<PAGE>   1
                                                                   Exhibit 10.57

                            SIXTH AMENDMENT TO LEASE


         THIS SIXTH AMENDMENT TO LEASE ("Amendment") is made as of the 29th day
of January, 1999 by and between MASSACHUSETTS INSTITUTE OF TECHNOLOGY, a
Massachusetts educational corporation with an address of 238 Main Street,
Cambridge, Massachusetts 02142 ("Lessor"), and MILLENNIUM PHARMACEUTICALS, INC.,
a Delaware corporation with an address of 640 Memorial Drive, Cambridge,
Massachusetts 02139 ("Lessee").

         Reference is made to a lease dated August 26, 1993 by and between
Lessor and Lessee, as amended by amendments dated as of May 18, 1994, January 9,
1996, June 12, 1996, March 1, 1997 and June 19, 1997 (collectively, the
"Lease"), concerning certain premises located at 640 Memorial Drive, Cambridge,
Massachusetts, as more particularly described in the Lease. A Notice of Lease
was filed with the Middlesex Southern Registry District of the Land Court on
March 2, 1994 as Document No. 939638, and noted on Certificate of Title No.
89497, as amended. Capitalized terms used in this Amendment which are defined in
the Lease and not otherwise defined herein shall have the same meaning in this
Amendment as in the Lease.

         Lessee desires (i) to lease approximately 75,450 square feet of
rentable area on the first and second floors of the Building as shown on the
plans attached hereto, collectively, as Exhibit I, currently occupied by
Lifeline Systems, Inc. ("Lifeline") (the "Additional Expansion Premises") and
(ii) to expand the Basement Space to include approximately 8,861 additional
square feet of rentable area approximately in the location shown on the plan
attached hereto as Exhibit II. Lessor is willing so to lease to Lessee the space
on the first and second floors of the Building and such additional Basement
Space, on the terms and conditions set forth in this Amendment.

         FOR GOOD AND VALUABLE CONSIDERATION, the receipt and legal sufficiency
of which are hereby acknowledged, Lessor and Lessee hereby agree to amend the
Lease as follows:

         1. Definitions. For purposes of the Lease, the following terms shall
have the meaning set forth opposite them:

                  "Area A" shall mean the portion of the Additional Expansion
                  Premises marked as "Area A" on Exhibit I, containing 51,353
                  square feet of rentable area.

                  "Area B" shall mean the portion of the Additional Expansion
                  Premises marked as "Area B" on Exhibit I, containing 24,097
                  square feet of rentable area.

                  "Area A Commencement Date" shall mean the date on which Lessor
                  delivers Area A to Lessee, free of occupants but otherwise in
                  the condition in which such space is redelivered to Lessor by
                  Lifeline, which date shall be 
<PAGE>   2

                  fifteen (15) days after Lifeline vacates Area A and delivers
                  possession thereof to Lessor.

                  "Area B Commencement Date" shall mean the date on which Lessor
                  delivers Area B to Lessee, free of occupants but otherwise in
                  the condition in which such space is redelivered to Lessor by
                  Lifeline, which date shall be fifteen (15) days after Lifeline
                  vacates Area B and delivers possession thereof to Lessor.

                  "Basement Space" shall mean, from and after the Second
                  Additional Basement Space Commencement Date, collectively the
                  Basement Space, as that term was amended and defined in the
                  Lease prior to this Amendment, together with the Second
                  Additional Basement Space.

                  "Office Tenant Improvement Costs" shall mean the actual
                  out-of-pocket costs and expenses paid by Lessee to third
                  parties in connection with the construction of alterations or
                  improvements to the Additional Expansion Premises to prepare
                  the same for office use by Lessee, which alterations and
                  improvements are intended to become part of the Building and
                  are not to be removed by Lessee. As an example but not in
                  limitation of the foregoing, there shall be excluded from
                  Office Tenant Improvement Costs (a) all costs and expenses
                  paid in connection with the construction of alterations or
                  improvements to the Additional Expansion Premises to prepare
                  the same for any use by Lessee other than office use
                  (including, without limitation, laboratory, research or
                  manufacturing use), (b) all costs and expenses paid in
                  connection with the Second Additional Basement Space, and (c)
                  all furniture costs. For purposes of the Lease, in no event
                  shall Office Tenant Improvement Costs exceed $17.50 per square
                  foot of rentable area of the Additional Expansion Premises
                  leased by Lessee hereunder.

                  "Second Additional Basement Space" shall mean that portion of
                  the basement floor of the Building containing approximately
                  8,861 square feet of rentable area shown cross-hatched on the
                  plan attached hereto as Exhibit II.

                  "Second Additional Basement Space Commencement Date" shall
                  mean the earlier of (i) the date on which the Second
                  Additional Basement Space is ready for occupancy by Lessee, or
                  (ii) February 15, 1999.

                  "Unamortized Office Tenant Improvement Amount" shall mean, as
                  of the date such determination is being made, the remaining
                  unamortized portion of Lessee's Office Tenant Improvement
                  Costs, amortized on a straight line basis over a period of
                  nine (9) years commencing on the Area A Commencement Date.




                                       2
<PAGE>   3

         2.       Delivery of Additional Expansion Premises to Lessee.

                  (a) Effective as of the Area A Commencement Date, Area A shall
                  be deemed to be part of the Premises for all purposes of the
                  Lease, without the necessity of any further written instrument
                  or other action by the parties, and all rights and obligations
                  of the parties under the Lease with respect to the Premises
                  shall apply equally to Area A. It is the current expectation
                  of Lessor and Lessee that the Area A Commencement Date will
                  occur between February 1, 1999 and March 1, 1999. Lessee
                  hereby acknowledges that Lifeline has given notice that it
                  intends to vacate Area A on or about January 31, 1999, so the
                  anticipated Area A Commencement Date is February 15, 1999.
                  From and after the date on which Lifeline vacates Area A, and
                  while Lifeline is removing its property therefrom, until the
                  Area A Commencement Date, Lessee shall have the right to enter
                  upon Area A to commence preparations for its occupancy
                  thereof, which entry shall be subject to all of the terms of
                  the Lease other than the obligation to pay Rent on account of
                  Area A. Lessee hereby agrees that any delay in the
                  construction of the temporary demising partition separating
                  Area A from Area B will not delay the Area A Commencement Date
                  hereunder. In the event that, for any reason whatsoever, the
                  Area A Commencement Date has not occurred by March 31, 1999,
                  Lessee shall have the right to terminate its obligation to
                  lease the Additional Expansion Premises by giving written
                  notice to Lessor, which termination shall be effective not
                  less than ten (10) days after the date on which such notice is
                  given to Lessor unless, prior to the expiration of such 10-day
                  period, the Area A Commencement Date occurs. Except as
                  otherwise set forth in clause (Y) below, Lessee's right so to
                  terminate its obligation to lease the Additional Expansion
                  Premises shall be Lessee's sole remedy hereunder or at law or
                  in equity for any such delay in the occurrence of the Area A
                  Commencement Date, and such termination shall not effect
                  Lessee's obligations under the Lease or Lessee's obligations
                  hereunder relating to the Second Additional Basement Space.

                  (b) Effective as of the Area B Commencement Date, Area B shall
                  be deemed to be part of the Premises for all purposes of the
                  Lease, without the necessity of any further written instrument
                  or other action by the parties, and all rights and obligations
                  of the parties under the Lease with respect to the Premises
                  shall apply equally to Area B. It is the current expectation
                  of Lessor and Lessee that the Area B Commencement Date will
                  occur between July 1, 1999 and August 1, 1999. In the
                  "Lifeline Termination Agreement" (defined below), Lessor has
                  required Lifeline to use reasonable efforts to give Lessor and
                  Lessee seven (7) days' advance notice of the date on which it
                  will vacate Area B. From and after the date on which Lifeline
                  vacates Area B, and while Lifeline is removing its property
                  therefrom, until the Area B Commencement Date, Lessee shall
                  have the right to enter upon Area B to commence preparations
                  for its occupancy thereof, which entry shall be subject to all
                  of the terms of the Lease other than the obligation to pay
                  Rent on account of Area B. In the event that, for any reason
                  whatsoever, the 



                                       3
<PAGE>   4

                  Area B Commencement Date has not occurred by August 31, 1999,
                  Lessee shall have the right to terminate its obligation to
                  lease Area B only by giving written notice to Lessor, which
                  termination shall be effective not less than ten (10) days
                  after the date on which such notice is given to Lessor unless,
                  prior to the expiration of such 10-day period, the Area B
                  Commencement Date occurs. Except as otherwise set forth in
                  clause (Z) below, Lessee's right so to terminate its
                  obligation to lease Area B shall be Lessee's sole remedy
                  hereunder or at law or in equity for any such delay in the
                  occurrence of the Area B Commencement Date, and such
                  termination shall not effect Lessee's obligations under the
                  Lease or Lessee's obligations hereunder with respect to Area A
                  or the Second Additional Basement Space.

                  (c) Lessee acknowledges that (i) the Additional Expansion
                  Premises are currently occupied by Lifeline pursuant to a
                  lease between Lessor, as lessor, and Lifeline, as lessee (the
                  "Lifeline Lease"), and (ii) contemporaneously with the
                  execution and delivery of this Amendment, Lessor and Lifeline
                  shall execute and deliver an agreement (the "Lifeline
                  Termination Agreement") terminating the Lifeline Lease in
                  phases consistent with the delivery of the Additional
                  Expansion Premises to Lessee as provided in this Amendment.
                  Lessor hereby represents to Lessee that the Lifeline
                  Termination Agreement provides, in part, that:

                                            (A) Lessor may, at any time after
                           March 31, 1999, terminate such agreement in its
                           entirety and maintain the Lifeline Lease in full
                           force and effect if Area A is not surrendered and
                           redelivered to Lessor in accordance with the
                           provisions of the Lifeline Termination Agreement by
                           March 31, 1999;

                                            (B) Lifeline is required to pay the
                           sum of $7,500.00 per day to Lessor for each day after
                           March 1 until the earlier of (1) the day on which
                           Lifeline surrenders and redelivers Area A to Lessor
                           in accordance with the provisions of the Lifeline
                           Termination Agreement, or (2) the effective date of
                           the termination of the Lifeline Termination Agreement
                           as therein provided;

                                            (C) Lessor may, at any time after
                           August 31, 1999, terminate such agreement as to Area
                           B if Area B is not surrendered and redelivered to
                           Lessor in accordance with the provisions of the
                           Lifeline Termination Agreement by August 31, 1999;
                           and

                                            (D) Lifeline is required to pay the
                           sum of $7,500.00 per day to Lessor for each day after
                           August 1 until the earlier of (1) the day on which
                           Lifeline surrenders and redelivers Area B to Lessor
                           in accordance with the provisions of the Lifeline
                           Termination Agreement, or (2) the effective date of
                           the termination of the Lifeline Termination Agreement
                           as to Area B as therein provided.

                                       4
<PAGE>   5


                  Lessor hereby agrees with Lessee that:

                                    (X) Lessor shall not exercise either of the
                           termination options under the Lifeline Termination
                           Agreement as described in clauses (A) and (C) above
                           within one-hundred twenty (120) days after March 31,
                           1999 or August 31, 1999 (as the case may be) without
                           the prior written consent of Lessee; provided,
                           however, that after the expiration of such 120-day
                           period from each of such relevant dates Lessor may
                           (but shall not be required to) exercise either of
                           such termination options without the necessity of
                           obtaining Lessee's prior written consent;

                                    (Y) Lessor shall make diligent efforts to
                           collect from Lifeline the amounts described in the
                           foregoing clause (B) when due and payable by Lifeline
                           to Lessor (if any), and shall pay over to Lessee,
                           promptly upon Lessor's receipt thereof, all amounts
                           so received by Lessor from Lifeline on account of
                           Lifeline's delay beyond March 1, 1999 in so
                           surrendering and redelivering Area A to Lessor; and

                                    (Z) Lessor shall make diligent efforts to
                           collect from Lifeline the amounts described in the
                           foregoing clause (D) when due and payable by Lifeline
                           to Lessor (if any), and shall pay over to Lessee,
                           promptly upon Lessor's receipt thereof, all amounts
                           so received by Lessor from Lifeline on account of
                           Lifeline's delay beyond August 1, 1999 in so
                           surrendering and redelivering Area B to Lessor.

                  (d) Effective as of the Second Additional Basement Space
                  Commencement Date, the definition of "Basement Space" set
                  forth in the Lease shall be deemed to be amended to include
                  the Second Additional Basement Space. It is the mutual
                  intention of Lessee and Lessor that the Second Additional
                  Basement Space shall be deemed to be part of both (i) the
                  Basement Space, and (ii) the Premises, for all purposes of the
                  Lease except as otherwise expressly provided in this
                  Amendment, and all rights and obligations of the parties
                  hereunder with respect to the Basement Space and the Premises
                  shall apply equally to the Second Additional Basement Space.
                  Notwithstanding the foregoing, (i) the area of the Second
                  Additional Basement Space shall not be included (a) in the
                  rentable area of the Premises for determining "Lessee's Share"
                  pursuant to Section 5.1 of the Lease, or (b) in determining
                  the number of parking spaces to which Lessee is entitled under
                  Section 9.0 of the Lease; (ii) the Second Additional Basement
                  Space shall be included in the Premises for purposes of
                  Section 13.0 of the Lease; and (iii) the Second Additional
                  Basement Space shall not be included in the Premises for
                  purposes of the "Work Letter" attached to the Lease as Exhibit
                  C.



                                       5
<PAGE>   6

                  (e) Notwithstanding the foregoing, upon the request of either
                  party the other party shall promptly execute and deliver a
                  written instrument setting forth the actual Area A
                  Commencement Date, the actual Area B Commencement Date and the
                  actual Second Additional Basement Space Commencement Date
                  after such dates have occurred.

                  (f) During the time period between the Area A Commencement 
                  Date and the Area B Commencement Date, Lessee shall provide 
                  to Lifeline access to and use of the loading dock located
                  within the Premises in common with Lessee.

                  (g) In connection with the expiration or termination of the
                  Lease, (i) Lessee shall not be required to remove from the
                  Additional Expansion Premises customary office improvements
                  made thereto by Lifeline or by Lessee, and (ii) Lessee shall
                  not be required to remove any animal storage facility
                  improvements made by Lessee in or to the Second Additional
                  Basement Space.

         3.       Term.

                  (a) Notwithstanding anything to the contrary contained in the
                  Lease, the Term of the Lease with respect to Area A shall
                  commence on the Area A Commencement Date, and shall expire on
                  the last day of the Term as provided in the Lease, unless the
                  Term is sooner terminated as provided in the Lease.

                  (b) Notwithstanding anything to the contrary contained in the
                  Lease, the Term of the Lease with respect to Area B shall
                  commence on the Area B Commencement Date, and shall expire on
                  the last day of the Term as provided in the Lease, unless the
                  Term is sooner terminated as provided in the Lease.

                  (c) Notwithstanding anything to the contrary contained in the
                  Lease, the Term of the Lease with respect to the Second
                  Additional Basement Space shall commence on the Second
                  Additional Basement Space Commencement Date, and shall expire
                  on the last day of the Term as provided in the Lease, unless
                  the Term is sooner terminated as provided in the Lease.

                  (d) Notwithstanding anything to the contrary contained in the
                  Lease or in this Amendment, (1) Lessee may not exercise any 
                  Extension Option with respect to a floor of the Additional
                  Expansion Premises which the named Lessee (or a permitted
                  sublessee or assignee of the type described in Section 8(j) of
                  the Lease) is not itself actually occupying in full as of both
                  the date on which Lessee purports to exercise an Extension
                  Option and the first day of the corresponding Extension Term,
                  and (2) Lessee may not exercise any Extension Option with
                  respect to the Additional Expansion Premises unless Lessee
                  simultaneously exercises, in accordance with the provisions of
                  the 


                                       6
<PAGE>   7

                  Lease, the same Extension Option with respect to all other 
                  portions of the Premises.

         4.       Rent.

                  (a) Lessee shall pay Basic Rent on account of the Additional
                  Expansion Premises as follows:

                           (i) for each Lease Year in the Initial Term,
                           commencing on the Area A Commencement Date (with
                           respect to Area A) and on the Area B Commencement
                           Date (with respect to Area B), $19.65 per square foot
                           of rentable area;

                           (ii) for each Lease Year in the first Extension Term
                           (if Lessee exercises the first Extension Option in
                           accordance with the requirements of the Lease), an
                           amount equal to one hundred percent (100%) of the
                           Fair Market Rent thereof less the Unamortized Office
                           Tenant Improvements Amount, but in no event will
                           Basic Rent be less than $19.65 per square foot of
                           rentable area; and

                           (iii) for each Lease Year in the second Extension
                           Term (if Lessee exercises the second Extension Option
                           in accordance with the requirements of the Lease), an
                           amount equal to one hundred percent (100%) of the
                           Fair Market Rent thereof.

                  Such amount shall be paid in equal monthly installments in the
                  manner and at the times provided in the Lease for the payment
                  of Basic Rent.

                  (b) Lessee shall pay Basement Rent on account of the Second
                  Additional Basement Space as follows:

                           (i) for each Lease Year in the Initial Term,
                           commencing on the Second Additional Basement Space
                           Commencement Date, $16.00 per square foot of rentable
                           area; and

                           (ii) for each Lease Year in an Extension Term (if
                           Lessee exercises an Extension Option in accordance
                           with the requirements of the Lease), an amount equal
                           to (A) for each Lease Year in the first Extension
                           Term, $16.00 per square foot of rentable area
                           increased by three (3%) percent per Lease Year in the
                           Initial Term, and (B) for each Lease Year in the
                           second Extension Term, the Basement Rent payable per
                           Lease Year during the first Extension Term increased
                           by three (3%) percent per Lease Year in the first
                           Extension Term.

                  Such amount shall be paid in equal monthly installments in the
                  same manner and at the same times as provided in the Lease
                  with respect to Basic Rent.



                                       7
<PAGE>   8

                  In addition to Basement Rent, Lessee shall pay to Lessor, as
                  Additional Rent, in connection with the Second Additional
                  Basement Space, all other fees and charges provided for (i) in
                  the Lease with respect to the Basement Space or Additional
                  Basement Space, or (ii) in this Amendment.

         5. Lessee's Share. From and after the Area A Commencement Date (and
assuming that the Area B Commencement Date has not then occurred), Lessee's
Share shall be 66.54%. From and after the Area B Commencement Date (and assuming
that the Area A Commencement Date has occurred previously), Lessee's Share shall
be 79.78%.

         6. Electricity. Electrical consumption in the Additional Expansion
Premises shall be measured by a separate electric meter. Lessee shall be solely
responsible for timely making all payments for electrical service directly to
the utility company providing electrical service to the Building. Lessor shall
have no obligation with respect to any such payment.

         7. Permitted Use.

                  (a) The Additional Expansion Premises shall be used only for
                  the Permitted Uses applicable to the portions of the Premises
                  other than the Basement Space as set forth in the Lease,

                  (b) The Second Additional Basement Space shall be used solely
                  for an animal storage facility and for general storage by
                  Lessee, and for no other purpose. Lessor makes no
                  representation or warranty of any type concerning the
                  permissibility of such use under applicable Legal Requirements
                  or the suitability of the Second Additional Basement Space for
                  such use. In addition to, and not in limitation of, the
                  provisions of the Lease relating to Lessee's use of the
                  Premises, Lessee hereby agrees to comply with all Legal
                  Requirements applicable to Lessee's use of the Second
                  Additional Basement Space and not to permit the emission of
                  any objectionable noise or odors from the Second Additional
                  Basement Space. Lessee shall be solely responsible, at its
                  sole cost and expense, for making such alterations, additions
                  and improvements to any animal storage facilities in the
                  Basement Space as may from time to time (i) be required to
                  maintain such facilities and the use thereof in compliance
                  with all Legal Requirements then applicable, or (ii) be
                  reasonably required by Lessor in order to prevent annoyance of
                  other tenants in the Building or disruption of their normal
                  business operations by reason of the operation of an animal
                  storage facility in the Basement Space.

         8. Delivery of the Second Additional Basement Space. Lessee
acknowledges that a portion of the Second Additional Basement Space is currently
leased to Pathology Services, Inc. ("Pathology"), another tenant of the
Building. In order to induce Pathology to relinquish its right to such space,
Lessee has agreed to assume the following obligations to Pathology:



                                       8
<PAGE>   9

                  (i) Lessee shall, at its sole cost and expense, pay for and
                  perform all work required to relocate Pathology's space in the
                  basement of the Building to substitute space identified by
                  Pathology and Lessor, including, without limitation: (A)
                  cleaning up and demolishing the shelving and other alterations
                  constructed or installed by or on behalf of Pathology in the
                  basement space which it currently occupies, (B) designing (or
                  paying for the design by Pathology) of the layout of such
                  substitute basement space, (C) installing demising partitions
                  to create the perimeter of the substitute basement space to
                  which Pathology will relocate, and installing all doors and
                  lighting in such substitute basement space as shown on Exhibit
                  III attached hereto, (D) installing in such substitute
                  basement space shelving of the same linear and square footage
                  as Pathology presently has in the basement space which it
                  currently occupies, as measured by Pathology's architect, (E)
                  patching the basement floor in such substitute basement space
                  to be occupied by Pathology and eliminating trip hazards, and
                  (F) moving (or reimbursing Pathology for the reasonable and
                  actual costs incurred by Pathology in moving) Pathology's
                  property from the basement space which it currently occupies
                  to such substitute basement space;

                  (ii) Lessee shall surrender three (3) On-Site Parking Spaces
                  to Lessor, one by October 31, 1998 and the other two by
                  December 31, 1998, which parking spaces shall then be leased
                  by Lessor to Pathology; and

                  (iii) Lessee shall pay the sum of $45,000.00 in cash to
                  Pathology within seven (7) days after the delivery to
                  Pathology of the completed substitute basement space to be
                  occupied by Pathology, and provide to Lessor evidence of such
                  payment. Lessor hereby acknowledges that such payment has been
                  made to Pathology.

                  Lessee acknowledges that Lessor has no obligation with respect
to any work to be performed in connection with the demising and finishing of any
such substitute basement space, or the demolition of the basement space
currently occupied by any other tenant of the Building, or the relocation of any
other tenant's property from the basement space which it currently occupies to
any such substitute basement space, or to pay any amount to any tenant of the
Building in connection with any of the foregoing. Lessee shall save Lessor
harmless and indemnified from any loss, cost and expense (including, without
limitation, reasonable attorneys' fees) arising out of or relating to (A) any
work performed by or on behalf of Lessee in the basement of the Building or
elsewhere in the Building or on the Land in connection with the relocation of
other tenants to substitute basement space, (B) any work performed by or on
behalf of Lessee in connection with the construction of the Second Additional
Basement Space, or (C) any claim by any other tenant of the Building alleging
that Lessee failed to perform fully all of its obligations described in this
Section.

         9. Right of First Offer. In the event that at any time during the Term
Lessor commences to market for lease any space in the Building which is not then
part of the 



                                       9
<PAGE>   10

Premises, then, provided that (i) an Event of Default is not then existing, and
(ii) the Lessee named herein (or a permitted sublessee or assignee of the type
described in Section 8(j) of the Lease) is then actually occupying the entire
Premises, Lessee shall have the right (the "Right of First Offer") to lease the
portion of the Building 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, by giving written notice of exercise to Lessor within
twenty (20) days of receipt of Lessor's notice.

                  If Lessee exercises its right under this Section 9 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 thereof 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 3.3 of the Lease. 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 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 9 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
the Lease, including, without limitation, Section 11.0(f). 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 9, 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 shall be
appropriately modified.

                  Lessee's Right of First Offer shall be subject and subordinate
to all rights of extension refusal set forth in any lease executed by Lessor
prior to the date of this Amendment, and shall further be subject and
subordinate (with respect to space on the third and fourth floors of the
Building, to the rights of Pathology).

         10. Construction. All work to be performed by or on behalf of Lessee in
the Additional Expansion Premises, the basement of the Building, or elsewhere on
the Land or in the Building in connection with Lessee's initial occupancy of any
of such spaces shall be performed (i) at Lessee's sole cost and expense, (ii) in
accordance with the terms of the Lease, and (iii) with respect to construction
to be performed in the Second Additional Basement Space, shall also be performed
in accordance with the provisions of the Supplemental Work Letter attached as
Exhibit II to the Second Amendment to Lease. Promptly after the completion of
construction of Lessee's improvements or alterations to the 



                                       10
<PAGE>   11

Additional Expansion Premises, Lessee shall provide to Lessor a reasonably
detailed breakdown of the actual out-of-pocket costs paid by Lessee in
connection therewith, allocated among office improvements and other
improvements, together with reasonable supporting documentation of such costs
and such allocation, certified as accurate by an officer of Lessee.

                  Lessor shall deliver the Additional Expansion Premises and the
Second Additional Basement Space to Lessee in the same condition in which they
are redelivered by Lifeline to Lessor, and Lessee agrees to accept them in their
"as is" condition. Lessor shall not be required to pay for or to perform any
work in the Additional Expansion Premises, the Second Additional Basement Space,
or elsewhere in the Building in order to prepare for Lessee's occupancy
hereunder.

                  Lessee shall, at its sole cost and expense and prior to the
expiration of the Lease Term, remove the temporary demising partition separating
Area A from Area B.

         11. Parking.

                  (a) In addition to the On-Site Parking Spaces which Lessee has
                  leased pursuant to Section 9.0 of the Lease prior to the date
                  of this Amendment, (1) effective on the Area A Commencement
                  Date, Lessor shall lease to Lessee an additional one hundred
                  (100) On-Site Parking Spaces, and (2) effective on the Area B
                  Commencement Date, Lessor shall lease to Lessee an additional
                  forty-eight (48) On-Site Parking Spaces. Lessee shall pay to
                  Lessor, as Additional Rent, for each On-Site Parking Space
                  leased pursuant to this subsection (b), in advance, commencing
                  on the Area A Commencement Date or the Area B Commencement
                  Date, as the case may be, and continuing thereafter on the
                  first calendar day of each month, (i) $75.00 per month during
                  the Initial Term, and (ii) thereafter, an amount equal to the
                  Fair Market Rent of such parking spaces as determined annually
                  in accordance with the Lease. Lessee shall have no right to
                  lease additional On-Site Parking Spaces in connection with its
                  lease of the Additional Expansion Premises other than as set
                  forth in this subsection (b).

                  (b) In addition to the On-Site Parking Spaces, (1) effective
                  on the Area A Commencement Date, Lessor shall lease to Lessee
                  an additional forty (40) parking spaces, and (2) effective on
                  the Area B Commencement Date, Lessor shall lease to Lessee an
                  additional twenty (20) 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 IV
                  attached. Lessor reserves the right to relocate all or any
                  portion of the Off-Site Parking Spaces within the area shown
                  on Exhibit IV 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. Lessee shall
                  pay to Lessor, as Additional Rent, for each Off-Site Parking
                  Space so leased, in advance, commencing on the Area A
                  Commencement Date or the Area B Commencement Date, as the case
                  may be, and continuing thereafter on the first calendar day of
                  each month, (i) $60.00 per month during 



                                       11
<PAGE>   12

                  calendar year 1999, and (ii) thereafter, an amount equal to
                  the Fair Market Rent of such parking spaces as determined
                  annually in the manner provided in Section 9.0 of the Lease.

                  Notwithstanding the foregoing, in the event that Lessor
                  hereafter reduces the number of the properties shown on
                  Exhibit IV 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. The provisions of the
                  preceding sentence of this paragraph shall not apply to any
                  Lessor other than MIT.

         12. Transportation of Animals and Related Materials. 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 the Lease (including, without limitation, Section 5 of the Second Amendment
to Lease).

         13. Utilities. Lessee shall pay for all electricity consumed within the
Basement Space and shall make such payment directly to the company which
provides such electrical service. Water and gas consumption in the Basement
Space shall be separately metered and Lessee shall pay all charges therefor
directly to the company which provides such services.

         14. Brokers. Lessor and Lessee each represents to the other that it has
dealt with no broker in connection with this Amendment other than Lynch, Murphy,
Walsh & Partners ("Broker"). Lessee shall be solely responsible for the payment
of all fees and commissions due to Broker in connection with this transaction,
and indemnifies and holds Lessor harmless form and against any claim by Broker
for any such fee or commission. Each of the parties hereby agrees to indemnify
and hold the other party harmless from and against any claims for commissions or
fees by any person or firm other than Broker by reason of any act of the
indemnifying party.

         15. No Services. Notwithstanding anything to the contrary contained in
the 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.

         16. Release.

                  (a) In consideration of the agreements contained in this 
                  Amendment, Lessee hereby releases and forever discharges
                  Lessor and its officers, directors, employees, agents and
                  servants (collectively, the "Lessor Released Parties"), of and
                  from any and all claims, demands, causes of action, costs,
                  expenses, liabilities and obligations, at law or in equity,
                  which 



                                       12
<PAGE>   13

                  Lessee ever had, now has, or hereafter may have against the
                  Lessor Released Parties or any of them, arising out of or
                  relating to the proposed subleasing of the Additional
                  Expansion Premises by Lessee from Lifeline. Lessee hereby
                  acknowledges that its execution and delivery of this Amendment
                  constitute Lessee's intention to enter into the transaction
                  described in this Amendment in full substitution for any
                  proposed sublease of the Additional Expansion Premises from
                  Lifeline.

                  (b) In consideration of the agreements contained in this 
                  Amendment, Lessor hereby releases and forever discharges
                  Lessee and its officers, directors, employees, agents and
                  servants (collectively, the "Lessee Released Parties"), of and
                  from any and all claims, demands, causes of action, costs,
                  expenses, liabilities and obligations, at law or in equity,
                  which Lessor ever had, now has, or hereafter may have against
                  the Lessee Released Parties or any of them, arising out of or
                  relating to the proposed subleasing of the Additional
                  Expansion Premises by Lessee from Lifeline.

         17. Conditions of Effectiveness. Notwithstanding anything contained
herein to the contrary, this Amendment shall not be effective unless and until
all of the following occur:

                  (a) Lessor unconditionally delivers to Lessee an executed
                  counterpart of this Amendment;

                  (b) Lessor receives the unconditional delivery of an executed
                  counterpart of an amendment to the lease between Lessor and
                  Pathology, acceptable in all respects to Lessor, pursuant to
                  which Pathology surrenders all of its right, title and
                  interest in and to any portion of the Second Additional
                  Basement Space which is currently leased by Pathology, and
                  otherwise consistent with the terms of this Amendment; and

                  (c) Lessor receives the unconditional delivery of an executed
                  counterpart of an agreement between Lessor and Lifeline
                  terminating the lease between Lessor and Lifeline, acceptable
                  in all respects to Lessor.

         Lessee acknowledges that Lessor's willingness to enter into this
Amendment is based, in part on Lessor's expectation that other tenants of the
Building, over whom Lessor has no control, will take the actions described in
this Section. Lessor makes no representation or warranty concerning whether or
not such other tenants will take such actions so that the foregoing conditions
to the effectiveness of this Amendment is satisfied in full.

         18. Notice of Amendment to Lease. Either party shall, at the request of
the other, execute and acknowledge a Notice of Amendment to Lease in mutually
satisfactory form.

         19. Authority. Contemporaneously with its execution of this Amendment,


                                       13
<PAGE>   14
Lessee shall furnish to Lessor a certified copy of the resolution of the Board
of Directors of Lessee authorizing Lessee to enter into this Amendment and to
execute and acknowledge the aforementioned Notice of Amendment to Lease.

         20. General. This Amendment constitutes the entire agreement of the
parties with respect to its subject matter, and no oral statement or prior
written matter shall have any force or effect. This Amendment shall not be
modified or canceled except by writing subscribed to by all parties. This
Amendment shall be governed by and construed in accordance with the laws of the
Commonwealth of Massachusetts. The captions of the several paragraphs in this
Amendment are for convenience only and shall not be considered in construing
this Amendment.

         In all other respects, the terms and provisions of the Lease are hereby
ratified and confirmed and remain in full force and effect and unamended.

         EXECUTED UNDER SEAL as of the date set forth above.


         LESSOR:                    MASSACHUSETTS INSTITUTE OF
                                    TECHNOLOGY


                                    By: /s/ Philip A. Trussell
                                        -------------------------------
                                        Name: Philip A. Trussell
                                        Title: Director of Real Estate
                                               Associate Treasurer


         LESSEE:                    MILLENNIUM PHARMACEUTICALS, INC.


                                    By: /s/ Janet C. Bush
                                        -------------------------
                                        Name: Janet C. Bush
                                        Title:  VP FINANCE




                                       14
<PAGE>   15
                              [FLOOR PLAN CHARTS]