Document:

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                                                                 Exhibit 10.3

                                                               EXECUTION COPY

                              AGREEMENT OF SUBLEASE

                                 by and between

                          TRUSTEES OF BOSTON UNIVERSITY

                                       and

                            COMBINATORX, INCORPORATED

                          Dated as of January 25, 2001

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                                TABLE OF CONTENTS

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<Caption>
SECTION                                                                       PAGE
<S>                                                                           <C>
1.    DESCRIPTION OF THE SUBLEASE PREMISES.....................................2

      1.1   Sublease Premises..................................................2
      1.2   Appurtenant Rights.................................................2
      1.3   Exclusions and Reservations........................................2

2.    TERM OF LEASE............................................................2

      2.1   Habendum...........................................................2
      2.1   Term Commencement Date.............................................2
      2.3   Parking............................................................3
      2.4   Option to Extend Term..............................................4
      2.5   Fair Market Rent...................................................5

3.    CONSTRUCTION.............................................................6

      3.1   Initial Construction...............................................6
      3.1A. Approval and Removal...............................................7
      3.1B. Decommission.......................................................8
      3.2   Preparation of Premises for Occupancy..............................8
      3.3   General Provisions Applicable to Construction......................9
      3.4   Force Majeure Delays...............................................9
      3.5   Tenant Delays......................................................9
      3.6   Access During Construction........................................10
      3.7   Signage...........................................................11

4.    USE OF THE SUBLEASE PREMISES............................................11

      4.1   Permitted Uses....................................................11
      4.2   Prohibited Uses...................................................12
      4.3   Licenses and Permits..............................................13
      4.4   Equipment.........................................................13
      4.5   Access............................................................13
      4.6   Extra Hazardous Use...............................................13

5.    RENT; UTILITIES.........................................................14

      5.1   Yearly Fixed Rent.................................................14
      5.2   Additional Rent...................................................15
      5.2A  Tax and Tax Fund Payments.........................................17
      5.3   Utilities.........................................................19
      5.4   Interruption or Curtailment of Services...........................20
      5.5   Payment to Mortgagee..............................................21
      5.6   Utility Deregulation..............................................21
      5.7   HVAC Services.....................................................21
      5.8   Sublessor Services................................................22
      5.9   Additional Rent...................................................23
</Table>

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<S>                                                                           <C>
6.    CHANGES OR ALTERATIONS BY SUBLESSOR.....................................23

7.    FIXTURES, EQUIPMENT AND IMPROVEMENTS REMOVAL BY SUBLESSEE...............24

8.    ALTERATIONS AND IMPROVEMENTS BY SUBLESSEE...............................24

9.    SUBLESSOR'S CONTRACTORS - MECHANICS' AND OTHER LIENS -
      STANDARD OF SUBLESSEE'S PERFORMANCE - COMPLIANCE WITH
      LAWS....................................................................25

10.   REPAIRS AND SECURITY BY SUBLESSEE.......................................26

11.   INSURANCE, INDEMNIFICATION, EXONERATION AND EXCULPATION.................27

      11.1  Insurance.........................................................27
      11.2  Certificates of Insurance.........................................27
      11.3  General...........................................................28
      11.4  Property of Sublessee.............................................28
      11.4A Release and Waiver of Subrogation.................................29
      11.5  Bursting of Pipes, etc............................................29
      11.6  Repairs and Alterations - No Diminution of Rental Value...........29
      11.7  Sublessor's Insurance.............................................29

12.   ASSIGNMENT, MORTGAGING, SUBLETTING, ETC.................................30

13.   MISCELLANEOUS COVENANTS.................................................33

      13.1  Rules and Regulations.............................................33
      13.2  Access to Premises - Shoring......................................33
      13.3  Accidents to Sanitary and other Systems...........................34
      13.4  Signs, Blinds and Drapes..........................................34
      13.5  Estoppel Certificate..............................................34
      13.6  Prohibited Items..................................................34
      13.7  Requirements of Law - Fines and Penalties.........................35
      13.8  Sublessee's Acts - Effects on Insurance...........................35
      13.9  Authority.........................................................35
      13.10 Miscellaneous.....................................................36
      13A.  SUBLESSOR REPRESENTATIONS.........................................36

14.   DAMAGE BY FIRE AND CONDEMNATION.........................................36

      14A.  DAMAGE BY FIRE....................................................36
      14B.  CONDEMNATION......................................................38

15.   DEFAULT AND ENFORCEMENT.................................................39

      15.1  Conditions of Limitation - Re-entry - Termination.................39
      15.2  Damages - Assignment for Benefit of Creditors.....................40
      15.3  Damages - Termination.............................................41
      15.4  Fees and Expenses.................................................42
</Table>

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<S>                                                                           <C>
      15.5  Sublessor's Remedies Not Exclusive................................42
      15.6  Grace Period......................................................42

16.   END OF TERM - ABANDONED PROPERTY; HOLDOVER..............................43

17.   SUBLEASE SUBORDINATE; SUBORDINATION TO AND INCORPORATION
      OF TERMS OF MAIN LEASE..................................................44

18.   QUIET ENJOYMENT.........................................................45

19.   ENVIRONMENTAL INDEMNITY.................................................45

20.   ENTIRE AGREEMENT - WAIVER - SURRENDER...................................46

      20.1  Entire Agreement..................................................46
      20.2  Waiver............................................................46
      20.3  Surrender.........................................................47

21.   INABILITY TO PERFORM - EXCULPATORY CLAUSE...............................47

23.   PARTIES BOUND - SEIZIN OF TITLE.........................................49

24.   SUBLESSEE EFFORTS REGARDING MINORITY PARTICIPATION......................49

25.   MISCELLANEOUS...........................................................50

      25.1  Separability .....................................................50
      25.2  Captions..........................................................50
      25.3  Broker............................................................50
      25.4  Governing Law.....................................................50
      25.5  Time of the Essence...............................................50
      25.6  Notice of Sublease................................................50
      25.7  Transfer..........................................................51
      25.8  Financial Capability..............................................51
      25.9  Notice to Mortgagee...............................................51
      25.10 Attorneys' Fees...................................................51
      25.11 Security Deposit..................................................51
      25.11ALetter of Credit..................................................52
      25.12 Option............................................................53
</Table>

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                              SCHEDULE OF EXHIBITS

EXHIBIT A     The Legal Description of the Lot

EXHIBIT B     Plan of Sublease Premises

EXHIBIT C     Confirmation of Term Commencement Date and Rentable Square Footage

EXHIBIT D     Parking Map

EXHIBIT E     Work Letter Agreement

EXHIBIT F     Environmental Report

EXHIBIT G     First Source Agreement

EXHIBIT H     Agreement Regarding Nondisturbance. Attornment and Other Matters

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                              AGREEMENT OF SUBLEASE

     This Agreement of Sublease ("Sublease") dated as of the 25 day of January,
2001 by and between Trustees of Boston University, a Massachusetts non-profit
educational corporation with an address at 715 Albany Street, Boston,
Massachusetts 02118 ("Sublessor"), and CombinatoRx Incorporated, a Delaware
corporation with an address at _________________________ ("Sublessee").

                                WITNESSETH THAT:

     WHEREAS, 650 Albany Street, LLC is the tenant under a certain Master Lease
dated as of June 30, 2000, between Ronald E. Bartlett and Kenneth G. Condon, as
Trustees of 650 Albany Street Medical Realty Trust, a Massachusetts nominee
trust under declaration of trust dated June 24, 1998, recorded with Suffolk
Registry of Deeds in Book 22655, Page 57, as landlord and 650 Albany Street,
LLC, as tenant (as amended or supplemented from time to time, the "Master
Lease"), a memorandum of which is recorded in the Suffolk County Registry of
Deeds, with respect to certain property located at 650 Albany Street, Boston,
Massachusetts 02118;

     WHEREAS, pursuant to an Agreement of Lease dated as of June 26, 1998
between Richard Moed and Kenneth G. Condon, as Trustees of 650 Albany Street
Medical Realty Trust, as landlord (the "Trust"), and Trustees of Boston
University, as tenant (the "Main Lease"), the Trust leased to Sublessor, as
tenant, approximately 69,161.72 rentable square feet of space (the "Main
Premises") located on the ground, second and third floors and portions of other
floors contained in the building to be known and numbered as 650 Albany Street,
Boston, Massachusetts 02118 (BioSquare, Building "C") (the "Building"), located
on a lot, the legal description of which lot is attached hereto as EXHIBIT A
(the "Lot" or "Property");

     WHEREAS, the interest of the Trust, as landlord, in the Main Lease has been
assigned to 650 Albany Street, LLC pursuant to that certain Assignment of Lease
dated as of June 30, 2000;

     WHEREAS, the Trust and 650 Albany Street, LLC are referred to collectively
herein as "Landlord"; and

     WHEREAS, Sublessor has agreed to sublease approximately 7,492 rentable
square feet of the Main Premises, which space is located on floor three (3) of
the Building and as shown on EXHIBIT B attached hereto (the "Sublease
Premises"), to Sublessee on the terms stated herein;

     NOW THEREFORE, in consideration of the mutual covenants herein contained
and for other good and valuable consideration, the receipt and sufficiency of
which are hereby acknowledged, Sublessor and Sublessee hereby agree as follows:

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1.   DESCRIPTION OF THE SUBLEASE PREMISES

     1.1    SUBLEASE PREMISES. Sublessor hereby leases to Sublessee and
Sublessee hereby hires from Sublessor the Sublease Premises as the same may from
time to time be constituted after changes therein, additions thereto and
eliminations therefrom pursuant to rights of Sublessor hereinafter reserved.

     1.2    APPURTENANT RIGHTS. Sublessee shall have, as appurtenant to the
Sublease Premises, rights to use in common with Sublessor and Landlord and other
occupants of the Building, subject to reasonable and uniform rules (as more
particularly described in Section 13.1 hereof), from time to time made by
Landlord or Sublessor of which Sublessee is given notice, those common roadways,
walkways, elevators, lobbies, hallways and stairways necessary or convenient
for access to that portion of the Building occupied by the Sublease Premises.

     1.3    EXCLUSIONS AND RESERVATIONS. All the perimeter walls of the Sublease
Premises except the inner surfaces thereof, any balconies, terraces or roofs
adjacent to the Sublease Premises, and any space in or adjacent to the Sublease
Premises used for shafts, stacks, pipes, conduits, wires and appurtenant
fixtures, ducts, electric or other utilities, telecommunications equipment or
other Building facilities, and the use thereof, as well as the right of access
through the Sublease Premises for the purpose of operation, maintenance and
repair, are expressly reserved by Sublessor and Landlord. The rentable square
footage of the Sublease Premises shall be measured according to BOMA standards
and shall be confirmed and verified by the Sublessor's architect for the
Building in consultation with Sublessee's space planner. The square footage of
the Sublease Premises as determined in accordance with the foregoing sentence
shall be binding on Sublessor and Sublessee. Sublessor and Sublessee agree to
sign a certificate in the form attached hereto as EXHIBIT C verifying the square
footage of the Sublease Premises in Paragraph 1.1 hereof. Failure of either
Sublessor or Sublessee to remeasure the Sublease Premises, on or before thirty
(30) days after the Term Commencement Date (as hereinafter defined), shall be
deemed a waiver by such party as to its right to remeasure and accordingly, if
the parties do not remeasure the Sublease Premises, the parties agree to bound
by the measurements as set forth herein.

2.   TERM OF LEASE

     2.1    HABENDUM. To have and to hold the Sublease Premises for a term of
five (5) years commencing on the Term Commencement Date (as hereinafter defined)
and ending on the day immediately prior to the fifth anniversary thereof (the
"Term of this Sublease" or "Original Term"), or on such earlier date upon which
said Term may expire or be cancelled or be terminated pursuant to any of the
conditions of limitation or other provisions of this Sublease or pursuant to
law (which date for the expiration, cancellation or termination of the Term
hereof shall hereafter be called the "Termination Date").

     2.2    TERM COMMENCEMENT DATE. The Term Commencement Date shall be the
earlier of (a) the date on which the Sublease Premises are deemed ready for
occupancy as

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provided in Section 3.2 or (b) the date on which Sublessee occupies all or any
part of the Sublease Premises.

     2.3    PARKING. Sublessee, on the following terms and conditions, shall
have the license to use and Sublessor shall deliver parking permits ("parking
permits") to Sublessee for the use of up to, but in no event at any time during
the Term of this Sublease, more than fourteen (14) non-reserved parking spaces
in the surface parking lots and garages serving Boston University Medical
Center, as designated from time to time by Sublessor during the Term of this
Sublease. During the Term, the non-reserved parking spaces shall be located in
the parking garage ("Parking Facility") as shown on the Parking Map, a copy of
which is attached hereto as EXHIBIT D. Except for particular spaces and areas
designated by Landlord for reserved parking, all parking in the Parking Facility
shall be on an unreserved, first-come, first-served basis. Sublessee
acknowledges that Landlord shall have the right to operate the Parking Facility
through the use of valet parking. Sublessee shall have the right to irrevocably
relinquish said parking permits during the Term provided Sublessee gives
Sublessor not less than thirty (30) days prior written notice of the number of
parking permits Sublessee elects to relinquish and the date upon which Sublessee
shall irrevocably relinquish any parking permit(s), which date of relinquishment
shall always occur on the last day of a month. Notwithstanding anything to the
contrary contained herein, if at any time during the Term, the parking spaces in
the Parking Facility are unavailable due to any condition including without
limitation Force Majeure events, casualty and/or temporary repairs. Sublessor
shall make available to Sublessee non-reserved parking spaces in any of the
other parking areas shown on the Parking Map.

     The use of the parking spaces shall be on the following terms and
conditions:

               a.  Sublessee shall pay Sublessor rent for each parking
                   permit ("Parking Rent") per month in an amount equal to
                   market rate rent announced by Sublessor from time to time.
                   The Parking Rent on the Term Commencement Date shall be $175
                   per parking permit.

               b.  Sublessor and Landlord shall not be responsible for money,
                   jewelry, automobiles or other personal property lost in or
                   stolen from the Parking Facility regardless of whether such
                   loss or theft occurs when the Parking Facility or other areas
                   therein are locked or otherwise secured against entry or
                   liable for any loss, injury or damage to persons using the
                   Parking Facility or automobiles or other property therein, it
                   being agreed that the use of the Parking Facility and the use
                   of the parking spaces shall be at the sole risk of Sublessee
                   and its employees.

               c.  Sublessor and Landlord shall have the right from time to time
                   to promulgate reasonable rules and regulations regarding the
                   Parking Facility, the parking permits, the parking 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

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                   direction of parking and the like, which rules and
                   regulations and any additions and amendments thereto
                   Sublessor shall use reasonable efforts to apply to all users
                   of the Parking Facility. Sublessee shall comply with and
                   cause its employees to comply with all such rules and
                   regulations as well as all reasonable additions and
                   amendments thereto.

               d.  Except for emergency repairs, Sublessee and its employees
                   shall not perform any work on any automobiles while located
                   in the Parking Facility.

               e.  Landlord shall have the right to temporarily close the
                   Parking Facility or certain areas therein in order to perform
                   necessary repairs, maintenance and improvement to the Parking
                   Facility.

               f.  Except in connection with an approved assignment of the
                   Sublease or an approved subletting of all or a portion of
                   the Sublease Premises, in accordance with the terms hereof,
                   Sublessee shall not transfer, assign or sublease any of the
                   parking permits (including without limitation parking access
                   cards and/or keys). Sublessor shall have the right to
                   terminate these parking permits with respect to any parking
                   permits that Sublessee desires to transfer, sublet or assign
                   in violation of the foregoing sentence.

               g.  Sublessor may elect to provide parking cards or keys to
                   control access to the Parking Facility. In such event,
                   Sublessor shall provide Sublessee with one card or key for
                   each parking permit that Sublessee is using hereunder,
                   provided that Sublessor shall have the right to require
                   Sublessee or its employees to place a reasonable deposit on
                   such access cards or keys and to pay a reasonable fee for any
                   lost or damaged cards or keys.

               h.  Sublessee shall pay to Sublessor, without any set-off or
                   deduction, all payments of Parking Rent in advance on or
                   before the first day of each calendar month during the Term
                   of this Sublease.

     2.4    OPTION TO EXTEND TERM So long as Sublessee is not, on the date
upon which the Sublessee exercises the extension option and at the commencement
of the extension period, in default under the provisions of this Sublease beyond
the applicable grace period set forth herein, if any, Sublessee may extend the
Term of this Sublease for one period of five years (referred to herein as the
"extension period"), by giving notice to Sublessor of its election to extend at
least twelve months in advance of the commencement of the extension period.
Prior to the exercise by Sublessee of such option, the expression "Term" shall
mean the original five-year term, and after the exercise by Sublessee of any
such option, the expression "Term" shall mean the Original Term as it may have
then been extended. Except as otherwise hereinafter set forth, all terms and
conditions of this Sublease shall remain in

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full force and effect with respect to the extension period. If Sublessee shall
give notice of its exercise of such option to extend in the manner and within
the time period provided aforesaid, the Term shall be extended upon the giving
of such notice without the requirement of any further action on the part of
either Sublessor or Sublessee.

     With respect to the extension period, (i) the Yearly Fixed Rent, as defined
in Section 5.1 hereof, payable during such extension period shall be the fair
market rent as of the commencement of such extension period determined in
accordance with the provisions of Section 2.5 hereof, (ii) the Additional Rent,
as defined in Section 5.2 hereof, payable during such extension period shall be
adjusted to reflect Sublessee's pro rata share of all such Additional Rent then
incurred by Sublessor in the operation and maintenance of the Building and the
Lot based on the rentable square footage of the Sublease Premises in relation to
the rentable square footage of the Building ("Sublessee's Proportionate Share")
and (iii) Parking Rent, as defined in Section 2.3 hereof, payable during such
extension period shall be the fair market rent as of the commencement of the
extension period. In addition to the foregoing, with respect to the extension
period, Sublessee shall continue to pay Additional Rent for Taxes, as defined in
Section 5.2A hereof, all utility expenses as set forth herein and any other
costs and expenses set forth herein.

     2.5       FAIR MARKET RENT "Fair market rent" shall mean the fair market
rent for the subject space as of the commencement of the period in question
under market conditions then existing. Fair market rent shall be determined by
agreement between Sublessor and Sublessee or their representatives, but if
Sublessor and Sublessee are unable to agree upon the fair market rent at least
ten months prior to the date upon which the fair market rent is to take effect,
then the fair market rent shall be determined by appraisal made as hereinafter
provided by a board of three reputable independent MAI certified real estate
appraisers, each of whom shall have at least ten years of experience in the
appraisal of research and office space in the metropolitan Boston area.
Sublessee and Sublessor shall each appoint one such appraiser and the two
appraisers so appointed shall appoint the third appraiser. The cost and expenses
of each appraiser appointed separately by Sublessee and Sublessor shall be borne
by the party who appoint the appraiser. The cost and expenses of the third
appraiser shall be shared equally by Sublessee and Sublessor. Sublessor and
Sublessee shall appoint their respective appraisers at least nine months prior
to the commencement of the period for which fair market rent is to be determined
and shall designate the appraisers so appointed by notice to the other party.
The two appraisers so appointed and designated shall appoint the third appraiser
at least eight months prior to the commencement of such period and shall
designate such appraiser by notice to Sublessor and Sublessee. The board of
three appraisers shall determine the fair market rent of the space in question
as of the commencement of the period to which the fair market rent shall apply,
which determination shall include the value of the Sublease Improvements (as
defined in Section 3.1 hereof). The appraisers shall notify Sublessor and
Sublessee of their determinations at least seven months prior to the
commencement of such period. If the determinations of the fair market rent of
any two or all three of the appraisers shall be identical in amount, said amount
shall be deemed to be the fair market rent of the subject space. If the
determinations of all three appraisers shall be different in amount, the average
of the two values nearest in amount shall be deemed the fair market rent. The
fair market rent of the subject space determined in

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accordance with the provisions of this Section shall be binding and conclusive
on Sublessor and Sublessee. Notwithstanding the foregoing, if either party shall
fail to appoint its appraiser within the period specified above (such party
referred to hereinafter as the "failing party"), the other party may serve
notice on the failing party requiring the failing party to appoint its appraiser
within ten days of the giving of such notice and if the failing party shall not
respond by appointment of its appraiser within said ten-day period, then the
appraiser appointed by the other party shall be the sole appraiser whose
determination of the fair market rent shall be binding and conclusive upon
Sublessee and Sublessor.

     Judgment on the determination made under the foregoing provision may be
entered in any court of competent jurisdiction pursuant to the provisions of
Section 14 of Chapter 251 of the General Laws of Massachusetts.

     Notwithstanding anything contained in this Section 2.5 or anywhere else in
this Sublease to the contrary, in no event shall the Yearly Fixed Rent for the
extension term be less than $46.00 per rentable square foot of the Sublease
Premises per annum for the extension period.

3.   CONSTRUCTION

     3.1    INITIAL CONSTRUCTION. Sublessor shall perform or cause Landlord to
perform the Sublease improvements as described in the Work Letter Agreement
attached hereto as EXHIBIT E (which Work Letter is hereby incorporated herein
and made a part hereof). Sublessor shall provide Sublessee with a tenant
allowance in the amount equal to the number of rentable square feet in the
Sublease Premises times $70.00, which equals $524,440.00 (the "Tenant
Allowance"). The Tenant Allowance shall be used for those costs incurred in
connection with the Sublease Improvements and approved by Sublessor (the
"Approved Sublessee Costs") and shall be disbursed in accordance with the
provisions of this Sublease. Approved Sublessee Costs may include the following
costs: the cost of preparing the Complete Plans (as hereinafter defined);
Sublessee's share of the Sublessor's cost of constructing common area walls and
corridor serving the third floor (which share is approximately $11,071.00);
Sublessee's share of the cost of the emergency generator as further described in
Exhibit E attached hereto; and the cost of constructing the Sublease
Improvements (as hereinafter defined), including architectural, contracting and
engineering fees associated with the Sublease Improvements. Sublessor shall
cooperate with, and shall use reasonable efforts to cause its architect and
engineer to cooperate with, Sublessee's architect and engineer in connection
with the preparation of Sublessee's construction drawings and specifications for
the Sublease Improvements. Sublessee shall cooperate with, and shall use
reasonable efforts to cause any architects, engineers and construction
consultants retained by Sublessee to cooperate with, Sublessor's contractor,
engineer, architects and subcontractors in connection with the construction of
the Sublease Improvements and Base Building Work (as hereinafter defined). No
later than February 28, 2001, time being of the essence, Sublessee shall provide
to Sublessor for approval complete sets of construction drawings and
specifications for the Sublease Improvements (the "Complete Plans") prepared at
Sublessee's expense by (a) Sublessor's architect or an

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architect approved by Sublessor and (b) Sublessor's engineer or an engineer
approved by Sublessor. The Complete Plans shall include but not be limited to:

     a.  Furniture and Equipment Layout Plans
     b.  Dimensioned Partition Plans
     c.  Dimensioned Electrical and Telephone Outlet Plans
     d.  Reflected Ceiling Plans
     e.  Door and Hardware Schedules
     f.  Room Finish Schedules including wall, carpet and floor tile colors
     g.  Electrical, mechanical, plumbing and structural engineering plans
     h.  All necessary construction details and specifications for work not
         otherwise specified.

     Sublessor and Sublessee shall initial the Complete Plans after the same
have been submitted by Sublessee and approved by Sublessor.

     All of Sublessee's construction, installation of furnishing, telephone
outlets and equipment, and later changes or additions to the Complete Plans
shall be reasonably coordinated with any work being performed by Sublessor in
such manner as to maintain harmonious labor relations and not to damage the
Building or the Lot or to interfere unreasonably with Building operations.
Except for the installation of furnishings and equipment and telephone data,
wiring, infrastructure and network which may be installed by various vendors
(subject to the reasonable approval of Sublessor provided Sublessee delivers to
Sublessor written notice prior to the commencement of any such installation work
specifying the name of such vendors), all at Sublessee's expense, all worked
described in the Complete Plans (the "Sublease Improvements") shall be performed
by a contractor (the "Contractor") of Sublessor's choice and at Sublessee's
expense.

     3.1A.  APPROVAL AND REMOVAL.

     Notwithstanding the foregoing, Sublessor shall not approve any
construction, alterations, or additions (whether such construction, alterations
or additions occur prior to or after the Term Commencement Date) requiring
unusual expense to readapt the Sublease Premises to office, research and
development use consistent with that of other comparable buildings in Boston on
the Termination Date or increasing the cost of construction, insurance or taxes
on the Building or of Sublessor's services called for in this Sublease unless
Sublessee first gives assurances acceptable to Sublessor that such readaptation
shall be made prior to the Termination Date without expense to Sublessor and
makes provisions acceptable to Sublessor for payment of any such increased costs
attributable to such construction, alterations and additions. Except as
otherwise provided herein, all alterations and additions shall be part of the
Building except such items as by writing at the time of approval the parties
agree either shall be removed by Sublessee on termination of this Sublease, or
shall be removed or left at Sublessee's election.

     To the extent any furnitures, trade fixtures and equipment are paid out of
Sublessee's own funds (and not paid out of any portion of the Tenant Allowance),
Sublessee shall be

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entitled to remove such furnitures, trade fixtures and equipment prior to the
Termination Date in accordance with the terms of this Sublease. With respect to
any alteration or addition made to the Sublease Premises after the Term
Commencement Date, which alteration or addition is made to replace, restore
and/or substitute an improvement constituting a portion of the Sublease
Improvements on the Term Commencement Date (or any replacement thereof), all
such alterations and/or additions shall remain part of the Building on the
Termination Date unless otherwise agreed to in writing by the parties hereto. If
such alteration and/or addition is not any such substitute, replacement or
restoration, Sublessee shall be entitled to remove such alteration or addition
in accordance with the terms of this Sublease on or prior to the Termination
Date. To the extent that any building systems are altered in order to
accommodate any such alteration or addition, all such building systems and
improvements thereto shall remain the property of Sublessor on the Termination
Date.

     3.1B.  DECOMMISSION. For purposes of this Section 3.1B, the term
"decommission" means (i) assessing all portions of the Sublease Premises where
radioactive materials were used or stored at any time during the Term hereof
(such portions to include, without limitation, walls, hot sinks, benchtops and
hoods) for radioactive contamination limits and (ii) clearing all such portions
that exceed acceptable contamination limits of radioactive contamination, in
accordance with all applicable laws. At least one hundred twenty (120) days
prior to the Termination Date, Sublessee shall provide Sublessor with a written
proposed decommission plan, which shall contain (i) the name, address and
telephone number of the contractor engaged by Sublessee to effectuate the
decommission, (ii) the cost of the decommission, (iii) a time sequence for the
decommission and (iv) Sublessee's covenant to complete the decommission prior to
the Termination Date. If Sublessee does not timely provide Sublessor a
satisfactory decommission plan, then Sublessor, in addition to all other rights
and remedies it has hereunder or at law or in equity, any, but shall not be
obligated to, undertake the decommission on the Sublessee's behalf and at the
Sublessee's cost and expense, in accordance with Section 15.4 hereof. Sublessee
hereby agrees to decommission the Sublease Premises prior to the Termination
Date in accordance with the decommission plan approved by the Sublessor and in
accordance with all applicable laws, without any expense to Sublessor.

     3.2    PREPARATION OF PREMISES FOR OCCUPANCY. Sublessor agrees to use
reasonable efforts to have the Sublease Premises ready for occupancy on or about
June 30, 2001which date shall, however, be extended for a period equal to that
of any delays due to Tenant Delays (as hereinafter defined) and Force Majeure
Delays (as hereinafter defined). The Sublease Premises shall be deemed ready for
occupancy on the date on which (a) the Sublease Improvements are ready for
occupancy as certified by Sublessor's architect with the exception of minor
items which can be completed without material interference with Sublessee and
other items which because of the season or weather or the nature of the item are
not practicable to do at the time and (b) a Certificate of Occupancy (temporary,
conditional or otherwise) has been issued for the Sublease Premises (the
"Completion Date"). Notwithstanding the foregoing, if Sublessor is unable to
complete construction of the Sublease Premises due to a Tenant Delay /or Force
Majeure Delay, then the Sublease

                                        8
<Page>

Premises shall be deemed ready for occupancy on the date on which they are
actually made available to Sublessee.

     To the extent that any certificate of occupancy delivered in connection
with the Sublease Premises is conditional or temporary in nature, Sublessor
agrees to obtain a permanent certificate of occupancy for the Building or the
Sublease Premises, as the case may be, with all reasonable due diligence and in
all events prior to the expiration of the temporary or conditional certificate
of occupancy.

     3.3    GENERAL PROVISIONS APPLICABLE TO CONSTRUCTION. All construction work
required or permitted by this Sublease, whether by Sublessor or Sublessee, shall
be done in a good and workmanlike manner and in compliance with all applicable
laws and all lawful ordinances, regulations and orders of governmental authority
and insurers of the Building. Either party may inspect the work of the other at
reasonable times and promptly shall give notice of observed defects. Sublessor's
obligations under Section 3.1 shall be deemed to have been performed when
Sublessee commences to occupy any portion of the Sublease Premises for the
Permitted Uses except for items which are incomplete or do not conform with the
requirements of Section 3.1 and as to which Sublessee shall in either case have
given written notice to Sublessor within sixty (60) days after the Term
Commencement Date. Failure to so notify Sublessor shall be deemed a waiver by
Sublessee of any incomplete or nonconforming items by Sublessor.

     3.4    FORCE MAJEURE DELAYS. "Force Majeure Delays" shall include delays
incurred on account of or resulting from lack of, unusual scarcity or inability
to obtain labor, supplies and materials (other than because of lack of funds);
strikes; riots; acts of God; weather and storm conditions; war; state of
emergency; casualty; eminent domain; governmental laws, regulations or
restrictions of any agencies, boards, authorities or the like; delays by any
such agencies, boards, authorities, or the like in granting, issuing or
delivering any permits, licenses, variances, approvals, consents, or the like
regarding the Sublease Premises, the Building and the Lot; any cause described
in Section 21 hereof; and any other cause whatsoever that is beyond the
reasonable control of Sublessor or Landlord (other than because of lack of
funds). Except as specifically provided herein to the contrary, whenever a
period of time is herein prescribed for the taking of any action by Sublessor,
Sublessor shall not be liable or responsible for, and there shall be excluded
from the computation of such period of time, any delays due to events of Force
Majeure.

     3.5    TENANT DELAYS. Whenever a period of time is herein prescribed for
the taking of any action by Sublessor, during the period commencing on the
execution date of this Sublease and ending on the Term Commencement Date,
Sublessor shall not be responsible for or liable, and there shall be excluded
from the computation of such period of time any of the following delays (a
"Tenant Delay"):

            a.   Sublessee's failure to furnish information or deliver plans in
                 accordance with this Sublease including Section 3.1 hereof or
                 the Work Letter Agreement or to respond to any request by
                 Sublessor for any approval or information within any time
                 period prescribed, or if

                                        9
<Page>

                 on time period is prescribed, then within five (5) business
                 days of such request; or

            b.   Sublessee's insistence on materials, finishes or installations
                 that have long lead times after having first been informed by
                 Sublessor that such materials, finishes or installations will
                 cause a delay; or

            c.   Changes in any plans and specifications requested by Sublessee
                 that delays Sublessor in the completion of the Sublease
                 Improvements or Base Building Work; or

            d.   The performance or nonperformance by a person or entity
                 employed by Sublessee in the completion of any work in the
                 Sublease Premises (all such work and such persons or entities
                 being subject to the prior approval of Sublessor); or

            e.   Any request by Sublessee for changes to the Sublease
                 Improvements that actually delay Sublessor in the completion of
                 any of the Sublease Improvements or Base Building Work; or

            f.   Any breach or default by Sublessee in the performance of
                 Sublessee's obligations under this Sublease that delays
                 Sublessor in the completion of any of the Sublease Improvements
                 or Base Building Work; or

            g.   Any delay resulting from Sublessee's access to the Sublease
                 Premises or having taken possession of the Sublease Premises
                 for any reason prior to substantial completion of the Sublease
                 Improvements or Base Building Work. For purposes of determining
                 the Term Commencement Date, the date of Substantial Completion
                 shall be determined in according with Section 3.2.

     All of the foregoing a through g being a "Tenant Delay" for purpose of this
Sublease.

     3.6    ACCESS DURING CONSTRUCTION. During the construction of the Sublease
Improvements, Sublessee shall have the right to enter the Sublease Premises for
the purpose of inspecting the Sublease Improvements and thirty (30) days prior
to the Term Commencement Date for the installation of Sublessee's equipment and
trade fixtures. Notwithstanding the foregoing, any such inspection or
installation shall be performed only upon reasonable prior notice to Sublessor
and at reasonable times designated by Sublessor so as not to interfere with the
performance of the Base Building Work and any work by Sublessor or Landlord and
the Sublease Improvements. If Sublessee's access shall interfere with the timely
completion of the Base Building Work and/or Sublease Improvements, Sublessee's
right to access shall be terminated immediately.

                                       10
<Page>

     3.7    SIGNAGE. Sublessor shall provide, at Sublessor's sole cost and
expense, or shall cause Landlord, at Landlord's sole cost and expense, to
provide a standard building directory in the lobby of the Building (and on each
floor leased by Sublessee) listing Sublessee as a tenant. Sublessee, at its sole
cost and expense, shall have the right to install (a) custom signage identifying
Sublessee on any full floor leased by Sublessee, provided that such signage is
not visible from outside the Building and which cost may be funded out of the
Tenant Improvement Allowance and (b) a sign on the main entry door serving the
Subleased Premises, the design of which sign shall be subject to Sublessor's
approval.

     Notwithstanding the foregoing, all signage installed by Sublessee shall be
first class, be compatible with all design and architectural guidelines
established for the Building, conform to the sign requirements for the Building
as enacted from time to time for the Building, conform to all laws, ordinances
and regulations including without limitation, all zoning laws and any
requirements of any historic and/or Boston agencies regarding the same and be
subject to the reasonable review and prior written approval of Landlord and
Sublessor. It shall be Sublessee's sole responsibility to apply for and obtain
all permits, licenses and governmental approvals (as may be required) for the
construction of any custom signage on any floor leased by Sublessee (such custom
signage being referred to as the "Sublessee Signage"). Sublessee agrees to
maintain all necessary licenses and permits for the Sublessee Signage and to
maintain the Sublessee Signage in good order, condition and repair at
Sublessee's sole cost and expense, it being understood that Landlord and
Sublessor shall have absolutely no responsibility for Sublessee Signage.
Sublessee shall defend, indemnify and save Landlord and Sublessor harmless in
connection with the Sublessee Signage as provided for in Section 11.3 herein.
Sublessor, at no cost and expense to Sublessor, shall cooperate with Sublessee
in obtaining the necessary permits, licenses and governmental approvals for
Sublessee Signage. Sublessor may at its option require the Sublessee at or prior
to the expiration of the Term to remove all Sublessee Signage and to repair any
damage cause by such removal.

4.   USE OF THE SUBLEASE PREMISES

     4.1    PERMITTED USES. Sublessee shall during the Term of this Sublease
occupy and use the Sublease Premises solely for office and biomedical research
and development uses in connection with Sublessee's discovery and development of
human therapeutics and research and development of drug discovery technology
platform subject to Section 4.2(iii) hereof and for no other purpose. As further
clarification to the preceding sentence, the term "continuously" shall mean
continuous use of the Sublease Premises by the Sublessee or other occupants
permitted under this Sublease for the Permitted Uses Monday through Friday from
9:00 A.M. to 5:00 P.M., subject to those normal periods of non-occupancy for
vacations and federal and state holidays and subject further to non-occupancy of
certain portions of the Sublease Premises due to the space needs of Sublessee
from time to time, it being understood and agreed by Sublessee that it shall
during the Term of the Sublease be responsible for the maintenance and operation
responsibilities for the entire Sublease Premises set forth herein as
Sublessee's responsibilities and for conveying to the general public the image
and appearance of continued presence and full occupancy of the entire Sublease
Premises. Service and utility areas (whether or not a part of the Sublease

                                       11
<Page>

Premises) shall be used only for the particular purpose for which they were
designated. It shall be Sublessee's full responsibility to obtain all permits,
licenses, conditional use permits and variances to conduct the foregoing uses in
the Sublessee Premises and to the extent that such uses are not allowed as of
right by all applicable laws, including, without limitation, the Boston Zoning
Code, as amended from time to time excluding the certificate of occupancy
(described in Section 3.2(c)), and any other certificates of occupancy
(permanent or otherwise) for the Building to the extent required by law. If
Sublessee shall change its use (with the permission of Sublessor), Sublessee
shall be responsible for obtaining any certificate(s) of occupancy required as a
result of the same.

     4.2    PROHIBITED USES. Sublessee shall not use, or suffer or permit the
use of, or suffer or permit anything to be done in the Sublease Premises or the
Building or any part thereof (i) which would violate any of the covenants,
agreements, terms, provisions and conditions of this Sublease, (ii) for any
unlawful purposes or in any unlawful manner, or (iii) which, in the reasonable
judgment of Sublessor or Landlord shall in any way (a) impair or tend to impair
the appearance or reputation of the Building, (b) impair or interfere with or
tend to impair or interfere with any of the Building services or the proper and
economic heating, cleaning, air conditioning or other servicing of the Building,
or (c) occasion discomfort, inconvenience or annoyance to any of the other
tenants or occupants of the Building, whether through the transmission of noise
or odors or otherwise. Without limiting the generality of the foregoing, no food
(except in connection with customary office vending machines, coffee service
facilities and lunch room facilities set forth on the Complete Plans or other
plans approved by Sublessor, provided such machines and facilities are used for
and by occupants of the Sublease Premises only and their guests and further
provided Sublessee pays any resulting increased costs pursuant to Section 13.8
and the other applicable provisions of this Sublease) shall be prepared or
served for public or commercial consumption on or about the Sublease Premises;
no intoxicating liquors or alcoholic beverages shall be sold or otherwise served
to the general public on or about the Sublease Premises; no lottery tickets
(even where the sale of such tickets is not illegal) shall be sold and no
gambling, betting or wagering shall otherwise be permitted on or about the
Sublease Premises; no combustible materials (except as disclosed to and approved
by Sublessor) shall be stored or warehoused; no loitering shall be permitted on
or about the Sublease Premises; and no loading or unloading of supplies or other
material to or from the Sublease Premises shall be permitted on the Lot except
during such hours as the Building is customarily open for business. The Sublease
Premises shall be maintained by Sublessee in a sanitary condition, kept free
from odors and kept free from rodents and laboratory animals of any kind and
vermin.

     Sublessee shall be responsible for the proper handling and disposal of all
its trash, rubbish and other wastes, and for compliance with all local, state
and federal laws applicable to the storage and disposal of any such wastes.
Sublessee shall also provide cleaning services to the Sublease Premises
according to cleaning standards generally prevailing in first class buildings in
the City of Boston and in accordance with any cleaning specifications or rules
and regulations promulgated from time to time by Landlord and Sublessor.

                                       12
<Page>

     4.3    LICENSES AND PERMITS. If any governmental license or permit shall be
required for the proper and lawful conduct of Sublessee's business, and if the
failure to secure such license or permit would in any way affect Landlord or
Sublessor, Sublessee, at Sublessee's expense, shall duly procure and thereafter
maintain such license or permit and submit the same to inspection by Landlord or
Sublessor. Sublessee, at Sublessee's expense, shall at all times comply with the
terms and conditions of each such license or permit.

     4.4    EQUIPMENT. Sublessee shall at all times install, maintain and
operate all equipment used or located in the Sublease Premises in accordance
with manufacturers' specifications and warranties.

     4.5    ACCESS. After the Term Commencement Date, Sublessee shall have
access to the Building twenty-four (24) hours per day, seven (7) days per week.
Sublessee agrees to use and comply with any security systems including security
card systems employed by Landlord and Sublessor from time to time during the
Term of this Sublease. It is Sublessor's understanding that Landlord currently
provides a security desk within the Building from 6:30 a.m. until 10:30 p.m.
seven days per week, it being understood by Sublessee that the provisions of a
security desk and security card systems are no warranty, representations or
guaranty by Landlord or Sublessor as to the safety or security of persons and
property within the Building, the Sublease Premises or the Building.
Notwithstanding the foregoing sentence, Sublessee shall be solely responsible
for the security of all persons and property within the Sublease Premises and
for access to the Sublease Premises including any security card system serving
the Sublease Premises.

     4.6    EXTRA HAZARDOUS USE. Sublessee covenants and agrees that Sublessee
will not do or permit anything to be done in or upon the Sublease Premises, or
bring in anything or keep anything therein, which would invalidate or be in
conflict with any insurance coverage maintained by or for the Sublessor with
respect to the Building as set forth in Section 11 hereof or which would
increase the rate of such insurance on the Sublease Premises or on the Building
above the standard rate applicable to the Sublease Premises or the Building; and
Sublessee further agrees that, in the event that the Sublessee shall do any of
the foregoing, Sublessee shall, at Sublessor's election, cease such activity or
promptly pay to Sublessor, on demand, any such increase resulting therefrom,
which shall be due and payable as additional rent hereunder.

     Sublessee shall not cause or permit any Hazardous Materials (as hereinafter
defined) to be used, generated, stored or disposed of on, under or about, or
transported to or from, the Sublease Premises or the Building (collectively,
"Hazardous Materials Activities") without first submitting to Sublessor at least
sixty (60) days prior to the Term Commencement Date, a complete and
comprehensive Hazardous Materials Inventory Statement listing the types and
quantities of all Hazardous Materials to be used, generated, stored or disposed
of, on, above under about, or transported to or from the Sublease Premises or
the Building (the "Inventory"). In addition, at least sixty (60) days prior to
the commencement of each subsequent lease year during the Term of this Sublease,
Sublessee shall update such Inventory by adding and/or deleting Hazardous
Materials from said Inventory, as appropriate, and deliver said updated
Inventory indicating all Hazardous Materials then

                                       13
<Page>

being used or to be used, generated, stored or disposed of, on, above, under,
about or transported to or from the Sublease Premises or the Building. Sublessor
shall have the right to disapprove of any Hazardous Materials listed on such
Inventories if Sublessor is of the opinion that the use, generation, storage or
disposal or transportation of such Hazardous Materials will violate any
applicable Regulations (as hereinafter defined) or will jeopardize human health,
safety or the environment. If Sublessor consents to any such Hazardous Materials
Activities, the Sublessee shall conduct them in strict compliance (at
Sublessee's expense) with all applicable Regulations and using all necessary and
appropriate precautions to prevent any spill, discharge, release or exposure to
persons or property. In no event shall Sublessor ever be liable to Sublessee for
any loss, costs, expenses, claims, damage or liability arising out of any
Hazardous Materials Activities on the Sublease Premises by or at the direction
of the Sublessee, whether or not such Hazardous Materials Activities were
consented to by Sublessor. Sublessee shall indemnify, defend with experienced
and competent counsel, and hold Sublessor harmless from and against any and all
loss, costs, expenses, claims, damages or liabilities arising out of all
Hazardous Materials Activities on the Sublease Premises, whether or not
consented to by Sublessor which obligation shall survive the termination of this
Sublease. If Sublessor consents to any Hazardous Materials Activities, prior to
using, storing or maintaining any Hazardous Materials on or about the Sublease
Premises, Sublessee shall provide Sublessor with a list of the types and
quantities thereof, and shall update such list as necessary for continued
accuracy. Sublessee shall also provide Sublessor with a copy of a Hazardous
Materials inventory statement, a Material Safety Data Sheet and any similar
document required by any applicable Regulations, and any update filed in
accordance with any applicable Regulations, and shall deliver the same to
Sublessor within ten (10) days of said filing. If Sublessee's activities violate
any Regulations or cause a spill, discharge, release or exposure to any persons
or property in violation of applicable law, Sublessee shall cease such
activities immediately. Sublessee shall immediately notify Sublessor both by
telephone and in writing of any such spill, discharge, release or exposure of
Hazardous Materials or of any condition constituting or posing an "imminent
hazard" under any Regulations. Sublessor and Sublessor's representatives and
employees may enter the Sublease Premises at any time during the Term to inspect
the Sublessee's compliance herewith, and any disclose any spill, discharge,
release, or exposure or any violation of any Regulations to any governmental
agency with jurisdiction.

     Sublessee shall undertake no environmental testing of the Property without
Sublessor's consent, which consent may be withheld in the Sublessor's sole
discretion. The provisions of this Section 4.6 shall survive the expiration or
earlier termination of this Sublease.

5.   RENT; UTILITIES

     5.1    YEARLY FIXED RENT. Commencing with the Term Commencement Date
Sublessee shall pay to Sublessor, without any set-off or deduction, at
Sublessor's office, or to such other person or at such other place as Sublessor
may designate by notice to Sublessee, the Yearly Fixed Rent. The Yearly Fixed
Rent shall be paid in equal monthly installments in advance on or before the
first day of each calendar month during the Term of

                                       14
<Page>

this Sublease and shall be apportioned for any fraction of a month in which the
Term Commencement Date or the last day of the Term of this Sublease may fall.
For purposes of this Sublease, "Yearly Fixed Rent" shall equal $344,632.00
($46.00 per rentable square foot) for each lease year of the Term. For purposes
of this Sublease, the first lease year shall include the first twelve (12)
calendar months of the Term, together with any partial month at the beginning
of the Term. Successive lease years shall be comprised of succeeding periods of
twelve (12) calendar months. Simultaneously with the execution of this Sublease,
Sublessee shall deliver to Sublessor the first monthly installment of Yearly
Fixed Rent.

     5.2    ADDITIONAL RENT. Commencing with the Term Commencement Date,
Sublessee shall pay to Sublessor without any set-off or deduction, at
Sublessor's office, or to such other person or at such other place as Sublessor
may designate by notice to Sublessee, the Additional Rent (as defined below).
The Additional Rent shall be paid in equal monthly installments in advance on
or before the first day of each calendar month during the Term of this Sublease
based upon a statement of Sublessor's good faith estimate of Additional Rent
with respect to Operating Expenses provided by Sublessor to Sublessee at least
thirty (30) days prior to the first day of each Building fiscal year (as
hereinafter defined) (the "Estimated Expense Statement"). Payments of Additional
Rent shall be apportioned for any fraction of a month occurring during the Term
in which the Term Commencement Date or the last day of the Term of the Sublease
may fall. Sublessor, in good faith, shall have the right to provide adjusted
Estimated Expense Statements during any Building fiscal year and in the event
Sublessor fails to provide an Estimated Expense Statement thirty (30) days prior
to the commencement of any given Building fiscal year, Sublessee shall continue
to pay Additional Rent based upon the immediately preceding Estimated Expense
Statement until such time as Sublessor provides Sublessee with a new Estimated
Expense Statement.

     Within six (6) months after the last day of each Building's fiscal year
during the Term of this Sublease, Sublessor shall furnish Sublessee with a
statement of actual Additional Rent for such Building fiscal year with respect
to Operating Expenses certified by an officer of Sublessor (the "Actual Expense
Statement"). In the event the Actual Expense Statement shows that there exists a
deficiency between the Additional Rent which was due by Sublessee and the actual
Additional Rent paid by Sublessee, Sublessee shall pay such deficiency to
Sublessor within thirty (30) days of receipt of such Actual Expense Statement.
In the event the Actual Expense Statement shows that an overpayment of
Additional Rent has been made by Sublessee then Sublessor shall credit the next
installments of Additional Rent due hereunder, or, in the event there is no such
Additional Rent due, Sublessor shall return such overpayment to Sublessee within
thirty (30) days of receipt of Sublessee's written notice requesting same.

     For purpose of this Sublease, "Operating Expenses" for any given Building
fiscal year shall equal the product of (a) Sublessee's Proportionate Share (as
defined in Section 2.4 hereof) times (b) all costs and expenses incurred
annually by Landlord and Sublessor in the operation and maintenance of the
Building and the Lot in accordance with generally accepted operational and
maintenance procedures consistent with the management of comparable office and
research/development buildings in the greater Boston area that are commonly
utilized by Boston University in other buildings in the Boston University

                                       15
<Page>

Medical Campus, as determined in accordance with GAAP, including, without
limiting the generality of the foregoing, all such costs and expenses in
connection with (1) insurance, all insurance deductibles, license fees,
security, janitorial service, landscaping, and snow removal, (2) wages,
salaries, management fees (whether managed by Landlord, Sublessor, and/or a
third party, or a combination of the foregoing), employee benefits, payroll
taxes, onsite office expenses, administrative and auditing expenses, and
equipment and materials for the operation, management, maintenance of the
Building and Lot, (3) any capital expenditures (amortized, with interest at a
rate equal to the prime rate from time to time (as published by The Wall Street
Journal) plus one percent (1%), over its estimated useful life according to
GAAP) made by Landlord or Sublessor for the purpose of reducing operating
expenses or complying with any governmental requirement enacted after the Term
Commencement Date and any capital expenditures (amortized as set forth herein)
associated with replacement of equipment or structural items, (4) the furnishing
of heat, air conditioning, utilities, and any other service (specifically
excluding any service to the extent to which Sublessor or Landlord is entitled
to special reimbursement by individual tenants and specifically excluding
electricity which is separately metered or submetered and which Sublessee pays
directly to the public utility providing same or to Sublessor), (5) the
furnishing of the repairs and other services, and (6) data processing charges
reasonably allocable to the Building.

     Notwithstanding anything to the contrary contained herein, the following
shall be excluded from Additional Rent: (1) wages, salaries, or other
compensation or benefits paid to any persons above the grade of Building manager
(or equivalent position); (2) debt service; (3) expenses of redecorating and
renovating space for new or existing tenants or for tenants renewing their
leases; (4) legal and accounting fees relating to (A) disputes with occupants of
the Building, or (B) disputes with purchasers, prospective purchasers, mortgages
or prospective mortgagees, or (C) negotiations of leases, contracts of sale or
mortgages; (5) brokerage commissions; (6) any rent under any ground or
underlying lease (including, without limitation, the Main Lease); (7) any fines
or penalties incurred due to violations by Landlord, Sublessor or any tenant or
other occupant of the Building of any law; (8) any amount incurred to a company
or other entity affiliated with Landlord or Sublessor to the extent the same
exceeds the amount which would have been incurred on a fair market basis in the
absence of such affiliation; (9) any interest, fines or penalties incurred
resulting from late payment by Landlord or Sublessor of any operating expense;
(10) costs incurred in connection with the removal, encapsulation or other
treatment of any Hazardous Materials (as defined below) not caused by Sublessee
(except to the extent expressly permitted under this Section 5.2); (11) any
amounts incurred for repairs or other work occasioned by fire, windstorm, or
other casualty (only to the extent Sublessor is reimbursed by insurance or would
have been reimbursed by insurance had Sublessor maintained the insurance it is
required to maintain under this Sublease) and specifically excluding the amount
of any deductibles); and (12) any costs incurred for cleaning or janitorial
services, utilities or other services if provided to one or more occupants of
the Building but not required by this Sublease to be provided to Sublessee
without separate charge.

                                       16
<Page>

     Sublessee shall have the right to inspect, copy and audit those portions of
Sublessor's and Landlord's book and records with respect to Operating Expenses.
Sublessee shall give Sublessor notice of the exercise of its inspection and
audit right hereunder with respect to any immediately preceding Building fiscal
year no later than sixty (60) days after receipt from Sublessor of the Actual
Expense Statement for such Building fiscal year. Sublessor shall, within ninety
(90) days of receipt of Sublessee's written request hereunder, make available or
shall cause Landlord to make available such books and records. If Sublessee
disputes the correctness of any Actual Expense Statement and Sublessor and
Sublessee disputes the correctness of any Actual Expense Statement and Sublessor
and Sublessee cannot resolve such dispute within thirty (30) days after such
dispute arises, then either Sublessor or Sublessee may require that such dispute
be resolved by a certified public accounting firm designated by the American
Arbitration Association (or any successor thereto), whose decision shall be
binding on Sublessee and Sublessor and whose cost shall be paid by the
nonprevailing party. If the dispute shall be determined in Sublessee's favor,
then Sublessor, within thirty (30) after the determination, shall refund to
Sublessee the amount of Sublessee's overpayment of Operating Expenses. The
provisions of this paragraph shall survive the expiration or earlier termination
of this Sublease.

     5.2A   TAX AND TAX FUND PAYMENTS. Commencing with the Term Commencement
Date, Sublessee shall pay to Sublessor as additional rent Sublessee's
proportionate share (as may be adjusted as set forth below) of all real estate
taxes (including, without limitation, all betterment assessments, amortized over
the longest period permitted by law, all reasonable tax abatement costs, all
charges in lieu of such taxes and any tax on any fixture installed in the
building (including the Sublease Premises) even if taxed as personal property)
imposed against the Building and the Lot, prorated with respect to any portion
of a calendar year in which the Term of this Sublease begins or ends
("Additional Rent for Taxes"). The term "real estate taxes" for the purpose
hereof shall include all gross receipts or similar taxes, if any, imposed or
levied upon, assessed against or measured by any Yearly Fixed Rent, Additional
Rent or other sum payable hereunder, and all sales, value added, use and similar
taxes, if any, at any time levied, assessed or payable on account of the leasing
or use of the Sublease Premises; provided, however, that nothing contained in
this Sublease shall require Sublessee to pay any franchise, corporate, estate,
inheritance, succession, capital levy or transfer tax of Sublessor or Landlord,
or any income, profits or revenue, gift or capital stock tax or charge upon the
Yearly Fixed Rent and Additional Rent payable by Sublessee under this Sublease,
or any interest or penalties or any real estate taxes (provided Sublessee is not
in default in its payments of Yearly Fixed Rent and Additional Rent hereunder).

     Notwithstanding anything to the contrary set forth herein, Sublessee's
proportionate share of all real estates taxes imposed against the Building and
the Lot shall be recalculated from time to time during the Term of this Sublease
to the extent Sublessor is successful in obtaining tax exempt status for the
Property or any portion thereof and/or enters into a so called pilot agreement
with the City of Boston with respect to the Property if and only if such tax
exemption or pilot agreement includes the Sublease Premises. "Pilot agreement"
shall mean any agreement entered into by and between Sublessor (or Landlord) and
the City of Boston for payment in lieu of taxes due to the Sublessor's (or
Landlord's) not-for-profit status. Any payments due under any pilot agreements
shall be referred to as "pilot payments". Any recalculation of real estate taxes
shall be as follows:

                                       17
<Page>

     The sum of:

     (a)    For those uses of the Sublease Premises or portions thereof which
are attributable to Sublessee's tax exempt or not-for-profit uses, Sublessee's
proportionate share of real estate taxes shall be equal to the product of (i)
any pilot payments for the Building or any portion thereof times (ii) the
fraction, the numerator of which shall be the number of rentable square feet of
Sublease Premises used for tax exempt or not-for-profit uses and the denominator
of which shall be the number of rentable square feet in the Building which are
the subject of the pilot agreement, and

     (b)    For retail or for profit uses (that is, any use which is ineligible
for tax exempt or not-for-profit status) of the Sublease Premises, Sublessee's
proportionate share of real estate taxes shall be equal to the product of (i)
tax bill for the portion of the Building used for retail or for-profit uses
times (ii) the fraction, the numerator of which shall be the number of rentable
square feet of Sublease Premises used for retail or for-profit uses and the
denominator of which shall be the number of rentable square feet in the Building
used for retail or for-profit uses. Sublessor and Sublessee acknowledge that the
proportionate share of real estate taxes due from Sublessee from time to time
during the Term of the Sublease may be recalculated as set forth in the
preceding sentences.

     Notwithstanding anything to the contrary contained herein, if different tax
treatment is accorded by the taxing authorities with respect to vacant space in
the Sublease Premises or different tax treatment is accorded by the taxing
authorities with respect to office, retail or research and redevelopment uses in
the Building or the Main Premises, as the case may be, Sublessee's proportionate
share of real estate taxes shall be recalculated from time to time during the
Term to reflect such different tax treatment and in all events Sublessee shall
be responsible for all real estate taxes attributable to the Sublease Premises.

     To the extent that Sublessor or Landlord receives a refund or reduction
with respect to real estate taxes payable by Sublessee under this Sublease after
such refund or reduction is actually received by Sublessor, Sublessor, after
deducting all reasonable expenses associated therewith, shall pass on to
Sublessee its share of such refund or reduction. The forgoing sentence shall
survive the expiration or sooner termination of this Sublease.

     Sublessee shall, with each monthly installment of Yearly Fixed Rent, make
tax fund payments to Sublessor in the amount of one twelfth (1/12) of the
estimated tax due. "Tax fund payments", with respect to any given fiscal year,
refer to such payments as Sublessor shall reasonably determine to be sufficient
to provide in the aggregate a fund adequate to pay all payments required from
Sublessee pursuant to Section 5.2A for such fiscal year when they become due and
payable. The term "fiscal year" shall mean the twelve month period commencing on
July 1 and ending on June 30th or such twelve month period designated by the
taxing authority for the City of Boston as a fiscal year from time to time.
Sublessor, within thirty days after Sublessee's request for a copy of the actual
tax bill (the "Tax Bill"), shall furnish Sublessee with a copy of the Tax Bill
for each fiscal year during the Term of this Sublease. Tax fund payments shall
be paid in equal monthly installments in

                                       18
<Page>

advance on or before the first day of each calendar month during the Term of the
Sublease based upon a statement of Sublessor's good faith estimate of Additional
Rent for Taxes provided by Sublessor to Sublessee at least thirty (30) days
prior to the first day of the fiscal year (the "Estimated Tax Statement").
Sublessor, in good faith, shall have the right to provide adjusted Estimated Tax
Statements during any fiscal year, and in the event Sublessor fails to provide
an Estimated Tax Statement thirty (30) days prior to commencement of any fiscal
year, Sublessee shall continue to pay Additional Rent for Taxes based upon the
immediately preceding Estimated Tax Statement until such time as Sublessor
provides Sublessee with a new Estimated Tax Statement. In the event that said
tax fund payments were not adequate to pay Sublessee's share of such real estate
taxes for a given fiscal year, Sublessee shall pay to Sublessor the amount by
which such aggregate is less than the amount of said share, such payment to be
made within thirty (30) days after Sublessee's receipt of a notice from
Sublessor of such amount together with the applicable Tax Bill and Sublessor's
calculation of Sublessee's proportionate share of real estate taxes. Any surplus
tax fund payments shall be accounted for to Sublessee after payment by Sublessor
of the real estate taxes on account of which they were made, and shall be
credited by Sublessor against future tax fund payments or refunded to Sublessee
at Sublessee's option. The two immediately preceding sentences shall survive the
expiration or sooner termination of this Sublease.

     5.3    UTILITIES.

            (a)  Sublessee shall be responsible for and shall pay prior to
                 delinquency all charges for water, electricity, steam,
                 telephone and other utilities and services rendered or supplied
                 to the Sublease Premises. If reasonably possible, all
                 utilities, including electricity (but specifically excluding
                 telephone, which telephone service and lines and installation
                 of lines shall be at Sublessee's sole cost and expense), will
                 be separately metered and provided directly by the utility
                 company. If not, Sublessor may submeter the Subleased Premises.
                 In such event, the cost of the submeter and connecting the
                 utility lines brought to the Subleased Premises to those lines
                 installed in Subleased Premises shall be paid by Sublessee to
                 Sublessor. The foregoing costs may be deducted from the Tenant
                 Allowance. Sublessee shall pay to Sublessor as additional rent
                 (a) all costs and expenses of any such utilities registered by
                 any such submeter and (b) with respect to any such utility that
                 shall not be provided directly by the applicable utility and
                 shall not be submetered, Sublessee's Proportionate Share of the
                 utility expenses (which shall include costs for electrical
                 energy not measured by any such submeter and costs for hot and
                 cold water for ordinary cleaning, toilet, lavatory and drinking
                 purposes, and for all Permitted Uses of Sublease and costs for
                 gas for all Permitted Uses of Sublease) based on the rentable
                 square footage of the Sublease Premises in relation to the
                 rentable square footage of the Building. To the extent that
                 Sublessee does not receive electricity, steam and other
                 utilities (specifically excluding telephones) directly from a
                 third-party

                                       19
<Page>

                 utility provider, Sublessor shall cause such utilities to be
                 furnished to the Sublease Premises through the building systems
                 twenty four (24) hours per day, seven (7) days per week.

            (b)  By reason of Sublessee's use of condenser water for its HVAC
                 systems, Sublessee shall also pay as additional rent to
                 Sublessor, Sublessee's allocable share of the costs for water
                 produced in total by the central plant of the Building.
                 Sublessee's allocable share of such costs shall be determined
                 by BTU or similar metering or by such other standard industrial
                 practice as Sublessor may reasonably employ.

            (c)  Sublessee acknowledges that it is installing certain equipment
                 that shall serve the Sublease Premises exclusively and that the
                 electricity consumed by such equipment shall be measured by a
                 meter of submeter. The cost of the meter or submeter and
                 installation of the meter or submeter shall be at Sublessee's
                 sole cost and expense. The foregoing costs may be deducted from
                 the Tenant Allowance.

     Sublessor shall not be liable in any way to Sublessee for any failure or
defect in the supply or character of electrical energy furnished to the Sublease
Premises by reason of any requirement, act or omission of the public utility or
utility provider serving the Building with electricity unless due to the
negligent act or omission of Sublessor. Sublessee's use of electrical energy in
the Sublease Premises shall not at any time exceed the capacity of any of the
electrical conductors and equipment in or otherwise serving the Sublease
Premises as of the Term Commencement Date. Sublessee agrees that it will not
make any alteration to the electrical equipment in the Sublease Premises without
the prior written consent of Sublessor in each instance first obtained in
accordance with the provisions of Section 8 and 9 hereof. Sublessee, at its own
expense, shall replace all light fixtures, bulbs, tubes, lamps, lenses, globes,
ballasts and switches initially installed by Sublessor. If Landlord or Sublessor
reasonably determines that Sublessee is using water and/or utilities in excess
of standard research and development tenants or using a disproportionate amount
of water and/or utilities in relation to other tenants or occupants in the
Building, Sublessor may assess Sublessee as additional rent charges for such
excessive consumption of water and/or utilities (collectively, "Excess
Utilities"). Sublessee shall pay all bills and/or invoices for Excess Utilities
within thirty (30) days after receipt of a bill and/or invoice.

     5.4    INTERRUPTION OR CURTAILMENT OF SERVICES. Landlord and Sublessor
reserve the right to interrupt, curtail, stop or suspend the furnishing of
services and the operation of Building systems, when necessary by reason of
accident or emergency, or of repairs, alterations, replacements or improvements
in the reasonable judgment of Landlord or Sublessor desirable or necessary to be
made, or of difficulty or inability in securing supplies or labor, or of
strikes, or of any other cause beyond the reasonable control of Landlord or
Sublessor, whether such other cause be similar or dissimilar to those
hereinabove specifically mentioned, until said cause has been removed.
Notwithstanding anything contained herein to the contrary, rent hereunder shall
abate if the entire Sublease Premises

                                       20
<Page>

are rendered untenantable for thirty (30) consecutive business days, Sublessee
does not use any portion of the Sublease Premises and such interruption of
services is due to Sublessor's negligence or omission or willful misconduct and
not caused by Sublessee's negligence, omission or willful misconduct. Except
where impossible due to emergency conditions or conditions beyond Landlord's or
Sublessor's control, Sublessor agrees to use reasonable efforts to provide
Sublessee with advance notice of any such interruptions, curtailments, stoppages
and suspensions of service or Building systems. Neither Landlord nor Sublessor
shall have any responsibility or liability for any such interruption,
curtailment, stoppage, or suspension of services or systems.

     5.5    PAYMENT TO MORTGAGEE. Sublessor reserves the right to provide in any
mortgage given by it of the Main Premises that some or all rents, issues, and
profits and all other amounts of every kind payable to Sublessor under this
Sublease shall be paid directly to mortgagee for Sublessor's account and
Sublessee covenants and agrees that it will, after receipt by it of written
notice from Sublessor designating such mortgagee to whom payments are to be made
by Sublessee, pay such amounts thereafter becoming due directly to such
mortgagee until excused therefrom by written notice from such mortgagee.

     5.6    UTILITY DEREGULATION. To the extent permitted by law, Sublessor or
Landlord shall have the right at any time and from time to time during the Term
to contract for or purchase electrical service from any company or third party
providing electricity services (the "Electricity Service Provider"). Sublessee
agrees to cooperate with Landlord, Sublessor and the Electricity Service
Provider and at all times and, as reasonably necessary, shall allow Landlord,
Sublessor, and the Electricity Service Provider reasonable access to any
electrical lines, feeders, risers, wiring and any other such machinery within
the Sublease Premises. Landlord and Sublessor shall not be liable or responsible
for any loss, damage, or expense that Sublessee may sustain or incur by reason
of any change, failure, interference, disruption or defect in the supply or
character of the electric energy furnished to the Sublease Premises, or if the
quantity or character of the electric energy supplied by the Electricity Service
Provider is no longer available or suitable for Sublessee's requirements, and no
such change, failure, defect, unavailability or unsuitability shall constitute
an actual or constructive eviction, in whole or in part, or entitle Sublessee to
any abatement or diminution of rent, or relieve Sublessee from any of its
obligations under the Sublease.

     5.7    HVAC SERVICES. It is Sublessor's intention that there shall be a
separate HVAC system serving each floor within the Building. Sublessee hereby
agrees that any such HVAC system exclusively serving the Sublease Premises (or a
portion thereof) shall be maintained and repaired at the sole cost and expense
of Sublessee (or at Sublessor's election, such system may be maintained and
repaired by Sublessor and the cost of such maintenance and repair shall be
charged to Sublessee as additional rent) and in such a manner so it is in good
working condition during the Term and upon the expiration or sooner termination
of this Sublease (provided that, notwithstanding anything to the contrary
contained in this Sublease, with respect to any replacement to or of any HVAC
system, exclusively serving the Sublease Premises (or a portion thereof), to the
extent the cost of such replacement should be considered to be a capital
expenditure under GAAP, (i) Sublessor shall make such replacement, (ii) the
capital expenditure shall be amortized, with interest at the prime rate,

                                       21
<Page>

over its estimated useful life according to GAAP and (iii) Sublessee shall
reimburse Sublessor as additional rent an amount equal to the product of (x) the
cost of the capital expenditure (together with interest as set forth above in
Section 5.2) times (y) a fraction, the numerator of which shall be the number of
years remaining in the Term (as it may be extended pursuant to Section 2.4
hereof) and the denominator of which shall be the number of years over which the
capital expenditure shall be amortized). Any payments to be made as additional
rent in the preceding clause (iii) shall be made in equal installments at the
commencement of each lease year remaining in the Term (as it may be extended
pursuant to Section 2.4 hereof). By way of example, if the replacement of an
HVAC system exclusively serving the Sublease Premises (or a portion thereof) is
$60,000 and is amortized over ten (10) years and there are three (3) lease years
remaining in the Term (as it may be extended pursuant to Section 2.4 hereof),
Sublessee shall pay at the commencement of each lease year remaining in the Term
as additional rent $6,000 (together with interest as aforesaid). To the extent
that an HVAC System serving the Sublease Premises (or a portion thereof) serves
other premises as well, Sublessee shall be billed for HVAC services for the
whole of the Sublease Premises or that portion of the Sublease Premises which is
served by an HVAC system also serving other premises (a "Building HVAC System")
as set forth in the next succeeding sentences. To the extent a Building HVAC
System serves the Sublease Premises (or a portion thereof), Landlord shall
provide HVAC services to the Sublease Premises or that portion of the Sublease
Premises during the hours of 8:00 A.M. to 6:00 P.M., and such HVAC services
shall either be billed or assessed as additional rent based on (i) readings as
recorded by the submeter or (ii) Sublessee's Proportionate Share of the HVAC
services. In addition, Landlord shall repair and maintain any such Building HVAC
System, the cost of which maintenance and repair shall be charged to Sublessee
as additional rent. Any HVAC services required by Sublessee before or after the
foregoing hours through a Building HVAC System or any Excess Utilities used by
Sublessee shall be at Sublessee's sole cost and expense, Sublessee hereby
agreeing to pay within thirty (30) days of receipt of a bill for such Excess
Utilities or such overtime HVAC services at overtime rates charged by the
Building from time to time (which shall not exceed Sublessor's actual
out-of-pocket cost (on a unit cost basis) of providing such HVAC service). In
addition, Sublessee shall notify Sublessor and Landlord at least 24 hours in
advance of any overtime Building HVAC System services that Sublessee shall
require. In addition, should Sublessee's particular use of the Sublease Premises
require any additional special temperature controls over the Building standard
temperature controls, Sublesses shall be responsible for installing such HVAC
systems.

     5.8    SUBLESSOR SERVICES.

            (a)  DOMESTIC WATER. Sublessor shall furnish or cause Landlord to
                 furnish twenty-four (24) hours per day, seven (7) days per
                 week, hot and cold water to the Sublease Premises (and to
                 lavatories in common areas) for ordinary cleaning, toilet,
                 lavatory and drinking purposes (in each case, as contemplated
                 by, and in accordance with the specifications therefor set
                 forth on Exhibit F-2 hereof).

            (b)  REPAIRS AND OTHER SERVICES. Except as otherwise provided in
                 Article 14, and subject to Sublessee's obligations in Article
                 10 and Section 5.7 or as

                                       22
<Page>

                 otherwise agreed in writing by the parties hereto, Sublessor
                 shall (a) keep and maintain in good operating condition the
                 Building's sanitary, electrical, elevator, heating, air
                 conditioning, ventilation, vacuum, water, sewer, plumbing,
                 mechanical, fire safety and other systems (specifically
                 excluding (except to the extent otherwise provided in Section
                 5.7 hereof) those systems used exclusively by Sublessee or
                 individual lessees or occupants in the Building), (b) provide
                 cleaning services to the common areas of the Building according
                 to the cleaning standards generally prevailing in comparable
                 research, development buildings in the City of Boston, (c) keep
                 all driveways, roadways, walkways, if any, on the Property
                 clean, and remove all snow therefrom and cause the Landlord to
                 do the same with respect to the Parking Facility, and (d)
                 provide grounds maintenance to all landscaped areas according
                 to the standards generally prevailing in comparable
                 research/development buildings in the City of Boston. Sublessor
                 shall also provide to the Sublease Premises and to Sublessee,
                 (A) twenty-four (24) hours per day, seven (7) days per week
                 elevator service (through 2 passenger elevators) and (B) during
                 hours of 9:00 A.M. to 5:00 P.M., Monday through Friday
                 (excluding all federal and state and municipal holidays), use
                 of the Building's loading docks and freight elevators subject
                 to periods of disuse. Sublessor's maintenance obligations and
                 Force Majeure Delays.

     5.9    ADDITIONAL RENT. All payments due from Sublessee to Sublessor,
Landlord, and/or any third party and/or provider including without limitation
Additional Rent. Additional Rent for Taxes, utility expenses, Parking Rent,
charges for the emergency generator as set forth in Exhibit E hereto, and all
other costs and expenses incurred by or assessed against Sublessee hereunder
shall constitute "additional rent" for purpose of this Sublease. Sublessee
hereby agrees to pay as additional rent. Sublessee's Proportionate Share of
actual out-of-pocket costs incurred for the installation, maintenance and
operation by Sublessor of the emergency generator and the use by Sublessee of
the emergency generator as described herein and in the Work Letter Agreement.

6.   CHANGES OR ALTERATIONS BY SUBLESSOR

     Sublessor reserves the right, exercisable by itself or its nominee, at any
time and from time to time without the same constituting an actual or
constructive eviction and without incurring any liability to Sublessee therefor
or otherwise affecting Sublessee's obligations under this Sublease, to make such
changes, alterations, additions, improvements, repairs or replacements in or to
the Building (including the Sublease Premises with respect to those repairs that
Sublessor is required or permitted to make pursuant to the express terms of this
Sublease) and the fixtures and equipment thereof, as well as in or to the street
entrances, halls, passages, elevators, escalators, and stairways thereof, as it
may deem necessary or desirable, and to change the arrangement and/or location
of entrances or passageways, doors and doorways, and corridors, elevators,
stairs, toilets, or other public parts of the Building, provided, however, that
except in cases of emergency, Sublessor's exercise of its rights hereunder shall
(A) not compromise any security system installed by

                                       23
<Page>

Sublessee and approved by Sublessor (if its approval is hereunder), (B) be done
after giving reasonable prior notice to Sublessee and (C) (i) shall be done in a
manner consistent with the maintenance of the Building as a good quality
research/development building (by reference to other comparable
research/development buildings in the Boston University Medical Campus), (ii)
shall not reduce the usable floor area of the Sublease Premises and (iii) shall
not (other than to a de minimis extent) adversely affect Sublessee's use of the
Sublease Premises for the Permitted Uses (including, without limitation,
Sublessee's access thereto). Nothing contained in this Article shall be deemed
to relieve Sublessee of any duty, obligation or liability of Sublessee with
respect to making or causing to be made any repair, replacement or improvement
or complying with any law, order or requirement of any governmental or other
authority. Neither this Sublease nor any use by Sublessee shall give Sublessee
any right or easement to use, or the use of any door or any passage or any
concourse connecting with any other building or to any public convenience, and
the use of such door, passages and concourses and of such conveniences may be
regulated or discontinued at any time and from time to time by Landlord or
Sublessor without notice to Sublessee and without affecting the obligation of
Sublessee hereunder or incurring any liability to Sublessee therefor.

7.   FIXTURES, EQUIPMENT AND IMPROVEMENTS - REMOVAL BY SUBLESSEE

     Except as otherwise expressly provided in Section 3.1A hereof or this
Section 7, all fixtures, equipment, improvements and appurtenances attached to
or built into the Sublease Premises prior to or during the Term, whether by
Sublessor at its expense or at the expense of Sublessee (either or both) or by
Sublessee shall be and remain part of the Sublease Premises and shall not be
removed by Sublessee at the end of the Term unless otherwise expressly provided
in this Sublease. Except as otherwise expressly provided in Section 3.1A hereof
or this Section 7, where not permanently affixed to the Sublease Premises, and
if furnished and installed by and at the sole expense of Sublessee (but
specifically excluding all items paid for by the Tenant Allowance ), all
removable electrical fixtures, cables, carpets, hoods and equipment, drinking or
tap water facilities, furniture, or trade fixtures or business equipment shall
not be deemed to be included in such fixtures, equipment, improvements and
appurtenances and may be, and upon the request of Sublessor will be, removed by
Sublessee upon the condition that such removal shall not damage the Sublease
Premises or the Building or any building systems serving the Sublease Premises
or Building, or create an unsafe condition, and that any damage to the Sublease
Premises or the Building arising from such removal shall be promptly repaired by
Sublessee in a manner satisfactory to Sublessor subject to Sublessor's rights
pursuant to Article 15 of this Sublease. The obligations of Sublessee under the
foregoing sentence shall survive the expiration or sooner termination of this
Sublease.

8.   ALTERATIONS AND IMPROVEMENTS BY SUBLESSEE

     Except as otherwise expressly provided herein, Sublessee shall make no
alterations, installations, removals, additions or improvements in or to the
Sublease Premises without Sublessor's prior written consent and then only by
contractors or mechanics approved by

                                       24
<Page>

Sublessor. No installations or work shall be undertaken or begun by Sublessee
until Sublessor has approved written plans and specifications therefor, and no
amendments or additions to such plans and specifications shall be made without
prior written consent of Sublessor. Any such work, alterations, installations,
removals, additions and improvements shall be done at the sole expense of
Sublessee and at such times and in such manner as Sublessor may from time to
time designate. If sublessee shall make any alterations, decorations,
installations, removals, additions or improvements which Sublessee may, under
Article 3 or 7 remove, then Sublessor may elect, at the time of approval
thereof, to require Sublessee at the expiration of this Sublease to remove the
same and to deliver to Sublessor the Sublease Premises to the same condition as
existed at the Term Commencement Date.

     Notwithstanding anything contained herein to the contrary and provided
Sublessee is not in default (after the expiration of all applicable notice and
cure periods) under the terms and conditions of this Sublease, Sublessee may
make non-structural alterations without the consent of Sublessor (being
alterations which do not affect the structure of the Building and/or any
Building systems including the mechanical, plumbing or electrical systems
serving the Building) which are less than $10,000.00 in any one instance,
provided, however, that (a) Sublessee shall provide Sublessor with not less than
thirty (30) days prior written notice before commencing such alterations and
copies of all permits necessary for such alternations, (b) said notice shall
contain a certification by Sublessee that such alteration (i) is a
non-structural alteration (for purpose of this Sublease ) and (ii) shall not
cost more than $10,000.00, and (c) such alterations are performed in accordance
with the terms of this Sublease. All structural alterations (regardless of the
cost) and all non-structural alterations costing $10,000.00 or more are subject
to Landlord's prior written consent. With respect to those consent and approval
rights of Sublessor set forth in Section 8 hereof, provided there is no default
(after the expiration of all applicable notice and cure periods) under this
Sublease, Sublessor shall not unreasonably withhold, delay or condition its
consent or approval so long as the proposed alterations and/or the architect,
engineer or other applicable persons or entities selected by Sublessee to
undertake the proposed alterations, are consistent with the quality of the
Building (including the Base Building Work), shall not violate any applicable
laws, shall maintain harmonious labor relations and shall not interfere with the
structural integrity and/or structural elements of the Building, operations and
rights of other occupants and tenants within the Building or any other
construction in or about the Building. In addition, Sublessee shall reimburse
Sublessor for all reasonable cost incurred by Sublessor in reviewing any plans
and specifications and contracts necessary to undertake such proposed
alterations and for all construction supervising fees, expenses and costs.

9.   SUBLESSOR'S CONTRACTORS - MECHANICS' AND OTHER LIENS - STANDARD OF
     SUBLESSEE'S PERFORMANCE - COMPLIANCE WITH LAWS

     Whenever Sublessee shall make any alterations, decorations, installations,
removals, additions or improvements or do any other work in or to the Sublease
Premises, Sublessee shall strictly observe the following covenants and
agreements:

                                       25
<Page>

     a. In no event shall any materials or equipment (other than freestanding
        equipment installed on or before the Term Commencement Date or
        after-acquired freestanding equipment) be incorporated in or added to
        the Sublease Premises in connection with any such alteration,
        decoration, installation, addition or improvement which is subject to
        any lien, charge, mortgage or other encumbrance of any kind whatsoever
        or is subject to any security interest or any form of title retention
        agreement. Any mechanic's lien filed against the Sublease Premises or
        the Building for work claimed to have been done for, or materials
        claimed to have been furnished to Sublessee shall be discharged by
        Sublessee within ten (10) days thereafter, at the expense of Sublessee,
        by filing the bond required by law or otherwise. If Sublessee fails so
        to discharge any lien, Sublessor may do so at Sublessee's expense and
        Sublessee shall reimburse Sublessor for any expense or cost incurred by
        Sublessor in so doing within ten (10) days after rendition of a bill
        therefor.

     b. All installations or work done by Sublessee under this or any other
        Article or this Sublease shall be at its own expense (unless
        otherwise expressly provided) and shall at all times comply with (i)
        laws, rules, orders and regulations of governmental authorities having
        jurisdiction thereof: (ii) orders, rules and regulations of any Board of
        Fire Underwriters, or any other body hereafter constituted exercising
        similar functions, and governing insurance rating bureaus; (iii) plans
        and specifications prepared by and at the expense of Sublessee
        theretofore submitted to Sublessor for its prior written approval
        (subject to the provisions of Article 8).

        Sublessee shall procure all necessary permits before undertaking any
        work in the Sublease Premises; do all such work in a good and
        workmanlike manner employing materials of good quality and complying
        with all governmental requirements, and defend, save harmless, exonerate
        and indemnify Landlord and Sublessor from all injury, loss or damage to
        any person or property occasioned by or growing out of such work.

10.  REPAIRS AND SECURITY BY SUBLESSEE

     Sublessee shall keep or cause to be kept all and singular the Sublease
Premises neat and clean and maintain in such good repair, order and condition as
the same are in on the Term Commencement Date or may be put in during the Term
hereof, reasonable use and wear thereof and damage by fire or casualty excepted.
Without limiting the generality of the foregoing, sublessee shall replace all
windows of the Sublease Premises with glass of the same quality whenever broken.
Sublease shall provide cleaning services to the Sublease Premises according to
cleaning standards generally prevailing in comparable research and development
buildings in the City of Boston and according to any cleaning specifications
adopted by Landlord or Sublessor from time to time during the Term of the
Sublease.

     Subject to Sublessor's rights pursuant to Section 15.4 of the Sublease, (a)
Sublessee shall make, as and when needed as a result of misuse by, or neglect or
improper conduct

                                       26
<Page>

(including, without limitation, the placement of any weight exceeding floor
load) of Sublessee or Sublessee's servants, contractors, employees, agents,
invitees or licensees or otherwise, all repairs in and about the Sublease
Premises necessary to preserve them in such repair, order and condition, which
repairs shall be in quality and class equal to the original work, and (b)
Sublessee shall replace, keep and maintain in good operating condition all
systems exclusively serving the Sublease Premises including any separate heating
and air conditioning system serving the Sublease Premises, if any such separate
system is installed (subject to the terms and provisions of Section 5.7 hereof),
all plumbing and sewage facilities within the Sublease Premises (including all
such facilities outside of the Sublease Premises, but exclusively serving the
Sublease Premises), any other mechanical and electrical or other special systems
and equipment wherever located if such systems and equipment were installed at
Sublessee's request or service exclusively the Sublease Premises, fixtures,
interior walls, floors, ceilings and sign within Sublease Premises and (c)
Sublessee shall replace and repair all damage to the Building and any Building
systems caused by Sublessee or their contractors, agents, invitees or employees.

11.  INSURANCE, INDEMNIFICATION, EXONERATION AND EXCULPATION

     11.1   INSURANCE. Sublessee shall maintain at its sole expense (a)
Comprehensive Public Liability Insurance naming Landlord, Sublessor, Sublessee
and (whenever Landlord or Sublessor shall so request) any mortgagee as
additional insureds against all claims and demands for injury to or death of
persons or damage to property which may be claimed to have occurred upon the
Sublease Premises in amounts not less than Five Hundred Thousand Dollars
($500,000) for property damage, One Million Dollars ($1,000,000) for injury or
death of one person, and Three Million Dollars($3,000,000) for injury or death
of more than one person in a single accident, and from time to time thereafter
in such higher amounts, if procurable, as may be reasonably required by Landlord
or Sublessor or a mortgagee or lender or any successor or replacement lender and
are customarily carried by responsible office, research and development [and
laboratory] tenants in the City of Boston, and (b) so-called contents and
improvements insurance adequately insuring all property belonging to or
removable by Sublessee and situated in the Sublease Premises.

     11.2   CERTIFICATES OF INSURANCE. Such insurance shall be effected with
insurers authorized to do business in Massachusetts under valid and enforceable
policies, and such policies shall name Landlord, Sublessor, Sublessee and any
additional parties designated by Landlord or Sublessor pursuant to Section 11.1
as the insureds as their respective interests appear. Such insurance shall
provide that it shall not be canceled without at least thirty (30) days prior
written notice to each insured named therein. On or before the Term Commencement
Date and thereafter prior to the expiration of each expiring policy, original
copies of the policies provided for in Section 11.1 issued by the respective
insurers, or certificates or binders of such policies setting forth in full the
provisions thereof and issued by such insurers, shall be delivered by Sublessee
to Landlord and Sublessor and certificates as aforesaid of such policies shall
upon request of Landlord and Sublessor be delivered by Sublessee to the holder
of any mortgage affecting the Sublease Premises.

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<Page>

     11.3   GENERAL. Sublessee shall save landlord and Sublessor harmless, and
shall exonerate and indemnify Landlord and Sublessor, from and against any and
all claims, liabilities or penalties assured by or on behalf of any person,
firm, corporation or public authority:

     a. On account of or based upon any injury to person or loss of or damage to
        property sustained or occurring on the Sublease Premises on accounts of
        or based upon the act, omission, fault, negligence or misconduct of any
        person whomsoever (other than Landlord or Sublessor or their respective
        agents.);

     b. On account of or based upon any injury to person or loss of or damage to
        property, sustained or occurring elsewhere (other than on the Sublease
        Premises) in or about the Building (and, in particular, without limiting
        the generality of the foregoing, on or about the elevators, stairways,
        public corridors, sidewalks, concourses, arcades, malls, galleries,
        vehicular tunnels, approaches, areaways, roof, or other appurtenances
        and facilities used in connection with the Building or Sublease
        Premises) arising out of the use or occupancy of the Building or
        Sublease Premises by Sublessee, or any person claiming by, through, or
        under Sublessee, unless such injury, loss or damage arose out of or
        resulted from the act, omission, fault, negligence or misconduct of
        Landlord or Sublessor;

     c. On account of or based upon (including monies due on account of) any
        work or thing whatsoever done in the Sublease Premises during the Term
        of this Sublease, and

     d. On account of or resulting from the failure of Sublessee to perform and
        discharge any of its covenants and obligations under this Sublease;

and, in respect of any of the foregoing items (a)-(d), from and against all
costs, expenses (including reasonable attorneys' fees), and liabilities incurred
in or in connection with any such claim, or any action or proceeding brought
thereon; and in case of any action or proceeding brought against Landlord or
Sublessor by reason of any such claim, Sublessee upon notice from Landlord or
Sublessor shall at Sublessee's expense resist or defend such action or
proceeding and employ counsel therefor reasonably satisfactory to Landlord or
Sublessor, as the case may be, it being agreed that such counsel as may act for
insurance underwriters of Sublessee engaged in such defense shall be deemed
satisfactory.

     11.4   PROPERTY OF SUBLESSEE. In addition to and not in limitation to the
foregoing, Sublessee covenants and agrees that all merchandise, furniture,
fixtures and property of every kind, nature and description which may be in or
upon the Sublease Premises or Building, in the public corridors, or on the
sidewalks, areaways and approaches adjacent thereto, during the Term of this
Sublease, shall be at the sole risk and hazard of Sublessee, and that if the
whole or any part thereof shall be damaged, destroyed, stolen or removed from
any cause or reason whatsoever, no part of said damage or loss shall be charged
to, or borne by Sublessor or Landlord.

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<Page>

     11.4A  RELEASE AND WAIVER OF SUBROGATION. Each of Sublessor and Sublessee
(the "damaged party") hereby releases the other party (the "released party")
from any liability to the damaged party on account of any damage to the damaged
party's property arising out of any casualty or other loss included within a
standard form of "all-risk" property insurance policy used in the Commonwealth
of Massachusetts (or, if the coverage provided thereby is broader, the fire and
casualty insurance actually carried by the damaged party), excepting, however,
any damage which is the result of the fault of negligence of the released party
or its employees, contractors, agents or invitees. Neither Sublessor nor
Sublessee shall obtain or accept any insurance policy which would be invalidated
by or would conflict with such release; except that either of the Sublessor or
Sublessee shall have the right to obtain a policy of insurance that would be
invalidated by or would conflict with such release (and, the release shall not
apply with respect to damage covered by such a policy), if it is no longer
possible for such party procuring the insurance in question to obtain a policy
which would not be invalidated and would not conflict with such release, and
such party so notifies the other party.

     11.5   BURSTING OF PIPES, ETC. Neither Landlord nor Sublessor shall be
liable for any injury or damage to persons or property resulting from fire,
explosion, falling plaster, steam gas, electricity, electrical disturbance,
water, rain or snow or leaks from any part of the Building or from the pipes,
appliances or plumbing works or from the roof, street or sub-surface or from any
other place or caused by dampness or by any other cause of whatever nature,
unless caused by or due to the willful misconduct or gross negligence of
Landlord, Sublessor or their respective agents, servants or employees; nor shall
Landlord, Sublessor or their respective agents be liable for any such damage
caused by other tenants or persons in the Building or caused by operations in
construction of any private, public or quasi-public work; nor shall Landlord or
Sublessor be liable for any latent defect in the Sublease Premises or in the
Building unless Sublessee provides Sublessor with written notice of such latent
defect not more than six (6) months after the Term Commencement Date and
Sublessor fails to diligently repair it.

     11.6   REPAIRS AND ALTERATIONS - NO DIMINUTION OF RENTAL VALUE. Except as
otherwise provided in Article 14, there shall be no allowance to Sublessee for
diminution of rental value and no liability on the part of Sublessor by reason
of inconvenience, annoyance or injury to Sublessee arising from any repairs,
alterations, additions, replacements or improvements made by Sublessor,
Sublessee or other in or to any portion of the Building or Sublease Premises, or
in or the fixtures, appurtenances, or equipment thereof, or for failure of
Landlord, Sublessor or their respective other to make any repairs, alterations,
additions or improvements in or to any portion of the Building or of the
Sublease Premises, or in or to the fixtures, appurtenances or equipment thereof,
provided however that any such work preformed by or on behalf of Sublessor shall
be subject to the provisions of Section 13.2 and Article 6.

     11.7   SUBLESSOR'S INSURANCE. Sublessor, throughout the Term, shall keep or
cause the Landlord to keep the Building insured for the "full replacement value"
thereof against loss or damage by perils customarily included under standard
"all-risk" policies. In addition, throughout the Term, Sublessor shall maintain
or cause the Landlord to maintain

                                       29
<Page>

commercial general liability insurance, with respect to the Building and the Lot
and the conduct or operation of business therein or thereon, with limits of not
less than One Million ($1,000,000) Dollars combined single limit for bodily
injury and property damage liability in any one occurrence and Three Million
($3,000,000.00) Dollars in the annual aggregate. Within thirty (30) days after
request, Sublessor shall deliver to Sublessee certificates of insurance, showing
that the insurance required to be maintained pursuant to the foregoing
provisions of this Section 11.7 is in force. All policies may be part of any
blanket policies carried by Landlord or Sublessor and shall be issued by
insurers authorized to do business in Massachusetts under valid and enforceable
policies.

12.  ASSIGNMENT, MORTGAGING, SUBLETTING, ETC.

     Sublessee covenants and agrees that neither this Sublease nor the term and
estate hereby granted nor any interest herein, will be assigned, mortgaged,
pledged, encumbered or otherwise transferred (whether voluntarily or by
operation of law), and that neither the Sublease Premises, nor any part thereof,
will be encumbered in any manner by reason of any act or omission on the part of
Sublessee, or used or occupied, or permitted to be used or occupied, or utilized
for any reason whatsoever, by anyone other than Sublessee, or for any use or
purpose other than as permitted hereunder, or be sublet, or offered or
advertised for subletting, without prior written consent of Sublessor and
Landlord in every case, which consent shall not be unreasonably withheld or
delayed.

     Sublessor's consent shall not be considered unreasonably withheld if: (1)
the proposed transferee's financial condition is unacceptable in the reasonable
judgment of Sublessor; (2) the proposed transferee's business is not suitable
for the Building considering the business of the other tenants and the
Building's prestige or would result in a violation of an exclusive right granted
to another tenant in the Building; (3) the proposed use is [substantially]
different than the Permitted Use in the reasonable judgment of Sublessor; (4)
the proposed transferee is a government agency or occupant of the BioSquare
Project (unless the proposed transferee is the Sublessor, pursuant to a proposed
Sub-Sublease having the same terms and conditions as this Sublease); (5)
Sublessee is in default at the time of such request or effective date of any
transfer; or (6) any portion of the Building or Sublease Premises would become
subject to additional or different governmental laws or regulations as
consequence of the proposed transfer and/or the proposed transferee's use and
occupancy of the Sublease Premises. Sublessee acknowledges that the foregoing is
not intended to be an exclusive list of the reasons for which Sublessor may
reasonably withhold its consent to a proposed transfer. Any attempted transfer
in violation of the terms of this Section shall, at Sublessor's option, be void.
Consent by Sublessor to one or more transfers shall not operate as a waiver of
Sublessor's rights as to any subsequent transfers. In addition, Sublessee shall
not, without Sublessor's consent, publicly advertise the proposed rental rate
for any transfer.

     For purposes of this Sublease, transfer shall mean the assignment
(collateral or otherwise), mortgage, sublease, transfer, pledge or encumbrance
by Sublessee of this Sublease or any interest therein or the grant by Sublessee
of any license, concession or other right of occupancy of the Sublease Premises
or any portion thereof. "Transfer" shall also include (a) if Sublessee is a
corporation, the dissolution or liquidation of the corporation, or

                                       30
<Page>

(b) if Sublessee is a partnership or other entity, the transfer of more than
twenty-five percent (25%) of the profit and loss participation in such
partnership or entity during the Term of this Sublease (whether or not in one or
more transfers) or the dissolution, merger of liquidation of the partnership. If
Sublessee is a limited or general partnership (or is comprised of two or more
persons, individually or as co-partners), Sublessee shall not be entitled to
change or convert to (i) a limited liability company, (ii) a limited liability
partnership or (iii) any other entity which possesses the characteristics of
limited liability without the prior written consent of Sublessor, which consent
may be given or withheld in Sublessor's sole discretion.

     Sublessee's sole remedy in the event that Sublessor shall wrongfully
withhold consent to or disapprove any assignment or sublease shall be to obtain
an order by a court of competent jurisdiction that Sublessor grant such consent;
in no event shall Landlord be liable for damages with respect to its granting or
withholding consent to any proposed assignment or sublease. If Sublessor shall
exercise any option to recapture the Sublease Premises, or shall deny a request
for consent to a proposed assignment or sublease, Sublessee shall indemnify,
defend and hold Sublessor harmless from and against any and all losses,
liabilities, damages, costs and claims that may be made against Sublessor by the
proposed assignee or Subtenant, or by any brokers or other persons claiming a
commission or similar compensation in connection with the proposed assignment or
sublease.

     If Sublessee requests Sublessor's consent to a transfer, Sublessee,
together with such request for consent, shall provide Sublessor with the name of
the proposed transferee and the nature of the business of the proposed
transferee, the term, use, rental rate and all other material terms and
conditions of the proposed transfer, including, without limitation, a copy of
the proposed assignment, sublease or other contractual documents and evidence
reasonably satisfactory to Sublessor that the proposed transferee is financially
responsible. Notwithstanding Sublessor's agreement to act reasonably under this
Section, Sublessor may, within forty-five (45) days after its receipt of all
information and documentation required herein, either (1) consent to or
reasonably refuse to consent to such transfer in writing; or (2) if Sublessee
proposes to sublease or assign the Sublease Premises to a third party, cancel
and terminate this Lease with respect to the portion of the Term and Sublease
Premises that Sublessee proposes to assign or sublet, upon forty-five (45) days'
notice.

     With respect to an assignment or sublease, Sublessor may recapture the
portion of the Sublease Premises that Sublessee proposes to assign or sublease
the Sublease Premises to a third party. Sublessor must exercise (or forego) its
recapture rights within forty-five (45) days of its receipt of Sublessee's
sublease/assignment notice. In order to effectuate its recapture rights,
Sublessor must terminate the Sublease with respect to that portion of the
Sublease Premises which it is recapturing and Sublessee shall have no further
obligations with respect to that portion of the Sublease Premises which are
recaptured (and there shall be a pro rata reduction in Rent based upon the
rentable square footage of the recaptured portion of the Sublease Premises
relative to the rentable square footage of Sublease Premises prior to
recapture), except as specifically set forth herein, and Sublessee shall at its
expense erect, if necessary, a demising wall to separate the remainder of the
Sublease Premises from that portion of the Sublease Premises which is being
recaptured and to take such other steps

                                       31
<Page>

as shall be necessary to make the portion of the Sublease Premises that is not
being recaptured into a self-contained, lawfully demisable rental unit.

     In addition, with respect to any assignment or sublease (specifically
excluding a permitted transfer), all "Excess Rents" from such sublease or
assignment shall be paid to Sublessor as additional rent. "Excess Rents" means
Sublessee's net profit from the sublease/assignment after first deducting
Sublessee's costs (which are reasonable, actual, and documented with no markup)
of the subleasing/assignment (including commissions, legal fees, and tenant
improvement costs amortized over the entire term of the Sublease (which are
reasonable, actual, and documented with no markup) required to induce the
Sublessee to sublease or the assignee to accept an assignment.

     In the event Sublessor is requested to consent to an assignment of this
Sublease or a subletting of the Subleased Premises including without limitation
a permitted transfer as defined below, Sublessee shall pay all costs and
expenses in connection with such assignment or subletting, including, without
limitation, any reasonable attorneys' fees of Sublessor in connection with its
review of the assignment or subletting documents, any cost of renovating,
altering or decorating the Subleased Premises for a new occupancy (if Sublessee
desires to do the same) and any leasing brokerage fees payable.

     The listing of any name other than that of Sublessee, whether on the doors
of the Sublease Premises or on the Building directory, or otherwise, shall not
operate to vest any right or interest in this Sublease or in the Sublease
Premises or be deemed to be the written consent of Sublessor mentioned in this
Article, it being expressly understood that any such listing is a privilege
extended by Sublessor revocable at will by written notice to Sublessee.

     If this Sublease is assigned, or if the Sublease Premises or any part
thereof is sublet or occupied by anybody other than Sublessee including without
limitation a permitted transfer (as defined below), Sublessor may at any time
and from time to time, collect rent and other charges from the assignees,
subtenant or occupant, and apply the net amount collected to the Rent and other
charges herein reserved, but no such assignment, sublease or collection shall be
deemed a waiver of this covenant, or the acceptance of the assignee, subtenant
or occupant as a tenant, or a release of Sublessee from the further performance
of covenants on the part of Sublessee herein contained, including without
limitation, Sublessee's obligation to pay the Yearly Fixed Rent and Additional
Rent. The consent by Sublessor to an assignment or subletting or occupancy shall
not in any way be construed to relieve Sublessee from obtaining the express
consent in writing of Sublessor to any further assignment or subletting or
occupancy. The terms and provisions of this paragraph shall apply to a permitted
transfer.

     Notwithstanding the foregoing, provided Sublessee is not in default after
the giving of notice and the expiration of the applicable grace period set forth
herein at the time of any notice or effective date of any transfer, Sublessee
shall have the right to make without Sublessor's prior written consent, but with
prior written notification to Sublessor, a transfer to (a) a parent, subsidiary,
an entity under common control with Sublessee, (b) any entity with which or into
which Sublessee may consolidate or merge, or (c) any person or entity

                                       32
<Page>

acquiring all or substantially all of the assets of Sublessee, provided that,
prior to any such transfer, Sublessee shall deliver to Sublessor an agreement in
form and substance reasonably satisfactory to Sublessor which contains an
appropriate covenant of assumption by such transferee of all obligations arising
under this Sublease from and after the effective date of such assignment; and
provided further that Sublessee shall have submitted to Sublessor prior thereto
financial statements satisfactory to Sublessor evidencing that such transferee
has a credit rating equal to or better than Sublessee on the date hereof and has
financial resources necessary to fulfill its obligations under the Sublease or
the sub-sublease, as applicable. The foregoing (a)--(c) shall be referred to
herein as a permitted transfer.

13.  MISCELLANEOUS COVENANTS

     13.1   RULES AND REGULATIONS. Sublessee and its servants, employees,
agents, visitors and licensees will faithfully observe such rules and
regulations as Landlord or Sublessor hereafter at any time or from time to time
may make and may communicate in writing to Sublessee and which in the reasonable
judgment of Landlord or Sublessor shall be necessary for the reputation, safety,
care or appearance of the Building and/or Lot the proper use of the Building
(including the Sublease Premises) for the Permitted Uses, or the preservation of
good order therein, or the operation or maintenance of the Building and or Lot,
or the equipment thereof, or the comfort of tenants or others in the Building.
In the case of any conflict between the provisions of this Sublease and any such
Rules and Regulations, the provisions of this Sublease shall control, provided
further that (a) nothing contained in this Sublease shall be construed to impose
upon Landlord or Sublessor, as the case may be any duty or obligation to enforce
such Rules and Regulations or the terms, covenants or conditions in any other
lease as against any other tenant and (b) Landlord or Sublessor, as the case may
be, shall not be liable to Sublessee for violation of the same by any other
tenant or its respective servants, employees, agents, visitors, invitees or
licensees.

     13.2   ACCESS TO PREMISES - SHORING. Sublessee shall: (i) permit Landlord
or Sublessor to erect, use and maintain pipes, ducts and conduits in and through
the Sublease Premises, provided the same does not reduce the floor area or
materially or adversely affect the appearance thereof; (ii) with advance oral
notice except in cases of emergency, permit Landlord, Sublessor and any
mortgagee and its representatives, to have free and unrestricted access to and
to enter upon the Sublease Premises at all reasonable hours for the purposes of
inspection or of making repairs, replacements or improvements in or to the
Sublease Premises or the Building or equipment (including, without limitation,
sanitary, electrical, heating, air conditioning or other systems) or of
complying with all laws, orders and requirements of governmental or other
authority or of exercising any right reserved to Landlord or to Sublessor by
this Sublease (including the right during the progress of any such repairs,
replacements or improvements or while performing work and furnishing materials
in connection with compliance with any such laws, orders or requirements to take
upon or through, or to keep and store within, the Sublease Premises all
necessary materials tools and equipment); and (iii) with advance oral notice,
permit Landlord or Sublessor, at reasonable times, to show the Sublease Premises
during ordinary business hours to any mortgagee, prospective purchaser of any
interest of Landlord or Sublessor in the Building, prospective mortgagee, or
prospective assignee of any mortgage, and during the period of

                                       33
<Page>

twelve (12) months prior to the termination date to any person contemplating the
leasing of the Sublease Premises or any part thereof. If prior to the
Termination Date, Sublessee shall have removed all of Sublessee's property
therefrom, Sublessor may immediately enter and alter, renovate and redecorate
the Sublease Premises, without elimination or abatement of Rent, or
incurring liability to Sublessee for any compensation, and such acts shall have
no effect upon this Sublease. If Sublessee shall not be personally present to
open and permit entry into the Sublease Premises at any time when for any reason
an entry therein shall be necessary or permissible, Landlord, Landlord's agents
or Sublessor must nevertheless be able to gain such entry by contacting a
responsible representative of Sublessee, whose name, address and telephone
number shall be furnished by Sublessee.

     13.3   ACCIDENTS TO SANITARY AND OTHER SYSTEMS. Sublessee shall give to
Sublessor prompt notice of any fire or accident in the Sublease Premises or in
the Building and of any damage to, or defective condition in, any part or
appurtenance of the Building's sanitary, electrical, heating and air
conditioning or other systems located in, or passing through, the Sublease
Premises.

     13.4   SIGNS, BLINDS AND DRAPES. Except as otherwise expressly provided in
this Sublease, Sublessee shall not place any signs on the exterior of the
Building or on or in any window, public corridor or door visible from the
exterior of the Sublease Premises without the prior written approval of
Sublessor, which approval shall not be unreasonably withheld. Sublessee shall be
responsible for obtaining any required sign permits for signs it erects. No
blinds may be put on or in any window nor may any Building drapes or blinds be
removed by Sublessee. Sublessee may hang its own drapes, provided that they
shall not, without the prior written approval of Sublessor, in any way interfere
with any Building drapery or blinds or be visible from the exterior of the
Building.

     13.5   ESTOPPEL CERTIFICATE. Sublessee shall at any time and from time to
time upon not less than ten (10) business days' prior notice by Landlord to
Sublessee or by Sublessor to Sublessee, execute, acknowledge and deliver to
Landlord or to Sublessor, as the case may be, a statement in writing certifying
that this Sublease is unmodified and in full force and effect (or if there have
been modifications, that the same is in full force and effect as modified and
stating the modifications), and the dates to which the Yearly Fixed Rent and
Additional Rent and other charges have been paid in advance, if any, and stating
whether or not to the best knowledge of the signer of such certificate Landlord
or Sublessor is in default in the performance of any covenant, agreement, term,
provision or condition contained in this Sublease and, if so, specifying each
such default of which the signer may have knowledge, it being intended that any
such statement delivered pursuant hereto may be relied upon by any prospective
purchaser of any interest of Landlord or Sublessor in the Building and/or Lot,
any mortgagee or prospective mortgagee, any lessee or prospective lessee
thereof, any prospective assignee of any mortgage, or any other party designated
by Landlord or Sublessor.

     13.6   PROHIBITED ITEMS. Sublessee shall not bring or permit to be brought
or kept in or on the Sublease Premises or elsewhere in the Building any
hazardous, inflammable, combustible or explosive fluid, material, chemical or
substance (except such as are related to

                                       34
<Page>

Sublessee's use of the Sublease Premises, provided that the same are stored and
handled in a proper fashion consistent with applicable legal standards) or take
any action with respect thereto in violation of, or in a manner that would give
rise to liability under any applicable law, including without limitation,
G.L. c. 21C or 21E.

     13.7   REQUIREMENTS OF LAW - FINES AND PENALTIES. Sublessee at its sole
expense shall comply with all laws, rules, orders and regulations of Federal,
State, County and Municipal Authorities and with any direction of any public
officer or officers (collectively, "Laws" or "Regulations") which shall impose
any duty upon Landlord, Sublessor or Sublessee with respect to and arising out
of Sublessee's particular use of the Sublease Premises and the duty to comply is
not applicable to the Building as a whole. Sublessee's use of the Sublease
Premises shall not cause the Building or the Property to exceed any thresholds
(reporting or otherwise) imposed by Laws and Regulations. Sublessee shall
cooperate with Landlord and Sublessor so that Sublessee's use of the Sublease
Premises shall not exceed any such thresholds. Sublessee shall reimburse and
compensate Landlord and Sublessor for all expenditures made by, or damages or
fines sustained or incurred by, Landlord and Sublessor due to nonperformance or
noncompliance with or breach or failure to observe any term, covenant or
condition of this Sublease upon Sublessee's part to be kept, observed, performed
or complied with. If Sublessee receives notices of any violation of law,
ordinance, order or regulation applicable to the Sublease Premises, it shall
give prompt notice thereof to Landlord and Sublessor.

     13.8   SUBLESSEE'S ACTS - EFFECTS ON INSURANCE. Sublessee shall not do or
permit to be done any act or thing upon the Sublease Premises or elsewhere in
the Building which will invalidate or be in conflict with any customary
insurance policies covering the Building and the fixtures and property therein
and shall not do, or permit to be done, any act or thing upon the Sublease
Premises which shall subject Landlord or Sublessor to any liability or
responsibility for injury to any person or persons or to property by reason of
any business or operation being carried out on said Sublease Premises or for any
other reason. Sublessee at its own expense shall comply with all rules, orders,
regulations or requirements of the Board of Fire Underwriters or any other
similar body having jurisdiction, and shall not (i) do, or permit anything to be
done, in or upon the Sublease Premises, or bring or keep anything therein,
except as now or hereafter permitted by the Fire Department, Board of
Underwriters, Fire Insurance Rating Organization, or other authority having
jurisdiction, and then only in such quantity and manner of storage as will not
increase the rate for any insurance applicable to the Building, or (ii) use of
the Sublease Premises in a manner which shall increase such insurance rates on
the Building or on property located therein, over that applicable when Sublessee
first took occupancy of the Sublease Premises hereunder. If by reason of failure
of Sublessee to comply with the provisions hereof the insurance rate applicable
to any policy of insurance shall at any time thereafter be higher than it
otherwise would be, then Sublessee shall reimburse Landlord or Sublessor, as the
case may be, for that part of any insurance premiums thereafter paid by Landlord
or Sublessor, as the case may be, which shall have been charged because of such
failure by Sublessee.

     13.9   AUTHORITY. Sublessee warrants and represents that as of the date of
this Agreement of Sublease (a) it is a duly organized corporation, validly
existing and authorized

                                       35
<Page>

to do business in the Commonwealth of Massachusetts, (b) it has the authority to
enter into and has duly executed this Agreement of Sublease, (c) the execution,
performance and delivery by Sublessee of this Agreement of Sublease is within
the powers of Sublessee, (d) all written information provided by Sublessee to
Sublessor in connection with this Agreement of Sublease is true and accurate,
(e) as of the execution of this Sublease, Sublessee has not transferred (as
defined in Article 12 hereof) this Sublease and (f) this Sublease is the legal,
valid and binding obligation of Sublessee, enforceable against Sublessee in
accordance with its terms, subject to bankruptcy, insolvency and other
limitations on creditors' rights generally and to equitable principles.

     13.10  MISCELLANEOUS. Sublessee shall not suffer or permit the Sublease
Premises or any fixtures, equipment or utilities therein or serving the same,
to be overloaded, damaged or defaced. Sublessee shall not permit any hole to be
drilled or made in any structural part of the Sublease Premises of the Building,
without the prior written consent of Sublessor, which consent shall not be
unreasonably withheld.

13A. SUBLESSOR REPRESENTATIONS

     Sublessor warrants and represents that as of the date of this Sublease (a)
it is a validly existing non-profit educational corporation under the laws of
the Commonwealth of Massachusetts, (b) it has the authority to enter into and
has duly executed this Agreement of Sublease, (c) the Main Lease is in full
force and effect and has a term longer than the Term (as may be extended
pursuant to Section 2.4 hereof) set forth herein, (d) Sublessor is the holder of
the tenant's interest under the Main Lease, (e) Sublessor is not in and has not
received notice of default under the Main Lease and to the best of Sublessor's
knowledge. Landlord is not in default under the Main Lease, (f) the execution,
performance and delivery by Sublessor of this Agreement of Sublease is within
the powers of Sublessor, and (g) this Sublease is the legal, valid and binding
obligation of Sublessor, enforceable against Sublessor in accordance with its
terms, subject to bankruptcy, insolvency and other limitations on creditors'
rights generally and to equitable principles.

14.  DAMAGE BY FIRE AND CONDEMNATION

14A. DAMAGE BY FIRE

     In the event of loss of, or damage to, the Sublease Premises or the
Building by fire or other insurable casualty, the rights and obligations of the
parties hereto shall be as follows:

            (a) If the Sublease Premises, or any part thereof, shall be damaged
by fire or other insurable casualty, Sublessee shall give prompt notice thereof
to Sublessor, and Sublessor, upon receiving such notice, shall proceed promptly
and with due diligence, subject to Force Majeure Delays and Tenant Delays, to
repair, or cause to be repaired, such damage. With respect to portions of the
Building outside of the Sublease Premises that shall be damaged by fire or other
casualty, Sublessor shall proceed promptly and with due diligence, subject to
Force Majeure Delays and Tenant Delays, to repair, or to cause to be repaired,
such damage after such damage occurs except as otherwise provided herein.

                                       36
<Page>

            (b) If the Sublease Premises, or any part thereof, shall be
rendered untenantable by reason of such damage, whether to the Sublease Premises
or to the Building, Yearly Fixed Rent and Additional Rent shall proportionately
(i.e., based on rentable square footage) abate for that portion of the Sublease
Premises which is untenantable for the period from the date of such damage to
the date when such damage shall have been repaired.

            (c) If, as a result of fire or other insurable casualty, the whole
or a substantial part of the Building is rendered untenantable, Sublessor,
within ninety (90) days from the date of such fire or casualty, may terminate
this Sublease by notice to Sublessee, specifying a date not less than twenty
(20) nor more than sixty (60) days after the giving of such notice on which the
Term of this Sublease shall terminate. If Sublessor does not so elect to
terminate this Sublease, then Sublessor shall proceed with diligence to repair
the damage to the Sublease Premises and all facilities serving the same, and the
remainder of the Main Premises which shall have occurred, and the Yearly Fixed
Rent and Additional Rent shall meanwhile proportionately abate, all as provided
in Paragraph (b) of this Article. Sublessor within one hundred twenty (120) days
after the fire or other insurable casualty shall notify Sublessee in writing
whether or not, in its reasonable judgment, the Building and the Sublease
Premises can be restored to substantially their condition prior to such damage
within twelve (12) months of the date of the casualty. If such notification
shall state that such restoration cannot be so accomplished, then Sublessee may
terminate this Sublease within thirty (30) days from Sublessee's receipt of such
notification. Furthermore, if Sublessee does not so terminate the Sublease and
if such damage is not repaired and the Sublease Premises and the remainder of
the Building restored to substantially the same condition as they were prior to
such damage within twelve (12) months from the date of such damage, Sublessee
within thirty (30) days from the expiration of such twelve (12) month period or
from the expiration of any extension thereof by reason of Force Majeure Delays
(the "Casualty Restoration Completion Date"), may terminate this Sublease by
notice to Sublessor, specifying a date not more than forty-five (45) days after
the giving of such notice on which the term of this Sublease shall terminate
(unless Sublessor completes such restoration within forty-five (45) days after
receipt of Sublessee's termination notice). The period within which the required
repairs may be accomplished shall be extended by the number of days lost as a
result of Force Majeure Delays and/or Tenant Delays. Substantial part for
purposes of this Section 14A shall mean 40% or more of the Building.

            If Sublessee fails to terminate in accordance within the time
periods set forth herein, Sublessee shall have waived its right to terminate.

            (d) If the Sublease Premises shall be rendered untenantable by fire
or other casualty during the last year of the Term of this Sublease, Sublessor
may terminate this Sublease effective as of the date of such fire or other
casualty upon notice to Sublessee given within sixty (60) days after such fire
or other casualty.

            (e) With respect to Articles 14A and 14B, Sublessor shall not be
required to repair or replace any of Sublessee's trade fixtures, business
machinery, equipment, cabinet

                                       37
<Page>

work, furniture, personal property or other installations or improvements not
originally installed by Sublessor or otherwise required to be insured by
Sublessee under the terms of this Sublease, or any damage to the Sublease
Premises or Building caused by Sublessee, or any damage to the Sublease Premises
or Building not covered by condemnation proceeds and no damages, compensation
or claim shall be payable by Sublessor for inconvenience, loss of business or
annoyance arising from any repair or restoration of any portion of the Sublease
Premises or of the Building.

            (f) The provisions of this Article shall be considered an express
agreement governing any instance of damage or destruction of the Building or the
Sublease Premises by fire or other insurable casualty, and any law now or
hereafter in force providing for such contingency in the absence of express
agreement shall have no application. Sublessor's obligation hereunder shall be
limited to its insurance proceeds.

            (g) In the event of any termination of this Sublease pursuant to
this Article, the Term of this Sublease shall expire as of the effective
termination date as fully and completely as if such date were the date herein
originally scheduled as the Termination Date; provided that Sublessor shall
within thirty (30) days thereafter refund any prepaid Rent. Sublessee shall have
access to the Sublease Premises for a period of thirty (30) days after the date
of termination in order to remove Sublessee's personal property.

            (h) Sublessor's architect's certificate, given in good faith, shall
be deemed conclusive of the statements therein contained and binding upon
Sublessee with respect to the performance and completion of any repair or
restoration work undertaken by Sublessor pursuant to this Article 14A or Article
14B.

14B. CONDEMNATION

     In the event that the whole or any substantial part of the Building shall
be taken or appropriated by eminent domain or shall be condemned for any public
or quasi-public use, or (by virtue of any such taking, appropriation or
condemnation) shall suffer any damage (direct, indirect or consequential) for
which Sublessor or Sublessee shall be entitled to compensation then (and in any
such event) this Sublease and the Term hereof may be terminated at the election
of Sublessor by a notice in writing of its election so to terminate which shall
be given by Sublessor to Sublessee within ninety (90) days following the date on
which Sublessor shall have received notice of such taking, appropriation or
condemnation. In the event that a substantial part of the Sublease Premises or
of the means of access thereto or of the parking areas serving the Building, if
any (unless replaced without undue delay by substitute facilities within a
reasonable walking distance from the Building) shall be so taken, appropriated
or condemned so as to substantially interfere with the use of the Sublease
Premises, then this Sublease and the term hereof may be terminated at the
election of Sublessee by a notice in writing of its election so to terminate
which shall be given by Sublessee to Sublessor within sixty (60) days following
the date on which Sublessee shall have received notice of such taking,
appropriation or condemnation. Substantial part for purposes of this Section 14B
shall mean 40% or more of the Building.

                                       38
<Page>

            Upon giving of any such notice of termination (either by Sublessor
or Sublessee), this Lease and the Term hereof shall terminate as of the date on
which Sublessee shall be required to vacate any part of the Sublease Premises or
shall be deprived of a substantial part of the means of access thereto. In the
event of any such termination, this Sublease and the Term hereof shall expire as
of the effective termination date as fully and completely as if such date were
the date herein originally scheduled as the Termination Date. If neither party
elects to terminate, Sublessor will with reasonable diligence and at Sublessor's
expense, restore the remainder of the Sublease Premises and Building, or the
remainder of the means of access and parking, to substantially the same
condition as practicable obtained prior to such taking, appropriation or
condemnation in which event a just proportion of the Yearly Fixed Rent and
Additional Rent, according to the nature and extent of the taking, appropriation
or condemnation and the resultant injury sustained by the Sublease Premises and
the means of access thereto, shall be abated until what remains of the Sublease
Premises and the means of access thereto shall have been restored as fully as
may be for permanent use and occupation by Sublessee hereunder. Except for any
separate award specifically reimbursing Sublessee for moving or relocation
expenses and Sublessee's personal property, equipment and trade fixtures, there
are expressly reserved to Sublessor all rights to compensation and damages
created, accrued or accruing by reason of any such taking, appropriation or
condemnation, in implementation and in confirmation of which Sublessee does
hereby acknowledge that Sublessor shall be entitled to receive and retain all
such compensation and damages, grants to Sublessor all and whatever rights (if
any) Sublessee may have to such compensation and damages, and agrees to execute
and deliver all and whatever further instruments of assignment with respect
thereto as Sublessor may from time to time reasonably request. In the event of
any taking of the Sublease Premises or any part thereof for temporary use, (i)
this Sublease shall be and remain unaffected thereby, and (ii) Sublessee shall
be entitled to receive for itself any award made for such use, provided, that if
any taking is for a period extending beyond the Term of this Sublease, such
award shall be apportioned between Sublessor and Sublessee as of the
Termination Date.

15.  DEFAULT AND ENFORCEMENT

     15.1   CONDITIONS OF LIMITATION - RE-ENTRY - TERMINATION. This Sublease and
the herein term and estate are upon the condition that if:

     (a)    Sublessee shall fail to perform or observe any of Sublessee's
covenants herein beyond the applicable grace period set forth herein consisting
of the payment when due of Yearly Fixed Rent, Additional Rent, Additional Rent
for Taxes, utility expenses, Parking Rent, and/or all other additional rent; or
(b) Sublessee or Guarantor (if any) shall be involved in financial difficulties
as evidenced by an admission in writing by Sublessee or Guarantor (if any) of
its inability to pay its debts generally as they become due, or by the making or
offering to make a composition of its debts with its creditors; or (c) Sublessee
or Guarantor (if any) shall make an assignment or trust mortgage, or other
conveyance or transfer of like nature, of all or a substantial part of its
property for the benefit of its creditors; or (d) the leasehold hereby created
shall be taken on execution or by other process of law and shall not be revested
in Sublessee within thirty (30) days thereafter; or (e) a receiver, sequester,
trustee or similar officer shall be appointed by a court of competent

                                       39
<Page>

jurisdiction to take charge of all or a substantial part of Sublessee's property
or Guarantor's (if any) property and such appointment shall not be vacated,
revoked, terminated or stayed within thirty (30) days thereafter; or (f) any
proceeding shall be instituted by or against Sublessee or Guarantor (if any)
pursuant to any of the provisions of any Act of Congress or State law relating
to bankruptcy, reorganization, arrangements, compositions or other relief from
creditors, and, in the case of any such proceeding instituted against it or
Guarantor (if any), if Sublessee or Guarantor (if any) shall fail to have such
proceeding dismissed, stayed or vacated within thirty (30) days or if Sublessee
or Guarantor (if any) is adjudged bankrupt or insolvent as a result of any such
proceeding; or (g) any event shall occur or any contingency shall arise whereby
this Sublease, or the term and estate thereby created, would (by operation of
law or otherwise) devolve upon or pass to any person, firm or corporation other
than Sublessee, except as expressly permitted under Article 12 hereof; or (h)
Sublessee shall fail to maintain the insurance set forth in Section 11.1 hereof;
or (i) Sublessee shall grant an interest, assign, mortgage, pledge, encumber or
otherwise transfer (whether voluntarily or by operation of law) the Sublease,
the Sublease Premises or any portion thereof in violation of Article 12 hereof;
or (j) Sublessee shall fail after three (3) business days notice to execute,
acknowledge or deliver to Landlord or to Sublessor, as the case may be, the
statements or estoppels certificates required in Section 13.5 hereof in addition
to the time period already set forth in Section 13.5 hereof; or (k) Sublessee
shall fail to comply with, perform or observe any other covenant set forth
herein (any of the foregoing, an "Event of Default"), Sublessor may, in a manner
consistent with applicable law, immediately or at any time thereafter, without
further demand or notice, enter into and upon the Sublease Premises (or any part
thereof in the name of the whole), and thereupon (and without prejudice to any
remedies which might otherwise be available for arrears of Rent or other charges
due hereunder or preceding breach of covenant and without prejudice to
Sublessee's liability for damages as hereinafter stated), upon such entry, this
Sublease shall terminate. The words "re-entry" and "re-enter" as used in this
Sublease are not restricted to their technical legal meaning.

     15.2   DAMAGES - ASSIGNMENT FOR BENEFIT OF CREDITORS. For the more
effectual securing by Sublessor of the Yearly Fixed Rent, Additional Rent and
other charges and payments reserved hereunder, it is agreed as a further
condition of this Sublease that if at any time Sublessee shall make an
assignment of its property for the benefit of its creditors under the terms of
which the debts provable by its creditors shall be debts provable against the
estate of insolvent debtors either under the laws of the Commonwealth of
Massachusetts or under some law or laws other than the Bankruptcy Act as now or
hereafter enacted, then and in any such case the same shall constitute a breach
of this Sublease, and the term and estate hereby created shall terminate ipso
facto, without entry or other action by Sublessor, and notwithstanding any other
provisions of this Sublease, Sublessor shall forthwith upon such termination,
without prejudice to any remedies which might otherwise be available for arrears
of Yearly Fixed Rent, Additional Rent or other charges due hereunder or
preceding breach of this Sublease, be ipso facto entitled to recover as
liquidated damages the sum of (a) the amount by which, at the time of such
termination of this Lease, (i) the aggregate of the Yearly Fixed Rent and
Additional Rent projected over the period commencing with such termination and
ending with the Termination Date stated in Section 2.1 exceeds (ii) the

                                       40
<Page>

aggregate projected rental value of the Sublease Premises for such period and
(b) in view of the uncertainty of prompt re-letting and the expense entailed in
re-letting the Sublease Premises, an amount equal to the Yearly Fixed Rent and
Additional Rent payable for and in respect of the calendar year next preceding
the date of termination, as aforesaid. Upon such termination and to the extent
permitted by law, Sublessor may immediately or at any time thereafter, without
demand or notice, enter into or upon the Sublease Premises (or any part thereof
in the name of the whole), and (without being taken or deemed to be guilty of
any manner of trespass or conversion, and without being liable to indictment,
prosecution or damages thereof) may expel Sublessee and those claiming under
Sublessee from the Sublease Premises and remove therefrom the effects of
Sublessee and those claiming under Sublessee.

     15.3   DAMAGES - TERMINATION. Upon the termination of this Sublease under
the provisions of this Article, and except as herein above in Section 15.2
otherwise provided. Sublessee shall pay to Sublessor the Yearly Fixed Rent and
Additional Rent payable by Sublessee to Sublessor up to the time of such
termination, and all unpaid interest, shall continue to be liable for any
preceding breach of covenant, and in addition, shall pay to Sublessor as
damages, at the election of Sublessor either:

(a) The amount by which, at the time of the termination of this Sublease (or at
any time thereafter if Sublessor shall have initially elected damages under
Subparagraph (b), below), (i) the aggregate of the Yearly Fixed Rent and
Additional Rent projected over the period commencing with such time and ending
on the originally scheduled Termination Date as stated in Section 2.1 or Section
2.4 (discounted to net present value using a 7% discount rate) exceeds (ii) the
aggregate projected fair market rental value of the Sublease Premises for such
period (discounted to net present value using a 7% discount rate), or,

(b) amounts equal to the Yearly Fixed Rent and Additional Rent which would have
been payable by Sublessee had this Sublease not been so terminated, payable upon
the due dates therefore specified herein following such termination and until
the originally-scheduled Termination Date as specified in Section 2.1, provided,
however, if Sublessor shall re-let the Sublease Premises during such period,
that Sublessor shall credit Sublessee with the net rents received by Sublessor
from such re-letting, such net rents to be determined by first deducting from
the gross rents as and when received by Sublessor from such re-letting the
expenses incurred or paid by Sublessor in terminating this Sublease, as well as
the expenses of reletting, including altering and preparing the Sublease
Premises for new tenants, brokers' commissions, and all other similar and
dissimilar expense properly chargeable against the Sublease Premises and the
rental therefrom, it being understood that any such re-letting may be for a
period equal to or shorter or longer than the remaining term of this Sublease;
and provided, further, that (i) in no event shall Sublessee be entitled to
receive any excess of such net rents over the sums payable by Sublessee to
Sublessor hereunder and (ii) in no event shall Sublessee be entitled in any suit
for the collection of damages pursuant to this Subparagraph(b) to a credit in
respect of any net rents from a re-letting except to the extent that such net
rents are actually received by Sublessor prior to the commencement of such suit.
If the Sublease Premises or any part thereof should be re-let in combination
with other space, then proper apportionment on a square foot area basis shall be
made of the Yearly

                                       41
<Page>

Fixed Rent and Additional Rent received from such re-letting and of the expenses
of re-letting.

     Suit(s) for the recovery of such damages, or any installments thereof, may
be brought by Sublessor from time to time at its election, and nothing contained
herein shall be deemed to require Sublessor to postpone suit until the date when
the Term of this Sublease would have expired it if it had not been terminated
hereunder.

     Nothing herein contained shall be construed as limiting or precluding the
recovery by Sublessor against Sublessee of any sums or damages to which, in
addition to the damages particularly provided above, Sublessor may lawfully be
entitled by reason of any default hereunder on the part of Sublessee.

     15.4   FEES AND EXPENSES. If Sublessee shall default in the performance of
any covenant on Sublessee's part to be performed as in this Sublease contained.
Sublessor may immediately, or at any time thereafter, subject (except in case of
emergency) to notice and expiration of any applicable grace period which may be
contained herein, perform the same for the account of Sublessee. If Sublessor at
any time is compelled to pay or elects to pay any sum of money, or do any act
which will require the payment of any sum or money, by reason of the failure of
Sublessee to comply with any provision hereof, or if Sublessor is compelled to
or does incur any expense, including, without limitation, reasonable attorneys'
fees, in instituting, prosecuting and/or defending any action or proceeding
instituted by reason of any default of Sublessee hereunder beyond notice and the
applicable cure period. Sublessee shall on demand pay to Sublessor by way of
reimbursement the sum or sums so paid by Sublessor with all interest, costs and
damages. Without limiting the generality of the foregoing, any Yearly Fixed Rent
and Additional Rent which is more than ten days in arrears shall bear interest
from the due date at the rate of 18% per annum.

     15.5   SUBLESSOR'S REMEDIES NOT EXCLUSIVE. The specified remedies to which
Sublessor may resort hereunder are cumulative and are not intended to be
exclusive of any remedies or means of redress to which Sublessor may at any time
be lawfully entitled, and Sublessor may invoke any remedy (including, without
limitation, the remedy of specific performance) allowed at law or in equity as
if specific remedies were not herein provided for.

     15.6   GRACE PERIOD. Notwithstanding anything to the contrary in this
Article contained, Sublessor agrees not to take any action to terminate this
Sublease and Sublessee shall not be deemed in default under this Sublease
(except as otherwise set forth in Section 15.4 in cases of emergency) (a) in the
case of default by Sublessee as set forth in Section 15.1(a) in the payment
when due of Yearly Fixed Rent, Additional Rent, Additional Rent for Taxes,
utility expenses, Parking Rent, and/or all other additional rent, if Sublessee
shall cure such default within five (5) days after written notice thereof given
by Sublessor to Sublessee, or (b) in the case of default by Sublessee in the
performance of any covenant as set forth in Section 15.1(l), if Sublessee shall
cure such default within a period of thirty (30) days after written notice
thereof given by Sublessor to Sublessee (except where the nature of the default
is such that remedial action should appropriately take place sooner, as
indicated

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<Page>

in such written notice), or with respect to covenants other than to pay a sum of
money within such additional period as may reasonably be required to required to
cure such default if (because of governmental restrictions or any other cause
beyond the reasonable control of Sublessee) the default is of such a nature that
it cannot be cured within such thirty (30) day period, provided, however, that
there shall be no extension of time beyond such thirty (30) day period for the
curing of any such default unless, not more than ten days after the receipt of
the notice of default, Sublessee in writing (i) shall specify the cause on
account of which the default cannot be cured during such period and shall advise
Sublessor of its intention to institute all steps necessary to cure the default
and (ii) shall as soon as may be reasonable duly institute and thereafter
diligently prosecute to completion all steps necessary to cure such default. All
other defaults as set forth in Section 15.1 shall have only those notice and
cure periods, if any, as set forth in Section 15.1 hereof. Notwithstanding
anything to the contrary contained herein, Sublessor shall not be required to
give more than two (2) notices of monetary default in the payment of Yearly
Fixed Rent. Additional Rent, Additional Rent for Taxes, utility expenses,
Parking Rent, and/or all other additional rent, in any lease year; thereafter
may such monetary default shall be automatic without the need for further
notice.

16.  END OF TERM - ABANDONED PROPERTY; HOLDOVER

     Upon the expiration or other termination of the Term of this Sublease.
Sublessee shall peaceably quit and surrender to Sublessor the Sublease Premises
(and all alterations and additions thereto which Sublessee in not entitled or
required to remove under the provisions of this Sublease), broom-clean, in good
order, repair and condition excepting only reasonable wear and tear and damage
by fire or other casualty for which, under other provisions of this Sublease,
Sublessee has no responsibility of repair or restoration. Sublessee's obligation
to observe or perform this covenant shall survive the expiration or other
termination of the Term of this Sublease. If the last day of the Term of this
Sublease or any renewal thereof falls on a day other than a Business Day, this
Sublease shall expire on the Business Day immediately preceding.

     Any personal property in which Sublessee has an interest which shall remain
in the Building or on the Sublease Premises after the expiration or termination
of the Term of this Sublease shall be conclusively deemed to have been
abandoned, and may be disposed of in such manner as Sublessor may see fit.
Notwithstanding the foregoing, Sublessee will, upon request of Sublessor made
not later than thirty (30) days after the expiration or termination of the Term
hereof, promptly remove from the Building any personal property or, if any part
thereof shall be sold, then Sublessor may receive and retain the proceeds of
such sale and apply the same, at its option, against the expenses of the sale,
the cost of moving and storage, any arrears of Rent payable hereunder by
Sublessee to Sublessor and any damages to which Sublessor may be entitled under
Article 15 hereof or pursuant to law, with the balance if any, to be paid to
Sublessee.

     In the event of holding over by Sublessee after expiration or other
termination of this Sublease, occupancy of the Sublease Premises subsequent to
such termination or expiration shall be that of a tenancy at sufferance and in
no event for month-to-month or year-to-year, but Sublessee shall, throughout
the entire holdover period, be subject to all the terms and

                                       43
<Page>

provisions of this Sublease and shall pay for its use and occupancy an amount
(on a per diem basis) equal to two hundred percent (200%) of the sum of the
Yearly Fixed Rent and Additional Rent (at the rental rate for the period
immediately preceding such holdover), and in no event shall such holdover
rental be less than the fair market rental for the Sublease Premises. No holding
over by Sublessee or payments of money by Sublessee to Sublessor after the
expiration of the term of this Sublease shall be construed to extend the Term or
prevent Sublessor for recovery of immediate possession of the Sublease Premises
by summary proceedings or otherwise. In addition to the obligation to pay the
amounts set forth above during any such holdover period, Sublessee also shall be
liable so Sublessor for all damage, including any consequential damage, which
Sublessor may suffer by reason of any holding over by Sublessee, and Sublessee
shall indemnify Sublessor against any and all claims made by any other tenant or
prospective tenant against Sublessor for delay by Sublessor in delivering
possession of the Sublease Premises to such other tenant or prospective tenant.

17.  SUBLEASE SUBORDINATE; SUBORDINATION TO AND INCORPORATION OF TERMS OF MAIN
     LEASE

     (a)    This Sublease shall be subject and subordinate to any mortgage now
or hereafter placed on the Main Premises, or any portions thereof or interest
therein. This Section 17 shall be self-operative and no further instrument of
subordination shall be required. In furtherance of the foregoing, Sublessee
agrees to enter into any subordination and attornment agreement with a
third-party lender which may be required by Landlord, Sublessor and any
third-party mortgagees or lien holders requesting the execution of such
documents within fifteen (15) days of any request. Sublessee agrees to execute
and deliver upon request from Landlord. Sublessor and Sublessor's lender a
subordination, non-disturbance and attornment agreement in a form substantially
attached hereto as Exhibit H.

     (b)    This Sublease is in all respects subject and subordinate to the
matters to which the Main Lease is or shall be subordinate.

     (c)    ASSIGNMENT OF LEASE AND/OR RENTS. With reference to any assignment
by Sublessor of its interest in this Sublease and/or the Rent payable hereunder,
conditional in nature or otherwise, which assignment is made to or held by a
bank, trust company, insurance company or other institutional lender holding a
mortgage on the Building, Sublessor and Sublessee agree:

            (i) that the execution thereof by Sublessor and acceptance thereof
by such Mortgage shall never be deemed an assumption by such Mortgagee of any of
the obligations of Sublessor hereunder, unless such Mortgagee shall, by written
notice sent to Sublessee, specifically otherwise elect; and

            (ii) that, except as aforesaid, such Mortgagee shall be treated as
having assumed Sublessor's obligations hereunder only upon foreclosure of such
Mortgagee's Mortgage and the taking possession of the Subleased Premises after
having given notice of its intention to succeed to the interest of Sublessor
under this Sublease.

                                       44
<Page>

18.  QUIET ENJOYMENT

     Sublessor covenants that if, and so long as, Sublessee keeps and performs
each and every covenant, agreement, term, provision and condition herein
contained on the part and on behalf of Sublessee to be kept and performed,
Sublessee shall quietly enjoy the Sublease Premises from and against the claims
of all persons claiming by, through or under Sublessor subject, nevertheless, to
the covenants, agreements, terms, provision and conditions of this Sublease.

     Without incurring any liability to Sublessee, Sublessor may (subject to
applicable restrictions imposed upon Sublessee as a consequence of its dealings
with federal governmental agencies, so long as Sublessor shall have been given
prior notice thereof) permit access to the Sublease Premises and open the same,
whether or not Sublessee shall be present, upon any demand of any receiver,
trustee, assignee for the benefit of creditors, sheriff, marshal or court
officer entitled to, or reasonably purporting to be entitled to, such access for
the purpose of taking possession of, or removing Sublessee's property or for any
other lawful purpose (but this provision and any action by Sublessor hereunder
shall not be deemed a recognition by Sublessor that the person or official
making such demand has any right or interest in or to this Sublease, or in or to
the Sublease Premises), or upon demand of any representative of the fire,
police, building, sanitation or other department of the city, county, state or
federal governments.

19.  ENVIRONMENTAL INDEMNITY

     (a)    Notwithstanding anything to the contrary contained in this Sublease,
Sublessee agrees to indemnify, defend and hold harmless Sublessor, Landlord, and
their respective parent, subsidiaries and affiliates, and their respective
officers, directors, shareholders and employees, from and against any and all
liabilities, losses, damages, suits, actions, causes of action, costs, expenses
(including without limitation reasonable attorneys' fees and disbursements and
court costs), penalties, fines, demands, judgements, claims or liens (including
without limitation claims or liens imposed under any so-called "Superfund" or
other environmental legislation) arising from or in connection with the
disposal, improper use, release or discharge of Hazardous Materials which are
stored, generated or otherwise brought onto, under, at or adjacent to the
Sublease Premises. Building or Property by or at the direction of Sublessee;
Sublessee's breach of the provisions of this Sublease relating to Hazardous
Materials; or Sublessee's failure to comply with any laws, regulations or
ordinances governing Hazardous Materials.

     (b)    For the purposes of this Section, the term "Hazardous Materials"
shall include without limitation any petroleum product, any flammable, explosive
or radioactive material, medical wastes or any oil, any hazardous or toxic
waste, substance or material, including without limitation substances defined as
"hazardous substances," "solid waste" or toxic substances" under any applicable
laws relating to any of the foregoing, air pollution (including noise and
odors), water pollution, liquid and solid waste, pesticides, drinking

                                       45
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water, community and employee health, environmental land use management,
stormwater, sediment control, nuisances, radiation, wetlands, endangered
species, environmental permitting and petroleum products, which laws may
include, but not be limited to; the Toxic Substance Control Act; the Clean Water
Act; the National Environmental Policy Act, as Amended; the Solid Waste Disposal
Act, as amended; the Comprehensive Environmental Response, Compensation and
Liability Act of 1980, as amended by the Superfund Amendments and
Reauthorization Act of 1986; The Hazardous Material Transportation Act, as
amended; the Resource Conservation and Recovery Act, as amended, the Clean Air
Act, as amended; the Emergency Planning and Community Right-To-Know Act, as
amended; the Occupational Safety and Health Act, as amended; comparable state
laws; and all rules and regulations promulgated pursuant to such laws and
ordinances.

     (c)    Sublessee hereby acknowledges receipt of the Environmental Report,
referred to in Exhibit F attached hereto.

     (d)    This Section 19 shall survive the expiration or termination of this
Sublease.

20.  ENTIRE AGREEMENT - WAIVER - SURRENDER

     20.1   ENTIRE AGREEMENT. This Sublease and the Exhibits made a part hereof
contain the entire and only agreement between the parties and any and all
statements and representations, written and oral, including previous
correspondence and agreements between the parties hereto, are merged herein.
Sublessee acknowledges that all representations and statements upon which it
relied in executing this Sublease are contained herein and that Sublessee in no
way relied upon any other statements or representations written or oral. Any
executory agreement hereafter made shall be ineffective to change, modify,
discharge or effect an abandonment of this Sublease in whole or in part unless
such executory agreement is in writing and signed by the party against whom
enforcement of the change, modification, discharge or abandonment is sought.
Nothing herein shall prevent the parties from agreeing to amend this Sublease
and the Exhibits made a part hereof as long as such amendment shall be in
writing and shall be duly signed by both parties.

     20.2   WAIVER. The failure of either party to seek redress for violation,
or to insist upon the strict performance, of any covenant or condition of this
Sublease, or (in the case of Sublessor) any of the Rules and Regulations
promulgated hereunder, shall not prevent a subsequent act, which would have
originally constituted a violation, from having all the force and effect of an
original violation. The receipt by Sublessor of Rent with knowledge of the
breach of any covenant of this Sublease shall not be deemed a waiver of such
breach. The failure of Sublessor to enforce any such Rules and Regulations
against Sublessee and/or any other tenant or subtenant in the Building shall not
be deemed a waiver of any such Rules and Regulations. No provisions of this
Sublease shall be deemed to have been waived by either party unless such waiver
be in writing signed by such party. No payment by Sublessee or receipt by
Sublessor of a lesser amount than the monthly rent herein stipulated shall be
deemed to be other than on account of the stipulated Rent, nor shall any
endorsement or statement on any check or any letter accompanying any check or
payment as Rent be deemed an accord and satisfaction, and Sublessor may accept
such check or

                                       46
<Page>

payment without prejudice to Sublessor's right to recover the balance of such
rent or pursue any other remedy in this Sublease provided.

     20.3   SURRENDER. No act or thing done by Sublessor during the Term hereby
demised shall be deemed an acceptance of a surrender of the Sublease Premises,
and no agreement to accept such surrender shall be valid, unless in writing
signed by Sublessor. No employee of Sublessor or of Sublessor's agents shall
have any power to accept the keys of the Sublease Premises prior to the
termination of this Sublease. The delivery of keys to any employee of Sublessor
or of Sublessor's agents shall not operate as a termination of the Sublease or a
surrender of the Sublease Premises. In the event that Sublessee at any time
desires to have Sublessor underlet the Sublease Premises for Sublessee's
account, Sublessor or Sublessor's agents are authorized to receive the keys for
such purposes without releasing Sublessee from any of the obligations under this
Sublease, and Sublessee hereby relieves Sublessor of any liability for loss of
or damage to any of Sublessee's effects in connection with such underletting.

21.  INABILITY TO PERFORM - EXCULPATORY CLAUSE

     Except as otherwise expressly provided in this Sublease, this Sublease and
the obligations of Sublessee to pay Rent hereunder and perform all other
covenants, agreements, terms, provisions and conditions hereunder on the part of
Sublessee to be performed shall in no way be affected, impaired or excused
because Sublessor is unable to fulfill any of its obligations under this
Sublease or is unable to supply or is delayed in supplying any service expressly
or impliedly to be supplied or is unable to make or is delayed in making any
repairs, replacements, additions, alterations, improvements or decorations or is
unable to supply or is delayed in supplying any equipment or fixtures if
Sublessor is prevented or delayed from doing so by reason of strikes or labor
troubles or any other similar or dissimilar cause whatsoever beyond Sublessor's
reasonable control, including but not limited to, governmental preemption in
connection with a national emergency or by reason of any rule, order or
regulation of any department of subdivision thereof or any governmental agency
or by reason of the conditions of supply and demand which have been or are
affected by war, hostilities or other similar or dissimilar emergency. In each
instance of inability of Sublessor to perform, Sublessor shall exercise
reasonable diligence to eliminate the cause of such inability to perform.

     Sublessee shall neither assert nor seek to enforce any claim for breach of
this Sublease against any of Landlord's or Sublessor's assets other than
Landlord's or Sublessor's interest in the Building of which the Sublease
Premises are a part and in the rents, issues and profits thereof, and Sublessee
agrees to look solely to such interest for the satisfaction of any liability of
Landlord or Sublessor under this Sublease, it being specifically agreed that in
no event shall Landlord or Sublessor (which terms shall include, without
limitation, any of the officers, trustees, directors, partners, beneficiaries,
joint ventures, members, stockholders or other principals or representatives,
disclosed or undisclosed, of Landlord, Sublessor or any managing agent) ever be
personally liable for any such liability. Sublessee specifically agrees and
acknowledges that neither Landlord nor Sublessor shall ever be liable for any
breaches of the Sublease by Landlord or Sublessor, as

                                       47
<Page>

the case may be, other than during the period of their respective ownership in
the Building. In no event shall Landlord or Sublessor ever be liable for
indirect, special, consequential or incidental damages (including without
limitation loss of profits, loss or use or loss of goodwill).

22.  BILLS AND NOTICES

     Any notice, consent, request, bill, demand or statement hereunder by either
party to the other party shall be in writing and, if received at Sublessor's or
Sublessee's address, shall be deemed to have been duly given when either (a)
delivered or served personally (b) three (3) days after mailed in a prepaid
envelope, deposited in the United States mails or (c) one (1) day after mailed
by a nationally recognized overnight delivery service, as evidence by the
records of the courier or delivery service, addressed to the respective party at
its address as stated below or if any address for notices shall have been duly
changed as hereinafter provided, if mailed as aforesaid to the party at such
changed address. Either party may at any time change the address for such
notices, consents, requests, bills, demands or statements by delivering or
mailing, as aforesaid, to the other party a notice stating the change and
setting forth the changed address, provided such changed address is within the
United States.

     Notices for purposes of the Sublease shall be as follows:

     If to SUBLESSOR:
     Mr. William J. Gasper
     Associate Vice President for Business Affairs
     Boston University Medical Campus
     Office of Financial and Business Affairs
     715 Albany Street
     Boston, MA 02118

     with a copy to:
     Todd L. Klipp
     Vice President and General Counsel
     Boston University - Office of the General Counsel
     125 Bay State Road
     Boston, MA 02215

     If to SUBLESSEE:
     PRIOR TO TERM COMMENCEMENT DATE:
     Mr. Alexis Borisy
     President and CEO
     CombinatoRx, Incorporated
     801 Albany Street, Suite G02
     Boston, MA 02118

                                       48
<Page>

     with a copy to:
     Peter Finn
     Rubin and Rudman, LLP
     50 Rowes Wharf
     Boston, MA 02110

     IF AFTER TERM COMMENCEMENT DATE:
     Mr. Alexis Borisy
     President and CEO
     CombinatoRx, Incorporated
     650 Albany Street
     Boston, MA 02118

     with a copy to:
     Peter Finn
     Rubin and Rudman, LLP
     50 Rowes Wharf
     Boston, MA 02110

     All bills and statements for reimbursement or other payments or charges due
from Sublessee to Sublessor hereunder shall be due and payable in full 30 days,
unless herein otherwise provided, after submission thereof by Sublessor to
Sublessee. Sublessee's failure to make timely payment of any amounts indicated
by such bills and statements, whether for work done by Sublessor at Sublessee's
request, reimbursement provided for by this Sublease or for any other sums
properly owing by Sublessee to Sublessor, shall be treated as default in the
payment of Rent, in which event Sublessor shall have all rights and remedies
provided in this Sublease for nonpayment of Rent.

     Sublessee hereby covenants that, prior to the filing of any suit for an
alleged default by Sublessor hereunder, it shall give notice to Landlord,
Sublessor and all mortgagees whom Sublessee has been notified in writing by
Sublessor to hold mortgages or deed of trust liens on the Property, Building or
Sublease Premises. Sublessee hereby covenants that Sublessor shall have thirty
(30) days after the receipt of such notice to cure any alleged default.

23.  PARTIES BOUND - SEIZIN OF TITLE

     The covenants, agreements, terms, provisions and conditions of this
Sublease shall bind and benefit the successors and assigns of the parties hereto
with the same effect as if mentioned in each instance where a party hereto is
named or referred to, except that no violation of the provisions of this Article
shall not be construed as modifying the conditions of limitation contained in
Article 15 hereof.

24.  SUBLESSEE EFFORTS REGARDING MINORITY PARTICIPATION

     Sublessee shall comply with applicable federal, state and municipal laws
including without limitation all requirements of the First Source Agreement, a
copy of which is

                                       49
<Page>

attached hereto as EXHIBIT G, as they pertain to Sublessee's use and occupancy
of the Sublease Premises. In furtherance of the foregoing, Sublessee agrees to
cooperate with Sublessor and Landlord to hire and train minority and female
workers from the residential area of the City of Boston of which the Building is
a part in connection with Sublessee's activities on the Sublease Premises.
Sublessee further agrees to cooperate with Sublessor and Landlord to provide
opportunities for minority, female and business enterprises based in the area of
the City of Boston in which the Building is located when purchasing supplies and
equipment. Sublessor and Landlord agrees to assist Sublessee in maximizing
opportunities for the minority, female and neighborhood resident labor forces
and business communities by identifying such job candidates and businesses with
which Sublessee may do business. Sublessee acknowledges that it has an
affirmative action policy in accordance with all applicable federal, state and
municipal laws and agrees that it will adhere to such policy in connection with
its use of the Sublease Premises.

25.  MISCELLANEOUS

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

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

     25.3   BROKER. Each party represents and warrants that it has not directly
or indirectly dealt, with respect to the subleasing of space in the Building,
with any broker or had its attention called to the Sublease Premises or other
space to let in the Building, by any broker other than Thompson Doyle Hennessey
& Everest (the "Broker"). Each party agrees to exonerate and save harmless and
indemnify the other against any claims for a commission by any other broker,
person or firm, with whom such party has dealt in connection with the execution
and delivery of this Sublease or out of negotiations between Sublessor and
Sublessee with respect to the subleasing of other space in the Building other
than the Broker.

     25.4   GOVERNING LAW. This Sublease is made pursuant to, and shall be
governed by, and construed in accordance with, the laws of the Commonwealth of
Massachusetts.

     25.5   TIME OF THE ESSENCE. With respect to all time periods or dates set
forth herein, including without limitation, those set forth in Article 3 hereof,
time shall be of the essence.

     25.6   NOTICE OF SUBLEASE. Neither party shall record this Sublease in the
Registry of Deeds or Registry District, provided however that either party shall
at the request of the other, execute and deliver a recordable Notice of this
Sublease in the form prescribed by Chapter 183, Section 4 of the Massachusetts
General Laws.

                                       50
<Page>

     25.7   TRANSFER. Sublessor shall have the right to transfer and assign, in
whole or in part, all of its rights and obligations hereunder and in the
Building and Property referred to herein, and in such event and upon such
transfer to and assumption by such transferee, Sublessor shall be released from
any further obligations hereunder, and Sublessee agrees to look solely to such
successor in interest of Sublessor for the performance of such obligations.

     25.8   FINANCIAL CAPABILITY. Sublessee acknowledges that the financial
capability of Sublessee to perform its obligations hereunder and the financial
capability of Guarantor to perform its obligation under the Guaranty are
material to Sublessor and that Sublessor would not enter into this Sublease but
for its belief, based on its review of Sublessee's and Guarantor's financial
statements, that Sublessee and Guarantor are capable of performing such
financial obligations. Sublessee and Guarantor hereby represent, warrant and
certify to Sublessor that the financial statements previously furnished to
Sublessor were at the time given true and correct in all respects and that there
have been no material adverse subsequent changes thereto as of the date of this
Sublease.

     25.9   NOTICE TO MORTGAGEE. Sublessee hereby covenants that, prior to the
filing of any suit for an alleged default by Sublessor hereunder, it shall give
Landlord, Sublessor and all mortgagees whom Sublessee has been notified to hold
mortgages or deed of trust liens on the Property, Building or Sublease Premises
notice and opportunity to cure such alleged default by Sublessor.

     25.10  ATTORNEYS' FEES. In the event that Sublessor should institute any
suit against Sublessee for violation of or to enforce any of the covenants or
conditions of this Sublease, or should Sublessee institute any suit against
Sublessor for violation of any of the covenants or conditions of this Sublease,
or should either party intervene in any suit in which the other is a party to
enforce or protect its interest or rights hereunder, the prevailing party in any
such suit shall be entitled to all of its reasonable costs and expenses and
reasonable fees of its attorney(s) (if and to the extent permitted by law) in
connection therewith.

     25.11  SECURITY DEPOSIT. Sublessee, concurrently with the execution of
this Sublease, has deposited with Sublessor a deposit (the "Security Deposit")
in the amount of Five Hundred Twenty Four Thousand Four Hundred Forty 00/100
Dollars ($524,440.00) to be held by Sublessor without interest as security for
the faithful performance and observance by Sublessee of the terms, conditions
and provisions of this Sublease, including without limitation the surrender of
possession of the Sublease Premises to Sublessor as herein provided. Sublessor
shall not be required to maintain the Security Deposit in a separate account. It
is agreed that in the event Sublessee defaults in respect of any of the terms,
provisions and conditions of this Sublease, including, but not limited to, the
payment of rent, Sublessor may apply or retain the whole or any part of the
Security Deposit to the extent required for the payment of any rent or any other
sum as to which Sublessee is in default or for any sum which Sublessor may
expend or may be required to expend by reason of Sublessee's default in respect
of any of the terms, covenants and conditions of this Sublease, including but
not limited to, any damages or deficiency in the reletting of the Subleased
Premises, whether such damages or deficiency accrue or accrues before or after
summary

                                       51
<Page>

proceedings or other reentry by Sublessor. The Security Deposit is not to be
used or applied by Sublessee as a substitute for rent due any month, but may be
so applied by Sublessor at any time at Sublessor's option in the event of a
default beyond the expiration of any applicable cure period. The use,
application or retention of the Security Deposit, or any portion thereof, by
Sublessor shall not prevent Sublessor from exercising any other right or remedy
provided by this Sublease or by law and shall not operate as a limitation on any
recovery to which Sublessor may otherwise be entitled. If Sublessor applies or
retains any part of the Security Deposit, Sublessee, upon written demand
therefor by Sublessor, shall deposit cash with Sublessor in such amount so that
Sublessor shall have the full deposit on hand at all times during the term of
this Sublease. If Sublessee shall fully and faithfully comply with all of the
terms, provisions, covenants and conditions of this Sublease, the balance of the
Security Deposit, if any, shall be returned to Sublessee within sixty (60) days
after the Termination Date and after the delivery of the entire possession of
the Sublease Premises.

     25.11A LETTER OF CREDIT. Sublessor agrees that the Security Deposit may be
provided in the form of an unconditional and irrevocable letter of credit (the
"LETTER OF CREDIT"), in a form and by an issuing bank approved by Sublessor. The
Letter of Credit shall provide that (a) Sublessor can draw upon the Letter of
Credit upon presenting a demand letter to the issuing bank stating that
Sublessee is in default under the Sublease after expiration of all applicable
notice and cure periods or Sublessee has failed to provide a replacement letter
of credit acceptable to Sublessor as required under the Sublease, and (b) the
Letter of Credit is transferable in whole and not in part by Sublessor to
Sublessor's transferee, without Sublessee's approval, should Sublessor transfer
or convey its interest in the Premises. The Letter of Credit shall not expire
until a minimum of sixty (60) days following the expiration of the term of this
Sublease. Sublessor shall have the right, from time to time, without prejudice
to any other remedy Sublessor may have on account thereof, to draw on the Letter
of Credit on account of, and to apply such drawn amounts to Sublessor's damages
arising from, or to cure, any event of default of Sublessee. If Sublessor shall
so apply sums drawn on the Letter of Credit, Sublessee shall immediately deliver
a replacement Letter of Credit in the same face amount as the original Letter of
Credit before it was drawn upon (or, if Sublessor shall have drawn down only a
portion of the Letter of Credit, Sublessee shall deliver a replacement Letter of
Credit or an amendment to the original Letter of Credit such that the aggregate
balance available to be drawn down by Landlord is restored to $524,440.00). If
the term of any Letter of Credit held by Sublessor shall expire prior to the
expiration date of this Sublease, and it is not extended or a new letter of
credit for an extended period of time is not substituted within ten (10) days
prior to the expiration date of the Letter of Credit, then Sublessor may make
demand for the principal amount of the Letter of Credit and hold such funds in
accordance with this Section 25.11 and 25.11A until the expiration date of the
term of the Sublease. At any time that Sublessee is in default under the terms
of this Sublease, Sublessor may make demand for the principal amount of the
Letter of Credit and hold such funds for the balance of the term of the Sublease
in accordance with this Section 25.11 and 25.11A. All costs and fees associated
with issuing and maintaining the Letter of Credit shall be borne by Sublessee.
The Letter of Credit should be issued in the original principal amount of
$524,400.00 and provided no event of default exists; at the commencement of the
thirteenth month after the Term Commencement

                                       52
<Page>

Date, at the commencement of the twenty-fifth month after the Commencement Date,
at the commencement of the thirty-seventh month after the Commencement Date and
at the commencement of the forty-ninth month after the Commencement Date, the
Security Deposit shall be reduced on each such date by an amount equal to
$104,888.00.

     25.12 OPTION. In the event that Sublessor has an ownership interest in a
new research building to be constructed on the site known as "Biosquare,"
located south of Albany Street (other than the already existing research
building at 650 and 700 Albany Street), and provided that at the time space in
such building is being offered to prospective tenants, (1) this Sublease is in
full force and effect; (2) no event of default by Sublessee has occurred; and
(3) Sublessee has not assigned or sublet any portion of the Sublease Premises to
any person or entity; then Sublessee shall have the option to lease a minimum of
two complete floors of space in such building at the rent and on the terms and
conditions generally being offered to prospective research tenants therein. In
the event Sublessee exercises such option, this Sublease shall terminate, if it
has not already expired or been terminated hereunder, effective as of the
commencement date of Sublessee's lease in such new building provided that no
event of default by Sublessee has occurred.

     IN WITNESS WHEREOF, Sublessor and Sublessee have caused this instrument to
be executed under seal, all as of the day and year first above written.

                                      SUBLESSOR:

                                      TRUSTEES OF BOSTON UNIVERSITY

                                      By:  /s/ William J. Gasper
                                         --------------------------------------
                                         William J. Gasper, Assistant Treasurer

                                      SUBLESSEE:

                                      COMBINATORX, INCORPORATED

                                      By:  /s/ Alexis Borisy
                                         --------------------------------------
                                      Print Name: Alexis Borisy
                                      Title: President

                                       53
<Page>
                                                                   April 5, 2001

                           FIRST AMENDMENT OF SUBLEASE

     THIS FIRST AMENDMENT OF SUBLEASE ("First Amendment of Sublease") dated as
of April __, 2001, by and between Trustees of Boston University (hereinafter
called "Sublessor") and CombinatoRx, Incorporated (hereinafter called
"Sublessee").

                                   WITNESSETH

     WHEREAS, Sublessor and Sublessee entered into that certain Agreement of
Sublease (the "Original Sublease") dated January 25, 2001 for approximately
7,492 rentable square feet on the third floor of the building located at 650
Albany Street (the "Original Sublease Premises"); and

     WHEREAS, in consideration of the premises herein contained and for other
good and valuable consideration, the receipt and sufficiency of which are hereby
acknowledged, Sublessor and Sublessee desire to amend the Original Sublease to
increase the Original Sublease Premises by an additional 4,278 rentable square
feet; and

     WHEREAS, the Original Sublease, as amended by this First Amendment of
Sublease, shall be referred to as the "Sublease";

     NOW, THEREFORE, it is hereby agreed by and between the parties hereto that
the Original Sublease is amended as follows:

     1.  TERMS. Terms not otherwise defined herein shall have the respective
meanings prescribed therefor in the Sublease.

     2.  SUBLEASE PREMISES. The Additional Sublease Premises shall consist of
4,278 rentable square feet located on the first floor of the Building located at
650 Albany Street (the "Additional Sublease Premises") as shown on Exhibit B-1
attached hereto. The Original Sublease Premises, together with the Additional
Sublease Premises, shall be referred to collectively as the "Sublease Premises."

     From time to time during the Term of this Sublease, to the extent that
there is storage space available in the Building, and without any obligation on
the part of Sublessor to provide storage space, Sublessee and Sublessor may
enter into a license for the same with the express understanding that such
license is terminable by either party on thirty (30) days notice and further
provided that the number of rentable square feet and the location of the storage
space may change on thirty (30) days notice from Sublessor to Sublessee. The use
of such storage space by Sublessee shall be on all of the same terms and
conditions as this Sublease, including without limitation the insurance
provisions of this Sublease, except as set forth in this paragraph and except
for the rent which shall be mutually agreed to by the parties. To the extent
that the parties elect to enter into a license agreement with respect to storage
space, the parties shall enter into an agreement memorializing the number of
square feet for, the location of and the rent for the

<Page>

                                       -2-

storage space and any other terms that the parties agree to. Otherwise, the use
of the storage space shall be governed by the terms and conditions of this
Sublease.

     3.  TERM OF LEASE.

         a.   Section 2.1 of the Original Sublease shall be deleted and
substituted with the following:

         2.1  HABENDUM. To have and to hold (A) the Original Sublease Premises
     for a term of five (5) years commencing on the Term Commencement Date for
     the Original Sublease Premises (as hereinafter defined) and ending on the
     day immediately prior to the fifth anniversary thereof; and (B) the
     Additional Sublease Premises for a term commencing on the Term Commencement
     Date for the Additional Sublease Premises (as hereinafter defined) and
     ending on the day immediately prior to the fifth anniversary of the Term
     Commencement Date for the Original Sublease Premises (the "Term of this
     Sublease" or "Original Term"), or on such earlier date upon which said Term
     may expire or be cancelled or be terminated pursuant to any of the
     conditions of limitation or other provisions of this Sublease or pursuant
     to law (which date for the expiration, cancellation or termination of the
     Term hereof shall hereafter be called the "Termination Date").

         b.   Section 2.2 of the Original Sublease shall be deleted and
substituted with the following:

         2.2  TERM COMMENCEMENT DATE. The Term Commencement Date for (A) the
     Original Sublease Premises shall be the earlier of (a) the date on which
     the Original Sublease Premises are deemed ready for occupancy as provided
     in Section 3.2 or (b) the date on which Sublessee occupies all or any part
     of the Original Sublease Premises and the Term Commencement Date for (B)
     the Additional Sublease Premises shall be the earlier of (a) the date on
     which the Additional Sublease Premises are deemed ready for occupancy as
     provided in Section 3.2 or (b) the date on which Sublessee occupies all or
     any part of the Additional Sublease Premises.

     4.  OPTION TO EXTEND TERM. Section 2.4 of the Original Sublease shall be
amended to add at the end thereof a new paragraph as follows:

         Sublessee shall have the right to exercise the extension option with
     respect to the entire Sublease Premises and may not exercise the extension
     option only with respect to a portion of the Sublease Premises.

     5.  INITIAL CONSTRUCTION. The first full paragraph of Section 3.1 of the
Original Sublease shall be deleted in its entirely and replaced with the
following:

         3.1  INITIAL CONSTRUCTION. Sublessor shall perform or cause Landlord to
     perform the Sublease Improvement as described in the Work Letter Agreement
     attached hereto as EXHIBIT E (which Work Letter is hereby incorporated
     herein and made a part hereof). Sublessor shall provide Sublessee with (A)
     a tenant allowance for the Original Sublease Premises in the amount equal
     to the number of rentable square feet in the

<Page>

                                       -3-

     Original Sublease Premises times $70.00, which equals $524,440.00 (the
     "Tenant Allowance for Original Sublease Premises") and (B) a tenant
     allowance for the Additional Sublease Premises in the amount equal to the
     number of rentable square feet in the Additional Sublease Premises times
     $50.00, which equals $213,900.00 (the "Tenant Allowance for the Additional
     Sublease Premises"). The Tenant Allowance for the Original Sublease
     Premises and the Tenant Allowance for the Additional Sublease Premises
     shall be referred to collectively as the "Tenant Allowance." The Tenant
     Allowance shall be used for those costs incurred in connection with the
     Sublease Improvements and approved by Sublessor (the "Approved Sublessee
     Costs") and shall be disbursed in accordance with the provisions of this
     Sublease. Approved Sublessee Costs may include the following costs: the
     cost of preparing the Complete Plans (as hereinafter defined); Sublessee's
     share of the Sublessor's cost of constructing common area walls and
     corridor serving the third floor (which share is approximately $11,072,00);
     Sublessee's share of the cost of the emergency generator as further
     described in Exhibit E attached hereto; and the cost of constructing the
     Sublease Improvements (as hereinafter defined), including architectural,
     contracting and engineering fees associated with the Sublease Improvements.
     Sublessor shall cooperate with, and shall use reasonable efforts to cause
     its architect and engineer to cooperate with, Sublessee's architect and
     engineer in connection with the preparation of Sublessee's construction,
     drawings and specifications for the Sublease Improvements. Sublessee shall
     cooperate with, and shall use reasonable efforts to cause any architects,
     engineers and construction drawings and specifications for the Sublease
     Improvements. Sublessee shall cooperate with, and shall use reasonable
     efforts to cause any architects, engineers and construction consultants
     retained by Sublessee to cooperate with, Sublessor's contractor, engineer,
     architects and subcontractors in connection with the construction of the
     Sublease Improvements and Base Building Work (as hereinafter defined).
     Sublessee shall provide to Sublessor for approval (A) with respect to the
     Original Sublease Premises, no later than February 28, 2001, time being of
     the essence, and (B) with respect to the Additional Sublease Premises, no
     later than April 13, 2001, time being of the essence, complete sets of
     construction drawings and specifications for the Sublease Improvements (the
     "Complete Plans") prepared at Sublessee's expense by (a) Sublessor's
     architect or an architect approved by Sublessor and (b) Sublessor's
     engineer or an engineer approved by Sublessor. The Complete Plans shall
     include but not be limited to:

          a.  Furniture and Equipment Layout Plans
          b.  Dimensioned Partition Plans
          c.  Dimensioned Electrical and Telephone Outlet Plans
          d.  Reflected Ceiling Plans
          e.  Door and Hardware Schedules
          f.  Room Finish Schedules including wall, carpet and floor tile colors
          g.  Electrical, mechanical, plumbing and structural engineering plans
          h.  All necessary construction details and specifications for work not
              otherwise specified.

     6.  PREPARATION TO PREMISES FOR OCCUPANCY. Section 3.2 of the Original
Sublease shall be amended to delete the first sentence in its entirely and to
substitute the following:

<Page>

                                       -4-

         Sublessor agrees to use reasonable efforts to have the Original
     Sublease Premises and the Additional Sublease Premises ready for occupancy
     on or about August 1, 2001, which dates shall, however, be extended for a
     period equal to that of any delays due to Tenant Delays (as hereinafter
     defined) and Force Majeure Delays (as hereinafter defined).

     Section 3.2 is further amended to add at the end thereof a new paragraph as
follows:

         Sublessee understands and agrees that the Original Sublease Premises
     and the Additional Sublease Premises may be ready for occupancy on
     different dates.

     7.  RENT. The amount of "Yearly Fixed Rent" set forth in line 8 of Section
5.1 of the Original Sublease shall be deleted and replaced with "$541,420.00".

     8.  ASSIGNMENT, MORTGAGE AND, SUBLET, ETC. The first full sentence of the
second paragraph of Section 12 of the Original Sublease shall be amended to
delete the period at the end thereof and to add the following:

         "; or (7) the proposed transferee is a not for profit, college or
     university."

     9.  SECURITY DEPOSIT. All references in Section 25.11 and 25.11A of the
Original Sublease to the amount "$524,440" shall be deleted and substituted with
the following: "$622,834.00." All references in Section 25.11 to the amount of
"$104,888.00" shall be substituted with the following: "$124,566.00". A new
paragraph shall be added to the end of Section 25.11A as follows:

         Sublessee hereby understands and agrees that the Letter of Credit was
     issued assuming that the Term Commencement Date shall occur on or about
     July 1, 2001. As the Term Commencement Date for the Sublease Premises shall
     occur later than July 1, 2001, Sublessee hereby agrees to amend the Letter
     of Credit to amend the date set forth therein so that the date set forth in
     the Letter of Credit reflects the actual Term Commencement Date for the
     entire Sublease Premises. In addition, if Sublessor incurs any fees and
     expenses to draw upon the Letter of Credit (including without limitation
     any travel expenses), Sublessee agrees to pay such fees and expenses as if
     those fees and expenses were additional rent due under the Sublease.

     10. EXHIBIT E. The amount of "$7,688.00" set forth in Paragraph 6 of
Exhibit E of the Original Sublease shall be deleted and substituted with the
following "$12,075.00".

     11. REPRESENTATIONS AND WARRANTIES. Sublessee hereby represents and
warrants to Sublessor that Sublessee has full authority to execute this First
Amendment of Sublease without the joinder or consent of any other party and that
Sublessee has not assigned any of its rights, title or interest in or to the
Sublease to any other party.

     12. MISCELLANEOUS. This First Amendment of Sublease shall be binding upon
and inure to the benefit of Sublessee and Sublessor and their respective heirs,
executors, administrators, personal and legal representatives, successors and
assigns. This first Amendment of Sublease embodies the entire agreement between
the parties relative to the
<Page>

                                       -5-

subject matter hereof, and there are no other oral or written agreements between
the parties, nor any representations made by either party relative to the
subject matter hereof, which are not expressly set forth herein. This First
Amendment of Sublease may be amended only by a written instrument executed by
the party or parties to be bound thereby. Sublessor shall have no obligations
under this First Amendment of Sublease if there is a default by Sublessee under
the Original Sublease or under this First Amendment of Sublease.

     13. BROKERS. Sublessee warrants that it has had no dealings with any broker
or agent in connection with this First Amendment of Sublease except for Thompson
Doyle Hennessey & Everest, and covenants to pay, hold harmless and indemnify
Sublessor from and against any and all costs, expense or liability for any
compensation, commissions and charges claimed by any broker or agent, other than
such designated broker(s), with respect to this First Amendment of Sublease or
the negotiation thereof, arising from a breach of the foregoing warranty.

     14. RATIFICATION. Except as herein specifically amended, the Original
Sublease and all of the terms, covenants and provisions thereof are hereby
ratified and reaffirmed and shall remain in full force and effect. The First
Amendment of Sublease is hereby deemed incorporated in the Original Sublease by
reference as of the date hereof; provided, however, in the event of any
inconsistencies between this First Amendment of Sublease shall govern and take
precedence.

     IN WITNESS WHEREOF, the parties hereto have caused this First Amendment of
Sublease to be executed and delivered by their respective duly authorized
officers or representatives, and to take effect as a sealed instrument, as of
the date first above written.

                                    SUBLESSOR:

                                    TRUSTEES OF BOSTON UNIVERSITY

                                    By:  /s/ William J. Gasper
                                       -----------------------------------------
                                       William J. Gasper, Assistant Treasurer

                                    SUBLESSEE:

                                    COMBINATORX, INCORPORATED

                                    By:  /s/ Alexis Borisy
                                         ---------------------------------------
                                    Print Name: ALEXIS BORISY
                                    Title: PRESIDENT & CEO

<Page>

                                                               Gadsby Hannah LLP
                                                                 August 13, 2001

                      AGREEMENT FOR TERMINATION OF SUBLEASE

     This AGREEMENT FOR TERMINATION OF SUBLEASE (the "Agreement") is entered
into as of the ____ day of August, 2001 by and between TRUSTEES OF BOSTON
UNIVERSITY, a Massachusetts non-profit educational corporation with an address
at 715 Albany Street, Boston, Massachusetts 02118 ("Sublessor"), and
COMBINATORX, INCORPORATED, _______________ ("Sublessee").

                                    RECITALS

     A.  Sublessor and Sublessee entered into that certain Agreement of Sublease
dated as of June 1, 2000 ("Sublease") with respect to Sublessee's occupancy of
approximately 2,530 rentable square feet of space (the "Subleased Premises") in
the building located at 801 Albany Street, Boston, Massachusetts (the
"Building").

     B.  Sublessee and Sublessor are entering into an even date herewith a
Second Amendment of Sublease for 11,572 square feet of space in the building
located at 650 Albany Street, Boston, Massachusetts ("Second Amendment").

     C.  Sublessee has requested and Sublessor has agreed to terminate the
Sublease upon the terms and subject to the conditions set forth herein.

     D.  Capitalized terms used herein and not otherwise defined shall have the
meaning set forth in the Sublease.

     NOW, THEREFORE, in consideration of the presents herein contained, and
other good and valuable consideration, the receipt and sufficiency of which are
hereby mutually acknowledged, Sublessor and Sublessee agree as follows:

                                    AGREEMENT

         1.   RECITALS. The parties acknowledge that the Recitals above set
forth are true and correct and are incorporated herein by reference.

         2.   SUBLEASE TERMINATION. Provided that there is no earlier Event of
Default under the Sublease on the part of the Sublessee and further provided
there is no Event of Default under the Sublease on the Termination Date (as
hereinafter defined), the Sublease (including without limitation Section 26 of
the Sublease) shall be deemed terminated (the "Termination") effective as of the
date set forth herein (the "Termination Date") as if the Termination Date was
the date originally set forth in the Sublease for expiration of the Term of the
Sublease. Effective as of the Termination Date, Sublessee shall have no further
rights to use or occupy the Subleased Premises or obligations (except for
Sublessee's Surviving Obligations as defined below) with respect to the
Subleased Premises. The Termination Date for the Subleased Date for the
Subleased Premises shall be 11:59 P.M. on September 30, 2001.

<Page>

     Upon execution of this Agreement, Sublessor shall have access to the entire
Subleased Premises for the purposes of showing the Subleased Premises to
prospective tenants.

     The provisions of this Paragraph 1 shall not limit Sublessee's obligation
to pay Yearly Fixed Rent, Parking Rent and additional rent accruing prior to the
Termination Date in accordance with the terms of the Sublease.

     Should Sublessee default under this Agreement and/or the Second Amendment,
(a) the Agreement shall at the sole option of Sublessor be of no further force
and effect and the parties shall have all of their original obligations set
forth in the Sublease and/or (b) Sublessor shall have all rights and remedies
set forth in this Agreement and the Sublease for any such breach and/or default
without any requirement of notice to Sublessee.

         3.   SURVIVING OBLIGATIONS. (a) SUBLESSEE. Notwithstanding any
provisions herein or in the Sublease to the contrary, the following obligations
of Sublessee shall survive the Termination of the Sublease (the "Sublessee's
Surviving Obligations"): (1) those obligations which are specified in the
Sublease to survive the expiration or earlier termination of the Sublease; (2)
the payment of the Yearly Fixed Rent, Parking Rent and additional rent payable
by Sublessee pursuant to the Sublease through and including the Termination
Date, including without limitation, any final reconciliations (appropriately
pro-rated and adjusted as provided in the Sublease) as if the Termination Date
was the date originally designated as the last day of the Term of the Sublease;
(3) the obligations of Sublessee regarding yielding-up and hold over of the
Subleased Premises as set forth in the Sublease and (4) the obligations of
Sublessee under this Agreement.

         (b)  SUBLESSOR. Notwithstanding any provisions herein or in the
Sublease to the contrary, the following obligations of Sublessor shall survive
the termination of the Sublease (the "Sublessor's Surviving Obligations"): (1)
those obligations which are specified in the Sublease to survive the expiration
or earlier termination of the Sublease; and (2) the obligations of Sublessor
under this Agreement.

         4.   SURRENDER OF SUBLEASED PREMISES. The Subleased Premises shall be
delivered and surrendered by Sublessee to Sublessor on or before the Termination
Date in the condition specified herein. On or before the Termination Date,
Sublessee shall surrender all keys to the applicable Subleased Premises, remove
all of its trade fixtures and personal property in the Subleased Premises,
repair all damage caused by such removal, and yield up the Subleased Premises
(including all installations and improvements made by Sublessee or Sublessor),
broom-clean and in the same good order and repair in which the Subleased
Premises were on the execution date of this Agreement, reasonable wear and tear
excepted.

     Sublessee shall deliver a certificate of the Department of Public Health
regarding the decommissioning of the Subleased Premises and any affected portion
of the Building.

         5.   RELEASE. As of the Termination Date, Sublessee shall be deemed to
have released and forever discharged Sublessor, Community Development
Corporation of Boston,

                                        2
<Page>

Inc. and their trustees, officers, directors, shareholders, agents, employees,
members, managers, attorneys, affiliates, assigns and beneficiaries, of and from
all debts, demands, actions, causes of action, suits, accounts, covenants,
contracts, agreements, damages, and any and all claims, demands and liabilities
whatsoever of every name and nature, both at law and in equity, which Sublessee
now has or ever had regarding the Main Lease, the Sublease or the Subleased
Premises, except for the Sublessor's Surviving Obligations as defined in
Paragraph 3 herein.

         6.   JURISDICTION/VENUE. Sublessor and Sublessee agree that any legal
action commenced to interpret or enforce this Agreement, or otherwise arising
out of this Agreement, shall be maintained in the Courts of Suffolk County,
Massachusetts.

         7.   COUNTERPARTS. This Agreement may be executed in one or more
counterparts, each of which shall be deemed to be an original and all of which
collectively shall constitute one and the same instrument.

         8.   AMENDMENT. This Agreement may not be amended except by a writing
signed by both parties.

         9.   GOVERNING LAW. This Agreement shall be governed by the laws of The
Commonwealth of Massachusetts without regard to conflict of laws.

         10.  ENTIRE AGREEMENT. This Agreement represents the entire
understanding between the parties with respect to the matters herein contained.
The submission of this document shall not be deemed an offer or option.

         11.  PARAGRAPH HEADINGS AND INTERPRETATION OF SECTIONS. The paragraph
headings throughout this Agreement are for convenience and reference only, and
the words contained therein shall in no way be held to explain, modify, amplify
or aid in the interpretation, construction or meaning of the provisions of this
Agreement. The provisions of this Agreement shall be construed as a whole,
according to their common meaning (except where a precise legal interpretation
is clearly evidenced), and not for or against either party. Use in this
Agreement of the words "including", "such as" or words of similar import, when
followed by any general term, statement or matter, shall not be construed to
limit such term, statement or matter to the specified item(s), whether or not
language of non-limitation, such as "without limitation" or "including but not
limited to ", or words of similar import, are used with reference thereto, but
rather shall be deemed to refer to all other terms or matters that could fall
within a reasonably broad scope of such term, statement or matter. All times set
forth herein shall be of the essence.

         12.  SUBMISSION NOT AN OFFER. The submission of this document for
examination, negotiation and execution does not constitute an offer, option or
reservation, and this document shall become effective and binding only upon the
execution and delivery hereof by both Sublessor and Sublessee.

         13.  BIND AND INURE. This Agreement shall be binding upon, and shall
inure to the benefit of, Sublessor and Sublessee, and their respective
successors and assigns.

                                        3
<Page>

         14.  SUBLESSEE'S REPRESENTATIONS AND WARRANTIES. Sublessee hereby
represents and warrants to Sublessor that Sublessee has full authority to
execute this Agreement without the joinder or consent of any other party and
that Sublessee has not assigned any of its rights, title or interest in or to
the Sublease to any other party. Sublessor hereby represents and warrants to
Sublessee that Sublessor has full authority to execute this Agreement without
the joinder or consent of any other party. The representations and warranties
contained in this paragraph shall survive the termination of the Sublease.

         15.  BROKERS. Sublessee and Sublessor represent and warrant to each
other that neither has dealt with any broker in connection with the termination
of the Sublease. Sublessee and Sublessor each agree to indemnify and hold the
other harmless from and against any liability, loss, cost, damage or expense,
including attorneys fees and court costs resulting from a breach of the above
warranty and representation. The provisions of this paragraph shall survive the
termination of the Sublease.

         16.  ENFORCEMENT. If either party hereto brings any action to enforce
the terms hereof or declare rights hereunder, the prevailing party in any such
action, on trial or appeal, shall be entitled to payment of its reasonable
attorneys' fees and costs by the non-prevailing party.

     IN WITNESS WHEREOF, Sublessor and Sublessee have executed this Agreement,
under seal, as of the date first above set forth.

                                    SUBLESSOR:

                                    TRUSTEES OF BOSTON UNIVERSITY

                                    By:  /s/ William J. Gasper
                                        ----------------------------------
                                    Name:  William J. Gasper
                                         ---------------------------------
                                    Title: Assistant Treasurer
                                               Trustees of
                                            Boston University
                                          --------------------------------
                                           (Hereunto Duly Authorized)

                                    SUBLESSEE:
                                    COMBINATORX, INCORPORATED

                                    By: /s/  Alexis Borisy
                                        ----------------------------------
                                    Name:     ALEXIS BORISY
                                          --------------------------------
                                    Title:  PRESIDENT & CEO
                                           -------------------------------

                                        4
<Page>
                                                                  EXECUTION COPY

                          SECOND AMENDMENT OF SUBLEASE

     THIS SECOND AMENDMENT OF SUBLEASE ("Second Amendment of Sublease") dated as
of August __, 2001, by and between Trustees of Boston University (hereinafter
called "Sublessor") and CombinatoRx, Incorporated (hereinafter called
"Sublessee").

                                   WITNESSETH

     WHEREAS, Sublessor and Sublessee entered into that certain Agreement of
Sublease dated January 25, 2001 for approximately 7,492 rentable square feet on
the third floor of the building (the "Building") located at 650 Albany Street
(the "Original Sublease Premises"); and

     WHEREAS, Sublessor and Sublessee entered into that certain First Amendment
of Sublease ("First Amendment of Sublease") dated April 5, 2001 for
approximately 4,278 rentable square feet on the first floor of the Building (the
"Additional Sublease Premises"); and

     WHEREAS, the Agreement of Sublease, as amended by the First Amendment of
Sublease, shall be referred to as the "Original Sublease"; and

     WHEREAS, the Original Sublease, as amended by this Second Amendment of
Sublease, shall be referred to as the "Sublease"; and

     WHEREAS, in consideration of the premises herein contained and for other
good and valuable consideration, the receipt and sufficiency of which are hereby
acknowledged, Sublessor and Sublessee desire to amend the Original Sublease to
increase the Sublease Premises by an additional 11,572 rentable square feet;

     NOW, THEREFORE, it is hereby agreed by and between the parties hereto that
the Original Sublease is amended as follows:

     1.  TERMS. Terms not otherwise defined herein shall have the respective
meanings prescribed therefor in the Sublease.

     2.  SUBLEASE PREMISES. The Additional Sublease Premises shall consist of
11,572 rentable square feet located on the second floor of the Building located
at 650 Albany Street (the "Second Amendment Additional Sublease Premises") as
shown on Exhibit B-2 attached hereto. The Original Sublease Premises and
Additional Sublease Premises, together with the Second Amendment Additional
Sublease Premises, shall be referred to collectively as the "Sublease Premises."

     3.  TERM OF LEASE.

         a.   Section 2.1 of the Original Sublease shall be deleted and
substituted with the following:

<Page>

                                       -2-

         2.1  HABENDUM. To have and to hold (A) the Original Sublease Premises
     for a term of five (5) years commencing on the Term Commencement Date for
     the Original Sublease Premises (as hereinafter defined) and ending on
     August 31, 2006; and (B) the Additional Sublease Premises for a term
     commencing on July 18, 2001 and ending on August 31, 2006; and (C) the
     Second Amendment Additional Premises for a term commencing on October 1,
     2001 and ending on August 31, 2006 (the "Term of this Sublease" or
     "Original Term"), or on such earlier date upon which said Term may expire
     or be cancelled or be terminated pursuant to any of the conditions of
     limitation or other provisions of this Sublease or pursuant to law (which
     date for the expiration, cancellation or termination of the Term hereof
     shall hereafter be called the "Termination Date").

         b. Section 2.2 of the Original Sublease shall be deleted and
substituted with the following:

     2.2 TERM COMMENCEMENT DATE. The Term Commencement Date for the Original
Sublease Premises shall be the earlier of (a) the date on which the Original
Sublease Premises are deemed ready for occupancy as provided in Section 3.2 or
(b) the date on which Sublessee occupies all or any part of the Original
Sublease Premises. The Term Commencement Date for the Additional Sublease
Premises shall be July 18, 2001. The Term Commencement Date for the Second
Amendment Additional Premises shall be October 1, 2001. Collectively, each of
the respective Term Commencement Dates shall be referred to herein as the "Term
Commencement Date".

         c.   Section 2.3 of the Original Sublease shall be amended as follows:
     the words "fourteen (14)" shall be deleted and the words "forty-six (46)"
     shall be substituted.

     4.  OPTION TO EXTEND TERM. Section 2.4 of the Original Sublease shall be
amended to add at the end thereof a new paragraph as follows:

         Sublessee shall have the right to exercise the extension option with
     respect to the entire Sublease Premises and may not exercise the extension
     option only with respect to a portion of the Sublease Premises.

     5.  CONDITION OF SECOND AMENDMENT ADDITIONAL SUBLEASE PREMISES.
Notwithstanding any of the terms and provisions of Sections 3.1 and 3.2 of the
Original Sublease, Sublessee hereby acknowledges and agrees that it is taking
the Second Amendment Additional Sublease Premises in "as is, where is" condition
without any representations or warranties by Sublessor, Sublessee hereby
acknowledging and agreeing that it has inspected the Second Amendment Additional
Sublease Premises and accepts said Second Amendment Additional Sublease Premises
in its current condition.

     6.  RENT. The third sentence of Section 5.01 of the Original Sublease shall
be deleted and replaced with the following: "For purposes of this Sublease, the
Yearly Fixed Rent for the Original Sublease Premises and the Additional Premises
shall equal $541,420.00 for each lease year of the Term and the Yearly Fixed
Rent for the Second Amendment Additional

<Page>

                                      -3-

Sublease Premises shall equal $659,604.00 for each lease year of the Term", for
a total Yearly Fixed Rent for the Sublease Premises of $1,201,024 for each lease
year of the Term.

     7.  SECURITY DEPOSIT. All references in Section 25.11 and 25.11A of the
Original Sublease to the amount "$622,834.00" shall be deleted and substituted
with the following: "$734,696.67."

     8.  REPRESENTATIONS AND WARRANTIES. Sublessee hereby represents and
warrants to Sublessor that Sublessee has full authority to execute this Second
Amendment of Sublease without the joinder or consent of any other party and that
Sublessee has not assigned any of its rights, title or interest in or to the
Sublease to any other party.

     9.  MISCELLANEOUS. This Second Amendment of Sublease shall be binding upon
and inure to the benefit of Sublessee and Sublessor and their respective heirs,
executors, administrators, personal and legal representatives, successors and
assigns. This Second Amendment of Sublease embodies the entire agreement between
the parties relative to the subject matter hereof, and there are no other oral
or written agreements between the parties, nor any representations made by
either party relative to the subject matter hereof, which are not expressly set
forth herein. This Second Amendment of Sublease may be amended only by a written
instrument executed by the party or parties to be bound thereby. Sublessor shall
have no obligations under this Second Amendment of Sublease if there is a
default by Sublessee under the Original Sublease or under this Second Amendment
of Sublease.

     10. BROKERS. Sublessee warrants that it has had no dealings with any broker
or agent in connection with this Second Amendment of Sublease except for GVA
Thompson Doyle Hennessey & Everest, and covenants to pay, hold harmless and
indemnify Sublessor from and against any and all costs, expense or liability for
any compensation, commissions and charges claimed by any broker or agent, other
than such designated broker(s), with respect to this Second Amendment of
Sublease or the negotiation thereof, arising from a breach of the foregoing
warranty.

     11. RATIFICATION. Except as herein specifically amended, the Original
Sublease and all of the terms, covenants and provisions thereof are hereby
ratified and reaffirmed and shall remain in full force and effect. The Second
Amendment of Sublease is hereby deemed incorporated in the Original Sublease by
reference as of the date hereof; provided, however, in the event of any
inconsistencies between this Second Amendment of Sublease and the Original
Sublease, the terms and provisions of this Second Amendment of Sublease shall
govern and take precedence.

<Page>

                                       -4-

     IN WITNESS WHEREOF, the parties hereto have caused this Second Amendment of
Sublease to be executed and delivered by their respective duly authorized
officers or representatives, and to take effect as a sealed instrument, as of
the date first above written.

                                     SUBLESSOR:

                                     TRUSTEES OF BOSTON UNIVERSITY

                                     By:
                                        ----------------------------------------
                                        William J. Gasper, Assistant Treasurer

                                     SUBLESSEE:

                                     COMBINATORX, INCORPORATED

                                     By: /s/ Alexis Borisy
                                        ----------------------------------------
                                     Print Name:  ALEXIS BORISY
                                     Title: PRESIDENT & CEO
<Page>

April 9, 2002

Mr. Alexis Borisy
President and CEO
CombinatoRx, Inc.
650 Albany Street, Floor I
Boston, MA 02118

     RE:  AGREEMENT OF SUBLEASE DATED JANUARY 25, 2001 BY AND BETWEEN TRUSTEES
          OF BOSTON UNIVERSITY AND COMBINATORX INCORPORATED AS AMENDED BY THAT
          CERTAIN FIRST AMENDMENT DATED APRIL 5, 2001 AND THAT CERTAIN SECOND
          AMENDMENT DATED SEPTEMBER 19, 2001 (COLLECTIVELY, THE "SUBLEASE")

Dear Alexis,

     Pursuant to our recent discussions, we are willing to amend the above
described Sublease provided that there is no event of default at the time of
this letter or at the time of the execution of a third amendment of Sublease and
provided that the following terms and conditions are satisfied:

     1.   CombinatoRx must expend at least $234,000 on improvements to the
          Sublease Premises, which improvements shall be permanent in nature and
          satisfactory to Boston University. Such improvements shall be
          completed on or before July 1, 2002, time being of the essence, and
          CombinatoRx shall submit paid invoices, a Certificate of Occupancy for
          the Tenant Improvements, an Architect's Certificate of Substantial
          Completion and evidence that there are no liens affecting the Premises
          or the Building.

     2.   Upon receipt of the forgoing and a satisfactory inspection of the
          Sublease Premises by Boston University, provided there is no event of
          default under the Sublease, the Security Deposit shall be reduced to
          $500,000. If the foregoing shall occur in accordance with the terms
          set forth herein, the Security Deposit shall thereafter be reduced to
          the following aggregate amounts provided there is no event of default
          under the Sublease as follows:

<Table>
                  <S>                   <C>
                  July 1, 2002          $  400,000
                  July 1, 2003          $  300,000
                  July 1, 2004          $  200,000
                  July 1, 2005          $  146,940
</Table>

<Page>

         All other terms and conditions of the Sublease shall remain unchanged.
If the terms and conditions of this letter are acceptable to you, please sign no
later than April 19, 2002 where indicated and we will ask our attorneys to
assist in the preparation of a sublease amendment.

Regards,

Michael J. Donovan
Associate Vice President

cc:      Ed Davis, CombinatoRx, Inc.
         William J. Gasper, Associate Vice President, Business Affairs
         Cynthia Keliher, Gadsby and Hannah
         Richard J. Towle, Senior Vice President
         Stephen A. Williams, Office of General Counsel

AGREED AND ACCEPTED BY:

COMBINATORX INCORPORATED

By: /s/ Edward Davis
   ----------------------------------
        Hereunto Duly Authorized

<Page>
                           THIRD AMENDMENT OF SUBLEASE

     THIS THIRD AMENDMENT OF SUBLEASE ("Third Amendment of Sublease") dated as
of September 11, 2002, by and between Trustees of Boston University (hereinafter
called "Sublessor") and CombinatoRx, Incorporated (hereinafter called
"Sublessee").

                                   WITNESSETH

     WHEREAS, Sublessor and Sublessee entered into that certain Agreement of
Sublease dated January 25, 2001 for Premises in the building (the "Building")
located at 650 Albany Street as amended by First Amendment of Sublease dated
April 5, 2001 and Second Amendment of Sublease dated August 2001 (collectively,
the "Original Sublease"); and

     WHEREAS, the Original Sublease, as amended by this Third Amendment of
Sublease, shall be referred to as the "Sublease"; and

     WHEREAS, in consideration of the premises herein contained and for other
good and valuable consideration, the receipt and sufficiency of which are hereby
acknowledged, Sublessor and Sublessee desire to amend the Original Sublease to
decrease the Security Deposit as set forth herein;

     NOW, THEREFORE, it is hereby agreed by and between the parties hereto that
the Original Sublease is amended as follows:

     1.  TERMS. Terms not otherwise defined herein shall have the respective
meanings prescribed therefor in the Sublease.

     2.  SECURITY DEPOSIT. All references in Section 25.11 and 25.11A of the
Original Sublease to the amount "$734,696.76" shall be deleted and substituted
with the following: "$400,000.00."

     3.  SECURITY DEPOSIT. The last sentence of the first paragraph of Section
25.11A is hereby deleted and the following is substituted in lieu thereof.

     Effective July 1, 2002, the Letter of Credit shall be in the amount of
     $400,000.00, and provided no event of default exists: (i) on July 1, 2003,
     the amount of the Letter of Credit shall be reduced to $300,000.00; and
     (ii) on July 1, 2004, the amount of the Letter of Credit shall be reduced
     to $200,000.00; and (iii) on July 1, 2005, the amount of the Letter of
     Credit shall be reduced to $146,940.00.

     4.  REPRESENTATIONS AND WARRANTIES. Sublessee hereby represents and
warrants to Sublessor that Sublessee has full authority to execute this Third
Amendment of Sublease without the joinder or consent of any other party and that
Sublessee has not assigned any of its rights, title or interest in or to the
Sublease to any other party.

<Page>

                                       -2-

     5.  MISCELLANEOUS. This Third Amendment of Sublease shall be binding upon
and inure to the benefit of Sublessee and Sublessor and their respective heirs,
executors, administrators, personal and legal representatives, successors and
assigns. This Third Amendment of Sublease embodies the entire agreement between
the parties relative to the subject matter hereof, and there are no other oral
or written agreements between the parties, nor any representations made by
either party relative to the subject matter hereof, which are not expressly set
forth herein. This Third Amendment of Sublease may be amended only by a written
instrument executed by the party or parties to be bound thereby. Sublessor shall
have no obligations under this Third Amendment of Sublease if there is default a
by Sublessee under the Original Sublease or under this Third Amendment of
Sublease.

     6.  BROKERS. Sublessee warrants that it has had no dealings with any
broker or agent in connection with this Third Amendment of Sublease, and
covenants to pay, hold harmless and indemnify Sublessor from and against any and
all costs, expense or liability for any compensation, commissions and charges
claimed by any broker or agent, with respect to this Third Amendment of
Sublease or the negotiation thereof, arising from a breach of the foregoing
warranty.

     7.  RATIFICATION. Except as herein specifically amended, the Original
Sublease and all of the terms, covenants and provisions thereof are hereby
ratified and reaffirmed and shall remain in full force and effect. The Third
Amendment of Sublease is hereby deemed incorporated in the Original Sublease by
reference as of the date hereof; provided, however, in the event of any
inconsistencies between this Third Amendment of Sublease and the Original
Sublease, the terms and provisions of this Third Amendment of Sublease shall
govern and take precedence.

     IN WITNESS WHEREOF, the parties hereto have caused this Third Amendment of
Sublease to be executed and delivered by their respective duly authorized
officers or representatives, and to take effect as a scaled instrument, as of
the date first above written.

                                   SUBLESSOR:

                                   TRUSTEES OF BOSTON UNIVERSITY

                                   By: /s/ William J. Gasper
                                      ---------------------------------------
                                      William J. Gasper, Assistant Treasurer

                                   SUBLESSEE:

                                   COMBINATORX, INCORPORATED

                                   By: /s/ Alexis Borisy
                                      ---------------------------------------
                                   Print Name: Alexis Borisy
                                   Title: President & CEO<Page>

                                                                  Exhibit 10.4

THIS WARRANT AND THE SHARES ISSUABLE HEREUNDER HAVE NOT BEEN REGISTERED UNDER
THE SECURITIES ACT OF 1933, AS AMENDED, AND MAY NOT BE SOLD, PLEDGED OR
OTHERWISE TRANSFERRED WITHOUT AN EFFECTIVE REGISTRATION THEREOF UNDER SUCH ACT
OR PURSUANT TO RULE 144 OR AN OPINION OF COUNSEL REASONABLY SATISFACTORY TO THE
CORPORATION AND ITS COUNSEL THAT SUCH REGISTRATION IS NOT REQUIRED.

                            WARRANT TO PURCHASE STOCK

<Table>
          <S>                      <C>
          Corporation:             COMBINATORX, INCORPORATED, a Delaware corporation
          Number of Shares:        128,000 (subject to adjustment pursuant to Article 2)
          Class of Stock:          $0.001 par value Common Stock
          Initial Exercise Price:  $3.75 per share (subject to adjustment pursuant to Article 2)
          Issue Date:              September 10, 2002
          Expiration Date:         September 9, 2007
</Table>

     THIS WARRANT CERTIFIES THAT, for good and valuable consideration, the
receipt of which is hereby acknowledged, ROCKPORT VENTURE SECURITIES, LLC, a
Delaware limited liability company or its assignee ("Holder") is entitled to
purchase the number of fully paid and nonassessable shares of the class of
securities (the "Shares") of the corporation (the "Company") at the initial
exercise price per Share (the "Warrant Price") all as set forth above and as
adjusted pursuant to Article 2 of this warrant, subject to the provisions and
upon the terms and conditions set forth in this warrant.

ARTICLE 1.   EXERCISE.

     1.1     METHOD OF EXERCISE. Holder may exercise this warrant by delivering
this warrant and a duly executed Notice of Exercise in substantially the form
attached as Appendix 1 to the principal office of the Company. Unless Holder is
exercising the conversion right set forth in Section 1.2, Holder shall also
deliver to the Company a check (for immediately available funds) for the
aggregate Warrant Price for the Shares being purchased.

     1.2     CASHLESS CONVERSION RIGHT. In lieu of exercising this warrant for
cash as specified in Section 1.1, Holder may from time to time convert this
warrant, in whole or in part, into a number of Shares determined by dividing (a)
the aggregate fair market value of the Shares or other securities otherwise
issuable upon exercise of this warrant minus the aggregate Warrant Price of such
Shares by (b) the fair market value of one Share. The fair market value of the
Shares shall be determined pursuant to Section 1.3.

     1.3     FAIR MARKET VALUE. If the Shares are traded regularly in a public
market, the fair market value of the Shares shall be the closing price of the
Shares (or the closing price of the Company's stock into which the Shares are
convertible) reported for the business day immediately before Holder delivers
its Notice of Exercise to the Company. If the Shares are not regularly traded in
a public market, the Board of Directors of the Company shall determine fair
market value in its reasonable good faith judgment.

     1.4     DELIVERY OF CERTIFICATE AND NEW WARRANT. Promptly after Holder
exercises or converts this warrant, the Company shall deliver to Holder
certificates for the Shares acquired and, if this warrant has not been fully
exercised or converted and has not expired, a new warrant representing the
Shares not so acquired.

     1.5     REPLACEMENT OF WARRANTS. On receipt of evidence reasonably
satisfactory to the Company of the loss, theft, destruction or mutilation of
this warrant and, in the case of loss, theft or destruction, on delivery of an
indemnity agreement reasonably satisfactory in form and amount to the Company
or, in the case of mutilation, on surrender and cancellation of this warrant,
the Company at its expense shall execute and deliver, in lieu of this warrant, a
new warrant of like tenor.

     1.6     SALE, MERGER, OR CONSOLIDATION OF THE COMPANY.

             1.6.1  "ACQUISITION." For the purpose of this warrant,
"Acquisition" means any sale, license, or other disposition of all or
substantially all of the assets (including intellectual property) of the
Company, or any

<Page>

reorganization, consolidation, or merger of the Company where the holders of the
Company's securities before the transaction beneficially own less than 50% of
the outstanding voting securities of the surviving entity after the transaction.

             1.6.2  AUTOMATIC EXERCISE OF WARRANT. Upon the closing of any
Acquisition, to the extent this warrant has not already been exercised, this
warrant shall be deemed to have been automatically (without the need for any
action on the part of the Holder) exercised immediately prior to the closing of
the said Acquisition by the cashless conversion method described in Section 1.2.

ARTICLE 2.   ADJUSTMENTS TO THE SHARES AND WARRANT PRICE.

     2.1     STOCK DIVIDENDS, SPLITS, ETC. If, after the Issue Date, the
Company declares or pays a dividend on its common stock payable in common stock
or other securities, or subdivides the outstanding common stock into a greater
amount of common stock, then upon exercise of this warrant (to the extent not
already exercised), for each Share acquired, Holder shall receive, without cost
to Holder, the total number and kind of securities to which Holder would have
been entitled had Holder owned the Shares of record as of the date the dividend
or subdivision occurred.

     2.2     RECLASSIFICATION, EXCHANGE OR SUBSTITUTION. Upon any
reclassification, exchange, substitution, or other event that results in a
change of the number and/or class of the securities issuable upon exercise or
conversion of this warrant, Holder shall be entitled to receive, upon exercise
or conversion of this warrant, the number and kind of securities and property
that Holder would have received for the Shares if this warrant had been
exercised immediately before such reclassification, exchange, substitution, or
other event. Such an event shall include any automatic conversion of the
outstanding or issuable securities of the Company of the same class or series as
the Shares to common stock pursuant to the terms of the Company's Certificate of
Incorporation upon the closing of a registered public offering of the Company's
common stock. The Company or its successor shall promptly issue to Holder a new
warrant for such new securities or other property. The new warrant shall provide
for adjustments which shall be as nearly equivalent as may be practicable to the
adjustments provided for in this Article 2 including, without limitation,
adjustments to the Warrant Price and to the number of securities or property
issuable upon exercise of the new warrant. The provisions of this Section 2.2
shall similarly apply to successive reclassifications, exchanges, substitutions,
or other events.

     2.3     ADJUSTMENTS FOR COMBINATIONS, ETC. If the outstanding Shares are
combined or consolidated, by reclassification or otherwise, into a lesser number
of shares, the Warrant Price shall be proportionately increased and the number
of Shares for which this warrant may still be exercised shall be proportionately
decreased. If the outstanding Shares are combined or consolidated, by
reclassification or otherwise, into a greater number of shares, the Warrant
Price shall be proportionately decreased and the number of Shares for which this
warrant may still be exercised shall be proportionately increased.

     2.4     ANTI-DILUTION ADJUSTMENTS. The Warrant Price shall also be subject
to adjustment under the circumstances and in the manner set forth in EXHIBIT A.
Notwithstanding any other provision of this warrant, this warrant may be
exercised for that number of Shares equal to (a) the "Number of Shares"
specified at the top of the first page of this warrant, multiplied by (b) the
"Initial Exercise Price" specified at the top of the first page of this warrant,
divided by (c) the then current Warrant Price as such may have been adjusted
pursuant to the provisions set forth in EXHIBIT A.

     2.5     NO IMPAIRMENT. The Company shall not, by amendment of its
Certificate of Incorporation or through a reorganization, transfer of assets,
consolidation, merger, dissolution, issue, or sale of securities or any other
voluntary action, avoid or seek to avoid the observance or performance of any of
the terms to be observed or performed under this warrant by the Company, but
shall at all times in good faith assist in carrying out all the provisions of
this Article 2 and in taking all such action as may be necessary or appropriate
to protect Holder's rights under this Article against impairment.

     2.6     CERTIFICATE AS TO ADJUSTMENTS. Upon each adjustment of the Warrant
Price, the Company at its expense shall promptly compute such adjustment, and
furnish Holder with a certificate of its Chief Financial Officer setting forth
such adjustment and the facts upon which such adjustment is based. The Company
shall, upon written request, furnish Holder a certificate setting forth the
Warrant Price in effect upon the date thereof and the series of

                                        2
<Page>

adjustments leading to such Warrant Price.

ARTICLE 3.   REPRESENTATIONS AND COVENANTS OF THE COMPANY.

     3.1     REPRESENTATIONS AND WARRANTIES. The Company hereby represents and
warrants to the Holder as follows:

             (a)    All Shares which may be issued upon the exercise of the
purchase right represented by this warrant, and all securities, if any, issuable
upon conversion of the Shares, shall, upon issuance, be duly authorized, validly
issued, fully paid and nonassessable, and free of any liens and encumbrances
except for restrictions on transfer provided for herein or under applicable
federal and state securities laws.

             (b)    The Company's capitalization table attached to this warrant
is true and complete as of the Issue Date.

     3.2     NOTICE OF CERTAIN EVENTS. If the Company proposes at any time (a)
to declare any dividend or distribution upon its common stock, whether in cash,
property, stock, or other securities and whether or not a regular cash dividend;
(b) to offer for subscription pro rata to the holders of any class or series of
its stock any additional shares of stock of any class or series or other rights;
(c) to effect any reclassification or recapitalization of common stock; or (d)
to merge or consolidate with or into any other corporation, or sell, lease,
license, or convey all or substantially all of its assets, or to liquidate,
dissolve or wind up, then, in connection with each such event, the Company shall
give Holder (1) at least 20 days prior written notice of the date on which a
record will be taken for such dividend, distribution, or subscription rights
(and specifying the date on which the holders of common stock will be entitled
thereto) or for determining rights to vote, if any, in respect of the matters
referred to in (a) and (b) above; and (2) in the case of the matters referred to
in (c) and (d) above at least 20 days prior written notice of the date when the
same will take place (and specifying the date on which the holders of common
stock will be entitled to exchange their common stock for securities or other
property deliverable upon the occurrence of such event).

     3.3     INFORMATION RIGHTS. So long as the Holder holds this warrant and/or
any of the Shares, the Company shall deliver to the Holder (at the same time as
delivered to the Company's stockholders) the annual audited financial statements
of the Company certified by INDEPENDENT public accountants of recognized
standing.

ARTICLE 4.   MISCELLANEOUS.

     4.1     TERM: NOTICE OF EXPIRATION. This warrant is exercisable in whole or
in part, at any time and from time to time on or before the Expiration Date set
forth above.

     4.2     LEGENDS. This warrant and the Shares (and the securities issuable,
directly or indirectly, upon conversion of the Shares, if any) shall be
imprinted with a legend in substantially the following form:

THIS SECURITY HAS NOT BEEN REGISTERED UNDER THE SECURITIES ACT OF 1933, AS
AMENDED, AND MAY NOT BE SOLD, PLEDGED OR OTHERWISE TRANSFERRED WITHOUT AN
EFFECTIVE REGISTRATION THEREOF UNDER SUCH ACT OR PURSUANT TO RULE 144 OR AN
OPINION OF COUNSEL REASONABLY SATISFACTORY TO THE CORPORATION AND ITS COUNSEL
THAT SUCH REGISTRATION IS NOT REQUIRED.

     4.3     COMPLIANCE WITH SECURITIES LAWS ON TRANSFER. This warrant and the
Shares issuable upon exercise of this warrant (and the securities issuable,
directly or indirectly, upon conversion of the Shares, if any) may not be
transferred or assigned in whole or in part without compliance with applicable
federal and state securities laws by the transferor and the transferee
(including, without limitation, the delivery of investment representation
letters and legal opinions reasonably satisfactory to the Company). The Company
shall not require Holder to provide an opinion of counsel if the transfer is to
an affiliate of Holder or if there is no material question as to the
availability of current information as referenced in Rule 144(c), Holder
represents that it has complied with Rule 144(d) and (e) in reasonable detail,
the selling broker represents that it has complied with Rule 144(f), and the
Company is provided with a copy of Holder's notice of proposed sale.

                                        3
<Page>

     4.4     TRANSFER PROCEDURE. Subject to the provisions of Section 4.3,
Holder may transfer all or part of this warrant or the Shares issuable upon
exercise of this warrant (or the securities issuable, directly or indirectly,
upon conversion of the Shares, if any) by giving the Company notice of the
portion of the warrant being transferred setting forth the name, address and
taxpayer identification number of the transferee and surrendering this warrant
to the Company for reissuance to the transferee(s) (and Holder, if applicable);
PROVIDED, HOWEVER, that Holder may transfer all or part of this warrant to its
affiliates at any time without notice to the Company, and such affiliate shall
then be entitled to all the rights of Holder under this warrant and any related
agreements, and the Company shall cooperate fully in ensuring that any stock
issued upon exercise of this warrant is issued in the name of the affiliate that
exercises the warrant. The terms and conditions of this warrant shall inure to
the benefit of, and be binding upon, the Company and the holders hereof and
their respective permitted successors and assigns. The Company shall have the
right to refuse to transfer any portion of this warrant to any person who
directly competes with the Company, unless the Company is filing financial
information with the SEC pursuant to the Securities Exchange Act of 1934.

     4.5     NOTICES. All notices and other communications from the Company to
the Holder, or vice versa, shall be deemed delivered and effective when given
personally or mailed by first-class registered or certified mail, postage
prepaid, at such address as may have been furnished to the Company or the
Holder, as the case may be, in writing by the Company or such Holder from time
to time. All notices to the Holder shall be addressed as follows:

                            Rockport Venture Securities, LLC
                            63 Main Street
                            Gloucester, MA 01936
                            Attention: Manager

     4.6     WAIVER. This warrant and any term hereof may be changed, waived,
discharged or terminated only by an instrument in writing signed by the party
against which enforcement of such change, waiver, discharge or termination is
sought.

     4.7     ATTORNEYS' FEES. In the event of any dispute between the parties
concerning the terms and provisions of this warrant, the party prevailing in
such dispute shall be entitled to collect from the other party all costs
incurred in such dispute, including reasonable attorneys' fees.

     4.8     GOVERNING LAW. This warrant shall be governed by and construed in
accordance with the laws of the Commonwealth of Massachusetts, without giving
effect to its principles regarding conflicts of law.

                            COMBINATORX, INCORPORATED

                            By: /s/ Edward Davis
                               -------------------------------------------------
                            Edward Davis
                            Executive Vice President and Chief Financial Officer
                            Hereunto Duly Authorized

<Page>

                                   APPENDIX 1

                               NOTICE OF EXERCISE

     1.   The undersigned hereby elects to purchase ___________ shares of
the ___________ stock of COMBINATORX, INCORPORATED pursuant to the terms of
the attached warrant, and tenders herewith payment of the purchase price of such
shares in full.

     2.   The undersigned hereby elects to convert the attached warrant into
shares in the manner specified in Section 1.2 of the warrant. This conversion is
exercised with respect to ___________ of the shares covered by the warrant.

     [STRIKE WHICHEVER OF PARAGRAPH 1 OR 2 THAT DOES NOT APPLY.]

     3.   Please issue a certificate or certificates representing said shares in
the name of the undersigned or in such other name as is specified below:

          Rockport Venture Securities, LLC
          63 Main Street
          Gloucester, MA 01936
          Attention: Manager

          OR Registered Assignee

          Name: ___________________

          Address: ________________

          _________________________

     4.   The undersigned represents it is acquiring the shares solely for its
own account and not as a nominee for any other party and not with a view toward
the resale or distribution thereof except in compliance with applicable
securities laws.

ROCKPORT VENTURE SECURITIES, LLC
or Registered Assignee

___________________________________
(Signature)

___________________________________
 (Date)

                                        5
<Page>

                                    EXHIBIT A

                            ANTI-DILUTION ADJUSTMENTS

(i)  If the corporation shall issue, after the "Issue Date" as set forth at
the top of the first page of this warrant (the "Original Purchase Date"), any
Additional Stock (as defined below in section (ii)) without consideration or for
a consideration per share less than the Warrant Price in effect immediately
prior to the issuance of such Additional Stock, the Warrant Price in effect
immediately prior to each such issuance shall forthwith (except as otherwise
provided in this clause (i)) be adjusted to a price determined by multiplying
such Warrant Price by a fraction, the numerator of which shall be the number of
shares of Common Stock outstanding immediately prior to such issuance plus the
number of shares of Common Stock which the aggregate consideration received by
the corporation for the total number of shares of Additional Stock so issued
would purchase at such Warrant Price in effect immediately prior to such
issuance, and the denominator of which shall be the number of shares of Common
Stock outstanding immediately prior to such issuance plus the number of shares
of such Additional Stock so issued. For the purpose of the above calculation,
the number of shares of Common Stock outstanding immediately prior to such
issuance shall be calculated on a fully diluted basis, as if all shares of
convertible Preferred Stock and all vested securities convertible into or
exchangeable for Common Stock at such time had been fully converted into or
exchanged for shares of Common Stock immediately prior to such issuance as of
such date.

     (A)  No adjustment of the Warrant Price shall be made in an amount less
     than one cent per share, PROVIDED that any adjustments which are not
     required to be made by reason of this sentence shall be carried forward and
     shall be either taken into account in any subsequent adjustment made prior
     to three (3) years from the date of the event giving rise to the adjustment
     being carried forward, or shall be made at the end of three (3) years from
     the date of the event giving rise to the adjustment being carried forward.
     Except to the limited extent provided for in subsections (B)(4) and (B)(5),
     no adjustment of such Warrant Price pursuant to this Section (i) shall have
     the effect of increasing the Warrant Price above the Warrant Price in
     effect immediately prior to such adjustment.

     (B)  For purposes of determining whether any Additional Stock (as defined
     below) was issued for consideration less than the Warrant Price pursuant to
     Section (i), the consideration deemed received by the corporation for the
     issue of any Additional Shares (as defined below) of Common Stock shall be
     computed as follows:

          (1)  CASH AND PROPERTY: Such consideration shall:

               (I)   insofar as it consists of cash, be computed at the
               aggregate amount of cash received by the corporation, excluding
               amounts paid or payable for accrued interest;

               (II)  insofar as it consists of property other than cash, be
               computed at the fair market value thereof at the time of such
               issue, as determined in good faith by the Board of Directors of
               the corporation; and

               (III) in the event Additional Shares (as defined below) of
               Common Stock are issued together with other shares or securities
               or other assets of the corporation for consideration which covers
               both, be the proportion of such consideration so received,
               computed as provided in clauses (I) and (II) above, as determined
               in good faith by the Board of Directors of the Corporation.

          (2)  OPTIONS AND CONVERTIBLE SECURITIES. The consideration per
          share received by the corporation for Additional Shares (as defined
          below) of Common Stock deemed to have been issued pursuant to Section
          (i)(B)(3), relating to options to purchase or rights to subscribe for
          Common Stock or securities convertible into or exchangeable for Common
          Stock, shall be determined by dividing

                                        6
<Page>

               (I)   the total amount, if any, received or receivable by the
               corporation as consideration for the issue of such options to
               purchase or rights to subscribe for Common Stock or securities
               convertible into or exchangeable for Common Stock, plus the
               minimum aggregate amount of additional consideration (as set
               forth in the instruments relating thereto, without regard to any
               provision contained therein for a subsequent adjustment of such
               consideration) payable to the corporation upon the exercise of
               such options to purchase Common Stock or the conversion or
               exchange of such convertible securities for Common Stock, or in
               the case of options for convertible securities that may be
               converted into Common Stock, the exercise of such options for
               such convertible securities and the conversion or exchange of
               such convertible securities, by

               (II)  the maximum number of shares of Common Stock (as set forth
               in the instruments relating thereto, without regard to any
               provision contained therein for a subsequent adjustment of such
               number) issuable upon the exercise of such options to purchase or
               rights to subscribe for Common Stock or securities convertible
               into or exchangeable for Common Stock.

          (3)  If the corporation at any time or from time to time after the
          Original Purchase Date shall issue any options to purchase or rights
          to subscribe for Common Stock or securities convertible into or
          exchangeable for Common Stock (excluding options to purchase or rights
          to subscribe for Common Stock or securities convertible into or
          exchangeable for Common Stock which, upon exercise, conversion or
          exchange thereof, would entitle the holder thereof to receive shares
          of Common Stock which are specifically excepted from the definition of
          Additional Shares of Common Stock by Section (ii) below) or shall fix
          a record date for the determination of holders of any class of
          securities entitled to receive any such options to purchase or rights
          to subscribe for Common Stock or securities convertible into or
          exchangeable for Common Stock, then the maximum number of shares of
          Common Stock (as set forth in the instrument relating thereto without
          regard to any provision contained therein for a subsequent adjustment
          of such number) issuable upon the exercise of such options to purchase
          or rights to subscribe for Common Stock or, in the case of options to
          purchase or rights to subscribe for Common Stock or securities
          convertible into or exchangeable for Common Stock therefor, the
          conversion or exchange of such securities convertible into or
          exchangeable for Common Stock, shall be deemed to be Additional Stock
          issued as of the time of such issue or, in case such a record date
          shall have been fixed, as of the close of business on such record
          date.

          (4)  In the event of any change in the number of shares of Common
          Stock deliverable or in the consideration payable to this corporation
          upon exercise of such options to purchase or rights to subscribe for
          Common Stock or securities convertible into or exchangeable for Common
          Stock, Including, but not limited to, a change resulting from the
          antidilution provisions thereof, the Warrant Price, to the extent in
          any way affected by or computed using such options, rights or
          securities, shall be recomputed to reflect such change, but no further
          adjustment shall be made for the actual issuance of Common Stock or
          any payment of such consideration upon the exercise of any such
          options or rights or the conversion or exchange of such securities.

          (5)  Upon the expiration of any such options or rights, the
          termination of any such rights to convert or exchange or the
          expiration of any options or rights related to such convertible or
          exchangeable securities, the Warrant Price, to the extent in any way
          affected by or computed using such options, rights or securities or
          options or rights related to such securities, shall be recomputed to
          reflect the issuance of only the number of shares of Common Stock (and
          convertible or exchangeable securities which remain in effect)
          actually issued upon the exercise of such options or rights, upon the
          conversion or exchange of such securities or upon the exercise of the
          options or rights related to such securities.

          (6)  The number of shares of Common Stock deemed issued and the
          consideration deemed paid therefor pursuant to Sections (i)(B) shall
          be appropriately adjusted to reflect any change, termination or
          expiration of the type described in either Section (i)(B)(4) or (5).

                                        7
<Page>

          (G)  the issuance of shares of capital stock of the Company in
          connection with any strategic alliances or strategic licensing
          agreements approved by the Board of Directors including the
          affirmative vote of the member of the Board of Directors appointed
          solely by the holders of Series C Preferred Stock;

          (H)  shares of Common Stock issued upon conversion of the Series
          Preferred Stock; and

          (I)  shares of Common Stock issued or issuable in a public
          offering before or in connection with which all outstanding shares of
          Series Preferred Stock will be converted to Common Stock.

END OF EXHIBIT A

                                      8

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