Document:

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                                                                   Exhibit 10.10

                              KENNEDY BISCUIT LOFTS

                            Cambridge, Massachusetts

                                    LANDLORD
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                  KENNEDY LOFTS ASSOCIATES LIMITED PARTNERSHIP,
                       a Massachusetts limited partnership

                                     TENANT
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                                ACUSPHERE, INC.,
                             a Delaware corporation

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                              KENNEDY BISCUIT LOFTS

                   Lease to Bechtel Infrastructure Corporation

                                TABLE OF CONTENTS

<TABLE>
<S>                                                                           <C>
Section 1.1 - RECITALS........................................................  1
Section 1.2 - DEFINITIONS.....................................................  1
Section 2.1 - PREMISES........................................................  3
Section 2.2 - APPURTENANT RIGHTS..............................................  3
Section 2.3 - LANDLORD'S RESERVATIONS.........................................  4
Section 2.4 - PARKING.........................................................  4
Section 2.5 - COMMENCEMENT DATE...............................................  5
Section 3.1 - ANNUAL FIXED RENT...............................................  6
Section 3.2 - REAL ESTATE TAXES...............................................  6
Section 3.3 - UTILITY CHARGES.................................................  7
Section 3.4 - ABOVE-STANDARD SERVICES.........................................  7
Section 3.5 - NO OFFSETS......................................................  7
Section 4.1 - CONSENT REQUIRED FOR TENANT'S ALTERATIONS.......................  8
Section 4.2 - OWNERSHIP OF ALTERATIONS........................................  8
Section 4.3 - CONSTRUCTION REQUIREMENTS FOR ALTERATIONS.......................  9
Section 4.4 - PAYMENT FOR TENANT ALTERATIONS.................................. 10
Section 5.1 - MAINTENANCE OF BUILDING AND COMMON AREAS BY LANDLORD............ 10
Section 5.2 - MAINTENANCE OF PREMISES BY TENANT............................... 11
Section 5.3 - DELAYS IN LANDLORD'S SERVICES................................... 11
Section 6.1 - PERMITTED USES.................................................. 12
Section 6.2 - LAWS AND REGULATIONS............................................ 13
Section 6.3 - RULES AND REGULATIONS........................................... 13
Section 6.4 - SAFETY COMPLIANCE............................................... 14
Section 6.5 - LANDLORD'S ENTRY................................................ 14
Section 6.6 - FLOOR LOAD...................................................... 14
Section 6.7 - PERSONAL PROPERTY TAX........................................... 15
Section 6.8 - ASSIGNMENT AND SUBLEASES........................................ 15
Section 7.1 - INDEMNITY....................................................... 18
Section 7.2 - LIABILITY INSURANCE............................................. 19
Section 7.3 - PERSONAL PROPERTY AT RISK....................................... 20
Section 7.4 - LANDLORD'S INSURANCE............................................ 21
Section 7.5 - WAIVER OF SUBROGATION........................................... 21
Section 8.1 - RESTORATION FOLLOWING CASUALTIES................................ 21
Section 8.2 - LANDLORD'S TERMINATION ELECTION................................. 22
Section 8.3 - TENANT'S TERMINATION ELECTION................................... 22
</TABLE>

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<TABLE>
<S>                                                                            <C>
Section 8.4   - CASUALTY AT EXPIRATION OF LEASE............................... 23
Section 8.5   - EMINENT DOMAIN................................................ 23
Section 8.6   - RENT AFTER CASUALTY OR TAKING................................. 24
Section 8.7   - TAKING AWARD.................................................. 24
Section 9.1   - TENANT'S DEFAULT.............................................. 24
Section 9.2   - DAMAGES....................................................... 26
Section 9.3   - CUMULATIVE RIGHTS............................................. 27
Section 9.4   - LANDLORD'S SELF-HELP.......................................... 27
Section 9.5   - ENFORCEMENT EXPENSES.......................................... 28
Section 9.6   - LATE CHARGES AND INTEREST ON OVERDUE PAYMENTS................. 28
Section 9.7   - LANDLORD'S RIGHT TO NOTICE AND CURE........................... 28
Section 10.1  - SUBORDINATION................................................. 29
Section 10.2  - ATTORNMENT BY TENANT.......................................... 29
Section 10.3  - AMENDMENT TO LEASE BY LANDLORD'S MORTGAGEE.................... 30
Section 10.4  - PREPAYMENT OF RENT NOT TO BIND MORTGAGEE...................... 30
Section 10.5  - TENANT'S DUTY TO NOTIFY MORTGAGEE; MORTGAGEE'S ABILITY
                TO CURE....................................................... 31
Section 10.6  - ESTOPPEL CERTIFICATES......................................... 31
Section 11.1  - CONDITION OF PREMISES......................................... 33
Section 12.1  - NOTICE OF LEASE............................................... 34
Section 12.2  - NOTICES....................................................... 34
Section 12.3  - SUCCESSORS AND LIMITATION ON LIABILITY OF THE LANDLORD........ 35
Section 12.4  - WAIVERS....................................................... 35
Section 12.5  - ACCEPTANCE OF PARTIAL PAYMENTS OF RENT........................ 35
Section 12.6  - INTERPRETATION AND PARTIAL INVALIDITY......................... 36
Section 12.7  - QUIET ENJOYMENT............................................... 36
Section 12.8  - BROKERAGE..................................................... 36
Section 12.9  - SURRENDER OF PREMISES AND HOLDING OVER........................ 37
Section 12.10 - GROUND LEASE.................................................. 38
Section 12.11 - CAMBRIDGE EMPLOYMENT PLAN..................................... 38
Section 12.12 - AUTHORIZATION................................................. 38
Section 12.13 - MISCELLANEOUS................................................. 38
</TABLE>

Exhibit A       -   Basic Lease Terms
Exhibit A-1     -   Floor Plan
Exhibit B       -   Legal Description
Exhibit C       -   List of Tenant's Final Plans
Exhibit D       -   Standard Services
Exhibit E       -   Rules and Regulations

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                                      LEASE

                                    ARTICLE I

                            RECITALS AND DEFINITIONS

Section 1.1 - RECITALS.

     This Lease (this "Lease") is entered into as of February 1, 2001 by and
between KENNEDY LOFTS ASSOCIATES LIMITED PARTNERSHIP, a Massachusetts limited
partnership (the "Landlord") and ACUSPHERE, INC., a Delaware corporation (the
"Tenant").

     In consideration of the mutual covenants herein set forth, the Landlord and
the Tenant do hereby agree to the terms and conditions set forth in this Lease.

Section 1.2 - DEFINITIONS.

     The following Terms have the meanings indicated or referred to below:

     "Additional Rent" means all charges payable by the Tenant pursuant to this
Lease other than Annual Fixed Rent, including without implied limitation the
Tenant's parking charges as provided in Section 2.4; amounts payable for special
services pursuant to Section 3.5; the Landlord's share of any sublease or
assignment proceeds pursuant to Section 6.8.

     "Annual Fixed Rent" - As defined in Exhibit A.

     "Building" means The Kennedy Biscuit Lofts located at 129 Franklin Street,
Cambridge, Massachusetts in which the Premises are located.

     "Commencement Date" - See Exhibit A.

     "Common Building Areas" means those portions of the commercial area of the
Building which are not part of the Premises and to which the Tenant has
appurtenant rights pursuant to Section 2.2.

     "External Causes" means collectively, (i) Acts of God, war, civil
commotion, fire, flood or other casualty, strikes or other extraordinary labor
difficulties, shortages of labor or materials or equipment in the ordinary
course of trade, government order or regulations or other cause not reasonably
within the Landlord's control and not due to the fault or neglect of the
Landlord, and (ii)

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any act, failure to act or neglect of the Tenant or the Tenant's servants,
agents, employees, licensees or any person claiming by, through or under the
Tenant, which delays the Landlord in the performance of any act required to be
performed by the Landlord under this Lease.

     "Land" means the parcel of land situated in Cambridge, Massachusetts,
described in Exhibit B.

     "Landlord's Original Address" - See Exhibit A.

     "Lease Year" means each period of one year during the Term commencing on
the Commencement Date or on any anniversary thereof.

     "Permitted Uses" - See Section 6.1.

     "Premises" means that portion of the Building which the Tenant is leasing
at any given time pursuant to the provisions of this Lease. See Exhibit A and
Section 2.1.

     "Property" means the Land and the Building.

     "Tenant's Original Address" - See Exhibit A.

     "Term" - See Exhibit A.

     "University Park" means the area in Cambridge, Massachusetts, bounded on
the North side by Massachusetts Avenue and Green Street, on the East side by
Landsdowne, Cross and Purrington Streets, on the South side by Pacific Street
and on the West side by Brookline Street.

                                   ARTICLE II
                                PREMISES AND TERM

Section 2.1 - PREMISES.

     The Landlord hereby leases to the Tenant, and the Tenant hereby leases from
the Landlord, for the Term, the Premises. The Premises shall exclude all
portions of the Building not shown on Exhibit A-1 and the entry and lobby of the
commercial area of the Building, the common stairways and stairwells,
sprinklers, electric and telephone closets, janitor closets, and pipes, ducts,
conduits, wires and

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appurtenant fixtures and equipment serving exclusively or in common other parts
of the Building. The Premises shall also exclude the Common Building Areas. The
Premises shall include the main office area, and kitchenette as shown on Exhibit
A-1. The Tenant acknowledges that, except as expressly set forth in this Lease,
there have been no representations or warranties made by or on behalf of the
Landlord with respect to the Premises, the Building or the Property or with
respect to the suitability of any of them for the conduct of the Tenant's
business. The taking of possession of the Premises by the Tenant shall establish
that the Premises and the Building were at such time in satisfactory condition,
order and repair.

Section 2.2 - APPURTENANT RIGHTS.

     The Tenant shall have, as appurtenant to the Premises, the nonexclusive
right to use in common with others, subject to reasonable rules of general
applicability to occupants of the Building from time to time made by the
Landlord of which the Tenant is given notice: (i) a dedicated entry, vestibules
lobby and the common stairways, in the Common Building Areas mechanical rooms,
electric and telephone closets, janitor closets and the pipes, sprinklers,
ducts, conduits, wires and appurtenant fixtures and equipment serving the
Premises in common with others, (ii) common walkways and driveways necessary or
reasonably convenient for access to the Building, (iii) access to the loading
area subject to rules and regulations then in effect (v) the common toilets,
corridors and vestibule of the Common Building Areas and (iv) access to a rest
room to be shared with the staff of Bright Horizons.

Section 2.3 - LANDLORD'S RESERVATIONS.

     The Landlord reserves the right from time to time, without unreasonable
interference with the Tenant's use: (i) to install, use, maintain, repair,
replace and relocate for service to the Premises and other parts of the
Building, or either, pipes, ducts, conduits, wires and appurtenant fixtures and
equipment, wherever located in the Premises or the Building, and (ii) to alter
or relocate any other common facility, provided that advance notice is given to
Tenant and that substitutions are substantially equivalent or better.

Section 2.4 - PARKING.

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     The Landlord shall provide and the Tenant shall pay for Parking Privileges
for use by the Tenant's employees and business invitees and visitors in
accordance with Exhibit A. The Tenant's Parking Privileges shall be on a
nonexclusive basis. The Tenant agrees that it and all persons claiming by,
through and under it, shall at all times abide by the reasonable rules and
regulations promulgated by the Landlord with respect to the use of the parking
facilities provided by the Landlord pursuant to this Lease.

     As provided in Exhibit A, the Tenant shall pay to the Landlord for the
Tenant's Parking Privileges the monthly rent at which the Landlord from time to
time offers to make Parking Privileges available to tenants and other users of
such parking facilities which pay rent therefor. Monthly parking charges shall
constitute Additional Rent and shall be payable at the time and in the fashion
in which Annual Fixed Rent under this Lease is payable, or at the option of the
Landlord, the Tenant shall enter into a separate lease agreement for such
parking rights for a period which shall have the same expiration date as the
Term and which, if this Lease provides for options on the part of the Tenant to
extend, shall be automatically extended upon the exercise of any of such
options.

Section 2.5 - COMMENCEMENT DATE.

     "Commencement Date" shall mean the date on which Annual Fixed Rent and
Additional Rent shall begin to accrue as more particularly set forth in Exhibit
A. Landlord shall deliver the Premises to Tenant on the Commencement Date in its
current "as is" condition, free of all tenants, occupants and their property,
broom-clean.

                                   ARTICLE III
                             RENT AND OTHER PAYMENTS

Section 3.1 - ANNUAL FIXED RENT.

     From and after the Commencement Date, and on the first day of each month
thereafter, the Tenant shall pay, without notice or demand, monthly installments
of one-twelfth (1/12th) of the Annual Fixed Rent in effect and applicable to the
Premises in advance for each full calendar month of the Term and of the
corresponding fraction of said one-twelfth (1/12th) for any fraction of a
calendar month at the

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beginning and end of the Term if it starts at the middle of a month. The Annual
Fixed Rent applicable to the Premises during the Term shall be as set forth in
Exhibit A.

Section 3.2 - Real Estate Taxes

From and after the Commencement Date, during the Term, included in the Annual
Base Rent is the annual Real Estate Tax for the Premises.

Section 3.3 - UTILITY CHARGES.

     During the Term, the Tenant shall pay directly to the provider of the
service, all separately metered charges for electricity and other services and
utilities furnished to the Premises. This includes electricity for lighting of
Tenant's Premises, office and other equipment and the operation of the HVAC fans
in the fan coil units located in the Premises. Landlord will provide heated
water for heating, chilled water for air conditioning available twenty-four
hours per day. Tenant shall be responsible for maintenance of the HVAC unit
located within the Premises.

Section 3.4 - ABOVE-STANDARD SERVICES.

     If the Tenant requests and the Landlord elects to provide any services to
the Tenant in addition to those described in Exhibit D, the Tenant shall pay to
the Landlord, as Additional Rent, the amount billed by Landlord for such
services at Landlord's standard rates as from time to time in effect. If the
Tenant has requested that such services be provided on a regular basis, the
Tenant shall, if requested by the Landlord, pay for such services at the time
and in the fashion in which Annual Fixed Rent under this Lease is payable.
Otherwise, the Tenant shall pay for such additional services within thirty (30)
days after receipt of an invoice from the Landlord. Tenant shall pay for such
work within thirty (30) days after receipt of an invoice from Landlord.

Section 3.5 - NO OFFSETS.

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                                   ARTICLE IV
                                   ALTERATIONS

Section 4.1 - CONSENT REQUIRED FOR TENANT'S ALTERATIONS.

     The Tenant shall not make alterations or additions to the Premises except
in accordance with the building standards from time to time in effect, with
construction rules and regulations from time to time promulgated by Landlord and
applicable to tenants in the Building, and with plans and specifications
therefor first approved by the Landlord. Such plans shall be incorporated into
this Lease as Exhibit C. Landlord's approval shall not be deemed to have
unreasonably withheld with respect to any alterations or additions which (i)
involve or might affect any structural or exterior element of the Building, any
area or element outside of the Premises, or any facility serving any area of the
Building outside of the Premises or any publicly accessible major interior
features of the Building, (ii) will require unusual expense to readapt the
Premises to normal use unless the Tenant first give assurance acceptable to the
Landlord that such readaptation will be made prior to such termination without
expense to the Landlord, or (iii) would not be compatible with existing
mechanical or electrical, plumbing, HVAC or other systems or floor load capacity
in the Building, in each case, as reasonably determined by the Landlord, or (iv)
would require HVAC, electrical, water usage in excess of base building capacity
allocated to Tenant (on a square foot basis), or (v) would require usage in
excess of remaining base building HVAC, electrical, water or other system
capacity. For any alterations, the Landlord agrees to be reasonable and timely
with regard to Tenant's request for approvals. At such time landlord grants
approval it shall notify Tenant as to whether or not such alteration or
additions must be removed upon termination of the lease.

Section 4.2 - OWNERSHIP OF ALTERATIONS.

     All alterations and additions shall be part of the Building and owned by
the Landlord, unless at the time of the termination of this Lease the Landlord
shall specify that the same must be removed. All movable equipment and
furnishings not attached to the Premises shall remain the property of the Tenant
and shall be removed by the Tenant upon termination or expiration of this Lease.
The Tenant shall repair any damage caused by the removal of any alterations,
additions or personal property from the Premises.

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Section 4.3 - CONSTRUCTION REQUIREMENTS FOR ALTERATIONS.

     All construction work by the Tenant shall be done in a good and workmanlike
manner employing only first-class materials and in compliance with all
applicable laws and all lawful ordinances, regulations and orders of Government
authority and insurers of the Building. The Landlord or Landlord's authorized
agent may (but without any implied obligation to do so) inspect the work of the
Tenant at reasonable times and with prior notice to Tenant and shall give notice
of observed defects. All of the Tenant's alterations and additions and
installation of furnishings shall be coordinated with any work being performed
by the Landlord and in such manner as to maintain harmonious labor relations and
not to damage the Building or interfere with Building construction or operation
and, except for installation of furnishings, shall be performed by the
Landlord's general contractor or by contractors or workmen first approved by the
Landlord, which approval the Landlord agrees not to unreasonably withhold or
delay. The Tenant, before starting any work, shall receive and comply with
Landlord's reasonable construction rules and regulations and shall cause
Tenant's contractors to comply therewith, shall secure all licenses and permits
necessary therefor and shall deliver to the Landlord a statement of the names of
all its contractors and subcontractors and the estimated cost of all labor and
material to be furnished by them and security satisfactory to the Landlord
protecting the Landlord against liens arising out of the furnishing of such
labor and material; and cause each contractor to carry worker's compensation
insurance in statutory amounts covering all the contractors and subcontractors'
employees and comprehensive general public liability insurance with such limits
as the Landlord may require reasonably, but in no event less than $1,000,000
(individual)/$3,000,000 (Occurrence) or in such other amounts as Landlord may
reasonably require based on the nature of the work to be performed covering
personal injury and death and property damage (all such insurance to be written
in companies approved reasonably by the Landlord and insuring the Landlord, such
individuals and entities affiliated with the Landlord and University Park as the
Landlord may designate, and the Tenant as well as the contractors and to contain
a requirement for at least thirty (30) days notice to the Landlord prior to
cancellation, non-renewal or material change), and to deliver to the Landlord
certificates of all such insurance.

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Section 4.4 - PAYMENT FOR TENANT ALTERATIONS.

     The Tenant agrees to pay promptly when due the entire cost of any work done
on the Premises by the Tenant, its agents, employees or independent contractors,
and not to cause or permit any liens for labor or materials performed or
furnished in connection therewith to attach to the Premises or the Property and
promptly to discharge any such liens which may so attach. If any such lien shall
be filed against the Premises or the Property and the Tenant shall fail to cause
such lien to be discharged within twenty (20) days after the filing thereof, the
Landlord may cause such lien to be discharged by payment, bond or otherwise
without investigation as to the validity thereof or as to any offsets or
defenses which the Tenant may have with respect to the amount claimed. The
Tenant shall reimburse the Landlord, as Additional Rent, for any cost so
incurred and shall indemnify and hold harmless the Landlord from and against any
and all claims, costs, damages, liabilities and expenses (including attorneys'
fees) which may be incurred or suffered by the Landlord by reason of any such
lien or its discharge.

                                    ARTICLE V
              RESPONSIBILITY FOR CONDITION OF BUILDING AND PREMISES

Section 5.1 - MAINTENANCE OF BUILDING AND COMMON AREAS BY LANDLORD.

     Except as otherwise provided in Article 8, the Landlord shall make such
repairs to the major structural elements of the Building, including the roof,
exterior walls and floor slabs as may be necessary to keep and maintain the same
in serviceable condition and maintain and make such repairs to the Common
Building Areas as may be necessary to keep them in good order, condition and
repair, including without limitation, the glass in the exterior walls of the
Building, and all mechanical systems and equipment serving the Building and not
exclusively serving the Premises. The Landlord shall further perform the
services on Exhibit D hereto. The Landlord shall in no event be responsible to
the Tenant for any condition in the Premises or the Building caused by an act or
negligent act of the Tenant, or any invitee or contractor of the Tenant.

Section 5.2 - MAINTENANCE OF PREMISES BY TENANT.

     The Tenant shall keep neat and clean and maintain in good order, condition
and repair the Premises and every part thereof and all

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Building and mechanical equipment exclusively serving the Premises, reasonable
wear and tear excepted and further excepting those repairs for which the
Landlord is responsible pursuant to Section 5.1 and damage by fire or other
casualty and as a consequent of the exercise of the power of eminent domain. The
Tenant shall be responsible for the cost of repairs which may be made necessary
by reason of damages to common areas in the Building by the Tenant, or any of
the contractors or invitees of the Tenant.

Section 5.3 - DELAYS IN LANDLORD'S SERVICES.

     The Landlord shall not be liable to the Tenant for any compensation or
reduction of rent by reason of inconvenience or annoyance or for loss of
business arising from the necessity of the Landlord or its agents entering the
Premises for any purposes authorized in this Lease, or for repairing the
Premises or any portion of the Building except to the extent due to the willful
or negligent acts or omissions of Landlord. In case the Landlord is prevented or
delayed from making any repairs, alterations or improvements, or furnishing any
services, or performing any other covenant or duty to be performed on the
Landlord's part, by reason of any External Cause, the Landlord shall not be
liable to the Tenant therefor, nor, except as expressly otherwise provided in
this Lease, shall the Tenant be entitled to any abatement or reduction of rent
by reason thereof, nor shall the same give rise to a claim in the Tenant's favor
that such failure constitutes actual or constructive, total or partial, eviction
from the Premises. The Landlord reserves the right to stop any service or
utility system when necessary by reason of accident or emergency, until
necessary repairs have been completed; provided, however, that in each instance
of stoppage, the Landlord shall exercise reasonable diligence to eliminate the
cause thereof. Except in case of emergency repairs, the Landlord will give the
Tenant reasonable advance notice of any contemplated stoppage and will use
reasonable efforts to avoid unnecessary inconvenience to the Tenant by reason
thereof. In no event shall the Landlord have any liability to the Tenant for the
unavailability of heat, light water or sewer, or any utility or service to be
provided by the Landlord to the extent that such unavailability is caused by
External Causes.

                                   ARTICLE VI
                                TENANT COVENANTS

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

Section 6.1 - PERMITTED USES.

     The Tenant shall occupy the Premises only for the Permitted Uses, which is
defined as office and general business use as may be permitted by University
Park zoning, and Tenant shall not injure or deface the Premises or the Property,
nor permit in the Premises any auction sale. The Tenant shall comply with any
and all OSHA regulations and shall hold Landlord harmless from any violations of
such regulations within Tenant's control. The Tenant shall comply with all
requirements of public authorities and of the Board of Fire Underwriters in
connection with methods of storage, use and disposal thereof. The Tenant shall
not permit in the Premises any nuisance, or the emission from the Premises of
any objectionable noise, odor or vibration, nor use or devote the Premises or
any part thereof for any purpose which is contrary to law or ordinance or liable
to invalidate or increase premiums for any insurance on the Building or its
contents or liable to render necessary any alteration or addition to the
Building, nor commit or permit any waste in or with respect to the Premises,
nor, except as permitted in the following paragraph, generate or dispose of any
oil, toxic substances, hazardous wastes, or hazardous materials (each a,
"Hazardous Material"), or, except as permitted in the following paragraph,
permit the same in or on the Premises or any parking areas provided for under
this Lease. The Tenant shall not, except as permitted in the following
paragraph, dump, flush or in any way introduce any Hazardous Materials into
septic, sewage or other waste disposal systems serving the Premises or any
parking areas provided for under this Lease.

Section 6.2 - LAWS AND REGULATIONS.

     The Tenant shall comply with all federal, state and local laws,
regulations, ordinances, executive orders, Federal guidelines, and similar
requirements in effect from time to time affecting the premises or the Tenant's
use of the premises, including without limitation, City of Cambridge ordinances
with respect to hazardous waste and any such requirements pertaining to
employment opportunity, anti-discrimination and affirmative action.

Section 6.3 - RULES AND REGULATIONS.

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     (a) The Tenant shall not obstruct in any manner any portion of the Property
not hereby leased; shall not permit the placing of any signs, curtains, blinds,
shades, awnings, aerials or flagpoles, or the like, visible from outside the
Premises other than those signs, curtains and the like shown on Tenant's Plans;
and shall comply with all reasonable rules and regulations of uniform
application to all occupants of the Building now or hereafter made by the
Landlord, of which the Tenant has been given notice, for the care and use of the
Property and the parking facilities relating thereto. The Landlord shall not be
liable to the Tenant for the failure of other occupants of the Building to
conform to any such rules and regulations. The Tenant shall not erect any signs,
symbols, advertisement or the like on the Premises or Building other than as
described in (b) without first obtaining the Landlord's written approval, which
approval shall not be unreasonably withheld. All such signs shall be purchased
and erected at the sole cost of the Tenant.

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Section 6.4 - SAFETY COMPLIANCE.

     The Tenant shall keep the Premises equipped with all safety appliances
required by law or ordinance or any other regulations of any public authority
because of any non-office use made by the Tenant and to procure all licenses and
permits so required because of such use and, if requested by the Landlord, do
any work so required because of such use, it being understood that the foregoing
provisions shall not be construed to broaden in any way the Tenant's Permitted
Uses. Tenant shall conduct such periodic tests, evaluations or certifications of
safety appliances and equipment as are required or recommended in accordance
with generally accepted standards to ensure that such safety appliances and
equipment remain in good working order, and shall provide to Landlord copies of
such reports, evaluations and certifications as they are periodically obtained
by Tenant.

Section 6.5 - LANDLORD'S ENTRY.

     The Tenant shall permit the Landlord and its agents, after reasonable
notice except in the case of emergencies, to enter the Premises (i) at all
reasonable hours for the purpose of inspecting or of making repairs to the same,
provided such entry does not unreasonably interfere with Tenant's use of the
Premises or interfere with Tenant's business, and (ii) showing the Premises to
prospective tenants (during the last twelve (12) months of the Term), and to
purchasers and mortgagees, in each case at all reasonable times.

Section 6.6 - FLOOR LOAD.

     The Tenant shall not place a load upon any floor in the Premises exceeding
the floor load per square foot of area which such floor was designed to carry
and which is allowed by law; and not move any safe, vault or other heavy
equipment in, about or out of the Premises except in such manner and at such
time as the Landlord shall in each instance authorize, which authorization shall
not be unreasonably withheld or delayed. The Tenant's machines and mechanical
equipment shall be placed and maintained by the Tenant at the Tenant's expense
in settings sufficient to absorb or prevent vibration or noise that may be
transmitted to the Building structure or to any other space in the Building.

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Section 6.7 - PERSONAL PROPERTY TAX.

     The Tenant shall pay promptly when due all taxes which may be imposed upon
personal property (including, without limitation, fixtures and equipment) in the
Premises to whoever assessed.

Section 6.8 - ASSIGNMENT AND SUBLEASES.

     The Tenant shall not assign, mortgage, pledge, hypothecate or otherwise
transfer this Lease, or sublet (which term, without limitation, shall include
granting of concessions, licenses and the like) the whole or any part of the
Premises without, in each instance, having first received the consent of the
Landlord in its sole discretion.

     Notwithstanding anything to the contrary contained in this Section, Tenant
shall have the right to assign or otherwise transfer this Lease or the Premises,
or part of the Premises, without obtaining the prior consent of Landlord, (a) to
its parent entity or to a wholly owned subsidiary or to an entity which is
wholly owned by the same entity which wholly owns Tenant, provided that (i) the
transferee shall, prior to the effective date of the transfer, deliver to
Landlord instruments evidencing such transfer and its agreement to assume and be
bound by all the terms, conditions and covenants of this Lease to be performed
by Tenant, all in form reasonably acceptable to Landlord, and (ii) at the time
of such transfer there shall not be an uncured Event of Default under this
Lease; or (b) to the purchaser of all or substantially all of its assets, or to
any entity into which the Tenant may be merged or consolidated (along with all
or substantially all of its assets) (the "Acquiring Company"), provided that (i)
the net assets of the Acquiring Company at the time of the transfer or merger
shall not be less than the net assets of Tenant at the time of the signing of
this Lease, (ii) the Acquiring Company continues to operate the business
conducted in the Premises consistent with the Permitted Uses described in
Exhibit A, (iii) the Acquiring Company shall assume in writing, in form
reasonably acceptable to Landlord, all of Tenant's obligations under this Lease,
(iv) Tenant shall provide to Landlord such additional information regarding the
Acquiring Company as Landlord shall reasonably request, and (v) Tenant shall pay
Landlord's reasonable third-party expenses incurred in connection therewith.
Unless Landlord shall have objected to the information or items described in
(b)(i), (iii) and (iv) above within ten (10) business days of their receipt by
Landlord, then Landlord

                                       13
<PAGE>   17

shall be deemed to have waived its right to object thereto. The transfers
described in this paragraph are hereinafter referred to as "Permitted
Transfers."

     Whether or not the Landlord consents, or is required to consent, to any
assignment or subletting, the Tenant named herein shall remain fully and
primarily liable for the obligations of the tenant hereunder, including, without
limitation, the obligation to pay Annual Fixed Rent and Additional Rent provided
under this Lease.

     The Tenant shall give the Landlord notice of any proposed sublease of the
Premises or assignment of the Lease, whether or not Landlord's consent is
required hereunder, specifying the provisions of the proposed subletting or
assignment, including (i) the name and address of the proposed subtenant or
assignee, (ii) a copy of the proposed subtenant's or assignee's most recent
annual financial statement, (iii) all of the terms and provisions upon which the
proposed subletting or assignment is to be made and such other information
concerning the proposed subletting or assignment is to be made and such other
information concerning the proposed subtenant or assignee as the Tenant has
obtained in connection with the proposed subletting or assignment. The Tenant
shall reimburse the Landlord promptly for reasonable legal and other expense
incurred by the Landlord in connection with any request by the Tenant for
consent to any assignment or subletting. If this Lease is assigned, or if the
Premises or any part thereof is sublet or occupied by anyone other than the
Tenant, the Landlord may collect rent and other charges from the assignee,
sublessee or occupant and apply the net amount collected to the rent and other
charges herein reserved, but no such assignment, subletting, occupancy or
collection shall be deemed a waiver of the prohibitions contained in this
Section 6.8 or the acceptance of the assignee, sublessee or occupant as a
tenant, or a release of the Tenant from the further performance by the Tenant of
covenants on the part of the Tenant herein contained. The Tenant shall pay to
the Landlord fifty percent (50%) of any amounts the Tenant receives from any
subtenant or assignee as rent, additional rent or other forms of compensation or
reimbursement which are in excess of the sum of (i) the then due and payable
proportionate monthly share of Annual Fixed Rent, Additional Rent and all other
monies due to Landlord pursuant to this Lease (allocable in the case of a
sublease to that portion of the Premises being subleased), and (ii) any
reasonable and necessary expenses incurred and paid by Tenant in connection with
such sublease or assignment, amortized over the term of the sublease or the

                                       14
<PAGE>   18

remainder of the Term of this Lease in the event of any assignment. The
preceding sentence shall not apply to any Permitted Transfers. The consent by
the Landlord to an assignment or subletting shall not be construed to relieve
the Tenant from obtaining the express consent in writing of the Landlord to any
further assignment or subletting.

     Landlord may elect, by delivery of notice to Tenant within thirty (30) days
of receipt of written notice from Tenant of any proposed assignment of this
Lease or sublease of the Premises, prior to approving or disapproving any
proposed assignment or sublease, to repossess the space proposed to be assigned
or sublet. Landlord may thereafter lease the repossessed space in such a manner
as the Landlord may in its sole discretion determine. In the event Landlord
elects to repossess the space as provided above, then all of the Tenant's rights
and obligations hereunder with respect to the repossessed space shall cease and
shall be of no further force and effect. The provisions of this paragraph shall
not apply to Permitted Transfers.

                                   ARTICLE VII
                             INDEMNITY AND INSURANCE

Section 7.1 - INDEMNITY.

     To the maximum extent this agreement may be made effective according to
law, the Tenant agrees to defend, indemnify and save harmless the Landlord from
and against all claims, loss, or damage of whatever nature arising from any
breach by Tenant of any obligation of Tenant under this Lease beyond applicable
notice and cure periods or from any act, omission or negligence of the Tenant,
or the Tenant's contractors, licensees, invitees, agents, servants or employees,
or arising from any accident, injury or damage whatsoever caused to any person
or property, occurring after the date that possession of the Premises is first
delivered to the Tenant and until the end of the Term and thereafter, so long as
the Tenant is in occupancy of any part of the Premises, in or about the Premises
or arising from any accident, injury or damage occurring outside the Premises
but within the Building, on the Land, on the access roads and ways, in the
parking facilities provided pursuant to the Lease, within University Park or any
adjacent area maintained by Landlord or any individual or entity affiliated with
Landlord, where such accident, injury or damage

                                       15
<PAGE>   19

results from an act or omission on the part of the Tenant or the Tenant's agents
or employees, licensees, invitees, servants or contractors, provided that the
foregoing indemnity shall not include any cost or damage arising from any act,
omission or negligence of the Landlord, or the Landlord's contractors,
licensees, invitees, agents, servants or employees.

     Landlord agrees to defend, indemnify and save harmless Tenant from legal
action, damages, loss, liability and any other expense in connection with loss
of life, bodily or personal injury or property damage, arising from or out of
the intentional or willful misconduct or gross negligence of Landlord, its
agents, employees, licensees, servants, invitees or contractors, which occur in
or about the Premises, outside the Premises but within the Building, on the
Land, on the access roads and ways, in the parking facilities provided pursuant
to the Lease, within University Park or any adjacent area maintained by
Landlord, except to the extent that such loss of life, bodily or personal injury
or property damage is due to the willful misconduct or act, omission or neglect
of Tenant, its agents, contractors, employees, licensees, invitees or servants.

     The foregoing indemnities and hold harmless agreements shall include
indemnity against reasonable attorneys' fees and all other costs, expenses and
liabilities incurred in connection with any such claim or proceeding brought
thereon, and the defense thereof.

Section 7.2 - LIABILITY INSURANCE.

     The Tenant agrees to maintain in full force from the date upon which the
Tenant first enters the Premises for any reason, throughout the Term, and
thereafter, so long as the Tenant is in occupancy of any part of the Premises, a
policy of comprehensive general liability insurance written by a company having
an Alfred M. Best Co. rating of A or better, and a financial size rating of XII
or higher, under which the Landlord (and any individuals or entities affiliated
with the Landlord and University Park, any ground lessor and any holder of a
mortgage on the Property of whom the Tenant is notified by the Landlord,
collectively with the Landlord, the "Named Insureds") and the tenant, as their
interests appear under this Lease are named as insureds, and under which the
insurer provides a contractual liability endorsement insuring against all cost,
expense and liability arising out of or based upon any and all claims,
accidents, injuries and damages described in Section 7.1, in the broadest form
of such

                                       16
<PAGE>   20

coverage from time to time available. Each such policy shall be noncancellable
and non-amendable (to the extent that any proposed amendment reduces the limits
or the scope of the insurance required in this Lease) with respect to the
Landlord and such ground lessors and mortgagees without thirty (30) days prior
notice to the Landlord and such ground lessors and mortgagees and a certificate
evidencing Tenant's insurance required hereunder shall be delivered to the
Landlord. The minimum limits of liability of such insurance as of the
Commencement Date shall be Three Million Dollars ($3,000,000.00) for combined
bodily injury (or death) and damage to property (per occurrence), and from time
to time during the Term such limits of liability shall be reasonably increased
to reflect such higher limits as are customarily required pursuant to new leases
of space in the Boston-Cambridge area with respect to similar properties and
similar uses.

Section 7.3 - PERSONAL PROPERTY AT RISK.

     The Tenant agrees to maintain in full force at all times throughout the
Term, policy(s) of all risk property damage insurance, naming Landlord (and the
Additional Named Insureds) and the Tenant as insureds as their interests may
appear, covering all of Tenant's leasehold improvements and alterations to the
extent of their full replacement costs as updated from time to time during the
Term.

     The Tenant agrees that all of the furnishings, fixtures, equipment, effects
and property of every kind, nature and description of the Tenant and of all
persons claiming by, through or under the Tenant which, during the continuance
of this Lease or any occupancy of the Premises by the Tenant or anyone claiming
under the Tenant, may be on the Premises or elsewhere in the Building or on the
Lot or parking facilities provided hereby, shall be at the sole risk and hazard
of the Tenant, and if the whole or any part thereof shall be destroyed or
damaged by fire, water or otherwise, or by the leakage or bursting of water
pipes, steam pipes, or other pipes, by theft or from any other cause, no part of
said loss or damage is to be charged to or be borne by the Landlord, except that
the Landlord shall in no event be exonerated from any liability to the Tenant or
to any person, for any injury, loss, damage or liability to the extent such
exoneration is prohibited by law.

Section 7.4 - LANDLORD'S INSURANCE.

                                       17
<PAGE>   21

     The Landlord shall carry such casualty and liability insurance upon and
with respect to operations at the building, as may from time to time be deemed
reasonably prudent by the Landlord or required by any mortgagee holding a
mortgage thereon or any ground lessor of the Land, and in any event, insurance
against loss by fire and the risks now covered by extended coverage endorsement
No. 4 in an amount at least equal to the full replacement cost of the Building,
exclusive of foundations, site preparation and other nonrecurring construction
costs.

Section 7.5 - WAIVER OF SUBROGATION.

     Any insurance carried by either party with respect to the Building, Land,
Premises, parking facilities or any property therein or occurrences thereon
shall without further request by either party, if it can be so written without
additional premium, or with an additional premium which the other party elects
to pay, include a clause or endorsement denying to the insurer rights of
subrogation against the other party to the extent rights have been waived by the
insured prior to occurrence of injury or loss. Each party, notwithstanding any
provisions of this Lease to the contrary, hereby waives any rights of recovery
against the other for injury or loss, including, without limitation, injury or
loss caused by negligence of such other party, due to hazards covered by
insurance actually carried or required to be carried hereunder.

                                  ARTICLE VIII
                           CASUALTY AND EMINENT DOMAIN

Section 8.1 - RESTORATION FOLLOWING CASUALTIES.

     If, during the Term, the Building or Premises shall be damaged by fire or
casualty, subject to the exceptions and limitations provided below, the Landlord
shall proceed promptly to exercise reasonable efforts to restore the Building or
Premises to substantially the condition thereof at the time of such damage, but
the Landlord shall not be responsible for delay in such restoration which may
result from any cause beyond the reasonable control of the Landlord. The
Landlord shall have no obligation to expend in the reconstruction of the
Building more than the actual amount of the insurance proceeds made available to
the Landlord by its insurer and not retained by the Landlord's mortgagee or
ground lessor. Any restoration of the

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<PAGE>   22

Building or the Premises shall be altered to the extent necessary to comply with
then current laws and applicable codes.

Section 8.2 - LANDLORD'S TERMINATION ELECTION.

     If the Landlord reasonably determines that the amount of insurance proceeds
available to the Landlord is insufficient to cover the cost of restoring the
Building or if in the reasonable opinion of the Landlord the Building has been
so damaged that it is appropriate for the Landlord to raze or substantially
alter the Building, then the Landlord may terminate this Lease by giving notice
to the Tenant within ninety (90) days after the date of the casualty or such
later date as is required to allow the Landlord a reasonable time to make either
such determination. Any such termination shall be effective on the date
designated in such notice from the Landlord, but in any event, not later than
ninety (90) days after such notice, and if no date is specified, effective upon
the delivery of such notice.

Section 8.3 - TENANT'S TERMINATION ELECTION.

     Unless the Landlord has earlier advised the Tenant of the Landlord's
election to terminate this Lease pursuant to Section 8.2, or to restore the
Premises and maintain this Lease in effect pursuant to Section 8.1, the Tenant
shall have the right after the expiration of ninety (90) days after any casualty
which materially impairs a material portion of the Premises to give a written
notice to the Landlord requiring the Landlord within ten (10) days thereafter to
exercise or waive any right of the Landlord to terminate this Lease pursuant to
Section 8.2 as a result of such casualty and if the Landlord fails to give
timely notice to the Tenant waiving any right under Section 8.2 to terminate
this Lease based on such casualty, the Tenant shall be entitled, at any time
until the Landlord has given notice to the Tenant waiving such termination
right, to give notice to the Landlord terminating this Lease.

Section 8.4 - CASUALTY AT EXPIRATION OF LEASE.

     If the Premises shall be damaged by fire or casualty in such a manner that
the Premises cannot, in the ordinary course, reasonably be expected to be
repaired within one hundred twenty (120) days from the commencement of repair
work and such damage occurs within the last two (2) years of the Term (as the
same may be extended), either party

                                       19
<PAGE>   23

shall have the right, by giving notice to the other not later than sixty (60)
days after such damage, to terminate this Lease. This Lease shall terminate as
of the date of any such notice given from Tenant to Landlord. This Lease shall
terminate ten (10) days after the giving of any such notice from Landlord to
Tenant, provided that Tenant has not validly exercised any then existing option
to extend the Term hereof (as provided in Section 2.6 of this Lease) within such
ten (10)-day period.

Section 8.5 - EMINENT DOMAIN.

     Except as hereinafter provided, if the Premises, or such portion thereof as
to tender the balance (if reconstructed to the maximum extent practicable in the
circumstances) unsuitable for the Tenant's purposes, shall be taken by
condemnation or right of eminent domain, the Landlord or the Tenant shall have
the right to terminate this Lease by notice to the other of its desire to do so,
provided that such notice is given not later than thirty (30) days after the
effective date of such taking. If so much of the Building shall be so taken that
the Landlord determines that it would be appropriate to raze or substantially
alter the Building, the Landlord shall have the right to terminate this Lease by
giving notice to the Tenant of the Landlord's desire to do so not later than
thirty (30) days after the effective date of such taking.

     Should any part of the Premises be so taken or condemned during the Term,
and should this Lease be not terminated in accordance with the foregoing
provisions, the Landlord agrees to use reasonable efforts to put what may remain
of the Premises into proper condition for use and occupation as nearly like the
condition of the Premises prior to such taking as shall be practicable, subject,
however, to applicable laws and codes then in existence and to the availability
of sufficient proceeds from the eminent domain taking not retained by any
mortgagee or ground lessor.

Section 8.6 - RENT AFTER CASUALTY OR TAKING.

     If the Premises shall be damaged by fire or other casualty, except as
provided below, the Annual Fixed Rent and Additional Rent shall be justly and
equitably abated and reduced according to the nature and extent of the loss of
use thereof suffered by the Tenant. If the fire or other casualty was caused by
the Tenant, such abatement shall be made only to the extent that the Landlord is
fully

                                       20
<PAGE>   24

compensated therefor by any lost rent insurance. In the event of a taking which
reduces the area of the Premises, a just proportion of the Annual Fixed Rent
shall be abated for the period of such taking.

Section 8.7 - TAKING AWARD.

     Except as otherwise provided in Section 8.6, the Landlord shall have and
hereby reserves and excepts, and the Tenant hereby grants and assigns to the
Landlord, all rights to recover for damages to the Building and the Land, and
the leasehold interest hereby created, and to compensation accrued or hereafter
to accrue by reason of such taking, damage or destruction, as aforesaid, and by
way of confirming the foregoing, the Tenant hereby grants and assigns to the
Landlord, all rights to such damages or compensation. Nothing contained herein
shall be construed to prevent the Tenant from prosecuting in any condemnation
proceedings a claim for relocation expenses, provided that such action shall not
affect the amount of compensation otherwise recoverable by the Landlord from the
taking authority pursuant to the preceding sentence.

                                   ARTICLE IX
                                     DEFAULT

Section 9.1 - TENANT'S DEFAULT.

     Each of the following shall constitute an Event of Default:

     (a) Failure on the part of the Tenant to pay the Annual Fixed Rent,
Additional Rent or other charges for which provision is made herein on or before
the date on which the same become due and payable, if such condition continues
for ten (10) days after Landlord delivers to Tenant notification of such
failure. Notwithstanding the foregoing, Landlord shall not be obligated to
notify Tenant of its failure to pay Annual Fixed Rent, Additional Rent or other
charges more than two (2) times during each Lease Year and if in any Lease Year
after the Landlord has twice provided notice to the Tenant of such failures, the
Tenant thereafter fails to make any payment referred in the preceding sentence
on or before its due date, such failure shall constitute an Event of Default.

     (b) Failure on the part of the Tenant to perform or observe any other term
or condition contained in this Lease if the Tenant shall not cure such failure
within thirty (30) days after notice from the

                                       21
<PAGE>   25

Landlord to the Tenant thereof, provided that in the case of breaches of
obligations under this Lease which are susceptible to cure but cannot be cured
within thirty (30) days through the exercise of due diligence, so long as the
Tenant commences such cure within thirty (30) days, such breach remains
susceptible to cure, and the Tenant diligently pursues such cure, such breach
shall not be deemed to create an Event of Default.

     (c) The taking of the estate hereby created on execution or by other
process of law; or a judicial declaration that the Tenant is bankrupt or
insolvent according to law; or any assignment of the property of the Tenant for
the benefit of creditors; or the appointment of a receiver, guardian,
conservator, trustee in bankruptcy or other similar officer to take charge of
all or any substantial part of the Tenant's property by a court of competent
jurisdiction; or the filing of an involuntary petition against the Tenant under
any provisions of the bankruptcy act now or hereafter enacted if the same is not
dismissed within ninety (90) days; the filing by the Tenant of any voluntary
petition for relief under provisions of any bankruptcy law now or hereafter
enacted.

     If an Event of Default shall exist, then, in any such case, whether or not
the Term shall have begun, the Landlord lawfully may, immediately or at any time
thereafter, give notice to the Tenant specifying the Event of Default and this
Lease shall come to an end on the date specified therein as fully and completely
as if such date were the date herein originally fixed for the expiration of the
Lease Term, and the Tenant will then quit and surrender the Premises to the
Landlord, but the Tenant shall remain liable as hereinafter provided.

Section 9.2 - DAMAGES.

     In the event that this Lease is terminated by Landlord pursuant to the
terms of Section 9.1 hereof, the Tenant covenants to pay to the Landlord
forthwith on the Landlord's demand, as compensation, an amount (the "Lump Sum
Payment") equal to the excess, if any, of the discounted present value of the
total rent reserved for the remainder of the Term over the then discounted
present fair rental value of the Premises for the remainder of the Term. In
calculating the rent reserved, there shall be included, in addition to the
Annual Fixed Rent and all Additional Rent, the value of all other considerations
agreed to be paid or performed by the Tenant over the remainder of the Term. In
addition, the Tenant shall pay punctually to the Landlord

                                       22
<PAGE>   26

all the sums ("Periodic Payments") and perform all the obligations which the
Tenant covenants in this Lease to pay and to perform in the same manner and to
the same extent and at the same time as if this Lease had not been terminated.
In calculating the amounts to be paid by the Tenant under the foregoing
covenant, the Tenant shall be credited with the net proceeds of any rent
obtained by reletting the Premises, after deducting all the Landlord's
reasonable expenses in connection with such reletting, including, without
limitation, all repossession costs, brokerage commissions, fees for legal
services and expenses of preparing the Premises for such reletting. The Tenant
shall also be entitled to credit against the last periodic payments which would
otherwise become due the amount, if any, paid to the Landlord as Lump Sum
Payment.

     The Landlord shall use its best efforts to (i) relet the Premises, or any
part or parts thereof, for a term or terms which may, at the Landlord's option,
exceed or be equal to or less than the period which would otherwise have
constituted the balance of the Term, and may grant such concessions and free
rent, in each case as the Landlord in its reasonable commercial judgment
considers advisable or necessary to relet the same, and (ii) make such
alterations, repairs and improvements in the Premises as the Landlord in its
reasonable commercial judgment considers advisable or necessary to relet the
same. Provided Landlord complies with the terms of the preceding sentence, no
action of the Landlord in accordance with the foregoing or failure to relet or
to collect rent under reletting shall operate to release or reduce the Tenant's
liability and the Landlord shall be entitled to seek to rent other properties of
the Landlord prior to reletting the Premises.

Section 9.3 - CUMULATIVE RIGHTS.

     The specific remedies to which the Landlord may resort under the terms of
this Lease are cumulative and are not intended to be exclusive of any other
remedies or means of redress to which it may be lawfully entitled in case of any
breach or threatened breach by the Tenant of any provisions of this Lease. In
addition to the other remedies provided in this Lease, the Landlord shall be
entitled to the restraint by injunction of the violation or attempted or
threatened violation of any of the covenants, conditions or provisions of this
Lease or to a decree compelling specific performance of any such covenants,
conditions or provisions. Nothing contained in this Lease shall limit or
prejudice the right of the Landlord to prove for and

                                       23
<PAGE>   27

obtain in proceedings for bankruptcy, insolvency or like proceedings by reason
of the termination of this Lease, an amount equal to the maximum allowed by any
statute or rule of law in effect at the time when, and governing the proceedings
in which, the damages are to be proved, whether or not the amount be greater,
equal to, or less than the amount of the loss or damages referred to above.

Section 9.4 - LANDLORD'S SELF-HELP.

     If the Tenant shall at any time default in the performance of any
obligation under this Lease, the Landlord shall have the right, but not the
obligation, upon reasonable (but in no event less than ten (10) days') notice to
the Tenant (except in case of emergency in which case no notice need be given),
to perform such obligation unless Tenant shall have cured such default within
such ten (10) day period. The Landlord may exercise its rights under this
Section without waiving any other of its rights or releasing the Tenant from any
of its obligations under this Lease.

Section 9.5 - ENFORCEMENT EXPENSES.

     Each party hereto shall promptly reimburse the other for all costs and
expenses, including without limitation reasonable legal fees, incurred by such
party in exercising and enforcing its rights under this Lease following the
other party's failure to comply with its obligations hereunder, whether or not
such failure constitutes an Event of Default pursuant to Sections 9.1 or 9.7
hereof.

Section 9.6 - LATE CHARGES AND INTEREST ON OVERDUE PAYMENTS.

     In the event that any payment of Annual Fixed Rent or Additional Rent shall
remain unpaid for a period of ten (10) days after the same are due, there shall
become due to the Landlord from the Tenant, as Additional Rent and as
compensation for the Landlord's extra administrative costs in investigating the
circumstances of late rent, a late charge of two percent (2%) of the amount
overdue. In addition, any Annual Fixed Rent and Additional Rent not paid when
due shall bear interest from the date due to the Landlord until paid at the
variable rate (the "Default Interest Rate") equal to the higher of (i) the rate
at which interest accrues on amounts not paid when due under the terms of the
Landlord's financing for the Building, as from time to time in

                                       24
<PAGE>   28

effect, and (ii) one hundred and twenty-five percent (125%) of the Prime Rate
(as defined in Section 3.3 (b) hereof).

Section 9.7 - LANDLORD'S RIGHT TO NOTICE AND CURE.

     The Landlord shall in no event be in default in the performance of any of
the Landlord's obligations hereunder unless and until the Landlord shall have
failed to perform such obligations within twenty (20) days, or such additional
time as is reasonably required to correct any such default (provided such breach
is susceptible to cure and Landlord shall have commenced to cure within said
twenty (20) days and shall diligently prosecute such cure to completion), after
notice by the Tenant to the Landlord expressly specifying wherein the Landlord
has failed to perform any such obligation.

                                    ARTICLE X
                     MORTGAGEES' AND GROUND LESSORS' RIGHTS

Section 10.1 - SUBORDINATION OF LEASE.

     This Lease and the estate of Tenant hereunder shall be subject and
subordinate to any ground lease, deed of trust, mortgage lien or charge or any
reciprocal easement agreement or other operating agreement which now encumber or
which at any time hereafter may encumber the Premises (such ground lease, deed
of trust, mortgage lien or charge, or any reciprocal easement agreement or other
operating agreement and any replacement, renewal, modification, consolidation or
extension thereof being hereinafter referred to as an "Encumbrance"). Any
Encumbrance shall be prior and paramount to this Lease and to the right of
Tenant hereunder and all persons claiming through and under Tenant, or
otherwise, in the Premises. Tenant's acknowledgment and agreement of
subordination provided for in this Section shall be self-operative and no
further instrument of subordination shall be required. However, Tenant, on
Tenant's behalf, and on behalf of all persons claiming through and under Tenant,
covenants and agrees that, from time to time at the request of Landlord or the
holder of any Encumbrance, Tenant will execute and deliver any necessary or
proper instruments or certificates reasonably necessary to acknowledge or
confirm the priority of the Encumbrance over this Lease and the subordination of
this Lease thereto or to evidence Tenant's consent to any Encumbrance. Tenant
agrees that it will not subordinate this

                                       25
<PAGE>   29

Lease to any other lien against the Property or the Premises without obtaining
prior written consent from Landlord's lender, if any. Notwithstanding the
foregoing, any holder of an Encumbrance may elect to the extent possible that
this Lease shall have priority over such Encumbrance and, upon notification of
such election by the holder of such Encumbrance, this Lease shall be deemed to
have priority over such Encumbrance, whether this Lease is dated prior to or
subsequent to the date of such Encumbrance.

Section 10.2 - ATTORNMENT BY TENANT.

     Tenant agrees that if the holder of any Encumbrance or any persons claiming
under said Encumbrance shall succeed to the interest of Landlord in this Lease,
Tenant shall recognize and attorn to said holder as Landlord under the terms of
this Lease. Tenant agrees that it will, upon the request of Landlord, execute,
acknowledge and deliver any and all instruments necessary or desirable to give
effect or notice of such attornment and failure of Tenant to execute any such
document or instrument on demand shall constitute a default by Tenant under the
terms of this Lease. If within twenty (20) days after submission of such
instrument Tenant fails to execute the same, Landlord is hereby authorized to
execute the same as attorney-in-fact for Tenant.

Section 10.3. - AMENDMENT TO LEASE BY LANDLORD'S MORTGAGEE.

     In the event Landlord's mortgagee succeeds to the interest of Landlord in
this Lease, and in the event such mortgagee is advised by its counsel that all
or any portion of the Rent payable under this Lease is or may be deemed to be
unrelated business income within the meaning of the Internal Revenue Code or
regulations issued thereunder, such mortgagee may elect to amend unilaterally
the calculation of Rent so that none of the Rent payable to such mortgagee under
this Lease will constitute unrelated business income; PROVIDED, HOWEVER, in no
event shall such amendment increase Tenant's payment obligations or other
liability under the Lease or reduce the Landlord's obligations under this Lease.
Tenant agrees to execute any document such mortgagee deems necessary to effect
such amendment to this Lease in accordance with this Section 10.3.

Section 10.4 - PREPAYMENT OF RENT NOT TO BIND MORTGAGEE.

                                       26
<PAGE>   30

     No Annual Fixed Rent, Additional Rent, or any other charge payable to the
Landlord shall be paid more than thirty (30) days prior to the due date thereof
under the terms of this Lease and payments made in violation of this provision
shall (except to the extent that such payments are actually received by a
mortgagee or ground lessor) be a nullity as against such mortgagee or ground
lessor and the Tenant shall be liable for the amount of such payments to such
mortgagee or ground lessor.

                                       27
<PAGE>   31

Section 10.5 - TENANT'S DUTY TO NOTIFY MORTGAGEE; MORTGAGEE'S ABILITY TO CURE.

     No act or failure to act on the part of the Landlord which would entitle
the Tenant, under the terms of this Lease, or any law, to be relieved of the
Tenant's obligations to pay Annual Fixed Rent or Additional Rent hereunder or to
terminate this Lease, shall result in a release or termination of such
obligations of the Tenant or a termination of this Lease unless (i) the Tenant
shall have first given written notice of the Landlord's act or failure to act to
the Landlord's mortgagees or ground lessors, if any, of whose identity and
address the Tenant shall have been given notice, specifying the act or failure
to act on the part of the Landlord which would give basis to the Tenant's
rights; and (ii) such mortgagees or ground lessors, after receipt of such
notice, have failed or refused to correct or cure the condition complained of
(if the condition complained of is susceptible to cure) within a reasonable time
thereafter, which shall include a reasonable time for such mortgagee or ground
lessors, to obtain possession of the Property if possession is necessary for the
mortgagee or ground lessor to correct or cure the condition and if the mortgagee
or ground lessor notifies the Tenant of its intention to take possession of the
Property and correct or cure such condition.

Section 10.6 - ESTOPPEL CERTIFICATES.

     The Tenant shall from time to time, upon not less than fifteen (15) days'
prior written request by the Landlord and at Landlord's expense on a form
provided by Landlord, execute, acknowledge and deliver to the Landlord a
statement in writing certifying to the Landlord or an independent third party,
with a true and correct copy of this Lease attached thereto, and provided that
each of the following shall be true, (i) that this Lease is unmodified and in
full force and effect (or, if there have been any modifications, that the same
is in full force and effect as modified and stating the modifications); (ii)
that the Tenant has no knowledge of any defenses, offsets or counterclaims
against its obligations to pay the Annual Fixed Rent and Additional Rent and to
perform its other covenants under this Lease (or if there are any defenses,
offsets, or counterclaims, setting them forth in reasonable detail); (iii) that
there are no known uncured defaults of the Landlord or the Tenant under this
Lease (or if there are known defaults, setting them forth in reasonable detail);
(iv) the dates to which the Annual Fixed Rent, Additional Rent and other charges
have been paid; (v) that the Tenant

                                       28
<PAGE>   32

has accepted, is satisfied with, and is in full possession of the Premises,
including all improvements, additions, and alterations thereto required to be
made by Landlord under the Lease; (vi) that the Landlord has satisfactorily
complied with all of the requirements and conditions precedent to the
commencement of the Term of the Lease as specified in the Lease; (vii) the Term,
the Commencement Date, and any other relevant dates and that the Tenant has been
in occupancy since the Commencement Date and paying rent since the specified
dates; (viii) that no monetary or other considerations, including, but not
limited to, rental concessions for Landlord, special tenant improvements or
Landlord's assumption of prior lease obligations of Tenant have been granted to
Tenant by Landlord for entering into the Lease, except as specified; (ix) that
Tenant has no notice of a prior assignment, hypothecation, or pledge of rents or
of the Lease; (x) that the Lease represents the entire agreement between
Landlord and Tenant; (xi) that no prepayment will be valid as to the party to
whom such certificate is addressed without the consent of such party; (xii) that
any notice to Tenant may be given it by certified or registered mail, return
receipt requested, or delivered, at the Premises, or at another address
specified; and (xiii) such other matters with respect to the Tenant and this
Lease as the Landlord may reasonably request and are reasonably acceptable to
Tenant's counsel. On the Commencement Date, the Tenant shall, at the request of
the Landlord, promptly execute, acknowledge and deliver to the Landlord a
statement in writing that the Commencement Date has occurred, that the Annual
Fixed Rent has begun to accrue and that the Tenant has taken occupancy of the
Premises. Any statement delivered pursuant to this Section may be relied upon by
any prospective purchaser, mortgagee or ground lessor of the Premises and shall
be binding on the Tenant.

                                       29
<PAGE>   33

                                   ARTICLE XI
                              CONDITION OF PREMISES

Section 11.1 - CONDITION OF PREMISES.

     Tenant acknowledges that it is accepting the Premises in its present
"as-is" condition with no expectation that Landlord will or should perform or
contribute towards the cost of any leasehold improvements required to prepare
the Premises for Tenant's occupancy.

                                   ARTICLE XII
                                  MISCELLANEOUS

Section 12.1 - NOTICE OF LEASE.

     The Tenant agrees not to record this Lease, but upon request of either
party, both parties shall execute and deliver a memorandum of this Lease in form
appropriate for recording or registration, an instrument acknowledging the
Commencement Date of the Term, and if this Lease is terminated before the Term
expires, an instrument in such form acknowledging the date of termination.

Section 12.2 - NOTICES.

     Whenever any notice, approval, consent, request, election, offer or
acceptance is given or made pursuant to this Lease, it shall be in writing.
Communications and payments shall be addressed, if to the Landlord, at the
Landlord's Address for Notices as set forth in Exhibit A or at such other
address as may have been specified by prior notice to the Tenant; and if to the
Tenant, at the Tenant's Original Address or at such other place as may have been
specified by prior notice to the Landlord. Any communication so addressed shall
be deemed duly given on the earlier of (i) the date received or (ii) on the
third business day following the day of mailing if mailed by registered or
certified mail, return receipt requested. If the Landlord by notice to the
Tenant at any time designates some other person to receive payments or notices,
all payments or notices thereafter by the Tenant shall be paid or given to the
agent

                                       30
<PAGE>   34

designated until notice to the contrary is received by the Tenant from the
Landlord.

Section 12.3 - SUCCESSORS AND LIMITATION ON LIABILITY OF THE LANDLORD.

     The obligations of this Lease shall run with the land, and this Lease shall
be binding upon and inure to the benefit of the parties hereto and their
respective successors and assigns, except that the original landlord named
herein and each successor landlord shall be liable only for obligations accruing
during the period of its ownership. The obligations of the Landlord shall be
binding upon the assets of the Landlord consisting of an equity ownership of the
Property but not upon other assets of the Landlord and neither the Tenant, nor
anyone claiming by, under or through the Tenant, shall be entitled to obtain any
judgment creating personal liability on the part of the Landlord or enforcing
any obligations of the Landlord against any assets of the Landlord other than an
equity ownership of the Property.

Section 12.4 - WAIVERS.

     The failure of the Landlord or the Tenant to seek redress for violation of,
or to insist upon strict performance of, any covenant or condition of this Lease
shall not be deemed a waiver of such violation nor prevent a subsequent act,
which would have originally constituted a violation, from having all the force
and effect of an original violation. The receipt by the Landlord of Annual Fixed
Rent or Additional Rent with knowledge of the breach of any covenant of this
Lease shall not be deemed a waiver or such breach. No provision of this Lease
shall be deemed to have been waived by either party. No consent or waiver,
express or implied, by either party to or of any breach of any agreement or duty
shall be construed as a waiver or consent to or of any other breach of the same
or any other agreement or duty.

Section 12.5 - ACCEPTANCE OF PARTIAL PAYMENTS OF RENT.

     No acceptance by the Landlord of a lesser sum than the Annual Fixed Rent
and Additional Rent then due shall be deemed to be other than a partial
installment of such rent due, nor shall any endorsement or statement on any
check or any letter accompanying any check or payment as rent be deemed an
accord and satisfaction, and the Landlord may accept such check or payment
without prejudice to the Landlord's

                                       31
<PAGE>   35

right to recover the balance of such installment or pursue any other remedy in
this Lease provided. The delivery of keys to any employee of the Landlord or to
the Landlord's agent or any employee thereof shall not operate as a termination
of this Lease or a surrender of the Premises.

Section 12.6 - INTERPRETATION AND PARTIAL INVALIDITY.

     If any term of this Lease, or the application thereof to any person or
circumstances, shall to any extent be invalid or unenforceable, the remainder of
this Lease, or the application of such term to persons or circumstances other
than those as to which it is invalid or unenforceable, shall not be affected
thereby, and each term of this Lease shall be valid and enforceable to the
fullest extent permitted by law. The titles of the Articles are for convenience
only and not to be considered in construing this Lease. This Lease contains all
of the agreements of the parties with respect to the subject matter thereof and
supersedes all prior dealings between them with respect to such subject matter,
and shall not be amended or modified, except by written instrument executed by
the parties hereto.

Section 12.7 - QUIET ENJOYMENT.

     So long as the Tenant pays Annual Fixed Rent and Additional Rent, performs
all other Tenant covenants of this Lease and observes all conditions hereof, the
Tenant shall peaceably and quietly have, hold and enjoy the Premises free of any
claims by, through or under the Landlord.

Section 12.8 - BROKERAGE.

     The Tenant represents and warrants that it has had no dealings with any
broker or agent in connection with this Lease and shall indemnify and hold
harmless the Landlord from claims for any brokerage commission arising out of
the Tenant's actions. In the event of any claims against the Landlord predicated
upon Tenant's breach of the foregoing representations and warranty the Tenant
agrees to defend the same and indemnify and hold the Landlord harmless against
any such claim.

Section 12.9 - SURRENDER OF PREMISES AND HOLDING OVER.

                                       32
<PAGE>   36

     The Tenant shall surrender possession of the Premises on the last day of
the Term and the Tenant waives the right to any notice of termination or notice
to quit. The Tenant covenants that upon the expiration or sooner termination of
this Lease, it shall, without notice, deliver up and surrender possession of the
Premises in the same condition in which the Tenant has agreed to keep the same
during the continuance of this Lease and in accordance with the terms hereof,
normal wear and tear excepted, first removing therefrom all goods and effects of
the Tenant, any additions or alterations Tenant has elected to take in
accordance with Section 4.2, and any leasehold improvements funded by Landlord
specified for removal pursuant to Section 4.2, and repairing all damage caused
by such removal. Upon the expiration of this Lease or if the Premises should be
abandoned by the Tenant, or this Lease should terminate for any cause, and at
the time of such expiration, vacation, abandonment or termination, the Tenant or
Tenant's agents, subtenants or any other person should leave any property of any
kind or character on or in the Premises, the fact of such leaving of property on
or in the Premises shall be conclusive evidence of intent by the Tenant, and
individuals and entities deriving their rights through the Tenant, to abandon
such property so left in or upon the Premises, and such leaving shall constitute
abandonment of the property. Landlord shall have the right and authority without
notice to the Tenant or anyone else, to remove and destroy, or to sell or
authorize disposal of such property, or any part thereof, without being in any
way liable to the Tenant therefor and the proceeds thereof shall belong to the
Landlord as compensation for the removal and disposition of such property.

     If the Tenant fails to surrender possession of the Premises upon the
expiration or sooner termination of this Lease, the Tenant shall pay to
Landlord, as rent for any period after the expiration or sooner termination of
this Lease an amount equal to twice the Annual Fixed Rent and the Additional
Rent required to be paid under this Lease as applied to any period in which the
Tenant shall remain in possession. Acceptance by the Landlord of such payments
shall not constitute a consent to a holdover hereunder or result in a renewal or
extension of the Tenant's rights of occupancy. Such payments shall be in
addition to and shall not affect or limit the Landlord's right of reentry,
Landlord's right to collect such damages as may be available at law, or any
other rights of the Landlord under this Lease or as provided by law.

                                       33
<PAGE>   37

Section 12.10 - GROUND LEASE.

     Landlord leases the Land pursuant to the ground lease (the "Ground Lease")
between the Landlord as lessee and Massachusetts Institute of Technology ("MIT")
as lessor dated as of August 20, 1986.

Section 12.11 - CAMBRIDGE EMPLOYMENT PLAN.

     The Tenant agrees to sign an agreement with the Employment and Training
Agency designated by the City Manager of the City of Cambridge as provided in
subsections (a)-(g) of Section 24-4 of Ordinance Number 1005 of the City of
Cambridge, adopted April 23, 1984.

Section 12.12 - AUTHORIZATION.

     Landlord and Tenant each represent and warrant that the persons signing
below have full authority and have been duly authorized to execute this Lease.

Section 12.13 - MISCELLANEOUS.

     In the event of a conflict between the terms contained in this Lease
(without regard to Exhibit A attached hereto) and the terms contained in Exhibit
A attached hereto, the terms contained in this Lease (without regard to Exhibit
A attached hereto) shall govern.

                                       34
<PAGE>   38

     WITNESS the execution hereof under seal as of the day and year first above
written.

                                        LANDLORD:

                                        KENNEDY LOFTS ASSOCIATES LIMITED
                                        PARTNERSHIP, a Massachusetts limited
                                        partnership

                                        By:  Kennedy Lofts Associates,
                                             Its general partner

                                             By:  Forest City 129 Franklin,
                                                  Inc.

                                                  By: /s/ Gayle Farris
                                                     ---------------------------
                                                  Name: Gayle Farris
                                                        ------------------------
                                                  Title: President
                                                         -----------------------

                                        TENANT:

                                        ACUSPHERE, INC.,
                                        a Delaware corporation

                                        By: /s/ Steven W. Delaney
                                           -------------------------------------
                                        Name: Steven W. Delaney
                                              ----------------------------------
                                        Title: VP Finance and Administration
                                               ---------------------------------

                                       35
<PAGE>   39

                                    EXHIBIT A

                                BASIC LEASE TERMS

Annual Fixed Rent:                 $48.00 per total rentable square foot.

Security Deposit:                  None

Term:                              Approximately nineteen (19) months starting
                                   on the Commencement Date plus or minus
                                   adjustment for other than beginning or end of
                                   month.

Landlord's Original Address:       Forest City 129 Franklin Street, Inc.
                                   Terminal Tower, 50 Public Square,
                                   Ste. 1100, Cleveland, Ohio 44113-2267
                                   Attention:  James Ratner, President

Landlord's Address for Notices:    Landlord's Original Address with a copy to:

                                   Forest City 129 Franklin Street, Inc.
                                   26 Landsdowne Street
                                   Cambridge, Massachusetts 02139-4234
                                   Attention: Gayle Farris
                                              President

Tenant's Address for Notices:      Acusphere, Inc.
                                   38 Sidney Street
                                   Cambridge, MA 02139
                                   Attention: Steve Delaney

Landlord's Mortgagee:              Massachusetts Housing Finance Agency
                                   50 Milk Street
                                   Boston, Massachusetts 02109

<PAGE>   40

Landlord's Ground Lessor:          Massachusetts Institute of Technology
                                   Office of the Treasurer
                                   238 Main Street, Suite #220
                                   Cambridge, Massachusetts 02142
                                   Attention: Director of Real Estate

Premises:                          Approximately 2,500 rentable square feet
                                   located on the first floor of the Building as
                                   shown on the floor plan attached hereto as
                                   Exhibit A-1.

Parking Privileges:                During the Term, Landlord shall provide, upon
                                   Tenant's request from time to time, one (1)
                                   parking space in the garage structure at 55
                                   Franklin Street. During the Term, the Tenant
                                   shall pay the market rate for such parking
                                   space (presently $185.00 per pass, per
                                   month). Tenant shall have the right to lease
                                   additional parking spaces, as available, on a
                                   month to month basis.

Permitted Uses:                    The Tenant shall occupy the Premises only for
                                   the Permitted Uses, which is defined as
                                   office and general business purposes, as
                                   permitted by University Park zoning.

Rentable Floor Area of the         2,500 square feet.
Premises:

Commencement Date:                 As of February 1, 2001.

<PAGE>   41

                                   EXHIBIT A-1

                                   FLOOR PLAN

<PAGE>   42

                                  Exhibit A-1

                               [MAP OF FLOOR PLAN]

                                                         129 FRANKLIN STREET
                                                         UNIVERSITY PARK MIT
                                                         FOREST CITY DEVELOPMENT

<PAGE>   43

                                    EXHIBIT B

                                LEGAL DESCRIPTION

<PAGE>   44

     Certain parcels of land situated in Cambridge, Middlesex County,
Commonwealth of Massachusetts, shown as Parcel 1 and Parcel 2 on a plan prepared
by Fay, Spofford & Thorndike, Inc., entitled: "Plan of Land in Cambridge, MA
owned by Massachusetts Institute of Technology dated February 6, 1989" bounded
and described as follows:

     PARCEL 1

     Beginning at a point, said point being the intersection of the southerly
street line of Green Street (Public Way) and the easterly street line of
Brookline Street (Public Way); thence running

     S.51[degrees]-36'-22"E.       by the southerly street line of Green Street
                                   (Public Way) Four Hundred Eleven and 14/100
                                   (411.14) feet; thence turning and running

     S.38[degrees]-25'-50"W.       by land, now or formerly, of Massachusetts
                                   Institute of Technology (PARCEL 3) Two
                                   Hundred and 22/100 (200.22) feet to a point
                                   on the northerly street line of Franklin
                                   Street; thence turning and running

     N.51[degrees]-34'-10"W.       by the northerly street line of Franklin
                                   Street (Public Way) Three Hundred
                                   Thirty-Seven and 60/100 (337.60) feet to a
                                   point on the northerly street line of
                                   Franklin Street; thence turning and running

     N.38[degrees]-25'-50"E.       by land, now or formerly, of Massachusetts
                                   Institute of Technology (PARCEL 2)
                                   Ninety-Eight and 90/100 (98.90) feet; thence
                                   turning and running

     N.51[degrees]-18'42"W.        by land, now or formerly, of Massachusetts
                                   Institute of Technology (PARCEL 2) Sixty-Five
                                   and 48/100 (65.48) feet to a point on the
                                   easterly street line of Brookline Street;
                                   thence turning and running

<PAGE>   45

     N.33[degrees]-51'-20"E.       by the easterly street line of Brookline
                                   Street (Public Way) One Hundred one and
                                   07/100 (101.07) feet to a point, said point
                                   being the intersection of the easterly street
                                   line of Brookline Street (Public Way) and the
                                   southerly street line of Green Street (Public
                                   Way), said point also being the point of
                                   beginning.

     Containing Seventy-Four Thousand Five Hundred Seventy-One (74,571) square
feet, more or less, according to said plan.

     Parcel 1 includes a portion of a parcel of registered land described as
Parcel Four on Transfer Certificate of Title No. 132076, said Parcel 4 being
bounded and described as follows:

     Northeasterly                 by Green Street, forty-five feet;

     Southeasterly                 by land now or formerly of Inez L. Clark et
                                   al, one hundred feet;

     Southwesterly                 by land now or formerly of Simplex Wire &
                                   Cable Company, forty-five feet; and

     Northwesterly                 by land now or formerly of National Biscuit
                                   Company, one hundred feet.

     All of said boundaries are determined by the court to be located as shown
on a plan, as modified and approved by the Court, filed in the Land Registration
office, a copy of a portion of which is filed in the Registry of Deeds for the
South Registry District of Middlesex County in Registration Book 84, Page 157,
with Certificate 12764, (Plan 8232A)

     PARCEL 2

     Beginning at a point, said point being the intersection of the easterly
street line of Brookline Street (Public Way) and the northerly street line of
Franklin Street (Public Way); thence running

     N.33[degrees]-51'-20"E.       by the easterly street line of Brookline
                                   Street (Public Way) Ninety-Nine and 52/100
                                   (99.52) feet; thence turning and running

     S.51[degrees]-18'-42"E.       by land, now or formerly, of Massachusetts
                                   Institute of Technology (PARCEL 1) Sixty-Five
                                   and 48/100

                                       2
<PAGE>   46

                                   (65.48) feet; thence turning and running

     S.38[degrees]-25'-50"W.       by land, now or formerly, of Massachusetts
                                   Institute of Technology (PARCEL 1)
                                   Ninety-Eight and 90/100 (98.90) feet to a
                                   point on the northerly street line of
                                   Franklin Street; thence turning and running

     N.51[degrees]-34'-10"W.       by the northerly street line of Franklin
                                   Street (Public Way) Fifty-Seven and 54/100
                                   (57.54) feet to a point, said point being the
                                   intersection of the northerly street line of
                                   Franklin Street (Public Way) and the easterly
                                   street line of Brookline Street (Public Way),
                                   said point also being the point of beginning.

     Containing Six Thousand Ninety-Two (6,092) square feet, more or less,
according to said plan.

                                       3
<PAGE>   47

                                    EXHIBIT C

                          LIST OF TENANT'S FINAL PLANS

                                [TO BE ATTACHED]

<PAGE>   48

                                    EXHIBIT D

                                STANDARD SERVICES

     Landlord shall provide, or cause to be provided, the following standard
services throughout the Term, which services may be modified from time to time
by Landlord:

     A.   Regular maintenance of interior plants and exterior landscaping of the
          Building and all University Park common areas.

     B.   Regular maintenance, sweeping and snow removal of exterior areas
          around the Building, parking areas and throughout University Park.

     C.   Complete interior and exterior cleaning of all windows two times per
          year.

     D.   Daily, weekday maintenance of hallways, passenger elevators, common
          area bathrooms, lobby areas and vestibules.

     E.   Periodic cleaning of stairwells, freight elevators, and back of house
          areas.

     F.   Daily, weekday rubbish removal of all common area trash receptacles.

     G.   Daily, weekday cleaning of tenant space in a manner comparable to
          similar first-class office space in the Cambridge area.

     H.   Maintenance and repair of all base Building mechanical, electrical,
          plumbing and life safety systems and all other building systems
          serving the common areas.

     I.   Operation and maintenance of Building surveillance and alarm systems,
          links to the University Park command center, and security officer
          services in the Building and throughout University Park as appropriate
          in Landlord's reasonable determination.

<PAGE>   49

     J.   Conditioned air for HVAC purposes shall be provided to the Premises
          from central mechanical equipment and shall be available 24 hours per
          day, 7 days per week; provided, however, Landlord reserves the right,
          pursuant to Section 3.5 of this Lease, to charge for conditioned air
          provided after normal business hours if Landlord reasonably determines
          that demand for such conditioned air is not consistently needed
          throughout the Building during such non-business hours. Any charges
          for conditioned air shall include Landlord's reasonable estimate of
          the cost of energy, additional equipment maintenance and wear and tear
          associated with such after hours use, but shall not include a
          surcharge or profit to Landlord.

     K.   All utilities for all interior common areas and exterior building
          lighting.

     L.   Regular maintenance of banners, building directories and other
          building standard directional signage and amenities.

     M.   Reasonably adequate water and sewer service to the Premises.

<PAGE>   50

                                    EXHIBIT E

                              RULES AND REGULATIONS

DEFINITIONS

Wherever in these Rules and Regulations the word "Tenant" is used, it shall be
taken to apply to and include the Tenant and its agents, employees, invitees,
licensees, contractors, any subtenants and is to be deemed of such number and
gender as the circumstances require. The word "Premises" is to be taken to
include the space covered by the Lease. The word "Landlord" shall be taken to
include the employees and agents of Landlord. Other capitalized terms used but
not defined herein shall have the meanings set forth in the Lease. Any consents
or approvals required of Landlord herein shall not be unreasonably withheld or
delayed.

GENERAL USE OF BUILDING

     A.   Space for admitting natural light into any public area or tenanted
          space of the Building shall not be covered or obstructed by Tenant
          except in a manner reasonably approved by Landlord.

     B.   Toilets, showers and other like apparatus shall be used only for the
          purpose for which they were constructed.

     C.   Intentionally Omitted.

     D.   No sign, advertisement, notice or the like, shall be used in the
          Building by Tenant (other than at its office or as permitted in the
          Lease). If Tenant violates the foregoing, Landlord may remove the
          violation without liability and may charge all costs and expenses
          incurred in so doing to Tenant.

     E.   Tenant shall not throw or permit to be thrown anything out of windows
          or doors or down passages or elsewhere in the Building, or bring or
          keep any pets therein, or commit or make any indecent or improper acts
          or noises. In addition, Tenant shall not do or permit anything which
          will obstruct, injure, annoy or interfere with other tenants or those

<PAGE>   51

          having business with them, or affect any insurance rate on the
          Building or violate any provision of any insurance policy on the
          Building.

     F.   Unless expressly permitted by the Landlord in writing:

          (1)  No additional locks or similar devices shall be attached to any
               door or window and no keys other than those provided by the
               Landlord shall be made for any door. If more than two keys for
               one lock are desired by the Tenant, the Landlord may provide the
               same upon payment by the Tenant. Upon termination of this lease
               or of the Tenant's possession, the Lessee shall surrender all
               keys to the Premises and shall explain to the Landlord all
               combination locks on safes, cabinets and vaults.

          (2)  In order to insure proper use and care of the Premises Tenant
               shall not install any shades, blinds, or awnings or any interior
               window treatment without consent of Landlord. Blinds must be
               building standard.

          (3)  All doors to the Premises are to be kept closed at all times
               except when in actual use for entrance to or exit from such
               Premises. The Tenant shall be responsible for the locking of
               doors and the closing of any transoms and windows in and to the
               Premises. Any damage or loss resulting from violation of this
               rule shall be paid for by the Tenant.

          (4)  The Tenant shall not install or operate any steam or internal
               combustion engine, boiler, machinery in or about the Premises, or
               carry on any mechanical business therein. All equipment of any
               electrical or mechanical nature shall be placed in settings which
               absorb and prevent any vibration, noise or annoyance.

     G.   Landlord shall designate the time when and the method whereby freight,
          small office equipment, furniture, safes and other like articles may
          be brought into, moved or

<PAGE>   52

          removed from the Building or Premises, and to designate the location
          for temporary disposition of such items.

     H.   In order to insure proper use and care of the Premises Tenant shall
          not allow anyone other than Landlord's employees or contractors to
          clean the Premises without Landlord's permission.

     I.   The Premises shall not be defaced in any way. No changes in the HVAC,
          electrical fixtures or other appurtenances of said Premises shall be
          made without the prior approval of Landlord and in accordance with
          Landlord's construction rules and regulations.

     J.   For the general welfare of all tenants and the security of the
          Building, Landlord may require all persons entering and/or leaving the
          Building on weekends and holidays and between the hours of 6:00 p.m.
          and 8:00 a.m. to register with the Building attendant or custodian by
          signing his name and writing his destination in the Building, and the
          time of entry and actual or anticipated departure, or other procedures
          deemed necessary by Lessor. Landlord may deny entry during such hours
          to any person who fails to provide satisfactory identification.

     K.   No animals, birds, pets, and no bicycles or vehicles of any kind shall
          be brought into or kept in or about said Premises or the lobby or
          halls of the Building. Tenant shall not cause or permit any unusual or
          objectionable odors, noises or vibrations to be produced upon or
          emanate from said Premises.

     L.   Unless specifically authorized by Landlord, employees or agents of
          Landlord shall not perform for nor be asked by Tenant to perform work
          other than their regularly assigned duties.

     M.   Landlord shall have the right to prohibit any advertising by Tenant
          which, in Landlord's reasonable opinion tends to impair the reputation
          of the Building or its desirability as an office building and, upon
          written notice from Landlord, Tenant shall promptly discontinue such
          advertising.

<PAGE>   53

     N.   Canvassing, soliciting and peddling in the Building is prohibited and
          Tenant shall cooperate to prevent the same from occurring.

     O.   All parking, Building operation, or construction rules and regulations
          which may be established from time to time by Landlord on a uniform
          basis shall be obeyed.

     P.   Tenant shall not place a load on any floor of said Premises exceeding
          the floor load limits as prescribed by the Landlord in its reasonable
          discretion.

     Q.   Tenant shall not install or use any air conditioning or heating device
          or system other than those approved by Landlord.

     R.   Landlord shall have the right to make such other and further
          reasonable rules and regulations as in the judgment of Landlord, may
          from time to time be needful for the safety, appearance, care and
          cleanliness of the Building and for the preservation of good order
          therein, and Tenant shall be given reasonable notice of same.

     S.   The access road and loading areas, parking areas, sidewalks,
          entrances, lobbies, halls, walkways, elevators, stairways and other
          common area provided by Landlord shall not be obstructed by Tenant, or
          used for other purpose than for ingress and egress.

     T.   In order to insure proper use and care of the Premises Tenant shall
          not install any call boxes or communications systems or wiring of any
          kind without Landlord's permission and direction.

     U.   In order to insure proper use and care of the Premises Tenant shall
          not manufacture any commodity, or prepare or dispense for sale, except
          through vending machines for the benefit of employees and invitees of
          Tenant, any foods or

<PAGE>   54

          beverages, tobacco, flowers, or other commodities or articles without
          the written consent of Landlord.

     V.   In order to insure use and care of the Premises Tenant shall not enter
          any janitors' closets, mechanical or electrical areas, telephone
          closets, loading areas, roof or Building storage areas without the
          written consent of Landlord.

     W.   In order to insure proper use and care of the Premises Tenant shall
          not place doormats in public corridors without consent of Landlord.<PAGE>   1
                                                                   Exhibit 10.11

                             MASTER LEASE AGREEMENT

COMDISCO, INC. - LESSOR

MASTER LEASE AGREEMENT DATED MAY 1, 1995 BY AND BETWEEN COMDISCO, INC.
("LESSOR") AND ACUSPHERE, INC. ("LESSEE").

IN CONSIDERATION OF THE MUTUAL AGREEMENTS DESCRIBED BELOW, THE PARTIES AGREE AS
FOLLOWS (ALL CAPITALIZED TERMS ARE DEFINED IN SECTION 14.19):

1.   PROPERTY LEASED.

     Lessor leases to Lessee all of the Equipment described on each Schedule. In
the event of a conflict, the terms of a Schedule prevail over this Master Lease.

2.   TERM.

     On the Commencement Date, Lessee will be deemed to accept the Equipment,
will be bound to its rental obligations for each item of Equipment and the term
of a Schedule will begin and continue through the Initial Term and thereafter
until terminated by either party upon prior written notice received during the
Notice Period. No termination may be effective prior to the expiration of the
Initial Term.

3.   RENT AND PAYMENT.

     Rent is due and payable in advance, in immediately available funds, on the
first day of each Rent interval to the payee and at the location specified in
Lessor's invoice. Interim Rent is due and payable when invoiced. If any payment
is not made when due, Lessee will pay interest at the Overdue Rate. Upon
Lessee's execution of each Schedule, Lessee will pay Lessor the Advance
specified on the Schedule. The Advance will be credited towards the final Rent
payment if Lessee is not then in default. No interest will be paid on the
Advance.

4.   SELECTION; WARRANTY AND DISCLAIMER OF WARRANTIES.

     4.1  SELECTION. Lessee acknowledges that it has selected the Equipment and
disclaims any reliance upon statements made by the Lessor.

     4.2  WARRANTY AND DISCLAIMER OF WARRANTIES. Lessor warrants to Lessee that,
so long as Lessee is not in default, Lessor will not disturb Lessee's quiet and
peaceful possession, and unrestricted use of the Equipment. To the extent
permitted by the manufacturer, Lessor assigns to Lessee during the term of the
Schedule any manufacturer's warranties for the Equipment. LESSOR MAKES NO OTHER
WARRANTY, EXPRESS OR IMPLIED AS TO ANY MATTER WHATSOEVER, INCLUDING, WITHOUT
LIMITATION, THE MERCHANTABILITY OF THE EQUIPMENT OR ITS FITNESS FOR A PARTICULAR
PURPOSE. Lessor is not responsible for any liability, claim, loss, damage or
expense of any kind (including strict liability in tort) caused by the Equipment
except for any loss or damage caused by the negligent acts of Lessor. In no
event is Lessor responsible for special, incidental or consequential damages.

5.   TITLE; RELOCATION OR SUBLEASE; AND ASSIGNMENT.

     5.1  TITLE. Lessee holds the Equipment subject and subordinate to the
rights of the Owner, Lessor, any Assignee and any Secured Party. Lessee
authorizes Lessor, as Lessee's agent, to prepare, execute and file in Lessee's
name precautionary Uniform Commercial Code financing statements showing the
interest of the Owner, Lessor, and any Assignee or Secured Party in the
Equipment and to insert serial numbers in Schedules as appropriate. Lessee will,
at its expense, keep the Equipment free and clear from any liens or encumbrances
of any kind (except any caused by Lessor) and will indemnify and hold Lessor,
Owner, any Assignee and Secured Party harmless from and against any loss caused
by Lessee's failure to do so.

     5.2  RELOCATION OR SUBLEASE. Upon prior written consent, Lessee may
relocate Equipment to any location within the continental United States provided
(i) the Equipment will not be used by an entity exempt from federal income tax,
(ii) all additional costs (including any administrative fees, additional taxes
and insurance coverage) are reconciled and promptly paid by Lessee.

     Lessee may sublease the Equipment upon the reasonable consent of the Lessor
and the Secured Party. Such consent to sublease will be granted if: (i) Lessee
meets the relocation requirements set out above, (ii) the sublease is expressly
subject and subordinate to the terms of this schedule, (iii) Lessee assigns its
rights in the sublease to Lessor and the Secured Party as additional collateral
and security, (iv) Lessee's obligation to maintain and insure the Equipment is
not altered, (v) all financing statements required to continue the Secured
Party's prior perfected security interest are filed, and (vi) the sublease is
not to a leasing entity affiliated with the manufacturer of the Equipment
described on the Schedule. Lessor acknowledges Lessee's right to sublease for a
term which extends beyond the expiration of the Initial Term. If Lessee
subleases the Equipment for a term extending beyond the expiration of such
Initial Term of the applicable Schedule, Lessee will remain obligated upon the
expiration of the Initial Term to return such Equipment, or, at Lessor's sole

<PAGE>   2

discretion to (i) return Like Equipment or (ii) negotiate a mutually acceptable
lease extension or purchase. If the parties cannot mutually agree upon the terms
of an extension or purchase, the term of the Schedule will extend upon the
original terms and conditions until terminated pursuant to Section 2.

     No relocation or sublease will relieve Lessee from any of its obligations
under this Master Lease and the relevant Schedule.

     5.3  ASSIGNMENT BY LESSOR. The terms and conditions of each Schedule have
been fixed by Lessor in order to permit Lessor to sell and/or assign or transfer
its interest or grant a security interest in each Schedule and/or the Equipment
to a Secured Party or Assignee. In that event, the term Lessor will mean the
Assignee and any Secured Party. However, any assignment, sale, or other transfer
by Lessor will not relieve Lessor of its obligations to Lessee and will not
materially change Lessee's duties or materially increase the burdens or risks
imposed on Lessee. The Lessee consents to and will acknowledge such assignments
in a written notice given to Lessee. Lessee also agrees that:

     (a)  The Secured Party will be entitled to exercise all of Lessor's rights,
          but will not be obligated to perform any of the obligations of Lessor.
          The Secured Party will not disturb Lessee's quiet and peaceful
          possession and unrestricted use of the Equipment so long as Lessee is
          not in default and the Secured Party continues to receive all Rent
          payable under the Schedule; and

     (b)  Lessee will pay all Rent and all other amounts payable to the Secured
          Party, despite any defense or claim which it has against Lessor.
          Lessee reserves its right to have recourse directly against Lessor for
          any defense or claim;

     (c)  Subject to and without impairment of Lessee's leasehold rights in the
          Equipment, Lessee holds the Equipment for the Secured Party to the
          extent of the Secured Party's rights in that Equipment.

6.   NET LEASE; TAXES AND FEES.

     6.1  NET LEASE. Each Schedule constitutes a net lease. Lessee's obligation
to pay Rent and all other amounts is absolute and unconditional and is not
subject to any abatement, reduction, set-off, defense, counterclaim,
interruption, deferment or recoupment for any reason whatsoever.

     6.2  TAXES AND FEES. Lessee will pay when due or reimburse Lessor for all
taxes, fees or any other charges (together with any related interest or
penalties not arising from the negligence of Lessor) accrued for or arising
during the term of each Schedule against Lessor, Lessee or the Equipment by any
governmental authority (except only Federal, state and local taxes on the
capital or the net income of Lessor). Lessor will file all personal property tax
returns for the Equipment and pay all property taxes due. Lessee will reimburse
Lessor for property taxes within thirty (30) days of receipt of an invoice.

7.   CARE, USE AND MAINTENANCE; ATTACHMENTS AND RECONFIGURATIONS; AND INSPECTION
     BY LESSOR.

     7.1  CARE, USE AND MAINTENANCE. Lessee will maintain the Equipment in good
operating order and appearance, protect the Equipment from deterioration, other
than normal wear and tear, and will not use the Equipment for any purpose other
than that for which it was designed. If commercially available, Lessee will
maintain in force a standard maintenance contract with the manufacturer of the
Equipment, or another party acceptable to Lessor, and will provide Lessor with a
complete copy of that contract. If Lessee has the Equipment maintained by a
party other than the manufacturer, Lessee agrees to pay any costs necessary for
the manufacturer to bring the Equipment to then current release, revision and
engineering change levels, and to re-certify the Equipment as eligible for
manufacturer's maintenance at the expiration of the lease term. The lease term
will continue upon the same terms and conditions until recertification has been
obtained.

     7.2  ATTACHMENTS AND RECONFIGURATIONS. Upon receiving the prior written
consent of Lessor, Lessee may reconfigure and install Attachments on the
Equipment. In the event of such a Reconfiguration or Attachment, Lessee will,
upon return of the Equipment, at its expense, restore the Equipment to the
original configuration specified on the Schedule in accordance with the
manufacturer's specifications and in the same operating order, repair and
appearance as when installed (normal wear and tear excluded). If any parts of
the Equipment are removed during a Reconfiguration or Attachment, Lessor may
require Lessee to provide additional security, satisfactory to the Lessor, in
order to ensure performance of Lessee's obligations set forth in this
subsection. Neither Attachments nor parts installed on Equipment in the course
of Reconfiguration will be accessions to the Equipment.

     7.3  INSPECTION BY LESSOR. Upon request, Lessee, during reasonable business
hours and subject to Lessee's security requirements, will make the Equipment and
its related log and maintenance records available to Lessor for inspection.

8.   REPRESENTATIONS AND WARRANTIES OF LESSEE. Lessee hereby represents,
warrants and covenants that with respect to the Master Lease and each Schedule
executed hereunder:

     (a)  The Lessee is a corporation duly organized and validly existing in
          good standing under the laws of the jurisdiction of its incorporation,
          is duly qualified to do business in each jurisdiction (including the
          jurisdiction where the Equipment is, or is to be, located) where its
          ownership or lease of property or the conduct of its business requires
          such qualification; and has full corporate power and authority to

                                       2
<PAGE>   3

          hold property under the Master Lease and each Schedule and to enter
          into and perform its obligations under such Lease.

     (b)  The execution and delivery by the Lessee of the Master Lease and each
          Schedule and its performance thereunder have been duly authorized by
          all necessary corporate action on the part of the Lessee, and the
          Master Lease and each Schedule are not inconsistent with the Lessee's
          Certificate of Incorporation or Bylaws, do not contravene any law or
          governmental rule, regulation or order applicable to it, do not and
          will not contravene any provision of, or constitute a default under,
          any indenture, mortgage, contract or other instrument to which it is a
          party or by which it is bound, and the Master Lease and each Schedule
          constitute legal, valid and binding agreements of the Lessee,
          enforceable in accordance with their terms.

     (c)  There are no actions, suits, proceedings or patent claims pending or,
          to the knowledge of the Lessee, threatened against or affecting the
          Lessee in any court or before any governmental commission, board or
          authority which, if adversely determined, will have a material adverse
          effect on the ability of the Lessee to perform its obligations under
          the Master Lease and each Schedule.

     (d)  The Equipment is personal property and when subjected to use by the
          Lessee will not be or become fixtures under applicable law.

     (e)  The Lessee has no material liabilities or obligations, absolute or
          contingent (individually or in the aggregate), except the liabilities
          and obligations of the Lessee as set forth in the Financial Statements
          and liabilities and obligations which have occurred in the ordinary
          course of business, and which have not been, in any case or in the
          aggregate, materially adverse to Lessee's going business.

     (f)  To the best of the Lessee's knowledge, the Lessee owns, possesses, has
          access to, or can become licensed on reasonable terms under all
          patents, patent applications, trademarks, trade names, inventions,
          franchises, licenses, permits, computer software and copyrights
          necessary for the operations of its business as now conducted, with no
          known infringement of, or conflict with, the rights of others.

     (g)  All material contracts, agreements and instruments to which the Lessee
          is a party are in full force and effect in all material respects, and
          are valid, binding and enforceable by the Lessee in accordance with
          their respective terms, subject to the effect of applicable bankruptcy
          and other similar laws affecting the rights of creditors generally,
          and rules of law concerning equitable remedies.

9.   DELIVERY AND RETURN OF EQUIPMENT.

     Lessee hereby assumes the full expense of transportation and in-transit
insurance to Lessee's premises and installation thereat of the Equipment. Upon
termination (by expiration or otherwise) of each Schedule, Lessee shall,
pursuant to Lessor's instructions and at Lessee's full expense (including,
without limitation, expenses of transportation and in-transit insurance), return
the Equipment to Lessor in the same operating order, repair, condition and
appearance as when received, less normal depreciation and wear and tear. Lessee
shall return the Equipment to Lessor at its address set forth herein or at such
other address within the continental United States as directed by Lessor,
provided, however, that Lessee's expense shall be limited to the cost of
returning the equipment to Lessor's address as set forth herein. During the
period subsequent to receipt of a notice under Section 2, Lessor may demonstrate
the Equipment's operation in place and Lessee will supply any of its personnel
as may reasonably be required to assist in the demonstrations.

10.  LABELING.

     Upon request, Lessee will mark the Equipment indicating Lessor's interest.
Lessee will keep all Equipment free from any other marking or labeling which
might be interpreted as a claim of ownership.

11.  INDEMNITY.

     Lessee will indemnify and hold Lessor, any Assignee and any Secured Party
harmless from and against any and all claims, costs, expenses, damages and
liabilities, including reasonable Attorneys' fees, arising out of the ownership
(for strict liability in tort only), selection, possession, leasing, operation,
control, use, maintenance, delivery, return or other disposition of the
Equipment. However, Lessee is not responsible to a party indemnified hereunder
for any claims, costs, expenses, damages and liabilities occasioned by the
negligent acts of such indemnified party. Lessee agrees to carry bodily injury
and property damage liability insurance during the term of the Master Lease in
amounts and against risks customarily insured against by the Lessee on equipment
owned by it. Any amounts received by Lessor under that insurance will be
credited against Lessee's obligations under this Section.

12.  RISK OF LOSS.

     Effective upon delivery and until the Equipment is returned, Lessee
relieves Lessor of responsibility for all risks of physical damage to or loss or
destruction of the Equipment. Lessee will carry casualty insurance for each item
of Equipment in an amount not less than the Casualty Value. All policies for
such insurance will name the Lessor and any Secured Party as additional insured
and as loss payee, and will provide for at least thirty (30) days prior written
notice to the Lessor of cancellation or expiration, and will insure Lessor's

                                       3
<PAGE>   4

interests regardless of any breach or violation by Lessee of any representation,
warranty or condition contained in such policies and will be primary without
right of contribution from any insurance effected by Lessor. Upon the execution
of any Schedule, the Lessee will furnish appropriate evidence of such insurance
acceptable to Lessor.

     Lessee will promptly repair any damaged item of Equipment unless such
Equipment has suffered a Casualty Loss. Within fifteen (15) days of a Casualty
Loss, Lessee will provide written notice of that loss to Lessor and Lessee will,
at Lessor's option, either (a) replace the item of Equipment with Like Equipment
and marketable title to the Like Equipment will automatically vest in Lessor or
(b) pay the Casualty Value and after that payment and the payment of all other
amounts due and owing, Lessee's obligation to pay further Rent for the item of
Equipment will cease.

13.  DEFAULT, REMEDIES AND MITIGATION.

     13.1 DEFAULT. The occurrence of any one or more of the following Events of
Default constitutes a default under a Schedule:

     (a)  Lessee's failure to pay Rent or other amounts payable by Lessee when
          due if that failure continues for five (5) days after written notice;
          or

     (b)  Lessee's failure to perform any other term or condition of the
          Schedule or the material inaccuracy of any representation or warranty
          made by the Lessee in the Schedule or in any document or certificate
          furnished to the Lessor hereunder if that failure or inaccuracy
          continues for ten (10) days after written notice; or

     (c)  An assignment by Lessee for the benefit of its creditors, the failure
          by Lessee to pay its debts when due, the insolvency of Lessee, the
          filing by Lessee or the filing against Lessee of any petition under
          any bankruptcy or insolvency law or for the appointment of a trustee
          or other officer with similar powers, the adjudication of Lessee as
          insolvent, the liquidation of Lessee, or the taking of any action for
          the purpose of the foregoing; or

     (d)  The occurrence of an Event of Default under any Schedule or other
          agreement between Lessee and Lessor or its Assignee or Secured Party.

     13.2 REMEDIES. Upon the occurrence of any of the above Events of Default,
Lessor, at its option, may:

     (a)  enforce Lessee's performance of the provisions of the applicable
          Schedule by appropriate court action in law or in equity;

     (b)  recover from Lessee any damages and or expenses, including Default
          Costs;

     (c)  with notice and demand, recover all sums due and accelerate and
          recover the present value of the remaining payment stream of all Rent
          due under the defaulted Schedule (discounted at the same rate of
          interest at which such defaulted Schedule was discounted with a
          Secured Party plus any prepayment fees charged to Lessor by the
          Secured Party or, if there is no Secured Party, then discounted at 6%)
          together with all Rent and other amounts currently due as liquidated
          damages and not as a penalty;

     (d)  with notice and process of law and in compliance with Lessee's
          security requirements, Lessor may enter on Lessee's premises to remove
          and repossess the Equipment without being liable to Lessee for damages
          due to the repossession, except those resulting from Lessor's, its
          assignees', agents' or representatives' negligence; and

     (e)  pursue any other remedy permitted by law or equity.

     The above remedies, in Lessor's discretion and to the extent permitted by
law, are cumulative and may be exercised successively or concurrently.

     13.3 MITIGATION. Upon return of the Equipment pursuant to the terms of
Section 13.2, Lessor will use its best efforts in accordance with its normal
business procedures (and without obligation to give any priority to such
Equipment) to mitigate Lessor's damages as described below. EXCEPT AS SET FORTH
IN THIS SECTION, LESSEE HEREBY WAIVES ANY RIGHTS NOW OR HEREAFTER CONFERRED BY
STATUTE OR OTHERWISE WHICH MAY REQUIRE LESSOR TO MITIGATE ITS DAMAGES OR MODIFY
ANY OF LESSOR'S RIGHTS OR REMEDIES STATED HEREIN. Lessor may sell, lease or
otherwise dispose of all or any part of the Equipment at a public or private
sale for cash or credit with the privilege of purchasing the Equipment. The
proceeds from any sale, lease or other disposition of the Equipment are defined
as either:

     (a)  if sold or otherwise disposed of, the cash proceeds less the Fair
          Market Value of the Equipment at the expiration of the Initial Term
          less the Default Costs; or

     (b)  if leased, the present value (discounted at three points over the
          prime rate as referenced in the Wall Street Journal at the time of the
          mitigation) of the rentals for a term not to exceed the Initial Term,
          less the Default Costs.

                                       4
<PAGE>   5

     Any proceeds will be applied against liquidated damages and any other sums
due to Lessor from Lessee. However, Lessee is liable to Lessor for, and Lessor
may recover, the amount by which the proceeds are less than the liquidated
damages and other sums due to Lessor from Lessee.

14.  ADDITIONAL PROVISIONS.

     14.1 BOARD ATTENDANCE. Lessor or its duly appointed representative will
have the right to attend Lessee's corporate Board of Directors meetings and
Lessee will give Lessor reasonable notice in advance of any special Board of
Directors meeting, which notice will provide an agenda of the subject matter to
be discussed at such board meeting. Lessee will provide Lessor with a certified
copy of the minutes of each Board of Directors meeting within thirty (30) days
following the date of such meeting held during the term of this Lease.

     14.2 FINANCIAL STATEMENTS. Lessee will provide to Lessor the financial
statements specified in this Section, prepared in accordance with generally
accepted accounting principles, consistently applied (the "Financial
Statements"); provided, however, after the effective date of the initial
registration statement covering a public offering of Lessee's securities, the
term "Financial Statements" will be deemed to refer to only those statements
required by the Securities and Exchange Commission, to be provided no less
frequently than quarterly. Lessee will provide to Lessor (i) as soon as
practicable (within (30) days) after the end of each month, the same information
which Lessee provides to its Board of Directors, but which will include not less
than a monthly income statement, balance sheet and statement of cash flows,
certified by Lessee's Chief Executive or Financial Officer to be true and
correct; and (ii) as soon as practicable (and in any event within ninety (90)
days) after the end of each fiscal year, audited balance sheets as of the end of
such year (consolidated if applicable), and related statements of income or
loss, retained earnings or deficit and changes in the financial position and
capital structure of Lessee for such year, setting forth in comparative form the
corresponding figures for the preceding fiscal year, and accompanied by an audit
report and opinion of the independent certified public accountants selected by
Lessee. Lessee will promptly furnish to Lessor any additional information
(including but not limited to tax returns, income statements, balance sheets,
and names of principal creditors) as Lessor reasonably believes necessary to
evaluate Lessee's continuing ability to meet financial obligations.

     14.3 OBLIGATIONS TO LEASE ADDITIONAL EQUIPMENT. Upon notice to Lessee,
Lessor will not be obligated to lease any Equipment which would have a
commencement Date after said notice if: (i) Lessee is in default under this
Master Lease or any Schedule; (ii) Lessee is in default under any loan
agreement, the result of which would allow the lender or any secured party to
demand immediate payment of the indebtedness; (iii) there is a material adverse
change in Lessee's credit standing; or (iv) Lessor determines (in reasonable
good faith) that Lessee will be unable to perform its obligations under this
Master Lease.

     14.4 MERGER AND SALE PROVISIONS. Lessee will notify Lessor of any proposed
Merger at least sixty (60) days prior to the closing date. Lessor may, in its
discretion, either (i) consent to the assignment of the Master Lease and all
relevant Schedules to the successor entity, or (ii) terminate the Master Lease
and all relevant Schedules. If Lessor elects to consent to the assignment,
Lessee and its successor will sign the assignment documentation provided by
Lessor. If Lessor elects to consent to the assignment, Lessee and its successor
will sign the assignment documentation provided by Lessor. If Lessor elects to
terminate the Master Lease and all relevant Schedules, then Lessee will pay
Lessor all amounts then due and owing and a termination fee equal to the present
value (discounted at 6%) of the remaining Rent for the balance of the Initial
Term(s) of all Schedules, and will return the Equipment in accordance with
Section 9.

     14.5 ENTIRE AGREEMENT. This Master Lease and associated Schedules supersede
all other oral or written agreements or understandings between the parties
concerning the Equipment including, for example, purchase orders. ANY AMENDMENT
OF THIS MASTER LEASE OR A SCHEDULE, MAY ONLY BE ACCOMPLISHED BY A WRITING SIGNED
BY THE PARTY AGAINST WHOM THE AMENDMENT IS SOUGHT TO BE ENFORCED.

     14.6 NO WAIVER. No action taken by Lessor or Lessee will be deemed to
constitute a waiver of compliance with any representation, warranty or covenant
contained in this Master Lease or a Schedule. The waiver by Lessor or Lessee of
a breach of any provision of this Master Lease or a Schedule will not operate or
be construed as a waiver of any subsequent breach.

     14.7 BINDING NATURE. Each Schedule is binding upon, and inures to the
benefit of Lessor and its assigns. LESSEE MAY NOT ASSIGN ITS RIGHTS OR
OBLIGATIONS.

     14.8 SURVIVAL OF OBLIGATIONS. All agreements, obligations including, but
not limited to those arising under Section 6.2, representations and warranties
contained in this Master Lease, any Schedule or in any document delivered in
connection with those agreements are for the benefit of Lessor and any Assignee
or Secured Party and survive the execution, delivery, expiration or termination
of this Master Lease.

     14.9 NOTICES. Any notice, request or other communication to either party by
the other will be given in writing and deemed received upon the earlier of
actual receipt or three days after mailing if mailed postage prepaid by regular
or airmail to Lessor (to the attention of "Lease Administrator") or Lessee, at
the address set out in the Schedule or, one day after it is sent by courier or
on the same day as sent via facsimile transmission, provided that the original
is sent by personal delivery or mail by the receiving party.

     14.10 APPLICABLE LAW. THIS MASTER LEASE HAS BEEN, AND EACH SCHEDULE WILL
HAVE BEEN MADE, EXECUTED AND DELIVERED IN THE STATE OF ILLINOIS AND WILL BE
GOVERNED AND CONSTRUED FOR ALL PURPOSES IN ACCORDANCE WITH THE LAWS OF THE STATE
OF ILLINOIS WITHOUT GIVING EFFECT TO CONFLICT OF LAW PROVISIONS. NO RIGHTS OR
REMEDIES

                                       5
<PAGE>   6

REFERRED TO IN ARTICLE 2A OF THE UNIFORM COMMERCIAL CODE WILL BE CONFERRED ON
LESSEE UNLESS EXPRESSLY GRANTED IN THIS MASTER LEASE OR A SCHEDULE.

     14.11 SEVERABILITY. If any one or more of the provisions of this Master
Lease or any schedule is for any reason held invalid, illegal or unenforceable,
the remaining provisions of this Master Lease and any such Schedule will be
unimpaired, and the invalid, illegal or unenforceable provision replaced by a
mutually acceptable valid, legal and enforceable provision that is closest to
the original intention of the parties.

     14.12 COUNTERPARTS. This Master Lease and any Schedule may be executed in
any number of counterparts, each of which will be deemed an original, but all
such counterparts together constitute one and the same instrument. If Lessor
grants a security interest in all or any part of a Schedule, the Equipment or
sums payable thereunder, only that counterpart Schedule marked "Secured Party's
Original" can transfer Lessor's rights and all other counterparts will be marked
"Duplicate".

     14.13 NONSPECIFIED FEATURES AND LICENSES PRODUCTS. If the Equipment is
supplied from Lessor's inventory and contains any features not specified in the
Schedule, Lessee grants Lessor the right to remove any such features. Any
removal will be performed by the manufacturer or another party acceptable to
Lessee, upon the request of Lessor, at a time convenient to Lessee, provided
that Lessee will not unreasonably relay the removal of such features.

     Lessee will obtain no title to Licensed Products which will at all times
remain the property of the owner of the Licensed Products. A license from the
owner may be required and it is Lessee's responsibility to obtain any required
license before the use of the Licensed Products. Lessee agrees to treat the
Licensed Products as confidential information of the owner, to observe all
copyright restrictions, and not to reproduce or sell the Licensed Products.

     14.14 ADDITIONAL DOCUMENTS. Lessee will, upon execution of this Master
Lease and as may be requested thereafter, provide Lessor with a secretary's
certificate of incumbency and authority and any other documents reasonably
requested by Lessor. Upon the execution of each Schedule with a purchase price
in excess of $1,000,000, Lessee will provide Lessor with an opinion from
Lessee's counsel in a form acceptable to Lessor regarding the representations
and warranties in Section 8.

     14.15 ELECTRONIC COMMUNICATIONS. Each of the parties may communicate with
the other by electronic means under mutually agreeable terms.

     14.16 LESSOR'S RIGHT TO MATCH. Lessee's rights under Section 5.2 and 7.2
are subject to Lessor's right to match any sublease or upgrade proposed by a
third party. Lessee will provide Lessor with the terms of the third party offer
and Lessor will have three (3) business days to match the offer. Lessee will
obtain such upgrade from or sublease the Equipment to Lessor if Lessor has
timely matched the third party offer.

     14.17 LANDLORD/MORTGAGEE WAIVER. Lessee agrees to provide Lessor with a
Landlord/Mortgagee Waiver with respect to the Equipment. Such waiver shall be in
a form satisfactory to Lessor.

     14.18 EQUIPMENT PROCUREMENT CHARGES/PROGRESS PAYMENTS. Lessee hereby agrees
that Lessor shall not, by virtue of its entering into this Lease, be required to
remit any payments in any manufacturer or other third party until Lessee accepts
the Equipment subject to this Lease.

     14.19 DEFINITIONS.

ADVANCE - means the amount due to Lessor by Lessee upon Lessee's execution of
each Schedule.

ASSIGNEE - means an entity to whom Lessor has sold or assigned its rights as
owner and Lessor of Equipment.

ATTACHMENT - means any accessory, equipment or device and the installation
thereof that does not impair the original function or use of the Equipment and
is capable of being removed without causing material damage to the Equipment and
is not an accession to the Equipment.

CASUALTY LOSS - means the irreparable loss or destruction of Equipment.

CASUALTY VALUE - means the greater of the aggregate Rent remaining to be paid
for the balance of the lease term or the Fair Market Value of the Equipment
immediately prior to the Casualty Loss. However, if a Casualty Value Table is
attached to the relevant Schedule its terms will control.

COMMENCEMENT CERTIFICATE - means the Lessor provided certificate which must be
signed by Lessee within ten (10) days of the Commencement Date as requested by
Lessor.

COMMENCEMENT DATE - is defined in each Schedule.

DEFAULT COSTS - means reasonable attorney's fees and remarketing costs resulting
from a Lessee default or Lessor's enforcement of its remedies.

EQUIPMENT - means the property described on a Schedule and any replacement of
that property required or permitted by this Master Lease or a Schedule but not
including any Attachment.

                                       6
<PAGE>   7

EVENT OF DEFAULT - means the events described in Subsection 13.1.

FAIR MARKET VALUE - means the aggregate amount which would be obtainable in an
arm's length transaction between an informed and willing buyer/user and an
informed and willing seller under no compulsion to sell.

INITIAL TERM - means the period of time beginning on the first day of the first
full Rent Interval following the Commencement Date for all items of Equipment
and continuing for the number of Rent Intervals indicated on a Schedule.

INSTALLATION DATE - means the day on which Equipment is installed and qualified
for a commercially available manufacturer's standard maintenance contract or
warranty coverage, if available.

INTERIM RENT - means the pro-rata portion of Rent due for the period from the
Commencement Date through but not including the first day of the first full Rent
Interval included in the Initial Term.

LICENSED PRODUCTS - means any software or other licensed products attached to
the Equipment.

LIKE EQUIPMENT - means replacement Equipment which is lien free and of the same
model, type, configuration and manufacture as Equipment.

LIKE PART - means a substituted part which is lien free and of the same
manufacturer and part number as the removed part, and which when installed on
the Equipment will be eligible for maintenance coverage with the manufacturer of
the Equipment.

MERGER - means any consolidation or merger of the Lessee with or into any other
corporation or entity, any sale or conveyance of all or substantially all of the
assets of the Lessee to any other person or entity or any stock acquisition of
the Lessee by any other person or entity.

NOTICE PERIOD - means the time period described in a Schedule during which
Lessee may give Lessor notice of the termination of the term of that Schedule.

OVERDUE RATE - means the lesser of five percent (5%) of the payment due or the
maximum rate permitted by the law of the state where the Equipment is located.

OWNER - means the owner of Equipment.

RECONFIGURATION - means any change to Equipment that would upgrade or downgrade
the performance capabilities of the Equipment in any way.

RENT - means the rent, including Interim Rent, Lessee will pay for each item of
Equipment expressed in a Schedule either as a specific amount or an amount equal
to the amount which Lessor pays for an item of Equipment multiplied by a lease
rate factor plus all other amounts due to Lessor under this Master Lease or a
Schedule.

RENT INTERVAL - means a full calendar month or quarter as indicated on a
Schedule.

SCHEDULE - means an Equipment Schedule which incorporates all of the terms and
conditions of this Master Lease and, for purposes of Section 14.12, its
associated Commencement Certificate(s).

SECURED PARTY - means an entity to whom Lessor has granted a security interest
in a Schedule and related Equipment for the purpose of securing a loan.

     IN WITNESS WHEREOF, the parties hereto have executed this Master Lease on
or as of the day and year first above written.

ACUSPHERE, INC.                 COMDISCO, INC.
as Lessee                       as Lessor

By: /s/ Sherri C. Oberg         By: /s/ James Labe
    -------------------------       --------------------------------------------
    Title: President and CEO        Title: President, Comdisco Ventures Division

                                                                         3/18/95

                                       7
<PAGE>   8

                                   ADDENDUM TO
                 MASTER LEASE AGREEMENT DATED AS OF MAY 1, 1995
                       BETWEEN ACUSPHERE, INC., AS LESSEE
                          AND COMDISCO, INC., AS LESSOR

The undersigned hereby agree that the terms and conditions of the
above-referenced Master Lease are hereby modified and amended as follows:

(a)  SECTION 4.2, WARRANTY AND DISCLAIMER OF WARRANTIES.

     In line 2 after the word "default", add the words "under this Master Lease
     Agreement or the relevant Schedule".

(b)  SECTION 5.1, TITLE.

     In line 6 after the word "Lessor" in the parenthetical, add the words",
     owner or any assignee."

(c)  SECTION 5.2, RELOCATION OR SUBLEASE.

     In line 1 after the word "consent", add the words "of Lessor".

(d)  SECTION 5.3, ASSIGNMENT BY LESSOR.

     To the end of the first paragraph, add the words", in the event Lessor has
     granted a security interest in a Schedule and related Equipment to a
     Secured Party and has given notice thereof to the Lessee:".

     In line 3 of subsection (a) after the word "default", add the words "under
     this Master Lease Agreement or the relevant Schedule".

(e)  SECTION 6.2, TAXES AND FEES.

     In line 2 after the word "Lessor" in the parenthetical, add the words
     ", owner or any assignee"; in line 4 after the word "Lessor" in the
     parenthetical, add the words", owner or any assignee".

(f)  SECTION 8, REPRESENTATIONS AND WARRANTIES OF LESSEE.

     In Subsection (b), line 3, after the word "Schedule", delete the words "are
     not inconsistent with" and replace with the words "do not contravene"; in
     line 5 before the word "indenture", insert the word "material", in line 7
     after the word "enforceable", add the words "against Lessee".

     Delete Subsection (f) in its entirety and replace with the following:

     "Except as otherwise disclosed to Lessor, Lessee is not aware of any
     infringement of, or conflict with, the rights of others in regards to any
     patents, patent applications, trademarks, trade names, inventions,
     franchises, licenses, permits, computer software and/or copyrights
     necessary for the operation of its business as now conducted."

(h)  SECTION 9, DELIVERY AND RETURN OF EQUIPMENT.

     Delete second, third and fourth sentences in their entirety.

<PAGE>   9

(i)  SECTION 11, INDEMNITY.

     In line 6 after the word "acts', add the words", willful misconduct or bad
     faith".

(j)  SECTION 13.1, DEFAULT.

     In line 1 of Subsection (b) after the word "inaccuracy", add the words
     "when made".

     In line 4 of Subsection (c) after the word "powers", add the words "(which
     has not been dismissed or stayed within sixty (60) days)".

(k)  SECTION 13.3, REMEDIES.

     In line 4 of Section (d) after the word "negligence", add the words
     ", willful misconduct or bad faith,".

(l)  SECTION 13.2, MITIGATION.

     In lines 1 and 2 of Subsection (b), delete the words "three points over the
     prime rate as referenced in the Wall Street Journal at the time of the
     mitigation), replace with the words and number "six percent (6%)".

(m)  SECTION 14.1, BOARD ATTENDANCE.

     Add the following sentence to the end of Section 14.1: "Provided, however,
     the Board of Directors shall retain the right to meet in an executive
     session."

(n)  SECTION 14.2, FINANCIAL STATEMENTS.

     In line 10, delete the word and number "ninety (90)" and replace with the
     words and number "one hundred and twenty (120)"; in the next to last line,
     delete the word "believes" and replace with the words "requests as".

(o)  SECTION 14.3, OBLIGATION TO LEASE ADDITIONAL EQUIPMENT.

     In line 1 after the word "Upon", add the word "prior".

     In line 5, delete clause (iv) in its entirety and replace with the
     following:

     "(iv) Lessor determines (in reasonable good faith) that Lessee will be
     unable to perform its obligations under this Master Lease due to the loss
     of key employees/founders, Lessee's inability to secure necessary financing
     to continue operations, and/or extreme changes to existing business
     conditions."

(p)  SECTION 14.7, BINDING NATURE.

     At the beginning of the second sentence, add the words "Except as provided
     in Section 14.4,".

(q)  SECTION 14.8, SURVIVAL OF OBLIGATIONS.

     In the last line after the word "execution", delete the comma and add the
     word "or"; after the word "delivery", delete the words "expiration or
     termination"; Add a last sentence as follows: "The

                                      -2-
<PAGE>   10

     obligations of Sections 6.2, 9 and 11 shall survive the execution or
     termination of this Master Lease.

(r)  SECTION 14.16, LESSOR'S RIGHT TO MATCH.

     In line 2 after the word "party", add the words "as to Equipment that is
     currently on lease from Lessor to Lessee".

Except as amended hereby, all other terms and conditions of the Master Lease
Agreement remain in full force and effect.

This Addendum to Master Lease is executed this 24th day of November, 1999.

ACUSPHERE, INC.,                    COMDISCO, INC.,
AS LESSEE                           AS LESSOR

By: /s/ Sherri C. Oberg             By: /s/ James Labe
   -------------------------------     -----------------------------------------

Title: President and CEO            Title: President, Comdisco Ventures Division
      ----------------------------        --------------------------------------

Date: 12/20/99                      Date: 1/6/00
     -----------------------------       ---------------------------------------

                                      -3-

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