Document:

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                              DRUGABUSE SCIENCES, INC.

                             2000 STOCK INCENTIVE PLAN

                      (AS ADOPTED EFFECTIVE _______ __, 2000)

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                                  TABLE OF CONTENTS

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ARTICLE 1.  INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1

ARTICLE 2.  ADMINISTRATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1
     2.1  Committee Composition. . . . . . . . . . . . . . . . . . . . . . . . . . .1
     2.2  Committee Responsibilities . . . . . . . . . . . . . . . . . . . . . . . .1
     2.3  Committee for Non-Officer Grants . . . . . . . . . . . . . . . . . . . . .1

ARTICLE 3.  SHARES AVAILABLE FOR GRANTS. . . . . . . . . . . . . . . . . . . . . . .2
     3.1  Basic Limitation . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2
     3.2  Annual Increase in Shares. . . . . . . . . . . . . . . . . . . . . . . . .2
     3.3  Additional Shares. . . . . . . . . . . . . . . . . . . . . . . . . . . . .2

ARTICLE 4.  ELIGIBILITY. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2
     4.1  Nonstatutory Stock Options and Restricted Shares . . . . . . . . . . . . .2
     4.2  Incentive Stock Options. . . . . . . . . . . . . . . . . . . . . . . . . .2

ARTICLE 5.  OPTIONS. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3
     5.1  Stock Option Agreement . . . . . . . . . . . . . . . . . . . . . . . . . .3
     5.2  Number of Shares . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3
     5.3  Exercise Price . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3
     5.4  Exercisability and Term. . . . . . . . . . . . . . . . . . . . . . . . . .3
     5.5  Effect of Change in Control. . . . . . . . . . . . . . . . . . . . . . . .3
     5.6  Modification or Assumption of Options. . . . . . . . . . . . . . . . . . .3
     5.7  Buyout Provisions. . . . . . . . . . . . . . . . . . . . . . . . . . . . .4

ARTICLE 6.  PAYMENT FOR OPTION SHARES. . . . . . . . . . . . . . . . . . . . . . . .4
     6.1  General Rule . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4
     6.2  Surrender of Stock . . . . . . . . . . . . . . . . . . . . . . . . . . . .4
     6.3  Exercise/Sale. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4
     6.4  Exercise/Pledge. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4
     6.5  Promissory Note. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4
     6.6  Other Forms of Payment . . . . . . . . . . . . . . . . . . . . . . . . . .5

ARTICLE 7.  RESTRICTED SHARES. . . . . . . . . . . . . . . . . . . . . . . . . . . .5
     7.1  Restricted Stock Agreement . . . . . . . . . . . . . . . . . . . . . . . .5
     7.2  Payment for Awards . . . . . . . . . . . . . . . . . . . . . . . . . . . .5
     7.3  Vesting Conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . .5
     7.4  Voting and Dividend Rights . . . . . . . . . . . . . . . . . . . . . . . .5

ARTICLE 8.  PROTECTION AGAINST DILUTION. . . . . . . . . . . . . . . . . . . . . . .5
     8.1  Adjustments. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5
     8.2  Dissolution or Liquidation . . . . . . . . . . . . . . . . . . . . . . . .6

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     8.3  Reorganizations. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6

ARTICLE 9.  DEFERRAL OF DELIVERY OF SHARES . . . . . . . . . . . . . . . . . . . . .6

ARTICLE 10.  AWARDS UNDER OTHER PLANS. . . . . . . . . . . . . . . . . . . . . . . .6

ARTICLE 11.  LIMITATION ON RIGHTS. . . . . . . . . . . . . . . . . . . . . . . . . .7
     11.1  Retention Rights. . . . . . . . . . . . . . . . . . . . . . . . . . . . .7
     11.2  Shareholders' Rights. . . . . . . . . . . . . . . . . . . . . . . . . . .7
     11.3  Regulatory Requirements . . . . . . . . . . . . . . . . . . . . . . . . .7

ARTICLE 12.  WITHHOLDING TAXES . . . . . . . . . . . . . . . . . . . . . . . . . . .7
     12.1  General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .7
     12.2  Share Withholding . . . . . . . . . . . . . . . . . . . . . . . . . . . .7

ARTICLE 13.  LIMITATION ON PAYMENTS. . . . . . . . . . . . . . . . . . . . . . . . .7
     13.1  Scope of Limitation . . . . . . . . . . . . . . . . . . . . . . . . . . .7
     13.2  Basic Rule. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8
     13.3  Reduction of Payments . . . . . . . . . . . . . . . . . . . . . . . . . .8
     13.4  Overpayments and Underpayments. . . . . . . . . . . . . . . . . . . . . .8
     13.5  Related Corporations. . . . . . . . . . . . . . . . . . . . . . . . . . .9

ARTICLE 14.  FUTURE OF THE PLAN. . . . . . . . . . . . . . . . . . . . . . . . . . .9
     14.1  Term of the Plan. . . . . . . . . . . . . . . . . . . . . . . . . . . . .9
     14.2  Amendment or Termination. . . . . . . . . . . . . . . . . . . . . . . . .9

ARTICLE 15.  DEFINITIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9

ARTICLE 16.  EXECUTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
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                              DRUGABUSE SCIENCES, INC.

                             2000 STOCK INCENTIVE PLAN

       ARTICLE 1.    INTRODUCTION.

              The Plan was adopted by the Board effective as of the date of
the Company's initial public offering.  The purpose of the Plan is to promote
the long-term success of the Company and the creation of shareholder value by
(a) encouraging Employees, Outside Directors and Consultants to focus on
critical long-range objectives, (b) encouraging the attraction and retention
of Employees, Outside Directors and Consultants with exceptional
qualifications and (c) linking Employees, Outside Directors and Consultants
directly to shareholder interests through increased stock ownership.  The
Plan seeks to achieve this purpose by providing for Awards in the form of
Restricted Shares or Options (which may constitute incentive stock options or
nonstatutory stock options).

              The Plan shall be governed by, and construed in accordance
with, the laws of the State of California (except their choice-of-law
provisions).

       ARTICLE 2.    ADMINISTRATION.

              2.1    COMMITTEE COMPOSITION.  The Plan shall be administered
by the Committee.  The Committee shall consist exclusively of two or more
directors of the Company, who shall be appointed by the Board.  In addition,
the composition of the Committee shall satisfy:

                     (a)    Such requirements as the Securities and
       Exchange Commission may establish for administrators acting under
       plans intended to qualify for exemption under Rule 16b-3 (or its
       successor) under the Exchange Act; and

                     (b)    Such requirements as the Internal Revenue
       Service may establish for outside directors acting under plans
       intended to qualify for exemption under section 162(m)(4)(C) of
       the Code.

              2.2    COMMITTEE RESPONSIBILITIES.  The Committee shall (a)
select the Employees, Outside Directors and Consultants who are to receive
Awards under the Plan, (b) determine the type, number, vesting requirements
and other features and conditions of such Awards, (c) interpret the Plan and
(d) make all other decisions relating to the operation of the Plan.  The
Committee may adopt such rules or guidelines as it deems appropriate to
implement the Plan.  The Committee's determinations under the Plan shall be
final and binding on all persons.

              2.3    COMMITTEE FOR NON-OFFICER GRANTS.  The Board may also
appoint a secondary committee of the Board, which shall be composed of two or
more directors of the

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Company who need not satisfy the requirements of Section 2.1.  Such secondary
committee may administer the Plan with respect to Employees and Consultants
who are not considered officers or directors of the Company under section 16
of the Exchange Act, may grant Awards under the Plan to such Employees and
Consultants and may determine all features and conditions of such Awards.
Within the limitations of this Section 2.3, any reference in the Plan to the
Committee shall include such secondary committee.

       ARTICLE 3.    SHARES AVAILABLE FOR GRANTS.

              3.1    BASIC LIMITATION.  The aggregate number of Options and
Restricted Shares awarded under the Plan shall not exceed (a) 750,000 plus
(b) the aggregate number of Common Shares remaining available for grants
under all Predecessor Plans on the date of the Company's initial public
offering plus (c) the additional Common Shares described in Sections 3.2 and
3.3.  No additional grants shall be made under the Predecessor Plans after
the date of the Company's initial public offering.  The limitations of this
Section 3.1 and Section 3.2 shall be subject to adjustment pursuant to
Article 8.

              3.2    ANNUAL INCREASE IN SHARES.  As of January 1 of each
year, commencing with the year 2001, the aggregate number of Options and
Restricted Shares that may be awarded under the Plan shall automatically
increase by a number equal to the lesser of (a) 6% of the total number of
Common Shares then outstanding or (b) 2,000,000.

              3.3    ADDITIONAL SHARES.  If Options granted under this Plan
or a Predecessor Plan are forfeited or terminate for any other reason before
being exercised, then the corresponding Common Shares shall again become
available for the grant of Options or Restricted Shares under this Plan.  If
Common Shares issued upon the exercise of Options granted under this Plan or
a Predecessor Plan are forfeited, then such Common Shares shall again become
available for the grant of NSOs and Restricted Shares under this Plan.  If
Restricted Shares issued under this Plan or a Predecessor Plan are forfeited,
then the corresponding Common Shares shall again become available for the
grant of NSOs and Restricted Shares under this Plan.  The aggregate number of
Common Shares that may be issued under the Plan upon the exercise of ISOs
shall not be increased when Restricted Shares or other Common Shares are
forfeited.

       ARTICLE 4.    ELIGIBILITY.

              4.1    NONSTATUTORY STOCK OPTIONS AND RESTRICTED SHARES.  Only
Employees, Outside Directors and Consultants shall be eligible for the grant
of NSOs and Restricted Shares.

              4.2    INCENTIVE STOCK OPTIONS.  Only Employees who are
common-law employees of the Company, a Parent or a Subsidiary shall be
eligible for the grant of ISOs.  In addition, an Employee who owns more than
10% of the total combined voting power of all classes of outstanding stock of
the Company or any of its Parents or Subsidiaries shall not be eligible for
the grant of an ISO unless the requirements set forth in section 422(c)(6) of
the Code are satisfied.

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       ARTICLE 5.    OPTIONS.

              5.1    STOCK OPTION AGREEMENT.  Each grant of an Option under
the Plan shall be evidenced by a Stock Option Agreement between the Optionee
and the Company.  Such Option shall be subject to all applicable terms of the
Plan and may be subject to any other terms that are not inconsistent with the
Plan.  The provisions of the various Stock Option Agreements entered into
under the Plan need not be identical.  Options may be granted in
consideration of a reduction in the Optionee's other compensation.  A Stock
Option Agreement may provide that a new Option will be granted automatically
to the Optionee when he or she exercises a prior Option and pays the Exercise
Price in the form described in Section 6.2.

              5.2    NUMBER OF SHARES.  Each Stock Option Agreement shall
specify the number of Common Shares subject to the Option and shall provide
for the adjustment of such number in accordance with Article 8.  Options
granted to any Optionee in a single fiscal year of the Company shall not
cover more than 1,000,000 Common Shares, except that Options granted to a new
Employee in the fiscal year of the Company in which his or her service as an
Employee first commences shall not cover more than 2,000,000 Common Shares.
The limitations set forth in the preceding sentence shall be subject to
adjustment in accordance with Article 8.

              5.3    EXERCISE PRICE.  Each Stock Option Agreement shall
specify the Exercise Price; provided that the Exercise Price under an ISO
shall in no event be less than 100% of the Fair Market Value of a Common
Share on the date of grant, and the Exercise Price under an NSO shall in no
event be less than 50% of the Fair Market Value of a Common Share on the date
of grant.  In the case of an NSO, a Stock Option Agreement may specify an
Exercise Price that varies in accordance with a predetermined formula while
the NSO is outstanding.

              5.4    EXERCISABILITY AND TERM.  Each Stock Option Agreement
shall specify the date or event when all or any installment of the Option is
to become exercisable.  The Stock Option Agreement shall also specify the
term of the Option; provided that the term of an ISO shall in no event exceed
10 years from the date of grant.  A Stock Option Agreement may provide for
accelerated exercisability in the event of the Optionee's death, disability
or retirement or other events and may provide for expiration prior to the end
of its term in the event of the termination of the Optionee's service.

              5.5    EFFECT OF CHANGE IN CONTROL.  The Committee may
determine, at the time of granting an Option or thereafter, that such Option
shall become exercisable as to all or part of the Common Shares subject to
such Option in the event that a Change in Control occurs with respect to the
Company or in the event that the Optionee is subject to an Involuntary
Termination after a Change in Control.  However, in the case of an ISO, the
acceleration of exercisability shall not occur without the Optionee's written
consent.  In addition, acceleration of exercisability may be required under
Section 8.3.

              5.6    MODIFICATION OR ASSUMPTION OF OPTIONS.  Within the
limitations of the Plan, the Committee may modify, extend or assume
outstanding options or may accept the cancellation of outstanding options
(whether granted by the Company or by another issuer) in return for the grant
of new options for the same or a different number of shares and at the same
or a different exercise price.  The foregoing notwithstanding, no
modification of an Option shall,

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without the consent of the Optionee, alter or impair his or her rights or
obligations under such Option.

              5.7    BUYOUT PROVISIONS.  The Committee may at any time (a)
offer to buy out for a payment in cash or cash equivalents an Option
previously granted or (b) authorize an Optionee to elect to cash out an
Option previously granted, in either case at such time and based upon such
terms and conditions as the Committee shall establish.

       ARTICLE 6.    PAYMENT FOR OPTION SHARES.

              6.1    GENERAL RULE.  The entire Exercise Price of Common
Shares issued upon exercise of Options shall be payable in cash or cash
equivalents at the time when such Common Shares are purchased, except as
follows:

                     (a)    In the case of an ISO granted under the Plan,
       payment shall be made only pursuant to the express provisions of
       the applicable Stock Option Agreement.  The Stock Option Agreement
       may specify that payment may be made in any form(s) described in
       this Article 6.

                     (b)    In the case of an NSO, the Committee may at
       any time accept payment in any form(s) described in this
       Article 6.

              6.2    SURRENDER OF STOCK.  To the extent that this Section 6.2
is applicable, all or any part of the Exercise Price may be paid by
surrendering, or attesting to the ownership of, Common Shares that are
already owned by the Optionee.  Such Common Shares shall be valued at their
Fair Market Value on the date when the new Common Shares are purchased under
the Plan.  The Optionee shall not surrender, or attest to the ownership of,
Common Shares in payment of the Exercise Price if such action would cause the
Company to recognize compensation expense (or additional compensation
expense) with respect to the Option for financial reporting purposes.

              6.3    EXERCISE/SALE.  To the extent that this Section 6.3 is
applicable, all or any part of the Exercise Price and any withholding taxes
may be paid by delivering (on a form prescribed by the Company) an
irrevocable direction to a securities broker approved by the Company to sell
all or part of the Common Shares being purchased under the Plan and to
deliver all or part of the sales proceeds to the Company.

              6.4    EXERCISE/PLEDGE.  To the extent that this Section 6.4 is
applicable, all or any part of the Exercise Price and any withholding taxes
may be paid by delivering (on a form prescribed by the Company) an
irrevocable direction to pledge all or part of the Common Shares being
purchased under the Plan to a securities broker or lender approved by the
Company, as security for a loan, and to deliver all or part of the loan
proceeds to the Company.

              6.5    PROMISSORY NOTE.  To the extent that this Section 6.5 is
applicable, all or any part of the Exercise Price and any withholding taxes
may be paid by delivering (on a form prescribed by the Company) a
full-recourse promissory note.

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              6.6    OTHER FORMS OF PAYMENT.  To the extent that this Section
6.6 is applicable, all or any part of the Exercise Price and any withholding
taxes may be paid in any other form that is consistent with applicable laws,
regulations and rules.

       ARTICLE 7.    RESTRICTED SHARES.

              7.1    RESTRICTED STOCK AGREEMENT.  Each grant of Restricted
Shares under the Plan shall be evidenced by a Restricted Stock Agreement
between the recipient and the Company.  Such Restricted Shares shall be
subject to all applicable terms of the Plan and may be subject to any other
terms that are not inconsistent with the Plan.  The provisions of the various
Restricted Stock Agreements entered into under the Plan need not be identical.

              7.2    PAYMENT FOR AWARDS.  Restricted Shares may be sold or
awarded under the Plan for such consideration as the Committee may determine,
including (without limitation) cash, cash equivalents, full-recourse
promissory notes and services rendered.

              7.3    VESTING CONDITIONS.  Each Award of Restricted Shares may
or may not be subject to vesting.  Vesting shall occur, in full or in
installments, upon satisfaction of the conditions specified in the Restricted
Stock Agreement. A Restricted Stock Agreement may provide for accelerated
vesting in the event of the Participant's death, disability or retirement or
other events.  The Committee may determine, at the time of granting
Restricted Shares or thereafter, that all or part of such Restricted Shares
shall become vested in the event that a Change in Control occurs with respect
to the Company or in the event that the Participant is subject to an
Involuntary Termination after a Change in Control.

              7.4    VOTING AND DIVIDEND RIGHTS.  The holders of Restricted
Shares awarded under the Plan shall have the same voting, dividend and other
rights as the Company's other shareholders.  A Restricted Stock Agreement,
however, may require that the holders of Restricted Shares invest any cash
dividends received in additional Restricted Shares.  Such additional
Restricted Shares shall be subject to the same conditions and restrictions as
the Award with respect to which the dividends were paid.

       ARTICLE 8.    PROTECTION AGAINST DILUTION.

              8.1    ADJUSTMENTS.  In the event of a subdivision of the
outstanding Common Shares, a declaration of a dividend payable in Common
Shares or a combination or consolidation of the outstanding Common Shares (by
reclassification or otherwise) into a lesser number of Common Shares,
corresponding adjustments shall automatically be made in each of the
following:

                     (a)    The number of Options and Restricted Shares
       available for future Awards under Article 3;

                     (b)    The limitations set forth in Section 5.2;

                     (c)    The number of Common Shares covered by each
       outstanding Option; or

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                     (d)    The Exercise Price under each outstanding
       Option.

In the event of a declaration of an extraordinary dividend payable in a form
other than Common Shares in an amount that has a material effect on the price
of Common Shares, a recapitalization, a spin-off or a similar occurrence, the
Committee shall make such adjustments as it, in its sole discretion, deems
appropriate in one or more of the foregoing.  Except as provided in this
Article 8, a Participant shall have no rights by reason of any issuance by
the Company of stock of any class or securities convertible into stock of any
class, any subdivision or consolidation of shares of stock of any class, the
payment of any stock dividend or any other increase or decrease in the number
of shares of stock of any class.

              8.2    DISSOLUTION OR LIQUIDATION.  To the extent not
previously exercised, Options shall terminate immediately prior to the
dissolution or liquidation of the Company.

              8.3    REORGANIZATIONS.  In the event that the Company is a
party to a merger or other reorganization, outstanding Options and Restricted
Shares shall be subject to the agreement of merger or reorganization.  Such
agreement shall provide for (a) the continuation of the outstanding Awards by
the Company, if the Company is a surviving corporation, (b) the assumption of
the outstanding Awards by the surviving corporation or its parent or
subsidiary, (c) the substitution by the surviving corporation or its parent
or subsidiary of its own awards for the outstanding Awards, (d) full
exercisability or vesting and accelerated expiration of the outstanding
Awards or (e) settlement of the full value of the outstanding Awards in cash
or cash equivalents followed by cancellation of such Awards.

       ARTICLE 9.    DEFERRAL OF DELIVERY OF SHARES.

              The Committee (in its sole discretion) may permit or require an
Optionee to have Common Shares that otherwise would be delivered to such
Optionee as a result of the exercise of an Option converted into amounts
credited to a deferred compensation account established for such Optionee by
the Committee as an entry on the Company's books.  Such amounts shall be
determined by reference to the Fair Market Value of such Common Shares as of
the date when they otherwise would have been delivered to such Optionee.  A
deferred compensation account established under this Article 9 may be
credited with interest or other forms of investment return, as determined by
the Committee. An Optionee for whom such an account is established shall have
no rights other than those of a general creditor of the Company.  Such an
account shall represent an unfunded and unsecured obligation of the Company
and shall be subject to the terms and conditions of the applicable agreement
between such Optionee and the Company.  If the conversion of Options is
permitted or required, the Committee (in its sole discretion) may establish
rules, procedures and forms pertaining to such conversion, including (without
limitation) the settlement of deferred compensation accounts established
under this Article 9.

       ARTICLE 10.   AWARDS UNDER OTHER PLANS.

              The Company may grant awards under other plans or programs.
Such awards may be settled in the form of Common Shares issued under this
Plan.  Such Common Shares shall be treated for all purposes under the Plan
like Restricted Shares and shall, when issued, reduce the number of Common
Shares available under Article 3.

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       ARTICLE 11.   LIMITATION ON RIGHTS.

              11.1   RETENTION RIGHTS.  Neither the Plan nor any Award
granted under the Plan shall be deemed to give any individual a right to
remain an Employee, Outside Director or Consultant.  The Company and its
Parents, Subsidiaries and Affiliates reserve the right to terminate the
service of any Employee, Outside Director or Consultant at any time, with or
without cause, subject to applicable laws, the Company's certificate of
incorporation and by-laws and a written employment agreement (if any).

              11.2   SHAREHOLDERS' RIGHTS.  A Participant shall have no
dividend rights, voting rights or other rights as a shareholder with respect
to any Common Shares covered by his or her Award prior to the time when a
stock certificate for such Common Shares is issued or, in the case of an
Option, the time when he or she becomes entitled to receive such Common
Shares by filing a notice of exercise and paying the Exercise Price.  No
adjustment shall be made for cash dividends or other rights for which the
record date is prior to such time, except as expressly provided in the Plan.

              11.3   REGULATORY REQUIREMENTS.  Any other provision of the
Plan notwithstanding, the obligation of the Company to issue Common Shares
under the Plan shall be subject to all applicable laws, rules and regulations
and such approval by any regulatory body as may be required.  The Company
reserves the right to restrict, in whole or in part, the delivery of Common
Shares pursuant to any Award prior to the satisfaction of all legal
requirements relating to the issuance of such Common Shares, to their
registration, qualification or listing or to an exemption from registration,
qualification or listing.

       ARTICLE 12.   WITHHOLDING TAXES.

              12.1   GENERAL.  To the extent required by applicable federal,
state, local or foreign law, a Participant or his or her successor shall make
arrangements satisfactory to the Company for the satisfaction of any
withholding tax obligations that arise in connection with the Plan.  The
Company shall not be required to issue any Common Shares or make any cash
payment under the Plan until such obligations are satisfied.

              12.2   SHARE WITHHOLDING.  To the extent that applicable law
subjects a Participant to tax withholding obligations, the Committee may
permit such Participant to satisfy all or part of such obligations by having
the Company withhold all or a portion of any Common Shares that otherwise
would be issued to him or her or by surrendering all or a portion of any
Common Shares that he or she previously acquired.  Such Common Shares shall
be valued at their Fair Market Value on the date when they are withheld or
surrendered.

       ARTICLE 13.   LIMITATION ON PAYMENTS.

              13.1   SCOPE OF LIMITATION.  This Article 13 shall apply to an
Award only if:

                     (a)    The independent auditors most recently
       selected by the Board (the "Auditors") determine that the after-
       tax value of such Award to the Participant, taking into account the
       effect of all federal, state and local income

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<PAGE>

       taxes, employment taxes and excise taxes applicable to the Participant
       (including the excise tax under section 4999 of the Code), will be
       greater after the application of this Article 13 than it was before
       the application of this Article 13; or

                     (b)    The Committee, at the time of making an Award
       under the Plan or at any time thereafter, specifies in writing
       that such Award shall be subject to this Article 13 (regardless of
       the after-tax value of such Award to the Participant).

If this Article 13 applies to an Award, it shall supersede any contrary
provision of the Plan or of any Award granted under the Plan.

              13.2   BASIC RULE.  In the event that the Auditors determine
that any payment or transfer by the Company under the Plan to or for the
benefit of a Participant (a "Payment") would be nondeductible by the Company
for federal income tax purposes because of the provisions concerning "excess
parachute payments" in section 280G of the Code, then the aggregate present
value of all Payments shall be reduced (but not below zero) to the Reduced
Amount.  For purposes of this Article 13, the "Reduced Amount" shall be the
amount, expressed as a present value, which maximizes the aggregate present
value of the Payments without causing any Payment to be nondeductible by the
Company because of section 280G of the Code.

              13.3   REDUCTION OF PAYMENTS.  If the Auditors determine that
any Payment would be nondeductible by the Company because of section 280G of
the Code, then the Company shall promptly give the Participant notice to that
effect and a copy of the detailed calculation thereof and of the Reduced
Amount, and the Participant may then elect, in his or her sole discretion,
which and how much of the Payments shall be eliminated or reduced (as long as
after such election the aggregate present value of the Payments equals the
Reduced Amount) and shall advise the Company in writing of his or her
election within 10 days of receipt of notice.  If no such election is made by
the Participant within such 10-day period, then the Company may elect which
and how much of the Payments shall be eliminated or reduced (as long as after
such election the aggregate present value of the Payments equals the Reduced
Amount) and shall notify the Participant promptly of such election.  For
purposes of this Article 13, present value shall be determined in accordance
with section 280G(d)(4) of the Code. All determinations made by the Auditors
under this Article 13 shall be binding upon the Company and the Participant
and shall be made within 60 days of the date when a Payment becomes payable
or transferable.  As promptly as practicable following such determination and
the elections hereunder, the Company shall pay or transfer to or for the
benefit of the Participant such amounts as are then due to him or her under
the Plan and shall promptly pay or transfer to or for the benefit of the
Participant in the future such amounts as become due to him or her under the
Plan.

              13.4   OVERPAYMENTS AND UNDERPAYMENTS.  As a result of
uncertainty in the application of section 280G of the Code at the time of an
initial determination by the Auditors hereunder, it is possible that Payments
will have been made by the Company which should not have been made (an
"Overpayment") or that additional Payments which will not have been made by
the Company could have been made (an "Underpayment"), consistent in each case
with the calculation of the Reduced Amount hereunder.  In the event that the
Auditors, based upon the

                                        8

<PAGE>

assertion of a deficiency by the Internal Revenue Service against the Company
or the Participant which the Auditors believe has a high probability of
success, determine that an Overpayment has been made, such Overpayment shall
be treated for all purposes as a loan to the Participant which he or she
shall repay to the Company, together with interest at the applicable federal
rate provided in section 7872(f)(2) of the Code; provided, however, that no
amount shall be payable by the Participant to the Company if and to the
extent that such payment would not reduce the amount which is subject to
taxation under section 4999 of the Code.  In the event that the Auditors
determine that an Underpayment has occurred, such Underpayment shall promptly
be paid or transferred by the Company to or for the benefit of the
Participant, together with interest at the applicable federal rate provided
in section 7872(f)(2) of the Code.

              13.5   RELATED CORPORATIONS.  For purposes of this Article 13,
the term "Company" shall include affiliated corporations to the extent
determined by the Auditors in accordance with section 280G(d)(5) of the Code.

       ARTICLE 14.   FUTURE OF THE PLAN.

              14.1   TERM OF THE PLAN.  The Plan, as set forth herein, shall
become effective on the date of the Company's initial public offering.  The
Plan shall remain in effect until it is terminated under Section 14.2.

              14.2   AMENDMENT OR TERMINATION.  The Board may, at any time
and for any reason, amend or terminate the Plan.  An amendment of the Plan
shall be subject to the approval of the Company's shareholders only to the
extent required by applicable laws, regulations or rules.  The amendment or
termination of the Plan shall not affect any Award previously granted under
the Plan.  No Awards shall be granted under the Plan after the termination
thereof.  The Plan shall terminate automatically 10 years after its adoption
by the Board, unless (a) the Plan is extended by the Board and (b) the
extension is approved within 12 months by a vote of the shareholders of the
Company.

       ARTICLE 15.   DEFINITIONS.

              15.1   "AFFILIATE" means any entity other than a Subsidiary, if
the Company and/or one or more Subsidiaries own not less than 50% of such
entity.

              15.2   "AWARD" means any award of an Option or a Restricted
Share under the Plan.

              15.3   "BOARD" means the Company's Board of Directors, as
constituted from time to time.

              15.4   "CAUSE" shall mean (a) the unauthorized use or
disclosure of the confidential information or trade secrets of the Company,
which use or disclosure causes material harm to the Company, (b) conviction
of, or a plea of "guilty" or "no contest" to, a felony under the laws of the
United States or any State thereof, (c) gross negligence, (d) willful
misconduct or (e) a failure to perform assigned duties that continues after
the Participant has received written notice of such failure from the Board.
The foregoing, however, shall not be

                                        9

<PAGE>

deemed an exclusive list of all acts or omissions that the Company (or the
Parent, Subsidiary or Affiliate employing the Participant) may consider as
grounds for the discharge of the Participant without Cause.

              15.5   "CHANGE IN CONTROL" means:

                     (a)    The consummation of a merger or consolidation
       of the Company with or into another entity or any other corporate
       reorganization, if persons who were not shareholders of the
       Company immediately prior to such merger, consolidation or other
       reorganization own immediately after such merger, consolidation or
       other reorganization 50% or more of the voting power of the
       outstanding securities of each of (i) the continuing or surviving
       entity and (ii) any direct or indirect parent corporation of such
       continuing or surviving entity;

                     (b)    The sale, transfer or other disposition of
       all or substantially all of the Company's assets;

                     (c)    A change in the composition of the Board, as
       a result of which 50% or fewer of the incumbent directors are
       directors who either (i) had been directors of the Company on the
       date 24 months prior to the date of the event that may constitute
       a Change in Control (the "original directors") or (ii) were
       elected, or nominated for election, to the Board with the
       affirmative votes of at least a majority of the aggregate of the
       original directors who were still in office at the time of the
       election or nomination and the directors whose election or
       nomination was previously so approved; or

                     (d)    Any transaction as a result of which any
       person is the "beneficial owner" (as defined in Rule 13d-3 under
       the Exchange Act), directly or indirectly, of securities of the
       Company representing at least 50% of the total voting power
       represented by the Company's then outstanding voting securities.
       For purposes of this Subsection (d), the term "person" shall have
       the same meaning as when used in sections 13(d) and 14(d) of the
       Exchange Act but shall exclude (i) a trustee or other fiduciary
       holding securities under an employee benefit plan of the Company
       or of a Parent or Subsidiary and (ii) a corporation owned directly
       or indirectly by the shareholders of the Company in substantially
       the same proportions as their ownership of the common stock of the
       Company.

A transaction shall not constitute a Change in Control if its sole purpose is
to change the state of the Company's incorporation or to create a holding
company that will be owned in substantially the same proportions by the
persons who held the Company's securities immediately before such transaction.

              15.6   "CODE" means the Internal Revenue Code of 1986, as amended.

              15.7   "COMMITTEE" means a committee of the Board, as described in
Article 2.

              15.8   "COMMON SHARE" means one share of the common stock of the
Company.

                                        10

<PAGE>

              15.9   "COMPANY" means DrugAbuse Sciences, Inc., a California
corporation.

              15.10  "CONSULTANT" means a consultant or adviser who provides
bona fide services to the Company, a Parent, a Subsidiary or an Affiliate as
an independent contractor.  Service as a Consultant shall be considered
employment for all purposes of the Plan, except as provided in Section 4.2.

              15.11  "EMPLOYEE" means a common-law employee of the Company, a
Parent, a Subsidiary or an Affiliate.

              15.12  "EXCHANGE ACT" means the Securities Exchange Act of
1934, as amended.

              15.13  "EXERCISE PRICE" means the amount for which one Common
Share may be purchased upon exercise of an Option, as specified in the
applicable Stock Option Agreement.

              15.14  "FAIR MARKET VALUE" means the market price of Common
Shares, determined by the Committee in good faith on such basis as it deems
appropriate.  Whenever possible, the determination of Fair Market Value by
the Committee shall be based on the prices reported in THE WALL STREET
JOURNAL. Such determination shall be conclusive and binding on all persons.

              15.15  "INVOLUNTARY TERMINATION" means the termination of the
Participant's service by reason of:

                     (a)    The involuntary discharge of the Participant
       by the Company (or the Parent, Subsidiary or Affiliate employing
       him or her) for reasons other than Cause; or

                     (b)    The voluntary resignation of the Participant
       following (i) a material adverse change in his or her title,
       stature, authority or responsibilities with the Company (or the
       Parent, Subsidiary or Affiliate employing him or her), (ii) a
       material reduction in his or her base salary or (iii) receipt of
       notice that his or her principal workplace will be relocated by
       more than 30 miles.

              15.16  "ISO" means an incentive stock option described in
section 422(b) of the Code.

              15.17  "NSO" means a stock option not described in sections 422
or 423 of the Code.

              15.18  "OPTION" means an ISO or NSO granted under the Plan and
entitling the holder to purchase Common Shares.

              15.19  "OPTIONEE" means an individual or estate who holds an
Option.

              15.20  "OUTSIDE DIRECTOR" means a member of the Board who is
not an Employee.  Service as an Outside Director shall be considered
employment for all purposes of the Plan, except as provided in Section 4.2.

                                        11

<PAGE>

              15.21  "PARENT" means any corporation (other than the Company)
in an unbroken chain of corporations ending with the Company, if each of the
corporations other than the Company owns stock possessing 50% or more of the
total combined voting power of all classes of stock in one of the other
corporations in such chain.  A corporation that attains the status of a
Parent on a date after the adoption of the Plan shall be considered a Parent
commencing as of such date.

              15.22  "PARTICIPANT" means an individual or estate who holds an
Award.

              15.23  "PLAN" means this DrugAbuse Sciences, Inc. 2000 Stock
Incentive Plan, as amended from time to time.

              15.24  "PREDECESSOR PLAN" means the DrugAbuse Sciences, Inc.
1994 Stock Plan, the DrugAbuse Sciences, Inc. 1999 Stock Plan A or the
DrugAbuse Sciences, Inc. 1999 Stock Plan B.

              15.25  "RESTRICTED SHARE" means a Common Share awarded under
the Plan.

              15.26  "RESTRICTED STOCK AGREEMENT" means the agreement between
the Company and the recipient of a Restricted Share that contains the terms,
conditions and restrictions pertaining to such Restricted Share.

              15.27  "STOCK OPTION AGREEMENT" means the agreement between the
Company and an Optionee that contains the terms, conditions and restrictions
pertaining to his or her Option.

              15.28  "SUBSIDIARY" means any corporation (other than the
Company) in an unbroken chain of corporations beginning with the Company, if
each of the corporations other than the last corporation in the unbroken
chain owns stock possessing 50% or more of the total combined voting power of
all classes of stock in one of the other corporations in such chain.  A
corporation that attains the status of a Subsidiary on a date after the
adoption of the Plan shall be considered a Subsidiary commencing as of such
date.

                                        12

<PAGE>

       ARTICLE 16.   EXECUTION.

              To record the adoption of the Plan by the Board on January 13,
2000, the Company has caused its duly authorized officer to execute this
document in the name of the Company.

                                       DRUGABUSE SCIENCES, INC.

                                       By: _________________________________

                                       Title: ______________________________

                                        13<PAGE>

                              DRUGABUSE SCIENCES, INC.

                         2000 EMPLOYEE STOCK PURCHASE PLAN

                      (AS ADOPTED EFFECTIVE _______ __, 2000)

<PAGE>

                                  TABLE OF CONTENTS

<TABLE>
<CAPTION>
                                                                                  Page
                                                                                  ----
<S>                                                                               <C>
SECTION 1.  PURPOSE OF THE PLAN. . . . . . . . . . . . . . . . . . . . . . . . . . .1

SECTION 2.  ADMINISTRATION OF THE PLAN . . . . . . . . . . . . . . . . . . . . . . .1
     (a)  Committee Composition. . . . . . . . . . . . . . . . . . . . . . . . . . .1
     (b)  Committee Responsibilities . . . . . . . . . . . . . . . . . . . . . . . .1

SECTION 3.  ENROLLMENT AND PARTICIPATION . . . . . . . . . . . . . . . . . . . . . .1
     (a)  Offering Periods . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1
     (b)  Accumulation Periods . . . . . . . . . . . . . . . . . . . . . . . . . . .1
     (c)  Enrollment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1
     (d)  Duration of Participation. . . . . . . . . . . . . . . . . . . . . . . . .2
     (e)  Applicable Offering Period . . . . . . . . . . . . . . . . . . . . . . . .2

SECTION 4.  EMPLOYEE CONTRIBUTIONS . . . . . . . . . . . . . . . . . . . . . . . . .2
     (a)  Frequency of Payroll Deductions. . . . . . . . . . . . . . . . . . . . . .2
     (b)  Amount of Payroll Deductions . . . . . . . . . . . . . . . . . . . . . . .3
     (c)  Changing Withholding Rate. . . . . . . . . . . . . . . . . . . . . . . . .3
     (d)  Discontinuing Payroll Deductions . . . . . . . . . . . . . . . . . . . . .3
     (e)  Limit on Number of Elections . . . . . . . . . . . . . . . . . . . . . . .3

SECTION 5.  WITHDRAWAL FROM THE PLAN . . . . . . . . . . . . . . . . . . . . . . . .3
     (a)  Withdrawal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3
     (b)  Re-Enrollment After Withdrawal . . . . . . . . . . . . . . . . . . . . . .3

SECTION 6.  CHANGE IN EMPLOYMENT STATUS. . . . . . . . . . . . . . . . . . . . . . .4
     (a)  Termination of Employment. . . . . . . . . . . . . . . . . . . . . . . . .4
     (b)  Leave of Absence . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4
     (c)  Death. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4

SECTION 7.  PLAN ACCOUNTS AND PURCHASE OF SHARES . . . . . . . . . . . . . . . . . .4
     (a)  Plan Accounts. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4
     (b)  Purchase Price . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4
     (c)  Number of Shares Purchased . . . . . . . . . . . . . . . . . . . . . . . .4
     (d)  Available Shares Insufficient. . . . . . . . . . . . . . . . . . . . . . .5
     (e)  Issuance of Stock. . . . . . . . . . . . . . . . . . . . . . . . . . . . .5
     (f)  Tax Withholding. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5
     (g)  Unused Cash Balances . . . . . . . . . . . . . . . . . . . . . . . . . . .5
     (h)  Shareholder Approval . . . . . . . . . . . . . . . . . . . . . . . . . . .5

SECTION 8.  LIMITATIONS ON STOCK OWNERSHIP . . . . . . . . . . . . . . . . . . . . .6
     (a)  Five Percent Limit . . . . . . . . . . . . . . . . . . . . . . . . . . . .6
     (b)  Dollar Limit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6

</TABLE>

                                       i

<PAGE>

<TABLE>
<S>                                                                                <C>
SECTION 9.  RIGHTS NOT TRANSFERABLE. . . . . . . . . . . . . . . . . . . . . . . . .7

SECTION 10.  NO RIGHTS AS AN EMPLOYEE. . . . . . . . . . . . . . . . . . . . . . . .7

SECTION 11.  NO RIGHTS AS A SHAREHOLDER. . . . . . . . . . . . . . . . . . . . . . .7

SECTION 12.  SECURITIES LAW REQUIREMENTS.. . . . . . . . . . . . . . . . . . . . . .7

SECTION 13.  STOCK OFFERED UNDER THE PLAN. . . . . . . . . . . . . . . . . . . . . .7
     (a)  Authorized Shares. . . . . . . . . . . . . . . . . . . . . . . . . . . . .7
     (b)  Anti-Dilution Adjustments. . . . . . . . . . . . . . . . . . . . . . . . .8
     (c)  Reorganizations. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8

SECTION 14.  AMENDMENT OR DISCONTINUANCE . . . . . . . . . . . . . . . . . . . . . .8

SECTION 15.  DEFINITIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8
     (a)  Accumulation Period. . . . . . . . . . . . . . . . . . . . . . . . . . . .8
     (b)  Board. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8
     (c)  Code . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8
     (d)  Committee. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9
     (e)  Company. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9
     (f)  Compensation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9
     (g)  Corporate Reorganization . . . . . . . . . . . . . . . . . . . . . . . . .9
     (h)  Eligible Employee. . . . . . . . . . . . . . . . . . . . . . . . . . . . .9
     (i)  Exchange Act . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9
     (j)  Fair Market Value. . . . . . . . . . . . . . . . . . . . . . . . . . . . .9
     (k)  IPO . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .10
     (l)  Offering Period. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
     (m)  Participant. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
     (n)  Participating Company. . . . . . . . . . . . . . . . . . . . . . . . . . 10
     (o)  Plan . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
     (p)  Plan Account . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
     (q)  Purchase Price . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
     (r)  Stock. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
     (s)  Subsidiary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

SECTION 15.  EXECUTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

</TABLE>

                                      ii

<PAGE>

                              DRUGABUSE SCIENCES, INC.

                         2000 EMPLOYEE STOCK PURCHASE PLAN

SECTION 1.    PURPOSE OF THE PLAN.

              The Plan was adopted by the Board effective as of the date of the
IPO.  The purpose of the Plan is to provide Eligible Employees with an
opportunity to increase their proprietary interest in the success of the Company
by purchasing Stock from the Company on favorable terms and to pay for such
purchases through payroll deductions.  The Plan is intended to qualify under
section 423 of the Code.

SECTION 2.    ADMINISTRATION OF THE PLAN.

              (a)    COMMITTEE COMPOSITION.  The Plan shall be administered by
the Committee.  The Committee shall consist exclusively of two or more directors
of the Company, who shall be appointed by the Board.

              (b)    COMMITTEE RESPONSIBILITIES.  The Committee shall interpret
the Plan and make all other policy decisions relating to the operation of the
Plan.  The Committee may adopt such rules, guidelines and forms as it deems
appropriate to implement the Plan.  The Committee's determinations under the
Plan shall be final and binding on all persons.

SECTION 3.    ENROLLMENT AND PARTICIPATION.

              (a)    OFFERING PERIODS.  While the Plan is in effect, two
overlapping Offering Periods shall commence in each calendar year.  The Offering
Periods shall consist of the 24-month periods commencing on each May 1 and
November 1, except that the first Offering Period shall commence on the date of
the IPO and end on April 30, 2002.

              (b)    ACCUMULATION PERIODS.  While the Plan is in effect, two
Accumulation Periods shall commence in each calendar year.  The Accumulation
Periods shall consist of the six-month periods commencing on each May 1 and
November 1, except that the first Accumulation Period shall commence on the date
of the IPO and end on October 31, 2000.

              (c)    ENROLLMENT.  Any individual who, on the day preceding the
first day of an Offering Period, qualifies as an Eligible Employee may elect to
become a Participant in the Plan for such Offering Period by executing the
enrollment form prescribed for this purpose by the Committee.  The enrollment
form shall be filed with the Company at the prescribed location not later than
10 business days prior to the commencement of such Offering Period.

              (d)    DURATION OF PARTICIPATION.  Once enrolled in the Plan, a
Participant shall continue to participate in the Plan until he or she ceases to
be an Eligible Employee, withdraws from the Plan under Section 5(a) or reaches
the end of the Accumulation Period in which his or

<PAGE>

her employee contributions were discontinued under Section 4(d) or 8(b).  A
Participant who discontinued employee contributions under Section 4(d) or
withdrew from the Plan under Section 5(a) may again become a Participant, if
he or she then is an Eligible Employee, by following the procedure described
in Subsection (c) above.  A Participant whose employee contributions were
discontinued automatically under Section 8(b) shall automatically resume
participation at the beginning of the earliest Accumulation Period ending in
the next calendar year, if he or she then is an Eligible Employee.

              (e)    APPLICABLE OFFERING PERIOD.  For purposes of calculating
the Purchase Price under Section 7(b), the applicable Offering Period shall be
determined as follows:

              (i)    Once a Participant is enrolled in the Plan for an
       Offering Period, such Offering Period shall continue to apply to
       him or her until the earliest of (A) the end of such Offering
       Period, (B) the end of his or her participation under
       Subsection (d) above or (C) re-enrollment for a subsequent
       Offering Period under Paragraph (ii) or (iii) below.

              (ii)   In the event that the Fair Market Value of Stock on
       the last trading day before the commencement of the Offering
       Period for which the Participant is enrolled is higher than on the
       last trading day before the commencement of any subsequent
       Offering Period, the Participant shall automatically be re-enrolled for
       such subsequent Offering Period.

              (iii)  Any other provision of the Plan notwithstanding, the
       Company (at its sole discretion) may determine prior to the
       commencement of any new Offering Period that all Participants
       shall be re-enrolled for such new Offering Period.

              (iv)   When a Participant reaches the end of an Offering
       Period but his or her participation is to continue, then such
       Participant shall automatically be re-enrolled for the Offering
       Period that commences immediately after the end of the prior
       Offering Period.

SECTION 4.    EMPLOYEE CONTRIBUTIONS.

              (a)    FREQUENCY OF PAYROLL DEDUCTIONS.  A Participant may
purchase shares of Stock under the Plan solely by means of payroll deductions.
Payroll deductions, as designated by the Participant pursuant to Subsection (b)
below, shall occur on each payday during participation in the Plan.

              (b)    AMOUNT OF PAYROLL DEDUCTIONS.  An Eligible Employee shall
designate on the enrollment form the portion of his or her Compensation that he
or she elects to have withheld for the purchase of Stock.  Such portion shall be
a whole percentage of the Eligible Employee's Compensation, but not less than 1%
nor more than 15%.

              (c)    CHANGING WITHHOLDING RATE.  If a Participant wishes to
change the rate of payroll withholding, he or she may do so by filing a new
enrollment form with the Company

                                       2

<PAGE>

at the prescribed location at any time.  The new withholding rate shall be
effective as soon as reasonably practicable after such form has been received
by the Company.  The new withholding rate shall be a whole percentage of the
Eligible Employee's Compensation, but not less than 1% nor more than 15%.

              (d)    DISCONTINUING PAYROLL DEDUCTIONS.  If a Participant wishes
to discontinue employee contributions entirely, he or she may do so by filing a
new enrollment form with the Company at the prescribed location at any time.
Payroll withholding shall cease as soon as reasonably practicable after such
form has been received by the Company.  (In addition, employee contributions may
be discontinued automatically pursuant to Section 8(b).)  A Participant who has
discontinued employee contributions may resume such contributions by filing a
new enrollment form with the Company at the prescribed location.  Payroll
withholding shall resume as soon as reasonably practicable after such form has
been received by the Company.

              (e)    LIMIT ON NUMBER OF ELECTIONS.  No Participant shall make
more than two elections under Subsection (c) or (d) above during any
Accumulation Period.

SECTION 5.    WITHDRAWAL FROM THE PLAN.

              (a)    WITHDRAWAL.  A Participant may elect to withdraw from the
Plan by filing the prescribed form with the Company at the prescribed location
at any time before the last day of an Accumulation Period.  As soon as
reasonably practicable thereafter, payroll deductions shall cease and the entire
amount credited to the Participant's Plan Account shall be refunded to him or
her in cash, without interest.  No partial withdrawals shall be permitted.

              (b)    RE-ENROLLMENT AFTER WITHDRAWAL.  A former Participant who
has withdrawn from the Plan shall not be a Participant until he or she
re-enrolls in the Plan under Section 3(c).  Re-enrollment may be effective only
at the commencement of an Offering Period.

SECTION 6.    CHANGE IN EMPLOYMENT STATUS.

              (a)    TERMINATION OF EMPLOYMENT.  Termination of employment as an
Eligible Employee for any reason, including death, shall be treated as an
automatic withdrawal from the Plan under Section 5(a).  (A transfer from one
Participating Company to another shall not be treated as a termination of
employment.)

              (b)    LEAVE OF ABSENCE.  For purposes of the Plan, employment
shall not be deemed to terminate when the Participant goes on a military leave,
a sick leave or another BONA FIDE leave of absence, if the leave was approved by
the Company in writing.  Employment, however, shall be deemed to terminate 90
days after the Participant goes on a leave, unless a contract or statute
guarantees his or her right to return to work.  Employment shall be deemed to
terminate in any event when the approved leave ends, unless the Participant
immediately returns to work.

              (c)    DEATH.  In the event of the Participant's death, the amount
credited to his or her Plan Account shall be paid to a beneficiary designated by
him or her for this purpose on

                                       3

<PAGE>

the prescribed form or, if none, to the Participant's estate.  Such form
shall be valid only if it was filed with the Company at the prescribed
location before the Participant's death.

SECTION 7.    PLAN ACCOUNTS AND PURCHASE OF SHARES.

              (a)    PLAN ACCOUNTS.  The Company shall maintain a Plan Account
on its books in the name of each Participant.  Whenever an amount is deducted
from the Participant's Compensation under the Plan, such amount shall be
credited to the Participant's Plan Account.  Amounts credited to Plan Accounts
shall not be trust funds and may be commingled with the Company's general assets
and applied to general corporate purposes.  No interest shall be credited to
Plan Accounts.

              (b)    PURCHASE PRICE.  The Purchase Price for each share of Stock
purchased at the close of an Accumulation Period shall be the lower of:

              (i)    85% of the Fair Market Value of such share on the
       last trading day in such Accumulation Period; or

              (ii)   85% of the Fair Market Value of such share on the
       last trading day before the commencement of the applicable
       Offering Period (as determined under Section 3(e)) or, in the case
       of the first Offering Period under the Plan, 85% of the price at
       which one share of Stock is offered to the public in the IPO.

              (c)    NUMBER OF SHARES PURCHASED.  As of the last day of each
Accumulation Period, each Participant shall be deemed to have elected to
purchase the number of shares of Stock calculated in accordance with this
Subsection (c), unless the Participant has previously elected to withdraw from
the Plan in accordance with Section 5(a).  The amount then in the Participant's
Plan Account shall be divided by the Purchase Price, and the number of shares
that results shall be purchased from the Company with the funds in the
Participant's Plan Account.  The foregoing notwithstanding, no Participant shall
purchase more than 2,000 shares of Stock with respect to any Accumulation Period
nor more than the amounts of Stock set forth in Sections 8(b) and 13(a).  The
Committee may determine with respect to all Participants that any fractional
share, as calculated under this Subsection (c), shall be (i) rounded down to the
next lower whole share or (ii) credited as a fractional share.

              (d)    AVAILABLE SHARES INSUFFICIENT.  In the event that the
aggregate number of shares that all Participants elect to purchase during an
Accumulation Period exceeds the maximum number of shares remaining available for
issuance under Section 13(a), then the number of shares to which each
Participant is entitled shall be determined by multiplying the number of shares
available for issuance by a fraction, the numerator of which is the number of
shares that such Participant has elected to purchase and the denominator of
which is the number of shares that all Participants have elected to purchase.

              (e)    ISSUANCE OF STOCK.  Certificates representing the shares of
Stock purchased by a Participant under the Plan shall be issued to him or her as
soon as reasonably practicable after the close of the applicable Accumulation
Period, except that the Committee may determine that such shares shall be held
for each Participant's benefit by a broker designated by

                                       4

<PAGE>

the Committee (unless the Participant has elected that certificates be issued
to him or her).  Shares may be registered in the name of the Participant or
jointly in the name of the Participant and his or her spouse as joint tenants
with right of survivorship or as community property.

              (f)    TAX WITHHOLDING.  To the extent required by applicable
federal, state, local or foreign law, a Participant shall make arrangements
satisfactory to the Company for the satisfaction of any withholding tax
obligations that arise in connection with the Plan.  The Company shall not be
required to issue any shares of Stock under the Plan until such obligations are
satisfied.

              (g)    UNUSED CASH BALANCES.  An amount remaining in the
Participant's Plan Account that represents the Purchase Price for any fractional
share shall be carried over in the Participant's Plan Account to the next
Accumulation Period.  Any amount remaining in the Participant's Plan Account
that represents the Purchase Price for whole shares that could not be purchased
by reason of Subsection (c) above, Section 8(b) or Section 13(a) shall be
refunded to the Participant in cash, without interest.

              (h)    SHAREHOLDER APPROVAL.  Any other provision of the Plan
notwithstanding, no shares of Stock shall be purchased under the Plan unless and
until the Company's shareholders have approved the adoption of the Plan.

SECTION 8.    LIMITATIONS ON STOCK OWNERSHIP.

              (a)    FIVE PERCENT LIMIT.  Any other provision of the Plan
notwithstanding, no Participant shall be granted a right to purchase Stock under
the Plan if such Participant, immediately after his or her election to purchase
such Stock, would own stock possessing more than 5% of the total combined voting
power or value of all classes of stock of the Company or any parent or
Subsidiary of the Company.  For purposes of this Subsection (a), the following
rules shall apply:

              (i)    Ownership of stock shall be determined after
       applying the attribution rules of section 424(d) of the Code;

              (ii)   Each Participant shall be deemed to own any stock
       that he or she has a right or option to purchase under this or any
       other plan; and

              (iii)  Each Participant shall be deemed to have the right
       to purchase 2,000 shares of Stock under this Plan with respect to
       each Accumulation Period.

              (b)    DOLLAR LIMIT.  Any other provision of the Plan
notwithstanding, no Participant shall purchase Stock with a Fair Market Value in
excess of the following limit:

              (i)    In the case of Stock purchased during an Offering
       Period that commenced in the current calendar year, the limit
       shall be equal to (A) $25,000 minus (B) the Fair Market Value of
       the Stock that the Participant previously purchased in the current
       calendar year (under this Plan and all other employee

                                       5

<PAGE>

       stock purchase plans of the Company or any parent or Subsidiary of the
       Company).

              (ii)   In the case of Stock purchased during an Offering
       Period that commenced in the immediately preceding calendar year,
       the limit shall be equal to (A) $50,000 minus (B) the Fair Market
       Value of the Stock that the Participant previously purchased
       (under this Plan and all other employee stock purchase plans of
       the Company or any parent or Subsidiary of the Company) in the
       current calendar year and in the immediately preceding calendar
       year.

              (iii)  In the case of Stock purchased during an Offering
       Period that commenced in the second preceding calendar year, the
       limit shall be equal to (A) $75,000 minus (B) the Fair Market
       Value of the Stock that the Participant previously purchased
       (under this Plan and all other employee stock purchase plans of
       the Company or any parent or Subsidiary of the Company) in the
       current calendar year and in the two preceding calendar years.

For purposes of this Subsection (b), the Fair Market Value of Stock shall be
determined in each case as of the beginning of the Offering Period in which such
Stock is purchased.  Employee stock purchase plans not described in section 423
of the Code shall be disregarded.  If a Participant is precluded by this
Subsection (b) from purchasing additional Stock under the Plan, then his or her
employee contributions shall automatically be discontinued and shall resume at
the beginning of the earliest Accumulation Period ending in the next calendar
year (if he or she then is an Eligible Employee).

SECTION 9.    RIGHTS NOT TRANSFERABLE.

              The rights of any Participant under the Plan, or any Participant's
interest in any Stock or moneys to which he or she may be entitled under the
Plan, shall not be transferable by voluntary or involuntary assignment or by
operation of law, or in any other manner other than by beneficiary designation
or the laws of descent and distribution.  If a Participant in any manner
attempts to transfer, assign or otherwise encumber his or her rights or interest
under the Plan, other than by beneficiary designation or the laws of descent and
distribution, then such act shall be treated as an election by the Participant
to withdraw from the Plan under Section 5(a).

SECTION 10.   NO RIGHTS AS AN EMPLOYEE.

              Nothing in the Plan or in any right granted under the Plan shall
confer upon the Participant any right to continue in the employ of a
Participating Company for any period of specific duration or interfere with or
otherwise restrict in any way the rights of the Participating Companies or of
the Participant, which rights are hereby expressly reserved by each, to
terminate his or her employment at any time and for any reason, with or without
cause.

                                       6

<PAGE>

SECTION 11.   NO RIGHTS AS A SHAREHOLDER.

              A Participant shall have no rights as a shareholder with respect
to any shares of Stock that he or she may have a right to purchase under the
Plan until such shares have been purchased on the last day of the applicable
Accumulation Period.

SECTION 12.   SECURITIES LAW REQUIREMENTS.

              Shares of Stock shall not be issued under the Plan unless the
issuance and delivery of such shares comply with (or are exempt from) all
applicable requirements of law, including (without limitation) the Securities
Act of 1933, as amended, the rules and regulations promulgated thereunder, state
securities laws and regulations, and the regulations of any stock exchange or
other securities market on which the Company's securities may then be traded.

SECTION 13.   STOCK OFFERED UNDER THE PLAN.

              (a)    AUTHORIZED SHARES.  The number of shares of Stock available
for purchase under the Plan shall be 375,000 (subject to adjustment pursuant to
this Section 13).  On May 1 of each year, commencing with May 1, 2001, the
aggregate number of shares of Stock available for purchase during the life of
the Plan shall automatically be increased by the number of shares necessary to
cause the number of shares then available for purchase to be restored to 375,000
(subject to adjustment pursuant to this Section 13).

              (b)    ANTI-DILUTION ADJUSTMENTS.  The aggregate number of shares
of Stock offered under the Plan, the 2,000-share limitation described in
Section 7(c) and the price of shares that any Participant has elected to
purchase shall be adjusted proportionately by the Committee for any increase or
decrease in the number of outstanding shares of Stock resulting from a
subdivision or consolidation of shares or the payment of a stock dividend, any
other increase or decrease in such shares effected without receipt or payment of
consideration by the Company, the distribution of the shares of a Subsidiary to
the Company's shareholders or a similar event.

              (c)    REORGANIZATIONS.  Any other provision of the Plan
notwithstanding, immediately prior to the effective time of a Corporate
Reorganization, the Offering Period and Accumulation Period then in progress
shall terminate and shares shall be purchased pursuant to Section 7, unless the
Plan is continued or assumed by the surviving corporation or its parent
corporation.  The Plan shall in no event be construed to restrict in any way the
Company's right to undertake a dissolution, liquidation, merger, consolidation
or other reorganization.

SECTION 14.   AMENDMENT OR DISCONTINUANCE.

              The Board shall have the right to amend, suspend or terminate the
Plan at any time and without notice.  Except as provided in Section 13, any
increase in the aggregate number of shares of Stock to be issued under the Plan
shall be subject to approval by a vote of the shareholders of the Company.  In
addition, any other amendment of the Plan shall be subject to approval by a vote
of the shareholders of the Company to the extent required by an applicable

                                       7

<PAGE>

law or regulation.  The Plan shall terminate automatically 10 years after its
adoption by the Board, unless (a) the Plan is extended by the Board and (b)
the extension is approved within 12 months by a vote of the shareholders of
the Company.

SECTION 15.   DEFINITIONS.

              (a)    "ACCUMULATION PERIOD" means a six-month period during which
contributions may be made toward the purchase of Stock under the Plan, as
determined pursuant to Section 3(b).

              (b)    "BOARD" means the Board of Directors of the Company, as
constituted from time to time.

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

              (d)    "COMMITTEE" means a committee of the Board, as described in
Section 2.

              (e)    "COMPANY" means DrugAbuse Sciences, Inc., a California
corporation.

              (f)    "COMPENSATION" means (i) salaries and commissions paid in
cash to a Participant by a Participating Company plus (ii) any pre-tax
contributions made by the Participant under section 401(k) or 125 of the Code.
"Compensation" shall exclude bonuses, incentive compensation (other than
commissions), overtime pay, shift premiums, all non-cash items, moving or
relocation allowances, cost-of-living equalization payments, car allowances,
tuition reimbursements, imputed income attributable to cars or life insurance,
severance pay, fringe benefits, contributions or benefits received under
employee benefit plans, income attributable to the exercise of stock options,
and similar items.  The Committee shall determine whether a particular item is
included in Compensation.

              (g)    "CORPORATE REORGANIZATION" means:

              (i)    The consummation of a merger or consolidation of the
       Company with or into another entity or any other corporate
       reorganization; or

              (ii)   The sale, transfer or other disposition of all or
       substantially all of the Company's assets or the complete
       liquidation or dissolution of the Company.

              (h)    "ELIGIBLE EMPLOYEE" means any employee of a Participating
Company whose customary employment is for more than five months per calendar
year and for more than 20 hours per week.  The foregoing notwithstanding, an
individual shall not be considered an Eligible Employee if his or her
participation in the Plan is prohibited by the law of any country which has
jurisdiction over him or her or if he or she is subject to a collective
bargaining agreement that does not provide for participation in the Plan.

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

              (j)    "FAIR MARKET VALUE" means the market price of Stock,
determined by the Committee as follows:

                                       8

<PAGE>

              (i)    If the Stock was traded on The Nasdaq National
       Market on the date in question, then the Fair Market Value shall
       be equal to the last-transaction price quoted for such date by The
       Nasdaq National Market;

              (ii)   If the Stock was traded on a stock exchange on the
       date in question, then the Fair Market Value shall be equal to the
       closing price reported by the applicable composite transactions
       report for such date; or

              (iii)  If none of the foregoing provisions is applicable,
       then the Fair Market Value shall be determined by the Committee in
       good faith on such basis as it deems appropriate.

Whenever possible, the determination of Fair Market Value by the Committee shall
be based on the prices reported in THE WALL STREET JOURNAL or as reported
directly to the Company by Nasdaq or a stock exchange.  Such determination shall
be conclusive and binding on all persons.

              (k)    "IPO" means the initial offering of Stock to the public
pursuant to a registration statement filed by the Company with the Securities
and Exchange Commission.

              (l)    "OFFERING PERIOD" means a 24-month period with respect to
which the right to purchase Stock may be granted under the Plan, as determined
pursuant to Section 3(a).

              (m)    "PARTICIPANT" means an Eligible Employee who elects to
participate in the Plan, as provided in Section 3(c).

              (n)    "PARTICIPATING COMPANY" means (i) the Company and (ii) each
present or future Subsidiary designated by the Committee as a Participating
Company.

              (o)    "PLAN" means this DrugAbuse Sciences, Inc. 2000 Employee
Stock Purchase Plan, as it may be amended from time to time.

              (p)    "PLAN ACCOUNT" means the account established for each
Participant pursuant to Section 7(a).

              (q)    "PURCHASE PRICE" means the price at which Participants may
purchase Stock under the Plan, as determined pursuant to Section 7(b).

              (r)    "STOCK" means the Common Stock of the Company.

              (s)    "SUBSIDIARY" means any corporation (other than the Company)
in an unbroken chain of corporations beginning with the Company, if each of the
corporations other than the last corporation in the unbroken chain owns stock
possessing 50% or more of the total combined voting power of all classes of
stock in one of the other corporations in such chain.

                                       9

<PAGE>

SECTION 16.   EXECUTION.

              To record the adoption of the Plan by the Board on January 13,
2000, the Company has caused its duly authorized officer to execute this
document in the name of the Company.

                              DRUGABUSE SCIENCES, INC.

                              By:___________________________

                              Title:________________________

                                     10

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