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                           ELITRA PHARMACEUTICALS INC.
                          2000 NON-EMPLOYEE DIRECTORS'
                                STOCK OPTION PLAN

                             STOCK OPTION AGREEMENT
                           (NONSTATUTORY STOCK OPTION)


         Pursuant to your Stock Option Grant Notice ("Grant Notice") and this
Stock Option Agreement, ELITRA PHARMACEUTICALS INC. (the "Company") has granted
you an option under its 2000 Non-Employee Directors' Stock Option Plan (the
"Plan") to purchase the number of shares of the Company's Common Stock indicated
in your Grant Notice at the exercise price indicated in your Grant Notice.
Defined terms not explicitly defined in this Stock Option Agreement but defined
in the Plan shall have the same definitions as in the Plan.

         The details of your option are as follows:

         1.       VESTING. Subject to the limitations contained herein, your
option will vest as provided in your Grant Notice, provided that vesting will
cease upon the termination of your Continuous Service.

         2.       NUMBER OF SHARES AND EXERCISE PRICE. The number of shares of
Common Stock subject to your option and your exercise price per share referenced
in your Grant Notice may be adjusted from time to time for Capitalization
Adjustments, as provided in the Plan.

         3.       METHOD OF PAYMENT. Payment of the exercise price is due in
full upon exercise of all or any part of your option. You may elect to make
payment of the exercise price in cash or by check or in any other manner
permitted by your Grant Notice, which may include one or more of the following:

                  (A)      In the Company's sole discretion at the time your
option is exercised and provided that at the time of exercise the Common Stock
is publicly traded and quoted regularly in The Wall Street Journal, pursuant to
a program developed under Regulation T as promulgated by the Federal Reserve
Board that, prior to the issuance of Common Stock, results in either the receipt
of cash (or check) by the Company or the receipt of irrevocable instructions to
pay the aggregate exercise price to the Company from the sales proceeds.

                  (B)      Provided that at the time of exercise the Common
Stock is publicly traded and quoted regularly in The Wall Street Journal, by
delivery of already-owned shares of Common Stock either that you have held for
the period required to avoid a charge to the Company's reported earnings
(generally six months) or that you did not acquire, directly or indirectly from
the Company, that are owned free and clear of any liens, claims, encumbrances or
security interests, and that are valued at Fair Market Value on the date of
exercise. "Delivery" for these purposes, in the sole discretion of the Company
at the time you exercise your option, shall include delivery to the Company of
your attestation of ownership of such shares of Common Stock in a form approved
by the Company. Notwithstanding the foregoing, you may not exercise your option
by tender to the Company of Common Stock to the extent such tender


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would violate the provisions of any law, regulation or agreement restricting the
redemption of the Company's stock.

                  (C)      Pursuant to the following deferred payment
alternative:

                           (I)      Not less than one hundred percent (100%) of
the aggregate exercise price, plus accrued interest, shall be due four (4) years
from date of exercise or, at the Company's election, upon termination of your
Continuous Service.

                           (II)     Interest shall be compounded at least
annually and shall be charged at the minimum rate of interest necessary to avoid
the treatment as interest, under any applicable provisions of the Code, of any
portion of any amounts other than amounts stated to be interest under the
deferred payment arrangement.

                           (III)    At any time that the Company is incorporated
in Delaware, payment of the Common Stock's "par value," as defined in the
Delaware General Corporation Law, shall be made in cash and not by deferred
payment.

                           (IV)     In order to elect the deferred payment
alternative, you must, as a part of your written notice of exercise, give notice
of the election of this payment alternative and, in order to secure the payment
of the deferred exercise price to the Company hereunder, if the Company so
requests, you must tender to the Company a promissory note and a security
agreement covering the purchased shares of Common Stock, both in form and
substance satisfactory to the Company, or such other or additional documentation
as the Company may request.

         4.       WHOLE SHARES. You may exercise your option only for whole
shares of Common Stock.

         5.       SECURITIES LAW COMPLIANCE. Notwithstanding anything to the
contrary contained herein, you may not exercise your option unless the shares of
Common Stock issuable upon such exercise are then registered under the
Securities Act or, if such shares of Common Stock are not then so registered,
the Company has determined that such exercise and issuance would be exempt from
the registration requirements of the Securities Act. The exercise of your option
must also comply with other applicable laws and regulations governing your
option, and you may not exercise your option if the Company determines that such
exercise would not be in material compliance with such laws and regulations.

         6.       TERM. You may not exercise your option before the commencement
of its term or after its term expires. The term of your option commences on the
Date of Grant and expires upon the earliest of the following:

                  (A)      three (3) months after the termination of your
Continuous Service for any reason other than your Disability or death, provided
that if during any part of such three- (3-) month period your option is not
exercisable solely because of the condition set forth in the preceding paragraph
relating to "Securities Law Compliance," your option shall not expire until the
earlier of the Expiration Date or until it shall have been exercisable for an
aggregate period of three (3) months after the termination of your Continuous
Service;


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                  (B)      twelve (12) months after the termination of your
Continuous Service due to your Disability;

                  (C)      eighteen (18) months after your death if you die
either during your Continuous Service or within three (3) months after your
Continuous Service terminates;

                  (D)      the Expiration Date indicated in your Grant Notice;
or

                  (E)      the day before the tenth (10th) anniversary of the
Date of Grant.

         7.       EXERCISE.

                  (A)      You may exercise the vested portion of your option
(and the unvested portion of your option if your Grant Notice so permits) during
its term by delivering a Notice of Exercise (in a form designated by the
Company) together with the exercise price to the Secretary of the Company, or to
such other person as the Company may designate, during regular business hours,
together with such additional documents as the Company may then require.

                  (B)      By exercising your option you agree that, as a
condition to any exercise of your option, the Company may require you to enter
into an arrangement providing for the payment by you to the Company of any tax
withholding obligation of the Company arising by reason of (1) the exercise of
your option, (2) the lapse of any substantial risk of forfeiture to which the
shares of Common Stock are subject at the time of exercise, or (3) the
disposition of shares of Common Stock acquired upon such exercise.

         8.       TRANSFERABILITY. Your option is not transferable, except (i)
by will or by the laws of descent and distribution, (ii) with the prior written
approval of the Company, by instrument to an inter vivos or testamentary trust,
in a form accepted by the Company, in which the option is to be passed to
beneficiaries upon the death of the trustor (settlor) and (iii) with the prior
written approval of the Company, by gift, in a form accepted by the Company, to
your "immediate family" as that term is defined in 17 C.F.R. 240.16a-1(e). The
term "immediate family" is defined in 17 C.F.R. 240.16a-1(e) to mean any child,
stepchild, grandchild, parent, stepparent, grandparent, spouse, sibling,
mother-in-law, father-in-law, son-in-law, daughter-in-law, brother-in-law, or
sister-in-law, and includes adoptive relationships. Your option is exercisable
during your life only by you or a transferee satisfying the above-stated
conditions. The right of a transferee to exercise the transferred portion of
your option after termination of your Continuous Service shall terminate in
accordance with your right to exercise your option as specified in your option.
In the event that your Continuous Service terminates due to your death, your
transferee will be treated as a person who acquired the right to exercise your
option by bequest or inheritance. In addition to the foregoing, the Company may
require, as a condition of the transfer of your option to a trust or by gift,
that your transferee enter into an option transfer agreement provided by, or
acceptable to, the Company. The terms of your option shall be binding upon your
transferees, executors, administrators, heirs, successors, and assigns.
Notwithstanding the foregoing, by delivering written notice to the Company, in a
form satisfactory to the Company, you may designate a third party who, in the
event of your death, shall thereafter be entitled to exercise your option.


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         9.       OPTION NOT A SERVICE CONTRACT. Your option is not a service
contract, and nothing in your option shall be deemed to create in any way
whatsoever any obligation on your part to continue in the service of the Company
or an Affiliate. In addition, nothing in your option shall obligate the Company
or an Affiliate, their respective shareholders, Boards of Directors, Officers or
Employees to continue any relationship that you might have as a Director or
Consultant for the Company or an Affiliate.

         10.      WITHHOLDING OBLIGATIONS.

                  (A)      At the time you exercise your option, in whole or in
part, or at any time thereafter as requested by the Company, you hereby
authorize withholding from payroll and any other amounts payable to you, and
otherwise agree to make adequate provision for (including by means of a
"cashless exercise" pursuant to a program developed under Regulation T as
promulgated by the Federal Reserve Board to the extent permitted by the
Company), any sums required to satisfy the federal, state, local and foreign tax
withholding obligations of the Company or an Affiliate, if any, which arise in
connection with your option.

                  (B)      Upon your request and subject to approval by the
Company, in its sole discretion, and compliance with any applicable conditions
or restrictions of law, the Company may withhold from fully vested shares of
Common Stock otherwise issuable to you upon the exercise of your option a number
of whole shares of Common Stock having a Fair Market Value, determined by the
Company as of the date of exercise, not in excess of the minimum amount of tax
required to be withheld by law. If the date of determination of any tax
withholding obligation is deferred to a date later than the date of exercise of
your option, share withholding pursuant to the preceding sentence shall not be
permitted unless you make a proper and timely election under Section 83(b) of
the Code, covering the aggregate number of shares of Common Stock acquired upon
such exercise with respect to which such determination is otherwise deferred, to
accelerate the determination of such tax withholding obligation to the date of
exercise of your option. Notwithstanding the filing of such election, shares of
Common Stock shall be withheld solely from fully vested shares of Common Stock
determined as of the date of exercise of your option that are otherwise issuable
to you upon such exercise. Any adverse consequences to you arising in connection
with such share withholding procedure shall be your sole responsibility.

                  (C)      You may not exercise your option unless the tax
withholding obligations of the Company and/or any Affiliate are satisfied.
Accordingly, you may not be able to exercise your option when desired even
though your option is vested, and the Company shall have no obligation to issue
a certificate for such shares of Common Stock or release such shares of Common
Stock from any escrow provided for herein.

         11.      NOTICES. Any notices provided for in your option or the Plan
shall be given in writing and shall be deemed effectively given upon receipt or,
in the case of notices delivered by mail by the Company to you, five (5) days
after deposit in the United States mail, postage prepaid, addressed to you at
the last address you provided to the Company.

         12.      GOVERNING PLAN DOCUMENT. Your option is subject to all the
provisions of the Plan, the provisions of which are hereby made a part of your
option, and is further subject to all


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interpretations, amendments, rules and regulations which may from time to time
be promulgated and adopted pursuant to the Plan. In the event of any conflict
between the provisions of your option and those of the Plan, the provisions of
the Plan shall control.


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