Document:

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                                                                   Exhibit 10.20

                                                                       EXECUTION

                              LEXINGTON TECHNOLOGY
                                     CENTER
                                125 Spring Street
                            Lexington, Massachusetts

                                   LEASE DATA

EXECUTION DATE:      January 30, 2004

TENANT:              NITROMED, INC., a Delaware corporation

MAILING ADDRESS
PRIOR TO OCCUPANCY:  12 Oak Park Drive
                     Bedford, MA  01730
                     Attention: Joseph Grimm

LANDLORD:            PM ATLANTIC LEXINGTON, LLC, a Delaware limited liability
                     company doing business as Patriot Partners

LANDLORD'S:
MAILING ADDRESS:     c/o Atlantic Management Company, Inc.
                     205 Newbury Street
                     Framingham, MA  01701
                     Attn: Joseph Zink

PROPERTY:            Approximately 95.6 acres in Lexington, Massachusetts, as
                     more particularly described in EXHIBIT 1, including the
                     buildings and other improvements from time to time existing
                     thereon, commonly known as "Lexington Technology Center".

BUILDING:            125 Spring Street, Lexington, Massachusetts

BUILDING LOT:        The lot, as the same may be reconfigured from time to time
                     in accordance with the provisions of this Lease, upon which
                     the Building is located.

PREMISES:            The entire Building, including loading docks, comprising
                     approximately 52,000 rentable square feet, of which 45,800
                     rentable square feet ("the "UPPER LEVEL SPACE") is on
                     floors 1 and 2 and 6,200 rentable square feet (the "LOWER
                     LEVEL SPACE") is on the lower level. The precise rentable
                     square footage of the Premises has been determined
                     utilizing the Standard Method for Measuring Floor Area in
                     Office Buildings, published by the Building Owners and
                     Managers Association International and dated June 7, 1996,
                     with the following specific modifications:

                     (a)   Lab exhaust shaft areas are included within "rentable
                           square footage".

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                     (b)   Freight elevator shaft area is included within
                           "rentable square footage".

                     (c)   Mechanical rooms and penthouse areas are treated as
                           common area.

                     All square footage measurements are deemed to be final and
                     conclusive and not subject to remeasurement.

ART. 3               TERM COMMENCEMENT DATE:         the Execution Date

                     ESTIMATED DELIVERY DATE:        July 8, 2004

                     LATE DELIVERY DATE:             The date that is thirty
                                                     (30) days after the
                                                     Estimated Delivery Date.
                                                     The Late Delivery Date
                                                     shall be extended on a
                                                     day-for-day basis in the
                                                     event of a Tenant Delay or
                                                     Event of Force Majeure
                                                     (both defined in Section
                                                     4.1). The maximum extension
                                                     on account of Events of
                                                     Force Majeure is ninety
                                                     (90) additional days after
                                                     the Outside Delivery Date,
                                                     as the same may have been
                                                     extended on account of
                                                     Tenant Delays.

                     OUTSIDE DELIVERY DATE:          The date that is ninety
                                                     (90) days after the
                                                     Estimated Delivery Date.
                                                     The Outside Delivery Date
                                                     shall be extended on a
                                                     day-for-day basis in the
                                                     event of a Tenant Delay or
                                                     Event of Force Majeure
                                                     (both defined in Section
                                                     4.1). The maximum extension
                                                     on account of Events of
                                                     Force Majeure is ninety
                                                     (90) additional days after
                                                     the Outside Delivery Date,
                                                     as the same may have been
                                                     extended on account of
                                                     Tenant Delays.

                     RENT COMMENCEMENT DATE:         The date that is thirty
                                                     (30) days after the earlier
                                                     of (a) the date on which
                                                     Landlord's Work is
                                                     Substantially Complete (or
                                                     deemed to be Substantially
                                                     Complete, in the event of
                                                     Tenant Delays), as defined
                                                     in

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                                                     Section 4.1(f), or (b) the
                                                     date Tenant upon which
                                                     takes occupancy of any part
                                                     of the Premises for
                                                     business purposes.

                     EXPIRATION DATE:                The last day of the month
                                                     in which the tenth (10th)
                                                     anniversary of the Rent
                                                     Commencement Date occurs,
                                                     unless earlier terminated
                                                     or extended as set forth
                                                     herein.

ART. 4               COSMETIC PLAN COMPLETION DATE:  February 10, 2004

                     CONSTRUCTION COMMENCEMENT       The date that is fifteen
                     DATE:                           (15) days after the
                                                     Execution Date. The
                                                     Construction Commencement
                                                     Date shall be extended on a
                                                     day-for-day basis in the
                                                     event of a Tenant Delay or
                                                     Event of Force Majeure
                                                     (both defined in Section
                                                     4.1). The maximum extension
                                                     on account of Event of
                                                     Force Majeure is thirty
                                                     (30) additional days after
                                                     the Execution Date.

                     LANDLORD'S CONTRIBUTION:        Up to Four Million Seven
                                                     Hundred Twenty Thousand
                                                     Dollars ($4,720,000), to be
                                                     paid by Landlord as
                                                     provided in Section 4.2.

ART. 5               PERMITTED USES: General office, research, development and
                     laboratory use.

ART. 6               YEARLY RENT:

<Table>
<Caption>
                           Rent            Yearly         Monthly
                          Year(1)           Rent          Payment      PSF(NNN)
                     -----------------  ------------   -------------   ---------
                     <S>                <C>            <C>             <C>
                     UPPER LEVEL SPACE
                             1          $    878,675   $   73,222.92   $  19.19
</Table>

----------
(1) For the purposes of this Lease, "Rent Year 1" shall be defined as the
twelve-(12)-month period commencing as of the Rent Commencement Date and ending
on the last day of the month in which the first (1st) anniversary of the Rent
Commencement Date occurs. Thereafter, "Rent Year" shall be defined as any twelve
(12) month period during the term of the Lease commencing as of the first (1st)
day of the month following the month in which any anniversary of the Rent
Commencement Date occurs.

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<Table>
                     <S>                <C>            <C>             <C>
                             2          $  1,322,477   $  110,206.42   $  28.88
                            3-5         $  1,442,931   $  120,244.25   $  31.51
                            6-10        $  1,626,131   $  135,510.92   $  35.51

                     LOWER LEVEL SPACE

                            1-10        $     62,000   $    5,166.67   $  10.00
</Table>

ART. 7               Total rentable square feet of   52,000 rentable square
                     the Premises                    feet, as set forth under
                                                     "Premises" above,
                                                     conclusive for all
                                                     purposes.

                     Total rentable square feet of
                     the Property (the "PROPERTY
                     SQUARE FOOTAGE"), as the same
                     may change, as reflected in
                     Section 2.5:                    361,000

                     125 Spring Street               52,000 rentable square feet

                     131 Spring Street               103,000 rentable square
                                                     feet

                     141 Spring Street               206,000 rentable square
                                                     feet

ART. 10              TENANT'S BUILDING PERCENTAGE    100% (which is the number
                     SHARE:                          of rentable square feet
                                                     contained in the Premises
                                                     divided by the number of
                                                     rentable square feet in the
                                                     Building).

                     TENANT'S PROPERTY SHARE:        12.69% (which is the number
                                                     of rentable square feet
                                                     contained in the Upper
                                                     Level Space divided by the
                                                     Property Square Footage),
                                                     subject to adjustment in
                                                     the event of changes to the
                                                     Property Square Footage.

ART. 12              LANDLORD'S CONSTRUCTION
                     REPRESENTATIVE:                 Joseph L. Zink

                     TENANT'S CONSTRUCTION
                     REPRESENTATIVE:                 Gordon Letts

ART. 23              SECURITY DEPOSIT:               $800,000 in cash or letter
                                                     of credit in accordance
                                                     with the requirements of
                                                     Section 23.

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ART. 27              BROKER:                         CB Richard Ellis/Lynch
                                                     Murphy Walsh Advisors and
                                                     Richards Barry Joyce &
                                                     Partners, LLC

EXHIBITS

Exhibit 1            Legal Description of Property

Exhibit 2            Plans for Leasehold Work and Base Building Work

Exhibit 3            Base Building Specifications

Exhibit 4            Plans for Cosmetic Upgrades

Exhibit 5            Description of Leasehold Work

Exhibit 6            Rules and Regulations

Exhibit 7            Hazardous Waste Management Program

Exhibit 8            Environmental Reports

Exhibit 9            Form of Letter of Credit

Exhibit 10           Excerpts from Zoning By-law

Exhibit 11           Construction Schedule, with Milestones

Exhibit 12           Plan showing parking area

Exhibit 13           Construction Contract

Exhibit 14           Budget for Leasehold Work and Cosmetic Upgrade

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       THIS INDENTURE OF LEASE (the "LEASE") is hereby made and entered into on
the Execution Date by and between Landlord and Tenant.

       Landlord does hereby demise and lease to Tenant, and Tenant does hereby
lease and take from Landlord, the Premises upon and subject to the covenants,
agreements, terms, provisions and conditions of this Lease for the term
hereinafter stated.

1.     REFERENCE DATA; NET LEASE; NON-TERMINABILITY

       1.1    Each reference in this Lease to any of the terms and titles
contained in any Exhibit attached to this Lease shall be deemed and construed to
incorporate the data stated under that term or title in such Exhibit. All
capitalized terms not otherwise defined herein shall have the meanings ascribed
to them as set forth in the Lease Data appearing on pages (i) - (iv) hereof (the
"LEASE DATA").

       1.2    This Lease is a net lease, and Rent (hereinafter defined) shall be
paid without notice or demand, and without setoff, counterclaim, defense,
abatement, suspension, deferment, reduction or deduction, except as expressly
provided herein. Except as expressly set forth in this Lease, all repair and
maintenance obligations, utilities, insurance and related costs shall be the
sole responsibility of Tenant.

       1.3    This Lease shall not terminate, nor shall Tenant have any right to
terminate this Lease, nor shall the obligations and liabilities of Tenant set
forth herein be otherwise affected, except as expressly provided herein.

       1.4    Tenant waives all rights (i) to any abatement, suspension,
deferment, reduction or deduction of or from Rent, and (ii) to quit, terminate
or surrender this Lease or the Premises or any part thereof, except as expressly
provided herein.

       1.5    It is the intention of the parties hereto that the obligations of
Tenant hereunder shall be separate and independent covenants and agreements,
that Rent shall continue to be payable in all events and that the obligations of
Tenant hereunder shall continue unaffected, unless the requirement to pay or
perform the same shall have been terminated pursuant to an express provision of
this Lease.

       1.6    Tenant agrees that it will remain obligated under this Lease in
accordance with all of its terms and provisions, and that it will not take any
action to terminate, rescind or avoid this Lease or any portion thereof,
notwithstanding (i) the bankruptcy, insolvency, reorganization, composition,
readjustment, liquidation, dissolution, termination, winding-up or other
proceeding affecting Landlord or any assignee of Landlord in any such
proceeding, and (ii) any action with respect to this Lease which may be taken by
any trustee or receiver of Landlord or of any assignee of Landlord in any such
proceeding or by any court in any such proceeding.

2.     DESCRIPTION OF PREMISES

       2.1    PREMISES. The Premises are those portions of the Building more
particularly described in EXHIBIT 2, intending to describe the entire Building,
as the Premises may from time

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to time be constituted after changes therein, additions thereto and eliminations
therefrom pursuant to the provisions hereof.

       2.2    APPURTENANT RIGHTS; TENANT'S ACCESS.

              (a)    Tenant shall have, as appurtenant to the Premises, rights
to use in common, with others entitled thereto, subject to the Rules and
Regulations (hereinafter defined) the access drives, walkways and Nitromed
Parking Area (defined in Section 2.3).

              (b)    From and after the Completion Date (defined in Section
4.1(f)) and until the end of the term hereof, Tenant shall have access to the
Building and the Premises twenty-four (24) hours a day, seven (7) days a week,
subject to the terms of this Lease.

              (c)    Commencing on the date hereof, Tenant shall have the right
to access the Premises for purposes reasonably related to installation of
Tenant's telecommunications equipment, furniture and personal property, provided
such access does not interfere with the preparation for or performance of
Landlord's Work (hereinafter defined). Tenant shall, prior to commencing any
work, moving in any property or occupying the Premises for any purpose, provide
Landlord with certificates of insurance evidencing that the insurance required
in Article 15 hereof is in full force and effect and covering any person or
entity entering the Property. Except to the extent caused by the negligence or
willful misconduct of any of the Landlord Parties, Tenant shall defend,
indemnify and hold Landlord, Landlord's agents, contractors and employees, and
any of the officers, trustees, directors, partners, beneficiaries, joint
venturers, members, stockholders or other principals or representatives and the
like, disclosed or undisclosed, thereof (collectively, the "LANDLORD PARTIES")
harmless from and against any and all claims, damages, losses, penalties, costs,
expenses and fees (including without limitation reasonable legal fees) for
injury to persons or property (collectively, "CLAIMS") resulting from or
relating to Tenant's access to and use of the Premises prior to the Rent
Commencement Date as provided under this Section 2.2(c). Tenant shall coordinate
any access to the Premises prior to the Completion Date with Landlord's
Construction Representative.

       2.3    PARKING. During the term hereof, commencing on the Completion
Date, Landlord will, subject to the terms hereof, make available for Tenant's
use the 138 parking spaces indicated on Exhibit 12 attached hereto (the
"NITROMED PARKING AREA") and 100% of the cost of maintaining the Nitromed
Parking Area (i.e., 69% of maintaining the entire parking area for 125 Spring
Street, a percentage obtained by dividing the number of parking spaces in the
Nitromed Parking Area (138) by the number of parking spaces in the entire
parking area (200)) shall be included within Building Operating Costs (defined
in Section 10.1) and paid by Tenant pursuant to Section 10. The parking spaces
shall be subject to such reasonable rules and regulations as may be in effect
for the use of the parking facilities from time to time. Landlord agrees that it
will not use the balance of the 125 Spring Street parking area for uses other
than parking for tenants or occupants of the Property (but not parking of
construction vehicles) or open space (which may be green space), and agrees that
it shall demise the Nitromed Parking Area with a physical boundary to separate
it from the balance of the 125 Spring Street parking area if it elects to use
such balance for parking.

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       2.4    EXCLUSIONS. In all buildings on the Property, the rooftops may be
used by Landlord for telecommunications, satellite or any other use, provided
such uses, at the time commenced, do not interfere with Tenant's use of the
Building or rooftop at such time. Tenant shall have the right to install
telecommunications equipment and/or equipment associated with the Permitted Use
on the rooftop, for its own business purposes only, and not for lease or use by
others, provided (a) Landlord first approves all plans for such equipment and
installation, which approval will not be unreasonably withheld, conditioned or
delayed, (b) such equipment does not interfere with Landlord's use of the
rooftop at the time Tenant's proposed use commences and (c) Tenant shall remove
all such equipment at the expiration of the Term, repairing any damage caused by
such removal, unless Landlord elects to waive such obligation to remove, which
Landlord may do at any time. Notwithstanding the provisions of Section 14.6 to
the contrary, Tenant shall be responsible for all roof repairs made necessary as
a result of the use or installation of Tenant's equipment on the rooftop.

       2.5    RIGHTS RESERVED TO LANDLORD.

              (a)    ALTERATIONS TO THE BUILDING. Landlord reserves the right,
exercisable by Landlord or its nominee, at any time and from time to time, to
make such changes, alterations, additions, improvements, repairs or replacements
in or to the Building (but only for the purposes of repairs, maintenance,
replacements and other rights expressly reserved to Landlord herein), as well as
in or to the street entrances and parking areas, provided, however, that there
be neither obstruction of access to, nor interference with, the use and
enjoyment by Tenant of the Premises or the 138 parking spaces indicated on
EXHIBIT 12.

              (b)    ADDITIONS TO THE PROPERTY. Landlord may at any time or from
time to time construct additional improvements in all or any part of the
Property, including, without limitation, adding additional buildings to the
Property or changing the location or arrangement of any improvement on the
Property or all or any part of the common areas thereof, or add or deduct any
land to or from the Property, or reconfigure lot lines within the Property. Such
construction shall not impact the first-class quality of the Building, the
Building Lot or affect access to or egress from the Building or the parking
areas serving the same or decrease the number or location of the 138 parking
spaces indicated on EXHIBIT 12; and Landlord shall use diligent efforts to
minimize interference with Tenant's use and enjoyment of the Premises.

              (c)    ACCESS TO THE PREMISES. (i) Subject to the terms hereof,
Tenant shall (x) upon as much advance notice as is practical under the
circumstances and no less than forty-eight (48) hours' notice in non-emergency
situations, permit Landlord and any mortgagee of the Building or the Property or
of the interest of Landlord therein (each, a "MORTGAGEE"), and their agents,
employees and contractors, to have access to and to enter upon the Premises for
the purposes of inspection, making repairs, replacements or improvements in or
to the Premises or the Building or equipment therein (including, without
limitation, sanitary, electrical, heating, air conditioning or other systems),
complying with all applicable laws, ordinances, rules, regulations, statutes,
by-laws, court decisions and orders and requirements of all public authorities
(collectively, "LEGAL REQUIREMENTS"), or exercising any right specifically
reserved to Landlord by this Lease; and (y) upon no less than forty-eight (48)
hours' notice, permit Landlord and its agents and employees, at reasonable
times, upon reasonable advance notice, to show the

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Premises during ordinary business hours to any prospective Mortgagee or
purchaser of the Building or the Property or of the interest of Landlord
therein, and during the last eighteen (18) months of the term hereof,
prospective tenants. If Landlord's access to the Premises for any purposes
permitted under this Lease requires Landlord to access or work in any controlled
or restricted laboratory areas within the Premises, then, except in case of
emergency, Landlord must be accompanied by a Tenant representative. Tenant shall
make a representative available during normal business hours to provide access
to the restricted areas of the Premises. If Tenant or its designated
representative shall not be personally present to permit entry into the Premises
when an entry therein shall be necessary due to an emergency, Landlord or
Landlord's agents may enter the same by a master key, or may forcibly enter the
same, without rendering Landlord or such agents liable therefor (if during such
entry Landlord or Landlord's agents shall accord reasonable care to Tenant's
property and to the ongoing operations areas and specifically excluding
Landlord's negligence and misconduct), and without in any manner affecting the
obligations and covenants of this Lease.

                     (ii)    Without incurring any liability to Tenant,
Landlord, after using reasonable efforts to reach Tenant and being unable to do
so, may permit access to the Premises and open the same, whether or not Tenant
shall be present, upon any demand of any receiver, trustee, assignee for the
benefit of creditors, sheriff, marshal or court officer entitled to, or
reasonably purporting to be entitled to, such access for the purpose of taking
possession of, or removing, Tenant's Property (hereinafter defined) or for any
other lawful purpose, but this provision and any action by Landlord hereunder
shall not be deemed a recognition by Landlord that the person or official making
such demand has any right or interest in or to this Lease, the Premises or
Tenant's Property (hereinafter defined), or upon demand of any governmental
official or representative.

              (d)    TENANT REMAINS OBLIGATED. Nothing contained in this Section
2.5 shall be deemed to relieve Tenant of any duty, obligation or liability of
Tenant with respect to making any repair, replacement or improvement expressly
set forth herein or complying with any Legal Requirements.

              (e)    MINIMIZE INTERFERENCE. Except in the event of an emergency,
Landlord shall use commercially reasonable efforts to minimize any interference
with Tenant's business operations and use and occupancy of the Premises in
connection with the exercise any of the foregoing rights under this Section 2.5.

3.     TERM OF LEASE

       3.1    HABENDUM; EARLY TERMINATION RIGHT. TO HAVE AND TO HOLD the
Premises for a term of years commencing on the Term Commencement Date and,
unless earlier terminated or extended pursuant to the terms hereof, ending on
the Expiration Date.

       Notwithstanding the foregoing, Tenant shall have a one time option to
terminate this lease at the end of the fifth (5th) Rent Year of the term by
giving Landlord notice on or before the end of the fourth (4th) Rent Year of the
term of its intention to terminate this lease, which notice shall be accompanied
by a payment equal to fifty percent (50%) of the termination fee of $4,200,000

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(which amount represents the sum of: one year's rent at the Rent Year 5 rate
plus the unamortized portion of Landlord's Contribution and Landlord's
transaction costs). The $2,100,000 balance of the termination fee shall be paid
on the Lease termination date.

       3.2    DECLARATION FIXING TERM COMMENCEMENT DATE, RENT COMMENCEMENT DATE,
AND EXPIRATION. Each of the parties hereto agrees to join in the execution, in
recordable form, of a statutory notice of lease and/or written declaration in
which shall be stated the Term Commencement Date, the Rent Commencement Date,
and the Expiration Date, which notice of lease may be recorded by Tenant with
the Middlesex South Registry of Deeds and the Registry District of the Land
Court (collectively, the "REGISTRY"). Upon the expiration or earlier termination
of this Lease, Landlord shall deliver to Tenant a notice of termination of lease
acknowledging the termination of this Lease and Tenant shall promptly execute
and deliver the same to Landlord for Landlord's execution and recordation with
the Registry. Tenant shall deliver the executed notice of termination of lease
within ten (10) business days of receipt thereof. Within twenty (20) days after
the Completion Date (defined in Section 4.1(f)), Landlord and Tenant shall
execute and deliver to one another a certificate memorializing the Rent
Commencement Date and Expiration Date.

4.     CONSTRUCTION

       4.1    LANDLORD'S WORK.

              (a)    BASE BUILDING AND EXTERIOR WORK. Landlord shall perform the
base building work described in the Base Building Specifications attached hereto
as EXHIBIT 3 and the work described in the cosmetic upgrade plans to be attached
hereto as EXHIBIT 4 (collectively, "BASE BUILDING WORK"), and the leasehold
improvement work described on EXHIBIT 5 attached hereto (the "LEASEHOLD WORK"),
as such exhibits may be amended from time to time in accordance with the
provisions of this Lease. The Base Building Work and the Leasehold Work are
referred to together herein as "LANDLORD'S WORK", and both are jointly detailed
in the plans attached hereto as EXHIBIT 2 (except for the fact that such plans
do not include the Cosmetic Upgrade, defined below). Landlord's Work shall be
performed in a good, first-class and workmanlike manner, in compliance with
EXHIBITS 2, 3, 4 and 5 and in compliance with all applicable laws and codes (in
the case of the work described in EXHIBIT 3) and in compliance with all
applicable zoning laws (in the case of the work described in EXHIBITS 4 and 5,
such zoning compliance to be evidenced by the delivery of the final certificate
of occupancy). Landlord's Work shall be performed by the Richmond Group, as
general contractor. On or before the Cosmetic Plan Completion Date, Landlord and
Tenant shall have agreed upon plans for cosmetic upgrades to the front entrance,
lobby, toilet cores, facade and landscaping of the Building, such work to be
performed by Landlord as part of the Base Building Work, provided the cost of
the same is less than $715,866. Tenant shall prepare and deliver to Landlord for
Landlord's approval plans for the cosmetic upgrade work. Landlord's approval of
such plans shall not be unreasonably withheld or delayed and shall be deemed
granted if not withheld within five (5) days after delivery to Landlord with
written request for approval. It shall be deemed reasonable for Landlord to
withhold approval if the cosmetic upgrade work would reasonably be expected to
delay completion of Landlord's Work. Failure to reach agreement upon plans for
the cosmetic upgrades by the Cosmetic Plan Completion Date shall constitute a
Tenant Delay

                                       -5-
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automatically, without need for action by Landlord. When agreed upon, such plans
(the "COSMETIC UPGRADE PLANS") shall be attached hereto as EXHIBIT 4 (such work
being described hereafter as the "COSMETIC UPGRADE").

              Subject to delays due to governmental regulation, unusual scarcity
of or inability to obtain labor or materials, labor difficulties, acts of God,
war, terrorism, unusually severe weather, casualty or other causes reasonably
beyond Landlord's control (collectively "EVENTS OF FORCE MAJEURE") and subject
to any Tenant Delay (hereinafter defined), Landlord shall use good faith
diligent efforts in the construction of Landlord's Work so as to have Landlord's
Work substantially completed on or before the Estimated Delivery Date, but
Tenant shall have no claim against Landlord for failure to complete construction
of Landlord's Work, Tenant's sole recourse being expressly set forth in Section
4.1(d) below.

              (b)    PLANS; CHANGE ORDERS. None of EXHIBITS 2, 3, 4 or 5 may be
changed without the consent of both Landlord and Tenant, each acting reasonably
and in good faith. In the event either desires to make a change order, it shall
advise the other in writing, and the other shall have ten (10) days within which
to approve or reject such request. In the case of change orders requested by
Tenant which would increase the cost or delay the completion of Landlord's Work,
it shall be deemed reasonable for Landlord to condition its approval upon
Tenant's bearing the economic cost of the change order (the foregoing shall not
be deemed to reduce Landlord's Contribution, however), or, if such increase or
delay is significant, to reject the requested change order. Landlord agrees that
a change order for an outdoor patio of the type previously presented by Tenant
would be accepted by Landlord, subject to Tenant's bearing the economic cost of
such change order. In the event any change order requested by Tenant and
approved by Landlord (including without limitation a change order relating to
the aforementioned patio) delays completion of Landlord's Work, the "Completion
Date" shall be the date upon which "Substantial Completion" (defined in Section
4.1(f)) would have been achieved, absent the change order. Tenant acknowledges
that is the intent of the parties that the entire Premises be improved as part
of Landlord's Work, and that it is a material inducement to Landlord to enter
into this Lease that the Leasehold Work be allocated reasonably throughout the
Building. Tenant hereby acknowledges that change order requests will be rejected
if they do not reflect a consistent and first-class leasehold improvement
package throughout the entire Building. Landlord's approvals of EXHIBITS 4 and 5
and any change orders requested by Tenant are given solely for the benefit of
Landlord and Tenant under this Section 4.1(b) and neither Tenant nor any third
party shall have the right to rely upon such approvals for any other purpose
whatsoever. Without limiting the foregoing, Tenant acknowledges that it has been
and will be responsible for all elements of the design of the Leasehold Work
(including, without limitation, compliance with Legal Requirements,
functionality of design, the structural integrity of the design, the
configuration of the Premises and the placement of Tenant's furniture,
appliances and equipment), and Landlord's approval of EXHIBITS 4 and 5 shall in
no event relieve Tenant of the responsibility therefor.

              (c)    TENANT DELAY. A "TENANT DELAY" shall be defined as any act
or, where there is a duty to act under this Lease or at law, any omission or
failure to act by Tenant and/or Tenant's agents, servants, employees,
consultants, contractors, subcontractors, licensees and/or subtenants
(collectively with Tenant, the "TENANT PARTIES") which causes a delay in the

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completion of Landlord's Work. Notwithstanding the foregoing, no event (other
than the failure to reach agreement on the Cosmetic Upgrade Plans by the
Cosmetic Plan Completion Date, which shall constitute a Tenant Delay
automatically, without need for action by Landlord), shall be deemed to be a
Tenant Delay until and unless Landlord has given Tenant written notice (the
"TENANT DELAY NOTICE") advising Tenant that a Tenant Delay has occurred or is
occurring.

              (d)    TENANT'S TERMINATION RIGHT; ABATEMENT FOR LATE DELIVERY.
Subject to extension on account of Tenant Delays and Events of Force Majeure (as
stated in the Lease Data, the maximum extension on account of Events of Force
Majeure shall be 30 days in the case of commencement of Landlord's Work and 90
days in the case of Substantial Completion of Landlord's Work), if Landlord's
Work has not commenced (as evidenced by issuance of a building permit and actual
start of construction) on or before the Construction Commencement Date or been
Substantially Completed on or before the Outside Delivery Date, Tenant may
terminate this Lease by providing written notice of such intent within thirty
(30) days after such date, TIME BEING OF THE ESSENCE; provided, however, that if
Landlord's Work has commenced or been Substantially Completed, as applicable,
within sixty (60) days after delivery of such notice, such termination notice
shall be null and void and the Lease shall continue in full force and effect. In
addition, subject to extension on account of Tenant Delays and, up to a maximum
of three (3) months, Events of Force Majeure, if Landlord's work has not been
substantially completed on or before the Late Delivery Date, then in addition to
the fact that the Rent Commencement Date shall be delayed on a day-for-day basis
as Substantial Completion is delayed, Tenant shall be entitled to two (2)
additional days of free rent for each day after the Late Delivery Date that
failure to achieve Substantial Completion continues (by way of illustration, if
the Estimated Delivery Date is July 8, 2004 and the Late Delivery Date is August
7, 2004, and there have been no Tenant Delays or Events of Force Majeure, and
Substantial Completion is achieved on August 17, 2004 (i.e., ten (10) days after
the Late Delivery Date), then Tenant shall be entitled to twenty (20) days of
free rent, such twenty-day period to be applied commencing upon the date that
otherwise would have been the Rent Commencement Date (i.e., the earlier of (i)
September 16, 2004 (30 days after Substantial Completion), or (ii) the date that
is 30 days after the date Tenant takes occupancy of any part of the Premises for
business purposes). Landlord agrees to use good faith diligent efforts to
perform Landlord's work expeditiously and to achieve the milestone dates set
forth on EXHIBIT 11, but the termination right set forth in the first sentence
of this Section 4.1(d) and the rent abatement right set forth in the second
sentence of this Section 4.1(d) shall be Tenant's sole and exclusive rights and
remedies for any delay in performing Landlord's Work.

              (e)    LANDLORD'S WARRANTY; SATISFACTION OF LANDLORD'S OBLIGATIONS

                     (i)     LANDLORD'S WARRANTY. Landlord warrants to Tenant
that (A) materials and equipment furnished in the performance of Landlord's Work
will be of good quality and new, (B) Landlord's Work will be free from defects
not inherent in the quality required or permitted under EXHIBITS 2, 3, 4 or 5,
(C) the Building shall be delivered free of mold and asbestos, and (D) the
Building shall be in accord with all applicable zoning regulations (delivery of
the final certificate of occupancy shall be deemed to be satisfaction of this
condition) and in accord with all covenants binding Landlord or running with the
Property. Any portion of Landlord's Work not conforming to the foregoing
requirements, including substitutions not

                                       -7-
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properly approved and authorized, may be considered defective. Landlord's
warranty excludes remedy for damage or defect caused by abuse, modifications not
made by Landlord, improper or insufficient maintenance, improper operation or
normal wear and tear and normal usage.

                     (ii)    WARRANTY PERIOD. Landlord shall be deemed to have
satisfied all of its obligations under this Article 4 (including, without
limitation, Landlord's warranty obligations under this Section 4.1(e)) except to
the extent that, on or before the date (the "WARRANTY EXPIRATION DATE") which is
fifteen (15) days prior to the expiration of the warranty by The Richmond Group
under its construction contract for Landlord's Work, TIME BEING OF THE ESSENCE,
Tenant gives written notice to Landlord setting forth with specificity the
manner in which Tenant believes that Landlord has failed to comply with its
obligations under this Article 4. Pursuant to such construction contract, The
Richmond Group's warranty expires on the date that is one (1) year after the
issuance of the temporary certificate of occupancy for the Building. A true,
correct and complete copy of its construction contract with The Richmond Group
is attached hereto as EXHIBIT 13.

                     (iii)   REPAIR OF DEFECTIVE WORK. Landlord agrees that it
shall, without cost to Tenant, correct any portion of Landlord's Work which is
found not to be in accordance with the requirements of the warranties set forth
in this Section 4.1(e), unless Tenant has previously given Landlord express
written acceptance of such condition, provided that Tenant gives Landlord
written notice of such condition promptly after it becomes aware of such
condition, and in any event on or before the Warranty Expiration Date.

              (f)    SUBSTANTIAL COMPLETION; PUNCHLIST. Landlord's Work shall be
deemed "SUBSTANTIALLY COMPLETE" and "SUBSTANTIAL COMPLETION" shall be deemed to
have occurred if Landlord's Work is entirely completed in accordance with
EXHIBITS 2, 3, 4 and 5, except for minor punch list items, the completion of
which shall not materially interfere with Tenant's use of the Premises and a
temporary certificate of occupancy reasonably acceptable to Tenant shall have
been approved for issuance for the Premises, such date being referred to
hereinafter as the "COMPLETION DATE". In the event of a Tenant Delay, the
Completion Date shall be the date upon which Landlord's Work would have been
Substantially Complete, absent such delay, as determined by Landlord in its
reasonable judgment in accordance with terms and provisions of this Lease. Prior
to delivery of the Premises to Tenant with Landlord's Work Substantially
Complete, Landlord and Tenant and their respective architects and
representatives shall inspect the Premises and mutually prepare a list (the
"PUNCHLIST") of outstanding items which need to be completed to make Landlord's
Work comply with EXHIBITS 2, 3, 4 and 5, as applicable ("PUNCHLIST ITEMS").
Landlord shall use good faith diligent efforts to complete all Punchlist Items
within ninety (90) days after the date of the Punchlist, and to satisfy all
conditions, if any, to the temporary certificate of occupancy, within the time
periods, if any, set forth in the temporary certificate of occupancy, time being
of the essence. If Landlord fails to complete any Punchlist Items or satisfy any
conditions to the temporary certificate of occupancy within the required time
periods, Tenant shall have the right to advise Landlord in writing that Tenant
intends to exercise self-help rights to complete the Punchlist Items or cause
such conditions to be satisfied, and if Landlord fails to complete the Punchlist
Items or cause such conditions to be satisfied within thirty (30) days after
delivery of such notice, Tenant may elect to complete such Punchlist Items or
cause such conditions to be satisfied itself, following which Landlord shall

                                       -8-
<Page>

reimburse Tenant for the reasonable costs of doing so, as detailed in a
requisition notice from Tenant to Landlord. If Landlord fails to make
reimbursement within thirty (30) days after receipt of the requisition notice
from Tenant, then Tenant may offset against the Rent payable hereunder the
reasonable costs incurred by it in completing the Punchlist Items or causing
such conditions to be satisfied. In all events, it shall be the responsibility
of Landlord to obtain the final certificate of occupancy.

              (g)    ASSIGNMENT OF CONSTRUCTION WARRANTIES. Upon the Warranty
Expiration Date, Landlord shall at Tenant's request assign to Tenant any and all
construction and manufacturers' warranties and guarantees with respect to
Landlord's Work and, to the extent that any such warranties and guarantees are
not assignable, Landlord agrees to enforce the same for the benefit of Tenant,
at Tenant's sole cost and expense, paid in advance.

              (h)    MEETINGS. Landlord and Tenant agree to have their
Construction Representatives attend weekly construction meetings during the
course of performance of Landlord's Work.

              (i)    MISCELLANEOUS. All times set forth in Section 4.1 shall be
of the essence. Each of Landlord and Tenant shall be entitled to rely upon
actions taken and consents given by the other's Construction Representative as
if the same had been taken or given by Landlord or Tenant itself.

       4.2    COST OF LANDLORD'S WORK.

              (a)    The Base Building Work shall be performed at Landlord's
sole cost and expense, except that Landlord's financial responsibility with
respect to the Cosmetic Upgrade shall not exceed $715,866, as set forth in
Section 4.2(b).

              (b)    The Leasehold Work shall be performed at Tenant's sole cost
and expense, except that Landlord shall contribute the Landlord's Contribution
to the cost of the Leasehold Work. The Cosmetic Upgrade shall be paid for by
Landlord up to $715,866 and by Tenant to the extent the cost of such work
exceeds $715,866. In the event the estimated amounts to be paid by Tenant (i.e.,
the amount by which Cosmetic Upgrade costs are estimated to exceed $715,866 plus
the amount by which estimated Leasehold Work costs exceed Landlord's
Contribution) exceed $200,000, Tenant shall deposit such estimated excess (the
"TENANT CONTRIBUTION") with Landlord prior to commencement of Landlord's Work.
Landlord shall pay the first $715,866 of the Cosmetic Upgrade Work and the first
$4,720,000 of the Leasehold Work and shall then pay for such work from Tenant's
Contribution. In the event the final cost of the Leasehold Work (or Cosmetic
Upgrade, as applicable) is less than the estimate therefor or Tenant terminates
this Lease in accordance with the provisions of Section 4.1(d), the portion of
Tenant's Contribution not used shall be applied against the Rent first coming
due hereunder or, in the case of a Lease termination pursuant to the provisions
of Section 4.1(d), refunded to Tenant. In the event the actual cost of the
Leasehold Work (or Cosmetic Upgrade, as applicable) exceeds the estimate
therefor, Tenant shall within thirty (30) days after demand therefor pay such
excess to Landlord. Any failure by Tenant to make payments under this Section
4.2(b) on a timely basis shall constitute a Tenant Delay. Landlord shall have no
obligation to continue performing Landlord's

                                       -9-
<Page>

Work during any period in which an Event of Default exists, including for
failure to have deposited amounts required to have been deposited under this
Section 4.2(b). Attached as EXHIBIT 14 for illustrative purposes only is a copy
of the current budget for the Leasehold Work and Cosmetic Upgrade, which has
been prepared by the general contractor and approved by Tenant. Landlord shall
use good faith efforts to cause the Leasehold Work and Cosmetic Upgrade to be
completed for a cost within that approved budget, provided the foregoing shall
not detract in any manner from Tenant's obligation to pay for the cost of the
Leasehold Work above Landlord's Contribution and the cost of the Cosmetic
Upgrade above $715,866. The Leasehold Work and Cosmetic Upgrade shall be priced
with Tenant's participation, and subcontractors shall be subject to a
competitive bid process, with major subcontracts being bid to three (3)
subcontractors. Landlord and Tenant have jointly selected and approved the MEP
subcontractors.

              (c)    Landlord's Contribution shall be made available for
application to the cost of the Leasehold Work, including all associated wiring
and cabling costs, but shall not be available for application to the cost of any
of Tenant's personal property or equipment, including decorations and artwork,
de-mountable partitions, signs, and trade fixtures. Up to ten percent (10%) of
the Landlord Contribution may be used for engineering and architectural costs.

              (d)    In the event the cost of the Leasehold Work is less than
the amount of Landlord's Contribution, Tenant may requisition the remaining
balance of Landlord's Contribution for additional leasehold improvements
approved by Landlord in accordance with all applicable provisions of this Lease
(Landlord hereby approves the outdoor patio previously presented to Landlord),
provided (i) Landlord shall have no obligation to advance funds on account of
Landlord's Contribution more than once per month; (ii) Landlord shall have the
right to have Landlord's Contribution paid directly to Tenant's contractors;
(iii) Landlord shall have no obligation to pay any portion of Landlord's
Contribution with respect to any requisition submitted after the date that is
the third (3rd) anniversary of the Rent Commencement Date; (iv) Landlord's
obligation to pay any portion of Landlord's Contribution shall be conditioned
upon there existing no Event of Default by Tenant in its obligations under this
Lease at the time that Landlord would otherwise be required to make such
payment; (v) Landlord's obligation to pay requisitions of Landlord's
Contribution shall be subject to simultaneous delivery of all lien waivers
relating to materials, services and work delivered or performed in connection
with Tenant's leasehold improvement work; and (vi) at least 75% of the
Landlord's Contribution shall have been used in connection with the Leasehold
Work. In the event Landlord is required hereunder to fund any part of Landlord's
Contribution but fails to do so, Tenant shall have the right to offset against
the Rent next payable hereunder an amount equal to the portion of Landlord's
Contribution required to have been funded but not funded. In the event the cost
of the Cosmetic Upgrade is less than $715,866, the Landlord's Contribution shall
be deemed to be increased by the difference between the actual cost of the
Cosmetic Upgrade and $715,866.

5.     USE OF PREMISES

       5.1    PERMITTED USE. Tenant shall during the term hereof use the
Premises only for the Permitted Uses and for no other purposes. Landlord
represents and warrants to Tenant that the Building is located within the Town
of Lexington's Commercial Regional Office (CRO) zoning

                                      -10-
<Page>

district, and that attached hereto as EXHIBIT 10 is a table of permitted uses
from the Town of Lexington's zoning by-law, listing uses permitted in a CRO
district.

       5.2    PROHIBITED USES.

              (a)    Notwithstanding any other provision of this Lease, Tenant
shall not use the Premises, the Building or the Property, or any part thereof,
or suffer or permit the use or occupancy of the Premises, the Building or the
Property or any part thereof by any of the Tenant Parties (i) in a manner which
would violate (A) any of the covenants, agreements, terms, provisions and
conditions of this Lease, (B) any other agreement or instrument of record as of
the Term Commencement Date or of which Tenant has received notice as of the Term
Commencement Date, or (C) any agreement or instrument entered into after the
Term Commencement Date affecting the Building or Property (including easements,
covenants and restrictions), provided the same do not materially increase the
obligations or derogate from the rights of Tenant under this Lease; (ii) for any
unlawful purposes or in any unlawful manner; (iii) which, in the reasonable
judgment of Landlord shall (A) impair the appearance or reputation of the
Building; (B) impair, interfere with or otherwise diminish the quality of any of
the Building services or the proper and economic heating, cleaning, ventilating,
air conditioning or other servicing of the Building; (C) occasion discomfort,
inconvenience or annoyance in any material respect (and Tenant shall not install
or use any electrical or other equipment of any kind which, in the reasonable
judgment of Landlord, will cause any such impairment, interference, discomfort,
inconvenience, annoyance or injury), or cause any injury or damage to other
tenants or occupants of the Property or their property; or (D) cause harmful air
emissions, animal or laboratory odors or noises, or any unusual or other
objectionable odors, noises or emissions to emanate from the Premises which
adversely affect the common areas or other tenants of the Property; or (iv) in a
manner which is inconsistent with the operation of the Building as a combination
office, research, development and laboratory facility of the first class in the
quality of its maintenance, use, or occupancy.

              (b)    With respect to the use and occupancy of the Premises and
the common areas of the Property, Tenant will not: (i) place or maintain any
trash, refuse or other articles on the footwalks or corridors adjacent to the
Building or elsewhere on the exterior of the Premises, nor obstruct any
driveway, corridor, footwalk, parking area or any other common areas of the
Building or Property; (ii) permit undue accumulations of or burn garbage, trash,
rubbish or other refuse within or without the Premises; (iii) permit the parking
of vehicles so as to interfere with the use of any driveway, corridor, footwalk,
parking area, or other common areas of the Property; (iv) receive or ship
articles of any kind outside the designated loading areas for the Building; (v)
conduct or permit to be conducted any auction, going out of business sale,
bankruptcy sale (unless directed by court order), or other similar type sale in
or connected with the Premises; (vi) use the name of Landlord, or any of
Landlord's affiliates or subsidiaries or any advertising film of the exterior of
the Building, the Property or any part thereof in any publicity, promotion,
trailer, press release, advertising, printed, or display materials without
Landlord's prior written consent; and (vii) cause or permit any material holes
to be drilled or made in any part of the Building other than as part of
Alterations approved by Landlord in writing in advance.

                                      -11-
<Page>

       5.3    LICENSES AND PERMITS. If any governmental license or permit shall
be required for the proper and lawful conduct of Tenant's business (other than
the certificate of occupancy, which shall be Landlord's responsibility), Tenant,
at Tenant's expense, shall duly procure and thereafter maintain such license and
submit the same to inspection by Landlord. Tenant, at Tenant's expense, shall at
all times comply with the terms and conditions of each such license or permit.
Tenant shall furnish all data and information to governmental authorities, with
a copy to Landlord, as required in accordance with Legal Requirements as they
relate to Tenant's use or occupancy of the Premises or the Building. Landlord
shall reasonably cooperate with Tenant, at no material cost to Landlord, in
connection with its application for any required licenses, permits and approvals
for the Permitted Uses and Tenant's occupancy of the Premises.

       5.4    DUE CARE. Tenant shall use reasonable care in connection with the
use of any materials, appliances or equipment so as not to pose any danger to
life, safety or health or cause damage, injury or death. Tenant shall operate
its business in accordance with the highest safety standards applicable to
Tenant's industry.

6.     RENT

       6.1    YEARLY RENT. During the term hereof, commencing on the Rent
Commencement Date, Tenant shall pay to Landlord the Yearly Rent, additional rent
and other charges in twelve (12) equal monthly installments, in advance and
without demand on the first day of each month for and in respect of such month.
The payment of Yearly Rent, additional rent and other charges reserved and
covenanted to be paid under this Lease with respect to the Premises
(collectively, "RENT") shall commence on the Rent Commencement Date. If the Rent
Commencement Date is on any day other than the first day of a calendar month,
Rent for such calendar month shall be prorated accordingly. Rent shall be
payable to Landlord or, if Landlord shall so direct in writing, to Landlord's
agent or nominee, in lawful money of the United States which shall be legal
tender for payment of all debts and dues, public and private, at the time of
payment, at the office of Landlord set forth in the Lease Data or such other
place as Landlord may designate in writing, and Rent in all circumstances shall
be payable without any setoff or deduction whatsoever, except as otherwise
expressly set forth herein.

       6.2    LATE PAYMENTS.

              (a)    Any payment of Yearly Rent due hereunder not paid when due
shall bear interest for each month or fraction thereof from the due date until
paid in full at the annual rate of four (4) percentage points over the so-called
prime rate charged from time to time by Bank of America, or its successor
national bank, or at any applicable lesser maximum legally permissible rate for
debts of this nature (the "DEFAULT RATE").

              (b)    Any payment of additional rent due hereunder not paid when
due shall bear interest for each month or fraction thereof from the due date
until paid in full at the Default Rate.

              (c)    Additionally, if Tenant fails to make any payment within
ten (10) days after notice that the same is due, Landlord may charge Tenant a
fee equal to one percent (1%) of the

                                      -12-
<Page>

delinquent payment to reimburse Landlord for its cost and inconvenience incurred
as a consequence of Tenant's delinquency.

7.     RENTABLE AREA

       All figures set forth herein which are based on the rentable area of the
Premises shall be conclusive and final.

8.     BUILDING SYSTEMS

       8.1    ELECTRIC CURRENT.

              (a)    METERED CHARGES. Tenant shall pay the full amount of any
electric charges attributable to the Building (including the exterior and 125
Spring Street parking area) as measured by the Building's electric meter, on or
before the due date therefor, directly to the supplier thereof. Landlord shall
reimburse Tenant for Landlord's 31% pro rata share of the cost of lighting the
125 Spring Street parking area within thirty (30) days after Tenant's request
therefor accompanied by the electric bill and evidence of payment; provided,
however, that if Landlord elects to use the balance of the parking area as open
space, it shall have no obligation to pay any portion of the parking area
lighting costs.

              (b)    REPLACEMENT BULBS. Tenant, at Tenant's sole cost and
expense, shall purchase and install all replacement bulbs used in the Premises.

              (c)    INTERRUPTION OF ELECTRICAL SERVICE. Landlord shall not in
any way be liable or responsible to Tenant for any loss, damage or expense which
Tenant may sustain or incur if the quantity, character, or supply of electrical
energy becomes no longer available or suitable for Tenant's requirements.

              (d)    ALTERATIONS TO ELECTRICAL EQUIPMENT. Tenant agrees that it
will not make any alteration or material addition to the electrical equipment in
the Premises which would adversely affect any base Building systems or equipment
without the prior written consent of Landlord in each instance, which consent
may be withheld in Landlord's reasonable discretion, and will promptly advise
Landlord of any other alteration or addition to such electrical equipment.

       8.2    WATER. Tenant shall pay to Landlord, as additional rent hereunder,
all water and sewer charges attributable to the Building and Building Lot,
pursuant to the municipal bill for the Building, within thirty (30) days after
demand therefor. Landlord shall pay the full amount due to the provider of such
water and sewer service prior to delinquency. At Landlord's election, Tenant
shall pay the Building's share of water and sewer charges directly to the
provider thereof.

       8.3    INTERRUPTION OR CURTAILMENT OF SERVICES.

              (a)    When necessary by reason of accident or emergency, or for
repairs, alterations, replacements or improvements which in the reasonable
judgment of Landlord are desirable or necessary to be made, Landlord reserves
the right, upon as much prior notice to

                                      -13-
<Page>

Tenant as is practicable under the circumstances, to interrupt, curtail, stop or
suspend (i) the furnishing of heating, elevator, air conditioning, and exterior
cleaning services, and (ii) the operation of the sanitary, plumbing, security
and electric systems. Except in case of emergency, Landlord shall give Tenant
notice of the exercise of its rights under this Section 8.3 and Landlord shall
use commercially reasonable efforts to minimize any interference with Tenant's
business operations and use and occupancy of the Premises in connection with
non-emergency interruptions and suspensions and to minimize the duration of any
interruption or suspension. In the event of a planned interruption of services
to perform scheduled repairs or maintenance, Landlord shall give Tenant such
prior written notice, not to exceed thirty (30) days, as is reasonable under the
circumstances in order that Tenant can take appropriate precautions to protect
its work. Landlord shall exercise reasonable diligence to eliminate the cause of
any such interruption, curtailment, stoppage or suspension, but there shall be
no diminution or abatement of Rent or other compensation due from Landlord to
Tenant hereunder, nor shall this Lease be affected or any of Tenant's
obligations hereunder reduced, and Landlord shall have no responsibility or
liability for any such interruption, curtailment, stoppage, or suspension of
services or systems. Notwithstanding the foregoing, in the event of an
interruption in services covered by Landlord's rental interruption insurance,
Landlord shall allow an abatement of Rent equal to the net recovery actually
obtained by Landlord under such coverage.

       8.4    ENERGY CONSERVATION. Notwithstanding anything to the contrary
contained herein, Landlord may request upon written notice to Tenant that Tenant
comply with such policies, programs and measures as may be necessary, required,
or expedient for the conservation and/or preservation of energy or energy
services (collectively, the "CONSERVATION PROGRAM").

       8.5    SECURITY. Landlord shall not be obligated to provide security
services to any of the Property, Building or Premises. Tenant, at Tenant's sole
cost, expense and responsibility, may install additional electronic card devices
and systems within the Premises and at the access points to the stairwells
provided such devices and systems shall be compatible with Landlord's electronic
card access system, if Landlord elects to install one.

9.     UTILITIES

       9.1    UTILITY SERVICES. Unless otherwise expressly provided herein,
commencing on the Completion Date, Tenant shall obtain and pay for all utilities
and services, consumed in and/or furnished to the Premises, together with all
taxes, penalties, surcharges and maintenance charges pertaining thereto. Upon
Substantial Completion of Landlord's Work, the Building will be served by
telephone, electric, gas and water and sewer, all of which shall be separately
metered. Landlord shall have the right to make any such payment if Tenant fails
to do so prior to delinquency, in which event Tenant shall reimburse Landlord
for the amount so paid upon demand therefor, together with interest at the
Default Rate until paid in full.

10.    OPERATING EXPENSES AND TAXES.

       10.1   DEFINITIONS. As used in this Article 10, the words and terms which
follow shall have the meanings set forth below:

                                      -14-
<Page>

              (a)    Taxes

                     (i)     "TAXES" shall mean the real estate taxes and other
taxes, levies and assessments imposed upon the Building, or on Landlord's
interest in the Building or such personal property (provided that to the extent
such taxes, levies, and assessments (amortized over the Term) are still assessed
against all or several of the buildings within the Property, or against the
Property as a whole, such amounts shall be allocated among the buildings in the
Property based on the assessor's records or, if the records do not provide a
separate allocation, based on square footage of the buildings in question unless
Landlord reasonably determines that such allocation should be made on another
reasonable basis); charges, fees and assessments (amortized over the Term) for
transit, housing, police, fire or other services or purported benefits to the
Building, specifically excluding so-called "linkage" fees; service or user
payments in lieu of taxes; and any and all other taxes, levies, betterments,
assessments and charges arising from the ownership, leasing, operation, use or
occupancy of the Building or based upon rentals derived therefrom, which are or
shall be imposed by federal, state, county, municipal or other governmental
authorities. Taxes shall not include any inheritance, estate, succession, gift,
franchise, rental, income or profit tax, capital stock tax, capital levy or
excise, or any income taxes arising out of or related to the ownership and
operation of the Building or Property, provided, however, that any of the same
and any other tax, excise, fee, levy, charge or assessment, however described,
that may in the future be levied or assessed as a substitute for or an addition
to, in whole or in part, any tax, levy or assessment which would otherwise
constitute "Taxes," whether or not now customary or in the contemplation of the
parties on the Execution Date of this Lease, shall constitute "Taxes". Taxes
shall not include any interest or penalties resulting from the late payment of
Taxes by Landlord provided that Tenant timely pays Tenant's Building Percentage
Share of Taxes pursuant to Section 10.2(a) below. "Taxes" shall also include
reasonable expenses (including without limitation legal and consultant fees) of
tax abatement or other proceedings contesting assessments or levies.

              (b)    "TAX PERIOD" shall be any fiscal/tax period with respect to
which Taxes are due and payable to the appropriate governmental taxing authority
(i.e., as mandated by the governmental taxing authority), any portion of which
period occurs during the term of this Lease, the first such Tax Period being the
one in which the Rent Commencement Date occurs.

              (c)    "OPERATING YEAR": shall mean a twelve-month fiscal year in
which occurs any part of the term of this Lease. The first Operating Year shall
be the calendar year in which the Rent Commencement Date occurs.

              (d)    Operating Costs

                     (i)     "BUILDING OPERATING COSTS" shall mean all
reasonable costs incurred and expenditures of whatever nature made by Landlord
in the operation and management of the Building or allocated to the Building,
including, without limitation, the costs of maintenance and repairs made
pursuant to Section 14.6 hereof (but specifically excluding Landlord Capital
Replacements, as defined in Section 14.6). Tenant's Property Share of Property
Operating Costs shall be included in Building Operating Costs in accordance with
Section 10.1(d)(ii). Building Operating Costs shall not include Excluded Costs
(hereinafter defined).

                                      -15-
<Page>

                     (ii)    "PROPERTY OPERATING COSTS" shall mean all
reasonable costs incurred and expenditures of whatever nature made in the
operation and management, repair, replacement, cleaning, insurance and
maintenance of the common areas of the Property (the "PROPERTY COMMON AREAS"),
including without limitation a commercially reasonable management fee, whether
paid to an affiliate of Landlord or to a third-party manager, and regarding any
shuttle bus service to the Property. To the extent that a cost included in
Property Operating Costs is also allocable to property other than the Property,
such cost shall be equitably allocated by Landlord to each parcel of property
which benefits from such cost. The allocation of costs and expenditures among
the various buildings in the Property shall be on the basis of the ratio of the
total rentable square feet of each building in the Property to the total
rentable square feet of the Property, unless such allocation would result in a
disproportionate charge (x) based upon the manner in which any subsequent
building in the Property is measured relative to the manner in which the
Building was measured, in which case the allocation shall be made equitably
among the buildings of the Property, or (y) based upon the relative usage of the
service on which such cost is based, in which case such allocation shall be
based upon such relative usage. Landlord and Tenant acknowledge that the
Building operates in many respects separately from the balance of the Property,
and therefore some Property Operating Costs will be allocated 100% to the
Building and others will be allocated 0% to the Building. Property Operating
Costs shall include, without limitation, the cost of operating any amenities in
the Property available to all tenants of the Property, such as bus shuttle
services, the costs of Landlord's management office for the Property and any
subsidy provided by Landlord for or with respect to any such amenity.

              (e)    "EXCLUDED COSTS" shall be defined as (i) any mortgage
charges (including interest, principal, points and fees); (ii) brokerage
commissions; (iii) salaries of executives and owners; (iv) the cost of work done
or services furnished by Landlord for a particular tenant; (v) the costs of
Landlord's Work and any contributions made by Landlord to any tenant of the
Property in connection with the build-out of its premises; (vi) franchise or
income taxes imposed on Landlord; (vii) costs paid directly by individual
tenants to suppliers, including tenant electricity, telephone and other utility
costs; (viii) the cost of any repairs made by Landlord pursuant to Article 18
below; (ix) depreciation of the buildings on the Property; (x) costs relating to
maintaining Landlord's existence as a corporation, partnership or other entity;
(xi) advertising and other fees and costs incurred in procuring tenants; (xii)
the cost of any items for which Landlord is reimbursed by insurance,
condemnation awards, refund, rebate or otherwise, and any expenses for repairs
or maintenance to the extent covered by warranties, guaranties and service
contracts; (xiii) expenses incurred by Landlord in order to comply with all
present laws, ordinances, requirements, orders, directives, rules and
regulations of federal, state, county and city governments and of all other
governmental authorities having or claiming jurisdiction over the Building and
Property, including without limitation the Americans with Disabilities Act of
1990 (as amended), the Federal Occupational Safety and Health Act of 1970 (as
amended) and any of said laws, rules and regulations relating to environmental,
health or safety matters, except to the extent the same relate to Tenant's
particular use of the Premises; (xiv) expenses incurred by Landlord to (A)
construct and/or renovate any buildings, structures, infrastructures,
improvements or amenities on the Property as part of Landlord's repositioning of
the same, and/or (B) lease space in the Property to new tenants or to retain
existing tenants including

                                      -16-
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leasing commissions, advertising and promotional expenditures; (xv) expenses
incurred by Landlord to resolve disputes, enforce or negotiate lease terms with
prospective or existing tenants or in connection with any financing, sale or
syndication of the Building or Property; (xvi) interest, principal, points and
fees, amortization or other costs associated with any debt and rent payable
under any lease to which this Lease is subject and all costs and expenses
associated with any such debt or lease and any ground lease rent, irrespective
of whether this Lease is subject or subordinate thereto; (xvii) expenses for the
replacement of any item covered under warranty; (xviii) cost to correct any
penalty or fine incurred by Landlord due to Landlord's violation of any federal,
state or local law or regulation; (xix) expenses for any item or service which
Tenant pays directly to a third party or separately reimburses Landlord and
expenses incurred by Landlord to the extent the same are actually reimbursed
from any other tenants, occupants of the Property, or third parties; (xx)
expenses for any item or service not provided to Tenant but exclusively to
certain other tenants in the Property; (xxi) a property management fee for the
Building in excess of four percent (4%) of the gross rents of the Building
(exclusive of capital expenditures, mark-ups, separate reimbursements by tenants
and ancillary income from other services [e.g., income from antennae or
satellite dishes, paid parking, security deposits and interest thereon, etc.])
applicable to the Building for the relevant calendar year; (xxii) salaries of
(A) employees above the grade of Property superintendent or Property manager,
and (B) employees whose time is not spent directly and solely in the operation
of the Property; (xxiii) Landlord's general corporate overhead and
administrative expenses; (xxiv) reserves; (xxv) fees paid to affiliates of
Landlord to the extent that such fees exceed the customary amount charged for
the service provided; (xxvi) Landlord Capital Replacements; (xxvii) the cost of
alterations, capital improvements, equipment replacement and other items which
under GAAP are properly classified as capital expenditures, except as otherwise
specifically provided herein; and (xxviii) costs which are the responsibility of
Landlord pursuant to Section 17.6.

       10.2   TAX PAYMENT.

              (a)    Tenant shall pay to Landlord, as additional rent, Tenant's
Building Percentage Share of Taxes. Landlord may make a good faith estimate of
the Taxes to be due by Tenant for any Tax Period or part thereof during the term
hereof, and Tenant shall pay to Landlord, on the Rent Commencement Date and on
the first (1st) day of each calendar month thereafter, an amount equal to
Tenant's Building Percentage Share of Taxes for such Tax Period or part thereof
divided by the number of months therein. Prior to delinquency, Landlord shall
pay all Taxes to the taxing authority. Landlord may estimate and re-estimate
Tenant's Building Percentage Share of Taxes (not more than once per year) and
deliver a copy of the estimate or re-estimate to Tenant. Thereafter, the monthly
installments of Tenant's Building Percentage Share of Taxes shall be
appropriately adjusted in accordance with the estimates so that, by the end of
the calendar year in question, Tenant shall have paid all of Tenant's Building
Percentage Share of Taxes as estimated by Landlord. Any amounts paid based on
such an estimate shall be subject to adjustment as herein provided when actual
Taxes are available for each Tax Period. If the total of such monthly
remittances is greater than Tenant's Building Percentage Share of the actual
Taxes due for such Tax Period, then, provided there is not an Event of Default
nor an event which, with the passage of time and/or the giving of notice would
constitute an Event of Default, Tenant may credit the difference against the
next installment of Yearly Rent due hereunder, except that if such difference is
determined after the end of the term hereof, Landlord shall

                                      -17-
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refund such difference to Tenant within thirty (30) days after such
determination to the extent that such difference exceeds any amounts then due
from Tenant to Landlord. If the total of such remittances is less than Tenant's
Building Percentage Share of the actual Taxes due for such Tax Period, Tenant
shall pay the difference to Landlord within thirty (30) days of Tenant's receipt
of an invoice therefor. Landlord's estimate for the next Tax Period shall be
based upon the actual Taxes attributable to the Building for the prior Tax
Period plus a reasonable adjustment based upon estimated increases in Taxes.

              (b)    Landlord covenants to pay the Taxes attributable to the
Building and the Property in a timely manner and in all events prior to the due
date of the respective tax bills. Landlord shall send a copy of each tax bill
for the Building to Tenant within ten (10) days after request for the same.
Landlord understands that it is imperative that Landlord pay such tax bills on
time to preserve all abatement rights for Landlord and Tenant as set forth
herein. Appropriate credit against Taxes shall be given for any refund obtained
by reason of a reduction in any Taxes by the assessors or the administrative,
judicial or other governmental agency responsible therefor after deduction of
Landlord's expenditures for reasonable legal fees and for other reasonable
expenses incurred in obtaining the Tax refund. Landlord's obligations under this
Section 10.2(b) shall survive expiration or termination of this Lease. Tenant
shall have the right, with prior notice to Landlord, to seek abatements of Taxes
in accordance with all applicable municipal procedures, and Landlord agrees to
cooperate reasonably with Tenant, at no cost to Landlord, in connection with
such abatement procedures. At Landlord's election made by notice to Tenant,
Landlord may direct that Tenant pay Taxes directly to the assessing authority.
In the event Tenant has made a payment of Taxes which applies to a period
occurring after expiration of the Term, Landlord shall refund the overpayment
within thirty (30) days after expiration of the Term.

       10.3   PAYMENT OF BUILDING OPERATING COSTS.

              (a)    Tenant shall pay to Landlord, as additional rent, Tenant's
Building Percentage Share of Building Operating Costs. Landlord may make a good
faith estimate of Tenant's Building Percentage Share of Building Operating Costs
for any Operating Year or part thereof during the term based upon Landlord's pro
forma budget, a copy of which shall be delivered to Tenant when available
(Landlord endeavoring to deliver such budget not later than thirty (30) days
after the start of each Operating Year), and Tenant shall pay to Landlord, on
the Rent Commencement Date and on the first (1st) day of each calendar month
thereafter, an amount equal to Tenant's Building Percentage Share of the
estimated Building Operating Costs for such Operating Year and/or part thereof
divided by the number of months therein. Landlord may estimate and re-estimate
Tenant's Building Percentage Share of Building Operating Costs (not more than
once per year) and deliver a copy of the estimate or re-estimate to Tenant.
Thereafter, the monthly installments of Tenant's Building Percentage Share of
Building Operating Costs shall be appropriately adjusted in accordance with the
estimations so that, by the end of the calendar year in question, Tenant shall
have paid all of Tenant's Building Percentage Share of Building Operating Costs
as estimated by Landlord. Any amounts paid based on such an estimate shall be
subject to adjustment as herein provided when actual Building Operating Costs
are available for each Operating Year.

                                      -18-
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              (b)    Landlord shall, within one hundred twenty (120) days after
the end of each Operating Year, deliver to Tenant a reasonably detailed
statement of the actual amount of Building Operating Costs for such Operating
Year ("YEAR END STATEMENT"), prepared in accordance with sound accounting
principles. If the total of such monthly remittances on account of any Operating
Year is greater than Tenant's Building Percentage Share of the actual Building
Operating Costs for such Operating Year, then, provided there is not an Event of
Default nor an event which, with the passage of time and/or the giving of notice
would constitute an Event of Default, Tenant may credit the difference against
the next installment of Yearly Rent due hereunder, except that if such
difference is determined after the end of the term hereof, Landlord shall refund
such difference to Tenant within thirty (30) days after such determination to
the extent that such difference exceeds any amounts then due from Tenant to
Landlord. If the total of such remittances is less than Tenant's Building
Percentage Share of the actual Building Operating Costs for such Operating Year,
Tenant shall pay the difference to Landlord within thirty (30) days of Tenant's
receipt of an invoice therefor. Landlord's estimate of Building Operating Costs
for the next Operating Year shall be based upon the actual Building Operating
Costs for the prior Operating Year as reflected in the Year-End Statement plus a
reasonable adjustment based upon estimated increases in Building Operating
Costs.

       10.4   PART YEARS. If the Rent Commencement Date or the Expiration Date
occurs in the middle of an Operating Year or Tax Period, Tenant shall be liable
for only that portion of the Building Operating Costs or Taxes, as the case may
be, with respect to such Operating Year or Tax Period within the term hereof.
Any credit pursuant to Section 10.2(b) for the years in which the Rent
Commencement Date or the Expiration Date occur shall be similarly pro-rated.

       10.5   SURVIVAL. Any obligations under this Article 10 which shall not
have been paid at the expiration or sooner termination of the term hereof shall
survive such expiration and shall be paid when and as the amount of same shall
be determined and be due.

       10.6   AUDIT RIGHT. Provided that Tenant notifies Landlord in writing on
or before the date which is one hundred eighty (180) days after Tenant's receipt
of the Year End Statement, TIME BEING OF THE ESSENCE, of Tenant's intention to
conduct an inspection or audit, Tenant may inspect or audit Landlord's records
relating to Building Operating Costs and Property Operating Costs for the year
that is the subject of such Year End Statement (but not any prior years). Tenant
shall not be liable for any Building Operating Cost which is not reported to it
within one (1) year after the end of the Lease Year in which such Building
Operating Cost was incurred. Tenant's audit or inspection shall be conducted
only at Landlord's offices in Massachusetts or the Massachusetts offices of
Landlord's property manager during business hours reasonably designated by
Landlord. Tenant shall pay the cost of such audit or inspection unless the final
reconciliation indicates that Building Operating Costs were overstated by more
than four (4%) percent, in which event Landlord shall pay the cost of such audit
or investigation, but not to the extent such cost exceeds the adjustment in
Building Operating Costs to Tenant. Tenant may not conduct an inspection or have
an audit performed more than once during any Operating Year. If such inspection
or audit reveals that an error was made in the calculation of Tenant's Building
Percentage Share of Building Operating Costs (including Property Operating
Costs) previously charged to Tenant, then, provided there is not an Event of
Default nor an event which, with the passage of time and/or the giving of notice
would constitute an Event of Default (in which event

                                      -19-
<Page>

no refund shall be due until such default has been cured), Landlord shall refund
to Tenant any overpayment of any such costs, or Tenant shall pay to Landlord any
underpayment of any such costs, as the case may be, within thirty (30) days
after notification thereof. Tenant shall maintain the results of any such audit
or inspection confidential and shall not be permitted to use any third party to
perform such audit or inspection, other than an independent firm of certified
public accountants or financial professionals with experience in commercial real
property management (A) reasonably acceptable to Landlord and (B) which agrees
with Landlord in writing to maintain the results of such audit or inspection
confidential.

11.    FIXTURES, EQUIPMENT AND IMPROVEMENTS--REMOVAL BY TENANT; EQUIPMENT
FINANCING RESTRICTIONS

       All fixtures, equipment, improvements and appurtenances attached to or
built into the Premises prior to or during the term hereof, whether by Landlord
or Tenant, shall be Landlord's property and shall be and remain part of the
Premises and shall not be removed by Tenant during or at the end of the term
hereof unless Landlord authorizes such removal in writing or elects to require
Tenant to remove such fixtures, equipment, improvements and appurtenances, at
Tenant's expense, in accordance with the provisions of Section 12. Tenant shall
remove (at Tenant's expense) all other property of Tenant. If removal of any of
the foregoing damages the Premises or the Building, Tenant shall repair any and
all damage to the Premises or the Building arising from the installation or
removal thereof. Landlord and Tenant agree that all of Landlord's Work shall be
required to remain in the Building after expiration of the Term. Nothing in this
Lease shall be construed to permit Tenant to grant any interest whatsoever in
(a) any fixtures (including without limitation all electric, plumbing, heating
and sprinkling systems, fixtures and outlets, vaults, paneling, molding,
shelving, radiator enclosures, cork, rubber, linoleum and composition floors,
ventilating, silencing, air conditioning and cooling equipment, whether or not
attached to or built into the Premises) within the Premises or (b) any item paid
in whole or in part with Landlord's Contribution without the consent of
Landlord.

12.    ALTERATIONS AND IMPROVEMENTS BY TENANT

       12.1   Tenant shall make no alterations, decorations, installations,
removals, additions or improvements (collectively, "ALTERATIONS") in or to the
Premises without Landlord's prior written consent and then only those made by
contractors or mechanics approved by Landlord, which approval shall not be
unreasonably withheld, conditioned or delayed. Notwithstanding the foregoing,
but provided that no building system serving any portion of the Building is
adversely affected, Tenant may make non-structural Alterations which do not
affect Building systems and cost less than $250,000 in any one instance
("PERMITTED ALTERATIONS") without Landlord's prior written consent but with
notice to Landlord and otherwise subject to the provisions of this Lease
including without limitation Article 13 below. Landlord agrees that an outdoor
patio of the type presented by Tenant prior to execution of this Lease would
qualify as a "Permitted Alteration". No Alterations other than Permitted
Alterations shall be undertaken or begun by Tenant until Landlord has approved
the contractor(s), written plans and specifications and a time schedule for such
work. Landlord agrees to respond to any request for approval of Alterations,
other than Permitted Alterations, and/or approval of the contractor(s), written
plans and specifications and a time schedule for such work within thirty (30)
days after receipt thereof. If Landlord fails to

                                      -20-
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respond to a request for approval within such thirty-day period, Tenant shall
have the right to send a second notice, indicating that Landlord's approval will
be deemed granted if not withheld within ten (10) days, and if Landlord shall
fail to respond within ten (10) days after delivery of such second notice,
Landlord's approval shall be deemed to have been granted. No amendments or
additions to such plans and specifications shall be made without the prior
written consent of Landlord. Landlord's consent and approval required under this
Article 12 shall not be unreasonably withheld, conditioned or delayed, except
for Alterations affecting the roof, structural elements, building systems and/or
the exterior of the Building, which shall be determined in Landlord's sole
discretion. Landlord's approval is solely given for the benefit of Landlord and
neither Tenant nor any third party shall have the right to rely upon Landlord's
approval of Tenant's plans for any other purpose whatsoever. Without limiting
the foregoing, Tenant shall be responsible for all elements of the design of
Tenant's plans (including, without limitation, compliance with Legal
Requirements, functionality of design, the structural integrity of the design,
the configuration of the Premises and the placement of Tenant's furniture,
appliances and equipment), and Landlord's approval of Tenant's plans shall in no
event relieve Tenant of the responsibility for such design. Landlord shall have
no liability or responsibility for any claim, injury or damage alleged to have
been caused by the particular materials (whether building standard or
non-building standard), appliances or equipment selected by Tenant in connection
with any work performed by or on behalf of Tenant. Any such Alterations shall be
done at Tenant's sole cost and expense. If Tenant shall make any Alterations,
then Landlord may elect at the time of approval of the Alteration to require
Tenant at the expiration or sooner termination of the term hereof to restore the
Premises to substantially the same condition as existed immediately prior to the
Alteration. Upon Tenant's request, Landlord agrees to make such election at the
time that Landlord receives Tenant's notice regarding Permitted Alterations or
approves Tenant's plans for any such Alterations. Tenant shall provide Landlord
with reproducible record drawings of all Alterations within sixty (60) days
after completion thereof.

       12.2   Landlord and Tenant recognize that to the extent Tenant elects to
perform any Alteration which affects the life/safety systems serving the
Building, Landlord may need to make arrangements to have supervisory personnel
on site. Accordingly, Landlord and Tenant agree as follows: Tenant shall give
Landlord at least forty-eight (48) hours' notice of any time when Tenant intends
to perform any such Alteration. Tenant shall reimburse Landlord, within thirty
(30) days after demand therefor, for the reasonable cost of Landlord's
supervisory personnel overseeing such Alterations.

13.    TENANT'S CONTRACTORS--MECHANICS' AND OTHER LIENS--STANDARD OF TENANT'S
PERFORMANCE

       Landlord agrees that the provisions of this Article 13 are not applicable
to the Leasehold Work, which shall be governed by the provisions of Article 4.
Whenever Tenant shall make any Alterations in or to the Premises, Tenant will
observe the following covenants and agreements:

       13.1   HARMONIOUS RELATIONS. Tenant agrees that it will not, either
directly or indirectly, use any contractors and/or materials if their use will
create any difficulty, whether in the nature of a labor dispute or otherwise,
with other contractors and/or labor engaged by Tenant

                                      -21-
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or Landlord or others in the construction, maintenance and/or operation of the
Property or any part thereof.

       13.2   LIENS. In no event shall any Encumbered Material (hereinafter
defined) be incorporated in or added to the Premises, so as to become a fixture
or otherwise a part of the Building, in connection with any Alteration. For
purposes hereof, "ENCUMBERED MATERIAL" shall mean any material or equipment
which is subject to any lien, charge, mortgage or other encumbrance of any kind
whatsoever or is subject to any security interest or any form of title retention
agreement not approved by Landlord in advance in writing, which approval may be
given or withheld in Landlord's sole discretion. No Alterations shall be
undertaken or begun by Tenant until plans and specifications (if applicable)
prepared by and at the expense of Tenant have been submitted to and approved by
Landlord where Landlord's approval is required hereunder. Except with respect to
work performed by Landlord or pursuant to a contract with Landlord, any
mechanic's lien filed against the Premises or the Building for work claimed to
have been done for, or materials claimed to have been furnished to, Tenant shall
be discharged by Tenant within ten (10) business days thereafter, at Tenant's
expense by filing the bond required by law or otherwise. If Tenant fails so to
discharge any lien, Landlord may do so at Tenant's expense and Tenant shall
reimburse Landlord for any expense or cost incurred by Landlord in so doing,
together with interest at the Default Rate until paid in full, within ten (10)
days after receipt of an invoice therefor. Mechanic's liens filed against the
Building with respect to work performed by Landlord or pursuant to a contract
with Landlord shall be the responsibility of Landlord.

       13.3   PERMITS. Unless Landlord and Tenant otherwise agree in writing,
Tenant shall procure or cause others to procure on its behalf all necessary
permits before undertaking any work in the Premises; do all of such work in a
good and workmanlike manner, employing materials of good quality; and defend,
save harmless, exonerate and indemnify the Landlord Indemnitees from and against
any and all Claims occasioned by or growing out of such work. Tenant shall cause
contractors employed by Tenant to (a) carry Worker's Compensation Insurance in
accordance with statutory requirements, (b) Automobile Liability Insurance and
Commercial General Liability Insurance (i) naming Landlord as an additional
insured and (ii) covering such contractors on or about the Premises in the
amounts stated in Article 15 hereof or in such other reasonable amounts as
Landlord shall require, and (c) submit certificates evidencing such coverage to
Landlord prior to the commencement of any such work.

       13.4   QUALITY AND PERFORMANCE. All Alterations shall be done in a good
and workmanlike manner by contractors approved by Landlord, which approval shall
not be unreasonably withheld, conditioned or delayed, and in compliance with
Landlord's construction rules and regulations for the Property attached as an
addendum to the Building Rules and Regulations, all insurance requirements of
this Lease, and Legal Requirements. Each party authorizes the other to rely upon
the written approval or other written authorizations on the other party's behalf
by its Construction Representative(s) in connection with design and
construction.

14.    MAINTENANCE AND REPAIRS --ANIMAL CARE AND TRANSPORTATION - BIOHAZARD
REMOVAL --FLOOR LOAD -- COMPLIANCE WITH LAW

                                      -22-
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       14.1   MAINTENANCE AND REPAIRS BY TENANT. Tenant shall keep the Premises
neat and clean and free of insects, rodents, vermin and other pests and in such
good repair, order and condition as the same are in on the Term Commencement
Date or in such better condition as the Premises may be put in during the term
hereof, reasonable wear and tear and damage by fire or by other casualty and
Landlord negligence excepted. Tenant shall be solely responsible, at Tenant's
sole cost and expense, for (a) the proper maintenance of all equipment and
appliances operated by Tenant, (b) cleaning all areas of the Premises to a
standard reasonably comparable to other combination office, research,
development and laboratory buildings in the Lexington area with a service
provider reasonably acceptable to Landlord; and (c) repairs, maintenance and
replacement (including without limitation capital repairs and replacements) of
all portions of the Building (including without limitation all Building systems)
other than the roof, floor slabs, exterior, exterior windows, exterior lighting,
foundation and structural elements of the Building, the roadways, walkways,
landscaping and parking areas serving the Building and the utility lines and
systems located outside the Building, so as to keep such portions of the
Building in the condition the same shall be in following completion of
Landlord's Work, reasonable wear and tear and casualty and Landlord negligence
excepted. Tenant shall maintain such service contracts relating to the HVAC
system and other Building systems as Landlord shall reasonably require. To the
extent the performance by Tenant of its obligations under this Section 14.1
and/or 17.7(b) would require an expenditure which under GAAP would properly be
classified as a capital expenditure, the repair or replacement shall be
performed by Landlord and the cost thereof (plus interest at a commercially
reasonable rate equal to the rate then available to Landlord to finance the cost
of the capital expenditure in question) shall be charged back to Tenant as
additional rent on a monthly basis, commencing on the month the capital
expenditure first occurs, the monthly amount being equal to the total amount of
the capital expenditure (plus interest as aforesaid) times a fraction, the
numerator of which is one (1) and the denominator of which is the number of
months in the useful life of the item in question, as reasonably determined by
Landlord. By way of example, if the capital expenditure plus interest is $60,000
and the useful life of the item is 120 months, the monthly additional rent
charge shall be $500 ($60,000 times 1/120 = $500). Such monthly additional rent
charge shall be payable until the earlier of (i) repayment in full of the
capital expenditure (plus interest as aforesaid) or (ii) expiration of the Term,
including extension periods.

       14.2   BIOHAZARD REMOVAL AND ANIMAL CARE. Tenant shall be responsible, at
its sole cost and expense, for janitorial and trash removal services and other
biohazard disposal services for the Building, including the laboratory areas
thereof. Such services shall be performed by Tenant's employees or by
contractors reasonably acceptable to Landlord and on a sufficient basis to
ensure that the Building and the Property are at all times kept neat, clean and
free of Hazardous Materials and biohazards as provided in Section 17.6. In
addition, Tenant shall be responsible, at Tenant's sole cost and expense, for
the care and safe storage of any animals housed within the Premises, including
without limitation all animal husbandry and custodial services with respect
thereto, in accordance with the highest standards applicable to Tenant's
industry.

       14.3   FLOOR LOAD--HEAVY MACHINERY. Tenant shall not place a load upon
any floor of the Premises exceeding the floor load per square foot of area of
125 pounds per square foot.

                                      -23-
<Page>

Landlord reserves the right to prescribe the weight and position of all safes,
heavy machinery, heavy equipment, freight, bulky matter or fixtures
(collectively, "HEAVY EQUIPMENT"), which shall be placed so as to distribute the
weight. Heavy Equipment shall be placed and maintained by Tenant at Tenant's
expense in settings sufficient in Landlord's reasonable judgment to absorb and
prevent vibration, noise and annoyance. Tenant shall not move any Heavy
Equipment into or out of the Building without observing all of Landlord's Rules
and Regulations with respect to the same. If such Heavy Equipment requires
special handling, Tenant agrees to employ only persons holding a Master Rigger's
License to do said work, and that all work in connection therewith shall comply
with Legal Requirements. Any such moving shall be at the sole risk and hazard of
Tenant and Tenant will defend, indemnify and save the Landlord Parties harmless
from and against any and all Claims resulting directly or indirectly from such
moving. Proper placement of all Heavy Equipment in the Premises shall be
Tenant's responsibility.

       14.4   ANIMAL TRANSPORTATION. No animals, animal waste, food or supplies
relating to the animals maintained from time to time in the animal storage areas
of the Premises shall be transported within multi-tenant Buildings except as
provided in this Section 14.4. In multi-tenant Buildings, all deliveries of
animals or animal food or supplies to Tenant at the Building shall be made prior
to 11:00 a.m. or after 3 p.m. At all times that animals are transported within
the Property Common Areas (whether from a single-tenant or a multi-tenant
Building), they shall be transported in an appropriate cage or other container.
At no time shall any animals, animal waste, food or supplies relating to the
animals be brought into, transported through, or delivered to the lobby of any
multi-tenant Building or be transported within any multi-tenant Building in
elevators other than the freight elevator.

       14.5   WASTE REMOVAL; RECYCLING. Throughout the term hereof, Tenant
shall, at its sole cost and expense: (a) keep any garbage, trash, rubbish and
refuse for the office areas of the Premises (collectively, "TRASH") in
vermin-proof containers within the interior of the Premises until removed; and
(b) cause all Trash to be removed from the Property pursuant to the Rules and
Regulations and otherwise in accordance with the standards of a first-class
office and laboratory facility.

       14.6   MAINTENANCE AND REPAIRS BY LANDLORD. Landlord shall repair and
maintain in the condition the same shall be in following completion of
Landlord's Work, reasonable wear and tear and casualty and Tenant negligence
excepted, the Building's roof, floor slabs, exterior, exterior windows, exterior
lighting, foundation and structural elements, as well as the Building Lot,
including the roadways, walkways, landscaping and parking areas serving the
Building and the utility lines and systems outside the Building, the costs of
all of which shall be included within Building Operating Costs, as set forth in
Section 10.1; provided, however, that capital repair and replacement costs
relating to the foregoing ("Landlord Capital Replacements") shall not be
included within Building Operating Costs and shall be at Landlord's sole
expense. Following completion of Landlord's redevelopment activities at the
balance of the Property (i.e., 131 and 141 Spring Street), Landlord shall
maintain such balance of the Property in a condition comparable to comparable
first-class office and research facilities. Notwithstanding any term or
condition of this Lease to the contrary, and in addition to its self-help rights
set forth in Section 4.1(f), Tenant shall have the right to perform or cause to
be performed any repair, maintenance or service required to be performed
hereunder by Landlord (other than performance of Landlord's

                                      -24-
<Page>

Work), so long as: (i) the repair, maintenance or service in question relates to
125 Spring Street, not the balance of the Property, (ii) Tenant has given
Landlord and any mortgage or other assignee of Landlord actually known to
Tenant, concurrent written notice of the need for the same and a statement of
Tenant's intention to exercise its self-help remedy pursuant to this Section
14.6; (iii) thirty (30) days have elapsed from the giving of said notice without
Landlord or such mortgagee or other assignee of Landlord commencing performance
of such repair, maintenance or service required to be performed hereunder by
Landlord; (iv) Tenant has given to such parties a second notice, delivered after
expiration of the thirty-day cure period described above, stating again its
intention to exercise its self-help remedy pursuant to this Section 14.6; and
(v) ten (10) days have elapsed from the giving of said second notice without
Landlord or such mortgage or other assignee from Landlord commencing performance
of such repair, maintenance or service required to be performed hereunder by
Landlord; provided, however, that in the event of emergency, Tenant shall have
the right to perform such repairs, maintenance or service to the extent
necessary to alleviate the emergency without complying with the notice and cure
procedures set forth above, but Tenant shall notify Landlord of the emergency
and the self-help activity as soon as is practicable under the circumstances.
Landlord shall reimburse Tenant for the reasonable cost of Tenant's performance
of Landlord's repair, maintenance or service obligation within thirty (30) days
after Tenant's demand therefor, which shall be accompanied by a detailed
description of the costs incurred and paid invoices for same, and upon
Landlord's failure to pay the same within such thirty-day period, Tenant shall
have the right to credit such cost against any future installments of Rent until
such cost is fully recouped by Tenant; provided, however, that no such credit in
any month shall exceed ten percent (10%) of the monthly payment of Yearly Rent
payable for such month (such 10% limitation shall not impair Tenant's ability to
"carry over" any unused credit to subsequent months, until such credit has been
exhausted).

15.    INSURANCE, INDEMNIFICATION, EXONERATION AND EXCULPATION

       15.1   GENERAL LIABILITY INSURANCE. Tenant shall procure, pay for and
keep in force throughout the term hereof (and for so long thereafter as Tenant
remains in occupancy) commercial general liability insurance insuring Tenant on
a claims made basis against all claims and demands for personal injury liability
(including, without limitation, bodily injury, sickness, disease, and death) or
damage to property which may be claimed to have occurred from and after the
Completion Date, of not less than Two Million Dollars ($2,000,000), and from
time to time thereafter shall be not less than such higher amounts, if
procurable, as may be reasonably required by Landlord (so long as not adjusted
more than once a year). Tenant shall also carry umbrella liability coverage in
an amount of no less than Ten Million Dollars ($10,000,000). Such policy shall
also include, to the extent commercially available, contractual liability
coverage covering Tenant's liability assumed under this Lease, including without
limitation the indemnification obligations contained in Sections 2.2(c), 15.5,
17.6(f) and 27.3 hereof. Tenant's insurance under this Section 15.1 shall be
primary over any liability insurance carried by Landlord and shall remain in
effect during the term of this lease.

       15.2   PROPERTY INSURANCE. Tenant shall take out and maintain throughout
the term hereof a policy of fire, vandalism, malicious mischief, extended
coverage and so-called "special form" coverage insurance insuring (i) all items
or components of Alterations installed by Tenant

                                      -25-
<Page>

(collectively, the "TENANT-INSURED IMPROVEMENTS"), and (ii) all of Tenant's
animals, furniture, equipment, fixtures and property of every kind, nature and
description related or arising out of Tenant's leasehold estate hereunder, which
may be in or upon the Premises, the Building or the Property (collectively,
"TENANT'S PROPERTY") in an amount equal to one hundred percent (100%) of the
replacement cost thereof.

       15.3   [INTENTIONALLY OMITTED].

       15.4   FORM OF INSURANCE. The insurance required pursuant to Sections
15.1 and 15.2 (collectively, "TENANT'S INSURANCE POLICIES") shall be effected
with insurers approved by Landlord, with a rating of not less than "B+" in the
current BEST'S INSURANCE REPORTS, and authorized to do business in the
Commonwealth of Massachusetts under valid and enforceable policies, and with
respect to the insurance required pursuant to Section 15.1, such insurance
policy(ies) shall list Landlord, Landlord's managing agent and persons claiming
by, through or under them, if any, as additional insureds. Tenant's Insurance
Policies shall each provide that it shall not be canceled or modified without at
least thirty (30) days' prior written notice to each insured named therein. On
or before the time any of the Tenant Parties shall first move any property into
the Premises, perform any work in the Premises or commence occupancy of the
Premises and thereafter not less than fifteen (15) days prior to the expiration
date of each expiring policy, Tenant shall deliver to Landlord certificates of
Tenant's Insurance Policies issued by the respective insurers, and upon request
of Landlord, Tenant shall deliver to any Mortgagee copies of the foregoing
documents.

       15.5   INDEMNIFICATION.

              (a)    Except to the extent caused by the negligence or willful
misconduct of any of the Landlord Parties (hereinafter defined), and to the
extent not prohibited by law, Tenant will defend, indemnify and save the
Landlord Indemnitees harmless from and against any and all Claims asserted by or
on behalf of any person, firm, corporation or public authority arising from :

                     (i)     Any injury to or death of any person, or loss of or
damage to property, sustained or occurring in, upon or at the Premises;

                     (ii)    Any injury to or death of any person, or loss of or
damage to property, sustained or occurring in or about the Building or Property
to the extent directly arising out of the use or occupancy of the Premises by or
the negligence or misconduct of any of the Tenant Parties; and

                     (iii)   On account of or based upon (including monies due
on account of) any work or thing whatsoever done (other than by Landlord or any
of the Landlord Parties) at the Premises during the term hereof and during the
period of time, if any, prior to the Term Commencement Date that any of the
Tenant Parties may have been given access to the Premises;

              (b)    Except to the extent caused by the gross negligence or
willful misconduct of any of the Tenant Parties, Landlord shall defend,
indemnify and save Tenant harmless from and against any and all Claims asserted
by or on behalf of any person, firm, corporation or public

                                      -26-
<Page>

authority arising from any injury to or death of any person, or loss of or
damage to property, sustained or occurring in or about the Building or the
Property to the extent arising from the negligence of willful misconduct of
Landlord or any of the Landlord Parties.

       15.6   WAIVER OF SUBROGATION; MUTUAL RELEASE. Landlord and Tenant each
hereby waives on behalf of its property insurers (none of which shall ever be
assigned any such claim or be entitled thereto due to subrogation or otherwise)
but not on its own behalf any and all rights of recovery, claim, action, or
cause of action against the other and its agents, officers, servants, partners,
shareholders, or employees (collectively, the "RELATED PARTIES") for any loss or
damage that may occur to or within the Premises, the Building or the Property or
any improvements thereto, or any personal property of such party therein which
is insured against under any property insurance policy actually being maintained
from time to time (including all deductible and retention amounts), even if not
required hereunder, including, in every instance, negligence by the other party
hereto and/or its Related Parties. Landlord and Tenant each agree to cause
appropriate clauses to be included in their property insurance policies
necessary to implement the foregoing provisions.

       15.7   LANDLORD'S INSURANCE. Landlord shall take out and maintain in
force throughout the term hereof, in a company or companies authorized to do
business in the Commonwealth of Massachusetts with a Best's rating of B+ or
higher: (a) all risk property insurance on the Building specifically including
Landlord's Work (exclusive of Tenant's personal property and the Tenant-Insured
Improvements) in an amount equal to the full replacement value of the Building
(exclusive of foundations and those items set forth in the preceding
parenthetical in this sentence), covering all risks of direct physical loss or
damage and so-called "extended coverage" risks; and, if the Building is located
in a flood zone, flood coverage to the extent the same is available, insuring
the Building and its rental value, (b) commercial general liability insurance
against claims of bodily injury, personal injury and property damage arising out
of Landlord's operation of the Building, in such amount as a prudent owner of
similar property would carry or as otherwise required by any Mortgagee with a
limit of not less than One Million Dollars ($1,000,000.00) each occurrence; and
(c) insurance against loss or damage from sprinklers and from leakage or
explosions or cracking of boilers, pipes carrying steam or water, or both,
pressure vessels or similar apparatus, in the so-called "broad form", in such
amounts as are customary and commercially reasonable for buildings in
Massachusetts which are of like kind and quality to the Building and have
laboratory uses, and insurance against such other hazards and in such amounts as
may from time to time be required by any bank, insurance company or other
lending institution holding a first mortgage on the Building, the Premises or
the Property. The foregoing insurance may be maintained in the form of a blanket
policy covering the Building and/or the other buildings in the Property as well
as other properties owned by Landlord. The costs of Landlord's insurance shall
be included within Building Operating Costs. At Tenant's request, Landlord shall
furnish to Tenant a certificate evidencing the insurance coverage required
hereunder.

16.    ASSIGNMENT, MORTGAGING AND SUBLETTING

       16.1   Except as otherwise set forth herein, Tenant shall not, without
Landlord's prior written consent, which consent shall not be unreasonably
withheld, conditioned or delayed,

                                      -27-
<Page>

assign, sublet, mortgage, license, transfer or encumber this Lease or the
Premises, in whole or in part, whether by changes in the ownership or control of
Tenant, or any direct or indirect owner of Tenant, whether at one time or at
intervals, by sale or transfer of stock, partnership or beneficial interests,
operation of law or otherwise (each of the foregoing, a "TRANSFER"). Any
purported Transfer made without Landlord's approval, if required hereunder,
shall be void and confer no rights upon any third person, provided that if there
is a Transfer, Landlord may collect rent from the transferee without waiving the
prohibition against Transfers, accepting the transferee, or releasing Tenant
from full performance under this Lease. In the event of any Transfer in
violation of this Article 16, Landlord shall have the right to terminate this
Lease upon thirty (30) days' written notice to Tenant given within sixty (60)
days after receipt of written notice from Tenant to Landlord of any Transfer, or
within one (1) year after Landlord first learns of the Transfer if no notice is
given. No Transfer shall relieve Tenant of its primary obligation as
party-Tenant hereunder, nor shall it reduce or increase Landlord's obligations
under this Lease. Landlord shall grant or withhold consent to any proposed
Transfer within twenty (20) days after delivery of written request for consent.
If Landlord fails to respond within such twenty-day period, Tenant shall have
the right to send a second request for consent, indicating in bold, capital type
that consent will be deemed granted if not withheld in writing within ten (10)
days, and if Landlord fails to respond to such second notice within ten (10)
days after delivery thereof, Landlord's consent to the proposed Transfer shall
be deemed granted.

       16.2   [INTENTIONALLY OMITTED]

       16.3   EXCEPTIONS TO REQUIREMENT FOR CONSENT. Notwithstanding anything to
the contrary herein contained, Tenant shall have the right, without obtaining
Landlord's consent, to make a Transfer to (a) an Affiliated Entity (hereinafter
defined), and (b) a Successor, provided that (i) prior to the effective date of
such Transfer, such Affiliated Entity or Successor, as the case may be, and
Tenant execute and deliver to Landlord an assignment and assumption agreement in
form and substance reasonably satisfactory to Landlord whereby such Affiliated
Entity or Successor, as the case may be, shall agree to be independently bound
by and upon all the covenants, agreements, terms, provisions and conditions set
forth in this Lease on the part of Tenant to be performed, and whereby such
Affiliated Entity or Successor, as the case may be, shall expressly agree that
the provisions of this Article 16 shall, notwithstanding such Transfer, continue
to be binding upon it with respect to all future Transfers (an "ASSUMPTION
AGREEMENT") (the provisions of this clause (i) shall apply only if there is to
be an actual assignment from Tenant to another legal entity, as opposed to a
merger or assignment by operation of law), and (ii) the net worth of all
entities primarily liable under this Lease following the assignment shall be no
lower than the higher of either (A) Tenant's net worth on the Execution Date or
(B) the net worth of all entities primarily liable under this Lease immediately
prior to the assignment. For the purposes hereof, an "AFFILIATED ENTITY" shall
be defined as any entity which is controlled by, is under common control with,
or which controls Tenant. For the purposes hereof, a "SUCCESSOR" shall be
defined as any entity into or with which Tenant is merged or with which Tenant
is consolidated or which acquires all or substantially all of Tenant's stock or
assets. Notwithstanding anything to the contrary herein, nothing in this Section
16 is intended to limit Tenant's offering and public trading of Tenant's stock.

                                      -28-
<Page>

       16.4   LISTING CONFERS NO RIGHTS. The listing of any name other than that
of Tenant, whether on the doors of the Premises or on the Building directory, or
otherwise, shall not operate to vest in any such other person, firm or
corporation any right or interest in this Lease or in the Premises or be deemed
to effect or evidence any consent of Landlord, it being expressly understood
that any such listing is a privilege extended by Landlord revocable at will by
written notice to Tenant.

       16.5   PROFITS IN CONNECTION WITH TRANSFERS. Tenant shall, within thirty
(30) days of receipt thereof, pay to Landlord as additional rent fifty percent
(50%) of any rental consideration as and when received by Tenant to be paid or
given in connection with any Transfer to any entity specifically excluding an
Affiliated Entity or Successor, either initially or over time, after deducting
(i) reasonable actual out-of-pocket legal and brokerage expenses incurred by
Tenant in connection therewith, plus (ii) the depreciated value (in accordance
with generally accepted accounting principles) of the cost of alterations and
improvements to the Premises performed at Tenant's expense to prepare the
Premises for Tenant's use and occupancy (i.e. amounts in excess of Landlord's
Contribution), prorated according to the fraction of rentable area of the
Premises affected by the Transfer, plus (iii) all other reasonable costs
incurred or concessions granted by Tenant in connection with such Transfer, to
the extent such net rental consideration exceeds the Rent payable hereunder.

       16.6   PROHIBITED TRANSFERS. Notwithstanding any contrary provision of
this Lease, Tenant shall have no right to make a Transfer unless on both (a) the
date on which Tenant notifies Landlord of its intention to enter into a Transfer
and (b) the date on which such Transfer is to take effect, there is no Event of
Default under this Lease. Notwithstanding anything to the contrary contained
herein, Tenant agrees that it shall be deemed reasonable for Landlord to
withhold consent to any proposed Transfer to (i) any tenant, subtenant or
occupant of other premises in the Building or the Property, so long as Landlord
has space to make available to such Party; (ii) government agencies; or (iii)
any tenants with whom Landlord shall have negotiated for space at the Property
in the nine (9) months immediately preceding such proposed Transfer (so long as
Landlord has space to make available to such tenants).

       16.7   RECAPTURE. In lieu of granting consent to any proposed assignment
or any sublease for substantially the remainder of the Term (that is, with less
than one (1) year remaining in the Term) (other than assignments or subleases
listed in Section 16.3, with respect to which Landlord's recapture right set
forth in this Section 16.7 shall not apply), Landlord may elect to terminate
this Lease as to the portion proposed to be subleased or assigned, by notice to
Tenant given within thirty (30) days after the request for consent, in which
event this Lease shall expire as to the affected space as of the date set forth
in Landlord's recapture notice, which date shall be no sooner than thirty (30)
days nor later than one hundred eighty (180) days after the date of such
recapture notice.

17.    MISCELLANEOUS COVENANTS

       17.1   RULES AND REGULATIONS. Tenant will observe and comply with the all
reasonable rules and regulations promulgated by Landlord from time to time with
respect to the Building or the Property or relating to construction within the
Property (collectively, the "RULES AND

                                      -29-
<Page>

REGULATIONS"). The current version of the Rules and Regulations is attached
hereto as EXHIBIT 6 and incorporated herein. In the case of any conflict between
the provisions of this Lease and any future rules and regulations, the
provisions of this Lease shall control. Landlord shall use commercially
reasonable efforts to apply the Rules and Regulations in a non-discriminatory
manner; provided that nothing contained in this Lease shall be construed to
impose upon Landlord any duty or obligation to enforce the Rules and Regulations
or the terms, covenants or conditions in any other lease as against any other
tenant and Landlord shall not be liable to Tenant for violation of the same by
any other tenant, its servants, employees, agents, contractors, visitors,
invitees or licensees. To the extent there is an inconsistency between the Rules
and Regulations and the provisions of this Lease, the provisions of this Lease
shall control.

       17.2   ACCESS TO PREMISES--SHORING. If an excavation shall be made upon
land adjacent to the Building or shall be authorized to be made in connection
with any of Landlord's repair, maintenance or restoration rights or obligations
hereunder, Tenant shall afford to the person or entity causing or authorized to
cause such excavation, license to enter upon the Premises for the purpose of
doing such work as said person or entity shall deem necessary to preserve the
Building from injury or damage and to support the same by proper foundations
without any claims for damages or indemnity against Landlord, or diminution or
abatement of rent. Landlord shall give Tenant reasonable notice prior to such
activity and shall use commercially reasonable efforts to minimize any
interference with Tenant's business operations and use and occupancy of the
Premises in connection with any such excavation.

       17.3   ACCIDENTS TO SANITARY AND OTHER SYSTEMS. Tenant shall give to
Landlord prompt notice of any fire or accident in the Building and of any damage
to, or defective condition in, any part or appurtenance of the Building
including, without limitation, acid waste neutralization systems, sanitary,
electrical, ventilation, heating and air conditioning or other systems located
in, or passing through, the Premises. Except as otherwise provided in Article
18, and subject to Tenant's obligations in Article 14, such damage or defective
condition shall be remedied by Landlord with reasonable diligence, but, subject
to Section 15.5 above, if such damage or defective condition was caused by any
of the Tenant Parties, the cost to remedy the same shall be paid by Tenant.

       17.4   SIGNS. Except as set forth in Section 25.1, Tenant will not place
or suffer to be placed or maintained on the exterior of the Premises, or any
part of the interior visible from the exterior thereof, any sign, banner,
advertising matter or any other thing of any kind (including, without
limitation, any hand-lettered advertising), and will not place or maintain any
decoration, letter or advertising matter on the glass of any window or door of
the Premises without first obtaining Landlord's written approval.

       17.5   ESTOPPEL CERTIFICATE. Each party shall at any time and from time
to time upon not less than fifteen (15) days' prior notice from the other,
execute, acknowledge and deliver to the requesting party a statement in writing
certifying that this Lease is unmodified and in full force and effect (or if
there have been modifications, that the same is in full force and effect as
modified and stating the modifications), and the dates to which Rent has been
paid in advance, if any, stating whether or not, to the best of its knowledge,
the other party is in default in performance of any covenant, agreement, term,
provision or condition contained in this Lease

                                      -30-
<Page>

and, if so, specifying each such default, and such other facts as the requesting
party may reasonably request, it being intended that any such statement
delivered pursuant to Landlord's request may be relied upon by any prospective
purchaser of the Building or of any interest of Landlord therein, any Mortgagee
or prospective Mortgagee thereof, any lessor or prospective lessor thereof, any
lessee or prospective lessee thereof, or any prospective assignee of any
mortgage thereof. TIME IS OF THE ESSENCE WITH RESPECT TO ANY SUCH REQUESTED
CERTIFICATE.

       Landlord warrants that: (i) Landlord owns the Property; (ii) Landlord has
the authority to enter into this Lease with Tenant; and (iii) there are no liens
or similar claims (excluding mortgages) upon Landlord or against the Building,
other than as disclosed in Landlord's title insurance policy, a copy of which
has been delivered to Tenant.

       17.6   PROHIBITED MATERIALS AND PROPERTY; ENVIRONMENTAL PROVISIONS.

              (a)    Tenant shall not be permitted to bring or keep in or on the
Premises or elsewhere in the Building or Property any flammable, combustible or
explosive fluid, material, chemical or substance, or any Hazardous Material
(hereinafter defined), other than those enumerated in Tenant's Hazardous Waste
Management Program (as hereafter defined), which are hereby expressly permitted
by Landlord ("TENANT'S HAZARDOUS MATERIALS"). Tenant's Hazardous Materials shall
at all times be brought upon, kept or used in accordance with (A) all applicable
Environmental Laws (hereinafter defined) and prudent environmental practice, (B)
Tenant's "HAZARDOUS WASTE MANAGEMENT PROGRAM," attached hereto as EXHIBIT 7, and
(C) with respect to medical waste and so-called "biohazard" materials, good
medical practice and the highest standards applicable to Tenant's industry.
Tenant shall be responsible for assuring that all laboratory uses are adequately
and properly vented. Tenant's Hazardous Waste Management Program shall be
updated as reasonably required by Landlord, but no less frequently than
annually.

              (b)    Tenant, at its sole cost and expense, shall comply with (i)
all applicable laws, statutes, ordinances, rules and regulations of any local,
state or federal governmental authority having jurisdiction concerning
environmental, health and safety matters, including, without limitation, the
laws listed in Section 17.6(c) below (collectively, "ENVIRONMENTAL LAWS"),
including but not limited to those relating to any discharge into the air,
surface, water, sewers, soil or groundwater of any Hazardous Material, whether
within or outside the Premises, Building or Property, and (ii) any applicable
rules, requirements and safety procedures of the Massachusetts Department of
Environmental Protection ("DEP"), the Town of Lexington Fire Marshall and any
insurer of the Property, Building or the Premises with respect to the use,
storage and disposal of any Hazardous Materials at or from the Premises.

              (c)    As used herein, the term "HAZARDOUS MATERIAL" means (x)
medical waste or "biohazard" materials, and (y) any hazardous, radioactive or
toxic substance, material or waste or petroleum derivative which is or becomes
regulated by any Environmental Law. The term "HAZARDOUS MATERIAL" includes,
without limitation, any material or substance which is (i) designated as a
"hazardous substance" pursuant to Section 1311 of the Federal Water Pollution
Control Act (33 U.S.C. Section 1317), (ii) defined as a "hazardous waste"
pursuant to Section 1004 of the Federal Resource Conservation and Recovery Act,
42 U.S.C. Section 6901 et seq.

                                      -31-
<Page>

(42 U.S.C. Section 6903), or (iii) defined as a "hazardous substance" pursuant
to Section 101 of the Comprehensive Environmental Response, Compensation and
Liability Act, 42 U.S.C. Section 9601 et seq. (42 U.S.C. Section 9601), or (iv)
defined as "hazardous substance" or "oil" under Chapter 21E of the General Laws
of Massachusetts.

              (d)    Any increase in the premium for insurance at the Property
arising from Tenant's use and/or storage of Tenant's Hazardous Materials shall
be at Tenant's expense. Tenant shall procure and maintain at its sole expense
such additional insurance as may be necessary to comply with any requirement of
any federal, state or local government agency with jurisdiction.

              (e)    Tenant shall reimburse Landlord upon demand, as additional
rent, for the reasonable costs of investigating Tenant's compliance with the
provisions of this Section 17.6, within thirty (30) days after demand therefor,
if such investigation reveals that Tenant is not in compliance. Tenant shall
execute affidavits, certifications and the like, as may be reasonably requested
by Landlord from time to time concerning Tenant's best knowledge and belief
concerning the presence of Hazardous Materials in or on the Premises or the
Building.

              (f)    Except with respect to (i) Hazardous Materials in or under
the Property as of the Completion Date, (ii) Claims relating to conditions at
the Property, Building or Premises as of the Completion Date (including without
limitation that certain environmental condition identified by DEP as Release
Tracking Number 03-0020730), (iii) Claims resulting from activities at the
portions of the Property commonly known as 131 and 141 Spring Street, and (iv)
the presence and/or removal of the existing 5,000 gallon underground storage
tank on the Building Lot (which Landlord currently intends to remove during the
performance of Landlord's Work) and (v) unless the same is used by Tenant, the
presence of the existing 300 gallon aboveground storage tank on the Building
Lot, Tenant hereby covenants and agrees to indemnify, defend and hold the
Landlord Indemnitees harmless from and against any and all Claims against any of
the Landlord Indemnitees arising out of (A) the presence of Hazardous Material
in, under or about the Building resulting from Tenant's use or operations, or
(B) the breach by Tenant of any of its obligations under this Section 17.6. This
indemnification of the Landlord Indemnitees by Tenant includes, without
limitation, reasonable costs incurred in connection with any investigation of
site conditions or any cleanup, remedial, removal or restoration work required
by any federal, state or local governmental agency or political subdivision
because of Hazardous Material present in the soil or ground water on, under or
about the Building resulting from Tenant's use or operations. The
indemnification and hold harmless obligations of Tenant under this Section
17.6(f) shall survive the expiration or any earlier termination of this Lease.
Without limiting the foregoing, if the presence of any Hazardous Material in the
Building or otherwise in the Property is caused by any of the Tenant Parties and
results in any contamination of any part of the Property or any adjacent
property, Tenant shall promptly take all actions at Tenant's sole cost and
expense as are necessary to return the Property or any adjacent property to
their condition as of the date of this Lease, provided that Tenant shall first
obtain Landlord's approval of such actions, which approval shall not be
unreasonably withheld, conditioned or delayed so long as such actions, in
Landlord's reasonable discretion, would not potentially have any adverse effect
on the Property, and, in any event, Landlord shall not withhold its approval of
any proposed actions which are required by applicable Environmental Laws.

                                      -32-
<Page>

              (g)    Prior to bringing any Hazardous Material into any part of
the Property, Tenant shall deliver to Landlord the following information with
respect thereto: (i) a description of handling, storage, use and disposal
procedures; and (ii) all plans or disclosures and/or emergency response plans
which Tenant has prepared, including without limitation Tenant's Hazardous Waste
Management Plan, and all plans which Tenant is required to supply to any
governmental agency or authority pursuant to any Environmental Law.

              (h)    Landlord represents that it has no knowledge of (i) any
contamination of any portion of the Property other than as disclosed in the
Environmental Reports (hereinafter defined) and that certain existing
environmental condition identified by DEP as Release Tracking Number 03-0020730;
and (ii) any claims by third parties relating to the presence of Hazardous
Materials in the Property. For purposes hereof, the "ENVIRONMENTAL REPORTS"
shall mean collectively the reports listed on EXHIBIT 8 attached hereto. Tenant
shall not perform any additional testing at the Property.

              (i)    Landlord hereby covenants and agrees with Tenant to
indemnify, defend and hold Tenant, its officers, agents, contractors and those
claiming by, through or under Tenant (collectively the "Tenant Indemnitees")
harmless from and against any and all Claims against any of the Tenant
Indemnitees which may arise out of (i) the release or discharge of any Hazardous
Material on or about the Property, Premises or Building by virtue of the acts of
Landlord or any of its tenants, contractors, agents or invitees, (ii) Claims
resulting from uses or activities at 131 and 141 Spring Street, including
without limitation the use or presence of any storage tanks thereon, (iii) the
presence of the Hazardous Materials located at the Property, Premises or
Building as of the Completion Date, (iv) the presence and/or removal of the
existing 5000 gallon underground storage tank on the Building Lot (which
Landlord currently intends to remove during the performance of the Landlord's
Work), or (v) unless the same is used by Tenant, the presence of the existing
300 gallon aboveground storage tank on the Building Lot.

              (j)    Any increase in the premium for Tenant's insurance at the
Premises directly and expressly attributable to Landlord's use and/or storage of
Hazardous Material at the Property shall be at Landlord's expense.

              (k)    Landlord shall execute affidavits, certifications and the
like, as may be reasonable requested by Tenant from time to time concerning
Landlord's best knowledge and belief concerning the presence of Hazardous
Materials in or on the Property or the Building.

       17.7   LEGAL REQUIREMENTS. If Tenant receives notice of any violation of
Legal Requirements applicable to the Premises, it shall give prompt notice
thereof to Landlord. The parties' obligations with respect to keeping the
Building Lot and Building in compliance with all Legal Requirements shall be as
follows: (a) Landlord shall be responsible, at its sole cost and expense (not to
be included within Building Operating Costs), for keeping in compliance with all
Legal Requirements the items it is required to maintain pursuant to Section
14.6, (b) Tenant shall be solely responsible, at its sole cost and expense, for
keeping in compliance with all Legal Requirements all elements of the Building
other than those for which the Landlord is responsible pursuant to clause (a)
above, with capital repairs and replacements to be treated as treated in the
last three sentences of Section 14.1, and (c) notwithstanding the provisions of
clause (a) to the

                                      -33-
<Page>

contrary, Tenant shall be solely responsible for causing the Building and
Building Lot (including elements that would otherwise be Landlord's
responsibility pursuant to Section 14.6) to comply with any Legal Requirement
imposed upon or applicable to the Building or Building Lot as a result of
Tenant's particular use thereof (as opposed to office and laboratory uses
generally), and in the event such compliance requires a capital expenditure, the
expenditure shall be made by Tenant directly, not pursuant to the last three
sentences of Section 14.1.

       17.8   TENANT'S ACTS--EFFECT ON INSURANCE. Tenant shall not do or permit
any Tenant Party to do any act or thing upon the Premises or elsewhere in the
Building which will invalidate or be in conflict with any insurance policies
covering the Building and/or the fixtures and property therein; and shall not
do, or permit to be done, any act or thing upon the Premises which shall subject
Landlord to any liability or responsibility for injury to any person or persons
or to property by reason of any business or operation being carried on upon said
Premises or for any other reason. If by reason of the failure of Tenant to
comply with the provisions hereof the insurance rate applicable to any policy of
insurance shall at any time thereafter be higher than it otherwise would be,
Tenant shall reimburse Landlord for that part of any insurance premiums which
shall have been charged because of such failure by Tenant.

18.    CASUALTY; TAKING

       18.1   DAMAGE.

              (a)    If the Premises become untenantable in whole or part
because of fire or other casualty covered by insurance required under this Lease
(or insurance actually carried, if more comprehensive than the insurance
required to be carried) ("CASUALTY"), or as the result of a taking of, or damage
to, the Building, thereon in connection with the exercise of any power of
eminent domain, condemnation, or purchase under threat or in lieu thereof (any
of the foregoing, a "TAKING"), then unless this Lease is terminated in
accordance with Section 18.2 below, Landlord shall use reasonable efforts to
restore the Building and/or the Premises as applicable in the manner set forth
herein. In the event of a Casualty or Taking, Landlord shall repair the Building
and the Premises so that the Building and the Premises are in substantially the
same condition as following completion of Landlord's Work as set forth in
Section 4.1, or in the event of a partial Taking which affects the Building and
the Premises, restore the remainder of the Building and the Premises not so
Taken to substantially the same condition as is reasonably feasible. If Landlord
and Tenant mutually agree that any element of the Tenant-Insured Improvements
can more effectively be repaired as an integral part of Landlord's repair work
to the Building or the Premises, such repair shall also be made by Landlord, but
at Tenant's sole cost and expense; in all other events, Tenant shall be
responsible for restoring Tenant-Insured Improvements, at Tenant's sole cost.
Subject to rights of Mortgagees, Legal Requirements, zoning laws, and building
codes then in existence and to delays for adjustment of insurance proceeds or
Taking awards, as the case may be, and Events of Force Majeure, Landlord shall
use diligent efforts to substantially complete such repair within one (1) year
from the date of said Casualty or Taking. Landlord's obligation to repair shall
be subject to rights of Mortgagees, Legal Requirements, zoning laws, and
building codes then in existence and to delays for adjustment of insurance
proceeds or Taking awards, as the case may be, and Events of Force Majeure.
Tenant agrees to cooperate with Landlord in such manner as Landlord may
reasonably

                                      -34-
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request to assist Landlord in collecting insurance proceeds due in connection
with any Casualty which affects the Premises or the Building. In no event shall
Landlord be required to expend more than the Net (hereinafter defined) insurance
proceeds Landlord receives (or would have received, had Landlord carried the
insurance coverage required to be carried hereunder) for damage to the Premises
and/or the Building or the Net Taking award attributable to the Premises and/or
the Building. "NET" means the insurance proceeds or Taking award actually paid
to Landlord (or which would actually have been paid to Landlord, had Landlord
carried the insurance coverage required to be carried hereunder) less all costs
and expenses, including adjusters and attorney's fees, of obtaining the same.
Tenant also shall be required to pay to Landlord Tenant's Building Percentage
Share of any deductible under any property insurance policy maintained by
Landlord, provided such deductible amount is prudent and of a size commonly
carried for Buildings comparable to the Building. Under no circumstances shall
Landlord be required to repair any damage to, or make any repairs to or
replacements of, Tenant's Property.

              (b)    Tenant shall notify Landlord in writing promptly after
becoming aware of any Casualty or Taking. Within sixty (60) days after it is
made aware of a Casualty or Taking, Landlord shall advise Tenant of the
following, in writing (the "LANDLORD CASUALTY/TAKING NOTICE"): (i) whether
Landlord elects to terminate this Lease pursuant to Section 18.2, if permitted;
(ii) if Landlord elects or is obligated to restore pursuant to Section 18.1(a),
the projected completion date of the restoration; and (iii) if the Net insurance
proceeds or Net Taking award are insufficient to cover the entire restoration,
the estimated amount by which such sums are insufficient.

       18.2   TERMINATION RIGHTS.

              (a)    LANDLORD'S TERMINATION RIGHTS. Landlord may terminate this
Lease upon thirty (30) days' prior written notice to Tenant:

                     (i)     if any portion of the Building or any material
means of access thereto is taken;

                     (ii)    if more than twenty-five percent (25%) of the Upper
Level Space is damaged by Casualty; or

                     (iii)   the estimated time to complete restoration exceeds
one (1) year.

              (b)    TENANT'S TERMINATION RIGHTS. Tenant may terminate this
Lease upon thirty (30) days written notice to Landlord:

                     (i)     if Landlord's Casualty/Taking Notice indicates that
the estimated time to complete restoration exceeds one (1) year;

                     (ii)    if Landlord fails to deliver Landlord's
Casualty/Taking Notice within sixty (60) days after it is made aware of a
Casualty or Taking, and fails again to deliver Landlord's Casualty/Taking Notice
within thirty (30) days after notice from Tenant to Landlord stating that
Landlord has failed to deliver Landlord's Casualty/Taking Notice and that the

                                      -35-
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continued failure to deliver Landlord's Casualty/Taking Notice for thirty (30)
days shall give rise to a Tenant right to terminate pursuant to this Section
18.2(b); or

                     (iii)   if Landlord fails to substantially complete
restoration prior to the projected date for substantial completion set forth in
Landlord's Casualty/Taking Notice, which projected date shall be extended on a
day-for-day basis on account of the occurrence of Tenant Delays or, up to a
maximum of ninety (90) days, Events of Force Majeure, and such failure to
achieve substantial completion persists for a period equal to the shorter of (A)
90 days or (B) one-half of the original estimated restoration period (e.g., for
45 days, in the case of an estimated restoration period of 90 days); provided,
however, that if substantial completion of the restoration occurs within thirty
(30) days after delivery of Tenant's termination notice, such termination notice
shall be deemed void and of no force or effect and this Lease shall continue in
full force and effect.

              (c)    EITHER PARTY MAY TERMINATE. Each of Landlord and Tenant
shall have the right, exercisable by notice to the other, to terminate this
Lease in the event: (i) a Casualty or Taking affecting the Premises occurs
during the last eighteen (18) months of the term hereof, and (A) such Casualty
or Taking to the Premises results in more than ten (10%) of the floor area of
the Premises being unsuitable for the Permitted Uses, or (B) the damage to the
Premises costs more than $500,000 to repair, or (C) the damage will take more
than one hundred twenty (120) days to restore, or (ii) the restoration cannot
occur because of rights of Mortgagees, Legal Requirements, zoning laws or
building codes then in existence, or the Landlord Casualty/Taking Notice
indicates that Net insurance proceeds or the Net Taking award are insufficient
to restore. The exercise of such termination right shall be made by notice
delivered within thirty (30) days after Landlord's Casualty/Taking Notice and
shall be effective on the date specified in such notice, which shall be no
sooner than 60 nor later than 90 days after the date of delivery of such notice.

              (d)    AUTOMATIC TERMINATION. In the case of a Taking of the
entire Premises, then this Lease shall automatically terminate as of the date of
possession by the Taking authority.

       18.3   ABATEMENT. If the Premises are untenantable in whole or in part as
a result of Casualty or Taking, the Yearly Rent and payments of Building
Operating Costs and Taxes payable hereunder during the period in which they are
untenantable shall be reduced or abated on a proportionate basis to reflect the
percentage of the Building that is untenantable, with Upper Level Space and
Lower Level Space being treated separately (i.e. if 75% of the Lower Level Space
and 10% of the Upper Level Space are untenantable, the rent abatement shall
equal 75% of the rent attributable to the Lower Level Space and 10% of the rent
attributable to the Upper Level Space.

       18.4   [INTENTIONALLY OMITTED].

       18.5   DISPOSITION OF AWARDS. Except for any separate award for Tenant's
movable trade fixtures, relocation expenses, loss of business and Tenant-Insured
Improvements, all Taking awards to Landlord or Tenant shall be Landlord's
property without Tenant's participation.

                                      -36-
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       18.6   TIME OF THE ESSENCE. All time periods set forth in this Section 18
shall be of the essence.

19.    DEFAULT

       19.1   EVENTS OF DEFAULT; REMEDIES. The occurrence of any one or more of
the following events shall constitute an "EVENT OF DEFAULT" hereunder by Tenant:

              (a)    The failure by Tenant to make any payment of Rent or any
other payment required hereunder, as and when due, where such failure shall
continue for a period of five (5) days after written notice thereof from
Landlord to Tenant; provided, however, that no notice shall be required after
the first such failure within any twelve-month period;

              (b)    [intentionally omitted];

              (c)    If Tenant shall fail to maintain any insurance required
hereunder;

              (d)    If Tenant shall make a Transfer in violation of the
provisions of Article 16 above, or if any event shall occur or any contingency
shall arise whereby this Lease, or the term and estate thereby created, would
(by operation of law or otherwise) devolve upon or pass to any person, firm or
corporation other than Tenant, except as expressly permitted under Article 16
hereof;

              (e)    The failure by Tenant to observe or perform any of the
covenants or provisions of this Lease to be observed or performed by Tenant,
other than as specified above, and such failure continues for more than thirty
(30) days after notice thereof from Landlord; provided, further, that if the
nature of Tenant's default is such that more than thirty (30) days are
reasonably required for its cure, then Tenant shall not be deemed to be in
default if Tenant shall commence such cure within said thirty (30) day period
and thereafter diligently prosecute such cure to completion, which completion
shall occur not later than ninety (90) days from the date of such notice from
Landlord;

              (f)    Tenant shall be involved in financial difficulties as
evidenced by an admission in writing by Tenant of Tenant's inability to pay its
debts generally as they become due, or by the making or offering to make a
composition of its debts with its creditors;

              (g)    Tenant shall make an assignment or trust mortgage, or other
conveyance or transfer of like nature, of all or a substantial part of its
property for the benefit of its creditors,

              (h)    an attachment on mesne process, on execution or otherwise,
or other legal process shall issue against Tenant or its property and a sale of
any of its assets shall be held thereunder;

              (i)    the leasehold hereby created shall be taken on execution or
by other process of law and shall not be revested in Tenant within thirty (30)
days thereafter;

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              (j)    a receiver, sequesterer, trustee or similar officer shall
be appointed by a court of competent jurisdiction to take charge of all or any
part of Tenant's property and such appointment shall not be vacated within
thirty (30) days; or

              (k)    any proceeding shall be instituted by or against Tenant
pursuant to any of the provisions of any Act of Congress or State law relating
to bankruptcy, reorganizations, arrangements, compositions or other relief from
creditors, and, in the case of any proceeding instituted against it, if Tenant
shall fail to have such proceedings dismissed within ninety (90) days or if
Tenant is adjudged bankrupt or insolvent as a result of any such proceeding.

Upon an Event of Default, Landlord may, by notice to Tenant, elect to terminate
this Lease; and thereupon (and without prejudice to any remedies which might
otherwise be available for arrears of Rent or preceding breach of covenant or
agreement and without prejudice to Tenant's liability for damages as hereinafter
stated), upon the giving of such notice, this Lease shall terminate as of the
date specified therein as though that were the Expiration Date. Without being
taken or deemed to be guilty of any manner of trespass or conversion, and
without being liable to indictment, prosecution or damages therefor, Landlord
may, forcibly if necessary, enter into and upon the Premises (or any part
thereof in the name of the whole); repossess the same, as of its former estate;
and expel Tenant and those claiming under Tenant. Wherever "Tenant " is used in
this Section 19.1, it shall be deemed to include any guarantor of any of
Tenant's obligations under this Lease. The words "re-entry" and "re-enter" as
used in this Lease are not restricted to their technical legal meanings.

       19.2   DAMAGES - TERMINATION.

              (a)    Upon the termination of this Lease under the provisions of
this Article 19, Tenant shall pay to Landlord Rent up to the time of such
termination, shall continue to be liable for any preceding breach of covenant,
and in addition, shall pay to Landlord as damages, at the election of Landlord,
either:

                     (i)     the amount (discounted to present value at the rate
of six percent (6%) per annum) by which, at the time of the termination of this
Lease (or at any time thereafter if Landlord shall have initially elected
damages under Section 19.2(a)(ii), below), (x) the aggregate of Rent projected
over the period commencing with such termination and ending on the Expiration
Date, exceeds (y) the aggregate projected rental value of the Premises for such
period, plus all Reletting Costs (hereinafter defined); or

                     (ii)    amounts equal to Rent which would have been payable
by Tenant had this Lease not been so terminated, payable upon the due dates
therefor specified herein following such termination and until the Expiration
Date, PROVIDED, HOWEVER, if Landlord shall re-let the Premises during such
period, that Landlord shall credit Tenant with the net rents received by
Landlord from such re-letting, such net rents to be determined by first
deducting from the gross rents as and when received by Landlord from such
re-letting the expenses incurred or paid by Landlord in terminating this Lease,
as well as the expenses of re-letting, including altering and preparing the
Premises for new tenants, brokers' commissions, and all other similar and
dissimilar expenses properly chargeable against the Premises and the rental
therefrom

                                      -38-
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(collectively, "RELETTING COSTS"), it being understood that any such re-letting
may be for a period equal to or shorter or longer than the remaining term of
this Lease; and PROVIDED, FURTHER, that (x) in no event shall Tenant be entitled
to receive any excess of such net rents over the sums payable by Tenant to
Landlord hereunder and (y) in no event shall Tenant be entitled in any suit for
the collection of damages pursuant to this Section 19.2(a)(ii) to a credit in
respect of any net rents from a re-letting except to the extent that such net
rents are actually received by Landlord prior to the commencement of such suit.
If the Premises or any part thereof should be re-let in combination with other
space, then proper apportionment on a square foot area basis shall be made of
the rent received from such re-letting and of the expenses of re-letting.

              (b)    In calculating the amount due under Section 19.2(a)(i),
above, there shall be included, in addition to the Yearly Rent, Tenant's
Building Percentage Share of Taxes and Building Operating Costs and all other
considerations agreed to be paid or performed by Tenant, on the assumption that
all such amounts and considerations would have increased at the rate of five
percent (5%) per annum for the balance of the full term hereby granted.

              (c)    Suit or suits for the recovery of such damages, or any
installments thereof, may be brought by Landlord from time to time at its
election, and nothing contained herein shall be deemed to require Landlord to
postpone suit until the date when the term of this Lease would have expired if
it had not been terminated hereunder. Landlord agrees to use reasonable efforts
to mitigate damages resulting from Tenant's default hereunder if and to the
extent required by law to do so.

       19.3   SELF-HELP; FEES AND EXPENSES.

              (a)    SELF-HELP. If Tenant shall default in the performance of
any covenant on Tenant's part to be performed in this Lease contained, including
without limitation the obligation to maintain the Building in the required
condition pursuant to Section 14 above, Landlord may, upon reasonable advance
notice, except that no notice shall be required in an emergency, immediately, or
at any time thereafter, without notice, perform the same for the account of
Tenant.

              (b)    REIMBURSEMENT OF FEES AND EXPENSES. If either Tenant or
Landlord at any time is compelled to pay or elects to pay any sum of money, or
do any act which will require the payment of any sum of money, by reason of the
failure of the other party to comply with any provision hereof, or if either is
compelled to or does incur any expense, including reasonable attorneys' fees, in
instituting, prosecuting, and/or defending any action or proceeding instituted
by reason of any default of the other hereunder, and prevails, the prevailing
party shall be entitled to reimbursement of the sum or sums so paid by it within
thirty (30) days after demand therefor, plus interest at the Default Rate until
paid in full.

       19.4   LANDLORD'S REMEDIES NOT EXCLUSIVE. The specified remedies to which
Landlord may resort hereunder are cumulative and are not intended to be
exclusive of any remedies or means of redress to which Landlord may at any time
be lawfully entitled, and Landlord may invoke any remedy (including the remedy
of specific performance) allowed at law or in equity as if specific remedies
were not herein provided for.

                                      -39-
<Page>

       19.5   NO WAIVER. Landlord's failure to seek redress for violation, or to
insist upon the strict performance, of any covenant or condition of this Lease,
or any of the Rules and Regulations promulgated hereunder, shall not prevent a
subsequent act, which would have originally constituted a violation, from having
all the force and effect of an original violation. The receipt by Landlord of
Rent with knowledge of the breach of any covenant of this Lease shall not be
deemed a waiver of such breach. The failure of Landlord to enforce any of such
Rules and Regulations against Tenant and/or any other tenant in the Building
shall not be deemed a waiver of any such Rules and Regulations. No provisions of
this Lease shall be deemed to have been waived by either party unless such
waiver be in writing signed by such party. No payment by Tenant or receipt by
Landlord of a lesser amount than the Rent herein stipulated shall be deemed to
be other than on account of the stipulated Rent, nor shall any endorsement or
statement on any check or any letter accompanying any check or payment as Rent
be deemed an accord and satisfaction, and Landlord may accept such check or
payment without prejudice to Landlord's right to recover the balance of such
Rent or pursue any other remedy in this Lease provided.

20.    SURRENDER; ABANDONED PROPERTY; HOLD-OVER

       20.1   SURRENDER.

              (a)    Upon the expiration or other termination of the term
hereof, Tenant shall (i) peaceably quit and surrender to Landlord the Premises
and all Alterations thereto required by Landlord to be removed pursuant to the
provisions of Article 12, broom clean, in good order, repair and condition
excepting reasonable wear and tear and damage by fire or other Casualty or acts
of Landlord Parties; (ii) remove any and all Hazardous Materials (but only to
the extent Tenant bears liability or responsibility for such Hazardous Materials
under Article 17), and all of Tenant's Property, (iii) deliver to Landlord a
certification from an industrial hygienist reasonably acceptable to Landlord
certifying that the Premises do not contain any Hazardous Materials (but only to
the extent Tenant bears liability or responsibility for such Hazardous Materials
under Article 17); and (iv) repair any damages to the Premises or the Building
caused by the installation or removal of Alterations or Tenant's Property.
Tenant's obligations under this Section 20.1(a) shall survive the expiration or
earlier termination of this Lease.

              (b)    No act or thing done by Landlord during the term hereby
demised shall be deemed an acceptance of a surrender of the Premises, and no
agreement to accept such surrender shall be valid, unless in writing signed by
Landlord. Unless otherwise agreed by the parties in writing, no employee of
Landlord or of Landlord's agents shall have any power to accept the keys of the
Premises prior to the termination of this Lease. The delivery of keys to any
employee of Landlord or of Landlord's agents shall not operate as a termination
of this Lease or a surrender of the Premises.

       20.2   ABANDONED PROPERTY. After the expiration or earlier termination
hereof, if Tenant fails to remove any property from the Building or the Premises
which Tenant is obligated by the terms of this Lease to remove, such property
(the "ABANDONED PROPERTY") shall be conclusively deemed to have been abandoned,
and may either be retained by Landlord as its property or sold or otherwise
disposed of in such manner as Landlord may see fit. If any item of

                                      -40-
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Abandoned Property shall be sold, Tenant hereby agrees that Landlord may receive
and retain the proceeds of such sale.

       20.3   HOLDOVER. If any of the Tenant Parties holds over after the end of
the term hereof, Tenant shall be deemed to be a tenant-at-sufferance but
otherwise subject to Tenant's obligations under this Lease; provided that
whether or not Landlord has accepted Rent, (i) Tenant shall pay Yearly Rent at
150% of the greater of (a) the highest rate of Yearly Rent payable during the
term or (b) the then fair market rental value of the Premises. In addition, with
respect to any holdover which persists for 30 days or more, Tenant shall be
liable for all actual damages, including without limitation consequential
damages, incurred by Landlord as a result of such holding over. Nothing
contained herein shall grant Tenant the right to holdover after the expiration
or earlier termination of the term hereof.

21.    MORTGAGEE RIGHTS

       21.1   SUBORDINATION. Tenant's rights and interests under this Lease
shall be (i) subject and subordinate to any future mortgages, deeds of trust,
overleases, or similar instruments covering the Premises and to all advances,
modifications, renewals, replacements, and extensions thereof (each of the
foregoing, a "MORTGAGE"), or (ii) if any Mortgagee elects, prior to the lien of
any present or future Mortgage. Tenant further shall attorn to and recognize any
successor landlord, whether through foreclosure or otherwise, as if the
successor landlord were the originally named landlord, provided such successor
assumes all obligations under the Lease. Notwithstanding anything to the
contrary in this Article 21 contained, as to any future Mortgage, the herein
provided subordination and attornment shall be effective only if the Mortgagee
agrees, by a written commercially reasonable instrument in recordable form
("NONDISTURBANCE AGREEMENT") that, as long as there is no Event of Default, this
Lease will not be affected and Tenant's possession and rights hereunder will not
be disturbed by any default in, termination, and/or foreclosure of, such
Mortgage. In no event shall such Mortgagee (i) have any liability for any act,
omission, negligence or default of any prior landlord; (ii) be bound by any
rents paid more than one month in advance to any prior landlord, (iii) be
subject to any offsets or defenses which Tenant might have against any prior
landlord under the Lease; (iv) be bound by any modification, amendment,
extension or cancellation of the Lease not consented to in writing by the
Mortgagee; (v) be required to perform any of Landlord's Work (unless such
Mortgagee expressly agrees to do so in writing, whether in a Nondisturbance
Agreement or otherwise); or (vi) have any liability for indirect or
consequential damages. Furthermore, as to any Event of Default by Tenant under
the Lease existing at the time of foreclosure, such foreclosure shall not
operate to waive or abate any action initiated by any prior landlord under the
Lease to terminate the same on account of such Event of Default. In no event
shall the Mortgagee have any personal liability as successor to Landlord, and
Tenant shall look only to the estate and property of the Mortgagee in the
Building and the parcel of land on which it is located for the satisfaction of
Tenant's remedies for the collection of a judgment (or other judicial process)
requiring the payment of money in the event of any default by Mortgagee as
Landlord under the Lease, and no other property or assets of the Mortgagee shall
be subject to levy, execution or other enforcement procedure for the
satisfaction of Tenant's remedies under or with respect to the Lease.

                                      -41-
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       21.2   NOTICES. Provided Tenant has been given the name and address of
such Mortgagees, Tenant shall give each Mortgagee a copy of any default notice
given to Landlord concurrently with the notice to Landlord, and each Mortgagee
shall have a reasonable opportunity thereafter to cure a Landlord default, and
Mortgagee's curing of any of Landlord's default shall be treated as performance
by Landlord.

       21.3   EXISTING MORTGAGE. Landlord represents to Tenant that the only
mortgagee of the Property as of the date hereof is Principal Life Insurance
Company.

22.    QUIET ENJOYMENT

       Landlord covenants that so long as Tenant keeps and performs each and
every covenant, agreement, term, provision and condition herein contained on the
part and on behalf of Tenant to be kept and performed, Tenant shall peaceably
and quietly hold, occupy and enjoy the Premises during the Term hereof from and
against the claims of all persons lawfully claiming by, through or under
Landlord subject, nevertheless, to the covenants, agreements, terms, provisions
and conditions of this Lease, any matters of record or of which Tenant has
knowledge and to any Mortgage to which this Lease is subject and subordinate, as
hereinabove set forth.

23.    SECURITY DEPOSIT

       Upon its execution of this Lease, Tenant shall deposit with Landlord the
amount of $800,000, in cash (the "CASH SECURITY DEPOSIT") or an irrevocable
demand letter of credit (the "LETTER OF CREDIT"), to be held as security for
Tenant's performance of its obligations under this Lease (such security, whether
in the form of a Cash Security Deposit or Letter of Credit, to be referred to
hereinafter as the "SECURITY DEPOSIT"). Landlord may, but shall not be required
to, draw on the Security Deposit and apply the whole or any part of the proceeds
thereof for any amounts due Landlord by reason of the occurrence of an Event of
Default. Upon such application, Tenant shall, within ten (10) days after
Landlord's request, restore the Security Deposit to its original amount by
either delivering cash or a new Letter of Credit complying with the provisions
hereof to Landlord. The Letter of Credit shall be in the form attached hereto as
EXHIBIT 9 or on such other form reasonably acceptable to Landlord, drawn on
Fleet Bank, N.A., or other FDIC-insured banking institution reasonably
acceptable to Landlord, and shall state that it is payable unconditionally to
the Landlord or order on demand upon presentation of a sight draft under the
Letter of Credit referencing this Lease and stating that there is an Event of
Default thereunder. The Letter of Credit shall, throughout the Term, and for a
period of thirty (30) days after the expiration of the Term, be in full force
and in compliance with the terms of this Lease. In the event that the Letter of
Credit shall have an expiration date before the date that is thirty (30) days
after the expiration of the Term, Tenant shall deliver to Landlord a new Letter
of Credit complying with the provisions hereof no later than thirty (30) days
prior to the expiration of the Letter of Credit, and if Tenant shall so fail to
deliver a new Letter of Credit, such failure shall constitute an Event of
Default and Landlord shall have the right to draw on the Letter of Credit and
hold the proceeds thereof as a Cash Security Deposit. Landlord shall have no
obligation to pay interest on the Cash Security Deposit or any the cash proceeds
of the Letter of Credit or segregate such amounts from Landlord's other funds.
Tenant shall not mortgage, pledge, grant a security interest in, or otherwise
encumber the Security Deposit. The Security Deposit or any

                                      -42-
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balance remaining (after application of the same by Landlord to cure Tenant's
defaults hereunder), shall be returned to Tenant within thirty (30) days after
the end of the Term, provided that Tenant has re-delivered possession of the
Premises to Landlord and fully performed all its obligations hereunder,
including, without limitation, payment to Landlord of all amounts due hereunder.
Notwithstanding anything herein to the contrary, provided there is no Event of
Default as of the end of the Fifth Rent Year, the amount of the Security Deposit
required hereunder shall be reduced as of such date to $400,000. Tenant shall
accomplish said reduction by providing Landlord with a substitute Letter of
Credit in the reduced amount complying with the terms hereof or an amendment to
the existing Letter of Credit in form and substance reasonably acceptable to
Landlord.

24.    TENANT'S OPTION TO EXTEND THE TERM OF THE LEASE

       24.1   Provided there is no Event of Default (a) at the time of Tenant's
exercise of such option, and (b) at the commencement of the Extension Term
(hereinafter defined), Tenant shall have the option to extend the term of this
Lease for two (2) additional five (5) year term(s) (each of the two terms, an
"EXTENSION TERM"), commencing as of the expiration of the initial term of this
Lease or the prior Extension Term, as the case may be. Tenant may exercise such
option to extend by giving Landlord written notice on or before the date twelve
(12) months prior to the expiration date of the then-current term of this Lease,
TIME BEING OF THE ESSENCE. Upon the timely giving of such notice, the term of
this Lease shall be deemed extended upon all of the terms and conditions of this
Lease, except that Yearly Rent shall be calculated in accordance with Section
24.2 below, Landlord shall have no obligation to construct or renovate the
Premises and Tenant shall have one (1) fewer option to further extend the term
hereof. If Tenant fails to give timely notice, as aforesaid, Tenant shall have
no further right to extend the term of this Lease. Notwithstanding the fact that
Tenant's exercise of the herein option to extend the term hereof shall be
self-executing, the parties shall promptly execute a lease amendment reflecting
such Extension Term after Tenant exercises such option. The execution of such
lease amendment shall not be deemed to waive any of the conditions to Tenant's
exercise of its rights under this Article 24.

       24.2   (a) The Yearly Rent during each Extension Term (the "EXTENSION
TERM YEARLY RENT") shall be an amount equal to 95% of the fair market rental
value of the Premises then demised to Tenant as of the commencement of each
Extension Term as determined in accordance with the process described below, for
renewals of space in the Lexington area of equivalent quality, size, utility,
build out and location, with the length of the Extension Term, but excluding the
value of the alterations and improvements to the Premises paid for by Tenant.
Within thirty (30) days after receipt of Tenant's notice to extend the term
hereof, Landlord shall deliver to Tenant written notice of its determination of
the Extension Term Yearly Rent. Tenant shall, within thirty (30) days after
receipt of such notice, notify Landlord in writing whether Tenant accepts or
rejects Landlord's determination of the Extension Term Yearly Rent ("TENANT'S
RESPONSE NOTICE"). If Tenant fails timely to deliver Tenant's Response Notice,
Tenant shall be deemed to have rejected Landlord's determination of the
Extension Term Yearly Rent.

              (b)    If Tenant rejects or is deemed to have rejected Landlord's
determination of the Extension Term Yearly Rent, then the Extension Term Yearly
Rent shall be determined in

                                      -43-
<Page>

accordance with the procedure set forth in this Section 24.2(b). In such event,
within five (5) business days after Tenant's rejection or deemed rejection of
Landlord's determination of the Extension Term Yearly Rent, Tenant and Landlord
shall each notify the other, in writing, of their respective selections of a
broker (respectively, "LANDLORD'S BROKER" and "TENANT'S BROKER"). Landlord's
Broker and Tenant's Broker shall then jointly select a third broker (the "THIRD
BROKER"). All of the brokers selected shall be individuals with at least ten
(10) years' commercial brokerage experience for office, research and laboratory
buildings in the area in which the Premises are located, and, in the case of the
Third Broker, shall not have acted in any capacity for either Landlord or Tenant
within five (5) years of his or her selection. If Tenant fails within such
five-business day period to notify Landlord of its selection of a qualified
broker, and fails again to do so within five business days after a second notice
from Landlord, then Landlord's determination of Extension Term Yearly Rent shall
be the Extension Term Yearly Rent and there shall be no arbitration procedure.
The three brokers shall determine the fair market rental value in accordance
with the requirements and criteria set forth in Section 24.1(a) above.
Landlord's Broker, Tenant's Broker and the Third Broker shall deliver their
determinations of the fair market rental value to Tenant and Landlord within
fifteen (15) days of their the appointment of the Third Broker. The
determination of the fair market rental value calculated by averaging the two
(2) determinations of the fair market rental value closest to one another shall
be the fair market rental value and 95% of such average shall be the Extension
Term Yearly Rent for the applicable Extension Term. Each party shall bear the
cost of its own broker and shall share equally in the cost of the Third Broker.

25.    SIGNAGE

       25.1   Landlord shall supply a sign on the building standard monument at
the entrance to the Property, at Landlord's sole cost and expense.

       25.2   Provided Tenant occupies at least 70% of the Building, Tenant
shall have the right to erect and maintain one sign on the exterior of the
Building (the "EXTERIOR SIGNAGE"), provided (i) the Exterior Signage complies
with all Legal Requirements and Tenant shall have obtained all required permits
prior to erecting the Exterior Signage, (ii) the location of the Exterior
Signage shall be subject to Landlord's prior written approval, which Landlord
may withhold in its sole discretion, (iii) the materials, design and lighting of
the Exterior Signage, and any requested changes thereto, shall be subject to
Landlord's prior written approval, which Landlord may withhold in its sole
discretion, and (iv) Tenant shall at all times maintain the Exterior Signage in
good order, condition and repair and shall remove the Exterior Signage at the
expiration or earlier termination of the term hereof or upon Landlord's written
demand after the failure of Tenant to comply with the provisions of this Section
25.2, and shall repair any damage to the Building caused by the Exterior Signage
or the installation or removal thereof. Landlord agrees to cooperate reasonably,
at no cost to Landlord, to assist Tenant in obtaining the permits necessary for
Exterior Signage, once approved by Landlord.

26.    BILLS AND NOTICES

       Any notice, consent, request, bill, demand or statement hereunder (each,
a "NOTICE") by either party to the other party shall be in writing and, shall be
deemed to have been duly given

                                      -44-
<Page>

when either delivered or served personally with receipt of delivery or delivered
via nationally recognized overnight courier with receipt of delivery addressed
to Landlord at its address as stated in the Lease Data, with a copy to Hale and
Dorr LLP, 60 State Street, Boston, MA 02109, Attention: Paul Jakubowski, Esq.,
and to Tenant at the Premises (or at Tenant's address as stated in the Lease
Data, if mailed prior to Tenant's occupancy of the Premises), with a copy to
Gadsby & Hannah LLP, 225 Franklin Street, Boston, MA 02110, Attention: Cynthia
Keliher, Esq. Either party may at any time change the address or specify an
additional address for such Notices by delivering or mailing, as aforesaid, to
the other party a notice stating the change and setting forth the changed or
additional address, provided such changed or additional address is within the
United States. Notices shall be effective upon the date of receipt or refusal
thereof.

27.    MISCELLANEOUS

       27.1   SEPARABILITY. If any provision of this Lease or portion of such
provision or the application thereof to any person or circumstance is for any
reason held invalid or unenforceable, the remainder of this Lease (or the
remainder of such provision) and the application thereof to other persons or
circumstances shall not be affected thereby.

       27.2   CAPTIONS. The captions are inserted only as a matter of
convenience and for reference, and in no way define, limit or describe the scope
of this Lease nor the intent of any provisions thereof.

       27.3   BROKER. Tenant and Landlord each warrants and represents that it
has dealt with no broker in connection with the consummation of this Lease other
than Broker. Tenant and Landlord each agrees to defend, indemnify and save the
other harmless from and against any Claims arising in breach of the
representation and warranty set forth in the immediately preceding sentence,
provided that Landlord shall be solely responsible for the payment of any
brokerage commissions to Broker.

       27.4   ENTIRE AGREEMENT. This Lease and EXHIBITS 1-14 attached hereto
contain the entire and only agreement between the parties and any and all
statements and representations, written and oral, including previous
correspondence and agreements between the parties hereto, are merged herein.
Tenant acknowledges that all representations and statements upon which it relied
in executing this Lease are contained herein and that Tenant in no way relied
upon any other statements or representations, written or oral. This Lease may
not be modified orally or in any manner other than by written agreement signed
by the parties hereto.

       27.5   GOVERNING LAW. This Lease is made pursuant to, and shall be
governed by, and construed in accordance with, the laws of the Commonwealth of
Massachusetts and any applicable local municipal rules, regulations, by-laws,
ordinances and the like.

       27.6   REPRESENTATION OF AUTHORITY. By his or her execution hereof, each
of the signatories on behalf of the respective parties hereby warrants and
represents to the other that he or she is duly authorized to execute this Lease
on behalf of such party. Upon request of either party, the other shall deliver,
evidence that any requisite resolution, corporate authority and any other
necessary consents have been duly adopted and obtained.

                                      -45-
<Page>

       27.7   EXPENSES INCURRED BY LANDLORD UPON TENANT REQUESTS. Each party
shall, upon demand, reimburse the other for all reasonable expenses, including,
without limitation, legal fees, incurred by the demanding party in connection
with all requests by such party for consents, approvals or execution of
collateral documentation related to this Lease, including, without limitation,
costs incurred by Landlord in the review and approval of Tenant's plans and
specifications in connection with proposed Alterations to be made by Tenant to
the Premises or requests by Tenant for Landlord's consent to make a Transfer.
Such costs, if payable by Tenant, shall be deemed to be additional rent under
this Lease.

       27.8   SURVIVAL. Without limiting any other obligation which may survive
the expiration or prior termination of the term of this Lease, all obligations
of each party to indemnify, defend, or hold the other party harmless, as set
forth in this Lease shall survive the expiration or prior termination of the
term of this Lease.

       27.9   LIMITATION OF LIABILITY. Tenant shall neither assert nor seek to
enforce any claim against Landlord or any of the Landlord Parties, or the assets
of Landlord or any of the Landlord Indemnitees, for breach of this Lease or
otherwise, other than against Landlord's interest in the Building and Building
Lot and in the uncollected rents, issues and profits thereof, and the proceeds
of any insurance, and Tenant agrees to look solely to such interest for the
satisfaction of any liability of Landlord under this Lease. This Section 27.9
shall not limit any right that Tenant might otherwise have to obtain injunctive
relief against Landlord. Landlord and Tenant specifically agree that in no event
shall Landlord or any of the Landlord Indemnitees ever be personally liable for
any obligation under this Lease. In no event shall either Tenant or Landlord or
any of the Tenant Indemnitees or Landlord Indemnitees ever be liable for
consequential or incidental damages or for lost profits. If by reason of
Landlord's failure to complete construction of the Building or Premises,
Landlord shall be held to be in breach of this Lease, Tenant's sole and
exclusive remedy shall be as set forth in Article 4 hereof.

       27.10  BINDING EFFECT. The covenants, agreements, terms, provisions and
conditions of this Lease shall bind and benefit the successors and assigns of
the parties hereto with the same effect as if mentioned in each instance where a
party hereto is named or referred to, except that no violation of the provisions
of Article 16 hereof shall operate to vest any rights in any successor or
assignee of Tenant.

       27.11  SEIZING OF TITLE. Upon any sale, transfer or other disposition of
the Building, Landlord shall be entirely freed and relieved from the performance
and observance thereafter of all covenants and obligations hereunder on the part
of Landlord to be performed and observed, it being understood and agreed in such
event (and it shall be deemed and construed as a covenant running with the land)
that the person succeeding to Landlord's ownership of said reversionary interest
shall thereupon and thereafter assume, and perform and observe, any and all of
such covenants and obligations of Landlord, including covenants and obligations
relating to construction warranties and disbursement of any remaining balance of
Landlord's Contribution. Landlord agrees that it shall not sell, transfer or
dispose of the Building prior to completion of the Landlord's Work.

                                      -46-
<Page>

       27.12  CONFIDENTIAL INFORMATION. Landlord hereby agrees that any and all
knowledge, information, data, materials, trade secrets, and other work product
of a confidential nature gained, obtained, derived, produced, generated or
otherwise acquired by Landlord with respect to Tenant's business (collectively
"Confidential Information"), if any, shall be kept confidential. Landlord shall
use diligent efforts to ensure that no Confidential Information is revealed,
divulged, communicated, related, or described to any person or entity without
the written consent of Landlord, except as may be required by applicable law.

                         [SIGNATURES ON FOLLOWING PAGE]

                                      -47-
<Page>

       IN WITNESS WHEREOF the parties hereto have executed this Indenture of
Lease in multiple copies, each to be considered an original hereof, as a sealed
instrument on the day and year noted in the Lease Data as of the Execution Date.

LANDLORD:

PM ATLANTIC LEXINGTON, LLC

By: /s/ Joseph L. Zink
    ----------------------------------
    Joseph L. Zink
    Duly Authorized Representative

TENANT:

NITROMED, INC.

By: /s/ Michael D. Loberg, Ph.D.
    ----------------------------------
    Michael D. Loberg, Ph.D.
    CEO and President

                                      -48-
<Page>

                                    EXHIBIT 1

                         [LEGAL DESCRIPTION OF PROPERTY]

                                EXHIBIT 1, PAGE 1

<Page>

       That certain parcel of land (of unregistered and registered titles) with
the buildings thereon known in part as Nos. 125, 131 and 141 Spring Street in
Lexington, Middlesex County, Massachusetts, shown as Lot "A" of 95.6 acres,
more or less, on a compiled plan entitled "Plan of Land in Lexington, Mass.
Prepared for Raytheon Company" dated March 11, 1987, by Dana F. Perkins and
Assoc., Inc., recorded with Middlesex South District Deeds as Plan No. 384 of
1987 at the End of book 17963, the parcel being bounded and described (inclusive
of the registered land) as follows:

       BEGINNING at a point on the northeast line of the 1961 layout of Route 2
and on the westerly line of Spring Street, as relocated by a 1964 layout, thence
RUNNING

       NORTHWESTERLY          by Route 2 by a curve to the right of 4850 feet of
                              radius, 237.16 feet; thence

       N 44DEG.14'10" E       by the 1960 layout of Route 2, 20.30 fee; thence

       N 54DEG. 14'16" W      by the 1960 layout of Route 2, 1211.86 feet to the
                              northbound access ramp down to Route 128; thence

       N 09DEG.39'07" W       by the ramp, 525 feet; thence

       N 27DEG.16'30" W       by the ramp, 277 feet; thence

       N 42DEG.24'53" W       by the ramp, 240.03 feet; thence

       N 51DEG.28'33" W       by the ramp, 685 feet; thence

       N 09DEG.12'32" W       by the 1960 layout of Route 128, 693.18 feet;
                              thence

       NORTHERLY              by Route 128 by a curve to the right of 4850 feet
                              of radius, 604.88 feet to Weston Street; thence

       NORTHEASTERLY          by Weston Street by a stone wall, about 380 feet
                              (the bound of "N 50 DEG.21'39" E 62.82" being
                              mistakenly shown since it lies WITHIN the 1960
                              layout per Sheet 10 of 10 of the layout plan
                              recorded with said Deeds as Plan 988 of 1960 in
                              Book 9622, Page 258); thence

<Page>

       EASTERLY and           by Shade Street by a stone wall, about 1080 feet;
       SOUTHEASTERLY          thence

       S 54 DEG.10'30" W      by land of Fofo and Plato A. Spilios, about 430
                              feet (this bound shown as 420.20 feet on a plan
                              recorded with said Deeds as Plan 108 of 1959 in
                              Book 9314, Page 75); thence

       S 33 DEG.26'58" W      by the Spilios land, 140.08 feet; thence

       S 35 DEG.33'02" E      by the Spilios land, 491.77 feet; thence

       N 58 DEG.24'08" E      by the Spilios land, 25.99 feet; thence

       S 31 DEG.35'52" E      by lands of Mazza, Buivio and McSweeney, 376.04
                              feet; thence

       S 52 DEG.42'52" E      by the McSweeney land and land of Gaposchkin,
                              252.17 feet; thence

       S 49 DEG.48'30" W      by land of William V. and Ulla C. Malkus, 51.22
                              feet; thence

       S 52 DEG.42'52" E      by the Malkus land, 137.26 feet; thence

       S 37 DEG.17'08" W      by the Malkus land, 24 feet; thence

       S 52 DEG.42'52" E      by the Malkus land, 54 feet; thence

       N 37 DEG.17'08" E      by the Malkus land, 74 feet; thence

       S 52 DEG.42'52" E      by the Malkus land and lands of Shepp (at a
                              point), Black, Kava, Cox, Rollins et al and Ward,
                              499.87 feet; thence

       N 52 DEG.04'00" E      by a stone wall by land of Ericson, 81.46 feet;
                              thence

       N 50 DEG.58'10" E      by a stone wall by land of Ericson, 97.44 feet;
                              thence

       N 51 DEG.20' 10" E     by a stone wall by land of Ericson, 27.37 feet;
                              thence

       S 52 DEG.42'52" E      by lands of Johnson, Neidorf, Fleishmann and
                              Lambie, 620 feet; thence

                                        2
<Page>

       S 09 DEG.33'02" E      by land of Diianni, 240.64 feet; thence

       N 88 DEG.26'58" E      by the Diianni land, 262.50 feet; thence

       N 07 DEG.13'20" E      by the Diianni land, 285.84 feet to the
                              southwesterly line of Shade Street, these last
                              four bounds being shown on a plan dated December
                              8, 1961 and recorded with said Deeds as Plan 1837
                              of 1961 in Book 9953, Page 340; thence

       S 38 DEG.47'54" E      by Shade Street, 124.11 feet; thence

       S 37 DEG.28'04" E      by Shade Street, 93.70 feet; thence

       SOUTHERLY              by Shade and Spring Streets by a curve to the
                              right of 73.22 feet of radius, 83.75 feet; thence

       S 28 DEG.03'56" W      by Spring Street, 62.30 feet; thence

       SOUTHWESTERLY          by Spring Street by a curve to the right of 889.74
                              feet of radius, 357.74 feet; thence

       S 51 DEG.06'10" W      by Spring Street, 139.07 feet to the northeasterly
                              end of the 1964 location; thence

       N 38 DEG.53'26" W      by Spring Street's 1964 location, 19.99 feet;
                              thence

       S 51 DEG.06'34" W      by Spring Street's 1964 location, 412.44 feet;
                              thence

       S 31 DEG.11'19" W      by Spring Street's 1964 location, 158.28 feet;
                              thence

       SOUTHWESTERLY          by Spring Street's 1964 location by a curve to the
       and SOUTHERLY          left of 1035 feet of radius, 287.24 feet; and
                              thence

       S 15 DEG.17'15" W      by Spring Street's 1964 location, 139.68 feet to
                              the point of beginning.

       For title to the unregistered portion of the premises, see deed of
Charles H. Resnick and Herbert Deitcher, as Trustees of Lexington Electronic
Realty Trust, to Raytheon Company dated as of January 1, 1991 and recorded on
December 18, 1991 with said Deeds, Book 21615, Page 379.

                                        3
<Page>

                               REGISTERED PARCELS

       Included within the above described premises are the following parcels of
REGISTERED LAND.

       Those certain parcels of land in Lexington, Middlesex County,
Massachusetts covered by Certificate of Title No. 191836 in South Registry
District of Middlesex County Registration Book 1089, Page 86, described as
follows:

                            LOT X(1) -- PLAN 6962-19

       EASTERLY               by Lots 229, 230, 231 and 232, as shown on plan
                              hereinafter mentioned, 260.67 feet;

       SOUTHERLY              by Lot Y on said plan, 254.28 feet;

       WESTERLY               by land now or formerly of Swenson Bro's, 336.44
                              feet;

       NORTHWESTERLY          by land now or formerly of Charles Hayden; 187.71
                              feet; and

       EASTERLY               157.36 feet; and

       NORTHERLY              25.99 feet by Lot X(2) on said plan.

       Said parcel is shown as Lot X(1) on Plan No. 6962-19 with Certificate No.
97314, Book 616, Page 164.

                               LOT 1 -- PLAN 6998B

       NORTHEASTERLY          by Shade Street by two lines measuring together
                              217.81 feet;

       EASTERLY               by a curving line forming the junction of said
                              Shade Street and Spring Street, 83.75 feet;

       SOUTHEASTERLY          by said Spring Street and by two lines measuring
                              together 78.54 feet; and

       WESTERLY               by land now or formerly of Iver Swenson et al,
                              Trustees, by two lines measuring together 337.73
                              feet.

       Said parcel is shown as Lot 1 on Plan 6998B with Certificate No. 88371,
Book 572, Page 21.

                                        4
<Page>

                        LOTS Z(1) AND Z(2) -- PLAN 6962D

       NORTHEASTERLY          by Lots 242, 243, 244, 245, 246, 247, 248, 249,
                              250 and 251, as shown on plan hereinafter
                              mentioned, 500 feet;

       SOUTHEASTERLY          207 feet;

       NORTHEASTERLY          8.68 feet; and

       SOUTHEASTERLY          649.70 feet by land now or formerly of Harry S.
                              Kelsey;

       SOUTHWESTERLY          by land now or formerly of Swenson Bro's, 252.15
                              feet; and

       NORTHWESTERLY          by Lot Z on said plan, 748 feet.

       Said parcel is shown as Lots Z(1) and Z(2) on Plan No. 6962D with
Certificate No. 19693, Book 132, Page 349.

                               LOT Y -- PLAN 6962D

       NORTHERLY              by Lot X, as shown on said plan hereinafter
                              mentioned 254.35 feet;

       EASTERLY and           by Lots 232, 233, 234, 235, 236, 237 and 238 on
       NORTHEASTERLY          said plan by two lines measuring together 367.32
                              feet;

       SOUTHEASTERLY          by Lot Z on said plan, 416 feet; and

       WESTERLY               by land now or formerly of Swenson Bro's, 423
                              feet.

       Said parcel is shown as Lot Y on Plan No. 6962D with Certificate No.
19693, Book 132, Page 349.

                             LOT 443 -- PLAN 6962-36

       NORTHEASTERLY          by Lot Z(3), as shown on plan hereinafter
                              mentioned 137.26 feet;

       SOUTHEASTERLY          24 feet; and

       NORTHEASTERLY          54 feet by Lot 444 on said plan;

                                        5
<Page>

       SOUTHEASTERLY          by Lot Z(1) on said plan, 673.69 feet;

       WESTERLY               by land now or formerly of Swenson Bro's, 360.09
                              feet; and

       NORTHWESTERLY          by said Swenson Bro's land and by Lot Y on said
                              plan, 511.29 feet.

       Said parcel is shown as Lot 443 on Plan No. 6962-36 with Certificate No.
164635, Book 953, Page 85.

                                        6
<Page>

                                    EXHIBIT 2

                 PLANS FOR LEASEHOLD WORK AND BASE BUILDING WORK

                                125 Spring Street
                            Lexington, Massachusetts

                                  Drawing List

                                January 26, 2004

Drawings prepared by Shepley Bulfinch Richardson & Abbott of Boston, MA

<Table>
<Caption>
                                                                              Permit Set
No.      Title                                                                Date
---      -----                                                                ----------
<S>      <C>                                                                  <C>
A000     Architectural Symbols, Abbreviations, General Notes
                 and Code Analysis                                            12/31/03
AD101    First Floor Demolition                                               12/31/03
AD102    Second Floor Demolition                                              12/31/03
A100     Basement Floor Plan                                                  12/31/03
A101     First Floor Plan                                                     12/31/03
A102     Second Floor Plan                                                    12/31/03
A901     Partition Types & Head Details                                       12/31/03

Drawings prepared by Cameron Fire Protection of East Douglas, MA

FP-1     First Floor Fire Protection Plan                                     12/31/03
FP-2     Second Floor Fire Protection Plan                                    12/31/03

Drawings prepared by North Shore Mechanical Contractors of Topsfield, MA

P000     Plumbing Schedule, Legend and Specifications                         12/31/03
P001     Basement Plumbing Plans                                              12/31/03
P101     First Floor Water Distribution Plan                                  12/31/03
P102     First Floor Waste and Vent Plumbing Plan                             12/31/03
P103     First Floor Process and Gas Piping Plan                              12/31/03
P201     Second Floor Plumbing Plan                                           12/31/03
P202     Second Floor Process and Gas Piping Plan                             12/31/03
P301     Plumbing Part Plans and Risers                                       12/31/03
P401     Plumbing Plans                                                       12/31/03

Drawings prepared by Environmental Systems of Attleboro, MA

M1       Basement HVAC Plan                                                   01/01/04
M2.1     First Floor HVAC Plan                                                01/01/04
M2.2     First Floor Piping HVAC Plan                                         01/01/04
M3.1     Second Floor HVAC Plan                                               01/01/04
M3.2     Second Floor HVAC Plan                                               01/01/04
M4       HVAC Roof Plan                                                       01/01/04
M5       HVAC Details                                                         01/01/04
M6.1     HVAC Schedules                                                       01/01/04
M6.2     HVAC Schedules                                                       01/01/04
</Table>

                                EXHIBIT 2, PAGE 1

<Page>

NitroMed Drawing List
Continued

<Table>
<Caption>
                                                                       Permit Set
No.      Title                                                         Date
---      -----                                                         ----------
<S>      <C>                                                           <C>
Drawings prepared by Interstate Electrical Services of North Billerica, MA

E1.1     Legend, Notes and Details                                     12/31/03
E1.2     Risers and One-Line Diagrams                                  12/31/03
E1.3     Fire Alarm Riser Diagram                                      12/31/03
E1.4     Schedules                                                     12/31/03
E1.5     Schedules                                                     12/31/03
E1.6     Mechanical Schedules                                          12/31/03
E2.1     Lighting First Floor Plan                                     12/31/03
E2.2     Lighting Second Floor Plan                                    12/31/03
E3.0     Power Basement Plan                                           12/31/03
E3.1     Power First Floor Plan                                        12/31/03
E3.2     Power Second Floor Plan                                       12/31/03
E4.1     Fire Alarm First Floor Plan                                   12/31/03
E4.2     Fire Alarm Second Floor Plan                                  12/31/03
</Table>

                                EXHIBIT 2, PAGE 2

<Page>

                                    EXHIBIT 3

                          BASE BUILDING SPECIFICATIONS

                                125 Spring Street

                        MEP/FP BASE BUILDING DESCRIPTION

HVAC SYSTEM:

The HVAC system shall be comprised of a central chilled water system, condenser
water system, hot water heating system and mechanical room located air-handling
units.

Air handlers shall be capable of delivering up to 1.5 CFM per SF outdoor air to
the space. The units will be complete with double wall construction, variable
frequency drives, filter section with 85% filters, chilled water coil, hot water
coil and vibration isolation. The supply air shall be distributed via supply
duct main risers. The supply duct risers shall be stubbed out 3' from the shaft
on each floor for future tenant fit-up. Variable frequency drives on the supply
fans are provided to vary the supply to the space as part of the Variable Air
Volume system (s) serving the office / support areas.

Chilled water shall be provided from centrifugal water-cooled chillers located
in the penthouse. The system shall consist of chillers, cooling towers, (cooling
towers part of a central plant remote from building), plate-and-frame heat
exchanger, piping and controls. The secondary pumps shall be provided with
variable frequency drives to maximize energy efficiency.

Hot water shall be provided by gas-fired hot water boilers and associated
primary and secondary piping systems.

Common areas, such as lobbies, toilets, equipment rooms, etc. shall be fully
fit-up including heating, air conditioning (where applicable), ventilation and
exhaust (toilet core) as part of base building.

PLUMBING SYSTEM:

The plumbing system shall consist of water service and gas service into the
building, storm drainage system, toilet cores and janitor's closets as well as
locations for PH neutralization systems.

Domestic water shall be distributed to toilet cores and mechanical penthouse as
required. Centralized risers shall also be provided for use as part of tenant
fit up. Domestic water shall provide sufficient water pressure to all tenant
areas.

                                EXHIBIT 3, PAGE 1

<Page>

The gas service into the building shall be sized to meet the base building
requirements as well as sized for future tenant loads.

ELECTRICAL SYSTEM:

Electric service to the building shall be provided via a single primary electric
service feed to the building primary switchgear. The building electric service
shall provide 480 volt, 1600 amp, 3 phase power to the building. The overall
electric service size for the building shall be 25 watts per square foot.

FIRE PROTECTION SYSTEM:

Fire protection system shall consist of service into the building, fire
department connection and distribution throughout the building. The distribution
shall consist of the primary loop on each floor with upturned hands as required
in tenant areas and complete distribution in common areas.

The fire alarm system shall be an expandable addressable system with fire
command center. Common areas shall be complete with detection and annunciation
devices as required.

The fire protection and fire alarm shall be in compliance with state and local
requirements.

                                EXHIBIT 3, PAGE 2

<Page>

        MEP ALLOCATION OF RESPONSIBILITY BETWEEN LANDLORD AND TENANT WORK

<Table>
<Caption>
ELEMENT            DESCRIPTION                        LANDLORD        TENANT
-------            -----------                        --------        ------
<S>                <C>                                   <C>             <C>
HVAC               A central chilled water plant         X
                   including centrifugal
                   chillers, cooling towers,
                   plate and frame heat
                   exchanger, primary / secondary
                   pumping systems and
                   distribution risers for tenant
                   cooling.

                   Cooling tower/condenser water         X
                   system sized for chilled water
                   plant and an additional 15%
                   for tenant supplemental
                   cooling.

                   Rooftop air handling units            X
                   providing a total of
                   approximately 1.5 cfm per
                   square foot with 100% outside
                   air.

                   Supplemental cooling as                               X
                   required by Tenant.

                   Hot water system via either           X
                   central utility steam or
                   gas-fired boilers, with pumps
                   and distribution risers, for
                   tenant area heating.

                   Vertical supply ductwork              X
                   extending 3' beyond vertical
                   shaft or base building core.
</Table>

                                EXHIBIT 3, PAGE 3

<Page>

<Table>
<Caption>
ELEMENT            DESCRIPTION                        LANDLORD        TENANT
-------            -----------                        --------        ------
<S>                <C>                                   <C>             <C>
                   Ductwork, VAV boxes, and              X
                   controls for HVAC in lobby
                   spaces and core areas,
                   including toilet exhaust
                   system.

                   All ducts within tenant space.                        X

                   Fan powered terminal boxes                            X
                   (perimeter) and VAV boxes
                   (interior) within tenant
                   space.

                   Diffusers within tenant space.                        X

                   Central computerized energy           X
                   management system.

                   Temperature controls within                           X
                   tenant space, and links to
                   base building system.

                   Tenant metering or                                    X
                   submetering.

                   Reserved locations for shafts         X
                   associated with tenant exhaust
                   ventilation systems.

                   Construction of drywall                               X
                   enclosure of exhaust shafts to
                   the extent located within
                   Tenant premises.
</Table>

                                EXHIBIT 3, PAGE 4

<Page>

<Table>
<Caption>
ELEMENT            DESCRIPTION                        LANDLORD        TENANT
-------            -----------                        --------        ------
<S>                <C>                                   <C>             <C>
                   All components of tenant                              X
                   exhaust systems, including
                   fume hoods, ductwork, exhaust
                   fans, controls and sound
                   attenuation.

                   Specialized tenant systems and                        X
                   equipment including
                   supplemental or spot cooling,
                   steam boilers, air and vacuum
                   systems and all related HVAC
                   equipment.

GAS                Gas service to building sized         X
                   for base building equipment,
                   and tenant usage.

                   Tenant metering and service,                          X
                   as required.

                   Gas piping to tenant                                  X
                   equipment.

PLUMBING           Building service, with                X
                   back-flow prevention.

                   Core and restroom plumbing and        X
                   fixtures to meet code
                   requirements.

                   Centralized riser to supply           X
                   tenant laboratory
                   requirements.

                   Tenant metering, submetering,                         X
                   and backflow prevention at
                   laboratory connections.
</Table>

                                EXHIBIT 3, PAGE 5

<Page>

<Table>
<Caption>
ELEMENT            DESCRIPTION                        LANDLORD        TENANT
-------            -----------                        --------        ------
<S>                <C>                                   <C>             <C>
                   Space for waste and vent              X
                   risers for tie-ins from
                   domestic (potable) use or
                   pre-treated uses.

                   Installation of Tenant's                              X
                   non-potable systems.

                   Distribution of domestic cold                         X
                   water from base building
                   risers.

                   Production and distribution of                        X
                   hot water for tenant use.

                   Production and distribution of        X
                   hot water in building
                   restrooms.

                   Laboratory waste lines from           X
                   the acid neutralization room
                   to exterior location.

                   Acid waste neutralization                             X
                   equipment and laboratory waste
                   lines.

                   Manifolds, piping, and other                          X
                   requirements for laboratory
                   gases, compressed air, vacuum
                   systems, steam and humidified
                   air.

                   Storm water system.                   X

                   Sanitary water waste system.          X
</Table>

                                EXHIBIT 3, PAGE 6

<Page>

<Table>
<Caption>
ELEMENT            DESCRIPTION                        LANDLORD        TENANT
-------            -----------                        --------        ------
<S>                <C>                                   <C>             <C>
ELECTRICAL         Single primary electric               X
                   service power feed to building
                   primary switchgear.

                   Building electrical service to        X
                   provide 480 Volt, 1600 amp, 3
                   phase, 4 wire secondary main
                   switchboards in main
                   electrical room. Overall
                   electric service size shall be
                   25 watts per square foot.

                   Feeder bus from utility               X
                   company transformers to main
                   switchboards.

                   Service from switchboard to                           X
                   point-of-use including
                   metering/check metering.

                   Tenant fit-up of panels,                              X
                   transformer, receptacles &
                   lighting in tenant area.

                   Light fixtures in tenant area                         X
                   to be building-standard lay-in
                   parabolic fluorescent troffer
                   with electronic ballast and
                   energy saving lamps.

                   Lighting and receptacles              X
                   serving core areas.

                   Emergency egress' and exit                            X
                   lighting in tenant area.
</Table>

                                EXHIBIT 3, PAGE 7

<Page>

<Table>
<Caption>
ELEMENT            DESCRIPTION                        LANDLORD        TENANT
-------            -----------                        --------        ------
<S>                <C>                                   <C>             <C>
                   Optional stand-by back-up                             X
                   electrical generator, transfer
                   switch, fuel piping, tanks,
                   controls and associated
                   modifications if required.

FIRE               Sprinkler service entrance            X
PROTECTION         including fire department
PROTECTION         connection, alarm valve flow
                   protection, fire pump and
                   standpipe in each stair.
                   Fire Department hose valves.          X

                   Core and stair area sprinkler         X
                   heads and piping.

                   Flow control valve station in         X
                   stair at each floor.

                   Primary loop on each floor.           X

                   All runouts, drops, heads and                         X
                   related equipment within
                   tenant premises.

                   Typical distribution as               X
                   required by code in vacant
                   spaces as necessary to secure
                   building occupancy permit.

                   Special extinguishing systems.                        X
</Table>

                                EXHIBIT 3, PAGE 8

<Page>

<Table>
<Caption>
ELEMENT            DESCRIPTION                        LANDLORD        TENANT
-------            -----------                        --------        ------
<S>                <C>                                   <C>             <C>
FIRE ALARM         Base building addressable fire        X
                   alarm system with fire command
                   center.

                   Detection and annunciation            X
                   devices in core areas and
                   stair entries.

                   Detection, annunciation and                           X
                   all wiring in tenant areas and
                   as required to tie into base
                   building system.

TELEPHONE          Telephone riser closet and
                   cable sleeves through floors.

                   Telephone and data wiring,                            X
                   conduits and outlets for
                   Tenant areas.

                   Audio-visual connections and                          X
                   systems for Tenant areas.
</Table>

                                EXHIBIT 3, PAGE 9

<Page>

                                    EXHIBIT 4

                           PLANS FOR COSMETIC UPGRADES

                             [AVAILABLE UPON REQUEST]

                                EXHIBIT 4, PAGE 1

<Page>

                                    EXHIBIT 5

                          DESCRIPTION OF LEASEHOLD WORK

                                EXHIBIT 5, PAGE 1

<Page>

                                                                       Exhibit 5

NITROMED INC. - TENANT IMPROVEMENTS
125 SPRING STREET, LEXINGTON, MASSACHUSETTS
BUDGET ESTIMATE

<Table>
<Caption>
                       DIVISION / DESCRIPTION                      QTY
----------------------------------------------------------------   -------------
<S>                                                                     <C>
DEMOLITION AND SITEWORK

 SAWCUT, REMOVE CONC., E&B & REPLACE SLAB FOR UNDERSLAB PIPE            460 LF
 CUT IN MECHANICAL ROOF OPENINGS                                          1 LS
 EXCAVATE AND STONE BASE FOR PADS & GENERATOR PAD                         1 LS
 DEMOLITION & SITEWORK FOR AMENITIES                                      1 LS
 PAVING FOR DUMPSTER BESIDE LOADING DOCK                                  1 ALW

REINFORCED CONCRETE

 CONCRETE EQUIPMENT PADS                                                  2 EA
 CORING FOR UTILITIES                                                     1 LS
 GENERATOR PAD                                                          250 SF
 CUT IN 2ND FLOOR OPENINGS                                                1 LS
 ELECTRICAL FLOOR BOX CUTS & REPAIR                                       2 EA
 CONCRETEWORK FOR AMENITIES                                               1 LS
 MISC SLAB CUTTING & PATCH @ VIVARIUM HOLDING RMS & TOILETS               1 LS

STRUCTURAL METALS & MISC. IRON

 OPENINGS FOR SMALL MECHANICAL PENETRATIONS                               8 EA
 SUPPLY & INSTALL MISCELLANEOUS STEEL                                     2 TON
 RIGGING                                                                  2 DY
 STRUCTURAL & MISC STEEL FOR AMENITIES                                    1 LS
 STAINLESS STEEL AUTOCLAVE ENCLOSURE TRIM

CARPENTRY/MILLWORK

 RECEPTIONIST AREA COUNTER                                                1 ALW
 STORAGE ROOM SHELVING
 COPY/PRINTER COUNTER & CABINETS                                         12 LF
 LAB COAT POLES & SHELF                                                   8 EA
 CONF RM CREDENZA'S W/BASE CABS (MAPLE EXT MELAMINE INT)                 40 LF
 MAILROOM P-LAM TOP W/P-LAM/MELAMINE BASE CABINETS                       24 LF
 P-LAM ABOVE COUNTER MAILROOM SLOTS                                      12 LF
 2 TIER ADJUSTABLE SHELVING (OFFICE AREA)                               350 LF
 COFFEE AREA P-LAM COUNTER W/P-LAM CABINETSLES BELOW                     16 LF
 KITCHEN CABINETS W/COUNTER ON EXPANDED SIDE OF KITCHEN                   8 LF
 BREAKROOM 30" COUNTER W/CABS  BELOW & SHELF ABOVE                        8 LF
 BREAKROOM 24" P-LAM COUNTER W/SHELF ABOVE                               16 LF
 SERVERY COUNTERS                                                        27 LF
 COAT AREA SHELF AND POLES                                                1 LS
 BLOCKING FOR CASEWORK, COUNTERS, SHELVES & MILLWORK                      1 LS
 GENERAL MILLWORK INSTALLATIONS LISTED ABOVE                              1 LS
 CUBICLE COUNTERS & SHELVING
 CARPENTRY AND BLOCKING FOR AMENITIES                                     1 LS
 MISCELLANEOUS CARPENTRY MATERIALS AND LABOR                              1 LS
</Table>

<Page>

NITROMED INC. - TENANT IMPROVEMENTS
125 SPRING STREET, LEXINGTON, MASSACHUSETTS
BUDGET ESTIMATE

<Table>
<Caption>
                       DIVISION / DESCRIPTION                      QTY
----------------------------------------------------------------   -------------
<S>                                                                    <C>
THERMAL & MOISTURE PROTECTION

 PITCH POCKETS                                                            1 LS
 FLASH DUCT AND VENT PENETRATIONS                                         1 LS
 PLUMBING AND VENT FLASHING                                               1 LS
 FLASHING ALL NEW OPENINGS                                                1 LS
 ROOF BLOCKING @ OPENINGS                                                 1 LS
 ROOFING, FLASHING & CAULKING FOR AMENITIES                               1 LS
 INTERIOR SEALANTS & CAULKING                                             1 LS

DOORS, FRAMES & HARDWARE

DOOR, FRAME, & HARDWARE ASSEMBLIES
 3'-0" x 7'-0" SEAMLESS METAL DOORS                                      34 EA
 PAIR 1'-0" & 3'-0" x 7'-0" SEAMLESS METAL DOORS                          1 PR
 4'-0" x 7'-0" SEAMLESS METAL DOORS                                       2 EA
 PAIR 1'-0" & 3'-0" x 7'-0" WOOD DOORS                                    9 PR
 3'-0" x 7'-0" STAIN GRADE 7 PLY ROTARY CUT DOORS                        87 EA
 PR 3'-0" x 7'-0" STAIN GRADE 7 PLY ROTARY CUT DOORS                      4 PR
 PR 4'-0" x 7'-0" STAIN GRADE 7 PLY ROTARY CUT DOORS                      1 PR
 4'-0" WOOD BIFOLD CLOSET DOORS                                           1 EA
 DOUBLE DOOR MACHINING                                                   16 PR
 DOOR CLOSERS                                                            45 EA
 SINGLE DOOR HARDWARE (CYLINDRICAL LOCKSETS)                            124 EA
 DOUBLE DOOR HARDWARE                                                    16 EA
 PRESSED METAL DOOR WELDED FRAMES (DOUBLE)                               10 EA
 PRESSED METAL DOOR WELDED FRAMES (SINGLE)                               35 EA
 PRESSED METAL DOOR FRAMES (DOUBLE)                                       6 EA
 PRESSED METAL DOOR FRAMES (SINGLE)                                      89 EA
 BORROWED LITES                                                          49 EA
 SINGLE DOOR & HARDWARE INSTALLATION                                    124 EA
 DOUBLE DOOR & HARDWARE INSTALLATION                                     16 EA
 ACCESS DOORS                                                             8 EA
 SPECIALTY DOOR HARDWARE @ ANIMAL AREA                                    1 LS
 DOORS, FRAMES & HARDWARE FOR AMENITIES                                   1 LS
 TEMPORARY DOORS                                                          4 EA

GLASS AND GLAZING

 BORROWED LITES                                                          49 EA
 PR 3'-0" x 7'-0" ALUM & GLASS INTERIOR DOORS                             2 PR
 BUTT GLAZING AT @ 43 EA OFFICES (5'x7")                               1505 SF
 MISC GLAZING AT 2ND FLOOR CONFERENCE ROOMS                             300 SF
 ALUM & GLASS SYSTEMS & DOORS & GLASS RAILS FOR AMENITIES                 1 LS
 REMOVE AND REPLACE 2ND FLOOR WINDOW FOR MATERIAL ACCESS                  1 LS
</Table>

<Page>

NITROMED INC. - TENANT IMPROVEMENTS
125 SPRING STREET, LEXINGTON, MASSACHUSETTS
BUDGET ESTIMATE

<Table>
<Caption>
                       DIVISION / DESCRIPTION                      QTY
----------------------------------------------------------------   -------------
<S>                                                                  <C>
GYPSUM WALLBOARD & METAL STUD

 SET DOOR FRAMES                                                        131 EA
 WALL BLOCKING                                                            1 LS
 NEW FULL HEIGHT DRYWALL PARTITIONS                                   19440 SF
 NEW 10' HIGH METAL STUD & DRYWALL PARTITIONS                         21460 SF
 6" METAL STUD & WALLBOARD RETURN AIR WALLS @ HOLDING RMS              4100 SF
 PREMIUM FOR ADDED LAYER OF BOARD FOR STC 45 WALL AT A.F.               950 SF
 PREMIUM FOR HARDBOARD @ ANIMAL ROOMS                                  2970 SF
 CUT IN NEW DOOR OPENINGS                                                 4 EA
 FILL IN EXISTING DOOR OPENINGS                                           3 EA
 GYP WALL BD W/INSUL & FURRING                                            1 LS
 GYP BD CEILING @ ANIMAL ROOMS & SPECIALTY ROOMS                       2327 SF
 MANLIFT                                                                  1 LS
 MODIFY VIVARIUM TOILET WALLS                                             1 LS
 SOUND SEAL WALL PENETRATIONS @ ANIMAL AREA                               1 LS
 GYP BOARD SYSTEMS FOR AMENITIES                                          1 LS
 DOOR BLOCKING                                                            1 LS

SUSPENDED CEILINGS

 2 x 2 ARMSTRONG TEGULAR SYSTEM @ FEATURE AREAS                       4,708 SF
 CREDIT NOT TO REPLACE CEILING IN EXEC LARGE CONFERENCE ROOM           -668 SF
 2 x 4 VINYL FACED GYP BD TILE W/SUSPENDED SYSTEM - GASKETED          3,424 SF
 2 x 4 VINYL FACED GYP BD W/WSTANDARD SUSPENSION SYSTEM              10,694 SF
 REPLACE VAVRIUM TOILET CEILINGS                                        485 SF
 ACOUSTICAL CEILINGS FOR AMENITIES                                        1 LS
 2 x 4 SECOND LOOK TILE W/SUSPENSION SYSTEM                          20,450 SF

FLOORING & TILE

 CARPET NO.1 & 2 (CARPET ALLOW 21.00/SY MAT 6.00/SY INSTALL)          2,500 SY
 ADD CARPET TYPE 2 @ 1ST & 2ND FLOOR OFFICE CORRIDORS                   477 SY
 CARPET NO.3 SPECIAL (CARPET ALLOW 26.00/SY MAT 6.00/SY INSTALL)        230 SY
 LOBBY FLOORING (THIN SET 12" x 12" SLATE)                              680 SF
 SHEET VINYL FLOORING W/FLASHED BASE                                      0 SF
 VINYL COMPOSITION TILE                                              14,211 SF
 DEDUCT VCT @ 1ST & 2ND FLOOR CORRIDORS                              -3,810 SF
 VINYL BASE                                                           6,200 LF
 TREAD COVERING @ ARCHITECTURAL STAIRWAY                                  1 LS
 EPOXY FLOOR W/FLASHED BASE                                           4,683 SF
 CERAMIC FLOOR TILE                                                   1,266 SF
 CERAMIC WALL TILE                                                    4,284 SF
 OTHER CERAMIC TILE FOR AMENITIES                                         1 LS
 FLOOR PREP                                                               1 LS

PAINTING

 PAINT INTERIOR LATEX PARTITIONS                                     81,500 SF
 PAINT DOORS & FRAMES                                                   152 EA
 PAINT GWB CEILINGS W/WATERBASED EPOXY                                1,475 SF
 PAINT WALL W/WATERBASED EPOXY                                         4500 SF
 PAINTING FOR AMENITIES                                                   1 LS
 PAINT MISCELLANEOUS                                                      1 LS
</Table>

<Page>

NITROMED INC. - TENANT IMPROVEMENTS
125 SPRING STREET, LEXINGTON, MASSACHUSETTS
BUDGET ESTIMATE

<Table>
<Caption>
                       DIVISION / DESCRIPTION                      QTY
----------------------------------------------------------------   -------------
<S>                                                                     <C>
SPECIALTIES AND FURNISHINGS

 CORNER GUARDS                                                           38 EA
 VINYL PROTECTIVE RAILS (ALLOW 320 LF)                                  340 LF
 FIRE EXTINGUISHERS AND CABINETS                                         12 EA
 FIRE EXTINGUISHERS                                                      12 EA
 VIVARIUM TOILET ACCESSORIES                                              2 EA
 VIVARIUM TOILET PARTITIONS                                               4 EA
 VIVARIUM ADA TOILET PARTITIONS                                           2 EA
 24" x 24" PASS THROUGH                                                   1 EA
 RETRACTABLE ACOUSTICAL PARTITION
 OFFICE CUBICLES W/COUNTERS & SHELVING
 WHITE BOARDS
 DOUBLE LOCKERS                                                          10 EA
 COAT HOOKS                                                              60 EA
 ELECTRIC PROJECTION SCREEN                                               2 EA
 REFRIGERATOR
 UNDERCOUNTER REFRIGERATOR
 MICROWAVE
 DISHWASHER
 LEVELOR OR EQUAL BLINDS & ROOM DARKENING @ 2 LABS                        1 ALW
 INTERIOR BLINDS @ CONF ROOMS                                             1 LS
 SHELVING ENVIRONMENTAL AND STORAGE ROOMS
 INTERIOR SIGNAGE                                                         1 ALW
 SPECIALTIES FOR AMENITIES                                                1 LS
 INSTALL SPECIALTIES                                                      1 LS

EQUIPMENT

 DUAL ACID WASTE EJECTOR                                                  1 EA
 CLEAN AIR COMPRESSOR                                                     1 EA
 VACUUM PUMP                                                              1 EA
 CO2 MANIFOLD                                                             1 EA
 ACID NEUTRALIZATION SKID                                                 1 EA
 TEMPERED HOT WATER SKID                                                  1 EA
 AUTOCLAVE (W/INTERGARAL STEAM COIL & WASTE TEMPERING)
 CAGEWASH
 TOTAL EQUIPMENT INCLUDING INSTALLATION AND PIPING                        1 LS
</Table>

<Page>

NITROMED INC. - TENANT IMPROVEMENTS
125 SPRING STREET, LEXINGTON, MASSACHUSETTS
BUDGET ESTIMATE

<Table>
<Caption>
                       DIVISION / DESCRIPTION                      QTY
----------------------------------------------------------------   -------------
<S>                                                                     <C>
LABORATORY CASEWORK & FUME HOODS

 P-LAM/PHENOLIC RESIN REAGENT SHELVING (2 SHELVES HIGH)                 182 LF
 24" PHENOLIC RESING BENCHTOPS 1" THICK                                  24 LF
 30" PHENOLIC RESING BENCHTOPS 1" THICK                                 343 LF
 36" PHENOLIC RESING BENCHTOPS 1" THICK                                  97 LF
 60" PHENOLIC RESING BENCHTOPS 1" THICK                                 189 LF
 72" PHENOLIC RESING BENCHTOPS 1" THICK                                 129 LF
 INSTALL BENCHTOPS                                                        1 LS
 P-LAM/PHENOLIC RESIN UTILITY CHASES                                     18 EA
 EPOXY RESIN SINKS                                                       22 EA
 DRYING RACKS                                                            22 EA
 P-LAM ADJUSTABLE WALL SHELVING (2 SHELVES HIGH - CONTINUOUS)           290 LF
 BASE CABINETS AND DRAWERS                                              596 LF
 WALL CABINETS                                                           83 LF
 KNEE SPACE SUPPORT AND BENCH SUPPORTS                                   70 LF
 INSTALL CASEWORK AND WALL SHELVING                                       1 LS
 4' CHEM FUME HOOD W/LIGHT & 1EA DUPL OUTLET                              9 EA
 6" CHEM FUME HOODS W/LIGHT & 2EA DUPL OUTLETS                            3 EA
 8" CHEM FUME HOODS W/CA, LIGHT & 2EA DUPL OUTLETS                       20 EA
 INSTALL CHEMICAL FUME HOODS                                             32 EA
3RD CHEMISTRY LAB
 P-LAM/PHENOLIC RESIN REAGENT SHELVING (2 SHELVES HIGH)                  44 LF
 30" PHENOLIC RESIN BENCHTOPS 1" THICK                                   74 LF
 60" PHENOLIC RESIN BENCHTOPS 1" THICK                                   44 LF
 INSTALL BENCHTOPS                                                        1 LS
 P-LAM/PHENOLIC RESIN UTILITY CHASES                                      5 EA
 EPOXY RESIN SINKS                                                        5 EA
 DRYING RACKS                                                             5 EA
 P-LAM ADJUSTABLE WALL SHELVING (2 SHELVES HIGH - CONTINUOUS)            44 LF
 BASE CABINETS AND DRAWERS                                              138 LF
 KNEE SPACE SUPPORT AND BENCH SUPPORTS                                   24 LF
 INSTALL CASEWORK AND WALL SHELVING                                       1 LS
 6' CHEM FUME HOODS W/LIGHT & 2 EA DUPL OUTLETS                           2 EA
 8' CHEM FUME HOODS W/CA, LIGHT & 2EA DUPL OUTLETS                        8 EA
 INSTALL CHEMICAL FUME HOODS                                             10 EA
</Table>

<Page>

NITROMED INC. - TENANT IMPROVEMENTS
125 SPRING STREET, LEXINGTON, MASSACHUSETTS
BUDGET ESTIMATE

<Table>
<Caption>
                       DIVISION / DESCRIPTION                      QTY
----------------------------------------------------------------   -------------
<S>                                                                      <C>
PLUMBING

 WATER CLOSETS                                                            2 EA
 ADA WATER CLOSETS                                                        2 EA
 URINALS                                                                  2 EA
 LAVATORIES                                                               4 EA
 ADA SHOWERS                                                              2 EA
 JANITORS SINK                                                            1 EA
 WATER COOLER                                                             1 EA
 DOMESTIC HOT WATER HEATER                                                1 EA
 HOSE BIBBS                                                               2 EA
 DOMESTIC BFP                                                             2 EA
 HVAC BFP                                                                 2 EA
 NPW BFP                                                                  2 EA
 IRRIGATION BFP                                                           1 EA
 KITCHEN / COFFEE /SERVERY SINKS                                          3 EA
 MOP BASIN                                                                1 EA
 LAB SINK CHEMISTRY (FIXTURES ONLY)                                      10 EA
 LAB SINK TISSUE CULTURE (TRIM ONLY)                                      2 EA
 LAB SINK BL2 (TRIM ONLY)                                                 2 EA
 LAB SINK RADIATION (TRIM ONLY)                                           1 EA
 LAB SINK PROCEDURE (TRIM ONLY)                                           3 EA
 LAB SINK ANALYTICAL (TRIM ONLY)                                          4 EA
 MILLI-Q CONNECTS (UNIT BY OTHERS)                                       12 EA
 TURRETS (CDA) - 1 EA, (VAC) - 16 EA
 ELIMINATE LAB GAS LOOP & ALL 12 TURRETTS                                 1 LS
 CAGEWASH SINK                                                            1 EA
 GLASSWASH SINK                                                           1 EA
 SURGERY SINK                                                             1 EA
 ICE MACHINE CONNECT                                                      2 EA
 VENDING CONNECT                                                          2 EA
 AUTOCLAVE CONNECTS (ASUMED W/INTERGRAL STEAM COIL)                       1 EA
 GLASSWASH CONNECTS                                                       1 EA
 EMERGENCY SHOWER                                                        11 EA
 RECESSED EMERGENCY EYEWASH                                               5 EA
 EYE WASH DECK MOUNTED                                                    6 EA
 EMERGENCY SHOWER / EYEWASH COMBINATION                                   2 EA
 NP HOT WATER HEATER                                                      2 EA
 DOMESTIC HOT WATER                                                       3 EA
 HOOD CONNECTS                                                           24 EA
 BSC CONNECTS (VAC)                                                       6 EA
 INCUBATOR CONNECTS                                                       8 EA
 ACID FLOOR DRAIN                                                         3 EA
 ACID FLOOR SINK                                                          2 EA
 DOMESTIC HOT WATER HEATER                                                1 EA
 NMR CONNECT                                                              1 EA
 NATURAL GAS PIPING
 CORING / SLEEVING
 SANITARY PIPING (L & M) & INSULATION
 DOMESTIC WATER PIPING (L & M)
 PERMIT / INSPECTIONS / TAGS / MARKERS / HANGERS
 NORMAL WORKING HOURS LABOR
 TOILET AREA RENOVATION WORK @ VIVARIUM
 ONE YEAR WARRANTY
 TOTAL PLUMBING BUDGET                                                    1 LS
 ADD SINKS TO ANIMAL FACILITY                                             1 LS
 AMENITY TOILET PLUMBING                                                  1 LS
 COMPLETE PLUMBING WORK @ 3RD CHEMISTRY LAB                               1 LS
</Table>

<Page>

NITROMED INC. - TENANT IMPROVEMENTS
125 SPRING STREET, LEXINGTON, MASSACHUSETTS
BUDGET ESTIMATE

<Table>
<Caption>
                       DIVISION / DESCRIPTION                      QTY
----------------------------------------------------------------   -------------
<S>                                                                       <C>
FIRE PROTECTION

 RECESSED HEADS
 CONCEALED HEADS
 ENGINEERING DESIGN
 HYDRAULIC CALCULATIONS
 FIRE PROTECTION FOR AMENITIES                                            1 LS
 SPRINKLER BUDGET                                                         1 LS

HVAC

 10 AIR CHANGES at LAB AREAS
 EXHAUST FOR 32 CFH'S
 SUPPLY VAV TERMINAL BOXES W/HOT WATER COILS
 CONSTANT VOLUME TERMINAL BOXES
 AVERAGE ANIMAL AREA AIR CHANGE - 15 AIR CHANGES
 OFFICE AREA TO MAINTAIN A POSITIVE PRESSURE TO LABS & VIVARIUM
 HVAC SETUP AS OFFICE AT 3RD CHEMISTRY LAB
 EXHAUST DUCT DISTRIBUTION FROM CFH'S
 GLYCOL COIL HEAT RECOVERY SYSTEM
 COMPLETE SUPPLY & EXHAUST DUCTWORK DISTRIBUTION SYSTEM
 EXTENSION AND ADDITION TO BASE BLD'G DDC SYSTEM
 PIPE AND DUCT INSULATION
 ONE YEAR SYSTEM WARRANTY
 FIVE YEAR COMPRESSOR WARRANTY
 1.5 CFM PER SF FURNISHED W/BASE BUILDING BY OTHERS
 GAS HUMIDIFIER                                                           1 LS
 FLUE (HUMIDIFIER)                                                        1 LS
 RGD'S                                                                    1 LS
 HEPA MODULES (4 EA)                                                      1 LS
 EXHAUST FANS (4)                                                         1 LS
 VAV'S (52)                                                               1 LS
 CW / HW PIPING                                                           1 LS
 DUCTWORK FAB                                                             1 LS
 DUCTWORK ROUGH                                                           1 LS
 DUCTWORK FINISH                                                          1 LS
 GLYCOL / CHEMICALS                                                       1 LS
 VFD'S                                                                    1 LS
 PIPE & DUCT INSULATION                                                   1 LS
 CONTROLS                                                                 1 LS
 START & TEST                                                             1 LS
 BALANCING                                                                1 LS
 COMPLETE HVAC WORK @ 3RD LAB                                             1 LS
 HVAC FOR AMENITIES                                                       1 LS
 CREDIT DUCTWORK @ LARGE CONFERENCE ROOM                                  1 LS
</Table>

<Page>

NITROMED INC. - TENANT IMPROVEMENTS
125 SPRING STREET, LEXINGTON, MASSACHUSETTS
BUDGET ESTIMATE

<Table>
<Caption>
                       DIVISION / DESCRIPTION                      QTY
----------------------------------------------------------------   -------------
<S>                                                                     <C>
ELECTRICAL

 PANELS & TRANSFORMERS
 GENERATOR AND AUTOMATIC TRANSFER SWITCH
 DISTRIBUTION
 HVAC POWER WIRING
 FIRE ALARM
 EXIT / EMERGENCY LIGHTING
 LIGHTING / SWITCHING
 POWER WIRING OUTLETS
 POWER TO CHEMICAL FUME HOODS                                            32 EA
 POWER TO ROOF EXHAUST FANS
 EQUIPMENT WIRING PER EQUIPMENT LIST DATED 10/22/03
 PARABOLIC LIGHT FIXTURES AT OFFICES / CONF AREAS
 TRIPLE GASKETED LIGHT FIXTURES @ ANIMAL ROOMS
 PRISMATIC LIGHT FIXTURES AT LABS AND SUPPORT AREAS
 FIRE ALARM DEVICES
 POWER WIRING AND DEVICES
 MECH WIRING, DISCONNECTS & INSTALLATION OF MOTOR STARTERS
 TEMPORARY POWER & LIGHTING
 DAILY CLEANUP TO A SITE DUMPSTER
 INTERLOCKS AT AIRLOCKS
 PRODUCT SUBMITTALS, OWNER'S MANUALS AND AS-BUILTS
 VOICE AND DATE OUTLET BOXES W/CONDUIT AND PULL STRING
 INTERNAL EMERGENCY BATTERY BACK-UP BALLASTS IN LIGHTS
 POWER TO NEW MECHNICAL EQUIPMENT
 TOTAL TENANT IMPROVEMENT ELECTRICAL BUDGET                               1 LS
 VOICE AND DATA OUTLETS (2 PER OFF, LAB & CUBICLE)                      312 EA
 HOLD OPENS AND CLASS 1 DIV 2 WIRING AT 141 & 142                         1 LS
 CARD ACCESS                                                              1 ALW
 SECURITY / ALARM MONITORING                                              1 ALW
 COMPLETE 3RD CHEMISTRY LAB ELECTRICAL                                    1 LS
 ELECTRICAL FOR AMENITIES                                                 1 LS
 CREDIT LIGHT & POWER AT EXISTING LARGE EXEC CONFERENCE RM                1 LS

SUPERVISION

 FIELD SUPERINTENDENT                                                    22 WKS
 PROJECT MANAGER (2.5 DAYS PER WEEK)                                     22 WKS
 PLANNER / ESTIMATOR                                                    4.0 WKS
 PROJECT SECRETARY, 1/4 TIME                                             22 WKS
 PROJECT ACCOUNTANT, 1/5 TIME                                            22 WKS
 PROJECT DIRECTOR                                                         4 WKS
 SUPERVISION FOR AMENITIES                                                1 LS
 CREDIT FOR CONCURRENT SUPERVISION                                        4 WKS
</Table>

<Page>

NITROMED INC. - TENANT IMPROVEMENTS
125 SPRING STREET, LEXINGTON, MASSACHUSETTS
BUDGET ESTIMATE

<Table>
<Caption>
                       DIVISION / DESCRIPTION                      QTY
----------------------------------------------------------------   -------------
<S>                                                                      <C>
GENERAL CONDITIONS

 JOBSITE TELEPHONE / FAX                                                  5 MO
 CONSTRUCT TEMPORARY OFFICE                                               1 LS
 SET UP FIELD OFFICE                                                      1 LS
 COURIER / OVERNITE POSTAGE                                               5 MO
 FIELD OFFICE FURNITURE                                                   1 LS
 FIELD OFFICE SUPPLIES & COPIER RENTAL                                    5 MO
 FIELD OFFICE COMPUTER / PRINTER
 MISC. TOOLS & SUPPLIES                                                   5 MO
 PROJECT SIGN                                                             1 LS
 TEMP DRINKING WATER                                                      5 MO
 JOBSITE CLEANUP LABOR                                                   22 WK
 JOBSITE DUMPSTER                                                        22 LDS
 FINAL CLEANING                                                           1 LS
 TEMP. TOILETS (6 EA)                                                     5 MO
 REPRODUCTION OF CONTRACT DOCUMENTS                                       1 LS
 PHOTOS                                                                   1 LS
 SAFETY & BARRICADES                                                      1 LS
 GENERAL CONDITIONS FOR AMENITIES                                         1 LS
 TEMP ELECTRIC                                                            5 MO

ENGINEERING

 PART 1 ARCHITECTURAL / ENGINEERING AGREEMENT                             1 LS
 PART 2 ARCHITECTURAL AGREEMENT                                           1 LS
 ARCHITECTURAL DESIGN FOR AMENITIES                                       1 LS
 SHEPLY BULFINCH RICHARDSON & ABBOTT DESIGN CREDIT                        1 LS
 NITROMED DIRECT PAYMENT                                                  1 LS
 STRUCTURAL ENGINEERING                                                   1 LS
 FIRE PROTECTION ENGINEERING                                              1 LS
 ELECTRICAL / MECHANICAL ENGINEERING
WINTER CONDITIONS

INSURANCE AND PERMITS

 GENERAL LIABILITY INSURANCE                                              1 LS
 TOWN OF LEXINGTON GENERAL BUILDING PERMIT ($12/1000)                     1 LS

OVERHEAD AND PROFIT                                                       1 LS

TOTAL COST

CONTINGENCY                                                               1 LS

TOTAL BUDGET COST
</Table>

<Page>

NIROMED INC. - TENANT IMPROVEMENTS
125 SPRING STREET, LEXINGTON, MASSACHUSETTS
BUDGET ESTIMATE

<Table>
<Caption>
                       DIVISION / DESCRIPTION                      QTY
----------------------------------------------------------------   -------------
<S>                                                                <C>
</Table>

ALTERNATIVES & CLARIFICATIONS
1.CARD ACCESS, SECURITY, TEL/DATA, ALARM MONITORING, DUMSTER AREA, RECEPTIONIARE
  ALLOWANCES, FINAL SCOPE TO BE DETERMINED.

<Page>

                                    EXHIBIT 6

                              RULES AND REGULATIONS

       In the event that any of the Rules and Regulations, as the same may be
amended from time to time, are inconsistent with the terms of the Lease, Tenant
shall observe the terms of the Lease. Rules and Regulations clearly intended to
apply to multi-tenant buildings at the Property shall apply only to multi-tenant
buildings, and not to single-tenant buildings.

       When required by the Rules and Regulations, Landlord's consent and/or
approval shall not be unreasonably withheld, conditioned or delayed.

       1.     The common 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 be used by them for any
              purposes other than ingress or egress to and from the Premises.

       2.     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 this 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 Tenant's expense at the time Tenant is installing
              safes, freight, furniture or bulky matter.

       3.     Tenant or the employees, agents, servants, visitors or licensees
              of Tenant shall not at any time place, lease 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. Except in connection with the
              Permitted Uses, no animals or birds shall be brought or kept in or
              about the Building, other than seeing eye dogs.

       4.     Tenant or the employees, agents, servants, visitors or licensees
              of Tenant shall not make noises, cause disturbances, create
              vibrations, odors or noxious fumes or use or operate any
              electrical devices or other devices that emit sound waves or are
              dangerous to other tenants and occupants of the Building or that
              interferes 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.

       5.     Tenant 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
              this Lease) and Tenant shall not permit or suffer anyone to: (a)
              cook in the premises (other than in microwave

                                EXHIBIT 6, PAGE 1

<Page>

              ovens or toaster ovens); (b) at any time sell, purchase or give
              away or permit the sale, purchase, or gift of food in any form,
              except that food vendors shall be permitted to deliver prepared
              food ordered by invitees of Tenant and to collect money for such
              deliveries.

       7.     Tenant shall not: (a) use the Premises for lodging or for any
              immoral or illegal purposes; (b) use the Premises to engage in the
              manufacture or sale 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.

       8.     Upon the termination of its tenancy, Tenant must return to
              Landlord all keys, access cards or other implements necessary for
              access to the Premises, whether furnished to or otherwise procured
              by Tenant. Tenant shall provide Landlord with the keys, access
              cards or other necessary implements necessary to access all
              portions of the Premises (it being understood that any such access
              by Landlord shall be subject to the terms of the Lease).

       9.     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.

       10.    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. Canvassing, soliciting and peddling in the
              Building are prohibited, and Tenant shall cooperate to prevent the
              same.

       11.    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.

       12.    The water and wash closets and other plumbing fixtures shall not
              be used for any purpose other than those for which they were
              constructed, and no sweepings, rubbish, rags, or other substances
              shall be thrown therein.

       13.    Tenant shall comply with all security measures from time to time
              established by Landlord for the Property.

       14.    All wiring installed in the Premises by Tenant or Tenant's agents
              shall be done in compliance with the rules and regulations of the
              State Building Code Commission.

       15.    Tenant shall become familiar with the proper use and handling of
              all fire extinguishers provided by Landlord in the Premises and
              Tenant shall be

                                EXHIBIT 6, PAGE 2

<Page>

              responsible for the periodic inspection and maintenance of said
              extinguishers in accordance with the manufacturer's instructions.

       16.    Tenant shall participate in Landlord's semi-annual fire drills for
              the Building and shall appoint a fire marshal representing the
              Tenant and one additional fire marshal for each group of 50
              employees.

       17.    Smoking is strictly prohibited by law in all areas of the Building
              including, without limitation, tenant premises, lobbies,
              elevators, rest rooms, vacant tenant spaces, entranceways,
              vestibules, and stairwells.). Tenant shall inform its employees of
              this law and shall be responsible for any violation of this law by
              its employees.

       18.    In the event Landlord has deposited a check from Tenant, and said
              check is returned to Landlord by Landlord's bank, then Landlord
              shall charge Tenant as additional rent a $35 processing fee (the
              "PROCESSING FEE") for the returned check. In addition, until
              Landlord is able to redeposit Tenant's check, Landlord shall
              charge interest on the uncollectible funds in accordance with the
              provisions of Section 6.2 of this Lease. In the event the fee
              charged to Landlord for the returned check increases, then the
              Processing Fee shall be increased accordingly.

       19.    Parking is strictly prohibited in all handicapped spaces (unless
              vehicle has the appropriate handicapped sticker or license plate),
              fire lanes, tow zones, and other "no parking" areas (the
              "RESTRICTED AREAS"). Violators of this rule will have their
              vehicles towed without notice at their own expense. Tenant shall
              be responsible for notifying its employees of this rule and shall
              be responsible for any violation of this rule by its employees,
              including, but not limited to, reimbursing Landlord for all costs
              incurred in towing Tenant's employees' vehicles from the
              restricted areas.

       20.    Tenant must notify Landlord at least twenty-four (24) hours in
              advance of any move-in and/or move-out, and at least forty-eight
              (48) hours of any major move in (including Tenant's initial move
              into the Premises) and/or move-out of the Premises.

       21.    In the event Landlord permits Tenant to hire its own contractors
              to perform any tenant construction work, Tenant shall make its
              contractors aware of these Rules and Regulations and shall be
              responsible for any violation of these Rules and Regulations by
              Tenant's contractors.

                                EXHIBIT 6, PAGE 3

<Page>

                                    EXHIBIT 7

                       HAZARDOUS WASTE MANAGEMENT PROGRAM

                             [AVAILABLE UPON REQUEST]

                                EXHIBIT 7, PAGE 1

<Page>

                                    EXHIBIT 8

                              ENVIRONMENTAL REPORTS

1.     GZA letter to Mr. Steven Rice, PM Atlantic Burlington LLC, dated 6/11/02
       - Review of Environmental Site Assessment Report (5 pages).

2.     URS Letter to Michael Donohue of Raytheon dated 6/11/02 regarding
       asbestos management services (1 page).

3.     Dames & Moore letter to Mr. Brian Balukons, Raytheon Company, dated
       10/1/96 - DC Health Building Phase II Asbestos Abatement Project (2
       pages).

4.     Dames & Moore letter to Mr. Brian Balukons, Raytheon Company, dated
       8/14/96 - DC Health Building Phase II Asbestos Abatement Project (2
       pages).

5.     Dames & Moore letter to Mr. Brian Balukons, Raytheon Company, dated
       5/17/96 - DC Health Building Phase II Asbestos Abatement Project (2
       pages).

6.     Executive Summary of Balsam Environmental Consultants, Inc. report dated
       7/26/93 (regarding asbestos abatement) - Note: Executive Summary only is
       on file, entire report has not been received/reviewed.

7.     Arcadis Phase I Environmental Site Assessment report, prepared by
       Raytheon Company, dated May 2002 (Approximately 60 pages plus
       Appendices).

                                EXHIBIT 8, PAGE 1

<Page>

                                    EXHIBIT 9

                            FORM OF LETTER OF CREDIT

                                EXHIBIT 9, PAGE 1

<Page>

                       DRAFT FOR DISCUSSION PURPOSES ONLY

FLEET NATIONAL BANK
C/O FLEET PENNSYLVANIA SERVICES, INC.
1 FLEET WAY
SCRANTON, PA 18507-1999
                                        DATE:

IRREVOCABLE STANDBY LETTER OF CREDIT NUMBER____________

BENEFICIARY:                               APPLICANT:

AMOUNT: USD
EXPIRY DATE:
EXPIRE PLACE: OUR COUNTERS

GENTLEMEN:

WE HEREBY ISSUE THIS IRREVOCABLE LETTER OF CREDIT NO._______________________IN
YOUR FAVOR, FOR THE ACCOUNT OF APPLICANT, FOR UP TO AN AGGREGATE AMOUNT OF USD
____________AVAILABLE BY YOUR DRAFT(S) DRAWN ON US AT SIGHT, ACCOMPANIED BY THE
FOLLOWING:

1.BENEFICIARY'S WRITTEN, DATED STATEMENT ON BENEFICIARY LETTERHEAD SIGNED BY A
PURPORTED OFFICER READING:

QUOTE
NAME OF APPLICANT) HAS NOT COMPLIED WITH THE TERMS AND CONDITIONS OF THE LEASE
AGREEMENT DATED ____________BETWEEN (NAME OF APPLICANT) AND (NAME OF
BENEFICIARY).
UNQUOTE

2.THE ORIGINAL OF THIS LETTER OF CREDIT AND AMENDMENT(S), IF ANY.

DATA CONTENT OF ANY REQUIRED DOCUMENTS PRESENTED UNDER THIS LETTER OF CREDIT
MUST BE CONSISTENT WITH THE DATA CONTENT OF ANY OTHER REQUIRED DOCUMENT(S)
PRESENTED UNDER THIS LETTER OF CREDIT.

PARTIAL DRAWINGS ARE PERMITTED.

IT IS A CONDITION OF THIS LETTER OF CREDIT THAT IT SHALL BE AUTOMATICALLY
EXTENDED WITHOUT AMENDMENT FOR PERIOD(S) OF ONE YEAR EACH FROM THE CURRENT OR
ANY FUTURE EXPIRATION DATE UNLESS AT LEAST THIRTY (30) DAYS PRIOR TO THE THEN
CURRENT EXPIRATION DATE WE SHALL NOTIFY THE BENEFICIARY IN WRITING, VIA
REGISTERED MAIL, AT THE ABOVE LISTED ADDRESS OF OUR INTENTION NOT TO RENEW THIS
LETTER OF CREDIT.

ANY SUCH NOTICE SHALL BE EFFECTIVE WHEN SENT BY US AND UPON SUCH NOTICE TO YOU
YOU MAY DRAW HEREUNDER, UP TO THE FULL AMOUNT THEN AVAILABLE, BY PRESENTATION OF
YOUR SIGHT DRAFT DRAWN ON US ACCOMPANIED BY THE ORIGINAL OF THIS LETTER OF
CREDIT, AND ALL AMENDMENTS THERETO, AND YOUR STATEMENT, ON YOUR LETTERHEAD

                       DRAFT FOR DISCUSSION PURPOSES ONLY
                                  LEASERKP.DOC

<Page>

                       DRAFT FOR DISCUSSION PURPOSES ONLY
PURPORTEDLY SIGNED BY AN AUTHORIZED REPRESENTATIVE, STATING THAT YOU ARE IN
RECEIPT OF FLEET NATIONAL BANK'S NOTICE OF NONRENEWAL UNDER LETTER OF CREDIT NO.
_______________AND APPLICANT HAS FAILED TO EXTEND SAID LETTER OF CREDIT OR
PROVIDE A REPLACEMENT LETTER OF CREDIT IN A FORM ACCEPTABLE TO YOU.

DRAFT(S) MUST STATE: "DRAWN UNDER FLEET NATIONAL BANK STANDBY L/C
NO. ______________ DATED__________________________."

THIS LETTER OF CREDIT IS TRANSFERABLE IN FULL AND NOT IN PART. ANY TRANSFER MADE
HEREUNDER MUST CONFORM STRICTLY TO THE TERMS HEREOF AND TO THE CONDITIONS OF
RULE 6 OF THE INTERNATIONAL STANDBY PRACTICES (ISP98) FIXED BY THE INTERNATIONAL
CHAMBER OF COMMERCE, PUBLICATION NO. 590.

SHOULD YOU WISH TO EFFECT A TRANSFER UNDER THIS CREDIT, SUCH TRANSFER WILL BE
SUBJECT TO THE RETURN TO US OF THE ORIGINAL CREDIT INSTRUMENT, ACCOMPANIED BY
OUR FORM OF TRANSFER, PROPERLY COMPLETED AND SIGNED BY AN AUTHORIZED SIGNATORY
OF YOUR FIRM, BEARING YOUR BANKERS STAMP AND SIGNATURE AUTHENTICATION AND
SUBJECT TO YOUR PAYMENT OF OUR CUSTOMARY TRANSFER CHARGES OF 1/4 OF 1% MINIMUM
$ 200.00.

DRAFTS AND DOCUMENTS MUST BE PRESENTED AT OUR OFFICE ADDRESSED: FLEET NATIONAL
BANK, C/O FLEET PENNSYLVANIA SERVICES INC., 1 FLEET WAY, SCRANTON, PA
18507-1999, ATTN: TRADE SERVICES DEPT. - STANDBY UNIT.

WE HEREBY AGREE WITH YOU THAT DRAFT(S) DRAWN UNDER AND IN COMPLIANCE WITH THE
TERMS OF THIS LETTER OF CREDIT SHALL BE DULY HONORED UPON DUE PRESENTATION TO
US.

THIS LETTER OF CREDIT IS SUBJECT TO THE INTERNATIONAL STANDBY PRACTICES (ISP98),
THE INTERNATIONAL CHAMBER OF COMMERCE, PUBLICATION NO. 590.

FORM AND CONTENTS ACCEPTED BY:

(SIGNATURE -MUST BE THE SAME AS THAT ON LETTER OF CREDIT APPLICATION)
AUTHORIZED SIGNATURE FOR

-----------------------------------
APPLICANT

                       DRAFT FOR DISCUSSION PURPOSES ONLY
                                  LEASERKP.DOC

<Page>

                                   EXHIBIT 10

                           EXCERPTS FROM ZONING BY-LAW

                               EXHIBIT 10, PAGE 1

<Page>

Section 4. Permitted Uses And Development Standards                           37

4.2 TABLE 1 PERMITTED USES AND DEVELOPMENT STANDARDS

              PART A RESIDENTIAL, INSTITUTIONAL, AGRICULTURAL USES

<Table>
<Caption>
                                                                                                      CB
                                                     RO                   RD            CR            CL     CR
Line                                                 RS     RT     RM     *      CN     S      CS     O      O      CM
--------------------------------------------------   ----   ----   ----   ----   ----   ----   ----   ----   ----   ----
<S>                                                  <C>    <C>    <C>    <C>    <C>    <C>    <C>    <C>    <C>    <C>
*For uses permitted in RD districts, see
subparagraph 4.1.1 and 8.3.3

1.    RESIDENTIAL USES

1.1   PERMITTED RESIDENTIAL USES
      (Must also comply with operating and
      development standards)

1.11  One-family dwelling                            Y      Y      Y      SP     Y      N      N      N      N      N

1.12  Two-family dwelling, semi-attached             N      Y      Y      SP*    Y      N      N      N      N      N
      dwelling

1.13  Conversion of one-family dwelling              SP     Y      Y      N      Y      N      N      N      N      N
      to two-family dwelling (see sub
      section 5.3 elsewhere in this
      By-Law)

1.14  Conversion of one-family dwelling              SP     SP     Y      SP*    SP     N      N      N      N      N
      to congregate living facility (see
      subsection 5.4 elsewhere in this
      By-Law)

1.15  Dwelling unit in commercial or                 Y      Y      Y      SP*    Y      Y      Y      Y      Y      Y
      institutional building for
      security, maintenance or
      administrative employee

1.16  (Reserved)

1.17  Temporary dwelling, which may                  Y      Y      Y      Y      N      N      N      N      N       N
      include a mobile home to replace a
      permanent dwelling which has been
      damaged or destroyed by fire,
      natural catastrophe, or by
      demolition or substantial
      reconstruction. (See subsection
      3.1.5)

1.18  Residential developments with three            SPS    SPS    N**          N      N      N      N      N      N
      or more dwelling units.  All                                 *      SPS
      residential developments with three
      or more dwelling units require a
      special permit with site plan
      review (SPS). See Section 9.

      TYPES OF DWELLINGS AND RESIDENTIAL
      FACILITIES The types of dwellings
      and residential facilities
      permitted vary according to the
      type of district and the type
      (three alternatives) of residential
      developments with three or more
      dwelling units. Listed below, for
      information purposes, is a general
      summary.  Subsection 9.2.2 controls
      which types of dwellings are
      permitted.

      1.181 One-family detached                      Y      Y      N**    SP*    N      N      N      N      N      N
                                                                   *

      1.182 One-family attached,                     SP     Y      N**    SP*    N      N      N      N      N      N
      two-family                                                   *
</Table>

<Page>

38                           Section 4. Permitted Uses And Development Standards

<Table>
<Caption>
                                                                                                      CB
                                                     RO                   RD            CR            CL     CR
Line                                                 RS     RT     RM     *      CN     S      CS     O      O      CM
--------------------------------------------------   ----   ----   ----   ----   ----   ----   ----   ----   ----   ----
<S>                                                  <C>    <C>    <C>    <C>    <C>    <C>    <C>    <C>    <C>    <C>
      1.183 Townhouse                                SP     SP     N**    SP*    N      N      N      N      N      N
                                                                   *

      1.184 Three-family, four-family,               N      N      N**    SP*    N      N      N      N      N      N
      multi-family                                                 *

      1.185 Rooming house, group quarters            N**    N**    N**    SP*    N      N      N      N      N      N
                                                                   *

      1.186 Group care facility, congregate living   N      N      N**    SP*    N      N      N      N      N      N
      facility, long term care facility, assisted                  *
      living residence, independent living
      residence

      1.187 Conversion of a municipal building to    SPS    SPS    N**    SP*    N      N      N      N      N      N
      residential use (see * subsection 9.8)

      * subject to a preliminary site development
      and use plan (see subsections 4.1.1 and
      8.3.3)

      ** Y, if accessory to a religious or
      educational use

      *** Development of new multi-family
      dwellings is not permitted in the RM
      district; these uses are permitted in RM
      districts in existence in January, 1985.

1.2   ACCESSORY USES FOR RESIDENTIAL USES (See
      also line 5, accessory uses permitted in all
      residential, institutional, agricultural
      uses)

1.21  Rooming units, without kitchen facilities,     Y      Y      Y      SP     N      N      N      N      N      N
      for not more than three persons in an
      existing dwelling, provided the building
      contains a dwelling unit occupied by a
      family

1.22  Accessory apartment in one-family dwelling     Y      Y      Y      SP     Y      N      N      N      N      N
      (See subsection 5.2 elsewhere in this
      By-Law)

1.23  Bed and Breakfast Home (see Section 5.5)       Y      N      N      N      N      N      N      N      N      N

1.24  Home occupation in which there is no           Y      Y      Y      SP     Y      N      N      N      N      N
      exterior evidence of the occupation, no
      employee who is not also a resident in the
      dwelling, and not more than one customer or
      client visits the dwelling at one time.

1.25  Home occupation, or office of a physician,     SP     SP     SP     SP     Y      N      N      N      N      N
      dentist or other professional person,
      residing in the dwelling, provided there is
      no exterior evidence of the occupation and
      each employee is also a resident in the
      dwelling; may have customers or clients
      visit the dwelling.

1.26  Tool shed, storage shed, garden house          Y      Y      Y      Y      Y      N      N      N      N      N
      subject to the same dimensional controls as
      a principal building

1.27  Greenhouse not used for commercial purposes    Y      Y      Y      Y      Y      N      N      N      N      N
      subject to the same dimensional controls as
      a principal building

1.28  Swimming pool (See subsection 5.8.1)           Y      Y      Y      SP     Y      N      N      N      N      N
</Table>

<Page>

Section 4. Permitted Uses And Development Standards                           39

<Table>
<Caption>
                                                                                                      CB
                                                     RO                   RD            CR            CL     CR
Line                                                 RS     RT     RM     *      CN     S      CS     O      O      CM
--------------------------------------------------   ----   ----   ----   ----   ----   ----   ----   ----   ----   ----
<S>                                                  <C>    <C>    <C>    <C>    <C>    <C>    <C>    <C>    <C>    <C>
1.29  Tennis court or court for a sport played       SP     SP     SP     SP     Y      N      N      N      N      N
      with a racquet or paddle including handball.
      (See subsection 5.8.1)

1.30  Satellite receiving antenna (See subsection    Y      Y      Y      SP     Y      N      N      N      N      N
      5.8.2)

1.31  Off-street parking for automobiles. If         Y      Y      Y      Y      Y      Y      Y      Y      Y      Y
      outdoor parking spaces are provided for more
      than four automobiles for a dwelling unit, a
      special permit is required.

1.32  An off-street parking space, which may be in   Y      Y      Y      N      N      N      N      N      N      N
      a garage or outdoors, for not more than one
      commercial vehicle, not larger than 10,000
      pounds, gross vehicle weight rating, which
      is used by a resident of the dwelling. Not
      more than one other commercial vehicle not
      in excess of 15,000 pounds, gross vehicle
      weight rating, which is used by a resident
      of the dwelling, may be parked in a garage
      only.

1.33  Outdoor storage of not more than one           Y      Y      Y      Y      Y      N      N      N      N      N
      unregistered automobile which shall be
      parked only in an area not within the
      minimum yard required for the principal
      dwelling and which is screened from the view
      of abutting lots and the street. This
      limitation does not apply to such vehicles
      stored within a building.

1.34  Convenience business or other commercial       N      N      N      SP     N      N      N      N      N      N
      uses in a multi-family development (see
      subsection 9.2.2)

2.    INSTITUTIONAL USES

2.1   PERMITTED INSTITUTIONAL USES
      (Must also comply with operating and
      development standards)

2.11  Churches, synagogues, and temples (including   Y      Y      Y      Y      Y      Y      Y      Y      Y      Y
      associated dwellings for religious personnel
      and associated buildings used for religious
      purposes)

2.12  Day care center (see Definition), school age   Y      Y      Y      Y      Y      Y      Y      Y      Y      Y
      child care program (see Definition), nursery
      school, kindergarten;

2.13  Family day care home (see Definition) for      Y      Y      Y      Y      Y      SP     SP     SP     SP     SP
      not more than six children
</Table>

<Page>

40                           Section 4. Permitted Uses And Development Standards

<Table>
<Caption>
                                                                                                      CB
                                                     RO                   RD            CR            CL     CR
Line                                                 RS     RT     RM     *      CN     S      CS     O      O      CM
--------------------------------------------------   ----   ----   ----   ----   ----   ----   ----   ----   ----   ----
<S>                                                  <C>    <C>    <C>    <C>    <C>    <C>    <C>    <C>    <C>    <C>
2.14  Elementary or secondary school, trade or       Y      Y      Y      Y      Y      Y      Y      Y      Y      Y
      vocational school for elementary and
      secondary school students; operated by a
      public agency, or by a religious sect or
      denomination, or a non-profit educational
      corporation; includes associated buildings
      and land used for educational purposes

2.15  Public or private non-profit, college or       Y      Y      Y      Y      Y      Y      Y      Y      Y      Y
      technical school, trade or vocational school
      operated for college age students; includes
      buildings, land or other facilities used for
      educational purposes but not including space
      used for revenue producing purposes not
      directly associated with the education of
      students; (for space used for revenue
      producing purposes, see commercial uses)

2.16  Public parks, playgrounds, municipal           Y      Y      Y      Y      Y      Y      Y      Y      Y      Y
      buildings or uses

2.17  Museum, art gallery, private library           SP     SP     SP     SP     Y      Y      N      Y      Y      N

2.18  Non-profit community service center or         SP     SP     SP     SP     Y      Y      N      Y      Y      Y
      charitable organization

2.19  Private, non-profit club or lodge of social,   SP     SP     SP     SP     Y      Y      N      Y      Y      Y
      fraternal, veterans, professional or
      political association, union hall; not
      including a recreational club

2.20  Private non-profit recreational facility       SP     SP     SP     SP     Y      Y      Y      Y      Y      Y
      such as golf course, tennis or swimming club

2.21  Cemetery                                       Y      Y      Y      N      Y      Y      Y      Y      Y      Y

2.3   ACCESSORY USES, INSTITUTIONAL USES (See also
      line 5, accessory uses permitted in all
      residential, institutional, agricultural
      uses)

2.31  Within a lodge or recreational club,           SP     SP     SP     SP     Y      Y      Y      Y      Y      Y
      kitchen, dining room, function room
      available for members but not open to the
      general public

2.32  Within a recreational club, place for the      SP     SP     SP     SP     Y      Y      Y      Y      Y      Y
      sale of related equipment, such as balls;
      snack bar

2.33  Within a school, kitchen and dining            SP     SP     SP     SP     Y      Y      Y      Y      Y      Y
      facilities for staff or students; dwelling
      units for staff

2.4   DEVELOPMENT STANDARDS

2.41  Uses and structures with less than 10,000      Y      Y      Y      SP     Y      Y      Y      Y      Y      Y
      square feet of gross floor area, including
      the area of any existing structure but not
      including any floor area devoted to parking,
      on a lot provided the use is permitted.
</Table>

<Page>

Section 4. Permitted Uses And Development Standards                           41

<Table>
<Caption>
                                                                                                      CB
                                                     RO                   RD            CR            CL     CR
Line                                                 RS     RT     RM     *      CN     S      CS     O      O      CM
--------------------------------------------------   ----   ----   ----   ----   ----   ----   ----   ----   ----   ----
<S>                                                  <C>    <C>    <C>    <C>    <C>    <C>    <C>    <C>    <C>    <C>
2.42  Uses and structures with 10,000 square feet    SPS    SPS    SPS    SPS    SPS    SPS    SPS    SPS    SPS    SPS
      or more of gross floor area, including the
      area of any existing structure but not
      including any floor area devoted to parking,
      on a lot provided the use is permitted and
      the SPGA grants a special permit with site
      plan. (See subsection 3.4 and 3.5) (A
      religious or non-profit educational use, as
      described in subparagraph 3.1.4.1, is
      permitted as a matter of right in all zoning
      districts.)

3.    AGRICULTURAL, NATURAL RESOURCE USES

3.1   PERMITTED AGRICULTURAL, NATURAL RESOURCES

3.11  Farm for the raising of crops                  Y      Y      Y      Y      Y      Y      Y      Y      Y      Y

3.12  Farm or ranch for the raising or boarding,     Y      Y      Y      Y      Y      Y      Y      Y      Y      Y
      breeding of cattle, poultry, horses or other
      livestock provided the area of the lot is at
      least five acres

3.13  Commercial greenhouse or nursery with retail   SP*    SP*    SP*    SP*    SP*    SP*    SP*    SP*    SP*    SP*
      sales (See subsection 5.6)

3.14  Roadside stand (for two year terms)            SP*    SP*    SP*    SP*    SP*    SP*    SP*    SP*    SP*    SP*

3.15  Removal from a lot of earth materials for      SP     N      N      N      N      N      N      N      SP     SP
      sale such as loam, sod, sand, gravel, stone,
      rock or clay

      * Y, if the use satisfies all of the
      requirements for the so-called agricultural
      exemption in The State Zoning Act, Chapter
      40A, Section 3

4.    COMMERCIAL USES IN RESIDENTIAL DISTRICTS

4.1   PERMITTED COMMERCIAL USES IN                                               For permitted commercial uses in
      RESIDENTIAL DISTRICTS                                                      commercial districts, see Part B of
                                                                                 this Table.

4.11  Privately owned for profit recreational        SP     SP     SP     SP
      facilities for golf, tennis or swimming

4.12  Horseback riding area, stables operated for    SP     SP     SP     SP
      profit

4.13  Utility substation or pumping station          Y      Y      Y      Y
      provided no public business office is
      permitted and all outdoor storage of
      equipment or material is permanently
      screened from the view of adjoining lots and
      the street. (See Section 10)

4.14  Seasonal sale of Christmas trees and wreaths   SP     SP     SP     SP

4.15  Wireless communication facility (See Section   SP     SP     SP     SP
      15)

5.    ACCESSORY AND TEMPORARY USES PERMITTED FOR
      ALL RESIDENTIAL, INSTITUTIONAL AND
      AGRICULTURAL USES

5.11  Off-street parking, off-street loading (See    Y      Y      Y      Y      Y      Y      Y      Y      Y      Y
      Section 11)
</Table>

<Page>

42                           Section 4. Permitted Uses And Development Standards

<Table>
<Caption>
                                                                                                      CB
                                                     RO                   RD            CR            CL     CR
Line                                                 RS     RT     RM     *      CN     S      CS     O      O      CM
--------------------------------------------------   ----   ----   ----   ----   ----   ----   ----   ----   ----   ----
<S>                                                  <C>    <C>    <C>    <C>    <C>    <C>    <C>    <C>    <C>    <C>
5.12  Dwelling unit in institutional building for    Y      Y      Y      SP     Y      Y      Y      Y      Y      Y
      security, maintenance or administrative
      personnel

5.13  Building for storage of tools, lawn and        Y      Y      Y      Y      Y      Y      Y      Y      Y      Y
      garden equipment and supplies subject to
      same dimensional controls as a principal
      building.

5.14  Greenhouse not used for commercial purposes    Y      Y      Y      SP     Y      Y      Y      Y      Y      Y
      subject to the same dimensional controls as
      a principal building

5.15  Swimming pool (See subsection 5.8.1)           Y      Y      Y      SP     Y      Y      Y      Y      Y      Y

5.16  Tennis court or court for a sport played       SP     SP     SP     SP     Y      Y      Y      Y      Y      Y
      with a racquet, includes handball (See
      subsection 5.8.1)

5.17  Satellite receiving antenna (See subsection    Y      Y      Y      SP     Y      Y      Y      Y      Y      Y
      5.8.2)

5.18  Parking of trucks or other equipment to be     Y      Y      Y      Y      Y      Y      Y      Y      Y      Y
      used for the maintenance of buildings and
      grounds only; shall be parked only in a
      garage or in an area not within the minimum
      yard for the principal building and shall be
      screened from the view of abutting lots and
      the street. (See Section 10)

5.19  Convenience business or other commercial       Y      Y      Y      SP     Y      Y      Y      Y      Y      Y
      uses in an institutional building; provided
      the use is conducted entirely within the
      principal building, is conducted primarily
      for the occupants or employees of the
      principal use and there is no evidence of
      the conduct of the accessory use from the
      street or from any lot line.

5.20  Accessory sign, as permitted by Section 13.    Y      Y      Y      SP     Y      Y      Y      Y      Y      Y

TEMPORARY USES                                                                   For permitted temporary uses in
                                                                                 commercial districts, see Part B of
                                                                                 this Table

5.21  Temporary building(s) or trailer(s)            Y      Y      Y      Y
      incidental to the construction of a building
      or land development. (See subsection 3.1.5)

5.22  Temporary structures and uses not otherwise    SP     SP     SP     SP
      permitted in the district provided the SPGA
      makes a finding that the proposed structure
      or use is compatible with the neighborhood.
      (See subsection 3.1.5)
</Table>

<Page>

Section 4. Permitted Uses And Development Standards                           43

TABLE I PERMITTED USES AND DEVELOPMENT STANDARDS (cont.)

                             PART B COMMERCIAL USES
        Note: Commercial Uses Are Not Permitted in Residential Districts
                          Except As Indicated in PART A

<Table>
<Caption>
Line                                                 CN     CRS    CS     CB     CLO    CRO    CM
--------------------------------------------------   ----   ----   ----   ----   ----   ----   ----
<S>                                                  <C>    <C>    <C>    <C>    <C>    <C>    <C>
      ALL COMMERCIAL USES

B.1   OPERATING STANDARDS

B.11  All operations are conducted entirely within   Y      Y      Y      Y      Y      Y      Y
      an enclosed building

B.12  Operations, in part or in whole, conducted     SP     Y      Y      SP     SP     SP     Y
      outdoors during operating hours and subject
      to the transition and screening requirements
      set forth in section 10.

B.13  Storage of equipment and products outdoors     N      Y      Y      Y      N      SP     SP
      during non-operating hours

B.2   DEVELOPMENT STANDARDS

B.21  Uses and structures with less than 10,000      Y      Y      Y      Y      Y      Y      Y
      square feet of gross floor area including
      the area of any existing structures but not
      including any floor area devoted to
      off-street parking, on a lot provided the
      use is permitted and complies with the
      operating and development standards in this
      Table.

B.22  Uses and structures with 10,000 or more        SPS    SPS    SPS    SPS    SPS    SPS    SPS
      square feet of gross floor area including
      the area of any existing structures but not
      including any floor area devoted to
      off-street parking, on a lot provided the
      SPGA grants an SPS as provided in
      subsections 3.4 and 3.5.

6.    OFFICE USES

6.1   PERMITTED OFFICE USES
      (Must also comply with operating and
      development standards)

6.11  Real estate development, management            N      Y      N      Y      Y      Y      Y

6.12  Finance, credit, investment but not a bank     N      Y      N      Y      Y      Y      Y
      (See line 7.15)

6.13  Medical, dental, psychiatric office, but not   Y      Y      N      Y      Y      Y      Y
      a clinic (see line 7.21)

      a. with related laboratory                     N      Y      N      Y      Y      Y      Y

6.14  Professional services such as law,             N      Y      N      Y      Y      Y      Y
      engineering, architecture, consulting
      service

6.15  Advertising, editing, composition, but not     N      N      N      N      Y      Y      Y
      Including printing or other reproduction
      service

6.16  Employment agency, office of a business,       N      Y      N      Y      Y      Y      Y
      professional, labor, civic or social
      association

6.17  Office of manufacturer's representative or     N      Y      N      Y      Y      Y      Y
      salesman with no sales or storage and
      distribution of products from the premises

6.18  Other business or administrative office, not   N      N      N      Y      Y      Y      Y
      elsewhere classified

6.2   DEVELOPMENT STANDARDS

6.21  Office located on a street level floor         Y      N      N      N      Y      Y      Y

6.22  Office located on any floor other than on a    N*     Y      N      Y      Y      Y      Y
      street level floor; * permitted in a
      basement
</Table>

<Page>

44                           Section 4. Permitted Uses And Development Standards

<Table>
<Caption>
Line                                                 CN     CRS    CS     CB     CLO    CRO    CM
--------------------------------------------------   ----   ----   ----   ----   ----   ----   ----
<S>                                                  <C>    <C>    <C>    <C>    <C>    <C>    <C>
6.23  Office space of all companies in a building    N      N      N      Y      Y      Y      Y
      occupies a total of more than 50% of the
      floor area in a building

6.24  Offices in which one company has not more      Y      Y      N      Y      Y      Y      Y
      than 1,000 square feet of floor area in a
      building

6.25  Offices in which one company has more than     N      Y      N      Y      Y      Y      Y
      1,000 square feet of floor area but not more
      than 2,500 square feet of floor area in a
      building

6.26  Building used for offices without limit as     N      N      N      N      N      Y      Y
      to the amount of floor area one company may
      occupy or the percentage of floor area
      occupied by offices.

7.    PERSONAL, BUSINESS SERVICES

7.1   PERMITTED PERSONAL, BUSINESS SERVICE USES
      (Must also comply with operating and
      development standards)

7.11  Beauty salon, barber shop                      Y      Y      Y      Y      Y      N      N

7.12  Laundry or dry cleaning pick-up station with   Y      Y      Y      N      N      N      N
      processing done elsewhere; laundry or dry
      cleaning with processing on the premises
      subject to the development standards for the
      district; self-service laundromat or dry
      cleaning

7.13  Tailor, dressmaker, shoe repair                Y      Y      Y      Y      N      N      N

7.14  Real estate sales or rental                    Y      Y      N      Y      Y      Y      Y

7.15  Bank, credit union                             N      Y      N      Y      Y      Y      Y

      a. automatic teller machine, which may be      SP     Y      Y      Y      Y      Y      Y
      either a principal use or an accessory use

      b. with drive-up window or auto-oriented       N      SP     N      N      N      SP     SP
      branch bank

7.16  Travel agency, insurance agency, ticket        N      Y      N      Y      Y      Y      Y
      agency

7.17  Photographic services including commercial     Y      Y      Y      Y      Y      Y      Y
      photography

7.18  Repair of household appliances, small tools    Y      Y      Y      Y      N      N      N
      or equipment, rental of equipment or tools
      for use in a home

7.19  Funeral parlor                                 N      N      Y      N      Y      N      N

7.20  Photocopying, reproduction services but not    Y      Y      Y      Y      Y      Y      Y
      commercial printing

7.21  Medical clinic for out-patient services        N      Y      N      Y      Y      Y      Y

7.22  For-profit school for instruction in arts,     N      Y      Y      Y      Y      Y      Y
      skills or vocational training

7.23  Commercial printing, publishing                N      N      Y      Y      Y      N      Y

7.24  Newspaper distribution agency                  N      N      Y      N      Y      N      Y

7.25  Office of veterinarian                         N      N      Y      N      N      N      N

7.26  Kennel, boarding of household pets             N      N      Y      N      N      N      N

7.27  Pet grooming service provided that it shall    N      Y      Y      Y      N      N      N
      be conducted entirely within the principal
      building and no pets shall be boarded
      overnight; where conducted as accessory to a
      kennel (line 7.26), those restrictions shall
      not apply

7.28  Private postal services (see definition)       N      Y      Y      N      Y      Y      Y

7.29  Recycling collection store (see also           N      N      SP     N      N      N      N
      paragraph 4.3.1)

7.3   DEVELOPMENT STANDARDS

7.31  Services with less than 1500 square feet of    Y      Y      Y      Y      Y      Y      Y
      floor area per establishment
</Table>

<Page>

Section 4. Permitted Uses And Development Standards                           45

<Table>
<Caption>
Line                                                 CN     CRS    CS     CB     CLO    CRO    CM
--------------------------------------------------   ----   ----   ----   ----   ----   ----   ----
<S>                                                  <C>    <C>    <C>    <C>    <C>    <C>    <C>
7.32  Services with 1500 or more square feet of      N      Y      Y      Y      Y      Y      Y
      floor area per establishment

8.    SALES OR RENTAL OF GOODS, EQUIPMENT

8.1   PERMITTED RETAIL SALES AND RENTAL USES
      (Must also comply with operating and
      development standards)

8.11  Convenience goods often bought on a daily      Y      Y      Y      Y      Y      N      N
      basis such as food, candy, newspapers,
      tobacco products,

8.12  General merchandise, department stores         N      Y      N      Y      N      N      N

8.13  Food, but not that intended for consumption    Y      Y      N      Y      N      N      N
      on the premises includes delicatessen or
      bakery, but not a take out or fast food
      service

8.14  Package liquor store, with no consumption of   N      SP     N      Y      N      N      N
      beverages on the premises

8.15  Apparel, fabrics and accessories               Y      Y      N      Y      N      N      N

8.16  Furniture, home furnishings, home appliances   N      Y      N      Y      N      N      N
      and equipment, carpets

8.17  Other retail goods such as books,              Y      Y      N      Y      N      N      N
      stationery, drugs, sporting goods, jewelry,
      photographic equipment and supplies,
      flowers, novelties, cards, footwear, and the
      like which are typically of a size that a
      customer can carry by hand

8.18  Hardware, paint, wallpaper                     Y      Y      Y      Y      N      N      N

8.19  Building materials                             N      Y      Y      Y      N      N      N

8.20  Lawn and garden supplies and equipment         N      Y      Y      N      N      N      N

8.21  Sale or rental of equipment and supplies       N      Y      Y      N      N      N      N
      such as office furniture, to other
      businesses

8.3   DEVELOPMENT STANDARDS

8.31  Stores with less than 2,000 square feet of     Y      Y      Y      Y      Y      N      N
      floor area per establishment

8.32  Stores with 2,000 or more square feet of       N      Y      Y      Y      N      N      N
      floor area per establishment

8.33  All sales or rental conducted entirely         Y      Y      Y      Y      Y      N      N
      within a fully enclosed building; temporary
      display of products outdoors during
      operating hours permitted

8.34  Sales or rental conducted in part outdoors     N      Y      Y      Y      N      N      N
      with permanent display of products during
      non-operating hours; subject to screening
      requirements in Section 10.

9.    EATING AND DRINKING, TRANSIENT
      ACCOMMODATIONS

9.1   PERMITTED EATING AND DRINKING
      ESTABLISHMENTS, TRANSIENT ACCOMMODATIONS
      (Must also comply with operating and
      development standards)

9.11  Restaurant                                     N      SP     N      SP     N      SP     SP

9.12  Fast food or take out service serving enough   N      SP     N      SP     N      N      N
      food to comprise a meal.

9.13  Take out or fast food service serving food     SP     SP     SP     SP     N      N      N
      or beverages, such as coffee, snacks, ice
      cream, or donuts, but not enough to comprise
      a meal.

9.14  Caterer or other establishment preparing       N      N      SP     N      N      N      N
      meals for groups of people

9.15  Drive-in or drive-thru food service            N      N      N      N      N      N      N
      establishment

9.16  Hotel, motel                                   N      N      N      SP     N      SP     SP
</Table>

<Page>

46                           Section 4. Permitted Uses And Development Standards

<Table>
<Caption>
Line                                                 CN     CRS    CS     CB     CLO    CRO    CM
--------------------------------------------------   ----   ----   ----   ----   ----   ----   ----
<S>                                                  <C>    <C>    <C>    <C>    <C>    <C>    <C>
10.   COMMERCIAL RECREATION, AMUSEMENT,
      ENTERTAINMENT

10.1  PERMITTED COMMERCIAL RECREATION, AMUSEMENT,
      ENTERTAINMENT USES (Must also comply with
      operating and development standards)

10.11 Movie theater (indoor)                         N      N      N      Y      N      N      N

10.12 Indoor athletic and exercise facilities,       N      N      Y      N      N      N      N
      weight reduction salon

11.   MOTOR VEHICLE-RELATED SALES AND SERVICE USES

11.1  PERMITTED MOTOR VEHICLE-RELATED SALES AND
      SERVICE USES (Must also comply with
      operating and development standards)

11.11 Motor vehicle sales or rental; includes        N      SP     SP     N      N      N      SP
      automobiles, trucks campers, vans,
      recreational vehicles, or trailers

11.12 Service station, sale of fuel and other        N      SP     SP     N      N      N      N
      motor oil products and accessories such as
      batteries, tires

11.13 Sales and installation of automotive parts     N      N      SP     N      N      N      N
      such as tires, mufflers, brakes and motor
      vehicle accessories

11.14 Motor vehicle maintenance and minor repairs    N      SP     SP     N      N      N      SP
      limited to engine tune-up, lubrication and
      installation of replacement parts,
      adjustment or replacement of brakes or
      tires, washing and polishing, but not
      including engine overhaul, body work or
      painting

11.15 Substantial motor vehicle repair including     N      N      SP     N      N      N      N
      engine overhaul, body work and painting

11.16 Car wash conducted entirely within a           N      N      SP     N      N      N      N
      building

11.17 Automobile parking lot where the parking       N      N      SP     SP     N      SP     SP
      spaces do not serve a principal use on the
      same lot and where no sales or service takes
      place.

11.18 Storage of automobiles or trucks where the     N      N      SP     N      N      N      N
      principal user of the vehicles is not on the
      same lot.

11.2  DEVELOPMENT STANDARDS

11.21 Activities conducted entirely within a fully   N      SP     SP     N      N      N      SP
      enclosed Building

11.22 Activities conducted outside of a building,    N      SP     SP     SP     N      SP     SP
      in an open area

11.23 Open-air storage of inoperable and             N      N      SP     N      N      N      N
      unregistered motor vehicles where accessory
      to a permitted principal use

12.   CONSTRUCTION, STORAGE, DISTRIBUTION AND
      INDUSTRIAL SERVICES

12.1  PERMITTED CONSTRUCTION, STORAGE,
      DISTRIBUTION AND INDUSTRIAL SERVICE USES
      (Must also comply with operating and
      development standards)

12.11 Laundry, dry-cleaning where clothes or other   N      N      SP     N      N      N      N
      fabrics are washed or cleaned; but not
      including carpets

12.12 Bakery                                         N      N      Y      N      N      N      N

12.13 Industrial services such as machine shop,      N      N      SP     N      N      N      Y
      welding

12.14 Commercial mover, associated storage           N      N      SP     N      N      N      Y
      facilities

12.15 Distribution center, parcel delivery,          N      N      N      N      N      Y      Y
      commercial mail delivery center
</Table>

<Page>

Section 4. Permitted Uses And Development Standards                           47

<Table>
<Caption>
Line                                                 CN     CRS    CS     CB     CLO    CRO    CM
--------------------------------------------------   ----   ----   ----   ----   ----   ----   ----
<S>                                                  <C>    <C>    <C>    <C>    <C>    <C>    <C>
12.16 Office, display or sales space of a            N      N      Y      N      N      N      N
      wholesale or distributing establishment,
      provided that not more than 25 per cent of
      the floor area is used for assembly of
      products

12.17 Shop and storage facilities for tradesmen      N      N      Y      N      N      N      N
      such as carpenter, plumber, electrician etc.
      engaged in the construction and repair of
      residential buildings and other light frame
      structures with incidental sale of building
      materials or products on the premises

12.18 Office, yard and storage facilities for        N      N      SP     N      N      N      N
      construction Company such as a general
      contractor, landscape contractor

12.19 Fuel oil dealer including sale and repair of   N      N      SP     N      N      N      N
      heating Equipment but not including bulk
      storage of fuel oil

13.   MANUFACTURING

13.1  PERMITTED MANUFACTURING USES
      (Must also comply with operating and
      development standards)

13.11 Light manufacturing                            N      N      N      N      N      N      Y

13.12 Laboratory engaged in research, experimental   N      N      N      N      N      Y      Y
      and testing activities, which may include
      the development of mock-ups and prototypes
      but not the manufacture of finished products

14.   UTILITY, COMMUNICATIONS AND TRANSPORTATION

14.1  PERMITED UTILITY, COMMUNICATIONS AND
      TRANSPORTATION USES (Must also comply with
      operating and development standards)

14.11 Substation, pumping station or automatic       SP     Y      Y      Y      Y      Y      Y
      telephone exchange of a regulated public
      utility

14.12 Radio, television studio, but without          N      Y      Y      N      N      Y      Y
      transmitting or receiving towers

14.13 Transmitting or receiving tower or antenna     N      N      N      N      N      N      Y
      for commercial activities other than those
      which are used exclusively for wireless
      communication facilities

14.14 Commercial ambulance service                   N      N      SP     N      N      N      N

14.15 Taxicab garage, parking area                   N      N      SP     N      N      N      N

14.16 Bus garage or storage facility                 N      N      SP     N      N      N      N

14.17 Parking, maintenance facilities for            N      N      SP     N      N      N      Y
      commercial vehicles where it is a principal
      use

14.18 Landing place for helicopters not including    N      N      N      N      N      SP     SP
      storage or maintenance facilities

14.19 Wireless communication facility (See section   SP*    SP*    SP*    SP*    SP*    SP*    SP*
      15) (* Y if concealed, see Section 15.3.2)

15.   OPEN-AIR, SEASONAL AND SPECIAL EVENTS

15.1  PERMITTED OPEN-AIR, SEASONAL AND SPECIAL
      EVENTS USES (Must also comply with operating
      and development standards)

15.11 Flea market                                    N      N      SP     N      N      N      N

15.12 Fund raising event conducted by Lexington      N      Y      Y      Y      N      N      N
      non-profit Organization provided permission,
      if required, is granted by the appropriate
      Town agency.

15.13 Seasonal sale of Christmas trees and wreaths   SP     Y      Y      N      SP     SP     SP
</Table>

<Page>

48                           Section 4. Permitted Uses And Development Standards

<Table>
<Caption>
Line                                                 CN     CRS    CS     CB     CLO    CRO    CM
--------------------------------------------------   ----   ----   ----   ----   ----   ----   ----
<S>                                                  <C>    <C>    <C>    <C>    <C>    <C>    <C>
16.   ACCESSORY USES FOR COMMERCIAL USES

16.1  Off-street parking for vehicles associated     Y      Y      Y      Y      Y      Y      Y
      with the Principal use; (See Section 11)
      NOTE: an off-street parking structure must
      comply with the dimensional Control for a
      building

16.2  Off-street loading for vehicles associated     Y      Y      Y      Y      Y      Y      y
      with the Principal use; (See Section 11)

16.3  Parking of trucks or other equipment to be     N      Y      Y      Y      Y      Y      Y
      used for the maintenance of the buildings
      and grounds only; shall be parked only in a
      garage or in an outdoor area not within the
      minimum yard for the principal building and
      shall be screened from the view of abutting
      lots and the street. (See Section 10)

16.4  Temporary overnight outdoor parking of         N      Y      Y      Y      Y      Y      Y
      freight carrying or material handling
      equipment

16.5  Building for storage of tools, lawn and        Y      Y      Y      Y      Y      Y      Y
      garden equipment and supplies subject to
      same dimensional controls as a principal
      building.

16.6  Dumpster or other refuse disposal equipment    Y      Y      Y      Y      Y      Y      Y
      subject to Section 10.

16.7  a. Convenience business use                    N      Y      Y      Y      Y      Y      y

      b. Commercial use not otherwise permitted in   N      SP     SP     SP     SP     SP     SP
      district provided the use is conducted
      entirely within the principal building, is
      conducted primarily for the employees or
      clientele of the principal use and not for
      the general public and there is no evidence
      of the conduct of the accessory use from the
      street or from any lot line.

16.8  Cafeteria, dining room, conference rooms,      N      Y      Y      Y      Y      Y      Y
      function rooms, recreational facilities for
      the employees and clientele of the principal
      use; if the use is not otherwise permitted
      in the district, it shall not be available
      to the general public and shall be conducted
      entirely within the principal building with
      no evidence of the existence of the use from
      the street or from any lot line

16.9  Accessory sign, as permitted by Section 13.    Y      Y      Y      Y      Y      Y      Y

16.10 Processing, storage and limited                N      N      N      N      N      Y      Y
      manufacturing of goods and materials related
      solely to research, experimental and testing
      activities

16.11 Uses accessory to permitted scientific         N      N      N      N      N      Y      Y
      research, development or related production
      activities

16.12 Temporary Building(s) or trailer(s)            Y      Y      Y      Y      Y      Y      Y
      incidental to the construction of a building
      or land. (See subsection 3.1.5)

17.   TEMPORARY USES

17.1  Temporary structures and uses not otherwise    SP     SP     SP     SP     SP     SP     SP
      permitted in the district provided the SPGA
      makes a finding that the proposed structure
      or use is compatible with the neighborhood
      (See subsection 3.1.5)

18.   PROHIBITED USES: ALL COMMERCIAL AND RESIDENTIAL
      DISTRICTS
</Table>

<Page>

Section 4. Permitted Uses And Development Standards                           49

<Table>
<Caption>
LINE                                                 CN     CRS    CS     CB     CLO    CRO    CM
--------------------------------------------------   ----   ----   ----   ----   ----   ----   ----
<S>                                                  <C>    <C>    <C>    <C>    <C>    <C>    <C>
18.1  Any use, structure, operation or activity      N      N      N      N      N      N      N
      not expressly permitted by this By-Law or
      not accessory to a permitted use, structure,
      operation or activity

18.2  Any use, structure, operation or activity      N      N      N      N      N      N      N
      whether otherwise permitted or accessory to
      a permitted use, structure, operation, or
      activity or not, which may be disturbing,
      detrimental or hazardous to persons working
      or living in the neighborhood by reason of
      special danger of fire, explosion, pollution
      of water ways or ground water, corrosive or
      toxic fumes or materials, excessive heat,
      smoke, soot, obnoxious dust or glare,
      excessively bright or flashing lights,
      electromagnetic radiation excessive noise or
      vibration

18.3  The following use are specifically             N      N      N      N      N      N      N
      prohibited. This is not intended to be an
      all inclusive list and the fact that a use,
      structure, operation or activity is not
      listed below does not mean it is permitted
      if it is excluded by 18.1 or 18.2.
      Prohibited uses are: junkyards (see
      definition), automobile graveyards,
      billboards.
</Table>

4.3 SUPPLEMENTARY COMMERCIAL USE REGULATIONS

4.3.1 RECYCLING COLLECTION STORE
In a recycling collection store (see Definition) sorting, limited cleaning,
compaction or shredding of containers or other light processing activities
necessary for efficient temporary storage and subsequent shipment to a recycling
processing facility is permitted.

4.4 HISTORIC PRESERVATION INCENTIVES

4.4.1  GENERAL OBJECTIVES
       a. Encourage preservation of buildings, structures, sites and settings,
          and elements of historical or architectural significance.
       b. Establish eligibility criteria for buildings, structures, sites and
          settings, and elements attaining protected status under
          paragraph 4.4.2.
       c. Expand economic options for the owner/investor, by broadening the
          permitted uses in various zoning districts and removing barriers
          presented by development standards governing those permitted uses.
       d. Permit the flexibility of development options by modifying dimensional
          requirements that might be an impediment to historic preservation.
       e. Provide incentives to preserve contributory elements of historic or
          architectural significance, such as settings and sites, objects,
          monuments, trees or other elements.

4.4.2  HISTORIC ELIGIBILITY DEFINED:
       a. Any historic element, as defined below, may qualify for eligibility
          under paragraph 4.4.2, Historic Preservation Incentives, if it is
          included on any of the following lists or surveys:
             1) National Register of Historic Places
             2) State (Commonwealth Of Massachusetts) Register Of Historic
                Places
             3) Inclusion by the Lexington Historical Commission in its
                Comprehensive Cultural Resources Survey, or identification by
                that Commission of historic and/or architectural significance
                and thereby potential inclusion in the Comprehensive Cultural
                Resources Survey
             4) Pending nominations in good standing to the National or State
                Registers
       b. Primary Qualifying Elements shall include the following: buildings,
          and other structures and

<Page>

50                           Section 4. Permitted Uses And Development Standards

          outbuildings located on the property.
       c. Secondary Qualifying Elements shall include the following: sites and
          setting, objects, monuments, trees or any element of historical,
          architectural and/or cultural significance which indicates their
          contributory value in establishing historical context.
       d. Priority in granting special permits under these historic preservation
          incentives shall, in all cases, be placed upon keeping buildings and
          structures IN PLACE, rather than moving them to other locations,
          provided that the existing siting can be shown to represent valid
          historical setting and context. Moving of buildings, structures and
          elements to other locations shall be considered only if no other
          preservation measures are practical or reasonable on the existing
          site, or if the proposed removal is to return a building, structure or
          element to an original or more historically accurate location. The
          SPGA shall determine the validity of any such requests.

4.4.3  SPECIAL PERMIT AUTHORIZED: The Board of Appeals, or the Planning Board
       where it is authorized to be the special permit granting authority
       (SPGA), may grant a special permit to authorize actions that would
       otherwise not comply with the provisions of this By-Law and that would
       allow the renovation, repair, adaptive reuse or, in limited instances,
       removal, of historic or architecturally significant buildings.

       a. The following uses, identified by the line in which they appear in
          Section 4.2 of this By-Law, that are not usually permitted in the
          districts identified below, may be allowed in those districts,
          provided the SPGA makes the findings listed in 4.4.4.:
             1.  1.13    Residential/Institutional/Agricultural Uses: the
                         conversion of single-family to two- family residences
                         in the RD, CB and CLO districts.
             2.  1.14    the conversion of single-family residences to
                         congregate living facilities in the CB and CLO
                         districts.
             3.  1.187   the conversion of municipal buildings to residential
                         use in the RM, CB and CLO districts.
             4.  1.21    the creation of Rooming Units in the CB, CLO and CN
                         districts.
             5.  1.22    the creation of Accessory Apartments in single-family
                         residences in the CB and CLO districts.
             6.  1.23    the creation of Bed and Breakfast Homes in the RT, RM,
                         RD, CN, CB, and CLO districts.
             7.  1.24    General Home Occupation Uses with a maximum of one
                         (1) employee other than an owner occupant and with a
                         maximum of 4 customers per hour, as an average
                         during the course of the business day, in all
                         districts.
             8.  1.25    Professional Office Home Occupation Uses with a maximum
                         of one (1) employee other than an owner occupant, in
                         all districts.
             9.  6.14    Office Uses, Professional Services, in CN districts.
             10. 6.15    Advertising/Editing, in CN and CB districts.
             11. 6.16    Employment Agency and similar uses, in CN districts.
             12. 6.17    Manufacturer's Representative and similar uses, in CN
                         districts.
             13. 6.18    Other Business and Administrative and similar uses, in
                         CN districts.
             14. 7.13    Professional and Business Services, Tailor, Dressmaker
                         And Shoe Repair, in CLO districts.
             15. 7.14    Real Estate Sales or Rental Office, in CS districts.
             16. 7.18    Repair of Household Appliances, in CLO districts.
             17. 7.28    Private Postal Service, in CB districts.
       b. Modifying 6.2, Development Standards for Offices (6.21 - 6.26) and
          7.3, Development Standards for Personal, Business Services (7.31 -
          7.32), provided that any negative impacts to the surrounding area can
          be feasibly mitigated.
       c. Modifying the standards in Table 2, Schedule Of Dimensional Controls,
          with regard to minimum: lot area; lot frontage; front, side and rear
          setbacks; maximum percentage of site coverage; and maximum
          height(stories).
       d. Modifying the standards in Section Five (5), Supplementary Use
          Regulations, sub-sections 5.2, 5.3, 5.4, 5.5.

<Page>

                                   EXHIBIT 11

                              CONSTRUCTION SCHEDULE

                             [AVAILABLE UPON REQUEST]

                               EXHIBIT 11, PAGE 1

<Page>

                                   EXHIBIT 12

                            PLAN SHOWING PARKING AREA

                             [AVAILABLE UPON REQUEST]

                               EXHIBIT 12, PAGE 1

<Page>

                                   EXHIBIT 13

                              CONSTRUCTION CONTRACT

                             [AVAILABLE UPON REQUEST]

                               EXHIBIT 13, PAGE 1

<Page>

                                   EXHIBIT 14

                            BUDGET FOR LEASEHOLD WORK

                             [AVAILABLE UPON REQUEST]

                               EXHIBIT 14, PAGE 1<Page>

                                                                   Exhibit 10.21

            [BOSTON UNIVERSITY SCHOOL OF MEDICINE LETTERHEAD]

March 26, 2003

Martin Feelisch, Ph.D.
2017 South Kirkwood Drive
Shreveport, Louisiana 71118

Dear Martin:

     I am pleased to offer you a position in the Section of Molecular
Medicine of the Department of Medicine at Boston University School of
Medicine. The details of this position are as follows:

1.  You will be proposed for appointment as Professor of Medicine.

2.  Your salary will be $165,000 per annum with the standard benefits
    package. We expect that you will contribute to your salary support
    through grant resources. to this end, NitroMed, Inc., will provide
    $65,000 per annum (with cost of living increases) for three years toward
    your salary. After year three, I expect that you will generate 80% of
    your salary from grants.

3.  NitroMed, Inc., has agreed to purchase up to $300,000 of equipment you
    requested during your visit on February 5, 2003, as needed.

4.  You will be given access for support for a postdoctoral fellow on the
    Cardiovascular Training Grant for up to three years.

5.  You will be provided access to a graduate student through the Graduate
    Program in Molecular Medicine.

6.  You will be given $50,000 per annum for supplies for three years as
    additional support from NitroMed, Inc.

7.  You will be given 1,500 sq. ft. of space in the Evans Biomedical Research
    Center through the Boston University School of Medicine. This space will
    be leased from Boston University by NitroMed, Inc., at $40 per sq. ft.
    for three years.

8.  We expect that you will work up to two days per week on NitroMed, Inc.
    projects under the terms of the existing license agreement between
    NitroMed, Inc. and the Trustees of Boston University. In addition, you
    will be given a position on the Scientific Advisory Board of NitroMed, Inc.

     We trust this letter details all the major issues we discussed, and
meets your projected needs adequately. We look forward with enthusiasm to
your joining us and to many years of gratifying academic productivity with
us. With best personal regards, we remain

                                Sincerely,

/s/ Joseph Loscalzo
Joseph Loscalzo, M.D., Ph.D.
Chairman, Department of Medicine

/s/ Aram Chobanian
Aram Chobanian, M.D.
Dean and Provost
BU School of Medicine

/s/ Michael Loberg
Michael Loberg, Ph.D.
Chief Executive Officer
NitroMed, Inc.

I have read and accepted the position as outlined above.

/s/ Martin Feelisch             May 5, 2003
-------------------------------------------
Martin Feelisch, Ph.D.                Date

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