<PAGE>


                                                                  EXHIBIT 10.4


                            LEASE EXTENSION AGREEMENT

                             DATED: DECEMBER 1, 2000


                  MASSACHUSETTS INSTITUTE OF TECHNOLOGY, LESSOR

                    MILLENNIUM PHARMACEUTICALS, INC., LESSEE

                  640 MEMORIAL DRIVE, CAMBRIDGE, MASSACHUSETTS

                                TABLE OF CONTENTS
                                -----------------
<TABLE>
<S>      <C>                                                              <C>
1.0      PARTIES AND PREMISES............................................  1

         1.1      PARTIES AND PREMISES...................................  1

         1.2      BASEMENT SPACE.........................................  2

         1.3      COMMON AREAS...........................................  3

         1.4      RIGHT OF FIRST OFFER...................................  3

2.0      TERM............................................................  5

         2.1      TERM; COMMENCEMENT DATE................................  5

         2.2      EXTENSION OPTION.......................................  5

3.0      RENT............................................................  5

         3.1      PAYMENT OF RENT........................................  5

         3.2      DETERMINATION OF FAIR MARKET RENT......................  6

4.0      PERMITTED USES................................................... 8

5.0      TAXES; OPERATING EXPENSES........................................ 8

         5.1      TAXES................................................... 8

         5.2      OPERATING EXPENSES...................................... 8

         5.3      PAYMENT OF TAXES AND OPERATING EXPENSES................ 10

         5.4      ABATEMENT OF TAXES..................................... 11

6.0      ELECTRIC SERVICE................................................ 11

7.0      INSURANCE....................................................... 12

         7.1      PUBLIC LIABILITY INSURANCE............................. 12

         7.2      CASUALTY INSURANCE..................................... 12

         7.3      CERTIFICATE OF INSURANCE............................... 12

         7.4      LESSOR'S INSURANCE..................................... 13



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7.5      WAIVER OF SUBROGATION........................................... 13

7.6      WAIVER OF RIGHTS................................................ 13

8.0      ASSIGNMENT AND SUBLETTING....................................... 14

9.0      PARKING......................................................... 16

9.1      ON-SITE PARKING SPACES...........................................16

9.2      OFF-SITE PARKING SPACES..........................................16

9.3      ADDITIONAL RENT FOR PARKING SPACES...............................17

10.0     LATE PAYMENT OF RENT............................................ 17

11.0     LESSEE'S COVENANTS.............................................. 17

12.0     Intentionally Omitted............................................22

13.0     CASUALTY AND EMINENT DOMAIN..................................... 22

         13.1     SUBSTANTIAL TAKING..................................... 22

         13.2     PARTIAL TAKING......................................... 23

         13.3     AWARDS................................................. 23

         13.4     SUBSTANTIAL CASUALTY................................... 23

         13.5     REPAIR AND RESTORATION................................. 23

         13.6     CASUALTY DURING LAST 18 MONTHS......................... 24

14.0     DEFAULTS; EVENTS OF DEFAULT; REMEDIES........................... 25

         14.1     DEFAULTS; EVENTS OF DEFAULT............................ 25

         14.2     TERMINATION............................................ 26

         14.3     SURVIVAL OF COVENANTS.................................. 26

         14.4     DAMAGES................................................ 26

         14.5     RIGHT TO RELET......................................... 27

         14.6     RIGHT TO EQUITABLE RELIEF.............................. 27

         14.7     RIGHT TO SELF HELP..................................... 28

         14.8     FURTHER REMEDIES....................................... 28

15.0     REAL ESTATE BROKER.............................................. 28

16.0     NOTICES......................................................... 28

17.0     NO WAIVERS...................................................... 29

18.0     SERVICES PROVIDED BY LESSOR..................................... 29

19.0     GROUND LEASES; MORTGAGES........................................ 30

         19.1     RIGHTS OF GROUND LESSORS AND MORTGAGEES................ 30

         19.2     LEASE SUBORDINATE...................................... 30



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20.0     NOTICE OF LEASE; ESTOPPEL CERTIFICATES.......................... 30

21.0     HOLDING OVER.................................................... 31

22.0     FORCE MAJEURE................................................... 31

23.0     ENTIRE AGREEMENT................................................ 31

24.0     SECURITY DEPOSIT................................................ 31

25.0     SATELLITE DISH...................................................32

26.0     EXISTING LEASE.................................................. 33

27.0     SUCCESSORS AND ASSIGNS.......................................... 33

28.0     APPLICABLE LAW, SEVERABILITY AND CONSTRUCTION................... 33

29.0     AUTHORITY....................................................... 33



EXHIBIT A:  Plan of the Premises

EXHIBIT B:  Plan of the Land

EXHIBIT C:  Items Designated for Removal

EXHIBIT D:  Lessor's Services

EXHIBIT E:  Lessee's Services

EXHIBIT F  Copy of Lessor's Certificate of Title

EXHIBIT G:  Location of Off Site Parking Spaces

EXHIBIT H:  Tenant Standards
</TABLE>


<PAGE>


                            LEASE EXTENSION AGREEMENT

Dated December 1, 2000

         This lease extension agreement (hereinafter this "Lease") is made
between MASSACHUSETTS INSTITUTE OF TECHNOLOGY, a Massachusetts educational
corporation with an office at Suite 200, 238 Main Street Cambridge, MA 02142
("Lessor") and MILLENNIUM PHARMACEUTICALS, INC., a Delaware corporation with it
principal office at 75 Sidney Street, Cambridge, MA 02142 ("Lessee").

         WHEREAS, Lessor and Lessee are the parties to an existing lease
agreement of the Premises (as defined below) dated August 26, 1993 which has
been previously amended by a number of amendments (said lease agreement as so
amended is hereafter referred to as the "Existing Lease"), and

         WHEREAS, the Existing Lease is scheduled to expire on December 31,
2003, subject to the right of the Lessee to extend the term for two additional
periods of five years each on terms and conditions set forth therein, and

         WHEREAS, Lessor and Lessee have agreed to extend the term of the
Existing Lease for an additional term of five years and preserve a further five
year extension option on the terms and conditions set forth below; and

         WHEREAS, the terms and conditions set forth below are intended to vary
and supersede the provisions of Existing Lease with respect to the Term of this
Lease as described in Section 2.0 below and to incorporate certain provisions of
the amendments to the Existing Lease into a single document to govern the
relationship of the parties during such Term,

NOW THEREFORE, the parties hereby agree as follows:

1.0      PARTIES AND PREMISES.

         1.1  PARTIES AND PREMISES. MASSACHUSETTS INSTITUTE OF TECHNOLOGY
              ("Lessor") hereby LEASES unto MILLENNIUM PHARMACEUTICALS, INC.
              ("Lessee"), the following premises:

                           Approximately 159,995 square feet of rentable area
                           consisting of the entire first, second, third and
                           fifth floors and the eastern portion of the fourth
                           floor, shown as the cross-hatched area on EXHIBIT A
                           attached hereto (the "Premises"), in the building
                           known as and numbered 640 Memorial Drive,


                                      -1-


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                           Cambridge, Massachusetts, containing a total of
                           182,124 rentable square feet (the "Building"), which
                           is located on the parcel of land shown on EXHIBIT B
                           attached hereto (the "Land"),

                  together with the benefit of, and subject to (as the case may
                  be) all rights, easements, covenants, conditions,
                  encumbrances, encroachments and restrictions of record as of
                  the date of this Lease, which matters are set forth on the
                  copy of Lessor's Certificate of Title to the Land attached
                  hereto as EXHIBIT F (the "Permitted Encumbrances"), which
                  Permitted Encumbrances shall not materially affect Lessee's
                  use or occupancy of the Premises for the "Permitted Uses"
                  hereunder (as defined in Section 4.0 below). Lessor shall have
                  the right, without the necessity of obtaining Lessee's consent
                  thereto or joinder therein, to grant, permit, or enter into
                  during the term of this Lease such additional rights,
                  easements, covenants, conditions, encumbrances, encroachments
                  and restrictions with respect to the Land as Lessor may deem
                  appropriate, PROVIDED THAT no such rights, easements,
                  covenants, conditions, encumbrances, encroachments or
                  restrictions shall materially affect Lessee's use of the
                  Premises for the "Permitted Uses" (as defined in Section 4.0
                  below).

                  Lessor hereby reserves the right to maintain, use, repair and
                  replace pipes, ducts, wires, meters and any other equipment,
                  machinery, apparatus and fixtures located within the Premises
                  and serving other parts of the Building. Lessee, its employees
                  and invitees shall have access to the Premises at all times,
                  subject to the provisions of Section 11.0(h) below.

         1.2      BASEMENT SPACE. Lessee hereby leases 21,027 square feet in the
                  basement of the Building, (the "Basement Space"). Lessee shall
                  pay on account of the Basement Space "Basement Rent" in the
                  amount of $18.00 per square foot per Lease Year, such amount
                  to be paid in advance in equal monthly installments in the
                  same manner and at the same times as "Basic Rent" (as defined
                  in Section 3.1 below). Except as otherwise expressly stated in
                  this Lease, the Basement Space shall be deemed to be part of
                  the Premises for all purposes of this Lease, and all rights
                  and obligations of the parties hereunder with respect to the
                  Premises shall apply equally to the Basement Space.
                  Notwithstanding the foregoing, (i) the area of the Basement
                  Space shall not be included (a) in the rentable area of the
                  Premises for determining "Lessee's Share" pursuant to Section
                  5.1 below, or (b) in determining the number of parking spaces
                  to which Lessee is entitled under Section 9.0 below; (ii) the
                  Basement Space shall not be included in the Premises for
                  purposes of Section 13.0 below.

                  The Basement Space shall be used solely for an animal storage
                  facility and for general storage by Lessee, and for no other
                  use. Lessor makes no representation or warranty of any type
                  concerning the permissibility of such use under applicable
                  Legal Requirements or the suitability of the Basement Space
                  for such use. In addition to, but not in limitation of, the
                  provisions of the Lease relating to Lessee's


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                  use of the Premises, Lessee hereby agrees to comply with all
                  Legal Requirements applicable to Lessee's use of the Basement
                  Space and not to permit the emission of any objectionable
                  noise or odors from the Basement Space.

                  No animals, animal waste, food or supplies relating to the
                  animals maintained from time to time in the Basement Space
                  shall be transported within the Building except as provided in
                  this Paragraph. Use of the freight elevator for the
                  transportation of animals, animal waste, food or supplies
                  between the Basement Space and Lessee's Premises on the upper
                  floors of the Building, shall be conducted in a manner which
                  does not unreasonably interfere with the use of the elevator
                  by any other tenants of the Building. All deliveries of
                  animals to Lessee at the Building shall occur after Building
                  operating hours. At all times that animals are transported on
                  the Land or within the Building, they shall be transported in
                  an appropriate cage or other container. At no time shall any
                  animals, animal waste, food or supplies relating to the
                  animals be brought into, transported through, or delivered to
                  the lobby of the Building.

                  Notwithstanding anything to the contrary elsewhere in this
                  Lease, Lessor is not providing any services to the Basement
                  Space. Lessee shall make its own arrangements for the cleaning
                  of such space as well as the provision of electricity, water,
                  gas, HVAC and any other utility or service. Electricity, water
                  and gas consumption in the Basement Space shall be separately
                  metered. Lessee shall pay all charges therefor directly to the
                  company which provides such service.

         1.3      COMMON AREAS. Lessor also grants to Lessee, and Lessee's
                  invitees, the right, in common with others entitled thereto,
                  to use for the purposes for which they were designed, the
                  common facilities of the Building, including but not limited
                  to, all entrances, hallways, elevator foyers, air shafts,
                  elevator shafts and elevators, stairwells and stairs,
                  restrooms, passenger elevators, freight elevator, loading
                  bays, conference center and the "On-Site Parking Area" (as
                  defined in Section 9.0 below) (collectively, the "Common
                  Areas"). Landlord hereby reserves the right to close the
                  cafeteria in the Building at any time that Lessor, in its sole
                  discretion, determines that there is insufficient usage of the
                  cafeteria to justify its continued operation.

         1.4      RIGHT OF FIRST OFFER. In the event that at any time during the
                  Term Lessor commences to market for lease any space on the
                  fourth floor of the Building which is not part of the Premises
                  as shown on EXHIBIT A attached hereto, Lessor shall notify
                  Lessee. Lessor's notice hereunder shall contain Lessor's good
                  faith determination of Fair Market Rent. Provided that (i) an
                  "Event of Default" (as defined in Section 14.1 below) is not
                  continuing as of the day on which Lessor gives such notice,
                  and (ii) the Lessee named herein or a Lessee Affiliate (as
                  defined in Section 8.0(i)) is then actually occupying sixty
                  percent (60%) of the entire Premises, Lessee shall have the
                  right (the "Right of First Offer") to lease the portion of the
                  fourth floor set forth in Lessor's notice for a term
                  commencing on the date on which Lessor delivers possession
                  thereof to Lessee, and ending on the last day of the Term,


                                      -3-


<PAGE>


                  by giving written notice of exercise to Lessor within twenty
                  (20) days of receipt of Lessor's notice; provided that, if at
                  any time during the first year after Lessee takes occupancy of
                  the space described in Lessor's notice, Lessee or a Lessee
                  Affiliate is not actually occupying such space in its
                  entirety, then if Lessor so elects, this Lease shall be deemed
                  to be amended as of the date on which Lessor sends notice
                  thereof to Lessee so as to delete such space from the Premises
                  for purposes of this Lease (with a commensurate adjustment in
                  Rent and Lessee's Share) for the remainder of the Term.

                  If Lessee exercises its right under this Section 1.4 to lease
                  such space, then such space shall become subject to all of the
                  terms of this Lease EXCEPT that Basic Rent therefor shall be
                  due and payable in an amount equal to the "Fair Market Rent"
                  therefor as of the date on which Lessor reasonably anticipates
                  delivering possession of the space to Lessee. "Fair Market
                  Rent" shall be determined in the manner provided in Section
                  3.2 of this Lease for the Extension Term; provided that unless
                  Lessee's notice of acceptance elects to determine Fair Market
                  Rent by appraisal as set forth in Section 3.2, Lessee shall be
                  deemed to have agreed to Lessor's good faith determination of
                  Fair Market Rent as set forth in Lessor's notice. In the event
                  that Lessee, for any reason whatsoever, fails to give such
                  notice to Lessor within such 20-day period, Lessee shall be
                  deemed to have waived its rights under this Section 1.4 with
                  respect to the space described in Lessor's notice for the
                  remainder of the Term.

                  Any space which is subjected to the terms of this Lease
                  pursuant to this Section 1.4 shall be delivered broom clean
                  but otherwise in the condition in which it is redelivered to
                  Lessor. Lessor shall have no obligation to perform any
                  preparatory work in such space in anticipation of Lessee's use
                  thereof or to provide any allowance to Lessee towards the
                  preparation thereof. All work performed by Lessee in such
                  space shall be subject to the provisions of Section 11.0(f)
                  below. Basic Rent shall be due and payable on account of such
                  space commencing on the day on which Lessor delivers
                  possession thereof to Lessee.

                  Lessor shall use reasonable diligence to regain possession of
                  any space with respect to which Lessee has exercised the Right
                  of First Offer herein contained, but Lessor shall not be
                  responsible for any delay by any occupant in vacating such
                  space. Effective upon the date on which Lessor delivers
                  possession to Lessee of any space which is subjected to the
                  terms of this Lease pursuant to this Section 1.4, such space
                  shall be deemed to be part of the Premises for all purposes of
                  this Lease except that Basic Rent therefor shall be computed
                  as hereinabove provided, and "Lessee's Share" (as defined in
                  Section 5.1 below) shall be appropriately modified.

                  The extension or renewal of the lease of an initial occupant
                  of space on the fourth floor of the Building shall serve to
                  defer Lessee's Right of First Offer with respect to such
                  space.


                                      -4-


<PAGE>


2.0.     TERM.

         2.1. COMMENCEMENT DATE. The initial term of this lease (the "Initial
         Term") shall commence January 1, 2004 (the "Commencement Date") and
         expire on the day immediately preceding the fifth (5th) anniversary
         thereof, unless sooner terminated as hereinafter provided. For purposes
         of this Lease, the phrase "Term" shall mean collectively (a) the
         Initial Term, and (b) if Lessee duly exercises the "Extension Option",
         the "Extension Term" (as these phrases are defined in Section 2.2
         below).

         2.2.  EXTENSION OPTION. Provided that both (i) an "Event of Default"
               (as defined in Section 14.1 below) is not outstanding on
               the day on which Lessee purports to exercise the Extension
               Option or prior to the first day of the Extension Term,
               and (ii) the Lessee named herein and any Lessee Affiliates (as
               defined in Section 8.0(i)) are actually occupying at least 60% of
               the Rentable Area of the Premises as of each of said dates,
               Lessee shall have the option ("Extension Option") to extend the
               Term of this Lease for one additional period of five (5) Lease
               Years (the "Extension Term"), unless sooner terminated as
               hereinafter provided, subject to all the terms of this Lease
               except for the change in Basic Rent as provided in Section 3.1 of
               this Lease. Lessee may exercise the Extension Option by giving
               written notice of exercise to Lessor not earlier than fifteen
               (15) months prior to, nor later than twelve (12) months prior to,
               the last day of the Initial Term. If Lessee fails to give such
               notice to Lessor within such time, Lessee shall be deemed to have
               waived the right to exercise the Extension Option.

3.0      RENT.

         3.1      PAYMENT OF RENT Lessee shall pay Lessor, without offset or
                  deduction and without previous demand therefor, as items
                  constituting rent (collectively, "Rent"):

                  (a)    Basic Rent, at the following rates, in equal monthly
                         installments, in advance, commencing on the
                         Commencement Date and continuing thereafter on the
                         first day of each calendar month or portion thereof
                         during the Term:

                         (i)      For the Initial Term Basic Rent shall be
                                  determined as follows. First, the parties
                                  shall determine the Fair Market Rent for the
                                  Premises in the manner set forth in Section
                                  3.2; provided that, solely for the purpose of
                                  determining Basic Rent for the Initial Term
                                  under this subparagraph (i), such amount shall
                                  not exceed $45.00 per square foot or be less
                                  than $39.00 per square foot. Basic Rent for
                                  the Initial Term shall be 93% of the amount so
                                  determined increased by $.63 per rentable
                                  square foot. For example, if Fair Market Rent
                                  for the Initial Term is determined to be $40
                                  per square foot, Basic Rent will be ($40 x
                                  .93) +$.63 = $37.83 per square foot.


                                      -5-


<PAGE>


                         (ii)     During the Extension Term, an amount equal to
                                  ninety three percent (93%) of the Fair Market
                                  Rent of the Premises as of the first day of
                                  the Extension Term, but in no event less than
                                  the Basic Rent payable by Lessee hereunder for
                                  the last Lease Year preceding the commencement
                                  of such Extension Term.

                         As used in this Lease, "Lease Year" means the twelve
                         (12) month period commencing on the Commencement Date,
                         or a successive twelve (12) month period included in
                         the Term commencing on an anniversary of that day, but
                         if the expiration of the Term or the earlier
                         termination of the Lease does not coincide with the
                         termination of such a twelve (12) month period, the
                         term "Lease Year" shall mean the portion of such twelve
                         (12) month period before such expiration or
                         termination.

                    (b)  All Basement Rent and other costs, charges, or expenses
                         which Lessee in this Lease agrees to pay, or which
                         Lessor pays or incurs as the result of a default by
                         Lessee hereunder, including any penalty or interest
                         which may be added for nonpayment or late payment
                         thereof as provided in this Lease (collectively,
                         "Additional Rent"). All recurring payments of
                         Additional Rent, such as payment on account of Basement
                         Rent, "Taxes" and "Operating Expenses" (as these terms
                         are hereinafter defined), shall be due and payable on
                         the same day on which Basic Rent is due. Unless
                         otherwise specifically provided in this Lease, all
                         non-recurring items constituting Additional Rent shall
                         be due and payable within ten (10) days after written
                         demand therefor by Lessor.

                  Basic Rent and Additional Rent shall be PRO-RATED for partial
                  months occurring at the beginning or the end of the Term.

                  All payments shall be made to Lessor or such agent, and at
                  such place, as Lessor shall, from time to time, in writing
                  designate, the following being now so designated:

                                            Meredith & Grew, Inc.
                                            160 Federal Street
                                            Boston, MA 02110-1701
                                            Attention: John Sullivan

         3.2      DETERMINATION OF FAIR MARKET RENT. As used in this Lease,
                  "Fair Market Rent" means the effective fair market rent for
                  the Premises or space being leased by Lessee pursuant to
                  Section 1.4 above, as the case may be, in its "as is"
                  condition, including those portions of "Lessee's Work" (as
                  defined below) and "Alterations" (as defined in Section
                  11.0(f) below) which Lessee is not permitted or required
                  hereunder to remove at the expiration or earlier termination
                  of this Lease, but exclusive of the Basement Space, as of the
                  day with respect to which such


                                      -6-


<PAGE>


                  determination is being made, for a term of five (5) years
                  (or, in connection with Section 1.4 above, for a term equal
                  to the then-remaining Term of this Lease or five (5) years,
                  as the case may be). Fair Market Rent shall be based upon
                  the rents generally in effect for similar premises for
                  research laboratory/research and development uses in similar
                  buildings in the Cambridge, Massachusetts area in which the
                  Premises is located, adjusted to a "net" lease basis. As
                  used herein the term "Lessee's Work" shall mean all
                  improvements, alterations and additions made to the Premises
                  by Lessee as part of the initial preparation thereof for
                  Lessee's occupancy

                  Not earlier than July 1, 2002 or later than October 1, 2002
                  Lessor shall provide to Lessee Lessor's good faith
                  determination of Fair Market Rent. If Lessor and Lessee are
                  unable to agree on the Fair Market Rent within twenty (20)
                  days thereafter, then Lessor and Lessee shall, not later than
                  sixty (60) days after Lessor receives Lessee's notice of
                  exercise, each retain a real estate professional with at least
                  ten (10) years' continuous experience in the business of
                  appraising or marketing commercial real estate in the
                  Cambridge, Massachusetts vicinity, who shall, within thirty
                  (30) days of his or her selection, prepare a written report
                  summarizing his or her conclusion as to Fair Market Rent.
                  Lessor and Lessee shall simultaneously exchange such reports;
                  PROVIDED, HOWEVER, that if one party has not obtained such a
                  report within one hundred (100) days after Lessor receives
                  Lessee's notice of exercise, then the determination set forth
                  in the other party's report shall be final and binding upon
                  the parties. If both parties receive reports within such time
                  and the lesser of the two determinations is within ten (10%)
                  percent of the higher determination, then the average of these
                  determinations shall be deemed to be Fair Market Rent. If
                  these determinations differ by more than ten (10%) percent,
                  then Lessor and Lessee shall mutually select a person with the
                  qualifications stated above (the "Final Professional") to
                  resolve the dispute as to Fair Market Rent. If Lessor and
                  Lessee cannot agree upon the designation of the Final
                  Professional within thirty (30) days of the exchange of the
                  first valuation reports, either party may apply to the
                  American Arbitration Association, the Greater Boston Real
                  Estate Board, or any successor thereto for the designation of
                  a Final Professional. Within ten (10) days of the selection of
                  the Final Professional, Lessor and Lessee shall each submit to
                  the Final Professional a copy of their respective real estate
                  professional's determination of Fair Market Rent. The Final
                  Professional shall not perform his or her own valuation but
                  rather shall, within thirty (30) days after such submissions,
                  select the submission which is closest to the determination of
                  Fair Market Rent which the Final Professional would have made
                  acting alone. The Final Professional shall give notice of his
                  or her selection to Lessor and Lessee and such decision shall
                  be final and binding upon Lessor and Lessee. Each party shall
                  pay the fees and expenses of its real estate professional and
                  counsel, if any, in connection with any proceeding under this
                  paragraph, and the losing party shall pay the fees and
                  expenses of the Final Professional.


                                      -7-


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                  If Lessee exercises its Extension Option hereunder, Fair
                  Market Rent shall be determined in the manner just described
                  except that (i) Lessor shall provide to Lessee Lessor's good
                  faith determination of Fair Market Rent within twenty (20)
                  days after Lessor receives Lessee's notice of exercise of the
                  Extension Option; and (ii) if Lessor and Lessee are unable to
                  agree on the Fair Market Rent within twenty (20) days
                  thereafter, then Lessee may, within ten (10) days after the
                  expiration of such twenty (20) day period, elect either to
                  withdraw its notice of exercise, in which event its right to
                  extend the Term shall terminate, or to request that the Fair
                  Market Rent be determined by appraisal. The sixty (60) day
                  period within which the parties must each select a real estate
                  professional to determine the Fair Market Rent for the
                  Premises shall commence upon the expiration of the ten (10)
                  day period during which Lessee may elect to withdraw its
                  notice of exercise.

4.0      PERMITTED USES. The premises shall be occupied continuously by Lessee
         and used for the following purposes (the "Permitted Uses") only and for
         no other:

                  To the extent permitted as a matter of right under the Zoning
                  Ordinance of the City of Cambridge, as amended from time to
                  time: laboratory, research and development, light
                  manufacturing (including a pilot plant but only if Lessor
                  determines, in its sole discretion, that such facility does
                  not constitute a use which is not compatible with the uses
                  being made by other lessees of the Building or which is unduly
                  hazardous in comparison to such other uses), and office uses.

5.0      TAXES; OPERATING EXPENSES

         5.1      TAXES. Lessee shall pay as Additional Rent its pro rata share
                  ("Lessee's Share") of all taxes, special or general
                  assessments, water rents, rates and charges, sewer rents and
                  other impositions and charges imposed by governmental
                  authorities of every kind and nature whatsoever, extraordinary
                  as well as ordinary and each and every installment thereof
                  which shall or may during the Term become due and payable or
                  become liens upon or for or with respect to the Land or any
                  part thereof and the Building or the Premises, or
                  appurtenances or equipment owned by Lessor thereon or therein
                  or any part thereof, or on this Lease, and any tax based on a
                  percentage fraction or capitalized value of the Rent (whether
                  in lieu of or in addition to the taxes hereinbefore described)
                  (collectively, "Taxes"). Taxes shall not include inheritance,
                  estate, excise, succession, transfer, gift, franchise, income,
                  gross receipt, or profit taxes except to the extent such are
                  in lieu of or in substitution for Taxes as now imposed on the
                  Building, the Land, the Premises or this Lease. "Lessee's
                  Share" shall be computed on the basis of a fraction whose
                  numerator is the number of rentable square feet in the
                  Premises (exclusive of the Basement Space) and whose
                  denominator is the total number of rentable square feet in the
                  Building. As of the date hereof, Lessee's Share is 87.85%.

         5.2      OPERATING EXPENSES. Lessee shall pay as Additional Rent
                  Lessee's Share of all reasonable expenses, costs, and
                  disbursements of every kind and nature (collectively,
                  "Operating Expenses") which Lessor shall pay or become
                  obligated to


                                      -8-


<PAGE>


                  pay in connection with the ownership, operation and
                  maintenance of the Building or the Land, including all
                  facilities in operation on the Commencement Date and such
                  additional facilities in subsequent years as may be
                  determined by Lessor to be necessary or beneficial for the
                  operation of the Building or the Land or the provision of
                  services to lessees, including, but not limited to:

                  (a)      all salaries, wages, fringe benefits, payroll taxes
                           and worker's compensation insurance premiums related
                           thereto of and for employees engaged in the operation
                           of the Building and the Land (with respect to
                           employees who are engaged in the operation of other
                           properties as well as the Building and the Land,
                           these amounts shall be pro-rated on the basis of the
                           relative amount of time spent by such employees on
                           the various properties);

                  (b)      painting, repairs, maintenance and cleaning of all
                           Common Areas;

                  (c)      utilities (including, without limitation,
                           electricity, water, sewer and gas) for all interior
                           Common Areas and lighting of exterior areas and the
                           "On-Site Parking Area" (as defined in Section 9.0
                           below);

                  (d)      maintenance and repair of the Building heating and
                           cooling systems, the plumbing systems, the fire
                           detection and suppression systems, the electrical
                           system and the elevators;

                  (e)      all maintenance, janitorial, and service agreements;

                  (f)      all insurance, including the cost of casualty and
                           liability insurance applicable to the On-Site Parking
                           Area, the Land, the Building and Lessor's personal
                           property used in connection therewith, including the
                           amount of any reasonable deductible payable by Lessor
                           in making repairs and restoration after a casualty;

                  (g)      maintenance of landscaped areas and paved areas, and
                           snow removal;

                  (h)      maintenance of the Building security system;

                  (i)      management fees and the fair market value of office
                           space for the manager of the Building for an office
                           not to exceed 500 square feet of usable area (but if
                           such office is used to manage properties other than
                           the Land and Building, such fair market rent shall be
                           pro-rated on a square footage basis among such
                           various properties);

                  (j)      capital items which reduce Operating Expenses
                           associated with the item which is the subject of such
                           expenditure, or which upgrade services or which are
                           at any time required by a governmental authority or
                           required by the provisions of any insurance policy
                           which is first adopted or first becomes


                                      -9-


<PAGE>


                           applicable to the Premises, the Building or the Land
                           after the date of this Lease, amortized over the
                           reasonable life of the capital items on a straight
                           line basis with the reasonable life being determined
                           by Lessor in accordance with generally accepted
                           accounting principles;

                  (k)      reasonable expenses incurred in pursuing an
                           application for an abatement of Taxes pursuant to
                           Section 5.4 below to the extent not deducted from the
                           abatement, if any, received;

                  (l)      legal (excluding legal fees with respect to lease
                           negotiations and enforcement of lease terms against
                           lessees), accounting and other professional fees and
                           disbursements (excluding leasing commissions);

                  (m)      all costs and expenses incurred by Lessor in
                           connection with the operation of the cafeteria in the
                           Building; PROVIDED, HOWEVER, that notwithstanding
                           anything to the contrary contained in this Lease, (i)
                           all subsidies or other amounts payable by Lessor to
                           the cafeteria operator, (ii) the cost of all services
                           which are separately invoiced to Lessor for the
                           cafeteria (e.g., cleaning), and (iii) the cost to
                           Lessor of supplying to the cafeteria separately
                           metered utilities shall be allocated 100% among the
                           occupants of the Building at the time that these
                           costs and expenses are incurred and no portion of
                           these costs and expenses shall be borne by Lessor
                           (Lessor hereby agreeing that any surplus received by
                           Lessor from the operation of the cafeteria shall be
                           applied by Lessor to reduce Operating Expenses); and

                  (n)      services to be provided by Lessor as set forth on
                           EXHIBIT D attached.

                  In the event that the average occupancy rate for the Building
                  is less than ninety-five (95%) percent for any fiscal year,
                  then for purposes of calculating Operating Expenses, the
                  Operating Expenses for such fiscal year shall be increased by
                  the additional costs and expenses that Lessor reasonably
                  estimates would have been incurred if the average occupancy
                  rate had been ninety-five (95%) percent for such fiscal year.
                  It is not the intent of this provision to permit Lessor to
                  charge Lessee for any Operating Expenses attributable to
                  unoccupied space, or to seek reimbursement from Lessee for
                  costs Lessor never incurred. Rather, the intent of this
                  provision is to allow Lessor to recover only those increases
                  in Operating Expenses properly attributable to occupied space
                  in the Building and this provision is designed to calculate
                  the actual cost of providing a variable Operating Expense
                  service to the portions of the Building receiving such
                  service. This "gross-up" treatment shall be applied only with
                  respect to variable Operating Expenses arising from services
                  provided to leased space in the Building in order to allocate
                  equitably such variable Operating Expenses to the lessees of
                  the Building.

         5.3      PAYMENT OF TAXES AND OPERATING EXPENSES. Within a reasonable
                  time (not to exceed ninety (90) days after the Commencement
                  Date, and thereafter within a


                                      -10-


<PAGE>


                  reasonable time (not to exceed ninety (90) days) after the
                  end of each fiscal year (or portion thereof) included in the
                  Term, Lessor shall deliver to Lessee (i) a statement of
                  actual Operating Expenses and Taxes for the fiscal year just
                  ended, together with reasonable supporting documentation
                  therefor, and (ii) a budget of Operating Expenses and Taxes
                  for the then-current fiscal year based on the actual
                  Operating Expenses and Taxes for the preceding year and
                  reasonably projected increases or decreases reasonably
                  anticipated by Lessor. Commencing on the first day of the
                  first calendar month after the delivery to Lessee of such
                  budget, Lessee shall pay to Lessor, as Additional Rent, on
                  account of its share of anticipated Operating Expenses and
                  Taxes for the then-current year, 1/12th of the total
                  annualized amount of Lessee's Share of Operating Expenses
                  and Taxes. Lessor reserves the right to revise the budget
                  during any fiscal year to cause it to more accurately
                  reflect the actual Taxes or Operating Expenses being paid or
                  incurred by Lessor, and upon any such revision the parties
                  shall make adjustments in the same time and manner as
                  hereinafter provided for fiscal year-end adjustments. Upon
                  delivery to Lessee of the statement of actual Operating
                  Expenses and Taxes for the preceding fiscal year, Lessor
                  shall adjust Lessee's account accordingly. If the total
                  amount paid by Lessee on account of the preceding fiscal
                  year is less than the amount due hereunder, Lessee shall pay
                  the balance due within twenty (20) days after delivery by
                  Lessor of such statement. If the total amount paid by Lessee
                  on account of the preceding fiscal year exceeds the amount
                  due hereunder, such excess shall be credited by Lessor
                  against the monthly installments of Additional Rent next
                  falling due or refunded to Lessee upon the expiration or
                  termination of this Lease (unless such expiration or
                  termination is the result of an "Event of Default" (as
                  defined in Section 14.1 below), in which case Lessor shall
                  credit such amount against any amount due from Lessee by
                  reason of such termination). Lessor's current fiscal year is
                  July 1 - June 30, but Lessor reserves the right to change
                  the fiscal year at any time during the Term.

                  Lessee shall have the right, upon written notice given to
                  Lessor, at Lessee's sole cost and expense to review Lessor's
                  books and records relating to the Operating Expenses and Taxes
                  for the Building and the Land for the prior fiscal year during
                  normal business hours at the office where these records are
                  maintained.

         5.4      ABATEMENT OF TAXES. Lessor may at any time and from time to
                  time make application to the appropriate governmental
                  authority for an abatement of Taxes. If (i) such an
                  application is successful and (ii) Lessee has made any payment
                  in respect of Taxes pursuant to this Section 5 for the period
                  with respect to which the abatement was granted, Lessor shall
                  (a) deduct from the amount of the abatement all third-party
                  expenses incurred by it in connection with the application,
                  (b) pay to Lessee Lessee's Share (adjusted for any period for
                  which Lessee had made a partial payment) of the abatement,
                  with interest, if any, paid by the governmental authority on
                  such abatement, and (c) retain the balance, if any.


                                      -11-


<PAGE>


6.0      ELECTRIC SERVICE. Lessee shall make its own arrangements for the
         provision of electricity to the Premises, and shall pay when due all
         charges therefor directly to the company which provides such electrical
         service.

7.0      INSURANCE

         7.1      PUBLIC LIABILITY INSURANCE. Lessee shall take out and maintain
                  in force throughout the Term (and for so long thereafter as
                  Lessee remains in occupancy) comprehensive public liability
                  insurance naming Lessor and persons claiming by, through or
                  under Lessor as additional insureds, against all claims and
                  demands for any injury to persons or property which may be
                  claimed to have occurred on the Premises, the Building, the
                  Land or on the ways adjoining the Land, in an amount which at
                  the beginning of the Term shall not be less than $1,000,000
                  for personal injury or death or property damage per
                  occurrence, and $5,000,000 in the aggregate for personal
                  injury or death or property damage, or such higher amounts as
                  Lessor thereafter determines to be consistent with sound
                  commercial practice in Cambridge. Such policy shall also
                  include contractual liability coverage covering Lessee's
                  liability assumed under this Lease.

         7.2      CASUALTY INSURANCE. Lessee shall take out and maintain
                  throughout the Lease Term a policy of fire, vandalism,
                  malicious mischief, extended coverage and so-called all risk
                  coverage insurance insuring (i) all items or components of
                  "Lessee's Work" which Lessee is by this Lease either entitled
                  to or required to remove upon the expiration or earlier
                  termination of this Lease (as identified and described in
                  EXHIBIT C) or "Alterations" (as defined in Section 11.0(f)
                  below) which Lessee is by this Lease either entitled to or
                  required to remove upon the expiration or earlier termination
                  of this Lease, and (ii) "Lessee's Property" (as defined in
                  Section 11.0(i) below) for the benefit of Lessee in an amount
                  equal to the replacement value thereof. Lessor shall be named
                  as a certificate holder on such policy. Lessor shall, at
                  Lessee's cost and expense, cooperate fully with Lessee and
                  execute any and all consents and other instruments and take
                  all other actions necessary to obtain the largest possible
                  recovery. Lessor shall not carry any insurance concurrent in
                  coverage and contributing in the event of loss with any
                  insurance required to be furnished by Lessee hereunder if the
                  effect of such separate insurance would be to reduce the
                  protection or the payment to be made under Lessee's insurance.

         7.3      CERTIFICATE OF INSURANCE. The insurance required by Sections
                  7.1 and 7.2 above shall be placed with insurers reasonably
                  satisfactory to Lessor and authorized to do business in
                  Massachusetts. Such insurance shall provide that it shall not
                  be amended or canceled with respect to the additional insureds
                  or certificate holders without thirty (30) days' prior written
                  notice to each of them. Lessee shall furnish to Lessor
                  certificates of insurance for all insurance required to be
                  maintained by Lessee under this Lease, together with evidence
                  satisfactory to Lessor of the payment of all premiums for such
                  policies. Lessee, at Lessor's request, shall also deliver such
                  certificates and evidence of payment of premiums to the holder
                  of any mortgage affecting the Land and Building.


                                      -12-


<PAGE>


         7.4      LESSOR'S INSURANCE. Lessor shall take out and maintain in
                  force throughout the Term, in a company or companies
                  authorized to do business in Massachusetts, casualty insurance
                  on the Building (exclusive of "Lessee's Property" and all
                  items or components of "Lessee's Work" which Lessee is by this
                  Lease either entitled to or required to remove upon the
                  expiration or earlier termination of this Lease or
                  "Alterations" which Lessee is by this Lease either entitled to
                  or required to remove upon the expiration or earlier
                  termination of this Lease, as to which Lessee is required to
                  maintain insurance pursuant to Section 7.2 above) in an amount
                  equal to the full replacement value of the Building (exclusive
                  of foundations and those items set forth in the preceding
                  parenthetical in this sentence), covering all risks of direct
                  physical loss or damage and so-called "extended coverage"
                  risks. This insurance may be maintained in the form of a
                  blanket policy covering the Building as well as other
                  properties owned by Lessor. Notwithstanding the foregoing
                  provisions of this Section 7.4, Lessor shall have the right,
                  at any time during the Term, to self-insure all or any portion
                  of the coverages required by this Section.

         7.5      WAIVER OF SUBROGATION. To the extent to which a waiver of
                  subrogation clause is available, Lessor and Lessee shall
                  obtain a provision in all insurance policies carried by such
                  party covering the Premises, including but not limited to
                  contents, fire and casualty insurance, expressly waiving any
                  right on the part of the insurer against the other party. If
                  extra cost is chargeable for such provision, then Lessee shall
                  pay such extra charge. Notwithstanding the foregoing, with
                  respect to such portion of the Term during which Lessor elects
                  to self-insure under Section 7.4 above, then for purposes of
                  this Section 7.5, Lessor shall be deemed to have maintained
                  fire and all-risk coverage in an amount equal to one hundred
                  (100%) percent of the insurable value of the Building (subject
                  to the exceptions and exclusions set forth in Section 7.4
                  above) with a waiver of subrogation clause contained therein.

         7.6      WAIVER OF RIGHTS. All claims, causes of action and rights of
                  recovery for any damage to or destruction of persons, property
                  or business which shall occur on or about the Premises, the
                  Building or the Land, which result from any of the perils
                  insured under any and all policies of insurance maintained by
                  Lessor or Lessee, are waived by each party as against the
                  other party, and the officers, directors, employees,
                  contractors, servants and agents thereof, regardless of cause,
                  including the negligence of the other party and its respective
                  officers, directors, employees, contractors, servants and
                  agents, but only to the extent of recovery, if any, under such
                  policy or policies of insurance; PROVIDED, HOWEVER, that (i)
                  this waiver shall be null and void to the extent that any such
                  insurance shall be invalidated by reason of this waiver, and
                  (ii) with respect to such portion of the Term during which
                  Lessor elects to self-insure under Section 7.4 above, then for
                  purposes of this Section 7.6, Lessor shall be deemed to have
                  maintained fire and all-risk coverage in an amount equal to
                  one hundred (100%) percent of the insurable value of the
                  Building (subject to the exceptions and exclusions set forth
                  in Section 7.4 above).


                                      -13-


<PAGE>


8.0      ASSIGNMENT AND SUBLETTING. (a) Lessee shall not mortgage, pledge,
         hypothecate, grant a security interest in, or otherwise encumber this
         Lease or any sublease hereinafter entered into by Lessee, or assign
         this Lease, or sublease the Premises or any portion thereof (the term
         "sublease" shall be deemed to include any arrangement pursuant to which
         a third party is permitted by Lessee to occupy all or any portion of
         the Premises), without obtaining, on each occasion, the prior written
         consent of Lessor, which consent shall not be unreasonably withheld or
         delayed. Lessee may only assign this Lease or sublease to persons or
         entities which will actually occupy the Premises or the portion thereof
         so subleased.

         (b) If Lessee wishes to assign this Lease or sublease all or any
         portion of the Premises, Lessee shall so notify Lessor in writing and
         request Lessor's consent thereto. Such notice shall include (i) the
         name of the proposed assignee or sublessee, (ii) a general description
         of the types of business conducted by the proposed assignee or
         sublessee and a reasonably detailed description of the business
         operations proposed to be conducted in the Premises by such person or
         entity, (iii) such financial information concerning Lessee and the
         proposed assignee or sublessee as Lessor may reasonably require (but
         such financial information shall not serve as the basis for a
         withholding of consent by Lessor), and (iv) all terms and provisions
         upon which such assignment or sublease is proposed to be made. Lessor
         shall have thirty (30) days from the day on which it receives Lessee's
         notice and such required information to give notice to Lessee that
         either (i) Lessor consents to such assignment or sublease, or (ii)
         Lessor reasonably withholds its consent to such assignment or sublease,
         in which case Lessor shall set forth the reasons therefor, or (iii)
         where applicable, Lessor is exercising its right of recapture pursuant
         to paragraph (e) below.

         (c) If Lessor consents to an assignment or sublease: (i) Lessee shall
         promptly deliver to Lessor a fully executed copy of said assignment or
         sublease, which shall be in the form previously submitted to Lessor for
         review; (ii) after any such assignment or sublease, Lessee shall remain
         primarily liable to Lessor hereunder (which liability shall be joint
         and several with the assignee or sublessee); and (iii) if the aggregate
         rent and other amounts payable to Lessee under or in connection with
         such assignment or sublease, after deduction of the costs reasonably
         incurred by Lessee in entering into such assignment or sublease
         (including, without limitation, reasonable attorneys' fees and
         expenses, brokerage commissions, and alteration costs amortized on a
         straight-line basis over the term of such sublease or, in the case of
         an assignment, over the remaining Term of this Lease), exceeds the Rent
         payable hereunder with respect to the portion of the Premises subject
         to such sublease (or, in the case of an assignment, the entire
         Premises) or if Lessee otherwise derives any net profit from such
         sublease or assignment, Lessee shall pay to Lessor, as Additional Rent,
         fifty percent (50%) of the entire amount of such excess or net profit
         immediately upon receipt thereof by Lessee. As used herein the phrase
         "the aggregate rent and other amounts payable to Lessee under or in
         connection with such assignment or sublease" shall include without
         limitation, payments received by Lessee for services such as
         glass-washing rendered by Lessee to such assignee or sublessee but only
         to the extent such payments exceed Lessee's actual costs for providing
         such services.

         (d) If Lessor reasonably withholds its consent to such assignment or
         sublease, Lessee shall not enter into the proposed assignment or
         sublease with such person or entity.


                                      -14-


<PAGE>


         (e) If Lessor elects, it shall have the right to consider Lessee's
         request for Lessor's consent to any assignment of the Lease, or a
         request for Lessor's consent to a sublease which either (i) has a
         proposed term (including extension options) of five years or more, or
         (ii) would cause more than fifty percent (50%) of the rentable area of
         the Premises (in the aggregate) to be subject to one or more subleases,
         as an offer to Lessor to release from this Lease that portion of the
         Premises which is proposed to be the subject of such sublease for the
         term of such proposed sublease or, in the case of a proposed assignment
         of this Lease, the entire Premises for the entire Lease Term. If Lessor
         accepts such offer, then (i) in the case of a proposed sublease, this
         Lease shall be deemed to be amended as of the proposed effective date
         of such sublease so as to delete the portion of the Premises which
         would have been subject thereto from the Premises for purposes of this
         Lease (with a commensurate adjustment in Rent and Lessee's Share) for
         the time period of what would have been the term of such sublease, or
         (ii) in the case of a proposed assignment, this Lease shall terminate
         as of the proposed effective date of such assignment as if such date
         was the last day of the Term.

         (f) Regardless of whether Lessor grants such consent, Lessee shall
         reimburse Lessor on demand, as Additional Rent, for all out of pocket
         costs and expenses (including, without limitation, attorneys' fees)
         reasonably incurred by Lessor in responding to a request for such
         consent, in an amount not to exceed $2,000.00 per request.

         (g) Lessee shall not be entitled to enter into any assignment or
         sublease, or to request Lessor's consent thereto, during the
         continuance of an Event of Default hereunder by Lessee.

         (h) Any assignment or sublease entered into pursuant to this Section
         8.0 shall be subject to all of the terms and provisions of this Lease,
         including without limitation this Section 8.0. If Lessee enters into
         any such assignment or sublease, Lessor may, at any time and from time
         to time after the occurrence of a default hereunder, collect rent from
         such assignee or sublessee, and apply the net amount collected against
         Lessee's obligations hereunder, but no such assignment or sublease or
         collection shall be deemed an acceptance by Lessor of such assignee or
         sublessee as a lessee hereunder or as a release of the original named
         Lessee hereunder.

         (i) In the event that Lessee desires to assign this Lease or to
         sublease the Premises (or any portion thereof) to any corporation,
         partnership, association or other business organization directly or
         indirectly controlling or controlled by Lessee or under common control
         with Lessee, or to any successor by merger, consolidation or purchase
         of all or substantially all of the assets of Lessee (each a "Lessee
         Affiliate"), Lessee shall give at least twenty (20) days' prior written
         notice thereof to Lessor (unless Lessee is prohibited by applicable
         laws, codes, rules or regulations, or by the terms of the operative
         merger agreement or purchase and sale agreement from providing notice
         to Lessor at such time, in which event such notice shall be provided to
         Lessor as soon as Lessee is no longer subject to such prohibition). No


                                      -15-


<PAGE>


         consent of Lessor shall be required for any such assignment or
         sublease. Any assignee or sublessee which claims an interest in this
         Lease pursuant to a transfer of the type described in this paragraph
         (i) shall be bound by all of the terms and conditions of this Lease.
         For the purpose of this Lease, the sale of Lessee's capital stock
         through any public exchange shall not be deemed an assignment or
         sublease of the Lease or of the Premises.

         (j) Notwithstanding anything contained in this Lease, Lessee shall not,
         either voluntarily or by operation of law, make any transfer of this
         Lease or the Premises (or any portion thereof) which results in Lessee
         (or anyone claiming by, through or under Lessee) collecting in
         connection with the Premises any rental or other charge based on the
         net income or on the profits of any person so as to render any part of
         the Rent due hereunder "unrelated business taxable income" of Lessor as
         described in Section 512 of the Internal Revenue Code of 1986, as
         amended, and any such transfer shall be void AB INITIO.

9.0      PARKING.

         9.1.     ON-SITE PARKING SPACES. Lessee shall have the right to lease
                  in the parking area on the Land (the "On-Site Parking Area")
                  up to one and one-half (1.5) spaces per 1,000 square feet of
                  rentable area in the Premises (the "On-Site Parking
                  Spaces"). Lessee hereby agrees to lease two hundred seventy
                  (270) On-Site Parking Spaces effective on the Commencement
                  Date. If Lessee leases any space pursuant to the Right of
                  First Offer set forth in Section 1.4 above, then Lessee
                  shall have the right to lease additional On-Site Parking
                  Spaces at the ratio of 1.5 spaces per 1,000 square feet of
                  rentable area so leased, by giving written notice of the
                  number of spaces so desired at the time that Lessee
                  exercises its Right of First Offer. Lessee shall have the
                  right to decrease (but not, except as expressly provided in
                  the next succeeding sentence, to increase) the number of
                  On-Site Parking Spaces so leased (but in no event to lease
                  more than the number of spaces set forth above) by giving
                  written notice to Lessor not less than thirty (30) days
                  prior to any 6-month anniversary of the Commencement Date,
                  which notice shall be effective to reduce the number of
                  On-Site Parking Spaces so leased effective upon such 6-month
                  anniversary. Once Lessee has decreased the number of On-Site
                  Parking Spaces leased by it, Lessee shall have the right
                  thereafter, by giving written notice to Lessor, to request
                  from time to time additional On-Site Parking Spaces (up to
                  an aggregate maximum of 1.5 spaces per 1,000 square feet of
                  rentable area in the Premises), and Lessor shall have up to
                  six (6) months to provide such spaces to Lessee.

         9.2.     OFF-SITE PARKING SPACES. In addition to the On-Site Parking
                  Spaces, Lessor shall lease to Lessee an additional sixty
                  (60) parking spaces (collectively, the "Off-Site Parking
                  Spaces") in a parking lot or lots in the vicinity of the
                  Building as shown cross-hatched on EXHIBIT G attached.
                  Lessor reserves the right to relocate all or any portion of
                  the Off-Site Parking Spaces within the area shown on EXHIBIT
                  G from time to time during the Term. Lessor shall use its
                  best efforts to spread the Off-Site Parking Spaces over the
                  fewest number of parking lots possible. Notwithstanding the
                  foregoing, in the event that Lessor hereafter


                                      -16-


<PAGE>


                  reduces the number of the properties shown on EXHIBIT G used
                  for parking purposes, and consequently is unable to provide
                  some or all of the Off-Site Parking Spaces on its own
                  property, the named Lessor shall, upon request by Lessee,
                  make reasonable efforts to lease all or a portion of such
                  spaces from a third party, in which event the rent payable
                  on account of such Off-Site Parking Spaces so leased shall
                  be the amount paid by the named Lessor to such third party
                  therefor, without markup.

         9.3      ADDITIONAL RENT FOR PARKING SPACES.Lessee shall pay for each
                  parking space leased hereunder, as Additional Rent, in advance
                  on the first calendar day of each month, an amount equal to
                  the Fair Market Rent of such parking spaces, as determined
                  annually. Fair Market Rent shall be determined in the manner
                  provided in Section 3.2 above for the Initial Term except that
                  if Lessor and Lessee are unable to agree on Fair Market Rent,
                  it shall be determined by one real estate professional (rather
                  than by two or three as provided in Section 3.2) who shall
                  have the qualifications stated in said Section and shall be
                  mutually acceptable to Lessor and Lessee.

10.0     LATE PAYMENT OF RENT. Lessee agrees that in the event that any payment
         of Basic Rent or Additional Rent shall remain unpaid at the close of
         business on the tenth business day after the same is due and payable
         hereunder (without reliance on any applicable grace period), such
         payment shall bear interest from the date the same was due at a rate
         equal to the "Prime Rate" as published from time to time in THE WALL
         STREET JOURNAL while such payment is overdue PLUS three (3%) percent,
         which shall be due and payable by Lessee as Additional Rent as
         compensation for Lessor's extra administrative costs in investigating
         the circumstances of late Rent. The assessment or collection of such a
         charge shall not be deemed to be a waiver by Lessor of any default by
         Lessee arising out of such failure to pay Rent when due.

11.0     LESSEE'S COVENANTS. Lessee covenants, at its sole cost and expense,
         during the Term and such further time as Lessee occupies any part of
         the Premises:

         (a)      to pay when due the Basic Rent and all Additional Rent, and,
                  if separately metered at any time during the Term, all
                  charges for electricity and other utilities;

         (b)      damage by fire or casualty and reasonable wear and tear only
                  excepted, to keep the Premises (including window glass) in as
                  good order, repair and condition as the same are in at the
                  commencement of the Term, or may be put in thereafter;

         (c)      not to injure, overload or deface the Premises or the
                  Building, nor to suffer or commit any waste therein, nor to
                  place a load upon any floor which exceeds the floor load
                  which the floor was designed to carry, nor to connect any
                  equipment or apparatus to any Building system (e.g.,
                  electrical, plumbing, mechanical) which exceeds the capacity
                  of such system, nor to permit on the Premises any auction
                  sale


                                      -17-


<PAGE>


                  or any nuisance or the emission therefrom of any objectionable
                  vibration, noise, or odor, nor to permit the use of the
                  Premises for any purpose other than the Permitted Uses, nor
                  any use thereof which is contrary to any laws, ordinances,
                  codes, rules and regulations, or the provisions of any
                  license, permit or other governmental consent or approval
                  required for or applicable now or at any time during the Term
                  to the Land, the Building or the Premises or Lessee's use
                  therefor (collectively, "Legal Requirements"), or which is
                  liable to invalidate or increase the premiums for any
                  insurance on the Building or its contents, or liable to
                  render necessary any alterations or additions to the
                  Building;

         (d)      not to obstruct in any manner any portion of the Building not
                  hereby leased, or the sidewalks or approaches to the Building,
                  or the On-Site Parking Area, or any hallways or Common Areas,
                  and to conform to all reasonable rules now or hereafter made
                  by Lessor for the care and use of the Building, its facilities
                  and approaches;

         (e)      to comply with all Legal Requirements and all
                  recommendations of Lessor's fire insurance rating
                  organization now or hereafter in effect, to keep the
                  Premises equipped with all safety appliances, and to procure
                  (and maintain in full force and effect) all licenses,
                  permits and other governmental consents and approvals
                  required by any Legal Requirement or by the provisions of
                  any applicable insurance policy because of the use made of
                  the Premises by Lessee (without hereby intending to vary the
                  provisions of Section 4.0 above), and, if requested by
                  Lessor, to make all repairs, alterations, replacements or
                  additions so required in and to the Premises;

         (f)      not to make any alterations, renovations, improvements
                  and/or additions to the Premises (collectively,
                  "Alterations") without on each occasion obtaining the prior
                  written consent of Lessor, which consent may be withheld by
                  Lessor in its reasonable discretion taking into account the
                  effect of such proposed Alterations on the structural
                  integrity of the Building, whether such proposed Alterations
                  would be detrimental to or incompatible with the Building
                  systems, and the effect of such proposed Alterations on the
                  external appearance of the Building (except that no such
                  prior written consent of Lessor shall be required for
                  Alterations which (i) shall not exceed $50,000 in each
                  instance, and (ii) do not affect the structural integrity of
                  the Building, and (iii) are not detrimental to or
                  incompatible with the Building systems, and (iv) do not
                  affect the exterior appearance of the Building, PROVIDED
                  that in each such case (x) Lessee shall still provide
                  advance notice to Lessor of the intended Alterations, and
                  (y) such Alterations shall be subject to all of the
                  provisions of this paragraph (f) other than the requirement
                  of Lessor's prior consent), or to make any holes in any part
                  of the Building or paint or place any signs, awnings, or the
                  like, visible from outside of the Premises. Prior to
                  commencing any Alterations, Lessee shall: secure all
                  necessary licenses, permits and other governmental consents
                  and approvals; obtain the written approval of Lessor as to
                  the plans and specifications for such work (where such
                  approval is required under this paragraph (f)); obtain the
                  written approval of Lessor as to the general contractor (or
                  as to each trade contractor if there is no general
                  contractor); cause each contractor and subcontractor to
                  carry


                                      -18-


<PAGE>


                  worker's compensation insurance in statutory amounts
                  covering all of the contractor's and subcontractor's
                  employees; and cause each general contractor (or each trade
                  contractor if there is no general contractor) and
                  subcontractor to carry comprehensive public liability
                  insurance in amounts reasonably satisfactory to Lessor (such
                  insurance to be written by companies reasonably satisfactory
                  to Lessor and insuring Lessee and Lessor as well as the
                  contractors and subcontractors). All Alterations shall be
                  consistent with the ""Tenant Standards" set forth on EXHIBIT
                  H attached hereto and shall be of a quality equal to or
                  better than that set forth therein. All Alterations (other
                  than Lessee's removable personal property and trade
                  fixtures) and all "Lessee's Work" shall remain part of the
                  Premises and shall not be removed upon the expiration or
                  earlier termination of the Term EXCEPT for those items which
                  Lessor designates for removal in a notice given to Lessee
                  either (a) at the time that Lessee requests Lessor's
                  approval of such Alteration (if such approval is required
                  hereunder) or (b) within ten (10) days after Lessee notifies
                  Lessor of its intent to make such Alteration (where Lessor's
                  prior approval is not required hereunder). Lessee shall pay
                  promptly when due the entire cost of such work. Lessee shall
                  not cause or permit any liens for labor or materials
                  performed or furnished in connection therewith to attach to
                  the Land or the Building, and shall discharge or bond any
                  such liens which may be filed or recorded against the
                  Premises within fifteen (15) days after the filing or
                  recording thereof. All such work shall be performed in a
                  good and workmanlike manner and in compliance with all Legal
                  Requirements and the provisions of all applicable insurance
                  policies. Promptly after the completion of any Alterations,
                  Lessee shall provide as-built plans thereof to Lessor.
                  Lessee shall indemnify and hold Lessor harmless from and
                  against any and all suits, demands, causes of action,
                  claims, losses, debts, liabilities, damages, penalties or
                  judgments, including, without limitation, reasonable
                  attorneys' fees, arising from injury to any person or
                  property occasioned by or growing out of such work, which
                  indemnity shall survive the expiration or termination of
                  this Lease;

         (g)      to save Lessor harmless and indemnified from any loss, cost
                  and expense (including, without limitation, reasonable
                  attorneys' fees) arising out of or relating to (i) a claim
                  of injury to any person or damage to any property while on
                  the Premises, if not due to the negligence or willful
                  misconduct of Lessor or its officers, agents, employees,
                  servants or contractors, or the breach of Lessor's
                  obligations under this Lease; or to (ii) a claim of injury
                  to any person or damage to any property anywhere alleged to
                  be occasioned by any omission, neglect or default of Lessee
                  or of anyone claiming by, through, or under Lessee, or any
                  officer, agent, employee, servant, contractor or invitee of
                  any of the foregoing. Lessor agrees to indemnify and hold
                  harmless Lessee from and against all loss, cost and expense
                  (including, without limitation, reasonable attorneys' fees)
                  arising out of or relating to a claim for personal injury or
                  property damage resulting from the negligence or willful
                  misconduct of Lessor or its officers, agents, employees,
                  servants or contractors, or from the breach of Lessor's
                  obligations or representations under this Lease. The
                  provisions of this clause (g) shall survive the expiration
                  or termination of this Lease;


                                      -19-


<PAGE>


         (h)      to permit Lessor and Lessor's agents to examine the Premises
                  at reasonable times (provided 24 hours' notice is given to
                  Lessee, except in case of emergency), and if Lessor shall so
                  elect (without hereby imposing any obligation on Lessor to
                  do so), to permit Lessor to make any repairs or additions
                  Lessor may deem necessary; and at Lessee's expense to remove
                  any Alterations, signs, awnings, aerials, flagpoles or the
                  like not consented to in writing; and to permit Lessor to
                  show the Premises to prospective purchasers and lessees (at
                  reasonable times on reasonable advance notice to Lessee) and
                  to keep affixed to any suitable part of the Premises, during
                  the nine (9) months preceding the expiration of the Term,
                  appropriate notices for letting or selling; any entry by
                  Lessor onto the Premises, whether made pursuant to this
                  paragraph or otherwise, shall be made in accordance with
                  Lessee's reasonable standard operating procedures as set
                  forth in writing and previously delivered to Lessor (but in
                  cases of emergencies Lessor shall be required only to use
                  reasonable efforts to comply with such standard operating
                  procedures);

         (i)      that all furniture, furnishings, fixtures and property of
                  every kind of Lessee and of all persons claiming by, through
                  or under Lessee which may be on the Premises from time to time
                  (collectively, "Lessee's Property") shall be at the sole risk
                  of Lessee, and Lessor shall not be liable if the whole or any
                  part thereof shall be destroyed or damaged by fire, water or
                  otherwise, or by the leakage or bursting of water pipes, steam
                  pipes, or other pipes, or by theft or from any other cause
                  unless caused by the negligence or willful misconduct of
                  Lessor, or its officers, agents, employees, servants or
                  contractors;

         (j)      to pay promptly when due, all taxes of any kind levied,
                  imposed or assessed on Lessee's Property, which taxes shall be
                  the sole obligation of Lessee, whether the same is assessed to
                  Lessee or to any other person and whether the property on
                  which such tax is levied, imposed or assessed shall be
                  considered part of the Premises or personal property;

         (k)      by the end of business on the last day of the Term (or the
                  effective date of any earlier termination of this Lease as
                  herein provided), to remove (1) all of Lessee's Property and
                  (2) the items or components of Alterations designated for
                  removal as provided in paragraph (f) above and (3) the items
                  or components of "Lessee's Work" designated for removal as
                  identified and described on EXHIBIT C, in each case whether
                  the same be permanently affixed to the Premises or not, and
                  to repair any damage caused by any such removal to Lessor's
                  reasonable satisfaction; and to remove the contents of all
                  neutralization tanks installed by Lessee in the Premises;
                  and peaceably to yield up the Premises clean and in good
                  order, repair and condition (reasonable wear and tear, and
                  damage by fire or other casualty or taking which Lessee is
                  not otherwise required by the terms of this Lease to repair
                  or replace only excepted); and to deliver the keys to the
                  Premises to Lessor. Any of Lessee's Property or those
                  Alterations designated for removal as provided in paragraph
                  (f) above which are not removed by such date shall be deemed
                  abandoned and may be removed and disposed of by Lessor in
                  such manner as Lessor may determine, and


                                      -20-


<PAGE>


                  Lessee shall pay to Lessor on demand, as Additional Rent, the
                  entire cost of such removal and disposition, together with the
                  costs and expenses incurred by Lessor in making any incidental
                  repairs and replacements to the Premises necessitated by
                  Lessee's failure to remove Lessee's Property or those
                  Alterations designated for removal as provided in paragraph
                  (f) above, as required herein, or by any other failure of
                  Lessee to comply with the terms of this Lease, and for use and
                  occupancy during the period after the expiration of the Term
                  and prior to Lessee's performance of its obligations under
                  this paragraph (k). Lessee shall further indemnify and hold
                  Lessor harmless from and against any and all suits, demands,
                  causes of action, claims, losses, debts, liabilities,
                  damages, penalties or judgments, including, without
                  limitation, reasonable attorneys' fees, resulting from
                  Lessee's failure or delay in surrendering the Premises as
                  above provided (such indemnity to survive the expiration or
                  termination of this Lease);

         (l)      to pay Lessor's reasonable expenses, including reasonable
                  attorneys' fees, incurred in enforcing any obligations of
                  Lessee under this Lease;

         (m)      not to generate, store or use any "Hazardous Materials" (as
                  hereinafter defined) in or on the Premises or elsewhere in
                  the Building or on the Land except those identified in
                  writing to Lessor from time to time, and then only in
                  compliance with any and all applicable Legal Requirements,
                  or dispose of Hazardous Materials from the Premises to any
                  other location except a properly approved disposal facility
                  and then only in compliance with any and all Legal
                  Requirements regulating such activity, nor permit any
                  occupant of the Premises to do so. As used in this Lease,
                  "Hazardous Materials" means and includes any chemical,
                  substance, waste, material, gas or emission which is
                  radioactive or deemed hazardous, toxic, a pollutant, or a
                  contaminant under any statute, ordinance, by-law, rule,
                  regulation, executive order or other administrative order,
                  judgment, decree, injunction or other judicial order of or
                  by any governmental authority, now or hereafter in effect,
                  relating to pollution or protection of human health or the
                  environment. By way of illustration and not limitation,
                  "Hazardous Materials" includes "oil", "hazardous materials",
                  "hazardous waste", and "hazardous substance" as defined in
                  the Comprehensive Environmental Response, Compensation and
                  Liability Act, 42 U.S.C. Section 9601 ET SEQ., as amended,
                  the Resource Conservation and Recovery Act of 1976, 42
                  U.S.C. Section 6902 ET SEQ., as amended, and the Toxic
                  Substances Control Act, 15 U.S.C. 8601 et SEQ., as amended,
                  the regulations promulgated thereunder, and Massachusetts
                  General Laws, Chapter 21C and Chapter 21E and the
                  regulations promulgated thereunder. If, at any time during
                  the Term, any governmental authority requires testing to
                  determine whether there has been any release of Hazardous
                  Materials by Lessee or anyone claiming by, through or under
                  Lessee, then Lessee shall reimburse Lessor upon demand, as
                  Additional Rent, for the reasonable costs thereof. Lessee
                  shall execute affidavits, certifications and the like, as
                  may be reasonably requested by Lessor from time to time
                  concerning Lessee's best knowledge and belief concerning the
                  presence of Hazardous Materials in or on the Premises, the
                  Building or the Land. Lessor reserves the right to enter


                                      -21-


<PAGE>


                  the Premises at reasonable times (provided twenty-four (24)
                  hours' notice is given to Lessee, except in case of
                  emergency) to inspect the same for Hazardous Materials, such
                  entry to be subject to the provisions of paragraph (h)
                  above. Lessee's obligations under this paragraph (m) shall
                  include, if at any time during the Term Lessee or anyone
                  claiming by, through or under Lessee uses or stores
                  radioactive materials on the Premises, compliance with all
                  so-called "close-out" procedures of the Nuclear Regulatory
                  Commission or other federal, state or local governmental
                  authorities having jurisdiction over radioactive materials,
                  regardless of whether or not such procedures are completed
                  prior to the expiration or earlier termination of the Term.
                  Lessee shall indemnify, defend, and hold harmless Lessor,
                  and the holder of any mortgage on the Building or the Land,
                  from and against any claim, cost, expense, liability,
                  obligation or damage, including, without limitation,
                  attorneys' fees and the cost of litigation, arising from or
                  relating to the breach by Lessee or anyone claiming by,
                  through or under Lessee of the provisions of this clause
                  (m), and shall immediately discharge or cause to be
                  discharged any lien imposed upon the Building or the Land in
                  connection with any such claim. Lessor shall indemnify,
                  defend, and hold harmless Lessee from and against any claim,
                  cost, expense, liability, obligation or damage, including,
                  without limitation, reasonable attorneys' fees and the cost
                  of litigation, arising from or relating to the presence
                  (whether now existing or hereafter arising) of Hazardous
                  Materials in, under or on the surface of the Land other than
                  that resulting from the generation, storage or use of
                  Hazardous Materials on the Premises or elsewhere in the
                  Building or on the Land by Lessee, or by anyone claiming by,
                  through or under Lessee, or any officer, agent, servant,
                  employee, contractor or invitee of any of the foregoing.
                  Lessor shall indemnify, defend, and hold harmless Lessee
                  from and against any claim, cost, expense, liability,
                  obligation or damage, including without limitation,
                  reasonable attorneys' fees and the cost of litigation,
                  arising from or relating to the presence of Hazardous
                  Materials in the Building (i) as of the date of this Lease,
                  or (ii) thereafter arising and resulting from the
                  generation, storage or use of Hazardous Materials in the
                  Building by the Lessor or any officer, agent, servant,
                  employee, contractor or invitee of any of the foregoing. The
                  provisions of this paragraph (m) shall survive the
                  expiration or termination of this Lease;

         (n)      not knowingly to permit any officer, agent, employee, servant,
                  contractor or visitor of Lessee, or of anyone claiming by,
                  through or under Lessee, to violate any covenant or obligation
                  of Lessee hereunder; and

         (o)      to provide and pay for the services outlined in EXHIBIT E
                  attached hereto.

12.0     Intentionally Omitted.

13.0     CASUALTY AND EMINENT DOMAIN.

         13.1     SUBSTANTIAL TAKING. In the event that the entire Building, or
                  more than fifty percent (50%) percent of the rentable area of
                  the Premises, shall be taken by any exercise of


                                      -22-


<PAGE>


                  the right of eminent domain or other lawful power in
                  pursuance of any public or other authority during the Term,
                  then this Lease shall terminate as of the time that
                  possession is taken by the taking authority. Further, in the
                  event that a material portion of the Premises is so taken
                  such that Lessee, in good faith, reasonably determines that
                  the remainder of the Premises will no longer be usable by
                  Lessee for the conduct of its normal business operations,
                  then Lessee shall have the right to terminate this Lease by
                  written notice to Lessor, in which case this Lease shall
                  terminate as of the time that possession is taken by the
                  taking authority.

         13.2     PARTIAL TAKING In the event that a taking occurs and this
                  Lease is not terminated as provided in Section 13.1 above,
                  then from and after the date possession is taken by the taking
                  authority Rent shall be abated by an amount representing that
                  part of the Rent properly allocable to the portion of the
                  Premises so taken, but this Lease shall otherwise continue in
                  full force and effect.

         13.3     AWARDS. Lessor reserves and excepts all rights to damage to
                  the Premises, the Building, the Land and the leasehold hereby
                  created, now accrued or hereafter accruing by reason of any
                  exercise of eminent domain, or by reason of anything lawfully
                  done in pursuance of any public or other authority and by way
                  of confirmation, Lessee grants to Lessor all of Lessee's
                  rights to such damages and covenants to execute and deliver
                  such further instruments of assignment thereof as Lessor may
                  from time to time request.

         13.4     SUBSTANTIAL CASUALTY. If the Premises are damaged by fire or
                  other casualty, Lessee shall promptly notify Lessor thereof.
                  If the Building or any part thereof shall be damaged by fire
                  or other casualty to the extent that substantial alteration or
                  reconstruction of the Building shall, in Lessor's sole
                  opinion, be required (whether or not the Premises shall have
                  been damaged), or if such casualty renders more than
                  thirty-three (33%) percent of the rentable area of the
                  Premises unusable by Lessee for the operation of its business
                  in the Premises, or if as a result of such casualty any
                  mortgagee of the Building requires that insurance proceeds
                  payable in connection with such casualty be used to retire the
                  mortgage debt, Lessor may, at its option, terminate this Lease
                  by notifying Lessee in writing of such termination within
                  sixty (60) days after the date of such damage, in which event
                  this Lease shall terminate on the date set forth in such
                  notice. If, in the reasonable determination of Lessee, such
                  casualty renders more than thirty-three (33%) percent of the
                  rentable area of the Premises unusable by Lessee for the
                  operation of its business in the Premises, or deprives Lessee
                  of all reasonable access to the Premises, then Lessee may
                  terminate this Lease as of the date of the occurrence of such
                  damage by written notice thereof to Lessor within sixty (60)
                  days after the date of such damage. In the event that this
                  Lease is terminated pursuant to this Section 13.4 Rent shall
                  be abated, to the extent the Premises are unusable for the
                  Permitted Uses, from and after the date of such damage to the
                  date of such termination of this Lease, and no further Rent
                  shall accrue or be payable after the date of such termination.


                                      -23-


<PAGE>


         13.5     REPAIR AND RESTORATION. In the event of a taking which does
                  not result in the termination of this Lease pursuant to
                  Section 13.1 above, or a casualty which does not result in the
                  termination of this Lease pursuant to Section 13.4 above, the
                  Premises shall be repaired and restored in the manner provided
                  in this Section. Lessor shall diligently act to restore the
                  Building and the Premises (exclusive of all items or
                  components of Lessee's Work or Alterations which Lessee is by
                  this Lease either entitled to or required to remove upon the
                  expiration or earlier termination of this Lease, and Lessee's
                  Property) or, in case of taking, what remains thereof, to
                  substantially the condition in which they existed prior to the
                  occurrence of such taking or casualty, provided, however,
                  that: (i) in no event shall Lessor be required to spend in
                  connection with restoring the Premises more than the amount of
                  insurance proceeds or taking award actually received and
                  allocable thereto (except that this limitation with respect to
                  insurance proceeds shall not apply to casualties occurring
                  during such time as Lessor self-insures pursuant to Section
                  7.4 above or to the extent Lessor insures the Premises for
                  less than full replacement value as set forth in Section 7.4);
                  (ii) Lessor shall not be required to restore or replace any of
                  Lessee's Work or any Alterations which Lessee is by this Lease
                  either entitled to or required to remove upon the expiration
                  or earlier termination of this Lease; (iii) Lessor shall not
                  be required to restore or replace any of Lessee's Property;
                  and (iv) promptly upon substantial completion of such work by
                  Lessor, Lessee shall diligently act to repair and/or restore
                  all of Lessee's Property and all items or components of
                  Lessee's Work or Alterations which Lessee is by this Lease
                  either entitled to or required to remove upon the expiration
                  or earlier termination of this Lease, to substantially the
                  same condition they were in prior to the occurrence of such
                  taking or casualty. Lessor shall not be liable for any
                  inconvenience or annoyance to Lessee or injury to the business
                  of Lessee resulting in any way from such taking or damage or
                  the repair thereof. Rent shall be abated from and after the
                  date of such taking or damage to the date on which Lessor
                  substantially completes the restoration described above, to
                  the extent the Premises are unusable for the Permitted Uses.

                  In the event that, having commenced its repair, restoration
                  and reconstruction work pursuant to this Section 13.5, Lessor
                  fails to substantially complete such work either (i) within
                  six (6) months from the date of such casualty, with respect to
                  work to be performed within the Premises, or (ii) nine (9)
                  months from the date of such casualty, with respect to work to
                  be performed elsewhere in the Building which is required for
                  the operation of Lessee's business in the Premises (which
                  periods shall be extended for any delays suffered by Lessor as
                  the result of Force Majeure or the acts or omissions of
                  Lessee, its employees, agents, contractors or servants),
                  Lessee shall have the further right to terminate this Lease on
                  at least thirty (30) days' prior written notice to Lessor,
                  such notice to be given within thirty (30) days of the
                  expiration of such six (6) or (9) month period (as
                  applicable).


                                      -24-


<PAGE>


         13.6     CASUALTY DURING LAST 18 MONTHS. Notwithstanding anything to
                  the contrary contained in this Lease, in the event that a
                  material portion of the Premises is damaged by a fire or other
                  casualty occurring during the last (18) eighteen months of the
                  Lease Term such that Lessor reasonably determines that Lessor
                  will not be able to substantially complete the repair,
                  restoration or reconstruction of the Premises within three (3)
                  months of the date of such casualty, Lessor shall so notify
                  Lessee and Lessee shall have the right, within thirty (30)
                  days after its receipt of Lessor's notice, to terminate this
                  Lease on thirty (30) days prior written notice to Lessor.
                  However, if Lessee has exercised an Extension Option prior to
                  the occurrence of such casualty or thereafter exercises an
                  Extension Option within the time period allowed therefor under
                  Section 2.2, then this Section 13.6 shall not apply and
                  neither party shall have the right to terminate this Lease
                  pursuant to this Section 13.6.

14.0     DEFAULTS; EVENTS OF DEFAULT; REMEDIES.

         14.1     DEFAULTS; EVENTS OF DEFAULT. The following shall, if any
                  requirement for notice or lapse of time or both has not been
                  met, constitute defaults hereunder, and, if such requirements
                  have been met, constitute "Events of Default" hereunder:

                  (a)      The failure of Lessee to perform or observe any of
                           Lessee's covenants or agreements hereunder concerning
                           the payment of money for a period of ten (10) days
                           after written notice thereof, PROVIDED, HOWEVER, that
                           Lessee shall not be entitled to such notice if Lessor
                           has given notice to Lessee of two or more previous
                           such failures within a twelve-month period, in which
                           event such failure shall constitute an Event of
                           Default hereunder upon the expiration of ten (10)
                           days after such payment was due;

                  (b)      The failure of Lessee to maintain the insurance
                           required hereunder in full force and effect;

                  (c)      The execution by Lessee of any assignment or sublease
                           without the prior written consent of Lessor;

                  (d)      The failure of Lessee to perform or observe any of
                           Lessee's other covenants or agreements hereunder for
                           a period of thirty (30) days after written notice
                           thereof (provided that, in the case of defaults not
                           reasonably curable in thirty (30) days through the
                           exercise of reasonable diligence, such 30-day period
                           shall be extended for so long as Lessee commences
                           cure within such period and thereafter prosecutes
                           such cure to completion continuously and with
                           reasonable diligence; or

                  (e)      If the leasehold hereby created shall be taken on
                           execution, or by other process of law, and such
                           taking is not vacated by a final order of a court of
                           competent jurisdiction within sixty (60) days
                           thereafter; or if any assignment shall be made of
                           Lessee's property for the benefit of creditors; or if
                           a receiver, guardian, conservator, trustee in
                           bankruptcy or similar officer shall


                                      -25-


<PAGE>


                           be appointed to take charge of all or any part of
                           Lessee's assets by a court of competent jurisdiction,
                           and such appointment is not vacated by a final order
                           of a court of competent jurisdiction within sixty
                           (60) days thereafter; or if a petition is filed by
                           Lessee under any bankruptcy or insolvency law; or if
                           a petition is filed against Lessee under any
                           bankruptcy or insolvency law and the same shall not
                           be dismissed within sixty (60) days from the date
                           upon which it is filed; or a lien or other
                           involuntary encumbrance is filed against Lessee's
                           leasehold (or against the Premises, the Building or
                           the Land based on a claim against Lessee) and is not
                           discharged or bonded within thirty (30) days after
                           the filing thereof.

         14.2     TERMINATION. If an Event of Default shall occur, Lessor may,
                  at its option, immediately or any time thereafter and without
                  demand or notice, enter upon the Premises or any part thereof
                  in the name of the whole and repossess the same as of Lessor's
                  former estate and dispossess Lessee and those claiming through
                  or under Lessee and remove their effects, without being deemed
                  guilty of any manner of trespass and without prejudice to any
                  remedies which might otherwise be used for arrears of rent or
                  preceding breach of covenant, and upon such entry this Lease
                  shall terminate. In lieu of making such entry, Lessor may
                  terminate this Lease upon ten (10) business days' prior
                  written notice to Lessee. Upon any termination of this Lease
                  as the result of an Event of Default, Lessee shall quit and
                  peacefully surrender the Premises to Lessor.

         14.3     SURVIVAL OF COVENANTS. No such termination of this Lease shall
                  relieve Lessee of its liability and obligations under this
                  Lease and such liability and obligations shall survive any
                  such termination. Lessee shall indemnify and hold Lessor
                  harmless from all loss, cost, expense, damage or liability
                  arising out of or in connection with such termination.

         14.4     DAMAGES. In the event of any such termination Lessee shall pay
                  to Lessor the Rent up to the time of such termination. Lessee
                  shall remain liable for, and shall pay on the days originally
                  fixed for such payment hereunder, the full amount of all Basic
                  Rent and Additional Rent as if this Lease had not been
                  terminated; PROVIDED, HOWEVER, if Lessor relets the Premises,
                  there shall be credited against such obligation the amount
                  actually received by Lessor each month from such lessee after
                  first deducting all costs and expenses incurred by Lessor in
                  connection with reletting the Premises.

                  Lessee further agrees to pay to Lessor, on demand, as and for
                  liquidated and agreed damages for Lessee's default, the amount
                  (discounted to present value at a discount rate equal to the
                  then-current yield on United States Treasury securities with a
                  maturity closest to what would have been the last day of the
                  Term if this Lease had not been terminated) by which:


                                      -26-


<PAGE>


                           (a)      the aggregate Rent which would have been
                                    payable under this Lease by Lessee from the
                                    date of such termination until what would
                                    have been the last day of the Term but for
                                    such termination, EXCEEDS

                           (b)      the greater of (i) the fair and reasonable
                                    rental value of the Premises for the same
                                    period, less Lessor's reasonable estimate of
                                    expenses to be incurred in connection with
                                    reletting the Premises, including, without
                                    limitation, all repossession costs,
                                    brokerage commissions, legal expenses,
                                    reasonable attorneys' fees, alteration
                                    costs, and expenses of preparation for
                                    such reletting, or (ii) the sum of (A) the
                                    amount actually received by Lessor from
                                    reletting the Premises (if any), and (B) the
                                    amount actually received by Lessor from
                                    Lessee pursuant to the preceding paragraph
                                    of this Section (if any).

                  If the Premises or any part thereof are relet by Lessor for
                  the period prior to what would have been the last day of the
                  Term but for such termination, or any portion thereof, the
                  amount of rent reserved upon such reletting shall be, PRIMA
                  FACIE, the fair and reasonable rental value for the part or
                  the whole of the Premises so relet during the term of the
                  reletting.

                  In lieu of any other damages hereunder, Lessor may by written
                  notice to Lessee, at any time within one (1) year after this
                  Lease is so terminated, elect to recover, and Lessee shall pay
                  as full and final liquidated damages, an amount equal to (i)
                  the Basic Rent and Additional Rent accrued under Sections 3.0
                  and 5.0 hereof respectively in the twelve (12) months ending
                  on the effective date of such termination, PLUS (ii) all Basic
                  Rent and Additional Rent which was unpaid as of the effective
                  date of such termination, LESS (iii) the amount received by
                  Lessor pursuant to the foregoing provisions of this Section
                  14.4 prior to the time of payment by Lessee of such liquidated
                  damages.

                  Nothing herein contained shall limit or prejudice the right of
                  Lessor to prove and obtain as liquidated damages by reason of
                  such termination, 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, such damages are to be
                  proved, whether or not such amount be greater, equal to, or
                  less than the amount of the difference referred to above.

         14.5     RIGHT TO RELET. At any time or from time to time after any
                  such termination, Lessor may relet the Premises or any part
                  thereof for such a term (which may be greater or less than the
                  period which would otherwise have constituted the balance of
                  the Term) and on such conditions (which may include
                  concessions or free rent) as Lessor, in its reasonable
                  discretion, may determine, and may collect and receive the
                  rents therefor. Lessor shall in no way be responsible or
                  liable for any failure to relet the Premises or any part
                  thereof, or for any failure to collect any rent due upon any
                  such reletting.


                                      -27-


<PAGE>


         14.6     RIGHT TO EQUITABLE RELIEF. In the event there shall occur an
                  Event of Default hereunder, Lessor shall be entitled to seek
                  to enjoin the continuation of the same and shall have the
                  right to invoke any right and remedy allowed at law or in
                  equity or by statute or otherwise as though re-entry and other
                  remedies were not provided for in this Lease.

         14.7     RIGHT TO SELF HELP. In the event of an Event of Default by
                  Lessee hereunder, Lessor shall have the right to perform such
                  defaulted obligation of Lessee, including the right to enter
                  upon the Premises to do so. Lessor shall, as a courtesy only,
                  notify Lessee of its intention to perform such obligation. In
                  the event of a default by Lessee hereunder which has not yet
                  continued beyond the expiration of the applicable grace period
                  but which Lessor determines constitutes an emergency
                  threatening imminent injury to persons or damage to property,
                  Lessor shall have the right to perform such defaulted
                  obligation of Lessee (including the right to enter upon the
                  Premises to do so) after giving Lessee such notice (if any) as
                  is reasonable under the circumstances. In either event, the
                  aggregate of (i) all sums so paid by Lessor, (ii) interest (at
                  the rate set forth in Section 10.0 above or the highest rate
                  permitted by law, whichever is less) on such sum, and (iii)
                  all necessary incidental costs and expenses in connection with
                  the performance of any such act by Lessor, shall be deemed to
                  be Additional Rent under this Lease and shall be payable to
                  Lessor immediately upon demand. Lessor may exercise its rights
                  under this Section 14.7 without waiving any other of its
                  rights or releasing Lessee from any of its obligations under
                  this Lease.

         14.8     FURTHER REMEDIES. Nothing in this Lease contained shall
                  require Lessor to elect any remedy for a default or Event of
                  Default by Lessee hereunder, and all rights herein provided
                  shall be cumulative with one another and with any other rights
                  and remedies which Lessor may have at law or in equity in the
                  case of such a default or Event of Default.

15.0     REAL ESTATE BROKER. Lessor and Lessee each represent to the other that
         they have dealt with no broker in connection with this Lease other than
         Meredith and Grew, Inc. and Insignia ESG, Inc. (collectively, the
         "Brokers"). Lessor is not obligated to pay any commission or fee to
         Meredith and Grew, Inc. in connection with this transaction but has
         agreed to pay a commission to Insignia ESG, Inc. as set forth in a
         separate agreement. Lessee agrees to indemnify and hold Lessor harmless
         from and against any claims for commissions or fees by any person other
         than the Brokers by reason of any act of Lessee or its representatives.
         Lessor agrees to indemnify and hold Lessee harmless from and against
         any claims for commissions or fees by the Brokers or any other person
         by reason of any act of Lessor or its representatives.

16.0     NOTICES. Whenever by the terms of this Lease notice, demand, or other
         communication shall or may be given either to Lessor or to Lessee, the
         same shall be in writing and shall be sent by hand delivery, or by
         registered or certified mail, postage prepaid, or by Federal Express or
         other similar overnight delivery service, to:


                                      -28-


<PAGE>


         Lessor:                          Massachusetts Institute of Technology
                                          238 Main Street - Suite 200
                                          Cambridge, Massachusetts  02142
                                          Attention:  Steven C. Marsh
                                          Managing Director of Real Estate



                  with a copy to:         Stuart T. Freeland, Esquire
                                          Rackemann, Sawyer & Brewster
                                          One Financial Center
                                          Boston, Massachusetts 02111

         Lessee                           Millennium Pharmaceuticals, Inc.
                                          75 Sidney Street
                                          Cambridge, Massachusetts 02139
                                          Attention:General Counsel

                  with a copy to:         Katharine E. Bachman, Esquire
                                          Hale and Dorr
                                          Sixty State Street
                                          Boston, MA 02109

         Any notice, demand or other communication shall be effective upon
         receipt by or tender for delivery to the intended recipient thereof.

17.0     NO WAIVERS. Failure of Lessor to complain of any act or omission on the
         part of Lessee, no matter how long the same may continue, shall not be
         deemed to be a waiver by Lessor of any of its rights hereunder. No
         waiver by Lessor at any time, expressed or implied, of any breach of
         any provision of this Lease shall be deemed a waiver of a breach of any
         other provision of this Lease or a consent to any subsequent breach of
         the same or any other provision. No acceptance by Lessor of any partial
         payment shall constitute an accord or satisfaction but shall only be
         deemed a partial payment on account; nor shall any endorsement or
         statement on any check or any letter accompanying any check or payment
         be deemed an accord and satisfaction, and Lessor may accept such check
         or payment without prejudice to Lessor's right to recover the balance
         of such installment or pursue any other remedy available to Lessor in
         this Lease or at law or in equity.

18.0     SERVICES PROVIDED BY LESSOR. Lessor shall furnish the services
         described on EXHIBIT "D" attached, the cost of which shall be included
         in Operating Expenses. Lessor shall not be held liable to anyone for
         cessation of any service rendered customarily to the Premises or
         Building or agreed to by the terms of this Lease, due to any accident,
         to the making of repairs, alterations or improvements, or to the
         occurrence of an event of "Force Majeure" (as defined in Section 22
         below).


                                      -29-


<PAGE>


19.0     GROUND LEASES; MORTGAGES.

         19.1     RIGHTS OF GROUND LESSORS AND MORTGAGEES No act or failure to
                  act on the part of Lessor which would entitle Lessee under the
                  terms of this Lease, or by law, to be relieved of Lessee's
                  obligations hereunder or to terminate this Lease, shall result
                  in a release or termination of such obligations or a
                  termination of this Lease unless (i) Lessee shall have first
                  given written notice to Lessor's ground lessors and mortgagees
                  of record of the act or failure to act on the part of Lessor
                  which Lessee claims as the basis of Lessee's rights; and (ii)
                  such ground lessors and mortgagees, after receipt of such
                  notice, have failed or refused to correct or cure the
                  condition within a reasonable time thereafter, but nothing in
                  this Lease shall be deemed to impose any obligation on any
                  such ground lessor or mortgagee to correct or cure any such
                  condition. No ground lessor shall be liable for the failure to
                  perform any of the obligations of Lessor hereunder unless and
                  until such ground lessor terminates its ground lease and takes
                  possession of the Premises, nor shall any mortgagee be liable
                  for the failure to perform any of the obligations of Lessor
                  hereunder unless and until such mortgagee enters upon and
                  takes possession of the Premises for purposes of foreclosure.

         19.2     LEASE SUBORDINATE. This Lease is and shall be subject and
                  subordinate to any ground lease or mortgage now or hereafter
                  on the Premises, and to all advances under any such mortgage
                  and to all renewals, amendments, extensions and consolidations
                  thereof, provided that the holder of such ground lessor's
                  interest or mortgagee's interest enters into a non-disturbance
                  and attornment agreement with Lessee which provides that in
                  the event that such ground lessor or mortgagee succeeds to
                  Lessor's interest hereunder, then, provided that Lessee is not
                  in default hereunder beyond the cure period provided in this
                  Lease, such party shall recognize and be bound by the terms of
                  this Lease. In the event that any ground lessor or the holder
                  of any mortgage succeeds to Lessor's interest in the Premises
                  or any portion thereof, Lessee hereby agrees to attorn to such
                  ground lessor or mortgagee. In confirmation of such
                  subordination, Lessee shall execute and deliver promptly any
                  certificate in recordable form that Lessor or any ground
                  lessor or any mortgagee may reasonably request.
                  Notwithstanding the foregoing provisions of this Section, the
                  holder of any mortgage on the Premises may at any time
                  subordinate its mortgage to this Lease by written notice to
                  Lessee.

                  Lessor hereby represents to Lessee that as of the date of this
                  Lease, there are no mortgages or ground leases encumbering the
                  Premises or any portion thereof.

20.0     NOTICE OF LEASE; ESTOPPEL CERTIFICATES. Lessor and Lessee agree that
         this Lease shall not be recorded. However, upon the request of either
         party, Lessor and Lessee shall execute and acknowledge a Notice of
         Lease in mutually acceptable and recordable form.


                                      -30-


<PAGE>


         From time to time during the Lease Term, and without charge, either
         party shall, within fifteen (15) business days of request by the other,
         certify by written instrument duly executed and acknowledged, to the
         requesting party or to any person reasonably specified by the
         requesting party, regarding (a) the existence of any amendments or
         supplements to this Lease; (b) the validity and force and effect of
         this Lease; (c) the existence of any known default or Event of Default;
         (d) the existence of any offsets, counterclaims or defenses; (e) the
         Commencement Date and the expiration date of the Lease Term; (f) the
         amount of Rent due and payable and the date to which Rent has been
         paid; and (g) such other matters as may be reasonably requested.

21.0     HOLDING OVER. If Lessee occupies the Premises after the day on which
         the Lease Term expires (or the effective date of any earlier
         termination as herein provided) without having entered into a new lease
         thereof with Lessor, Lessee shall be a tenant-at-sufferance only,
         subject to all of the terms and provisions of this Lease at (i) two (2)
         times the then-effective Basic Rent stated in Section 3.0 above for the
         first three (3) months thereof, and (ii) thereafter, at three (3) times
         the then-effective Basic Rent stated in Section 3.0 above. Such a
         holding over, even if with the consent of Lessor, shall not constitute
         an extension or renewal of this Lease. For purposes of this Section,
         the failure of Lessee to complete by the last day of the Lease Term or
         the effective date of any earlier termination as herein provided the
         "close-out" procedures required by the Nuclear Regulatory Commission or
         any other federal, state or local governmental agency having
         jurisdiction over the use of radioactive materials within the Premises
         shall constitute a holding over and subject Lessee to the provisions of
         this Section.

22.0     FORCE MAJEURE. Neither Lessor nor Lessee shall be deemed to be in
         default hereunder (and the time for performance of any of their
         respective obligations hereunder other than the payment of money shall
         be postponed) for so long as the performance of such obligation is
         prevented by strike, lock-out, act of God, absence of materials or any
         other matter not reasonably within the control of the party which must
         perform the obligation (collectively, "Force Majeure").

23.0     ENTIRE AGREEMENT. No oral statement or prior written matter except the
         Existing Lease shall have any force or effect. This Agreement shall not
         be modified or canceled except by writing subscribed to by all parties.

24.0     SECURITY DEPOSIT. Lessee has deposited with Lessor $80,732.00 (the
         "Security Deposit") as security for the full and faithful payment and
         performance by Lessee of its obligations under this Lease from and
         after the date of execution hereof by Lessee, and not as a prepayment
         of Rent. Lessor may commingle the Security Deposit in one or more bank
         accounts with other funds of Lessor, and the Security Deposit shall
         earn interest at the rate actually paid to Lessor from time to time on
         such account (which interest shall be included in the term "Security
         Deposit" for the purposes of this Lease). Lessor may use the Security
         Deposit to cure any Event of Default by Lessee (whether occurring prior
         to the Commencement Date hereunder or thereafter), and Lessee shall
         immediately pay to Lessor on demand, as Additional Rent, the amount so
         expended and such additional amount as is required to cause the
         Security Deposit at all times to equal the amount set forth above.
         Lessor shall


                                      -31-


<PAGE>


         assign the Security Deposit to any successor owner of the Building and
         thereafter Lessor shall have no further responsibility therefor. Upon
         the expiration (or earlier termination) of the Lease Term, Lessor shall
         inspect the Premises, make such deductions from the Security Deposit as
         may be required to cure any Event of Default by Lessee hereunder, and,
         if Lessee is not then in default hereunder, pay the balance of the
         Security Deposit, if any, to Lessee within thirty (30) days of such
         expiration or termination. If Lessee is in default hereunder at the
         time of such expiration or termination, then Lessor shall be entitled
         to retain so much of the Security Deposit as Lessor reasonably
         estimates to be Lessee's liability to Lessor hereunder and shall pay
         the balance, if any, to Lessee within such 30-day period.

25.0     SATELLITE DISH. Lessee shall have the right to maintain the existing
         satellite dish antenna not exceeding twenty-four (24) inches in
         diameter on the roof of the Building provided that:

         (a)      such antenna shall be used solely by Lessee and those
                  occupying all or portions of the Premises pursuant to an
                  assignment or sublease with Lessee made in accordance with the
                  provisions of Section 8.0 of this Lease, unless Lessor
                  otherwise agrees in writing;

         (b)      to the extent to which the issuer of the warranty on the roof
                  requires, as a condition to the continued validity of such
                  warranty, that only contractors approved by such issuer
                  perform work on the roof, Lessee shall employ only such
                  contractors as are approved by such issuer and shall submit
                  evidence of such approval to Lessor reasonably satisfactory to
                  Lessor prior to commencing any work on the roof;

         (c)      Lessee shall, at its sole cost, maintain such antenna in good
                  operating condition and in accordance with all applicable
                  Legal Requirements, the provisions of applicable insurance
                  policies, and the requirements of all existing restrictions,
                  easements and encumbrances of record affecting the Land; and

         (d)      Lessee shall, at its sole cost, remove such antenna on or
                  prior to the date on which the Term expires or this Lease is
                  terminated, and shall restore the surface of the roof to the
                  condition in which it was prior to the installation of such
                  antenna, again using only such contractor as is approved by
                  the issuer of the warranty covering the roof of the Building,
                  and Lessee shall submit evidence of such approval to Lessor
                  reasonably satisfactory to Lessor prior to commencing any work
                  on the roof.


                  "All work done by or on behalf of Lessee pursuant to this
                  Section 25.0 shall be subject to the requirements set forth
                  elsewhere in this Lease with respect to the performance of
                  Alterations. Lessor may inspect such work at any time or times
                  and shall promptly give notice to Lessee of any observed
                  defects. Lessee shall


                                      -32-


<PAGE>


                  indemnify, defend and hold harmless Lessor from and against
                  any and all liability, damage, penalties or judgments and from
                  and against any claims, actions, proceedings and expenses and
                  costs in connection therewith, including reasonable attorneys'
                  fees, resulting from any work performed by or on behalf of
                  Lessee pursuant to this Section 25.0. Such antenna shall be at
                  Lessee's sole risk, Lessor shall have no responsibility to
                  maintain any insurance on it, and Lessor shall not otherwise
                  be responsible for any damage or destruction to such antenna
                  unless such damage or destruction is caused by Lessor's
                  negligence."

26.0     EXISTING LEASE. The Existing Lease as it may hereafter be amended,
         shall remain in full force and effect until the Commencement Date
         hereunder after which the obligations of the parties in respect to the
         Premises, the Building and the Land shall be governed by this Lease
         except for obligations under the Existing Lease which, in accordance
         with its terms, are intended to survive its expiration. Notwithstanding
         the foregoing, if an Event of Default occurs under the Existing Lease
         prior to the Commencement Date hereunder, then, for the purpose of
         calculating damages under the Existing Lease, the remaining term of the
         Existing Lease will be deemed to include the Term of this Lease at the
         Rent set forth in Sections 3.0 and 5.0 hereof.

27.0     SUCCESSORS AND ASSIGNS. The terms, covenants and conditions of this
         Lease shall run with the Land, and be binding upon and inure to the
         benefit of Lessor and Lessee and their respective successors and
         permitted assigns.

28.0     APPLICABLE LAW, SEVERABILITY AND CONSTRUCTION. This Lease shall be
         governed by and construed in accordance with the laws of Massachusetts
         and, if any provisions of this Lease shall to any extent be invalid,
         the remainder of this Lease, and the application of such provisions in
         other circumstances, shall not be affected thereby. The titles of the
         several Sections contained herein are for convenience only and shall
         not be considered in construing this Lease. Whenever the singular is
         used and when required by the context it shall include the plural, and
         the neuter gender shall include the masculine and feminine. The
         Exhibits attached to this Lease are incorporated into this Lease by
         reference. This Lease may be executed in several counterparts, each of
         which shall be an original, but all of which shall constitute one and
         the same instrument. The term "Lessor" whenever used herein, shall mean
         only the owner at the time of Lessor's interest herein, and no covenant
         or agreement of Lessor, express or implied, shall be binding upon any
         person except for defaults occurring during such person's period of
         ownership nor binding individually upon any fiduciary, any shareholder,
         officer or director, or any beneficiary under any trust, and the
         liability of Lessor, in any event, shall be limited to Lessor's
         interest in the Building. If Lessee is several persons or a
         partnership, Lessee's obligations are joint or partnership and also
         several. Unless repugnant to the context, "Lessor" and "Lessee" mean
         the person or persons, natural or corporate, named above as Lessor and
         as Lessee respectively, and their respective heirs, executors,
         administrators, successors and assigns.

29.0     AUTHORITY. Contemporaneously with the signing of this Lease, Lessee
         shall furnish to Lessor a certified copy of the resolution of the Board
         of Directors of Lessee authorizing


                                      -33-


<PAGE>


         Lessee to enter into this Lease, and Lessor shall furnish appropriate
         evidence of the authority of Lessor to enter into this Lease

         WITNESS the execution hereof in counterparts under seal the day and
year first above written.


         LESSOR:                                 MASSACHUSETTS INSTITUTE OF
                                                 TECHNOLOGY


                                           By:   /s/ STEVEN C. MARSH
                                                 Steven C Marsh, its Managing
                                                 Director of Real Estate
                                                 Hereunto duly authorized


         LESSEE:                                 MILLENNIUM PHARMACEUTICALS,
                                                 INC.


                                           By:   /s/ KEVIN P. STARR
                                                 Kevin P. Starr
                                                 Chief Financial Officer
                                                 Hereunto duly authorized




                                      -34-


<PAGE>


                                    EXHIBIT A

                                    PREMISES

                               [see attached plan]

[graphic]





                                      -35-


<PAGE>


                                    EXHIBIT B

                                    SITE PLAN

                               [see attached plan]

[graphic]




                                      -36-


<PAGE>


                                    EXHIBIT C

                          ITEMS DESIGNATED FOR REMOVAL

                               [see attached copy]




                                      -37-


<PAGE>


                                    EXHIBIT D

                           SERVICES PROVIDED BY LESSOR

         This Exhibit is incorporated by reference into the Lease dated December
1, 2000 by and between Massachusetts Institute of Technology, as Lessor, and
Millennium Pharmaceuticals, Inc., as Lessee. Terms defined in or by reference in
the Lease not otherwise defined herein shall have the same meaning herein as
therein.

Lessor shall provide the following services at the Building:

1.       Heating and air conditioning services for the Premises as demised at
         the start of the Term for normal office operations between the hours of
         8:00 a.m. and 6:00 p.m., Monday through Friday, except on national or
         state holidays. Excluded from such services are air conditioning
         requirements for computers or other exceptional office machinery. If
         Lessee requests air conditioning or heating services at hours other
         than those set forth above, Lessor shall provide such service, and
         Lessee shall pay Lessor's costs to furnish such service as Additional
         Rent.

2.       Maintenance of the following:

                  All Building heating equipment, electrical equipment, and
                  plumbing systems in public areas only; all Building air
                  conditioning equipment, excluding special air conditioning
                  equipment; all window frames and glass, unless the damage to
                  any of the above is caused by the willful neglect or misuse by
                  Lessee.

3.       Nightly (Monday-Friday) cleaning of the public corridors, stairwells,
         lobbies, bathrooms; and cleaning of the windows, both inside and out,
         two (2) times per year.

4.       Extermination of all public and tenanted areas of the Building, as the
         management of the Building deems necessary.

5.       Structural maintenance of the Premises including repairs to the roof,
         exterior walls of the building and structural damage to the floors.

6.       Lettering for up to a maximum of three names in the Building directory
         located in the main lobby.

7.       Snow removal, landscaping maintenance, cafeteria management, and other
         services as deemed necessary by Lessor for the normal operation of the
         Building.

8.       Security for the Building as reasonably determined by Lessor after
         consulting with Lessee and other tenants in the Building.


                                      -38-


<PAGE>







                                    EXHIBIT E

                           SERVICES PROVIDED BY LESSEE

         This Exhibit is incorporated by reference into the Lease dated December
1, 2000 by and between Massachusetts Institute of Technology, as Lessor, and
Millennium Pharmaceuticals, Inc., as Lessee. Terms defined in or by reference in
the Lease not otherwise defined herein shall have the same meaning herein as
therein.


         Lessee shall provide and pay for all maintenance of and repairs to the
Premises necessary to keep the Premises in good condition or in as good a
condition as the Premises were at the beginning of the Term or may be put in
thereafter (damage from taking or casualty or reasonable wear and tear only
excepted). Such repairs and maintenance shall include but not be limited to the
following:

          A.   The maintenance and repair of any plumbing systems within the
               Premises (and serving solely the Premises), and the repair of any
               damage to the Premises or to the Building caused by the
               malfunction of such plumbing systems;

          B.   The maintenance and repair of all electrical wiring, outlets,
               switches and light fixtures within the Premises (and serving
               solely the Premises);

          C.   The maintenance and repair of all hardware within the Premises;

          D.   The maintenance and repair of all walls, doors, ceilings, and
               floors.

          E.   The replacement of fluorescent light tubes and ballasts. This
               service is available through Building management on a time and
               materials basis.





                                      -1-


<PAGE>


                                    EXHIBIT F

                      COPY OF LESSOR'S CERTIFICATE OF TITLE

         This Exhibit is incorporated by reference into the Lease dated December
1, 2000 by and between Massachusetts Institute of Technology, as Lessor, and
Millennium Pharmaceuticals, Inc., as Lessee. Terms defined in or by reference in
the Lease not otherwise defined herein shall have the same meaning herein as
therein.


                               [See attached copy]





                                      -1-


<PAGE>


                                    EXHIBIT G

                       LOCATION OF OFF SITE PARKING SPACES

                               [see attached plan]

[graphic]



                                       -2-


<PAGE>


                                    EXHIBIT H

                                TENANT STANDARDS

                               [see attached copy]



                                      -3-