<PAGE>

                                                                   EXHIBIT 10.29

                                                                           FINAL

                            CAMBRIDGE SCIENCE CENTER
                            CAMBRIDGE, MASSACHUSETTS

                      OFFICE AND LABORATORY LEASE AGREEMENT

                                     BETWEEN

   MA-RIVERVIEW/245 FIRST STREET, L.L.C., A DELAWARE LIMITED LIABILITY COMPANY
                                  ("LANDLORD")

                                       AND

                      VIACELL, INC., A DELAWARE CORPORATION
                                   ("TENANT")

<PAGE>

                                TABLE OF CONTENTS

<TABLE>
<S>                                                                                              <C>
I.    BASIC LEASE INFORMATION................................................................     1
II.   LEASE GRANT............................................................................     6
III.     APPROVAL OF INITIAL ALTERATIONS; POSSESSION/ADJUSTMENT OF LAB COMMENCEMENT DATE.....     6
IV.      RENT................................................................................     8
V.       COMPLIANCE WITH LAWS; USE...........................................................    15
VI.      SECURITY DEPOSIT....................................................................    16
VII.     SERVICES TO BE FURNISHED BY LANDLORD................................................    17
VIII.    LEASEHOLD IMPROVEMENTS..............................................................    20
IX.      REPAIRS AND ALTERATIONS.............................................................    21
X.       USE OF ELECTRICAL AND OTHER UTILITY SERVICES BY TENANT..............................    23
XI.      ENTRY BY LANDLORD; RESERVATION OF CERTAIN RIGHTS....................................    24
XII.     ASSIGNMENT AND SUBLETTING...........................................................    25
XIII.    LIENS...............................................................................    27
XIV.     INDEMNITY AND WAIVER OF CLAIMS......................................................    28
XV.      INSURANCE...........................................................................    28
XVI.     SUBROGATION.........................................................................    29
XVII.      CASUALTY DAMAGE...................................................................    29
XVIII.     CONDEMNATION......................................................................    30
XIX.     EVENTS OF DEFAULT...................................................................    31
XX.      REMEDIES............................................................................    31
XXI.     LIMITATION OF LIABILITY.............................................................    32
XXII.      NO WAIVER.........................................................................    33
XXIII.     QUIET ENJOYMENT...................................................................    33
XXIV.      INTENTIONALLY OMITTED.............................................................    33
XXV.       HOLDING OVER......................................................................    33
XXVI.      SUBORDINATION TO MORTGAGES; ESTOPPEL CERTIFICATE..................................    33
XXVII.     ATTORNEYS' FEES...................................................................    34
XXVIII.       NOTICE.........................................................................    34
XXIX.      EXCEPTED RIGHTS...................................................................    34
XXX.       SURRENDER OF PREMISES.............................................................    35
XXXI.      MISCELLANEOUS.....................................................................    35

</TABLE>

                                        i

<PAGE>

<TABLE>
<S>                                                                                              <C>
XXXII.     ENVIRONMENTAL SUBSTANCES..........................................................    38
XXXIII.        MEDICAL WASTE POLICY..........................................................    40
XXXIV.        LAB STANDARDS..................................................................    42
XXXV.         ENTIRE AGREEMENT...............................................................    43
CAMBRIDGE SCIENCE CENTER AT 245 FIRST STREET.................................................     9
1)    OFFICE AREAS (ALL FLOORS)..............................................................     7
2)    RESTROOMS..............................................................................     8
3) LOBBY, ELEVATOR, CORRIDOR, INTERIOR STAIRWAYS (EXCLUDING EMERGENCY EXIT
STAIRWAYS) AND ENTRANCE AREAS................................................................     9
4)    JANITORIAL ITEMS/AREAS.................................................................     9
5)    FITNESS CENTER (IF APPLICABLE) (PLEASE BREAK OUT COST AS SEPARATE BID).................     9
6)    LOCKER ROOMS (IF APPLICABLE)...........................................................    10
7)    LOADING DOCK, VAN PARKING AREAS, TRASH RECYCLING AREAS.................................    10
8)    GENERAL BUILDING COMMON AREA SERVICES..................................................    10
BASE CHARGES SHUTDOWN RECONNECT..............................................................    19
ADDITIONAL CHARGES...........................................................................    19
</TABLE>

                                       ii

<PAGE>

EXHIBIT A       OUTLINE AND LOCATION OF PREMISES
EXHIBIT A-1     LAB SPACE MATRIX
EXHIBIT B       BUILDING RULES AND REGULATIONS
EXHIBIT C       FORM OF LETTER OF CREDIT
EXHIBIT C-1     ALTERNATIVE FORM OF LETTER OF CREDIT
EXHIBIT D       WORK LETTER
EXHIBIT D-1     RESPONSIBILITIES MATRIX
EXHIBIT D-2     LANDLORD'S WORK
EXHIBIT E       ADDITIONAL PROVISIONS
EXHIBIT F       FORM OF NOTICE OF LEASE
EXHIBIT G       EXTERIOR SIGNAGE
EXHIBIT H       OFFERING SPACE
EXHIBIT H-1     EXPANSION SPACE
EXHIBIT I       COMMENCEMENT LETTER
EXHIBIT J       COMMENCEMENT DATE AGREEMENT
EXHIBIT K       LIST OF ENVIRONMENTAL SUBSTANCES
EXHIBIT L       RIGHT OF FIRST REFUSAL SPACE
EXHIBIT M       CLEANING SPECIFICATIONS
EXHIBIT N       CONSTRUCTION RULES AND REGULATIONS

                                        i

<PAGE>

                      OFFICE AND LABORATORY LEASE AGREEMENT

         THIS OFFICE AND LABORATORY LEASE AGREEMENT (the "Lease") is made and
entered into as of the ____ day of December, 2003, by and between
MA-RIVERVIEW/245 FIRST STREET, L.L.C., A DELAWARE LIMITED LIABILITY COMPANY
("Landlord") and VIACELL, INC., A DELAWARE CORPORATION ("Tenant").

I.       BASIC LEASE INFORMATION.

         A.       "Buildings" shall mean those buildings located at 245 First
                  Street, Cambridge, Massachusetts 02142 and commonly known as
                  Cambridge Science Center, comprised of two buildings, the
                  first being the Science Building ("Science Building"), and the
                  second being the Office Building ("Office Building").

         B.       "Rentable Square Footage of the Building" is deemed to be
                  130,512 square feet with respect to the Science Building and
                  148,552 square feet with respect to Office Building. "Rentable
                  Square Footage of the Buildings" is deemed to be 279,064
                  square feet.

         C.       "Premises" shall mean the area shown on EXHIBIT A to this
                  Lease. The Premises are located on the 1st and 2nd floors of
                  the Science Building and known as suite numbers 100 and 200
                  (collectively, the "Lab Space") and on the 15th floor of the
                  Office Building and known as suite number 1500 (the "Office
                  Space"). The "Rentable Square Footage of the Premises" is
                  deemed to be approximately 42,944 square feet (consisting of
                  2,858 square feet of lab space on the first floor and 22,051
                  square feet of lab space on the 2nd floor of the Science
                  Building, and 18,035 square feet of office space on the 15th
                  floor of the Office Building). If the Premises include one or
                  more floors in their entirety, the elevator lobby located on
                  such full floor(s) shall be considered part of the Premises
                  and Tenant shall have exclusive rights to the use of the
                  restroom facilities thereon. Landlord and Tenant stipulate and
                  agree that the Rentable Square Footage of the Building and the
                  Rentable Square Footage of the Premises are correct and shall
                  not be remeasured.

                                        1

<PAGE>

         D.       "Base Rent": Lab Base Rent (as defined below) and Office Base
                  Rent (as defined below) are sometimes collectively referred to
                  as "Base Rent".

                  (i)      Lab Base Rent. The Base Rent for that portion of the
                           Premises located in the Science Building ("Lab Base
                           Rent") shall commence on the Lab Rent Commencement
                           Date (as defined below) and shall be as follows:

<TABLE>
<CAPTION>
                                ANNUAL RATE
                                 PER SQUARE        ANNUAL         MONTHLY
           PERIOD                   FOOT          BASE RENT      BASE RENT
----------------------------  ---------------   -------------   -----------
<S>                           <C>               <C>             <C>
Lab Rent Commencement Date -      $40.00        $  996,360.00   $ 83,030.00
 2nd anniversary of Lab Rent
      Commencement Date

        Years 3-4                 $44.00        $1,095,996.00   $ 91,333.00
        Years 5-6                 $45.00        $1,120,905.00   $ 93,408.75
        Years 7-8                 $47.00        $1,170,723.00   $ 97,560.25
       Years 9-10                 $50.00        $1,245,450.00   $103,787.50
</TABLE>

                  (ii)     Office Base Rent. The Base Rent for that portion of
                           the Premises located in the Office Building ("Office
                           Base Rent") shall commence on the Office Rent
                           Commencement Date (as defined below) and be as
                           follows:

<TABLE>
<CAPTION>
                           ANNUAL RATE
                           PER SQUARE      ANNUAL      MONTHLY
         PERIOD)               FOOT       BASE RENT   BASE RENT
-------------------------  -----------   -----------  ----------
<S>                        <C>           <C>          <C>
Office Rent Commencement      $23.00     $414,805.00  $34,567.08
Date - 2nd anniversary of
Office Rent Commence Date

        Years 3-5             $25.00     $450,875.00  $37,572.92

  Years 6-Expiration of       $28.00     $504,980.00  $42,081.67
      Initial Term
</TABLE>

                  Notwithstanding anything to the contrary contained herein,
                  provided that at the time the abatement hereinafter referred
                  to is scheduled to be applicable, Tenant is not in default
                  beyond any applicable notice, grace and cure periods, Tenant
                  shall be entitled to an abatement of Office Base Rent in the
                  amount of $34,567.08 per month for 3 consecutive full calendar
                  months of the Term (defined below), beginning with the 1st
                  full calendar month in which Office Base Rent is due hereunder
                  (the "Office Base Rent Abatement Period"). The total amount of
                  Office Base Rent abated during the Office Base Rent Abatement
                  Period shall equal $103,701.25 (the "Abated Office Base
                  Rent"). During the Office Base Rent Abatement Period, only
                  Office Base Rent shall be abated with

                                        2

<PAGE>

                  respect to the Office Space, and all Additional Rent (defined
                  below) and other costs and charges specified in this Lease
                  shall remain as due and payable pursuant to the provisions of
                  this Lease.

                  Notwithstanding anything to the contrary contained herein,
                  provided that at the time the abatement hereinafter referred
                  to is scheduled to be applicable, Tenant is not in default
                  beyond any applicable notice, grace and cure periods, Tenant
                  shall be entitled to an abatement of Lab Base Rent in the
                  amount of $83,030.00 for the 1st full calendar month in which
                  Lab Base Rent is due hereunder (the "Lab Base Rent Abatement
                  Period"). The total amount of Lab Base Rent abated during the
                  Lab Base Rent Abatement Period shall equal $83,030.00 (the
                  "Abated Lab Base Rent"). During the Lab Base Rent Abatement
                  Period, only Lab Base Rent shall be abated with respect to the
                  Lab Space, and all Additional Rent (defined below) and other
                  costs and charges specified in this Lease shall remain as due
                  and payable pursuant to the provisions of this Lease.

         E.       "Tenant's Pro Rata Share for the Office Building": 12.14%.
                  "Tenant's Pro Rata Share for the Science Building: 19.09%

         F.       "Base Year" for Office Taxes: Fiscal Year (defined below) 2005
                  (e.g., July 1, 2004 to June 30, 2005). "Base Year" for Office
                  Expenses: calendar year 2004.

                  For purposes hereof, "Fiscal Year" shall mean the Base Year
                  for Office Taxes and each period of July 1 to June 30
                  thereafter.

         G.       "Term": A period of 10 years from the Lab Rent Commencement
                  Date (as defined below). With respect to the Office Space, the
                  Term shall commence upon execution of this Lease (the "Office
                  Commencement Date") and with respect to the Lab Space, the
                  Term shall commence 150 days after the date on which Landlord
                  has Substantially Completed Landlord's Work (as defined in
                  III.B.1 below) (the "Lab Commencement Date"), and, unless
                  terminated early or extended in accordance with this Lease,
                  end with respect to the entire Premises on the last day of the
                  month in which the tenth anniversary of the Lab Rent
                  Commencement Date occurs (the "Termination Date"). Promptly
                  after the determination of the Lab Rent Commencement Date,
                  Landlord and Tenant shall enter into a commencement letter
                  agreement in the form attached as EXHIBIT I. As Tenant is
                  entitled to register or record a notice or memorandum of this
                  Lease pursuant to the terms of Section XXXI, Landlord and
                  Tenant shall also execute and Tenant may register or record,
                  as appropriate, at Tenant's cost and expense, a Notice of
                  Lease in the form attached as EXHIBIT F.

                  Notwithstanding the foregoing, upon the following terms but
                  not otherwise, if (i) Landlord is delayed in achieving the
                  Substantial Completion of Landlord's Work, by the date
                  therefor set forth in Section B.1.B of the Work Letter, or
                  (ii) Tenant is delayed in the performance of the Initial Lab
                  Alterations by a Landlord Delay (as defined in the Work
                  Letter), and (iii) any such delay is not due to a Tenant
                  Delay, then the Lab Rent Commencement Date shall be delayed by
                  the number of days that completion of the Initial Lab
                  Alterations is so delayed, provided that the Lab Rent
                  Commencement Date shall not be postponed by the number of days
                  of Landlord Delay if and to the extent that Tenant is not
                  actually delayed thereby. In addition to the foregoing, in the
                  event the aggregate number of days of

                                        3

<PAGE>

                  Landlord Delay, which cause Tenant to be actually delayed,
                  exceeds 30 days, then (a) Tenant shall be entitled to an
                  abatement of Lab Base Rent equal to one day for each day of
                  such delay, up to 30 days, and (b) thereafter, Tenant shall be
                  entitled to an abatement of Lab Base Rent equal to two days
                  for each day of such delay, up to an additional 30 days. If
                  Substantial Completion of Landlord's Work has not occurred
                  within such 90-day period, Tenant shall have the option to
                  terminate this Lease upon 30 days' prior written notice to
                  Landlord, provided that such termination notice shall be void
                  and have no force or effect if Substantial Completion of
                  Landlord's Work occurs during such 30-day notice period. There
                  shall be no abatement of Lab Base Rent attributable to the
                  period following the aforesaid 90-day period, unless and until
                  Tenant provides a notice of termination hereunder. If Tenant
                  provides such a notice and the same becomes void as aforesaid,
                  Tenant shall be entitled to an abatement of Lab Base Rent
                  equal to two days for each day from and after the giving of
                  the termination notice to the date upon which Substantial
                  Completion of Landlord's Work occurs.

                  Without limitation of the foregoing, there shall be no
                  postponement of the Lab Rent Commencement Date to the extent
                  that Substantial Completion of Landlord's Work is delayed on
                  account of Tenant Delay. The abatement of Lab Base Rent as set
                  forth above shall constitute Tenant's sole remedy and
                  liquidated damages for any delay in Tenant's ability to occupy
                  the Premises related to Landlord's Work.

         H.       Tenant allowance(s) for the Lab Space: an amount not to exceed
                  $2,490,900.00, as further described in the attached EXHIBIT D;
                  provided, however, Tenant shall be permitted to use any unused
                  portion of the Tenant allowance for any purposes for which
                  Tenant allowance(s) for the Office Space may be used, provided
                  such use of the Tenant allowance shall be in accordance with
                  the terms and provisions of this Lease.

                  Tenant allowance(s) for the Office Space: an amount not to
                  exceed $901,750.00, as further described in the attached
                  EXHIBIT D; provided, however, Tenant shall be permitted to use
                  any unused portion of the Tenant allowance for any purposes
                  for which Tenant allowance(s) for the Lab Space may be used,
                  provided such use of the Tenant allowance shall be in
                  accordance with the terms and provisions of this Lease.

                  Drawing Allowance: an amount not to exceed $128,832.00, as
                  further described in the attached EXHIBIT D.

                  Additional Allowance: an amount not to exceed $750,000.00, as
                  further described in the attached EXHIBIT D.

         I.       "Security Deposit": $1,411,165.00, subject to reduction in
                  accordance with Section VI, which shall be delivered to
                  Landlord in the form of a Letter of Credit.

         J.       "Guarantor(s)": Intentionally Omitted

                                        4

<PAGE>

         K.       "Broker(s)": Richard Barry Joyce & Partners, LLC and Trammell
                  Crow Company.

         L.       "Permitted Use": With respect to the Office Space, general
                  office purposes, as a non-retail sales office, for a call
                  center and for accessory uses related thereto, and with
                  respect to the Lab Space, (a) Technical office for research
                  and development, laboratory and research facility and (b)
                  subject to applicable requirements of the Cambridge Zoning
                  Ordinance, limited manufacturing as an accessory use.

         M.       "Notice Addresses":

                  Tenant:

                  On and after the Commencement Date, notices shall be sent to
                  Tenant at the Premises. Prior to the Commencement Date,
                  notices shall be sent to Tenant at the following address:

<TABLE>
<S>                               <C>
131 Clarendon Street, 3rd Floor   With a copy to:
Boston, Massachusetts  02116      Goodwin Procter LLP
Phone #:  (617) 603-4633          Exchange Place
Fax #:  (617) 247-4733            Boston, Massachusetts  02109
Attention:  Jeffrey Sacher        Phone #: 617-570-1440
                                  Fax #: 617-227-8591
                                  Attention: Joseph W. Haley,
                                  Esq.
</TABLE>

                  Notices shall be sent to Landlord at the following address
                  (except for Rent payments):

<TABLE>
<S>                                     <C>
Landlord:                               With a copy to:

MA-Riverview/245 First Street, L.L.C.   Equity Office Properties Trust
c/o Equity Office Properties Trust      Two North Riverside Plaza

245 First Street                        Chicago, Illinois 60606
Cambridge, Massachusetts  02142         Attention:  Boston Regional Counsel
Attention:  Property Manager
</TABLE>

                  Rent (defined in Section IV.A) is payable to the order of
                  EQUITY OFFICE PROPERTIES at the following address: CAMBRIDGE
                  SCIENCE CENTER (SCIENCE BUILDING AND OFFICE
                  BUILDING)-DEPARTMENT 11202, P.O. BOX 30376, HARTFORD,
                  CONNECTICUT 06150.

         N.       "Business Day(s)" are Monday through Friday of each week,
                  exclusive of New Year's Day, Memorial Day, Independence Day,
                  Labor Day, Thanksgiving Day and Christmas Day ("Holidays").
                  Landlord may designate additional Holidays, provided that the
                  additional Holidays are commonly recognized by other office
                  buildings in the area where the Building is located.

                                        5

<PAGE>

         O.       "Landlord Work" means the work that Landlord is obligated to
                  perform in the Premises pursuant to the separate work letter
                  agreement (the "Work Letter"), attached as EXHIBIT D.

         P.       "Law(s)" means all applicable statutes, codes, ordinances,
                  orders, rules and regulations of any municipal or governmental
                  entity.

         Q.       "Normal Business Hours" for the Building are 8:00 A.M. to 6:00
                  P.M. on Business Days and 8:00 A.M. to 1:00 P.M. on Saturdays.

         R.       "Property" means the Buildings and the parcel(s) of land on
                  which they are located and, the garage and other improvements
                  serving the Building or Buildings, if any, and the parcel(s)
                  of land on which they are located.

         S.       "Office Rent Commencement Date" means the date that is the
                  earlier of (i) 90 days after the date of this Lease, and (ii)
                  move-in and commencement of business by Tenant in the Office
                  Space.

         T.       "Lab Rent Commencement Date" means the date that is the
                  earlier of (i) 150 days after the Lab Commencement Date, and
                  (ii) move in and commencement of business by Tenant in the Lab
                  Space, subject to the provisions of Section I.G above.

II.      LEASE GRANT.

         Landlord leases the Premises to Tenant and Tenant leases the Premises
from Landlord, together with the right in common with others to use the common
building loading dock, and any other portions of the Property that are
designated by Landlord for the common use of tenants and others, such as
sidewalks, unreserved parking areas, common corridors, elevator foyers, stairs,
elevators, restrooms, vending areas and lobby areas, subject to the provisions
of Article XI below (the "Common Areas"). In addition, Tenant shall have the
right to use (a) a pro rata portion of the ducts, sleeves and risers through the
Science Building and Office Building, as reasonably designated by Landlord,
subject to the provisions of Article IX below, and (b) a pro rata portion of the
third level of the Annex, the PH treatment room on the first floor of the
Science Building, and the roof of the Science Building (subject to the
provisions of Section XI of EXHIBIT E), each in the locations shown on EXHIBIT
A, and as described in the matrix attached as EXHIBIT A-1.

III.     APPROVAL OF INITIAL ALTERATIONS; POSSESSION/ADJUSTMENT OF LAB
         COMMENCEMENT DATE.

         A.       APPROVAL OF INITIAL ALTERATIONS; POSSESSION WITH RESPECT TO
                  THE OFFICE SPACE

         1.       Tenant shall complete the Initial Alterations (as defined in
                  the Work Letter) in accordance with the terms and provisions
                  of the Work Letter. Tenant shall submit for Landlord's
                  approval, such approval not to be unreasonably withheld or
                  delayed, the plans and specifications prepared by Olson, Lewis
                  & Dioli Architects, Tenant's Architect, for the demolition and
                  reconstruction of the Office Space. The plans and
                  specifications shall be submitted to Landlord for its review

                                        6

<PAGE>

                  and approval at the space plan phase, the permitting phase,
                  and the construction documents phase. Landlord shall review
                  and respond with its approval or detailed comments to each
                  phase of the plans and specifications for the Office Space
                  within 5 business days of receiving the initial draft thereof,
                  and any failure to respond shall constitute the basis for a
                  claim of Landlord Delay. In the event that Landlord requires
                  changes to the proposed plans, Landlord shall review and
                  respond with its approval or detailed comments to Tenant's
                  submission of revised plans within 5 business days. Landlord
                  shall pay the Tenant Allowance for the Office Space in
                  accordance with the Work Letter.

         2.       Subject to Landlord's obligations under Section IX.B. and
                  Landlord's representation and warranty that the Office
                  Building and the building systems are in good working order
                  and repair, the Office Space is accepted by Tenant in "as is"
                  condition and configuration. By taking possession of the
                  Office Space, Tenant agrees that the Office Space is in good
                  order and satisfactory condition, and that, except as set
                  forth herein, there are no representations or warranties by
                  Landlord regarding the condition of the Office Space or the
                  Office Building.

         B.       ADJUSTMENT OF COMMENCEMENT DATE; POSSESSION WITH RESPECT TO
                  THE LAB SPACE.

         1.       Landlord's Work in the Lab Space to be performed by Landlord
                  under the provisions of the Work Letter shall be deemed to be
                  "Substantially Complete" on the date that (a) Landlord's Work
                  has been completed, other than any details of construction,
                  mechanical adjustment or any other similar matter, the
                  noncompletion of which does not materially interfere with or
                  delay the prosecution of Tenant's construction of the Initial
                  Lab Alterations (but no sooner than 10 days after delivery of
                  Landlord's written notice of the date upon which Landlord
                  anticipates that Substantial Completion of Landlord's Work
                  shall occur), and (b) the City of Cambridge has issued a
                  Certificate of Occupancy for Landlord's Work (which may be
                  designated as a temporary or conditional Certificate, pending
                  completion of punchlist items). However, if Landlord is
                  delayed in the performance of Landlord's Work as a result of
                  any Tenant Delay(s) (defined below), Landlord's Work shall be
                  deemed to be Substantially Complete on the date that Landlord
                  could reasonably have been expected to Substantially Complete
                  Landlord Work's absent any Tenant Delay. "Tenant Delay" means
                  any act or omission of Tenant or its agents, employees,
                  vendors or contractors in contravention of Tenant's
                  obligations under this Lease that actually delays the
                  Substantial Completion of Landlord's Work, including, without
                  limitation: (1) Tenant's failure to furnish information or
                  approvals within any time period specified in this Lease,
                  including the failure to prepare or approve preliminary or
                  final plans by any applicable due date; (2) Tenant's selection
                  of equipment or materials that have long lead times after
                  first being informed by Landlord that the selection may result
                  in a delay; (3) changes requested or made by Tenant to
                  previously approved plans and specifications; or (4) if the
                  performance of any portion of Landlord's Work depends on the
                  prior or simultaneous performance of work by Tenant, a delay
                  by Tenant or Tenant's contractor(s) in the completion of such
                  work.

                                        7

<PAGE>

                  "Landlord Delay" means any act or omission of Landlord or its
                  agents, employees, vendors or contractors in contravention of
                  Landlord's obligations under this Lease that actually delays
                  the completion of the Initial Lab Alterations.

         B.       Subject to Landlord's obligation to perform Landlord's Work
                  and Landlord's obligations under Section IX.B, the Lab Space
                  is accepted by Tenant in "as is" condition and configuration.
                  By occupying the Lab Space for the purpose of conducting the
                  Permitted Uses therein, Tenant agrees that Landlord's Work has
                  been Substantially Completed, and that there are no
                  representations or warranties by Landlord regarding the
                  condition of the Lab Space or the Science Building. The Lab
                  Commencement Date and Termination Date shall be determined by
                  Section I.G.

         C.       If Tenant takes possession of the Premises before the Lab
                  Commencement Date, such possession shall be subject to the
                  terms and conditions of this Lease and Tenant shall pay Rent
                  (defined in Section IV.A.) to Landlord for each day of
                  possession before the Lab Commencement Date (subject to the
                  terms and provisions of Section I.D. above).

         D.       Promptly following the Substantial Completion of Landlord's
                  Work in the Lab Space, Tenant shall construct the Initial Lab
                  Alterations in accordance with the Work Letter. Promptly
                  following execution of this Lease, Tenant shall construct the
                  Initial Office Alterations in accordance with the Work Letter.

IV.      RENT.

         A.       Payments. As consideration for this Lease, commencing on the
                  Office Rent Commencement Date with respect to the Office Space
                  and the Lab Rent Commencement Date with respect to the Lab
                  Space, Tenant shall pay Landlord, without any setoff or
                  deduction (except as otherwise provided in Sections I.D.,
                  I.G., VII.B, XVII and XVIII), the total amount of Office Base
                  Rent and Additional rent due with respect to the Office Space
                  and the total amount of Lab Base Rent and Additional Rent due
                  with respect to the Lab Space for the Term. "Additional Rent"
                  means all sums (exclusive of Base Rent) that Tenant is
                  required to pay Landlord. Additional Rent and Base Rent are
                  sometimes collectively referred to as "Rent". Tenant shall pay
                  and be liable for all rental and use taxes (but excluding
                  income taxes), if any, imposed upon or measured by Rent under
                  applicable Law. Base Rent and recurring monthly charges of
                  Additional Rent shall be due and payable in advance on the
                  first day of each calendar month without notice or demand. All
                  other items of Rent shall be due and payable by Tenant on or
                  before 30 days after billing by Landlord accompanied by
                  reasonable substantiation therefor. All payments of Rent shall
                  be by good and sufficient check or by other means (such as
                  automatic debit or electronic transfer) acceptable to
                  Landlord. If Tenant fails to pay any item or installment of
                  Rent when due, Tenant shall pay Landlord an administration fee
                  equal to 5% of the past due Rent, provided that Tenant shall
                  be entitled to a grace period of 10 days for the first 2 late
                  payments of Rent in a given calendar year. If the Term
                  commences on a day other than the first day of a calendar
                  month or terminates on a day other than the last day of a
                  calendar month, the monthly Base Rent and Tenant's Pro Rata
                  Share of any Tax Excess (defined in Section IV.B.1.),

                                        8

<PAGE>

                  Expense Excess (defined in Section IV.B.1.), Expenses (defined
                  in Section IV.C.) and Taxes (defined in Section IV.D.) for the
                  month shall be prorated based on the number of days in such
                  calendar month. Landlord's acceptance of less than the correct
                  amount of Rent shall be considered a payment on account of the
                  earliest Rent due. No endorsement or statement on a check or
                  letter accompanying a check or payment shall be considered an
                  accord and satisfaction, and either party may accept the check
                  or payment without prejudice to that party's right to recover
                  the balance or pursue other available remedies. Tenant's
                  covenant to pay Rent is independent of every other covenant in
                  this Lease.

         B.       1.      Expense Excess and Tax Excess with Respect to the
                  Office Building. Tenant shall pay Tenant's Pro Rata Share for
                  the Office Building of the amount, if any, by which Expenses
                  (defined in Section IV.C.) relating to the Office Building
                  ("Office Expenses") for each calendar year during the Term
                  exceed Office Expenses for the Base Year (the "Expense
                  Excess") and also the amount, if any, by which Taxes (defined
                  in Section IV.D.) reasonably apportioned to the Office
                  Building ("Office Taxes") for each Fiscal Year during the Term
                  exceed Office Taxes for the Base Year (the "Tax Excess")
                  (including in the foregoing the Office Building's share of
                  Expenses and Taxes reasonably apportioned to the common areas
                  of the Property on a pro rata square footage basis). If Office
                  Expenses and/or Office Taxes in any calendar year or Fiscal
                  Year decrease below the amount of Office Expenses and/or
                  Office Taxes for the Base Year, Tenant's Pro Rata Share of
                  Office Expenses and/or Office Taxes, as the case may be, for
                  that calendar year or Fiscal Year shall be $0. Landlord shall
                  provide Tenant with a good faith estimate of the Expense
                  Excess and of the Tax Excess for each calendar year or Fiscal
                  Year during the Term. On or before the first day of each
                  month, Tenant shall pay to Landlord a monthly installment
                  equal to one-twelfth of Tenant's Pro Rata Share of Landlord's
                  estimate of the Expense Excess and one-twelfth of Tenant's Pro
                  Rata Share of Landlord's estimate of the Tax Excess. If
                  Landlord determines that its good faith estimate of the
                  Expense Excess or of the Tax Excess was incorrect by a
                  material amount, Landlord may provide Tenant with a revised
                  estimate. After its receipt of the revised estimate, Tenant's
                  monthly payments shall be based upon the revised estimate. If
                  Landlord does not provide Tenant with an estimate of the
                  Expense Excess by January 1 of a calendar year, or the Tax
                  Excess by the start of each new Fiscal Year, Tenant shall
                  continue to pay monthly installments based on the previous
                  calendar year's or Fiscal Year's estimate(s), as the case may
                  be, until Landlord provides Tenant with the new estimate. Upon
                  delivery of the new estimate, an adjustment shall be made for
                  any month for which Tenant paid monthly installments based on
                  the previous calendar or Fiscal Year's estimate(s). Tenant
                  shall pay Landlord the amount of any underpayment within 30
                  days after receipt of the new estimate. Any overpayment shall
                  be refunded to Tenant within 30 days or credited against the
                  next due future installment(s) of Additional Rent.

                  As soon as is practical following the end of each calendar
                  year or Fiscal Year, as the case may be, but in no event later
                  than 180 days after the end of any given year, Landlord shall
                  furnish Tenant with a statement of the actual Office Expenses
                  and Expense Excess and the actual Office Taxes and Tax Excess
                  for the prior calendar year or Fiscal Year, as the case may
                  be. Landlord shall not be

                                        9

<PAGE>

                  entitled to submit a revised statement to Tenant after such
                  180 day period, except for the adjustment of Office Taxes, Tax
                  Excess, and insurance claims as to which the information for
                  such adjustment was not available within such 180-day period.
                  If the estimated Expense Excess and/or estimated Tax Excess
                  for the prior calendar year or Fiscal Year, as the case may
                  be, is more than the actual Expense Excess and/or actual Tax
                  Excess for the prior calendar year or Fiscal Year, as the case
                  may be, Landlord shall apply any overpayment by Tenant against
                  Additional Rent due or next becoming due, provided if the Term
                  expires before the determination of the overpayment, Landlord
                  shall refund any overpayment to Tenant after first deducting
                  the amount of Rent due. If the estimated Expense Excess and/or
                  estimated Tax Excess for the prior calendar year or Fiscal
                  Year, as the case may be, is less than the actual Expense
                  Excess and/or actual Tax Excess for such prior calendar year
                  or Fiscal Year, as the case may be, Tenant shall pay Landlord,
                  within 30 days after its receipt of the statement of Office
                  Expenses and/or Office Taxes, any underpayment for the prior
                  calendar year.

                  2.       Expense and Taxes with Respect to the Science
                  Building. Tenant shall pay Tenant's Pro Rata Share for the
                  Science Building of Expenses relating to the Science Building
                  for each calendar year during the Term (the "Lab Expenses")
                  and Taxes reasonably apportioned to the Science Building for
                  each Fiscal Year during the Term (the "Lab Taxes") (including
                  in the foregoing the Science Building's share of Expenses and
                  Taxes reasonably apportioned to the common areas of the
                  Property on a pro rata square footage basis). Landlord shall
                  provide Tenant with a good faith estimate of the Lab Expenses
                  and of the Lab Taxes for each calendar year or Fiscal Year
                  during the Term. On or before the first day of each month,
                  Tenant shall pay to Landlord a monthly installment equal to
                  one-twelfth of Tenant's Pro Rata Share of Landlord's estimate
                  of the Lab Expenses and one-twelfth of Tenant's Pro Rata Share
                  of Landlord's estimate of the Lab Taxes. If Landlord
                  determines that its good faith estimate of the Lab Expenses or
                  of the Lab Taxes was incorrect by a material amount, Landlord
                  may provide Tenant with a revised estimate. After its receipt
                  of the revised estimate, Tenant's monthly payments shall be
                  based upon the revised estimate. If Landlord does not provide
                  Tenant with an estimate of the Lab Expenses by January 1 of a
                  calendar year, or the Lab Taxes by the start of each new
                  Fiscal Year, Tenant shall continue to pay monthly installments
                  based on the previous calendar year's or Fiscal Year's
                  estimate(s), as the case may be, until Landlord provides
                  Tenant with the new estimate. Upon delivery of the new
                  estimate, an adjustment shall be made for any month for which
                  Tenant paid monthly installments based on the previous
                  calendar or Fiscal Year's estimate(s). Tenant shall pay
                  Landlord the amount of any underpayment within 30 days after
                  receipt of the new estimate. Any overpayment shall be refunded
                  to Tenant within 30 days or credited against the next due
                  future installment(s) of Additional Rent.

                  As soon as is practical following the end of each calendar
                  year or Fiscal Year, as the case may be, but in no event later
                  than 180 days after the end of any given year, Landlord shall
                  furnish Tenant with a statement of the actual Lab Expenses and
                  the actual Lab Taxes for the prior calendar year or Fiscal
                  Year, as the case may be. Landlord shall not be entitled to
                  submit a revised statement to Tenant after such 180 day
                  period, except for the adjustment of Lab Taxes and insurance

                                       10

<PAGE>

                  claims as to which the information for such adjustment was not
                  available within such 180-day period. If the estimated Lab
                  Expenses and/or estimated Lab Taxes for the prior calendar
                  year or Fiscal Year, as the case may be, is more than the
                  actual Lab Expenses and/or actual Lab Taxes for the prior
                  calendar year or Fiscal Year, as the case may be, Landlord
                  shall apply any overpayment by Tenant against Additional Rent
                  due or next becoming due, provided if the Term expires before
                  the determination of the overpayment, Landlord shall refund
                  any overpayment to Tenant after first deducting the amount of
                  Rent due. If the estimated Lab Expenses and/or estimated Lab
                  Taxes for the prior calendar year or Fiscal Year, as the case
                  may be, is less than the actual Lab Expenses and/or actual Lab
                  Taxes for such prior calendar year or Fiscal Year, as the case
                  may be, Tenant shall pay Landlord, within 30 days after its
                  receipt of the statement of Lab Expenses and/or Lab Taxes, any
                  underpayment for the prior calendar year.

         C.       Expenses Defined. "Expenses" means all actual costs and
                  expenses incurred in each calendar year in connection with
                  operating, maintaining, repairing, and managing the Office
                  Building, with respect to Office Expenses, all actual costs
                  and expenses incurred in each calendar year in connection with
                  operating, maintaining, repairing, and managing the Science
                  Building, with respect to Lab Expenses, and all actual costs
                  and expenses incurred in each calendar year in connection with
                  operating, maintaining, repairing, and managing the common
                  areas of the Property allocated to each of the Science
                  Building and the Office Building on a pro rata square footage
                  basis, including, but not limited to:

                  1.       Labor costs, including, wages, salaries, social
                           security and employment taxes, medical and other
                           types of insurance, uniforms, training, and
                           retirement and pension plans for personnel working
                           full time at the Property, including the general
                           manager of the Property, but excluding costs for
                           salaries and benefits of other managerial or
                           executive level personnel.

                  2.       Management fees, the cost of equipping and
                           maintaining a management office, accounting and
                           bookkeeping services, legal fees not attributable to
                           leasing or collection activity, and other reasonable
                           administrative costs; provided, however, such
                           management fees as to the Office Space shall not
                           exceed 4% of gross rent (it being expressly
                           understood that Office Expenses for the Base Year
                           shall include such a 4% management fee), and, as to
                           the Lab Space, shall not exceed 3% of gross rent
                           (provided that in no event shall Tenant pay a
                           percentage of management fees for the Lab Space in
                           excess of the percentage of management fees charged
                           to other tenants of the Science Building). Landlord,
                           by itself or through an affiliate, shall have the
                           right to directly perform or provide any services
                           under this Lease (including management services),
                           provided that the cost of any such services shall not
                           exceed the cost that would have been incurred had
                           Landlord entered into an arms-length contract for
                           such services with an unaffiliated entity of
                           comparable skill and experience. Any office space
                           leased for a management office shall not be
                           attributed rental obligations exceeding the rental
                           obligations under an arm's-length lease for similar
                           space.

                                       11

<PAGE>

                  3.       The cost of services provided by Landlord to all of
                           the tenants, including amounts paid to service
                           providers and the rental and purchase cost of parts,
                           supplies, tools and equipment.

                  4.       Premiums and commercially reasonable deductibles for
                           insurance paid by Landlord for insurance, including
                           workers compensation, fire and extended coverage,
                           earthquake, general liability, rental loss, elevator,
                           boiler and other insurance as is customarily carried
                           from time to time by owners of comparable office and
                           lab buildings, provided that the premiums for such
                           insurance shall not exceed the premiums for such
                           insurance with commercially reasonable deductibles.

                  5.       Electrical Costs (defined below) and charges for
                           water, gas, and sewer, but excluding those charges
                           for which Landlord is entitled to be reimbursed by
                           tenants. "Electrical Costs" means: (a) charges paid
                           by Landlord for electricity for the Property; and (b)
                           costs incurred in connection with an energy
                           management program for the Property, which program
                           saves electrical costs. Electrical Costs shall be
                           adjusted as follows: (i) amounts entitled to be
                           received by Landlord as reimbursement for above
                           standard electrical consumption shall be deducted
                           from Electrical Costs; (ii) the cost of electricity
                           incurred to provide overtime HVAC to specific tenants
                           (as reasonably estimated by Landlord) shall be
                           deducted from Electrical Costs; and (iii) the cost of
                           electricity to individual tenant spaces in the
                           Building shall be deducted from Electrical Costs. (It
                           is expressly understood that Tenant shall pay (x)
                           directly to the utility company for the cost of
                           electrical service to the Premises measured by meters
                           or reimburse Landlord for the cost of electrical
                           service to the Premises measured by checkmeter, and
                           (y) to Landlord its pro rata share of electricity for
                           checkmetered base building mechanical services, such
                           as hot water, condenser water, water and sewer
                           service, and gas service, accordance with Section X.A
                           below.)

                  6.       The amortized cost of only such capital items and
                           capital improvements made to the Property which are:
                           (a) performed primarily to reduce operating expense
                           costs of the Property; or (b) required to comply with
                           any Laws that are enacted, or first interpreted to
                           apply to the Property, after the date of this Lease.
                           The cost of capital improvements shall be amortized
                           by Landlord over the lesser of the Payback Period
                           (defined below) or 10 years. The amortized cost of
                           capital improvements may, at Landlord's option,
                           include actual or imputed interest at the rate that
                           Landlord would reasonably be required to pay to
                           finance the cost of the capital improvement. "Payback
                           Period" means the reasonably estimated period of time
                           that it takes for the cost savings resulting from a
                           capital improvement to equal the total cost of the
                           capital improvement.

                  7.       With respect to Lab Expenses only, expenses of
                           periodic routine testing (as distinguished from any
                           testing in response to a hazardous materials
                           discovery or release or any remediation in connection
                           therewith) to assure that the Lab Space is free of
                           hazardous materials, agents or substances, and to
                           assure compliance with codes, regulations and Laws.

                                       12

<PAGE>

                  8.       Any fees, costs and expenses relating to operating,
                           managing, owning and maintaining the fitness center
                           in the Property.

                  9.       The costs of Landlord's Work and Landlord's initial
                           capital improvements in the Science Building and
                           Common Areas and the equipping thereof, and any
                           repairs occasioned by the defective installation of
                           the same.

                  If Landlord incurs Expenses for the Property together with one
                  or more other buildings or properties, whether pursuant to a
                  reciprocal easement agreement, common area agreement or
                  otherwise, the shared costs and expenses shall be equitably
                  prorated and apportioned between the Property and the other
                  buildings or properties. Expenses shall not include: the cost
                  of capital items or improvements (except as set forth above);
                  depreciation; interest (except as provided above for the
                  amortization of capital improvements); principal payments of
                  mortgage and other non-operating debts of Landlord; legal
                  costs in negotiating, interpreting or enforcing leases,
                  including without limitation assignment or sublease matters,
                  any disputes with tenants or eviction proceedings, and any
                  like legal costs in connection with any other parties to a
                  reciprocal easement agreement, common area agreement or
                  similar agreement; the cost of repairs or other work to the
                  extent Landlord is entitled to be reimbursed by insurance or
                  condemnation proceeds or warranties or guaranties; costs in
                  connection with leasing space in the Building, including
                  brokerage commissions; lease concessions, including rental
                  abatements and construction allowances, granted to specific
                  tenants; costs incurred in connection with the sale, financing
                  or refinancing of the Building; fines, interest and penalties
                  incurred due to the late payment of Taxes (defined in Section
                  IV.D) or Expenses; advertising or promotional expenses; costs
                  for services separately charged or chargeable to another
                  tenant; costs of correcting violations of applicable Law and
                  codes for which Landlord is liable under this Lease; costs to
                  restore the Building after a casualty because Landlord did not
                  obtain or maintain replacement cost "All Risk" property
                  insurance coverage, except for deductibles thereunder;
                  organizational expenses associated with the creation and
                  operation of the entity which constitutes Landlord; or any
                  penalties or damages that Landlord pays to Tenant under this
                  Lease or to other tenants in the Building under their
                  respective leases; costs, liability or damages associated with
                  the negligence or misconduct of Landlord or its agents,
                  employees or contractors; and where Landlord or an affiliate
                  is providing a service or item, an amount in excess of what
                  the cost of such service or item would be in an unrelated
                  arm's length transaction. If the Office Building is not at
                  least 95% occupied during any calendar year or if Landlord is
                  not supplying services to at least 95% of the total Rentable
                  Square Footage of the Office Building at any time during a
                  calendar year, Expenses for the Office Building shall be
                  determined as if the Office Building had been 95% occupied and
                  Landlord had been supplying services to 95% of the Rentable
                  Square Footage of the Office Building during that calendar
                  year. If Tenant pays for its Pro Rata Share of Expenses based
                  on increases over a "Base Year" and Expenses for a calendar
                  year are determined as provided in the prior sentence,
                  Expenses for the Base Year as to the Office Building shall
                  also be determined as if the Office Building had been 95%
                  occupied and Landlord had been supplying services to 95% of
                  the Rentable

                                       13

<PAGE>

                  Square Footage of the Office Building. The extrapolation of
                  Expenses under this Section shall be performed by
                  appropriately adjusting the cost of those components of
                  Expenses that are impacted by changes in the occupancy of the
                  Office Building.

         D.       Taxes Defined. "Taxes" shall mean: (1) all real estate taxes
                  and other assessments on the Building and/or Property,
                  including, but not limited to, assessments for special
                  improvement districts and building improvement districts,
                  taxes and assessments levied in substitution or
                  supplementation in whole or in part of any such taxes and
                  assessments and the Property's share of any real estate taxes
                  and assessments under any reciprocal easement agreement,
                  common area agreement or similar agreement as to the Property,
                  [provided, however, to the extent that there is an increase in
                  the assessments on the Property which is caused by the
                  conversion of the Science Building for use as laboratory
                  space, such increase shall be allocated to the Science
                  Building only]; (2) all personal property taxes for property
                  that is owned by Landlord and used in connection with the
                  operation, maintenance and repair of the Property; and (3) all
                  costs and fees incurred in connection with seeking reductions
                  in any tax liabilities described in (1) and (2) with respect
                  to years for which Tenant had an obligation to pay Tax Excess
                  or Lab Taxes, including, without limitation, any costs
                  incurred by Landlord for compliance, review and appeal of tax
                  liabilities. Without limitation, Taxes shall not include any
                  income, capital levy, franchise, capital stock, gift, estate
                  or inheritance tax. If an assessment is payable in
                  installments, Taxes for the year shall include the amount of
                  the installment and any interest due and payable during that
                  year. For all other real estate taxes, Taxes for that year
                  shall, at Landlord's election, include either the amount
                  accrued, assessed or otherwise imposed for the year or the
                  amount due and payable for that year, provided that Landlord's
                  election shall be applied consistently throughout the Term. If
                  a change in Taxes is obtained for any year of the Term during
                  which Tenant paid Tenant's Pro Rata Share of any Tax Excess or
                  any Lab Taxes, then Taxes for that year will be retroactively
                  adjusted and Landlord shall provide Tenant with a credit, if
                  any, based on the adjustment, or if after the end of the Term
                  shall pay Tenant such amount. Likewise, if a change is
                  obtained for Taxes for the Base Year, Taxes for the Base Year
                  shall be restated and the Tax Excess for all subsequent years
                  shall be recomputed. Tenant shall pay Landlord the amount of
                  Tenant's Pro Rata Share of any such increase in the Tax Excess
                  within 30 days after Tenant's receipt of a statement from
                  Landlord.

         E.       Audit Rights. Tenant may, within 90 days after receiving
                  Landlord's statement of Expenses (or within 90 days after
                  receiving any revised statement thereof), give Landlord
                  written notice ("Review Notice") that Tenant intends to review
                  Landlord's records of the Expenses for that calendar year.
                  Within a reasonable time after receipt of the Review Notice,
                  Landlord shall make all pertinent records available for
                  inspection that are reasonably necessary for Tenant to conduct
                  its review. If any records are maintained at a location other
                  than the office of the Building, Tenant may either inspect the
                  records at such other location or pay for the reasonable cost
                  of copying and shipping the records. If Tenant retains an
                  agent to review Landlord's records, the agent must be with a
                  licensed CPA, a CPA firm, or a national real estate service
                  provider, in each case paid on an

                                       14

<PAGE>

                  hourly, non-contingency fee basis. Tenant shall be solely
                  responsible for all of its own costs, expenses and fees
                  incurred for the audit unless such audit reveals a greater
                  than 5% overstatement for any applicable period in which case
                  Landlord shall pay for the audit. Within 60 days after the
                  records are made available to Tenant, Tenant shall have the
                  right to give Landlord written notice (an "Objection Notice")
                  stating in reasonable detail any objection to Landlord's
                  statement of Expenses for that year. If Tenant fails to give
                  Landlord an Objection Notice within the 60 day period or fails
                  to provide Landlord with a Review Notice within the 90 day
                  period described above, Tenant shall be deemed to have
                  approved Landlord's statement of Expenses and shall be barred
                  from raising any claims regarding the Expenses for that year.
                  If Tenant provides Landlord with a timely Objection Notice,
                  Landlord and Tenant shall work together in good faith to
                  resolve any issues raised in Tenant's Objection Notice. If
                  Landlord and Tenant determine that Expenses for the calendar
                  year are less than reported, Landlord shall provide Tenant
                  with a credit against the next installment of Rent in the
                  amount of the overpayment by Tenant or, if after the end of
                  the Term shall pay Tenant such amount. Likewise, if Landlord
                  and Tenant determine that Expenses for the calendar year are
                  greater than reported, Tenant shall pay Landlord the amount of
                  any underpayment within 30 days. The records obtained by
                  Tenant shall be treated as confidential. In no event shall
                  Tenant be permitted to examine Landlord's records or to
                  dispute any statement of Expenses unless Tenant has paid and
                  continues to pay all Rent when due.

V.       COMPLIANCE WITH LAWS; USE.

         A.       Tenant's Obligation. The Premises shall be used only for the
Permitted Use and for no other use whatsoever. Tenant acknowledges that, except
as set forth in Section III.A.2 and Section V.B below, neither Landlord nor any
agent of Landlord has made any representation as to the condition of the
Property or suitability of the Property for Tenant's intended use. Tenant shall
not use or permit the use of the Premises for any purpose which is illegal,
dangerous to persons or property or which, in Landlord's reasonable opinion,
unreasonably disturbs any other tenants of the Buildings or interferes with the
operation of the Buildings. Tenant shall comply with all Laws, including the
Americans with Disabilities Act, regarding the operation of Tenant's business
and the use, condition, configuration and occupancy of the Premises. Tenant,
within 10 days after receipt, shall provide Landlord with copies of any notices
it receives regarding a violation or alleged violation of any Laws. Tenant shall
reimburse and compensate Landlord for all expenditures made by, or damages or
fines sustained or incurred by, Landlord due to any violations of Laws by Tenant
or any Tenant Related Parties with respect to the Premises. Tenant shall comply
with the rules and regulations of the Buildings attached as EXHIBIT B and such
other reasonable rules and regulations not inconsistent with the terms of this
Lease adopted by Landlord from time to time. Tenant shall also cause its agents,
contractors, subcontractors, employees, customers, and subtenants to comply with
all rules and regulations. Landlord shall not discriminate against Tenant in
Landlord's enforcement of the rules and regulations. Tenant shall obtain and pay
for all permits and shall promptly take all actions necessary to comply with all
Laws, including, without limitation, the Occupational Safety and Health Act,
regulating Tenant's specific use of the Premises or the Property. Tenant shall
maintain in full force and effect all certifications or permissions to provide
its services required by any authority having jurisdiction to authorize,
franchise or regulate such services. Tenant shall be solely responsible for
procuring and complying at all times with any and all necessary permits directly
relating or incident to: the

                                       15

<PAGE>

conduct of its specific activities on the Premises; its scientific
experimentation, transportation, storage, handling, use and disposal of any
chemical or radioactive or bacteriological substances or organisms or other
hazardous wastes or environmentally dangerous substances or materials or medical
waste, including without limitation the obtaining of an industrial discharge
permit from the Massachusetts Water Resources Authority; its conduct of animal
research activities; and its storage of fuel, chemicals, or other regulated
materials permitted hereunder. Within ten (10) business days of a request by
Landlord, Tenant shall furnish Landlord with copies of all such permits,
together with a certificate certifying that such permits are all of the permits
which Tenant is required to maintain with respect to the Premises.

         B.       Landlord's Obligation. Landlord, at its sole cost and expense
(except to the extent properly included in Expenses), shall be responsible for
correcting any violations of Title III of the Americans with Disabilities Act
with respect to the Premises and the Common Areas of the Building, provided that
Landlord's obligation with respect to the Premises shall be limited to
violations that arise out of Landlord's Work and/or the condition of the
Premises prior to the installation of any furniture, equipment and other
personal property of Tenant. In addition, Landlord shall comply with all other
Laws relating to the Common Areas provided that compliance with such Laws is not
the responsibility of Tenant under this Lease, and provided further that
Landlord's failure to comply therewith would prohibit Tenant from obtaining or
maintaining a certificate of occupancy, or its equivalent, for the Premises, or
would unreasonably and materially affect the safety of Tenant's employees or
create a significant health hazard for Tenant's employees. Notwithstanding the
foregoing, Landlord shall have the right to contest any alleged violation in
good faith, including, without limitation, the right to apply for and obtain a
waiver or deferment of compliance, the right to assert any and all defenses
allowed by Law and the right to appeal any decisions, judgments or rulings to
the fullest extent permitted by Law. Landlord, after the exhaustion of any and
all rights to appeal or contest, will make all repairs, additions, alterations
or improvements necessary to comply with the terms of any final order or
judgment. Notwithstanding the foregoing, Tenant, not Landlord, shall be
responsible for the correction of any violations that arise out of or in
connection with any claims brought under any provision of the Americans with
Disabilities Act other than Title III, the specific nature of Tenant's business
in the Premises (other than general office use), the acts or omissions of
Tenant, its agents, employees or contractors, Tenant's arrangement of any
furniture, equipment or other property in the Premises, any repairs,
alterations, additions or improvements performed by or on behalf of Tenant
(other than the Landlord Work) and any design or configuration of the Premises
specifically requested by Tenant after being informed that such design or
configuration may not be in strict compliance with the ADA.

VI.      SECURITY DEPOSIT.

         The Security Deposit shall be in the form of an irrevocable letter of
credit (the "Letter of Credit"), which Letter of Credit shall: (a) be in the
amount of $1,411,165.00; (b) be in one (1) of the two (2) forms attached hereto
as EXHIBIT C; (c) name Landlord as its beneficiary; (d) be drawn on an FDIC
insured financial institution satisfactory to the Landlord; (e) expressly allow
Landlord to draw upon it: (i) in the event that the Tenant is in Default under
the Lease by delivering to the issuer of the Letter of Credit written notice
that Landlord is entitled to draw thereunder pursuant to the terms of this
Lease; or (ii) if Tenant, within 60 days prior to expiration of the Letter of
Credit then held by Landlord, fails to provide Landlord with a replacement
Letter of Credit meeting the requirements herein; (f) expressly state that it
will be honored by the issuer without inquiry into the accuracy of any such
notice or statement made by Landlord; (g) expressly permit multiple or partial
draws up to the stated amount of

                                       16

<PAGE>

the Letter of Credit; (h) expressly provide that it is transferable to any
successor of Landlord, provided that Landlord pays any transfer fee reasonably
imposed by the issuer of the Letter of Credit; and (i) expire no earlier than 60
days after the Termination Date.

         Notwithstanding anything herein to the contrary, provided Tenant is not
in default beyond applicable notice, grace and cure periods under this Lease as
of the effective date of any reduction of the Security Deposit, Tenant shall
have the right to reduce the amount of the Security Deposit to be as follows:
(i) $1,058,373.80 effective as of the earlier of (the "First Security Deposit
Reduction Date") (a) the third anniversary of the Commencement Date, or (b) the
date Tenant successfully completes its initial public offering, raising at a
minimum $100,000,000; and (ii) $705,582.50 effective as of the third anniversary
of the First Security Deposit Reduction Date. Such reduction shall be
accomplished by having Tenant provide Landlord with a substitute Letter of
Credit in the reduced amount.

         If Landlord draws on the Letter of Credit as permitted in this Lease or
the Letter of Credit, then, upon demand of Landlord, Tenant shall restore the
amount available under the Letter of Credit to its original amount by providing
Landlord with an amendment to the Letter of Credit evidencing that the amount
available under the Letter of Credit has been restored to its original amount or
to the reduced amount, if applicable, in accordance with the foregoing
paragraph. In the alternative, Tenant may provide Landlord with cash, to be held
by Landlord in accordance with this Article, equal to the restoration amount
required under the Letter of Credit.

VII.     SERVICES TO BE FURNISHED BY LANDLORD.

         A.       1.      OFFICE BUILDING

                  Landlord agrees to furnish Tenant with the following services
                  in the Office Building: (1) Water service for use in the
                  lavatories on each floor on which the Premises are located and
                  for the existing and any future kitchen/pantries that may be
                  part of Tenant's Initial Alterations; (2) Heat and air
                  conditioning in season during Normal Business Hours, at such
                  temperatures and in such amounts as are standard for
                  comparable buildings or as required by governmental authority.
                  Tenant, upon such advance notice as is reasonably required by
                  Landlord, shall have the right to receive HVAC service during
                  hours other than Normal Business Hours at an initial rate of
                  $25.00 per hour, as increased from time to time based upon
                  increases in the actual cost thereof (provided that such cost
                  shall be allocated on a pro rata square footage basis, if
                  other tenants are using this service simultaneously with
                  Tenant); (3) Maintenance and repair of the Property as
                  described in Section IX.B.; (4) Janitor service on Business
                  Days in accordance with the cleaning specification attached
                  hereto as EXHIBIT M. If Tenant's use, floor covering or other
                  improvements require special services in excess of the
                  standard services for the Buildings, Tenant shall pay the
                  actual incremental additional cost attributable to the special
                  services; (5) Elevator service; (6) Electricity to the
                  Premises for general office use, in accordance with and
                  subject to the terms and conditions in Article X; (7) security
                  for the Building, garage and Building lobby; (8) 24 hours
                  access, 7 days a week 365 days per year to the Premises and
                  parking garage; and (9) such other services as Landlord
                  reasonably determines are necessary or appropriate for the
                  Property.

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                  Tenant shall, at Tenant's sole cost and expense, install
                  separate HVAC units in the call center portion of the
                  Premises, which units shall be separately metered for
                  electrical use and such electrical costs shall be paid by
                  Tenant directly to the utility provider. Tenant shall be
                  permitted to use the two cooling units located in the Office
                  Space, provided, such units are being provided "as is" and
                  Landlord makes no representations or warranties with respect
                  to the use or condition of such units. Tenant shall be solely
                  responsible for the maintenance and repair of such units.
                  Tenant shall pay to Landlord monthly the standard charge for
                  condenser water relating to Tenant's supplemental cooling as
                  reasonably determined by Landlord from time to time.
                  Landlord's current charge for condenser water is $12.68 per
                  ton per month, which charge shall increase from time to time
                  based upon increases in the actual cost thereof.

                  2.       SCIENCE BUILDING.

                  Landlord agrees to furnish Tenant with the following services
                  and facilities in the Science Building:

                  HVAC System: The HVAC system shall be comprised of a central
                  chilled water system, condenser water system, hot water
                  heating system and custom air-handling units.

                  Air Handling Units: Custom-built air handlers shall deliver
                  approximately 1.75 CFM per SF of 100% outdoor air to the Lab
                  Space. Two units are located outdoors on the Annex roof. The
                  remaining unit is indoors, located on level 3B of the Annex,
                  and serves the Annex levels 1 and 2. The units are sized to
                  provide 100% outside air to the space. The units are complete
                  with double wall construction, dual supply fans, variable
                  frequency drives, filter section with 30% and 85% filters,
                  chilled water coil and hot water coil . The supply air is
                  distributed via medium pressure supply duct main through the
                  Science Building; the medium pressure duct is stubbed out
                  approximately 3' from the shaft on each floor for future
                  tenant fit-up. Variable frequency drives on the supply fans
                  are provided to vary the supply to the space as part of the
                  Variable Air Volume (VAV) supply air/exhaust air system.

                  Chilled Water: Chilled water shall be provided from a 1200-ton
                  central chilled water plant located on the first floor of the
                  Annex. The system shall consist of water-cooled centrifugal
                  chillers, cooling towers mounted on the Annex roof, and a
                  pumping system, piping and controls. Chilled water pumps shall
                  be constant volume and shall run 24/7.

                  Cooling Tower: The cooling tower/condenser water system shall
                  consist of cooling towers, pumps, piping and controls. The
                  cooling tower/condenser water system is sized for an
                  additional 25% capacity for tenant supplemental cooling. The
                  piping distribution shall include vertical risers, capped and
                  valved on each floor, for tenant usage. Condenser water pumps
                  shall be constant volume and shall run 24/7. Condenser water
                  fans shall be equipped with VFD's. Tenant's condenser water
                  system shall be isolated from the primary condenser water loop
                  and the secondary pumping system shall have VFD's provided
                  with the pumps.

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<PAGE>

                  Heating: Hot water shall be provided by gas-fired boilers. The
                  system is complete with primary/secondary pumping, piping and
                  controls. Piping shall include piping to the rooftop units as
                  well as vertical risers in the Science Building, capped and
                  valved on each floor for future tenant fit-up. Differential
                  bypass shall be provided with constant volume secondary pumps.
                  All future tenant reheat and hot water coils will be two-way
                  control. Heating only is provided in areas reserved for
                  Tenant's equipment and storage. Any cross ventilation and/or
                  cooling required in these areas shall be provided by Tenant,
                  based on equipment installed by Tenant.

                  Plumbing System: The plumbing system shall consist of water
                  service and gas service into the Science Building, storm
                  drainage system, toilet cores and janitor's closets, as well
                  as locations for tenant PH neutralization systems on the first
                  floor. Showers shall be provided at the first floor bathroom
                  for tenant fitness use.

                  Domestic Water: Domestic water shall be distributed to toilet
                  cores and mechanical penthouse as required. Centralized risers
                  shall also be provided for use as part of tenant fit up.
                  Domestic water is complete with booster pump to provide
                  sufficient water pressure at all floors.

                  Gas: The gas service into the Science Building shall be sized
                  to meet the base building requirements and future tenant
                  loads. Tenant is responsible for its own gas metering.

                  Electrical System: Electric service to the Science Building
                  shall be via an exterior Nstar substation (primary switchgear
                  and pad-mounted transformer) located behind a secure screened
                  wall area. The substation is provided with a dual feed primary
                  electric service (normal and standby) with automatic transfer.
                  The Science Building electric service provided is 480/277
                  volt, 3-phase, 4-wire at 4000 ampere. The overall electric
                  service size for the Science Building is approximately 27
                  watts per square foot.

                  Distribution: Within the Science Building core, a bus duct
                  riser for Tenant's use shall provide approximately 15 watts
                  per SF (lighting/receptacles/lab equipment) for lab space.
                  Tenant shall be responsible for its own electric metering and
                  distribution from each floor's respective un-metered bus duct
                  to Tenant's space.

                  Generator: The Science Building shall be provided with a 300Kw
                  diesel fired life safety generator. The generator shall serve
                  the fire pump, smoke control system, fire alarm, system,
                  elevator, emergency egress and exit lighting.

                  Tel/Data: Telephone service to the Science Building shall be
                  established with a main distribution feed on the first floor
                  and distributed to stacked tel/data rooms located on each
                  floor. High-speed fiber data service shall also be provided.

                  Fire Protection: Fire protection system consists of service
                  into the Science Building, fire department connection, and
                  distribution throughout the Science Building. Sprinkler
                  distribution shall be provided in finished common areas and
                  provided as required by code in vacant Tenant spaces.
                  Modification to sprinkler

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<PAGE>

                  piping and distribution shall be performed by Tenant to suit
                  its layout and hazard index.

                  Fire Alarm: The fire alarm system shall be an expandable
                  addressable high-rise system. Common areas are complete with
                  detection and notification and annunciation devices as
                  required.

                  Cleaning: Tenant shall provide its own cleaning services to
                  the Lab Space according to cleaning standards generally
                  prevailing in comparable research and development buildings in
                  the City of Cambridge and according to any cleaning
                  specifications adopted by Landlord from time to time during
                  the Term of this Lease.

         B.       Landlord's failure to furnish, or any interruption or
                  termination of, services due to the application of Laws, the
                  failure of any equipment, the performance of repairs,
                  improvements or alterations, or the occurrence of any event or
                  cause beyond the reasonable control of Landlord (a "Service
                  Failure") shall not render Landlord liable to Tenant,
                  constitute a constructive eviction of Tenant, give rise to an
                  abatement of Rent, nor relieve Tenant from the obligation to
                  fulfill any covenant or agreement. However, if the Premises,
                  or a material portion of the Premises, is made untenantable
                  for a period in excess of 3 consecutive Business Days as a
                  result of the Service Failure, then Tenant, as its sole
                  remedy, shall be entitled to receive an abatement of Rent
                  payable hereunder during the period beginning on the 4th
                  consecutive Business Day of the Service Failure and ending on
                  the day the service has been restored. If the entire Premises
                  has not been rendered untenantable by the Service Failure, the
                  amount of abatement that Tenant is entitled to receive shall
                  be prorated based upon the percentage of the Premises rendered
                  untenantable and not used by Tenant. In no event, however,
                  shall Landlord be liable to Tenant for any loss or damage,
                  including the theft of Tenant's Property (defined in Article
                  XV), arising out of or in connection with the failure of any
                  security services, personnel or equipment.

VIII.    LEASEHOLD IMPROVEMENTS.

         All improvements to the Premises, including, without limitation,
standard installed lab equipment (collectively, "Leasehold Improvements"), shall
be owned by Landlord upon the completion of construction of such Leasehold
Improvements and shall remain upon the Premises without compensation to Tenant.
However, Landlord, by written notice to Tenant within 30 days prior to the
Termination Date, may require Tenant to remove, at Tenant's expense, any
Leasehold Improvements or Alterations that are performed by or for the benefit
of Tenant and, in Landlord's reasonable judgment, are of a nature that would
require removal and repair costs that are materially in excess of the removal
and repair costs associated with standard office or laboratory improvements
(collectively referred to as "Required Removables"). Without limitation, it is
agreed that Required Removables include internal stairways, raised floors,
personal baths and showers, vaults, rolling file systems, additional mechanical
shafts and risers installed by Tenant, and structural alterations and
modifications of any type. Landlord agrees that none of Tenant's planned Initial
Alterations constitute Required Removables. The Required Removables designated
by Landlord shall be removed by Tenant before the Termination Date, provided
that upon prior written notice to Landlord, Tenant may remain in the Premises
for up to 5 days after the Termination Date for the sole purpose of

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<PAGE>

removing the Required Removables. Tenant's possession of the Premises shall be
subject to all of the terms and conditions of this Lease, including the
obligation to pay Rent on a per diem basis at the rate in effect for the last
month of the Term. Tenant shall repair damage caused by the installation or
removal of Required Removables. If Tenant fails to remove any Required
Removables or perform related repairs in a timely manner, Landlord, at Tenant's
expense, may remove and dispose of the Required Removables and perform the
required repairs. Tenant, within 30 days after receipt of an invoice, shall
reimburse Landlord for the reasonable costs incurred by Landlord.
Notwithstanding the foregoing, Tenant, at the time it requests approval for a
proposed Alteration (defined in Section IX.C), may request in writing that
Landlord advise Tenant whether the Alteration or any portion of the Alteration
will be designated as a Required Removable. Within 10 days after receipt of
Tenant's request, Landlord shall advise Tenant in writing as to which portions
of the Alteration, if any, will be considered to be Required Removables. All
specialized equipment, trade fixtures and furnishings not attached to the
Premises shall remain the property of the Tenant and must be removed by the
Tenant upon termination or expiration of this Lease. Notwithstanding any
provision hereof to the contrary, the following shall constitute personal
property of Tenant which shall be removed by Tenant upon termination or
expiration of this Lease, absent the express agreement of Landlord and Tenant to
the contrary: all moveable personal property, and furniture, furnishings and
equipment, such as computers, servers, phone system, work stations, power poles,
desks, tables, chairs, projectors, and lab equipment such as portable freezers,
refrigerators, mixers, centrifuges, biosafety cabinets, cage washers,
autoclaves, stirrers, rotors, ovens, incubators, cell sorters, flow Cytometers,
microscopes, water baths, unaffixed lab tables, pumps, gas cylinders, and
regulators. It is expressly understood and agreed that the following shall
become the property of Landlord upon the installation thereof and shall remain
on the Premises upon termination or expiration of this Lease: generators, fume
hoods, and affixed tables, benches and cabinets (except for biosafety cabinets).

IX.      REPAIRS AND ALTERATIONS.

         A.       Tenant's Repair Obligations. Tenant shall, at its sole cost
                  and expense, keep the Premises in good condition and repair,
                  reasonable wear and tear, casualties and takings excepted.
                  Tenant's repair obligations include, without limitation,
                  repairs to: (1) floor covering; (2) interior partitions; (3)
                  doors; (4) the interior side of demising walls; (5)
                  electronic, phone and data cabling and related equipment
                  (collectively, "Cable") that is installed by or for the
                  exclusive benefit of Tenant and located in the Premises or
                  other portions of the Buildings; (6) supplemental air
                  conditioning units, private showers and kitchens, including
                  hot water heaters, plumbing, and similar facilities serving
                  Tenant exclusively; and (7) Alterations performed by
                  contractors retained by Tenant, including related HVAC
                  balancing. All work shall be performed in accordance with the
                  rules and procedures described in Section IX.C. below. If
                  Tenant fails to make any repairs to the Premises for more than
                  30 days after notice from Landlord (although notice shall not
                  be required if there is an emergency), Landlord may make the
                  repairs, and Tenant shall pay the reasonable cost of the
                  repairs to Landlord within 30 days after receipt of an invoice
                  accompanied by reasonable substantiation, together with an
                  administrative charge in an amount equal to 3% of the cost of
                  the repairs.

         B.       Landlord's Repair Obligations; Utility Installations. Landlord
                  shall keep and maintain in good repair and working order and
                  make repairs to and perform

                                       21

<PAGE>

                  maintenance upon: (1) structural elements of the Building; (2)
                  mechanical (including HVAC), electrical, plumbing and
                  fire/life safety systems serving the Building in general or
                  constituting base building systems and equipment; (3) Common
                  Areas; (4) the roof of the Building; (5) exterior windows of
                  the Building; (6) the parking garage and (7) elevators serving
                  the Building. Landlord shall promptly make repairs
                  (considering the nature and urgency of the repair) for which
                  Landlord is responsible. In addition, Landlord may elect, at
                  the expense of and after notice to Tenant, to repair any
                  damage or injury to the Building 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,
                  neglect or improper conduct of Tenant or any Tenant Related
                  Parties (hereinafter defined). Landlord reserves the right to
                  install, use, maintain, repair, replace and relocate utility
                  chases, pipes, wiring, meters, and other equipment and
                  fixtures in and through the Buildings to service other
                  portions of the Property.

         C.       Alterations. Tenant shall not make alterations, additions or
                  improvements to the Premises or install any Cable in the
                  Premises or other portions of the Buildings (collectively
                  referred to as "Alterations") without first obtaining the
                  written consent of Landlord in each instance, which consent
                  shall not be unreasonably withheld or delayed. However,
                  Landlord's consent shall not be required for any Alteration
                  that satisfies all of the following criteria (a "Cosmetic
                  Alteration"): (1) is of a cosmetic nature such as painting,
                  wallpapering, hanging pictures and installing carpeting; (2)
                  is not visible from the exterior of the Premises or Buildings
                  or from the Common Areas of the Property; (3) will not affect
                  the systems or structure of the Buildings; and (4) does not
                  require work to be performed inside the walls or above the
                  ceiling of the Premises. Further, Landlord's consent shall not
                  be required for non-structural, non-mechanical and
                  non-electrical Alterations to the Premises that are not
                  visible from the exterior of the Premises or the Buildings or
                  from the Common Areas of the Property, the cost of which in
                  any given instance is less than $50,000 ("Minor Alterations").
                  However, even though consent is not required, the performance
                  of Cosmetic Alterations or Minor Alterations shall be subject
                  to all the other applicable provisions of this Section IX.C.
                  Prior to starting work, Tenant shall furnish Landlord with
                  plans and specifications reasonably acceptable to Landlord;
                  names of contractors reasonably acceptable to Landlord
                  (provided that Landlord may designate specific contractors
                  with respect to Buildings systems); copies of contracts;
                  necessary permits and approvals; evidence of contractor's and
                  subcontractor's insurance in amounts reasonably required by
                  Landlord; and any security for performance that is reasonably
                  required by Landlord for Alterations having a cost in excess
                  of $100,000. Changes to the plans and specifications for
                  Alterations having a cost in excess of $50,000, or for
                  Alterations which result in non-compliance with any of the
                  criteria referenced above for Cosmetic Alterations or Minor
                  Alterations, must also be submitted to Landlord for its
                  approval, which approval shall not be unreasonably withheld or
                  delayed. Alterations shall be constructed in a good and
                  workmanlike manner using materials of a quality that is at
                  least equal to the quality designated by Landlord as the
                  minimum standard for the Buildings, by a contractor reasonably
                  approved by Landlord whose labor will work without
                  interference and in harmony with other labor working on the
                  Property. Landlord may designate reasonable rules, regulations
                  and procedures for the performance of work in the Building
                  and, to the extent reasonably necessary to

                                       22

<PAGE>

                  avoid disruption to the occupants of the Buildings, shall have
                  the right to designate the time when Alterations may be
                  performed. A copy of Landlord's current construction rules and
                  regulations is attached hereto as EXHIBIT N. For all
                  Alterations after the initial Alterations, if review by
                  Landlord of Tenant's plans for Alterations other than Cosmetic
                  Alterations reasonably requires consultation with a third
                  party architect or engineer, then Tenant shall reimburse
                  Landlord within 30 days after receipt of an invoice for sums
                  paid by Landlord for such third party examination of Tenant's
                  plans. In addition, for all Alterations after the initial
                  Alterations, within 30 days after receipt of an invoice from
                  Landlord, Tenant shall pay Landlord a fee for Landlord's
                  oversight and coordination of any non-Cosmetic Alterations
                  equal to 3% of the cost of the non-Cosmetic Alterations (it
                  being expressly understood that no such fee shall be paid to
                  Landlord for the Landlord's Work, the Initial Improvements, or
                  any initial improvements in the Expansion Space (as defined in
                  Section VII.A of EXHIBIT E). Upon completion, Tenant shall
                  furnish "as-built" plans in print and electronic CAD format
                  (except for Cosmetic Alterations), completion affidavits, full
                  and final waivers of lien and receipted bills covering all
                  labor and materials. Tenant shall assure that the Alterations
                  comply with all insurance requirements and Laws. Landlord's
                  approval of an Alteration shall not be a representation by
                  Landlord that the Alteration complies with applicable Laws or
                  will be adequate for Tenant's use. Tenant shall pay, as an
                  additional charge, the entire increase in real estate taxes on
                  the Building which shall, at any time prior to or after the
                  Commencement Date, result from or be reasonably attributable
                  to any alteration, addition or improvement to the Premises
                  made by or for the account of Tenant materially in excess of
                  the Building standard improvements for the Building.

                  It shall be a condition of Landlord's approval of the Initial
                  Improvements and of any subsequent Alterations involving MEP
                  systems that Tenant provide Landlord with (a) a certification
                  of an acoustical engineer satisfactory to Landlord that all
                  equipment installed by Tenant, when evaluated in the context
                  of the anticipated use of the entire Property, will comply
                  with the City of Cambridge Noise Ordinance, and (b) a
                  certification from a qualified engineer satisfactory to
                  Landlord that the equipment installed by Tenant will meet all
                  applicable legal requirements, and will not result in the
                  reentrainment of exhaust into base building systems.

X.       USE OF ELECTRICAL AND OTHER UTILITY SERVICES BY TENANT.

         A.       Tenant shall pay directly to the proper authorities charged
                  with the collection thereof all charges for separately metered
                  electricity (Office Building and Science Building), separately
                  check metered gas (Office Building and Science Building),
                  separately check metered water and sewer charges (Science
                  Building), telephone (Office Building and Science Building)
                  and other separately metered or check metered utilities or
                  services used or consumed on the Premises whether called
                  charge, tax, assessment, fee or otherwise including, without
                  limitation, all such charges to be paid as the service from
                  time to time becomes due. In addition, Tenant shall pay to
                  Landlord when billed the cost of metered gas and electrical
                  service for the base building air, chilled water, and heated
                  water provided to the Lab Space. Electrical service to the
                  Premises may be furnished by one or more companies providing
                  electrical generation,

                                       23

<PAGE>

                  transmission and distribution services, and the cost of
                  electricity may consist of several different components or
                  separate charges for such services, such as generation,
                  distribution and stranded cost charges. Landlord shall have
                  the exclusive right to select any company providing electrical
                  service to the Premises, to aggregate the electrical service
                  for the Property and Premises with other buildings, to
                  purchase electricity through a broker and/or buyers group and
                  to change the providers and manner of purchasing electricity.
                  Landlord shall be entitled to receive a fee (if permitted by
                  Law) for the selection of utility companies and the
                  negotiation and administration of contracts for electricity,
                  provided that the amount of such fee shall not exceed 50% of
                  any savings obtained by Landlord. As part of Tenant's Initial
                  Alterations to the Office Space, Tenant shall install in
                  accordance with specifications provided by Landlord, at
                  Tenant's sole cost and expense, a separate check meter to
                  measure and bill Tenant for the electricity used on the 15th
                  floor of the Office Space. Except as aforesaid, as part of
                  Tenant's Initial Alterations to the Lab Space, Tenant shall
                  install in accordance with specifications provided by
                  Landlord, at Tenant's sole cost and expense, separate meters
                  and wiring to measure and bill Tenant for the utilities used
                  in each space. The meters and checkmeters in the Lab Space
                  shall include, without limitation, airflow sensors in the main
                  duct and BTU meters in the hot water and condenser water lines
                  entering the Lab Space, as well as checkmeters for water and
                  sewer and gas service.

         B.       Tenant's use of electrical and other services shall not
                  exceed, either in voltage, rated capacity, or overall load,
                  that which Landlord deems to be standard for the Building,
                  consistent with provisions of Article VII above. If Tenant
                  requests permission to consume excess electrical service,
                  Landlord may condition consent upon the installation of
                  utility service upgrades, meters, submeters, air handlers or
                  cooling units, as reasonably appropriate), and the additional
                  usage (to the extent permitted by Law), installation and
                  maintenance costs shall be paid by Tenant. Landlord shall have
                  the right to separately meter electrical usage for the
                  Premises and to measure electrical usage by survey or other
                  commonly accepted methods.

XI.      ENTRY BY LANDLORD; RESERVATION OF CERTAIN RIGHTS.

                  Landlord, its agents, contractors and representatives may
         enter the Premises to inspect or show the Premises, to clean and make
         repairs, alterations or additions to the Premises, inspect and to
         conduct tests in order to monitor Tenant's compliance with legal
         requirements governing environmental substances, and to conduct or
         facilitate repairs, alterations or additions to any portion of the
         Building, including other tenants' premises, subject to the conditions
         of this Article XI. Tenant shall always have the opportunity to escort
         the persons entering the Premises pursuant hereto. Except in
         emergencies, or to provide janitorial and other Building services in
         the Office Building, after Normal Business Hours, Landlord shall
         provide Tenant with reasonable prior notice of entry into the Premises,
         which may be given orally in the event of circumstances of urgency
         where written notice is impractical; entry to show the Premises or for
         routine repairs, inspections, or tests are not such circumstances.
         Landlord shall use reasonable efforts to schedule and conduct such
         entries so as to minimize disruption of Tenant's use of the Premises.
         If reasonably necessary for the protection and safety of Tenant and its
         employees, Landlord shall have the right to temporarily close all or a
         portion of

                                       24

<PAGE>

         the Premises to perform repairs, alterations and additions. However,
         except in emergencies, Landlord will not close the call center portion
         of the Premises or disrupt utility services to such portion of the
         Premises and will not close the rest of the Premises if the work can
         reasonably be completed on weekends and after Normal Business Hours.
         Entry by Landlord shall not constitute constructive eviction or entitle
         Tenant to an abatement or reduction of Rent. Landlord reserves the
         right to make additions to the Buildings and alter or relocate
         entranceways, common areas or other facilities (including driveways,
         walkways and parking areas), and to grant easements and other rights.
         Provided, however, that Landlord's activities pursuant to the foregoing
         do not have a direct, material adverse effect on the Premises, or
         Tenant's use thereof, or on Tenant's access rights.

XII.     ASSIGNMENT AND SUBLETTING.

         A.       Except in connection with a Permitted Transfer (defined in
                  Section XII.E. below), Tenant shall not assign, sublease,
                  transfer or encumber any interest in this Lease or allow any
                  third party to use any portion of the Premises (collectively
                  or individually, a "Transfer") without the prior written
                  consent of Landlord, which consent shall not be unreasonably
                  withheld or delayed if Landlord does not elect to exercise its
                  termination rights under Section XII.B below. Notwithstanding
                  any term or provision herein to the contrary, Tenant may allow
                  Viacord and Tenant's other subsidiaries and affiliates to
                  occupy portions of the Premises, provided such occupancy is
                  otherwise in accordance with the terms and provisions of this
                  Lease. Without limitation, it is agreed that Landlord's
                  consent shall not be considered unreasonably withheld if: (1)
                  in the case of an assignment, the proposed transferee's does
                  not have a net worth equal to or greater than the net worth of
                  the Tenant as of the date of this Lease; (2) the proposed
                  transferee's use, or would result in a violation of the
                  Permitted Uses; (3) in Landlord's reasonable judgment, the
                  proposed transferee is a governmental agency whose activities
                  will not result in a greater demand on building services than
                  the demand created by activities conducted by Tenant in the
                  Premises, will not result in an increase in occupancy per
                  square foot in excess of Tenant's occupancy per square foot,
                  and will not result in an increase in the Expenses of the
                  Property; (4) the proposed transferee is an occupant of the
                  Buildings (Notwithstanding the foregoing, Landlord will not
                  withhold its consent solely because the proposed transferee is
                  an occupant of the Building if Landlord does not have space
                  available for lease in the Building that is comparable to the
                  space Tenant desires to Transfer or if Landlord is not willing
                  to lease such comparable space for a comparable period to such
                  other Building occupant. For purposes hereof, Landlord shall
                  be deemed to have comparable space if it has space available
                  on any comparable floor of the Building that is approximately
                  the same size as the space Tenant desires to Transfer at the
                  time of the proposed commencement of the proposed Transfer and
                  for approximately a comparable period); (5) Tenant is in
                  default after the expiration of the notice and cure periods in
                  this Lease; or (6) any portion of the Buildings or Premises
                  would likely become subject to additional or different Laws as
                  a consequence of the proposed Transfer (unless such legal
                  compliance is limited to the Premises during the period of the
                  transferee's occupancy, and Landlord is assured that the
                  transferee will be solely liable therefor). Any attempted
                  Transfer in violation of this Article shall, at

                                       25

<PAGE>

                  Landlord's option, be void. Consent by Landlord to one or more
                  Transfer(s) shall not operate as a waiver of Landlord's rights
                  to approve any subsequent Transfers. In no event shall any
                  Transfer or Permitted Transfer release or relieve Tenant from
                  any obligation under this Lease.

         B.       As part of its request for Landlord's consent to a Transfer,
                  Tenant shall provide Landlord with financial statements for
                  the proposed transferee, a complete copy of the proposed
                  assignment, sublease and other contractual documents and such
                  other information as Landlord may reasonably request. Landlord
                  shall, by written notice to Tenant within 20 days of its
                  receipt of the required information and documentation, either:
                  (1) consent to the Transfer by the execution of a consent
                  agreement in a form reasonably designated by Landlord or
                  reasonably refuse to consent to the Transfer in writing; or
                  (2) if Tenant is proposing to lease 50% or more of the
                  Premises for substantially the balance of the Term, exercise
                  its right to terminate this Lease with respect to the portion
                  of the Premises that Tenant is proposing to assign or sublet.
                  Any such termination shall be effective on the proposed
                  effective date of the Transfer for which Tenant requested
                  consent. Tenant shall pay Landlord a review fee of $1,500.00
                  for Landlord's review of any Permitted Transfer or requested
                  Transfer, provided if Landlord's actual reasonable costs and
                  expenses (including reasonable attorney's fees) exceed
                  $1,500.00, Tenant shall reimburse Landlord for its actual
                  reasonable costs and expenses in lieu of a fixed review fee.

         C.       Except for Permitted Transfers, Tenant shall pay Landlord 50%
                  of all rent and other consideration which Tenant receives as a
                  result of a Transfer that is in excess of the Rent payable to
                  Landlord for the portion of the Premises and Term covered by
                  the Transfer. Tenant shall pay Landlord for Landlord's share
                  of any excess within 30 days after Tenant's receipt of such
                  excess consideration. Tenant may deduct from the excess all
                  reasonable and customary expenses directly incurred by Tenant
                  attributable to the Transfer (other than Landlord's review
                  fee), including brokerage fees, legal fees and construction
                  costs. If Tenant is in Monetary Default (defined in Section
                  XIX.A. below), Landlord may require that all sublease payments
                  be made directly to Landlord, in which case Tenant shall
                  receive a credit against Rent in the amount of any payments
                  received (less Landlord's share of any excess).

         D.       Except as provided below with respect to a Permitted Transfer,
                  if Tenant is a corporation, limited liability company,
                  partnership, or similar entity, and if, in a single
                  transaction or a series of related transactions, the group of
                  persons or entities which owns or controls a majority of the
                  voting shares/rights at any time changes in a material way for
                  any reason (including but not limited to a merger,
                  consolidation or reorganization but excluding (1) a sale or
                  transfer by the Tenant of a minority interest in Tenant to a
                  person or entity previously not a part of or affiliated with
                  such ownership group and (2) transfers among members of such
                  group), such change of ownership or control shall constitute a
                  Transfer. The foregoing shall not apply to the initial public
                  offering of stock in Tenant quoted on a national market system
                  for securities transactions, nor, thereafter, to any transfers
                  of stock over such national market system for securities
                  transactions, so long as Tenant is an entity whose outstanding
                  stock is quoted on a national market system for securities
                  transactions, or if at least 80% of its voting stock is

                                       26

<PAGE>

                  owned directly or indirectly by another entity, the voting
                  shares/rights of which are so listed or quoted.

         E.       Notwithstanding any of the foregoing provisions of this
                  Section XII, Tenant may assign its entire interest under this
                  Lease to a successor to Tenant (or have a change in ownership
                  and/or control of Tenant as provided in clause D above) by
                  purchase, merger, consolidation, reorganization,
                  recapitalization or otherwise without the consent of Landlord,
                  provided that all of the following conditions are satisfied (a
                  "Permitted Transfer"): (1) Tenant is not in default, after the
                  expiration of applicable notice, grace and cure periods, under
                  this Lease; (2) Tenant's successor shall own all or
                  substantially all of the assets of Tenant which were owned by
                  Tenant immediately before the proposed purchase, merger,
                  consolidation, reorganization or recapitalization; (3)
                  Tenant's successor shall have a net worth which is at least
                  equal to Tenant's net worth as reflected in the most recent
                  regularly prepared balance sheet prior to the proposed
                  purchase, merger, consolidation, reorganization or
                  recapitalization; (4) the Permitted Use does not allow the
                  Premises to be used for on site retail purposes; and (5)
                  Tenant shall give Landlord written notice at least 20 days
                  prior to the effective date of the proposed purchase, merger,
                  consolidation, reorganization or recapitalization. Tenant's
                  notice to Landlord shall include information and documentation
                  showing that each of the above conditions has been satisfied.
                  Landlord agrees to treat and keep as confidential and not
                  disclose to any third party (i) such notice, (ii) the identity
                  of the parties to the proposed transaction or (iii) the terms
                  of the proposed transaction; provided, however (a) Landlord
                  shall be permitted to provide such information to its
                  mortgagee, subject to the same confidentiality requirements,
                  and (b) Landlord shall not be required to keep confidential
                  (aa) information which has come within the public domain
                  through no fault or action of Landlord or its representatives,
                  (bb) information which was known to Landlord on a
                  non-confidential basis prior to its disclosure hereunder, (cc)
                  information which becomes available to Landlord on a
                  non-confidential basis from any third party, and (dd)
                  information that is independently developed by Landlord. If
                  requested by Landlord, Tenant's successor shall sign a
                  commercially reasonable form of assumption agreement.

XIII.    LIENS.

         Tenant shall not permit mechanic's or other liens to be placed upon the
Property, Premises or Tenant's leasehold interest in connection with any work or
service done or purportedly done by or for benefit of Tenant. Landlord shall
have the right to require Tenant to post a performance or payment bond in
connection with any work or service done or purportedly done by or for the
benefit of Tenant having a cost in excess of $100,000. Tenant acknowledges and
agrees that all such work or service is being performed for the sole benefit of
Tenant and not for the benefit of Landlord. If a lien is so placed, Tenant
shall, within 10 days of notice from Landlord of the filing of the lien, fully
discharge the lien by settling the claim which resulted in the lien or by
bonding or insuring over the lien in the manner prescribed by the applicable
lien Law. If Tenant fails to discharge the lien, then, in addition to any other
right or remedy of Landlord, Landlord may bond or insure over the lien. Tenant
shall reimburse Landlord for any amount paid by Landlord to bond or insure over
the lien, including, without limitation, reasonable attorneys' fees (if and to
the extent permitted by Law) within 30 days after receipt of an invoice from
Landlord, accompanied by reasonable substantiation.

                                       27

<PAGE>

XIV.     INDEMNITY AND WAIVER OF CLAIMS.

         A.       Except to the extent caused by the negligence or willful
                  misconduct of Landlord or any Landlord Related Parties
                  (defined below), and subject to Article XVI below, Tenant
                  shall indemnify, defend and hold Landlord, its trustees,
                  members, principals, beneficiaries, partners, officers,
                  directors, employees, Mortgagee(s) (defined in Article XXVI)
                  and agents ("Landlord Related Parties") harmless against and
                  from all liabilities, obligations, damages, penalties, claims,
                  actions, costs, charges and expenses, including, without
                  limitation, reasonable attorneys' fees and other professional
                  fees (if and to the extent permitted by Law), which may be
                  imposed upon, incurred by or asserted against Landlord or any
                  of the Landlord Related Parties and arising out of or in
                  connection with any damage or injury occurring in the Premises
                  or any acts or omissions (including violations of Law) of
                  Tenant, the Tenant Related Parties (defined below) or any of
                  Tenant's transferees, contractors or licensees.

         B.       Except to the extent caused by the negligence or willful
                  misconduct of Tenant or any Tenant Related Parties (defined
                  below), and subject to Article XVI below, Landlord shall
                  indemnify, defend and hold Tenant, its trustees, members,
                  principals, beneficiaries, partners, officers, directors,
                  employees and agents ("Tenant Related Parties") harmless
                  against and from all liabilities, obligations, damages,
                  penalties, claims, actions, costs, charges and expenses,
                  including, without limitation, reasonable attorneys' fees and
                  other professional fees (if and to the extent permitted by
                  Law), which may be imposed upon, incurred by or asserted
                  against Tenant or any of the Tenant Related Parties and
                  arising out of or in connection with the acts or omissions
                  (including violations of Law) of Landlord, the Landlord
                  Related Parties or any of Landlord's contractors.

         C.       Landlord and the Landlord Related Parties shall not be liable
                  for, and Tenant waives, all claims for loss or damage to
                  Tenant's business or loss, theft or damage to Tenant's
                  Property or the property of any person claiming by, through or
                  under Tenant resulting from: (1) wind or weather; (2) the
                  failure of any sprinkler, heating or air-conditioning
                  equipment, any electric wiring or any gas, water or steam
                  pipes; (3) the backing up of any sewer pipe or downspout; (4)
                  the bursting, leaking or running of any tank, water closet,
                  drain or other pipe; (5) water, snow or ice upon or coming
                  through the roof, skylight, stairs, doorways, windows, walks
                  or any other place upon or near the Buildings; (6) any act or
                  omission of any party other than Landlord or Landlord Related
                  Parties; and (7) any causes not reasonably within the control
                  of Landlord. Tenant shall insure itself against such losses
                  under Article XV below.

         D.       Except as specifically provided to the contrary, the limits of
                  either party's insurance shall not limit such party's
                  liability under this Lease.

XV.      INSURANCE.

         Tenant shall carry and maintain the following insurance ("Tenant's
Insurance"), at its sole cost and expense: (1) Commercial General Liability
Insurance applicable to the Premises and its appurtenances providing, on an
occurrence basis, a minimum combined single limit of

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<PAGE>

$5,000,000.00, of which up to $4,000,000.00 may be provided by an umbrella
policy; (2) Special Form Property/Business Interruption Insurance, including
earthquake (provided that earthquake coverage may have a limit of
$2,000,000.00), written at replacement cost value and with a replacement cost
endorsement covering all of Tenant's trade fixtures, equipment, furniture and
other personal property within the Premises ("Tenant's Property"); (3) Workers'
Compensation Insurance as required by the state in which the Premises is located
and in amounts as may be required by applicable statute; and (4) Employers
Liability Coverage of at least $5,000,000.00 per occurrence. Any company writing
any of Tenant's Insurance shall have an A.M. Best rating of not less than
A-VIII. All Commercial General Liability Insurance policies shall name Tenant as
a named insured and Landlord (or any successor), Equity Office Properties Trust,
a Maryland real estate investment trust, EOP Operating Limited Partnership, a
Delaware limited partnership, Landlord's property managers, mortgagees and their
respective successors and assigns as their interests shall appear, as additional
insureds. All policies of Tenant's Insurance shall contain endorsements that the
insurer(s) shall give Landlord and its designees at least 30 days' advance
written notice of any change, cancellation, termination or lapse of insurance.
Tenant shall provide Landlord with a certificate of insurance evidencing
Tenant's Insurance prior to the earlier to occur of the Commencement Date or the
date Tenant is provided with possession of the Premises for any reason, and upon
renewals at least 15 days prior to the expiration of the insurance coverage.
Landlord shall maintain so called All Risk property insurance on the Buildings
at replacement cost value, as reasonably estimated by Landlord. Landlord shall
also maintain Commercial General Liability insurance applicable to the Property,
providing, on an occurrence basis, a minimum combined single limit of at least
$2,000,000. Except as specifically provided to the contrary, the limits of
either party's' insurance shall not limit such party's liability under this
Lease.

XVI.     SUBROGATION.

         Notwithstanding anything in this Lease to the contrary, Landlord and
Tenant hereby waive and shall cause their respective insurance carriers to waive
any and all rights of recovery, claim, action or causes of action against the
other and their respective trustees, principals, beneficiaries, partners,
officers, directors, agents, and employees, for any loss or damage that may
occur to Landlord or Tenant or any party claiming by, through or under Landlord
or Tenant, as the case may be, with respect to Tenant's Property, the Buildings,
the Premises, any additions or improvements to the Buildings or Premises, or any
contents thereof, including all rights of recovery, claims, actions or causes of
action arising out of the negligence of Landlord or any Landlord Related Parties
or the negligence of Tenant or any Tenant Related Parties, which loss or damage
is (or would have been, had the insurance required by this Lease been carried)
covered by insurance, including any deductible thereunder. The foregoing shall
not preclude the recovery of any such deductible amounts as Expenses, to the
extent provided under Section IV.C.4 above.

XVII.    CASUALTY DAMAGE.

         A.       If all or any part of the Premises or a material portion of
                  the parking spaces or all reasonable means of access to the
                  Premises is damaged by fire or other casualty, Tenant shall
                  immediately notify Landlord in writing. During any period of
                  time that any portion of the Premises or the parking spaces or
                  a reasonable means of access to the Premises is rendered
                  unusable as a result of a fire or other casualty, the Rent
                  shall abate to the extent of the portion of the Premises,
                  parking or access that is untenantable and not used by Tenant.
                  Landlord shall

                                       29

<PAGE>

                  have the right to terminate this Lease if: (1) the Building
                  shall be damaged so that, in Landlord's reasonable judgment,
                  substantial alteration or reconstruction of the Building shall
                  be required (whether or not the Premises has been damaged);
                  (2) Landlord is not permitted by Law to rebuild the Building
                  in substantially the same form as existed before the fire or
                  casualty; (3) the Premises have been materially damaged and
                  there is less than 2 years of the Term remaining on the date
                  of the casualty; (4) any Mortgagee requires that the insurance
                  proceeds be applied to the payment of the mortgage debt; or
                  (5) a material uninsured loss to the Building occurs. Landlord
                  may exercise its right to terminate this Lease by notifying
                  Tenant in writing within 60 days after the date of the
                  casualty. If Landlord does not terminate this Lease, Landlord
                  shall commence and proceed with reasonable diligence to repair
                  and restore the Building, the parking garage and the Leasehold
                  Improvements (excluding any Alterations that were performed by
                  Tenant in violation of this Lease). However, in no event shall
                  Landlord be required to spend more than the insurance proceeds
                  received by Landlord. Landlord shall not be liable for any
                  loss or damage to Tenant's Property or to the business of
                  Tenant resulting in any way from the fire or other casualty or
                  from the repair and restoration of the damage. Landlord and
                  Tenant hereby waive the provisions of any Law relating to the
                  matters addressed in this Article, and agree that their
                  respective rights for damage to or destruction of the Premises
                  shall be those specifically provided in this Lease.

         B.       If all or any portion of the Premises shall be made
                  untenantable by fire or other casualty, Landlord shall, with
                  reasonable promptness, cause an architect or general
                  contractor selected by Landlord to provide Landlord and Tenant
                  with a written estimate of the amount of time required to
                  substantially complete the repair and restoration of the
                  Premises and make the Premises tenantable again, using
                  standard working methods ("Completion Estimate"). If the
                  Completion Estimate indicates that the Premises cannot be made
                  tenantable within 270 days from the date the repair and
                  restoration is started, then regardless of anything in Section
                  XVII.A above to the contrary, either party shall have the
                  right to terminate this Lease by giving written notice to the
                  other of such election within 10 days after receipt of the
                  Completion Estimate.

XVIII.   CONDEMNATION.

         Either party may terminate this Lease if the whole or any material part
of the Premises shall be taken or condemned for any public or quasi-public use
under Law, by eminent domain or private purchase in lieu thereof (a "Taking").
Landlord shall also have the right to terminate this Lease if there is a Taking
of any portion of the Building or Property which would leave the remainder of
the Building unsuitable for use as an office building in a manner comparable to
the Building's use prior to the Taking. In order to exercise its right to
terminate the Lease, Landlord or Tenant, as the case may be, must provide
written notice of termination to the other within 45 days after the terminating
party first receives notice of the Taking. Any such termination shall be
effective as of the date the physical taking of the Premises or the portion of
the Building or Property occurs. If this Lease is not terminated, the Rentable
Square Footage of the Building, the Rentable Square Footage of the Premises and
Tenant's Pro Rata Share shall, if applicable, be appropriately adjusted. In
addition, Rent for any portion of the Premises taken or condemned shall be
abated during the unexpired Term of this Lease effective when the

                                       30

<PAGE>

physical taking of the portion of the Premises occurs. All compensation awarded
for a Taking, or sale proceeds, shall be the property of Landlord, any right to
receive compensation or proceeds being expressly waived by Tenant. However,
Tenant may file a separate claim at its sole cost and expense for Tenant's
Property and Tenant's reasonable relocation expenses, provided the filing of the
claim does not diminish the award which would otherwise be receivable by
Landlord.

XIX.     EVENTS OF DEFAULT.

         There shall be considered to be an "Event of Default" by Tenant under
this Lease upon the occurrence of any of the following events of default:

         A.       Tenant's failure to pay when due all or any portion of the
                  Rent, if the failure continues for 5 business days after
                  written notice to Tenant ("Monetary Default").

         B.       Tenant's failure (other than a Monetary Default) to comply
                  with any term, provision or covenant of this Lease, if the
                  failure is not cured within 20 days after written notice to
                  Tenant. However, if Tenant's failure to comply cannot
                  reasonably be cured within 20 days, Tenant shall be allowed
                  additional time (not to exceed 180 days) as is reasonably
                  necessary to cure the failure so long as: (1) Tenant commences
                  to cure the failure within 20 days, and (2) Tenant diligently
                  pursues a course of action that will cure the failure and
                  bring Tenant back into compliance with the Lease. However, if
                  Tenant's failure to comply creates a hazardous condition, the
                  failure must be cured immediately upon notice to Tenant.

         C.       Tenant or any Guarantor becomes insolvent, makes a transfer in
                  fraud of creditors or makes an assignment for the benefit of
                  creditors, or admits in writing its inability to pay its debts
                  when due.

         D.       The leasehold estate is taken by process or operation of Law.

XX.      REMEDIES.

         A.       Upon any Event of Default (as provided in Section XIX),
                  Landlord shall have the right without notice or demand (except
                  as provided in Article XIX) to pursue any of its rights and
                  remedies at Law or in equity, including any one or more of the
                  following remedies:

                  1.       Terminate this Lease, in which case Tenant shall
                           immediately surrender the Premises to Landlord. If
                           Tenant fails to surrender the Premises, Landlord may,
                           in compliance with applicable Law and without
                           prejudice to any other right or remedy, enter upon
                           and take possession of the Premises and expel and
                           remove Tenant, Tenant's Property and any party
                           occupying all or any part of the Premises. Tenant
                           shall pay Landlord on demand the amount of all past
                           due Rent and other losses and damages which Landlord
                           may suffer as a result of Tenant's default, whether
                           by Landlord's inability to relet the Premises on
                           satisfactory terms or otherwise, including, without
                           limitation, all Costs of Reletting (defined below)
                           and any deficiency that may arise from reletting or
                           the failure to

                                       31

<PAGE>

                           relet the Premises. "Costs of Reletting" shall
                           include all costs and expenses incurred by Landlord
                           in reletting or attempting to relet the Premises,
                           including, without limitation, reasonable legal fees,
                           brokerage commissions, the cost of alterations and
                           the value of other concessions or allowances granted
                           to a new tenant.

                  2.       In lieu of calculating damages under Sections XX.A.1
                           above, Landlord may elect to receive as damages the
                           sum of (a) all Rent accrued through the date of
                           termination of this Lease or Tenant's right to
                           possession, and (b) an amount equal to the total Rent
                           that Tenant would have been required to pay for the
                           remainder of the Term discounted to present value at
                           the Prime Rate (defined in Section XX.B. below) then
                           in effect, minus the then present fair rental value
                           of the Premises for the remainder of the Term,
                           similarly discounted, after deducting all anticipated
                           Costs of Reletting.

         B.       Unless expressly provided in this Lease, the repossession or
                  re-entering of all or any part of the Premises shall not
                  relieve Tenant of its liabilities and obligations under the
                  Lease. No right or remedy of Landlord shall be exclusive of
                  any other right or remedy. Each right and remedy shall be
                  cumulative and in addition to any other right and remedy now
                  or subsequently available to Landlord at Law or in equity. If
                  Landlord declares Tenant to be in default after the expiration
                  of applicable notice, grace and cure periods, Landlord shall
                  be entitled to receive interest on any unpaid item of Rent at
                  a rate equal to the Prime Rate plus 4%. For purposes hereof,
                  the "Prime Rate" shall be the per annum interest rate publicly
                  announced as its prime or base rate by a federally insured
                  bank selected by Landlord in the state in which the Building
                  is located. Forbearance by Landlord to enforce one or more
                  remedies shall not constitute a waiver of any default.

XXI.     LIMITATION OF LIABILITY.

         NOTWITHSTANDING ANYTHING TO THE CONTRARY CONTAINED IN THIS LEASE, THE
LIABILITY OF LANDLORD (AND OF ANY SUCCESSOR LANDLORD) TO TENANT SHALL BE LIMITED
TO THE INTEREST OF LANDLORD IN THE PROPERTY. TENANT SHALL LOOK SOLELY TO
LANDLORD'S INTEREST IN THE PROPERTY FOR THE RECOVERY OF ANY JUDGMENT OR AWARD
AGAINST LANDLORD. NEITHER LANDLORD NOR ANY LANDLORD RELATED PARTY SHALL BE
PERSONALLY LIABLE FOR ANY JUDGMENT OR DEFICIENCY. BEFORE FILING SUIT FOR AN
ALLEGED DEFAULT BY LANDLORD, TENANT SHALL GIVE LANDLORD AND THE MORTGAGEE(S)
(DEFINED IN ARTICLE XXVI BELOW) WHOM TENANT HAS BEEN NOTIFIED HOLD MORTGAGES
(DEFINED IN ARTICLE XXVI BELOW) ON THE PROPERTY, BUILDINGS OR PREMISES, NOTICE
AND REASONABLE TIME TO CURE THE ALLEGED DEFAULT. WITHOUT LIMITING THE FOREGOING,
IN NO EVENT SHALL LANDLORD OR ANY MORTGAGEES OR LANDLORD RELATED PARTIES EVER BE
LIABLE FOR ANY CONSEQUENTIAL OR INCIDENTAL DAMAGES OR ANY LOST PROFITS OF
TENANT. LIKEWISE, EXCEPT AS SET FORTH IN ARTICLE XXV BELOW, TENANT SHALL NEVER
BE LIABLE FOR ANY CONSEQUENTIAL OR INCIDENTAL DAMAGES OR ANY LOST PROFITS OR
LANDLORD.

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<PAGE>

XXII.    NO WAIVER.

         Either party's failure to declare a default immediately upon its
occurrence, or delay in taking action for a default shall not constitute a
waiver of the default, nor shall it constitute an estoppel. Either party's
failure to enforce its rights for a default shall not constitute a waiver of its
rights regarding any subsequent default. Receipt by Landlord of Tenant's keys to
the Premises shall not constitute an acceptance or surrender of the Premises.

XXIII.   QUIET ENJOYMENT.

         Tenant shall, and may peacefully have, hold and enjoy the Premises,
subject to the terms of this Lease, provided Tenant is not in default after the
expiration of applicable notice, grace and cure periods. This covenant and all
other covenants of Landlord shall be binding upon Landlord and its successors
only during its or their respective periods of ownership of the Building, and
shall not be a personal covenant of Landlord or the Landlord Related Parties.

XXIV.    INTENTIONALLY OMITTED.

XXV.     HOLDING OVER.

         If Tenant fails to surrender the Premises at the expiration or earlier
termination of this Lease, occupancy of the Premises after the termination or
expiration shall be that of a tenancy at sufferance. Tenant's occupancy of the
Premises during the holdover shall be subject to all the terms and provisions of
this Lease and Tenant shall pay an amount (on a per month basis without
reduction for partial months during the holdover) equal to 150% of the greater
of: (1) the sum of the Base Rent and Additional Rent due for the period
immediately preceding the holdover; or (2) the fair market gross rental for the
Premises as reasonably determined by Landlord. No holdover by Tenant or payment
by Tenant after the expiration or early termination of this Lease shall be
construed to extend the Term or prevent Landlord from immediate recovery of
possession of the Premises by summary proceedings or otherwise. In addition to
the payment of the amounts provided above, if Landlord is unable to deliver
possession of the Premises to a new tenant, or to perform improvements for a new
tenant, as a result of Tenant's holdover and Tenant fails to vacate the Premises
within 30 days after Landlord notifies Tenant of Landlord's inability to deliver
possession, or perform improvements, Tenant shall be liable to Landlord for all
damages, including, without limitation, consequential damages, that Landlord
suffers from the holdover. Notwithstanding the foregoing, Tenant shall not be
liable for consequential damages unless the holdover continues for 45 or more
days after the termination of this Lease or Tenant's right to possession.

XXVI.    SUBORDINATION TO MORTGAGES; ESTOPPEL CERTIFICATE.

         Tenant accepts this Lease subject and subordinate to any mortgage(s),
deed(s) of trust, ground lease(s) or other lien(s) now or subsequently arising
upon the Premises, the Building or the Property, and to renewals, modifications,
refinancings and extensions thereof (collectively referred to as a "Mortgage");
provided, however, that such subordination shall be expressly conditioned on
Mortgagee agreeing in the form of a commercially reasonable non-disturbance
agreement not to disturb Tenant under the Lease and to commit to fund the
initial Tenant Allowance as set forth in EXHIBIT D with respect to the Premises,
and as set forth in Section VII of EXHIBIT E with respect to the Expansion
Space, if Landlord does not do so. The party having the benefit of a Mortgage
shall be referred to as a "Mortgagee". This clause shall be self-

                                       33

<PAGE>

operative, but upon request from a Mortgagee, Tenant shall execute a
commercially reasonable subordination and non-disturbance agreement in favor of
the Mortgagee. In lieu of having the Mortgage be superior to this Lease, a
Mortgagee shall have the right at any time to subordinate its Mortgage to this
Lease. If requested by a successor-in-interest to all or a part of Landlord's
interest in the Lease, Tenant shall, without charge, attorn to the
successor-in-interest. Landlord and Tenant shall each, within 10 days after
receipt of a written request from the other, execute and deliver an estoppel
certificate to those parties as are reasonably requested by the other (including
a Mortgagee or prospective purchaser). The estoppel certificate shall include a
statement certifying that this Lease is unmodified (except as identified in the
estoppel certificate) and in full force and effect, describing the dates to
which Rent and other charges have been paid, representing that, to such party's
actual knowledge, there is no default (or stating the nature of the alleged
default) and indicating other matters with respect to the Lease that may
reasonably be requested.

XXVII.   ATTORNEYS' FEES.

         If either party institutes a suit against the other for violation of or
to enforce any covenant or condition of this Lease, or if either party
intervenes in any suit in which the other is a party to enforce or protect its
interest or rights, the prevailing party shall be entitled to all of its costs
and expenses, including, without limitation, reasonable attorneys' fees.

XXVIII.  NOTICE.

         If a demand, request, approval, consent or notice (collectively
referred to as a "notice") shall or may be given to either party by the other,
the notice shall be in writing and delivered by hand or sent by registered or
certified mail with return receipt requested, or sent by overnight or same day
courier service at the party's respective Notice Address(es) set forth in
Article I, except that if Tenant has vacated the Premises (or if the Notice
Address for Tenant is other than the Premises, and Tenant has vacated such
address) without providing Landlord a new Notice Address, Landlord may serve
notice in any manner described in this Article or in any other manner permitted
by Law. Each notice shall be deemed to have been received or given on the
earlier to occur of actual delivery or the date on which delivery is refused,
or, if Tenant has vacated the Premises or the other Notice Address of Tenant
without providing a new Notice Address, 3 days after notice is deposited in the
U.S. mail or with a courier service in the manner described above. Either party
may, at any time, change its Notice Address (other than to a post office box
address) by giving the other party written notice of the new address in the
manner described in this Article.

XXIX.    EXCEPTED RIGHTS.

         This Lease does not grant any rights to light or air over or about the
Buildings. Landlord excepts and reserves exclusively to itself the use of: (1)
roofs, (2) subject to the terms of Article II above, telephone, electrical and
janitorial closets, (3) subject to the terms of Article II above, equipment
rooms, Building risers or similar areas that are used by Landlord for the
provision of Building services, (4) rights to the land and improvements below
the floor of the Premises, (5) the improvements and air rights above the
Premises, (6) the improvements and air rights outside the demising walls of the
Premises, and (7) the areas within the Premises used for the installation of
utility lines and other installations serving occupants of the Building.
Notwithstanding the foregoing, (a) Tenant shall have the right from time to time
to install its telecom systems, wires and conduits in the Building, subject to
the prior written approval of

                                       34

<PAGE>

Landlord which shall not be unreasonably withheld, and Tenant's compliance with
this Lease (other than the foregoing sentence), including without limitation
Section IX.C. and (b) Tenant shall have the Roof Rights with respect to the
Science Building set forth in EXHIBIT E. Landlord has the right to change the
Building's and Buildings' name or address. Landlord also has the right to make
such other changes to the Property and Buildings as Landlord deems appropriate,
provided the changes do not materially affect Tenant's ability to use the
Premises for the Permitted Use and the parking garage. Landlord shall also have
the right (but not the obligation) to temporarily close the Building and/or
Buildings if Landlord reasonably determines that there is an imminent danger of
significant damage to the Building, Buildings or of personal injury to
Landlord's employees or the occupants of the Building or Buildings. The
circumstances under which Landlord may temporarily close the Building or
Buildings shall include, without limitation, electrical interruptions,
hurricanes and civil disturbances. A closure of the Building or Buildings under
such circumstances shall not constitute a constructive eviction nor (except as
provided in Section VIIB) entitle Tenant to an abatement or reduction of Rent.

XXX.     SURRENDER OF PREMISES.

         At the expiration or earlier termination of this Lease, Tenant shall
remove Tenant's Property (defined in Article XV) from the Premises, and quit and
surrender the Premises to Landlord, broom clean, and in good order, condition
and repair, ordinary wear and tear and damage by casualty or condemnation
excepted. Tenant shall also be required to remove the Required Removables in
accordance with Article VIII. If Tenant fails to remove any of Tenant's Property
within 2 days after the termination of this Lease, Landlord, at Tenant's sole
cost and expense, shall be entitled (but not obligated) to remove and store
Tenant's Property. Landlord shall not be responsible for the value, preservation
or safekeeping of Tenant's Property. Tenant shall pay Landlord, upon demand, the
expenses and storage charges incurred for Tenant's Property. In addition, if
Tenant fails to remove Tenant's Property from the Premises or storage, as the
case may be, within 30 days after written notice, Landlord may deem all or any
part of Tenant's Property to be abandoned, and title to Tenant's Property shall
be deemed to be immediately vested in Landlord. Tenant shall, prior to the
expiration of the Term or upon the earlier termination thereof, cause to be
performed by a qualified environmental consultant approved by Landlord an
inspection of the Lab Space (including visual inspection, geiger counter
evaluation, airborne and surface monitoring) to confirm that the Lab Space is
free of biological, chemical and radioactive hazards. Tenant shall deliver a
copy of the inspection report ("Inspection Report") to Landlord. If the report
is not reasonably satisfactory to Landlord, Landlord shall so notify Tenant,
indicating the nature of Landlord's dissatisfaction. Tenant shall be responsible
for abating or, at Landlord's election if the Term hereof has expired, paying
the cost of abating any condition(s) in accordance with the approved Inspection
Report.

XXXI.    MISCELLANEOUS.

         A.       This Lease and the rights and obligations of the parties shall
                  be interpreted, construed and enforced in accordance with the
                  Laws of the state in which the Building is located and
                  Landlord and Tenant hereby irrevocably consent to the
                  jurisdiction and proper venue of such state. If any term or
                  provision of this Lease shall to any extent be invalid or
                  unenforceable, the remainder of this Lease shall not be
                  affected, and each provision of this Lease shall be valid and
                  enforced to the fullest extent permitted by Law. The headings
                  and titles to the Articles and

                                       35

<PAGE>

                  Sections of this Lease are for convenience only and shall have
                  no effect on the interpretation of any part of the Lease.

         B.       Tenant shall not record this Lease or any memorandum or notice
                  without Landlord's prior written consent; provided, however,
                  Landlord agrees to consent to the recordation or registration
                  of a memorandum or notice of this Lease, at Tenant's cost and
                  expense in the form attached hereto as EXHIBIT F, if the
                  initial term of this Lease or the initial term plus any
                  renewal terms granted exceed, in the aggregate, 7 years. If
                  this Lease is terminated before the Term expires, upon
                  Landlord's request the parties shall execute, deliver and
                  record an instrument acknowledging the above and the date of
                  the termination of this Lease, and Tenant appoints Landlord
                  its attorney-in-fact in its name and behalf to execute the
                  instrument if Tenant shall fail to execute and deliver the
                  instrument after Landlord's request therefor within 10 days.

         C.       Landlord and Tenant hereby waive any right to trial by jury in
                  any proceeding based upon a breach of this Lease.

         D.       Whenever a period of time is prescribed for the taking of an
                  action by Landlord or Tenant, the period of time for the
                  performance of such action shall be extended by the number of
                  days that the performance is actually delayed due to strikes,
                  acts of nature, shortages of labor or materials, war, civil
                  disturbances and other causes beyond the reasonable control of
                  the performing party ("Force Majeure"). However, events of
                  Force Majeure shall not extend any period of time for the
                  payment of Rent or other sums payable by either party or any
                  period of time for the written exercise of an option or right
                  by either party and shall not apply with respect to Section
                  VIIB.

         E.       Landlord shall have the right to transfer and assign, in whole
                  or in part, all of its rights and obligations under this Lease
                  and in the Building, Buildings and/or Property referred to
                  herein, and upon such transfer by Landlord of all of its
                  interests in the Property. Landlord shall be released from any
                  further obligations hereunder, and Tenant agrees to look
                  solely to the successor in interest of Landlord for the
                  performance of such obligations.

         F.       Landlord and Tenant each represent that they have dealt
                  directly with and only with the Broker as a broker in
                  connection with this Lease. Each of Landlord and Tenant shall
                  indemnify and hold the other and their respective Related
                  Parties harmless from all claims of any other brokers claiming
                  to have dealt with the indemnifying party in connection with
                  this Lease.

         G.       Tenant covenants, warrants and represents that: (1) each
                  individual executing, attesting and/or delivering this Lease
                  on behalf of Tenant is authorized to do so on behalf of
                  Tenant; (2) this Lease is binding upon Tenant; and (3) Tenant
                  is duly organized and legally existing in the state of its
                  organization and is qualified to do business in the state in
                  which the Premises are located. Landlord hereby makes the same
                  covenant, representation and warranty to Tenant. If there is
                  more than one Tenant, or if Tenant is comprised of more than
                  one party or entity, the obligations imposed upon Tenant shall
                  be joint and several obligations of all the parties and
                  entities. If Tenant is a partnership, then each present and

                                       36

<PAGE>

                  future partner shall be personally bound by and upon all of
                  the covenants, agreements, terms, provisions and conditions to
                  be performed by Tenant. Landlord may request (and Tenant shall
                  comply) that Tenant, at the time that Tenant admits any new
                  partner to its partnership, require each new partner to
                  execute an agreement in form and substance satisfactory to
                  Landlord under which the new partner shall agree to be
                  personally bound by and upon all of the covenants, agreements,
                  terms, provisions and conditions to be performed by Tenant,
                  without regard to when the new partner is admitted to the
                  partnership (or when any obligations under any of covenants,
                  agreements, terms, provisions and conditions accrue). Notices,
                  payments and agreements given or made by, with or to any one
                  person or entity shall be deemed to have been given or made
                  by, with and to all of them.

         H.       Time is of the essence with respect to Tenant's exercise of
                  any expansion, renewal or extension rights granted to Tenant.
                  This Lease shall create only the relationship of landlord and
                  tenant between the parties, and not a partnership, joint
                  venture or any other relationship. This Lease and the
                  covenants and conditions in this Lease shall inure only to the
                  benefit of and be binding only upon Landlord and Tenant and
                  their permitted successors and assigns.

         I.       The expiration of the Term, whether by lapse of time or
                  otherwise, shall not relieve either party of any obligations
                  which accrued prior to or which may continue to accrue after
                  the expiration or early termination of this Lease. Without
                  limiting the scope of the prior sentence, it is agreed that
                  Tenant's obligations under Sections IV.A, IV.B., VIII, XIV,
                  XX, XXV, XXX, XXXII and XXXIII shall survive the expiration or
                  early termination of this Lease.

         J.       Landlord has delivered a copy of this Lease to Tenant for
                  Tenant's review only, and the delivery of it does not
                  constitute an offer to Tenant or an option. This Lease shall
                  not be effective against any party hereto until an original
                  copy of this Lease has been signed by both parties.

         K.       All understandings and agreements previously made between the
                  parties with respect to the Premises are superseded by this
                  Lease, and neither party is relying upon any warranty,
                  statement or representation not contained in this Lease. This
                  Lease may be modified only by a written agreement signed by
                  Landlord and Tenant.

         L.       Subject to restrictions on disclosure under applicable law,
                  Tenant, within 15 days after request, shall provide Landlord
                  with a current financial statement and such other information
                  as Landlord may reasonably request in order to create a
                  "business profile" of Tenant and determine Tenant's ability to
                  fulfill its obligations under this Lease. Landlord, however,
                  shall not require Tenant to provide such information unless
                  Landlord is requested to produce the information in connection
                  with a proposed financing or sale of the Building. Upon
                  written request by Tenant and prior to Tenant being required
                  to disclose such financial information, Landlord shall enter
                  into a commercially reasonable confidentiality agreement
                  covering any confidential information that is disclosed by
                  Tenant.

         M.       Subject to the provisions of this Section M, so long as no
                  Event of Default has

                                       37

<PAGE>

                  occurred and remains outstanding under this Lease, and
                  provided Tenant's employees execute Landlord's standard waiver
                  of liability form, then Tenant's employees (the "Fitness
                  Center Users") shall be entitled to use the Property's fitness
                  center (the "Fitness Center"). The use of the Fitness Center
                  shall be subject to the reasonable rules and regulations
                  (including rules regarding hours of use) established from time
                  to time by Landlord for the Fitness Center. There shall be no
                  separate charge to Tenant for the use of the Fitness Center;
                  however, the costs of operating, maintaining and repairing the
                  Fitness Center shall be included as part of Expenses to the
                  extent provided in Section IV.C. above. Tenant acknowledges
                  that the provisions of this Section shall not be deemed to be
                  a representation by Landlord that Landlord shall continuously
                  maintain the Fitness Center (or any other fitness facility)
                  throughout the Term of this Lease, and Landlord shall have the
                  right, at Landlord's sole discretion, to expand, contract,
                  eliminate or otherwise modify the Fitness Center. No
                  expansion, contraction or modification of the Fitness Center,
                  and no termination of Tenant's or the Fitness Center Users'
                  rights to the Fitness Center shall constitute a constructive
                  eviction or entitle Tenant to an abatement or reduction in
                  Rent.

XXXII.   ENVIRONMENTAL SUBSTANCES.

         "Environmental Law(s)" means all statutes, Laws, rules, regulations,
codes, ordinances, standards, guidelines, authorizations and orders of federal,
state and local public authorities pertaining to any of the Environmental
Substances or to environmental compliance, contamination, cleanup or disclosures
of any release or threat of release to the environment, of any hazardous or
toxic substances, wastes or materials, any pollutants or contaminants which are
included under or regulated by any municipal, county, state or federal statutes,
Laws, rules, regulations, codes, ordinances, standards, guidelines,
authorizations or orders, including, without limitation, the Toxic Substances
Control Act, 15 U.S.C. Section 2601, et seq.; the Clean Water Act, 33 U.S.C.
Section 1251, et seq.; the Clean Air Act, 42 U.S.C. Section 7401, et seq.; the
Safe Drinking Water Act, 42 U.S.C. Section 300f-300j, et seq.; the Federal Water
Pollution Control Act, 33 U.S.C. Section 1321, et seq.; the Solid Waste Disposal
Act, 42 U.S.C. Section 6901, et seq.; the Comprehensive Environmental Response,
Compensation and Liability Act of 1980, 42 U.S.C. Section 9601 et seq.; the
Federal Resource Conservation and Recovery Act, 42 U.S.C. Section 6901 et seq.;
the Superfund Amendments and Reauthorization Act of 1986, Public Law No. 99-499
(signed into law October 17, 1986); M.G.L. c.21C; and oil and hazardous
materials as defined in M.G.L. c.21E, as any of the same are from time to time
amended, and the rules and regulations promulgated thereunder, and any judicial
or administrative interpretation thereof, including any judicial or
administrative orders or judgments, and all other federal, state and local
statutes, Laws, rules, regulations, codes, ordinances, standards, guidelines,
authorizations and orders regulating the generation, storage, containment or
disposal of any Environmental Substances, including but not limited to those
relating to lead paint, radon gas, asbestos, storage and disposal of oil and
hazardous wastes, substances and materials, and underground and above-ground oil
storage tanks; and any amendments, modifications or supplements of any of the
foregoing.

         "Environmental Substances" means, but shall not be limited to, any
hazardous substances, hazardous waste, environmental substances, oil, petroleum
products and any waste or substance, which because of its quantitative
concentration, chemical, biological, radioactive, flammable, explosive,
infectious or other characteristics, constitutes or may

                                       38

<PAGE>

reasonably be expected to constitute or contribute to a danger or hazard to
public health, safety or welfare or to the environment, including without
limitation any asbestos (whether or not friable) and any asbestos-containing
materials, lead paint, waste oils, solvents and chlorinated oils,
polychlorinated biphenyls (PCBs), toxic metals, etchants, pickling and plating
wastes, explosives, reactive metals and compounds, pesticides, herbicides, radon
gas, urea formaldehyde foam insulation and chemical, biological and radioactive
wastes, or any other similar materials which are mentioned under or regulated by
any Environmental Law; and the regulations adopted under these acts, and
including any other products or materials subsequently found by an authority of
competent jurisdiction to have adverse effects on the environment or the health
and safety of persons.

         Tenant shall not cause or permit any Environmental Substances to be
generated, produced, brought upon, used, stored, treated or disposed of in or
about or on the Building by Tenant, its agents, employees, contractors,
subtenants or invitees without (i) Landlord's prior written consent, and (ii)
strictly complying with all applicable Environmental Laws and Laws pertaining to
the transportation, storage, use or disposal of such Environmental Substances,
including obtaining proper permits. Landlord may take into account any factors
or facts that Landlord reasonably believes relevant in determining whether to
grant its consent. Landlord consents to Tenant's use in the Lab Space of the
Environmental Substances listed in EXHIBIT K. From time to time at Landlord's
request, Tenant shall execute affidavits, representations and the like
concerning Tenant's best knowledge and belief regarding the presence or absence
of Environmental Substances on the Premises or the Property, and shall provide
copies of all required permits for Tenant's activities in the Premises.
Furthermore, on a quarterly basis beginning on the Commencement Date or more
often if reasonably required by Landlord's mortgagee(s), Tenant shall provide
Landlord with a list detailing the types and amounts of all Environmental
Substances being generated, produced, brought upon, used, stored, treated or
disposed of by or on behalf of Tenant in or about or on the Premises, Building
or Property and, upon Landlord's request, copies of any manifests or other
federal, state or municipal filings by Tenant with respect to such Environmental
Substances. Tenant agrees to pay the cost of any environmental inspection or
assessment requested by any lender that holds a security interest in the
Property or this Lease, or by any insurance carrier, to the extent that such
inspection or assessment pertains to any release, threat of release,
contamination, claim of contamination, loss or damage or determination of
condition (together, "Environmental Incidents") in the Premises other than
Environmental Incidents arising prior to the date Tenant occupies the Premises
for the conduct of its business or migrating to the Premises from some other
part of the Building through no fault, act or omission of Tenant.

         If Tenant's transportation, storage, use or disposal of Environmental
Substances on the Property results in the contamination of the soil or surface
or ground water or loss or damage to person(s) or property, Tenant agrees to:
(a) notify Landlord immediately of any release, threat of release,
contamination, claim of contamination, loss or damage; (b) after consultation
with Landlord, clean up the release, threat of release, or contamination in full
compliance with all applicable statutes, regulations and standards and (c)
indemnify, defend and hold Landlord, ground landlord, if any, and the Landlord
Related Parties harmless from and against any claims, suits, causes of action,
costs and fees, including attorneys' fees and costs, arising from or connected
with any such release, threat of release, contamination, claim of contamination,
loss or damage. In the event of such contamination, Tenant agrees to cooperate
fully with Landlord and provide such documents, affidavits and information as
may be requested by Landlord (1) to comply with any Environmental Law or Laws,
(2) to comply with the reasonable request of any lender, purchaser or tenant,
and/or (3) for any other reasonable reason deemed

                                       39

<PAGE>

necessary by Landlord. Tenant shall notify Landlord promptly in the event of any
spill or other release of any Environmental Substance at, in, on, under or about
the Premises which is required to be reported to a governmental authority under
any Environmental Law or Laws, shall promptly forward to Landlord copies of any
notices received by Tenant relating to alleged violations of any Environmental
Law or Laws and shall promptly pay when due any fine or assessment against
Landlord, Tenant, or the Premises relating to any violation during the Term of
any Environmental Law or Laws by Tenant, its employees, agents, independent
contractors, or invitees or with respect to the Premises or Property. If any
governmental authority files a lien against the Premises due to any act or
omission, intentional or unintentional, of Tenant, its agents, employees, or
invitees, or for which Tenant is responsible, resulting in the releasing,
spilling, leaking, leaching, pumping, emitting, pouring, emptying or dumping of
any Environmental Substance, Tenant shall, within thirty (30) days from the date
that Tenant is first given notice of such lien (or within such shorter period of
time as may be specified by Landlord if such governmental authority takes steps
to cause the Premises to be sold pursuant to such lien) either (A) pay the claim
and remove the lien or (B) furnish a cash deposit, bond or such other security
as is satisfactory in all respects to Landlord and sufficient to discharge the
lien completely.

         The provisions of this Section XXXII survive the expiration or earlier
termination of this Lease.

XXXIII.  MEDICAL WASTE POLICY.

         Tenant hereby agrees to furnish to Landlord upon demand, written
evidence that Tenant has established a written policy (the "Medical Waste
Policy") concerning the identification, collection, storage, decontamination and
disposal of Hazardous Medical Waste (defined below) and Infectious Waste
(defined below). Tenant is responsible for the proper containment and
identification of its Hazardous Medical Waste and Infectious Waste, the disposal
of the Hazardous Medical Waste and Infectious Waste and the transportation of
the Hazardous Medical Waste and Infectious Waste using a properly qualified
agent (including, but not limited to, Stericycle). Landlord shall have the right
to reasonably designate an area within the Premises for the pick-up of Hazardous
Medical Waste and Infectious Waste.

         Hazardous Medical Waste is defined as used needles and syringes, gloves
and linen, uniforms and laundry, and cleaning equipment or materials used to
clean any of the foregoing; any solid, liquid or gas that is capable of
producing harmful affects on humans or the environment; material that is
ignitable, corrosive, reactive or toxic; or any materials that are classified as
hazardous medical waste by Law.

         Infectious Waste is defined as any waste that contains pathogens or is
capable of producing infectious disease; material contaminated by potentially
infectious materials (taking into consideration the factors necessary for
induction of disease, which include, but are not limited to, adequate dose,
resistance of host, portal of entry and presence of a pathogen and virulence);
material that contains pathogens with sufficient virulence and quantity so that
exposure to the waste by a susceptible host could result in an infectious
disease; or wastes capable of causing disease. Including but not limited to:

         A.       Cultures and stocks of agents infectious to humans, and
associated biologicals (including but not limited to cultures from medical
laboratories; waste from the production of biologicals; discarded live and
attenuated vaccines, and culture dishes and devices used to

                                       40

<PAGE>

transfer, inoculate and mix cultures);

         B.       Human pathological wastes [including but not limited to
tissue, organs and body parts (except teeth and the contiguous structures of
bone and gum), and body fluids that are removed during medical procedures and
specimens of body fluids and their containers];

         C.       Discarded waste blood and blood components (including but not
limited to serum and plasma) and saturated material containing free flowing
blood and blood components (including but not limited to lab specimens);

         D.       Discarded sharps used in human patient care, medical research
or clinical or pharmaceutical laboratories (including but not limited to
hypodermic, I.V., and other medical needles; hypodermic and I.V. syringes;
Pasteur pipettes; scalpel blades; blood vials; and broken or unbroken glassware
in contact with infectious agents, including slides or cover slips); and

         E.       Discarded hypodermic, I.V. and other medical needles,
hypodermic, I.V., syringes, sharps and scalpel blades and whether used or unused
(as it is often difficult to determine if they have been used).

         Tenant further agrees that such Medical Waste Policy shall incorporate
the following elements: (a) Tenant's employees and agents shall be expressly
forbidden from disposing of any Hazardous Medical Waste or Infectious Waste
within the Premises or the Building in a manner which is contrary to the terms
of the Medical Waste Policy; (b) all such Hazardous Medical Waste and Infectious
Waste shall be collected, stored, decontaminated and removed from the Premises
and the Building by a qualified party in compliance with all applicable Laws and
guidelines (including, without limitation, the Occupational Safety and Health
Act) of any local, state or federal entity having jurisdiction over this matter;
(c) Infectious Waste shall be separated from other waste by containing it in
disposable red plastic bags/containers which are impervious to moisture; (d)
needles and sharps shall be contained in disposable rigid containers which can
be sealed with a tight fitting lid; (e) all spills of Infectious Waste shall be
wiped immediately using a spill kit that contains instructions and disposable
red plastic bags; (f) any spillage, or injury from handling Infectious Waste
shall be immediately reported to Landlord and Landlord shall immediately be
given a specific incident report; and (g) Tenant and its employees and agents
shall at all times employ proper procedures, including, without limitation, the
use of tags, signs or other appropriate written communication, to prevent
accidental injury or illness to other tenants in the Building (including their
employees, agents and invitees) resulting from Tenant's collection, storage,
decontamination and disposal of Hazardous Medical Waste and Infectious Waste.
Tenant hereby covenants and agrees that at all times during the Term, Tenant and
its employees and agents shall adhere to the terms and conditions of the Medical
Waste Policy. Tenant agrees to indemnify, defend and hold Landlord and the
Landlord Related Parties harmless from and against any and all liabilities,
obligations, damages, penalties, claims, costs, charges or expenses, including
without limitation, attorney's fees, clean-up costs, fines or penalties arising
out of or resulting from Tenant's violation of this Paragraph.

         The provisions of this Section XXXIII survive the expiration or earlier
termination of this Lease.

                                       41

<PAGE>

XXXIV.   LAB STANDARDS.

         Tenant shall keep and maintain the Lab Space in accordance with (i) the
Institute of Laboratory Animal Resources "Guide for the Care and Use of
Laboratory Animals", (ii) the Animal Welfare Act (7 U.S.C. 2131 et. Seq.), and
(iii) all other applicable Federal, State and local laws, guidelines and
policies relating to the operation and maintenance of biomedical laboratory
facilities (collectively, the "Lab Standards").

A.       Landlord acknowledges that as part of Tenant's operations in the Lab
         Space, Tenant shall perform certain medical research work on animals
         (the "Permitted Animals"). Tenant shall at all times keep and maintain
         the Permitted Animals utilized by Tenant in accordance with the Lab
         Standards. All animals brought onto the Property shall be transported
         in accordance with such rules and regulations as Landlord shall
         reasonably designate. All animals kept in the Lab Space shall be caged
         or restrained at all times. In no event shall Tenant use or occupy the
         Lab Space in a manner that would be inconsistent with the character and
         dignity of the Building or the Cambridge Science Center and Landlord
         may require Tenant to immediately cease any business, procedures,
         activities or other use which is causing disturbance of, or
         interference with Landlord's operation and management of the Cambridge
         Science Center or the use and occupancy thereof by any tenant therein.

B.       Without limiting the limitations imposed by the Permitted Use clause,
         Tenant shall not use or permit the Lab Space to be used for any purpose
         that would allow animal, medical or medicinal odors, fumes or noises to
         emanate from the Lab Space. In the event such odors, fumes or noises do
         emanate from the Lab Space, Tenant, at its sole cost and expense, shall
         be responsible for taking whatever steps are necessary in accordance
         with all applicable Laws and the terms of this Lease in order to either
         eliminate such odors, fumes or noises or to keep such odors, fumes or
         noises from emanating from the Buildings in a manner approved by
         Landlord. Such steps may include the installation of an exhaust system
         or sound proofing in accordance with plans and specifications approved
         by Landlord. If Landlord and Tenant are unable to reach an agreement on
         the course of action Tenant will take to correct the odor or noise
         problem, as the case may be, within 10 days after the date Landlord
         first contacts Tenant to inform Tenant of the odor or noise problem,
         Landlord (in its reasonable discretion) shall determine the course of
         action Tenant shall take to correct the odor or noise problem. Such
         work to correct the odor or noise problem shall be completed by Tenant
         within 30 days of the date a determination is made by either Landlord
         or Landlord and Tenant (as applicable) as to the scope of work Tenant
         shall perform.

C.       Tenant agrees to be solely responsible for the disposal of all medical,
         infectious and hazardous waste (including without limitation, all
         needles, syringes, bloodbags, bandages and vials) and all animal bodies
         or parts that are generated in the Tenant's Lab Space and to indemnify
         and hold Landlord harmless from and against all liabilities,
         obligations, damages, penalties, claims, costs, charges and expenses
         which may be imposed upon, incurred by, or asserted against Landlord in
         connection with the generation and existence of such medical,
         infectious and/or hazardous waste (including without limitation, all
         needles, syringes, bloodbags, bandages and vials) and all animal bodies
         or parts and the removal thereof from the Lab Space. Tenant agrees to
         comply with all Laws, ordinances, orders, rules, and regulations of any
         governmental or regulatory agency with respect to the generation,
         existence, removal, storage and disposal of any such medical,
         infectious and/or hazardous waste (including without

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<PAGE>

         limitation, all needles, syringes, bloodbags, bandages and vials) and
         all animal bodies and parts.

D.       Tenant agrees to contract with a licensed and insured medical waste
         disposal vendor acceptable to Landlord for the lawful disposal of all
         medical, infectious and hazardous waste (including without limitation,
         all needles, syringes, blood bags, bandages and vials) and all animal
         bodies and parts that are generated in Tenant's Lab Space, and to
         provide a copy of such contract to Landlord. If vendors are changed,
         Tenant agrees to notify Landlord of such change prior to the effective
         date thereof and to provide the appropriate documentation to Landlord.
         In no event shall any medical, infectious and/or hazardous waste be
         placed or stored outside of the Lab Space, it being agreed that all
         such materials shall be kept in the Lab Space until picked up by the
         approved medical waste disposal vendor.

E.       Tenant, at Tenant's sole cost and expense, shall obtain and maintain
         throughout the Term any licenses, permits or zoning approvals required
         by any governmental body for the conduct of Tenant's business and
         medical uses with the Lab Space.

F.       In the event Tenant's activities in the Project results in any
         disturbance, disruption of or interference with the business of the
         Project, including, but not limited to, demonstrations, pickets,
         boycotts and/or confrontations or disputes on or about the Project
         opposing or supporting Tenant's activities (a "Use Dispute"), then
         Tenant shall take all actions necessary to resolve the Use Dispute and
         to have the demonstrators, picketers or other individuals engaged in
         the Use Dispute removed from the Project in an expeditious manner.
         Tenant shall have no claim for damages against Landlord or any of the
         Landlord Related Parties, as a result of the above actions.

XXXV.    ENTIRE AGREEMENT.

         This Lease and the following exhibits and attachments which are hereby
incorporated into and made a part of this Lease constitute the entire agreement
between the parties and supersede all prior agreements and understandings
related to the Premises, including all lease proposals, letters of intent and
other documents: EXHIBIT A (Outline and Location of Premises), EXHIBIT B
(Building Rules and Regulations), EXHIBIT C (Form of Letter of Credit), EXHIBIT
D (Work Letter), EXHIBIT E (Additional Provisions), EXHIBIT F (Form of Notice of
Lease [(for recording])), EXHIBIT G (Exterior Signage), EXHIBIT H (Offering
Space), EXHIBIT H-1 (Expansion Space), EXHIBIT I (Commencement Letter), EXHIBIT
J (Commencement Date Agreement), EXHIBIT K (List of Environmental Substances),
EXHIBIT L (Right of First Refusal Space), EXHIBIT M (Cleaning Specifications),
and EXHIBIT N (Construction Rules and Regulations).

                                       43

<PAGE>

         Landlord and Tenant have executed this Lease as of the day and year
first above written.

WITNESS/ATTEST:                    LANDLORD:

                                   MA-RIVERVIEW/245 FIRST STREET, L.L.C., A
                                   DELAWARE LIMITED LIABILITY COMPANY

                                   By:  Equity Office Management, L.L.C., a
                                        Delaware limited liability company, its
                                        non-member manager



/s/ Kim Ruby                            By: /s/ Maryann Gilligan Suydam
---------------------------------           ------------------------------------
Name (print):  Kim Ruby
_________________________________           Name: Maryann Gilligan Suydam

_________________________________           Its: Senior Vice President,
_________________________________           Boston Region
Name (print):____________________

WITNESS/ATTEST:                         TENANT:

/s/ Sara McManus                        VIACELL, INC., A DELAWARE CORPORATION
--------------------------------
Name (print): Sara McManus

                                        By: /s/ Jeffrey A. Sacher
/s/ Karen Swartz
--------------------------------
Name (print):  Karen Swartz             Name: Jeffrey A. Sacher

                                        Title: CFO

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                                    EXHIBIT A

                        OUTLINE AND LOCATION OF PREMISES

         This Exhibit is attached to and made a part of the Lease by and between
MA-RIVERVIEW/245 FIRST STREET, L.L.C., A DELAWARE LIMITED LIABILITY COMPANY
("Landlord") and VIACELL, INC., A MASSACHUSETTS CORPORATION ("Tenant") for space
in the Building located at 245 First Street, Cambridge, Massachusetts 02142.

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                                   EXHIBIT A-1

                                LAB SPACE MATRIX

                                  See attached

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                                    EXHIBIT B

                         BUILDING RULES AND REGULATIONS

         The following rules and regulations shall apply, where applicable, to
the Premises, the Buildings, the parking garage (if any), the Fitness Center,
the Property and the appurtenances. Capitalized terms have the same meaning as
defined in the Lease.

1.       Sidewalks, doorways, vestibules, halls, stairways and other similar
         areas shall not be obstructed by Tenant or used by Tenant for any
         purpose other than ingress and egress to and from the Premises. No
         rubbish, litter, trash, or material shall be placed, emptied, or thrown
         in those areas. At no time shall Tenant permit Tenant's employees to
         loiter in Common Areas or elsewhere about the Buildings or Property.

2.       Plumbing fixtures and appliances shall be used only for the purposes
         for which designed, and no sweepings, rubbish, rags or other unsuitable
         material shall be thrown or placed in the fixtures or appliances.
         Damage resulting to fixtures or appliances by Tenant, its agents,
         employees or invitees, shall be paid for by Tenant, and Landlord shall
         not be responsible for the damage.

3.       Except as otherwise provided in Exhibit E, Section V, no signs,
         advertisements or notices shall be painted or affixed to windows, doors
         or other parts of the Buildings, except those of such color, size,
         style and in such places as are first approved in writing by Landlord.
         All tenant identification and suite numbers at the entrance to the
         Premises shall be installed by Landlord, at Tenant's cost and expense,
         using the standard graphics for the Buildings. Except in connection
         with the hanging of lightweight pictures and wall decorations, no
         nails, hooks or screws shall be inserted into any part of the Premises
         or Buildings except by the Building maintenance personnel.

4.       Landlord shall provide and maintain in the Atrium between the Buildings
         an alphabetical directory board or other directory device listing
         tenants, and no other directory shall be permitted unless previously
         consented to by Landlord in writing.

5.       Tenant shall not place any lock(s) on any door in the Premises or
         Buildings without Landlord's prior written consent and Landlord shall
         have the right to retain at all times and to use keys to all locks
         within and into the Premises. A reasonable number of keys to the locks
         on the entry doors in the Premises shall be furnished by Landlord to
         Tenant at Tenant's cost. All keys shall be returned to Landlord at the
         expiration or early termination of this Lease.

6.       All contractors, contractor's representatives and installation
         technicians performing work in the Buildings shall be subject to
         Landlord's prior approval in accordance with the requirements of this
         Lease, and shall be required to comply with Landlord's standard rules,
         regulations, policies and procedures, which may be revised from time to
         time; provided, however, that no fees, costs or charges contained
         therein shall be applicable to Tenant or its contractors with respect
         to the Initial Alterations.

7.       Movement in or out of the Buildings of furniture or office equipment,
         or dispatch or receipt by Tenant of merchandise or materials requiring
         the use of elevators, stairways,

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         lobby areas or loading dock areas, shall be restricted to hours
         designated by Landlord. Tenant shall obtain Landlord's prior approval
         by providing a detailed listing of the activity. If approved by
         Landlord, the activity shall be under the supervision of Landlord and
         performed in the manner required by Landlord. Tenant shall assume all
         risk for damage to articles moved and injury to any persons resulting
         from the activity. If equipment, property, or personnel of Landlord or
         of any other party is damaged or injured as a result of or in
         connection with the activity, Tenant shall be solely liable for any
         resulting damage or loss.

8.       Landlord shall have the right to approve the weight, size, or location
         of heavy equipment or articles in and about the Premises. Damage to the
         Buildings or Property by the installation, maintenance, operation,
         existence or removal of property of Tenant shall be repaired at
         Tenant's sole expense.

9.       Corridor doors, when not in use, shall be kept closed.

10.      Tenant shall not: (1) make or permit any improper, objectionable or
         unpleasant noises or odors in the Buildings, or otherwise interfere in
         any way with other tenants or persons having business with them; (2)
         solicit business or distribute, or cause to be distributed, in any
         portion of the Buildings or Property, handbills, promotional materials
         or other advertising; or (3) conduct or permit other activities in the
         Buildings or Property that might, in Landlord's sole opinion,
         constitute a nuisance.

11.      Except as permitted by Section XXXIV of the Lease with respect to the
         Lab Space, no animals, except those assisting handicapped persons,
         shall be brought into the Buildings or kept in or about the Premises.

12.      Tenant shall not use or occupy the Premises in any manner or for any
         purpose which might injure the reputation or impair the present or
         future value of the Premises or the Buildings. Tenant shall not use, or
         permit any part of the Premises to be used, for lodging, sleeping or
         for any illegal purpose.

13.      Tenant shall not take any labor action which would violate Landlord's
         labor contracts or which would cause a work stoppage, labor related
         picketing, labor disruption or dispute, or interfere with Landlord's or
         any other tenant's or occupant's business or with the rights and
         privileges of any person lawfully in the Buildings ("Labor
         Disruption"). Tenant shall take the actions necessary to resolve the
         Labor Disruption, and shall have labor pickets removed. If there occurs
         any picketing or other disruption relating to the Premises, including
         Tenant's activities therein, Tenant shall take the actions necessary to
         resolve such disruption and shall have the pickets removed. Tenant
         shall have no claim for damages against Landlord or any of the Landlord
         Related Parties, nor shall the date of the commencement of the Term be
         extended as a result of the above actions.

14.      Tenant shall not install, operate or maintain in the Premises or in any
         other area of the Buildings, electrical equipment that would overload
         the electrical system beyond its capacity for proper, efficient and
         safe operation as determined solely by Landlord. Tenant shall not
         furnish cooling or heating to the Premises, including, without
         limitation, the use of electric or gas heating devices, without
         Landlord's prior written consent. Tenant shall not use more than its
         proportionate share of telephone lines and other telecommunication
         facilities available to service the Building in which the Premises are

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         located; it being understood by Landlord that Tenant will be operating
         a call center in the Office Space.

15.      Tenant shall not operate or permit to be operated a coin or token
         operated vending machine or similar device (including, without
         limitation, telephones, lockers, toilets, scales, amusement devices and
         machines for sale of beverages, foods, candy, cigarettes and other
         goods), except for machines for the exclusive use of Tenant's
         employees.

16.      Bicycles and other vehicles are not permitted inside the Buildings or
         on the walkways outside the Buildings, except in areas designated by
         Landlord. Bicycles may be parked on the first level of the parking
         garage.

17.      Landlord may from time to time adopt systems and procedures for the
         security and safety of the Buildings, its occupants, entry, use and
         contents. Tenant, its agents, employees, contractors, guests and
         invitees shall comply with Landlord's systems and procedures of which
         Landlord has given Tenant reasonable prior written notice, provided
         that such systems and procedures do not materially adversely affect
         Tenant's use of the Premises for the Permitted Use.

18.      Landlord shall have the right to prohibit the use of the name of the
         Buildings or any image thereof and the name of the Landlord by Tenant
         if in Landlord's sole opinion such use may impair the reputation of the
         Buildings or their desirability. Upon written notice from Landlord,
         Tenant shall refrain from and discontinue such publicity immediately.
         Notwithstanding the foregoing, Tenant's mere use of the address of the
         Premises in its advertising shall not violate this provision.

19.      Tenant shall not canvass, solicit or peddle in or about the Buildings
         or the Property.

20.      Neither Tenant nor its agents, employees, contractors, guests or
         invitees shall smoke or permit smoking in the Common Areas, unless the
         Common Areas have been declared a designated smoking area by Landlord,
         nor shall the above parties allow smoke from the Premises to emanate
         into the Common Areas or any other part of the Buildings. Landlord
         shall have the right to designate the Buildings (including the
         Premises) as a non-smoking building.

21.      Landlord shall have the right to designate and approve standard window
         coverings for the Premises and to establish rules to assure that the
         Buildings present a uniform exterior appearance. Tenant shall ensure,
         to the extent reasonably practicable, that window coverings are closed
         on windows in the Premises while they are exposed to the direct rays of
         the sun.

22.      Deliveries to and from the Premises shall be made only at the times, in
         the areas and through the entrances and exits designated by Landlord.
         Tenant shall not make deliveries to or from the Premises in a manner
         that might interfere with the use by any other tenant of its premises
         or of the Common Areas, any pedestrian use, or any use which is
         inconsistent with good business practice.

23.      The work of cleaning personnel in the Office Space shall not be
         hindered by Tenant after 5:30 P.M., and cleaning work may be done at
         any time when the Office Space is

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         vacant. Exterior windows may be cleaned at any time. Tenant shall
         provide adequate waste and rubbish receptacles to prevent unreasonable
         hardship to the cleaning service in the Office Space. (Tenant is
         responsible for the cleaning of the Lab Space.)

24.      Tenant shall comply with Landlord's rules and regulations with regard
         to the use of the loading dock and access areas of the Property for the
         proper management of the transportation and delivery of hazardous,
         medical, animal and other regulated materials, to assure compliance
         with the requirements of law and the proper operation of a
         multi-tenant, mixed use science and office complex.

25.      Fitness Center Rules. Tenant shall cause its employees (whether members
         or prospective members of the Fitness Center) to comply with the
         following Fitness Center rules and regulations (subject to change from
         time to time as Landlord may solely determine):

         a.       No guests will be permitted to use the Fitness Center without
                  the prior written consent of Landlord or Landlord's
                  representative.

         b.       The Fitness Center shall be open during the hours of _____
                  A.M. to _____ P.M. Monday through Friday and from _____ A.M.
                  to _____ P.M. on Saturday. The Fitness Center shall be closed
                  on Sunday and on Holidays. Fitness Center Users are not
                  allowed to be in the Fitness Center other than the hours set
                  forth herein.

         c.       All Fitness Center Users must execute Landlord's Waiver of
                  Liability prior to use of the Fitness Center and agree to all
                  terms and conditions outlined therein.

         d.       All Fitness Center Users shall use the Fitness Center and
                  exercise at their own risk.

         e.       Those Fitness Center Users with medical conditions such as
                  high blood pressure, heart disease, respiratory problems or
                  any other conditions or situations which may make any form of
                  exercise dangerous to one's health, such as pregnancy or
                  medication(s), must consult with and receive consent from
                  their physician prior to joining the Fitness Center and/or
                  prior to using the Fitness Center.

         f.       If any Fitness Center User feels faint, dizzy, sick,
                  experiences pain and/or has difficulty breathing while using
                  the Fitness Center, such Fitness Center User shall immediately
                  stop what he/she is doing and cool down. If such Fitness
                  Center User does not feel better, he/she shall contact the
                  security office at the Building or call 911 for assistance.

         g.       If a Fitness Center User notices any faulty or malfunctioning
                  equipment, hazardous conditions, situations, safety concerns,
                  or feels uncomfortable while using the Fitness Center for any
                  reason, such Fitness Center User shall report the situation to
                  Landlord's property manager or building staff personnel
                  immediately.

         h.       Individual membership and guest keycards to the Fitness Center
                  shall not be

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                  shared and shall only be used by the individual such keycard
                  was issued to by Landlord. Failure to abide by this rule shall
                  result in immediate termination of such Fitness Center User's
                  right to use the Fitness Center.

         i.       All Fitness Center Users and guests (if any) must have a
                  pre-authorized keycard to enter the Fitness Center.

         j.       Fitness Center Users agree to keep the Fitness Center in a
                  neat and orderly fashion, including, but not limited to,
                  wiping off all equipment after having completed use.

         k.       Fitness Center Users shall not store anything in the Fitness
                  Center, except to the extent temporarily stored in the locker
                  rooms during the use of the Fitness Center by such Fitness
                  Center Users.

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                                    EXHIBIT C

                            FORM OF LETTER OF CREDIT

Tenant may provide the Letter of Credit in the form set forth in this EXHIBIT C
or in the form attached hereto as EXHIBIT C-1.

Filling Out the Letter of Credit Form. Letter of Credit Form below should be
completed as follows:

         (a) The addressee (Beneficiary) is the Landlord.

         (b) The address for Landlord (Beneficiary) should be the property
management office for the building in question.

         (c) Applicant (upper right hand corner) is the Tenant.

         (d) The bank fills in the remaining information required in the upper
right hand corner and the address information required at the end of the Letter
of Credit.

         (e) The required Letter of Credit amount should be completed in the
first paragraph.

         (f) The Landlord name and Tenant name should be completed in the last 2
lines of paragraph #2.

         (g) No amount should be filled in at paragraph #2. The amount required
in this section would not be known until the actual draw is made by Landlord
upon the Letter of Credit.

                        LETTER OF CREDIT FORM

                      [Name of Financial Institution]

                                Irrevocable Standby
                                Letter of Credit
                                No. ______________________
                                Issuance Date:____________
                                Expiration Date:__________
                                Applicant:________________

Beneficiary

[Insert Name of Landlord]
[Insert Building management office address]
________________________________
________________________________
________________________________

Ladies/Gentlemen:

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         We hereby establish our Irrevocable Standby Letter of Credit in your
favor for the account of the above referenced Applicant in the amount of
____________________ U.S. Dollars ($____________________) available for payment
at sight by your draft drawn on us when accompanied by the following documents:

1. An original copy of this Irrevocable Standby Letter of Credit.

2. Beneficiary's dated statement purportedly signed by an authorized signatory
or agent reading: "This draw in the amount of ______________________ U.S.
Dollars ($____________) under your Irrevocable Standby Letter of Credit No.
____________________ represents funds due and owing to us pursuant to the terms
of that certain lease by and between ______________________, as landlord, and
_____________, as tenant, and/or any amendment to the lease or any other
agreement between such parties related to the lease."

         It is a condition of this Irrevocable Standby Letter of Credit that it
will be considered automatically renewed for a one year period upon the
expiration date set forth above and upon each anniversary of such date, unless
at least 60 days prior to such expiration date or applicable anniversary
thereof, we notify you in writing, by certified mail return receipt requested or
by recognized overnight courier service, that we elect not to so renew this
Irrevocable Standby Letter of Credit. A copy of any such notice shall also be
sent, in the same manner, to: Equity Office Properties Trust, 2 North Riverside
Plaza, Chicago, Illinois 60606, Attention: Treasury Department. In addition to
the foregoing, we understand and agree that you shall be entitled to draw upon
this Irrevocable Standby Letter of Credit in accordance with 1 and 2 above in
the event that we elect not to renew this Irrevocable Standby Letter of Credit
and, in addition, you provide us with a dated statement purportedly signed by an
authorized signatory or agent of Beneficiary stating that the Applicant has
failed to provide you with an acceptable substitute irrevocable standby letter
of credit in accordance with the terms of the above referenced lease. We further
acknowledge and agree that: (a) upon receipt of the documentation required
herein, we will honor your draws against this Irrevocable Standby Letter of
Credit without inquiry into the accuracy of Beneficiary's signed statement and
regardless of whether Applicant disputes the content of such statement; (b) this
Irrevocable Standby Letter of Credit shall permit partial draws and, in the
event you elect to draw upon less than the full stated amount hereof, the stated
amount of this Irrevocable Standby Letter of Credit shall be automatically
reduced by the amount of such partial draw; and (c) you shall be entitled to
transfer your interest in this Irrevocable Standby Letter of Credit from time to
time and more than one time without our approval and without charge. In the
event of a transfer, we reserve the right to require reasonable evidence of such
transfer as a condition to any draw hereunder.

         This Irrevocable Standby Letter of Credit is subject to the Uniform
Customs and Practice for Documentary Credits (1993 revision) ICC Publication No.
500.

         We hereby engage with you to honor drafts and documents drawn under and
in compliance with the terms of this Irrevocable Standby Letter of Credit.

         All communications to us with respect to this Irrevocable Standby
Letter of Credit must be addressed to our office located at______________ to the
attention of______.

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                                                     Very truly yours,

                                                     __________________

                                                          [name]

                                                          [title]

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                                   EXHIBIT C-1

                      ALTERNATIVE FORM OF LETTER OF CREDIT

IRREVOCABLE STANDBY LETTER OF CREDIT NO. SVBSF____

DATE: ______________, 2003

BENEFICIARY:
EOP-___________________
C/O ___________________
_______________________
_______________________
ATTN: _________________

APPLICANT:

_______________________
_______________________
_______________________

AMOUNT: US$__________ (_______________________________________ AND 00/100 U.S.
DOLLARS)

EXPIRATION DATE: _________________

LOCATION: AT OUR COUNTERS IN SANTA CLARA, CALIFORNIA

GENTLEMEN:

WE HEREBY ESTABLISH OUR IRREVOCABLE STANDBY LETTER OF CREDIT NO. SVBSF____ IN
YOUR FAVOR AVAILABLE BY YOUR DRAFTS DRAWN ON US AT SIGHT AND ACCOMPANIED BY THE
FOLLOWING DOCUMENTS:

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

2.   BENEFICIARY'S DATED STATEMENT SIGNED BY ONE OF ITS AUTHORIZED OFFICERS
     FOLLOWED BY THEIR DESIGNATED TITLE CERTIFYING THE FOLLOWING:

"THIS DRAW IN THE AMOUNT OF US$______________(SPECIFY AMOUNT) _____________ U.S.
DOLLARS UNDER YOUR IRREVOCABLE LETTER OF CREDIT NO. SVBSF____ REPRESENTS FUNDS
DUE AND OWING TO US PURSUANT TO THE TERMS OF THAT CERTAIN LEASE BY AND BETWEEN
EOP-_________________________ AS LANDLORD, AND
_________________________________, AS TENANT, AND/OR ANY AMENDMENT TO THE LEASE
OR ANY OTHER AGREEMENT BETWEEN SUCH PARTIES RELATED TO THE LEASE."

PARTIAL DRAWS ARE ALLOWED. THIS LETTER OF CREDIT MUST ACCOMPANY ANY DRAWINGS
HEREUNDER FOR ENDORSEMENT OF THE DRAWING AMOUNT AND WILL

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BE RETURNED TO THE BENEFICIARY UNLESS IT IS FULLY UTILIZED.

THIS LETTER OF CREDIT SHALL BE AUTOMATICALLY EXTENDED FOR AN ADDITIONAL PERIOD
OF ONE YEAR, WITHOUT AMENDMENT, FROM THE PRESENT OR EACH FUTURE EXPIRATION DATE;
PROVIDED, HOWEVER, THAT THE ISSUING BANK SHALL NOTIFY YOU BY REGISTERED
MAIL/OVERNIGHT COURIER SERVICE AT THE ABOVE ADDRESS WITH A COPY OF SUCH NOTICE
TO: EQUITY OFFICE PROPERTIES TRUST, 2 NORTH RIVERSIDE PLAZA, CHICAGO, IL 60606,
ATTENTION: TREASURY DEPARTMENT, AT LEAST 60 DAYS PRIOR TO SUCH EXPIRATION DATE,
THAT THIS LETTER OF CREDIT SHALL EXPIRE ON SUCH DATE. IN NO EVENT SHALL THIS
LETTER OF CREDIT

                                   PAGE 1 OF 2

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IRREVOCABLE STANDBY LETTER OF CREDIT NO. SVBSF____
DATED _______________, 2003

BE AUTOMATICALLY EXTENDED BEYOND _____________________. UPON RECEIPT OF SUCH
NOTICE OF EXPIRATION OR NON-RENEWAL YOU MAY DRAW YOUR SIGHT DRAFT DRAWN ON US
FOR THE AVAILABLE AMOUNT UNDER THIS STANDBY LETTER OF CREDIT ACCOMPANIED BY YOUR
DATED STATEMENT SIGNED BY ONE OF YOUR AUTHORIZED OFFICERS, FOLLOWED BY THEIR
DESIGNATED TITLE, CERTIFYING THE FOLLOWING: "WE ARE IN RECEIPT OF YOUR NOTICE
THAT YOU HAVE ELECTED NOT TO RENEW (OR NOT TO EXTEND THE EXPIRATION DATE OF)
YOUR IRREVOCABLE STANDBY LETTER OF CREDIT NO. SVBSF____ AND APPLICANT HAS FAILED
TO PROVIDE US WITH AN ACCEPTABLE SUBSTITUTE IRREVOCABLE STANDBY LETTER OF CREDIT
IN ACCORDANCE WITH THE TERMS OF THE ABOVE REFERENCED LEASE."

THIS LETTER OF CREDIT MAY ONLY BE TRANSFERRED IN ITS ENTIRETY BY THE ISSUING
BANK UPON OUR RECEIPT OF THE ATTACHED "EXHIBIT A" DULY COMPLETED AND EXECUTED BY
THE BENEFICIARY AND ACCOMPANIED BY THE ORIGINAL LETTER OF CREDIT AND ALL
AMENDMENT(S), IF ANY. OUR TRANSFER FEE 1/4 OF 1% (MIN. $250.00) WILL BE PAID BY
THE APPLICANT.

DRAFT(S) AND DOCUMENTS MUST INDICATE THE NUMBER AND DATE OF THIS LETTER OF
CREDIT.

DOCUMENTS MUST BE FORWARDED TO US BY OVERNIGHT DELIVERY SERVICE OR HAND
DELIVERED TO: SILICON VALLEY BANK. 3003 TASMAN DRIVE, SANTA CLARA, CA 95054,
ATTN: INTERNATIONAL DIVISION.

WE HEREBY AGREE WITH THE DRAWERS, ENDORSERS AND BONAFIDE HOLDERS THAT THE DRAFTS
DRAWN UNDER AND IN ACCORDANCE WITH THE TERMS AND CONDITIONS OF THIS CREDIT SHALL
BE DULY HONORED UPON PRESENTATION TO THE DRAWEE, IF NEGOTIATED ON OR BEFORE THE
EXPIRATION DATE OF THIS CREDIT. WE FURTHER ACKNOWLEDGE AND AGREE THAT UPON
RECEIPT OF THE DOCUMENTATION REQUIRED HEREIN, WE WILL HONOR YOUR DRAWS AGAINST
THIS IRREVOCABLE STANDBY LETTER OF CREDIT WITHOUT INQUIRY INTO THE ACCURACY OF
BENEFICIARY'S SIGNED STATEMENT AND REGARDLESS OF WHETHER APPLICANT DISPUTES THE
CONTENT OF SUCH STATEMENT.

THIS CREDIT IS SUBJECT TO THE UNIFORM CUSTOMS AND PRACTICE FOR DOCUMENTARY
CREDITS (1993 REVISION), INTERNATIONAL CHAMBER OF COMMERCE, PUBLICATION NO. 500.

___________________________                          ___________________________
  AUTHORIZED SIGNATURE                               AUTHORIZED SIGNATURE

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                                   EXHIBIT "A"

DATE:

TO: SILICON VALLEY BANK
    3003 TASMAN DRIVE                       RE: STANDBY LETTER OF CREDIT
    SANTA CLARA, CA 95054                   NO. ISSUED BY
    ATTN:INTERNATIONAL DIVISION.                SILICON VALLEY BANK, SANTA CLARA
         STANDBY LETTERS OF CREDIT               L/C AMOUNT: US$

GENTLEMEN:

FOR VALUE RECEIVED, THE UNDERSIGNED BENEFICIARY HEREBY IRREVOCABLY TRANSFERS TO:

(NAME OF TRANSFEREE)
(ADDRESS)

ALL RIGHTS OF THE UNDERSIGNED BENEFICIARY TO DRAW UNDER THE ABOVE LETTER OF
CREDIT UP TO ITS AVAILABLE AMOUNT AS SHOWN ABOVE AS OF THE DATE OF THIS
TRANSFER.

BY THIS TRANSFER, ALL RIGHTS OF THE UNDERSIGNED BENEFICIARY IN SUCH LETTER OF
CREDIT ARE TRANSFERRED TO THE TRANSFEREE. TRANSFEREE SHALL HAVE THE SOLE RIGHTS
AS BENEFICIARY THEREOF, INCLUDING SOLE RIGHTS RELATING TO ANY AMENDMENTS,
WHETHER INCREASES OR EXTENSIONS OR OTHER AMENDMENTS, AND WHETHER NOW EXISTING OR
HEREAFTER MADE. ALL AMENDMENTS ARE TO BE ADVISED DIRECT TO THE TRANSFEREE
WITHOUT NECESSITY OF ANY CONSENT OF OR NOTICE TO THE UNDERSIGNED BENEFICIARY.

THE ORIGINAL OF SUCH LETTER OF CREDIT IS RETURNED HEREWITH, AND WE ASK YOU TO
ENDORSE THE TRANSFER ON THE REVERSE THEREOF, AND FORWARD IT DIRECTLY TO THE
TRANSFEREE WITH YOUR CUSTOMARY NOTICE OF TRANSFER.

SINCERELY,

______________________________
     (BENEFICIARY'S NAME)

______________________________
   SIGNATURE OF BENEFICIARY

SIGNATURE AUTHENTICATED

______________________________
        (NAME OF BANK)

______________________________
     AUTHORIZED SIGNATURE

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                                    EXHIBIT D

                                   WORK LETTER

         This Exhibit is attached to and made a part of the Office and
Laboratory Lease Agreement dated as of December ___, 2003, by and between
MA-Riverview/245 First Street, L.L.C., a Delaware limited liability company
("Landlord") and Viacell, Inc., a Delaware corporation ("Tenant") for space in
the Building located at 245 First Street, Cambridge, Massachusetts.

A. WORK LETTER RELATING TO THE OFFICE SPACE. As used in this Section A of the
Work Letter, the "Office Space" shall be deemed to mean the Office Space, as
initially defined in the attached Lease.

I.       ALTERATIONS AND ALLOWANCE.

         A.       Tenant, following the delivery of the Office Space by Landlord
                  and the full and final execution and delivery of the Lease to
                  which this Exhibit is attached and all prepaid rental and
                  security deposits required under such agreement, shall have
                  the right to perform alterations and improvements in the
                  Office Space (the "Initial Office Alterations").
                  Notwithstanding the foregoing, Tenant and its contractors
                  shall not have the right to perform Initial Office Alterations
                  in the Office Space unless and until Tenant has complied with
                  all of the terms and conditions of Article IX of the Lease,
                  including, without limitation, approval by Landlord of the
                  final plans for the Initial Office Alterations and the
                  contractors to be retained by Tenant to perform such Initial
                  Office Alterations. Tenant shall be responsible for all
                  elements of the design of Tenant's plans (including, without
                  limitation, compliance with law, functionality of design, the
                  structural integrity of the design, the configuration of the
                  premises and the placement of Tenant's furniture, appliances
                  and equipment), and Landlord's approval of Tenant's plans
                  shall in no event relieve Tenant of the responsibility for
                  such design. Landlord's approval of the contractors to perform
                  the Initial Office Alterations shall not be unreasonably
                  withheld. The parties agree that Landlord's approval of the
                  general contractor to perform the Initial Office Alterations
                  shall not be considered to be unreasonably withheld if any
                  such general contractor (i) does not have trade references
                  reasonably acceptable to Landlord, (ii) does not maintain
                  insurance as required pursuant to the terms of this Lease,
                  (iii) does not have the ability to be bonded for the work in
                  an amount of the total estimated cost of the Initial Office
                  Alterations, (iv) does not provide current financial
                  statements reasonably acceptable to Landlord, (v) is not
                  licensed as a contractor in the state/municipality in which
                  the Premises is located, and (vi) will work without
                  interference and in harmony with other labor on the Property.
                  Tenant acknowledges the foregoing is not intended to be an
                  exclusive list of the reasons why Landlord may reasonably
                  withhold its consent to a general contractor.

                  Landlord hereby approves The Richmond Group to serve as
                  Tenant's general contractor for the Initial Office
                  Alterations, provided that (a) Tenant and the Richmond Group
                  (or any successor general contractor which may be approved by
                  Landlord in accordance with this Lease) shall use union
                  carpenters for Initial

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                  Office Alterations, and (b) Tenant shall cause all labor
                  performing the Initial Office Alterations to work without
                  interference and in harmony with other labor working on the
                  Property.

         B.       Landlord agrees to contribute the sum of $901,750.00 (the
                  "Office Allowance") toward the cost of performing the Initial
                  Office Alterations in preparation of Tenant's occupancy of the
                  Office Space.

                  The Office Allowance may only be used for (i) the cost of
                  preparing design and construction documents and mechanical and
                  electrical plans for the Initial Office Alterations, (ii)
                  telecommunications and computer wiring and cabling in
                  connection with the Initial Office Alterations, (iii) hard
                  costs in connection with the Initial Office Alterations, (iv)
                  furniture for the Office Space, (iv) Tenant's actual moving
                  expenses in connection with moving to the Office Space, and
                  (v) management of the construction of the improvements to the
                  Office Space. The Office Allowance, less a 10% retainage
                  (which retainage may be reduced to 5% retainage when any
                  particular subcontractor's component of the job has reached
                  50% completion and may be released to a subcontractor who has
                  completed his or her work), shall be paid to Tenant or, at
                  Landlord's option, to the order of the general contractor that
                  performs the Initial Office Alterations, in periodic
                  disbursements within 25 days after receipt of the following
                  documentation: (i) an application for payment and sworn
                  statement of contractor substantially in the form of AIA
                  Document G-702 covering all work for which disbursement is to
                  be made to a date specified therein; (ii) a certification from
                  an architect registered in Massachusetts substantially in the
                  form of the Architect's Certificate for Payment which is
                  located on AIA Document G702, Application and Certificate of
                  Payment; (iii) Contractor's, subcontractor's and material
                  supplier's waivers of liens which shall cover all Initial
                  Office Alterations for which disbursement is being requested
                  and all other statements and forms required for compliance
                  with the mechanics' lien laws of the state in which the
                  Premises is located, together with all such invoices,
                  contracts, or other supporting data as Landlord or Landlord's
                  Mortgagee may reasonably require; (iv) a cost breakdown for
                  each trade or subcontractor performing the Initial Office
                  Alterations; (v) plans and specifications for the Initial
                  Office Alterations, together with a certificate from an
                  architect registered in Massachusetts that such plans and
                  specifications comply in all material respects with all Laws
                  affecting the Building, Property and Premises; (vi) copies of
                  all construction contracts for the Initial Office Alterations,
                  together with copies of all change orders, if any; (vii) a
                  request to disburse from Tenant containing an approval by
                  Tenant of the work done and a good faith estimate of the cost
                  to complete the Initial Office Alterations; and (viii) written
                  evidence of paid bills for which Tenant is seeking
                  reimbursement. Upon completion of the Initial Office
                  Alterations, and prior to final disbursement of the Office
                  Allowance, Tenant shall furnish Landlord with: (1) general
                  contractor and architect's completion affidavits, (2) full and
                  final waivers of lien, (3) receipted bills covering all labor
                  and materials expended and used, (4) as-built plans of the
                  Initial Office Alterations in print and electronic CAD format,
                  and (5) the certification of Tenant's architect that the
                  Initial Office Alterations have been installed in accordance
                  with the approved plans, and in accordance with applicable
                  Laws, codes and ordinances. In no event shall Landlord be
                  required to disburse the Office Allowance more than one time
                  per month. If the cost of the Initial Office Alterations
                  exceeds the Office Allowance, Tenant shall be entitled to the
                  Office

                                        2

<PAGE>

                  Allowance in accordance with the terms hereof, but each
                  individual disbursement of the Office Allowance shall be
                  disbursed in the proportion that the Office Allowance bears to
                  the total cost for the Initial Office Alterations, subject to
                  the retainage provision referenced above. Notwithstanding
                  anything herein to the contrary, Landlord shall not be
                  obligated to disburse any portion of the Office Allowance
                  during the continuance of an uncured Event of Default under
                  the Lease, and Landlord's obligation to disburse shall only
                  resume when and if such Event of Default is cured.

         C.       If Tenant does not submit a request for payment of the entire
                  Office Allowance to Landlord in accordance with the provisions
                  contained in this Exhibit by June 30, 2005, any unused amount
                  shall accrue to the sole benefit of Landlord, it being
                  understood that Tenant shall not be entitled to any credit,
                  abatement or other concession in connection therewith. Tenant
                  shall be responsible for all applicable state sales or use
                  taxes, if any, payable in connection with the Initial Office
                  Alterations and/or Office Allowance.

         D.       Tenant agrees to accept the Office Space in its "as-is"
                  condition and configuration, it being agreed that Landlord
                  shall not be required to perform any work or, except as
                  provided above with respect to the Office Allowance, incur any
                  costs in connection with the construction or demolition of any
                  improvements in the Office Space

         E.       This Exhibit shall not be deemed applicable to any additional
                  space added to the Office Space at any time or from time to
                  time, whether by any options under the Lease or otherwise, or
                  to any portion of the original Office Space or any additions
                  to the Office Space in the event of a renewal or extension of
                  the original Term of the Lease, whether by any options under
                  the Lease or otherwise, unless expressly so provided in the
                  Lease or any amendment or supplement to the Lease.

B. WORK LETTER RELATING TO LAB SPACE. As used in this Section B of the Work
Letter, the "Lab Space" shall be deemed to mean the Lab Space, as initially
defined in the attached Lease. Landlord and Tenant have agreed that the work to
be performed by the respective parties shall be in accordance with the matrix
attached hereto as SCHEDULE D-1. This Work Letter shall set forth the
obligations of Landlord and Tenant with respect to the improvements to be
performed in the Lab Space for Tenant's use.

I.       Landlord's Work

A.       All improvements described in this Work Letter to be constructed in and
         upon the Lab Space by Landlord are described in SCHEDULE D-2 and are
         hereinafter referred to as the "Landlord Work." It is agreed that
         construction of the Landlord Work will be completed at Landlord's sole
         cost and expense in a good and workmanlike manner with due diligence.
         Landlord shall enter into a direct contract for the Landlord Work with
         a general contractor selected by Landlord. In addition, Landlord shall
         have the right to select and/or approve of any subcontractors used in
         connection with the Landlord Work.

B.       Landlord shall construct the Landlord Work described on SCHEDULE D-2
         attached hereto at Landlord's expense. Until Substantial Completion of
         Landlord's Work, Landlord shall have exclusive occupancy of the Lab
         Space. Landlord shall use diligent efforts to

                                        3

<PAGE>

         achieve Substantial Completion of Landlord's Work by June 1, 2004,
         subject to any Tenant Delay. Landlord shall provide Tenant with 10
         days' prior written notice of the date upon which Landlord anticipates
         that Substantial Completion of Landlord's Work shall occur. Landlord
         shall complete any punchlist items promptly after Substantial
         Completion, and Tenant shall provide access to Landlord's contractors
         to permit the same.

C.       Except as set forth in Section I.G of this Lease, notwithstanding
         anything herein to the contrary, any delay in the completion of the
         Landlord Work or inconvenience suffered by Tenant during the
         performance of Landlord's Work shall not subject Landlord to any
         liability for any loss or damage resulting therefrom or entitle Tenant
         to any credit, abatement or adjustment of Rent or other sums payable
         under the Lease.

D.       This Exhibit shall not be deemed applicable to any additional space
         added to the Lab Space at any time or from time to time, whether by any
         options under the Lease or otherwise, or to any portion of the original
         Lab Space or any additions to the Lab Space in the event of a renewal
         or extension of the original Term of the Lease, whether by any options
         under the Lease or otherwise, unless expressly so provided in the Lease
         or any amendment or supplement to the Lease.

II.      Tenant's Work

         A.       When Substantial Completion of Landlord's Work has occurred,
                  and the full and final execution and delivery of the Lease to
                  which this Exhibit is attached and all prepaid rental and
                  security deposits required under such agreement, Tenant shall
                  have the right to perform alterations and improvements in the
                  Premises (the "Initial Lab Alterations") (the Initial Office
                  Alterations and the Initial Lab Alterations being referred to
                  herein, collectively, as the "Initial Alterations"), which
                  Initial Lab Alterations shall include the work described as
                  Tenant's responsibility on EXHIBIT D-1. Notwithstanding the
                  foregoing, Tenant and its contractors shall not have the right
                  to perform Initial Lab Alterations in the Lab Space unless and
                  until Tenant has complied with all of the terms and conditions
                  of Article IX of the Lease, including, without limitation,
                  approval by Landlord of the final plans for the Initial Lab
                  Alterations and the contractors to be retained by Tenant to
                  perform such Initial Lab Alterations. Landlord acknowledges
                  that Tenant's plans will include the running of conduits for
                  power from the rooftop generator and for telephone/data
                  through the Buildings to the Premises, and agrees not to
                  unreasonably withhold its consent to the same, subject to the
                  compliance by Tenant with the requirements of this Lease.
                  Tenant shall submit for Landlord's approval, such approval not
                  to be unreasonably withheld or delayed, the plans and
                  specifications prepared by Olson, Lewis & Dioli Architects,
                  Tenant's Architect, for the Initial Lab Alterations. Tenant
                  shall use the mechanical, electrical and plumbing engineer
                  approved by Landlord for the design and installation of the
                  Initial Lab Alterations. The plans and specifications shall be
                  submitted to Landlord for its review and approval at the space
                  plan phase, the permitting phase, and the construction
                  documents phase. Landlord shall review and respond with its
                  approval or detailed comments to each phase of such plans and
                  specifications for the Lab Space within 10 business days of
                  receiving the initial draft thereof, and any failure to
                  respond shall constitute the basis for a claim of Landlord
                  Delay. In the event that Landlord requires changes to the

                                        4

<PAGE>

                  proposed plans, Landlord shall review and respond with its
                  approval or detailed comments to Tenant's submission of
                  revised plans within 10 business days for work which
                  materially affects structure or mechanical, plumbing or
                  electrical systems, and for all other work within 5 business
                  days. Tenant shall be responsible for all elements of the
                  design of Tenant's plans (including, without limitation,
                  compliance with law, functionality of design, the structural
                  integrity of the design, the configuration of the Initial Lab
                  Alterations and the placement of Tenant's furniture,
                  appliances and equipment), and Landlord's approval of Tenant's
                  plans shall in no event relieve Tenant of the responsibility
                  for such design. Landlord's approval of the contractors to
                  perform the Initial Lab Alterations shall not be unreasonably
                  withheld. The parties agree that Landlord's approval of the
                  general contractor to perform the Initial Lab Alterations
                  shall not be considered to be unreasonably withheld if any
                  such general contractor (i) does not have trade references
                  reasonably acceptable to Landlord, (ii) does not maintain
                  insurance as required pursuant to the terms of this Lease,
                  (iii) does not have the ability to be bonded for the work in
                  an amount of the total estimated cost of the Initial Lab
                  Alterations, (iv) does not provide current financial
                  statements reasonably acceptable to Landlord, (v) is not
                  licensed as a contractor in the state/municipality in which
                  the Premises is located, and (vi) will work without
                  interference and in harmony with other labor on the Property.
                  Tenant acknowledges the foregoing is not intended to be an
                  exclusive list of the reasons why Landlord may reasonably
                  withhold its consent to a general contractor.

                  Landlord hereby approves the Richmond Group to serve as
                  Tenant's general contractor for the Initial Lab Alterations,
                  provided that (a) Tenant and the Richmond Group (or any
                  successor general contractor which may be approved by Landlord
                  in accordance with this Lease) shall use union carpenters for
                  Initial Lab Alterations, and (b) Tenant shall cause all labor
                  performing the Initial Lab Alterations to work without
                  interference and in harmony with other labor working on the
                  Property.

         B.       Landlord agrees to contribute the sum of $2,490,900.00 (the
                  "Lab Allowance") toward the cost of performing the Initial Lab
                  Alterations in preparation of Tenant's occupancy of the Lab
                  Space. The Lab Allowance may only be used for (i) the cost of
                  preparing design and construction documents and mechanical and
                  electrical plans for the Initial Lab Alterations for the Lab
                  Space, (ii) telecommunications and computer wiring and cabling
                  in connection with the Initial Lab Alterations for the Lab
                  Space, (iii) hard costs in connection with the Initial Lab
                  Alterations for the Lab Space, (iv) furniture for the Lab
                  Space, (iv) Tenant's actual moving expenses in connection with
                  moving to the Lab Space, and (v) management of the
                  construction of the improvements to the Lab Space. The Lab
                  Allowance, less the retainage (which retainage shall be
                  governed by the same provisions as apply to the Office
                  Allowance), shall be paid to Tenant or, at Landlord's option,
                  to the order of the general contractor that performed the
                  Initial Lab Alterations, in periodic disbursements within 25
                  days after receipt of the following documentation: (i) an
                  application for payment and sworn statement of contractor
                  substantially in the form of AIA Document G-702 covering all
                  work for which disbursement is to be made to a date specified
                  therein; (ii) a certification from an architect registered in
                  Massachusetts substantially in the form of the Architect's
                  Certificate for Payment which is located on AIA Document G702,
                  Application and Certificate of Payment;

                                        5

<PAGE>

                  (iii) Contractor's, subcontractor's and material supplier's
                  waivers of liens which shall cover all Initial Lab Alterations
                  for which disbursement is being requested and all other
                  statements and forms required for compliance with the
                  mechanics' lien laws of the state in which the Premises is
                  located, together with all such invoices, contracts, or other
                  supporting data as Landlord or Landlord's Mortgagee may
                  reasonably require; (iv) a cost breakdown for each trade or
                  subcontractor performing the Initial Lab Alterations; (v)
                  plans and specifications for the Initial Lab Alterations,
                  together with a certificate from an architect registered in
                  Massachusetts that such plans and specifications comply in all
                  material respects with all Laws affecting the Building,
                  Property and Premises; (vi) copies of all construction
                  contracts for the Initial Lab Alterations, together with
                  copies of all change orders, if any; (vii) a request to
                  disburse from Tenant containing an approval by Tenant of the
                  work done and a good faith estimate of the cost to complete
                  the Initial Lab Alterations; and (viii) written evidence of
                  paid bills for which Tenant is seeking reimbursement. Upon
                  completion of the Initial Lab Alterations, and prior to final
                  disbursement of the Lab Allowance, Tenant shall furnish
                  Landlord with: (1) general contractor and architect's
                  completion affidavits, (2) full and final waivers of lien, (3)
                  receipted bills covering all labor and materials expended and
                  used, (4) as-built plans of the Initial Lab Alterations in
                  print and electronic CAD format, and (5) the certification of
                  Tenant's architect that the Initial Lab Alterations have been
                  installed in a good and workmanlike manner in accordance with
                  the approved plans, and in accordance with applicable Laws,
                  codes and ordinances. In no event shall Landlord be required
                  to disburse the Lab Allowance more than one time per month. If
                  the cost of the Initial Lab Alterations exceeds the Lab
                  Allowance, Tenant shall be entitled to the Lab Allowance in
                  accordance with the terms hereof, but each individual
                  disbursement of the Lab Allowance shall be disbursed in the
                  proportion that the Lab Allowance bears to the total cost for
                  the Initial Lab Alterations, subject to the retainage
                  provisions referenced above. Notwithstanding anything herein
                  to the contrary, Landlord shall not be obligated to disburse
                  any portion of the Lab Allowance during the continuance of an
                  uncured default under the Lease, and Landlord's obligation to
                  disburse shall only resume when and if such default is cured.

C.       In no event shall the Lab Allowance be used for the purchase of
         equipment, furniture or other items of personal property of Tenant,
         except as expressly set forth herein. If Tenant does not submit a
         request for payment of the entire Lab Allowance to Landlord in
         accordance with the provisions contained in this Exhibit by June 30,
         2005, any unused amount shall accrue to the sole benefit of Landlord,
         it being understood that Tenant shall not be entitled to any credit,
         abatement or other concession in connection therewith. Tenant shall be
         responsible for all applicable state sales or use taxes, if any,
         payable in connection with the Initial Lab Alterations and/or Lab
         Allowance.

D.       Except for Landlord's obligation to complete Landlord's Work as
         provided herein, Tenant agrees to accept the Lab Space in its "as-is"
         condition and configuration, it being agreed that, except as otherwise
         set forth in the Lease, Landlord shall not be required to perform any
         work or, except as provided above with respect to Landlord's Work and
         the Lab Allowance, incur any costs in connection with the construction
         or demolition of any improvements in the Lab Space.

E.       This Exhibit shall not be deemed applicable to any additional space
         added to the Lab

                                        6

<PAGE>

         Space at any time or from time to time, whether by any options under
         the Lease or otherwise, or to any portion of the original Lab Space or
         any additions to the Lab Space in the event of a renewal or extension
         of the original Term of the Lease, whether by any options under the
         Lease or otherwise, unless expressly so provided in the Lease or any
         amendment or supplement to the Lease.

C.       DRAWING ALLOWANCE AND ADDITIONAL ALLOWANCE. In addition to the
Allowance set forth in Sections A and B above, Landlord agrees to provide the
following additional allowance:

         1. Drawing Allowance. Provided Tenant is not in default after the
         expiration of applicable notice, grace and cure periods, Landlord
         agrees to contribute the sum of $128,832.00 ("Drawing Allowance")
         toward the cost of architectural and engineering drawings for Tenant's
         improvements to the Office Space and Lab Space. Within 5 business days
         after execution of this Lease, Landlord shall pay to Tenant that
         portion of the Drawing Allowance equal to $85,888.00. The remainder of
         the Drawing Allowance shall be paid by Landlord to Tenant within 30
         days after receipt by Landlord of receipted bills covering the cost of
         the architectural and engineering drawings. If Tenant does not submit a
         request for payment of the entire Drawing Allowance to Landlord in
         accordance with the provisions contained in this Exhibit by June 30,
         2005, any unused amount shall accrue to the sole benefit of Landlord,
         it being understood that Tenant shall not be entitled to any credit,
         abatement or other concession in connection therewith. Tenant shall be
         responsible for all applicable state sales or use taxes, if any,
         payable in connection with the Initial Alterations and/or Drawing
         Allowance.

         2. Additional Allowance. Provided Tenant is not in default after the
         expiration of applicable notice, grace and cure periods, Landlord
         agrees to contribute an additional sum of up to $750,000.00
         ("Additional Allowance") toward the cost of performing the Initial
         Alterations in preparation of Tenant's occupancy of the Office Space
         and the Lab Space; provided, Tenant shall pay to Landlord, as
         Additional Rent, commencing on the 49th month of the initial Term of
         the Lease, the amount of $22,121.38 per month (as adjusted if less than
         the maximum Additional Allowance is drawn, pursuant to the same
         calculation). The Additional Allowance shall be paid in accordance with
         Sections A.I.B. and B.II.B. above. If Tenant does not submit a request
         for payment of the entire Additional Allowance to Landlord in
         accordance with the provisions contained in this Exhibit by June 30,
         2005, any unused amount shall accrue to the sole benefit of Landlord,
         it being understood that Tenant shall not be entitled to any credit,
         abatement or other concession in connection therewith. Tenant shall be
         responsible for all applicable state sales or use taxes, if any,
         payable in connection with the Initial Alterations and/or Additional
         Allowance.

D.       CONFORMANCE WITH MEP STANDARDS; BALANCING OF SYSTEMS. Tenant shall
         assure that the plans for the Initial Improvements conform with the MEP
         standards for the Office Building and the Science Building prepared by
         AHA Consulting Engineers on behalf of Landlord. Tenant shall be
         responsible for the rebalancing of any base building systems in the
         Office Building and the Science Building required by the installation
         of the Initial Improvements.

                                        7

<PAGE>

         IN WITNESS WHEREOF, Landlord and Tenant have entered into this Exhibit
as of the date first written above.

WITNESS/ATTEST:                  LANDLORD:

                                 MA-RIVERVIEW/245 FIRST STREET, L.L.C., A
                                 DELAWARE LIMITED LIABILITY

                                 COMPANY

                                 By: By: Equity Office Management, L.L.C., a
                                         Delaware limited liability company, its
                                         non-member manager

                                         By: __________________________

___________________________              Name: ________________________

Name (print): _____________              Its: _________________________

Name (print): _____________

WITNESS/ATTEST:                  TENANT:

                                 VIACELL, INC., A DELAWARE CORPORATION

___________________________      By: _____________________________

Name (print): _____________      Name: ___________________________

___________________________      Title: __________________________

Name (print): ________________

                                        8

<PAGE>

                                  SCHEDULE D-1

CAMBRIDGE SCIENCE CENTER AT 245 FIRST STREET

UPDATED 5.20.03

Responsibilities Matrix

<TABLE>
<CAPTION>
                                    DESCRIPTION                                    SHELL/CORE     TENANT
--------------------------------------------------------------------------------   ----------     ------
<S>                                                                                <C>            <C>
SITEWORK AND         Perimeter sidewalks, street curbs, landscaping, and
UTILITIES            structured parking                                                X

                     Telephone service provided to main distribution feed
                     on first floor and distributed to the stacked tel/data
                     rooms on each floor.  High-speed fiber data service is
                     also provided                                                     X

                     Domestic sanitary sewer connection to street                      X

                     Lab waste sanitary sewer connection from tenant pH
                     room in first floor to street                                     X

                     Roof/storm drainage                                               X

                     Electric service                                                  X

                     Gas service                                                       X

                     Domestic and fire protection water service to building.           X

CODE COMPLIANCE      Building construction in accordance with
                     requirements of Massachusetts State Building Code, 6th
                     edition.                                                          X            X

STRUCTURE            Floor live load capacity of 150 psf at the first                  X
                     floor, 100 psf on floors 2-6

                     Live load increases for special tenant loads at floors                         X
                     and roof

                     Floor to floor heights vary from 11'-5" to 17'-10".
                     Floor to floor height of 8'-10" in Tenant Equipment               X
                     and Storage area on level 3A

                     Capacity in structure to accommodate tenant dunnage               X
                     and roof equipment

                     Dunnage at roof for tenant equipment                                           X

                     Framed openings for base building supply air and                  X
                     tenant exhaust shafts

                     Framed openings for additional tenant shafts and risers                        X
</TABLE>

                                        9

<PAGE>

<TABLE>
<S>                                                                                   <C>           <C>
                     Miscellaneous metal items such as brackets or supports
                     and concrete housekeeping pads required for tenant
                     supplied equipment                                                             X
</TABLE>

                                       10

<PAGE>

<TABLE>
<S>                  <C>                                                              <C>           <C>
EXTERIOR             Exterior wall consisting of concrete and glass                   X

                     Window system at punched openings consisting of
                     aluminum mullions with painted finish, insulating
                     glass units                                                      X

                     Entry canopy consisting of metal framing with skylight           X

                     Two bay loading dock with receiving area and access to           X
                     Tenant Equipment and Storage areas

                     Overhead coiling doors at loading area                           X

                     Acoustic roof screen to conceal tenant exhaust fans              X
                     and standby generators

                     Additional penthouse and/or screening for tenant
                     equipment, to be built in accordance with base                                 X
                     building design and city requirements

ROOFING              Roofing system consisting of single-ply EPDM with                X
                     rigid insulation

                     Roofing penetrations for tenant equipment or systems                           X

                     Walkway pads to base building mechanical equipment               X

                     Walkway pads to tenant equipment                                               X

COMMON AREAS         Finished first floor atrium, elevator lobbies and
                     egress corridors, including flooring, drywall and
                     lighting on multi-tenant floors                                  X

                     Finished toilet rooms with thin-set ceramic tile
                     floors and walls, drywall, acoustic ceilings, lavatory
                     counters                                                         X

                     Showers located in first floor bathroom to support               X
                     tenant fitness activities

                     Janitor, electrical and telephone closets                        X

                     Finished exit stairways with painted walls                       X

                     Finished loading area with 2 truck bays                          X

                     First floor main mechanical/electrical rooms for base            X
                     building equipment

                     Doors and frames at common areas: hollow metal frames;
                     hollow metal doors at service areas, solid core wood             X
                     doors at other areas, and lever hardware

                     Doors, frames, and hardware to tenant areas                                    X

ELEVATORS            Two traction passenger elevators with 3,000 pound                X
                     capacity and new quality cab finishes
</TABLE>

                                       11

<PAGE>

<TABLE>
<S>                  <C>                                                              <C>           <C>
                     A new hydraulic service elevator with 4,500 pound
                     capacity serving levels 1 - 5 and located with secure
                     access to the Loading area                                        X

WINDOW TREATMENT     Supply and installation of building standard blinds                            X
                     for all windows

TENANT AREAS         Partitions, ceilings, flooring, painting, finishes,
                     doors, millwork, equipment and all build-out within
                     tenant area                                                                    X

                     Finishes at multi-tenant corridors                               X

                     Shaft enclosures for base building supply and tenant             X
                     exhaust ductwork

HVAC                 A new 1200 ton central chilled water plant including
                     centrifugal chillers, cooling towers, and pumping
                     systems.  Condenser water valved and capped supply and
                     return lines are available at each floor for tenant
                     cooling. Chilled water plant capacity of approximately           X
                     100 square foot per ton

                     Additional 25% capacity at cooling tower for
                     supplemental tenant cooling needs.  Condenser water
                     valved and capped supply and return lines are
                     available at each floor for additional tenant cooling            X
                     needs

                     Outdoor custom air handling units (indoor unit serving
                     the Annex) providing a total of approximately 1.75 cfm
                     per square foot with 100% outside air.  Unit supply              X
                     fans will have VFD's

                     Gas modular boiler system, with constant speed
                     secondary pumps and distribution risers and hot water
                     supply and returns valved and capped at each level for           X
                     tenant area heating

                     Vertical supply ductwork sized based on a 60% lab, 40%
                     office fit-up, extending approximately 3' beyond
                     vertical shaft or base building core.  Lab areas sized           X
                     for approximately 2 cfm per sq ft and office areas
                     sized for approximately 1.4 cfm per sq ft

                     Occupant load for heating and cooling systems design
                     based on approximately 150 sf/person in office and lab           X
                     areas
</TABLE>

                                       12

<PAGE>

<TABLE>
<S>                  <C>                                                              <C>           <C>
                     Ductwork, VAV boxes, and controls for HVAC in lobby              X
                     spaces and core areas, including toilet exhaust system

                     Equipment, controls and equipment rooms for 24 hour
                     cooling systems for tenant areas.  Chilled water plant
                     available 24/7 for tenant space cooling needs.                   X
                     Cooling tower condenser water plant available 24/7 for
                     special tenant cooling needs

                     All medium and low pressure ductwork within tenant                             X
                     space

                     Variable volume and/or constant volume terminal boxes
                     with hot water reheat and/or radiation (perimeter) and                         X
                     VAV boxes (interior) within tenant space

                     Diffusers within tenant space                                                  X

                     Central computerized energy DDC management system with           X
                     front-end computer and expandability for tenant use

                     DDC temperature controls systems for base building               X
                     equipment

                     DDC temperature controls for all tenant equipment.
                     Wire interlocking and programming to base building                             X
                     system by tenant

                     Pre-coordinated exhaust shaft, exhaust fan and                   X
                     horizontal duct layout locations

                     All components of tenant exhaust systems, including
                     fume hoods, ductwork, exhaust fans, controls and sound                         X
                     attenuation

                     Steam generators and distribution                                              X

                     Lightning protection system                                                    X

                     Steam and humidified air systems                                               X

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

                     Air flow sensors and HW BTU meters                                             X

GAS                  Gas service to building and base building equipment              X

                     Tenant metering and service, as required                                       X

PLUMBING             Domestic water service, with back-flow prevention and
                     booster pump to provide minimum of 40 psi at all floors          X

                     Core restroom plumbing fixtures to meet code                     X
                     requirements
</TABLE>

                                       13

<PAGE>

<TABLE>
<S>                  <C>                                                              <C>           <C>
                     Tenant metering and sub metering, at laboratory                                 X
                     connections

                     Distribution of domestic cold water from base building                         X
                     risers

                     Production and distribution of hot water for tenant use                        X

                     Production and distribution of hot water in building             X
                     restrooms

                     Kitchen, cafeteria and specialized tenant plumbing                             X

                     Pits for lab waste treatment equipment/sampling and
                     under-slab waste lines at first floor tenant areas               X
                     (excluding Annex)

                     Reserved space for tenant laboratory acid waste
                     neutralization systems on first floor with sanitary              X
                     connection to street

                     Extension of sanitary waste, lab waste & venting                               X
                     system into tenant areas

                     Industrial waste discharge permits and approvals                               X

                     Manifolds, piping, and other requirements for
                     non-potable water, laboratory gases, compressed air,                           X
                     vacuum systems, pH system and laboratory pure water

                     Vent risers and roof penetrations for tenant sanitary            X
                     waste and lab waste

ELECTRICAL           Utility Company primary dual feed electric service               X

                     Exterior utility company primary switchgear,                     X
                     transformer and equipment

                     Automatic transfer of dual primary feeders from normal           X
                     to alternate circuit

                     Secondary service feeders from utility transformer to            X
                     Base Building switchboard

                     4000 ampere, 480/277-volt, 3 phase, 4-wire switchboard
                     in Main Electric Room.  (Equates to approximately 27             X
                     watts per square foot)

                     Un-metered 480/277-volt bus duct vertical riser routed
                     through stacked electrical rooms on each floor for               X
                     tenant use

                     Allocation from bus duct of approximately 8 watts/sf
                     (lighting/receptacles/HVAC) for office space and
                     approximately 15 watts/sf (lighting/receptacles/lab              X
                     equipment/HVAC) for lab space, based on a 60/40
                     lab/office distribution

                     Lighting & receptacles serving core areas                        X
</TABLE>

                                       14

<PAGE>

<TABLE>
<S>                  <C>                                                              <C>           <C>
                     Temporary lighting in shell space code minimum                   X

                     300 kw life safety emergency generator, serving fire
                     pump; smoke evacuation systems; stair pressurization
                     systems; fire alarm system; elevator (one passenger
                     elevator and freight elevator); common area emergency            X
                     egress lighting and exit signs; and capacity to serve
                     emergency egress and exit lighting in tenant areas

                     All metering equipment and connection shall be the                             X
                     responsibility of the Tenant

                     Bus duct plug-in unit and service to tenant space                              X

                     Tenant panels, transformers, receptacles, lighting,                            X
                     etc. in tenant area

                     Tenant stand-by generator at pre-coordinated rooftop
                     locations.  Associated distribution equipment located                          X
                     in Tenant space

                     Tenant service, panels, transformers, receptacles,                             X
                     lighting, etc. (normal and stand-by power)

                     Emergency egress lighting and exit signs in tenant area                        X

                     Tenant UPS System and associated equipment                                     X

FIRE PROTECTION      Fire service entrance including fire department
                     connection, alarm valve flow protection, fire pump and
                     standpipe hose outlets in each egress stair                      X

                     Core and stair area sprinkler heads and piping                   X

                     Flow control valve station in stair at each floor                X

                     Primary distribution on each floor adequate to support           X
                     ordinary hazard

                     All run outs, drops, heads and related equipment                               X
                     within tenant premises

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

                     Modification of sprinkler piping & head layout to suit                         X
                     tenant layout and hazard index

                     Special extinguishing systems                                                  X

                     Fire extinguisher cabinets at core area with                     X
                     appropriate fire extinguisher

                     Fire extinguisher cabinets at tenant area with                                 X
                     appropriate fire extinguisher
</TABLE>

                                       15

<PAGE>

<TABLE>
<S>                  <C>                                                              <C>           <C>
FIRE ALARM           Base building expandable analog/addressable fire alarm           X
                     system

                     Detection, notification and annunciation devices in              X
                     core areas and stair entries

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

TEL/DATA             Underground tel/data service from First Street to main           X
                     telephone room on the first floor

                     Stacked tel/data riser rooms on each floor with cable            X
                     sleeves through floors

                     Telephone and data wiring, conduit, sleeves, etc. from                         X
                     building distribution room(s) to tenant spaces

                     Tenant's telephone and data wiring, conduit, equipment                         X
                     and outlets

                     Tenant's audio-visual systems and connections                                  X

ACCESS CONTROL       24/7 security guard at reception desk in lobby                   X

                     Card reader at main building entry into the Cambridge            X
                     Science Center from the Atrium

                     Junction boxes, conduit and door frames necessary for
                     installation of tenant access control system at all
                     tenant entry doors, elevators and egress doors to                X
                     egress stairs/corridors

                     Access controls and wiring at tenant entry doors,                              X
                     elevators and egress doors to egress stairs/corridors

                     Security system including access controls, CCTV, etc.
                     as required by tenant within Base Building areas (eg:
                     elevator floor access control) and within tenant spaces                        X
</TABLE>

                                       16

<PAGE>

                                  SCHEDULE D-2

                                 LANDLORD'S WORK

Plans prepared by Perkins Will, as follows:

First Floor Plan - Sheet Number A-201 dated 5/30/03
Second Floor Plan - Sheet Number A-202 dated 5/30/03
Third Floor Plan - Sheet Number A-203A dated 5/30/03
Fourth Floor Plan - Sheet Number A-204 dated 5/30/03

                                       17

<PAGE>

                                    EXHIBIT E

                              ADDITIONAL PROVISIONS

         This Exhibit is attached to and made a part of the Lease by and between
MA-RIVERVIEW/245 FIRST STREET, L.L.C., A DELAWARE LIMITED LIABILITY COMPANY
("Landlord") and VIACELL, INC., A MASSACHUSETTS CORPORATION ("Tenant") for space
in the Building located at 245 First Street, Cambridge, Massachusetts 02142.

I.       PARKING.

         A.       During the initial Term, commencing on the Office Space
                  Commencement Date Tenant agrees to lease from Landlord and
                  Landlord agrees to lease to Tenant a total of 52 unreserved
                  parking spaces (collectively, the "Spaces") in, or on the roof
                  of, the Building garage ("Garage") for the use of Tenant and
                  its employees. No deductions or allowances shall be made for
                  days when Tenant or any of its employees does not utilize the
                  parking facilities or for Tenant utilizing less than all of
                  the Spaces; provided however that Tenant may choose to lease
                  less than the 52 spaces from time to time and reserve the
                  right to lease the balance of the 52 spaces provided that
                  Tenant must lease the balance or lose its priority rights to
                  such spaces within 30 days after Landlord has given written
                  notice to Tenant that the Building has achieved 90% occupancy.
                  Tenant shall have the right to lease or otherwise use an
                  additional 36 unreserved parking spaces on a month-to month
                  basis until such spaces are leased to a new tenant of the
                  Building. Landlord agrees to give Tenant 30 days prior written
                  notice of its obligation to yield up such additional spaces.
                  Motorcycles are allowed in the Garage. Landlord covenants and
                  agrees that Landlord shall not grant to any future tenant of
                  the Property the contractual right to lease more than 1.2
                  spaces per 1,000 square feet of leased space.

         B.       During the initial Term, Tenant shall pay Landlord, as
                  Additional Rent in accordance with Article IV of the Lease,
                  the sum of $175.00 per month for each unreserved Space leased
                  by Tenant hereunder for the first 5 years of the Term and
                  thereafter, as such rates may be adjusted from time to time to
                  reflect the then current rate for parking in similar parking
                  facilities in the Kendall Square/East Cambridge area. During
                  the construction of the Initial Improvements, Tenant's
                  contractors and subcontractors shall have the right to park in
                  the Garage for a cost of $5.00 per day (regardless of the
                  number of trips in and out of the Garage by any such
                  contractor or subcontractor in that day).

         C.       Except for particular spaces and areas designated by Landlord
                  for reserved parking, all parking in the Garage and surface
                  parking areas serving the Building shall be on an unreserved,
                  first-come, first-served basis.

         D.       Landlord shall not be responsible for money, jewelry,
                  automobiles or other personal property lost in or stolen from
                  the Garage or the surface parking areas regardless of whether
                  such loss or theft occurs when the Garage or other areas
                  therein are locked or otherwise secured. Except as caused by
                  the negligence or willful misconduct of Landlord and without
                  limiting the terms of the preceding

                                        1

<PAGE>

                  sentence, Landlord shall not be liable for any loss, injury or
                  damage to persons using the Garage or the surface parking
                  areas or automobiles or other property therein, it being
                  agreed that, to the fullest extent permitted by Law, the use
                  of the Spaces shall be at the sole risk of Tenant and its
                  employees.

         E.       Landlord shall have the right from time to time to designate
                  the location of the Spaces and to promulgate reasonable rules
                  and regulations regarding the Garage, the surface parking
                  areas, if any, the Spaces and the use thereof, including, but
                  not limited to, rules and regulations controlling the flow of
                  traffic to and from various parking areas, the angle and
                  direction of parking and the like. Tenant shall comply with
                  and cause its employees to comply with all such rules and
                  regulations as well as all reasonable additions and amendments
                  thereto.

         F.       Tenant shall not store or permit its employees to store any
                  automobiles in the Garage or on the surface parking areas
                  without the prior written consent of Landlord. Except for
                  emergency repairs, Tenant and its employees shall not perform
                  any work on any automobiles while located in the Garage or on
                  the Property. If it is necessary for Tenant or its employees
                  to leave an automobile in the Garage or on the surface parking
                  areas overnight, Tenant shall provide Landlord with prior
                  notice thereof designating the license plate number and model
                  of such automobile.

         G.       Landlord shall have the right to temporarily close the Garage
                  or certain areas therein in order to perform necessary
                  repairs, maintenance and improvements to the Garage or the
                  surface parking areas, if any. During such period, the
                  Additional Rent for the parking spaces as to which Tenant is
                  denied access shall be abated on a per space, per diem basis.

         H.       Other than in connection with a sublease or assignment of this
                  Lease, Tenant shall not assign or sublease any of the Spaces
                  without the consent of Landlord.

         I.       Landlord shall provide Tenant with one card or key for each
                  Space that Tenant is leasing hereunder, provided that Landlord
                  shall have the right to condition the issuance of a
                  replacement and or key any lost or damaged cards or keys to
                  Tenant's payment of the actual cost thereof.

         J.       Landlord hereby reserves the right to enter into a management
                  agreement or lease with an entity for the Garage ("Garage
                  Operator"). In such event, Tenant, upon request of Landlord,
                  shall enter into a parking agreement with the Garage Operator
                  and pay the Garage Operator the monthly charge established
                  hereunder, and Landlord shall have no liability for claims
                  arising through acts or omissions of the Garage Operator
                  unless caused by Landlord's negligence or willful misconduct,
                  provided that Landlord shall not be relieved of its
                  responsibility hereunder to provide the parking rights herein
                  described. It is understood and agreed that the identity of
                  the Garage Operator may change from time to time during the
                  Term. In connection therewith, any parking lease or agreement
                  entered into between Tenant and a Garage Operator shall be
                  freely assignable by such Garage Operator or any successors
                  thereto.

II.      FIRST RENEWAL OPTION.

                                        2

<PAGE>

         A.       Tenant shall have the right to extend the Term (the "First
                  Renewal Option") for one additional period of 5 years
                  commencing on the day following the Termination Date of the
                  initial Term and ending on the fifth anniversary of the
                  Termination Date (the "First Renewal Term"), if:

                  1.       Tenant delivers written notice of exercise of the
                           First Renewal Option ("First Renewal Notice") not
                           less than 12 full calendar months prior to the
                           expiration of the initial Term; and

                  2.       Tenant is not in default under the Lease beyond any
                           applicable cure periods at the time that Tenant
                           delivers its First Renewal Notice or at the time
                           Tenant delivers its First Binding Notice (defined
                           below); and

                  3.       Not more than 50% of the Premises is sublet for the
                           remainder of the Initial Term at the time that Tenant
                           delivers its First Renewal Notice or at the time
                           Tenant delivers its First Binding Notice; and

                  4.       Except for a Permitted Transfer, the Lease has not
                           been assigned prior to the date that Tenant delivers
                           its First Renewal Notice or prior to the date Tenant
                           delivers its First Binding Notice; and

         B.       The Base Rent rate per rentable square foot for the Premises
                  during the First Renewal Term shall equal the Prevailing
                  Market (defined below) rate per rentable square foot for the
                  Premises.

         C.       Tenant shall pay Additional Rent (i.e., Expense Excess and Tax
                  Excess) for the Premises during the First Renewal Term in
                  accordance with Article IV of the Lease.

         D.       If Tenant timely delivers Tenant's First Renewal Notice,
                  Landlord shall advise Tenant not less than 11 months prior to
                  the expiration of the initial Term of the applicable Base Rent
                  rate for the Premises for the First Renewal Term. Tenant,
                  within 15 days after the date on which Landlord advises Tenant
                  of the applicable Base Rent rate for the First Renewal Term,
                  shall either (i) give Landlord final binding written notice
                  ("First Binding Notice") of Tenant's exercise of its option,
                  or (ii) if Tenant disagrees with Landlord's determination,
                  provide Landlord with written notice of rejection (the "First
                  Rejection Notice"). If Tenant fails to provide Landlord with
                  either a First Binding Notice or First Rejection Notice within
                  such 15 day period, Tenant's First Renewal Option shall be
                  null and void and of no further force and effect. If Tenant
                  provides Landlord with a First Binding Notice, Landlord and
                  Tenant shall enter into the First Renewal Amendment upon the
                  terms and conditions set forth herein. If Tenant provides
                  Landlord with a First Rejection Notice, Landlord and Tenant
                  shall work together in good faith to agree upon the Prevailing
                  Market Base Rent rate for the Premises during the First
                  Renewal Term. Upon agreement Tenant shall provide Landlord
                  with First Binding Notice and Landlord and Tenant shall enter
                  into the First Renewal Amendment in accordance with the terms
                  and conditions hereof. Notwithstanding the foregoing, if
                  Landlord and Tenant are unable to agree upon the Prevailing
                  Market Base Rent rate for the Premises for the First Renewal

                                        3

<PAGE>

                  Term within 30 days after the date on which Tenant provides
                  Landlord with a First Rejection Notice, Tenant, by written
                  notice to Landlord (the "First Arbitration Notice") within 5
                  days after the expiration of such 30 day period, shall have
                  the right to have the Prevailing Market rate determined in
                  accordance with the arbitration procedures described in
                  Section E below. If Landlord and Tenant are unable to agree
                  upon the Prevailing Market rate for the Premises within the 30
                  day period described and Tenant fails to timely exercise its
                  right to arbitrate, Tenant's First Renewal Option shall be
                  deemed to be null and void and of no further force and effect.

         E.       Arbitration Procedure.

                  1.       If Tenant provides Landlord with a First Arbitration
                           Notice, Landlord and Tenant, within 5 days after the
                           date of the First Arbitration Notice, shall each
                           simultaneously submit to the other, in a sealed
                           envelope, its good faith estimate of the Prevailing
                           Market rate for the Premises during the First Renewal
                           Term (collectively referred to as the "Estimates").
                           If the higher of such Estimates is not more than 105%
                           of the lower of such Estimates, then Prevailing
                           Market rate shall be the average of the two
                           Estimates. If the Prevailing Market rate is not
                           resolved by the exchange of Estimates, then, within 7
                           days after the exchange of Estimates, Landlord and
                           Tenant shall each select an appraiser to determine
                           which of the two Estimates most closely reflects the
                           Prevailing Market rate for the Premises during the
                           First Renewal Term. Each appraiser so selected shall
                           be certified as an MAI appraiser or as an ASA
                           appraiser and shall have had at least 5 years
                           experience within the previous 10 years as a real
                           estate appraiser working in Cambridge, Massachusetts,
                           or shall be a licensed commercial real estate broker
                           with at least 10 years of experience working in
                           Cambridge, Massachusetts, with working knowledge of
                           current rental rates and practices. For purposes
                           hereof, an "MAI" appraiser means an individual who
                           holds an MAI designation conferred by, and is an
                           independent member of, the American Institute of Real
                           Estate Appraisers (or its successor organization, or
                           in the event there is no successor organization, the
                           organization and designation most similar), and an
                           "ASA" appraiser means an individual who holds the
                           Senior Member designation conferred by, and is an
                           independent member of, the American Society of
                           Appraisers (or its successor organization, or, in the
                           event there is no successor organization, the
                           organization and designation most similar).

                  2.       Upon selection, Landlord's and Tenant's appraisers
                           shall work together in good faith to agree upon which
                           of the two Estimates most closely reflects the
                           Prevailing Market rate for the Premises. The Estimate
                           chosen by such appraisers shall be binding on both
                           Landlord and Tenant as the Base Rent rate for the
                           Premises during the First Renewal Term. If either
                           Landlord or Tenant fails to appoint an appraiser
                           within the 7 day period referred to above, the
                           appraiser appointed by the other party shall be the
                           sole appraiser for the purposes hereof. If the two
                           appraisers cannot agree upon which of the two
                           Estimates most closely reflects the Prevailing Market
                           within 20 days after their appointment, then, within
                           10 days after the expiration of such 20 day period,
                           the two appraisers shall select a third appraiser
                           meeting the

                                        4

<PAGE>

                           aforementioned criteria. Once the third appraiser
                           (i.e. arbitrator) has been selected as provided for
                           above, then, as soon thereafter as practicable but in
                           any case within 14 days, the arbitrator shall make
                           his determination of which of the two Estimates most
                           closely reflects the Prevailing Market rate and such
                           Estimate shall be binding on both Landlord and Tenant
                           as the Base Rent rate for the Premises. If the
                           arbitrator believes that expert advice would
                           materially assist him, he may retain one or more
                           qualified persons to provide such expert advice. The
                           parties shall share equally in the costs of the
                           arbitrator and of any experts retained by the
                           arbitrator. Any fees of any appraiser, counsel or
                           experts engaged directly by Landlord or Tenant,
                           however, shall be borne by the party retaining such
                           appraiser, counsel or expert.

                  3.       If the Prevailing Market rate has not been determined
                           by the commencement date of the First Renewal Term,
                           Tenant shall pay Base Rent upon the terms and
                           conditions in effect during the last month of the
                           initial Term for the Premises until such time as the
                           Prevailing Market rate has been determined. Upon such
                           determination, the Base Rent for the Premises shall
                           be retroactively adjusted to the commencement of the
                           First Renewal Term for the Premises. If such
                           adjustment results in an underpayment of Base Rent by
                           Tenant, Tenant shall pay Landlord the amount of such
                           underpayment within 30 days after the determination
                           thereof. If such adjustment results in an overpayment
                           of Base Rent by Tenant, Landlord shall credit such
                           overpayment against the next installment of Base Rent
                           due under the Lease and, to the extent necessary, any
                           subsequent installments, until the entire amount of
                           such overpayment has been credited against Base Rent.

         F.       If Tenant is entitled to and properly exercises its First
                  Renewal Option, Landlord shall prepare an amendment (the
                  "First Renewal Amendment") to reflect changes in the Base
                  Rent, Term, Termination Date and other appropriate terms. The
                  First Renewal Amendment shall be:

                  1.       sent to Tenant within a reasonable time after receipt
                           of the First Binding Notice; and

                  2.       executed by Tenant and returned to Landlord in
                           accordance with the terms herein.

                  An otherwise valid exercise of the First Renewal Option shall
                  be fully effective whether or not the First Renewal Amendment
                  is executed.

         G.       For purposes of this Paragraph II only, "Prevailing Market"
                  shall mean the arms length fair market annual rental rate per
                  rentable square foot under new or renewal leases and
                  amendments entered into on or about the date on which the
                  Prevailing Market is being determined hereunder for space
                  comparable to the Premises in the Building and office
                  buildings comparable to the Building in Cambridge,
                  Massachusetts. The determination of Prevailing Market shall
                  take into account any material economic differences between
                  the terms of the Lease and any comparison lease, such as rent
                  abatements, construction costs and

                                        5

<PAGE>

                  other concessions and the manner, if any, in which the
                  Landlord under any such lease is reimbursed for operating
                  expenses and taxes. The determination of Prevailing Market
                  shall also take into consideration any reasonably anticipated
                  changes in the Prevailing Market rate from the time such
                  Prevailing Market rate is being determined and the time such
                  Prevailing Market rate will become effective under the Lease.

III.     SECOND RENEWAL OPTION.

         A.       If Tenant properly exercises its First Renewal Option pursuant
                  to Paragraph II above, Tenant shall have the right to extend
                  the Term (the "Second Renewal Option") for one additional
                  period of 5 years commencing on the day following the
                  Termination Date of the First Renewal Term and ending on the
                  tenth anniversary of the Termination Date (the "Second Renewal
                  Term"), if:

                  1.       Tenant delivers written notice of exercise of the
                           Second Renewal Option ("Second Renewal Notice") not
                           less than 12 full calendar months prior to the
                           expiration of the First Renewal Term; and

                  2.       Tenant is not in default under the Lease beyond any
                           applicable cure periods at the time that Tenant
                           delivers its Second Renewal Notice or at the time
                           Tenant delivers its Second Binding Notice (defined
                           below); and

                  3.       Not more than 50% of the Premises is sublet for the
                           remainder of the Initial Term at the time that Tenant
                           delivers its Second Renewal Notice or at the time
                           Tenant delivers its Second Binding Notice; and

                  4.       Except for Permitted Transfers, the Lease has not
                           been assigned prior to the date that Tenant delivers
                           its Second Renewal Notice or prior to the date Tenant
                           delivers its Second Binding Notice; and

         B.       The Base Rent rate per rentable square foot for the Premises
                  during the Second Renewal Term shall equal the Prevailing
                  Market (defined below) rate per rentable square foot for the
                  Premises.

         C.       Tenant shall pay Additional Rent (i.e., Expense Excess and Tax
                  Excess) for the Premises during the Second Renewal Term in
                  accordance with Article IV of the Lease.

         D.       If Tenant timely delivers Tenant's Second Renewal Notice,
                  Landlord shall advise Tenant not less than 11 months prior to
                  the expiration of the First Renewal Term of the applicable
                  Base Rent rate for the Premises for the Second Renewal Term.
                  Tenant, within 15 days after the date on which Landlord
                  advises Tenant of the applicable Base Rent rate for the Second
                  Renewal Term, shall either (i) give Landlord final binding
                  written notice ("Second Binding Notice") of Tenant's exercise
                  of its option, or (ii) if Tenant disagrees with Landlord's
                  determination, provide Landlord with written notice of
                  rejection (the "Second Rejection Notice"). If Tenant fails to
                  provide Landlord with either a Second Binding Notice or Second
                  Rejection Notice within such 15 day period, Tenant's Second
                  Renewal Option shall be null and void and of no further force
                  and effect. If Tenant provides

                                        6

<PAGE>

                  Landlord with a Second Binding Notice, Landlord and Tenant
                  shall enter into the Second Renewal Amendment upon the terms
                  and conditions set forth herein. If Tenant provides Landlord
                  with a Second Rejection Notice, Landlord and Tenant shall work
                  together in good faith to agree upon the Prevailing Market
                  Base Rent rate for the Premises during the Second Renewal
                  Term. Upon agreement Tenant shall provide Landlord with Second
                  Binding Notice and Landlord and Tenant shall enter into the
                  Second Renewal Amendment in accordance with the terms and
                  conditions hereof. Notwithstanding the foregoing, if Landlord
                  and Tenant are unable to agree upon the Prevailing Market Base
                  Rent rate for the Premises for the Second Renewal Term within
                  30 days after the date on which Tenant provides Landlord with
                  a Second Rejection Notice, Tenant, by written notice to
                  Landlord (the "Second Arbitration Notice") within 5 days after
                  the expiration of such 30 day period, shall have the right to
                  have the Prevailing Market rate determined in accordance with
                  the arbitration procedures described in Section E below. If
                  Landlord and Tenant are unable to agree upon the Prevailing
                  Market rate for the Premises within the 30 day period
                  described and Tenant fails to timely exercise its right to
                  arbitrate, Tenant's Second Renewal Option shall be deemed to
                  be null and void and of no further force and effect.

         E.       Arbitration Procedure.

                  1.       If Tenant provides Landlord with a Second Arbitration
                           Notice, Landlord and Tenant, within 5 days after the
                           date of the Second Arbitration Notice, shall each
                           simultaneously submit to the other, in a sealed
                           envelope, its good faith estimate of the Prevailing
                           Market rate for the Premises during the Second
                           Renewal Term (collectively referred to as the
                           "Estimates"). If the higher of such Estimates is not
                           more than 105% of the lower of such Estimates, then
                           Prevailing Market rate shall be the average of the
                           two Estimates. If the Prevailing Market rate is not
                           resolved by the exchange of Estimates, then, within 7
                           days after the exchange of Estimates, Landlord and
                           Tenant shall each select an appraiser to determine
                           which of the two Estimates most closely reflects the
                           Prevailing Market rate for the Premises during the
                           Second Renewal Term. Each appraiser so selected shall
                           be certified as an MAI appraiser or as an ASA
                           appraiser and shall have had at least 5 years
                           experience within the previous 10 years as a real
                           estate appraiser working in Cambridge, Massachusetts,
                           or shall be a licensed commercial real estate broker
                           with at least 10 years of experience working in
                           Cambridge, Massachusetts, with working knowledge of
                           current rental rates and practices. For purposes
                           hereof, an "MAI" appraiser means an individual who
                           holds an MAI designation conferred by, and is an
                           independent member of, the American Institute of Real
                           Estate Appraisers (or its successor organization, or
                           in the event there is no successor organization, the
                           organization and designation most similar), and an
                           "ASA" appraiser means an individual who holds the
                           Senior Member designation conferred by, and is an
                           independent member of, the American Society of
                           Appraisers (or its successor organization, or, in the
                           event there is no successor organization, the
                           organization and designation most similar).

                                        7

<PAGE>

                  2.       Upon selection, Landlord's and Tenant's appraisers
                           shall work together in good faith to agree upon which
                           of the two Estimates most closely reflects the
                           Prevailing Market rate for the Premises. The Estimate
                           chosen by such appraisers shall be binding on both
                           Landlord and Tenant as the Base Rent rate for the
                           Premises during the Second Renewal Term. If either
                           Landlord or Tenant fails to appoint an appraiser
                           within the 7 day period referred to above, the
                           appraiser appointed by the other party shall be the
                           sole appraiser for the purposes hereof. If the two
                           appraisers cannot agree upon which of the two
                           Estimates most closely reflects the Prevailing Market
                           within 20 days after their appointment, then, within
                           10 days after the expiration of such 20 day period,
                           the two appraisers shall select a third appraiser
                           meeting the aforementioned criteria. Once the third
                           appraiser (i.e. arbitrator) has been selected as
                           provided for above, then, as soon thereafter as
                           practicable but in any case within 14 days, the
                           arbitrator shall make his determination of which of
                           the two Estimates most closely reflects the
                           Prevailing Market rate and such Estimate shall be
                           binding on both Landlord and Tenant as the Base Rent
                           rate for the Premises. If the arbitrator believes
                           that expert advice would materially assist him, he
                           may retain one or more qualified persons to provide
                           such expert advice. The parties shall share equally
                           in the costs of the arbitrator and of any experts
                           retained by the arbitrator. Any fees of any
                           appraiser, counsel or experts engaged directly by
                           Landlord or Tenant, however, shall be borne by the
                           party retaining such appraiser, counsel or expert.

                  3.       If the Prevailing Market rate has not been determined
                           by the commencement date of the Second Renewal Term,
                           Tenant shall pay Base Rent upon the terms and
                           conditions in effect during the last month of the
                           First Renewal Term for the Premises until such time
                           as the Prevailing Market rate has been determined.
                           Upon such determination, the Base Rent for the
                           Premises shall be retroactively adjusted to the
                           commencement of the Second Renewal Term for the
                           Premises. If such adjustment results in an
                           underpayment of Base Rent by Tenant, Tenant shall pay
                           Landlord the amount of such underpayment within 30
                           days after the determination thereof. If such
                           adjustment results in an overpayment of Base Rent by
                           Tenant, Landlord shall credit such overpayment
                           against the next installment of Base Rent due under
                           the Lease and, to the extent necessary, any
                           subsequent installments, until the entire amount of
                           such overpayment has been credited against Base Rent.

         F.       If Tenant is entitled to and properly exercises its Second
                  Renewal Option, Landlord shall prepare an amendment (the
                  "Second Renewal Amendment") to reflect changes in the Base
                  Rent, Term, Termination Date and other appropriate terms. The
                  Second Renewal Amendment shall be:

                  1.       sent to Tenant within a reasonable time after receipt
                           of the Second Binding Notice; and

                  2.       executed by Tenant and returned to Landlord in
                           accordance with the terms herein.

                                        8

<PAGE>

                  An otherwise valid exercise of the Second Renewal Option shall
                  be fully effective whether or not the Second Renewal Amendment
                  is executed.

         G.       For purposes of this Paragraph III only, "Prevailing Market"
                  shall mean the arms length fair market annual rental rate per
                  rentable square foot under new or renewal leases and
                  amendments entered into on or about the date on which the
                  Prevailing Market is being determined hereunder for space
                  comparable to the Premises in the Building and office
                  buildings comparable to the Building in Cambridge,
                  Massachusetts. The determination of Prevailing Market shall
                  take into account any material economic differences between
                  the terms of the Lease and any comparison lease, such as rent
                  abatements, construction costs and other concessions and the
                  manner, if any, in which the Landlord under any such lease is
                  reimbursed for operating expenses and taxes. The determination
                  of Prevailing Market shall also take into consideration any
                  reasonably anticipated changes in the Prevailing Market rate
                  from the time such Prevailing Market rate is being determined
                  and the time such Prevailing Market rate will become effective
                  under the Lease.

IV.      THIRD RENEWAL OPTION.

         A.       If Tenant properly exercises its Second Renewal Option
                  pursuant to Paragraph III above, Tenant shall have the right
                  to extend the Term (the "Third Renewal Option") for one
                  additional period of 5 years commencing on the day following
                  the Termination Date of the Second Renewal Term and ending on
                  the fifteenth anniversary of the Termination Date (the "Third
                  Renewal Term"), if:

                  1.       Tenant delivers written notice of exercise of the
                           Third Renewal Option ("Third Renewal Notice") not
                           less than 12 full calendar months prior to the
                           expiration of the Second Renewal Term; and

                  2.       Tenant is not in default under the Lease beyond any
                           applicable cure periods at the time that Tenant
                           delivers its Third Renewal Notice or at the time
                           Tenant delivers its Third Binding Notice (defined
                           below); and

                  3.       Not more than 50% of the Premises is sublet for the
                           remainder of the Initial Term at the time that Tenant
                           delivers its Third Renewal Notice or at the time
                           Tenant delivers its Third Binding Notice; and

                  4.       Except for Permitted Transfers, the Lease has not
                           been assigned prior to the date that Tenant delivers
                           its Third Renewal Notice or prior to the date Tenant
                           delivers its Third Binding Notice; and

         B.       The Base Rent rate per rentable square foot for the Premises
                  during the Third Renewal Term shall equal the Prevailing
                  Market (defined below) rate per rentable square foot for the
                  Premises.

         C.       Tenant shall pay Additional Rent (i.e., Expense Excess and Tax
                  Excess) for the Premises during the Third Renewal Term in
                  accordance with Article IV of the Lease.

                                        9

<PAGE>

         D.       If Tenant timely delivers Tenant's Third Renewal Notice,
                  Landlord shall advise Tenant not less than 11 months prior to
                  the expiration of the Second Renewal Term of the applicable
                  Base Rent rate for the Premises for the Third Renewal Term.
                  Tenant, within 15 days after the date on which Landlord
                  advises Tenant of the applicable Base Rent rate for the Third
                  Renewal Term, shall either (i) give Landlord final binding
                  written notice ("Third Binding Notice") of Tenant's exercise
                  of its option, or (ii) if Tenant disagrees with Landlord's
                  determination, provide Landlord with written notice of
                  rejection (the "Third Rejection Notice"). If Tenant fails to
                  provide Landlord with either a Third Binding Notice or Third
                  Rejection Notice within such 15 day period, Tenant's Third
                  Renewal Option shall be null and void and of no further force
                  and effect. If Tenant provides Landlord with a Third Binding
                  Notice, Landlord and Tenant shall enter into the Third Renewal
                  Amendment upon the terms and conditions set forth herein. If
                  Tenant provides Landlord with a Third Rejection Notice,
                  Landlord and Tenant shall work together in good faith to agree
                  upon the Prevailing Market Base Rent rate for the Premises
                  during the Third Renewal Term. Upon agreement Tenant shall
                  provide Landlord with Third Binding Notice and Landlord and
                  Tenant shall enter into the Third Renewal Amendment in
                  accordance with the terms and conditions hereof.
                  Notwithstanding the foregoing, if Landlord and Tenant are
                  unable to agree upon the Prevailing Market Base Rent rate for
                  the Premises for the Third Renewal Term within 30 days after
                  the date on which Tenant provides Landlord with a Third
                  Rejection Notice, Tenant, by written notice to Landlord (the
                  "Third Arbitration Notice") within 5 days after the expiration
                  of such 30 day period, shall have the right to have the
                  Prevailing Market rate determined in accordance with the
                  arbitration procedures described in Section E below. If
                  Landlord and Tenant are unable to agree upon the Prevailing
                  Market rate for the Premises within the 30 day period
                  described and Tenant fails to timely exercise its right to
                  arbitrate, Tenant's Third Renewal Option shall be deemed to be
                  null and void and of no further force and effect.

         E.       Arbitration Procedure.

                  1.       If Tenant provides Landlord with a Third Arbitration
                           Notice, Landlord and Tenant, within 5 days after the
                           date of the Third Arbitration Notice, shall each
                           simultaneously submit to the other, in a sealed
                           envelope, its good faith estimate of the Prevailing
                           Market rate for the Premises during the Third Renewal
                           Term (collectively referred to as the "Estimates").
                           If the higher of such Estimates is not more than 105%
                           of the lower of such Estimates, then Prevailing
                           Market rate shall be the average of the two
                           Estimates. If the Prevailing Market rate is not
                           resolved by the exchange of Estimates, then, within 7
                           days after the exchange of Estimates, Landlord and
                           Tenant shall each select an appraiser to determine
                           which of the two Estimates most closely reflects the
                           Prevailing Market rate for the Premises during the
                           Third Renewal Term. Each appraiser so selected shall
                           be certified as an MAI appraiser or as an ASA
                           appraiser and shall have had at least 5 years
                           experience within the previous 10 years as a real
                           estate appraiser working in Cambridge, Massachusetts,
                           or shall be a licensed commercial real estate broker
                           with at least 10 years of experience working in
                           Cambridge, Massachusetts, with working

                                       10

<PAGE>

                           knowledge of current rental rates and practices. For
                           purposes hereof, an "MAI" appraiser means an
                           individual who holds an MAI designation conferred by,
                           and is an independent member of, the American
                           Institute of Real Estate Appraisers (or its successor
                           organization, or in the event there is no successor
                           organization, the organization and designation most
                           similar), and an "ASA" appraiser means an individual
                           who holds the Senior Member designation conferred by,
                           and is an independent member of, the American Society
                           of Appraisers (or its successor organization, or, in
                           the event there is no successor organization, the
                           organization and designation most similar).

                  2.       Upon selection, Landlord's and Tenant's appraisers
                           shall work together in good faith to agree upon which
                           of the two Estimates most closely reflects the
                           Prevailing Market rate for the Premises. The Estimate
                           chosen by such appraisers shall be binding on both
                           Landlord and Tenant as the Base Rent rate for the
                           Premises during the Third Renewal Term. If either
                           Landlord or Tenant fails to appoint an appraiser
                           within the 7 day period referred to above, the
                           appraiser appointed by the other party shall be the
                           sole appraiser for the purposes hereof. If the two
                           appraisers cannot agree upon which of the two
                           Estimates most closely reflects the Prevailing Market
                           within 20 days after their appointment, then, within
                           10 days after the expiration of such 20 day period,
                           the two appraisers shall select a third appraiser
                           meeting the aforementioned criteria. Once the third
                           appraiser (i.e. arbitrator) has been selected as
                           provided for above, then, as soon thereafter as
                           practicable but in any case within 14 days, the
                           arbitrator shall make his determination of which of
                           the two Estimates most closely reflects the
                           Prevailing Market rate and such Estimate shall be
                           binding on both Landlord and Tenant as the Base Rent
                           rate for the Premises. If the arbitrator believes
                           that expert advice would materially assist him, he
                           may retain one or more qualified persons to provide
                           such expert advice. The parties shall share equally
                           in the costs of the arbitrator and of any experts
                           retained by the arbitrator. Any fees of any
                           appraiser, counsel or experts engaged directly by
                           Landlord or Tenant, however, shall be borne by the
                           party retaining such appraiser, counsel or expert.

                  3.       If the Prevailing Market rate has not been determined
                           by the commencement date of the Third Renewal Term,
                           Tenant shall pay Base Rent upon the terms and
                           conditions in effect during the last month of the
                           First Renewal Term for the Premises until such time
                           as the Prevailing Market rate has been determined.
                           Upon such determination, the Base Rent for the
                           Premises shall be retroactively adjusted to the
                           commencement of the Third Renewal Term for the
                           Premises. If such adjustment results in an
                           underpayment of Base Rent by Tenant, Tenant shall pay
                           Landlord the amount of such underpayment within 30
                           days after the determination thereof. If such
                           adjustment results in an overpayment of Base Rent by
                           Tenant, Landlord shall credit such overpayment
                           against the next installment of Base Rent due under
                           the Lease and, to the extent necessary, any
                           subsequent installments, until the entire amount of
                           such overpayment has been credited against Base Rent.

                                       11

<PAGE>

         F.       If Tenant is entitled to and properly exercises its Third
                  Renewal Option, Landlord shall prepare an amendment (the
                  "Third Renewal Amendment") to reflect changes in the Base
                  Rent, Term, Termination Date and other appropriate terms. The
                  Third Renewal Amendment shall be:

                  1.       sent to Tenant within a reasonable time after receipt
                           of the Third Binding Notice; and

                  2.       executed by Tenant and returned to Landlord in
                           accordance with the terms herein.

                  An otherwise valid exercise of the Third Renewal Option shall
                  be fully effective whether or not the Third Renewal Amendment
                  is executed.

         G.       For purposes of this Paragraph III only, "Prevailing Market"
                  shall mean the arms length fair market annual rental rate per
                  rentable square foot under new or renewal leases and
                  amendments entered into on or about the date on which the
                  Prevailing Market is being determined hereunder for space
                  comparable to the Premises in the Building and office
                  buildings comparable to the Building in Cambridge,
                  Massachusetts. The determination of Prevailing Market shall
                  take into account any material economic differences between
                  the terms of the Lease and any comparison lease, such as rent
                  abatements, construction costs and other concessions and the
                  manner, if any, in which the Landlord under any such lease is
                  reimbursed for operating expenses and taxes. The determination
                  of Prevailing Market shall also take into consideration any
                  reasonably anticipated changes in the Prevailing Market rate
                  from the time such Prevailing Market rate is being determined
                  and the time such Prevailing Market rate will become effective
                  under the Lease.

V.       EXTERIOR SIGNAGE.

         A.       Tenant, at Tenant's sole cost and expense, subject to
                  governmental restrictions, regulations and approval, shall
                  have the exclusive right to erect 1 sign identifying Tenant
                  (the "Exterior Sign") on the Science Building exterior at the
                  location shown on EXHIBIT G attached hereto, on the terms set
                  forth herein. At least 30 days prior to Tenant's submission of
                  an application for governmental approval of the proposed
                  Exterior Sign, Tenant shall submit detailed drawings of its
                  proposed Exterior Sign to Landlord for Landlord's review and
                  approval, such approval not to be unreasonably withheld. Such
                  drawings shall include, without limitation, detailed
                  information concerning the size, material, shape, color,
                  lettering, and method of installation of the proposed Exterior
                  Sign. The approved Exterior Sign plans shall be attached
                  hereto as a part of EXHIBIT G upon approval. Tenant shall be
                  solely responsible for the obtaining of all governmental
                  approvals required in connection with the Exterior Sign, at
                  Tenant's sole cost and expense. All maintenance and repair of
                  the Exterior Sign shall be at Tenant's sole cost and expense.

         B.       Landlord, upon the expiration date or sooner termination of
                  this Lease, shall have the right to remove the Exterior Sign
                  at Tenant's sole cost and expense. In addition, Landlord, at
                  Tenant's sole cost and expense, shall have the right to remove
                  the Exterior Sign at any time during the Term at Tenant's sole
                  cost and

                                       12

<PAGE>

                  expense (1) in the event of a Lease assignment other than
                  pursuant to a Permitted Transfer, (2) if Tenant or a party
                  pursuant to a Permitted Transfer occupies less than 75% of the
                  rentable square feet of the Premises, or (3) if Tenant
                  defaults under any term or condition of the Lease and fails to
                  cure such default within any applicable notice, grace and cure
                  period and Landlord subsequently terminates the Lease.

         C.       No other tenant identification signage may be attached to the
                  exterior of the Science Building. Landlord expressly reserves
                  the right to install building identification signage on the
                  Science Building and to install any signage on the Office
                  Building and Common Areas.

VI.      RIGHT OF FIRST OFFER; CONDITIONS.

         A.       During the Term hereof, Tenant shall have a continuous right
                  of first offer (the "Right of First Offer"), after initial
                  lease up with respect to the space located on the 2nd and 3rd
                  floors of the Science Building, after initial lease up with
                  respect to any space on the 16th floor of the Office Building,
                  and on any space on the 14th and 17th floors of the Office
                  Building, each as shown on the demising plan attached hereto
                  as EXHIBIT H (the "Offering Space"). Tenant's Right of First
                  Offer shall be exercised as follows: at any time after
                  Landlord has determined that the initial or existing tenant in
                  the Offering Space will not extend or renew the term of its
                  lease for the Offering Space (but prior to leasing such
                  Offering Space to a party other than the initial or existing
                  tenant and not more than twelve (12) months prior to the
                  proposed commencement date for the Offering Space), Landlord
                  shall advise Tenant (the "Advice") of the terms under which
                  Landlord is prepared to lease the Offering Space to Tenant for
                  the remainder of the Term, which terms shall reflect the
                  Prevailing Market (hereinafter defined) rate for such Offering
                  Space as reasonably determined by Landlord. Tenant may lease
                  such offering Space in its entirety only, under such terms, by
                  delivering written notice of exercise to Landlord (the "Notice
                  of Exercise") within 15 business days after the date of the
                  Advice, except that Tenant shall have no such Right of First
                  Offer and Landlord need not provide Tenant with an Advice, if:

                  1.       Tenant is in default under the Lease beyond any
                           applicable cure periods at the time that Landlord
                           would otherwise deliver the Advice; or

                  2.       More than 50% of the Premises is sublet for the
                           remainder of the Initial Term or any extension
                           thereof (other than pursuant to a Permitted Transfer,
                           as defined in Article XII of the Lease) at the time
                           Landlord would otherwise deliver the Advice; or

                  3.       the Lease has been assigned (other than pursuant to a
                           Permitted Transfer, as defined in Article XII of the
                           Lease) prior to the date Landlord would otherwise
                           deliver the Advice; or

                  4.       Tenant is not occupying the Premises on the date
                           Landlord would otherwise deliver the Advice; or

                                       13

<PAGE>

                  5.       the Offering Space is not intended for the exclusive
                           use of Tenant during the Term; or

                  6.       the existing tenant in the Offering Space is
                           interested in extending or renewing its lease for the
                           Offering Space or entering into a new lease for such
                           Offering Space.

         On or before the expiration of such 15 business day period, Tenant
         shall either accept Landlord's terms, or shall agree to lease the
         Offering Space but elect to have the rent therefor determined by
         arbitration in accordance with the Arbitration Procedure employed for
         the Renewal Options under clause E of Sections II, III and IV above (it
         being agreed that such rent arbitration shall be binding upon the
         parties). In the event Tenant rejects or is deemed to have rejected the
         offer set forth in the Advice, Landlord shall be free for a period of
         12 months after the date of the rejection or deemed rejection
         ("Marketing Period") to lease the Offering Space to a third party or
         parties on terms not materially more favorable to such party or parties
         than the terms set forth in the Advice (with respect to rental rate,
         "materially" as used herein shall mean a rental rate that is more than
         five percent (5%) lower than the financial terms set forth in the
         Advice, including, without limitation, net effective rent, tenant
         improvement allowance, brokerage fees and other economic
         considerations). In the event Landlord has not by the expiration of the
         Marketing Period executed a letter of intent with a third party
         complying with the foregoing sentence, then Tenant's right of first
         offer shall again apply to the Offering Space.

         B.       Terms for Offering Space.

                  1.       The term for the Offering Space shall commence upon
                           the commencement date stated in the Advice and
                           thereupon such Offering Space shall be considered a
                           part of the Premises, provided that all of the terms
                           stated in the Advice (or as determined by rent
                           arbitration) shall govern Tenant's leasing of the
                           Offering Space and otherwise the terms and conditions
                           of this Lease shall apply to the Offering Space.

                  2.       Tenant shall pay Base Rent and Additional Rent for
                           the Offering Space in accordance with the terms and
                           conditions of the Advice, which terms and conditions
                           shall reflect the Prevailing Market rate for the
                           Offering Space as determined in Landlord's reasonable
                           judgment, or as determined by rent arbitration.

                  3.       The Offering Space (including improvements and
                           personalty, if any) shall be accepted by Tenant in
                           its condition and as-built configuration existing on
                           the earlier of the date Tenant takes possession of
                           the Offering Space or as of the date the term for
                           such Offering Space commences, unless the Advice
                           specifies any work to be performed by Landlord in the
                           Offering Space, in which case Landlord shall perform
                           such work in the Offering Space. If Landlord is
                           delayed delivering possession of the Offering Space
                           due to the holdover or unlawful possession of such
                           space by any party, Landlord shall use reasonable
                           efforts to obtain possession of the space, and the
                           commencement of the term for the Offering Space shall
                           be postponed until the date

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<PAGE>

                           Landlord delivers possession of the Offering Space to
                           Tenant free from occupancy by any party.

         C.       Termination of Right of First Offer. The rights of Tenant
                  hereunder with respect to the Offering Space shall terminate
                  on the earlier to occur of: (i) the expiration of the Term of
                  this Lease; and (ii) the date Landlord would have provided
                  Tenant an Advice if Tenant had not been in violation of one or
                  more of the conditions set forth in Section A above.

         D.       Offering Amendment. If Tenant exercises its Right of First
                  Offer, Landlord shall prepare an amendment (the "Offering
                  Amendment") adding the Offering Space to the Premises on the
                  terms set forth in the Advice and reflecting the changes in
                  the Base Rent, Rentable Square Footage of the Premises,
                  Tenant's Pro Rata Share and other appropriate terms. A copy of
                  the Offering Amendment shall be sent to Tenant within a
                  reasonable time after Landlord's receipt of the Notice of
                  Exercise executed by Tenant, and Tenant shall execute and
                  return the Offering Amendment to Landlord within 15 days
                  thereafter, but an otherwise valid exercise of the Right of
                  First Offer shall be fully effective whether or not the
                  Offering Amendment is executed.

         E.       Definition of Prevailing Market. For purposes of this Right of
                  First Offer provision, "Prevailing Market" shall mean the
                  annual rental rate per square foot for space comparable to the
                  Offering Space in the Building and for space comparable to the
                  Offering Space in buildings comparable to the Building in the
                  Cambridge, Massachusetts area under leases and renewal and
                  expansion amendments being entered into at or about the time
                  that Prevailing Market is being determined, giving appropriate
                  consideration to tenant concessions, brokerage commissions,
                  tenant improvement allowances, existing improvements in the
                  space in question, and the method of allocating operating
                  expenses and taxes. Notwithstanding the foregoing, space
                  leased under any of the following circumstances shall not be
                  considered to be comparable for purposes hereof: (i) the lease
                  term is for less than the lease term of the Offering Space,
                  (ii) the space is encumbered by the option rights of another
                  tenant, or (iii) the space has a lack of windows and/or an
                  awkward or unusual shape or configuration. The foregoing is
                  not intended to be an exclusive list of space that will not be
                  considered to be comparable.

VII.     RIGHT OF EXPANSION; CONDITIONS

         A.       Tenant shall have the right to expand ("Expansion Right") into
                  the balance of the 2nd floor of the Science Building
                  (approximately 9,000 square feet) ("Lab Expansion Space") and
                  into that portion of the 16th Floor of the Office Building
                  shown as the "16A Space" ("Office Expansion Space") on EXHIBIT
                  H-1, if:

                  1.       Landlord receives notice ("Expansion Notice") of
                           Tenant's exercise of the Expansion Right on or before
                           December 31, 2004; and

                  2.       Tenant is not in default under the Lease beyond any
                           applicable cure periods at the time that Tenant
                           delivers the Expansion Notice;

                                       15

<PAGE>

                  3.       Not more than 50% of the Premises is sublet for the
                           remainder of the Initial Term at the time that Tenant
                           delivers the Expansion Notice; and

                  4.       Except for a Permitted Transfer, the Lease has not
                           been assigned prior to the date Tenant delivers the
                           Expansion Notice.

                  Notwithstanding the foregoing, Landlord shall have the right
                  to substitute for the 16A Space the same 4,792 square feet of
                  space on another floor of the Office Building chosen by
                  Landlord, in the event that Landlord has the opportunity to
                  lease the entirety of the 16th Floor of the Office Building to
                  a single tenant prior to the exercise by Tenant of the right
                  of expansion set forth herein. If there is a choice of floor
                  available, Landlord shall designate the floor closest to the
                  15th Floor of the Office Building for the alternative space.

         B.       The Base Rent with respect to the Lab Expansion Space shall be
                  at the annual rental rate per square foot for the Lab Space
                  set forth in Section I.D. of the Lease and the Base Rent with
                  respect to the Office Expansion Space shall be at the annual
                  rental rate per square foot for the Office Space set forth in
                  Section I.D. of the Lease.

         C.       Tenant shall pay Additional Rent (i.e., Lab Expenses and Lab
                  Taxes with respect to the Lab Expansion Space and Excess
                  Expenses and Excess Taxes with respect to the Office Expansion
                  Space) in accordance with Article IV of the Lease.

         D.       Landlord shall contribute the sum of One Hundred Dollars
                  ($100) per square foot with respect to the Lab Expansion Space
                  and Fifty Dollars ($50) per square foot with respect to the
                  Office Expansion Space, and in each case the $3.00 per square
                  foot architectural and engineering allowance to be disbursed
                  in accordance with the provisions of EXHIBIT D.

         E.       The Rent Commencement Date with respect to the Lab Expansion
                  Space shall be 150 days after Landlord delivers vacant
                  possession of the Lab Expansion Space following the Expansion
                  Notice with respect to the Lab Expansion Space. The Rent
                  Commencement Date with respect to the Office Expansion Space
                  shall be 90 days after Tenant delivers vacant possession of
                  the Office Expansion Space following the Expansion Notice with
                  respect to the Office Expansion Space.

         F.       If Tenant exercises the Expansion Right, Landlord shall
                  prepare an amendment (the "Expansion Amendment") adding the
                  Lab Expansion Space or the Office Expansion Space, or both, as
                  applicable, to the Premises on the terms set forth herein and
                  reflecting the changes in the Base Rent, Rentable Square
                  Footage of the Premises, Tenant's Pro Rata Share and other
                  appropriate terms. A copy of the Expansion Amendment shall be
                  sent to Tenant within a reasonable time after Landlord's
                  receipt of the Expansion Notice and Tenant shall execute and
                  return the Expansion Amendment to Landlord within 15 days
                  thereafter, but an otherwise valid exercise of the Expansion
                  Right shall be fully effective whether or not the Expansion
                  Amendment is executed.

                                       16

<PAGE>

VIII.    RIGHT OF FIRST REFUSAL; CONDITIONS.

         A.       During the Term hereof, Tenant shall have a continuous right
                  of first refusal (the "Right of First Refusal"), with respect
                  to the space located on the balance of the 2nd floor of the
                  Science Building and any space on the 16th Floor of the Office
                  Building, each as shown on the demising plan attached hereto
                  as EXHIBIT L (the "Right of First Refusal Space"). Tenant's
                  Right of First Refusal shall be exercised as follows: at any
                  time after Landlord has received a letter of intent ("LOI") to
                  lease any such space from a third party which Landlord is
                  willing to accept, Landlord shall advise Tenant (the "Advice")
                  of the terms of the LOI. Tenant may lease such offering Space
                  in its entirety only, in accordance with the terms of the LOI,
                  by delivering written notice of exercise to Landlord (the
                  "Notice of Exercise") within 3 business days after the date of
                  the Advice, except that Tenant shall have no such Right of
                  First Refusal and Landlord need not provide Tenant with an
                  Advice, if:

                  1.       Tenant is in default under the Lease beyond any
                           applicable cure periods at the time that Landlord
                           would otherwise deliver the Advice; or

                  2.       the Premises, or any portion thereof, is sublet
                           (other than pursuant to a Permitted Transfer, as
                           defined in Article XII of the Lease) at the time
                           Landlord would otherwise deliver the Advice; or

                  3.       the Lease has been assigned (other than pursuant to a
                           Permitted Transfer, as defined in Article XII of the
                           Lease) prior to the date Landlord would otherwise
                           deliver the Advice; or

                  4.       Tenant is not occupying the Premises on the date
                           Landlord would otherwise deliver the Advice; or

                  5.       the Right of First Refusal Space is not intended for
                           the exclusive use of Tenant during the Term; or

                  6.       the existing tenant in the Right of First Refusal
                           Space is interested in extending or renewing its
                           lease for the Right of First Refusal Space or
                           entering into a new lease for such Right of First
                           Refusal Space.

         In the event Tenant rejects or is deemed to have rejected the offer set
         forth in the Advice, Landlord shall be free for a period of 12 months
         after the date of the rejection or deemed rejection ("Marketing
         Period") to lease the Right of First Refusal Space to a third party or
         parties on terms not materially more favorable to such party or parties
         than the terms set forth in the Advice (with respect to rental rate,
         "materially" as used herein shall mean a rental rate that is more than
         five percent (5%) lower than the financial terms set forth in the
         Advice, including, without limitation, net effective rent, tenant
         improvement allowance, brokerage fees and other economic
         consideration). In the event Landlord has not by the expiration of the
         Marketing Period executed a letter of intent with a third party
         complying with the foregoing sentence, then Tenant's right of first
         offer shall again apply to the Right of First Refusal Space.

         B.       Terms for Right of First Refusal Space.

                                       17

<PAGE>

                  1.       The term for the Right of First Refusal Space shall
                           commence upon the commencement date stated in the
                           Advice and thereupon such Offering Space shall be
                           considered a part of the Premises, provided that all
                           of the terms stated in the Advice shall govern
                           Tenant's leasing of the Right of First Refusal Space
                           and only to the extent that they do not conflict with
                           the Advice, the terms and conditions of this Lease
                           shall apply to the Right of First Refusal Space.

                  2.       Tenant shall pay Base Rent and Additional Rent for
                           the Offering Space in accordance with the terms and
                           conditions of the Advice, which terms and conditions
                           shall reflect the Prevailing Market rate for the
                           Right of First Refusal Space as determined in
                           Landlord's reasonable judgment.

                  3.       The Right of First Refusal Space (including
                           improvements and personalty, if any) shall be
                           accepted by Tenant in its condition and as-built
                           configuration existing on the earlier of the date
                           Tenant takes possession of the Right of First Refusal
                           Space or as of the date the term for such Right of
                           First Refusal Space commences, unless the Advice
                           specifies any work to be performed by Landlord in the
                           Right of First Refusal Space, in which case Landlord
                           shall perform such work in the Right of First Refusal
                           Space. If Landlord is delayed delivering possession
                           of the Right of First Refusal Space due to the
                           holdover or unlawful possession of such space by any
                           party, Landlord shall use reasonable efforts to
                           obtain possession of the space, and the commencement
                           of the term for the Right of First Refusal Space
                           shall be postponed until the date Landlord delivers
                           possession of the Right of First Refusal Space to
                           Tenant free from occupancy by any party.

         C.       Termination of Right of First Refusal. The rights of Tenant
                  hereunder with respect to the Right of First Refusal Space
                  shall terminate on the earlier to occur of: (i) the expiration
                  of the Term of this Lease; and (ii) the date Landlord would
                  have provided Tenant an Advice if Tenant had not been in
                  violation of one or more of the conditions set forth in
                  Section A above.

         D.       Right of First Refusal Amendment. If Tenant exercises its
                  Right of First Right of First Refusal, Landlord shall prepare
                  an amendment (the "Right of First Refusal Amendment") adding
                  the Right of First Refusal Space to the Premises on the terms
                  set forth in the Advice and reflecting the changes in the Base
                  Rent, Rentable Square Footage of the Premises, Tenant's Pro
                  Rata Share and other appropriate terms. A copy of the Right of
                  First Refusal Amendment shall be sent to Tenant within a
                  reasonable time after Landlord's receipt of the Notice of
                  Exercise executed by Tenant, and Tenant shall execute and
                  return the Right of First Refusal Amendment to Landlord within
                  15 days thereafter, but an otherwise valid exercise of the
                  Right of First Refusal shall be fully effective whether or not
                  the Right of First Refusal Amendment is executed.

IX.      TENANT'S EXISTING LEASE LIABILITY

         A.       Provided Tenant is not in default under this Lease beyond any
                  applicable cure periods, from and after the expiration of the
                  Office Base Rent Abatement Period,

                                       18

<PAGE>

                  Tenant shall receive a rent credit hereunder on a monthly
                  basis equal to the rent paid by Tenant after that date under
                  that certain Lease between Molded Antennae for
                  Telecommunications, Inc., as landlord, and Viacord Inc., as
                  tenant, dated April 20, 1999 with respect to office space at
                  551 Boylston Street, Boston, Massachusetts, until its date of
                  expiration on September 30, 2004, or earlier termination of
                  said Lease, provided Tenant shall remain responsible for
                  removal of any equipment and any restoration or environmental
                  clean up if required under the Existing Office Lease. Tenant
                  shall provide Landlord with evidence of the rent paid under
                  the aforesaid lease together with any payment of rent
                  hereunder as to which Tenant applies such credit.

         B.       Provided Tenant is not in default under this Lease beyond any
                  applicable cure periods, from and after the Lab Base Rent
                  Abatement Period, Tenant shall receive a rent credit hereunder
                  on a monthly basis equal to the rent paid by Tenant after that
                  date under that certain Lease dated February 24, 2000, as
                  amended by a First Amendment dated May 31, 2001, a Second
                  Amendment dated as of November 14, 2001, and a Third Amendment
                  dated as of July 17, 2002, between ARE-One Innovation Drive,
                  LLC, as landlord, and Tenant, as tenant, with respect to
                  research and development space at One Innovation Drive,
                  Worcester, Massachusetts, until its date of expiration on
                  February 28, 2005 or earlier termination of said Lease,
                  provided Tenant shall remain responsible for removal of any
                  equipment and any restoration or environmental clean up if
                  required under the Existing Office Lease. Tenant shall provide
                  Landlord with evidence of the rent paid under the aforesaid
                  lease together with any payment of rent hereunder as to which
                  Tenant applies such credit.

X.       EARLY TERMINATION RIGHT RELATING TO OFFICE SPACE.

         Tenant shall have the one time option ("Office Termination Option") to
         terminate the portion of the Lease relating to the Office Space
         originally demised under this Lease on the 6th anniversary of the Term
         of the Lease (the "Office Early Termination Date"), if:

                  1.       Tenant delivers written notice ("Early Termination
                           Notice") of Tenant's exercise of the Office
                           Termination Option at least 12 months prior to the
                           Office Early Termination Date; and

                  2.       Tenant is not in default under the Lease beyond any
                           applicable cure periods at the time that Tenant
                           delivers the Early Termination Notice;

                  3.       Not more than 50% of the Premises is sublet for the
                           remainder of the Initial Term at the time that Tenant
                           delivers the Early Termination Notice;

                  4.       Except for a Permitted Transfer, the Lease has not
                           been assigned prior to the date Tenant delivers the
                           Early Termination Notice; and

                  5.       Tenant shall not have sublet the Office Space for a
                           term extending beyond the Office Early Termination
                           Date.

         It shall be a condition precedent to the effectiveness of the Early
         Termination Notice that Tenant shall pay to Landlord together with the
         Early Termination Notice an amount

                                       19

<PAGE>

         (collectively, the "Termination Fee") equal to the sum of (i) the
         unamortized balance, as of the Early Termination Date, of the sum of
         the Tenant allowance for the Office Space described in Section 1.H. of
         this Lease, the Drawing Allowance for the Office Space described in
         Exhibit D of this Lease, any Additional Allowance used by Tenant for
         the Office Space, all brokerage and legal fees incurred by Landlord in
         connection with this Lease and 50% of the Viacell lease assumption
         costs, amortized on a straight line basis with interest thereon at the
         rate of eleven percent (11%) per annum over the initial Term of this
         Lease, and (ii) 6 months of Office Base Rent, Expense Excess and Tax
         Excess, all at the rate applicable to the 6 months immediately
         preceding the Early Termination Date.

XI.      ROOF RIGHTS.

         A.       Tenant shall have the right to its allocation of space on the
                  roof of the Science Building for the purpose of installing (in
                  accordance with Section IX.C of the Lease), operating and
                  maintaining an emergency generator and/ or a satellite dish
                  solely for Tenant's business activities in the Premises and
                  not for use by third parties, as approved by the Landlord (the
                  "Rooftop Equipment"). The exact location of the space on the
                  roof to be leased by Tenant shall be designated by Landlord
                  and shall not exceed 344 square feet (the "Roof Space"), and
                  shall be in the location designated in EXHIBIT A. Landlord
                  reserves the right to relocate the Roof Space as reasonably
                  necessary during the Term at Landlord's expense, with a
                  minimum of disruption to Tenant's business activities in the
                  Premises. Landlord's designation shall take into account
                  Tenant's use of the Rooftop Equipment. Notwithstanding the
                  foregoing, Tenant's right to install the Rooftop Equipment
                  shall be subject to the approval rights of Landlord and
                  Landlord's architect and/or engineer with respect to the plans
                  and specifications of the Rooftop Equipment, the manner in
                  which the Rooftop Equipment is attached to the roof of the
                  Building, the compliance of the Rooftop Equipment with
                  applicable governmental requirements, including air quality
                  requirements and the requirements of the City of Cambridge
                  with respect to noise and screening, and the manner in which
                  any cables and utility service are run to and from the Rooftop
                  Equipment. The precise specifications and a general
                  description of the Rooftop Equipment along with all documents
                  Landlord reasonably requires to review the installation of the
                  Rooftop Equipment (the "Plans and Specifications") shall be
                  submitted to Landlord for Landlord's written approval no later
                  than 20 days before Tenant commences to install the Rooftop
                  Equipment. Tenant shall be solely responsible for obtaining
                  all necessary governmental and regulatory approvals and for
                  the cost of installing, operating, maintaining and removing
                  the Rooftop Equipment. Tenant shall notify Landlord upon
                  completion of the installation of the Rooftop Equipment. If
                  Landlord determines that the Rooftop Equipment does not comply
                  with the approved Plans and Specifications, that the Building
                  has been damaged during installation of the Rooftop Equipment
                  or that the installation was defective, Landlord shall notify
                  Tenant of any noncompliance or detected problems and Tenant
                  immediately shall cure the defects. If the Tenant fails to
                  immediately cure the defects, Tenant shall pay to Landlord
                  upon demand the cost, as reasonably determined by Landlord, of
                  correcting any defects and repairing any damage to the
                  Building caused by such installation. If at any time,
                  Landlord, in its sole discretion, deems it necessary,Tenant
                  shall provide and install, at Tenant's sole

                                       20

<PAGE>

                  cost and expense, appropriate aesthetic screening, reasonably
                  satisfactory to Landlord, for the Rooftop Equipment.

         B.       Landlord agrees that Tenant, upon reasonable prior written
                  notice to Landlord, shall have access to the roof of the
                  Science Building and the Roof Space for the purpose of
                  installing, maintaining, repairing and removing the Rooftop
                  Equipment, and its appurtenances, if any, all of which shall
                  be performed by Tenant or Tenant's authorized representative
                  or contractors, which shall be approved by Landlord, at
                  Tenant's sole cost and risk. It is agreed, however, that only
                  authorized engineers, employees or properly authorized
                  contractors of Tenant or persons under their direct
                  supervision will be permitted to have access to the roof of
                  the Science Building and the Roof Space. Tenant further agrees
                  to exercise firm control over the people requiring access to
                  the roof of the Science Building and the Roof Space in order
                  to keep to a minimum the number of people having access to the
                  roof of the Science Building and the Roof Space and the
                  frequency of their visits.

         C.       It is further understood and agreed that the installation,
                  maintenance, operation and removal of the Rooftop Equipment
                  and any appurtenances is not permitted to damage the Science
                  Building or the roof thereof, or interfere with the use of the
                  Science Building and roof by Landlord. Tenant agrees to be
                  responsible for any damage caused to the roof or any other
                  part of the Science Building, which may be caused by Tenant or
                  any of its agents or representatives.

         D.       Tenant agrees to install only equipment which will not cause
                  unreasonable interference to Landlord or existing tenants of
                  the Building. In the event Tenant's equipment causes such
                  interference, Tenant will take any steps necessary to
                  eliminate the interference. If said interference cannot be
                  eliminated within a reasonable period of time, in the judgment
                  of Landlord, then Tenant agrees to remove the Rooftop
                  Equipment from the Roof Space.

         E.       Tenant shall, at its sole cost and expense, and at its sole
                  risk, install, operate and maintain the Rooftop Equipment in a
                  good and workmanlike manner, and in compliance with all
                  Building, electric, communication, and safety codes,
                  ordinances, standards, regulations and requirements, now in
                  effect or hereafter promulgated, of the Federal Government,
                  and of the state, city and county in which the Building is
                  located, including without limitation, all requirements of the
                  City of Cambridge. Under this Lease, the Landlord and its
                  agents assume no responsibility for the licensing, operation
                  and/or maintenance of Tenant's equipment. The Rooftop
                  Equipment shall be connected to Landlord's power supply in
                  strict compliance with all applicable Building, electrical,
                  fire and safety codes. Neither Landlord nor its agents shall
                  be liable to Tenant for any stoppages or shortages of
                  electrical power furnished to the Rooftop Equipment or the
                  Roof Space because of any act, omission or requirement of the
                  public utility serving the Building, or the act or omission of
                  any other tenant, invitee or licensee or their respective
                  agents, employees or contractors, or for any other cause
                  beyond the reasonable control of Landlord, and Tenant shall
                  not be entitled to any rental abatement for any such stoppage
                  or shortage of electrical power. Neither Landlord nor its
                  agents shall have any responsibility or liability for the
                  conduct or safety of any of Tenant's representatives, repair,
                  maintenance

                                       21

<PAGE>

                  and engineering personnel while in or on any part of the
                  Building or the Roof Space.

         F.       Except for the generator, the Rooftop Equipment and any
                  appurtenances thereto shall remain the personal property of
                  Tenant, and shall be removed by Tenant at its own expense at
                  the expiration or earlier termination of this Lease or
                  Tenant's right to possession hereunder. Tenant shall repair
                  any damage caused by such removal, including the patching of
                  any holes to match, as closely as possible, the color
                  surrounding the area where the equipment and appurtenances
                  were attached. Tenant agrees to maintain all of the Tenant's
                  equipment placed on or about the roof or in any other part of
                  the Building in proper operating condition and maintain same
                  in satisfactory condition as to appearance and safety in
                  Landlord's sole discretion. Such maintenance and operation
                  shall be performed in a manner to avoid any interference with
                  any other tenants or Landlord. Tenant agrees that at all times
                  during the Term, it will keep the roof of the Building and the
                  Roof Space free of all trash or waste materials produced by
                  Tenant or Tenant's agents, employees or contractors. It is
                  expressly agreed that the generator shall remain on the Roof
                  Space and shall become the property of Landlord upon the
                  expiration of the Term or earlier termination thereof.

         G.       In light of the specialized nature of the Rooftop Equipment,
                  Tenant shall be permitted to utilize the services of its
                  choice for installation, operation, removal and repair of the
                  Rooftop Equipment and its appurtenances, subject to the
                  reasonable approval of Landlord. Notwithstanding the
                  foregoing, Tenant must provide Landlord with prior written
                  notice of any such installation, removal or repair and
                  coordinate such work with Landlord in order to avoid voiding
                  or otherwise adversely affecting any warranties granted to
                  Landlord with respect to the roof. If necessary, Tenant, at
                  its sole cost and expense, shall retain any contractor having
                  a then existing warranty in effect on the roof to perform such
                  work (to the extent that it involves the roof), or, at
                  Tenant's option, to perform such work in conjunction with
                  Tenant's contractor.

         H.       Tenant shall not allow any provider of generators or satellite
                  dishes or related services ("Rooftop Equipment Services") to
                  locate any equipment on the roof of the Science Building or in
                  the Roof Space for any purpose whatsoever, nor may Tenant use
                  the Roof Space and/or Rooftop Equipment to provide Rooftop
                  Equipment Services to an unaffiliated tenant, occupant or
                  licensee of another building, or to facilitate the provision
                  of Rooftop Equipment Services on behalf of another Rooftop
                  Equipment Services provider to an unaffiliated tenant,
                  occupant or licensee of the Science Building or any other
                  building.

         I.       Tenant acknowledges that Landlord may at some time establish a
                  standard license agreement (the "License Agreement") with
                  respect to the use of roof space by tenants of the Building.
                  Tenant, upon request of Landlord, shall enter into such
                  License Agreement with Landlord provided that such agreement
                  does not materially alter the rights of Tenant hereunder with
                  respect to the Roof Space.

         J.       Tenant specifically acknowledges and agrees that the terms and
                  conditions of Article XIV of the Lease (Indemnity and Waiver
                  of Claims) shall apply with full

                                       22

<PAGE>

                  force and effect to the Roof Space and any other portions of
                  the roof accessed or utilized by Tenant, its representatives,
                  agents, employees or contractors.

         K.       If Tenant defaults under any of the terms and conditions of
                  this Section, and Tenant fails to cure said default within the
                  time allowed by Article XIX of the Lease, Landlord shall be
                  permitted to exercise all remedies provided under the terms of
                  the Lease.

                                       23

<PAGE>

                                    EXHIBIT F

                             FORM OF NOTICE OF LEASE

                                 NOTICE OF LEASE

         Notice is hereby given, pursuant to the provisions of Chapter 183,
Section 4 and Chapter 185, Section 71 of the Massachusetts General Laws, of the
following Lease:

         LANDLORD:         MA - Riverview/245 First Street, L.L.C.
                           c/o Equity Office Properties Trust
                           245 First Street
                           Cambridge, Massachusetts 02142

         TENANT:           Viacell, Inc.
                           245 First Street
                           Cambridge, Massachusetts 02142

         DATE OF
         EXECUTION:        As of December ___, 2003

         PREMISES:         42,944 square feet of rentable floor area located on
                           the 15th floor of the building known as the Office
                           Building, 245 First Street, Cambridge, Massachusetts
                           02142, ("Office Building") and suite numbers 1000 and
                           2000 on the 1st and 2nd floors of the building known
                           as the Science Building, 245 First Street, Cambridge,
                           Massachusetts 02142 ("Science Building") together
                           with the right in common with others to use the
                           Common Areas (as defined in the Lease) of the
                           buildings known as the Office Building and the
                           Science Building in the Cambridge Science Center, 245
                           First Street, Cambridge, Massachusetts 02142
                           (collectively, the "Buildings"), the parcel(s) of
                           land on which the Buildings are located and, the
                           garage and other improvements serving the Buildings,
                           if any, and the parcel(s) of land on which they are
                           located.

                           Tenant has rights to expand the Premises as described
                           in the Option to Expand, below.

                           For Landlord's title see _________________________.

         TERM:             Commencing on the Lab Rent Commencement Date and
                           continuing for a period of ten (10) years, subject to
                           the Options to Extend both described below.

         TERMINATION

                                       24

<PAGE>

         RIGHTS:           Tenant has the right to terminate the Lease with
                           respect to that portion of the Premises located in
                           the Office Building on the sixth anniversary of the
                           commencement date of the Lease, upon the terms and
                           conditions set forth in the Lease.

         OPTIONS TO        Tenant may extend the term for three (3) additional
         EXTEND:           periods of five (5) years, on the terms and
                           conditions set forth in the Lease.

         OPTION TO
         EXPAND:           Tenant has a right until December 31, 2004 to expand
                           the Premises onto the balance of the 2nd floor of the
                           Science Building and the 16A Space on the 16th floor
                           of the Office Building on the terms and conditions
                           set forth in the Lease.

         RIGHT OF
         FIRST OFFER:      Tenant has a right of first offer during the
                           Term with respect to the 2nd and 3rd floors of
                           Science Building and the 14th, 16th and 17th floors
                           of the Office Building on the terms and conditions
                           set forth in the Lease.

         EXTERIOR
         SIGNAGE:          Appurtenant to the Premises, Tenant has the right to
                           install, repair, maintain and replace one (1) sign on
                           the exterior of the building known as the Science
                           Building, 245 First Street, Cambridge, Massachusetts
                           at the location, and on the terms and conditions set
                           forth in the Lease.

         The Lease contains additional terms and conditions not enumerated
         herein. This instrument is executed as a notice of the Lease only and
         shall not be deemed to vary any terms and conditions of the Lease.

                         [SIGNATURES ON FOLLOWING PAGE.]

                                       25

<PAGE>

         WITNESS, the execution hereof under seal as of this ___ day of
December, 2003.

                                    LANDLORD:

                                    MA-RIVERVIEW/245 FIRST STREET,
                                    L.L.C., a Delaware limited liability company


                                    By: By: Equity Office Management, L.L.C., a
                                            Delaware limited liability company,
                                            its non-member manager

                                            By: ______________________

                                            Name: ____________________

                                            Its: Authorized Signatory

                                     TENANT:

                                     VIACELL, INC.

                                     By:___________________________
                                        Name:
                                        Title:

                                     By:___________________________
                                        Name:
                                        Title:

                                       26

<PAGE>

STATE OF ___________ )
                     ) ss.
COUNTY OF___________ )                                   _____________ __, 2003

         Then personally appeared before me the above-named ___________________,
the ____________ of Equity Office Management, L.L.C. agent for MA-Riverview/245
First Street, L.L.C. and acknowledged the foregoing to be his/her free act and
deed and the free act and deed of MA-Riverview/245 First Street, L.L.C.

                                       Notary Public:
                                       My Commission Expires:

                                       27

<PAGE>

                          COMMONWEALTH OF MASSACHUSETTS

         ____________, ss.                              _______________ __, 2003

         Then personally appeared before me the above-named ________________,
the ____________ of Viacell, Inc., and acknowledged the foregoing to be his/her
free act and deed and the free act and deed of Viacell, Inc.

                                       Notary Public:
                                       My Commission Expires:

                          COMMONWEALTH OF MASSACHUSETTS

         ____________, ss.                              _______________ __, 2003

         Then personally appeared before me the above-named _________________,
the ____________ of Viacell, Inc., and acknowledged the foregoing to be his/her
free act and deed and the free act and deed of Viacell, Inc.

                                       Notary Public:
                                       My Commission Expires:

                                       28

<PAGE>

                                    EXHIBIT G

                                EXTERIOR SIGNAGE

       (To be attached upon submittal by Tenant and approval by Landlord)

                                        1

<PAGE>

                                    EXHIBIT H

                                 OFFERING SPACE

                                        1

<PAGE>

                                    EXHIBIT I

                               COMMENCEMENT LETTER

Date ______________________

Tenant ____________________
Address ___________________
        ___________________

Re:      Commencement Letter with respect to that certain Lease dated as of the
         _____ day of December, 2003, by and between EOP-RIVERVIEW/245 FIRST
         STREET, L.L.C., A DELAWARE LIMITED LIABILITY COMPANY, as Landlord, and
         VIACELL, INC., as Tenant, for 42,943 rentable square feet in the
         Building located at 245 First Street, Cambridge, Massachusetts 02142.

Dear __________________:

         In accordance with the terms and conditions of the above referenced
Lease, Tenant accepts possession of the Premises and agrees:

1.       The Lab Rent Commencement Date of the Lease is _______________________;

2.       The Termination Date of the Lease is ____________________________.

         Please acknowledge your acceptance of possession and agreement to the
terms set forth above by signing all 3 counterparts of this Commencement Letter
in the space provided and returning 2 fully executed counterparts to my
attention.

Sincerely,

________________________
Property Manager

Agreed and Accepted:

         Tenant:______________________

         By: _________________________
         Name: _______________________
         Title: ______________________
         Date: _______________________

                                        2

<PAGE>

                                    EXHIBIT J

                           COMMENCEMENT DATE AGREEMENT

         Reference is made to that certain Lease by and between
EOP-RIVERVIEW/245 FIRST STREET, L.L.C., A DELAWARE LIMITED LIABILITY COMPANY,
Landlord and ________________________, Tenant, and dated __________, a Notice of
which is filed for registration with the Suffolk Registry District of the Land
Court as Document No._____.

         Landlord and Tenant hereby confirm and agree that the Lab Rent
Commencement Date under the Lease is __________, 200__.

         This Commencement Date Agreement is executed as a sealed instrument as
of __________, 200_.

                                        3

<PAGE>

         IN WITNESS WHEREOF, Landlord and Tenant have executed this exhibit as
of the day and year first above written.

WITNESS/ATTEST:                   LANDLORD:

                                  EOP-RIVERVIEW/245 FIRST STREET, L.L.C., A
                                  DELAWARE LIMITED LIABILITY COMPANY

                                  By: EOP Operating Limited Partnership, a
                                      Delaware limited partnership, its
                                      sole member

                                      By: Equity Office Properties Trust, a
                                          Maryland real estate investment trust,
                                          its general partner

/s/ Kim Ruby
----------------------------              By:/S/ Maryann Gilligan Suydam
                                             -----------------------------------
Name (print): Kim Rudy                    Name: MARYANN GILLIGAN SUYDAM

Name (print):_______________              Title: Senior Vice President
                                                 Boston Region

WITNESS/ATTEST:                   TENANT:  VIACELL, INC., A DELAWARE CORPORATION

/s/ Sara McManus                  By: EXHIBIT - DO NOT EXECUTE
----------------------------

Name(print): Sara                 Name: EXHIBIT - DO NOT EXECUTE
McManus_________
_____________________________     Title: EXHIBIT - DO NOT EXECUTE

Name (print): _______________

                               [ACKNOWLEDGEMENTS]

                                        4

<PAGE>

                                    EXHIBIT K

                        LIST OF ENVIRONMENTAL SUBSTANCES

                                        5

<PAGE>

                                    EXHIBIT L

                          RIGHT OF FIRST REFUSAL SPACE

                                        6

<PAGE>

                                    EXHIBIT M

                             CLEANING SPECIFICATIONS

                       JANITORIAL CLEANING SPECIFICATIONS

Janitorial services will cover the specifications as follows and it is expected
that all building areas will be maintained and the necessary spot cleanings
performed to ensure the continued satisfaction of the EOP client and employee
base. Services shall include, but not be limited to, the following:

1)   OFFICE AREAS (ALL FLOORS)

     a)   NIGHTLY SERVICES (FIVE (5) NIGHTS PER WEEK)

          i)   Empty all waste receptacles. Clean, and reline when needed.
               Remove material to designated areas.

          ii)  Remove recycling material when container is full (see weekly)

          iii) Vacuum all carpeted main traffic and use areas, including
               conference rooms, reception areas, interior stairwells, hallways
               and corridors with the exception of individual offices (see
               weekly). Spot vacuum/clean all others areas as needed.

          iv)  Wash and sanitize all drinking fountains.

          v)   Damp mop spillage in uncarpeted office areas.

          vi)  Spot clean carpets to remove light spillage. Report large spills
               and stains to supervisor.

          vii) Assure all designated locked doors are closed after area has been
               cleaned.

          viii) Activate all alarm systems as instructed by occupant (if
               applicable).

          ix)  Arrange chairs at desk and conference room tables and turn off
               lights upon exiting.

          x)   Clean conference room tables and remove any remaining food items.

          xi)  Clean and sweep all lunchroom/eating areas. Wash and wipe tables
               and counter tops and clean sinks.

          xii) Remove scuff marks on floor as needed.

     b)   WEEKLY SERVICES

          i)   Remove recycling material when container is full.

          ii)  Vacuum all carpeted areas completely, private offices and cubicle
               interiors, desk knee area spaces and under waste containers.

          iii) Dust and wipe clean with damp or treated cloth all office
               furniture, files, and cubicle partition tops, (DO NOT MOVE
               PAPERS).

                                        7

<PAGE>

          iv)  Remove all finger marks and smudges from all vertical surfaces,
               including doors, door frames, around light switches, private
               entrance glass, and partitions.

          v)   Damp wipe and polish all glass furniture tops.

          vi)  Damp mop hard surfaced floors and/or uncarpeted surface floors.

          vii) Sweep uncarpeted floors employing dust control techniques with
               exception of lunchroom (which is to be performed nightly)

     c)   MONTHLY SERVICES

          i)   Dust and wipe clean chair bases and arms, telephones, cubicle
               shelves, window sills, relite ledges and all other horizontal
               surfaces as needed to maintain clean appearance (DO NOT MOVE
               PAPERS).

          ii)  Edge vacuum all carpeted areas, as needed.

2)   RESTROOMS

     a)   NIGHTLY SERVICES (FIVE (5) NIGHTS PER WEEK)

          i)   Clean and sanitize all mirrors, brightwork, countertops and
               enameled surfaces.

          ii)  Wash and disinfect all basins, urinals, bowls (cleaning underside
               of rim) and fixtures using scouring powder to remove stains.

          iii) Wash both sides of all toilet seats with soap and/or
               disinfectant.

          iv)  Clean flushometers, piping, toilet seat hinges, and other metal.

          v)   Empty, clean, and damp wipe all waste receptacles.

          vi)  Sweep, wet mop, and sanitize entire floor, including around
               toilet seats and under urinals.

          vii) Damp wipe all walls, partitions, doors, and outside surfaces of
               all dispensers, as needed.

          viii) Fill toilet paper, soap, towels, and sanitary napkin dispensers
               (if applicable).

          ix)  Wash and disinfect all showers including shower walls, floors,
               brightwork and doors (if applicable).

          x)   Replace trash liner.

     b)   WEEKLY SERVICES

          i)   Flush water through P-trap weekly to ensure elimination of odor.

     c)   MONTHLY SERVICES

          i)   Machine scrub floors.

                                        8

<PAGE>

3)   LOBBY, ELEVATOR, CORRIDOR, INTERIOR STAIRWAYS (EXCLUDING EMERGENCY EXIT
     STAIRWAYS) AND ENTRANCE AREAS

     a)   NIGHTLY SERVICE (FIVE (5) NIGHTS PER WEEK)

          i)   Sweep and spot mop all stone, vinyl or composition lobby floors.

          ii)  Vacuum and spot clean all carpeted floor and mats.

          iii) Dust and polish all brightwork, including mirrors and elevator
               call buttons.

          iv)  Dust and polish all metal surfaces in elevators, including
               tracks, and elevator doors.

          v)   Vacuum and spot clean all carpet in elevators.

          vi)  Clean and polish all trash receptacles

          vii) Dust all fire extinguisher cabinets and/or units.

          viii) Spot clean all doors.

          ix)  All furniture should be cleaned as necessary (including
               directories)

          x)   Wash, disinfect and dry polish water coolers (if applicable).

          xi)  Clean glass entrance doors, adjacent glass panels and tracks
               (i.e. relites) (if applicable).

          xii) Spot sweep and/or spot vacuum all interior stairways (excluding
               emergency exit stairways) and landings (if applicable).

          xiii) Maintain lobby floor as recommended by manufacturer.

     b)   WEEKLY SERVICES

          i)   Wet mop all stone, vinyl or composition lobby floors (daily spot
               mopping may satisfy this need)

          ii)  Sweep and/or vacuum all interior stairways (excluding emergency
               exit stairways) and landings (if applicable).

4)   JANITORIAL ITEMS/AREAS

     a)   NIGHTLY SERVICES (FIVE (5) NIGHTS PER WEEK)

          i)   Keep janitorial rooms in a clean, neat and orderly condition.

          ii)  Maintain all janitorial carts and equipment in safe and clean
               condition.

5)   FITNESS CENTER (IF APPLICABLE) (PLEASE BREAK OUT COST AS SEPARATE BID)

     a)   NIGHTLY SERVICE

          i)   Vacuum all exposed carpeted floors.

          ii)  Spot clean all mirrors and walls.

          iii) Spray and disinfect fitness center equipment nightly

     b)   WEEKLY SERVICES

          i)   Edge vacuum all carpeted areas, as needed.

          ii)  Dust all ledges, as needed

          iii) Clean mirrors completely.

          iv)  Stocking supplies and towels

                                        9

<PAGE>

6)   LOCKER ROOMS (IF APPLICABLE)

     a)   NIGHTLY SERVICES (FIVE (5) NIGHTS PER WEEK)

          i)   Perform complete building restroom cleaning specifications to
               restroom and locker room areas.

          ii)  Clean and disinfect showers completely, including walls, doors,
               floors, and floor drains.

7)   LOADING DOCK, VAN PARKING AREAS, TRASH RECYCLING AREAS

     a)   NIGHTLY SERVICES (FIVE (5) NIGHTS PER WEEK)

          i)   Empty and reline all waste receptacles.

          ii)  Sweep ramps, loading bays and parking areas for trash and
               cigarette butts.

8)   GENERAL BUILDING COMMON AREA SERVICES

     a)   NIGHTLY SERVICE(FIVE (5) NIGHTS PER WEEK)

          i)   Spot clean and restock, as needed all janitorial service closets.

          ii)  Pick up and compact all recycle trash, including boxes in
               accordance with tenants recycle specifications.

          iii) Vacuum all garage lobbies and elevator carpets

                                       10

<PAGE>

                                    EXHIBIT N

                       CONSTRUCTION RULES AND REGULATIONS

                              RULES AND REGULATIONS

                   FOR DESIGN AND CONSTRUCTION OF TENANT WORK

1.       DEFINITIONS

         1.0 Building:              Cambridge Science Center, Cambridge MA

         1.1 Building Manager       Kathleen LaShoto, or such other individual
                                    as landlord may designate, from time to
                                    time.

         1.2 Manager of
             Engineering            Michael Gill, or such other individual as
                                    landlord may designate, from time to time.

         1.3 Assistant Property     Anne Bilodeau, or such other individual as
             Manager                landlord may designate, from time to time.

         1.4 Consultant:            Any architectural, engineering or design
                                    consultant engaged by a Tenant in connection
                                    with Tenant Work.

         1.5 Contractor:            Any Contractor engaged by Tenant of the
                                    Building for the performance of any Tenant
                                    Work, and any Subcontractor employed by any
                                    such Contractor.

         1.6 Plans:                 All architectural, electrical and mechanical
                                    construction drawings and specifications
                                    required for the proper construction of the
                                    Tenant Work.

         1.7 Regular Business:      Monday through Friday, 8:00 a.m. through
                                    6:00 p.m., holidays and weekends excluded.

         1.8 Tenant:                Any occupant of the Building.

         1.9 Tenant Work:           Any alterations, improvements, additions,
                                    repairs or installations on the building
                                    performed by or on behalf of any Tenant.

         1.10 Tradeperson:          Any employee (including without limitation,
                                    any mechanic laborer, or Tradeperson)
                                    employed by a Contractor performing Tenant
                                    Work.

2.       GENERAL

         2.1      All Tenant Work shall be performed in accordance with these
                  Rules and

                                       11

<PAGE>

                  Regulations and the applicable provisions of the Lease.

         2.2      The provisions of these Rules and Regulations shall be
                  incorporated in all agreements governing the performance of
                  all Tenant Work, including, without limitation, any agreements
                  governing services to be rendered by each Contractor and
                  Consultant.

         2.3      Except as otherwise provided in these Rules and Regulations,
                  all inquires, submissions and approvals in connection with any
                  Tenant Work shall be processed through the Building Manager.

3.       RECONSTRUCTION NOTIFICATION AND APPROVALS

         3.1      Approval to Commence Work:

                  A)       Tenant shall submit to Building Manager, for the
                           approval of the Landlord, the names of all
                           prospective Contractors prior to issuing any bid
                           packages to such Contractors.

                  B)       No Tenant Work shall be undertaken by any Contractor
                           or Tradeperson unless and until all the matters set
                           forth in Article 4.3 below have been received for the
                           Tenant Work in question and unless Building Manager
                           has approved the matters set forth in Article 4.3
                           below.

         3.2      No Tenant Work shall be performed unless, at least two weeks
                  before any Tenant Work is to begin, all of the following have
                  been provided to the Building Manager and approved. In the
                  event that Tenant proposes to change any of the following, the
                  Building Manager shall be immediately notified of such change
                  and such change shall be subject to the approval of the
                  Building Manager:

                  A)       Schedule for the work, indication start and
                           completion dates, any phasing and special working
                           hours, and also a list of anticipated shutdowns of
                           building systems.

                  B)       List of all Contractors and Subcontractors, including
                           addresses, telephone numbers, emergency (after hours)
                           telephone numbers, trades employed, and the union
                           affiliation, if any, of each Contractor and
                           Subcontractor.

                  C)       Names and telephone numbers of the supervisors of the
                           work.

                  D)       Copies of all necessary governmental permits,
                           licenses and approvals.

                  E)       Proof of current insurance, to the limits set out in
                           Exhibit A to these Rules and Regulations, naming
                           Landlord ( Equity Office Properties Trust) as
                           additional insured parties.

                  F)       Notice of the involvement of any Contractor in any
                           ongoing and/or threatened labor dispute.

                                       12

<PAGE>

                  G)       Payment, Performance and Lien Bonds from sureties
                           acceptable to Landlord, in form acceptable to
                           Landlord, naming Landlord as an additional obligee.

                  H)       Evidence that Tenant has made provision for either
                           written waivers of lien from all Contractors and
                           suppliers of material, or other appropriate
                           protective measures approved by Landlord.

                           I)       A pre-existing condition survey as specified
                                    in Article 7.2 c.

3.3      Reporting Incidents:

         All accidents, disturbances, labor disputes or threats thereof, and
         other noteworthy events pertaining to the Building or the Tenant's
         property shall be reported immediately to the Building Manager. A
         written report must follow within 24 hours.

4.       CONSTRUCTION SCHEDULE

         4.1      Coordination:

                  A)       All Tenant Work shall be carried out expeditiously
                           and with minimum disturbance and disruption to the
                           operation of the Building and without causing
                           discomfort, inconvenience, or annoyance to any of the
                           other tenants or occupants of the Building or the
                           public at large.

                  B)       All schedules for the performance of construction,
                           including materials deliveries, must be coordinated
                           through the Building Manager. The Building Manager
                           shall have the right, without incurring any liability
                           to any Tenant, to stop activities and/or to require
                           rescheduling of Tenant Work based upon adverse impact
                           on the tenants or occupants of the Building or on the
                           maintenance or operation of the Building.

                  C)       If any Tenant Work requires the shutdown of risers
                           and mains for electrical, mechanical, sprinkler, and
                           plumbing work, such work shall be supervised by a
                           representative of Landlord, the cost of which shall
                           be charged directly to the tenant at the prevailing
                           building rate. No Tenant Work will be performed in
                           the Building's mechanical or electrical equipment
                           rooms without both Landlord's prior approval and the
                           supervision of a representative of Landlord, the cost
                           of which shall be reimbursed by the Tenant to the
                           Landlord. Tenant shall provide the Building Manager
                           with at least one week to schedule such work.

         4.2      Time Restrictions:

                  A)       Subject to Paragraph 5.1 of these Rules and
                           Regulations, general construction work will generally
                           be permitted at all times, including during Regular
                           Business hours.

                  B)       Tenant shall provide the Building Manager with at
                           least forty eight (48) hours notice before proceeding
                           with Special Work, as hereinafter defined, and such
                           Special Work will be permitted only at times agreed
                           to by the

                                       13

<PAGE>

                           Building Manager during periods outside of Regular
                           Business Hours. "Special Work" shall be defined as
                           the following operations:

                           1. All utility disruptions, shutoffs and turnovers.

                           2. Activities involving high levels of noise,
                              including demolition, coring, drilling and
                              ramsetting.

                           3. Activities resulting in excessive dust or odors,
                              including demolition, staining and spray painting.

                           4. All construction work which will require access to
                              multi-tenant areas or other tenant areas.

                  C)       The delivery of construction materials to the
                           Building, their distribution within the Building, and
                           the removal of waste materials shall also be confined
                           to periods outside Regular Business Hours, unless
                           otherwise specifically permitted in writing by the
                           Building Manager. Costs for use of the freight
                           elevator after Regular Business Hours shall be billed
                           directly to such tenant at the then prevailing rate.

                  D)       If coordination, labor disputes or other
                           circumstances require, the Building Manager may
                           change the hours during which regular construction
                           work can be scheduled and/or restrict or refuse entry
                           to and exit from the Building by any Contractor.

5.       CONTRACTOR PERSONNEL

         5.1      Work in History:

                  A)       All Contractors shall be responsible for employing
                           skilled and competent personnel and suppliers who
                           shall abide by the rules and regulations herein set
                           forth as amended from time to time by Landlord.

                  B)       No Tenant shall at any time, either directly or
                           indirectly, employ, permit the employment, or
                           continue the employment of any contractor if such
                           employment or continued employment will or does
                           interfere or cause any labor disharmony, coordination
                           difficulty, delay or conflict with any other
                           contractors engaged in construction work in or about
                           the Building or the complex in which the Building is
                           located.

C)       Should a work stoppage or other action occur anywhere in or about the
         Building as a result of the presence, anywhere in the Building, or a
         Contractor engaged directly or indirectly by a Tenant, or should such
         Contractor be deemed by Landlord to have violated any applicable rules
         or regulations, then upon twelve hours written notice, Landlord may,
         without incurring any liability to Tenant or said contractor, require
         any such Contractor to vacate the premises demised by such Tenant and
         the Building, and to cease all further construction work therein.

         5.2      Conduct:

                                       14

<PAGE>

                  A)       While in or about the Building, all Tradepersons
                           shall perform in a dignified, quiet, courteous, and
                           professional manner at all times. Tradepersons shall
                           wear clothing suitable for their work and shall
                           remain full attired at all times. All Contractors
                           will be responsible for their Tradepersons' proper
                           behavior and conduct.

                  B)       The Building Manager reserves the right to remove any
                           one who, or any contractor which; is causing a
                           disturbance to any tenant or occupant of the Building
                           or any other person using or servicing the Building;
                           is interfering with the work of others; or is in any
                           other way displaying conduct or performance not
                           compatible with the Landlord's standards.

         5.3      Access:

                  A)       All Contractors and Tradepersons shall contact the
                           Building Manager prior to commencing work, to confirm
                           work location and Building access, including elevator
                           usage and times of operation. Access to the Building
                           before and after Regular Business Hours or any other
                           hours designated from time to time by the Building
                           Manager and all day on weekends and holidays will
                           only be provided when forty eight (48) hours advanced
                           notice is given to the Building Manager.

                  B)       No Contractor or Tradepersons will be permitted to
                           enter any private or public space in the Building,
                           other than the common areas of the Building necessary
                           to give direct access to the premises of Tenant for
                           which he has been employed, without the prior
                           approval of the Building Manager.

                  C)       All Contractors and Tradepersons must obtain
                           permission from the Building Manager prior to
                           undertaking work in any space outside of the Tenant's
                           premises. This requirement specifically includes
                           ceiling spaces below the premises where any work
                           required must be undertaken at the convenience of the
                           affected Tenant and outside of Regular Business
                           Hours. Contractors undertaking such work shall ensure
                           that all work, including work required to reinstate
                           removed items and cleaning, be completed prior to
                           opening of the next business day. Any cleaning or
                           repairs costs incurred by Landlord, as a result of
                           work outside the construction area shall be charged
                           to the Tenant.

                  D)       Contractors shall ensure that all furniture,
                           equipment and accessories in areas potentially
                           affected by any Tenant Work shall be adequately
                           protected by means of drop cloths or other
                           appropriate measures. In addition, all Contractors
                           shall be responsible for maintaining security to the
                           extent required by the Building Manager.

                  E)       Temporary access doors for tenant construction areas
                           connecting with a public corridor will be building
                           standards, i.e., door, frame, hardware and lockset. A
                           copy of the key will be furnished to the Building
                           Manager.

         5.4      Safety:

                  A)       All Contractors shall police ongoing construction
                           operations and activities

                                       15

<PAGE>

                           at all times, keeping the premises orderly,
                           maintaining cleanliness in and about the premises,
                           and ensuring safety and protection of all areas,
                           including truck docks, elevators, lobbies, and all
                           other public areas which are used for access to the
                           premises.

                  B)       All Contractors shall appoint a supervisor who shall
                           be responsible for all safety measures, as well as
                           for compliance with all applicable government laws,
                           ordinances, rules and regulations such as, for
                           example, "OSHA" and "Right-to-Know" legislation.

                  C)       Any damage caused by Tradepersons or other Contractor
                           employees shall be the responsibility of the Tenant
                           employing the Contractor. Costs for repairing such
                           damage shall be charged directly to such Tenant.

         5.5      Parking:

                  A)       No parking of contractor or sub-contractor vehicles
                           will be provided in the truck dock, handicapped or
                           fire access lanes, or any private ways in or
                           surrounding the property. Vehicles so parked will be
                           towed at the expense of the Tenant who has engaged
                           the Contractor for whom the owner of such vehicle is
                           employed.

                  B)       Garage parking is available on-site at the prevailing
                           rate. Rates may be obtained from the garage
                           management office.

6.       BUILDING MATERIALS

         6.1      Delivery:

                  A)       All deliveries of construction materials shall be
                           made at the predetermined times approved by the
                           Building Manager and shall be effected safely and
                           expeditiously only at the location determined by the
                           Building Manager.

         6.2      Transportation in Building:

                  A)       Distribution of materials from delivery point to the
                           work area in the Building shall be accomplished with
                           the least disruption to the operation of the Building
                           possible. Elevators will be assigned for material
                           delivery and will be controlled by the Building
                           Management.

                  B)       Contractors shall provide adequate protection to all
                           carpets, wall surfaces, doors and trim in all public
                           areas through which materials are transported.
                           Contractors shall continuously clean all such areas.
                           Protective measures shall include runners over
                           carpet, padding in elevators and any other measures
                           determined by the Building Manager.

                  C)       Any damage caused to the Building through the
                           movement of construction materials or otherwise shall
                           be the responsibility of Tenant who has engaged the
                           Contractor involved. Charges for such damage will be
                           submitted by the Landlord directly to the Tenant.
                           Prior to the

                                       16

<PAGE>

                           commencement of tenant work, a pre-existing condition
                           survey shall be submitted to the Building Manager.
                           Such survey shall be used at the completion of the
                           project to determine, if any, the extent of damage to
                           the building systems or finishes.

         6.3      Storage and Placement:

                  A)       All construction materials shall be stored only in
                           the premises where they are to be installed. No
                           storage of materials will be permitted in any public
                           areas, loading docks or corridors leading to the
                           premises.

                  B)       No flammable, toxic, or otherwise hazardous materials
                           may be brought in or about the Building unless: (i)
                           authorized by the Building Manager, (ii) all
                           applicable laws, ordinances, rules and regulations
                           are complied with, and (iii) all necessary permits
                           have been obtained. All necessary precautions shall
                           be taken by the contractor handling such materials
                           against damage or injury caused by such materials.

                  C)       All materials required for the construction of the
                           premises must comply with Building Standards, must
                           conform with the plans and specifications approved by
                           Landlord, and must be installed in the locations
                           shown on the drawings approved by the Landlord.

                  D)       All work shall be subject to reasonable supervision
                           and inspection by Landlord's Representative.

                  E)       No alterations to approved plans will be made without
                           prior knowledge and approval of the Building Manager.
                           Such changes shall be documented on the as-build
                           drawings required to be delivered to Landlord
                           pursuant to Paragraph 10 of the rules and
                           regulations.

                  F)       All protective devices (e.g., temporary enclosures
                           and partitions) and materials, as well as their
                           placement, must be approved by the Building Manager.

                  G)       It is the responsibility of Contractors to ensure
                           that the temporary placement of materials does not
                           impose a hazard to the Building or its occupants,
                           either through overloading, or interference with
                           Building systems, access, egress or in any other
                           manner whatsoever.

                  H)       All existing and/or new openings made through the
                           floor slab for piping, cabling, etc. must be packed
                           solid with fiberglass insulation to make opening
                           smoke tight. All holes in the floor slab at abandoned
                           floor outlets, etc. will be filled with solid
                           concrete.

         6.4      Salvage and Waste Removal:

                  A)       All rubbish, waste and debris shall be neatly and
                           cleanly removed from the Building by Contractors
                           daily unless otherwise approved by the Building
                           Manager. The Building's trash compactor shall not be
                           used for construction or other debris. For any
                           demolition and debris, each

                                       17

<PAGE>

                           Contractor must make arrangements with the Building
                           Manager for the scheduling and location of an
                           additional dumpster to be supplied at the cost of the
                           Tenant engaging such Contractor. Where, in the
                           opinion of the Building Manager, such arrangements
                           are not practical, such Contractors will make
                           alternative arrangements for removal at the cost of
                           the Tenant engaging such Contractors.

                  B)       Toxic or flammable water is to be properly removed
                           daily and disposed of in full accordance with all
                           applicable laws, ordinances, rules and regulations.

                  C)       Contractors shall, prior to removing any item
                           (including, without limitation, building standard
                           doors, frames and hardware, light fixtures, ceiling
                           diffusers, ceiling exhaust fans, sprinkler heads,
                           fire horns, ceiling speakers and smoke detectors)
                           from the Building, notify the Building Manager that
                           it intends to remove such item. At the election of
                           Building Manager, Contractors shall deliver any such
                           items to the Building Manager. Such items will be
                           delivered, without cost, to an area designated by the
                           Building Manager which area shall be within the
                           Building or the complex in which the Building is
                           located.

7.       PAYMENT OF CONTRACTORS

                  Tenant shall promptly pay the cost of all Tenant Work so that
                  Tenant's premises and the Building shall be free of liens for
                  labor or materials. If any mechanic's lien is filed against
                  the Building or any part thereof which is claimed to be
                  attributable to the Tenant, its agents, employees or
                  contractors, Tenant shall give immediate notice of such lien
                  to the Landlord and shall promptly discharge the same by
                  payment or filing any necessary bond within 10 days after
                  Tenant has first notice of such mechanic's lien.

8.       CONFLICT BETWEEN RULES AND REGULATIONS AND LEASE

In the event of any conflict between the Lease and these Rules and Regulations,
the terms of the Lease shall control.

                                       18

<PAGE>

                                    EXHIBIT A

                                    CAMBRIDGE
                              BASE BUILDING CHARGES

Contractors desiring to work on the Building Systems must coordinate all work
with the Management Office at 621-3441.

All work must be scheduled a minimum of one business day prior to the start of
work. A work order will be issued listing the system affected and the time of
shutdown. No work will commence until the work order has been signed by an
authorized representative of the construction company.

Contractors must obtain credit approval from the Office of the building prior to
any work authorization.

                               FIRE ALARM SHUTDOWN

<TABLE>
<S>                                  <C>                 <C>
Base Charges                         Shutdown            Reconnect
8:00 a.m to 5:00 p.m.                $125.00                N/C

5:00 p.m. to 8:00 a.m.               $175.00              $175.00
Saturday                             $225.00              $225.00
Sunday                               $250.00              $250.00
</TABLE>

Additional Charges

Labor charge (per person) for Fire Alarm Watch (required when servicing or
testing fire alarm system)

<TABLE>
<S>                         <C>
5:00 p.m. to 8:00 a.m.      $60.00 per hour
Saturday                    $60.00 per hour
Sunday                      $80.00 per hour
</TABLE>

Labor charge (per person) for Sprinkler System Shutdown (when engineers are
draining, filling or on standby).

<TABLE>
<S>                         <C>
5:00 a.m. to 8:00 a.m.      $60.00 per hour
Saturday                    $60.00 per hour
Sunday                      $80.00 per hour
</TABLE>

Contractor may not proceed with any work until authorization to begin work has
been obtained from engineering. This is in effect each day Life Safety work is
being performed.

                                       19

<PAGE>

                                ELEVATOR CHARGES

Depends on the Special Request?

                                       20

<PAGE>

                                    EXHIBIT B

                                       TO

                              RULES AND REGULATIONS

                   FOR DESIGN AND CONSTRUCTION OF TENANT WORK

INSTALLATION OF CABLES

         1.1      Computer and Telephone Cables

                  1.1.1    Layout

                           A layout of cables must be submitted to the Building
                           Manager for approval prior to installation.

                  1.1.2    Installation

                           A)       Cables installed above the ceiling must be
                                    Teflon coated or encased in metal conduit.

                           B)       Cables must be tagged every 15' and color
                                    coded.

                           C)       Cables must be properly affixed to the
                                    framing above the duct work so that they are
                                    self-supporting. Do not fasten to light
                                    fixtures.

                           D)       Cables must not sag and will be installed in
                                    the shortest possible runs.

                           E)       Connections (connectors, splices, etc.) must
                                    be securely installed so that they will not
                                    pull apart if cable is accidentally touched
                                    or pulled.

         1.2      Electrical Floor Outlet Cables

                  1.2.1    Layout

                           A layout of cables must be submitted to the Building
                           Manager for approval prior to installation.

                  1.2.2    Installation

                           A)       Cables must be tagged every 15'and color
                                    coded.

                                       21

<PAGE>

                           B)       Runs will be as short and as free of slack
                                    as possible.

                           C)       Cables are to be installed in tenant's own
                                    ceiling then down partitions into the
                                    ceiling of the tenant below.

                           D)       Cables must be properly secured so that they
                                    are self supporting.

                           E)       All connections (connectors, splices, etc.)
                                    must be located in the tenant's own space to
                                    avoid damage from below.

                           F)       Cables must be secured with clamps where
                                    they pass through the floor to prevent
                                    connections from separating.

                           G)       Where feasible, install cables above duct
                                    work and other materials in the ceiling.

         1.3      Electrical Work

                  All power wiring in Mechanical Rooms, Electric Rooms and
                  Telephone rooms must be in EMT.

         1.4      Security System

                  1.4.1    Layout

                           A layout of the security system wiring must be
                           submitted to the Building Manager for approval prior
                           to installation.

                  1.4.2    Installation

                           A)       All wiring for the security system will be
                                    tagged every 15'.

                                       22

<PAGE>

                                    EXHIBIT C

                                       TO

                              RULES AND REGULATIONS

                   FOR DESIGN AND CONSTRUCTION OF TENANT WORK

1.       WELDING AND HEAT CUTTING WORK

         1.1      Definition

                  Welding and heat cutting activities as well as soldering and
                  brazing shall be included in "Special Work" category as
                  defines in section 5.2 (B). They require the tenant to provide
                  the Building Manager with at least forty eight (48) hours
                  notice before proceeding and must be performed during periods
                  outside of regular business hours.

         1.2      Permitting

                  The Contractor must obtain a permit from the Cambridge Fire
                  Department before commencing work.

         1.3      Precautions

                  Because welding and other hot work is a fire hazard, the
                  Contractor must observe the following precautions and
                  procedures (when possible, work should be done in a
                  non-combustible area):

                  A)       No sprinkler impairments are allowed during "Special
                           Work" and while the fire watch is in place. The
                           sprinkler impairment restriction is for the floor the
                           "Special Work" is taking place on and the floor above
                           and the floor below.

                  B)       Smoke Detectors in the work area should be
                           de-activated by the Building Manager for the duration
                           of the work. The Building Manager will re-activate
                           smoke detectors when the work is complete.

                  C)       Combustible materials shall be located at least 50
                           feet from hot work operations and shall be covered
                           with non-combustible materials.

                  D)       All flammable liquids and other hazards must be
                           removed.

                  E)       All floor and wall openings must be covered with
                           non-combustible material.

                  F)       Containers, tanks, ducts, etc. must be cleaned and
                           purged of flammable vapors, liquids, dusts etc.

                                       23

<PAGE>

                  G)       A minimum of one multipurpose ABC rated portable fire
                           extinguisher must be provided within 10 feet of the
                           work area. The extinguisher should be fully charged
                           and have been properly serviced within the last year.
                           It is the responsibility of the contractor to provide
                           fire extinguishers. Building extinguishers should not
                           be used. A standpipe hose should also be readily
                           available.

                  H)       A fire watch should be maintained on the floor levels
                           where the work was conducted plus the next two floors
                           below for at least one hour after welding or burning
                           has ceased. The fire watch shall consist of a member
                           of the Cambridge Fire Department. If there is a
                           chance that slag could enter into a utility or
                           elevator shaft, then the fire watch should cover the
                           base of the shaft as well as the intermediate floors.

                  I)       A member of the Cambridge Fire Department shall be on
                           site, at Tenant cost, for all "Special Work".

GENERAL NOTES: All contractors to adhere to EOP Indoor Air Quality Guidelines.
Contractor to coordinate with building engineer for smoke detector bypass.

A2 - GC to be responsible for obtaining any required dust permit.

Tenant card access to be independent of base building card access system.

All systems installed shall not impede access to building HVAC system for
routine maintenance.

Owner will require a copy of the air balancing report.

Length of flex duct shall not exceed five (5) feet.

All heat pumps that will be relocated shall have new ball valves located at the
unit for balancing and for isolation means. All relocated heat pumps shall have
new stainless steel flexible hoses installed.

Nylon straps shall use 5/16" self-tapping screws for attachment. Stainless Steel
straps are acceptable.

Exhaust shall comply with EOP IAQ guidelines.

GC or Electrical sub to remove all abandoned electrical wiring, conduit, and
cable. They shall also remove all abandoned Tele-data cabling and equipment.

Leak Detection System shall have audible alarm, solenoid valve on cold water
feed that will shut on water sensor activation, and drain pan under heater shall
be piped to drain.

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This should comply with EOP Leak Detection Building Standard.

Owner will require a copy of the hydraulic calculations prior to construction.

Owner will require GC to provide owner with a copy of bagging permit for smoke
detectors.

                           All electrical feeders from panel room shall be in
                           conduit per Building Riser Management Policy.

                           All electrical panels shall have type written
                           directories.

                           GC to provide owner their Lock Out Tag Out program
                           for review. If program does not meet EOP standards
                           then GC to adhere to EOP policy.

                           All fire alarm conduit to have color-coding
                           consistent with EOP Fire Alarm Riser Policy.

                           GC to provide owner with complete set of MSDS sheets
                           for any product brought onto property.

                           Owner will require a complete set of As Built
                           drawings in hard copy and in CAD at the completion of
                           the project.

                           Building fire alarm vendor will make final
                           connections to the fire alarm system.

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                          INDOOR AIR QUALITY GUIDELINES

                           FOR TENANT IMPROVEMENT WORK

PURPOSE

In today's society, it is common for individuals to spend upwards of 90% of
their time in an indoor environment, whether at work or at home which makes
planning for good IAQ an important consideration. Tenant improvement work (TIW)
can adversely affect the indoor air quality (IAQ) in tenant spaces. The
following guidelines will minimize these adverse effects by utilizing sound
Architectural, Engineering and Construction Methods. Tenants are responsible for
the design, engineering and the work performed by their consultants and
contractors. During TIW it is important to isolate the construction area from
all occupied and public areas of the building. All parties involved in
designing, approving and constructing your space have an important role to play
in keeping the workplace comfortable and free of indoor pollutants such as dust,
chemicals and volatile organic compounds that can originate from construction
materials and building furnishings. Where feasible, occupants should be involved
in decisions affecting their work environment and be considered for temporary
relocation away from construction.

Please share these guidelines with your Architects, Engineers (A/E) and
Contractors at the earliest phase of your planning. Contact the Property Manager
if you have questions about these guidelines.

CONTENTS

                  Architect and Engineers Responsibilities

                  Contractor Responsibilities Pre-Construction Phase

                  Contractor Responsibilities Construction Phase

                  Completion Phase

ARCHITECT/ENGINEERS RESPONSIBILITIES

1.   The A/E shall specify building materials, furnishes, furniture and office
     equipment with products that have the lowest toxic-emitting potential as
     compared with similar products. The Architect should contact the Property
     Manager for names of Indoor Air Quality Material Consultants for this
     information if needed. New carpet must have a green label certified by the
     Carpet and Rug Institute (CRI) and be installed according to CRI
     installation

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     guidelines.

2.   The A/E shall avoid specifying materials containing chemicals listed as
     potentially carcinogenic, mutagenic, teratogenic, neurotoxic or
     "sensitizing." The following materials will not be allowed in new
     installations.

          -    Materials containing more than trace (>0.1%) amounts of asbestos.

          -    Materials that contain halogenated hydrocarbon solvents (i.e.,
               methylene choride, tetrachloroethylene, trichloroethylene,
               trichloroethane).

          -    HVAC components internally lined with permeable manmade mineral
               fiber products unless coated with "Tuffcoat" or other tough,
               resilient coating or mat surface that provides a smooth,
               non-shedding surface in contact with the air stream.

          -    Paints and sealants specified for "outdoor" and/or "marine"
               users.

3.   The A/E shall review and indicate on the project drawings the route for the
     contractor to enter and deliver materials to the construction site. These
     routes are known as passageways which are required to isolate the
     construction site from occupied spaces and common areas such as lobbies,
     elevator and other tenant spaces. Where feasible, construction site
     passageways abutting tenant occupied locations shall incorporate single
     chamber "air locks" (two sets of doors or plastic strip doors at opposite
     ends of an enclosed chamber or small room) into each construction site
     entrance. Plastic strip doors shall be minimum 0.120" thick material with
     full overlap. Once installed, the air lock shall remain in place for the
     duration of the project or until such a time as its presence restricts
     final completion of the renovations. Contractor passage routes should avoid
     or minimally intersect tenant occupied areas of the building.

4.   The A/E shall stamp/certify the renovation drawings after checking that
     conflicts with the building's mechanical, plumbing, electrical, and
     sprinkler systems are absent or minimized. Additional drawings shall be
     prepared showing any required modifications. The Engineer's design must
     provide for proper air distribution and ventilation to all occupied areas
     with re-configured partitioning and/or HVAC systems. The Engineer's design
     for all HVAC systems serving the project area must provide at least the
     minimum outside air ventilation rate, on the basis of actual occupancy,
     required by the building code, mechanical code or ventilation code
     applicable at the time the facility was constructed.

5.   The A/E shall document existing site conditions prior to the start of work.
     Before finalizing the design, the Designer shall determine the HVAC system

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     capacity (CFM and supply air temperature) available to the project area.
     This determination may be from record ("as-built") drawings where available
     or measurements when record drawings are not available or their accuracy is
     in question.

CONTRACTOR RESPONSIBILITIES (PRE-CONSTRUCTION PHASE)

1.   The Contractor will assist the Property Manager, in providing
     pre-construction information sessions to the tenant and adjacent tenants
     during project planning stages and/or at least 24 hours prior to project
     initiation. The information sessions should address the following:

          -    Project scope and schedule.

          -    Anticipated construction impacts on indoor air quality (IAQ) or
               workplace conditions.

          -    Strategy to minimize impact (e.g., engineering controls, material
               selection).

          -    System to log, investigate and resolve occupant complaints
               related to construction impacts on IAQ or workplace conditions.

2.   Prior to starting work, the Contractor shall furnish copies of MSDS forms
     to the Property Manager for all materials to be installed during the
     planned renovations.

CONTRACTOR RESPONSIBILITIES (CONSTRUCTION PHASE)

1.   Contractors shall construct and use only the construction site passageways
     indicated on the project drawings as approved by the Property Manager. All
     persons and materials passing to the construction site should be fully in
     the air lock and the door to the tenant occupied are closed before opening
     the construction site door (or flaps). At lease one (set of) air lock doors
     (or flaps) must remain closed throughout the renovation process. All
     persons leaving the site shall clean their feet on a floor mat in the air
     lock prior to entering the tenant occupied part of the building. The
     Contractor shall clean the floor mat regularly.

2.   Tenant is responsible for assuring that contractors minimize and contain
     the spread of odors and contaminants. Activities that have potential to
     emit airborne contaminants must be coordinated with the Property Manager.
     The Contractor shall:

          -    Isolate all return air pathways from the construction area.

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          -    Cut and cap all supply air ducts serving the construction area
               except for temporary ducts supplying air to the construction area
               for temporary heat and air conditioning.

          -    Install a temporary exhaust to outdoors sufficient to maintain
               the construction area at a pressure of -0.02" wg relative to
               adjacent occupied spaces. Temporary exhaust to outdoors may be
               through existing building exhaust systems or through temporary
               louvers installed in place of windows or exterior doors.

3.   The Contractor shall maintain air tight duct work throughout the renovation
     process to avoid spreading construction related debris and/or airborne
     contaminants to the interior of any mechanical system component or to any
     construction free zone. Existing HVAC exhaust duct work that is directly
     vented outside the building may remain operational during the renovation
     process. Upon completion of construction, the Contractor shall remove all
     installed seals and temporary ductwork.

4.   The Contractor shall install and maintain air-tight seals at all openings
     between tenant occupied areas of the building and the construction site
     (e.g., doorways, corridors, air plenums, chases, open conduits and duct
     work) throughout the course of the renovation activities. Upon completion
     of construction, the Contractor shall remove all installed barriers and
     seals.

5.   The Property Manager will coordinate and direct the Contractor in assuring
     that the rest of the building outside the project area remains unaffected
     by the project. In particular, HVAC systems altered for the purposes of
     controlling renovation site contaminants must continue to provide at least
     the minimum outside air ventilation rate to all occupied spaces. The
     ventilation rate should be based on actual occupancy, required by the
     building code, mechanical code, or ventilation code applicable at the time
     the facility was constructed.

     The Contractor shall maintain the construction site at negative pressure
     (at least -0.02" w.c.) relative to tenant occupied spaces by operating
     temporary exhaust equipment at the renovation area. Exhaust fans should
     discharge construction area air directly outside the building through
     available windows or doorways. Preparations should be made to replace
     designated windows or doors with appropriate temporary weatherproof exhaust
     equipment manifolds. Upon completion of construction, the Contractor shall
     restore all repositioned windows and doors to original condition and
     location.

     Where renovation sites lack access to perimeter windows or doorways,
     "negative air machines" with HEPA and/or activated-carbon filters may be
     utilized to re-circulate air to the building, preferably to unoccupied
     building locations. (Special note: while HEPA filtration is highly
     efficient at particulate extraction, activated carbon filters may be
     ineffective at removing odors and

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     gaseous contaminants to the satisfaction of building occupants).

7.   The Contractor shall use only application-approved materials with the
     lowest content by volume of toxic or irritating chemicals. New carpet must
     have a green label certified by the Carpet and Rug Institute (CRI) and be
     installed according to CRI installation guidelines. The Contractor shall
     avoid materials containing chemicals listed as potentially carcinogenic,
     mutagenic, teratogenic, neurotoxicor "sensitizing". The following materials
     will not be allowed in new installations:

          -    Materials containing greater than trace (0.1%) amounts of
               asbestos.

          -    Materials containing any holgenated hydrocarbon solvents (i.e.,
               methylene chloride, tetrachloroethylene, trichloroethylene,
               trichloroethane).

          -    HVAC components internally lined with permeable man-made mineral
               fiber products unless coated with "Tuffcoat" or other tough
               resilient coating or mat surfaces that provides a smooth,
               non-shedding surface in contact with the air stream.

          -    Paints and sealants specified for "outdoor" and/or "marine" uses.

8.   The Contractor shall maintain the work area clean and free of open
     containers of paint, cleaners, chemicals, loose trash and garbage. The
     Contractor's flammable and hazardous substances shall be stored to prevent
     spillage and in accordance with National Fire Protection Association (NFPA)
     codes and OSHA regulations.

9.   Electrically powered tools shall be utilized in place of combustion engine
     equipment.

10.  Unless approved by product specifications, the Contractor shall not install
     wet or water damaged building materials. The Contractor shall protect
     stored materials from water and moisture prior to installation. The
     Contractor shall protect new building assemblies from water damage
     following installation and inspect for signs of ineffective water and
     moisture control (e.g., condensation on pipes and ducts and roof and drain
     leaks) following installation.

CONSTRUCTION RESPONSIBILITIES (COMPLETION PHASE)

1.   The Contractor shall clean, or be responsible for the Landlord's costs to
     clean all air plenums and mechanical system components determined to have
     deteriorated as a result of the Contractor's work activities. The original
     existing site conditions, as documented by the Contractor and accepted by
     the Property manager, shall be used to resolve conflicts related to
     building

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     components requiring decontamination. All cleaning shall meet the
     satisfaction of the Property Manager.

2.   All Projects, including renovation, shall include air and, where
     appropriate, water balancing in accordance with the Professional Engineer
     stamped/certified mechanical drawings. The Contractor must notify the
     Landlord's representative 48 hours before the altered mechanical systems
     are ready for balancing. The Air Balancing Contractor will be hired and
     coordinated by the Property Manager. Costs for balancing will be charged to
     the Tenant.

3.   Newly installed building materials, finishes, furniture and office
     equipment have a tendency to off-gas volatile organic compounds soon after
     they are installed. The newly renovated space should be ventilated and
     exhausted directly to the outside for a period of 48-72 hours prior to
     occupancy.

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