Document:

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                           SYNTA PHARMACEUTICALS CORP.
                          DIRECTOR COMPENSATION POLICY

     The Board of Directors of Synta Pharmaceuticals Corp. (the "Company") has
approved the following policy which establishes compensation to be paid to
non-employee directors of the Company, effective January 1, 2005, to provide an
inducement to obtain and retain the services of qualified persons to serve as
members of the Company's Board of Directors. Each such director will receive as
compensation for his or her services (i) a stock option grant upon his or her
initial appointment or election to the Board of Directors of the Company and
(ii) an annual fee payable in cash and/or stock, all as further set forth
herein.

APPLICABLE PERSONS

     This Policy shall apply to each director of the Company who (a) is not an
employee of the Company or any Affiliate and (b) does not receive compensation
as a consultant to the Company or any Affiliate unless such compensation is
received solely for services provided as a member of the Scientific Advisory
Board (each, an "Outside Director"). Affiliate shall mean a corporation which is
a direct or indirect parent or subsidiary of the Company, as determined pursuant
to Section 424 of the Internal Revenue Code of 1986, as amended.

STOCK OPTION GRANT UPON INITIAL APPOINTMENT OR ELECTION AS A DIRECTOR

     NUMBER OF SHARES

     Each new Outside Director on the date of his or her initial appointment or
election to the Board of Directors, shall be granted a non-qualified stock
option to purchase 60,000 shares of the Company's common stock under the
Company's then applicable stockholder-approved stock plan (the "Stock Plan"),
subject to automatic adjustment in the event of any stock split or other
recapitalization affecting the Company's common stock.

     VESTING PROVISION

     Such option shall vest as to 25% of such grant on the first anniversary of
the date of grant of the option and as to an additional 6.25% of such grant on
the last day of each calendar quarter of the Company thereafter, provided such
Outside Director continues to serve as a member of the Board of Directors.
However, in the event of termination of service of an Outside Director, such
option shall vest to the extent of a pro rata portion through the Outside
Director's last day of service based on the number of days accrued in the
applicable period prior to his or her termination of service.

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     EXERCISE PRICE AND TERM OF OPTION

     Each option granted shall have an exercise price per share equal to the
Fair Market Value (as defined in the Stock Plan) of the shares of common stock
of the Company on the date of grant of the option, have a term of ten years and
shall be subject to the terms and conditions of the Stock Plan. Each such option
grant shall be evidenced by the issuance of a non-qualified stock option
agreement.

     EARLY TERMINATION OF OPTION UPON TERMINATION OF SERVICE

     If an Outside Director:

     a.   ceases to be a member of the Board of Directors for any reason other
          than death or disability, any then vested and unexercised options
          granted to such Outside Director may be exercised by the director
          within a period of three months after the date the director ceases to
          be a member of the Board of Directors and in no event later than the
          expiration date of the option; or

     b.   ceases to be a member of the Board of Directors by reason of his or
          her death or disability, any then vested and unexercised options
          granted to such director may be exercised by the director (or by the
          director's personal representative, or the director's survivors)
          within a period of one year after the date the director ceases to be a
          member of the Board of Directors and in no event later than the
          expiration date of the option.

ANNUAL FEE

     Each Outside Director shall be compensated on an annual basis for providing
services to the Company. Except as otherwise set forth in this Policy, director
compensation shall be paid for the period from July 1 through June 30 of each
year. Each Outside Director shall receive compensation consisting of one of the
following combinations of cash and/or a grant of common stock, subject to
certain contractual restrictions, under the Stock Plan, at the election of each
Outside Director, as follows:

     o    $40,000 cash,
     o    $30,000 cash and such number of shares of the Company's common stock
          as is equal to $10,000 on the date of grant of the shares,
     o    $20,000 cash and such number of shares of the Company's common stock
          as is equal to $20,000 on the date of grant of the shares,
     o    $10,000 cash and such number of shares of the Company's common stock
          as is equal to $30,000 on the date of grant of the shares, or
     o    such number of shares of the Company's common stock as is equal to
          $40,000 on the date of the grant of the shares.

     The number of shares to be received by an Outside Director shall be
calculated by dividing the total dollar amount that the Outside Director has
elected to be paid in shares of common stock by the Fair Market Value (as
defined in the Stock Plan) of the shares of common

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stock of the Company on the last business day prior to the date of grant of the
shares (rounded down to the nearest whole number so that no fractional shares
shall be issued).

     ELECTION

     Each Outside Director shall make an election on the form provided by the
Company, indicating the combination of his or her annual compensation, prior to
each annual meeting of stockholders. If the Company does not schedule an annual
meeting of stockholders to be held on or before June 30th of any year, each
Outside Director shall make his or her election by June 15th of the applicable
year.

     CASH PAYMENTS

     Any cash portion to be paid to an Outside Director shall be paid quarterly
in arrears as of the last day of each calendar quarter. If an Outside Director
dies, resigns or is removed during any quarter, he or she shall be entitled to a
cash payment on a pro rata basis through his or her last day of service.

     RESTRICTED STOCK GRANTS

     Shares of common stock shall be granted at the first meeting of the Board
of Directors following each annual stockholders meeting, or if no such meeting
of the Board of Directors shall occur before June 30 of the applicable year, by
unanimous written consent dated June 30 of that year. The shares shall be
subject to a lapsing repurchase right such that the shares shall be subject to
forfeiture to the Company if such Outside Director does not continue to serve as
a member of the Board of Directors as of the end of the applicable quarter as
follows: the repurchase right shall lapse as to 25% of each such grant on each
of September 30, December 31, March 31 and June 30 thereafter, provided such
Outside Director continues to serve as a member of the Board of Directors as of
the applicable date.

     INITIAL ANNUAL FEE UPON INSTITUTION OF POLICY

     On the date of adoption of this Policy, each Outside Director then serving
shall be entitled to receive compensation prorated for the period from January
1, 2005 through June 30, 2005. Each Outside Director shall make an election on
or before January 14, 2005 as to the combination of cash and/or stock to be
received. The Board of Directors shall, by unanimous written consent dated
January 18, 2005, grant any shares to be issued as part of such compensation.
The shares to be issued shall be subject to a lapsing repurchase right such that
the Company's repurchase right shall lapse as to 50% of each such grant on each
of March 31, 2005 and June 30, 2005, provided such Outside Director continues to
serve as a member of the Board of Directors as of the applicable date.

     INITIAL ANNUAL FEE FOR NEWLY APPOINTED OR ELECTED DIRECTORS

     Each Outside Director who is first appointed or elected to the Board of
Directors after the date of the adoption of this Policy shall receive his or her
first year's annual fee prorated in accordance with the terms of this Policy
from the beginning of the next calendar quarter after his or her initial
appointment or election through the following June 30. Each such Outside
Director

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shall make an election prior to the beginning of the next calendar quarter after
his or her initial appointment or election as to the combination of cash and/or
stock. The Board of Directors shall, by unanimous written consent dated the date
of the first day of such quarter, grant any shares to be issued to such Outside
Director as part of such compensation. Any such shares shall be subject to a pro
rata lapsing repurchase right as of the last day of each quarter remaining in
such initial period, provided such Outside Director continues to serve as a
member of the Board of Directors as of the end of the applicable quarter.

     PURCHASE PRICE AND OTHER PROVISIONS APPLICABLE TO ALL STOCK GRANTS

     Shares granted shall have a purchase price equal to the par value of the
common stock on the date of grant and shall be subject to the terms and
conditions of the Stock Plan. The terms of such grant shall be evidenced by a
restricted stock agreement to be entered into between the Company and the
Outside Director. In addition, in the event of termination of service of an
Outside Director, the Company's lapsing repurchase right shall be deemed to have
lapsed to the extent of a pro rata portion of the shares through the Outside
Director's last day of service based on the number of days accrued in the
applicable period prior to his or her termination of service.

BOARD COMMITTEE COMPENSATION

     Each Outside Director shall also receive an annual fee of $5,000 for each
Committee of the Board of Directors on which such individual serves. However,
the Chairman of each Committee, other than the Audit Committee, shall receive an
annual fee of $10,000, and the Chairman of the Audit Committee shall receive an
annual fee of $15,000 for services as Chairman. Payment shall commence effective
January 1, 2005 and shall be made quarterly in arrears on the last day of each
calendar quarter and upon death, resignation or removal, payment shall be made
pro rata through the last day of service.

EXPENSES

     Upon presentation of documentation of such expenses reasonably satisfactory
to the Company, each Outside Director shall be reimbursed for his or her
reasonable out-of-pocket business expenses incurred in connection with attending
meetings of the Board of Directors, Committees thereof or in connection with
other Board related business.

AMENDMENTS

     The Board of Directors shall review this Policy from time to time to assess
whether any amendments in the type and amount of compensation provided herein
should be adjusted in order to fulfill the objectives of this Policy.

DATED:  January 11, 2005<Page>

                                                                   Exhibit 10.5

                       DUFFY HARTWELL LIMITED PARTNERSHIP
                                COMMERCIAL LEASE

1.   PARTIES:

DUFFY HARTWELL LIMITED PARTNERSHIP, a Massachusetts limited partnership located
at 411 Waverley Oaks Rd. Waltham MA, LESSOR, which expression shall include its
successors and assigns where the context so admits, does hereby lease to
SHIONOGI BIORESEARCH, CORP. a Massachusetts corporation located at 187 East
Emerson St. Lexington MA c/o LanBo Chen, LESSEE, which expression shall include
its successors, and assigns where the context so admits, and the LESSEE hereby
leases the following described Premises:

2.   PREMISES:

Twenty-four Thousand, Four Hundred and Twenty (24,420) sq. ft., more or less,
(the "Leased Premises") in the LESSOR'S Building located at 45 Hartwell Ave.
Lexington MA, including exclusive use of the loading platform all as shown on
Exhibit A, "Floor Plan", attached hereto, together with the right to use in
common, with others entitled thereto, any hallways, and stairways necessary for
access to said Leased Premises.

Appurtenant to the Premises the LESSEE shall have the right, in common with
others entitled thereto, to use access ways, driveways, walkways and any other
common facilities necessary for access to or beneficial use of the Leased
Premises.

LESSEE shall have right to use four parking spaces per one thousand square feet
of net leased space as unassigned parking spaces in the parking areas adjacent
to the Buildings on the site. LESSEE shall have rights in common with other
lessees to use of the common entrance serving the Leased Premises.

The Leased Premises shall be delivered "AS-IS" for build out by the LESSEE to
its requirements, at LESSEE'S sole cost. See Exhibit B, "Buildout Obligations"
for obligations of each party, cost allowance to LESSEE, and contingencies.

3.   TERM:

The term of this lease shall be for Ten (10) years commencing on the
Commencement Date (defined below) and ending on November 30, 2006.

The Commencement Date shall be the earlier of completion of the LESSEE'S work
and fit up of the Lease Premises, or December 1, 1996. The LESSEE's work shall
be deemed complete upon issuance of a certificate of occupancy for the Premises
by the Town of Lexington MA

4.   RENT:

The LESSEE shall pay to LESSOR rent at the rates per year, shown below, which
rent shall be payable in advance in the monthly installments shown below on the
first day of each month.

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<Table>
<Caption>
        YEAR      ANNUAL RENT      MO. RENT    $/SF RATE
     ----------   ------------   -----------   ---------
        <S>       <C>            <C>            <C>
        1-5       $ 383,382.40   $ 31,990.20    $ 15.72
        6-10      $ 481,562.40   $ 40,130.20    $ 19.72
</Table>

The parties acknowledge that the exact area of the Lease Premises shall be
measured from the interior surface of the exterior windows and the center line
of demising walls for net usable space, to this will be added a prorata share of
common areas of the building to determine Rentable Space.

5.   SECURITY DEPOSIT:

Upon the execution of this lease, the LESSEE shall pay to the LESSOR the amount
of $36,060, which shall be held as a security for the LESSEE'S performance as
herein provided and promptly refunded to the LESSEE at the end of this lease
subject to the LESSEE'S satisfactory compliance with the conditions hereof.

6.   RENT ADJUSTMENT:

     A.   TAX ADJUSTMENT

If in any tax year commencing with the fiscal year 1998 (the fiscal year ending
June 30, 1998), the real estate taxes on the land and buildings, of which the
Leased Premises are a part, are assessed an increase in value attributable to
the LESSEE's improvements, LESSEE shall pay the real estate taxes attributable
to that increase in assessed valuation. In the event the taxes otherwise levied
on the real estate are in excess of the amount of the real estate taxes thereon
for the fiscal year 1997 (hereinafter called the "Base Year"), LESSEE will pay
to LESSOR as additional rent hereunder, when and as designated by notice in
writing by LESSOR, Fifty (50%) percent of such excess. Such share of increased
real estate taxes shall be paid as may occur in each year of the term of this
lease or any extension or renewal thereof and proportionately for any part of a
fiscal year. LESSOR'S demand shall be accompanied by a copy of the applicable
tax bill or bills and a statement showing the manner of calculation of LESSEE'S
proportionate share of such taxes. If the LESSOR obtains an abatement of any
such excess real estate tax, a proportionate share of such abatement, less the
reasonable fees and costs incurred in obtaining the same, if any, shall be
refunded to the LESSEE. LESSEE may itself, or with any co-tenant, seek review of
the assessed valuation of the property of witch the Leased Premises are a part,
or otherwise seek abatement of real estate taxes in any year in which the LESSOR
declines to seek such review or reduction, provided it shall do so at its own
cost or expense.

For purposes of this adjustment the fiscal year 1997 tax rate shall be $1.08 per
square foot, or $54,472.08 for the land and building of which the lease premises
are a part.

LESSEE shall not be required to pay any income, profits, excise, franchise,
estate, succession, inheritance or transfer taxes of LESSOR or any other party.

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     B.   OPERATING COSTS

The LESSEE shall pay to the LESSOR as additional rent hereunder within thirty
(30) days after notice in writing by LESSOR, Fifty (50%) per cent of any
operating costs incurred during the calendar year which are in excess of $4.00
per square foot. LESSOR'S demand shall be accompanied by a statement of the
applicable operating costs and a statement showing the manner of calculation of
LESSEE'S proportionate share of such costs. In the event LESSEE wishes
verification of the costs and its share, LESSOR will present substantiation of
charges, if requested, authorize its' independent C.P.A. to provide
certification of the statement and charges to the LESSEE, and LESSEE shall bear
the expense of the C.P.A. certification. In the alternative, LESSEE may at its
own expense audit LESSOR'S books and records with respect to operating costs
(but only as regards this particular property, and not of any other property or
other affiliates of LESSOR). The operating costs increase shall be prorated
should this lease be in effect with respect to only a portion of any calendar
year, or which pertain to less than a fully occupied building. Operating costs
are defined for the purpose of this agreement as:

     Maintenance Expenses of LESSOR for building structure and exterior grounds.
     Management Expenses (allocated at Five (5%) percent of gross rent)
     Premiums for Casualty and public liability Insurance

Exceptions to Operating Costs are defined in Exhibit E.

     C.   BUILDING ACCESS

The LESSEE shall have unlimited access to the Building without charge.

7.   UTILITIES:

The LESSEE shall pay, as they become due, all bills for electricity, water and
sewer use and other utilities (whether they are used for furnishing heat,
cooling or other purposes) that are furnished to the Leased Premises and which
are separately metered. The LESSOR agrees to provide utility services to the
LEASED PREMISES, all subject to interruption due to any accident, to the making
of repairs, alterations, or improvements, to labor difficulties, to trouble in
obtaining fuel, electricity, service, or supplies from the sources from which
they are usually obtained for said building, or to any cause beyond the LESSOR'S
control, provided LESSOR shall make reasonable and diligent efforts to restore
service in the event of any such-disruption.

LESSOR shall have no obligation to provide utilities or equipment other than the
utilities and equipment within the premises as of the Commencement Date of this
lease which include the HVAC now serving the Leased Premises. In the event
LESSEE requires additional utilities or equipment, the installation and
maintenance thereof shall be the LESSEE'S sole obligation, provided that such
installation shall be the subject to the written consent of the LESSOR. Costs
for the installation of separate metering for utilities shall be borne by the
LESSOR.

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8.   USE OF LEASED PREMISES:

The LESSEE shall use the Leased Premises only for the purpose of office, light
manufacturing and R&D purposes including without limitation biotechnological
research, development and production.

9.   COMPLIANCE WITH LAW:

The LESSEE acknowledges that no trade or occupation shall be conducted in the
Leased Premises or use made thereof which will be unlawful, improper, noisy or
offensive, or contrary to any law or any municipal by-law or ordinance in force
in the Town of Lexington in which the premises are situated. LESSEE shall not be
responsible to make alterations, installations, additions or improvements to the
Leased Premises required by applicable law except if required due to
improvements installed by or special or extraordinary uses by LESSEE.

10.  FIRE INSURANCE:

The LESSEE shall not permit any use of the Leased Premises which will make
voidable any insurance on the property of which the Leased Premises are a part,
or on the contents of said property or which shall be contrary to any law or
regulation from time to time established by the New England Fire Insurance
Rating Association, or any similar body succeeding to its powers. The LESSEE
shall on demand reimburse the LESSOR, and all other tenants all extra insurance
premiums caused by the LESSEE'S use of the premises.

11.  MAINTENANCE:

     A.   LESSEE'S OBLIGATIONS

The LESSEE agrees to maintain the Leased Premises in as good condition as at the
beginning of the term, fair wear and tear and damage by fire and other casualty
excepted. Also excepted are elements which are LESSOR'S obligation to maintain
hereunder. LESSEE, whenever necessary, shall replace plate glass and other glass
therein. Upon occupancy the LESSEE acknowledges that, except for any latent
defects, the Leased Premises are then in good condition as at Lease execution,
and the glass whole. The LESSEE shall not permit the Leased Premises to be
overloaded, damaged, stripped, or defaced, nor suffer any waste. LESSEE shall
obtain written consent of LESSOR before erecting any sign on the exterior of the
Leased Premises, which consent shall not be unreasonably withheld or delayed.
LESSEE shall be responsible for maintenance of the HVAC, plumbing, and other
facilities which LESSEE shall install within the Leased Premises, and for
cleaning of and trash removal from the Leased Premises.

     B.   LESSOR'S OBLIGATIONS

The LESSOR agrees to maintain the structure, roof, foundation, and exterior of
the building of which the Leased Premises are a part, and such mechanical,
electrical and plumbing facilities, and fire protection facilities as are common
to lessees of the building, and parking lot, exterior lighting, exterior window
frames and the common areas of the building in the same condition as it is at
the commencement of the term or as it may be put in during the

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term of this lease, but in any event in good, clean, tenantable and working
order, condition and repair, reasonable wear and tear, damage by fire and other
casualty only excepted (subject to the provisions of Section 18, below), unless
such maintenance is required because of the LESSEE or those for whose conduct
the LESSEE is legally responsible. LESSOR shall maintain access ways and common
areas of the land in neat and orderly condition including clearance of snow and
ice in the walkways and parking lot. LESSOR shall keep the building and common
areas under its control in compliance with all current and future zoning laws
and other applicable municipal laws, regulations and ordinances.

12.  ALTERATIONS/ADDITIONS:

The LESSEE shall design, construct and maintain such tenant improvements as it
may require, at LESSEE'S sole cost, and subject to the prior written approval of
plans by the LESSOR, which approval shall not be unreasonably withheld or
delayed. Thereafter LESSEE may make alterations and additions provided the
LESSOR consents thereto in writing. LESSOR shall respond within five business
days of receipt of LESSEE'S plans. All such allowed alterations shall be at
LESSEE'S expense and shall be in quality at least equal to the approved
construction. LESSEE shall not permit any mechanics' liens, or similar liens, to
remain upon the Leased Premises for labor and material furnished to LESSEE or
claimed to have been furnished to LESSEE in connection with work of any
character performed or claimed to have been performed at the direction of LESSEE
and shall cause any such lien to be released of record forthwith without cost to
LESSOR. Any alterations or improvements made by the LESSEE shall become the
property of the LESSOR at the termination of occupancy as provided herein except
for LESSEE'S trade improvements, alterations, installations, fixtures and
equipment which shall remain the LESSEE'S property and shall be removed by
LESSEE upon termination of the Lease, with the prompt repair by LESSEE of any
and all damages occasioned by their removal. To confirm the foregoing, LESSEE
will submit its plans for any alteration or improvement to LESSOR in writing
before installation with a request for removal at LESSEE'S expense upon
termination of this lease, and LESSOR'S approval of such request, shall be on
the condition that LESSEE shall restore and repair all damages caused by the
removal.

13.  ASSIGNMENT SUBLEASING:

The LESSEE shall not assign or sublet the whole or any part of the Leased
Premises without LESSOR'S prior written consent which shall not be unreasonably
withheld or delayed. Notwithstanding such consent, LESSEE shall remain liable to
LESSOR for the payment of all rent and for the full performance of the covenants
and conditions of this lease. However, LESSEE may, without obtaining such
consent, make an assignment to any successor in interest by way of merger or
other reorganization (except bankruptcy reorganization), "going public" or
"going private" transaction or acquisition of substantially all the assets or
stock of LESSEE, or an assignment of leasehold rights as a component of security
interest for a reputable financing institution.

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14.  SUBORDINATION:

     This lease shall be subject and subordinate to any and all mortgages, deeds
of trust and other instruments in the nature of a mortgage, now or any time
hereafter, which may constitute a lien or liens on the property of which the
Leased Premises are a part and the LESSEE shall, when requested, promptly
execute and deliver such written instruments as shall be necessary to show the
subordination of this lease to said mortgages, deeds, of trust or other such
instruments in the nature of a mortgage, provided, however, that the mortgagee
executes and delivers to LESSEE a non-disturbance and recognition agreement
providing in substance that should the mortgagee or any party holding by,
through on under the mortgagee (including without limitation any purchaser at
foreclosure) acquire title to the property, then, as long as LESSEE is not in
default, the mortgagee or such other party shall recognize this Lease and not
disturb LESSEE'S rights hereunder.

15.  LESSOR'S ACCESS:

The LESSOR or agents of the LESSOR may, at reasonable times and upon appropriate
notice, (normally one day's prior notice) enter to view the Leased Premises and
may remove placards and signs not approved and affixed to the exterior of the
Leased Premises as herein provided, and make repairs and alterations as LESSOR
should elect to do. The LESSOR may show the Leased Premises to others, and at
any time within six (6) months before the expiration of the term, may affix to
any suitable part of the lease premises a notice for letting or selling the
Leased Premises or property of which the Leased Premises are a part and keep the
same so affixed without hindrance or molestation. LESSOR shall use best effort
to minimize inconvenience and interference with LESSEE and LESSEE'S business
operations.

16.  INDEMNIFICATION & LIABILITY:

The LESSEE shall save the LESSOR harmless from all loss and damage occasioned by
the use or escape of water or by the bursting of pipes, as well as from any
claim or damage resulting from neglect in removing snow or ice from the
sidewalks bordering upon the premises so leased, or by any nuisance made or
suffered on the Leased Premises, unless such loss is caused by the neglect of
the LESSOR. The removal of snow and ice from the sidewalks bordering upon the
Leased Premises shall be LESSOR'S responsibility. LESSOR shall save the LESSEE
harmless from loss or damage occasioned by acts or omissions of the LESSOR, its
employees or agents.

17.  LESSEE'S LIABILITY INSURANCE:

          (a)  The LESSEE shall maintain with respect to the Leased Premises and
the property of which the Leased Premises are a part comprehensive public
liability insurance in the amount of $1 million Combined Single Limit and
property damage insurance in the amount of the value of the replacement of
LESSEE'S personal property and improvements in responsible companies qualified
to do business in the state. The LESSEE shall deposit with the LESSOR
certificates for such insurance at or prior to the commencement of the term, and
thereafter within (30) days prior to the expiration of any

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such policies. All such insurance certificates shall provide that such policies
shall not be canceled without at least ten (10) days prior written notice to
each assured named therein.

          (b)  All fire and property casualty insurance which either party
carries with respect to the building, Leased Premises or any property therein,
whether or not required, shall include provisions which deny to the insurer
acquisition by subrogation of rights of recovery against the other party to the
extent such rights have been waived by the insured party prior to occurrence of
loss, insofar as and to the extent that such provisions may be effective without
making it impossible to obtain insurance coverage from responsible companies
qualified to do business in the Commonwealth of Massachusetts (even though extra
premium may result therefrom). In the event that any extra premium is payable by
either party as a result of this provision, the other party shall reimburse the
party paying such premium the amount of such extra premium. If at the request of
one party, this non subrogation provision is waived as to such party, then the
obligation of reimbursement by such party shall cease for such period of time as
such waiver shall be effective. Each party shall be entitled to have duplicates
or certificates of any policies containing such provisions. Each party hereby
waives all rights of recovery against the other for loss or injury against which
the waiving party is protected by insurance containing said non-subrogation
provisions, reserving, however, any rights with respect to any excess of loss or
injury over the amount recovered from such insurance.

18.  FIRE, CASUALTY AND EMINENT DOMAIN:

Should fifty (50%) percent or more of the Leased Premises, or the property of
which they are a part, be substantially damaged by fire or other casualty, or be
taken by eminent domain, the LESSOR may elect to terminate this lease. If the
LESSOR does not elect to terminate, or if the damage is less than fifty (50%)
percent of the Leased Premises or of the property, LESSOR shall then diligently
restore the building, property and Leased Premises to substantially their
condition at the inception of the Lease, as soon as reasonably possible. When
such fire, casualty, or taking renders the Leased Premises substantially
unsuitable for their intended use, a just and proportionate abatement of rent
shall be made, and the LESSEE, may elect to terminate this lease if:

          (a)  the LESSOR fails to give written notice within thirty (30) days
of the fire, casualty or taking of intention to restore Leased Premises, to the
condition existing at inception of the lease, and before LESSEE'S improvements
or

          (b)  the LESSOR fails to restore the Leased Premises to the condition
substantially the same at inception of the Lease ( December 1, 1996) within on
hundred and eighty (180) days of said fire, casualty or taking.

The LESSOR reserves, and the LESSEE grants to the LESSOR, all rights which the
LESSEE may have for damages or injury to the Leased Premises for any taking by
eminent domain, except for damage to the LESSEE'S fixtures, improvements,
additions, property, or equipment.

19.  LATE PAYMENT, DEFAULT AND BANKRUPTCY:

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     A.   LATE PAYMENT: LESSEE agrees that because actual damages for a late
payment or a dishonored check are difficult to fix or ascertain, but recognizing
that damage and injury result therefore, LESSEE agrees that if payments of rent
and other obligations are not received in hand by LESSOR five (5) business days
after the date is due, LESSEE agrees to pay liquidated damages of $100.00 plus
18% per annum on the delinquent amount from the due date. The postmark on the
payment received plus two (2) days, shall be conclusive evidence of whether the
payment is delinquent. However, LESSOR is not responsible for late deliveries by
U.S. Mail. LESSEE agrees to pay a liquidated damage of $25.00 for each
dishonored check. In the event that two or more of the LESSEE'S checks are
dishonored in a 12 month period, the LESSOR, in addition to other Rights, shall
have the right to demand payment by Certified Check or Money Order.

     B.   DEFAULT AND BANKRUPTCY: In the event that (a) the LESSEE shall default
in the payment of any installment of rent or other sum herein specified and such
default shall continue for ten (10) days after written notice of payment
default, or if such written notice of payment default is required in three
events or more in any calendar year, thereafter ten days after the payment due
date without written notice being required for the balance of such year; or (b)
the LESSEE shall default in the observance or performance of any other of the
LESSEE'S material covenants, agreement, or obligations hereunder and such
default shall not be corrected within thirty (30) days after written notice
thereof from LESSOR, of if such default is not susceptible to cure within thirty
days, in the event the LESSEE shall fail to commence to cure within the thirty
days or thereafter diligently to prosecute such cure to completion; or (c) the
LESSEE shall be declared bankrupt or insolvent according to law, or, if any
assignment shall be made of LESSEE'S property for the benefit of creditors, then
the LESSOR shall have the right thereafter, while such default continues, to
re-enter and take complete possession of the Leased Premises, to declare the
term of this lease ended, and remove the LESSEE'S effects, without prejudice to
any remedies which might be otherwise used for arrears of rent or other default.
The LESSEE shall indemnify the LESSOR against all loss of rent and other
payments which the LESSOR may incur by reason of such termination during the
residue of the term. LESSOR shall make reasonable efforts to relet the Leased
Premises, and net rents received by the LESSOR shall be credited to the LESSEE'S
obligations hereunder. If the LESSEE shall default, after reasonable notice
thereof, in the observance or performance of any conditions or covenants on
LESSEE'S part to be observed or performed under or by virtue of any of the
provisions in any article of this lease and shall fail to cure such default
within the applicable cure period, then the LESSOR, without being under any
obligation to do so and without thereby waiving such default, may remedy such
default for the account and at the expense of the LESSEE. If the LESSOR makes
any expenditures or incurs any obligations for the payment of money in
connection therewith, including but not limited to, reasonable attorney's fees
in instituting, prosecuting or defending any action or proceeding, such sums
paid or obligations insured, with interest at the rate of 12 per cent per annum
and costs, shall be paid to the LESSOR by the LESSEE as additional rent.

20.  NOTICE:

Any notice from the LESSOR to the LESSEE relating to the Leased Premises or to
the occupancy thereof, shall be deemed duly served, if delivered in hand at the
Leased Premises addressed to the LESSEE, or if mailed to the Leased Premises,
registered or

                                        8
<Page>

certified mail, return receipt requested, postage prepaid, addressed to the
LESSEE. Any notice from the LESSEE to the LESSOR relating to the Leased Premises
or to the occupancy thereof, shall be deemed duly served, if mailed to the
LESSOR by registered or certified mail, return receipt requested, postage
prepaid, addresses to the LESSOR at such address as the LESSOR may from time to
time advise in writing. Until such advice all rent shall be paid and all notices
sent to the LESSOR at 411 Waverley Oaks Road, Waltham MA 02154. All Notices
under this Lease shall be in writing.

21.  SURRENDER:

The LESSEE shall at the expiration or other termination of this lease remove all
LESSEE'S goods and effects from the Leased Premises, (including, without hereby
limiting the generality of the foregoing all signs and lettering affixed or
painted by the LESSEE, either inside or outside the Leased Premises). LESSEE
shall deliver to the LESSOR the Leased Premises and all keys, locks thereto, and
subject to the provisions of Section 12, above, the fixtures connected therewith
and all alterations and additions made to or upon the Leased Premises, in good
condition, fair wear and tear, damage by fire or other casualty and elements
which are the LESSOR'S responsibility to maintain and repair excepted. In the
event of the LESSEE'S failure to remove any of LESSEE'S property from the
premises, LESSOR is hereby authorized, without liability to LESSEE for loss or
damage thereto, and at the sole risk of LESSEE, to remove and store any of the
property at LESSEE'S expense, or to retain same under LESSOR'S control or to
sell at public or private sale, without notice, any or all of the property not
so removed and to apply the net proceeds of such sale to the payment of any sum
hereunder, or to destroy such property.

22.  BROKERAGE:

The Brokers named herein: Fallon Hines and O'Connor, Inc. and Leggat
McCall/Grubb & Ellis warrant that they are duly licensed as such by the
Commonwealth of Massachusetts, and join in this agreement and become parties
hereto, insofar as any provisions of this agreement expressly apply to them, and
to any amendments or modifications of such provisions to which they agree in
writing.

LESSOR agrees to pay the above named Brokers upon the term commencement date a
fee for professional services as agreed between LESSOR and Brokers under a
separate agreement.

Each party represents and warrants that it has not retained or dealt with any
other broker or brokers in connection with this Lease, and each party agrees to
indemnify, defend and save harmless the other party from any claims for fees or
commissions arising out of its dealings with any other broker with respect to
this Lease.

24.  QUIET ENJOYMENT

LESSOR covenants and agrees that upon paying rent and performing all the
covenants and conditions of the Lease LESSEE shall and may peacefully and
quietly have, hold and enjoy the Lease Premises for the term specified, subject
to the terms of the Lease.

                                        9
<Page>

25.  OTHER PROVISIONS:

It is also understood and agreed that:

  a. The attached Commercial Lease Addendum and the following Exhibits are
     incorporated by reference:

               Exhibits:      A. Layout of Leased Premises

                              B. Buildout Obligations

                              C. INTENTIONALLY OMMITTED

                              D. Right of First Refusal on Additional Space

                              E. Exclusions from Operating Expenses

                              F. INTENTIONALLY OMMITTED

                              G. INTENTIONALLY OMMITTED

                              H. INTENTIONALLY OMMITTED

                              I. Hazardous Waste Provisions

  b. LESSEE shall have a Five Year option to extend the term of the Lease at
     market rates prevailing at the time of exercise of such option(s) for
     office space. Such option shall be exercised by written notice to LESSOR no
     less than six months prior to the expiration of the then current term. See
     Addendum Part D for procedure.

  c. LESSEE shall have a Right of First Refusal on additional space in the
     building, in accordance with provisions of Exhibit D.

  d. For Hazardous Waste Provisions, see Exhibit I.

  e. LESSOR approval of LESSEE requests,  under any provisions of this Lease,
     shall not be unreasonably withheld or delayed.

  f. At the request of either, the parties shall mutually execute and deliver a
     notice of lease in recordable form pursuant to Massachusetts General Laws,
     Chapter 183, Section 4, and either party may record such notice in the
     applicable registry of deeds.

IN WITNESS WHEREOF, the said parties hereunto set their hand and seal as of this
4th day of November, 1996.

SHIONOGI BIORESEARCH CORP.                   DUFFY HARTWELL LIMITED PARTNERSHIP
LESSEE                                       LESSOR

/S/ LAN BO CHEN                              /S/ NORMAN J. DUFFY
-----------------------                      ----------------------------
Lan Bo Chen                                  NORMAN J. DUFFY,
President                                    General Partner

                                       10
<Page>

                       DUFFY HARTWELL LIMITED PARTNERSHIP
                            COMMERCIAL LEASE ADDENDUM

A.   LESSEE OBLIGATIONS

1.   LESSEE shall not change the color or appearance of the outside of the
Leased Premises except upon the prior written consent of the LESSOR. However,
LESSEE may install a its own emergency power generator to the exterior rear of
the building.

2.   LESSEE shall not post signs on or about the Premises without LESSOR'S prior
approval, however LESSEE shall be entitled to reasonable signage to be erected a
LESSEE'S own cost and expense, and in compliance with any relevant municipal
regulations.

3.   The parking areas shall not be used for storage of unused, damaged or
unregistered vehicles, nor shall the LESSEE store merchandise or other materials
in the parking areas.

4.   LESSEE shall not otherwise store vehicles, containers, or refuse outside
the Leased Premises, except for routine parking of vehicles and delivery or
pickup of products or materials.

5.   LESSEE shall be responsible to dispose of LESSEE trash and refuse.

6.   The LESSEE may maintain insurance required by this Lease under a blanket
policy of insurance which insures the LESSEE and any affiliates of the LESSEE.

7.   No animals, reptiles or pets of any kind shall be kept in or about the
building, except for research purposes in accordance with applicable laws and
regulations.

B.   LESSOR OBLIGATIONS

1.   LESSOR shall, at its own cost and expense, maintain in good condition and
repair all structural components of the building containing the Leased Premises,
including the foundation, floor, walls, exterior, roof, common area, if any, of
the Building, landscaping, parking areas and access ways.

2.   LESSOR shall remove snow and ice from the access roadway, the parking
areas, and the walkways which serve the building, provide exterior lighting, and
LESSOR will remove snow or ice from the roof of the building if, as and when the
conditions cause roof leakage or threaten ice falls over access ways.

3.   LESSOR shall maintain with insurance companies, licensed in Massachusetts,
all risk fire insurance policies with extended coverage insuring the property
containing the Leased Premises against loss or damage caused by fire or casualty
in an amount equal to the full replacement cost of the Building.

C.   SUBLEASING PROVISION

                                       11
<Page>

The following provisions supplements the provisions of Section 13,
"Assignment-Subleasing" above.

(i)    If, after November 30, 2001, LESSEE requests consent of LESSOR for
sublease or assignment of all or a material portion of the Lease Premises,
LESSOR may refuse consent for the purpose of re-lease of the Leased Premises or
the portion thereof to the assignee, the sub-LESSEE or to a third party. Upon
the mutual agreement of the parties, hereto, this lease shall then terminate at
a mutually agreed date as to the Leased Premises or the portion thereof, as if
the Lease had expired on its termination date. However, LESSEE may withdraw the
request for consent for sublease or assignment within five business days of
receipt of notice by LESSOR of LESSOR'S intent to refuse consent for the purpose
of re-lease.

(ii)   The LESSOR shall be deemed to approve any assignment or sub-lease to a
parent, subsidiary or affiliate of the LESSEE upon written assurance by LESSEE
that the subsequent use will be in conformance with and subject to section 8,
above, "USE OF LEASED PREMISES".

(iii)  Provided that LESSEE pays all rent and other charges under this Lease,
LESSEE shall be entitled to all rent and consideration received in connection
with any assignment or subleasing, even if in excess of the rent hereunder.

D.   MARKET RATE RENT FOR EXTENSION OPTIONS

Upon receipt of written notice from the LESSEE of intent to extend, under
Section 25(b) of the Lease, LESSOR shall respond within thirty days with a
quotation for market rate rent. For this purpose "market rate" shall mean the
rate for office space in comparable buildings in the general area, and not for
space with the specialized improvements installed by the LESSEE (the parties
agreeing that LESSEE shall not be charged rent for or with respect to any
laboratory, biotechnological, specialized or trade improvements which LESSEE
make to the Leased Premises at LESSEE'S own expense). Fair market rate shall
reflect the provisions of this Lease for escalation of real estate taxes,
operating costs and for utility charges. The LESSEE shall respond within thirty
(30) days agreeing to the quotation, rejecting the extension or requesting third
party determination of market rate. In the later event each party shall then
appoint a realty broker who has at least ten years experience in commercial real
estate brokerage and/or appraisal in the Greater Boston area, and who is
familiar with similar commercial property in the Lexington area, they shall
confer, and each shall recommend a market rate by writing to the parties. In the
event their recommendations are joint or equal, this shall be market rate. If
the recommendations differ by 5% or less, their average shall be deemed market
rate. In the event their rates differ by a greater amount they shall jointly
nominate a third such broker who shall make an independent recommendation of
market rate. The two closest of the three recommendations shall then be averaged
to establish the market rate. Each party hereto shall pay the expense of its
nominee broker, and each shall share equally the expense of a third, if
required. However, in no event shall market rate, determined as aforesaid, be
less than the rate then payable at the time of exercise of the option, by the
LESSEE. The Market Rate shall be binding on both parties and shall be reflected
in a Lease amendment.

                                       12
<Page>

                                   EXHIBIT B.

                              BUILDOUT OBLIGATIONS

a) LESSOR's OBLIGATIONS

The LESSOR shall deliver the Leased Premises AS-IS with respect to the layout
and location of offices, rooms, corridors, lighting, bathrooms, plumbing,
electrical services, floors, dock area and climate controls, free and clear of
all tenants or occupants.

As to the building and land the LESSOR shall repair the base building, structure
and roof where necessary, and shall upgrade the landscaping. The later shall
include screening the boundary line which abuts the Federal Express parcel.

Upon completion of the design and construction by LESSEE of tenant improvements
and upon occupancy of the Leased Premises the LESSOR shall pay to the LESSEE an
allowance for tenant improvements of One Hundred Thousand ($100,000.00) Dollars
within thirty (30) days of completion and occupancy, and if LESSOR fails to do
so, LESSEE shall have a credit for such amount against it next payment or
payments for rent hereunder.

b) LESSEE's OBLIGATIONS

LESSEE shall be responsible to layout, design and construct all tenant
improvements and to obtain LESSOR'S prior approval of such layout and design.

In the event LESSEE elects to contract with an independent contractor for its
buildout of its tenant improvements, that work shall be subject to the
reasonable oversight by LESSOR. LESSEE shall reimburse LESSOR for this oversight
service at the rate of $50.00 per hour of on-site oversight and consultation,
not to exceed $25,000.00.

The LESSEE may design, construct and maintain at its own expense a Japanese
garden at a mutually agreed location and, as agreed, in size.

c) SPECIAL PROVISION FOR PERMIT CONTINGENCY

(i)     If, within ninety (90) days of Lease execution, despite LESSEE'S good
        faith efforts, LESSEE has been unable to obtain any permit or approval
        necessary to construct its leasehold improvements or to use and occupy
        the Leased Premises for LESSEE'S intended use or is prevented from doing
        so by any applicable laws and regulations, then LESSEE may terminate
        this Lease by notice to LESSOR. In that event LESSEE shall forfeit its
        security deposit and restore the Leased Premises to the condition prior
        to undertaking any improvements or changes thereon, if any.

(ii)    In the event after the ninety day period in (i) above LESSEE wishes to
        continue its efforts to obtain such permits or approvals, LESSEE may, by
        paying an amount equal to six month's rent obtain an additional ninety
        day period during which it may terminate this lease. In the event LESSEE
        subsequently terminates the Lease in addition to the obligations in
        (i) above, LESSEE shall forfeit the security deposit and the amount
        paid under this clause. In the event LESSEE does not terminate the

                                       13
<Page>

        Lease the amount paid, equal to six month's rent shall be credited to
        LESSEE'S rental obligations for the period following the second ninety
        day period.

(iii)   In the event that LESSEE is denied a building permit, certificate of
        occupancy or other required governmental approval due to any problems
        with respect to the base building, or in the event that any corrective
        work with respect to the base building shall be required by any
        governmental authority or pursuant to any applicable laws, codes or
        regulations, LESSOR shall perform any necessary corrective work at
        LESSOR'S own cost and expense as soon as possible, and the commencement
        of LESSEE'S obligations to pay the rent and other charges due hereunder
        shall be postponed by any resulting period of delay.

d) SPECIAL PROVISION FOR FINANCING

LESSEE may from time to time grant security interests in or make equipment
leases with respect to LESSEE'S current or future installations, fixtures,
equipment, improvements, additions and property in the Leased Premises in order
to finance the same or LESSEE'S business, and LESSOR shall upon LESSEE'S request
execute and deliver reasonable instruments confirming the same.

                                       14
<Page>

                                    EXHIBIT C

                                CLEANING SCHEDULE

                      INTENTIONALLY OMMITED FROM THIS LEASE

                                       15
<Page>

                                   EXHIBIT D.

                   RIGHT OF FIRST REFUSAL ON ADDITIONAL SPACE

LESSEE shall have a right of first refusal on additional lease space as it
becomes available during the term of this Lease Agreement or any extension of
such term. This right is subject to any preexisting rights of other LESSEES. The
LESSOR will use its best efforts to accommodate LESSEE'S space requirements.

The procedure for effecting the Right of First Refusal shall be exercised in the
following manner:

(i)     LESSEE shall in any quarter year of the lease term or its extension give
        to LESSOR written notice of its projected space requirements and its
        interest in space that is available or may become available for lease.

(ii)    LESSOR, within ten days of LESSEE'S notice, shall give written response
        describing to LESSEE the availability of or the projected availability
        of floor space. "Availability" shall mean and include any vacant space
        and any space which is or may become free of leasehold commitment. Such
        LESSOR notice will contain the rental rate for which such space will be
        offered.

(iii)   If the LESSOR can provide such space by relocation of an existing
        lessee, LESSOR shall, at the earliest reasonable date consistent with
        discussion with the existing lessee, respond to the LESSEE's notice as
        set forth in the first paragraph of this Section.

(iv)    LESSEE shall have fourteen (14) days to exercise its right by written
        notice to LESSOR to accept or reject LESSOR'S notice and proposal.

(v)     In the event LESSEE, by writing, accepts such additional space the
        parties will forthwith, within 30 days of LESSEE'S written response,
        execute a lease agreement or lease modification to reflect the
        additional space, its rental rate, the adjusted term of Lease, if any,
        and such other changes as may be required to reflect the additional
        space.

(vi)    In the event LESSEE does not accept the LESSOR'S proposal within the 14
        day period, or in the event the parties are unable to conclude a lease
        agreement for the additional premises within the above thirty day
        period, the LESSEE shall be deemed to have refused the space and LESSOR
        may offer and contract for lease of the space to third parties, the
        LESSEE'S rights under this provision having lapsed as to the proposed
        premises.

(vii)   This right shall be an on going right throughout the term of the Lease
        or any period of extension.

                                       16
<Page>

                                    EXHIBIT E

                         EXCLUSIONS FROM OPERATING COSTS

The following items shall be excluded in computing LESSEE'S share of operating
costs applicable to the Leased Premises:

1.   Any ground lease rental;

2.   Costs of capital repairs or capital replacements (except as specifically
permitted in this paragraph 2), capital improvements and equipment; except
those: (a) required by laws enacted on or after the date the temporary
certificate of occupancy issued for the LESSEE work shall be validly issued with
the cost of any such improvements and equipment depreciated or amortized over
the usual life of the improvement and/or equipment, or (b) installed at the
Leased Premises to reduce operating costs, with the cost of any such
improvements and equipment depreciated or amortized at an annual rate reasonably
calculated to equal the amount of operating costs to be saved in each calendar
year throughout the term (as determined at the time LESSOR elected to proceed
with the capital improvement or acquisition of the capital equipment to reduce
operating costs); however, as respects (a) and (b) above, only depreciation or
amortization attributable to a given calendar year shall be included in
operating costs for such year. Depreciation or amortization shall be calculated
on straight line basis and at interest rates calculated at market rates and
terms then prevailing for borrowers similar to LESSOR.

3.   Rentals for items (except when needed in connection with normal repairs and
maintenance of the building which shall be permitted) which if purchased, rather
than rented, would constitute a capital improvement specifically excluded in
Subsection 2, above;

4.   Costs incurred by LESSOR for the repair for replacement of damage to the
building or its contents caused by fire or other casualty;

5.   Depreciation, amortization, lender's fees and interest payments except as
permitted pursuant to Subsection 2, above, and, if permitted, then determined in
accordance with generally accepted accounting principles, consistently applied
(as applied to commercial real estate) in accordance with the anticipated useful
life of such item (as reasonably determined by LESSOR);

6.   Overhead and profit increments paid to LESSOR or to subsidiaries or
affiliates of LESSOR for goods and/or services in the building to the extent the
same exceeds the cost of such goods and/or services rendered by unaffiliated
third parties on a competitive basis;

7.   Advertising and promotional expenditures,  and the costs of acquiring and
installing signs in or on the building identifying the owner of the building;

8.   Interest,  principal,  points and fees on debts or amortization on any
mortgage or mortgages or any other debt instrument encumbering the building or
property;

                                       17
<Page>

9.   Any costs associated with gift taxes, excise taxes, income taxes, transfer
taxes or capital levies;

10.  Costs incurred in connection with upgrading the building to comply with
handicap, hazardous material, fire and safety codes which were in effect prior
to the date of the lease or which become effective after date of the Lease;

11.  Tax penalties incurred as a result of LESSOR'S negligence,  inability or
unwillingness to make payments when due, not attributable to LESSEE'S failure to
make payments to LESSOR for such items in accordance with the lease;

12.  Any and all costs arising from the presence of hazardous materials or
substances (as defined by applicable Federal, Massachusetts and local laws) now
or hereafter pertaining to the building ("Hazardous Substances") and property in
or about the building including, without limitation, Hazardous Substances in the
ground, water, or soil;

13.  LESSOR'S general corporate overhead and general and  administrative
expenses except as contained and allowed in the 5% Management Fee per provision
in Clause 6.B., above.

14.  Costs of any items for which LESSOR is reimbursed by insurance, or
otherwise compensated by parties other than LESSEE'S of the building;

15.  Any legal fees associated with the sale or refinancing of the building;

16.  Costs for any separate utility meters LESSOR may install in the
building, unless the installation is required by a utility company or
governmental entity.

17.  Costs for construction for compliance with, or penalties assessed for
non-compliance with the Americans with Disabilities Act of 1990 (42. U.S.C.
1281-1283).

18.  Expenses incurred as a result of the LESSOR'S negligence or the negligence
of another lessee.

19.  Costs of procuring tenants for the building, including without limitation
advertising, brokerage commissions and inducements paid or credited to such
tenants for buildout costs.

20.  Costs for special work or services to particular tenants.

                                       18
<Page>

                                   EXHIBIT I.

                           HAZARDOUS WASTE PROVISIONS

a) "HAZARDOUS WASTE DEFINITION: "Hazardous Materials" for purposes hereof shall
mean any chemical, substance, materials or waste or component thereof which is
now or hereafter listed, defined or regulated as a hazardous or toxic chemical,
substance, material or waste or component thereof by any federal, state or local
governing or regulatory body having jurisdiction, or which would trigger any
employee or community "right to know" requirements adopted by any such body, or
for which any such body has adopted any requirements for the preparation or
distribution of a materials safety data sheet ("MSDS").

b) REGULATION OF HAZARDOUS MATERIALS: LESSEE shall not transport, use, store,
maintain, generate, manufacture, handle, dispose, release or discharge any
Hazardous Materials except in strict conformance with applicable federal, state
and municipal laws and regulations. However, the foregoing provisions shall not
prohibit the transportation to and from, and use, storage, maintenance and
handling within the Leased Premises of Hazardous Materials customarily used in
the business or activity expressly permitted to be undertaken in the Leased
Premises under Article 8 hereunder, provided: (a) such Hazardous Materials shall
be used and maintained only in such quantities as are reasonably necessary for
such permitted use of the Leased Premises and in the ordinary. course of
LESSEE'S business therein, strictly in accordance with applicable Law, highest
prevailing standards, and the manufacturers' instructions therefor; (b) such
Hazardous Materials shall not be disposed of, released or discharged in the
Building or be transported to and from the Leased Premises except in strict
compliance with all applicable Laws, and as LESSOR shall reasonably require; (c)
if any applicable Law or LESSOR'S trash removal contractor requires any such
Hazardous Materials to be disposed of separately from ordinary trash, LESSEE
shall make arrangements at LESSEE'S expense for disposal directly with a
qualified and licensed disposal company at a lawful disposal site (subject to
scheduling and approval by LESSOR); and (d) any remaining such Hazardous
Materials shall be completely, properly, and lawfully removed from the Building
upon expiration or earlier termination of this Lease.

c) NOTICES TO LESSOR: LESSEE shall promptly notify LESSOR of: (a) any
enforcement, cleanup or other regulatory action taken or threatened by any
governmental or regulatory authority with respect to the presence of any
Hazardous Materials released, discharged or disposed of by LESSEE on the Leased
Premises or the property of which the Leased Premises are a part, or the
migration thereof from or to other property; (b) any demands or claims, made or
threatened by any party relating to any loss or inquiry resulting from any
Hazardous Materials on the Leased Premises; (c) any release discharge or
non-routine, improper or unlawful disposal or transportation of any Hazardous
Materials on or from the Leased Premises or in violation of this Article; and
(d) any matters where LESSEE is required by Law to give a notice to any
governmental or regulatory authority respecting any Hazardous Materials on the
Leased Premises. LESSOR shall have the right (but not the obligation) to join
and participate, as a party, in any legal proceedings or actions affecting the
Leased Premises initiated in connection with any environmental, health or safety
law. At such times as LESSOR may reasonably

                                       19
<Page>

request, LESSEE shall provide LESSOR with written list, certified to be true and
complete, identifying any Hazardous Materials then used, stored, or maintained
upon the Leased Premises, the use and approximate quantity of each such
materials, a copy of any MSDS issued by the manufacturer therefor, and such
other information as LESSOR may reasonably require or as may be required by Law.

d) INDEMNIFICATION OF LESSOR: If any Hazardous Materials are released,
discharged or disposed of by LESSEE or any other occupant of the Leased
Premises, or their employees, agents, invitees or contractors, on or about the
Building in violation of the foregoing provisions, LESSEE shall immediately,
properly and in compliance with applicable Laws clean up, remediate and remove
the Hazardous Materials from the Building and any other affected property and
clean or replace any affected personal property (whether or not owned by
LESSOR), at LESSEE'S expense (without limited LESSOR'S other remedies therefor).
LESSEE shall further be required to indemnify and hold LESSOR, LESSOR'S
directors, officers, employees and agents harmless from and against any and all
claims, demands, liabilities, losses, damages, penalties and judgments directly
or indirectly arising out of or attributable to a violation of the provisions of
this provision by LESSEE, LESSEE'S occupants, employees, contractors or agents.
Any clean up, remediation and removal work shall be subject to LESSOR'S prior
written approval (except in emergencies), and shall include, without limitation,
any testing, investigation, and the preparation and implementation of any
remedial action plan required by any governmental body having jurisdiction or
reasonably required by LESSOR. If LESSOR or any Lender or governmental body
arranges for any tests or studies showing that this Article has been violated,
LESSEE shall pay for the costs of such tests. The provisions of this Article
shall survive the expiration or earlier termination of this Lease."

e) PREEXISTING CONDITIONS AND CONDITIONS CAUSED BY THIRD PARTIES: LESSEE shall
not in any manner be liable or responsible for, be made to bear any costs and
expenses regarding, be required to test, contain, remediate, remove, clean up or
do any work or take any other action with respect to, be responsible for
compliance with applicable laws and regulations regarding, and does not
indemnify LESSOR or any other party with respect to, any hazardous or toxic
substances, materials or wastes or any other pollutants which were or are
brought, generated, stored, used, located, installed, disposed of, spilled,
released, emitted or discharged on, in or from the Leased Premises, building or
property by any party other than Lessee or Lessee's employees, agents,
contractors, licensees, sublessees or invitees. Without limiting the foregoing,
Lessee shall not be responsible or liable for any such substances, materials,
wastes or pollutants pre-existing on the Leased Premises, building or property
prior to the commencement of this Lease.

f) REPRESENTATION: LESSOR represents that to the best of LESSOR'S knowledge and
belief LESSOR has no knowledge of hazardous wastes on the land or in the
building other than disclosed to D.E.P. as background and down gradient
contamination affecting the general area in which the property is located.
LESSOR warrants that to the best of its knowledge and belief no friable asbestos
is present upon the premises. LESSOR agrees to indemnify and save harmless the
LESSEE from any liability arising out of any such contamination of the property
which preexists this Lease Agreement.

                                       20
<Page>

                       DUFFY HARTWELL LIMITED PARTNERSHIP

November 5, 1996

Shionogi BioResearch Corp.
187 East Emerson St.
Lexington MA

Re:  Lease Agreement for 45 Hartwell Ave. Lexington MA

Sirs:

This letter supplements the letter of November 1, 1996.

The parties to the above Agreement concur that the Lease Agreement, now dated
November 4, 1996 precedes certain determinations by Shionogi which may effect
several Lease provisions.

Shionogi must design build-out for its needs, which build-out will reflect use
or replacement of HVAC, plumbing, gas and other facilities presently installed
in the building. As a consequence several provisions of the Lease Agreement will
or may require adjustment.

These include:

     Maintenance Obligations under Section 11. The Lessee shall be responsible
     for maintenance of all facilities which it installs. The Lessor shall be
     responsible for maintenance and repair of any HVAC, plumbing or facilities
     which serve the lessees in common, or which are presently installed and
     Shionogi determines to use them rather than replace them. This arrangement
     is also reflected in Exhibit B "Buildout Obligations" where the Lessee is
     to be compensated for work whose costs are normally borne by a Lessor.

     Operating Costs provisions of Section 6B, which is currently shown as $4.00
     per square foot will be adjusted when the build-out design of the Lessee
     determines what use or replacement of existing heating and air conditioning
     is contemplated. That $4.00 per square foot figure includes square foot
     allowances estimated at $1.03 for HVAC, $.80 for cleaning, and $.10 for
     water and sewer charges. The Lessee's HVAC plans will determine the final
     base amount for operating costs. This will then be reflected in Section 6B.

     Section 6C contemplates that the Lessee has unlimited access to the Leased
     Premises. Presently no additional costs are contemplated for HVAC. If the
     final plans of the Lessee make use of common HVAC facilities the Lessor
     shall provide such HVAC service, but reserves the right to charge for use
     out of normal business hours. Normal business hours are deemed to be 7:00AM
     to 6:00PM Monday through Friday and 8:00AM to 1:00PM on Saturday. In the
     event plans so indicate,

                                       21
<Page>

     the prospective charge for such use will be reflected in additional wording
     in Section 6C.

     Lessor's obligations to maintain and service, as shown in the Addendum,
     Part B 1. will be adapted should additional maintenance and service
     obligations result.

     To the extend that operating costs are shifted to the Lessor by these
     changes, the base rent shown on the lease, which is net of operating costs
     which are included in the $4.00 per square foot estimate, may be adjusted.

Another matter of concern is what facilities, which Shionogi will install in the
building as fixtures (i.e.: attached to the building) may be removed, as of
right, upon surrender of the Leased Premises, under provisions of Section 21,
"Surrender". Both parties contemplate that, upon a listing of specific or
generic items by Shionogi and a joint review, we shall amend the Agreement to
show in an exhibit the items to be regarded as tools of the trade of Shionogi,
for which it shall have a right to detach and remove.

Upon resolution of the above items the parties will prepare and execute a lease
amendment to reflect the resolution of the open items. The parties agree to
execute a notice of lease and an appropriate agreement of recognition and
non-disturbance with respect to the present mortgagee of the property, Duffy
Bros. Management Co., Inc.

We trust this letter reflects our agreement as to resolving and defining open
items in the Lease Agreement. Please sign Shionogi's assent and return a copy
with two copies of the executed Lease for our execution and return.

Very truly yours

/S/ NORMAN J. DUFFY
--------------------

Norman J Duffy

ASSENT

/S/ LAN BO CHEN
---------------

                                       22
<Page>

                       FIRST AMENDMENT TO COMMERCIAL LEASE

Duffy Hartwell LLC, as successor in interest to Duffy Hartwell Limited
Partnership, ("LESSOR") and Synta Pharmaceuticals Corporation, as successor in
interest to Shionogi BioResearch Corp., ("LESSEE") (the LESSOR and the LESSEE
are collectively referred to as the "Parties" in this first Amendment) are
landlord and tenant, respectively, under a certain Commercial Lease (`Lease
Agreement") dated November 4, 1996, for approximately 24,420 rentable square
feet, more or less, in the building located at 45 Hartwell Avenue, Lexington, MA
and hereby agree as follows:

Whereas, the Parties have agreed to amend the Lease Agreement by this First
Amendment to the Commercial Lease ("First Amendment") to extend the Term of the
Lease Agreement and to adjust relevant provisions of the Lease Agreement
pursuant to the terms and conditions stated herein.

Now therefore, for consideration of $1.00 and other mutual and valuable
consideration, the receipt and sufficiency of which is hereby acknowledged by
both LESSOR and LESSEE, effective on and after the date of execution set forth
below, the Lease Agreement is hereby amended to reflect the following changes
for the Lease Term and Extended Term:

3.   TERM:
     ----

     This paragraph is hereby deleted and replaced with the following: The
     Initial Term of this lease shall be for ten (10) years commencing on the
     Commencement Date (as defined in the Lease Agreement) and ending on
     November 30, 2006. The Extended Term of this lease shall be for five (5)
     years commencing on December 1, 2006 and ending on November 30, 2011.
     Unless otherwise specified herein, any reference to "term" or "Term" shall
     include both the Initial and Extended Term.

4.   RENT:
     ----

     This paragraph is hereby amended with the addition of the following: During
     the Extended Term, the LESSEE shall pay to the LESSOR base rent at the rate
     of $522,832.20 dollars per year, payable in advance in monthly installments
     of $43,569.35, commencing December 1, 2006. Thereafter, during the Extended
     Term of the lease. LESSEE shall pay base rent and additional rent to the
     LESSOR monthly, in advance, not later than the first day of each calendar
     month.

5.   SECURITY DEPOSIT:
     ----------------

     This paragraph is hereby amended with the addition of the following: Upon
     the execution of this First Amendment, the LESSEE shall pay to the LESSOR
     the amount of $7,509.35 dollars which, in addition to the $36,060.00
     previously paid, shall be held as a security for the LESSEE'S performance
     as herein provided and promptly refunded to the LESSEE at the end of this
     lease subject to the LESSEE'S satisfactory compliance with the conditions
     hereof. The LESSEE shall maintain at all times a security deposit
     equivalent to a minimum of one month's base rent, including, if applicable,
     any and options to renew.

<Page>

6.   RENT ADJUSTMENT:
     ---------------

     A. TAX ADJUSTMENT: Section 6A of the Lease Agreement is hereby amended by
     deleting the numbers "1998" and "1997" and inserting in lieu thereof the
     numbers "2007" and "2006'", respectively. The second full paragraph of
     Section 6A is hereby deleted in its entirety.

     B. OPERATING COSTS,: Section 6B of the Lease Agreement is hereby amended by
     deleting the first sentence in its entirety and inserting in lieu thereof
     the following sentence: "During the Extended Term, the LESSEE shall pay to
     the LESSOR as additional rent hereunder within thirty (30) days after
     receipt of written notice from LESSOR, 50% of any increase in operating
     expenses over those incurred during the calendar year 2006.

22.  BROKERAGE:
     ---------

     This paragraph is hereby supplemented with the addition of the following:
     LESSOR and LESSEE represent to each other that neither party has dealt with
     any broker or brokers in connection with this First Amendment other than
     RICHARDS BARRY JOYCE & PARTNERS AND GLENN COMMERCIAL GROUP, which will be
     paid by the LESSOR in full and without contribution from LESSEE pursuant to
     a separate agreement. LESSOR and LESSEE agree that each will hold harmless
     and indemnify the other from any loss, cost, damage and expense, including
     reasonable attorney's fees incurred by LESSOR or LESSEE for a commission or
     finder's fee as a result of the falseness of this representation.

25.  OTHER PROVISIONS:
     ----------------

     a.   Section 25(a) of the Lease Agreement is hereby deleted and replaced
          with the following: "The attached Commercial Lease Addendum, with the
          exception of subparagraph D. Market Rate Rent for Extension Options
          which has been exercised by this First Amendment and is hereby deleted
          as moot, and the following Exhibits are incorporated by reference:

          Exhibits:   A. Layout of Leased Premises
                      B. Buildout Obligations - Excepting Paragraphs (a)-(c)
                         which are hereby deleted as moot.
                      C. INTENTIONALLY OMITTED
                      D. Right of First Refusal on Additional Space
                      E. Exclusions from Operating Expenses
                      F. INTENTIONALLY OMITTED
                      G. INTENTIONALLY OMITTED
                      H. INTENTIONALLY OMITTED
                      I. Hazardous Waste Provisions"

     b.   Section 25(b) of the Lease Agreement is hereby deleted in its
          entirety.

     The Lease Agreement is further amended by inserting the following:

                                       2
<Page>

     26.  OPTION TO EXTEND:
          ----------------

          Provided the LESSEE is not in material default hereunder after any
          notice and grace periods. LESSEE shall have one (1) five (5) year
          option to extend the lease term at a rent equal to the greater of the
          following: (a) market rate for equivalent lab space in similarly
          located buildings in Lexington within one (1) mile of the Leased
          Premises (including, without limitation, taking into consideration the
          age and condition of the building) ("Market Rate"); or (b) the rent
          then in effect as of the expiration date of the then current lease
          term. In no event shall the rent for the option term be less than the
          current total rent at the end of the initial term. LESSEE must give
          LESSOR written notice it is exercising its extension option no later
          than nine (9) months prior to the expiration of the then cu rent lease
          term. If LESSEE notifies LESSOR as provided herein. LESSOR shall
          notify LESSEE of its good faith estimate of the Market Rate for the
          extended tetra; then within thirty (30) days of receiving the LESSOR'S
          Market Rate for the extended term the LESSEE shall either:
          (1) deliver a written notice accepting the rent rate, and thereafter
          the parties shall fully execute a Lease amendment within thirty (30)
          days from the date the LESSOR receives LESSEE'S written notice
          accepting the rent rate, which lease amendment shall be on the same
          terms and conditions as the Lease Agreement except as otherwise
          provided in this Paragraph 26 and except that the base rent shall be
          the Market Rate and the lease term shall be extended by five (5)
          years; or
          (2) deliver a written notice disagreeing with the LESSOR'S Market Rate
          for the extended term, said notice to include LESSEE'S good faith
          estimate of the Market Rate for the extended term, and the LESSOR and
          LESSEE shall attempt to agree upon the rent rate using their best
          good-faith efforts. If LESSOR and LESSEE fail to reach an agreement
          within thirty (30) days following LESSOR'S receipt of LESSEE'S
          above-mentioned written notice of disagreement ("Outside Agreement
          Date"), then:
          (i)  LESSOR and LESSEE shall each appoint, at their own cost and
               expense, within ten (10) business days of the Outside Agreement
               Date, one arbitrator who shall by profession be a current
               commercial real estate broker or appraiser of comparable
               properties in Lexington within one (1) mile from the Leased
               Premises, and who has been active in such field over the last
               five (5) years. The two (2) arbitrators shall confer and within
               thirty (30) days from the date the last arbitrator was appointed,
               shall each recommend a Market Rate in writing to both parties. In
               the event their recommendation is joint or equal, then this
               recommendation shall be the rent rate for the extended terra; and
          (ii) In the event the arbitrators recommendation of the Market Rate
               differs by five percent (5%) or less, then the average shall be
               the rent rate for the extended team; and
         (iii) In the event the arbitrators recommendation differs by more than
               five percent (5%), then the two arbitrators so appointed shall,
               within five (5) business days of the date of the last written
               recommendation, agree upon and appoint a third arbitrator who
               shall be qualified under the same criteria set forth hereinabove
               for qualification of the initial two arbitrators. The third
               arbitrator shall, within fifteen (15) days after his/her
               appointment, recommend a Market Rate in writing to both

                                       3
<Page>

               parties, and the two (2) closest of the three (3) recommendations
               shall then be averaged to establish the rent rate for the
               extended term: and
          (iv) If either LESSOR or LESSEE fails to appoint an arbitrator within
               ten (10) business days after the applicable Outside Agreement
               Date, the arbitrator appointed by one of them shall reach a
               decision, notify LESSOR and LESSEE thereof, and such arbitrator's
               decision shall be binding upon LESSOR and LESSEE; and
          (v)  If the two arbitrators fail to agree upon and appoint a third
               arbitrator, or both parties fail to appoint an arbitrator, and
               this matter has not been otherwise resolved, then the appointment
               of the third arbitrator shall be made by the American Arbitration
               Association (or, if not available, an equivalent arbitration
               association) subject to the instructions set forth in this
               Paragraph 26; and
          (vi) The cost of arbitration, as well as the above-mentioned third
               arbitrator, shall be paid by LESSOR and LESSEE equally; and
         (vii) Notwithstanding the above, in no event shall the Market Rate or
               rent for the option term be less than the current total rent at
               the end of the initial term.

          In the event the rent for the option term is being established in
          accordance with Paragraph 26(2) above, then the parties shall fully
          execute a lease amendment within thirty (30) days from the date the
          rent rate is established in accordance with the above, which lease
          amendment shall be on the same terms and conditions as the Lease
          Agreement except as otherwise provided in this Paragraph 26 and except
          that the base rent shall be the Market Rate and the lease term shall
          be extended by five (S) years front the date the Lease Agreement would
          have expired had the option to extend not been exercised. LESSEE shall
          be responsible for all payments necessary to maintain a security
          deposit equivalent to one (1) month's base rent. All other terms and
          provisions under the Lease Agreement, as amended, shall continue
          through the extended lease term. In the event the LESSEE does not
          provide payment or has not delivered an executed lease amendment or
          written notice as provided in this Paragraph 26 and subparagraphs (1)
          and (2) above, the LESSEE shall be deemed to have waived its option to
          extend the lease term and this Lease Agreement shall terminate upon
          the expiration of the then current term.

Notwithstanding the above, LESSEE accepts the Leased Premises in its current "AS
IS" condition and acknowledges that the Leased Premises are currently occupied
by the LESSEE and that the Leased Premises, as delivered and currently
constituted, is suitable for the LESSEE'S intended use. LESSEE acknowledges that
all work, if any, contemplated in the Lease Agreement and this First Amendment
to the Lease Agreement, including but not limited to the Exhibit B thereto, to
be performed by the LESSOR has been completed to the full satisfaction of the
LESSEE.

The Parties acknowledge that the Lease Agreement and this First Amendment
represent the entire agreement between the Parties and that no other
modification, written or otherwise, exists between the Parties. The normal rule
of construction that any ambiguities be resolved against the drafting party
shall not apply to the interpretation of the Lease Agreement or this First
Amendment or any exhibits or amendments thereto.

                                       4
<Page>

All other terms and provisions wider the Lease Agreement shall remain unchanged,
are in full force and effect, and are hereby ratified and affirmed. LESSOR and
LESSEE hereby acknowledge and confirm that, to the best of their respective
knowledge, neither the LESSOR nor the LESSEE is in default of any other term or
condition of the Lease Agreement. In the event of a conflict between this First
Amendment and the Lease Agreement, the terms of this First Amendment shall
govern. All capitalized terms used but not defined herein shall have the same
definitions ascribed to such terms in the Lease Agreement.

IN WITNESS WHEREOF, the said Parties hereto set their hands and seals this 30
day of August, 2006.

LESSEE                                        LESSOR
Synta Pharmaceuticals Corporation,            Duffy Hartwell LLC,
as successor in interest to                   as successor in interest to
Shionogi BioResearch Corp.,                   Duffy Hartwell LLC,

By: /s/ KEITH EHRLICH                         By: /s/ STEPHEN P. DUFFY
    -----------------                             --------------------
Vice President, Finance and Administration    Hartwell Management LLC, Manager
Duly Authorized                               Steven P. Duffy, Duly Authorized

                                       5

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