Document:

<PAGE>

                                                                    Exhibit 10.2

                             SUMMARY OF BASIC TERMS

                                      LEASE

                          OF BUILDING AT 205 BROADWAY,

                         CAMBRIDGE, MASSACHUSETTS 02139

                                       TO

                                VARIAGENICS, INC.

                            DATED AS OF MAY 15, 1998

================================================================================

      The following is a summary of certain basic terms of this Lease which is
intended for the convenience and reference of the parties. In addition, some of
the following items or terms are incorporated into this Lease by reference to
the item or term or to this "Summary of Basic Terms".

1.    Landlord: BHX, LLC, a Massachusetts limited liability company, as Trustee
      of 205 Broadway Realty Trust under Declaration of Trust dated March 24,
      1998 and recorded with the Middlesex South Registry of Deeds on March 24,
      1998 as Instrument No. 1185.

2.    Tenant: Variagenics, Inc., a Delaware corporation.

3A.   Premises: The building (the "Building") situated on Landlord's Property
      and depicted on the Site Plan (the "Site Plan") attached as Exhibit B to
      this Lease.

3B.   Landlord's Property: The real property with the Building and any other
      improvements now or hereafter thereon, now commonly known as 205 Broadway,
      Cambridge, Massachusetts ("Landlord's Property'), as described on Exhibit
      A to this Lease.

4A.   Tenant's Work: As set forth in Section 2.5 and on Exhibit C.

4B.   Tenant Improvement Allowance: Subject to the terms of Section 2.5, an
      allowance of up to $273,098.00 will be available to Tenant to reimburse it
      for remodeling and improvements to the interior of the Building subject to
      the terms of this Lease.

5A.   Lease Term: From the Commencement Date until the last day of the tenth
      (10th) Lease Year (expected to be May 31, 2008), subject to the terms of
      this Lease.

5B.   Commencement Date: June 1,1998.
<PAGE>

5C.   Rights of Extension: One (1), five (5) year option pursuant to Section
      2.3.

6.    Use: For only those uses permitted by Section 5.1.

7.    Tenant's Trade Style (d/b/a): Not Applicable.

8.    Security Deposit: $2,000,000 to be made available to Landlord as of the
      date of this Lease, subject to the terms of Section 11.9, under the terms
      of an irrevocable letter of credit which Tenant causes to be issued to
      Landlord as beneficiary substantially in the form of Exhibit F attached to
      this Lease (the "Letter of Credit").

9.    Tenant's Parking Allocation: [84]. The rate to be changed for the parking
      spaces is as set forth in Section 1.3.

10.   Fixed Minimum Rent

                                       ANNUAL                            MONTHLY
      PERIOD                            RATE                              RATE
      --------------------------------------------------------------------------

A.    Fixed Minimum Rent for the Initial Term (as defined in Section 1.1) is as
      follows:

      From the Commencement Date
      Through the Last Day of the Tenth Lease Year    $975,350.00     $81,279.17

      Notwithstanding the foregoing, the Fixed Minimum Rent for July 1998 shall
      be equal to one-half of the Monthly Rate.

B.    To the extent this Lease is extended pursuant to its terms, the Fixed
      Minimum Rent shall be as follows: for the Extension Term (as defined in
      Section 1.1) the annual Fixed Minimum Rent for the Premises shall be equal
      to the greater of (a) 95% of the then applicable Fair Market Rent as
      determined by the method set forth in Section 12.13 or (b) $975,350.00.

11A.  Additional Rent: Tenant shall pay (i) all Taxes, Insurance Costs, and
      Operating Costs, and (ii) Other Additional Rent.

11B.  Taxes: Payable monthly (for the Fiscal Year ending June 30, 1998, in the
      estimated amount of $8,817.80 per month).

11C.  Insurance Costs: Payable monthly (for calendar year 1998, in the estimated
      amount of $221.67 per month).

11D.  Operating Costs: Payable monthly (for calendar year 1998, in the estimated
      amount of $15,267.51 per month).

                                       2
<PAGE>

11E.  Tenant's Direct Payment of Utilities: Tenant shall promptly pay prior to
      the date when due all charges related to its use of gas, electric, water,
      and sewer service to the appropriate public utility.

11F.  Other Additional Rent: Includes all fees, charges, expenses, fines,
      assessments, indemnities, or other sums other than Fixed Minimum Rent and
      Taxes, Insurance Costs, and Operating Costs due under this Lease.

12.   First Payment: First month's Fixed Minimum Rent in the amount of
      $81,279.17, plus the first month's installment of Taxes in the amount of
      $8,817.80, plus the first month's installment of Insurance Costs in the
      amount of $221.67, plus the first month's installment of Operating Costs
      in the amount of $15,267.51 plus the first month's parking charges in the
      amount of $7,140.00, totaling $112,726.15 have been paid upon execution of
      this Lease.

13.   Broker: Davis & DeMarco, having an office at 27 Christina Street, Newton,
      Massachusetts 02161; and Equis Corporation, having an office at 160
      Federal Street, 13th Floor, Boston, Massachusetts 02110

14A.  Tenant's Address For Notices, Telephone Number Fax Number and Taxpayer
      Identification No.:

      1.    Before the Commencement Date:

      One Kendall Square
      Cambridge, MA 02139
      Attn: Eleonora Brown
      Telephone: (617) 588-5302; Fax: (617) 588-5399

      2.    After the Commencement Date:

      205 Broadway (or such other address as may be assigned to the Premises by
                   Landlord pursuant to Section 7.2)
      Cambridge, MA 02139
      Attn: Eleonora Brown
      Telephone:  (617) 588-5302; Fax: (617) 588-5399

      3.    Tenant F.I.D.#04-3182077 with a copy to:

      Mintz, Levin, Cohn, Ferris, Glovsky and Popeo, P.C.
      One Financial Center
      Boston, Massachusetts 02111
      Attn: Joel R. Bloom, Esq.
      Telephone: 617-542-6000
      Facsimile: 617-542-2241

                                       3
<PAGE>

      Provided, that (1) notice given to Tenant's counsel is not deemed notice
      to Tenant and (2) Landlords failure to deliver any notice to Tenant's
      counsel will not affect the validity or effectiveness of any notice or
      notification received by Tenant.

14B.  Landlord's Address for Notices:

      205 Broadway Realty Trust
      BHX, LLC, Trustee
      First Needham Place
      250 First Avenue, Suite 200
      Needham, Massachusetts 02194-2805
      Attention: Robert A. Schiager
      Tel: (781) 707-4000; Fax: (781) 707-4001

      with a copy to:

      Vorys, Sater, Seymour and Pease LLP
      Suite 2100, Atrium Two
      221 E. Fourth Street
      Cincinnati, OH 45202-0236
      Attn: Charles C. Bissinger, Jr., Esq.
      Telephone: 513-723-4000
      Facsimile: 513-723-4056

      Provided, that (1) notice given to Landlord's counsel is not deemed notice
      to Landlord and (2) Tenant's failure to deliver any notice to Landlord's
      counsel will not affect the validity or effectiveness of any notice or
      notification received by Landlord.

14C.  Guarantor: None; accordingly, the terms of this Lease which apply
      expressly to the capitalized term "Guarantor" are of no effect until there
      is made a Guarantor of Lease by a written amendment executed by Landlord
      and Tenant.

                                       4
<PAGE>

                                      LEASE

      THIS LEASE made as of the 15th day of May, 1998, between BHX, LLC, a
Massachusetts limited liability company, as Trustee of 205 Broadway Realty Trust
under Declaration of Trust dated March 24, 1998 and recorded with the Middlesex
South Registry of Deeds on March 24, 1998 as Instrument No. 1185 (hereinafter
called "Landlord"), and Variagenics, Inc., a Delaware corporation, having a
place of business at One Kendall Square, Cambridge, Massachusetts 02139
(hereinafter called "Tenant").

                              W I T N E S S E T H:

                                    ARTICLE I

      Section 1.1 Certain Definitions. In addition to the words and terms
defined elsewhere in this Lease, the following words and terms shall have in
this Lease the meanings set forth in this Section:

            "Alternative Parking Facilities" means any combination of substitute
outdoor, surface parking or indoor garage parking that Landlord from time to
time arranges to be available to Tenant either at the property known as 210
Broadway and/or at other locations in the Kendall Square area. Landlord shall
have the right to change, from time to time, the Alternative Parking Facility or
Facilities then available to Tenant and may use any combinations of Alternative
Parking Facilities as Landlord may select from time to time.

            "Applicable Interest Rate" means the lesser of (a) a rate per annum
equal 3% plus the prime rate charged by Fleet National Bank, Boston,
Massachusetts (or any successor), in effect on the day the payment became due
and subject to change thereafter or (b) the maximum rate permitted by applicable
law.

            "Building" means the one-story building, with a mezzanine area
located on the Land as depicted on the Site Plan.

            "Cambridge Zoning Ordinance" means the Zoning Ordinance of the City
of Cambridge, Massachusetts, as amended by Ordinances 1187, 1189, 1192, 1193,
1194, 1195, 1196 and 1197. Any reference to a specific provision of the
Cambridge Zoning Ordinance will be construed to include any comparable provision
of the Cambridge Zoning Ordinance as amended or superseded after the date of
this Lease.

            "Common Areas" means (i) those areas designated on the Site Plan as
common areas as of the date of this Lease and any future areas on Landlord's
Property which Landlord designates by notice to Tenant from time to time as
"common areas", less (ii) those areas which Landlord eliminates from time to
time by notice to Tenant from Landlord's previous designation as a common area.

            "Common Facilities" means those facilities, if any, located on the
Land which Landlord designates from time to time as "common facilities".

                                       5
<PAGE>

            "Extension Term" means the period of time beginning at the end of
the Initial Term and ending on the last day of the fifteenth (15th) Lease Year.

            "Future Building" means any and all buildings constructed on the
Land excluding the Building.

            "Future Building Lease Notice" means a notice to Tenant from
Landlord that leasable square footage of a Future Building has been occupied by
another tenant.

            "Future Improvements" means any and all Future Buildings and any and
all other improvements constructed on the Land after the date of this Lease.

            "Initial Term" means the period beginning at 12:01 A.M. on the
Commencement Date and ending at 11:59 P.M. on the last day of the tenth (10th)
Lease Year.

            "Land" means the land described in Exhibit A attached hereto and
incorporated by reference herein as depicted on the Site Plan.

            "Landlord's Property" means the Land, the Building and all present
or future appurtenances and/or improvements to the Land and/or the Building.

            "Leasable Square Footage of the Future Buildings" means, as of any
date of determination, the aggregate number of square feet of Landlord's
leasable floor area in all Future Buildings less the square footage of Common
Areas, Common Facilities, and parking areas located within such buildings.
Notwithstanding anything to the contrary in the immediately preceding sentence,
until Landlord gives a Future Building Lease Notice to Tenant with respect to a
Future Building, the leasable square footage of such Future Building will be
excluded for purposes of determining aggregate leasable floor area in all Future
Buildings.

            "Leasable Square Footage of the Premises" means an agreed-on 39,014
square feet.

            "Lease Term" means the Initial Term and, if the Tenant timely and
properly exercises its right to extend pursuant to Section 2.3 of this Lease,
the Extension Term.

            "Lease Year" means the twelve (12) month period beginning on the
Commencement Date and on each anniversary of the Commencement Date throughout
the Lease Term; provided, however, that if the Commencement Date occurs on a
date other than the first day of a month, the first Lease Year shall consist of
the portion of the calendar month in which the Commencement Date occurs and the
next subsequent 12 calendar months, and the first day of each Lease Year
thereafter shall be the first day of the month after the month in which the
Commencement Date occurs.

            "Minimum Number of Parking Spaces" means 40 parking spaces.

                                       6
<PAGE>

            "Parking Area" means that portion of Landlord's Property which is
used as of the date of this Lease as a parking lot as depicted on the Site Plan.

            "Parking Space Shortfall" means the excess, if any, at any time of
(i) the Minimum Number of Parking Spaces over (ii) the number of parking spaces
then available for use by Tenant on Landlord's Property.

            "Premises" means the Building.

            "Site Plan" means the site plan attached hereto as Exhibit B which
depicts the approximate size and layout of the Land, the Building and the
Parking Area.

            "Tenant's Share" means, as of any date of determination, an amount
(expressed as a percentage) equal to (i) the Leasable Square Footage of the
Premises divided by (ii) the Total Leasable Square Footage of All Buildings. The
percentage determined by the preceding sentence will rounded upward to the
nearest hundredth of one percent. Except as set forth in the following sentence,
prior to the date of a Future Building Lease Notice, Tenant's Share shall be one
hundred percent (100%). Notwithstanding anything to the contrary contained
herein, except for Tenant's Share of Taxes, Insurance Costs and Operating Costs
attributable to any future parking garage, Tenant shall have no obligation for
any Taxes, Insurance Costs or Operating Costs attributable to any Future
Buildings until the date of the Future Building Lease Notice.

            "Total Leasable Square Footage of All Buildings" means, as of any
date of determination, the sum of the Leasable Square Footage of the Premises
and the Leasable Square Footage of all Future Buildings.

      Section 1.2 Lease of the Premises. Landlord does hereby lease the Premises
to Tenant, and Tenant hereby leases the Premises from Landlord, upon and subject
to the terms and provisions of this Lease and all zoning ordinances, and
easements, restrictions, and conditions of record.

      Section 1.3 Parking.

            (a) Except as hereinafter set forth, during the Lease Term Tenant
shall be allocated approximately eighty-four (84) parking spaces in the Parking
Area. Tenant shall pay (i) eighty-five dollars ($85.00) per month for each such
allocated space during the Initial Term and (ii) during the Extension Term, if
any, the greater of (A) $85.00 per space or (B) 95% of the Fair Market Parking
Charge as determined in accordance with Section 12.13.

            (b) Landlord shall have the unrestricted and unconditional right to
restrict and/or terminate Tenant's rights to use all and/or any portions of the
Parking Area on a temporary and/or permanent basis from time to time in
connection with (i) the proposed or actual construction of Future Improvements
and/or (ii) the performance of such soil tests, environmental tests, remediation
activities and other testing and/or monitoring as Landlord determines to
undertake thereon. Except as provided in Sections 1.3(c) and 1.3(d) hereof,
Landlord shall have no obligation to provide alternative or replacement parking
spaces due to

                                       7
<PAGE>

any such restrictions and/or termination. Further, there shall be no reduction,
diminution or offset against Fixed Minimum Rent or Additional Rent under this
Lease by reason of any such restrictions and/or termination; provided, however,
that the amounts due under Section 1.3(a) shall be abated proportionately based
upon the number of spaces which are not available for Tenant's use and the time
period during which such spaces are not available.

            (c) In the event that, due to restrictions placed on all or any
portions of the Parking Area by Landlord, and/or the termination of Tenant's
rights therein, the number of parking spaces available to Tenant on Landlord's
Property is reduced to less than the Minimum Number of Parking Spaces, then
Landlord shall make available to Tenant, at one or more Alternative Parking
Facilities, a sufficient number of Parking Spaces to eliminate the Parking Space
Shortfall until such time as the Parking Space Shortfall is eliminated. The
monthly parking charge for each space made available to Tenant in Alternative
Parking Facilities shall be equal to (i) the rate per month that otherwise would
have been in effect under Section 1.3(a) if the parking spaces are outdoor,
surface parking and (ii) the rate per month that otherwise would have been in
effect under Section 1.3(d) if the parking spaces are in a parking garage.
Tenant shall comply, and shall cause its employees, visitors, guests, licensees
and invitees to comply, with all rules, regulations and requirements imposed by
the operator(s) of any Alternative Parking Facilities.

            (d) In the event that any Future Improvements include a parking
garage, then, at such time as parking spaces in such parking garage are made
available for use, Tenant shall be allocated a sufficient number of spaces in
such parking garage to eliminate any Parking Space Shortfall; provided, however,
that Landlord may, at its option, reduce the number of spaces in the parking
garage which are allocated to Tenant to not less than fifteen (15) spaces in the
parking garage, in which event, Landlord shall make available to Tenant, at one
or more Alternative Parking Facilities (which Alternative Parking Facility will
be located at 210 Broadway if permitted by applicable law), a sufficient number
of parking spaces to eliminate any resulting Parking Space Shortfall). The
monthly rate to be paid by Tenant for spaces in such parking garage shall be as
follows:

            Period After Garage Opening         Monthly Rate
            ---------------------------         ------------
            First 12 months                     $ 95.00 per space
            Second 12 months                    $105.00 per space
            Balance of Initial Term             $125.00 per space
            Extension Term                      Greater of (i) $125.00 per
                                                space or (ii) 95% of the Fair
                                                Market Parking Charge as
                                                determined by the method set
                                                forth in Section 12.13.

Tenant shall comply, and shall cause it employees, visitors, guests, licensees
and invitees to comply, with all rules and regulations promulgated by Landlord
from time to time regarding access to, and/or use of, any such parking garage.
Tenant acknowledges that Landlord may restrict and/or control access to such
parking garage and/or may assign reserved spaces in such parking garage to
others.

                                       8
<PAGE>

            (e) All parking charges payable by Tenant pursuant to this Section
1.3 shall be paid without offset or deduction for any reason, in advance, on the
first day of each calendar month during the Lease Term following the
Commencement Date and also on the Commencement Date all or a proportionate
amount of such parking charges shall be paid for the month in which the
Commencement Date occurs. Any prorations or other adjustments due to (i) changes
in the number of parking spaces available or (ii) changes in availability of
spaces in a parking garage on Landlord's Property shall be adjusted not later
than the first day of the following calendar month.

      Section 1.4 Common Areas and Facilities. The Premises are leased subject
to, and with the benefit of, the non-exclusive right to use in common with
others at any time entitled thereto the Common Areas and Common Facilities for
all such purposes as such areas and/or facilities may be designated by Landlord,
but only in connection with business in the Building. Landlord shall have the
right from time to time to (i) designate or change the locations, size or
configuration of the Building, including, without limitation the Common Areas
and/or Common Facilities, (ii) modify or replace Common Facilities, and (iii)
construct Future Improvements on Landlord's Property which may include
excavating around the walls of the Building.

                                   ARTICLE II

      Section 2.1 Lease Term. The Lease Term shall be the Initial Term unless
Tenant timely and properly exercises its right to extend under Section 2.3
hereof.

      Section 2.2 Commencement Date. The "Commencement Date" of the Lease Term
shall be as set forth in the Summary of Basic Terms.

      Section 2.3 Right to Extend. Provided (x) Tenant is not in default beyond
any applicable grace period provided for herein before exercising Tenant's right
to extend the Lease and at the time the extended term is to be effective and (y)
Tenant delivers to Landlord on or prior to the date the extended term is to be
effective, a Letter of Credit which meets all of the requirements of Section
11.9, Tenant shall have the right to extend the Lease Term for one (1)
successive period of five (5) years for, and during, the Extension Term, by
giving Landlord written notice specifying such extension, which notice must be
received by Landlord at least one year prior to the expiration date of the
Initial Term. If such extension becomes effective, the Lease Term shall be
automatically extended upon the same terms and conditions except that (i) Fixed
Minimum Rent shall be payable for such extended term as set forth in Item 10 of
the Summary of Basic Terms, (ii) the amounts payable by Tenant for parking
charges will be subject to increase in accordance with Section 1.3 hereof, and
(iii) there shall be no further right to extend or renew beyond the period
expressly set forth in this Section 2.3. The right of extension is personal to
Tenant and is not exercisable by any subtenant or assignee permitted hereunder.
In the event that the Lease Term is extended pursuant to this Section 2.3, if
requested in writing by Landlord or Tenant, the parties shall execute a notice
of exercise or amendment to notice of lease in recordable form and Tenant may,
at its expense, record the same in the Middlesex South District Registry of
Deeds. The rights in this Section 2.3 are personal to Variagenics, Inc. and are
not assignable or transferable, except in connection with an assignment or
sublease made pursuant to, and in compliance with, Section 7.12(b)(ii). On any
other permitted assignment (or request

                                       9
<PAGE>

for assignment) of this Lease or on any other permitted sublease (or request for
sublease) of this Lease for all or any portion of the Premises, the rights under
this Section 2.3 will lapse and be of no further force and effect.

      Section 2.4 Landlord's Work. Landlord shall have the right, but not the
obligation, to perform any improvements to the Building or other portions of
Landlord's Property which Landlord in its sole discretion deems necessary or
advisable. Tenant shall have no claim for damages against Landlord if Landlord
fails to perform any or all of Landlord's Work. Tenant acknowledges that
Landlord may (but shall not be obligated to) demolish all or any portion of the
area of the Building which is identified on the Site Plan as "Potential
Demolition Area" provided that Landlord restores any damage to the remainder of
the Building due to such demolition.

      Section 2.5 Tenant's Work.

            (a) Tenant agrees to perform all of "Tenant's Work" as specified
herein and on Exhibit C. All of Tenant's Work shall be done in a good and
workmanlike manner using new and high quality materials and in accordance with
the (i) provisions of all laws, rules, regulations and insurance requirements
applicable thereto and (ii) the plans and specifications that have been approved
in writing by Landlord. Tenant shall at its sole cost and expense do all work
necessary and take all other steps required in order to obtain and maintain a
Certificate of Occupancy for the Premises and Tenant's use thereof during the
Initial Term and any Extension Term. Tenant's Work will comply with all other
requirements of this Lease, including Section 7.4.

            (b) Tenant will submit to Landlord not more often than once in each
month an application ("Tenant's Work Application") with respect to the total
number of square feet which has been certified by Tenant's architect as being
completed pursuant to the plans and specifications approved by Landlord during
the previous calendar month (the "Completed Space"). Tenant's Work Application
will detail the direct, out-of-pocket cost (per square foot) actually paid by
Tenant to its contractors and subcontractors to complete the Completed Space
("Actual Per Square Foot Cost") and will be accompanied by a certification from
Tenant's architect confirming the number of square feet of Completed Space, and
confirming that the Tenant's Work is in compliance with the plans and
specifications approved by Landlord and all applicable laws, rules, regulations
and governmental requirements. Within 30 days after Landlord receives Tenant's
Work Application made in compliance with this Section 2.5 (provided that there
does not then exist a default of Tenant or any fact or circumstance which, with
the passage of time, the giving of notice, or the satisfaction of any other
condition, or all of them, could constitute a default under this Lease),
Landlord will pay to Tenant an amount equal to (A) the excess, if any of, the
lesser of (1) $7.00 multiplied by the number of square feel of Completed Space
as set forth in Tenant's Work Application or (2) the Actual Per Square Foot Cost
of the Completed Space as set forth in Tenant's Work Application (the lesser
amount being the "Landlord's Contribution") over (B) all previous payments of
the Landlord's Contribution. In no event, however, will Landlord's Contribution
with respect to all of Tenant's Work exceed a total sum of $273,098.00. In no
event will any portion of Landlord's Contribution be used to pay the cost of
replacement of the roof on the Building. Tenant will receive the monthly
Landlord's Contribution in the form of a cash payment made to Tenant unless
Landlord, at its option, by written notice to Tenant elects to have all or any
portion of the Landlord's Contribution deducted

                                       10
<PAGE>

from the immediately following payments of Fixed Minimum Rent. In support of
each Tenant's Work Application land as a precondition) to receive Landlord's
Contribution, Tenant will deliver to Landlord construction contracts, payment
applications and construction draws, lien waivers, affidavits and other
documentation, satisfactory to Landlord, demonstrating the direct, out-of-pocket
cost paid by Tenant in connection with the Completed Space (including, without
limitation, architectural services). Tenant will be solely responsible for all
costs of Tenant's Work in excess of the Landlord's Contribution and shall
provide to Landlord such evidence of payment thereof as Landlord may from lime
to time request. Landlord, may at its option, inspect the Tenant's Work and take
such other actions as Landlord deems appropriate to confirm that the same is in
compliance with the approved plans and specifications therefor and to verify the
information contained in any Tenant's Work Application and/or any certification
by Tenant's architect.

            (c) In addition to Landlord's Contribution, Tenant agrees to expend
not less than One Million Five Hundred Thousand and No/100 Dollars
($1,500,000.00) on Tenant's Work ("Tenant's Contribution"), of which not less
than One Million and No/00 Dollars ($1,000,000.00) shall be expended on or
before December 31, 1998, subject to extension due to delays resulting from
Interruption of utility services, breakage, strikes, inability after exercise of
reasonable diligence to obtain supplies or for any cause or causes beyond the
reasonable control of Tenant (which shall never include the lack of capital
available to Tenant). The balance of Tenant's Contribution shall be expended on
or before December 31, 1999. subject to extension due to delays resulting from
interruption of utility services, breakage, strikes, inability after exercise of
reasonable diligence to obtain supplies or for any cause or causes beyond the
reasonable control of Tenant (which shall never include the lack of capital
available to Tenant). Tenant shall provide such contracts, invoices, receipts
and other documentation as Landlord may request to confirm the amounts so
expended by Tenant. Until the termination of this Lease, Tenant will, as between
Landlord and Tenant, be entitled to any depreciation deductions attributable to
Tenant's Work.

      Section 2.6 Approval of Plans and Specifications. If Tenant's Work as set
forth on Exhibit C does not refer to complete plans and specifications approved
by Landlord, then Tenant shall promptly following execution of this Lease cause
such complete plans and specifications to be prepared at Tenant's cost and
submitted to Landlord for Landlord's prior written approval before Tenant's Work
is commenced. Landlord shall not unreasonably withhold or delay such approval.
Without limiting Landlord's discretion, Landlord will not be deemed unreasonable
for withholding its consent to any alteration or addition (i) which would not be
compatible with the existing mechanical, electrical, plumbing, or HVAC systems
servicing any portion of Landlord's Property, unless such plans and
specifications include upgrades to such systems to make them compatible with
such alterations or additions, (ii) which could, in Landlord's reasonable
judgment, adversely affect Landlord's ability to construct any or all of the
Future Improvements. (iii) which involves or might affect any structural or
exterior element of the Building or the roof (except that Tenant may locate HVAC
equipment on the roof so long as such HVAC equipment is compatible with the
structural elements of the Building or such plans and specifications include
upgrades to the structural elements to make them compatible with such
alterations or additions), (iv) which would exceed any live load which the roof
or any floor was designed to carry, or (v) which involves any penetration of the
roof (except that (A) not more than a total of 5

                                       11
<PAGE>

roof penetrations are permitted provided that such penetrations comply with all
other provisions of this Lease and are for the sole purpose of venting or HVAC
systems and (B) roof penetrations for skylights are permitted provided that such
penetrations comply with the other provisions of this Lease). Landlord's
approval of any plans and specifications pursuant to this Section or any other
provisions of this Lease shall not, and shall not be deemed to be a
certification, representation, or warranty by Landlord that the plans and
specifications are adequate, complete, or in compliance with applicable codes
and legal requirements.

      Section 2.7 Sign Criteria. Except for signage (a) which complies with all
applicable laws, rules, ordinances, regulations and other governmental
requirements and (b) which is (i) located inside the Building and which is not
visible outside of the Building or (ii) expressly permitted pursuant to Exhibit
D, Tenant shall not erect, place or install any signage on Landlord's Property.
All costs of obtaining permits and approvals, creating and installing such sign
shall be paid by Tenant. Tenant shall maintain all signage in good repair and
condition. Notwithstanding anything to the contrary in this Section 2.7 or in
Exhibit D, Tenant will not erect any permitted exterior signage on or before the
date on which Tenant commences the operation of its business on the Premises.

                                   ARTICLE III

      Section 3.1 Fixed Minimum Rent. In consideration of the Lease of the
Premises pursuant to this Lease, Tenant shall pay therefor Fixed Minimum Rent in
the applicable amount set forth in the Summary of Basic Terms ("Fixed Minimum
Rent') payable in equal monthly installments of one-twelfth of the annual Fixed
Minimum Rent which shall be paid without offset or deduction for any reason, in
advance, on the first day of each calendar month during the Lease Term following
the Commencement Date, and also on the Commencement Date all or a proportionate
part of the Fixed Minimum Rent shall be paid for all or any part of a month.
Fixed Minimum Rent and Additional Rent shall be paid either (a) by an
"electronic funds transfer' system arranged by and among Tenant, Tenant's bank
and Landlord, or (b) by check sent to Landlord's office First Needham Place, 250
First Avenue, Suite 200, Needham, Massachusetts 02194 or at such other place as
Landlord shall from time to time designate in writing. If Tenant is using
checks, rent checks shall be made payable to 205 Broadway Realty Trust or to
such other entity or trade-style as Landlord may designate from time to time in
writing. The parties hereto acknowledge and agree that the obligations owing by
Tenant under this section are rent reserved under this Lease, for all purposes
hereunder, and are rent reserved within the meaning of Section 502(b)(6) of the
United States Bankruptcy Code of 1978, as amended (11 U.S.C. Section 101 et
seq.) (the "Bankruptcy Code").

      Section 3.2 Certain Additional Rent. Tenant shall pay, without offset or
deduction for any reason, Additional Rent on account of Taxes, Insurance Costs,
the charges for parking spaces as set forth in Section 1.3 and Operating Costs,
the amounts more particularly set forth in Article IV hereof and Section 1.3,
and all other fees, charges, expenses, fines, assessments or other sums payable
by Tenant to Landlord hereunder. If Tenant fails to pay any Additional Rent,
Landlord shall have all the rights and remedies for failure to pay Fixed Minimum
Rent. The parties hereto acknowledge and agree that the obligations owing by
Tenant under this section are

                                       12
<PAGE>

rent reserved under this Lease, for all purposes hereunder, and are rent
reserved within the meaning of Section 502(b)(6) of the Bankruptcy Code or any
successor provision thereto.

      Section 3.3 Triple Net Lease. Landlord and Tenant intend that the rent
payable under this Lease shall be absolute triple net annual Fixed Minimum Rent
and Additional Rent to Landlord as described herein during the Lease Term.
Tenant shall pay all costs, expenses and obligations of every kind and nature
whatsoever relating to the Premises and all expenses and obligations of every
kind and nature whatsoever relating to the operation, maintenance, upkeep,
replacement or repair of Landlord's Property, without any deduction or offset
unless expressly provided otherwise herein.

                                   ARTICLE IV

      Section 4.1 Certain Definitions Applicable to Tenant's Payment of Real
Estate Taxes, Insurance, Electricity and Operating Costs. As used in this Lease,
the following definitions shall apply: (a) the term "Taxes" shall mean all
taxes, assessments, betterments, water or sewer entrance fees and charges
including general, special, ordinary and extraordinary, environmental (but
without in any way modifying the respective rights and obligations of the
parties pursuant to Section 5.1), or any other charges (including charges for
the use of municipal services if billed separately from other taxes), levied,
assessed or imposed at any time by any governmental authority upon or against
Landlord's Property exclusive of ("Excluded Taxes") any estate, inheritance,
gift, net worth, franchise, or income taxes on the net income of Landlord. This
definition of Taxes is based upon the present system of real estate taxation in
the Commonwealth of Massachusetts; if taxes upon rentals or any other basis
shall be substituted, in whole or in part, for the present ad valorem real
estate taxes, the term Taxes shall be deemed changed to the extent to which
there is such a substitution for the present ad valorem real estate taxes
(including any of the Excluded Taxes if the same constitute any of the
substituted taxes) and in such event Taxes shall be determined as though
Landlord's Property is the only property owned by Landlord; (b) the term
"Insurance" shall mean such casualty, liability, rent loss, and other insurance
as Landlord maintains with respect to Landlord's Property, including, without
limitation, any insurance referenced in Section 4.3(b) and any other insurance
Landlord is required to maintain by Landlord's lenders with respect to
Landlord's Property; (c) the term "Fiscal Year" shall mean July 1 through June
30 next following, or such other tax period as may be established by law for the
payment of Taxes; and (d) the term "Operating Costs" shall mean the items set
forth in Section 4.5 hereof.

      Section 4.2 Payment of Real Estate Taxes and Other Taxes.

      (a) Tenant shall pay to Landlord as Additional Rent an amount equal to
Tenant's Share of all of the Taxes. In the event that Landlord gives a Future
Building Lease Notice to Tenant, Landlord will prorate the Taxes for the Fiscal
Year in which such notice is given to account for the change in the Tenant's
Share effective on the date of such Future Building Lease Notice. Taxes shall be
estimated in good faith by Landlord at the end of each Fiscal Year (for the
following Fiscal Year), and thereafter be payable to Landlord in equal estimated
monthly installments together with the payment of Fixed Minimum Rent, subject to
readjustment when the actual amount of Tenant's Share of the Taxes is
determined. After readjustment, any shortage

                                       13
<PAGE>

shall be due and payable by Tenant within 15 days of demand by Landlord, and any
excess shall be credited against future Additional Rent obligations (provided
that there does not then exist a default of Tenant or any fact or circumstance
which, with the passage of time, the giving of notice, or the satisfaction of
any other condition, or all of them, could constitute default of this Lease), or
refunded if the Lease Term has ended and Tenant has no further obligations to
Landlord. If the taxing authority provides an estimated tax bill, then monthly
installments of Tenant's Share of the Taxes shall be based thereon until the
final tax bill is ascertained. Landlord shall furnish to Tenant, upon Tenant's
request, but not more than once in any Fiscal Year, a copy of the tax bill or
any estimated tax bill.

      (b) If, after Tenant shall have made any payment under this Section 4.2.
Landlord shall receive a refund (the "Refund") of any portion of the Tenant's
Share of the Taxes paid on account of any Fiscal Year for which such payments
shall have been made as a result of an abatement of such Taxes, by final
determination of legal proceedings, settlement or otherwise ("Proceedings"),
Landlord shall, within thirty (30) days after receiving the refund, pay to
Tenant an amount equal to Tenant's proportionate share of the Refund (provided,
however, that Landlord shall not be obligated to pay such amount to Tenant if
there then exists a default of Tenant or any fact or circumstance which, with
the passage of time, the giving of notice, or the satisfaction of any other
condition, or all of them, could constitute default of this Lease unless and
until the same is cured by Tenant), which payment to Tenant shall be
appropriately adjusted if Tenant's original payment covered a different period
than covered by the Refund, less all expenses reasonably incurred by Landlord in
connection with such proceedings (including, but not limited to, reasonable
attorneys' fees, costs and appraisers' fees). Landlord shall have sole control
of all Proceedings. From time to time as may be reasonably requested by Tenant,
Landlord shall provide to Tenant information regarding any pending Proceedings.
Until such time as Landlord commences construction of a Future Building (but not
at any time thereafter), Landlord agrees to take such actions as may be
requested in writing by Tenant and deemed by Landlord to be commercially
reasonable in connection with the initiation and prosecution of such Proceedings
provided that Tenant pays all costs and expenses in connection therewith within
thirty (30) days after demand by Landlord therefor.

      (c) If the Commencement Date of this Lease is not on July 1, or the
expiration or termination of this Lease is not on June 30, Tenant's obligation
in respect of Taxes shall be prorated. If the final tax bill for the Fiscal Year
in which such expiration or termination of this Lease occurs shall not have been
received by Landlord, then within thirty (30) days after the receipt of the tax
bill for such Fiscal Year, Landlord and Tenant shall make appropriate
adjustments of estimated payments.

      (d) Without limiting the generality of the foregoing, Tenant shall pay all
rent and personal property taxes attributable to its signs or any other personal
property including but not limited to its trade fixtures, equipment, the
existing or any future floor coverings, wall treatments and light fixtures in
the Premises.

                                       14
<PAGE>

      Section 4.3 Payment of Insurance Costs.

      (a) Tenant shall pay to Landlord as Additional Rent an amount equal to
Tenant's Share of all of the Insurance Costs for Landlord's cost for Insurance
("Insurance Costs") in any calendar year. In the event that (i) Landlord gives a
Future Building Lease Notice to Tenant and (ii) the Insurance Costs include the
cost of insurance for the Future Buildings. Landlord will prorate the Insurance
Costs for the calendar year in which such notice is given to account for the
change in the Tenant's Share effective on the date of such Future Building Lease
Notice. In the event that the Insurance Costs do not include the cost of
insurance for the Future Buildings, Tenant's Share of the Insurance Costs shall
remain at one hundred percent (100%) and Tenant shall pay an equitable portion
of the Insurance Costs attributable to the parking garage included in any Future
Building based upon the number of parking spaces made available to Tenant
therein. The cost of any blanket insurance covering the Premises and one or more
other buildings (including any Future Buildings) shall be allocated in a manner
reasonably determined by Landlord. The Insurance Costs shall be estimated in
good faith by Landlord at the end of each calendar year (for the following
calendar year), and thereafter be payable to Landlord in equal estimated monthly
installments together with the Fixed Minimum Rent, subject to re-adjustment when
Tenant's Share of the actual Insurance Costs is determined. After readjustment,
any shortage shall be due and payable by Tenant within 15 days of demand by
Landlord, and any excess shall be credited against future Additional Rent
obligations (provided, however, that Landlord shall not be obligated to pay such
amount to Tenant if there then exists a default of Tenant or any fact or
circumstance which, with the passage of time, the giving of notice, or the
satisfaction of any other condition, or all of them, could constitute a default
of this Lease unless and until the same is cured by Tenant), or refunded to
Tenant if the Lease Term has ended and Tenant has no further obligations to
Landlord. Landlord shall furnish to Tenant, upon Tenant's request but not more
than once in any calendar year, a copy of the Insurance premium bill.

      (b) Such Insurance Costs include the cost of insuring the entire
Landlord's Property, including without limitation, the Building and any Future
Improvements, and all operations conducted in connection therewith, with such
policies, coverages and companies and in such limits as may be selected by
Landlord, including, but not limited to, fire insurance with extended or with
all-risk coverage, rental and business interruption coverage, comprehensive
public liability insurance covering personal injury, rent loss, deaths and
property damage with a personal injury endorsement covering false arrest,
detention or imprisonment, malicious prosecution, libel and slander, and
wrongful entry or eviction, workers' compensation insurance, plate glass
insurance, contractual liability insurance and fidelity bonds.

      Section 4.4 Payment for Utilities. Landlord shall cause the Premises to be
separately metered or submetered for gas, electric, water, and sewer service.
Tenant shall be responsible for paying the bills for all such utility services
in its name. Tenant shall promptly pay prior to the date when due all charges
related to its use of gas, electric, water, and sewer service to the appropriate
public utility, and Tenant will provide to Landlord evidence of Tenant's payment
thereof within fifteen (15) days after Landlord's request.

      Section 4.5 Common Area and Other Operating Costs.

                                       15
<PAGE>

      (a) Tenant shall pay to Landlord as Additional Rent an amount equal to the
sum of:

            (i) all of the Operating Costs of the Building;

            (ii) Tenant's Share of the Operating Costs of the Common Areas,
Common Facilities, and other portions of Landlord's Property excluding the
Building and any Future Buildings. In the event that Landlord gives a Future
Building Lease Notice to Tenant, Landlord will prorate the Operating Costs
described in this clause (ii) of Section 4.5(a) for the calendar year in which
such notice is given to account for the change in the Tenant's Share effective
on the date of such Future Building Lease Notice; and

            (iii) a prorata share of the Operating Costs of any parking garage
included as part of any Future Improvements ("Future Parking Garage") based on
the number of parking spaces then allocated to Tenant in the Future Parking
Garage in comparison to the total number of parking spaces in the Future Parking
Garage. Landlord will make from time to time a reasonable allocation of the
Operating Costs of any Future Building, of which the Future Parking Garage is a
part, to the Future Parking Garage.

      (b) The Operating Costs shall be estimated in good faith by Landlord at
the end of each calendar year (for the following calendar year) and thereafter
be payable in equal estimated monthly installments, together with the Fixed
Minimum Rent, subject to readjustment when actual Operating Costs are
determined. After readjustment, any shortage shall be due and payable by Tenant
within 15 days of demand by Landlord and any excess shall be credited against
future Operating Costs obligations (provided, however, that Landlord shall not
be obligated to pay such amount to Tenant if there then exists a default of
Tenant or any fact or circumstance which, with the passage of time, the giving
of notice, or the satisfaction of any other condition, or all of them, could
constitute a default of this Lease unless and until the same is cured by
Tenant), or refunded if the Lease Term has ended and Tenant has no further
obligations to Landlord. Landlord shall provide Tenant upon request with
reasonable supporting documentation for the Operating Costs.

      (c) Notwithstanding anything to the contrary in this Section 4.5, Tenant
will not be liable for the Operating Costs of any Future Buildings ("Excluded
Portions of Landlord's Property") exclusive of those Operating Costs which are
allocated to any Future Parking Garage by Landlord pursuant to Section
4.5(a)(iii) above.

      (d) "Operating Costs" shall include any and all costs of operating,
managing, maintaining, repairing, replacing and insuring the Building, Common
Areas, Common Facilities, Future Parking Garage, and the remainder of Landlord's
Property exclusive of those costs allocated by Landlord to the Excluded Portions
of Landlord's Property. Such costs shall be those which Landlord deems to be
reasonable and appropriate including, but not limited to, all costs and expenses
for services provided in the Building and other costs and expenses, whether
expended or incurred in repairing (including but not limited to roof repairs and
maintenance), lighting, cleaning, painting, waterproofing, maintaining
(including, but not limited to, preventive maintenance) and improving (provided
that items required to be capitalized by Landlord's accountants including
improvements made by Landlord to comply with changes in law in

                                       16
<PAGE>

accordance with Section 7.6 shall be amortized over their applicable tax
amortization period with interest at the rate of 10% per annum, and only the
current portion thereof shall be included within Operating Costs) the Building,
Common Areas, Common Facilities, Future Parking Garage, and the remainder of
Landlord's Property (exclusive of the Excluded Portions of Landlord's Property);
removing rubbish and debris which is not removed by the applicable tenant or
occupant; providing pest and vermin control; providing, maintaining, repairing
and replacing of paving, curbs, walkways, landscaping, planters, roof, walls,
drainage, on-site water tines, sanitary sewer lines, storm water lines,
electrical lines and other equipment serving the Premises and/or other property
on which Landlord's Property or any part thereof is constructed or is to be
constructed; all surcharges, costs and expenses that may result from any
environmental or other laws, rules, regulations, guidelines or orders (excluding
costs associated with Hazardous Substances which are present on the Landlord's
Property (x) as of the date hereof or (y) through no fault of Tenant or any
other Tenant Party); a management fee equal to three percent (3.0%) of the gross
rents payable to Landlord with respect to Landlord's Property (exclusive of the
Excluded Portions of Landlord's Property), which management fee may be payable
to an affiliate of Landlord; and an administrative charge equal to ten percent
(10%) of the total of all Operating Costs (exclusive of such administrative
charge, management fee, Taxes, Insurance Costs and charges from any public
utility). "Operating Costs" do not include payments of (i) debt service and any
other mortgage charges, (ii) brokerage commissions, (iii) legal fees
attributable to (A) individual lease and tenant matters unless the matter
involves enforcing compliance with rules and regulations or other standards or
requirements for the benefit of all tenants on Landlord's Property and (B)
financings and refinancing of Landlord's Property, (iv) salaries of executives
and owners of Landlord other than the property manager and those working under
the direct supervision of such property manager, (v) general overhead and
administrative expenses of Landlord's home office not directly attributable to
the management or operation of Landlord's Property, (vi) costs of special
services rendered to Tenant or other tenants for which a separate charge by
Landlord is made; and (vii) "Structural Repair Costs" (as defined in Section
6.2) in excess of the amounts provided in Section 6.2.

                                    ARTICLE V

      Section 5.1 Use.

      (a) Subject to the terms of this Lease (including the other subparagraphs
of this Section 5.1), the Premises shall be used and occupied by Tenant solely
for the following specific uses:

            (i)   General office use;

            (ii)  Technical office for research and development, laboratory and
                  research facility (as defined and used in, and limited by, the
                  Cambridge Zoning Ordinance); and

            (iii) Limited manufacturing activity as an accessory use (as defined
                  and used in, and limited by, the Cambridge Zoning Ordinance).

                                       17
<PAGE>

Notwithstanding anything to the contrary contained in this Lease, under no
circumstances shall any portion of the Premises be used by any person, firm,
entity, business, enterprise or governmental authority in the business of
providing environmental engineering or environmental consulting services, nor
shall any environmental engineering or environmental consulting services be
rendered or performed on the Premises.

      (b) Before Tenant may begin its use and occupancy of the Premises, Tenant
will provide to Landlord a statement ("Hazardous Substances Statement"), setting
forth in detail, and to Landlord's satisfaction, (i) all licenses and permits
that any Tenant Party is required to obtain or will obtain in connection with
any Environmental Activity at the Premises, (ii) a list of all Hazardous
Substances expected to be used as part of any Environmental Activity and a copy
of each Tenant Party's reporting documentation required to be furnished to or by
any governmental authority, including, any right to know list, material safety
data sheets, or similar such documents, and (iii) a description of all of each
Tenant Party's planned Environmental Activities at the Premises. Landlord will
have the right to select and engage one or more consultants ("Landlord's
Consultant") to review the Hazardous Substances Statement and to investigate the
Tenant Parties' planned Environmental Activities. If Landlord's Consultant
determines that (1) any Tenant Party does not possess the requisite licenses or
permits with respect to its planned Environmental Activities or (2) any Tenant
Party's planned Environmental Activities present an unusual risk of
contamination of the Building or any other portion of Landlord's Property or any
violation of any Environmental Requirements, Landlord will have the right to
prohibit all or any portion of such Tenant Party's use of the Premises until
Landlord is reasonably satisfied that the applicable licenses and permits with
respect to such Tenant Party's use of the Premises have been obtained and that
no such contamination or violation will occur. The Environmental Activities
which have been established pursuant to this Section 5.1(b) are referred to as
the "Permitted Environmental Activities." The licenses and permits which are
required for the Permitted Environmental Activities are collectively referred to
as the "Required Permits". There shall not be any changes in the Permitted
Environmental Activities unless the terms of this Section 5.1 are complied with
by Tenant as in the case of the initial review of Tenant's planned Environmental
Activities as of the date that Tenant first takes occupancy of the Premises. In
the event of any change in Tenant's planned Environmental Activities Tenant
shall pay the costs of Landlord's Consultant in connection therewith. Landlord's
consent to the Permitted Environmental Activities after the review or
completion, to Landlord's reasonable satisfaction, of any inspection of Tenant
shall not, and shall not be deemed to, be a certification, representation or
warranty by Landlord that (A) Tenant is in compliance with applicable
Environmental Requirements, (B) the Required Permits are all of the licenses,
permits, and approvals required under applicable law, (C) no damage to the
Building (including any contamination) may occur by virtue of any Environmental
Activities by a Tenant Party, or (D) any Environmental Activities by a Tenant
Party pose acceptable risks to human and animal health and the environment.

      (c) Landlord will have the further right to (i) change the consultants
from time to time who are Landlord's Consultants and (ii) have Landlord's
Consultant inspect, from time to time (including on the termination of this
Lease), the Premises to determine whether (A) the use of the Premises by all
Tenant Parties complies with the Permitted Environmental Activities, (B) the
Required Permits are still in full force and effect, (C) any additional permits
or licenses or

                                       18
<PAGE>

approvals may be necessary or required, (D) any Tenant Party may be in violation
of any Environmental Laws, and/or (E) any portion of Landlord's Property or the
surrounding environment has been contaminated as a result of the Environmental
Activities of any Tenant Party. If Landlord's Consultant determines through its
inspection that any Tenant Party is not in compliance with the requirements of
this Section 5.1, Tenant will reimburse Landlord immediately on Landlord's
request for the cost to Landlord of Landlord's Consultant to conduct the
inspection. On each anniversary of the Commencement Date during the Lease Term
(and more often as requested by Landlord with reasonable advance notice) and on
any termination of this Lease, Tenant will certify to Landlord (a "Tenant
Environmental Certification") that, except as previously disclosed in writing to
Landlord pursuant to Section 5.1(i): (1) the Hazardous Substances Statement
remains true and correct (or if any permitted changes have occurred, an
explanation of those changes to Landlord's reasonable satisfaction), (2) there
have occurred no Environmental Activities other than the Permitted Environmental
Activities since the last anniversary date, (3) all Tenant Parties are in
compliance with all Environmental Requirements; applicable use regulations in
Section 4 of the Cambridge Zoning Ordinance; and all RDNA Requirements. (4) all
Required Permits are valid and in full force and effect and that those Required
Permits are the only licenses and permits required with respect to the
Environmental Activities of all Tenant Parties under any Environmental
Requirements, and (5) no Hazardous Substances contamination of the Premises, any
other portion of Landlord's Property, or the surrounding environment has
occurred from any Environmental Activity by a Tenant Party.

      (d) Subject to any rights of cure contained in this Lease, Tenant's right
to use the Premises is conditioned on all Tenant Parties obtaining and keeping
in full force and effect all necessary licenses and permits, in addition to the
Required Permits, required with respect to use and occupancy of the Premises by
the Tenant Parties and the Environmental Activities from the City of Cambridge,
the Commonwealth of Massachusetts and any other government authority.

      (e) In addition to the other terms defined in this Lease, as used in this
Lease (whether or not underscored):

            (i) "Environmental Activity" means any actual, proposed (by Tenant
or any other Tenant Party) or threatened use, storage, holding, existence,
Release, emission, discharge, generation, manufacturing, producing, refining,
creating, processing, abatement, removal, disposition, handling, transportation
or disposal of any Hazardous Substance from, under, into or on the Premises or
any other portion of Landlord's Property or otherwise relating to any Use of any
of Landlord's Property, which is regulated, or for which standards of conduct or
liability are imposed, by any Environmental Requirements, by any Tenant Party or
which presents an unusual risk to human or animal health or to the environment.

            (ii) "Environmental Law" means the Comprehensive Environmental
Response, Compensation, and Liability Act ("CERCLA"), 42 U.S.C.ss.9601 et seq.,
the Resource Conservation and Recovery Act, 42 U.S.C.ss.6901 et seq. the
Hazardous Materials Transportation Act, 49 U.S.C.ss.1802 et seq., the Toxic
Substances Control Act, 15 U.S.C. ss.2601 et seq., the Federal Water Pollution
Control Act, 33 U.S.C.ss.1251 et seq., the Clean Water Act, 33 U.S.C.ss.1321 et
seq., the Clean Air Act, 42 U.S.C.ss.7401 et seq., the Massachusetts Oil and
Hazardous Material Release Prevention and Response Act, Chapter 21E of the
Massachusetts General Laws,

                                       19
<PAGE>

all regulations promulgated thereunder, and any other federal, state, county,
municipal, local or other statute, law, ordinance or regulation (including, any
state or local board of health rules, regulation, or code), or any common law
(including common law that may impose strict liability or liability based on
negligence), which may relate to or deal with human health, the environment,
natural resources, or Hazardous Substances, all as may be from time to time
amended or modified.

            (iii) "Environmental Liability" means any liability, obligation,
indebtedness, or duty of, any claim or demand against, any requirement imposed
on, or any amount owed by or payable from, Tenant or Landlord, which is based
on, results from, is in connection with, arises out of, or otherwise is related
to any Environmental Activity by a Tenant Party, whether the foregoing described
liability is contingent or absolute, primary or secondary, liquidated or
unliquidated. due or to become due, and however created, incurred, acquired,
owing or arising. Notwithstanding the foregoing in this definition of
Environmental Liability, the term "Environmental Liability"' will not include,
and Tenant will not be liable to Landlord under this Lease for, any liability
for any contamination, claim of contamination, loss or damage arising in
connection with Hazardous Substances to the extent the same is the result of (A)
Hazardous Substances existing in the Building and Landlord's Property prior to
the Commencement Date, (B) migration of Hazardous Substances from any site onto
Landlord's Property not caused directly or indirectly by any Tenant Party, or
(C) the generation, manufacture, production, handling, release, storage, use or
disposal of any Hazardous Substances at the Building or Landlord's Property by
(1) Landlord or by its employees, agents, or independent contractors, or (2) any
tenants of Landlord's Property other than Tenant, its subtenants and assignees
and any other Tenant Parties.

            (iv) "Environmental Requirements" means all applicable present and
future laws, including Environmental Laws, authorizations, approvals, judgments,
injunctions, decrees, concessions, grants, orders, franchises, agreements and
other restrictions and requirements (whether or not arising under statutes or
regulations), including the RDNA Requirements, relating to any Hazardous
Substances or Environmental Activity.

            (v) "Hazardous Substances" means, at any time, (A) any "hazardous
substance" as defined in ss.101(14) of CERCLA (42 U.S.C. ss.9601(14)) or
regulations promulgated thereunder; (B) any "hazardous waste," or "infectious
waste," as such terms are defined in any Environmental Law at such time; (C)
asbestos, ureaformaldehyde, polychlorinated biphenyls ("PCBs"), bio-medical
materials or waste, nuclear fuel or material, chemical waste, radioactive
material, explosives, known carcinogens, petroleum products and by-products and
other dangerous, toxic or hazardous pollutants, contaminants, chemicals,
materials or substances which may be hazardous to human or animal health or the
environment or which are listed or identified in, or regulated by, any
Environmental Law; (D) materials or substances which are subject to control
under the RDNA Requirements, and (E) any additional substances or materials
which at such time are classified or considered to be hazardous or toxic under
any Environmental Law.

            (vi) "RDNA Requirements" means, collectively. Chapter 8.20 of the
Cambridge Municipal Ordinance, Recombinant DNA Technology, and the National
Institutes of

                                       20
<PAGE>

Health Guidelines cited therein. Any reference to a specific provision of the
applicable code or guidelines will be construed to include any comparable
provision of the applicable code or guidelines as amended or superseded after
the date of this Lease.

            (vii) "Release" includes, but is not limited to, spilling, leaking,
pumping, emitting, emptying, discharging, injecting, escaping, contaminating,
teaching, disposing, releasing or dumping into the environment.

            (viii) "Tenant Party" means any or all of (A) Tenant or its
affiliates, subsidiaries, owners, directors, officers, employees, agents.
invitees, licensees, independent contractors, or any other persons or entities
with respect to whose conduct Tenant is liable under applicable law (including
any successor or assign of the foregoing) or (B) any sublessee of Tenant or the
sublessee's affiliates, subsidiaries, owners, directors, officers, employees,
agents, invitees, licensees, independent contractors, or any other persons or
entities with respect to whose conduct the sublessee is liable under applicable
law (including any successor or assign of the foregoing).

            (ix) "Use" includes but is not limited to, use, ownership,
development, construction, maintenance, management, operation or occupancy.

      (f) Tenant may not dump, flush or in any way Release or introduce any
Hazardous Substances into the HVAC system of the Building and/or any septic,
sewage, storm water, or other waste disposal systems serving the Premises or any
other portion of Landlord's Property except for discharges into the public
sanitary sewer system in compliance with applicable Environmental Requirements
and in accordance with the Hazardous Substances Statement.

      (g) Tenant will, at its expense, (i) keep the Premises equipped with all
safety appliances required by law because of any use of the Premises other than
general office use and (ii) do any work to the Premises required by applicable
law as a result of any Environmental Activity, it being understood that the
foregoing provisions will not be construed to broaden in any way Tenant's
permitted use of the Premises.

      (h) Tenant will be liable for (i) any damage to the Building or any other
portion of Landlord's Property (including any loss of use of all or any portion
of the Building or any other portion of Landlord's Property) and (ii) for all
costs and expenses of any investigation, cleanup, detoxification,
decontamination of, or other response, removal, or remedial action with respect
to, the Building or any other portion of Landlord's Property (or the environment
with respect thereto) which, in any case, arises out of any Environmental
Activity by a Tenant Party. Tenant's obligations under this Section 5.1(h) shall
survive the termination of this Lease for any reason whatsoever and shall be in
addition to any indemnification or insurance obtained, or requested to be
obtained, under this Lease. Landlord shall be responsible for all costs and
expenses of any investigation, cleanup, detoxification, decontamination of, or
other response, removal or remedial action with respect to the Building or any
other portion of Landlord's Property (or the environment with respect thereto)
which arises out of any Environmental Activity of Landlord (but not any tenants
of Landlord) other than those matters, if any, disclosed in environmental
reports previously delivered to Tenant.

                                       21
<PAGE>

      (i) Tenant will (A) promptly notify Landlord of, and deliver to Landlord
copies of, all communications between Tenant and any governmental authorities
which relate to Environmental Activities, Environmental Requirements, or
Hazardous Substances affecting Tenant, including any oral or written warnings,
notices of violation of, or any permit proceedings under, any Environmental
Requirements that are received by Tenant with respect to any Environmental
Activities by a Tenant Party; (B) notify Landlord immediately after obtaining
knowledge of the Release or alleged Release in a reportable quantity (as defined
under applicable Environmental Law) of any Hazardous Substance on, in, under or
affecting the Premises or any other portion of Landlord's Property or any
surrounding area, and any noncompliance with any Environmental Requirement; and
(C) notify Landlord immediately of any litigation, suit or administrative
proceeding against a Tenant Party with respect to any Environmental Activities.

      (j) Tenant will identify Tenant's confidential information to Landlord
("Confidential Information") during the course of Landlord's investigations and
inspections of Tenant's Environmental Activities contemplated by this Section
5.1. Tenant will clearly and conspicuously mark any written information or
document as confidential and will take measures to separate all Confidential
Information from all other information provided to Landlord. If information,
that is considered by Tenant to be confidential, is provided orally, Tenant will
reduce in a writing to Landlord what portion or portions of the information
Tenant considers to be Confidential Information. Landlord will undertake
reasonable measures (in the context of the importance of the relevant
Confidential Information to Tenant) to protect against the disclosure by its
employees of Confidential Information and will include a non-disclosure
provision in its agreements with Landlord's Consultants with respect to
Confidential Information. Landlord will be authorized to disclose Confidential
Information (i) to such of its employees who have a need to know, (ii) to
Landlord's Consultants, (iii) to Landlord's attorneys, (iv) to Landlord's
mortgagees and ground lessors to the extent required by the applicable financing
or lease documents, or (v) pursuant to any order or requirement of any
governmental authority or otherwise having the force of law. Notwithstanding
anything to the contrary in this Section 5.1(j), Landlord will have the right to
disclose Confidential Information (A) to any applicable governmental authority
if Landlord and Landlord's Consultant reasonably believe that an imminent and
substantial endangerment to human or animal health or the environment exists or
(B) which Landlord can demonstrate has become part of the public domain by
proper and lawful means through the publication or communication by others at
the time of disclosure by Tenant to Landlord or, after this disclosure to
Landlord by Tenant, has become a part of the public domain by proper and lawful
means through the publication or communication by persons, entities or
authorities (other than Landlord) who have been authorized by Tenant to make the
publication and disclosure.

      Section 5.2 Prohibited and Required Uses. In addition to its obligations
under Section 5.1 and elsewhere under the terms of this Lease, Tenant will
procure and maintain in full force and effect all licenses and permits which are
required for any use made of the Premises. Tenant shall cause any fire lanes in
the front, sides and rear of the Premises to be kept free of all parking
associated with its business or occupancy and in compliance with all applicable
regulations. Tenant shall conduct its business at all times so as not to create
any nuisance and so as to not interfere with the business of other tenants and
occupants of Landlord's Property. Tenant shall at

                                       22
<PAGE>

its own cost install such extra sound-proofing, noise control systems and odor
control systems as may be needed to eliminate noise, vibrations and odors, if
any, emanating from the Premises being heard, felt or smelled outside the
Premises. Tenant will not permit in the Premises or any other portion of
Landlord's Property (a) any nuisance or (b) any Release of any Hazardous
Substances except as otherwise permitted under the terms of this Lease.

      Section 5.3 Compliance with Laws: Additional Restrictions. In its use of
the Premises, Tenant shall comply with any and all applicable laws, statutes,
ordinances, rules, regulations, codes and requirements of governmental
authorities. Tenant in its use of the Premises will not do any act which is in
contravention of, nor omit to do any act required of it by, any law, order or
regulation of any federal, state, county or municipal authority or by any lawful
order of any public official including, without limitation, all legal
requirements related to Environmental Activities.

                                   ARTICLE VI

      Section 6.1 Landlord's Common Area and Common Facilities Services. The
enumeration of items in Section 4.5 as being subject to Additional Rent for
Operating Costs shall not impose any obligation upon Landlord to provide such
services except to the extent required in the opinion of Landlord and to the
extent practical in relation to the then existing conditions but in no event
shall the failure of Landlord to perform any such work or service constitute a
breach of Landlord's obligations hereunder.

      Section 6.2 Repair Services. Within 30 days or longer if reasonably
required following receipt of notice of the need therefor, during the Lease
Term, Landlord will make necessary structural repairs in or to the Building in
which the Premises are located with regard to: the roof; load bearing walls;
structural columns; foundations; and structural elements of the floors (but not
floor coverings). Provided, however: (a) the cost for any such repairs made
necessary by any act, default or negligence of Tenant, its invitees, employees,
agents, licensees, or contractors may be charged entirely to Tenant who shall
pay for the same as Additional Rent promptly upon billing therefor; (b) Tenant
shall be responsible for the cost of said repairs and obligations under Section
7.4 with respect to the Premises; (c) Tenant shall in all circumstances, be
responsible for one hundred percent (100%) of all costs and/or expenses related
to the roof; and (d) damage from fire or other casualty, or taking by eminent
domain shall be governed by ARTICLES IX and X of this Lease. The cost of
structural repairs to structural elements of the Building (other than the roof)
other than those repairs which are (i) the responsibility of Tenant pursuant to
clauses (a), (b) or (c) of this Section 6.2 or other provisions of this Lease or
(ii) governed by Articles IX or X of this Lease (the "Structural Repair Costs")
shall be paid by Landlord. Structural Repair Costs so paid by Landlord shall be
amortized over the remaining useful life of the repaired structural element (as
determined by Landlord's accountants) with interest at the rate of 10% per annum
and only the current portion thereof shall be included in Operating Costs.

      Section 6.3 Interruption: Delay. Landlord shall have no responsibility or
liability for failure or interruption of any such repairs or services referred
to in this Article VI, or for any interruption in utility services, caused by
breakage, accident, strikes, repairs, inability after exercise of reasonable
diligence to obtain supplies or otherwise furnish services, or for any cause

                                       23
<PAGE>

or causes beyond the reasonable control of Landlord (which will never include
the lack of capital available to Landlord), nor in any event for any indirect or
consequential damages; and failure or omission on the part of Landlord to
furnish such service or make such repair shall not be construed as an eviction
of Tenant, nor render Landlord liable in damages, nor entitle Tenant to an
abatement of Fixed Minimum Rent or Additional Rent, nor release Tenant from the
obligation to fulfill any of its covenants under this Lease, except as provided
in Articles IX and X hereof with respect to eminent domain and damage by fire or
other casualty. Subject to Section 7.13, in the event that the Landlord shall at
any time fail to make or perform any material act on its part to be performed as
in this Lease provided, and either (a) Landlord has failed to cure such default
within thirty (30) days after notice from Tenant to Landlord (or such longer
time, not to exceed sixty (60) additional days, as may be reasonably required to
cure such default) or (b) there exists a substantial, imminent threat to persons
or property and Tenant has either (i) made good faith efforts to contact
Landlord without success or (ii) contacted Landlord but Landlord is unable or
unwilling to take actions sufficient to rectify the situation, then, and only
then, Tenant may take such actions as Tenant reasonably deems necessary to cure
such failure by Landlord to so act. Landlord shall reimburse Tenant for all
amounts so incurred by Tenant to cure such failure by Landlord within thirty
(30) days after Landlord receives written demand therefor from Tenant,
accompanied by evidence reasonably satisfactory to Landlord of the amounts so
incurred, but Tenant shall not have any right of set off with respect thereto
and shall in no event deduct any such amounts from payments of Fixed Minimum
Rent or Additional Rent.

      Section 6.4 Notice to Tenant of Certain Releases of Hazardous Substances.
Landlord shall provide prompt written notice to Tenant of any Release of
Hazardous Substances on Landlord's Property after the date hereof (other than a
Release by a Tenant Party) of which Landlord has actual knowledge and which
presents an unusual risk to the health of occupants of the Building or has a
material and adverse affect on Tenant's use of the Building.

                                   ARTICLE VII

      Section 7.1 Rent. Tenant will promptly pay the Fixed Minimum Rent and
Additional Rent, including without limitation any and all fees, charges,
expenses, fines, assessments or other sums payable by Tenant to Landlord (or to
the applicable provider of utilities) at the time and in the manner provided for
in this Lease, all of which shall be deemed to be obligations to pay Fixed
Minimum Rent or Additional Rent.

      Section 7.2 Address Change. Landlord reserves the right to change the
address of the Building from 205 Broadway to another address selected by
Landlord. Landlord will provide reasonable advance notice to Tenant of the
address change of the Building. In the event that such a change of address
occurs after September 1, 1998, Landlord shall pay all of Tenant's reasonable
costs associated therewith.

      Section 7.3 No Waste. Tenant shall not overload, damage or deface
Landlord's Property nor shall it suffer or permit the same to be done, nor shall
it commit any waste with respect to Landlord's Property. Tenant shall initiate
and carry out a program of regular maintenance and repair of the Premises so as
to impede, to the extent possible, deterioration by ordinary wear and tear or by
its use of the Premises. Without limiting the foregoing, Tenant shall not
overload the

                                       24
<PAGE>

electrical distribution system serving the Premises or use equipment which would
exceed the capacity of any of the electrical conductors or equipment serving the
Premises.

      Section 7.4 Maintenance, Repairs, and Yield-Up.

            (a) Tenant agrees that from the Commencement Date until the end of
the Lease Term and during any holdover, it will keep the Building neat and clean
and maintain the same in good repair and condition, reasonable wear and tear,
and damage by "Casualty"' (hereinafter defined) excepted. Tenant's obligation to
so maintain and repair the Building shall apply to all of the Building,
including, without limitation, all doors, glass, fixtures, interior walls,
floors, ceilings, and any other systems. There is excepted from Tenant's
obligations under this Section 7.4 only (i) damage caused by those hazards which
are covered by the policies of insurance carried by Landlord with respect to
Landlord's Property ("Casualty"') and (ii) repairs and work which are otherwise
the specific responsibility of Landlord hereunder (however, in no event will
Landlord have any responsibility for any damage (including any contamination)
which arises out of any Environmental Activity by a Tenant Party). Without
limiting the foregoing or anything else in this Section 7.4 or Section 6.2,
Tenant and not Landlord shall be solely responsible for the maintenance and
repair of the Building and all the pipes, wires, conduits, utilities and other
installations serving the Building.

            (b) At the end of the Lease Term or sooner termination of this
Lease, Tenant will:

                  (i) peaceably surrender or deliver up the Building to
Landlord;

                  (ii) at Landlord's sole option:

                        (A) except as set forth in Section 7.4(d), remove, at
Tenant's sole cost and expense, all erections, alterations and additions made to
or upon the Building, in which event, Tenant shall, at its sole cost and
expense, repair, restore and readapt the Building to the same condition as
existing upon execution of this Lease,

                        (B) except as set forth in Section 7.4(d), remove, at
Tenant's sole cost and expense, those erections, alterations and additions made
to or upon the Building as may be designated by Landlord, in which event (1)
Tenant shall, at its sole cost, repair and restore any damages resulting from
such removal and (2) Tenant shall leave all other erections, alterations and
additions in good repair and condition, in which event all such other erections,
alterations and additions shall become the property of Landlord without payment
to the Tenant of any nature; or

                        (C) leave all erections, alterations and additions in
good repair and condition in which event such erections, alterations, and
additions shall become the property of Landlord without payment to Tenant of any
nature;

                  (iii) leave the Premises, broom clean, with all utilities
safely capped, and in good repair and condition, reasonable wear and tear, and
damage by Casualty excepted; and

                                       25
<PAGE>

                  (iv) remove all signs and lettering and all personal property,
goods and effects belonging to Tenant or anyone claiming through or under
Tenant.

            (c) Tenant will not make any structural change in, or addition to,
the Building or make any roof penetration without first obtaining, on each
occasion, Landlord's consent in writing (which consent will not be unreasonably
delayed), and then only at Tenant's expense, and in a lawful manner and upon
such terms and conditions as Landlord, by such writing, shall approve, which
shall include without implied limitation maintenance of insurance in form and
substance reasonably satisfactory to Landlord. Any such alteration or addition
shall be consistent in appearance with the rest of the Building and Landlord's
Property and shall be made only after duly obtaining all required permits and
licenses from all governmental authorities. Tenant will deliver to Landlord in
writing a schedule setting forth the details and location of all such
alterations or additions. Notwithstanding anything to the contrary in this
Section 7.4(c). Tenant may undertake separate, minor alterations to the interior
of the Premises which cost less than $25,000 each (each a "Minor Alteration")
without Landlord's prior written consent so long as: (i) the Minor Alteration
complies with Section 2.6, (ii) the Minor Alteration does not require a building
permit from the City of Cambridge, in which case Landlord's prior consent shall
be required (which consent will not be unreasonably delayed), and (iii) on the
termination of this Lease (for whatever cause), Tenant shall, unless directed
otherwise in writing by Landlord or as otherwise provided in this Section 7.4,
readapt, repair and restore the Premises to the condition the same were in prior
to each such Minor Alteration, regardless of whether Landlord's consent was
required or obtained with respect thereto.

            (d) With respect to Tenant's Work and any other alterations or
additions made by Tenant (whether or not a Minor Alternation), Tenant may, at
anytime, request that Landlord agree in writing that such work, alteration or
addition remain part of the Premises in accordance with Section 7.4(b)(ii)(B)(2)
at the end of the Lease Term or sooner termination of this Lease. With respect
to each request made by Tenant pursuant to the preceding sentence, (i) if such
work, alteration or addition is consistent with standard office and/or
laboratory use, Landlord will not unreasonably withhold its agreement that such
work, alteration or addition remain a part of the Premises upon the expiration
of this Lease at the end of the Lease Term in accordance with Section
7.4(b)(ii)(B)(2) of this Lease (but such agreement shall not apply in the event
of a termination of this Lease due to a default by Tenant) and (ii) in all other
instances, Landlord may, in its sole discretion withhold its agreement that such
work, alteration or addition remain a part of the Premises. Tenant shall not be
required to remove any work, alteration or addition which Landlord has so agreed
need not be removed so long as (1) Tenant complies with Section 7.4(b)(ii)(B)
and (2) the Lease has not been terminated due to a default by Tenant.

      Section 7.5 Trade Fixtures and Equipment. Any trade fixtures installed by
Tenant in, or attached or affixed by it to, the Building shall be removed by
Tenant from the Building on the termination of this Lease (for whatever cause).
Any removal by Tenant shall be without damage to, or destruction of, any part of
the Building. Tenant shall have the right, at any time and from time to time
during the Lease Term, to remove any of its movable equipment which is not
affixed, attached to, or a part of, the Building. In addition, at the expiration
of this Lease, Tenant shall remove all of Tenant's movable equipment, unless
Landlord gives Tenant a written waiver

                                       26
<PAGE>

for same. At any time that Tenant removes its movable equipment. Tenant shall
promptly repair the Building as a result of any damage to, or destruction of,
the Building caused by the removal of its movable equipment.

      Section 7.6 Compliance with Laws and Insurance Requirements. In addition
to its other obligations under this Lease, Tenant, in its use of the Premises
and at its sole expense, shall comply with all laws, orders and regulations of
Federal, State, County and City authorities, and with any direction of any
public officer or officers, pursuant to law, including, without limitation, (a)
City of Cambridge ordinances with respect to animal experiments and insect and
rodent control and (b) all legal requirements related to the use, storage,
discharge, release, removal or existence of Hazardous Substances, which shall
impose any violation, order or duty upon Landlord or Tenant with respect to the
use of the Premises. Tenant agrees that the Premises shall be kept in a sanitary
and safe condition in accordance with all applicable Federal and State laws and
the by-laws, rules, regulations and ordinances of the City of Cambridge, and in
accordance with all directions, rules and regulations of the Health Officer,
Fire Marshall, Building Inspector and other proper officers of the governmental
agencies having jurisdiction thereover. Tenant shall not do or permit to be done
any act or thing upon the Premises which will invalidate, or be in conflict
with, the insurance policies covering Landlord's Property, or the Premises, and
fixtures and property therein. Tenant, at its sole expense, shall comply with
all rules, orders, regulations or requirements of the Board of Fire
Underwriters, or any other similar body relating to Tenant's use of the
Premises, and shall not do or permit anything to be done, in or upon the
Premises, or bring or keep anything therein, except as now or hereafter
permitted by the Fire Department, Board of Fire Underwriters, Fire Insurance
Rating Bureau, or other authority having jurisdiction and then only in such
quantity and manner of storage as not to increase the rate for the insurance
applicable to Landlord's Property, or the Premises, or use the Premises in a
manner which shall increase the rate of insurance on Landlord's Property, or on
property located therein over the rate in effect at the commencement of this
Lease. If by reason of the failure of Tenant to comply with the provisions of
this section including, but not limited to, the use to which Tenant puts the
Premises, the insurance rate shall at the beginning of this Lease or any time
thereafter be higher than it otherwise would be, then Tenant shall reimburse
Landlord, as Additional Rent hereunder, for that part of all insurance premiums
thereafter paid by Landlord which shall have been charged because of such
failure or use by Tenant, and shall make such reimbursement within fifteen (15)
days after billing therefor by Landlord. In the event of a change in law
occurring after the date of this Lease which requires alterations to be made to
the Building, the following shall apply:

      (i) if the alterations (A) are required in whole or in part because the
Building or any portion thereof is being used for any purpose other than general
office use, because of the number of employees or others present in the
Building, because of any reason related to any special use of the Building by
any Tenant Party or because the Tenant has subleased all or a portion of the
Building, or (B) would not be required if the Building were leased to a person
or entity other than Tenant for general office use, then, in any such event, the
cost of such alterations shall be paid by Tenant; and

      (ii) in all other cases, the cost of such alterations shall be paid for by
Landlord and such alterations shall be treated as a capital improvement to be
amortized over the applicable tax

                                       27
<PAGE>

amortization period with interest at the rate of 10% per annum, and only the
current portion thereof shall be included within Operating Costs.

      Section 7.7 Contents at Tenant's Risk. All inventory, equipment, goods,
merchandise, furniture, fixtures and property of every kind which may be on or
about Landlord's Property shall be at the sole risk and hazard of Tenant; and if
the whole or any part thereof shall be destroyed or damaged by fire, water or
otherwise, or by the use or abuse of water or by the leaking or bursting of
water pipes, or by rising water, or by roof or other structural leak, or in any
other way or manner, no part of such loss or damage shall be charged to or borne
by Landlord in any case whatsoever, except that to the extent required by
applicable Massachusetts law, the foregoing shall not exculpate Landlord from
its own negligent acts or omissions. Tenant agrees to maintain full and adequate
insurance coverage on all of its property at the Premises and in Landlord's
Property, including physical damage, theft and business interruption insurance.
Such insurance on Tenant's property shall, subject to Section 12.4, contain a
waiver of subrogation clause in favor of Landlord, or shall name Landlord as an
additional insured for the sole purpose of preventing a subrogation claim
against Landlord.

      Section 7.8 Exoneration and Indemnification. Tenant will exonerate,
indemnify, defend, save and hold harmless Landlord (and any and all persons
claiming by, through or under Landlord) from and against all claims, damages,
proceedings, defenses thereof, liabilities, costs, and expenses of any kind and
nature, including legal fees, arising from any or all of the following: (i) any
breach of this Lease by Tenant or those for whom Tenant is responsible; (ii) any
Environmental Activity (whether or not it is a Permitted Environmental Activity)
by a Tenant Party; or (iii) any act, omission or negligence of Tenant, or
Tenant's contractors or licensees, or of the agents, servants, employees or
business invitees of Tenant, or Tenant's contractors or licensees, or persons
coming onto Landlord's Property for the purpose of visiting or dealing with any
one or one or more of the foregoing, or arising from any accident, injury or
damage occurring outside of the Premises but, in, on or about Landlord's
Property, which such accident, damage or injury results or is claimed to have
resulted from the negligence or misconduct on the part of Tenant or Tenant's
contractors or licensees, or of the agents, servants, employees or business
invitees of Tenant, or Tenant's contractors or licensees, except that to the
extent required by applicable Massachusetts law, the foregoing shall not apply
to Landlord's negligent acts and omissions. This exoneration, indemnification
and hold harmless agreement shall survive the termination of this Lease for any
reason whatsoever and shall be in addition to any insurance obtained, or
requested to be obtained, under this Lease.

      During the Lease Term and any period of holding over, Tenant shall
maintain in full force and effect a policy of comprehensive public liability and
property damage insurance under which Landlord (and any person in privity of
estate with Landlord), Landlord's mortgagee(s), and Tenant are named as
insureds. Each such policy shall be non-cancelable with respect to Landlord
without thirty (30) days' prior written notice to Landlord and Tenant shall
deliver to Landlord prior to the Commencement Date and thereafter at least
thirty (30) days prior to the expiration of any then effective coverage a
satisfactory written certificate of insurance coverages or the renewal or
replacement of such coverages. The minimum limits of liability of such liability
insurance shall be Two Million Dollars ($2,000,000.00) for injury (or death) to
any one person, and Two Million Dollars ($2,000,000.00) for injury (or death) to
more than one person,

                                       28
<PAGE>

and Two Million Dollars ($2,000,000.00) with respect to damage to property,
together with an overall umbrella coverage of an additional Four Million Dollars
($4,000,000.00). Tenant shall not permit any contractor to do any work at or
furnish any materials to be incorporated into the Premises, whether or not
included in Tenant's Work, without first delivering to Landlord satisfactory
evidence of the contractor's comprehensive liability insurance, workers'
compensation insurance and statutory lien bonds (for all alterations other than
Minor Alteration, as defined in Section 7.4), each reasonably acceptable to
Landlord and complying with any insurance specifications provided by Landlord.
Tenant shall also provide and pay for window and plate glass insurance with
respect to the Premises in amounts and with companies satisfactory to Landlord,
and Tenant shall provide Landlord with a certificate evidencing such insurance
and containing a provision that the same may not be canceled without thirty (30)
days' prior written notice to Landlord and Tenant shall provide Landlord with
such a certificate prior to the Commencement Date and thereafter at least thirty
(30) days prior to the expiration of any such coverage. All insurance
requirements imposed upon Tenant or its contractors under this Lease shall be
subject to the further requirement that the forms of coverage and the insurers
providing the insurance be licensed in the Commonwealth of Massachusetts, be in
sound financial condition, carry an A+ or better Best's rating, and be
reasonably acceptable to Landlord. Tenant agrees that Landlord shall not be
responsible or liable to Tenant, or to those claiming by, through or under
Tenant, for any loss or damage that may be occasioned by or through the acts or
omissions of persons occupying or using adjoining premises or any part of
Landlord's Property, or otherwise, or for any loss or damage resulting to Tenant
or those claiming by, through or under Tenant, or its or their property, except
that to the extent required by applicable Massachusetts law, the foregoing shall
not exculpate Landlord from its negligent acts and omissions.

      Section 7.9 Landlord's Access. In addition to its rights under Section S.1
of this Lease, Landlord or its representatives shall have the right without
charge to it and without reduction in Fixed Minimum Rent or Additional Rent, at
reasonable times and on reasonable advance notice and in such manner as shall
not unreasonably interfere with Tenant's business (subject, in non-emergency
situations, to Landlord's compliance with the security protocols of Tenant which
Landlord has approved in writing prior to the implementation thereof; provided,
however, that Tenant shall modify and/or waive provisions of said security
protocols to the extent reasonably necessary to accommodate such entry by
Landlord or its representatives while preserving the confidentiality rights of
Tenant recognized under this Lease), to enter to view the Premises for any
reasonable purpose (including, without limitation, showing the Premises to
prospective purchasers, tenants and lenders) and, if Landlord so elects, to make
entry for the purpose of investigating repair or maintenance problems and to
make such repairs or changes as Landlord deems advisable, and to maintain, use,
repair, replace, relocate or introduce pipes, ducts, wires, meters and any other
Landlord's fixtures serving or to serve the Premises or other parts of
Landlord's Property, or to maintain or repair any portion of Landlord's
Property, and, in case of an emergency, whether resulting from circumstances in
the Premises or elsewhere in or on Landlord's Property, Landlord or its
representatives may enter the Premises at any time to take such measures as may
be needed to address such emergency. Such access shall include, but not be
limited to, the right to open floors, walls, ceilings, and building systems for
the foregoing purposes. Landlord may, during the twelve (12) months next
preceding the expiration of the

                                       29
<PAGE>

Lease Term, show the Premises to parties wishing to lease or purchase the same
and to place a "For Lease", "For Rent" or "For Sale" sign in the window or on
the Premises.

      Section 7.10 No Liens. Tenant shall not permit any mechanics', laborers'
or materialmen's liens to stand against Landlord's Property or Tenant's
interests in the Premises or lease estate, for any labor or materials furnished
to Tenant or claimed to have been furnished to Tenant in connection with work of
any character performed or claimed to have been performed in or on the Premises
by or at the direction or sufferance of Tenant. Landlord may condition the right
of Tenant to do Tenant's Work or to do any other work which could result in a
lien upon Landlord's Property or Tenant's interests in the Premises or lease
estate on the delivery and recording of statutory lien bonds (for all
alterations other than a Minor Alteration, as defined in Section 7.4) or
indemnities satisfactory to Landlord.

      Section 7.11 Compliance with Regulations. Tenant covenants that Tenant,
its agents, employees, servants, licensees, invitees, and visitors will comply
with all such reasonable rules and regulations as Landlord may from time to time
hereafter promulgate to regulate the conduct generally of all the tenants of
Landlord's Property. Landlord, however, shall have the reasonable right to
change said rules and regulations and to waive any one or more of them in the
case of any one or more tenants.

      Section 7.12 Subletting and Assignment.

            (a) Tenant shall not assign, mortgage, pledge or encumber this Lease
nor underlet all or any part of the Premises, nor permit or allow the use of all
or any part of the Premises by third party users, such as concessionaires,
without, on each occasion, obtaining Landlord's written consent thereto. As used
herein, the term "assign" or "assignment" shall be deemed to include, without
limitation: (i) any transfer of Tenant's interest in this Lease by operation of
law, the merger or consolidation of Tenant with or into any other firm or
corporation; or (ii) the transfer or sale of a controlling interest in Tenant
whether by sale of its capital stock or otherwise.

            (b) (i) Notwithstanding anything to the contrary in Section 7.12(a),
Landlord will not unreasonably withhold or delay its consent to any sublease of
all or any portion of the Premises, so long as (A) the sublease of space in the
Building to such subtenant will not, in Landlord's sole discretion, violate the
terms of (1) any lease affecting the Landlord's Property, (2) any lease
affecting the property located at 210 Broadway or (3) any agreement, instrument,
law, rule, regulation or requirement which is binding upon Landlord and/or
Landlord's Property; provided, however, that, for purposes of clauses (1), (2)
and (3) above, the use of the subleased portion of the Premises for a
biotechnology use will not, in and of itself, be a violation of any such lease,
or any agreement or instrument voluntarily entered into by Landlord; (B) the
subtenant and its proposed use is of a character consistent with the operation
of a first class research and development and/or office building; (C) each of
Landlord's mortgagees have consented in writing to the sublease if such
mortgagee's consent is required pursuant to the terms of the applicable
financing documents; (D) the subtenant's proposed use of the Premises is
permitted under the terms of this Lease; (E) the subtenant does not intend to
engage in any Environmental Activities or, if such subtenant intends to engage
in any Environmental Activities,

                                       30
<PAGE>

the Tenant and the proposed subtenant have fully complied with Section 5.1 with
respect to such Environmental Activities and such Environmental Activities are
Permitted Environmental Activities; (F) the Letter of Credit will remain in full
force and effect and continue to be available to Landlord under the terms of
this Lease; (G) the subtenant is qualified to do business in the Commonwealth of
Massachusetts and has all applicable permits and licenses to do business from
the Premises; (H) Tenant pays to Landlord all of Landlord's reasonable expenses
arising out of such sublease up to a maximum, for each sublease request, of
$5,000.00 plus the fees and expenses of Landlord's Consultant; (I) there does
not then exist a default of Tenant or any fact or circumstance which, with the
passage of time, the giving of notice, or the satisfaction of any other
condition, or all of them, could constitute a default under this Lease and no
default will be created as a result of the proposed sublease or the proposed use
by the subtenant; (J) there are not more than a total of two (2) subtenants,
including the proposed subtenant under the proposed sublease, in occupancy of
the Premises or portions thereof; (K) the proposed subtenant is not in the
business of providing environmental engineering or environmental consulting
services; and (L) the proposed sublease prohibits any assignment of the sublease
or any sub-sublease of any portion of the Premises without the prior written
consent of Landlord, which consent may be granted or denied in Landlord's sole
discretion.

            (ii) Notwithstanding anything to the contrary in Section 7.12(a),
provided that Landlord receives not less than thirty (30) days prior written
notice thereof, Landlord's consent shall not be required for an assignment or a
sublease of all (but not less than all) of the Premises to (A) any entity which
controls the legal and beneficial ownership of Tenant, (B) any entity controlled
by, or under common control with. Tenant, (C) any corporation resulting from the
merger or consolidation with Tenant or (D) an entity acquiring alt or
substantially all of Tenant's assets so long as, in each instance, (1) there is
no change in the use of the Premises; (2) Tenant is the surviving corporation in
any merger or consolidation or, if Tenant is not the surviving corporation, the
surviving corporation assumes all of the obligations of Tenant under this Lease
by executing an assignment and assumption agreement with respect to this Lease
in form and substance satisfactory to Landlord; (3) the assignee or subleasee
has a net worth, as determined by generally accepted accounting principles, on
the date of such sublease or assignment equal to or greater than Tenant's net
worth, determined in accordance with generally accepted accounting principles,
as of the date of this Lease; (4) the Letter of Credit will remain in full force
and effect and continue to be available to Landlord under the terms of this
Lease; (5) the subtenant or assignee is qualified to do business in the
Commonwealth of Massachusetts and has all applicable permits and licenses to do
business from the Premises; (6) Tenant pays to Landlord all of Landlord's
reasonable expenses arising out of such sublease or assignment; (7) there does
not then exist a default of Tenant or any fact or circumstance which, with the
passage of time, the giving of notice, or the satisfaction of any other
condition, or all of them, could constitute a default under this Lease and no
default wilt be created as a result of the proposed sublease or assignment or
the proposed use by the subtenant or assignee; (8) the proposed assignee or
subtenant is not in the business of providing environmental engineering or
environmental consulting services; and (9) in the case of a sublease, the
proposed sublease prohibits any assignment of the sublease or any sub-sublease
of any portion of the Premises without the prior written consent of Landlord,
which consent may be granted or denied in Landlord's sole discretion. In the
event that the giving of the thirty (30) day notice required under this Section
would be a violation of applicable securities laws, such thirty (30) day notice
requirement shall

                                       31
<PAGE>

not apply so long as Tenant provides such notice at the earliest time at which
such notice may be given without being such a violation and Tenant complies with
all of the other provisions of this Section.

            (c) In the event of the assignment or subletting by Tenant, Tenant
shall remain primarily liable jointly and severally with the assignee or
sub-tenant for the payment of any and all Fixed Minimum Rent and Additional Rent
which may become due by the terms of this Lease and for the performance of all
covenants, agreements and conditions on the part of Tenant to be performed
hereunder. Tenant shall also pay to Landlord fifty percent (50%) of any rent
received as a result of the assignment or sublet which exceeds all of the rental
payable or reserved hereunder for the same time period on a per square foot
basis after deducting the actual direct out-of-pocket third-party costs which
are (i) incurred by Tenant for (A) leasing commissions and additional tenant
improvements (excluding Tenant's Work and other amounts incurred by Tenant in
meeting its obligations under Section 2.5) paid in connection with such
assignment or sublease or (B) additional services actually provided by Tenant to
such assignee or subtenant to the extent that Tenant is not otherwise paid
amounts in connection with such services, and (ii) documented to Landlord's
reasonable satisfaction by invoices, contracts, canceled checks and the like. No
such assignment or sublease shall be valid or effective unless it is approved in
advance in writing by Landlord, and the assignee, or sublessee, by a document
satisfactory to Landlord, shall covenant in writing at Landlord's option, to be
bound directly to the Landlord. No modification of the terms of this Lease or
any course of dealing between Landlord and any assignee or sublessee of Tenant's
interest herein shall operate to release or impair Tenant's obligations
hereunder or the obligation of any Guarantor (as defined in Section 11.1).

            (d) Notwithstanding anything to the contrary contained in this
Section 7.12 or other provisions of this Lease, in the event that Tenant seeks
Landlord's consent to an assignment of this Lease or a sublease of all of the
Premises (exclusive of any permitted assignment or sublease set forth in Section
7.12(b)(ii)), Landlord at its option may terminate this Lease. In such an event,
(i) Landlord may enter into a new lease with the proposed assignee or sublessee
or any other party on any terms and provisions acceptable to Landlord in
Landlord's sole discretion for the Premises and (ii) unless there are less than
twenty-four (24) months then remaining in the Lease Term, Landlord shall pay to
Tenant the unamortized portion of the costs incurred by Tenant for tenant
improvements (such costs to be amortized over the initial ten year Lease Term on
a straight line basis) as documented to the reasonable satisfaction of Landlord
(such documentation to be provided promptly upon request).

            (e) Tenant shall not enter into any arrangements with any sub-tenant
or assignee to circumvent, or which has the effect of circumventing. (i) its
obligation to share rents received from a sublease or assignment, or (ii) any of
the other provisions of this Section 7.12.

      Section 7.13 Construction of Future Improvements on Landlord's Property.
Tenant acknowledges that Landlord has plans to construct an additional building
and other improvements on Landlord's Property, including, without limitation, on
the Parking Area. Tenant agrees to cooperate with Landlord in connection with
Landlord's plans to construct such additional building and improvements on
Landlord's Property and the construction of such

                                       32
<PAGE>

building and improvements and that neither Tenant nor any Tenant Party shall
take any action which will interfere with such plans or construction. Landlord
will plan such construction and related staging in a manner which it considers
reasonable under the circumstances to minimize (to the extent consistent with
the efficient performance of such construction) any material interference with
Tenant's access to and/or use of the Premises during the performance of such
construction. Tenant acknowledges that from time to time that dust, noise,
vibrations, water leakage, and interruptions to power and other utilities
(including water and sewer) may, among other construction related interference
occur in connection with Landlord's construction activities on Landlord's
Property. Tenant is responsible to safeguard, insure, and protect adequately its
property (including any sensitive electronic equipment and computers) during the
construction process and Landlord will not be liable to Tenant for any direct or
indirect damage or loss suffered by Tenant as a result of Landlord's
construction activities. Tenant will notify Landlord if any such construction
related interference should occur. Upon receipt of written notice from Tenant,
Landlord will undertake those measures which it considers reasonable under the
circumstances to minimize (to the extent consistent with the efficient
performance of Landlord's construction) any material interference with Tenant's
access and/or use of the Premises during the performance of any such
construction by Landlord. Tenant shall not be entitled to any abatement of rent
or to claim any constructive eviction as a result of Landlord's construction
activities; provided, however, that for each business day for which Tenant is
denied access to the Building due to Landlord's construction activities blocking
physical access to and from the Building for more than four (4) hours between
8:00 a.m. and 5:00 p.m.. Tenant shall be entitled to the abatement of the Fixed
Minimum Rent, Taxes, Insurance Costs and Operating Costs attributable to that
day.

      Section 7.14 Relocation of Premises. In the event that, as a result of (1)
a change in zoning of all or any portion of Landlord's Property, (2) any
petition to change the zoning of all or any portion of Landlord's Property
and/or (3) an agreement entered into by Landlord or which binds all or any
portion of Landlord's Property which, in any case, restricts Landlord's Property
so that, in Landlord's reasonable judgment, (x) Landlord cannot construct more
than 180,000 square feet of new office space on Landlord's Property (said space
being in addition to the space located in the Building) or (y) Landlord will not
be able to obtain a building permit (which is not issued as an "at risk" permit)
to construct more than 180,000 square feet of new office space on Landlord's
Property (said space being in addition to the space located in the Building)
with not less than 220 parking spaces on Landlord's Property without obtaining a
special permit or variance, then, in either or both of such events, Landlord
shall have the unrestricted and unconditional right, at Landlord's sole option,
one time only during the Lease Term (including during any Extension Term), to
relocate the Premises to space suitable for biotechnology use, on one or more
contiguous floors (and which is not basement space) at a building which Landlord
or one or more of its affiliates may construct (I) on any other portions of
Landlord's Property, including, without limitation, the Parking Area (the "New
205 Broadway Building") or (II) on the property located across Broadway from the
Building and known as 210 Broadway, Cambridge, Massachusetts ("210 Broadway").
Landlord will give Tenant written notice of Landlord's intention to relocate the
Premises (a "Relocation Notice"), and Tenant will complete such relocation
within one hundred eighty (180) days after receipt of such written notice. If
Tenant is relocated to the New 205 Broadway Building or 210 Broadway as provided
in this Section 7.14, effective on the date of such relocation, this Lease will
be amended by (a) deleting

                                       33
<PAGE>

the description of the original Premises and substituting for it a description
of the new space, (b) including appropriate provisions regarding Tenant's
obligations for Taxes, Insurance and Operating Costs with respect to the new
space, and (c) if the Premises are relocated to 210 Broadway, any or all of the
parking spaces provided to Tenant under this Lease may also be relocated to 210
Broadway (provided that, in such event, not less than 15 of such parking spaces
shall be located on 210 Broadway) Landlord agrees to (i) pay the costs of tenant
improvements reasonably required to build-out a portion of the new space
equivalent in size to the portion of the Premises built-out by Tenant at the
time of the Relocation Notice so as to make the new space comparable to (or, at
Landlord's option, better than) the Premises in terms of (A) quality of
materials, finishes, construction and levels of improvement, and (B) amounts of
office space and laboratory space, (ii) pay up to $25,000.00 of the "soft costs"
incurred by Tenant in connection with such relocation for fees of architects,
engineers and project managers, and (iii) reimburse Tenant for its actual moving
costs to such new space, to the extent such costs are reasonable. Tenant shall
not be obligated to relocate to new space which does not comply with the
provisions of this Section 7.14 provided that Tenant specifies in writing to
Landlord, within three (3) days after demand, the specific reasons why such new
space does not so comply and Landlord fails to cure such noncompliance. If
Tenant fails to relocate to the new premises designated by Landlord within the
time period set forth in this Section 7.14, Tenant will be in default of this
Lease, time being of the essence.

                                  ARTICLE VIII

      Section 8.1 Subordination to Mortgages. Tenant agrees that this Lease is
and shall be and remain subordinate to the lien of any present or future
mortgage or mortgages, or ground lease, upon all or any portion of Landlord's
Property, irrespective of the time of execution or time of recording of any such
mortgage or mortgages, or ground lease, and to all renewals, extensions, and
modifications therefor or amendments thereto. Tenant agrees that it will, upon
ten (10) days' advance written request from Landlord or any holder of a mortgage
on all or a portion of Landlord's Property or the ground lessor thereof,
execute, acknowledge. and deliver any and all instruments reasonably deemed
necessary or desirable by Landlord, or such holder to give effect to, or notice
of, such subordination so long as such mortgagee provides Tenant with the
benefit of such mortgagee's standard non-disturbance agreement reasonably
acceptable to Tenant (without limiting the generality of the foregoing, Tenant
agrees that the form of Subordination, Non-Disturbance and Attornment Agreement
attached hereto as Exhibit H is acceptable to Tenant). Upon ten (10) days'
advance written request from Landlord, any holder of a mortgage or ground lease
on Landlord's Property or any successor in interest to Landlord, whether by
purchase, foreclosure, deed in lieu of foreclosure or otherwise, Tenant shall
enter into an attornment agreement, in the form requested by such party, with
such party.

      Section 8.2 Lease Superior at Mortgagee's Election. At the request in
writing of any mortgagee or any or ground lessor of Landlord's Property, this
Lease shall be deemed superior to such mortgage, or ground lease, whether this
Lease was executed before or after such mortgage, or ground lease, and Tenant
shall execute such documents in recordable form as such mortgagee, or ground
lessor, shall request.

                                       34
<PAGE>

      Section 8.3 Notice to Mortgagee. Upon receipt of a written request from
Landlord or any holder of a mortgage on all or any part of Landlord's Property,
or the ground lessor thereof, Tenant will thereafter send any such holder copies
of all notices of default or termination or both given by Tenant to Landlord in
accordance with any provision of this Lease. In the event of any failure by
Landlord to perform, fulfill or observe any agreement by Landlord herein or any
breach by Landlord of any representation or warranty of Landlord herein, any
such holder or ground lessor may at its election cure such failure or breach for
and on behalf of Landlord within twenty (20) business days after the time
provided herein for Landlord to cure the same or such longer period as may be
reasonably necessary to cure the default.

      Section 8.4 Estoppel Certificate By Tenant and Other Documents. Tenant
agrees, at any time and from time to time, upon not less than ten (10) days'
prior written request by Landlord or any holder of a mortgage on all or a
portion of Landlord's Property or the ground lessor thereof, (1) to execute,
acknowledge and deliver to Landlord a statement in writing certifying that
(except as may be otherwise specified by Tenant): (a) this Lease is presently in
full force and effect and unmodified; (b) Tenant has accepted possession of the
Premises; (c) any improvements required by the terms of this Lease to be made by
Landlord have been completed to the satisfaction of Tenant; (d) no rent under
this Lease has been paid more than 30 days in advance of its due date; (e) the
addresses for notices to be sent to Tenant is as set forth in this Lease or as
specified in such certificate; (f) Tenant as of the date of executing the
certificate has no charge, lien or claim of offset under this Lease, or
otherwise, against rents or other charges due or to become due thereunder; and
(g) such other information as Landlord, such holder or ground lessor may
reasonably request about this Lease or Tenant's occupancy; and (2) to deliver
information in form satisfactory to Landlord and such holder or ground lessor
concerning Tenant's operations, including but not limited to historic and
current financial statements of Tenant and information relative to any
Environmental Activities by a Tenant Party. In addition, Tenant agrees that the
holder of a mortgage or ground lease on Landlord's Property or such successor in
interest shall not be: (i) bound by any payment of an installment of Fixed
Minimum Rent or Additional Rent which may have been made more than 30 days
before the due date of such installment; (ii) bound by any amendment or
modification to this Lease made without the consent of such holder of a mortgage
or ground lease on Landlord's Property or such successor in interest; (iii)
liable for any previous act or omission of Landlord (or its predecessors in
interest); (iv) responsible for any monies owing by Landlord to the credit of
Tenant or subject to any credits, offsets, claims, counterclaims, demands or
defenses which Tenant may have against Landlord (or any of their predecessors in
interest); (v) bound by any covenant to undertake or complete any construction
of the Premises or any portion thereof except that, during the first two (2)
years of the Lease Term, such holder or successor may be liable for the unpaid
balance, if any, of the Landlord's Contribution pursuant to Section 2.5; or (vi)
obligated to make any payment to Tenant other than any security deposit actually
delivered to holder of a mortgage or ground lease on Landlord's Property or such
successor in interest. Further, the Tenant agrees that it will not seek to
terminate this Lease by reason of any act or omission of Landlord until Tenant
shall have given written notice of such act or omission to the holder of such
mortgage or ground lease (at such holders last address furnished to Tenant) and
following the giving of such notice such holder shall have the right, but shall
not be obligated, to remedy such act or omission within twenty (20) business
days after the time period provided for in this Lease for Landlord to cure the
same or such longer period as may be reasonably necessary to cure the same.
Tenant shall enter into a

                                       35
<PAGE>

written agreement confirming the foregoing from time to time upon written
request from Landlord and/or the holder of a mortgage or ground lease on
Landlord's Property.

                                   ARTICLE IX

      Section 9.1 Eminent Domain: Right to Terminate and Abatement in Rent, If
the Premises or more than fifty percent (50%) of the leasable floor area
thereof, shall be taken, or if a conveyance shall be made in anticipation
thereof, for any street or other public use, by action of the municipal, state,
federal or other authorities, or shall receive any substantial direct or
consequential damage for which Landlord or Tenant shall be entitled to
compensation by reason of anything lawfully done in pursuance of any public
authority, after the execution hereof and before the expiration of the Lease
Term, then this Lease and the Lease Term shall terminate at the election of
Landlord or Tenant (given by written notice by one party to the other within 60
days of the taking or within 60 days of notice of the taking to Landlord), and
such election may be made in case of any such taking notwithstanding the entire
interest of Landlord may have been divested by such taking; and if neither
Tenant nor Landlord does so elect, then in case of any such taking or
destruction of, or damage to, the Premises, rendering the same or any part
thereof unfit for use and occupation, a just proportion of the Fixed Minimum
Rent hereinbefore reserved according to the nature and extent of the injury
sustained by the Premises, shall be suspended or abated until the Premises or,
in case of such taking, what may remain thereof, shall have been put in proper
condition for use and occupation. To the extent that the Premises, upon having
been put in proper condition for use and occupation are smaller, the Fixed
Minimum Rent hereinbefore reserved shall be reduced for the balance of the Lease
Term in the same proportion which the reduction in space bears to the original
leasable square footage of the Premises and the Additional Rent based on Taxes,
Insurance Costs and Operating Costs shall be adjusted as appropriate.

      Section 9.2 Restoration. If this Lease is not terminated as provided in
Section 9.1, Landlord shall apply so much of the available proceeds of the
eminent domain award as are required to restore Landlord's Property and the
Premises to a condition, to the extent practical, substantially the same as that
immediately preceding the taking, but subject to zoning laws and building codes
then in existence. If the available proceeds of the eminent domain award are
insufficient for that purpose, Landlord shall have no obligation to expend funds
in excess of said proceeds, and Landlord shall have the right to select which
portions of Landlord's Property, if any, shall be restored, but Tenant may
terminate this Lease if Landlord elects not to restore the Premises to a useable
state. The term "available proceeds" shall mean the amount of the award paid to
Landlord, less cost of obtaining the same (including attorneys' fees and
appraisal fees) and less the amount thereof required to be paid to a mortgagee
or ground lessor.

      Section 9.3 Landlord to Control Eminent Domain Action. Landlord reserves
all rights to compensation for damage to the Premises or any part thereof, or
the leasehold hereby created, heretofore accrued or hereafter to accrue, by
reason of any taking for public use of the Premises or any portion thereof, or
right appurtenant thereto, or privilege or easement in, through, under or over
the same, and, by way of confirmation of the foregoing, Tenant hereby assigns to
Landlord all rights to such damages heretofore accrued or hereafter accruing
during the Lease Term. Provided, however, nothing herein contained shall limit
Tenant's right to any separate award for

                                       36
<PAGE>

the taking of (a) personal property, moving expenses, or other items the payment
of which shall not reduce the award payable to Landlord or (b) the cost of
improvements made to the Premises by Tenant at Tenant's cost (excluding amounts
paid for by Landlord's Contribution) based upon the lower of (i) the fair market
value of such improvements or (ii) the unamortized cost of such improvements
based upon a ten (10) year useful life.

                                    ARTICLE X

      Section 10.1 Damage From Casualty. If following the execution hereof and
prior to the expiration of the Lease Term the Premises shall be damaged or
destroyed in whole or in part by fire or other casualty, this Lease shall,
except as hereinafter provided in this Article X, remain in full force and
effect and Landlord shall, upon notice of such damage from Tenant and proceeding
with reasonable dispatch, repair or rebuild so much of the Premises as have been
damaged by fire or the elements and as were originally constructed by Landlord
(and not the responsibility of Tenant to repair, restore and/or replace under
this Lease) to substantially their condition at the time of such damage or
destruction (subject, however, to zoning laws and building codes then in
existence), but Landlord shall not be responsible for any delay which may result
by reason of adjustment of insurance claims, collection of insurance proceeds,
labor troubles, or from any cause beyond Landlord's reasonable control, nor
shall Landlord be obligated to commence repair or restoration work prior to
receipt of sufficient insurance proceeds, nor shall Landlord be required to
expend sums in excess of net recovered insurance proceeds". The term "net
recovered insurance proceeds" shall mean the amount of any insurance proceeds
actually recovered by Landlord, less the cost of obtaining the same (including
attorney's fees and appraisal fees) and less the amount thereof required to be
paid to a mortgagee or a ground lessor. Tenant shall concurrently repair or
restore so much of the Premises (1) as were constructed by Tenant, or (2) are
the responsibility of Tenant under this Lease and shall repair and restore its
fixtures, improvements, and personal property. Notwithstanding the foregoing, to
the extent that (i) the insurance coverages required to be maintained by Tenant
are inadequate to cover the cost of repairing and/or rebuilding the improvements
to the Premises made by Tenant, and (ii) the net recovered insurance proceeds
include a recovery for improvements to the Premises made by Tenant then, after
deducting from the net recovered insurance proceeds all amounts necessary to
effect the repair and/or rebuilding of the portions of the Premises which do not
constitute improvements made by Tenant, Landlord shall, at its option, (a) use
remaining net recovered insurance proceeds to repair or restore all or any
portions of the improvements made by Tenant and/or (b) make funds available to
Tenant, under procedures similar to those set forth in Section 2.5, from
remaining net recovered insurance proceeds for Tenant's repair and restoration
of the improvements made by Tenant.

      Section 10.2 Abatement of Rent. In the event that the provisions of
Section 10.1 of this ARTICLE X shall become applicable, the Fixed Minimum Rent
shall be abated or reduced proportionately for so long as and only to the extent
rent loss insurance proceeds, if any, are available to Landlord during any
period in which, by reason of any such damage or destruction, there is
substantial interference with the operation of the business of Tenant in the
Premises, having regard to the extent to which Tenant may be required to
discontinue its business in the Premises, and such abatement or reduction shall
continue for the period commencing with such

                                       37
<PAGE>

destruction or damage and ending with the substantial completion by Landlord of
such work, repair and/or reconstruction as Landlord may do.

      Section 10.3 Limitation on Landlord's and Tenant's Obligations. Landlord
and Tenant shall not be obligated to do any repair or restoration work if
Landlord or Tenant elects to terminate this Lease as provided for in this
ARTICLE X.

      Section 10.4 Landlord's Right to Terminate. Notwithstanding the foregoing,
Landlord may terminate this Lease following: (i) damage or destruction to the
Premises to the extent of fifty percent (50%) or more of the cost of replacement
thereof or (ii) the refusal of the applicable insurance carrier to pay funds
sufficient for the cost to repair or replace or the refusal of any applicable
mortgagee or ground lessor to release the insurance proceeds for such purposes.
Landlord may exercise the right to so terminate this Lease by written notice to
Tenant given within sixty (60) days of the date of the damage, or sixty (60)
days from the date Landlord receives written notice of such damage, whichever is
later. Such notice of termination shall be effective on the date thereof.

      Section 10.5 Tenant's Right to Terminate. If the Premises are damaged by
fire or other casualty and either (a) Landlord does not elect to substantially
repair or restore the same to their former condition but only as to portions
constructed by Landlord within ninety (90) days following Tenant's written
notice of the damage to Landlord, or (b) Landlord, having made the election to
substantially repair or restore as aforesaid, fails to substantially complete
such repair or restoration within one (1) year following Tenant's written notice
of the damage to Landlord (or such longer period as may be required to
substantially complete such repair or restoration due to any cause or causes
beyond the reasonable control of Landlord (which will never include the lack of
available capital to Landlord)), then, in either such event, Tenant may
thereafter terminate this Lease upon sixty (60) days prior written notice to
Landlord unless such repair or restoration is substantially completed within
such 60-day period.

                                   ARTICLE XI

      Section 11.1 Tenant's Default. Subject to applicable provisions of law and
the provisions of Section 12.6 hereof, this Lease is upon the condition that:
(a) if Tenant shall neglect or fail to pay when first due Fixed Minimum Rent or
any installment thereof, or Additional Rent, or, as applicable, any installment
thereof, and such neglect or failure shall continue for five (5) days after
notice to it from Landlord; or (b) if Tenant shall neglect or fail to pay when
first due Fixed Minimum Rent or any installment thereof, or Additional Rent or,
as applicable, any installment thereof, and Landlord shall have sent two or more
notices to Tenant pursuant to Section 11.1(a) during the preceding twelve (12)
months; or (c) if any Environmental Liability has been incurred, exists, or is
applicable which poses an imminent and substantial endangerment to human or
animal health or the environment or has a material adverse effect on the
Premises or any other portion of Landlord's Property and such Environmental
Liability is not fully discharged and satisfied within the "Specified Cure
Period" (hereinafter defined); (d) if Tenant shall neglect or fail to perform or
observe any of the obligations, covenants or undertakings herein on its part to
be performed or observed which are not governed by clauses (a), (b) and/or (c)
above and/or any of clauses (e) through (n) below, and such neglect or failure
shall continue

                                       38
<PAGE>

beyond the expiration of the Specified Cure Period; or (e) if any case,
petition, proceeding or other action under any existing or future bankruptcy,
insolvency, reorganization, dissolution, liquidation or arrangement or
readjustment of debt law or any similar existing or future law of any applicable
jurisdiction, or any laws amendatory thereof or supplemental thereto (the
"Bankruptcy Laws") shall be filed by Tenant or any guarantor of Tenant's
obligations ("Guarantor"); or (f) if any other proceedings are instituted by
Tenant or any Guarantor under any of the Bankruptcy Laws; or (g) if any
involuntary proceedings shall be instituted against Tenant or any Guarantor
under any of the Bankruptcy Laws and not be dismissed within sixty (60) days, or
Tenant or Guarantor shall be unable to pay its or his financial obligations when
they become due, or if there is a material adverse change from the date of this
Lease in the financial condition of either Tenant or Guarantor as reflected in
financial statements delivered to Landlord and any holder of a mortgage on all
or a portion of Landlord's Property; or (h) if Tenant or any Guarantor shall
execute an assignment of its property for the benefit of its creditors, or if at
any time the Guarantor would be financially unable to honor the obligations of
the Guaranty in the event a default were to exist at such time; (i) if any
Hazardous Substances Statement or any Tenant Environmental Certification was
false in any material respect when made or furnished or when treated as being
made or furnished; or (j) if a receiver or other similar officer for Tenant or
any Guarantor shall be appointed and not be discharged within sixty (60) days;
or (k) if the estate hereby created shall be taken by execution or by other
process of law and is not redeemed by Tenant within thirty (30) days thereafter;
or (I) if Tenant abandons (provided, however, that vacating the Premises does
not, in and of itself, constitute abandonment) or surrenders the Premises; or
(m) if Tenant is dissolved or liquidated; or (n) an Event of Default is deemed
to have occurred under Section 11.9; then, (except in the case of a default
under clause (e) or (f) above in which event this Lease (to the fullest extent
now or hereafter permitted by law) shall terminate automatically)), Landlord
may, immediately or at any time thereafter (notwithstanding any license or
waiver of any former breach or waiver of the benefit hereof, or consent in a
former instance), and without demand or notice, in person or by agent or
attorney, re-enter the Premises or any part thereof and repossess the same as of
its former estate, or terminate this Lease by written notice to Tenant, and in
either event expel Tenant and those claiming through or under it and remove
their effects without being deemed guilty of any manner of trespass and without
prejudice to any remedy which might otherwise be used for arrears of Fixed
Minimum Rent or Additional Rent or breach of covenant, and upon entry or written
notice of termination, or automatic termination, both as aforesaid, this Lease
shall terminate and the Landlord, in addition to all other remedies which it may
have at law or equity, and not in limitation thereof, shall have the remedies
provided in this ARTICLE XI. As used in clause (d) above, "Specified Cure
Period" means thirty (30) days after the date on which Tenant is sent a notice
(the "Default Notice") that Tenant has neglected or failed to perform or observe
any of the obligations, covenants or undertakings on Tenant's part to be
performed or observed under this Lease, provided, however, that (A) the Landlord
shall extend the Specified Cure Period for up to an additional sixty (60) days
upon receipt of a written request from Tenant for such extension within thirty
(30) days after the date of the Default Notice if and only if, all of the
following conditions are satisfied: (1) Tenant shall have commenced to cure such
neglect or failure within ten (10) days after the date of the Default Notice and
shall thereafter diligently and continuously pursue such cure to completion, (2)
such neglect or failure is such that it cannot be cured within thirty (30) days
after the date of the Default Notice in spite of Tenant's best efforts to do so,
but is capable of being cured within the Specified Cure Period as extended by
Landlord under the

                                       39
<PAGE>

terms of this Section 11.1, as demonstrated by a written plan of cure provided
by Tenant to Landlord which plan has been approved by Landlord (such approval
not to be unreasonably withheld), and (3) the continuing existence of such
neglect or failure shall not have a material adverse effect the Premises or any
other portion of Landlord's Property; (B) in the event that Landlord has
extended the Specified Cure Period pursuant to the foregoing clause (A), then
Landlord shall extend the Specified Cure Period for up to ninety (90) additional
days (i.e. for a total of 180 days after the Default Notice) upon receipt of a
written request for such extension from Tenant within seventy-five (75) days
after the Default Notice if, and only if, all of the following conditions are
satisfied: (1) such request for extension is accompanied by a $500,000.00
increase (the "First Increase") in the amount of the Security Deposit (either in
cash or by a letter of credit obtained at the sole cost of Tenant which meets
all of the requirements of Section 11.9 and is otherwise acceptable to
Landlord), and (2) Tenant shall have commenced to cure such neglect or failure
within ten (10) days after the Default Notice and shall have thereafter
diligently and continuously pursued such cure in compliance with the plan of
cure previously approved by Landlord, and (3) Tenant shall, during such
extension period, diligently and continuously pursue such cure to completion and
in compliance with the plan of cure previously approved by Landlord; and (C) in
the event that Landlord has extended the Specified Cure Period pursuant to the
foregoing clause (B), then Landlord shall extend the Specified Cure Period for
up to one hundred eighty-five (185) additional days (i.e., for a total of 365
days after the Default Notice) upon receipt of a written request for such
extension from Tenant within one hundred sixty-five (165) days after the Default
Notice if, and only if, all of the following conditions are satisfied: (1) such
request for extension is accompanied by a second $500,000.00 increase (the
"Second Increase") in the amount of the Security Deposit (either in cash or by a
letter of credit obtained at the sole cost of Tenant which meets all of the
requirements of Section 11.9 and is otherwise acceptable to Landlord), (2)
Tenant shall have commenced to cure such neglect or failure within ten (10) days
after the Default Notice and shall have thereafter diligently and continuously
pursued such cure in compliance with the plan of cure previously approved by
Landlord, and (3) Tenant shall, during such extension period, diligently and
continuously pursue such cure to completion and in compliance with the plan of
cure previously approved by Landlord. Notwithstanding anything to the contrary
in this Section 11.1, if, during a Specified Cure Period, there occurs an
additional instance in which Tenant has neglected or failed to perform or
observe any of the obligations, covenants or undertakings on Tenant's part to be
performed or observed under this Lease, the maximum cure period, with respect to
such additional failure of Tenant, will be the shorter of (X) the cure period
otherwise available under this Lease with respect to such additional failure of
Tenant or (Y) the remainder of such Specified Cure Period plus thirty (30)
additional days. In the event that Tenant is not diligently and continuously
pursuing such cure to completion in compliance with the plan of cure previously
approved by Landlord, then, in addition to Landlord's other rights and remedies
at law, in equity and/or under this Lease, Landlord may, at its option (I)
terminate the Specified Cure Period effective immediately upon notice to Tenant
and/or (II) apply the First Increase, the Second Increase and/or any other
portion of the Security Deposit toward efforts to effect such cure. The First
Increase (if previously delivered to Landlord) and the Second Increase (if
previously delivered to Landlord), reduced by all costs and expenses incurred by
Landlord in connection with any extension of the Specified Cure Period and/or
the existence and/or cure of any neglect or failure of Tenant to perform or
observe any Tenant's obligations, undertakings or agreements under this Lease
shall be returned to Tenant upon completion of the cure of such

                                       40
<PAGE>

neglect or failure within the Specified Cure Period in accordance with the plan
of cure previously approved by Landlord; provided, however, that such amount
shall not be returned to Tenant if there exists a default, or any circumstance
or fact which, with the passage of time, the giving of notice, or the
satisfaction of any other condition, or all of them, could constitute a default
of this Lease unless and until all of the same have been cured by Tenant. Except
as set forth in the preceding two (2) sentences, the First Increase and Second
Increase shall be added to, and become a part of, the Security Deposit and the
use thereof governed by Section 11.9 and other provisions of this Lease
applicable to the Security Deposit. As used herein, "Event of Default" shall
mean a default under this Lease which has not been cured within any applicable
cure period. Notwithstanding anything to the contrary in this Section 11.1,
Tenant's lack of capital or funds is not a permitted excuse to justify why a
default cannot be cured within the applicable cure period.

      Section 11.2 Landlord's Remedies.

            (a) If this Lease is terminated or if Landlord shall re-enter the
Premises as set forth in Section 11.1, or in the event of the termination of
this Lease, or of re-entry, by or under any proceeding or action or any
provision of law by reason of a default under this Lease on the part of Tenant.
Tenant covenants and agrees forthwith to pay and be liable for, on the days
originally fixed herein for the payment thereof, amounts equal to the several
installments of Fixed Minimum Rent, all Additional Rent and other charges
reserved as they would, under the terms of this Lease, become due if this Lease
had not been terminated or if Landlord had not entered or reentered, as set
forth in Section 11.1, and whether the Premises be re-let or remain vacant, in
whole or in part, or for a period less than the remainder of the Lease Term, or
for the whole thereof, but, in the event the Premises be re-let by Landlord,
Tenant shall be entitled to a credit in the net amount of rent and other charges
received by Landlord in re-letting, after deduction of all reasonable expenses
incurred in re-letting the Premises (including, without limitation, remodeling
costs, brokerage fees and the like) and in obtaining possession of the Premises,
together with interest thereon at the Applicable Interest Rate, and in
collecting the rent in connection therewith, in the following manner: amounts
received by Landlord after re-letting shall first be applied against such
Landlord's expenses, together with interest thereon at the Applicable Interest
Rate, until the same are recovered, and until such recovery, Tenant shall pay,
as of each day when a payment would fall due under this Lease, the amount which
Tenant is obligated to pay under the terms of this Lease (Tenant's liability
prior to any such re-letting and such recovery not in any way to be diminished
as a result of the fact that such re-letting might be for a rent higher than the
rent provided for in the Lease); when and if such expenses have been completely
recovered, the amounts received from re-letting by Landlord as have not
previously been applied shall be credited against Tenant's obligations as of
each day when a payment would fall due under this Lease, and only the net amount
thereof shall be payable by Tenant. Further, Tenant shall not be entitled to any
credit of any kind for any period after the date when the term of this Lease is
scheduled to expire according to its terms. Tenant agrees that Landlord may,
without terminating this Lease, re-let the Premises or any part or parts
thereof, either in the name of Landlord or otherwise for a term or terms which
may, at Landlord's option, be less than or exceed the period which would
otherwise have constituted the balance of the Lease Term and may grant
concessions or free rent consistent with market conditions for similar
properties in Cambridge, Massachusetts at the time. The good faith failure of
Landlord to re-let the Premises

                                       41
<PAGE>

or any part or parts thereof, or, if the Premises are re-let, for the good faith
failure to collect the rents due under such re-letting, shall not release or
affect Tenant's liability for damage so long as Landlord does not act
arbitrarily or capriciously. Any suit brought to collect the amount of
deficiency for any month or other period shall not prejudice in any way the
right of Landlord to collect the deficiency for any subsequent month or period
by a similar proceeding. Landlord, at Landlord's option may make such
alterations, repairs, replacements and decorations on the Premises as Landlord
in Landlord's sole judgment considers advisable and necessary for the purpose of
re-letting the Premises, and the making of such alterations or decorations shall
not operate or be construed to release Tenant from liability hereunder.

            (b) Landlord may elect, in lieu of its continuing remedies under
Section 11.2(a) above, to have Tenant pay liquidated damages, which election may
be made by notice to Tenant at any time after termination of this Lease under
Section 11.1 and whether Landlord has collected any amounts as provided in
Section 11.2(a) or 11.2(c) before giving such liquidated damage notice to
Tenant. On the giving of such liquidated damage notice to Tenant by Landlord,
Tenant shall forthwith pay to Landlord as damages, in addition to all sums which
were due prior to the date of such termination and any amounts owing under
Section 11.2(c), a sum equal to the amount by which the Fixed Minimum Rent and
Additional Rent for the remainder of the Lease Term (discounted to the then
present value using a discount rate of eight percent (8.0%)) exceeds the fair
rental value of the Premises for the remainder of the Lease Term (discounted to
the then present value using a discount rate of eight percent (8.0%)). For the
purposes of computing damages payable pursuant to this Section 11.2(b), it is
agreed that there shall be payable to Landlord as part of such damages at the
time of such termination the product of the Additional Rent due with respect to
Taxes, Insurance Costs and Operating Costs for the most recently ended fiscal,
calendar or Lease Year, as the case may be, times the number of years remaining
of the Lease Term, it being assumed that the amount of such Additional Rent
payments so payable for the most recently ended fiscal, calendar year or Lease
Year would have remained constant for each subsequent year of the full Lease
Term.

            (c) In addition to Tenant's obligations under Sections 11.2(a) and
11.2(b), Tenant also will indemnify and save Landlord harmless from and against
(i) all reasonable expenses which Landlord may incur, including, without
limitation, legal expenses, attorneys' fees, brokerage fees, and the cost of
putting the Premises in good order or preparing the same for rental, (ii) any
damage to the Building or any other portion of Landlord's Property (including
any loss of use of all or any portion of the Building or any other portion of
Landlord's Property) and (iii) for all costs and expenses of any investigation,
cleanup, detoxification, decontamination of, or other response, removal, or
remedial action with respect to, the Building or any other portion of Landlord's
Property (or the environment with respect thereto) which, in any case, arises
out of any Environmental Activity by a Tenant Party.

      Section 11.3 Reimbursement of Landlord. In the event of any default by
Tenant in the payment of any Fixed Minimum Rent or Additional Rent, Tenant will,
in addition to paying Landlord all amounts due under the terms and provisions of
this Lease, including without limitation Section 11.10, reimburse Landlord for
all reasonable expenses incurred by Landlord in collecting such rent or in
obtaining possession of, or in re-letting the Premises, or in defending any
action, including expenses for reasonable counsel fees and commissions. Tenant
further

                                       42
<PAGE>

agrees that, if on termination of this Lease by expiration or otherwise, Tenant
shall fail to remove any of its property from the Premises as provided for
herein, Landlord shall be authorized, in its sole option, and in Tenant's name
and on its behalf, either (i) to cause such property to be removed and placed in
storage for the account and at the expense of Tenant; or (ii) to sell such
property at public or private sale, with or without notice, and to apply the
proceeds thereof, after the payment of all expenses of removal, storage and
sale, to the indebtedness, if any, of Tenant to Landlord, the surplus, if any,
to be paid to Tenant; prior to the removal of such property Landlord may charge
Tenant a fair rental amount for the storage of such property. All sums payable
by Tenant under this ARTICLE XI shall be deemed Additional Rent.

      Section 11.4 Landlord's Right to Perform Tenant's Covenants. Tenant
covenants and agrees that, if it shall at any time fail to make any payment or
perform any other act on its part to be made or performed as in this Lease
provided, Landlord, in its sole discretion may after due notice to, or demand
upon, Tenant, make any payment or perform any other act on the part of Tenant to
be made and performed as in this Lease provided, in such manner and to such
extent as Landlord may reasonably deem desirable, and in exercising any such
rights, Landlord may pay necessary and incidental costs and expenses, employ
counsel, and incur and pay reasonable attorneys' fees. The making of any such
payment or the performing of any other act by Landlord pursuant to this Article
shall not waive, or release Tenant from, any obligations of Tenant in this Lease
contained. All sums so paid by Landlord and all reasonably necessary and
incidental costs and expenses in connection with the performance of any such act
by Landlord shall, except as otherwise in this Lease expressly provided, be
payable to Landlord on demand, and Tenant covenants to pay any such sum or sums
promptly, and Landlord shall have (in addition to any other right or remedy of
Landlord) the same rights and remedies in the event of the non-payment thereof
by Tenant as in the case of default by Tenant in the payment of the Fixed
Minimum Rent. Whenever practicable, Landlord, before proceeding as provided in
this Section 11.4, shall give Tenant notice in writing of the failure of Tenant
which Landlord proposes to remedy, and shall allow Tenant such length of time as
may be reasonable in the circumstances, consistent with any grace periods
contained herein, but not exceeding 15 days from the giving of notice, to remedy
the failure itself and, if Tenant shall not remedy the failure in the time so
allowed, Landlord shall be deemed to have given "due notice" and may proceed as
provided in this Section 11.4; provided, however, that nothing in this section
shall prevent Landlord from acting without notice to Tenant in case of any
emergency wherein there is danger to property or person or where there may exist
any violation of legal requirements including but not limited to Hazardous
Substances, in which event no notice shall be required.

      Section 11.5 Cumulative Remedies. The specified remedies to which Landlord
may resort under the terms of this Lease, or under the provisions of applicable
law, are cumulative and not intended to be exclusive of any other remedies or
means of redress to which Landlord may be lawfully entitled in case of any
breach or threatened breach by Tenant of any provisions of this Lease. The
failure of Landlord to insist in any one or more cases upon the strict
performance of any of the covenants of this Lease or to exercise any option
contained herein shall not be construed as a waiver or a relinquishment for the
future of such covenant or option. Receipt by Landlord of any Fixed Minimum Rent
or Additional Rent payment with knowledge of the breach of any covenants hereof
shall not be deemed a waiver of such breach. No waiver by Landlord of any
provision of this Lease shall be deemed to have been made unless expressed in

                                       43
<PAGE>

writing and signed by it. In addition to the other remedies provided in this
Lease, Landlord shall be entitled to restraint by injunction of any violation or
attempted or threatened violation of any of the covenants, conditions or
provisions of this Lease.

      Section 11.6 Expenses of Enforcement. Tenant agrees to pay all reasonable
expenses and reasonable attorneys' fees incurred by Landlord in enforcing any
obligation or any remedies hereunder including without limitation in connection
with collection of Fixed Minimum Rent or Additional Rent, recovery by Landlord
of the Premises, or in any litigation in which Landlord shall become involved by
reason of any act or negligence of Tenant or any breach of this Lease by Tenant.
Landlord agrees to pay all reasonable expenses and reasonable attorneys' fees
incurred by Tenant in enforcing any obligation of Landlord or any remedies of
Tenant hereunder or in any litigation in which Tenant shall become involved by
reason of any act or negligence of Landlord or any breach of this Lease by
Landlord.

      Section 11.7 Landlord's Default. Landlord shall not be deemed to be in
default hereunder unless such default shall remain uncured for more than thirty
(30) days following written notice from Tenant specifying the nature of such
default, or such longer period as may be reasonably required to correct such
default. Landlord's liability to keep, maintain, and repair shall always be
limited to the cost of making such repair or accomplishing such maintenance or
repair. In no event whatsoever shall Landlord be liable for consequential,
punitive damages, special damages or any indirect damages (including lost
profits). Notwithstanding anything to the contrary contained herein, so long as
Tenant shall be in default under any term or provision of this Lease, Tenant
shall not be entitled to enforce any obligation from Landlord or seek any cure
of Landlord's defaults under this Lease. The provisions of this Section 11.7 are
further subject to the provisions of ARTICLES IX and X dealing with eminent
domain and fire and other casualty.

      Section 11.8 Limitation of Landlord's Liability. The obligations of
Landlord hereunder shall be binding upon Landlord and each succeeding owner of
the Landlord's interest hereunder only during the period of such ownership and
Landlord and each succeeding owner shall have no liability whatsoever except for
its obligations during each such respective period. Tenant hereby agrees for
itself and each succeeding holder of Tenant's interest, or any portion thereof,
hereunder, that any judgment, decree or award obtained against Landlord or any
succeeding owner of the Landlord's interest, which is in any manner related to
this Lease, the Premises or Tenant's use and occupancy of the Premises, the
Common Areas or Common Facilities of Landlord's Property, whether at law or in
equity, shall be satisfied out of the Landlord's equity in the Building to the
extent of Landlord's interests in the Building and such succeeding owner, and
further agrees to look only to such assets and to no other assets of the
Landlord, or such succeeding owner, for satisfaction. Neither Landlord nor any
party executing this Lease on behalf of Landlord, nor any partner, limited or
general, or any officer, director, employee, member, trustee or beneficiary of
Landlord, nor any subsequent Landlord, or any partner, limited or general, or
any officer, director, employee, member, trustee or beneficiary of any
subsequent Landlord shall have any personal liability hereunder. The remedies
provided to Tenant in this Lease are exclusive, and Landlord will not be liable
under any theory of recovery, whether based on contract, tort or otherwise.

                                       44
<PAGE>

      Section 11.9 Security Deposit.

      (a) The Security Deposit, in the form of the Letter of Credit described
below and as provided in the Summary of Basic Terms, is security for the
faithful performance and observance by Tenant of the terms, provisions and
conditions of this Lease. It is agreed that in the event Tenant defaults in
respect of any of the terms, provisions and conditions of this Lease, Landlord
may use, apply or retain the whole or any part of the Security Deposit to the
extent required for payment of any Fixed Minimum Rent, Additional Rent, or any
other sum as to which Tenant is in default or for any sum which Landlord may
expend or may be required to expend by reason of Tenant's default in respect of
any of the terms, covenants and conditions of this Lease, including but not
limited to (i) any damage or deficiency accrued before or after summary
proceedings or other re-entry by Landlord, including the costs of such
proceeding or re-entry, (ii) any amounts Landlord is required to pay arising
from, or in connection with, any Environmental Activities by a Tenant Party
(including, for example, any fines, penalties, or other costs imposed by the
City of Cambridge as a result of any alleged violation of the Cambridge Zoning
Ordinance or the RDNA ordinance, (Chapter 8.20 of the Cambridge Municipal
Code)), and (iii) reasonable attorney's fees. It is agreed that Landlord shall
always have the right to apply the Security Deposit, or any part thereof, as
aforesaid, without notice and without prejudice to any other remedy or remedies
which Landlord may have, or Landlord may pursue any other such remedy or
remedies in lieu of applying the Security Deposit or any part thereof. If the
Security Deposit is in the form of cash, no interest shall be payable on the
Security Deposit, Landlord shall hold the Security Deposit in escrow and
Landlord shall not commingle the Security Deposit with other funds of Landlord
(other than other security deposits). If Landlord shall apply the Security
Deposit in whole or in part in accordance with this Section 11.9, Tenant shall
upon demand pay to Landlord the amount so applied to restore the Security
Deposit to its original amount. Because Taxes, Insurance Costs, Operating
Expenses and other Additional Rent are subject to annual reconciliation based on
actual amounts (collectively "Final Amounts Due") determined to be due, in
addition to the other rights provided herein to Landlord regarding the Security
Deposit, Landlord shall have the right, in its discretion, upon the end of this
Lease and delivery of the Premises in accordance with the terms hereof to hold
all or a portion of the Security Deposit (or whatever amount remains after
Landlord exercises Its other rights hereunder) until ninety (90) days alter the
determination of Final Amounts Due at which time Landlord has the right to
deduct the Final Amounts Due from the remaining Security Deposit and return any
balance of the Security Deposit to Tenant. If the remaining Security Deposit, if
any, is not sufficient to pay Tenant's obligations hereunder, Tenant shall pay
the same within ten (10) days of billing from Landlord. In the event of a sale
or other transfer of Landlord's Property, or leasing of the entire Landlord's
Property Including the Premises subject to Tenant's tenancy hereunder, Landlord
shall transfer the Security Deposit then remaining to the vendee or lessee and
Landlord shall thereupon be released from all liability for the return of such
Security Deposit to Tenant; and Tenant agrees to look solely to the new landlord
for the return of the Security Deposit then remaining. The holder of any
mortgage upon Landlord's Property shall never be responsible to Tenant for the
Security Deposit or its application or return unless the Security Deposit shall
actually have been received in hand by such holder. Tenant further covenants
that it will not assign or encumber or attempt to assign or encumber the
Security Deposit and that neither Landlord not its successors or assigns shall
be bound by any such assignment, encumbrance, attempted assignment or attempted
encumbrance.

                                       45
<PAGE>

      (b) The Letter of Credit (as defined in the Summary of Basic Terms) must
meet the following conditions as of the dale of execution of this Lease: it must
be (i) a clean, unconditional, and irrevocable letter of credit which is duly
issued naming Landlord as beneficiary; (ii) initially expiring on June 1,1999;
however, Tenant will (A) cause the Letter of Credit to renew automatically
annually as of each June 1 so that the Letter of Credit remains in full force
and effect until twelve (12) months following the end of the Lease Term or (B)
provide a replacement Letter of Credit in the amount and form required by this
Section 11.9 at least 90 days before the applicable expiry date; (iii) in the
amount of $2,000,000 (USD) as may be reduced as provided in Section 11.9(e)
below; (iv) issued by a U.S. domestic bank acceptable to Landlord; (v) which may
be drawn on by Landlord in accordance with the terms of the Letter of Credit for
all of the payments required to be made from time to time by Tenant to Landlord
under this Lease and/or as otherwise provided in this Lease; and (vi)
substantially in the form of Exhibit F attached hereto and/or on terms and in
form otherwise satisfactory to Landlord. If at any time during the Lease Term,
the issuer of the Letter of Credit gives notice of its election not to renew,
extend and/or reissue the Letter of Credit, then the Tenant shall, on or before
the date forty-five (45) days prior to the expiration of the term of the
existing Letter of Credit held by Landlord, deliver to Landlord a new Letter of
Credit satisfying the conditions hereof in replacement of such expiring Letter
of Credit or cash in the full amount of the Security Deposit. In addition, if at
any time during the Lease Term, the issuer of the Letter of Credit fails to
cause the transfer of the Letter of Credit in accordance with Landlord's
instructions and Tenant timely fails to deliver to Landlord a new Letter of
Credit satisfying the conditions hereof naming Landlord's proposed transferee as
beneficiary, then such failure shall be deemed an Event of Default under Section
11.1(n) of this Lease and Landlord shall have the right, at any time after such
event, without giving further notice to Tenant, to draw down the entire amount
of the Letter of Credit and to hold proceeds thereof as the Security Deposit
hereunder. In the event that Tenant timely fails to deliver to Landlord a
replacement Letter of Credit or cash in the full amount of the Security Deposit,
then such failure shall be deemed an Event of Default under Section 11.1(n) of
this Lease and Landlord shall have the right. at any time after such event,
without giving further notice to Tenant, to draw down the entire amount of the
Letter of Credit and to hold the proceeds thereof as the Security Deposit
hereunder. From time to time, within ten (10) days after requested by Landlord
or the holder of a first mortgage on the Premises. Tenant shall execute any and
all documents and take any and all actions as may be requested by Landlord or
such holder to effect a change in the beneficiary of the Letter of Credit to a
person or entity specified by Landlord or such holder.

      (c) On or before the first day of each Lease Year, Tenant will notify
Landlord of the amount of the letter of credit fee (expressed as a per annum
percentage of the undrawn face amount of the Letter of Credit) charged by the
issuer of the Letter of Credit (the "`Letter of Credit Fee") for the applicable
Lease Year. Subject to the next following sentence, Landlord will reimburse
Tenant an amount each Lease Year equal to 50% of the Letter of Credit Fee for
that Lease Year (the "L/C Fee Reimbursement"); however, in no event may the L/C
Fee Reimbursement exceed an amount equal to 50% of a Letter of Credit Fee based
on 1.5% per annum of the undrawn face amount of the Letter of Credit. Tenant
will receive the L/C Fee Reimbursement in the form of a cash payment made to
Tenant within 30 days after Tenant has made payment of the applicable Letter of
Credit Fee directly to the issuer of the Letter of Credit; provided, however,
that Landlord shall not be obligated to make such payment to Tenant if there

                                       46
<PAGE>

then exists a default of Tenant or any fact or circumstance which, with the
passage of time, the giving of notice, or the satisfaction of any other
condition, or all of them, could constitute a default under this Lease, unless
and until the same is cured by Tenant. In support of its application to receive
the L/C Fee Reimbursement, Tenant will deliver to Landlord all documentation,
satisfactory to Landlord, demonstrating the direct, out-of-pocket cost paid by
Tenant for the Letter of Credit Fee. Tenant will be solely responsible for all
of the Letter of Credit Fee (and all other expense and charges of the issuer of
the Letter of Credit) in excess of the L/C Fee Reimbursement.

      (d) If (i) Landlord shall reasonably feel insecure with the financial
creditworthiness of the financial institution issuing the Letter of Credit and
Tenant shall fail, within twenty (20) days alter Landlord's notice, to either
(A) provide a replacement Letter of Credit in the full amount of the Security
Deposit in the form attached as Exhibit F or on terms and/or in form otherwise
satisfactory to Landlord from a financial Institution that is federally insured
and has offices in Boston and is reasonably approved by Landlord, or (B) provide
Landlord with cash in the full amount of the Security Deposit; or (ii) Tenant
fails to provide Landlord with a cash security deposit or a replacement Letter
of Credit satisfying the conditions of this Section 11.9 In the full amount of
the Security Deposit within seven (7) days alter (1) any proceedings under the
Bankruptcy Laws or any insolvency law are instituted by or against the financial
institution issuing the Letter of Credit, or (2) the financial Institution
Issuing the Letter of Credit is taken over by the Federal Deposit Insurance
Corporation, the Resolution Trust Corporation or a similar entity, then any such
failure shall be deemed an Event of Default under Section 11.1(n) and Landlord
shall have all rights and remedies provided hereunder (including, but not
limited to, the right to draw upon the Letter of Credit) without any further
notice. Subject to the provisions of this Section 11.9, Landlord shall return
the Security Deposit within 30 days after the end of tile Lease Term.

      (e) Subject to the other terms of this Section 11.9, upon receipt of a
written request from Tenant at any time after the second Lease Year, Landlord
will agree to a reduction in the amount of the Letter of Credit by a total sum
equal to $500,000.00 so long as all of the following conditions are met as of
the date on which such reduction occurs (the "First Reduction Date"): (i) there
does not exist a default under this Lease or any fact, event, or circumstance
which, with the passage of time, the giving of notice, the satisfaction of any
other condition, or all of them, could constitute a default, (ii) Tenant has
consummated a public offering of stock and is listed on a national securities
exchange (as defined in the Securities Exchange Act of 1933), (iii) Tenant's
tangible net worth, as of the First Reduction Date, is greater than or equal to
$75,000,000 as determined In accordance with generally accepted accounting
principles ("GAAP") consistently applied ("tangible net worth" meaning Tenant's
book net worth less all intangible assets as determined by GAAP), (iv) Tenant's
cash and cash equivalents, as of the First Reduction Date, are greater than or
equal to $10,000,000 as determined in accordance with GAAP consistently applied,
and (v) Tenant shall have expended in excess of $1,500,00000 (excluding
Landlord's Contribution) on Tenant's Work and other improvements to the Premises
approved by the Landlord (such expenditures to be evidenced by invoices,
receipts, contracts and other documentation as may be reasonably required by
Tenant).

                                       47
<PAGE>

      (f) Subject to the other terms of this Section 11.9, upon receipt of a
written request from Tenant at any time after the fifth Lease Year, Landlord
will agree to a reduction in the amount of the Letter of Credit by a total sum
equal to $500,000.00 so long as alt of the following conditions are met as of
the date on which such reduction occurs (the "Second Reduction Date"): (i) there
does not exist a default under this Lease or any fact, event, or circumstance
which, with the passage of time, the giving of notice, the satisfaction of any
other condition, or all of them, could constitute a default, (ii) Tenant has
consummated a public offering of stock and is listed on a national securities
exchange (as defined in the Securities Exchange Act of 1933), (iii) Tenant's
tangible net worth, as of the Second Reduction Date, is greater than or equal to
$75,000,000 as determined in accordance with GAAP consistently applied
("tangible net worth" meaning Tenant's book net worth less all intangible assets
as determined by GAAP), (iv) Tenant's cash and cash equivalents, as of the
Second Reduction Date, are greater than or equal to $10,000,000 as determined in
accordance with GAAP consistently applied, and (v) Tenant shall have expended in
excess of $3,000,000.00 (excluding Landlord's Contribution) on Tenant's Work and
other improvements to the Premises approved by the Landlord (such expenditures
to be evidenced by invoices, receipts, contracts and other documentation as may
be reasonably required by Tenant).

      Section 11.10 Late Payment and Administrative Expense. If Tenant shall
fail to pay Fixed Minimum Rent, Additional Rent or other charges after the same
become due and payable under this Lease, such unpaid amounts shall bear interest
from the due date thereof to the date of payment at the Applicable interest Rate
("Interest Payment"). In addition, if Landlord is required to redeposit any
check which is returned for insufficient funds or if Tenant shall fail to pay
Fixed Minimum Rent, Additional Rent or other charges after the same become due
and payable, then Tenant shall also pay to Landlord an administrative expense
charge ("Administrative Expense") of five percent (5.0%) of the amount thereof
for each calendar month or part thereof after the due date of such payment until
such payment is received by Landlord. The provisions herein for Interest Payment
and Administrative Expense shall not be construed to relieve Tenant of the
obligation to pay Fixed Minimum Rent, Additional Rent and all other charges when
due under this Lease and shall be in addition to and not in limitation of
Landlord's other remedies as provided for in this Lease.

      Section 11.11 Tenant's Request for Landlord's Action. In the event that at
Tenant's request Landlord is required to take any action pursuant to this Lease,
Tenant shall pay as Additional Rent Landlord's reasonable attorneys' fees,
expenses and disbursements in connection with such action, with payment to be
made by Tenant within fifteen (15) days after billing therefor by Landlord.

                                   ARTICLE XII

                            Miscellaneous Provisions

      Section 12.1 Broker.

            (a) Tenant represents that it has not dealt with any person in
connection with the Premises or the negotiation or execution of this Lease other
than officers or employees of

                                       48
<PAGE>

Landlord and the Broker, if any, designated in the Summary of Basic Terms.
Tenant shall indemnify and save harmless Landlord from and against all claims,
liabilities, costs and expenses incurred as a result of any breach of the
foregoing representation by Tenant. The broker's fee payable to Broker for this
Lease shall be payable by Landlord subject to and in accordance with the terms
of a separate written agreement between Landlord and Broker.

            (b) Landlord represents that it has not dealt with any person in
connection with the Premises or the negotiation or execution of this Lease other
than officers or employees of Landlord and the Broker, if any, designated in the
Summary of Basic Terms. Landlord shall indemnify and save harmless Tenant from
and against all claims, liabilities, costs and expenses incurred as a result of
any breach of the foregoing representation by Landlord.

      Section 12.2 Quiet Enjoyment. Tenant shall, upon paying all Fixed Minimum
Rent and Additional Rent due hereunder and observing and performing all of the
terms, covenants and conditions on Tenant's part to be observed and performed,
peaceably and quietly have and hold the Premises without hindrance or
molestation by any person or persons lawfully claiming by, through or under,
Landlord, subject, however, to the terms of this Lease.

      Section 12.3 Notices. All notice, demand, request or statement required or
intended to be given or delivered under the terms of Lease shall be in writing
and be delivered and shall be deemed to have been given or delivered if by
delivered in hand, by overnight courier service, electronic facsimile
reproduction or by U.S. certified mail, return receipt requested, or by
facsimile as long as a confirming copy is simultaneously sent by overnight
courier or U.S. certified mail as set forth above to the address or addresses
set forth in the Summary of Basic Terms or to such other place as may be
designated from time to time by written notice to the other party.

      Section 12.4 Waiver of Subrogation. Landlord and Tenant hereby release
each other, to the extent of their respective insurance coverages, from any and
all liability for any loss or damage caused by fire, any of the extended
coverage casualties, or other casualties insured against, even if such fire or
other casualty shall be brought about by the fault or negligence of the party
benefited by the release or its agents, Landlord and Tenant each agree that
their respective fire, extended coverage, and other insurance policies will
include a waiver of subrogation clause so long as the same is obtainable.

      Section 12.5 Entire Agreement: Execution and Headnotes. This Lease
together with all Exhibits referred to herein and the Summary of Basic Terms,
sets forth the entire agreement between the parties hereto and cannot be
modified or amended, except in a writing duly executed by the respective
parties. This Lease supersedes all previous written and oral negotiations,
understandings and agreements regarding the subject matter of this Lease.
Landlord has made no representations to Tenant on which Tenant has relied in
entering into this Lease except any representations expressly stated in this
Lease. This Lease is executed as a sealed instrument and in multiple
counterparts, all copies of which are identical, and any one of which is to be
deemed to be complete in itself and may be introduced in evidence or used for
any purpose without the production of any other copy. Time is of the essence of
the obligations of the parties to be performed within a specific time frame in
this Lease. The headnotes throughout this Lease are

                                       49
<PAGE>

for convenience of reference only, and shall in no way be held or deemed to
define, limit, explain, describe, modify or add to the interpretation,
construction or meaning of any provision of this Lease.

      Section 12.6 Partial Invalidity. The invalidity of one or more phrases,
sentences, clauses, Sections or Articles contained in this Lease shall not
affect the remaining portions of this Lease or any part thereof, and if any one
or more of the phrases, clauses, sentences, Sections or Articles contained in
this Lease should be declared invalid by the final order, decree or judgment of
a court of competent jurisdiction, including all appeals therefrom, this Lease
shall be construed as if such invalid phrases, clauses, sentences, Sections or
Articles had not been inserted in this Lease.

      Section 12.7 No Waiver.

      No assent, express or implied, by Landlord to any breach of any agreement
or condition herein contained on the part of Tenant to be performed or observed,
and no waiver, express or implied, of any such agreement or condition shall be
deemed to be a waiver of or an assent to any succeeding breach of the same or
any other agreement or condition; the acceptance by Landlord of Fixed Minimum
Rent or Additional Rent due hereunder (whether such payment is made by Tenant or
another party or entity), or silence by Landlord as to any breach, shall not be
construed as waiving any of the Landlord's rights hereunder unless such waiver
shall be in writing. No payment by Tenant or acceptance by Landlord of a lesser
amount than shall be due Landlord from Tenant shall be deemed to be anything but
payment on account, and the acceptance by Landlord of a check for a lesser
amount with an endorsement or statement thereon, or upon a letter accompanying
said check, that said lesser amount is payment in full shall not be deemed an
accord and satisfaction, and Landlord may accept said check without prejudice to
recover the balance due or pursue any other remedy.

      Section 12.8 Holdover. If Tenant remains in the Premises beyond the
expiration of this Lease at the end of the Lease Term, or sooner following an
early termination as provided for herein, such holding over shall not be deemed
to create any tenancy, but Tenant shall be a daily Tenant at sufferance only
subject to all of Tenant's obligations set forth herein, but at a daily rate
equal to one and one-half (1.5) times the Fixed Minimum Rent, then in effect,
and Additional Rent and other charges provided for under this Lease. The
acceptance of a purported rent check following termination shall not constitute
the creation of a tenancy at will, it being agreed that Tenant's status shall
remain that of a daily Tenant at sufferance, at the aforesaid daily rate. Tenant
shall also pay to Landlord all damages, if any, sustained by reason of any such
holding over. Otherwise, such holding over shall be on the terms and conditions
set forth in this Lease as far as applicable.

      Section 12.9 Summary of Basic Terms. The Summary of Basic Terms which is
affixed to this Lease sets forth certain basic terms and information which is
thereafter referred to in the main text of this Lease. Every reference to the
Summary of Basic Terms, or to a particular item thereon, shall have the effect
of incorporating the Summary, or the particular item thereof, into the main text
of this Lease.

                                       50
<PAGE>

      Section 12.10 When Lease Becomes Binding. The submission of this document
for examination and negotiation does not constitute an offer to lease or a
reservation or an option for the Premises, and this document shall become
effective and binding only upon the execution and delivery hereof by both
Landlord and Tenant. All negotiations, considerations, representations and
understandings between Landlord and Tenant are incorporated herein and may be
modified or altered only by agreement in writing between Landlord and Tenant,
and no act or omission of any employee or agent of Landlord shall alter, change
or modify any of the provisions hereof.

      Section 12.11 As-Is. Tenant represents to Landlord that it has leased the
Premises after a full and complete examination of the same and accepts the
Premises in "AS IS" condition, including the condition and adequacy of the
heating, air conditioning, electrical, plumbing and other systems. Tenant,
acknowledges that neither Landlord, nor Landlord's agents, has made any
representation or promises with respect to the Premises, the Building, or the
land upon which it stands, and no rights, easements or licenses are acquired by
Tenant, by implication or otherwise, except as may be set forth expressly in
this Lease. The execution and delivery of this Lease by Tenant shall be
conclusive evidence, as against Tenant, that Tenant accepts the Premises "AS
IS", with all faults.

      Section 12.12 No Recordation: Notice of Lease. Tenant shall not record
this Lease with any registry of deeds or with the land court. Tenant may, at its
expense, record a notice of lease in form and substance satisfactory to Landlord
executed by Landlord and Tenant with the Middlesex South District Registry of
Deeds. At the end of the Lease Term or sooner termination of this Lease, the
parties agree to execute a notice of termination of lease in recordable form and
Landlord may, at its expense, record the same in the Middlesex South District
Registry of Deeds.

      Section 12.13 Fair Market Rent and Fair Market Parking Charge.

      (a) Within thirty (30) days after Tenant gives to Landlord written notice
of exercise of the extension option pursuant to Section 2.3, hereof, Landlord
and Tenant shall simultaneously exchange proposals setting forth their opinions
as to the Fair Market Rent and the fair market parking charge for parking spaces
during any Extension Term ("Fair Market Parking Charge"). Landlord and Tenant
shall negotiate in good faith for not less than fifteen (15) business days after
the exchange of proposals (such fifteen (15) business day period being herein
called the "Negotiation Period") to attempt to agree upon the Fair Market Rent
and the Fair Market Parking Charge, and, in the course of such negotiations,
each party may from time to time submit modified proposals to the other. If the
parties agree upon the Fair Market Rent and the Fair Market Parking Charge prior
to the determination of the arbitrator pursuant to section 12.13(b) hereof,
whether such agreement is reached during or after the Negotiation Period, the
Fair Market Rent and the Fair Market Parking Charge shall be so agreed.

      (b) If the parties are unable to agree upon the Fair Market Rent and the
Fair Market Parking Charge within the Negotiation Period then each party shall,
upon selection of an arbitrator pursuant to Section 12.13(c) hereof,
simultaneously exchange and submit to the arbitrator for binding arbitration a
proposal as to which of Fair Market Rent, the Fair Market Parking Charge, or
both, on which they cannot agree (the amount or amounts on which they cannot
agree is collectively referred to as the "Disputed Rate"). Within thirty (30)
days after both

                                       51
<PAGE>

parties have submitted such proposals to the arbitrator, the arbitrator shall
select one of the proposals as more closely approximating the Disputed Rate
appropriate for the Extension Term and, unless the parties have then agreed upon
the Disputed Rate, the proposed Disputed Rate forth in such proposal selected by
the arbitrator shall be deemed to be the Disputed Rate.

      (c) If the parties are unable to agree upon the Disputed Rate within the
Negotiation Period, then the parties shall within fifteen (15) days after the
end of the Negotiation Period (such fifteen (15) day period being herein called
the "Selection Period"), attempt to agree upon an arbitrator to whom to submit
the determination of the Disputed Rate for binding arbitration pursuant to
Section 12.13(b) hereof. If the parties are unable to agree upon an arbitrator
within the Selection Period, then at the end of the Selection Period, each party
shall select an arbitrator and, within fifteen (15) days after the end of the
Selection Period, the arbitrators shall agree upon an arbitrator to whom the
determination of the Disputed Rate shall be submitted for binding arbitration
pursuant to Section 12.13(b) hereof. If such arbitrators are unable to agree
promptly upon an arbitrator, an arbitrator shall be selected by the American
Arbitration Association. Any arbitrator selected by either party, by the
arbitrators selected by the parties or by the American Arbitration Association
shall be independent of both parties and shall have at least 10 years
experience, either as a licensed real estate broker or salesperson or as an
appraiser. Such arbitrator shall determine the Disputed Rate within thirty (30)
days of selection. The parties shall share equally the fees and expenses of the
arbitrator to whom the determination of the Disputed Rate is submitted. Landlord
and Tenant shall each pay the fee of the arbitrator selected by it.

      Section 12.14 Confidentiality. Tenant acknowledges that the terms under
which Landlord has leased the Premises to Tenant, (including without limitation,
the rental rate(s), term and other financial and business terms, constitute
confidential information of Landlord ("Confidential Information"). Tenant
covenants and agrees to keep the Confidential Information completely
confidential; provided, however, that (i) such Confidential Information may be
disclosed by Tenant to those of its officers, employees, attorneys, accountants,
lenders and financial advisors who need to know such information in connection
with Tenant's use and occupancy of the Premises and for financial reporting and
credit related activities (it being understood that Tenant shall inform its
representatives of the confidential nature of such Confidential Information and
that such representatives shall be directed by Tenant, and shall each expressly
agree, to treat such Confidential information confidentially in accordance with
the terms of this Section), and (ii) unless required by applicable law, any
other disclosure of such information may only be made if Landlord consents in
writing prior to any such disclosure. In furtherance of and not in limitation of
the foregoing, Tenant understands and agrees that during the period of any
negotiation of the terms of this Lease, the disclosure of Tenant's possible
interest in leasing the Premises and the terms thereof could have a material
adverse effect on Landlord's business. BY ITS RECEIPT OF A DRAFT OF THIS LEASE.
TENANT ACKNOWLEDGES AND AGREES THAT, WITHOUT THE PRIOR WRITTEN CONSENT OF
LANDLORD, EXCEPT AS PROVIDED IN CLAUSES (i) AND (ii) OF THIS SECTION 12.14,
TENANT WILL NOT, AND TENANT WILL DIRECT ITS REPRESENTATIVES NOT TO, PRIOR TO THE
EXECUTION OF THIS LEASE, DISCLOSE TO ANY PERSON EITHER THE FACT THAT DISCUSSIONS
OR NEGOTIATIONS ARE TAKING PLACE CONCERNING THE POSSIBLE LEASE TRANSACTION
BETWEEN TENANT AND LANDLORD OR ANY OF THE TERMS, CONDITIONS OR OTHER FACTS WITH
RESPECT TO SUCH POSSIBLE LEASE

                                       52
<PAGE>

TRANSACTION, INCLUDING THE STATUS THEREOF. THE TERM "PERSON" AS USED HEREIN
SHALL BE BROADLY INTERPRETED TO INCLUDE, WITHOUT LIMITATION, ANY CORPORATION,
LIMITED LIABILITY COMPANY, GOVERNMENTAL AGENCY OR BODY, PARTNERSHIP. ASSOCIATION
OR INDIVIDUAL.

      Section 12.15 Tenant's Execution of Documents. In the event that Tenant
fails to execute and deliver to Landlord or Landlord's mortgagee or any other
third party documents required to be executed and delivered by Tenant hereunder,
including without limitation documents required to be delivered under Sections
8.1 and 8.4 of this Lease, within the time frames provided herein, Tenant hereby
appoints Landlord as Tenant's attorney-in-fact coupled with an interest to
execute, acknowledge (if applicable) and deliver any such documents for and on
behalf of Tenant without any liability to Tenant in relation thereto.

      Section 12.16 Tenant's Financial Statements. From time to time as
requested by Landlord, Tenant shall provide to Landlord, any actual or potential
mortgagee and any actual or potential ground lessor or any representative of any
of the foregoing, copies of Tenant's annual financial statements (audited or
reviewed, if available) and quarterly financial statements, all certified as
true and correct by the president or chief financial officer of Tenant, and such
other information regarding Tenant's financial condition as Landlord may
reasonably request.

                                  ARTICLE XIII

      Section 13.1 Right of First Opportunity.

      (a) Grant of Right. In the event that Landlord sends a Notice of
Relocation to Tenant in accordance with Section 7.14 hereof, Tenant shall have
the right, subject to the rights of any "Major Tenant" (hereinafter defined),
for a period of sixty (60) days thereafter to lease any Additional Space
(hereinafter defined) which is then available for lease on and subject to the
terms and conditions set forth in this Section 13.1. As used herein, "Additional
Space" means leaseable space which is then available in the building in which
Tenant is to be relocated. As used herein. "Major Tenant" means any person or
entity which has executed a lease for 39,000 or more square feet in the
buildings located and/or to be located on Landlord's Property 210 Broadway or
both, excluding Tenant. During the "Option Period" (as hereinafter defined),
Landlord will not enter into any lease of any Additional Space to a third party
(a "Third-Party Lease") other than a Major Tenant unless and until Landlord has
given to Tenant a Notice of Availability (as defined in Paragraph (b) of this
Section 13.1) with respect to such Additional Space and Tenant has failed to
exercise its right to lease such Additional Space pursuant to Paragraph (c) of
this Section 13.1 and any Third Party Lease of such Additional Space (other than
a lease to a Major Tenant) shall be at an effective rent and on other terms
which, in the aggregate, are not substantially more favorable to the tenant than
those specified in the Notice of Availability.

      (b) Notices of Availability. Simultaneously with the delivery of the
Notice of Relocation to Tenant, Landlord shall give written notice to Tenant
specifying any Additional Space which is available for lease. Any such notice (a
"Notice of Availability) shall specify, in addition to the Additional Space
which is available for lease, the date on or about which the

                                       53
<PAGE>

Additional Space is to become available for lease (if it is not then available),
the effective rent (including Fixed Minimum Rent and Additional Rent, if
applicable) at which Landlord is willing to lease the Additional Space, and such
other terms which Landlord desires to specify. If, with respect to any
Additional Space as to which Landlord has given a Notice of Availability and as
to which Tenant has failed to exercise its right to lease pursuant to Paragraph
(c) of this Section 13.1, Landlord desires to enter into a Third-Party Lease at
an effective rent or on other terms which are, in the aggregate, substantially
more favorable to the tenant than those set forth in the Notice of Availability,
Landlord shall, before entering into such Third-Party Lease, give another Notice
of Availability (a "Follow-up Notice") to Tenant, specifying the proposed terms
which are more favorable to the tenant than those set forth in the prior Notice
of Availability. Tenant shall not disclose to third parties, other than Tenant's
employees, consultants and other agents who have a need to know, the contents of
any Notice of Availability.

      (c) Exercise of Right. Provided that, on the date of exercise, there does
not exist a default of Tenant or any fact or circumstance which, with the
passage of time, the giving of notice, or the satisfaction of any other
condition, or all of them, could constitute a default under this Lease, Tenant
shall have the right, exercisable by written notice given by Tenant and received
by Landlord within the Option Period (as defined below), and subject to the
limitation set forth in Paragraph (f) of this Section 13.1, to lease all or any
part of the Additional Space specified in a Notice of Availability up to a
maximum of 20,000 square feet. Tenant's notice of exercise Shall specify the
portion of the Additional Space as to which Tenant is exercising its right to
lease. As used herein, "Option Period" shall mean the period of thirty (30) days
after Landlord gives the subject Notice of Availability to Tenant; provided,
however, that the Option Period with respect to any Notice of Availability which
is a Follow-up Notice shall be the period of five (5) days after Landlord gives
such Notice of Availability to Tenant.

      (d) Addition of Space to Lease. If Tenant exercises its right to lease any
Additional Space pursuant to Paragraph (c) of this Section 13.1, then, as of the
date which is the later of (i) ten (10) days after Landlord's receipt of
Tenant's notice of exercise of its right to lease the Additional Space or (ii)
the date on which the Additional Space becomes available, such Additional Space
shall be added to and become a part of the Premises and subject to the terms and
conditions of this Lease, provided that the terms and conditions of this Lease
with respect to such Additional Space shall be modified by the terms specified
in the subject Notice of Availability. Promptly after Tenant exercises its right
to lease any Additional Space pursuant to Paragraph (c) of this Section 13.1,
Landlord and Tenant shall enter into an amendment of this Lease incorporating
such Additional Space as part of the Premises and incorporating the terms
specified in the subject Notice of Availability with respect to such Additional
Space.

      (e) Lapse of Right. With respect to any Additional Space as to which
Landlord gives Tenant a Notice of Availability, if Landlord does not receive
Tenant's notice of exercise pursuant to Paragraph (c) of this Section 13.1
within the Option Period, Tenant's right of first opportunity provided for in
this Article 13 shall lapse and Landlord shall be free to lease the Additional
Space to third parties on terms which are, in the aggregate, not substantially
more favorable to the tenant than those specified in the Notice of Availability.

                                       54
<PAGE>

      (f) Limitation. Tenant's right of first opportunity provided for in this
Section 13.1 is subject to the limitation that the configuration, size and
location of any Additional Space leased by Tenant pursuant to the terms thereof
shall be established in a manner to assure that the Additional Space leased by
Tenant, as well as any residual space, in the subject building is functional and
marketable, as determined by Landlord in its reasonable discretion.

      (g) Rights Personal to Party Executing this Lease. The rights in this
Article 13 are personal to Variagenics, Inc. and are not assignable or
transferable, except in connection with an assignment or sublease made pursuant
to, and in compliance with, Section 7.12(b)(ii). On any other permitted
assignment (or request for assignment) of this Lease or on any other permitted
sublease (or request for sublease) of this Lease for a portion of the Premises,
the rights Under this Article 13 will lapse and be of no further force and
effect.

                                          TENANT:

                                          VARIAGENICS, INC.

                                          By:   /s/  Fred D. Ledley, M.D.
                                             ----------------------------
                                             Name:  Fred D. Ledley, M.D.
                                                 -----------------------
                                             Title:  President and CEO
                                                   -------------------
                                                   Duly Authorized

                                          LANDLORD:

                                          205 BROADWAY REALTY TRUST

                                          BY:   BHX, LLC, its Trustee and not
                                                for itself

                                          By:   /s/  Robert A. Schlager
                                             ----------------------------
                                          Name: Robert A. Schlager
                                             Title:  Treasurer
                                                     Duly Authorized

                                       55
<PAGE>

                                    EXHIBIT A

      A certain parcel of land with the buildings thereon situated in Cambridge,
Middlesex County, Massachusetts, being bounded and described as follows:

      NORTHEASTERLY           by Hampshire Street, three hundred seventy-one and
                              72/100 (371.72) feet;

      SOUTHEASTERLY           by land now or formerly of East Coast Realty Co.
                              by two lines measuring one hundred thirty-six and
                              29/100 (136.29) feet and seventy-one and 61/100
                              (71.61) feet, respectively;

      SOUTHWESTERLY           by Broadway, forty-two and 05/100 (42.05) feet;

      SOUTHWESTERLY           again by Markes Street three hundred fifty-two and
                              70/100 (352.70) feet, more or less; and,

      NORTHWESTERLY           by Clark Street, two hundred forty-six and 50/100
                              (246.50) feet.

      Said parcel contains approximately 87,063.16 square feet of land and is a
portion of the premises shown on a plan entitled "Plan of Land in Cambridge"
dated December 3, 1946 by Edward Smith, C.E., being Plan 1919 of 1946, recorded
with Middlesex South District Registry of Deeds in Book 7058, Page 174.

      Or however otherwise the said premises may be bounded, measured and
described, meaning and intending to describe and meaning and intending to convey
and hereby conveying the entire premises described in the deed to Morningstar
Limited Partnership described below.

      Certain portions of the above described parcel are also shown on the
following plans:

            1. Plan of land in Cambridge owned by Barbour Stockwell Company,
      recorded with said Deeds, Book 5894, Page 113.

            2. Plan of land in Cambridge owned by Barbour Stockwell Company,
      recorded with said Deeds in Book 5894, Page 115.

            3. Plan of land in Cambridge owned by Barbour Stockwell Company,
      recorded with said Deed sin Book 5894, Page 117.
<PAGE>

                                    EXHIBIT B

                                    SITE PLAN

                                       2
<PAGE>

                                    EXHIBIT C

                                  TENANT'S WORK

1.    Tenant will perform all work necessary to equip and open its office and
      laboratory facilities in accordance with all applicable building codes and
      other laws. In addition, Tenant shall install a new roof membrane on the
      Building together with related flashings, accessories and all else
      necessary and customary in reroofing (but specifically excluding any
      repairs or structural defects in the framing system to support such roof,
      which structural repairs, if any, shall remain and be the responsibility
      of Landlord), on or before November 1, 1998 subject to extension due to
      delays resulting from interruption of utility services, breakage, strikes,
      inability after exercise of reasonable diligence to obtain supplies or for
      any cause or causes beyond the reasonable control of Tenant (which shall
      never include the lack of capital available to Tenant). Work shall be
      performed as provided in Section 2.5 of this Lease.

2.    Tenant will provide scaled, complete working drawings and specifications
      to the Landlord prepared by an architect registered in the Commonwealth of
      Massachusetts prior to commencing any major construction or remodeling
      work. All work to be performed must be in compliance with Federal, State,
      and local building codes and regulations. Tenant will obtain any and all
      permits necessary to complete its work, including, without limitation,
      building, electrical and plumbing permits associated with its work to be
      performed hereunder. Copies of all permits must be submitted to the
      Landlord, together with certificates of insurance for Tenant's
      contractors, prior to commencement of the related work. At the completion
      of each phase of Tenant's Work, Tenant will obtain and maintain a
      certificate of occupancy for the applicable portion of the Building and
      provide a copy of same to the Landlord.

3.    Tenant will use only contractors reasonably approved by Landlord to
      perform Tenant's Work. Notwithstanding anything to the contrary herein,
      should Tenant elect to utilize (i) Siena Construction, (ii) C.E. Floyd, or
      (iii) Ellenzweig Associates, each of such contractors shall be deemed to
      satisfy the requirements of this paragraph, provided that Tenant gives
      Landlord at least ten (10) days prior written notice of such proposed
      contractor. When Tenant knows the identity of such contractor's major
      subcontractor (i.e. those whose contracts exceed $50,000) Tenant shall
      identify them in writing to Landlord.

4.    Tenant's Work will consist primarily of tenant fit out and repairs to the
      Building for office and laboratory use generally in accordance with the
      drawing attached hereto as Exhibit C-1 and the installation of a new roof
      (as described in paragraph 1 above of this Exhibit C) on the Building.
      Tenant's Work, and the plans and specifications therefor, will be subject
      to Landlord's prior written approval, which approval will not be
      unreasonably withheld.

                                       3
<PAGE>

                                    EXHIBIT D

                                  SIGN CRITERIA

      Capitalized words and terms used in this Exhibit which are not defined
elsewhere in this Lease shall have the meanings provided in Articles 2
(Definitions) and 7 (Signs and Illumination) of the Cambridge Zoning Ordinance.
Tenant may erect, place or install, or have erected, placed or installed, up to
three (3) stationary Wall Signs, only in the locations and of a size no larger
than that shown on the attached sketch, provided that such Signs also are in
full conformance with the following restrictions and requirements:

1.    No individual Wall Sign may exceed twenty-five (25) square feet in area.
      The area of Tenant's Wall Signs shall be calculated as provided for in
      Section 7.14 of the Cambridge Zoning Ordinance.

2.    Tenant's Wall Sign(s) shall display the name of the Tenant and no other
      name.

3.    All Signs must comply with all applicable design, placement, permit,
      certification and other requirements of the Cambridge Zoning Ordinance.
      Tenant shall simultaneously give Landlord copies of all applications and
      other materials submitted to the City of Cambridge and also shall promptly
      give Landlord copies of any permits, certifications, or notices of
      violation issued by the City of Cambridge with respect to Signs.

4.    All Signs shall be subject to Landlord's prior written approval, which
      shall not be unreasonably withheld or delayed. Tenant shall provide to
      Landlord, before the erection, placement or installation of any Wall
      Sign(s), a scaled drawing illustrating the proposed Tenant signage,
      proposed structural supports, actual commutations, certification and
      registration stamp of a structural engineer attesting to the design of the
      structural support and such other materials and documentation as Landlord
      may require. Tenants shall provide Landlord with color chips of actual
      color(s) proposed.

5.    The Wall Sign(s) shall be illuminated only by Natural Illumination or as
      allowed under Section 7.16.22.C of the Cambridge Zoning Ordinance. Any
      illumninated Sign shall be provided with a time clock to regulate the
      hours of Sign illumination, at the expense of the Tenant, which shall be
      operable from within the Building. Tenant shall pay the cost of any
      electricity consumed for such Sign or time clock.

6.    All fastenings shall be concealed where possible. All electrical devices,
      wiring and the like shall be contained within the horizontal electrical
      raceway behind the Sign lettering, which raceway shall not extend beyond
      the most extreme lettering locations. Raceway wiring shall interface with
      a junction box and wiring furnished installed and connected by the Tenant
      at the proposed general location of the Tenant signage.

                                       4
<PAGE>

7.    Tenants shall furnish and install all required cutting, patching,
      blocking, cleaning, bolsters, scaffolding, ladders, staging, protection
      boards, and the like to support and install the signage. Protection shall
      be provided during the erection, placement, installation or maintenance of
      any Sign(s) for the existing roofing membrane and attendant flashings to
      preclude any cutting, puncturing, scraping, marring or the like. A
      Landlord-approved roofing contractor shall repair any accidental
      penetration of roofing membrane or other damage resulting from tenant
      signage installation or maintenance, at the expense of the Tenant.

                                       5
<PAGE>

      EXECUTED as a sealed instrument as of the day and year first above
written.

WITNESS:                                  LENDER:

                                          KEYBANK NATIONAL ASSOCIATION

_______________________________           By:________________________________
Name:                                        Joseph B. Bator, Vice President
                                             Hereunto duly authorized

                                             LANDLORD:

                                             205 BROADWAY REALTY TRUST

                                                By:  BHX, LLC, AS TRUSTEE

Name:____________________________               By:___________________________
                                                Name:  Eric D. Schlager
                                                   Title:  Member
                                                   Hereunto duly authorized

                                             TENANT:

                                             VARIAGENICS, INC.

Name:____________________________               By:___________________________
                                                Name:  Fred Ledley
                                                   Title:  President and CEO
                                                   Hereunto duly authorized

                                       6
<PAGE>

                          COMMONWEALTH OF MASSACHUSETTS

_________________________, ss.                        ___________________, 1998

      Then personally appeared the above-named Joseph B. Bator, Vice President
of KeyBank National Association, and acknowledged the foregoing instrument to be
his first act and deed on behalf of said corporation, before me

      [AFFIX SEAL]                           _________________________________
                                             Notary Public
                                             My Commission Expires:

                          COMMONWEALTH OF MASSACHUSETTS

_________________________, ss.                        ___________________, 1998

      Then personally appeared the above-named Eric D. Schlager, Member of the
BHX, LLC, Trustee of 205 Broadway, and acknowledged the foregoing instrument to
be his first act and deed on behalf of said corporation, before me

      [AFFIX SEAL]                           _________________________________
                                             Notary Public
                                             My Commission Expires:

                          COMMONWEALTH OF MASSACHUSETTS

_________________________, ss.                        ___________________, 1998

      Then personally appeared the above-named Fred Ledley, President and CEO of
Variagenics, Inc., and acknowledged the foregoing instrument to be his first act
and deed on behalf of said corporation, before me

      [AFFIX SEAL]                           _________________________________
                                             Notary Public
                                             My Commission Expires:

                                       7
<PAGE>

                                    EXHIBIT E

                                VARIAGENICS, INC.

                             SECRETARY'S CERTIFICATE

      The undersigned, Fred D. Ledley, Secretary of Variagenics, Inc. (the
"Corporation"), does hereby certify as follows:

      1. I am the duly elected, qualified and acting Secretary of the
Corporation and I am authorized to execute this certificate on behalf of the
Corporation.

      2. Attached hereto as Exhibit A are true, correct and complete copies of
resolutions duly adopted by the consent of the Board of Directors of the
Corporation on May __, 1998, which resolutions have not been amended, modified
or rescinded since the date of adoption thereof.

      3. The following persons are the duly qualified and acting officers of the
Corporation, duly elected to the respective offices set forth opposite such
name, and the signature appearing opposite the name of such officer is such
officer's genuine and authentic signature:

      NAME                    OFFICE                  SIGNATURE
      ----                    ------                  ---------

      Fred D. Ledley    President & Secretary         ________________________

      IN WITNESS WHEREOF, I have hereunto set my hand on behalf of the
Corporation this ___ day of May 1998.

                                          ----------------------------------
                                          Fred D. Ledley, Secretary

                                       8
<PAGE>

                                VARIAGENICS INC.

                                    EXHIBIT A

RESOLVED:   That the Corporation enter into a lease agreement with BHX, LLC as
            trustee of 205 Broadway Realty Trust for a period of ten (10) years
            with a five (5) year option to extend, in the form approved by the
            President in his sole discretion (the "Lease"); and that the
            President of this Corporation be, and he hereby is, authorized,
            empowered and directed in the name and on behalf of this Corporation
            and under its seal, if so desired, to negotiate, execute and deliver
            the Lease for such space and to negotiate, execute and deliver such
            further instruments, documents, certificates and filings as may be
            necessary or convenient in connection with the leasing of such
            space, such lease and such additional documents and instruments to
            have such terms and provisions as the officer executing the same
            shall judge advisable, and to do and perform such acts and deeds as
            such officer deems necessary or appropriate in order to effectuate
            the purposes and intents of this resolution.

RESOLVED:   That any officer of the Corporation be, and each of them hereby is,
            authorized and directed to do or cause to be done any and all such
            other acts and things and to execute and deliver any and all such
            further documents, instrument and certificates, in the name and on
            behalf of the Corporation, as they or any of them may deem necessary
            or appropriate to carry into effect the full intent and purpose of
            the foregoing resolution, the taking of any such actions or the
            execution or delivery of any such documents, instruments or
            certificates by such officer or officers to be conclusive evidence
            that the same were authorized by this resolution.

                                       9
<PAGE>

                                    EXHIBIT F

                          NAME OF FINANCIAL INSTITUTION
                        IRREVOCABLE LETTER OF CREDIT FORM

                                                      Date: __________
19____                                                Amount: $2,000,000 USD
Credit No.  ________________________________

Beneficiary; BHX, LLC, a Massachusetts limited liability company,
             as Trustee of 205 Broadway Realty Trust
             First Needham Place
             250 First Avenue, Suite 200
             Needham, MA 02194-2505

Gentlemen:

      We hereby establish our unconditional, irrevocable Letter of Credit No.
________in your favor and for the account of Variagenics, Inc. whereby we
irrevocably authorize you to draw on us from time to time at sight prior to the
expiration hereof, and in the manner provided herein, up to $2,000,000 USD. Such
drawing(s) will be unconditionally available to you upon your presentation of
your draft(s) (which draft(s) shall have been signed by one purporting to be a
duly authorized representative of the Beneficiary) on which shall be indicated
"Drawn under [Name of Financial Institution] Letter of Credit No ._______,"
together with your certification to us that either (i) a default has occurred
under a certain Lease between BHX, LLC, as Trustee of 205 Broadway Realty Trust
and Variagenics, Inc. beyond any applicable notice and cure periods or (ii) you
are otherwise entitled to draw upon this Letter of Credit under the terms of
said Lease. Multiple partial drawings are permitted.

      Each draft is to be accompanied by a copy of this Letter of Credit and
shall be honored when presented between 9:00 am. and 5:00 p.m. on any Business
Day (by which is meant any day other than Saturday, Sunday or any day [Name of
Financial Institution] is prohibited from conducting commercial banking
transactions] at [Name of Financial Institution] office at [Address of Financial
Institution].

      This Letter of Credit may be transferred, in whole, but not in part,
without charge one or more times upon receipt of Beneficiary's written
instructions. This Letter of Credit shall remain in full force and effect until
5:00 p.m. Eastern Standard Time on _______________,_______. This Irrevocable
Letter of Credit shall be automatically renewed, extended and/or reissued after
____________________, for successive one (1) year periods unless the Bank
provides Beneficiary with not less than forty-five (45) days prior written
notice to the attention of Robert A. Schlager at the above listed address (or
any other address and/or to the attention of any other party of which new
address and/or such new party the Beneficiary notifies the Bank) that Bank
elects not to renew, extend and/or reissue this Irrevocable Letter of Credit.

                                       10
<PAGE>

      This Irrevocable Letter Of Credit is subject to the Uniform Customs and
Practices for Documentary Credits (1993 revision), I.C.C. Publication No. 500.

                                          ------------------------------------
                                          By:
                                          Duly Authorized

                                       11
<PAGE>

             SUBORDINATION, NON-DISTURBANCE AND ATTORNMENT AGREEMENT

      This SUBORDINATION, NON-DISTURBANCE AND ATTORNMENT AGREEMENT is made and
entered into as of this ____ day of ________, 1998, by and among KEYBANK
NATIONAL ASSOCIATION (the "Lender"), BHX, LLC, TRUSTEE OF 205 BROADWAY REALTY
TRUST, a Massachusetts nominee trust created under a Declaration of Trust dated
March 24, 1998, recorded with Middlesex South District Registry of Deeds (the
"Registry") on March 24, 1998, as Instrument No. 1185 (the "Landlord"), and
Variagenics, Inc. (the "Tenant").

                             PRELIMINARY STATEMENTS

      A. The Landlord and the Tenant intend to enter into a Lease (the "Lease")
of a portion of the real property with the improvements thereon known as and
numbered 205 Broadway, Middlesex County, Massachusetts as more fully described
in the Lease (the "Demised Premises"). The Landlord is the current owner of the
Demised Premises.

      B. The Lender is the holder of a Mortgage Note dated March 24, 1998, in
the original principal amount of $7,500,000.00 made by the Landlord in favor of
the Lender (the "Note"), which Note is secured, inter alia, by a Mortgage,
Security Agreement and Assignment of Leases dated of even date with the Note (as
the same may be amended, renewed, modified, consolidated, replaced, extended,
increased or restated from time to time, the "Mortgage") and recorded with the
Registry on March 24, 1998, as Instrument No. 1189 covering the premises more
particularly described in the Mortgage, including the Demised Premises (the
"Property"). In addition, the Landlord has entered into and delivered that
certain Assignment of Rents and Leases in favor of the Lender, dated of even
date with the Note (as the same may be amended, renewed, modified, consolidated,
replaced, extended, increased or restated from time to time, the "Assignment")
covering the Property, which Assignment was recorded with the Registry on March
24, 1998, as Instrument No. 1190.

      C. The parties hereto desire to enter into this Subordination,
Non-Disturbance and Attornment Agreement.

      NOW, THEREFORE, in consideration of the mutual covenants hereinafter set
forth and other good and valuable consideration, the receipt and sufficiency of
which are hereby acknowledged, the Tenant, the Landlord and the Lender hereby
covenant and agree as follows:

      1. Subordination. The Tenant hereby agrees with the Lender that all of its
right, title and interest as lessee under the Lease shall be subject and
subordinate to the right, title and interest of the Lender under the Mortgage
and Assignment (and any amendment, renewal, modification, consolidation,
replacement, extension, increase or restatement thereof).

      2. Non-Disturbance. So long as no default on the part of Tenant exists
under the Lease and continues beyond the expiration of any applicable periods of
notice and grace, nor any other event has occurred, which has continued to exist
beyond the expiration of any applicable

                                       12
<PAGE>

periods of notice and grace, as would entitle the Landlord to terminate the
Lease or would cause, without any further action on the part of Landlord, the
termination of the Lease or would entitle the Landlord to dispossess the Tenant
thereunder, the Lease shall not be terminated, nor shall such Tenant's use,
possession or enjoyment of the Demised Premises or rights under the Lease be
interfered with in any foreclosure or other action or proceeding in the nature
of foreclosure or by way of any deed in lieu of any such action or proceeding,
instituted under or in connection with the Mortgage, or, in case Lender takes
possession of the Property pursuant to any provisions of the Mortgage or the
Assignment of Leases, unless the Landlord under the Lease would have had such
right if the Mortgage or the Assignment of Leases had not been made. Neither the
person or entity acquiring the interest of the lessor under the Lease as a
result of any such action or proceeding or by way of any deed in lieu of any
such action or proceeding (hereinafter called the "Purchaser") nor Lender, if
Lender takes possession of the Property or otherwise succeeds to the lessor's
interest under the Lease, shall be: (a) liable for any act or omission of any
prior lessor under the Lease; or (b) liable for the return of any security
deposit which Tenant under the Lease has paid to any prior lessor under the
Lease, except to the extent that the amount thereof is turned over to the
Purchaser or the Lender, as the case may be; or (c) subject to any offsets or
defenses which the Tenant under the Lease might have against any prior lessor
under the Lease; or (d) bound by the payment of any base rent, percentage rent
or any other payments which the Tenant under the Lease might have paid for more
than the current month to any prior lessor under the Lease; or (e) bound by any
amendment or modification of the Lease made without Lender's prior written
consent and not otherwise permitted under the Mortgage and/or the Assignment; or
(f) except with respect to an assignment or sublease pursuant to Section 7.12
(b)(ii) of the Lease, bound by any consent by any lessor under the Lease to any
assignment of the lessee's interest in the Lease or sublease of all or any
portion of the Property made without Lender's prior written consent and not
otherwise permitted under the Mortgage and/or the Assignment; or (g) personally
liable for any default under the Lease or any covenant or obligation on its part
to be performed thereunder as lessor, it being acknowledged that Tenant's sole
remedy in the event of such default shall be to proceed against the Purchaser's
or Lender's interest in the Property. Notwithstanding anything contained herein
to be contrary, if Lender or any Purchaser succeeds to the lessor's interests
under the Lease, such party shall have absolutely no obligation to perform any
leasehold improvements or other construction obligations in the Property on the
part of Landlord to have been performed other than (i) any ongoing maintenance
and repair obligations which are required to be performed by the Landlord under
the terms of the Lease and (ii) Landlord's Contribution, as set forth in Section
2.5 of the Lease, for a period ending two years after the Commencement Date of
the Lease.

      3. Attornment. Unless the Lease is terminated in accordance with Paragraph
2, if the interests of the lessor under the Lease shall be transferred by reason
of the exercise of the power of sale contained in the Mortgage (if applicable),
or by any foreclosure or other proceeding for enforcement of the Mortgage, or by
deed in lieu of foreclosure or such other proceeding, or if the Lender takes
possession of the Property pursuant to any provisions of the Mortgage or the
Assignment, the lessee thereunder shall be bound to the Purchaser or the Lender,
as the case may be, under all of the terms, covenants and conditions of the
Lease for the balance of the term thereof and any extensions or renewals thereof
which may be effected in accordance with any option therefor in the Lease, with
the same force and effect as if the Purchaser or Lender were the lessor under
the Lease, and Tenant does hereby attorn to the Purchaser or Lender, as the same

                                       13
<PAGE>

may be (if it takes possession of the Property), as its lessor under the Lease.
Such attornment shall be effective and self-operative without the execution of
any further instruments upon the succession by Purchaser to the interest of the
lessor under the Lease or the taking of possession of the Property by Lender.
Nevertheless, Tenant shall, from time to time, execute and deliver such
instruments evidencing such attornment as Purchaser or Lender may require. The
respective rights and obligations of Purchaser, Lender and Tenant upon such
attornment. to the extent of the then remaining balance of the term of the Lease
and any extensions and renewals, shall be and are the same as now set forth in
the Lease except as otherwise expressly provided in Paragraph 2.

      4. Assignment of Leases. Tenant hereby acknowledges that all of the
Landlord's right, title and interest as lessor under the Lease is being duly
assigned to Lender pursuant to the terms of the Assignment, and that pursuant to
the terms thereof all rental payments under the Lease shall continue to be paid
to Landlord in accordance with the terms of the Lease unless and until Tenant is
otherwise notified in writing by Lender. Upon receipt of any such written notice
from Lender, Tenant covenants and agrees to make payment of all rental payments
then due or to become due under the Lease directly to Lender or to Lender's
agent designated in such notice and to continue to do so until otherwise
notified in writing by Lender. Landlord hereby irrevocably directs and
authorizes Tenant to make rental payments directly to Lender following receipt
of such notice without any obligation to inquire as to whether any default
exists under the Mortgage or the Assignment or the indebtedness secured thereby,
and notwithstanding any notice or claim of Landlord to the contrary, and that
Landlord shall have no right or claim against Tenant for or by reason of any
rental payments made by Tenant to Lender following receipt of such notice.
Tenant further acknowledges and agrees: (a) that under the provisions of the
Assignment, the Lease cannot be terminated except as provided in the Lease (nor
can Landlord accept any surrender of the Lease) or modified in any of its terms,
or consent by Landlord given to the waiver or release of Tenant from the
performance or observance of any obligation under the Lease, without the prior
written consent of Lender except as otherwise provided in the Assignment, and
without such consent no rent may be collected or accepted by Landlord more than
one month in advance and (b) that the interest of Landlord as lessor under the
Lease has been assigned to Lender for the purposes specified in the Assignment,
and Lender assumes no duty, liability or obligation under the Lease by reason of
the Mortgage and/or the Assignment, except only under the circumstances, terms
and conditions specifically set forth in the Mortgage, the Assignment and
herein.

      5. Notice of Default by Lessor. Tenant, as lessee under the Lease, hereby
covenants and agrees to give Lender written notice properly specifying wherein
the lessor under the Lease has failed to perform any of the covenants or
obligations of the lessor under the Lease, simultaneously with the giving of any
notice of such default to the lessor under the provisions of the Lease. Tenant
agrees that Lender shall have the right, but not the obligation, within the time
period specified in the Lease plus an additional twenty (20) business days (or,
if no time period is specified, a reasonable time, provided that the Lender is
diligently prosecuting the same) for cure by Landlord (or within such additional
time as is reasonably required to cure any such default, provided Lender shall
be diligently prosecuting the same) to correct or remedy, or cause to be
corrected or remedied, each such default before Tenant may take any action,
except for its rights of self-help under Section 6.3 of the Lease, -under the
Lease by reason of such default. Such notices to Lender shall be delivered to:

                                       14
<PAGE>

                        KeyBank National Association
                        127 Public Square
                        Cleveland, Ohio 44114
                        Attention:  Robert Bowes, Esquire

      with a copy to:   KeyBank National Association
                        70 Federal Street
                        Boston, MA 02110
                        Attention: Joseph Bator, Vice President
                        Commercial Real Estate Division

or to such other address as the Lender shall have designated to Tenant by giving
written notice to Tenant at the Property, Attention: Eleonora Brown, or to such
other address as may be designated by written notice from Tenant to Lender.

      6. No Further Subordination. Except as expressly provided to the contrary
in Paragraph 2 hereof, Landlord and Tenant covenant and agree with Lender that
there shall be no further subordination of the interest of lessee under the
Lease to any lender or to any other party without first obtaining the prior
written consent of Lender. Any attempt to effect a further subordination of
lessee's interest under the Lease without first obtaining the prior written
consent of Lender shall be null and void.

      7. As to Landlord and Tenant. As between Landlord and Tenant, Landlord and
Tenant covenant and agree that nothing herein contained nor anything done
pursuant to the provisions hereof shall be deemed or construed to modify the
Lease.

      8. As to Landlord and Lender. As between Landlord and Lender, Landlord and
Lender covenant and agree that nothing herein contained nor anything done
pursuant to the provisions hereof shall be deemed or construed to modify the
Mortgage or the Assignment.

      9. Title of Paragraphs. The titles of the paragraphs of this Agreement are
for convenience and reference only, and the words contained therein shall in no
way be held to explain, modify, amplify or aid in the interpretation,
construction or meaning of the provisions of this agreement.

      10. Governing Law. This Agreement shall be governed by and construed in
accordance with the laws of The Commonwealth of Massachusetts.

      11. Binding Agreement. The terms "Lender," "Landlord" and "Tenant" shall
be construed to include the heirs, executors, administrators, successors and
assigns of the respective parties hereto, including, in the case of Lender, an
assignee(s) of the Lender and anyone who succeeds to title to the Property after
foreclosure or a deed in lieu thereof, and this Agreement shall inure to their
benefit and be binding on them.

                                       15
<PAGE>

      12. No Modification Unless in Writing, Etc. No modification, amendment,
waiver or release of any provision of this Agreement or of any right,
obligation, claim or cause of action arising hereunder shall be valid or
effective unless in writing and signed by the party against whom the same is
sought to be asserted.

      13. Severability. In the event that any provision or provisions of this
Agreement shall for any reason be held invalid, illegal or unenforceable by the
final ruling of a court of competent jurisdiction, the remaining provisions of
this Agreement shall not be affected thereby, and in the place of such invalid,
illegal or unenforceable provision there shall be substituted a like, but valid,
legal and enforceable provision which most nearly accomplishes the original
intention of the parties, as evidenced by this Agreement.

      14. Further Assurances. The Landlord and the Tenant from time to time
shall execute and deliver at the Lender's request all instruments that may be
reasonably necessary or appropriate to evidence their agreements hereunder.

      15. Counterparts. This Agreement may be executed in one or more
counterparts, each of which shall be deemed an original and all such
counterparts shall constitute one and the same instrument.

                                       16<PAGE>

                                                                    Exhibit 10.3

                                    AMENDMENT
                                       TO
                                 LOAN DOCUMENTS

         This Amendment to Loan Documents is entered into as of June 24, 1999
(the "Amendment"), by and between IMPERIAL BANK ("Bank") and VARIAGENICS, INC.
("Borrower").

                                    RECITALS

A. Borrower and Bank are parties to that certain Loan Agreement dated as of July
10, 1998, as amended (thc "Loan Agreement"), to that certain General Security
Agreement dated as of June 10, 1998, as amended (the "Security Agreement"), to
that certain Promissory Note (Equipment Loans) and that certain Promissory Note
(Bridge Loan), both executed in connection with the Loan Agreement and dared as
of July 10, 1.998 (collectively, the "Notes"). The parties desire to amend the
Loan Agreement, the Security Agreement, and the Notes in accordance with the
terms of this Amendment

         NOW, THEREFORE, the parties agree as follows:

A. Sections 1a, 1b and 1c of the Loan Agreement are amended in their entirety to
read as follows:

              1.   Equipment Loans.

                   a    OUTSTANDING EQUIPMENT LOANS. Subject to the terms and
conditions of this Agreement, Bank has made advances in an aggregate outstanding
principal amount equal to Three Hundred Thousand Dollars ($300,000) ("the
Equipment Loans"). Borrower may not request or receive any further Equipment
Loans. Equipment Loans, once repaid, may not be reborrowed.

                   b.   [Intentionally omitted.]

                   c.   PAYMENT OF EQUIPMENT LOANS. Borrower shall pay the
aggregate amount of the Equipment Loans in thirty-three (33) equal monthly
installments of principal, plus all accrued interest, beginning on March 31,
1999 and continuing on the last day of each month through the Equipment Loan
Maturity Date, at which time all amounts due under this Section 1 shall be
immediately due and payable. Borrower may prepay any Equipment Loans without
penalty or premium.

                   Without limiting Borrower's obligations under Section
12(b)(vi) of this Agreement, if any Qualified Equipment purchased with the
proceeds of any Equipment Loan is at any lime sold, assigned or otherwise
transferred, Borrower will prepay the outstanding principal of the Equipment
Loans, on the date of such sale, assignment or transfer, in an amount equal to
the fair market value of the proceeds received by Borrower on the dare of such
sale, assignment, or transfer. Any such optional

<PAGE>

or mandatory prepayments shall reduce each of the remaining installment payments
of principal on the Equipment Loans in such mariner among Equipment Loans as
Bank shall determine.

         B. The first sentence of Section 1d is hereby amended in its entirety
to read as follows: "The obligations of Borrower in respect of the Equipment
Loans and any interest accrued thereon shall be evidenced by a Promissory Note
executed and delivered to Bank on the date hereof, in the face amount of
$1,200,000, as amended from rime to time including without limitation by that
certain Amendment to Loan Documents dated as of June 24, 1999."

         C. Section 2a of the Loan Agreement is hereby amended in its entirety
to read as follows:

                   a.    COMMITMENT TO MAKE BRIDGE LOANS. Bank hereby commits,
subject to all the terms and conditions of this Agreement, and prior to the
termination of Bank's commitment to make Bridge Loans hereunder as hereinafter
provided, to make loans to Borrower from time to time ("Bridge Loans") in such
amounts up to, but not exceeding in the aggregate unpaid balance at any time,
the Bridge Loan Commitment Amount at such time. Bank's commitment to make Bridge
Loans hereunder shall terminate on the Bridge Loan Maturity Date, Bank shall
have no obligation hereunder to make any Bridge Loans to Borrower after that
date, and all amounts due under this Section 2 shall be immediately due and
payable on such date. Notwithstanding the foregoing, Bank's commitment to make
Bridge Loans hereunder may terminate at any time in accordance with Sections 13
or 14 hereof, subject to the forbearance extended under this Amendment. Bank's
commitment to make Bridge Loans hereunder shall terminate on the date on which
any mandatory prepayment shall be required pursuant to Section 4 hereof.

         D. The reference to "July 9,1999" in Section 2(c) of the Loan Agreement
is hereby amended to read "the Bridge Loan Maturity Date".

         E. Section 3 of the Loan Agreement is hereby deleted in its entirety.

         F. Part (b) of the first sentence of Section 5 of the Loan Agreement is
hereby amended in its entirety to reed as follows: "(b) on the aggregate
outstanding principal amount of Bridge Loans at the rate of one percent (1.0%)
per annum in excess of the Bank's Prime Rate, provided that that portion of the
Bridge Loan advanced by Bank from and after June 24, 1999 through the date of
the Equity Event shall bear interest, on the average outstanding daily balance
thereof, at a rate equal to two percent (2%) per annum in excess of the Bank's
Prime Rate".

         G. The last sentence of Section 5 is hereby deleted from the Loan
Agreement.

         H. Section 8 of the Loan Agreement is amended by adding the following
to the end of the first paragraph thereof:

<PAGE>

         Such Letter of Credit shall have a expiration date of no later than
         June 30, 2000. Borrower shall pledge cash in the form of a certificate
         of deposit at the Bank, on terms reasonably acceptable to Bank, in an
         amount equal to fifty percent (50%) of the face amount of the Letter of
         Credit at any given time as long as Bank has any obligations
         thereunder.

         I. Certain defined terms in Section 9 of the Loan Agreement are hereby
added or amended to read as follows:

                  "Bank Expenses" means all: reasonable costs or expenses
         (including reasonable attorneys' fees and expenses) incurred in
         connection with the preparation, negotiation, administration, and
         enforcement of the Loan Documents; reasonable Collateral audit fees;
         and Bank's reasonable attorneys' fees and expenses incurred in
         amending, enforcing or defending the Loan Documents (including fees and
         expenses of appeal), incurred before, during and after an Insolvency
         Proceeding, whether or not suit is brought.

                  "Bridge Loan Commitment Amount" means a credit extension of up
         to Nine Hundred Thousand Dollars ($900,000), provided that Borrower
         will have a right to request no more than Four Hundred Thousand Dollars
         ($400,000) plus the Three Hundred Thousand Dollars ($300,000) already
         outstanding on June 24, 1999, until the Equity Event occurs.

                  "Bridge Loan Maturity Date" means July 31, 1999.
         Notwithstanding the foregoing, if the Equity Event occurs on or before
         July 31, 1999, "Bridge Loan Maturity Date" shall thereafter mean June
         30, 2000.

                  "Equipment Loan Maturity Date" means November 30, 2001.

                  "Equity Event" means both (i) the conversion of all
         convertible debt owing by Borrower into equity and (ii) the receipt by
         Borrower of cash proceeds from the sale or issuance of its equity
         securities in an amount of not less than Five Million Dollars
         ($5,000,000) after June 24, 1999, both of which must occur on or before
         July 31, 1999.

                  "Subsidiary" means any corporation or partnership in which (i)
         any general partnership interest or (ii) more than 50% of the stock of
         which by the terms thereof ordinary voting power to elect the Board of
         Directors, managers or trustees of the entity, at the time as of which
         any determination is being made, is owned by Borrower, either directly
         or through an Associated Person.

         J. The definition of "Equipment and Bridge Loan Commitment Amount is
hereby deleted from the Loan Agreement.

<PAGE>

         K. The words "prior to the closing of a Qualified Financing" are hereby
deleted from the definition of "Quick Ratio" in Section 9 of the Loan Agreement.

         L. A new Section 11j is hereby added to the Loan Agreement to read as
follows:

                  i. YEAR 2000. Borrower and its Subsidiaries have reviewed the
         areas within their operations and business which could be adversely
         affected by, and have developed or are developing a program to address
         on a timely basis, the Year 2000 Problem and have made related
         appropriate inquiry of material suppliers and vendors, and based on
         such review and program, the Year 2000 Problem will not have a
         Materially Adverse Effect upon its financial condition, operations or
         business as now conducted. "Year 2000 Problem" means the possibility
         that any computer applications or equipment used by Borrower may be
         unable to recognize and properly perform date sensitive functions
         involving certain dates prior to and any dates on or after December 31,
         1999.

         M. Sections 12(a)(ii)(B) and (C) arc hereby deleted from the Loan
Agreement.

         N. The following new affirmative covenants are added to Section 12a of
the Loan Agreement to read as follows:

                  x. YEAR 2000 COMPLIANCE. Borrower shall perform all acts
         reasonably necessary to ensure that Borrower and any business in which
         Borrower holds a substantial interest become Year 2000 Compliant in a
         timely manner. Such acts shall include, without limitation, performing
         a comprehensive review and assessment of all Borrower's systems and
         adopting a detailed plan, with itemized budget, for the remediation,
         monitoring and testing of such systems. Borrower shall also take
         reasonably necessary steps to ensure that it will not be materially
         adversely affected as a result of any customer, supplier or vendor's
         failure to become Year 2000 complaint. As used in this paragraph, "Year
         2000 Compliant" shall mean, in regard to any entity, that all software,
         hardware, firmware, equipment, goods or systems utilized by or material
         to the business operations or financial condition of such entity, will
         properly perform date sensitive functions before, during and after the
         year 2000. Borrower shall immediately upon request, provide to Bank
         such certifications or other evidence of Borrower's compliance with the
         terms of this paragraph as Bank may from time to time require.

                  xi. MINIMUM REVENUE. Borrower shall have revenue of not less
         than Two Million Two Hundred Fifty Thousand Dollars ($2,250,000) for
         the fiscal year ending on December 31, 1999. Borrower shall have

<PAGE>

         revenue of not less than One Million Five Hundred Thousand Dollars
         ($1,500,000) for each fiscal quarter thereafter.

                  xii  EQUITY EVENT. The Equity Event shall occur on or before
         July 31, 1999.

         O. The reference in Section 12(c)(i)(A) of the Loan Agreement to "30
days" is hereby amended to read "25 days". The reference in Section 12(c)(i)(B)
of the Loan Agreement to "30 days" is hereby amended to read "25 days". The
reference in Section 12(c)(i)(C) of the Loan Agreement to "90 days" is hereby
amended to read "120 days".

         P. The reference in the first paragraph of the Security Agreement to
"the Loan Agreement, dated as of the date hereof is hereby amended to read "the
Loan Agreement, dated as of July 10".

         Q. The last sentence of the paragraph on the first page of the Security
Agreement entitled "COLLATERAL", which reads "Collateral shall not include any
patents, registered trademarks, service marks or copyrights" is hereby deleted
from the Loan Agreement, but the original language shall be reinstated
automatically without the need for further amendment upon the occurrence of the
Equity Event on or before July 31, 1999.

         R. The following new Sections 15 and 16 are hereby added to the
Security Agreement to read as follows;

                  15. The Collateral shall include any and all certificates of
         deposit pledged by Obligor to Bank to secure all of Obligor's
         indebtedness and obligations under the Loan Agreement, including
         certificate of deposit number 4275670001 held by Bank, together with
         all proceeds and substitutions thereof any interest thereon, and all
         cash and noncash proceeds of the foregoing, but subject to reduction
         from time to time in accordance with Section 8 hereof.

                  16. Prior to the maturity of any certificates of deposit
         pledged as Collateral held by Bank pursuant hereto (the "CD
         Collateral"), Obligor and Bank shall agree upon a security or
         instrument similar in form, quality and substance in the original CD
         Collateral in which the proceeds of the CD Collateral can be reinvested
         on maturity. Upon maturity of the CD Collateral in accordance with its
         terms, or in the event the CD Collateral otherwise becomes payable
         during the term of this Agreement, such maturing CD Collateral may be
         presented for payment, exchange, or otherwise marketed by Bank on
         behalf of Obligor and the proceeds therefrom used to purchase the
         security or instrument agreed to by Obligor and Bank in accordance with
         the immediately preceding sentence. If no agreement has been made, such
         proceeds shall be placed into an interest bearing account offered by
         Bank in which Bank has a first priority security

<PAGE>

         interest until such time as an agreement as to the security replacing
         the original CD Collateral can be reached. Bank may retain any such
         successor collateral and the proceeds therefrom as CD Collateral in
         accordance with the terms of this Agreement Notwithstanding termination
         of this Agreement, Bank's Lien on the CD Collateral shall remain in
         effect for so long as any obligations of Obligor to Bank, under the
         Loan Agreement or otherwise, are outstanding. This Section 16 shall be
         subject to the right of the Borrower to reduce the amount of the CD
         Collateral in accordance with Section 8 hereof.

         S. The Compliance Certificate to be delivered after the date of this
Amendment shall be in substantially the form of EXHIBIT B hereto.

         T. The Notes are amended to conform to the changes in the Loan
Agreement and the Security Agreement effected by this Amendment.

         U. Unless otherwise defined, all capitalized terms in this Amendment
shall be as defined in the Loan Agreement Except as amended, the Loan Agreement,
the Security Agreement, and the Notes remain in full force and effect.

         V. Borrower acknowledges that it is in default under Sections
12(a)(ii), 12(b)(i), and 12(c)(i) of the Loan Agreement. Bank does not waive
Borrower's obligation to comply with such provisions or any other failure by
Borrower to perform its obligations under the Loan Documents. Borrower
acknowledges that Bank has not exercised many of its rights which have arisen as
a result of Borrower's failure to perform its obligations under the Loan
Documents, including without limitation the right to charge a higher interest
rate under Section 6 of the Loan Agreement, and Bank reserves all of its rights
arising from any such failure. However, Bank agrees to forbear from exercising
such rights until July 31, 1999, at which time, if the Equity Event has occurred
and if no material Event of Default has occurred which is continuing on such
date, Bank hereby agrees to waive the defaults mentioned above. Borrower
represents and warrants that the representations and warranties contained in the
Loan Agreement are true and correct as of the date of this Amendment, and that
no Event of Default, except as mentioned above, has occurred and is continuing.

         W. This Amendment may be executed in two or more counterparts, each of
which shall be deemed an original, but all of which together shall constitute
one instrument.

         X. As a condition to the effectiveness of this Amendment, Bank shall
have received, in form and substance satisfactory to Bank, the following:

                  (a) this Amendment, duly executed by Borrower,

                  (b) six affirmation of subordination agreements;

<PAGE>

                  (c) payment of an amendment fee equal to Three Thousand
Dollars ($3,000) plus all Bank Expenses incurred through the date of this
Amendment;

                  (d) Corporate Resolutions to Borrow;

                  (e) an intellectual property security agreement;

                  (f) Pledge and Security Agreement;

                  (g) a warrant to purchase stock;

                  (h) four amendments to UCC filings, which will have the
collateral description on the attached EXHIBIT A;

                  (i) Amendment to Stock Purchase Warrant;

                  (j) Assignment Separate from Certificate, with stock
certificates;

                  (k) an audit of the Collateral, the results of which shall be
satisfactory to Bank; and

                  (l) such other documents, and completion of such other
matters, as Bank may reasonably deem necessary or appropriate.

         Y. Attached hereto is a schedule of all amounts that Borrower owes on
account of any Indebtedness for Borrowed Money.

         Z. Borrower shall take such actions as Bank reasonably requests to
complete its due diligence (including obtaining fully executed copies of all
documents necessary to perfect Bank's security interest in Borrower's
intellectual property) concerning Borrower's intellectual property by July 21,
1999, and to perfect its security interest in Borrower's intellectual property
an or after August 1, 1999, should such perfection be permitted under the Loan
Documents as hereby amended, and any failure by Borrower to fully cooperate with
Bank on these matters shall constitute an Event of Default under Section 13 of
the Loan Agreement. No public filing will be made to perfect Bank's security
interest in Borrower's intellectual property until August 1, 1999 and then only
if the Equity Event has not yet occurred as of that date.

         AA. Bank hereby agrees that it will release all its liens on Borrower's
intellectual property if the Equity Event occurs by July 31, 1999 and if no
Event of Default has occurred and is continuing under Sections 13 (i), (ix)
(with respect to an assignment for the benefit of creditors only), (x) and (xi)
of the Loan Agreement at such time.

<PAGE>

         IN WITNESS WHEREOF, the undersigned have executed this Amendment as of
the first date above written.

VARIAGENICS, INC.

By: /s/ RICHARD P. SHEA
   ---------------------------------
Title: VICE PRESIDENT, FINANCE
      ------------------------------
IMPERIAL BANK

By: /s/ KAREN DUNN
   ---------------------------------
Title: VICE PRESIDENT
      ------------------------------

<PAGE>

                                    EXHIBIT A
                        COLLATERAL DESCRIPTION ATTACHMENT
                         TO LOAN AND SECURITY AGREEMENT

         All personal property of Borrower (herein referred to as "Borrower" or
"Debtor") whether presently existing or hereafter created, written, produced or
acquired, including, but not limited to:

         (i) all accounts receivable, accounts, chattel paper, contract fights
(including, without limitation, royalty agreements, license agreements and
distribution agreements), documents, instruments, money, deposit accounts and
general intangibles, including, without limitation, returns, repossessions,
books and records relating thereto, and equipment containing said books and
records, all investment property, including securities and securities
entitlements;

         (ii) all software, computer source codes and other computer programs
(collectively, the "Software Products"), and all common law and statutory
copyrights and copyright registrations, applications for registration, now
existing or hereafter arising, United States of America and foreign, obtained or
to be obtained on or in connection with the Software Products, or any parts
thereof or any underlying or component elements of the Software Products
together with the right to copyright and all rights to renew or extend such
copyrights and the right (but not the obligation) of Bank (herein referred to as
"Bank" or "Secured Party") to sue in its own name and/or the name of the Debtor
for past, present and future infringements of copyright;

         (iii) all goods, including, without limitation, equipment and inventory
(including, without limitation, all export inventory);

         (iv) all guarantees and other security therefor;

         (v) all trademarks, service marks, trade names and service names and
the goodwill associated therewith;

         (vi) (a) all patents and patent applications filed in the United States
Patent and Trademark Office or any similar office of any foreign jurisdiction,
and interests under patent license agreements, including, without limitation,
the inventions and improvements described and claimed therein, (b) licenses
pertaining to any patent whether Debtor is licensor or licensee, (c) all income,
royalties, damages, payments, accounts and accounts receivable now or hereafter
due and/or payable under and with respect thereto, including, without
limitation, damages and payments for past, present or future infringements
thereof, (d) the right (but not the obligation) to sue for past, present and
future infringements thereof, (e) all rights corresponding thereto throughout
the world in all jurisdictions in which such patents have been issued or applied
for, and (f) the reissues, divisions, continuations, renewals, extensions and
continuations-in-part with any of the foregoing (all of the foregoing patents
and applications and interests under patent license agreements, together with
the items described in clauses (a) through (f) in this paragraph arc sometimes
herein individually and collectively referred to as the "Patents"); and

<PAGE>

         (vii) all products and proceeds, including, without limitation,
insurance proceeds, of any of the foregoing.

<PAGE>

                                    EXHIBIT B

                             COMPLIANCE CERTIFICATE

TO:   IMPERIAL BANK
FROM: VARIAGENICS, INC.

The undersigned authorized officer of Variagenics, Inc. hereby certifies that in
accordance with the terms and conditions of the Loan and Security Agreement
between Borrower and Bank (the "Agreement"), (i) Borrower is in complete
compliance for the period ending _________ all required covenants except as
noted below and (ii) all representations and warranties of Borrower stated in
the Agreement are true and correct in all material respects as of the date
hereof. Attached herewith are the required documents supporting the above
certification. The Officer further certifies that these are prepared in
accordance with Generally Accepted Accounting Principles (GAAP) and are
consistently applied from one period to the next except as explained in an
accompanying letter or footnotes.

         Please indicate compliance status by circling Yes/No under "Complies"
column.

<TABLE>
<CAPTION>
REPORTING COVENANT                          REQUIRED                             COMPLIES
------------------                          --------                             --------
<S>                                         <C>                                 <C>     <C>
Monthly financial statements                Monthly within 25 days              Yes     No
Quarterly financial statements              Quarterly within 25 days            Yes     No
Annual (CPA Audited)                        FYE within 120 days                 Yes     No
A/R and A/Pagings                           Monthly within 20 days              Yes     No
</TABLE>

<TABLE>
<CAPTION>
FINANCIAL COVENANT                           REQUIRED            ACTUAL          COMPLIES
------------------                           --------            ------          --------
<S>                                         <C>               <C>               <C>     <C>
Maintain on a monthly basis:
     Minimum Quick Ratio                    1.40:1.00           _____:1.00      Yes     No
     Minimum Revenue (annual/quarterly)              *        $                 Yes     No
</TABLE>

* Borrower shall have revenue of not less than $2,250,000 for the fiscal year
ending on 12/31/99. Borrower shall have revenue of not less than $1,500,000 for
each fiscal quarter thereafter.

Comments Regarding Exceptions: See Attached.

Sincerely,

SIGNATURE
         --------------------------------
TITLE
     ------------------------------------
DATE
    -------------------------------------

<PAGE>

           SCHEDULE OF ALL BORROWER'S INDEBTEDNESS FOR BORROWED MONEY

Imperial Bank
Indebtedness and Uncollateralized Portion of LC
FY 1999

<TABLE>
<CAPTION>
         ACCOUNT PER T/B                                              MAY
         ---------------                                              ---
<S>                                                               <C>
         Capital Lease Short-Term                                   166,298
         Capital Lease Long-Term                                    279,073
         Long-Term Borrowing                                        572,728
         Encumbered Cash                                          1,000,000
                                                                  ---------
         Total Indebtedness                                       2,018,099
                                                                  =========
</TABLE>

Source: [{"source": "alea-institute/alea-institute/kl3m-data-edgar-agreements/train-00005-of-00352.parquet"}, [{"source": "alea-institute/alea-institute/kl3m-data-edgar-agreements/train-00005-of-00352.parquet"}]]