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                           ELITRA PHARMACEUTICALS INC.

                 2000 NON-EMPLOYEE DIRECTORS' STOCK OPTION PLAN

                             ADOPTED AUGUST 18, 2000
                 APPROVED BY STOCKHOLDERS _______________, 2000

                      EFFECTIVE DATE: _______________, 2000
                             TERMINATION DATE: NONE

1.       PURPOSES.

         (a)      ELIGIBLE OPTION RECIPIENTS. The persons eligible to receive
Options are the Non-Employee Directors of the Company.

         (b)      AVAILABLE OPTIONS. The purpose of the Plan is to provide a
means by which Non-Employee Directors may be given an opportunity to benefit
from increases in value of the Common Stock through the granting of Nonstatutory
Stock Options.

         (c)      GENERAL PURPOSE. The Company, by means of the Plan, seeks to
retain the services of its Non-Employee Directors, to secure and retain the
services of new Non-Employee Directors and to provide incentives for such
persons to exert maximum efforts for the success of the Company and its
Affiliates.

2.       DEFINITIONS.

         (a)      "AFFILIATE" means any parent corporation or subsidiary
corporation of the Company, whether now or hereafter existing, as those terms
are defined in Sections 424(e) and (f), respectively, of the Code.

         (b)      "ANNUAL GRANT" means an Option granted annually to all
Non-Employee Directors who meet the specified criteria pursuant to subsection
6(b) of the Plan.

         (c)      "ANNUAL MEETING" means the annual meeting of the stockholders
of the Company.

         (d)      "BOARD" means the Board of Directors of the Company.

         (e)      "CODE" means the Internal Revenue Code of 1986, as amended.

         (f)      "COMMON STOCK" means the common stock of the Company.

         (g)      "COMPANY" means Elitra Pharmaceuticals Inc., a Delaware
corporation.

         (h)      "CONSULTANT" means any person, including an advisor, (i)
engaged by the Company or an Affiliate to render consulting or advisory services
and who is compensated for such services or (ii) who is a member of the Board of
Directors of an Affiliate. However, the


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term "Consultant" shall not include either Directors of the Company who are not
compensated by the Company for their services as Directors or Directors of the
Company who are merely paid a director's fee by the Company for their services
as Directors.

         (i)      "CONTINUOUS SERVICE" means that the Optionholder's service
with the Company or an Affiliate, whether as an Employee, Director or
Consultant, is not interrupted or terminated. The Optionholder's Continuous
Service shall not be deemed to have terminated merely because of a change in the
capacity in which the Optionholder renders service to the Company or an
Affiliate as an Employee, Consultant or Director or a change in the entity for
which the Optionholder renders such service, provided that there is no
interruption or termination of the Optionholder's Continuous Service. For
example, a change in status from a Non-Employee Director of the Company to a
Consultant of an Affiliate or an Employee of the Company will not constitute an
interruption of Continuous Service. The Board or the chief executive officer of
the Company, in that party's sole discretion, may determine whether Continuous
Service shall be considered interrupted in the case of any leave of absence
approved by that party, including sick leave, military leave or any other
personal leave.

         (j)      "DIRECTOR" means a member of the Board of Directors of the
Company.

         (k)      "DISABILITY" means the permanent and total disability of a
person within the meaning of Section 22(e)(3) of the Code.

         (l)      "EMPLOYEE" means any person employed by the Company or an
Affiliate. Mere service as a Director or payment of a director's fee by the
Company or an Affiliate shall not be sufficient to constitute "employment" by
the Company or an Affiliate.

         (m)      "EXCHANGE ACT" means the Securities Exchange Act of 1934, as
amended.

         (n)      "FAIR MARKET VALUE" means, as of any date, the value of the
Common Stock determined as follows:

                  (i)      If the Common Stock is listed on any established
stock exchange or traded on the Nasdaq National Market or the Nasdaq SmallCap
Market, the Fair Market Value of a share of Common Stock shall be the closing
sales price for such stock (or the closing bid, if no sales were reported) as
quoted on such exchange or market (or the exchange or market with the greatest
volume of trading in the Common Stock) on the last market trading day prior to
the day of determination, as reported in The Wall Street Journal or such other
source as the Board deems reliable.

                  (ii)     In the absence of such markets for the Common Stock,
the Fair Market Value shall be determined in good faith by the Board.

         (o)      "INITIAL GRANT" means an Option granted to a Non-Employee
Director who meets the specified criteria pursuant to subsection 6(a) of the
Plan.


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         (p)      "IPO DATE" means the effective date of the initial public
offering of the Common Stock.

         (q)      "NON-EMPLOYEE DIRECTOR" means a Director who is not an
Employee.

         (r)      "NONSTATUTORY STOCK OPTION" means an Option not intended to
qualify as an incentive stock option within the meaning of Section 422 of the
Code and the regulations promulgated thereunder.

         (s)      "OFFICER" means a person who is an officer of the Company
within the meaning of Section 16 of the Exchange Act and the rules and
regulations promulgated thereunder.

         (t)      "OPTION" means a Nonstatutory Stock Option granted pursuant to
the Plan.

         (u)      "OPTION AGREEMENT" means a written agreement between the
Company and an Optionholder evidencing the terms and conditions of an individual
Option grant. Each Option Agreement shall be subject to the terms and conditions
of the Plan.

         (v)      "OPTIONHOLDER" means a person to whom an Option is granted
pursuant to the Plan or, if applicable, such other person who holds an
outstanding Option.

         (w)      "PLAN" means this Elitra Pharmaceuticals Inc. 2000
Non-Employee Directors' Stock Option Plan.

         (x)      "RULE 16B-3" means Rule 16b-3 promulgated under the Exchange
Act or any successor to Rule 16b-3, as in effect from time to time.

         (y)      "SECURITIES ACT" means the Securities Act of 1933, as amended.

3.       ADMINISTRATION.

         (a)      ADMINISTRATION BY BOARD. The Board shall administer the Plan.
The Board may not delegate administration of the Plan to a committee.

         (b)      POWERS OF BOARD. The Board shall have the power, subject to,
and within the limitations of, the express provisions of the Plan:

                  (i)      To determine the provisions of each Option to the
extent not specified in the Plan.

                  (ii)     To construe and interpret the Plan and Options
granted under it, and to establish, amend and revoke rules and regulations for
its administration. The Board, in the exercise of this power, may correct any
defect, omission or inconsistency in the Plan or in any Option Agreement, in a
manner and to the extent it shall deem necessary or expedient to make the Plan
fully effective.

                  (iii)    To amend the Plan or an Option as provided in Section
12.


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                  (iv)     Generally, to exercise such powers and to perform
such acts as the Board deems necessary or expedient to promote the best
interests of the Company that are not in conflict with the provisions of the
Plan.

         (c)      EFFECT OF BOARD'S DECISION. All determinations,
interpretations and constructions made by the Board in good faith shall not be
subject to review by any person and shall be final, binding and conclusive on
all persons.

4.       SHARES SUBJECT TO THE PLAN.

         (a)      SHARE RESERVE. Subject to the provisions of Section 11
relating to adjustments upon changes in the Common Stock, the Common Stock that
may be issued pursuant to Options shall not exceed in the aggregate five hundred
thousand (500,000) shares of Common Stock; plus an annual increase to be added
on the date of the Annual Meeting, commencing in 2001 and ending in (and
including) 2009, equal to the lesser of: (i) one-half of one percent (0.5%) of
the shares of Common Stock outstanding on the last day of the preceding calendar
year (rounded to the nearest whole share); or (ii) such number of shares of
Common Stock as determined by the Board.

         (b)      REVERSION OF SHARES TO THE SHARE RESERVE. If any Option shall
for any reason expire or otherwise terminate, in whole or in part, without
having been exercised in full, the shares of Common Stock not acquired under
such Option shall revert to and again become available for issuance under the
Plan.

         (c)      SOURCE OF SHARES. The shares of Common Stock subject to the
Plan may be unissued shares or reacquired shares, bought on the market or
otherwise.

5.       ELIGIBILITY.

         The Options as set forth in section 6 automatically shall be granted
under the Plan to all Non-Employee Directors.

6.       NON-DISCRETIONARY GRANTS.

         (a)      INITIAL GRANTS. Without any further action of the Board, and
subject to the provisions of Section 11 relating to adjustments upon changes in
Common Stock, after the IPO Date, each person who is elected or appointed for
the first time to be a Non-Employee Director automatically shall, upon the date
of his or her initial election or appointment to be a Non-Employee Director by
the Board or stockholders of the Company, be granted an Initial Grant to
purchase forty thousand (40,000) shares of Common Stock on the terms and
conditions set forth herein.

         (b)      ANNUAL GRANTS. Without any further action of the Board, and
subject to the provisions of Section 11 relating to adjustments upon changes in
Common Stock, on the day following each Annual Meeting commencing with the
Annual Meeting in 2001, each person who is then a Non-Employee Director
automatically shall be granted an Annual Grant to purchase


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fifteen thousand (15,000) shares of Common Stock on the terms and conditions set
forth herein; PROVIDED, HOWEVER, that if the person has not been serving as a
Non-Employee Director for the entire period since the preceding Annual Meeting,
then the number of shares subject to the Annual Grant shall be reduced pro rata
for each full quarter prior to the date of grant during which such person did
not serve as a Non-Employee Director.

7.       OPTION PROVISIONS.

         Each Option shall be in such form and shall contain such terms and
conditions as required by the Plan. Each Option shall contain such additional
terms and conditions, not inconsistent with the Plan, as the Board shall deem
appropriate. Each Option shall include (through incorporation of provisions
hereof by reference in the Option or otherwise) the substance of each of the
following provisions:

         (a)      TERM. No Option shall be exercisable after the expiration of
ten (10) years from the date it was granted.

         (b)      EXERCISE PRICE. The exercise price of each Option shall be one
hundred percent (100%) of the Fair Market Value of the stock subject to the
Option on the date the Option is granted. Notwithstanding the foregoing, an
Option may be granted with an exercise price lower than that set forth in the
preceding sentence if such Option is granted pursuant to an assumption or
substitution for another option in a manner satisfying the provisions of Section
424(a) of the Code.

         (c)      CONSIDERATION. The purchase price of stock acquired pursuant
to an Option may be paid, to the extent permitted by applicable statutes and
regulations, in any combination of (i) cash or check, (ii) delivery to the
Company of other Common Stock, (ii) deferred payment or (iv) any other form of
legal consideration that may be acceptable to the Board. The purchase price of
Common Stock acquired pursuant to an Option that is paid by delivery to the
Company of other Common Stock acquired, directly or indirectly from the Company,
shall be paid only by shares of the Common Stock of the Company that have been
held for more than six (6) months (or such longer or shorter period of time
required to avoid a charge to earnings for financial accounting purposes). 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
not be made by deferred payment.

         In the case of any deferred payment arrangement, 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 amounts other than amounts stated to be interest
under the deferred payment arrangement.

         (d)      TRANSFERABILITY. An Option shall be transferable to the extent
provided in the Option Agreement. If the Option Agreement does not provide for
transferability, then the Option shall not be transferable except by will or by
the laws of descent and distribution and shall be exercisable during the
lifetime of the Optionholder only by the Optionholder. Notwithstanding the
foregoing, the Optionholder may, by delivering written notice to the Company, in
a form


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satisfactory to the Company, designate a third party who, in the event of the
death of the Optionholder, shall thereafter be entitled to exercise the Option.

         (e)      VESTING GENERALLY. Options shall vest and become exercisable
as follows:

                  (i)      Initial Grants shall provide for vesting of 1/36th of
the shares each month after the date of grant.

                  (ii)     Annual Grants shall provide for vesting of 1/12th of
the shares each month after the date of the grant.

         (f)      TERMINATION OF CONTINUOUS SERVICE. In the event an
Optionholder's Continuous Service terminates (other than upon the Optionholder's
death or Disability), the Optionholder may exercise his or her Option (to the
extent that the Optionholder was entitled to exercise it as of the date of
termination) but only within such period of time ending on the earlier of (i)
the date three (3) months following the termination of the Optionholder's
Continuous Service, or (ii) the expiration of the term of the Option as set
forth in the Option Agreement. If, after termination, the Optionholder does not
exercise his or her Option within the time specified in the Option Agreement,
the Option shall terminate.

         (g)      EXTENSION OF TERMINATION DATE. If the exercise of the Option
following the termination of the Optionholder's Continuous Service (other than
upon the Optionholder's death or Disability) would be prohibited at any time
solely because the issuance of shares would violate the registration
requirements under the Securities Act, then the Option shall terminate on the
earlier of (i) the expiration of the term of the Option set forth in subsection
7(a) or (ii) the expiration of a period of three (3) months after the
termination of the Optionholder's Continuous Service during which the exercise
of the Option would not be in violation of such registration requirements.

         (h)      DISABILITY OF OPTIONHOLDER. In the event an Optionholder's
Continuous Service terminates as a result of the Optionholder's Disability, the
Optionholder may exercise his or her Option (to the extent that the Optionholder
was entitled to exercise it as of the date of termination), but only within such
period of time ending on the earlier of (i) the date twelve (12) months
following such termination or (ii) the expiration of the term of the Option as
set forth in the Option Agreement. If, after termination, the Optionholder does
not exercise his or her Option within the time specified herein, the Option
shall terminate.

         (i)      DEATH OF OPTIONHOLDER. In the event (i) an Optionholder's
Continuous Service terminates as a result of the Optionholder's death or (ii)
the Optionholder dies within the three-month period after the termination of the
Optionholder's Continuous Service for a reason other than death, then the Option
may be exercised (to the extent the Optionholder was entitled to exercise the
Option as of the date of death) by the Optionholder's estate, by a person who
acquired the right to exercise the Option by bequest or inheritance or by a
person designated to exercise the Option upon the Optionholder's death, but only
within the period ending on the earlier of (1) the date eighteen (18) months
following the date of death or (2) the expiration of


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the term of such Option as set forth in the Option Agreement. If, after death,
the Option is not exercised within the time specified herein, the Option shall
terminate.

8.       COVENANTS OF THE COMPANY.

         (a)      AVAILABILITY OF SHARES. During the terms of the Options, the
Company shall keep available at all times the number of shares of Common Stock
required to satisfy such Options.

         (b)      SECURITIES LAW COMPLIANCE. The Company shall seek to obtain
from each regulatory commission or agency having jurisdiction over the Plan such
authority as may be required to grant Options and to issue and sell shares of
Common Stock upon exercise of the Options; provided, however, that this
undertaking shall not require the Company to register under the Securities Act
the Plan, any Option or any stock issued or issuable pursuant to any such
Option. If, after reasonable efforts, the Company is unable to obtain from any
such regulatory commission or agency the authority which counsel for the Company
deems necessary for the lawful issuance and sale of stock under the Plan, the
Company shall be relieved from any liability for failure to issue and sell stock
upon exercise of such Options unless and until such authority is obtained.

9.       USE OF PROCEEDS FROM STOCK.

         Proceeds from the sale of stock pursuant to Options shall constitute
general funds of the Company.

10.      MISCELLANEOUS.

         (a)      STOCKHOLDER RIGHTS. No Optionholder shall be deemed to be the
holder of, or to have any of the rights of a holder with respect to, any shares
subject to such Option unless and until such Optionholder has satisfied all
requirements for exercise of the Option pursuant to its terms.

         (b)      NO SERVICE RIGHTS. Nothing in the Plan or any instrument
executed or Option granted pursuant thereto shall confer upon any Optionholder
any right to continue to serve the Company as a Non-Employee Director or shall
affect the right of the Company or an Affiliate to terminate (i) the employment
of an Employee with or without notice and with or without cause, (ii) the
service of a Consultant pursuant to the terms of such Consultant's agreement
with the Company or an Affiliate or (iii) the service of a Director pursuant to
the Bylaws of the Company or an Affiliate, and any applicable provisions of the
corporate law of the state in which the Company or the Affiliate is
incorporated, as the case may be.

         (c)      INVESTMENT ASSURANCES. The Company may require an
Optionholder, as a condition of exercising or acquiring stock under any Option,
(i) to give written assurances satisfactory to the Company as to the
Optionholder's knowledge and experience in financial and business matters and/or
to employ a purchaser representative reasonably satisfactory to the Company who
is knowledgeable and experienced in financial and business matters and that he
or she is capable of evaluating, alone or together with the purchaser
representative, the merits and


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risks of exercising the Option; and (ii) to give written assurances satisfactory
to the Company stating that the Optionholder is acquiring the stock subject to
the Option for the Optionholder's own account and not with any present intention
of selling or otherwise distributing the stock. The foregoing requirements, and
any assurances given pursuant to such requirements, shall be inoperative if
(iii) the issuance of the shares upon the exercise or acquisition of stock under
the Option has been registered under a then currently effective registration
statement under the Securities Act or (iv) as to any particular requirement, a
determination is made by counsel for the Company that such requirement need not
be met in the circumstances under the then applicable securities laws. The
Company may, upon advice of counsel to the Company, place legends on stock
certificates issued under the Plan as such counsel deems necessary or
appropriate in order to comply with applicable securities laws, including, but
not limited to, legends restricting the transfer of the stock.

         (d)      WITHHOLDING OBLIGATIONS. The Optionholder may satisfy any
federal, state or local tax withholding obligation relating to the exercise or
acquisition of stock under an Option by any of the following means (in addition
to the Company's right to withhold from any compensation paid to the
Optionholder by the Company) or by a combination of such means: (i) tendering a
cash payment; (ii) authorizing the Company to withhold shares from the shares of
the Common Stock otherwise issuable to the Optionholder as a result of the
exercise or acquisition of stock under the Option, provided, however, that no
shares of Common Stock are withheld with a value exceeding the minimum amount of
tax required to be withheld by law; or (iii) delivering to the Company owned and
unencumbered shares of the Common Stock.

11.      ADJUSTMENTS UPON CHANGES IN STOCK.

         (a)      CAPITALIZATION ADJUSTMENTS. If any change is made in the stock
subject to the Plan, or subject to any Option, without the receipt of
consideration by the Company (through merger, consolidation, reorganization,
recapitalization, reincorporation, stock dividend, dividend in property other
than cash, stock split, liquidating dividend, combination of shares, exchange of
shares, change in corporate structure or other transaction not involving the
receipt of consideration by the Company), the Plan will be appropriately
adjusted in the class(es) and maximum number of securities subject both to the
Plan pursuant to subsection 4(a) and to the nondiscretionary Options specified
in Section 5, and the outstanding Options will be appropriately adjusted in the
class(es) and number of securities and price per share of stock subject to such
outstanding Options. The Board shall make such adjustments, and its
determination shall be final, binding and conclusive. (The conversion of any
convertible securities of the Company shall not be treated as a transaction
"without receipt of consideration" by the Company.)

         (b)      DISSOLUTION OR LIQUIDATION. In the event of a dissolution or
liquidation of the Company, then all outstanding Options shall terminate
immediately prior to such event.

         (c)      ASSET SALE, MERGER, CONSOLIDATION OR REVERSE MERGER. In the
event of (i) a sale, lease or other disposition of all or substantially all of
the assets of the Company, (ii) a merger or consolidation in which the Company
is not the surviving corporation or (iii) a reverse merger in which the Company
is the surviving corporation but the shares of Common Stock


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outstanding immediately preceding the merger are converted by virtue of the
merger into other property, whether in the form of securities, cash or otherwise
(individually, a "Corporate Transaction"), then any surviving corporation or
acquiring corporation shall assume any Options outstanding under the Plan or
shall substitute similar Options (including an option to acquire the same
consideration paid to the stockholders in the Corporate Transaction for those
outstanding under the Plan). In the event any surviving corporation or acquiring
corporation refuses to assume such Options or to substitute similar Options for
those outstanding under the Plan, then with respect to Options held by
Optionholders whose Continuous Service has not terminated, the vesting of such
Options (and the time during which such Options may be exercised) shall be
accelerated in full, and the Options shall terminate if not exercised at or
prior to such Corporate Transaction. With respect to any other Options
outstanding under the Plan, such Options shall terminate if not exercised prior
to such Corporate Transaction.

12.      AMENDMENT OF THE PLAN AND OPTIONS.

         (a)      AMENDMENT OF PLAN. The Board at any time, and from time to
time, may amend the Plan. However, except as provided in Section 11 relating to
adjustments upon changes in stock, no amendment shall be effective unless
approved by the stockholders of the Company to the extent stockholder approval
is necessary to satisfy the requirements of Rule 16b-3 or any Nasdaq or
securities exchange listing requirements.

         (b)      STOCKHOLDER APPROVAL. The Board may, in its sole discretion,
submit any other amendment to the Plan for stockholder approval.

         (c)      NO IMPAIRMENT OF RIGHTS. Rights under any Option granted
before amendment of the Plan shall not be impaired by any amendment of the Plan
unless (i) the Company requests the consent of the Optionholder and (ii) the
Optionholder consents in writing.

         (d)      AMENDMENT OF OPTIONS. The Board at any time, and from time to
time, may amend the terms of any one or more Options; provided, however, that
the rights under any Option shall not be impaired by any such amendment unless
(i) the Company requests the consent of the Optionholder and (ii) the
Optionholder consents in writing.

13.      TERMINATION OR SUSPENSION OF THE PLAN.

         (a)      PLAN TERM. The Board may suspend or terminate the Plan at any
time. No Options may be granted under the Plan while the Plan is suspended or
after it is terminated.

         (b)      NO IMPAIRMENT OF RIGHTS. Suspension or termination of the Plan
shall not impair rights and obligations under any Option granted while the Plan
is in effect except with the written consent of the Optionholder.


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14.      EFFECTIVE DATE OF PLAN.

         The Plan shall become effective on the IPO Date, but no Option shall be
exercised unless and until the Plan has been approved by the stockholders of the
Company, which approval shall be within twelve (12) months before or after the
date the Plan is adopted by the Board.

15.      CHOICE OF LAW.

         All questions concerning the construction, validity and interpretation
of this Plan shall be governed by the law of the State of California, without
regard to such state's conflict of laws rules.


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