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                              DRUGABUSE SCIENCES, INC.

                         2000 EMPLOYEE STOCK PURCHASE PLAN

                      (AS ADOPTED EFFECTIVE _______ __, 2000)


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                                  TABLE OF CONTENTS

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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

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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

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                              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


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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

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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

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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

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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

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       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.

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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


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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:

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<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.

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<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:________________________


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