Document:

<PAGE>

                                                                 Exhibit 10.10

                          FULL RECOURSE PROMISSORY NOTE

                                                                  June 23, 2000

$299,999.38

         FOR VALUE RECEIVED, Don M. Hardison (the "Maker") promises to pay to
the order of Exact Laboratories a Delaware corporation (the "Holder"), having an
address at 63 Great Road, Maynard, Massachusetts 01754, or its assigns, the
principal sum of $299,999.38, together with interest on the principal of this
Note outstanding at the rate of 9.5% per year. All principal and accrued
interest shall be paid on, or prior to, ten years from the date hereof.

         Interest on this Note shall be computed on the basis of a year of 365
days for the actual number of days elapsed. All payments by the Maker under this
Note shall be in immediately available funds.

         Every amount overdue under this Note shall bear interest from and after
the date on which such amount first became overdue at an annual rate which is
two (2) percentage points above the rate per year specified in the first
paragraph of this Note. Such interest on overdue amounts under this Note shall
be payable on demand and shall accrue and be compounded monthly until the
obligation of the Maker with respect to the payment of such interest has been
discharged (whether before or after judgment).

         In no event shall any interest charged, collected or reserved under
this Note exceed the maximum rate then permitted by applicable law.

         All payments by the Maker under this Note shall be made without
set-off, defense or counterclaim and be free and clear and without any deduction
or withholding for any taxes or fees of any nature whatever, unless the
obligation to make such deduction or withholding is imposed by law.

         Maker agrees that: (i) upon the failure to pay when due the principal
balance and accrued interest hereunder; (ii) if Maker (1) commences any
voluntary proceeding under any provision of Title 11 of the United States Code,
as now or hereafter amended, or commences any other proceeding, under any law,
now or hereafter in force, relating to bankruptcy, insolvency, reorganization,
liquidation, or otherwise to the relief of debtors or the readjustment of
indebtedness, (2) makes any assignment for the benefit of creditors or a
composition or similar arrangement with such creditors, or (3) appoints a
receiver, trustee or similar judicial officer or agent to take charge of or
liquidate any of its property or assets; or (iii) upon the commencement against
Maker of any involuntary proceeding of the kind described in paragraph (ii),
principal and accrued interest under this Note shall become immediately due and
payable without presentment, demand, protest or notice of any kind.

         The Maker shall remain personally liable to the Holder with respect to
all of the obligations under this Note and the Holder shall have full recourse
against Maker.

<PAGE>
                                      -2-

         No delay or omission on the part of the Holder in exercising any right
under this Note shall operate as a waiver of such right or of any other right of
the Holder, nor shall any delay, omission or waiver on any one occasion be
deemed a bar to or waiver of the same or any other right on any future occasion.

         None of the terms or provisions of this Note may be excluded, modified
or amended except by a written instrument duly executed by the Holder and the
Maker expressly referring to this Note and setting forth the provision so
excluded, modified or amended.

         Maker hereby forever waives presentment, demand, presentment for
payment, protest, notice of protest, notice of dishonor of this Note and all
other demands and notices in connection with the delivery, acceptance,
performance and enforcement of this Note.

         This Note shall be governed and construed in accordance with the laws
of the Commonwealth of Massachusetts applicable to agreements made and performed
entirely in such State, without regard to conflict of laws principles thereof,
and shall be binding upon the successors or assigns of the Maker and shall inure
to the benefit of the successors and assigns of the Holder.

                                                         /s/ Don M. Hardison
                                                         ----------------------
                                                         Don M. Hardison<PAGE>

                                                                 Exhibit 10.11

                        C. B. REALTY LIMITED PARTNERSHIP
                               26 WINDSONG LANDING
                                CHATHAM, MA 02633

                          LEASE AMENDMENT AND EXTENSION

This is an amendment and an extension to a lease dated December 10, 1996 between
C. B. Realty Limited Partnership and Exact Labs, Inc. That lease, including all
conditions, terms amendments and extensions, remains intact except as amended
below.

DEMISED PREMISES: That space presently occupied by Exact Labs, Inc. at 63 Great
Road, Maynard, Massachusetts. To the presently occupied space is added 1, 539
square feet of second floor space, presently occupied by Anro Engineering. This
will take effect June 9, 2000 and the rent will be $11.00NNN per rentable square
foot. Also added will be 4,540 square feet of second floor space, presently
occupied by Environmental Project Control at $11.00NNN per rentable square foot.
The term for all space under this lease will run until June 30, 2003.

ANNUAL FIXED RENT: The annual fixed rent for the presently occupied space per
rentable square foot, plus common area charges, will be as follows. Utility
expense to be paid by the LESSEE.

<TABLE>
<S>                                                    <C>
First Floor space....................................  $11.00NNN
Second Floor space...................................  $10.50NNN
</TABLE>

LANDLORD IMPROVEMENTS/REPAIRS: Landlord agrees to replace leaking skylight and
if other skylights fail or other roof problems occur to take immediate action to
remedy. Landlord agrees to repaint and recarpet the first floor common areas.

RIGHT OF FIRST REFUSAL: Landlord hereby grants a right of first refusal on space
as it becomes available in the building.

OPTION TO RENEW: Exact Labs, Inc. shall have one (1) option to renew for three
(3) years at fair market value. Notice to exercise shall be given no less than
six (6) months prior to termination of existing leases. If LESSEE decides not to
renew for an additional three (3) years it guarantees to renew either (A) the
new 6,079 square feet second floor space added under this amendment or (B) the
presently occupied 6,453 square feet of first floor space for one (1) additional
year if requested by the LANDLORD.

<PAGE>

It is agree that this is a binding contract between the parties.

EXACT LABS, INC.                                     C. B. REALTY LIMITED
                                                     PARTNERSHIP

/s/ Stanley Lapidus                                  /s/ Thomas R. Patton III
---------------------------                          --------------------------
STANLEY LAPIDUS                                      THOMAS R. PATTON III
ITS: PRESIDENT                                       ITS: GENERAL PARTNER
DATE: 4/25/2000                                      DATE: 4/25/00

<PAGE>

                        C. B. REALTY LIMITED PARTNERSHIP
                               26 WINDSONG LANDING
                                CHATHAM, MA 02633

                          LEASE AMENDMENT AND EXTENSION

This is an amendment and an extension to a lease date December 10, 1996 between
C.B. Realty Limited Partnership and Exact Labs, Inc. That lease, including all
conditions, terms, amendments and extensions, remains intact except as amended
below.

DEMISED PREMISES: That space presently occupied by Exact Labs, Inc. at 63 Great
Road, Maynard, Massachusetts.

TERM: July 1, 2000 to June 30, 2003

ANNUAL FIXED RENT: The annual fixed rent per rentable square foot, plus common
area charges, will be as follows. Utility expense to be paid by the LESSEE.

<TABLE>
         <S>                                           <C>
         First Floor space...........................  $11.00NNN
         Second Floor space..........................  $10.50NNN
</TABLE>

LANDLORD IMPROVEMENTS/REPAIRS: Landlord agrees to replace leaking skylight and
if other skylights fail or other roof problems occur to take immediate action to
remedy. Landlord agrees to repaint and recarpet the first floor common areas.

RIGHT OF FIRST REFUSAL: Landlord hereby grants a right of first refusal on space
as it becomes available in the building with the exception of 1,539 feet on the
second floor which is a right of first refusal with another tenant.

OPTION TO RENEW: Exact Labs, Inc. shall have one (1) option to renew for three
(3) years at fair market value. Notice to exercise shall be given no less than
six (6) months prior to termination of existing lease.

It is agree that this is a binding contract between the parties.

EXACT LABS, INC.                        C. B. REALTY LIMITED
                                        PARTNERSHIP

/s/ Stanley Lapidus                     /s/ Thomas R. Patton III
--------------------------------        --------------------------
Stanley Lapidus                         Thomas R. Patton III
Its: President Date:                    Its: General Partner Date:
                                                                   ------------

<PAGE>

                        C. B. REALTY LIMITED PARTNERSHIP
                               27 WINDSONG LANDING
                                CHATHAM, MA 02633

LEASE AMENDMENT

This is an amendment to a lease dated December 10, 1996 between C.B. Realty
Limited Partnership and Exact Laboratories, Inc. That lease, including all
conditions, terms and amendments thereto, remains intact except as amended
below.

DEMISED PREMISES: To the present occupied space will be added 1,578 rentable
square feet on the first floor of the building at 63 Great Road, Maynard,
Massachusetts as outlined on the attached Addendum "A".

TERM: February 1, 1999 to June 30, 2000.

ANNUAL FIXED RENT: The annual fixed rent per rentable square foot of said space
will be $12.00, including common area charges (1998-$3.07) which common area
charges may be adjusted annually. Utility expenses to be paid by LESSEE.

SUBLEASE: Paragraph 16 of the lease dated December 10, 1996 between the parties
requires permission to sublease and C. B. Realty Limited Partnership hereby
grants such permission.

TENANT IMPROVEMENTS: Landlord agrees to deliver space with the walls and ceiling
in good condition and repainted and the floors in good condition. Landlord
agrees to provide hot and cold water to the space and a method to remove the
same.

It is agree that this is a binding contract between the parties.

EXACT LABORATORIES, INC.                    C. B. REALTY LIMITED
                                            PARTNERSHIP

/s/ Stanley Lapidus                         /s/ Thomas R. Patton III
-------------------------------             -----------------------------------
Stanley Lapidus                             Thomas R. Patton III
Its: President Date: 1/21/99                Its: General Partner Date: 12/30/98
                     ----------                                        --------

<PAGE>

                                 LEASE AMENDMENT

This is an amendment to a lease dated December 10, 1996 between C. B. Realty
Limited Partnership and Exact Laboratories, Inc. That lease, including all
conditions and terms, remains intact except as amended below.

DEMISED PREMISES: To the present occupied space will be added 4,653 rentable
square feet on the second floor of the building at 63 Great Road, Maynard,
Massachusetts as shown as Space "A" on the attached plan.

DATE OF OCCUPANCY: September 1, 1997

TERM: September 1, 1997 to June 30, 2000.

ANNUAL FIXED RENT: The annual fixed rent rentable square foot of said space will
be as follows, plus the common area charges. Utility expenses to be paid by the
LESSEE. per

<TABLE>
     <S>                                                    <C>        <C>
     September 1, 1997 - December 31, 1998................. $7.25      [$33,734.25/12 = $2,811.19/MO]
     January 1, 1999 - December 31, 1999................... $8.00      [$37,224/12 = $3,102.00/MO]
     January 1, 2000 - June 30, 2000....................... $8.50
</TABLE>

SUBLEASE: Paragraph 16 of the lease dated December 10, 1996 between the parties
requires permission to sublease and C. B. Realty Limited Partnership hereby
grants such permission.

TENANT IMPROVEMENTS: Landlord agrees to deliver space with walls in good
condition and repainted and recarpeted. Exact Laboratories agrees to contribute
$4,500.00 toward the installation of new carpet with color to be chosen by them.

                                 LEASE EXTENSION

This is an extension of a lease dated December 10, 1996 between C. B. Realty
Limited Partnership and Exact Laboratories, Inc. as amended above. That lease
including all amendments, all conditions and all terms remain intact excepted as
amended below.

TERM: To continue in effect until June 30, 2000.

It is agree that this is a binding contract between the parties.

EXACT LABORATORIES, INC.                C. B. REALTY LIMITED
                                        PARTNERSHIP

/s/ Stanley Lapidus                     /s/ Thomas R. Patton III
-----------------------------           ---------------------------------------
Stanley Lapidus                         Thomas R. Patton III
Its: President  Date: 7/22/97           Its: General Partner  Date: 7/7, 1997
                      -------                                       -----------

<PAGE>

                                      LEASE

         THIS INSTRUMENT IS A LEASE between LANDLORD and TENANT as the parties
hereinafter named and which relates to space in the building (the "Building") at
63 Great Road, Maynard, Massachusetts 01754.

         The parties to this instrument hereby agree with each other as follows:

         1. DEFINITIONS: The following constitute the definitions of the terms
hereinafter employed.

Date: December 10, 1996

LANDLORD: C. B. Realty Limited Partnership

LANDLORD Office: 407 Old Harbor Road, Chatham, Massachusetts 02633

TENANT: Exact Laboratories, Inc.

TENANT'S Mailing Address: 12 Old Evergreen Road, Bedford, N.H. 03116

Lease Term: Three (3) Years

Planned Commencement Date: January 1, 1997

Expiration Date: December 31, 1999

Base Rent: Annual Rate: $12.00 (which includes common area charges) plus
utilities

Common Area Charges: $3.07 for the first year and to be adjusted annually

Option to Renew: TENANT shall have one (1) option to renew for three (3) years
                 at fair market value. TENANT shall give six (6) months notice
                 to exercise the option.

Permitted Uses:  Office space, laboratory and light manufacturing space

Premises:  4,875 rentable square feet on the first floor at 63 Great Road,
           Maynard, Massachusetts, as further shown on the attached plan
           indicated as Exhibit "A."

Guarantors: None

Security Deposit: $4,875

<PAGE>

2. PREMISES - DEMISE. LANDLORD hereby leases to TENANT and TENANT hereby takes
from LANDLORD, the Premises, upon and subject to the terms, provisions and
conditions of this Lease, and subject to all easements, restrictions, and
conditions of record and laws and ordinances applicable thereto. The premises
are conveyed together with the right to use in common with others entitled
thereto, as long as they do not interfere with TENANT'S quiet enjoyment and use
of the Premises as office space, laboratory and light manufacturing space, the
hallways, stairways and elevators necessary for access to the Premises and
lavatories nearest thereto along with the right to use in common with others
entitled thereto, parking area and sidewalks serving the Premises but reserving
and excepting to the LANDLORD the use of the demising walls, the area above the
ceilings of the Premises and the right to install, maintain, use, repair and
replace pipes, ducts, conduits, wires and appurtenant fixtures leading through
the Premises in locations which will not interfere with TENANT'S use thereof.
LANDLORD agrees not to lease to tenants that will occupy their Premises with a
density of employees so as to create an overburdened or intolerable parking
situation. LANDLORD will use its best efforts to maintain a "Normal" parking
ratio.

3. TERM. (a) The Term of this Lease shall be for three (3) years, commencing
upon the later of the Planned Commencement Date as set forth herein and the date
on which the LANDLORD has completed the agreed upon improvements of the Premises
and expiring on the Expiration Date provided.

(b) By taking occupancy of the Premises, TENANT shall be deemed to have accepted
the Premises, to have acknowledged that the same are in the condition called for
hereunder and to have agreed that as of that time, all of the obligations of the
LANDLORD imposed under this Lease shall have been performed.

4. RENT. (a) TENANT will pay the Base Rent plus common area charges and at the
rate set forth in Section 1, Definitions, in equal monthly payments, in advance,
without setoff, deduction or demand, in lawful money of the United States, on
the first day of each and every month during the Term, at LANDLORD'S Office or
to such other payee and/or at such other place as the LANDLORD may from time to
time designate in writing. TENANT shall, in addition thereto, pay such
additional rent ("Additional Rent") as is elsewhere required in this Lease.
Common area charges for the first year of this lease are $3.07 per rentable
square foot and may be adjusted up or down in succeeding years. The LANDLORD
agrees to make available upon reasonable notice access to books and records if
TENANT request to review the common area charges.

(b) TENANT agrees to pay to LANDLORD as Additional Rent, an amount equal to five
percent (5%) of any amount due as Base or Additional Rent (or other payments due
hereunder) if said payments are not paid within five (5) business days after
their due date upon written notification to LESSEE by LESSOR; or, if there shall
be no due date, within five (5) days after demand; provided, however, that
nothing herein contained shall be construed or implemented in such a manner as
to allow the LANDLORD to charge or receive interest in excess of the maximum
lawful rate then allowed by law. Said sum shall be payable in addition to and
not in exclusion of other remedies herein provided or otherwise allowed to the
LANDLORD.

<PAGE>

5. TENANT'S ACCEPTANCE, USE AND OCCUPANCY, LANDLORD'S WORK.

(a) The TENANT agrees that on the Commencement Date, TENANT shall accept, take
and hold the Premises at the Base Rate hereinabove specifically reserved and
payable as aforesaid and upon and subject to the terms and conditions herein
contained and shall use and occupy the Premises throughout the term hereof only
for the Permitted Uses and for no other purpose whatsoever without the prior
written consent of the LANDLORD.

(b) TENANT hereby acknowledges that it is not relying on any warranty or
representation of the LANDLORD except as expressly set forth herein, including,
without limitation, any warranty or representations as to applicable laws or
requirements of public agencies as to the uses to which the Premises may be put,
the availability of permits or the like or the condition of the Premises. TENANT
agrees that TENANT'S Work shall be completed, at its own expense, in full
compliance with all laws, ordinances, rules and regulations applicable thereto.
LANDLORD represents that, to the best of its knowledge, the Premises and the
property at which it is located are in compliance with all applicable laws and
requirements and that the LANDLORD has not received and has no knowledge of any
citation or notice for any such failure to comply.

(c) TENANT agrees that it shall at all times conduct its business in a manner
consistent with other businesses in the building and in accordance with
applicable laws.

6. TENANT'S COVENANTS. TENANT further agrees to perform, cause to be performed
or to observe, as the case may be, the following provisions during the entire
Lease Term.

(a) The outside walls, roof, doors, sidewalks, entries, passages, public
corridors and staircases and other parts of the Building which are not occupied
by the TENANT shall not be obstructed or used for any other purpose than ingress
or egress.

(b) The TENANT shall not install or permit the painting, inscription or
installation of any signs, advertisements, displays, lights, awnings, shades,
draperies or any other matter on or visible from the outside of the Premises or
Building other than those approved by the LANDLORD in writing for the purpose of
identifying and locating the Premises with LANDLORD'S approval not to
unreasonably be withheld and subject to any need of LANDLORD to replace the same
for reasonable periods from time to time for LANDLORD'S paramount needs. Such of
the foregoing as may be permitted to be placed by TENANT shall be maintained in
a first-class condition by TENANT at TENANT'S sole cost. LANDLORD hereby permits
the TENANT to locate signs identifying and locating the TENANT'S Premises on the
front of the building where the Premises is located and on all doors leading
into the Premises, however, LANDLORD retains the right of approval of all such
signs and locations thereof.

(c) The TENANT shall not construct, maintain, use or operate within the Premises
or elsewhere in the Building (or on the outside of the Building) any facility,
equipment or machinery which produces sound, noise, odor or vibration which is
audible, visible or discernible, beyond the interior of the Premises; nor shall
TENANT permit any act or thing upon the Premises the effect of which shall be to
disturb the normal sensibilities and peaceful occupancy of other TENANTS of the
Premises. LANDLORD agrees to enforce these provisions upon all tenants in the
building.

<PAGE>

(d) TENANT shall not, except in the ordinary course of its business, bring or
keep inflammable, combustible or explosive fluids or other chemical or similar
substances into or within the Building or otherwise use the Premises for any
dangerous, or extra hazardous use or use which will increase the cost of
LANDLORD'S insurance.

(e) TENANT shall not permit the Premises to be used for lodging or dwelling
purposes.

(f) TENANT shall conduct TENANT'S business in the Premises in such a manner that
TENANT'S invitees shall not collect, line up or congregate on or about the
Building or its common areas, but shall be entirely accommodated within the
Premises.

(g) TENANT will not install in the Premises any fixtures, equipment or machinery
that will place a load on any floor exceeding the floor load per square foot of
area which such floor was designed to carry as prescribed by LANDLORD. TENANT
agrees to pay for all costs required to properly distribute the weight of any
such items as required by LANDLORD, and that all damage caused to the building
resulting from the delivery or removal of any safe, heavy articles, or any other
article of TENANT'S property shall be repaired at the expense of the TENANT. All
moving of furniture, materials and equipment outside of the Premises (and inside
of the Premises, if constituting a major renovation or change) shall be under
the direct control and supervision of the LANDLORD, who shall, however, not be
responsible for the damage to or charges for moving same. TENANT agrees to
promptly remove from the public areas adjacent to and/or within the Building any
of TENANT'S property there delivered or deposited.

(h) The TENANT will not install or operate in the Premises any electrically
operated equipment or other machinery except ordinary and customary equipment
for the operation of its business without first obtaining the prier written
consent of the LANDLORD. No such equipment or machinery shall cause an overload
for the Building or any of its systems. Without limitation, TENANT shall not
install any other equipment of any kind or nature whatsoever which will or may
overload the floor or necessitate any changes, replacements or additions to the
Premises or the Building without the prior written consent of the LANDLORD,
which LANDLORD may condition upon TENANT paying for any such change, replacement
or addition.

(i) TENANT will not do or permit anything to be done on the Premises or the
Building or bring or keep anything therein which shall in any way increase the
rate of fire or other insurance on said Building nor on the property kept
therein or obstruct or interfere with the rights of other TENANTS or in any way
injure or annoy them or those having business with them or conflict with them or
conflict with the fire laws or regulations or with any insurance policy upon
said Building or any part thereof (or recommendations of any casualty insurance
rating bureau) or with any statutes, rules or regulations enacted or established
by the state or local jurisdiction in which the Premises are located or the
Federal Government.

(j) LANDLORD and TENANT shall comply with all present and future laws, rules,
regulations, ordinances, requirements and orders of public authorities,
including, without limitation, building and zoning laws, requirements of The
Board of Health and requirements of any other federal, state or local agencies
having jurisdiction of the Premises, including, without

<PAGE>

limitation, any structural change required by any of the same, but shall not be
responsible for any violation of law presently existing by reason of the
construct; of Premises unless the same can practicably be corrected as part of
TENANT'S Work and TENANT fails to do so. TENANT shall furthermore comply with
all recommendations and requirements, within reason, of LANDLORD'S insurance
carrier, and any casualty insurance rating bureau or similar bodies as long as
it does not materially restrict the use of the Premises for office purposes. All
tenants shall have provisions similar to this in their leases.

(k) TENANT shall maintain the Premises in good and safe condition and repair,
free from rubbish, dirt, refuse and garbage; store all trash and garbage in
approved receptacles within the Premises and empty into dumpster provided by
LANDLORD; notify LANDLORD promptly after the same shall come to the attention of
TENANT of the need of any repairs or replacements to the Premises.

(1) TENANT shall pay all taxes assessed by any taxing authority upon its
equipment, goods and effects whether or not the same are affixed to the real
estate, including stock in trade and signs or any taxes or the like due to use
of the Premises. LANDLORD shall pay all real estate taxes and all other
assessments and charges assessed by any taxing authority relating to its
ownership of the property and buildings where the Premises is located.

(m) TENANT shall cause the Premises to remain heated so as to prevent damage to
the Building and not place a burden on other heating systems and keep windows
and doors closed to the extent feasible to retain heat and prevent damage and to
keep water out.

7. RULES AND REGULATIONS. TENANT covenants and agrees that such reasonable rules
and regulations as the LANDLORD may from time to time make, shall be faithfully
kept, observed and performed by the TENANT and by its agents, servants,
employees, and invitees unless waived in writing by the LANDLORD. The Rules and
Regulations of The Mill Pond Building, 63 Great Road, Maynard, Massachusetts are
hereby attached and incorporated as part of this lease. See Exhibit "C" attached
hereto and incorporated as part of this Lease.

8. ACCESS TO THE PREMISES AND BUILDING BY TENANT. In all events, TENANT is
responsible for providing security to the Premises and its own personnel, and
TENANT shall indemnify, defend with counsel of LANDLORD'S approval, not to be
unreasonably withheld, and save LANDLORD harmless from any claim for injury to
person or damage to property asserted by any personnel, employee, guest, invitee
or agent of TENANT which is suffered or occurs in or about the Premises or in or
about the Building by reason of the act of any person affiliated with TENANT
including its personnel, employees, guests, invitees or agents. LANDLORD shall
have the right to exclude any disorderly persons from the Building at any time.

9. ACCESS TO THE PREMISES BY LANDLORD. After reasonable notice, except in the
case of an emergency, LANDLORD, its agents and invitees may enter the Premises
at all reasonable times to examine, inspect or to protect the same or prevent
damage or injury to the same or to make such repairs, alterations or
improvements to the Building or the Premises, or any part thereof as the
LANDLORD may deem necessary or desirable or which may be required by law,
whether or not attributable to any use, act or omission of TENANT; or to exhibit
the same to prospective

<PAGE>

purchasers, mortgagees, governmental authorities, and other parties having an
interest therein, and during the last six (6) months of the term of this Lease
to prospective TENANTS. Should any locks be changed, TENANT will furnish
LANDLORD with a current set of keys on a continuing basis. LANDLORD will honor
and accommodate the confidential nature of TENANT'S business in exercising the
aforesaid right of access.

The LANDLORD further reserves the right, in its sole discretion, to modify,
supplement, or make additions to the Building or to build separate buildings on
the parcel upon which the Building is now located and in connection therewith,
to alter, modify, or supplement any or all of the common areas serving the
Building as long as the exercise of this right will not interfere with TENANT'S
quiet use and enjoyment of the Premises.

10. ALTERATIONS - REMOVAL - TRADE FIXTURES. TENANT shall not make any
alterations, installations, changes, additions or improvements in or to the
Premises or any part thereof or in or to the Building except as expressly
provided in this Section 10 or as set forth in Exhibits "A" or "B". All such
alterations and other improvements shall be made at TENANT'S sole expense and
shall become the property of LANDLORD and be surrendered with the Premises upon
the expiration of this Lease, unless and to the extent that LANDLORD shall
specify to the contrary. TENANT hereby agrees to indemnify and hold LANDLORD
harmless from any and all claims, costs, demands and expenses resulting from
such work performed in the Premises by TENANT. TENANT'S furniture, equipment and
supplies provided by TENANT shall remain the property of the TENANT and so long
as TENANT is not in default hereunder, such furniture, equipment and supplies
may be removed by TENANT (and shall be removed by TENANT if so directed by
LANDLORD) at the expiration or prior termination of this Lease and TENANT shall
repair any damage to Premises resulting from such removal. All alterations,
installations, changes, replacements, additions to or improvements upon the
Premises made without LANDLORD'S consent shall likewise at the election of the
LANDLORD remain upon the Premises and be surrendered, or removed, as aforesaid.
If TENANT shall fail to remove, after notice has been given, any property or
other item as aforesaid then at the election of LANDLORD, TENANT shall continue
to pay a sum equal to the Base Rent and Additional Rent provided for hereunder
on account of use and occupancy for a period ending five (5) days after such
removal. TENANT may, from time to time, at its sole cost and expense, pursuant
to the plans approved in advance in writing by LANDLORD, redecorate the Premises
and make nonstructural alterations to the Premises, provided that such
alterations shall not injure the safety of the structure of the Premises or the
Building and shall be done in a good and workmanlike manner and in conformity
with applicable Governmental regulations and plans and specifications approved
in writing by LANDLORD, which approval shall not unreasonably be withheld.
TENANT shall not make any other alteration, improvement or addition to the
Premises, including, without limitation, any structural change in the Premises,
without first having obtained LANDLORD'S written consent thereto, which consent
LANDLORD may withhold in its absolute discretion. LANDLORD may condition any
such approval or consent by reserving the right to require the Premises to be
restored to the same condition they were in prior to the making of the same, and
by requiring TENANT to give satisfactory evidence of its financial capacity to
pay for the work to be done. All such work shall be done by a contractor
approved by LANDLORD, which consent may not be unreasonably withheld, in
accordance with all applicable laws and ordinances and the requirements of
LANDLORD'S insurers.

<PAGE>

All salvage from any such work shall belong to TENANT but all such
installations, erections, alterations and changes, except for trade fixtures,
shall belong to LANDLORD and become part of the realty except TENANT is allowed
to retain ownership of all computer related wiring, blackboards and chalkboards
and the telephone system master panel as installed in the Premises by TENANT,
however any damage caused by the removal of the same shall be repaired in a
professional manner immediately upon removal of said items and should TENANT not
do so within five (5) days LANDLORD has the right to remedy the same and charge
the TENANT for said work.

LANDLORD, upon request of TENANT, and at the expense of TENANT, after it shall
have given approval to any such plans, alterations, installations, erections or
changes, shall execute and deliver such instrument as may be necessary to obtain
any permit or license for the same. TENANT agrees to obtain and pay for any such
required permit or license.

Without limitation at the expiration or sooner termination of the term hereof,
TENANT shall yield up the Premises in accordance with the provisions of this
paragraph, and in such condition as the same is required to be maintained
hereunder and otherwise in accordance with the provisions of this Lease.

Notwithstanding the above it is understood and agreed that the LANDLORD shall
obtain and pay for any required permits or licenses needed to complete the work
outlined in Exhibits "A" and "B".

11. TENANT'S BUSINESS OPPORTUNITIES. LANDLORD assumes no liability or
responsibility whatsoever with respect to the conduct and operation of the
business to be conducted in the Premises or the activities therefrom of TENANT
and its Agents. The LANDLORD shall not be liable for any damage, accident or
injury to any person or persons or property resulting from the activities of
TENANT conducted on or from the Premises, and TENANT shall defend, indemnify and
hold LANDLORD harmless of and from any claims or liabilities resulting from the
activities of TENANT conducted on the Premises.

12. LANDLORD'S SERVICES. The LANDLORD shall maintain the outside common areas in
a reasonably neat manner; provided, however, that the LANDLORD shall not be
liable for failure to furnish, or for suspension or delays in furnishing, any of
such services caused by causes beyond the reasonable control of LANDLORD.

13. REPAIRS AND CARE OF THE PREMISES. (a) LANDLORD shall, after reasonable
written notice of the need therefore, make all necessary repairs and
replacements to the exterior walls, roofs, foundation, common areas and
facilities of the Building and to the heating, interior structural elements,
ventilating and air conditioning systems serving the Premises, and to all wires,
ducts, pipes and conduits to the point where the same are properly connected to
the Premises, all as necessary to keep them in the same condition they were in
upon the Commencement Date subject to the provisions of Sections 19 and 20
hereof and except for repairs and replacements necessitated by the act or
neglect of TENANT or its Agents, which shall be made by TENANT. LANDLORD shall
be responsible for all repairs and replacements not necessitated by the act or

<PAGE>

neglect of TENANT or its Agents. LANDLORD agrees to make all necessary repairs
required to maintain a HVAC system on the premises capable of providing an
office environment with a temperature range between 65-78 degrees F in
compliance with the Commonwealth of Massachusetts Energy Code. Upon notification
of failure of HVAC system by TENANT, the LANDLORD agrees to make necessary
repairs within 24 hours except as delayed by the procurement of necessary repair
or replacement parts.

         (b) TENANT shall make all repairs, replacements, alterations, and
improvements to the Premises including without limitation, wiring, plumbing,
pipes, conduits and other utilities and sprinklers, fixtures and equipment and
all glass, including that in windows and all casings and framework of doors and
windows for any act, omission or neglect of TENANT or anyone for whom TENANT
shall be responsible. TENANT'S all also comply with any board of insurance
underwriters to the extent attributable to TENANT'S particularized use of the
Premises. TENANT shall at all times keep and maintain the Premises in a neat and
clean condition.

14. TENANT'S PROPERTY. To the fullest extent permitted by law, all personal
property of the TENANT or its agents in the Premise or in the Buildings, shall
be a the sole risk of the TENANT or its agents, as the case may be. The LANDLORD
shall not be liable for any injury or damage to the TENANT or its Agents in or
on the Premises or to the property of TENANT resulting from the use of the
heating, air-conditioning, electrical or plumbing apparatus or any other cause;
nor shall LANDLORD in any event, be liable for damages or injury resulting from
water, steam or other causes. TENANT hereby expressly releases LANDLORD from any
liability incurred or claimed by reason of such damage or injury. LANDLORD shall
not be liable in damages nor shall this Lease be affected for conditions arising
or resulting (and which may affect the Building of which the Premises are a
part) due to construction of contiguous premises. Notwithstanding the above,
TENANT will be responsible for own Premises unless damages or injury is caused
by negligence or fault of LANDLORD or any other tenant.

15. UTILITIES. TENANT shall, during the term hereof, pay directly to the proper
authorities charged with the collection of all charges for electricity and gas
consumed on or in connection with the use and occupancy of the Premises. TENANT
shall be responsible for all of its telephone charges. LANDLORD shall be
responsible for all charges relating to water and sewer use in connection with
the use and occupancy of the Premises. LANDLORD shall be responsible for all of
the costs associated with the remetering of all the utilities into the Premises.

LANDLORD shall not be liable for any interruption or failure in the supply of
any such utilities to the Premises except where caused by the acts or failures
of the LANDLORD. TENANT agrees that it will at all times keep sufficient heat in
the Building to prevent existing pipes therein from freezing.

16. ASSIGNMENT OR SUBLETTING. TENANT agrees that it shall not, without the prior
written consent of the LANDLORD, which LANDLORD may not unreasonably withhold,
hypothecate, pledge or otherwise encumber this Lease, assign its interest
herein, or make any sublease or permit occupancy of the Premises or any part
thereof by anyone other than the TENANT, voluntarily or by operation of law. If
TENANT shall be a corporation, any transfer of a majority

<PAGE>

of the capital stock of said corporation shall be deemed to be an assignment of
this Lease. If TENANT shall be a partnership or limited partnership a transfer
of any partnership interest therein shall be deemed such an assignment and if
TENANT shall be a Trust, any transfer of beneficial interest therein shall be
such an assignment. Notwithstanding any assignment or subletting by TENANT,
TENANT shall remain primarily liable for the performance and observance of the
covenants and agreements herein contained on the part of TENANT to be performed
and observed, such liability to be joint and several with that of any assignee
or sublessee, as the cage may be, any such assignee or sublessee by its
acceptance of an interest in or under this Lease thereby agreeing so to be
bound. Without limitation, it is expressly understood and agreed that no
assignment of TENANT'S interest in this Lease or sublease shall be effective
until such time as TENANT shall deliver to LANDLORD an agreement from the
assignee to sublessee, which agreement shall be reasonably satisfactory to
LANDLORD in form and substance and shall provide that the assignee agrees with
LANDLORD to be liable as aforesaid.

If TENANT shall request permission to sublet or assign, LANDLORD may condition
its consent upon an agreement by TENANT to pay to the LANDLORD, as Addition
Rent, an amount equal to one half of all payments received by TENANT in
consideration thereof, whether as rent or otherwise, in excess of the Base and
Additional Rent reserved hereunder after allowing TENANT to recover the costs of
subletting. LANDLORD furthermore shall have the right in such case to notify
TENANT that LANDLORD elects to terminate this Lease and to deal with TENANT'S
proposed sublessee or assignee for a direct lease, such termination to be
effective upon the execution by LANDLORD of a direct Lease with such sublessee
or assignee in which case TENANT is released from this Lease with respect to the
area at issue. Alternatively, LANDLORD shall have the right in such case to
terminate this Lease with the same force and effect as if the term of the Lease
had expired on the date fixed herein for such expiration but only as to the area
to be sublet. TENANT does hereby release LANDLORD of and from any claim which
TENANT may have by reason of LANDLORD'S activity in dealing with such assignee
or sublessee to the extent permitted by law.

The above shall not apply to any assignment or sublease between TENANT and any
of its affiliates, subsidiaries, partners, parent corporations, joint ventures
or sister corporations.

17. DEFAULT. (a) If TENANT or any guarantor of TENANT ("Guarantor") shall make
an assignment of its assets for the benefit of creditors by trust mortgage or
otherwise, or if TENANT or Guarantor shall file a voluntary petition in
bankruptcy for reorganization or liquidation or otherwise seek relief for the
payment of its debts, or if any involuntary petition in bankruptcy or for
receivership be instituted against the TENANT or Guarantor, or if TENANT or any
Guarantor shall make a composition with the creditors and the same be not
dismissed within sixty (60) days of the filing thereof or if the TENANT or
Guarantor be adjudged bankrupt or insolvent or, if TENANT or Guarantor shall
fail to pay its monetary obligations in due course as they mature, then and in
any of said events this Lease shall immediately cease and terminate, at the
option of the LANDLORD, with the same force and effect as though the date of
said event were the day herein fixed for the expiration of the term of this
Lease.

<PAGE>

(b) If TENANT shall fail to pay the Base Rent, or any installment thereof as
aforesaid and/or any Additional Rent or other payment or any installment thereof
as herein provided, and such default shall continue for five (5) business days
after written notice thereof by LANDLORD; or if TENANT shall violate or fail or
neglect to keep and perform any of the covenants, conditions and agreements
herein contained on the part of TENANT to be kept and performed, and such
default shall continue for twenty (20) business days after TENANT shall receive
Notice of such default (which period shall be extended for a reasonable time in
case of a default which cannot reasonably be cured within said twenty (20) days
period, if TENANT shall promptly commence to cure such default and thereafter
diligently prosecute such cure to completion), then and in each and every such
event from thenceforth, and at all times thereafter, at the option of LANDLORD,
TENANT'S right of possession shall thereupon: cease and terminate and LANDLORD
shall be entitled to the possession of the Premises, any process of law, any
notice to quit, or of intention to re-enter being hereby expressly waived by
TENANT. LANDLORD'S right and option may be exercised by entry, or in lieu
thereof, of written notice to TENANT terminating this Lease and TENANT'S right
to possession. TENANT hereby expressly waives any and all rights of redemption
granted by or under any present or future laws in the event of TENANT being
evicted or dispossessed for any cause or in the event LANDLORD terminates this
Lease or in the event of such re-entry, by process of law or otherwise, TENANT
nevertheless shall remain liable for any and all damage, deficiency or loss of
value or Rent, however, designated which the LANDLORD may sustain. LANDLORD
shall have full power, which is hereby acceded to by TENANT, to re-let the
Premises, and whether or not there has been such re-letting, LANDLORD shall have
the right each month to sue for and recover all sums previously due and not
previously paid as well as all sums thereafter due and payable including,
without limitation, any loss of Rents (or monthly deficit) with the right
reserved to LANDLORD to bring any action(s) or proceedings(s) for the recovery
of any deficit(s) remaining unpaid without being obligated to await the
expiration of the term of this Lease for a final determination of TENANT'S
account. Additionally, LANDLORD may elect at any time, upon notice to TENANT, to
accelerate the payment of Base Rent, Additional Rent and all other sums due or
to become due under the Lease, as reasonably estimated by LANDLORD, in which
case TENANT shall forthwith pay such sum to LANDLORD after receiving a credit
for (i) such sums as may previously have been paid under this Section 17 net of
such expenses as may be deducted under clause (c) of this Section 17; and (ii)
the reasonable value of TENANT'S leasehold estate for the balance of the term
fixed herein at which time TENANT is released from the terms of this Lease. The
commencement or maintenance of any one or more actions shall not bar LANDLORD
from bringing other or subsequent actions for further accruals pursuant to
provisions of this Section 17. It is further understood that no waiver of any
breach of any covenant, condition or agreement herein contained shall operate as
a waiver of the covenant, condition or agreement itself or of any subsequent
breach thereof. No provision of this Lease shall be deemed to have been waived
by LANDLORD unless such waiver shall be in writing signed by the LANDLORD. No
payment by TENANT or receipt by LANDLORD of a lesser amount than the monthly
installment of Base Rent herein stipulated or otherwise payable under the Lease
shall be deemed to be other than on account of the oldest overdue Base Rent nor
shall any enforcement or statement on any check or any letter accompanying any
check or payment as rent be deemed an accord and satisfaction. The LANDLORD may
accept such check or payment without prejudice to the LANDLORD'S right to
recover the balance of such Rent or pursue any other remedy in this Lease.

<PAGE>

         (c) The net proceeds of any such re-letting shall first be applied to
the expenses thereof, including any costs in refitting and redecorating the
Premises, leasing commissions and other costs any expenses incurred therein. The
net proceeds resulting therefrom shall be applied to TENANT'S liability under
this Lease. LANDLORD'S re-letting of the Premises following a default by TENANT
under this Lease may be on such terms, provisions and conditions as LANDLORD
shall reasonably deem appropriate and may be for such terms (or terms) as the
LANDLORD may select whether longer or shorter than the remaining term of this
Lease.

         (d) TENANT shall, following default under this Lease, reimburse
LANDLORD for interest upon all sums due to the LANDLORD (from the date such sums
shall have been due to the date of payment thereof) at a rate equal to the
so-called "prime" rate of the Bank of Boston, (or similar major money center or
national bank selected by LANDLORD should said bank not be in existence at any
relevant time) plus two and one-half percent (2 1/2%); provided, however, that
nothing herein contained shall be construed or implemented in such manner as to
allow LANDLORD to charge or receive interest in excess of the maximum lawful
rate then allowed by law.

18. TENANT'S INSURANCE. (a) TENANT shall maintain with respect to the Premises
and its activities thereof or therefrom, broad form comprehensive general
liability insurance, with a minimum limit of coverage of One Million Dollars
($1,000,000.00), which names LANDLORD as well as TENANT as parties insured.
TENANT shall deliver a certificate of such insurance to LANDLORD upon the
commencement of this Lease and continuing evidence of such coverage annually.
Such insurance policy shall be in a form reasonably satisfactory to LANDLORD and
shall be placed with a company qualified to do business in the location of the
Premises and which is acceptable to LANDLORD and shall provide the same cannot
be cancelled without at least thirty (30) days prior written notice to LANDLORD.

Renewal insurance certificates shall be provided to LANDLORD not less than
thirty (30) days preceding the expiration of the prior policy.

         (b) TENANT shall carry, with respect to its personal property, fixtures
and equipment upon and its leasehold improvements to the Premises, insurance
against fire and the so-called extended equal to the full replacement value
thereof, and such other insurance and coverages as may be required by law or be
dictated by prudent business practices.

         (c) TENANT shall carry workmen's compensation insurance covering all
employees, and if TENANT shall contract with any independent contractor for the
furnishing of labor, materials or services to TENANT with regard to the
Premises, TENANT shall require such independent contractor to maintain workmen's
compensation insurance covering all its employees and all the employees of any
subcontractors.

         (d) The limits and nature of insurance hereinabove provided may, from
time to time, be increased and expanded consistent with reasonable amounts
required for comparable space in the market so as to provide comparable
protection subject to conditions existing from time to time.

<PAGE>

         (e) Subject to the provisions of Paragraph 14, the TENANT hereby
releases the LANDLORD to the extent of LANDLORD'S insurance coverage form any
and all liability for any loss or damage to the Premises caused by fire or any
of the said extended coverage casualties or any other casualty insured against,
even if such fire or other casualty shall be brought about by the fault or
negligence of the LANDLORD or its agents; provided, however, this release shall
be in force and effect only with respect to loss or damage occurring during such
time as the TENANT'S policies covering such loss or damage shall contain a
clause to the effect that this release shall not affect said policies or the
right of TENANT to recover thereunder. The TENANT agrees that its fire and other
casualty insurance policies will include such a clause so long as same is
available at no extra cost to TENANT.

         (f) The LANDLORD hereby releases the TENANT to the extent of the
LANDLORD'S insurance coverage, from any and all liability for any loss or damage
to the Building caused by fire or any of the extended coverage casualties or any
other casualty insured against, even if such fire or other casualty shall be
brought about by the fault or negligence of the TENANT or its Agents; provided,
however, this release shall be in full force and effect only with respect to
loss or damage occurring during such time as the LANDLORD'S policies covering
such loss or damage shall contain a clause to the effect that this release shall
not affect said policies or the right of the LANDLORD to recover thereunder.

The LANDLORD agrees that its fire and other casualty insurance policies will
include such a clause so long as the same is includable without extra cost, or
if extra cost is chargeable therefor, so long as the TENANT pays such allocable
share of extra cost. If extra cost is chargeable therefore, the LANDLORD will
advise the TENANT thereof and of the amount thereof. The TENANT at its election
may pay the same, but shall not be obligated to do so.

The LANDLORD presently insures the property for fire and casualty in excess of
$1,500,000 and for liability in excess of $2,000,000 and agrees to maintain at
least this coverage.

If requested in writing the LANDLORD shall deliver a certificate of such
insurance to TENANT upon the commencement of this Lease and annually.

19. CASUALTY. (a) In case of damage by fire or other casualty to the Premises,
the Building or any part thereof, unless this Lease shall be terminated pursuant
to this Section 19, LANDLORD shall, as soon as is reasonably possible
thereafter, having due regard to the collection of proceeds of any insurance
policies or delays in obtaining funds, and the necessity of obtaining permits,
approvals or the like, repair and restore the damaged portion of the Premises
(but not including TENANT'S leasehold improvements therein) and the common areas
of the Building, and during any period that TENANT is deprived of the use of
such damaged portion of the Premises TENANT shall be required to pay Base Rent
only with respect to that portion of the Premise which it is able to occupy-Base
rent payable hereunder by TENANT for such space shall be that portion of the
total Base Rent which the amount of rentable floor area remaining that can be
occupied, bears to the Premise's Gross Rentable Area. All proceeds of insurance
shall belong to LANDLORD and no compensation, or claim, or diminution of rent
will be allowed, or paid, by landlord, or be payable to TENANT by reason of
inconvenience, annoyance, or injury to

<PAGE>

business arising from such damage or the necessity of repairing the Premises or
any portion of the Building of which they are a part, however the necessity may
occur. In the event that any such damage by fire or other casualty to the
Premises shall be material or untenantable to the extent of fifty (50%) percent
of more in any respect, LANDLORD or TENANT shall have the right to terminate
this Lease and the term hereof by giving written notice of that effect to TENANT
within thirty (30) days after any such occurrence.

         (b) Without limitation, in no event, however, need LANDLORD restore any
portion of the Building which is not necessary for access to the Premises and
not necessary for the use and enjoyment of the Premises by the TENANT.

         (c) Upon notification from LANDLORD and if Lease has not been
terminated and there is at lease a year left on the lease, TENANT shall complete
the work of restoration by repairing and/or restoring any portion of the
Premises so damaged which were initially constructed by TENANT pursuant to
Section 5(b) and any additions and alternations previously made by TENANT.
Unless otherwise agreed by LANDLORD, all work shall be done pursuant to plans
and specifications approved by LANDLORD. Regardless of the time remaining on the
lease the TENANT agrees to return the Premises to the condition in which it was
received if LANDLORD repairs the Building reasonable wear and tear excepted.

20. CONDEMNATION. (a) if the whole or any part of the Premises or Building shall
be taken or condemned for public or quasi-public use or purpose by any competent
authority, or conveyed in lieu thereof (a "Taking"), TENANT shall have no claim
against the LANDLORD and shall not have any claim or right to any portion of
such taking; and all rights of the TENANT to damages therefor, if any, are
hereby assigned by the TENANT to the LANDLORD. Upon such Taking, if the term of
this Lease shall terminate, TENANT shall have no claim against the LANDLORD for
the value of any unexpired term of this lease. TENANT, however, shall be
entitled to claim, prove and receive in a condemnation proceeding such awards as
may be allowed for damages to or the taking of fixtures, equipment and other
property installed by it and which it is herein permitted to remove from the
Premises at the end of the term and any moving expenses but only if such awards
shall be separately awarded in addition to (and not out of or in diminishment of
) the award made to LANDLORD.

         (b) If after the execution of this Lease and prior to the expiration of
the term of this Lease, the whole or any material part of the Building, any
material part of the land upon which the Building is located shall be taken,
then the term of this Lease shall cease as of the time when Landlord shall give
Notice to TENANT of its election to terminate this Lease. Notice of such
terminations shall be given by LANDLORD to TENANT within thirty (30) days after
LANDLORD shall receive notice of such Taking, and the termination shall be
effective as of the time that possession of the part so taken shall be required
for public use, and any apportionment or adjustment of rent shall be as of the
time of termination.

         (c) In the event of a temporary taking, TENANT shall continue to pay
the Base and Additional Rent and other sums due hereunder if TENANT can use the
Premises for their general office, laboratory and light manufacturing uses, but
shall receive a credit for all sums

<PAGE>

actually received by LANDLORD on account of this Lease, up to the amount of
TENANT'S obligation during the period of such temporary taking hereunder.

         (d) If the Lease shall not be terminated as aforesaid, LANDLORD shall
have such obligation as to reconstruction as is provided in Section 19 hereof
treating any awards received by LANDLORD as if they were proceeds of insurance
in the application of such Section 19.

         (e) TENANT shall, upon notice from LANDLORD, begin to work of
completing the Premises insofar as TENANT was obliged to complete the same
pursuant to section 5(b) and 19(c). All work done pursuant to this Section 20
shall be done and in the same manner and of the same quality as the original
construction or any alterations or additions. All of TENANT'S work shall be done
pursuant to TENANT'S plans and specifications prepared by LANDLORD'S
construction representative for the restoration, but at TENANT'S expense, and
all work which TENANT is obliged to do shall be done at TENANT'S expense.
TENANT'S contractor shall coordinate with LANDLORD and LANDLORD'S contractor
shall not interfere with the operation of the business, and shall observe such
rules and regulations, not inconsistent herewith, as LANDLORD shall promulgate
from time to time.

         (f) During the period of restoration, the Base Rent reserved hereunder
shall be suspended or abated according to that proportion of the area of the
Premises rendered unusable. There shall be no abatement or suspension of Base
Rent hereunder if there shall be no actual physical damage to the area of the
Premises and no impairment of access or of TENANT'S ability to use the space,
nor, in any case shall there be an abatement of TENANT'S obligation to pay
Additional Rent, or other charges due under this Lease. If TENANT shall be
permanently deprived of any portion of the area of the Premises, the Base Rent
shall be proportionally abated for the balance of the term.

21. MECHANIC'S LIEN. TENANT will not permit any mechanic's lien or liens to be
placed upon the Premises or any improvements thereon and if any such lien is
filed on account of the act of TENANT, TENANT shall promptly and continuously
contest it and post a bond (in form reasonably satisfactory to LANDLORD and any
Holder) to secure payment of such sum or pay same. In the event of any proposed
work by TENANT with respect to which such a lien might arise, LANDLORD may
require TENANT to provide it in advance with so-called waivers of liens or a
bond against liens or other assurances that no such liens will arise. In the
event TENANT fails to post bond against or pay any such lien, the same shall be
deemed a substantial default under this lease.

22. HOLDING OVER. If the TENANT shall, with the knowledge and consent of the
LANDLORD, continue to remain in the Premises after the expiration or prior
termination of the term of this Lease, then and in such event, TENANT shall by
virtue of this agreement, become a TENANT from month to month, at a rent to be
agreed upon by the parties. Said monthly tenancy shall commence on Th first
(1st) day next after the end of the term herein demised; the TENANT shall give
to the LANDLORD at least thirty (30) days Notice of any intention to quit the
Premises; and TENANT shall be entitled to thirty (30) days Notice to quit said
Premises, except in the event of nonpayment of Rent in which case Notice to quit
being expressly waived; provided, however, that in the event that the TENANT
shall hold over after the expiration of the

<PAGE>

term without LANDLORD's consent, then at any time prior to LANDLORD's acceptance
of rent, however designated from TENANT, as a monthly TENANT hereunder, the
LANDLORD at its option, any forthwith re-enter and take possession of said
Premises without process or by any legal process in the force in the
Commonwealth of Massachusetts applicable to TENANTS-at-sufferance. Nothing in
this Section 22 shall be deemed to consent to any occupation of the Premises
after the term.

23. SUBORDINATION. (a) The rights and interest of the TENANT under this Lease
shall at the election of the holder of any present or future mortgage be (i)
subject and subordinate to the lien of any present or future mortgage upon the
Premises or any Property of which the Premises are a part and any modification,
amendment, consolidation or extension thereof and to any and all advances to be
made thereunder, and to the interest thereon and any sums due to the mortgage
thereunder; or (ii) prior to the lien of any such present or future mortgage.
The holder of any such mortgage ("Holder") may from time to time make and/or
change the foregoing elections and shall give written notice thereof to the
TENANT each such time. Failure to give such notice shall not, however, affect
the rights of such Holder. Without limitation, the Holder may also elect, by
like notice to TENANT, to make some provisions hereof subject and subordinate to
the lien of its mortgage while granting other provisions hereof priority to the
lien of its mortgage. In the event of any such elections (and upon notification
by the Holder to that effect) the rights and interest of the TENANT under this
Lease shall be deemed to be subordinate to, or to have priority over, as the
case may be, the lien of such mortgage, irrespective of the time of execution or
time of recording of any such mortgage. TENANT's agreement to subordinate this
lease may be conditioned on the grant of a non-disturbance agreement as long as
TENANT is not in default.

         (b) Whether the lien of any mortgage upon the Premises or any property
of which the Premises are a part shall be superior to subordinate to this Lease
and the lien hereof, the TENANT agrees that it will, upon request, attorn to the
Holder or anyone claiming under such Holder and their respective successors and
assigns in the event of foreclosure of or similar action taken under such
mortgage.

         (c) TENANT agrees that it will, upon request of LANDLORD from time to
time, execute, acknowledge and deliver any and all instruments deemed by the
LANDLORD or the Holder necessary or desirable to evidence or to give notice of
such subordination or priority as long as it is consistent with the terms of
this Lease. TENANT also agrees that if it shall fail at any time to execute,
acknowledge and deliver any such instrument requested by LANDLORD, LANDLORD may,
in addition to any other revenues available to it, execute, acknowledge and
deliver such instrument as the attorney-in-fact of TENANT and in TENANT's name;
and TENANT does hereby make, constitute and irrevocably appoint the LANDLORD as
its attorney-in-fact and in its name, place and stead so to do. The word
"mortgage" as used herein includes mortgages, deeds of trust or other similar
instruments and modifications, consolidation, extension, renewals, replacements
and substitutions thereof.

         (d) Upon entry and taking possession of the Building for any purpose,
Holder shall have all rights of LANDLORD, but during the period of such
possession LANDLORD, not Holder, shall have the duty to perform all of
LANDLORD'S obligations hereunder. No Holder shall be liable, either as a
mortgagee or as holder of a collateral assignment of this Lease, to

<PAGE>

perform, or be liable tin damages for failure to perform, any of the obligations
of LANDLORD unless and until Holder shall succeed to LANDLORD'S interest herein
through foreclosure, deed-in-lieu or in other fashion, and thereafter Holder
shall not be liable for the performance of those obligations which arise during
the period and interest in this Lease; such liability to be limited to the same
extent at LANDLORD'S liability it limited pursuant to Section 26 hereof.

         (e) So long as any present or future mortgage shall remain in effect
and if TENANT has been informed thereof by written notice, TENANT shall not
alter, modify, amend, change, surrender or cancel this Lease nor pay the Rent
due hereunder in advance for more than thirty (30) days, except as may be
required herein, without the prior written consent of the Holder and TENANT will
not seek to be made an adverse or defendant party in action or proceeding
brought to enforce or foreclose such mortgage.

         (f) In the event that LANDLORD shall utilize a so-called
"sale-leaseback" form of financing either in lieu of, or in conjunction with,
mortgage financing, then the rights and benefits hereinabove conferred upon a
Holder shall be conferred upon the Ground Lessor under such sale-leaseback
arrangement, and the foregoing provisions of this Section 23 shall be deemed to
be modified to the extent reasonably required so as to be applicable to such
sale-leaseback arrangement as long as TENANT has a non-disturbance agreement.

24. NOTICES. (a) All Notices required or desired to be given hereunder by either
party to the other shall be in writing handcarried or given by Certified Mail or
Registered Mail, and Return Receipt Requested with sufficient postage prepaid.
Notices to the respective parties shall be addressed to LANDLORD at LANDLORD'S
Office, and if to the TENANT at the Mailing Address of TENANT. Either party may,
by like Notice, designate a new address to which said Notices shall be directed.

(b) If the Premises or any part thereof of the Building are at any time subject
to a Mortgage of LANDLORD's interest in this Lease or the Rent therefrom are
assigned, and the TENANT is given Notice thereof, including the post office
address of such assignee, then notwithstanding any contrary rule of law, the
TENANT shall not terminate this Lease or abate Rent for any default or take any
other action on the part of the LANDLORD without first giving Notice by
handcarrying or by Certified or Registered Mail, Return Receipt Requested, to
such assignee or such other recipient as may be so designated, specifying the
default in reasonable detail and affording such assignee or other recipient a
reasonable opportunity to make performance, at its election, for and on behalf
of the LANDLORD.

25. SUCCESSORS - ASSIGNS. All rights, remedies and liabilities of either of the
parties hereto, shall extend to its respective heirs, successors, executors,
administrators and assigns, except that the LANDLORD named herein and any owner
of LANDLORD'S interest in this Lease shall be liable only for the obligations of
the LANDLORD hereunder accruing during the period of its ownership. No owner,
partnership, joint venture, Trustee, beneficiary, partner, officer, director or
shareholder thereof shall be personally responsible or liable with respect to
any of the covenants, conditions or provisions of this Lease to be performed by
the LANDLORD. In the event of a default by LANDLORD under this Lease, TENANT
agrees that in all events LANDLORD'S liability shall be limited to the actual
equity interest of LANDLORD in the Building for the satisfaction of TENANT'S
remedies under this Lease. In the event that two or

<PAGE>

more individuals, corporation, partnerships or their business associations shall
be named as TENANT, their obligations to pay rent and perform all other
obligations hereunder shall be joint and several. In the event that the TENANT
named in this Lease shall be a partnership or other business association shall
not be subject to personal liability hereunder, but such Partnership or
association shall be liable hereunder in its capacity as partnership or
association. Nothing in this Section shall constitute consent to any transfer of
TENANT'S interest in the Lease.

26. SECURITY DEPOSIT. TENANT has deposited with the LANDLORD herewith the sum
set forth in Section 1 hereof, representing a Security Deposit. At the
expiration or earlier termination of this Lease, whichever shall first occur,
LANDLORD shall return said Security Deposit or what may remain thereof to TENANT
after during any default of TENANT. LANDLORD need not segregate said sum nor pay
interest thereon.

If at any time during the term of this Lease LANDLORD shall use all or any part
of the Security Deposit to cure TENANT'S default, which LANDLORD is obligated to
do, TENANT shall upon demand, deposit with LANDLORD such part of said Security
Deposit as shall have been used.

27. COMPLETE AGREEMENT. This Lease contains the entire and only agreement
between the parties, and no oral statements or representations or prior written
matter not contained or referred to in this instrument shall have any force or
effect. This Lese shall not be modified in any way except by a writing
subscribed by the parties hereto.

28. SELF-HELP. If TENANT shall default in the performance or observance of any
agreement, condition or other provisions in this Lease contained on this part to
be performed or observed, and shall not cure such default within twenty (20)
days after notice in writing from the LANDLORD specifying the default (or, in
the event such default shall require more than twenty (20) days to be cured, if
the TENANT shall not, within said period, commence to cure such default and
thereafter, with due diligence, prosecute the curing of such default to
completion), LANDLORD may, at is option, without waiving any claim for breach of
agreement, at any time thereafter cure such default for the account of the
TENANT, and the TENANT shall reimburse a landlord for any amount paid and any
expense or contractual liability so incurred including reasonable attorneys'
fees whereupon the default will be deemed cured. LANDLORD may cure the default
of the TENANT prior to the expiration of such waiting period, but after Notice,
which Notice need not be in writing if confirmed forthwith by Notice in writing
to the TENANT, if it is necessary to protect the real estate or the interest of
LANDLORD therein, or to prevent injury or damage to person or property. Any
amount payable by TENANT to LANDLORD pursuant to the provision of this Section
29 shall be paid as part of and at the time for payment of the next installment
of Base Rent thereafter coming due.

29. DELAYS. In any case where either party hereto is required to do any act,
other than the making of any payment of Rent or delivering the Premises for
Occupancy, however, designated or other monetary sum due LANDLORD hereunder, the
time for performance thereof shall be extended for a period equal to any delay
caused by or resulting from any act of God, war, civil commotion, fire,
casualty, labor difficulties, shortages of labor, materials or equipment,
governmental regulations or other causes beyond such party's reasonable control
(herein

<PAGE>

"Outside Circumstances"), whether such time be designed by a fixed date, a fixed
time, or a "reasonable time."

30. WAIVER. Failure of either party to complain of any act or omission on the
part of the other party, no matter how long the same may continue, shall not be
deemed to be a waiver by said party of any of this right hereunder. No waiver by
either party at any time shall be effective unless in writing and signed by the
party adversely affected by the breach with respect to which waiver is asserted
to have been made. No waiver of any breach of any provision of this Lease shall
be deemed a waiver of a breach of any other provision of this Lease or a consent
to any subsequent breach of the same or any other provision. If any action by
either party shall require the consent or approval of the other party, the other
party's consent to or approval of such action on any one occasion shall not be
deemed a consent or approval of any other action on the same or any subsequent
occasion. Each and every right and remedy which either party may have under this
Lease or by operation of law, either at law or in equity, with respect to any
breach, shall be distinct and separate from every other such right and remedy;
all such rights and remedies shall be cumulative, and none of them shall be
deemed inconsistent with the other, not such right or remedy whether or not
exercised, shall be deemed to be in exclusion of any other, and any two or more
or call of such rights and remedies may be exercised at the same time or
successively, except where in this Lese otherwise expressly provided. LANDLORD
and TENANT hereby waive all rights to claim a trial by jury.

31. DELAYED POSSESSION. If LANDLORD shall be unable to give possession of the
Premises on the date set forth in Section 3 hereof for reason, LANDLORD shall
not be subject to any liability for such failure to give possession on said
date. No such failure to give possession on said date shall in any other respect
affect the validity of this Lease or the obligations of TENANT hereunder. If
permission is given to TENANT to enter into the possession of the Premises (or
to occupy premises other than the Premises) prior to the date specified as the
Commencement Date of the term of this Lese, TENANT covenants and agrees that
such occupancy shall be deemed to be under all the terms, covenants, conditions
and provisions of this Lease except for monetary obligations.

32. QUIET ENJOYMENT. LANDLORD covenants and agrees that upon TENANT'S paying the
Rent payable hereunder and performing and observing the covenant sand provisions
of this Lease on its party to be performed and observed, TENANT shall peaceably
and quietly enjoy the Premises, subject, however to the terms, covenants and
conditions of this Lease.

33. ADDITIONAL AGREEMENTS. (a) Feminine and neuter pronouns shall be substituted
for those of the masculine form and the plural shall be substituted for the
singular number in any place places herein in which the context may require such
substitution or substitutions. The LANDLORD herein for convenience has been
referred to in neuter form.

         (b) After the commencement of the term of this Lease and whenever, from
time to time, requested during the term of this Lease, TENANT agrees to deliver
to LANDLORD or to any mortgagee, holder of a deed or trust or Ground Lessor or
such other person designated by LANDLORD within fifteen (15) days after written
request therefore a certificate stating, if the same be true, that TENANT has
entered into occupancy of the Premises in accordance with the provisions of this
Lease, that this Lease is in full force and effect, that LANDLORD has

<PAGE>

performed the construction required of LANDLORD and any other information
reasonably requested. LANDLORD agrees to provide a similar certificate should
the TENANT's bank request the same.

         (c) TENANT shall not record this Lease. Any such recording by TENANT
shall constitute a material breach of this Lease and shall entitle LANDLORD, at
its election, to immediately terminate this Lease. Either party may record a
Notice of Lease with respect hereto which the other agrees to execute in form
suitable for recording.

         (d) If any term, covenant, condition or provision of this Lease (or the
application thereof to any person or circumstance) be determined to be invalid
or unenforceable of the remainder of this Lease (or the application of such term
or provision to other persons and circumstances) shall not be affected thereby.
Each term, covenant, condition and provision of this Lease shall be valid and be
enforced to the fullest extent permitted by law.

         (e) All heading used herein are for convenience only and do not
constitute a part of this Lease or affect its meaning.

         (f) This Lease shall be construed in accordance with the laws of the
commonwealth of Massachusetts.

         (g) Time shall be construed to be of the essence hereof whenever any
act hereunder is required to be done at a certain time or within a prescribed
period of time, subject always to the provisions of Section 30 hereof.

         (h) If landlord shall require the services of an attorney to enforce
TENANT'S obligations under this Lease, or an architect, engineer or other
professional person to any way deal with TENANT under this Lease, then if
LANDLORD prevails in Court, Arbitration or Mediation proceedings TENANT shall
pay to LANDLORD upon demand all reasonable costs thereby incurred by LANDLORD.

If TENANT shall require the services of an attorney to enforce LANDLORD's
obligations under this Lease, or an architect, engineer to other professional
person to any way deal with LANDLORD under this Lease, then if TENANT prevails
in COURT, Arbitration or Mediation proceedings LANDLORD shall pay to TENANT upon
demand all reasonable costs thereby incurred by TENANT.

         (i) In no case shall LANDLORD be deemed to be in default under this
Lease unless TENANT shall have first given LANDLORD notice in writing specifying
the nature of the default complained of and LANDLORD shall have failed to cure
said default within a reasonable period of time after receipt of such notice.

Unless specifically set forth elsewhere in this LEASE in no case shall TENANT be
deemed to be in default under this Lease unless LANDLORD shall have first given
TENANT notice in writing specifying the nature of the default complained of and
TENANT shall have failed to cure said default within a reasonable period of time
after receipt of such notice.

<PAGE>

         (j) LANDLORD agrees to complete the work shown on the attached plan
which shall include the demolition of office partitions and patching floors
where partitions have been removed. Building new partitions as shown on the
plan. Add sidelight at doors. Recarpet the entire space except in tiled areas
including upgraded carpet. Add quarry tile floor at vestibule. Installation of
44 linear feet of cabinets and 22 linear feet of countertop. Necessary plumbing
for two benches. Upgrade electric fixtures in President's Office and conference
room and the installation of new lenses. TENANT agrees to contribute $17,850.00
toward completion of said work. Fifty percent (50%) $8,925 will be paid with the
execution of this lease and the remaining $8,925 will be paid upon occupancy of
the space.

         IN WITNESS WHEREOF, LANDLORD and TENANT have caused this Lease to be
signed sealed and delivered as of the day first above written.

LANDLORD:                                            TENANT:
C.F. REALTY LIMITED PARTNERSHIP                      EXACT LABORATORIES, INC.

By:                                                  By:
   ------------------------------                       ------------------------
   Thomas R. Patton III                              Stanley Lapidus

Its: General Partner                                 Its: President

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