate the Premises, without elimination or
abatement of rent, or incurring liability to Tenant for any compensation, and
such acts shall have no effect upon this Lease. If Tenant shall not be
personally present to open and permit an entry into the Premises at any time
when for any reason an entry therein shall be necessary or permissible, Landlord
or Landlord's agents may enter the same by a master key, or may forcibly enter
the same, without rendering Landlord or such agents liable therefor (if during
such entry Landlord or Landlord's agents shall accord reasonable care to
Tenant's property), and without in any manner affecting the obligations and
covenants of this Lease. Provided that Landlord shall incur no additional
expense thereby, Landlord shall exercise its rights of access to the Premises
permitted under any of the terms and provisions of this Lease in such manner as
to minimize to the extent practicable interference with Tenant's use and
occupation of the Premises. If an excavation shall be made upon land adjacent to
the Premises or shall be authorized to be made, Tenant shall afford to the
person causing or authorized to cause such excavation, license to enter upon the
Premises for the purpose of doing such work as said person shall deem necessary
to preserve the Building from injury or damage and to support the same by proper
foundations without any claims for damages or indemnity against Landlord, or
diminution or abatement of rent.

     17.3 ACCIDENTS TO SANITARY AND OTHER SYSTEMS. Tenant shall give to Landlord
prompt notice of any fire or accident in the Premises or in the Building and of
any damage to, or defective condition in, any part or appurtenance of the
Building including, without limitation, sanitary, electrical, ventilation,
heating and air conditioning or other systems located in, or passing through,
the Premises. Except as otherwise provided in Articles 18 and 20, and subject to
Tenant's obligations in Article 14, such damage or defective condition shall be
remedied by Landlord with reasonable diligence, but if such damage or defective
condition was caused by Tenant or by the employees, licensees, contractors or
invitees of Tenant, the cost to remedy the

                                      -47-
<PAGE>   56

same shall be paid by Tenant. In addition, all reasonable costs incurred by
Landlord in connection with the investigation of any notice given by Tenant
shall be paid by Tenant if the reported damage or defective condition was caused
by Tenant or by the employees, licensees, contractors, or invitees of Tenant.
Tenant shall not be entitled to claim any eviction from the Premises or any
damages arising from any such damage or defect unless the same (i) shall have
been occasioned by the negligence of the Landlord, its agents, servants or
employees and (ii) shall not, after notice to Landlord of the condition claimed
to constitute negligence, have been cured or corrected within a reasonable time
after such notice has been received by Landlord; and in case of a claim of
eviction unless such damage or defective condition shall have rendered the
Premises untenantable and they shall not have been made tenantable by Landlord
within a reasonable time.

     17.4 SIGNS, BLINDS AND DRAPES.

     (a)  Tenant shall put no signs in any part of the Building. No signs or
blinds may be put on or in any window or elsewhere if visible from the exterior
of the Building, nor may the building standard drapes or blinds be removed by
Tenant. Tenant may hang its own drapes, provided that they shall not in any way
interfere with the building standard drapery or blinds or be visible from the
exterior of the Building and that such drapes are so hung and installed that
when drawn, the building standard drapery or blinds are automatically also
drawn. Any signs or lettering in the public corridors or on the doors shall
conform to Landlord's building standard design. Neither Landlord's name, nor the
name of the Building or any Center, Office Park or other Park of which the
Building is a part, or the name of any other structure erected therein shall be
used without Landlord's consent in any advertising material (except on business
stationery or as an address in advertising matter), nor shall any such name, as
aforesaid, be used in any undignified, confusing, detrimental or misleading
manner.

     (b)  Provided that and for so long as Akamai Technologies, Inc., itself or
an Assignee or Affiliated Entity (as those terms are defined in Article 16) is
occupying and paying rent on not less than seventy percent (70%) of the entirety
of Floors 1 through 5 of the Building, excluding the retail portions thereof,
Tenant (or an Assignee or Affiliated Entity occupying the Premises as aforesaid)
shall have the right to erect and maintain signage on the exterior of the
Building (the "Exterior Signage") as described in and subject to the
restrictions contained in Exhibit 7 attached hereto, and as shown on the plan
attached hereto as part of said Exhibit 7, provided (i) the Exterior Signage
complies with all applicable laws and shall not interfere with the Landlord's
signage program for the Building and Complex (and Tenant shall have obtained any
necessary permits prior to erecting the Exterior Signage), (ii) the Exterior
Signage shall be located as shown on the plan contained in Exhibit 7, (iii) the
materials, design and lighting of the Exterior Signage, and any requested
changes thereto, shall be subject to Landlord's prior written approval, which
approval shall not be unreasonably withheld, and (iv) Tenant shall at all times
maintain the Exterior Signage in good order and condition and shall remove the
Exterior Signage at the expiration or earlier termination of the term hereof or
upon Landlord's written demand after the failure of condition (ii) above, and
shall repair any damage to the Building caused by the Exterior Signage or its
installation or removal. Tenant's signage rights pursuant to the foregoing
provision shall be exclusive as to all portions of the Building; provided,
however, that the retail tenant(s) of the Building shall have the right to erect
signage not more than twenty (20) feet above ground level on the exterior of the
side(s) of the Building on which their premises have window frontage. Any such
signage by retail tenant(s) (x) shall be in accordance with all applicable law,
and (y) with respect to the signage immediately facing Building 500 in the

                                      -48-
<PAGE>   57

Complex, so long as Akamai Technologies, Inc., itself or an Assignee or
Affiliated Entity collectively are occupying at least seventy percent (70%) of
said Building 500, such signage shall be subject to Tenant's approval, which
approval shall not be unreasonably withheld, delayed or conditioned. Landlord
agrees, at Tenant's cost, to reasonably cooperate with Tenant in obtaining any
necessary governmental approvals, permits, etc. in connection with the Exterior
Signage. Tenant shall have the right, from time to time throughout the term of
the Lease, to replace its signage (if any) with signage which is equivalent to
the signage being replaced, subject to all of the terms and conditions of this
Article 17.4 and Exhibit 7.

     17.5 ESTOPPEL CERTIFICATE. Either party shall at any time and from time to
time upon not less than twenty (20) days' prior notice by the other party,
execute, acknowledge and deliver to the requesting party a statement in writing
certifying that this Lease is unmodified and in full force and effect (or if
there have been modifications, that the same is in full force and effect as
modified and stating the modifications), and the dates to which the Yearly Rent
and other charges have been paid in advance, if any, stating whether or not the
other party is in default in performance of any covenant, agreement, term,
provision or condition contained in this Lease and, if so, specifying each such
default and such other facts as the requesting party may reasonably request, it
being intended that any such statement delivered pursuant hereto may be relied
upon by any prospective purchaser of the Building or of the Building and the
land or of any interest of Landlord therein, any mortgagee or prospective
mortgagee thereof, any lessor or prospective lessor thereof, any lessee or
prospective lessee thereof, or any prospective assignee of any mortgage thereof.
Time is of the essence in respect of any such requested certificate, Tenant
hereby acknowledging the importance of such certificates in mortgage financing
arrangements, prospective sale and the like. Tenant hereby appoints Landlord
Tenant's attorney-in-fact in its name and behalf to execute such statement if
Tenant shall fail to execute such statement within such twenty-(20)-day period.

     17.6 PROHIBITED MATERIALS AND PROPERTY. Tenant shall not bring or permit to
be brought or kept in or on the Premises or elsewhere in the Building (i) any
inflammable, combustible or explosive fluid, material, chemical or substance
including, without limitation, any hazardous substances as defined under
Massachusetts General Laws chapter 21E, the Federal Comprehensive Environmental
Response Compensation and Liability Act (CERCLA), 42 USC Section 9601 et seq.,
as amended, under Section 3001 of the Federal Resource Conservation and Recovery
Act of 1976, as amended, or under any regulation of any governmental authority
regulating environmental or health matters (except for standard office supplies
stored in proper containers), (ii) any materials, appliances or equipment
(including, without limitation, materials, appliances and equipment selected by
Tenant for the construction or other preparation of the Premises and furniture
and carpeting) which pose any danger to life, safety or health or may cause
damage, injury or death; (iii) any unique, unusually valuable, rare or exotic
property, work of art or the like unless the same is fully insured under
all-risk coverage, or (iv) any data processing, electronic, optical or other
equipment or property of a delicate, fragile or vulnerable nature unless the
same are housed, shielded and protected against harm and damage, whether by
cleaning or maintenance personnel, radiations or emanations from other equipment
now or hereafter installed in the Building, or otherwise. Nor shall Tenant cause
or permit any potentially harmful air emissions, odors of cooking or other
processes, or any unusual or other objectionable odors or emissions to emanate
from or permeate the Premises.

     17.7 REQUIREMENTS OF LAW--FINES AND PENALTIES. Tenant at its sole expense
shall comply with all laws, rules, orders and regulations, including, without
limitation, all energy-

                                      -49-
<PAGE>   58

related requirements, of Federal, State, County and Municipal Authorities and
with any direction of any public officer or officers, pursuant to law, which
shall impose any duty upon Landlord or Tenant with respect to or arising out of
Tenant's use or occupancy of the Premises. In addition, Tenant shall, at
Tenant's sole expense, for so long as the Parking and Traffic Demand Management
Plan dated May 9, 1999 as approved by (and subject to the conditions set for in
such approval) the City of Cambridge on July 9, 1999 remains applicable to the
Complex, offer to subsidize mass transit monthly passes for all of its employees
and otherwise cooperate with Landlord in encouraging employees to seek alternate
modes of transportation. Tenant shall reimburse and compensate Landlord for all
expenditures made by, or damages or fines sustained or incurred by, Landlord due
to nonperformance or noncompliance with or breach or failure to observe any
item, covenant, or condition of this Lease upon Tenant's part to be kept,
observed, performed or complied with. If Tenant receives notice of any violation
of law, ordinance, order or regulation applicable to the Premises, it shall give
prompt notice thereof to Landlord. Landlord shall comply with any laws, rules,
orders, regulations, energy requirements ("Laws") and with any direction of any
public office or officer relating to the maintenance or operation of the
Building as an office building, and the costs so incurred by Landlord shall be
included in Operating Costs in accordance with the provisions of Article 9.
Landlord hereby represents to Tenant that, as of the Execution Date of the
Lease, Landlord has not received notice from any governmental agency that the
Building or Premises are in violation of any applicable laws.

     17.8 TENANT'S ACTS--EFFECT ON INSURANCE. Tenant shall not do or permit to
be done any act or thing upon the Premises or elsewhere in the Building which
will invalidate or be in conflict with any insurance policies covering the
Building and the fixtures and property therein; and shall not do, or permit to
be done, any act or thing upon the Premises which shall subject Landlord to any
liability or responsibility for injury to any person or persons or to property
by reason of any business or operation being carried on upon said Premises or
for any other reason. Tenant at its own expense shall comply with all rules,
orders, regulations and requirements of the Board of Fire Underwriters, or any
other similar body having jurisdiction, and shall not (i) do, or permit anything
to be done, in or upon the Premises, or bring or keep anything therein, except
as now or hereafter permitted by the Fire Department, Board of Underwriters,
Fire Insurance Rating Organization, or other authority having jurisdiction, and
then only in such quantity and manner of storage as will not increase the rate
for any insurance applicable to the Building, or (ii) use the Premises in a
manner which shall increase such insurance rates on the Building, or on property
located therein, over that applicable when Tenant first took occupancy of the
Premises hereunder. If by reason of the failure of Tenant to comply with the
provisions hereof the insurance rate applicable to any policy of insurance shall
at any time thereafter be higher than it otherwise would be, the Tenant shall
reimburse Landlord for that part of any insurance premiums thereafter paid by
Landlord, which shall have been charged because of such failure by Tenant.

     17.9 MISCELLANEOUS. Tenant shall not suffer or permit the Premises or any
fixtures, equipment or utilities therein or serving the same, to be overloaded,
damaged or defaced, nor permit any hole to be drilled or made in any part
thereof. Tenant shall not suffer or permit any employee, contractor, business
invitee or visitor to violate any covenant, agreement or obligations of the
Tenant under this Lease.

18.  DAMAGE BY FIRE, ETC.

     (a)  During the entire term of this Lease, and adjusting insurance
coverages to reflect current values from time to time:--(i) Landlord shall keep
the Building (excluding work,

                                      -50-
<PAGE>   59

installations, improvements and betterments made in the Premises after the Term
Commencement Date [called "Over-Building-Standard Property"] and any other
property installed by or at the expense of Tenant) insured against loss or
damage caused by any peril covered under fire, extended coverage and all risk
insurance in an amount equal to one hundred percent (100%) replacement cost
value above foundation walls; and (ii) Tenant shall keep its personal property
in and about the Premises and the Over-Building-Standard Property insured
against loss or damage caused by any peril covered under fire, extended coverage
and all risk insurance in an amount equal to one hundred percent (100%)
replacement cost value. Such Tenant's insurance shall insure the interests of
both Landlord and Tenant as their respective interests may appear from time to
time and shall name Landlord as an additional insured; and the proceeds thereof
shall be used only for the replacement or restoration of such personal property
and the Over-Building-Standard Property.

     (b)  If any portion of the Premises required to be insured by Landlord
under the preceding paragraph shall be damaged by fire or other insured
casualty, Landlord shall proceed with diligence, subject to the then applicable
statutes, building codes, zoning ordinances, and regulations of any governmental
authority, and at the expense of Landlord (but only to the extent of insurance
proceeds made available to Landlord by any mortgagee and/or ground lessor of the
real property of which the Premises are a part) to repair or cause to be
repaired such damage, provided, however, in respect of any over-Building
Standard Property as shall have been damaged by such fire or other casualty and
which (in the judgment of Landlord) can more effectively be repaired as an
integral part of Landlord's repair work on the Premises, that such repairs to
such Tenant's alterations, decorations, additions and improvements shall be
performed by Landlord but at Tenant's expense; in all other respects, all
repairs to and replacements of Tenant's property and Over-Building-Standard
Property shall be made by and at the expense of Tenant. If the Premises or any
part thereof shall have been rendered unfit for use and occupation hereunder by
reason of such damage the Yearly Rent or a just and proportionate part thereof,
according to the nature and extent to which the Premises shall have been so
rendered unfit, shall be suspended or abated until the Premises (except as to
the property which is to be repaired by or at the expense of Tenant) shall have
been restored as nearly as practicably may be to the condition in which they
were immediately prior to such fire or other casualty. Tenant agrees to
cooperate with Landlord in such manner as Landlord may reasonably request in
assisting Landlord in collecting insurance proceeds due in connection with any
casualty which affects the Premises. Landlord shall not be liable for delays in
the making of any such repairs which are due to government regulation,
casualties and strikes, unavailability of labor and materials, and other causes
beyond the reasonable control of Landlord, nor shall Landlord be liable for any
inconvenience or annoyance to Tenant or injury to the business of Tenant
resulting from delays in repairing such damage.

     (c)  LANDLORD'S TERMINATION RIGHTS. If (i) the Premises are so damaged by
fire or other casualty (whether or not insured) at any time during the last
thirty months of the term hereof that the cost to repair such damage is
reasonably estimated to exceed one third of the total Yearly Rent payable
hereunder for the period from the estimated date of restoration until the
Termination Date, or (ii) the Building (whether or not including any portion of
the Premises) is so damaged by fire or other casualty (whether or not insured)
that substantial alteration or reconstruction or demolition of the Building
shall in Landlord's judgment be required, then and in either of such events,
this Lease and the term hereof may be terminated at the election of Landlord by
a notice in writing of its election so to terminate which shall be given by
Landlord to Tenant within sixty (60) days following such fire or other casualty,
the effective termination date

                                      -51-
<PAGE>   60

of which shall be not less than thirty (30) days after the day on which such
termination notice is received by Tenant.

         (d) TENANT'S TERMINATION RIGHTS. In the event that the premises or the
Building are damaged by fire or other casualty to such an extent so as to render
the premises untenantable, and if Landlord shall fail to substantially complete
said repairs or restoration within two hundred fifty (250) days (sixty (60) days
in the case of a fire or other casualty occurring during the last twelve (12)
months of the term hereof, as the same may have been extended) after the date of
such fire or other casualty for any reason other than Tenant's fault, Tenant may
terminate this Lease by giving Landlord written notice as follows:

         (i)   Said notice shall be given after said two hundred fifty (250) day
               period or sixty (60) day period, as the case may be.

         (ii)  Said notice shall set forth an effective date which is not
               earlier than thirty (30) days after Landlord receives said
               notice.

         (iii) If said repairs or restoration are substantially complete on or
               before the date thirty (30) days (which thirty-(30)-day period
               shall be extended by the length of any delays caused by Tenant or
               Tenant's contractors) after Landlord receives such notice, said
               notice shall have no further force and effect.

         (iv)  If said repairs or restoration are not substantially complete on
               or before the date thirty (30) days (which thirty-(30)-day period
               shall be extended by the length of any delays caused by Tenant or
               Tenant's contractors) after Landlord receives such notice, the
               Lease shall terminate as of said effective date.

          (e)  GENERAL PROVISIONS RELATING TO TERMINATION BASED UPON CASUALTY.
In the event of any termination of this Lease pursuant to this Article 18:

         (i)   The term hereof shall expire as of such effective termination
               date as though that were the Termination Date as stated in
               Exhibit 1 and the Yearly Rent shall be apportioned as of such
               date.

         (ii)  If the Premises or any part thereof shall have been rendered
               unfit for use and occupation by reason of such damage the Yearly
               Rent for the period from the date of the fire or other casualty
               to the effective termination date, or a just and proportionate
               part thereof, according to the nature and extent to which the
               Premises shall have been so rendered unfit, shall be abated.

         (iii) If a Restructuring Rent Event, as defined in Paragraph 1 of the
               Rider to this Lease, occurs, and if Landlord draws upon any
               Letter of Credit which Landlord is holding pursuant to Paragraph
               1 of the Rider to this Lease for the purpose of making a
               Restructuring Rent Payment, AND if the Lease is subsequently
               terminated by either party pursuant to this Article 18 based upon
               a fire or other casualty, then Landlord shall, within thirty (30)
               days of the effective termination date of such casualty, pay to
               Tenant a Casualty Termination Payment, as hereinafter defined.
               The "Casualty Termination Payment" shall be defined as the amount
               of principal which would remain unpaid at the effective
               termination

                                      -52-
<PAGE>   61

               date on a loan (i) in the original principal amount of the
               Restructuring Rent Payment, (ii) with interest at the rate of the
               rate per annum announced by Fleet Bank, N.A., or its successor,
               from time to time as its "prime" rate, plus one-quarter percent
               (1/4%), (iii) which is repaid on a direct reduction basis in
               equal monthly payments of principal and interest, and (iv) with a
               term commencing with the application of the Restructuring Rent
               Payment and ending as of the expiration of the then-current term
               of the Lease. If, prior to the termination of the Lease based
               upon a fire or other casualty, there have been two Restructuring
               Rent Payments pursuant to Paragraph 1.C.6 of the Rider to this
               Lease, the Casualty Termination Payment shall be calculated
               separately for each such Restructuring Rent Payment.

19.  WAIVER OF SUBROGATION

     In any case in which Tenant shall be obligated to pay to Landlord any loss,
cost, damage, liability, or expense suffered or incurred by Landlord, Landlord
shall allow to Tenant as an offset against the amount thereof (i) the net
proceeds of any insurance collected by Landlord for or on account of such loss,
cost, damage, liability or expense, provided that the allowance of such offset
does not invalidate or prejudice the policy or policies under which such
proceeds were payable, and (ii) if such loss, cost, damage, liability or expense
shall have been caused by a peril against which Landlord has agreed to procure
insurance coverage under the terms of this Lease, the amount of such insurance
coverage, whether or not actually procured by Landlord.

     In any case in which Landlord or Landlord's managing agent shall be
obligated to pay to Tenant any loss, cost, damage, liability or expense suffered
or incurred by Tenant, Tenant shall allow to Landlord or Landlord's managing
agent, as the case may be, as an offset against the amount thereof (i) the net
proceeds of any insurance collected by Tenant for or on account of such loss,
cost, damage, liability, or expense, provided that the allowance of such offset
does not invalidate the policy or policies under which such proceeds were
payable and (ii) the amount of any loss, cost, damage, liability or expense
caused by a peril covered by fire insurance with the broadest form of property
insurance generally available on property in buildings of the type of the
Building, whether or not actually procured by Tenant.

     The parties hereto shall each procure an appropriate clause in, or
endorsement on, any property insurance policy covering the Premises and the
Building and personal property, fixtures and equipment located thereon and
therein, pursuant to which the insurance companies waive subrogation or consent
to a waiver of right of recovery in favor of either party, its respective agents
or employees. Having obtained such clauses and/or endorsements, each party
hereby agrees that it will not make any claim against or seek to recover from
the other or its agents or employees for any loss or damage to its property or
the property of others resulting from fire or other perils covered by such
property insurance.

20.  CONDEMNATION - EMINENT DOMAIN

     (a)  In the event that the Premises or any part thereof, or the whole or
any part of the Building, shall be taken or appropriated by eminent domain or
shall be condemned for any public or quasi-public use, or (by virtue of any such
taking, appropriation or condemnation) shall suffer any damage (direct, indirect
or consequential) for which Landlord or Tenant shall be entitled to
compensation, then (and in any such event) this Lease and the term hereof may be
terminated at

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<PAGE>   62

the election of Landlord by a notice in writing of its election so to terminate
which shall be given by Landlord to Tenant within sixty (60) days following the
date on which Landlord shall have received notice of such taking, appropriation
or condemnation. In the event that a substantial part of the Premises or of the
means of access thereto shall be so taken, appropriated or condemned, then (and
in any such event) this Lease and the term hereof may be terminated at the
election of Tenant by a notice in writing of its election so to terminate which
shall be given by Tenant to Landlord within sixty (60) days following the date
on which Tenant shall have received notice of such taking, appropriation or
condemnation.

     (b)  Upon the giving of any such notice of termination (either by Landlord
or Tenant) this Lease and the term hereof shall terminate on or retroactively as
of the date on which Tenant shall be required to vacate any part of the Premises
or shall be deprived of a substantial part of the means of access thereto,
provided, however, that Landlord may in Landlord's notice elect to terminate
this Lease and the term hereof retroactively as of the date on which such
taking, appropriation or condemnation became legally effective. In the event of
any such termination, this Lease and the term hereof shall expire as of such
effective termination date as though that were the Termination Date as stated in
Exhibit 1, and the Yearly Rent shall be apportioned as of such date.

     (c)  If a Restructuring Rent Event, as defined in Paragraph 1 of the Rider
to this Lease, occurs, and if Landlord draws upon any Letter of Credit which
Landlord is holding pursuant to Paragraph 1 of the Rider to this Lease for the
purpose of making a Restructuring Rent Payment, AND if the Lease is subsequently
terminated by either party pursuant to this Article 20 based upon taking or
condemnation, as aforesaid, then Landlord shall, within thirty (30) days of the
effective termination date of such taking, pay to Tenant a Taking Termination
Payment, as hereinafter defined. The "Taking Termination Payment" shall be
defined as the amount of principal which would remain unpaid at the effective
termination date on a loan (i) in the original principal amount of the
Restructuring Rent Payment, (ii) with interest at the rate of the rate per annum
announced by Fleet Bank, N.A., or its successor, from time to time as its
"prime" rate, plus one-quarter percent (1/4%), (iii) which is repaid on a direct
reduction basis in equal monthly payments of principal and interest, and (iv)
with a term commencing with the application of the Restructuring Rent Payment
and ending as of the expiration of the then-current term of the Lease. If, prior
to the termination of the Lease based upon a taking, there have been two
Restructuring Rent Payments pursuant to Paragraph 1.C.6 of the Rider to this
Lease, the Taking Termination Payment shall be calculated separately for each
such Restructuring Rent Payment.

     (d)  If neither party (having the right so to do) elects to terminate
Landlord will, with reasonable diligence and at Landlord's expense, restore the
remainder of the Premises, or the remainder of the means of access, as nearly as
practicably may be to the same condition as obtained prior to such taking,
appropriation or condemnation in which event (i) the Total Rentable Area shall
be equitably adjusted, (ii) a just proportion of the Yearly Rent, according to
the nature and extent of the taking, appropriation or condemnation and the
resulting permanent injury to the Premises and the means of access thereto,
shall be permanently abated, and (iii) a just proportion of the remainder of the
Yearly Rent, according to the nature and extent of the taking, appropriation or
condemnation and the resultant injury sustained by the Premises and the means of
access thereto, shall be abated until what remains of the Premises and the means
of access thereto shall have been restored as fully as may be for permanent use
and occupation by Tenant hereunder. Except for any award specifically
reimbursing Tenant for moving or relocation expenses, there are expressly
reserved to Landlord all rights to compensation and

                                      -54-
<PAGE>   63

damages created, accrued or accruing by reason of any such taking, appropriation
or condemnation, in implementation and in confirmation of which Tenant does
hereby acknowledge that Landlord shall be entitled to receive all such
compensation and damages, grant to Landlord all and whatever rights (if any)
Tenant may have to such compensation and damages, and agree to execute and
deliver all and whatever further instruments of assignment as Landlord may from
time to time request. In the event of any taking of the Premises or any part
thereof for temporary (i.e., not in excess of one (1) year) use, (i) this Lease
shall be and remain unaffected thereby, and (ii) Tenant shall be entitled to
receive for itself any award made to the extent allocable to the Premises in
respect of such taking on account of such use, provided, that if any taking is
for a period extending beyond the term of this Lease, such award shall be
apportioned between Landlord and Tenant as of the Termination Date or earlier
termination of this Lease.

21.  DEFAULT

     21.1 CONDITIONS OF LIMITATION - RE-ENTRY - TERMINATION. This Lease and the
herein term and estate are, upon the condition that if (a) subject to Article
21.7, Tenant shall neglect or fail to perform or observe any of the Tenant's
covenants or agreements herein, including (without limitation) the covenants or
agreements with regard to the payment when due of rent, additional charges,
reimbursement for increase in Landlord's costs, or any other charge payable by
Tenant to Landlord (all of which shall be considered as part of Yearly Rent for
the purposes of invoking Landlord's statutory or other rights and remedies in
respect of payment defaults); or (b) Tenant shall desert or abandon the Premises
or the same shall become vacant (whether or not the keys shall have been
surrendered or the rent shall have been paid); or (c) Tenant shall be involved
in financial difficulties as evidenced by an admission in writing by Tenant of
Tenant's inability to pay its debts generally as they become due, or by the
making or offering to make a composition of its debts with its creditors; or (d)
Tenant shall make an assignment or trust mortgage, or other conveyance or
transfer of like nature, of all or a substantial part of its property for the
benefit of its creditors, or (e) an attachment on mesne process, on execution or
otherwise, or other legal process shall issue against Tenant or its property and
a sale of any of its assets shall be held thereunder; or (f) any judgment, final
beyond appeal or any lien, attachment or the like in excess of $250,000.00 shall
be entered, recorded or filed against Tenant in any court, registry, etc. and
Tenant shall fail to pay such judgment within thirty (30) days after the
judgment shall have become final beyond appeal or to discharge or secure by
surety bond such lien, attachment, etc. within thirty (30) days of such entry,
recording or filing, as the case may be; or (g) the leasehold hereby created
shall be taken on execution or by other process of law and shall not be revested
in Tenant within thirty (30) days thereafter; or (h) a receiver, sequesterer,
trustee or similar officer shall be appointed by a court of competent
jurisdiction to take charge of all or any part of Tenant's property and such
appointment shall not be vacated within thirty (30) days; or (i) any proceeding
shall be instituted by or against Tenant pursuant to any of the provisions of
any Act of Congress or State law relating to bankruptcy, reorganizations,
arrangements, compositions or other relief from creditors, and, in the case of
any proceeding instituted against it, if Tenant shall fail to have such
proceedings dismissed within thirty (30) days or if Tenant is adjudged bankrupt
or insolvent as a result of any such proceeding, or (j) any event shall occur or
any contingency shall arise whereby this Lease, or the term and estate thereby
created, would (by operation of law or otherwise) devolve upon or pass to any
person, firm or corporation other than Tenant, except as expressly permitted
under Article 16 hereof, or (k) for so long as Building 500 in the Complex is
owned by Landlord or an affiliate of Landlord, Tenant shall default beyond any
applicable notice or cure period under that certain lease dated as of September
22, 1999 between Landlord and Tenant for premises at Building 500 in the
Complex, as amended (the

                                      -55-
<PAGE>   64
"Building 500 Lease") - then, and in any such event (except as hereinafter in
Article 21.2 otherwise provided) Landlord may, by notice to Tenant, elect to
terminate this Lease; and thereupon (and without prejudice to any remedies which
might otherwise be available for arrears of rent or other charges due hereunder
or preceding breach of covenant or agreement and without prejudice to Tenant's
liability for damages as hereinafter stated), upon the giving of such notice,
this Lease shall terminate as of the date specified therein as though that were
the Termination Date as stated in Exhibit 1. Without being taken or deemed to be
guilty of any manner of trespass or conversion, and without being liable to
indictment, prosecution or damages therefor, Landlord may, forcibly if
necessary, enter into and upon the Premises (or any part thereof in the name of
the whole); repossess the same as of its former estate; and expel Tenant and
those claiming under Tenant. Wherever "Tenant" is used in subdivisions (c),
(d), (e), (f), (g), (h) and (i) of this Article 21.1, it shall be deemed to
include any one of (i) any corporation of which Tenant is a controlled
subsidiary and (ii) any guarantor of any of Tenant's obligations under this
Lease. The words "re-entry" and "re-enter" as used in this Lease are not
restricted to their technical legal meanings.

     21.2 INTENTIONALLY OMITTED.

     21.3 DAMAGES - TERMINATION. Upon the termination of this Lease under the
provisions of this Article 21, then except as hereinabove in Article 21.2
otherwise provided, Tenant shall pay to Landlord the rent and other charges
payable by Tenant to Landlord up to the time of such termination, shall continue
to be liable for any preceding breach of covenant, and in addition, shall pay to
Landlord as damages, at the election of Landlord

     either:

          (x)  the amount by which, at the time of the termination of this Lease
(or at any time thereafter if Landlord shall have initially elected damages
under subparagraph (y), below), (i) the aggregate of the rent and other charges
projected over the period commencing with such termination and ending on the
Termination Date as stated in Exhibit 1 exceeds (ii) the aggregate projected
rental value of the Premises for such period;

     or:

          (y)  amounts equal to the rent and other charges which would have been
payable by Tenant had this Lease not been so terminated, payable upon the due
dates therefor specified herein following such termination and until the
Termination Date as specified in Exhibit 1, provided, however, if Landlord shall
re-let the Premises during such period, that Landlord shall credit Tenant with
the net rents received by Landlord from such re-letting, such net rents to be
determined by first deducting from the gross rents as and when received by
Landlord from such re-letting the expenses incurred or paid by Landlord in
terminating this Lease, as well as the expenses of re-letting, including
altering and preparing the Premises for new tenants, brokers' commissions, and
all other similar and dissimilar expenses properly chargeable against the
Premises and the rental therefrom, it being understood that any such re-letting
may be for a period equal to or shorter or longer than the remaining term of
this Lease; and provided, further, that (i) in no event shall Tenant be entitled
to receive any excess of such net rents over the sums payable by Tenant to
Landlord hereunder and (ii) in no event shall Tenant be entitled in any suit for
the collection of damages pursuant to this Subparagraph (y) to a credit in
respect of any net rents from a re-letting except to the extent that such net
rents are

                                      -56-
<PAGE>   65

actually received by Landlord prior to the commencement of such suit. If the
Premises or any part thereof should be re-let in combination with other space,
then proper apportionment on a square foot area basis shall be made of the rent
received from such re-letting and of the expenses of re-letting.

     In calculating the rent and other charges under Subparagraph (x), above,
there shall be included, in addition to the Yearly Rent, Tax Excess and
Operating Expense Excess and all other considerations agreed to be paid or
performed by Tenant, on the assumption that all such amounts and considerations
would have remained constant (except as herein otherwise provided) for the
balance of the full term hereby granted.

     Suit or suits for the recovery of such damages, or any installments
thereof, may be brought by Landlord from time to time at its election, and
nothing contained herein shall be deemed to require Landlord to postpone suit
until the date when the term of this Lease would have expired if it had not been
terminated hereunder.

     Nothing herein contained shall be construed as limiting or precluding the
recovery by Landlord against Tenant of any sums or damages to which, in addition
to the damages particularly provided above, Landlord may lawfully be entitled by
reason of any default hereunder on the part of Tenant.

     21.4 FEES AND EXPENSES.

          (a)  If Tenant shall default in the performance of any covenant on
Tenant's part to be performed as in this Lease contained, Landlord may, upon
reasonable advance notice, except that no notice shall be required in an
emergency, immediately, or at any time thereafter, without notice, perform the
same for the account of Tenant. If Landlord at any time is compelled to pay or
elects to pay any sum of money, or do any act which will require the payment of
any sum of money, by reason of the failure of Tenant to comply with any
provision hereof, or if Landlord is compelled to or does incur any expense,
including reasonable attorneys' fees, in instituting, prosecuting, and/or
defending any action or proceeding instituted by reason of any default of Tenant
hereunder, Tenant shall on demand pay to Landlord by way of reimbursement the
sum or sums so paid by Landlord with all costs and damages, plus interest
computed as provided in Article 6 hereof.

          (b)  Tenant shall pay Landlord's cost and expense, including
reasonable attorneys' fees, incurred (i) in enforcing any obligation of Tenant
under this Lease or (ii) as a result of Landlord, without its fault, being made
party to any litigation pending by or against Tenant or any persons claiming
through or under Tenant. Tenant shall not be obligated to make any payment to
Landlord of any attorneys' fees incurred by Landlord unless judgment is entered
(final, and beyond appeal) in favor of Landlord in the lawsuit relating to such
fees. Landlord shall pay, upon demand by Tenant, reasonable attorneys' fees
incurred by Tenant in connection with any lawsuit between Landlord and Tenant
where judgment is entered (final, and beyond appeal) in favor of Tenant.

     21.5 WAIVER OF REDEMPTION. Tenant does hereby waive and surrender all
rights and privileges which it might have under or by reason of any present or
future law to redeem the Premises or to have a continuance of this Lease for the
term hereby demised after being

                                      -57-
<PAGE>   66

dispossessed or ejected therefrom by process of law or under the terms of this
Lease or after the termination of this Lease as herein provided.

     21.6 LANDLORD'S REMEDIES NOT EXCLUSIVE. The specified remedies to which
Landlord may resort hereunder are cumulative and are not intended to be
exclusive of any remedies or means of redress to which Landlord may at any time
be lawfully entitled, and Landlord may invoke any remedy (including the remedy
of specific performance) allowed at law or in equity as if specific remedies
were not herein provided for.

     21.7 GRACE PERIOD. Notwithstanding anything to the contrary in this Article
contained, Landlord agrees not to take any action to terminate this Lease (a)
for default by Tenant in the payment when due of any sum of money, if Tenant
shall cure such default within five (5) business days after written notice
thereof is given by Landlord to Tenant, or (b) for default by Tenant in the
performance of any covenant other than a covenant to pay a sum of money, if
Tenant shall cure such default within a period of thirty (30) days after written
notice thereof given by Landlord to Tenant (except where the nature of the
default is such that remedial action should appropriately take place sooner, as
indicated in such written notice), or within such additional period as may
reasonably be required to cure such default if (because of governmental
restrictions or any other cause beyond the reasonable control of Tenant) the
default is of such a nature that it cannot reasonably be cured within such
thirty-(30)-day period, provided, however, (1) that there shall be no extension
of time beyond such thirty-(30)-day period for the curing of any such default
unless, not more than ten (10) days after the receipt of the notice of default,
Tenant in writing (i) shall specify the cause on account of which the default
cannot be cured during such period and shall advise Landlord of its intention
duly to institute all steps necessary to cure the default and (ii) shall, as
soon as reasonably practicable, duly institute and thereafter diligently
prosecute to completion all steps necessary to cure such default and, (2) that
no notice of the opportunity to cure a default need be given, and no grace
period whatsoever shall be allowed to Tenant, if the default is incurable or if
the covenant or condition the breach of which gave rise to default had, by
reason of a breach on two (2) prior occasions within the immediately preceding
twelve (12) month period, been the subject of a notice hereunder to cure such
default.

     Notwithstanding anything to the contrary in this Article 21.7 contained,
except to the extent prohibited by applicable law, any statutory notice and
grace periods provided to Tenant by law are hereby expressly waived by Tenant.

22.  END OF TERM - ABANDONED PROPERTY

     Upon the expiration or other termination of the term of this Lease, Tenant
shall peaceably quit and surrender to Landlord the Premises and all alterations
and additions thereto, broom clean, in good order, repair and condition (except
as provided herein and in Articles 8.7, 18 and 20) excepting only ordinary wear
and use and damage by fire or other casualty for which, under other provisions
of this Lease, Tenant has no responsibility of repair or restoration. Tenant
shall remove all of its property and, to the extent specified by Landlord, all
alterations and additions made by Tenant and all partitions wholly within the
Premises, and shall repair any damages to the Premises or the Building caused by
their installation or by such removal. Tenant's obligation to observe or perform
this covenant shall survive the expiration or other termination of the term of
this Lease.

                                      -58-
<PAGE>   67

     Tenant will remove any personal property from the Building and the Premises
upon or prior to the expiration or termination of this Lease and any such
property which shall remain in the Building or the Premises thereafter shall be
conclusively deemed to have been abandoned, and may either be retained by
Landlord as its property or sold or otherwise disposed of in such manner as
Landlord may see fit. If any part thereof shall be sold, that Landlord may
receive and retain the proceeds of such sale and apply the same, at its option,
against the expenses of the sale, the cost of moving and storage, any arrears of
Yearly Rent, additional or other charges payable hereunder by Tenant to Landlord
and any damages to which Landlord may be entitled under Article 21 hereof or
pursuant to law.

     If Tenant or anyone claiming under Tenant shall remain in possession of the
Premises or any part thereof after the expiration or prior termination of the
term of this Lease without any agreement in writing between Landlord and Tenant
with respect thereto, then, prior to the acceptance of any payments for rent or
use and occupancy by Landlord, the person remaining in possession shall be
deemed a tenant-at-sufferance. Whereas the parties hereby acknowledge that
Landlord may need the Premises after the expiration or prior termination of the
term of the Lease for other tenants and that the damages which Landlord may
suffer as the result of Tenant's holding-over cannot be determined as of the
Execution Date hereof, in the event that Tenant so holds over, Tenant shall pay
to Landlord in addition to all rental and other charges due and accrued under
the Lease prior to the date of termination, charges (based upon fair market
rental value of the Premises) for use and occupation of the Premises thereafter
and, in addition to such sums and any and all other rights and remedies which
Landlord may have at law or in equity, an additional use and occupancy charge in
the amount of fifty percent (50%) of either the Yearly Rent and other charges
calculated (on a daily basis) at the highest rate payable under the terms of
this Lease, but measured from the day on which Tenant's hold-over commenced and
terminating on the day on which Tenant vacates the Premises or the fair market
value of the Premises for such period, whichever is greater. In addition, Tenant
shall save Landlord, its agents and employees, harmless and will exonerate,
defend and indemnify Landlord, its agents and employees, from and against any
and all damages which Landlord may suffer on account of Tenant's hold-over in
the Premises after the expiration or prior termination of the term of the Lease.
Notwithstanding the foregoing, Tenant shall not be liable for consequential
damages incurred by Landlord based upon any holdover by Tenant after the
expiration or prior termination of the term of the Lease unless such holdover
continues for sixty (60) or more days after the termination of this Lease or
Tenant's right to possession.

23.  SUBORDINATION

     (a)  Subject to any mortgagee's or ground lessor's election, as hereinafter
provided for, this Lease is subject and subordinate in all respects to all
matters of record (including, without limitation, deeds and land disposition
agreements), ground leases and/or underlying leases, and all mortgages, any of
which may now or hereafter be placed on or affect such leases and/or the real
property of which the Premises are a part, or any part of such real property,
and/or Landlord's interest or estate therein, and to each advance made and/or
hereafter to be made under any such mortgages, and to all renewals,
modifications, consolidations, replacements and extensions thereof and all
substitutions therefor. This Article 23 shall be self-operative and no further
instrument or subordination shall be required. In confirmation of such
subordination, Tenant shall execute, acknowledge and deliver promptly any
certificate or instrument that Landlord and/or any mortgagee and/or lessor under
any ground or underlying lease and/or their respective successors in interest
may request, subject to Landlord's, mortgagee's and ground

                                      -59-
<PAGE>   68

lessor's right to do so for, on behalf and in the name of Tenant under certain
circumstances, as hereinafter provided. Tenant acknowledges that, where
applicable, any consent or approval hereafter given by Landlord may be subject
to the further consent or approval of such mortgagee and/or ground lessor; and
the failure or refusal of such mortgagee and/or ground lessor to give such
consent or approval shall, notwithstanding anything to the contrary in this
Lease contained, constitute reasonable justification for Landlord's withholding
its consent or approval. Landlord hereby represents to Tenant that, as of the
Execution Date of this Lease, there is no mortgage affecting the Premises or the
Building. Notwithstanding anything to the contrary in this Article 23 contained,
as to any future mortgages, ground leases, and/or underlying lease or deeds of
trust, the herein provided subordination and attornment shall be effective only
if the mortgagee, ground lessor or trustee therein, as the case may be, agrees,
by a written instrument in recordable form and in the customary form of such
mortgagee, ground lessor, or trustee ("Nondisturbance Agreement") that, as long
as Tenant shall not be in terminable default of the obligations on its part to
be kept and performed under the terms of this Lease, this Lease will not be
affected and Tenant's possession hereunder will not be disturbed by any default
in, termination, and/or foreclosure of, such mortgage, ground lease, and/or
underlying lease or deed of trust, as the case may be.

     (b)  Any such mortgagee or ground lessor may from time to time subordinate
or revoke any such subordination of the mortgage or ground lease held by it to
this Lease. Such subordination or revocation, as the case may be, shall be
effected by written notice to Tenant and by recording an instrument of
subordination or of such revocation, as the case may be, with the appropriate
registry of deeds or land records and to be effective without any further act or
deed on the part of Tenant. In confirmation of such subordination or of such
revocation, as the case may be, Tenant shall execute, acknowledge and promptly
deliver any certificate or instrument that Landlord, any mortgagee or ground
lessor may request, subject to Landlord's, mortgagee's and ground lessor's right
to do so for, on behalf and in the name of Tenant under certain circumstances,
as hereinafter provided.

     (c)  Without limitation of any of the provisions of this Lease, if any
ground lessor or mortgagee shall succeed to the interest of Landlord by reason
of the exercise of its rights under such ground lease or mortgage (or the
acceptance of voluntary conveyance in lieu thereof) or any third party
(including, without limitation, any foreclosure purchaser or mortgage receiver)
shall succeed to such interest by reason of any such exercise or the expiration
or sooner termination of such ground lease, however caused, then such successor
may, upon notice and request to Tenant (which, in the case of a ground lease,
shall be within thirty (30) days after such expiration or sooner termination),
succeed to the interest of Landlord under this Lease, provided, however, that
such successor shall not: (i) be liable for any previous act or omission of
Landlord under this Lease; (ii) be subject to any offset, defense, or
counterclaim which shall theretofore have accrued to Tenant against Landlord;
(iii) have any obligation with respect to any letter of credit unless it shall
have been physically delivered to such successor; or (iv) be bound by any
previous modification of this Lease or by any previous payment of Yearly Rent
for a period greater than one (1) month, made without such ground lessor's or
mortgagee's consent where such consent is required by applicable ground lease or
mortgage documents. In the event of such succession to the interest of the
Landlord -- and notwithstanding that any such mortgage or ground lease may
antedate this Lease -- the Tenant shall attorn to such successor and shall ipso
facto be and become bound directly to such successor in interest to Landlord to
perform and observe all the Tenant's obligations under this Lease without the
necessity of the execution of any further instrument. Nevertheless, Tenant
agrees at any time and from time to time during the term

                                      -60-
<PAGE>   69

hereof to execute a suitable instrument in confirmation of Tenant's agreement to
attorn, as aforesaid, subject to Landlord's, mortgagee's and ground lessor's
right to do so for, on behalf and in the name of Tenant under certain
circumstances, as hereinafter provided.

     (d)  The term "mortgage(s)" as used in this Lease shall include any
mortgage or deed of trust. The term "mortgagee(s)" as used in this Lease shall
include any mortgagee or any trustee and beneficiary under a deed of trust or
receiver appointed under a mortgage or deed of trust. The term "mortgagor(s)" as
used in this Lease shall include any mortgagor or any grantor under a deed of
trust.

     (e)  Tenant hereby irrevocably constitutes and appoints Landlord or any
such mortgagee or ground lessor, and their respective successors in interest,
acting singly, Tenant's attorney-in-fact to execute and deliver any such
certificate or instrument for, on behalf and in the name of Tenant, but only if
Tenant fails to execute, acknowledge and deliver any such certificate or
instrument within twenty (20) days after Landlord or such mortgagee or such
ground lessor has made written request therefor.

     (f)  Notwithstanding anything to the contrary contained in this Article 23,
if all or part of Landlord's estate and interest in the real property of which
the Premises are a part shall be a leasehold estate held under a ground lease,
then: (i) the foregoing subordination provisions of this Article 23 shall not
apply to any mortgages of the fee interest in said real property to which
Landlord's leasehold estate is not otherwise subject and subordinate; and (ii)
the provisions of this Article 23 shall in no way waive, abrogate or otherwise
affect any agreement by any ground lessor (x) not to terminate this Lease
incident to any termination of such ground lease prior to its term expiring or
(y) not to name or join Tenant in any action or proceeding by such ground lessor
to recover possession of such real property or for any other relief. As of the
Execution Date of this Lease, there is no ground lease of the Building or the
real property of which the Building is a part.

     (g)  In the event of any failure by Landlord to perform, fulfill or observe
any agreement by Landlord herein, in no event will the Landlord be deemed to be
in default under this Lease permitting Tenant to exercise any or all rights or
remedies under this Lease until the Tenant shall have given written notice of
such failure to any mortgagee (ground lessor and/or trustee) of which Tenant
shall have been advised and until a reasonable period of time shall have elapsed
following the giving of such notice, during which such mortgagee (ground lessor
and/or trustee) shall have the right, but shall not be obligated, to remedy such
failure.

24.  QUIET ENJOYMENT

     Landlord covenants that if, and so long as, Tenant keeps and performs each
and every covenant, agreement, term, provision and condition herein contained on
the part and on behalf of Tenant to be kept and performed, Tenant shall quietly
enjoy the Premises from and against the claims of all persons claiming by,
through or under Landlord subject, nevertheless, to the covenants, agreements,
terms, provisions and conditions of this Lease and to the mortgages, ground
leases and/or underlying leases to which this Lease is subject and subordinate,
as hereinabove set forth.

     Without incurring any liability to Tenant, Landlord may permit access to
the Premises and open the same, whether or not Tenant shall be present, upon any
demand of any receiver,

                                      -61-
<PAGE>   70

trustee, assignee for the benefit of creditors, sheriff, marshal or court
officer entitled to, or reasonably purporting to be entitled to, such access for
the purpose of taking possession of, or removing, Tenant's property or for any
other lawful purpose (but this provision and any action by Landlord hereunder
shall not be deemed a recognition by Landlord that the person or official making
such demand has any right or interest in or to this Lease, or in or to the
Premises), or upon demand of any representative of the fire, police, building,
sanitation or other department of the city, state or federal governments.

25.  ENTIRE AGREEMENT -- WAIVER -- SURRENDER

     25.1 ENTIRE AGREEMENT. This Lease and the Exhibits made a part hereof
contain the entire and only agreement between the parties and any and all
statements and representations, written and oral, including previous
correspondence and agreements between the parties hereto, are merged herein.
Tenant acknowledges that all representations and statements upon which it relied
in executing this Lease are contained herein and that the Tenant in no way
relied upon any other statements or representations, written or oral. Any
executory agreement hereafter made shall be ineffective to change, modify,
discharge or effect an abandonment of this Lease in whole or in part unless such
executory agreement is in writing and signed by the party against whom
enforcement of the change, modification, discharge or abandonment is sought.

     25.2 WAIVER. The failure of either party to seek redress for violation, or
to insist upon the strict performance, of any covenant or condition of this
Lease, or any of the Rules and Regulations promulgated hereunder, shall not
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 of rent with knowledge of the breach of any covenant of this Lease
shall not be deemed a waiver of such breach. The failure of Landlord to enforce
any of such Rules and Regulations against Tenant and/or any other tenant in the
Building shall not be deemed a waiver of any such Rules and Regulations. No
provisions of this Lease shall be deemed to have been waived by either party
unless such waiver be in writing signed by such party. No payment by Tenant or
receipt by Landlord of a lesser amount than the monthly rent herein stipulated
shall be deemed to be other than on account of the stipulated rent, nor shall
any endorsement or statement on any check or any letter accompanying any check
or payment as rent be deemed an accord and satisfaction, and Landlord may accept
such check or payment without prejudice to Landlord's right to recover the
balance of such rent or pursue any other remedy in this Lease provided.

     25.3 SURRENDER. No act or thing done by Landlord during the term hereby
demised shall be deemed an acceptance of a surrender of the Premises, and no
agreement to accept such surrender shall be valid, unless in writing signed by
Landlord. No employee of Landlord or of Landlord's agents shall have any power
to accept the keys of the Premises prior to the termination of this Lease. The
delivery of keys to any employee of Landlord or of Landlord's agents shall not
operate as a termination of the Lease or a surrender of the Premises. In the
event that Tenant at any time desires to have Landlord underlet the Premises for
Tenant's account, Landlord or Landlord's agents are authorized to receive the
keys for such purposes without releasing Tenant from any of the obligations
under this Lease, and Tenant hereby relieves Landlord of any liability for loss
of or damage to any of Tenant's effects in connection with such underletting.

                                      -62-
<PAGE>   71

26.  INABILITY TO PERFORM - EXCULPATORY CLAUSE

     Except as provided in Article 4.1, 4.2, 8.8, 18 and 20 hereof, this Lease
and the obligations of Tenant to pay rent hereunder and perform all the other
covenants, agreements, terms, provisions and conditions hereunder on the part of
Tenant to be performed shall in no way be affected, impaired or excused because
Landlord is unable to fulfill any of its obligations under this Lease or is
unable to supply or is delayed in supplying any service expressly or impliedly
to be supplied or is unable to make or is delayed in making any repairs,
replacements, additions, alterations, improvements or decorations or is unable
to supply or is delayed in supplying any equipment or fixtures if Landlord is
prevented or delayed from so doing by reason of strikes or labor troubles or any
other similar or dissimilar cause whatsoever beyond Landlord's reasonable
control, including but not limited to, governmental preemption in connection
with a national emergency or by reason of any rule, order or regulation of any
department or subdivision thereof of any governmental agency or by reason of the
conditions of supply and demand which have been or are affected by war,
hostilities or other similar or dissimilar emergency. In each such instance of
inability of Landlord to perform, Landlord shall exercise reasonable diligence
to eliminate the cause of such inability to perform.

     Tenant shall neither assert nor seek to enforce any claim against Landlord,
or Landlord's agents or employees, or the assets of Landlord or of Landlord's
agents or employees, for breach of this Lease or otherwise, other than against
Landlord's interest in the Building of which the Premises are a part and the
Complex and in the uncollected rents, issues and profits thereof, and Tenant
agrees to look solely to such interest for the satisfaction of any liability of
Landlord under this Lease, it being specifically agreed that in no event shall
Landlord or Landlord's agents or employees (or any of the officers, trustees,
directors, partners, beneficiaries, joint venturers, members, stockholders or
other principals or representatives, and the like, disclosed or undisclosed,
thereof) ever be personally liable for any such liability. This paragraph shall
not limit any right that Tenant might otherwise have to obtain injunctive relief
against Landlord or to take any other action which shall not involve the
personal liability of Landlord to respond in monetary damages from Landlord's
assets other than the Landlord's interest in said real estate, as aforesaid. In
no event shall Landlord or Landlord's agents or employees (or any of the
officers, trustees, directors, partners, beneficiaries, joint venturers,
members, stockholders or other principals or representatives and the like,
disclosed or undisclosed, thereof) ever be liable for consequential or
incidental damages. Without limiting the foregoing, in no event shall Landlord
or Landlord's agents or employees (or any of the officers, trustees, directors,
partners, beneficiaries, joint venturers, members, stockholders or other
principals or representatives and the like, disclosed or undisclosed, thereof)
ever be liable for lost profits of Tenant. If by reason of Landlord's failure to
acquire title to the real property of which the Premises are a part or to
complete construction of the Building or Premises, Landlord shall be held to be
in breach of this Lease, Tenant's sole and exclusive remedy shall be as set
forth in Article 4 hereof.

27.  BILLS AND NOTICES

     Any notice, consent, request, bill, demand or statement hereunder by either
party to the other party shall be in writing and, if received at Landlord's or
Tenant's address, shall be deemed to have been duly given when either delivered
or served personally or mailed in a postpaid envelope, deposited in the United
States mail addressed to Landlord at its address as stated in Exhibit 1 and to
Tenant at the Premises (or at Tenant's address as stated in Exhibit 1, if mailed
prior to Tenant's occupancy of the Premises), or if any address for notices
shall have been duly

                                      -63-
<PAGE>   72

changed as hereinafter provided, if mailed as aforesaid to the party at such
changed address. Either party may at any time change the address or specify an
additional address for such notices, consents, requests, bills, demands or
statements by delivering or mailing, as aforesaid, to the other party a notice
stating the change and setting forth the changed or additional address, provided
such changed or additional address is within the United States.

     If Tenant is a partnership, Tenant, for itself, and on behalf of all of its
partners, hereby appoints Tenant's Service Partner, as identified on Exhibit 1,
to accept service of any notice, consent, request, bill, demand or statement
hereunder by Landlord and any service of process in any judicial proceeding with
respect to this Lease on behalf of Tenant and as agent and attorney-in-fact for
each partner of Tenant.

     All bills and statements for reimbursement or other payments or charges due
from Tenant to Landlord hereunder shall be due and payable in full twenty (20)
days, unless herein otherwise provided, after submission thereof by Landlord to
Tenant. Tenant's failure to make timely payment of any amounts indicated by such
bills and statements, whether for work done by Landlord at Tenant's request,
reimbursement provided for by this Lease or for any other sums properly owing by
Tenant to Landlord, shall be treated as a default in the payment of rent, in
which event Landlord shall have all rights and remedies provided in this Lease
for the nonpayment of rent.

28.  PARTIES BOUND -- SEIZIN OF TITLE

     The covenants, agreements, terms, provisions and conditions of this Lease
shall bind and benefit the successors and assigns of the parties hereto with the
same effect as if mentioned in each instance where a party hereto is named or
referred to, except that no violation of the provisions of Article 16 hereof
shall operate to vest any rights in any successor or assignee of Tenant and that
the provisions of this Article 28 shall not be construed as modifying the
conditions of limitation contained in Article 21 hereof.

     If, in connection with or as a consequence of the sale, transfer or other
disposition of the real estate (land and/or Building, either or both, as the
case may be) of which the Premises are a part, Landlord ceases to be the owner
of the reversionary interest in the Premises, Landlord shall be entirely freed
and relieved from the performance and observance thereafter of all covenants and
obligations hereunder on the part of Landlord to be performed and observed, it
being understood and agreed in such event (and it shall be deemed and construed
as a covenant running with the land) that the person succeeding to Landlord's
ownership of said reversionary interest shall thereupon and thereafter assume,
and perform and observe, any and all of such covenants and obligations of
Landlord.

29.  MISCELLANEOUS

     29.1 SEPARABILITY. If any provision of this Lease or portion of such
provision or the application thereof to any person or circumstance is for any
reason held invalid or unenforceable, the remainder of the Lease (or the
remainder of such provision) and the application thereof to other persons or
circumstances shall not be affected thereby.

     29.2 CAPTIONS, ETC. The captions are inserted only as a matter of
convenience and for reference, and in no way define, limit or describe the scope
of this Lease nor the intent of any

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<PAGE>   73

provisions thereof. References to "State" shall mean, where appropriate, the
District of Columbia and other Federal territories, possessions, as well as a
state of the United States.

     29.3 BROKER. Tenant represents and warrants that it has not directly or
indirectly dealt, with respect to the leasing of office space in the Building or
any Center, Office Park or other Park of which it is a part (called "Building,
etc." in this Article 29.3) with any broker or had its attention called to the
Premises or other space to let in the Building, etc. by anyone other than the
broker, person or firm, if any, designated in Exhibit 1. Tenant agrees to
defend, exonerate and save harmless and indemnify Landlord and anyone claiming
by, through or under Landlord against any claims arising in breach of the
representation and warranty set forth in the immediately preceding sentence,
provided that Landlord shall be solely responsible for the payment of brokerage
commissions to the brokers, persons or firms, if any, designated in Exhibit 1.
Landlord represents and warrants that, in connection with the execution and
delivery of the Lease, it has not directly or indirectly dealt with any broker
other than the brokers designated on Exhibit 1. Landlord agrees to defend,
exonerate and save harmless Tenant and anyone claiming by, through, or under
Tenant against any claims arising in breach of the representation and warranty
set forth in the immediately preceding sentence.

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

     29.5 ARBITRATION. Any disputes relating to provisions or obligations in
this Lease as to which a specific provision for a reference to arbitration is
made herein shall be submitted to arbitration in accordance with the provisions
of applicable state law (as identified on Exhibit 1), as from time to time
amended. Except as specifically otherwise provided below, arbitration
proceedings, including the selection of an arbitrator, shall be conducted
pursuant to the rules, regulations and procedures from time to time in effect as
promulgated by the American Arbitration Association. Prior written notice of
application by either party for arbitration shall be given to the other at least
ten (10) days before submission of the application to the said Association's
office in the City wherein the Building is situated (or the nearest other city
having an Association office). The arbitrator shall hear the parties and their
evidence. The decision of the arbitrator shall be binding and conclusive, and
judgment upon the award or decision of the arbitrator may be entered in the
appropriate court of law (as identified on Exhibit 1); and the parties consent
to the jurisdiction of such court and further agree that any process or notice
of motion or other application to the Court or a Judge thereof may be served
outside the State wherein the Building is situated by registered mail or by
personal service, provided a reasonable time for appearance is allowed. The
costs and expenses of each arbitration hereunder and their apportionment between
the parties shall be determined by the arbitrator in his award or decision. No
arbitrable dispute shall be deemed to have arisen under this Lease prior to (i)
the expiration of the period of twenty (20) days after the date of the giving of
written notice by the party asserting the existence of the dispute together with
a description thereof sufficient for an understanding thereof; and (ii) where a
Tenant payment (e.g., Tax Excess or Operating Expense Excess under Article 9
hereof) is in issue, the amount billed by Landlord which is not disputed by
Tenant in good faith having been paid by Tenant. Notwithstanding the foregoing,
the parties hereby agree that (i) except as set forth in (ii) below, the
arbitrator for any disputes relating to Article 4 of this Lease shall be the
"Initial Arbitrator", or the "Alternate Arbitrator" if the Initial

                                      -65-
<PAGE>   74

Arbitrator is not available, and (ii) the arbitrators for any disputes relating
to the Certificate of Occupancy Test, as set forth in Article 4.0(l) of this
Lease, shall be a panel of three (the "Initial Three Arbitrators"), consisting
of the Initial Arbitrator, with the Alternate Arbitrator serving as a substitute
if the Initial Arbitrator is not available, plus the "Landlord's Arbitrator" and
the "Tenant's Arbitrator", with the "Landlord's Alternate Arbitrator" and/or the
"Tenant's Alternate Arbitrator" serving as a substitute if the Landlord's
Arbitrator or the Tenant's Arbitrator, as the case may be, is not available. All
of such individuals shall be chosen as follows: Within seven (7) days after the
date hereof, Landlord and Tenant shall each designate one arbitrator and one
alternate arbitrator, to be known as Landlord's Arbitrator, Landlord's Alternate
Arbitrator, Tenant's Arbitrator and Tenant's Alternate Arbitrator, respectively.
Landlord's Arbitrator and Tenant's Arbitrator shall, within thirty (30) days
after the date hereof, designate two individuals to serve as the Initial
Arbitrator and the Alternate Arbitrator, respectively. Any decision to be made
by the Initial Three Arbitrators shall be made as follows: Landlord's Arbitrator
and Tenant's Arbitrator (or the Alternate Arbitrator sitting in his/her stead)
shall each render a decision on the matter, and the Initial Arbitrator (or the
Alternate Arbitrator sitting in his/her stead) shall choose which of the
decisions made by the Landlord's Arbitrator or Tenant's Arbitrator is correct,
and such decision shall then be binding on the parties.

     29.6 GOVERNING LAW. This Lease is made pursuant to, and shall be governed
by, and construed in accordance with, the laws of the State wherein the Building
is situated and any applicable local municipal rules, regulations, by-laws,
ordinances and the like.

     29.7 ASSIGNMENT OF RENTS. With reference to any assignment by Landlord of
its interest in this Lease, or the rents payable hereunder, conditional in
nature or otherwise, which assignment is made to or held by a bank, trust
company, insurance company or other institutional lender holding a mortgage or
ground lease on the Building, Tenant agrees:

          (a)  that the execution thereof by Landlord and the acceptance thereof
by such mortgagee and/or ground lessor shall never be deemed an assumption by
such mortgagee and/or ground lessor of any of the obligations of the Landlord
thereunder, unless such mortgagee and/or ground lessor shall, by written notice
sent to the Tenant, specifically otherwise elect; and

          (b)  that, except as aforesaid, such mortgagee and/or ground lessor
shall be treated as having assumed the Landlord's obligations thereunder only
upon foreclosure of such mortgagee's mortgage or deed of trust or termination of
such ground lessor's ground lease and the taking of possession of the demised
Premises after having given notice of its exercise of the option stated in
Article 23 hereof to succeed to the interest of the Landlord under this Lease.

     29.8 REPRESENTATION OF AUTHORITY. By his execution hereof each of the
signatories on behalf of the respective parties hereby warrants and represents
to the other that he is duly authorized to execute this Lease on behalf of such
party. If Tenant is a corporation, Tenant hereby appoints the signatory whose
name appears below on behalf of Tenant as Tenant's attorney-in-fact for the
purpose of executing this Lease for and on behalf of Tenant.

     29.9 EXPENSES INCURRED BY LANDLORD UPON TENANT REQUESTS. Tenant shall, upon
demand, reimburse Landlord for all reasonable expenses, including, without
limitation, legal fees, incurred by Landlord in connection with all requests by
Tenant for consents, approvals or execution of collateral documentation related
to this Lease, including, without limitation, costs incurred by Landlord in the
review and approval of Tenant's plans and specifications in

                                      -66-
<PAGE>   75

connection with proposed alterations to be made by Tenant to the Premises,
requests by Tenant to sublet the Premises or assign its interest in the Lease,
the execution by Landlord of estoppel certificates requested by Tenant (except
that there shall be no charge for the first such estoppel certificate requested
by Tenant in any calendar year), and requests by Tenant for Landlord to execute
waivers of Landlord's interest in Tenant's property in connection with third
party financing by Tenant. Such costs shall be deemed to be additional rent
under the Lease.

     29.10 RETAIL AREA. Landlord agrees that retail uses in the Building will be
consistent with the types of retail uses in other office buildings of comparable
quality in the metropolitan Boston area, and that no construction activity for
retail uses will be allowed in the Building lobby except to the extent that such
construction activity relates to a door into the lobby from such retail area and
cannot reasonably be performed outside the Building lobby, and then only if
separated from the Building lobby by a painted construction barrier. So long as
Akamai Technologies, Inc., itself, or an Assignee or Affiliated Entity (as those
terms are defined in Article 16) collectively are occupying at least seventy
percent (70%) of the Premises then demised to Tenant, Landlord agrees that any
door into the lobby from such retail area shall be used for emergency egress
only, except that, as shown on Lease Plan, Exhibit 2, Sheet 1, the retail
premises located on the first floor of the Building shall have access to the
common bathrooms on the first floor through the doors shown on Lease Plan,
Exhibit 2, Sheet 1. Reaccess to the lobby from such bathrooms shall be
controlled by Tenant's security system, subject to emergency access as required
by law.

     29.11 SURVIVAL. Without limiting any other obligation of the Tenant which
may survive the expiration or prior termination of the term of the Lease, all
obligations on the part of Tenant to indemnify, defend, or hold Landlord
harmless, as set forth in this Lease (including, without limitation, Tenant's
obligations under Articles 13(d), 15.3, and 29.3) shall survive the expiration
or prior termination of the term of the Lease.

                                      -67-
<PAGE>   76

     IN WITNESS WHEREOF the parties hereto have executed this Indenture of Lease
in multiple copies, each to be considered an original hereof, as a sealed
instrument on the day and year noted in Exhibit 1 as the Execution Date.

LANDLORD:                               TENANT:
TECHNOLOGY SQUARE LLC,                  AKAMAI TECHNOLOGIES, INC.
a Delaware limited liability company

By: Beacon Capital Partners L.P.,
    a Delaware limited partnership
    d/b/a Beacon Capital Partners
    Limited Partnership, its manager

    By: Beacon Capital Partners, Inc., a
        Maryland corporation, its general
        partner

        By: /s/ Thomas Ragno            By: /s/ Kathryn L. Jorden
            -----------------------         --------------------------------
        Name: Thomas Ragno                     (Name)            (Title)
        Title: Senior Vice President           Hereunto Duly Authorized


                                      -68-
<PAGE>   77

                                    EXHIBIT 2

                                   LEASE PLAN


                                      -69-
<PAGE>   78

                                   EXHIBIT 2-1

                                 PLAN OF COMPLEX


                                      -70-
<PAGE>   79

                                    EXHIBIT 3

                          REQUIREMENTS FOR TENANT PLANS

                             Intentionally Omitted.


                                      -71-
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                                    EXHIBIT 4

                                BUILDING SERVICES

A.   General Cleaning (Monday through Friday)

     1.   All stone, ceramic, tile, marble, terrazzo and other unwaxed flooring
          to be swept nightly, using approved dust-down preparation.

     2.   All wood, linoleum, vinyl-asbestos, vinyl and other similar types of
          floors to be swept or dry mopped nightly, using dust-down preparation;
          all carpeting and rugs in the main traffic areas (corridors, reception
          areas, etc.) to be vacuumed nightly and all other carpeted areas to be
          vacuumed at least once each week.

     3.   Wax all public areas monthly.

     4.   Hand dust all furniture, files and fixtures nightly.

     5.   Empty all waste receptacles nightly and remove waste paper and waste
          materials, including folded paper boxes and cartons, to a designated
          area.

     6.   Empty and clean all ash trays and screen all sand urns nightly.

     7.   Wash and clean all water fountains and coolers nightly. Sinks and
          floors adjacent to sinks to be washed nightly.

     8.   Hand dust all door and other ventilating louvers within reach, as
          necessary, but not less often than monthly.

     9.   Dust all telephones as necessary.

     10.  Keep lockers and janitor sink rooms in a neat, orderly condition at
          all times.

     11.  Wipe clean all bright metal work as necessary.

     12.  Check all stairwells throughout entire building nightly and keep in
          clean condition.

     13.  Metal doors and trim of all public elevator cars to be properly
          maintained and kept clean.

B.   Common Area Lavatories

     1.   Sweep and wash all lavatory floors nightly, using proper non-scented
          disinfectants.

                                      -72-
<PAGE>   81

     2.   Clean all mirrors, powder shelves, bright work and enameled surfaces
          in all lavatories nightly. Scour, wash and disinfect all basins, bowls
          and urinals using non-scented disinfectants.

     3.   Police lavatories during the day with matron or porter to pick up
          waste and replenish materials.

     4.   Wash all toilet seats nightly.

     5.   Fill toilet tissue holders nightly.

     6.   Empty paper towel receptacles nightly.

     7.   Empty sanitary disposal receptacles nightly.

     8.   Thoroughly clean all wall tile and stall surfaces as necessary.

C.   High Dusting

     Do all high dusting (not reached in nightly cleaning) quarterly which
     includes the following:

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

     2.   Dust exposed pipes, ventilation and air conditioning louvers, ducts
          and high moldings.

D.   Window Cleaning

     1.   All exterior windows (except for any retail/commercial areas) from the
          second floor and above will be cleaned inside and outside at least
          three (3) times per calendar year except when cleaning is rendered
          impracticable by inclement weather.

     2.   Entrance doors and elevator lobby glass to be cleaned daily and kept
          in a clean condition at all times during the day.

     3.   Wipe down all metal window frames as necessary but not less often than
          monthly.

E.   Building Lobbies

     1.   Floors to be swept and washed or vacuumed nightly, and machine
          scrubbed according to Building Standard frequency.

     2.   Carpeting in passenger elevator cabs to be vacuum cleaned nightly.

     3.   Lobby walls to be dusted as often as necessary, but not less than
          weekly.

                                      -73-
<PAGE>   82

     4.   Screen and clean sand urns nightly.

     5.   Clean all unpainted metal work in a manner appropriate to original
          finish.

F.   Porters

     Necessary number of day porters under supervision will be assigned for the
     following services:

     1.   Service all public and building operating space throughout the
          Building.

     2.   Keep elevator cars clean and neat during the day.

     3.   Maintain lobbies clean and, during wet weather, mopped dry to the
          extent practicable.

     4.   Dust and rub down all elevator doors, frames, telephone booths and
          directories daily.

     5.   Sweep sidewalks, ramps, etc. daily.

     6.   Clean roofs and setbacks as often as necessary.

     7.   Maintain firehose and equipment clean.

     8.   Lay and remove lobby runners as necessary.

     9.   Replenish toilet tissue, towels and other supplies in lavatories.

     10.  Maintain fan rooms, motor rooms and air conditioning rooms in clean
          condition.

     11.  Check stairways and keep same neat and clean during the day.

     12.  Clean exterior columns, exterior signs and metal work, standpipe and
          sprinkler system, walkways and stairs as necessary.

     13.  If directed by superintendent, fill towel and soap dispensers and
          perform any emergency cleaning required.


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                                    EXHIBIT 5

                            FORM OF LETTER OF CREDIT

BENEFICIARY:                                 ISSUANCE DATE:

                                             ________________, 2000

TECHNOLOGY SQUARE LLC
c/o Beacon Capital Partners                  IRREVOCABLE STANDBY
                                             LETTER OF CREDIT NO.

ACCOUNTEE/APPLICANT:                    MAXIMUM/AGGREGATE
                                             CREDIT AMOUNT:
AKAMAI TECHNOLOGIES, INC.                    USD: $10,228,140.00
[TENANT]

LADIES AND GENTLEMEN:

     We hereby establish our irrevocable letter of credit in your favor for
account of the applicant up to an aggregate amount not to exceed Ten Million Two
Hundred Twenty-Eight Thousand One Hundred Forty and 00/100 US Dollars
($10,228,140.00) available by your draft(s) drawn on ourselves at sight
accompanied by:

     Your statement, signed by a purportedly authorized officer/official
certifying that the Beneficiary is entitled to draw upon this Letter of Credit
(in the amount of the draft submitted herewith) pursuant to Paragraph 1 of the
Rider to the Lease (the "Lease") dated ___________, 2000 by and between
TECHNOLOGY SQUARE LLC, as Landlord, and AKAMAI TECHNOLOGIES, INC., as Tenant,
for premises at Building 600, Technology Square, Cambridge, Massachusetts.

     Draft(s) must indicate name and issuing bank and credit number and must be
presented at this office.

     You shall have the right to make partial draws against this Letter of
Credit, from time to time.

     You shall be entitled to assign your interest in this Irrevocable Standby
Letter of Credit from time to time to your lender(s) and/or your successors in
interest without our approval and without charge. In the event of an assignment,
we reserve the right to require reasonable evidence of such assignment as a
condition to any draw hereunder.

     Except as otherwise expressly stated herein, this Letter of Credit is
subject to the "Uniform Customs and practice for Documentary Credits,
International Chamber of Commerce, Publication No. 500 (1993 Revision)".

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<PAGE>   84

     This Letter of Credit shall expire at our office on ________________, 2001
(the "Stated Expiration Date"). It is a condition of this Letter of Credit that
the Stated Expiration Date shall be deemed automatically extended without
amendment for successive one (1) year period s from such Stated Expiration Date,
unless at least forty-five (45) days prior to such Stated Expiration Date )or
any anniversary thereof) we shall notify you and the Accountee/Applicant in
writing by registered mail (return receipt) that we elect not to consider this
Letter of Credit extended for any such additional one (1) year period.


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<PAGE>   85

                                    EXHIBIT 6

                          BASE BUILDING SPECIFICATIONS


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<PAGE>   86


                                    EXHIBIT 7

                                EXTERIOR SIGNAGE

Specifications set forth in report by Sasaki Associates dated August 3, 2000
titled "Technology Square, Cambridge, MA, Site Signage Program, 100% CD's"

See also 2 sheets attached plans.


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<PAGE>   87

                                    EXHIBIT 8

                           TENANT'S REMOVABLE PROPERTY

1.   Antennae
2.   Satellite Dishes
3.   Network Operations Center
4.   Computer Equipment
5.   Telephone Switch and Equipment
6.   Signage (Interior and Exterior)
7.   Kitchen Equipment (Only if not built in)
8.   Security System (Only if installed by Tenant)
9.   Generators


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<PAGE>   88

                                 RIDER TO LEASE

                         LANDLORD: Technology Square LLC
                        TENANT: Akamai Technologies, Inc.

The subject Lease is hereby amended as follows:

1.   LETTERS OF CREDIT

     A.   DELIVERY OF LETTERS OF CREDIT. Tenant shall deliver to Landlord, on
the date that Tenant executes and delivers the Lease to Landlord, an Irrevocable
Standby Letter of Credit ("Initial Letter of Credit") which shall be (1) in the
form attached hereto as Exhibit 5, (2) issued by a bank reasonably acceptable to
Landlord upon which presentment may be made in Boston, Massachusetts, (3) in the
Letter of Credit Amount, as hereinafter defined, and (4) for a term of one (1)
year, subject to extension in accordance with the terms of the Letter of Credit.
The Letter of Credit Amount shall initially be $5,114,070.00. In addition,
Tenant shall, on the Term Commencement Date, deliver to Landlord either: (i) an
amendment to the Initial Letter of Credit, in form reasonably acceptable to
Landlord, increasing the Letter of Credit Amount from $5,114,070.00 to
$10,228,140.00 ("Letter of Credit Amendment"), or (ii) a second Letter of Credit
conforming to the requirements of this Subparagraph A ("Second Letter of
Credit"), in the amount of $5,114,070.00. Tenant's failure to deliver either the
Letter of Credit Amendment or the Second Letter of Credit shall be deemed to be
a default by Tenant in its obligations under the Lease with the same notice and
cure period as would be applicable as if such failure were a failure to pay
Yearly Rent when due under the Lease. If Tenant elects to provide a Second
Letter of Credit in lieu of a Letter of Credit Amendment, then the Initial
Letter of Credit and the Second Letter of Credit shall be collectively referred
to herein as the "Letter of Credit" and the Letter of Credit Amount shall be
defined as the sum of the amounts of Initial Letter of Credit and the Second
Letter of Credit. The Letter of Credit shall be subject to reduction as set
forth below. Tenant shall, on or before the date thirty (30) days prior to the
expiration of the term of the Letter of Credit, deliver to Landlord a new Letter
of Credit satisfying the foregoing conditions ("Substitute Letter of Credit") in
lieu of the Letter of Credit then being held by Landlord. Such Letter of Credit
shall be automatically renewable in accordance with the second to last
grammatical paragraph of Exhibit 5; provided that, in such event, Tenant shall
be required to deliver a Substitute Letter of Credit satisfying the conditions
hereof, on or before the date thirty (30) days prior to the expiration of the
term of such Letter of Credit, if the issuer of such Letter of Credit gives
notice of its election not to renew such Letter of Credit for any additional
period pursuant thereto. Upon written request of Tenant, Landlord shall deliver
to the issuing bank an instruction authorizing the issuing bank to reduce the
Letter of Credit Amount in accordance with the schedule set forth herein.

     B.   RENT RESTRUCTURING EVENT. A "Rent Restructuring Event" shall be
defined as :

     1.   Any monetary default or material non-monetary default by Tenant in its
     obligations under the Lease which is not cured after the giving of any
     applicable notice and the expiration of any applicable grace periods
     ("Event of Default"); or

     2.   If, at any time, both of the following conditions occur: (i) the price
     per share for Tenant's common stock as traded on a nationally-recognized
     exchange and calculated on the basis of a thirty (30) day trailing average
     and adjusted for any stock splits, reverse

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<PAGE>   89

     stock splits or mergers from and after the Execution Date, is less than
     $20.00 (a "Low Stock Price Event"), and (ii) Tenant does not, within ten
     (10) days after notice from Landlord that Landlord claims that such Low
     Stock Price Event constitutes a Rent Restructuring Event, provide Landlord
     with a certification from Tenant's Chief Financial Officer, or from the
     independent certified public accountant that prepared Tenant's most recent
     financial statement in accordance with Subparagraph J hereof, or from
     another independent certified public accountant reasonably acceptable to
     Landlord, that, as of the date of Landlord's notice, the aggregate amount
     of cash, cash equivalents, and short term investments held by Tenant and
     which is free and clear of any liens or encumbrances is equal to or greater
     than $50,000,000.00.

     C.   EFFECT OF RENT RESTRUCTURING EVENT. If any Rent Restructuring Event
occurs, then:

     1.   If the Rent Restructuring Event is an Event of Default, Landlord may,
     at its election, (a) exercise its rights under Paragraph 1.K of this Rider
     to draw down the Default Draw Amount, and/or in addition thereto, (b)
     Landlord may, in its sole discretion, draw (i) the balance of the Letter of
     Credit or (ii) fifty percent (50%) of the balance of the Letter of Credit
     and apply such amount as a payment of Yearly Rent under the Lease; or

     2.   If the Rent Restructuring Event is not an Event of Default, Landlord
     may, at its election and in its sole discretion, draw (i) the entire Letter
     of Credit or (ii) fifty percent (50%) of the Letter of Credit, and apply
     such amount as a payment of Yearly Rent under the Lease; and

     3.   Upon the application of any payment pursuant to Clauses 1 or 2 above
     (each of which is referred to herein as a "Restructuring Rent Payment"),
     then the amount of monthly payments of Yearly Rent payable by Tenant
     thereafter under the Lease shall be reduced by an amount equal to the
     Monthly Rent Reduction Amount, as hereinafter defined; and

     4.   Except as set forth in Clause 6 of this Paragraph C, in no event shall
     Landlord draw down the Letter of Credit (either in whole or in part) and
     apply the proceeds as a Restructuring Rent Payment more than once during
     the term hereof. Landlord's election to draw down the Letter of Credit
     (either in whole or in part) and apply the proceeds as a Restructuring Rent
     Payment must be made within ninety (90) days following the Rent
     Restructuring Event in question (or, in the case of a Rent Restructuring
     Event that continues over a period of time, within ninety (90) days
     following the last day thereof); and

     5.   Landlord's right to draw down the Letter of Credit, either in whole or
     in part, and apply the proceeds as a Restructuring Rent Payment, shall
     expire upon the occurrence of both of the following events:

          (a)  At least two (2) years shall have passed since Tenant has
          provided Landlord with the Initial Letter of Credit, and

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<PAGE>   90

          (b)  Tenant's Cash Flow (as defined in Subparagraph H below),
          aggregated over four (4) consecutive fiscal quarters (beginning not
          sooner than the quarter containing the first anniversary of the date
          Tenant provides Landlord with the Initial Letter of Credit), is
          positive; and

     6.   If Landlord exercises its right to draw down the Letter of Credit,
     either in whole or in part, and apply the proceeds as a Restructuring Rent
     Payment before the Term Commencement Date, when the Letter of Credit Amount
     is only $5,114,070.00, then when the Letter of Credit Amount is increased
     to $10,228,140.00 after the Term Commencement Date, Landlord shall draw
     down the same percentage of the increased Letter of Credit Amount and apply
     such proceeds as a Restructuring Rent Payment (e.g., if Landlord drew down
     the fifty (50%) of the Initial Letter of Credit, then Landlord shall draw
     down the fifty (50%) percent of Second Letter of Credit, or of the
     increased amount in the Initial Letter of Credit, as affected by the Letter
     of Credit Amendment, as the case may be); and

     7.   Landlord shall have no obligation to draw down the Letter of Credit if
     a Rent Restructuring Event occurs; and

     8.   If a Rent Restructuring Event occurs but Landlord does not exercise
     its right to draw upon the Letter of Credit based upon such Rent
     Restructuring Event, Landlord shall, if the same or a different Rent
     Restructuring Event occurs, have the right to draw upon the Letter of
     Credit to make a Restructuring Rent Payment as if the first such Rent
     Restructuring Event had not previously occurred; and

     9.   If a Rent Restructuring Event occurs and Landlord elects to draw upon
     the Letter of Credit to make a Rent Restructuring Payment, then (except as
     provided in Clause 6 of this Subparagraph C) Landlord shall have no further
     right to draw upon the Letter of Credit to make a subsequent Rent
     Restructuring Payment; provided however, that the provisions of this Clause
     9 shall not affect Landlord from drawing upon the Letter of Credit based
     upon a subsequent Event of Default for the purposes of paying a Default
     Draw Amount, as hereinafter defined, or from drawing upon the Letter of
     Credit pursuant to Subparagraph L of this Paragraph 1, if Tenant fails
     timely to deliver a Substitute Letter of Credit.

     D.   MONTHLY RENT REDUCTION PAYMENT. The "Monthly Rent Reduction Payment"
shall be equal to the amount of the monthly payment of principal and interest
which would be necessary to fully pay a loan, in the amount of the Restructuring
Rent Payment with interest at the rate of the rate per annum announced by Fleet
Bank, N.A., or its successor, from time to time as its "prime" rate, plus
one-quarter percent (1/4%), which is repaid on a direct reduction basis in equal
monthly payments of principal and interest over a term commencing with the
application of the Restructuring Rent Payment and ending as of the expiration of
the then-current term of the Lease.

     E.   REDUCTION DATE. "Reduction Date" shall be defined as the second
anniversary of the Full Rent Commencement Date, and each anniversary of the Full
Rent Commencement Date which occurs thereafter during the term of the Lease.

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<PAGE>   91

     F.   REDUCTION CONDITIONS. Tenant shall be deemed to have satisfied the
"Reduction Conditions" with respect to any Reduction Date, if, as of such
Reduction Date, all of the following are satisfied:

     1.   Tenant is not in monetary default, or in material non-monetary
     default, in either case beyond any applicable notice and cure periods, of
     any of its obligations under the Lease as of such Reduction Date;

     2.   The Lease is in full force and effect; and

     3.   Tenant has not been in either monetary default, or in material
     non-monetary default, in either case beyond any applicable notice and cure
     periods, on more than one occasion during the immediately preceding twelve
     (12) months of the term of the Lease.

     G.   REDUCTION AMOUNT. The "Reduction Amount" with respect to any Reduction
Date shall be based upon Tenant's Cash Flow, as hereinafter defined, during
Tenant's last full twelve month fiscal year immediately preceding the Reduction
Date in question, as follows. If Tenant's Cash Flow for the immediately
preceding fiscal year is:

     1.   Not positive, then the Reduction Amount shall be zero;

     2.   Positive, but less than or equal to $5,000,000.00, then the Reduction
     Amount shall be $1,000,000.00; or

     3.   More than $5,000,000.00, but less than or equal to $10,000,000.00,
     then the Reduction Amount shall be $1,250,000.00; or

     4.   More than $10,000,000.00, but less than or equal to $15,000,000.00,
     then the Reduction Amount shall be $1,500,000.00; or

     5.   More than $15,000,000.00, but less than or equal to $20,000,000.00,
     then the Reduction Amount shall be $1,750,000.00; or

     6.   Greater than $20,000,000.00, then the Reduction Amount shall be
     $2,000,000.00.

In no event, however, shall the Letter of Credit Amount ever be reduced below
$3,409,380.00.

     H.   DEFINITION OF CASH FLOW. Tenant's Cash Flow for any period shall mean
the sum of (i) Tenant's net income attributable to common stock holders, (ii)
interest on convertible debt that is accrued but not yet paid or payable, (iii)
depreciation and (iv) amortization, all as reflected in the audited financial
statements for period in question. Stock compensation amortization may be added
as part of the definition of Cash Flow, provided that said adjustment is as
reported in the audited financial statements of Tenant for the relevant
reporting period.

     I.   EFFECT OF SATISFACTION OF RENT REDUCTION CONDITIONS. If, on any
Reduction Date, Tenant satisfies all of the Reduction Conditions, then the
Letter of Credit Amount shall be reduced by the applicable Reduction Amount, if
any. Such reduction in the Letter of Credit Amount may be effected by an
amendment, in form reasonably acceptable to Landlord, to the

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<PAGE>   92

existing Letter(s) of Credit then being held by Landlord, or by Tenant's
delivery to Landlord of a substitute Letter of Credit satisfying all of the
requirements of the Letter of Credit to be provided to Tenant except that the
Letter of Credit Amount for such substitute Letter of Credit shall be in the
appropriately reduced amount. In the latter event, Landlord shall exchange the
Letter(s) of Credit then being held by Landlord for such substitute Letter of
Credit.

     J.   TENANT'S FINANCIAL STATEMENTS. Tenant shall deliver to Landlord
financial statements as and when made publicly available, if Tenant's stock is
then publicly traded. If Tenant's stock is not then publicly traded, Tenant
shall deliver to Landlord (i) within ninety (90) days following the end of its
fiscal year, copies of Tenant's annual financial statements, prepared by an
independent certified public accounting firm reasonably acceptable to Landlord
and in form reasonably acceptable to Landlord, and (ii) within forty-five (45)
days following the end of each of its fiscal quarters, copies of Tenant's
quarterly financial statements certified by Tenant's chief financial officer and
in form reasonably acceptable to Landlord. All such financial statements shall
be prepared in accordance with generally accepted accounting principles,
consistently applied.

     K.   EFFECT OF TENANT DEFAULT. In the event that Tenant is in default of
its obligations under the Lease, beyond the expiration of applicable notice and
grace periods, then the Landlord shall have the right, at any time after such
event, without giving any further notice to Tenant, to draw down from said
Letter of Credit (Substitute Letter of Credit or Additional Letter of Credit, as
defined below, as the case may be) (a) the amount necessary to cure such default
or (b) if such default cannot reasonably be cured by the expenditure of money,
to exercise all rights and remedies Landlord may have on account of such
default, the amount which, in Landlord's opinion, is necessary to satisfy
Tenant's liability on account thereof ("Default Draw Amount"). The foregoing
shall be in addition to Landlord's other rights to draw down the Letter of
Credit (Substitute Letter of Credit or Additional Letter of Credit, as the case
may be) pursuant to this Paragraph 1. In the event of any such draw by the
Landlord, Tenant shall, within fifteen (15) business days of written demand
therefor, deliver to Landlord an additional Letter of Credit satisfying the
foregoing conditions ("Additional Letter of Credit"), except that the amount of
such Additional Letter of Credit shall be the Default Draw Amount.
Notwithstanding anything to the contrary herein contained, if Landlord draws
upon the Letter of Credit to make a Rent Restructuring Payment, in no event
shall Tenant have any obligation to provide to Landlord an Additional Letter of
Credit in the amount of such Rent Restructuring Payment. In addition, in the
event of a termination based upon the default of Tenant under the Lease, or a
rejection of the Lease pursuant to the provisions of the Federal Bankruptcy
Code, Landlord shall have the right to draw upon the Letter of Credit (from time
to time, if necessary) to cover the full amount of damages and other amounts due
from Tenant to Landlord under the Lease. Any amounts so drawn shall, at
Landlord's election, be applied first to any unpaid rent and other charges which
were due prior to the filing of the petition for protection under the Federal
Bankruptcy Code.

     L.   EFFECT OF FAILURE TO DELIVER SUBSTITUTE LETTER OF CREDIT. In the event
that Tenant fails timely to deliver to Landlord a Substitute Letter of Credit,
then the Landlord shall have the right, at any time after such event, without
giving any further notice to Tenant and without limiting its other remedies on
account thereof, to draw down the Letter of Credit (or Substitute Letter of
Credit and/or Additional Letter(s) of Credit) and to hold the proceeds thereof
("Cash Proceeds") in a segregated bank account in the name of the Landlord in
accordance with the provisions of this Paragraph 1.

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<PAGE>   93

     M.   RETURN OF LETTER OF CREDIT AT END OF TERM. To the extent that Landlord
has not previously drawn upon any Letter of Credit, Substitute Letter of Credit,
Additional Letter of Credit or Cash Proceeds (collectively "L/C Equivalent")
held by the Landlord, and to the extent that Tenant is not otherwise in default
of its obligations under the Lease as of the termination date of the Lease,
Landlord shall return such L/C Equivalent to Tenant on the termination of the
term of the Lease.

     N.   LETTER OF CREDIT NOT A MEASURE OF LIQUIDATED DAMAGES. In no event
shall the proceeds of any Letter of Credit be considered as a measure of
liquidated damages.

2.   TENANT'S OPTION TO EXTEND THE TERM OF THE LEASE

     A.   On the conditions, which conditions Landlord may waive, at its
election, by written notice to Tenant at any time, (i) that Tenant is not in
default of its covenants and obligations under the Lease, and (ii) that Akamai
Technologies, Inc., itself, or an Assignee or Affiliated Entity (as those terms
are defined in Article 16) collectively are occupying at least seventy percent
(70%) of the Premises then demised to Tenant, both as of the time of option
exercise and as of the commencement of the hereinafter described additional
term, Tenant shall have the option to extend the term of this Lease for two (2)
additional five (5) year terms, each such additional term commencing as of the
expiration of the initial term of the Lease or the previous extension term, as
the case may be. Tenant may exercise such option to extend by giving Landlord
written notice on or before the date fifteen (15) months prior to the expiration
date of the initial term of the Lease or the previous extension term, as the
case may be. Upon the timely giving of such notice, the term of this Lease shall
be deemed extended upon all of the terms and conditions of this Lease, except
that Landlord shall have no obligation to construct or renovate the Premises and
that the Yearly Rent, Operating Costs in the Base Year, and Tax Base during such
additional term shall be as hereinafter set forth. If Tenant fails to give
timely notice, as aforesaid, Tenant shall have no further right to extend the
term of this Lease, time being of the essence of this Paragraph 2.

     B.   YEARLY RENT

     The Yearly Rent during the additional term(s) shall be based upon the Fair
Market Rental Value, as defined in Paragraph 3 of this Rider, as of the
commencement of the additional term in question, of the Premises then demised to
Tenant, provided however, that in no event shall the sum of Yearly Rent,
Operating Expense Excess and Tax Excess payable by Tenant for any twelve-(12)-
month period during an additional term be less than the sum of Yearly Rent,
Operating Expense Excess and Tax Excess payable by Tenant in respect of the
twelve-(12)-month period immediately preceding the commencement of the
additional term. Tenant shall have the right, on and after the date eighteen
(18) months prior to the expiration date of the initial term of the Lease or the
previous extension term, as the case may be, to request in writing that Landlord
advise Tenant of Landlord's designation of the Fair Market Rental Value
applicable during the additional term. Landlord shall, within thirty (30) days
after receipt of Tenant's request, advise Tenant in writing of such designation
of the Fair Market Rental Value.

     C.   TENANT'S TERMINATION RIGHT AFTER THE FAIR MARKET RENTAL VALUE IN
          RESPECT OF AN ADDITIONAL TERM IS DETERMINED.

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     If Tenant has exercised its right to extend the term of the Lease in
respect of an additional term, and if Tenant, in accordance with Subparagraph
(C) of Paragraph 3 of this Rider, timely elects to arbitrate the Fair Market
Rental Value applicable to such additional term, Tenant shall have the right to
terminate the term of the Lease as follows: Tenant may exercise such right by
giving written notice to Landlord on or before the date fifteen (15) days after
the Yearly Rent for the extension term is either agreed to by the parties or is
determined by the arbitrators, as the case may be. The effective termination
date shall be the later of (i) twelve (12) months after Landlord receives such
termination notice from Tenant, or (ii) the date that this Lease would have
expired had Tenant not exercised the extension option in question. If Tenant
timely exercises such termination right, then: (i) the Yearly Rent payable by
Tenant for the period commencing as of the day after the expiration of the then
current term of the Lease through the effective termination date shall be based
upon the Fair Market Rental Value, as determined by the arbitrators or as agreed
to by the parties, as the case may be, and (ii) Tenant shall be required to
reimburse Landlord, within ten (10) days of billing therefor, for any and all
reasonable out-of-pocket expenses incurred by Landlord in connection with the
arbitration proceedings; and (iii) Landlord shall have the right, by notice
("Landlord's Extension Notice") given to Tenant within thirty (30) days after
the receipt of Tenant's termination notice, to extend the Term of the Lease for
a period ending on the date eighteen (18) months after the expiration of the
Term, prior to any extension pursuant to Paragraph C above ("Short Extended
Term"). If Landlord timely gives Landlord's Extension Notice, then the Term of
the Lease shall be automatically extended for the Short Extended Term and the
Yearly Rent during the Short Extended Term shall be based upon the Fair Market
Rental Value, as determined by the arbitrators or as agreed to by the parties,
as the case may be.

     D.   Tenant shall have no further option to extend the term of the Lease
other than the two (2) additional five (5) year terms herein provided.

     E.   Notwithstanding the fact that upon Tenant's exercise of the herein
option(s) to extend the term of the Lease such extension shall be
self-executing, as aforesaid, the parties shall promptly execute a lease
amendment reflecting such additional term after Tenant exercises the herein
option, except that the Yearly Rent payable in respect of such additional term,
the Operating Costs in the Base Year during such additional term, and the Tax
Base during such additional term, may not be set forth in said amendment.
Subsequently, after such Yearly Rent, Operating Costs in the Base Year, and Tax
Base are determined, the parties shall execute a written agreement confirming
the same. The execution of such lease amendment shall not be deemed to waive any
of the conditions to Tenant's exercise of its rights under this Paragraph 2,
unless otherwise specifically provided in such lease amendment.

3.   DEFINITION OF FAIR MARKET RENTAL VALUE

     For the purposes of this Rider:

     A.   "Fair Market Rental Value" shall be computed as of the date in
question at the then current annual rental charge (i.e., the sum of Yearly Rent
plus escalation and other charges), including provisions for subsequent
increases and other adjustments for leases or agreements to lease then currently
being negotiated, or executed in comparable space located in the Complex, or if
no leases or agreements to lease are then currently being negotiated or executed
in the Complex, the Fair Market Rental Value shall be determined by reference to
leases or agreements to lease then currently being negotiated or executed for
comparable space located elsewhere in

                                      -86-
<PAGE>   95

first-class office buildings located in East Cambridge, Massachusetts. In
determining Fair Market Rental Value, the following factors, among others, shall
be taken into account and given effect: size, location of Premises, lease term,
condition of building, economic concessions then being granted by the landlord,
the absence of certain costs to be incurred by landlord (e.g., brokerage
commissions, tenant improvement costs), and services provided by the landlord.

     B.   Notwithstanding anything to the contrary herein contained, the parties
hereby agree that upon the determination of any Fair Market Rental Value,
Landlord shall have the right, exercisable by written notice to Tenant on or
before the time that Landlord gives Tenant its initial designation of Fair
Market Rental Value:

          (1)  to change Operating Costs in the Base Year as stated on Exhibit 1
               from the amount stated on Exhibit 1 to an amount equal to the
               actual amount of Operating Costs for the immediately preceding
               Operating Year, and

          (2)  to change the Tax Base as stated on Exhibit 1 from the amount
               stated on Exhibit 1 to an amount equal to the actual amount of
               Taxes for the immediately preceding fiscal/tax year for which
               Landlord has actual data.

          If Landlord shall exercise such right, the amount of Yearly Rent
payable hereunder shall be commensurately adjusted to reflect such change in
Operating Costs in the Base Year and in Tax Base.

     C.   DISPUTE AS TO FAIR MARKET RENTAL VALUE

          Landlord shall initially designate Fair Market Rental Value and
Landlord shall furnish data in support of such designation. If Tenant disagrees
with Landlord's designation of a Fair Market Rental Value, Tenant shall have the
right, by written notice given within thirty (30) days after Tenant has been
notified of Landlord's designation, to submit such Fair Market Rental Value to
arbitration. Fair Market Rental Value shall be submitted to arbitration as
follows: Fair Market Rental Value shall be determined by impartial arbitrators,
one to be chosen by the Landlord, one to be chosen by Tenant, and a third to be
selected, if necessary, as below provided. The unanimous written decision of the
two first chosen, without selection and participation of a third arbitrator, or
otherwise, the written decision of a majority of three arbitrators chosen and
selected as aforesaid, shall be conclusive and binding upon Landlord and Tenant.
Landlord and Tenant shall each notify the other of its chosen arbitrator within
ten (10) days following the call for arbitration and, unless such two
arbitrators shall have reached a unanimous decision within thirty (30) days
after their designation, they shall so notify the President of the Boston Bar
Association (or such organization as may succeed to said Boston Bar Association)
and request him to select an impartial third arbitrator, who shall be a real
estate broker with at least ten (10) years' experience dealing with like types
of properties in the Cambridge office market, to determine Fair Market Rental
Value as herein defined. Such third arbitrator and the first two chosen shall,
subject to commercial arbitration rules of the American Arbitration Association,
hear the parties and their evidence and render their decision within thirty (30)
days following the conclusion of such hearing and notify Landlord and Tenant
thereof. Landlord and Tenant shall bear the expense of the third arbitrator (if
any) equally. The decision of the arbitrator shall be binding and conclusive,
and judgment upon the award or decision of the arbitrator may be entered in the
appropriate court of law (as identified on Exhibit 1); and the parties consent
to the

                                      -87-
<PAGE>   96

jurisdiction of such court and further agree that any process or notice of
motion or other application to the Court or a Judge thereof may be served
outside the State wherein the Building is situated by registered mail or by
personal service, provided a reasonable time for appearance is allowed. If the
dispute between the parties as to a Fair Market Rental Value has not been
resolved before the commencement of Tenant's obligation to pay rent based upon
such Fair Market Rental Value, then Tenant shall pay Yearly Rent and other
charges under the Lease in respect of the Premises in question based upon the
rate in effect immediately before the commencement of Tenant's obligation to pay
rent based upon such Fair Market Rental Value until either the agreement of the
parties as to the Fair Market Rental Value, or the decision of the arbitrators,
as the case may be, at which time Tenant shall pay any underpayment of rent and
other charges to Landlord, or Landlord shall refund any overpayment of rent and
other charges to Tenant, in either case with interest at the rate set forth in
Article 6 hereof.

4.   ANTENNA AREA

     Tenant shall have the right to use the Antenna Area, as hereinafter
defined, to install one or more satellite dishes and/or antennae (collectively,
the "Antenna") for a period commencing as of the date that Tenant installs the
Antenna, as hereinafter defined, in the Antenna Area ("Term Commencement Date in
respect of the Antenna Area") and terminating as of the expiration or earlier
termination of the term of the Lease. The "Antenna Area" shall be an area or
areas on the roof of the Building containing approximately an aggregate of 2700
square feet of rentable area in an area to be designated by Landlord, provided
that if such area consists of two or more non-contiguous areas, such areas must
be reasonably suitable for Tenant's purposes of installing, maintaining and
operating the Antenna. Tenant shall be permitted to use the Antenna Area solely
for the Antenna installed in accordance with specifications approved by Landlord
in advance utilizing a frequency or frequencies and transmission power
identified in such approved specifications which Tenant will be installing in
the Antenna Area and no other frequencies or transmission power shall be used by
Tenant without Landlord's prior written consent, which shall not be unreasonably
withheld or delayed, except for matters of aesthetics, which shall be determined
in Landlord's sole discretion. Such installation shall be designed in such
manner as to be easily removable and so as not to damage the roof of the
Building. The Antenna and any replacement shall be subject to Landlord's
approval, which shall not be unreasonably withheld or delayed, except for
matters of aesthetics, which shall be determined in Landlord's sole discretion.
Tenant's use of the Antenna Area shall be upon all of the conditions of the
Lease, except as follows:

     A.   Tenant shall have no obligation to pay Yearly Rent, Tax Excess or
Operating Expense Excess in respect of the Antenna Area.

     B.   Landlord shall have no obligation to provide any services to the
Antenna Area.

     C.   Tenant shall have no right to make any changes, alterations, signs,
decoration, or other improvements (which changes, alterations, signs, decoration
or other improvements, together with the Antenna, are hereby collectively
referred to as "Rooftop Installations") to the Antenna Area or to the Antenna
without Landlord's prior written consent, which consent shall not be
unreasonably withheld or delayed, except for matters of aesthetics, which shall
be determined in Landlord's sole discretion.

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     D.   Landlord shall provide Tenant with 24-hour access to the Antenna Area,
subject to Landlord's reasonable security procedures and restrictions based on
emergency conditions and to other causes beyond Landlord's reasonable control.
Tenant shall give Landlord reasonable advance written notice of the need for
access to the Antenna Area (except that such notice may be oral in an
emergency), and Landlord must be present during any entry by Tenant onto the
Antenna Area. Each notice for access shall be in the form of a work order
referencing the lease and describing, as applicable, the date access is needed,
the name of the contractor or other personnel requiring access, the name of the
supervisor authorizing the access/work, the areas to which access is required,
the Building common elements to be impacted (risers, electrical rooms, etc.) and
the description of new equipment or other Rooftop Installations to be installed
and evidence of Landlord's approval thereof. In the event of an emergency, such
notice shall follow within five (5) days after access to the Antenna Area.

     E.   At the expiration or prior termination of Tenant's right to use the
Antenna Area, Tenant shall remove all Installations (including, without
limitation, the Antenna) from the Antenna Area.

     F.   Tenant shall be responsible for the cost of repairing any damage to
the roof of the Building caused by the installation or removal of any Rooftop
Installations.

     G.   Tenant shall have no right to sublet the Antenna Area, except in
connection with an assignment or sublease permitted hereunder or otherwise
approved by Landlord in accordance with the terms hereof.

     H.   No other person, firm or entity (including, without limitation, other
tenants, licensees or occupants of the Building) shall have the right to benefit
from the services provided by the Antenna other than Tenant.

     I.   In the event that Landlord performs repairs to or replacement of the
roof, Tenant shall, to the extent reasonably required, at Tenant's cost, remove
the Antenna until such time as Landlord has completed such repairs or
replacements. Tenant recognizes that there may be an interference with Tenant's
use of the Antenna in connection with such work. Landlord shall use reasonable
efforts to complete such work as promptly as possible and to perform such work
in a manner which will minimize or, if reasonably possible, eliminate any
interruption in Tenant's use of the Antenna.

     J.   Any services required by Tenant in connection with Tenant's use of the
Antenna Area or the Antenna shall be installed by Tenant, at Tenant's expense,
subject to Landlord's prior approval.

     K.   To the maximum extent permitted by law, all Rooftop Installations in
the Antenna Area shall be at the sole risk of Tenant, and Landlord shall have no
liability to Tenant in the event that any Rooftop Installations are damaged for
any reason, except to the extent caused by the gross negligence or willful
misconduct of Landlord, its agents or contractors.

     L.   Tenant shall take the Antenna Area "as-is" in the condition in which
the Antenna Area is in as of the Term Commencement Date in respect of the
Antenna Area.

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<PAGE>   98

     M.   Tenant shall comply with all applicable laws, ordinances and
regulations in Tenant's use of the Antenna Area and the Antenna.

     N.   Landlord shall have the right, upon thirty (30) days notice to Tenant,
to require Tenant to relocate the Antenna Area to another area ("Relocated
Rooftop Area") on the roof of the Building suitable for the use of Rooftop
Installations. In such event, Tenant shall, at Landlord's cost and expense, on
or before the thirtieth (30th) day after Landlord gives such notice, relocate
all of its Rooftop Installations from the Antenna Area to the Relocation Rooftop
Area.

     O.   In addition to complying with the applicable construction provisions
of the Lease, Tenant shall not install or operate Rooftop Installations in any
portion of the Antenna Area until (x) Tenant shall have obtained Landlord's
prior written approval, which approval will not be unreasonably withheld or
delayed, of Tenant's plans and specifications for the placement and installation
of the Rooftop Installations in the Premises, and (y) Tenant shall have obtained
and delivered to Landlord copies of all required governmental and
quasi-governmental permits, approvals, licenses and authorizations necessary for
the lawful installation, operation and maintenance of the Rooftop Installations.
The parties hereby acknowledge and agree, by way of illustration and not
limitation, that Landlord shall have the right to withhold its approval of
Tenant's plans and specifications hereunder, and shall not be deemed to be
unreasonable in doing so, if Tenant's intended placement or method of
installation or operation of the Rooftop Installations (i) may subject other
licensees, tenants or occupants of the Building, or other surrounding or
neighboring landowners or their occupants, to signal interference, Tenant hereby
acknowledging that a shield may be required in order to prevent such
interference, (ii) does not minimize to the fullest extent practicable the
obstruction of the views from the windows of the Building that are adjacent to
the Rooftop Installations, if any, (iii) does not complement (in Landlord's sole
judgment, which shall not, however, require Tenant to incur unreasonable
expense) the design and finish of the Building, (iv) may damage the structural
integrity of the Building or the roof thereof, or (v) may constitute a violation
of any consent, approval, permit or authorization necessary for the lawful
installation of the Rooftop Installations.

     P.   In addition to the indemnification provisions set forth in the Lease
which shall be applicable to the Antenna Area, Tenant shall, to the maximum
extent permitted by law, indemnify, defend, and hold Landlord, its agents,
contractors and employees harmless from any and all claims, losses, demands,
actions or causes of actions suffered by any person, firm, corporation, or other
entity arising from Tenant's use of the Antenna Area.

     Q.   Landlord shall have the right to designate or identify the Rooftop
Installations with or by a lease or license number (or other marking) and to
place such number (or marking) on or near such Rooftop Installations.

     R.   (i) Tenant recognizes that Landlord may wish to (and Landlord hereby
reserves the right to) install a central Building system (the "Central Building
System") capable of, among other things, providing Tenant with the type of
service (to be) provided by Tenant's Rooftop Installations. If Landlord elects
to install the Central Building System, and provided that such Central Building
System is capable of providing service comparable to that provided by Tenant's
Rooftop Installations, (i) Tenant shall, upon Landlord's request and at Tenant's
expense, remove its Rooftop Installations and other Alterations (including any
existing cabling) from the Building and repair any damage caused their
installation or removal, (ii) Tenant may, at Tenant's

                                      -90-
<PAGE>   99

expense and subject to the provisions of this Agreement (including, without
limitation, subparagraph P hereof), have access to and use (and tie into) the
Central Building System for the uses permitted hereunder, and (ii) commencing
upon Tenant's use of the Central Building System and continuing thereafter
throughout the term, the Yearly Rent payable hereunder shall be adjusted to be
that which is reasonably designated by Landlord from time to time based upon
Landlord's determination of the fair market value of the access rights to the
Central Building System granted herein.

          (ii) Landlord shall maintain, repair or replace the Central Building
System, in accordance with the standards for the repair and maintenance of such
systems generally prevailing in the industry from time to time, so as to
eliminate any material interruption or other adverse effects caused by
malfunction, damage or destruction of the Central Building System, the cost of
which shall be borne by Tenant if the problem was caused by the act or omission
of Tenant or its agents, contractors or employees. Notwithstanding the
foregoing, Landlord's obligation to maintain, repair or replace the Central
Building System shall apply only to the extent necessary to reach premises in
the Building that are then used by tenants after the malfunction, damage or
destruction or that, if damaged or destroyed, will be again used by tenants upon
the completion of restoration or repair thereof. In no event shall Tenant have
any claim or right to make any claim against Landlord whatsoever for any
damages, including, without limitation, consequential or incidental damages, or
lost profits, in any such circumstance.

5.   GENERATOR AREA

     Landlord hereby demises and leases to Tenant, and Tenant hereby hires and
takes from Landlord, an area containing approximately 730 square feet of
rentable area on that portion of the roof of the Building ("Generator Area") for
a generator for emergency use only ("Generator") for a term commencing as of the
date of installation of the Generator ("Term Commencement Date in respect of the
Generator") and terminating as of the expiration or earlier termination of the
term of the Lease. Said demise of the Generator Area shall be upon all of the
same terms and conditions of the Lease, except as set forth in this Paragraph 5.
Tenant shall not install or operate the Generator until Tenant has obtained and
submitted to Landlord copies of all required governmental permits, licenses, and
authorizations necessary for the installation and operation of the Generator. In
addition, Tenant shall comply with all reasonable construction rules and
regulations promulgated by Landlord in the installation, maintenance and
operation of the Generator. Tenant shall be permitted to use the Generator Area
solely for the maintenance and operation of the Generator, and the Generator and
Generator Area are solely for the benefit of Tenant. All electricity generated
by the Generator may only be consumed by Tenant in the Premises.

     A.   Tenant shall have no obligation to pay Yearly Rent, Tax Excess or
Operating Expense Excess in respect of the Generator Area.

     B.   Landlord shall have no obligation to provide any services including,
without limitation, electric current, to the Generator Area.

                                      -91-
<PAGE>   100

     C.   Tenant shall have no right to make any changes, alterations,
additions, decorations or other improvements (collectively "Installations") to
the Generator Area without Landlord's prior written consent, , which shall not
be unreasonably withheld or delayed, except for matters of aesthetics, which
shall be determined in Landlord's sole discretion.

     D.   Tenant shall be responsible for the cost of repairing any damage to
the Building, or the cost of any necessary improvements to the Building, caused
by or as a result of the installation of the Generator and/or any Installations.

     E.   Tenant shall have no right to sublet the Generator Area or to assign
its interest hereunder, except in connection with an assignment or sublease
permitted hereunder or otherwise approved by Landlord in accordance with the
terms hereof.

     F.   To the maximum extent permitted by law, the Generator and all
Installations in the Generator Area shall be at the sole risk of Tenant, and
Landlord shall have no liability to Tenant in the event that the Generator or
any Installations are damaged for any reason, except to the extent caused by the
gross negligence or willful malfeasance of Landlord, its agents or contractors.

     G.   Tenant shall take the Generator Area "as-is" in the condition in which
the Generator Area is in as of the Term Commencement Date in respect of the
Generator, without any obligation on the part of Landlord to prepare or
construct the Generator Area for Tenant's use or occupancy. Without limiting the
foregoing, Landlord makes no warranties or representations to Tenant as to the
suitability of the Generator Area for the installation and operation of the
Generator.

     H.   In addition to and without limiting Tenant's obligations under the
Lease, Tenant shall comply with all applicable environmental and fire prevention
laws, ordinances and regulations in Tenant's use of the Generator Area.

     I.   In addition to and without limiting Tenant's obligations under the
Lease, Tenant covenants and agrees that the installation and use of the
Generator and Installations shall not adversely affect the insurance coverage
for the Building. If for any reason, the installation or use of the Generator
and/or the Installations shall result in an increase in the amount of the
premiums for such coverage, then Tenant shall be liable for the full amount of
any such increase.

     J.   Tenant shall, at Tenant's sole cost and expense, repair and maintain
the Generator and Installations.

     K.   In addition to and without limiting the insurance provisions of the
Lease, Tenant shall procure, keep in force and pay for Commercial General
Liability Insurance in respect of the Generator Area of not less than Ten
Million ($10,000,000.00) Dollars in the event of personal injury to any number
of persons or damage to property, arising out

                                      -92-
<PAGE>   101

of any one occurrence and such insurance shall name Landlord as an additional
insured party.

     L.   In addition to and without limiting the indemnification provisions set
forth in the Lease, Tenant shall, to the maximum extent permitted by law,
indemnify, defend, and hold Landlord harmless from any and all claims, losses,
demands, actions, or causes of actions suffered by any person, firm,
corporation, or other entity arising from Tenant's use of the Generator Area.

     M.   Notwithstanding anything to the contrary herein or in the Lease
contained, in the event that at any time during the term of the Lease in respect
of the Generator Area, Landlord determines, in its sole but bona fide business
judgment, that the periodic testing of the Generator interferes with the
operation of the Building or the operations of any of the occupants of the
Building, then Tenant shall, upon notice from Landlord, cause all further
testing of the Generator to occur after normal business hours. Other than for
periodic testing as aforesaid, in no event shall Tenant be entitled to operate
the Generator except in cases of a power outage to the Premises or any portion
thereof.


                                      -93-