<PAGE>
                                                                   EXHIBIT 10.18


                          [Spaulding & Slye Letterhead]

October 15, 1998

Ms. Catherine Parker
Novirio Pharmaceuticals, Inc.
125 CambridgePark Drive
Cambridge, MA 02140

Re:      Lease between CambridgePark One Limited Partnership ("Landlord") and
         Novirio Pharmaceuticals, Inc. ("Tenant") for approximately 7,970 square
         feet on the third floor of the building located at 125 CambridgePark
         Drive, Cambridge, Massachusetts (the "Lease")

Dear Cathy:

In connection with the Lease, Landlord agrees to the following:

1.       Landlord will issue to Tenant, at no additional cost, three parking
         access cards (in addition to the 24 to which Tenant is entitled to
         under the Lease) for use of the so-called blue parking lot at
         CambridgePark. Such additional access cards are to be used no more than
         two times each month by a visitor or guest of Tenant. At Landlord's
         sole option, such cards may be immediately and permanently revoked if
         used more than two times in any month.

2.       Provided that there is a conference center available to all tenants of
         CambridgePark, Tenant will be permitted to rent the conference center,
         subject to availability, at the then existing rate established by
         Landlord. The rate of use of the conference center is subject to change
         from time to time by Landlord.

We look forward to your tenancy at 125 CambridgePark Drive and to a mutually
advantageous relationship. If you have any questions, please contact me at (617)
491-6732.

Sincerely,

/s/ John M. Kane
John M. Kane
Assistant Vice President
<PAGE>
                            DATE OF LEASE EXECUTION:

                                   ARTICLE I
                                 REFERENCE DATA

1.1      SUBJECTS REFERRED TO:

         Each reference in this Lease to any of the following subjects shall be
construed to incorporate the data stated for that subject in this Section 1.1:

LANDLORD:   CambridgePark One Limited Partnership

MANAGING AGENT:   Spaulding and Slye Services Limited Partnership

LANDLORD'S & MANAGING AGENT'S ADDRESS:

                                 Spaulding and Slye Services Limited Partnership
                                 125 CambridgePark Drive
                                 Cambridge, MA  02140

LANDLORD'S REPRESENTATIVE:  John M. Kane

TENANT:    Novirio Pharmaceuticals, Inc., a Massachusetts corporation.

TENANT'S ADDRESS (FOR NOTICE AND BILLING):

           Novirio Pharmaceuticals, Inc.
           125 CambridgePark Drive
           Cambridge, MA 02140

TENANT'S REPRESENTATIVE:     _____________________________

BUILDING:  The building located at 125 CambridgePark Drive, Cambridge,
           Massachusetts.

LOT:   The parcel of land on which the Building is located and described in
       Exhibit A.

PREMISES:  The space located on the third (3rd) floor of the Building as shown
           on Exhibit B.

RENTABLE FLOOR AREA OF THE PREMISES:  approximately 7,970 square feet

TOTAL RENTABLE FLOOR AREA OF THE BUILDING:     approximately 183,290 square feet

SCHEDULED TERM COMMENCEMENT DATE:  December 1, 1998

LEASE TERM OR TERM:   Commencing on the Term Commencement Date as defined in
                      Section 3.1 hereof and continuing for five (5) years
                      thereafter,
<PAGE>
                      plus the partial month at the beginning of the Term, if
                      any, unless sooner terminated as provided herein

ANNUAL RENT:    $34.50 per square foot of Rentable Floor Area of the Premises,
                or $22,913.75 per calendar month, and proportionally at such
                rate for any partial month (net of Tenant's charges for
                electrical consumption in the Premises).

BASE ANNUAL ELECTRICITY CHARGE:     $ 1.00 per square foot of Rentable Floor
                                    Area of the Premises

BASE ANNUAL OPERATING COSTS:        $9.00 per square foot of Rentable Floor
                                    Area of the Premises

TENANT'S PROPORTIONATE SHARE:   4.35% based upon the ratio of the Rentable Floor
                                Area of the Premises to the Total Rentable Floor
                                Area of the Building, as the same may be
                                adjusted from time to time to reflect changes in
                                such Rentable Floor Areas.

PERMITTED USES:   Office Uses

COMMERCIAL GENERAL LIABILITY INSURANCE:

               $1,000,000 bodily injury, property damage combined single limit
               per occurrence, $2,000,000 annual aggregate.

BROKER:  Spaulding and Slye Services Limited Partnership and
         Fallon Hines & O'Connor, Inc.

SECURITY DEPOSIT: $112,000.00

TENANT'S PARKING ACCESS CARDS:  24

TENANT IMPROVEMENT ALLOWANCE: $63,760


1.2      EXHIBITS.

         The exhibits listed below in this section are incorporated in this
Lease by reference and are to be construed as part of this Lease:

         EXHIBIT A         Description of Lot

         EXHIBIT B         Plan showing Premises.

         EXHIBIT C         Landlord's Services

         EXHIBIT D         Rules and Regulations


                                      -2-
<PAGE>
                                TABLE OF CONTENTS

<TABLE>
<CAPTION>
                                                                            Page
<S>                                                                         <C>
ARTICLE II
    PREMISES AND TERM.....................................................    6
    2.1       DESCRIPTION OF PREMISES.....................................    6
    2.2       TERM........................................................    6

ARTICLE III
    CONSTRUCTION..........................................................    6
    3.1       TERM COMMENCEMENT DATE......................................    6
    3.2       DELIVERY OF PREMISES........................................    7
    3.3       PREPARATION OF PREMISES FOR OCCUPANCY.......................    8
    3.4       GENERAL PROVISIONS APPLICABLE TO CONSTRUCTION...............    8
    3.5       ALTERATIONS AND ADDITIONS...................................    9
    3.6       REPRESENTATIVES.............................................   10

ARTICLE IV
    RENT..................................................................   10
    4.1       ANNUAL RENT.................................................   10
    4.2       ANNUAL OPERATING COST ESCALATION............................   10
    4.3       ESTIMATED ANNUAL OPERATING EXPENSE ESCALATION PAYMENT.......   12
    4.4       ELECTRICITY.................................................   13
    4.5       CHANGE OF FISCAL YEAR.......................................   14
    4.6       PAYMENTS....................................................   14

ARTICLE V
    LANDLORD'S COVENANTS..................................................   14
    5.1       LANDLORD'S COVENANTS DURING THE TERM........................   14
                  5.1.1        Building Services..........................   14
                  5.1.2        Additional Building Services...............   15
                  5.1.3        Repairs....................................   15
                  5.1.4        Tenant Directory...........................   15
                  5.1.5        Food Service...............................   15
                  5.1.6        Quiet Enjoyment............................   16
    5.2       INTERRUPTIONS...............................................   16

ARTICLE VI
    TENANT'S COVENANTS....................................................   17
    6.1       TENANT'S COVENANTS DURING THE TERM..........................   17
                  6.1.1        Tenant's Payments..........................   17
                  6.1.2        Repairs and Yielding Up....................   17
                  6.1.3        Occupancy and Use..........................   17
</TABLE>


                                      -3-
<PAGE>
<TABLE>
<S>                                                                         <C>
                  6.1.4        Rules and Regulations......................   18
                  6.1.5        Safety Appliances..........................   18
                  6.1.6        Assignment and Subletting..................   18
                  6.1.7        Indemnity..................................   20
                  6.1.8        Tenant's Insurance.........................   20
                  6.1.9        Tenant's Worker's Compensation Insurance...   21
                  6.1.10       Landlord's Right of Entry..................   21
                  6.1.11       Loading....................................   21
                  6.1.12       Landlord's Costs...........................   21
                  6.1.13       Tenant's Property..........................   21
                  6.1.14       Labor or Materialmen's Liens...............   22
                  6.1.15       Changes or Additions.......................   22
                  6.1.16       Holdover...................................   22
                  6.1.17       Security...................................   22
                  6.1.18       Tenant Financial Statements................   22

ARTICLE VII
    DAMAGE AND DESTRUCTION; CONDEMNATION..................................   22
    7.1       FIRE OR OTHER CASUALTY......................................   22
    7.2       EMINENT DOMAIN..............................................   24

ARTICLE VIII
    RIGHTS OF MORTGAGEE...................................................   25
    8.1       PRIORITY OF LEASE...........................................   25
    8.2       RIGHTS OF MORTGAGE HOLDERS; LIMITATION OF MORTGAGEE'S
              LIABILITY...................................................   26
    8.3       MORTGAGEE'S ELECTION........................................   26
    8.4       NO PREPAYMENT OR MODIFICATION, ETC..........................   27
    8.5       NO RELEASE OR TERMINATION...................................   27
    8.6       CONTINUING OFFER............................................   27
    8.7       MORTGAGEE'S APPROVAL........................................   27

ARTICLE IX
    DEFAULT...............................................................   28
    9.1       EVENTS OF DEFAULT...........................................   28
    9.2       TENANT'S OBLIGATIONS AFTER TERMINATION......................   28

ARTICLE X
    MISCELLANEOUS.........................................................   29
    10.1      NOTICE OF LEASE.............................................   29
    10.2      RELOCATION..................................................   29
    10.3      NOTICES FROM ONE PARTY TO THE OTHER.........................   30
    10.4      BIND AND INURE..............................................   30
    10.5      NO SURRENDER................................................   30
    10.6      NO WAIVER, ETC..............................................   30
    10.7      NO ACCORD AND SATISFACTION..................................   31
</TABLE>


                                      -4-
<PAGE>
<TABLE>
<S>                                                                         <C>
    10.8      CUMULATIVE REMEDIES.........................................   31
    10.9      LANDLORD'S RIGHT TO CURE....................................   31
    10.10     ESTOPPEL CERTIFICATE........................................   32
    10.11     WAIVER OF SUBROGATION.......................................   32
    10.12     ACTS OF GOD.................................................   32
    10.13     BROKERAGE...................................................   32
    10.14     SUBMISSION NOT AN OFFER.....................................   32
    10.15     APPLICABLE LAW AND CONSTRUCTION.............................   33
    10.16     AUTHORITY...................................................   33

ARTICLE XI
    SECURITY DEPOSIT......................................................   34
</TABLE>













                                      -5-
<PAGE>
                                   ARTICLE II
                                PREMISES AND TERM

2.1      DESCRIPTION OF PREMISES.

         Subject to and with the benefit of the provisions of this Lease,
Landlord hereby leases to Tenant, and Tenant leases from Landlord, Tenant's
Space in the Building, excluding exterior faces of exterior walls, the common
facilities area and building service fixtures and equipment serving exclusively
or in common other parts of the Building. Tenant's Space, with such exclusions,
is hereinafter referred to as the Premises.

         Tenant shall have, as appurtenant to the Premises, the right to use in
common with others entitled thereto: (a) common walkways, driveways, hallways,
lobbies, ramps, loading docks and stairways located in the Building or on the
parcel on which the Building is located (the "Lot"), (b) building service
fixtures and equipment serving the Premises including elevators, (c) the parking
facility, if any, on a first-come, first-served basis in the location from time
to time designated by Landlord, Tenant's use not to exceed the number of
Tenant's Parking Access Cards, and (d) if the Premises include less than the
entire Rentable Floor Area of any floor, the common toilets in the central core
area of such floor. Such rights shall be always subject to the Rules and
Regulations set forth in Exhibit D, attached hereto and incorporated herein by
reference, as the same may be amended by the Landlord from time to time and such
other reasonable Rules and Regulations applicable to all tenants of the Building
from time to time established by the Landlord by notice to Tenant, and to the
right of the Landlord to designate and change from time to time such areas,
facilities, fixtures and equipment so long as any such designations or changes
do not unreasonably interfere with Tenant's use and enjoyment of the Premises.

2.2      TERM.

         To have and to hold for a period (the "Term") commencing on the Term
Commencement Date (as defined in Section 3.1 hereof) and continuing for the
Term, unless sooner terminated as provided herein.

                                  ARTICLE III
                                  CONSTRUCTION

3.1      TERM COMMENCEMENT DATE.

         The Term of this Lease shall commence on the date (the "Term
Commencement Date") which is the earlier of (a) the date on which the Premises
shall be deemed ready for occupancy in accordance with Section 3.3. below (but
not sooner than the Scheduled Term Commencement Date); or (b) the date on which
Tenant commences beneficial use of the Premises. Tenant shall, in all events, be
treated as having commenced beneficial use of the Premises when it begins to
move into the Premises furniture and equipment for its regular business
operations.

         As soon as may be convenient after the Term Commencement Date has been
determined, Landlord and Tenant agree to join with each other in the execution,
in recordable form, of a


                                      -6-
<PAGE>
written Declaration in which the Term Commencement Date and specified term of
this Lease shall be stated.

3.2      DELIVERY OF PREMISES.

         Tenant acknowledges that Tenant has had an opportunity to inspect the
Premises. Except as set forth hereinafter, the Premises, shall be delivered to
Tenant As Is, Where Is with all faults and without representation, warranty or
guaranty of any kind by Landlord to Tenant. Landlord shall perform the work
identified as set forth in the Plans, as defined below ("Landlord's Work").
Landlord agrees to use reasonable efforts to recover the Premises from the
existing tenant thereof in a manner which will permit completion of Landlord's
Work prior to the Scheduled Term Commencement Date.

         Subject to the provisions hereof, Landlord shall undertake all work to
prepare the Premises for Tenant's use and occupancy in accordance with Plans
approved as set forth below at Landlord's cost and expense, except that Tenant
shall reimburse Landlord for all amounts in excess of the Tenant Improvement
Allowance as set forth below. For purposes hereof, Landlord shall submit a
complete set of proposed plans and specifications, together with the projected
budget therefor as reasonably determined by the Landlord (collectively, "Plans")
to Tenant. No later than three (3) business days after Landlord's submission,
Tenant shall either approve or disapprove the Plans, specifying by notice to
Landlord in detail the respects, if any, in which the Plans are disapproved.
Tenant agrees to act reasonably in approving or disapproving Plans. If Tenant
disapproves the Plans, Landlord shall submit to Tenant revised Plans which
respond to the items of disapproval specified in Tenant's notice no later than
three (3) business days from Tenant's notice of disapproval. Thereafter, Tenant
shall have three (3) business days from submission of the Plans to Tenant to
approve or disapprove the revised Plans in accordance with the foregoing and in
the case of disapproval, Landlord shall have an additional three (3) business
days to submit revised Plans responding to the items of disapproval specified in
Tenant's notice. The parties shall work diligently and in good faith to agree
upon approved Plans in order that a complete set of approved Plans ("Final
Plans") will be available no later than the Design Completion Date.

         Tenant shall pay an amount equal to all costs incurred by Landlord in
completing Landlord's Work (including all design and engineering costs) in
excess of the Tenant Improvement Allowance. Upon selection of a contractor for
Landlord's Work by Landlord, Landlord may bill Tenant for such excess by notice
to Tenant setting forth the total estimated cost of Landlord Work based upon the
final bid of such contractor. Tenant shall pay such excess to Landlord within
ten (10) days of Landlord's notice. In addition, Tenant shall pay an amount
equal to all additional costs incurred by Landlord as a result of Landlord's
Work, including change orders signed by Tenant and Landlord. Amounts due and
payable on account of such additional costs shall be paid by Tenant to Landlord
within ten (10) days of Landlord's invoice to Tenant therefor. Landlord shall
not be obligated to continue Landlord's Work after such ten (10) day period if
such payment has not yet been received by Landlord, until such payment is
received by Landlord. Upon completion of Landlord's Work, Landlord shall
determine the total cost of Landlord's Work, and deliver a notice to Tenant
setting forth in reasonable detail the total cost of Landlord's Work, together
with the balance, if any owed by Tenant to Landlord or the amount of any credit
to which Tenant is entitled. If Tenant owes a balance to Landlord, Tenant


                                      -7-
<PAGE>
shall pay such amount to Landlord within ten (10) days of such notice. If Tenant
is entitled to a credit, such amount shall be credited to the next payment of
Annual Rent payable by Tenant to Landlord hereunder.

         Landlord will not approve any construction, alterations, or additions
requiring unusual expense to readapt the Premises to normal office use on lease
termination or increasing the cost of construction, insurance or taxes on the
Building or of Landlord's services called for by Section 5.1 unless Tenant first
gives assurances acceptable to Landlord that such readaptation will be made
prior to such termination without expense to Landlord and makes provisions
acceptable to Landlord for payment of such increased cost. Landlord will also
disapprove any alterations or additions requested by Tenant which will delay
completion of the Premises. Tenant's construction, installation of furnishings,
and later changes or additions shall be coordinated with any work being
performed by Landlord in such manner as to maintain harmonious labor relations
and not to damage the Building or Lot or interfere with Building operations.

3.3      PREPARATION OF PREMISES FOR OCCUPANCY.

         Landlord agrees to use reasonable efforts to substantially complete
Landlord's Work, if any, no later than the Scheduled Term Commencement Date,
subject to delays beyond Landlord's reasonable control, delays caused by Tenant
and Tenant's failure to comply with the provisions of Section 3.2 hereof. The
Premises shall be deemed ready for occupancy on the date on which Landlord's
Work is substantially completed as certified by Landlord's architect, with the
exception of minor items which can be fully completed without material
interference with Tenant and other items which because of the season or weather
or the nature of the item are not practicable to do at the time, provided that
none of said items is necessary to make the Premises tenantable for the
Permitted Uses; provided, however, that if Landlord is unable to complete
construction due to delay in Tenant's compliance with any of the provisions
hereof or due to other delays caused by Tenant (including, without limitation,
Tenant's failure to comply with the provisions of Section 3.2 hereof and any
changes to Landlord's Work requested by Tenant), then the Premises shall be
deemed ready for occupancy no later than the Scheduled Term Commencement Date.

3.4      GENERAL PROVISIONS APPLICABLE TO CONSTRUCTION.

         All construction work required or permitted by this Lease, whether by
Landlord or by Tenant, shall be done in a good and workmanlike manner and in
compliance with all applicable laws and all lawful ordinances, regulations and
orders of governmental authority and insurers of the Building and the Lot.
Either party may inspect the work of the other at reasonable times and promptly
shall give notice of observed defects. Landlord's obligations under Sections 3.2
and 3.3, if any, shall be deemed to have been performed when Tenant commences to
occupy any portion of the Premises for the Permitted Uses except for items which
are incomplete or do not conform with the requirements of Section 3.1 and as to
which Tenant shall in either case have given written notice to Landlord within
three (3) weeks after such commencement. If Tenant shall not have commenced to
occupy the Premises for the Permitted Uses within thirty (30) days after the
Term Commencement Date, a certificate of completion by a licensed architect or
registered engineer shall be conclusive evidence that Landlord has performed all
such obligations


                                      -8-
<PAGE>
except for items stated in such certificate to be incomplete or not in
conformity with such requirements. Tenant acknowledges that the Building may be
undergoing substantial renovation during the Term of the Lease. Tenant
acknowledges that its quiet enjoyment and access to the Demised Premises during
the Term may be disturbed by the noise, dust, vibrations and other effects of
demolition in the Building, provided, however, that Landlord shall use
reasonable efforts to avoid undue interference with Tenant's use of the
Premises.

3.5      ALTERATIONS AND ADDITIONS.

         This Section 3.5 shall apply before and during the Term. Tenant shall
not make any alterations and additions to the Premises except in accordance with
plans and specifications first approved by Landlord. In no event shall any
alterations or additions be considered or approved by Landlord which (a) involve
or might affect any structural or exterior element of the Building or building
mechanical, electrical or plumbing systems, including the common facilities of
the Building, or (b) will require unusual expense to readapt the Premises to
normal office use on Lease termination or increase the cost of construction or
of insurance or taxes on the Building or the Lot. All alterations and additions
shall become a part of the Premises, unless and until Landlord, at its option,
shall specify the same for removal pursuant to Section 6.1.2. All of Tenant's
alterations and additions and installation and delivery of telephone systems,
furnishings, and equipment shall be coordinated with any work being performed by
Landlord and shall be performed in such manner, and by such persons as shall
maintain harmonious labor relations and not cause any damage to the Building or
interference with Building construction or operation and, except for
installation of furnishings, equipment and telephone systems, and except as
otherwise expressly set forth herein, shall be performed by general contractors
first approved by Landlord. Before commencing any work Tenant shall: secure all
licenses and permits necessary therefor; deliver to Landlord a statement of the
names of all its contractors and subcontractors (the identity of which must have
been previously approved by Landlord as hereinabove contemplated) and the
estimated cost of all labor and material to be furnished by them; and cause each
contractor to carry (i) worker's compensation insurance in statutory amounts
covering all the contractor's and subcontractor's employees and (ii)
comprehensive public liability insurance with such limits as Landlord may
reasonably require, but in no event less than a combined single limit of
$1,500,000 (all such insurance to be written in companies approved by Landlord
and insuring Landlord and Tenant as well as the contractors), and to deliver to
Landlord certificates of all such insurance. Tenant agrees to pay promptly when
due, and to defend and indemnify Landlord from and against, the entire cost of
any work done on the Premises by Tenant, its agents, employees or independent
contractors, and not to cause or permit any liens for labor or materials
performed or furnished in connection therewith to attach to the Building or the
Lot and immediately to discharge any such liens which may so attach. Tenant
shall pay within fourteen (14) days after being billed therefor by Landlord, as
additional rent, one hundred percent (100%) of any increase in real estate taxes
on the Premises not otherwise billed to Tenant which shall, at any time after
the commencement of the Term, result from any alteration, addition or
improvement to the Premises made by or on behalf of Tenant.

         In connection with the installation of telecommunication equipment by
Tenant, such installation shall occur only in such locations and in such a
manner as approved in writing by the Landlord and none of such wires, ducts or
equipment shall be located in areas outside the Premises (provided, however,
that Tenant may install wires and cables in risers and ducts outside


                                      -9-
<PAGE>
the Premises which are in existence on the date of this Lease and for which
there exists, in Landlord's sole discretion, adequate space for Tenant's wires
and cables). Telephone switches, antennae, electronic distribution boxes and
similar equipment shall only be located within the Premises. Landlord shall not
be liable for any loss, damage or interruption of service related to such
facilities.

3.6      REPRESENTATIVES.

         Each party authorizes the other to rely in connection with their
respective rights and obligations under this Article III upon approval and other
actions on the party's behalf by Landlord's Representative in the case of
Landlord or Tenant's Representative in the case of Tenant or by any person
designated in substitution or addition by notice to the other party.

                                   ARTICLE IV
                                      RENT

4.1      ANNUAL RENT.

         Tenant agrees to pay rent to Landlord without any offset or reduction
whatever (except as made in accordance with the express provisions of this
Lease), the Annual Rent in equal monthly installments in advance on the first
day of each calendar month included in the Term after the Term Commencement
Date; and for any portion of a calendar month at the beginning or end of the
Term, at the proportionate rate payable for such portion, in advance.

4.2      ANNUAL OPERATING COST ESCALATION.

         In addition to Annual Rent, Tenant shall pay to Landlord as additional
rent, Tenant's Proportionate Share of Annual Operating Costs (as hereinafter
defined) which is in excess of Base Annual Operating Costs ("Tenant's Escalation
Payment"). Tenant's Proportionate Share of Annual Operating Costs shall be
determined by multiplying Annual Operating Costs by Tenant's Proportionate
Share. In the event that the Building is not fully occupied, such Annual
Operating Costs shall be adjusted to reflect the costs which would be incurred
if the Building were 95% occupied.

         Annual Operating Costs shall mean the actual expenses paid or incurred
by Landlord in the operation, maintenance and management of the Building and Lot
and all real estate taxes and assessments, general or special, ordinary or
extraordinary, foreseen or unforeseen, imposed upon the Building and Lot and any
future improvement of whatever kind thereto or thereon. Annual Operating Costs
shall include without limitation:

         (a)      real estate taxes on the Building and Lot and off-site parking
areas (or an equitable portion thereof to the extent such off-site parking areas
are used by tenants of more than one building); (b) installments and interest on
assessments for public betterment or public improvements; (c) expenses of any
proceedings for abatement of taxes and assessments with respect to any fiscal
year or fraction of a fiscal year; (d) service, repair, replacement and other
maintenance to the Building and Lot and components thereof; (e) wages and
salaries (and taxes and other charges imposed upon employers with respect to
such wages and salaries) and fringe benefits and worker's compensation insurance
premiums paid to persons employed by the


                                      -10-
<PAGE>
Landlord for rendering service in the operation, maintenance, and repair of the
Building and Lot and related facilities and off-site parking areas and
amenities; (f) cost of independent contractors hired for the operation,
maintenance and repair of the Building and Lot and related facilities and
amenities (which payments may be to affiliates of Landlord provided the same are
at reasonable rates consistent with the type of occupancy and the services
rendered); (g) costs of electricity, steam, water, fuel, heating, lighting, air
conditioning, sewer, and other utilities chargeable to the operation and
maintenance of the Building and Lot net of tenant's electric (collectively,
"Utility Charges"); (h) cost of insurance including insurance deductible for and
relating to the Building and the Lot, including fire and extended coverage (or
such greater coverages as Landlord may elect to carry), elevator, boiler,
sprinkler leakage, water damage, public liability and property damage, plate
glass, and rent protection; (i) costs of supplies; (j) costs of window cleaning,
janitorial services, security services, landscaping, snow and ice removal and
painting; (k) sales or use taxes on supplies and services; (l) consulting,
accounting fees, legal, tax appeal, engineering and other professional fees and
expenses; (m) management fees; (n) contributions, costs or expenses related to
common areas or facilities and off-site parking areas of any office park or
development of which the Building or Lot are a part, (o) alterations and
improvements to the Building and Lot which are not capital in nature made by
reason of any requirement of any insurance underwriters or any federal, state,
or local statutes, regulations, ordinances, or any other duly constituted public
authorities having jurisdiction over the Building and Lot; and (p) all Expense
of Operation of the Food Services as defined in section 5.1.5 and (q) without
limiting any of the foregoing, any other expense or charge which, in accordance
with sound accounting and management principles generally accepted, would be
construed as an operating expense. The term Operating Costs shall not include
the interest and amortization on mortgages for the Building and Lot or leasehold
interests therein; any charge for depreciation; leasing commissions or legal
fees for the negotiation and enforcement of leases; and the cost of special
services rendered to tenants (including Tenant) for which a special charge is
made.

         In the event Landlord shall make a capital expenditure for Essential
Capital Improvements, as hereinafter defined, during any year, the annual
amortization of such expenditure (determined by dividing the amount of the
expenditure by the useful life of the improvement, as determined by Landlord),
together with interest at the greater of the Prime Rate prevailing plus 2% or
Landlord's actual borrowing rate for such Essential Capital Improvements shall
be deemed part of Annual Operating Costs for each year of such useful life. As
used herein, "Essential Capital Improvement" means any of the following:

         (i)      a labor saving device, energy saving device or other
installation, improvement or replacement which reduces Operating Costs as
referred to above, whether or not voluntary or required by governmental mandate;
or

         (ii)     an installation, change, improvement, addition, alteration, or
removal of any architectural barriers, whether or not the foregoing are
structural in nature, made by reason of any governmental requirement whether or
not such governmental requirement exists on the date of the execution of this
Lease if such governmental requirement is or will be applicable generally to
similar office buildings; or


                                      -11-
<PAGE>
         (iii)    an installation or improvement which directly enhances the
health or safety of tenants in the Building generally, whether or not voluntary
or required by governmental mandate (as for example, without limitation, for
life safety or security); or

         (iv)     costs or expenditures incurred in replacing compressors and
refrigeration equipment in order to comply with regulations regarding ozone
depleting refrigerants or resulting from the excessive cost of or inability to
obtain such materials.

         In no event shall the amount of Controllable Operating Costs (as
defined below) included in Operating Costs in any year exceed the product of (x)
Controllable Operating Costs for 1998 and (y) the sum of (1) one hundred percent
(100%) and (2) the product of five percent (5%) and the difference between such
year and 1998. In illustration of the foregoing, in the year 2001, Controllable
Operating Costs may not exceed 115% of Controllable Operating Costs for 1998
(115% being the sum of 100% and 5% times 3, or the difference between 2001 and
1998). For purposes hereof, "Controllable Operating Costs" shall be equal to all
Operating Costs other than real estate taxes, Utility Charges, cost of insurance
and snow removal and cleaning costs.

4.3      ESTIMATED ANNUAL OPERATING EXPENSE ESCALATION PAYMENT.

         If, with respect to any fiscal year or fraction thereof during the
Term, Landlord estimates that Tenant will be obligated to pay Tenant's
Escalation Payment, then Tenant shall pay, as additional rent, on the first day
of each month of such fiscal year and each ensuing fiscal year thereafter, an
estimate equal to 1/12th of Tenant's Escalation Payment for the respective
fiscal year ("Estimated Monthly Operating Expense Cost Payments"), with an
appropriate additional payment or refund to be made within 30 days after
Landlord's Statement (as hereafter defined) is delivered to Tenant. Landlord may
adjust such Estimated Monthly Annual Operating Cost Payment from time to time
and at any time during a fiscal year, and Tenant shall pay, as additional rent,
on the first day of each month following receipt of Landlord's notice thereof,
the adjusted Estimated Monthly Annual Operating Cost Payment.

         As soon as practicable after the end of each fiscal year ending during
the Term and after lease termination, Landlord shall render a statement
("Landlord's Statement") in reasonable detail and according to usual accounting
practices certified by Landlord and showing for the preceding fiscal year or
fraction thereof, as the case may be, Landlord's Annual Operating Costs,
Tenant's Proportionate Share thereof, and Tenant's Escalation Payment, as
defined above. Landlord shall use reasonable efforts to render Landlord's
Statement with ninety (90) days after the end of each fiscal year, but
Landlord's failure to do so shall not affect Tenant's obligations hereunder.

         Tenant, its authorized agent or representative, or a public accounting
firm selected by Tenant, shall have the right, exercisable by written notice
given to Landlord ("Tenant's Audit Notice") within thirty (30) days after
Landlord's Statement is rendered with respect to any applicable calendar year or
portion thereof, to inspect those portions of the books of Landlord relating to
Landlord's Operating Costs at the offices of Landlord's Managing Agent during
business hours, upon not less than thirty (30) days' advance written notice to
Landlord, for the purpose of verifying information set forth in Landlord's
Statements and conducting an audit. Any such inspection and audit shall be
completed within sixty (60) days after Tenant's Audit


                                      -12-
<PAGE>
Notice to Landlord and shall be at the sole cost and expense of Tenant, unless
it is determined that Landlord's Operating Costs have been overstated by greater
than five percent (5%) in Landlord's Statement in which case Landlord shall
reimburse Tenant for the reasonable cost of the audit, provided, however, that
if Landlord disagrees with such audit, the amount of Landlord's Operating Costs
shall be determined by arbitration in accordance with the rules of the American
Arbitration Association. To the extent that Landlord's Operating Costs have been
misstated in Landlord's Statement an appropriate credit to Tenant or payment to
Landlord shall be made. Notwithstanding any other provision of this Lease, in
the event that Tenant fails or is unable to exercise its right to conduct an
audit with respect to any calendar year or portion thereof by giving Tenant's
Audit Notice to Landlord within thirty (30) days after delivery of Landlord's
Statement with respect to such calendar year or portion thereof, or fails to
complete such audit and notify Landlord of the results thereof within sixty (60)
days after Tenant's Audit Notice, then such right shall lapse with respect to
such calendar year, or portion thereof, as the case may be, time being of the
essence with respect to the exercise thereof, and Tenant shall be conclusively
deemed to have consented to the amount shown on such Landlord's Statement as the
actual amount of Landlord's Operating Costs for such calendar year, or portion
thereof, as the case may be. In the event that Tenant shall timely exercise its
right to conduct such an audit with respect to any calendar year, or portion
thereof, Tenant shall hold, and shall cause its auditors, agents and
consultants, and their respective employees to hold, any information obtained in
conducting such audit in confidence, and not to disclose such information to any
party without the prior written consent of Landlord, which may be given or
withheld in Landlord's sole discretion (provided, however, that the foregoing
shall not be deemed to limit or impair Tenant's rights to disclose such
information in connection with any legal action brought by Tenant against
Landlord to enforce its rights under this Section 4.3).

4.4      ELECTRICITY.

         Tenant will be billed for electricity for Tenant's lights and outlet
consumption on a monthly basis based on an annual estimate of $1.00 per rentable
square foot. Should the actual average expense to Landlord per square foot for
Tenant's electricity be different, an additional charge or a credit will be made
at the end of each year's occupancy to be paid with or credited against the next
monthly charge for Tenant's electricity. Notwithstanding the foregoing, Landlord
reserves the right to assess Tenant's charge for electricity based on an
engineer's survey of Tenant's electrical usage conducted from time to time or on
the sub-metering of all or part of the Premises. Such charges for Tenant's
electricity shall be paid by Tenant as additional rent at the same time and in
the same manner as payments of Annual Rent.

         Tenant covenants and agrees that its use of electric current shall not
exceed 4.0 watts per square foot of usable floor area and that its total
connected lighting load will not exceed the maximum load from time to time
permitted by applicable governmental regulations. In the event Tenant introduces
into the Premises personnel or equipment which overloads the capacity of the
Building's electrical system or in any other way interferes with the system's
ability to perform properly, supplementary systems including check meters may,
if and as needed, at Landlord's option, be provided by Landlord, at Tenant's
expense. Landlord shall not in any way be liable or responsible to Tenant for
any loss or damage or expense which Tenant may sustain or incur if, during the
Term of this Lease, either the quantity or character of electric current is
changed or


                                      -13-
<PAGE>
electric current is no longer available or suitable for Tenant's requirements
due to a factor or cause beyond Landlord's control.

         Landlord reserves the exclusive right to provide electric and other
utility service to the Building. Tenant may request permission from Landlord
(which consent may be withheld in its sole discretion) to arrange electric and
other utility service exclusively serving the Premises. Should such permission
be granted, however, such service shall be installed only in such locations and
in such manner as shall be specifically approved by Landlord in its sole
discretion, Tenant shall be responsible for restoration of any damage caused by
such installation and Tenant shall be responsible for removal of such
installations at the termination of this Lease. Landlord may limit Tenant's
choice of electrical or other utility providers in order to avoid proliferation
of such services to the Building or for any other reason. In no event, however,
shall Landlord be responsible for any damages or inconvenience caused by
interruption in or poor quality of electricity or other utility services
provided to the Building or the Premises unless such damages are caused by the
negligence of Landlord, its agents or employees.

4.5      CHANGE OF FISCAL YEAR.

         Landlord shall have the right from time to time to change the periods
of accounting under Section 4.2 to any annual period other than a calendar year,
and upon any such change all items referred to in Section 4.2 shall be
appropriately apportioned. In all Landlord's Statements rendered under Section
4.2, amounts for periods partially within and partially without the accounting
periods shall be appropriately apportioned, and any items which are not
determinable at the time of a Landlord's Statement shall be included therein on
the basis of Landlord's estimate, and with respect thereto Landlord shall render
promptly after determination a supplemental Landlord's Statement, and
appropriate adjustment shall be made according thereto. All Landlord's
Statements shall be prepared on an accrual basis of accounting.

4.6      PAYMENTS.

         All payments of Annual Rent and additional rent shall be made to
Managing Agent, or to such other person as Landlord may from time to time
designate. If any installment of Annual Base Rent or additional rent or payments
due on account of leasehold improvements is paid more than 10 days after the due
date thereof, at Landlord's election, it shall bear interest at a rate equal to
the average prime commercial rate from time to time established by the three
largest national banks in Boston, Massachusetts plus 4% per annum from such due
date, which interest shall be immediately due and payable as further additional
rent.

                                   ARTICLE V
                              LANDLORD'S COVENANTS

5.1      LANDLORD'S COVENANTS DURING THE TERM.

         Landlord covenants during the Term:

         5.1.1    Building Services. To furnish during normal working hours
heat, air-conditioning, elevator service and hot and chilled water service and
after normal working hours on business days cleaning service as shown in Exhibit
C. "Normal working hours" shall


                                      -14-
<PAGE>
mean the hours of 8:00 a.m. through 5:00 p.m. Monday through Friday and the
hours of 8:00 a.m. through 1:00 p.m. on Saturdays, and no hours on legal
holidays and Sundays; provided, however, that Tenant shall have access to the
Building 24 hours a day, 365 days a year, by means of a key or other access
device to the main lobby of the Building to be provided to Tenant by Landlord.
Tenant shall pay when due all amounts and charges for such services during hours
other than normal working hours and shall indemnify and hold harmless Landlord
from and against any and all claims, liabilities, damages, losses, costs and
expenses (including reasonable attorneys' fees) in connection therewith.
Landlord is not and shall not be required to furnish to Tenant or any other
occupant of the Premises telephone or other communication service.

         5.1.2    Additional Building Services. To furnish, through Landlord's
employees or independent contractors, reasonable additional Building operation
services upon reasonable advance request of Tenant at equitable rates including
a reasonable administrative fee from time to time established by Landlord to be
paid by Tenant;

         5.1.3    Repairs. Except as otherwise provided in Article VII, to make
such repairs to the roof, exterior walls, floor slabs, other structural
components and common facilities of the Building and all common walkways,
driveways, loading docks and parking facilities serving the Building as may be
necessary to keep them in serviceable condition; and

         5.1.4    Tenant Directory. To include Tenant's name on the Tenant
directory maintained by Landlord in the main lobby of the Building and on the
floor of the Building on which the Premises are located, and to provide a
Building standard sign on or adjacent to the entrance door to the Premises.

         5.1.5    Food Service. Landlord (or any affiliate or agent designated
by Landlord) may provide, within the Building or any building in the office park
in which the Building is located known as CambridgePark (an "Office Park
Building"), a food service of a size, type, location and serving capacity as
Landlord shall deem suitable, in its sole discretion. All losses incurred by
Landlord in operating the food service facility during any fiscal year and
properly allocable to the Building and other Office Park Buildings (the "Food
Service Losses") shall be added to the Landlord's Annual Operating Costs for the
year in which such losses were incurred for the purpose of calculating the
Tenant's Escalation Payment pursuant to Section 4.2. All profits realized by the
Landlord in operating the food service facility during any fiscal year and
properly allocable to the Building and other Office Park Buildings (the "Food
Service Profits") shall be credited against the Landlord's Annual Operating
Costs for the Building and other Office Park Buildings for such year. For the
purposes of this Section 5.1.5, the Food Service Profits of Losses for any year
shall be calculated by deducting from the Gross Receipts of the Food Service (as
hereinafter defined) all Expenses of Operation (as hereinafter defined). Gross
Receipts of the Food Service as used herein are defined to mean the total amount
in dollars of the actual prices charged, in cash, for food and beverages served
at the facility, excluding sums collected for any sales tax or excise tax. The
Expenses of Operation of the food service shall mean all expenses of operating
the food service facility, including without limitation, salaries, wages,
employment taxes and fringe benefits, food service administration costs, food
costs, concessionaire's costs, operating costs, equipment maintenance and repair
costs, if any, plus an annual return to the Landlord upon its investment in
establishing the food service facility (including without


                                      -15-
<PAGE>
limitation the cost of furniture, equipment, furnishings, and related mechanical
systems) equal to fifteen percent (15%) of its investment or $50,000, whichever
is less.

         If during any six-month period, the mathematical average of the number
of luncheon meals served by the food service facility per day is fewer than 300,
or the Food Service Losses incurred by the Landlord in operating the food
service facility during such six-month period exceed $25,000, then the Landlord
shall have the right and option, in its sole discretion, to take any steps
necessary to reduce or eliminate the losses (including without limitation,
modification or termination of the food service), unless one hundred percent
(100%) of the tenants occupying the Building agree that the Landlord's Annual
Operating Costs hereunder for the purpose of calculating the Annual Operating
Expense Escalation shall include one hundred percent (100%) of the Food Service
Losses, without limitation.

         Landlord reserves the right to approve Tenant's use of a food service
operator other than the Landlord's food service operator, if any. Such approval
will not be unreasonably withheld.

         5.1.6    Quiet Enjoyment. That Landlord has the right to make this
Lease and that Tenant on paying the rent and performing its obligations
hereunder shall peacefully and quietly have, hold and enjoy the Premises
throughout the Term without any manner of hindrance or molestation from Landlord
or anyone claiming under Landlord, subject however to all the terms and
provisions hereof. Landlord represents and warrants to the Tenant that it holds
fee simple title to the Building and the Lot.

5.2      INTERRUPTIONS.

         Landlord shall not be liable to Tenant for any compensation or
reduction of rent by reason of inconvenience or annoyance, injury, death or for
loss of business arising from power or other utility losses or shortages, air
pollution or contamination, or from the necessity of Landlord's entering the
Premises for any of the purposes in this Lease authorized, or for repairing the
Premises or any portion of the Building or the Lot or for any interruption or
termination (by reason of any cause reasonably beyond Landlord's control,
including without limitation, loss of any applicable license or government
approval) of the food service provided by Landlord pursuant to Section 5.1.5. In
case Landlord is prevented or delayed from making any repairs, alterations or
improvements, or furnishing any service or performing any other covenant or duty
to be performed on Landlord's part, by reason of any cause beyond Landlord's
reasonable control, Landlord shall not be liable to Tenant therefor, nor, except
as expressly otherwise provided in Article VII, shall Tenant be entitled to any
abatement or reduction of rent by reason thereof, nor shall the same give rise
to a claim in Tenant's favor that such failure constitutes actual or
constructive total or partial, eviction from the Premises.

         Landlord reserves the right to stop any service or utility system when
necessary by reason of accident or emergency or until necessary repairs have
been completed. Except in case of emergency repairs, Landlord will give Tenant
reasonable advance notice of any contemplated stoppage and will use reasonable
efforts to avoid unnecessary inconvenience to Tenant by reason thereof.


                                      -16-
<PAGE>
         Landlord also reserves the right to institute such policies, programs
and measures as may be necessary, required or expedient for the conservation or
preservation of energy or energy services or as may be necessary or required to
comply with applicable codes, rules, regulations or standards.

                                   ARTICLE VI
                               TENANT'S COVENANTS

6.1      TENANT'S COVENANTS DURING THE TERM.

         Tenant covenants during the Term and such further time as Tenant
occupies any part of the Premises:

         6.1.1    Tenant's Payments. To pay when due (a) all Annual Rent, (b)
all taxes which may be imposed on Tenant's personal property in the Premises
(including, without limitation, Tenant's fixtures and equipment) regardless to
whomever assessed, (c) as additional rent, Tenant's Escalation Payments, (d) all
charges by public utilities for electricity, telephone (including service
inspections therefor) and other services rendered to the Premises not otherwise
required hereunder to be furnished by Landlord without charge and not consumed
in connection with any services required to be furnished by Landlord without
charge, (e) as additional rent, all costs for Landlord's Work attributable to
change orders and any work performed in the Premises by Landlord or Tenant in
excess of Landlord's Work, and (f) as additional rent, all charges to Landlord
for services rendered pursuant to Section 5.1.2 hereof.

         6.1.2    Repairs and Yielding Up. Except as otherwise provided in
Article VII and Section 5.1.3, to keep the Premises in good order, repair and
condition, reasonable wear only excepted; and at the expiration or termination
of this Lease peaceably to yield up the Premises and all alterations and
additions therein, including all telephone and data wiring installed by or at
the request of Tenant, in such order, repair and condition, first removing all
goods and effects of Tenant and any alterations and additions, the removal of
which is required by agreement or specified to be removed by Landlord by notice
to Tenant, and repairing all damage caused by such removal and restoring the
Premises and leaving them in broom-clean condition.

         6.1.3    Occupancy and Use. Continuously from the Commencement Date, to
use and occupy the Premises only for the Permitted Uses; not to injure or deface
the Building or the Lot; to keep the Premises clean and in a neat and orderly
condition; and not to permit in the Premises any use thereof which is improper,
offensive, contrary to law or ordinances, or liable to create a nuisance or to
create an unsafe or hazardous condition, or to invalidate or increase the
premiums for any insurance on the Building or its contents or liable to render
necessary any alteration or addition to the Building; not to dump, flush, or in
any way introduce any Hazardous Materials or any other toxic substances into the
septic, sewage or other waste disposal system serving the Premises, not to
generate, store or dispose of Hazardous Materials in or on the Premises, or the
Lot or dispose of Hazardous Materials from the Premises to any other location
without the prior written consent of Landlord and then only in compliance with
the Resource Conservation and Recovery Act of 1976, as amended, 42 U.S.C.
Section 6901 et seq., and all other applicable laws, ordinances and regulations;
to notify Landlord of any incident which would require the filing of a notice
under applicable federal, state, or local law; not to use, store or dispose of
Hazardous


                                      -17-
<PAGE>
Materials on the Premises without first submitting to Landlord a list of all
such Hazardous Materials and all permits required therefor and thereafter
providing to Landlord on an annual basis Tenant's certification that all such
permits have been renewed with copies of such renewed permits; and to comply
with the orders and regulations of all governmental authorities with respect to
zoning, building, fire, health and other codes, regulations, ordinances or laws
applicable to the Premises. As used herein, "Hazardous Materials" shall mean and
include, any petroleum product and all hazardous or toxic substances or wastes
including any asbestos-containing materials, waste oils, solvents and
chlorinated oils, polychlorinated biphenyls (PCBs), or substances which are
included under or regulated by any federal, state or local law, rule or
regulation (whether now existing or hereafter enacted or promulgated, as they
may be amended from time to time) pertaining to the environment, contamination
or clean-up (all such laws, rules and regulations being referred to collectively
as the "Environmental Laws"), including, without limitation, the Comprehensive
Environmental Response Compensation and Liability Act of 1980, as amended, 42
U.S.C. Section 9601 and regulations adopted pursuant to said Act.
Notwithstanding the foregoing, Tenant may use cleaning solvents and other
materials ordinary and customary to office use in usual amounts, provided the
use, storage and disposal of the same are in strict compliance with all
Environmental Laws.

         6.1.4    Rules and Regulations. To comply with the Rules and
Regulations set forth in Exhibit D and all other reasonable Rules and
Regulations hereafter made by Landlord, of which Tenant has been given notice,
for the care and use of the Building and the Lot and their facilities and
approaches, it being understood that Landlord shall not be liable to Tenant for
the failure of other tenants of the Building to conform to such Rules and
Regulations.

         6.1.5    Safety Appliances. To keep the Premises equipped with all
safety appliances required by law or ordinance or any other regulation of any
public authority because of any use made by Tenant and to procure all licenses
and permits so required because of such use and, if requested by Landlord, to do
any work so required because of such use, it being understood that the foregoing
provisions shall not be construed to broaden in any way Tenant's Permitted Uses.

         6.1.6    Assignment and Subletting.

                  Not without the prior written consent of Landlord to assign,
mortgage, pledge, encumber, sell or transfer this Lease, in whole or in part, to
make any sublease, or to permit occupancy of the Premises or any part thereof by
anyone other than Tenant, voluntarily or by operation of law (it being
understood that in no event shall Landlord consent to any such assignment,
sublease or occupancy if the same is on terms more favorable to the successor
occupant than to the then occupant when Landlord or an affiliate of Landlord has
reasonably equivalent space available in the Building or another Office Park
Building or will have such space available on the effective date of the proposed
assignment, sublease or occupancy); as additional rent, to reimburse Landlord
promptly for reasonable legal and other expenses incurred by Landlord in
connection with any request by Tenant for consent to assignment or subletting;
no assignment or subletting shall affect the continuing primary liability of
Tenant (which, following assignment, shall be joint and several with the
assignee); no consent to any of the foregoing in a specific instance shall
operate as a waiver in any subsequent instance. Landlord's consent to any
proposed assignment or subletting is required both as to the terms and
conditions thereof, and as to the creditworthiness of the proposed assignee or
subtenant given the nature of


                                      -18-
<PAGE>
the proposed assignment or sublease and the consistency of the proposed
assignee's or subtenant's business with other uses and tenants in the Building.
In the event that any assignee or subtenant pays to Tenant any amounts in excess
of the Annual Rent and additional rent then payable hereunder, or pro rata
portion thereof on a square footage basis for any portion of the Premises,
Tenant shall promptly pay fifty percent (50%) of said excess to Landlord as and
when received by Tenant. If Tenant requests Landlord's consent to assign this
Lease or sublet more than twenty-five (25%) of the Premises, Landlord shall have
the option ("Landlord's Recapture Right"), exercisable by written notice to
Tenant given within ten (10) days after receipt of such request, to terminate
this Lease as of a date specified in such notice which shall be not less than
thirty (30) or more than sixty (60) days after the date of such notice. Landlord
may, in its sole discretion, withhold consent to any proposed assignment or
subletting to another tenant of the Building or an affiliate of such tenant or
an entity (or affiliate of any entity) with which Landlord was negotiating for
space in the Building during the preceding twelve (12) months.

         If, at any time during the Term of this Lease, Tenant is:

                           (i)      a corporation, limited liability company or
a trust (whether or not having shares of beneficial interest) and there shall
occur any change in the identity of any of the persons then having power to
participate in the election or appointment of the directors, trustees or other
persons exercising like functions and managing the affairs of Tenant; or

                           (ii)     a partnership or association or otherwise
not a natural person (and is not a corporation, limited liability company or a
trust) and there shall occur any change in the identity of any of the persons
who then are members of such partnership or association or who comprise Tenant;

         Tenant shall so notify Landlord and Landlord may terminate this Lease
by notice to Tenant given within ninety (90) days thereafter if, in Landlord's
reasonable judgment, the credit of Tenant is thereby materially impaired. This
paragraph shall not apply if the initial Tenant named herein is a corporation
and the outstanding voting stock thereof is listed on a recognized securities
exchange.

         Notwithstanding the foregoing (but without derogating from Landlord's
Recapture Right), Landlord agrees not to unreasonably withhold its consent to an
assignment of this Lease or a sublease of a portion of the Premises by Tenant
provided that (a) Tenant is not in default hereunder beyond any applicable grace
period (provided that it shall be a condition of the approval of any applicable
grace period (provided that it shall be a condition of the approval of any
assignment or sublease that the default in question is cured prior to the
expiration of the applicable grace period), (b) Landlord determines in its
reasonable discretion that the proposed assignee or sublessee (i) is a
first-class office establishment and would use the leased premises solely for
the Permitted Uses, and (ii) has a net worth equal to or greater than the
greater of (x) the net worth of Tenant as of the date of execution of this Lease
or (y) the net worth of Tenant at the time of such request, as evidenced by
financial statements of Tenant and the proposed assignee or sublessee in scope
and substance satisfactory to Landlord and in conformity with generally accepted
accounting principles and, if requested by Landlord, certified by a certified
public accountant acceptable to Landlord, (c) the proposed assignee or sublessee
shall not be (i) a tenant of the Building or an affiliate of such tenant or (ii)
an entity (or an


                                      -19-
<PAGE>
affiliate of any entity) with which Landlord was negotiating for space in the
Building during the preceding twelve (12) months, and (d) the proposed
assignment or sublease will not result in a breach of any covenant or obligation
of Landlord under any other lease or permit any other tenant to terminate or
modify its lease. In the case of any assignment hereunder, the proposed assignee
must specifically assume and agree in writing to be bound by all of the
obligations of the Tenant hereunder.

         6.1.7    Indemnity. To defend, with counsel approved by Landlord, all
actions against Landlord, Managing Agent, any partner, member, trustee,
stockholder, officer, director, employee or beneficiary of Landlord or Managing
Agent, holders of mortgages secured by the Premises or the Building and Lot and
any other party having an interest in the Premises ("Indemnified Parties") with
respect to, and to pay, protect, indemnify and save harmless, to the extent
permitted by law, all Indemnified Parties from and against, any and all
liabilities, losses damages, costs, expenses (including reasonable attorneys'
fees and expenses), causes of action, suits, claims, demands or judgments of any
nature arising from or related to (i) injury to or death of any person, or
damage to or loss of property, on the Premises or on adjoining sidewalks,
streets or ways, or connected with the use, condition or occupancy of any of the
foregoing unless caused by the negligence of Landlord or its servants or agents,
(ii) violation of this Lease, or (iii) any act, fault, omission, or other
misconduct of Tenant or its agents, employees, contractors, licensees,
sublessees or invitees or (iv) the use, generation, storage or disposal of
Hazardous Materials by Tenant or its agents, employees or invitees on the
Premises, the Building or Lot or any portion thereof or any surrounding area,
including, without limitation, any and all liabilities, losses, damages, costs,
expenses (including reasonable attorneys' fees and expenses), causes of action,
suits, claims, demands or judgments of any nature arising from or related to
removal or other remediation of any Hazardous Materials or precautions required
to protect against the release of Hazardous Materials by Tenant or its agents,
employees, contractors, licensees, sublessees or invitees into the environment
to the extent required by any Environmental Laws (as defined below).

         6.1.8    Tenant's Insurance. To maintain (a) all risk property
insurance in amounts sufficient to fully cover Tenant's improvements and all
property in the Premises which is not owned by Landlord and (b) commercial
general liability insurance on the Premises, with Landlord named as an
additional insured, indemnifying Landlord and Tenant against all claims and
demands for (i) injury to or death of any person or damage to or loss of
property, on the Premises, or connected with the use, condition or occupancy of
any of the foregoing unless caused by the negligence of Landlord or its servants
or agents, or (ii) any act, fault or omission, or other misconduct of Tenant or
its agents, employees, contractors, licensees, sublessees or invitees, in
amounts which shall, at the beginning of the Term, be at least equal to the
limits set forth in Section 1.1, and from time to time during the Term, shall be
for such higher limits, if any, as are customarily carried in the area in which
the Premises are located on property similar to the Premises and used for
similar purposes, and shall be written on the "Occurrence Basis," and to furnish
Landlord with certificates thereof. Such insurance shall be effected under valid
and enforceable policies with insurers authorized to do business in
Massachusetts as stock or mutual companies that are rated in the current edition
of Best's Key Rating Guide, Property and Casualty as A and as Class VII or
higher. Such policies shall name Landlord and Tenant as the insureds as their
respective interests may appear. Not later than the first to occur of (a) the
Commencement Date or (b) the commencement of any activities by Tenant in or
about the


                                      -20-
<PAGE>
Premises and thereafter not less than thirty (30) days prior to the expiration
dates of the expiring policies theretofore furnished pursuant to this Section
6.1.8, Tenant shall deliver to Landlord certificates of insurance issued by the
insurers evidencing all such policies in form satisfactory to Landlord,
accompanied by evidence satisfactory to Landlord of payment of the first
installment of the premiums. Each such policy shall provide that it may not be
canceled and that its form, terms or conditions may not be changed without at
least thirty (30) days' prior written notice to each insured named therein.

         6.1.9    Tenant's Worker's Compensation Insurance. To keep all of
Tenant's employees working in the Premises covered by worker's compensation
insurance in statutory amounts and to furnish Landlord with certificates
thereof.

         6.1.10   Landlord's Right of Entry. Upon prior oral or written notice
to Tenant (except in the event of an emergency when no such notice shall be
required), to permit Landlord and Landlord's agents entry: to examine the
Premises at reasonable times and, if Landlord shall so elect, to make repairs or
replacements; to remove, at Tenant's expense, any changes, additions, signs,
curtains, blinds, shades, awnings, aerials, or the like not consented to in
writing; and to show the Premises to prospective tenants during the twelve (12)
months preceding expiration of the Term and to prospective purchasers and
mortgagees at all reasonable times.

         6.1.11   Loading. Not to place Tenant's Property, as defined in Section
6.1.13, upon the Premises so as to exceed a rate of fifty (50) pounds of live
load per square foot and not to move any safe, vault or other heavy equipment
in, about or out of the Premises except in such manner and at such times as
Landlord shall in each instance approve. Tenant's business machines and
mechanical equipment which cause vibration or noise that may be transmitted to
the Building structure or to any other leased space in the Building shall be
placed and maintained by Tenant in settings of cork, rubber, spring, or other
types of vibration eliminators sufficient to eliminate such vibration or noise.

         6.1.12   Landlord's Costs. In case Landlord shall be made party to any
litigation commenced by or against Tenant or by or against any parties in
possession of the Premises or any part thereof claiming under Tenant, to pay, as
additional rent, all costs including, without implied limitation, reasonable
counsel fees incurred by or imposed upon Landlord in connection with such
litigation to the extent that Landlord prevails in such litigation and, as
additional rent, also to pay all such costs and fees incurred by Landlord in
connection with the successful enforcement by Landlord of any obligations of
Tenant under this Lease.

         6.1.13   Tenant's Property. All the furnishings, fixtures, equipment,
effects and property of every kind, nature and description of Tenant and of all
persons claiming by, through or under Tenant which, during the continuance of
this Lease or any occupancy of the Premises by Tenant or anyone claiming under
Tenant, may be on the Premises or elsewhere in the Building or on the Lot
("Tenant'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 leakage or bursting of water pipes, steam pipes, or other
pipes, by theft, or from any other cause, no part of said loss or damage is to
be charged to or to be borne by Landlord unless due to the gross negligence or
willful misconduct of Landlord.


                                      -21-
<PAGE>
         6.1.14   Labor or Materialmen's Liens. To pay promptly when due the
entire cost of any work done on the Premises by Tenant, its agents, employees,
or independent contractors; not to cause or permit any liens for labor or
materials performed or furnished in connection therewith to attach to the
Premises; and immediately to discharge or bond over any such liens which may so
attach.

         6.1.15   Changes or Additions. Not to make any changes or additions to
the Premises without Landlord's prior written consent and only in accordance
with Article III hereto, provided that Tenant shall reimburse Landlord for all
reasonable costs incurred by Landlord in reviewing Tenant's proposed changes or
additions, and provided further that, in order to protect the functional
integrity of the Building, all changes and additions shall be performed by
contractors selected from a list of approved contractors prepared by Landlord
from time to time.

         6.1.16   Holdover. To pay to Landlord the greater of one hundred fifty
percent (150%) of (a) the then fair market rent as conclusively determined by
Landlord or (b) the total of the Annual Rent and all additional rent then
applicable for each month or portion thereof Tenant shall retain possession of
the Premises or any part thereof after the termination of this Lease, whether by
lapse of time or otherwise, and also to pay all damages sustained by Landlord on
account thereof (with due credit for all sums previously paid by Tenant to
Landlord pursuant to this Section 6.1.6); the provisions of this subsection
shall not operate as a waiver by Landlord of the right of reentry provided in
this Lease. At the option of Landlord exercised by a written notice given to
Tenant while such holding over continues, such holding over shall constitute an
extension of this Lease for a period of one year.

         6.1.17   Security. To indemnify, 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 or the Lot by reason of the act
of any intruder or any other person in or about the Premises, the Building or
the Lot other than employees or agents of Landlord or Landlord's contractors,
mortgagees, assets or affiliates.

         6.1.18   Tenant Financial Statements. In connection with a proposed
sale or financing of the Building or Lot, or in connection with a default by
Tenant which continues after notice and the expiration of any applicable cure
period, Tenant shall provide Landlord with Tenant's most recent financial
statements (audited, if available) within thirty (30) days of Landlord's notice
to Tenant requesting the same.

                                  ARTICLE VII
                      DAMAGE AND DESTRUCTION; CONDEMNATION

7.1      FIRE OR OTHER CASUALTY.

         7.1.1    Subject to the provisions of Section 7.1.2 hereof, in the
event during the Term hereof the Premises shall be partially damaged (as
distinguished from "substantially damaged" as such term is hereinafter defined)
by fire, explosion, casualty or any other occurrence covered or as may be
required to be covered, as herein provided, by Landlord's insurance or by such
casualty plus required demolition, or by action taken to reduce the impact of
any such event,


                                      -22-
<PAGE>
Landlord shall forthwith proceed to repair such damage and restore the Premises,
or so much thereof as was originally constructed or delivered by Landlord to
substantially its condition at the time of such fire, explosion, casualty or
occurrence, provided that Landlord shall not be obligated to expend for such
repair an amount in excess of the insurance proceeds recovered as a result of
such damage and, further provided that Tenant is not then in default of any of
its obligations under this Lease beyond any applicable cure period. Landlord
shall not be responsible for any delay which may result from any cause beyond
Landlord's reasonable control.

         7.1.2    If, however, (i) the Premises should be damaged or destroyed
(a) by fire or other casualty (1) to the extent of twenty-five percent (25%) or
more of the cost of replacement, or (2) so that twenty-five (25%) or more of the
principal area contained in the Premises shall be rendered untenantable, or (b)
by any casualty other than those which would be covered by a usual and customary
casualty insurance policy with so-called "all-risk" coverage (hereinafter
"substantially damaged"), or (ii) the Premises shall be damaged in whole or in
part during the last year of the Term, or (iii) there shall be damage to the
Premises of a character as cannot reasonably be expected to be repaired within
nine (9) months from the date of casualty, or (iv) such restoration involves the
demolition of or repair of damage to twenty-five percent (25%) or more of the
Premises, or (v) applicable law requires the demolition of the Building or
forbids the rebuilding of the damaged portion of the Building, or (vi) such
restoration requires repairs in an amount in excess of the insurance proceeds
recovered or recoverable, or (vii) Landlord's mortgagee shall require that the
insurance proceeds from such damage or destruction be applied against the
principal balance due on any mortgage, Landlord may, at its option, either
terminate this Lease or elect to repair the Premises and Landlord shall notify
Tenant as to its election within ninety (90) days after such fire or casualty.
If Landlord elects to terminate this Lease, the Term hereof shall end on the
date specified in the notice (which shall be the end of a calendar month and not
sooner than thirty (30) days after such election was made). If Landlord does not
elect to terminate this Lease, then Landlord shall perform such repairs set
forth in Section 7.1.3 hereof and Tenant shall perform such repairs in the
Building as set forth in Section 7.1.4 hereof, and the Term shall continue
without interruption and this Lease shall remain in full force and effect.

         If Landlord has not elected to terminate this Lease and if there shall
be damage to the Premises of a character as cannot (in the judgment of
Landlord's engineer) reasonably be expected to be repaired within nine (9)
months from the date of casualty, then Tenant may, at its option, terminate this
Lease provided that Tenant's election shall be made by notice to Landlord within
thirty (30) days of Landlord's delivery of the estimate of Landlord's engineer
as to the time period required for restoration.

         7.1.3    If Landlord does not elect to terminate this Lease as provided
in Section 7.1.2 hereof and if Tenant is not then in default of any of its
obligations under the Lease beyond any applicable cure period provided for
herein, Landlord shall, provided any third party mortgagee of the Building makes
insurance proceeds available for restoration, promptly after adjustment of any
insurance claim reconstruct as much of the Premises as was originally
constructed by Landlord (it being understood by Tenant that Landlord shall not
be responsible for any reconstruction of leasehold improvements, which
reconstruction is the sole responsibility of Tenant) to substantially its
condition at the time of such damage, but Landlord shall not be


                                      -23-
<PAGE>
responsible for any delays which may result from any cause beyond Landlord's
reasonable control. If Landlord fails to substantially complete such repairs
within twelve (12) months from the date of casualty, then Tenant may, at its
option, terminate this Lease provided that Tenant's election shall be made by
notice to Landlord within thirty (30) days after the end of such nine (9) month
period, and provided further that such election shall be null and void and of no
force and effect if Landlord substantially completes such repairs within thirty
(30) days after the date of such notice.

         7.1.4    If Landlord does not elect to terminate this Lease as provided
in Section 7.1.2 hereof, Tenant shall, at its own cost and expense, repair and
restore the Premises in accordance with the provisions of Section 6.1.15 hereof
to the extent not required to be repaired by Landlord pursuant to the provisions
of this Section 7.1, including, but not limited to, the repairing and/or
replacement of its merchandise, trade fixtures, furnishings and equipment in a
manner and to at least a condition equal to that prior to its damage or
destruction. Tenant agrees to commence the performance of its work when notified
by Landlord that the work to be performed by Tenant can, in accordance with good
construction practices, then be commenced and Tenant shall complete such work as
promptly thereafter as is practicable, but in no event more than 120 days
thereafter.

         7.1.5    All proceeds payable from Landlord's insurance policies with
respect to the Premises shall belong to and shall be payable to Landlord. If
Landlord does not elect to terminate this Lease as provided in Section 7.1.2
hereof, Landlord shall disburse and apply so much of any insurance recovery as
shall be necessary against the cost to Landlord of restoration and rebuilding of
Landlord's work referred to in Section 7.1.3 hereof, subject to the prior rights
of any lessor under a ground or underlying lease covering the Building and/or
the holder of any mortgage liens against the Building.

         7.1.6    In the event that the provisions of Section 7.1.1 or Section
7.1.2 shall become applicable, the Annual Rent and additional rent shall be
abated or reduced proportionately during any period in which, by reason of 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
destruction or damage and ending with the completion by Landlord of such work of
repair and/or reconstruction as Landlord is obligated to do.

7.2      EMINENT DOMAIN.

         If, after the execution and before termination of this Lease, the
entire Premises shall be taken by eminent domain or destroyed by the action of
any public or quasi-public authority, or in the event of conveyance in lieu
thereof, the Term shall cease as of the day possession shall be taken by such
authority, and Tenant shall pay Annual Rent and additional rent up to that date
with a pro-rata refund by Landlord of such Annual Rent and additional rent as
shall have been paid in advance for a period subsequent to the date of the
taking of possession.

         If less than twenty-five percent (25%) of the Premises shall be so
taken or conveyed, this Lease shall cease only with respect to the parts so
taken or conveyed, as of the day possession shall be taken, and Tenant shall pay
rent up to that day, with an appropriate refund by Landlord


                                      -24-
<PAGE>
of such rent as may have been paid in advance for a period subsequent to the
date of the taking of possession, and thereafter the Annual Rent shall be
equitably adjusted. Pending agreement of such rental adjustment, Tenant agrees
to pay to Landlord the Annual Rent and additional rent in effect immediately
prior to the taking by eminent domain. Landlord shall at its expense make all
necessary repairs or alterations so as to constitute the remaining premises a
complete architectural unit as soon as reasonably practicable.

         If more than twenty-five percent (25%) of the Premises shall be so
taken or conveyed, then the Term shall cease only as respects the part so taken
or conveyed, from the day possession shall be taken, and Tenant shall pay rent
to that date with an appropriate refund by Landlord of such rent as may have
been paid in advance for a period subsequent to the date of the taking of
possession, but Landlord shall have the right to terminate this Lease upon
notice to Tenant in writing within thirty (30) days after such taking of
possession. If Landlord does not elect to terminate the Lease, all of the terms
herein provided shall continue in effect except that the Annual Rent and
additional rent shall be equitably adjusted, and Landlord shall make all
necessary repairs or alterations so as to constitute the remaining premises a
complete architectural unit as soon as reasonably practicable.

         In the event that this Lease is not terminated as aforesaid, and
Landlord fails to substantially complete necessary repairs or alterations so as
to constitute the remaining premises a complete architectural unit within twelve
(12) months from the date of the taking, then Tenant may, at its option,
terminate this Lease provided that Tenant's election shall be made by notice to
Landlord within thirty (30) days after the end of such twelve (12) month period,
and provided further that such election shall be null and void and of no force
and effect if Landlord substantially completes such repairs within thirty (30)
days after the date of such notice.

         All compensation awarded for any such taking or conveyance, whether for
the whole or a part of the Premises, shall be the property of Landlord, whether
such damages shall be awarded as compensation for diminution in the value of the
leasehold or of the fee of or underlying leasehold interest in the Premises, and
Tenant hereby assigns to Landlord all of Tenant's right, title and interest in
and to any and all such compensation; provided, however, that Tenant shall be
entitled to seek a separate award for Tenant's stock, trade fixtures and
relocation expense.

         In the event of any taking of the Premises or any part thereof for
temporary use, this Lease shall be and remain unaffected thereby and rent shall
not abate.

                                  ARTICLE VIII
                               RIGHTS OF MORTGAGEE

8.1      PRIORITY OF LEASE.

         This Lease is and shall continue to be subject and subordinate to any
presently existing mortgage or deed of trust of record covering the Lot or
Building or both (the "mortgaged premises"). The holder of any such presently
existing mortgage or deed of trust shall have the election to subordinate the
same to the rights and interests of Tenant under this Lease exercisable by
filing with the appropriate recording office a notice of such election,
whereupon the Tenant's rights and interests hereunder shall have priority over
such mortgage or deed of trust. Landlord


                                      -25-
<PAGE>
shall endeavor to obtain a Non-Disturbance Agreement from the existing mortgagee
of the mortgaged premises.

         Unless the option provided for in the next following sentence shall be
exercised, this Lease shall be superior to and shall not be subordinate to, any
mortgage, deed of trust or other voluntary lien hereafter placed on the
mortgaged premises. The holder of any such mortgage, deed of trust or other
voluntary lien shall have the option to subordinate this Lease to the same,
provided that such holder enters into an agreement with Tenant by the terms of
which the holder will agree to recognize the rights of Tenant under this Lease
and to accept Tenant as tenant of the Premises under the terms and conditions of
this Lease in the event of acquisition of title by such holder through
foreclosure proceedings or otherwise and Tenant will agree to recognize the
holder of such mortgage as Landlord in such event, which agreement shall be made
to expressly bind and inure to the benefit of the successors and assigns of
Tenant and of the holder and upon anyone purchasing the mortgaged premises at
any foreclosure sale. Any such mortgage to which this Lease shall be
subordinated may contain such terms, provisions and conditions as the holder
deems usual or customary.

8.2      RIGHTS OF MORTGAGE HOLDERS; LIMITATION OF MORTGAGEE'S LIABILITY.

         The word "mortgage" as used herein includes mortgages, deeds of trust
or other similar instruments evidencing other voluntary liens or encumbrances,
and modifications, consolidations, extensions, renewals, replacements and
substitutes thereof. The word "holder" shall mean a mortgagee, and any
subsequent holder or holders of a mortgage. Until the holder of a mortgage shall
enter and take possession of the Premises for the purpose of foreclosure, such
holder shall have only such rights of Landlord as are necessary to preserve the
integrity of this Lease as security. Upon entry and taking possession of the
Premises for the purpose of foreclosure, such holder shall have all the rights
of Landlord. Notwithstanding any other provision of this Lease to the contrary,
including without limitation Section 10.4, no such holder of a mortgage shall be
liable, either as mortgagee or as assignee, to perform, or be liable in damages
for failure to perform any of the obligations of Landlord unless and until such
holder shall enter and take possession of the Premises for the purpose of
foreclosure, and such holder shall not in any event be liable to perform or for
failure to perform the obligations of Landlord under Section 3.2. Upon entry for
the purpose of foreclosure, such holder shall be liable to perform all of the
obligations of Landlord (except for the obligations under Section 3.2), subject
to and with the benefit of the provisions of Section 10.4, provided that a
discontinuance of any foreclosure proceeding shall be deemed a conveyance under
said provisions to the owner of the equity of the Premises.

8.3      MORTGAGEE'S ELECTION.

         Notwithstanding any other provision to the contrary contained in this
Lease, if prior to substantial completion of Landlord's obligations under
Article III, any holder of a first mortgage on the mortgaged premises enters and
takes possession thereof for the purpose of foreclosing the mortgage, such
holder may elect, by written notice given to Tenant and Landlord at any time
within ninety (90) days after such entry and taking of possession, not to
perform Landlord's obligations under Article III, and in such event such holder
and all persons claiming under it


                                      -26-
<PAGE>
shall be relieved of all obligations to perform, and all liability for failure
to perform, said Landlord's obligations under Article III, and Tenant may
terminate this Lease and all its obligations hereunder by written notice to
Landlord and such holder given within thirty (30) days after the day on which
such holder shall have given its notice as aforesaid.

8.4      NO PREPAYMENT OR MODIFICATION, ETC.

         Tenant shall not pay Annual Rent, additional rent, or any other charge
more than ten (10) days prior to the due date thereof. No prepayment of Annual
Rent, additional rent or other charge, no assignment of this Lease and no
agreement to modify so as to reduce the rent, change the Term, or otherwise
materially change the rights of Landlord under this Lease, or to relieve Tenant
of any obligations or liability under this Lease, shall be valid unless
consented to in writing by Landlord's mortgagees of record, if any.

8.5      NO RELEASE OR TERMINATION.

         No act or failure to act on the part of Landlord which would entitle
Tenant under the terms of this Lease, or by law, to be relieved of Tenant's
obligations hereunder or to terminate this Lease, shall result in a release or
termination of such obligations or a termination of this Lease unless (i) Tenant
shall have first given written notice of Landlord's act or failure to act to
Landlord's mortgagees of record, if any, specifying the act or failure to act on
the part of Landlord which could or would give basis to Tenant's rights and (ii)
such mortgagees, after receipt of such notice, have failed or refused to correct
or cure the condition complained of within a reasonable time thereafter, but
nothing contained in this Section 8.5 shall be deemed to impose any obligation
on any such mortgagee to correct or cure any such condition. "Reasonable time"
as used above means and includes a reasonable time to obtain possession of the
mortgaged premises, if the mortgagee elects to do so, and a reasonable time to
correct or cure the condition if such condition is determined to exist.

8.6      CONTINUING OFFER.

         The covenants and agreements contained in this Lease with respect to
the rights, powers and benefits of a mortgagee (particularly, without limitation
thereby, the covenants and agreements contained in this Article VIII) constitute
a continuing offer to any person, corporation or other entity, which by
accepting or requiring an assignment of this Lease or by entry or foreclosure
assumes the obligations herein set forth with respect to such mortgagee; such
mortgagee is hereby constituted a party to this Lease as an obligee hereunder to
the same extent as though its name were written hereon as such; and such
mortgagee shall be entitled to enforce such provisions in its own name. Tenant
agrees on request of Landlord to execute and deliver from time to time any
agreement which may reasonably be deemed necessary to implement the provisions
of this Article VIII.

8.7      MORTGAGEE'S APPROVAL.

         Landlord's obligation to perform its covenants and agreements hereunder
is subject to the condition precedent that this Lease be approved by the holder
of any mortgage of which the Premises are a part and by the issuer of any
commitment to make a mortgage loan which is in effect on the date hereof.


                                      -27-
<PAGE>
                                   ARTICLE IX
                                     DEFAULT

9.1      EVENTS OF DEFAULT.

         If any default by Tenant continues, in case of Annual Rent, additional
rent or any other monetary obligation to Landlord for more than five (5) days
after notice (provided that no such notice shall be required if Tenant has
defaulted in any monetary obligation within the previous twelve (12) month
period), or if Tenant fails to provide an estoppel certificate in accordance
with Section 10.10 hereof, or if any default by Tenant continues in any other
case for more than thirty (30) days after notice and such additional time, if
any, as is reasonably necessary to cure the default if the default is of such a
nature that it cannot reasonably be cured in thirty (30) days and Tenant
promptly commences to cure such default and diligently pursues such cure without
interruption to completion; or if Tenant becomes insolvent, fails to pay its
debts as they fall due, files a petition under any chapter of the U.S.
Bankruptcy Code, 11 U.S.C. 101 et seq., as it may be amended (or any similar
petition under any insolvency law of any jurisdiction), or if such petition is
filed against Tenant; or if Tenant proposes any dissolution, liquidation,
composition, financial reorganization or recapitalization with creditors, makes
an assignment or trust mortgage for benefit of creditors, or if a receiver,
trustee, custodian or similar agent is appointed or takes possession with
respect to any property of Tenant; or if the leasehold hereby created is taken
on execution or other process of law in any action against Tenant; then, and in
any such case, Landlord and the agents and servants of Landlord may, in addition
to and not in derogation of any remedies for any preceding breach of covenant,
immediately or at any time thereafter while such default continues and without
further notice, at Landlord's election, do any one or more of the following: (1)
give Tenant written notice stating that the Lease is terminated, effective upon
the giving of such notice or upon a date stated in such notice, as Landlord may
elect, in which event the Lease shall be irrevocably extinguished and terminated
as stated in such notice without any further action, or (2) with or without
process of law, in a lawful manner enter and repossess the Premises as of
Landlord's former estate, and expel Tenant and those claiming through or under
Tenant, and remove its and their effects, without being guilty of trespass, in
which event the Lease shall be irrevocably extinguished and terminated at the
time of such entry, or (3) pursue any other rights or remedies permitted by law.
Any such termination of the Lease shall be without prejudice to any remedies
which might otherwise be used for arrears of rent or prior breach of covenant,
and in the event of such termination Tenant shall remain liable under this Lease
as hereinafter provided. Tenant hereby waives all statutory rights (including,
without limitation, rights of redemption, if any) to the extent such rights may
be lawfully waived, and Landlord, without notice to Tenant, may store Tenant's
effects and those of any person claiming through or under Tenant at the expense
and risk of Tenant and, if Landlord so elects, may sell such effects at public
auction or private sale and apply the net proceeds to the payment of all sums
due to Landlord from Tenant, if any, and pay over the balance, if any, to
Tenant.

9.2      TENANT'S OBLIGATIONS AFTER TERMINATION.

         In the event that this Lease is terminated under any of the provisions
contained in Section 9.1 or shall be otherwise terminated for breach of any
obligation of Tenant, Tenant covenants to pay forthwith to Landlord, as
compensation, (i) the excess of the total rent reserved for the residue of the
Term over the rental value of the Premises for said residue of the Term and (ii)
the


                                      -28-
<PAGE>
unamortized portion of the actual out-of-pocket costs and expenses incurred by
Landlord in completing Landlord's Work and fees and commissions paid to the
Broker, amortized on a straight-line reduction basis from 100% to 0% over the
Term of the Lease set forth in Section 1.1 hereof. In calculating the rent
reserved, there shall be included, in addition to the Annual Rent and all
additional rent, the value of all other consideration agreed to be paid or
performed by Tenant for said residue. Tenant further covenants as an additional
and cumulative obligation after any such ending to pay punctually to Landlord
all the sums and perform all the obligations which Tenant covenants in this
Lease to pay and to perform in the same manner and to the same extent and at the
same time as if this Lease had not been terminated. In calculating the amounts
to be paid by Tenant under the next foregoing covenant, Tenant shall be credited
with any amount paid to Landlord as compensation as provided in the first
sentence of this Section 9.2 and also with the net proceeds of any rents
obtained by Landlord by reletting the Premises, after deducting all Landlord's
expenses in connection with such reletting, including, without implied
limitation, all repossession costs, brokerage commissions, fees for legal
services and expenses of preparing the Premises for such reletting, it being
agreed by Tenant that Landlord may (i) relet the Premises or any part or parts
thereof for a term or terms which may at Landlord's option be equal to or less
than or exceed the period which would otherwise have constituted the balance of
the Term and may grant such concessions and free rent as Landlord in its sole
judgment considers advisable or necessary to relet the same and (ii) make such
alterations, repairs and decorations in the Premises as Landlord in its sole
judgment considers advisable or necessary to relet the same, and no action of
Landlord in accordance with the foregoing or failure to relet or to collect rent
under reletting shall operate or be construed to release or reduce Tenant's
liability as aforesaid.

         Nothing contained in this Lease shall, however, limit or prejudice the
right of Landlord to prove and obtain in proceedings for bankruptcy or
insolvency by reason of the termination of this Lease, an amount equal to the
maximum allowed by any statute or rule of law in effect at the time when, and
governing the proceedings in which, the damages are to be proved, whether or not
the amount be greater, equal to, or less than the amount of the loss or damages
referred to above.

                                    ARTICLE X
                                  MISCELLANEOUS

10.1     NOTICE OF LEASE.

         Upon request of either party, both parties shall execute and deliver,
after the Term begins, a notice of this Lease in form appropriate for recording
or registration, and if this Lease is terminated before the Term expires, an
instrument in such form acknowledging the date of termination.

10.2     RELOCATION.

         During all but the last six (6) months of the Term, Landlord reserves
the right to relocate the Premises to comparable space within the Building or
another Office Park Building by giving Tenant prior written notice of such
intention to relocate provided that the new Premises shall be substantially
similar to the Premises in area and use for Tenant's purpose and such relocation


                                      -29-
<PAGE>
shall be made in order to lease the Premises to a tenant who will occupy a
majority of the floor of the Building on which the Premises are located. If
within thirty (30) days after receipt of such notice, Landlord and Tenant have
not agreed on the space to which the Premises are to be relocated and the timing
of such relocation, this Lease shall terminate on that date which is sixty (60)
days after the Tenant's receipt of such notice. If Landlord and Tenant do so
agree, then the Lease shall be deemed amended by deleting the description of the
original Premises and substituting thereof a description of such comparable
space and, if such relocation is to another Office Park Building owned by a
party other than Landlord, by reexecuting the Lease with the owner of such other
Office Park Building being substituted for the Landlord hereunder. Landlord
agrees to pay the reasonable costs of moving Tenant to such other space within
the Building or another Office Park Building, including, without limitation,
moving costs and the costs of improving the new premises so that they are
substantially similar to the Premises and all reasonable costs incurred by
Tenant as a result of relocating the Premises. Any such relocation shall be made
during evenings or weekends and shall be done in a manner designed to minimize
inconvenience to Tenant.

10.3     NOTICES FROM ONE PARTY TO THE OTHER.

         All notices required or permitted hereunder shall be in writing and
addressed, if to the Tenant, at Tenant's Address or such other address as Tenant
shall have last designated by notice in writing to Landlord and, if to Landlord,
at Landlord's Address or such other address as Landlord shall have last
designated by notice in writing to Tenant. Any notice shall have been deemed
duly given if mailed to such address postage prepaid, registered or certified
mail, return receipt requested, when deposited with the U.S. Postal Service, or
if delivered to such address by hand, when so delivered.

10.4     BIND AND INURE.

         The obligations of this Lease shall run with the land, and this Lease
shall be binding upon and inure to the benefit of the parties hereto and their
respective successors and assigns, except that the Landlord named herein and
each successive owner of the Premises shall be liable only for the obligations
accruing during the period of its ownership. The obligations of Landlord shall
be binding upon the assets of Landlord which comprise the Building and the Lot
but not upon other assets of Landlord. No individual partner, member, trustee,
stockholder, officer, director, employee or beneficiary of Landlord shall be
personally liable under this Lease and Tenant shall look solely to Landlord's
interest in the Building and the Lot in pursuit of its remedies upon an event of
default hereunder, and the general assets of the individual partners, trustees,
stockholders, officers, employees or beneficiaries of Landlord shall not be
subject to levy, execution or other enforcement procedure for the satisfaction
of the remedies of Tenant.

10.5     NO SURRENDER.

         The delivery of keys to any employee of Landlord or to Landlord's agent
or any employee thereof shall not operate as a termination of this Lease or a
surrender of the Premises.

10.6     NO WAIVER, ETC.


                                      -30-
<PAGE>
         The failure of Landlord to seek redress for violation of, or to insist
upon the strict performance of any covenant or condition of this Lease or any of
the Rules and Regulations referred to in Section 6.1.4, whether heretofore or
hereafter adopted by Landlord, shall not be deemed a waiver of such violation
nor prevent a subsequent act, which would have originally constituted a
violation, from having all the force and effect of an original violation, nor
shall the failure of Landlord to enforce any of said Rules and Regulations
against any other tenant in the Building be deemed a waiver of any such Rules or
Regulations. The receipt by Landlord of Annual Rent or additional rent with
knowledge of the breach of any covenant of this Lease shall not be deemed a
waiver of such breach by Landlord, unless such waiver be in writing and signed
by Landlord. No consent or waiver, express or implied, by Landlord to or of any
breach of any agreement or duty shall be construed as a waiver or consent to or
of any other breach of the same or any other agreement or duty.

10.7     NO ACCORD AND SATISFACTION.

         No acceptance by Landlord of a lesser sum than the Annual Rent and
additional rent then due shall be deemed to be other than on account of the
earliest installment of such rent due, nor shall any endorsement or statement on
any check or any letter accompanying any check or payment as rent be deemed as
accord and satisfaction, and Landlord may accept such check or payment without
prejudice to Landlord's right to recover the balance of such installment or
pursue any other remedy in this Lease provided.

10.8     CUMULATIVE REMEDIES.

         The specific remedies to which Landlord may resort under the terms of
this Lease are cumulative and are not intended to be exclusive of any other
remedies or means of redress to which it may be lawfully entitled in case of any
breach or threatened breach by Tenant of any provisions of this Lease. In
addition to the other remedies provided in this Lease, Landlord shall be
entitled to the restraint by injunction of the violation or attempted or
threatened violation of any of the covenants, conditions or provisions of this
Lease or to a decree compelling specific performance of any such covenants,
conditions or provisions.

10.9     LANDLORD'S RIGHT TO CURE.

         If Tenant shall at any time default in the performance of any
obligation under this Lease, Landlord shall have the right, but shall not be
obligated, to enter upon the Premises and to perform such obligation,
notwithstanding the fact that no specific provision for such substituted
performance by Landlord is made in this Lease with respect to such default. In
performing such obligation, Landlord may make any payment of money or perform
any other act. All sums so paid by Landlord (together with interest at the rate
of 4% per annum in excess of the then prime commercial rate of interest being
charged by the three largest national banks in Boston, Massachusetts) and all
necessary incidental costs and expenses in connection with the performance of
any such act by Landlord, shall be deemed to be additional rent under this Lease
and shall be payable to Landlord immediately on demand. Landlord may exercise
the foregoing rights without waiving any other of its rights or releasing Tenant
from any of its obligations under this Lease.


                                      -31-
<PAGE>
10.10    ESTOPPEL CERTIFICATE.

         Tenant agrees, from time to time, upon not less than 15 days' prior
written request by Landlord, to execute, acknowledge and deliver to Landlord a
statement in writing certifying that this Lease is unmodified and in full force
and effect; that Tenant has no defenses, offsets or counterclaims against its
obligations to pay the Annual Rent and additional rent and to perform its other
covenants under this Lease; that there are no uncured defaults of Landlord or
Tenant under this Lease (or, if there have been modifications, that this Lease
is in full force and effect as modified and stating the modifications, and, if
there are any defenses, offsets, counterclaims, or defaults, setting them forth
in reasonable detail); and the dates to which the Annual Rent, additional rent
and other charges have been paid. Any such statement delivered pursuant to this
Section 10.10 shall be in a form reasonably acceptable to and may be relied upon
by any prospective purchaser or mortgagee of premises which include the Premises
or any prospective assignee of any such mortgagee.

10.11    WAIVER OF SUBROGATION.

         Any insurance carried by either party with respect to the Premises and
property therein or occurrences thereon shall include a clause or endorsement
denying to the insurer rights of subrogation against the other party to the
extent rights have been waived by the insured prior to occurrences of injury or
loss. Each party, notwithstanding any provisions of this Lease to the contrary,
hereby waives any rights of recovery against the other for injury or loss due to
hazards covered by insurance containing such clause or endorsement to the extent
of the indemnification received thereunder.

10.12    ACTS OF GOD.

         In any case where either party hereto is required to do any act, delays
caused by or resulting from Acts of God, war, civil commotion, fire, flood or
other casualty, labor difficulties, shortages of labor, materials or equipment,
government regulations, unusually severe weather, or other causes beyond such
party's reasonable control shall not be counted in determining the time during
which work shall be completed, whether such time be designated by a fixed date,
a fixed time or a "reasonable time," and such time shall be deemed to be
extended by the period of such delay.

10.13    BROKERAGE.

         Tenant and Landlord represent and warrant that they dealt with no
brokers in connection with this transaction other than the Broker and agree to
defend, with counsel approved by the other, indemnify and save the other
harmless from and against any and all cost, expense or liability for any
compensation, commissions or charges claimed by a broker or agent, other than
the Broker in connection with this Lease. Landlord hereby agrees to pay the
brokerage fees to the Broker in connection with the execution and delivery of
this Lease.

10.14    SUBMISSION NOT AN OFFER.

         The submission of a draft of this Lease or a summary of some or all of
its provisions does not constitute an offer to lease or demise the Premises, it
being understood and agreed that


                                      -32-
<PAGE>
neither Landlord nor Tenant shall be legally bound with respect to the leasing
of the Premises unless and until this Lease has been executed by both Landlord
and Tenant and a fully executed copy has been delivered to each of them.

10.15    APPLICABLE LAW AND CONSTRUCTION.

         This Lease shall be governed by and construed in accordance with the
laws of the Commonwealth of Massachusetts. If any term, covenant, condition or
provision of this Lease or the application thereof to any person or
circumstances shall be declared invalid or unenforceable by the final ruling of
a court of competent jurisdiction having final review, the remaining terms,
covenants, conditions and provisions of this Lease and their application to
persons or circumstances shall not be affected thereby and shall continue to be
enforced and recognized as valid agreements of the parties, and in the place of
such invalid or unenforceable provision, there shall be substituted a like, but
valid and enforceable provision which comports to the findings of the aforesaid
court and most nearly accomplishes the original intention of the parties.

         There are no oral or written agreements between Landlord and Tenant
affecting this Lease. This Lease may be amended, and the provisions hereof may
be waived or modified, only by instruments in writing executed by Landlord and
Tenant.

         The titles of the several Articles and Sections contained herein are
for convenience only and shall not be considered in construing this Lease.

         Unless repugnant to the context, the words "Landlord" and "Tenant"
appearing in this Lease shall be construed to mean those named above and their
respective heirs, executors, administrators, successors and assigns, and those
claiming through or under them respectively. If there be more than one tenant,
the obligations imposed by this Lease upon Tenant shall be joint and several.

10.16    AUTHORITY.

         Tenant represents and warrants to Landlord (which representations and
warranties shall survive the delivery of this Lease) that: (a) Tenant (i) is
duly organized, validly existing and in good standing under the laws of its
state of incorporation, (ii) has the corporate power and authority to carry on
businesses now being conducted and is qualified to do business in every
jurisdiction where such qualification is necessary and (iii) has the corporate
power to execute and deliver and perform its obligations under this Lease and
(b) the execution, delivery and performance by Tenant of its obligations under
this Lease have been duly authorized by all requisite corporate action and will
not violate any provision of law, any order of any court or other agency of
government, the corporate charter or by-laws of the Tenant or any indenture,
agreement or other instrument to which it is a party or by which it is bound.

         Landlord represents and warrants to Tenant (which representations and
warranties shall survive the delivery of this Lease) that: (a) Landlord (i) is
duly organized, validly existing and in good standing under the laws of its
state of incorporation, (ii) has the power and authority to carry on businesses
now being conducted and is qualified to do business in every jurisdiction where
such qualification is necessary and (iii) has the power to execute and deliver
and perform its obligations under this Lease and (b) the execution, delivery and
performance by Landlord of


                                      -33-
<PAGE>
its obligations under this Lease have been duly authorized by all requisite
action and will not violate any provision of law, any order of any court or
other agency of government, the partnership agreement or other governing
instruments of the Landlord or any indenture, agreement or other instrument to
which it is a party or by which it is bound.

                                   ARTICLE XI
                                SECURITY DEPOSIT

         Upon the execution of the Lease, Tenant shall provide to Landlord
either a cash deposit in the amount of the Security Deposit or an irrevocable
and unconditional letter of credit in the amount of the Security Deposit (in
either case, the "Security Deposit") issued by a bank or other institution
reasonably satisfactory to Landlord and in form and substance reasonably
satisfactory to Landlord, naming Landlord, its successors and assigns as the
beneficiary and expiring no less than one (1) month after the Term Expiration
Date or one (1) year from the Term Commencement Date so long as the same is
self-renewing for additional periods of one (1) year each through the end of the
Term (the "Letter of Credit"). Landlord shall be permitted to draw upon the
Letter of Credit in the event of (a) a default by Tenant in any of its
obligations hereunder and the expiration of any applicable cure period, in which
event Landlord may draw upon all or a portion of the Letter of Credit and apply
the proceeds as described below, or (b) failure by Tenant to provide to Landlord
a replacement or substitute Letter of Credit in the amount of the Security
Deposit, and otherwise subject to the conditions set forth above, no less than
thirty (30) days prior to the expiration date of the Letter of Credit then held
by Landlord, in which event Landlord may draw upon all of the Letter of Credit
and hold the cash proceeds thereof as the Security Deposit hereunder.
Notwithstanding the foregoing, so long as Tenant is not in default of any of its
obligations under this Lease, the Security Deposit and if applicable, the Letter
of Credit, shall be reduced on the first anniversary date of this Lease, and on
each subsequent anniversary date, by the amount of $22,913.75.

         The Security Deposit is being delivered by Tenant to Landlord as
security for the faithful performance and observance by Tenant of the terms,
provisions and conditions of the Lease. If the Security Deposit is provided to
Landlord in cash, the Security Deposit shall be held in an account to be
selected by Landlord in its sole and absolute discretion, with no interest
thereon to Tenant. On termination of the Term, the Security Deposit, or the
portion thereof then held by Landlord, shall be returned to Tenant, provided
there exists no breach or default of any provisions of this Lease by Tenant.
Landlord shall not have any obligation to segregate the Security Deposit from
other funds held by Landlord.

         If all or any part of the Security Deposit is applied to an obligation
of Tenant hereunder, Tenant shall immediately upon request by Landlord restore
the Security Deposit to its original amount. Tenant shall not have the right to
call upon Landlord to apply all or any part of the Security Deposit to cure any
default or fulfill any obligation of Tenant, but such use shall be solely in the
discretion of Landlord. Upon any conveyance by Landlord of its interest under
this Lease, the Security Deposit may be delivered by Landlord to Landlord's
grantee or transferee. Upon any delivery, Tenant hereby releases Landlord herein
named of any and all liability with respect to look solely to such grantee or
transferee. It is further understood that this provision shall also apply to
subsequent grantees and transferees.


                                      -34-
<PAGE>
         EXECUTED as a sealed instrument in two or more counterparts on the day
and year first above written.

                               LANDLORD:

                               CAMBRIDGEPARK ONE LIMITED PARTNERSHIP

                               By:      Its Agent:  Spaulding and Slye Services
                                        Limited Partnership

                               By: /s/ ILLEGIBLE
                                   ___________________________
                                   Sr. VP

                               TENANT:

                               NOVIRIO PHARMACEUTICALS, INC.


                               By: /s/ Jean-Pierre Sommodossi
                                   _______________________________________
                                        Name: J.P. Sommodossi
                                        Title: Ex. President and Chairman
                                        Hereunto duly authorized





                                      -35-
<PAGE>
                                    Exhibit A

                              PROPERTY DESCRIPTION

That certain parcel of land in Cambridge, Middlesex, Massachusetts on the
northerly side of Rindge Avenue Extension as shown on the plan entitled "Plan of
Land Cambridge, Mass." dated Dec. 18, 1981, prepared by Harry R. Feldman, Inc.,
and recorded in the Middlesex South Registry of Deeds as Plan No. 560 of 1983,
more particularly bounded and described as follows:

Southerly:        By Rindge Avenue Extension, three hundred (300.00) feet

Westerly:         By land in part now or formerly of Plewelling and George B.
                  Dodge, Trustees of Dodge Realty Trust, and in part now or
                  formerly of Boston & Maine Railroad, three hundred and seven
                  and 49/100 (307.49) feet

Northerly:        By a curve with a length of twenty-three and 42/100 (23.42)
                  feet;

Westerly:         Thirteen and 86/100 (13.86) feet;

Southerly:        By a curve with a length of twenty-three and 42/100 (23.42)
                  feet;

Westerly:         Forty-one and 44/100 (41.44) feet;

Northerly:        By a curve with a length of three hundred ninety-nine and
                  78/100 (399.78) feet;

Easterly:         Forty-three and 74/100 (43.74) feet; all of the preceding six
                  bounds by land now or formerly of Boston & Maine Railroad;

Southerly:        By land now or formerly of Peter A. Frasse & Co. Inc.
                  seventy-eight and 43/100 (78.34) feet;

Easterly:         By land of Peter A. Frasse & Co. Inc., four hundred
                  thirty-three and 91/100 (433.91) feet;
<PAGE>
                                    EXHIBIT B

                              PLAN SHOWING PREMISES

                             [Graphic of Floor Plan]
<PAGE>
                                    EXHIBIT C

                               LANDLORD'S SERVICES

I.       CLEANING

         A.       GENERAL

                  1.       All cleaning work will be performed between 5 p.m.
                           and 12 midnight, Monday through Friday, unless
                           otherwise necessary for stripping, waxing, etc.

                  2.       Abnormal waste removal (e.g., computer installation
                           paper, bulk packaging, wood or cardboard crates,
                           refuse from cafeteria operation, etc.) shall be
                           Tenant's responsibility.

         B.       DAILY OPERATIONS (5 TIMES PER WEEK)

                  1.       Tenant Areas

                           a.       Empty and clean all waste receptacles; wash
                                    receptacles as necessary.

                           b.       Vacuum all rugs and carpeted areas.

                           c.       Empty, damp-wipe and dry all ashtrays.

                  2.       Lavatories

                           a.       Sweep and wash floors with disinfectant.

                           b.       Wash both sides of toilet seats with
                                    disinfectant.

                           c.       Wash all mirrors, basins, bowls, urinals.

                           d.       Spot clean toilet partitions.

                           e.       Empty and disinfect sanitary napkin disposal
                                    receptacles.

                           f.       Refill toilet tissue, towel, soap, and
                                    sanitary napkin dispensers.

                  3.       Public Areas

                           a.       Wipe down entrance doors and clean glass
                                    (interior and exterior).


                                      C-1
<PAGE>
                           b.       Vacuum elevator carpets and wipe down doors
                                    and walls.

                           c.       Clean water coolers.

         C.       OPERATIONS AS NEEDED (BUT NOT LESS THAN EVERY OTHER DAY)

                  1.       Tenant and Public Areas

                           a.       Buff all resilient floor areas.

         D.       WEEKLY OPERATIONS

                  1.       Tenant Areas, Lavatories, Public Areas

                           a.       Hand-dust and wipe clean all horizontal
                                    surfaces with treated cloths to include
                                    furniture, office equipment, window sills,
                                    door ledges, chair rails, baseboards,
                                    convector tops, etc., within normal reach.

                           b.       Remove finger marks from private entrance
                                    doors, light switches, and doorways.

                           c.       Sweep all stairways.

         E.       MONTHLY OPERATIONS

                  1.       Tenant and Public Areas

                           a.       Thoroughly vacuum seat cushions on chairs,
                                    sofas, etc.

                           b.       Vacuum and dust grillwork.

                  2.       Lavatories

                           a.       Wash down interior walls and toilet
                                    partitions.

         F.       AS REQUIRED AND WEATHER PERMITTING

                  1.       Entire Building

                           a.       Clean inside of all windows.

                           b.       Clean outside of all windows.


                                      C-2
<PAGE>
         G.       YEARLY

                  1.       Public Areas

                           a.       Strip and wax all resilient tile floor
                                    areas.

II.      HEATING, VENTILATING, AND AIR CONDITIONING

                  1.       Heating, ventilating, and air conditioning as
                           required to provide reasonably comfortable
                           temperatures for normal business day occupancy
                           (excepting holidays); Monday through Friday from 8:00
                           a.m. to 5:00 p.m. and Saturday from 8:00 a.m. to 1:00
                           p.m.

                  2.       Maintenance of any additional or special air
                           conditioning equipment and the associated operating
                           cost will be at Tenant's expense, which is estimated
                           at $50 per hour.

III.     WATER

                           Hot water for lavatory purposes and cold water for
                           drinking, lavatory and toilet purposes, and cold
                           water for Tenant's kitchen and Tenant's hot water
                           heater (Tenant is to supply hot water heater for
                           Tenant's kitchen, if any).

IV.      ELEVATORS (IF BUILDING IS ELEVATORED)

                           Elevators for the use of all tenants and the general
                           public for access to and from all floors of the
                           Building. Programming of elevators (including, but
                           not limited to, service elevators) shall be as
                           Landlord from time to time determines best for the
                           Building as a whole.

V.       RELAMPING OF LIGHT FIXTURES

                           Tenant will reimburse Landlord for the cost of lamps,
                           ballasts and starters and the cost of replacing same
                           within the Premises.

VI.      CAFETERIA AND VENDING INSTALLATIONS


                                      C-3
<PAGE>
         1.       Any space to be used primarily for lunchroom or cafeteria
                  operation shall be Tenant's responsibility to keep clean and
                  sanitary, it being understood that Landlord's approval of such
                  use must be first obtained in writing.

         2.       Vending machines or refreshment service installations by
                  Tenant must be approved by Landlord in writing and shall be
                  restricted in use to employees and business callers. All
                  cleaning necessitated by such installations shall be at
                  Tenant's expense.

VII.     ELECTRICITY

         A.       Landlord, at Landlord's expense, shall furnish electrical
                  energy required for lighting, electrical facilities,
                  equipment, machinery, fixtures, and appliances used in or for
                  the benefit of the Premises, in accordance with the provisions
                  of the Lease of which this Exhibit is part.

         B.       Tenant shall not, without prior written notice to Landlord in
                  each instance, connect to the Building electric distribution
                  system any fixtures, appliances or equipment other than normal
                  office machines such as personal computers, desk-top
                  calculators and typewriters, or any fixtures, appliances or
                  equipment which Tenant on a regular basis operates beyond
                  normal building operating hours. In the event of any such
                  connection, Tenant agrees to an increase in the ANNUAL
                  ESTIMATED ELECTRICAL COST TO THE PREMISES and a corresponding
                  increase in Annual Rent by an amount which will reflect the
                  cost to Landlord of the additional electrical service to be
                  furnished by Landlord, such increase to be effective as of the
                  date of any such installation. If Landlord and Tenant cannot
                  agree thereon, such amount shall be conclusively determined by
                  a reputable independent electrical engineer or consulting firm
                  to be selected by Landlord and paid equally by both parties,
                  and the cost to Landlord will be included in Landlord's
                  Operating Costs provided in Section 4.2 hereof.

         C.       Tenant's use of electrical energy in the Premises shall not at
                  any time exceed the capacity of any of the electrical
                  conductors or equipment in or otherwise serving the Premises.
                  In order to insure that such capacity is not exceeded and to
                  avert possible adverse effect upon the Building electric
                  service, Tenant shall not, without prior written notice to
                  Landlord in each instance, connect to the Building electric
                  distribution system any fixtures, appliances or equipment
                  which operate on a voltage in excess of 120 volts nominal or
                  make any alteration or addition to


                                      C-4
<PAGE>
                  the electric system of the Premises. Unless Landlord shall
                  reasonably object to the connection of any such fixtures,
                  appliances or equipment, all additional risers or other
                  equipment required therefor shall be provided by Landlord, and
                  the cost thereof shall be paid by Tenant upon Landlord's
                  demand. In the event of any such connection, Tenant agrees to
                  an increase in the ANNUAL ESTIMATED ELECTRICAL COST TO THE
                  PREMISES such increase to be effective as of the date of any
                  such connection. If Landlord and Tenant cannot agree thereon,
                  such amount shall be conclusively determined by a reputable
                  independent electrical engineer or consulting firm to be
                  selected by Landlord and paid equally by both parties, and the
                  cost to Landlord will be included in Landlord's Operating
                  Costs provided in Section 4.2 hereof.

         D.       If at any time after the date of this Lease, the rates at
                  which Landlord purchases electrical energy from the public
                  utility supplying electric service to the Building, or any
                  charges incurred or taxes payable by Landlord in connection
                  therewith, shall be increased or decreased, the ANNUAL
                  ESTIMATED ELECTRICAL COST TO THE PREMISES shall be increased
                  or decreased, as the case may be, by an amount equal to the
                  estimated increase or decrease, as the case may be, in
                  Landlord's cost of furnishing the electricity referred to in
                  Paragraph A above as a result of such increase or decrease in
                  rates, charges, or taxes. If Landlord and Tenant cannot agree
                  thereon, such amount shall be conclusively determined by a
                  reputable independent electrical engineer or consulting firm
                  to be selected by Landlord and paid equally by both parties,
                  and the cost to Landlord will be included in Landlord's
                  Operating Costs as provided in Section 4.2 hereof. Any such
                  increase or decrease shall be effective as of the date of the
                  increase or decrease in such rate, charge or taxes.

         E.       Landlord may, at any time, elect to discontinue the furnishing
                  of electrical energy. In the event of any such election by
                  Landlord: (1) Landlord agrees to give reasonable advance
                  notice of any such discontinuance to Tenant (which notice
                  shall be no less than ninety (90) days in advance); (2)
                  Landlord agrees to permit Tenant to receive electrical service
                  directly from the public utility supplying service to the
                  Building and to permit the existing feeders, risers, wiring
                  and other electrical facilities serving the Premises to be
                  used by Tenant and/or such public utility for such purpose to
                  the extent they are suitable and safely capable; (3) Landlord
                  agrees to pay such charges and costs, if any, as such public
                  utility may impose in connection with the installation of
                  Tenant's meters and to make or, at such public utility's
                  election, to pay for such other installations as such public


                                      C-5
<PAGE>
                  utility may require, as a condition of providing comparable
                  electrical service to Tenant; and (4) Tenant shall thereafter
                  pay, directly to the utility furnishing the same, all charges
                  for electrical services to the Premises.

















                                      C-6
<PAGE>
                                    EXHIBIT D

                              RULES AND REGULATIONS

         The following rules and regulations have been formulated for the safety
and well-being of all tenants of the Building and to insure compliance with
governmental and other requirements. Strict adherence to these rules and
regulations is necessary to guarantee that each and every tenant will enjoy a
safe and undisturbed occupancy of its premises in the Building. Any continuing
violation of these rules and regulations by Tenant shall constitute a default by
Tenant under the Lease.

         Landlord may, upon request of any tenant, waive the compliance by such
tenant of any of the following rules and regulations, provided that (i) no
waiver shall be effective unless signed by Landlord's authorized agent, (ii) any
such waiver shall not relieve such tenant from the obligation to comply with
such rule or regulation in the future unless otherwise agreed to by Landlord,
(iii) no waiver granted to any tenant shall relieve any other tenant from the
obligation of complying with these rules and regulations, unless such other
tenant has received a similar written waiver from the Landlord, and (iv) any
such waiver shall not relieve Tenant from any liability to Landlord for any loss
or damage occasioned as a result of Tenant's failure to comply with any rule or
regulation

         1.       The entrances, lobbies, passages, corridors, elevators, halls,
                  courts, sidewalks, vestibules, and stairways shall not be
                  encumbered or obstructed by Tenant, Tenant's agents, servants,
                  employees, licensees or visitors or used by them for any
                  purposes other than ingress or egress to and from the
                  Premises. Landlord shall have the right to control and operate
                  portions of the Building and the facilities furnished for
                  common use of the tenants in such manner as Landlord deems
                  best for the benefit of the tenants generally.

         2.       The moving in or out of all safes, freight, furniture, or
                  bulky matter of any description shall take place during the
                  hours which Landlord may determine from time to time. Landlord
                  reserves the right to inspect all freight and bulky matter to
                  be brought into the Building and to exclude from the Building
                  all freight and bulky matter which violates any of these Rules
                  and Regulations or the Lease of which these Rules and
                  Regulations are a part. Landlord reserves the right to have
                  Landlord's structural engineer review Tenant's floor loads on
                  the Premises at


                                      D-1
<PAGE>
                  Tenant's expense, but no more often than once each year or as
                  otherwise reasonably necessary or prudent.

         3.       Tenant, or the employees, agents, servants, visitors or
                  licensees of Tenant shall not at any time place waste or
                  discard any rubbish, paper, articles, or objects of any kind
                  whatsoever outside the doors of the Premises or in the
                  corridors or passageways of the Building. No animals or birds
                  shall be brought or kept in or about the Building. Bicycles
                  shall not be permitted in the Building.

         4.       Tenant shall not place objects against glass partitions or
                  doors or windows or adjacent to any common space which would
                  be unsightly from the Building corridors or from the exterior
                  of the Building and will promptly remove the same upon notice
                  from Landlord.

         5.       Tenant shall not make noises, cause disturbances, create
                  vibrations, odors (other than ordinarily acceptable tenant
                  kitchen odors in the building) or noxious fumes or use or
                  operate any electric or electrical devices or other devices
                  that emit sound waves or are dangerous to other tenants and
                  occupants of the Building or that would interfere with the
                  operation of any device or equipment or radio or television
                  broadcasting or reception from or within the Building or
                  elsewhere, or with the operation of roads or highways in the
                  vicinity of the Building, and shall not place or install any
                  projections, antennae, aerials, or similar devices inside or
                  outside of the Premises, without the prior written approval of
                  Landlord.

         6.       Tenant may not (without Landlord's approval therefor, which
                  approval will be signified on Tenant's Plans submitted
                  pursuant to the Lease) and Tenant shall not permit or suffer
                  anyone to: (a) cook in the Premises except as accessory to the
                  use of a coffee room/kitchenette containing a microwave oven;
                  (b) place vending or dispensing machines of any kind in or
                  about the Premises; (c) at any time sell, purchase or give
                  away, or permit the sale, purchase, or gift of food in any
                  form.

         7.       Tenant shall not: (a) use the Premises for lodging,
                  manufacturing or for any illegal purposes; (b) use the
                  Premises to engage in the manufacture or sale of, or permit
                  the use of spirituous, fermented, intoxicating or alcoholic
                  beverages on the Premises; (c) use the Premises to engage in
                  the manufacture or sale of, or permit the use of, any illegal
                  drugs on the Premises.


                                      D-2
<PAGE>
         8.       No awning or other projections (including antennae) shall be
                  attached to the outside walls or windows. No curtains, blinds,
                  shades, screens or signs other than those furnished by
                  Landlord shall be attached to, hung in, or used in connection
                  with any window or door of the Premises without prior written
                  consent of Landlord.

         9.       No signs, advertisement, object, notice or other lettering
                  shall be exhibited, inscribed, painted or affixed on any part
                  of the outside or inside of the Premises if visible from
                  outside of the Premises. Interior signs on doors shall be
                  painted or affixed for Tenant by Landlord or by sign painters
                  first approved by Landlord at the expense of Tenant and shall
                  be of a size, color and style acceptable to Landlord.

         10.      Tenant shall not use the name of the Building or use pictures
                  or illustrations of the Building in advertising or other
                  publicity without prior written consent of Landlord. Landlord
                  shall have the right to prohibit any advertising by Tenant
                  which, in Landlord's opinion, tends to impair the reputation
                  of the Building or its desirability for offices, and upon
                  written notice from Landlord, Tenant will refrain from or
                  discontinue such advertising.

         11.      Door keys for doors in the Premises will be furnished at the
                  Commencement of the Lease by Landlord. Tenant shall not affix
                  additional locks on doors and shall purchase duplicate keys
                  only from Landlord and will provide to Landlord the means of
                  opening of safes, cabinets, or vaults left on the Premises. In
                  the event of the loss of any keys so furnished by Landlord,
                  Tenant shall pay to Landlord the cost thereof. Each tenant
                  shall, upon the termination of its tenancy, restore to
                  Landlord all keys of offices, storage and toilet rooms either
                  furnished to, or otherwise procured by, such tenant.

         12.      Tenant shall cooperate and participate in all security
                  programs affecting the Building.

         13.      Tenant assumes full responsibility for protecting its space
                  from theft, robbery and pilferage, which includes keeping
                  doors locked and other means of entry to the Premises closed
                  and secured.


                                      D-3
<PAGE>
         14.      Tenant shall not make any room-to-room canvass to solicit
                  business from other tenants in the Building, and shall not
                  exhibit, sell or offer to sell, use, rent or exchange any item
                  or services in or from the Premises unless ordinarily embraced
                  within Tenant's use of the Premises as specified in its Lease.
                  Canvassing, soliciting and peddling in the Building are
                  prohibited and Tenant shall cooperate to prevent the same.
                  Peddlers, solicitors and beggars shall be reported to the
                  Management Office.

         15.      Tenant shall not mark, paint, drill into, or in any way deface
                  any part of the Building or Premises. No boring, driving of
                  nails or screws (except for picture hanging, etc.), cutting or
                  stringing of wires shall be permitted, except with the prior
                  written consent of Landlord, and as Landlord may direct.
                  Tenant shall not construct, maintain, use or operate within
                  their respective premises any electrical device, wiring or
                  apparatus in connection with a loud speaker system or other
                  sound system, except as reasonably required as part of a
                  communication system approved in writing by Landlord, prior to
                  the installation thereof. Tenant shall not install any
                  resilient tile or similar floor covering in the Premises
                  except with the prior written approval of Landlord. The use of
                  cement or other similar adhesive material is expressly
                  prohibited.

         16.      Tenant shall not waste electricity or water and agrees to
                  cooperate fully with Landlord to assure the most effective
                  operation of the Building's heating and air conditioning and
                  shall refrain from attempting to adjust controls. Tenant shall
                  keep corridor doors closed except when being used for access.

         17.      The water and wash closets and other plumbing fixtures shall
                  not be used for any purposes other than those for which they
                  were constructed, and no sweepings, rubbish, rags, or other
                  substances shall be thrown therein. All damage resulting from
                  misuse of said fixtures shall be borne by the tenant who, or
                  whose servant, employees, agents, licensees, invitees,
                  customers or guests shall have caused the same.

         18.      Building employees shall not be required to perform, and shall
                  not be requested by any tenant or occupant to perform, any
                  work outside of their regular duties, unless under specific
                  instructions from the office of the Managing Agent of the
                  Building. The requirements of tenants will be attended to only
                  upon application to Landlord, and any special requirements
                  shall be billed to Tenant (and paid


                                      D-4
<PAGE>
                  when the next installment of rent is due) in accordance with
                  the schedule of charges maintained by Landlord from time to
                  time or at such charge as is agreed upon in advance by
                  Landlord and Tenant.

         19.      Tenant may request heating and/or air conditioning during
                  other periods in addition to normal working hours by
                  submitting its request in writing to the office of the
                  Managing Agent of the Building no later than 2:00 p.m. the
                  preceding work day (Monday through Friday) on forms available
                  from the office of the Managing Agent. The request shall
                  clearly state the start and stop hours of the "off-hour"
                  service. Tenant shall submit to the Building Manager a list of
                  personnel authorized to make such request. The Tenant shall be
                  charged for such operation in the form of additional rent;
                  such charges are to be determined by the Managing Agent and
                  shall be fair and reasonable and reflect the additional
                  operating costs involved.

         20.      Tenant covenants and agrees that its use of the Premises shall
                  not cause a discharge of more than the gallonage per foot of
                  Premises Design Floor Area per day of sanitary
                  (non-industrial) sewage allowed under the sewage discharge
                  permit for the Building. Discharges in excess of that amount,
                  and any discharge of industrial sewage, shall only be
                  permitted if Tenant, at its sole expense, shall have obtained
                  all necessary permits and licenses therefor, including without
                  limitation permits from state and local authorities having
                  jurisdiction thereof. Tenant shall submit to Landlord on
                  December 31 of each year of the Term of this Lease a
                  statement, certified by an authorized officer of Tenant, which
                  contains the following information: name of all chemicals,
                  gases, and hazardous substances, used, generated, or stored on
                  the Premises; type of substance (liquid, gas or granular);
                  quantity used, stored or generated per year; method of
                  disposal; permit number, if any, attributable to each
                  substance, together with copies of all permits for such
                  substances; and permit expiration date for each substance. No
                  flammable, combustible or explosive fluid, chemical or
                  substance shall be brought into or kept upon the Premises, the
                  Building or the Lot (other than those fluids or chemicals
                  customarily used by tenants of other first-class office
                  buildings in connection with office purposes and then only
                  those types and quantities permitted under Landlord's policies
                  of insurance for the Building).


                                      D-5
<PAGE>
         21.      Landlord reserves the right to exclude from the Building at
                  all times any person who is not known or does not properly
                  identify himself to the Building management. Landlord may, at
                  its option, require all persons admitted to or leaving the
                  Building between the hours of 6:00 p.m. and 8:00 a.m., Monday
                  through Friday, and at any hour on Saturdays, Sundays and
                  legal holidays, to register. Each tenant shall be responsible
                  for all persons for whom it authorizes entry into the
                  Building, and shall be liable to Landlord for all acts or
                  omissions of such persons.

         22.      Landlord reserves the right to inspect all freight to be
                  brought into the Building and to exclude from the Building all
                  freight which violates any of these rules and regulations.
                  There shall not be used in any space or in the common halls of
                  the Building, either by any tenant or by jobbers or others in
                  the delivery or receipt of merchandise, any hand trucks,
                  except those equipped with rubber tires and side guards.









D-6