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                                                                    EXHIBIT 10.2

                                                                  EXECUTION COPY

                           SECOND AMENDMENT TO LEASE

     This SECOND AMENDMENT TO LEASE (this "Second Amendment") is dated as of
this 22nd day of December, 1997, to be effective as of the 1st day of June,
1997, by and among MASSACHUSETTS TURNPIKE AUTHORITY, a body politic and
corporate organized pursuant to the laws of the Commonwealth of Massachusetts
with offices at Ten Park Plaza, Suite 5170, Boston, Massachusetts 02116
(hereinafter referred to as "LANDLORD"), ALLSTON LANDING LIMITED PARTNERSHIP, a
Massachusetts limited partnership with offices at One Kendall Square, Cambridge,
Massachusetts 02139 (hereinafter referred to as "TENANT"), and GENZYME
CORPORATION, with offices at One Kendall Square, Cambridge, Massachusetts 02139
(hereinafter referred to as "GUARANTOR").

                              W I T N E S S E T H:

     WHEREAS, Landlord and Tenant entered into that certain Lease dated as of
June 1, 1992, as amended by that certain First Amendment to Lease dated as of
July 26, 1995 by and between Landlord and Tenant (as amended, the "EXISTED
LEASE") for the demise of the land and improvements defined in the Existing
Lease as the "PREMISES", which Premises are comprised of therein described and
defined Development Parcel and Holding Parcel (which Holding Parcel includes the
Inaccessible Parcel) and which demise includes a right of first refusal to the
therein described and defined Adjoining Parcels;

     WHEREAS, initial capitalized terms used herein and not otherwise defined
shall have the meanings respectively ascribed to such terms in the Existing
Lease;

     WHEREAS, Section 2.1.2 of the Existing Lease provides that Landlord may
terminate the Existing Lease as to the Holding Parcel if Tenant has not
Commenced Material and Substantial Construction of at least 200,000 square feet
of FAR Floor Area of Improvements on the Holding Parcel by June 1, 1997;

     WHEREAS, Section 2.1.3 of the Existing Lease provides that, in addition to
Landlord's remedies set forth in Section 2.1.2 of the Existing Lease, Tenant
shall either provide access to Landlord over the Development Parcel in order to
provide access to the Inaccessible Parcel or pay Rent with respect to the
Inaccessible Parcel as if such Parcel was improved with 80,000 square feet of
FAR Floor Area of Improvements if Tenant has not Commenced Material and
Substantial Construction of at least 80,000 square feet of Improvements on the
Inaccessible Parcel by June 1, 1997;

     WHEREAS, no such Construction had commenced on either the Holding Parcel or
the Inaccessible Parcel as aforesaid as of June 1, 1997;

     WHEREAS, on account of no such Construction having commenced as aforesaid,
the Existing Lease grants Landlord the right to terminate the Existing Lease as
to the Holding Parcel;

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     WHEREAS, if the Existing Lease is terminated as to the Holding Parcel,
Tenant's rights to the Adjoining Parcels are terminated;

     WHEREAS, Tenant desires to continue to lease and develop the Holding Parcel
(inclusive of the Inaccessible Parcel) upon the terms and conditions set forth
herein; and

     WHEREAS, Landlord and Tenant desire to amend certain provisions of the
Existing Lease as more specifically set forth herein.

     NOW, THEREFORE, in consideration of the premises and mutual promises and
covenants contained herein and in the Existing Lease, and for other good and
valuable consideration, the receipt and sufficiency of which are hereby
acknowledged, Landlord and Tenant hereby agree as follows:

     1. Definitions. The definitions of Adjusted Rent, Development Parcel Rent,
Holding Parcel Rent, Premises, Rent and Term as set forth in Section 1.1 of the
Existing Lease are hereby deleted in their entirety, and the following
definitions, in addition to the definition of Inaccessible Parcel Rent, are
respectively substituted therefor:

     "ADJUSTED RENT: Commencing on the 30th, and redetermined on the 40th, 50th
     and 60th anniversaries of the Date of Lease Execution (June 1, 1992), to be
     in effect as so determined for the respective ten Lease Years following the
     30th, 40th and 50th anniversaries and for the five Lease Years following
     the 60th anniversary, whichever is the lesser of (i) Fair Market Value
     Rent, assuming that the "MAXIMUM FAR FLOOR AREA OF IMPROVEMENTS" (defined
     as 130,490 square feet of initial Improvements plus the Maximum FAR Floor
     Area of Additional Improvements (as hereinafter defined)) have been
     constructed on the Premises, ascertained in accordance with $4.1.4 (but
     never less than Rent payable during the immediately preceding Lease Year)
     or (ii) the sum of (A) $1.80 multiplied by 130,490 (the total square feet
     of FAR Floor Area of initial Improvements constructed on the Development
     Parcel), increased by 5% per annum, cumulatively, from the Date of Lease
     Execution until the beginning of the Lease Year in question (calculated as
     [$1.80 (l+ (x) (. 05))x 130,490] (x being the Lease Year in question)),
     plus (B)(1)if either Landlord or Tenant terminate this Lease with respect
     to the Holding Parcel (exclusive of the Inaccessible Parcel) in accordance
     with Sections 4.2.1.1(e) and 4.2.1.1(f) of this Lease, respectively, the
     product of $1.80 multiplied by the greater of (v) 80,000 or (w) the total
     square feet of FAR Floor Area constructed on that portion of the Premises
     formerly referred to as the Inaccessible Parcel, increased by 5% per annum,
     cumulatively, from the Date of Lease Execution until the beginning of the
     Lease Year in question (calculated as [$1.80 (1+(x) (. 05)) x (y)] (x being
     the Lease Year in question and y being the greater of clause (v) and (w)
     above); or (2) if neither Landlord or Tenant terminate this Lease with
     respect to the Holding Parcel (exclusive of the Inaccessible Parcel) as
     provided herein, the product of $1.60 multiplied by 620,160 (the Maximum
     FAR Floor Area of Additional Improvements (as hereinafter defined)),
     increased by 5% per annum, cumulatively, from the Date of Lease Execution
     until the beginning of the Lease Year in question (calculated as [$1.60
     (1+(x)(. 05))x 620,160] (x being the Lease Year in question). (For an
     example, see Section 4.1.6.)

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     DEVELOPMENT PARCEL RENT: The sum of (a) (i) from and after June 1, 1997,
     $272,724.10 per annum (100% of the product of $2.09 [$1.80 increased by
     16.1%, the CPI Escalation for the initial five Lease Years] multiplied by
     130,490 or the total square feet of FAR Floor Area of initial Improvements
     constructed on the Development Parcel) through the last day of the month in
     which the Development Plan Rent Commencement Date (as hereinafter defined)
     occurs, (ii) from and after the first day of the month following the
     Development Plan Rent Commencement Date, $245,451.69 per annum (90% of the
     product of $2.09 multiplied by 130,490) through the last day of the month
     in which the fifth anniversary of the Development Plan Rent Commencement
     Date occurs, and (iii) $272,724.10 per annum (100% of the product of $2.09
     multiplied by 130,490) for any period thereafter, PLUS (b) from and after
     the Development Plan Rent Commencement Date: (i) if either Landlord or
     Tenant terminate this Lease with respect to the Holding Parcel (exclusive
     of the Inaccessible Parcel) in accordance with Sections 4.2.1.1(e) and
     4.2.1.1(f) of this Lease, respectively, the product of $2.09 multiplied by
     the greater of (A) 80,000 or (B) the total square feet of FAR Floor Area
     constructed on that portion of the Premises formerly referred to as the
     Inaccessible Parcel; or (ii) if neither Landlord nor Tenant terminate this
     Lease with respect to the Holding Parcel (exclusive of the Inaccessible
     Parcel) as provided herein, $1,038,147.84 per annum (90% of the product of
     620,160, being the maximum FAR Floor Area of additional Improvements which
     could potentially be constructed on the Premises ("MAXIMUM FAR FLOOR AREA
     OF ADDITIONAL IMPROVEMENTS"), multiplied by $1.86 through the last day of
     the month in which the fifth anniversary of the Development Plan Rent
     Commencement Date occurs, and $1,153,497.60 per annum (100% of the product
     of the Maximum FAR Floor Area of Additional Improvements, multiplied by
     $1.86) for any period thereafter; subject to increase on the tenth
     anniversary of the Date of Lease Execution (June 1, 1992) and every fifth
     anniversary thereafter by the a mount equal to the CPI Escalation
     multiplied by the sum of the amounts set forth in clause (a) and clause
     (b). Development Parcel Rent shall be due and payable from the Date of
     Lease Execution (June 1, 1992) until the commencement of Adjusted Rent.
     (For an example, see Section 4.1.6.)

     HOLDING PARCEL RENT: (a) $1.00 multiplied by the number of total square
     feet of land area included within that portion of the Holding Parcel
     exclusive of the Inaccessible Parcel which have been improved and upon
     which parking facilities have been constructed, as more fully provided in
     Section 4.1.l, PLUS (b) $250.00 annually for each parking space striped on
     that portion of the Holding Parcel exclusive of the Inaccessible Parcel,
     PLUS (c) $.50 multiplied by the number of total square feet of the
     remainder of the land area included within that portion of the Holding
     Parcel exclusive of the Inaccessible Parcel; subject to increase on the
     tenth anniversary of the Date of Lease Execution (June 1, 1992)and every
     five years thereafter by the amount equal to the CPI Escalation multiplied
     by the sum of the amounts set forth in clauses (a), (b) and (c). From and
     after the Development Plan Rent Commencement Date, no Holding Parcel Rent
     shall be payable.

     INACCESSIBLE PARCEL RENT: The product of $2.09 multiplied by the greater of
     (i) 80,000 or (ii) the total square feet of FAR Floor Area of Improvements
     constructed on the Inaccessible Parcel, subject to increase on the tenth
     anniversary of the Date of Lease Execution (June 1, 1992) and every five
     years thereafter by an amount equal to the CPI Escalation multiplied by the
     aforementioned product. From and after the Development

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     Plan Rent Commencement Date, no Inaccessible Parcel Rent shall be payable.

     PREMISES: The land and improvements located on the lot described in
     Appendix A attached to the Existing Lease, which lot consists of the
     Development Parcel and the Holding Parcel (which Holding Parcel includes
     the Inaccessible Parcel) as the same are initially established and
     described in said Appendix A. Effective as of the Development Plan
     Commencement Date, the Inaccessible Parcel shall be deemed to have been
     moved from the Holding Parcel to the Development Parcel. The Holding
     Parcel, exclusive of the Inaccessible Parcel, may be eliminated from the
     Premises by Landlord upon the terms and conditions set forth in this Lease.

     RENT: The sum of all Holding Parcel Rent, Inaccessible Parcel Rent,
     Development Parcel Rent and Adjusted Rent, per annum.

     TERM: From the Date of Lease Execution (June 1, 1992) until the sixty-fifth
     anniversary of such Date."

     2. Section 2.1, Premises. The first sentence of Section 2.1 of the Existing
Lease is hereby deleted in its entirety, and the following text is substituted
therefor:

     "Landlord leases the Premises to Tenant and Tenant leases the Premises from
     Landlord for the Term (unless, with respect to all and/or certain portions
     of the Premises, earlier terminated in accordance with the provisions of
     the Lease), subject to the terms of this Lease and all matters of record
     existing as of the Date of Lease Execution and matters referred to herein,
     to all of which Tenant shall conform."

     3. Section 2.1.1. Development Parcel. Holding Parcel and Inaccessible
Parcel. The text of Section 2.1.1 of the Existing Lease is hereby revised as
follows:

          a.   The first paragraph of Section 2.1.1 is hereby deleted in its
     entirety, and the following text is substituted therefor:

               "The Premises consist of the Development Parcel, the Holding
               Parcel and the Inaccessible Parcel (the initial boundaries of
               which are described on Appendix A)."

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          b.   The second sentence of the second paragraph of Section 2.1.l is
     hereby deleted in its entirety.

          c.   The third and fourth paragraphs of Section 2.1.1 are hereby
     deleted in their entirety.

          d.   The fifth paragraph of Section 2.1.1 shall be revised by adding
     to the last sentence thereof the clause:

               "(exclusive of the Inaccessible Parcel), but Tenant shall be
               permitted to use portions of the Holding Parcel for surface
               parking."

     4.   SECTION 2.1.2. Section 2.1.2 of the Existing Lease is hereby deleted
in its entirety.

     5.   SECTION 2.1.3. Section 2.1.3 of the Existing Lease is hereby deleted
in its entirety, and the following new Section 2.1.3 is substituted therefor:

          "2.1.3 Development of Inaccessible Parcel. Tenant shall be entitled to
     construct Improvements on the Inaccessible Parcel from time to time subject
     to and in accordance with Section 3.2 hereof. Until such time as Tenant
     constructs Improvements on the Inaccessible Parcel, Tenant shall pay
     Inaccessible Parcel Rent with respect to the Inaccessible Parcel calculated
     as if the Inaccessible Parcel were improved with 80,000 square feet of FAR
     Floor Area of Improvements.

          From and after the date that Tenant constructs Improvements on the
     Inaccessible Parcel that contain more than 80,000 square feet of FAR Floor
     Area, Tenant shall pay Inaccessible Parcel Rent with respect to the
     Inaccessible Parcel based upon the actual square footage of FAR Floor Area
     of such Improvements, as if such Improvements had been included in the
     initial Development Parcel. Such Rent shall be subject to such increases
     and adjustments as are then and thereafter applicable to the Improvements
     on the initial Development Parcel."

     6.   SECTION 4.1.1. HOLDING PARCEL RENT. Section 4.1.1 of the Existing
Lease is hereby deleted in its entirety, and the following text is substituted
therefor:

          "4.1.1 HOLDING PARCEL RENT. Holding Parcel Rent will be as set forth
     in Section 1.1, except that Holding Parcel Rent will continue to be paid
     with respect to any land area within public or private right of way
     hereafter established whether or not Landlord retains any fee interest
     therein. As of June 1, 1997, the Holding Parcel Rent computed in accordance
     with $1.1 is equal to $15,652.93 per month. The calculation of Holding
     Parcel Rent as of June 1, 1997 is detailed on Schedule 4.1.1 attached
     hereto."

     7.   SECTION 4.1.1.1, INACCESSIBLE PARCEL RENT. The following text is added
as Section 4.1.1.1 of the Existing Lease following Section 4.1.1 of the
Existing Lease:

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          "4.1.1.1 INACCESSIBLE PARCEL RENT. Inaccessible Parcel Rent will be as
set forth in Section 1.1. As of June 1, 1997, the Inaccessible Parcel Rent
computed in accordance with $1.1 is equal to $13,933.33 per month (or $2.09 x
80,000 =Section 167,200.00 per annum or $13,933.33 per month). "

     8.   SECTION 4.1.2. DEVELOPMENT PARCEL RENT. Section 4.1.2 of the Existing
Lease shall be deleted in its entirety, and the following text shall be
substituted therefor:

     "4.1.2 DEVELOPMENT PARCEL RENT. Development Parcel Rent during the Term
     shall be as set forth in Section 1.1, except that the amount set forth in
     clause (b) described under "Development Parcel Rent" shall not be due and
     payable to Landlord until the Development Plan Rent Commencement Date. The
     amount set forth in clause (b) of Development Parcel Rent shall not be
     reduced for any reason, including, without limitation, the fact that Tenant
     is permitted to develop more than 75% but less than 100% of the FAR Floor
     Area as set forth in the Development Plan (the "DEVELOPMENT PLAN FLOOR
     AREA") or if Tenant is prohibited from developing at least 75% of the
     Development Plan Floor Area and does not terminate the Lease as to the
     Holding Parcel in accordance with the provisions of Section 4.2.1.1(f)
     hereof."

     9.   SECTION 4.2.1.1, DEVELOPMENT OF THE HOLDING PARCEL. The following text
is added as Section 4.2.1.1 of the Existing Lease following Section 4.2.1 of the
Existing Lease:

     "4.2.1.1" DEVELOPMENT OF THE HOLDING PARCEL.

     (a) PRELIMINARY DEVELOPMENT PLAN.

     Notwithstanding any provisions of the Existing Lease to the contrary,
     within sixty (60) days after the date of this Second Amendment (the
     "PRELIMINARY DEVELOPMENT PLAN PERIOD"), Tenant shall present to Landlord
     for its review a preliminary development plan and development timetable for
     the Holding Parcel (the "PRELIMINARY DEVELOPMENT PLAN").

     (b) DEVELOPMENT PLAN.

     During the three (3) months following the Preliminary Development Period
     (which three (3) months, together with the Preliminary Development Plan
     Period, shall be hereinafter referred to as the "Development Plan Period
     "), Landlord and Tenant shall negotiate in good faith the terms of a final
     development plan and development timetable for the Holding Parcel (the
     "DEVELOPMENT PLAN") which is consistent with the approved master plan set
     forth in Appendix F of the Existing Lease and mutually acceptable to
     Landlord and Tenant in each party's sole discretion. The Development Plan
     shall include, without limitation, (i) an agreement of Tenant to grant
     Landlord and its successors, assigns, lessees and/or licensees an exclusive
     access easement, in form and substance satisfactory to Landlord, along the
     westerly boundary of the Holding Parcel from Western Avenue to the
     southerly edge of the Holding Parcel and (ii) an identification of each
     Leasehold Mortgage Parcel (as hereinafter defined) and each Sale-Leaseback
     Parcel (as hereinafter defined).

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     To the extent the parties agree to the terms and conditions of the
     Development Plan, the parties agree to enter into an amendment to the
     Existing Lease, as amended hereby, as necessary and appropriate to reflect
     the terms of the Development Plan.

     Tenant acknowledges that Landlord's ability to enter into an amendment to
     the Lease as aforesaid as well as this Second Amendment is derived from M.
     G. L. Chapter 81A which provides that Landlord must submit to the
     Metropolitan Highway System Advisory Board ("ADVISORY BOARD") before the
     final execution thereof by Landlord all contracts, plans, agreements and
     memoranda of understanding relative to land use plans, air rights, zoning
     restrictions and environmental impacts associated with the development of
     the Holding Parcel (any such agreement is herein referred to as a
     "DEVELOPMENT CONTRACT") for review by the Advisory Board.

     (c) MEPA REVIEW.

     Upon completion of the Development Plan (but in any event no later than
     four (4) months after the expiration of the Development Plan Period),
     Tenant shall file a preliminary environmental impact report (the "PEIR")
     complying with all provisions of the Massachusetts Environmental Policy Act
     and the regulations enacted pursuant thereto (collectively, "MEPA") with
     the Commonwealth of Massachusetts Department of Environmental Affairs or
     any other successor agency ("DEP"). Tenant shall simultaneously provide
     Landlord with a copy of the PEIR.

     Upon Tenant's receipt of comments from DEP, Tenant shall submit a thorough
     response to such comments to DEP as soon as practicable (but in any event
     no later than two (2) months after receipt of such comments), and shall
     simultaneously provide Landlord with a copy of such response.

     Within twelve (12) months after the Development Plan Period, Tenant shall
     have complied with the provisions of the Massachusetts Environmental Policy
     Act and the regulations enacted pursuant thereto (collectively, "MEPA") and
     shall have received all permits and/or approvals required thereunder.

     Such twelve-month period shall be extended for up to an additional four (4)
     months if Tenant is diligently and continuously pursuing all applicable
     MEPA permits and/or approvals.

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     (d) DEVELOPMENT PLAN RENT COMMENCEMENT DATE. Tenant shall pay Rent in the
     amount set forth in clause (b) of Development Parcel Rent commencing on the
     earlier of (i) the date on which a permit (or other successor
     permission) entitling Tenant to have temporary or permanent occupancy of
     such Improvements, or portions thereof, is issued or Available To Be Issued
     (hereafter defined) by the City of Boston or when Tenant commences
     occupancy of such Improvements in connection with its business, if earlier
     (Tenant shall give prompt notice of said permit issuance to Landlord), or
     (ii) the date which is eighteen (18) months after all MEPA permits and/or
     approvals have been obtained (but in any event not longer than thirty-four
     (34) months after the expiration of the Development Plan Period) [which
     earlier date shall hereinafter be referred to as the "DEVELOPMENT PLAN RENT
     COMMENCEMENT DATE"].

     "AVAILABLE TO BE ISSUED" shall mean that, but for delays neither caused by
     Tenant nor reasonably preventable by Tenant, could then have been
     substantially completed such that a permit entitling Tenant to have
     temporary or permanent occupancy would be issued.

     (e) LANDLORD'S TERMINATION OPTION. Notwithstanding any provisions of the
     Existing Lease to the contrary, if Tenant fails to comply with any of the
     provisions of subparagraphs (a), (b) and (c) above of this Section 4.2.1.1,
     upon four (4) months prior written notice to Tenant, Landlord may terminate
     the Lease as to the Holding Parcel (exclusive of the Inaccessible Parcel)
     and/or negotiate and conclude a lease transaction regarding all or a
     portion of the Holding Parcel (exclusive of the Inaccessible Parcel) with
     any other potential developers for any development on any terms and
     conditions acceptable to Landlord in its sole discretion. Landlord shall
     use reasonable efforts to require that the lease agreement embodying any
     such lease transaction contain covenants by the lessee to review the scope
     of the lessee's proposed construction with Tenant, to consider the
     coordination of such construction with Tenant, and to provide Tenant with
     the opportunity to comment on the lessee's proposed construction schedule.
     On or before the termination date specified in Landlord's notice to Tenant,
     Tenant shall surrender the Holding Parcel (exclusive of the Inaccessible
     Parcel) to Landlord in accordance with the provisions of the Lease,
     including, without limitation, Section 5.1.9 thereof.

     (f) TENANT'S TERMINATION OPTION. If for whatever reason prior to the
     commencement of the construction of the Improvements described in the
     Development Plan mutually agreed to by the parties Tenant is prohibited
     from developing at least 75% of the Development Plan Floor Area, upon at
     least four (4) months prior written notice to Landlord (which notice must
     be given within sixty (60) days of the date Tenant determines it is unable
     to develop at least 75% of the Development Plan Floor Area), Tenant may
     terminate the Lease as to the Holding Parcel (exclusive of the Inaccessible
     Parcel). On or before the

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     termination date specified in Tenant's notice to Landlord, Tenant shall
     surrender the Holding Parcel (exclusive of the Inaccessible Parcel) to
     Landlord in accordance with the provisions of the Lease, including, without
     limitation, Section 5.1.9 thereof."

     10.  SECTION 4.1.3, CPI ESCALATION. The first sentence of Section 4.1.3 of
the Existing Lease is hereby deleted in its entirety, and the following text is
substituted therefor:

          "The term "CPI Escalation" shall mean the sum from time to time of
          each five successive years' percentage increase in the CPI commencing
          in the case of the initial five Lease Years with CPI with a period
          which includes the Date of Lease Execution (June 1, 1992), and for
          each subsequent five Lease Years commencing with CPI for each
          subsequent five year anniversary of the Date of the Lease Execution
          (June 1, 1992), but no percentage increase shall be included to the
          extent that such increase in CPI exceeds 5% per annum for such period
          and if there is no percentage increase in CPI or a percentage increase
          in CPI of less than 3% per annum for such period, then for the
          purposes of calculating "CPI Escalation" 3% shall be included as the
          annual percentage increase for such period. Notwithstanding any
          provisions of the Existing Lease, as amended hereby, to the contrary,
          the parties hereby acknowledge and agree that the CPI Escalation for
          the initial five Lease Years is 16.1%."

     The last sentence of Section 4.1.3 of the Existing Lease is hereby deleted
in its entirety, and the following text shall be substituted therefor:

          "Accordingly, the CPI escalation for Lease Years l-5 is 23.03% (4% +
          4.16% + 4.87% + 5% (because 5.65% exceeds the 5% cap) + 5% (because
          5.93% exceeds the 5% cap))."

     11.  SECTION 4.1.4. ADJUSTED RENT. Section 4.1.4 of the Existing Lease is
hereby deleted in its entirety, and the following text is substituted therefor:

          "4.1.4 ADJUSTED RENT. Adjusted Rent during the Term shall be set forth
          in Section 1.1 and shall be determined respectively for the 30th,
          40th, 50th and 60th anniversaries of the Date of the Lease Execution
          (June 1, 1992) respectively and, as so determined, remain in effect
          until the next such anniversary (or, finally, the end of the Term)."

     12.  SECTION 4.1.6. EXAMPLES.

          (a) Section 4.1.6(l) of the Existing Lease is hereby deleted in its
          entirety, and the following text is substituted therefor:

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          "(1) Assume it is the beginning of the seventh Lease Year. Tenant has
          built 130,490 sq. ft. of FAR Floor Area of initial Improvements on the
          Premises, the Development Plan Rent Commencement Date has occurred,
          and neither Landlord nor Tenant has terminated this Lease with respect
          to the Holding Parcel (exclusive of the Inaccessible Parcel) as
          provided herein. As of the date of the Development Plan Rent
          Commencement Date, Holding Parcel Rent and Inaccessible Parcel Rent
          will be $1,283,599.53 (90% of the sum of $272,724.10 ($2.09 x
          130,490), plus $1,153,497.60 ($1.86 x 620,160))."

          (b) Section 4.1.6(2) of the Existing Lease is hereby deleted in its
          entirety, and the following text is substituted therefor:

          "(2) Assume it is the thirtieth anniversary of the Date of Lease
          Execution (June 1, 1992); neither Landlord nor Tenant terminated this
          Lease respect to the Holding Parcel (exclusive of the Inaccessible
          Parcel); the Premises are not fully developed as there are 630,490
          square feet (as opposed to 750,650 square feet) of FAR Floor Area of
          Improvements on the Premises. The initial Improvements were 130,490
          square feet of FAR Floor Area and 500,000 square feet of FAR Floor
          Area of Improvements were constructed. Adjusted Rent is to be
          determined in accordance with Section 1.l. Fair Market Value Rent
          (assuming Maximum FAR Floor Area of Improvements is constructed on the
          Premises), in accordance with the procedure set forth in 4. Section
          1.5, has been determined to be $3,500,000 a sum which is greater than
          the amount of Rent paid by Tenant with respect to the previous Lease
          Therefore, in determining Adjusted Rent, Tenant shall pay the lesser
          of Fair market Value Rent or the product of clause (ii) of the
          Adjusted Rent Formula set forth in Section 1.1 which is the sum of the
          products obtained under clause (A) and clause (B) of the Adjusted Rent
          formula set forth in Section 1.1 each respectively increased by 5% per
          annum, cumulatively, from the Date of Lease Execution (June 1, 1992)
          until the beginning of the thirty-first Lease Year or the sum of
          $587,205.00 [$1.80 (1 + (30)(.05)) x 130,490], plus the sum of
          $2,480,640.00 [$1.60 (1 + (30)(.05)) x 620,160] resulting in a sum of
          $3,067,845.00 ($587,205.00 + $2,480,40.00)."

     13.  SECTION 12.1, TENANT'S RIGHT TO MORTGAGE. Section 12.1 of the Existing
Lease is hereby deleted in its entirety, and the following text is substituted
therefor:

     "12.1 RIGHT TO MORTGAGE.

     (a)  Tenant shall have the right from time to time to grant one or more
     separate leasehold mortgages encumbering all or any functionally distinct
     portion of the Premises and the Improvements located thereon (each such
     portion of the Premises so mortgaged, a "LEASEHOLD MORTGAGE PARCEL"),
     assign and lease back all or a portion of the Premises and the Improvements
     located thereon incidental to a so-called sale-leaseback financing (each
     such portion of the Premises subject to a so-called sale-leaseback
     financing, a "SALE-LEASEBACK PARCEL") and grant a security interest under
     the Uniform Commercial Code in all or a portion of its interest in the
     Premises and all or a portion of the Improvements

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     (each a "LEASEHOLD MORTGAGE" and collectively, the "LEASEHOLD MORTGAGES"),
     to secure the payment of any loan or loans obtained by Tenant from one or
     more recognized institutional lenders or other recognized financing sources
     (collectively, "LEASEHOLD MORTGAGEE"); provided, however, that Tenant shall
     give prior written notice to Landlord of its intent to exercise such rights
     hereunder, including in such notice the name, address of each such proposed
     Leasehold Mortgagee, the amount of such loan or loans and a description of
     the Leasehold Mortgage Parcel or the Sale-Leaseback Parcel, as the case may
     be, and thereafter promptly furnish any other information regarding each
     such Leasehold Mortgagee which Landlord may reasonably request. The intent
     of this provision is to enable Tenant to separately finance those
     Improvements on the Premises used principally for manufacturing purposes,
     for office and administrative purposes, and for research and development
     purposes, and for parking facilities. The Leasehold Mortgage having the
     first priority from time to time with respect to each Leasehold Mortgage
     Parcel is the "FIRST LEASEHOLD MORTGAGE" with respect to that respective
     Leasehold Mortgage Parcel; and the holder thereof is the "FIRST LEASEHOLD
     MORTGAGE" with respect to that respective Leasehold Mortgage Parcel. All
     Leasehold Mortgages are sometimes referred to as "PERMITTED FINANCING."

     (b)  Landlord agrees to consider amendments to this Lease which may be
     reasonably required to enable Tenant to obtain separate financing for each
     functionally distinct portion of the Premises. Tenant will submit such
     amendments to Landlord who will review the same and indicate those that are
     acceptable, and as to those which are not, specifying the reasons therefor
     and what changes would make the same acceptable to Landlord. To the extent
     such functionally distinct portion of the Premises is identified on the
     Development Plan, Landlord shall not deem such amendment unacceptable
     provided such amendment otherwise complies with this Section 12.1. At
     Tenant's request, Landlord will enter into separate (i.e., non-cross
     default) ground leases for each functionally distinct portion of the
     Premises, such separate ground leases to be on the same terms as contained
     in this Lease with only such changes as are necessary to accommodate
     separate leasing. In addition to the written notice from Tenant required in
     accordance with paragraph (a), Tenant shall deliver to Landlord a new lease
     upon the same terms and conditions of the Existing Lease as amended hereby,
     covering the Leasehold Mortgage Parcel or the Sale-Leaseback Parcel, as the
     case may be (except to the extent any such terms and conditions do not
     apply to the respective Leasehold Mortgage Parcel or the Sale-Leaseback
     Parcel), and a notice or memorandum thereof, in form and substance suitable
     for recording with the Suffolk County Registry of Deeds and the Suffolk
     Registry District of the Land Court (each a "PERMITTED FINANCING LEASE").
     Landlord shall use reasonable efforts to obtain approval, execute and
     deliver the Permitted Financing Lease as soon as reasonably practicable
     thereafter. Landlord and Tenant agree to negotiate in good faith, execute
     and deliver all other documents, instruments, amendments, restatements,
     agreements and contracts reasonably necessary in connection with the
     execution and delivery of the Permitted Financing Lease, including, but not
     limited to any Landlord Consent, Waiver and Estoppel Agreement by and among
     Landlord, Tenant and Leasehold Mortgagee, reasonably requested by such
     Leasehold Mortgagee.

     (c)  Notwithstanding any provisions of this Lease to the contrary: (i) the
     configuration of any and all Leasehold Mortgage Parcels and/or any and all
     Sale-Leaseback Parcels shall

                                       11
<Page>

     be documented in the Development Plan; (ii) Landlord shall not be required
     to enter into any amendments to this Lease, any Permitted Financing Lease
     or any other documents in connection therewith (collectively, the
     "PERMITTED FINANCING LEASE DOCUMENTS") in order to assist Tenant in
     financing any portion of the Improvements if Landlord is required to pay
     any out-of-pocket expenses in connection therewith and/or if any provisions
     of any such Permitted Financing Lease Document in any way increase
     Landlord's obligations or decrease the economic benefits derived by
     Landlord hereunder; and (iii) Tenant shall promptly (but not later than ten
     (10) days after Landlord's delivery to Tenant of a statement of such costs)
     reimburse Landlord for all actual costs (out-of-pocket and otherwise)
     expended or incurred by Landlord in connection with assisting Tenant in
     arranging financing for any portion of the Improvements, including, without
     limitation, the negotiation and review of any Permitted Financing Lease
     Documents.

     14.  ADJOINING PARCELS. Tenant hereby relinquishes all of its rights in and
to the Adjoining Parcels. In that regard, Article XIV and Appendix C of the
Existing Lease are hereby deleted in their entirety.

     15.  ENTIRE AGREEMENT. This Second Amendment constitutes the entire
agreement between Landlord and Tenant regarding the subject matter hereof and
supersedes all oral statements and prior writings thereto, including, without
limitation, that certain letter dated as of June 18, 1997 from Landlord to
Tenant. Except for those set forth in this Second Amendment, no representations,
warranties, or agreements have been made by Landlord or Tenant to the other with
respect to this Second Amendment or the obligations of Landlord or Tenant in
connection herewith.

     16.  NO OFFER. Submission of this Second Amendment to Tenant shall not be
construed as an offer, and Tenant shall not have any rights under this Second
Amendment unless Landlord executes a copy of this Second Amendment and delivers
it to Tenant.

     17.  LANDLORD FEES. Within ten (10) days after Landlord's delivery to
Tenant of a statement of such costs, Tenant shall reimburse Landlord for fifty
percent (50%) of all costs (including, without limitation, reasonable attorneys'
fees) expended or incurred by Landlord in connection with the drafting and
negotiating of this Second Amendment.

     18.  MISCELLANEOUS. The parties hereto acknowledge and agree that, except
as specifically amended by the terms of this Second Amendment, all of the terms,
covenants and provisions of the Existing Lease are hereby ratified and confirmed
and shall remain in full force and effect throughout the balance of the Term as
defined in this Second Amendment. From and after the date hereof, all references
in the Existing Lease to the terms "the Lease" or "this Lease" shall mean and be
the Existing Lease as affected by this Second Amendment.

                                       12
<Page>

     IN WITNESS WHEREOF, Landlord, Tenant and Guarantor have caused this Second
Amendment to Lease to be executed by their duly authorized representatives as a
Massachusetts instrument under seal on the date and year first above written.

                                        LANDLORD:
APPROVED:                               MASSACHUSETTS TURNPIKE AUTHORITY
MASSACHUSETTS TURNPIKE AUTHORITY

   /s/ Robert M. Ruzzo                  By:   /s/ James E. Rooney
-----------------------------              ---------------------------------
Name: Robert M. Ruzzo,                        Name: James E. Rooney,
      General Counsel                         Title: Chief Financial Officer


                                        TENANT:

                                        ALLSTON LANDING LIMITED
                                        PARTNERSHIP

                                        By: Allston Landing Corporation
                                        Its Sole General Partner

                                        By:   /s/ David J. McLachlan
-----------------------------              ----------------------------------
Name:                                         Name:  David J. McLachlan,
                                              Title: Executive Vice President


                                        GUARANTOR:

                                        GENZYME CORPORATION

                                        By:   /s/ David J. McLachlan
                                           ---------------------------------
                                              Name:  David J. McLachlan
                                              Title: Executive Vice President

                                       13
<Page>

                                 SCHEDULE 4.1.1

             HOLDING PARCEL (PROPER) RENT CALCULATION (AS OF 6/1/97)

The area of the Holding Parcel (excluding the area of the Inaccessible Parcel)
is:  185,598 s.f.

Of the total area, the Landlord has determined the following areas to be
improved land used for access and parking:

<Table>
              <S>                               <C>
              Main parking lot:                 54,608 s.f.
              New parking:                       2,560 s.f.
              Access road to parking:           16,640 s.f.

              TOTAL PARKING:                    73,808 s.f.
</Table>

The unimproved area of the Holding Parcel is:

                         185,598 - 73,808 = 111,790 s.f.

Base rent has been computed at $0.50 (before escalation) for the unimproved area
of the Holding Parcel, and base rent has been computed at $1.00 (before
escalation) for the improved land. In addition, there is a parking fee of
$1.00/day (before escalation) for every working day (261 weekdays, less 11
holidays = 250 days), on the 149 spaces which are on the improved land.

<Table>
<Caption>
                                                                                        WITH EXCEPTION OF
                                                                                        PARKING FEE, ESCALATED
                                               ORIGINAL                                 BY 16.1%
                                               --------                                 ----------------------
<S>                                 <C>                                                 <C>
Improved land rent =                73,808 s. f. x $1.00 =$73,808                       $  85,691.09

Unimproved land rent =              111,790 s. f. x $0.50 =$55,895                      $  64,894.10

Parking fee =                       149 SPACES X 250 DAYS X $1/DAY = $37,250            $  37.250.00
                                    ----------------------------------------            ------------

Holding Parcel Proper Total =               $ 166,953                                   $ 187,835.19

                                                                        DIVIDED BY 12 = $  15,652.93
</Table>

* The CPI Escalation for Lease Years l-5 is 16.1%.

                                       14