Document:

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                                                                    EXHIBIT 10.2

                                 NORTHWEST PARK

                                      LEASE

                                 BY AND BETWEEN

                             MTP LIMITED PARTNERSHIP
                                   (LANDLORD)

                                       AND

                                ACME PACKET, INC.
                                    (TENANT)

                               AT 11 NORTH AVENUE

                            BURLINGTON, MASSACHUSETTS

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                                TABLE OF CONTENTS

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<S>                                                                           <C>
TABLE OF CONTENTS                                                              2

ARTICLE 1 REFERENCE DATA                                                       4

   1.1     SUBJECT REFERRED TO                                                 4
   1.2     EXHIBITS                                                            5

ARTICLE 2 PREMISES AND TERM                                                    6

   2.1     PREMISES                                                            6
   2.2     TERM                                                                6

ARTICLE 3 IMPROVEMENTS                                                         6

   3.1     PERFORMANCE OF WORK AND APPROVAL OF LANDLORD'S WORK                 6
   3.2     ACCEPTANCE OF THE PREMISES                                          7
   3.3     TENANT'S WORK                                                       7
   3.4     ALLOWANCE                                                           7

ARTICLE 4 RENT                                                                 7

   4.1     THE FIXED RENT                                                      7
   4.2     ADDITIONAL RENT                                                     8
     4.2.1    REAL ESTATE TAXES                                                8
     4.2.2    PERSONAL PROPERTY TAXES                                          8
     4.2.3    OPERATING COSTS                                                  8
     4.2.4    INSURANCE                                                       10
     4.2.5    UTILITIES                                                       11
   4.3     LATE PAYMENT OF RENT                                               11
   4.4     LETTER OF CREDIT                                                   11
     4.4.1    AMOUNT OF LETTER OF CREDIT                                      11
     4.4.2    RENEWAL OF LETTER OF CREDIT                                     11
     4.4.3    DRAWS TO CURE DEFAULTS                                          11
     4.4.4    DRAWS TO PAY DAMAGES                                            11
     4.4.5    DRAWS FOR FAILURE TO DELIVER SUBSTITUTE LETTER OF CREDIT        12
     4.4.6    TRANSFERABILITY                                                 12
     4.4.7    RETURN OF LETTER OF CREDIT AT END OF TERM                       12

ARTICLE 5 LANDLORD'S COVENANTS                                                12

   5.1     AFFIRMATIVE COVENANTS                                              12
     5.1.1    HEAT AND AIR-CONDITIONING                                       12
     5.1.2    ELECTRICITY                                                     12
     5.1.3    WATER                                                           12
     5.1.4    FIRE ALARM                                                      12
     5.1.5    REPAIRS                                                         12
     5.1.6    LANDLORD'S INSURANCE                                            12
     5.1.7    LANDLORD'S INDEMNIFICATION                                      12
   5.2     INTERRUPTION                                                       13

ARTICLE 6 TENANT'S ADDITIONAL COVENANTS                                       13

   6.1     AFFIRMATIVE COVENANTS                                              13
     6.1.1    PERFORM OBLIGATIONS                                             13
     6.1.2    USE                                                             13
     6.1.3    REPAIR AND MAINTENANCE                                          13
     6.1.4    COMPLIANCE WITH LAW                                             13
     6.1.5    INDEMNIFICATION                                                 14
     6.1.6    LANDLORD'S RIGHT TO ENTER                                       14
     6.1.7    PERSONAL PROPERTY AT TENANT'S RISK                              14
     6.1.8    PAYMENT OF LANDLORD'S COST OF ENFORCEMENT                       14
     6.1.9    YIELD UP                                                        14
     6.1.10   RULES AND REGULATIONS                                           15
     6.1.11   ESTOPPEL CERTIFICATE                                            15
     6.1.12   LANDLORD'S EXPENSES RE CONSENTS                                 15
   6.2     NEGATIVE COVENANTS                                                 15
     6.2.1    ASSIGNMENT AND SUBLETTING                                       15
     6.2.2    NUISANCE                                                        16
     6.2.3    HAZORDOUS WASTES AND MATERIALS                                  16
     6.2.4    FLOOR LOAD; HEAVY EQUIPMENT                                     16
     6.2.5    INSTALLATION, ALTERATIONS OR ADDITIONS                          16
     6.2.6    ABANDONMENT                                                     17
     6.2.7    SIGNS                                                           17
     6.2.8    PARKING AND STORAGE                                             17

ARTICLE 7 CASUALTY OR TAKING                                                  17

   7.1     TERMINATION                                                        17
   7.2     RESTORATION                                                        17
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<S>                                                                           <C>
   7.3     AWARD                                                              18

ARTICLE 8 DEFAULTS                                                            18

   8.1     EVENTS OF DEFAULT                                                  18
   8.2     REMEDIES                                                           18
   8.3     REMEDIES CUMULATIVE                                                19
   8.4     LANDLORD'S RIGHT TO CURE DEFAULTS                                  19
   8.5     EFFECT OF WAIVERS OF DEFAULT                                       19
   8.6     NO WAIVER, ETC.                                                    19
   8.7     NO ACCORD AND SATISFACTION                                         19

ARTICLE 9 RIGHTS OF MORTGAGE HOLDERS                                          19

   9.1     RIGHTS OF MORTGAGE HOLDERS                                         19
   9.2     LEASE SUPERIOR OR SUBORDINATE TO MORTGAGES                         19

ARTICLE 10 MISCELLANEOUS PROVISIONS                                           20

   10.1    NOTICES FROM ONE PARTY TO THE OTHER                                20
   10.2    QUIET ENJOYMENT                                                    20
   10.3    LEASE NOT TO BE RECORDED                                           20
   10.4    LIMITATION OF LANDLORD'S LIABILITY                                 20
   10.5    ACTS OF GOD                                                        20
   10.6    LANDLORD'S DEFAULT                                                 20
   10.7    BROKERAGE                                                          20
   10.8    APPLICABLE LAW AND CONSTRUCTION                                    20
</Table>

                                        3
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                                 NORTHWEST PARK

                                      LEASE

                                    ARTICLE 1
                                 REFERENCE DATA

1.1   SUBJECT REFERRED TO.

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

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<S>                                     <C>
DATE OF THIS LEASE:                     July 10, 2006

BUILDING:                               The single story Building containing
                                        approximately 29,227 rentable square
                                        feet located in Northwest Park in
                                        Burlington, Massachusetts (hereinafter
                                        referred to as the "Park") located at
                                        and known as 11 North Avenue (the
                                        Building and such parcel of land
                                        hereinafter being collectively referred
                                        to as the "Property").

PREMISES:                               The entire Building, substantially as
                                        shown on Exhibit A attached hereto.

RENTABLE FLOOR
AREA OF PREMISES:                       Approximately 29,227 rentable square
                                        feet

LANDLORD:                               MTP Limited Partnership

ORIGINAL NOTICE
ADDRESS OF LANDLORD:                    c/o Nordblom Management Company, Inc.
                                        15 Third Avenue
                                        Burlington, Massachusetts 01803

TENANT:                                 Acme Packet, Inc., a Delaware Corporation

ORIGINAL NOTICE                         11 North Avenue
ADDRESS OF TENANT:                      Burlington, Massachusetts 01803

EXPIRATION DATE:                        June 30, 2010

COMMENCEMENT DATE:                      The date of this Lease.

DELIVERY DATE:                          The date which is the latest to occur of
                                        (i) ninety (90) days from full execution
                                        of this Lease, (ii) Landlord's final
                                        approval of the plans for Tenant's Work
                                        (defined in Section 3.3) and (iii)
                                        issuance of a building permit from the
                                        Town of Burlington.

RENT COMMENCEMENT DATE:                 September 1, 2006

ANNUAL FIXED RENT RATE:                 September 1, 2006 - August 31, 2007      $321,492.00
                                        September 1, 2007 - August 31, 2008      $350,724.00
                                        September 1, 2008 - June 30, 2010        $379,944.00

MONTHLY FIXED RENT RATE:                September 1, 2006 - August 31, 2007      $26,791.00
                                        September 1, 2007 - August 31, 2008      $29,227.00
                                        September 1, 2008 - June 30, 2010        $31,662.00

LETTER OF CREDIT AMOUNT:                $100,000.00, subject to reduction
                                        pursuant to Section 4.4.

ALLOWANCE:                              $50,000.00

TENANT'S PERCENTAGE:                    The ratio of the Rentable Floor Area of
                                        the Premises to the total rentable area
                                        of the Building, which shall initially
                                        be deemed to be 100%.

INITIAL ESTIMATE OF
TENANT'S PERCENTAGE OF
TAXES FOR THE TAX YEAR:                 $46,560.00
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<S>                                     <C>
INITIAL ESTIMATE OF
TENANT'S PERCENTAGE OF
OPERATING COSTS FOR THE
CALENDAR YEAR:                          $62,640.00

PERMITTED USES:                         General offices, research and
                                        development and light manufacturing, and
                                        shipping and receiving ancillary
                                        thereto.

PUBLIC LIABILITY INSURANCE LIMITS:

COMMERCIAL GENERAL LIABILITY:

                                        $3,000,000 per occurrence
                                        $5,000,000 general aggregate
</Table>

1.2   EXHIBITS

      The Exhibits listed below in this section are incorporated in this Lease
      by reference and are to be construed as a part of this Lease.

      EXHIBIT A                         Plan showing the Premises

      EXHIBIT B                         Description of Landlord's Work

      EXHIBIT B-1                       Space Plan Showing Tenant's Work

      EXHIBIT C                         Work Change Order

      EXHIBIT D                         Rules and Regulations

      EXHIBIT E                         Form Tenant Estoppel Certificate

      EXHIBIT F                         Form of Letter of Credit

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                                    ARTICLE 2
                                PREMISES AND TERM

2.1   PREMISES. Landlord hereby leases to Tenant and Tenant hereby leases from
      Landlord, subject to and with the benefit of the terms, covenants,
      conditions and provisions of this Lease, the Premises, excluding the use
      of the roof of the Building for telecommunications equipment, Landlord
      reserving the right, from time to time, without unreasonable interference
      with Tenant's use of the Premises, to install, use and repair
      telecommunications equipment on the roof of the Building. Except in the
      case of an emergency, Landlord shall use reasonable efforts to provide
      Tenant with notice prior to Landlord installation, use or repair of
      telecom equipment on the roof of the Building. Tenant shall have, as
      appurtenant to the Premises, rights to use in common, subject to
      reasonable rules from time to time made by Landlord of which Tenant is
      given notice: (a) the common walkways and driveways necessary for access
      to the Building and (b) the common parking areas serving the Building. As
      of the date of this Lease, the Premises are in compliance with the
      Massachusetts building code.

      Tenant shall be permitted to use up to 102 parking spaces in the parking
      area serving the Building.

      Landlord reserves the right from time to time, without unreasonable
      interference with use of the Premises: (a) 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, wherever located in the Premises or Building, (b) to alter or
      relocate any other common facility, (c) to make any repairs and
      replacements to the Premises which Landlord may deem necessary, and (d) in
      connection with any excavation made upon adjacent land of Landlord or
      others, to enter, and to license others to enter, upon the Premises to do
      such work as the person causing such excavation deems necessary to
      preserve the wall of the Building from injury or damage and to support the
      same. Except in an emergency, Landlord shall use reasonable efforts to
      provide Tenant with notice prior to entering the Premises in connection
      with Landlord's exercise of its rights under this paragraph.

2.2   TERM. TO HAVE AND TO HOLD for a term beginning on the Commencement Date
      and ending on the Expiration Date, unless sooner terminated as hereinafter
      provided.

                                    ARTICLE 3
                                  IMPROVEMENTS

3.1   PERFORMANCE OF WORK AND APPROVAL OF LANDLORD'S WORK. A. Landlord shall
      cause to be performed the work described in Exhibit B, the "Landlord's
      Work". All such work shall be done in a good and workmanlike manner
      employing good materials and so as to conform to all applicable building
      laws. Tenant agrees that Landlord may make any changes in such work which
      may become reasonably necessary or advisable, other than substantial
      changes, without approval of Tenant, provided written notice is promptly
      given to Tenant; and Landlord may make substantial changes in such work,
      with the written approval of Tenant, which shall not be unreasonably
      withheld or delayed. Landlord agrees that Tenant may make changes in such
      work with the approval of Landlord and the execution by Landlord and
      Tenant of a Work Change Order, in the form attached hereto as Exhibit C.
      Landlord shall use diligence to cause Landlord's Work to be Substantially
      Completed (as defined in subparagraph B below) no later than the Delivery
      Date, subject to the provisions of Section 10.5 hereof, and any Tenant
      Delay (defined in Subparagraph C below). If Landlord fails to
      Substantially Complete the Landlord's Work by the Delivery Date, and such
      failure is not due to a Tenant Delay or a delay contemplated by Section
      10.5 hereof, then the Fixed Rent shall be abated on a day-for-day basis
      for each day during the period commencing on the Rent Commencement Date
      and ending on the date on which the Landlord's Work is Substantially
      Completed.

      B. The term "Substantially Completed" or "Substantially Complete" as used
      herein shall mean that the Landlord's Work has been completed, or is
      complete, with the exception of minor items which can be fully completed
      without material interference with Tenant's Work or Tenant's use of the
      Premises and other items which because of the season or weather or the
      nature of the item are not practicable to do at the time, provided that
      none of said items is necessary to make the Premises tenantable for the
      Permitted Uses; provided, however, if at the time Landlord's Work would
      have been substantially completed, such work cannot be completed because
      of a Tenant Delay (hereinafter defined), then, notwithstanding Landlord's
      inability to actually complete Landlord's Work, such work shall be deemed
      to be "Substantially Completed" on the date that such work would have been
      substantially completed but for such Tenant Delay, but Landlord shall not
      be relieved from the obligation to actually complete Landlord's Work.

      C. For the purposes hereof, "Tenant Delay" shall be defined as any
      material delay in the completion of Landlord's Work actually caused by (i)
      special work or long lead-time items for which Landlord identifies a
      specified period of Tenant Delay at the time of its approval of any change
      orders requested by Tenant under Section 3.1 hereof for which Landlord
      identifies a specified period of Tenant Delay at the time of its approval
      (and Tenant does not withdraw or after such special work, long lead-time
      item or change order which avoids such delay), (ii) the delay of Tenant in
      preparing or submitting plans to Landlord for the Tenant's Work, or
      supplying, submitting or approving any other plans, specifications or
      giving

                                        6
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      authorizations or supplying information reasonably required by Landlord or
      its contractors in any instance to perform the Landlord's Work within such
      time as shall be reasonably required for the expeditious prosecution of
      the work to be performed by Landlord, (iii) any contractors employed by
      Tenant including, without limitation, entities furnishing communications,
      data processing or other service or equipment directly to Tenant (and not
      under Landlord's contractor(s)), (iv) any failure to comply with this
      Article 3 or (v) any material interference with the performance of
      Landlord's Work by Tenant or any of its agents, employees, engineers or
      contractors. Tenant shall pay to Landlord, within thirty days of demand,
      all increased costs to Landlord for Landlord's Work that are caused by any
      Tenant Delay.

3.2   ACCEPTANCE OF THE PREMISES. Tenant or its representatives may, at
      reasonable times, enter upon the Premises during the progress of the work
      to inspect the progress thereof and to determine if the work is being
      performed in accordance with the requirements of Section 3.1. Tenant shall
      promptly give to Landlord notices of any alleged failure by Landlord to
      comply with those requirements. Landlord's Work shall be deemed approved
      by Tenant when Tenant occupies the Premises for the conduct of its
      business, except for items of Landlord's Work which are uncompleted or do
      not conform to Exhibit B and as to which Tenant shall, in either case,
      have given written notice to Landlord prior to such occupancy. A
      certificate of completion by a licensed architect or registered engineer
      shall be conclusive evidence that Landlord's Work has been completed
      except for items stated in such certificate to be incomplete or not in
      conformity with Exhibit B.

3.3   TENANT'S WORK. Tenant shall perform all tenant improvement work
      substantially as shown on the space plan attached hereto as Exhibit B-1
      (the "Tenant's Work"). During the performance of the Tenant's Work, Tenant
      shall not be obligated to pay Fixed Rent to Landlord unless the Rent
      Commencement Date has occurred. Tenant acknowledges that Landlord's Work
      may be performed concurrently with all or any portion of Tenant's Work,
      and agrees to cooperate with Landlord in scheduling Tenant's Work with
      Landlord to minimize interference with Landlord's Work. All Tenant's Work
      shall be performed by and at the expense of Tenant in accordance with all
      applicable laws and in accordance with and subject to the applicable
      provisions of this Lease, including, without limitation, Section 6.2.5.
      The architectural, electrical and mechanical construction drawings, plans
      and specifications (called "plans") necessary to perform the Tenant's Work
      shall be Tenant's sole responsibility and at its expense, and shall be
      submitted to Landlord for its approval. Landlord shall approve or
      disapprove in writing the initial submission of any plans within ten (10)
      business days of receipt thereof. If any of such plans are disapproved by
      Landlord, Landlord shall provide Tenant with specific reasons for such
      disapproval and the foregoing submission process shall be repeated until
      all plans have been approved by Landlord. With Landlord's prior written
      consent, which shall not be unreasonably withheld or delayed, Tenant shall
      have the right to enter the Premises during the performance of Landlord's
      Work, during normal business hours and without payment of rent, but
      otherwise subject to all the terms and conditions of this Lease, including
      Sections 4.2.4 and 6.2.5, to perform the Tenant's Work, so long as such
      work does not interfere with the performance of Landlord's Work.

3.4   ALLOWANCE. Landlord shall make a contribution toward the cost of Tenant's
      Work equal to the Allowance specified in Section 1.1. When Tenant has
      completed the Tenant's Work, Tenant shall submit to Landlord requisition
      for payment, in a form reasonably acceptable to Landlord, setting forth
      the costs incurred for Tenant's Work. The costs of Tenant's Work shall
      include all costs incurred by Tenant for labor and materials, contractor's
      fees, and fees of designers, architects and engineers. Landlord shall not
      be required to pay the Allowance directly to Tenant but hereby agrees that
      Tenant shall be entitled to a rental abatement in the amount of the
      Allowance in accordance with the provisions Section 4.1 of this Lease, on
      the express condition that all of the following criteria have been
      satisfied as of the date of such rental abatement:

      (a)    Tenant's Work has been completed to Landlord's reasonable
             satisfaction and in accordance with the plans approved by Landlord;

      (b)    Landlord has received sworn statements and waivers of lien from all
             contractors, subcontractors, materialmen and suppliers;

      (c)    Tenant is not then in default under this Lease; and

      Any costs of Tenant's Work in excess of the Allowance shall be paid for
      solely by Tenant.

                                    ARTICLE 4
                                      RENT

4.1   THE FIXED RENT. Commencing on the Rent Commencement Date, Tenant covenants
      and agrees to pay rent to Landlord at the Original Address of Landlord or
      at such other place or to such other person or entity as Landlord may by
      notice in writing to Tenant from time to time direct, at the Annual Fixed
      Rent Rate, in equal installments at the Monthly Fixed Rent Rate (which is
      1/12th of the Annual Fixed Rent Rate), in advance, without notice or
      demand, and without setoff, abatement (except as set forth below),
      suspension, deferment, reduction or deduction, except as otherwise
      expressly provided herein, on the first day of each calendar month
      included in the term; and for any portion of a calendar month following
      the Rent Commencement Date, at the rate for the first Lease Year payable
      in advance for such portion. It is the intention of the parties hereto
      that the obligations of Tenant hereunder shall be separate and independent
      covenants and agreements, that the Annual Fixed Rent, the Additional Rent
      and all other sums payable by Tenant to Landlord shall continue to be
      payable in all events and that the obligations of Tenant hereunder shall
      continue unaffected, unless the requirement to pay or perform the same
      shall have been terminated

                                        7
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      pursuant to an express provision of this Lease. Notwithstanding anything
      to the contrary contained in this paragraph, the monthly installments of
      Fixed Rent coming the under this Lease shall be abated upon full
      satisfaction of the conditions set forth in Section 3.4 above and
      continuing until Tenant has received a rent abatement in an amount equal
      to the Allowance.

      If Landlord shall give notice to Tenant that all rent and other payments
      due hereunder are to be made to Landlord by electronic funds transfers, so
      called, or by similar means, Tenant shall make all such payments as shall
      be due after receipt of said notice by means of said electronic funds
      transfers (or such similar means as designated by Landlord).

4.2   ADDITIONAL RENT. Commencing on the earlier to occur of (i) the Rent
      Commencement Date and (ii) the date Tenant first occupies the Premises for
      the conduct of its business, Tenant covenants and agrees to pay, as
      Additional Rent, insurance costs, utility charges, personal property taxes
      and its pro rata share of taxes and operating costs with respect to the
      Premises as provided in this Section 4.2 as follows:

      4.2.1  REAL ESTATE TAXES. Tenant shall pay to Landlord, as additional
             rent, for each tax period partially or wholly included in the term,
             Tenant's Percentage (as defined in Article 1, hereof of taxes (as
             hereafter defined). Tenant shall remit to Landlord, on the first
             day of each calendar month, estimated payments on account of Taxes,
             such monthly amounts to be sufficient to provide Landlord, by the
             time real estate tax payments are due and payable to any
             governmental authority responsible for collection of same, a sum
             equal to the Tenant's Percentage of Taxes, as such taxes are
             reasonably estimated by Landlord from time to time on the basis of
             the most recent tax data available. The initial calculation of the
             monthly estimated payments shall be based upon the initial Estimate
             of Tenant's Percentage of Taxes for the Tax Year and upon quarterly
             payments being due to the governmental authority on August 1,
             November 1, February 1 and May 1, and shall be made when the
             Commencement Date has been determined. Upon written request from
             Tenant to Landlord, Tenant shall have the right, within sixty (60)
             days following the end of each fiscal year, to review a copy of the
             tax bill for the preceding fiscal year at Landlord's offices. If
             the total of such monthly remittances for any Tax Year is greater
             than the Tenant's Percentage of Taxes for such Tax Year, Landlord
             shall promptly pay to Tenant, or credit against the next accruing
             payments to be made by Tenant pursuant to this subsection 4.2.1,
             the difference; if the total of such remittances is less than the
             Tenant's Percentage of Taxes for such Tax Year, Tenant shall pay
             the difference to Landlord at least ten (10) days prior to the date
             or dates within such Tax Year that any Taxes become due and payable
             to the governmental authority (but in any event no earlier than ten
             (10) days following a written notice to Tenant, which notice shall
             set forth the manner of computation of Tenant's Percentage of
             Taxes).

             If, after Tenant shall have made reimbursement to Landlord pursuant
             to this subsection 4.2.1, Landlord shall receive a refund of any
             portion of Taxes paid by Tenant with respect to any Tax Year during
             the term hereof as a result of an abatement of such Taxes by legal
             proceedings, settlement or otherwise (without either party having
             any obligation to undertake any such proceedings), Landlord shall
             promptly pay to Tenant, or credit against the next accruing
             payments to be made by Tenant pursuant to this subsection 4.2.1,
             the Tenant's Percentage of the refund (less the proportional, pro
             rata expenses, including attorneys' fees and appraisers, fees,
             incurred in connection with obtaining any such refund), as relates
             to Taxes paid by Tenant to Landlord with respect to any Tax Year
             for which such refund is obtained, unless Tenant requests in
             writing that Landlord pay any such refund to Tenant.

             In the event this Lease shall commence, or shall end (by reason of
             expiration of the term or earlier termination pursuant to the
             provisions hereof), on any date other than the first or last day of
             the Tax Year, or should the Tax Year or period of assessment of
             real estate taxes be changed or be more or less than one (1) year,
             as the case may be, then the amount of Taxes which may be payable
             by Tenant as provided in this subsection 4.2.1 shall be
             appropriately apportioned and adjusted.

             The term "Taxes" shall mean all taxes, assessments, betterments and
             other charges and impositions (including, but not limited to, fire
             protection service fees and similar charges) levied, assessed or
             imposed at any time during the term by any governmental authority
             upon or against the Property, or taxes in lieu thereof, and
             additional types of taxes to supplement real estate taxes due to
             legal limits imposed thereon. If, at any time during the term of
             this Lease, any tax or excise on rents or other taxes, however
             described, are levied or assessed against Landlord with respect to
             the rent reserved hereunder, either wholly or partially in
             substitution for, or in addition to, real estate taxes assessed or
             levied on the Property, such tax or excise on rents shall be
             included in Taxes; however, Taxes shall got include franchise,
             estate, inheritance, succession, capital levy, transfer, income or
             excess profits taxes assessed on Landlord. Taxes shall include any
             estimated payment made by Landlord on discount of a fiscal tax
             period for which the actual and final amount of taxes for such
             period has not been determined by the governmental authority as of
             the date of any such estimated payment.

      4.2.2  PERSONAL PROPERTY TAXES. Tenant shall pay all taxes charged,
             assessed or imposed upon the personal property of Tenant in or upon
             the Premises.

      4.2.3  OPERATING COSTS. Tenant shall pay to Landlord the Tenant's
             Percentage (as defined in Article 1 hereof) of Operating Costs (as
             hereinafter defined) incurred by Landlord in any calendar year.

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             Tenant shall remit to Landlord, on the first day of each calendar
             month, estimated payments on account of Operating Costs, such
             monthly amounts to be sufficient to provide Landlord, by the end of
             the calendar year, a sum equal to the Operating Costs, as
             reasonably estimated by Landlord from time to time. The initial
             monthly estimated payments shall be in an amount equal to 1/12th of
             the Initial Estimate of Tenant's Percentage of Operating Costs for
             the calendar year. Following the end of each calendar year,
             including the first calendar year, Landlord shall deliver to Tenant
             a reasonably detailed statement of the Operating Costs payable
             under this Section 4.2.3 for such calendar year, prepared,
             allocated and computed in accordance with generally accepted
             accounting principles (the "Annual Operating Statement"). If, at
             the expiration of the calendar year in respect of which monthly
             installments of Operating Costs shall have been made as aforesaid,
             the total of such monthly remittances is greater than the actual
             Operating Costs for such calendar year, Landlord shall credit
             against the next accruing payments to be made by Tenant pursuant to
             this subsection 4.2.3, the difference, unless Tenant requests in
             writing that Landlord pay any such difference to Tenant; if the
             total of such remittances is less than the Operating Costs for such
             calendar year, Tenant shall pay the difference to Landlord within
             twenty (20) days from the date Landlord furnishes to Tenant the
             Annual Operating Statement. Any reimbursement for Operating Costs
             due and payable by Tenant with respect to periods of less than
             twelve (12) months shall be equitably prorated.

             The term "Operating Costs" shall mean all costs and expenses
             incurred for the operation, cleaning, maintenance, repair and
             upkeep of the Property, and the portion of such costs and expenses
             with regard to the common areas, facilities and amenities of the
             Park which is equitably allocable to the Property, including,
             without limitation, all costs of maintaining and repairing the
             Property and the Park (including snow removal, landscaping and
             grounds maintenance, operation and maintenance of parking lots,
             sidewalks, walking paths, access roads and driveways, security,
             operation and repair of heating and air-conditioning equipment,
             elevators, lighting and any other Building equipment or systems)
             and of all repairs and replacements (other than repairs or
             replacements for which Landlord has received full reimbursement
             from contractors or from others) necessary to keep the Property and
             the Park in good working order, repair, appearance and condition;
             all costs of any reasonable insurance carried by Landlord relating
             to the Property; all costs related to provision of heat (including
             oil, electric, steam and/or gas), air-conditioning, and water
             (including sewer charges) and other utilities to the Building;
             payments under all service contracts relating to the foregoing; all
             compensation, fringe benefits, payroll taxes and workmen's
             compensation insurance premiums related thereto with respect to any
             employees of Landlord or its affiliates engaged in security and
             maintenance of the Property and the Park; attorneys' fees and
             disbursements (exclusive of any such fees and disbursements
             incurred in tax abatement proceedings) and auditing and other
             professional fees and expenses incurred in connection with the
             Park; and a reasonable management fee consistent with management
             fees charged by landlord's of comparable buildings in the
             Burlington area.

             There shall not be included in such Operating Costs (i) brokerage
             fees (including rental fees) related to the operation of the
             Building; (ii) interest and depreciation charges incurred on the
             Property; (iii) expenditures made by Tenant with respect to a)
             cleaning, maintenance and upkeep of the Premises, except to the
             extent provided by Landlord at Tenant's request or pursuant to the
             terms and conditions of this Lease, and (b) the provision of
             electricity to the Premises; (iv) mortgage charges (including
             principal and interest); (v) the cost of work done or services
             supplied by Landlord for a particular tenant in the Park for which
             Landlord has the right to be reimbursed by such tenant; (vi) any
             cost incurred by the gross negligence or willful misconduct of the
             Landlord, its agents and employees; (vii) except to the extent
             caused by or attributable to Tenant, penalties, fines and other
             costs incurred due to violation by the Landlord of any lease or any
             laws, rules, regulations or ordinances applicable to the Building
             and any interest or penalties due for late payment by Landlord of
             any of the expenses; (viii) expenses to prepare, renovate, repaint,
             redecorate or perform any other work in any space leased to an
             existing or prospective tenant or other occupant of the Park other
             than Tenant (except as otherwise agreed to); (ix) expenses incurred
             by Landlord to resolve disputes, enforce or negotiate lease terms
             with prospective or existing tenants other than Tenant or in
             connection with any financing, sale or syndication of the Building;
             (x) fees paid to affiliates of Landlord to the extent that such
             fees exceed the customary amount charged for the services provided
             by unaffiliated persons or entities of similar skill, competence
             and experience; (xi) to the extent that insurance proceeds are
             unavailable due to Landlord's failure to maintain replacement cost
             insurance, costs and expenses incurred by Landlord in connection
             with the repair of damage to the Building caused by fire or other
             casualty, insured or required to be insured against hereunder;
             (xii) reserves for Operating Costs; (xiii) amortization and
             depreciation of the Building (except as set forth below with
             respect to capital items); (xiv)costs to repair any items related
             to the Building or the Property covered by warranty; and (xv) costs
             that are capital in nature, except for an annual amortization for
             capital expenditures specified in the next paragraph below.

             If, during the term of this Lease, Landlord shall replace any
             capital items or make any capital expenditures in order to comply
             with laws in effect after the Commencement Date, or to effect
             savings in Operating Costs, or to replace worn-out items
             (collectively the "capital expenditures") the total amount of which
             is not properly included in Operating Costs for the calendar year
             in which they were made, there shall nevertheless be included in
             Operating Costs for each calendar year in which and after such
             capital expenditure is made the annual charge-off of such capital
             expenditure. (Annual charge-off shall be determined by (i) dividing
             the original cost of the capital expenditure by the number of years
             of useful life thereof [The useful life shall be

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             reasonably determined by Landlord in accordance with generally
             accepted accounting principles and practices in effect at the time
             of acquisition of the capital item.]; and (ii) adding to such
             quotient an interest factor computed on the unamortized balance of
             such capital expenditure based upon an interest rate reasonably
             determined by Landlord as being the interest rate then being
             charged for long-term mortgages by institutional lenders on like
             properties within the locality in which the Building is located.)
             Provided, further, that if Landlord reasonably concludes on the
             basis of engineering estimates that a particular capital
             expenditure will effect savings in Operating Costs and that such
             annual projected savings will exceed the annual charge-off of
             capital expenditure computed as aforesaid, then and in such events,
             the annual charge-off shall be determined by dividing the amount of
             such capital expenditure by the number of years over which the
             projected amount of such savings shall fully amortize the cost of
             such capital item or the amount of such capital expenditure; and by
             adding the interest factor, as aforesaid.

             Upon Tenant's written request (the "Tenant's Audit Notice"), which
             request must be made by Tenant within sixty (60) days after
             Landlord delivers to Tenant the Annual Operating Statement, Tenant
             shall have the right to inspect or audit Landlord's books of
             account with respect to matters set forth in the Annual Operating
             Statement. Tenant's audit or inspection shall commence no later
             than thirty (30) days after Tenant's Audit Notice and shall be
             conducted only at Landlord's offices where said books of account
             are kept during business hours reasonably designated by Landlord.
             Tenant shall pay all costs of such audit or inspection. Tenant may
             not conduct an inspection or have an audit performed under this
             Section 4.2.3 more than once with respect to any period covered by
             any Annual Operating Statement from Landlord. Landlord shall keep
             full and accurate books of account covering the Operating Costs and
             the Annual Operating Statement shall accurately reflect the same
             and Tenant's share thereof. Such audit or inspection may only be
             made by Tenant or a nationally, recognized certified public
             accounting firm or a reputable auditing company which is not
             compensated on a contingency fee basis. All non-public information
             about Landlord and/or the Property discovered during the course of
             such examination shall be kept confidential.

      4.2.4  INSURANCE. Tenant shall, at its expense, as Additional Rent, take
             out and maintain throughout the term the following insurance
             protecting Landlord:

             4.2.4.1 Commercial general liability insurance naming Landlord,
                     Tenant, and Landlord's managing agent and any mortgagee of
                     which Tenant has been given notice as insureds or
                     additional insureds and indemnifying the parties so named
                     against all claims and demands for death or any injury to
                     person or damage to property which may be claimed to have
                     occurred on the Premises (or the Property, insofar as used
                     by customers, employees, servants or invitees of the
                     Tenant), in amounts which shall, at the beginning of the
                     term, be at least equal to the limits set forth in Section
                     1.1, and, which, from time to time during the term, shall
                     be for such higher limits, if any, as are customarily
                     carried in the area in which the Premises are located on
                     property similar to the Premises and used for similar
                     purposes, $5,000,000.00 umbrella liability for bodily
                     injury, personal injury and property damage, naming
                     Landlord, and its managing agent and mortgagee, as
                     additional insureds; and workmen's compensation insurance
                     with statutory limits covering all of Tenant's employees
                     working on the Premises.

             4.2.4.2 Fire insurance with the usual extended coverage
                     endorsements covering all Tenant's furniture, furnishings,
                     fixtures and equipment, the Tenant's Work and any other
                     contents or improvements in the Premises installed at
                     Tenant's expense by or on behalf of Tenant during the term.

             4.2.4.3 All such policies shall be obtained from responsible
                     companies qualified to do business and in good standing in
                     Massachusetts, which companies and the amount of insurance
                     allocated thereto shall be subject to Landlord's reasonable
                     approval. Tenant agrees to furnish Landlord with
                     certificates evidencing all such insurance prior to the
                     beginning of the term hereof and evidencing renewal just
                     prior to the expiration of any such policy. Each such
                     policy shall be non-cancelable with respect to the interest
                     of Landlord without at least ten (10) days, prior written
                     notice thereto. In the event provision for any such
                     insurance is to be by a blanket insurance policy, the
                     policy shall allocate a specific and sufficient amount of
                     coverage to the Premises.

             4.2.4.4 All insurance which is carried by either party with respect
                     to the Building, Premises or to furniture, furnishings,
                     fixtures, or equipment therein or alterations or
                     improvements thereto, whether or not required, shall
                     include provisions which either designate the other party
                     as one of the insured or deny to the insurer acquisition by
                     subrogation of rights of recovery against the other party
                     to the extent such rights have been waived by the insured
                     party prior to occurrence of loss or injury, insofar as,
                     and to the extent that, such provisions may be effective
                     without making it impossible to obtain insurance coverage
                     from responsible companies qualified to do business in the
                     state in which the Premises are located (even though extra
                     premium may result therefrom). In the event that extra
                     premium is payable by either party as a result of this
                     provision, the other party shall reimburse the party paying
                     such premium the amount of such extra premium. If at the
                     request of one party, this non-subrogation provision is
                     waived, then the obligation of reimbursement shall cease
                     for such period of time as such waiver shall be effective,
                     but

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                     nothing contained in this subsection shall derogate from or
                     otherwise affect releases elsewhere herein contained of
                     either party for claims. Each party shall be entitled to
                     have certificates of any policies containing such
                     provisions. Each party hereby waives all rights of recovery
                     against the other for loss or injury against which the
                     waiving party is protected by insurance containing said
                     provisions, reserving, however, any rights with respect to
                     any excess of loss or injury over the amount recovered by
                     such insurance. Tenant shall not acquire as insured under
                     any insurance carried on the Premises any right to
                     participate in the adjustment of loss or to receive
                     insurance proceeds and agrees upon request promptly to
                     endorse and deliver to Landlord any check or other
                     instruments in payment of loss in which Tenant is named as
                     payee.

      4.2.5  UTILITIES. Tenant shall pay directly to the respective utility
             providers all charges for the cost of electricity and gas furnished
             or consumed on the Premises, and all charges for telephone and
             other utilities or services not supplied by Landlord, whether
             designated as a charge, tax, assessments, fee or otherwise, all
             such charges to be paid as the same from time to time become due.
             Tenant shall pay to Landlord, upon demand, all charges, including
             sewer charges, for Tenant's water usage at the Premises. It is
             understood that water is supplied by Landlord pursuant to
             Subsection 5.1.3, but the Premises are separately metered to
             Landlord and not Tenant. Except as otherwise provided in Article 5,
             it is understood and agreed that Tenant shall make its own
             arrangements for the installation or provision of all such
             utilities and that Landlord shall be under no obligation to furnish
             any utilities to the Premises and shall not be liable for any
             interruption or failure in the supply of any such utilities to the
             Premises.

4.3   LATE PAYMENT OF RENT. If any installment of rent is paid after the date
      the same was due, and if on prior occasion in the twelve (12) month period
      prior to the date such installment was due an installment of rent was paid
      after the same was due, then Tenant shall pay Landlord a late payment fee
      equal to five (5%) percent of the overdue payment.

4.4   LETTER OF CREDIT. The performance of Tenant's obligations under this Lease
      shall be secured by a letter of credit throughout the term hereof in
      accordance with and subject to the following terms and conditions:

      4.4.1  AMOUNT OF LETTER OF CREDIT. (a) Concurrently with Tenant's
             execution and delivery of this Lease. Tenant shall deliver to
             Landlord an irrevocable standby letter of credit (the "Original
             Letter of Credit") which shall be (i) in the form of Exhibit F
             attached to this Lease or in a form reasonably acceptable to both
             Landlord and Tenant (the "Form LC"), (ii) issued by a bank
             reasonably satisfactory to Landlord upon which presentment may be
             made in Boston, Massachusetts, (iii) in the amount equal to the
             Letter of Credit Amount, and (iv) for a term of at least 1 year,
             subject to the provisions of Section 4.4.2 below. The original
             Letter of Credit, any Additional Letter(s) of Credit and Substitute
             Letter(s) of Credit are referred to herein as the "Letter of
             Credit."

             (b) On the conditions that (i) Tenant is not in default under this
             Lease at the time of the reduction, and (ii) either (x) Tenant has
             achieved a profitable calendar year and Tenant provides Landlord
             with an audited statement reporting such profitable calendar year,
             which statement shall be prepared by Tenant's accountant using
             generally accepted accounting principles, or (y) Tenant has a
             minimum of $10,000,000.00 of unrestricted cash and securities at
             any time after the end of the 3rd lease year and provides Landlord
             with reasonable evidence of the same, then the Letter of Credit
             Amount shall be reduced to $75,000.00. This reduction shall only be
             affected one time during the term of this Lease.

      4.4.2  RENEWAL OF LETTER OF CREDIT. Each Letter of Credit shall be
             automatically renewable in accordance with the second to last
             paragraph of the Form LC; provided however, that Tenant shall be
             required to deliver to Landlord a new letter of credit (a
             "Substitute Letter of Credit") satisfying the requirements for the
             Original Letter of Credit under Section 4.4.1 on or before the date
             30 days prior to the expiration of the term of the Letter of Credit
             then in effect, if the issuer of such Letter of Credit gives notice
             of its election not to renew such Letter of Credit for any
             additional period pursuant thereto. Should any letter of Credit
             contain a final expiration date, in addition to a current
             expiration date, such final expiration date shall be no earlier
             than 45 days following the Expiration Date of this Lease.

      4.4.3  DRAWS TO CURE DEFAULTS. If the Fixed Rent, Additional Rent or any
             other sum payable to Landlord hereunder shall be overdue and unpaid
             or should Landlord make payments on behalf of the Tenant, or Tenant
             shall fail to perform any of the terms of this Lease in all cases
             beyond the expiration of all applicable notice and cure periods,
             then Landlord shall have the right, at any time thereafter to draw
             down from the Letter of Credit the amount necessary to cure such
             default. In the event of any such draw by the Landlord, Tenant
             shall, within 30 days of written demand therefor, deliver to
             Landlord an additional Letter of Credit ("Additional Letter of
             Credit") satisfying the requirements for the Original Letter of
             Credit, except that the amount of such Additional Letter of Credit
             shall be the amount of such draw.

      4.4.4  DRAWS TO PAY DAMAGES. In addition, if (i) this Lease shall have
             been terminated as a result of Tenant's default under this Lease
             beyond the expiration of the applicable cure period, and/or (ii)
             this Lease shall have been rejected in a bankruptcy or other
             creditor-debtor proceeding, then Landlord shall have the right at
             any time thereafter to draw down from the Letter of Credit an
             amount sufficient to pay any and all damages payable by Tenants on
             account of such termination or rejection, as the case may be,
             pursuant to Article 8 hereof. In the event of bankruptcy or other

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             creditor-debtor proceeding against Tenant, all proceeds of the
             Letter of Credit shall be deemed to be applied first to the payment
             of rent and other charges due Landlord for all periods prior to the
             filing of such proceedings.

      4.4.5  DRAWS FOR FAILURE TO DELIVER SUBSTITUTE LETTER OF CREDIT. If Tenant
             fails timely to deliver to Landlord a Substitute Letter of Credit,
             then Landlord shall have the right, at any time thereafter, without
             giving any notice to Tenant, to draw down the Letter of Credit and
             to hold the proceeds thereof ("Security Proceeds") in a bank
             account in the name of Landlord, which may be withdrawn and applied
             by Landlord under the same circumstances and for the same purposes
             as if the Security Proceeds were a Letter of Credit. Upon any such
             application of Security Proceeds by Landlord, Tenant shall, within
             30 days of written demand therefor, deliver to Landlord an
             Additional Letter of Credit in the amounts of Security Proceeds so
             applied.

      4.4.6  TRANSFERABILITY. Landlord shall (i) transfer its beneficial
             interest under the Letter of Credit or any Security Proceeds in
             connection with Landlord's sale or transfer of the Building, or
             (ii) be entitled to transfer its beneficial interest under the
             Letter of Credit or any Security proceeds in connection with the
             addition, deletion or modification of any beneficiaries under the
             Letter of Credit, and the Letter of Credit shall specifically state
             on its face that it is transferable by Landlord, its successors and
             assigns. Tenant agrees to pay Landlord upon demand, as Additional
             Rent, all costs and fees charged to effect such transfer.

      4.4.7  RETURN OF LETTER OF CREDIT AT END OF TERM. Within 30 days after the
             expiration of the term, to the extent Landlord has not previously
             drawn upon any Letter of Credit or Security Proceeds held by
             Landlord, Landlord shall return the same to Tenant provided that
             there is not at such time any continuing default of any of Tenant's
             obligations under this Lease.

                                    ARTICLE 5
                              LANDLORD'S COVENANTS

5.1   AFFIRMATIVE COVENANTS. Landlord covenants with Tenant:

      5.1.1  HEAT AND AIR-CONDITIONING. To furnish to the Premises, separately
             metered and at the direct expense of Tenant as hereinabove
             provided, heat and air-conditioning (reserving the right, at any
             time, to change energy or heat sources) sufficient to maintain the
             Premises at comfortable temperatures (subject to all federal,
             state, and local regulations relating to the provision of heat),
             during such hours of the day and days of the year that the Building
             is normally open.

      5.1.2  ELECTRICITY. To furnish to the Premises, separately metered and at
             the direct expense of Tenant as hereinabove provided, reasonable
             electricity for Tenant's Permitted Uses. If Tenant Shall require
             electricity in excess of reasonable quantities for Tenant's
             Permitted Uses and if (i) in Landlord's reasonable judgment,
             Landlord's facilities are inadequate for such excess requirements,
             or (ii) such excess use shall result in an additional burden on the
             Building utilities systems and additional cost to Landlord on
             account thereof, as the case may be, (a) Tenant shall, upon demand,
             reimburse Landlord for such additional cost, as aforesaid, or (b)
             Landlord, upon written request, and at the sole cost and expense of
             Tenant, will furnish and install such additional wire, conduits,
             feeders, switchboards and appurtenances as reasonably may be
             required to supply such additional requirements of Tenant (if
             electricity therefor is then available to Landlord), provided that
             the same shall be permitted by applicable laws and insurance
             regulations and shall not cause permanent damage or injury to the
             Building or cause or create a dangerous or hazardous condition or
             entail excessive or unreasonable alterations or repairs.

      5.1.3  WATER. To furnish water for ordinary cleaning, lavatory, toilet and
             shower facilities and for all kitchen appliances and sinks.

      5.1.4  FIRE ALARM. To maintain fire alarm systems within the Building.

      5.1.5  REPAIRS. Except as otherwise expressly provided herein, to make
             such repairs and replacements to the roof, exterior walls, floor
             slabs and other structural components of the Building, and to the
             plumbing, electrical, heating, ventilating and air-conditioning
             systems of the Building as may be necessary to keep them in good
             repair and condition (exclusive of equipment installed by Tenant
             and except for those repairs required to be made by Tenant pursuant
             to Section 6.1.3 hereof and repairs or replacements occasioned by
             any act or negligence of Tenant, its servants, agents, customers,
             contractors, employees, invitees, or licensees).

      5.1.6  LANDLORD'S INSURANCE. To take out and maintain throughout the term
             all-risk casualty insurance in an amount equal to 100% of the
             replacement cost of the Building but specifically excluding the
             Tenant's Work and any improvements installed by Tenant during the
             term.

      5.1.7  LANDLORD'S INDEMNIFICATION. To save Tenant harmless, and to
             exonerate and indemnify Tenant from and against any and all claims,
             liabilities or penalties asserted by or on behalf of any person,
             firm, corporation or public authority on account of injury, death,
             damage or loss to the person or property in or upon the common
             areas of the Property arising out of the negligence, fault or
             misconduct of Landlord, its agents, servants, employees or
             contractors. In respect of all of the

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             foregoing, Landlord shall indemnify Tenant from and against all
             costs, expenses (including reasonable attorney's fees), and
             liabilities incurred in or in connection with any such claim,
             action or proceeding brought thereon; and, in case of any action or
             proceeding brought against Tenant by reason of any such claim,
             Landlord, upon notice from Tenant and at Landlord's expense, shall
             resist or defend such action or proceeding and employ counsel
             therefor reasonably satisfactory to Tenant.

5.2   INTERRUPTION. Landlord shall be under no responsibility or liability for
      failure or interruption of any of the above-described services, repairs or
      replacements caused by breakage, accident, strikes, repairs, inability to
      obtain supplies, labor or materials, or for any other causes beyond the
      control of the Landlord, and in no event for any indirect or consequential
      damages to Tenant; and failure or omission on the part of the Landlord to
      furnish any of same for any of the reasons set forth in this paragraph
      shall not be construed as an eviction of Tenant, actual or constructive,
      nor entitle Tenant to an abatement of rent, nor render the Landlord liable
      in damages, nor release Tenant from prompt fulfillment of any of its
      covenants under this Lease.

      Notwithstanding the foregoing, if Landlord fails to provide any service
      that it is required to provide above so that Tenant's ability to conduct
      business at the Premises is materially adversely affected for a period of
      five (5) consecutive business days after written notice thereof from
      Tenant to Landlord, then, provided that such failure or Landlord's
      inability to cure such condition is not (i) due to a cause beyond
      Landlord's reasonable control and/or (ii) generally affecting other
      buildings in the vicinity of the Premises (such as a neighborhood power
      outage or a water main break) or a fire or other casualty or taking (which
      shall be governed by Article 7 below) or the fault or negligence of Tenant
      or any of its agents, employees or contractors, the Fixed Rent and
      Additional Rent shall be equitably abated based upon the impact thereof on
      Tenant's ability to conduct business in the Premises until such service(s)
      is restored to their level prior to the interruption.

                                    ARTICLE 6
                          TENANT'S ADDITIONAL COVENANTS

6.1   AFFIRMATIVE COVENANTS. Tenant covenants at all times during the term and
      for such further time (prior or subsequent thereto) as Tenant occupies the
      Premises or any part thereof:

      6.1.1  PERFORM OBLIGATIONS. To perform promptly all of the obligations of
             Tenant set forth in this Lease; and to pay when due the Fixed Rent
             and Additional Rent and all charges, rates and other sums which by
             the terms of this Lease are to be paid by Tenant.

      6.1.2  USE. To use the Premises only for the Permitted Uses, and from time
             to time to procure all licenses and permits necessary therefor, at
             Tenant's sole expense. As of the Date of this Lease, Landlord
             represents and warrants that the Permitted Uses are in compliance
             with all applicable zoning codes. With respect to any licenses or
             permits for which Tenant may apply, pursuant to this subsection
             6.1.2 or any other provision hereof, Tenant shall furnish Landlord
             copies of applications therefor on or before their submission to
             the governmental authority.

      6.1.3  REPAIR AND MAINTENANCE. To maintain the Premises in neat order and
             condition, to contract for cleaning and janitorial services, in
             accordance with cleaning and janitorial standards generally
             prevailing throughout the term in comparable buildings in the area,
             and to perform all routine and ordinary repairs to the Premises and
             to any plumbing, heating, electrical, ventilating and
             air-conditioning systems located within the Premises and installed
             by Tenant such as are necessary to keep them in good working order,
             appearance and condition, as the case may require, reasonable use
             and wear thereof and damage by fire or by unavoidable casualty only
             excepted; to keep all glass in windows and doors of the Premises
             (except glass in the exterior walls of the Building) whole and in
             good condition with glass of the same quality as that injured or
             broken; and to make as and when needed as a result of misuse by, or
             neglect or improper conduct of Tenant or Tenant's servants,
             employees, agents, invitees or licensees or otherwise, all repairs
             necessary, which repairs and replacements shall be in quality and
             class equal to the original work. (Landlord, upon default of Tenant
             hereunder and upon prior notice to Tenant, may elect, at the
             expense of Tenant, to perform all such cleaning and maintenance and
             to make any such repairs or to repair any damage or injury to the
             Building or the Premises caused by moving property of Tenant in or
             out of the Building, or by installation or removal of furniture or
             other property, or by misuse by, or neglect, or improper conduct
             of, Tenant or Tenant's servants, employees, agents, contractors,
             customers, patrons, invitees, or licensees.)

      6.1.4  COMPLIANCE WITH LAW. To make all repairs, alterations, additions or
             replacements to the Premises required by any law or ordinance or
             any order or regulation of any public authority to the extent the
             same are Tenant's responsibility under this Lease; to keep the
             Premises equipped with all safety appliances so required; and to
             comply with the orders and regulations of all governmental
             authorities with respect to zoning, building, fire, health and
             other codes, regulations, ordinances or laws applicable to Tenant's
             particular use of the Premises, except that Tenant may defer
             compliance so long as the validity of any such law, ordinance,
             order or regulations shall be contested by Tenant in good faith and
             by appropriate legal proceedings, if Tenant first gives Landlord
             appropriate assurance or security against any loss, cost or expense
             on account thereof.

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      6.1.5  INDEMNIFICATION. To save harmless, exonerate and indemnify
             Landlord, its agents (including, without limitation, Landlord's
             managing agent) and employees (such agents and employees being
             referred to collectively as the "Landlord Related Parties") from
             and against any and all claims, liabilities or penalties asserted
             by or on behalf of any person, firm, corporation or public
             authority on account of injury, death, damage or loss to person or
             property in or upon the Premises and the Property arising out of
             the use or occupancy of the Premises by Tenant or by any person
             claiming by, through or under Tenant (including, without
             limitation, all patrons, employees and customers of Tenant), or
             arising out of any delivery to or service supplied to the Premises,
             or on account of or based upon anything whatsoever done on the
             Premises, except if the same was caused by the willful negligence,
             fault or misconduct of Landlord or the Landlord Related Parties. In
             respect of all of the foregoing, Tenant shall indemnify Landlord
             and the Landlord Related Parties from and against all costs,
             expenses (including reasonable attorneys' fees), and liabilities
             incurred in or in connection with any such claim, action or
             proceeding brought thereon; and, in case of any action or
             proceeding brought against Landlord or the Landlord Related Parties
             by reason of any such claim, Tenant, upon notice from Landlord and
             at Tenant's expense, shall resist or defend such action or
             proceeding and employ counsel therefor reasonably satisfactory to
             Landlord.

      6.1.6  LANDLORD'S RIGHT TO ENTER. To permit Landlord and its agents to
             enter into and examine the Premises at reasonable times and to show
             the Premises, and to make repairs to the Premises and to install,
             use and repair telecommunications equipment on the roof of the
             Building, provided that Landlord agrees not to unreasonably
             interfere with Tenant's use of the Premises while exercising its
             right to enter pursuant to this subsection 6.1.6, and, during the
             last six (6) months prior to the expiration of this Lease, to keep
             affixed in suitable places notices of availability of the Premises.
             Except in the case of an emergency, Landlord shall use reasonable
             efforts to provide Tenant with notice prior to Landlord exercising
             its right to enter the Premises pursuant to this subsection 6.1.6.
             However, notwithstanding the foregoing, Landlord shall give Tenant
             reasonable prior notice whenever Landlord requires access to the
             Premises to show the Premises.

      6.1.7  PERSONAL PROPERTY AT TENANT'S RISK. All of the furnishings,
             fixtures, equipment, effects and property of every kind, nature and
             description of Tenant and of all persons claiming by, through or
             under Tenant which, during the continuance of this Lease or any
             occupancy of the premises by Tenant or anyone claiming under
             Tenant, may be on the Premises, shall be at the sole risk and
             hazard of Tenant and if the whole or any part thereof shall be
             destroyed or damaged by fire, water or otherwise, or by the leakage
             or bursting of water pipes, steam pipes, or other pipes, by theft
             or from any other cause, no part of said loss or damage is to be
             charged to or to be borne by Landlord, except that Landlord shall
             in no event be indemnified or held harmless or exonerated from any
             liability to Tenant or to any other person, for any injury, loss,
             damage or liability to the extent prohibited by law.

      6.1.8  PAYMENT OF LANDLORD'S COST OF ENFORCEMENT. To pay on demand
             Landlord's expenses, including reasonable attorneys' fees, incurred
             in enforcing any obligation of Tenant under this Lease or in curing
             any default by Tenant under this Lease as provided in Section 8.4.

      6.1.9  YIELD UP. At the expiration of the term or earlier termination of
             this Lease; to surrender all keys to the Premises; to remove all of
             its trade fixtures, personal property and signs in or on the
             Premises; to deliver to Landlord stamped architectural plans
             showing the Premises at yield up (which may be the initial plans if
             Tenant has made no installations after the Commencement Date); to
             remove such installations made by it as Landlord may request
             (including computer and telecommunications wiring and cabling, it
             being understood that if Tenant leaves such wiring and cabling in a
             useable condition, Landlord, although having the right to request
             removal thereof, is less likely to so request) and all Tenant's
             signs wherever located; to repair all damage caused by such removal
             and, if requested by Landlord, to restore the Premises, or any
             portion thereof, to open office or R&D configuration if Tenant had
             previously made alterations to such area other than those typical
             of office or R&D space, and to yield up the Premises (including all
             installations and improvements not designated by Landlord for
             removal, except for trade fixtures and such of said installations
             or improvements as Landlord shall request Tenant to remove),
             broom-clean and in the same good order and repair in which Tenant
             is obliged to keep and maintain the Premises by the provisions of
             this Lease, reasonable wear and tear, and damage by casualty and
             condemnation excepted. Any property not so removed shall be deemed
             abandoned and, if Landlord so elects, deemed to be Landlord's
             property, and may be retained or removed and disposed of by
             Landlord in such manner as Landlord shall determine and Tenant
             shall pay Landlord the entire cost and expense incurred by it in
             effecting such removal and disposition and in making any incidental
             repairs and replacements to the Premises and for use and occupancy
             during the period after the expiration of the term and prior to its
             performance of its obligations under this subsection 6.1.9. Tenant
             shall further indemnify Landlord against all loss, cost and damage
             resulting from Tenant's failure and delay in surrendering the
             Premises as above provided. Landlord hereby confirms that the
             Landlord's Work (as defined in Article 3) shall not be required to
             be removed by Tenant at the end of the term.

             If the Tenant remains in the Premises beyond the expiration or
             earlier termination of this Lease, such holding over shall be
             without right and shall not be deemed to create any tenancy, but
             the Tenant shall be a tenant at sufferance only at a daily rate of
             rent equal to two (2) times the rent and other charges in effect
             under this Lease as of the day prior to the date of expiration of
             this Lease.

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      6.1.10 RULES AND REGULATIONS. To comply with the Rules and Regulations set
             forth in Exhibit D, and with all reasonable Rules and Regulations
             hereafter made by Landlord, of which Tenant has been given notice.

      6.1.11 ESTOPPEL CERTIFICATE. Upon not less than ten (10) days' prior
             written request by Landlord, to execute, acknowledge and deliver to
             Landlord a statement in writing, which may be in the form attached
             hereto as Exhibit E or in another form reasonably similar thereto,
             or such other form as Landlord may provide from time to time,
             certifying all or any of the following: (i) that this Lease is
             unmodified and in full force and effect, (ii) whether the term has
             commenced and Fixed Rent and Additional Rent have become payable
             hereunder and, if so, the dates to which they have been paid, (iii)
             whether or not Landlord is in default in performance of any of the
             terms of this Lease, (iv) whether Tenant has accepted possession of
             the Premises, (v) whether Tenant has made any claim against
             Landlord under this Lease and, if so, the nature thereof and the
             dollar amount, if any, of such claim, (vi) whether there exist any
             offsets or defenses against enforcement of any of the terms of this
             Lease upon the part of Tenant to be performed, and (vii) such
             further information with respect to the Lease or the Premises as
             Landlord may reasonably request. Any such statement delivered
             pursuant to this subsection 6.1.11 may be relied upon by any
             prospective purchaser or mortgagee of the Premises, or any
             prospective assignee of such mortgage. Tenant shall also deliver to
             Landlord such financial information as may be reasonably required
             by Landlord to be provided to any mortgagee or prospective
             purchaser of the Premises, provided, further that the party
             provided with such financial information agrees in a written
             document reasonably acceptable to such party to keep the financial
             information confidential.

      6.1.12 LANDLORD'S EXPENSES RE CONSENTS. To reimburse Landlord promptly on
             demand for all reasonable legal expenses incurred by Landlord in
             connection with all requests by Tenant for consent or approval
             hereunder.

6.2   NEGATIVE COVENANTS. Tenant covenants at all times during the term and such
      further time (prior or subsequent thereto) as Tenant occupies the Premises
      or any part thereof:

      6.2.1  ASSIGNMENT AND SUBLETTING. Not to assign, transfer, mortgage or
             pledge this Lease or to sublease (which term shall be deemed to
             include the granting of concessions and licenses and the like) all
             or any part of the Premises or suffer or permit this Lease or the
             leasehold estate hereby created or any other rights arising under
             this Lease to be assigned, transferred or encumbered, in whole or
             in part, whether voluntarily, involuntarily or by operation of law,
             or permit the occupancy of the Premises by anyone other than Tenant
             without the prior written consent of Landlord, except for Permitted
             Transfers (hereinafter defined). In the event Tenant desires to
             assign this Lease or sublet any portion or all of the Premises,
             Tenant shall notify Landlord in writing of Tenant's intent to so
             assign this Lease or sublet the Premises and the proposed effective
             date of such subletting or assignment, and shall request in such
             notification that Landlord consent thereto. Except in the case of a
             Permitted Transfer, Landlord may terminate this Lease in the case
             of a proposed assignment, or suspend this Lease pro tanto for the
             period and with respect to the space involved in the case of a
             proposed subletting, by giving written notice of termination or
             suspension to Tenant within thirty (30) days of Tenant's
             notification to Landlord of Tenant's intent to sublease or assign
             as aforesaid, with such termination or suspension to be effective
             as of the effective date of such assignment or subletting. If
             Tenant then notifies Landlord that Tenant chooses not to assign or
             sublet, then such termination or suspension shall not be effective
             as to that particular transaction for which Tenant delivered notice
             of its intent to sublease or assign. If Landlord does not so
             terminate or suspend, Landlord's consent shall not be unreasonably
             withheld, conditioned or delayed to an assignment or to a
             subletting, provided that the following conditions are met:

             (i)     the assignee or subtenant shall use the Premises only for
                     the Permitted Uses or for any one of the non-ancillary
                     Permitted Uses individually;

             (ii)    the proposed assignee or subtenant has a net worth and
                     creditworthiness reasonably acceptable to Landlord;

             (iii)   the amount of the aggregate rent to be paid by the proposed
                     subtenant is not less than the then current market rate for
                     comparable subleases of premises substantially similar to
                     the Premises; and

             (iv)    the proposed assignee or subtenant is not then a tenant in
                     the Building or the Park, or an entity with which Landlord
                     is currently in negotiations or with which Landlord has
                     negotiated during the preceding six months regarding the
                     possibility of leasing space in the Building or the Park.

             Tenant shall furnish Landlord with any information reasonably
             requested by Landlord to enable Landlord to determine whether the
             proposed assignment or subletting complies with the foregoing
             requirements, including without limitation, financial statements
             relating to the proposed assignee or subtenant.

             Tenant shall, as Additional Rent, reimburse Landlord promptly for
             Landlord's reasonable legal expenses incurred in connection with
             any request by Tenant for such consent. If Landlord consents
             thereto, or in the case of a Permitted Transfer, no such subletting
             or assignment shall in

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             any way impair the continuing primary liability of Tenant hereunder
             (unless otherwise explicitly agreed to by Landlord in its consent),
             and no consent to any subletting or assignment in a particular
             instance shall be deemed to be a waiver of the obligation to obtain
             the Landlord's written approval in the case of any other subletting
             or assignment.

             If for any assignment or sublease consented to by Landlord
             hereunder Tenant receives rent or other consideration, either
             initially or over the term of the assignment or sublease, in excess
             of the rent called for hereunder, or in case of sublease of part,
             in excess of such rent fairly allocable to the part, after
             appropriate adjustments to assure that all other payments called
             for hereunder are appropriately taken into account and after
             deduction for reasonable expenses of Tenant in connection with the
             assignment or sublease (provided, however, all such costs shall be
             amortized over the term of the sublease in question), including
             brokerage commissions, marketing expenses, tenant inducements
             consistent with inducements being made by other similar tenants
             subletting or assigning its lease for comparable premises in the
             Burlington area, reasonable attorney's fees, and advertsing fees,
             to pay to Landlord as additional rent fifty (50%) percent of the
             excess of each such payment of rent or other consideration received
             by Tenant promptly after its receipt.

             Whenever Tenant lists with a broker or brokers or otherwise
             advertises, holds out or markets the Premises or any part thereof
             for sublease or assignment, Tenant shall give Nordblom Company, as
             brokers, a non-exclusive listing with respect to such sublease or
             assignment.

             If at any time during the term of this Lease, there is a name
             change, reformation or reorganization of the Tenant entity, Tenant
             shall so notify Landlord and deliver evidence reasonably
             satisfactory to Landlord documenting such name change, reformation
             or reorganization. If, at any time during the term of this Lease,
             there is a transfer of a controlling interest in the stock,
             membership or general partnership interests of Tenant, Tenant shall
             so notify Landlord and any such transfer shall be deemed an
             assignment of this Lease. The provisions of the preceding sentence
             shall not apply if Tenant is a publicly traded company.

             Notwithstanding the foregoing provisions of this Subsection 6.2.1,
             Tenant may assign this Lease or sublet the Premises, without
             Landlord's consent, to any entity (a) which controls or is
             controlled by or is under common control with Tenant; or (b) which
             purchases all or substantially all of Tenant's stock or assets; or
             (c) with or into which Tenant is merged or consolidated, provided
             that (i) the assignee or sublessee agrees to assume and perform, in
             full, the obligations of Tenant under this Lease by written
             instrument in form satisfactory to Landlord, which instrument shall
             be delivered to Landlord at least fifteen (15) days prior to the
             effective date of any such transaction, (ii) Tenant remains fully
             and primarily liable under this Lease (unless otherwise agreed to
             at the time), (iii) the use of the Premises remains unchanged, (iv)
             the successor to Tenant has a net worth computed in accordance with
             generally accepted accounting principles at least equal to or
             greater than the net worth of Tenant immediately prior to such
             merger, consolidation, transfer or transaction permitted herein,
             and further provided that proof reasonably satisfactory to Landlord
             of such net worth shall have been delivered to Landlord at least
             fifteen (15) days prior to the effective date of any such
             transaction (the "Permitted Transfer").

      6.2.2  NUISANCE. Not to injure, deface or otherwise harm the Premises; nor
             commit any nuisance; nor permit in the Premises any vending machine
             (except such as is used for the sale of merchandise to employees of
             Tenant) or inflammable fluids or chemicals (except such as are
             customarily used in connection with standard office equipment); nor
             permit any cooking to such extent as requires special exhaust
             venting; nor permit the emission of any objectionable noise or
             odor; nor make, allow or suffer any waste; nor make any use of the
             Premises which is improper, offensive or contrary to any law or
             ordinance or which will invalidate any of Landlord's insurance; nor
             conduct any auction, fire, "going out of business" or bankruptcy
             sales.

      6.2.3  HAZARDOUS WASTES AND MATERIALS. Not to dispose of any hazardous
             wastes, hazardous materials or oil on the Premises or the Property,
             or into any of the plumbing, sewage, or drainage systems thereon,
             and to indemnify and save Landlord harmless from all claims,
             liability, loss or damage arising on account of the use or disposal
             of hazardous wastes, hazardous materials or oil, including, without
             limitation, liability under any federal, state, or local laws,
             requirements and regulations, or damage to any of the aforesaid
             systems. Tenant shall comply with all governmental reporting
             requirements with respect to hazardous wastes, hazardous materials
             and oil, and shall deliver to Landlord copies of all reports filed
             with governmental authorities.

      6.2.4  FLOOR LOAD; HEAVY EQUIPMENT. Not to place a load upon any floor of
             the Premises exceeding the floor load per square foot area which
             such floor was designed to carry and which is allowed by law.
             Landlord reserves the right to prescribe the weight and position of
             all heavy business machines and equipment, including safes, which
             shall be placed so as to distribute the weight. Business machines
             and mechanical equipment which cause vibration or noise shall be
             placed and maintained by Tenant at Tenant's expense in settings
             sufficient to absorb and prevent vibration, noise and annoyance.
             Tenant shall not move any safe, heavy machinery, heavy equipment,
             freight or fixtures into or out of the Premises except in such
             manner and at such time as Landlord shall in each instance
             authorize.

      6.2.5  INSTALLATION, ALTERATIONS OR ADDITIONS. Not to make any
             installations, alterations or additions in, to or on the Premises
             nor to permit the making of any holes in the walls (except for
             normal office

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             wall hangings, pictures, and the like), partitions, ceilings or
             floors nor the installation or modification of any locks or
             security devices without on each occasion obtaining the prior
             written consent of Landlord, and then only pursuant to plans and
             specifications approved by Landlord in advance in each instance
             (which consent and approval shall not be required for alterations
             (i) that cost less than $5,000,00 and which do not alter the
             Premises floor plan or impact the systems or structure of the
             Building, or (ii) which are decorative or cosmetic in nature, such
             as painting and carpeting); Tenant shall pay promptly when due the
             entire cost of any work to the Premises undertaken by Tenant so
             that the Premises shall at all times be free of liens for labor and
             materials, and at Landlord's request Tenant shall furnish to
             Landlord a board or other security acceptable to Landlord assuring
             that any work in excess of $5,000.00 commenced by Tenant will be
             completed in accordance with the plans and specifications therefore
             approved by Landlord and assuring that the Premises will remain
             free of any mechanics' lien or other encumbrance arising out of
             such work. In any event, Tenant shall forthwith bond against or
             discharge any mechanics' liens or other encumbrances that may arise
             out of such work. Tenant shall procure all necessary licenses and
             permits at Tenant's sole expense before undertaking such work. All
             such work shall be done in a good and workmanlike manner employing
             materials of good quality and so as to conform with all applicable
             zoning, building, fire, health and other codes, regulations,
             ordinances and laws. Tenant shall save Landlord harmless and
             indemnified from all injury. loss, claims or damage to any person
             or property occasioned by or growing out of such work.

             Except for security interests granted prior to the Date of this
             Lease, not to grant a security interest in, or to lease, any
             personal property being installed in the Premises (including,
             without limitation, demountable partitions) without first obtaining
             an agreement, for the benefit or Landlord, from the secured party
             or lessor that such property will be removed within ten (10)
             business days after notice from Landlord of the expiration or
             earlier termination of this Lease and that a failure to so remove
             will subject such property to the provisions of subsection 6.1.9 of
             the Lease.

      6.2.6  ABANDONMENT. Not to vacate the Premises during the term.

      6.2.7  SIGNS. Not without Landlord's prior written approval, which
             approval shall not be unreasonably withheld, to paint or place any
             signs or place any curtains, blinds, shades, awnings, aerials, or
             the like, visible from outside the Premises. Tenant may, at is sole
             expense, install its identifying sign on the exterior of the
             Building in a location approved by Landlord. Such sign shall comply
             with all local regulations and shall conform with the sign policy
             for the Park and shall be maintained by Tenant, at its expense, in
             good condition and repair.

      6.2.8  PARKING AND STORAGE. Not to permit any storage of materials outside
             of the Premises; not to permit the use of the parking areas for
             either temporary or permanent storage of trucks; nor permit the use
             of the Premises for any use for which heavy tracking would be
             customary.

                                    ARTICLE 7
                               CASUALTY OR TAKING

7.1   TERMINATION. A In the event that the Premises, or any material part
      thereof, shall be taken by any public authority or for any public use, or
      shall be destroyed or damaged by fire or casualty, or by the action of any
      public authority, then this Lease may be terminated at the election of
      Landlord. Such election, which may be made notwithstanding the fact that
      Landlord's entire interest may have been divested, shall be made by the
      giving of notice by Landlord to Tenant within sixty (60) days after the
      date of the taking or casualty.

      B. In the event that the Premises are destroyed or damaged by fire or
      casualty, or by the action of public authority, and, in the reasonable
      opinion of an independent architect or engineer selected by Landlord,
      cannot be repaired or restored within two hundred seventy (270) days from
      the date of the casualty or taking, then this Lease may be terminated at
      the election of Landlord or Tenant, which election shall be made by the
      giving of notice to the other party within thirty (30) days after the date
      the opinion of the architect or engineer is made available to the parties.
      Landlord shall use reasonable efforts to obtain the estimate of the time
      for restoration within thirty (30) days after the casualty or taking, but
      in any event shall provide such estimate within sixty (60) days after the
      taking or casualty.

7.2   RESTORATION. If neither party elects to so terminate as provided in this
      Article 7, this Lease shall continue in force and a just proportion of the
      rent reserved, according to the nature and extent of the damages sustained
      by the Premises, shall be suspended or abated until the Premises, or what
      may remain thereof, shall be put by Landlord in proper condition for use,
      which Landlord covenants to do with reasonable diligence to the extent
      permitted by the net proceeds of insurance recovered or damages awarded
      for such taking, destruction or damage and subject to zoning and building
      laws or ordinances then in existence. "Landlord's restoration work shall
      exclude the Tenant's Work and any other improvements or installations made
      by or on behalf of Tenant. "Net proceeds of insurance recovered or damages
      awarded" refers to the gross amount of such insurance or damages less the
      reasonable expenses of Landlord incurred in connection with the
      collections of the same, including without limitation, fees and expenses
      for legal and appraisal services. If Landlord shall not have restored the
      Premises within two hundred seventy (270) days from the date of the taking
      or casualty, Tenant shall have the right to terminate this Lease by
      giving notice of such termination to Landlord, to be effective at the
      expiration of thirty (30) days from the giving of such notice; provided
      however, that such termination will be rendered ineffective if, prior to
      the expiration of said 30-day period, Landlord shall have completed such
      restoration.

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7.3   AWARD. Irrespective of the form in which recovery may be had by law, all
      rights to damages or compensation shall belong to Landlord in all cases,
      except in the case of a taking by a public authority, awards made to
      Tenant for its personal property, fixtures and relocation expenses. Except
      for such awards, Tenant hereby grants to Landlord all of Tenant's rights
      to such damages and covenants to deliver such further assignments thereof
      as Landlord may from time to time request.

                                    ARTICLE 8
                                    DEFAULTS

8.1   EVENTS OF DEFAULT. (a) If Tenant shall default in the performance of any
      of its obligations to pay the Fixed Rent, Additional Rent or any other sum
      due Landlord hereunder and if such default shall continue for ten (10)
      days after written notice from Landlord designating such default or if
      within thirty (30) days after written notice from Landlord to Tenant
      specifying any other default or defaults Tenant has not commenced
      diligently to correct the default or defaults so specified or has not
      thereafter diligently pursued such correction to completion, or (b) if any
      assignment shall be made by Tenant or any guarantor of Tenant for the
      benefit of creditors, or (c) if Tenant's leasehold interest shall be taken
      on execution, or (d) if a lien or other involuntary encumbrance is filed
      against Tenant's leasehold interest or Tenant's other property (other than
      a landlord's lien), including said leasehold interest, and is not
      discharged within ten (10) days thereafter or otherwise dealt with to the
      satisfaction of Landlord, or (e) if a petition is filed by Tenant or any
      guarantor of Tenant for liquidation, or for reorganization or an
      arrangement under any provision of any bankruptcy law or code as then in
      force and effect, or (f) if an involuntary petition under any of the
      provisions of any bankruptcy law or code is filed against Tenant or any
      guarantor of Tenant and such involuntary petition is not dismissed within
      sixty (60) days thereafter, then, and in any of such cases, Landlord and
      the agents and servants of Landlord lawfully may, in addition to and not
      in derogation of any remedies for any preceding breach of covenant,
      immediately or at any time thereafter without demand or notice and with
      process of law enter into and upon the Premises or any part thereof in the
      name of the whole or mail a notice of termination addressed to Tenant, and
      repossess the same as of landlord's former estate and expel Tenant and
      those claiming through or under Tenant and remove its and their effects
      (forcibly, if necessary) without being deemed guilty of any manner of
      trespass and without prejudice to any remedies which might otherwise be
      used for arrears of rent or prior breach of covenants, and upon such entry
      or mailing as aforesaid this Lease shall terminate. Tenant hereby waiving
      all statutory rights to the Premises (including without limitation rights
      of redemption, if any, to the extent such rights may be lawfully waived)
      and Landlord, without notice to Tenant, may store Tenant's effects, and
      those of any person claiming through or under Tenant, at the expense and
      risk of Tenant, and, if Landlord so elects, may sell such effects at
      public auction or private sale and apply the net proceeds to the payment
      of all sums due to Landlord from Tenant, if any, and pay over the balance,
      if any, to Tenant.

8.2   REMEDIES. In the event that this Lease is terminated under any of the
      provisions contained in Section 8.1 or shall be otherwise terminated for
      breach of any obligation of Tenant, Tenant covenants to pay forthwith to
      Landlord, as compensation, the excess of the total rent reserved for the
      residue of the term over the rental value of the Premises for said residue
      of the term. In calculating the rent reserved there shall be included, in
      addition to the Fixed Rent and Additional Rent, the value of all other
      considerations agreed to be paid or performed by Tenant for said residue.
      Tenant further covenants as additional and cumulative obligations after
      any such termination, to pay punctually to Landlord all the sums and to
      perform all the obligations which Tenant covenants in this Lease to pay
      and to perform in the same manner and to the same extent and at the same
      time as if this Lease had not been terminated. In calculating the amounts
      to be paid by Tenant pursuant to the next preceding sentence Tenant shall
      be credited with any amount paid to Landlord as compensation as in this
      Section 8.2 provided and also with the net proceeds of any rent obtained
      by Landlord by reletting the Premises, after deducting all Landlord's
      expense in connection with such reletting, including, without limitation,
      all repossession costs, brokerage commissions, reasonable fees for legal
      services and expenses of preparing the Premises for such reletting, it
      being agreed by Tenant that Landlord shall (i) use reasonable efforts to
      relet the Premises or any part or parts thereof, for a term or terms which
      may at Landlord's option be equal to or less than or exceed the period
      which would otherwise have constituted the balance of the term and may
      grant such concessions and free rent as Landlord in its sole judgement
      considers advisable or necessary to relet the same and (ii) make such
      alterations, repairs and decorations in the Premises as Landlord in its
      sole judgment considers advisable or necessary to relet the same, and no
      action of Landlord in accordance with the foregoing or failure to relet
      or to collect rent under reletting shall operate or be construed to
      release or reduce Tenant's liability as aforesaid. For the purposes of
      this paragraph, marketing of the Premises in a manner similar to the
      way Landlord markets its other premises in the suburban market shall be
      deemed to satisfy Landlord's obligation to use such "reasonable efforts."
      In no event shall Landlord be required (i) to solicit or entertain
      negotiations with any other prospective tenants for the Premises until
      Landlord obtains full and complete possession of the Premises including,
      without limitation, the undisputed right to re-let the Premises fee of
      any claim of Tenant, (ii) to lease the Premises to a tenant whose
      proposed use, in Landlord's sole but bona fide judgment, would violate
      any restrictions by which Landlord is bound, (iii) to re-let the Premises
      before leasing other comparable vacant space in the Building, (iv) to
      lease the Premises for a rental less than the current fair market rental
      then prevailing for similar office space in the Building, or (v) to enter
      into a lease with any proposed tenant that does not have, in Landlord's
      reasonable opinion, sufficient financial resources or operating experience
      to operate the Premises in a manner comparable to other tenants in the
      Building. In no event, however, shall Tenant's liability hereunder be
      diminished or reduced if or to the extent such reasonable efforts of
      Landlord to re-let are not successful.

      Nothing contained in this Lease shall limit or prejudice the right of
      Landlord to prove for and obtain in proceedings for bankruptcy or
      insolvency by reason of the termination of this Lease, an amount equal to
      the

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      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 than, equal to, or less than the
      amount of the loss or damages referred to above.

8.3   REMEDIES CUMULATIVE. Any and all rights and remedies which Landlord may
      have under this Lease, and at law and equity, shall be cumulative and
      shall not be deemed inconsistent with each other, and any two or more of
      all such rights and remedies may be exercised at the same time insofar as
      permitted by law.

8.4   LANDLORD'S RIGHT TO CURE DEFAULTS. Landlord may, but shall not be
      obligated to, cure, at any time in emergency situations and after the
      expiration of all applicable grace periods hereunder in all other cases,
      without notice, any default by Tenant under this Lease; and whenever
      Landlord so elects, all costs and expenses incurred by Landlord, including
      reasonable attorneys' fees, in curing a default shall be paid, as
      Additional Rent, by Tenant to Landlord on demand, together with lawful
      interest thereon from the date of payment by Landlord to the date of
      payment by Tenant.

8.5   EFFECT OF WAIVERS OF DEFAULT. Any consent or permission by Landlord to any
      act or omission which otherwise would be a breach of any covenant or
      condition herein, shall not in any way be held or construed (unless
      expressly so declared) to operate so as to impair the continuing
      obligation of any covenant or condition herein, or otherwise, except as to
      the specific instance, operate to permit similar acts or omissions.

8.6   NO WAIVER, ETC. The failure of Landlord to seek redress for violation of,
      or to insist upon the strict performance of, any covenant or condition of
      this Lease 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
      Landlord of rent with knowledge of the breach of any covenant of this
      Lease shall not be deemed to have been a waiver of such breach by
      Landlord. No consent or waiver, express or implied, by Landlord to or of
      any breach of any agreement or duty shall be construed as a waiver or
      consent to or of any other breach of the same or any other agreement or
      duty.

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

                                    ARTICLE 9
                           RIGHTS OF MORTGAGE HOLDERS

9.1   RIGHTS OF MORTGAGE HOLDERS. The word "mortgage" as used herein includes
      mortgages, deeds of trust or other similar instruments evidencing other
      voluntary liens or encumbrances, and modifications, consolidations,
      extensions, renewals, replacements and substitutes thereof. The word
      "holder" shall mean a mortgagee, and any subsequent holder or holders of a
      mortgage. Until the holder of a mortgage shall enter and take possession
      of the Property for the purpose of foreclosure, such holder shall have
      only such rights of Landlord as are necessary to preserve the integrity of
      this Lease as security. Upon entry and taking possession of the Property
      for the purpose of foreclosure, such holder shall have all the rights of
      Landlord. No such holder of a mortgage shall be liable either as mortgagee
      or as assignee, to perform, or be liable in damages for failure to
      perform, any of the obligations of Landlord unless and until such holder
      shall enter and take possession of the Property for the purpose of
      foreclosure. Upon entry for the purpose of foreclosure, such holder shall
      be liable to perform all of the obligations of Landlord, subject to and
      with the benefit of the provisions of Section 10.4, provided that a
      discontinuance of any foreclosure proceeding shall be deemed a conveyance
      under said provisions to the owner of the equity of the Property.

      The covenants and agreements contained in this Lease with respect to the
      rights, powers and benefits of a holder of a mortgage (particularly,
      without limitation thereby, the covenants and agreements contained in this
      Section 9.1) constitute a continuing offer to any person, corporation or
      other entity, which by accepting a mortgage subject to this Lease, assumes
      the obligations herein set forth with respect to such holder, such holder
      is hereby constituted a party of this Lease as an obligee hereunder to the
      same extent as though its name were written hereon as such: and such
      holder shall be entitled to enforce such provisions in its own name.
      Tenant agrees on request of Landlord to execute and deliver from time to
      time any agreement which may be necessary to implement the provisions of
      this Section 9.1.

9.2   LEASE SUPERIOR OR SUBORDINATE TO MORTGAGES. It is agreed that the
      rights and interest of Tenant under this Lease shall be (i) subject or
      subordinate to any present or future mortgage or mortgages and to any
      and all advances to be made thereunder, and to the interest of the
      holder thereof in the Premises or any property of which the Premises
      are a part if Landlord shall elect by notice to Tenant to subject or
      subordinate the rights and interest of Tenant under this Lease to such
      mortgage or (ii) prior to any present or future mortgage or mortgages,
      if Landlord shall elect, by notice to Tenant, to give the rights and
      interest of Tenant under this Lease priority to such mortgage; in the
      event of either of such elections and upon notification by Landlord to
      that effect, the rights and interest of Tenant under this Lease should
      be deemed to be subordinate to, or have priority over, as the case may
      be, said mortgage or mortgages, irrespective of the time of execution
      or time of recording of any such mortgage or mortgages (provided that,
      in the case of subordination of this Lease to any future mortgages, the
      holder thereof agrees not to disturb the possession of Tenant so long as

                                       19
<Page>

      Tenant is not in default hereunder and Tenant and the holder execute a
      so-called subordination, non-disturbance and attornment agreement in
      the holder's usual and customary form, with such commercially
      reasonable changes that are acceptable to the parties). Tenant agrees
      it will, upon not less than ten (10) days' prior written request by
      Landlord, execute, acknowledge and deliver any and all instruments
      deemed by Landlord necessary or desirable to give effect to or notice
      of such subordination or priority. Any mortgage to which this Lease
      shall be subordinated may contain such terms, provisions and conditions
      as the holder deems usual or customary.

                                   ARTICLE 10
                            MISCELLANEOUS PROVISIONS

10.1  NOTICES FROM ONE PARTY TO THE OTHER. All notices required or permitted
      hereunder shall be in writing and addressed, if to the Tenant, at the
      Original Notice Address of Tenant or such other address as Tenant shall
      have last designated by notice in writing to Landlord and, if to Landlord,
      at the Original Notice Address of Landlord or such other address as
      Landlord shall have last designated by notice in writing to Tenant. Any
      notice shall be deemed duly given when mailed to such address postage
      prepaid, by registered or certified mail, return receipt requested, or
      when delivered to such address by hand.

10.2  QUIET ENJOYMENT. Landlord agrees that upon Tenant's paying the rent and
      performing and observing the agreements, conditions and other provisions
      on its part to be performed and observed, Tenant shall and may peaceably
      and quietly have, hold and enjoy the Premises during the term hereof
      without any manner of hindrance or molestation from Landlord or anyone
      claiming under Landlord, subject, however, to the terms of this Lease.

10.3  LEASE NOT TO BE RECORDED. Tenant agrees that it will not record this
      Lease.

10.4  LIMITATION OF LANDLORD'S LIABILITY. The term "Landlord" as used in this
      Lease, so far as covenants or obligations to be performed by Landlord
      are concerned, shall be limited to mean and include only the owner or
      owners at the time in question of the Property, and in the event of any
      transfer or transfers of title to said property, the Landlord (and in
      case of any subsequent transfers or conveyances, the then grantor)
      shall be concurrently freed and relieved from and after the date of
      such transfer or conveyance, without any further instrument or
      agreement of all liability as respects the performance of any covenants
      or obligations on the part of the Landlord contained in this Lease
      thereafter to be performed, it being intended hereby that the covenants
      and obligations contained in this Lease on the part of Landlord, shall,
      subject as aforesaid, be binding on the Landlord, its successors and
      assigns, only during and in respect of their respective successive
      periods of ownership of said leasehold interest or fee, as the case may
      be. Tenant, its successors and assigns, shall not assert nor seek to
      enforce any claim for breach of this Lease against any of Landlord's
      assets other than Landlord's interest in the Property and in the rents,
      issues and profits thereof, and Tenant agrees to look solely to such
      interest for the satisfaction of any liability or claim against
      Landlord under this Lease, it being specifically agreed that in no
      event whatsoever shall Landlord (which term shall include, without
      limitation, any general or limited partner, trustees, beneficiaries,
      officers, directors, or stockholders of Landlord) ever be personally
      liable for any such liability.

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

10.6  LANDLORD'S DEFAULT. Landlord shall not be deemed to be in default in the
      performance of any of its obligations hereunder unless it shall fail to
      perform such obligations and such failure shall continue for a period of
      thirty (30) days or such additional time as is reasonably required to
      correct any such default after written notice has been given by Tenant to
      Landlord specifying the nature of Landlord's alleged default. Landlord
      shall not be liable in any event for incidental or consequential damages
      to Tenant by reason of Landlord's default, whether or not notice is given.
      Except as otherwise set forth herein, Tenant shall have no right to
      terminate this Lease for any default by Landlord hereunder and no right,
      for any such default, to offset or counterclaim against any rent due
      hereunder.

10.7  BROKERAGE. Landlord and Tenant warrant and represent to the other that it
      has dealt with no broker in connection with the consummation of this
      Lease, other than Nordblom Company or Grubb & Ellis, and in the event of
      any brokerage claims, other than by Nordblom Company or Grubb & Ellis,
      against either party predicated upon prior dealings with the other party,
      Landlord and Tenant, each agree to defend the same and indemnify and hold
      the other party harmless against any such claim. Tenant shall not be
      responsible for the payment of the broker's fee due to Nordblom Company or
      Grubb & Ellis.

10.8  APPLICABLE LAW AND CONSTRUCTION. This Lease shall be governed by and
      construed in accordance with the laws of the Commonwealth of Massachusetts
      and, if any provisions of this Lease shall to any extent be invalid, the
      remainder of this Lease shall not be affected thereby. There are no oral
      or written agreements between Landlord and Tenant affecting this Lease.
      This Lease may be amended, and the provisions hereof may be waived or
      modified, only by instruments in writing executed by Landlord and Tenant.
      The titles of the several Articles and Sections contained herein are for
      convenience only and shall not be considered in construing this Lease.
      Unless repugnant to the context, the words "Landlord" and "Tenant"
      appearing in

                                       20
<Page>

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

WITNESS the execution hereof under seal on the day and year first above written:

                                   Landlord:
                                   MTP LIMITED PARTNERSHIP
                                   By: Middlesex Turnpike Corp., general partner

                                   By: /s/ Peter C. Nordblom
                                      --------------------------------
                                           Peter C. Nordblom
                                           President

                                   Tenant:
                                   ACME PACKET, INC.

                                   /s/ Keith Seidman
                                   -----------------------------------
                                   By: Keith Seidman
                                   Its: Chief Financial Officer
                                   Hereunto duly authorized

                                       21
<Page>

                                    EXHIBIT A

                            PLAN SHOWING THE PREMISES

[GRAPHIC]

                                       22
<Page>

                                    EXHIBIT B

                          PLAN SHOWING LANDLORD'S WORK

[GRAPHIC]

Landlord, at its expense will perform the following work:

     Demolish the walls highlighted in yellow on the above plan.

     Complete the exterior construction of the main entrance and front corner of
     the building.

     Carpet the existing offices on the North Avenue Side with the same new
     carpet as the open office area on the North Avenue Side. Remove and dispose
     of the remaining "old" carpeting on the Route 3 Side and replace with a
     combination of the same new carpet as the North Avenue Side or vinyl floor
     tile depending on the Tenant's requirement. Any upgrades to the carpet or
     vinyl tile will be accommodated through the execution by Landlord and
     Tenant of a Work Change Order in the form attached hereto as Exhibit C.

     Remove and dispose of the "old", 2' x 4' fluorescent light fixtures on the
     Route 3 Side and replace with new energy-efficient, 2' x 4', paracube
     fixtures subject to the Tenant's requirement. Any upgrades to the lighting
     fixtures will be accommodated through the execution by Landlord and Tenant
     of a Work Change Order in the form attached hereto as Exhibit C.

                                       23
<Page>

                                   EXHIBIT B-1

                        SPACE PLAN SHOWING TENANT'S WORK

[GRAPHIC]

                                       24
<Page>

                                    EXHIBIT C

                                WORK CHANGE ORDER

Lease Date:                             Date:
               --------------------           ----------------------------------

Landlord:                               Work Change Order No.:
               --------------------                            -----------------

Tenant:                                 Building Address:
               --------------------                       ----------------------

Premises:      -----------------------------------------------------------------

Tenant directs Landlord to make the following additions to Landlord's work:

Description of additional work:

Work Change Order Amount:

Amount of Previous Work Change Orders:

This Work Change Order:

Total Amount of Work Change Orders:

Landlord approves this Work Change Order and Tenant agrees to pay to Landlord
the Total Amount of Work Change Orders at the earlier of ten days following
receipt of the Certificate of Occupancy of the premises or occupancy of the
premises by Tenant.

Tenant:                                 Landlord:

By:                                     By:
    -------------------------------         -------------------------------

Title:                                  Title:
       ----------------------------            ----------------------------

                                       25
<Page>

                                    EXHIBIT D

                              RULES AND REGULATIONS

1.     The sidewalks, entrances, passages, corridors, vestibules, halls, or
       stairways in or about the Building shall not be obstructed by Tenant.

2.     Tenant shall not place objects against glass partitions, doors or windows
       which would be unsightly from the Building corridor or from the exterior
       of the Building.

3.     Tenant shall not waste electricity or water in the Building premises and
       shall cooperate fully with Landlord to assure the most effective
       operation of the Building heating and air conditioning systems. All
       regulating and adjusting of heating and air-conditioning apparatus shall
       be done by the Landlord's agents or employees.

4.     Tenant shall not use the Premises so as to cause any increase above
       normal insurance premiums on the Building.

5.     No bicycles, vehicles, or animals of any kind shall be brought into or
       kept in or about the Premises. No space in the Building shall be used for
       the sale of merchandise of any kind at auction or for storage thereof
       preliminary to such sale.

6.     Tenant shall cooperate with Landlord in minimizing loss and risk thereof
       from fire and associated perils.

7.     The water and wash closets and other plumbing fixtures shall not be used
       for any purposes other than those for which they were designed and
       constructed and no sweepings, rubbish, rags, acid or like substance shall
       be deposited therein. All damages resulting from any misuse of the
       fixtures shall be borne by the Tenant.

8.     Landlord reserves the right to establish, modify, and enforce reasonable
       parking rules and regulations, provided such rules and obligations do not
       diminish Tenant's rights under the Lease.

9.     Landlord reserves the right at any time to rescind, alter or waive any
       rule or regulation at any time prescribed for the Building and to impose
       additional reasonable rules and regulations when in its judgment deems it
       necessary, desirable or proper for its best interest and for the best
       interest, provided such rules and regulations do not diminish Tenant's
       rights under the Lease.

10.    Tenant acknowledges that the Building has been designated a non-smoking
       building. At no time shall Tenant permit its agents, employees,
       contractors, guests or invitees to smoke in the Building or, except in
       specified locations, directly outside the Building.

11.    Tenant shall furnish a chair mat for each desk chair located on carpet in
       the Premises.

                                       26
<Page>

                                    EXHIBIT E

                           TENANT ESTOPPEL CERTIFICATE

TO: _______________________ ("Mortgagee" or "Purchaser")

THIS IS TO CERTIFY THAT:

1.     The undersigned is the tenant (the "Tenant") under that certain lease
       (the "Lease") dated _______, 20__, by and between ________ as landlord
       (the "Landlord"), and the undersigned, as Tenant, covering those certain
       premises commonly known and designated as __________ (the "Premises") in
       the building located at ____________, _____________, Massachusetts.

2.     The Lease is attached hereto as Exhibit A and (i) constitutes the entire
       agreement between the undersigned and the Landlord with respect to the
       Premises, (ii) is the only Lease between the undersigned and the Landlord
       affecting the Premises and (iii) has not been modified, changed, altered
       or amended in any respect, except (if none, so state):

       ________________________________________
       ________________________________________
       ________________________________________

3.     The undersigned has accepted and now occupies the Premises as of the date
       hereof, and all improvements, if any, required by the terms of the Lease
       to be made by the Landlord have been completed and all construction
       allowances to be paid by Landlord have been paid. In addition, the
       undersigned has made no agreement with Landlord or any agent,
       representative or employee of Landlord concerning free rent, partial
       rent, rebate of rental payments or any other type of rental or other
       economic inducement or concession except (if none, so state):

       ________________________________________
       ________________________________________
       ________________________________________

4.

       (1)  The term of the Lease began (or is scheduled to begin) on ________,
            20__ and will expire on ________, 20__;

       (2)  The fixed rent for the Premises has been paid to and including
            ________________, 20__;

       (3)  The fixed rent being paid pursuant to the Lease is at the annual
            rate of $____________; and

       (4)  The escalations payable by Tenant under the Lease are currently
            $______, based on a pro rata share of ______%, and have been
            reconciled through ________, 20__.

5.     (i) No party to the Lease is in default, (ii) the Lease is in full force
       and effect, (iii) the rental payable under the Lease is accruing to the
       extent therein provided thereunder, (iv) as of the date hereof the
       undersigned has no charge, lien or claim of off-set (and no claim for any
       credit or deduction) under the Lease or otherwise, against rents or other
       charges due or to become due thereunder or on account of any prepayment
       of rent more than one (1) month in advance of its due date, and (v)
       Tenant has no claim against Landlord for any security, rental, cleaning
       or other deposits, except (if none, so state):

       ________________________________________
       ________________________________________
       ________________________________________

6.     Since the date of the Lease there are no actions, whether voluntary or
       otherwise, pending against the undersigned under the bankruptcy,
       reorganization, arrangement, moratorium or similar laws of the United
       States, any state thereof of any other jurisdiction.

7.     Tenant has not sublet, assigned or hypothecated or otherwise transferred
       all or any portion of Tenant's leasehold interest.

8.     Neither Tenant nor Landlord has commenced any action or given or received
       any notice for the purpose of terminating the Lease, nor does Tenant have
       any right to terminate the Lease, except (if none, so state):

9.     Tenant has no option or preferential right to purchase all or any part of
       the Premises (or the real property of which the Premises are a part) nor
       any right or interest with respect to the Premises or the real property
       of which the Premises are a part. Tenant has no right to renew or extend
       the term of the Lease or expand the Premises except (if none, so state):

10.    The undersigned acknowledges that the parties named herein are relying
       upon this estoppel certificate and the accuracy of the information
       contained herein in making a loan secured by the Landlord's interest in
       the Premises, or in connection with the acquisition of the Property of
       which the Premises is a part.

                                       27
<Page>

EXECUTED UNDER SEAL AS OF _______________, 20__.

                                        TENANT:

                                        ------------------------------

                                        By:
                                              ------------------------
                                        Name:
                                        Title:
                                        Duly Authorized

                                       28
<Page>

                                    EXHIBIT F

                            FORM OF LETTER OF CREDIT

BENEFICIARY:                            ISSUANCE DATE:     ___________, _______

____________________                         IRREVOCABLE STANDBY
                                             LETTER OF CREDIT NO. _____________

ACCOUNTEE/APPLICANT:                         MAXIMUM/AGGREGATE
                                             CREDIT AMOUNT:
____________________                              USD $_____________
____________________
____________________

GENTLEMEN:

We hereby establish our irrevocable letter of credit in your favor for account
of the applicant up to an aggregate amount not to exceed __________________ US
Dollars ($ ______) available by your draft(s) drawn on ourselves at sight
accompanied by:

Your statement, signed by a purportedly authorized officer/official certifying
that the Beneficiary is entitled to draw upon this Letter of Credit (in the
amount of the draft submitted herewith) pursuant to Section 4.4 of the lease
(the "Lease") dated ______________, ______ by and between ___________________,
as Landlord, and _______________, as Tenant, relating to the premises at
________________________.

Draft(s) must indicate name and issuing bank and credit number and must be
presented at this office.

You shall have the right to make partial draws against this Letter of Credit,
from time to time.

Except as otherwise expressly stated herein, this Letter of Credit is subject to
the "Uniform Customs and Practice for Documentary Credits, International Chamber
of Commerce, Publication No. 500 (1993 Revision)."

This Letter of Credit shall expire at our office on _______________, ______ (the
"Stated Expiration Date"). It is a condition of this Letter of Credit that the
Stated Expiration Date shall be deemed automatically extended without amendment
for successive one (1) year periods from such Stated Expiration Date, unless at
least forty-five (45) days prior to such Stated Expiration Date) or any
anniversary thereof) we shall notify the Beneficiary and the Accountee/Applicant
in writing by registered mail (return receipt) that we elect not to consider
this Letter of Credit extended for any such additional one (1) year period.

We engage with you that all drafts drawn under and in compliance with the terms
of this letter of credit will be duly honored on presentation to us.

                                        Very truly yours,

                                        Authorized Signatory

                                       29Exhibit 4.6

 

	
  Number LU
  [     ]

  	
  Units
  [         ]

  

 

The
shares of Common Stock and Warrants which comprise each Unit are separately
transferable.  The shares of Common Stock
and Warrants which comprise each Unit may be evidenced by Common Stock
Certificates and Warrant Certificates to be issued to the holder of this Unit
Certificate upon surrender of this Unit Certificate to the Transfer Agent of
the Company.

 

LIGHTSPACE
CORPORATION

INCORPORATED
UNDER THE LAWS OF THE STATE OF DELAWARE

 

UNITS

CUSIP

THIS CERTIFIES THAT:

 

IS THE OWNER OF

 

Each Unit (“Unit”) consists of (i) eight
shares of Common Stock, par value $0.0001 per share, (ii) eight warrants to
purchase on e share of common stock at $1.00 per share (the “$1.00 Unit
Warrants”), (iii) two warrants to purchase one share of common stock at $1.25
per share (the “$1.25 Unit Warrants”) and (iv) two warrants to purchase one
share of common stock at $1.63 per share (the “$1.63 Unit Warrants”, and
collectively with the $1.00 Unit Warrants and the $1.25 Unit Warrants, the “Unit
Warrants”).  The Company will furnish to
each Unitholder who so requests, the designations, powers, preferences and
relative, participating, optional or other special rights, if any, of the
Company’s securities.  Each Unit Warrant
entitles the holder to purchase one share of Common Stock of the Company for
the applicable exercise price at any time until April 30, 2011 at 5:00 p.m.
Eastern Time.  Copies of the Warrant
Agreement are on file at the Company and are available to any Warrant Holder on
written request and without cost.

 

	
  DATED:

  	
  COUNTERSIGNED

  
	
   

  	
   

  	
  CONTINENTAL
  STOCK 

  
	
   

  	
   

  	
  TRANSFER
  & TRUST 

  
	
   

  	
   

  	
  COMPANY

  
	
   

  	
   

  	
  JERSEY
  CITY, NJ

  
	
   

  	
   

  	
  TRANSFER
  AGENT AND REGISTRAR

  
	
   

  	
   

  	
   

  
	
   

  	
  BY:

  	
   

  
	
   

  	
   

  	
   

  
	
   

  	
  [Seal]

  	
   

  
	
   

  	
   

  	
   

  
	
  /s/
  James Craig Louney

  	
   

  	
  /s/
  Gary Florindo

  
	
  ASSISTANT
  SECRETARY

  	
   

  	
  PRESIDENT

  
				

 

 

 

 

The following abbreviations,
when used in the inscription on the face of this certificate, shall be
construed as though they were written out in full according to applicable laws
or regulations:

	
  TEN COM — as tenants in common

  	
  UNIF GIFT MIN ACT -

  	
   

  	
  Custodian

  	
   

  
	
  TEN ENT — as tenants by the entireties

  	
   

  	
  (Cust)

  	
   

  	
  (Minor)

  
	
  JT TEN — as joint tenants with right of
  survivorship 

  	
   

  	
  under Uniform Gifts to Minors

  
	
  and not as tenants in common

  	
   

  	
   

  
	
   

  	
   

  	
   

  
	
   

  	
   

  	
   

  
	
   

  	
   

  	
  Act

  	
   

  
	
   

  	
   

  	
  (State)

  
	
   

  	
   

  	
   

  
							

 

Additional
abbreviations may also be used though not in the above list.

For
Value Received, ________________ hereby sell, assign and transfer unto

PLEASE INSERT SOCIAL SECURITY

OR OTHER IDENTIFYING NUMBER OF ASSIGNEE

                                                                                                                                                                                                            

	
  (PLEASE PRINT OR TYPEWRITE NAME AND ADDRESS,
  INCLUDING ZIP CODE, OF ASSIGNEE)

  
	
   

  	
   

  	
   

  
	
   

  	
   

  	
   

  
	
   

  	
   

  	
   

  
	
   

  	
   

  	
   

  
	
   

  	
   

  	
   

  
	
   

  	
   

  	
   

  	
  Shares

  
	
  of the stock represented by the within Certificate, and do hereby
  irrevocably constitute and appoint

  
	
   

  	
   

  	
   

  
	
   

  	
   

  	
   

  
	
   

  	
   

  	
   

  	
  Attorney 

  
	
  to transfer the said stock on the books of the within named
  Corporation with full power of substitution

  in the premises.

  
	
   

  	
   

  	
   

  
	
   

  	
   

  	
   

  
	
  Dated _______________________

  	
   

  	
   

  
	
   

  	
   

  	
   

  
	
   

  	
   

  	
   

  
	
   

  	
   

  	
   

  
	
   

  	
   

  	
   

  
	
   

  	
   

  	
   

  
	
   

  	
  NOTICE: THE
  SIGNATURE TO THIS ASSIGNMENT MUST CORRESPOND WITH THE NAME AS WRITTEN UPON
  THE FACE OF THE CERTIFICATE IN EVERY PARTICULAR, WITHOUT ALTERATION OR
  ENLARGEMENT OR ANY CHANGE WHATSOEVER.

  
						

 

 

THE CORPORATION WILL FURNISH TO ANY STOCKHOLDER, UPON
REQUEST AND WITHOUT CHARGE, A FULL STATEMENT OF THE DESIGNATIONS, RELATIVE
RIGHTS, PREFERENCES AND LIMITATIONS O FTHE SHARES OF EACH CLASS AND SERIES
AUTHORIZED TO BE ISSUED, SO FAR AS THE SAME HAVE BEEN DETERMINED, AND OF THE
AUTHORITY, IF ANY, OF THE BOARD TO DIVIDE THE SHARES INTO CLASSES OR SERIES AND
TO DETERMINE AND CHANGE THE RELATIVE RIGHTS, PREFERENCES AND LIMITATIONS OF ANY
CLASS OR SERIES.  SUCH REQUEST MAY BE
MADE TO THE SECRETARY OF THE CORPORATION OR TO THE TRANSFER AGENT NAMED ON THIS
CERTIFICATE.

	
   

  

 

THE
SIGNATURE TO THE ASSIGNMENT MUST CORRESPOND TO THE NAME AS WRITTEN UPON THE
FACE OF THIS CERTIFICATE IN EVERY PARTICULAR, WITHOUT ALTERATION OR ENLARGEMENT
OR ANY CHANGE WHATSOEVER, AND MUST BE GUARANTEED BY A COMMERCIAL BANK OR TRUST
COMPANY OR A MEMBER FIRM OF A NATIONAL OR REGIONAL OR OTHER RECOGNIZED STOCK
EXCHANGE IN CONFORMANCE WITH A SIGNATURE GUARANTEE MEDALLION PROGRAM.

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