BEACON CAPITAL PARTNERS INC
8-K, 1999-12-07
REAL ESTATE INVESTMENT TRUSTS
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<PAGE>

                       SECURITIES AND EXCHANGE COMMISSION

                             Washington, D.C. 20549

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

                                    FORM 8-K

                                 CURRENT REPORT


                     Pursuant to Section 13 or 15(d) of the
                         Securities Exchange Act of 1934


                Date of Report (Date of earliest event reported)
                                DECEMBER 6, 1999


                          BEACON CAPITAL PARTNERS, INC.
               (Exact name of registrant as specified in charter)


        MARYLAND                      000-24905                  04-3403281
(State or other jurisdiction   (Commission file number)        (IRS employer
        of incorporation)                                   identification no.)


          ONE FEDERAL STREET, 26TH FLOOR, BOSTON, MASSACHUSETTS, 02110
               (Address of principal executive offices) (Zip code)


       Registrant's telephone number, including area code: (617) 457-0400


<PAGE>


ITEM 5 - OTHER EVENTS

         On June 24, 1998 the Company purchased a four-building complex known as
Technology Square and an adjacent building known as The Draper Building from a
partnership managed by The Prudential Insurance Company of America
("Prudential"). The properties are located in Cambridge, MA, adjacent to One
Kendall Square and M.I.T. and consist of 1,026,000 square feet. The purchase
price for the properties was $123 million.

         The Draper Building is 100% leased to The Charles Stark Draper
Laboratory, Inc. ("Draper") on a long-term lease which expires on October 19,
2001. The lease contained extension options through October 19, 2051. The lease
states that the first extension option was "to be exercisable by notice from
Tenant to Landlord given not later than the end of the 23rd year of the Term
[October 19, 1999]." All subsequent extension options were only exercisable if
Draper had exercised its first extension option. The Company did not receive a
notice from Draper stating that it was exercising its extension option under the
lease. The lease also contains an option to acquire The Draper Building and a
right of first offer to acquire The Draper Building, each under certain
circumstances. See the lease documents attached hereto as Exhibits 99.1, 99.2,
and 99.3 for the specific provisions.

         Draper has now requested that the Company submit a proposal for a new
lease.

         The extension options in the lease provided for fixed rental rates
which were substantially below the current market rate. Prior to the occurrence
of the event described above, the Company had valued The Draper Building under
the assumption that Draper would exercise its extension options. The Company
does not believe that this assumption is still warranted.

ITEM 7 - FINANCIAL STATEMENTS, PRO FORMA FINANCIAL INFORMATION AND EXHIBITS

(c)      Exhibits

Exhibit 99.1 - Fourth Amendment and Restatement of Lease by and between
               The Prudential Insurance Company of America, successor to Gerald
               W. Blakeley, Jr., Ferdinand Colloredo-Mansfeld, and John M.
               Hines, as Trustees of CC&F Cambridge Trust, and Draper, dated as
               of July 1, 1981.

Exhibit 99.2 - Amendment to Fourth Amendment and Restatement of Lease by
               and between Asahi Seimei Prudential Associates, Number Three and
               Draper, dated as of February 6, 1998.

Exhibit 99.3 - Fifth Amendment to Lease by and between Technology Square LLC and
               Draper, dated as of June 23, 1998.

Exhibit 99.4 - Letter to Draper from Technology Square LLC, dated as of December
               1, 1999.



<PAGE>



                                   SIGNATURES



         Pursuant to the requirements of the Securities Exchange Act of 1934,
the Registrant has duly caused this report to be signed on its behalf by the
undersigned thereunto duly authorized.


                                        BEACON CAPITAL PARTNERS, INC.



Date: December 6, 1999                  By: /s/ RANDY J. PARKER
                                            ---------------------------
                                            Randy J. Parker
                                            Senior Vice President and
                                            Chief Financial Officer






<PAGE>


                                                   EXHIBIT INDEX
<TABLE>
<CAPTION>

      EXHIBIT NO.           DESCRIPTION
      -----------           -----------
<S>                         <C>
      Exhibit 99.1          Fourth Amendment and Restatement of Lease by and between The
                            Prudential Insurance Company of America, successor to Gerald W.
                            Blakeley, Jr., Ferdinand Colloredo-Mansfeld, and John M. Hines, as
                            Trustees of CC&F Cambridge Trust, and Draper, dated as of July 1,
                            1981.

      Exhibit 99.2          Amendment to Fourth Amendment and Restatement of Lease by and
                            between Asahi Seimei Prudential Associates, Number Three and
                            Draper, dated as of February 6, 1998.

      Exhibit 99.3          Fifth Amendment to Lease by and between Technology Square LLC
                            and Draper, dated as of June 23, 1998.

      Exhibit 99.4          Letter to Draper from Technology Square LLC, dated as of December
                            1, 1999.
</TABLE>


<PAGE>

                                  EXHIBIT 99.1





                              555 TECHNOLOGY SQUARE


                                  DRAPER LEASE


<PAGE>


                                FOURTH AMENDMENT

                                       AND

                              RESTATEMENT OF LEASE

         AGREEMENT made and entered into as of this first day of July, 1981, by
and between THE PRUDENTIAL INSURANCE COMPANY OF AMERICA, hereinafter called
"Landlord," successor to GERALD W. BLAKELEY, JR., FERDINAND COLLOREDO-MANSFELD,
and JOHN M. HINES, as Trustees of CC&F Cambridge Trust under Declaration of
Trust dated August 15, 1974, and THE CHARLES STARK DRAPER LABORATORY, INC., a
Massachusetts corporation, hereinafter call "Tenant."

         WHEREAS, Landlord's predecessor and Tenant entered into a lease (the
"Lease") dated August 16, 1974 of premises in Cambridge, Middlesex County,
Massachusetts, a First Amendment of the Lease dated as of March 11, 1975, a
Second Amendment and Restatement of Lease dated December 17, 1975 and a Third
Amendment of Lease dated February 2, 1977; and

         WHEREAS, Landlord and Tenant desire further to amend the Lease and to
consolidate the amendments and Lease into a restatement of the Lease in its
entirety;

         NOW THEREFORE, Landlord and Tenant agree that the Lease is amended in
its entirety, effective as of the date set forth above, to read as follows

         In consideration of the mutual promises and covenants of the parties
herein set forth, the parties do hereby agree as follows:

                                    ARTICLE I

                                 REFERENCE DATA

         1.1      SUBJECTS REFERRED TO

         Each reference in this Lease to any of the following subjects shall be
construed to incorporate the data stated for that subject in this Article:

         LANDLORD'S ADDRESS:     Northeastern Real Estate
                                 Investment office
                                 Prudential Center - Fortieth Floor
                                 Boston, Massachusetts 02199

         TENANT'S ADDRESS:       555 Technology Square
                                 Cambridge, Massachusetts 02139


                                        1

<PAGE>


         TECHNOLOGY SQUARE: The land in Cambridge, Massachusetts bounded by Main
and Portland Streets, Broadway and the Boston & Albany Railroad right of way.

         LOT: A parcel of land in Cambridge, Massachusetts described in
Exhibit A.

         BUILDINGS: The office-laboratory building (the "Main Building) the
parking garage (the "Garage") and the separate facility in the Garage (the
"Environmental Test Laboratory"), all located on the Lot.

         PREMISES: The Lot and the Buildings.

         PERMITTED USES: General office, laboratory, scientific research,
technological development and educational activities and uses normally incident
to all of the foregoing uses. Any activities in which The Charles Stark Draper
Laboratory, Inc. is currently involved as of the date of this Lease so long as
any such activity will not result in a violation of any law or ordinance when
carried on within the Premises. Any other lawful use first approved by Landlord,
which approval is not to be unreasonably withheld or delayed, provided, however,
Landlord shall not be deemed unreasonable in withholding approvals for uses
which are inconsistent with and materially detrimental to the uses being made of
the remaining portion of Technology Square.

         INITIAL TERM:  25 years

         COMMENCEMENT DATE:  October 20, 1976

         ANNUAL FIXED RENT: The Annual Fixed Rent commencing as of the date of
this Fourth Amendment and Restatement of Lease shall be $2,922,925.

         PUBLIC LIABILITY INSURANCE:

              BODILY INJURY:           $1,000,000
              PROPERTY DAMAGE:           $100,000

1.2      EXHIBITS.  There are incorporated as part of this Lease

              EXHIBIT A - Description of Lot
              EXHIBIT B - Cross Easements
              EXHIBIT C - Tenant Leasehold Improvements

1.3      TABLE OF ARTICLES AND SECTIONS

ARTICLE I - REFERENCE DATA


                                        2

<PAGE>

<TABLE>
<CAPTION>                                                                                                 PAGE

<S>      <C>                                                                                               <C>
1.1      Subjects Referred To........................................................................       1
1.2      Exhibits....................................................................................       2
1.3      Table of Articles and Sections..............................................................       2

ARTICLE II - PREMISES, TERM AND RENT

2.1      The Premises................................................................................       5
2.2      Tenant's Appurtenant Rights.................................................................       5
2.3      Landlord's Reservations.....................................................................       6
2.4      Habendum....................................................................................       6
2.5      Fixed Rent Payments.........................................................................       6
2.6      Real Estate Taxes...........................................................................       6
2.7      Payments of Additional Rent; No Right to Offset.............................................      10
2.8      Extension Options...........................................................................      10
2.9      Purchase Options............................................................................      13
2.10     Right of First Refusal......................................................................      19
2.11     Purchase Rights Following Casualty and Eminent Domain.......................................      25
2.12     Use of the Roof.............................................................................      26

ARTICLE III - CONSTRUCTION, ALTERATIONS AND ADDITIONS

3.1      Tenant's Alterations and Additions..........................................................      29
3.2      Construction Work...........................................................................      32

ARTICLE IV - LANDLORD'S COVENANTS

4.1      Landlord's Covenants Re Buildings' Defects..................................................      32
4.2      Quiet Enjoyment.............................................................................      33
</TABLE>

                                        3

<PAGE>

<TABLE>
<S>      <C>                                                                                               <C>
4.3      Tenant's Security Requirements..............................................................      33
4.4      Casualty Insurance..........................................................................      33

ARTICLE V - TENANT'S COVENANTS

5.1      Payments....................................................................................      35
5.2      Repair and Yield Up.........................................................................      35
5.3      Use.........................................................................................      36
5.4      Obstructions; items Visible From Exterior; Rules and Regulations............................      37
5.5      Safety Appliances; Licenses.................................................................      38
5.6      Assignment; Sublease........................................................................      38
5.7      Indemnity; Liability Insurance..............................................................      40
5.8      Personal Property at Tenant's Risk..........................................................      41
5.9      Right of Entry..............................................................................      42
5.10     Floor Load..................................................................................      43
5.11     Personal Property Taxes.....................................................................      42
5.12     Costs of Enforcement by Landlord............................................................      42

ARTICLE VI - CASUALTY AND TAKING

6.1      Casualty....................................................................................      42
6.2      Taking......................................................................................      45
6.3      Rent Adjustment.............................................................................      46
6.4      Eminent Domain Damages Reserved.............................................................      47
6.5      Temporary Taking............................................................................      48

ARTICLE VII - DEFAULT
</TABLE>

                                        4

<PAGE>

<TABLE>
<S>      <C>                                                                                               <C>
7.1      Events of Default...........................................................................      49
7.2      Damages.....................................................................................      50

ARTICLE VIII - MISCELLANEOUS

8.1      Net Rentable Area defined...................................................................      52
8.2      Notices of Lease; Consents or Approvals; Notices; Bind and Inure............................      53
8.3      Landlord's or Tenant's Failure to Enforce...................................................      54
8.4      Acceptance of Partial Payments of Rent; Delivery of Keys....................................      55
8.5      Cumulative Remedies.........................................................................      55
8.6      Partial Invalidity..........................................................................      56
8.7      Self-Help:  Landlord........................................................................      56
8.8      Self-Help:  Tenant..........................................................................      57
8.9      Estoppel Certificates.......................................................................      58
8.10     Waiver of Subrogation.......................................................................      59
8.11     All Agreements Contained....................................................................      60
8.12     Brokerage...................................................................................      60
8.13     Acts of God.................................................................................      60
8.14     Definitions.................................................................................      60

ARTICLE IX - RIGHTS OF MORTGAGEE

9.1      Lease Superior..............................................................................      61
9.2      Advance Payments of Rent....................................................................      62
9.3      Rights of Holder of Mortgage to Notice of Defaults by Landlord and to
         Cure Same...................................................................................      62
</TABLE>


                                        5

<PAGE>



                                   ARTICLE II
                             PREMISES, TERM AND RENT

         2.1 Landlord hereby leases to Tenant and Tenant hereby hires from
Landlord the Premises.

         2.2 Tenant shall have appurtenant rights to use, subject to reasonable
rules from time to time made by Landlord of which Tenant is given notice: (a)
that portion of the visitors' parking area (not to be used for more than ten
(10) of Tenant's officers or employees) located on Parcel 2 described in Exhibit
B or in Technology Square (without implied obligation on Landlord's part to
supervise parking in such spaces), (b) common walkways, sidewalks and driveways
necessary for access to the Premises, as from time to time maintained in
Technology Square and (c) other easements, to the extent set forth in Exhibit B,
on other parts of Technology Square.

         2.3 Landlord reserves the right from time to time, without unreasonable
interference with Tenant's use of the Premises to alter or relocate any facility
used in common with other occupants of Technology Square provided service is
maintained at least equal to that originally provided herein, and that
substitutions are substantially equivalent or better in quality of construction.

         2.4 Tenant shall have and hold the Premises for a period commencing on
the Commencement Date and continuing for the Term unless sooner terminated as
provided in this Lease.

         2.5 Tenant shall pay, without notice or demand, monthly installments of
1/12 of the Annual Fixed Rent (sometimes hereinafter referred to as "fixed
rent") in advance for each full

                                        6

<PAGE>


calendar month of the Term and of the corresponding fraction of said 1/12 for
any fraction of a calendar month at the beginning or end of the Term.

         2.6 During the Term Tenant shall pay directly to the taxing authority
the real estate taxes assessed on the Premises as additional rent. The term
"real estate taxes" shall mean all taxes and special assessments of every kind
and nature assessed by any governmental authority on the Premises which are
assessed because of or in connection with the ownership, leasing and operation
of the Premises except that there shall be excluded from such taxes all income
taxes, excess profit taxes, excise taxes, franchise taxes, estate, succession,
inheritance and transfer taxes; provided, however, that if at any time during
the Term the present system of ad valorem taxation of real property shall be
changed so that in lieu of the whole or any part of the ad valorem tax on real
property, there shall be assessed on Landlord a capital levy or other tax on the
gross rents received with respect to the Premises, or a federal, state, county,
municipal, or other local income, franchise, excise or similar tax, assessment,
levy or charge (distinct from any now in effect) measured by or based, in whole
or in part, upon any such gross rents, then any and all of such taxes,
assessments, levies or charges to the extent so measured or based, shall be
deemed to be included within the term "real estate tax" but only to the extent
that the same would be payable if the Premises was the only property of
Landlord. Real estate taxes relating to any period prior to the Commencement
Date or following the Term whether assessed before or during the Term shall be
prorated between Landlord and Tenant on the basis of the period of the Term
included within the period for which such assessment relates. If by law, a real
estate tax or any part thereof may be payable in installments (whether or not
interest shall accrue on the unpaid balance thereof) over a period

                                        7

<PAGE>



of time, Tenant shall have the right to request the public authority to permit
such installment payments over the longest period of time allowed by law and
thereafter Tenant shall be obligated to pay only such instal1ments which become
due during the Term.

         Included in Tenant's obligations in this Section 2.6 shall be the
obligation to pay any periodic real estate tax escrow payment of which Tenant
has been given notice as and when required by an Institutional Mortgagee (as
such term is defined in Section 8.14). In the event that Landlord restructures
the existing mortgage financing on the Premises, Landlord shall use reasonable
and good faith efforts to eliminate the necessity to make such real estate tax
escrow payments to any future Institutional Mortgagee.

         Landlord shall promptly forward to Tenant, all bills and demands for
real estate taxes and all notices requiring tax escrow payments which Tenant is
required to pay. Tenant shall, except as otherwise herein provided, pay all real
estate taxes which it is obligated to pay under this Lease before the end of
twenty (20) days after receipt of any bill therefor, or before the expiration of
such time as payment may be made without incurring interest or penalty,
whichever date is later. Tenant shall promptly thereafter furnish Landlord with
receipted bills evidencing payment of such real estate tax. Tenant shall make
all tax escrow payments which Tenant is required to pay pursuant to the
preceding paragraph, before the expiration of such time as the payment may be
made without causing a default under the provisions of the applicable mortgage.

         The Tenant shall have the right to contest at its expense, any real
estate taxes by appropriate proceedings diligently conducted in good faith; but
to the extent that they are a lien on the Premises, only after paying such
taxes, filing a surety bond to remove such lien or

                                        8

<PAGE>


paying or placing in an escrow arrangement reasonably satisfactory to Landlord
and any Institutional Mortgagee the full amount of such real estate taxes,
together with all reasonably foreseeable interest and penalties that may become
a charge on the Premises in such proceedings and Landlord shall, in such event,
be held harmless and indemnified by Tenant from any loss or damage to Landlord's
title in the Premises resulting from the nonpayment of such real estate taxes.
Upon final conclusion of all such proceedings, Tenant shall pay whatever may be
due and at that time the escrow funds together with any interest thereon shall
simultaneously be released to Tenant. Any refund or other payment received by
Tenant or payable to others as a result of such abatement or other appropriate
proceeding conducted by Tenant shall be the property of Tenant. Tenant may at
its own expense at any time, endeavor to obtain a lowering of the assessed
valuation upon the Premises, for the purposes of reducing taxes, and Landlord
shall cooperate in effecting such reduction. Landlord shall not be required to
join in proceedings referred to in this Section unless Landlord is a necessary
party to such proceedings and Tenant requests such joinder and Landlord shall in
such event be held harmless and indemnified by Tenant from any costs and
expenses incidental to such participation by Landlord.

         2.7 Except as otherwise specifically provided herein, any sum, amount,
item or charge designated or considered as additional rent in this Lease shall
be paid by Tenant to Landlord on the first day of the month following the date
on which Landlord notifies, Tenant of the amount payable, or on the tenth day
after giving of such notice, whichever shall be later. Any such notice shall
specify in reasonable detail the basis of such additional rent. Fixed rent

                                        9

<PAGE>


and additional rent shall be paid by Tenant to Landlord without offset,
abatement or deduction, except as otherwise specifically provided in this Lease.

         2.8 Tenant shall have the following options to extend the Term of this
Lease provided in each case that Tenant is not in default under clauses (a) or
(c) of Section 7.1:

                  2.8.1 if this Lease is then in effect, an option to extend the
Term from 25 to 35 years, upon all the terms, conditions and provisions of this
Lease except as hereinafter provided, to be exercisable by notice from Tenant to
Landlord given not later than the end of the 23rd year of the Term.

         If Tenant exercises such option, the Annual Fixed Rent shall be the
lesser of (a) the then fair rental value of the Premises or (b) the sum of (A)
$2,154,846 plus (B) the product of (i) $768,079 and (ii) the Consumers Price
Index (United States All Services) for the 270th month of the Term divided by
such Consumers Price Index for the month of October, 1976, but in no event shall
the fixed rent as determined under this clause (b) exceed $3,691,004;

                  2.8.2 if Tenant has exercised its option under subsection
2.8.1, and if this Lease is then in effect an option to extend the Term from 35
to 55 years, upon all the terms, conditions and provisions of this Lease except
as hereafter provided, to be exercisable by notice from Tenant to Landlord given
not later than the end of the 33rd year of the Term.

         If Tenant exercises such option, the Annual Fixed Rent shall be the
lesser of (a) the then fair rental value of the Premises or (b) the sum of (A)
the fixed rent determined under subsection 2.8.1 minus $768,079 plus (B) the
product of (i) $768,079 and (ii) the Consumers Price Index (United States All
Services ) for the 390th month of the Term divided by such Consumers Price Index
for the first month of the extension of the Term pursuant to subsection

                                       10

<PAGE>


2.8.1, but in no event shall the fixed rent as determined under this clause (b)
exceed $4,459,083;

                  2.8.3 if Tenant has exercised its option under subsection
2.8.2, and if this Lease is then in effect an option to extend the Term from 55
to 75 years, upon all the terms, conditions and provisions of this Lease except
as hereinafter provided, to be exercisable by notice from Tenant to Landlord
given not later than the end of the 53rd year of the Term.

         If Tenant exercises such option, the Annual Fixed Rent shall be the
lesser of (a) the then fair rental value of the Premises or (b) the sum of (A)
the fixed rent determined under subsection 2.8.2 minus $768,079 plus (b) the
product of (i) $768,079 and (ii) the Consumers Price Index (United States All
Services) for the 630th month of the Term divided by such Consumers Price Index
for the first month of the extension of the Term pursuant to subsection 2.8.2,
but in no event shall the fixed rent as determined under this clause (b) exceed
$5,227,162.

                  2.8.4 The Consumers Price Index (United States All Services)
referred to above is the Index number in the column for "All Services" in the
table entitled Consumers Price Index-United States Average prepared by the
Bureau of Labor Statistics of the United States Department of Labor. In the
event such Index is not in existence when any of the foregoing determinations
are to be made, or the basis for calculating such Index shall have been changed,
the parties shall use such equivalent Index as is published by the United States
Bureau of Labor Statistics or by any successor governmental agency or if none is
published by such agency, then such equivalent Index as may then be published by
a non-governmental agency.

                                       11

<PAGE>


         If the then "fair rental value" as used in this Section 2.8 shall not
be agreed upon by Landlord and Tenant, then such "fair rental value" shall be
determined by three appraisers, one selected by Landlord, one by Tenant and the
third by the two appraisers so selected, all of whom shall have had at least ten
(10) years experience in appraising commercial real estate in the Greater Boston
area. In determining such fair rental value, the appraisers shall disregard the
value of any leasehold improvements made by or at the expense of Tenant. The
cost of such appraisal shall be borne equally by Landlord and Tenant.

         2.9 Landlord hereby grants to Tenant the following options to purchase
the Premises, including all easements appurtenant thereto (hereinafter in
Sections 2.9, 2.10 and 2.11 collectively the "Property") provided, in each case,
that this Lease shall be in effect at the time of the exercise by Tenant of its
rights hereunder and Tenant is not then in default under clauses (a) or (c) of
Section 7.1:

                  A. the option to purchase the entire Property exercisable by
notice of intention to purchase hereinafter described, given within the last
month of any fifth year of the Term, if the real estate taxes as defined in
Section 2.6 exceed, after the conclusion of any contest or abatement proceedings
with respect thereto, the amount of $964,747 for two successive years during the
five year period immediately preceding the time when such option may be
exercised. The Purchase Price shall be 120% of the fair market value of the
Property, treated as encumbered by this Lease and any Institutional Mortgage
held by an Institutional Mortgagee which by its terms cannot then be prepaid and
without regard to the value of any leasehold improvements made, by or at the
expense of Tenant, as determined by three appraisers, one selected by Landlord,
one by Tenant, and the third by the two appraisers so

                                       12

<PAGE>


selected, all of whom shall have had at least ten years experience in appraising
commercial real estate in the greater Boston area. The reasonable cost of such
appraisal shall be borne by Tenant. In no event, however, shall the purchase
price be less than $32,160,000; and

                  B. the option to purchase the entire Property exercisable by
notice of intention to purchase hereinafter described, given within the last
month of: (i) the thirty-fifth year of the Term provided that Tenant shall have
exercised its option to extend the Term set forth in subsection 2.8.2; (ii) the
fifty-fifth year of the Term provided that Tenant shall have exercised its
option to extend the Term set forth in subsection 2.8.3; and (iii) the
seventy-third year of the Term. The purchase price shall be ninety percent (90%)
of the fair market value of the Property, treated as encumbered by this Lease
and without regard to the value of any leasehold improvements made by or at the
expense of Tenant after the Commencement Date, as determined by three
appraisers, one selected by Landlord, one by Tenant and the third by the two
appraisers so selected, all of whom shall have had at least, ten years
experience in appraising commercial real estate in the greater Boston area. The
cost of such appraisal shall be borne equally by Landlord and Tenant unless
Tenant withdraws its notice of intention to purchase, in which case Tenant shall
pay the entire cost of the appraisal.

         At the time any of such options is exercisable, Tenant shall notify
Landlord of Tenant's intention to purchase the Property, but without any
obligation to do so except as hereinafter provided, together with notification
to Landlord of the appraiser selected by Tenant. Within 60 days after the
determination of fair market value of the Property by the appraisers as provided
above, Tenant shall confirm to Landlord or withdraw its notice of intention to
purchase. The failure by Tenant to either confirm or withdraw within such 60 day
period shall be deemed to

                                       13

<PAGE>


be a withdrawal. The closing of the purchase (hereinafter the "Closing Date")
shall occur on the sixtieth day after notice by Tenant to Landlord of Tenant's
confirmed decision to purchase or on the next succeeding business day if such
sixtieth day shall occur on a nonbusiness day.

         If Tenant exercises any option to purchase, the purchase price shall be
paid by a check or checks drawn by a Boston bank or banks on the Federal Reserve
Bank of Boston or in such other manner as will make the consideration available
in Boston to Landlord for investment on the Closing Date and the Property in its
then physical condition shall be simultaneously conveyed at noon on the Closing
Date by a good and sufficient quitclaim deed running to Tenant or such nominee
as shall have been designated by at least 30 days' notice to Landlord, delivered
at the Middlesex Registry of Deeds or such other office where such deed is to be
recorded or filed in order to charge third parties with notice thereof,
conveying a good and clear record and marketable title thereto subject only to,
and with the benefit of, the following matters affecting the Property on the
Closing Date:

         1. Rights and easements now or hereafter affecting the Property as
described in Exhibit B.

         2. Easements and agreements hereafter affecting the Property, so far as
in force and applicable on the Closing Date, voluntarily created by Landlord at
any time with Tenant's approval.

         3. Utility easements hereafter affecting the Property and serving the
Lot or the remaining part of Technology Square, so far as in force and
applicable on the Closing Date, voluntarily created by Landlord without Tenant's
approval if and to the extent the same (a) do not adversely affect the operation
of the Main Building as an office/laboratory facility, the

                                       14

<PAGE>


Environmental Test Laboratory as a laboratory facility, or the Garage as a
garage building and (b) can be relocated at the election and expense of the
owner of the Property.

         4. Real estate taxes assessed or to be assessed upon the Property, for
the fiscal period in which the conveyance is made.

         5. Balances, if any, remaining due and unpaid on account of betterment
assessments on the Property.

         6. In the case of a purchase by Tenant pursuant to clause A of the
first paragraph of this Section 2.9, any Institutional Mortgage held by an
Institutional Mortgagee on the Property which by its terms cannot then be
prepaid.

         7. In the case of a purchase by Tenant pursuant to Section 2.10.1, any
mortgage referred to in Landlord's notice of intention to sell the Property.

         8. Any mortgage on the Property which Tenant desires to have remain
thereon after the Closing Date and which is not required to be discharged by
virtue of Tenant's purchase of the Property.

         9. This Lease.

         10. Laws and regulations of any governmental authority.

         11. Any changes in the Property which may have occurred as a result of,
and any easements or restrictions imposed by, takings by eminent domain.

         12. Such state of facts that an accurate survey would show.

         Closing adjustments of the usual and customary items shall be made
between the parties taking into account the provisions of this Lease and the
respective obligations of the parties with respect to the payment of such items.
In addition there shall be a credit to Tenant, as

                                       15

<PAGE>


purchaser, for the amount secured by any mortgage on the Property to which the
deed is subject or, in the case of a purchase by Tenant pursuant to clause A of
the first paragraph of this Section 2.9, a credit to Landlord, as seller, for
any prepayment penalties required to be paid in order to discharge an
Institutional Mortgage held by an Institutional Mortgagee on the Property at the
Closing Date.

         In the event the Property is subject to a mortgage immediately prior to
the purchase of the Property by Tenant and such mortgage is not to remain
outstanding after the purchase, there shall be paid directly by official bank or
certified check to the holder of such mortgage, for the purpose of discharging
the same, such portion of the purchase price as is necessary to pay all amounts
(including without limitation any prepayment penalties) secured by such
mortgage, and the remaining balance of the purchase price shall be paid to
Landlord. The preceding sentence shall not require Tenant to pay a purchase
price for the Property in excess of the amount elsewhere established in this
Lease.

         Notwithstanding the foregoing provisions of this Section 2.9 or the
provisions of Sections 2.10 or 2.11, if the Rule Against Perpetuities or any
other rule of law limits the time within which Tenant's rights under those
Sections may be exercised, then no option to purchase granted to Tenant
hereunder or under the provisions of Sections 2.10 or 2.11 may be exercised
later than the expiration of twenty years after the death of the last survivor
of the following persons: Michael R. O'Connor and Catherine A. O'Connor,
children of Joseph F. O'Connor and Patricia R. O'Connor, 17 Ardsmore Road,
Melrose, Massachusetts; Craig Driscoll and Kelley Driscoll, children of David C.
Driscoll and Sheila M. Driscoll, 143 Arlington Street, Winchester,
Massachusetts; Edwin H. Porter III, Timothy Porter, Mary

                                       16

<PAGE>



Porter, Patrick Porter, Christopher Porter, Phyllis Porter, William Porter and
Benjamin Porter, children of Edwin H. Porter, Jr. and Sue E. Porter, 19
Mayflower Road, Winchester, Massachusetts; and Stephen S. Abbott, Cathryn C.
Abbott and David H. Abbott, children of William S. Abbott and Susan S. Abbott,
Herring Way, Plymouth, Massachusetts.

         The rights and options of Tenant set forth in this Section 2.9 are not
severable from the leasehold estate created by this Lease and may not be
assigned to any party unless this Lease is simultaneously assigned to such
party.

         In the event Tenant exercises any right to purchase the property
pursuant to (a) the option set forth in clause A of the first paragraph of this
Section 2.9 or (b) the option set forth in clause B of the first paragraph of
this Section 2.9, and thereafter defaults in its obligations to Landlord and
fails to complete the purchase of the Property after having exercised its right
to do so, Landlord may sell the Property to any third party at any time
thereafter on such terms and conditions as Landlord may choose, free and clear
of all rights of Tenant under the option set forth in clause A of the first
paragraph of this Section 2.9 in the case of (a), or free and clear of all
rights of Tenant under the options set forth in clause B of the first paragraph
of this Section 2.9 in the case of (b). Landlord shall not assert any claims
against Tenant on account of such default or failure and such default shall not
constitute a default under this Lease except as specifically provided in this
Section 2.9.

         2.10 Landlord hereby grants to Tenant the following options to purchase
the Property provided, in each case, that this Lease shall be in effect at the
time of the exercise by Tenant of its rights hereunder and Tenant is not then in
default under clauses (a) or (c) of Section 7.1:

                                       17

<PAGE>


                  2.10.1 In the event Landlord shall decide to offer the
Property for sale, Landlord shall first give notice to Tenant of its intention
to sell the Property and Tenant shall have the right, for a period of 30 days
after Landlord's notice of intention to sell, to notify Landlord of Tenant's
interest in purchasing the Property. If Tenant so notifies Landlord and the
parties agree on a purchase price, which shall in no event be for an amount less
than the amount (including without limitation any prepayment penalties) secured
by an Institutional Mortgage or Mortgages on the Property held by an
Institutional Mortgagee at the time of such purchase, the Property shall be sold
by Landlord to Tenant at that price. If a selling price is not agreed upon
within such 30 day period, the fair market value of the Property, treated as
encumbered by this Lease and without regard to the value of any leasehold
improvements made by or at the expense of Tenant, shall be determined by three
appraisers, one selected by Landlord, one by Tenant, and the third by the two
appraisers so selected, all of whom shall have had at least ten years experience
in appraising commercial real estate in the greater Boston area. The cost of
such appraisal shall be borne equally by Landlord and Tenant unless Landlord
withdraws its notice of intention to sell, in which case the entire cost of the
appraisal shall be borne by Landlord. Tenant shall have the option to purchase
the Property at its fair market value, as so determined, exercisable by notice
to Landlord given within 40 days after such determination of fair market value,
unless within 10 days of such determination Landlord shall have withdrawn its
notice of intention to sell in which case Tenant shall not have the option to
purchase the Property and Landlord shall not sell the Property to a third party
without first complying with the above procedures and providing Tenant the
opportunity of purchasing the Property.

                                       18

<PAGE>


         If at the time Landlord gives notice to Tenant of its intention to sell
the Property, the Property is subject to an institutional Mortgage held by an
Institutional Mortgagee which by its terms is transferable without acceleration
or penalty and which either (a) by its terms cannot be prepaid or (b) contains a
prepayment penalty, and Landlord intends to sell the Property subject to such
mortgage, then such notice shall indicate such intention and include copies of
all relevant mortgage documents and a statement as to the current status of the
mortgage, includ ing without limitation, (i) the then outstanding balance of
principal, (ii) current interest rate, (iii) current payment schedule, and (iv)
date of most recent payment. At the request of Tenant, Landlord shall use its
best efforts to obtain from the holder of the mortgage, prior to the time the
Property is submitted to appraisers for a determination of fair market value, a
right to prepay such mortgage at the lowest possible fixed sum penalty. In the
event the Property is to be offered subject to such mortgage and is submitted to
appraisers for a determination of fair market value, the appraisers shall be
instructed to consider the effect of such mortgage on the value of the Property.
In the event the purchase price of the Property, as determined above in this
subsection 2.10.1, is less than the amount (including without limitation any
prepayment penalties) secured by any Institutional Mortgage or Mortgages on the
Property held by an Institutional Mortgagee, then Landlord shall be deemed to
have exercised its right to withdraw its notice of intention to sell the
Property as provided in this subsection 2.10.1.

         If Tenant exercises its right to purchase the Property, the provisions
of Section 2.9 (dealing with the form of the purchase price, the place of
delivery thereof, the form of the deed, the matters to which the deed is subject
and the closing adjustments) shall apply to the sale, and the purchase shall
occur (hereinafter the "Closing Date") on the 60th day after

                                       19

<PAGE>



Tenant's exercise of its right to purchase, or on the next succeeding business
day if such 60th day shall occur on a nonbusiness day. If Tenant does not
exercise its right to purchase the Property, Landlord shall have the right to
sell the Property to any third party for a period of one year from the last date
on which Tenant could have exercised its right to purchase the Property, free
and clear of any rights of Tenant under this Section 2.10, but subject to all
other provisions of this Lease.

         2.10.2 Except in accordance with the provisions of subsection 2.10.1,
Landlord shall not sell the Property to a third party unless (a) Landlord has
received a bona fide written offer to purchase the Property, (b) Landlord has
given Tenant a copy of the offer together with (i) indication that Landlord is
willing to accept the offer and (ii) an offer by Landlord to Tenant to sell the
Property on the same terms and conditions set forth in the offer, and (c) Tenant
shall not have agreed to purchase the Property in accordance with the offer
within 60 days after Tenant's receipt of the notice and offer.

         In the event Tenant agrees to purchase the Property, Tenant shall
comply with all the terms and conditions of the offer, except that in no event
shall Tenant be required to pay the consideration or complete the purchase in
less than 120 days from the date of Landlord's notice and offer.

         In the event Tenant shall not have agreed to purchase the Property
within the time specified above, Landlord shall have the right to sell the
Property to any third party in accordance with the terms and conditions set
forth in the offer, and free and clear of any rights of Tenant under this
Section 2.10, but, shall not be free to sell the Property on terms and

                                       20

<PAGE>


conditions different from those set forth therein without first complying with
the provisions of this subsection 2.10.2.

                  2.10.3 The foregoing rights of Tenant set forth in this
Section 2.10 shall apply to (a) any transfers and sales of portions of the
Property and (b) any transfers and sales of the controlling interest in Landlord
but shall be inapplicable to transfers and sales which, because made to
Affiliates of Landlord, because limited to a portion of such interest, or for
any other reason, do not affect the power to control Landlord and shall be
inapplicable to the placing of any bona fide mortgage on such interest, to the
foreclosure thereof and to the delivery of a deed or any other transfer in lieu
of such foreclosure.

                  2.10.4 The rights of Tenant set forth in this Section 2.10
shall be inapplicable to transfers and sales between Landlord and Affiliates of
Landlord and shall also be inapplicable to the placing of an Institutional
Mortgage on the Property, the foreclosure thereof by an Institutional Mortgagee
and the delivery of a deed in lieu of foreclosure to anyone other than an
Affiliate of Landlord; and upon the foreclosure of any such mortgage on the
Property or the delivery of a deed in lieu of such foreclosure, all rights and
options of Tenant set forth in this Section 2.10 shall terminate.

                  2.10.5 The rights and options of Tenant set forth in this
Section 2.10 are not severable from the leasehold estate created by this Lease
and may not be assigned to any party unless this Lease is simultaneously
assigned to such party.

                  2.10.6 In the event Tenant exercises any right to purchase the
Property pursuant to the options set forth in this Section 2.10 and thereafter
defaults in its obligations to Landlord and fails to purchase the Property,
Landlord may sell the Property to any third party

                                       21

<PAGE>



at any time thereafter on such terms and conditions as Landlord may choose, free
and clear of all rights of Tenant under this Section 2.10, but without waiving
any claims against Tenant on account of such default or failure. Landlord shall
not, however, seek specific performance of Tenant's obligation to purchase the
Property and such default shall not constitute a default under this Lease except
as specifically provided in this Section 2.10.

         2.11 In the event Landlord elects to terminate this Lease pursuant to
the applicable provisions of Section 6.1 or 6.2 then Tenant shall have the right
for a period of 30 days after such termination to notify Landlord of Tenant's
intention of purchasing the Property or any remaining portion thereof owned by
Landlord. If Tenant so notifies Landlord and the parties agree on a purchase
price, which shall in no event be for an amount less than the amount (including
without limitation any prepayment penalties) secured by an Institutional
Mortgage or Mortgages on the Property held by an Institutional Mortgagee at the
time of such purchase (after application of any insurance proceeds or eminent
domain award), the Property shall be sold by Landlord to Tenant at that price.
If a selling price is not agreed upon within such 30 day period, the fair market
value of the Property or such remaining portion thereof, treated as unencumbered
by this Lease, shall be determined by three appraisers, one selected by
Landlord, one by Tenant, and the third by the two appraisers so selected, all of
whom shall have had at least ten years experience in appraising commercial real
estate in the greater Boston area. The cost of such appraisal shall be borne by
Tenant. Tenant shall have the option to purchase the Property or such remaining
portion thereof at its fair market value as determined by such appraisal, but in
no event for an amount less than the amount (including without limitation any
prepayment penalties) secured by an Institutional Mortgage or

                                       22

<PAGE>



Mortgages on the Property held by an Institutional Mortgagee at the time of such
purchase (after application of any insurance proceeds or eminent domain award),
exercisable by notice to Landlord given within 30 days after such determination
by the appraisers. If Tenant exercises its right to purchase the Property or
such remaining portion thereof, the provisions of Section 2.9 (dealing with the
form of the purchase price, the place of the delivery thereof, the form of the
deed, the matters to which the deed is subject and the closing adjustments)
shall apply to the sale and the purchase shall occur on the 60th day after
Tenant's exercise of its right to purchase, or on the next succeeding business
day if such 60th day shall occur on a nonbusiness day.

         2.12 In addition to any other rights which Tenant has pursuant to this
Lease, Tenant shall have the following rights with respect to the use of the
roof of the Main Building:

                  2.12.1 to install, use and maintain up to five (5) twelve inch
diameter dish-type antennae and one whip-type antenna;

                  2.12.2 (i) to construct at Tenant's sole cost and expense a
permanent improvement (the "Penthouse Laboratory") architecturally compatible
with the existing penthouse, pursuant to architectural plans and specifications
either (a) designed by Skidmore, Owings & Merrill, architects, or (b) approved
by Landlord, which approval shall not unreasonably be withheld, and not
containing more than 3,000 square feet of Net Rentable Area without Landlord's
approval, which approval shall not unreasonably be withheld, and thereafter to
use the space within the Penthouse Laboratory without any obligation on Tenant's
part to pay rent for such space.

                                       23

<PAGE>


                         (ii) alternatively, at Tenant's request Landlord shall
construct the Penthouse Laboratory at its expense and at Tenant's request
install equipment and other leasehold improvements in a manner consistent with
the standards set forth in Article III and with the specifications contained in
Exhibit C of the Second Amendment and Restatement of Lease and upon completion
Tenant shall pay Landlord as additional Annual Fixed Rent, at the times and in
the manner provided in Section 2.5, an amount equal to $5.71 per square foot of
Net Rentable Area in the Penthouse Laboratory less the reasonable value of any
such equipment or leasehold improvements which Landlord is not required to
install or provide in the Penthouse Laboratory. In the event that Tenant has
constructed any portion of the Penthouse Laboratory which Landlord can utilize
(e.g., the concrete floor constructed prior to the Commencement Date), Landlord
will credit Tenant the reasonable value thereof toward the initial payments due
for the Additional Annual Fixed Rent payable under this Section.

                         (iii) In the event that Landlord shall fail to commence
construction of the Penthouse Laboratory within three months after request
therefor by Tenant, or following commencement shall cease to use due diligence
to complete construction, then Tenant may, but shall not be obligated to,
commence or complete, as the case may be, construction of the Penthouse
Laboratory subject to the provisions of clause (i) above and in a manner
consistent with the scope requirements set forth in clause (ii) above and
thereafter to use the space within the Penthouse Laboratory without any
obligation to pay rent for such space until Tenant receives from Landlord the
cost to Tenant of such construction. Upon such payment to Tenant, Tenant shall
thereafter pay as additional Annual Fixed Rent, at the times and in the manner
provided in Section 2.5, an amount equal to $5.71 per square foot of Net
Rentable Area in the

                                       24

<PAGE>


Penthouse Laboratory adjusted as provided in clause (ii) above. Landlord's
failure to commence or complete construction as the case may be or to pay such
construction costs to Tenant shall not constitute a default by Landlord under
this Lease, and Tenant's sole remedy for such failure shall be to seek a money
judgment against Landlord for such construction costs. The obligation of
Landlord to pay such costs to Tenant shall be binding upon the successors and
assigns of Landlord, except that such obligation shall not be binding upon the
holder of an Institutional Mortgage on the Lot or Buildings or both or upon any
successor or assign of such holder or upon the grantee of a deed in lieu of
foreclosure of such an Institutional Mortgage or upon any successor of such
grantee or upon any purchaser from the holder of such an Institutional Mortgage
at foreclosure sale or upon any successor to such a purchaser.

                                   ARTICLE III
                     CONSTRUCTION, ALTERATIONS AND ADDITIONS

         3.1 Tenant shall not make alterations and additions to the Premises
beyond those improvements described in Exhibit C except in accordance with plans
and specifications therefor first approved by Landlord, provided that such
approval shall not be required for alterations and additions to the Premises
which (a) do not affect (i) the structural integrity of the roof, exterior
walls, floor slabs or foundations of the Premises, (ii) the external appearance
of the Buildings (except as otherwise provided in Section 2.12), and (b) do not
alter (i) the elevator system, (ii) the chilled water or hot water heating
risers, (iii) the primary transformers, and switching equipment related thereto,
the main electrical panel, the six (6) main vertical electrical buss ducts or
(iv) the equipment within the central mechanical rooms on

                                       25

<PAGE>


the roof or in the basement of the six story section of the Main Building
excluding equipment provided exclusively in connection with Tenant's leasehold
improvements; provided, however, in the case of all alterations and additions,
Tenant shall deliver to Landlord, plans and specifications therefor at least
fifteen (15) days before starting work thereon. In the event any plans and
specifications which are submitted during the Term indicate an alteration to the
basic systems and equipment serving the Buildings which will require unusual
expense upon the part of Landlord to restore, Tenant shall, upon request of
Landlord made within thirty (30) days after receiving such plans and
specifications, acknowledge responsibility either to (i) readapt such system or
equipment for either normal office use or (at Tenant's option) the purposes for
which they were suitable at the commencement of the Term, or (at Tenant's
option) (ii) pay for the expense of such readaptation, at the expiration or
termination of this Lease. Landlord acknowledges the unique character of
Tenant's operations and the consequent need for flexibility in the use of the
Premises and agrees to cooperate with Tenant in effecting desired alterations
and additions. Landlord shall not be deemed uncooperative or unreasonable for
withholding approval of any desired alteration or addition for which approval is
required hereunder which will (i) require unusual expense upon the part of
Landlord to readapt the Premises so as to be suitable for either the uses for
which they are suitable at the commencement of the Term or normal office uses
unless Tenant first gives reasonable assurances acceptable to Landlord for
payment of the expense to adapt to either standard at Tenant's option or (ii)
affect the external appearance or structural integrity of the Buildings. All
alterations and additions shall be of a quality consistent with the Buildings
and shall be part of the Buildings until they are removed by Tenant from time to
time during the Term or

                                       26

<PAGE>


pursuant to and to the extent permitted by Section 5.2. All of Tenant's
alterations and additions and installations of furnishings shall be coordinated
with any work being performed by Landlord and in such manner as to avoid labor
difficulties and not to permanently damage the Buildings or Lot or unnecessarily
interfere with operation of the Buildings and any work which requires Landlord's
approval shall be performed by contractors or workmen first approved by
Landlord, which approval shall not be unreasonably withheld or delayed. Tenant,
before its work is started, shall: secure all licenses and permits necessary
therefor; deliver to Landlord a statement of the names of all its contractors
and subcontractors and the estimated cost of all labor and material to be
furnished by them; in the event that any one contract or job involves costs
exceeding $500,000, provide security reasonably satisfactory to Landlord to
protect Landlord from any lien claims for such labor and material; and cause
each contractor to carry workmen's compensation insurance in statutory amounts
covering all the contractor's and subcontractor's employees and comprehensive
public liability insurance with limits not less than $300,000-$500,000, and
property damage insurance with limits of not less than $100,000 or in the case
of each such insurance such higher limits as may from time to time be
customarily required by landlords of high quality office buildings in the
Boston-Cambridge area (all such insurance to be written in companies approved by
Landlord and, except for workmen's compensation insurance, insuring Landlord and
Tenant as well as the contractors), and to deliver to Landlord at its request,
certificates of all such insurance. Tenant agrees to pay promptly when due the
entire cost of any work done on the premises by Tenant, its agents, employees,
or independent contractors, and not to cause or permit any liens for labor or

                                       27

<PAGE>


materials performed or furnished in connection therewith to attach to the
Premises and immediately to discharge any such liens which may so attach.

         3.2 All construction work required or permitted by this Lease shall be
done in a good and workmanlike manner and in compliance with all applicable laws
and all lawful ordinances, regulations and orders of governmental authority and
reasonable requirements of the insurers of the Buildings. Each party may
(without any implied obligation) observe or inspect the work of the other at
reasonable times and shall promptly give notice of observed defects, provided
that failure to exercise such right to observe or inspect or failure to observe
any defects shall not charge either party with knowledge of such defect or an
obligation to give such notice. Each party authorizes the other to rely in
connection with design and construction upon approval and other actions on the
party's behalf by any person hereafter designated as construction representative
by notice to the party relying.

                                   ARTICLE IV
                              LANDLORD'S COVENANTS

         4.1 Landlord shall, without cost to Tenant, correct any defects in
design, materials, workmanship or performance in the work performed by Landlord
in constructing (i) the Buildings and related facilities in accordance with
Article III of the Second Amendment and Restatement of Lease, notice of which
defects Landlord has been given notice before or during the first five full
calendar years of the Term, and (ii) the basic structural elements of the
Buildings (e.g., roof, exterior walls, floor slabs and foundations) during the
Initial Term which do not result from ordinary wear and tear of such structural
elements; provided Landlord shall not be required to correct any such defects
until notice of such defects is received by Landlord.

                                       28

<PAGE>


         4.2 Landlord covenants that Landlord has the right to make this Lease
and that Tenant, on paying the rent and performing the tenant obligations in
this Lease, shall peacefully and quietly have, hold and enjoy the Premises and
the appurtenant rights in Section 2.2, subject to all of the terms and
provisions hereof.

         4.3 Landlord recognizes that the special nature of Tenant's use of the
Premises requires special security requirements. Accordingly, any other
provision of this Lease to the contrary notwithstanding, Landlord agrees that
any rights reserved to it to enter the Premises shall take due account of such
security requirements, and that except in case of emergency when prior notice is
not possible Landlord will not exercise such rights without reasonable prior
notice to Tenant and that at all times Landlord shall exercise reasonable
diligence when in the Premises to avoid unnecessary inconvenience to Tenant.

         4.4 Landlord shall carry such insurance upon the Buildings as may from
time to time be required by any Institutional Mortgagee holding a first mortgage
thereon and in any event insurance against loss by fire and the hazards now
covered by extended coverage #4 endorsement in an amount at least equal to 80%
of the replacement value of the Buildings, exclusive of foundations, with an
agreed amount endorsement (including insurance against loss in case of fire or
casualty of monthly installments of fixed rent and any additional rent which may
become due under Section 2.6 and this Section 4.4). In the event Landlord is
carrying such insurance, (a) Landlord shall also carry such additional insurance
upon the Buildings as Tenant may from time to time require and (b) Landlord
shall supply copies and certificates of all such insurance (together with
detailed itemization of all premiums therefor) to Tenant issued by or on behalf
of the insurers named therein by a duly authorized agent and containing

                                       29

<PAGE>


the insurers' undertaking not to cancel such insurance or decrease the amount or
scope of the coverage thereof without ten days' prior written notice to Tenant
(but no such undertaking shall name Tenant as an insured in said policies or
create in Tenant any interest in them). In the event Landlord is carrying such
insurance, Tenant shall pay as additional rent all premium's for insurance
required to be carried by Landlord pursuant to this Section 4.4 prior to the
date when such premiums are due but in no event less than twenty-five (25) days
following receipt of notice of such premiums; provided, however, that in the
event Tenant is able to obtain a commitment for insurance on the Buildings with
equal or more extensive coverage as carried by Landlord pursuant to this Section
4.4, with companies qualified to do business and in good standing in
Massachusetts and reasonably acceptable to Landlord and any Institutional
Mortgagee, then Tenant's obligations to pay such insurance premiums as provided
herein shall be limited to an amount equal to the premium required pursuant to
such commitment for insurance; and provided, further, that at Landlord's
election, exercisable by at least ninety days' prior written notice to Tenant,
Tenant shall carry at its expense such insurance otherwise required to be
carried by Landlord under this Section 4.4, in which event Tenant shall supply
copies and certificates thereof to Landlord issued by or on behalf of the
insurers named therein by a duly authorized agent and containing the insurers'
undertaking not to cancel such insurance or decrease the amount or scope of the
coverage thereof without ten days' prior written notice to Landlord.

                                    ARTICLE V
                               TENANT'S COVENANTS

                                       30

<PAGE>


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

         5.1 to pay when due all fixed rent and additional rent and as further
additional rent to pay all charges for utility services rendered to the Premises
and reasonable service inspections therefor made by the utility companies;

         5.2 except as otherwise provided in Article VI and Section 4.1 to keep
the Premises in good order, repair and condition, reasonable wear and tear
excepted, and at the expiration or termination of this Lease to return to
Landlord all keys for doors in the Premises, to disclose to Landlord the
combination of any safes, cabinets or vaults left in the Premises on Lease
termination, and peaceably to yield up the Premises including, except as
hereinafter provided, all alterations and additions thereto in good order,
repair and condition, reasonable wear and tear and casualty excepted, first
removing: all goods and effects of Tenant; all installations made by or on
behalf of Tenant the disclosure of which to third parties would, because of
security classifications or otherwise, be in violation of any federal or state
laws or regulations; all so-called false floors such as but not limited to a
raised floor in a computer room; and all chases except those chases (and the
conduits and ductwork therein) existing as of the Commencement Date of the
Initial Term, and conduits and ductwork which are wall-mounted or are otherwise
exposed to view within the Net Rentable Area above the floor slab and below the
hung ceiling and outside the electric closets and telephone closets; and to the
extent elected by Tenant all alterations, additions, installations or other
improvements made by or at the expense of Tenant; and repairing any damage
caused by such removal and restoring the portion of the Premises repaired in
connection with such removal to (i) substantially the

                                       31

<PAGE>


condition of the Premises at the Commencement Date of Initial Term or, at
Tenant's option, (ii) a condition suitable for normal office use, in either case
reasonable wear and tear and casualty excepted, and leaving the Premises
reasonably clean and neat;

         5.3 continuously from the commencement of the Term to occupy the
Premises so that the same are not abandoned or vacant; not to use and occupy
toilet rooms, air conditioning rooms, fan rooms, janitors' closets, electrical
closets or those portions of the Premises not included in Net Rentable Area,
including without limitation the roof of the Main Building (except as otherwise
provided in Section 2.12) for purposes for which they were not primarily
designed; not to injure or deface the Buildings or Lot, not to permit in the
Premises any auction sale; not to use or devote the Premises or any part thereof
for any purpose other than the Permitted Uses, not to use or devote the parking
area in the Garage for any purpose other than the parking of automobiles,
motorcycles and bicycles; and not to make any use of the Premises which is
contrary to law or ordinance or any use of the Premises or the parking area in
the Garage which invalidates or would invalidate if allowed to continue any
insurance on the Buildings described in Section .

         5.4 not to obstruct in any manner any portion of the Lot used by Tenant
in common with others; not to permit the placing of any signs on the Lot or on
the outside windows or exterior or roofs of the Buildings or any awnings,
aerials or flagpoles visible from outside the Premises without the prior consent
of Landlord; to keep the exterior of the Buildings (including without limitation
the interior and exterior sides of windows) and the lot (including without
limitation the open plaza area, the landscaping, the common roadways and
walkways on the Lot, the visitor parking area and the loading area) in a neat
and clean condition

                                       32

<PAGE>



consistent with similar first class facilities in the Boston/ Cambridge area;
and to comply with all reasonable Rules and Regulations of which Tenant is given
notice made by Landlord for the care and use of the common walkways, sidewalks
and driveways on the Lot, visitor parking areas and their facilities and
approaches and by the owner or owners of Technology Square for the care and use
of such common areas and facilities as may from time to time be maintained off
the Lot and in Technology Square and as are available to Tenant, provided that
such Rules and Regulations shall not be inconsistent with other provisions of
this Lease; Landlord shall not be liable to Tenant nor shall Tenant be entitled
to any abatement of rent for the failure of others to conform to such Rules and
Regulations, but Landlord shall use its best efforts to see that others conform
to such Rules and Regulations.

         5.5 to keep the Premises equipped with all safety appliances required
by law or ordinance or any other regulation of any public authority and to do
any work and to procure all licenses and permits so required, and to use all
available equipment and methods to eliminate or minimize disturbances to third
parties complaining of disturbances arising from Tenant's use or operation of
electrical or electronic devices or other devices that emit sound or other waves
outside the Buildings or Lot, it being understood that the foregoing provisions
shall not be construed to broaden in any way Tenant's Permitted Uses or Tenant's
rights to make alterations and additions set forth in Section 3.1;

         5.6 not without the prior consent of Landlord, which consent will not
unreasonably be withheld or delayed, to assign, mortgage, pledge or otherwise
transfer this Lease or to make any sublease or to permit occupancy of the
Premises or any part thereof by anyone other than Tenant, except that Landlord's
consent shall not be required in connection with (a) an

                                       33

<PAGE>


assignment, or sublease to Massachusetts Institute of Technology or a joint
venture of which Tenant is one of the joint venturers and the joint venture is
occupying space in the Main Building or the Environmental Test Laboratory, or
(b) an assignment to a parent or subsidiary corporation of Tenant or in
connection with any merger, consolidation or private reorganization of Tenant,
or (c) subleases to (i) any tenant now or hereafter in occupancy in Technology
Square or in any building owned and operated by an Affiliate of Landlord in the
Greater Boston area; (ii) any company listed on the New York or American Stock
Exchanges or in the then latest lists published by Fortune Magazine of the
leading (first and second "500") industrial firms, insurance companies, banking
institutions and international firms; (iii) any law, accounting, architectural,
engineering or management or business consultant firm, banking institution or
insurance company, which has been in business in the Boston-Cambridge or other
major metropolitan area for longer than 10 years; or (iv) any dealer in
investment or securities accredited by the New York Stock Exchange; provided,
however, that consent shall not be required in connection with any sublease if
either the Lot or the remaining part of Technology Square is not owned by an
Affiliate of Landlord at the time of the sublease; as additional rent, Tenant
shall reimburse Landlord promptly for reasonable legal and other expenses
incurred by Landlord in connection with any request by Tenant for consent to
assignment or subletting; no assignment or subletting shall affect the
continuing primary liability of Tenant (which, following assignment, shall be
joint and several with the assignee); no consent to any of the foregoing in a
specific instance shall operate as a waiver in any subsequent instance and no
assignment shall be binding upon Landlord or any of Landlord's mortgagees unless
Tenant shall deliver to Landlord an instrument in recordable form which

                                       34

<PAGE>


contains a covenant of assumption by the assignee running to Landlord and all
persons claiming by, through or under Landlord. Tenant shall have the right
without the consent of Landlord to sublease all or any portion of the parking
area in the Garage for parking of automobiles;

         5.7 to defend with counsel first approved by Landlord, save harmless,
and indemnify Landlord from any liability for injury, loss, accident or damage
to any person or property, and from any claims, actions, proceedings and
expenses and costs in connection therewith (including, without limitation,
reasonable counsel fees) (i) arising from (a) the omission, fault, willful act,
negligence or other misconduct of Tenant or (b) from any use made or thing done
or occurring on the Premises not due to the omission, fault, willful act,
negligence or other misconduct of Landlord, its agents, employees or independent
contractors, or (ii) resulting from the failure of Tenant to perform and
discharge its covenants and obligations under this Lease; to maintain in
responsible companies qualified to do business and in good standing in
Massachusetts, public liability insurance covering the Premises insuring
Landlord as well as Tenant with limits which shall, at the commencement of the
Term, be at least equal to those stated in Section 1.1 and from time to time
during the Term shall be for such higher limits, if any, as are customarily
carried by tenants in first class office buildings in the Boston-Cambridge area,
and to deposit promptly with Landlord upon request certificates for such
insurance, and all renewals thereof, bearing the endorsement that the policies
will not be cancelled until after 10 days' written notice to Landlord;

         5.8 that all of the furnishings, fixtures, equipment, effects and
property of every kind, nature and description of Tenant and of all persons
claiming by, through or under Tenant

                                       35

<PAGE>



which, during the continuance of this Lease or any occupancy of the Premises by
Tenant or anyone claiming under Tenant, may be on the Premises, shall be at the
sole risk and hazard of Tenant, and if the whole or any part thereof shall be
destroyed or damaged by fire, water or otherwise, or by the accidental discharge
of sprinklers, or by the leakage or bursting of water pipes, steam pipes, or
other pipes, by theft or from any other cause, no part of said loss or damage is
to be charged to or to be borne by Landlord, except that Landlord shall in no
event be indemnified or held harmless or exonerated from any damage or liability
caused by the omission, fault, willful act, negligence or other misconduct of
Landlord, its agents, employees or independent contractors;

         5.9 to permit Landlord and Landlord's agents after reasonable notice,
except in emergencies, and always subject to the security measures which Tenant
has in effect: to enter the Premises so as to perform its obligations contained
in Section 4.1; to examine the Premises at reasonable times and at reasonable
intervals, if Landlord shall so elect; to remove, at Tenant's expense and after
notice to Tenant, any alterations, additions, signs, curtains, blinds, shades,
awnings, aerials, flagpoles, or the like not consented to by Landlord where such
consent is required; and, to show the Premises to prospective tenants during the
two years preceding expiration of the Term and to prospective purchasers and
mortgagees at all reasonable times;

         5.10 not to place a load upon the Premises exceeding the design live
load limits for which the buildings were designed;

         5.11 to pay promptly when due all taxes which may be imposed upon
personal property in the Premises whether assessed to Tenant or to other
occupants of or licensees or

                                       36

<PAGE>


concessionaires in the Premises, provided that Tenant may defer the payment
thereof during such time as Tenant is contesting the amount thereof;

         5.12 as additional rent, to pay all reasonable costs, counsel and other
fees incurred by Landlord in connection with the successful enforcement by
Landlord of any obligations of Tenant under this Lease.

                                   ARTICLE VI
                               CASUALTY AND TAKING

         6.1 In case during the last ten (10) years of the Initial Term or the
last ten (10) years of any extension thereof all or any part of the Main
Building containing in excess of fifty (50%) percent of the Net Rentable Area
thereof is damaged by fire or other casualty to the extent that such part is
unsuitable for Tenant's use, this Lease shall, except as hereinafter provided,
terminate at Landlord's election by notice given to Tenant within 90 days after
such damage and in such event this Lease shall terminate on the 60th day after
such notice is given unless within such 60 day period Tenant shall exercise any
option then available to it to extend the Term, in which case such notice of
termination by Landlord shall have no force or effect.

         In case Landlord shall not elect to terminate this Lease, Landlord
shall notify Tenant within 90 days following such damage to the Main Building of
the time within which Landlord reasonably expects the damage can be repaired,
including the basis for such estimate, and Tenant shall have the right to
terminate this Lease (a) if the time estimated by Landlord shall exceed eighteen
(18) months and (b) if the remainder of the Premises not damaged is insufficient
for use for Tenant's purposes as determined in good faith by Tenant and Landlord
receives with the notice hereinafter referred to a certificate to that effect
signed by Tenant, by

                                       37

<PAGE>


notice given to Landlord within 60 days after Landlord's notice of its estimated
time for repair, specifying the effective date of termination which shall be not
less than 60 days after the date on which such notice of termination is given.

         If in any case of damage to the Premises this Lease is not so
terminated, Landlord shall promptly and diligently (commencing not later than
the expiration of all periods in which either party may terminate this Lease
pursuant to the foregoing provisions of this Section 6.1) restore the Premises
to substantially their condition prior to such damage, provided, however, that
Landlord shall not be required to restore items installed or paid for entirely
by Tenant which Tenant is required to remove, or may remove, pursuant to Section
5.2, other than those items which have been constructed or installed by Landlord
and paid for by Tenant as of the date of this Fourth Amendment and Restatement
of Lease and which (a) is insured at Tenant's expense pursuant to Section 4.4 or
(b) Tenant requests Landlord (in a timely manner following such damage) to
restore and agrees to reimburse Landlord for the expenses of such restoration.

         All proceeds of fire and other casualty insurance shall be held by the
institutional Mortgagee holding the first mortgage on the Premises for
application to or toward the cost of restoration upon such conditions as such
mortgagee may prescribe. If at the time of occurrence of any fire or other
casualty covered by insurance there shall be no mortgage of the Premises which
is held by an Institutional Mortgagee which is required to apply such insurance
proceeds toward the cost of such restoration, then such proceeds shall be held,
as a segregated fund to be applied to or toward the cost of restoration, by a
bank or trust company designated by Landlord with the approval of Tenant, which
approval shall not unreasonably be withheld, and any charges of such bank or
trust company shall be paid out of the insurance proceeds.

                                       38

<PAGE>


         6.2 In case during the Term (a) all or any part of the Main Building
containing in excess of fifty (50%) percent of the Net Rentable Area thereof is
taken by eminent domain, or (b) twenty-five (25%) percent or more of the Net
Rentable Area of the Main Building is taken by eminent domain and the eminent
domain proceeds are not sufficient to restore the remaining portion of the Main
Building to a condition satisfactory to Tenant for its use of such remaining
portion (unless Tenant shall agree to supply the deficiency), this Lease shall
terminate at Landlord's election, which may be made notwithstanding Landlord's
entire interest may have been divested, by notice given to Tenant within 90 days
after the taking in the case of (a) or the determination of the pro tanto award
in the case of (b) and in such event this Lease shall terminate on the 60th day
after such notice is given.

         In case of such taking of more than fifty (50%) percent of the Net
Rentable Area of the Main Building or more than thirty-five (35%) percent of the
Net Rentable Area on the ground floor of the Main Building and the remainder of
the Premises is insufficient for use for Tenant's purposes as determined in good
faith by Tenant and Landlord receives with the notice hereinafter referred to a
certificate to that effect signed by Tenant, Tenant may terminate this Lease by
notice given to Landlord within 60 days after such taking specifying the
effective date of termination which shall be not less than 60 days after the
date on which such notice of termination is given.

         If in any case of taking the Premises are rendered unfit for use and
occupation and this Lease is not so terminated, Landlord shall promptly and
diligently (commencing not later than the expiration of all periods in which
either party may terminate this Lease pursuant to the foregoing provisions of
this Section 6.2) put the remaining portion of the Premises into

                                       39

<PAGE>


substantially their condition prior to such taking and as nearly as possible
suitable for Tenant's continued use, provided, however, that Landlord shall not
be required to restore items installed or paid for entirely by Tenant which
Tenant is required to remove, or may remove, pursuant to Section 5.2 other than
those items which are incorporated in the Buildings as of the date of this
Fourth Amendment and Restatement of the Lease or which Landlord has agreed to
restore pursuant to a separate written agreement.

         6.3 In the event of any casualty or taking, a just proportion of the
fixed rent and additional rent according to the nature and extent of the injury
shall be abated until the Premises or what remains thereof after a taking shall
have been put by Landlord in proper condition for use and occupancy; plus a
reasonable time not in any event exceeding six months for Tenant to restore its
leasehold improvements and move in personal property and in case of a taking
which permanently reduces the area of the Premises or otherwise permanently
affects the Buildings or Lot, a just proportion of the fixed rent and additional
rent shall be abated for the remainder of the Term.

         6.4 Landlord reserves to itself any and all rights to receive awards
made for damages to the Premises and the leasehold hereby created, or any one or
more of them, accruing by reason of exercise of eminent domain or by reason of
anything lawfully done in pursuance of public or other authority. Tenant hereby
releases and assigns to Landlord all Tenant's rights to such awards, and
covenants to deliver such further assignment and assurances thereof as Landlord
may from time to time request, hereby irrevocably designating and appointing
Landlord as its attorney-in-fact to execute and deliver in Tenant's name and
behalf all such further assignments thereof.

                                       40

<PAGE>


         Notwithstanding the foregoing provisions of this Section, Tenant and
anyone claiming under it at its and their expense may, jointly with Landlord,
appear, claim and prove, if so allowed, in the proceedings relative to any such
awards, and may receive therefrom, such portion thereof as represents the value
of the alterations, additions, installations and improvements made by or for the
account of Tenant and anyone claiming under it in the Premises other than those
which Landlord is obligated to restore pursuant to Section 6.2, but not more
than the total of expenditures for such alterations, additions, installations
and improvements less depreciation from the respective dates of the making of
such alterations, additions, installations or improvements to the date of the
taking computed on a straight-line basis over the Term of this Lease which is in
force at the time of such taking, or the useful life of such items, whichever is
shorter. Such right of Tenant shall be subject and subordinate to the
application of all such awards to the prior payment in full of all mortgages at
the time of such taking on the Buildings and Lot, or either; provided (a) that
the mortgages to which Tenant's rights are subordinated are held by
Institutional Mortgagees and such mortgages do not encumber property other than
the Premises or secure obligations unrelated to the Premises, (b) that such
subordination shall be effective in the event the holder of such mortgage or
mortgages applies the eminent domain award toward full payment of the amount
secured by such mortgage or mortgages, and (c) that in applying such awards to
the payment of such mortgages, Landlord's share of such award shall be applied
and exhausted first before any portion of Tenant's share of such award is so
applied.

                                       41

<PAGE>


         Further notwithstanding the foregoing provisions, Tenant and anyone
claiming under it shall be entitled to appear, claim, prove and receive, if
allowed, an award for personal property, relocation and moving expenses.

         6.5 In the event of any taking of the Premises or any part thereof for
temporary use, (i) this Lease shall be and remain unaffected thereby, and (ii)
Tenant shall be entitled to receive for itself such portion or portions of any
award made for such use with respect to the period of the taking which is within
the Term, provided that if such taking shall remain in force at the expiration
or earlier termination of this Lease, Tenant shall then pay to Landlord a sum
equal to the reasonable cost of performing Tenant's obligations under Section
5.2 with respect to surrender of the Premises or that portion thereof which is
subject to the temporary taking and upon such payment shall be excused from such
obligations.

                                   ARTICLE VII
                                     DEFAULT

         7.1 If any default by Tenant continues after notice, (a) in case of
fixed rent or additional rent for more than 15 days, or (b) in any other case
for more than 30 days and such additional time, if any, as is reasonably
necessary to cure the default if the default is of such nature that it cannot
reasonably be cured in 30 days; or (c) if Tenant makes any assignment for the
benefit of creditors, commits any act of bankruptcy and files a petition under
any bankruptcy or insolvency law, or if such a petition is filed against Tenant
and is not dismissed within 90 days, or if Tenant is adjudicated a bankrupt
under any bankruptcy law, or if a receiver or similar officer becomes entitled
to Tenant's leasehold hereunder and it is not returned to Tenant within 90 days,
or if such leasehold is taken and sold on execution or other

                                       42

<PAGE>


process of law in any action against Tenant (all of which events shall be
considered as defaults); then in any such case, whether or not the Term shall
have begun, Landlord may immediately, or at any time while such default
continues, give notice to Tenant (with a copy to Tenant's attorney of whose name
and address Landlord shall have been given notice) specifying the default and a
date not less than ten days after the giving of such notice on which this Lease
shall terminate and, unless Tenant shall cure such default within such ten day
period, this Lease shall terminate on the date specified therein as fully and
completely as if such date were the date herein originally fixed for the
expiration of the Term, and Tenant will then quit and surrender the Premises,
but Tenant shall remain liable as hereinafter provided.

         7.2 In the event that this Lease is terminated under any of the
provisions contained in Section 7.1 or shall be otherwise terminated for breach
of any obligation of Tenant, Tenant covenants to pay forthwith to Landlord, as
compensation, an amount equal to the then present worth of the excess, if any of
the total rent reserved for the residue of the Term, over the then present worth
of the rental value of the Premises for said residue of the Term. The present
worth of "total rent reserved" and "rental value" shall be determined by
discounting the gross amounts in accordance with accepted financial practice at
eight (8%) percent per year from the respective dates that payments of rent
would be due and payable. In calculating the rent reserved there shall be
included, in addition to the fixed rent and all additional rent, the value of
all other considerations agreed to be paid or performed by Tenant for said
residue. Tenant further covenants as an additional and cumulative obligation
after any such ending to pay punctually to Landlord all the sums and perform all
the obligations which Tenant covenants in this Lease to pay and to perform in
the same manner and to the same extent and at the same

                                       43

<PAGE>


time as if this Lease had not been terminated. In calculating the amounts to be
paid by Tenant under the next foregoing covenant Tenant shall be credited with
any amount paid to Landlord as compensation as in this Section 7.2 provided and
also with the net proceeds of any rent obtained by reletting the Premises, after
deducting all Landlord's expenses in connection with such reletting, including,
without limitation, all repossession costs, brokerage commissions, fees for
legal services and expenses of preparing the Premises for such reletting, it
being agreed that Landlord may (i) relet the Premises, or any part or parts
thereof, for a term or terms which may, at Landlord's option, be equal to or
less than or exceed the period which would otherwise have constituted the
balance of the Term, and may grant such concessions and free rent as Landlord in
its sole judgment considers advisable or necessary to relet the same and (ii)
make such alterations, repairs and decorations in the Premises as Landlord in
its sole judgment considers advisable or necessary to relet the same, and no
action of Landlord in accordance with the foregoing or failure to relet or to
collect rent under reletting shall operate or be construed to release or reduce
Tenant's liability as aforesaid.

         In lieu of any other damages or indemnity and in lieu of full recovery
by Landlord of all sums payable under all the foregoing provisions of this
Section 7.2, Landlord may, by written notice to Tenant, at any time after this
Lease is terminated under any of the provisions contained in Section 7.1 or is
otherwise terminated for breach of any obligation of Tenant and before such full
recovery, elect to recover, and Tenant shall thereupon pay, as liquidated
damages, an amount equal to the fixed rent accrued (whether or not paid in whole
or in part) under Section 2.5 in the 12 months ended next prior to such
termination plus the amount of fixed rent and additional rent of any kind
accrued and unpaid at the time of termination and

                                       44

<PAGE>


less the amount of any recovery by Landlord under the foregoing provisions of
this Section 7.2 up to the time of payment of such liquidated damages.

         Nothing contained in this Lease shall limit or prejudice the right of
Landlord to prove for and obtain in proceedings for bankruptcy, insolvency or
like proceedings by reason of the termination of this Lease, an amount equal to
the maximum allowed by any statute or rule of law in effect at the time when,
and governing the proceedings in which, the damages are to be proved whether or
not the amount be greater, equal to, or less than the amount of the loss or
damages referred to above.

                                  ARTICLE VIII
                                  MISCELLANEOUS

         8.1 The "Net Rentable Area" of a floor in the Main Building shall be
computed by measuring to the inside finish of permanent glass and masonry
building walls. The "Net Rentable Area" of the Environmental Test Laboratory
shall be computed by measuring to the inside finish of the demising walls. Net
Rentable Area of a floor in the Main Building shall include all area within
outside walls, less stairs, elevator shafts, flues, stacks, pipe shafts and
vertical ducts with their enclosing walls required for the building and special
leasehold improvements existing as of the date of this Fourth Amendment and
Restatement of Lease, but shall not exclude other vertical shafts or chases
required or desired by Tenant to accommodate other special equipment of Tenant.
Toilets, air conditioning rooms, fan rooms, janitors' closets, and electrical
closets within and exclusively serving only that floor of the Main Building or
the Environmental Test Laboratory, as the case may be, shall be included in Net
Rentable Area. No deductions shall be made in determining Net Rentable Area on
account of

                                       45

<PAGE>


columns or projections necessary to the building. The Space containing the
principal mechanical equipment for the Main Building located of the first floor
and mezzanine area of the Main Building shall not be included in determining the
Net Rentable Area. The total Net Rentable Area of the Main Building shall be (a)
the sum of the Net Rentable Area of each floor of the Main Building, calculated
as above, less (b) 300 square feet. Any airhandling or mechanical equipment
placed within the Garage and outside of the demising walls of the Environmental
Test Laboratory shall not be included in determining the Net Rentable Area of
the Environmental Test Laboratory.

         8.2 The titles of the Articles are for convenience only and not to be
considered in construing this Lease. Tenant agrees not to record this Lease, but
upon request of either party both parties shall execute and deliver a Memorandum
of this Lease in form appropriate for recording or registration, an instrument
acknowledging the date of commencement of the Term, and if this Lease is
terminated before the Term expires, an instrument in such form acknowledging the
date of termination. Whenever any notice, approval, consent, request, election,
offer or acceptance is given or made pursuant to this Lease it shall be in
writing. Communications and payments shall be addressed, if to Landlord, at
Landlord's Address or at such other address as may have been specified by prior
notice to Tenant; and if to Tenant, at Tenant's Address or at such other place
as may have been specified by prior notice to Landlord. Any communication so
addressed shall be deemed duly served on the second business day following the
day of mailing if mailed by registered or certified mail, return receipt
requested. If Landlord by notice to Tenant at any time designates some other
person to receive payments or notices, all payments or notices thereafter by
Tenant shall be paid or given

                                       46

<PAGE>


to the agent designated until notice to the contrary is received by Tenant from
Landlord. All payments required under this Lease shall be deemed sufficiently
paid if made by check collected on first presentation. The obligations of this
Lease shall run with the land, and this Lease shall be binding upon and inure to
the benefit of the parties hereto and their respective successors and assigns,
except that the Landlord named herein and each successive owner of the Premises
shall be liable only for obligations accruing during the period of its
ownership. The obligations of Landlord shall be binding upon the assets of
Landlord consisting of the Buildings and Lot but not upon other assets of
Landlord.

         8.3 The failure of Landlord or of Tenant to seek redress for violation
of, or to insist upon strict performance of, any covenant or condition of this
Lease, shall not be deemed a waiver of such violation nor prevent a subsequent
act, which would have originally constituted a violation. The receipt by
Landlord of fixed rent or additional rent with knowledge of the breach of any
covenant of this Lease shall not be deemed a waiver of such breach. No provision
of this Lease shall be deemed to have been waived by Landlord, or by Tenant,
unless such waiver be in writing signed by the party to be charged. No consent
or waiver, express or implied, by Landlord or Tenant to or of any breach of any
agreement or duty shall be construed as a waiver or consent to or of any other
breach of the same or any other agreement or duty.

         8.4 No acceptance by Landlord of a lesser sum than the fixed rent and
additional rent then due shall be deemed to be other than on account of the
earliest installment of such rent due, 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

                                       47

<PAGE>


check or payment without prejudice to Landlord's right to recover the balance of
such installment or pursue any other remedy in this Lease provided. The delivery
of keys to any employee of Landlord or to Landlord's agent or any employee
thereof shall not operate as a termination of this lease or a surrender of the
Premises.

         8.5 The specific remedies to which Landlord may resort under the terms
of this Lease are cumulative and are not intended to be exclusive of any other
remedies or means of redress to which it may be lawfully entitled in case of any
breach or threatened breach by Tenant of any provisions of this Lease. In
addition to the other remedies provided in this Lease, Landlord shall be
entitled to the restraint by injunction of the violation or attempted or
threatened violation of any of the covenants, conditions or provisions of this
Lease or to a decree compelling specific performance of any such covenants,
conditions or provisions.

         8.6 If any term of this Lease, or the application thereof to any person
or circumstances, shall to any extent be invalid or unenforceable, the remainder
of this Lease, or the application of such terms to persons or circumstances
other than those as to which it is invalid or unenforceable, shall not be
affected thereby, and each term of this Lease shall be valid and enforceable to
the fullest extent permitted by law.

         8.7 If Tenant shall at any time default in the performance of any
obligation under this Lease, Landlord shall have the right, upon 30 days' notice
to Tenant (except in case of emergency in which case no notice need be given)
but not the obligation, and subject to the provision of Section 4.3, to perform
such obligation notwithstanding the fact that no specific provision for such
substituted performance is made in this Lease with respect to such default. In
performing such obligation, Landlord may make any payment of money or perform
any

                                       48

<PAGE>


other reasonable act. All sums so paid by Landlord (together with interest at
the rate of 8% per annum) and all necessary incidental costs and expenses
including without limitation legal fees in connection with enforcement of its
rights under this Section by Landlord, shall be deemed to be additional rent
under this Lease and shall be payable to Landlord immediately on demand.
Landlord may exercise its rights under this Section without waiving any other of
its rights or releasing Tenant from any of its obligations under this Lease.

         8.8 If Landlord shall at any time default in the performance of any
obligation under this Lease, Tenant shall have the right, upon 30 days' notice
to Landlord and to mortgagees if any, of whose identity and address Tenant shall
have received notice (except in case of emergency in which case no notice need
be given), but not the obligation, to perform such obligation notwithstanding
the fact that no specific provision for such substituted performance is made in
this Lease with respect to such default. In performing such obligation, Tenant
may make any payment of money or perform any other act. Without limiting the
generality of the foregoing, Tenant shall have, upon giving notice as aforesaid,
the right to pay any real estate tax or betterment assessment on the Building
and Lot, the lien of which would have priority over this Lease, if Landlord
shall not have paid the same within six months after the date on which interest
shall begin to accrue on said tax or assessment, but only if Landlord shall not
at the time of payment by Tenant be prosecuting an abatement proceeding with
respect to such tax or assessment. All sums so paid by Tenant (together with
interest at the rate of 8% per annum) and all necessary incidental costs and
expenses, including, without limitation, legal fees in connection with
enforcement of its rights under this Section by Tenant, shall be payable to
Tenant by Landlord immediately on demand made upon Landlord of which copy is
given

                                       49

<PAGE>


simultaneously to any mortgagee referred to in the first sentence of this
Section. If such sums, interest, costs and expenses are not paid within 30 days
after such demand, Tenant may deduct the same from any rents, addition rents and
other payments due Landlord thereafter accruing despite any changes of ownership
and the provisions with respect thereto in Section 8.2, provided, that if within
30 days after such demand Landlord or any such mortgagee shall give notice to
Tenant that it disputes the default of Landlord or the action taken or the sums
paid by Tenant to remedy it, Tenant shall not deduct as aforesaid with respect
to disputed items until the dispute is settled by court decision, mutual
agreement or otherwise and may then deduct as aforesaid with respect to any
items determined by such settlement to be payable to it by Landlord if the same
are not paid to it within 10 days after such settlement. Tenant may exercise its
rights under this Section without waiving any other of its rights or releasing
Landlord from any of its obligations under this Lease.

         8.9 Tenant agrees form time to time, upon not less than fifteen days'
prior written request by Landlord, to execute, acknowledge and deliver to
Landlord a statement in writing certifying to an independent third party that
this Lease is unmodified and in full force and effect and that Tenant has no
knowledge of any defenses, offsets or counterclaims against its obligations to
pay the fixed rent and additional rent and to perform its other covenants under
this Lease and that there are no known uncured defaults of Landlord or Tenant
under this Lease (or, if there have been any modifications that the same is in
full force and effect as modified and stating the modifications and, if there
are any defenses, offsets, counterclaims, or defaults, setting them forth in
reasonable detail), the dates to which the fixed rent, additional rent and other
charges have been paid, and the extent to which Tenant has exercised the

                                       50

<PAGE>


options set forth in Sections 2.8, 2.9 and 2.10. Any such statement delivered
pursuant to this Section 8.9 may be relied upon by any prospective purchaser or
mortgagee of the Premises or any prospective assignee of any mortgage of the
Premises.

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

         8.11 This Lease contains all of the agreement of the parties with
respect to the subject matter thereof and supersedes all prior dealings between
them with respect to such subject matter except as the same may be expressly set
forth herein.

         8.12 Tenant represents and warrants that it has had no dealings with
any broker or agent in connection with this Lease.

         8.13 In any case where either party hereto is required to do any act,
delays caused by or resulting from Acts of God, war, civil commotion, fire,
flood or other casualty, strikes or other extraordinary labor difficulties,
shortages of labor or materials or equipment in the ordinary course of trade,
government regulations or other causes not reasonably within such

                                       51

<PAGE>


party's control and not due to the fault or neglect of such party shall not be
counted in determining the time during which such act shall be completed,
whether such time be designated by a fixed date, a fixed time or "a reasonable
time", and such time shall be deemed to be extended by the period of such delay.
Financial inability of either party shall not be considered to be a circumstance
or cause beyond the reasonable control of that party.

         8.14 The following terms shall have the following meanings:

         The word "Term" refers as of any particular time to the Initial Term
and also to any extension thereof with respect to which Tenant has, as of that
time, exercised an extension option set forth in Section 2.8.

         The term "Affiliate of Landlord" refers respectively to (i) any
corporation, partnership, trust association or other business organization
directly or indirectly (through other entities or otherwise) owning, controlling
or holding, whether with or without power to vote, 30% or more of the entire
beneficial interest in Landlord, (ii) any corporation or trust with transferable
shares, 30% or more of whose outstanding capital stock or shares of beneficial
interest of any class is directly or indirectly (through other entities or
otherwise) owned, controlled or held, whether with or without power to vote, by
Landlord or any Affiliate of Landlord as defined in (i) above, and (iii) any
partnership, association or other business organization 30% or more of the
beneficial interest in which, whether with or without power to vote, is directly
or indirectly (through other entities or otherwise) owned, controlled or held by
Landlord or any Affiliate of Landlord.

         The term "Institutional Mortgage" shall mean a mortgage originally
granted to a bank or trust company, a savings bank, a savings and loan
association, an insurance company, a

                                       52

<PAGE>


pension or retirement fund, or a mortgage company or real estate investment
trust having gross assets of at least $25,000,000; and the term "Institutional
Mortgagee" shall mean the holder from time to time of an Institutional Mortgage
except when such holder is an Affiliate of Landlord.

                                   ARTICLE IX
                               RIGHTS OF MORTGAGEE

         9.1 This Lease shall be superior to and shall not be subordinated to
any mortgage or other voluntary lien or other incumbrance on the Lot or
Buildings, or both, which are separately and together hereinafter in this
Article IX referred to as "the mortgaged premises." The word "mortgagee" as used
in this Lease shall include the holder for the time being whenever the context
permits.

         9.2 No fixed rent, additional rent, or any other charge payable to
Landlord shall be paid more than 30 days prior to the due date thereof under the
terms of this Lease and payments made in violation of this provision shall
(except to the extent that such payments are actually received by a mortgagee)
be a nullity as against such mortgagee (except an Affiliate of Landlord) and
Tenant shall be liable for the amount of such payments to such mortgagee.

         9.3 No act or failure to act on the part of Landlord which would
entitle Tenant under the terms of this Lease, or by law, to be relieved of
Tenant's obligations to pay fixed rent or additional rent hereunder or to
terminate this Lease, shall result in a release or termination of such
obligations or a termination of this Lease unless (i) Tenant shall have first
given written notice of Landlord's act or failure to act to Landlord's
Institutional Mortgagees of record, if

                                       53

<PAGE>


any, of whose identity and address Tenant shall have been given notice,
specifying the act or failure to act on the part of Landlord which would give
basis to Tenant's rights; and (ii) such mortgagees, after receipt of such
notice, have failed or refused to correct or cure the condition complained of
within a reasonable time thereafter; provided, however, that nothing contained
in this Section 9.3 shall: (a) be deemed to impose any obligation on any such
mortgagees to correct or cure any such condition; or (b) affect Tenant's rights
under Section 8.8 or Article VI. "Reasonable time" as used above in connection
with Tenant's right to terminate this Lease means and includes a reasonable time
for such mortgagees to obtain possession of the mortgaged premises if possession
is necessary for the mortgagee to correct or cure the condition and if the
mortgagee notifies Tenant of its intention to take possession of the mortgaged
premises and correct or cure such condition.

         EXECUTED as a sealed instrument in two or more counterparts on the day
and year first above written.


                                       Landlord


                                       THE PRUDENTIAL INSURANCE COMPANY
                                       OF AMERICA


                                       By [SIGNATURE]




                                       Tenant


                                       THE CHARLES STARK DRAPER
                                       LABORATORY, INC.


                                       By [SIGNATURE]

                                       54

<PAGE>


                                    EXHIBIT A

                               DESCRIPTION OF LOT

A parcel of land in Cambridge, Middlesex County, Massachusetts being shown as
Lot 20 on a plan entitled "New Division of Land Court 30711 in Cambridge, Mass."
dated September 23, 1974, changed September 27, 1974, by Raymond C. Pressey,
Inc. Registered Land surveyors, a copy of a portion of which is to be filed with
Middlesex South Registry District of the Land Court, bounded and described
according to said plan as follows:

NORTHEASTERLY            By Broadway by two lines respectively measuring four
                         hundred fifty-three and 83/100 (453.83) feet and two
                         hundred and 15/100 (200.15) feet;

SOUTHEASTERLY            by land now or formerly of the Boston & Albany Railroad
                         Company and Harvard Street a total distance of four
                         hundred seven and 95/100 (407.95) feet;

SOUTHWESTERLY            one hundred ninety-four and 54/100 (194.54) feet;

SOUTHEASTERLY            forty-three and 71/100 (43.71) feet; and

SOUTHERLY                twenty-two and 55/100 (22.55) feet, all by Lot 18 on
                         said plan;

SOUTHERLY,               one hundred forty-four and 97/100 (144.97) feet by Lot
AGAIN                    17 on said plan;

WESTERLY                 one hundred one and 89/100 (101.89) feet; and

SOUTHERLY                nine and 85/100 (9.85) feet, both by Lot 16 on said
                         plan;

WESTERLY                 two hundred nine and 71/100 (209.71) feet; and

SOUTHERLY                two hundred eighty-eight and 58/100 (288.58) feet, both
                         by Lot 19 on said plan; and

NORTHWESTERLY            by Portland Street, three hundred six and 89/100
                         (306.89) feet.


<PAGE>


                                    EXHIBIT B

                                 CROSS EASEMENTS

I.     The Lot is subject to the following:

       A.   Rights granted by Wyman Street Trust and The Wilmington Trust to
            Cambridge Electric Light Company by instrument dated May 7, 1970
            filed with Middlesex South Registry District of the Land Court as
            Document No. 477831.

       B.   Easements set forth in a Declaration of Easement by Gerald W.
            Blakeley, Jr., et al, Trustees of Cabot, Cabot & Forbes Land Trust
            dated March 11, 1975 and to be filed with said Registry District.
            Landlord reserves the right to relocate such easements, to the
            extent permitted by and subject to the provisions of, said
            Declaration of Easements, and subject also to Tenant's reasonable
            approval.

       C.   Easements reserved in a deed of the Lot from Gerald W. Blakeley,
            Jr., et al, Trustees of Cabot, Cabot & Forbes Land Trust to Landlord
            dated March 11, 1975 to be filed with said Registry District and
            recorded with Middlesex South District Registry of Deeds.

       D.   Foundation, Grade Beam and Encroachment Agreement dated March 11,
            1975 between the Trustees of Technology Square Trust and the
            Trustees of CC&F Cambridge Trust, to be filed with said Registry
            District.

II.    Tenant shall have the following rights with respect to portions of
       Technology Square not included within the Lot:

       A.   Easements set forth in said Declaration of Easements referred to in
            I. B. above. Landlord agrees not to consent to the relocation of
            such easements by the owner of the servient estate without Tenant's
            reasonable approval.

       B.   Rights and easements set forth in said deed to Landlord referred to
            in I. C. above.

       C.   Foundation, Grade Beam and Encroachment Agreement dated March 11,
            1975 between the Trustees of Technology Square Trust and the
            Trustees of CC&F Cambridge Trust, to be filed with said Registry
            District.

       D.   The right to locate utility lines in the second parcel (hereinafter
            referred to as "Parcel 2") of land described in said deed to
            Landlord referred to in I. C. above, so long as they do not
            interfere with then existing utility easements, and subject to any
            matters now of record affecting said Parcel 2.

       E.   No superstructures shall be built on Parcel 2 without written
            consent of Tenant.

       F.   General rights of passage (pedestrian and vehicular) over Parcel 2
            which may be in common with others from time to time entitled.


<PAGE>


       G.   To the extent not provided on the Lot or by the rights and easements
            referred to in II. B. above, Tenant shall have the right to use of
            50 visitor parking spaces on Parcel 2 as provided in clause (b) of
            Section 2.2. To the extent possible, Landlord will cause any such
            spaces in Parcel 2 to be located so as to be reasonably convenient
            to the principal entrance of the Main Building. In the event of the
            purchase by Tenant of the Lot and Buildings pursuant to any option
            granted to it by the Lease, Tenant shall have no further rights to
            use parking spaces in Parcel 2 beyond the use of parking spaces then
            in use by Tenant pursuant to said clause (b).

III.   Landlord shall have the right and obligation during the Term and Tenant
       shall have the right in the event Tenant shall purchase the Lot and
       Building pursuant to any option granted to it by the Lease:

       A.   To cause the owners of portions of Technology Square not included in
            the Lot to perform their maintenance obligations set forth in said
            Declaration of Easements; and

       B.   To maintain Parcel 2 and the area described as "Easement No. 1" in
            said deed to Landlord referred to in I. C. above, to the extent of
            the maintenance obligations set forth in clauses (c) and (d) of the
            subsection 4.1.1.

IV.    Tenant shall have the exclusive use of the loading docks, if any,
       constructed for the Main Building and the Environmental Test
       Laboratory, and the service driveways providing access solely thereto.
       The plaza area in the interior courtyard of the Main Building shall be
       an open plaza for the exclusive use of the Tenant without implied
       obligation on Landlord to enforce such exclusivity.


<PAGE>


                                    EXHIBIT C

                          TENANT LEASEHOLD IMPROVEMENTS

1.     Twenty-five isolated test piers consisting of concrete blocks resting on
       suitable crushed stone set flush with ground floor in four-story
       building.

       Approximate sizes are as follow:

            17 piers - 5 1/2' x 5 1/2' x 3'
             7 piers - 7 1/2' x 7 1/2' x 3'
             1 pier - 5' x 9' x 3'

2.     One isolated test pier consisting of a 10' x 10' x 9' concrete block
       resting on suitable crushed stone with approximately 3' projecting up
       above ground floor level

3.     Provide pits for Cryogenic Laboratory at ground floor level

4.     Provide transformer bank and automatic switching as part of basic
       building equipment at Landlord's expense. Increase transformer capacity
       at Tenant's expense in proportion to Tenant's power requirements.

5.     Two overhead motor-operated metal doors in the exterior wall at the
       ground floor level; size 20' wide by 14' high

6.     Two openings in the exterior wall at ground floor level for optical tubes
       12" x 12" approximately four feet above finish floor to bring in azimuth
       reference to building interior.

7.     Two bays of concrete working surface at roof level of eight-story
       building with live-load design of 80 pounds per square foot

8.     Provide and install one interconnecting elevator or stairway from ground
       floor to second floor


<PAGE>


9.     10,600 sq. ft. of Class 100,000 clean room space meeting Federal
       standard. This will include, without limitation, 10,600 sq. ft. gypsum
       board ceilings; 10,600 sq. ft. sheet vinyl flooring; 2,550 of clean room
       walls with nonshedding laminate finish; thirty clean room doors, clean
       rooms including environmental systems and equipment per specification in
       CC&F letter dated June 12, 1974

10.    One 400 sq. ft. class 100 clean room per CC&F letter dated June 12, 1974.

11.    9,000 sq. ft. of computer rooms with following specifications for air
       conditioning system:

                  75DEG.   +/- 1DEG.   temperature control
                  40%      +/- 5%      relative humidity

       This includes, without limitation, raised floor for additional area and
       two-hour rated enclosure walls.

12.    Exhaust systems for forty fume hoods (individual systems) including
       noncorrosive materials and equipment as required; modify supply air
       systems if and as required

13.    One 400 ft(2) refrigerated garbage storage room

14.    Twelve each safety showers, large wash sinks, and floor drains including
       supply and waste piping, fixtures and trim

15.    Provide Halon system beneath raised floor for 13,000 sq. ft. of computer
       area

16.    Capability in basic building design to add additional wet stacks (one at
       each end of service cores) if needed in future. This would primarily be
       vertical riser space plus provisions at ground floor level to tie into
       sewer system.

17.    Provisions to monitor building mechanical, electrical and specialty items
       and equipment, including emergency generator(s) at CSDL security guard
       station.

18.    Additional emergency generator capacity of 300 KVA


<PAGE>


19.    One 300 sq. ft. chemical and flammable waste storage room

20.    One 300 sq. ft. LPG storage room

21.    Provide and install three food service areas for cold food including
       sink, refrigerator, counter top and related mill work

22.    Provide and install one hot food service area including sink,
       refrigerator, counter top and related mill work, stove with grill and
       ovens, venting systems, ceramic wall and floor tile and metal pan ceiling
       tile.

23.    Provide and install four pantries

24.    Provide and install one private toilet and shower

25.    Provide two large classrooms with separate temperature-humidity control,
       ventilation, light control, built-in speaker systems and acoustical
       treatment. Rooms would have raised platforms in front; ceilings would be
       10' from floor to false ceiling. Walls would be security type

26.    Provide 600 sq. ft. paint shop with suitable exhaust system

27.    Provide one dock leveler

28.    Provide one flag pole, the location and design of which is approved by
       Skidmore, Owings & Merrill

29.    Provide one Logo sign the location and design of which is approved by
       Skidmore, Owings & Merrill

30.    Provide one hoist at loading dock

31.    Provide zoned paging (one zone per floor per building segment)

32.    Mechanical and/or electrical connections to equipment

33.    Special light fixtures and switching


<PAGE>


 34.    Installation of 100 HP motor generator set for 370/68 computer with
        related mechanical and electrical work

 35.    Installation of local floor electrical panels, panel boards and
        distribution system

 36.    Installation of local dry transformers

 37.    Installation of telephone facilities

 38.    Additional electrical work including special grounding system where
        needed

 39.    Additional modifications to HVAC systems for laboratory areas

 40.    Modifications to sprinkler system to provide additional coverage if and
        as required

 41.    Installation of 18-8 stainless steel sinks and drains

 42.    Installation of systems to handle acid wastes where required

 43.    Installation of compressed air distribution system

*44.    Installation of nitrogen supply system including an external storage
        tank

 45.    Installation of security system including wiring, panels, locks,
        switches, vault doors, central console, and work related thereto

 46.    Installation of photo laboratory and reproduction center

 47.    Mill work

 48.    Installation of draperies and/or blinds

 49.    Installation of carpeting in selected areas

 50.    Additional raised flooring for laboratory areas

 51.    Installation of bridge cranes and other special requirements for
        environmental test laboratory

*52.    Installation of additional pits for cryogenic laboratory

*53.    Installation of 10' x 10' x 300' tunnel for test track

*54.    Expansion of Environmental Test Laboratory


<PAGE>


55.    Installation of additional dock levelers, hoists and cranes for shipping
       and Laboratory use

*      The installation of the items preceded by an asterisk (*) must be either
       completed prior to the commencement of the Term of this Lease or
       thereafter, pursuant to architectural plans and specifications drawn by
       Skidmore, Owings & Merrill prior to the commencement of the Term of this
       Lease. Any expansion of the Environmental Test Laboratory shall be
       performed by Landlord and the Annual Fixed Rent will be adjusted
       in accordance [unintelligible text].

<PAGE>

                               EXHIBIT 99.2

             AMENDMENT TO FOURTH AMENDMENT AND RESTATEMENT OF LEASE

         THIS AMENDMENT TO FOURTH AMENDMENT AND RESTATEMENT OF LEASE (THIS
"AMENDMENT") IS MADE AND ENTERED INTO AS OF THIS 6TH DAY OF FEBRUARY, 1998 BY
AND BETWEEN ASAHI SEIMEI PRUDENTIAL ASSOCIATES, NUMBER THREE ("LANDLORD") AND
THE CHARLES STARK DRAPER LABORATORY, INC. ("TENANT").

                                    RECITALS

         A. Landlord's predecessor and Tenant entered into that certain Fourth
Amendment and Restatement of Lease, dated as of July 1, 1981 (the "Lease"),
pursuant to which Tenant leases premises from Landlord at 555 Technology Square,
Cambridge, Massachusetts, upon the terms and conditions set forth in the Lease.
Capitalized terms that are not otherwise defined in this Amendment shall have
the same meanings herein as are ascribed to such terms in the Lease.

         B. Landlord and Tenant have discussed Landlord's desire to market the
Property, and, in exchange for the consideration payable by Landlord as
described below, Tenant is willing to waive certain options to purchase the
Property which are set forth in the Lease, upon any sale of the Property that
may occur within one year from the date hereof.

         C. Landlord and Tenant desire to further amend the Lease as set forth
herein.

                                   AGREEMENTS

         NOW THEREFORE, for and in consideration of the Recitals set froth
above, the mutual covenants contained herein and other good and valuable
consideration, the receipt, adequacy, and sufficiency of which hereby are
acknowledged, Landlord and Tenant hereby agree as follows:

         1. RECITALS INCORPORATED. The Recitals set forth above are incorporated
in this Amendment and shall be deemed terms and provisions hereof, to the same
extent as if fully set forth in this Paragraph 1.

         2. OPTION WAIVER CONSIDERATION. Upon the mutual execution and deliver
of this Agreement, Tenant shall have the right to deduct from the next monthly
installment of Annual Fixed Rent due under the Lease, the sum of the One Hundred
Twenty-Five Thousand Dollars ($125,000).

         3. TENANT'S LIMITED WAIVER OF CERTAIN PURCHASE OPTIONS. Tenant hereby
irrevocably waives and forever relinquishes any and all rights of Tenant under
Section 2.10.1 and

                                                         1

<PAGE>


Section 2.10.2 of the Lease (the "Purchase Options"), BUT ONLY to the extent
such rights would apply to Landlord's marketing and sale of the Property during
the period commencing on the date hereof and terminating on the one-year
anniversary of the date hereof (the "Free Transfer Period"). Accordingly,
provided that such sale or transfer closes (i.e., the recordation of a deed or
deeds from Landlord to a purchaser, or, if applicable, the delivery of
assignments of ownership interests by Landlord's partners to a purchaser) not
later than the last day of the Free Transfer Period, Landlord shall have the
right during the Free Transfer Period to sell or transfer its interest in the
Property free and clear of the Purchase Options. Upon the closing of any such
sale or transfer during the Free Transfer Period, or if no sale or other
transfer of the Property closes during the Free Transfer Period, Tenant's rights
under the Purchase Options shall be reinstated and in full force and effect with
respect to any future sales of the Property to a third party, subject to and in
accordance with the terms of the Lease.

         4. MISCELLANEOUS. This Amendment modifies and amends the Lease. The
terms and provisions hereof shall supersede any contrary terms and provisions
contained in the Lease. The Lease, as hereby amended and modified, is hereby
ratified and remains in full force and effect. The provisions of this Amendment
shall be binding upon and inure to the benefit of the parties hereto and their
respect successors and permitted assigns. No provision of this Amendment shall
be construed against any party on the ground that such party (or its counsel)
drafted such provision or caused it to be drafted. The titles of the Paragraphs
hereto have been inserted as a matter of convenience of reference only, and
shall not control or affect the meaning, interpretation or construction of this
Amendment. This Amendment may be executed and delivered in any number of
counterparts, each of which shall be considered an original but all of which
shall constitute a single agreement.


                                        2

<PAGE>


         IN WITNESS WHEREOF, the parties have executed this Amendment as of the
date first set forth above.

LANDLORD                            ASAHI SEIMEI PRUDENTIAL ASSOCIATES, NUMBER
                                    THREE

                                    BY:  THE PRUDENTIAL INSURANCE COMPANY OF
                                    AMERICA

                                       By: /s/ Leigh M. Rae
                                          -------------------------------------
                                       Name:  LEIGH M. RAE

                                       Title: VICE PRESIDENT


TENANT                              THE CHARLES STARK DRAPER LABORATORY, INC.

                                       By: /s/ D.C. Driscoll
                                          -------------------------------------
                                       Name:  D.C. DRISCOLL

                                       Title: VICE PRESIDENT AND TREASURER


                                       3

<PAGE>

                                  EXHIBIT 99.3

                              555 Technology Square
                            Cambridge, Massachusetts
                                 "the Buildings"


                            FIFTH AMENDMENT TO LEASE
                       Execution Date: As of June 23, 1998

LANDLORD:         Technology Square LLC, successor-in-interest to CC&F
                  Cambridge Trust

TENANT:           The Charles Stark Draper Laboratory, Inc.

LEASE EXECUTION DATE:
                  August 16, 1974

TERMINATION DATE:
                  October 19, 2001

PREVIOUS LEASE AMENDMENTS:
                  First Amendment of Lease dated as of March 11, 1975
                  Second Amendment and Restatement of Lease dated
                         December 17, 1975
                  Third Amendment of Lease dated February 2, 1977
                  Fourth Amendment and Restatement of Lease dated
                         July 1, 1981

         WHEREAS, Section 4.4 of the above-referenced lease requires that
Landlord maintain insurance on the Buildings against loss by fire and hazards
covered by extended coverage endorsement and requires that Tenant reimburse
Landlord for the premiums for such insurance;

         WHEREAS, Tenant desires to maintain such casualty insurance on the
Buildings rather than Landlord;

         WHEREAS, Landlord is willing to allow Tenant to maintain casualty
insurance on the Buildings on the terms and conditions hereinafter set forth;

         NOW THEREFORE, the above-referenced lease, as previously amended ("the
Lease") is hereby further amended as follows:


                                        1

<PAGE>


         1.       TENANT'S RIGHT TO MAINTAIN CASUALTY INSURANCE ON THE
BUILDINGS

         A. Effective as of June 23, 1998, Section 4.4 of the Lease shall,
subject to Subparagraph B of this Paragraph 1, be deleted in its entirety and
the following shall be substituted in its place:

         "Throughout the term of the Lease, Tenant shall, at Tenant's sole cost
and expense, keep the Buildings insured against loss or damage caused by any
peril covered under fire, extended coverage and all risk insurance (including,
without limitation, coverage for flood, earthquake, demolition, increased cost
of construction, extra expense, and boiler and machinery coverage) in an amount
equal to one hundred percent (100%) replacement cost value, exclusive of
foundations, with an agreed amount endorsement (including insurance against loss
in case of monthly installments of fixed rent and any additional rent which may
become due under Section 2.6 and this Section 4.4 for a period of at least one
year after any casualty). In addition, Tenant shall obtain, at Landlord's
request, such coverage for such additional perils as Landlord's mortgagee(s) may
reasonably require. Such insurance shall insure the interests of both Landlord
and Tenant as their respective interests may appear from time to time and shall
name Landlord and Landlord's mortgagees as named insured parties.

         Such insurance shall be effected with insurers approved by Landlord and
Landlord's mortgagees (which approval shall not be unreasonably withheld),
authorized to do business in the Commonwealth of Massachusetts under valid and
enforceable policies wherein Tenant names Landlord and Landlord's mortgagees as
named insured parties. 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. At the time of execution and delivery of this Fifth
Amendment by Tenant, and thereafter not less than thirty (30) days prior to the
expiration date of each expiring policy, original copies of the policies
provided for in this Section 4.4, issued by the insurer, or certificates of such
policy setting forth in full the provisions thereof and issued by such insurer
together with evidence reasonably 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 Buildings."

         B. Landlord shall have the right at any time, upon thirty (30) days
written notice ("Casualty Insurance Change Notice") to Tenant, to revert to the
original obligations of the parties with respect to casualty insurance. If
Landlord gives Tenant the Casualty Insurance Change Notice, then, effective as
of the date thirty (30) days after Landlord gives Tenant the Casualty Insurance
Change Notice, Subparagraph A of this Paragraph 1 shall be deleted in its
entirety, and for the remainder of the term of the Lease, Section 4.4 of the
Lease shall be reinstated and shall be in full force and effect.

         2. As hereby amended, the Lease is ratified, confirmed and approved in
all respects.

                                        2

<PAGE>


         EXECUTED UNDER SEAL as of the date first above written.

LANDLORD:
TECHNOLOGY SQUARE LLC, 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: [SIGNATURE]
                                    Name:
                                    Title:
                                    Hereunto Duly Authorized

                           Date Signed: 1/24/98

TENANT:
THE CHARLES STARK DRAPER LABORATORY, INC.

By:      [SIGNATURE]
         Name:
         Title:
         Hereunto Duly Authorized

Date Signed:      1/21/99





                                                         3

<PAGE>

                                  EXHIBIT 99.4

                   [Beacon Capital Partners, Inc. letterhead]


December 1, 1999



BY CERTIFIED MAIL AND COURIER

The Charles Stark Draper Laboratory, Inc.
555 Technology Square
Cambridge, MA 02139

Attention:  Mr. David C. Driscoll

Re:  555 TECHNOLOGY SQUARE, CAMBRIDGE, MA

Dear Mr. Driscoll:

This is with reference to that certain Fourth Amendment and Restatement of Lease
dated as of July 1, 1981, as amended (the "Lease"), the present parties to which
are Technology Square LLC, a Delaware limited liability company ("Landlord"),
and The Charles Stark Draper Laboratory, Inc., a Massachusetts corporation
("Tenant").

Pursuant to Section 2.8.1 of the Lease, Tenant had an option to extend the
original term of the Lease upon notice to be given to Landlord on or before
October 19, 1999. Tenant did not extend the Term of the Lease. Therefore, the
Term of the Lease will expire on October 19, 2001.

At this point in time, Landlord would like to begin showing the Premises to
prospective tenants in accordance with Section 5.9 of the Lease. Please let us
know whom at your office our agent should contact to coordinate showing of the
premises.

Thank you for your anticipated cooperation.

Very truly yours,

TECHNOLOGY SQUARE LLC

By:      Beacon Capital Partners, L.P.,
         its sole member

         By:      Beacon Capital Partners, Inc.
                  its sole general partner


<PAGE>


                  By: /s/ THOMAS RAGNO
                      ------------------------------------
                      Name:  Thomas Ragno
                      Title: Senior Vice President



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