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                           ACADIA PHARMACEUTICALS INC.
                        2000 EMPLOYEE STOCK PURCHASE PLAN

               ADOPTED BY THE BOARD OF DIRECTORS DECEMBER 20, 2000
                  APPROVED BY STOCKHOLDERS ____________, 200___


1.       PURPOSE.

         (a) The purpose of the Plan is to provide a means by which Employees of
the Company and certain designated Related Corporations may be given an
opportunity to purchase shares of the Common Stock of the Company.

         (b) The Company, by means of the Plan, seeks to retain the services of
such Employees, to secure and retain the services of new Employees and to
provide incentives for such persons to exert maximum efforts for the success of
the Company and its Related Corporations.

         (c) The Company intends that the Purchase Rights granted under the Plan
be considered options issued under an Employee Stock Purchase Plan.

2.       DEFINITIONS.

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

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

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

         (d) "COMMITTEE" means a committee appointed by the Board in accordance
with Section 3(c) of the Plan.

         (e) "COMMON STOCK" means the Common Stock of the Company.

         (f) "COMPANY" means ACADIA Pharmaceuticals Inc., a Delaware
corporation.

         (g) "CORPORATE TRANSACTION" means the occurrence of any one or more of
the following:

                  (i) a sale, exchange or other disposition of all or
substantially all of the assets of the Company;

                  (ii) a sale, exchange or other disposition of all or
substantially all of the outstanding securities of the Company;


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                  (iii) a merger or consolidation following which the Company is
not the surviving corporation;

                  (iv) a merger following which the Company is the surviving
corporation but the shares of Common Stock outstanding immediately preceding the
merger are converted by virtue of the merger into other property, whether in the
form of securities, cash or otherwise; or

                  (v) any other transaction described as a "corporate
transaction" in Treasury Regulations Section 1.425-1(a)(1)(ii), as amended from
time to time.

         (h) "DIRECTOR" means a member of the Board.

         (i) "ELIGIBLE EMPLOYEE" means an Employee who meets the requirements
set forth in the Offering for eligibility to participate in the Offering,
provided that such Employee also meets the requirements for eligibility to
participate set forth in the Plan.

         (j) "EMPLOYEE" means any person, including Officers and Directors, who
is employed for purposes of Section 423(b)(4) of the Code by the Company or a
Related Corporation. Neither service as a Director nor payment of a director's
fee shall be sufficient to make an individual an Employee of the Company or a
Related Corporation.

         (k) "EMPLOYEE STOCK PURCHASE PLAN" means a plan that grants Purchase
Rights intended to be options issued under an "employee stock purchase plan," as
that term is defined in Section 423(b) of the Code.

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

         (m) "FAIR MARKET VALUE" means the value of a security, as determined in
good faith by the Board. If the security is listed on any established stock
exchange or traded on the Nasdaq National Market or the Nasdaq SmallCap Market,
the Fair Market Value of the security, unless otherwise determined by the Board,
shall be the closing sales price (rounded up where necessary to the nearest
whole cent) for such security (or the closing bid, if no sales were reported) as
quoted on such exchange or market (or the exchange or market with the greatest
volume of trading in the relevant security of the Company) on the Trading Day
prior to the relevant determination date, as reported in THE WALL STREET JOURNAL
or such other source as the Board deems reliable.

         (n) "OFFERING" means the grant of Purchase Rights to purchase shares of
Common Stock under the Plan to Eligible Employees.

         (o) "OFFERING DATE" means a date selected by the Board for an Offering
to commence.

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


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         (q) "PARTICIPANT" means an Eligible Employee who holds an outstanding
Purchase Right granted pursuant to the Plan.

         (r) "PLAN" means this ACADIA Pharmaceuticals Inc. 2000 Employee Stock
Purchase Plan.

         (s) "PURCHASE DATE" means one or more dates during an Offering
established by the Board on which Purchase Rights granted under the Plan shall
be exercised and as of which purchases of shares of Common Stock shall be
carried out in accordance with such Offering.

         (t) "PURCHASE PERIOD" means a period of time specified within an
Offering beginning on the Offering Date or on the next day following a Purchase
Date within an Offering and ending on a Purchase Date, at the end of which there
shall be purchased shares of Common Stock on behalf of Participants. An Offering
may consist of one or more Purchase Periods.

         (u) "PURCHASE RIGHT" means an option to purchase shares of Common Stock
granted pursuant to the Plan.

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

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

         (x) "TRADING DAY" means any day the exchange(s) or market(s) on which
shares of Common Stock are listed, whether it be any established stock exchange,
the Nasdaq National Market, the Nasdaq SmallCap Market or otherwise, is open for
trading.

3.       ADMINISTRATION.

         (a) The Board shall administer the Plan unless and until the Board
delegates administration to a Committee, as provided in Section 3(c). Whether or
not the Board has delegated administration, the Board shall have the final power
to determine all questions of policy and expediency that may arise in the
administration of the Plan.

         (b) The Board (or the Committee) shall have the power, subject to, and
within the limitations of, the express provisions of the Plan:

                  (i) To determine when and how Purchase Rights to purchase
shares of Common Stock shall be granted and the provisions of each Offering of
such Purchase Rights (which need not be identical).

                  (ii) To designate from time to time which Related Corporations
of the Company shall be eligible to participate in the Plan.

                  (iii) To construe and interpret the Plan and Purchase Rights
granted under the Plan, and to establish, amend and revoke rules and regulations
for the administration of the Plan.


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The Board, in the exercise of this power, may correct any defect, omission or
inconsistency in the Plan, in a manner and to the extent it shall deem necessary
or expedient to make the Plan fully effective.

                  (iv) To amend the Plan as provided in Section 15.

                  (v) Generally, to exercise such powers and to perform such
acts as it deems necessary or expedient to promote the best interests of the
Company and its Related Corporations and to carry out the intent that the Plan
be treated as an Employee Stock Purchase Plan.

         (c) The Board may delegate administration of the Plan to a Committee of
the Board composed of one (1) or more members of the Board. If administration is
delegated to a Committee, the Committee shall have, in connection with the
administration of the Plan, the powers theretofore possessed by the Board,
subject, however, to such resolutions, not inconsistent with the provisions of
the Plan, as may be adopted from time to time by the Board. The Board may
abolish the Committee at any time and revest in the Board the administration of
the Plan. If administration is delegated to a Committee, references to the Board
in this Plan and in the Offering document shall thereafter be deemed to be to
the Board or the Committee, as the case may be.

4.       SHARES OF COMMON STOCK SUBJECT TO THE PLAN.

         (a) Subject to the provisions of Section 14 relating to adjustments
upon changes in stock, the shares of Common Stock that may be sold pursuant to
Purchase Rights granted under the Plan shall not exceed in the aggregate one
hundred fifty thousand (150,000) shares of Common Stock, plus an annual increase
to be added on the day of each Annual Meeting beginning in 2002 equal to the
least of the following amounts: (i) one percent (1%) of the Company's
outstanding shares on the record date for the Annual Meeting; (ii) two hundred
fifty thousand (250,000) shares of Common Stock; or (iii) such number of shares
of Common Stock as determined by the Board, which number shall be less than each
of (i) and (ii). If any Purchase Right granted under the Plan shall for any
reason terminate without having been exercised, the shares not purchased under
such Purchase Right shall again become available for issuance under the Plan.

         (b) The shares of Common Stock subject to the Plan may be unissued
shares or shares that have been bought on the open market at prevailing market
prices or otherwise.

5.       GRANT OF PURCHASE RIGHTS; OFFERING.

         (a) The Board may from time to time grant or provide for the grant of
Purchase Rights to purchase shares of Common Stock under the Plan to Eligible
Employees in an Offering (consisting of one or more Purchase Periods) on an
Offering Date or Offering Dates selected by the Board. Each Offering shall be in
such form and shall contain such terms and conditions as the Board shall deem
appropriate, which shall comply with the requirement of Section 423(b)(5) of the
Code that all Employees granted Purchase Rights to purchase shares of Common
Stock under the Plan shall have the same rights and privileges. The terms and
conditions of an


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Offering shall be incorporated by reference into the Plan and treated as part of
the Plan. The provisions of separate Offerings need not be identical, but each
Offering shall include (through incorporation of the provisions of this Plan by
reference in the document comprising the Offering or otherwise) the period
during which the Offering shall be effective, which period shall not exceed
twenty-seven (27) months beginning with the Offering Date, and the substance of
the provisions contained in Sections 6 through 9, inclusive; provided, however,
that each Offering, as so incorporated into the Plan, shall constitute a
separate plan for purposes of Section 423(b) of the Code.

         (b) If a Participant has more than one Purchase Right outstanding under
the Plan, unless he or she otherwise indicates in agreements or notices
delivered hereunder: (i) each agreement or notice delivered by that Participant
shall be deemed to apply to all of his or her Purchase Rights under the Plan,
and (ii) a Purchase Right with a lower exercise price (or an earlier-granted
Purchase Right, if different Purchase Rights have identical exercise prices)
shall be exercised to the fullest possible extent before a Purchase Right with a
higher exercise price (or a later-granted Purchase Right, if different Purchase
Rights have identical exercise prices) shall be exercised.

6.       ELIGIBILITY.

         (a) Purchase Rights may be granted only to Employees of the Company or,
as the Board may designate as provided in Section 3(b), to Employees of a
Related Corporation. Except as provided in Section 6(b), an Employee shall not
be eligible to be granted Purchase Rights under the Plan unless, on the Offering
Date, such Employee has been in the employ of the Company or the Related
Corporation, as the case may be, for such continuous period preceding such
Offering Date as the Board may require, but in no event shall the required
period of continuous employment be greater than two (2) years. In addition, the
Board may provide that no Employee shall be eligible to be granted Purchase
Rights under the Plan unless, on the Offering Date, such Employee's customary
employment with the Company or the Related Corporation is more than twenty (20)
hours per week and more than five (5) months per calendar year.

         (b) The Board may provide that each person who, during the course of an
Offering, first becomes an Eligible Employee shall, on a date or dates specified
in the Offering which coincides with the day on which such person becomes an
Eligible Employee or which occurs thereafter, receive a Purchase Right under
that Offering, which Purchase Right shall thereafter be deemed to be a part of
that Offering. Such Purchase Right shall have the same characteristics as any
Purchase Rights originally granted under that Offering, as described herein,
except that:

                  (i) the date on which such Purchase Right is granted shall be
the "Offering Date" of such Purchase Right for all purposes, including
determination of the exercise price of such Purchase Right;

                  (ii) the period of the Offering with respect to such Purchase
Right shall begin on its Offering Date and end coincident with the end of such
Offering; and


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                  (iii) the Board may provide that if such person first becomes
an Eligible Employee within a specified period of time before the end of the
Offering, he or she shall not receive any Purchase Right under that Offering.

         (c) No Employee shall be eligible for the grant of any Purchase Rights
under the Plan if, immediately after any such Purchase Rights are granted, such
Employee owns stock possessing five percent (5%) or more of the total combined
voting power or value of all classes of stock of the Company or of any Related
Corporation. For purposes of this Section 6(c), the rules of Section 424(d) of
the Code shall apply in determining the stock ownership of any Employee, and
stock which such Employee may purchase under all outstanding Purchase Rights and
options shall be treated as stock owned by such Employee.

         (d) An Eligible Employee may be granted Purchase Rights under the Plan
only if such Purchase Rights, together with any other rights granted under all
Employee Stock Purchase Plans of the Company and any Related Corporations, as
specified by Section 423(b)(8) of the Code, do not permit such Eligible
Employee's rights to purchase stock of the Company or any Related Corporation to
accrue at a rate which exceeds twenty five thousand dollars ($25,000) of Fair
Market Value of such stock (determined at the time such rights are granted) for
each calendar year in which such rights are outstanding at any time.

         (e) Officers of the Company and any designated Related Corporation, if
they are otherwise Eligible Employees, shall be eligible to participate in
Offerings under the Plan. Notwithstanding the foregoing, the Board may provide
in an Offering that Employees who are highly compensated Employees within the
meaning of Section 423(b)(4)(D) of the Code shall not be eligible to
participate.

7.       PURCHASE RIGHTS; PURCHASE PRICE.

         (a) On each Offering Date, each Eligible Employee, pursuant to an
Offering made under the Plan, shall be granted a Purchase Right to purchase up
to that number of shares of Common Stock purchasable either with a percentage or
with a maximum dollar amount, as designated by the Board, but in either case not
exceeding fifteen percent (15%), of such Employee's Earnings (as defined by the
Board in each Offering) during the period that begins on the Offering Date (or
such later date as the Board determines for a particular Offering) and ends on
the date stated in the Offering, which date shall be no later than the end of
the Offering.

         (b) The Board shall establish one (1) or more Purchase Dates during an
Offering as of which Purchase Rights granted under the Plan and pursuant to that
Offering shall be exercised and purchases of shares of Common Stock shall be
carried out in accordance with such Offering.

         (c) In connection with each Offering made under the Plan, the Board may
specify a maximum number of shares of Common Stock that may be purchased by any
Participant pursuant to such Offering. In connection with each Offering made
under the Plan, the Board may specify a maximum aggregate number of shares of
Common Stock that may be purchased by all Participants pursuant to such
Offering. In addition, in connection with each Offering that contains more than
one Purchase Date, the Board may specify a maximum aggregate number of


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shares of Common Stock that may be purchased by all Participants on any given
Purchase Date under the Offering. If the aggregate purchase of shares of Common
Stock issuable upon exercise of Purchase Rights granted under the Offering would
exceed any such maximum aggregate number, then, in the absence of any Board
action otherwise, a pro rata allocation of the shares of Common Stock available
shall be made in as nearly a uniform manner as shall be practicable and
equitable.

         (d) The purchase price of shares of Common Stock acquired pursuant to
Purchase Rights granted under the Plan shall be not less than the lesser of:

                  (i) an amount equal to eighty-five percent (85%) of the Fair
Market Value of the shares of Common Stock on the Offering Date; or

                  (ii) an amount equal to eighty-five percent (85%) of the Fair
Market Value of the shares of Common Stock on the Purchase Date.

8.       PARTICIPATION; WITHDRAWAL; TERMINATION.

         (a) An Eligible Employee may become a Participant in the Plan pursuant
to an Offering by delivering a participation agreement to the Company within the
time specified in the Offering, in such form as the Company provides. Each such
agreement shall authorize payroll deductions of up to the maximum percentage
specified by the Board of such Participant's Earnings (as defined in each
Offering) during the Offering. The payroll deductions made for each Participant
shall be credited to a bookkeeping account for such Participant under the Plan
and shall be deposited with the general funds of the Company. To the extent
provided in the Offering, a Participant may reduce (including to zero) or
increase such payroll deductions. To the extent provided in the Offering, a
Participant may begin such payroll deductions after the beginning of the
Offering. A Participant may make additional payments into his or her account
only if specifically provided for in the Offering and only if the Participant
has not already had the maximum permitted amount withheld during the Offering.

         (b) At any time during an Offering, a Participant may terminate his or
her payroll deductions under the Plan and withdraw from the Offering by
delivering to the Company a notice of withdrawal in such form as the Company may
provide. Such withdrawal may be elected at any time prior to the end of the
Offering, except as provided in the Offering. Upon such withdrawal from the
Offering by a Participant, the Company shall distribute to such Participant all
of his or her accumulated payroll deductions (reduced to the extent, if any,
such deductions have been used to acquire shares of Common Stock for the
Participant) under the Offering, without interest (unless otherwise specified in
the Offering), and such Participant's interest in that Offering shall be
automatically terminated. A Participant's withdrawal from an Offering shall have
no effect upon such Participant's eligibility to participate in any other
Offerings under the Plan, but such Participant shall be required to deliver a
new participation agreement in order to participate in subsequent Offerings
under the Plan.

         (c) Purchase Rights granted pursuant to any Offering under the Plan
shall terminate immediately upon a Participant ceasing to be an Employee for any
reason or for no reason


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(subject to any post-employment participation period required by law) or other
lack of eligibility. The Company shall distribute to such terminated or
otherwise ineligible Employee all of his or her accumulated payroll deductions
(reduced to the extent, if any, such deductions have been used to acquire shares
of Common Stock for the terminated or otherwise ineligible Employee) under the
Offering, without interest (unless otherwise specified in the Offering).

         (d) Purchase Rights granted under the Plan shall not be transferable by
a Participant otherwise than by will or the laws of descent and distribution, or
by a beneficiary designation as provided in Section 13 and, during a
Participant's lifetime, shall be exercisable only by such Participant.

9.       EXERCISE.

         (a) On each Purchase Date during an Offering, each Participant's
accumulated payroll deductions and other additional payments specifically
provided for in the Offering (without any increase for interest) shall be
applied to the purchase of shares of Common Stock up to the maximum number of
shares of Common Stock permitted pursuant to the terms of the Plan and the
applicable Offering, at the purchase price specified in the Offering. No
fractional shares shall be issued upon the exercise of Purchase Rights granted
under the Plan unless specifically provided for in the Offering.

         (b) The amount, if any, of accumulated payroll deductions remaining in
each Participant's account after the purchase of shares of Common Stock that is
less than the amount required to purchase one share of Common Stock on the final
Purchase Date of an Offering shall be held in each such Participant's account
for the purchase of shares of Common Stock under the next Offering under the
Plan, unless such Participant withdraws from such next Offering, as provided in
Section 8(b), or is not eligible to participate in such Offering, as provided in
Section 6, in which case such amount shall be distributed to the Participant
after said final Purchase Date, without interest (unless otherwise specified in
the Offering). The amount, if any, of accumulated payroll deductions remaining
in a Participant's account after the purchase of shares of Common Stock that is
equal to the amount required to purchase one (1) or more whole shares of Common
Stock on the final Purchase Date of the Offering shall be distributed in full to
the Participant at the end of the Offering without interest (unless otherwise
specified in the Offering).

         (c) No Purchase Rights granted under the Plan may be exercised to any
extent unless the shares of Common Stock to be issued upon such exercise under
the Plan are covered by an effective registration statement pursuant to the
Securities Act and the Plan is in material compliance with all applicable
federal, state, foreign and other securities and other laws applicable to the
Plan. If on a Purchase Date during any Offering hereunder the shares of Common
Stock are not so registered or the Plan is not in such compliance, no Purchase
Rights granted under the Plan or any Offering shall be exercised on such
Purchase Date, and the Purchase Date shall be delayed until the shares of Common
Stock are subject to such an effective registration statement and the Plan is in
such compliance, except that the Purchase Date shall not be delayed more than
twelve (12) months and the Purchase Date shall in no event be more than
twenty-seven (27) months from the Offering Date. If, on the Purchase Date under
any Offering hereunder, as delayed to the maximum extent permissible, the shares
of Common Stock are not


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registered and the Plan is not in such compliance, no Purchase Rights granted
under the Plan or any Offering shall be exercised and all payroll deductions
accumulated during the Offering (reduced to the extent, if any, such deductions
have been used to acquire shares of Common Stock) shall be distributed to the
Participants, without interest (unless otherwise specified in the Offering).

10.      COVENANTS OF THE COMPANY.

         (a) During the terms of the Purchase Rights granted under the Plan, the
Company shall ensure that the amount of shares of Common Stock required to
satisfy such Purchase Rights are available.

         (b) The Company shall seek to obtain from each federal, state, foreign
or other regulatory commission or agency having jurisdiction over the Plan such
authority as may be required to issue and sell shares of Common Stock upon
exercise of the Purchase Rights granted under the Plan. If, after reasonable
efforts, the Company is unable to obtain from any such regulatory commission or
agency the authority that counsel for the Company deems necessary for the lawful
issuance and sale of shares of Common Stock under the Plan, the Company shall be
relieved from any liability for failure to issue and sell shares of Common Stock
upon exercise of such Purchase Rights unless and until such authority is
obtained.

11.      USE OF PROCEEDS FROM SHARES OF COMMON STOCK.

         Proceeds from the sale of shares of Common Stock pursuant to Purchase
Rights granted under the Plan shall constitute general funds of the Company.

12.      RIGHTS AS A STOCKHOLDER.

         A Participant shall not be deemed to be the holder of, or to have any
of the rights of a holder with respect to, shares of Common Stock subject to
Purchase Rights granted under the Plan unless and until the Participant's shares
of Common Stock acquired upon exercise of Purchase Rights granted under the Plan
are recorded in the books of the Company (or its transfer agent).

13.      DESIGNATION OF BENEFICIARY.

         (a) A Participant may file a written designation of a beneficiary who
is to receive any shares of Common Stock and/or cash, if any, from the
Participant's account under the Plan in the event of such Participant's death
subsequent to the end of an Offering but prior to delivery to the Participant of
such shares of Common Stock or cash. In addition, a Participant may file a
written designation of a beneficiary who is to receive any cash from the
Participant's account under the Plan in the event of such Participant's death
during an Offering.

         (b) The Participant may change such designation of beneficiary at any
time by written notice. In the event of the death of a Participant and in the
absence of a beneficiary validly designated under the Plan who is living at the
time of such Participant's death, the Company


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shall deliver such shares of Common Stock and/or cash to the executor or
administrator of the estate of the Participant, or if no such executor or
administrator has been appointed (to the knowledge of the Company), the Company,
in its sole discretion, may deliver such shares of Common Stock and/or cash to
the spouse or to any one or more dependents or relatives of the Participant, or
if no spouse, dependent or relative is known to the Company, then to such other
person as the Company may designate.

14.      ADJUSTMENTS UPON CHANGES IN SECURITIES; CORPORATE TRANSACTIONS.

         (a) If any change is made in the shares of Common Stock, subject to the
Plan, or subject to any Purchase Right, without the receipt of consideration by
the Company (through merger, consolidation, reorganization, recapitalization,
reincorporation, stock dividend, dividend in property other than cash, stock
split, liquidating dividend, combination of shares, exchange of shares, change
in corporate structure or other transaction not involving the receipt of
consideration by the Company), the Plan shall be appropriately adjusted in the
type(s), class(es) and maximum number of shares of Common Stock subject to the
Plan pursuant to Section 4(a), and the outstanding Purchase Rights granted under
the Plan shall be appropriately adjusted in the type(s), class(es), number of
shares and purchase limits of such outstanding Purchase Rights. The Board shall
make such adjustments, and its determination shall be final, binding and
conclusive. (The conversion of any convertible securities of the Company shall
not be treated as a "transaction not involving the receipt of consideration by
the Company.")

         (b) In the event of a Corporate Transaction, then: (i) any surviving or
acquiring corporation may continue or assume Purchase Rights outstanding under
the Plan or may substitute similar rights (including a right to acquire the same
consideration paid to stockholders in the transaction described in this Section
14(b)) for those outstanding under the Plan, or (ii) if any surviving or
acquiring corporation does not assume such Purchase Rights or does not
substitute similar rights for Purchase Rights outstanding under the Plan, then,
the Participants' accumulated payroll deductions (exclusive of any accumulated
interest which cannot be applied toward the purchase of shares of Common Stock
under the terms of the Offering) shall be used to purchase shares of Common
Stock immediately prior to the Corporate Transaction under the ongoing Offering,
and the Participants' Purchase Rights under the ongoing Offering shall terminate
immediately after such purchase.

15.      AMENDMENT OF THE PLAN.

         (a) The Board at any time, and from time to time, may amend the Plan.
However, except as provided in Section 14 relating to adjustments upon changes
in securities and except as to amendments solely to benefit the administration
of the Plan, to take account of a change in legislation or to obtain or maintain
favorable tax, exchange control or regulatory treatment for Participants or the
Company or any Related Corporation, no amendment shall be effective unless
approved by the stockholders of the Company to the extent stockholder approval
is necessary for the Plan to satisfy the requirements of Section 423 of the
Code, any Nasdaq or other securities exchange listing requirements or other
applicable laws or regulations. Currently under the Code, stockholder approval
within twelve (12) months before or after the adoption of the amendment is
required where the amendment shall increase the amount of shares of Common Stock
reserved


                                     - 10 -
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for issuance pursuant to Purchase Rights under the Plan or make certain
modifications to the provisions as to eligibility for participation in the Plan.

         (b) It is expressly contemplated that the Board may amend the Plan in
any respect the Board deems necessary or advisable to provide Employees with the
maximum benefits provided or to be provided under the provisions of the Code and
the regulations promulgated thereunder relating to Employee Stock Purchase Plans
and/or to bring the Plan and/or Purchase Rights granted under the Plan into
compliance therewith.

         (c) The rights and obligations under any Purchase Rights granted before
amendment of the Plan shall not be impaired by any amendment of the Plan except
(i) with the consent of the person to whom such Purchase Rights were granted,
(ii) as necessary to comply with any laws or governmental regulations, or (iii)
as necessary to ensure that the Plan and/or Purchase Rights granted under the
Plan comply with the requirements of Section 423 of the Code.

16.      TERMINATION OR SUSPENSION OF THE PLAN.

         (a) The Board in its discretion may suspend or terminate the Plan at
any time. Unless sooner terminated, the Plan shall terminate at the time that
all of the shares of Common Stock reserved for issuance under the Plan, as
increased and/or adjusted from time to time, have been issued under the terms of
the Plan. No Purchase Rights may be granted under the Plan while the Plan is
suspended or after it is terminated.

         (b) Any benefits, privileges, entitlements and obligations under any
Purchase Rights granted under the Plan while the Plan is in effect shall not be
impaired by suspension or termination of the Plan except (i) as expressly
provided in the Plan or with the consent of the person to whom such Purchase
Rights were granted, (ii) as necessary to comply with any laws, regulations, or
listing requirements, or (iii) as necessary to ensure that the Plan and/or
Purchase Rights granted under the Plan comply with the requirements of Section
423 of the Code.

17.      EFFECTIVE DATE OF PLAN.

         The Plan shall become effective as determined by the Board, but no
Purchase Rights granted under the Plan shall be exercised unless and until the
Plan has been approved by the stockholders of the Company within twelve (12)
months before or after the date the Plan is adopted by the Board, which date may
be prior to the effective date set by the Board.


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                           ACADIA PHARMACEUTICALS INC.

                        2000 EMPLOYEE STOCK PURCHASE PLAN
                                    OFFERING

               ADOPTED BY THE BOARD OF DIRECTORS DECEMBER 20, 2000


         In this document, capitalized terms not otherwise defined shall have
the same definitions of such terms as in the ACADIA Pharmaceuticals Inc. 2000
Employee Stock Purchase Plan.

1.       GRANT; OFFERING DATE.

         (a) The Board hereby authorizes an Offering pursuant to the following
terms.

         (b) The first Offering hereunder (the "Initial Offering") shall begin
on the effective date of the initial public offering of the shares of the Common
Stock and end on [IPO Date + 2 years]. The Initial Offering shall consist of
four (4) Purchase Periods, with the first Purchase Period ending on
______________, the second Purchase Period ending on __________, the third
Purchase Period ending on ________________, and the fourth Purchase Period
ending on ________________. Thereafter, an Offering shall begin on each
[_________] and each Offering shall be two (2) years in duration, with four (4)
Purchase Period(s) each of which shall be approximately six (6) months in
length. Each Offering shall end on the day prior to the first day of the
subsequent Offering except as provided below. Except as provided below, a
Purchase Date is the last day of a Purchase Period or of an Offering, as the
case may be.]

         (c) Notwithstanding the foregoing: (i) if any Offering Date falls on a
day that is not a Trading Day, then such Offering Date shall instead fall on the
next subsequent Trading Day and (ii) if any Purchase Date falls on a day that is
not a Trading Day, then such Purchase Date shall instead fall on the immediately
preceding Trading Day.

         (d) Prior to the commencement of any Offering, the Board may change any
or all terms of such Offering and any subsequent Offerings. The granting of
Purchase Rights pursuant to each Offering hereunder shall occur on each
respective Offering Date unless prior to such date (i) the Board determines that
such Offering shall not occur, or (ii) no shares of Common Stock remain
available for issuance under the Plan in connection with the Offering.

         (e) Notwithstanding anything in this Section 1 to the contrary, if on
the first day of the new Purchase Period during the Offering the Fair Market
Value of the shares of Common Stock is less than it was on the Offering Date for
that Offering, that day shall become the next Offering Date, and the Offering
that would otherwise have continued in effect shall immediately terminate and
the Employees who were employed in the terminated Offering shall automatically
be enrolled in the new Offering that starts such day.

2.       ELIGIBLE EMPLOYEES.

         (a) All Employees of the Company and each of its Related Corporations
incorporated in the United States shall be granted Purchase Rights to purchase
shares of Common Stock under


                                       1.
<PAGE>

each Offering on the Offering Date of such Offering, provided that each such
Employee otherwise meets the employment requirements of Section 6(a) of the Plan
and is employed by the Company or a Related Corporation prior to the Offering
Date.

         (b) Notwithstanding the foregoing, the following Employees shall NOT be
Eligible Employees or be granted Purchase Rights under an Offering: (i)
part-time or seasonal Employees whose customary employment is twenty (20) hours
per week or less or five (5) months per calendar year or less; (ii) five percent
(5%) stockholders (including ownership through unexercised and/or unvested stock
options) as described in Section 6(c) of the Plan; or (iii) Employees in
jurisdictions outside of the United States if, as of the Offering Date of the
Offering, the grant of such Purchase Rights would not be in compliance with the
applicable laws of any jurisdiction in which the Employee resides or is
employed.

         (c) Notwithstanding the foregoing, each person who first becomes an
Eligible Employee during any Offering shall, on the day after the FIRST Purchase
Date during that Offering in which such person FIRST satisfies the service
requirement to become an Eligible Employee, receive a Purchase Right under such
Offering, which Purchase Right shall thereafter be deemed to be a part of the
Offering. Such Purchase Right shall have the same characteristics as any
Purchase Rights originally granted under the Offering except that:

                  (i) the date on which such Purchase Right is granted shall be
the "Offering Date" of such Purchase Right for all purposes, including
determination of the exercise price of such Purchase Right; and

                  (ii) the Offering for such Purchase Right shall begin on its
Offering Date and end coincident with the end of the ongoing Offering.

3.       PURCHASE RIGHTS.

         (a) Subject to the limitations contain herein and in the Plan, on each
Offering Date each Eligible Employee shall be granted a Purchase Right to
purchase the number of shares of Common Stock purchasable with up to fifteen
percent (15%) of such Eligible Employee's Earnings paid during the period of
such Offering beginning after such Eligible Employee first commences
participation; PROVIDED, HOWEVER, that no Eligible Employee may have more than
fifteen percent (15%) of such Eligible Employee's Earnings applied to purchase
shares of Common Stock under all ongoing Offerings under the Plan and all other
plans of the Company intended to qualify as Employee Stock Purchase Plans under
Section 423 of the Code.

         (b) For this Offering, "Earnings" means the total compensation paid to
an Employee, including all salary, wages (including amounts elected to be
deferred by the employee, that would otherwise have been paid, under any cash or
deferred arrangement or other deferred compensation program established by the
Company), overtime pay, commissions, bonuses, and other remuneration paid
directly to the Employee, but excluding profit sharing, the cost of employee
benefits paid for by the Company, education or tuition reimbursements, imputed
income arising under any Company group insurance or benefit program, traveling
expenses, business and moving expense reimbursements, income received in
connection with stock


                                       2.
<PAGE>

options, contributions made by the Company under any employee benefit plan, and
similar items of compensation.

         (c) Notwithstanding the foregoing, the maximum number of shares an
Eligible Employee may purchase on any Purchase Date in an Offering shall be such
number of shares as has a Fair Market Value (determined as of the Offering Date
for such Offering) equal to (x) $25,000 multiplied by the number of calendar
years in which the Purchase Right under such Offering has been outstanding at
any time, minus (y) the Fair Market Value of any other shares (determined as of
the relevant Offering Date with respect to such shares) which, for purposes of
the limitation of Section 423(b)(8) of the Code, are attributed to any of such
calendar years in which the Purchase Right is outstanding. The amount in clause
(y) of the previous sentence shall be determined in accordance with regulations
applicable under Section 423(b)(8) of the Code based on (i) the number of shares
previously purchased with respect to such calendar years pursuant to such
Offering or any other Offering under the Plan, or pursuant to any other Company
plans intended to qualify as Employee Stock Purchase Plans under Section 423 of
the Code, and (ii) the number of shares subject to other Purchase Rights
outstanding on the Offering Date for such Offering pursuant to the Plan or any
other such Company Employee Stock Purchase Plan.

         (d) The maximum aggregate number of shares of Common Stock available to
be purchased by all Eligible Employees under an Offering shall be the number of
shares of Common Stock remaining available under the Plan on the Offering Date.
If the aggregate purchase of shares of Common Stock upon exercise of Purchase
Rights granted under the Offering would exceed the maximum aggregate number of
shares available, the Board shall make a pro rata allocation of the shares
available in a uniform and equitable manner.

         (e) Notwithstanding the foregoing, the maximum number of shares of
Common Stock that an Eligible Employee may purchase during any Offering shall
not exceed Ten Thousand (10,000) shares.

4.       PURCHASE PRICE.

         The purchase price of shares of Common Stock under the Offering shall
be the lesser of: (i) eighty-five percent (85%) of the Fair Market Value of such
shares of Common Stock on the Offering Date or (ii) or eighty-five percent (85%)
of the Fair Market Value of such shares of Common Stock on the Purchase Date, in
each case rounded up to the nearest whole cent per Share. For the Initial
Offering, the Fair Market Value of the shares of Common Stock at the time when
the Offering commences shall be the price per share at which shares are first
sold to the public in the Company's initial public offering as specified in the
final prospectus for that initial public offering.

5.       PARTICIPATION.

         (a) An Eligible Employee may elect to participate in an Offering on the
Offering Date or as of the first day following any Purchase Date; provided,
however, that a person who first becomes an Eligible Employee during an Offering
may elect to participate at the Offering Date applicable to such Eligible
Employee in accordance with Section 2(b) of this Offering


                                       3.
<PAGE>

document. An Eligible Employee shall become a Participant in an Offering by
delivering an enrollment form authorizing payroll deductions. Such deductions
must be in whole percentages of Earnings, with a minimum percentage of one
percent (1%) and a maximum percentage of fifteen percent (15%). A Participant
may not make additional payments into his or her account. The agreement shall be
made on such enrollment form as the Company provides, and must be delivered to
the Company prior to the date participation is to be effective, unless a later
time for filing the enrollment form is set by the Company for all Eligible
Employees with respect to a given Offering.

         (b) A Participant may increase or reduce (including to zero) his or her
participation level once during the six (6) month period ending on a Purchase
Date, excluding only each ten (10) business day period immediately preceding a
Purchase Date (or such shorter period of time as determined by the Company and
communicated to Participants). In addition, a Participant may reduce his or her
participation level to zero percent (0%) at any time during the course of an
Offering, excluding only each ten (10) business day period immediately preceding
a Purchase Date (or such shorter period of time as determined by the Company and
communicated to Participants). Any such change in participation shall be made by
delivering a notice to the Company or a designated Related Corporation in such
form and at such time as the Company provides.

         (c) A Participant may withdraw from an Offering and receive his or her
accumulated payroll deductions from the Offering (reduced to the extent, if any,
such deductions have been used to acquire shares of Common Stock for the
Participant on any prior Purchase Dates) without interest, at any time prior to
the end of the Offering, excluding only each ten (10) business day period
immediately preceding a Purchase Date (or such shorter period of time determined
by the Company and communicated to Participants), by delivering a withdrawal
notice to the Company in such form as the Company provides. A Participant who
has withdrawn from an Offering shall not again participate in such Offering, but
may participate in subsequent Offerings under the Plan in accordance with the
terms thereof.

         (d) Notwithstanding the foregoing or any other provision of this
Offering document or of the Plan to the contrary, neither the enrollment of any
Eligible Employee in the Plan nor any forms relating to participation in the
Plan shall be given effect until such time as a registration statement covering
the registration of the shares under the Plan that are subject to the Offering
has been filed by the Company and has become effective.

6.       PURCHASES.

         Subject to the limitations contained herein, on each Purchase Date,
each Participant's accumulated payroll deductions (without any increase for
interest) shall be applied to the purchase of whole shares, up to the maximum
number of shares permitted under the Plan and the Offering.

7.       NOTICES AND AGREEMENTS.

         Any notices or agreements provided for in an Offering or the Plan shall
be given in writing, in a form provided by the Company, and unless specifically
provided for in the Plan or


                                       4.
<PAGE>

this Offering, shall be deemed effectively given upon receipt or, in the case of
notices and agreements delivered by the Company, five (5) days after deposit in
the United States mail, postage prepaid.

8.       EXERCISE CONTINGENT ON STOCKHOLDER APPROVAL.

         The Purchase Rights granted under an Offering are subject to the
approval of the Plan by the stockholders of the Company as required for the Plan
to obtain treatment as a tax-qualified Employee Stock Purchase Plan.

9.       OFFERING SUBJECT TO PLAN.

         Each Offering is subject to all the provisions of the Plan, and the
provisions of the Plan are hereby made a part of the Offering. The Offering is
further subject to all interpretations, amendments, rules and regulations which
may from time to time be promulgated and adopted pursuant to the Plan. In the
event of any conflict between the provisions of an Offering and those of the
Plan (including interpretations, amendments, rules and regulations which may
from time to time be promulgated and adopted pursuant to the Plan), the
provisions of the Plan shall control.











                                       5.