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                                                                    Exhibit 10.4

300,000 SHARES OF COMMON STOCK                          GRANT DATE: MAY 27, 2004

                           SYNTA PHARMACEUTICALS CORP.

                      NON-QUALIFIED STOCK OPTION AGREEMENT

     SYNTA PHARMACEUTICALS CORP., a Delaware corporation (the "Company"), grants
to KEITH R. GOLLUST (the "Optionee"), as of the date set forth above, the right
and option (this "Option") to purchase from the Company up to 300,000 shares
(the "Option Shares") of the Common Stock, $.000l par value, of the Company (the
"Common Stock"). This Option is subject to the following terms and conditions:

     1.   OPTION PRICE. The price to be paid for each share of Common Stock upon
exercise of the whole or any part of this Option shall be $2.7108 (the "Purchase
Price").

     2.   VESTING. This Option shall be exercisable with respect to 150,000
shares of the Option Shares as of the Grant Date, and the remainder of the
Option Shares will become exercisable thereafter in eight equal cumulative
quarterly installments of 18,750 shares, the first such installment occurring on
August 27, 2004, PROVIDED THAT Optionee on the applicable installment date is
providing services to the Company as a director, advisor or consultant. If the
Optionee is granted the right to receive any new, substituted or additional
securities or other property (including money paid other than as a regular cash
dividend) pursuant to Section 6, then such new or substituted securities
(together with the Option Shares, the "Option Securities") or other property
shall be issued upon the exercise of this Option subject to the same vesting
schedule applicable to this Option.

     3.   OPTION PERIOD. This Option shall terminate and be of no further force
or effect at 5:00 P.M., Boston time, on May 27, 2014.

     4.   EXERCISE OF OPTION; PAYMENT FOR SHARES. This Option may be exercised
at any time and from time to time, subject to the limitations of Sections 2 and
3 and set forth elsewhere in this Agreement, for up to the aggregate number of
shares of Option Securities specified herein, but in no event for the purchase
of other than whole shares. A written notice of exercise in the form of Exhibit
A attached hereto, signed by the Optionee or his heirs or permitted assignees
(the "Exercising Party"), shall be delivered to the Company at its principal
office specifying the number of Option Securities with respect to which this
Option is being exercised. Such notice shall be accompanied by this Agreement
and by payment of the purchase price of the Option Securities being acquired,
which payment may be (a) in United States dollars in cash, by check or by wire
transfer to a deposit account specified by the Company, (b) at the discretion of
the Company, through delivery to the Company of shares of its capital stock held
by the Exercising Party for at least six (6) months prior to the exercise of
this Option or retention by the Company of shares otherwise issuable upon
exercise of this Option, in each case having a Fair Market Value (as defined in
Section 7 below) as of the date of exercise equal to the number of exercised
shares multiplied by the Purchase Price, (c) at the discretion of the Company,
in accordance with a cashless exercise program established with a securities
brokerage firm, or (d) by any combination of (a), (b), or (c) above.

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     5.   NO RIGHTS AS STOCKHOLDERS NO RIGHT TO CONTINUING RELATIONSHIP. The
Optionee shall not be deemed, for any purpose, to have any rights whatsoever
with respect to Option Securities to which this Option shall not have been
exercised and payment made as aforesaid. The Optionee shall have no rights as a
stockholder with respect to shares of Option Securities until the date of
issuance of such shares. No adjustment shall be made for dividends (ordinary or
extraordinary, whether in cash, securities or other property) or distributions
or other rights for which the record date is prior to the date such Option
Securities are issued, except as provided in Section 6. The Optionee shall not
be deemed to have any rights to a continued relationship with the Company by
virtue of the grant or exercise of this Option. The Optionee acknowledges that
he has no right to continue as a director, advisor or consultant of the Company
and that the Company, its Board, and/or its shareholders may terminate or remove
the Optionee from his position as a director, advisor, or consultant with or
without reason or cause at any time so long as such action to terminate or
remove is in accordance with the Company's by-laws and applicable law.

     6.   EXTRAORDINARY EVENTS. Upon the occurrence of any of the following
events, the Optionee's rights with respect to the Option Securities shall be
adjusted as hereinafter provided:

          (a)  STOCK DIVIDENDS AND STOCK SPLITS. If (i) the shares of the
Company's Common Stock shall be subdivided or combined into a greater or smaller
number of shares or if the Company shall issue any shares of Common Stock as a
stock dividend on its outstanding Common Stock, or (ii) additional shares or new
or different shares or other securities of the Company or other non-cash assets
are distributed with respect to such shares of Common Stock, the number of
shares of Common Stock deliverable upon the exercise of the Optionee's rights
pursuant to this Option shall be appropriately increased or decreased
proportionately, and appropriate adjustments may be made in the purchase price
per share to reflect such events.

          (b)  CONSOLIDATIONS OR MERGERS. If the Company is to be consolidated
with or acquired by another entity in a merger, sale of all or substantially all
of the Company's assets or otherwise (an "Acquisition"), the Board of Directors
of any entity assuming the obligations of the Company hereunder, shall either
(i) make appropriate provision for the continuation of this Option by
substituting on an equitable basis for the Option Securities either the
consideration payable with respect to the outstanding shares of Common Stock in
connection with the Acquisition or securities of any successor or acquiring
entity; or (ii) upon written notice to the Optionee, provide that the Option
must be exercised (either to the extent then exercisable or, at the discretion
of the Board of Directors, all Option Securities being made fully exercisable
for purposes of this subparagraph) prior to a specified date at the end of which
period this Option shall terminate; or (iii) terminate this Option in exchange
for a cash payment equal to the excess of the Fair Market Value of the Option
Securities (either to the extent then exercisable or, at the discretion of the
Board of Directors, all Option Securities being made fully exercisable for
purposes of this subparagraph) over the exercise price thereof.

          (c)  RECAPITALIZATION OR REORGANIZATION. In the event of a
recapitalization or reorganization of the Company (other than a transaction
described in subparagraph (b) above) pursuant to which securities of the Company
or of another corporation are substituted or exchanged for the outstanding
shares of Common Stock, the Optionee upon exercising the

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Option shall be entitled to receive for the Purchase Price the securities which
would have been received if this Option had been exercised prior to such
recapitalization or reorganization.

     7.   FAIR MARKET VALUE. The fair market value ("Fair Market Value") of the
Option Securities for purposes of this Option shall be an amount per share
determined as follows:

          (1)  If the Option Securities are listed on a national securities
     exchange or traded in the over-the-counter market and sales prices are
     regularly reported for the Option Securities, the per share fair
     market value shall be the closing or last price of the Option
     Securities on the composite tape or other comparable reporting system
     for the trading day immediately preceding the applicable date;

          (2)  If the Option Securities are not traded on a national
     securities exchange but are traded on the over-the-counter market, if
     sales prices are not regularly reported for the Option Securities for
     the trading day referred to in clause (1), and if bid and asked prices
     for the Option Securities are regularly reported, the per share fair
     market value shall be the mean between the bid and the asked price for
     the Option Securities at the close of trading in the over-the-counter
     market for the trading day on which Option Securities were traded
     immediately preceding the applicable date; and

          (3)  If the Option Securities are neither listed on a national
     securities exchange nor traded in the over-the-counter market, the per
     share fair market value shall be such value as the Company's Board of
     Directors, in good faith, shall determine.

     8.   NON-ASSIGNABILITY OF OPTION RIGHTS. Except as set forth below, the
Option shall (a) not be assignable or transferable by the Optionee, either
voluntarily or by operation of law, except by will or the laws of descent and
distribution; (b) be exercisable only by the Optionee during the life of the
Optionee; and (c) not be transferred, assigned, pledged, hypothecated or
disposed of in any other way (whether by operation of law or otherwise), or be
subject to execution, attachment or similar process. Notwithstanding the
foregoing, the Optionee may upon written notice to the Company at any time
assign or transfer the Option to a tax exempt organization as defined in
Section501(c)(3) of the United States Internal Revenue Code of 1986, as amended
(the "Code"), to a private foundation as defined in Section509(a) of the Code,
or to a charitable remainder trust under Section664 of the Code, provided that:

          (i)   such transferee shall automatically be bound by the terms of
     this Option;
          (ii)  if requested, Optionee shall provide the Company with reasonable
     documentation verifying the federal tax exempt status of such transferee;
     and
          (iii) if this Option terminates for any reason, the Optionee or his
     personal representative shall give notice to such transferee of such
     termination.

     9.   INVESTMENT REPRESENTATION; COMPLIANCE WITH LISTING REQUIREMENTS AND
LAW. The Optionee, by acceptance of this Option, hereby represents and warrants
that this Option and any and all shares of the Option Securities which the
Optionee shall acquire upon the exercise of this Option are being and will be
acquired for his own account for investment and not with a view to, or for sale
in connection with, any distribution thereof. It shall be a condition to the
Optionee's right to purchase the Option Securities that the Company may require
such steps or satisfaction

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of such conditions as the counsel for the Company may reasonably deem necessary
to comply with any law, rule or regulation applicable to the issuance of such
Option Securities, including, without limitation, (a) that the Option Securities
reserved for issue upon the exercise of this Option shall have been duly listed,
upon official notice of issuance, upon any national securities exchange on which
the Option Securities may then be listed, and (b) that either (i) a registration
statement under the Securities Act of 1933, as amended (the "Act"), and the
rules and regulations promulgated thereunder with respect to such shares shall
be in effect or (ii) in the opinion of counsel for the Company the proposed
purchase shall be exempt from registration under the Act and the Optionee shall
have made such undertakings and agreements with the Company as the Company may
reasonably require. The certificates representing the shares of Option
Securities purchased under this Option may contain such legends as counsel for
the Company shall deem necessary to comply with such applicable law, rule or
regulation.

     The exercise of this Option shall be subject to the requirement that if, at
any time, counsel to the Company shall determine that the listing, registration
or qualification of the Option Securities upon any securities exchange or under
any state or federal law, or the consent or approval of any governmental or
regulatory body, or that the disclosure of non-public information or the
satisfaction of any other condition is necessary as a condition of, or in
connection with, the issuance or purchase of the Option Securities, such shares
may not be issued or this Option exercised, in whole or in part, unless such
listing, registration, qualification, consent or approval, or satisfaction of
such condition shall have been effected or obtained on conditions acceptable to
the Company. Nothing herein shall be deemed to require the Company to apply for
or to obtain such listing, registration or qualification, or to satisfy such
condition.

     10.  PAYMENT OF TAXES.

          (a)  The Company's obligation to deliver the Option Securities upon
the exercise of this Option shall be subject to the satisfaction by the
Exercising Party of all applicable federal, state and local income and
employment tax withholding requirements.

          (b)  Upon the exercise of this Option, the Exercising Party shall pay
to the Company, or authorize it to deduct from other amounts payable to the
Exercising Party, the amount of any taxes that the Company or any of its
subsidiaries is required to withhold with respect to such exercise. Subject to
the prior approval of the Company, which may be withheld by the Company in its
discretion, the Exercising Party may elect to satisfy such obligations, in whole
or in part, by (i) causing the Company to withhold shares of the Option
Securities otherwise issuable pursuant to the exercise of this Option, or (ii)
delivering to the Company, at the time this Option is exercised, shares of the
Company's capital stock held by the Exercising Party for at least six (6) months
prior to the exercise of the Option. The shares of the Company's capital stock
so delivered or withheld shall have a Fair Market Value equal to such
withholding obligation. The Fair Market Value of the shares of the Company's
capital stock used to satisfy such withholding obligation shall be determined by
the Company as of the date that the amount of tax to be withheld is to be
determined.

          (c)  Notwithstanding the foregoing, in the event that the Exercising
Party is a person required to file reports under Section 16(a) of the Securities
Exchange Act of 1934, as amended, no election to use shares of the Company's
capital stock for the payment of

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withholding taxes shall be effective unless made in compliance with any
applicable requirement of Rule 16b-3 (unless it is intended that the transaction
not qualify for exemption under Rule 16b-3).

     11.  MISCELLANEOUS. This Option may not be altered or amended except by a
written instrument signed by the Company and the Optionee. This Option contains
the entire agreement and understanding between the Company and the Optionee with
respect to the subject matter hereof, and supersedes all prior or
contemporaneous agreements or understandings. This Option shall be governed by
and construed in accordance with the laws of the State of Delaware, without
regard to any conflict of laws principles. If any provision of this Option shall
be determined to be illegal and unenforceable, the remaining provisions shall be
severable and enforceable in accordance with their terms. All the terms and
provisions of this Option shall be binding upon and inure to the benefit of the
parties hereto and, subject to the terms and provisions of Section 8 their
respective heirs, legal representatives, successors and permitted assigns.

     IN WITNESS WHEREOF, the Company has caused this Option to be executed on
its behalf and its corporate seal to be hereunto affixed as of the date first
set forth above.

                                           SYNTA PHARMACEUTICALS CORP.

                                           By: /S/ DR. SAFI BAHCALL
                                               ---------------------------------
                                           Name: Dr. Safi Bahcall
                                           Title: President and Chief Executive
                                                  Officer

The undersigned hereby accepts and agrees to the terms and conditions contained
in this Option as of the date specified above.

                                           /S/ KEITH R. GOLLUST
                                           -------------------------------------
                                           KEITH R. GOLLUST

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EXHIBIT A

                                 EXERCISE NOTICE

Synta Pharmaceuticals Corp.
45 Hartwell Avenue
Lexington, MA 02421
Attn.: Chief Financial Officer

     This Exercise Notice is pursuant to a Non-Qualified Stock Option Agreement
dated as of May 27, 2004 (the "Option"), by and between Synta Pharmaceuticals
Corp. (the "Company") and Keith R. Gollust. Unless otherwise noted herein,
capitalized terms used in this Exercise Notice have the meanings set forth in
the Option. The undersigned, the recipient or permitted assignee of the
Optionee, hereby elects today to exercise the Option to purchase ____________
shares of the Option Securities of the Company (the "Purchased Shares"), and
with this Exercise Notice the undersigned is delivering to you one or more of
the following in payment of the aggregate exercise price for the shares (the
"Exercise Price"):

     (a)  $_____________ in cash, by personal check or by wire transfer;

     (b)  stock certificates for _____________ shares of the Company's capital
stock (the "Certificates") with a Fair Market Value of $________,accompanied by
duly executed stock power(s) for each Certificate; or

     (c)  notice of the undersigned's consent for the Company to retain
___________ shares of the Option Securities with a Fair Market Value of
$___________________ .

Accordingly, please issue a stock certificate for the shares in the
undersigned's name and have it delivered to the undersigned at the address
indicated below. Notwithstanding, the undersigned understands that the Company
may issue a stock certificate for less than the total number of Purchased Shares
in the event the Company withholds shares in order to satisfy any applicable
withholding tax obligation of the Company. The undersigned acknowledges his or
its responsibility to comply with the tax withholding requirements set forth in
Section 10 of the Option.

     The undersigned hereby acknowledge that he or it has been given the
opportunity to ask questions of, and to obtain such information from, the
Company as he or it deems necessary to evaluate the merits of making an
investment in the Option Securities of the Company.

     The undersigned hereby confirms that he or it is acquiring the Option
Securities for the undersigned's own account for investment and not with any
present intention of selling or otherwise distributing the shares, and the
undersign confirms that he or it will in no event sell, transfer, pledge or
otherwise dispose of the shares prior to (a) receipt of an opinion of counsel
for the Company authorizing any such proposed sale, transfer, pledge or other
disposition, (b) receipt of a "no action" letter from the Securities and
Exchange Commission or (c) registration of the Option Securities under the
Securities Act of 1933, as amended. The undersigned

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understands that the certificate representing the Option Securities will bear a
legend noting these restrictions on transferability.

                                      Dated:
--------------------------------            --------------------------
Print Name

--------------------------------
Signature

Address:
        ------------------------
--------------------------------

Social Security No. or E.I.N.:
                              -----------

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                                                                   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.

                                        5
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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

                                        6
<Page>

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:

                                        7
<Page>

     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.

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                                   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

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